Electromagnetic shielding material and preparation method and application thereof

Abstract

The invention discloses an electromagnetic shielding material as well as a preparation method and application thereof. The electromagnetic shielding material comprises a transparent conductive ITO (Indium Tin Oxide) film substrate; the periodic nanocrystalline pixel arrays are respectively positioned on the upper surface and the lower surface of the ITO film substrate; the periodic nanocrystalline pixel array is formed by arranging a plurality of nanocrystalline units according to a specific pattern, the patterns of the nanocrystalline units on the upper surface and the lower surface are complementary and are shaped like a Chinese character'tian 'or' 8 ', cells occupied by nanocrystalline on the upper surface are smaller than cells occupied by nanocrystalline on the lower surface, such as combinations of a cross shape / an open square ring, an H shape / a 2 shape and the like, and therefore the periodic nanocrystalline pixel array is formed. According to the present invention, with the cooperation of the global conductivity of the ITO substrate and the local electromagnetic attenuation characteristic of the nanocrystalline pixel, the electromagnetic shielding efficiency is more than or equal to 40 dB (0.01 MHz-10 GHz) and the global light transmittance is more than or equal to 60%, such that the material is suitable for the electronic device display window requiring high light transmittance and strong electromagnetic shielding, and the problems that the traditional metal shielding material is opaque, and the shielding efficiency of the conductive polymer is insufficient are solved.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic shielding materials technology, specifically relating to a nanocrystalline electromagnetic shielding material with a pixel-transparent structure, its preparation method, and its application. Background Technology

[0002] With the rapid development of electronic technology, electromagnetic interference (EMI) has become increasingly serious, posing a threat to the normal operation of electronic equipment and information security. Electromagnetic shielding materials, as an effective solution, have been widely researched and applied. Developing highly efficient electromagnetic shielding materials to suppress or eliminate electromagnetic interference has become a key aspect of ensuring the reliability and safety of modern electronics industry.

[0003] Traditional electromagnetic shielding materials mainly include metal sheets, metal fiber composites, and conductive polymers, playing a vital role in numerous applications. However, as electronic devices evolve towards thinner, lighter, more flexible, intelligent, and multifunctional designs, these materials exhibit limitations in certain specialized applications. For instance, metal sheets are heavy and opaque, making them unsuitable for applications requiring light transmission, such as display windows, touchscreens, and protective covers for optical sensors. While conductive polymers possess some light transmittance, their conductive networks often become sparse when pursuing high transmittance, resulting in limited electromagnetic shielding effectiveness and failing to meet the increasingly stringent shielding requirements of fields like 5G communication and high-end displays.

[0004] To overcome the shortcomings of traditional materials, researchers have recently turned their attention to novel materials with nanoscale microstructures. Among these, nanocrystalline materials have gradually become a hot topic in electromagnetic shielding material research due to their excellent physical properties and tunable microstructure. These materials are typically composed of nanoscale grains, possessing high resistivity, high permeability, low coercivity, and excellent soft magnetic properties, enabling them to effectively reflect and absorb electromagnetic waves. However, despite the great potential of nanocrystalline materials in electromagnetic shielding, especially in wave absorption, most existing research and technology still focus on preparing opaque bulk or thick-film materials. These materials are usually made by blending nanocrystalline particles with a polymer matrix and filling them in a high proportion. Their inherent high filling density and microstructure characteristics prevent visible light from penetrating, thus failing to meet the aforementioned special application scenarios requiring light transmittance.

