Electromagnetic wave-shielding material and method for manufacuring same

Abstract

The present invention relates to a method for producing an electromagnetic wave-shielding material and an electromagnetic wave-shielding material produced thereby, the method comprising: a liquid metal particle fragmentation step for fragmenting, using an ultrasonic homogenizer, liquid metal particles included in a liquid metal solution in which a liquid metal and a solvent have been mixed; a pretreated liquid metal production step for obtaining a pretreated liquid metal in which the liquid metal particles have been fragmented after removing the solvent of the liquid metal solution in which the liquid metal particles have been fragmented; a liquid metal composite production step for obtaining a liquid metal composite solution by mixing the pretreated liquid metal with a base resin solution; a liquid metal film production step for producing a liquid metal composite film by applying the liquid metal composite solution to a flexible sheet provided with a mask and drying same; a liquid metal activation step for activating a liquid metal by applying acoustic energy to the liquid metal composite film; and an electromagnetic wave-shielding material production step for producing an electromagnetic wave-shielding material by transferring the liquid metal composite film in which the liquid metal has been activated onto a base film.

Description

Electromagnetic shielding material and method of manufacturing the same

[0001] The present invention relates to an electromagnetic shielding material capable of having high elasticity while simultaneously exhibiting excellent electromagnetic shielding efficiency, and a method for manufacturing the same.

[0002] With the recent advancement of electronic and communication technologies, it has become possible to use unit circuits with various functions in a densely packed space. However, along with this, the problem of electromagnetic interference (EMI), which causes device malfunctions due to mutual interference of electromagnetic waves between adjacent circuits, is becoming serious.

[0003] In order to solve the problem of electromagnetic interference, it is necessary to first reduce the number or output of electronic devices that generate electromagnetic waves and to block the leakage of electromagnetic waves from electronic devices and the inflow of electromagnetic waves into electronic devices. In the case of electromagnetic shielding materials to block the leakage and inflow of electromagnetic waves, materials such as copper, silver, CNT, graphene, carbon black (CB), carbon fiber (CF), and MXene, which have electrically conductive properties, are mainly used alone or in combination with polymers.

[0004] In addition, as the demand for flexible electronic devices such as foldable, wearable, and stretchable devices increases, research is being conducted on electromagnetic shielding materials such as electrically conductive copper, silver, and CNTs as shielding materials for these devices. However, conventional solid-state electrically conductive materials suffer from a rapid degradation in performance and a limit in stretching characteristics when stretched, as the internal particles become spaced further apart, destroying the conductive network structure.

[0005] As an alternative to existing solid-state electrically conductive materials, liquid metal (LM) in liquid form has excellent deformability; when implemented as an electromagnetic shielding material by filling it into an elastomer composite or film, it can provide properties that contrast with solid-state materials, such as enhanced electromagnetic shielding characteristics even during stretching.

[0006] However, electromagnetic shielding materials manufactured using such liquid metals exhibit excessively high resistance values ​​before stretching, which actually degrades their electromagnetic shielding performance. In addition, since liquid metals manufactured using electromagnetic shielding materials have unevenly distributed droplets within the polymer film and must be manufactured within a specific thickness range, there are limitations in terms of material thickness for their application in light and thin electronic devices.

[0007] Furthermore, when a liquid metal is coated onto a transparent resin film such as polyethyleneterephthalate (PET) to form a liquid metal conductive layer, the electromagnetic shielding material exhibits certain electromagnetic shielding characteristics, but the liquid metal rapidly oxidizes in the air to form metal oxides, and the liquid metal conductive layer, which cannot fix its shape, acts as a contaminant, making it impossible to use directly as an electromagnetic shielding material.

[0008] The first objective of the present invention is to provide an electromagnetic shielding material having high elasticity and not experiencing degradation of electromagnetic shielding performance even under tensile deformation, and a method for manufacturing the same.

[0009] The second objective of the present invention is to provide an electromagnetic shielding material that can be manufactured in the form of a film with a thinner thickness compared to conventional electromagnetic shielding films and has excellent initial electromagnetic shielding performance before stretching, and a method for manufacturing the same.

[0010] The third objective of the present invention is to provide an electromagnetic shielding material and a method for manufacturing the same, which maintains the same electromagnetic shielding performance as before stretching or exhibits higher electromagnetic shielding performance even when stretched by more than 100%, and has excellent oxidation stability and anti-contamination effects.

[0011] To achieve the objective of the present invention, the present invention discloses a method for manufacturing an electromagnetic shielding material comprising: a liquid metal particle grinding step in which liquid metal particles contained in a liquid metal solution, which is a mixture of liquid metal and a solvent, are ground using an ultrasonic homogenizer; a pretreatment liquid metal manufacturing step in which the solvent of the liquid metal solution in which the liquid metal particles are ground is removed to obtain a pretreatment liquid metal in which the liquid metal particles are ground; a liquid metal composition manufacturing step in which the pretreatment liquid metal is mixed with a base resin solution to obtain a liquid metal composition solution; a liquid metal film manufacturing step in which the liquid metal composition solution is applied to a flexible sheet equipped with a mask and dried to manufacture a liquid metal composition film; a liquid metal activation step in which acoustic energy is applied to the liquid metal composition film to activate the liquid metal; and an electromagnetic shielding material manufacturing step in which the liquid metal-activated liquid metal composition film is transcribed onto a base film to manufacture an electromagnetic shielding material.

