Composite film with low solar absorptivity and low infrared emissivity and preparation method thereof

Abstract

The invention discloses a composite film with low solar absorptivity and low infrared emissivity and a preparation method thereof, and relates to a thermal control composite film and a preparation method thereof. The invention aims to solve the problems that the solar absorptivity and the absorption-emission ratio of the conventional thermal control film cannot be further reduced, the environmental stability of the film is poor and the preparation process is complicated. The composite film is composed of a substrate, a transition material layer I, a transition material layer II, a reflecting layer, a transition material layer II and a dielectric layer in sequence from bottom to top. The preparation method comprises the following steps: 1, film layer deposition pretreatment; and 2, depositing a film layer. The invention is used for the composite film with low solar absorptivity and low infrared emissivity and the preparation thereof.

Description

Technical Field

[0001] The present invention relates to a thermal control composite film and a preparation method thereof. Background Art

[0002] Thermal radiation is the only way for a spacecraft to dissipate heat into outer space, and the thermal control coating is a key factor for the spacecraft to dissipate heat externally. In the traditional low-temperature deep space environment, aerospace thermal control coatings with low solar absorptance and high infrared emissivity are generally used, such as white paint, second surface mirror (OSR), etc. with low solar absorptance and high infrared emissivity.

[0003] However, for scenarios such as Venus, Mercury, and lunar surface exploration, the temperature will remain at a relatively high level and the temperature difference between day and night is large under the sunlight environment. Under the illumination condition, the solar irradiance heat flow is absorbed by the thermal control coating on the spacecraft surface and enters the spacecraft, resulting in an increase in the internal temperature; at the same time, under the cryogenic space condition, the thermal control coating on the spacecraft surface dissipates heat to the space environment in the form of infrared thermal radiation, resulting in a decrease in its temperature. According to the Stefan-Boltzmann law, when the spacecraft reaches the thermal equilibrium state, its surface temperature is determined by the absorption-emission ratio, and a low absorption-emission ratio corresponds to a lower equilibrium temperature.

[0004] In the new application scenarios, new indexes are proposed for the thermal control film: low solar absorptance and low infrared emissivity; reducing the maximum value of the external heat flux under high-temperature working conditions and lowering the temperature of the cabin wall; at the same time, in the low-temperature environment, the low infrared emissivity reduces the heat loss, reduces the external heat dissipation of the spacecraft interior, and provides a heat preservation effect; the solar absorptance is less than the infrared emissivity, obtaining a low absorption-emission ratio, reducing the equilibrium temperature of the spacecraft cabin wall, and ensuring a comfortable working environment for the personnel inside the spacecraft and the normal operation of the equipment.

[0005] However, in the existing aerospace low-solar-absorptance and low-infrared-emissivity thermal control film technology, there are problems such as insufficiently low solar absorptance, insufficiently low absorption-emission ratio, poor environmental stability of the film, and complex preparation process.

[0006] Therefore, there is an urgent need to develop a composite film with low cost, which can significantly reduce the solar absorptance and absorption-emission ratio at the same time, and has stable properties, so as to cope with the high-temperature alternating environment in deep space exploration. Summary of the Invention

[0007] The present invention aims to solve the problems existing in the existing thermal control film, such as the inability to further reduce the solar absorptance and absorption-emission ratio, poor environmental stability of the film, and complex preparation process, and further provides a low-solar-absorptance and low-infrared-emissivity composite film and a preparation method thereof.

[0008] A low-solar-absorptance and low-infrared-emissivity composite film is composed of a substrate, a transition material layer I, a transition material layer II, a reflection layer, a transition material layer II, and a dielectric layer from bottom to top in sequence;

[0009] The described dielectric layer is formed by alternating dielectric material layer I and dielectric material layer II, and both the bottommost layer and the topmost layer from bottom to top in the dielectric layer are dielectric material layer I; let the total number of dielectric material layer I and dielectric material layer II in the dielectric layer be n, where n = 5 - 13 and n is an odd number.

