Electromagnetic wave attenuating film

Abstract

A thin electromagnetic wave attenuation film capable of attenuating electromagnetic waves at millimeter-wave frequencies is provided. The electromagnetic wave attenuation film of the present invention is characterized by comprising: a dielectric substrate having a front and a back side, a thin-film conductive layer disposed on the front side, and a planar inductor or bonding layer disposed on the back side. The thin-film conductive layer includes a plurality of metal plates, and the natural logarithm of the value of the thickness T of the metal plates normalized to a skin depth d falls within a predetermined numerical range in a specific frequency band. Furthermore, the electromagnetic wave attenuation film of the present invention can be used in a specific frequency band and has the following configuration: the dielectric substrate has an uneven surface on the front side consisting of a first region with relatively low recesses and a second region with relatively high recesses; the thin-film conductive layer includes a plurality of metal plates disposed in the first region, the first region being discretely arranged, and the second region being disposed between the plurality of first regions. A top coating layer may also be provided on the thin-film conductive layer.

Description

Technical Field

[0001] Embodiments of the present invention relate to an electromagnetic wave attenuation film capable of capturing incident waves and attenuating reflected waves. Background Technology

[0002] Radio waves with frequencies in the gigahertz (GHz) band are used in mobile communications such as mobile phones, wireless LANs, and automatic toll collection (ETC) systems.

[0003] As an electromagnetic wave absorbing sheet for absorbing such electromagnetic waves, Patent Document 1 proposes a laminated sheet made by stacking a rubber-like electromagnetic wave absorbing sheet with a paper-like sheet such as corrugated paper.

[0004] Furthermore, in order to absorb higher frequency radio waves, Patent Document 2 proposes an electromagnetic wave absorbing sheet that can absorb radio waves in the frequency band above 20 GHz by aligning the longitudinal direction of flat soft magnetic particles in the surface direction of the sheet.

[0005] In addition, it is known that an electromagnetic wave absorber having a filling structure of particles having ε-Fe2O3 (ε-Fe2O3) crystals in a magnetic phase exhibits electromagnetic wave absorption performance in the range of 25 to 100 GHz (see Patent Document 3).

[0006] Patent document 4 proposes a metal-plastic composite film with linear traces suitable for electromagnetic wave absorbers, which has a plastic film and a single or multiple metal film disposed on at least one side thereof, wherein numerous substantially parallel and discontinuous linear traces are formed on the metal film in multiple directions with irregular widths and intervals.

[0007] Patent document 5 discloses an electromagnetic wave absorption structure comprising: a resonant layer having a plurality of patch conductors having various resonant frequencies arranged in a predetermined periodic pattern; a dielectric layer that causes multiple reflections of electromagnetic waves resonating in the resonant layer; and a reflective conductor layer that reflects electromagnetic waves incident from the dielectric layer toward the dielectric layer side.

[0008] Furthermore, the aforementioned electromagnetic wave absorbing sheets are used not only in electronic devices but also in building interiors. Additionally, as described in Patent Document 6, acrylate copolymer modified resins such as epoxy resin, polyurethane resin, chlorinated rubber-based resin, vinyl chloride-based resin, alkyd resin, unsaturated polyester resin, and epoxy acrylate resin can be used as the electromagnetic wave absorbing material. Alternatively, rubber-based materials such as polyamide-imide or synthetic rubber, as described in Patent Document 7, can also be used.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2011-233834

[0012] Patent Document 2: Japanese Patent Application Publication No. 2015-198163

[0013] Patent Document 3: Japanese Patent Application Publication No. 2008-060484

[0014] Patent Document 4: International Publication No. 2010 / 093027

[0015] Patent Document 5: Japanese Patent Application Publication No. 2020-009829

[0016] Patent Document 6: Japanese Patent No. 2612592

[0017] Patent Document 7: Japanese Patent Application Publication No. 2006-86422 Summary of the Invention

[0018] The problem that the invention aims to solve

[0019] In recent years, in order to achieve high-capacity, high-speed, and multi-location simultaneous connectivity for data transmission and reception, the practical application of wireless communication using millimeter-wave bands above 30 GHz has been initiated, and the development of millimeter-wave corresponding devices to make this possible is underway. In addition, the use of vehicle-mounted radar equipment with extremely narrow directional characteristics is also developing.

[0020] Interference caused by diffuse reflection of electromagnetic waves within the equipment enclosure can lead to malfunctions. Therefore, suppressing electromagnetic noise is important as a technology for utilizing electromagnetic waves.

[0021] As a method to suppress electromagnetic noise, electromagnetic wave absorbing sheets like those mentioned above are considered, but most of them currently correspond to frequencies of around 20 GHz to tens of GHz, rather than the millimeter wave band.

[0022] While electromagnetic wave absorbers exist that absorb millimeter-wave electromagnetic waves, currently practical electromagnetic wave absorbers are relatively thick to maintain absorption performance. Therefore, it is difficult to assemble them into the housings of increasingly integrated devices to suppress electromagnetic noise.

[0023] In view of the above, the objective is to provide a thin electromagnetic wave attenuation film capable of attenuating electromagnetic waves at millimeter-wave frequencies. Furthermore, since electromagnetic wave absorbers installed in electronic devices, building interiors, etc., are used continuously over long periods, the objective is also to provide an electromagnetic wave attenuation film with excellent environmental resistance, such as weather resistance and heat resistance. It should be noted that the electromagnetic wave attenuation film of the present invention is considered to be a film capable of stably and locally containing an electromagnetic field. That is, the electromagnetic wave attenuation film of the present invention is considered to be a film capable of capturing an electromagnetic field. "Capturing" an electromagnetic field is a state in which electric and magnetic fields can stably and locally exist. In addition, a portion of the captured electromagnetic field is converted into heat and absorbed, and a portion is re-emitted. That is, the energy of the captured electromagnetic field is converted into thermal energy and re-emitted electromagnetic wave energy. This re-emitting is generally considered to have low directivity, thus reducing electromagnetic waves towards the mirror reflection direction, and attenuating the reflected wave. Therefore, the reflected electromagnetic wave can be attenuated by the conversion of the incident electromagnetic wave into absorption caused by heat and scattering caused by re-emitting. Because electromagnetic waves are attenuated through a mechanism different from the past, attenuation can be achieved with a thin structure of less than 1 / 4 of the wavelength, which was previously impossible to attenuate. Furthermore, according to the embodiments of this application, incredibly, attenuation can be achieved with wavelengths of 10... -2 A membrane with a thickness on the order of magnitude that attenuates electromagnetic waves.

[0024] Methods for solving problems

[0025] This invention relates to an electromagnetic wave attenuation film for use in a specific frequency band of millimeter waves, comprising: a dielectric substrate having a front and a back side, a thin-film conductive layer disposed on the front side, and a planar inductor or bonding layer disposed on the back side, the thin-film conductive layer comprising a plurality of discretely arranged metal plates. A top coating layer may also be provided on the thin-film conductive layer.

[0026] The electromagnetic wave attenuation film of the present invention is characterized in that the natural logarithm of the normalized value of the thickness T of the metal plate, with skin depth d, falls within a predetermined numerical range in a specific frequency band. Specifically, it satisfies -1.0 ≤ ln(T / d) ≤ 0.0 in the 27 GHz to 34 GHz frequency band, -2.0 ≤ ln(T / d) ≤ -0.5 in the 35 GHz to 50 GHz frequency band, or -2.5 ≤ ln(T / d) ≤ -1.0 in the 57 GHz to 90 GHz frequency band.

[0027] In another electromagnetic wave attenuation film according to the present invention, the dielectric substrate has an uneven surface on its front side, consisting of a first region with relatively low recesses and a second region with relatively high recesses. The thin-film conductive layer comprises a plurality of metal plates disposed in the first region. The first regions are discretely arranged, and the second regions are disposed between the plurality of first regions. Specifically, it is used in frequency bands of 27 GHz to 34 GHz, 35 GHz to 50 GHz, or 57 GHz to 90 GHz.

