Preparation method of wave-absorbing electromagnetic shielding film for 6G electronic device

Abstract

The invention belongs to the technical field of electronic materials, and particularly relates to a preparation method of a wave-absorbing electromagnetic shielding film for a 6G electronic device. The preparation method comprises the following steps: doping naphthol blue black containing multi-polar functional groups and a nano-copper powder sol solution into epoxy resin glue, and heating and curing to form the film. The minimum wave absorbing efficiency of the electromagnetic shielding film with the thickness of 1 mm within the range of 0.3-3.0 THz is-30.56 dB, the average wave absorbing efficiency is-17.82 dB, and the effective bandwidth of the electromagnetic shielding film with the wave absorbing efficiency smaller than or equal to-10 dB is 0.64-3.00 THz. Meanwhile, the highest electromagnetic shielding effectiveness of the electromagnetic shielding film is 50.73 dB, and the average shielding effectiveness of the electromagnetic shielding film is 37.79 dB; the electromagnetic shielding film can be used for wave-absorbing electromagnetic protection of 6G electronic devices.

Description

Technical Field

[0001] This invention belongs to the field of electronic materials, specifically relating to a method for preparing a microwave-absorbing electromagnetic shielding film for 6G electronic devices. Background Technology

[0002] Electromagnetic shielding materials are key materials for 6G technology (Zhu Hongwei. New Materials in the 6G Era. Nature Journal, 2023, 45(2): 109-112.). Electromagnetic protection is mainly achieved through electromagnetic shielding, which physically blocks electric, magnetic, and electromagnetic fields by absorbing, reflecting, or canceling electromagnetic energy. Electromagnetic shielding is classified into three types according to its working principle: electric field shielding, magnetic field shielding, and electromagnetic field shielding. Electromagnetic shielding is also classified into two types based on energy conversion: one directly reflects electromagnetic waves with almost no energy conversion; the other absorbs electromagnetic waves and converts them into heat energy. In the field of 6G technology, due to the increasing integration of electronic devices, reflected electromagnetic waves can cause secondary pollution from stray electromagnetic waves, and absorbing electromagnetic shielding films can solve this problem.

[0003] For absorbing materials, the academic community usually defines their effective bandwidth as the frequency range with absorption efficiency ≤ -10dB. For 6G technology, the frequency range is 0.3~3THz. It is hoped that insulating electromagnetic shielding films can be developed to solve the problems of circuit short circuits and eddy current losses caused by conductive electromagnetic shielding films.

[0004] Fudan University Yiwu Research Institute has disclosed a method for preparing a copper powder-reinforced terahertz composite absorbing film (CN121248980 A). Using polyurethane-modified epoxy resin as raw material, silane coupling agent-modified alumina, chitosan-coated silica, and substituted thiophenol-substituted self-assembled nano-copper powder are added sequentially. After stirring, a curing agent and dispersant are added to obtain a mixture. The mixture is then poured into a coating machine and coated to prepare the copper powder-reinforced terahertz composite absorbing film. The film exhibits a minimum absorption efficiency of -26.7 dB in the 0.3-3.0 THz frequency band, and an effective bandwidth of less than -10 dB across the entire frequency band. This composite absorbing material can be used for electromagnetic protection of 6G electronic devices.

[0005] Based on the theoretical foundation of the above work, this invention proposes a method for preparing a microwave-absorbing electromagnetic shielding film for 6G electronic devices. Compared with patent CN 121248980 A, this method does not use inorganic additives such as silane coupling agent-modified alumina or chitin-coated silica. Instead, it adds organic pigments, such as naphthol blue-black, which can effectively enhance the microwave absorption performance and shielding efficiency. The minimum microwave absorption efficiency is -30.56 dB (99.9% of electromagnetic waves are absorbed), and the maximum electromagnetic shielding efficiency is 50.73 dB (99.999% of electromagnetic waves are shielded). Furthermore, this electromagnetic shielding film is DC insulated, which is innovative. Summary of the Invention

[0006] The purpose of this invention is to propose a method for preparing a microwave-absorbing electromagnetic shielding film for 6G electronic devices, providing a new material for electromagnetic protection of 6G technology.

