UV-protection PVB composite film, preparation method therefor, and use thereof

Abstract

The present invention belongs to the technical field of functional films, and particularly relates to a UV-protection PVB composite film, a preparation method therefor, and the use thereof. The UV-protection PVB composite film comprises an EVA / PVB composite film formed by an EVA film and a PVB film, wherein an ultraviolet light conversion layer is provided between the EVA film and the PVB film, the EVA film contains an ultraviolet light conversion agent, the PVB film contains an ultraviolet light absorber, and the ultraviolet light conversion layer is formed by coating with a transparent ultraviolet light conversion coating, and contains the ultraviolet light conversion agent, perhydropolysilazane, α-Al2O3 and a solvent. The ultrathin inorganic ultraviolet light conversion layer is designed which uses the perhydropolysilazane as a film-forming substance and the α-Al2O3 as a dispersion aid, and therefore exhibits excellent dispersibility, transparency and durability, thus reducing the use amount of light conversion agents, improving the light conversion efficiency, and solving the problem that light conversion agents added to EVA films are difficult to disperse and thus cannot achieve effective light conversion.

Description

A UV-blocking PVB composite film, its preparation method, and its application. Technical Field

[0001] This invention belongs to the field of functional thin film technology, specifically relating to a UV-resistant PVB composite film, its preparation method, and its application. Background Technology

[0002] A solar photovoltaic cell is an assembly of multi-layered functional components with a "sandwich" structure. The typical design has a middle layer of light-converting cells, with the top and bottom layers encapsulated by glass plates, and photovoltaic encapsulation film used to bond the glass and cells together.

[0003] Encapsulation and protection of photovoltaic cells are crucial for extending their lifespan and improving their efficiency. The main function of photovoltaic encapsulation film is to protect the cells, providing multiple protective measures such as insulation, dustproofing, moisture resistance, and UV protection, thereby ensuring the normal operation of photovoltaic cells in various environments.

[0004] Photovoltaic encapsulation films require light transmittance, strong adhesion, and high UV resistance and water resistance. Currently, photovoltaic encapsulation film technology is gradually maturing, with transparent EVA films and transparent POE films being widely used. However, in long-term engineering applications, EVA films have revealed several problems. EVA films are prone to yellowing due to UV aging, affecting visible light absorption. Furthermore, EVA is a copolymer of ethylene and vinyl acetate, and its ester groups are easily hydrolyzed during aging to form acetic acid, which readily absorbs moisture. Direct contact with the solar cell can lead to power degradation. POE films offer good resistance to potential-induced degradation, but their compatibility with processing aids is generally poor, posing a risk of aid precipitation and migration. After lamination with the solar cell, bubbles often appear, leading to reduced assembly yield.

[0005] There are also methods to form multi-layered composite films through multi-layer co-extrusion to achieve complementary film properties. However, when preparing EVA / POE composite films through multi-layer co-extrusion, the compatibility between the two materials is poor due to the polar nature of EVA resin and the non-polar nature of POE resin. This results in weak interfacial adhesion, interfacial defects, and unsatisfactory application effects.

[0006] On the other hand, short-wavelength ultraviolet (UV) light in the 280-380nm range is not a photoelectric conversion light source. Direct exposure to it on heterojunction solar cells can damage them and affect cell lifespan. To reduce the impact of UV light on the cells, the encapsulating film must not only maintain good encapsulation and light transmittance, but also block and convert 280-380nm UV light. Converting UV light into longer-wavelength light above 400nm not only improves the photoelectric conversion efficiency of solar cells but also reduces UV damage to heterojunction solar cells.

[0007] Existing technologies typically disperse a light-converting agent in the resin used to prepare the encapsulation film, thereby converting low-wavelength light in incident sunlight into long-wavelength light, thus maximizing the utilization of sunlight.

[0008] Chinese invention patent publication number CN114958215A discloses a UV light conversion encapsulating film and its preparation method, wherein the light conversion layer is formed by extrusion of a base resin, a UV light conversion agent, a crosslinking agent, a co-crosslinking agent, a silane coupling agent, and an additive.

