Composite camouflage coating compatible with visible light-near infrared-intermediate infrared stealth and preparation method of composite camouflage coating

Abstract

The invention discloses a composite camouflage coating compatible with visible light-near infrared-intermediate infrared stealth and a preparation method of the composite camouflage coating. The composite camouflage coating comprises a base material bottoming layer, a bridging layer, a hyperspectral material coating and an intermediate infrared material coating which are sequentially arranged from inside to outside. Compared with a traditional unilateral hyperspectral stealth coating, the composite camouflage coating compatible with visible light, near infrared and intermediate infrared stealth has the advantages that the compatibility effect of infrared stealth of all wave bands is improved, the practical reliability of the coating is remarkably improved, and the difficulty of a production process is reduced. The fabric can be applied to fabric base materials of tents, camouflage nets, clothes and the like.

Description

Technical Field

[0001] This invention relates to the field of camouflage coatings, and more specifically, to a composite camouflage coating compatible with visible light, near-infrared, and mid-infrared stealth, and its preparation method. Background Technology

[0002] Stealth technology derived from plant biomimicry is widely used in military camouflage, with green leaves being one of the most typical camouflage simulation targets. Hyperspectral imaging technology is an important means of detecting and distinguishing real plants from camouflage materials, with its typical detection spectral range being the visible-near infrared band (400-2500 nm). With the advent of hyperspectral thermal infrared remote sensing technology, its detection spectral range has gradually extended to the thermal infrared band (8-14 μm).

[0003] Traditional camouflage materials have evolved from simply matching visible light for stealth to effectively mimicking near-infrared characteristics such as "green peaks," "red edges," "near-infrared plateaus," and "water absorption valleys" of green vegetation. Correspondingly, the field of thermal infrared stealth has developed low-emission coatings for metals, semiconductors, and electrochromic infrared. Many existing thin-film synthesis and preparation techniques have improved the similarity to real vegetation profiles to some extent, and many coatings have achieved relatively ideal thermal infrared stealth performance. However, to date, there is still no camouflage coating or thin-film system that truly combines optical performance across all wavelengths, and it is impossible to completely indistinguish from real vegetation.

[0004] Patent CNCN202310704325.7 discloses a multilayer thin film for visible-near-infrared hyperspectral and mid-infrared stealth. It achieves compatibility between the visible-near-infrared bands and mid-infrared stealth by placing a near-infrared absorption-compatible mid-infrared stealth layer made of metal or metal-like material between the visible-near-infrared hyperspectral control layer and the near-infrared hyperspectral control layer. However, its structure is complex, the process is cumbersome, and the number of composite layers is excessive. Furthermore, the coating is mainly composed of stacked dielectric materials, making it impossible to add binders, resulting in poor reliability and unsuitability for long-term use in natural environments.

[0005] Patent CN202210806494.7 discloses a green plant leaf-like coating material that uses polyvinyl alcohol as a film-forming agent and combines camouflage pigments and water-absorbing material lithium chloride to achieve hyperspectral camouflage. This material has high spectral similarity, but does not have the stealth effect of being compatible with thermal infrared.

[0006] Some camouflage coatings, even if they meet the stealth performance requirements, cannot be put into actual production and military use due to their complex structure, difficult manufacturing process, poor weather resistance, poor adhesion between the coating and the substrate, expensive raw materials, and other reasons. Faced with increasingly advanced detection systems, plant stealth technology faces considerable challenges and difficulties. Summary of the Invention

[0007] The purpose of this invention is to provide a composite camouflage coating compatible with visible light, near-infrared and mid-infrared stealth and its preparation method, so as to solve the technical problems existing in the background art.