[0028] The effects of the invention

[0029] According to embodiments of the present invention, a thin electromagnetic wave attenuation film capable of attenuating radio waves at millimeter-wave frequencies can be provided. Furthermore, an electromagnetic wave attenuation film with excellent weather resistance can be provided. Attached Figure Description

[0030] [ Figure 1 This is a schematic plan view illustrating the electromagnetic wave attenuation film according to the first embodiment of the present invention.

[0031] [ Figure 2 To show Figure 1 A schematic diagram of a portion of the cross section of line II.

[0032] [ Figure 3 To illustrate the case with a top coating Figure 1 A schematic diagram of a portion of the cross section of line II.

[0033] [ Figure 4 (a) is an image showing the simulation results of the electric field strength without a support cage, and (b) is a partial enlarged view of (a).

[0034] [ Figure 5 (a) is an image showing the simulation results of the electric field strength with a support cage, and (b) is a partial enlarged view of (a).

[0035] [ Figure 6 This is a schematic plan view illustrating the electromagnetic wave attenuation film according to the second embodiment of the present invention.

[0036] [ Figure 7 To show Figure 6 A schematic diagram of a portion of the cross section of line II-II.

[0037] [ Figure 8 To illustrate the case with a top coating Figure 6 A schematic diagram of a portion of the cross section of line II-II.

[0038] [ Figure 9The graph shows the simulation results of electromagnetic wave attenuation caused by changes in the thickness of the metal plate.

[0039] [ Figure 10 [A graph showing the electromagnetic wave attenuation characteristics at 27 GHz in Example 1A.]

[0040] [ Figure 11 [A graph showing the electromagnetic wave attenuation characteristics at 28 GHz in Example 1A.]

[0041] [ Figure 12 [A graph showing the electromagnetic wave attenuation characteristics at 31 GHz for Example 1A.]

[0042] [ Figure 13 [A graph showing the electromagnetic wave attenuation characteristics at 34 GHz in Example 1A.]

[0043] [ Figure 14 [A graph showing the electromagnetic wave attenuation characteristics of Example 1B at 28 GHz corresponding to the metal area ratio.]

[0044] [ Figure 15 [A graph showing the electromagnetic wave attenuation characteristics of a circular metal plate in Example 1C.]

[0045] [ Figure 16 [A graph showing the electromagnetic wave attenuation characteristics of a rectangular metal plate in Example 1C.]

[0046] [ Figure 17 [A graph showing the electromagnetic wave attenuation characteristics of a hexagonal metal plate in Example 1C.]

[0047] [ Figure 18 [A graph showing the electromagnetic wave attenuation characteristics of a convex metal plate in Example 1C.]

[0048] [ Figure 19 [A graph showing the electromagnetic wave attenuation characteristics of a triangular metal plate in Example 1C.]

[0049] [ Figure 20 [A graph showing the electromagnetic wave attenuation characteristics of a cross-shaped metal plate in Example 1C.]

[0050] [ Figure 21 [A graph showing the electromagnetic wave attenuation characteristics of Example 1D.]

[0051] [ Figure 22 [A graph showing the electromagnetic wave attenuation characteristics when a top coating is provided in Example 1A.]

[0052] [ Figure 23[A graph showing the electromagnetic wave attenuation characteristics at 35 GHz in Example 2A.]

[0053] [ Figure 24 [A graph showing the electromagnetic wave attenuation characteristics at 39 GHz in Example 2A.]

[0054] [ Figure 25 [A graph showing the electromagnetic wave attenuation characteristics at 41 GHz in Example 2A.]

[0055] [ Figure 26 [A graph showing the electromagnetic wave attenuation characteristics at 45 GHz in Example 2A.]

[0056] [ Figure 27 [A graph showing the electromagnetic wave attenuation characteristics at 50 GHz in Example 2A.]

[0057] [ Figure 28 [A graph showing the electromagnetic wave attenuation characteristics of Example 2B at 39 GHz corresponding to the metal area ratio.]

[0058] [ Figure 29 [A graph showing the electromagnetic wave attenuation characteristics of a circular metal plate in Example 2C.]

[0059] [ Figure 30 [A graph showing the electromagnetic wave attenuation characteristics of a rectangular metal plate in Example 2C.]

[0060] [ Figure 31 [A graph showing the electromagnetic wave attenuation characteristics of a hexagonal metal plate in Example 2C.]

[0061] [ Figure 32 [A graph showing the electromagnetic wave attenuation characteristics of a convex metal plate in Example 2C.]

[0062] [ Figure 33 [A graph showing the electromagnetic wave attenuation characteristics of a triangular metal plate in Example 2C.]

[0063] [ Figure 34 [A graph showing the electromagnetic wave attenuation characteristics of a cross-shaped metal plate in Example 2C.]

[0064] [ Figure 35A [A graph showing the electromagnetic wave attenuation characteristics of a ring-shaped metal plate in Example 2C.]

[0065] [ Figure 35B [A graph showing the electromagnetic wave attenuation characteristics of a modified example obtained by overlapping two layers of annular electromagnetic wave attenuation films in Example 2C.]

[0066] [ Figure 36[A graph showing the electromagnetic wave attenuation characteristics of Example 2D.]

[0067] [ Figure 37 [A graph showing the electromagnetic wave attenuation characteristics when a top coating is provided in Example 2A.]

[0068] [ Figure 38 [A graph showing the electromagnetic wave attenuation characteristics at 57 GHz in Example 3A.]

[0069] [ Figure 39 [A graph showing the electromagnetic wave attenuation characteristics at 66 GHz in Example 3A.]

[0070] [ Figure 40 [A graph showing the electromagnetic wave attenuation characteristics at 71 GHz in Example 3A.]

[0071] [ Figure 41 [A graph showing the electromagnetic wave attenuation characteristics at 81 GHz in Example 3A.]

[0072] [ Figure 42 [A graph showing the electromagnetic wave attenuation characteristics at 86 GHz in Example 3A.]

[0073] [ Figure 43 [A graph showing the electromagnetic wave attenuation characteristics at 90 GHz in Example 3A.]

[0074] [ Figure 44 [A graph showing the electromagnetic wave attenuation characteristics of Example 3B at 81 GHz corresponding to the metal area ratio.]

[0075] [ Figure 45 [A graph showing the electromagnetic wave attenuation characteristics of a rectangular metal plate in Example 3C.]

[0076] [ Figure 46 [A graph showing the electromagnetic wave attenuation characteristics of a hexagonal metal plate in Example 3C.]

[0077] [ Figure 47 [A graph showing the electromagnetic wave attenuation characteristics of a convex metal plate in Example 3C.]

[0078] [ Figure 48 [A graph showing the electromagnetic wave attenuation characteristics of a triangular metal plate in Example 3C.]

[0079] [ Figure 49 [A graph showing the electromagnetic wave attenuation characteristics of a cross-shaped metal plate in Example 3C.]

[0080] [ Figure 50 [A graph showing the electromagnetic wave attenuation characteristics of Example 3A.]

[0081] [ Figure 51 [A graph showing the electromagnetic wave attenuation characteristics of Example 3D.]

[0082] [ Figure 52 [A graph showing the electromagnetic wave attenuation characteristics when a top coating is provided in Example 3A.]

[0083] [ Figure 53 This is a graph showing the relationship between the size of the metal plate and the wavelength of the attenuated electromagnetic wave. Detailed Implementation

[0084] The electromagnetic wave attenuation film 1 comprises: a dielectric substrate (dielectric layer) 10, a thin-film conductive layer 30 formed on the front side 10a of the dielectric substrate 10, and a planar inductor 50 formed on the back side 10b of the dielectric substrate. The thin-film conductive layer is a thin conductive layer. The thin-film conductive layer includes multiple metal plates. Additionally, the thin-film conductive layer may include a support cage (described later). The planar inductor is conductive, generating a current near the surface inside the planar inductor through an external magnetic flux. Furthermore, it has the function of generating a magnetic field near the surface outside the planar inductor along with this current. The planar inductor can be shaped as a slab. The dielectric substrate is an insulating substrate sandwiched between the thin-film conductive layer and the planar inductor. In other words, the thin-film conductive layer and the planar inductor are separated in the thickness direction of the dielectric substrate while sandwiching the dielectric substrate. It should be noted that the front side can be the side where the electromagnetic wave is incident. The back side is the side of the dielectric substrate opposite to the front side. The dielectric substrate 10 may have a first region 121 with a relatively lower front and a second region 122 surrounding the first region with a relatively higher front. The thin-film conductive layer located on the second region 122 is referred to as a support cage. In other words, the thin-film conductive layer contains a support cage on the second region 122.