[0012] The above liquid metal may be at least one liquid metal selected from the group consisting of a liquid metal containing gallium (Ga), gallinstan which is a gallium-indium-tin alloy, and a gallium-indium eutectic alloy (EGaIn).

[0013] The above liquid metal solution may be a solution containing the liquid metal and the solvent in a weight ratio of 1:2 to 1:10.

[0014] The above liquid metal particle grinding step can be performed by grinding the liquid metal particles in an ultrasonic homogenizer composed of a probe sonicator by applying an acoustic field having an amplitude of 50 μm to 80 μm to the liquid metal solution.

[0015] The above pretreatment liquid metal manufacturing step can be performed by removing the solvent of the liquid metal solution using an inert gas containing an element selected from the group consisting of nitrogen, helium, neon, krypton, xenon, and argon.

[0016] The base resin included in the above base resin solution may be at least one resin selected from the group consisting of silicone rubber, ethylene vinyl acetate (EVA), thermoplastic elastomers (TPE), polyether block amide, and polyurethane.

[0017] In the step of manufacturing the liquid metal composition above, the weight ratio of the pretreated liquid metal and the base resin contained in the base resin solution may be 4:1 to 13:1.

[0018] The above liquid metal activation step can be performed by applying an acoustic field having an amplitude of 40 μm to 50 μm to the liquid metal composition film in an ultrasonic homogenizer consisting of a probe sonicator.

[0019] The liquid metal-activated liquid metal composition film can be formed with a thickness of 7 μm to 12 μm.

[0020] To achieve the above objective, the present invention also discloses an electromagnetic shielding material manufactured through the method of manufacturing the electromagnetic shielding material.

[0021] The effects of the present invention obtained through the above-described solution are as follows.

[0022] An electromagnetic shielding material having high elasticity and not degrading electromagnetic shielding performance even under tensile deformation can be realized through a liquid metal particle grinding step in which liquid metal particles contained in a liquid metal solution are ground, and a liquid metal composition manufacturing step in which a pretreated liquid metal is mixed with a base resin solution to obtain a liquid metal composition solution.

[0023] Through a liquid metal film manufacturing step in which a liquid metal composition solution is applied to a flexible sheet to manufacture a liquid metal composition film, and a liquid metal activation step in which acoustic energy is applied to the liquid metal composition film to activate the liquid metal, it is possible to manufacture an electromagnetic shielding material with a thinner thickness compared to existing electromagnetic shielding films, and to manufacture an electromagnetic shielding material with excellent initial electromagnetic shielding performance before stretching.

[0024] By applying a liquid metal composition solution to a flexible sheet and applying acoustic energy to a dried liquid metal composition film to activate the liquid metal, it is possible to manufacture an electromagnetic shielding material that maintains the same electromagnetic shielding performance as before stretching or exhibits higher electromagnetic shielding performance even when stretched by more than 100%, and has excellent oxidation stability and anti-contamination effects.

[0025] FIG. 1 is a conceptual diagram showing a method for manufacturing an electromagnetic shielding material according to an embodiment of the present invention.

[0026] FIG. 2 is a block diagram showing a method for manufacturing the electromagnetic shielding material of FIG. 1.

[0027] Figure 3 is a strain photograph of an electromagnetic shielding film showing the strain of the electromagnetic shielding material manufactured through the method of manufacturing the electromagnetic shielding material of Figure 1.

[0028] Figure 4 is a graph showing the initial resistance of an electromagnetic shielding material manufactured through the method of manufacturing an electromagnetic shielding material of Figure 1 and the initial resistance of an electromagnetic shielding material of a comparative example.

[0029] Figure 5 is a graph showing the initial resistance of an electromagnetic shielding material according to the liquid metal content manufactured through the method of manufacturing an electromagnetic shielding material of Figure 1, and the initial resistance of an electromagnetic shielding material of a comparative example (liquid metal content exceeding the limit).

[0030] Figure 6 is a scanning electron microscopy (SEM) image showing the distribution of liquid metal particles according to the liquid metal content and degree of elongation of an electromagnetic shielding material manufactured through the method of manufacturing an electromagnetic shielding material of Figure 1.

[0031] Figure 7 is a scanning electron microscopy (SEM) image showing the distribution of liquid metal particles according to the liquid metal content after 75% stretching of the electromagnetic shielding material manufactured by the method of manufacturing the electromagnetic shielding material of Figure 1, and the distribution of liquid metal particles of the electromagnetic shielding material of the comparative example (excess liquid metal content) after 75% stretching.

[0032] Figure 8 is a scanning electron microscopy (SEM) image showing the distribution of liquid metal particles according to the liquid metal content after 400% stretching of the electromagnetic shielding material manufactured by the method of manufacturing the electromagnetic shielding material of Figure 1, and the distribution of liquid metal particles of the electromagnetic shielding material of the comparative example (excess liquid metal content) after 400% stretching.

[0033] FIG. 9 is a graph showing the electromagnetic shielding effect according to the liquid metal content of the electromagnetic shielding material manufactured through the method of manufacturing the electromagnetic shielding material of FIG. 1, and the electromagnetic shielding effect of the electromagnetic shielding material of a comparative example (liquid metal content exceeding the limit).

[0034] FIG. 10 is a conceptual diagram and image showing the appearance of a deformed state according to the design of an electromagnetic shielding material manufactured through the method of manufacturing an electromagnetic shielding material of FIG. 1.

