A composite material with high shielding and high light transmission and a preparation method thereof

Abstract

The application discloses a kind of composite material with high shielding and high light transmittance and preparation method thereof, belong to electromagnetic shielding technical field.The composite material of the application includes metal screen shielding interlayer, and the light-transmitting conductive film arranged on the two sides of metal screen shielding interlayer.The application realizes performance promotion by structure optimization technology to the metal screen structure parameter control, and is provided with the light-transmitting conductive film of high transparency and low resistance on the two sides of metal screen interlayer, utilizes diversified electromagnetic shielding mechanism synergistic effect, better moderates the relationship between high light transmittance and strong shielding performance, so that the high light transmittance electromagnetic shielding film has strong electromagnetic shielding while having high transparency, has wide application prospect in aerospace, photoelectric detection, man-machine interaction, visual window and the like field.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of composite material with high shielding and high light transmittance and its preparation method, belong to electromagnetic shielding technical field. BACKGROUND

[0002] With the increasing complexity of electromagnetic environment, not only requires excellent shielding effect on electromagnetic waves, but also requires high visible light transmittance.

[0003] Flexible transparent electromagnetic shielding technology, not only through optical band without affecting the normal use of optoelectronic equipment, meet the applicability and mechanical stability for complex application scenarios, but also realize the shielding of application frequency band electromagnetic waves, it is the difficulty of current electromagnetic shielding technology. At present, the main transparent electromagnetic shielding materials are mainly divided into two kinds: one is continuous film, such as conductive oxide base, graphene base, transparent conductive polymer base film, etc. The second is aperture type film, which is connected to each other to form a conductive network at the microscale, and a certain gap is left to ensure the light transmittance at the macro level, typical of metal mesh base, metal nanowire base film, etc.

[0004] However, a single material system is difficult to well balance the relationship between visible light transmittance and electromagnetic shielding performance. The metal elements in conductive oxide are mostly rare metals, such as indium in ITO, which is expensive and increases the cost of application. The intrinsic conductivity of conductive polymer is low, and some conductive polymers such as polyacetylene are easily oxidized and degraded in air, with poor stability. Carbon nanomaterials for transparent shielding film have low shielding performance and cannot meet the general application requirements. The transparent shielding film based on metal mesh structure has high conductivity and flexible processing method, which can effectively improve the anti-electromagnetic interference performance of optical window, and has little effect on the observation transmittance of optical window while realizing strong electromagnetic shielding performance. It has become an important choice to replace traditional shielding film materials, but the metal mesh structure cannot have high transmittance and strong shielding performance.

[0005] In view of the difficulties of single material in the field of light shielding, in order to improve the comprehensive performance by using composite structure, the following two directions are mainly improved. One is to select multiple material systems for compounding, so as to complement each other and realize the performance synergy between multiple components. The second is to design shielding structure, starting from the transmission mechanism of microwave electromagnetic wave, fully utilizing the structure parameter design and shielding characteristics of materials, and designing the best composite shielding structure.

[0006] As disclosed in Chinese patent CN 113079683 A, a method for preparing a composite material by compositing transparent conductive layers on both sides of a substrate is disclosed, a double-sided shielding structure is verified, and it is verified that as the thickness of the substrate increases, the visible light transmittance remains basically unchanged, but the shielding effectiveness increases substantially. The composite process changes with different composite materials, mainly magnetron sputtering, spin coating, roll coating, scraping coating, CVD and other methods, and the shielding effectiveness of the high-transmittance electromagnetic shielding film prepared based on this structure is greater than 30 dB, and the transmittance is between 70-90%; but the applicability of the metal mesh structure in this composite structure is not considered, and the preparation process is also relatively complex.

[0007] As disclosed in Chinese patent CN 116476459 A, an embedded electromagnetic shielding transparent body and a preparation method thereof are disclosed, which can prevent the metal mesh layer and the wave-absorbing layer from being exposed, and can also prevent electromagnetic reflection from causing secondary pollution. However, this structure cannot greatly improve the overall shielding effectiveness, and the transmittance can only be about 60%, and the embedded structure results in low strength of the internal metal mesh layer.

