Electromagnetic wave absorbing member

Abstract

The present invention provides an electromagnetic wave absorbing member (10) having a resistive layer (20), a barrier layer (30), and a reflective layer (40), the resistive layer (20), the barrier layer (30), and the reflective layer (40) being laminated in the order of the resistive layer (20), the barrier layer (30), and the reflective layer (40). The resistive layer (20) has a plurality of regions having the same area in a plan view of the electromagnetic wave absorbing member (10) and different electromagnetic wave absorption characteristics, each region has two or more types of conductor patterns (22) formed parallel to each other on the isolation layer (30), and each of the two or more types of conductor patterns (22) is configured from a plurality of units arranged in one direction at a fixed interval. At least one of the shape of the units constituting the conductor pattern (22) in the region, the size of the units, and the arrangement interval of the units is different from the other adjacent regions.

Description

Technical Field

[0001] This invention relates to an electromagnetic wave absorbing component.

[0002] This application claims priority based on Japanese Patent Application No. 2023-053539, filed in Japan on March 29, 2023, the contents of which are incorporated herein by reference. Background Technology

[0003] A sheet-like electromagnetic wave absorbing member is known that selectively absorbs electromagnetic waves of a specified frequency. For example, the electromagnetic wave absorbing member has a first frequency-selective shielding layer and a second frequency-selective shielding layer. In this electromagnetic wave absorbing member, through the fine line pattern formed on the FSS (Frequency Selective Surface) elements of the first and second frequency-selective shielding layers, each layer absorbs electromagnetic waves of a specified frequency, and as a whole, selectively shields two electromagnetic waves of different frequencies.

[0004] Patent document 1 describes a frequency selection surface that can be configured with fewer circuit elements than the number of conductors.

[0005] Patent document 2 describes an electromagnetic wave absorber having a structure in which a full-surface conductor layer made of conductors, a first dielectric layer, a high-resistivity conductor layer having a specified range of surface resistivity, a second dielectric layer, and a pattern layer having multiple patterns made of conductors are stacked in sequence, wherein at least one of the sizes and shapes of each pattern in the pattern layer is different from the adjacent other patterns.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 6861907

[0009] Patent Document 2: Japanese Patent No. 4461974 Summary of the Invention

[0010] (a) Technical problems to be solved

[0011] However, in the inventions described in Patent Documents 1 and 2, when the thickness deviation of the isolation layer is large, an electromagnetic wave absorbing component with stable performance cannot be obtained.

[0012] The present invention was made in view of the above circumstances, and its object is to provide an electromagnetic wave absorbing component with stable performance when the thickness deviation of the insulating layer is large.

[0013] (II) Technical Solution

[0014] The present invention provides the following electromagnetic wave absorbing component.

[0015] [1] An electromagnetic wave absorbing component, comprising a resistive layer, an insulating layer, and a reflective layer, wherein...

[0016] The resistive layer, the insulating layer, and the reflective layer are stacked in the order of resistive layer, insulating layer, and reflective layer.

[0017] The resistive layer has multiple regions with equal area and different electromagnetic wave absorption characteristics in a top view of the electromagnetic wave absorbing component.

[0018] The regions each have two or more conductor patterns formed parallel to each other on the isolation layer.

[0019] The two or more conductor patterns are each composed of multiple units arranged in one direction at certain intervals.

[0020] At least one of the shape, size, and spacing of the units constituting the conductor pattern in the region differs from that in adjacent regions.

[0021] [2] According to the electromagnetic wave absorbing component described in [1], the region is repeatedly arranged at certain intervals.

[0022] (III) Beneficial Effects

[0023] According to the present invention, an electromagnetic wave absorbing component that can achieve stable performance when the thickness deviation of the insulating layer is large can be provided. Attached Figure Description

[0024] Figure 1 The image shows a cross-sectional view of an electromagnetic wave absorbing member along its thickness direction, illustrating one embodiment of the present invention.

[0025] Figure 2 This is a top view illustrating a region of the resistive layer of an electromagnetic wave absorbing member according to one embodiment of the present invention.

[0026] Figure 3 A top view showing an example of a resistive layer constituting an electromagnetic wave absorbing member of one embodiment of the present invention.

[0027] Figure 4 A top view showing an example of a resistive layer constituting an electromagnetic wave absorbing member of one embodiment of the present invention.

[0028] Figure 5 A top view showing an example of a resistive layer constituting an electromagnetic wave absorbing member of one embodiment of the present invention. Detailed Implementation

[0029] An embodiment of the electromagnetic wave absorbing component of the present invention will be described.

[0030] In addition, specific details have been provided in this embodiment to better understand the spirit of the invention, and the invention is not limited thereto unless otherwise specified.

[0031] In this specification, "conductor pattern" refers to a collection of geometric units, specifically an object that selectively absorbs electromagnetic waves of a certain frequency. In other words, it can be said that a "conductor pattern" possesses the same function as a so-called antenna.

[0032] In this specification, "electromagnetic waves in the millimeter wave region" refers to electromagnetic waves with wavelengths of 1mm to 10mm. That is, it can be said that "electromagnetic waves in the millimeter wave region" refers to electromagnetic waves with frequencies of 30GHz to 300GHz.

[0033] In this specification, the "~" sign indicating a numerical range means that the values ​​before and after it are included as the lower and upper limits.

[0034] Electromagnetic wave absorbing components

[0035] Figure 1 The image shows a cross-sectional view of an electromagnetic wave absorbing member along its thickness direction, illustrating one embodiment of the present invention. Figure 2 A top view of one region of an electromagnetic wave absorbing member according to one embodiment of the present invention is shown for illustrative purposes.

[0036] like Figure 1 As shown, the electromagnetic wave absorbing member 10 of this embodiment includes a resistive layer 20, an insulating layer 30, and a reflective layer 40. Furthermore, the resistive layer 20, the insulating layer 30, and the reflective layer 40 are stacked in the order of resistive layer 20, insulating layer 30, and reflective layer 40.

