Radiation modulated multilayer film structure and method of making the same

Abstract

The application discloses a radiation regulation multilayer film structure and a preparation method thereof. The radiation regulation multilayer film structure comprises a plurality of first regulation layers, the refractive index of the first regulation layers to specific waveband electromagnetic waves E is N1; a plurality of second regulation layers, the refractive index of the second regulation layers to specific waveband electromagnetic waves E is N2; wherein the first regulation layers and the second regulation layers are low dielectric loss materials, the first regulation layers and the second regulation layers are alternately stacked to form a multilayer structure with periodic refractive index change, and N1>N2. The radiation regulation film is formed by the high and low refractive index low dielectric loss material thin films arranged in a multilayer manner, and the low emissivity in the 3-25 mu m infrared waveband is realized, and meanwhile, the high transmissivity in the 2-18 GHz microwave frequency band is also achieved.

Description

Technical Field

[0001] This invention relates to the field of radiation modulation technology, and in particular to a radiation-modulated multilayer film structure and its preparation method. Background Technology

[0002] In aerospace environments, heat exchange between spacecraft and the external environment primarily occurs through radiation. Therefore, radiation-induced thermal protection materials suitable for such environments must possess low emissivity in the infrared band (3–25 μm) to effectively provide radiative insulation for heat-sensitive components. Currently widely used multilayer thermal insulation materials typically employ an inner low-emissivity thin film, constructed using vacuum deposition techniques, which can significantly suppress infrared radiation.

[0003] However, traditional thermal insulation films generally lack transmission capability in the 2–18 GHz communication microwave frequency band. This is mainly because the film structure extensively uses metal layers, which exhibit high reflectivity and low transmittance characteristics to microwaves. Current research on radiation-insulating materials focuses primarily on optimizing thermal radiation performance, while insufficient attention is paid to electromagnetic compatibility with microwave communication.

[0004] For example, the publication number "CN115287597A" discloses "A method for preparing an infrared mid-wave high emissivity and long-wave low emissivity composite thin film." This method prepares an infrared mid-wave high emissivity and long-wave low emissivity composite thin film. The composite thin film has a four-layer structure, including a high-reflectivity layer, a dielectric layer, an infrared radiation layer, and a protective layer. The high-reflectivity layer is made of gold, silver, copper, aluminum, titanium, or an alloy, ensuring high reflectivity in the infrared band on different substrates. The dielectric layer is made of ZrO2, SiO2, Al2O3, Si3N4, HfO2, or Ge, which can change the electromagnetic... The transmission path of the wave in the multilayer film modulates the selectivity of the infrared spectrum of the thin film; the infrared radiating layer is usually Ag, Cr, Zr, Ni or Cu, which can enhance the emissivity of specific infrared bands based on intrinsic infrared optical properties; the protective layer is metal Ge, which can prevent the ultrathin metal of the infrared radiating layer from being oxidized and can effectively broaden the absorption band of specific infrared bands, so that the emissivity of the composite film is about 0.8 in the mid-wave infrared band (3~5μm) and about 0.1 in the long-wave infrared band (8~14μm), achieving selectivity of emissivity in the infrared atmospheric window band.

[0005] Although this technology can optimize thermal radiation performance, it uses a variety of metal materials. The dielectric properties of metals are characterized by high conductivity, which will generate strong eddy current loss and Joule heat loss under the action of electromagnetic waves, resulting in significant dielectric loss. Especially in the microwave band, it will severely absorb or reflect electromagnetic waves, resulting in extremely low microwave transmittance. Summary of the Invention

[0006] In view of the problem of insufficient electromagnetic compatibility of existing heat insulation films for microwave communication, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to provide a radiation-controlled multilayer film structure and its preparation method, which aims to increase microwave communication capability while maintaining radiation insulation capability.

[0008] To address the aforementioned technical problems, this invention provides a radiation-controlled multilayer film structure: comprising a radiation-controlled film, divided into several first control layers, wherein the refractive index of the first control layers for electromagnetic waves E in a specific wavelength band is N1; and several second control layers, wherein the refractive index of the second control layers for electromagnetic waves E in a specific wavelength band is N2; wherein the first control layers and the second control layers are both low dielectric loss materials, and the first control layers and the second control layers are alternately stacked to form a multilayer structure with periodic refractive index changes, wherein N1 > N2.

[0009] In a preferred embodiment of the radiation-controlled multilayer film structure described in this invention, the wavelength of the electromagnetic wave E is 3~20μm.

[0010] As a preferred embodiment of the radiation-controlled multilayer film structure of the present invention, wherein: the refractive index difference between N1 and N2 is >1, and the first control layer and the second control layer form constructive interference and a photonic bandgap.

