Low-emissivity energy-saving base film for building and preparation method thereof

Abstract

The present application relates to the technical field of functional film, in particular to a low-radiation energy-saving base film for building and a preparation method thereof.The present application overcomes the problem that the mechanical property and optical property of the energy-saving base film in the prior art cannot be considered simultaneously.The present application is prepared from a PET substrate with a skin-core structure, a functional coating and a seven-layer magnetron sputtering film;the skin layer of the PET substrate is PET modified by melt grafting with UVA and HALS additives;the functional coating comprises a water-based PUA emulsion, nano-silicon dioxide and KH550;the seven-layer magnetron sputtering film comprises, from bottom to top, a TiON bottom layer, a Nb2O5 lower layer, an Ag-Pd-Ti lower layer, an AZO layer, an Ag-Pd-Ti upper layer, a Nb2O5 upper layer and a TiON top layer.Through the synergistic effect of grafting modification, functional coating and multi-layer sputtering, the present application maintains the mechanical property while realizing the balance of visible light transmittance and infrared thermal radiation reflectance, and can be applied to the energy-saving field such as building glass.

Description

Technical Field

[0001] This invention relates to the field of functional thin film technology, specifically to low-emissivity energy-saving base films for buildings and their preparation methods. Background Technology

[0002] Architectural and automotive glass are the main application areas for energy-saving films. The core technological requirement is to effectively block infrared heat energy in solar radiation while maximizing the transmission of visible light to save energy consumption for lighting and air conditioning. Early energy-saving films, although having high infrared reflectivity, had extremely low visible light transmittance and were called "heat-reflective films," which seriously affected indoor lighting.

[0003] Currently, commercial energy-saving base films generally employ magnetron sputtering technology to deposit multilayer film systems on optical-grade PET substrates to achieve "high light transmittance and high heat insulation." However, the inorganic sputtered layer and the organic PET substrate have vastly different physicochemical properties and mismatched coefficients of thermal expansion, severely impacting product lifespan. Furthermore, the core functional layer, silver, is chemically reactive and easily corroded and oxidized, leading to a decline in heat insulation performance. The PET substrate itself will yellow and become brittle under long-term ultraviolet radiation, resulting in decreased mechanical properties and affecting the overall performance stability.

[0004] To address the contradiction between visible light transmittance and infrared thermal radiation reflectance, existing technologies have developed selective spectral thin films based on a "dielectric layer-metal layer-dielectric layer" structure. Among these, the silver layer, due to its excellent properties of high transmittance in the visible light region and high reflectance in the infrared region, has become the core functional metal layer. However, the single silver layer structure has limited ability to balance light transmittance and thermal insulation: if the silver layer is too thin, the light transmittance is high but the infrared reflection is insufficient; if the silver layer is too thick, the thermal insulation performance is good but the light transmittance will decrease, and it will also face the problem of oxidation.

[0005] To address these issues, existing technologies have developed complex double-silver or even triple-silver multilayer film systems. By precisely controlling the thickness of each dielectric and metal layer and utilizing the principle of thin-film interference, it is possible to broaden the infrared reflection bandwidth while simultaneously enhancing the visible light region. However, this method, which relies purely on optimizing the film system structure, ignores the limitations of the PET substrate itself. Issues such as substrate aging and poor adhesion between the substrate and the film layers remain fundamental obstacles to achieving long-term, stable performance in high-end energy-saving films. Therefore, existing technologies still suffer from the inability to simultaneously achieve optimal mechanical and optical properties in energy-saving base films.

[0006] To this end, a low-emissivity energy-saving base film for buildings and its preparation method were proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a low-emissivity energy-saving base film for building applications and its preparation method. This invention is prepared from a core-skin structured PET substrate, a functional coating, and a seven-layer magnetron sputtered film. The skin layer of the PET substrate is PET that has been melt-grafted and modified with UVA and HALS. The functional coating comprises an aqueous PUA emulsion, nano-silica, and KH550. The seven-layer magnetron sputtered film, from bottom to top, consists of a TiON bottom layer, a Nb2O5 bottom layer, an Ag-Pd-Ti bottom layer, an AZO layer, an Ag-Pd-Ti top layer, a Nb2O5 top layer, and a TiON top layer. This invention, through the synergistic effect of graft modification, functional coating, and multilayer sputtering, maintains mechanical properties while achieving a balance between visible light transmittance and infrared thermal radiation reflectivity, making it applicable to energy-saving fields such as architectural glass and automotive windows.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] This invention provides a method for preparing a low-emissivity energy-saving base film for buildings, comprising the following preparation process:

[0010] 4-6 parts of grafted PET chips were used as the skin layer A, and 88-92 parts of optical-grade PET chips were used as the core layer B. These were added to a three-layer co-extrusion film equipment according to an A / B / A structure, with an extrusion temperature of 280-300℃ to obtain the extrudate. The extrudate was cooled by cold rollers and then biaxially stretched. The longitudinal stretching temperature was 90-110℃, with a stretch ratio of 3.5-3.8 times; the transverse stretching temperature was 110-130℃, with a stretch ratio of 4.0-4.2 times to obtain the stretched film. The stretched film was heated to 225-240℃ and heat-set for 15-30 seconds; then slowly cooled to 60-80℃ and processed through a micro-... The concave roller coating unit delivers the functional coating liquid to the coating head. The micro-concave roller rotates in the opposite direction to the film, uniformly transferring a measured amount of coating liquid to the side of the film to be sputtered to obtain a coated film. The coated film is placed in a multi-stage hot air oven for segmented drying. The drying stage temperature is 90-110℃ for 5 seconds, and the curing stage temperature is 140-160℃ for 10 seconds. After cooling to room temperature by a cooling roller, it is wound up to obtain a modified PET substrate, wherein the dry coating thickness is 0.8-1.2μm, and the total substrate thickness is 48-52μm.