[0037] The reflective layer 40 is disposed on the other side (back side) 20b of the resistive layer 20. The insulating layer 30 is disposed between the resistive layer 20 and the reflective layer 40. That is, the resistive layer 20 and the reflective layer 40 are stacked via the insulating layer 30.

[0038] The resistive layer 20 can be a single layer, or it can be like... Figure 1 The diagram includes a substrate 21 and a conductor pattern 22 formed on the substrate 21.

[0039] When the resistive layer 20 is a single layer, the resistive layer 20 is made of the same material as the conductor pattern 22 described later.

[0040] "Resistive layer"

[0041] The resistive layer 20 is composed of a frequency selective surface (FSS). A frequency selective surface is a surface that can shield or transmit electromagnetic waves of a specific frequency by forming a continuous structure with a shape below the wavelength using conductive components or the like.

[0042] Figure 2 This is a top view showing one region of the resistive layer in this embodiment as an example. (See attached image.) Figure 2 As shown, the resistive layer 20 has a flat substrate 21 and a conductor pattern 22 formed on one surface 21a of the substrate 21. The conductor pattern 22 is composed of a first conductor pattern 51, a second conductor pattern 52 and a third conductor pattern 53.

[0043] (First conductor pattern)

[0044] like Figure 2 As shown, the first conductor pattern 51 is composed of multiple first units u1. Each first unit u1 is a geometric shape.

[0045] That is, the first conductor pattern 51 can also be said to be a collection of the first unit u1 of geometric figures.

[0046] Each of the first units u1 functions as an antenna. The first conductor pattern 51 can also be, for example, a thin line pattern of an FSS element.

[0047] In the first conductor pattern 51, a plurality of first arrays R1 are formed, the first arrays R1 being formed by a plurality of first units u1 along... Figure 2 The first conductor pattern 51 is arranged in the direction indicated by the double arrow P. That is, it can be said that the first conductor pattern 51 has a plurality of first arrays R1. The first conductor pattern 51 can be constructed in such a way that a plurality of first arrays R1 are formed on the substrate 21 at predetermined intervals along the direction indicated by the double arrow P.

[0048] There are no particular restrictions on the spacing between the multiple first arrays R1. The spacing between the first arrays R1 can be regular or irregular.

[0049] like Figure 2 As shown, the first unit u1 has a cross-shaped structure that is symmetrical from top to bottom and left to right. Specifically, the first unit u1 has one cross-shaped portion S1 and four end portions T1. The cross-shaped portion S1 is composed of... Figure 2 The straight section parallel to the x-axis and the straight section parallel to the y-axis are formed. Each end T1 of the straight section is connected to the two ends of the straight section parallel to the x-axis and the two ends of the straight section parallel to the y-axis in a manner orthogonal to each straight section.

[0050] By adjusting the x-axis length of the first unit u1 and the x-axis length of each of the four end units T1, the electromagnetic wave transmission characteristics of the first unit u1, which functions as an antenna, can be adjusted. The electromagnetic wave transmission characteristics can also be adjusted in the y-axis direction in the same way.

[0051] However, the shape of the first unit u1 is not limited to a cross shape. The shape of the first unit u1 is not particularly limited as long as the frequency at which the transmission amount of the electromagnetic wave transmitted by the first conductor pattern 51 exhibits a maximum value is A [GHz].

[0052] For example, the shapes of the first unit u1 graphic can be listed as circles, rings, straight lines, rectangles, polygons, H-shapes, Y-shapes, V-shapes, etc.

[0053] In the resistive layer 20, the shapes of the plurality of first units u1 are identical. However, the shapes of the plurality of first units u1 may not be identical. In other embodiments of the invention, the shapes of the plurality of first units u1 may be identical or different, provided that the transmission characteristics can be adjusted for the target frequency.

[0054] The first conductor pattern 51 selectively transmits electromagnetic waves with a frequency of A [GHz]. The frequency value A [GHz] is the frequency at which the transmission amount of the electromagnetic waves transmitted by the first conductor pattern 51 exhibits a maximum value in the range of 20GHz to 110GHz.

[0055] The first conductor pattern 51 transmits electromagnetic waves with a frequency of A [GHz] determined by the above method X.

[0056] For the resistive layer 20 in this embodiment, the frequency value A is preferably 20GHz to 110GHz, more preferably 60GHz to 100GHz, even more preferably 65GHz to 95GHz, and particularly preferably 70GHz to 90GHz. If the frequency value A is within the range of said values, the resistive layer 20 can transmit electromagnetic waves in the millimeter-wave region, making it easy to apply to automotive parts, roadside components, building exterior wall materials, windows, communication equipment, radio telescopes, etc.

[0057] There are no particular limitations on the material of the first unit u1, as long as the transmission characteristics can be adjusted for the target frequency.

[0058] The material of the first unit u1 can be, for example, a thin wire of metal, a conductive film, or a fixing material for conductive paste.

[0059] As a metallic material, examples include copper, aluminum, tungsten, iron, molybdenum, nickel, titanium, silver, gold, or alloys containing two or more of these metals (e.g., stainless steel, carbon steel, brass, phosphor bronze, zirconium copper alloy, beryllium copper, iron-nickel, nickel-chromium alloy, nickel-titanium, iron-chromium-aluminum alloy (Kanthal), Hastelloy, rhenium-tungsten, etc.).

[0060] Materials that can be used for conductive thin films include metal particles, carbon nanoparticles, and carbon fibers.

[0061] The spacing between the ends of the pattern that serves as the first unit u1 is not particularly limited, as long as the transmission characteristics can be adjusted for the target frequency.

[0062] For example, the spacing between the ends of the pattern that forms the first unit u1 can be all the same or different. However, for the sake of ease of designing a resistive layer that is not easily affected by the surrounding environment and for increasing the accuracy of the frequency band of the absorbed electromagnetic waves during manufacturing, it is preferable that the spacing between the ends of the pattern that forms the first unit u1 is the same.

