A silver-based reflective heat-insulating window film with radio frequency transmissivity and its preparation method

Abstract

This invention discloses a silver-based reflective heat-insulating window film with radio frequency (RF) transmittance and its preparation method. The window film adopts a multi-layer composite structure, including a transparent polymer substrate, a high-performance curing layer, a composite functional layer deposited by magnetron sputtering, an RF transparent layer, and a release layer with pressure-sensitive adhesive. The composite functional layer is composed of a first dielectric layer (SiO2), a silver functional layer (8-15 nm thick), and a second dielectric layer (ITO) sequentially. The preparation method includes key steps such as substrate pretreatment, coating and UV curing of the curing layer, magnetron sputtering deposition of the functional layer, coating and curing of the RF transparent layer, interlayer lamination, and curing. By precisely controlling the silver layer thickness at the nanometer level and supplementing it with specific dielectric and RF transparent layers, this invention enables the window film to maintain high reflectivity (≥85%) for near-infrared light to achieve efficient heat insulation, while simultaneously exhibiting high transmittance (≥60%) for RF signals in the 1-5 GHz frequency band, thus achieving a balance between heat insulation performance and communication signal transmittance.

Description

Technical Field

[0001] This invention relates to the field of functional materials technology, specifically to a window film and its preparation method, particularly a silver-based reflective heat-insulating window film that combines high-efficiency near-infrared reflective heat insulation performance with excellent radio frequency signal transmission. Background Technology

[0002] Window film, a functional material applied to glass surfaces, is widely used in the automotive and construction industries. Its main functions include heat insulation, sun protection, explosion protection, and enhanced privacy. Among these, heat insulation performance is one of the core indicators, directly affecting energy efficiency and driving comfort.

[0003] In existing technologies, the main technical approaches to achieving the heat insulation function of window films include absorptive heat insulation and reflective heat insulation. For example, Invention 1 (CN104175664A) and Invention 2 (CN104175665A), which are relatively close to the technical solution of this invention, disclose the use of a functional adhesive layer containing a specific organic heat-insulating material (such as N,N',N''-tetratetra[4-(dibutylamino)phenyl]-1,4-cyclohexadiene-3,6-diammonium hexafluoroantimonate) to achieve heat insulation by utilizing the absorption of near-infrared light by this material. Although this type of technical solution can provide a certain heat insulation effect and can be colored by adding dyes, its heat insulation capacity depends on the absorption efficiency of the material molecules, and has problems such as limited improvement in heat insulation performance, possible attenuation of the absorbing material due to long-term light exposure, and sacrificing too much visible light transmittance in pursuit of high heat insulation. More importantly, this type of solution does not consider the transmittance of radio frequency signals at all.

[0004] On the other hand, reflective heat-insulating window films based on metal layers (such as silver and aluminum) deposit a functional metal layer on a substrate using techniques such as magnetron sputtering. This layer utilizes the high reflectivity of the metal to the near-infrared band of sunlight to achieve efficient heat insulation, and its performance is generally superior to absorptive heat insulation. However, traditional metal film layers (especially continuous and thick metal layers) have a strong shielding effect on electromagnetic waves, which severely hinders the transmission of radio frequency signals such as GPS, mobile communication (4G / 5G), and ETC. This leads to problems such as navigation failure and weak communication signals in cars after the film is applied, failing to meet the urgent needs of modern intelligent transportation and the Internet of Things era for high radio frequency transmittance of car windows.

[0005] Therefore, there is an urgent need in this field for an innovative window film solution that breaks through the limitations of traditional technologies: it must inherit the high efficiency and long-lasting heat insulation advantages of metal-based reflective heat insulation window films, while fundamentally solving the problem of shielding radio frequency signals, so as to achieve an excellent balance between heat insulation performance and radio frequency transmission performance. Summary of the Invention

[0006] To address the aforementioned shortcomings, this invention discloses a silver-based reflective heat-insulating window film with radio frequency transmittance and its preparation method. Through innovative layered structure design and precise process control, this invention simultaneously achieves high reflectivity and heat insulation for near-infrared light and efficient transmission of radio frequency signals in commonly used communication bands within a single window film product, thereby meeting the high-end demands of modern automobiles and buildings for multifunctional integrated window films.

