A photovoltaic backsheet and photovoltaic module

Abstract

The application discloses a photovoltaic backboard, which comprises a weather-resistant layer, a water vapor barrier layer and a water-based adhesive layer arranged in sequence, wherein the weather-resistant layer comprises polyester, preferably polyethylene terephthalate; and the water vapor barrier layer comprises polyester, preferably polyethylene terephthalate. The application also provides a preparation method of the photovoltaic backboard and a photovoltaic module. The photovoltaic backboard provided by the application is environment-friendly without fluorine in the weather-resistant layer, and the weather-resistant layer provides UV blocking and weather resistance for the backboard; the water vapor barrier layer is added with barrier fillers, so that the water vapor barrier performance of the backboard is improved; and the water-based adhesive layer has good resin adhesion and adhesion to adhesive films.

Description

Technical Field

[0001] This application relates to the photovoltaic field, specifically to a photovoltaic backsheet and a photovoltaic module. Background Technology

[0002] The photovoltaic backsheet is located on the back of the photovoltaic module, protecting and supporting the photovoltaic cells, and has excellent insulation, barrier properties, and weather resistance. Photovoltaic backsheets typically have a three-layer structure, using PET polyester film as the substrate, with 10–30 μm fluoropolymer layers laminated or coated on both surfaces of the substrate as the air-side weather-resistant layer and the cell-side adhesive layer.

[0003] While fluorinated materials have excellent weather resistance, they are expensive, difficult to degrade, and cause significant environmental pollution. In traditional production processes, the preparation of both inner and outer layers requires the preparation of PET films before offline coating or film lamination, resulting in low production efficiency and high costs. Meanwhile, in order to improve the power of the module, single-glass modules often use high-reflectivity encapsulant films as the back adhesive film, which greatly reduces the UV resistance requirement of the cell surface adhesive layer. Summary of the Invention

[0004] To address the aforementioned issues, this application provides a photovoltaic backsheet comprising a double-coated weather-resistant layer and a moisture barrier layer, as well as an online-coated water-based adhesive layer. The entire backsheet is integrally molded, greatly simplifying the production process, significantly reducing production costs, and improving production efficiency. The weather-resistant layer is fluorine-free and environmentally friendly, providing UV protection and weather resistance for the backsheet. The moisture barrier layer contains a barrier filler, which enhances the moisture barrier performance of the backsheet. The water-based adhesive layer exhibits excellent resin adhesion and bonding to the adhesive film.

[0005] This application provides a photovoltaic backsheet, comprising a weather-resistant layer, a moisture barrier layer, and a water-based adhesive layer arranged sequentially. The weather-resistant layer comprises polyester, preferably polyethylene terephthalate; the moisture barrier layer comprises polyester, preferably polyethylene terephthalate.

[0006] Further, the weather-resistant layer comprises, by mass fraction: 85%–95% polyethylene terephthalate, 3%–15% reflective pigment, 0.2%–2% light stabilizer, 0.2%–2% first chain extender, and 0.5%–3% first hydrolysis-resistant stabilizer.

[0007] Furthermore, the reflective pigment is selected from one or more of the following: rutile titanium dioxide, zirconium oxide, zinc oxide, silicon oxide, barium sulfate, zinc sulfide, calcium carbonate, aluminum oxide, and carbon black.

[0008] The light stabilizer is selected from one or more of hindered amine light stabilizers, benzophenone UV absorbers, salicylate UV absorbers, benzotriazole UV absorbers, and triazine UV absorbers; the first chain extender is selected from epoxy chain extenders; the first hydrolysis resistant stabilizer is selected from one or two of monomeric carbodiimide and polymeric carbodiimide.

[0009] Further, the water vapor barrier layer comprises, by mass fraction: 85%–95% polyethylene terephthalate, 1%–5% barrier filler, 0.2%–2% antioxidant, 0.2%–2% second chain extender, and 0.5%–3% second hydrolysis resistant stabilizer.

[0010] Furthermore, the barrier filler is selected from one or more of layered silicates, modified nano-montmorillonite, mica powder, and silica; the antioxidant is selected from one or more of hindered phenolic antioxidants, phosphite antioxidants, and organosulfur antioxidants.

[0011] The second chain extender is selected from epoxy chain extenders; the second hydrolysis-resistant stabilizer is selected from one or both of monomeric carbodiimide and polymeric carbodiimide.

[0012] Furthermore, the thickness of the photovoltaic backsheet is 150μm to 350μm.

[0013] The thickness of the water vapor barrier layer is 70μm to 330μm.

[0014] The thickness of the weather-resistant layer is 20μm to 80μm.

[0015] The thickness of the water-based adhesive layer is 0.05 μm to 1 μm.

[0016] This application provides a method for preparing a photovoltaic backsheet, comprising the following steps:

[0017] Preparation of weather-resistant masterbatch and barrier functional masterbatch;

[0018] Prepare an aqueous coating solution;

[0019] Barrier functional masterbatch and weather-resistant masterbatch are melted separately according to the formula, and cast sheets are obtained by double-layer co-extrusion process;

[0020] The cast sheet is stretched and coated with an aqueous coating liquid. The aqueous coating liquid crosslinks and cures to form an aqueous adhesive pre-coating layer, thus obtaining the photovoltaic backsheet.

[0021] Furthermore, the weather-resistant masterbatch is prepared by the following method:

[0022] Preparation of color masterbatch and weather-resistant functional masterbatch;

[0023] The color masterbatch is mixed with the weather-resistant functional masterbatch to obtain the weather-resistant masterbatch.

[0024] Furthermore, the reflective pigment is mixed evenly with polyethylene terephthalate and then melt-extruded using a twin-screw extruder to produce color masterbatch;

[0025] The light stabilizer, the first chain extender, the first hydrolysis resistant stabilizer and polyethylene terephthalate are mixed evenly and then melt-extruded through a twin-screw extruder to produce a weather-resistant functional masterbatch.

[0026] The second chain extender, the second hydrolysis-resistant stabilizer, the barrier filler, the antioxidant, and polyethylene terephthalate are mixed evenly and then melt-extruded using a twin-screw extruder to produce a barrier functional masterbatch.

[0027] Furthermore, the mass fraction of polyethylene terephthalate in the masterbatch is 40% to 60%;

[0028] The mass fraction of polyethylene terephthalate in the weather-resistant masterbatch is 60% to 90%.

[0029] The barrier masterbatch contains 50% to 80% polyethylene terephthalate by mass.

[0030] Furthermore, the cast sheet is preheated and stretched longitudinally, then corona-treated and coated with an aqueous coating liquid on the surface of the water vapor barrier layer. After preheating, it is stretched laterally and then heat-set to allow the aqueous coating liquid to crosslink and solidify to form an aqueous adhesive pre-coating layer.