[0007] The method for preparing a microwave-absorbing electromagnetic shielding film for 6G electronic devices proposed in this invention comprises the following steps: (1) Preparation of nano copper powder Add copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water to a three-necked flask, stir, heat to 70-80℃, add a 20%-30% glucose aqueous solution dropwise, continue stirring for 30-40 minutes, cool, pour into centrifuge tubes, place in a centrifuge, centrifuge at 2000-3000 rpm for 5-10 minutes, remove the supernatant, wash the lower solid-liquid mixture with methanol, centrifuge, remove the supernatant, place the centrifuge tubes in a vacuum oven, and dry at 40-50℃ for 2-3 hours to obtain nano-copper powder; wherein, the weight ratio of copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water is 1:(3-4):(1600-1700):(2500-2600); wherein, the weight ratio of copper hydroxide to glucose aqueous solution is 1:(10-20). (2) Preparation of nano copper powder sol solution Ethyl acetate, acrylic resin, butyl acetate and cyclohexanone were added sequentially to a three-necked flask, heated to 40-50°C, and stirred for 30-40 minutes. Then, under a nitrogen atmosphere, the nano-copper powder prepared in step (1) was added, and stirring was continued for 2-3 hours. After cooling, a nano-copper powder sol solution was obtained. The weight ratio of ethyl acetate, acrylic resin, butyl acetate, cyclohexanone and nano-copper powder was 1:(4-5):(1-1.5):(1.5-2):(2.5-3). The weight average molecular weight of the acrylic resin was 50,000-75,000. (3) Preparation of electromagnetic shielding film Naphthol blue-black was ground into powder with a particle size of 800-1000 mesh and added to a three-necked flask. Bisphenol A type epoxy resin glue was added and stirred. Then, the nano copper powder sol solution prepared in step (2) was added and stirred. Diethylenetriamine was added and then placed in a mold and heated to 70-80℃ to cure, thus obtaining a wave-absorbing electromagnetic shielding film for 6G electronic devices. The weight ratio of naphthol blue-black, bisphenol A type epoxy resin glue, diethylenetriamine and nano copper powder sol solution was 1:(3-4):(1-1.4):(4-5). The thickness of the wave-absorbing electromagnetic shielding film was 0.5-2.0 mm.

[0008] Referring to the literature (Materials Today Physics, 2025, 51: 101655), the performance testing method for this electromagnetic shielding film when used for electromagnetic protection is as follows: the wave-absorbing electromagnetic shielding film used for 6G electronic devices is cut into 2cm×2cm pieces, placed in a fixture, and then placed in a terahertz time-domain spectroscopy system. The electromagnetic wave absorption efficiency and electromagnetic shielding efficiency of the electromagnetic shielding film in the frequency range of 0.3~3.0 THz are tested using transmission mode and reflection mode.

[0009] Referring to the standard GB / T 31838.4-2019 "Dielectric and resistive properties of solid insulating materials - Part 4: Resistive properties (DC method) Insulation resistance", the wave-absorbing electromagnetic shielding film was found to be a DC insulating material.

[0010] The present invention has the following advantages: (1) Compared with patent CN 121248980 A, the electromagnetic shielding film prepared by the present invention has a lower minimum wave absorption efficiency (better wave absorption performance) and a higher electromagnetic shielding efficiency (more thorough electromagnetic wave isolation) under the same thickness (1mm).

[0011] (2) It was discovered for the first time that organic pigments can enhance the terahertz absorption performance of the nano-copper / epoxy resin system, thus pioneering a new type of terahertz absorbing material system.

[0012] (3) The addition of organic pigments greatly enriches the types of functional groups, which enhances the absorption effects such as polarization relaxation, vibration relaxation, and valence resonance, thereby improving the absorption and shielding effects.

[0013] Shaanxi University of Science and Technology conducted an in-situ study on the growth of MAX phase coatings on porous carbonized wood (CW) and their terahertz electromagnetic shielding performance (Huang Jiaxuan. In-situ Growth of MAX Phase Coatings on Porous Carbonized Wood and Their Terahertz Electromagnetic Shielding Performance. Master's Thesis, Shaanxi University of Science and Technology, 2021). The study investigated the effects of different MAX phase materials, different biological directions, and different porous carbonized wood matrices on the electrical conductivity and electromagnetic shielding performance of the materials. The results showed that the electromagnetic shielding performance of MAX@CW composites was superior to that of pure CW. Furthermore, the shielding mechanism of CW is mainly based on the absorption of electromagnetic waves, while that of MAX@CW is mainly based on the reflection of electromagnetic waves. Among them, Ti2AlC@pine exhibited the highest electrical conductivity, reaching 3495 S / m, and also showed the best electromagnetic shielding performance, reaching a maximum shielding performance of over 65 dB at a frequency of 1.1 THz. The MAX phase material used in this study is very expensive, which is not conducive to its promotion and application; the prepared Ti2AlC@pine wood is a conductive material, mainly reflecting electromagnetic waves and lacking insulation properties, thus limiting its application scenarios. This invention does not use MAX phase materials; the different material systems result in different wave absorption and shielding mechanisms.

