Heat-conducting electromagnetic shielding multilayer composite film and preparation method and application thereof

Abstract

The invention discloses a heat-conducting electromagnetic shielding multilayer composite film as well as a preparation method and application thereof. The heat-conducting electromagnetic shielding multilayer composite film comprises an insulating heat-conducting layer, a magnetic shielding layer, a conductive shielding layer and an insulating heat-conducting layer which are sequentially stacked, the insulating heat-conducting layer is a cellulose film containing heat-conducting filler, and the magnetic shielding layer is a cellulose film containing magnetic filler and expanded microspheres. And the conductive shielding layer is a cellulose membrane containing conductive filler and expanded microspheres. The heat-conducting electromagnetic shielding multilayer composite film has the advantages of excellent in-plane heat conduction performance, excellent electromagnetic shielding performance, high mechanical strength, small thickness and the like, the preparation process is simple, convenient, green and environment-friendly, and the heat-conducting electromagnetic shielding multilayer composite film has very wide application prospects in the fields of 5G communication, consumer electronics, new energy batteries, national defense and military industry and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic protection, and in particular to a heat-conductive electromagnetic shielding multilayer composite film and a preparation method and application thereof. Background Art

[0002] With the rapid development of the electronics and communications industries, various electronic communications products have gradually tended to be miniaturized, integrated, and high-power, which has brought many conveniences to people's production and life. However, it has also brought problems such as poor heat dissipation of electronic components and communication equipment and electromagnetic wave interference, which ultimately lead to a decrease in the operating stability of electronic equipment and a shortened service life. In addition, a large amount of electromagnetic radiation in the living environment can also cause potential harm to human health. Electromagnetic shielding film is an electronic material film used to reduce electromagnetic interference or electromagnetic radiation, which has a very broad application prospect in the field of electromagnetic protection. However, the existing electromagnetic shielding film mainly relies on reflective electromagnetic shielding to play a role, and does not directly absorb and eliminate electromagnetic radiation, which is easy to cause secondary pollution of electromagnetic waves and cannot fully meet the actual application requirements.

[0003] Therefore, it is of great significance to develop an absorption-type electromagnetic shielding film with excellent thermal conductivity and electromagnetic shielding performance. Summary of the invention

[0004] The object of the present invention is to provide a heat-conducting electromagnetic shielding multilayer composite film and a preparation method and application thereof.

[0005] The technical solution adopted by the present invention is:

[0006] A heat-conductive electromagnetic shielding multilayer composite film, which comprises an insulating heat-conductive layer, a magnetic shielding layer, a conductive shielding layer and an insulating heat-conductive layer stacked in sequence; the insulating heat-conductive layer is a cellulose film containing a heat-conductive filler; the magnetic shielding layer is a cellulose film containing a magnetic filler and expanded microspheres; the conductive shielding layer is a cellulose film containing a conductive filler and expanded microspheres.

[0007] Preferably, the thermally conductive electromagnetic shielding multilayer composite film comprises the following components in percentage by mass:

[0008] Thermal conductive filler: 5% to 30%;

[0009] Conductive filler: 10% to 25%;

[0010] Magnetic filler: 20%~60%;

[0011] Expanded microspheres: 15% to 30%;

[0012] Cellulose: 10%~30%.

[0013] Further preferably, the thermally conductive electromagnetic shielding multilayer composite film comprises the following components in percentage by mass:

[0014] Thermal conductive filler: 10% to 20%;

[0015] Conductive filler: 15% to 25%;

[0016] Magnetic filler: 20%~35%;

[0017] Expanded microspheres: 15% to 25%;

[0018] Cellulose: 10%~25%.

[0019] Preferably, the thermally conductive filler is at least one of hexagonal boron nitride powder, carbon fiber powder, and aluminum oxide powder.

[0020] Preferably, the particle size of the thermally conductive filler is 1 μm to 100 μm.

[0021] Preferably, the conductive filler is at least one of graphene powder, MXene powder and fullerene powder.

[0022] Preferably, the MXene powder is at least one of titanium carbide MXene powder, zirconium carbide MXene powder, and manganese carbide MXene powder.

[0023] Preferably, the particle size of the conductive filler is 1 μm to 10 μm.

[0024] Preferably, the magnetic filler is at least one of ferroferric oxide powder, sendust powder and carbonyl iron powder.

[0025] Preferably, the particle size of the magnetic filler is 1 μm to 50 μm.

[0026] Preferably, the expanded microspheres are hollow polyacrylate microspheres.

[0027] Preferably, the particle size of the polyacrylate hollow microspheres is 6 μm to 15 μm, the expansion temperature is 80° C. to 135° C., and the expansion multiple is 2 to 5 times.

[0028] Preferably, the expanded microspheres have been subjected to plasma surface modification treatment.

[0029] Further preferably, the expanded microspheres are subjected to a surface modification treatment using peroxide plasma.

[0030] Preferably, the cellulose is at least one of carboxymethyl cellulose, bacterial cellulose and hydroxypropyl methyl cellulose.

[0031] Preferably, the mass ratio of the thermally conductive filler to the cellulose in the insulating thermally conductive layer is 1-5:1.

[0032] Preferably, the insulating heat-conducting layer has a thickness of 10 μm to 100 μm.