[0010] A preparation method of a composite film with low solar absorptance and low infrared emissivity is carried out according to the following steps:

[0011] I. Pretreatment before film layer deposition:

[0012] Ion beam bombardment is carried out on the substrate at normal temperature or under heating conditions to obtain an ion beam bombarded substrate;

[0013] II. Depositing film layers:

[0014] By using electron beam evaporation method, magnetron sputtering method or vacuum ion coating method, a transition material layer I, a transition material layer II, a reflective layer, a transition material layer II and a dielectric layer are sequentially deposited on the ion beam bombarded substrate to obtain a composite film with low solar absorptance and low infrared emissivity.

[0015] The beneficial effects of the present invention are as follows:

[0016] I. The composite film with low solar absorptance and low infrared emissivity provided by the present invention can significantly reduce the solar absorptance and the absorption - emission ratio. The structure of the composite film consists of a transition layer, a reflective layer and a dielectric layer. The transition layer ensures good bonding force between the substrate and the reflective layer, and between the reflective layer and the dielectric layer; the reflective layer enables the composite film to have low infrared emissivity; the dielectric layer can improve the environmental stability such as antioxidant, waterproof and wear - resistant properties of the reflective layer while increasing the reflectivity in the visible band. The dielectric layer adopts a stacked structure of one - dimensional photonic crystal, which is formed by alternately stacking two materials with different refractive indices in one direction, and can form photonic bandgap and photonic localization characteristics. The photonic bandgap uses the constructive interference effect generated by the refractive index difference to form broadband high - reflection characteristics in the corresponding band. Through optical design of the multi - layer film and matching combination of different film thicknesses, high - reflection effect in the visible band can be achieved, thereby obtaining low solar absorptance and low absorption - emission ratio, and solving the problem that the solar absorptance and absorption - emission ratio of the existing thermal control film cannot be further reduced.

[0017] II. The composite film with low solar absorptance and low infrared emissivity provided by the present invention can maintain stable performance after solar irradiation experiment, ultraviolet irradiation experiment, high - low temperature resistance experiment and damp - heat aging experiment. The solar - band absorptance and infrared - band emissivity of the film are basically the same as the initial state. This technology is a low - cost, safe and simple film preparation technology; the optical properties of the film are stable, which is suitable for high - temperature deep - space exploration, ensuring the smooth progress of tasks such as planetary exploration, and at the same time reducing the production process cost.

[0018] III. The materials used in the low solar absorptivity and low infrared emissivity composite film prepared by the present invention have low production costs, are easy to store, and have no safety hazards.

[0019] The present invention relates to a low solar absorptivity and low infrared emissivity composite film and a preparation method thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of the low solar absorptivity and low infrared emissivity composite film of the present invention. 101 is a substrate, 102 is a transition material layer I, 103 is a transition material layer II, 104 is a reflective layer, 105 is a dielectric material layer I, 106 is a dielectric material layer II, and 107 is a dielectric layer;

[0021] Figure 2 It is an absorptivity diagram of the low solar absorptivity and low infrared emissivity composite film prepared in Example 1 in the visible to infrared wavelength range (0.25 μm - 25 μm);

[0022] Figure 3 It is an absorptivity diagram of the low solar absorptivity and low infrared emissivity composite film prepared in Example 2 in the visible to infrared wavelength range (0.25 μm - 25 μm);

[0023] Figure 4 It is an absorptivity diagram of the low solar absorptivity and low infrared emissivity composite film prepared in Example 3 in the visible to infrared wavelength range (0.25 μm - 25 μm);

[0024] Figure 5 It is an absorptivity diagram of the low solar absorptivity and low infrared emissivity composite film prepared in Example 4 in the visible to infrared wavelength range (0.25 μm - 25 μm);

[0025] Figure 6 It is an absorptivity diagram of the low solar absorptivity and low infrared emissivity composite film prepared in Example 5 in the visible to infrared wavelength range (0.25 μm - 25 μm). DETAILED DESCRIPTION OF THE INVENTION

[0026] DETAILED DESCRIPTION OF THE INVENTION I, in combination with Figure 1 DETAILED DESCRIPTION: A low solar absorptivity and low infrared emissivity composite film in this embodiment is composed of a substrate, a transition material layer I, a transition material layer II, a reflective layer, a transition material layer II, and a dielectric layer from bottom to top in sequence;

[0027] The dielectric layer is composed of dielectric material layer I and dielectric material layer II arranged alternately, and the bottom layer and the top layer of the dielectric layer from bottom to top are both dielectric material layer I; Let the total number of dielectric material layer I and dielectric material layer II in the dielectric layer be n, where n = 5 - 13 and n is an odd number.

