Infrared selective low-emission wave-transparent double-sided thermal control composite film and preparation method thereof

Abstract

This invention relates to an infrared-selective low-emissivity, microwave-transparent double-sided thermally controlled composite thin film and its preparation method, belonging to the field of functional thin film technology. The film comprises, in sequence, a front film system, a substrate, and a back film system; the front film system faces the heat source, and the back film system faces internal components; both the front and back film systems include a first layer, a second layer, and a third layer formed by alternating stacking of two materials with different refractive indices, wherein the refractive indices of the first and third layers are greater than that of the second layer. The infrared-selective low-emissivity, microwave-transparent double-sided thermally controlled composite thin film prepared by this invention is low in cost, significantly reduces infrared emissivity while maintaining good microwave transmittance, and exhibits stable properties.

Description

Technical Field

[0001] This invention relates to the field of functional thin film technology, and more particularly to thermal control materials, and especially to an infrared selective low-emission transparent double-sided thermal control composite thin film and its preparation method. Background Technology

[0002] Thermal control materials play an important role in spacecraft thermal control systems, including multilayer thermal insulation materials, thermal conductive materials, thermal control interface materials, and thermal control coatings. Among them, the thermal control coatings that have been applied include germanium-plated thin films, grayscale thermal control thin films, optical solar reflectors, white paint, black paint, etc., which can be used to ensure the temperature control and stable operation of spacecraft during deep space exploration.

[0003] For hypersonic vehicles experiencing high-speed cruise in near-space, the excessively high temperature of the nose cone can radiate inwards, damaging internal components. A thermal control film can be installed within the nose cone to reduce radiative heat flux while maintaining microwave transmission performance, thus not affecting the operation of internal components. Currently, research on low-infrared emissivity thermal control film technology is limited and insufficient. Furthermore, existing thermal control films suffer from problems such as insufficiently low infrared emissivity, poor microwave transmittance, poor environmental stability, and complex fabrication processes.

[0004] Therefore, there is an urgent need to develop a novel infrared-selective, low-emission, transparent, double-sided thermally controlled composite film and its preparation method. Summary of the Invention

[0005] This invention provides an infrared selective low-emissivity transparent double-sided thermal control composite film and its preparation method. The prepared infrared selective low-emissivity transparent double-sided thermal control composite film is low in cost, can significantly reduce infrared emissivity while having good microwave transmittance and stable properties.

[0006] The present invention provides an infrared selective low-emission transparent double-sided thermal control composite film in a first aspect, comprising: a front film system, a substrate, and a back film system; the front film system faces the heat source, and the back film system faces the internal components; both the front film system and the back film system comprise a first layer, a second layer, and a third layer formed by alternating stacking of two materials with different refractive indices, wherein the refractive indices of the first layer and the third layer are greater than the refractive index of the second layer.

[0007] Preferably, the refractive indices of the first layer and the third layer are both greater than 3.4; the refractive index of the second layer does not exceed 2.

[0008] Preferably, the temperature of the heat source is 300~500℃, and the self-radiation temperature of the internal components is 100~200℃.

[0009] Preferably, the first layer and the third layer are selected from PbTe, Si or GaAs.

[0010] Preferably, the second layer is selected from SiO2, Al2O3 or MgF2.

[0011] Preferably, the infrared selective low emission transparent double-sided thermal control composite film comprises, in sequence: the third layer, the second layer, the first layer of the front film system, the substrate, and the first layer, the second layer, and the third layer of the reverse film system.

[0012] Preferably, the third layer and the first layer in the front film system are made of the same material; the first layer and the third layer in the back film system are made of the same material.

[0013] Preferably, the thickness ratio of the first layer to the third layer in the front film system is (0.9~1.1):(0.9~1.1), and the thickness of the second layer is greater than the sum of the thicknesses of the first layer and the third layer; the thickness ratio of the first layer to the third layer in the reverse film system is (0.9~1.1):(0.9~1.1), and the thickness of the second layer is greater than the sum of the thicknesses of the first layer and the third layer.

[0014] Preferably, the front-side film system has an average reflectivity greater than 85% and an infrared emissivity less than 0.45 in the 3-6 μm band; the reverse-side film system has an average reflectivity greater than 85% and an infrared emissivity less than 0.47 in the 5-9 μm band.

