Preparation method of flexible conductive film with infrared camouflage effect

Abstract

The invention discloses a preparation method of a flexible conductive film with an infrared camouflage effect, and the method comprises the following steps: (1) processing a metal mask plate, and enabling the metal mask plate to comprise a hollow region, a grid region and a solid region at the same time; (2) the metal mask plate is attached to a hydrophobic substrate, hydrophilic modification is conducted on the hydrophobic substrate, and a substrate with different areas corresponding to different hydrophilic characteristics is obtained; (3) spraying the dispersion liquid containing the conductive nanowires on the surface of the substrate, and obtaining conductive network structures with different mesh sizes in different areas of the substrate; and (4) blade-coating the surface of the substrate with an organic solvent containing a high-molecular polymer, drying, and stripping to obtain the flexible conductive film. The film prepared by the method disclosed by the invention has high transmittance in a visible light wave band, and a substrate image covered by the film can be presented; in the middle and far infrared bands, the infrared emissivity of different blocks of the film is in differential distribution, so that the film has an infrared camouflage effect and can adapt to multi-spectrum compatible stealth.

Description

Technical Field

[0001] The invention relates to a method for preparing a flexible conductive film with infrared camouflage effect. Background Art

[0002] With the development of detection technology, single-band camouflage technology has been unable to cope with full-spectrum detection threats, and the development of multi-spectrum compatible stealth technology is imminent. Transparent conductive films can present the image of the substrate they cover, and can also avoid the interference of the visible light camouflage coating on the infrared characteristics of the surface. At present, transparent conductive films such as ITO and AZO have been widely used for infrared camouflage. However, its poor flexibility limits its application in clothing and other fields; in addition, the single infrared characteristics of existing transparent conductive films make them easy to be exposed in certain environments. Summary of the invention

[0003] Purpose of the invention: The purpose of the present invention is to provide a method for preparing a flexible conductive film with an infrared camouflage effect. On the one hand, the film prepared by this method has high transmittance in the visible light band and can present the image of the substrate covered by the film. On the other hand, in the mid- and far-infrared bands, the infrared emissivity corresponding to different blocks of the film is distributed in a graded manner, so that it has an infrared camouflage effect, and thus has a multi-spectrum compatible stealth effect.

[0004] Technical solution: The method for preparing the flexible conductive film with infrared camouflage effect of the present invention comprises the following steps:

[0005] (1) processing the metal mask plate so that the metal mask plate includes a hollow area, a grid area, and a solid area at the same time;

[0006] (2) laminating the metal mask plate on the hydrophobic substrate to modify the hydrophobic substrate to be hydrophilic, thereby obtaining a substrate with different regions corresponding to different hydrophilic properties;

[0007] (3) spraying a dispersion containing conductive nanowires onto the surface of a substrate. Due to differences in hydrophilicity and droplet wetting properties between different regions, a conductive network structure in which the conductive nanowires are arranged in different ways (different arrangements result in different mesh sizes) is obtained in different regions of the substrate.

[0008] (4) Scraping an organic solvent containing a high molecular weight polymer onto the surface of the substrate, and peeling it off after drying to obtain a flexible conductive film.

[0009] Wherein, in step (1), a femtosecond laser is used to process the metal mask; wherein, in the grid area, the porosity is 36-40%.

[0010] Wherein, in step (2), the hydrophobic substrate is a glass substrate hydrophobically modified by a silane coupling agent; or the hydrophobic substrate is a PTFE (polytetrafluoroethylene) substrate or a PFA substrate.

[0011] Wherein, in step (2), the hydrophobic substrate is subjected to hydrophilic modification, specifically, the hydrophobic substrate attached with the metal mask is placed in an oxygen plasma treatment machine for hydrophilic modification.

[0012] Wherein, the hydrophilic modification is carried out in air, argon or oxygen atmosphere, and the time of the hydrophilic modification is 100 to 120 seconds.

[0013] Wherein, in step (3), the conductive nanowire is a silver nanowire or a copper nanowire; the diameter of the conductive nanowire is 25 to 30 nm, and the length is 20 to 25 μm.