[0009] Chinese invention patent publication number CN104610881A discloses an ultra-high cutoff EVA encapsulating film for photovoltaic applications, which is prepared by dispersing 87-98% ethylene-vinyl acetate copolymer, 0.01-1% rare earth organic light-converting agent, 0.05-5% antioxidant, 0.03-4% ultraviolet absorber, 0.25-2% crosslinking agent, and 0.1-4% silane coupling agent.

[0010] In practical applications, dispersing the light-converting agent in the film is difficult, as most of the agent tends to agglomerate and fail to effectively perform its light-converting function. Furthermore, the film thickness is typically 0.3-0.5 mm, resulting in a large volume fraction, requiring a significant amount of light-converting agent to disperse and achieve the desired UV cutoff conversion effect.

[0011] Existing UV light conversion films cannot completely convert all UV light into visible light, resulting in a decrease in UV light conversion efficiency. Some UV light will still directly irradiate the heterojunction solar cell, causing damage to the cell. Summary of the Invention

[0012] Currently, single EVA film encapsulation is susceptible to hydrolytic aging, which can easily lead to the formation of acetic acid and cause potential-induced degradation (PID). Furthermore, ultraviolet radiation can cause photovoltaic modules to age, resulting in sealant discoloration, backsheet cracking, and reduced battery life.

[0013] To improve photovoltaic power generation efficiency and effectively prevent photovoltaic cell power degradation, this invention proposes a UV-resistant PVB composite film. Through the combination of EVA and PVB films and the conversion and absorption of ultraviolet light, it can not only convert ultraviolet light into usable photovoltaic light and improve photovoltaic conversion efficiency, but also effectively prevent ultraviolet light from passing through the radiating cells, thereby increasing the lifespan of photovoltaic cells.

[0014] In view of the above, in order to achieve the aforementioned technical effects, the specific technical solution adopted by the present invention is as follows:

[0015] Firstly, the first solution is to provide a UV-transmitting PVB composite film, comprising an EVA / PVB composite film formed by an EVA film and a PVB film, with a UV conversion layer between the EVA film and the PVB film; the EVA film contains a UV light conversion agent; the PVB film contains a UV absorber; the UV conversion layer is formed by applying a transparent UV conversion coating, which contains a UV conversion agent, perhydropolysilazane, α-Al2O3, and a solvent.

[0016] Furthermore, the thickness of the UV-resistant PVB composite film is 0.3-0.6 mm; specifically, the thickness ratio of the EVA film to the PVB film is 2:1.

[0017] Furthermore, the thickness of the ultraviolet light conversion layer is controlled at 100-1000nm. This ultra-thin ultraviolet light conversion layer not only saves the amount of light conversion agent and improves the light conversion efficiency, but also avoids the problem that a large amount of light conversion agent added to the EVA film is difficult to disperse and cannot effectively achieve light conversion.

[0018] Specifically, the UV conversion coating contains perhydropolysilazane and α-Al2O3. The perhydropolysilazane forms a transparent inorganic silica coating, exhibiting excellent lightfastness and providing long-lasting protection for the light-converting agent. α-Al2O3 effectively assists in the dispersion of the light-converting agent.

[0019] Furthermore, the ultraviolet light conversion agent includes, but is not limited to, one or more of rare earth organic conversion agents, organic fluorescent pigments, rare earth inorganic conversion agents, and perovskite quantum dots in combination. Rare earth europium organic complexes or rare earth samarium organic complexes are particularly selected.

[0020] Furthermore, the ultraviolet absorber is selected from at least one of phenyl benzoate, 2,4,6-tris(2'-butoxyphenyl)-1,3,5-triazine, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-(2'-hydroxy-3',5'-di-tert-phenyl)-5-chlorobenzotriazole, 2,2'-methylenebis(4-tert-octyl-6-benzotriazolephenol), and resorcinol benzoate.

