A heat-insulating film and a method for manufacturing the same

Abstract

The application discloses a kind of heat insulation films and preparation methods thereof.The heat insulation film includes substrate layer, hard coating layer, first dielectric layer, first barrier layer, noble metal layer, second barrier layer, second dielectric layer and adhesive layer from inside to outside.The first dielectric layer is aluminum-doped zinc oxide, the noble metal layer is a silver-gold alloy layer with controllable thickness, and has a gradient distribution of gold content in the thickness direction;The second dielectric layer is formed into a layered composite structure by alternately stacking titanium dioxide and hafnium oxide.The preparation method includes substrate cleaning and surface activation, hard coating layer coating and curing, magnetron sputtering of dielectric layer and barrier layer, alloying deposition of noble metal layer, alternating sputtering of layered composite dielectric, and adhesive layer coating and compounding.The application realizes excellent infrared barrier performance while maintaining high visible light transmittance through the synergistic design of multi-layer structure and components, significantly improves the stability in a humid and hot environment, and reduces the risk of performance degradation.

Description

Technical Field

[0001] This invention relates to the technical field of energy-saving materials, and in particular to a heat-insulating film and its preparation method. Background Technology

[0002] With increasing demands for energy conservation and comfort, heat-insulating films are widely used in architectural glass and automotive windows to reduce the proportion of solar radiation heat entering the interior. While meeting insulation requirements, heat-insulating films must also maintain high visible light transmittance to ensure indoor brightness and clear visibility.

[0003] Most existing heat-insulating films adopt a "dielectric-metal-dielectric" or "dielectric-metal-dielectric-metal-dielectric" structure, with the metal layer typically being a silver layer. Although the silver layer can provide a certain infrared reflection effect, its corrosion resistance is poor, and it is prone to oxidation and sulfidation reactions in humid, hot, or polluted environments, leading to increased sheet resistance and decreased optical performance, thus limiting the long-term stability of the film.

[0004] To improve the corrosion resistance of silver layers, some researchers have attempted to add a higher proportion of gold to form a silver-gold alloy layer. This method improves corrosion resistance to some extent, but the high cost of gold and the fact that excessive doping reduces visible light transmittance make the overall cost-effectiveness low. Therefore, existing technologies struggle to achieve a balance between thermal insulation performance and long-term stability. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned problems existing in the prior art and provide a heat insulation film and its preparation method. By improving the structure of the dielectric layer, noble metal layer and barrier layer, the stability of the film layer in humid and hot environment is significantly improved while maintaining good heat insulation performance, thereby extending service life and reducing the risk of performance degradation.

[0006] To achieve the above objectives, the first aspect of the present invention provides a heat insulation film comprising, from the inside out, a substrate layer, a hard coating layer, a first dielectric layer, a first barrier layer, a noble metal layer, a second barrier layer, a second dielectric layer, and an adhesive layer;

[0007] The first dielectric layer is an aluminum-doped zinc oxide layer;

[0008] The noble metal layer is a silver-gold alloy layer with a thickness of 8–12 nm and an Au content of 2%–6%. The noble metal layer has a gradient distribution along the thickness direction.

[0009] The second dielectric layer is a layered composite structure composed of titanium dioxide and hafnium oxide.

[0010] As a further improvement of the present invention, the Au atom fraction in the 0.6 to 1.2 nm region near the two sides of the noble metal layer is 2.5% to 6.0%, and the Au atom fraction in the central region is not higher than 1.5%.

[0011] As a further improvement of the present invention, the second dielectric layer is formed by alternating stacking of titanium dioxide and hafnium oxide, with each cycle containing 3 to 6 nm thick titanium dioxide and 0.6 to 1.2 nm thick hafnium oxide, and repeated for 8 to 14 cycles.