[0008] As disclosed in Chinese patent CN 106714533 B, a graphene / double-layer metal mesh transparent electromagnetic shielding device with bidirectional wave-absorbing effect is prepared, which realizes the purpose of improving the shielding performance without changing the transmittance, but the number of layers of the composite material is basically seven or eight, and the composite process is more complex than ordinary composite materials. SUMMARY

[0009] In view of the defects and deficiencies of the prior art, the present application provides a composite material with high shielding and high transmittance and a preparation method thereof. The composite material prepared by the method can simultaneously have high shielding performance and high transmittance, and the preparation process is simple, the raw materials are economical and affordable, and the production cost can be effectively reduced.

[0010] The flexible stainless steel mesh as a metal mesh material not only has certain advantages in price, but also has good corrosion resistance. The present application forms a composite structure based on a transparent conductive film and a stainless steel mesh, improves the mechanical properties and shielding effectiveness of the composite material by the performance advantages of the transparent conductive film and the stainless steel material, strengthens the internal reflection and absorption through the composite structure, improves the overall shielding performance, and uses the high-transmittance conductive film to make the structure design of the sandwiched stainless steel mesh more simple. At the same time, the composite material is prepared by a hot-pressing composite process, which ensures the mechanical performance advantage of the internal stainless steel mesh.

[0011] The first object of the present application is to provide a composite material with high shielding and high transmittance, which comprises a metal mesh shielding sandwich layer and a light-transmitting conductive film arranged on both sides of the metal mesh shielding sandwich layer.

[0012] In an embodiment, the material of the metal mesh comprises one or more of stainless steel, silver, and copper.

[0013] In an embodiment, the stainless steel is SUS316 stainless steel.

[0014] In an embodiment, the light-transmissive conductive film is a single-layer or multi-layer film prepared by compounding one or more of a conductive polymer, silver nanowires, and a conductive oxide with a transparent substrate.

[0015] In an embodiment, the sheet resistance (Rs) of the light-transmissive conductive film is 40-50 ohms, and the light transmittance is greater than 85%.

[0016] In an embodiment, the metal mesh is in the form of a UD cloth, the wire diameter is 0.02-0.08 mm, the wire spacing is 0.4-1.6 mm, and the thickness of the metal mesh is 0.04-0.13 mm; further preferably, the wire diameter is 0.05 mm, the wire spacing is 1.0 mm, and the thickness of the metal mesh is 0.1 mm.

[0017] In an embodiment, the transparent substrate is selected from one or more of glass, polyethylene terephthalate film, polyimide film, polyvinyl alcohol film, polyurethane film, polystyrene film, or polydimethylsiloxane film.

[0018] In an embodiment, the conductive polymer is selected from one or more of polyacetylene, polyaniline, polypyrrole, and related derivative polymers thereof.

[0019] In an embodiment, the conductive oxide is selected from one or more of ITO, FTO, and AZO.

[0020] In an embodiment, the thickness of the light-transmissive conductive film is 0.08-0.15 mm; preferably, the thickness is 0.12 mm.

[0021] A second object of the present application is to provide a method for preparing the composite material with high shielding and high light transmittance as described above, the method comprising the following steps:

[0022] (1) Preparation of metal mesh

[0023] The metal mesh is prepared in the form of a UD cloth; wherein the wire diameter of the metal fibers in the metal mesh is 0.02-0.08 mm, the wire spacing is 0.4-1.6 mm, the thickness of the metal mesh is 0.04-0.13 mm, the unit cell structure of the metal mesh is square, i.e., the warp and weft densities are the same, and the coverage factor of the metal fibers is 10%; then the metal mesh is subjected to ultrasonic treatment with an organic solvent, water washing, and blow drying; the surface of the metal mesh is then treated with an oxygen plasma cleaning machine, water washing, and blow drying, to obtain the metal mesh after drying;

[0024] (2) Preparation of light-transmitting conductive film

[0025] The conductive substance is dispersed in a mixed solution of water and isopropyl alcohol to form a conductive substance dispersion liquid; the transparent substrate after cleaning and drying is laid on an operation table, and then the conductive substance dispersion liquid is coated on the transparent substrate to obtain a light-transmitting conductive film;

[0026] (3) The light-transmitting conductive film prepared in step (2) is hot-pressed on both sides of the metal mesh obtained in step (1) to obtain a high-shielding and high-transmittance composite material.

[0027] In an embodiment, the organic solvents in step (1) are acetone and anhydrous ethanol in sequence.

[0028] In an embodiment, the ultrasonic treatment time in step (1) is 10-30 min.

[0029] In an embodiment, the concentration of the conductive substance dispersion liquid in step (2) is 0.5 mg / ml.