[0011] Preferably, the preparation method of grafted PET chips is as follows: PET chips are placed in a vacuum drying oven and dried at 150℃ for 4-6 hours to obtain dried chips; 100 parts of dried chips and 0.3-0.6 parts of pyromellitic dianhydride are added to a co-rotating twin-screw extruder (L / D ratio ≥ 40:1) through the main feed port; 1-1.5 parts of UVA additives, 0.8-1.2 parts of HALS additives, and 0.2-0.4 parts of initiator 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane are premixed into a homogeneous liquid at room temperature, and then fed into the twin-screw extruder by a high-precision metering pump. The material is injected into five zones (rear of the melting zone), with the following temperatures: conveying zone (zones 1-2) 250-265℃; melting zone (zones 3-4) 275-285℃; reaction mixing zone (zones 5-7) 285-295℃; venting zone (zones 8-9) 280-290℃; and die head 270-280℃. The screw speed is maintained at 250-350 rpm. A vacuum port is set in zone 8, and the vacuum degree is maintained at -0.08 to -0.10 MPa to obtain the molten material. The molten material is cooled in a water bath, dried by blowing, granulated, and vacuum dried at 160℃ for 8 hours to obtain grafted PET chips.

[0012] Preferably, the preparation method of the functional coating liquid is as follows: 0.5 parts by mass of 3-aminopropyltriethoxysilane are slowly added dropwise to 15 parts of deionized water and stirred at 100 rpm for 30-60 min to dissolve and obtain a solution; 16 parts of aqueous PUA emulsion are added to a reaction vessel, and 2.5 parts of nano-silica aqueous dispersion are added under stirring at 50-100 rpm and stirred for 40 min; the solution is then slowly added and stirred at 100 rpm for 20 min to obtain a mixture; the mixture is diluted with 66 parts of deionized water, and 0.4 parts of aziridine crosslinking agent are added, and the mixture is dispersed and stirred at high speed for 15 min, maintaining a speed of 100-150 rpm for 15 min; then filtered through a 10 μm filter and allowed to stand for 30 min to defoam to obtain the functional coating liquid;

[0013] Preferably, the continuous roll-to-roll magnetron sputtering coating includes: cleaning a modified PET substrate via online plasma glow discharge cleaning at a power of 1.0 kW and an argon flow rate of 200 sccm to obtain treated PET; then, following a bottom-to-top sequence, under vacuum conditions ≤ 5.0 × 10⁻⁴ Pa, working pressure of 0.35 Pa, and substrate linear velocity of 1.5 m / min, performing mid-frequency pulse reactive sputtering on a Ti target at a power of 12 kW and argon, nitrogen, and oxygen flow rates of 150, 25, and 5 sccm, respectively, to obtain a 25 nm thick TiON underlayer; performing mid-frequency pulse reactive sputtering on a Nb target at a power of 15 kW and argon and oxygen flow rates of 120 and 30 sccm, respectively, to obtain a 35 nm thick Nb₂O₅ underlayer; and finally, pulsed DC sputtering on an Ag-Pd-Ti alloy target at a power of 8 kW and an argon flow rate of 200 sccm, to obtain a 14 nm thick layer. A lower Ag-Pd-Ti layer was formed; an AZO target was sputtered at a medium-frequency pulse (18 kW) with argon and oxygen flow rates of 180 sccm and 3 sccm, respectively, to obtain a 70 nm thick AZO layer; an Ag-Pd-Ti alloy target was sputtered at a pulsed DC (7 kW) with argon flow rate of 200 sccm, to obtain a 12 nm thick Ag-Pd-Ti upper layer; a Nb target was sputtered at a medium-frequency pulse (13 kW) with argon and oxygen flow rates of 120 sccm and 28 sccm, respectively, to obtain a 30 nm thick Nb₂O₅ upper layer; and a Ti target was sputtered at a medium-frequency pulse (10 kW) with argon, nitrogen, and oxygen flow rates of 150, 20, and 3 sccm, respectively, to obtain a 25 nm thick TiON top layer. The thickness of each layer was controlled in real time using an optical film thickness monitoring system. The seven-layer composite material was then wound up to obtain a low-emissivity energy-saving base film.

