CN111303782A - Packaging adhesive film for photovoltaic module and preparation method thereof - Google Patents

Abstract

The invention discloses an encapsulation adhesive film for photovoltaic modules and a preparation method thereof. The encapsulating adhesive film for photovoltaic modules includes at least two adhesive film layers, and the adhesive film layer with the highest reflectivity in each adhesive film layer is arranged close to the cell, and the adhesive film layer with the highest reflectivity is sensitive to light in the wavelength range of 400nm-1100nm. Reflectivity ≥ 90%. The encapsulation film for photovoltaic modules is prepared by the following method: after mixing the raw materials of each layer of the encapsulation film for photovoltaic modules respectively, add them to different extruders, and then inject them into the same die, and extrude them from the T die. Winding, pre-crosslinking. The photovoltaic encapsulation adhesive film of the invention has a multi-layer structure, can solve the problems of low reflection efficiency and high cost, and has a simple and efficient preparation process.

Description

A kind of encapsulation film for photovoltaic module and preparation method thereof

technical field

The invention belongs to the technical field of photovoltaic modules, and in particular relates to a packaging adhesive film for photovoltaic modules and a preparation method thereof.

Background technique

Photovoltaic power generation has become more and more popular due to its clean, environmentally friendly and renewable characteristics, and has developed rapidly in recent years. The encapsulation film used for photovoltaic modules has an important influence on the performance and service life of photovoltaic modules.

At present, the most common solar photovoltaic module structure is glass/encapsulation film/cell/encapsulation film/glass. In the above photovoltaic module structure, the front-side adhesive film generally requires higher light transmittance, so that more sunlight It can be absorbed by the battery, and the adhesive film on the back generally requires a higher reflectivity, so that the sunlight leaking from the battery is reflected by the adhesive film on the back to the battery for secondary use, so as to improve the power generation efficiency and reduce the cost of power generation. . The common practice, as disclosed in JP1994177412A, can achieve the effect of improving the power of photovoltaic modules by adding highly reflective fillers to the encapsulation film, but it has the disadvantage of being relatively expensive, so it has not been applied on a large scale. With the release of the "531 New Deal" in the photovoltaic industry, the industry's demand for cost reduction is becoming more and more urgent.

Therefore, based on the defects of the prior art and the needs of industry development, the present invention develops an encapsulation adhesive film for photovoltaic modules and a preparation method thereof. The adhesive film has a multi-layer structure, and different reflective fillers are selected according to the functions of different layers. The cost of the adhesive film can be significantly reduced, and the preparation and processing method is simple.

SUMMARY OF THE INVENTION

In view of the technical problems existing in the prior art, the present invention provides an encapsulation film for photovoltaic modules and a preparation method thereof. The photovoltaic encapsulation adhesive film has a multi-layer structure, can solve the problems of low reflection efficiency and high cost, and has a simple and efficient preparation process.

In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

An encapsulating adhesive film for photovoltaic modules, which is used for the lower side adhesive film of a photovoltaic module cell, comprising at least two adhesive film layers, and the adhesive film layer with the highest reflectivity in each adhesive film layer is arranged close to the cell, and the reflectance is The highest reflectivity of the film layer to the light in the wavelength range of 400nm-1100nm is ≥90%.

Preferably, the encapsulating adhesive film for photovoltaic modules includes a first adhesive film layer and a second adhesive film layer, wherein the first adhesive film layer is a reflective adhesive film layer, and the first adhesive film layer is 400nm-1100nm The reflectivity of light in the wavelength range is ≥90%.

Further preferably, the reflectivity of the first adhesive film layer to light in the wavelength range of 400nm-700nm is ≥90%.

Preferably, the second adhesive film layer is a transparent layer or a reflective adhesive film layer.

More preferably, when the second adhesive film layer is a reflective adhesive film layer, the reflectivity of the first adhesive film layer is greater than the reflectivity of the second adhesive film layer. Most preferably, the reflectivity of the second adhesive film layer in the wavelength range of 400nm-1100nm is 40-65%.