[0007] The present invention includes the following technical solutions.

[0008] A method for preparing a silver-based reflective heat-insulating window film with radio frequency transmissivity, characterized by comprising the following steps: (1) Substrate pretreatment: Provide a transparent polyester film substrate with a thickness of 50-125μm, at a power density of 100-300W / m 2 The surface tension is reduced to 50-60 dyn / cm by corona or plasma treatment. (2) Hardening layer coating and curing: Apply a high-performance hard coating to one side of the treated substrate, with a wet film thickness of 5-15 μm, dry at 80-100℃ for 2-5 minutes, and then cure under nitrogen protection at 600-1000 mJ / cm 2 The high-performance hard coating is cured by ultraviolet light energy to form a hardened layer; the solid content of the coating is 30-50%, and the viscosity is 20-50 cP. (3) Deposition of composite functional layer: A first dielectric layer, a silver functional layer and a second dielectric layer are sequentially deposited on the hardened layer by magnetron sputtering to form a composite functional layer; wherein, the first dielectric layer is a SiO2 layer with a thickness of 15-25 nm, a sputtering power of 3-5 kW and a working pressure of 0.3-0.5 Pa; the silver functional layer has a thickness of 8-15 nm, a sputtering power of 0.8-1.5 kW and a working pressure of 0.4-0.6 Pa; the second dielectric layer is an ITO layer with a thickness of 30-50 nm, a sputtering power of 4-6 kW and a working pressure of 0.3-0.5 Pa; (4) Coating and curing of the radio frequency transparent layer: Coating the radio frequency transparent layer onto the composite functional layer with a wet film thickness of 3-8 μm, drying at 60-80℃ for 1-3 minutes, and then curing in air at 300-600 mJ / cm 2 The coating is cured by ultraviolet light energy to form a radio frequency transparent layer; the solid content of the radio frequency transparent layer coating is 20-35%, the viscosity is 15-35 cP, and the refractive index after curing is 1.45-1.55. (5) Preparation of release film with adhesive: Provide a transparent release film with pressure-sensitive adhesive layer; the pressure-sensitive adhesive layer is formed by coating an acrylic pressure-sensitive adhesive onto a polyester release film, and the dry adhesive thickness is 10-25 μm; (6) Interlayer lamination: The base film with radio frequency transparent layer obtained in step (4) is laminated with the adhesive release film obtained in step (5). The lamination temperature is 25-40℃ and the lamination pressure is 0.3-0.6 MPa. (7) Curing and post-treatment: Curing is carried out at 40-55℃ for 48-72 hours, then cut and rolled to obtain the finished window film.

[0009] Furthermore, in the above preparation method, the raw materials of the high-performance hard coating in step (2) include, by weight: 40-60 parts of aliphatic polyurethane acrylate oligomer, 15-25 parts of pentaerythritol triacrylate monomer, 5-15 parts of hexafunctional dipentaerythritol hexaacrylate monomer, 10-20 parts of nano alumina sol (particle size 10-30 nm), 2-5 parts of a mixture of photoinitiator 184 and photoinitiator TPO, 0.3-1 parts of leveling agent BYK-333, and 30-50 parts of propylene glycol methyl ether acetate solvent.

[0010] The present invention also discloses a silver-based reflective heat-insulating window film with radio frequency transmissivity, which is prepared by the above-described preparation method.

[0011] Furthermore, in the aforementioned silver-based reflective heat-insulating window film, the total thickness of the window film is 75-200 μm, wherein the thickness of the transparent polyester film substrate is 50-125 μm, the thickness of the hardened layer is 3-8 μm, the total thickness of the composite functional layer is 50-90 nm, the thickness of the radio frequency transparent layer is 2-6 μm, and the thickness of the pressure-sensitive adhesive layer is 10-25 μm.

[0012] Furthermore, the aforementioned silver-based reflective heat-insulating window film has an average reflectivity of not less than 35% in the 380-780 nm visible light band and an average reflectivity of not less than 85% in the 900-2500 nm near-infrared band.

[0013] Furthermore, the above-mentioned silver-based reflective heat-insulating window film has an average radio frequency signal transmittance of not less than 65% in the 1-3 GHz frequency range, and a signal transmittance of not less than 60% in the 5G communication frequency bands: 3.3-3.6 GHz and 4.8-5.0 GHz.

