A multi-layered light-converting encapsulant film and photovoltaic module

Abstract

This invention discloses a multilayered light conversion encapsulating film and a photovoltaic module. The film includes a stacked ultraviolet (UV) light blocking layer and a light conversion layer. The UV light blocking layer comprises a first matrix resin and UV light absorbing functional components dispersed therein, while the light conversion layer comprises a second matrix resin and a light conversion agent dispersed therein. The UV light blocking layer has a transmittance of less than 20% for UV light with wavelengths of 280-330 nm and a transmittance of more than 70% for UV light with wavelengths of 330-380 nm. This invention, through a discrete structural design of the spectrally selective UV light blocking layer and light conversion layer, effectively blocks high-energy UV light to protect the solar cells and encapsulation materials while maintaining high transmittance in the UV light conversion excitation band. This provides sufficient excitation light for the light conversion agent, improves the light conversion efficiency of the film and the initial power output of the photovoltaic module, and enhances its long-term weather resistance and reliability.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic encapsulation materials technology, and in particular to a multi-layered light conversion encapsulation film and a photovoltaic module. Background Technology

[0002] During long-term outdoor operation, the encapsulation materials and cell performance of photovoltaic modules are significantly affected by the ultraviolet region (280~400 nm) of the solar spectrum. Based on the different interaction mechanisms between photon energy and materials, this ultraviolet region can be divided into the high-energy ultraviolet band (280~330 nm, photon energy ≥3.76 eV) and the photoconversion-excited ultraviolet band (330~380 nm, photon energy 3.26~3.76 eV).

[0003] Among them, the photon energy in the high-energy ultraviolet band is significantly higher than the dissociation energy threshold of key chemical bonds in the passivation layer of photovoltaic cells and polymer encapsulation materials. For example, the Si in the passivation layer of high-efficiency photovoltaic cells (such as TOPCon) The H bond energy is approximately 3.5 eV (corresponding to a wavelength threshold of approximately 354 nm). The C bonds in encapsulating resins (such as EVA and POE) have a bond energy of approximately 3.5 eV. C key, C The dissociation energy thresholds of weak chemical bonds such as O bonds are concentrated in the range of 3.6~3.8 eV (corresponding to wavelength thresholds of approximately 326~344 nm). When photon energy exceeds these thresholds, it easily triggers chemical bond breakage, free radical generation, and chain oxidation reactions, leading to battery passivation failure, yellowing of the encapsulant film, and interface delamination, severely affecting the long-term reliability and efficiency stability of the module.

[0004] To address UV damage and improve the utilization rate of solar spectrum in photovoltaic modules, encapsulant materials with UV management functions have been developed in the photovoltaic encapsulation field. Existing technical solutions mainly fall into two categories: one involves simultaneously incorporating UV absorbers (or "blockers") and light conversion agents into a single encapsulant system, aiming to achieve the dual functions of UV shielding and spectral conversion; the other employs a multilayer structure, physically separating the UV blocker layer and the light conversion layer.

[0005] For example, existing technology (such as CN114958215A) discloses a multilayer UV light conversion encapsulating film, which includes a UV cutoff layer and a UV light conversion layer. This solution reduces direct interference between functional materials to some extent through layered design, aiming to block unconverted ultraviolet light to protect the battery.

[0006] However, such existing solutions still have significant shortcomings.

[0007] First, the "ultraviolet cutoff layer" used in these films typically aims to achieve broad-spectrum, high-intensity ultraviolet shielding (e.g., blocking all ultraviolet light below 380 nm), without considering the correlation between photon energy and chemical bond stability to selectively differentiate between the high-energy ultraviolet band (280–330 nm) and the photoconversion-excited ultraviolet band (330–380 nm). This indiscriminate absorption, while blocking high-energy ultraviolet light, also absorbs a large amount of light in the 330–380 nm band, which can effectively act as a light conversion agent and excite the light source. In effect, this severely inhibits the effective operation of the light conversion layer, leading to a decrease in the overall photoluminescence quantum yield (PLQY) of the film.

[0008] Secondly, in existing solutions, UV absorbers are typically dispersed directly in the resin matrix in powder form. Due to the lack of targeted pre-dispersion processes and solubilizing systems, high-melting-point solid absorbers are prone to recrystallization or micro-agglomeration during processing and cooling. The precipitated microcrystals not only produce light scattering effects, reducing the transmittance of the film in the visible and ultraviolet bands, but also migrate to the surface during long-term aging, leading to a decline in cutoff performance and deterioration in appearance.

[0009] Third, existing compounding schemes are mostly based on empirical selection and do not fully consider the synergistic and competitive relationships between the physicochemical properties of different UV absorbers (such as melting point, solubility parameters, and spectral tailing characteristics).

[0010] Therefore, there is an urgent need for a novel light conversion encapsulation film capable of precise spectral control. The ideal solution should efficiently shield the highly damaging, high-energy ultraviolet band to protect the battery and encapsulation materials, while maximizing the transmittance of the light conversion excitation ultraviolet band. This ensures the light conversion agent receives sufficient and effective excitation light, achieving a synergistic optimization of component reliability protection and photoelectric conversion efficiency improvement. Summary of the Invention

[0011] This invention addresses the problems in existing technologies where interference between ultraviolet absorbers and light conversion agents occurs due to blending or migration, and where conventional ultraviolet cutoff layers indiscriminately absorb both high-energy ultraviolet wavelengths and light-conversion-excited ultraviolet wavelengths, thus inhibiting effective excitation of the light conversion agent. The invention provides a multilayered light conversion encapsulation film. This film achieves efficient cutoff of high-energy ultraviolet light to protect the battery and encapsulation materials while maintaining high transmittance in the light-conversion-excited ultraviolet wavelengths, thereby ensuring the light conversion agent receives sufficient excitation light. The technical solution provided by this invention is as follows: On the one hand, the present invention provides a multilayer light conversion encapsulating film, comprising a stacked ultraviolet light blocking layer and a light conversion layer; The ultraviolet light blocking layer comprises a first matrix resin and an ultraviolet light absorbing functional component dispersed therein, and the light conversion layer comprises a second matrix resin and a light conversion agent dispersed therein; The ultraviolet cut-off layer has a transmittance of less than 20% for ultraviolet light with a wavelength of 280~330nm and a transmittance of more than 70% for ultraviolet light with a wavelength of 330~380nm.

[0012] In one specific embodiment, the ultraviolet light absorbing functional component comprises a premix of an ultraviolet absorber and a co-crosslinking agent A; the ultraviolet absorber comprises at least two of ethylhexyl triazine ketone, ethylhexyl salicylate, diethylhexylbutamidotriazine ketone, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide; the co-crosslinking agent A comprises at least two of 4-acryloylmorpholine, EO(3)trimethylolpropane triacrylate, 3-(propoxy)propanetriol triacrylate, triallyl isocyanurate, and tetramethyltetravinylcyclotetrasiloxane; wherein, based on the total mass of the ultraviolet light absorbing functional component, the mass percentage of the ultraviolet absorber is 10% to 25%, and the mass percentage of the co-crosslinking agent A is 75% to 90%.

[0013] In one specific embodiment, the ultraviolet absorber comprises diethylhexylbutamidotriazine ketone, and also comprises at least one of ethylhexyl salicylate, ethylhexyltriazine ketone, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide; Among them, based on the total mass of the ultraviolet absorber, the mass percentage of diethylhexylbutamidotriazine is 5% to 35%.

[0014] In one specific embodiment, the ultraviolet absorber comprises diethylhexylbutamidotriazinone and ethylhexyl salicylate, and also comprises at least one of ethylhexyltriazinone and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide; Based on the total mass of the ultraviolet absorber, the mass percentage of diethylhexylbutamidotriazine ketone is 10% to 30%, and the mass percentage of ethylhexyl salicylate is 50% to 90%.

[0015] In one specific embodiment, the ultraviolet absorber is composed of diethylhexylbutamidotriazinone, ethylhexyl salicylate, ethylhexyltriazinone, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide; Based on the total mass of the ultraviolet absorber, the mass percentage of ethylhexyl salicylate is 50%~80%, and the mass percentage of N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide is 1%~10%. The remaining amount of ultraviolet absorber is ethylhexyl triazine ketone and diethylhexylbutamidotriazine ketone, with a mass ratio of 1:(2~5).

[0016] In one specific embodiment, the ultraviolet absorber is composed of diethylhexylbutamidotriazinone, ethylhexyl salicylate, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide; Based on the total mass of the ultraviolet absorber, the mass percentage of N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide is 1% to 10%. The remaining amount of ultraviolet absorber is diethylhexylbutamidotriazine ketone and ethylhexyl salicylate, with a mass ratio of 1:(1~3).

[0017] In one specific implementation, the co-crosslinking agent A is composed of 4-acryloylmorpholine and EO(3)trimethylolpropane triacrylate; The mass ratio of 4-acryloylmorpholine to EO(3)trimethylolpropane triacrylate is 1:(2~5).

[0018] In one specific implementation, the thickness ratio of the ultraviolet light cutoff layer to the light conversion layer is 1:(0.2~4.0).

[0019] In one specific embodiment, the ultraviolet light blocking layer comprises the following components, by weight: First matrix resin: 100 parts; Ultraviolet absorber: 0.05~0.5 parts; Crosslinking agent A: 0.4~1.2 parts; Crosslinking agent: 0.3~1.0 parts; Coupling agent: 0.1~0.6 parts; Light stabilizer: 0.05~0.3 parts; Antioxidant: 0.01~0.2 parts.

[0020] In one specific embodiment, the light conversion layer comprises the following components, by weight: Second matrix resin: 100 parts; Light conversion agent: 0.01~0.5 parts; Crosslinking agent: 0.3~1.0 parts; Crosslinking agent B: 0.4~1.2 parts; Coupling agent: 0.1~0.6 parts; Light stabilizer: 0.05~0.3 parts; Antioxidant: 0.01~0.2 parts.

[0021] In one specific embodiment, the first matrix resin is an ethylene-vinyl acetate copolymer, wherein the vinyl acetate content is 26-35 wt% and the melt index is 4-30 g / 10 min.

[0022] In one specific embodiment, the second matrix resin is an ethylene-α-olefin copolymer or an ethylene-vinyl acetate copolymer; The ethylene-α-olefin copolymer is selected from at least one of ethylene-1-butene copolymer, ethylene-1-octene copolymer, and ethylene-propylene-1-hexene copolymer.

[0023] In one specific embodiment, the crosslinking agent is selected from at least one of 1,1-di-tert-butylperoxide-3,3,5-trimethylcyclohexane, tert-butylperoxide-3,5,5-trimethylhexanoate, and benzoyl peroxide.

[0024] In one specific embodiment, the co-crosslinking agent B is selected from at least one of trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, triallyl isocyanurate, tetramethyltetravinylcyclotetrasiloxane, 4-acryloylmorpholine, 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, neopentyl glycol diacrylate, polyethylene glycol 200 diacrylate, EO(3)trimethylolpropane triacrylate, and 3(propoxy)propanetriol triacrylate.

[0025] In one specific embodiment, the coupling agent is a silane coupling agent selected from at least one of vinyltrimethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, aminopropyltrimethoxysilane, bis(3-triethoxysilylpropyl)amine, N,N-dimethyl-3-aminopropyltrimethoxysilane, 1,3,5-tris(trimethoxysilylpropyl)isocyanate, n-dodecyltrimethoxysilane, n-octyltrimethoxysilane, and cyclohexyltrimethoxysilane.

[0026] In one specific embodiment, the light stabilizer is selected from at least one of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, hexadecyl 3,5-di-tert-butyl-4-hydroxybenzoate, (1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, mono(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, and poly{[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidinyl)imino]}.

[0027] In one specific embodiment, the antioxidant is selected from at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3,5-di-tert-butyl-4-hydroxybenzyl diethylphosphonate, and 4,4'-p-isopropyl diphenyl C12-15-ol phosphite.

[0028] On the other hand, the present invention also provides a method for preparing a multilayer optical conversion encapsulating film, the method comprising the following steps: The first matrix resin is mixed with the ultraviolet light absorption functional component to obtain the ultraviolet light blocking layer melt; The second matrix resin is mixed with a light conversion agent to obtain a light conversion layer melt; The ultraviolet light cutoff layer melt and the light conversion layer melt are simultaneously extruded through a co-extrusion die and cooled to solidify, resulting in a multi-layered light conversion encapsulation film.

[0029] In one specific implementation scheme, the method for preparing the ultraviolet light absorbing functional component includes: The ultraviolet absorber is mixed with a portion of the crosslinking agent A to obtain a mixture; Heat the mixture to 50-60℃ and perform the first stirring. Then another portion of crosslinking agent A is added and the temperature is raised to 90~100℃ for a second stirring to form a UV absorption functional component.