[0033] Preferably, the mass ratio of the magnetic filler, the expanded microspheres and the cellulose in the magnetic shielding layer is 2-7:2-5:1.

[0034] Preferably, the thickness of the magnetic shielding layer is 20 μm to 150 μm.

[0035] Preferably, the mass ratio of the conductive filler, the expanded microspheres and the cellulose in the conductive shielding layer is 10:1-5:1-5.

[0036] Preferably, the thickness of the conductive shielding layer is 10 μm to 70 μm.

[0037] A method for preparing the thermally conductive electromagnetic shielding multilayer composite film as described above comprises the following steps:

[0038] 1) using plasma to perform surface treatment on expanded microspheres to obtain surface-modified expanded microspheres;

[0039] 2) adding water to disperse the conductive filler, the surface modified expanded microspheres and the cellulose to form a dispersion, and then filtering to form a conductive shielding layer, and then adding water to disperse the magnetic filler, the surface modified expanded microspheres and the cellulose to form a dispersion, and then coating it on one side of the conductive shielding layer and drying to form a magnetic shielding layer, thereby obtaining a conductive shielding layer-magnetic shielding layer composite structure;

[0040] Alternatively, the magnetic filler, the surface modified expanded microspheres and the cellulose are dispersed in water to form a dispersion, and then filtered to form a magnetic shielding layer, and then the conductive filler, the surface modified expanded microspheres and the cellulose are dispersed in water to form a dispersion, and then coated on one side of the magnetic shielding layer and dried to form a conductive shielding layer, thereby obtaining a conductive shielding layer-magnetic shielding layer composite structure;

[0041] 3) The thermal conductive filler and cellulose are dispersed in water to prepare a dispersion, which is then coated on both sides of the conductive shielding layer-magnetic shielding layer composite structure and dried to form an insulating thermal conductive layer, which is then heat treated to obtain a thermal conductive electromagnetic shielding multilayer composite film.

[0042] Preferably, a method for preparing the thermally conductive electromagnetic shielding multilayer composite film as described above comprises the following steps:

[0043] 1) using plasma to perform surface treatment on expanded microspheres to obtain surface-modified expanded microspheres;

[0044] 2) adding water to the conductive filler, the surface modified expanded microspheres and the cellulose, stirring and dispersing them, and ultrasonically dispersing them to prepare a dispersion liquid, and then filtering and drying them to form a conductive shielding layer, and then adding water to the magnetic filler, the surface modified expanded microspheres and the cellulose, stirring and dispersing them to prepare a dispersion liquid, and then coating them on one side of the conductive shielding layer and drying them to form a magnetic shielding layer, thereby obtaining a conductive shielding layer-magnetic shielding layer composite structure;

[0045] Alternatively, the magnetic filler, the surface modified expanded microspheres and the cellulose are added with water, stirred and dispersed to form a dispersion, and then filtered and dried to form a magnetic shielding layer, and then the conductive filler, the surface modified expanded microspheres and the cellulose are added with water, stirred and dispersed and ultrasonically dispersed to form a dispersion, and then coated on one side of the magnetic shielding layer and dried to form a conductive shielding layer, thereby obtaining a conductive shielding layer-magnetic shielding layer composite structure;

[0046] 3) Add water to the thermal conductive filler and cellulose, stir and disperse them to form a dispersion, then coat them on both sides of the conductive shielding layer-magnetic shielding layer composite structure, dry them to form an insulating thermal conductive layer, and then perform heat treatment to obtain a thermal conductive electromagnetic shielding multilayer composite film.

[0047] Preferably, the plasma in step 1) is oxygen plasma.

[0048] Preferably, the surface treatment time in step 1) is 10 min to 60 min.

[0049] Preferably, the stirring and dispersing in step 2) is carried out at a stirring speed of 300 rpm to 800 rpm, and the stirring and dispersing time is 30 min to 180 min.

[0050] Preferably, the coating method in step 2) is spin coating.

[0051] Preferably, the spin coating is performed at a spin coating speed of 1000 rpm to 3000 rpm, and the spin coating time is 5 s to 30 s.

[0052] Preferably, the drying in step 2) is carried out at a temperature of 40° C. to 100° C., and the drying time is 10 min to 180 min.

[0053] Preferably, the stirring and dispersing in step 3) is carried out at a stirring speed of 300 rpm to 800 rpm, and the stirring and dispersing time is 30 min to 180 min.

[0054] Preferably, the coating method in step 3) is spin coating.

[0055] Preferably, the spin coating is performed at a spin coating speed of 1000 rpm to 3000 rpm, and the spin coating time is 5 s to 30 s.

[0056] Preferably, the drying in step 3) is carried out at a temperature of 40° C. to 100° C., and the drying time is 10 min to 180 min.

[0057] Preferably, the heat treatment in step 3) is carried out at a temperature of 60° C. to 140° C., and the treatment time is 20 min to 100 min.

[0058] Further preferably, the heat treatment in step 3) is carried out at a temperature of 80°C to 120°C, and the treatment time is 30min to 60min.

[0059] An electronic device comprises the above-mentioned heat-conductive electromagnetic shielding multi-layer composite film.

[0060] Preferably, the electronic device is a communication device.