[0028] The low solar absorptance and low infrared emissivity composite film in this specific embodiment is composed of the following structures: a transition layer for enhancing the adhesion to the substrate, a transition layer for protecting the reflective layer and enhancing the adhesion of the reflective layer, a high reflective layer, and a stacked dielectric structure formed by materials with different refractive indices.

[0029] The beneficial effects of this embodiment are as follows:

[0030] First, the low solar absorptance and low infrared emissivity composite film provided in this embodiment can significantly reduce the solar absorptance and the absorption-emission ratio. The structure of this composite film consists of a transition layer, a reflective layer, and a dielectric layer. The transition layer ensures good adhesion between the substrate and the reflective layer, and between the reflective layer and the dielectric layer; the reflective layer endows the composite film with low infrared emissivity; the dielectric layer can improve the environmental stability of the reflective layer such as oxidation resistance, waterproofness, and wear resistance, while increasing the reflectivity in the visible band. The dielectric layer adopts a stacked structure of one-dimensional photonic crystals, which is formed by alternately stacking two materials with different refractive indices in one direction, and can form photonic band gaps and photonic localization characteristics. The photonic band gap uses the constructive interference effect generated by the refractive index difference to form broadband high-reflection characteristics in the corresponding band. Through optical design of the multilayer film and matching combinations of different film thicknesses, a high-reflection effect in the visible band can be achieved, thereby obtaining a low solar absorptance and a low absorption-emission ratio, and solving the problem that the solar absorptance and the absorption-emission ratio of existing thermal control films cannot be further reduced.

[0031] Second, the low solar absorptance and low infrared emissivity composite film provided in this embodiment can maintain stable performance after solar irradiation experiments, ultraviolet irradiation experiments, high and low temperature resistance experiments, and damp heat aging experiments. The solar band absorptance and the infrared band emissivity of the film are basically the same as those in the initial state. This technology is a low-cost, safe, and simple film preparation technology; the optical properties of the film are stable, suitable for high-temperature deep space exploration, ensuring the smooth progress of tasks such as planetary exploration, and at the same time reducing the production process cost.

[0032] Third, the materials used to prepare the low solar absorptance and low infrared emissivity composite film in this embodiment have low production costs, are easy to store, and have no safety hazards.

[0033] Specific embodiment two: The difference between this embodiment and specific embodiment one is that: the substrate is a hard substrate or an organic flexible substrate; the hard substrate is quartz glass, single-polished silicon wafer, or aluminum plate; the organic flexible substrate is polyethylene terephthalate, polyethylene naphthalate, polydimethylsiloxane, polyurethane, polyimide, or perfluoroethylenepropylene copolymer. Others are the same as in specific embodiment one.

[0034] Embodiment 3: The difference between this embodiment and Embodiment 1 or 2 is that the material of the transition material layer I is Cr, In or Ni; the material of the transition material layer II is Al2O3, TiO2, Ti3O5 or SiO2. Others are the same as Embodiment 1 or 2.

[0035] Embodiment 4: The difference between this embodiment and Embodiment 1 to 3 is that the material of the reflective layer is one or an alloy of several of Ag, Al, Au, Cu and Ti. Others are the same as Embodiment 1 to 3.

[0036] Embodiment 5: The difference between this embodiment and Embodiment 1 to 4 is that the material of the dielectric material layer I is SiO2, Al2O3 or cerium-doped silica; the material of the dielectric material layer II is ZrO2, Nb2O5, TiO2, Ti3O5, Ta2O5, Si3N4, HfO2 or WO3. Others are the same as Embodiment 1 to 4.

[0037] Embodiment 6: The difference between this embodiment and Embodiment 1 to 5 is that the total thickness of the transition material layer I and the transition material layer II is 3 nm to 30 nm. Others are the same as Embodiment 1 to 5.