[0085] Furthermore, if the electromagnetic wave attenuated by the electromagnetic wave attenuation film has a frequency f that becomes a single minimum value, this frequency f is taken as the attenuation center frequency f. Alternatively, if the electromagnetic wave attenuated by the electromagnetic wave attenuation film has multiple minimum values, the frequency of the average of the multiple frequencies from the maximum attenuation minimum to -3dB is taken as the attenuation center frequency. The attenuation center wavelength can be obtained by dividing the speed of light in the dielectric substrate by the attenuation center frequency f described below.

[0086] In addition, the electromagnetic wave attenuation film 1 may also have a top coating 200 for achieving impedance matching with air and improving the weather resistance of the sheet.

[0087] Figure 1 A schematic plan view is provided to illustrate the electromagnetic wave attenuation film 1 according to the first embodiment of the present invention. Figure 2 To show Figure 1 A schematic diagram of a portion of the cross section of line II.

[0088] The dielectric substrate 10 is formed of a dielectric and can form a capacitor by being sandwiched between conductive materials. The dielectric substrate 10 can be an insulating material.

[0089] A representative example of the material constituting the dielectric substrate 10 is a synthetic resin. There are no particular limitations on the type of synthetic resin, as long as it possesses sufficient strength, flexibility, and processability along with insulation. The synthetic resin can be a thermoplastic resin. Examples of synthetic resins include: polyesters such as polyethylene terephthalate (PET); polyarylene sulfides such as polyphenylene sulfide; polyolefins such as polyethylene and polypropylene; polyamides, polyimides, polyamide-imides, polyethersulfones, polyetheretherketones, polycarbonates, acrylic resins, polystyrene, etc. These materials can be used as monomers, mixed in two or more forms, or as a laminate. Furthermore, the dielectric substrate 10 may contain conductive particles, insulating particles, magnetic particles, or a mixture thereof.

[0090] In embodiments of the present invention, the thickness of the dielectric substrate can be sufficiently thin relative to the wavelength of the electromagnetic wave. It is known that when the dielectric substrate is sufficiently thin relative to the wavelength of the electromagnetic wave, traveling waves are not generated within the dielectric substrate. "Sufficiently thin" can be defined as less than half the wavelength. When less than half the wavelength, traveling waves do not guide. This is a phenomenon known as electromagnetic wave cut-off. Further, it can be defined as less than 1 / 10 of the wavelength. Generally, when the difference in the propagation distance of the electromagnetic waves is less than 1 / 10 of the wavelength, no substantial phase difference is generated. That is, when the distance between the metal plate and the planar inductor is less than 1 / 10 of the wavelength in the dielectric substrate, the electromagnetic waves re-emitted by the metal plate and the reflected waves of the planar inductor will not have a substantial phase difference due to this distance. It is believed that electromagnetic waves will not guide within a sufficiently thin dielectric substrate held by a conductor; typically, when it becomes that thin, the electromagnetic waves are blocked (cut off), so that no local electric or magnetic field exists in such a dielectric substrate. It should be noted that the wavelength in the embodiments of the present invention can be used as the attenuation center wavelength. Furthermore, unexpectedly, attenuation was achieved even when the dielectric substrate was less than 1 / 100th of the wavelength. This thickness is comparable to the unevenness of a highly precise mirror, thus achieving attenuation with a structure that is essentially thin relative to the scale of electromagnetic waves.

[0091] Through various experiments and simulations, the inventors discovered that even within a sufficiently thin dielectric substrate, stable stationary localization of electric and magnetic fields induced by electromagnetic waves can occur. The thickness of the dielectric substrate 10 can be set to 5 μm or more and 300 μm or less. Furthermore, the thickness of the dielectric substrate 10 can be set to 5 μm or more and 100 μm or less. This is thinner than half the wavelength of a millimeter-wave band, and even thinner than 1 / 10 the wavelength of a millimeter-wave band. Therefore, although the electromagnetic wave attenuation film is a thin film, it can attenuate electromagnetic waves in the millimeter-wave band. The thickness of the dielectric substrate 10 can be constant or variable.

[0092] The dielectric substrate 10 can be a single layer or multiple layers. The front surface of the dielectric substrate 10 can also have irregularities. The dielectric substrate 10 can have a carrier 11 and a base layer 12 on the carrier 11. The front surface of the base layer 12 can also have irregularities. The carrier 11 can be an extruded film. The extruded film can be an unstretched film or a stretched film. The base layer 12 can consist of two layers: a forming layer and an anchoring layer. Furthermore, to improve the adhesion between the base layer 12 and the metal plate and the planar inductor, an adhesive layer can also be provided. The base layer 12, the forming layer, the anchoring layer, and the adhesive layer can be made of the same materials as those constituting the dielectric substrate.

[0093] The carrier 11 forms the back side 10b in the dielectric substrate 10, and the base layer 12 forms the front side 10a in the dielectric substrate 10. If the front side 10a has irregularities, an irregularity structure can also be provided in the base layer 12. That is, the front side 10a of the dielectric substrate 10 has irregularities corresponding to the irregularities of the base layer 12, and the back side 10b of the dielectric substrate 10 is substantially flat.

[0094] In electromagnetic wave attenuation film 1, the characteristics vary according to the uneven shape described in section 10a. This aspect will be discussed later.

[0095] The thin-film conductive layer 30 covers all or part of the front side 10a in a plan view of the electromagnetic wave attenuation film 1. The planar inductor 50 covers all or part of the back side 10b. As long as it does not significantly impair the performance of the electromagnetic wave attenuation film 1, there may be areas not covered by the thin-film conductive layer 30 or the planar inductor 50, such as a portion of the periphery of the electromagnetic wave attenuation film 1.

[0096] The materials of the thin-film conductive layer 30 and the planar inductor 50 are not particularly limited as long as they are conductive. From the viewpoint of corrosion resistance and cost, aluminum, copper, silver, gold, platinum, tin, nickel, cobalt, chromium, molybdenum, iron, and their alloys are preferred. The thin-film conductive layer 30 and the planar inductor 50 can be formed, for example, by vacuum evaporation on the dielectric substrate 10. The planar inductor 50 can also be a conductive compound. Furthermore, the planar inductor 50 can be a continuous surface or have a mesh, patch, or other pattern.

[0097] The thickness of the thin-film conductive layer 30 can be set to be between 10 nm and 1000 nm. When it is less than 10 nm, the function of attenuating electromagnetic waves may be reduced. When it exceeds 1000 nm, the productivity may be reduced.

[0098] The planar inductor 50 can be a casting, a rolled metal plate, a metal foil, a vapor-deposited film, a sputtered film, or a coating. The thickness of the rolled metal plate can be 0.1 mm or more and 5 mm or less. The thickness of the metal foil can be 5 μm or more and less than 100 μm. When the planar inductor 50 is a vapor-deposited film, a sputtered film, or a coating, the thickness can be 0.5 μm or more and less than 5 mm. The thickness of the planar inductor 50 can be 0.5 μm to 5 mm. Furthermore, when the planar inductor 50 is a casting, the thickness is not specific, but the maximum size can be 10 mm or more. Additionally, the thickness of the planar inductor 50 can be greater than the skin depth calculated from the attenuation center wavelength. Furthermore, the thickness of the planar inductor 50 can be thicker than the thickness of the thin-film conductive layer 30.

[0099] The thin-film conductive layer 30 and the planar inductor 50 can be made of the same metal species. This same metal species can be the same pure metal or an alloy of the same metal (e.g., both are aluminum alloys), or the thin-film conductive layer 30 can be made of a pure metal and the planar inductor 50 can be made of an alloy of the metal of the thin-film conductive layer 30. Alternatively, the thin-film conductive layer 30 and the planar inductor 50 can also be made of different metal species.