[0008] The present invention provides a composite camouflage coating compatible with visible light, near-infrared and mid-infrared stealth, comprising a substrate underlayer, a bridging layer, a hyperspectral material coating and a mid-infrared material coating arranged sequentially from the inside to the outside;

[0009] The substrate is radar cloth, and the substrate underlayer is a polyvinyl alcohol adhesive coating after cross-linking with a cross-linking agent; the bridging layer is a mixture of polyvinyl alcohol adhesive and polyvinyl alcohol aqueous solution; the hyperspectral material coating is a mixture of polyvinyl alcohol aqueous solution, water-absorbing material (AWM) and highly reflective pigment; the mid-infrared coating is a mixture of polyvinyl alcohol aqueous solution, water-absorbing inorganic salt, highly reflective pigment and low emissivity pigment (XDF).

[0010] In a preferred embodiment, the crosslinking agent includes at least one of epoxy crosslinking agent, nano-silica, and organosilicon crosslinking agent.

[0011] In a preferred embodiment, the absorbent material is silica gel-coated water-absorbing inorganic salt composite microparticles; the water-absorbing inorganic salt is at least one of anhydrous LiCl, anhydrous CaCl2, and anhydrous MgCl2.

[0012] In a preferred embodiment, the highly reflective pigments are cobalt green, highly reflective yellow, and highly reflective black, and the quantities are proportioned according to the requirements of visible light colorimetry and reflectance curves.

[0013] In a preferred embodiment, the XDF low-emissivity material is a doped low-emissivity mixed powder, which is prepared by mixing rare earth oxides, semiconductor powders, flake metal powders, and infrared-transmitting pigments and fillers in a certain proportion.

[0014] In a preferred embodiment, the infrared-transmitting pigment is an infrared-transmitting color powder that filters visible light in the 400nm-650nm range.

[0015] A method for preparing a composite camouflage coating compatible with visible light, near-infrared, and mid-infrared stealth includes the following steps:

[0016] Step 1: Prepare the substrate and apply the underlayer: The standard radar cloth is polished to remove gloss and fixed on the casting stage. The polyvinyl alcohol aqueous solution and the organosilicon crosslinking agent are crosslinked. The crosslinking agent dosage is 4%. After doping and full dispersion, the modified polyvinyl alcohol adhesive is obtained. It is coated in two layers with the thickness controlled at 5-10 μm.

[0017] Step 2: Preparation of bridging layer: Mix modified polyvinyl alcohol adhesive and polyvinyl alcohol aqueous solution at a ratio of 1:1, disperse thoroughly, and then coat by scraping. Coat in two coats, with the thickness controlled at 5-10 μm.

[0018] Step 3: Preparation of hyperspectral coating: Add 3% AWM to the polyvinyl alcohol aqueous solution, disperse it fully to obtain a mixture, and seal and keep it at 40℃ for later use. Then add the dispersed high-reflectivity pigment to the above mixture, and coat it onto the bridging layer in layers. After each coating, bake it at 80℃ until it is surface dry. The final thickness is controlled at 300-350μm.

[0019] Step 4: Preparation of mid-infrared material coating: Mix and disperse the low-emission pigment with the prepared polyvinyl alcohol mixture at a ratio of 10:90, and coat it onto the bridging layer in multiple layers. After each coating, bake at 80°C until surface dry. The final thickness is controlled at 20-30μm.

[0020] Step 5: Curing: Place the material coated in Step 8 into an electric heating drying oven for curing. The curing time is 1 hour and the curing temperature is 50°C, thus obtaining the visible light-near infrared-mid infrared stealth composite camouflage coating.

[0021] In a preferred embodiment, in step 3, the absorbent material is prepared by the sol-gel method, in which pretreated anhydrous inorganic salt powder is uniformly dispersed in a modifier sol, gelled, and then calcined at high temperature to obtain a surface-coated powder absorbent material.

[0022] The beneficial effects of the technical solution of this invention are:

[0023] This invention provides a composite camouflage coating compatible with visible light, near-infrared, and mid-infrared wavelengths. Compared to traditional one-sided hyperspectral camouflage coatings, it improves the compatibility of infrared camouflage across different wavelengths, significantly enhances the coating's practical reliability, and reduces manufacturing complexity. It can be applied to fabric substrates such as tents, camouflage nets, and clothing. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the composite coating structure in an embodiment of the present invention;

[0025] Figure 2 The visible-near-infrared hyperspectral stealth reflectance spectrum of the composite coating in this embodiment of the invention;

[0026] Figure 3 This is a mid-infrared stealth thermal image from an embodiment of the present invention. Detailed Implementation

[0027] The present invention will now be described in further detail. The embodiments of the invention are given for the purpose of illustration and description, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose.