[0014] Wherein, in step (3), the mass concentration of the conductive nanowires in the dispersion containing the conductive nanowires is 0.5 to 1.0 mg / mL; and the dispersion is ethanol or isopropanol.

[0015] Wherein, in step (3), during the spraying process, the spraying rate is 8 to 9 μL / s, the spraying distance is maintained at 10 to 12 cm, and the aperture of the spray gun used is 0.3 to 0.35 mm.

[0016] Wherein, in step (3), the loading amount of the conductive nanowires on the substrate is 20 to 100 μg / cm 2 .

[0017] Wherein, in step (4), the high molecular polymer is cellulose, PDMS or polyurethane; the organic solvent is N,N'-dimethylformamide; the drying temperature is 60-80°C, the drying time is 1.5-2h, and the drying is used to remove the residual solvent.

[0018] The present invention uses the regionalized hydrophilicity of the substrate to make the droplets exhibit different wetting behaviors on its surface, thereby generating conductive network structures with different mesh sizes in different regions, thereby producing differentiated transmission characteristics for electromagnetic waves in different bands; wherein, the mesh size of the film in the hydrophilic area is about several hundred nanometers, and the mesh size in the hydrophobic area is between several microns and more than ten microns.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the film prepared by the method of the present invention has high transmittance in the visible light band, and can present the image of the substrate covered by the film; in the mid- and far-infrared bands, the infrared emissivity of different blocks of the film is distributed in a graded manner, so it has an infrared camouflage effect and can adapt to multi-spectrum compatible stealth; in addition, the film also has good flexibility, so that it can fit well to various curved substrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is an optical photograph of the metal mask after processing in Example 1;

[0021] Figure 2 The contact angle images of different regions of the substrate after contact with the droplet in Example 1;

[0022] Figure 3 The scanning electron microscope images of the silver nanowire conductive network in different regions of the substrate in Example 1;

[0023] Figure 4 This is a mesh size distribution diagram of different conductive networks in Example 1;

[0024] Figure 5 The images of the film prepared in Example 1 at the beginning and after deformation are shown;

[0025] Figure 6 1 is a curve of visible light transmittance and infrared emissivity at different regions of the film prepared in Example 1;

[0026] Figure 7 The optical and infrared images of the film prepared in Example 1 after covering the surface of the camouflage clothing;

[0027] Figure 8 The scanning electron microscope images of the silver nanowire conductive network in different regions of the substrate in Example 2;

[0028] Fig. 9 3 and 4 are curves of visible light transmittance and infrared emissivity at different regions of the film prepared in Example 2. DETAILED DESCRIPTION

[0029] Example 1

[0030] The method for preparing the flexible conductive film with infrared camouflage effect of the present invention comprises the following steps:

[0031] (1) The glass substrate was ultrasonically cleaned with acetone, ethanol and deionized water for 10 min respectively to remove residual oil and impurities on the surface of the glass sheet;

[0032] (2) placing the above glass sheet and a sample bottle containing 5 mL of trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane in a glass bottle with a capacity of 500 mL, sealing the glass bottle and heating it to 100° C. and maintaining it for 6 hours, and obtaining a hydrophobically modified glass substrate by evaporation coating;

[0033] (3) Processing metal mask by femtosecond laser, Figure 1This is an optical photograph of the metal mask after processing in this embodiment. In the figure, area 1 is a hollow area, area 2 is a grid area, the size of the square hole in the grid area is 0.6 mm, the size (width) of the grid between adjacent square holes is 0.4 mm, the porosity of the grid area is 36%, and area 3 is a solid area;

