Visible high absorption-infrared low radiation-microwave high transmission film system structure

Abstract

The invention discloses a visible high absorption-infrared low radiation-microwave high transmission film system structure. The structure comprises a refractive index gradient absorption layer, a Fabry-Perot cavity layer and a substrate layer from top to bottom in sequence, the refractive index gradient absorption layer comprises a first dielectric layer I, a second dielectric layer I and a third dielectric layer from bottom to top; the Fabry-Perot cavity layer comprises a plurality of groups of first dielectric layers II and second dielectric layers II which are alternately stacked, wherein the first dielectric layers I are arranged close to the substrate. According to the thin film structure disclosed by the invention, the absorptivity exceeding 0.99 is realized in a visible light region of a wave band of 380-780 nm, and the reflectivity and the visibility are remarkably reduced. And in infrared radiation window wave bands of 3-5 microns and 8-14 microns, the radiance lower than 0.05 is maintained, and the infrared stealth requirement is met. And in a microwave frequency band of 5-30 GHz, the transmittance of more than 0.90 is achieved, and the compatibility with microwave communication is realized.

Description

Technical Field

[0001] The present invention relates to the field of multi-spectral stealth technology, and in particular to a film system structure with high visible absorption, low infrared radiation and high microwave transmission. Background Art

[0002] With the rapid development of multi-spectral detection technology, the demand for visible light-infrared-microwave coordinated stealth is becoming increasingly urgent. Satellites, high-altitude aircraft and other operating platforms in dark backgrounds urgently need a multi-spectral stealth material that can maintain low visible reflectivity (high absorption rate) while having low infrared emissivity and high microwave transmittance.

[0003] Traditional stealth materials have the problem of band function splitting. For example, the patent with announcement number CN117343608A proposes an infrared stealth coating material based on aluminum powder and MXene, which improves the traditional infrared stealth coating material aluminum powder to make it compatible with visible light with high absorption rate. This patent uses aluminum powder, MXene, adhesive and directional agent as the main raw materials, and uses MXene with both low infrared emissivity and high visible light absorption rate to partially replace the aluminum powder of infrared stealth material, solving the problem of strong reflectivity of aluminum powder to visible light. Another example is a patent with announcement number CN116200705A showing a stealth material compatible with visible light and infrared, which is achieved by using HfO in the dielectric layer. 3 A visible light stealth coating Cr is arranged on the alternating stacking structure of the metal film layer Mo. 2 O 3 , reaching an absorptivity of 0.95 in the visible light range of 300-800nm, an emissivity of 0.10 in the infrared window bands of 3-5μm and 8-14μm, and an emissivity of 0.80 in the non-window band of 5-8μm. However, these traditional methods have insufficient microwave transmittance due to their metal matrix, which seriously hinders the transmission of satellite communication signals.

[0004] The latest research, such as the article Nanostructured Ge / ZnS Films for Multispectral Camouflage with Low Visibility and Low Thermal Emission, proposes a nanostructured multifunctional photonic film with spectral selection characteristics. The film consists of a Ge / ZnS one-dimensional photonic crystal structure at the bottom and a YbF 3 / ZnS / Ge / ZnS nano-layer stealth structure, through the high optical loss of Ge material in the visible light band and the gradient refractive index structure design to achieve visible-near infrared absorption; based on the photonic band gap and the lossless characteristics of Ge / ZnS in the infrared to achieve low thermal radiation; with the help of the low conductivity of the material to achieve high microwave transmission. However, this material has too many total layers and has high requirements for film thickness uniformity, resulting in high complexity of the preparation process and difficulty in manufacturing. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a film system structure with high visible absorption, low infrared radiation and high microwave transmittance. Through the coordinated design of multi-layer thin film stacking and metal microstructure, it can achieve efficient absorption in the visible band and suppress infrared radiation while maintaining high transmittance in the microwave band.