[0005] In summary, the field of electromagnetic shielding materials currently faces a prominent contradiction: on the one hand, the market demand for high-performance electromagnetic shielding is increasingly urgent; on the other hand, in key components such as display windows and transparent sensor covers, materials must maintain high visible light transmittance while providing effective electromagnetic shielding. Existing technologies, whether traditional metallic materials or conventional nanocrystalline materials, struggle to achieve an ideal balance between these seemingly contradictory key performance indicators of "high shielding effectiveness" and "high optical transmittance." Therefore, developing a novel nanocrystalline electromagnetic shielding material that combines excellent electromagnetic shielding effectiveness with good visible light transmittance has become a crucial direction for breakthroughs in this technological field. Summary of the Invention

[0006] In view of the above, the purpose of this invention is to provide a nanocrystalline electromagnetic shielding material with a pixel-transparent structure, its preparation method and application. This material combines the excellent electromagnetic shielding performance of nanocrystalline materials with the design of a pixel-transparent structure, and can effectively shield electromagnetic interference while meeting the requirements of light transmission performance. It achieves a balance between electromagnetic shielding and light transmission performance and has important application value.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a pixel-transparent nanocrystalline electromagnetic shielding material, comprising: Transparent and conductive ITO (indium tin oxide) thin film substrate; Periodic nanocrystalline pixel arrays located on the upper and lower surfaces of an ITO thin film substrate, respectively; The periodic nanocrystalline pixel array is composed of multiple nanocrystalline units arranged in a specific pattern, and the patterns of the nanocrystalline units on the upper and lower surfaces are different, wherein the upper surface nanocrystalline units occupy fewer cells than the lower surface.

[0008] The nanocrystalline unit patterns on the upper and lower surfaces are superimposed to form a figure-eight or grid pattern, including but not limited to one of the following combinations: a cross-shaped pattern on the upper surface + an open square ring pattern on the lower surface; an H-shaped pattern on the upper surface + a type 2 pattern on the lower surface; a type 7 pattern on the upper surface + a type 6 pattern on the lower surface; or a type 4 pattern on the upper surface + a mirrored type 6 pattern on the lower surface. The transmittance and electromagnetic shielding effectiveness are adjusted by changing the proportion of nanocrystals in the pixel unit structure. Combined with an ITO film as a substrate, the material as a whole possesses good transmittance and conductivity. By using different pattern designs on the upper and lower surfaces, the phase difference of light passing through the material changes, thereby reducing interference and superposition. This design improves the uniformity of light transmission, allowing light to pass through the material more evenly. A sparser pattern is designed on the upper surface to ensure sufficient transmittance, while a denser pattern is designed on the lower surface to enhance the electromagnetic shielding effect.

[0009] Preferably, the minimum arrangement period of the periodic nanocrystalline pixel array is 7mm×7mm, wherein the size of each nanocrystalline unit is 1mm×1mm.

[0010] Preferably, the nanocrystalline units account for 15%-40% of the 7mm×7mm periodic units and are filled within an area of ​​5mm×5mm at the center point. The nanocrystalline units on the upper surface occupy a smaller cell than those on the lower surface to avoid the upper surface nanocrystalline units being too dense, which would reduce light transmittance, and the lower surface nanocrystalline units being too sparse, which would weaken the shielding effect.

[0011] Preferably, the nanocrystalline units on the upper and lower surfaces are superimposed in a figure-eight or grid pattern. This pattern design makes the superimposed patterns complementary, enhancing the electromagnetic wave shielding capability.

[0012] Preferably, the ITO thin film substrate has a thickness of 0.125-0.25 mm, a sheet resistance of 3-12 Ω / □, and a visible light transmittance of ≥85%.

[0013] Preferably, the material of the nanocrystalline unit is selected from at least one of iron-based nanocrystals, cobalt-based nanocrystals, and nickel-based nanocrystals.

[0014] Preferably, the single-layer thickness of the nanocrystalline unit is 0.02-0.05 mm, the electromagnetic shielding effectiveness in the 0.01 MHz–10 GHz frequency band is ≥40 dB, and the global light transmittance is ≥60%.

[0015] Secondly, embodiments of the present invention also provide a method for preparing the nanocrystalline electromagnetic shielding material with the pixel-transparent structure as described above, comprising: S1, ITO film substrate selection: Select a suitable ITO film as a transparent conductive substrate; S2, Pixel pattern mask fabrication: Periodic pixel pattern masks are fabricated on the upper and lower surfaces of the ITO thin film substrate using photolithography. S3, Fabrication of nanocrystalline pixel array: Nanocrystalline materials are deposited on a periodic pixel pattern mask by magnetron sputtering or chemical vapor deposition to form a periodic nanocrystalline pixel array.