[0014] Furthermore, the aforementioned silver-based reflective heat-insulating window film has a total solar reflectance of not less than 40% and a visible light transmittance adjustable within the range of 10%-50%.

[0015] Furthermore, in the aforementioned silver-based reflective heat-insulating window film, the water contact angle of the radio frequency transparent layer surface is greater than 90°, and the pencil hardness is not less than 2H.

[0016] Furthermore, in the aforementioned silver-based reflective heat-insulating window film, the first dielectric layer is a SiO2 layer, the silver functional layer is a continuous nano-silver layer, and the second dielectric layer is a composite oxide layer of In2O3 and SnO2.

[0017] The present invention also discloses the application of the above-mentioned silver-based reflective heat-insulating window film with radio frequency transmissivity in automobile windows or building window glass.

[0018] Compared with the prior art, the present invention has the following outstanding advantages: 1. This innovative solution resolves the long-standing industry dilemma of the incompatibility between high heat insulation and effective signal transmission. Through a unique composite structure design of a "dielectric layer-nano-silver layer-dielectric layer" and the synergistic effect of the radio frequency transparent layer, it achieves selective high reflectivity of solar radiation heat and efficient transmission of electromagnetic waves in communication bands. 2. Excellent performance and long-lasting stability. Compared to traditional solutions relying on organic dyes for heat insulation, this invention's inorganic metal reflective system offers higher heat insulation efficiency, slower performance degradation, and significantly improved weather resistance. 3. Reliable structure and wide applicability. The multi-layered structure design balances adhesion, flexibility, and environmental stability, meeting the stringent requirements of demanding applications such as automotive curved glass film, and possesses broad market prospects. Attached Figure Description

[0019] Figure 1 Flowchart of the manufacturing process of the silver-based reflective heat-insulating window film with radio frequency transmissivity described in this invention; Figure 2 A schematic diagram of the structure of the silver-based reflective heat-insulating window film with radio frequency transmissivity described in this invention. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Table 1: Main Raw Materials Table 2: Raw Material Composition and Parameters of High-Performance Hard Coatings A method for preparing a silver-based reflective heat-insulating window film with radio frequency transmissivity, such as... Figure 1 As shown, it includes the following steps: (1) Substrate pretreatment: A transparent polyethylene terephthalate (PET) film substrate with a thickness of 75 μm is provided, and the power density is 200 W / m 2The surface tension is reduced to 55 dyn / cm by corona treatment.

[0022] (2) Hardening layer coating and curing: A high-performance hard coating is applied to one side of the treated substrate, with a wet film thickness of 10 μm. It is dried at 90°C for 3 minutes, and then cured under nitrogen protection at 800 mJ / cm. 2 The coating is cured by ultraviolet light energy to form a hardened layer; the high-performance hard coating has a solid content of 40% and a viscosity of 35 cP, and its raw materials include, by weight: 50 parts of aliphatic polyurethane acrylate oligomer, 20 parts of pentaerythritol triacrylate monomer, 10 parts of hexafunctional dipentaerythritol hexaacrylate monomer, 15 parts of nano alumina sol (particle size 20 nm), 3.5 parts of a mixture of photoinitiator 184 and photoinitiator TPO (mass ratio 1:1), 0.6 parts of leveling agent BYK-333, and 40 parts of propylene glycol methyl ether acetate solvent.

[0023] (3) Deposition of composite functional layer: A first dielectric layer (SiO2 layer), a silver functional layer, and a second dielectric layer (ITO layer) are sequentially deposited on the hardened layer by magnetron sputtering to form a composite functional layer. The specific parameters are as follows: the thickness of the first dielectric layer is 20 nm, the sputtering power is 4 kW, and the working pressure is 0.4 Pa; the thickness of the silver functional layer is 10 nm, the sputtering power is 1.2 kW, and the working pressure is 0.5 Pa; the thickness of the second dielectric layer is 40 nm, the sputtering power is 5 kW, and the working pressure is 0.4 Pa.

[0024] (4) Coating and curing of the radio frequency transparent layer: The radio frequency transparent layer coating is applied to the composite functional layer with a wet film thickness of 5 μm. It is dried at 70°C for 2 minutes, and then cured in air at 450 mJ / cm 2 The coating is cured by ultraviolet light energy to form a radio frequency transparent layer; the solid content of the radio frequency transparent layer coating is 28%, the viscosity is 25 cP, and the refractive index after curing is 1.50.