[0015] Secondly, a method for preparing an infrared-selective, low-emission, transparent, double-sided thermally controlled composite thin film includes: The substrate was pretreated and then bombarded with an ion beam to obtain the initial substrate. The infrared selective low emission transmittance double-sided thermal control composite film was obtained by depositing a front film system and a back film system on the upper and lower surfaces of the initial substrate respectively using electron beam evaporation.

[0016] Preferably, the ion beam bombardment uses argon ions, with an ion beam current of 8~11A, a voltage of 120V, and a bombardment time of 5~10min.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The infrared selective low-emissivity transparent double-sided thermal control composite thin film provided by the present invention consists of a front film system, a substrate, and a back film system. Both the front and back film systems adopt a one-dimensional photonic crystal stacked structure, which is formed by alternating stacking of two materials with different refractive indices in one direction to form photonic band gap and photonic localization characteristics. The photonic band gap utilizes the constructive interference effect generated by the difference in refractive index to form broadband high reflectivity characteristics in the corresponding band. The high refractive index material is selected from PbTe, Si, or GaAs, and the low refractive index material is selected from SiO2, Al2O3, or MgF2. The optical design of the multilayer film of the front and back film systems is carried out. By matching and combining different film thicknesses, a high reflectivity effect in a specific infrared band can be achieved, thereby obtaining low infrared emissivity. The front-side film system, a high-temperature heat source reflector, has an average reflectivity greater than 90% in the 3–6 μm wavelength band, primarily targeting high-temperature heat sources of 300–500°C, and exhibits low emissivity in the 2.5–25 μm band. The reverse-side film system, acting as a radiation suppression layer, has an average reflectivity greater than 90% in the 5–9 μm wavelength band, primarily targeting its own radiation of 100–200°C, and also exhibits low emissivity in the 2.5–25 μm band. Thus, this double-sided thermal control composite film effectively reduces radiation transfer efficiency, protecting internal components from high-temperature damage, while also possessing microwave transmittance properties to protect internal electronic components from high-temperature damage and ensure stable operation during hypersonic vehicle operation.

[0018] (2) The infrared selective low emission transmittance double-sided thermal control composite film prepared by the present invention can maintain stable performance after being kept at high temperature of 100℃, 150℃ and 200℃ for 2 hours. The infrared reflectivity of the front and back sides of the composite film is basically the same as the initial state, the optical performance is stable, and it has good transmittance in the microwave 2.6~18GHz band.

[0019] (3) The infrared selective low emission transparent double-sided thermal control composite film provided by the present invention uses materials with low production cost, is easy to store and has no safety hazards, thus reducing the production process cost. Moreover, the preparation method is simple and easy to operate, and is suitable for mass production. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of an infrared selective low-emission transparent double-sided thermal control composite film provided in an embodiment of the present invention; Figure 2 , 3These are the reflectance curves of the front and back films of Embodiment 1 provided by the present invention in the infrared band (2.5~25μm); Figure 4 , 5 These are the reflectance curves of the front and back films of Embodiment 2 provided by the present invention in the infrared band (2.5~25μm); Figure 6 , 7 These are the reflectance curves of the front and back films of Embodiment 3 provided by the present invention in the infrared band (2.5~25μm); Figure 8 , 9 These are the reflectance curves of the front and back films of Embodiment 4 provided by the present invention in the infrared band (2.5~25μm); Figure 10 This is a reflectance curve of the reverse side of the composite film of Comparative Example 1 provided by the present invention in the infrared band (2.5~25μm); Figure 11 This is a reflectance curve of the reverse side of the composite film of Comparative Example 2 provided by the present invention in the infrared band (2.5~25μm); Figure 12 This is a reflectance curve of the reverse side of the composite film of Comparative Example 3 provided by the present invention in the infrared band (2.5~25μm); Figure 13 These are the reflectance curves of the front side of the composite films of Comparative Examples 4 and 5 provided by the present invention in the infrared band (2.5~25μm). Figure 14 This is a reflectance curve of the reverse side of the composite film of Comparative Example 5 provided by the present invention in the infrared band (2.5~25μm); Reference numerals: 1-Front-side membrane system; first layer 101 of the front-side membrane system; second layer 102 of the front-side membrane system; third layer 103 of the front-side membrane system; 2-Reverse membrane system; 201-first layer of the reverse membrane system; 202-second layer of the reverse membrane system; 203-third layer of the reverse membrane system; 3-Substrate. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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 some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] The following is the concept of the present invention, which provides an infrared selective low-emission transparent double-sided thermal control composite film, such as... Figure 1 As shown, it includes, in sequence: front film system 1, substrate 3 and back film system 2; front film system 1 faces the heat source, and back film system 2 faces the internal components; both front film system 1 and back film system 2 include a first layer, a second layer and a third layer obtained by alternating stacking of two materials with different refractive indices, and the refractive indices of the first layer and the third layer are greater than the refractive index of the second layer.