[0016] Preferably, the mask design in step S2 is a 1mm×1mm pattern arranged within a 7mm×7mm periodic cell; the deposition conditions in step S3 satisfy: magnetron sputtering with a base vacuum ≤5×10 -5 Pa, sputtering power DC 100–200W, or chemical vapor deposition with carrier gas H2 / Ar mixture and deposition temperature 250–300℃.

[0017] Thirdly, embodiments of the present invention also provide an application of the nanocrystalline electromagnetic shielding material with the pixel-transparent structure described above, for use in electronic device display windows that simultaneously meet the requirements of electromagnetic shielding effectiveness ≥40dB and light transmittance ≥60%, and the compatible electromagnetic interference frequency bands include 0.01MHz–10GHz.

[0018] Compared with the prior art, the beneficial effects of the present invention include at least the following: (1) Excellent electromagnetic shielding performance: The nanocrystalline pixel pattern structure in the periodic nanocrystalline pixel array can effectively reflect and absorb electromagnetic waves, and the shielding effectiveness can reach more than 40 dB.

[0019] (2) Good light transmittance: ITO film, as a transparent substrate, combined with the design of nanocrystalline pixel pattern structure, enables the material to meet the requirements of light transmittance while shielding electromagnetic interference.

[0020] (3) Lightweight, high strength and good processing performance: The material has a low density and light weight, while having high strength and hardness, making it suitable for applications where weight and strength are required. Using photolithography and magnetron sputtering processes, the material is easy to process and can meet the needs of complex shaped parts. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the preparation method of the nanocrystalline electromagnetic shielding material with pixel-transparent structure provided in the embodiments of the present invention; Figure 2 This is a schematic diagram of the structure of the nanocrystalline electromagnetic shielding material with pixel-transparent structure provided in Embodiment 1 of the present invention; Figure 3 The pixel-transparent nanocrystalline electromagnetic shielding material provided in Embodiment 1 of this invention exhibits electromagnetic shielding effectiveness in the 0.01MHz-0.1MHz range. Figure 4 The pixel-transparent nanocrystalline electromagnetic shielding material provided in Embodiment 2 of the present invention has an upper and lower unit structure and an electromagnetic shielding effectiveness in the range of 0.1MHz-1MHz. Figure 5 The pixel-transparent nanocrystalline electromagnetic shielding material provided in Embodiment 3 of the present invention has an upper and lower unit structure and an electromagnetic shielding effectiveness in the range of 0.1MHz-1MHz. Figure 6 The pixel-transparent nanocrystalline electromagnetic shielding material provided in Embodiment 4 of the present invention has an upper and lower unit structure and an electromagnetic shielding effectiveness in the range of 0.1MHz-1MHz. Figure 7 The electromagnetic shielding effectiveness of the single ITO transparent film provided in Comparative Example 1 of this invention is in the range of 0.1MHz-1MHz. 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 the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of this invention.

[0024] The inventive concept of this invention is to address the problem of balancing electromagnetic shielding and light transmission performance in existing technologies. This invention provides a nanocrystalline electromagnetic shielding material with a pixel-transparent structure, its preparation method, and its applications. Through a structural design of an ITO sandwich double-sided nanocrystalline pixel array, periodic nanocrystalline pixel units are constructed on the upper and lower surfaces of the ITO film. Utilizing the synergistic effect of pixelated local functional enhancement and global coverage by a transparent conductive substrate, the electromagnetic shielding bottleneck of traditional ITO films is overcome while maintaining high light transmittance (≥60%). Its core innovation lies in establishing spatial decoupling between the light transmission channel and the electromagnetic attenuation channel by precisely controlling the local distribution (rather than global coverage) of the nanocrystalline pixels. By adjusting the pixel density (10%-40%), nanocrystalline type (Fe / Co / Ni-based combination), and unit pattern, it can be freely combined to adapt to broadband requirements from kHz to GHz.