[0100] The thin-film conductive layer 30 may have a top coating 200 on the side opposite to the dielectric substrate. Figure 3 To illustrate when a top coating is applied Figure 1A schematic diagram of a portion of the cross-section of line II. The planar inductor 50 may also have a top coating 200 on the surface opposite to the dielectric substrate. The thickness of the top coating 200 may be set to 0.1 μm or more and 50 μm or less. Further, it may be set to 1 μm or more and 5 μm or less. The top coating 200 may be a single layer or multiple layers. The material of the top coating 200 may be a monomer, mixture, or composite of urethane resin, acrylic resin, polyamide, polyimide, polyamide-imide, epoxy resin, or silicone resin. In addition, it may contain insulating particles, magnetic particles, conductive particles, or a mixture thereof. The particles may be inorganic particles. By providing the top coating 200, the impedance is matched with the air impedance of the propagating electromagnetic wave, thereby effectively attenuating the electromagnetic wave for the thin film conductive layer. In addition, the thin film conductive layer 30 and the planar inductor 50 may be endowed with corrosion resistance, chemical resistance, heat resistance, abrasion resistance, and impact resistance. For example, by using cross-linked acrylic resins, cross-linked epoxy resins, polyamides, polyimides, polyamide-imides, and silicone resins, heat resistance can be improved while solvent resistance is enhanced. Furthermore, by using urethane resins, impact resistance can be improved; and by using silicone resins, abrasion resistance can be improved.

[0101] The dielectric substrate 10 may also have a first region 121 that is relatively lower on the front and a second region 122 that is relatively higher on the front. The plan view shape of the first region 121 may be a square, hexagon, cross, other polygon, circle, or ellipse. The corners of the square, hexagon, cross, or other polygon may be rounded.

[0102] The first region 121 is discretely arranged. The first region 121 is arranged in a two-dimensional matrix at predetermined intervals. The second region 122 surrounds the first region 121 in a plan view of the electromagnetic wave attenuation film 1. The thin-film conductive layer 30 on the first region 121 includes a metal plate. That is, a metal plate is provided on the first region 121. In other words, the metal plate is located on the first region 121. The plan view shape of the metal plate can be a square, hexagon, cross, other polygon, circle, or ellipse. The corners of the square, hexagon, cross, or other polygon can be rounded. Based on the above arrangement of the first region 121, the second region 122 is formed in a mesh or lattice pattern in a plan view.

[0103] The surfaces of the first region 121 and the second region 122 that contact the thin-film conductive layer 30 are generally parallel to the back surface. Alternatively, a portion or all of the surfaces may be roughened. As described later, by making a portion or all of the surfaces of the first region 121 and the second region 122 that contact the thin-film conductive layer 30 roughened, the resistance of the thin-film conductive layer 30 can be adjusted.

[0104] like Figure 2As shown, the thin-film conductive layer 30 is formed on the top of the first region 121 and the second region 122. On the other hand, the thin-film conductive layer 30 is absent on the side 122a of the second region 122, which extends further upward than the first region 121, thus exposing the dielectric substrate 10. Therefore, the thin-film conductive layer 30 of the first region 121 and the thin-film conductive layer 30 of the second region 122 can be electrically insulating. If they can be electrically insulating, a portion of the side 122a can also be covered by the thin-film conductive layer 30.

[0105] The metal plates in each first region can be shaped along the planar view shape of the first region 121. That is, they can be the same or similar in shape to the planar view shape of the first region 121. In addition, the dielectric substrate 10 may also include multiple metal plates of the same shape and size in planar view. Furthermore, the first regions 121 can be discrete while remaining parallel to each other, and the arrangement density can be approximately uniform.

[0106] It is believed that the electromagnetic wave attenuation film 1 exhibits a unique mechanism at a specific wavelength through the above-described structure.

[0107] The electromagnetic waves incident on the electromagnetic wave attenuation film of the present invention are as follows. Specifically, the electromagnetic field and current generated by the incident wave are considered to be as follows.

[0108] First, according to Faraday's law, the change in magnetic flux of the incident wave passing through the metal plate will induce an alternating current in the planar inductor 50 at the same level as the incident surface of the planar inductor 50. According to Ampere's law, this alternating current will generate a changing magnetic field in the dielectric substrate adjacent to the planar inductor 50. Furthermore, the changing magnetic field becomes a magnetic flux that varies with permeability as a coefficient.

[0109] According to Henry's Law, the electric field generated by a changing magnetic flux usually induces a current in the direction that suppresses the magnetic flux. However, in the configuration of this application, contrary to expectation, it instead acts in the direction that enhances the current. As a result, a current greater than that induced by the incident wave flows in the metal plate. That is, although the area of ​​the metal plate is narrower than that of the planar inductor 50, it can generate a current of the same magnitude as that of the planar inductor 50.

[0110] The direction of the current generated in the metal plate is opposite to that of the planar inductor 50. A closed circuit is formed by the opposite currents flowing in the metal plate and the planar inductor 50, and the displacement current flowing between them. Since a closed circuit is formed only between the metal plate and the planar inductor 50, and no current flux at the same level as the electromagnetic wave attenuation film is generated in the space outside the film, no reflected wave is generated. Furthermore, the phase shift π between the reflected wave from the planar inductor 50 and the electromagnetic wave re-emitted by the current through the metal plate cancels each other out.

[0111] Based on the above principles, the reflected wave from the electromagnetic wave attenuation film is attenuated. From an energy perspective, as described below, this is considered to be due to the synergistic effect of multiple mechanisms.

[0112] As shown in the simulation of the magnetic field density later, the first mechanism is the generation of an electromagnetic field that produces non-traveling periodic oscillations caused by the incident wave. First, the incident wave induces a magnetic flux in the tangential direction of the planar inductor 50, which is located on the back side of the dielectric substrate 10. The induced magnetic flux generates an electric field perpendicular to the planar inductor 50 in a direction extending from a pair of opposite edges of the thin-film conductive layer 30 (i.e., the metal plate) on the first region 121. Next, when the electromagnetic wave is incident on the planar inductor, a current is induced near the surface of the planar inductor by the varying magnetic flux. The current induced within the planar inductor generates a magnetic field in the dielectric substrate 10 near the surface of the planar inductor. This electric field, the metal plate, and the current in the planar inductor 50 generate a magnetic field between the metal plate and the planar inductor 50 in the same direction as the magnetic flux induced by the planar inductor 50. Here, the metal plate is plate-shaped and made of metal. The electric field generated within the dielectric substrate varies periodically with the same period as the incident wave. This periodic variation in the magnetic field causes the electric field between the thin-film conductive layer 30 and the planar inductor 50 to vary periodically. As a result, a non-traveling, periodically varying electromagnetic field is generated between the thin-film conductive layer 30 and the planar inductor 50. As shown in the current density simulation later, the magnetic field within the periodically varying electromagnetic field induces an alternating current in the metal plate. Furthermore, the periodically varying electric field generates a periodically varying potential in the metal plate. The electromagnetic field does not travel and remains stationary; the induced alternating current generates power loss, and as a result, the energy of the electromagnetic field is converted into heat to absorb the electromagnetic wave. Additionally, it is believed that the alternating current induced in the metal plate re-emits electromagnetic waves from the side of the metal plate opposite to the surface in contact with the dielectric substrate 10.

[0113] That is, it is believed that a portion of the energy of the electromagnetic wave captured by the electromagnetic wave attenuation film is converted into heat energy, and the remainder is re-emitted. Furthermore, according to classical electromagnetic theory expressed by Maxwell's equations, the frequency of the induced alternating current becomes the same as the incident wave frequency; therefore, the frequency of the re-emitted electromagnetic wave is the same as the incident wave frequency. As a result, electromagnetic waves with the same frequency as the incident wave are re-emitted. Additionally, considering the vibrating electromagnetic field as quanta, it is believed that the quanta lose energy and re-emit lower-energy, longer-wavelength electromagnetic waves. Furthermore, it is believed that re-emitting includes induced emission and spontaneous emission caused by the incident electromagnetic wave. It is believed that induced emission emits electromagnetic waves coherent with the reflected wave reflected in the direction of the incident wave's reflection, i.e., the direction of specular reflection. It is believed that spontaneous emission decays over time. Furthermore, it is believed that when the electromagnetic wave attenuation film does not possess diffraction, interference, or refraction structures, the spatial distribution of spontaneous emission approximates Lambertian reflection.

