A broadband electromagnetic shielding coating and preparation method thereof

Abstract

The present invention discloses a broadband electromagnetic shielding coating and a preparation method thereof, and relates to the field of electromagnetic shielding technology. The broadband electromagnetic shielding coating comprises a first conductive layer, a magnetic conductive layer and a second conductive layer; the magnetic conductive layer is located between the first conductive layer and the second conductive layer. The present invention can attenuate electromagnetic waves layer by layer through a three-layer structure, thereby blocking the propagation of electromagnetic waves, and the magnetic conductive layer located in the middle can improve the shielding effect of the material on electromagnetic waves at low frequencies through high magnetic permeability.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic shielding, and in particular to a broadband electromagnetic shielding coating and a preparation method thereof. Background Art

[0002] With the continuous innovation and development of modern industrial technology, in the field of electronic information industry, various types of communication equipment and electronic products are increasing rapidly and becoming more and more popular. However, electronic and electrical equipment are very likely to generate electromagnetic radiation and be susceptible to electromagnetic interference from the outside world while working, thus causing electromagnetic wave pollution in the air and causing serious interference to the normal operation of electronic and electrical equipment. In particular, electromagnetic interference from the outside world to electronic and electrical equipment can cause equipment damage and personal injury in severe cases. Therefore, certain protective measures must be taken, and a functional electromagnetic shielding coating is usually applied to the surface of electronic and electrical equipment.

[0003] The electromagnetic shielding coating after the electromagnetic shielding coating is completely film-formed and cured can block the transmission route of external electromagnetic waves, making it difficult for electromagnetic waves to enter the interior of electronic and electrical equipment, thereby protecting precision equipment. With the rapid development of communication electronics and power supply technology, the sensitivity of equipment is getting higher and higher, and the interference of low-frequency and high-frequency electromagnetic radiation is becoming more and more important. It is becoming more and more important to reduce the impact of low-frequency electromagnetic radiation on weak current equipment. At present, there are more studies on electromagnetic shielding materials in the medium and high frequency bands of 100MHz~18GHz in China, and fewer studies on electromagnetic shielding materials for bands below 100MHz and above 18GHz. Especially at low frequencies, the electromagnetic shielding effect of most materials is not very ideal, so the research and development of low-frequency electromagnetic shielding materials will still be the mainstream of market development in the future. Summary of the invention

[0004] In view of the deficiencies in the above-mentioned background technology, the present invention mainly solves the problem that the electromagnetic shielding coating in the prior art has poor broadband (200kHz~40GHz) and especially low-frequency (200kHz~100MHz) electromagnetic shielding performance. The present invention provides a broadband electromagnetic shielding coating and a preparation method thereof. The coating can attenuate electromagnetic waves layer by layer through a three-layer structure, thereby blocking the propagation of electromagnetic waves, and the magnetic conductive layer in the middle can improve the shielding effect of the material on electromagnetic waves at low frequencies through high magnetic permeability.

[0005] The first object of the present invention is to provide a broadband electromagnetic shielding coating, the broadband electromagnetic shielding coating comprising a first conductive layer, a magnetic conductive layer and a second conductive layer; the magnetic conductive layer is located between the first conductive layer and the second conductive layer;

[0006] The first conductive layer and the second conductive layer are both formed by curing a conductive paste, wherein the conductive paste comprises the following components in parts by weight: 25-55 parts of resin, 3-16 parts of curing agent, 25-125 parts of conductive filler, 0.5-1.5 parts of dispersant, 0.5-1.5 parts of anti-settling agent, and 15-85 parts of solvent;

[0007] The magnetic conductive layer is formed by curing the magnetic conductive slurry, wherein the magnetic conductive slurry comprises the following components in parts by weight: 25 to 55 parts of resin, 3 to 16 parts of curing agent, 25 to 125 parts of magnetic conductive filler, 0.5 to 1.5 parts of dispersant, 0.5 to 1.5 parts of anti-settling agent, and 15 to 85 parts of solvent.

[0008] Preferably, the thickness of the first conductive layer is 15-90 μm; the thickness of the magnetic conductive layer is 150-900 μm; and the thickness of the second conductive layer is 200-450 μm.