[0063] (Second conductor pattern)

[0064] like Figure 2 As shown, the second conductor pattern 52 is composed of multiple second units u2.

[0065] The second conductor pattern 52 is formed in the same manner as the first conductor pattern 51.

[0066] The second conductor pattern 52 selectively transmits electromagnetic waves with a frequency of B [GHz] that satisfies the following equation (2). The frequency value B [GHz] is the frequency at which the transmission amount of the electromagnetic wave transmitted by the second conductor pattern 52 exhibits a maximum value. The frequency value B [GHz] satisfies the following equation (1).

[0067]

[0068] As shown in equation (2) above, the second conductor pattern 52 transmits electromagnetic waves with a frequency of 1.037×A [GHz] to 1.30×A [GHz]. Preferably, the second conductor pattern 52 transmits electromagnetic waves with a frequency of 1.17×A [GHz] to 1.30×A [GHz].

[0069] Since the second conductor pattern 52 transmits electromagnetic waves with frequencies above 1.037 × Å [GHz], the peak of the transmission of electromagnetic waves based on the second conductor pattern 52 and the peak of the transmission of electromagnetic waves based on the first conductor pattern 51 fully overlap in the frequency band above Å [GHz]. As a result, compared to a film having only the first conductor pattern 51, the overall electromagnetic wave absorption film can transmit electromagnetic waves in a frequency band above Å [GHz].

[0070] Since the second conductor pattern 52 transmits electromagnetic waves with frequencies below 1.30 × Å [GHz], the frequency difference between the peak of electromagnetic wave transmission based on the second conductor pattern 52 and the peak of electromagnetic wave transmission based on the first conductor pattern 51 becomes smaller in frequency bands above Å [GHz]. As a result, a single peak is formed where the transmission of electromagnetic waves transmitted by the electromagnetic wave absorbing film as a whole reaches its maximum value.

[0071] In summary, since the second conductor pattern 52 transmits electromagnetic waves with frequencies of 1.037×A [GHz] to 1.30×A [GHz], the transmission amount of electromagnetic waves transmitted by the electromagnetic wave absorbing film as a whole is expanded to the high-frequency band.

[0072] The material of the second unit u2 constituting the second conductor pattern 52 is not particularly limited as long as it is in a form that can absorb electromagnetic waves of B [GHz], and is not particularly limited as long as its absorption characteristics can be adjusted for the target frequency.

[0073] The material of the second unit u2 is described in the same way as the material of the first unit u1.

[0074] (Third conductor pattern)

[0075] like Figure 2 As shown, the third conductor pattern 53 is composed of multiple third units u3.

[0076] The third conductor pattern 53 is formed in the same manner as the first conductor pattern 51.

[0077] The third conductor pattern 53 selectively transmits electromagnetic waves with a frequency of C [GHz] that satisfies the following equation (3). The frequency value C [GHz] is the frequency at which the transmission amount of the electromagnetic wave transmitted by the third conductor pattern 53 exhibits a maximum value. The frequency value C [GHz] satisfies the following equation (2).

[0078]

[0079] As shown in equation (3) above, the third conductor pattern 53 transmits electromagnetic waves with a frequency of 0.60×A [GHz] to 0.963×A [GHz]. Preferably, the third conductor pattern 53 transmits electromagnetic waves with a frequency of 0.60×A [GHz] to 0.83×A [GHz].

[0080] Since the third conductor pattern 53 transmits electromagnetic waves with frequencies above 0.60 × Å [GHz], the frequency difference between the peak of electromagnetic wave transmission based on the third conductor pattern 53 and the peak of electromagnetic wave transmission based on the first conductor pattern 51 becomes smaller in frequency bands below Å [GHz]. As a result, a single peak is formed where the transmission of electromagnetic waves transmitted by the entire resistive layer 20 reaches its maximum value.

[0081] Since the third conductor pattern 53 transmits electromagnetic waves with frequencies below 0.963 × A [GHz], the peak of the transmission of electromagnetic waves based on the third conductor pattern 53 and the peak of the transmission of electromagnetic waves based on the first conductor pattern 51 fully overlap in the frequency band below A [GHz]. As a result, compared to a film having only the first conductor pattern 51, the overall electromagnetic wave absorption film can transmit electromagnetic waves in a frequency band below A [GHz].

[0082] In summary, since the third conductor pattern 53 transmits electromagnetic waves with frequencies ranging from 0.60×A[GHz] to 0.963×A[GHz], the overall transmission amount of electromagnetic waves transmitted by the resistive layer 20 is expanded to the low-frequency band.

[0083] The material of the third unit u3 constituting the third conductor pattern 53 is not particularly limited as long as it is in a form that can transmit electromagnetic waves of C[GHz], and is not particularly limited as long as its transmission characteristics can be adjusted for the target frequency.

[0084] The material of the third unit u3 is described in the same way as the material of the first unit u1.

[0085] exist Figure 2 In the resistive layer 20 shown, the first array R1, the second array R2, and the third array R3 are arranged adjacent to each other in the direction indicated by the double arrow P. Thus, with the first array R1, the second array R2, and the third array R3 positioned adjacent to each other on the substrate 21, the frequency bands of the electromagnetic waves selectively transmitted by the second conductor pattern 52 and the third conductor pattern 53 overlap, with reference to the frequency value A [GHz] of the peak position of the electromagnetic wave selectively transmitted by the first conductor pattern 51. As a result, the transmission region of the electromagnetic waves transmitted by the resistive layer 20 as a whole easily expands to both the high-frequency side and the low-frequency side, with reference to the frequency value A [GHz] of the peak position.

[0086] Figure 2 The intervals d1 between the first unit u1 and the second unit u2, d2 between the second unit u2 and the third unit u3, and d3 between the third unit u3 and the first unit u1 shown in the figure can be the same or different from each other.

[0087] The interval d1 can be, for example, 0.2mm~4mm, 0.3mm~2mm, or 0.5mm~1mm.

