Thermal infrared low-radiation imitation green leaf multilayer film and preparation method thereof

Abstract

The invention belongs to the technical field of camouflage materials, and particularly relates to a thermal infrared low-radiation imitation green leaf multilayer film and a preparation method thereof. Comprising a substrate, a long-wave infrared regulation and control layer, a medium-wave infrared regulation and control layer and a green-leaf-imitating hyperspectral regulation and control layer which are arranged in sequence, the long-wave infrared regulation and control layer is stacked on the substrate according to a periodic structure of MHML, the medium-wave infrared regulation and control layer is stacked on the long-wave infrared regulation and control layer according to a periodic structure of (HM) 2L, and the green-leaf-imitating hyperspectral regulation and control layer is stacked on the medium-wave infrared regulation and control layer according to a periodic structure of (LM) 3 (HM) 3 (HL) (HM); h is a high-refractive-index material, M is a medium-refractive-index material, and L is a low-refractive-index material. Aiming at the problems of poor compatibility, large radar wave transmission influence, strict multi-layer film thickness control requirements and the like in the prior art, by optimizing the film system structure, the green-leaf-imitating hyperspectral camouflage characteristic is realized in the visible light-near infrared band, and the low-radiation performance is realized in the thermal infrared dual-band.

Description

Technical Field

[0001] The invention belongs to the technical field of camouflage materials, and in particular relates to a thermal infrared low-radiation green leaf imitation multilayer film and a preparation method thereof. Background Art

[0002] With the rapid development of detection technology, hyperspectral imaging technology has become an important means of target identification due to its high spectral resolution, wide detection band and rich data output. This technology can accurately identify the subtle differences between the target and the environmental reflection spectrum, making it difficult for traditional visible light camouflage technology to meet current application needs. At the same time, with the continuous advancement of optical camouflage technology, researchers have begun to focus on the development of multi-band compatible camouflage technology to adapt to and counter the increasingly complex multi-band detection technology. This trend requires optical camouflage materials to be effective not only in visible light, but also to achieve low characteristic signals in infrared and other spectral bands to improve the survival rate and concealment of targets in complex environments.

[0003] Existing visible light camouflage technology mainly uses multi-layer film systems such as non-metallic visible light laser infrared multi-band compatible stealth film and its preparation method (patent CN112346160A), such as a high-spectral stealth coating and its preparation method and high-spectral stealth coating (patent CN111218197A) coatings or polyurethane microcapsules with internally encapsulated liquids, high-spectral stealth materials for vegetation environments and their preparation methods and applications (patent CN116688884A) stealth capsules to achieve accurate simulation of green leaf characteristic peaks. The above-mentioned film system has the following disadvantages: (1) It is not compatible with stealth in the high-spectral band (0.4-2.5μm); (2) Its total film thickness is relatively large, which is not conducive to preparation; (3) The toxic tellurium element used in it is easy to cause harm to practitioners. The disadvantages of the coating and capsule system are: (1) its thickness and uniformity are difficult to control, which will lead to unstable optical properties; (2) its stability is poor and it is easily affected by factors such as light, oxygen, and humidity, resulting in failure of stealth performance; (3) a large amount of toxic solvents are required in its preparation, which is not conducive to the development concept of green chemistry; (4) it is not compatible with thermal infrared dual-band (3-5μm and 8-14μm) camouflage.

[0004] In the existing research results of optical camouflage multilayer film systems, the control accuracy of the film thickness usually reaches the 0.1nm level. This high-precision requirement poses a challenge to large-scale industrial production and limits its feasibility in practical engineering applications. In addition, in order to achieve low infrared emissivity, most metal materials such as aluminum, silver, chromium, etc. are used, but they have high reflection to radar waves, which is not conducive to the design of radar stealth performance. Furthermore, the current multilayer film system has certain limitations in camouflage function. It is difficult to be compatible with camouflage in the visible light-near infrared band (0.4-2.5μm), low radiation characteristics in the thermal infrared dual band (3-5μm and 8-14μm), and radar transmittance. These problems limit its application potential in complex environments.

