Electromagnetic wave absorbing composite materials including conductive wires and their preparation methods

Abstract

This invention provides an electromagnetic wave absorbing composite material and its preparation method. The electromagnetic wave absorbing composite material comprises: a polymer composite containing a refractive index adjusting material; and multiple conductive lines formed on at least one surface of the polymer composite. The electromagnetic waves reflected within the matching frequency (f) range derived by mathematical formulas 1 to 3 described in this invention are below 0.2 dB.

Description

Technical Field

[0001] This invention relates to the structural design of an electromagnetic wave absorbing composite material and the electromagnetic wave absorbing composite material realized therefrom. The electromagnetic wave absorbing composite material determines the organic relationship between the thickness, refractive index, and conductive wire specifications (linewidth, spacing, etc.) of the polymer composite and derives a designable formula to maximize the electromagnetic wave absorption capability within the target matching frequency band. At the same time, it finds the optimal conditions that maximize the absorption capability of the incident electromagnetic wave at a set matching frequency, thereby minimizing the electromagnetic interference between electronic components that are trending towards miniaturization and thinning. Background Technology

[0002] Recently, with the development of electrical and electronic components and next-generation information and communication equipment, the operating frequency of circuits is increasing to the gigahertz (GHz) high-frequency band. In particular, with the trend of devices becoming more multifunctional and miniaturized, the tiny electromagnetic waves generated by general electronic components can cause malfunctions due to electromagnetic interference between electronic components, and the problems of electromagnetic waves and electromagnetic pollution that are harmful to the human body due to signal quality degradation and electromagnetic radiation are becoming increasingly serious.

[0003] To address the problems caused by the generation of electromagnetic waves and improve the performance of electronic components, research is underway on electromagnetic wave shielding materials that absorb and shield electromagnetic waves. However, existing electromagnetic wave shielding materials have the following problems.

[0004] First, a method for dispersing magnetic materials within shielding materials was introduced to achieve excellent electromagnetic wave absorption. However, most magnetic materials suffer from a problem: due to resonance at high frequencies, their permeability almost disappears in the GHz band. Furthermore, the spin-directional nature of magnetic materials makes it difficult to fine-tune electromagnetic wave energy absorption to suit the complex designs of devices or circuits. Moreover, while increasing conductivity can enhance electromagnetic wave absorption when dispersing large amounts of magnetic material, this leads to a decrease in the mechanical and physical properties of electronic components (including impact strength), severely limiting their application as electromagnetic wave shielding materials.

[0005] Secondly, a multi-layer electromagnetic wave shielding material is introduced, which can absorb and shield electromagnetic waves even in the GHz band as described above, while having almost no decrease in the mechanical and electrical physical properties as described above. However, there are the following problems: due to the thickness of the multi-layer structure, it is difficult to use in electronic components that are trending towards miniaturization and thinning. Moreover, the process of converting incident electromagnetic wave energy into heat by the multi-layer electromagnetic wave shielding material cannot be effectively controlled, which may lead to malfunctions of electronic components.

[0006] Third, previous studies have investigated electromagnetic wave shielding materials with conductive lines formed on at least one surface of the composite. However, it has been difficult to determine and control the organic relationship between the components constituting the composite based on the target frequency. In general, to absorb a specific frequency, precise control of the composite's physical properties, such as refractive index, thickness, material composition, and dispersed metallic materials, is required. Therefore, to absorb electromagnetic waves and provide effective electromagnetic wave shielding within the GHz band required for 5G, in addition to a structural design that maximizes electromagnetic wave absorption, a structural design for absorbing materials capable of absorbing specific frequencies (5G band) is essential. However, currently, no research has been conducted that can effectively absorb and shield electromagnetic waves while simultaneously possessing the GHz matching frequency required for 5G.

[0007] Therefore, there is an urgent need to study the structural design of electromagnetic wave absorbing composite materials and the electromagnetic wave absorbing composite materials realized through them. The electromagnetic wave absorbing composite materials can maximize the electromagnetic wave absorption capacity in the target matching frequency band by determining the organic relationship between the thickness, refractive index, and conductive wire specifications (linewidth, spacing, etc.) of the polymer composite material and deriving a designable formula. At the same time, it is necessary to find the optimal conditions that can maximize the absorption capacity of incident electromagnetic waves at a set matching frequency, thereby minimizing the electromagnetic interference between electronic components that are trending towards miniaturization and thinning. Summary of the Invention

[0008] The technical problem to be solved by the present invention

[0009] The present invention is proposed to overcome the aforementioned problems.

[0010] The first problem to be solved by the present invention is to provide an electromagnetic wave absorbing composite material and its preparation method, which is used in devices for emitting electromagnetic waves and can absorb most of the electromagnetic waves in a specific frequency band, and the electromagnetic wave reflection capability is close to 0dB.

[0011] Furthermore, the second problem to be solved by the present invention is to provide an electromagnetic wave absorbing composite material and its preparation method, which effectively shields electromagnetic waves in the target frequency region by maximizing electromagnetic wave absorption capability while minimizing magnetic wave reflection capability.

[0012] Furthermore, the third problem to be solved by the present invention is to provide an electromagnetic wave absorbing composite material and its preparation method, which has a low overall reflection capability over a wide frequency band.

[0013] Furthermore, the fourth problem to be solved by the present invention is to provide a structural design of an electromagnetic wave absorbing composite material and an electromagnetic wave absorbing composite material realized therefrom. The electromagnetic wave absorbing composite material can maximize the electromagnetic wave absorption capability within the target matching frequency band by determining the organic relationship between the thickness, refractive index, and specifications (linewidth, spacing, etc.) of the polymer composite material and deriving a designable formula. At the same time, it can find the optimal conditions that maximize the absorption capability of the incident electromagnetic wave at the set matching frequency, thereby minimizing electromagnetic interference between electronic components that are trending towards miniaturization and thinning.

[0014] Technical solution

[0015] To address the aforementioned problem, the present invention provides an electromagnetic wave absorbing composite material comprising: a polymer composite containing a refractive index adjusting material; and multiple conductive lines formed on at least one surface of the polymer composite, wherein the electromagnetic waves reflected within a matching frequency f range derived by the following mathematical formulas 1 to 3 are below 0.2 dB.

[0016] Mathematical formula 1:

[0017]

[0018] At this point, f is a frequency with a lower limit of 15 and an upper limit of 80.

[0019] D eff The effective spacing of the conductive lines is represented by the following mathematical formula 2.

[0020] n eff The effective refractive index of the electromagnetic wave absorbing composite material is represented by the following mathematical formula 3.

[0021] c is the speed of light in free space.

[0022] Mathematical formula 2:

[0023] D eff =1.53exp(0.23(Da))

[0024] D is the average spacing of the conductive lines.

[0025] a is the average linewidth of the conductive line.

[0026] Mathematical formula 3:

[0027]

[0028] n is the average refractive index of the polymer composite.

[0029] D is the average spacing of the conductive lines.

[0030] d is the thickness of the polymer composite.

[0031] Furthermore, according to one embodiment of the present invention, it can be an electromagnetic wave absorbing composite material, characterized in that the average spacing D of the conductive wires is 0.5 to 10 mm.

[0032] Furthermore, according to another embodiment of the present invention, it can be an electromagnetic wave absorbing composite material, characterized in that the thickness d of the polymer composite is 100 to 2000 μm.

[0033] In addition, another embodiment of the present invention may be an electromagnetic wave absorbing composite material, characterized in that the average linewidth 'a' of the conductive wire is 50 to 500 μm.