[0088] The interval d2 can be, for example, 0.2mm~4mm, 0.3mm~2mm, or 0.5mm~1mm.

[0089] The interval d3 can be, for example, 0.2mm~4mm, 0.3mm~2mm, or 0.5mm~1mm.

[0090] If the intervals d1, d2, and d3 are within the stated numerical range, the transmission area of ​​the electromagnetic waves transmitted by the entire resistive layer 20 is more easily expanded based on the value A [GHz] of the peak position frequency.

[0091] In the resistive layer 20, the first unit u1, the second unit u2, and the third unit u3 have the same shape. However, the shapes of the first unit u1, the second unit u2, and the third unit u3 may not be the same. That is, in other embodiments of the present invention, the shapes of the first unit u1, the second unit u2, and the third unit u3 may be the same or different.

[0092] Regarding the electromagnetic wave absorbing component 10 in this embodiment, as follows: Figure 3 As shown, the resistive layer 20 has two regions, 20A and 20B, with equal areas and different electromagnetic wave absorption characteristics in a top view of the electromagnetic wave absorbing member 10. Regions 20A and 20B have the same shape. Regarding the electromagnetic wave absorbing member 10 of this embodiment, in a top view of the electromagnetic wave absorbing member 10, the two regions 20A and 20B have a shape similar to that of the electromagnetic wave absorbing member 10 (here, a square). Regarding the electromagnetic wave absorbing member 10 of this embodiment, in a top view of the electromagnetic wave absorbing member 10, the two regions 20A and two regions 20B are arranged diagonally across the resistive layer 20, with the diagonals of the two regions 20A orthogonal to the diagonals of the two regions 20B. Thus, regions 20A and 20B are adjacent and arranged in a lattice pattern.

[0093] Region 20A and Region 20B respectively have, for example, the first conductor pattern 51, the second conductor pattern 52 and the third conductor pattern 53 described above.

[0094] At least one of the shapes, sizes, and arrangement intervals of the units (first unit u1, second unit u2, third unit u3) of the constituent conductor patterns 22 (first conductor pattern 51, second conductor pattern 52, third conductor pattern 53) in region 20A differs from that in the adjacent region 20B. Therefore, the electromagnetic wave transmission characteristics of regions 20A and 20B are different.

[0095] For example, as described above, when region 20A has multiple conductor pattern groups, it is preferable that region 20B has the same type of conductor pattern group, and at least one of the surface area, thickness, and arrangement spacing of the conductor pattern groups is reduced to a predetermined degree. Specifically, relative to the conductor pattern group in region 20A, the surface area or thickness of each conductor pattern group in region 20B is preferably 99-60%, more preferably 95-80%. Furthermore, relative to region 20A, the arrangement spacing of region 20B is preferably 99-60%, more preferably 90-70%.

[0096] The substrate 21 is not particularly limited as long as it is flat and can form the first conductor pattern 51, the second conductor pattern 52 and the third conductor pattern 53 on one of its surfaces 21a. The substrate 21 can be a single-layer structure or a multi-layer structure.

[0097] The thickness of the substrate 21 can be, for example, 5μm~500μm, 15μm~200μm, or 25μm~100μm.

[0098] The thicknesses of the first conductor pattern 51, the second conductor pattern 52, and the third conductor pattern 53 are not particularly limited. These thicknesses can be varied arbitrarily according to the desired characteristics. Furthermore, these three thicknesses can be the same or different from each other; considering productivity, it is preferable that they are the same. In addition, from the perspective of balancing electromagnetic wave transmittance and surface tracking, the thicknesses of the first conductor pattern 51, the second conductor pattern 52, and the third conductor pattern 53 are preferably 10 nm to 300 μm, more preferably 40 nm to 100 μm, and particularly preferably 80 nm to 1 μm.

[0099] The material of the substrate 21 can be appropriately selected according to the application of the electromagnetic wave absorbing component 10.

[0100] For example, to make the electromagnetic wave absorbing member 10 transparent, the substrate 21 may be made of a transparent material. Alternatively, to make the electromagnetic wave absorbing member 10 adaptable to curved surfaces, the substrate 21 may be made of a flexible material. To improve the transparency and three-dimensional formability of the electromagnetic wave absorbing member 10, the surface of the substrate 21 may be made smooth.

[0101] For example, the substrate 21 may be made of resin. The resin may be a thermoplastic resin or a thermosetting resin. However, considering the three-dimensional formability of the electromagnetic wave absorbing member 10, the substrate 21 preferably comprises a thermoplastic resin.

[0102] Examples of thermoplastic resins include polyolefin resins, polyester resins, polyester-polyether resins, polyacrylic resins, polystyrene resins, polyimide resins, polyimide amide resins, polyamide resins, polyurethane resins, polycarbonate resins, polyarylate resins, melamine resins, epoxy resins, urethane resins, silicone resins, and fluoropolymers.

[0103] Specific examples of polyolefin resins include polypropylene and polyethylene. Specific examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate.

[0104] The substrate 21 may contain any components without impairing the effects of the present invention. Examples of such components include inorganic fillers, colorants, curing agents, anti-aging agents, light stabilizers, flame retardants, conductive agents, antistatic agents, plasticizers, etc.

[0105] It is possible to further improve the electromagnetic wave absorption performance of the electromagnetic wave absorbing component 10 by appropriately setting the thickness, dielectric constant, conductivity, and magnetic permeability of the substrate 21.

[0106] When considering the electrical characteristics of the electromagnetic wave to be absorbed, the substrate 21 can also be a layer with a high dielectric constant. If the substrate 21 is a layer with a high dielectric constant, the thickness of the electromagnetic wave absorbing member 10 can be relatively thin.

[0107] The resistive layer 20 can be fabricated, for example, by the following method.

[0108] First, prepare a substrate 21. Then, form a first conductor pattern 51, a second conductor pattern 52, and a third conductor pattern 53 on one side 21a of the substrate 21.