[0014] The University of Electronic Science and Technology of China (UESTC) has developed an optically transparent terahertz shielding hydrogel material with a thickness of only 500 μm, a shielding effectiveness exceeding 40 dB in the 0.5-4.5 THz band, and excellent visible light transparency and mechanical tensile properties (Tang Qian. Research on Broadband Terahertz Electromagnetic Shielding Based on Gel. Master's Thesis, UESTC, 2024). Addressing the stability issue of hydrogels, a gradient dielectric constant hydrogel-based material with an environmentally stable structure and an average reflection loss of 49.03 dB was designed and prepared using a one-step copolymerization method. The outer layer is an elastomer-coated hydrogel to suppress water evaporation; the core layer is an organic hydrogel; and the surface layer is a hydrophobic elastomer, exhibiting ultra-high visible light transparency. This material has a core-layer structure, relying on water to absorb terahertz electromagnetic waves. This invention prepares a single-layer material with a different structure; this invention utilizes organic pigments to enhance the absorption performance of the nano-copper composite film, resulting in a different absorption mechanism. Attached Figure Description

[0015] Figure 1 This is a scanning electron microscope (SEM) image of the microwave-absorbing electromagnetic shielding film for 6G electronic devices prepared in Example 1.

[0016] Figure 2 The image shows the X-ray photoelectron spectrum (XPS) of the microwave-absorbing electromagnetic shielding film for 6G electronic devices prepared in Example 1.

[0017] Figure 3 The image shows the absorption performance of the microwave-absorbing electromagnetic shielding film for 6G electronic devices prepared in Example 1.

[0018] Figure 4 The electromagnetic shielding performance diagram is shown for the microwave absorbing electromagnetic shielding film prepared in Example 1 for use in 6G electronic devices.

[0019] Figure 5 The image shows the Cole-Cole diagram of the microwave-absorbing electromagnetic shielding film for 6G electronic devices prepared in Example 1.

[0020] Figure 6 The image shows the microwave absorption performance of the composite thin film prepared in Comparative Example 1.

[0021] Figure 7 The image shows the microwave absorption performance of the composite thin film prepared in Comparative Example 2.

[0022] Figure 8 The image shows the microwave absorption performance of the composite thin film prepared in Comparative Example 3. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Example 1

[0024] (1) Preparation of nano copper powder Copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water were added to a three-necked flask, stirred, and heated to 70°C. A 20% (w / w) glucose aqueous solution was added dropwise, and stirring was continued for 30 minutes. After cooling, the mixture was poured into centrifuge tubes and centrifuged at 2000 rpm for 5 minutes. The supernatant was removed, and the lower solid-liquid mixture was washed with methanol, centrifuged, and the supernatant was removed. The centrifuge tubes were then placed in a vacuum oven and dried at 40°C for 2 hours to obtain nano-copper powder. The weight ratio of copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water was 1:3:1600:2500; the weight ratio of copper hydroxide to glucose aqueous solution was 1:10. (2) Preparation of nano copper powder sol solution Ethyl acetate, acrylic resin, butyl acetate and cyclohexanone were added sequentially to a three-necked flask, heated to 50°C and stirred for 40 minutes. Then, under a nitrogen atmosphere, the nano-copper powder prepared in step (1) was added, and stirring was continued for 3 hours. After cooling, a nano-copper powder sol solution was obtained. The weight ratio of ethyl acetate, acrylic resin, butyl acetate, cyclohexanone and nano-copper powder was 1:4:1:1.5:2.5. The weight average molecular weight of acrylic resin was 50,000. (3) Preparation of electromagnetic shielding film Naphthol blue-black was ground into powder with a particle size of 800-1000 mesh and added to a three-necked flask. Bisphenol A type epoxy resin glue was added and stirred. Then, the nano copper powder sol solution prepared in step (2) was added and stirred. Diethylenetriamine was added and then placed in a mold and heated to 70°C to cure, thus obtaining a wave-absorbing electromagnetic shielding film for 6G electronic devices. The weight ratio of naphthol blue-black, bisphenol A type epoxy resin glue, diethylenetriamine and nano copper powder sol solution was 1:3:1:4. The thickness of the wave-absorbing electromagnetic shielding film was 1.0 mm.

[0025] Referring to the literature (Materials Today Physics, 2025, 51: 101655), the performance testing method for this electromagnetic shielding film when used for electromagnetic protection is as follows: the wave-absorbing electromagnetic shielding film used for 6G electronic devices is cut into 2cm×2cm pieces, placed in a fixture, and then placed in a terahertz time-domain spectroscopy system. The electromagnetic wave absorption efficiency and electromagnetic shielding efficiency of the electromagnetic shielding film in the frequency range of 0.3~3.0 THz are tested using transmission mode and reflection mode.

[0026] Referring to the standard GB / T 31838.4-2019 "Dielectric and resistive properties of solid insulating materials - Part 4: Resistive properties (DC method) Insulation resistance", the wave-absorbing electromagnetic shielding film was found to be a DC insulating material.

[0027] Figure 1 This is a scanning electron microscope (SEM) image of the microwave-absorbing electromagnetic shielding film for 6G electronic devices prepared in Example 1. Figure 1 It can be seen that the film has a relatively rich microstructure, similar to that of a typical epoxy resin composite adhesive.