[0030] By adopting the above technical solution, the multilayer light conversion encapsulating film and photovoltaic module provided by the present invention have the following beneficial effects: 1. This invention, through a specific compounded ultraviolet light absorption functional component and a multilayer discrete structure design, enables the ultraviolet light cutoff layer to precisely achieve efficient cutoff (transmittance <20%) for the high-energy ultraviolet band of 280~330nm and efficient transmission (transmittance >70%) for the light-converting excitation ultraviolet band of 330~380nm. This spectral selectivity modulation overcomes the technical limitations of conventional ultraviolet cutoff layers' broadband indiscriminate absorption. While effectively blocking high-energy ultraviolet light that easily causes chemical bond breakage to protect the battery passivation layer and encapsulation materials, it maximizes the retention of the 330~380nm band, which can be used as a light conversion agent to effectively excite the light source, thus fundamentally solving the technical antagonism between ultraviolet protection and light conversion efficiency.

[0031] 2. Based on the aforementioned high selective transmittance, the excitation light flux transmitted to the light conversion layer in the 330-380nm range is significantly increased, resulting in an effective photoluminescence quantum yield (PLQY) of over 90% for the light conversion agent in the film under 350nm excitation. When encapsulated into a photovoltaic module, compared to a fully shielded solution using conventional broadband absorbers, the visible light generated by the fully excited and down-converted light effectively compensates for energy loss in the ultraviolet band, significantly improving the initial output power of the module. This invention achieves a substantial breakthrough in the photoelectric conversion efficiency of the module through precise spectral matching and efficient energy transfer, while ensuring ultraviolet protection.

[0032] 3. This invention utilizes a high-ratio premixing of crosslinking agent A and ultraviolet absorber, along with a gradient heating process, to effectively suppress the migration and microcrystal precipitation of high-melting-point solid absorbers by leveraging the solvation and chemical anchoring effects of crosslinking agent A. This avoids the attenuation of transmittance in the 330-380nm wavelength band due to light scattering, ensuring the long-term stability of the spectral selectivity transmittance index. Regarding the long-term reliability of the module, the film of this application maintains a power decay rate within a reasonable range after undergoing rigorous ultraviolet aging, significantly outperforming solutions without a cutoff layer. More importantly, this formulation system successfully overcomes the technical bottlenecks of easy additive precipitation and cutoff performance degradation over service time in traditional highly dispersed systems without sacrificing photoelectric gain, achieving synergistic optimization of high initial photoelectric conversion efficiency and long-term operational reliability. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the two-layer light conversion encapsulation film provided in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the three-layer light conversion encapsulation film provided in Embodiment 7 of the present invention; Figure 3 This is a microscope image of the two-layer light conversion encapsulation film provided in Embodiment 1 of the present invention; Figure 4 This is a microscope image of the three-layer light conversion encapsulation film provided in Embodiment 7 of the present invention.

[0035] The following is supplementary explanation of the attached figures: 1-Ultraviolet light cutoff layer; 2-Light conversion layer. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. In the description of the invention, it should be understood that the terms "upper," "lower," "top," "bottom," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein.

[0038] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included. For example, a specified range from “1 to 10” should be considered to include any and all subranges between the minimum value 1 and the maximum value 10. Exemplary subranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0039] Please see Figure 1 , Figure 2This invention provides a multilayer light conversion encapsulating film, comprising a stacked ultraviolet (UV) light blocking layer 1 and a light conversion layer 2. The UV light blocking layer 1 can be disposed on the side closer to the solar cell or on the side farther from the solar cell. In specific embodiments, the film can be a two-layer structure comprising only one UV light blocking layer 1 and one light conversion layer 2, or a three-layer structure with UV light blocking layers 1 disposed on both sides of the light conversion layer 2.

[0040] In one specific embodiment, the ultraviolet (UV) light blocking layer comprises a first matrix resin and a UV-absorbing functional component dispersed therein, and the light conversion layer comprises a second matrix resin and a light conversion agent dispersed therein. The UV light blocking layer has a transmittance of less than 20% for UV light with wavelengths of 280–330 nm and a transmittance of more than 70% for UV light with wavelengths of 330–380 nm. It should be noted that the transmittance of the above-mentioned UV light blocking layer was obtained under independent testing conditions, i.e., it was prepared and tested separately without the light conversion layer.

[0041] It should be noted that the spectral cutoff boundary of this invention is set at 330 nm instead of the conventional 320 nm. This is based on the matching relationship between photon energy and the stability of chemical bonds in the material, as well as the molecular absorption characteristics of the UV absorber. On the one hand, 330 nm corresponds to a photon energy of approximately 3.76 eV. This energy threshold is higher than the dissociation energy of weak chemical bonds such as CO and CN bonds in the encapsulation material. Extending the cutoff boundary to 330 nm can more comprehensively eliminate high-energy photons that cause yellowing and delamination of the film. On the other hand, when this invention selects triazinone-based UV absorbers (such as ethylhexyltriazinone and diethylhexylbutamidotriazinone), they typically have a steep absorption edge, with the effective absorption tail usually extending to around 325-330 nm. Within this tail region, the molar extinction coefficient of the absorber remains relatively high. By incorporating the absorption tail region (320nm to 330nm) into the ultraviolet cutoff band, it is ensured that the absorber maintains a high extinction coefficient throughout the entire 280nm to 330nm band, and the second ultraviolet band above 330nm is completely within the low absorption window of the absorber. Thus, high transmittance in this band is naturally achieved without sacrificing protective performance.

[0042] Furthermore, sacrificing the 320nm to 330nm wavelength band for system stability is the optimal choice in terms of overall efficiency. Although a wider transmission band theoretically provides more excitation light, the light conversion agent selected in this invention typically has its absorption spectrum peak in the 340nm to 360nm range, with a relatively low molar absorptivity in the 320nm to 330nm band. This means that even if photons in this band pass through the cutoff layer, the efficiency of absorption by the light conversion agent and conversion into visible light is relatively low (relatively low quantum yield). Conversely, photons in this band possess high energy sufficient to damage the encapsulation material. Therefore, classifying the 320nm to 330nm band as the cutoff band, while slightly reducing the total energy input of the excitation light, avoids damage to the encapsulation material from inefficient excitation light and significantly reduces the risk of quenching of the light conversion agent due to aging of the surrounding matrix.

[0043] Setting the cutoff upper limit to 330nm can fully utilize the molecular characteristics of the absorber, ensuring true low transmittance in the first ultraviolet band, while avoiding including the absorption tail region of the absorber in the second ultraviolet band, thus ensuring true high transmittance in the second ultraviolet band and avoiding the problem of insufficient transmittance in the 320-330nm band caused by absorber tailing in the conventional 320nm cutoff scheme.

[0044] In one specific embodiment, the ultraviolet light absorbing functional component comprises a premix of an ultraviolet absorber and a co-crosslinking agent A. The ultraviolet absorber comprises at least two of ethylhexyl triazine ketone, ethylhexyl salicylate, diethylhexylbutamidotriazine ketone, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide. The co-crosslinking agent A comprises at least two of 4-acryloylmorpholine, EO(3)trimethylolpropane triacrylate, 3-(propoxy)propanetriol triacrylate, triallyl isocyanurate, and tetramethyltetravinylcyclotetrasiloxane.

[0045] Based on the total mass of the ultraviolet light absorbing functional components, the mass percentage of the ultraviolet absorber is 10-25%, which can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or any value between them. The mass percentage of the crosslinking agent A is 75-90%, which can be 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, or any value between them.

[0046] Understandably, in the ultraviolet light absorbing functional components of this invention, the ultraviolet absorber comprises at least two of four specific components, and the crosslinking agent A comprises at least two of five specific components. It is important to emphasize that the core technical problem this invention aims to solve is to achieve high selective transmittance of the ultraviolet light cutoff layer, i.e., efficient cutoff (transmittance <20%) for the 280–330 nm high-energy ultraviolet band, while simultaneously achieving efficient transmission (transmittance >70%) for the 330–380 nm light-conversion-excited ultraviolet band. This technical indicator directly relates to the initial power output and photoluminescence quantum yield of photovoltaic modules, both of which are core standards determining the commercial value of photovoltaic modules. Regarding aging rate, this application only needs to meet industry standards and be not significantly different from existing technologies; there is no need to pursue long-term weather resistance exceeding that of fully shielded solutions.

[0047] Through extensive creative work and screening experiments, this invention has discovered that achieving the aforementioned high selective transmittance (280-330nm transmittance <20% and 330-380nm transmittance >70%) requires more than just any UV absorber. Existing technologies typically list a large number of common UV absorbers (such as benzotriazoles and benzophenones) for those skilled in the art to choose from or combine, but this general approach has its drawbacks. Specifically, existing technologies employ a full shielding strategy (covering all ultraviolet light below 380nm), which does not require simultaneous consideration of shielding in the 280-330nm band and high transmittance in the 330-380nm band. Therefore, their technical solutions are fundamentally different from the goal of pursuing high selective transmittance in this application. Existing technologies do not recognize that solubility and precipitation issues negatively impact high selective transmittance. Ultraviolet absorbers are often accompanied by uneven dispersion and precipitation problems. If uneven dispersion leads to microcrystal precipitation, the transmittance in the 330-380nm band will also fail to meet the requirement of >70% due to light scattering effects.

[0048] Through systematic screening and compounding experiments, this invention creatively discovered that, among common ultraviolet absorbers, only a specific combination of four components—ethylhexyl triazine, ethylhexyl salicylate, diethylhexylbutamidotriazine, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide—can achieve both high cutoff efficiency in the 280–330 nm wavelength range and high transmittance in the 330–380 nm wavelength range. The selection of these four absorbers was not random or conventional, but rather based on a comprehensive consideration of their molecular absorption spectral characteristics, solubility parameter matching, and synergistic crystallization behavior.

[0049] The combination of specific UV absorbers achieves precise control of the spectral edge and synergistic improvement of solubility. The four UV absorbers selected in this invention possess unique complementary spectral characteristics: ethylhexyl triazine and diethylhexylbutamidotriazine have extremely high molar extinction coefficients in the 280–320 nm wavelength range, ensuring transmittance <20% in this band; ethylhexyl salicylate, being liquid, has a steep absorption edge and rapidly cuts off above 320 nm, helping to reduce parasitic absorption in the 330–380 nm band; while oxamide absorbers exhibit some spectral tailing, their excellent migration resistance allows them to synergistically maintain long-term stability with other components. If only a single UV absorber is used, its absorption spectrum typically exhibits a fixed tailing characteristic, making it difficult to form a cutoff edge at 330 nm. For example, while some highly efficient absorbers exhibit strong absorption in the 280–320 nm range, their absorption tail may extend to 340 nm, resulting in a transmittance of less than 70% in the 330–380 nm band. Conversely, some high-transmittance absorbers may have insufficient extinction coefficients in the 280–330 nm band, leading to a cutoff rate of less than 20%. This invention, by compounding at least two of the four specific components mentioned above, utilizes the complementary absorption spectra of different molecular structures to effectively balance the cutoff capabilities of different ultraviolet wavelengths. This creates a superimposed high absorption region in the 280–330 nm band, while simultaneously achieving rapid cutoff above 330 nm, thus precisely matching the spectral boundary at 330 nm. Furthermore, different ultraviolet absorbers exhibit varying solubility parameters. To achieve a cutoff effect of less than 20% transmittance in the 280–330 nm band, a sufficient concentration of the absorber in the matrix must be ensured. However, if only a single solid absorbent is used, when its concentration approaches or exceeds its solubility limit in the co-crosslinking agent A and the resin matrix, the supersaturated absorbent molecules easily cross the nucleation energy barrier and recrystallize during the cooling process after film extrusion. According to Mie scattering theory, when the absorbent precipitates and forms microcrystals, these microcrystals become light scattering centers. Although the absorbent molecules themselves have weak intrinsic absorption in the 330-380 nm wavelength range, the scattering effect generated by the microcrystals will indiscriminately attenuate the light intensity in this wavelength range, resulting in a significant decrease in transmittance, which may not meet the >70% requirement of this invention. By introducing another absorbent, a co-solvent effect or eutectic effect can be generated, which disrupts the crystal lattice energy of the single component and significantly improves the apparent solubility of the mixed system in the co-crosslinking agent A. This synergistic effect allows the absorbent to remain in a supercooled solution state with molecular-level dispersion after processing and cooling, avoiding the formation of microcrystals. Eliminating microcrystalline scattering centers means that most photons in the 330-380nm wavelength band can pass through the cutoff layer to reach the light conversion layer, thus ensuring a transmittance greater than 70%. At the same time, molecular-level dispersion also ensures the uniformity of absorber distribution in the 280-330nm wavelength band, avoiding absorption blind zones caused by local agglomeration, and ensuring that the transmittance in this band is consistently less than 20%.