[0005] Based on the above problems, there is an urgent need to provide a thermal infrared low-radiation green leaf-like multilayer film and a preparation method thereof that does not use metal materials. Summary of the invention

[0006] The purpose of the present invention is to provide a thermal infrared low-radiation imitation green leaf multilayer film and a preparation method thereof, so as to realize the spectral characteristics of simulated vegetation in the visible light-near infrared band (0.4-2.5μm) and the low-radiation characteristics in the mid-infrared band (3-5μm) and the long infrared band (8-14μm).

[0007] To achieve the above-mentioned object, the present invention provides a thermal infrared low-radiation green leaf imitation multilayer film, comprising a substrate, a long-wave infrared regulation layer, a medium-wave infrared regulation layer and a green leaf imitation high-spectrum regulation layer stacked in sequence;

[0008] The long-wave infrared regulation layer is stacked and arranged in parallel to the substrate in the periodic order of LMHM, the medium-wave infrared regulation layer is stacked and arranged in parallel to the long-wave infrared regulation layer in the periodic order of LMHMH, and the green leaf-like hyperspectral regulation layer is stacked and arranged in parallel to the medium-wave infrared regulation layer in the periodic order of MHLHMHMHMHMLMLML;

[0009] Among them, H represents a high refractive index material with a refractive index of 3.5-5, preferably 3.9-4.5, M represents a medium refractive index material with a refractive index of 2.1-2.8, preferably 2.2-2.6, and L represents a low refractive index material with a refractive index of 1.3-2, preferably 1.4-1.7.

[0010] In the thermal infrared low-radiation green leaf imitation multilayer film, the long-wave infrared regulation layer, the medium-wave infrared regulation layer, and the green leaf imitation high-spectral regulation layer are multilayer structures formed by alternating stacking of multiple dielectric material layers with different refractive indices, and the multiple dielectric materials with different refractive indices include materials with non-zero extinction coefficients.

[0011] Furthermore, the high refractive index material H is Ge, the medium refractive index material M is ZnS, and the low refractive index material L is YbF 3 .

[0012] Furthermore, the long-wave infrared regulation layer, the medium-wave infrared regulation layer and the green leaf-like hyperspectral regulation layer are all a periodic structure, that is, the thermal infrared low-radiation green leaf-like multilayer film includes a substrate, YbF 3 Film, ZnS film, Ge film, ZnS film, YbF 3 Film, ZnS film, Ge film, ZnS film, Ge film, ZnS film, Ge film, YbF 3 Film, Ge film, ZnS film, Ge film, ZnS film, Ge film, ZnS film, Ge film, ZnS film, Ge film, ZnS film, YbF 3 Film, ZnS film, YbF 3 Film, ZnS film, YbF 3 membrane.

[0013] Furthermore, the thicknesses of the four LMHM layers of the long-wave infrared regulation layer are 883xnm, 231x nm, 510x nm, and 139x nm, respectively, and the value range of x is 95%-105%. That is, the thicknesses of the four MHML layers of the long-wave infrared regulation layer from right to left are 838-928nm, 229-243nm, 484.5-535.5nm, and 132-146nm, respectively. The specific thicknesses of the film layers from inside to outside are: 883nm, 231nm, 510nm, and 139nm; and the thicknesses can float within ±5%.

[0014] Furthermore, the thicknesses of the five LMHMH film layers of the mid-wave infrared regulation layer are 427x nm, 152x nm, 168x nm, 447x nm, and 234x nm, respectively, and the value range of x is 95%-105%. That is, the five layers (HM) of the mid-wave infrared regulation layer 2 The thickness of the L film from right to left is 405-449nm, 144-160nm, 159-177nm, 424-470nm, 222-246nm. The specific thickness of the film from inside to outside is 427nm, 152nm, 168nm, 447nm, 234nm, and the thickness can fluctuate within ±5%.