[0011] As a preferred embodiment of the radiation-controlled multilayer film structure of the present invention, the material of the first control layer is selected from a material with a refractive index N1 of 3.4 to 4.2, and the material of the second control layer is selected from a material with a refractive index of 1.4 to 2.4.

[0012] As a preferred embodiment of the radiation-controlled multilayer film structure of the present invention, the material of the first control layer is selected as Ge or Si, and the material of the second control layer is selected as ZnS, ZnSe, or BaF2.

[0013] As a preferred embodiment of the radiation-controlled multilayer film structure of the present invention, the thickness of each of the first control layer and the second control layer is 350~1700nm.

[0014] As a preferred embodiment of the radiation-controlled multilayer membrane structure of the present invention, it further includes: a base layer, which is membrane-like, and a radiation-controlled membrane is provided on at least one side of the base layer for forming a membrane structure; and a bonding layer disposed between the base layer and the radiation-controlled membrane; wherein the base layer, the radiation-controlled membrane, and the bonding layer are all made of non-metallic materials.

[0015] As a preferred embodiment of the radiation-controlled multilayer film structure of the present invention, wherein: the thermal expansion coefficient of the base layer is α1, the thermal expansion coefficient of the radiation-controlled film at the point closest to the base layer at 200° is α2, and the thermal expansion coefficient of the bonding layer is α3; wherein α1 > α3 > α2 or α2 > α3 > α1.

[0016] As a preferred embodiment of the radiation-controlled multilayer film structure of the present invention, wherein: the refractive index of the bonding layer is N3, the refractive index of the base layer is N4, and N1 > N2 > N3 > N4.

[0017] As a preferred embodiment of the radiation-controlled multilayer film structure of the present invention, the material of the bonding layer is selected as ZnS, and the material of the base layer is selected as one of Si, PI, and SiO2.

[0018] The beneficial effects of this invention are as follows: By using multilayered, overlapping thin films of high and low refractive index and low dielectric loss materials, low emissivity in the 3~25μm infrared band is achieved while high transmittance in the 2~18GHz microwave band is also achieved. By designing different materials, thicknesses, and number of layers, the matching with the refractive index of the materials can be adjusted (to meet the optical path difference condition), ensuring the realization of constructive interference and photonic bandgap effect, achieving low infrared emission and high microwave transmission, thereby realizing heat insulation function without affecting communication.

[0019] By setting a bonding layer between the substrate and the radiation control film, the difference in thermal expansion coefficient and refractive index between the substrate and the radiation control film is alleviated, which plays a role in adapting to different substrates, enhancing bonding and thermal buffering, and preventing excessive refractive index difference from affecting the heat insulation capacity.

[0020] This invention also provides a method for preparing a multilayer film, comprising the following steps:

[0021] S1. Select a substrate and pre-clean the substrate; S2. Dry the substrate with nitrogen gas and place it in a vacuum environment; S3. Based on the multilayer membrane structure design, deposit multilayer membranes layer by layer.

[0022] As a preferred embodiment of the multilayer film and its preparation method described in this invention, wherein: S3.1, based on the complex refractive index of each layer material, a transmission matrix for the corresponding layer is constructed; S3.2 Obtain the total transmission matrix of the entire multi-layer structure by multiplying the matrix layer by layer; S3.3 Calculate the spectral response of the total reflectivity, transmittance and absorptivity as a function of wavelength based on the total transmission matrix; S3.4. Based on the calculation results of the total transfer matrix, select a multilayer membrane structure design that meets the requirements.

[0023] As a preferred embodiment of the multilayer film and its preparation method described in this invention, in step S3.4, the target average emissivity and average transmittance are set as fitness functions, the thickness of each layer of the radiation-controlled film is used as a variable, and a fast non-dominated sorting genetic algorithm model is used for optimization.

[0024] The beneficial effects of this invention are: by using a multi-objective optimization algorithm to simultaneously optimize microwave transmission performance and infrared low emission performance, the thickness of the thin film is precisely optimized, and the multilayer film with the best thickness, material, and number of layers is selected. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the radiation modulation film of the present invention.

[0027] Figure 2 This is a schematic diagram of the structure of the multilayer film of the present invention.

[0028] Figure 3 This is an infrared emissivity diagram of a 17-layer overlapping radiation modulation film according to the present invention.

[0029] Figure 4 This is a microwave transmittance diagram of a 17-layer overlapping radiation modulation film according to the present invention.

[0030] Figure 5 This is an infrared emissivity diagram of a 9-layer overlapping radiation modulation film according to the present invention.

[0031] Figure 6 This is a microwave transmittance diagram of a 9-layer overlapping radiation modulation film according to the present invention.

