Transparent electromagnetic shielding copper mesh grid, and preparation method and application thereof

Abstract

The application provides a transparent electromagnetic shielding metal copper mesh and a preparation method and application thereof. The preparation method of the transparent electromagnetic shielding metal copper mesh comprises the following steps: coating an ink layer on an electromagnetic shielding substrate, then converting the ink layer into a patterned metal copper mesh deposited on the surface of the electromagnetic shielding substrate by using a femtosecond laser reduction direct writing method, and finally cleaning the ink which is not converted into the metal mesh by using a cleaning solution to obtain the transparent electromagnetic shielding metal copper mesh. The preparation raw materials of the ink include a copper salt, water, a reducing low-carbon alcohol and a nanometer material, and the nanometer material includes at least one of a high-conductivity nanometer material and a high-magnetic-conductivity nanometer material. The transparent electromagnetic shielding metal copper mesh is prepared by using the femtosecond laser reduction direct writing method, the shielding effectiveness is effectively improved under the condition of ensuring the high light transmittance of the electromagnetic shielding material by adjusting the line width and period of the metal copper mesh, the process method is simple and feasible, and the high-efficiency and low-cost manufacturing of the transparent electromagnetic shielding metal copper mesh is realized.

Description

Technical Field

[0001] This invention relates to the field of laser direct writing technology, and in particular to a transparent electromagnetic shielding metal copper grid, its preparation method, and its application. Background Technology

[0002] With the widespread use of electronic devices and wireless communication technologies, electromagnetic radiation is ubiquitous in daily life. In the defense and aerospace fields, the development of electronic warfare and radar stealth technologies places extremely high demands on electromagnetic shielding materials for the shielding and anti-interference of critical equipment and communication systems. Especially in high-density electronic equipment environments, mutual interference between devices can lead to performance degradation or equipment failure. Meanwhile, high optical transparency is required in specific areas such as touchscreens, displays, and aircraft cockpits. Therefore, the design and development of transparent electromagnetic shielding materials has become a key technology for reducing the impact of electromagnetic radiation.

[0003] Metal mesh electromagnetic shielding materials are materials that reduce the impact of electromagnetic waves by blocking or reflecting them. Compared with other types of electromagnetic shielding materials, metal mesh has high conductivity, which can effectively reflect electromagnetic waves and reduce their penetration. At the same time, the structural design of the mesh allows for shielding of multi-frequency electromagnetic waves while maintaining transparency in the visible light band. Therefore, the period, linewidth, and material properties of the metal mesh are important parameters affecting shielding effectiveness.

[0004] Existing manufacturing technologies primarily rely on photolithography-based metal mesh fabrication techniques, such as metal nanomaterial sintering, selective electrodeposition, magnetron sputtering, and metal evaporation. These techniques involve fabricating a conductive micron or nanometer metal mesh on a transparent substrate to shield electromagnetic waves, while the mesh's fine structure allows visible light to pass through. The manufacturing process includes photoresist coating, photomask exposure, development, metal deposition, and photoresist removal. For large-area applications, this process is complex, difficult to process, and costly. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in the prior art. Therefore, one object of this invention is to provide a transparent electromagnetic shielding metal copper mesh, its preparation method, and its application.

[0006] In a first aspect, the present invention provides a method for fabricating a transparent electromagnetic shielding metal copper mesh using femtosecond laser reduction direct writing, the method comprising: An ink layer is coated on an electromagnetic shielding substrate. Then, a femtosecond laser reduction direct writing method is used to transform the ink layer into a patterned metal copper grid deposited on the surface of the electromagnetic shielding substrate. Finally, the ink that has not been transformed into a metal grid is cleaned with a cleaning solution to obtain a transparent electromagnetic shielding metal copper grid. The raw materials for preparing the ink include copper salt, water, reducing low-carbon alcohol, and nanomaterials, wherein the nanomaterials include at least one of high electrical conductivity nanomaterials and high magnetic permeability nanomaterials.