[0028] Figure 2 The X-ray photoelectron spectrum (XPS) of the microwave-absorbing electromagnetic shielding film for 6G electronic devices prepared in Example 1 is shown below. Figure 2 It can be seen that the film contains elements such as copper, oxygen, carbon, nitrogen, and sulfur, among which the sulfur element comes from naphthol blue black (its chemical formula is C22H14N6Na2O9S2).

[0029] Figure 3 The image shows the absorption performance of the microwave-absorbing electromagnetic shielding film for 6G electronic devices prepared in Example 1. Figure 3 It can be seen that the thin film has a minimum absorption efficiency of -30.56 dB and an average absorption efficiency of -17.82 dB in the range of 0.3-3.0 THz. The effective bandwidth with an absorption efficiency of ≤ -10 dB is 0.64~3.00 THz.

[0030] Figure 4 The electromagnetic shielding performance diagram is shown for the microwave absorbing electromagnetic shielding film prepared in Example 1 for use in 6G electronic devices. Figure 4 It can be seen that the highest electromagnetic shielding effectiveness of the thin film is 50.73 dB, and the average shielding effectiveness is 37.79 dB.

[0031] comprehensive Figure 3 , Figure 4 It can be seen that in the lower frequency band, such as 0.3-0.64THz, the absorption efficiency of the film is -5.1 to -10.0dB, which means it can absorb 68% to 90% of electromagnetic waves. In this frequency band, the electromagnetic shielding efficiency is 42.3-50.1dB, which means it can shield more than 99.99% of electromagnetic waves. This further indicates that the film has electromagnetic protection function in the entire 6G frequency band of 0.3-3.0THz, and is wave absorption dominant.

[0032] Figure 5 The Cole-Cole diagram of the microwave-absorbing electromagnetic shielding film for 6G electronic devices prepared in Example 1 is shown below. Figure 5 It can be seen that thin films have abundant dielectric losses, interfacial polarization losses, dipole polarization losses, and ion conduction losses. Example 2

[0033] (1) Preparation of nano copper powder Copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water were added to a three-necked flask, stirred, and heated to 80°C. A 30% (w / w) glucose aqueous solution was added dropwise, and stirring was continued for 40 minutes. After cooling, the mixture was poured into centrifuge tubes and centrifuged at 3000 rpm for 10 minutes. The supernatant was removed, and the lower solid-liquid mixture was washed with methanol, centrifuged, and the supernatant was removed. The centrifuge tubes were placed in a vacuum oven and dried at 50°C for 3 hours to obtain nano-copper powder. The weight ratio of copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water was 1:4:1700:2600; the weight ratio of copper hydroxide to glucose aqueous solution was 1:20. (2) Preparation of nano copper powder sol solution Ethyl acetate, acrylic resin, butyl acetate and cyclohexanone were added sequentially to a three-necked flask, heated to 40°C and stirred for 30 minutes. Then, under a nitrogen atmosphere, the nano-copper powder prepared in step (1) was added, and stirring was continued for 2 hours. After cooling, a nano-copper powder sol solution was obtained. The weight ratio of ethyl acetate, acrylic resin, butyl acetate, cyclohexanone and nano-copper powder was 1:5:1.5:2:3. The weight average molecular weight of acrylic resin was 75,000. (3) Preparation of electromagnetic shielding film Naphthol blue-black was ground into powder with a particle size of 800-1000 mesh and added to a three-necked flask. Bisphenol A type epoxy resin glue was added and stirred. Then, the nano copper powder sol solution prepared in step (2) was added and stirred. Diethylenetriamine was added and then placed in a mold and heated to 80°C to cure, thus obtaining a wave-absorbing electromagnetic shielding film for 6G electronic devices. The weight ratio of naphthol blue-black, bisphenol A type epoxy resin glue, diethylenetriamine and nano copper powder sol solution was 1:4:1.4:5. The thickness of the wave-absorbing electromagnetic shielding film was 0.5 mm.

[0034] Referring to the literature (Materials Today Physics, 2025, 51: 101655), the performance testing method for this electromagnetic shielding film when used for electromagnetic protection is as follows: the wave-absorbing electromagnetic shielding film used for 6G electronic devices is cut into 2cm×2cm pieces, placed in a fixture, and then placed in a terahertz time-domain spectroscopy system. The electromagnetic wave absorption efficiency and electromagnetic shielding efficiency of the electromagnetic shielding film in the frequency range of 0.3~3.0 THz are tested using transmission mode and reflection mode.

[0035] The film's lowest absorption efficiency was -22.11 dB and the average absorption efficiency was -14.33 dB in the 0.3-3.0 THz range. The effective bandwidth with absorption efficiency ≤ -10 dB was 0.89~2.86 THz. Meanwhile, the highest electromagnetic shielding efficiency of the film was 40.12 dB and the average shielding efficiency was 28.16 dB.