[0025] like Figure 1 As shown in the embodiment, a method for preparing a nanocrystalline electromagnetic shielding material with a pixel-transparent structure includes the following steps: S1, ITO film substrate selection: Select a suitable ITO film as a transparent conductive substrate.

[0026] Specifically, an ITO film with a thickness of 0.125 mm and a sheet resistance of 3 Ω / □ was selected and subjected to ultrasonic cleaning (deionized water → ethanol) and plasma activation pretreatment.

[0027] S2, Pixel pattern mask fabrication: Periodic pixel pattern masks are fabricated on the upper and lower surfaces of the ITO thin film substrate using photolithography.

[0028] Specifically, the process involves spin-coating photoresist on both sides of an ITO thin film, baking, ultraviolet exposure using a mask, development, and hard baking to form a periodic pixel pattern mask.

[0029] S3, Fabrication of nanocrystalline pixel array: Nanocrystalline materials are deposited on a periodic pixel pattern mask by magnetron sputtering or chemical vapor deposition to form a periodic nanocrystalline pixel array.

[0030] Specifically, nanocrystalline material is deposited in the mask area to a thickness of 0.02 mm by magnetron sputtering or chemical vapor deposition (CVD) → the mask is removed to form a periodic nanocrystalline pixel array.

[0031] The following description, in conjunction with Examples 1-4, Comparative Example 1, and others, illustrates the principles of the law. Figure 3-7 The electromagnetic shielding effectiveness curves shown further verify the electromagnetic shielding effectiveness of the nanocrystalline electromagnetic shielding material with pixel-transparent structure provided in the embodiments of the present invention.

[0032] Example 1 S101, ITO thin film substrate selection: A 0.125 mm thick ITO film was selected as the transparent conductive substrate, ensuring that the sheet resistance of the ITO film was 3 Ω / □ and the visible light transmittance was ≥85%. The ITO film was cleaned to remove surface dust, impurities, and organic residues. Using an ultrasonic cleaning device, it was first ultrasonically cleaned with deionized water for 10 minutes, then ultrasonically cleaned with ethanol for 10 minutes. After purging with nitrogen, it was placed in an 80°C vacuum oven for 30 minutes.

[0033] S102, Pixel pattern mask fabrication: Pre-treated ITO thin films were spin-coated with positive photoresist (AZ4620) on both sides at 1200 rpm to a thickness of 1.2 μm, followed by baking at 100℃ for 90 seconds. A periodic pixel pattern was designed, with each pixel unit being a 1 mm × 1 mm square arranged in a 7 mm × 7 mm array. The pixel pattern on the upper surface was cross-shaped, and the pixel pattern on the lower surface was an open square ring, as shown below. Figure 2 As shown. Based on the designed pixel pattern, a mask pattern is drawn. The top and bottom surfaces are exposed to ultraviolet light, immersed in developer for 60 seconds, rinsed with deionized water, and then hard-baked at 110°C for 120 seconds to form an etch-resistant mask.

[0034] S103, fabrication of nanocrystalline pixel array: Place the ITO thin film on the sample stage of the magnetron sputtering equipment, ensuring that the upper and lower surfaces of the ITO thin film face the two sputtering targets respectively, and evacuate the equipment to 10°C. -4 To minimize interference from impurity gases, iron-based nanocrystalline materials were sputtered onto the upper and lower surfaces of an ITO thin film at pressures below Pa. During sputtering, sputtering power, gas pressure, and sputtering time were controlled to ensure a deposited nanocrystalline material thickness of 0.02 mm. After removing the mask, the electromagnetic shielding effectiveness of the obtained nanocrystalline electromagnetic shielding material was as follows: Figure 3 As shown.

[0035] Example 2 Unlike Example 1, in S102, the pixel pattern on the upper surface is H-shaped, and the pixel pattern on the lower surface is type 2, resulting in the electromagnetic shielding effectiveness of the nanocrystalline electromagnetic shielding material as shown in Example 1. Figure 4 As shown.