[0007] The method for fabricating transparent electromagnetic shielding copper mesh using femtosecond laser reduction direct writing according to the present invention utilizes a high-energy focused laser beam of a femtosecond laser to reduce metal ions on the substrate surface and directly form the metal on the substrate surface. The femtosecond laser method eliminates the need for a mask, significantly simplifying the manufacturing process by adjusting the laser scanning path. Simultaneously, the highly focused spot of the femtosecond laser enables the fabrication of metal meshes at the micron or even nanoscale, ensuring transparency in the visible light band while meeting the electromagnetic shielding requirements of different frequency bands. Specifically, the femtosecond laser method can balance high transmittance and shielding effectiveness. By designing and optimizing the laser scanning path and laser processing parameters, the linewidth, period, and thickness of the metal mesh are precisely controlled, achieving effective electromagnetic shielding while maintaining high transmittance. Furthermore, the present invention uses the aforementioned ink to prepare the copper mesh, enabling the femtosecond laser to fabricate high-precision metal meshes and further optimizing the electromagnetic shielding material performance. Specifically, adding nanomaterials to the ink can enhance the conductivity and / or permeability of the metal mesh, thereby improving the electromagnetic shielding effect of the copper mesh.

[0008] According to the method for fabricating transparent electromagnetic shielding copper mesh using femtosecond laser reduction direct writing provided by the present invention, the linewidth of the transparent electromagnetic shielding copper mesh is 10-50 μm, and the period is 10-150 μm, preferably 20-40 μm, and the period is 60-120 μm. By ensuring the linewidth and period of the transparent electromagnetic shielding copper mesh are within the above ranges, the electromagnetic shielding effect of the transparent electromagnetic shielding copper mesh is improved while maintaining good light transmittance.

[0009] According to the method for preparing transparent electromagnetic shielding metal copper mesh by femtosecond laser reduction direct writing provided by the present invention, the thickness of the transparent electromagnetic shielding metal copper mesh is 5-15 μm.

[0010] It should be noted that the present invention does not impose a particular limitation on the specific shape of the metal copper mesh; for example, it can be a rectangular metal mesh (such as...). Figure 2 As shown), it can also be a rhomboid metal mesh, or a triangular metal mesh (such as...). Figure 4 (as shown in the image) etc.

[0011] According to the method for fabricating transparent electromagnetic shielding metal copper mesh using femtosecond laser reduction direct writing provided by the present invention, the process parameters of the femtosecond laser reduction direct writing method include: the center pulse width of the femtosecond laser is 10. -15 -10 -12The laser wavelength is 500-1100 nm, the pulse repetition frequency is 100 kHz-1 MHz, the laser power is 0.5-8 W, the spot diameter is 10-300 μm, and the spot movement speed is 1-500 mm / s. Using these femtosecond laser process parameters, copper mesh grids with suitable linewidth, period, and thickness can be fabricated, thereby improving the electromagnetic shielding effect and light transmittance of transparent electromagnetic shielding copper mesh grids.

[0012] In some embodiments of the present invention, the electromagnetic shielding substrate includes one of quartz, glass, polyethylene terephthalate film, polycarbonate, and polyimide film.

[0013] In some embodiments of the present invention, the high-conductivity nanomaterial is selected from at least one of graphite, carbon powder, and metallic silver. Selecting these substances as high-conductivity nanomaterials can enhance the conductivity of the copper mesh.

[0014] In some embodiments of the present invention, the high permeability nanomaterial is selected from at least one of iron(II,III) oxide, spinel ferrite, cobalt oxide, and metallic nickel. Selecting the above substances as high permeability nanomaterials can enhance the permeability of the copper mesh grid, thereby improving the electromagnetic shielding effect of the copper mesh grid.

[0015] According to the method for preparing transparent electromagnetic shielding metal copper grid by femtosecond laser reduction direct writing provided by the present invention, the reducing low-carbon alcohol is selected from at least one of methanol, ethylene glycol, propylene glycol, and glycerol.

[0016] In some embodiments of the present invention, the copper salt is selected from at least one of copper chloride, copper nitrate, and copper formate.

[0017] In some embodiments of the present invention, the volume ratio of water to the reducing lower alcohol is 1:(3-6). Controlling the volume ratio of water to the reducing lower alcohol within the above range can ensure the reducing ability of the material system, while effectively dissolving the metal salt and maintaining the diffusion ability of metal ions.

[0018] In some embodiments of the present invention, the mass ratio of water to copper salt is 1:(1-10). Controlling the mass ratio of water to copper salt within the above range can effectively dissolve the metal salt, release metal ions into the solution to participate in the reaction, and avoid the metal ions being unable to nucleate due to too low a concentration, or the metal salt being incompletely dissolved due to insufficient solvent.