[0024] It should be noted that, as Figure 1 As shown, the front film system 1 includes a first layer 101, a second layer 102, and a third layer 103; the back film system 2 includes a first layer 201, a second layer 202, and a third layer 203. Both the front and back film systems are formed by alternating stacks of high-refractive-index, low-refractive-index, and high-refractive-index materials.

[0025] In this invention, novel performance indicators are proposed for the thermal control film in response to new application scenarios: the thermal control film employs a double-sided design. The front side is designed with high reflectivity in a specific wavelength band to reflect high-temperature heat sources, directly reflecting the incident radiant heat from the high-temperature radiator back, fundamentally preventing heat injection. The back side is designed with low emissivity in a specific wavelength band. Thus, even if the substrate experiences a temperature increase due to heat absorption, the ability of its inner surface to radiate energy inward is weakened, effectively protecting the internal precision equipment and solving the problem of internal radiative heating.

[0026] In this invention, the number of layers in the front and back film systems can be increased, for example, to four or five layers. The three-layer front and back film systems chosen in this invention not only simplify the preparation process and reduce costs, but also ensure that the resulting double-sided thermally controlled composite film still significantly reduces infrared emissivity, exhibits good microwave transmittance, and maintains stable properties.

[0027] In some preferred embodiments, the refractive indices of the first and third layers are both greater than 3.4; the refractive index of the second layer does not exceed 2.

[0028] In some preferred embodiments, the temperature of the heat source is 300~500°C (e.g., 300°C, 320°C, 350°C, 380°C, 400°C, 420°C, 450°C, 460°C, 480°C or 500°C), and the self-radiated temperature of the internal components is 100~200°C (e.g., 100°C, 120°C, 150°C, 160°C, 180°C or 200°C).

[0029] In some preferred embodiments, the first and third layers are selected from PbTe, Si, or GaAs.

[0030] In some preferred embodiments, the second layer is selected from SiO2, Al2O3 or MgF2.

[0031] In this invention, to ensure the thermal control composite film has good microwave transmittance, all layers are made of inorganic materials. Furthermore, for both the front and back film systems, the first layer is one of the core functional layers of the entire system, exhibiting strong Fresnel reflection at the interface; the second layer, acting as an optical spacer, provides optical thickness, induces constructive interference, and effectively balances and releases the internal stress of the entire film system, preventing layer detachment and improving the reliability and durability of the composite film; the third layer, as a secondary reflective and protective layer, further enhances reflectivity and provides some protection.

[0032] In some preferred embodiments, such as Figure 1 As shown, the infrared selective low emission transmittance double-sided thermal control composite film sequentially includes: the third layer 103, the second layer 102, the first layer 101 of the front film system, the substrate 3, and the first layer 201, the second layer 202, and the third layer 203 of the reverse film system.

[0033] It should be noted that in specific application scenarios, the third layer 103 of the front film system faces the heat source, while the third layer 203 of the back film system faces the internal components.

[0034] In this invention, the front film system is a high-temperature reflective surface facing the high-temperature heat source, mainly reflecting high-temperature radiation of 300~500℃ with high reflectivity; the back film system is a self-suppressing surface facing the internal components, suppressing its own internal radiation of 100~200℃ with low emissivity. The thermal control composite film is designed using all-inorganic materials with low dielectric loss to ensure good microwave transmittance. The reflectivity of the front and back film layers is calculated using the effective interface method to design the film system.

[0035] In some preferred embodiments, the third layer in the front film system is made of the same material as the first layer; the first layer in the back film system is made of the same material as the third layer.

[0036] In some preferred embodiments, the third layer of the front film system is PbTe, the second layer is SiO2, and the first layer is PbTe; the third layer of the reverse film system is PbTe, the second layer is SiO2, and the first layer is PbTe.