More preferably, the transparent layer includes a matrix resin, and there is no need to add a white filler, and there is no requirement for reflection of light.

Preferably, the encapsulating adhesive film for photovoltaic modules further comprises a third adhesive film layer, the first adhesive film layer and the third adhesive film layer are located on both sides of the second adhesive film layer, and the third adhesive film layer is a reflective adhesive film or transparent layer.

More preferably, the reflectivity of the first adhesive film layer is greater than or equal to the reflectivity of the third adhesive film layer.

Preferably, the reflective adhesive film layer comprises a matrix resin and a reflective filler, and the reflective filler is selected from titanium dioxide, calcium carbonate, wollastonite, mica powder, magnesium hydroxide, aluminum hydroxide, composite titanium dioxide, talc, One or more of barium sulfate, glass beads and zinc sulfide.

Preferably, the particle size D50 of the reflective filler is less than or equal to 1 μm.

More preferably, the reflective filler of the first adhesive film layer is titanium dioxide; the reflective filler of the second adhesive film layer or the third adhesive film layer is calcium carbonate, wollastonite, talc, mica powder or glass microparticles. beads.

Preferably, the matrix resin is one or more polymers selected from the group consisting of ethylene-vinyl acetate copolymer, metallocene-catalyzed polyethylene, metallocene-catalyzed ethylene butene copolymer, and metallocene-catalyzed ethylene octene copolymer compounds, metallocene-catalyzed ethylene pentene copolymers, ethylene propylene copolymers, ethylene methyl acrylate copolymers, and ethylene methyl methacrylate copolymers. More preferably, the matrix resin is EVA or POE.

Preferably, the first adhesive film layer and the second adhesive film layer further include a tackifier, a crosslinking agent and an auxiliary agent.

Preferably, the tackifier may be one or more of a silane coupling agent and an alkoxysilane oligomer.

Preferably, the crosslinking agent may be one or more of a peroxide crosslinking agent and a photoinitiator.

Preferably, the auxiliary agent may be one or more of antioxidants, hindered amine light stabilizers, ultraviolet absorbers and plasticizers.

Preferably, the pre-crosslinking degree of the encapsulating film for photovoltaic modules is 0.5-70%. The heat resistance of the encapsulation film varies according to the formula. For example, when some non-low fluidity film is selected, the high reflectivity film will overflow during the film lamination process and contaminate the cell. Pre-crosslinking It will reduce the fluidity of the film and solve the overflow problem.

The invention also provides a preparation method of the encapsulation film for photovoltaic modules, the specific steps are as follows: after mixing the raw materials of each layer of the encapsulation film for photovoltaic modules respectively, add them into different extruders, and then inject into the same die head, T-die extrusion, winding, and pre-crosslinking are performed to obtain the encapsulating film for photovoltaic modules.

Preferably, the temperature of the extruder is 60-110°C, and the temperature of the T-die is 70-110°C.

Preferably, the pre-crosslinking manner is ultraviolet cross-linking, irradiation cross-linking or microwave cross-linking.

The encapsulating adhesive film for photovoltaic modules of the present invention has a multi-layer structure, and is used in combination with fillers with different reflectances, which can significantly reduce the cost of the encapsulating adhesive film for photovoltaic modules, and improve the reflectivity of the encapsulating adhesive film for photovoltaic modules, thereby improving the The effect of the power of the photovoltaic module, and the preparation method of the encapsulation film for the photovoltaic module of the present invention is simple and easy to implement, which is beneficial to large-scale production.

Description of drawings

FIG. 1 is one of the schematic diagrams of the encapsulation film for photovoltaic modules in the specific embodiment.

FIG. 2 is the second schematic diagram of the encapsulation film for photovoltaic modules in the specific embodiment.