[0035] FIG. 11 is a conceptual diagram showing a more detailed manufacturing method of the electromagnetic shielding material of FIG. 1 and a graph showing the conductivity and EMI shielding performance of the electromagnetic shielding material.

[0036] FIG. 12 is a graph showing the designable mechanism, conductivity, and EMI shielding performance of an electromagnetic shielding material manufactured through the method of manufacturing an electromagnetic shielding material of FIG. 1.

[0037] FIG. 13 is a conceptual diagram of the application of electromyographic testing to a mouse and a graph of the monitoring results of an electromagnetic shielding material manufactured through the method of manufacturing the electromagnetic shielding material of FIG. 1.

[0038] Hereinafter, the electromagnetic shielding material and the method for manufacturing the same related to the present invention will be described in more detail with reference to the drawings.

[0039] In this specification, identical or similar reference numbers are assigned to identical or similar components even in different embodiments, and redundant descriptions thereof are omitted.

[0040] In describing the embodiments disclosed in this specification, if it is determined that a detailed description of related prior art could obscure the essence of the embodiments disclosed in this specification, such detailed description is omitted.

[0041] The attached drawings are intended only to facilitate understanding of the embodiments disclosed in this specification, and the technical concept disclosed in this specification is not limited by the attached drawings; it should be understood that all modifications, equivalents, and substitutions included within the concept and technical scope of the present invention are included.

[0042] In the following description, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0043] In this application, terms such as “comprising” or “having” are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0044]

[0045] FIG. 1 is a conceptual diagram showing a method for manufacturing an electromagnetic shielding material according to an embodiment of the present invention.

[0046] Figure 2 is a block diagram showing a method for manufacturing the electromagnetic shielding material of Figure 1.

[0047] Referring to FIGS. 1 and 2, a method for manufacturing an electromagnetic shielding material according to an embodiment of the present invention includes a liquid metal particle grinding step (S110), a pretreatment liquid metal manufacturing step (S120), a liquid metal composition manufacturing step (S130), a liquid metal film manufacturing step (S140), a liquid metal activation step (S150), and an electromagnetic shielding material manufacturing step (S160).

[0048] The liquid metal particle grinding step (S110) is performed by grinding the liquid metal particles contained in the liquid metal solution, which is a mixture of liquid metal and a solvent, using an ultrasonic homogenizer.

[0049] Liquid metal refers to a metallic substance that maintains a liquid phase at room temperature due to a low melting point. Liquid metal is not particularly limited as long as it is a metallic substance that maintains a liquid phase at room temperature, and may be, for example, a single-element liquid metal selected from the group consisting of mercury, cesium, radium, francium, rubidium, and gallium, or a liquid metal containing gallium such as a gallium-tin (Ga-Sn) alloy, or at least one liquid metal selected from the group consisting of gallinstan, a gallium-indium-tin alloy, and a gallium-indium eutectic alloy (EGaIn).

[0050] Since these liquid metals basically possess metallic properties, they have high conductivity (mercury: ~1.1 x 10⁶ S / m, cesium: ~5 x 10⁶ S / m, gallium: ~1.8 x 10⁶ S / m, EGaIn: ~3.4 x 10⁶ S / m) and are liquid at room temperature, they can be injected into a suitable polymer mold to fabricate flexible electrodes. Gallium-based liquid metals containing gallium have relatively low toxicity, reactivity, and radioactivity, so they can be applied to various flexible devices or wearable devices.

[0051] In particular, gallium-indium eutectic alloys are metals that form alloys with a mass ratio of 75% gallium and 25% indium, and exist in a liquid state at room temperature due to their low melting point of 15.5 °C. Additionally, gallium-indium eutectic alloys have high conductivity (3.4 x 10³ S / cm) and very low viscosity, about half that of water. Furthermore, compared to other liquid metals, gallium-indium eutectic alloys are relatively less toxic and reactive, and are safe due to their low vapor pressure. Additionally, a gallium oxide film several nanometers thick formed on the surface lowers surface tension, allowing for molding into shapes other than spherical and enabling stable injection into narrow spaces such as microchannels.

[0052] The above solvent may be a solvent having, for example, high solubility, volatility, low toxicity, etc., and may be a solvent selected from the group consisting of, for example, methyl ethyl ketone (MEK), isopropyl alcohol (IPA), toluene, ethyl acetate, dichloromethane (DCM), methyl isobutyl ketone (MIBK), and acetone.

[0053] The above liquid metal solution may be prepared as a solution containing the liquid metal and the solvent in a weight ratio of 1:2 to 1:10. If the weight ratio of the liquid metal and the solvent is smaller than 1:2, such as 1:1, the crushing and dispersion of the liquid metal particles within the solution may not be performed smoothly, and excessive energy may be consumed during the crushing process of the liquid metal particles. Additionally, if the weight ratio of the liquid metal and the solvent is larger than 1:10, such as 1:11, it may be difficult to achieve uniform crushing and dispersion of the liquid metal particles.

[0054] The above liquid metal particle crushing step (S110) is not particularly limited as long as it is performed as a process capable of crushing and uniformly dispersing the liquid metal particles contained in the liquid metal solution. For example, it may be performed by crushing the liquid metal particles by applying an acoustic field having an amplitude of 50 μm to 80 μm to the liquid metal solution in an ultrasonic homogenizer composed of a probe sonicator. Here, the amplitude of 50 μm to 80 μm may be defined as the amplitude formed by the probe tip of the probe sonicator. Additionally, the frequency of the probe sonicator may be set to 15 kHz to 25 kHz.

