Flexible electromagnetic wave absorber

Abstract

The present invention provides a flexible electromagnetic wave absorber that is lightweight and bendable by being composed of a single dielectric layer and a single absorber layer, and thus can be easily applied for electromagnetic wave absorption of an aircraft. The flexible electromagnetic wave absorber according to the present invention comprises: a dielectric layer; an adhesive layer evenly distributed on the upper surface of the dielectric layer and bonded to the dielectric layer; a film layer on the upper surface of the adhesive layer, which is bonded to the adhesive layer; and a conductor layer applied in a predetermined shape onto the film layer.

Description

Flexible electromagnetic wave absorber

[0001] The present invention relates to an electromagnetic wave absorber, and more specifically, to a lightweight and thin flexible electromagnetic wave absorber and technology related thereto, which is easy to apply to a body with many curved parts (aircraft, drones, etc.).

[0002] Radar Cross Section (RCS) is a numerical value that quantitatively represents the power density of backscatter on a radar receiver when electromagnetic waves are incident on an object. To improve the survivability of military aircraft, stealth technology that reduces this RCS is essential.

[0003] The following two conventional stealth technologies are primarily used to reduce RCS. Shaping technology involves designing the shape of an object to guide or minimize the reflection of radar waves in a specific direction, while radar-absorbing material (RAM) application technology involves applying materials to the surface of an object that absorb electromagnetic waves and dissipate them as thermal energy. However, with the advancement of radar technology, it has become difficult to guarantee the survivability of aircraft and other objects solely through the application of shaping technology. Furthermore, existing technologies for applying RAM face limitations in their application due to drawbacks such as low durability, increased weight, and material toxicity.

[0004] To overcome the limitations of existing technologies, research on Radar Absorbing Structures (RAS), in which the load-bearing structure itself can absorb electromagnetic waves, has been actively conducted. Meanwhile, conventional electromagnetic wave absorbers are generally designed to absorb electromagnetic waves by forming an absorbing material on a metal plate and stacking multiple dielectric layers at regular intervals.

[0005] FIG. 1 is a perspective view of an electromagnetic wave absorber disclosed in registered patent No. 10-2094743, comprising an absorber layer (100), a first dielectric layer (200), a second dielectric layer (300), a third dielectric layer (400), and a fourth dielectric layer (500).

[0006] FIG. 2 is a cross-sectional view of an electromagnetic wave absorber disclosed in registered patent No. 10-2232193, wherein the electromagnetic wave absorber comprises a plurality of dielectric layers including a first dielectric layer (121), a second dielectric layer (122), a third dielectric layer (123), and a fourth dielectric layer (124), and a first electromagnetic wave absorbing layer (131) and a second electromagnetic wave absorbing layer (132), and is stacked in the order of the first dielectric layer (121), a pattern layer (110), a second dielectric layer (122), a first electromagnetic wave absorbing layer (131), a third dielectric layer (123), a second electromagnetic wave absorbing layer (132), and a fourth dielectric layer (124).

[0007] However, these conventional electromagnetic wave absorbers are difficult to manufacture due to their complex structures and are particularly difficult to apply to surfaces of bodies (aircraft, drones, etc.) that have many curved parts. In addition, multilayer structures increase weight and thickness, limiting the potential for lightweighting and thinning. Therefore, there is a need for a new structure of electromagnetic wave absorber that can overcome the existing disadvantages by achieving lightweighting and thinning while maintaining flexibility so that it can be easily applied to curved surfaces.

[0008]

[0009] The present invention aims to provide a flexible electromagnetic wave absorber that is lightweight, thin, and flexible, while also achieving excellent electromagnetic wave absorption performance.

[0010] In addition, the present invention has another objective of providing a flexible electromagnetic wave absorber that can exhibit a double-layer effect without stacking dielectrics in multiple layers and can have a thin thickness, thereby minimizing the degradation of flight performance of a drone.