[0014] The present invention also provides a low-emissivity energy-saving base film for building, which, from bottom to top, consists of a modified PET substrate, a TiON bottom layer, a Nb2O5 bottom layer, an Ag-Pd-Ti bottom layer, an AZO layer, an Ag-Pd-Ti top layer, an Nb2O5 top layer, and a TiON top layer.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] 1. This invention introduces pyromellitic dianhydride into the skin layer for melt grafting, forming a branched network structure on the PET molecular chain. This not only improves the interfacial compatibility and modulus matching between the skin layer and the core PET layer, but also effectively suppresses chain breakage caused by shear stress during co-extrusion and stretching. At the same time, the resulting gradient interface structure can effectively buffer and dissipate external stress. Compared with the stress concentration and microcrack propagation problems caused by abrupt modulus changes between inorganic film layers and organic substrates in the prior art, the integrated stable structure of this invention improves the tensile strength and fatigue fracture resistance of the base film.

[0017] 2. This invention employs melt grafting technology to firmly anchor UVA and HALS onto the molecular chain of the PET skin layer through chemical bonds, achieving permanent endogenous UV protection for the substrate. Simultaneously, the external dense organic-inorganic hybrid coating and TiON sputtered top layer constitute a physical barrier, effectively isolating water and oxygen erosion. Through the dual protection system of internal chemical anchoring and external physical barrier, the surface protection of UVA and the point removal mechanism of HALS work together to form a complete protection chain against aging factors such as ultraviolet rays, damp heat, and oxidation.

[0018] 3. This invention employs an asymmetric double silver layer structure, introducing an AZO layer as the central dielectric layer, which, in conjunction with the high refractive index dielectric layers on both sides, constructs a highly efficient dual-band antireflection structure. Compared with conventional single silver or symmetric double silver film systems, it allows for more precise control of thin film interference effects, maximizing visible light transmittance while broadening the infrared high reflectivity region. In addition, the modified substrate and functional coating provide an ultra-smooth, high surface energy substrate, ensuring superior film quality and fewer defects in the sputtered silver layer, thereby fundamentally reducing light scattering and absorption losses and achieving a balance between visible light transmittance and infrared thermal radiation reflectivity.

[0019] 4. This invention employs a multi-anchoring scheme involving surface functionalization, hybrid coating bridging, and alloy deposition. Graft modification introduces polar functional groups into the PET skin layer, increasing surface energy. The functional coating can form strong chemical bonds. Simultaneously, the nano-silica in the coating increases the mechanical interlocking force through a physical filling effect. The active metal Ti in the sputtered Ag-Pd-Ti alloy target further enhances the bonding force between the metal layer and the dielectric layer. Through the gradient interface of the synergistic effect of chemical bonding and physical anchoring, the film adhesion is far superior to that of a single physical method relying on plasma treatment.

[0020] 5. This invention achieves a balance between high visible light transmittance and high infrared thermal radiation reflectance, two core optical indicators, through the synergistic matching of grafted PET, functional coatings, and sputtered film systems in terms of chemical structure, physical properties, and process parameters. Compared with existing technologies that focus on optimizing the optical design of sputtered film systems while ignoring the limitations of substrate performance, this invention significantly improves overall performance and can be widely applied in energy-saving fields such as architectural glass and automotive windows. Attached Figure Description

[0021] Figure 1 The tensile strength retention rate of the energy-saving base film obtained in Examples 1, 5, and Comparative Examples 8-12 of this invention is shown. Detailed Implementation

[0022] 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. 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.

[0023] The intrinsic viscosity of the optical-grade PET chips is 0.65. The UVA additive is 2-(2'-hydroxy-5'-methacryloyloxyethylphenyl)-2H-benzotriazole, CAS number 96478-09-0; the HALS additive is 1,2,2,6,6-pentamethyl-4-piperidinyl methacrylate, CAS number 68548-08-3; the mass percentages of silver, palladium, and titanium in the Ag-Pd-Ti alloy target are 96.5%, 2%, and 1.5%, respectively, and the remaining metal targets are commercially available materials; the KH550 is 3-aminopropyltriethoxysilane; the aqueous PUA emulsion is an aqueous polyurethane acrylate emulsion with a solid content of 40%, an average particle size of 100 nm, and a pH value of 7.5±0.5; the nano-silica aqueous dispersion has a solid content of 30% and an average particle size of 20 nm; the aziridine crosslinking agent is polyaziridine crosslinking agent SaC-100, CAS number 64265-57-2.

[0024] Please see Figure 1 This invention provides a low-emissivity energy-saving base film for buildings and its preparation method. The technical solution is as follows:

[0025] Example 1

[0026] By mass, PET chips were placed in a vacuum drying oven and dried at 150°C for 5 hours to obtain dried chips. 100 parts of the dried chips and 0.5 parts of pyromellitic dianhydride were added to a co-rotating twin-screw extruder through the main feed port. 1.2 parts of 2-(2'-hydroxy-5'-methacryloyloxyethylphenyl)-2H-benzotriazole, 1.0 part of 1,2,2,6,6-pentamethyl-4-piperidinyl methacrylate, and 0.3 parts of the initiator 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane were premixed at room temperature to form a homogeneous liquid. This liquid was injected into the fifth zone of the twin-screw extruder through a high-precision metering pump, maintaining a screw speed of 300 rpm to obtain a molten material. The molten material was cooled in a water bath, dried by blowing, granulated, and vacuum dried at 160°C for 8 hours to obtain grafted PET chips.