[0015] Furthermore, the thicknesses of the 16 MHLHMHMHMHMLMLML film layers of the green leaf-like hyperspectral control layer are: 31x nm, 66x nm, 27x nm, 49x nm, 56x nm, 116x nm, 47x nm, 112x nm, 49x nm, 54x nm, 61x nm, 20x nm, 49x nm, 16x nm, 25x nm, 75x nm, and the value range of x is 95%-105%. The specific film layer thicknesses from inside to outside are: 31nm, 66nm, 27nm, 49nm, 56nm, 116nm, 47nm, 112nm, 49nm, 54nm, 61nm, 20nm, 49nm, 16nm, 25nm, 75nm, and the thicknesses of the above film layers can float within ±5%.

[0016] Furthermore, the substrate is quartz, PI (polyimide), PET (polyethylene terephthalate), PEI (polyetherimide), SiO 2 , a type of silicon.

[0017] Furthermore, the thermal infrared low-radiation green leaf imitation multilayer film has a spectral characteristic of 0.4-2.5 μm similar to that of green vegetation, and appears green when observed by the naked eye;

[0018] The emissivity for 3-5μm mid-wave infrared is less than 0.5;

[0019] The emissivity for 8-14μm long-wave infrared is less than 0.5.

[0020] The present invention also provides a method for preparing the thermal infrared low-radiation green leaf imitation multilayer film as described in any of the above items, comprising: sequentially preparing a film structure of a long-wave infrared regulation layer, a medium-wave infrared regulation layer, and a green leaf imitation high-spectral regulation layer on a substrate through a coating process.

[0021] Furthermore, the coating process adopts electron beam evaporation coating process, and the background vacuum degree during evaporation is ≤2.0×10 -3 Pa, the deposition rate of medium refractive index materials and low refractive index materials is ≤0.8nm / s, and the deposition rate of high refractive index materials is ≤1.2nm / s.

[0022] Furthermore, the substrate needs to be pre-treated, the surface is cleaned with deionized water to remove debris, then immersed in anhydrous ethanol and cleaned in an ultrasonic cleaner, and finally the substrate is naturally air-dried or the surface is blown dry with a hair dryer.

[0023] The present invention provides a thermal infrared low-radiation imitation green leaf multilayer film. When in use, the substrate of the thermal infrared low-radiation imitation green leaf multilayer film is bonded to the surface of a camouflaged target, for example, by evaporation, bonding, and the like.

[0024] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0025] 1. The present invention provides a thermal infrared low-radiation green leaf imitation multilayer film. Through the optimized design of the film system arrangement, the multilayer film exhibits good high-spectral camouflage characteristics of imitating green vegetation in the visible light-near infrared band, and achieves low-radiation performance in the thermal infrared dual-band range.

[0026] 2. The periodic multilayer film structure of the present invention is composed of high, medium and low refractive index material layers, all of which are preferred window materials for the infrared band, have good thermal matching, small residual thermal stress, and are all non-metallic materials, which reduces interference with electromagnetic transmission in the radar band.

[0027] 3. The thickness of the multilayer film prepared by the present invention is no more than 5 μm, which has the advantages of light weight and greater thickness tolerance, reducing the requirement for precise control of the thickness of each film layer. The thickness of each film layer is small, and the subsequent process has limited impact on the surface of the film layer formed in the previous process, ensuring uniform bonding between film layers. The thickness of the overall multilayer film is more uniform, which simplifies the production process, while ensuring the stability and consistency of the camouflage performance, providing a feasible solution for practical industrial applications.

[0028] 4. The process of the present invention is simple, has good repeatability, and has low requirements on equipment and technology. The obtained multilayer film can realize the spectral characteristics of simulated vegetation in the visible light-near infrared band (0.4-2.5μm), and the low radiation characteristics in the mid-infrared band (3-5μm) and the long infrared band (8-14μm). BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structure of the thermal infrared low-radiation green leaf imitation multilayer film of the present invention;

[0030] Figure 2 It is a schematic diagram of the structure of each regulating layer in the thermal infrared low-radiation green leaf imitation multilayer film of the present invention;

[0031] Figure 3 It is a simulated reflectivity spectrum of the thermal infrared low-radiation imitation green leaf multilayer film of the present invention in the 0.4-2.5 μm band;

[0032] Figure 4 It is a simulated reflectivity spectrum of the thermal infrared low-radiation green leaf imitation multilayer film of the present invention in the 3-14 μm band;

[0033] Figure 5 The experimental reflectivity spectrum of the multilayer film prepared in Example 1 in the 0.4-2.5 μm band;

[0034] Figure 6This is the experimental reflectivity spectrum of the multilayer film prepared in Example 1 in the 3-14 μm band.