[0011] The problems solved by the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0012]

[0013] A flexible electromagnetic wave absorber according to one aspect of the present invention comprises: a dielectric layer; an adhesive layer evenly distributed on the upper surface of the dielectric layer and bonded to the dielectric layer; a film layer bonded to the adhesive layer on the upper surface of the adhesive layer; and a conductor layer applied or coated in a predetermined shape on the film layer.

[0014] Additionally, a flexible electromagnetic wave absorber according to another aspect of the present invention comprises: a first conductor layer made of a flexible material; a first adhesive layer made of a flexible material disposed on the first conductor layer; a dielectric layer made of a flexible material distributed on the first adhesive layer; a second adhesive layer made of a flexible material evenly distributed on the dielectric layer and adhered to the dielectric layer; a film layer adhered to the second adhesive layer on the upper surface of the second adhesive layer; and a second conductor layer made of a flexible material applied or coated on the film layer in a predetermined shape.

[0015] In addition, a flexible electromagnetic wave absorber according to another aspect of the present invention comprises a dielectric layer; and a conductive polymer coating layer applied to at least one surface of the dielectric layer to achieve a double-layer effect.

[0016]

[0017] According to the flexible electromagnetic wave absorber of the present invention, it consists of a single dielectric layer and a single absorber layer (conductor layer or conductive polymer layer), and is lightweight and flexible, making it easy to apply to absorb electromagnetic waves reaching a curved gas.

[0018] According to the flexible electromagnetic wave absorber of the present invention, it is composed of a single dielectric layer and a single absorber layer, making it lightweight and flexible. It is easy to apply for electromagnetic wave absorption for the purpose of directly wrapping or blocking modules that cause RCS (Radar Cross Section) reflection in areas where stealth treatment from the outside is difficult due to conductive objects inside the gas, and by placing a conductor layer at the bottom layer, it can effectively absorb electromagnetic waves in areas where the material of the object to which the flexible electromagnetic wave absorber is attached is not a conductor and has a large degree of bending in shape, and has the effect of handling not only primary reflection but also secondary reflection on its own.

[0019] The flexible electromagnetic wave absorber according to the present invention can secure a performance of -4 dB when coated on one side and an additional -3 dB when coated on both sides, is optimized in the X-band and can be extended to the Ku-band, can reduce the thickness from 1.5 mm to 1 mm or less, and can achieve cost reduction and ease of manufacturing.

[0020] The effects of the present invention are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0021]

[0022] FIG. 1 is a perspective view of an electromagnetic wave absorber disclosed in registered patent No. 10-2094743,

[0023] FIG. 2 is a cross-sectional view of an electromagnetic wave absorber disclosed in Registered Patent No. 10-2232193,

[0024] FIG. 3 is a cross-sectional view of an electromagnetic wave absorber according to a first embodiment of the present invention,

[0025] FIG. 4 is an exemplary diagram showing a conductive layer of an electromagnetic wave absorber according to a first embodiment of the present invention.

[0026] FIG. 5 is a graph showing the absorption performance of an electromagnetic wave absorber according to an embodiment of the present invention.

[0027] FIG. 6 is a graph showing the absorption performance of an electromagnetic wave absorber according to another embodiment of the present invention,

[0028] FIG. 7 is a cross-sectional view of an electromagnetic wave absorber according to a second embodiment of the present invention,

[0029] FIG. 8 is a cross-sectional view of an electromagnetic wave absorber according to a third embodiment of the present invention,

[0030] FIG. 9 is a graph showing the absorption performance of an electromagnetic wave absorber according to a third embodiment of the present invention,

[0031] FIG. 10 is a graph showing the absorption performance of an electromagnetic wave absorber according to another embodiment of the present invention, and

[0032] FIG. 11 is a graph of absorption performance with and without coating according to the third embodiment of the present invention.