[0028] like Figure 1 As shown, the technical solution of the present invention provides a composite camouflage coating compatible with visible light, near-infrared and mid-infrared stealth, comprising a substrate underlayer, a bridging layer, a hyperspectral material coating and a mid-infrared material coating arranged sequentially from the inside to the outside.

[0029] The substrate is radar cloth, and the substrate underlayer is a polyvinyl alcohol adhesive coating after cross-linking with a cross-linking agent; the cross-linking agent includes at least one of epoxy cross-linking agent, nano silica, and organosilicon cross-linking agent.

[0030] The bridging layer is a mixture of polyvinyl alcohol adhesive and polyvinyl alcohol aqueous solution; the hyperspectral material coating is a mixture of polyvinyl alcohol aqueous solution, water-absorbing material and highly reflective pigment; the water-absorbing material is silica gel-coated water-absorbing inorganic salt composite microparticles; the water-absorbing inorganic salt is at least one of anhydrous LiCl, anhydrous CaCl2, and anhydrous MgCl2; the highly reflective pigment is cobalt green, highly reflective yellow and highly reflective black, and the quantities are proportioned according to the requirements of visible light colorimetry and reflectance curve.

[0031] The mid-infrared coating is a mixture of polyvinyl alcohol aqueous solution, water-absorbing inorganic salt, highly reflective pigment, and XDF low-emissivity pigment; the XDF low-emissivity material is a doped low-emissivity mixed powder, which is prepared by mixing rare earth oxides, semiconductor powders, flake metal powders, and infrared-transmitting pigment fillers in a certain proportion; the infrared-transmitting pigment is an infrared-transmitting color powder that filters visible light in the 400nm-650nm range.

[0032] In the aforementioned composite coating, the undercoat and bridging layer enhance adhesion to the substrate, significantly improving the reliability of the composite coating. However, because the hyperspectral coating contains a large number of water molecules, which act as lubricants, it is difficult for the film to bond tightly to the substrate after formation. The swelling from water absorption and the stress contraction from water loss easily cause it to detach from the fabric. The modified polyvinyl alcohol adhesive exhibits significantly increased adhesion to the fabric. Through the strengthening and transition of intermolecular forces in the bridging layer, the overall adhesion of the composite coating is ultimately improved, and it demonstrates a more ideal effect in dealing with the stress caused by the deformation of the coating due to water absorption and loss.

[0033] In the aforementioned composite coating, the hyperspectral material coating is modulated with three pigments—green-yellow, blue-green, and black—to simulate vegetation color. The vegetation colors are referenced from the national military standards GJB798-90 and GJB1082-91, specifically the dark green, medium green, emerald green, and yellow-green numbers. In the 400nm-680nm visible light band, it simulates the visible light "green peak" characteristic. At 680nm-780nm, it simulates the "red edge" phenomenon; at 780nm-1300nm, it simulates the "near-infrared plateau" characteristic; and at 1450nm and 1930nm, it simulates the "water absorption valley" characteristic. Cobalt green has a positive effect on increasing the "red edge slope" but a negative effect on the "near-infrared plateau" and "water absorption valley" characteristics; therefore, its maximum content should be controlled. The water retention and absorption mechanism of polyvinyl alcohol mixed with water-absorbing material in hyperspectral material coating is beneficial to reflecting the "water absorption valley" and simulating the transpiration and respiration characteristics of plants, but it is not conducive to the reliability of the coating. Therefore, it is preferable to control the total thickness of hyperspectral material coating at 250-300μm.

[0034] Compared to traditional single-component inorganic salts as absorbent materials, the micropores on the surface of the silica gel coating effectively control the rate of water absorption by the inorganic salts, preventing excessive precipitation of inorganic salts on the coating surface and greatly improving the overall reliability of the hyperspectral coating.