[0050] The formulation of co-crosslinking agent A achieves a balance between polarity matching and functionality. The five co-crosslinking agents selected in this invention (4-acryloylmorpholine, EO(3)trimethylolpropane triacrylate, 3-(propoxy)propanetriol triacrylate, triallyl isocyanurate, and tetramethyltetravinylcyclotetrasiloxane) have all been screened, and their common characteristic is the presence of strongly polar groups and unsaturated double bonds, enabling them to form specific intermolecular interactions with the aforementioned four UV absorbers. In this application, co-crosslinking agent A serves not only as a crosslinking monomer but also as a solvent matrix for the UV absorber. Since the UV absorber employs at least two compounding systems, its overall polarity characteristics become complex. Using only a single co-crosslinking agent A may result in insufficient polarity matching, making it impossible to simultaneously dissolve multiple absorbers, or the viscosity may be too high / too low, affecting the dispersion effect. This invention, by compounding at least two of the following, including 4-acryloylmorpholine and EO(3)trimethylolpropane triacrylate, can construct a solvent environment with a wider polarity range. For example, 4-acryloylmorpholine has good wettability and low viscosity, which facilitates initial penetration; while multifunctional acrylates have stronger polarity and anchoring ability. The synergistic effect of these two ensures that the compounded UV absorber molecules can be fully solubilized, forming a homogeneous and stable premix. This homogeneous state helps improve the transmittance in the 330–380 nm wavelength range. If the co-crosslinking agent A is a single component, some absorbers may not dissolve sufficiently, forming nanoscale aggregates during subsequent cooling or aging. According to Mie scattering theory, these aggregates will significantly scatter photons in the 330–380 nm wavelength range, causing the transmittance index to fail.

[0051] Understandably, in the ultraviolet light absorbing functional component, the mass percentage of co-crosslinking agent A is controlled to be 75-90%. It should be noted that this percentage refers to the relative content of co-crosslinking agent A in the ultraviolet light absorbing functional component (i.e., the premixture of ultraviolet absorber and co-crosslinking agent A), rather than the absolute amount added in the entire film formulation. A key innovation of this invention lies in pre-constructing a premixed system with a high proportion of co-crosslinking agent A and ultraviolet absorber, using co-crosslinking agent A as a solvent matrix to solve the dissolution and dispersion problems of ultraviolet absorbers. Existing technologies typically directly physical blend ultraviolet absorber powder into the resin matrix without considering its solubility limit and dispersion uniformity in the matrix.

[0052] A high proportion of co-crosslinking agent A helps maintain the metastable state of the supercooled solution during the premixing stage. The core UV absorbers selected in this invention (such as diethylhexylbutamidotriazinone, ethylhexyltriazinone, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide) are mostly high-melting-point solids (melting point ≥ 92℃). During film extrusion, the extruder barrel temperature is typically controlled within the range of 50~90℃, which is lower than or close to the melting point of some UV absorbers. If powder is added directly, it is difficult to completely melt and dissolve in the resin matrix. This invention introduces a high proportion (75~90%) of co-crosslinking agent A as a solvent matrix to form a premix with the absorber, and heats it to 90~100℃ during the premixing stage. Utilizing the high matching of solubility parameters between co-crosslinking agent A molecules and absorber molecules, the apparent solubility of the absorber in the system is significantly improved, allowing it to achieve molecular-level dissolution at temperatures below its own melting point. When the content of co-crosslinking agent A is below 75%, the solvated molecules in the system are insufficient to accommodate the high concentration of absorber molecules, resulting in a thermodynamically unstable state at room temperature and easy phase separation. Conversely, when the content is above 90%, the premix itself has excessively low viscosity and high polarity, leading to decreased compatibility with the first matrix resin and potentially weakened interlayer adhesion. Therefore, 75-90% helps maintain homogeneous dissolution of the premix at processing temperatures and a metastable supercooled state at room temperature. Suppressing microcrystal precipitation helps improve the transmittance in the 330-380 nm wavelength range. Once the ultraviolet absorber precipitates and forms microcrystals, it will strongly scatter incident light according to the Mie scattering theory. Since the 280-330 nm wavelength range is intrinsically absorbed by the absorber molecules, the scattering effect is mainly manifested as a significant decrease in transmittance in the 330-380 nm wavelength range. This invention achieves molecular-level dispersion through a high proportion of co-crosslinking agent A, eliminating microcrystal scattering centers and ensuring that most photons in the 330-380 nm wavelength range can pass through the cutoff layer to reach the light conversion layer. If the proportion of co-crosslinker A is insufficient, precipitation will occur, and even if the total amount of absorbent remains unchanged, the transmittance in the 330-380 nm wavelength range will decrease due to scattering losses. The synergistic effect between specific functional groups enhances dispersion stability. Co-crosslinker A molecules contain abundant polar groups (such as the morpholine ring carbonyl group in 4-acryloylmorpholine, the ester group in acrylates, and the oxygen atom in siloxanes), which can form intermolecular polar interactions with the triazine ring in triazinone absorbent molecules or intermolecular hydrogen bonds with the amide group in oxalamide. This specific intermolecular interaction significantly reduces the lattice energy of the absorbent molecules, hindering their orderly arrangement and stacking during cooling. A high proportion of co-crosslinker A ensures that the absorbent molecules are surrounded by polar solvent molecules, effectively forming a solvation effect and further inhibiting the nucleation process.

[0053] Furthermore, co-crosslinking agent A also plays a role in chemical anchoring. During the film lamination and curing stage, the unsaturated double bonds in co-crosslinking agent A participate in the free radical polymerization reaction, becoming part of the crosslinked polymer network. Since the absorbent molecules are tightly bound to co-crosslinking agent A through the aforementioned polar interactions, as the crosslinked network forms, the absorbent molecules are physically locked within the network mesh, forming a semi-interpenetrating or anchored structure. This structure effectively limits the migration ability of absorbent molecules during long-term thermo-oxidative aging, preventing their migration and accumulation on the film surface. In contrast, if the content of co-crosslinking agent A is too low, a dense anchored network cannot be formed, and the absorbent is prone to migration and precipitation under long-term ultraviolet irradiation, leading to a decline in cutoff performance and surface contamination.

[0054] Therefore, in this invention, the mass percentage of crosslinking agent A in the ultraviolet light absorption functional component is controlled to be 75-90%. This proportion not only ensures the dissolution and molecular-level dispersion of the ultraviolet absorber during processing, eliminates the risk of light scattering, and guarantees high transmittance in the 330-380nm wavelength band, but also achieves long-term anchoring of the absorber through a chemical crosslinking network, solving the technical bottleneck of easy precipitation and poor weather resistance of absorbers in traditional physical blending schemes.

[0055] In one specific embodiment, the ultraviolet absorber comprises diethylhexylbutamidotriazine ketone, and also comprises at least one of ethylhexyl salicylate, ethylhexyltriazine ketone, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide; Based on the total mass of the ultraviolet absorber, the mass percentage of diethylhexylbutyramidotriazinone is 5% to 35%, which can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, or any value between them.

[0056] As a preferred embodiment, this invention selects diethylhexylbutamidotriazine ketone (HEB) as the core component of the ultraviolet absorber, and coordinates it with other absorbers and a high proportion of co-crosslinking agent A to solve the problems of dispersion, stability, and efficient cutoff of high-melting-point solid ultraviolet absorbers. This invention has found that to achieve high selectivity transmittance indicators of less than 20% in the 280-330 nm wavelength range and greater than 70% in the 330-380 nm wavelength range, not only are specific spectral characteristics required for the absorber, but it is also necessary for it to maintain a molecular-level dispersion in the matrix for a long period of time. HEB, due to its unique molecular structure, is more conducive to achieving this balance.

[0057] HEB helps improve the stability of high-efficiency cutoff performance in the 280-330nm wavelength range. The HEB molecule contains amide groups (-CONH-) in its side chains, which, compared to common triazinone or salicylate absorbers, allow for the formation of a stronger hydrogen bond network between molecules, resulting in higher lattice energy and better migration resistance. This makes HEB less prone to photolysis or volatilization loss under long-term UV irradiation and high-temperature, high-humidity environments, effectively maintaining the high-efficiency cutoff performance of the UV cutoff layer in the 280-330nm wavelength range (transmittance <20%). If the system does not contain HEB or its content is too low, after long-term aging, the effective concentration may decrease due to absorber degradation or migration, easily increasing the transmittance in the 280-330nm wavelength range and exceeding the 20% limit, leading to protection failure. Therefore, the presence of HEB helps ensure long-term reliable cutoff function. The polarity matching between HEB and co-crosslinking agent A achieves chemical anchoring, helping to maintain high transmittance in the 330-380nm wavelength range. The amide groups in HEB molecules and the polar groups (such as the morpholine ring carbonyl group) in co-crosslinking agent A (such as 4-acryloylmorpholine) exhibit extremely high solubility parameter matching. During the premixing stage, they form strong dipole-dipole interactions or hydrogen-bonded complexes. During the curing stage, co-crosslinking agent A participates in the polymerization reaction to form a crosslinking network, anchoring HEB molecules within the network through chemical bonds. This anchoring structure effectively limits the migration ability of HEB molecules during long-term thermo-oxidative aging, preventing their migration and accumulation on the film surface or recrystallization due to migration. If the absorbent migrates or recrystallizes, microcrystalline scattering centers will form. According to Mie scattering theory, this will significantly attenuate the light intensity in the 330–380 nm wavelength band, causing the transmittance in this band to drop below 70%. Therefore, the stable dispersion of HEB helps to ensure the long-term maintenance of high transmittance in the 330–380 nm wavelength band.

[0058] Furthermore, rationally controlling the HEB content (5%~35%) helps balance the solubility limit and performance requirements. This invention has found that controlling the HEB content within a specific range helps to both leverage its performance advantages and avoid its physical defects affecting the selected transmittance. If the HEB content is too low, the proportion of highly stable components in the system is insufficient, failing to form an effective performance anchoring network. This may lead to a decrease in the migration resistance and cutoff performance of the UV cutoff layer after long-term aging, failing to fully utilize HEB as a core component and making it difficult to maintain long-term stability of transmittance in the 280~330nm wavelength range. If the HEB content is higher than 35%, although stability improves, HEB, as a high-melting-point solid powder, has an increased solubility load in the co-crosslinking agent A and liquid components. This may exceed the solubility limit, easily inducing supersaturated precipitation and forming microcrystals during processing and cooling. The light scattering effect generated by these microcrystals may lead to a decrease in transmittance in the 330~380nm wavelength range. Therefore, controlling the upper limit of HEB helps HEB to completely dissolve in the system and maintain molecular-level dispersion, avoiding physical scattering losses. The synergistic effect of HEB with other components further optimizes selective transmittance. In addition to HEB, other components (ethylhexyl salicylate, ethylhexyl triazine, and oxalamide) play auxiliary and synergistic roles. For example, liquid ethylhexyl salicylate acts as a dispersion medium, wetting HEB solid particles, reducing their surface energy, and assisting HEB in better dissolving in co-crosslinking agent A; ethylhexyl triazine can form a eutectic mixture with HEB, further suppressing HEB's crystallization tendency; and oxalamide can enhance the hydrogen bond network, improving overall migration resistance. This compound system, with HEB as the core and other components as auxiliary components, collectively solves the problem that a single component cannot simultaneously achieve high cutoff efficiency, high dispersion stability, and high transmittance, thus more effectively achieving the technical indicators of high efficiency cutoff in the 280–330 nm wavelength range and high transmittance in the 330–380 nm wavelength range.

[0059] In summary, this invention, based on intermolecular interactions, crystal growth kinetics, and photochemical stability, controls the mass percentage of diethylhexylbutyramidotriazinone to be 5%–35%. This approach, through a reasonable amount of HEB added, ensures both the long-term stability of the cutoff function in the 280–330 nm wavelength range and avoids light scattering caused by microcrystal precipitation. This achieves a balance between high transmittance and long-term weather resistance in the 330–380 nm wavelength range, more effectively realizing the technical objective of high selective transmittance of this invention.

[0060] In one specific embodiment, the ultraviolet absorber comprises diethylhexylbutamidotriazinone and ethylhexyl salicylate, and also comprises at least one of ethylhexyltriazinone and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide; Based on the total mass of the ultraviolet absorber, the mass percentage of diethylhexylbutyramidotriazine ketone is 10% to 30%, which can be 10%, 15%, 20%, 25%, 30%, or any value between them.

[0061] The mass percentage of ethylhexyl salicylate is 50% to 90%, and can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, and any value between them.

[0062] As a preferred embodiment, this invention selects diethylhexylbutamidotriazine (HEB) and ethylhexyl salicylate (EHS) as the core binary components of the ultraviolet absorber, and works in conjunction with other optional components to solve the problems of dispersion, stability and efficient cutoff of high-melting-point solid ultraviolet absorbers.