[0006] The present invention proposes a film system structure with high visible absorption, low infrared radiation and high microwave transmission, and its technical solution is as follows:

[0007] The film system structure is composed of multiple hierarchical structures, which are, from top to bottom, a refractive index gradient absorption layer, a Fabry-Perot (hereinafter referred to as FP) cavity layer, and a substrate layer. The refractive index gradient absorption layer includes a first dielectric layer, a second dielectric layer, and a third dielectric layer. The FP cavity layer includes a first dielectric layer and a second dielectric layer. The substrate layer is a polyimide (hereinafter referred to as PI) coated with a metal film.

[0008] More specifically, a film system structure with high visible absorption, low infrared radiation and high microwave transmission includes, from top to bottom: a refractive index gradient absorption layer, a Fabry-Perot cavity layer and a substrate layer; the refractive index gradient absorption layer includes, from bottom to top, a first dielectric layer I, a second dielectric layer I and a third dielectric layer; the Fabry-Perot cavity layer includes a plurality of groups of alternately stacked first dielectric layers II and second dielectric layers II, wherein the first dielectric layer I is arranged close to the substrate.

[0009] The refractive index gradient layer has anti-reflection properties, effectively absorbs visible light, and reduces the visibility of the film.

[0010] The FP cavity interference layer constructs a double cavity resonance through a dielectric layer of a specific thickness to enhance the absorption in the visible light band.

[0011] The substrate layer uses a metal coating as an infrared reflection medium to reduce infrared radiation. The overall thickness of the refractive index gradient absorption layer and the FP cavity layer is much smaller than the infrared wavelength and does not affect the reflectivity of the metal coating to infrared waves.

[0012] The dielectrics are all low-conductivity dielectric materials, and the overall thickness is negligible compared to the microwave wavelength, ensuring the high microwave transmittance of the film structure.

[0013] The surface of the metal coating is provided with a periodic slit microstructure to improve the overall microwave transmittance of the device.

[0014] Furthermore, the periodic slit structure of the infrared low-radiation substrate layer is composed of square metal units, and its infrared radiation rate and side length ratio satisfy the relationship Where W is the side length of the square unit, P is the unit period, and R is the infrared reflectivity.

[0015] Furthermore, the relationship between microwave transmittance and microstructure parameters is as follows: under the same period P, the larger the slit width S=PW, the higher the microwave transmittance; at the same time, as the period P decreases, the microwave transmittance generally increases. Preferably, when the period P≤1mm, by adjusting the W / P ratio, high microwave transmittance can be achieved while ensuring low infrared radiation.

[0016] Preferably, the substrate layer is polyimide coated with a periodic slit microstructure metal film.

[0017] Preferably, the periodic slit microstructure is composed of periodically arranged square metal units, with a period of less than or equal to 1 mm; the slit width is less than or equal to 100 microns. The period is 0.05 to 1 mm, more specifically 0.1 mm, 0.2 mm, 0.5 mm, 1 mm. The slit width is 0.5 to 150 microns; when the above structure is selected, the emissivity is less than 0.2.

[0018] Preferably, the Fabry-Perot cavity layer is composed of two groups of alternately stacked first dielectric layers II and second dielectric layers II. Further, the Fabry-Perot cavity layer is composed of first dielectric layer II / second dielectric layer II / first dielectric layer II / second dielectric layer II from bottom to top.

[0019] Preferably, the first dielectric layer I and the first dielectric layer II are independently selected from materials with a refractive index of 3-5; the second dielectric layer I and the second dielectric layer II are independently selected from materials with a refractive index of 2-3; and the third dielectric layer is selected from materials with a refractive index range of 1-2.

[0020] Preferably, the first dielectric layer I and the first dielectric layer II are each independently selected from Ge or Si; the second dielectric layer I and the second dielectric layer II are each independently selected from ZnS or HfO 2 ; The third dielectric layer is selected from MgF 2 or YbF 3 ; The metal film is Au.

[0021] Preferably, the thickness of the metal layer is 80-120 nm; the thickness of the first dielectric layer II is 250-400 nm; the thickness of the second dielectric layer II is 10-550 nm; the thickness of the first dielectric layer I is 5-15 nm; and the thickness of the second dielectric layer I is 20-50 nm.