[0035] In the aforementioned composite coating, the mid-infrared characteristics of the mid-infrared coating are mainly achieved through the synergistic effect of the infrared optical properties of the low-emissivity XDF material within the coating and the physical-thermal effect of water molecule evaporation in the coating's water-retention mechanism. With the XDF content controlled at 10%-15%, a low emissivity effect can be achieved relatively easily and stably. The 650nm "infrared penetrating material," through appropriate filtering of the visible light band, effectively enhances the slope of the "red edge" while maintaining good infrared transmittance.

[0036] This solution discloses a method for preparing a composite camouflage coating compatible with visible light, near-infrared, and mid-infrared stealth, comprising the following steps:

[0037] Step 1: Prepare the substrate and apply the underlayer: The standard radar cloth is polished to remove gloss and fixed on the casting stage. The polyvinyl alcohol aqueous solution and the organosilicon crosslinking agent are crosslinked. The crosslinking agent dosage is 4%. After doping and full dispersion, the modified polyvinyl alcohol adhesive is obtained. It is coated in two layers with the thickness controlled at 5-10 μm.

[0038] Step 2: Preparation of bridging layer: Mix modified polyvinyl alcohol adhesive and polyvinyl alcohol aqueous solution at a ratio of 1:1, disperse thoroughly, and then coat by scraping. Coat in two coats, with the thickness controlled at 5-10 μm.

[0039] Step 3: Preparation of hyperspectral coating: Add 3% AWM to a polyvinyl alcohol aqueous solution, disperse it fully to obtain a mixture, and seal and keep it warm at 40℃ for later use. Then, add the dispersed high-reflectivity pigment to the above mixture and coat it onto the bridging layer in layers. After each coating, bake it at 80℃ until it is surface dry. The final thickness is controlled at 250-300μm. The water-absorbing material is prepared by the sol-gel method. The pretreated anhydrous inorganic salt powder is uniformly dispersed in the modifier sol, gelled, and calcined at high temperature to obtain the powder water-absorbing material with surface coating.

[0040] Step 4: Preparation of mid-infrared material coating: Mix and disperse the low-emission pigment with the prepared polyvinyl alcohol mixture at a ratio of 10:90, and coat it onto the bridging layer in multiple layers. After each coating, bake at 80°C until surface dry. The final thickness is controlled at 20-30μm.

[0041] Step 5: Curing: Place the material coated in Step 8 into an electric heating drying oven for curing. The curing time is 1 hour and the curing temperature is 50°C, thus obtaining the visible light-near infrared-mid infrared stealth composite camouflage coating.

[0042] Example 1

[0043] Step 1: Substrate preparation: Select standard radar cloth, perform gloss reduction polishing treatment, and fix it on the casting stage;

[0044] Step 2: Prepare the substrate and apply the underlayer: Crosslink the polyvinyl alcohol aqueous solution with the organosilicon crosslinking agent at a dosage of 4%. After the doping is fully dispersed, the modified polyvinyl alcohol adhesive is obtained and applied in two coats with a thickness controlled at 8 μm.

[0045] Step 3: Preparation of bridging layer: Mix modified polyvinyl alcohol adhesive and polyvinyl alcohol aqueous solution at a ratio of 1:1, disperse thoroughly, and then coat by scraping in two coats with a thickness controlled at 8μm.

[0046] Step 4: Preparation of Water-Absorbent Material (AWM): The sol-gel method was used to prepare the material. Anhydrous LiCl powder was dehydrated and pretreated by filtration: after drying in a blower at 50°C for 30 min, the powder was filtered through an 800-mesh filter to control the particle size and then set aside. Silica gel was dissolved in anhydrous ethanol and fully dispersed to obtain a silica gel solution. The pretreated anhydrous inorganic salt powder was uniformly dispersed in the silica gel solution, thoroughly mixed, and allowed to gel. It was then dried in a blower at a constant temperature of 50°C until the anhydrous ethanol completely evaporated, resulting in inorganic salt powder AWM coated with silica gel.