[0035] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0036] 1-ZnS thin film; 2-Ge film; 3-YbF 3 membrane. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] See also Figure 1 and 2 The present invention provides a thermal infrared low-radiation green leaf imitation multilayer film, comprising: a substrate, a long-wave infrared regulation layer, a medium-wave infrared regulation layer, and a green leaf imitation hyperspectral regulation layer sequentially arranged on the substrate surface. The long-wave infrared regulation layer is stacked on the substrate according to the periodic structure of MHML, and the rightmost L is the starting coating layer of the long-wave infrared regulation layer; the medium-wave infrared regulation layer is arranged according to (HM) 2 The periodic structure of L is stacked on the long-wave infrared regulation layer, and the rightmost L is the starting coating layer of the medium-wave infrared regulation layer. The green leaf-like hyperspectral regulation layer is (LM) 3 (HM) 3 The periodic structure of (HL)(HM) is stacked on the mid-wave infrared regulation layer; and the rightmost M is the starting coating layer of the green leaf-like hyperspectral regulation layer.

[0039] The substrate is used as a mechanical support, and its thickness can be adjusted appropriately according to needs. Specifically, the substrate can be made of solid material or flexible material. Preferably, the substrate is SiO 2 , to provide good mechanical stability and chemical inertness.

[0040] The long-wave infrared control layer is used to adjust the waveform of the long-wave infrared band. Specifically, the high refractive index material (H) is Ge, the medium refractive index material (M) is ZnS, and the low refractive index material (L) is YbF 3 , arranged according to the periodic structure of MHML, the physical thickness of each layer can be precisely designed according to the emissivity requirements of the long-wave infrared band. Figure 2 , YbF is prepared on the substrate in sequence 3 Film 1, ZnS film 2, Ge film 3 and ZnS film 2.

[0041] The mid-wave infrared control layer is used to adjust the waveform of the mid-wave infrared band. Specifically, the high refractive index material (H) is Ge, the medium refractive index material (M) is ZnS, and the low refractive index material (L) is YbF 3 , according to (HM) 2 The periodic structure of L is arranged, and the physical thickness of each layer can be precisely designed according to the emissivity requirements of the mid-wave infrared band. Figure 2 , YbF 3 Film 1, ZnS film 2, Ge film 3, ZnS film 2 and Ge film 3.

[0042] The green leaf-like hyperspectral control layer is used to finely simulate the waveform of vegetation in the visible light-near infrared band, and is also compatible with the dual-band low-radiation characteristics of thermal infrared. Specifically, the high refractive index material (H) is Ge, the medium refractive index material (M) is ZnS, and the low refractive index material (L) is YbF 3 , according to (LM) 3 (HM) 3 The periodic structure of (HL)(HM) is arranged, and the physical thickness of each layer can be finally determined according to the emissivity requirements. Figure 2 On the Ge film 3 of the mid-wave infrared control layer, ZnS film 2, Ge film 3, YbF 3 Film 1, Ge film 3, ZnS film 2, Ge film 3, ZnS film 2, Ge film 3, ZnS film 2, Ge film 3, ZnS film 2, YbF 3 Film 1, ZnS film 2, YbF 3 Film 1, ZnS film 2, YbF 3 Membrane 1.

[0043] Through the above structural design, the multilayer film of the present invention can achieve predetermined spectral regulation in different bands, effectively improving the camouflage effect, while maintaining the lightness and simplicity of the film structure.