Description of reference numbers:

100-encapsulation adhesive film, 101-first adhesive film layer, 102-second adhesive film layer, 103-third adhesive film layer.

Detailed ways

The following specific examples are further descriptions of the methods and technical solutions provided by the present invention, but should not be construed as limiting the present invention.

1-2 schematically show cross sections of the structure of the photovoltaic encapsulation adhesive film of the present embodiment. It should be noted that the thickness of each structure in Fig. 1-2 represents one example, and the size of each structure of the photovoltaic encapsulation adhesive film of the present invention is not limited to the size shown in Fig. 1-2.

The reagents, materials, etc. used in this embodiment can be obtained from commercial sources unless otherwise specified. The titanium dioxide in the example is D50≤1μm, which is tested by Screen 3# filter screen (with a pore size of about 10μm), and the titanium dioxide with a filter pressure value of <0.5bar/g (titanium dioxide and linear low-density polymer are mixed with a twin-screw extruder. Ethylene (LLDPE) is mixed to make a 70% concentration of color masterbatch. According to the requirements of European standard EN13900-5:2005, low density polyethylene (LDPE) is used as the base resin to dilute the color masterbatch to 8%. The concentration of titanium dioxide is detected and filtered. Pressure value).

In each example of this specific implementation manner, in the reflective adhesive film layer, 100 parts by weight of matrix resin, 5-50 parts by weight of reflective filler, 0.01-5 parts by weight of crosslinking agent, and 0.01-10 parts by weight of tackifier parts, 0-5 parts by weight of additives. In the transparent layer, the matrix resin is 100 parts by weight, the crosslinking agent is 0.01-5 parts by weight, the tackifier is 0.01-10 parts by weight, and the auxiliary agent is 0-5 parts by weight.

FIG. 1 shows an example of a photovoltaic encapsulation adhesive film. The encapsulation adhesive film 100 includes a first adhesive film layer 101 and a second adhesive film layer 102 .

Example 1

An encapsulation adhesive film 100 for photovoltaic modules, the structure is shown in FIG. 1 , comprising a first adhesive film layer 101 and a second adhesive film 102 , wherein the first adhesive film layer 101 is a reflective adhesive film layer, and the second adhesive film layer 102 for the transparent layer.

The first adhesive film layer 101 is a reflective adhesive film layer, and the raw material composition is as follows: VA mass fraction is 33% ethylene-vinyl acetate copolymer, titanium dioxide, cross-linking agent tert-butyl isopropyl peroxycarbonate, auxiliary cross-linking agent Trimethylolpropane triacrylate and tackifier gamma-aminopropyltriethoxysilane.

The second adhesive film layer 102 is a transparent layer, which is composed of 24% ethylene-vinyl acetate copolymer with VA mass fraction, cross-linking agent tert-butyl isopropyl peroxycarbonate, and auxiliary cross-linking agent trimethylolpropane triglyceride. Acrylates, hindered amine light stabilizers, bis-2,2,6,6-tetramethylpiperidinol sebacate, UV absorbers 2,2-tetramethylenebis(3,1-benzoxanil) oxazin-4-one), tackifier γ-aminopropyltriethoxysilane composition.

The resin composition of the first adhesive film layer 101 and the resin composition of the second adhesive film layer 102 are fully mixed and put into different extruders. ; The extruded material of the above-mentioned first adhesive film layer 101 and the extruded material of the second adhesive film layer 102 are melted and then entered into the T-die head through the distributor to be extruded into a film, and then transferred to the bottom of the electron radiation device with 80keV energy after cooling. The above-mentioned adhesive film is irradiated with electrons at an intensity of 30 kGy, and after the radiation is rolled up, a double-layer co-extruded encapsulation adhesive film E1 is obtained. The thickness of the E1 film is 0.5mm, the first film layer 101 is 0.1mm (calculated by the distributor), and the second film layer 102 is 0.4mm (calculated by the distributor). The degree of connection is 10%.