[0109] When forming each conductor pattern, the frequency at which the transmission amount of electromagnetic waves transmitted by each conductor pattern reaches a maximum value is specified as a value [GHz].

[0110] There is no particular restriction on the order in which the various conductor patterns are formed. The conductor patterns can be formed in the same process or in different processes.

[0111] There are no particular limitations on the method for forming each conductor pattern, as long as it is a scheme that can form a specified frequency. Examples of methods for forming each conductor pattern include the following.

[0112] A printing method for printing conductor patterns on one side 21a of a substrate 21 using conductive paste.

[0113] A development method for developing conductor patterns on one side 21a of a substrate 21.

[0114] A method for depositing a metal thin film on one side 21a of a substrate 21 by sputtering, vacuum evaporation, or lamination of metal foil, and for forming a pattern of the metal thin film on one side 21a of the substrate 21 by photolithography.

[0115] A method of placing a metal wire on one surface 21a of a substrate 21.

[0116] "Isolation layer"

[0117] An isolation layer 30 is disposed on the other side 20b of the resistive layer 20.

[0118] The insulating layer 30 has two surfaces, namely surfaces 30a and 30b. One surface 30a of the insulating layer 30 is opposite to the other surface 20b of the resistive layer 20. A reflective layer 40 is disposed on the other surface 30b of the insulating layer 30.

[0119] The isolation layer 30 can be a single-layer structure or a multi-layer structure.

[0120] The material of the insulating layer 30 can be appropriately selected according to the application, and examples include plastic film, paper, cloth, non-woven fabric, rubber sheet, and foam sheet. Among them, foam sheet is preferred from the perspective of increasing thickness and easily achieving lightweight.

[0121] As a foamed sheet, for example, the resin constituting the plastic film can be foamed and formed into a sheet-like foamed sheet. Specific examples of foamed sheets include polyethylene foam, polypropylene foam, polyurethane foam, etc.

[0122] Taking into account the wavelength shortening effect brought about by the isolation layer 30, the thickness of the isolation layer 30 can be appropriately changed in accordance with the wavelength of the electromagnetic wave to be absorbed and the relative permittivity of the isolation layer 30.

[0123] Taking into account the wavelength shortening effect brought about by the isolation layer 30, it is preferable that the thickness of the isolation layer 30 satisfies the following equation (3).

[0124]

[0125] In equation (3) above, λ is the wavelength of the transmitted electromagnetic wave, and ε is the relative permittivity of the isolation layer 30. The thickness of the isolation layer 30 can be appropriately adjusted according to the absorption characteristics. For example, it can be varied within the range of 0.1 times to 3.0 times the thickness of the isolation layer 30 obtained by equation (3) above.

[0126] When the relationship between the thickness of the isolation layer 30 and the wavelength λ satisfies the above equation (3), the electromagnetic wave absorbing member 10 becomes a so-called λ / 4 structure. As a result, the maximum value of the electromagnetic wave absorption based on the electromagnetic wave absorbing member 10 is further increased.

[0127] The thickness of the isolation layer 30 can be appropriately set according to the wavelength λ of the electromagnetic wave to be absorbed. For example, the thickness of the isolation layer 30 can be 25μm~5000μm, 300μm~4000μm, or 1000μm~3000μm.

[0128] The insulating layer 30 can be made of a material with a high dielectric constant. If the insulating layer 30 is a layer with a high dielectric constant, the thickness of the insulating layer 30 can be relatively thin.

[0129] Taking into account the dielectric constant of the isolation layer 30, the isolation layer 30 preferably contains at least one selected from the group consisting of barium titanate, titanium oxide and strontium titanate.

[0130] "Reflective layer"

[0131] The reflective layer 40 has two surfaces, namely surfaces 40a and 40b. One surface 40a of the reflective layer 40 is opposite to the other surface 30b of the insulating layer 30.

[0132] The reflective layer 40 is not particularly limited in shape as long as it can reflect electromagnetic waves that are transmitted to and through the electromagnetic wave absorbing member 10. A portion of the electromagnetic waves transmitted to the electromagnetic wave absorbing member 10 will be reflected or absorbed by the resistive layer 20. On the other hand, electromagnetic waves that are neither reflected nor absorbed by the resistive layer 20 will be transmitted through it. Electromagnetic waves that have been transmitted through the resistive layer 20 will be reflected back towards the resistive layer 20 at the reflective layer 40.

[0133] For example, as long as the reflective layer 40 is conductive in the direction of either of its two surfaces, namely surfaces 40a and 40b, it can reflect electromagnetic waves that have been transmitted through the resistive layer 20. Specifically, the reflective layer 40 can be a structure formed by bonding aluminum foil or copper foil, or a metal plate, to a resin film such as polyethylene terephthalate. Alternatively, a transparent conductive film such as ITO (indium tin oxide) or a mesh formed of metal wires can be used instead of metal foil or metal plate. Among these, a metal plate is preferred in terms of conductivity.

[0134] Alternatively, considering the reflective properties of the reflective layer 40, metal wires, conductive wires, twisted wires containing metal wires and conductive wires, and conductive films can be disposed on the other side 40b of the reflective layer 40. The conductive film can be disposed on the surface 40b by printing methods such as screen printing, gravure printing, inkjet printing, sputtering, vacuum evaporation, or photolithography.

[0135] When the insulating layer 30 is formed on a conductive object such as a metal, the conductive object such as the metal acts as a reflective layer 40, so the reflective layer 40 can be omitted.

[0136] For the purpose of applying the electromagnetic wave absorbing member 10 to the surface of various articles, an adhesive layer may also be provided on the other side 40b of the reflective layer 40. When providing an adhesive layer on the other side 40b of the reflective layer 40, a release film may be provided on the side of the adhesive layer opposite to the side in contact with the other side 40b. The release film is removed when using the electromagnetic wave absorbing member 10. By covering the adhesive surface with a release film, the operability during circulation is improved.