[0031] Further, the aqueous coating liquid comprises, by mass fraction: 10%–25% of a first aqueous polyurethane resin, 5%–10% of a tackifying resin, 2%–4% of an aqueous crosslinking agent, 0.1%–0.5% of a hydrolysis-resistant agent, 0.1%–0.5% of an antiblocking agent, 0.1%–0.5% of a leveling agent, and 0.1%–0.5% of a defoamer.

[0032] Furthermore, the glass transition temperature of the first waterborne polyurethane resin is 30℃~80℃; the glass transition temperature of the tackifying resin is -20℃~25℃.

[0033] The tackifying resin is selected from one or more of the following: a second waterborne polyurethane resin, a waterborne polyester resin, and a waterborne acrylic resin, preferably a waterborne acrylic resin.

[0034] The aqueous crosslinking agent is an aqueous blocked isocyanate crosslinking agent;

[0035] The hydrolysis-resistant agent is selected from monomeric carbodiimide or polymeric carbodiimide;

[0036] The anti-blocking agent is selected from silicon dioxide;

[0037] The leveling agent is selected from polyether-modified silicone leveling agents;

[0038] The defoamer is selected from alkyl-modified organosiloxane defoamers.

[0039] Furthermore, the photovoltaic backsheet prepared is the aforementioned photovoltaic backsheet.

[0040] This application also provides a photovoltaic module, which includes the aforementioned photovoltaic backsheet or a photovoltaic backsheet prepared by the aforementioned method.

[0041] Furthermore, it also includes glass, encapsulant film one, battery string assembly, encapsulant film two, wherein the glass, encapsulant film one, battery string assembly, encapsulant film two, and photovoltaic backsheet are stacked in sequence.

[0042] The photovoltaic backsheet provided in this application uses the weather-resistant layer as the outer layer to provide ultraviolet shading and weather resistance, and does not contain fluorine-containing materials, which is both environmentally friendly and reduces costs. The water vapor barrier layer contains a barrier filler, which can improve the water vapor barrier performance of the photovoltaic backsheet, thereby overcoming the problem of reduced hydrophobic and water-blocking performance when using polyester materials as the weather-resistant layer, making up for the defects in water-blocking performance, and reducing the corrosion of water vapor to the inside of the photovoltaic module.

[0043] The photovoltaic backsheet provided in this application, manufactured using a double-layer co-extrusion process, exhibits strong interlayer bonding, is less prone to delamination, and requires online application of water-based coating liquid without offline rewinding, resulting in a photovoltaic backsheet with uniform coating and excellent adhesion. The integrated molding process of double-layer co-extrusion and online coating significantly simplifies the production steps, improves production efficiency, and substantially reduces production costs. Attached Figure Description

[0044] The accompanying drawings are provided to better understand this application and do not constitute an undue limitation thereof. Wherein:

[0045] Figure 1 This is a schematic diagram of the structure of the photovoltaic backsheet provided in this application.

[0046] Explanation of reference numerals in the attached figures

[0047] 1-Weather-resistant layer, 2-Moisture barrier layer, 3-Water-based adhesive layer. Detailed Implementation

[0048] The following description provides exemplary embodiments of this application, including various details to aid understanding, and should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this application. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0049] This application provides a photovoltaic backsheet, which includes a weather-resistant layer 1, a moisture barrier layer 2, and a water-based adhesive layer 3 arranged sequentially. The weather-resistant layer 1 includes polyester, preferably polyethylene terephthalate; the moisture barrier layer 2 includes polyester, preferably polyethylene terephthalate.

[0050] In the photovoltaic backsheet, the weather-resistant layer 1 and the water vapor barrier layer 2 are formed by double-layer co-extrusion; the water-based adhesive layer 3 is formed by online coating and drying of water-based coating liquid.

[0051] Specifically, the weather-resistant layer 1 and the water vapor barrier layer 2 are joined together by a double-layer co-extrusion process in the following way:

[0052] The raw materials of the weather-resistant layer 1 are prepared into weather-resistant masterbatch, and the raw materials of the water vapor barrier layer 2 are prepared into barrier functional masterbatch. Then, the weather-resistant masterbatch and the barrier functional masterbatch are respectively melted and combined together using a double-layer co-extrusion process.

[0053] The photovoltaic backsheet provided in this application uses the weather-resistant layer 1 as the outer layer to provide ultraviolet shading and weather resistance, and does not contain fluorine-containing materials, which is both environmentally friendly and reduces costs. The water vapor barrier layer 2 contains a barrier filler, which can improve the water vapor barrier performance of the photovoltaic backsheet, thereby overcoming the problem of reduced hydrophobic and water-blocking performance when using polyester material as the weather-resistant layer 1, making up for the defects in water-blocking performance, and reducing the corrosion of water vapor to the inside of the photovoltaic module.

[0054] In this application, the aqueous coating liquid includes: a first aqueous polyurethane resin, a tackifying resin, an aqueous crosslinking agent, a hydrolysis-resistant agent, an antiblocking agent, a leveling agent, and a defoamer.

[0055] In some embodiments, the aqueous coating liquid is composed of a first aqueous polyurethane resin, a tackifying resin, an aqueous crosslinking agent, a hydrolysis-resistant agent, an antiblocking agent, a leveling agent, a defoamer, and deionized water.

[0056] In this application, the aqueous coating liquid comprises, by mass fraction: 10% to 25% of a first aqueous polyurethane resin, more preferably 15% to 25%; 5% to 10% of a tackifying resin, more preferably 7% to 10%; 2% to 4% of an aqueous crosslinking agent, more preferably 2% to 3%; 0.1% to 0.5% of a hydrolysis-resistant agent, more preferably 0.2% to 0.4%; 0.1% to 0.5% of an antiblocking agent, more preferably 0.2% to 0.4%; 0.1% to 0.5% of a leveling agent, more preferably 0.2% to 0.4%; and 0.1% to 0.5% of a defoamer, more preferably 0.2% to 0.4%.

[0057] In some embodiments, the aqueous coating liquid comprises 10%–25% of a first aqueous polyurethane resin, 5%–10% of a tackifying resin, 2%–4% of an aqueous crosslinking agent, 0.1%–0.5% of a hydrolysis-resistant agent, 0.1%–0.5% of an antiblocking agent, 0.1%–0.5% of a leveling agent, 0.1%–0.5% of a defoamer, and the balance being deionized water.

[0058] Specifically, in the aqueous coating liquid, the mass fraction of the first aqueous polyurethane resin can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, or 25%.

[0059] Specifically, in the aqueous coating liquid, the mass fraction of the tackifying resin can be 5%, 5.5%, 6%, 6.5%, 7%, 7.8%, 8%, 8.5%, 9%, 9.5%, or 10%.