[0038] Embodiment 7: The difference between this embodiment and Embodiment 1 to 6 is that the thickness of the reflective layer is 50 nm to 300 nm. Others are the same as Embodiment 1 to 6.

[0039] Embodiment 8: The difference between this embodiment and Embodiment 1 to 7 is that the total thickness of the dielectric layer is 200 nm to 700 nm. Others are the same as Embodiment 1 to 7.

[0040] Embodiment 9: A method for preparing a low solar absorptance and low infrared emissivity composite film, which is carried out according to the following steps:

[0041] I. Pretreatment before film layer deposition:

[0042] Ion beam bombardment is carried out on the substrate at normal temperature or under heating conditions to obtain an ion beam bombarded substrate;

[0043] II. Depositing film layers:

[0044] The transition material layer I, the transition material layer II, the reflective layer, the transition material layer II and the dielectric layer are sequentially deposited on the ion beam bombarded substrate by electron beam evaporation, magnetron sputtering or vacuum ion plating to obtain a low solar absorptance and low infrared emissivity composite film.

[0045] Embodiment 10: The difference between this embodiment and Embodiment 9 is that: in Step 1, under the conditions of a temperature of 10°C to 400°C, an ion beam current of 7 A to 20 A, and a voltage of 100 V to 200 V, the substrate is bombarded with an argon ion beam for 5 min to 10 min; in Step 2, the electron beam evaporation method specifically refers to carrying out under a vacuum degree of 5×10 -3 Pa to 5×10 -4 Pa and an evaporation rate of 0.2 nm / s to 1.5 nm / s. Others are the same as Embodiment 9.

[0046] The following examples are used to verify the beneficial effects of the present invention:

[0047] Example 1:

[0048] A low solar absorptance and low infrared emissivity composite film, which is composed of a substrate, a first transition material layer (with a thickness of 10 nm), a second transition material layer (with a thickness of 3 nm), a reflective layer (with a thickness of 100 nm), a second transition material layer (with a thickness of 3 nm), a first dielectric material layer (with a thickness of 59.79 nm), a second dielectric material layer (with a thickness of 47.51 nm), a first dielectric material layer (with a thickness of 95.74 nm), a second dielectric material layer (with a thickness of 29.90 nm), and a first dielectric material layer (with a thickness of 155.10 nm) from bottom to top in sequence.

[0049] The substrate is polyimide, and the surface of the substrate needs to be kept clean and blown clean with argon.

[0050] The material of the first transition material layer is Cr; the material of the second transition material layer is TiO2.

[0051] The material of the reflective layer is Ag.

[0052] The material of the first dielectric material layer is SiO2; the material of the second dielectric material layer is Nb2O5.

[0053] The preparation method of the above-mentioned low solar absorptance and low infrared emissivity composite film is carried out according to the following steps:

[0054] I. Pretreatment before film layer deposition:

[0055] Under normal temperature, an ion beam current of 7 A, and a voltage of 100 V, the substrate is bombarded with an argon ion beam for 8 min to obtain the substrate bombarded by the ion beam;

[0056] II. Depositing film layers:

[0057] Using the electron beam evaporation method, a transition material layer I, a transition material layer II, a reflective layer, a transition material layer II, a dielectric material layer I, a dielectric material layer II, a dielectric material layer I, a dielectric material layer II, and a dielectric material layer I are sequentially deposited on the substrate after ion beam bombardment to obtain a composite thin film with low solar absorptance and low infrared emissivity.

