High-weather-resistance ultraviolet-blocking photovoltaic backboard base film and preparation method and application of high-weather-resistance ultraviolet-blocking photovoltaic backboard base film

Abstract

The invention belongs to the technical field of photovoltaic cell materials, and particularly discloses a high-weather-resistance ultraviolet blocking photovoltaic backboard base film and a preparation method and application thereof. The high-weather-resistance ultraviolet blocking photovoltaic backboard base film is of a multi-layer structure and comprises the surface layer and the core layer, the modified master batch containing the ultraviolet light absorber and the ultraviolet blocking agent is added when the surface layer is prepared, the weather resistance of the base film can be improved (more than 60 H), the base film can have high blocking performance in the ultraviolet band, and the service life of the base film is prolonged. Normal use of the photovoltaic backboard in drought and high ultraviolet radiation weather is ensured, and durability and power generation efficiency of photovoltaic accessories are improved. The composition and the structure of the base film are redesigned, various ultraviolet light absorbers and blocking agents are compounded for use, and meanwhile, a three-layer co-extrusion and two-way stretching preparation process is adopted, so that the base film can be endowed with good weather resistance, radiation resistance and mechanical property, the production cost of the base film is reduced, and the base film has a good application prospect and a relatively high economic value.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic cell materials, and specifically relates to a highly weather-resistant ultraviolet-blocking photovoltaic backplane base film and a preparation method and application thereof. Background Art

[0002] Green and clean energy, as one of the key elements in addressing climate change and carrying out environmental protection, has become an important part of the energy development strategy of countries around the world. As a clean and renewable energy source, solar energy has an increasingly wide range of applications, including household, commercial and industrial electricity, transportation and other fields. Photovoltaic power generation has the advantages of being clean and safe, and plays an important role in the energy transformation process. Photovoltaic modules are the core components of photovoltaic power generation systems, and their structure mainly includes front panel glass, EVA film, battery cells and back panels. Among them, the back panel is located on the back of the photovoltaic module, and its function is to isolate the inside of the module from the outside world to extend the service life of the photovoltaic module.

[0003] However, with the continuous expansion of the application field of photovoltaic cells, the installation environment of photovoltaic modules has become more and more complex, and the market has increasingly higher requirements for the weather resistance of isolation backsheets, in order to extend the service life of photovoltaic modules in different outdoor environments. Therefore, improving the weather resistance and UV resistance of the backsheet and developing differentiated backsheet materials to meet the requirements of different scenarios are of great significance for improving the power generation efficiency and service life of photovoltaic modules and reducing production costs.

[0004] To this end, Chinese patent application CN114516969A (Yinjinda New Materials) provides a highly weather-resistant photovoltaic backplane, including a modified PE film (surface layer), a modified BOPET film (middle layer), a fluorine material film (surface layer) and a composite adhesive layer arranged between the films, wherein the modified BOPET film is used as the backplane base film, and is prepared by a three-layer co-extrusion and biaxial stretching process, and each layer thereof contains barium sulfate and / or titanium dioxide, and benzotriazole or triazine ultraviolet absorbers may also be added, which mainly play the role of supporting, blocking water vapor, and resisting ultraviolet aging. Similar to this patent, the existing backplane base film also uses PET (polyethylene terephthalate) as the main material, and improves the weather resistance and ultraviolet blocking performance of the backplane by using functional additives or setting functional coatings. In addition, the weather resistance of the backplane can also be improved by improving the production process, for example, increasing the shaping time, adjusting the horizontal stretching temperature, etc. However, the weather resistance of existing backplane base films is generally PCT 48H, and further processing is required to achieve better anti-ultraviolet and anti-yellowing properties, which cannot meet the urgent demand for high weather resistance products in the market. In addition, the existing backplane base films still have deficiencies in the process of using ultraviolet blocking agents during production, which will also have an adverse effect on the weather resistance of the base film. Therefore, it is urgent to develop a highly weather-resistant ultraviolet blocking photovoltaic backplane base film and its preparation method. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] The technical problem to be solved by the present invention is to provide a highly weather-resistant UV-blocking photovoltaic backplane base film and a preparation method thereof. By redesigning the composition and structure of the base film and compounding a variety of UV absorbers and barrier agents, the weather resistance of the backplane base film can be effectively improved, and it can have a higher barrier performance in the ultraviolet band, thereby meeting the use requirements of the photovoltaic backplane in different outdoor environments.