Example 2

An encapsulation adhesive film 100 for photovoltaic modules, the structure is shown in FIG. 1 , comprising a first adhesive film layer 101 and a second adhesive film, wherein the first adhesive film layer 101 and the second adhesive film layer 102 are both reflective adhesive film layers .

The first adhesive film layer 101 is composed of raw materials as follows: VA mass fraction is 28% ethylene-vinyl acetate copolymer, titanium dioxide, crosslinking agent 2,5-dimethyl-2,5-bis(tert-butylperoxy) ) hexane, co-crosslinking agent trimethylolpropane trimethacrylate/pentaerythritol triacrylate complex (mass ratio is 3:2), hindered amine light stabilizer bis-2,2 sebacic acid , 6,6-Tetramethylpiperidinol ester and tackifier vinyltrimethoxysilane.

The second adhesive film layer 102 is composed of 33% VA mass fraction of ethylene-vinyl acetate copolymer, calcium carbonate, cross-linking agent tert-butyl isopropyl peroxycarbonate, and auxiliary cross-linking agent triallyl isocyanurate , hindered amine light stabilizer bis-2,2,6,6-tetramethylpiperidinol sebacate, UV absorber 2,2-tetramethylenebis(3,1-benzoxazine- 4-keto), tackifier γ-aminopropyltriethoxysilane composition.

The above-mentioned resin composition of the first adhesive film layer 101 and the resin composition of the second adhesive film layer 102 are fully mixed and then added to different extruders. ℃; The extruded material of the above-mentioned first adhesive film layer 101 and the extruded material of the second adhesive film layer 102 are melted and then enter the T-die head through the distributor to be extruded into a film, and then transferred to the bottom of the electron radiation device with 1.0MeV energy after cooling. , the above-mentioned adhesive film is irradiated with electrons at an intensity of 20kGy, and after the radiation is rolled up, a double-layer co-extrusion encapsulation adhesive film E2 is obtained. The thickness of the E2 film is 0.7mm, the first film layer 101 is 0.3mm (calculated by the distributor), and the second film layer 102 is 0.4mm (calculated by the distributor). The degree of connection is 40%. The E2 first adhesive film layer 101 and the E2 second adhesive film layer 102 of corresponding thickness are extruded separately, and their reflectances (400-1100 nm) are 93% and 50%, respectively.

Example 3

An encapsulation adhesive film for photovoltaic modules, the structure is shown in FIG. 2, including a first adhesive film layer 101, a second adhesive film layer 102 and a third adhesive film layer 103, wherein the first adhesive film layer 101 and the second adhesive film layer 101. The film layers 102 are all reflective adhesive film layers, and the third adhesive film layer 103 is a transparent layer.

The first adhesive film layer 101 is composed of raw materials as follows: metallocene catalyzed polyethylene, tert-butyl peroxyisopropyl carbonate, titanium dioxide, sensitizer triallyl isocyanurate/pentaerythritol triacrylate compound (3:2 mass ratio), hindered amine light stabilizer bis-2,2,6,6-tetramethylpiperidinol sebacate and vinyltrimethoxysilane.

The second adhesive film layer 102 is made of ethylene-vinyl acetate copolymer with a mass fraction of VA of 33%, glass microbeads (refractive index of 1.93), triallyl isocyanurate as a co-crosslinking agent, hindered amine light stabilized bis-2,2,6,6-tetramethylpiperidinol sebacate, UV absorber 2,2-tetramethylenebis(3,1-benzoxazin-4-one), increased The adhesive consists of vinyltriethoxysilane oligomers.

The third adhesive film layer 103 is composed of metallocene-catalyzed ethylene butene copolymer, cross-linking agent t-butyl isopropyl peroxycarbonate, co-cross-linking agent trimethylolpropane triacrylate, hindered amine light stabilizer decanedi Acid bis-2,2,6,6-tetramethylpiperidinol ester, UV absorber 2,2-tetramethylenebis(3,1-benzoxazin-4-one), tackifier γ - Composed of a copolymerized mixture of methacryloyloxypropyltrimethoxysilane and vinyltris(2-methoxyethoxy)silane monomers.