[0137] Examples of adhesives that form the adhesive layer include: heat-sealing adhesives that bond by heat; adhesives that exhibit adhesion by wetting; and pressure-sensitive adhesives (adhesives) that bond by pressure. Among these, from the perspective of simplicity, pressure-sensitive adhesives are preferred.

[0138] Specific examples of adhesives include acrylic adhesives, urethane adhesives, rubber adhesives, polyester adhesives, silicone adhesives, and polyvinyl ether adhesives. Preferably, at least one adhesive is selected from the group consisting of acrylic adhesives, urethane adhesives, and rubber adhesives, and more preferably, acrylic adhesives.

[0139] Furthermore, the electromagnetic wave absorbing member 10 of this embodiment may have a protective layer formed on one surface 20a of the resistive layer 20.

[0140] There are no particular limitations on the form of the protective layer as long as it can protect the resistive layer 20.

[0141] According to the electromagnetic wave absorbing member 10 of this embodiment, the resistive layer 20 has two regions, 20A and 20B, with equal areas and different electromagnetic wave transmission characteristics in a top view of the electromagnetic wave absorbing member 10. At least one of the shape, size, and spacing of the units constituting the conductor pattern 22 in region 20A differs from that in the adjacent region 20B. Therefore, the electromagnetic wave transmission characteristics of regions 20A and 20B are different. Thus, by constructing the resistive layer 20 with regions 20A and 20B having different electromagnetic wave transmission characteristics, the electromagnetic wave transmission characteristics of the resistive layer 20 become the characteristics obtained by averaging the electromagnetic wave transmission characteristics of regions 20A and 20B. As a result, even if the thickness deviation of the insulating layer 30 is large, the thickness deviation will be offset, resulting in an electromagnetic wave absorbing member 10 with stable performance.

[0142] In addition, electromagnetic wave absorption characteristics refer to the electromagnetic wave transmittance of resistive layer 20 (region 20A, region 20B).

[0143] <Other Implementation Plans>

[0144] Furthermore, the present invention is not limited to the above-described embodiments.

[0145] For example, it can also be used as follows Figure 4 (a), (b) Figure 5 The components of the electromagnetic wave absorbing components in the first to sixth modifications shown in (a), (b), and (c).

[0146] like Figure 4 As shown in (a) of the first modified example of the electromagnetic wave absorbing member 100, the resistive layer 120 has two regions, namely regions 120A and 120B, which have equal areas and different electromagnetic wave transmission characteristics in a top view of the electromagnetic wave absorbing member 100. Regions 120A and 120B have the same shape. Regarding the electromagnetic wave absorbing member 100 of this embodiment, in a top view of the electromagnetic wave absorbing member 100, regions 120A and 120B have a shape similar to that of the electromagnetic wave absorbing member 100 (here, a square). Regarding the electromagnetic wave absorbing member 100 of this embodiment, in a top view of the electromagnetic wave absorbing member 100, regions 120A and 120B are alternately arranged in an adjacent manner, and eight regions 120A and eight regions 120B are arranged in a grid pattern.

[0147] Region 120A and Region 120B respectively have, for example, the first conductor pattern 51, the second conductor pattern 52 and the third conductor pattern 53 described above.

[0148] At least one of the shapes, sizes, and arrangement intervals of the units (first unit u1, second unit u2, third unit u3) of the constituent conductor patterns 22 (first conductor pattern 51, second conductor pattern 52, third conductor pattern 53) in region 120A differs from that in the adjacent region 120B. Therefore, the electromagnetic wave transmission characteristics of regions 120A and 120B are different.

[0149] Furthermore, the surface area, thickness, and arrangement spacing of the conductor pattern groups in regions 120A and 120B are preferably related to the above. Figure 3 Regions 20A and 20B are the same.

[0150] like Figure 4As shown in (b) of the second modified example of the electromagnetic wave absorbing member 200, the resistive layer 220 has two regions, 220A and 220B, with equal areas and different electromagnetic wave transmission characteristics in a top view of the electromagnetic wave absorbing member 200. Regions 220A and 220B have the same shape. Regarding the electromagnetic wave absorbing member 200 of this embodiment, in a top view of the electromagnetic wave absorbing member 200, regions 220A and 220B have a shape similar to that of the electromagnetic wave absorbing member 200 (here, a square). Regarding the electromagnetic wave absorbing member 200 of this embodiment, in a top view of the electromagnetic wave absorbing member 200, regions 220A and 220B are alternately arranged in an adjacent manner, and 32 regions 220A and 32 regions 220B are arranged in a lattice pattern.

[0151] Regions 220A and 220B respectively have, for example, the first conductor pattern 51, the second conductor pattern 52 and the third conductor pattern 53 described above.

[0152] At least one of the shapes, sizes, and arrangement intervals of the units (first unit u1, second unit u2, third unit u3) of the constituent conductor patterns 22 (first conductor pattern 51, second conductor pattern 52, third conductor pattern 53) in region 220A differs from that in the adjacent region 220B. Therefore, the electromagnetic wave transmission characteristics of regions 220A and 220B are different.

[0153] Furthermore, the surface area, thickness, and arrangement spacing of the conductor pattern groups in regions 220A and 220B are preferably related to the above. Figure 3 Regions 20A and 20B are identical. Furthermore, the number of different regions is not limited to two; there can be three or more. For example, regions 220A, 220B, and 220C can be repeated. In this case, based on region 220B, at least one of the surface area, thickness, and arrangement interval of the conductor pattern group in region 220A is preferably 101-150%, more preferably 105-130%. At least one of the surface area, thickness, and arrangement interval of the conductor pattern group in region 220C is preferably 99-60%, more preferably 95-70%. In this case, a repeating arrangement of regions 220A, 220B, and 220C in that order is preferred.