[0063] A high EHS content helps improve transmittance in the 330–380 nm wavelength range. Controlling the EHS content within the range of 50%–90% provides sufficient liquid solvent matrix to completely dissolve HEB and other optional solid components. The ester structure of EHS has good compatibility with triazine ketone molecules, significantly reducing the surface energy of the solid absorber. If the EHS content is too low, the liquid solvent volume is insufficient, which may make it difficult to completely encapsulate and dissolve the high-melting-point HEB particles, leading to uneven dispersion and microcrystal precipitation, resulting in Mie scattering. If the EHS content is too high, although the dispersibility is excellent, the proportion of the highly efficient cutoff component (HEB) in the system is excessively diluted, which may affect the stability of the UV absorber's cutoff performance. Furthermore, EHS itself has weak photodegradation stability, and excessively high content will affect the long-term weather resistance of the system. Therefore, a range of 50%–90% helps to achieve a balance between complete dissolution and maintaining efficient cutoff.

[0064] Furthermore, the synergistic effect of HEB and EHS helps solve the technical problem of high selective transmittance. By controlling HEB at 10%~30% and EHS at 50%~90%, this invention ensures that the UV absorber remains in a molecularly dispersed state in the co-crosslinking agent A system. This state eliminates the risk of microcrystalline scattering and, physically, facilitates the transmission of photons in the 330~380nm wavelength band (transmittance >70%). Simultaneously, sufficient HEB ensures adequate optical density in the 280~330nm wavelength band for efficient cutoff (transmittance <20%). Based on this, the addition of optional components can further fine-tune the spectral edges or enhance stability. In addition, the synergistic effect of HEB and EHS also solves the solubility problem of other introduced components. After establishing the core ratio of HEB and EHS, this invention optionally introduces ethylhexyltriazinone (EHT) or N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide. Since HEB and EHS have established a stable dissolution environment, EHT, as a structurally similar triazine ketone, can easily integrate into the system and further inhibit HEB crystallization through lattice interlocking. Meanwhile, oxalamide, a relatively poorly soluble component, can form polar interactions between its amide groups and the ester groups of EHS under sufficient EHS solubilization, significantly lowering its apparent melting point and allowing it to exist stably in the system without precipitation. The specific ratio of HEB to EHS further facilitates the dissolution of other components. Within this framework, phase separation and scattering of the overall system due to insufficient solubility of EHT or oxalamide can be avoided.

[0065] In summary, based on solubility balance, crystallization kinetics, and spectral selectivity requirements, this invention controls the mass percentage of diethylhexylbutamidotriazine ketone to be 10%–30% and the mass percentage of ethylhexyl salicylate to be 50%–90%. This approach establishes the core synergistic role of HEB and EHS, contributing to the efficient cutoff and long-term stability of the ultraviolet light cutoff layer in the 280–330 nm wavelength range. Furthermore, the ample liquid solvent environment eliminates microcrystalline scattering, thereby improving transmittance in the 330–380 nm wavelength range. It also provides a stable dissolution platform for the optional addition of other functional components, ultimately achieving a balance between initial component efficiency and long-term reliability.

[0066] In one specific embodiment, the ultraviolet absorber is composed of diethylhexylbutamidotriazinone, ethylhexyl salicylate, ethylhexyltriazinone, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide; Based on the total mass of the ultraviolet absorber, the mass percentage of ethylhexyl salicylate is 50% to 80%, which can be 50%, 55%, 60%, 65%, 70%, 75%, 80% and any value between them; the mass percentage of N-(2-ethoxyphenyl)-N´-(2-ethylphenyl)-oxalamide is 1% to 10%, which can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% and any value between them. The balance of the ultraviolet absorber is ethylhexyl triazine ketone and diethylhexylbutamidotriazine ketone, with a mass ratio of 1:(2~5), which can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5 and any value between them. More preferably, the mass ratio of ethylhexyl triazine ketone and diethylhexylbutamidotriazine ketone is 1:3.

[0067] As a preferred embodiment, the present invention further synergistically optimizes the solubility stability and spectral selectivity of a system containing all four ultraviolet absorbers by specifically controlling the contents of ethylhexyl salicylate and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide, as well as the mass ratio of ethylhexyl triazine ketone (EHT) to diethylhexylbutamidotriazine ketone (HEB).

[0068] Controlling the oxalamide content balances stability gains with the risk of precipitation. N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide exhibits excellent migration resistance and thermal stability, and its dense intermolecular hydrogen bond network helps improve the long-term weather resistance of the UV cutoff layer. However, oxalamide has a relatively high melting point and limited solubility in solvent systems composed of co-crosslinking agent A and EHS. If the oxalamide content is too high, it may preferentially precipitate due to supersaturation during processing and cooling, forming microcrystalline scattering centers, which in turn affects the high transmittance in the 330-380 nm wavelength range. Therefore, this invention preferably controls its content in a low range of 1% to 10%. Within this range, oxalamide can both play its role as a stability anchor and avoid exceeding the solubility limit due to excessive addition, thereby improving long-term reliability while reducing the potential negative impact on spectral transmittance.

[0069] The specific ratio of HEB to EHT achieves a balance between solubility and synergistic effect. In the four-component system of this invention, HEB and EHT are the main solid UV absorbers, and their ratio is crucial to the homogeneity and stability of the system. Understandably, the melting point of HEB (approximately 92-102°C) is lower than that of EHT (approximately 128-132°C), meaning that under the same processing temperature and solvent conditions, HEB has better solubility and compatibility than EHT. Therefore, in this preferred embodiment, controlling the HEB content to be higher than that of EHT helps ensure that the bulk of the solid absorbent can be fully dissolved in EHS and crosslinking agent A, fundamentally reducing the risk of microcrystal precipitation due to the poor solubility of the solid components, thereby ensuring high transmittance in the 330-380 nm wavelength range. Although EHT has relatively weak solubility, its addition also has specific effects. On the one hand, although EHT and HEB have similar core frameworks, their side-chain functional groups differ. An appropriate amount of EHT molecules can embed into the crystal growth points of HEB, disrupting the ordered stacking that may form between HEB molecules, generating a lattice doping effect, and further suppressing the crystallization tendency of HEB during cooling. On the other hand, the polarity parameter of EHT may be closer to that of oxalamide. The presence of an appropriate amount of EHT may help promote the dispersion and dissolution of the poorly soluble component oxalamide in the system, acting as a bridging agent for the co-solvent. Controlling the mass ratio of EHT to HEB at 1:(2~5) is based on a trade-off between solubility limits and synergistic effects. If the EHT ratio is too high, the overall solubility load of the system increases due to EHT's higher melting point, potentially increasing the risk of precipitation. If the EHT ratio is too low, its lattice disruption and co-solution assistance effects may not be significant enough to fully realize the stability gains brought by the compounding. Therefore, this specific ratio range helps to optimize the overall crystal behavior and compatibility with a small amount of EHT while ensuring good dissolution of the main component (HEB). Furthermore, in a solvent environment composed of co-crosslinking agent A and liquid EHS, the two molecules cannot form their own pure single-component crystal lattices due to subtle differences in molecular size, steric hindrance of side chains, and dipole moments. EHT molecules embed themselves into the lattice growth points of HEB, while HEB molecules hinder the ordered arrangement of EHT. This lattice interlocking and doping effect can significantly increase the activation energy barrier for crystal nucleation and reduce the crystal growth rate. Within this ratio range, the crystallization initiation temperature of the mixed system is lower than that of the single component. This means that at conventional film cooling rates, the system is more likely to cross the crystallization region and form a metastable amorphous state or an undercooled solution, thereby fundamentally inhibiting the formation of microcrystals.

[0070] Furthermore, the four-component synergy achieves a balance between dynamic stability and spectral performance. In this preferred configuration, a high content of liquid EHS provides the basic solvent environment, HEB, as an easily soluble solid component, provides the main cutoff capability and stability, a small amount of EHT helps inhibit crystallization and promotes oxalamide dissolution, and trace amounts of oxalamide provide migration-resistant anchors. This hierarchical component design allows each component to maintain a molecular-level dispersion during processing and use under the anchoring effect of the crosslinking agent A. This eliminates the risk of microcrystalline scattering, thus further contributing to the balance between high transmittance and long-term weather resistance in the 330–380 nm wavelength range, achieving synergistic optimization of initial component efficiency and long-term reliability.

[0071] In summary, the present invention preferably controls the content of ethylhexyl salicylate to be 50%~80%, the content of oxalamide to be 1%~10%, and the mass ratio of ethylhexyl triazine ketone to diethylhexylbutamidotriazine ketone to be 1:(2~5). This scheme, by precisely controlling the solubility characteristics and interactions of each component, maximizes the utilization of the advantages of each component while avoiding the risk of precipitation of high-melting-point components, thus more effectively solving the technical problem of high selective transmittance.

[0072] In one specific embodiment, the ultraviolet absorber is composed of diethylhexylbutamidotriazinone, ethylhexyl salicylate, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide; Based on the total mass of the ultraviolet absorber, the mass percentage of N-(2-ethoxyphenyl)-N´-(2-ethylphenyl)-oxalamide is 1% to 10%, and can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, and any value between them. The balance of the ultraviolet absorber is diethylhexylbutamidotriazine ketone and ethylhexyl salicylate, with a mass ratio of 1:(1~3), which can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3 and any value between them.

[0073] As a preferred embodiment, this invention, in a three-component system containing only HEB, EHS, and oxalamide, specifically defines the mass ratio between HEB and EHS, rather than simply defining the content ranges of each separately. This invention has found that in this system, HEB, as a high-melting-point solid component, provides core cutoff performance and stability, while EHS, as a liquid component, provides key dissolution and dispersion dynamics; a solute-solvent dependency exists between the two. If only the content ranges of each are defined independently, it may not be possible to ensure sufficient solubility of EHS at high HEB content, or sufficient cutoff efficiency of HEB at high EHS content. Therefore, by controlling the mass ratio of HEB to EHS to be 1:(1~3), the dissolution and performance balance of the system can be more precisely controlled.

[0074] The mass ratio limits the solubility load of HEB, ensuring molecular-level dispersion. As a high-melting-point solid powder, the solubility of HEB in the system is limited by the volume and polarity of the liquid components (mainly EHS and co-crosslinking agent A). EHS acts not only as an absorbent but also as a co-solvent for HEB. If the EHS content is relatively low, the liquid EHS molecules may not be sufficient to form a complete solvation shell on the surface of the HEB solid particles, potentially leaving some HEB particles exposed. During processing and cooling, these exposed HEB particles easily act as nuclei, inducing crystallization and forming microcrystals. According to Mie scattering theory, these microcrystals will scatter photons in the 330-380 nm wavelength range, reducing transmittance. By limiting the ratio to at least 1:1, each unit mass of HEB is solvated and coated with at least an equal mass of EHS, reducing the risk of precipitation due to insufficient solvent. The mass ratio also limits the dilution effect of EHS, ensuring cutoff efficiency and stability. While EHS aids in dispersion, as a salicylate absorber, its photodegradation stability and molar extinction coefficient are lower than those of HEB. If the EHS content is too high, the proportion of unstable liquid components in the system will be excessive, diluting the concentration of the highly efficient and stable HEB component. To achieve a cutoff effect of <20% transmittance in the 280–330 nm wavelength range, it may be necessary to increase the total amount of UV absorber added, which increases the solubility load of the co-crosslinking agent A, potentially inducing precipitation. Furthermore, excessively high EHS content makes the system more susceptible to photodegradation and yellowing under long-term UV irradiation, affecting the long-term transmittance retention in the 330–380 nm wavelength range. By limiting the ratio to no more than 1:3, HEB maintains a sufficiently dominant position in the system, effectively improving cutoff efficiency and maintaining the overall weather resistance of the system.

[0075] A specific ratio helps achieve overall dissolution equilibrium with oxalamide. In this embodiment, the system also contains 1% to 10% oxalamide (both are high-melting-point solids). This means that EHS not only needs to dissolve HEB, but also needs to assist in the dissolution of oxalamide. The mass ratio of HEB to EHS is the result of overall consideration. At this ratio, the EHS content, while meeting the dissolution requirements of HEB, still has surplus dissolving capacity to synergistically dissolve a small amount of oxalamide with the crosslinking agent A. If the HEB content is too high, too much EHS will be occupied by HEB, which may lead to insufficient dissolution of oxalamide and preferential precipitation; if the HEB content is too low, although the dissolving capacity is strong, as mentioned above, the cutoff performance will be sacrificed. Therefore, this ratio helps to achieve the coexistence and homogeneous stability of the three components: HEB, EHS, and oxalamide. Ratio control optimizes the crystallization kinetics. Within a ratio range of 1:(1~3), EHS molecules and HEB molecules form a specific association structure at the microscale. This association structure changes the stacking mode of HEB molecules and increases the activation energy barrier for crystal nucleation. Compared to the extreme ratios that might occur in independent ranges, this ratio range ensures that the system tends to form a supercooled solution rather than a crystal precipitate during cooling. This kinetic stability helps to simultaneously achieve high transmittance (no scattering) in the 330–380 nm wavelength range and high cutoff (uniform absorption) in the 280–330 nm wavelength range.