[0037] In some preferred embodiments, the third layer of the front film system is GaAs, the second layer is MgF2, and the first layer is GaAs; the third layer of the reverse film system is Si, the second layer is Al2O3, and the first layer is Si.

[0038] In some preferred embodiments, the thickness ratio of the first layer to the third layer in the front film system is (0.9~1.1):(0.9~1.1), and the thickness of the second layer is greater than the sum of the thicknesses of the first layer and the third layer; the thickness ratio of the first layer to the third layer in the reverse film system is (0.9~1.1):(0.9~1.1), and the thickness of the second layer is greater than the sum of the thicknesses of the first layer and the third layer.

[0039] It should be noted that (0.9~1.1): (0.9~1.1) refers to any ratio from 0.9:1.1 to 1.1:0.9, for example, it can be 0.9:1.1, 0.9:1, 1:1, 1:0.9, 1.1:1 or 1.1:0.9.

[0040] In some preferred embodiments, the front-side film system has an average reflectivity greater than 85% and an infrared emissivity less than 0.45 in the 3-6 μm band; the reverse-side film system has an average reflectivity greater than 85% and an infrared emissivity less than 0.47 in the 5-9 μm band.

[0041] In this invention, the infrared-selective low-emissivity transparent double-sided thermally controlled composite thin film consists of a front film system, a substrate, and a back film system. Both the front and back film systems adopt a one-dimensional photonic crystal stacked structure, formed by alternating stacking of two materials with different refractive indices in one direction, creating photonic bandgap and photonic localization characteristics. The photonic bandgap utilizes the constructive interference effect generated by the refractive index difference to form broadband high-reflectivity characteristics in the corresponding wavelength band. The high-refractive-index material is selected from PbTe, Si, or GaAs, and the low-refractive-index material is selected from SiO2, Al2O3, or MgF2. By optically designing the multilayer films of the front and back film systems and matching and combining different film thicknesses, a high-reflectivity effect in a specific infrared band can be achieved, thereby obtaining low infrared emissivity. The front-side film system, a high-temperature heat source reflector, has an average reflectivity greater than 90% in the 3-6 μm wavelength band, primarily targeting high-temperature heat sources of 300-500℃, and exhibits low emissivity in the 2.5-25 μm wavelength band. The reverse-side film system, acting as a radiation suppression layer, has an average reflectivity greater than 90% in the 5-9 μm wavelength band, primarily targeting its own radiation of 100-200℃, and exhibits low emissivity in the 2.5-25 μm wavelength band. Thus, this double-sided thermal control composite film effectively reduces radiation transfer efficiency, protecting internal components from high-temperature damage, while also possessing microwave transmittance properties, without affecting the operation of internal components. Furthermore, since the internal electronic components of hypersonic vehicles (speeds exceeding Mach 5) typically withstand temperatures between 100 and 300℃, the infrared-selective low-emissivity transparent double-sided thermal control composite film prepared in this invention can protect the internal electronic components of hypersonic vehicles from high-temperature damage and ensure stable operation during hypersonic vehicle operation.

[0042] This invention also provides a method for preparing an infrared selective low-emission transparent double-sided thermally controlled composite thin film, comprising: The substrate was pretreated and then bombarded with an ion beam to obtain the initial substrate. The infrared selective low emission transmittance double-sided thermal control composite film was obtained by depositing a front film system and a back film system on the upper and lower surfaces of the initial substrate respectively using electron beam evaporation.

[0043] Specifically, if the substrate is a rigid substrate (e.g., including but not limited to quartz glass) or an organic flexible substrate (e.g., including but not limited to polyimide), the substrate surface needs to be kept clean. Therefore, pretreatment includes, but is not limited to, purging with argon gas. If the substrate is rigid, it can be cleaned and then purged with argon gas to ensure that the substrate surface is free of dust, etc.

[0044] In some preferred embodiments, argon ions are used for ion beam bombardment, with an ion beam current of 8-11A, a voltage of 120V, and a bombardment time of 5-10min.

[0045] The ion beam bombardment uses argon ions, with an ion beam current of 8~11A (e.g., 8A, 9A, 10A or 11A), a voltage of 120V, and a bombardment time of 5~10min (e.g., 5min, 6min, 7min, 8min, 9min or 10min).

[0046] In this invention, the adhesion of the film layer is increased by bombardment with an ion beam.