[0033]

[0034] Further objects, features, and advantages of the present invention can be more clearly understood from the following detailed description and the accompanying drawings.

[0035] Before providing a detailed description of the present invention, it should be understood that the present invention is capable of various modifications and may have various embodiments, and that the examples described below and illustrated in the drawings are not intended to limit the present invention to specific embodiments, but rather include all modifications, equivalents, and substitutions that fall within the spirit and scope of the present invention.

[0036] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0037] The terms used in this specification are used merely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprising" or "having" are intended to indicate 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.

[0038] Furthermore, in the description referring to the attached drawings, identical components are assigned the same reference numeral regardless of drawing symbols, and redundant descriptions thereof are omitted. In describing the present invention, if it is determined that a detailed description of related prior art could unnecessarily obscure the essence of the present invention, such detailed description is omitted.

[0039]

[0040] FIG. 3 is a cross-sectional view of an electromagnetic wave absorber according to an embodiment of the present invention, and FIG. 4 is an exemplary diagram showing a conductive layer of an electromagnetic wave absorber according to an embodiment of the present invention.

[0041] An electromagnetic wave absorber according to one embodiment of the present invention may include a dielectric layer (310), an adhesive layer (320), a film layer (330), and a conductor layer (340).

[0042] The dielectric layer (310) is a part that comes into direct contact with a target object (e.g., gas) and reflects and absorbs electromagnetic waves. The dielectric layer (310) is any one of cork, EVA (ethylene-vinyl acetate copolymer), butyl rubber, neoprene, rubber sheet, EPDM (Ethylene Propylene Diene Monomer), NBR (acrylonitrile-butadiene rubber), PVC nitrile, SBR (Styrene Butadiene Rubber), EPDM (Ethylene Propylene Diene Monomer), polymer absorber, silicone rubber, polymer film, and polyurethane, and preferably has a dielectric constant (εr) of 1.2 to 4.0.

[0043] The adhesive layer (320) may be any one of a thermoplastic silicone adhesive, a polyurethane adhesive, an epoxy adhesive, a pressure-sensitive adhesive, and an acrylic adhesive, which have excellent adhesion and deformability. The adhesive layer (320) is dispensed so as to be evenly distributed on the upper surface of the dielectric layer (310).

[0044] The film layer (330) must have heat resistance, mechanical strength, and chemical resistance, and may be any one of a polyimide (PI) film, a polytetrafluoroethylene (PTFE) film, a polycarbonate (PC) film, a polyester (PET) film, and a polysulfone (PSU) film. The film layer (330) preferably has a dielectric constant (εr) of 3.4 to 3.5.

[0045] The conductive grid-shaped lines formed on the film layer (330) may be made of a magnetic conductor that is an iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo), manganese (Mn), or neodymium (Nd) metal or metal alloy.

[0046] The lines of the conductive grid shape may be composed of a metal-based conductor, a metal alloy-based conductor, a carbon-based conductor, an oxide-based conductor, a conductive polymer, or a mixture thereof. The metal-based conductor may be a non-magnetic metal such as gold (Au), silver (Ag), copper (Cu), aluminum (Al), platinum (Pt), or palladium (Pd). The metal alloy-based conductor may be a non-magnetic metal alloy containing metals such as gold (Au), silver (Ag), copper (Cu), aluminum (Al), platinum (Pt), or palladium (Pd). The carbon-based conductor may be a conductive material containing carbon, such as carbon nanotubes, carbon nanofibers, carbon black, carbon fibers, graphene, or a mixture thereof. The oxide-based conductor may be a conductive oxide such as CrO2.

[0047] The conductor layer (340) serves to absorb, scatter, and reflect electromagnetic waves, and may also serve to cause a skin effect of electromagnetic waves on the surface of the conductor layer. It may be formed on the film layer (330) by applying or coating at least one of carbon black, carbon nanofiber, carbon nanotube, and carbon fiber, or a mixture thereof, in a predetermined shape. The conductor layer (340) preferably has a dielectric constant (εr) of 10 to 50.