[0007] (II) Technical solution

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] A highly weather-resistant UV-blocking photovoltaic backsheet base film, comprising a surface layer and a core layer;

[0010] The raw materials for preparing the surface layer include PET polyester chips with an intrinsic viscosity of 0.7-0.8dl / g and modified masterbatch;

[0011] The raw materials for preparing the modified masterbatch include ultraviolet absorber, ultraviolet blocker, and PET polyester chips with an intrinsic viscosity of 0.7-0.8dl / g;

[0012] The ultraviolet absorber is selected from one or more of benzotriazole or triazine ultraviolet absorbers;

[0013] The ultraviolet blocking agent is selected from two or more of nano cerium oxide, nano titanium dioxide, nano silicon dioxide, nano zinc oxide, nano iron oxide, and nano aluminum oxide;

[0014] The raw materials for preparing the core layer include PET polyester chips with an intrinsic viscosity of 0.7-0.8 dl / g.

[0015] As a preferred embodiment of the present invention, the thickness ratio of the surface layer to the core layer is 1:5-6.

[0016] As a preferred embodiment of the present invention, in the raw materials for preparing the surface layer, the mass ratio of PET polyester chips to modified masterbatch is 38-42:8-12.

[0017] As a preferred embodiment of the present invention, in the raw materials for preparing the modified masterbatch, the mass ratio of ultraviolet absorber to ultraviolet blocker is 1-5:5-10, and the mass ratio of the total amount of ultraviolet absorber and ultraviolet blocker to PET polyester chips is 2-3:17-18.

[0018] As a preferred embodiment of the present invention, the modified masterbatch is prepared by an extrusion granulation process.

[0019] As a preferred embodiment of the present invention, the ultraviolet absorber is selected from two or more types of benzotriazole or triazine ultraviolet absorbers.

[0020] Specifically, the benzotriazole ultraviolet absorber includes but is not limited to 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole (THUV-328, CAS: 25973-55-1), 2-(2H-benzotriazole-2-yl)p-cresol (UV-P, CAS: 2440-22-4), 2-(2H-benzotriazole-2)-4,6-bis(1-methyl-1-phenylethyl)phenol (UV-234, CAS: 70321-86-7), and 2,2'-methylenebis(4-tert-octyl-6-benzotriazolephenol) (UV-360, CAS: 103597-45-1).

[0021] Specifically, the triazine ultraviolet absorber includes but is not limited to 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-hexyloxy-phenol (UV1577, CAS: 147315-50-2) and 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl)-5-octyloxyphenol (UV-1164, CAS: 2725-22-6).

[0022] As a preferred embodiment of the present invention, the ultraviolet absorber is a mixture of 2-(2H-benzotriazole-2-yl)-p-cresol (UV-P) and 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole (THUV-328) or 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-hexyloxy-phenol (UV1577) in a mass ratio of 1-2:1-2.

[0023] As a preferred embodiment of the present invention, the size of the ultraviolet blocking agent is 100-500nm.

[0024] Specifically, the ultraviolet blocker is a mixture of cerium oxide and titanium dioxide in a mass ratio of 1-2:1-2.

[0025] As a preferred embodiment of the present invention, the PET polyester chips with an intrinsic viscosity of 0.7-0.8 dl / g are commercially available and can be purchased. For example, Wankai's high-viscosity PET polyester chips have an intrinsic viscosity of 0.72 dl / g.

[0026] As a preferred embodiment of the present invention, the backplane base film is a multi-layer structure with the number of layers being ≥2.

[0027] Specifically, the backsheet base film is an ABA three-layer structure, with surface layers (A layers) disposed on both sides of the core layer (B layer). The two surface layers have the same composition and structure, and the thickness ratio of the three layers is 1 (A layer): 5-6 (B layer): 1 (A layer). The backsheet base film is preferably prepared by a three-layer co-extrusion and biaxial stretching process.