[0032] Figure 7 This is an infrared emissivity diagram of a 15-layer overlapping radiation modulation film according to the present invention.

[0033] Figure 8 This is a microwave transmittance diagram of a 15-layer overlapping radiation modulation film according to the present invention.

[0034] Figure 9 This is the infrared emissivity diagram for Comparative Example 1.

[0035] Figure 10 This is a microwave transmittance diagram for Comparative Example 1.

[0036] Figure 11 The image shows the infrared emissivity of Comparative Example 2.

[0037] Figure 12 This is a microwave transmittance diagram for Comparative Example 2.

[0038] Figure 13 The image shows the infrared emissivity of Comparative Example 3.

[0039] Figure 14 This is a microwave transmittance diagram for Comparative Example 3. Detailed Implementation

[0040] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0041] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0042] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0043] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0044] Table 1 Ge 4.00 BaF2 1.40 Si 3.40 Si 3.40 ZnS 2.30 PI 1.70 ZnSe 2.40 SiO2 1.50

[0045] Table 1 shows approximate data on the refractive index of the materials used in this invention. Depending on the wavelength, the refractive index of each material will vary with the wavelength, but the final refractive index error is within ±0.2.

[0046] Example 1

[0047] Reference Figures 1-5 The first embodiment of the present invention provides a radiation-controlled multilayer film structure, including a radiation-controlled film 100, which is divided into several first control layers 101, the first control layers 101 having a refractive index of N1 for electromagnetic waves E in a specific band; and several second control layers 102, the second control layers 102 having a refractive index of N2 for electromagnetic waves E in a specific band.

[0048] In this structure, both the first control layer 101 and the second control layer 102 are low dielectric loss materials. Several first control layers 101 and several second control layers 102 are stacked alternately to form a multilayer structure with periodic refractive index changes. The refractive index N1 of the first control layer 101 is greater than the refractive index N2 of the second control layer 102, and the difference between the refractive indices of N1 and N2 is greater than 1. The material and thickness of each first control layer 101 and second control layer 102 are selected independently, as long as the material of each first control layer 101 and second control layer 102 can satisfy N1 > N2 and the difference between N1 and N2 is greater than 1. The refractive index of N1 is in the range of 3.4 to 4.2, the refractive index of N2 is in the range of 1.4 to 2.4, and the sum of the thicknesses of all first control layers 101 and second control layers 102 is less than the wavelength of microwaves.

[0049] The wavelength of electromagnetic wave E is 3~20μm. The first control layer 101 and the second control layer 102 form constructive interference and a photonic bandgap, reflecting and refracting infrared radiation within the wavelength range of electromagnetic wave E. The constructive interference occurs because infrared electromagnetic waves are reflected at the interfaces of each control layer. Since the optical path difference determined by the layer thickness and refractive index satisfies the constructive interference condition, the intensity of the reflected light is enhanced after superposition, resulting in a broadband high reflectivity. The photonic bandgap is formed by the periodic refractive index variation structure created by the alternating stacking of the first control layer 101 and the second control layer 102, creating a "bandgap" for infrared electromagnetic waves, preventing their penetration, and further enhancing the reflection effect.

[0050] Furthermore, the material of the first control layer 101 is selected as Ge or Si, and the material of the second control layer 102 is selected as ZnS, ZnSe, or BaF2. The thickness of each of the first control layer 101 and the second control layer 102 is 350~1700nm. By selecting non-metallic materials, the influence of the high dielectric loss of metallic materials on electromagnetic waves is further avoided, making the film as a whole "transparent" to the microwave band. The thickness of each of the first control layer 101 and the second control layer 102 can be different as needed, as long as it can ultimately achieve the formation of constructive interference and photonic bandgap effect.

[0051] Meanwhile, the materials of the first control layer 101 and the second control layer 102 are both non-metallic low dielectric loss materials, which absorb very little electromagnetic waves in the 2~18GHz microwave band; at the same time, the total thickness of the multilayer film is in the μm range, which is much smaller than the microwave wavelength (centimeter range), so electromagnetic waves can penetrate the multilayer structure almost "unimpeded", ultimately achieving high microwave transmittance, thus shielding thermal radiation without affecting the passage of microwaves used for communication.

[0052] During use, the first control layer 101 of the radiation control film 100 is made of a high-refractive-index material, and the second control layer 102 is made of a low-refractive-index material (the "high" and "low" here refer to the comparison between the first control layer 101 and the second control layer 102). When high-refractive-index and low-refractive-index materials are stacked alternately, due to the significant difference in refractive index between the two layers, electromagnetic waves in the infrared band are reflected at each layer interface. These reflected lights produce constructive interference due to the optical path difference (determined by the layer thickness and refractive index): that is, after the reflected lights from different interfaces are superimposed, the reflection intensity in the infrared band is enhanced, forming a broadband high reflectivity.