[0021] Furthermore, the second approach is: This invention provides a method for preparing a UV-transmitting PVB composite film, the specific preparation method of which is as follows:

[0022] S1. Preparation of PVB film:

[0023] Weigh out the following components by weight: 80-85 parts PVB resin powder, 15-25 parts plasticizer, 0.05-0.1 parts antioxidant, and 0.1-0.2 parts UV absorber. Add these components to a high-speed mixer and disperse evenly. Quantitatively convey the mixture to the twin-screw extruder feed inlet using a loss-in-weight weighing system. Set the twin-screw extrusion process as follows: Stage 1: 165-175℃; Stage 2: 180-185℃; Stage 3: 190-195℃; Stage 4: 170-180℃; Die temperature: 140-150℃. The mixture flows out through a T-die, is pre-shaped by a constant-temperature roller, continuously tested by a front thickness gauge, and then enters the longitudinal stretching device for longitudinal stretching and the transverse stretching device for transverse stretching. Finally, the thickness gauge guides the film to the take-up roller for winding, resulting in a PVB film.

[0024] Preparation of S2. EVA membrane:

[0025] Weigh out the following components by weight: 99-100 parts EVA resin, 0.005-0.2 parts UV conversion agent, 0.1-0.3 parts antioxidant, and 0.2-0.5 parts crosslinking agent. Add these components to a high-speed mixer and disperse evenly. Quantitatively convey the mixture to the twin-screw extruder feed inlet using a loss-in-weight weighing system. Set the twin-screw extrusion process as follows: first stage 50-60℃; second stage 80-90℃; third stage 90-100℃; fourth stage 110-120℃; die temperature 110-120℃. The mixture flows out through a T-die, undergoes roller casting, pressure roller shaping, edge trimming, and winding to obtain the EVA film.

[0026] S3. Composite film formation:

[0027] Weigh out the following components by weight: 0.05-0.5 parts of UV conversion agent, 5-15 parts of perhydropolysilazane, 1-3 parts of α-Al2O3, and 55-65 parts of solvent. Disperse them evenly at high speed to prepare a UV conversion coating. Apply the UV conversion coating to the surface of the EVA film cast by S2 to form a UV conversion layer. After treatment with ammonia steam and drying, laminate the pre-made PVB film of S1 onto the UV conversion layer. After embossing, cooling, trimming, and winding, a UV-resistant PVB composite film is obtained.

[0028] As a preferred technical solution, the plasticizer in step S1 is at least one of dipropylene glycol dibenzoate, triethylene glycol diisooctanoate, and triethylene glycol di-n-heptanoate.

[0029] As a preferred technical solution, the antioxidant mentioned in steps S1 and S2 is at least one of antioxidant 1010, antioxidant 1076, antioxidant 618, antioxidant 1330, and antioxidant 1098.

[0030] As a preferred technical solution, the front thickness gauge and the rear thickness gauge mentioned in step S1 are connected through a PLC control system to control the stretching speed and achieve uniform and stable stretching ratio and thickness control. Particularly preferred is that the thickness of the PVB film is controlled within 0.1-0.2 mm.

[0031] As a preferred technical solution, the EVA resin in step S2 is selected with a vinyl acetate content of 25-35% (w).

[0032] As a preferred technical solution, the crosslinking agent in step S2 is one or a combination of two of dicumyl peroxide and tert-butyl peroxide (2-ethylhexyl) carbonate.

[0033] As a preferred technical solution, the thickness of the EVA film in step S2 is 0.2-0.4 mm.

[0034] As a preferred technical solution, the perhydropolysilazane mentioned in step S3 is preferably a perhydropolysilazane obtained by ammonolysis. Perhydropolysilazane obtained by ammonolysis is readily soluble in solvents, which is beneficial for the dispersion of the light-converting agent.

[0035] Conventional methods for preparing UV conversion coatings use organic emulsions for film formation. However, the light-converting agent within the coating is easily affected by water and oxygen, and its transparency deteriorates after prolonged light exposure. This invention utilizes a coating formed by dispersing a light-converting agent with a fully hydrogenated polysilazane. This coating, once sprayed, rapidly forms a transparent inorganic silica coating, avoiding the influence of water and oxygen on the light-converting agent and maintaining its transparency for a long time. As an excellent UV conversion layer, it achieves highly efficient light conversion.

[0036] As a preferred technical solution, the α-Al2O3 in step S3 is selected from spherical α-Al2O3 powder with a particle size range of 10-30nm; the spherical α-Al2O3 powder assists in the dispersion of the ultraviolet light conversion agent, prevents agglomeration, and promotes the coatability and leveling properties of the coating.