[0036] Referring to the standard GB / T 31838.4-2019 "Dielectric and resistive properties of solid insulating materials - Part 4: Resistive properties (DC method) Insulation resistance", the wave-absorbing electromagnetic shielding film was found to be a DC insulating material. Example 3

[0037] (1) Preparation of nano copper powder Copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water were added to a three-necked flask, stirred, and heated to 70°C. A 30% (w / w) glucose aqueous solution was added dropwise, and stirring was continued for 30 minutes. After cooling, the mixture was poured into centrifuge tubes and centrifuged at 3000 rpm for 5 minutes. The supernatant was removed, and the lower solid-liquid mixture was washed with methanol, centrifuged, and the supernatant was removed. The centrifuge tubes were placed in a vacuum oven and dried at 40°C for 3 hours to obtain nano-copper powder. The weight ratio of copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water was 1:4:1600:2600; the weight ratio of copper hydroxide to glucose aqueous solution was 1:10. (2) Preparation of nano copper powder sol solution Ethyl acetate, acrylic resin, butyl acetate and cyclohexanone were added sequentially to a three-necked flask, heated to 50°C and stirred for 30 minutes. Then, under a nitrogen atmosphere, the nano-copper powder prepared in step (1) was added, and stirring was continued for 3 hours. After cooling, a nano-copper powder sol solution was obtained. The weight ratio of ethyl acetate, acrylic resin, butyl acetate, cyclohexanone and nano-copper powder was 1:5:1:2:2.5. The weight average molecular weight of acrylic resin was 75,000. (3) Preparation of electromagnetic shielding film Naphthol blue-black was ground into powder with a particle size of 800-1000 mesh and added to a three-necked flask. Bisphenol A type epoxy resin glue was added and stirred. Then, the nano copper powder sol solution prepared in step (2) was added and stirred. Diethylenetriamine was added and then placed in a mold and heated to 70°C to cure, thus obtaining a wave-absorbing electromagnetic shielding film for 6G electronic devices. The weight ratio of naphthol blue-black, bisphenol A type epoxy resin glue, diethylenetriamine and nano copper powder sol solution was 1:3:1.4:4. The thickness of the wave-absorbing electromagnetic shielding film was 2.0 mm.

[0038] Referring to the literature (Materials Today Physics, 2025, 51: 101655), the performance testing method for this electromagnetic shielding film when used for electromagnetic protection is as follows: the wave-absorbing electromagnetic shielding film used for 6G electronic devices is cut into 2cm×2cm pieces, placed in a fixture, and then placed in a terahertz time-domain spectroscopy system. The electromagnetic wave absorption efficiency and electromagnetic shielding efficiency of the electromagnetic shielding film in the frequency range of 0.3~3.0 THz are tested using transmission mode and reflection mode.

[0039] The film's lowest absorption efficiency was -27.34 dB and the average absorption efficiency was -16.78 dB in the 0.3-3.0 THz range. The effective bandwidth with absorption efficiency ≤ -10 dB was 0.73~2.74 THz. Meanwhile, the highest electromagnetic shielding efficiency of the film was 46.69 dB and the average shielding efficiency was 33.46 dB.

[0040] Referring to the standard GB / T 31838.4-2019 "Dielectric and resistive properties of solid insulating materials - Part 4: Resistive properties (DC method) Insulation resistance", the wave-absorbing electromagnetic shielding film was found to be a DC insulating material. Example 4

[0041] (1) Preparation of nano copper powder Copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water were added to a three-necked flask, stirred, and heated to 75°C. A 25% (w / w) glucose aqueous solution was added dropwise, and stirring was continued for 35 minutes. After cooling, the mixture was poured into centrifuge tubes and centrifuged at 2500 rpm for 8 minutes. The supernatant was removed, and the lower solid-liquid mixture was washed with methanol, centrifuged, and the supernatant was removed. The centrifuge tubes were placed in a vacuum oven and dried at 45°C for 2.5 hours to obtain nano-copper powder. The weight ratio of copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water was 1:3.5:1650:2550; the weight ratio of copper hydroxide to glucose aqueous solution was 1:15. (2) Preparation of nano copper powder sol solution Ethyl acetate, acrylic resin, butyl acetate and cyclohexanone were added sequentially to a three-necked flask, heated to 45°C and stirred for 35 minutes. Then, under a nitrogen atmosphere, the nano-copper powder prepared in step (1) was added, and stirring was continued for 2.5 hours. After cooling, a nano-copper powder sol solution was obtained. The weight ratio of ethyl acetate, acrylic resin, butyl acetate, cyclohexanone and nano-copper powder was 1:4.5:1.2:1.8:2.7. The weight average molecular weight of the acrylic resin was 60,000. (3) Preparation of electromagnetic shielding film Naphthol blue-black was ground into powder with a particle size of 800-1000 mesh and added to a three-necked flask. Bisphenol A type epoxy resin glue was added and stirred. Then, the nano copper powder sol solution prepared in step (2) was added and stirred. Diethylenetriamine was added and then placed in a mold and heated to 75°C to cure, thus obtaining a wave-absorbing electromagnetic shielding film for 6G electronic devices. The weight ratio of naphthol blue-black, bisphenol A type epoxy resin glue, diethylenetriamine and nano copper powder sol solution was 1:3.5:1.2:4.5. The thickness of the wave-absorbing electromagnetic shielding film was 1.0 mm.