[0047] Unless otherwise specified, the raw materials used in this invention can be products that are readily available on the market.

[0048] The present invention will be further described below by way of examples, but the scope of protection of the present invention is not limited to these embodiments.

[0049] Example 1 An infrared-selective, low-emission, transparent, double-sided thermal control composite film, such as Figure 1 As shown, from top to bottom, the layers include: the third layer 103 of the front film system 1 is PbTe with a thickness of 257nm, the second layer 102 is SiO2 with a thickness of 730nm, the first layer 101 is PbTe with a thickness of 260nm, the substrate 3 is polyimide, the first layer 201 of the reverse film system 2 is PbTe with a thickness of 425nm, the second layer 202 is SiO2 with a thickness of 1202nm, and the third layer 203 is PbTe with a thickness of 420nm.

[0050] The preparation method of the above-mentioned infrared selective low-emission transparent double-sided thermal control composite film includes: (1) The surface of the polyimide substrate is purged with argon gas to ensure that the surface is clean; then the cleaned substrate is bombarded with argon ions at room temperature (e.g., 25°C) with an ion beam current of 10A, a voltage of 120V and a bombardment time of 5min to obtain the initial substrate. (2) According to the above material layup sequence and thickness, the upper surface of the initial substrate obtained in step (1) is deposited with PbTe of 260 nm, SiO2 of 730 nm and PbTe of 257 nm in sequence according to the above thickness using electron beam evaporation; then PbTe of 425 nm, SiO2 of 1202 nm and PbTe of 420 nm are deposited on the lower surface of the initial substrate according to the above thickness to obtain infrared selective low emission transmittance double-sided thermal control composite film.

[0051] The infrared-selective low-emission, high-transmittance, double-sided thermally controlled composite film prepared in this embodiment exhibits the following reflectance curve in the 2.5–25 μm wavelength range: Figure 2 , 3 As shown, the front side faces 300~500℃, with an average reflectivity greater than 90% in the 3~6μm band and an infrared emissivity of 0.334 at 500℃; the back side faces its own radiation at 100~200℃, with an average reflectivity greater than 90% in the 5~9μm band and an infrared emissivity of 0.389 at 200℃.

[0052] Example 2 An infrared-selective, low-emission, transparent, double-sided thermal control composite film, such as Figure 1 As shown, from top to bottom, the layers include: the third layer 103 of the front film system 1 is PbTe with a thickness of 260 nm, the second layer 102 is SiO2 with a thickness of 660 nm, the first layer 101 is PbTe with a thickness of 230 nm, the substrate 3 is polyimide, the first layer 201 of the reverse film system 2 is PbTe with a thickness of 390 nm, the second layer 202 is SiO2 with a thickness of 940 nm, and the third layer 203 is PbTe with a thickness of 430 nm.

[0053] The preparation method of the above-mentioned infrared selective low-emission transparent double-sided thermal control composite film includes: (1) The surface of the polyimide substrate is purged with argon gas to ensure that the surface is clean; then the cleaned substrate is bombarded with argon ions at room temperature (e.g., 25°C) with an ion beam current of 10A, a voltage of 120V and a bombardment time of 10min to obtain the initial substrate. (2) According to the above material layup sequence and thickness, the upper surface of the initial substrate obtained in step (1) is deposited with PbTe of 230 nm, SiO2 of 660 nm and PbTe of 260 nm in sequence according to the above thickness using electron beam evaporation; then PbTe of 390 nm, SiO2 of 940 nm and PbTe of 430 nm are deposited on the lower surface of the initial substrate according to the above thickness to obtain an infrared selective low emission transmittance double-sided thermal control composite film.

[0054] The infrared-selective low-emission, high-transmittance, double-sided thermally controlled composite film prepared in this embodiment exhibits the following reflectance curve in the 2.5–25 μm wavelength range: Figure 4 , 5 As shown, the front side faces 400~500℃, with an average reflectivity greater than 90% in the 3~4.5μm band and an infrared emissivity of 0.336 at 500℃; the back side faces its own radiation at 150~200℃, with an average reflectivity greater than 90% in the 5~7μm band and an infrared emissivity of 0.388 at 200℃.