[0053] Simultaneously, the structure with periodic refractive index changes creates a photonic bandgap: electromagnetic waves in the infrared band cannot propagate through the multilayer film and can only be reflected, thus forming a "bandgap" in this band, further enhancing the infrared reflection effect. By precisely designing the thickness of each layer, the photonic bandgap can cover a wide infrared range of 3~25μm, ultimately achieving "wideband infrared high reflectivity," and thus exhibiting low emissivity (emissivity is directly related to reflectivity, with high reflectivity corresponding to low emissivity).

[0054] Example 2

[0055] Reference Figures 2-4 This is the second embodiment of the present invention. This embodiment differs from the first embodiment in that it includes a radiation control film 100 and a base layer 200, which is in the form of a film. The radiation control film 100 is provided on at least one side of the base layer 200 to form a film structure. A bonding layer 300 is disposed between the base layer 200 and the radiation control film 100.

[0056] The base layer 200, the radiation control film 100, and the bonding layer 300 are all made of non-metallic materials. The coefficient of thermal expansion of the base layer 200 is α1, the coefficient of thermal expansion of the radiation control film 100 closest to the base layer 200 is α2, and the coefficient of thermal expansion of the bonding layer 300 is α3; α1>α3>α2 or α2>α3>α1.

[0057] The base layer 200, serving as the substrate for the multilayer film, is a commonly used coated substrate in existing technologies. It provides support for the bonding layer 300 and the subsequently stacked radiation modulation films 100, ensuring the integrity and mechanical stability of the multilayer film structure. Whether using a rigid or flexible substrate, it must meet the dimensional stability requirements during the thin film deposition process to avoid affecting the overall uniformity of the multilayer film structure due to substrate deformation. In the multilayer film structure, the base layer 200 does not directly participate in radiation modulation, but a non-metallic material is still required to avoid microwave loss. The material for the base layer 200 is selected from Si, PI, and SiO2.

[0058] The refractive index of the bonding layer 300 is N3, and the refractive index of the base layer 200 is N4, with N1 > N2 > N3 > N4. The bonding layer 300 is made of ZnS with low dielectric loss. Compared with the base layer 200 and the radiation modulation layer, the refractive index of the bonding layer 300 for electromagnetic wave E is moderate, and its coefficient of thermal expansion is also moderate compared with the base layer 200 and the radiation modulation layer. The thickness of the bonding layer 300 is between 80 and 100 nm. The base layer 200 and the radiation modulation film 100 are bonded together without affecting the radiation modulation performance.

[0059] Meanwhile, the coefficient of thermal expansion of the bonding layer 300 is also between that of the base layer 200 and the radiation control film 100, which can alleviate the difference in the coefficient of thermal expansion between the base layer 200 and the radiation control film 100, reduce the stress concentration caused by thermal expansion and contraction of the base layer 200 and the radiation control film 100, reduce the risk of interface damage, and ensure the structural stability of the multilayer membrane structure under extreme temperature differences.

[0060] During use, the bonding layer 300 is made of ZnS material, which can form a tight bond with the base layer 200 (such as the oxide layer of silicon or the organic surface of PI) through chemical bonds (such as Zn~O bonds) or van der Waals forces; it has high chemical compatibility with the radiation modulation film 100 (such as ZnSe, which belongs to the chalcogenide group and is compatible with the semiconductor properties of Ge and Si), which can reduce interface defects, improve the interlayer bonding strength, and ensure the integrity of the multilayer film structure.

[0061] The bonding layer 300 is disposed between the radiation modulation film 100 and the base layer 200, so that the refractive index changes gradually, reducing ineffective reflection at the interface; it stabilizes the propagation path of infrared electromagnetic waves in the high and low refractive index layers, ensures the effectiveness of constructive interference and photonic bandgap effect, and indirectly supports the low infrared emissivity characteristics.

[0062] The remaining structure is the same as that in Example 1.

[0063] Example 3

[0064] Reference Figure 6 This is the third embodiment of the present invention, which provides a method for preparing a multilayer film, including the following steps: S1. Select a substrate and pre-clean the substrate; S2. Dry the substrate with nitrogen gas and place it in a vacuum environment; S3. Based on the multilayer membrane structure design, deposit multilayer membranes layer by layer.

[0065] Furthermore, S3.1, based on the complex refractive index of each layer of material, construct the transfer matrix for the corresponding layer: , Where Mj is the single-layer transmission matrix of the j-th layer. It is the phase thickness. , Let be the wave impedance of the j-th layer material, for TE mode For TM mode , Let dj be the complex refractive index of the j-th layer, and dj be the actual thickness of that layer. Let be the incident angle of the layer, and be the complex permittivity. The materials here are all non-magnetic, and their magnetic permeability is 1.