[0061] The beneficial effects of the present invention are: the thermally conductive electromagnetic shielding multi-layer composite film of the present invention has the advantages of excellent in-plane thermal conductivity, excellent electromagnetic shielding performance, high mechanical strength, small thickness, etc., and its preparation process is simple and green and environmentally friendly. It has very broad application prospects in 5G communications, consumer electronics, new energy batteries, national defense and military industries and other fields.

[0062] Specifically:

[0063] 1) The heat-conductive electromagnetic shielding multilayer composite film of the present invention contains expanded microspheres, and the particle size of the expanded microspheres can be regulated by adjusting the temperature. The volume of the expanded microspheres increases, and large pores can be formed inside the composite film, thereby enhancing the multiple reflections of electromagnetic waves inside the composite film, thereby transforming the electromagnetic shielding mechanism from reflective shielding to absorptive shielding, and realizing the regulation of the electromagnetic shielding type by temperature;

[0064] 2) The thermally conductive electromagnetic shielding multilayer composite film of the present invention adopts a multilayer structure design. Different layers can respectively realize the functions of conductive shielding, magnetic shielding and in-plane thermal conductivity. By changing the composition and dosage of the functional filler, the in-plane thermal conductivity and electromagnetic shielding efficiency of the composite film can be adjusted in a large range. The in-plane thermal conductivity can reach up to 6.22 W·m -1 ·K -1 , electromagnetic shielding effectiveness (EMI SE) can reach up to 45.0dB;

[0065] 3) The preparation process of the thermal conductive electromagnetic shielding multilayer composite film of the present invention is simple, has no VOC emissions throughout the process, is green and environmentally friendly, and is suitable for large-scale industrial production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a schematic structural diagram of the heat-conducting electromagnetic shielding multilayer composite film of the present invention.

[0067] Description of the accompanying drawings: 10, insulating thermal conductive layer; 20, magnetic shielding layer; 30, conductive shielding layer; 40, insulating thermal conductive layer.

[0068] Figure 2 It is a graph showing the electromagnetic shielding effectiveness test results of the multilayer composite films and the thermal conductive electromagnetic shielding multilayer composite films in Examples 1 to 5 and Comparative Examples 1 to 2.

[0069] Figure 3 It is a test result diagram of the electromagnetic shielding absorption and reflection ratio of the multilayer composite film and the thermal conductive electromagnetic shielding multilayer composite film in Examples 1 to 5 and Comparative Examples 1 to 2.

[0070] Figure 4 It is a graph showing the test results of thermal conductivity of the heat-conductive electromagnetic shielding multi-layer composite films in Examples 1 to 5 and Comparative Examples 1 to 2. DETAILED DESCRIPTION

[0071] The present invention will be further explained and illustrated below in conjunction with specific embodiments.

[0072] Embodiment 1:

[0073] A heat-conducting electromagnetic shielding multilayer composite film (schematic diagram as shown in Figure 1 Its composition is shown in the following table:

[0074] Table 1 Composition of a thermal conductive electromagnetic shielding multilayer composite film

[0075]

[0076] Note:

[0077] Sendust powder: Jiangsu Baona Electromagnetic New Materials Co., Ltd., brand BNWFA-150, the mass percentages of iron, silicon and aluminum are 85%, 9.6% and 5.4% respectively.

[0078] Polyacrylate hollow microspheres: Akzo Nobel NV, brand 031DU40.

[0079] The preparation method of the above-mentioned thermal conductive electromagnetic shielding multilayer composite film is as follows:

[0080] 1) placing the polyacrylate hollow microspheres into a plasma treatment machine, setting the power to 100 W, the oxygen flow rate to 30 mL / min, and treating for 20 min to obtain surface-modified expanded microspheres;

[0081] 2) Ti3C2-MXene, surface modified expanded microspheres, carboxymethyl cellulose and deionized water were mixed in a mass ratio of 10:5:2:1000, stirred for 30 min at a stirrer speed of 500 rpm, ultrasonicated for 20 min, and stirred and ultrasonicated alternately for 3 times in total to obtain a dispersion; the dispersion was vacuum filtered for 2 h, and then vacuum dried at 40 ° C for 60 min to obtain a conductive shielding layer (thickness of 42 μm);

[0082] 3) Mixing sendust powder, surface modified expanded microspheres, carboxymethyl cellulose and deionized water in a mass ratio of 5:2:1:20, and stirring for 2 hours at a stirrer speed of 400 rpm to obtain a dispersion; spreading the conductive shielding layer on a desktop homogenizer, dripping the dispersion, controlling the spin coating speed to 2000 rpm, spin coating for 10 seconds, and then baking at 50°C for 15 minutes to form a magnetic shielding layer, thereby obtaining a conductive shielding layer-magnetic shielding layer composite structure;

[0083] 4) Mix hexagonal boron nitride powder, carboxymethyl cellulose and deionized water in a mass ratio of 1:1:40, and then stir for 2 hours at a stirrer speed of 600 rpm to obtain a dispersion; spread the conductive shielding layer-magnetic shielding layer composite structure on a desktop coater, add the dispersion dropwise, control the spin coating speed to 2000 rpm, spin coat for 10 seconds, and then bake at 50°C for 30 minutes to form an insulating thermal conductive layer, then turn the conductive shielding layer-magnetic shielding layer composite structure over and repeat the above operation to prepare an insulating thermal conductive layer to obtain a multilayer composite film (thickness of 100 μm), and then heat treat at 60°C for 30 minutes to obtain a thermally conductive electromagnetic shielding multilayer composite film.