[0027] By mass, 0.5 parts of 3-aminopropyltriethoxysilane were slowly added dropwise to 15 parts of deionized water and stirred at 100 rpm for 40 min to dissolve and obtain a solution. 16 parts of aqueous PUA emulsion (40% solid content) were added to a reaction vessel, and 2.5 parts of nano-silica aqueous dispersion (30% solid content) were added under stirring at 80 rpm and stirred for 40 min. The solution was then slowly added and stirred at 100 rpm for 20 min to obtain a mixture. The mixture was diluted with 66 parts of deionized water, and 0.4 parts of aziridine crosslinking agent were added. The mixture was dispersed and stirred at high speed for 15 min while maintaining a speed of 150 rpm. The mixture was then filtered through a 10 μm filter and allowed to stand for 30 min to defoam to obtain a functional coating liquid.

[0028] Five grafted PET slices were used as the cortex layer A, and five optical-grade PET slices were used as the core layer B. 90 parts were added to a three-layer co-extrusion film equipment and melt-extruded according to an A / B / A structure to obtain an extrudate. The extrudate was cooled by a cold roller and subjected to biaxial stretching. The longitudinal stretching temperature was 100℃ with a stretch ratio of 3.6 times, and the transverse stretching temperature was 120℃ with a stretch ratio of 4.2 times to obtain a stretched film. The stretched film was heated to 230℃ and heat-set for 20 seconds. It was then slowly cooled to 70℃ and the functional coating liquid was delivered to the coating head through a micro-grooved roller coating unit. The micro-grooved roller rotated in the opposite direction to the film to evenly transfer a fixed amount of coating liquid to the side of the film to be sputtered to obtain a coated film. The coated film was placed in a multi-stage hot air oven for segmented drying. The drying stage temperature was 100℃ for 5 seconds, and the curing stage temperature was 150℃ for 10 seconds. After being cooled to room temperature by a cooling roller, it was wound up to obtain a modified PET substrate with a dry coating thickness of 1μm and a total substrate thickness of 50μm.

[0029] The modified PET substrate was coated by continuous roll-to-roll magnetron sputtering, with the layers from bottom to top being TiON bottom layer, Nb2O5 bottom layer, Ag-Pd-Ti bottom layer, AZO layer, Ag-Pd-Ti top layer, Nb2O5 top layer, and TiON top layer. The specific preparation process is as follows:

[0030] Modified PET substrate was subjected to online plasma glow discharge cleaning at a power of 1.0 kW and an argon flow rate of 200 sccm to obtain the treated PET; the vacuum degree was 5.0 × 10⁻⁶, following the bottom-to-top sequence. -4Under the conditions of 0.35 Pa working gas pressure and 1.5 m / min substrate linear velocity, medium-frequency pulsed reactive sputtering was performed on a Ti target at a power of 12 kW with argon, nitrogen, and oxygen flow rates of 150, 25, and 5 sccm, respectively, yielding a 25 nm thick TiON underlayer; medium-frequency pulsed reactive sputtering was performed on a Nb target at a power of 15 kW with argon and oxygen flow rates of 120 and 30 sccm, respectively, yielding a 35 nm thick Nb₂O₅ underlayer; pulsed DC sputtering was performed on an Ag-Pd-Ti alloy target at a power of 8 kW with an argon flow rate of 200 sccm, yielding a 14 nm thick Ag-Pd-Ti underlayer; medium-frequency pulsed sputtering was performed on an AZO target at a power of 18 kW with argon and oxygen flow rates of 180 and 3 sccm, respectively, yielding a 70 nm thick AZO layer; and pulsed DC sputtering was performed on an Ag-Pd-Ti alloy target at a power of 7 kW with an argon flow rate of 200 sccm, yielding a 12 nm thick Ag-Pd-Ti layer. An Ag-Pd-Ti top layer was formed; a Nb target was sputtered at a medium-frequency pulsed reactivity with a power of 13kW and argon and oxygen flow rates of 120sccm and 28sccm, respectively, to obtain a 30nm thick Nb2O5 top layer; a Ti target was sputtered at a medium-frequency pulsed reactivity with a power of 10kW and argon, nitrogen, and oxygen flow rates of 150, 20, and 3sccm, respectively, to obtain a 25nm thick TiON top layer. The thickness of each layer was controlled in real time by an optical film thickness monitoring system. The seven-layer composite material with the coating completed was then wound up to obtain a low-emissivity energy-saving base film.

[0031] Examples 2-5 follow the same preparation method and parameter conditions as Example 1, with differences shown in Table 1.

[0032]

[0033] Comparative Example 1: Refer to Example 1, except that optical-grade PET chips are used as the substrate and are not modified or coated.

[0034] Comparative Example 2 is the same as Example 1, except that the grafted PET chips are directly coated with the functional coating liquid without three-layer extrusion.

[0035] Comparative Example 3 is the same as Example 1, except that the skin and core layers are directly melt-extruded without a coating process.

[0036] Comparative Example 4 is the same as Example 1, except that no stretching treatment is performed.