[0154] like Figure 5As shown in (a) of the third modified example of the electromagnetic wave absorbing member 300, the resistive layer 320 has two regions, namely regions 320A and 320B, which have equal areas and different electromagnetic wave transmission characteristics in a top view of the electromagnetic wave absorbing member 300. Regions 320A and 320B have the same shape. With respect to the electromagnetic wave absorbing member 300 of this embodiment, regions 320A and 320B are arranged along one direction of the electromagnetic wave absorbing member 300 in a top view. That is, regions 320A and 320B are arranged in a strip shape along one direction of the electromagnetic wave absorbing member 300.

[0155] Regions 320A and 320B respectively have, for example, the first conductor pattern 51, the second conductor pattern 52 and the third conductor pattern 53 described above.

[0156] At least one of the shapes, sizes, and arrangement intervals of the units (first unit u1, second unit u2, third unit u3) of the constituent conductor patterns 22 (first conductor pattern 51, second conductor pattern 52, third conductor pattern 53) in region 320A differs from that of the adjacent region 320B. Therefore, the electromagnetic wave transmission characteristics of regions 320A and 320B are different.

[0157] Furthermore, the surface area, thickness, and arrangement spacing of the conductor pattern groups in regions 320A and 320B are preferably related to the above. Figure 3 Regions 20A and 20B are the same.

[0158] like Figure 5 As shown in (b) of the fourth modified example of the electromagnetic wave absorbing member 400, the resistive layer 420 has two regions, namely regions 420A and 420B, which have equal areas and different electromagnetic wave transmission characteristics in a top view of the electromagnetic wave absorbing member 400. Regions 420A and 420B have the same shape. In the electromagnetic wave absorbing member 400 of this embodiment, regions 420A and 420B are arranged along one direction of the electromagnetic wave absorbing member 400 in a top view. That is, regions 420A and 420B are arranged in a strip shape along one direction of the electromagnetic wave absorbing member 400. In the electromagnetic wave absorbing member 400 of this embodiment, regions 420A and 420B are arranged alternately in an adjacent manner in a top view of the electromagnetic wave absorbing member 400, and the two regions 420A and the two regions 420B are arranged in a strip shape.

[0159] Regions 420A and 420B respectively have, for example, the first conductor pattern 51, the second conductor pattern 52 and the third conductor pattern 53 described above.

[0160] At least one of the shapes, sizes, and arrangement intervals of the units (first unit u1, second unit u2, third unit u3) of the constituent conductor patterns 22 (first conductor pattern 51, second conductor pattern 52, third conductor pattern 53) in region 420A differs from that of the adjacent region 420B. Therefore, the electromagnetic wave transmission characteristics of regions 420A and 420B are different.

[0161] Furthermore, the surface area, thickness, and arrangement spacing of the conductor pattern groups in regions 420A and 420B are preferably related to the above. Figure 3 Regions 20A and 20B are the same.

[0162] like Figure 5 As shown in (c) of the fifth modified example of the electromagnetic wave absorbing member 500, the resistive layer 520 has two regions, namely regions 520A and 520B, which have equal areas and different electromagnetic wave transmission characteristics in a top view of the electromagnetic wave absorbing member 500. Regions 520A and 520B have the same shape. In this embodiment of the electromagnetic wave absorbing member 500, regions 520A and 520B are arranged along one direction of the electromagnetic wave absorbing member 500 in a top view. That is, regions 520A and 520B are arranged in a strip shape along one direction of the electromagnetic wave absorbing member 500. In this embodiment of the electromagnetic wave absorbing member 500, regions 520A and 520B are arranged alternately in an adjacent manner in a top view, and five regions 520A and five regions 520B are arranged in a strip shape.

[0163] Regions 520A and 520B respectively have, for example, the first conductor pattern 51, the second conductor pattern 52 and the third conductor pattern 53 described above.

[0164] At least one of the shapes, sizes, and arrangement intervals of the units (first unit u1, second unit u2, third unit u3) of the constituent conductor patterns 22 (first conductor pattern 51, second conductor pattern 52, third conductor pattern 53) in region 520A differs from that in the adjacent region 520B. Therefore, the electromagnetic wave transmission characteristics of regions 520A and 520B are different.

[0165] Furthermore, the surface area, thickness, and arrangement spacing of the conductor pattern groups in regions 520A and 520B are preferably related to the above. Figure 3Regions 20A and 20B are identical. Furthermore, the number of different regions is not limited to two; there can be three or more. For example, regions 520A, 520B, and 520C can be repeated. In this case, based on region 520B, at least one of the surface area, thickness, and arrangement spacing of the conductor pattern group in region 520A is preferably 101-150%, more preferably 105-130%. At least one of the surface area, thickness, and arrangement spacing of the conductor pattern group in region 520C is preferably 99-60%, more preferably 95-70%. In this case, an array repeating in the order of regions 520A, 520B, and 520C is preferred.

[0166] Example

[0167] The present invention will be further described in detail below through embodiments and comparative examples, but the present invention is not limited to the following embodiments.

[0168] [Comparative Example 1]

[0169] Fabrication of Electromagnetic Wave Absorbing Components

[0170] A water-washable ink pattern is printed on a substrate made of PET film (trade name: PET50A4160, manufactured by TOYOBOCO., LTD.) with a thickness of 50μm, and a copper film with a thickness of 100nm is deposited by vapor deposition to form a copper film.

[0171] Then, the ink is washed with water to remove the copper film on the washed ink, thereby patterning it into a conductor pattern to obtain a resistive layer.

[0172] On the back of the obtained resistive layer, a 1.80 mm thick foamed urethane sheet (manufactured by INOAC CORPORATION) is stacked sequentially as an insulating layer, and an aluminum vapor-deposited PET film (bending stiffness: 8.33 Pa·mm) is stacked sequentially. 4 ), to fabricate electromagnetic wave absorbing components with absorptive properties in the 76~81GHz band.