[0009] Preferably, the thickness of the first conductive layer is 40-60 μm; the thickness of the magnetic conductive layer is 350-550 μm; and the thickness of the second conductive layer is 250-350 μm.

[0010] Preferably, the conductive filler is one or more of gold powder, silver powder, aluminum powder, copper powder, silver-coated copper powder, carbon black, carbon nanotubes, and carbon fiber; the magnetic filler is one or more of nickel powder, carbonyl iron powder, iron-silicon-aluminum alloy powder, iron-silicon-chromium alloy powder, and iron-nickel alloy powder.

[0011] Preferably, the nickel powder is one or more of spherical nickel powder, flaky nickel powder, block nickel powder and dendritic nickel powder.

[0012] Preferably, the resin is one or more of silicone resin, epoxy resin, acrylic resin, and polyurethane resin;

[0013] The curing agent is one or more of polyamide, polyetheramine and fatty amine;

[0014] Preferably, the dispersant is DISPERBYK-110 dispersant; the anti-settling agent is paraffin and / or organic bentonite; and the solvent is one or more of toluene, xylene, acetone, butanone, isopropanol, propylene glycol methyl ether acetate, and n-butanol.

[0015] The second object of the present invention is to provide a method for preparing a broadband electromagnetic shielding coating, comprising the following steps:

[0016] Resin, curing agent, conductive filler, dispersant, anti-settling agent and solvent are weighed in parts by weight, and then the weighed raw materials of each component are mixed and stirred evenly using a homogenizer to obtain conductive paste I;

[0017] Weigh the resin, curing agent, magnetic conductive filler, dispersant, anti-settling agent and solvent according to weight, then mix the weighed raw materials of each component, and stir them evenly using a homogenizer to obtain a magnetic conductive slurry;

[0018] Resin, curing agent, conductive filler, dispersant, anti-settling agent and solvent are weighed in parts by weight, and then the weighed raw materials of each component are mixed and stirred evenly using a homogenizer to obtain conductive paste II;

[0019] The conductive paste I is coated on the surface of the substrate by using an air compression spraying process, and then heated and cured in an oven to obtain a first conductive layer of the electromagnetic shielding material coating;

[0020] Then, the magnetic conductive slurry is sprayed on the first conductive layer, and then heated and cured in an oven to obtain a magnetic conductive layer of the electromagnetic shielding material coating;

[0021] Finally, the conductive slurry II is sprayed on the basis of the magnetic conductive layer, and then heated and cured in an oven to obtain the second conductive layer of the electromagnetic shielding material coating, that is, the broadband electromagnetic shielding coating.

[0022] The preferred compression spraying process parameters are: spraying pressure of 0.2~0.8MPa, spraying distance of 10~60cm, spraying angle of 80~100°, and spray gun moving speed of 15~45cm / s.

[0023] The third object of the present invention is to provide a coating for use in broadband electromagnetic shielding.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The electromagnetic shielding coating prepared by the present invention is a three-layer structural material, including a first conductive layer, a magnetic conductive layer and a second conductive layer, wherein the magnetic conductive layer is located between the first conductive layer and the second conductive layer. In the present invention, the three-layer structure can attenuate the electromagnetic waves layer by layer, thereby blocking the propagation of the electromagnetic waves, and the magnetic conductive layer located in the middle layer can improve the shielding effect of the overall coating material on electromagnetic waves at low frequencies by shunting the magnetic field. The three-layer structural design can construct a Fabry-Perot cavity between the upper and lower conductive layers, significantly extend the transmission path of the internal electromagnetic waves in the cavity at low frequencies, increase the effect of the electromagnetic waves and the low-frequency magnetic fillers in the cavity, thereby achieving effective shielding of low-frequency electromagnetic waves. Compared with existing electromagnetic shielding coating materials, the electromagnetic shielding coating material provided by the present invention can meet the use of a wide frequency band of 200kHz~40GHz, and at the same time has the characteristics of excellent electromagnetic shielding effectiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a structural diagram of a broadband electromagnetic shielding coating.