[0037] As a preferred technical solution, the solvent in step S3 is selected from at least one of toluene, n-hexane, and xylene.

[0038] As a preferred technical solution, the coating process in step S3 employs ultrasonic spraying. Ultrasonic spraying uses ultrasound to fully liquefy and refine the coating material, thereby enabling the UV light-converting agent to be fully dispersed and forming a highly efficient light-converting coating.

[0039] Furthermore, this invention provides an application of a UV-resistant PVB composite film as a photovoltaic encapsulating film in photovoltaic modules. The photovoltaic modules are photoelectric conversion cell modules that use sunlight as a light source, such as crystalline silicon solar cells, amorphous silicon solar cells, thin-film silicon solar cells, heterojunction solar cells, cadmium sulfide / cadmium telluride solar cells, and dye-sensitized solar cells.

[0040] The UV-resistant PVB composite film is a functional film used to encapsulate photovoltaic modules and prevent oxygen and moisture from impacting and corroding them. Polyvinyl butyral (PVB) is a functional resin synthesized from polyvinyl alcohol and butyral acetal. PVB film has excellent transparency and extremely high mechanical strength, and is resistant to low temperatures, ultraviolet light, heat, and hydrolysis, as well as strong adhesion. When used as a photovoltaic encapsulation film, it can directly contact the solar cell without causing potential-induced degradation. By combining EVA and PVB films, the PVB film layer directly contacts the solar cell during photovoltaic encapsulation, avoiding the problem of power degradation caused by the hydrolysis of EVA film in contact with the solar cell, which easily produces acetic acid.

[0041] More importantly, the UV-blocking PVB composite film has a light conversion function. By spraying an ultra-thin UV conversion layer between the EVA film and the PVB film, the light conversion layer absorbs photons of short-wavelength light, such as UV light, and converts them into longer-wavelength light, which is then emitted and absorbed by the photoconductor layer of the photovoltaic cell and converted into electricity. This allows UV light to be efficiently converted into photovoltaic light, avoiding the defects of large-scale dispersion of UV conversion agents in the film, which is difficult to disperse and costly.

[0042] Compared with the prior art, the outstanding features and significant advantages of this invention are as follows:

[0043] 1. This invention discloses a UV-transmitting PVB composite film. By designing an ultra-thin inorganic ultraviolet conversion layer, the ultraviolet conversion layer uses a fully hydrogenated polysilazane as the film-forming material and α-Al₂O₃ as the dispersing agent, exhibiting excellent dispersibility, transparency, and durability. This not only saves on the amount of light-converting agent used but also avoids the problem of light-converting agents being difficult to disperse and ineffectively achieving light conversion when added to EVA films.

[0044] 2. The present invention provides a UV-resistant PVB composite film, comprising an EVA / PVB composite film formed by an EVA film and a PVB film, wherein the PVB layer has excellent transparency and extremely high mechanical strength, and is resistant to low temperature, light, heat, and hydrolysis, as well as strong adhesion. When used as a photovoltaic encapsulation film, it can directly contact the solar cell without causing potential-induced degradation of the solar cell.

[0045] 3. The preparation process of this invention is easy to control. It can achieve continuous and stable mass production by using conventional screw extruders, biaxial stretching machines, casting machines, ultrasonic spraying machines, etc. Attached Figure Description

[0046] To further clarify the technical implementation scheme of the present invention, the present invention will be further described below with reference to the accompanying drawings:

[0047] Figure 1 is a schematic diagram of a UV-resistant PVB composite film according to the present invention. Wherein:

[0048] 1-PVB film; 2-UV conversion layer; EVA film; Detailed Implementation

[0049] The following examples are intended to further describe the implementation process of the technical content of the present invention, and are not intended to limit the scope of protection of the claims of the present invention. Unless otherwise specified in the examples, all conditions are performed under conventional conditions or the manufacturer's recommended process conditions. Example 1

[0050] S1. Preparation of PVB film:

[0051] Weigh the raw materials according to the formula by weight, as shown in Table 1-1:

[0052] Table 1-1

[0053]

[0054] The weighed raw materials are added to a high-speed mixer and dispersed evenly. The raw materials are then quantitatively conveyed to the twin-screw extruder feed inlet using a loss-in-weight weighing system. The twin-screw extrusion process is set as follows: first stage 165℃; second stage 180℃; third stage 190℃; fourth stage 170℃; die head temperature 140℃. The material flows out through a T-die and is pre-shaped at 50-60℃ using a constant-temperature roller. After continuous testing by a front thickness gauge, it enters a longitudinal stretching device at 70-80℃ for 3.5 times longitudinal stretching, and further stretches at 80-90℃ for 3 times transverse stretching. A rear thickness gauge then measures the thickness after stretching. The front and rear thickness gauges are connected to a PLC control system to control the stretching speed and traction rollers, thereby controlling the stretching speed to achieve a uniform and stable stretching ratio, keeping the thickness at 0.15mm. Finally, the film is wound up by a take-up roller to obtain a PVB film.

[0055] Preparation of S2. EVA membrane:

[0056] Weigh the raw materials according to the formula by weight, as shown in Table 1-2:

[0057] Table 1-2

[0058]

[0059] The weighed material is added to a high-speed mixer and dispersed evenly. It is then quantitatively conveyed to the twin-screw extruder feed port through a loss-in-weight weigher. The twin-screw extrusion process is set as follows: first stage 50℃; second stage 80℃; third stage 90℃; fourth stage 110℃; die head temperature 120℃. The material flows out through a T-die orifice, is then cast on rollers, shaped by pressure rollers, trimmed, and wound up to obtain an EVA film with a thickness of 0.35mm.

[0060] S3. Composite film formation:

[0061] Prepare the UV conversion coatings according to the parts by weight, as shown in Table 1-3:

[0062] Table 1-3

[0063]

[0064] The weighed UV conversion coating raw materials were dispersed in a high-speed mixer at 12,000 rpm for 3 minutes to obtain a uniform UV conversion coating. The surface of the S2 cast EVA film was ultrasonically sprayed to fully disperse the UV conversion coating, forming a highly efficient light-converting coating with a thickness of 200 nm. After curing with ammonia steam and drying, the pre-fabricated PVB film from S1 was laminated onto the UV conversion layer. Following embossing, cooling, edge trimming, and winding, a UV-transmitting PVB composite film was obtained. The structure of the UV-transmitting PVB composite film is shown in Figure 1. Example 2

[0065] S1. Preparation of PVB film:

[0066] Weigh the raw materials according to the formula by weight, as shown in Table 2-1:

[0067] Table 2-1

[0068]

[0069] The weighed raw materials are added to a high-speed mixer and dispersed evenly. The raw materials are then quantitatively conveyed to the twin-screw extruder feed inlet using a loss-in-weight weighing system. The twin-screw extrusion process is set as follows: first stage 165℃; second stage 180℃; third stage 190℃; fourth stage 170℃; die head temperature 140℃. The material flows out through a T-die and is pre-shaped at 50-60℃ using a constant-temperature roller. After continuous testing by a front thickness gauge, it enters a longitudinal stretching device at 70-80℃ for 3.5 times longitudinal stretching, and further stretches at 80-90℃ for 3 times transverse stretching. A rear thickness gauge then measures the thickness after stretching. The front and rear thickness gauges are connected to a PLC control system to control the stretching speed and traction rollers, thereby controlling the stretching speed to achieve a uniform and stable stretching ratio, keeping the thickness at 0.2mm. Finally, the film is wound up by a take-up roller to obtain a PVB film.

[0070] Preparation of S2. EVA membrane:

[0071] Weigh the raw materials according to the formula by weight, as shown in Table 2-2:

[0072] Table 2-2

[0073]

[0074] The weighed material is added to a high-speed mixer and dispersed evenly. It is then quantitatively conveyed to the twin-screw extruder feed port through a loss-in-weight weigher. The twin-screw extrusion process is set as follows: first stage 50℃; second stage 80℃; third stage 90℃; fourth stage 110℃; die head temperature 120℃. The material flows out through a T-die orifice, is then cast on rollers, shaped by pressure rollers, trimmed, and wound up to obtain an EVA film with a thickness of 0.4mm.