[0012] As a further improvement of the present invention, the first dielectric layer comprises, from the outside to the inside, a ZAO-I sublayer, a transition region and a ZAO-II sublayer, wherein the thickness of the ZAO-I sublayer is 15–30 nm, the thickness of the ZAO-II sublayer is 30–55 nm, and the thickness of the transition region is 2–6 nm.

[0013] As a further improvement of the present invention, the aluminum atomic fraction in the ZAO-I sublayer of the first dielectric layer is 2.0% to 3.5%, and the aluminum atomic fraction in the ZAO-II sublayer is 0.6% to 1.5%.

[0014] As a further improvement of the present invention, the first barrier layer and the second barrier layer are aluminum oxide and silicon oxynitride, respectively, with a thickness of 0.4 to 1.2 nm.

[0015] As a further improvement of the present invention, the hard coating is a siloxane-based organic-inorganic hybrid coating with a thickness of 1.5 to 4.0 μm; the adhesive layer is an acrylate pressure-sensitive adhesive layer with a thickness of 12 to 25 μm; and the substrate layer is a polyethylene terephthalate film with a thickness of 25 to 50 μm.

[0016] A second aspect of the present invention provides a method for preparing the heat-insulating film as described above, comprising the following steps:

[0017] (1) Clean and surface activate the substrate layer;

[0018] (2) Apply and cure a hard coating on the substrate layer;

[0019] (3) The first dielectric layer was deposited by magnetron sputtering in a mixed atmosphere of oxygen and argon;

[0020] (4) A first barrier layer is formed by reactive sputtering;

[0021] (5) Sequential deposition of silver-gold alloy to form a noble metal layer;

[0022] (6) A second barrier layer is formed by reactive sputtering;

[0023] (7) A second dielectric layer is formed by depositing titanium dioxide and hafnium oxide in a layered composite manner using an alternating sputtering method;

[0024] (8) Apply an adhesive layer to the outside of the second dielectric layer and laminate a release film.

[0025] As a further improvement of the present invention, a thin layer of oxygen-nitrogen-containing titanium compound with a thickness of 0.2 to 0.5 nm is deposited before step (5).

[0026] As a further improvement of the present invention, the oxygen supply in steps (3) and (7) adopts a pulse modulation method, with an average flow rate of 5 to 20 sccm, a pulse frequency of 0.5 to 2.0 Hz, and a duty cycle of 20% to 60%.

[0027] The present invention, by adopting the above technical solution, has the following beneficial effects:

[0028] Traditional heat insulation films often uniformly dope 15%–20% gold into the silver layer to improve its corrosion resistance. While this method improves stability, it introduces two significant problems: first, excessive gold leads to enhanced visible light absorption and reduced light transmittance; second, the high amount of precious metal significantly increases costs, limiting its application to high-end applications. This invention introduces a "thickness-differentiated" Au distribution strategy in the precious metal layer: forming Au-rich regions of 2.5%–6% near the two outer surfaces, while controlling the Au content in the center to ≤1.5%. This layout does not rely on increasing the total Au content, but rather achieves a balance between "low gold content, low cost" and "high stability" by strengthening the surface layer's resistance to sulfidation and oxidation while maintaining high light transmittance in the center. Compared to uniform doping, this approach significantly reduces sheet resistance drift and color difference after damp heat aging. Furthermore, this invention employs a layered composite structure of alternating stacks of TiO2 and HfO2, with the thickness of a single cycle controlled at the nanometer level. At the optical level, the periodic stacking achieves the dual functions of high refractive index and phase modulation, enabling the film to maintain high visible light transmittance while enhancing near-infrared reflectance. At the stability level, the high density and diffusion-blocking effect of HfO2 effectively prevents the migration of oxygen and metal ions, thereby inhibiting film degradation. Test results show that after aging at 85℃ / 85%RH for 1000 hours, the sheet resistance and color difference of this layered composite structure are significantly optimized.