[0027] Among them, 1 is the first conductive layer, 2 is the magnetic conductive layer, and 3 is the second conductive layer. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0029] The purpose of the present invention is to provide a broadband electromagnetic shielding coating and a preparation method thereof, in view of the fact that in the prior art, there have been more studies on electromagnetic shielding materials in the mid-to-high frequency bands of 100 MHz ~ 18 GHz, while there have been fewer studies on electromagnetic shielding materials in the bands below 100 MHz and above 18 GHz, especially at low frequencies, the electromagnetic shielding effects of most materials are not very ideal.

[0030] The specific principle of the three-layer structure in the present invention to construct a Fabry-Perot cavity to enhance the transmission path of low-frequency magnetic field electromagnetic waves is as follows:

[0031] First, the following assumptions are made: the conductive layer is a lossy dielectric layer; the impedance of the magnetic layer is much smaller than that of the conductive layer, and can be approximately regarded as a lossless dielectric layer. For a composite structure of a single conductive layer and a magnetic layer, such as a conductive layer / magnetic layer / substrate structure or a magnetic layer / conductive layer / substrate structure, the reflection effect of the magnetic layer on electromagnetic waves can be ignored, and the transmittance of the coating is:

[0032]

[0033] In the formula, , ; Z0, Z1, Z2 are air impedance, lossy dielectric layer (conductive layer) impedance and magnetic layer impedance respectively; is the transmission coefficient of the lossy dielectric layer (conductive layer);

[0034] is the skin depth of the conductive layer, where oh is the electromagnetic wave frequency, s is the conductivity of the conductive layer, m is the magnetic permeability of the conductive layer, m 0 is the vacuum permeability, d is the thickness of the conductive layer. The thickness of the conductive layer in the present invention is greater than its skin depth, and the impedance of the conductive layer is much greater than the impedance of the magnetic layer and the air impedance, so it can be approximately regarded as Z2≈Z0, and the above formula can be simplified to:

[0035]

[0036] Where Rs is the resistance of the conductive layer. The above formula shows that for a composite structure of a single conductive layer and a magnetic conductive layer, such as a conductive layer / magnetic conductive layer / substrate structure or a magnetic conductive layer / conductive layer / substrate structure, the transmission coefficient is independent of frequency. The reduction in shielding effectiveness caused by an increase in the thickness of the conductive layer is only due to a reduction in the coating resistance.

[0037] For the conductive / magnetic / conductive structure proposed in the present invention, a magnetic conductive layer of limited thickness is located between two lossy dielectric layers (conductive layers). According to the effective medium theory, electromagnetic waves will be reflected, absorbed, transmitted, and reflected multiple times between the conductive layers. The transmission coefficient of this structure can be approximately expressed as:

[0038]

[0039] In the formula, is the transmission coefficient of the magnetic permeability layer, e 0 and m 0 are the vacuum dielectric constant and vacuum magnetic permeability, e 2 and m 2 are the dielectric constant and magnetic permeability of the magnetic layer, oh The frequency of electromagnetic waves i is an imaginary number, and L is the physical thickness of the magnetic conductive layer. is the reflection factor of the lossy medium surface, which can be calculated using the following formula:

[0040]

[0041] From the transmission coefficient of the conductive / magnetic / conductive structure, it can be seen that its phase term It is determined by the frequency of electromagnetic waves and the thickness of the magnetic layer, so efficient shielding of electromagnetic waves in a specific band can be achieved by controlling the thickness of the magnetic layer. In addition, the higher the magnetic permeability of the magnetic layer, the stronger the ability to absorb and lose electromagnetic waves reflected multiple times between the magnetic layer and the conductive layer, the lower the transmission coefficient, and the higher the shielding effectiveness.