[0060] Specifically, in the aqueous coating liquid, the mass fraction of the aqueous crosslinking agent can be 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4%.

[0061] Specifically, in the aqueous coating solution, the mass fraction of the hydrolysis-resistant agent can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%.

[0062] Specifically, in the aqueous coating liquid, the mass fraction of the anti-blocking agent can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%.

[0063] Specifically, in the aqueous coating liquid, the mass fraction of the leveling agent can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%.

[0064] Specifically, in the aqueous coating liquid, the mass fraction of the defoamer can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%.

[0065] In this application, the glass transition temperature of the first waterborne polyurethane resin is 30°C to 80°C, preferably 40°C to 70°C.

[0066] Specifically, the glass transition temperature of the first waterborne polyurethane resin can be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C.

[0067] The first waterborne polyurethane resin has a relatively high glass transition temperature (Tg), which can give the waterborne adhesive layer good adhesion and hardness, and avoid adhesion that leads to winding difficulties.

[0068] In this application, the glass transition temperature of the tackifying resin is -20°C to 25°C.

[0069] Specifically, the glass transition temperature of the tackifying resin can be -20℃, -15℃, -10℃, -5℃, 0℃, 5℃, 10℃, 15℃, 20℃, or 25℃.

[0070] The tackifying resin is selected from water-based resins with a glass transition temperature (Tg) of -20℃ to 25℃. It not only gives the water-based adhesive layer good adhesion, but also improves the adhesion between the water-based adhesive layer and the high-reflectivity adhesive film in the photovoltaic module. At the same time, since the tackifying resin has a relatively low Tg, it can play an auxiliary role in film formation and improve the film-forming properties of the water-based coating liquid.

[0071] Specifically, the tackifying resin is selected from one of the following: a second waterborne polyurethane resin, a waterborne polyester resin, and a waterborne acrylic resin, preferably a waterborne acrylic resin.

[0072] The aqueous crosslinking agent described in this application is an aqueous blocked isocyanate crosslinking agent.

[0073] In this application, the hydrolysis-resistant agent is selected from one or both of monomeric carbodiimide or polymeric carbodiimide.

[0074] In this application, the anti-blocking agent is silicon dioxide, preferably fumed silicon dioxide with a D50 particle size of 50nm to 150nm.

[0075] The particle size of the silica can be 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, 105nm, 110nm, 115nm, 120nm, 125nm, 130nm, 135nm, 140nm, 145nm or 150nm.

[0076] If the silica particle size is too large, it may cause a decrease in the adhesion of the water-based adhesive layer; if the particle size is too small, it may lead to insufficient anti-blocking effect.

[0077] In this application, the leveling agent is selected from polyether-modified silicone leveling agents.

[0078] Specifically, the polyether-modified silicone leveling agent may be selected from BYK410, BYK345, BYK307, etc.

[0079] In this application, the defoamer is selected from alkyl-modified organosiloxane defoamers.

[0080] Specifically, the alkyl-modified organosiloxane defoamers are TEGO Antifoam 2-89, DF819, BYK9730, etc.

[0081] In this application, the weather-resistant layer 1 includes polyethylene terephthalate, reflective pigment, light stabilizer, first chain extender, and first hydrolysis-resistant stabilizer.

[0082] In some embodiments, the weather-resistant layer 1 is composed of polyethylene terephthalate, reflective pigment, light stabilizer, first chain extender, and first hydrolysis-resistant stabilizer.

[0083] The weather-resistant layer 1 comprises, by mass fraction: 85%–95% polyethylene terephthalate, 3%–15% reflective pigment, 0.2%–2% light stabilizer, 0.2%–2% first chain extender, and 0.5%–3% first hydrolysis-resistant stabilizer.

[0084] In some embodiments, the weather-resistant layer 1 is composed of 85% to 95% polyethylene terephthalate, 3% to 15% reflective pigment, 0.2% to 2% light stabilizer, 0.2% to 2% first chain extender, and 0.5% to 3% first hydrolysis-resistant stabilizer.

[0085] Specifically, in the weather-resistant layer 1, the mass fraction of polyethylene terephthalate (PET) can be 85%, 85.5%, 86%, 86.5%, 87%, 87.5%, 88%, 88.5%, 89%, 89.5%, 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, or 95%.

[0086] Specifically, in the weather-resistant layer 1, the mass fraction of the reflective pigment can be 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, or 15%.

[0087] Specifically, in the weather-resistant layer 1, the mass fraction of the light stabilizer can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%.

[0088] Specifically, in the weather-resistant layer 1, the mass fraction of the first chain extender can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%.

[0089] Specifically, in the weather-resistant layer 1, the mass fraction of the first hydrolysis-resistant stabilizer can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, or 3%.

[0090] In this application, the reflective pigment is selected from one or more of rutile titanium dioxide, zirconium oxide, zinc oxide, silicon oxide, barium sulfate, zinc sulfide, calcium carbonate, aluminum oxide, and carbon black.

[0091] The light stabilizer is selected from one or more of hindered amine light stabilizers, benzophenone UV absorbers, salicylates UV absorbers, benzotriazole UV absorbers, and triazine UV absorbers.

[0092] The first chain extender is an epoxy chain extender, which is selected from glycidyl ester type epoxy compounds or glycidyl ether type epoxy compounds; preferably, the epoxy equivalent in the epoxy chain extender is 300 to 600.

[0093] The first hydrolysis-resistant stabilizer is selected from monomeric carbodiimide and / or polymeric carbodiimide.

[0094] In some embodiments, the weather-resistant layer 1 is composed of polyethylene terephthalate (PET), rutile titanium dioxide, hindered amine light stabilizer, benzophenone UV absorber, glycidyl ether epoxy compound, and polymeric carbodiimide.

[0095] In some embodiments, the weather-resistant layer 1 is composed of polyethylene terephthalate (PET), rutile titanium dioxide, barium sulfate, hindered amine light stabilizer, benzotriazole UV absorber, glycidyl ether epoxy compound, and polymeric carbodiimide.

[0096] In some embodiments, the weather-resistant layer 1 is made of polyethylene terephthalate (PET).

[0097] It consists of 85%–95% rutile titanium dioxide, 3%–15% hindered amine light stabilizer and benzophenone UV absorber (mass ratio of hindered amine light stabilizer to benzophenone UV absorber is 5:6), 0.2%–2% glycidyl ether epoxy compound and 0.5%–3% polymeric carbodiimide.

[0098] In some embodiments, the weather-resistant layer 1 is made of polyethylene terephthalate (PET).