[0055] The above liquid metal particle grinding step (S110) can be specifically performed by putting the liquid metal solution into a glass vial and sealing it, then placing the glass vial containing the liquid metal solution into a water bath at room temperature and applying an acoustic field having an amplitude of 50 μm to 80 μm to the water in the bath for 10 to 40 minutes.

[0056] The pretreatment liquid metal manufacturing step (S120) is performed by removing the solvent from the liquid metal solution in which the liquid metal particles are crushed to obtain a pretreatment liquid metal in which the liquid metal particles are crushed. Here, the liquid metal solution in which the liquid metal particles are crushed can be subjected to a process of first removing the solvent by decanting the solvent by centrifuging, for example, at 2000 rpm to 2500 rpm, and drying under inert gas conditions.

[0057] The above-mentioned inert gas may be, for example, an inert gas comprising an element selected from the group consisting of nitrogen, helium, neon, krypton, xenon, and argon. These gases are very stable and have almost no reactivity, which has the advantage of effectively drying the liquid metal solution to obtain a high yield of pretreated liquid metal.

[0058] The step of manufacturing a liquid metal composition (S130) is performed by mixing the pretreated liquid metal with a base resin solution to obtain a liquid metal composition solution.

[0059] The above base resin solution is in the form of a mixture of a solvent and a resin, and can be smoothly mixed with the above-mentioned pre-treated liquid metal. It can be manufactured as a resin solution mixed with a solvent having elasticity, durability, chemical resistance, etc., as a base for an electromagnetic shielding material.

[0060] The above resin is a resin having properties such as elasticity, durability, abrasion resistance, chemical resistance, and lightness, and may be, for example, at least one resin selected from the group consisting of silicone rubber, ethylene vinyl acetate (EVA), thermoplastic elastomers (TPE), polyether block amide, and polyurethane. In addition, the thermoplastic elastomer (TPE) may specifically be a resin selected from the group consisting of styrene block copolymer (TPE-s), thermoplastic polyolefin elastomer (TPE-o), thermoplastic polyurethane (TPU), and thermoplastic polyamide (TPA).

[0061] The above solvent is a solvent having high solubility and polarity for the resin, and for example, a solvent selected from the group consisting of N-Methyl-2-pyrrolidone (NMP), Dimethylformamide (DMF), Tetramethylurea (TMU), DMSO (Dimethyl sulfoxide), and Dimethylacetamide (DMAc) may be used.

[0062] In the step of manufacturing a liquid metal composition (S130), the weight ratio of the pretreated liquid metal and the base resin contained in the base resin solution may be, for example, 4:1 to 13:1.

[0063] If the weight ratio of the pre-treated liquid metal and the base resin contained in the base resin solution is lower than 4:1, such as 3:1, the initial electromagnetic shielding effect of the electromagnetic shielding material is almost non-existent, and the increase in the electromagnetic shielding effect may be very minimal even when the electromagnetic shielding material is stretched. In addition, if the weight ratio of the pre-treated liquid metal and the base resin contained in the base resin solution is higher than 13:1, such as 14:1, the electromagnetic shielding effect may rapidly decrease when the electromagnetic shielding material is stretched by more than 150%.

[0064] The liquid metal film manufacturing step (S140) is performed by applying the liquid metal composition solution to a flexible sheet equipped with a mask and drying it to manufacture a liquid metal composition film.

[0065] The above flexible sheet is manufactured from a liquid metal composition film, and since acoustic energy is applied to activate the liquid metal, a sheet made of a material having certain mechanical strength, heat resistance, chemical stability, etc. may be used. Accordingly, the above flexible sheet may be a sheet selected from the group consisting of, for example, polyimide sheets, polytetrafluoroethylene (PTFE) sheets, polyoxymethylene (POM) sheets, polysulfone sheets, polypropylene sheets, and Teflon sheets.

[0066] The above liquid metal film manufacturing step (S140) can be performed, for example, through a screen printing process, wherein the mask can be produced by cutting a metal or polyethylene terephthalate (PET) film with a CO2 laser cutter. Additionally, the liquid metal film manufacturing step (S140) is performed by drying the manufactured liquid metal composition film at a temperature of 70°C to 90°C for 20 to 30 hours to remove the solvent remaining in the liquid metal composition solution.

[0067] The liquid metal composition film produced through the liquid metal film manufacturing step (S140) can be formed with a thickness of, for example, 7 μm to 12 μm. Accordingly, even when the electromagnetic shielding material containing the liquid metal composition film is manufactured by forming the liquid metal composition film on a base film having a thickness in the mm range, the liquid metal composition film itself is formed with a very thin thickness of 7 μm to 12 μm, so it can be manufactured as a thin film type flexible electromagnetic shielding material with a greatly reduced overall thickness.

[0068] The liquid metal activation step (S150) is performed by activating the liquid metal by applying acoustic energy to the liquid metal composition film. Specifically, the liquid metal activation step (S150) may be performed by applying an acoustic field having an amplitude of 40 μm to 50 μm to the liquid metal composition film in an ultrasonic homogenizer composed of a probe sonicator. Here, the amplitude of 40 μm to 50 μm may be defined as the amplitude formed by the probe tip of the probe sonicator. Additionally, the frequency of the probe sonicator may be set to 15 kHz to 25 kHz.