[0048] Through various experiments, the inventor discovered that if the difference between the dielectric constant of the dielectric layer (310) and the dielectric constant of the film layer (330) is within 0.5, electromagnetic wave scattering and reflection in the X-band occur well, resulting in excellent absorption performance. This appears to be because the surface impedance of the electromagnetic wave absorber becomes closer to the free-space impedance, thereby improving the absorption performance of electromagnetic waves.

[0049] The electromagnetic wave absorber comprising a dielectric layer (310), an adhesive layer (320), a film layer (330), and a conductor layer (340) according to one embodiment of the present invention is made of a flexible material, so it is very useful for application to a body with many bends.

[0050] FIG. 5 is a graph showing the absorption performance of an electromagnetic wave absorber according to one embodiment of the present invention, and FIG. 6 is a graph showing the absorption performance of an electromagnetic wave absorber according to another embodiment of the present invention.

[0051] One embodiment of the present invention illustrated in FIG. 5 is an absorption performance graph in which the dielectric layer (310) of the electromagnetic wave absorber is formed of cork, showing an absorption performance of -15dB or more in the 8 to 12 GHz band, and another embodiment of the present invention illustrated in FIG. 6 is an absorption performance graph in which the dielectric layer (310) of the electromagnetic wave absorber is formed of PE foam, showing an absorption performance of -15dB or more in the 8 to 12 GHz band, as well as an absorption performance of up to -25dB in the 10 GHz band.

[0052]

[0053] FIG. 7 is a cross-sectional view of an electromagnetic wave absorber according to a second embodiment of the present invention.

[0054] An electromagnetic wave absorber according to a second embodiment of the present invention may include a first conductor layer (710), a first adhesive layer (720), a dielectric layer (730), a second adhesive layer (740), a film layer (750), and a second conductor layer (760).

[0055] The first conductive layer (710) is a part that comes into direct contact with the target object (e.g., gas) and performs a secondary reflection function against electromagnetic waves. It can be implemented as carbon cloth, and carbon cloth can be produced by heat-treating polymer fibers such as polyacrylonitrile (PAN) or rayon to convert them into a material in which carbon atoms are the main components.

[0056] The first adhesive layer (720) is disposed on the first conductor layer (710) and bonds the first conductor layer (710) and the dielectric layer (730) together, and is made of a material with excellent durability and flexibility, and may be any one of a silicone-based adhesive, a polyurethane adhesive, a flexible adhesive film, a flexible epoxy, a silicone-based conductive adhesive, a flexible polymer-based adhesive, or a flexible polymer film.

[0057] The dielectric layer (730) is a portion that reflects and absorbs electromagnetic waves. The dielectric layer (730) is any one of cork, EVA (ethylene-vinyl acetate copolymer), butyl rubber, neoprene, rubber sheet, EPDM (Ethylene Propylene Diene Monomer), NBR (acrylonitrile-butadiene rubber), PVC nitrile, SBR (Styrene Butadiene Rubber), EPDM (Ethylene Propylene Diene Monomer), polymer absorber, silicone rubber, polymer film, and polyurethane, and preferably has a dielectric constant (εr) of 1.2 to 4.0.

[0058] The second adhesive layer (740) may be any one of a thermoplastic silicone adhesive, a polyurethane adhesive, an epoxy adhesive, a pressure-sensitive adhesive, and an acrylic adhesive, which have excellent adhesion and deformability. The second adhesive layer (740) is dispensed so as to be evenly distributed on the upper surface of the dielectric layer (730).

[0059] The film layer (750) must have heat resistance, mechanical strength, and chemical resistance, and may be any one of a polyimide (PI) film, a polytetrafluoroethylene (PTFE) film, a polycarbonate (PC) film, a polyester (PET) film, and a polysulfone (PSU) film. The film layer (750) preferably has a dielectric constant (εr) of 3.4 to 3.5.