[0084] The total thickness of the thermally conductive electromagnetic shielding multilayer composite film in this embodiment is 105 μm, wherein the thickness of the insulating thermal conductive layer is 17.5 μm, the thickness of the magnetic shielding layer is 28 μm, and the thickness of the conductive shielding layer is 42 μm.

[0085] Embodiment 2:

[0086] A heat-conducting electromagnetic shielding multilayer composite film (schematic diagram as shown in Figure 1 Its composition is shown in the following table:

[0087] Table 2 Composition of a thermal conductive electromagnetic shielding multilayer composite film

[0088]

[0089] The preparation method of the above-mentioned thermal conductive electromagnetic shielding multilayer composite film is as follows:

[0090] 1) placing the polyacrylate hollow microspheres into a plasma treatment machine, setting the power to 100 W, the oxygen flow rate to 30 mL / min, and treating for 20 min to obtain surface-modified expanded microspheres;

[0091] 2) Ti3C2-MXene, surface modified expanded microspheres, carboxymethyl cellulose and deionized water were mixed in a mass ratio of 10:5:2:1000, and then stirred for 30 minutes at a stirrer speed of 500 rpm, and ultrasonicated for 20 minutes, and stirred and ultrasonicated alternately for 3 times in total to obtain a dispersion; the dispersion was vacuum filtered for 2 hours, and then vacuum dried at 40°C for 60 minutes to obtain a conductive shielding layer (thickness of 45 μm);

[0092] 3) Mixing sendust powder, surface modified expanded microspheres, carboxymethyl cellulose and deionized water in a mass ratio of 5:2:1:20, and stirring for 2 hours at a stirrer speed of 400 rpm to obtain a dispersion; spreading the conductive shielding layer on a desktop homogenizer, dripping the dispersion, controlling the spin coating speed to 2000 rpm, spin coating for 10 seconds, and then baking at 70°C for 10 minutes to form a magnetic shielding layer, thereby obtaining a conductive shielding layer-magnetic shielding layer composite structure;

[0093] 4) Mix hexagonal boron nitride powder, carboxymethyl cellulose and deionized water in a mass ratio of 1:1:40, and then stir for 2 hours at a stirrer speed of 600 rpm to obtain a dispersion; spread the conductive shielding layer-magnetic shielding layer composite structure on a desktop coater, add the dispersion dropwise, control the spin coating speed to 2000 rpm, spin coat for 10 seconds, and then bake at 70°C for 15 minutes to form an insulating thermal conductive layer, then turn the conductive shielding layer-magnetic shielding layer composite structure over and repeat the above operation to prepare an insulating thermal conductive layer to obtain a multilayer composite film (thickness 110 μm), and then heat treat at 80°C for 30 minutes to obtain a thermally conductive electromagnetic shielding multilayer composite film.

[0094] The total thickness of the heat-conductive electromagnetic shielding multilayer composite film in this embodiment is 140 μm, wherein the thickness of the insulating heat-conductive layer is 20 μm, the thickness of the magnetic shielding layer is 45 μm, and the thickness of the conductive shielding layer is 55 μm.

[0095] Embodiment 3:

[0096] A heat-conducting electromagnetic shielding multilayer composite film (schematic diagram as shown in Figure 1 Its composition is shown in the following table:

[0097] Table 3 Composition of a thermal conductive electromagnetic shielding multilayer composite film

[0098]

[0099] The preparation method of the above-mentioned thermal conductive electromagnetic shielding multilayer composite film is as follows:

[0100] 1) placing the polyacrylate hollow microspheres into a plasma treatment machine, setting the power to 100 W, the oxygen flow rate to 30 mL / min, and treating for 20 min to obtain surface-modified expanded microspheres;

[0101] 2) Ti3C2-MXene, surface modified expanded microspheres, carboxymethyl cellulose and deionized water were mixed in a mass ratio of 10:5:2:1000, and then stirred for 30 minutes at a stirrer speed of 500 rpm, and ultrasonicated for 20 minutes, and stirred and ultrasonicated alternately for 3 times in total to obtain a dispersion; the dispersion was vacuum filtered for 2 hours, and then vacuum dried at 40°C for 60 minutes to obtain a conductive shielding layer (thickness of 50 μm);

[0102] 3) Mixing sendust powder, surface modified expanded microspheres, carboxymethyl cellulose and deionized water in a mass ratio of 5:2:1:20, and stirring for 2 hours at a stirrer speed of 400 rpm to obtain a dispersion; spreading the conductive shielding layer on a desktop homogenizer, dripping the dispersion, controlling the spin coating speed to 2000 rpm, spin coating for 10 seconds, and then baking at 70°C for 10 minutes to form a magnetic shielding layer, thereby obtaining a conductive shielding layer-magnetic shielding layer composite structure;

[0103] 4) Mix hexagonal boron nitride powder, carboxymethyl cellulose and deionized water in a mass ratio of 2:1:40, and then stir for 2 hours at a stirrer speed of 600 rpm to obtain a dispersion; spread the conductive shielding layer-magnetic shielding layer composite structure on a desktop coater, add the dispersion dropwise, control the spin coating speed to 2000 rpm, spin coat for 10 seconds, and then bake at 70°C for 15 minutes to form an insulating thermal conductive layer, then turn the conductive shielding layer-magnetic shielding layer composite structure over and repeat the above operation to prepare an insulating thermal conductive layer to obtain a multilayer composite film (thickness 115 μm), and then heat treat at 80°C for 40 minutes to obtain a thermally conductive electromagnetic shielding multilayer composite film.