[0099] It consists of 85%–95% rutile titanium dioxide and 3%–15% barium sulfate (the mass ratio of rutile titanium dioxide to barium sulfate is 5:2), 0.2%–2% hindered amine light stabilizer and benzotriazole UV absorber (the mass ratio of hindered amine light stabilizer to benzotriazole UV absorber is 5:6), 0.2%–2% glycidyl ether epoxy compound, and 0.5%–3% polymeric carbodiimide.

[0100] In this application, the water vapor barrier layer 2 includes polyethylene terephthalate, barrier filler, antioxidant, second chain extender, and second hydrolysis resistant stabilizer.

[0101] In some embodiments, the water vapor barrier layer 2 is composed of polyethylene terephthalate, barrier filler, antioxidant, second chain extender, and second hydrolysis-resistant stabilizer.

[0102] The water vapor barrier layer 2 comprises, by mass fraction, 85%–95% polyethylene terephthalate, 1%–5% barrier filler, 0.2%–2% antioxidant, 0.2%–2% second chain extender, and 0.5%–3% second hydrolysis resistant stabilizer.

[0103] In some embodiments, the water vapor barrier layer 2 is composed of 85% to 95% polyethylene terephthalate, 1% to 5% barrier filler, 0.2% to 2% antioxidant, 0.2% to 2% second chain extender, and 0.5% to 3% second hydrolysis resistant stabilizer by mass fraction.

[0104] Specifically, in the moisture barrier layer 2, the mass fraction of polyethylene terephthalate (PET) can be 85%, 85.5%, 86%, 86.5%, 87%, 87.5%, 88%, 88.5%, 89%, 89.5%, 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, or 95%.

[0105] Specifically, in the water vapor barrier layer 2, the mass fraction of the barrier filler can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, or 5%.

[0106] Specifically, in the water vapor barrier layer 2, the mass fraction of the antioxidant can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%.

[0107] Specifically, in the water vapor barrier layer 2, the mass fraction of the second chain extender can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%.

[0108] Specifically, in the water vapor barrier layer 2, the mass fraction of the second hydrolysis-resistant stabilizer can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, or 3%.

[0109] In this application, the barrier filler is selected from one or more of layered silicates, modified nano-montmorillonite, mica powder, and silica, preferably p-aminobenzoate modified montmorillonite.

[0110] The antioxidant is selected from one or more of hindered phenolic antioxidants, phosphite antioxidants, and organosulfur antioxidants. Examples of hindered phenolic antioxidants include IRGANOX-1010, IRGANOX-1076, RGANOX-1098, and IRGANOX-1135 (Ciba Specialty Chemicals). Examples of phosphite antioxidants include STAB-1178, STAB-317, STAB-517, STAB-2112, STAB-1500, and STAB-AS4500 (Chang Chun Chemical Co., Ltd., Taiwan).

[0111] The second chain extender is an epoxy chain extender, which is selected from glycidyl ester type epoxy compounds or glycidyl ether type epoxy compounds; preferably, the epoxy equivalent in the epoxy chain extender is 300 to 600.

[0112] Specifically, the epoxy equivalent in the epoxy chain extender can be 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, 500, 510, 520, 530, 540, 550, 560, 570, 580, 590, or 600.

[0113] The second hydrolysis-resistant stabilizer is selected from monomeric carbodiimide and / or polymeric carbodiimide.

[0114] In some embodiments, the water vapor barrier layer 2 is composed of 85%–95% polyethylene terephthalate (PET), 1%–5% nano-montmorillonite, 0.2%–2% hindered phenolic antioxidants and phosphite antioxidants (the mass ratio of hindered phenolic antioxidants to phosphite antioxidants is 5:2), 0.2%–2% glycidyl ether type epoxy compound, and 0.5%–3% polymeric carbodiimide by mass fraction.

[0115] In this application, the thickness of the photovoltaic backsheet is 150μm to 350μm. For example, it can be 150μm, 160μm, 170μm, 180μm, 190μm, 200μm, 210μm, 220μm, 230μm, 240μm, 250μm, 260μm, 270μm, 280μm, 290μm, 300μm, 310μm, 320μm, 330μm, 340μm, or 350μm.

[0116] The thickness of the water vapor barrier layer 2 is 70μm to 330μm. For example, it can be 70μm, 80μm, 90μm, 100μm, 105μm, 110μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm, 210μm, 220μm, 230μm, 240μm, 250μm, 260μm, 270μm, 280μm, 290μm, 300μm, 310μm, 320μm, or 330μm.

[0117] The thickness of the weather-resistant layer 1 is 20μm to 80μm. For example, it can be 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm or 80μm.

[0118] The thickness of the aqueous adhesive layer 3 is 0.05 μm to 1 μm. For example, it can be 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm, or 1 μm.

[0119] The thickness of the weather-resistant layer 1 and the water vapor barrier layer 2 is adjusted by the extrusion equipment during the preparation process, and the thickness of the water-based adhesive layer 3 is also controlled by adjusting the coating thickness of the water-based coating liquid during the preparation process.

[0120] The thicknesses of the weather-resistant layer 1, the water vapor barrier layer 2, and the water-based adhesive layer 3 can be obtained using a microscope.

[0121] This application provides a method for preparing a photovoltaic backsheet, comprising the following steps:

[0122] Step 1: Prepare weather-resistant masterbatch and barrier function masterbatch;

[0123] Step 2: Prepare the water-based coating solution;

[0124] Step 3: Melt the barrier masterbatch and weather-resistant masterbatch separately according to the formula, and use a double-layer co-extrusion process to obtain the cast sheet;

[0125] Step 4: Stretch the cast sheet and coat its surface with an aqueous coating liquid. The aqueous coating liquid crosslinks and cures to form an aqueous adhesive pre-coating layer, thus obtaining the photovoltaic backsheet.

[0126] In step 1: the weather-resistant masterbatch is prepared by the following method:

[0127] Preparation of color masterbatch and weather-resistant functional masterbatch;

[0128] The color masterbatch is mixed with the weather-resistant functional masterbatch to obtain the weather-resistant masterbatch.

[0129] Specifically, step 1 includes steps 1a, 1b, and 1c, wherein steps 1a, 1b, and 1c are not in any particular order.

[0130] In step 1a, the preparation method of the color masterbatch is as follows:

[0131] The reflective pigment is mixed evenly with polyethylene terephthalate (PET resin) and melt-extruded through a twin-screw extruder to produce a masterbatch.

[0132] Specifically, the mass fraction of PET resin in the masterbatch is 40% to 60%, for example, it can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, or 60%.

[0133] Specifically, the melt extrusion temperature is 210℃~265℃, for example, it can be 210℃, 215℃, 220℃, 225℃, 230℃, 235℃, 240℃, 245℃, 250℃, 255℃, 260℃ or 265℃.