[0069] The above liquid metal composition film has improved electrical conductivity and increased electromagnetic shielding efficiency as smaller nanoparticles fill the spaces between the nanoparticles and the micropores of the solid oxide film formed on the surface of the liquid metal nanoparticles through the application of an acoustic field having an amplitude of 40 μm to 50 μm.

[0070] Here, if the amplitude of the acoustic field is smaller than 40 μm, the process of nanoparticles filling the micropores of the liquid metal nanoparticles and the spaces between the nanoparticles is not carried out smoothly, so the effect of improving the electrical conductivity and electromagnetic shielding efficiency of the liquid metal composition film is negligible, and if the amplitude of the acoustic field exceeds 50 μm, uneven distribution of the liquid metal occurs within the liquid metal composition film, which may degrade the performance of the electromagnetic shielding material.

[0071] The diameter of the probe tip of the probe sonicator that applies the acoustic field can be formed to be, for example, 2 mm to 9 mm, and the gap between the probe tip and the liquid metal composition film can be set to be 0.5 mm to 2 mm. In addition, the application of the acoustic field to the liquid metal composition film can be performed for 20 to 60 seconds, and can be performed in water, such as in a water tank or glass bottle filled with water, to improve the efficiency of the acoustic field application.

[0072] The step of manufacturing an electromagnetic shielding material (S160) is performed by transcribing the liquid metal-activated liquid metal composition film onto a base film to manufacture an electromagnetic shielding material. Here, the base film material may be the same resin as the resin used in the base resin solution.

[0073] The present invention provides an electromagnetic shielding material manufactured by the above-described method for manufacturing an electromagnetic shielding material. This electromagnetic shielding material has the advantage of possessing high elasticity and not experiencing a degradation in electromagnetic shielding performance even under tensile deformation. Furthermore, it can be manufactured in the form of a film with a thinner thickness compared to conventional electromagnetic shielding films and is characterized by excellent initial electromagnetic shielding performance before stretching. Therefore, it can be manufactured as an electromagnetic shielding material or an electromagnetic absorbing material with high elasticity and can be utilized as a material for constituting wires and circuits of various electronic devices.

[0074]

[0075] Hereinafter, the electromagnetic shielding material and the method for manufacturing the same according to the present invention will be described in more detail with reference to the examples and drawings.

[0076]

[0077] [Example 1]

[0078] A liquid metal solution was prepared by mixing 5g of gallium-indium eutectic alloy (EGaIn) and 15ml of acetone. The prepared liquid metal solution was placed in a glass vial, sealed, and placed into a water bath filled with water at room temperature. Using a probe sonicator, an acoustic field having an amplitude of 63μm and a frequency of 15kHz to 25kHz was applied to the water in the bath for 20 minutes to pulverize the liquid metal particles of the liquid metal solution.

[0079] The liquid metal solution in which the above liquid metal particles were crushed was centrifuged at 2200 rpm to decant the solvent, and dried for 24 hours under argon (Ar) gas conditions to obtain a pretreated liquid metal in which the liquid metal particles were crushed.

[0080] The base resin solution was prepared by mixing polyurethane and dimethylacetamide (DMAc, 200 mg / ml) solvent using a THINKY mixer for 10 minutes.

[0081] The above pretreatment liquid metal and base resin solution were mixed such that the weight ratio of the above pretreatment liquid metal to polyurethane was 11:1, and the mixture was mixed using a THINKY mixer for 10 minutes to obtain a liquid metal composition solution.

[0082] The above liquid metal composition solution was applied to a Teflon sheet formed with a polyethylene terephthalate (PET) film mask and dried at 80°C for 24 hours to obtain a liquid metal composition film. Here, the liquid metal composition film was formed with a thickness of 10 μm.

[0083] The liquid metal composition film was activated by applying an acoustic field having an amplitude of 43 μm and a frequency of 20 kHz to 25 kHz for 30 seconds using a probe sonicator. Here, the acoustic field was applied while the liquid metal composition film was fixed to a glass plate with Scotch tape and seated inside a glass bottle filled with water. In addition, the probe tip diameter of the probe sonicator applying the acoustic field was formed to be 6 mm, and the gap between the probe tip and the liquid metal composition film was set to 1 mm.

[0084] As described above, a liquid metal composition film in which the liquid metal is activated was transferred onto a polyurethane film to remove the Teflon sheet and a flexible electromagnetic shielding material was manufactured.

[0085]

[0086] [Example 2]

[0087] A flexible electromagnetic shielding material was prepared in the same manner as in Example 1, except that the weight ratio of the pre-treated liquid metal and polyurethane was mixed to be 5:1 during the preparation process of the liquid metal composition solution.

[0088]

[0089] [Example 3]

[0090] A flexible electromagnetic shielding material was prepared in the same manner as in Example 1, except that the weight ratio of the pre-treated liquid metal and polyurethane was mixed to be 7:1 during the preparation process of the liquid metal composition solution.

[0091]

[0092] [Example 4]

[0093] A flexible electromagnetic shielding material was prepared in the same manner as in Example 1, except that the weight ratio of the pre-treated liquid metal and polyurethane was mixed to be 9:1 during the preparation process of the liquid metal composition solution.