[0047] Step 5: Preparation of hyperspectral material layer matrix: Add 3% AWM to polyvinyl alcohol aqueous solution, disperse thoroughly, and then seal and keep warm at 40℃ for later use.

[0048] Step 6: Color matching of hyperspectral material layer (taking GJB1082-91 medium green MG1151 as a color matching example): Weigh the coloring pigments and functional fillers according to the formula ratio in the table below.

[0049] Table 1: Proportion of Component Raw Materials in the Examples:

[0050] High leukorrhea (65%) High anti-black (25%) Cobalt green (60%) Nano Semiconductors 6 3.5 2 0.2

[0051] After thorough grinding and dispersion, set aside for later use.

[0052] Step 7: Preparation of the hyperspectral coating: The dispersed pigment and the prepared polyvinyl alcohol mixture are mixed and dispersed at a ratio of 3:97. The mixture is then coated onto the bridging layer in multiple layers, and each layer is dried at 80°C until surface dry, with the final thickness controlled at 300 μm.

[0053] Step 8: XDF preparation:

[0054] Table 2: Proportion of each component of XDF in the examples:

[0055] rare earth oxides Nano Semiconductors Flake aluminum powder Infrared penetrating powder 20% 5% 60% 15%

[0056] Disperse thoroughly and set aside.

[0057] Step 9: Preparation of mid-infrared material coating: Mix and disperse the low-emission pigment with the prepared polyvinyl alcohol mixture at a ratio of 10:90. Apply the mixture in multiple layers to the bridging layer, and bake at 80°C until surface dry after each layer. The final thickness is controlled at 25 μm.

[0058] Step 10: Curing: Place the material coated in Step 8 into an electric heating drying oven for curing. The curing time is 1 hour and the curing temperature is 50°C, thus obtaining the visible light-near infrared-mid infrared stealth composite camouflage coating.

[0059] Table 3: Infrared emissivity of coatings with different XDF addition amounts:

[0060] XDF content 0% 5% 10% 15% Coating emissivity 0.95 0.78 0.5 0.42

[0061] Table 4: Reliability and Weather Resistance Tests of the Visible-Near-Infrared-Mid-Infrared Stealth Composite Camouflage Coating

[0062] Serial Number Testing items Test results 1 Adhesion to substrate after drying 25.7 MPa 2 Adhesion after 800h xenon lamp aging 24.8 MPa 3 Outdoor sunshine (168h) No peeling; adhesion test result: 22.6 MPa. 4 Outdoor sunshine (720h) No peeling; adhesion test result: 19.8 MPa. 5 Resistant to damp heat (168h) No peeling; adhesion test result: 20.2 MPa.

[0063] The adhesion data was measured using a high and low temperature universal testing machine, and the test method was the pull-out test.

[0064] Figure 2 This is the visible-near-infrared hyperspectral stealth reflectance spectrum of the composite coating in this embodiment of the invention. Figure 3 This is a mid-infrared stealth thermal image from an embodiment of the present invention, with a heat source temperature of 60°C. Figure 3 The image on the left shows a composite camouflage coating that is compatible with visible light, near-infrared, and mid-infrared stealth; the image on the right shows a composite coating that does not contain low-emission pigments for mid-infrared coating.

[0065] As can be seen from the above embodiments, the present invention uses a multi-layer composite structure, which effectively balances the hyperspectral and thermal infrared stealth properties of the material. At the same time, by using a bridging layer, the weather resistance and reliability of the material are greatly improved while simplifying the manufacturing process, making the material possible to be mass-produced and put into practical use.

[0066] Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art and related fields based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described and explained in the present invention, unless otherwise specified or limited, shall be implemented according to conventional means in the art.