[0058] Figure 2 Absorptance diagram of the composite thin film with low solar absorptance and low infrared emissivity prepared in Example 1 in the visible to infrared band (0.25 μm - 25 μm); as can be seen from the figure, on the polyimide substrate, from bottom to top, there is a stacked structure of a transition layer Cr, a transition layer TiO2, a reflective layer Ag, a transition layer TiO2, and a dielectric layer SiO2 / Nb2O5. The absorptance of the prepared composite thin film with low solar absorptance and low infrared emissivity in the solar band (250 nm - 2500 nm) is 0.055, and the emissivity in the infrared band (2.5 μm - 25 μm) is 0.088, with an absorption-emission ratio of 0.63. After the composite thin film with low solar absorptance and low infrared emissivity is heated at 200 °C for 2 h, the absorptance in the solar band is 0.059, and the emissivity in the infrared band is 0.087; after the composite thin film with low solar absorptance and low infrared emissivity is cooled at -196 °C for 14 days, the absorptance in the solar band is 0.056, and the emissivity in the infrared band is 0.088; after the composite thin film with low solar absorptance and low infrared emissivity is irradiated with ultraviolet light for 100 ESH (equivalent sunshine hours), the absorptance in the solar band is 0.057, and the infrared emissivity is 0.088, remaining stable and the absorption-emission ratio is always less than 1.

[0059] Example 2:

[0060] A composite thin film with low solar absorptance and low infrared emissivity, which is composed of a substrate, a transition material layer I (with a thickness of 5 nm), a transition material layer II (with a thickness of 10 nm), a reflective layer (with a thickness of 125 nm), a transition material layer II (with a thickness of 10 nm), a dielectric material layer I (with a thickness of 52.32 nm), a dielectric material layer II (with a thickness of 56.29 nm), a dielectric material layer I (with a thickness of 83.98 nm), a dielectric material layer II (with a thickness of 29.59 nm), and a dielectric material layer I (with a thickness of 149.15 nm) from bottom to top.

[0061] The substrate is quartz glass, and the surface of the substrate needs to be kept clean. The substrate is ultrasonically cleaned with acetone, methanol, and ultrapure water in sequence, and the ultrasonic cleaning time is 20 min for each, and then dried with argon.

[0062] The material of the transition material layer I is Cr; the material of the transition material layer II is Al2O3.

[0063] The material of the reflective layer is Ag.

[0064] The material of the medium material layer I is SiO2; the material of the medium material layer II is Ti3O5.

[0065] The preparation method of the above-mentioned composite thin film with low solar absorptance and low infrared emissivity is carried out according to the following steps:

[0066] I. Pretreatment before film layer deposition:

[0067] Under the conditions of normal temperature, an ion beam current of 20 A and a voltage of 150 V, the substrate is bombarded with argon ion beam for 10 min to obtain the ion beam bombarded substrate;

[0068] II. Depositing film layers:

[0069] By using the electron beam evaporation method, a transition material layer I, a transition material layer II, a reflective layer, a transition material layer II, a medium material layer I, a medium material layer II, a medium material layer I, a medium material layer II and a medium material layer I are sequentially deposited on the ion beam bombarded substrate to obtain the composite thin film with low solar absorptance and low infrared emissivity.

[0070] Figure 3 Absorptance diagram of the composite thin film with low solar absorptance and low infrared emissivity prepared in Example 2 in the visible to infrared band (0.25 μm - 25 μm); as can be seen from the figure, on the quartz glass substrate, from bottom to top are the transition layer Cr, the transition layer Al2O3, the reflective layer Ag, the transition layer Al2O3, and the laminated structure of the dielectric layer SiO2 / Ti3O5. The absorptance of the prepared composite thin film with low solar absorptance and low infrared emissivity in the solar band (250 nm - 2500 nm) is 0.055, the emissivity in the infrared band (2.5 μm - 25 μm) is 0.094, and the absorption-emission ratio is 0.59. After the composite thin film with low solar absorptance and low infrared emissivity is heated at 200 °C for 2 h, the absorptance in the solar band is 0.061, and the emissivity in the infrared band is 0.085; after the composite thin film with low solar absorptance and low infrared emissivity is cooled at -196 °C for 14 days, the absorptance in the solar band is 0.061, and the emissivity in the infrared band is 0.080; after the composite thin film with low solar absorptance and low infrared emissivity is irradiated with ultraviolet light for 100 ESH (equivalent sunshine hours), the absorptance in the solar band is 0.059, and the emissivity in the infrared band is 0.115, remaining stable and the absorption-emission ratio is always less than 1.