[0134] In step 1b, the preparation method of the weather-resistant functional masterbatch is as follows:

[0135] The light stabilizer, the first chain extender, the first hydrolysis resistant stabilizer and PET resin are mixed evenly and then melt-extruded through a twin-screw extruder to produce a weather-resistant functional masterbatch.

[0136] Specifically, the mass fraction of PET resin in the weather-resistant functional masterbatch is 60% to 90%, for example, it can be 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, or 90%.

[0137] Specifically, the melt extrusion temperature is 210℃~265℃, for example, it can be 210℃, 215℃, 220℃, 225℃, 230℃, 235℃, 240℃, 245℃, 250℃, 255℃, 260℃ or 265℃.

[0138] In step 1c, the preparation steps of the barrier functional masterbatch are as follows:

[0139] The second chain extender, the second hydrolysis-resistant stabilizer, the barrier filler, the antioxidant, and PET resin are mixed evenly and then melt-extruded using a twin-screw extruder to produce a barrier functional masterbatch.

[0140] Specifically, in the barrier functional masterbatch, the mass fraction of PET resin is 50% to 80%, for example, it can be 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, or 80%.

[0141] Specifically, the melt extrusion temperature is 210℃~265℃, for example, it can be 210℃, 215℃, 220℃, 225℃, 230℃, 235℃, 240℃, 245℃, 250℃, 255℃, 260℃ or 265℃.

[0142] In step 2, the preparation steps of the aqueous coating liquid are as follows: the first aqueous polyurethane resin, tackifying resin, aqueous crosslinking agent, hydrolysis resistant agent, antiblocking agent, leveling agent and defoamer are mixed in a certain proportion and stirred evenly to obtain the aqueous coating liquid.

[0143] The proportions and types of the components in the aqueous coating solution can be found in the foregoing description.

[0144] In step 3, according to the raw material ratio, the color masterbatch, weather-resistant functional masterbatch, and the remaining polyethylene terephthalate (in the weather-resistant layer formula, the total content of polyethylene terephthalate minus the polyethylene terephthalate in the color masterbatch and weather-resistant functional masterbatch is the remaining polyethylene terephthalate) are mixed and melted in the weather-resistant layer barrel. The barrier functional masterbatch and the remaining polyethylene terephthalate (in the water vapor barrier layer formula, the total content of polyethylene terephthalate minus the content of polyethylene terephthalate in the barrier functional masterbatch is the remaining polyethylene terephthalate) are mixed and melted in the water vapor barrier layer barrel. The extrusion ratio is adjusted by the die distributor, and after double-layer co-extrusion and cooling, a cast sheet is obtained.

[0145] The melt extrusion temperature is 260℃~285℃, and the cooling temperature is 25℃~30℃.

[0146] In step 4, the casting sheet is preheated for the first time, then stretched longitudinally. The surface of the water vapor barrier layer 2 of the casting sheet is corona treated and coated with an aqueous coating liquid. Then it is preheated for the second time, stretched laterally, and then heat-set to allow the aqueous coating liquid to crosslink and solidify to form an aqueous adhesive layer 3. After cooling and winding, the integrally molded photovoltaic backsheet is obtained.

[0147] Specifically, the first preheating temperature is 60℃ to 95℃, for example, it can be 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃ or 95℃.

[0148] The longitudinal stretching temperature is 100℃~110℃, for example, it can be 100℃, 105℃ or 110℃.

[0149] The longitudinal stretching ratio is 3.0 to 3.5 times, for example, it can be 3.0 times, 3.1 times, 3.2 times, 3.3 times, 3.4 times or 3.5 times.

[0150] The second preheating temperature is 80℃~90℃, for example, it can be 80℃, 82℃, 84℃, 86℃, 88℃ or 90℃.

[0151] The transverse stretch ratio is 3.0 to 4.0 times, for example, it can be 3.0 times, 3.1 times, 3.2 times, 3.3 times, 3.4 times, 3.5 times, 3.6 times, 3.7 times, 3.8 times, 3.9 times, or 4.0 times.

[0152] The transverse stretching temperature is 100℃~130℃, for example, it can be 100℃, 105℃, 110℃, 115℃, 120℃, 125℃ or 130℃.

[0153] The heat setting temperature is 210℃~240℃, for example, it can be 210℃, 215℃, 220℃, 225℃, 230℃, 235℃ or 240℃.

[0154] The heat setting time is 0.1 to 1.2 min, for example, it can be 0.1 min, 0.2 min, 0.3 min, 0.4 min, 0.5 min, 0.6 min, 0.7 min, 0.8 min, 0.9 min, 1 min, 1.1 min, or 1.2 min.

[0155] The cooling and winding temperature can be either 60℃~70℃ or room temperature.

[0156] The photovoltaic backsheet prepared by the preparation method described in this application is the aforementioned photovoltaic backsheet.

[0157] The photovoltaic backsheet preparation method provided in this application utilizes a double-layer co-extrusion process, resulting in a backsheet with strong interlayer bonding and minimal delamination. Furthermore, the online coating with an aqueous coating solution eliminates the need for offline rewinding, leading to a photovoltaic backsheet with a uniform coating and excellent adhesion. The integrated molding process of double-layer co-extrusion and online coating significantly simplifies the production process, increases efficiency, and substantially reduces production costs.

[0158] This application provides a photovoltaic module, including the aforementioned photovoltaic backsheet.

[0159] The photovoltaic module also includes glass, encapsulant film one, battery string, encapsulant film two, and the glass, encapsulant film one, battery string, encapsulant film two, and photovoltaic backsheet are stacked in sequence.

[0160] In some embodiments, the photovoltaic module further includes a front glass, a transparent front encapsulating film, a photovoltaic cell string, and a high-reflectivity back encapsulating film, wherein the front glass, the transparent front encapsulating film, the photovoltaic cell string, the high-reflectivity back encapsulating film, and the photovoltaic backsheet are sequentially stacked. The water-based adhesive layer 3, combined with the high-reflectivity back encapsulating film, does not require UV resistance. By selecting resins with different Tg values, coating adhesion and bonding with the encapsulating film are ensured. The coating thickness requirement is low, and the amount of raw materials used is small, significantly reducing material consumption and thus saving costs.

[0161] The solar backsheet film provided by this invention was tested for the following main properties.

[0162] Water vapor transmission rate test:

[0163] The test shall be conducted in accordance with the requirements of GB / T 26253-2010. The test conditions are: temperature (38±2)℃, relative humidity 100%. Three samples shall be tested, the average value shall be taken, and the maximum value shall be reported.