The resin composition of the first adhesive film layer 101, the resin composition of the second adhesive film layer 102 and the third adhesive film layer 103 are fully mixed and then added to different extruders, and the temperature of the extruder is 80°C. , the temperature of the T die head is 95°C; the extruded material of the first adhesive film layer 101, the extruded material of the second adhesive film layer 102 and the extruded material of the third adhesive film layer 103 are melted and then enter the T die through the distributor The head is extruded to form a film, which is cooled and transferred to the bottom of an electron radiation device with an energy of 0.8MeV, and the above-mentioned adhesive film is irradiated with electrons at an intensity of 250kGy. The thickness of the E3 film is 0.7mm, the first film layer 101 is 0.3mm (calculated by the distributor), the second film layer 102 is 0.3mm (calculated by the distributor), and the third film layer 103 is 0.1 mm mm (calculated by the dispenser), the pre-crosslinking degree of the E3 film was measured to be 70%. The E3 first adhesive film layer 101 and the E3 second adhesive film layer 102 with corresponding thicknesses are extruded separately, and their reflectances (400-1100 nm) are 92% and 55%, respectively.

Example 4

An encapsulating adhesive film 100 for photovoltaic modules, the structure is shown in FIG. 2 , comprising a first adhesive film layer 101, a second adhesive film layer 102 and a third adhesive film layer 103, wherein the first adhesive film layer 101, the second adhesive film layer 101, the second adhesive film layer 103 The adhesive film layer 102 and the third adhesive film layer 103 are both reflective adhesive film layers.

The first adhesive film layer 101 is composed of raw materials as follows: VA mass fraction is 33% ethylene-vinyl acetate copolymer, tert-butyl isopropyl peroxycarbonate, titanium dioxide, sensitizer triallyl isocyanurate / pentaerythritol triacrylate compound (mass ratio of 3:2), hindered amine light stabilizer bis-2,2,6,6-tetramethylpiperidinol sebacate and vinyltrimethoxy Silane.

The second adhesive film layer 102 is composed of ethylene methyl acrylate copolymer, barium sulfate, triallyl isocyanurate, a co-crosslinking agent, and a hindered amine light stabilizer, bis-2,2,6,6-sebacic acid. Tetramethylpiperidinol ester, UV absorber 2,2-tetramethylenebis(3,1-benzoxazin-4-one), tackifier vinyltriethoxysilane oligomer.

The third adhesive film layer 103 is composed of 28% VA mass fraction of ethylene-vinyl acetate copolymer, wollastonite, cross-linking agent tert-butyl isopropyl peroxycarbonate, and auxiliary cross-linking agent trimethylolpropane triacrylate , hindered amine light stabilizer bis-2,2,6,6-tetramethylpiperidinol sebacate, UV absorber 2,2-tetramethylenebis(3,1-benzoxazine- 4-keto), tackifier γ-methacryloyloxypropyltrimethoxysilane and vinyl tris(2-methoxyethoxy)silane monomer copolymerization mixture.

The above-mentioned resin composition of the first adhesive film layer 101, the resin composition of the second adhesive film layer 102 and the third adhesive film layer 103 are fully mixed and then added to different extruders, and the temperature of the extruder is 85 ℃ , the temperature of the T die head is 95°C; the extruded material of the first adhesive film layer 101, the extruded material of the second adhesive film layer 102 and the extruded material of the third adhesive film layer 103 are melted and then enter the T die through the distributor The head is extruded to form a film, which is cooled and transferred to the bottom of an electron radiation device with an energy of 0.8MeV, and the above film is irradiated with electrons at an intensity of 30kGy. The thickness of E4 film is 0.7mm, the first film layer 101 is 0.3mm (calculated by the distributor), the second film layer 102 is 0.2mm (calculated by the distributor), and the third film layer 103 is 0.2mm mm (calculated by the dispenser), the pre-crosslinking degree of the E4 film was measured to be 30%. The E4 first adhesive film layer 101 , the E4 second adhesive film layer 102 , and the E4 second adhesive film layer 103 with corresponding thicknesses are extruded separately, and their reflectances (400-1100 nm) are 92%, 65%, and 40%, respectively.