[0034] Furthermore, according to one embodiment of the present invention, it can be an electromagnetic wave absorbing composite material, characterized in that the electromagnetic wave absorption capacity of the electromagnetic wave absorbing composite material is more than 80%.

[0035] In addition, another embodiment of the present invention may be an electromagnetic wave absorbing composite material, characterized in that the refractive index adjusting material includes any one or more of magnetic materials, metallic materials, carbon materials, ceramic materials, and MXene.

[0036] Furthermore, another embodiment of the present invention may be an electromagnetic wave absorbing composite material, characterized in that the conductive wire comprises any one or more of the following: iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo), manganese (Mn), neodymium (Nd), gold (Au), silver (Ag), copper (Cu), aluminum (Al), platinum (Pt), carbon nanotubes, carbon nanofibers, carbon black, carbon fiber, and graphene or palladium (Pd) metals or their alloy conductors, MXene or polypyrrole, polyaniline, polyacetylene, polypphenylenevinylene, polythiophene, polyethylenedioxythiophene, polyphenylenesulfide, or conductive polymers synthesized therefrom.

[0037] Furthermore, according to one embodiment of the present invention, it can be an electromagnetic wave absorbing composite material, characterized in that a plurality of said polymer composites are laminated, and conductive lines are formed on the top surface of the laminated polymer composites.

[0038] In addition, another embodiment of the present invention may be an electromagnetic wave absorbing composite material, characterized in that the conductive wire is a shape including mesh, circular, polygonal, open ring or a combination of more than one of these.

[0039] Furthermore, according to one embodiment of the present invention, it may be an electromagnetic wave absorbing composite material, characterized in that the conductive wires are formed at multiple intervals or a single interval.

[0040] In addition, another embodiment of the present invention may be an electromagnetic wave absorbing composite material, characterized in that when the conductive lines are formed at multiple intervals, they have a reflectivity of less than 30%.

[0041] In addition, another embodiment of the present invention may be an electromagnetic wave absorbing composite material, characterized in that the electromagnetic wave absorbing composite material has an electromagnetic wave reflectivity of less than 0.5 dB at a frequency of 26 GHz.

[0042] In addition, another embodiment of the present invention may be an electromagnetic wave absorbing composite material, characterized in that the electromagnetic wave absorbing composite material is an electromagnetic wave absorbing composite material whose reflected electromagnetic waves are less than 0.1dB within the matching frequency f range derived by the mathematical formulas 1 to 3.

[0043] Furthermore, the present invention provides an electromagnetic wave absorbing circuit module, comprising: a circuit board on which devices are mounted; and any one of the above-mentioned electromagnetic wave absorbing composite materials, disposed on the circuit board in such a manner as to cover at least one surface of at least the devices.

[0044] Furthermore, the present invention provides an electronic device comprising the aforementioned electromagnetic wave absorption circuit module.

[0045] Furthermore, this invention provides a method for preparing an electromagnetic wave absorbing composite material, comprising: step (1), preparing a polymer composite containing a refractive index adjusting material; and step (2), forming conductive lines on the polymer composite. By adjusting the average refractive index, thickness, linewidth, and spacing of the conductive lines of the polymer composite, the electromagnetic waves reflected within the matching frequency f range derived by the following mathematical formulas 1 to 3 are below 0.2 dB.

[0046] Mathematical formula 1:

[0047]

[0048] At this point, the lower limit of f is 15, and the upper limit is a frequency of 80.

[0049] D eff The effective spacing of the conductive lines is represented by the following mathematical formula 2.

[0050] neff The effective refractive index of the electromagnetic wave absorbing composite material is represented by the following mathematical formula 3.

[0051] c is the speed of light in free space.

[0052] Mathematical formula 2:

[0053] D eff =1.53exp(0.23(Da))

[0054] D is the average spacing of the conductive lines.

[0055] a is the average linewidth of the conductive line.

[0056] Mathematical formula 3:

[0057]

[0058] n is the average refractive index of the polymer composite.

[0059] D is the average spacing of the conductive lines.

[0060] d is the thickness of the polymer composite.

[0061] Furthermore, in the method for preparing electromagnetic wave absorbing composite materials according to an embodiment of the present invention, the polymer composite in step (1) may also include a refractive index adjusting material.

[0062] Furthermore, according to another embodiment of the present invention, the method for preparing an electromagnetic wave absorbing composite material is characterized in that, in step (1), a plurality of the polymer composites are laminated, and in step (2), conductive lines are formed on the top surface of the polymer composites laminated in step (1).

[0063] Furthermore, according to another embodiment of the method for preparing an electromagnetic wave absorbing composite material, step (2) is characterized in that a fiber mixture is used to sew (set) conductive wires onto any surface of the polymer composite, wherein the fiber mixture comprises iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo), manganese (Mn), neodymium (Nd), gold (Au), silver (Ag), copper (Cu), aluminum (Al), platinum (Pt) carbon nanotubes, carbon nanofibers, carbon black, carbon fibers, etc. Conductive polymers including fiber and graphene or palladium (Pd) metals or as metal alloys, MXene or polypyrrole, polyaniline, polyacetylene, polypphenylenevinylene, polythiophene, polyethylenedioxythiophene, polyphenylenesulfide or as a composite thereof, and at least one of polyurethane, polyamide, polyester, acrylic, polyolefin, cellulose, carbon, and glass.

[0064] Beneficial effects

[0065] The electromagnetic wave absorbing composite material of the present invention provides an electronic component for emitting electromagnetic waves that absorbs more than 90% of electromagnetic waves in a specific frequency band while exhibiting electromagnetic wave reflection close to 0dB. This effectively shields the electromagnetic waves between electronic components, and contributes to miniaturization and thinning without any degradation in the mechanical or electrical physical properties of the electronic components.

[0066] Furthermore, the electromagnetic wave absorbing composite material according to the present invention can maximize the electromagnetic wave absorption capability within the target matching frequency band by determining the organic relationship between the thickness, refractive index, and conductive wire specifications (linewidth, spacing, etc.) of the polymer composite and deriving a designable formula. At the same time, it can find the optimal conditions that can maximize the absorption capability of incident electromagnetic waves at a set matching frequency, and can be designed to have a low overall reflection capability in a wide frequency range, thereby minimizing the electromagnetic interference between electronic components that are trending towards miniaturization and thinning, and improving the stability of electronic components. Attached Figure Description

[0067] Figure 1 This is a diagram illustrating the electromagnetic wave absorbing composite material according to the present invention.

[0068] Figure 2a This is a diagram illustrating a refractive index-adjusting material comprising an electromagnetic wave absorbing composite material according to the present invention.

[0069] Figure 2b and 2c This is a diagram according to the present invention used to illustrate the average spacing and average line width of conductive lines.

[0070] Figure 2d This is a schematic diagram illustrating a plurality of spaced conductive lines according to an embodiment of the present invention.

[0071] Figure 3 This is a graph showing the absorption capacity, reflection capacity, and shielding capacity of the electromagnetic wave absorbing composite material prepared according to Example 1.

[0072] Figure 4 and 5 The graphs show the absorption capacity, reflection capacity, and shielding capacity of the electromagnetic wave absorbing composite materials prepared according to Examples 2 to 3, respectively.

[0073] Figure 6 and 7 The graphs show the absorption capacity, reflection capacity, and shielding capacity of the electromagnetic wave absorbing composite materials prepared according to Comparative Examples 1 and 2, respectively.

[0074] the following Figure 8 and 9 The graphs show the absorption energy, reflection capability, and shielding capability of the electromagnetic wave absorbing composite materials prepared according to Examples 4 and 5, respectively.