[0076] In summary, the present invention limits the mass ratio of diethylhexylbutamidotriazine to ethylhexyl salicylate to 1:(1~3), based on a comprehensive consideration of solubility balance, performance dilution effect, and synergistic dissolution of multiple components. This ratio ensures effective solvation and dispersion of solid HEB by liquid EHS, avoiding the risk of insufficient solvent precipitation or solute failure that may occur due to independent range limitations, thereby more reliably achieving the high selective transmittance technical indicator of the ultraviolet light cutoff layer.

[0077] In a preferred embodiment, the co-crosslinking agent A can also be a compound system, preferably a combination of 4-acryloylmorpholine (ACMO) and EO(3)trimethylolpropane triacrylate (EO(3)TMPTA). It should be noted that a single type of co-crosslinking agent cannot simultaneously meet the requirements of rapid dispersion of the UV-absorbing functional component during processing and high-strength anchoring after curing. Therefore, this invention, through a preferred specific ratio of compounding, can promote the synergistic optimization of reaction kinetics and crosslinking network performance.

[0078] Specifically, 4-Acryloylmorpholine (ACMO), as a monofunctional monomer, exhibits low viscosity and high reactivity. During premixing and extrusion processing, ACMO can rapidly wet the surface of the UV absorber powder, reducing system viscosity and promoting molecular-level dispersion. Simultaneously, its rapid reaction rate helps to quickly lock the absorber's dispersion in the early stages of processing, reducing the risk of thermal degradation due to prolonged processing time and slightly improving the initial light transmittance of the film and the component power. However, if the ACMO ratio is too high, although the processing performance is excellent, the mechanical properties of the film decrease, and the long-term locking ability of the absorber is weakened. If the ACMO ratio is too low, the system viscosity is too high, which is detrimental to the initial wetting and dispersion of the UV absorber and may lead to micro-agglomeration.

[0079] In contrast, EO(3)trimethylolpropane triacrylate (EO(3)TMPTA), as a multifunctional monomer, can form a high-density three-dimensional cross-linked network. During the curing stage, the multiple reaction sites provided by EO(3)TMPTA significantly increase the cross-linking density, thereby endowing the film with excellent tensile strength, compressive strength, and creep resistance. More importantly, the high cross-linking density network structure can more effectively chemically anchor the dispersed UV absorber molecules, preventing their migration or precipitation during long-term service.

[0080] Based on the above mechanism, the present invention limits the total mass of the crosslinking agent A to 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, and any value between them. Within this ratio range, the content of ACMO is sufficient to ensure the dispersion efficiency and reaction rate during processing, while the high proportion of EO(3)TMPTA ensures the mechanical strength and anchoring ability of the final cured network. Therefore, a compounding ratio of 1:(2~5) helps to balance the high transmittance, high reliability, and excellent processability of the ultraviolet light cutoff layer.

[0081] In one specific implementation, the thickness ratio of the ultraviolet light cutoff layer 1 to the light conversion layer 2 is 1:(0.2~4.0), for example, 1:0.2, 1:0.5, 1:1, 1:2, 1:3, 1:4, etc. The main function of the ultraviolet light cutoff layer 1 is to achieve efficient absorption of the ultraviolet light band while maintaining the transmission of the high-conversion-excited ultraviolet wavelength. Its thickness needs to ensure that the ultraviolet absorber has sufficient absorption intensity per unit optical path to control the transmittance of the 280~330 nm wavelength band below 20%. If the layer is too thin, it may lead to incomplete ultraviolet light cutoff, failing to adequately protect the solar cell and the light conversion layer 2; if it is too thick, it may affect the overall transmittance of the film due to excessive absorption, increasing costs and reducing mechanical properties. The main function of the light conversion layer 2 is to absorb the light converted to excite the ultraviolet wavelength (330~380 nm) transmitted through the ultraviolet light cutoff layer 1 and convert it into visible light. The thickness must ensure that the light conversion agent can fully absorb the excitation light, while avoiding visible light reabsorption loss or decreased film flexibility due to excessive thickness. By controlling the thickness ratio of the ultraviolet light cutoff layer 1 to the light conversion layer 2 within the range of 1:(0.2~4.0), it can be ensured that the ultraviolet light cutoff layer 1 has sufficient thickness to effectively cut off the 280~330 nm wavelength band, while the light conversion layer 2 can fully absorb the transmitted light and convert it into ultraviolet light, avoiding visible light reabsorption loss due to excessive layer thickness, thereby maintaining the high transmittance of the film in the visible light band.

[0082] It should be noted that the term "thickness" as used in this invention refers to the average thickness. Due to the characteristics of the multilayer co-extrusion process, the film may exhibit slight thickness fluctuations in the transverse or longitudinal direction. Therefore, the thicknesses of the ultraviolet light blocking layer 1 and the light conversion layer 2 are obtained by measuring at least five different points randomly selected on the surface of the prepared film using a precision thickness gauge or cross-sectional microscope, and then taking the arithmetic mean. Those skilled in the art will understand that the local thickness at individual measurement points may fluctuate within ±5%, and as long as the average thickness falls within the range or proportion defined by this invention, it is considered to fall within the protection scope of this invention.

[0083] In one specific embodiment, the ultraviolet light blocking layer 1 comprises the following components by weight: First matrix resin: 100 parts; Ultraviolet absorber: 0.05~0.5 parts, which can be 0.05 parts, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, etc.; Co-crosslinking agent A: 0.4~1.2 parts, which can be 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts, 1.1 parts, 1.2 parts, etc.; Crosslinking agent: 0.3~1.0 parts, which can be 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts, etc.; Coupling agent: 0.1~0.6 parts, which can be 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, etc.; Light stabilizer: 0.05~0.3, which can be 0.05 parts, 0.1 parts, 0.2 parts, 0.3 parts, etc.; Antioxidant: 0.01~0.2 parts, which can be 0.01 parts, 0.02 parts, 0.06 parts, 0.08 parts, 0.1 parts, 0.2 parts, etc.

[0084] The amount of ultraviolet absorber added is controlled within the range of 0.05~0.5 parts. Although excessive amounts can enhance the initial ultraviolet light cutoff effect, long-term ultraviolet aging may lead to accelerated yellowing of the film due to the degradation of the absorber itself or the accumulation of by-products. The total amount of co-crosslinking agent A ranges from 0.4 to 1.2 parts. There are two ways to add it: one is to add it all at once to the ultraviolet absorber and mix it; the other is to add it in steps, that is, to premix a portion of co-crosslinking agent A with the ultraviolet absorber (at this time, the total amount of co-crosslinking agent A and ultraviolet absorber should be controlled within 0.2~1.5 parts), and the remaining portion of co-crosslinking agent A is added together with other resins, monomers and other raw materials when preparing the ultraviolet light cutoff layer. The amount of crosslinking agent is 0.3~1.0 parts, which works synergistically with co-crosslinking agent A to regulate the crosslinking density and reaction rate of the system, ensuring that the film forms a stable and uniform three-dimensional network structure during the lamination process. If the crosslinking agent content is too low, insufficient crosslinking will result in decreased mechanical strength and heat resistance of the film; if it is too high, it may lead to excessively rapid crosslinking, affecting leveling and interfacial adhesion. The addition of co-crosslinking agent A can optimize crosslinking efficiency and improve the uniformity of the crosslinking network, but excessive amounts may introduce too many active sites, potentially leading to excessive local crosslinking or increased side reactions. The amount of coupling agent is 0.1~0.6 parts; excessive addition will slow down the crosslinking speed of the system, affecting the efficiency of film forming and lamination processes. The amount of light stabilizer is 0.05~0.3 parts; appropriately increasing its content helps to inhibit yellowing caused by UV aging, but excessive amounts will also interfere with the crosslinking reaction kinetics, requiring a balance between anti-yellowing and process suitability.

[0085] In one specific embodiment, the light conversion layer 2 comprises the following components by weight: Second matrix resin: 100 parts; Light conversion agent: 0.01~0.5 parts, which can be 0.01 parts, 0.04 parts, 0.06 parts, 0.08 parts, 0.1 parts, 0.2 parts, 0.4 parts, 0.5 parts, etc.; Crosslinking agent: 0.3~1.0 parts, which can be 0.3 parts, 0.4 parts, 0.6 parts, 0.8 parts, 1.0 parts, etc.; Co-crosslinking agent B: 0.4~1.2 parts, which can be 0.4 parts, 0.5 parts, 0.6 parts, 0.8 parts, 1.0 parts, 1.2 parts, etc.; Coupling agent: 0.1~0.6 parts, which can be 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, etc.; Light stabilizer: 0.05~0.3 parts, which can be 0.05 parts, 0.06 parts, 0.08 parts, 0.1 parts, 0.2 parts, 0.3 parts, etc.; Antioxidant: 0.01~0.2 parts, which can be 0.01 parts, 0.02 parts, 0.04 parts, 0.06 parts, 0.08 parts, 0.1 parts, 0.2 parts, etc.

[0086] The dosage of the light conversion agent is controlled within the range of 0.01 to 0.5 parts. Due to the high cost of the light conversion agent, excessive addition will significantly increase the cost of the encapsulant film raw materials, which is detrimental to the economics of large-scale applications. Simultaneously, while excessive addition may enhance the ultraviolet light conversion intensity, it will also introduce more optical scattering and absorption centers, reducing the transmittance of the encapsulant film in the visible light band, thus limiting the overall power output of the module. Conversely, if its content is too low, the absorption and conversion ability of ultraviolet light will be correspondingly weakened, and the spectral gain potential will decrease. It is worth noting that within this dosage range, the light conversion agent can maintain a good dispersion and effective excitation concentration in the matrix, and its intrinsic quantum conversion efficiency (PLQY) is basically unaffected. Therefore, while controlling costs and maintaining visible light transmittance, it is still possible to achieve efficient spectral conversion of ultraviolet light, thereby achieving comprehensive optimization of encapsulant film performance, cost, and module output power. In practical implementation, the light conversion agent can be a product provided by Ruiers New Materials Co., Ltd., such as grade B102 or B112. These materials are rare-earth organic complexes or composite fluorescent systems, characterized by strong ultraviolet absorption, high quantum efficiency, and good photothermal stability, effectively achieving wavelength conversion from ultraviolet to visible light. Of course, this invention does not strictly limit the source of the light conversion agent; any commercially available light conversion material with similar chemical structure, optical properties, and thermal stability can be used as a substitute, as long as it meets the functional requirements of the light conversion layer in this system.

[0087] In one specific embodiment, the first matrix resin is an ethylene-vinyl acetate copolymer, wherein the vinyl acetate content is 26-35 wt% and the melt index is 4-30 g / 10min (test conditions: 190℃, 2.16 kg). This range of vinyl acetate content ensures that the copolymer possesses good optical transparency, flexibility, and compatibility with photovoltaic encapsulation systems. Controlling the melt index within the above range is beneficial for achieving suitable rheological properties and processing window during co-extrusion molding, thereby ensuring the interlayer bonding quality and thickness uniformity of the film during multilayer co-extrusion, while maintaining the crosslinking reactivity and molding stability of the final film during the lamination process.

[0088] In one specific embodiment, the second matrix resin is an ethylene-α-olefin copolymer or an ethylene-vinyl acetate copolymer; wherein the ethylene-α-olefin copolymer is selected from at least one of ethylene-1-butene copolymer, ethylene-1-octene copolymer, and ethylene-propylene-1-hexene copolymer. The selection of this second matrix resin is based on its good optical transparency, flexibility, weather resistance, and compatibility with the photovoltaic encapsulation system. Ethylene-α-olefin copolymers have low crystallinity and excellent resistance to damp heat aging, making them particularly suitable for encapsulation scenarios with high long-term reliability requirements; ethylene-vinyl acetate copolymers, due to their high polarity, exhibit excellent interfacial adhesion properties, which helps to enhance the adhesion strength between the film and materials such as solar cells and glass. By selecting the above resins, it can be ensured that the light conversion layer 2 achieves efficient spectral conversion while maintaining the overall mechanical integrity, environmental stability, and process adaptability of the film.

[0089] In one specific embodiment, the crosslinking agent is selected from at least one of 1,1-bis-tert-butylperoxide-3,3,5-trimethylcyclohexane (TMCH), tert-butylperoxide-3,5,5-trimethylhexanoate (TBPIN), and benzoyl peroxide (BPO). Preferably, TMCH and TBPIN are used alone or in combination to achieve controlled crosslinking over a wide temperature range, balancing reaction rate and network integrity while avoiding excessive yellowing. In a specific embodiment, TBPIN (CAS No. 13122) provided by Zheng Hua can be selected as the crosslinking agent. 18 4) Or similar commercially available products such as TMCH provided by Lanzhu; the above raw materials are all commonly used commodities in this field, and other alternative products that meet technical standards can also be selected according to process and performance requirements in actual production.