[0029] Preferably, the first dielectric layer employs an outer high-aluminum ZAO layer and an inner low-aluminum ZAO layer, with a transition region in between, allowing for a gradual transition in refractive index and carrier concentration. This structure reduces film stress and color shift, improves interface matching with the metal layer, and simultaneously optimizes the film's light transmittance, electrical properties, and mechanical stability, solving the common problems of cracking and performance inconsistency in single ZAO layers. Furthermore, the barrier layer configuration of this invention effectively blocks ion and moisture penetration without affecting light transmittance, preventing color shift and additional absorption.

[0030] This invention employs a pulse modulation method for oxygen supply: by controlling the average flow rate, frequency, and duty cycle, a dynamic balance between oxidation and reduction on the target surface is achieved, avoiding instability in the deposition process. The direct effect is more stable film thickness and refractive index, reducing batch-to-batch variations; the indirect effect is a reduction in defects and oxygen vacancies, resulting in a denser and more uniform film. Attached Figure Description

[0031] Figure 1 This is the XRD characterization diagram of the first dielectric layer in Example 1;

[0032] Figure 2 XPS depth profile of Au content in the noble metal layer in Example 1;

[0033] Figure 3 This is an XPS image of oxygen in the second barrier layer in Example 1;

[0034] Figure 4 This is an XPS image of nitrogen in the second barrier layer in Example 2. Detailed Implementation

[0035] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0036] Unless otherwise defined, all scientific and technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art.

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0038] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0039] The present invention will now be described in detail with reference to specific embodiments, which are intended to understand rather than limit the invention.

[0040] Example 1: This example provides a heat insulation film, which includes, from the inside out, a substrate layer, a hard coating layer, a first dielectric layer, a first barrier layer, a noble metal layer, a second barrier layer, a second dielectric layer, and an adhesive layer.

[0041] Substrate layer: 38μm thick polyethylene terephthalate (PET) film is selected.

[0042] Hard coating: A 2.5 μm thick coating is formed on the surface of a PET substrate by spin coating of methacryloyloxypropyltrimethoxysilane (KH-570), nano silica dispersion (30% solid content) and photoinitiator 1173 in a mass ratio of 100:30:2. The coating is then cured by irradiation under 365 nm ultraviolet light for 30 s to obtain a dense organic-inorganic hybrid hard coating.

[0043] First dielectric layer: Aluminum-doped zinc oxide (AZO) was deposited on the hard coating surface using DC magnetron sputtering. The film thickness was 60 nm, the aluminum atomic fraction was 2.5%, and the deposition atmosphere was a mixture of argon and oxygen at a total pressure of 0.6 Pa and an oxygen volume fraction of 15%. X-ray diffraction (XRD) characterization results showed that the film had a hexagonal wurtzite structure, such as... Figure 1 As shown, curve A is ZnO and curve B is ZAO.

[0044] First barrier layer: An alumina (Al2O3) layer with a thickness of 0.7 nm was formed on the surface of the first dielectric layer by radio frequency reactive sputtering. The sputtering atmosphere was Ar+O2, and the total pressure was 0.5 Pa.

[0045] Noble metal layer: A silver-gold alloy layer with a total thickness of 10 nm is deposited on the surface of the first barrier layer. The alloy composition is controlled using a dual-target co-sputtering method, wherein:

[0046] The Au atom fraction is 4.0% in the 0.8 nm region closest to both the top and bottom surfaces.

[0047] The Au atom fraction in the central region is 1.0%;

[0048] The total Au content in the overall alloy is controlled at 3.5%.

[0049] The thickness-oriented Au content distribution was verified by in-depth X-ray photoelectron spectroscopy (XPS), such as... Figure 2 As shown.

[0050] Second barrier layer: A 0.7 nm thick silicon oxynitride (SiON) layer was deposited on the surface of the noble metal layer using Si target reactive sputtering. The deposition atmosphere was Ar + O2 + N2, with a total pressure of 0.6 Pa and an O2 to N2 volume fraction ratio controlled at 3:7. The O / (O+N) atomic ratio in the resulting thin layer was controlled at 0.4.