[0036] Example 3 Unlike Example 1, in S102, the pixel pattern on the upper surface is type 7 and the pixel pattern on the lower surface is type 6, resulting in the electromagnetic shielding effectiveness of the nanocrystalline electromagnetic shielding material as follows: Figure 5 As shown.

[0037] Example 4 Unlike Example 1, in S102, the pixel pattern on the upper surface is type 4, and the pixel pattern on the lower surface is a mirror type 6, resulting in the electromagnetic shielding effectiveness of the nanocrystalline electromagnetic shielding material as follows: Figure 6 As shown.

[0038] Comparative Example 1 Unlike the previous example, only an ITO film with a thickness of 0.125 mm, visible light transmittance ≥85%, sheet resistance of 3 Ω / □, and no patterned design was selected. Its electromagnetic shielding effectiveness is as follows: Figure 7 As shown.

[0039] The specific embodiments described above illustrate the technical solution and beneficial effects of the present invention in detail. It should be understood that the above description is only the most preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An electromagnetic shielding material, characterized in that, include: Transparent conductive ITO thin film substrate; Periodic nanocrystalline pixel arrays located on the upper and lower surfaces of an ITO thin film substrate, respectively; The periodic nanocrystalline pixel array is composed of multiple nanocrystalline units arranged in a specific pattern, and the patterns of the nanocrystalline units on the upper and lower surfaces are different, wherein the upper surface nanocrystalline units occupy fewer cells than the lower surface.

2. The electromagnetic shielding material according to claim 1, characterized in that, The minimum arrangement period of the periodic nanocrystalline pixel array is 7mm×7mm, and the size of each nanocrystalline unit is 1mm×1mm.

3. The electromagnetic shielding material according to claim 2, characterized in that, The nanocrystalline units account for 15%-40% of the 7mm×7mm periodic units and are filled within an area of ​​5mm×5mm at the center point.

4. The electromagnetic shielding material according to claim 1 or 3, characterized in that, The superimposed patterns of the nanocrystalline units on the upper and lower surfaces form a figure-eight or grid pattern.

5. The electromagnetic shielding material according to claim 1, characterized in that, The ITO thin film substrate has a thickness of 0.125-0.25 mm, a sheet resistance of 3-12 Ω / □, and a visible light transmittance of ≥85%.

6. The electromagnetic shielding material according to claim 1, characterized in that, The material of the nanocrystalline unit is selected from at least one of iron-based nanocrystalline, cobalt-based nanocrystalline, and nickel-based nanocrystalline.

7. The electromagnetic shielding material according to claim 1 or 6, characterized in that, The nanocrystalline unit has a single-layer thickness of 0.02-0.05 mm, an electromagnetic shielding effectiveness of ≥40 dB in the 0.01 MHz–10 GHz frequency band, and a global light transmittance of ≥60%.

8. A method for preparing an electromagnetic shielding material as described in any one of claims 1-7, characterized in that, include: S1, ITO film substrate selection: Select a suitable ITO film as a transparent conductive substrate; S2, Pixel pattern mask fabrication: Periodic pixel pattern masks are fabricated on the upper and lower surfaces of the ITO thin film substrate using photolithography. S3, Fabrication of nanocrystalline pixel array: Nanocrystalline materials are deposited on a periodic pixel pattern mask by magnetron sputtering or chemical vapor deposition to form a periodic nanocrystalline pixel array.

9. The method for preparing the electromagnetic shielding material according to claim 8, characterized in that, The mask design in step S2 is a 1mm×1mm pattern arranged within a 7mm×7mm periodic cell; the deposition conditions in step S3 satisfy: magnetron sputtering with a base vacuum ≤5×10 -5 Pa, sputtering power DC 100–200W, or chemical vapor deposition with carrier gas H2 / Ar mixture and deposition temperature 250–300℃.

10. An application of the electromagnetic shielding material as described in any one of claims 1-7, characterized in that, For display windows of electronic devices that need to simultaneously meet the requirements of electromagnetic shielding effectiveness ≥40dB and light transmittance ≥60%, the compatible electromagnetic interference frequency bands include 0.01MHz–10GHz.

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