Claims

1. A composite camouflage coating compatible with visible light, near-infrared, and mid-infrared stealth, characterized in that, It includes, from the inside out, a substrate underlayer, a bridging layer, a hyperspectral material coating, and a mid-infrared material coating; The substrate is radar cloth, and the substrate underlayer is a polyvinyl alcohol adhesive coating after cross-linking with a cross-linking agent. The bridging layer is a mixture of polyvinyl alcohol adhesive and polyvinyl alcohol aqueous solution; the hyperspectral material coating is a mixture of polyvinyl alcohol aqueous solution, water-absorbing material and highly reflective pigment; the mid-infrared coating is a mixture of polyvinyl alcohol aqueous solution, water-absorbing inorganic salt, highly reflective pigment and low emissivity pigment.

2. The composite camouflage coating compatible with visible light, near-infrared, and mid-infrared stealth as described in claim 1, characterized in that, The crosslinking agent includes at least one of epoxy crosslinking agent, nano-silica, and organosilicon crosslinking agent.

3. The composite camouflage coating compatible with visible light, near-infrared, and mid-infrared stealth as described in claim 1, characterized in that, The absorbent material is silica gel-coated water-absorbing inorganic salt composite microparticles; The water-absorbing inorganic salt is at least one of anhydrous LiCl, anhydrous CaCl2, and anhydrous MgCl2.

4. The composite camouflage coating compatible with visible light, near-infrared, and mid-infrared stealth as described in claim 1, characterized in that, The highly reflective pigments are cobalt green, highly reflective yellow, and highly reflective black, and their quantities are proportioned according to the requirements of visible light colorimetry and reflectance curves.

5. The composite camouflage coating compatible with visible light, near-infrared, and mid-infrared stealth as described in claim 1, characterized in that, The XDF low-emissivity material is a doped low-emissivity mixed powder, which is prepared by mixing rare earth oxides, semiconductor powders, flake metal powders, and infrared-transmitting pigments and fillers in a certain proportion.

6. The composite camouflage coating compatible with visible light, near-infrared, and mid-infrared stealth as described in claim 5, characterized in that: The infrared-transmitting pigment is an infrared-transmitting color powder that filters visible light in the 400nm-650nm range.

7. A method for preparing a composite camouflage coating compatible with visible light, near-infrared, and mid-infrared stealth according to any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Prepare the substrate and apply the underlayer: The standard radar cloth is polished to remove gloss and fixed on the casting stage. The polyvinyl alcohol aqueous solution and the organosilicon crosslinking agent are crosslinked. The crosslinking agent dosage is 4%. After doping and full dispersion, the modified polyvinyl alcohol adhesive is obtained. It is coated in two layers with the thickness controlled at 5-10 μm. Step 2: Preparation of bridging layer: Mix modified polyvinyl alcohol adhesive and polyvinyl alcohol aqueous solution at a ratio of 1:1, disperse thoroughly, and then coat by scraping. Coat in two coats, with the thickness controlled at 5-10 μm. Step 3: Preparation of hyperspectral coating: Add 3% AWM to the polyvinyl alcohol aqueous solution, disperse it fully to obtain a mixture, and seal and keep it at 40℃ for later use. Then add the dispersed high-reflectivity pigment to the above mixture, and coat it onto the bridging layer in layers. After each coating, bake it at 80℃ until it is surface dry. The final thickness is controlled at 300-350μm. Step 4: Preparation of mid-infrared material coating: Mix and disperse the low-emission pigment with the prepared polyvinyl alcohol mixture at a ratio of 10:90, and coat it onto the bridging layer in multiple layers. After each coating, bake at 80°C until surface dry. The final thickness is controlled at 20-30μm. Step 5: Curing: Place the material coated in Step 8 into an electric heating drying oven for curing. The curing time is 1 hour and the curing temperature is 50°C, thus obtaining the visible light-near infrared-mid infrared stealth composite camouflage coating.

8. The method for preparing a composite camouflage coating compatible with visible light, near-infrared, and mid-infrared stealth according to claim 7, characterized in that, In step 3, the absorbent material is prepared by the sol-gel method, in which pretreated anhydrous inorganic salt powder is uniformly dispersed in a modifier sol, gelled, and then calcined at high temperature to obtain a powder absorbent material with a surface coating.

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