[0114] Attenuation center wavelength and Figure 2 The dimension W1 in the planar direction of the thin film conductive layer 30 formed on the first region 121 is shown (refer to...). Figure 7 (Hereinafter referred to as "width W1"). That is, by changing the size W1, the wavelength of the electromagnetic wave attenuated according to the first mechanism can be changed, and the attenuation of the electromagnetic wave can be set with a high degree of freedom and ease in the electromagnetic wave attenuation film 1. Therefore, a configuration can be formed that can easily capture linearly polarized electromagnetic waves in the frequency band of 15 GHz and above to 150 GHz.

[0115] It is believed that periodic variations in non-traveling electromagnetic fields occur between opposite edges of the planar shape of the metal plate. Therefore, for the first mechanism to occur, it is preferable that the edges are of a certain length. Based on this and the inventors' research results, the portion of the thin-film conductive layer with a width W1 of 0.25 mm or more can be defined as the metal plate. When multiple W1 values ​​are available in a certain metal plate, the largest value can be defined as the W1 of that metal plate. By setting W1 within a range of approximately 0.25 mm to 4 mm, electromagnetic waves in the frequency band above 15 GHz and below 150 GHz can be attenuated. The relationship between the frequency of the attenuated electromagnetic waves and the width of the metal plate is as follows: Figure 53 As shown, this is represented as a straight line on a graph with each element as a logarithm. That is, the frequency of the attenuated electromagnetic wave is a power function of the width of the metal plate. The power of this function is approximately -1, roughly inversely proportional.

[0116] The multiple metal plates contained in the thin-film conductive layer can be configured with various sizes of metal plates W1. In this case, the attenuation peaks of the various electromagnetic waves overlap, which can widen the bandwidth of the electromagnetic waves that can be attenuated.

[0117] The second mechanism involves the confinement of the electromagnetic field by the thin-film conductive layer 30 and the planar inductor 50. In the electromagnetic wave attenuation film 1, the dielectric substrate 10 is sandwiched between the thin-film conductive layer 30 and the planar inductor 50 in the first region 121. Therefore, the electric field generated in the dielectric substrate 10 of the electromagnetic wave attenuation film 1 due to electromagnetic waves is confined within the dielectric substrate 10 between the thin-film conductive layer 30 containing the metal plate and the planar inductor 50 due to the charge and current of the metal plate. That is, the metal plate suppresses the electromagnetic field and confines it within the dielectric substrate 10. In other words, the metal plate can function as a choke. In other words, the metal plate can be a choke plate that functions as a choke.

[0118] Furthermore, it is believed that the periodic variation of the confined electric field can also induce magnetic flux in the first region. This leads to the accumulation of the oscillating electromagnetic field in the first region, increasing its energy density. Generally, higher energy density results in easier attenuation; therefore, this mechanism can effectively attenuate electromagnetic waves. In the second mechanism, the higher the dielectric loss tangent of the dielectric substrate 10, the greater the energy loss of the electromagnetic field accumulated within the dielectric substrate. Additionally, the magnetic field accumulated in the dielectric substrate, accompanied by a large current on the metal plate, generates a large potential difference in the electric field accumulated in the dielectric substrate. The large current and large potential difference increase the power loss, which is their product. This power loss consumes the energy of the electromagnetic wave, resulting in electromagnetic wave attenuation.

[0119] The third mechanism involves power loss in a circuit comprising a capacitor formed by opposing thin-film conductive layers 30, a planar inductor 50, and a dielectric substrate 10 between them. In the electromagnetic wave attenuation film 1, the dielectric substrate 10 is sandwiched between the thin-film conductive layer 30 and the planar inductor 50 in either the first region 121 or the second region 122. Therefore, the first region 121, the second region 122, and the dielectric substrate 10 function as a capacitor. Consequently, electromagnetic waves incident on the dielectric substrate 10 of the electromagnetic wave attenuation film 1 are attenuated by the circuit containing the capacitor.

[0120] The larger the capacitance of a capacitor, the more charge it stores, and thus the more energy it stores. Therefore, the larger the capacitance, the better it can handle high energy.

[0121] The capacitance is inversely proportional to the thickness of the dielectric substrate 10; therefore, from this perspective, a thinner dielectric substrate 10 is preferable. Furthermore, the distance between the thin-film conductive layer 30 and the planar inductor 50 is determined by the thickness of the dielectric substrate 10; therefore, the resistance between the thin-film conductive layer 30 and the planar inductor 50 is proportional to the thickness of the dielectric substrate 10. When the resistance of the dielectric substrate 10 is low, the leakage current in the dielectric substrate 10 increases, and the current flowing in the circuit of the capacitor including the thin-film conductive layer 30 and the planar inductor 50 increases. Therefore, power loss due to leakage current is easily increased, and electromagnetic wave energy is easily absorbed due to power loss. Furthermore, in the electromagnetic wave attenuation film 1 of the embodiment of the present invention, even if the thickness of the dielectric substrate 10 at the location where the metal plate is disposed is changed, the wavelength of the attenuated electromagnetic field will not shift; therefore, the thickness of the dielectric substrate 10 can be designed according to the characteristics of the circuit including the capacitor.

[0122] As described above, electromagnetic waves incident on the electromagnetic wave attenuation film 1 generate an electromagnetic field in the dielectric substrate 10 near the surface of the planar inductor through a first mechanism, and are trapped by a second mechanism. Thus, the electromagnetic wave attenuation film 1 can capture electromagnetic waves. The captured electromagnetic waves are attenuated due to electric field losses and power losses caused by the second mechanism, and power losses caused by the circuitry in the third mechanism. Furthermore, by providing the top coating layer 200, which matches the air impedance of the propagating electromagnetic waves, the electromagnetic waves can be effectively attenuated for the thin-film conductive layer. Figure 53 As shown, the wavelength of the attenuated electromagnetic wave can be changed by altering the size W1 of the metal plate. More specifically, as... Figure 53 In this way, the frequency at which the reflected wave becomes extremely small, i.e., the frequency at which the attenuation becomes extremely large, exhibits a very high degree of approximation to the power of the size of the metal plate. Therefore, the electromagnetic wave attenuation characteristics can be set with a high degree of freedom and simplicity in the electromagnetic wave attenuation film 1. Therefore, it is also easy to set it to capture linearly polarized, circularly polarized, or elliptically polarized electromagnetic waves in the frequency band above 15 GHz and below 150 GHz.

[0123] exist Figure 53 In the simulation, the metal plate is square, and W1 is the length of one side.

[0124] The dielectric substrate of the electromagnetic wave attenuation film 1 in the first embodiment has a first region 121 and a second region 122, at least a portion of the side surface 122a of the second region 122 is exposed and not covered by the thin film conductive layer 30. As a result, the area where electromagnetic waves can be incident can be easily increased without increasing the planar view area of ​​the electromagnetic wave attenuation film, thereby effectively capturing and attenuating electromagnetic waves.

[0125] In the electromagnetic wave attenuation film 1 of the first embodiment, the thin film conductive layer 30 on the second region 122, which serves as a support cage, mainly improves the attenuation of electromagnetic waves by enhancing the second and third mechanisms.

[0126] Furthermore, in the inventor's research, it is believed that the electric field becomes stronger at the periphery of the metal plate, and a potential is also generated in the support cage near the periphery.

[0127] Figure 4 The simulation results of the electric field strength without the support cage are shown. Figure 5 The simulation results of the electric field strength with a supporting cage are shown. Figure 4 and Figure 5 In (b), the periphery of the metal plate in (a) is enlarged, and the metal plate is labeled with symbol A and the support cage with symbol B.

[0128] Compare Figure 4 (b) and Figure 5 (b) It can be seen that, in Figure 5 In (b), the electric field strength at the periphery of the metal plate becomes stronger. That is, it is believed that the potential generated in the support cage contributes to further increasing the power loss in the first mechanism.