[0037] Comparative Example 5 is the same as Example 1, except that no heat setting treatment is performed.

[0038] Comparative Example 6 is the same as Example 1, except that it is not dried in sections, and is dried at 100°C for 15 seconds.

[0039] Comparative Example 7 is the same as Example 1, except that it is not dried in stages, and is dried at 150°C for 15 seconds.

[0040] Comparative Example 8 is the same as Example 1, except that magnetron sputtering coating is not performed.

[0041] Experimental Example 1: Mechanical Property Testing

[0042] The low-emissivity energy-saving base films prepared in Examples 1-4 and Comparative Examples 1-8 were subjected to mechanical property tests according to the test conditions of GB / T 1040.3-2018. A universal testing machine was used with a clamp spacing of 50 mm and a tensile speed of 500 mm / min. The longitudinal and transverse tensile strengths were tested three times and the average value was taken. The test results are shown in Table 2.

[0043]

[0044] As shown in Table 2, the mechanical properties of the energy-saving base film obtained in the comparative examples, through adjustments to the components and processes, are significantly reduced compared to the examples. Comparative Examples 1-3 show that the optical-grade PET lacks the chemical bonding of grafted monomers, and the absence of a functional coating liquid as an interfacial bridge results in low surface polarity and poor adhesion of the substrate. This leads to thermal stress mismatch when exposed to sputtering coating, causing rapid propagation of microcracks during stretching and a decrease in mechanical properties. Omitting melt extrusion prevents the grafted PET chips from being uniformly blended with the core optical-grade PET, forming a weak boundary layer at the interface. Uneven penetration of the coating liquid during coating causes localized stress unevenness, affecting mechanical properties. Without a functional coating liquid as a buffer layer, the surface roughness of the film increases after extrusion, and microscopic defects are magnified into crack propagation paths during stretching, leading to a decrease in strength and toughness. Comparative Examples 4-5 show that the stretching process increases segment slip and hydrogen content. The bond rearrangement synergy, without a stretching process, leads to excessively rapid extrusion cooling and curing, resulting in residual stress in the amorphous region. This stress, combined with the thermal stress of the coating layer, causes a decrease in mechanical properties. The lack of a heat-setting process amplifies thermal shrinkage during high-temperature coating, causing a mismatch in thermal expansion with the Nb2O5 layer, resulting in micro-warping. The lack of stress relaxation increases fatigue fracture sensitivity, further degrading performance. Combined with the results of Comparative Examples 6-7, it is clear that segmented drying ensures gradual curing of the coating, avoiding bubbles and stress concentration. Low-temperature single drying leads to uneven evaporation of the emulsion solvent, increasing coating porosity and decreasing performance. High-temperature single drying accelerates emulsion crosslinking but induces thermal degradation, and uneven coating thickness affects overall performance. Comparative Example 8 shows that the seven-layer coating provides uniform stress distribution and optical buffering. Without coating, the coating is directly exposed, easily leading to hydrolytic degradation in conjunction with environmental humidity. Interfacial polarity is unstable, and the stretching orientation cannot achieve the coating gradient reinforcement, resulting in reduced mechanical properties.

[0045] In summary, this invention, through the synergy of graft modification and melt extrusion, forms a branched network, improves the core-skin interfacial modulus, suppresses chain breakage induced by extrusion shear, and enhances adhesion through bridging during the coating process. Simultaneously, during functional coating, nanofilling improves coating toughness, buffers the thermal shock of the sputtered TiON substrate, and further enhances mechanical properties in synergy with the aziridine crosslinking agent-cured network. Furthermore, the temperature gradient process of stretching, heat setting, and segmented drying releases residual stress and stabilizes crystallinity. This invention, through the chemical modification of grafted PET, the nano-bridging of functional coatings, the gradient buffering of multilayer sputtering, and the synergistic effect of the stretching-setting-drying process gradient, forms a stable core-skin-coating-film structure, significantly improving the mechanical properties of the base film.

[0046] Experimental Examples 5-7 follow the same preparation methods and parameter conditions as the examples, with differences shown in Table 3.

[0047]

[0048] Comparative Example 9 was the same as Example 1, except that it was modified with 2-(2'-hydroxy-5'-methacryloyloxyethylphenyl)-2H-benzotriazole in an amount of 2.2 parts.

[0049] Comparative Example 10 was the same as Example 1, except that it was modified with 1,2,2,6,6-pentamethyl-4-piperidinyl methacrylate in an amount of 2.2 parts.

[0050] Comparative Example 11 is the same as Example 1, except that melt grafting is not performed and the material is added directly in the three-layer extrusion process.

[0051] Comparative Example 12 is the same as Example 1, except that a single Ag-Pd-Ti layer is used, while the rest of the sputtering process remains the same.

[0052] Comparative Example 13 is the same as Example 1, except that an Ag-Pd alloy target is used, while the rest of the sputtering process remains unchanged.