[0051] Second dielectric layer: Titanium dioxide (TiO2) and hafnium oxide (HfO2) were alternately deposited on the surface of the second barrier layer, forming 10 cycles. Each cycle consisted of 4.5 nm thick TiO2 and 0.9 nm thick HfO2, with a total thickness of approximately 54 nm. The deposition atmosphere was Ar+O2, with a total pressure of 0.5 Pa. X-ray diffraction characterization showed that both were amorphous.

[0052] Adhesive layer: An acrylate pressure-sensitive adhesive with a thickness of 18μm is coated on the surface of the second dielectric layer and a polyester release film is laminated thereon.

[0053] The specific preparation method includes the following steps:

[0054] (1) Substrate pretreatment: The PET film is cleaned in a vacuum chamber with ion source, ion energy 200eV, time 30s, to remove surface organic contaminants.

[0055] (2) Hard coating deposition: KH-570, nano SiO2 dispersion and photoinitiator 1173 are mixed at a mass ratio of 100:30:2 and a 2.5 μm thick coating is formed on the surface of PET substrate by spin coating. The coating is cured by irradiation under a 365 nm ultraviolet lamp for 30 s to obtain a hard coating.

[0056] (3) Deposition of the first dielectric layer: An AZO film with a thickness of 60 nm and an aluminum atomic fraction of 2.5% was deposited by DC magnetron sputtering. The atmosphere during deposition was a mixture of argon and oxygen, with a total pressure of 0.6 Pa and an oxygen volume fraction of 15%.

[0057] (4) Deposition of the first barrier layer: Under the condition of oxygen partial pressure of 0.5 Pa, an aluminum oxide layer with a thickness of 0.7 nm is formed by reactive sputtering.

[0058] (5) Deposition of noble metal layer: The dual-target co-sputtering method is used to first deposit a 2.5 nm pure Ag layer, then deposit a 5.0 nm Ag-Au alloy layer (Au content 3.5 at%), and finally deposit a 2.5 nm Ag layer to form a noble metal layer with an overall thickness of 10 nm.

[0059] (6) Deposition of the second barrier layer: A SiON layer with a thickness of 0.7 nm was deposited using a radio frequency reactive sputtering Si target in an Ar+O2+N2 atmosphere. The volume fraction ratio of O2 to N2 was controlled at 3:7, and the total pressure was 0.6 Pa. XPS analysis showed that the O / (O+N) atomic ratio was 0.4. Figure 3 and Figure 4 As shown, after RSF correction, the original spectra of these two original spectra have O / (O+N)=0.4.

[0060] (7) Second dielectric layer deposition: TiO2 and HfO2 were deposited alternately under the condition of O2 / Ar=0.12 to complete 10 cycles. During this process, oxygen supply was pulsed with an average flow rate of 10 sccm, a pulse frequency of 1.0 Hz, a duty cycle of 40%, and the thickness tolerance was controlled within ±2 nm.

[0061] (8) Adhesive layer preparation: Apply an acrylate pressure-sensitive adhesive with a thickness of 18 μm to the surface of the second dielectric layer and attach a polyester release film.

[0062] Example 2: The difference from Example 1 is that TiO2 and HfO2 are stacked once each, with the total thickness maintained at approximately 54 nm. For example, TiO2 45 nm + HfO2 9 nm are deposited. The other layers remain unchanged.

[0063] Example 3: The only difference from Example 1 is that oxygen pulse modulation is not used during the deposition of the second dielectric layer: the oxygen supply is changed to a continuous constant flow mode; the average flow rate is still set to 10 sccm, but no pulse frequency or duty cycle is applied. The remaining layer structure, materials, and setpoint parameters are the same as in Example 1.

[0064] Example 4: The only difference from Example 1 is that the first dielectric layer is changed from a single AZO to a layered structure.