[0025] (5) Preparation of release film with adhesive: Provide a transparent release film with pressure-sensitive adhesive layer; the pressure-sensitive adhesive layer is formed by coating an acrylic pressure-sensitive adhesive onto a polyester release film, and the dry adhesive thickness is 18 μm.

[0026] (6) Interlayer lamination: The base film with radio frequency transparent layer obtained in step (4) is laminated with the adhesive release film obtained in step (5). The lamination temperature is 30℃ and the lamination pressure is 0.4 MPa.

[0027] (7) Curing and post-treatment: The film is cured at 50°C for 60 hours, then slit and rolled to obtain the finished window film. The structure of the finished window film is as follows: Figure 2 As shown.

[0028] Example 2 A method for preparing a silver-based reflective heat-insulating window film with radio frequency transmissivity is basically the same as that in Example 1, except that the following parameters are used to achieve higher infrared reflective heat insulation performance: (1) The substrate is a PET film with a thickness of 125μm.

[0029] (2) The wet film thickness of the hard coating is 15 μm, and the UV curing energy is 1000 mJ / cm. 2 .

[0030] (3) The parameters of the composite functional layer are adjusted as follows: the thickness of the first dielectric layer (SiO2) is 25 nm; the thickness of the silver functional layer is 12 nm; and the thickness of the second dielectric layer (ITO) is 45 nm.

[0031] (4) The wet film thickness of the radio frequency transparent layer is 3 μm, and the curing energy is 600 mJ / cm. 2 .

[0032] (5) The dry adhesive layer thickness is 25μm.

[0033] Example 3 A method for preparing a silver-based reflective heat-insulating window film with radio frequency transmissivity is basically the same as that in Example 1, except that the following parameters are used to optimize the radio frequency signal transmission performance: (1) The substrate is a PET film with a thickness of 50 μm.

[0034] (2) The thickness of the wet film of the hard coating is 5 μm.

[0035] (3) The parameters of the composite functional layer are adjusted as follows: the thickness of the first dielectric layer (SiO2) is 15 nm; the thickness of the silver functional layer is 8 nm; and the thickness of the second dielectric layer (ITO) is 35 nm.

[0036] (4) The wet film thickness of the radio frequency transparent layer is 8 μm, the solid content of the coating is 20%, and the curing energy is 300 mJ / cm. 2 After curing, the refractive index is 1.45.

[0037] (5) The dry adhesive layer thickness is 10μm.

[0038] (7) The curing time is 48 hours.

[0039] Comparative Example 1: A method for preparing a heat-insulating window film, the steps of which are basically the same as those in Example 1, the difference being: In step (3), instead of using magnetron sputtering to deposit the silver-based composite functional layer, a heat-insulating adhesive layer as described in prior art document 1 is coated. Specifically, a mixture consisting of a heat-insulating substance (N,N',N''-tetratetra[4-(dibutylamino)phenyl]-1,4-cyclohexadiene-3,6-diammonium hexafluoroantimonate), acrylic adhesive, curing agent, methyl ethyl ketone (MEK), and toluene (mass ratio 1.5:35:0.2:15:8) is coated and heat-cured at 100°C for 60 seconds to form a heat-insulating adhesive layer with a thickness of approximately 15 μm. The remaining steps remain unchanged.

[0040] Comparative Example 2 A method for preparing a window film, the steps of which are basically the same as those in Example 1, the difference being: Step (4) is omitted, i.e., the radio frequency transparent layer is not coated and cured on the composite functional layer. The remaining steps remain unchanged.

[0041] Comparative Example 3 A method for preparing a window film, the steps of which are basically the same as those in Example 1, the difference being: In step (3), the composite functional layer structure is changed to a single continuous thick silver layer. Specifically, a continuous silver layer with a thickness of 50 nm is deposited by magnetron sputtering at a sputtering power of 3 kW and a working pressure of 0.5 Pa. No SiO2 or ITO dielectric layers are deposited. The remaining steps remain unchanged.