[0044] The present invention is further described below with reference to specific embodiments.

[0045] Embodiment 1

[0046] The structure of the long-wave infrared control layer in this embodiment is ZnS / Ge / ZnS / YbF 3 , the coating thickness parameters are set to 120nm, 508nm, 233nm, 888nm, YbF 3 It is the contact layer with the substrate; the structure of the medium-wave infrared regulation layer is (Ge / ZnS) 2 / YbF 3 The coating thickness parameters are set to 229nm, 456nm, 160nm, 130nm, 465nm, YbF 3It is the contact layer with the long-wave infrared regulation layer; the structure of the green leaf hyperspectral regulation layer is (YbF 3 / ZnS) 3 (Ge / ZnS) 3 (Ge / YbF 3 )(Ge / ZnS), the coating thickness parameters are set to 77nm, 23nm, 15nm, 60nm, 19nm, 59nm, 54nm, 47nm, 110nm, 41nm, 113nm, 60nm, 50nm, 22nm, 64nm, and 35nm. The ZnS on the far right is the transition layer with the medium-wave infrared regulation layer.

[0047] Use SiO 2 As a substrate, first use deionized water to clean the surface to remove debris, then soak it in anhydrous ethanol and clean it in an ultrasonic cleaner, and finally let the substrate dry naturally or use a hair dryer to blow dry the surface to ensure that the substrate surface is clean and dust-free.

[0048] Electron beam evaporation coating process is used on SiO 2 ZnS, Ge and YbF were prepared on the substrate in the above order. 3 Thin films, in turn, on SiO 2 The long-wave infrared regulation layer, the medium-wave infrared regulation layer, and the green leaf-like hyperspectral regulation layer are evaporated on the substrate. During the preparation process, the background vacuum is maintained at no more than 2.0×10 -3 Pa, ZnS and YbF 3 The deposition rate of Ge is not more than 0.8nm / s, and the deposition rate of Ge is not more than 1.2nm / s to ensure the uniformity and quality of the film layer.

[0049] The test reflectivity spectrum of the above embodiment 1 in the 0.4-2.5 μm band is as follows: Figure 5 As shown. It can be seen that Example 1 clearly simulates the spectral characteristics of typical green vegetation in the 0.4-2.5μm band. Among them, a weak absorption peak with a reflectivity of less than 15% is formed at 550nm, which effectively simulates the "green peak" feature caused by chlorophyll absorption; the reflection rises rapidly to 70% in the range of 680-750nm, effectively simulating the "red edge" feature; in the range of 780-1300nm, the reflectivity is maintained at about 65%, which effectively simulates the "near-infrared plateau" feature caused by multiple scattering in plant tissues; the lower reflectivity near 1450nm and 1940nm effectively simulates the "water absorption band" feature in vegetation. Therefore, the present invention can confuse the detector through a reflectivity spectrum similar to that of green leaves, thereby achieving the purpose of camouflage.

[0050] The test reflectivity spectrum of the above embodiment 1 in the 3-14 μm band is as follows: Figure 6 As shown. Figure 6It can be seen that the multilayer film of the first embodiment not only has excellent high-spectral characteristics for simulating green vegetation and realizing visible light-near infrared camouflage, but is also compatible with low radiation in the dual-band range of thermal infrared. The average reflectivities at 3-5μm and 8-14μm are 0.86 and 0.74 respectively, and the average emissivities in the corresponding bands are 0.14 and 0.26 respectively, which has excellent infrared low-radiation characteristics.

[0051] Compared with the traditional visible light camouflage technology, the multilayer film material provided by the present invention achieves low thermal infrared radiation by simulating the plant reflection spectrum. Compared with the existing multilayer film design structure, the multilayer film of the present invention has a greater thickness tolerance, and the materials used are all non-metallic materials, with better thermal matching and less residual thermal stress, and less electromagnetic transmission interference to the radar band. Therefore, it has obvious advantages in counteracting hyperspectral detection, thermal infrared detection and radar compatibility.