[0065] The first dielectric layer consists of the ZAO-I sublayer, the transition region, and the ZAO-II sublayer, from the outside to the inside, with a total thickness of 60 nm.

[0066] ZAO-I sublayer: 22 nm thick, 3.0% aluminum atomic fraction, and 30% oxygen volume fraction during deposition;

[0067] Transition region: 4 nm thick, with oxygen partial pressure gradually decreasing;

[0068] ZAO-II sublayer: 34 nm thick, 1.0% aluminum atom fraction, and 10% oxygen volume fraction at deposition.

[0069] The other layers (substrate layer, hard coating layer, barrier layer, noble metal layer, second dielectric layer, adhesive layer) are the same as in Example 1; the total Au content of the noble metal layer is still 3.5 at%, maintaining the thickness gradient distribution.

[0070] Example 5: The only difference from Example 1 is that, before depositing the silver-gold alloy layer, a 0.3 nm thick oxygen-nitrogen titanium compound (TiOxNy) nucleation layer is first sputtered under an Ar+O2+N3 atmosphere. The other layers are the same as in Example 1.

[0071] Comparative Example 1

[0072] The only difference between this comparative example and Example 1 is the structure of the second dielectric layer:

[0073] The second dielectric layer: A single titanium dioxide (TiO2) film was used instead of the TiO2 / HfO2 layered composite structure, with a total thickness of 54 nm. The deposition atmosphere was Ar+O2, and the total pressure was 0.5 Pa, resulting in amorphous TiO2. The other layers and preparation methods were the same as in Example 1.

[0074] Performance test results:

[0075] The film exhibits a visible light transmittance of 85% and an infrared blocking rate of 95%. After aging at 85°C / 85%RH for 1000 hours, the film resistivity drift is approximately 15%, and the color difference ΔE is 1.8. Compared to Example 1, the initial optical performance is similar, but the performance degrades more rapidly after long-term damp heat aging, indicating that the TiO2 / HfO2 layered composite structure in Example 1 has a significant advantage in improving stability.

[0076] Comparative Example 2

[0077] The only difference between this comparative example and Example 1 is the structure of the noble metal layer:

[0078] Noble metal layer: A silver-gold alloy layer with a thickness of 10 nm is deposited on the surface of the first barrier layer. The total Au content is fixed at 3.5 at%, and it is uniformly distributed in the thickness direction without the gradient characteristics of enrichment on the surface and decrease in the middle.

[0079] The other layers (substrate layer, hard coating layer, first dielectric layer, first barrier layer, second barrier layer, second dielectric layer, adhesive layer) and their preparation methods are the same as in Example 1.

[0080] Performance test results:

[0081] The film exhibits a visible light transmittance of 84% and an infrared blocking rate of approximately 94%. After aging at 85°C / 85%RH for 1000 hours, the film resistivity drift is approximately 20%, and the color difference ΔE is 2.1. Compared to Example 1, its transmittance and near-infrared blocking performance are similar, but its damp heat stability is significantly reduced.

[0082] Detection methods

[0083] 1. Visible light transmittance

[0084] The transmittance of the sample was measured using a spectrophotometer (wavelength range 380-780 nm) under D65 light source conditions, and the weighted average value was taken as the visible light transmittance.

[0085] 2. Infrared blocking rate

[0086] Transmittance was measured in the 780–1200 nm band using the same spectrophotometer, and the average value was calculated. Infrared blocking rate is 100% − average transmittance.

[0087] 3. Sheet resistor drift

[0088] The initial resistance of the sample was measured using a four-probe tester. The sample was then aged in a constant temperature and humidity chamber at 85 ℃ and 85%RH for 1000 h. After aging, the resistance was measured again. The resistance drift was expressed as a percentage of the difference before and after the initial value.