[0019] In some embodiments of the present invention, the mass ratio of the nanomaterial to the copper salt is 1:(1-100). Controlling the mass ratio of the nanomaterial to the copper salt within the above range can enhance the electrical conductivity and / or magnetic permeability of the shielding material, thereby improving the electromagnetic shielding effect of the copper mesh.

[0020] In some embodiments of the present invention, the diameter of the nanomaterial is 20-100 nm. By controlling the diameter of the nanomaterial within the above range, the nanomaterial can be uniformly dispersed, avoiding severe agglomeration due to excessively high surface energy or precipitation due to excessively high density.

[0021] According to the method for preparing transparent electromagnetic shielding metal copper grids by femtosecond laser reduction direct writing provided by the present invention, the preparation method of the ink includes: dissolving the copper salt in a mixed solvent of water and a reducing low-carbon alcohol and heating and stirring, then adding the nanomaterials, mixing and stirring, and then heating to remove water. First, the copper salt is dissolved in a mixed solvent of water and a reducing low-carbon alcohol and heated and stirred to allow the copper salt to fully react with water, obtaining a basic copper salt. Then, the basic copper salt and nanomaterials are mixed and stirred to allow the nanomaterials to be fully dispersed in the solution. Finally, the water is removed by heating to obtain the ink for preparing transparent electromagnetic shielding metal copper grids.

[0022] In some embodiments of the present invention, the heating and stirring temperature is 170-190°C, and the time is 10 min-2 h. By controlling the heating and stirring temperature and time within the above range, the copper salt and water can react fully to obtain basic copper salt, thereby enabling femtosecond laser direct writing to obtain a transparent electromagnetic shielding metal copper grid.

[0023] In some embodiments of the present invention, the heating temperature for removing water is 70-120°C, and the heating time is 2-24 h.

[0024] In a second aspect, the present invention provides a transparent electromagnetic shielding copper mesh grid, which is prepared by the method described above. Therefore, the copper mesh grid exhibits excellent electromagnetic shielding performance and good light transmittance.

[0025] In a third aspect, the present invention proposes the application of the above-mentioned transparent electromagnetic shielding metal copper mesh in the field of electronic radar shielding.

[0026] This invention has at least the following technical effects: (1) The present invention utilizes the femtosecond laser reduction direct writing method to prepare transparent electromagnetic shielding metal copper mesh, which has the characteristics of high flexibility, high adaptability and no need for mask, thus realizing the high-efficiency and low-cost manufacturing of transparent electromagnetic shielding metal copper mesh.

[0027] (2) By adjusting the line width and period of the copper mesh, the present invention can effectively improve the shielding efficiency while ensuring the high light transmittance of the electromagnetic shielding material. The process is simple and feasible. Furthermore, the ink used to prepare the copper mesh can further enhance the conductivity and / or magnetic permeability of the material while ensuring the high conductivity of the copper mesh, thereby effectively improving the electromagnetic shielding efficiency of the copper mesh. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 This is a physical image of the ink provided in Embodiment 1 of the present invention; Figure 2 This is a diagram of the metal copper mesh structure provided in Embodiment 1 of the present invention; Figure 3 This is a physical image of the metal copper mesh grid provided in Embodiment 1 of the present invention; Figure 4 This is a diagram of a metal copper mesh structure according to an embodiment of the present invention. Detailed Implementation

[0030] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. The invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way.

[0031] Example 1 (1) Measure 6 mL of ethylene glycol and 1.5 mL of deionized water and mix them evenly as a mixed solvent. Weigh 4 g of copper nitrate and add it to the mixed solvent until it is completely dissolved to obtain a copper ion solution. (2) Heat the copper ion solution to 170°C for 25 min. After the solution produces bubbles and releases a yellow-brown gas, cool the solution to room temperature to obtain a basic copper nitrate dispersion. (3) Weigh 50 mg of graphene (graphene sheet diameter is 30 nm-40 nm) and add it to basic copper nitrate dispersion. Place the mixed liquid in an ultrasonic vibrator with a frequency of 40 kHz and vibrate for 2 h to obtain a uniformly dispersed suspension. (4) Place the suspension on a magnetic stirring platform with heating function, set the temperature to 120℃, set the magnetic stirring speed to 1000 r / min, heat for 12 h, and finally obtain copper ion ink; (5) Apply the ink evenly to the surface of the polyimide film using a scraper. (6) Set the metal grid line width to 30 μm, the grid period to 200 μm, adjust the focusing spot diameter to 30 μm, and set the scanning path to move linearly along the periodic grid; (7) A femtosecond laser with a pulse width of 1030 nm, a repetition frequency of 100 fs, and a repetition frequency of 100 kHz was used to reduce copper ion ink for direct writing of metal copper grid. The laser power was 3.5 W, the spot diameter was 40 μm, and the scanning speed was 300 mm / s. After processing, the excess metal ion membrane is rinsed off with deionized water and ethanol, and then dried with compressed air.