[0129] In the electromagnetic wave attenuation film 1, the third mechanism also plays a crucial role. When an electric field is generated in the dielectric substrate 10, the electromagnetic field is confined beneath the metal plate. That is, a high-energy-density electromagnetic field is generated beneath the metal plate. It is believed that the confined electromagnetic field is attenuated through power losses generated by the second mechanism and dielectric losses from the third mechanism.

[0130] In the inventors' research, it has been found that the attenuation generated by the first mechanism varies depending on the admittance (reciprocal of resistance) of the metal constituting the metal plate. Good electromagnetic wave attenuation is achieved when the admittance (siemens / m) is above 10 million. Silver is known to be the material with the highest admittance among conventional conductors, with an admittance of 61–66 × 10⁻⁶. 6 Therefore, the upper limit of admittance is approximately 70 million. Metals with admittances between 5 million and 70 million can be used. The metal constituting the metal plate can be a strongly magnetic, paramagnetic, diamagnetic, or antimagnetic material. Examples of strongly magnetic metals are nickel, cobalt, iron, or their alloys. Examples of paramagnetic metals are aluminum, tin (β-tin), or their alloys. Examples of diamagnetic metals are gold, silver, copper, tin (α-tin), zinc, or their alloys. An example of an antimagnetic alloy is brass, an alloy of copper and zinc. An example of an antimagnetic metal is chromium. Metal plates made of these metals exhibit good electromagnetic wave attenuation.

[0131] On the other hand, in this invention, the surface of the metal plate can also be oxidized, nitrided, or nitrided. The metal oxide or metal nitride on the surface of the metal plate can be formed through surface treatment. Surface treatment can be chemical treatment using chemicals, heat treatment, or both. Additionally, an oxide film can be present within the metal plate, or a layer composed of a mixture of metal and metal oxides can be formed. In such a configuration, the resistance of the metal plate increases, the voltage drop increases, and the power loss increases, thereby improving the attenuation of electromagnetic waves.

[0132] In addition, the metal plate 30A can be a multilayer film made by laminating films of different materials. The materials of the laminated films can be conductors or insulators.

[0133] An example of the manufacturing steps of electromagnetic wave attenuation film 1 will be described.

[0134] First, a dielectric substrate 10 is formed. When a resin forming the irregularities is layered on a carrier 11, and a first region and a second region are formed on the surface, the dielectric substrate 10 having a base layer 12 is completed. The resin forming the base layer 12 can be a photosensitive resin. In this case, photolithography can be used. The photosensitive resin can be a negative resist or a positive resist. The base layer 12 can also be formed from a photocurable resin. The base layer 12 can also be formed from a thermoplastic resin. In this case, thermal transfer can be used. The base layer 12 can also be formed from a thermosetting resin. The resin can be a solvent-soluble resin (oil-based ink). Alternatively, the resin can be a water-soluble resin (water-based ink).

[0135] Next, a thin-film conductive layer 30 and a planar inductor 50 are formed on the front side 10a and back side 10b of the dielectric substrate 10, respectively. The thin-film conductive layer 30 and the planar inductor 50 can be formed by physical deposition. Physical deposition can be evaporation or sputtering. Either the thin-film conductive layer 30 or the planar inductor 50 can be formed first, and their materials can be different. Furthermore, the planar inductor 50 can be any of a casting, a rolled metal sheet, a metal foil, an evaporated film, a sputtered film, or a coated film. The casting can be made of cast iron or an aluminum alloy. The rolled metal sheet can be made of steel, stainless steel, aluminum, or an aluminum alloy. The plating can be electrolytic plating or electroless plating. The plating can be copper plating, electroless nickel plating, electrolytic nickel plating, zinc plating, electrolytic chromium plating, or a layer thereof.

[0136] It is important that the metal plate and the portion thereof in the thin-film conductive layer 30 are not connected. When they are connected, the aforementioned width W1 changes, and the attenuation of electromagnetic waves may differ from what is intended. Therefore, an additional step of removing the thin-film conductive layer 30 formed on the side of the second region can be added. This step can be performed using laser etching or the like.

[0137] When setting the top coating layer 200, there are no particular restrictions on the coating method; any appropriate method can be selected from those used in film manufacturing. Examples of coating methods include gravure coating, reverse coating, gravure-reverse coating, mold coating, and flow coating.

[0138] In the above manufacturing steps, the carrier 11 can be peeled off after the base layer 12 is formed. In this way, a single-layer dielectric substrate consisting only of the base layer 12 is formed.

[0139] As another example of the manufacturing process, a thin-film conductive layer 30 and a planar inductor 50 may be formed on a dielectric substrate, and then an uneven shape may be formed on the side of the thin-film conductive layer 30. In this case, a printing plate transfer is preferably used. In the case of thermal transfer, the printing plate is pressed against the thin-film conductive layer 30 and heated.

[0140] In this manufacturing step, the thin conductive layer 30, pressed by the printing plate, stretches and easily becomes connected to the metal plate and other parts. As a way to eliminate this situation, besides the laser etching described above, methods involving the shape of the printing plate can be employed. For example, if the periphery of the protrusion forming the first region is sharply formed in the printing plate, then when the printing plate is pressed against the thin conductive layer 30, the periphery of the metal plate is cut off. This ensures that the metal plate does not connect to other parts during transfer.

[0141] Reference Figures 6 to 9 The second embodiment of the present invention will be described. In the following description, common components as described above are marked with the same symbols and repeated descriptions are omitted. It is believed that the first, second, and third mechanisms described above are also present in the second embodiment.

[0142] Figure 6 and Figure 7 The electromagnetic wave attenuation film 61 of the second embodiment is shown. Figure 6 To illustrate a schematic plan view of the electromagnetic wave attenuation film according to the second embodiment of the present invention, Figure 7 To show Figure 6 A schematic diagram of a portion of the cross-section of line II-II. Additionally, Figure 8 To illustrate when a top coating is applied Figure 6 A schematic diagram of a portion of the cross section of line II-II.

[0143] The electromagnetic wave attenuation film 61 comprises a dielectric substrate 62, multiple metal plates 30A, and a planar inductor 50. The thickness of the metal plates 30A can be set to less than 1000 nm.

[0144] The dielectric substrate 62 of the second embodiment can be made of the same material and structure as the dielectric substrate of the first embodiment. The dielectric substrate 62 can be composed of a substrate layer provided on the carrier 11, or it can be composed of only the carrier 11. Both the front surface 62a and the back surface 62b are flat or rough surfaces. A planar inductor 50 is provided on the back surface 62b, but an adhesive layer can also be provided between the back surface 62b and the planar inductor 50. The adhesive layer and the planar inductor 50 can be formed using the same material and the same manufacturing method as in the first embodiment. A plurality of metal plates 30A are disposed on the front surface 62a side. The metal plates 30A can be formed by etching after being formed by a deposition method. The deposition method can be physical deposition or chemical deposition. Physical deposition is suitable for the formation of the metal plates. Physical deposition can be vacuum evaporation or sputtering. Vacuum evaporation has high productivity and is preferred. The metal plate can be formed by printing a mask layer in the shape of a metal plate in a pattern, and then removing the excess thin film conductive layer by etching. The etching solution used for etching can be a sodium hydroxide solution. The concentration of the sodium hydroxide solution can be set to between 0.001 mol / L and 1 mol / L. The metal of the metal plate 30A can be the same metal as in the first embodiment. The metal plates are discretely arranged. The attenuation center frequency is expressed as a power function of the width of the metal plate. Multiple metal plates 30A can be of the same shape and size and arranged at certain intervals. In other words, two or more metal plates 30A of the same shape and size can also be arranged at certain intervals. That is, the entire front 62a is not covered by a metal layer, and the dielectric substrate 62 is exposed in the areas where no metal plate 30A is arranged.