[0089] 4. Color difference ΔE

[0090] Using a spectrophotometer, the chromaticity values ​​before and after aging were measured under D65 light source conditions, and the color difference ΔE was calculated.

[0091] Table 1

[0092]

[0093] Conclusion: The test results show that the heat-insulating film of the present invention exhibits excellent performance in both visible light transmittance and infrared blocking rate. Furthermore, its sheet resistance drift and color difference under humid heat aging conditions are significantly lower than those of the comparative sample. This demonstrates that by introducing a thickness gradient distribution in the noble metal layer, employing a layered composite structure of titanium dioxide and hafnium oxide in the second dielectric layer, and optimizing the barrier layer and process conditions, the environmental stability of the film can be effectively improved, maintaining stable optical and electrical performance during long-term use.

[0094] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A heat-insulating film, characterized in that, From the inside out, it includes a substrate layer, a hard coating layer, a first dielectric layer, a first barrier layer, a noble metal layer, a second barrier layer, a second dielectric layer, and an adhesive layer. The first dielectric layer comprises aluminum-doped zinc oxide; The noble metal layer is a silver-gold alloy layer with a thickness of 8–12 nm and an Au content of 2%–6%. The noble metal layer has a gradient distribution along the thickness direction. The second dielectric layer comprises a layered composite structure composed of titanium dioxide and hafnium oxide; The Au atomic fraction in the 0.6–1.2 nm region near the two sides of the noble metal layer is 2.5%–6.0%, and the Au atomic fraction in the central region is no higher than 1.5%. The second dielectric layer is composed of alternating stacks of titanium dioxide and hafnium oxide. Each cycle consists of 3–6 nm thick titanium dioxide and 0.6–1.2 nm thick hafnium oxide, and the cycle repeats for 8–14 cycles.

2. The heat-insulating film according to claim 1, characterized in that: The first dielectric layer comprises, from the outside to the inside, a ZAO-I sublayer, a transition region, and a ZAO-II sublayer. The thickness of the ZAO-I sublayer is 15–30 nm, the thickness of the ZAO-II sublayer is 30–55 nm, and the thickness of the transition region is 2–6 nm.

3. The heat-insulating film according to claim 2, characterized in that: The aluminum atomic fraction in the ZAO-I sublayer of the first dielectric layer is 2.0% to 3.5%, and the aluminum atomic fraction in the ZAO-II sublayer is 0.6% to 1.5%.

4. The heat-insulating film according to claim 1, characterized in that: The first barrier layer and the second barrier layer are aluminum oxide and silicon oxynitride, respectively.

5. The heat-insulating film according to claim 1, characterized in that: The hard coating is a siloxane-based organic-inorganic hybrid coating; the adhesive layer is an acrylic pressure-sensitive adhesive layer; and the substrate layer is a polyethylene terephthalate film.

6. A method for preparing a heat-insulating film according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Clean and surface activate the substrate layer; (2) Apply and cure a hard coating on the substrate layer; (3) The first dielectric layer was deposited by magnetron sputtering in a mixed atmosphere of oxygen and argon; (4) A first barrier layer is formed by reactive sputtering; (5) Sequential deposition of silver-gold alloy to form a noble metal layer; (6) A second barrier layer is formed by reactive sputtering; (7) A second dielectric layer is formed by depositing titanium dioxide and hafnium oxide in a layered composite manner using an alternating sputtering method; (8) Apply an adhesive layer to the outside of the second dielectric layer and laminate a release film.

7. The method for preparing the heat-insulating film according to claim 6, characterized in that: Before step (5), a thin layer of oxygen-nitrogen-containing titanium compound with a thickness of 0.2 to 0.5 nm is deposited.

8. The method for preparing the heat-insulating film according to claim 6, characterized in that: The oxygen supply in steps (3) and (7) adopts pulse modulation, with an average flow rate of 5 to 20 sccm, a pulse frequency of 0.5 to 2.0 Hz, and a duty cycle of 20% to 60%.

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