[0104] The total thickness of the heat-conductive electromagnetic shielding multilayer composite film in this embodiment is 150 μm, wherein the thickness of the insulating heat-conductive layer is 22.5 μm, the thickness of the magnetic shielding layer is 47 μm, and the thickness of the conductive shielding layer is 58 μm.

[0105] Embodiment 4:

[0106] A heat-conducting electromagnetic shielding multilayer composite film (schematic diagram as shown in Figure 1 Its composition is shown in the following table:

[0107] Table 4 Composition of a thermal conductive electromagnetic shielding multilayer composite film

[0108]

[0109] The preparation method of the above-mentioned thermal conductive electromagnetic shielding multilayer composite film is as follows:

[0110] 1) placing the polyacrylate hollow microspheres into a plasma treatment machine, setting the power to 100 W, the oxygen flow rate to 30 mL / min, and treating for 20 min to obtain surface-modified expanded microspheres;

[0111] 2) Ti3C2-MXene, surface modified expanded microspheres, carboxymethyl cellulose and deionized water were mixed in a mass ratio of 10:5:2:1000, and then stirred for 30 minutes at a stirrer speed of 500 rpm, and ultrasonicated for 20 minutes, and stirred and ultrasonicated alternately for 3 times in total to obtain a dispersion; the dispersion was vacuum filtered for 2 hours, and then vacuum dried at 40°C for 50 minutes to obtain a conductive shielding layer (thickness of 48 μm);

[0112] 3) Mixing sendust powder, surface modified expanded microspheres, carboxymethyl cellulose and deionized water in a mass ratio of 7:3:1:20, and stirring for 2 hours at a stirrer speed of 500 rpm to obtain a dispersion; spreading the conductive shielding layer on a desktop homogenizer, dripping the dispersion, controlling the spin coating speed to 2000 rpm, spin coating for 10 seconds, and then baking at 70°C for 10 minutes to form a magnetic shielding layer, thereby obtaining a conductive shielding layer-magnetic shielding layer composite structure;

[0113] 4) Mix hexagonal boron nitride powder, carboxymethyl cellulose and deionized water in a mass ratio of 2:1:40, and then stir for 2 hours at a stirrer speed of 700 rpm to obtain a dispersion; spread the conductive shielding layer-magnetic shielding layer composite structure on a desktop coater, add the dispersion dropwise, control the spin coating speed to 2000 rpm, spin coat for 10 seconds, and then bake at 70°C for 15 minutes to form an insulating thermal conductive layer, then turn the conductive shielding layer-magnetic shielding layer composite structure over and repeat the above operation to prepare an insulating thermal conductive layer to obtain a multilayer composite film (thickness 140 μm), and then heat treat at 80°C for 40 minutes to obtain a thermally conductive electromagnetic shielding multilayer composite film.

[0114] The total thickness of the heat-conductive electromagnetic shielding multilayer composite film in this embodiment is 180 μm, wherein the thickness of the insulating heat-conductive layer is 27.5 μm, the thickness of the magnetic shielding layer is 67 μm, and the thickness of the conductive shielding layer is 58 μm.

[0115] Embodiment 5:

[0116] A heat-conducting electromagnetic shielding multilayer composite film (schematic diagram as shown in Figure 1 Its composition is shown in the following table:

[0117] Table 5 Composition of a thermally conductive electromagnetic shielding multilayer composite film

[0118]

[0119] The preparation method of the above-mentioned thermal conductive electromagnetic shielding multilayer composite film is as follows:

[0120] 1) placing the polyacrylate hollow microspheres into a plasma treatment machine, setting the power to 100 W, the oxygen flow rate to 30 mL / min, and treating for 20 min to obtain surface-modified expanded microspheres;

[0121] 2) Ti3C2-MXene, surface modified expanded microspheres, carboxymethyl cellulose and deionized water were mixed in a mass ratio of 10:5:2:1000, and then stirred for 30 minutes at a stirrer speed of 500 rpm, and ultrasonicated for 20 minutes, and stirred and ultrasonicated alternately for 3 times in total to obtain a dispersion; the dispersion was vacuum filtered for 2 hours, and then vacuum dried at 40°C for 60 minutes to obtain a conductive shielding layer (thickness of 50 μm);

[0122] 3) Mixing sendust powder, surface modified expanded microspheres, carboxymethyl cellulose and deionized water in a mass ratio of 7:3:1:20, and stirring for 2 hours at a stirrer speed of 500 rpm to obtain a dispersion; spreading the conductive shielding layer on a desktop homogenizer, dripping the dispersion, controlling the spin coating speed to 2000 rpm, spin coating for 10 seconds, and then baking at 70°C for 10 minutes to form a magnetic shielding layer, thereby obtaining a conductive shielding layer-magnetic shielding layer composite structure;