[0060] The conductive grid-shaped lines formed on the film layer (750) may be made of a magnetic conductor that is an iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo), manganese (Mn), or neodymium (Nd) metal or metal alloy.

[0061] The lines of the conductive grid shape may be composed of a metal-based conductor, a metal alloy-based conductor, a carbon-based conductor, an oxide-based conductor, a conductive polymer, or a mixture thereof. The metal-based conductor may be a non-magnetic metal such as gold (Au), silver (Ag), copper (Cu), aluminum (Al), platinum (Pt), or palladium (Pd). The metal alloy-based conductor may be a non-magnetic metal alloy containing metals such as gold (Au), silver (Ag), copper (Cu), aluminum (Al), platinum (Pt), or palladium (Pd). The carbon-based conductor may be a conductive material containing carbon, such as carbon nanotubes, carbon nanofibers, carbon black, carbon fibers, graphene, or a mixture thereof. The oxide-based conductor may be a conductive oxide such as CrO2.

[0062] The second conductor layer (760) serves to absorb, scatter, and reflect electromagnetic waves, and may also serve to cause a skin effect of electromagnetic waves on the surface of the second conductor layer. It may be formed on the film layer (750) by applying or coating at least one of carbon black, carbon nanofiber, carbon nanotube, and carbon fiber, or a mixture thereof, in a predetermined shape. The second conductor layer (760) preferably has a dielectric constant (εr) of 10 to 50.

[0063] In addition, if the difference between the dielectric constant of the dielectric layer (730) and the dielectric constant of the film layer (750) is within 0.5, electromagnetic wave scattering and reflection in the X-band occur well, and the absorption performance is excellent.

[0064] Meanwhile, the conductive layer of the electromagnetic wave absorber according to the second embodiment of the present invention may be the first embodiment shown in FIG. 4.

[0065] According to the flexible electromagnetic wave absorber of the second embodiment of the present invention, it is composed of a single dielectric layer and a single absorber layer (first conductor layer), making it lightweight and flexible. It is easy to apply for electromagnetic wave absorption for the purpose of directly wrapping or blocking modules that cause RCS (Radar Cross Section) reflection in areas where stealth treatment from the outside is difficult due to conductive objects inside the gas, and by placing a second conductor layer at the bottom layer, it can effectively absorb electromagnetic waves in areas where the material of the object to which the flexible electromagnetic wave absorber is attached is not a conductor and has a large degree of bending in shape, and it can handle not only primary reflection but also secondary reflection on its own.

[0066]

[0067] FIG. 8 is a cross-sectional view of an electromagnetic wave absorber according to a third embodiment of the present invention. The electromagnetic wave absorber according to the third embodiment of the present invention may include a coating layer (810), a dielectric layer (820), an adhesive layer (830), a film layer (840), and a conductor layer (850).

[0068] The coating layer (810) is a conductive polymer layer applied to one or both sides of the dielectric layer (820). In one embodiment of the present invention, PEDOT:PSS is used. The thickness of the coating layer is formed in the range of 30 nm to 2 µm, and has characteristics such as a dielectric constant (εr) of 6 to 20 and a loss rate (tanδ) of 0.1 to 0.3.

[0069] The dielectric layer (820) is a part that comes into direct contact with a target object (e.g., gas) and reflects and absorbs electromagnetic waves. The dielectric layer (820) is any one of cork, EVA (ethylene-vinyl acetate copolymer), butyl rubber, neoprene, rubber sheet, EPDM (Ethylene Propylene Diene Monomer), NBR (acrylonitrile-butadiene rubber), PVC nitrile, SBR (Styrene Butadiene Rubber), EPDM (Ethylene Propylene Diene Monomer), polymer absorber, silicone rubber, polymer film, and polyurethane, and preferably has a dielectric constant (εr) of 1.2 to 4.0.