[0075] S3. Composite film formation:

[0076] Prepare the UV conversion coatings according to the parts by weight, as shown in Table 2-3:

[0077] Table 2-3

[0078]

[0079] The weighed UV conversion coating raw materials were dispersed in a high-speed mixer at 12,000 rpm for 3 minutes to obtain a uniform UV conversion coating. The surface of the EVA film cast by S2 was ultrasonically sprayed to fully disperse the UV conversion coating, thereby forming a high-efficiency light conversion coating with a thickness of 200 nm. After curing and drying by ammonia steam treatment, the pre-made PVB film of S1 was laminated on the UV conversion layer. After embossing, cooling, trimming, and rolling, a UV-proof PVB composite film was obtained. Comparative Example 1

[0080] The EVA and PVB films are made using the base film pre-fabricated in Example 1. No light-converting layer is designed. After direct lamination, they are embossed, cooled, trimmed, and rolled up to obtain a UV-resistant PVB composite film. Comparative Example 2

[0081] The EVA and PVB films use the base film pre-made in Example 1. The UV light conversion coating is applied according to conventional methods, using acrylic emulsion as the coating matrix and dispersing the light conversion agent in it. The coating is applied according to step S3 of Example 1 to ensure that the coating thickness and the amount of light conversion agent per unit coating are consistent with the light conversion coating in Example 1. After the PVB film is laminated, it is embossed, cooled, trimmed, and rolled up to obtain a UV-proof PVB composite film. Performance Comparison Analysis 1

[0082] According to the requirements of GB / T29848-2013 "Ethylene-vinyl acetate copolymer (EVA) film for photovoltaic module encapsulation", the PVB composite film was tested, as shown in Table 3-1:

[0083] Table 3-1

[0084]

[0085] Analysis of the light transmittance and yellowing resistance index of the PVB composite film shows that the PVB composite film of this invention has excellent light transmittance, especially for long-wavelength light sources. Comparative Example 1 did not involve a light conversion layer, and ultraviolet light transmission affected the aging of the film; Comparative Example 2 used a traditional organic emulsion as a light conversion coating, which has poor transparency and is prone to yellowing due to aging.

[0086] Obviously, the PVB composite film of the present invention is used as an encapsulation film for photovoltaic modules. It is mainly based on an ultra-thin inorganic ultraviolet light conversion layer. The ultraviolet light conversion layer uses all-hydrogen polysilazane as the film-forming material and α-Al2O3 as a dispersing agent, which has excellent dispersibility, transparency and durability.

[0087] The above-described specific implementations and comparative examples illustrate the principles and positive effects of the present invention. Obviously, the present invention is not limited to the detailed process described above. Under the premise of understanding the technical intent of the present invention, those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of raw materials for the products of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A UV-transmitting PVB composite film, comprising an EVA / PVB composite film formed by an EVA film and a PVB film, wherein an ultraviolet light conversion layer is formed between the EVA film and the PVB film; the EVA film contains an ultraviolet light conversion agent; the PVB film contains an ultraviolet absorber; the ultraviolet light conversion layer is formed by coating a transparent ultraviolet light conversion coating, the ultraviolet light conversion coating comprising an ultraviolet light conversion agent, perhydropolysilazane, α-Al2O3, and a solvent.

2. The UV-blocking PVB composite film according to claim 1, characterized in that: The thickness of the UV-resistant PVB composite film is 0.3-0.6 mm; the thickness ratio of the EVA film to the PVB film is 2:

1.

3. The UV-resistant PVB composite film according to claim 1, characterized in that: The thickness of the ultraviolet conversion layer is controlled between 100-1000 nm.

4. The UV-resistant PVB composite film according to claim 1, characterized in that: The ultraviolet light conversion agent includes, but is not limited to, one or more of rare earth organic light conversion agents, organic fluorescent pigments, rare earth inorganic light conversion agents, and perovskite quantum dots; the ultraviolet absorber is selected from at least one of phenyl benzoate, 2,4,6-tris(2'-butoxyphenyl)-1,3,5-triazine, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-(2'-hydroxy-3',5'-di-tert-phenyl)-5-chlorobenzotriazole, 2,2'-methylenebis(4-tert-octyl-6-benzotriazolephenol), and resorcinol benzoate.