[0075] Figure 10 and 11 It is a graph showing the reflectivity of conductive lines with multiple intervals.

[0076] Figure 12 and 13 The graphs show the absorption capacity, reflection capacity, and shielding capacity of the electromagnetic wave absorbing composite materials prepared according to Comparative Examples 3 and 4, respectively.

[0077] Figure 14 and 15 The graphs show the absorption capacity, reflection capacity, and shielding capacity of the electromagnetic wave absorbing composite materials prepared according to Example 6 and Comparative Example 5, respectively. Detailed Implementation

[0078] The embodiments of the present invention will now be described in detail to enable those skilled in the art to readily implement the invention. The present invention can be implemented in various different forms and is not limited to the embodiments described herein.

[0079] As mentioned above, traditional electromagnetic wave shielding materials have the following problems: they do not conform to the trend of miniaturization / thinning of electronic components, they are difficult to design with a specific matching frequency, and at a specific matching frequency, they cannot maximize the shielding ability by maximizing the electromagnetic wave absorption capacity or minimizing the reflection capacity through structural design.

[0080] Therefore, the present invention seeks to solve the aforementioned problem by providing an electromagnetic wave absorbing composite material, the electromagnetic wave absorbing composite material comprising: a polymer composite containing a refractive index adjusting material; multiple conductive lines formed on at least one surface of the polymer composite, wherein the electromagnetic waves reflected within the matching frequency f range derived by the following mathematical formulas 1 to 3 are less than 0.2 dB.

[0081] Mathematical formula 1:

[0082]

[0083] At this point, f is a frequency with a lower limit of 15 and an upper limit of 80.

[0084] D eff The effective spacing of the conductive lines is represented by the following mathematical formula 2.

[0085] n eff The effective refractive index of the electromagnetic wave absorbing composite material is represented by the following mathematical formula 3.

[0086] c is the speed of light in free space.

[0087] Mathematical formula 2:

[0088] D eff =1.53 exp(0.23(Da))

[0089] D is the average spacing of the conductive lines.

[0090] a is the average linewidth of the conductive line.

[0091] Mathematical formula 3:

[0092]

[0093] n is the average refractive index of the polymer composite.

[0094] D is the average spacing of the conductive lines.

[0095] d is the thickness of the polymer composite.

[0096] Therefore, this invention can maximize the electromagnetic wave absorption capability within the target matching frequency band by determining the organic relationship between the thickness, refractive index, and conductive line specifications (linewidth, spacing, etc.) of the polymer composite and deriving a designable formula. At the same time, it can find the optimal conditions that can maximize the absorption capability of incident electromagnetic waves at a set matching frequency, thereby minimizing the electromagnetic interference between electronic components that are trending towards miniaturization and thinning, and improving the stability of electronic components.

[0097] Figure 1 This is a diagram illustrating the electromagnetic wave absorbing composite material according to the present invention.

[0098] Specifically, refer to Figure 1 The electromagnetic wave absorbing composite material 100 according to the present invention includes a polymer composite 10 containing a refractive index adjusting material 20 inside.

[0099] The polymer composite 10 serves as a polymer substrate, in which a refractive index adjusting material 20 is dispersed. Conductive lines are formed on at least one surface of the polymer composite 10. As a key variable, it needs to be controlled so that a specific matching frequency can be set together with the refractive index adjusting material 20 and the conductive lines 30, and the absorption capacity can be maximized within the set frequency band.

[0100] That is, since the polymer composite 10 is a factor that determines the electromagnetic wave shielding capability of the electromagnetic wave absorbing composite material 100, the refractive index, thickness, matching frequency of the polymer composite 10 suitable for the final electromagnetic wave absorbing composite material 100, target absorption capability and reflection capability can be controlled.

[0101] Referring to Figure 2 below, the polymer composite 10 contains a refractive index adjusting material 20.

[0102] At this time, the refractive index adjusting material 20 can be the material that affects the refractive index in this invention, but it is not limited to this. It can also be a material that adjusts physical properties such as magnetic permeability and dielectric constant.

[0103] According to one embodiment of the present invention, when the refractive index adjusting material adjusts the dielectric constant, the refractive index adjusting material can have a dielectric constant of 3 to 15. In this case, if the dielectric constant is less than 3, the target absorption capacity may not be achieved. Furthermore, if the dielectric constant is greater than 15, the conductive wire pattern may not be able to operate independently due to excessively high conductivity.

[0104] There are no particular limitations on the form of this refractive index adjusting material. It can be sphere-shaped, plate-shaped, flake-shaped, rod-shaped, wire-shaped, hollow sphere-shaped, hollow tube-shaped, hollow wire-shaped, or hollow flake-shaped. It can be contained in the polymer composite 10 in this form. More preferably, the refractive index adjusting material 20 can be contained in a dispersed form in the polymer substrate forming the polymer composite 10.

[0105] Furthermore, for the same purpose, the refractive index adjusting material 20 may be selected from known materials, and as a non-limiting example, the refractive index adjusting material 20 may include at least one selected from the group consisting of magnetic materials, metallic materials, carbon materials, ceramic materials, and MXene, and preferably, may be composed of a plurality of magnetic particles having different resonant frequencies from one another.

[0106] In this case, according to one embodiment of the present invention, when the refractive index adjusting material is a magnetic material, it can be iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo), manganese (Mn), or neodymium (Nd) metal or metal alloy particles. Furthermore, these magnetic materials can be particles coated with one or more dielectrics selected from titanium oxide, barium-titanium oxide, and strontium-titanium oxide. Additionally, the magnetic material can be particles coated with a magnetic material on one or more carbon-based conductors selected from carbon nanotubes, carbon nanofibers, carbon black, carbon fiber, and graphene. Furthermore, the magnetic material can be iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo), manganese (Mn), or neodymium (Nd) metal or metal alloy particles. At this point, considering the size of the refractive index adjustment material, the coating thickness of the magnetic material can be from 50 nm to 5 μm.

[0107] When the refractive index adjusting material is contained in a polymer composite in a dispersed form, the content of the refractive index adjusting material can be from 0.01% to 80% by weight. However, there is no particular limitation when the majority of the polymer composite is formed solely of the refractive index adjusting material, and the majority of the polymer composite can also be formed of the refractive index adjusting material.

[0108] Furthermore, when the refractive index adjusting material is contained in the polymer composite in particulate form, it can have a size of 1 nm to 50 μm, preferably 10 nm to 20 μm, but it can be a general size that is in line with the purpose of this invention, and therefore there is no particular limitation.

[0109] Refer to the following Figure 1 Multiple conductive lines 30 are formed on at least one surface of the polymer composite 10.

[0110] The conductive wires 30, formed within the polymer composite 10, are a key factor in determining the matching frequency and absorption capacity. Specifically, the conductive wires 30, based on their shape, allow only specific frequencies to pass through, drastically reducing reflection and maximizing absorption within that frequency band. Furthermore, the matching frequency for the target frequency band can be obtained by controlling the shape, linewidth, and spacing of these conductive wires, and the electromagnetic wave shielding effect can be significantly improved by absorbing most electromagnetic waves at these specific frequencies.

[0111] On the other hand, the polymer composite 10 and the conductive wire 30 satisfy the following mathematical formulas 1 to 3. Mathematical formulas 1 to 3 will be explained below.

[0112] Mathematical formula 1:

[0113]

[0114] At this point, f is a frequency with a lower limit of 15 and an upper limit of 80.

[0115] D eff The effective spacing of the conductive lines is represented by the following mathematical formula 2.

[0116] n eff The effective refractive index of the electromagnetic wave absorbing composite material is represented by the following mathematical formula 3.