[0053] Experiment Example 2 Weather Resistance Test

[0054] The low-emissivity energy-saving base films prepared in Examples 1, 5-7, Comparative Examples 1, and 8-13 were tested for silver layer oxidation resistance and UV aging resistance. Silver layer oxidation resistance: The change in haze of the film before and after aging was tested according to GB / T 2410-2008, and the films were aged in a constant temperature and humidity chamber at 85℃ and 85%RH for 500 hours. UV aging resistance: The UV aging resistance of the energy-saving base films was tested according to GB / T 16422.2-2014, using a xenon arc lamp to simulate UV irradiation at an intensity of 0.68 W / m²@340 nm for 1000 hours. Tensile strength before and after aging was tested according to GB / T 1040.3-2018, and the tensile strength retention rate is shown in Table 4. The tensile strength retention rates of Examples 1, 5, and Comparative Examples 8-12 are shown in Table 4. Figure 1 As shown.

[0055]

[0056] As shown in Table 4, the weather resistance of the energy-saving base film obtained in the comparative examples, obtained by adjusting the components and processes, was significantly reduced compared to the examples. In Comparative Example 1, the optical-grade PET chips without any modification or coating were used as the substrate. After long-term aging, the molecular chains broke down, leading to a sharp decline in mechanical properties. Furthermore, the lack of a functional coating resulted in poor adhesion to the subsequent magnetron sputtering film, failing to effectively block moisture and oxygen, ultimately leading to severe cracking and film peeling during the aging process. In Comparative Example 8, without magnetron sputtering coating, only a modified PET substrate and coating were used. The absence of a silver layer resulted in no radiation reflection function. More importantly, the lack of a barrier layer meant that the nano-silica and PUA in the coating solution could not effectively block ultraviolet diffusion, exacerbating UV aging after substrate exposure. Combined with Comparative Examples 9-10, the lack of HALS-like additives that can capture and scavenge free radicals resulted in the inability to effectively inhibit polymer degradation, damaging the adhesion foundation of the sputtered film and leading to… The antioxidant properties deteriorate; the lack of UVA to absorb ultraviolet light and convert it into harmless heat energy to protect the polymer means that the generated free radicals cannot be effectively eliminated, leading to rapid polymer degradation and affecting the overall weather resistance. In Comparative Example 11, melt grafting, through the action of an initiator, connects the functional groups of UVA and HALS to the PET macromolecular chain in the form of chemical bonds. Direct blending and addition, with the additives only physically dispersed in the system, easily leads to migration and precipitation, resulting in uneven distribution, poor and unstable protective effect. In Comparative Example 12, the adjustment to a single silver layer structure not only greatly weakens the ability to reflect infrared light (i.e., low-emissivity function), but also makes the thin silver layer more susceptible to oxidation and corrosion, resulting in a significant increase in haze variation. Combined with the results of Comparative Example 13, it can be seen that adding a trace amount of active titanium metal to the silver alloy enhances the bonding force between the silver alloy layer and the upper and lower dielectric layers during sputtering and can fill defects in the silver lattice, greatly improving the density and antioxidant corrosion resistance of the silver layer.

[0057] In summary, melt grafting endows PET with excellent UV resistance from within, while the functional coating provides physical protection and enhances adhesion from the outside, synergistically constructing a dual protection system to ensure the high stability of the substrate in harsh environments. Simultaneously, the dual effects of UVA and HALS—surface protection and spot removal—form a complete protection chain against UV degradation. Furthermore, the stable and reliable modified coating substrate provides a solid and flat adhesion platform for the precise seven-layer sputtered film. The selection of the Ag-Pd-Ti alloy target in the sputtering process also ensures excellent adhesion and oxidation resistance from the film's own structure. Through the interfacial activation of melt-grafted PET, the tough network of the multifunctional coating, the dual photostabilization mechanism of UV-HALS, and the gradient barrier film, a complete chain of synergistic protection is formed.

[0058] Comparative Example 14 is the same as Example 1, except that no AZO layer is sputtered, while the rest of the sputtering process remains the same.

[0059] Comparative Example 15 is the same as Example 1, except that the Nb2O5 layer is not sputtered, while the rest of the sputtering process remains the same.

[0060] Comparative Example 16 is the same as Example 1, except that from bottom to top, it consists of an AZO layer, an Ag-Pd-Ti top layer, an Nb2O5 top layer, and a TiON top layer.

[0061] Experimental Example 3: Optical Performance

[0062] The low-emissivity energy-saving base films prepared in Examples 1-4 and Comparative Examples 12-16 were subjected to optical performance tests. The visible light transmittance and infrared thermal radiation reflectance were tested according to GB / T 2680-2021. The infrared thermal radiation reflectance was measured for solar radiation with a wavelength range of 950-2500nm using a spectrophotometer and an integrating sphere accessory. The test results are shown in Table 5.