[0090] In one specific embodiment, the co-crosslinking agent B is selected from at least one of trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, triallyl isocyanurate, tetramethyltetravinylcyclotetrasiloxane, 4-acryloylmorpholine, 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, neopentyl glycol diacrylate, polyethylene glycol 200 diacrylate, EO(3)trimethylolpropane triacrylate, and 3(propoxy)glycerol triacrylate. The aforementioned co-crosslinking agent B, through its multifunctional structure, effectively constructs and enhances the three-dimensional network during the crosslinking process, thereby improving the crosslinking density, mechanical strength, and thermal stability of the film. For example, 1,6-hexanediol diacrylate acts as a liquid reactive monomer in the system. Its low viscosity and high fluidity help achieve uniform dispersion and participate in the crosslinking copolymerization reaction, thereby improving the crosslinking uniformity and network flexibility while optimizing the rheological behavior and interfacial bonding performance of the film during lamination. Acrylic ester co-crosslinking agents such as trimethylolpropane triacrylate provide high crosslinking activity and efficiency, while triallyl isocyanurate and tetramethyltetravinylcyclotetrasiloxane further enhance the stability of the crosslinked network against damp heat aging. By selecting one or more of the above co-crosslinking agents and controlling their dosage, the mechanical properties, processing adaptability, and long-term reliability of the film can be balanced while ensuring sufficient crosslinking. In specific implementation, co-crosslinking agent B can be ethoxylated trimethylolpropane trimer (CAS No. 28961) provided by Guojing. 43 5) 1,6-Hexanediol diacrylate or tetramethyltetravinylcyclotetrasiloxane (product code V4) supplied by Siliconware. These products are common commodities in the field, and in practice, other similar crosslinking aids that meet the performance requirements can be selected as substitutes according to system requirements.

[0091] In one specific embodiment, the coupling agent is a silane coupling agent selected from at least one of vinyltrimethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, aminopropyltrimethoxysilane, bis(3-triethoxysilylpropyl)amine, N,N-dimethyl-3-aminopropyltrimethoxysilane, 1,3,5-tris(trimethoxysilylpropyl)isocyanate, n-dodecyltrimethoxysilane, n-octyltrimethoxysilane, and cyclohexyltrimethoxysilane. The aforementioned silane coupling agent can improve the interfacial adhesion, weather resistance, and system compatibility of the film by forming a chemical or physical bond between the hydrolyzable alkoxy group and the matrix resin, inorganic interface, or functional additives.

[0092] Among them, 1,3,5-tris(trimethoxysilylpropyl)isocyanate (TAIC) contains both polar and nonpolar groups in its molecular structure, exhibiting moderate viscosity and good miscibility. It can serve as a highly efficient dispersion medium, promoting the uniform blending and stable dispersion of various functional additives such as UV absorbers (e.g., diethylhexylbutamidotriazinone), light converters, light stabilizers, and antioxidants in the matrix resin. Furthermore, TAIC can effectively dissolve powder components such as diethylhexylbutamidotriazinone under heating conditions (e.g., 98°C), improving the system's uniformity. In addition, the trimethoxysilyl groups at the ends of the TAIC molecule can generate silanol groups under humid or hydrolytic conditions, thereby forming strong Si-O-Si covalent bonds with the surface of inorganic substrates such as glass, enhancing the interfacial adhesion between the coating and the substrate.

[0093] Other silane coupling agents, such as γ-(methacryloyloxy)propyltrimethoxysilane, can participate in the copolymerization and crosslinking network of the resin through their olefin bonds; aminopropyl silanes can interact with the polar groups in the resin through their amino groups; long-chain alkyl silanes (such as n-dodecyltrimethoxysilane) help improve compatibility with hydrophobic interfaces. By selecting one or more of the above silane coupling agents, the adhesion performance, weather resistance, and functional stability of the adhesive film at different interfaces can be specifically optimized. In specific implementations, coupling agents such as KH570 and 171 from Siliconware Precision Industries Co., Ltd. can be selected.

[0094] In one specific embodiment, the light stabilizer is selected from bis(1,2,2,6,6) Pentamethyl 4 Piperidinyl sebacate, bis(2,2,6,6) Tetramethyl 4 Piperidinyl sebacate, 3,5 Second Uncle Ding Ji 4 Hexadecyl hydroxybenzoate, (1) Octyloxy 2,2,6,6 Tetramethyl 4 Piperidinyl sebacate, mono(1,2,2,6,6) Pentamethyl 4 Piperidinyl sebacate and poly[6] [(1,1,3,3 Tetramethylbutylamino] 1,3,5 Triazine 2,4 [2,2,6,6] Tetramethyl 4 At least one of the following: piperidinyl (imino) [], for example, Liansheng's UV770. The above-mentioned light stabilizers are mainly hindered amine light stabilizers and their esterified derivatives, which can effectively inhibit photo-oxidative aging and yellowing of the encapsulant film during long-term outdoor use through multiple mechanisms such as capturing free radicals generated under ultraviolet irradiation, decomposing hydrogen peroxide, and quenching excited-state molecules. Sebacic acid ester hindered amines (such as diesters and monoesters) have good thermal stability and low migration, making them suitable for the processing and service environment of photovoltaic encapsulant films; while polymeric hindered amines, due to their high molecular weight characteristics, exhibit excellent extraction resistance and long-term stability in the encapsulant film system. By selecting one or more of the above-mentioned light stabilizers and controlling their addition amount, the mechanical property decay of the encapsulant film can be significantly delayed, high transmittance in the visible light region can be maintained, and the long-term reliability of the interfacial bonding between the encapsulant film and the solar cell, glass, etc. can be ensured, thereby improving the overall durability and power generation stability of the photovoltaic module.

[0095] In one specific embodiment, the antioxidant is selected from pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3,5-di-tert-butyl-4-hydroxybenzyl diethylphosphonate, and 4,4'-p-isopropyl diphenyl C12 15 At least one of the alcohol phosphites can be used, for example, the antioxidant Liansheng 1076 can be selected. The aforementioned antioxidants include two main types: hindered phenols and phosphites. They can effectively delay the thermo-oxidative aging of the film during processing, lamination, and long-term use through multiple mechanisms such as capturing free radicals, decomposing hydrogen peroxide, and inhibiting chain oxidation reactions. Among them, hindered phenolic antioxidants (such as pentaerythritol ester and octadecyl ester) can provide highly efficient initial antioxidant protection, inhibiting oxidative degradation before resin crosslinking; phosphite antioxidants (such as diethylphosphonate and C12...) 15 Alcohol phosphites, acting as auxiliary antioxidants, effectively decompose hydroperoxides generated during processing and aging, and synergistically enhance the long-term thermal and color stability of the system with hindered phenols. By selecting one or more of the above antioxidants, the mechanical properties, optical transparency, and interfacial adhesion strength of the film can be maintained over a wide temperature range.

[0096] On the other hand, the present invention also provides a method for preparing a multilayer optical conversion encapsulating film, the method comprising the following steps: The first matrix resin is mixed with the ultraviolet light absorption functional component to obtain the ultraviolet light blocking layer melt; The second matrix resin is mixed with a light conversion agent to obtain a light conversion layer melt; The ultraviolet light cutoff layer melt and the light conversion layer melt are simultaneously extruded through a co-extrusion die and cooled to solidify, resulting in a multi-layered light conversion encapsulation film.

[0097] In one specific implementation scheme, the method for preparing the ultraviolet light absorbing functional component includes: The ultraviolet absorber is mixed with a portion of the crosslinking agent A to obtain a mixture; Heat the mixture to 50-60℃ and perform the first stirring. Then another portion of crosslinking agent A is added and the temperature is raised to 90~100℃ for a second stirring to form a UV absorption functional component.

[0098] It should be noted that the gradient heating premixing process preferred in this invention aims to solve the technical problem of high melting point solid absorbents being prone to precipitation and agglomeration during processing and cooling, thereby effectively improving the transmittance of the ultraviolet light cutoff layer in the 330~380nm wavelength range.

[0099] The ultraviolet absorber system of this invention preferably comprises liquid ethylhexyl salicylate (EHS) and high-melting-point solid triazine ketones or oxalamide absorbers. Direct high-temperature mixing can easily lead to imbalances in the ratio due to the volatilization loss of liquid EHS, and the solid powder is prone to hard agglomeration at high temperatures due to excessive surface energy, hindering subsequent dissolution. At a low temperature range of 50-60°C, liquid EHS maintains a stable liquid phase, effectively wetting the surface of the solid absorber powder. The polar interaction between its ester groups and solid molecules allows for the formation of a preliminary solvation layer on the particle surface. This process effectively reduces the surface energy of the solid particles, preventing powder agglomeration and avoiding premature volatilization of EHS, thus laying a good dispersion foundation for subsequent high-temperature dissolution. Solid absorbers such as ethylhexyl triazine ketone, diethylhexylbutamidotriazine ketone, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide typically have melting points above 92°C, making them difficult to completely dissolve when directly added to a resin matrix. This invention utilizes co-crosslinking agent A as a highly polar solvent matrix. Within a temperature range of 90-100°C, the thermal motion of co-crosslinking agent A molecules intensifies, allowing them to penetrate deep into the crystal lattice of the solid absorbent. Through hydrogen bonding or dipole interactions, the crystal structure is disrupted, resulting in complete dissolution within co-crosslinking agent A, forming a homogeneous, transparent, supercooled solution. The upper temperature limit is controlled below 100°C to prevent thermal decomposition or crosslinking reactions of co-crosslinking agent A or liquid EHS due to excessively high temperatures, ensuring the chemical stability of the premix.

[0100] Furthermore, this invention employs a stepwise addition strategy of the co-crosslinking agent A, adding a portion during the low-temperature wetting stage and another portion during the high-temperature dissolution stage. This operation effectively controls the viscosity and heat capacity of the mixed system. At the low temperature stage, a small amount of co-crosslinking agent A is sufficient for wetting, preventing insufficient stirring shear force due to excessively low system viscosity. At the high temperature stage, the remaining co-crosslinking agent A provides sufficient solvent volume, ensuring that the system remains unsaturated or metastable after complete dissolution of the solid absorbent, preventing supersaturation precipitation due to insufficient solvent. If a conventional one-time high-temperature mixing process is used, the solid absorbent may recrystallize during film cooling due to incomplete dissolution, forming microcrystals with a size of 0.1–10 μm. According to Mie scattering theory, these microcrystals will strongly scatter photons in the 330–380 nm wavelength band, potentially leading to a decrease in transmittance in this band.

[0101] This invention preferably employs a gradient-temperature premixing process, which is more conducive to the molecular-level dispersion of the ultraviolet absorber and eliminates microcrystalline scattering centers. This contributes to the efficient cutoff of ultraviolet light in the 280-330nm wavelength range and the high transmittance in the 330-380nm wavelength range of the ultraviolet cutoff layer. Simultaneously, the homogeneous solution formed by premixing, after co-extrusion with the first matrix resin, allows the crosslinking agent A to participate in the curing reaction, chemically anchoring the absorber molecules within the crosslinking network. This further prevents migration and precipitation during long-term aging, ensuring the long-term weather resistance of the component.

[0102] In summary, the preparation method provided by this invention, particularly the gradient temperature premixing process for the ultraviolet light absorption functional component, helps to achieve the spectral selectivity of this application. This process not only solves the dispersion problem of high-melting-point solid absorbers but also eliminates the potential for light scattering at its source, ensuring that the light conversion layer can obtain a sufficient and stable excitation source, thus achieving synergistic optimization of component reliability protection and photoelectric conversion efficiency improvement.

[0103] This invention also provides a photovoltaic module comprising a multilayer structured light conversion encapsulating film according to any of the aforementioned embodiments. This encapsulating film, as a key material for module encapsulation, is disposed between the solar cells and a cover plate (such as glass) and / or between the solar cells and a backsheet. Through the synergistic effect of its ultraviolet light blocking layer 1 and light conversion layer 2, it effectively shields against high-energy ultraviolet damage while converting some ultraviolet light into visible light, thereby improving the module's utilization efficiency of the solar spectrum. This photovoltaic module features high initial power output, excellent long-term weather resistance, and reliability, and is particularly suitable for encapsulating high-efficiency cells sensitive to ultraviolet radiation (such as HJTs, TOPCons, and BCs). It can be widely used in applications such as ground-mounted power plants, distributed photovoltaics, and building-integrated photovoltaics.