[0034] (4) Covering the processed metal mask on the hydrophobic substrate to ensure that the two are in contact, and then treating it with an oxygen plasma treatment machine in an air environment for 120 seconds to obtain a glass substrate with regionalized hydrophilic properties; Figure 2 The contact angle images of different areas of the substrate in Example 1 after contact with the droplet, wherein in the hydrophilic area, the droplet spreads rapidly after contacting the substrate surface, and the contact angle decreases from 15° to 4° within 0.9s. The smaller contact angle makes the difference in evaporation rate between the center and the edge of the droplet smaller, thereby generating a random network; in contrast, the contact angle of the droplet in the hydrophobic area slowly decreases from 46° to 32° within 35s, and the larger contact angle makes the difference in evaporation rate between the center and the edge of the droplet larger, the capillary effect is significant, and the silver nanowires are driven to generate a micro-network structure;

[0035] (5) Spraying a silver nanowire-ethanol dispersion with a mass concentration of 0.5 mg / mL onto the surface of the glass substrate, wherein the diameter of the silver nanowire is 30 nm and the length is 25 μm; the spraying rate is 8 μL / s, the spraying distance is maintained at 10 cm, the aperture of the spray gun used is 0.3 mm, and the silver nanowire loading is controlled by a balance to be 60 μg / cm 2 , Figure 3 The scanning electron microscope images of the silver nanowire conductive network in different regions of the substrate in Example 1; Figure 3 It can be seen that a conductive network with different pore sizes was successfully prepared on the substrate surface; Figure 4 This is the pore size distribution diagram obtained by ImageJ software, in which the pores in the hydrophilic area are mainly located around 250nm, while in the hydrophobic area, the pores are concentrated in a few microns to more than ten microns;

[0036] (6) Disperse 5 g of polyurethane masterbatch in 20 mL of N,N'-dimethylformamide, stir at room temperature for 4 h to ensure that the polyurethane is completely dissolved therein, and then let it stand for 10 min to remove residual bubbles to obtain a polyurethane solution; apply the polyurethane solution on the surface of a substrate, place it in a vacuum oven at 80 °C and dry it for 2 h to remove residual solvent, and peel the film off the substrate to obtain a flexible conductive film. Figure 5 These are optical images of the film after various deformations, proving its good flexibility.

[0037] Figure 6 is the visible light transmittance and infrared emissivity curve of the film in different regions prepared in Example 1, Figure 6It can be seen that when the substrate is included, the visible light transmittance at a wavelength of 550 nm is higher than 70%, and the infrared emissivity of the corresponding regions 1 to 3 of the film are 0.27, 0.47 and 0.58 respectively. Figure 7 These are optical and infrared images of the film prepared in Example 1 covered on the surface of camouflage clothing. Since the film has good visible light transmittance, the film visually presents a color characteristic similar to that of the substrate, and presents a typical camouflage pattern under an infrared thermal imager, that is, infrared imaging of varying depths. When covered on the surface of the human body, it can hide the thermal radiation characteristics of the human body itself and enable it to achieve infrared camouflage for the human body in a variety of background environments such as cities and woodlands.

[0038] Example 2

[0039] The method for preparing the flexible conductive film with infrared camouflage effect of the present invention comprises the following steps:

[0040] (1) The glass substrate was ultrasonically cleaned with acetone, ethanol and deionized water for 10 min respectively to remove residual oil and impurities on the surface of the glass sheet;

[0041] (2) placing the above glass sheet and a sample bottle containing 5 mL of trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane in a glass bottle with a capacity of 500 mL, sealing the glass bottle and heating it to 100° C. and maintaining it for 6 hours, and obtaining a hydrophobically modified glass substrate by evaporation coating;

[0042] (3) The metal mask is processed by femtosecond laser, and the structure of the metal mask after processing in Example 2 is the same as that in Example 1;

[0043] (4) Covering the processed metal mask on the hydrophobic substrate to ensure that the two are in contact, and then treating it with an oxygen plasma treatment machine in an air environment for 120 seconds to obtain a glass substrate with regionalized hydrophilic properties;

[0044] (5) Spraying a silver nanowire-ethanol dispersion with a mass concentration of 0.5 mg / mL onto the surface of the glass substrate, wherein the diameter of the silver nanowire is 30 nm and the length is 25 μm; the spraying rate is 8 μL / s, the spraying distance is maintained at 10 cm, the aperture of the spray gun used is 0.3 mm, and the silver nanowire loading is controlled by a balance to be 40 μg / cm 2 , Figure 8 The silver nanowire conductive network structure in different regions of Example 2. Compared with Example 1, the density of the random network is reduced, but there is no obvious difference in the micro-network structure;