[0063]

[0064] As shown in Table 5, the optical performance of the energy-saving base film obtained by adjusting the composition and process in the comparative examples is significantly reduced compared to the examples. In Comparative Example 12, the single-layer design reduces the total thickness of the metal layer, resulting in insufficient free electron density in the infrared band and reduced plasma reflection efficiency. Simultaneously, the lack of a lower buffer layer increases interfacial stress and reduces visible light transmittance. In Comparative Example 13, the reduction in titanium usage weakens the adhesion of silver to the dielectric layer, drastically decreasing film quality and reducing the film's conductivity, thus significantly weakening its ability to reflect long-wave infrared radiation. Furthermore, the discontinuous and rough film layer also reduces visible light transmittance due to light scattering. Comparative Example 14 shows that the AZO layer, as the dielectric layer, works together with the upper and lower Nb2O5 and Ag-Pd-Ti layers to transmit light through optical... Interference reduces light reflection and increases visible light transmittance. Simultaneously, AZO provides an excellent growth surface for the underlying Ag-Pd-Ti layer, ensuring the long-term stability of the silver layer. The absence of an AZO layer affects the film quality of the underlying silver layer and reduces the overall durability of the film system. Comparative Example 15 shows that the Nb2O5 layer, a high-refractive-index dielectric material, is the core of the dielectric layer, metal layer, and dielectric-layer antireflection structure. Without sputtering the Nb2O5 layer, this antireflection effect completely disappears, and the entire film system will primarily exhibit metallic reflective characteristics, resulting in extremely low visible light transmittance. In Comparative Example 16, the lack of a bottom dielectric layer prevents the formation of an effective interference antireflection structure, leading to low transmittance. Furthermore, the single-layer thin silver design cannot simultaneously achieve high transmittance and high infrared reflectance, significantly reducing performance and failing to maintain a balance between visible light transmittance and infrared thermal radiation reflectance.

[0065] In summary, this invention forms an interference cavity through seven-layer sputtering deposition. The double-layer TiON provides oxygen barrier and a refractive index gradient, offering excellent adhesion to the substrate and imparting wear and corrosion resistance to the energy-saving film, protecting the internal functional layers. The double Nb2O5 dielectric enhances the reflection peak, while the AZO layer buffers and optimizes electrical stability. The synergistic combination of these high and low refractive index materials constructs a highly efficient dual-band antireflection structure, maximizing visible light transmittance. The double Ag-Pd-Ti functional layers synergistically enhance the plasma effect; the addition of Pd and Ti synergistically improves the chemical stability and film quality of the silver layer, inhibiting Ag aggregation and improving infrared thermal radiation reflectivity. The multi-layer sputtering coating and modified PET substrate process work together to form a highly efficient optically selective barrier: a deposition layer structure of bottom layer blocking, dielectric enhancement, dual-functional reflection, and top layer protection. Combined with alloy doping and pulsed precision deposition, this achieves an excellent balance between visible light transmittance and infrared thermal radiation reflectivity.

[0066] Comparative Example 17 is the same as Example 1, except that 3-aminopropyltriethoxysilane is not added to the functional coating liquid, while the other components remain unchanged.

[0067] Comparative Example 18 is the same as Example 1, except that no nano-silica is added to the functional coating liquid, while the other components remain unchanged.

[0068] Comparative Example 19 is the same as Example 1, except that the TiON substrate is not sputtered, while the rest of the sputtering process remains the same.

[0069] Experiment Example 4: Peel Strength Test

[0070] The low-emissivity energy-saving base films obtained in Examples 1-4, Comparative Examples 1, 3, 13, and 17-19 were subjected to peel strength tests. The tests were conducted according to GB / T 2790-2013 using the 180° peel test method at a peel speed of 300 mm / min, a temperature of 23±2℃, and a humidity of 50±5%. The test results are shown in Table 6.

[0071]

[0072] As shown in Table 6, the peel strength of the energy-saving base film obtained in the comparative examples, through adjustments to the components and processes, is significantly lower than that in the examples. In Comparative Example 1, by grafting PET and using a functional coating to increase surface energy and polar group density, chemical anchoring points are formed. Without removal modification and coating, the surface energy of pure PET is low. Plasma cleaning only provides physical roughening and cannot compensate for the lack of chemical bonds, resulting in weakened adhesion of the sputtered TiON underlayer, concentration of interfacial stress, and easy delamination during peeling. In Comparative Example 3, the coating process ensures that the functional coating uniformly bridges the grafted PET and the sputtered layer, forming a gradient interface. After removing the coating, the surface is smooth after extrusion and stretching, but lacks a buffer layer. During sputtering, atomic deposition under working pressure directly acts on PET, causing uneven thermal stress, reducing van der Waals forces and hydrogen bond contributions, and decreasing peel strength. In Comparative Example 13, the lack of Ti leads to poor crystallization of the functional layer, resulting in poor peel strength under pulsed DC. Sputtering easily forms loose Ag particles, reducing mechanical interlocking with the substrate, making the interface sensitive to oxidation, and deteriorating the overall weather resistance. It also fails to promote oxide formation, affecting peel strength. In Comparative Examples 17-18, removing KH-550 prevents the formation of a Si-O-Si network to bridge the PUA and inorganic sputtered layer. The coating liquid is dispersed solely by the PUA emulsion during stirring, resulting in a mismatch in interfacial polarity and weak adhesion of the sputtered TiON during the curing stage. Removing nano-silica results in a low viscosity of the stirred mixture, leading to uneven coating, unstable hydrogen bond network formation, and coating fragmentation during peeling. Comparative Example 19 shows that the TiON underlayer acts as a barrier layer, providing high hardness and an oxygen diffusion barrier. Matching the refractive index with the functional coating creates a gradient transition. The TiON layer firmly adheres to the surface of the functional coating treated with the silane coupling agent. The subsequent Nb2O5 layer, being inorganic like the TiON layer, exhibits improved adhesion and peel strength.