[0173] As a resistive layer, it forms a layer with... Figure 2 The conductor pattern layer is shown. Specifically, among the three patterns of large, medium, and small sizes, the medium-sized pattern has the highest transmittance at 79 GHz. The large pattern is formed by increasing the length of the cross portion of the medium pattern by 20%, and the small pattern is formed by reducing the length of the cross portion of the medium pattern by 20%. Furthermore, the widths of the large, medium, and small patterns are all set to be the same. In addition, as examples of different thicknesses on the insulating layer side, examples with insulating layer thicknesses of 2.00 mm and 2.20 mm were also fabricated using the same configuration.

[0174] [Comparative Example 2]

[0175] Fabrication of Electromagnetic Wave Absorbing Components

[0176] As a resistive layer, while maintaining the same pattern width as the large, medium, and small patterns of Comparative Example 1, the length of the cross portion was reduced to 90% of each. In addition, the distance between the patterns was reduced to 75% of that of Comparative Example 1. Otherwise, the electromagnetic wave absorbing member of Comparative Example 2 was manufactured in the same manner as Comparative Example 1.

[0177] [Example 1]

[0178] In addition to forming Figure 3 Apart from the layer shown, which serves as a resistive layer, the electromagnetic wave absorbing component of Example 1 was fabricated in the same manner as Comparative Example 1. In addition, the size of each unit was set to 32mm × 32mm, with 15 × 15 large, medium and small patterns identical to those in Comparative Example 1 arranged in one unit, and 20 × 20 large, medium and small patterns identical to those in Comparative Example 2 arranged in another unit.

[0179] [Example 2]

[0180] In addition to forming Figure 4 Apart from the layer shown in (a), which serves as a resistive layer, the electromagnetic wave absorbing member of Example 2 was fabricated in the same manner as Comparative Example 1. In addition, the size of each unit was set to 12mm × 12mm, with 7 × 7 large, medium and small patterns identical to those in Comparative Example 1 arranged in one unit, and 9 × 9 large, medium and small patterns identical to those in Comparative Example 2 arranged in the other unit.

[0181] [Example 3]

[0182] In addition to forming Figure 4 Apart from the layer shown in (b), which serves as a resistive layer, the electromagnetic wave absorbing member of Example 3 was fabricated in the same manner as Comparative Example 1. In addition, the size of each unit was set to 7mm × 7mm, with 4 × 4 large, medium and small patterns identical to those in Comparative Example 1 arranged in one unit, and 5 × 5 large, medium and small patterns identical to those in Comparative Example 2 arranged in the other unit.

[0183] [Example 4]

[0184] In addition to forming Figure 5 Apart from the layer shown in (a), which serves as a resistive layer, the electromagnetic wave absorbing member of Example 4 was fabricated in the same manner as Comparative Example 1. In addition, the size of each unit was set to a strip with a width of 32 mm. One unit was configured with 15 rows of large, medium and small patterns identical to those in Comparative Example 1, and the other unit was configured with 20 rows of large, medium and small patterns identical to those in Comparative Example 2.

[0185] [Example 5]

[0186] In addition to forming Figure 5 Apart from the layer shown in (b), which serves as a resistive layer, the electromagnetic wave absorbing member of Example 5 was fabricated in the same manner as Comparative Example 1. In addition, the size of each unit was set to a strip with a width of 12 mm. One unit was arranged with 7 rows of large, medium and small patterns identical to those in Comparative Example 1, and the other unit was arranged with 7 rows of large, medium and small patterns identical to those in Comparative Example 2.

[0187] [Example 6]

[0188] In addition to forming Figure 5 Apart from the layer shown in (c), which serves as a resistive layer, the electromagnetic wave absorbing member of Example 6 was fabricated in the same manner as Comparative Example 1. Furthermore, each unit was sized as a 7mm wide strip, with one unit containing four rows of large, medium, and small patterns identical to those in Comparative Example 1, and the other unit containing four rows of large, medium, and small patterns identical to those in Comparative Example 2.

[0189] [evaluate]

[0190] The electromagnetic wave absorbing components of Comparative Examples 1 and 2 and Examples 1 to 6 were evaluated as follows. The results are shown in Table 1.

[0191] [Electromagnetic wave absorption]

[0192] The electromagnetic wave absorption characteristics of the electromagnetic wave absorbing components were evaluated by using the free-space method and a network analyzer to obtain the S11 values ​​(reflection coefficients) at 76-81 GHz for the electromagnetic wave absorbing components of Comparative Examples 1 and 2 and Examples 1-6.

[0193] [Table 1]

[0194]

[0195] As shown in Table 1, the electromagnetic wave absorbing components of Examples 1-6 exhibit excellent electromagnetic wave absorption properties.

[0196] On the other hand, it can be seen that the electromagnetic wave absorbing components of Comparative Examples 1 and 2 have poor electromagnetic wave absorption properties.

[0197] Industrial applicability

[0198] The electromagnetic wave absorbing component of the present invention can be suitably used as an electromagnetic wave absorbing component in transportation equipment such as automobiles.

[0199] Explanation of reference numerals in the attached figures

[0200] 10: Electromagnetic wave absorbing component; 20: Resistive layer; 20A, 20B: Regions; 21: Substrate; 22: Conductor pattern; 30: Insulating layer; 40: Reflective layer; 51: First conductor pattern; 52: Second conductor pattern; 53: Third conductor pattern.

Claims

1. An electromagnetic wave absorbing component, comprising a resistive layer, an insulating layer, and a reflective layer, wherein, The resistive layer, the insulating layer, and the reflective layer are stacked in the order of resistive layer, insulating layer, and reflective layer. The resistive layer has multiple regions with equal area and different electromagnetic wave absorption characteristics in a top view of the electromagnetic wave absorbing component. The regions each have two or more conductor patterns formed parallel to each other on the isolation layer. The two or more conductor patterns are each composed of multiple units arranged in one direction at certain intervals. At least one of the shape, size, and spacing of the units constituting the conductor pattern in the region differs from that in adjacent regions.

2. The electromagnetic wave absorbing component according to claim 1, wherein, The area is set up repeatedly at certain intervals.

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