[0066] In the single-layer matrix of the j-th layer, based on the material of that layer, input parameters such as its refractive index, thickness, electromagnetic wave wavelength, incident angle, and dielectric constant to obtain the transmission matrix Mj.

[0067] S3.2. By multiplying the matrices layer by layer, the total transfer matrix of the entire multilayer structure is obtained. Based on the transfer matrices of each layer, the transfer matrices of each layer are multiplied in stacking order to obtain the total transfer matrix of the entire multilayer membrane structure. The formula for calculating the total transfer matrix is: , Among them, M j M is the transmission matrix for a single layer, and M is the total transmission matrix for a multi-layer structure, which is also the individual transmission matrices of M. j The product of matrices, m1, 2, 3, and 4, corresponds to the four elements of the matrix. The total transmission matrix includes the combined effect of all layers on electromagnetic waves. Based on the total transmission matrix and the boundary conditions of electromagnetic waves in the incident medium and the substrate, the reflectivity and transmittance of the multilayer film structure for a specific waveband can be derived.

[0068] S3.3 Calculate the overall reflectivity, transmittance, and absorptivity as a function of wavelength based on the overall transmission matrix. Calculate the infrared reflectivity and microwave transmittance of the multilayer film structure based on the transmission matrices of each layer and the overall transmission matrix. The formulas for further calculating reflectivity and transmittance based on the overall transmission matrix are as follows: , , , Where r is the reflectance at the corresponding wavelength, and t is the transmittance at the corresponding wavelength. Emission rate.

[0069] The formulas for calculating the average emissivity and average transmittance of a multilayer film structure are as follows: , , Where T is temperature, d is the differential symbol, λ is the integrand, and I is the wavelength. BBThis is the formula for blackbody radiation. The incident angle is 3~20μm for infrared and 2~18GHz for microwave.

[0070] S3.4. Based on the calculation results of the total transfer matrix, select the multilayer membrane structure design that meets the requirements, set the target average emissivity and average transmittance as fitness functions, use the thickness of each layer of the radiation control membrane 100 as variables, and use the fast undominated sorting genetic algorithm model for unbiased optimization design.

[0071] Among them, unbiased optimization design refers to using "average infrared reflectivity" and "average microwave transmittance" as equally important fitness functions, both of which are optimization objectives (to be maximized simultaneously), without setting artificial weights.

[0072] The fast non-dominated sorting genetic algorithm evaluates individuals (a set of membrane thickness parameters) through "non-dominated sorting": if an individual is better at one objective but worse at another, it is not prioritized, thus avoiding the optimization being dominated by a single objective; it retains individuals with a wide performance distribution through "crowding degree calculation" to prevent the optimization process from getting stuck in local optima (such as optimizing only infrared performance while sacrificing microwave performance); the final Pareto front (the set of optimal solutions) contains multiple equilibrium solutions that "cannot improve one objective without degrading another," covering different performance balance states.

[0073] After obtaining the Pareto front, the Pareto front is screened using an "evaluation weight function" to select the best solution. The evaluation weight function is a preset function that calculates the quantitative indicators of infrared and microwave performance. The calculated values ​​of this function are used to rank the various optimized solutions of the Pareto front, and the solution with the highest score is selected.

[0074] For example, the evaluation weight function can be expressed as: .

[0075] Where α is the weighting coefficient for infrared performance (0 < α < 1), and 1 ~ α are the weighting coefficients for microwave performance, R IR T represents the reflectivity in the infrared band. MW The transmittance in the microwave band is denoted by α. By adjusting the value of α, the emphasis can be adjusted; for example, when emphasizing infrared performance, α is set to 0.6. Based on the F-values ​​of each optimized solution of the Pareto front calculated by this function, the solution with the highest score is taken as the final parameters of the multilayer film structure.

[0076] Test Instance

[0077] Based on the multilayer film preparation method described above, the experimental data for the following samples are given.

[0078] refer to Figure 3 , Figure 4 A multilayer film structure sample 1 is a radiation control film 100 with 17 overlapping first control layers 101 and second control layers 102. The base layer 200 of this sample is a flexible PI substrate with a thickness of 125 μm, and a ZnS material bonding layer 300 with a thickness of 80 nm. The thickness of each layer in the radiation control film 100 of this sample is as follows: 1250nm, 1250nm, 382nm, 762nm, 883nm, 935nm, 397nm, 1174nm, 1029nm, 840nm, 410nm, 1250nm, 1158nm, 1250nm, 1109nm, 1250nm, 965nm.