[0052] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A thermal infrared low-radiation green leaf imitation multilayer film, characterized in that: It includes a substrate, a long-wave infrared regulation layer, a medium-wave infrared regulation layer and a green leaf-like hyperspectral regulation layer which are stacked in sequence; The long-wave infrared regulation layer is stacked and arranged in parallel to the substrate in the periodic order of LMHM, the medium-wave infrared regulation layer is stacked and arranged in parallel to the long-wave infrared regulation layer in the periodic order of LMHMH, and the green leaf-like hyperspectral regulation layer is stacked and arranged in parallel to the medium-wave infrared regulation layer in the periodic order of MHLHMHMHMHMLMLML; Among them, H represents a high refractive index material with a refractive index of 3.5-5, M represents a medium refractive index material with a refractive index of 2.1-2.8, and L represents a low refractive index material with a refractive index of 1.3-2.

2. The thermal infrared low-radiation green leaf imitation multilayer film according to claim 1, characterized in that: The high refractive index material H is Ge, the medium refractive index material M is ZnS, and the low refractive index material L is YbF3; And / or, the substrate is one of quartz, PI, PET, PEI, SiO2, and silicon.

3. The thermal infrared low-radiation green leaf imitation multilayer film according to claim 2, characterized in that: The thermal infrared low-radiation green leaf imitation multilayer film includes a substrate, a YbF3 film, a ZnS film, a Ge film, a ZnS film, a YbF3 film, a ZnS film, a Ge film, a ZnS film, a Ge film, a ZnS film, a Ge film, a YbF3 film, a Ge film, a ZnS film, a Ge film, a ZnS film, a ZnS film, a Ge film, a ZnS film, a YbF3 film, a ZnS film, a YbF3 film, a ZnS film, and a YbF3 film, which are stacked in sequence.

4. The thermal infrared low-radiation green leaf imitation multilayer film according to claim 3, characterized in that: In each LMHM periodic unit of the long-wave infrared regulation layer, the thicknesses of the LMHM layers are 883x nm, 231x nm, 510x nm, and 139x nm, respectively, and the value range of x is 95%-105%.

5. The thermal infrared low-radiation green leaf imitation multilayer film according to claim 3, characterized in that: In each LMHMH periodic unit of the medium-wave infrared regulation layer, the thicknesses of the LMHMH layers are 427x nm, 152x nm, 168x nm, 447x nm, and 234x nm, respectively, and the value range of x is 95%-105%.

6. The thermal infrared low-radiation green leaf imitation multilayer film according to claim 3, characterized in that: In each MHLHMHMHMHMLMLML periodic unit of the green leaf imitation hyperspectral regulation layer, the thicknesses of each MHLHMHMHMHMLMLML layer are respectively: 31xnm, 66x nm, 27x nm, 49x nm, 56x nm, 116x nm, 47x nm, 112x nm, 49x nm, 54x nm, 61x nm, 20x nm, 49x nm, 16x nm, 25x nm, 75x nm, and the value range of x is 95%-105%.

7. The thermal infrared low-radiation green leaf imitation multilayer film according to any one of claims 1 to 6, characterized in that: The thermal infrared low-radiation green leaf imitation multilayer film has a spectral characteristic of 0.4-2.5 μm and appears green under naked eye observation; The emissivity for 3-5μm mid-wave infrared is less than 0.5; The emissivity for 8-14μm long-wave infrared is less than 0.

5.

8. A method for preparing the thermal infrared low-radiation green leaf imitation multilayer film according to any one of claims 1 to 7, characterized in that: include: The film structures of the long-wave infrared regulation layer, the medium-wave infrared regulation layer and the green leaf-like hyperspectral regulation layer are prepared in sequence on the substrate through a coating process.

9. The preparation method according to claim 8, characterized in that: The coating process adopts electron beam evaporation coating process, and the background vacuum degree during evaporation is ≤2.0×10 -3 Pa, the deposition rate of medium refractive index materials and low refractive index materials is ≤0.8nm / s, and the deposition rate of high refractive index materials is ≤1.2nm / s.

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