[0042] Comparative Example 4 A method for preparing a window film, the steps of which are basically the same as those in Example 1, the difference being: In step (3), the structure and process of the composite functional layer are changed to make the silver layer too thick and continuous. The specific parameters are: the thickness of the silver functional layer is adjusted to 25 nm, the sputtering power is 2 kW, and the working pressure is 0.4 Pa; no second dielectric layer (ITO layer) is deposited. The remaining steps remain unchanged.

[0043] Comparative Example 5 A method for preparing a window film, employing a multilayer composite structure similar to that in prior art document 2. Specifically: Two layers of transparent PET substrate (50μm and 75μm thick, respectively) are provided. A UV-curable scratch-resistant layer is coated on the outer side of the first PET substrate, and a dyed heat-insulating adhesive layer containing dyes and organic heat-insulating substances is coated on the inner side. A second PET substrate layer is laminated onto the dyed heat-insulating adhesive layer, and a UV-blocking pressure-sensitive adhesive layer containing UV absorbers is coated on its inner side. Finally, a release film is laminated. No magnetron sputtered metal layer or dedicated RF transparent layer is used.

[0044] Test Example 1: Comparison of near-infrared reflective heat insulation performance Objective: To verify the reflective heat insulation advantages of the silver-based composite functional layer of the present invention in the near-infrared band compared with traditional absorption heat insulation solutions.

[0045] method: Using a UV-Vis-NIR spectrophotometer, and referring to the national standard GB / T 2680, the reflectance spectra of the window film samples prepared in Example 1, Example 2, Comparative Example 1 (traditional absorption heat insulation) and Comparative Example 3 (single thick silver layer) in the 780-2500 nm near-infrared band were tested.

[0046] The average reflectance (Reflectance_avg) and solar infrared blocking rate of each sample in the 900-2500 nm band were calculated (according to ISO 13837 standard), and the results are shown in Table 3.

[0047] Table 3: Comparison of Near-Infrared Reflective Thermal Insulation Performance (*P<0.01 vs Comparative Example 1) Conclusion: Examples 1 and 2 showed significantly higher average reflectance to near-infrared light than Comparative Example 1, which relied on molecular absorption (P<0.01), demonstrating the fundamental advantages of reflective thermal insulation. Although Comparative Example 3 (a single thick silver layer) had slightly higher reflectance, it severely blocked radio frequency signals (see Test Example 2). The present invention achieves a balance between high reflectivity thermal insulation and radio frequency transmission.

[0048] Test Example 2 Radio frequency signal transmission performance evaluation Objective: To verify that the present invention, through a composite functional layer structure and radio frequency transparent layer design, effectively solves the problem of radio frequency signal shielding by the metal layer while maintaining thermal insulation performance.

[0049] method: The samples were tested in a microwave anechoic chamber using a vector network analyzer (model: Keysight N5224B) with a standard gain horn antenna.

[0050] The signal transmittance (transmission loss) of Example 1, Comparative Example 2 (without RF transparent layer), Comparative Example 3 (single thick silver layer), and Comparative Example 4 (ultra-thick continuous silver layer) in common communication frequency bands (GPS L1: 1.575 GHz, 4G LTE: 1.8-2.6 GHz, 5G Sub-6: 3.3-3.6 GHz) was measured.

[0051] The results are shown in Table 4.

[0052] Table 4: Evaluation of Radio Frequency Signal Transmission Performance (*P<0.01 vs all comparative groups; Note: The smaller the negative value of transmittance, the smaller the signal attenuation and the better the performance. -3dB is approximately equal to 50% signal power loss).

[0053] Conclusion: As shown in Table 4, Example 1 exhibits excellent RF transmission (minimal signal attenuation) across all frequency bands, significantly outperforming all comparative examples (P<0.01). Comparative Example 2 suffers increased signal attenuation due to the lack of impedance matching and protection from the RF transparent layer. Comparative Examples 3 and 4, due to the formation of continuous, excessively thick electromagnetic shielding layers, result in strong signal blockage.

[0054] Test Example 3 Accelerated aging performance stability test Objective: To verify the performance and durability of window films (especially the radio frequency transparent layer and composite functional layer) under long-term use conditions.