[0071] Example 3:

[0072] A composite film with low solar absorptance and low infrared emissivity, which consists of a substrate, a transition material layer I (with a thickness of 5 nm), a transition material layer II (with a thickness of 5 nm), a reflective layer (with a thickness of 80 nm), a transition material layer II (with a thickness of 5 nm), a dielectric material layer I (with a thickness of 50.84 nm), a dielectric material layer II (with a thickness of 61.29 nm), a dielectric material layer I (with a thickness of 77.00 nm), a dielectric material layer II (with a thickness of 42.15 nm), and a dielectric material layer I (with a thickness of 139.86 nm) from bottom to top in sequence.

[0073] The substrate is perfluoroethylene propylene, and the surface of the substrate needs to be kept clean and blown clean with argon gas.

[0074] The material of the transition material layer I is In; the material of the transition material layer II is Al2O3.

[0075] The material of the reflective layer is Ag.

[0076] The material of the dielectric material layer I is SiO2; the material of the dielectric material layer II is ZrO2.

[0077] The preparation method of the above-mentioned composite film with low solar absorptance and low infrared emissivity is carried out according to the following steps:

[0078] I. Pretreatment before film layer deposition:

[0079] Under the conditions of normal temperature, an ion beam current of 10 A and a voltage of 120 V, the substrate is bombarded with argon ion beam for 5 minutes to obtain the substrate bombarded by the ion beam.

[0080] II. Depositing film layers:

[0081] Using the electron beam evaporation method, the transition material layer I, the transition material layer II, the reflective layer, the transition material layer II, the dielectric material layer I, the dielectric material layer II, the dielectric material layer I, the dielectric material layer II, and the dielectric material layer I are sequentially deposited on the substrate bombarded by the ion beam to obtain the composite film with low solar absorptance and low infrared emissivity.

[0082] Figure 4Absorbance graph of the low solar absorptance and low infrared emissivity composite film prepared in Example 3 in the visible to infrared band (0.25 μm - 25 μm); as can be seen from the figure, on the perfluoroethylene-propylene substrate, from bottom to top in sequence is the transition layer In, the transition layer Al2O3, the reflective layer Ag, the transition layer Al2O3, and the laminated structure of the dielectric layer SiO2 / ZrO2. The solar band (250 nm - 2500 nm) absorbance of the prepared low solar absorptance and low infrared emissivity composite film is 0.052, the infrared band (2.5 μm - 25 μm) emissivity is 0.079, and the absorption-emission ratio is 0.66. After the low solar absorptance and low infrared emissivity composite film is heated at 200 °C for 2 h, the solar band absorbance is 0.080 and the infrared band emissivity is 0.084; after the low solar absorptance and low infrared emissivity composite film is cooled at -196 °C for 14 days, the solar band absorbance is 0.056 and the infrared band emissivity is 0.071; after the low solar absorptance and low infrared emissivity composite film is irradiated with ultraviolet light for 500 ESH (equivalent sunshine hours), the solar band absorbance is 0.092 and the infrared band emissivity is 0.122, remaining stable and the absorption-emission ratio is always less than 1.

[0083] Example 4:

[0084] A low solar absorptance and low infrared emissivity composite film, which is composed of a substrate, a transition material layer I (with a thickness of 5 nm), a transition material layer II (with a thickness of 10 nm), a reflective layer (with a thickness of 100 nm), a transition material layer II (with a thickness of 10 nm), a dielectric material layer I (with a thickness of 51.20 nm), a dielectric material layer II (with a thickness of 59.72 nm), a dielectric material layer I (with a thickness of 79.15 nm), a dielectric material layer II (with a thickness of 38.49 nm), and a dielectric material layer I (with a thickness of 142.79 nm) from bottom to top in sequence.

[0085] The substrate is polyimide, and the surface of the substrate needs to be kept clean and blown clean with argon.

[0086] The material of the transition material layer I is Ni; the material of the transition material layer II is Ti3O5.

[0087] The material of the reflective layer is Ag.

[0088] The material of the dielectric material layer I is SiO2; the material of the dielectric material layer II is Ta2O5.