[0032] in, Figure 1 This is a photograph of the ink used in Example 1; Figure 2 It is the metal mesh structure designed in Example 1. Figure 3 The image shows the actual copper mesh grid produced. The copper mesh grid has an electromagnetic shielding effectiveness of >30 dB in the 8-12 GHz range.

[0033] Example 2 (1) Measure 6 mL of ethylene glycol and 1.5 mL of deionized water and mix them evenly as a mixed solvent. Weigh 4 g of copper nitrate and add it to the mixed solvent until it is completely dissolved to obtain a copper ion solution. (2) Heat the copper ion solution to 170°C for 25 min. After the solution produces bubbles and releases a yellow-brown gas, cool the solution to room temperature to obtain a basic copper nitrate dispersion. (3) Weigh 50 mg of graphene (graphene sheet diameter is 30 nm-40 nm) and add it to basic copper nitrate dispersion. Place the mixed liquid in an ultrasonic vibrator with a frequency of 40 kHz and vibrate for 2 h to obtain a uniformly dispersed suspension. (4) Place the suspension on a magnetic stirring platform with heating function, set the temperature to 120℃, set the magnetic stirring speed to 1000 r / min, heat for 12 h, and finally obtain copper ion ink; (5) Apply the ink evenly to the surface of the polyimide film using a scraper. (6) Set the metal grid line width to 30 μm, the grid period to 400 μm, adjust the focusing spot diameter to 30 μm, and set the scanning path to move linearly along the periodic grid; (7) A femtosecond laser with a pulse width of 1030 nm, a repetition frequency of 100 fs, and a repetition frequency of 100 kHz was used to reduce copper ion ink for direct writing of metal copper grid. The laser power was 3.5 W, the spot diameter was 40 μm, and the scanning speed was 300 mm / s. After processing, the excess metal ion membrane is rinsed off with deionized water and ethanol, and then dried with compressed air.

[0034] Among them, the electromagnetic shielding effectiveness of the copper mesh grid is >20 dB in the 8-12 GHz range.

[0035] Comparative Example 1 (1) Measure 6 mL of ethylene glycol and 1.5 mL of deionized water and mix them evenly as a mixed solvent. Weigh 4 g of copper nitrate and add it to the mixed solvent until it is completely dissolved to obtain a copper ion solution. (2) Heat the copper ion solution to 170°C for 25 min. After the solution produces bubbles and releases a yellow-brown gas, cool the solution to room temperature to obtain a basic copper nitrate dispersion. (3) Place the basic copper nitrate dispersion on a magnetic stirring platform with heating function, set the temperature to 120℃, set the magnetic stirrer speed to 1000 r / min, and heat for 12 h to finally obtain copper ion ink; (4) Apply the ink evenly to the surface of the polyimide film using a scraper; (5) Set the metal grid line width to 30 μm, the grid period to 100 μm, adjust the focusing spot diameter to 30 μm, and set the scanning path to move linearly along the periodic grid. (6) A femtosecond laser with a pulse width of 1030 nm, a repetition frequency of 100 fs, and a repetition frequency of 100 kHz was used to reduce copper ion ink for direct writing of metal copper grid. The laser power was 3.5 W, the spot diameter was 40 μm, and the scanning speed was 300 mm / s.

[0036] Because the ink lacks nanomaterials, the femtosecond laser processing area lacks non-uniform nucleation sites for metal atoms. Furthermore, compared to inks containing nanomaterials, the ink in Comparative Example 1 primarily absorbs laser energy through metal ions. This results in excessively deep laser beam penetration within the ink, leading to overly dispersed laser energy and an inability to meet the required temperature for metal ion reduction. Consequently, the ink used in Comparative Example 1 cannot form a metal mesh.