[0055] method: The samples from Example 1 and Comparative Example 1 were placed in a xenon lamp aging test chamber (according to standard ASTM G155, Cycle 1) to simulate sunlight exposure (0.55 W / m²). 2 (@340nm) and intermittently sprayed, to conduct a 1000-hour accelerated aging test.

[0056] Before aging, and after aging for 500 hours and 1000 hours, the visible light transmittance at 550 nm, the average reflectance at 900-2500 nm, and the signal transmittance at 2.4 GHz were tested.

[0057] The results are shown in Table 5.

[0058] Table 5: Performance stability test after accelerated aging (Comparative Example 1 has good initial radio frequency transmittance because it has no metal layer, but poor thermal insulation performance.) Conclusion: After 1000 hours of accelerated aging, the attenuation rate of all core properties (transmission, reflection, and radio frequency transmission) of Example 1 was less than 3%, demonstrating excellent stability. In contrast, the organic heat insulation layer of Comparative Example 1 degraded due to ultraviolet radiation and heat and humidity, resulting in a significant decrease (more than 30%) in near-infrared reflection (absorption) performance, and potential fading. This proves that the magnetron sputtering inorganic functional layer and ultraviolet-cured radio frequency transparent layer structure used in this invention has superior weather resistance and long-term performance retention compared to the organic absorption system.

[0059] Test Example 4 Comprehensive test of adhesion and flexural strength of multi-layer structures Objective: To verify the ability of the multilayer structure of the preferred embodiment of the present invention (Example 2) to resist physical stress during processing and use, and to compare it with relevant comparative examples that reveal the role of key features, so as to ensure its reliability in practical applications.

[0060] method: The following series of tests were performed on Example 2 and the targeted comparative samples, and the results are summarized in Table 6 below.

[0061] Table 6: Comprehensive Test of Adhesion and Bending Resistance of Multilayer Structures Overall conclusion: As can be seen from Table 6 above, the preferred embodiment of the present invention (Example 2) exhibits comprehensive and excellent mechanical reliability and environmental stability, and its performance is significantly better than that of the comparative example lacking key design features.

[0062] Test Example 5 Actual vehicle signal strength simulation test Objective: To verify the impact of applying the window film of this invention on the signal reception of in-vehicle communication devices under simulated real-world application scenarios.

[0063] method: Set up a simulated vehicle environment (a metal shielded box with an opening of standard car window size).

[0064] A GPS signal simulator and a 4G / 5G base station simulator are fixedly placed outside the box.

[0065] A commercial GPS receiver and a 4G / 5G signal tester are placed in fixed positions inside the box.

[0066] The signal strength (GPS signal-to-noise ratio SNR, 4G / 5G RSRP reference signal received power) received by the equipment inside the box was tested at the window openings: (a) without film, (b) with the film of Example 1, and (c) with a mainstream metal heat insulation film (claiming high heat insulation).

[0067] The results are shown in Table 7.

[0068] Table 7: Simulation Test of Actual Vehicle Signal Strength (*P<0.01 vs. no film and Example 1 group; the more negative the signal strength, the weaker the signal) Conclusion: As shown in Table 7, after applying the window film of Example 1, the in-vehicle GPS and mobile communication signal strength is only slightly attenuated (<3 dB) compared to the baseline state without film, which does not affect the normal use of various in-vehicle navigation, ETC, mobile communication, and IoT devices. However, after applying traditional high-heat-insulating metal film, the signal is severely blocked (attenuation >15 dB), leading to navigation failure, dropped calls, and other problems. This invention solves the industry pain point of the high-end window film field where "heat insulation and signal strength" are mutually exclusive.