[0055] Example 3 An infrared-selective, low-emission, transparent, double-sided thermal control composite film, such as Figure 1 As shown, from top to bottom, the layers include: the third layer 103 of the front film system 1 is PbTe with a thickness of 350 nm, the second layer 102 is SiO2 with a thickness of 720 nm, the first layer 101 is PbTe with a thickness of 290 nm, the substrate 3 is polyimide, the first layer 201 of the reverse film system 2 is PbTe with a thickness of 420 nm, the second layer 202 is SiO2 with a thickness of 1110 nm, and the third layer 203 is PbTe with a thickness of 590 nm.

[0056] The preparation method of the above-mentioned infrared selective low-emission transparent double-sided thermal control composite film includes: (1) The surface of the polyimide substrate is purged with argon gas to ensure that the surface is clean; then the cleaned substrate is bombarded with argon ions at room temperature (e.g., 25°C) with an ion beam current of 10A, a voltage of 120V and a bombardment time of 5min to obtain the initial substrate. (2) According to the above material layup sequence and thickness, the upper surface of the initial substrate obtained in step (1) is deposited with 290 nm PbTe, 720 nm SiO2 and 350 nm PbTe in sequence according to the above thickness using electron beam evaporation; then, the lower surface of the initial substrate is deposited with 420 nm PbTe, 1110 nm SiO2 and 590 nm PbTe in accordance with the above thickness to obtain an infrared selective low emission transmittance double-sided thermal control composite film.

[0057] The infrared-selective low-emission, high-transmittance, double-sided thermally controlled composite film prepared in this embodiment exhibits the following reflectance curve in the 2.5–25 μm wavelength range: Figure 6 , 7 As shown, the front side faces 300~400℃, with an average reflectivity greater than 90% in the 4.5~6μm band and an infrared emissivity of 0.343 at 400℃; the back side faces self-radiation at 100~150℃, with an average reflectivity greater than 90% in the 7~9μm band and an infrared emissivity of 0.349 at 150℃.

[0058] Example 4 An infrared-selective, low-emission, transparent, double-sided thermal control composite film, such as Figure 1 As shown, from top to bottom, the layers include: the third layer 103 of the front film system 1 is GaAs with a thickness of 280 nm, the second layer 102 is MgF2 with a thickness of 780 nm, the first layer 101 is GaAs with a thickness of 300 nm, the substrate 3 is polyimide, the first layer 201 of the reverse film system 2 is Si with a thickness of 460 nm, the second layer 202 is Al2O3 with a thickness of 976 nm, and the third layer 203 is Si with a thickness of 460 nm.

[0059] The preparation method of the above-mentioned infrared selective low-emission transparent double-sided thermal control composite film includes: (1) The surface of the polyimide substrate is purged with argon gas to ensure that the surface is clean; then the cleaned substrate is bombarded with argon ions at room temperature (e.g., 25°C) with an ion beam current of 10A, a voltage of 120V and a bombardment time of 5min to obtain the initial substrate. (2) According to the above material layup sequence and thickness, the upper surface of the initial substrate obtained in step (1) is deposited with GaAs of 300 nm, MgF2 of 780 nm and GaAs of 280 nm in sequence according to the above thickness using electron beam evaporation method; then, on the lower surface of the initial substrate, Si of 460 nm thickness, Al2O3 of 976 nm thickness and Si of 460 nm thickness are deposited to obtain an infrared selective low emission transmittance double-sided thermal control composite film.

[0060] The infrared-selective low-emission, high-transmittance, double-sided thermally controlled composite film prepared in this embodiment exhibits the following reflectance curve in the 2.5–25 μm wavelength range: Figure 8 , 9 As shown, the front side faces 300~500℃, with an average reflectivity greater than 85% in the 3~6μm band and an infrared emissivity of 0.442 at 500℃; the back side faces self-radiation at 100~200℃, with an average reflectivity greater than 85% in the 5~9μm band and an infrared emissivity of 0.470 at 200℃.

[0061] Comparative Example 1 Comparative Example 1 is basically the same as Example 3, except that the membrane structure is different: there is no reverse membrane system.

[0062] Specifically, the composite film comprises, from top to bottom, the third layer 103 of the front film system being PbTe with a thickness of 350 nm, the second layer 102 being SiO2 with a thickness of 720 nm, the first layer 101 being PbTe with a thickness of 290 nm, and the substrate 3 being polyimide.