[0104] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. The raw materials used and their optional sources are as follows: the first matrix resin is ethylene-vinyl acetate copolymer (EVA), which can be the product with the grade E282PV manufactured by Hanwha TotalEnergies; the second matrix resin is ethylene-1-octene copolymer (POE), which can be the product with the grade ENGAGE PV manufactured by Dow Chemical. POE resin of 8669; UV absorbers include ethylhexyl salicylate and diethylhexylbutamidotriazine, both commercially available light stabilizers, such as BASF's Uvinul® N35T and Mfsorb® 513 respectively; UV absorbers also include ethylhexyltriazine and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide, both commercially available light stabilizers, such as Mfsorb® 507 and UV312 from Nanjing Milan Chemical Co., Ltd.; crosslinking agent can be tert-butyl peroxide-3,5,5-trimethylhexanoate (TBPIN, CAS No. 13122-18-4) provided by Zhenghua; crosslinking aids... Coupling agent A can be 4-acryloylmorpholine provided by Hemox and EO(3)trimethylolpropane triacrylate provided by Guojing; co-crosslinking agent B can be tetramethyltetravinylcyclotetrasiloxane (code V4) provided by Sikco and triallyl isocyanurate (TAIC) provided by Huaxing; coupling agent can be γ-(methacryloyloxy)propyltrimethoxysilane (code KH570) provided by Sikco; light stabilizer can be bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate (code UV770) provided by Liansheng; antioxidant can be pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (code 1076) provided by Liansheng. In addition, light conversion agent with wavelength conversion function, brand B102, provided by Ruiers New Materials Co., Ltd., can be selected.

[0105] Example 1 A multilayer light conversion encapsulating film and its preparation method are disclosed. The film comprises two layers: an ultraviolet light cutoff layer and a light conversion layer, with a thickness ratio of approximately 1.6:1. The ultraviolet light cutoff layer has a thickness of approximately 215 μm, and the light conversion layer has a thickness of approximately 135 μm.

[0106] The composition of the ultraviolet light blocking layer, by weight, is as follows: First matrix resin: 100 parts, with a vinyl acetate content of 28 wt% and a melt index of 25 g / 10 min (test conditions: 190℃, 2.16 kg). The ultraviolet light absorbing functional component comprises a premixture of an ultraviolet absorber and a co-crosslinking agent A. Based on the total mass of the ultraviolet light absorbing functional component, the mass percentage of the ultraviolet absorber is 16.7%, and the mass percentage of the co-crosslinking agent A is 83.3%. Ultraviolet absorber: 0.2 parts; of which, ethylhexyl salicylate 0.16 parts and diethylhexylbutamidotriazinone 0.04 parts; That is, ethylhexyl salicylate accounts for 80% of the total mass of the ultraviolet absorber, and diethylhexylbutamidotriazinone accounts for 20%; Co-crosslinking agent A: 1 part; of which, 0.25 parts of 4-acryloylmorpholine and 0.75 parts of EO(3)trimethylolpropane triacrylate; That is, the mass ratio of 4-acryloylmorpholine to EO(3)trimethylolpropane triacrylate is 1:3; Crosslinking agent: 0.6 parts; Coupling agent: 0.3 parts; Light stabilizer: 0.2 parts; Antioxidant: 0.04 parts.

[0107] The composition of the light conversion layer, by weight, is as follows: Second matrix resin: 100 parts; Light conversion agent: 0.2 parts; Crosslinking agent: 0.8 parts; Crosslinking agent B: 0.7 parts; Coupling agent: 0.3 parts; Light stabilizer: 0.2 parts; Antioxidant: 0.04 parts.

[0108] The preparation method of ultraviolet light absorbing functional components includes the following steps: Mix the formulated amount of UV absorber with 80% of the total amount of crosslinking agent A, heat to 55°C, and stir for 30 minutes; add the remaining 20% ​​of the total amount of crosslinking agent A, continue heating to 95°C, and stir for 50 minutes until the system becomes a homogeneous and transparent solution; cool naturally to room temperature to obtain a clear and transparent premix of UV absorption functional components.

[0109] The preparation method of the multilayer optical conversion encapsulating film includes the following steps: The first matrix resin is mixed evenly with the above-mentioned ultraviolet light absorption functional components, crosslinking agent, coupling agent, light stabilizer, and antioxidant, and then melt-plasticized through extruder A to obtain an ultraviolet light blocking layer melt; the second matrix resin is mixed evenly with light conversion agent, co-crosslinking agent B, crosslinking agent, coupling agent, light stabilizer, and antioxidant, and then melt-plasticized through extruder B to obtain a light conversion layer melt; Extruder A is used to melt the ultraviolet light cutoff layer material. The set temperatures (SV) of its barrels 1 to 4, screen changer and flow channel are +50℃, +85℃, +85℃, +85℃, +85℃ and +86℃, respectively. Extruder B is used to melt the light conversion layer material. The SV of the corresponding sections are +55℃, +90℃, +90℃, +90℃ and +90℃, respectively. The two melts are merged by the distributor (temperature controlled at +90℃~+92℃) and enter the co-extrusion die (temperature of each section is uniformly set at +92℃~+93℃). They are extruded and cooled simultaneously to obtain a double-layer light conversion encapsulation film with tight interlayer bonding and uniform optical performance.

[0110] like Figure 3 As shown, Figure 3 This is a microscope image of the two-layer light conversion encapsulating film provided in Embodiment 1 of the present invention. Figure 3 As can be seen, the cross-section of the bilayer film prepared in Example 1 exhibits a homogeneous and transparent structure, and no obvious micron-level phase separation or crystal point precipitation was observed.

[0111] Example 2 The light conversion encapsulating film of Example 1 is used in reference, except that the ratio of ultraviolet absorbers in the ultraviolet light absorption functional components is adjusted.

[0112] By weight, the ultraviolet absorber is 0.2 parts; of which, ethylhexyl salicylate is 0.14 parts, ethylhexyl triazine is 0.02 parts, and diethylhexylbutamidotriazine is 0.04 parts. Specifically, ethylhexyl salicylate accounts for 70% of the total mass of the UV absorber, ethylhexyl triazine ketone accounts for 10%, and diethylhexylbutamidotriazine ketone accounts for 20%; the mass ratio of ethylhexyl triazine ketone to diethylhexylbutamidotriazine ketone is 1:2; The composition and preparation method of the light conversion layer, as well as the film preparation process, are the same as in Example 1.

[0113] Example 3 The light conversion encapsulating film of Example 1 is used in reference, except that the ratio of ultraviolet absorbers in the ultraviolet light absorption functional components is adjusted.

[0114] The ultraviolet absorber is 0.2 parts by weight; including 0.1 parts of ethylhexyl salicylate, 0.02 parts of ethylhexyl triazine, 0.06 parts of diethylhexylbutamidotriazine, and 0.02 parts of N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide. Specifically, ethylhexyl salicylate accounts for 50% of the total mass of the UV absorber, ethylhexyl triazine ketone accounts for 10%, diethylhexylbutamidotriazine ketone accounts for 30%, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide accounts for 10%; the mass ratio of ethylhexyl triazine ketone to diethylhexylbutamidotriazine ketone is 1:3; The composition and preparation method of the light conversion layer, as well as the film preparation process, are the same as in Example 1.

[0115] Example 4 The light conversion encapsulating film of Example 1 is used in reference, except that the ratio of ultraviolet absorbers in the ultraviolet light absorption functional components is adjusted.

[0116] By weight, the ultraviolet absorber is 0.2 parts; of which, ethylhexyl salicylate is 0.12 parts, diethylhexylbutamidotriazine is 0.06 parts, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide is 0.02 parts. That is, ethylhexyl salicylate accounts for 60% of the total mass of the ultraviolet absorber, diethylhexylbutamidotriazinone accounts for 30%, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide accounts for 10%; the mass ratio of diethylhexylbutamidotriazinone to ethylhexyl salicylate is 1:2; The composition and preparation method of the light conversion layer, as well as the film preparation process, are the same as in Example 1.

[0117] Example 5 Referring to the light conversion encapsulating film of Example 1, the difference is that the mass ratio of ultraviolet absorber to crosslinking agent A in the ultraviolet light absorption functional component is adjusted.

[0118] By weight, the composition of the ultraviolet light blocking layer includes: Ultraviolet absorber: 0.2 parts; of which, ethylhexyl salicylate 0.16 parts and diethylhexylbutamidotriazinone 0.04 parts; That is, ethylhexyl salicylate accounts for 80% of the total mass of the ultraviolet absorber, and diethylhexylbutamidotriazinone accounts for 20%; Co-crosslinking agent A: 0.6 parts; of which, 0.15 parts are 4-acryloylmorpholine and 0.45 parts are EO(3)trimethylolpropane triacrylate; That is, the mass ratio of 4-acryloylmorpholine to EO(3)trimethylolpropane triacrylate is 1:3; The ultraviolet light absorbing functional component comprises a premixture of an ultraviolet absorber and a crosslinking agent A, wherein, based on the total mass of the ultraviolet light absorbing functional component, the mass percentage of the ultraviolet absorber is 25% and the mass percentage of the crosslinking agent A is 75%. The composition and preparation method of the light conversion layer, as well as the film preparation process, are the same as in Example 1.

[0119] Example 6 Referring to the light conversion encapsulating film of Example 1, the difference is that the mass ratio of ultraviolet absorber to crosslinking agent A in the ultraviolet light absorption functional component is adjusted.

[0120] By weight, the composition of the ultraviolet light blocking layer includes: Ultraviolet absorber: 0.2 parts; of which, ethylhexyl salicylate 0.16 parts and diethylhexylbutamidotriazinone 0.04 parts; That is, ethylhexyl salicylate accounts for 80% of the total mass of the ultraviolet absorber, and diethylhexylbutamidotriazinone accounts for 20%; Co-crosslinking agent A: 1.8 parts; of which, 4-acryloylmorpholine 0.45 parts, EO(3)trimethylolpropane triacrylate 1.35 parts; That is, the mass ratio of 4-acryloylmorpholine to EO(3)trimethylolpropane triacrylate is 1:3; The ultraviolet light absorbing functional component comprises a premixture of an ultraviolet absorber and a crosslinking agent A, wherein, based on the total mass of the ultraviolet light absorbing functional component, the mass percentage of the ultraviolet absorber is 10% and the mass percentage of the crosslinking agent A is 90%. The composition and preparation method of the light conversion layer, as well as the film preparation process, are the same as in Example 1.

[0121] Example 7 Referring to the light conversion encapsulation film of Example 1, the difference is that the film adopts a three-layer structure, including a first ultraviolet light cut-off layer, a light conversion layer and a second ultraviolet light cut-off layer stacked in sequence, and the thickness ratio of the first ultraviolet light cut-off layer, the light conversion layer and the second ultraviolet light cut-off layer is approximately 1:1.4:1.

[0122] like Figure 4 As shown, Figure 4 This is a microscope image of the three-layer light conversion encapsulating film provided in Embodiment 7 of the present invention. Figure 4 As can be seen, the cross-section of the three-layer film prepared in Example 7 exhibits a homogeneous and transparent structure, and no obvious micron-level phase separation or crystal point precipitation was observed.

[0123] Example 8 Referring to the light conversion encapsulation film of Example 1, the difference is that the preparation process of the ultraviolet light absorption functional component is changed, and instead of using a gradient temperature premixing process, a one-time high-temperature mixing process is used.

[0124] The preparation method of ultraviolet light absorbing functional components includes the following steps: Mix the prescribed amount of ultraviolet absorber with the total amount of crosslinking agent A, heat directly to 95°C, stir for 80 minutes until the system becomes a homogeneous and transparent solution; cool naturally to room temperature to obtain a clear and transparent premix of ultraviolet light absorbing functional components.

[0125] The content of the remaining components and the film preparation process are the same as in Example 1.

[0126] Comparative Example 1 Referring to the light conversion encapsulation film of Example 1, the difference is that the ultraviolet light blocking layer in Example 1 is replaced with conventional UV blocking agent 1, which is UV-531.

[0127] Comparative Example 2 Referring to the light conversion encapsulation film of Example 1, the difference is that the ultraviolet light blocking layer in Example 1 is replaced with a conventional UV blocking agent 2, which is UV328.

[0128] Comparative Example 3 Referring to the light conversion encapsulation film of Example 1, the difference is that this film only contains a light conversion layer and does not have an ultraviolet light blocking layer.

[0129] Comparative Example 4 Referring to the light conversion encapsulation film of Example 1, the difference is that the mass ratio of ultraviolet absorber to co-crosslinking agent A in the ultraviolet light absorption functional component is adjusted, and the content of co-crosslinking agent A is too low.

[0130] By weight, the composition of the ultraviolet light blocking layer includes: Ultraviolet absorber: 0.2 parts; of which, ethylhexyl salicylate 0.16 parts and diethylhexylbutamidotriazinone 0.04 parts; That is, ethylhexyl salicylate accounts for 80% of the total mass of the ultraviolet absorber, and diethylhexylbutamidotriazinone accounts for 20%; Co-crosslinking agent A: 0.2 parts; of which, 4-acryloylmorpholine 0.05 parts, EO(3)trimethylolpropane triacrylate 0.15 parts; That is, the mass ratio of 4-acryloylmorpholine to EO(3)trimethylolpropane triacrylate is 1:3; The ultraviolet light absorbing functional component comprises a premixture of an ultraviolet absorber and a crosslinking agent A, wherein, based on the total mass of the ultraviolet light absorbing functional component, the mass percentage of the ultraviolet absorber is 50% and the mass percentage of the crosslinking agent A is 50%. The composition and preparation method of the light conversion layer, as well as the film preparation process, are the same as in Example 1.