[0042] To achieve the above purpose, see Figure 1 As shown, the present invention provides a broadband electromagnetic shielding coating, which includes a first conductive layer 1, a magnetic conductive layer 2 and a second conductive layer 3; the magnetic conductive layer 2 is located between the first conductive layer 1 and the second conductive layer 3;

[0043] The first conductive layer 1 and the second conductive layer 3 are both formed by curing a conductive paste, wherein the conductive paste comprises the following components in parts by weight: 25-55 parts of resin, 3-16 parts of curing agent, 25-125 parts of conductive filler, 0.5-1.5 parts of dispersant, 0.5-1.5 parts of anti-settling agent, and 15-85 parts of solvent;

[0044] The magnetic conductive layer 2 is formed by curing the magnetic conductive slurry, wherein the magnetic conductive slurry comprises the following components in parts by weight: 25-55 parts of resin, 3-16 parts of curing agent, 25-125 parts of magnetic conductive filler, 0.5-1.5 parts of dispersant, 0.5-1.5 parts of anti-settling agent, and 15-85 parts of solvent.

[0045] The conductive filler and magnetic conductive filler provided by the present invention exhibit excellent magnetic permeability and electrical conductivity characteristics, which are crucial to ensuring the effectiveness of the electromagnetic shielding coating. In the present invention, the selected resin exhibits excellent wetting properties for various electromagnetic shielding fillers. During the coating curing process, the resin can be spread on the surface of the electromagnetic shielding filler to form an extremely thin nanoscale resin layer, which not only ensures the effective bonding between the electromagnetic shielding fillers, but also promotes the formation of a conductive circuit or a magnetic conductive circuit between the filler particles through the tunnel effect or magnetic exchange effect. At the same time, the curing agent exhibits good reactivity, which helps to reduce the curing temperature of the resin, accelerate the curing process, and increase the crosslinking density of the resin. In addition, the dispersant and the anti-settling agent promote the uniform distribution of the electromagnetic shielding filler inside the resin through the electrostatic effect and the steric hindrance effect, and enhance the wetting effect of the resin on the filler. The solvent plays the role of diluting the coating, ensuring the process feasibility of the coating, and by optimizing the rheological properties of the coating, the directional arrangement of the electromagnetic shielding filler inside the coating is achieved, thereby further improving the electrical conductivity and magnetic permeability of the coating and enhancing its shielding effectiveness.

[0046] Wherein, the thickness of the first conductive layer is 15-90 μm; the thickness of the magnetic conductive layer is 150-900 μm; and the thickness of the second conductive layer is 200-450 μm.

[0047] The thickness of the first conductive layer is 40-60 μm; the thickness of the magnetic conductive layer is 350-550 μm; and the thickness of the second conductive layer is 250-350 μm.

[0048] The conductive filler is one or more of gold powder, silver powder, aluminum powder, copper powder, silver-coated copper powder, carbon black, carbon nanotubes, and carbon fibers; wherein the D50 of each type of conductive filler is: gold powder-7μm; silver powder-6.4μm; aluminum powder-24μm; copper powder-26μm; silver-coated copper powder-28μm; carbon black-45μm; carbon nanotube (length)-2μm; carbon fiber-1.5mm. Among them, gold powder, silver powder, aluminum powder, copper powder, and silver-coated copper powder were purchased from Guangzhou Yinfeng Metal Technology Co., Ltd.; carbon black, carbon nanotubes, and carbon fibers were purchased from Shanghai Lishuo Composite Materials Technology Co., Ltd.

[0049] The magnetic filler is one or more of nickel powder, carbonyl iron powder, sendustine aluminum alloy powder, iron silicon chromium alloy powder, and iron nickel alloy powder. The D50 of each type of magnetic filler is: flaky nickel powder-25μm; spherical nickel powder-20μm; blocky nickel powder-15μm; dendritic nickel powder (length) 60μm; carbonyl iron powder-2μm; sendustine aluminum powder-21μm; iron silicon chromium powder-28μm; iron nickel alloy-8.5μm. Spherical nickel powder, flaky nickel powder, blocky nickel powder, and dendritic nickel powder are all purchased from Ningbo Jinlei Nanomaterial Technology Co., Ltd.; carbonyl iron powder, sendustine aluminum alloy powder, iron silicon chromium alloy powder, and iron nickel alloy powder are all purchased from Ganzhou Blue Ocean New Materials Co., Ltd.

[0050] The nickel powder is one or more of spherical nickel powder, flaky nickel powder, block nickel powder and dendritic nickel powder.