[0070] The adhesive layer (830) may be any one of a thermoplastic silicone adhesive, a polyurethane adhesive, an epoxy adhesive, a pressure-sensitive adhesive, and an acrylic adhesive, which have excellent adhesion and deformability. The adhesive layer (830) is dispensed so as to be evenly distributed on the upper surface of the dielectric layer (820).

[0071] The film layer (840) must have heat resistance, mechanical strength, and chemical resistance, and may be any one of a polyimide (PI) film, a polytetrafluoroethylene (PTFE) film, a polycarbonate (PC) film, a polyester (PET) film, and a polysulfone (PSU) film. The film layer (830) preferably has a dielectric constant (εr) of 3.4 to 3.5.

[0072] The conductive grid-shaped lines formed on the film layer (840) may be made of a magnetic conductor that is an iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo), manganese (Mn), or neodymium (Nd) metal or metal alloy.

[0073] The lines of the conductive grid shape may be composed of a metal-based conductor, a metal alloy-based conductor, a carbon-based conductor, an oxide-based conductor, a conductive polymer, or a mixture thereof. The metal-based conductor may be a non-magnetic metal such as gold (Au), silver (Ag), copper (Cu), aluminum (Al), platinum (Pt), or palladium (Pd). The metal alloy-based conductor may be a non-magnetic metal alloy containing metals such as gold (Au), silver (Ag), copper (Cu), aluminum (Al), platinum (Pt), or palladium (Pd). The carbon-based conductor may be a conductive material containing carbon, such as carbon nanotubes, carbon nanofibers, carbon black, carbon fibers, graphene, or a mixture thereof. The oxide-based conductor may be a conductive oxide such as CrO2.

[0074] The conductor layer (850) serves to absorb, scatter, and reflect electromagnetic waves, and may also serve to cause a skin effect of electromagnetic waves on the surface of the conductor layer. It may be formed on the film layer (830) by applying or coating at least one of carbon black, carbon nanofiber, carbon nanotube, and carbon fiber, or a mixture thereof, in a predetermined shape. The conductor layer (850) preferably has a dielectric constant (εr) of 10 to 50.

[0075] In addition, if the difference between the dielectric constant of the dielectric layer (820) and the dielectric constant of the film layer (840) is within 0.5, electromagnetic wave scattering and reflection in the X-band occur well, and the absorption performance is excellent.

[0076]

[0077] FIG. 9 is a graph showing the absorption performance of an electromagnetic wave absorber according to a third embodiment of the present invention, and FIG. 10 is a graph showing the absorption performance of an electromagnetic wave absorber according to another embodiment of the present invention.

[0078] The third embodiment of the present invention illustrated in FIG. 9 is an absorption performance graph in which the dielectric layer (820) of the electromagnetic wave absorber is formed of cork, showing an absorption performance of -15dB or more in the 8 to 12 GHz band, and another embodiment of the present invention illustrated in FIG. 10 is an absorption performance graph in which the dielectric layer (320) of the electromagnetic wave absorber is formed of PE foam, showing an absorption performance of -15dB or more in the 8 to 12 GHz band, as well as an absorption performance of up to -25dB in the 10 GHz band.

[0079]

[0080] According to the third embodiment of the present invention, the electromagnetic wave absorption performance when single-sided and double-sided coatings are applied is as follows. It was confirmed that an additional absorption performance of approximately -4 dB is secured when coated on one side, and an additional performance improvement of -3 dB is achieved when coated on both sides. Thus, the electromagnetic wave absorber of the present invention can secure electromagnetic wave absorption performance equivalent to or greater than that of a conventional multilayer structure while realizing an ultra-thin structure of 1 mm or less.

[0081] In addition, it shows optimized performance in the X-band (8~12 GHz) and can be applied up to the Ku-band.

[0082]

[0083] FIG. 11 is a graph of absorption performance with and without coating according to the third embodiment of the present invention.