[0094]

[0095] [Comparative Example 1]

[0096] A flexible electromagnetic shielding material was prepared in the same manner as in Example 1, except that the weight ratio of the pre-treated liquid metal and polyurethane was mixed to be 3:1 during the preparation process of the liquid metal composition solution.

[0097]

[0098] [Comparative Example 2]

[0099] A flexible electromagnetic shielding material was manufactured in the same manner as in Example 1, except that the process of activating the liquid metal of the liquid metal composition film by applying an acoustic field was not performed.

[0100]

[0101] Photographs and graphs showing various performances of the electromagnetic shielding materials of Examples 1, 2, 3, and 4 and Comparative Examples 1 and 2 are illustrated in FIGS. 3 to 9.

[0102] Figure 3 is a strain photograph of an electromagnetic shielding film showing the strain of the electromagnetic shielding material manufactured through the method of manufacturing the electromagnetic shielding material of Figure 1.

[0103] Referring to FIG. 3, it can be seen that in the electromagnetic shielding material of Example 1, the liquid metal is distributed relatively uniformly throughout the electromagnetic shielding material even before deformation (a) and after 300% deformation (b).

[0104] Figure 4 is a graph showing the initial resistance of an electromagnetic shielding material manufactured through the method of manufacturing an electromagnetic shielding material of Figure 1 and the initial resistance of an electromagnetic shielding material of a comparative example.

[0105] Referring to FIG. 4, it can be seen that the electromagnetic shielding material (a) of Comparative Example 3, which did not undergo the process of activating the liquid metal of the liquid metal composition film by applying an acoustic field with an amplitude of 43 μm, has a very large initial resistance value in the initial state with less than 50% deformation applied compared to the electromagnetic shielding material (b) of Example 1. In other words, it can be seen that the electromagnetic shielding material of the example has a low initial resistance in the state before deformation, so it is at a level where it can be immediately applied to electronic devices, etc. as an electromagnetic shielding material or a conductive material.

[0106] Figure 5 is a graph showing the initial resistance of an electromagnetic shielding material according to the liquid metal content manufactured through the method of manufacturing an electromagnetic shielding material of Figure 1, and the initial resistance of an electromagnetic shielding material of a comparative example (liquid metal content exceeding the limit).

[0107] Referring to FIG. 5, it can be seen that, with the exception of Example 3(a), the electromagnetic shielding materials of Example 1(c) and Example 4(b) exhibit very low resistance in an initial state of 50% or less. Ultimately, it can be confirmed that the electromagnetic shielding material, in which liquid metal activation is performed by applying an acoustic field to a liquid metal composition film, has a lower initial resistance as the liquid metal content increases.

[0108] Figure 6 is a scanning electron microscopy (SEM) image showing the distribution of liquid metal particles according to the liquid metal content and degree of elongation of the electromagnetic shielding material manufactured through the method of manufacturing the electromagnetic shielding material of Figure 1.

[0109] Referring to FIG. 6, it can be seen that the electromagnetic shielding material of Example 2 (a) before stretching and the electromagnetic shielding material of Example 3 (c) before stretching generally exhibit a spherical liquid metal particle shape, while the electromagnetic shielding material of Example 2 (b) after 100% stretching and the electromagnetic shielding material of Example 3 (d) after 100% stretching exhibit an elliptical liquid metal particle shape in the stretching direction. In other words, it can be confirmed that the higher the content of liquid metal particles, the higher the distribution density of particles within the electromagnetic shielding material, and the shape change becomes more pronounced. The elliptical particle shape can be seen as a cause that increases the contact ratio between particles and lowers the resistance of the electromagnetic shielding material.

[0110] Figure 7 is a scanning electron microscopy (SEM) image showing the distribution of liquid metal particles according to the liquid metal content after 75% stretching of the electromagnetic shielding material manufactured by the method of manufacturing the electromagnetic shielding material of Figure 1, and the distribution of liquid metal particles of the electromagnetic shielding material of the comparative example (excess liquid metal content) after 75% stretching.

[0111] Referring to Fig. 7, it can be seen that after stretching the electromagnetic shielding materials of Example 1(c), Example 2(a), and Example 3(b) by 75% in the vertical direction, some of the larger particles among the stretched liquid metal particles were destroyed and shrank to remain in a cocoon shape. Therefore, it can be seen that a conductive network was additionally formed in the direction perpendicular to the stretching direction (orthogonal direction). In other words, it can be confirmed that conductivity is maintained even without further stretching, as the oxide film on the surface of the liquid metal particles is destroyed and remains in a cocoon shape.

[0112] Figure 8 is a scanning electron microscopy (SEM) image showing the distribution of liquid metal particles according to the liquid metal content after 400% stretching of the electromagnetic shielding material manufactured by the method of manufacturing the electromagnetic shielding material of Figure 1, and the distribution of liquid metal particles of the electromagnetic shielding material of the comparative example (excessive liquid metal content) after 400% stretching.

[0113] Referring to FIG. 8, it can be seen that the electromagnetic shielding materials of Examples 3(a) and (b) are stretched up to 400% after the plastic deformation point occurring at 75%, respectively, and that the shape of the internal particles also changes to a cocoon shape in the direction of stretching due to the plastic deformation of the polymer. This can be seen as maintaining low resistance because when the electromagnetic shielding material is deformed by an external force (stretching) while the liquid metal particle content is high, the liquid metal particles become more closely packed compared to their initial shape (before stretching), the oxide film on the surface is destroyed, and the contact surface between particles is maintained in a larger state, thereby forming a conductive network better.