[0051] The resin is one or more of silicone resin, epoxy resin, acrylic resin, and polyurethane resin;

[0052] The curing agent is one or more of polyamide, polyetheramine and fatty amine;

[0053] The dispersant is DISPERBYK-110 dispersant; the anti-settling agent is paraffin and / or organic bentonite; the solvent is one or more of toluene, xylene, acetone, butanone, isopropanol, propylene glycol methyl ether acetate, and n-butanol.

[0054] A second aspect of the present invention provides a method for preparing a broadband electromagnetic shielding coating, comprising the following steps:

[0055] Resin, curing agent, conductive filler, dispersant, anti-settling agent and solvent are weighed in parts by weight, and then the weighed raw materials of each component are mixed and stirred evenly using a homogenizer to obtain conductive paste I;

[0056] Weigh the resin, curing agent, magnetic conductive filler, dispersant, anti-settling agent and solvent according to weight, then mix the weighed raw materials of each component, and stir them evenly using a homogenizer to obtain a magnetic conductive slurry;

[0057] Resin, curing agent, conductive filler, dispersant, anti-settling agent and solvent are weighed in parts by weight, and then the weighed raw materials of each component are mixed and stirred evenly using a homogenizer to obtain conductive paste II;

[0058] The conductive paste I is coated on the surface of the substrate using an air compression spraying process, and then heated and cured in an oven to obtain a first conductive layer of the electromagnetic shielding material coating.

[0059] Then, the magnetic conductive slurry is sprayed on the basis of the first conductive layer, and then heated and cured in an oven to obtain a magnetic conductive layer of the electromagnetic shielding material coating.

[0060] Finally, the conductive slurry II is sprayed on the basis of the magnetic conductive layer, and then heated and cured in an oven to obtain the second conductive layer of the electromagnetic shielding material coating, that is, the broadband electromagnetic shielding coating.

[0061] Among them, the compression spraying process parameters are: spraying pressure is 0.2~0.8MPa, spraying distance is 10~60cm, spraying angle is 80~100°, and spray gun moving speed is 15~45cm / s.

[0062] It should be noted that the key to influencing the performance of electromagnetic shielding coatings is to enhance the electromagnetic interaction between electromagnetic shielding fillers, which is reflected in the two key factors in the preparation of coatings: ensuring the uniformity of the coating and improving the density of the coating. The present invention first uses mean stirring and dispersion to adsorb the dispersant and the anti-settling agent on the surface of the electromagnetic shielding filler, and uses the electrostatic effect and steric hindrance effect of the two to obtain a stably suspended slurry; secondly, the "wet spray drying" process is used to solidify after any layer of spraying is completed, so that the solvent inside the coating evaporates and leaves, and the next layer of paint film can fill the gap left by the evaporation of the previous layer of solvent, which enhances the density of the coating on the one hand, and reduces the average spacing between the electromagnetic shielding fillers on the other hand, thereby improving the electromagnetic shielding effectiveness of the coating.

[0063] A third aspect of the present invention provides an application of the above coating in broadband electromagnetic shielding.

[0064] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0065] Example

[0066] A method for preparing a broadband electromagnetic shielding coating comprises the following steps:

[0067] Step 1. Preparation of substrate

[0068] An epoxy plastic plate with a thickness of 0.5 mm was used as the substrate of the coating material, and the surface of the substrate was cleaned with alcohol to ensure that there were no dust particles on the surface of the substrate.

[0069] Step 2. Prepare slurry

[0070] Step 2.1 Preparation of conductive paste I

[0071] Resin, curing agent, conductive filler, dispersant, anti-settling agent and solvent are weighed in parts by weight, and then the weighed raw materials of each component are mixed and stirred evenly using a homogenizer to obtain conductive paste I;

[0072] Among them, the stirring speed of the homogenizer is 500~3000r / min, and the stirring time is 5~20min.

[0073] Step 2.2 Preparation of magnetic slurry

[0074] Weigh the resin, curing agent, magnetic conductive filler, dispersant, anti-settling agent and solvent according to weight, then mix the weighed raw materials of each component, and stir them evenly using a homogenizer to obtain a magnetic conductive slurry;

[0075] Among them, the stirring speed of the homogenizer is 500~3000r / min, and the stirring time is 5~20min.