[0117] c is the speed of light in free space.

[0118] Frequency f (GHz)

[0119] With the development of wireless electronics, communications, computers, electronic vehicle applications, radar, and especially communication technologies towards fifth generation (5G), one objective of this invention is to provide a high-frequency 5G electromagnetic wave absorbing composite material for shielding millimeter-band frequencies. Therefore, the frequency f can be from 15 GHz to 80 GHz, more preferably from 15 to 45 GHz. Specifically, in this invention, f1 will represent the lower limit of the matching frequency f, and f2 will represent the upper limit of the matching frequency f.

[0120] At this point, in order to absorb this specific frequency f, it is necessary to finely control the comprehensive physical properties of the electromagnetic wave absorbing composite material, such as its refractive index, thickness, material composition, and dispersed metallic materials. Therefore, in order to absorb electromagnetic waves and provide effective electromagnetic wave shielding materials even within the GHz band required by 5G, in addition to the structural design that can maximize the ability to absorb electromagnetic waves, it is also necessary to have a structural design of electromagnetic wave absorbing composite materials that can absorb specific frequencies (5G band).

[0121] Therefore, this invention determines the organic relationship between each physical property contained in the electromagnetic wave absorbing composite material as described in the above mathematical formula 1, and derives it into a formula.

[0122] Effective interval D eff

[0123] In the above mathematical formula 1, the effective spacing refers to the spacing D of the conductive lines, taking into account the influence of the average linewidth a and the wavelength of the electromagnetic wave. eff And it has the relationship with the average spacing D of the conductive lines as shown in the following mathematical formula 2.

[0124] Mathematical formula 2:

[0125] D eff =1.53 exp(0.23(Da))

[0126] D is the average spacing of the conductive lines.

[0127] a is the average linewidth of the conductive line.

[0128] Effective refractive index n eff

[0129] In the mathematical formula 1, the effective refractive index refers to the refractive index of the electromagnetic wave absorbing composite material that takes into account the thickness of the electromagnetic wave absorbing composite material in free space, and has the relationship with the average refractive index n of the electromagnetic wave absorbing composite material as shown in the following mathematical formula 3.

[0130] Mathematical formula 3:

[0131]

[0132] n is the average refractive index of the polymer composite.

[0133] D is the average spacing of the conductive lines.

[0134] d is the thickness of the polymer composite.

[0135] In the mathematical formula 3, as for the purposes of this invention, the average refractive index n is an important variable in the design of electromagnetic wave absorbing composite materials that maximize the absorption capability of incident electromagnetic waves while setting a specific matching frequency or GHz band, thereby minimizing electromagnetic interference between electronic components. This is because the spacing of the conductive lines required for the matching frequency varies with the refractive index, and the electromagnetic wave absorption capability is highly dependent on the spacing of the conductive lines.

[0136] Next, we will refer to Figures 3 to 12 For the mathematical formulas 1 to 3, the relationship between the thickness of the polymer composite 10, the average spacing D of the conductive lines, the average linewidth a of the conductive lines, and the refractive index of the polymer composite 10 is explained in sequence.

[0137] First, refer to Figure 4 and 5 This is explained in order to determine the relationship between the matching frequency and the absorption capacity based on the thickness d of the polymer composite 10.

[0138] Figure 4 and 5 Yes, in Examples 2 and 3, the spacing D of the conductive lines 30 and the average linewidth a of the conductive lines 30 were kept constant at 1.5 mm and 250 μm, respectively. After preparing the electromagnetic wave absorbing composite material 100 according to the present invention by changing the thickness d of the polymer composite 10, the absorption capacity, reflection capacity and shielding capacity were evaluated at specific frequencies recorded in the graph, and the results were displayed in graphs.

[0139] It can be seen that, under all conditions such as thickness, linewidth, and line spacing as described above, the frequency is consistently between 18 and 40 GHz, while the reflection capability of each embodiment is below 0.2 dB. Furthermore, as can be seen from Embodiments 2 and 3 above, the target matching frequency band of the electromagnetic wave absorbing composite material 100 according to the present invention decreases with increasing thickness d of the polymer composite 10. Ultimately, it can be concluded that the thickness d of the polymer composite 10 is the main factor determining the matching frequency and absorption capability of the electromagnetic wave absorbing composite material 100.

[0140] Therefore, the polymer composite 10 is not particularly limited, as suitable polymer materials can be selected considering the specific matching frequency and absorption capacity. However, as a non-limiting example, it can be a thermosetting or thermoplastic material, and polymer materials such as epoxy resin, silicone rubber, polyurethane, polyethylene, polyethylene terephthalate (PET), polyethersulfone (PES), polyacrylate (PAR), polyimide (PI), and polycarbonate (PC) can be used, or a mixture of two or more of these can be prepared. More preferably, it can be thermoplastic polyurethane.

[0141] Furthermore, the thickness d of the polymer composite 10 can be appropriately controlled according to the target matching frequency and absorption capacity. For example, it can have a thickness d of 100 to 2000 μm. Preferably, it can have a thickness of 200 to 500 μm to achieve a matching frequency band within the 5G band. However, if the thickness of the polymer composite 10 is less than 100 μm, the absorption capacity may not be fully expressed. If the thickness of the polymer composite 10 exceeds 2000 μm, it may be too thick to be suitable for 5G terminal devices.

[0142] Next, in order to determine the relationship between the matching frequency and absorption capacity of the spacing D of the conductive wires 30, reference will be made to... Figure 6 and 7 Let me explain.

[0143] Figure 6 and 7 The graph is a chart in which, in Comparative Examples 1 and 2, the thickness d of the polymer composite 10 and the linewidth a of the conductive line 30 are kept constant at 200 μm and 150 μm, respectively, and the absorption capacity, reflection capacity and shielding capacity are evaluated at specific frequencies recorded in the graph after the spacing D of the conductive line 30 is changed to 0.3 mm and 12 mm and the electromagnetic wave absorbing composite material 100 according to the present invention is prepared, and the results are displayed.

[0144] Reference Figure 6 and 7 It can be seen that, compared with Example 1, Comparative Examples 1 and 2 exhibited very high reflectivity exceeding 0.2 dB, while their absorption capacity decreased significantly. Therefore, the spacing D of the conductive wires 30 is the main factor determining the absorption capacity, reflectivity, and shielding capacity.

[0145] Therefore, the average spacing D of the conductive wires 30 can be 0.5 to 10 mm, more preferably 0.5 to 2 mm. However, the preferred range refers to the spacing when the wires 30 have a single spacing; when the conductive wires 30 have multiple spacings as described later, the average spacing D can be in the range of 0.5 to 10 mm. In this case, as... Figure 2a As shown, the average spacing D of the conductive lines refers to, according to an embodiment of the present invention, the average spacing between one conductive line and another adjacent conductive line when the conductive lines are formed in a grid pattern. Furthermore, the average spacing of the conductive lines may include both D1 and D2, but is preferably D2, that is, the portion forming the conductive lines refers to the spacing between the outermost periphery of the omitted conductive line and the outermost periphery of the adjacent conductive line.

[0146] At this time, according to an embodiment of the present invention, if the average spacing of the conductive lines is less than 0.5 mm, there may be a problem that the reflection capability in the matching frequency band is not reduced due to interference between the conductive lines. If the average spacing of the conductive lines exceeds 10 mm, there may be a problem that the absorption capability cannot be fully expressed.

[0147] Next, in order to determine the relationship between the matching frequency and the absorption capacity of the linewidth 'a' of the conductive line 30, reference will be made to... Figure 8 and Figure 9 Please provide an explanation.