[0037] Comparative Example 2 (1) Measure 6 mL of ethylene glycol and 1.5 mL of deionized water and mix them evenly as a mixed solvent. Weigh 4 g of copper nitrate and add it to the mixed solvent until it is completely dissolved to obtain a copper ion solution. (2) Weigh 50 mg of graphene and add it to the copper ion solution. Place the mixed liquid in an ultrasonic vibrator with a frequency of 40 kHz and vibrate for 2 h to obtain a uniformly dispersed suspension. (3) Place the suspension on a magnetic stirring platform with heating function, set the temperature to 120℃, set the magnetic stirrer speed to 1000 r / min, heat for 12 h, and finally obtain copper ion ink; (4) Apply the ink evenly to the surface of the polyimide film using a scraper; (5) Set the metal grid line width to 30 μm, the grid period to 100 μm, adjust the focusing spot diameter to 30 μm, and set the scanning path to move linearly along the periodic grid. (6) A femtosecond laser with a pulse width of 1030 nm, a repetition frequency of 100 fs, and a repetition frequency of 100 kHz was used to reduce copper ion ink for direct writing of metal copper grid. The laser power was 3.5 W, the spot diameter was 40 μm, and the scanning speed was 300 mm / s.

[0038] Because the ink production process lacks the crucial step of heating and stirring to prepare basic copper salts, the ink consists of acidic salts completely dissolved in the solvent. Strong acid anions possess strong oxidizing properties. Compared to strong acid-weak base salts, basic salts are less stable and more easily decompose into intermediate products and be reduced to elemental metals under laser heating and reducing solvents. Therefore, the ink used in Comparative Example 2 also failed to produce a metallic copper grid.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fabricating transparent electromagnetic shielding metal copper mesh using femtosecond laser reduction direct writing, characterized in that, include: An ink layer is coated on an electromagnetic shielding substrate. Then, a femtosecond laser reduction direct writing method is used to transform the ink layer into a patterned metal copper grid, which is deposited on the surface of the electromagnetic shielding substrate. Finally, the ink that has not been transformed into a metal grid is cleaned with a cleaning solution to obtain a transparent electromagnetic shielding metal copper grid. The raw materials for preparing the ink include copper salts, water, reducing low-carbon alcohols, and nanomaterials, including high electrical conductivity nanomaterials and high magnetic permeability nanomaterials. The high magnetic permeability nanomaterial is selected from at least one of iron oxide, spinel ferrite, cobalt oxide, and metallic nickel. The method for preparing the ink includes: dissolving the copper salt in a mixed solvent of water and the reducing low-carbon alcohol and heating and stirring, then adding the nanomaterial, mixing and stirring, and then heating to remove water. The volume ratio of water to the reducing low-carbon alcohol is 1:(3-6), the mass ratio of water to the copper salt is 1:(1-10), and the heating and stirring temperature is 170-190℃ for 10 min-2 h.

2. The method according to claim 1, characterized in that, The transparent electromagnetic shielding metal copper mesh has a line width of 10-50 μm and a period of 10-150 μm; And / or, the thickness of the transparent electromagnetic shielding metal copper mesh is 5-15 μm.

3. The method according to claim 2, characterized in that, The transparent electromagnetic shielding metal copper mesh has a linewidth of 20-40 μm and a period of 60-120 μm.

4. The method according to claim 1 or 2, characterized in that, The process parameters of the femtosecond laser reconstruction method include: the center pulse width of the femtosecond laser is 10. -15 -10 -12 The laser wavelength is 500-1100 nm, the pulse repetition frequency is 100 kHz-1 MHz, the laser power is 0.5-8 W, the spot diameter is 10-300 μm, and the spot movement speed is 1-500 mm / s. And / or, the electromagnetic shielding substrate includes one of quartz, glass, polyethylene terephthalate film, polycarbonate, and polyimide film.

5. The method according to claim 1, characterized in that, The high conductivity nanomaterial is selected from at least one of graphite, carbon powder, and metallic silver; And / or, the reducing lower alcohol is selected from at least one of methanol, ethylene glycol, propylene glycol, and glycerol; And / or, the copper salt is selected from at least one of copper chloride, copper nitrate, and copper formate.

6. The method according to claim 1, characterized in that, The mass ratio of the nanomaterial to the copper salt is 1:(1-100). And / or, the nanomaterial has a diameter of 20-100 nm.

7. The method according to claim 1, characterized in that, The heating temperature for removing water is 70-120℃, and the heating time is 2-24 h.

8. A transparent electromagnetic shielding metal copper mesh, characterized in that, It is prepared by any one of the methods described in claims 1-7.

9. The application of the transparent electromagnetic shielding metal copper mesh grid as described in claim 8 in the field of electronic radar shielding.

Images