[0076] Step 2.3 Preparation of conductive paste II

[0077] Resin, curing agent, conductive filler, dispersant, anti-settling agent and solvent are weighed in parts by weight, and then the weighed raw materials of each component are mixed and stirred evenly using a homogenizer to obtain conductive paste II.

[0078] Among them, the stirring speed of the homogenizer is 500~3000r / min, and the stirring time is 5~20min.

[0079] Step 3. Preparation of coating

[0080] Firstly, the conductive paste I is coated on the surface of the epoxy plastic substrate by using an air compression spraying process, and then heated and cured in an oven to obtain a first conductive layer of the electromagnetic shielding material coating.

[0081] Then, the magnetic conductive slurry is sprayed on the basis of the first conductive layer, and then heated and cured in an oven to obtain a magnetic conductive layer of the electromagnetic shielding material coating.

[0082] Finally, the conductive slurry II is sprayed on the basis of the magnetic conductive layer, and then heated and cured in an oven to obtain the second conductive layer of the electromagnetic shielding material coating, thereby finally obtaining the electromagnetic shielding coating material.

[0083] The compression spraying process parameters are: spraying pressure of 0.2~0.8MPa, spraying distance of 10~60cm, spraying angle of 80~100°, and spray gun moving speed of 15~45cm / s.

[0084] The specific composition ratios of each embodiment are shown in Table 1 below.

[0085] Table 1 Composition of electromagnetic shielding coating in each embodiment

[0086]

[0087] The technical parameters of each embodiment are shown in Table 2 below.

[0088] Table 2 Process parameters of each embodiment

[0089]

[0090] The electromagnetic shielding effectiveness test results of the coatings prepared in various embodiments are shown in Table 3.

[0091] Table 3 Electromagnetic shielding effectiveness test results of various embodiments

[0092]

[0093] It can be seen from Table 3 that the electromagnetic shielding coating material prepared by the present invention has an excellent shielding effect on electromagnetic waves at 10MHz~40GHz, and still has a certain shielding ability at a low frequency of 200KHz~10MHz, so the electromagnetic shielding coating material prepared by the present invention can be used in a wide frequency range. In summary, it is explained that the electromagnetic shielding coating material prepared by the present invention can not only meet the requirements of use in a wide frequency range, but also has the characteristics of high shielding effectiveness.

[0094] In addition, two groups of comparative examples are used to illustrate the enhancement effect of the Fabry-Perot cavity constructed by the three-layer structure of the first conductive layer / magnetic conductive layer / second conductive layer in the present invention on the low-frequency electromagnetic shielding effectiveness, as follows:

[0095] Comparative Example 1

[0096] A magnetic conductive coating, comprising:

[0097] A magnetic conductive slurry was prepared according to the composition ratio of Example 1 in Table 1, and a magnetic conductive coating with a thickness of 150 μm (the thickness of the magnetic conductive layer in Example 1) was prepared according to the construction process of Example 1 in Table 2.

[0098] Comparative Example 2

[0099] A conductive coating comprising:

[0100] A conductive paste was prepared using the components of the first conductive layer of Example 1 in Table 1, and a conductive coating with a thickness of 215 μm was prepared according to the construction process of Example 1 in Table 2. It should be noted that the thickness of 215 μm is the sum of the thicknesses of the first conductive layer and the second conductive layer in Example 1.

[0101] Table 4 Electromagnetic shielding effectiveness test results of Example 1, Comparative Example 1 and Comparative Example 2

[0102]

[0103] It can be seen from Table 4 that the electromagnetic shielding effectiveness of Comparative Examples 1 and 2 is lower than that of Example 1. The sum of the electromagnetic shielding effectiveness of Comparative Examples 1 and 2 has no significant difference from that of Example 1 in the high frequency band (>100MHz), while the electromagnetic shielding effectiveness in the range of 200kHz~100MHz is lower than that of Example 1. It can be seen that the Fabry-Perot cavity constructed in Example 1 significantly enhances the multiple reflections of electromagnetic waves between the first conductive layer and the second conductive layer, and utilizes the magnetic conductive layer to achieve efficient absorption of this part of the electromagnetic waves.