[0148] the following Figure 8 and 9 Yes, in Examples 4 and 5, the spacing D of the conductive wires 30 and the thickness d of the polymer composite 10 were set to 1.5 mm and 400 μm, respectively. After preparing the electromagnetic wave absorbing composite material 100 according to the present invention by changing the line width a of the conductive wires 30, the absorption capacity, reflection capacity and shielding capacity were evaluated at a specific frequency, and the results were displayed in graphs.

[0149] It is now known that, under all the conditions of thickness, linewidth, spacing, etc., as described above, while displaying a frequency range of 18–40 GHz, the reflection capability of each embodiment is less than 0.2 dB. Furthermore, as can be seen from embodiments 4 and 5 as described above, the electromagnetic wave absorbing composite material 100 according to the present invention can adjust the target matching frequency band by appropriately designing the linewidth a of the conductive lines 30.

[0150] Therefore, the linewidth 'a' of the conductive line 30 is the main factor determining the matching frequency and reflection capability.

[0151] Therefore, the linewidth 'a' of the conductive line can be 50 to 500 μm, more preferably 100 to 300 μm. In this case, as... Figure 2cAs shown, according to one embodiment of the present invention, when the conductive line is formed as a circle, the average line width 'a' refers to the longest width of the guiding wire. Furthermore, as another embodiment of the present invention, when the conductive line is formed as a polygon, it also refers to the longest direction, either horizontally or vertically.

[0152] At this time, according to one embodiment of the present invention, if the line width of the conductive line is less than 50 μm, there may be a problem that the absorption capacity cannot be fully expressed; if the line width of the conductive line exceeds 500 μm, there may be a problem that the reflection capacity in the matching frequency band will not be reduced due to interference between the conductive lines.

[0153] Furthermore, the conductive wire may include any one or more conductive polymers selected from iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo), manganese (Mn), neodymium (Nd), gold (Au), silver (Ag), copper (Cu), aluminum (Al), platinum (Pt), carbon nanotubes, carbon nanofibers, carbon black, carbon fiber, and graphene or palladium (Pd) metals or their alloys, MXene or polypyrrole, polyaniline, polyacetylene, polypphenylenevinylene, polythiophene, polyethylenedioxythiophene, polyphenylenesulfide, or their composites.

[0154] At this time, the conductive lines can be any combination of a grid, a circle, a polygon, an open ring, or a combination thereof. More specifically, the conductive lines can be formed by periodically arranged conductive lines, and can be curved rather than straight. Preferably, the conductive lines can be arranged periodically in a grid pattern, which can further improve the electromagnetic wave absorption efficiency.

[0155] Furthermore, the conductive lines 30 can be formed at multiple intervals or at a single interval.

[0156] That is, according to an embodiment of the electromagnetic wave absorbing composite material 100 of the present invention, such as... Figure 1 As shown, the conductive lines 30 can also be formed at single intervals, according to another embodiment of the present invention, such as Figure 2d As shown, the conductive lines 30 can be formed at multiple intervals.

[0157] Usually, such as Figure 1 As shown, the reflectivity at a specific frequency of the matched conductive line 30 with a single interval can be reduced by appropriately controlling the interval or line width, as described above. However, as in Figure 10 and 11 As shown by dotted or dashed lines, the reflectivity may increase sharply at mismatched frequencies. That is, when high-frequency matching is performed by controlling the spacing or line width of the conductive lines 30, the reflectivity can gradually decrease from low to high frequencies, while when low-frequency matching is performed, the reflectivity can increase from high to low frequencies.

[0158] On the contrary, such as Figure 2d As shown, for conductive lines 30 with multiple intervals, such as in Figure 10 and 11 As shown by the solid line, the reflectivity can be relatively low overall across a wide frequency band. More preferably, when the conductive lines are formed at multiple intervals, the reflectivity can be less than 30% or less than 1.5 dB.

[0159] As described above, the present invention can maintain a constant reflection capability not only at a specific matching frequency but also over a wide frequency band by diversifying the spacing of the conductive lines 30. While the present invention describes two different types of spacing for the plurality of spacings, this is only a preferred embodiment and is not limited thereto; it can be stated that the plurality of spacings of the conductive lines 30 have at least two different types of spacing.

[0160] On the other hand, the conductive lines can be formed on any surface of the polymer composite, covering an area of ​​25% to 65%, and more preferably, on any surface of the uppermost surface of the laminated polymer composite, covering an area of ​​30% to 50%. In this case, if the area of ​​the conductive lines is less than 25%, there may be a problem that the absorption capacity cannot be fully expressed; if the area of ​​the conductive lines exceeds 65%, there may be a problem that the reflection capacity in the matched frequency band will not decrease due to interference between the conductive lines.

[0161] On the other hand, in order to determine the mathematical formula 3 for the refractive index, Comparative Examples 3 and 4 were prepared as follows. In Comparative Examples 3 and 4, other conditions were the same as in Example 1, but electromagnetic wave absorbing composite materials were prepared by changing the refractive index adjusting material contained in the conductive polymer composite 10 so that the average refractive index n of the polymer composite was 2 and 18, respectively. The absorption capacity, reflection capacity, and shielding capacity at specific frequencies are shown in the figure. Figure 12 and 13 And Tables 1 and 2.

[0162] Reference Figure 12 and 13As shown in Tables 1 and 2, at the same measurement frequency of 22.5 GHz as in Example 1, Comparative Examples 3 and 4 exhibited reflectivity significantly higher than the target of less than 0.2 dB. Therefore, it is determined that the average refractive index n of the polymer composite as described above is the main factor determining the matching frequency, reflectivity, and absorption capacity. Furthermore, by appropriately designing the thickness d of the polymer composite 10 to control the average refractive index n, a target matching frequency can be set, and an effective electromagnetic wave absorbing composite material can be designed.

[0163] As described above, since the average refractive index n is a factor that must be considered in setting the target matching frequency and designing an effective electromagnetic wave absorbing composite material in this invention, the average refractive index n can be 3 to 15, more preferably 4 to 10. In this case, if the average refractive index is less than 3, there may be a problem of not achieving the target absorption capacity. Furthermore, if the average refractive index exceeds 15, there may be a problem of the conductive wire pattern not being able to operate independently due to excessively high conductivity.

[0164] Next, in order to confirm that if either the thickness of the polymer composite or the average linewidth of the conductive lines of the present invention does not meet the conditions of the present invention, it will be impossible to simultaneously exhibit the target of a minimized reflection capability of less than 0.2 dB or a frequency band suitable for 5G, Example 6 and Comparative Example 5 were prepared, and the results are shown in […]. Figure 14 and 15 .

[0165] In Example 6 and Comparative Example 5, as shown in Table 1 below, the polymer composites of Example 1 were prepared by changing the thickness and the average spacing of the conductive lines. The absorption, reflection and shielding capabilities were evaluated at specific frequencies, and the results are shown in Table 2.

[0166] Referring to Tables 1 and 2, unlike Embodiment 1, Embodiment 6 only shows a matching frequency of 14 to 18 GHz, and unlike Embodiment 1, Comparative Example 5 shows a reflection capability far exceeding the target of the present invention of less than 0.2 dB, rather than the target of the present invention of less than 0.2 dB.

[0167] As can be seen from the results described above, if any one of the following—the thickness of the polymer composite, the average linewidth of the conductive lines, and the average spacing—does not meet the conditions of this invention, then this invention cannot achieve the target matching frequency, reflection capability, and absorption capability. Furthermore, it has been determined that through their specific design, the target matching frequency can be set and an effective electromagnetic wave absorbing composite material can be designed.