[0079] The first control layer 101 and the second control layer 102 are alternately arranged in sequence, and the materials of each layer are Ge, ZnS, Ge, ZnS, Ge, ZnS, Ge, ZnS, Ge, ZnS, Ge, ZnS, Ge.

[0080] refer to Figure 3 The sample achieved an average infrared emissivity of 0.12 in the 3–25 μm range, with an infrared emissivity of 0.09 in the 8–20 μm range, demonstrating low emissivity. (Reference) Figure 4 The transmittance of the samples in the range of 2 to 18 GHz was higher than ~0.25 dB, and the actual transmittance was higher than 0.992.

[0081] refer to Figure 5 , Figure 6 Another sample 2 is a multilayer film structure with a radiation modulation film 100 having nine overlapping first modulation layers 101 and second modulation layers 102. The base layer 200 of this sample uses a 125 μm thick flexible PI substrate, and an 80 nm thick ZnS material bonding layer 300. The thickness of each layer in the radiation modulation film 100 of this sample is as follows: 1698, 1490, 1695, 1450, 1263, 1190, 827, 1420, 522.

[0082] The first control layer 101 and the second control layer 102 are alternately arranged in sequence, and the materials of each layer are Ge, BaF2, Ge, BaF2, Ge, BaF2, Ge, ZnS, and Ge, respectively.

[0083] refer to Figure 5 The sample achieved an average infrared emissivity of 0.07 in the 3–25 μm range, with an infrared emissivity of 0.05 in the 8–20 μm range, demonstrating low emissivity. (Reference) Figure 6 The transmittance of the samples in the range of 2 to 18 GHz was higher than ~0.25 dB, and the actual transmittance was higher than 0.993.

[0084] refer to Figure 7 , Figure 8 Another sample 3 is a multilayer film structure with 15 overlapping first control layers 101 and second control layers 102 in a radiation control film 100. The base layer 200 of this sample uses a 125 μm thick flexible PI substrate and an 80 nm thick ZnS material bonding layer 300. The thickness of each layer in the radiation control film 100 of this sample is as follows: 1215, 1480, 1027, 1370, 1440, 1129, 597, 1069, 535, 1397, 964, 865, 1140, 807, 454.

[0085] The first control layer 101 and the second control layer 102 are alternately arranged in sequence, and the materials of each layer are Ge, ZnSe, Ge, ZnSe, Ge, ZnSe, Ge, ZnSe, Ge, ZnSe, Ge, ZnSe, Ge, ZnSe, Ge.

[0086] refer to Figure 7 The sample achieved an average infrared emissivity of 0.12 in the 3–25 μm range, with an infrared emissivity of 0.09 in the 8–20 μm range, demonstrating low emissivity. (Reference) Figure 8 The transmittance of the samples in the range of 2 to 18 GHz was higher than ~0.25 dB, and the actual transmittance was higher than 0.989.

[0087] Based on the above test examples, in terms of the number of layers, the 17-layer radiation modulation film 100, composed of alternating Ge / ZnS layers with a thickness of 382~1250nm, has an average emissivity of 0.12 in the 3~25μm infrared band (as low as 0.09 in the 8~20μm band) and a transmittance >0.992 in the 2~18GHz microwave band. With more layers, the infrared broadband low emissivity characteristics are more stable, and the microwave transmittance remains high. The 9-layer radiation modulation film 100, composed of alternating Ge / BaF2 and Ge / ZnS layers with a thickness of 522~1698nm, has an average infrared emissivity as low as 0.07 in the 3~25μm band (0.05 in the 8~20μm band) and a transmittance >0.993 in the 2~18GHz microwave band. With fewer layers but appropriate thickness, the infrared emissivity in local bands is even lower, and due to the thinner overall thickness, the microwave transmittance is slightly higher than that of the 17-layer film. The radiation modulation film 100, consisting of 15 layers of alternating Ge / ZnSe, has a thickness of 454~1480nm. Its average infrared emissivity is 0.12 in the 3~25μm range (0.09 in the 8~20μm range), and its microwave transmittance in the 2~18GHz range is >0.989. When the number of layers is moderate, its infrared performance is comparable to that of a 17-layer film, but its microwave transmittance is slightly lower.