[0104] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A broadband electromagnetic shielding coating, characterized in that: The broadband electromagnetic shielding coating is composed of a first conductive layer, a magnetic conductive layer and a second conductive layer; the magnetic conductive layer is located between the first conductive layer and the second conductive layer; The first conductive layer and the second conductive layer are both formed by curing a conductive paste, wherein the conductive paste is composed of the following components in parts by weight: 25-55 parts of resin, 3-16 parts of curing agent, 25-125 parts of conductive filler, 0.5-1.5 parts of dispersant, 0.5-1.5 parts of anti-settling agent, and 15-85 parts of solvent; The magnetic conductive layer is formed by curing the magnetic conductive slurry, wherein the magnetic conductive slurry is composed of the following components in parts by weight: 25-55 parts of resin, 3-16 parts of curing agent, 25-125 parts of magnetic conductive filler, 0.5-1.5 parts of dispersant, 0.5-1.5 parts of anti-settling agent, and 15-85 parts of solvent; The conductive filler is one or more of gold powder, silver powder, aluminum powder, copper powder, silver-coated copper powder, carbon black, carbon nanotubes, and carbon fibers; The magnetic conductive filler is one or more of nickel powder, carbonyl iron powder, iron-silicon-aluminum alloy powder, iron-silicon-chromium alloy powder, and iron-nickel alloy powder; The resin is one or more of silicone resin, epoxy resin, acrylic resin, and polyurethane resin; The curing agent is one or more of polyamide, polyetheramine and fatty amine; The dispersant is DISPERBYK-110 dispersant; The anti-settling agent is paraffin and / or organic bentonite; The solvent is one or more of toluene, xylene, acetone, butanone, isopropanol, propylene glycol methyl ether acetate, and n-butanol; The thickness of the first conductive layer is 15-90 μm; the thickness of the magnetic conductive layer is 150-900 μm; and the thickness of the second conductive layer is 200-450 μm.

2. The broadband electromagnetic shielding coating according to claim 1, characterized in that: The thickness of the first conductive layer is 40-60 μm; the thickness of the magnetic conductive layer is 350-550 μm; and the thickness of the second conductive layer is 250-350 μm.

3. The broadband electromagnetic shielding coating according to claim 1, characterized in that: The nickel powder is one or more of spherical nickel powder, flaky nickel powder, block nickel powder and dendritic nickel powder.

4. A method for preparing a broadband electromagnetic shielding coating according to any one of claims 1 to 3, characterized in that: The following steps are involved: Resin, curing agent, conductive filler, dispersant, anti-settling agent and solvent are weighed in parts by weight, and then the weighed raw materials of each component are mixed and stirred evenly using a homogenizer to obtain conductive paste I; Weigh the resin, curing agent, magnetic conductive filler, dispersant, anti-settling agent and solvent according to weight, then mix the weighed raw materials of each component, and stir them evenly using a homogenizer to obtain a magnetic conductive slurry; Resin, curing agent, conductive filler, dispersant, anti-settling agent and solvent are weighed in parts by weight, and then the weighed raw materials of each component are mixed and stirred evenly using a homogenizer to obtain conductive paste II; The conductive paste I is coated on the surface of the substrate by using an air compression spraying process, and then heated and cured in an oven to obtain a first conductive layer of the electromagnetic shielding coating; Then, the magnetic conductive slurry is sprayed on the first conductive layer, and then heated and cured in an oven to obtain a magnetic conductive layer of the electromagnetic shielding coating; Finally, the conductive slurry II is sprayed on the basis of the magnetic conductive layer, and then heated and cured in an oven to obtain the second conductive layer of the electromagnetic shielding coating, that is, the broadband electromagnetic shielding coating.

5. The method for preparing a broadband electromagnetic shielding coating according to claim 4, characterized in that: The process parameters of air compression spraying are: spraying pressure is 0.2~0.8MPa, spraying distance is 10~60cm, spraying angle is 80~100°, and spray gun moving speed is 15~45cm / s.

6. Use of the coating according to any one of claims 1 to 3 in broadband electromagnetic shielding.

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