[0168] Furthermore, it was determined that the present invention can maximize the electromagnetic wave absorption capability within the target matching frequency band of the electromagnetic wave absorbing composite material determined by mathematical formulas 1 to 3 only when the thickness of the polymer composite, the average linewidth of the conductive lines, and their average spacing all meet the conditions of the present invention. A relational formula for designing their organic relationship was also derived, and the optimal conditions for maximizing the absorption capability of the incident electromagnetic waves at the set matching frequency were confirmed.

[0169] On the other hand, the electromagnetic wave absorption rate of the electromagnetic wave absorbing composite material according to the present invention can be 90% or more. As can be seen from Examples 1 to 6 and Comparative Examples 1 to 5 described above, all examples show an electromagnetic wave absorption rate close to 90%, but the comparative examples that do not satisfy mathematical formulas 1 to 3 of the present invention show a significantly lower absorption rate.

[0170] In particular, the electromagnetic wave absorbing composite material according to the present invention can have an electromagnetic wave reflectivity of less than 0.5 dB at a frequency of 26 GHz. Furthermore, the electromagnetic waves reflected within the matching frequency f range derived by the mathematical formulas 1 to 3 can be less than 0.1 dB.

[0171] This is the general frequency band required by 5G, and even at this time it has an electromagnetic wave reflection capability of less than 0.5dB. Therefore, according to the recent development trend of the information and communication industry, it can be applied to various electronic component materials.

[0172] Therefore, the present invention provides an electromagnetic wave absorbing circuit module, which includes a circuit board on which devices are mounted and an electromagnetic wave absorbing composite material according to the present invention disposed on the circuit board in such a way as to cover at least one surface of at least the devices, and provides an electronic device including these electromagnetic wave absorbing circuit modules.

[0173] The circuit module is not particularly limited, but as a non-limiting example, it can be a circuit module that can be used in the frequency band required for 5G, and the electronic device can be an electronic device in all industrial fields that requires electromagnetic shielding, including more than one electronic component.

[0174] Next, a method for preparing the electromagnetic wave absorbing composite material according to the present invention will be described. However, to avoid repetition, descriptions of parts that overlap with the technical concept of the electromagnetic wave absorbing composite material will be omitted.

[0175] This invention provides a method for preparing an electromagnetic wave absorbing composite material, comprising: step (1) preparing a polymer composite; and step (2) forming conductive lines on the polymer composite. By adjusting the average refractive index, thickness, linewidth, and spacing of the conductive lines of the polymer composite, the electromagnetic waves reflected within the matching frequency f range derived by the following mathematical formulas 1 to 3 are below 0.2 dB.

[0176] Mathematical formula 1:

[0177]

[0178] At this point, f is a frequency with a lower limit of 15 and an upper limit of 80.

[0179] D eff The effective spacing of the conductive lines satisfies the following mathematical formula 2.

[0180] n eff The effective refractive index of the electromagnetic wave shielding composite material that satisfies the following mathematical formula 3 is:

[0181] c is the speed of light in free space.

[0182] Mathematical formula 2:

[0183] D eff =1.53 exp(0.23(Da))

[0184] D is the average spacing of the conductive lines.

[0185] a is the average linewidth of the conductive line.

[0186] Mathematical formula 3:

[0187]

[0188] n is the average refractive index of the polymer complex.

[0189] D is the average spacing of the conductive lines.

[0190] d is the thickness of the polymer composite.

[0191] First, in order to prepare the polymeric composite of step (1), a polymeric composite solution containing polymeric substances and solvents is prepared.

[0192] The polymer material is not particularly limited. As a non-limiting example, it can be a thermosetting or thermoplastic material, such as epoxy resin, silicone rubber, polyurethane, polyethylene, polyethylene terephthalate (PET), polyethersulfone (PES), polyacrylate (PAR), polyimide (PI), polycarbonate (PC), or a mixture of two or more of these materials. More preferably, it can be thermoplastic polyurethane.

[0193] Furthermore, the solvent can be any substance commonly used in the technical field to which this invention pertains, and there are no particular limitations. However, as a non-limiting example, diethyl propanediol, dipropylene glycol methyl ether, dimethylformamide (DMF), etc., can be used as solvents. Preferably, dimethylformamide (DMF) can be used as a solvent.

[0194] Furthermore, the polymer and solvent in the polymer solution can be a mixture of components that meet the purpose of the present invention. As a non-limiting example, the contents of the polymer and solvent can be 60-80:20-40 by weight, respectively.

[0195] According to one embodiment of the present invention, when a polymer solution is prepared using polyurethane and acetone (dimethyl formaldehyde), it can be prepared by stirring in a stirrer at 1000-3000 rpm for 2 to 10 minutes, then casting the mixed material to a thickness of 30-200 μm, and drying at 50-150°C to remove the acetone solvent, thereby preparing a polymer composite.

[0196] At this point, the polymer composite prepared as described above can be obtained by laminating multiple polymer composites and pressing them at a temperature of 80–150°C and a pressure of 5–15 MPa for 2–10 minutes to obtain a single polymer composite. During pressing, a thickness gauge can be used to control the thickness of the polymer composite to be prepared.

[0197] Next, the polymer composite prepared in step (1) as described above may further include a refractive index adjusting material. The shape of this refractive index adjusting material is not particularly limited. It may be sphere-shaped, plate-shaped, flake-shaped, rod-shaped, wire-shaped, hollow sphere-shaped, hollow tube-shaped, hollow wire-shaped, or hollow flake-shaped. It may be contained in the polymer composite 10 in this form. More preferably, the refractive index adjusting material 20 may be contained in a dispersed form in the polymer substrate forming the polymer composite 10.

[0198] Furthermore, for the same purpose, the refractive index adjusting material 20 may be selected from known materials, and as a non-limiting example, the refractive index adjusting material 20 may include at least one of magnetic materials, metallic materials, carbon materials, ceramic materials, and MXene, and as an example, it may be composed of a plurality of magnetic particles having different resonant frequencies from one another.

[0199] In this case, according to one embodiment of the present invention, when the refractive index adjusting material is a magnetic material, it can be iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo), manganese (Mn), or neodymium (Nd) metal or metal alloy particles. Furthermore, these magnetic materials can be particles coated with one or more dielectrics selected from titanium oxide, barium-titanium oxide, and strontium-titanium oxide. Additionally, the magnetic material can be particles coated with a magnetic material on one or more carbon-based conductors selected from carbon nanotubes, carbon nanofibers, carbon black, carbon fiber, and graphene. Furthermore, the magnetic material can be iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo), manganese (Mn), or neodymium (Nd) metal or metal alloy particles. At this point, considering the size of the refractive index adjustment material, the coating thickness of the magnetic material can be from 50 nm to 5 μm.

[0200] Furthermore, when the refractive index adjusting material is contained in the polymer composite in particulate form, it can have a size of 1 nm to 50 μm, preferably 10 nm to 20 μm, but it can be a general size that is in line with the purpose of this invention, and therefore there is no particular limitation.

[0201] Furthermore, there are no particular limitations on the method of including the refractive index adjusting material in the polymer composite, but for example, it can be formed by adding the required amount of refractive index adjusting material to the polymer composite and dispersing it evenly using a homogenizer, an ultrasonic disperser, or a 3-roll mill.

[0202] Next, step (1) may be a polymer composite formed by laminating at least one polymer composite, and then may include the step of forming conductive lines on any surface of the polymer composite laminated in step (2) with an area of ​​25% to 35%.