[0030] In an embodiment, the coating method in step (2) is selected from one or more of magnetron sputtering, electron beam evaporation, evaporation, electroplating, wire bar coating, pulling method, spin coating method or chemical vapor deposition method.

[0031] In an embodiment, the hot-pressing in step (3) is performed using a hot press (CARVER 4128) at a temperature of 100-120°C, a pressure of 6-10 mpa, and a hot-pressing time of 10-15 min.

[0032] A third object of the present application is to provide an application of the high-shielding and high-transmittance composite material described above in the fields of aerospace, photoelectric detection, human-computer interaction, visual window, etc.

[0033] The present application has the following advantages:

[0034] (1) The preparation of the high-shielding and high-transmittance composite material of the present application is performed by providing a light-transmitting conductive film with high transparency and low resistance on both sides of the metal mesh sandwich, when the incident microwave electromagnetic wave is reflected by the first conductive film and enters the interior, the electromagnetic wave entering the interior will also produce a large amount of reflection and transmission when reaching the second layer of stainless steel mesh, and continue to enter the third layer of light-transmitting conductive film; the electromagnetic wave will undergo multiple reflections between the two layers of light-transmitting conductive film and the stainless steel mesh layer, better moderating the relationship between high light transmission and strong shielding performance, so that the high-transmittance electromagnetic shielding film has high transparency and strong electromagnetic shielding at the same time.

[0035] (2) Since the metal mesh itself has a contradictory relationship between light transmission performance and electromagnetic shielding performance, although parameter optimization and performance improvement can be carried out through structure optimization, the shielding mechanism of the metal mesh material is relatively single, and the upper limit of the electromagnetic shielding efficiency will inevitably be restricted by the better visual effect. The metal mesh is compounded with the light-transmitting conductive film, on the one hand, the shielding mechanism of the material is multiple, the shielding efficiency is improved, and the conductivity of the light-transmitting conductive film itself can also improve the overall performance of the composite material. The light-transmitting conductive film has less loss of overall light transmission performance after compounding, and the visual performance is not greatly attenuated. The light transmission performance still reaches 80%-90%, but the shielding efficiency of the composite material can be improved from about 30dB to about 60dB, and the overall performance improvement effect is good. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 FIG. 1 is a structural diagram of a high shielding and high light transmission composite material of the present application; 1 is a metal mesh; 2 is a light-transmitting conductive film;

[0037] Figure 2 FIG. 1 is a structural diagram of a high shielding and high light transmission composite material of the present application; 1 is a metal mesh; 2 is a light-transmitting conductive film; DETAILED DESCRIPTION

[0038] The present application will be further described below in conjunction with examples, but the embodiments of the present application are not limited thereto.

[0039] Example 1

[0040] A preparation method of a high shielding and high light transmission composite material, the method comprising the following steps:

[0041] (1) Metal mesh preparation

[0042] A 200mmx200mm metal mesh is prepared by using SUS316 stainless steel as a base material in the form of UD cloth; wherein the wire diameter of the metal fiber in the metal mesh is 0.05mm, the wire distance is 1mm, the metal mesh unit structure is square, that is, the warp and weft densities are the same, and the coverage factor of the metal fiber is 10%; the thickness of the metal mesh is 0.1mm;

[0043] (2) Pretreatment of the metal mesh

[0044] The metal mesh prepared in step (1) is sequentially placed in acetone and anhydrous ethanol and ultrasonically treated at room temperature for 30min, and then washed with deionized water and dried. Then the surface of the metal mesh is treated by an oxygen plasma cleaning machine for 10min, washed with deionized water and dried to obtain a surface pretreated metal mesh;

[0045] (3) Preparation of light-transmitting conductive film

[0046] Silver nanowires with length of 25±3 μm and diameter of 30±2 nm were dispersed in a mixed solution of water and isopropyl alcohol (volume ratio of water to isopropyl alcohol was 1:1) to form a silver nanowire dispersion, and the concentration of silver nanowires in the mixed solution was 0.5 mg / ml; the cleaned and dried PET was laid on the operation table, and then the silver nanowire dispersion was uniformly dropped on the upper edge of the PET substrate, and a silver nanowire light-transmitting conductive film (square resistance was 45 ohms) was prepared by wire bar coating at a speed of 60 mm / s;

[0047] (4) The silver nanowire light-transmitting conductive film prepared in step (4) was hot-pressed on both sides of the surface-preprocessed metal mesh obtained in step (2), and the hot-pressing instrument was a hot press (CARVER 4128), the temperature was 120°C, the pressure was 10 mpa, and the hot-pressing time was 15 min; a high-shielding and high-transmittance composite material was obtained.