[0123] 4) Mix hexagonal boron nitride powder, carboxymethyl cellulose and deionized water in a mass ratio of 3:1:40, and then stir for 2 hours at a stirrer speed of 700 rpm to obtain a dispersion; spread the conductive shielding layer-magnetic shielding layer composite structure on a desktop coater, add the dispersion dropwise, control the spin coating speed to 2000 rpm, spin coat for 10 seconds, and then bake at 70°C for 20 minutes to form an insulating thermal conductive layer, then turn the conductive shielding layer-magnetic shielding layer composite structure over and repeat the above operation to prepare an insulating thermal conductive layer to obtain a multilayer composite film (thickness 155 μm), and then heat treat at 80°C for 60 minutes to obtain a thermally conductive electromagnetic shielding multilayer composite film.

[0124] The total thickness of the heat-conductive electromagnetic shielding multilayer composite film in this embodiment is 190 μm, wherein the thickness of the insulating heat-conductive layer is 30 μm, the thickness of the magnetic shielding layer is 70 μm, and the thickness of the conductive shielding layer is 60 μm.

[0125] Comparative Example 1:

[0126] A thermal conductive electromagnetic shielding multilayer composite film, the composition of which is shown in the following table:

[0127] Table 6 Composition of a thermally conductive electromagnetic shielding multilayer composite film

[0128]

[0129] The preparation method of the above-mentioned thermal conductive electromagnetic shielding multilayer composite film is as follows:

[0130] 1) Ti3C2-MXene, carboxymethyl cellulose and deionized water were mixed in a mass ratio of 10:5:500, and then stirred for 30 minutes at a stirrer speed of 500 rpm, and ultrasonicated for 20 minutes, and stirred and ultrasonicated alternately for 3 times in total to obtain a dispersion; the dispersion was vacuum filtered for 2 hours, and then vacuum dried at 40°C for 60 minutes to obtain a conductive shielding layer (thickness of 40 μm);

[0131] 2) Mix hexagonal boron nitride powder, carboxymethyl cellulose and deionized water in a mass ratio of 1:1:40, and then stir for 2 hours at a stirrer speed of 500 rpm to obtain a dispersion; spread the conductive shielding layer on a desktop coater, add the dispersion dropwise, control the spin coating speed to 2000 rpm, spin coat for 10 seconds, and then bake at 50°C for 20 minutes to form an insulating thermal conductive layer, then turn the conductive shielding layer over and repeat the above operation to prepare an insulating thermal conductive layer to obtain a multilayer composite film (thickness 88 μm), and then heat treat at 60°C for 30 minutes to obtain a thermally conductive electromagnetic shielding multilayer composite film.

[0132] The total thickness of the heat-conductive electromagnetic shielding multilayer composite film in this comparative example is 88 μm, wherein the thickness of the insulating heat-conductive layer is 24 μm, and the thickness of the conductive shielding layer is 40 μm.

[0133] Comparative Example 2:

[0134] A heat-conducting electromagnetic shielding multilayer composite film (with the same structure as in Example 1), the composition of which is shown in the following table:

[0135] Table 7 Composition of a thermally conductive electromagnetic shielding multilayer composite film

[0136]

[0137] The preparation method of the above-mentioned thermal conductive electromagnetic shielding multilayer composite film is as follows:

[0138] 1) Ti3C2-MXene, polyacrylate hollow microspheres, carboxymethyl cellulose and deionized water were mixed in a mass ratio of 10:5:5:1000, stirred for 30 min at a stirrer speed of 500 rpm, and ultrasonicated for 20 min, and stirred and ultrasonicated alternately for 3 times in total to obtain a dispersion; the dispersion was vacuum filtered for 2 h, and then vacuum dried at 40 ° C for 50 min to obtain a conductive shielding layer (thickness of 45 μm);

[0139] 2) Mixing sendust powder, polyacrylate hollow microspheres, carboxymethyl cellulose and deionized water in a mass ratio of 3:1:1:20, stirring for 2 hours at a stirrer speed of 500 rpm to obtain a dispersion; spreading the conductive shielding layer on a desktop homogenizer, dripping the dispersion, controlling the spin coating speed to 2000 rpm, spin coating for 10 seconds, and then baking at 50° C. for 15 minutes to form a magnetic shielding layer, thereby obtaining a conductive shielding layer-magnetic shielding layer composite structure;

[0140] 3) Mix hexagonal boron nitride powder, carboxymethyl cellulose and deionized water in a mass ratio of 1:1:40, and then stir for 2 hours at a stirrer speed of 600 rpm to obtain a dispersion; spread the conductive shielding layer-magnetic shielding layer composite structure on a desktop glue spreader, add the dispersion dropwise, control the spin coating speed to 2000 rpm, spin coat for 10 seconds, and then bake at 50°C for 20 minutes to form an insulating thermal conductive layer, then turn the conductive shielding layer-magnetic shielding layer composite structure over and repeat the above operation to prepare an insulating thermal conductive layer to obtain a multilayer composite film (thickness 106 μm), and then heat treat at 60°C for 30 minutes to obtain a thermally conductive electromagnetic shielding multilayer composite film.