[0203] The conductive lines in step (2) can be prepared using various methods without particular limitations. For example, a mask can be made by photolithography or laser processing, and conductive lines made of chromium (Cr), chromium oxide (Cr), etc. can be formed in a non-conductive resin. Then, the conductive lines made of chromium (Cr), chromium oxide (Cr), etc. can be electroplated with nickel (Ni) layers, copper (Cu), etc. to form conductive lines.

[0204] At this point, step (2) can be performed by using a fiber mixture to sew conductive wires onto any surface of the polymer composite. The fiber mixture may contain iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo), manganese (Mn), neodymium (Nd), gold (Au), silver (Ag), copper (Cu), aluminum (Al), platinum (Pt) carbon nanotubes, carbon nanofibers, or carbon black. Conductive polymers including black, carbon fiber and graphene or palladium (Pd) metals or as metal alloys, MXene or polypyrrole, polyaniline, polyacetylene, polypphenylenevinylene, polythiophene, polyethylenedioxythiophene, polyphenylenesulfide or as a composite thereof, and at least one of polyurethane, polyamide, polyester, acrylic, polyolefin, cellulose, carbon, and glass.

[0205] Furthermore, according to one embodiment of the present invention, when polyurethane is used as a mixture material for conductive wires and sewn into a polymer composite, the electromagnetic properties of the material are not affected because it is non-conductive and has a low refractive index.

[0206] After obtaining the desired thickness of the polymer composite, a conductive mesh is sewn using Ag@Nylon thread as the conductive thread and polyurethane thread as the top thread. The spacing of the conductive mesh can then be adjusted by changing the sewing machine settings.

[0207] The present invention will be described in more detail below by way of examples; however, the following examples are not intended to limit the scope of the invention, but should be understood as helping to understand the invention. Specific Implementation

[0209] Example 1

[0210] A 200 ml thermoplastic polyurethane (TPU) solution was prepared, wherein 30 wt% of TPU was dissolved in dimethylformamide (DMF). Carbonyl iron powder (CIP; BASF AG, model EW) was mixed with the prepared TPU solution at a mass ratio of 2:8 and stirred in a stirrer at 2000 rpm for 5 minutes to prepare a polymer composite.

[0211] Next, the prepared polymer composite was cast to a thickness of 100 μm using a doctor blade to prepare a film, which was then dried at 110 °C to remove the DMF solvent. Then, five polymer composites were laminated and hot-pressed at 120 °C and 10 MPa for 5 minutes to prepare a single-layer film with a thickness of 400 μm.

[0212] Next, using Ag@Nylon (SOITEX, France) wires as conductive wires and polyurethane wires (MYUNGSUNG, South Korea) wires as upper wires, conductive wires with a line width of 250 μm and a spacing of 1.5 mm were formed in a polymer composite laminated with a thickness of 400 μm to prepare an electromagnetic wave absorbing composite material.

[0213] Examples 2 and 3

[0214] As shown in Table 1 below, electromagnetic wave absorbing composite materials were prepared in the same manner as in Example 1, except that the thickness of the polymer composite was varied.

[0215] Examples 4 and 5

[0216] As shown in Table 1 below, electromagnetic wave absorbing composite materials were prepared in the same manner as in Example 1, except that the average linewidth of the conductive lines was changed.

[0217] Example 6

[0218] As shown in Table 1 below, electromagnetic wave absorbing composite materials were prepared in the same manner as in Example 1, except that the average spacing of the conductive lines was changed.

[0219] Example 7

[0220] like Figure 2d As shown, except that the conductive wires are prepared with multiple different intervals of 1 mm and 3 mm, the electromagnetic wave absorbing composite material was prepared in the same manner as in Example 1.

[0221] Examples 8 and 9

[0222] Except for the fabrication of conductive wires with different individual spacings of 1 mm and 3 mm, the electromagnetic wave absorbing composite material was prepared in the same manner as in Example 1.

[0223] Comparison of Examples 1 and 2

[0224] As shown in Table 1 below, electromagnetic wave absorbing composite materials were prepared in the same manner as in Example 1, except that the average spacing of the conductive lines was changed.

[0225] Compare Examples 3 and 4

[0226] The electromagnetic wave absorbing composite material was prepared in the same manner as in Example 1, except that the average refractive index n of the polymer composite was changed by adjusting the mass ratio of TPU to CIP, which is a refractive index adjusting material contained in the polymer composite.

[0227] Comparative Example 5

[0228] As shown in Table 1 below, electromagnetic wave absorbing composite materials were prepared in the same manner as in Example 1, except that the thickness of the polymer composite was changed to prepare different materials.

[0229] Table 1

[0230]

[0231] Experiment Example 1: Assessing Absorption Capacity

[0232] To evaluate the absorption capacity of the electromagnetic wave absorbing composite materials prepared in the examples or comparative examples in Table 1, specific frequencies listed in Table 2 were measured using a vector network analyzer (Keysight N5291A), as shown in Table 2 below.

[0233] Experimental Example 2: Evaluation of Reflectivity

[0234] To evaluate the reflection capability of the electromagnetic wave absorbing composite materials prepared in the examples or comparative examples in Table 1, specific frequencies listed in Table 2 were measured using a vector network analyzer (Keysight N5291A), as shown in Table 2 below.

[0235] Experiment Example 3: Evaluation of Shielding Capability

[0236] Based on the results of Experiments 1 to 3, the overall shielding capability of the electromagnetic wave absorbing composite materials prepared in the Examples or Comparative Examples is shown in Table 2 below.

[0237] Table 2

[0238]

[0239] Experiment Example 4: Evaluating Reflectivity Based on Multiple Spacing and Single Spacing Conductive Wires

[0240] To evaluate the reflection capability of the electromagnetic wave absorbing composite materials of Examples 7 to 9, measurements were performed using a vector network analyzer (Keysight N5291A). Figure 10 and 11 As shown.

[0241] Referring to Tables 1 and 2,

[0242] As demonstrated in Examples 2 and 3, which modify the thickness of the polymer composite based on Example 1, the target matching frequency band of the electromagnetic wave absorbing composite material 100 according to the present invention decreases as the thickness d of the polymer composite 10 increases. Therefore, the thickness d of the polymer composite 10 is the primary factor determining the matching frequency and absorption capacity of the electromagnetic wave absorbing composite material 100.

[0243] Furthermore, comparative examples 1 and 2, which varied the spacing of the conductive wires based on Example 1, showed a very high reflectivity exceeding 0.2 dB compared to Example 1, while the absorption capacity was significantly reduced. This indicates that the spacing D of the conductive wires 30 is the primary factor determining the absorption capacity, reflectivity, and shielding capacity.

[0244] Furthermore, through Examples 4 and 5, which modify the linewidth of the conductive lines based on Example 1, it is evident that, under all conditions such as thickness, linewidth, and line spacing as described above, a frequency range of 18–40 GHz was achieved, while the reflection capability of each example was less than 0.2 dB. Moreover, through Examples 4 and 5 as described above, it is evident that the electromagnetic wave absorbing composite material 100 according to the present invention can control the target matching frequency band by appropriately designing the linewidth 'a' of the conductive lines 30; thus, the linewidth 'a' of the conductive lines 30 is a major factor determining the matching frequency and reflection capability.

[0245] Furthermore, comparative examples 3 and 4, which varied the average refractive index n of the polymer composite based on Example 1, showed a reflectivity significantly higher than the target of the present invention (less than 0.2 dB) at the same measurement frequency of 22.5 GHz as in Example 1. Therefore, it is determined that the average refractive index n of the polymer composite, as described above, is the main factor determining the matching frequency, reflectivity, and absorption capacity. Furthermore, by appropriately designing the thickness d of the polymer composite 10 to control the average refractive index n, a target matching frequency can be set, and an effective electromagnetic wave absorbing composite material can be designed.