Example 5

An encapsulating adhesive film 100 for photovoltaic modules, the structure is shown in FIG. 2 , comprising a first adhesive film layer 101, a second adhesive film layer 102 and a third adhesive film layer 103, wherein the first adhesive film layer 101 and the third adhesive film layer 101 The adhesive film layer 103 has the same composition and thickness, and the three adhesive film layers are all reflective adhesive film layers.

The first adhesive film layer 101 is composed of raw materials as follows: VA mass fraction is 28% ethylene-vinyl acetate copolymer, tert-butyl isopropyl peroxycarbonate, titanium dioxide, sensitizer triallyl isocyanurate / pentaerythritol triacrylate compound (mass ratio of 1:3), hindered amine light stabilizer bis-2,2,6,6-tetramethylpiperidinol sebacate and vinyltrimethoxy A copolymeric mixture of silane and methylvinyldiethoxysilane monomers.

The second adhesive film layer 102 is composed of metallocene-catalyzed ethylene octene copolymer, barium sulfate, triallyl isocyanurate as co-crosslinking agent, hindered amine light stabilizer bis-2,2,6 sebacate, 6-Tetramethylpiperidinol ester, UV absorber 2,2-tetramethylenebis(3,1-benzoxazin-4-one), tackifier vinyltriethoxysilane oligomer composition.

The resin composition of the first adhesive film layer 101 and the resin composition of the second adhesive film layer 102 were fully mixed and then added to different extruders. The temperature of the extruder was 80°C, and the temperature of the T die was 95 ℃; the extruded material of the first adhesive film layer 101 is melted and divided into two layers by the distributor, and together with the melted extruded material of the second adhesive film layer 102, it enters the T-die and extrudes into a film, and is cooled and conveyed to 0.6MeV Below the energy electron radiation equipment, electron radiation is performed on the above-mentioned radiation pre-crosslinked surface with an intensity of 20 kGy, and after radiation, the three-layer co-extrusion packaging film E5 is obtained by winding up. The thickness of the E5 film is 0.5mm, the first film layer 101 is 0.2mm (calculated by the distributor), the second film layer 102 is 0.1mm (calculated by the distributor), and the third film layer 103 is 0.2mm mm (calculated by the dispenser), the pre-crosslinking degree of the E5 film was measured to be 4%. The E5 first adhesive film layer 101 and the E5 second adhesive film layer 102 with corresponding thicknesses were extruded separately, and their reflectances (400-1100 nm) were 91% and 44%, respectively.

Example 6

An encapsulation adhesive film 101 for photovoltaic modules includes a first adhesive film layer 101 and a second adhesive film layer 102, wherein the first adhesive film layer 101 is a reflective adhesive film layer, and the second adhesive film layer 102 is a transparent layer.

The first adhesive film layer 101 is composed of raw materials as follows: VA mass fraction is 33% ethylene-vinyl acetate copolymer, titanium dioxide, photoinitiator benzophenone and photoinitiator 2-methyl-2-(4- Morpholinyl)-1-[4-(methylthio)phenyl]-1-propanone, thermal initiator tert-butyl isopropyl peroxycarbonate and thermal initiator 2,5-dimethyl-2,5 - Bis(tert-butylperoxy)hexane, co-crosslinker trimethylolpropane triacrylate and tackifier γ-aminopropyltriethoxysilane.