5. A method for preparing a UV-transmitting PVB composite film according to any one of claims 1-4, characterized in that: S1. Preparation of PVB film: Weigh out the following components by weight: 80-85 parts PVB resin powder, 15-25 parts plasticizer, 0.05-0.1 parts antioxidant, and 0.1-0.2 parts UV absorber. Add these components to a high-speed mixer and disperse evenly. Quantitatively convey the mixture to the twin-screw extruder feed inlet using a loss-in-weight weighing system. Set the twin-screw extrusion process as follows: Stage 1: 165-175℃; Stage 2: 180-185℃; Stage 3: 190-195℃; Stage 4: 170-180℃; Die temperature: 140-150℃. The mixture flows out through a T-die, is pre-shaped by a constant-temperature roller, continuously tested by a front thickness gauge, and then enters the longitudinal stretching device for longitudinal stretching and the transverse stretching device for transverse stretching. Finally, the thickness gauge guides the film to the take-up roller for winding, resulting in a PVB film. Preparation of S2. EVA membrane: Weigh out the following components by weight: 99-100 parts EVA resin, 0.005-0.2 parts UV conversion agent, 0.1-0.3 parts antioxidant, and 0.2-0.5 parts crosslinking agent. Add these components to a high-speed mixer and disperse evenly. Quantitatively convey the mixture to the twin-screw extruder feed inlet using a loss-in-weight weighing system. Set the twin-screw extrusion process as follows: first stage 50-60℃; second stage 80-90℃; third stage 90-100℃; fourth stage 110-120℃; die temperature 110-120℃. The mixture flows out through a T-die, undergoes roller casting, pressure roller shaping, edge trimming, and winding to obtain the EVA film. S3. Composite film formation: Weigh out the following components by weight: 0.05-0.5 parts of UV conversion agent, 5-15 parts of perhydropolysilazane, 1-3 parts of α-Al2O3, and 55-65 parts of solvent. Disperse them evenly at high speed to prepare a UV conversion coating. Apply the UV conversion coating to the surface of the EVA film cast by S2 to form a UV conversion layer. After treatment with ammonia steam and drying, laminate the pre-made PVB film of S1 onto the UV conversion layer. After embossing, cooling, trimming, and winding, a UV-resistant PVB composite film is obtained.

6. The method for preparing a UV-transmitting PVB composite film according to claim 5, characterized in that: The plasticizer mentioned in step S1 is at least one of dipropylene glycol dibenzoate, triethylene glycol diisooctanoate, and triethylene glycol di-n-heptanoate; the antioxidant mentioned in steps S1 and S2 is at least one of antioxidant 1010, antioxidant 1076, antioxidant 618, antioxidant 1330, and antioxidant 1098; the crosslinking agent mentioned in step S2 is one or a combination of two of dicumyl peroxide and tert-butyl peroxide (2-ethylhexyl) carbonate.

7. The method for preparing a UV-transmitting PVB composite film according to claim 5, characterized in that: In step S3, the perhydropolysilazane is selected from perhydropolysilazane obtained by ammonolysis; the α-Al2O3 is selected from spherical α-Al2O3 powder with a particle size range of 10-30 nm; and the solvent is selected from at least one of toluene, n-hexane, and xylene.

8. The method for preparing a UV-transmitting PVB composite film according to claim 5, characterized in that: The EVA resin used in step S2 has a vinyl acetate content of 25-35% (w).

9. The application of the UV-blocking PVB composite film according to any one of claims 1-8, characterized in that: It is used as a photovoltaic encapsulating film in photovoltaic modules.

10. The application of the UV-resistant PVB composite film according to claim 9, characterized in that: The photovoltaic module is a photoelectric conversion cell module that uses sunlight as a light source, which is one of the following: crystalline silicon solar cell, amorphous silicon solar cell, thin-film silicon solar cell, heterojunction solar cell, cadmium sulfide / cadmium telluride solar cell, or dye-sensitized solar cell.

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