[0028] A method for preparing a highly weather-resistant UV-blocking photovoltaic backplane base film comprises the following steps:

[0029] (1) Preparation of modified masterbatch

[0030] The ultraviolet absorber and the ultraviolet blocker are fully mixed and dispersed, mixed with PET polyester chips with an intrinsic viscosity of 0.7-0.8 dl / g, and then extruded and granulated to obtain a modified masterbatch;

[0031] The ultraviolet absorber is selected from one or more of benzotriazole or triazine ultraviolet absorbers;

[0032] The ultraviolet blocking agent is selected from two or more of nano cerium oxide, nano titanium dioxide, nano silicon dioxide, nano zinc oxide, nano iron oxide, and nano aluminum oxide;

[0033] (2) Preparation of backplane base film

[0034] PET polyester chips with a characteristic viscosity of 0.7-0.8dl / g are mixed with modified masterbatch as raw materials for preparing the surface layer; then they are separately fed with raw materials for preparing the core layer, and are successively subjected to melt extrusion and biaxial stretching treatment to obtain a highly weather-resistant UV-blocking photovoltaic backplane base film.

[0035] As a preferred embodiment of the present invention, in step (1), the mass ratio of the ultraviolet absorber to the ultraviolet blocker is 1-5:5-10, and the mass ratio of the total amount of the ultraviolet absorber and the ultraviolet blocker to the PET polyester chips is 2-3:17-18.

[0036] As a preferred embodiment of the present invention, in step (1), the ultraviolet absorber is selected from two or more types of benzotriazole or triazine ultraviolet absorbers.

[0037] Specifically, the benzotriazole ultraviolet absorber includes but is not limited to 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole (THUV-328, CAS: 25973-55-1), 2-(2H-benzotriazole-2-yl)p-cresol (UV-P, CAS: 2440-22-4), 2-(2H-benzotriazole-2)-4,6-bis(1-methyl-1-phenylethyl)phenol (UV-234, CAS: 70321-86-7), and 2,2'-methylenebis(4-tert-octyl-6-benzotriazolephenol) (UV-360, CAS: 103597-45-1).

[0038] Specifically, the triazine ultraviolet absorber includes but is not limited to 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-hexyloxy-phenol (UV1577, CAS: 147315-50-2) and 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl)-5-octyloxyphenol (UV-1164, CAS: 2725-22-6).

[0039] Specifically, the ultraviolet absorber is a mixture of 2-(2H-benzotriazole-2-yl)-p-cresol (UV-P) and 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole (THUV-328) or 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-hexyloxy-phenol (UV1577) in a mass ratio of 1-2:1-2.

[0040] As a preferred embodiment of the present invention, in step (1), the size of the ultraviolet blocking agent is 100-500nm.

[0041] Specifically, the ultraviolet blocker is a mixture of cerium oxide and titanium dioxide in a mass ratio of 1-2:1-2.

[0042] As a preferred embodiment of the present invention, in step (1), the method for fully mixing and dispersing the ultraviolet absorber and the ultraviolet blocker is: mixing and spraying the ultraviolet absorber and the ultraviolet blocker with a solvent (such as dimethylsiloxane), and then introducing an inert gas (such as nitrogen) for stirring and dispersion. The technical parameters of the spraying are: inlet air temperature 160-200°C, outlet air temperature 60-100°C, feed amount 10-30ml / min. The technical parameters of the stirring and dispersing are: rotation speed 300-500r / min, temperature 80-120°C, time 5-15h.

[0043] As a preferred embodiment of the present invention, in step (1), the technical parameters of the extrusion granulation are: temperature 180-275°C.

[0044] As a preferred embodiment of the present invention, in step (2), the mass ratio of the PET polyester chips to the modified masterbatch is 38-42:8-12.

[0045] Specifically, the raw material for preparing the core layer includes PET polyester chips with an intrinsic viscosity of 0.7-0.8 dl / g.

[0046] Specifically, the PET polyester chips with an intrinsic viscosity of 0.7-0.8 dl / g are commercially available and can be purchased.

[0047] As a preferred embodiment of the present invention, in step (2), when the backplane base film is an ABA three-layer structure, that is, a surface layer (A layer) is respectively arranged on both sides of the core layer (B layer), three-layer co-extrusion can be adopted to melt extrude so as to form an ABA three-layer structure.