[0042] Referring to the literature (Materials Today Physics, 2025, 51: 101655), the performance testing method for this electromagnetic shielding film when used for electromagnetic protection is as follows: the wave-absorbing electromagnetic shielding film used for 6G electronic devices is cut into 2cm×2cm pieces, placed in a fixture, and then placed in a terahertz time-domain spectroscopy system. The electromagnetic wave absorption efficiency and electromagnetic shielding efficiency of the electromagnetic shielding film in the frequency range of 0.3~3.0 THz are tested using transmission mode and reflection mode.

[0043] The film's lowest absorption efficiency was -25.16 dB and the average absorption efficiency was -17.66 dB in the 0.3-3.0 THz range. The effective bandwidth with absorption efficiency ≤ -10 dB was 0.69~2.98 THz. Meanwhile, the highest electromagnetic shielding efficiency of the film was 49.11 dB and the average shielding efficiency was 31.88 dB.

[0044] Referring to the standard GB / T 31838.4-2019 "Dielectric and resistive properties of solid insulating materials - Part 4: Resistive properties (DC method) Insulation resistance", the wave-absorbing electromagnetic shielding film was found to be a DC insulating material. Comparative Example 1

[0045] The naphthol blue-black in Example 1 was replaced with basic black BL (CAS No. 92-31-9), while other parameters and amounts remained unchanged, as follows: (1) Preparation of nano copper powder Copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water were added to a three-necked flask, stirred, and heated to 70°C. A 20% (w / w) glucose aqueous solution was added dropwise, and stirring was continued for 30 minutes. After cooling, the mixture was poured into centrifuge tubes and centrifuged at 2000 rpm for 5 minutes. The supernatant was removed, and the lower solid-liquid mixture was washed with methanol, centrifuged, and the supernatant was removed. The centrifuge tubes were then placed in a vacuum oven and dried at 40°C for 2 hours to obtain nano-copper powder. The weight ratio of copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water was 1:3:1600:2500; the weight ratio of copper hydroxide to glucose aqueous solution was 1:10. (2) Preparation of nano copper powder sol solution Ethyl acetate, acrylic resin, butyl acetate and cyclohexanone were added sequentially to a three-necked flask, heated to 50°C and stirred for 40 minutes. Then, under a nitrogen atmosphere, the nano-copper powder prepared in step (1) was added, and stirring was continued for 3 hours. After cooling, a nano-copper powder sol solution was obtained. The weight ratio of ethyl acetate, acrylic resin, butyl acetate, cyclohexanone and nano-copper powder was 1:4:1:1.5:2.5. The weight average molecular weight of acrylic resin was 50,000. (3) Preparation of electromagnetic shielding film Alkaline black BL was ground into powder with a particle size of 800~1000 mesh and added to a three-necked flask. Bisphenol A type epoxy resin glue was added and stirred. Then, the nano copper powder sol solution prepared in step (2) was added and stirred. Then, diethylenetriamine was added and placed in a mold. The mixture was heated to 70°C to cure, and a wave-absorbing electromagnetic shielding film for 6G electronic devices was obtained. The weight ratio of alkaline black BL, bisphenol A type epoxy resin glue, diethylenetriamine and nano copper powder sol solution was 1:3:1:4. The thickness of the wave-absorbing electromagnetic shielding film was 1.0 mm.

[0046] Referring to the literature (Materials Today Physics, 2025, 51: 101655), the performance testing method for this electromagnetic shielding film when used for electromagnetic protection is as follows: the wave-absorbing electromagnetic shielding film used for 6G electronic devices is cut into 2cm×2cm pieces, placed in a fixture, and then placed in a terahertz time-domain spectroscopy system. The electromagnetic wave absorption efficiency and electromagnetic shielding efficiency of the electromagnetic shielding film in the frequency range of 0.3~3.0 THz are tested using transmission mode and reflection mode.

[0047] Figure 6 The image shows the microwave absorption performance of the composite thin film prepared in Comparative Example 1. Figure 6 It can be seen that the effective bandwidth of the thin film is 1.38-3.0THz, the minimum absorption efficiency is -19.93dB, and the average absorption efficiency is -11.32dB.

[0048] Naphthol Blue-Black in Example 1 is a black acidic dye, while Basic Black BL in Comparative Example 1 is a black basic dye. Although both are black organic compounds, their effects are significantly different, indicating that the effect of organic additives is not determined by color.