[0145] Alternatively, multiple metal plates 30A of the same shape and size as the individual metal plates 30A in a plurality of metal plates 30A that differ in shape, size, or both can be configured. In other words, multiple metal plates of different shapes and sizes can be configured, as can multiple metal plates of the same shape and size. The configuration of the metal plates can be set to a certain interval and a certain direction. Alternatively, the intervals can be different and the directions can also be different. Furthermore, the intervals can be different but the directions can be the same. Alternatively, a portion of the intervals can be fixed and a portion of the directions can be the same. In addition, multiple metal plates of different shapes and sizes can be used as a metal plate group. The configuration intervals of the metal plates constituting the metal plate group can be all or partly fixed, or all different. The directions of the metal plates constituting the metal plate group can be all or partly constant, or all different. In a metal plate group having multiple metal plates of different shapes and sizes, the spectrum of the attenuation frequency of each metal plate can be different to attenuate multiple frequency bands, or the attenuation frequency can be broadbanded. In addition, when the configuration intervals of the metal plates are different, the spectrum of the attenuation frequency can also be different. When the directions of the metal plate group are different, the dependence of the polarization wave of the attenuation can be different. The multiple metal plates that make up the metal plate group each have different attenuation frequencies, and the difference in their frequencies can be regular.

[0146] Multiple metal plate assemblies can also be configured. Multiple metal plate assemblies can also be configured, consisting of metal plates with the same shape, size, and arrangement as the metal plates constituting a particular metal plate assembly. By including multiple different metal plates in the thin-film conductive layer, broadbanding, attenuation of multiple frequencies of electromagnetic waves, or both, can be achieved.

[0147] The metal plate can be divided into multiple metal segments. In other words, the metal plate can be composed of multiple metal segments. These multiple metal segments within the metal plate can be electrically connected. These multiple metal segments can be connected via wiring. The wiring can have impedance. This impedance can be matched to the metal segments. The wiring and the multiple metal segments within the metal plate can function as a whole. The multiple metal segments can have properties different from when they exist individually. Specifically, the resonant frequency and attenuation may differ depending on whether they exist individually or within the metal plate. Furthermore, the cross-sectional shape of the metal plate can be planar, polyhedral, or curved. In the case of a polyhedron or curved surface, the distance between its bottom and top, i.e., its height, can be set to 50 μm or less. Additionally, the ratio of this height to the distance between opposite edges of the metal plate can be set to 1:100 or more and 1:10 or less.

[0148] The attenuation property of the electromagnetic wave attenuation film in the second embodiment can be set by changing the width W1 of the metal plate in the same way as in the first embodiment, and it is also easy to set it in a way that captures linearly polarized electromagnetic waves in the frequency band of 15 GHz and above to 150 GHz.

[0149] Furthermore, since the carrier 11 of the plastic film can be directly used as the dielectric substrate 62, the electromagnetic wave attenuation film of the second embodiment can be manufactured more easily than the electromagnetic wave attenuation film involved in the first embodiment.

[0150] Alternatively, a carrier with a rough surface on part or all of the front 62a and back 62b can be used as the dielectric substrate 62. By making part or all of the front 62a rough, the admittance of the metal plate 30A can be adjusted.

[0151] In the prior art, including Patent Document 5, it is believed that by making the resonant conductor thicker than the skin depth, sufficient alternating current is generated in the resonant layer, thereby attenuating electromagnetic waves through the power loss of this alternating current. However, the inventors have discovered that when the thickness of the metal plate 30A is less than the skin depth, the attenuation of electromagnetic waves actually increases.

[0152] Figure 9 The simulation results of electromagnetic wave attenuation caused by the thickness variation of metal plate 30A are shown. The metal plate is made of aluminum. The incident wave is a linearly polarized sinusoidal wave, incident perpendicularly to the electromagnetic wave attenuation film. It should be noted that in the simulation, the planar inductor is considered a perfectly conductive conductor. The attenuation of the electromagnetic wave as the electromagnetic wave attenuation film is expressed using the monostable RCS (Rader Cross-Section) as a reference for the case with only the planar inductor. It should be noted that the vertical axis representing the electromagnetic wave attenuation is expressed in decibels (dB). The monostable RCS is an indicator of the ease with which an object can be detected using monostable radar, and can be calculated using Equation 1. It should be noted that the monostable radar transmits and receives signals at the same location.

[0153] [Mathematical Expression 1]

[0154]

[0155] in,

[0156] |Er|: Incident electric field intensity

[0157] |Ei|: Received scattered electric field intensity

[0158] R: Distance between the target and the radar

[0159] The simulation results are as follows Figure 9 As shown, significant attenuation of electromagnetic waves was observed when the thickness was between 40 nm and 400 nm. Conversely, attenuation of electromagnetic waves was observed to decrease when the thickness was less than 40 nm.

[0160] It should be noted that if the thickness of the metal plate 30A formed by combining the conductive layer and the cladding layer is less than 1000 nm, it can be stably film-formed.

[0161] It can be seen that, Figure 9 The observed phenomenon has an interesting relationship with skin depth. At 41 GHz, the skin depth of aluminum is approximately 400 nm. That is, when the thickness of the metal plate is less than the skin depth of the material, the attenuation of electromagnetic waves increases. Furthermore, when the thickness is less than 1 / e of the skin depth... 2 At this point, the attenuation of electromagnetic waves decreases. This is believed to be because, when the conductive layer is thicker than the skin depth, sufficient resistance cannot be obtained, the voltage drop required for power loss cannot be achieved, and the current is concentrated only near the center of the metal plate, thus reducing the current in the region where a potential difference is generated. On the other hand, even if the thickness of the conductive layer is less than the skin depth, when it is less than 1 / e of the skin depth... 2 At that time, sufficient current cannot be obtained for power loss. It should be noted that, needless to say, power loss is the product of current and voltage. That is, if sufficient electromagnetic wave attenuation is obtained within the range of Equation 2 of the following Ln function, which is expressed as the natural logarithm of the value of the metal plate thickness T normalized to the skin depth d.

[0162] -2≤ln(T / d)≤0…(2)

[0163] Furthermore, when using a metal with low admittance in the metal plate, electromagnetic wave attenuation can be achieved even within the range of Formula 3 below. Additionally, when the area of ​​the metal plate occupies a large proportion of the front surface of the dielectric substrate, electromagnetic wave attenuation can be achieved even within the range of Formula 3 below. In the case of such a large area, the proportion of the metal plate area to the front surface of the dielectric substrate can be set to 50% or more and 90% or less.

[0164] 0<ln(T / d)≤1…(3)

[0165] According to equations 1 and 2, the attenuation of electromagnetic waves can be obtained within the range of equation 4 below.

[0166] -2≤ln(T / d)≤1…(4)

[0167] It should be noted that, in the embodiments of the present invention, the epidermal depth can be calculated using the attenuation center frequency f. That is, when using the attenuation center frequency f, the epidermal depth d is calculated by the following formula 5 as is known.

[0168] [Mathematical Expression 2]

[0169]

[0170] in,

[0171] ρ = resistivity of the metal plate

[0172] ω = angular frequency of the current = 2π × decay center frequency f

[0173] μ = Absolute permeability of the metal plate

[0174] Furthermore, in the simulation results, the attenuation increased when the thickness of the metal plate was thinner than the skin depth. This is believed to be because the current generated by the magnetic flux of the dielectric substrate of the metal plate also reaches the opposite side of the dielectric substrate. This current emits electromagnetic waves that cancel out the reflected waves generated by the dielectric inductor, with a phase shift of π. Additionally, it is believed that as the thickness of the metal plate becomes thinner than the skin depth, the current in the metal plate is restricted. As a result, a magnetic field is generated not only near the center of the metal plate but also throughout the entire region of the metal plate. The current induced by this magnetic field also occurs throughout the entire region of the metal plate, increasing the emission of electromagnetic waves that cancel out the reflected waves generated by the dielectric inductor, thus further attenuating the reflected waves.

[0175] Furthermore, the electric field of the dielectric substrate between the metal plate and the dielectric inductor attracts both the metal plate and the inductor. When the electric field changes periodically, the force attracting the metal plate also changes periodically. Therefore, the electric field of the dielectric substrate between the metal plate and the inductor causes the metal plate to vibrate. The energy of this vibration is converted into heat and lost. Therefore, it is believed that the force of the electromagnetic field acting on the metal plate also contributes to the attenuation of electromagnetic waves.

[0176] Furthermore, when the non-traveling periodic variations of the electromagnetic field are captured as quanta, the state of being bound by the electromagnetic field and having the quanta captured can be considered as a state with zero momentum. In addition, since the thickness of the metal plate is on the order of hundreds of nm, it is believed that it may also affect the energy levels within the metal plate.