[0048] Specifically, the technical parameters of the three-layer co-extrusion are: temperature 240-290°C.

[0049] As a preferred embodiment of the present invention, in step (2), after the melt extrusion (such as three-layer co-extrusion), the cast sheet is first cooled and then subjected to a biaxial stretching treatment.

[0050] Specifically, the temperature of the casting rollers in the cooling casting is 15-35°C.

[0051] As a preferred embodiment of the present invention, in step (2), the biaxial stretching treatment is sequentially longitudinal stretching and transverse stretching, and the technical parameters of the longitudinal stretching are: preheating zone temperature 74-82°C, stretching zone temperature 30-82°C, shaping zone temperature 30-50°C, and stretching ratio 3-3.5 times; the technical parameters of the transverse stretching are: preheating zone temperature 100-110°C, stretching zone temperature 118-124°C, shaping zone temperature 217-225°C, cooling zone temperature 30-180°C, and stretching ratio 3-3.5 times.

[0052] Application of a highly weather-resistant UV-blocking photovoltaic backplane base film in the preparation of a photovoltaic backplane.

[0053] (III) Beneficial effects

[0054] The high weather-resistant UV-blocking photovoltaic backplane base film provided by the present invention is a multilayer structure, including a surface layer and a core layer. The surface layer is added with a modified masterbatch containing an ultraviolet absorber and an ultraviolet blocker during preparation, which can not only improve the weather resistance of the base film (more than 60H), but also enable the base film to have a higher barrier performance in the ultraviolet band, effectively absorb and reflect ultraviolet rays, ensure the normal use of the photovoltaic backplane in arid and high ultraviolet radiation weather, improve the durability and power generation efficiency of photovoltaic accessories, and help promote the popularization and utilization of renewable energy. The present invention redesigns the composition and structure of the base film, and uses a variety of ultraviolet absorbers and blockers in a compound manner. At the same time, a three-layer co-extrusion and biaxial stretching preparation process is adopted, which can give the base film good weather resistance, radiation resistance and mechanical properties, and reduce the production cost of the base film. The obtained backplane base film can also be used in parts such as building exterior walls and roofs. In addition to providing effective waterproofing and thermal insulation effects, it can also reduce the energy consumption of buildings.

[0055] The preparation method of the photovoltaic backplane base film provided by the present invention is simple, the raw materials are easily available, and the PET (polyethylene terephthalate) polyester chips with good weather resistance and high mechanical strength and the ultraviolet absorber and barrier agent of specific composition are used, and the preparation process that can improve the mechanical properties, temperature resistance and anti-aging properties of the base film is matched, which can not only prolong the service life of the photovoltaic backplane, but also enhance the efficiency of the photovoltaic module, achieve the purpose of energy saving and consumption reduction, and meet the current social requirements for green environmental protection. At the same time, the method is highly operable, low in production cost, and easy to carry out industrial production and application. DETAILED DESCRIPTION

[0056] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, comparative examples and experimental examples. Those skilled in the art should understand that the following embodiments and experimental examples are only used to illustrate the technical scheme and technical effects of the present invention and should not be regarded as any limitation on the protection scope of the present invention. Based on the following embodiments, other technical schemes obtained by ordinary technicians in the field without paying creative labor, such as technical schemes obtained after modification, deformation or simple replacement, all belong to the protection scope of the present invention.

[0057] The raw materials, reagents, equipment, etc. used in the embodiments, comparative examples and experimental examples are all commercially available products unless otherwise specified. Among them, high-viscosity PET polyester chips with an intrinsic viscosity of 0.72 dl / g were purchased from Wankai, product number: 112240506. The methods used are all conventional methods unless otherwise specified. The terms, abbreviations, etc. involved therein have the conventional meanings in this field.

[0058] Example 1

[0059] This embodiment provides a highly weather-resistant UV-blocking photovoltaic backplane base film, which is an ABA three-layer structure, with surface layers (A layers) arranged on both sides of the core layer (B layer), and the thickness ratio of the surface layer to the core layer is 1:6:1.