[0049] Referring to the standard GB / T 31838.4-2019 "Dielectric and resistive properties of solid insulating materials - Part 4: Resistive properties (DC method) Insulation resistance", the wave-absorbing electromagnetic shielding film was found to be a DC insulating material. Comparative Example 2

[0050] Acid Green 25 (CAS No. 4403-90-1, molecular formula C28H23N2NaO8S2) was used instead of Naphthol Blue Black in Example 1, with other parameters and amounts remaining unchanged, as follows: (1) Preparation of nano copper powder Copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water were added to a three-necked flask, stirred, and heated to 70°C. A 20% (w / w) glucose aqueous solution was added dropwise, and stirring was continued for 30 minutes. After cooling, the mixture was poured into centrifuge tubes and centrifuged at 2000 rpm for 5 minutes. The supernatant was removed, and the lower solid-liquid mixture was washed with methanol, centrifuged, and the supernatant was removed. The centrifuge tubes were then placed in a vacuum oven and dried at 40°C for 2 hours to obtain nano-copper powder. The weight ratio of copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water was 1:3:1600:2500; the weight ratio of copper hydroxide to glucose aqueous solution was 1:10. (2) Preparation of nano copper powder sol solution Ethyl acetate, acrylic resin, butyl acetate and cyclohexanone were added sequentially to a three-necked flask, heated to 50°C and stirred for 40 minutes. Then, under a nitrogen atmosphere, the nano-copper powder prepared in step (1) was added, and stirring was continued for 3 hours. After cooling, a nano-copper powder sol solution was obtained. The weight ratio of ethyl acetate, acrylic resin, butyl acetate, cyclohexanone and nano-copper powder was 1:4:1:1.5:2.5. The weight average molecular weight of acrylic resin was 50,000. (3) Preparation of electromagnetic shielding film Acid Green 25 was ground into powder with a particle size of 800~1000 mesh and added to a three-necked flask. Bisphenol A type epoxy resin glue was added and stirred. Then, the nano copper powder sol solution prepared in step (2) was added and stirred. Then, diethylenetriamine was added and placed in a mold. The mixture was heated to 70°C to cure, and a wave-absorbing electromagnetic shielding film for 6G electronic devices was obtained. The weight ratio of Acid Green 25, bisphenol A type epoxy resin glue, diethylenetriamine and nano copper powder sol solution was 1:3:1:4. The thickness of the wave-absorbing electromagnetic shielding film was 1.0 mm.

[0051] Referring to the literature (Materials Today Physics, 2025, 51: 101655), the performance testing method for this electromagnetic shielding film when used for electromagnetic protection is as follows: the wave-absorbing electromagnetic shielding film used for 6G electronic devices is cut into 2cm×2cm pieces, placed in a fixture, and then placed in a terahertz time-domain spectroscopy system. The electromagnetic wave absorption efficiency and electromagnetic shielding efficiency of the electromagnetic shielding film in the frequency range of 0.3~3.0 THz are tested using transmission mode and reflection mode.

[0052] Figure 7The image shows the microwave absorption performance of the composite thin film prepared in Comparative Example 2. Figure 7 It can be seen that the effective bandwidth of the thin film is 2.56-3.0THz, the minimum absorption efficiency is -12.29dB, and the average absorption efficiency is -7.15dB.

[0053] Naphthol Blue-Black in Example 1 is a black acidic dye, while Acid Green 25 in Comparative Example 1 is a green acidic dye. Although both are acidic organic compounds, their effects are significantly different, indicating that the effect of organic additives is related to their molecular structure.

[0054] Referring to the standard GB / T 31838.4-2019 "Dielectric and resistive properties of solid insulating materials - Part 4: Resistive properties (DC method) Insulation resistance", the wave-absorbing electromagnetic shielding film was found to be a DC insulating material. Comparative Example 3

[0055] Acid Red 73 (molecular formula C22H14N4O7S2·Na2) was used instead of Naphthol Blue Black in Example 1, with other parameters and amounts remaining unchanged, as follows: (1) Preparation of nano copper powder Copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water were added to a three-necked flask, stirred, and heated to 70°C. A 20% (w / w) glucose aqueous solution was added dropwise, and stirring was continued for 30 minutes. After cooling, the mixture was poured into centrifuge tubes and centrifuged at 2000 rpm for 5 minutes. The supernatant was removed, and the lower solid-liquid mixture was washed with methanol, centrifuged, and the supernatant was removed. The centrifuge tubes were then placed in a vacuum oven and dried at 40°C for 2 hours to obtain nano-copper powder. The weight ratio of copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water was 1:3:1600:2500; the weight ratio of copper hydroxide to glucose aqueous solution was 1:10. (2) Preparation of nano copper powder sol solution Ethyl acetate, acrylic resin, butyl acetate and cyclohexanone were added sequentially to a three-necked flask, heated to 50°C and stirred for 40 minutes. Then, under a nitrogen atmosphere, the nano-copper powder prepared in step (1) was added, and stirring was continued for 3 hours. After cooling, a nano-copper powder sol solution was obtained. The weight ratio of ethyl acetate, acrylic resin, butyl acetate, cyclohexanone and nano-copper powder was 1:4:1:1.5:2.5. The weight average molecular weight of acrylic resin was 50,000. (3) Preparation of electromagnetic shielding film Acid Red 73 was ground into powder with a particle size of 800-1000 mesh and added to a three-necked flask. Bisphenol A type epoxy resin glue was added and stirred. Then, the nano copper powder sol solution prepared in step (2) was added and stirred. Diethylenetriamine was added and then placed in a mold and heated to 70°C to cure, thus obtaining a wave-absorbing electromagnetic shielding film for 6G electronic devices. The weight ratio of Acid Red 73, bisphenol A type epoxy resin glue, diethylenetriamine and nano copper powder sol solution was 1:3:1:4. The thickness of the wave-absorbing electromagnetic shielding film was 1.0 mm.