[0141] The total thickness of the heat-conductive electromagnetic shielding multilayer composite film in this comparative example is 110 μm, wherein the thickness of the insulating heat-conductive layer is 18.5 μm, the thickness of the magnetic shielding layer is 25 μm, and the thickness of the conductive shielding layer is 48 μm.

[0142] Performance Test:

[0143] The electromagnetic shielding effectiveness test results of the multilayer composite films (before heat treatment) and the thermally conductive electromagnetic shielding multilayer composite films (after heat treatment) in Examples 1 to 5 and Comparative Examples 1 to 2 are as follows: Figure 2 (a is before heat treatment, b is after heat treatment).

[0144] The electromagnetic shielding absorption and reflection ratio test results of the multilayer composite films (before heat treatment) and the thermal conductive electromagnetic shielding multilayer composite films (after heat treatment) in Examples 1 to 5 and Comparative Examples 1 to 2 are as follows: Figure 3 (a is before heat treatment, b is after heat treatment).

[0145] The thermal conductivity test results of the heat-conductive electromagnetic shielding multilayer composite films in Examples 1 to 5 and Comparative Examples 1 to 2 are as follows: Figure 4 shown.

[0146] The test results of thermal conductivity and electromagnetic shielding performance of the multilayer composite films (before heat treatment) and the thermal conductive electromagnetic shielding multilayer composite films (after heat treatment) in Examples 1 to 5 and Comparative Examples 1 to 2 are shown in the following table:

[0147] Table 8 Test results of thermal conductivity and electromagnetic shielding performance of multilayer composite films and thermal conductive electromagnetic shielding multilayer composite films

[0148]

[0149] Note:

[0150] In-plane thermal conductivity: Referring to the "ISO 22007-2 standard and thermal diffusivity transient plane heat source test method", the samples were tested using the TPS2500S thermal constant analyzer from Sweden's Hotdisk company. During the test, the probe was placed in the middle of the sample to be tested to ensure that the sample to be tested and the probe were tightly fitted. Each sample to be tested was tested 3 times, and then the average value was taken.

[0151] EMI SE (Electromagnetic Shielding Effectiveness): The ZNA-43 vector network analyzer from Rohde & Schwarz was used to test the electromagnetic parameters of the samples using the waveguide method, and then the electromagnetic shielding effectiveness of the samples was calculated. The test frequency range was 8.2 GHz to 12.4 GHz.

[0152] Depend on Figures 2 to 4 From Table 8, we can see that:

[0153] a) The thermally conductive electromagnetic shielding multilayer composite film in Examples 1 to 5 (composite of a magnetic shielding layer containing iron silicon aluminum powder, a conductive shielding layer containing Ti3C2-MXene, and an insulating thermal conductive layer containing hexagonal boron nitride powder) has excellent thermal conductivity and electromagnetic shielding performance;

[0154] b) After the multilayer composite films in Examples 2 to 5 were heat treated (i.e., the final thermally conductive electromagnetic shielding multilayer composite films were obtained), the absorption / reflection ratio of the electromagnetic shielding performance increased;

[0155] c) Compared with the thermal conductive electromagnetic shielding multilayer composite films in Examples 1 to 5, the thermal conductive electromagnetic shielding multilayer composite film in Comparative Example 1 lacks modified expanded microspheres and magnetic shielding layers, while compared with the thermal conductive electromagnetic shielding multilayer composite films in Examples 1 to 5, the thermal conductive electromagnetic shielding multilayer composite film in Comparative Example 2 has relatively reduced contents of conductive fillers and magnetic fillers, increased content of cellulose, and the heat treatment temperature does not reach the microsphere expansion temperature, which does not cause a significant increase in the volume of the microspheres, and thus the electromagnetic shielding effectiveness is low;

[0156] d) Compared with the thermal conductive electromagnetic shielding multilayer composite films in Examples 2 to 5, the heat treatment temperature of the thermal conductive electromagnetic shielding multilayer composite film in Example 1 did not reach the microsphere expansion temperature, the pores in the film did not change much, and the difference before and after the heat treatment was not obvious, and it was still a reflective electromagnetic shielding method;

[0157] e) Compared with the thermally conductive electromagnetic shielding multilayer composite film in Example 2, the thermally conductive electromagnetic shielding multilayer composite film in Example 3 has an increased content of the thermally conductive filler hexagonal boron nitride powder in the insulating thermally conductive layer, and the thermal conductivity of the composite film is improved;

[0158] f) The thermally conductive electromagnetic shielding multilayer composite film in Example 4 has a higher content of magnetic filler sendust powder and expanded microspheres in the magnetic shielding layer than the thermally conductive electromagnetic shielding multilayer composite film in Example 3, and the total electromagnetic shielding effectiveness and absorption efficiency / reflection efficiency ratio of the composite film are increased;

[0159] g) The thermally conductive electromagnetic shielding multilayer composite film in Example 5 is compared with the thermally conductive electromagnetic shielding multilayer composite film in Example 4, in which the content of the thermally conductive filler hexagonal boron nitride powder in the insulating thermally conductive layer and the heat treatment time are increased, and the electromagnetic shielding effectiveness, absorption efficiency / reflection efficiency ratio and thermal conductivity of the composite film are increased;

[0160] In summary, the thermally conductive electromagnetic shielding multilayer composite film of the present invention has excellent thermal conductivity and electromagnetic shielding performance. This is because the spin coating method makes it easy for the thermally conductive filler to be oriented in the layer, thereby easily forming a thermal conductive path in the insulating thermally conductive layer, thereby improving the in-plane thermal conductivity of the composite film. The magnetic filler added to the composite film can provide magnetic loss, and the conductive filler can form a conductive path in the conductive shielding layer, which significantly improves the conductivity of the composite film and provides dielectric loss. The expanded microspheres can increase the pores in the composite film, thereby realizing multiple reflection losses of electromagnetic waves inside the film. In addition, the preparation process of the thermally conductive electromagnetic shielding multilayer composite film is simple, safe and environmentally friendly, and can be widely used in 5G communications, consumer electronics, new energy batteries, national defense and military industries and other fields.