The second adhesive film layer 102 is composed of ethylene-vinyl acetate copolymer with a mass fraction of VA of 28%, a crosslinking agent tert-butyl isopropyl peroxycarbonate, a photoinitiator benzoin dimethyl ether, and a co-crosslinking agent trimethylolpropane Triacrylate, tackifier γ-aminopropyltriethoxysilane composition.

The resin composition of the first adhesive film layer 101 and the resin composition of the second adhesive film layer 102 were fully mixed and then added to different extruders. The temperature of the extruder was 85°C, and the temperature of the T die was 90 ℃; The extruded material of the above-mentioned first adhesive film layer 101 and the extruded material of the second adhesive film layer 102 are melted and then enter the T-die head through the distributor to be extruded into a film, and the irradiation intensity is 1800W/ The UV lamp of m ² irradiates both sides of the film successively for 100s, and after cooling, slitting and coiling, the film is wound to obtain a double-layer co-extrusion packaging film E6. The thickness of the E6 film is 0.3mm, the first film layer 101 is 0.2mm (calculated by the distributor), and the second film layer 102 is 0.1mm (calculated by the distributor). The degree of connection is 10%.

The descriptions of the above embodiments are only used to help understand the method and the core idea of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can also be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims (11)

1. A packaging adhesive film for a photovoltaic module is used for a lower adhesive film of a photovoltaic module cell, and is characterized by at least comprising two adhesive film layers, wherein the adhesive film layer with the highest reflectivity in each adhesive film layer is arranged close to the cell, and the reflectivity of the adhesive film layer with the highest reflectivity to light with the wavelength range of 400nm-1100nm is more than or equal to 90%.

2. The packaging adhesive film for the photovoltaic module according to claim 1, comprising a first adhesive film layer and a second adhesive film layer, wherein the first adhesive film layer is a reflective adhesive film layer, and the reflectivity of the first adhesive film layer to light with a wavelength range of 400nm-1100nm is not less than 90%.

3. The encapsulant film for photovoltaic module as claimed in claim 2, wherein the first film layer has a reflectance of 90% or more with respect to light having a wavelength of 400nm to 700 nm.

4. The encapsulant film for photovoltaic module as claimed in claim 2, wherein the second film layer is a transparent layer or a reflective film layer.

5. The encapsulant film as claimed in claim 2, wherein when the second film layer is a reflective film layer, the reflectivity of the first film layer is greater than the reflectivity of the second film layer.

6. The encapsulant film for photovoltaic module as claimed in claim 2, further comprising a third film layer, wherein the first and third film layers are disposed on two sides of the second film layer, and the third film layer is a reflective film layer or a transparent layer.

7. The encapsulant film for photovoltaic modules as claimed in claim 2, wherein the reflective film layer comprises a matrix resin and a reflective filler, and the reflective filler is selected from one or more of titanium dioxide, calcium carbonate, wollastonite, mica powder, magnesium hydroxide, aluminum hydroxide, composite titanium dioxide, talc, barium sulfate, glass beads and zinc sulfide.

8. The photovoltaic packaging film of claim 7, wherein the reflective filler of the first film layer is titanium dioxide.

9. The encapsulant film for photovoltaic module as claimed in claim 7, wherein the reflective filler has a particle size D50 ≤ 1 μm.

10. The encapsulant film for photovoltaic modules according to any one of claims 1 to 9, wherein the pre-crosslinking degree of the encapsulant film for photovoltaic modules is 0.5 to 70%.

11. The preparation method of the packaging adhesive film for the photovoltaic module as claimed in any one of claims 1 to 10, comprising the following steps: respectively and uniformly mixing the raw materials of each layer of the packaging adhesive film for the photovoltaic module, adding the raw materials into different extruders, injecting the raw materials into the same die head, extruding the raw materials by a T die head, rolling the raw materials and pre-crosslinking the raw materials to obtain the packaging adhesive film for the photovoltaic module.

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