[0056] Referring to the literature (Materials Today Physics, 2025, 51: 101655), the performance testing method for this electromagnetic shielding film when used for electromagnetic protection is as follows: the wave-absorbing electromagnetic shielding film used for 6G electronic devices is cut into 2cm×2cm pieces, placed in a fixture, and then placed in a terahertz time-domain spectroscopy system. The electromagnetic wave absorption efficiency and electromagnetic shielding efficiency of the electromagnetic shielding film in the frequency range of 0.3~3.0 THz are tested using transmission mode and reflection mode.

[0057] Figure 8 The image shows the microwave absorption performance of the composite thin film prepared in Comparative Example 1. Figure 8 It can be seen that the effective bandwidth of the thin film is 2.99-3.0THz, the minimum absorption efficiency is -11.91dB, and the average absorption efficiency is -6.71dB.

[0058] Naphthol Blue-Black in Example 1 is a black acidic dye, while Acid Red 73 in Comparative Example 3 is a red acidic dye. Although both are acidic organic compounds, their effects are significantly different, indicating that the effect of organic additives is related to their structure.

[0059] Referring to the standard GB / T 31838.4-2019 "Dielectric and resistive properties of solid insulating materials - Part 4: Resistive properties (DC method) Insulation resistance", the wave-absorbing electromagnetic shielding film was found to be a DC insulating material.

Claims

1. A method for preparing a microwave-absorbing electromagnetic shielding film for 6G electronic devices, characterized in that: (1) Preparation of nano copper powder Add copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water to a three-necked flask, stir, heat to 70-80℃, add a 20%-30% glucose aqueous solution dropwise, continue stirring for 30-40 minutes, cool, pour into centrifuge tubes, place in a centrifuge, centrifuge at 2000-3000 rpm for 5-10 minutes, remove the supernatant, wash the lower solid-liquid mixture with methanol, centrifuge, remove the supernatant, place the centrifuge tubes in a vacuum oven, and dry at 40-50℃ for 2-3 hours to obtain nano-copper powder; wherein, the weight ratio of copper hydroxide, diethylenetriamine, potassium hydroxide, and deionized water is 1:(3-4):(1600-1700):(2500-2600); wherein, the weight ratio of copper hydroxide to glucose aqueous solution is 1:(10-20). (2) Preparation of nano copper powder sol solution Ethyl acetate, acrylic resin, butyl acetate and cyclohexanone were added sequentially to a three-necked flask, heated to 40-50°C, and stirred for 30-40 minutes. Then, under a nitrogen atmosphere, the nano-copper powder prepared in step (1) was added, and stirring was continued for 2-3 hours. After cooling, a nano-copper powder sol solution was obtained. The weight ratio of ethyl acetate, acrylic resin, butyl acetate, cyclohexanone and nano-copper powder was 1:(4-5):(1-1.5):(1.5-2):(2.5-3). The weight average molecular weight of the acrylic resin was 50,000-75,000. (3) Preparation of electromagnetic shielding film Naphthol blue-black was ground into powder with a particle size of 800-1000 mesh and added to a three-necked flask. Bisphenol A type epoxy resin glue was added and stirred. Then, the nano copper powder sol solution prepared in step (2) was added and stirred. Diethylenetriamine was added and then placed in a mold and heated to 70-80℃ to cure, thus obtaining a wave-absorbing electromagnetic shielding film for 6G electronic devices. The weight ratio of naphthol blue-black, bisphenol A type epoxy resin glue, diethylenetriamine and nano copper powder sol solution was 1:(3-4):(1-1.4):(4-5). The thickness of the wave-absorbing electromagnetic shielding film was 0.5-2.0 mm.

2. The microwave-absorbing electromagnetic shielding film for 6G electronic devices according to claim 1, characterized in that, The performance testing method for electromagnetic protection is as follows: the electromagnetic shielding film for 6G electronic devices is cut into 2cm×2cm pieces, placed in a fixture, and then placed in a terahertz time-domain spectroscopy system. The electromagnetic shielding film’s electromagnetic wave absorption efficiency and electromagnetic shielding efficiency in the frequency range of 0.3~3.0 THz are tested using transmission mode and reflection mode.

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