[0114] Figure 9 is a graph showing the electromagnetic shielding effect according to the liquid metal content of the electromagnetic shielding material manufactured through the method of manufacturing the electromagnetic shielding material of Figure 1, and the electromagnetic shielding effect of the electromagnetic shielding material of the comparative example (liquid metal content exceeding the limit).

[0115] Referring to Fig. 9, the electromagnetic shielding effect (EMI SE) according to the elongation of the material T In the characteristic graph, it can be confirmed that the electromagnetic shielding materials of Example 1 (11:1), Example 2 (5:1), Example 3 (7:1), and Example 4 (9:1) exhibit high electromagnetic shielding performance under the application conditions of 10 GHz electromagnetic waves (a) and 28 GHz electromagnetic waves (b), even when deformation of more than 100% occurs.

[0116] On the other hand, it can be confirmed that the electromagnetic shielding performance of Comparative Example 1 (3:1) does not increase significantly when deformation of 100% or more occurs.

[0117] Figure 10 is a conceptual diagram and image showing the appearance of a deformed state according to the design of an electromagnetic shielding material manufactured through the method of manufacturing an electromagnetic shielding material of Figure 1.

[0118] Referring to FIG. 10, when the electromagnetic shielding material of the embodiments is stretched while printed on a soft substrate, the liquid metal nanoparticles deform from a spherical shape to an ellipsoidal shape as in (a). Additionally, (b) shows a photographic image and SEM image of the electromagnetic shielding material of the embodiments having a thickness of approximately 5 μm. Additionally, (c) shows a photographic image of the electromagnetic shielding material of the embodiments before and after stretching. Additionally, (d) shows a photographic image of the electromagnetic shielding material of the embodiments attached to the skin, showing smooth contact even in a state of compressive deformation. Additionally, (e) is a graph showing the change in conductivity of the electromagnetic shielding material of the embodiments when released from deformation compared to a rigid filler-based composite. In (e), it can be confirmed that the electromagnetic shielding performance of the electromagnetic shielding material of the embodiments (This work) is maintained consistently even with a change in elasticity of approximately 500%.

[0119] Figure 11 is a conceptual diagram showing a more detailed manufacturing method of the electromagnetic shielding material of Figure 1, and a graph showing the conductivity and EMI shielding performance of the electromagnetic shielding material.

[0120] Referring to FIG. 11, a photographic image (b) can be seen showing a character pattern (KIST) formed using a liquid metal composition solution (a) prepared during the manufacturing process of the electromagnetic shielding material of the example. (c), (d), and (e) show the process of stencil printing (c) the liquid metal composition solution onto a flexible sheet (Teflon sheet), activating it (d) by applying acoustic energy, and then transferring (e) the liquid metal composition from the flexible sheet to a base film (thin film soft substrate). (f), (g), (h), (i), (j), and (k) disclose graphs showing the conductivity and electromagnetic shielding performance of the electromagnetic shielding materials of Examples 1, 2, 3, 4, 5 and Comparative Example 1.

[0121] In particular, (g) and (h) show the electromagnetic shielding performance of the examples and comparative examples when acoustic fields of 10 GHz and 28 GHz are applied during the liquid metal activation step. According to (g) and (h), it can be confirmed that the electromagnetic shielding performance of the electromagnetic shielding material of the examples is significantly improved when an acoustic field of 10 GHz to 28 GHz is applied compared to before the application of the acoustic field.

[0122] Figure 12 is a graph showing the designable mechanism, conductivity, and EMI shielding performance of an electromagnetic shielding material manufactured through the method of manufacturing an electromagnetic shielding material of Figure 1.

[0123] Referring to FIG. 12, the electromagnetic shielding material (a) of the embodiments maintains a programmed state of liquid metal particles that maintains an ellipsoidal shape within the matrix even after being stretched and after the mechanical stress is released.

[0124] Referring to (b), the electromagnetic shielding material of the embodiments can be seen through SEM images as having been permanently deformed into an ellipsoid even after the shape of the liquid metal particles designed in the base film (polymer matrix) was recovered at strain rates of 75%, 100%, and 400%.

[0125] (c) shows the programmable design characteristics of the electromagnetic shielding materials of the example.

[0126] (d) is a graph showing the change in conductivity before and after programming induced by various modifications of the electromagnetic shielding materials of the examples.

[0127] (e) is a graph showing the improved electromagnetic shielding performance of the electromagnetic shielding materials of the example after a continuous programming process.

[0128] (f) and (g) are graphs showing the conductivity and electromagnetic shielding performance of the electromagnetic shielding materials of the examples and comparative examples according to the type of base film.

[0129] Figure 13 is a conceptual diagram of the application of electromyographic (EMG) testing to a mouse and a graph of the monitoring results of the electromagnetic shielding material manufactured through the method of manufacturing the electromagnetic shielding material of Figure 1.

[0130] Referring to FIG. 13, the electromagnetic shielding material of the embodiment is implanted into the hind leg muscle of a rat in (a) for monitoring electromyography (EMG) signals of a rat and connected to an external signal generator, and artificial noise is introduced using this external signal generator. Here, the electromagnetic shielding material of the embodiment is applied conformally to the skin at the site where the EMG electrode is placed.