[0060] This embodiment also provides a method for preparing a highly weather-resistant UV-blocking photovoltaic backplane base film, comprising the following steps:

[0061] (1) Preparation of modified masterbatch

[0062] In parts by mass, 20 parts of ultraviolet absorber 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 40 parts of ultraviolet blocker nano cerium oxide and 40 parts of nano titanium dioxide (size of about 300nm) are mixed with 10 parts of solvent dimethylsiloxane and sprayed (technical parameters are: inlet air temperature 180℃, outlet air temperature 80℃, feed amount 20ml / min), and then nitrogen is introduced and stirred and dispersed at 400r / min and 100℃ for 10h to obtain a nano-composite with good dispersibility; the nano-composite is mixed with PET polyester chips with a characteristic viscosity of 0.72dl / g (the mass percentage of the two is 10%:90%) and then extruded and granulated (temperature 235℃) to obtain a modified masterbatch.

[0063] (2) Preparation of backplane base film

[0064] PET polyester chips with a characteristic viscosity of 0.72 dl / g are mixed with a modified masterbatch (the mass percentage of the two is 94%:6%) to serve as the raw material for preparing the surface layer; then they are separately fed with the raw material for preparing the core layer (PET polyester chips with a characteristic viscosity of 0.72 dl / g), and are successively subjected to three-layer co-extrusion (technical parameters: temperature 275°C), cooling casting (casting roller temperature 25°C), and biaxial stretching (technical parameters for longitudinal stretching: preheating zone temperature 80°C, stretching zone temperature 65°C, shaping zone temperature 40°C, and stretching ratio 3.3 times; technical parameters for transverse stretching: preheating zone temperature 105°C, stretching zone temperature 120°C, shaping zone temperature 220°C, cooling zone temperature 50°C, and stretching ratio 3.3 times) to obtain a highly weather-resistant UV-blocking photovoltaic backplane base film.

[0065] This embodiment also provides an application of a highly weather-resistant UV-blocking photovoltaic backplane base film in the preparation of a photovoltaic backplane.

[0066] Example 2

[0067] This embodiment provides a highly weather-resistant UV-blocking photovoltaic backplane base film, which is an ABA three-layer structure, with surface layers (A layers) arranged on both sides of the core layer (B layer), and the thickness ratio of the surface layer to the core layer is 1:6:1.

[0068] This embodiment also provides a method for preparing a highly weather-resistant UV-blocking photovoltaic backplane base film, comprising the following steps:

[0069] (1) Preparation of modified masterbatch

[0070] In parts by mass, 10 parts of ultraviolet absorbers 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole and 10 parts of 2-(2H-benzotriazole-2-yl)p-cresol, 40 parts of ultraviolet blockers nano cerium oxide and 40 parts of nano titanium dioxide (size of about 300nm) are mixed with 10 parts of solvent dimethylsiloxane and sprayed (technical parameters are: inlet air temperature 180℃, outlet air temperature 80℃, feed amount 20ml / min), and then nitrogen is introduced and stirred and dispersed at 400r / min and 100℃ for 10h to obtain a nano-composite with good dispersibility; the nano-composite is mixed with PET polyester chips with a characteristic viscosity of 0.72dl / g (the mass percentage of the two is 10%:90%) and then extruded and granulated (temperature 235℃) to obtain a modified masterbatch.

[0071] (2) Preparation of backplane base film

[0072] PET polyester chips with a characteristic viscosity of 0.72 dl / g are mixed with a modified masterbatch (the mass percentage of the two is 94%:6%) to serve as the raw material for preparing the surface layer; then they are separately fed with the raw material for preparing the core layer (PET polyester chips with a characteristic viscosity of 0.72 dl / g), and are successively subjected to three-layer co-extrusion (technical parameters: temperature 275°C), cooling casting (casting roller temperature 25°C), and biaxial stretching (technical parameters for longitudinal stretching: preheating zone temperature 80°C, stretching zone temperature 65°C, shaping zone temperature 40°C, and stretching ratio 3.3 times; technical parameters for transverse stretching: preheating zone temperature 105°C, stretching zone temperature 120°C, shaping zone temperature 220°C, cooling zone temperature 50°C, and stretching ratio 3.3 times) to obtain a highly weather-resistant UV-blocking photovoltaic backplane base film.

[0073] This embodiment also provides an application of a highly weather-resistant UV-blocking photovoltaic backplane base film in the preparation of a photovoltaic backplane.