[0161] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A thermally conductive electromagnetic shielding multilayer composite film, characterized in that: The composition includes an insulating thermally conductive layer, a magnetic shielding layer, a conductive shielding layer and an insulating thermally conductive layer which are stacked in sequence; the insulating thermally conductive layer is a cellulose film containing a thermally conductive filler; the magnetic shielding layer is a cellulose film containing a magnetic filler and expanded microspheres; the conductive shielding layer is a cellulose film containing a conductive filler and expanded microspheres.

2. The thermally conductive electromagnetic shielding multilayer composite film according to claim 1, characterized in that: The thermally conductive electromagnetic shielding multilayer composite film comprises the following components in percentage by mass: Thermal conductive filler: 5% to 30%; Conductive filler: 10% to 25%; Magnetic filler: 20%~60%; Expanded microspheres: 15% to 30%; Cellulose: 10%~30%.

3. The thermally conductive electromagnetic shielding multilayer composite film according to claim 1 or 2, characterized in that: The thermally conductive filler is at least one of hexagonal boron nitride powder, carbon fiber powder, and aluminum oxide powder; the conductive filler is at least one of graphene powder, MXene powder, and fullerene powder; the magnetic filler is at least one of ferroferric oxide powder, sendust powder, and carbonyl iron powder.

4. The thermally conductive electromagnetic shielding multilayer composite film according to claim 3, characterized in that: The particle size of the thermal conductive filler is 1 μm to 100 μm; the particle size of the conductive filler is 1 μm to 10 μm; and the particle size of the magnetic filler is 1 μm to 50 μm.

5. The thermally conductive electromagnetic shielding multilayer composite film according to claim 1 or 2, characterized in that: The expanded microspheres are hollow polyacrylate microspheres; the particle size of the hollow polyacrylate microspheres is 6 μm to 15 μm, the expansion temperature is 80° C. to 135° C., and the expansion multiple is 2 to 5 times.

6. The thermally conductive electromagnetic shielding multilayer composite film according to claim 1 or 2, characterized in that: The cellulose is at least one of carboxymethyl cellulose, bacterial cellulose and hydroxypropyl methyl cellulose.

7. The thermally conductive electromagnetic shielding multilayer composite film according to claim 1 or 2, characterized in that: The mass ratio of the thermally conductive filler and cellulose in the insulating thermally conductive layer is 1-5:1; the mass ratio of the magnetic filler, expanded microspheres and cellulose in the magnetic shielding layer is 2-7:2-5:1; the mass ratio of the conductive filler, expanded microspheres and cellulose in the conductive shielding layer is 10:1-5:1-5.

8. The thermally conductive electromagnetic shielding multilayer composite film according to claim 1 or 2, characterized in that: The thickness of the insulating heat-conducting layer is 10 μm to 100 μm; the thickness of the magnetic shielding layer is 20 μm to 150 μm; and the thickness of the conductive shielding layer is 10 μm to 70 μm.

9. A method for preparing a thermally conductive electromagnetic shielding multilayer composite film according to any one of claims 1 to 8, characterized in that: The following steps are involved: 1) Using plasma to perform surface treatment on expanded microspheres to obtain surface-modified expanded microspheres; 2) adding water to disperse the conductive filler, the surface modified expanded microspheres and the cellulose to form a dispersion, and then filtering to form a conductive shielding layer, and then adding water to disperse the magnetic filler, the surface modified expanded microspheres and the cellulose to form a dispersion, and then coating it on one side of the conductive shielding layer and drying to form a magnetic shielding layer, thereby obtaining a conductive shielding layer-magnetic shielding layer composite structure; Alternatively, the magnetic filler, the surface modified expanded microspheres and the cellulose are dispersed in water to form a dispersion, and then filtered to form a magnetic shielding layer, and then the conductive filler, the surface modified expanded microspheres and the cellulose are dispersed in water to form a dispersion, and then coated on one side of the magnetic shielding layer and dried to form a conductive shielding layer, thereby obtaining a conductive shielding layer-magnetic shielding layer composite structure; 3) The thermal conductive filler and cellulose are dispersed in water to prepare a dispersion, which is then coated on both sides of the conductive shielding layer-magnetic shielding layer composite structure and dried to form an insulating thermal conductive layer, which is then heat treated to obtain a thermal conductive electromagnetic shielding multilayer composite film.

10. An electronic device, characterized in that: The invention comprises the thermal conductive electromagnetic shielding multilayer composite film as described in any one of claims 1 to 8.

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