[0063] The reflectance curves of the front and back sides of the composite film in the 2.5~25μm wavelength range are shown below. Figure 6 , Figure 10 As shown, the front side faces 300~400℃, with an average reflectivity greater than 90% in the 4.5~6μm band and an infrared emissivity of 0.343 at 400℃; the back side is a polyimide substrate, with an average reflectivity of 5.72% in the 7~9μm band and an infrared emissivity of 0.862 at 150℃ for its own radiation at 100~150℃.

[0064] Comparative Example 2 Comparative Example 2 is basically the same as Example 3, except that the film structure is different: the reverse film system is only PbTe with a thickness of 420nm.

[0065] Specifically, the composite film comprises, from top to bottom, the following layers: the third layer 103 of the front film system is PbTe with a thickness of 350 nm, the second layer 102 is SiO2 with a thickness of 720 nm, the first layer 101 is PbTe with a thickness of 290 nm, the substrate 3 is polyimide, and the first layer 201 of the reverse film system 2 is PbTe with a thickness of 420 nm.

[0066] The reflectance curves of the front and back sides of the composite film in the 2.5~25μm wavelength range are shown below. Figure 6 , Figure 11 As shown, its front side faces 300~400℃, with an average reflectivity greater than 90% in the 4.5~6μm band and an infrared emissivity of 0.343 at 400℃; the back side faces its own radiation at 100~150℃, with an average reflectivity of 69.13% in the 7~9μm band and an infrared emissivity of 0.435 at 150℃.

[0067] Comparative Example 3 Comparative Example 3 is basically the same as Example 3, except that the film structure is different: the reverse film system includes a first layer and a second layer.

[0068] Specifically, the composite film comprises, from top to bottom, the following layers: the third layer 103 of the front film system is PbTe with a thickness of 350 nm, the second layer 102 is SiO2 with a thickness of 720 nm, the first layer 101 is PbTe with a thickness of 290 nm, the substrate 3 is polyimide, the first layer 201 of the reverse film system 2 is PbTe with a thickness of 420 nm, and the second layer 202 is SiO2 with a thickness of 1110 nm.

[0069] The reflectance curves of the front and back sides of the composite film in the 2.5~25μm wavelength range are shown below. Figure 6 , Figure 12 As shown, its front side faces 300~400℃, with an average reflectivity greater than 90% in the 4.5~6μm band and an infrared emissivity of 0.343 at 400℃; the back side faces its own radiation at 100~150℃, with an average reflectivity of 60.39% in the 7~9μm band and an infrared emissivity of 0.541 at 150℃.

[0070] Comparative Example 4 Comparative Example 4 is basically the same as Example 3, except that the film structure is different: the front film system only includes the first layer and the second layer.

[0071] Specifically, the composite film comprises, from top to bottom, the following layers: the second layer 102 of the front film system 1 is SiO2 with a thickness of 720 nm, the first layer 101 is PbTe with a thickness of 290 nm, the substrate 3 is polyimide, the first layer 201 of the reverse film system 2 is PbTe with a thickness of 420 nm, the second layer 202 is SiO2 with a thickness of 1110 nm, and the third layer 203 is PbTe with a thickness of 590 nm.

[0072] The reflectance curves of the front and back sides of the composite film in the 2.5~25μm wavelength range are shown below. Figure 13 , 7 As shown, its front side faces 300~400℃, with an average reflectivity of 57.33% in the 4.5~6μm band and an infrared emissivity of 0.494 at 400℃; the back side faces its own radiation at 100~150℃, with an average reflectivity greater than 90% in the 7~9μm band and an infrared emissivity of 0.349 at 150℃.

[0073] Comparative Example 5 Comparative Example 5 is basically the same as Example 3, except that the film structure is different.

[0074] Specifically, the composite film comprises, from top to bottom, the following layers: the second layer 102 of the front film system 1 is SiO2 with a thickness of 720 nm, the first layer 101 is PbTe with a thickness of 290 nm, the substrate 3 is polyimide, the second layer 202 of the reverse film system 2 is SiO2 with a thickness of 1110 nm, and the third layer 203 is PbTe with a thickness of 590 nm.

[0075] The reflectance curves of the front and back sides of the composite film in the 2.5~25μm wavelength range are shown below. Figure 13 , 14 As shown, its front side faces 300~400℃, with an average reflectivity of 57.33% in the 4.5~6μm band and an infrared emissivity of 0.494 at 400℃; the back side faces its own radiation at 100~150℃, with an average reflectivity of 80.96% in the 7~9μm band and an infrared emissivity of 0.449 at 150℃.