[0069] The above are merely a few preferred embodiments of the present invention, described in a relatively specific and detailed manner, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for preparing a silver-based reflective heat-insulating window film with radio frequency transmissivity, characterized in that, Includes the following steps: (1) Substrate pretreatment: Provide a transparent polyester film substrate with a thickness of 50-125μm, at a power density of 100-300W / m 2 The surface tension is reduced to 50-60 dyn / cm by corona or plasma treatment. (2) Hardening layer coating and curing: Apply a high-performance hard coating to one side of the treated substrate, with a wet film thickness of 5-15 μm, dry at 80-100℃ for 2-5 minutes, and then cure under nitrogen protection at 600-1000 mJ / cm 2 The high-performance hard coating is cured by ultraviolet light energy to form a hardened layer; the solid content of the coating is 30-50%, and the viscosity is 20-50 cP. (3) Deposition of composite functional layer: A first dielectric layer, a silver functional layer and a second dielectric layer are sequentially deposited on the hardened layer by magnetron sputtering to form a composite functional layer; wherein, the first dielectric layer is a SiO2 layer with a thickness of 15-25 nm, a sputtering power of 3-5 kW and a working pressure of 0.3-0.5 Pa; the silver functional layer has a thickness of 8-15 nm, a sputtering power of 0.8-1.5 kW and a working pressure of 0.4-0.6 Pa; the second dielectric layer is an ITO layer with a thickness of 30-50 nm, a sputtering power of 4-6 kW and a working pressure of 0.3-0.5 Pa; (4) Coating and curing of the radio frequency transparent layer: Coating the radio frequency transparent layer onto the composite functional layer with a wet film thickness of 3-8 μm, drying at 60-80℃ for 1-3 minutes, and then curing in air at 300-600 mJ / cm 2 The coating is cured by ultraviolet light energy to form a radio frequency transparent layer; the solid content of the radio frequency transparent layer coating is 20-35%, the viscosity is 15-35 cP, and the refractive index after curing is 1.45-1.

55. (5) Preparation of release film with adhesive: Provide a transparent release film with pressure-sensitive adhesive layer; the pressure-sensitive adhesive layer is formed by coating an acrylic pressure-sensitive adhesive onto a polyester release film, and the dry adhesive thickness is 10-25 μm; (6) Interlayer lamination: The base film with radio frequency transparent layer obtained in step (4) is laminated with the adhesive release film obtained in step (5). The lamination temperature is 25-40℃ and the lamination pressure is 0.3-0.6 MPa. (7) Curing and post-treatment: Curing is carried out at 40-55℃ for 48-72 hours, then cut and rolled to obtain the finished window film.

2. The preparation method according to claim 1, characterized in that, The raw materials of the high-performance hard coating in step (2) include, by weight: 40-60 parts of aliphatic polyurethane acrylate oligomer, 15-25 parts of pentaerythritol triacrylate monomer, 5-15 parts of hexafunctional dipentaerythritol hexaacrylate monomer, 10-20 parts of nano alumina sol (particle size 10-30 nm), 2-5 parts of a mixture of photoinitiator 184 and photoinitiator TPO, 0.3-1 parts of leveling agent BYK-333, and 30-50 parts of propylene glycol methyl ether acetate solvent.

3. A silver-based reflective heat-insulating window film with radio frequency transmissivity, characterized in that, It is prepared by the preparation method described in claim 1 or 2.

4. The window film according to claim 3, characterized in that, The total thickness of the window film is 75-200 μm, of which the thickness of the transparent polyester film substrate is 50-125 μm, the thickness of the hardening layer is 3-8 μm, the total thickness of the composite functional layer is 50-90 nm, the thickness of the radio frequency transparent layer is 2-6 μm, and the thickness of the pressure-sensitive adhesive layer is 10-25 μm.

5. The window film according to claim 3, characterized in that, The average reflectance of the window film is not less than 35% in the visible light band of 380-780 nm and not less than 85% in the near-infrared band of 900-2500 nm.

6. The window film according to claim 3, characterized in that, The average radio frequency signal transmittance of the window film is not less than 65% in the 1-3 GHz frequency range, and the signal transmittance in the 5G communication bands of 3.3-3.6 GHz and 4.8-5.0 GHz is not less than 60%.

7. The window film according to claim 3, characterized in that, The total solar reflectance of the window film is not less than 40%, and the visible light transmittance is adjustable within the range of 10%-50%.

8. The window film according to claim 3, characterized in that, The surface of the radio frequency transparent layer of the window film has a water contact angle greater than 90° and a pencil hardness of not less than 2H.

9. The window film according to any one of claims 3 to 8, characterized in that, In the composite functional layer of the window film, the first dielectric layer is a SiO2 layer, the silver functional layer is a continuous nano-silver layer, and the second dielectric layer is a composite oxide layer of In2O3 and SnO2.

10. The application of the silver-based reflective heat-insulating window film with radio frequency transmissivity as described in any one of claims 3 to 9 on automotive windows or building window glass.

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