[0164] Adhesion strength test with adhesive film:

[0165] The test was conducted according to GB / T 2790. A 300×300mm tempered glass sample was taken, and a double-layer adhesive film, a non-adhesive PET film, and a backing plate were sequentially layered on the tempered glass. The sample was then placed in a laminator for lamination (refer to the process documentation for setting the lamination parameters). After lamination, the sample was placed in a standard test environment to cool to room temperature. The laminated sample was then cut into strips with a width of (10±0.5)mm and a length of 250–300mm using a knife. The sample 3cm from the edge of the laminated sample was removed. Three strips were tested from the middle of the laminated sample. For samples difficult to start, it was recommended to manually separate the backing plate from the adhesive film by 10-20mm using a hot air gun. The sample was then fixed on a tensile testing machine, and peeled at a speed of 100mm / min along a 180-degree direction. The data was recorded, and the average value was taken, with the minimum value also reported.

[0166] DH1000 Aging and White Adhesive Film Adhesion Test:

[0167] First, prepare the sample according to the above-mentioned method for measuring the adhesion to the white adhesive film. Then, conduct the test according to the requirements of clause 4.13 in IEC61215-2:2016. Place the sample in a high and low temperature test chamber and test it for 1000 hours at a constant temperature and humidity of 85℃±2℃ and 85%RH±5%RH. Cut strips of the laminate with a width of (10±0.5)mm and a length of 250-300mm using a knife. Remove the sample 3cm from the edge of the laminate and test 3 strips in the middle of the laminate. For samples that are difficult to start, it is recommended to manually separate the backing plate from the adhesive film by 10-20mm using a hot air blower. Then fix the sample on a tensile testing machine and peel it in a 180-degree direction at a speed of 100mm / min. Record the data, take the average value of the test results, and report the minimum value.

[0168] UV 120kWh aging test:

[0169] The test was conducted according to the requirements of Clause 4.10 of IEC61215-2:2016. The sample was placed in an ultraviolet aging chamber at a test temperature of (60±5)℃. The ultraviolet irradiation in the range of 280nm to 400nm reached 120kWh / m2 (EVA surface), of which the ultraviolet radiation in the wavelength range of 280nm to 320nm was 3% to 10% of the total ultraviolet radiation.

[0170] Example

[0171] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0172] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0173] Example 1

[0174] In this embodiment, the solar cell backsheet comprises, by mass fraction, 90.8% polyethylene terephthalate resin, 7% reflective pigment (rutile titanium dioxide), 0.5% hindered amine light stabilizer, 0.6% benzophenone UV absorber, 0.5% glycidyl ether epoxy chain extender, and 0.6% polymeric carbodiimide; the moisture barrier layer comprises, by mass fraction, 93% polyethylene terephthalate resin, 5% modified nano-montmorillonite, and hindered phenolic... The aqueous coating liquid comprises, by mass fraction: 0.6% antioxidant, 0.2% phosphite antioxidant, 1.2% polymeric carbodiimide; 0.5% glycidyl ether type epoxy compound chain extender; and 20% waterborne polyurethane resin (Tg 65℃), 5% waterborne acrylic resin (Tg 12℃), 3.0% waterborne blocked isocyanate crosslinking agent, 0.2% polymeric carbodiimide, 0.1% 80nm silica, 0.1% leveling agent, 0.2% defoamer, and the balance being deionized water.

[0175] The method for preparing the solar cell backsheet is as follows:

[0176] Step 1: Preparation of color masterbatch, weather-resistant functional masterbatch, and barrier functional masterbatch;

[0177] The preparation method of color masterbatch is as follows:

[0178] The reflective pigment (rutile titanium dioxide) is mixed evenly with PET resin and melt-extruded through a twin-screw extruder to produce a color masterbatch. The color masterbatch contains 50% polyethylene terephthalate by mass, and the melt extrusion temperature is 210℃.

[0179] The preparation method of weather-resistant functional masterbatch is as follows:

[0180] Hindered amine light stabilizer (light stabilizer), glycidyl ether type epoxy compound chain extender (first chain extender), polymeric carbodiimide (first hydrolysis resistant stabilizer) and PET resin are mixed evenly and melt-extruded through a twin-screw extruder to produce weather-resistant functional masterbatch. In the weather-resistant functional masterbatch, polyethylene terephthalate accounts for 60% by mass, and the melt extrusion temperature is 210°C.

[0181] The preparation steps of the barrier function masterbatch are as follows:

[0182] The glycidyl ether type epoxy compound chain extender (second chain extender), polymeric carbodiimide (second hydrolysis-resistant stabilizer), modified nano-montmorillonite (barrier filler), phosphite antioxidant (antioxidant) are mixed evenly with PET resin and melt-extruded through a twin-screw extruder to produce a barrier functional masterbatch. In the barrier functional masterbatch, polyethylene terephthalate accounts for 60% by mass, and the melt extrusion temperature is 210°C.

[0183] Step 2: Prepare the aqueous coating solution;

[0184] The waterborne polyurethane resin (Tg65℃) (first waterborne polyurethane resin), waterborne acrylic resin (Tg12℃) (tackifying resin), waterborne blocked isocyanate crosslinking agent (waterborne crosslinking agent), polymeric carbodiimide (hydrolysis resistant agent), silica (anti-blocking agent), leveling agent and defoamer are mixed in a certain proportion and stirred evenly to obtain the waterborne coating liquid.

[0185] Step 3: According to the raw material ratio, mix the color masterbatch, weather-resistant functional masterbatch, and the remaining polyethylene terephthalate (in the weather-resistant layer formula, the total content of polyethylene terephthalate minus the polyethylene terephthalate in the color masterbatch and weather-resistant functional masterbatch is the remaining polyethylene terephthalate) and melt them in the weather-resistant layer barrel. Mix the barrier functional masterbatch and the remaining polyethylene terephthalate (in the water vapor barrier layer formula, the total content of polyethylene terephthalate minus the content of polyethylene terephthalate in the barrier functional masterbatch is the remaining polyethylene terephthalate) and melt them in the water vapor barrier layer barrel. Adjust the extrusion ratio through the die distributor, and after double-layer co-extrusion and cooling, obtain the cast sheet.

[0186] The melt extrusion temperature is 260°C, and the cooling temperature is 30°C.

[0187] Step 4 involves preheating the cast sheet for the first time, followed by longitudinal stretching. The surface of the water vapor barrier layer of the cast sheet is then subjected to corona treatment and coated with an aqueous coating liquid. After a second preheating, the sheet is stretched laterally and then heat-set to allow the aqueous coating liquid to crosslink and solidify to form an aqueous adhesive layer. The sheet is then cooled and rolled up to obtain the integrally molded photovoltaic backsheet.

[0188] The first preheating temperature is 70℃. The longitudinal stretching temperature is 100℃. The second preheating temperature is 80℃. The transverse stretching temperature is 100℃. The heat setting temperature is 210℃. The heat setting time is 0.1 min. The thicknesses of the weather-resistant layer, the water vapor barrier layer, and the water-based adhesive pre-coating layer are 50μm, 255μm, and 0.5μm, respectively, with a longitudinal stretching ratio of 3.2 times and a transverse stretching ratio of 3.8 times. Relevant properties are shown in Table 1.