[0246] Furthermore, unlike Example 1, Example 6 only shows a matching frequency of 14 to 18 GHz, and unlike Example 1, Comparative Example 5 shows a reflection capability far exceeding the target of the present invention of less than 0.2 dB, rather than the target of the present invention of less than 0.2 dB.

[0247] On the other hand, in the case of the conductive lines 30 with multiple intervals prepared according to Example 7, such as in Figure 10 and 11 As shown by the solid line, it exhibits a generally low reflectivity over a wide frequency band. In contrast, the reflectivity is lower when the conductive lines have a single spacing. Figure 10 and 11 As can be seen from Example 8 (dashed line) or Example 9 (dotted line), the reflectivity increases sharply at mismatched frequencies.

[0248] As can be seen from the results described above, if any one of the following—the thickness of the polymer composite, the average linewidth of the conductive lines, and the average spacing—does not meet the conditions of this invention, the invention cannot achieve the target matching frequency, reflection capability, and absorption capability. Furthermore, it has been determined that through their specific design, the target matching frequency can be set and an effective electromagnetic wave absorbing composite material can be designed.

[0249] Furthermore, it was determined that the present invention can maximize the electromagnetic wave absorption capability within the target matching frequency band of the electromagnetic wave absorbing composite material determined by mathematical formulas 1 to 3 only when the thickness of the polymer composite, the average linewidth of the conductive lines, and their average spacing all meet the conditions of the present invention. A relational formula for designing their organic relationship was also derived, and the optimal conditions for maximizing the incident electromagnetic wave absorption capability at the set matching frequency were confirmed.

Claims

1. An electromagnetic wave absorbing composite material, characterized in that, include: Polymer composite, containing refractive index adjusting materials; and Multiple conductive lines are formed on at least one surface of the polymer composite. The electromagnetic waves reflected within the matching frequency f range, derived from the following mathematical formulas 1 to 3, are below 0.2 dB: [Mathematical Expression 1] At this point, f is a frequency with a lower limit of 15 and an upper limit of 80. The effective spacing of the conductive lines is represented by the following mathematical formula 2. The effective refractive index of the electromagnetic wave absorbing composite material is represented by the following mathematical formula 3. c is the speed of light in free space. [Mathematical Expression 2] [01] D is the average spacing of the conductive lines. a is the average linewidth of the conductive line. [Mathematical Expression 3] n is the average refractive index of the polymer composite. D is the average spacing of the conductive lines. d is the thickness of the polymer composite. In particular, the average refractive index n of the polymer complex in mathematical formula 3 is 3-15.

2. The electromagnetic wave absorbing composite material according to claim 1, characterized in that, The average spacing (D) of the conductive lines is 0.5 to 10 mm.

3. The electromagnetic wave absorbing composite material according to claim 1, characterized in that, The thickness (d) of the polymer composite is 100 to 2000 μm.

4. The electromagnetic wave absorbing composite material according to claim 1, characterized in that, The average linewidth (a) of the conductive line is 50 to 500 μm.

5. The electromagnetic wave absorbing composite material according to claim 1, characterized in that, The electromagnetic wave absorption rate of the electromagnetic wave absorbing composite material is over 80%.

6. The electromagnetic wave absorbing composite material according to claim 1, characterized in that, The refractive index adjusting material includes any one or more of magnetic materials, metallic materials, carbon materials, ceramic materials, and MXene.

7. The electromagnetic wave absorbing composite material according to claim 1, characterized in that, The conductive wire comprises any one or more of the following conductive polymers: iron, cobalt, nickel, molybdenum, manganese, neodymium, gold, silver, copper, aluminum, platinum, carbon nanotubes, carbon nanofibers, carbon black, carbon fibers, and graphene or palladium metals or alloys thereof; MXene or polypyrrole; polyaniline; polyacetylene; poly(p-phenylenevinylene); polythiophene; polyethylene dioxythiophene; polyphenylene sulfide; or synthetic polymers thereof.

8. The electromagnetic wave absorbing composite material according to claim 1, characterized in that, Laminate multiple of the aforementioned polymer composites. Conductive lines are formed on the top surface of the laminated polymer composite.

9. The electromagnetic wave absorbing composite material according to claim 1, characterized in that, The conductive wires are in the form of a grid, a circle, a polygon, an open ring, or a combination of more than one of these shapes.

10. The electromagnetic wave absorbing composite material according to claim 1, characterized in that, The conductive lines are formed at multiple intervals or at a single interval.

11. The electromagnetic wave absorbing composite material according to claim 10, characterized in that, When the conductive lines are formed at multiple intervals, they have a reflectivity of less than 30% for electromagnetic waves in the frequency range of 18 to 40 GHz.

12. The electromagnetic wave absorbing composite material according to claim 1, characterized in that, The electromagnetic wave absorbing composite material has an electromagnetic wave reflectivity of less than 0.5 dB at a frequency of 26 GHz.

13. The electromagnetic wave absorbing composite material according to claim 1, characterized in that, The electromagnetic waves reflected within the matching frequency (f) range derived by the mathematical formulas 1 to 3 are below 0.1 dB.

14. An electromagnetic wave absorption circuit module, characterized in that, include: Circuit board, on which components are mounted; as well as The electromagnetic wave absorbing composite material according to claim 1 is disposed on a circuit board in such a way as to cover at least one surface of the device.

15. An electronic device, characterized in that, include: The electromagnetic wave absorption circuit module according to claim 14.

16. A method for preparing an electromagnetic wave absorbing composite material, characterized in that, include: Step (1): Prepare a polymer composite containing a refractive index regulating material. as well as Step (2), forming conductive lines on the polymer composite, By adjusting the average refractive index, thickness, linewidth, and spacing of the conductive lines of the polymer composite, the electromagnetic waves reflected within the matching frequency f range derived from the following mathematical formulas 1 to 3 are below 0.2 dB: [Mathematical Expression 1] At this point, the lower limit of f is 15 and the upper limit is 80. The effective spacing of the conductive lines is represented by the following mathematical formula 2. The effective refractive index of the electromagnetic wave absorbing composite material is represented by the following mathematical formula 3. c is the speed of light in free space. [Mathematical Expression 2] [02] D is the average spacing of the conductive lines. a is the average linewidth of the conductive line. [Mathematical Expression 3] n is the average refractive index of the polymer composite. D is the average spacing of the conductive lines. d is the thickness of the polymer composite. In particular, the average refractive index n of the polymer complex in mathematical formula 3 is 3-15.

17. The method for preparing the electromagnetic wave absorbing composite material according to claim 16, In step (1), multiple polymer composites are laminated. In step (2), conductive lines are formed in the polymer composite laminated in step (1).

18. The method for preparing the electromagnetic wave absorbing composite material according to claim 16, characterized in that, In step (2), a fiber mixture is used to sew conductive wires onto any surface of the polymer composite. The fiber mixture comprises any one or more of the following: iron, cobalt, nickel, molybdenum, manganese, neodymium, gold, silver, copper, aluminum, platinum carbon nanotubes, carbon nanofibers, carbon black, carbon fibers, and graphene or palladium metals or conductors as metal alloys; MXene or polypyrrole, polyaniline, polyacetylene, poly(p-phenylenevinylene), polythiophene, polyethylene dioxythiophene, polyphenylene sulfide or conductive polymers as composites thereof; and at least one of the following: polyurethane, polyamide, polyester, acrylic, polyolefin, cellulose, carbon, and glass.

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