[0074] Embodiment 3-5

[0075] The preparation method of the highly weather-resistant UV-blocking photovoltaic backplane base film provided in Examples 3-5 is basically the same as that in Example 1, with the only difference being that the type and amount of UV absorber and / or UV blocker are different, as detailed in Table 1 below.

[0076] In other embodiments of the present invention, the raw materials, dosage, parameter conditions, etc. of the backplane base film can be arbitrarily set within a given range without affecting the overall performance of the base film.

[0077] Comparative Examples 1-5

[0078] The preparation methods of the photovoltaic backplane base films provided in Comparative Examples 1-5 are basically the same as those in Example 1, with the only difference being that ultraviolet absorbers and / or ultraviolet blockers are added or not, and the types and amounts of the two are different. Detailed information is shown in Table 1 below.

[0079] Table 1 Preparation materials of backplane base film in Examples and Comparative Examples

[0080]

[0081] Experimental example

[0082] 1. Moisture and heat aging test

[0083] Experimental method: Take the backplane base film prepared in Experimental Examples 1-5 and Comparative Examples 1-5, and test it according to the standard GB / T 13542.2-2009 Plastic Film Tensile Performance Test Method. Use a long strip base film with a length of 200mm and a width of 15mm, a gauge length of 100mm, and a stretching speed of 100±10mm / min to test the initial tensile strength and initial elongation at break of the film, 5 strips in each horizontal and vertical directions. Use the same method to cut 5 strips of base film in each vertical and horizontal direction, and put it into a high-voltage accelerated aging tester (manufacturer: Demaisheng Measurement and Control / DMS-PCT-40), set the temperature to 121°C, the humidity to 100%, and the time to 60H. Use the same stretching parameters to perform performance tests after aging, and the results are shown in Table 2 below. Among them, the elongation at break retention rate = the average elongation at break after aging / the initial elongation at break retention rate × 100%.

[0084] 2. UV blocking rate test

[0085] Experimental method: Take the backplane base film prepared in Experimental Examples 1-5 and Comparative Examples 1-5, cut it into A4 samples in the vertical and horizontal directions, and put it into the test slot (the testing instrument is purchased from Linshang Technology, product model LS182), read the UV blocking rate value and record it, read 3 points on an A4 sample, and take the average value. The results are shown in Table 2 below.

[0086] Table 2 Performance test results of the backplane base film in the embodiments and comparative examples

[0087]

[0088] Conclusion: It can be seen from Table 2 that the backplane base film provided by the present invention has good weather resistance (≥PCT 60H), has high barrier performance in the ultraviolet band, can effectively absorb and reflect ultraviolet rays, and ensure the normal use of the photovoltaic backplane in arid and high ultraviolet radiation weather.

[0089] The present invention redesigns the composition and structure of the base film, compounds a variety of ultraviolet absorbers and barriers, and adopts a three-layer co-extrusion and biaxial stretching preparation process, thereby giving the backplane base film good weather resistance, radiation resistance and mechanical properties, reducing the production cost of the base film, facilitating industrial production, and having good application prospects and high economic value.

[0090] Although the technical scheme and technical effects of the present invention have been described in detail above by means of general description, specific embodiments and experimental examples, for those skilled in the art, any modification, replacement or improvement made without departing from the spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A highly weather-resistant UV-blocking photovoltaic backsheet base film, characterized in that: The back sheet base film comprises a surface layer and a core layer; The raw materials for preparing the surface layer include PET polyester chips with an intrinsic viscosity of 0.7-0.8dl / g and modified masterbatch; The raw materials for preparing the modified masterbatch include ultraviolet absorber, ultraviolet blocker, and PET polyester chips with an intrinsic viscosity of 0.7-0.8dl / g; The ultraviolet absorber is selected from one or more of benzotriazole or triazine ultraviolet absorbers; The ultraviolet blocking agent is selected from two or more of nano cerium oxide, nano titanium dioxide, nano silicon dioxide, nano zinc oxide, nano iron oxide, and nano aluminum oxide; The raw materials for preparing the core layer include PET polyester chips with an intrinsic viscosity of 0.7-0.8 dl / g.

2. The backplane base film according to claim 1, characterized in that: The thickness ratio of the surface layer to the core layer is 1:5-6.