[0045] (6) Disperse 5 g of polyurethane masterbatch in 20 mL of N,N'-dimethylformamide, stir at room temperature for 4 h to ensure that the polyurethane is completely dissolved therein, and then let it stand for 10 min to remove residual bubbles to obtain a polyurethane solution; apply the polyurethane solution on the surface of the substrate, place it in a vacuum oven at 80 °C and dry it for 2 h to remove the residual solvent, and peel the film off the substrate to obtain a flexible conductive film. Fig. 9 The visible light transmittance and infrared emissivity curves of different regions of the film prepared in Example 2 show good visible light transmittance as a whole, and the infrared emissivities of different regions are 0.62 and 0.48 respectively.

[0046] Comparative Example 1

[0047] Comparative Example 1 is different from Example 1 only in that the diameter of the silver nanowires used is 50nm, and the visible light transmittance of different regions of the prepared flexible conductive film at a wavelength of 550nm is higher than 80%, and the infrared emissivity is 0.61 and 0.54 respectively. The smaller infrared emissivity contrast is due to the fact that under the same loading amount, the silver wires with larger diameters have a smaller number density, so the random network produces larger pores, which increases the infrared light transmission.

Claims

1. A method for preparing a flexible conductive film with infrared camouflage effect, characterized in that: The steps include: (1) processing the metal mask plate so that the metal mask plate includes a hollow area, a grid area, and a solid area at the same time; (2) laminating the metal mask plate on the hydrophobic substrate, and performing hydrophilic modification on the hydrophobic substrate to obtain a substrate with different regions corresponding to different hydrophilic properties; (3) spraying a dispersion containing conductive nanowires onto a substrate surface to obtain a conductive network structure with different mesh sizes in different regions of the substrate; (4) Scraping an organic solvent containing a high molecular weight polymer onto the surface of the substrate, and peeling it off after drying to obtain a flexible conductive film.

2. The preparation method according to claim 1, characterized in that: In step (1), a femtosecond laser is used to process the metal mask; wherein the porosity of the grid area is 36-40%.

3. The preparation method according to claim 1, characterized in that: In step (2), the hydrophobic substrate is a glass substrate hydrophobically modified by a silane coupling agent; or the hydrophobic substrate is a PTFE substrate or a PFA substrate.

4. The preparation method according to claim 1, characterized in that: In step (2), the hydrophobic substrate is subjected to hydrophilic modification, specifically, the hydrophobic substrate attached with the metal mask is placed in an oxygen plasma treatment machine for hydrophilic modification.

5. The preparation method according to claim 4, characterized in that: The hydrophilic modification is performed in air, argon or oxygen atmosphere, and the time of the hydrophilic modification is 100 to 120 seconds.

6. The preparation method according to claim 1, characterized in that: In step (3), the conductive nanowire is a silver nanowire or a copper nanowire; the conductive nanowire has a diameter of 25 to 30 nm and a length of 20 to 25 μm.

7. The preparation method according to claim 1, characterized in that: In step (3), the mass concentration of the conductive nanowires in the dispersion containing the conductive nanowires is 0.5 to 1.0 mg / mL; and the dispersion is ethanol or isopropanol.

8. The preparation method according to claim 1, characterized in that: In step (3), during the spraying process, the spraying rate is 8 to 9 μL / s, the spraying distance is maintained at 10 to 12 cm, and the aperture of the spray gun used is 0.3 to 0.35 mm.

9. The preparation method according to claim 1, characterized in that: In step (3), the loading amount of the conductive nanowires on the substrate is 20 to 100 μg / cm 2 .

10. The preparation method according to claim 1, characterized in that: In step (4), the high molecular polymer is cellulose, PDMS or polyurethane; the drying temperature is 60-80° C., and the drying time is 1.5-2 hours.

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