[0073] In summary, introducing polar functional groups onto the PET surface fundamentally alters the surface properties of the substrate and increases its surface energy. Silane coupling agents act as connectors between the organic polymer substrate and the inorganic metal film, providing stable bonding through chemical bonds. PUA emulsion, as the film-forming host, provides a carrier for the coupling agent and nanoparticles, ensuring the coating exhibits excellent flexibility. Nano-silica enhances the coating's mechanical strength and wear resistance, and increases the physical anchoring effect. Simultaneously, TiON forms strong chemical bonds with functional groups such as silanol groups on the functional coating surface, firmly welding the entire inorganic film system to the modified substrate. Through the synergistic effect of PET grafting modification, functional coating bridging, and multilayer sputtering processes, a high-adhesion optical barrier is formed. The multiple protection mechanisms of surface functionalization, hybrid coatings, and alloy deposition layers significantly improve film stability and anti-detachment performance.

[0074] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a low-emissivity energy-saving base film for buildings, characterized in that, The preparation process includes the following: Grafted PET chips are used as the skin layer A and optical-grade PET chips are used as the core layer B. The layers are melt-extruded and cooled. After cooling, the layers are biaxially stretched. The functional coating liquid is applied through a micro-grooved roller to obtain a coated film. The film is then dried in sections, cooled, and wound up to obtain a modified PET substrate. The modified PET substrate is then subjected to continuous roll-to-roll magnetron sputtering to obtain the low-emissivity energy-saving base film. The grafted PET chips are obtained by melt grafting PET chips, UVA-type additives, and HALS-type additives; the functional coating liquid is obtained by stirring KH550, water-based PUA emulsion, and nano-silica aqueous dispersion.

2. The method for preparing a low-emissivity energy-saving base film for buildings according to claim 1, characterized in that, The method for preparing the grafted PET chips is as follows: the PET chips are vacuum dried, and pyromellitic dianhydride is added to a co-rotating twin-screw extruder through the main feed port. The UVA-type auxiliary agent and the HALS-type auxiliary agent are injected into the extruder through a metering pump, and the melt is extruded to obtain a melt material. The material is then cooled in a water tank, pelletized, and dried to obtain the grafted PET chips.

3. The method for preparing a low-emissivity energy-saving base film for buildings according to claim 1, characterized in that, The preparation method of the functional coating liquid is as follows: KH550 is dissolved in deionized water to obtain a solution; the aqueous PUA emulsion and the nano silica aqueous dispersion are added to a reaction vessel; the solution is then added and stirred and mixed; the solution is diluted with deionized water, aziridine is added, stirred and dispersed, filtered and allowed to stand to defoam to obtain the functional coating liquid.

4. The method for preparing a low-emissivity energy-saving base film for buildings according to claim 1, characterized in that, The modified PET substrate is prepared by placing the coated film in a multi-segment hot air oven, drying it in segments, cooling it to room temperature by a cooling roller, and then winding it up to obtain the modified PET substrate.

5. The method for preparing a low-emissivity energy-saving base film for buildings according to claim 4, characterized in that, The method for preparing the coated film is as follows: the skin layer A and the core layer B are melt-extruded according to the A / B / A structure to obtain the extruded material; then cooled by a cold roller, biaxially stretched, and heat-set; then the functional coating liquid is transported to the coating head through a micro-grooved roller coating unit and uniformly transferred to the film surface to obtain the coated film.

6. The method for preparing a low-emissivity energy-saving base film for buildings according to claim 1, characterized in that, The continuous roll-to-roll magnetron sputtering coating process includes: from bottom to top, medium-frequency pulse reactive sputtering of a Ti target to obtain a TiON bottom layer; medium-frequency pulse reactive sputtering of an Nb target to obtain a Nb2O5 bottom layer; pulsed DC sputtering of an Ag-Pd-Ti alloy target to obtain an Ag-Pd-Ti bottom layer; medium-frequency pulse sputtering of an AZO target to obtain an AZO layer; pulsed DC sputtering of an Ag-Pd-Ti alloy target to obtain an Ag-Pd-Ti top layer; medium-frequency pulse reactive sputtering of an Nb target to obtain a Nb2O5 top layer; and medium-frequency pulse reactive sputtering of a Ti target to obtain a TiON top layer. The thickness of each layer is controlled in real time by an optical film thickness monitoring system, and the coated composite material is then rolled up to obtain the low-emissivity energy-saving base film.

7. A low-emissivity energy-saving base film for building applications, characterized in that, From bottom to top, the layers are: modified PET substrate, TiON bottom layer, Nb2O5 bottom layer, Ag-Pd-Ti bottom layer, AZO layer, Ag-Pd-Ti top layer, Nb2O5 top layer, and TiON top layer; the energy-saving base film is prepared by the preparation method described in any one of claims 1-6.

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