[0131] (b) shows the setup for measuring electromyography (EMG) signals in a mouse muscle through a photograph.

[0132] (c) shows the electromyography signal of the measurement site without applying the electromagnetic shielding material of the example, and (d) shows the electromyography signal with the electromagnetic shielding material of the example applied. In (c), it can be confirmed that internal noise occurs in the electromyography signal.

[0133] (e) and (f) are graphs showing cell viability when noise is generated in an electromyography signal to which the electromagnetic shielding material of the example is applied.

[0134] (g) and (h) are SEM images (PLMC) of the femoral fascia and abdominal muscle endothelial cells of a mouse for monitoring electromyography signals when the electromagnetic shielding material of the Example is applied, and SEM images (Control) of the femoral fascia and abdominal muscle endothelial cells of a mouse for monitoring electromyography signals when the electromagnetic shielding material of Comparative Example 2 is applied.

[0135] When considering the performance test results of these embodiments, it can be confirmed that the electromagnetic shielding material according to the present invention can be effectively utilized in products such as electromagnetic shielding materials requiring flexibility, electromagnetic absorbing materials, wires of various electronic devices, circuits, and biosignal measurement materials.

[0136] In addition, the electromagnetic shielding material according to the present invention can be utilized as a material with excellent electromagnetic shielding efficiency not only in the existing X-band (8~12GHz) range but also in higher bands such as the Ka band (26.5GHz~40GHz) or W band frequencies.

[0137]

[0138] The foregoing description is merely illustrative, and various modifications may be made by those skilled in the art without departing from the scope and technical spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

[0139] The present invention can realize an electromagnetic shielding material having high elasticity and not degrading in electromagnetic shielding performance even during tensile deformation, and can manufacture an electromagnetic shielding material with a thinner thickness compared to existing electromagnetic shielding films, and provides a method for manufacturing an electromagnetic shielding material with excellent initial electromagnetic shielding performance before stretching, and can provide a method for manufacturing an electromagnetic shielding material that maintains the same electromagnetic shielding performance as before stretching or exhibits higher electromagnetic shielding performance even when stretched by more than 100%, and has excellent oxidation stability and anti-contamination effects.

Claims

1. A liquid metal particle grinding step in which liquid metal particles contained in a liquid metal solution, which is a mixture of liquid metal and a solvent, are ground using an ultrasonic homogenizer; A pretreatment liquid metal manufacturing step of removing the solvent from the liquid metal solution in which the liquid metal particles are crushed to obtain a pretreatment liquid metal in which the liquid metal particles are crushed; A step for manufacturing a liquid metal composition by mixing the above-mentioned pretreated liquid metal with a base resin solution to obtain a liquid metal composition solution; A liquid metal film manufacturing step of applying the above liquid metal composition solution to a flexible sheet equipped with a mask and drying it to manufacture a liquid metal composition film; A liquid metal activation step of activating the liquid metal by applying acoustic energy to the above liquid metal composition film; A step of manufacturing an electromagnetic shielding material by transcribing the liquid metal-activated liquid metal composition film onto a base film to manufacture an electromagnetic shielding material; comprising Method for manufacturing an electromagnetic shielding material.

2. In Paragraph 1, The above liquid metal is at least one liquid metal selected from the group consisting of a liquid metal containing gallium (Ga), gallinstan which is a gallium-indium-tin alloy, and a gallium-indium eutectic alloy (EGaIn). Method for manufacturing an electromagnetic shielding material.

3. In Paragraph 1, The above liquid metal solution is a solution containing the liquid metal and the solvent in a weight ratio of 1:2 to 1:10, Method for manufacturing an electromagnetic shielding material.

4. In Paragraph 1, The above liquid metal particle grinding step is performed by grinding the liquid metal particles in an ultrasonic homogenizer composed of a probe sonicator by applying an acoustic field having an amplitude of 50 μm to 80 μm to the liquid metal solution. Method for manufacturing an electromagnetic shielding material.

5. In Paragraph 1, The above pretreatment liquid metal manufacturing step is performed by removing the solvent of the liquid metal solution using an inert gas containing an element selected from the group consisting of nitrogen, helium, neon, krypton, xenon, and argon. Method for manufacturing an electromagnetic shielding material.

6. In Paragraph 1, The base resin included in the above base resin solution is at least one resin selected from the group consisting of silicone rubber, ethylene vinyl acetate (EVA), thermoplastic elastomers (TPE), polyether block amide, and polyurethane, Method for manufacturing an electromagnetic shielding material.

7. In Paragraph 1, In the step of manufacturing the liquid metal composition above, the weight ratio of the pretreated liquid metal to the base resin contained in the base resin solution is 4:1 to 13:1, Method for manufacturing an electromagnetic shielding material.

8. In Paragraph 1, The above liquid metal activation step is performed by applying an acoustic field having an amplitude of 40 μm to 50 μm to the liquid metal composition film in an ultrasonic homogenizer consisting of a probe sonicator, Method for manufacturing an electromagnetic shielding material.

9. In Paragraph 1, The liquid metal-activated liquid metal composition film is formed with a thickness of 7 μm to 12 μm, Method for manufacturing an electromagnetic shielding material.

10. An electromagnetic shielding material manufactured through the method of manufacturing an electromagnetic shielding material according to any one of paragraphs 1 to 9.

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