[0022] As a further preference, in the Fabry-Perot cavity layer, in a group of first dielectric layer II and second dielectric layer II close to the substrate, the thickness of the first dielectric layer II is 300-350 nm; the thickness of the second dielectric layer II is 400-500 nm; in another group of first dielectric layer II and second dielectric layer II, the thickness of the first dielectric layer II is 330-400 nm; the thickness of the second dielectric layer II is 10-30 nm.

[0023] More specifically, the film structure of high visible absorption, low infrared radiation and high microwave transmission is PI-Au (100nm) / Ge (322nm) / ZnS (471nm) / Ge (354nm) / ZnS (18) / Ge (8nm) / ZnS (39nm) / MgF 2 (85nm).

[0024] The nanostructured film of the present invention exhibits excellent spectral selectivity in the visible light, infrared and microwave bands. Specifically, the film achieves an absorptivity of more than 0.99 in the visible light region of the 380-780nm band, thereby significantly reducing reflectivity and visibility. In the infrared radiation window bands of 3-5μm and 8-14μm, the emissivity is maintained below 0.05, meeting the requirements of infrared stealth. In the microwave frequency band of 5-30GHz, the transmittance reaches more than 0.90, achieving compatibility with microwave communications. At the same time, the overall film system of the present invention has fewer layers and a simple structure, which is suitable for large-scale manufacturing.

[0025] The film system structure of the present invention is suitable for the multi-spectral stealth requirements of satellites, high-altitude aircraft, etc. under dark backgrounds, and is compatible with microwave communication functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the membrane system structure.

[0027] Figure 2 Schematic diagram of the periodic microstructure of the gold layer of the film structure.

[0028] Figure 3 The visible absorption spectrum of the film structure is shown in FIG.

[0029] Figure 4 It is the infrared radiation spectrum diagram of the film system structure.

[0030] Figure 5 It is the microwave transmission spectrum diagram of the film structure. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0032] The markings in the drawings of the specification include: substrate layer 1, metal layer 2, first dielectric layer I 3, second dielectric layer I 4, first dielectric layer II 5, second dielectric layer II 6, and third dielectric layer 7.

[0033] Example 1

[0034] In this embodiment, the specific structure of the nanostructured film is as follows: Figure 1 As shown, the layers from bottom to top are substrate layer, FP cavity layer, and refractive index gradient absorption layer. The substrate layer is a PI substrate layer 1 plated with a metal layer 2. The FP cavity layer includes two sets of stacked first dielectric layers I3 and second dielectric layers I4. The refractive index gradient absorption layer includes a first dielectric layer II5, a second dielectric layer II6, and a third dielectric layer 7.

[0035] The materials of the first dielectric layer I and the first dielectric layer II in the FP cavity layer and the refractive index gradient absorption layer are both Ge; the materials of the second dielectric layer I and the second dielectric layer II are both ZnS.

[0036] The FP cavity layer is composed of two groups of stacked first dielectric layers I3 and second dielectric layers I4. In the group close to the substrate: the thickness of the first dielectric layer I (Ge) is 322nm; the thickness of the second dielectric layer I (ZnS) is 471nm; in the second group closer to the outside: the thickness of the first dielectric layer I is 354nm; the thickness of the second dielectric layer I is 18nm.

[0037] The thickness of the first dielectric layer II (Ge) in the refractive index gradient absorption layer is 8 nm; the thickness of the second dielectric layer II (ZnS) is 39 nm; the thickness of the third dielectric layer (MgF 2 ) thickness is 85nm.

[0038] The metal layer 2 is engraved with a periodic slit structure, such as Figure 2 As shown in the figure, the slit structure is composed of periodically arranged square metal films to meet the microwave transmission performance. The metal layer 2 is preferably made of Au with a thickness of 100nm. The structural period is P, and the side length of the Au unit is W. The infrared emissivity of the film structure can be calculated by the formula Regulate (as shown in Table 1).

[0039] Table 1. Slit width under different periods and infrared radiation rate requirements

[0040]

[0041] The visible absorption spectrum of the composite film structure is as follows Figure 3As shown (P = 0.2 mm, slit width = 5 μm). It can be seen from the figure that the absorptivity of the film in the entire visible light band exceeds 0.99, specifically, the absorptivity reaches 0.9958, which effectively reduces visibility.