[0084] Compared to before the coating, the results after application show lower reflection loss (dB) across the entire frequency band, indicating improved absorption performance. In particular, an improvement of approximately 3 to 5 dB or more was confirmed in the 9–11 GHz range. While the curve before coating slightly exceeds or approaches the -12 dB target line in some sections, the curve after coating stably stays below the -12 dB target line across the entire X-band (7.8–12.2 GHz), demonstrating that the target absorption performance can be achieved across the entire band through the coating.

[0085] It can be seen that the coating significantly improves peak absorption performance, as the lowest reflection loss (optimal frequency) is about -20 dB (around 10–11 GHz) before coating, whereas after coating it is about -25 dB or higher (maximum performance around 11 GHz).

[0086] In other words, a double-layer effect is achieved without stacking the dielectric in two layers, and the total thickness can be reduced to 1 mm or less.

[0087]

[0088] The electromagnetic wave absorber according to the third embodiment of the present invention provides a structure that is significantly lighter and thinner compared to conventional ferrite-based paints (thickness of 2 mm or more, weight increase of 5 to 10 times). Accordingly, it is possible to minimize the increase in drag and the degradation of flight performance of the drone airframe, and the manufacturing process is simple with significant cost-saving effects. In addition, it is optimized for realizing stealth performance of drones, making it highly useful in military and civilian fields.

[0089] The electromagnetic wave absorber according to the third embodiment of the present invention can be applied to the surface of a curved drone body, and is lighter and thinner than existing ferrite-based materials, thereby preventing a decrease in flight performance, and can secure performance of -4 dB when coated on one side and an additional -3 dB when coated on both sides. It is optimized for the X-band and can be extended to the Ku-band. The thickness can be reduced from 1.5 mm to 1 mm or less, making it easy to apply to drones.

[0090]

[0091] The embodiments described in this specification and the accompanying drawings are merely illustrative of a part of the technical concept included in the present invention. Accordingly, since the embodiments disclosed in this specification are intended to explain, not limit, the technical concept of the present invention, it is obvious that the scope of the technical concept of the present invention is not limited by these embodiments. All variations and specific embodiments that can be easily deduced by a person skilled in the art within the scope of the technical concept included in the specification and drawings of the present invention should be interpreted as being included within the scope of the rights of the present invention.

Claims

Genome layer; An adhesive layer evenly distributed on the upper surface of the dielectric layer and bonded to the dielectric layer; A film layer bonded to the adhesive layer on the upper surface of the adhesive layer; and A conductive layer applied or coated in a predetermined shape on the above film layer. A flexible electromagnetic wave absorber comprising In claim 1, A flexible electromagnetic wave absorber characterized in that the dielectric layer is any one of cork, EVA (ethylene-vinyl acetate copolymer), butyl rubber, neoprene, rubber sheet, EPDM (Ethylene Propylene Diene Monomer), NBR (acrylonitrile-butadiene rubber), PVC nitrile, SBR (Styrene Butadiene Rubber), EPDM (Ethylene Propylene Diene Monomer), polymer absorber, silicone rubber, polymer film, and polyurethane. In claim 2, A flexible electromagnetic wave absorber characterized in that the second adhesive layer is one of a polyurethane adhesive, an epoxy adhesive, a pressure-sensitive adhesive, and an acrylic adhesive. In claim 3, A flexible electromagnetic wave absorber characterized in that the film layer is any one of the polyimide (PI) film, polytetrafluoroethylene (PTFE) film, polycarbonate (PC) film, polyester (PET) film, and polysulfone (PSU) film. In claim 4, A flexible electromagnetic wave absorber characterized in that the second conductor layer is at least one of carbon black, carbon nanofiber, carbon nanotube, and carbon fiber, or a mixture thereof. In claim 5, A flexible electromagnetic wave absorber characterized in that the difference between the dielectric constant of the dielectric layer and the dielectric constant of the film layer is within 0.