[0089] The preparation method of the above-mentioned low solar absorptance and low infrared emissivity composite film is carried out according to the following steps:

[0090] I. Pretreatment before film layer deposition:

[0091] Under the conditions of normal temperature, an ion beam current of 15 A, and a voltage of 180 V, the substrate was bombarded with an argon ion beam for 5 min to obtain an ion beam-bombarded substrate;

[0092] II. Depositing a film layer:

[0093] Using the electron beam evaporation method, a transition material layer I, a transition material layer II, a reflective layer, a transition material layer II, a dielectric material layer I, a dielectric material layer II, a dielectric material layer I, a dielectric material layer II, and a dielectric material layer I were successively deposited on the ion beam-bombarded substrate to obtain a low solar absorptance and low infrared emissivity composite film.

[0094] Figure 5 Absorptance diagram of the low solar absorptance and low infrared emissivity composite film prepared in Example 4 in the visible to infrared band (0.25 μm - 25 μm); as can be seen from the figure, on the polyimide substrate, from bottom to top in sequence is a stacked structure of a transition layer Ni, a transition layer Ti3O5, a reflective layer Ag, a transition layer Ti3O5, and a dielectric layer SiO2 / Ta2O5. The solar band (250 nm - 2500 nm) absorptance of the prepared low solar absorptance and low infrared emissivity composite film is 0.048, the infrared band (2.5 μm - 25 μm) emissivity is 0.076, and the absorption-emission ratio is 0.63. After the low solar absorptance and low infrared emissivity composite film was heated at 200 °C for 2 h, the solar band absorptance was 0.056 and the infrared band emissivity was 0.078; after the low solar absorptance and low infrared emissivity composite film was cooled at -196 °C for 14 days, the solar band absorptance was 0.053 and the infrared band emissivity was 0.073; after the low solar absorptance and low infrared emissivity composite film was irradiated with ultraviolet light for 500 ESH (equivalent sunshine hours), the solar band absorptance was 0.088 and the infrared band emissivity was 0.118, remaining stable and the absorption-emission ratio always being less than 1.

[0095] Example 5:

[0096] A composite film with low solar absorptance and low infrared emissivity, which is composed of a substrate, a transition material layer I (with a thickness of 10 nm), a transition material layer II (with a thickness of 5 nm), a reflective layer (with a thickness of 100 nm), a transition material layer II (with a thickness of 5 nm), a dielectric material layer I (with a thickness of 60.75 nm), a dielectric material layer II (with a thickness of 75.18 nm), a dielectric material layer I (with a thickness of 78.8 nm), a dielectric material layer II (with a thickness of 86.35 nm), a dielectric material layer I (with a thickness of 14.47 nm), a dielectric material layer II (with a thickness of 47.58 nm), a dielectric material layer I (with a thickness of 45.03 nm), a dielectric material layer II (with a thickness of 10.82 nm), a dielectric material layer I (with a thickness of 66.71 nm), a dielectric material layer II (with a thickness of 11.41 nm), a dielectric material layer I (with a thickness of 42.58 nm), a dielectric material layer II (with a thickness of 44.05 nm), and a dielectric material layer I (with a thickness of 48.75 nm) from bottom to top.

[0097] The substrate is polyimide, and the surface of the substrate needs to be kept clean and blown clean with argon gas.

[0098] The material of the transition material layer I is Cr; the material of the transition material layer II is Al2O3.

[0099] The material of the reflective layer is Al.

[0100] The material of the dielectric material layer I is SiO2; the material of the dielectric material layer II is Ta2O5.

[0101] The preparation method of the above composite film with low solar absorptance and low infrared emissivity is carried out according to the following steps:

[0102] I. Pretreatment before film deposition:

[0103] Under the conditions of normal temperature, an ion beam current of 7 A and a voltage of 200 V, the substrate is bombarded with argon ion beam for 8 min to obtain the ion beam bombarded substrate;

[0104] II. Depositing film layers:

[0105] Using the electron beam evaporation method, the transition material layer I, the transition material layer II, the reflective layer, the transition material layer II, the dielectric material layer I, the dielectric material layer II, the dielectric material layer I, the dielectric material layer II, the dielectric material layer I, the dielectric material layer II, the dielectric material layer I, the dielectric material layer II, the dielectric material layer I, the dielectric material layer II, the dielectric material layer I, the dielectric material layer II, and the dielectric material layer I are successively deposited on the ion beam bombarded substrate to obtain the composite film with low solar absorptance and low infrared emissivity.