[0131] Comparative Example 5 The light conversion encapsulating film of Example 1 is used, except that the ultraviolet absorber in Example 1 is replaced with pure ethylhexyl salicylate.

[0132] Comparative Example 6 The light conversion encapsulating film of Example 1 is used, except that the crosslinking agent A in Example 1 is replaced with pure 4-acryloylmorpholine.

[0133] Test case The performance of the light conversion encapsulating films and their corresponding photovoltaic modules prepared in the examples and comparative examples was characterized.

[0134] A single-layer adhesive film containing only an ultraviolet light cutoff layer was prepared separately, and its average transmittance in the 280~330nm band (high-energy ultraviolet band) and the 330~380nm band (photoconversion-excited ultraviolet band) was measured using an ultraviolet-visible spectrophotometer.

[0135] The photoluminescence quantum yield (PLQY) of the light conversion encapsulating film was measured using a photoluminescence spectroscopy system at an excitation wavelength of 350 nm.

[0136] Each encapsulant film was encapsulated into a standard photovoltaic module, and its initial output power and power degradation rate after UV aging test were tested (the module was placed in an accelerated UV aging chamber and irradiated under specified conditions at 120 kWh / m²). 2 ).

[0137] For detailed test data, please refer to Table 1.

[0138] Table 1 Performance test results of light conversion encapsulation film

[0139] Based on the above test data, it is evident that this invention, through a specific compound of ultraviolet light absorption functional components and a multilayer structure design, fundamentally solves the technical challenge of high selective transmittance in ultraviolet light cutoff layers. Specifically, it achieves a synergistic balance between efficient cutoff (transmittance <20%) in the 280–330 nm high-energy ultraviolet band and efficient transmission (transmittance >70%) in the 330–380 nm light-conversion-excited ultraviolet band. This technical indicator directly determines the excitation efficiency of the light conversion agent and the initial power output of the photovoltaic module, and is the core embodiment of the value of this invention.

[0140] Regarding spectral selectivity transmittance, the UV cutoff layers of Examples 1-7 of this invention, under independent testing, maintained transmittance of <20% in the 280-330nm high-energy UV band, achieving efficient cutoff of high-energy UV light; simultaneously, transmittance remained >70% in the 330-380nm light conversion excitation band, providing sufficient excitation light source for the light conversion agent. In contrast, Comparative Examples 1-2 used conventional broadband UV cutoff agents, which, although achieving better cutoff in the 280-330nm band (transmittance <1%), also exhibited indiscriminate absorption in the 330-380nm excitation band (transmittance only 10%-12%), severely inhibiting the effective excitation of the light conversion agent; Comparative Examples 5-6, due to their single formulation, could not simultaneously meet the dual-band transmittance requirements, and thus failed to achieve the high selective transmittance index of this invention.

[0141] Regarding photoluminescence quantum yield (PLQY) and initial power, due to the high transmittance of the ultraviolet cutoff layer in this invention to the 330-380nm excitation band, the photoconverter can obtain sufficient excitation light source, resulting in a photoluminescence quantum yield (PLQY) of >90% for the encapsulated film. When encapsulated into a photovoltaic module, the initial output power reaches a high level. Compared to Comparative Examples 1-2, the initial power of the module of this invention is increased by approximately 3-4W, and the PLQY is increased by approximately 30 percentage points, demonstrating significant photoelectric gain. Although Comparative Example 3 has a slightly higher initial power due to the absence of an ultraviolet cutoff layer, this scheme lacks shielding against high-energy ultraviolet light in the 280-330nm range, posing a long-term risk of damage to the battery passivation layer and aging of the encapsulation material, and is not a technical solution to be considered in practice.

[0142] Regarding the impact of the preparation process on spectral selectivity, the comparison between Example 8 and Example 1 demonstrates the importance of the gradient temperature premixing process for achieving high selective transmittance. Example 8 did not employ the gradient temperature process, resulting in decreased dispersion uniformity of the UV-absorbing functional component, increased risk of microcrystal precipitation, and a drop in transmittance in the 330–380 nm band to near the lower limit required by this invention. PLQY and initial power also deteriorated to some extent. This indicates that the preferred gradient temperature process of this invention can effectively eliminate light scattering risks, ensuring a stable transmittance of over 70% in the 330–380 nm band, thereby ensuring that the light conversion agent obtains a sufficient and stable excitation source.

[0143] Regarding the long-term reliability of the components, Examples 1-7 of this invention achieve high initial power while maintaining the same power decay rate after UV aging as Comparative Examples 1-3, meeting the requirements of photovoltaic module industry standards. Comparative Example 4, due to its excessively low content of co-crosslinking agent A, suffers from severe absorber precipitation, resulting in a decrease in transmittance at 330-380 nm and a significant increase in aging decay rate. This demonstrates the necessity of the specific compounding ratio of this invention for maintaining long-term stability of spectral selectivity.

[0144] In summary, the core advantage of this invention lies in its high selectivity transmittance, achieved for the first time through a specific blend of ultraviolet light absorption functional components and a multilayer structure design, resulting in transmittance of <20% for 280-330nm and >70% for 330-380nm. This effectively shields against high-energy ultraviolet damage while maximizing the retention of the light conversion excitation source, leading to a PLQY of over 90% for the encapsulant film and a significant increase in the initial power of the module. Regarding long-term reliability, this invention is on par with existing technologies and meets industry standards. This technical solution successfully solves the problem of synergistic optimization between initial efficiency and long-term reliability of photovoltaic modules, demonstrating significant commercial application value.

Claims

1. A multilayer light conversion encapsulating film, characterized in that, It includes a stacked ultraviolet light blocking layer and a light conversion layer; The ultraviolet light blocking layer comprises a first matrix resin and an ultraviolet light absorbing functional component dispersed therein, and the light conversion layer comprises a second matrix resin and a light conversion agent dispersed therein; The ultraviolet light cutoff layer has a transmittance of less than 20% for ultraviolet light with a wavelength of 280~330nm and a transmittance of more than 70% for ultraviolet light with a wavelength of 330~380nm.

2. The light conversion encapsulating film according to claim 1, characterized in that, The ultraviolet light absorption functional component includes a premix of ultraviolet absorber and crosslinking agent A; The ultraviolet absorber comprises at least two of ethylhexyl triazine ketone, ethylhexyl salicylate, diethylhexylbutamidotriazine ketone, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide; The co-crosslinking agent A comprises at least two of 4-acryloylmorpholine, EO(3)trimethylolpropane triacrylate, 3-(propoxy)propanetriol triacrylate, triallyl isocyanurate, and tetramethyltetravinylcyclotetrasiloxane. Based on the total mass of the ultraviolet light absorbing functional components, the mass percentage of the ultraviolet absorber is 10% to 25%, and the mass percentage of the crosslinking agent A is 75% to 90%.

3. The light conversion encapsulating film according to claim 2, characterized in that, The ultraviolet absorber comprises diethylhexylbutamidotriazine ketone, and also comprises at least one of ethylhexyl salicylate, ethylhexyltriazine ketone, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide; The mass percentage of the diethylhexylbutamidotriazine ketone is 5% to 35%, based on the total mass of the ultraviolet absorber.

4. The light conversion encapsulating film according to claim 3, characterized in that, The ultraviolet absorber comprises diethylhexylbutamidotriazinone and ethylhexyl salicylate, and also comprises at least one of ethylhexyltriazinone and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide; Based on the total mass of the ultraviolet absorber, the mass percentage of diethylhexylbutamidotriazine ketone is 10% to 30%, and the mass percentage of ethylhexyl salicylate is 50% to 90%.

5. The light conversion encapsulating film according to claim 3, characterized in that, The ultraviolet absorber is composed of diethylhexylbutamidotriazinone, ethylhexyl salicylate, ethylhexyltriazinone, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide; Specifically, based on the total mass of the ultraviolet absorber, the mass percentage of ethylhexyl salicylate is 50%~80%, and the mass percentage of N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide is 1%~10%. The remaining amount of the ultraviolet absorber is ethylhexyl triazine ketone and diethylhexylbutamidotriazine ketone, with a mass ratio of 1:(2~5).

6. The light conversion encapsulating film according to claim 3, characterized in that, The ultraviolet absorber is composed of diethylhexylbutamidotriazinone, ethylhexyl salicylate, and N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide; Based on the total mass of the ultraviolet absorber, the mass percentage of N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-oxalamide is 1% to 10%. The remaining amount of the ultraviolet absorber is diethylhexylbutamidotriazinone and ethylhexyl salicylate, with a mass ratio of 1:(1~3).

7. The light conversion encapsulating film according to claim 2, characterized in that, The co-crosslinking agent A is composed of 4-acryloylmorpholine and EO(3) trimethylolpropane triacrylate; The mass ratio of 4-acryloylmorpholine to EO(3)trimethylolpropane triacrylate is 1:(2~5).

8. The light conversion encapsulating film according to claim 1, characterized in that, The thickness ratio of the ultraviolet light cutoff layer to the light conversion layer is 1:(0.2~4.0).

9. The light conversion encapsulating film according to claim 2, characterized in that, By weight, the ultraviolet light blocking layer comprises the following components: First matrix resin: 100 parts; Ultraviolet absorber: 0.05~0.5 parts; Crosslinking agent A: 0.4~1.2 parts; Crosslinking agent: 0.3~1.0 parts; Coupling agent: 0.1~0.6 parts; Light stabilizer: 0.05~0.3 parts; Antioxidant: 0.01~0.2 parts.

10. The light conversion encapsulating film according to claim 1, characterized in that, The light conversion layer comprises the following components in parts by weight: Second matrix resin: 100 parts; Light conversion agent: 0.01~0.5 parts; Crosslinking agent: 0.3~1.0 parts; Crosslinking agent B: 0.4~1.2 parts; Coupling agent: 0.1~0.6 parts; Light stabilizer: 0.05~0.3 parts; Antioxidant: 0.01~0.2 parts.

11. The light conversion encapsulating film according to claim 1, characterized in that, The first matrix resin is an ethylene-vinyl acetate copolymer, wherein the vinyl acetate content is 26~35 wt% and the melt index is 4~30 g / 10min; And / or, The second matrix resin is an ethylene-α-olefin copolymer or an ethylene-vinyl acetate copolymer; the ethylene-α-olefin copolymer is selected from at least one of ethylene-1-butene copolymer, ethylene-1-octene copolymer, and ethylene-propylene-1-hexene copolymer.

12. The light conversion encapsulating film according to claim 10, characterized in that, The co-crosslinking agent B is selected from at least one of the following: trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, triallyl isocyanurate, tetramethyltetravinylcyclotetrasiloxane, 4-acryloylmorpholine, 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, neopentyl glycol diacrylate, polyethylene glycol 200 diacrylate, EO(3)trimethylolpropane triacrylate, and 3(propoxy)propanetriol triacrylate.

13. The light conversion encapsulating film according to claim 9 or 10, characterized in that, The crosslinking agent is selected from at least one of 1,1-bis-tert-butylperoxide-3,3,5-trimethylcyclohexane, tert-butylperoxide-3,5,5-trimethylhexanoate, and benzoyl peroxide; And / or, The coupling agent is a silane coupling agent selected from at least one of vinyltrimethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, aminopropyltrimethoxysilane, bis(3-triethoxysilylpropyl)amine, N,N-dimethyl-3-aminopropyltrimethoxysilane, 1,3,5-tris(trimethoxysilylpropyl)isocyanate, n-dodecyltrimethoxysilane, n-octyltrimethoxysilane, and cyclohexyltrimethoxysilane. And / or, The light stabilizer is selected from at least one of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, hexadecyl 3,5-di-tert-butyl-4-hydroxybenzoate, (1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, mono(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, and poly{[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidinyl)imino]}; And / or, The antioxidant is selected from at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3,5-di-tert-butyl-4-hydroxybenzyl diethylphosphonate, and 4,4'-p-isopropyl diphenyl C12-15-ol phosphite.

14. A method for preparing a multilayer light conversion encapsulating film as described in any one of claims 1 to 13, characterized in that, The preparation method includes the following steps: The first matrix resin is mixed with the ultraviolet light absorption functional component to obtain the ultraviolet light blocking layer melt; The second matrix resin is mixed with a light conversion agent to obtain a light conversion layer melt; The ultraviolet light cutoff layer melt and the light conversion layer melt are simultaneously extruded through a co-extrusion die and cooled to form the multi-layered light conversion encapsulation film.

15. The preparation method according to claim 14, characterized in that, The preparation method of the ultraviolet light absorption functional component includes: The ultraviolet absorber is mixed with a portion of the crosslinking agent A to obtain a mixture; The mixture is heated to 50-60°C and stirred for the first time. Then another portion of crosslinking agent A is added and the temperature is raised to 90~100℃ for a second stirring to form the ultraviolet light absorption functional component.

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