[0088] In terms of thickness, a single-layer thickness of 350–1250 nm can well satisfy the conditions for constructive interference and photonic bandgap in the infrared band, resulting in high reflectivity and low emissivity. For some layers exceeding 1250 nm (such as 1698 nm and 1490 nm in 9-layer structures), low emissivity can still be achieved as long as it matches the material's refractive index. Regarding the total thickness, a smaller total thickness (e.g., 9 layers) results in higher microwave transmittance because the total thickness is much smaller than the microwave wavelength, reducing propagation loss. Simultaneously, the total thickness must be matched to the infrared band; too thin a layer weakens the photonic bandgap effect, while too thick a layer may increase absorption. In the experiment, a single-layer thickness of 350–1700 nm and μm-level total thickness control ensured the synergy between low infrared emissivity and high microwave transmittance.

[0089] In summary, more layers are not necessarily better. The key lies in the matching degree between the periodic structure and the infrared band. The thickness must meet the optical path difference condition of constructive interference and the total thickness must be much smaller than the microwave wavelength. Material properties are the basis for the effect of the number of layers and thickness.

[0090] Comparative Example 1

[0091] Comparative Example 1 is based on Sample 2 in the test example, but the number of overlapping layers of the first control layer 101 and the second control layer 102 in the radiation control film 100 is adjusted to 7 layers, while other conditions remain the same as in Example 1.

[0092] The thickness and material of each layer are as follows: 971, 994, 990, 997, 670, 973, 633.

[0093] The first control layer 101 and the second control layer 102 are alternately arranged in sequence, and the materials of each layer are Ge, BaF2, Ge, BaF2, Ge, BaF2, and Ge, respectively.

[0094] refer to Figure 9 , Figure 10 The average infrared emissivity of Comparative Example 1 is 0.15. Its microwave transmittance in the 2–18 GHz range is 0.985.

[0095] Although the low-layer comparative example 1 meets the microwave transmittance requirements, its infrared emissivity exceeds the standard. This is because the material arrangement of the low-layer is difficult to maintain a wide-band (3~20 micrometers) photonic bandgap, which leads to enhanced infrared absorption and ultimately results in the failure to meet the heat control requirements.

[0096] Comparative Example 2

[0097] Based on sample 2 in the test example, Comparative Example 2 adjusts the number of overlapping layers of the first control layer 101 and the second control layer 102 in the radiation control film 100 to 9 layers, with some layer thicknesses exceeding the requirements of Example 1, while other conditions remain consistent with Example 1.

[0098] The thickness and material of each layer are as follows: 2300, 1490, 2900, 1450, 500, 1790, 827, 820, 522.

[0099] The first control layer 101 and the second control layer 102 are alternately arranged in sequence, and the materials of each layer are Ge, BaF2, Ge, BaF2, Ge, BaF2, Ge, ZnS, and Ge, respectively.

[0100] refer to Figure 11 , Figure 12 The average infrared emissivity of Comparative Example 2 is 0.17. Its microwave transmittance in the 2–18 GHz range is 0.985.

[0101] Although the low-layer comparative example 2 meets the microwave transmittance requirements, its infrared emissivity exceeds the standard. This is because the high-thickness material arrangement causes a redshift in the interference phenomenon, making it difficult to form interference peaks in the target band between multiple layers, thus leading to enhanced infrared absorption and unsatisfactory heat control.

[0102] Comparative Example 3

[0103] Comparative Example 3 is based on Sample 2 in the test example. The number of overlapping layers of the first control layer 101 and the second control layer 102 in the radiation control film 100 is adjusted to 9 layers. TiO2 is used as the material for some layers. Other conditions are the same as in Example 1.

[0104] The thickness and material of each layer are as follows: 1698, 1490, 1695, 1450, 1263, 1190, 827, 1420, 522.

[0105] The first control layer 101 and the second control layer 102 are alternately arranged in sequence, and the materials of each layer are Ge, TiO2, Ge, TiO2, Ge, TiO2, Ge, TiO2, Ge.

[0106] refer to Figure 13 , Figure 14 The average infrared emissivity of Comparative Example 2 is 0.39. Its microwave transmittance in the 2–18 GHz range is 0.971.

[0107] Although the low-layer comparative example 2 meets the microwave transmittance requirements, its infrared emissivity exceeds the standard. This is because the high refractive index and extinction coefficient of titanium dioxide material enhance the absorption of the infrared band, resulting in insufficient heat control.

[0108] Table 2 Average infrared emissivity 0.07 0.15 0.17 0.39 microwave transmittance 0.993 0.985 0.985 0.971

[0109] Table 2 shows a comparison of the data of Comparative Examples 1, 2, and 3 with Sample 2 in the Test Example. It can be seen that changes in the number of layers, thickness, or the use of metal materials will all lead to a slight decrease in microwave transmittance and a corresponding increase in average infrared emissivity, resulting in substandard heat control.