3. The backplane base film according to claim 1, characterized in that: In the raw materials for preparing the surface layer, the mass ratio of PET polyester chips to modified masterbatch is 38-42:8-12; And / or, in the raw materials for preparing the modified masterbatch, the mass ratio of the ultraviolet absorber to the ultraviolet blocker is 1-5:5-10, and the mass ratio of the total amount of the ultraviolet absorber and the ultraviolet blocker to the PET polyester chips is 2-3:17-18.

4. The backplane base film according to claim 1, characterized in that: The ultraviolet absorber is selected from two or more benzotriazole or triazine ultraviolet absorbers; The benzotriazole ultraviolet absorber includes but is not limited to 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-(2H-benzotriazole-2-yl)-p-cresol, 2-(2H-benzotriazole-2)-4,6-bis(1-methyl-1-phenylethyl)phenol, and 2,2'-methylenebis(4-tert-octyl-6-benzotriazolephenol); The triazine ultraviolet absorbers include, but are not limited to, 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-hexyloxy-phenol and 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl)-5-octyloxyphenol.

5. The backplane base film according to claim 1, characterized in that: The ultraviolet absorber is a mixture of 2-(2H-benzotriazole-2-yl)-p-cresol and 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole or 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-hexyloxy-phenol in a mass ratio of 1-2:1-2; And / or, the ultraviolet blocking agent is a mixture of cerium oxide and titanium dioxide in a mass ratio of 1-2:1-2.

6. The backplane base film according to claim 1, characterized in that: The backplane base film is an ABA three-layer structure, with surface layers (A layers) arranged on both sides of a core layer (B layer).

7. A method for preparing a highly weather-resistant UV-blocking photovoltaic backplane base film as claimed in any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: (1) Preparation of modified masterbatch The ultraviolet absorber and the ultraviolet blocker are fully mixed and dispersed, mixed with PET polyester chips with an intrinsic viscosity of 0.7-0.8 dl / g, and then extruded and granulated to obtain a modified masterbatch; (2) Preparation of backplane base film PET polyester chips with a characteristic viscosity of 0.7-0.8dl / g are mixed with modified masterbatch as raw materials for preparing the surface layer; then they are separately fed with raw materials for preparing the core layer, and are successively subjected to melt extrusion and biaxial stretching treatment to obtain a highly weather-resistant UV-blocking photovoltaic backplane base film.

8. The preparation method according to claim 7, characterized in that: In step (1), the method for fully mixing and dispersing the ultraviolet absorber and the ultraviolet blocker is: mixing the ultraviolet absorber, the ultraviolet blocker and the solvent, spraying, and then introducing an inert gas for stirring and dispersion; the technical parameters of the spraying are: inlet air temperature 160-200°C, outlet air temperature 60-100°C, feed amount 10-30ml / min; the technical parameters of the stirring and dispersing are: rotation speed 300-500r / min, temperature 80-120°C, time 5-15h; And / or, in step (1), the technical parameters of the extrusion granulation are: temperature 180-275°C; And / or, in step (2), when the backplane base film is an ABA three-layer structure, it is melt-extruded by three-layer co-extrusion, and the technical parameters of the three-layer co-extrusion are: temperature 240-290°C, pressure 1-2MPa, and time 10-60min.

9. The preparation method according to claim 7, characterized in that: In step (2), after the melt extrusion, the cast sheet is first cooled and then subjected to biaxial stretching treatment, and the temperature of the casting roller during the cooling of the cast sheet is 15-35° C.; And / or, the biaxial stretching treatment is longitudinal stretching and transverse stretching in sequence, and the technical parameters of the longitudinal stretching are: preheating zone temperature 74-82°C, stretching zone temperature 30-82°C, shaping zone temperature 30-50°C, and stretching ratio 3-3.5 times; the technical parameters of the transverse stretching are: preheating zone temperature 100-110°C, stretching zone temperature 118-124°C, shaping zone temperature 217-225°C, cooling zone temperature 30-180°C, and stretching ratio 3-3.5 times.

10. Use of the highly weather-resistant UV-blocking photovoltaic backplane base film according to any one of claims 1 to 6 in the preparation of a photovoltaic backplane.

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