[0189] Example 2

[0190] The difference between the solar cell backsheet of this embodiment and that of Embodiment 1 lies only in the formulation of the weather-resistant layer. The weather-resistant layer of this embodiment comprises, by mass fraction, 92.8% polyethylene terephthalate resin, 5% reflective pigment (the reflective pigment is rutile titanium dioxide), 0.5% hindered amine light stabilizer, 0.6% benzophenone UV absorber, 0.5% glycidyl ether type epoxy chain extender, and 0.6% polymeric carbodiimide; the relevant properties are shown in Table 1.

[0191] Example 3

[0192] The difference between the solar cell backsheet of this embodiment and that of Embodiment 1 lies only in the formulation of the water vapor barrier layer. The water vapor barrier layer of this embodiment comprises, by mass fraction: 94% polyethylene terephthalate resin, 4% layered silicate, 0.6% hindered phenolic antioxidant, 0.2% phosphite antioxidant, and 1.2% polymeric carbodiimide. Relevant properties are shown in Table 1.

[0193] Example 4

[0194] The solar cell backsheet in this embodiment differs from that in Embodiment 1 only in the formulation of the water vapor barrier layer. The water vapor barrier layer in this embodiment comprises, by mass fraction: 93% polyethylene terephthalate resin, 5% mica powder, 0.6% hindered phenolic antioxidant, 0.2% phosphite antioxidant, and 1.2% polymeric carbodiimide. Relevant properties are shown in Table 1.

[0195] Example 5

[0196] The difference between the solar cell backsheet in this embodiment and that in Embodiment 1 lies only in the formulation of the aqueous coating solution. The aqueous coating solution in this embodiment comprises, by mass fraction: 25% aqueous polyurethane resin (Tg 75℃), 10% aqueous polyester resin (Tg 20℃), 3.0% aqueous blocked isocyanate crosslinking agent, 0.2% polymeric carbodiimide, 0.1% 80nm silica, 0.1% leveling agent, 0.2% defoamer, and the balance being deionized water. Relevant properties are shown in Table 1.

[0197] Example 6

[0198] The difference between the solar cell backsheet in this embodiment and that in Embodiment 1 lies only in the formulation of the aqueous coating solution. The aqueous coating solution in this embodiment comprises, by mass fraction: 20% aqueous polyurethane resin (Tg 40℃), 5% aqueous acrylic resin (Tg -10℃), 3.0% aqueous blocked isocyanate crosslinking agent, 0.2% polymeric carbodiimide, 0.1% 80nm silica, 0.1% leveling agent, 0.2% defoamer, and the balance being deionized water. Relevant properties are shown in Table 1.

[0199] Example 7

[0200] The only difference between the solar cell backsheet of this embodiment and that of Embodiment 1 is the thickness of the weather-resistant layer, the water vapor barrier layer, and the water-based adhesive layer. In this embodiment, the thicknesses of the weather-resistant layer, the water vapor barrier layer, and the water-based adhesive layer are 30 μm, 275 μm, and 0.2 μm, respectively. Relevant performance parameters are shown in Table 1.

[0201] Example 8

[0202] The only difference between the solar cell backsheet of this embodiment and that of Embodiment 1 is the thickness of the weather-resistant layer, the water vapor barrier layer, and the water-based adhesive layer. In this embodiment, the thicknesses of the weather-resistant layer, the water vapor barrier layer, and the water-based adhesive layer are 40 μm, 265 μm, and 0.8 μm, respectively. Relevant performance parameters are shown in Table 1.

[0203] Comparative Example 1

[0204] The difference between the solar cell backsheet in this embodiment and that in Embodiment 1 lies only in the formulation of the weather-resistant layer. The weather-resistant layer in this embodiment, by mass fraction, comprises: 95.8% polyethylene terephthalate resin, 2% rutile titanium dioxide, 0.5% hindered amine light stabilizer, 0.6% benzophenone UV absorber, 0.5% glycidyl ether epoxy chain extender, and 0.6% polymeric carbodiimide. Relevant properties are shown in Table 1.

[0205] Comparative Example 2

[0206] The difference between the solar cell backsheet in this embodiment and that in Embodiment 1 lies only in the formulation of the water vapor barrier layer. In this embodiment, the water vapor barrier layer comprises, by mass fraction: 98% polyethylene terephthalate resin, 0.6% hindered phenolic antioxidant, 0.2% phosphite antioxidant, and 1.2% polymeric carbodiimide, and contains no barrier filler. Relevant properties are shown in Table 1.

[0207] Comparative Example 3

[0208] The difference between the solar cell backsheet in this embodiment and that in Embodiment 1 lies only in the formulation of the aqueous coating solution. The aqueous coating solution in this embodiment comprises, by mass fraction: 20% aqueous polyurethane resin (Tg 20℃), 5% aqueous polyester resin (Tg 12℃), 3.0% aqueous blocked isocyanate crosslinking agent, 0.2% polymeric carbodiimide, 0.1% 80nm silica, 0.1% leveling agent, 0.2% defoamer, and the balance being deionized water. Relevant properties are shown in Table 1.

[0209] Comparative Example 4

[0210] The solar cell backsheet in this embodiment differs from that in Embodiment 1 only in the formulation of the aqueous coating solution. The aqueous coating solution in this embodiment comprises, by mass fraction: 20% aqueous polyurethane resin (Tg 75℃), 10% aqueous polyester resin (Tg 40℃), 3.0% aqueous blocked isocyanate crosslinking agent, 0.2% polymeric carbodiimide, 0.1% 80nm silica, 0.1% leveling agent, 0.2% defoamer, and the balance being deionized water. Relevant properties are shown in Table 1.

[0211] Comparative Example 5

[0212] The difference between the solar cell backsheet in this embodiment and that in Embodiment 1 is that no tackifying resin is added to the aqueous coating solution in this embodiment. The aqueous coating solution in this embodiment comprises, by mass fraction: 20% polyurethane resin (Tg 65℃), 3.0% aqueous blocked isocyanate crosslinking agent, 0.2% polymeric carbodiimide, 0.1% 80nm silica, 0.1% leveling agent, 0.2% defoamer, and the balance being deionized water; relevant properties are shown in Table 1.

[0213] Comparative Example 6

[0214] The only difference between the solar cell backsheet in this comparative example and Example 1 is the absence of anhydrous adhesive pre-coating. The polyester barrier core layer, after corona treatment, is directly used for bonding to the high-reflectivity backing film. Relevant properties are shown in Table 1.