[0110] It is important to note that the constructions and arrangements of this application shown in several different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those who consult this disclosure will readily understand that many modifications are possible (e.g., changes in the size, dimensions, structure, shape and proportion of various elements, as well as parameter values ​​(e.g., temperature, pressure, etc.), mounting arrangements, use of materials, color, orientation, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in this application). For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of elements may be inverted or otherwise changed, and the nature or number or position of discrete elements may be altered or changed. Therefore, all such modifications are intended to be included within the scope of the invention. The order or sequence of any process or method steps may be changed or rearranged according to alternative embodiments. Therefore, the invention is not limited to the particular embodiments but extends to a variety of modifications that still fall within the scope of the appended claims.

[0111] Furthermore, in order to provide a concise description of exemplary embodiments, not all features of actual embodiments (i.e., those features that are not relevant to the currently considered best mode for carrying out the invention, or those features that are not relevant to implementing the invention) may be omitted.

[0112] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A radiation-controlled multilayer film structure, characterized in that: include, Radiation modulation film (100), divided into Several first control layers (101), wherein the refractive index of the first control layer (101) for electromagnetic waves E in a specific band is N1; Several second control layers (102), the refractive index of the second control layer (102) for electromagnetic waves E of a specific band is N2; Wherein, the first control layer (101) and the second control layer (102) are both low dielectric loss materials, and the first control layer (101) and the second control layer (102) are stacked alternately to form a multilayer structure with periodic refractive index changes, wherein N1 > N2.

2. The radiation-controlled multilayer film structure according to claim 1, characterized in that: The wavelength of the electromagnetic wave E is 3~20μm.

3. The radiation-controlled multilayer film structure according to claim 1 or 2, characterized in that: The refractive index difference between N1 and N2 is greater than 1, and the first control layer (101) and the second control layer (102) form constructive interference and photonic bandgap in the 3~20μm band.

4. The radiation-controlled multilayer film structure according to claim 3, characterized in that: The first control layer (101) is made of a material with a refractive index N1 of 3.4 to 4.2, and the second control layer (102) is made of a material with a refractive index of 1.4 to 2.

4.

5. The radiation-controlled multilayer film structure according to claim 4, characterized in that: The material of the first control layer (101) is selected as Ge or Si, and the material of the second control layer (102) is selected as ZnS, ZnSe or BaF2.

6. The radiation-modulated multilayer film structure according to any one of claims 1, 2, 4, and 5, characterized in that: The thickness of each of the first control layer (101) and the second control layer (102) is 350~1700nm.

7. The radiation-controlled multilayer film structure according to claim 6, characterized in that: It also includes, The base layer (200) is membrane-like, and a radiation modulation membrane (100) is provided on at least one side of the base layer (200). A bonding layer (300) is disposed between the base layer (200) and the radiation modulation film (100); The base layer (200), radiation modulation film (100), and bonding layer (300) are all made of non-metallic materials.

8. The radiation-controlled multilayer film structure according to claim 7, characterized in that: The coefficient of thermal expansion of the base layer (200) is α1, the coefficient of thermal expansion of the radiation control film (100) closest to the base layer (200) is α2, and the coefficient of thermal expansion of the bonding layer (300) is α3. The α1 > α3 > α2 or α2 > α3 > α1.

9. The radiation-controlled multilayer film structure according to claim 7 or 8, characterized in that: The refractive index of the bonding layer (300) is N3, and the refractive index of the base layer (200) is N4, wherein N2 > N3 > N4 or N4 > N3 > N2.

10. The radiation-controlled multilayer film structure according to claim 9, characterized in that: The bonding layer (300) is made of ZnS, and the base layer (200) is made of one of Si, PI, or SiO2.

11. A method for preparing a multilayer film, used to prepare the radiation-controlled multilayer film structure according to any one of claims 1 to 10, characterized in that: Includes the following steps S1. Select a substrate and pre-clean the substrate; S2. Dry the substrate with nitrogen gas and place it in a vacuum environment; S3. Select a multilayer membrane structure design and deposit multilayer membranes layer by layer.

12. The method for preparing a multilayer film according to claim 11, characterized in that: S3.1 Construct the transfer matrix of the corresponding layer based on the complex refractive index of each layer material; S3.2 Obtain the total transmission matrix of the entire multi-layer structure by multiplying the matrix layer by layer; S3.3 Calculate the spectral response of the total reflectivity, transmittance and absorptivity as a function of wavelength based on the total transmission matrix; S3.

4. Based on the calculation results of the total transfer matrix, select a multilayer membrane structure design that meets the requirements.

13. The method for preparing a multilayer film according to claim 12, characterized in that: In S3.4, the target average emissivity and average transmittance are set as fitness functions, and the thickness of each layer of the radiation control film (100) is used as a variable. The fast non-dominated sorting genetic algorithm model is used for optimization.

Images