[0076] Comparative Example 6 Comparative Example 6 is basically the same as Example 3, except that the film structure is different.

[0077] Specifically, the composite film comprises, from top to bottom, the following layers: the third layer 103 of the front film system 1 is PbTe with a thickness of 350 nm, the second layer 102 is SiO2 with a thickness of 720 nm, the first layer 101 is PbTe with a thickness of 290 nm, the substrate 3 is polyimide, and the first layer 201 of the reverse film system 2 is PbTe with a thickness of 290 nm, the second layer 202 is SiO2 with a thickness of 720 nm, and the third layer 203 is PbTe with a thickness of 350 nm.

[0078] The reflectance curves of the front and back sides of the composite film in the 2.5~25μm wavelength range are as follows: Figure 6 As shown, its front side faces 300~400℃, with an average reflectivity greater than 90% in the 4.5~6μm band and an infrared emissivity of 0.343 at 400℃; the back side faces its own radiation at 100~150℃, with an average reflectivity of 69.97% in the 7~9μm band and an infrared emissivity of 0.474 at 150℃.

[0079] It should be noted that the infrared emissivity mentioned in this invention refers to the average emissivity in the 2.5~25μm band.

[0080] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An infrared-selective, low-emissivity, wave-transmitting, double-sided thermal control composite film, characterized in that, In order, it includes: the front membrane system, the substrate, and the back membrane system; The front film system faces the heat source, and the back film system faces the internal components; both the front film system and the back film system include a first layer, a second layer and a third layer formed by alternating stacking of two materials with different refractive indices, and the refractive indices of the first layer and the third layer are greater than the refractive index of the second layer.

2. The infrared selective low-emission transparent double-sided thermal control composite film according to claim 1, characterized in that, The refractive indices of the first and third layers are both greater than 3.4; the refractive index of the second layer does not exceed 2; and / or, The temperature of the heat source is 300~500℃, and the self-radiation temperature of the internal components is 100~200℃.

3. The infrared selective low-emission transparent double-sided thermal control composite film according to claim 1, characterized in that, The first layer and the third layer are selected from PbTe, Si or GaAs.

4. The infrared selective low-emission transparent double-sided thermal control composite film according to claim 1, characterized in that, The second layer is selected from one of SiO2, Al2O3 or MgF2.

5. The infrared selective low-emission transparent double-sided thermal control composite film according to claim 1, characterized in that, In order, they include: The third, second, and first layers of the front film system, the substrate, and the first, second, and third layers of the reverse film system.

6. The infrared selective low-emission transparent double-sided thermal control composite film according to claim 1, characterized in that, The third layer of the front film system is made of the same material as the first layer; the first layer of the back film system is made of the same material as the third layer.

7. The infrared selective low-emission transparent double-sided thermal control composite film according to claim 1, characterized in that, The thickness ratio of the first layer to the third layer in the front film system is (0.9~1.1):(0.9~1.1), and the thickness of the second layer is greater than the sum of the thicknesses of the first layer and the third layer; the thickness ratio of the first layer to the third layer in the reverse film system is (0.9~1.1):(0.9~1.1), and the thickness of the second layer is greater than the sum of the thicknesses of the first layer and the third layer.

8. An infrared-selective low-emission, wave-transmitting, double-sided thermally controlled composite film as described in any one of claims 1 to 7, characterized in that: The front-side film system has an average reflectivity greater than 85% and an infrared emissivity less than 0.45 in the 3-6 μm band; the reverse-side film system has an average reflectivity greater than 85% and an infrared emissivity less than 0.47 in the 5-9 μm band.

9. A method for preparing an infrared-selective low-emission transparent double-sided thermally controlled composite thin film as described in any one of claims 1 to 8, characterized in that, include: The substrate was pretreated and then bombarded with an ion beam to obtain the initial substrate. The infrared selective low emission transmittance double-sided thermal control composite film was obtained by depositing a front film system and a back film system on the upper and lower surfaces of the initial substrate respectively using electron beam evaporation.

10. The preparation method according to claim 9, characterized in that, The ion beam bombardment uses argon ions, with an ion beam current of 8~11A, a voltage of 120V, and a bombardment time of 5~10min.

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