[0215] Table 1 shows the performance parameters of the solar cells in each embodiment and comparative example.

[0216]

[0217]

[0218] Summary: As shown in Table 1, the photovoltaic backsheet described in this application has low water vapor transmission rate and strong water vapor barrier performance. Furthermore, the photovoltaic backsheet produced using a double-layer co-extrusion process exhibits good interlayer bonding, is less prone to delamination, and the online application of the water-based coating eliminates the need for offline rewinding, resulting in a photovoltaic backsheet with uniform coating and good adhesion. The integrated molding process of double-layer co-extrusion and online coating greatly simplifies the production steps, improves production efficiency, and significantly reduces production costs.

[0219] Although the embodiments of this application have been described above in conjunction with the specific embodiments described, this application is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the teachings of this specification and without departing from the scope of protection of the claims of this application, and these are all within the scope of protection of this application.

Claims

1. A photovoltaic backsheet, wherein, The material comprises, in sequence, a weather-resistant layer, a moisture barrier layer, and a water-based adhesive layer. The weather-resistant layer comprises, by mass fraction: 85%–95% polyethylene terephthalate, 3%–15% reflective pigment, 0.2%–2% light stabilizer, 0.2%–2% first chain extender, and 0.5%–3% first hydrolysis-resistant stabilizer. The water vapor barrier layer comprises, by mass fraction: 85%~95% polyethylene terephthalate, 1%~5% barrier filler, 0.2%~2% antioxidant, 0.2%~2% second chain extender, and 0.5%~3% second hydrolysis resistant stabilizer; The water-based adhesive layer is formed by cross-linking and curing of an water-based coating liquid; The aqueous coating liquid comprises, by mass fraction: 10%~25% first aqueous polyurethane resin, 5%~10% tackifying resin, 2%~4% aqueous crosslinking agent, 0.1%~0.5% hydrolysis resistant agent, 0.1%~0.5% antiblocking agent, 0.1%~0.5% leveling agent, and 0.1%~0.5% defoamer; The glass transition temperature of the first waterborne polyurethane resin is 30℃~80℃; the glass transition temperature of the tackifying resin is -20℃~25℃.

2. The photovoltaic backsheet according to claim 1, wherein, The reflective pigment is selected from one or more of the following: rutile titanium dioxide, zirconium oxide, zinc oxide, silicon oxide, barium sulfate, zinc sulfide, calcium carbonate, aluminum oxide, and carbon black. The light stabilizer is selected from one or more of hindered amine light stabilizers, benzophenone UV absorbers, salicylate UV absorbers, benzotriazole UV absorbers, and triazine UV absorbers; the first chain extender is selected from epoxy chain extenders; the first hydrolysis resistant stabilizer is selected from one or two of monomeric carbodiimide and polymeric carbodiimide.

3. The photovoltaic backsheet according to claim 1, wherein, The barrier filler is selected from one or more of layered silicates, modified nano-montmorillonite, mica powder, and silica; the antioxidant is selected from one or more of hindered phenolic antioxidants, phosphite antioxidants, and organosulfur antioxidants. The second chain extender is selected from epoxy chain extenders; the second hydrolysis-resistant stabilizer is selected from one or both of monomeric carbodiimide and polymeric carbodiimide.

4. The photovoltaic backsheet according to any one of claims 1-3, wherein, The thickness of the photovoltaic backsheet is 150μm~350μm. The thickness of the water vapor barrier layer is 70μm~330μm. The thickness of the weather-resistant layer is 20μm~80μm. The thickness of the water-based adhesive layer is 0.05μm to 1μm.

5. A method for preparing a photovoltaic backsheet according to any one of claims 1-4, wherein, Includes the following steps: Preparation of weather-resistant masterbatch and barrier functional masterbatch; Prepare an aqueous coating solution; The barrier function masterbatch and weather-resistant masterbatch are melted separately according to the ratio, and a casting sheet composed of a weather-resistant layer and a water vapor barrier layer is obtained by a double-layer co-extrusion process. The cast sheet is stretched and coated with an aqueous coating liquid. The aqueous coating liquid crosslinks and cures to form an aqueous adhesive layer, thus obtaining the photovoltaic backsheet.

6. The preparation method according to claim 5, wherein, The weather-resistant masterbatch is prepared by the following method: Preparation of color masterbatch and weather-resistant functional masterbatch; The color masterbatch is mixed with the weather-resistant functional masterbatch to obtain the weather-resistant masterbatch.

7. The preparation method according to claim 6, wherein, The reflective pigment is uniformly mixed with polyethylene terephthalate and then melt-extruded using a twin-screw extruder to produce color masterbatch. The light stabilizer, the first chain extender, the first hydrolysis resistant stabilizer and polyethylene terephthalate are mixed evenly and then melt-extruded through a twin-screw extruder to produce a weather-resistant functional masterbatch. The second chain extender, the second hydrolysis-resistant stabilizer, the barrier filler, the antioxidant, and polyethylene terephthalate are mixed evenly and then melt-extruded using a twin-screw extruder to produce a barrier functional masterbatch.

8. The preparation method according to claim 7, wherein, The mass fraction of polyethylene terephthalate in the masterbatch is 40%~60%; The mass fraction of polyethylene terephthalate in the weather-resistant masterbatch is 60%~90%; The barrier masterbatch contains 50% to 80% polyethylene terephthalate by mass.

9. The preparation method according to any one of claims 5-8, wherein, The casting is preheated and then stretched longitudinally. Corona treatment and water-based coating are applied to the surface of the water vapor barrier layer. After preheating, it is stretched laterally and then heat-set to allow the water-based coating to crosslink and solidify to form a water-based adhesive layer.

10. The preparation method according to claim 5, wherein, The tackifying resin is selected from one or more of the following: second waterborne polyurethane resin, waterborne polyester resin, and waterborne acrylic resin. The aqueous crosslinking agent is an aqueous blocked isocyanate crosslinking agent; The hydrolysis-resistant agent is selected from monomeric carbodiimide or polymeric carbodiimide; The anti-blocking agent is selected from silicon dioxide; The leveling agent is selected from polyether-modified silicone leveling agents; The defoamer is selected from alkyl-modified organosiloxane defoamers.

11. The preparation method according to claim 10, wherein, The tackifying resin is an aqueous acrylic resin.

12. A photovoltaic module, wherein, The photovoltaic backsheet includes the photovoltaic backsheet described in any one of claims 1-4 or the photovoltaic backsheet prepared in any one of claims 5-11.

13. The photovoltaic module according to claim 12, wherein, It also includes glass, encapsulant film one, battery string, encapsulant film two, and the glass, encapsulant film one, battery string, encapsulant film two, and photovoltaic backsheet are stacked in sequence.

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