5. In claim 5, A flexible electromagnetic wave absorber characterized in that the first conductor layer performs a secondary reflection function against electromagnetic waves and is a carbon cloth produced by heat-treating polymer fibers of polyacrylonitrile or rayon to convert them into a material mainly composed of carbon atoms. A first conductor layer made of a flexible material; A first adhesive layer made of a flexible material disposed on the first conductor layer; A dielectric layer of a flexible material distributed on the first adhesive layer; A second adhesive layer made of a flexible material that is evenly distributed on the dielectric layer and adheres to the dielectric layer; A film layer bonded to the second adhesive layer on the upper surface of the second adhesive layer; and A second conductive layer made of a flexible material that is applied or coated in a predetermined shape on the above film layer. A flexible electromagnetic wave absorber comprising In claim 8, A flexible electromagnetic wave absorber characterized in that the dielectric layer is any one of cork, EVA (ethylene-vinyl acetate copolymer), butyl rubber, neoprene, rubber sheet, EPDM (Ethylene Propylene Diene Monomer), NBR (acrylonitrile-butadiene rubber), PVC nitrile, SBR (Styrene Butadiene Rubber), EPDM (Ethylene Propylene Diene Monomer), polymer absorber, silicone rubber, polymer film, and polyurethane. In claim 9, A flexible electromagnetic wave absorber characterized in that the second adhesive layer is one of a polyurethane adhesive, an epoxy adhesive, a pressure-sensitive adhesive, and an acrylic adhesive. In claim 10, A flexible electromagnetic wave absorber characterized in that the film layer is any one of the polyimide (PI) film, polytetrafluoroethylene (PTFE) film, polycarbonate (PC) film, polyester (PET) film, and polysulfone (PSU) film. In claim 11, A flexible electromagnetic wave absorber characterized in that the second conductor layer is at least one of carbon black, carbon nanofiber, carbon nanotube, and carbon fiber, or a mixture thereof. In claim 12, A flexible electromagnetic wave absorber characterized in that the difference between the dielectric constant of the dielectric layer and the dielectric constant of the film layer is within 0.

5. In claim 13, A flexible electromagnetic wave absorber characterized in that the first conductor layer performs a secondary reflection function against electromagnetic waves and is a carbon cloth produced by heat-treating polymer fibers of polyacrylonitrile or rayon to convert them into a material mainly composed of carbon atoms. Genome layer; and A conductive polymer coating layer applied to at least one surface of the dielectric layer to realize a double-layer effect A flexible electromagnetic wave absorber comprising A flexible electromagnetic wave absorber according to claim 15, characterized in that the coating layer is formed with a thickness of 30 nm to 2 µm. In claim 16, A flexible electromagnetic wave absorber characterized by the coating layer being selectively applied to one side or both sides, and providing improved absorption performance when applied to both sides compared to when applied to one side. In claim 17, An adhesive layer evenly distributed on the upper surface of the dielectric layer and bonded to the dielectric layer; A film layer bonded to the adhesive layer on the upper surface of the adhesive layer; and A conductive layer applied or coated in a predetermined shape on the above film layer. A flexible electromagnetic wave absorber further comprising In claim 18, A flexible electromagnetic wave absorber for a drone, characterized in that the dielectric layer is any one of cork, EVA (ethylene-vinyl acetate copolymer), butyl rubber, neoprene, rubber sheet, EPDM (Ethylene Propylene Diene Monomer), NBR (acrylonitrile-butadiene rubber), PVC nitrile, SBR (Styrene Butadiene Rubber), EPDM (Ethylene Propylene Diene Monomer), polymer absorber, silicone rubber, polymer film, and polyurethane. A flexible electromagnetic wave absorber according to any one of claims 15 to 19, wherein the thickness of the electromagnetic wave absorber is 1 mm or less.

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