[0048] Example 2

[0049] The difference from Example 1 was that only the wire diameter and wire spacing of the metal fibers in the metal mesh in step (1) were adjusted according to Table 1, and the other parameters and conditions were the same as those in Example 1.

[0050] Table 1. Wire diameter and wire spacing of metal fibers in metal mesh

[0051] Number Wire diameter (mm) Wire spacing (mm) Metal mesh thickness (mm) 1 0.02 0.4 0.04 2 0.02 1.0 0.04 3 0.02 1.6 0.04 4 0.05 0.4 0.1 5 0.05 1.6 0.1 6 0.08 0.4 0.13 7 0.08 1.0 0.13 8 0.08 1.6 0.13

[0052] Comparative Example 1

[0053] The difference from Example 1 was that the metal mesh after step (2) was directly used as a shielding and light-transmitting material.

[0054] Comparative Example 2

[0055] The difference from Example 1 was that the silver nanowire light-transmitting conductive film in step (4) was replaced by a high-transparency PET film, and the other parameters and conditions were the same as those in Example 1.

[0056] Comparative Example 3

[0057] The difference from Example 1 was that the concentration of silver nanowires in the mixed solution in step (3) was adjusted to 1.5 mg / ml and 1.2 mg / ml, respectively, and the square resistance of the obtained silver nanowire light-transmitting conductive film was 15 ohms and 30 ohms, respectively; and the other parameters and conditions were the same as those in Example 1.

[0058] Comparative Example 4

[0059] The difference from Example 1 was that the silver nanowire light-transmitting conductive films with square resistance of 15 ohms, 30 ohms and 45 ohms, respectively, were directly hot-pressed, and the intermediate metal mesh was omitted; and the other parameters and conditions were the same as those in Example 1.

[0060] Result measurement

[0061] The high shielding and high light transmittance composite materials prepared in Examples 1 to 2 and Comparative Examples 1 to 4 were subjected to performance measurement, and the results are shown in Table 2.

[0062] Table 2. Performance of composite materials

[0063]

[0064] The above examples are not intended to limit the scope of the present application, and the described steps are not intended to limit the order of execution. Those skilled in the art can make obvious improvements to the present application in combination with existing common knowledge, which also falls within the protection scope defined by the claims of the present application.

Claims

1. A method for preparing a composite material having high shielding and high light transmission, characterized by, The method comprises the following steps: (1) Metal mesh preparation SUS316 stainless steel metal mesh is prepared in the form of UD cloth; wherein the linear diameter of the metal fiber in the metal mesh is 0.05 mm, the linear distance is 1.0 mm, the thickness of the metal mesh is 0.1 mm, the metal mesh cell structure is square, that is, the warp and weft densities are the same, and the coverage factor of the metal fiber is 10%; then the metal mesh is treated with an organic solvent for 30 min, washed with water, and dried; then the surface of the metal mesh is treated with an oxygen plasma cleaning machine, washed with water, and dried, and the metal mesh is obtained after drying; (2) Preparation of light-transmitting conductive film Silver nanowires with a length of 25±3 μm and a diameter of 30±2 nm are dispersed in a mixed solution of water and isopropyl alcohol to form a silver nanowire dispersion liquid, the volume ratio of water to isopropyl alcohol is 1:1, and the concentration of silver nanowires in the silver nanowire dispersion liquid is 0.5 mg / ml; the cleaned and dried PET is laid on the operation table, then the silver nanowire dispersion liquid is uniformly dropped on the upper edge of the PET substrate, and a silver nanowire light-transmitting conductive film is prepared by wire bar coating at a speed of 60 mm / s; The sheet resistance of the silver nanowire light-transmitting conductive film is 45 ohms; (3) The silver nanowire light-transmitting conductive film prepared in step (2) is hot-pressed on both sides of the metal mesh obtained in step (1), to obtain a composite material with high shielding and high light-transmitting properties; the hot-pressing temperature is 120°C, the pressure is 10 mpa, and the hot-pressing time is 15 min.

2. The production method according to claim 1, characterized by, The hot-pressing in step (3) is performed by a hot press.

3. The composite material prepared by the method of any one of claims 1 or 2.

4. The use of the composite material of claim 3 in the fields of aerospace, photoelectric detection, human-computer interaction, and visual window.

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