[0042] The infrared absorption spectrum of the composite film structure is shown in Figure 4 In the atmospheric window bands of 3-5μm and 8-14μm, the infrared emissivity is as low as 0.0395 and 0.0289 respectively, reflecting the excellent low infrared emissivity characteristics.

[0043] In this embodiment, the selected period P = 0.2 mm, the slit width = 5 μm, and its microwave transmission spectrum is as follows Figure 5 As shown. By adjusting the period P and the slit width, high transmittance effects in different microwave frequency bands can be achieved. In the range of 5-30GHz, the microwave transmittance of some structures is as high as 0.98, which can be flexibly adjusted according to needs to meet the requirements of high microwave transmittance.

[0044] In this embodiment, by optimizing MgF 2 The thickness combination of ZnS and Ge layers, combined with the design of the gold slit structure, the overall film structure not only achieves high absorption and low radiation characteristics in the visible and infrared bands, but also maintains high transmittance in the microwave band. The synergistic effect of this multi-layer nanostructure enables the film to achieve excellent spectral selectivity, which is suitable for stealth applications compatible with microwave communications under dark backgrounds.

[0045] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. The present invention is not limited to the above examples. Any changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A film structure with high visible absorption, low infrared radiation and high microwave transmission, characterized in that: It includes, from top to bottom: a refractive index gradient absorption layer, a Fabry-Perot cavity layer and a substrate layer; the refractive index gradient absorption layer includes, from bottom to top, a first dielectric layer I, a second dielectric layer I and a third dielectric layer; the Fabry-Perot cavity layer includes a plurality of groups of alternately stacked first dielectric layers II and second dielectric layers II, wherein the first dielectric layer I is arranged close to the substrate.

2. The film system structure with high visible absorption, low infrared radiation and high microwave transmission according to claim 1 is characterized in that: The substrate layer is polyimide coated with a periodic slit microstructure metal film.

3. The film system structure with high visible absorption, low infrared radiation and high microwave transmission according to claim 2 is characterized in that: The periodic slit microstructure is composed of periodically arranged square metal units, with a period of less than or equal to 1 mm and a slit width of less than or equal to 100 microns.

4. The film system structure with high visible absorption, low infrared radiation and high microwave transmission according to claim 1, characterized in that: The Fabry-Perot cavity layer is composed of two groups of alternately stacked first dielectric layers II and second dielectric layers II.

5. The film structure with high visible absorption, low infrared radiation and high microwave transmission according to claim 1, characterized in that: The first dielectric layer I and the first dielectric layer II are each independently selected from materials with a refractive index of 3-5; the second dielectric layer I and the second dielectric layer II are each independently selected from materials with a refractive index of 2-3; and the third dielectric layer is selected from materials with a refractive index range of 1-2.

6. The film system structure with high visible absorption, low infrared radiation and high microwave transmission according to claim 2 is characterized in that: The first dielectric layer I and the first dielectric layer II are each independently selected from Ge or Si; the second dielectric layer I and the second dielectric layer II are each independently selected from ZnS or HfO2; the third dielectric layer is selected from MgF2 or YbF3; and the metal film is Au.

7. The film system structure with high visible absorption, low infrared radiation and high microwave transmission according to claim 4, characterized in that: The thickness of the metal layer is 80-120 nm; the thickness of the first dielectric layer II is 250-400 nm; the thickness of the second dielectric layer II is 10-550 nm; the thickness of the first dielectric layer I is 5-15 nm; and the thickness of the second dielectric layer I is 20-50 nm.

8. The film system structure with high visible absorption, low infrared radiation and high microwave transmission according to claim 7, characterized in that: In the Fabry-Perot cavity layer, in a group of first dielectric layer II and second dielectric layer II close to the substrate, the thickness of the first dielectric layer II is 300-350nm; the thickness of the second dielectric layer II is 400-500nm; in another group of first dielectric layer II and second dielectric layer II, the thickness of the first dielectric layer II is 330-400nm; the thickness of the second dielectric layer II is 10-30nm.

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