[0106] Figure 6Absorbance graph of the visible and infrared bands (0.25 μm to 25 μm) of the low solar absorptance and low infrared emissivity composite film prepared in Example 5; As can be seen from the figure, on the polyimide substrate, from bottom to top, there is a stacked structure of a transition layer Cr, a transition layer Al2O3, a reflective layer Al, a transition layer Al2O3, and a dielectric layer SiO2 / Ta2O5. The solar band (250 nm to 2500 nm) absorbance of the prepared low solar absorptance and low infrared emissivity composite film is 0.041, the infrared band (2.5 μm to 25 μm) emissivity is 0.135, and the absorption-emission ratio is 0.30.

[0107] Electron beam evaporation process in Examples 1 to 5

[0108]

Claims

1. A composite film with low solar absorptance and low infrared emissivity, characterized in that It consists of a substrate, a transition material layer I, a transition material layer II, a reflective layer, a transition material layer II, and a dielectric layer in sequence from bottom to top; The dielectric layer is formed by alternating dielectric material layer I and dielectric material layer II, and the bottommost layer and the topmost layer of the dielectric layer from bottom to top are both dielectric material layer I; Let the total number of dielectric material layer I and dielectric material layer II in the dielectric layer be n, where n = 5 - 13 and n is an odd number.

2. The low solar absorptance and low infrared emissivity composite film according to claim 1, wherein The substrate is a hard substrate or an organic flexible substrate; the hard substrate is quartz glass, a single-polished silicon wafer, or an aluminum plate; the organic flexible substrate is polyethylene terephthalate, polyethylene naphthalate, polydimethylsiloxane, polyurethane, polyimide, or perfluorinated ethylene-propylene copolymer.

3. A low solar absorptance and low infrared emissivity composite film according to claim 1, characterized in that The material of the transition material layer I is Cr, In, or Ni; the material of the transition material layer II is Al2O3, TiO2, Ti3O5, or SiO2.

4. The low solar absorptance and low infrared emissivity composite film according to claim 1, characterized in that The material of the reflective layer is one or an alloy of several of Ag, Al, Au, Cu, and Ti.

5. The low solar absorptance and low infrared emissivity composite film according to claim 1, characterized in that The material of the dielectric material layer I is SiO2, Al2O3, or cerium-doped silica; the material of the dielectric material layer II is ZrO2, Nb2O5, TiO2, Ti3O5, Ta2O5, Si3N4, HfO2, or WO3.

6. The low solar absorptance and low infrared emissivity composite film according to claim 1, wherein The total thickness of the transition material layer I and the transition material layer II is 3nm - 30nm.

7. The low solar absorptance and low infrared emissivity composite film according to claim 1, wherein The thickness of the reflective layer is 50nm - 300nm.

8. A low solar absorptance and low infrared emissivity composite film according to claim 1, characterized in that The total thickness of the dielectric layer is 200nm - 700nm.

9. The preparation method of a composite film with low solar absorptance and low infrared emissivity as described in claim 1, characterized in that It is carried out according to the following steps: I. Pretreatment before film deposition: Ion beam bombardment is carried out on the substrate at room temperature or under heating conditions to obtain an ion beam bombarded substrate; II. Depositing the film layer: Using electron beam evaporation, magnetron sputtering, or vacuum ion plating, the transition material layer I, the transition material layer II, the reflective layer, the transition material layer II, and the dielectric layer are sequentially deposited on the ion beam bombarded substrate to obtain a low solar absorptance and low infrared emissivity composite thin film.

10. The preparation method of a composite film with low solar absorptance and low infrared emissivity according to claim 9, characterized in that In Step 1, the substrate is bombarded with argon ion beam for 5 min to 10 min under the conditions of a temperature of 10 °C to 400 °C, an ion beam current of 7 A to 20 A, and a voltage of 100 V to 200 V; in Step 2, the electron beam evaporation method specifically is carried out under the conditions of a vacuum degree of 5×10 -3 Pa to 5×10 -4 Pa and an evaporation rate of 0.2 nm / s to 1.5 nm / s.

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