[0177] Thus, the phenomena observed in the embodiments of the present invention can be explained not only by classical electromagnetism, but also by classical mechanics or quantum mechanics.

[0178] Therefore, while Equation 4 reasonably defines this range, it is not a strictly calculated range that considers all physical phenomena. Thus, when determining whether a product falls within the range of the above equation, it is appropriate to consider and interpret the observed physical phenomena.

[0179] It should be noted that in conventional technologies, examples of using conductors that are thinner than the skin depth are not commonly seen. Therefore, it is believed that the implementation of the present invention differs from previous methods in its interaction mechanism with electromagnetic waves in the millimeter-wave band.

[0180] Regarding a specific frequency band, the relationship between the thickness of the metal plate representing the preferred electromagnetic wave attenuation and the skin depth will be explained in detail in the embodiments involved in the second embodiment described later.

[0181] The embodiments of the present invention will be further described using examples.

[0182] (Examples related to the first implementation method)

[0183] First, a master template for nickel electroforming was prepared. A photoresist pattern was formed on the surface of a silicon wafer using photolithography. The photoresist used was positive, and the film thickness was 10 μm. The resulting photoresist pattern was as follows: in the XY coordinate system, within a square region with one side measuring 14 cm, square openings were positioned at coordinates where both the X and Y coordinates were arranged in a periodic square grid. The area exposed by the i-line was the inner region of this square.

[0184] Furthermore, using this master template for nickel electroforming, a nickel mold was obtained with a pattern of protrusions on the surface regularly arranged in planar views of squares.

[0185] Next, UV-curable resin is dropped onto the patterned surface of the nickel mold, and the easy-to-bond side of the PET film, which has been treated with an easy-to-bond coating on one side, is placed on the UV-curable resin. The UV-curable resin is then spread evenly on the patterned surface using a roller, and UV light is irradiated through the transparent PET film to cure the UV-curable resin.

[0186] The PET film was demolded from the nickel mold, resulting in a textured layer made of UV-curable resin and a dielectric portion made of PET film.

[0187] A 500 nm thick Al film was formed on both sides of a dielectric substrate using vacuum evaporation, thus creating a thin-film conductive layer and a planar inductor.

[0188] The above describes the manufacturing steps of the embodiment according to the first embodiment. In this step, multiple nickel molds are made to change the parameters of the uneven layer surface, thereby producing the electromagnetic wave attenuation film of Examples 1 to 3.

[0189] The electromagnetic wave attenuation films involved in each embodiment are all about 60 μm thick and weigh about 0.02 g, which are thin and light.

[0190] (A variation of the first embodiment that includes a top coating layer)

[0191] In the embodiment of the first implementation, an electromagnetic wave attenuation film is produced by providing a top coating 200 manufactured through the following steps.

[0192] An acrylic resin composition comprising 80 parts by weight of methyl methacrylate monomer and 20 parts by weight of cyclohexyl methacrylate is used as the main component. The solid content of this acrylic resin composition is set at 100 parts by weight. To this composition, 6 parts by weight of a hydroxyphenyltriazine UV absorber (ADK STAB LA-46 manufactured by ADEKA Co., Ltd.), 6 parts by weight of other hydroxyphenyltriazine UV absorbers (Tinuvin 479 manufactured by Ciba Specialty Chemicals Corp.), 3 parts by weight of a benzotriazole UV absorber (Tinuvin 329 manufactured by Ciba Specialty Chemicals Corp.), and 5 parts by weight of a hindered amine free radical supplement (Tinuvin manufactured by Ciba Specialty Chemicals Corp.) are added. 292”), further mixing a main agent solution with a solid content of 33 parts by mass obtained by adding ethyl acetate solvent for solid component adjustment, and a hexamethylene diisocyanate type curing agent solution with a solid content of 75 parts by mass obtained by adding ethyl acetate solvent for solid component adjustment, so that the ratio of the main agent solution to the curing agent solution is 10:1 (at this time, the ratio of the number of hydroxyl groups in the main agent solution to the number of isocyanate groups in the curing agent solution is 1:2), and further coating the coating liquid with a solid content of 20 parts by mass adjusted by adding ethyl acetate as a solvent to achieve a thickness of 6 μm after solvent evaporation, thereby obtaining the top coating 200. The prepared electromagnetic wave attenuation film has a thickness of about 70 μm and a weight of about 0.02 g, which is thin and light.

[0193] (Examples related to the second implementation method)

[0194] [27GHz~34GHz]

[0195] (Example 1A)

[0196] For the general theory described in Equation 4, the range of the preferred relationship between the thickness T of the metal plate and the skin depth d, which represents the electromagnetic wave attenuation, can be found in a specific frequency band in the millimeter wave band. This will be explained below.

[0197] The simulations performed in the 27 GHz to 34 GHz frequency band are described. A PET film with a thickness (H1) of 50 μm was used as the dielectric substrate, and a metal plate as a thin-film conductive layer was set on one side of the film at certain intervals in both the X and Y coordinates. Furthermore, an aluminum plate inductor with a thickness (T2) of approximately 2 mm was set on the other side of the dielectric substrate, and simulations were performed.

[0198] For frequencies of 27GHz, 28GHz, 31GHz, and 34GHz, simulations were performed based on the relationship between the attenuation of electromagnetic waves by each metal type and Ln(T1 / d).

[0199] Through Table 1, Table 2 and Figures 10 to 13 To illustrate the results of the simulation. Figure 10 A graph showing the electromagnetic wave attenuation characteristics at 27 GHz in Example 1A. Figure 11 A graph showing the electromagnetic wave attenuation characteristics at 28 GHz in Example 1A. Figure 12 A graph showing the electromagnetic wave attenuation characteristics at 31 GHz in Example 1A. Figure 13 A graph illustrating the electromagnetic wave attenuation characteristics at 34 GHz for Example 1A is provided. Figures 10-13 In the figure, (a) represents the values ​​of admittance and skin depth, (b) represents the composition of the electromagnetic wave attenuation film, and (c) to (e) represent the attenuation characteristics of silver, copper, and aluminum, respectively. The graph is as follows: the natural logarithm of the normalized value of the metal plate thickness T1 with skin depth d is used as the horizontal axis, and the attenuation in the patterned metal plate with the reflectance of the metal plate of the same area as the dielectric substrate set to 100 (reference) is used as the vertical axis, and the relationship between the two is shown in the figure.

[0200] [Table 1]

[0201]

[0202] [Table 2]

[0203] W1(mm) 3.05 2.9 2.7 2.4 W3(mm) 1.57 1.49 1.39 1.24

[0204] When an absorption of 10 dB or more is considered a standard for good attenuation of electromagnetic wave attenuation films, as shown in Table 1 and... Figures 10 to 13 It is evident that the electromagnetic wave attenuation film satisfying -1.0≤ln(T1 / d)≤0.0 in the frequency band of 27GHz to 34GHz achieved good attenuation.

[0205] It should be noted that the good attenuation characteristics of around 10dB are not limited to the values ​​of the parameters used in Example 1A. Of course, it is expected that this can be achieved in a configuration with a certain width. For example, a configuration in which the width W1 of the metal plate is 2.4mm to 3mm, the distance W3 between adjacent metal plates is 1.2mm to 1.5mm, the thickness H1 of the dielectric substrate is 5μm to 300μm, and the thickness T2 of the planar inductor is 0.5μm to 5mm can also be expected to have good attenuation characteristics of around 10dB.

[0206] (Example 1B)

[0207] Similar to Example 1A, a dielectric substrate was prepared by varying the ratio of the total area of ​​the metal plates serving as the thin-film conductive layer to the total area of ​​the XY plane of the dielectric substrate on one side of a PET film with a thickness (H1) of 50 μm. Furthermore, an aluminum plate inductor with a thickness (T2) of approximately 2 mm was prepared on the other side of the dielectric substrate for simulation. Aluminum was used as the metal plate, with a width W1 set to 2.9 mm and a thickness T1 set to 297.6 nm. The ratio of the metal area was changed by adjusting the distance W3 between the metal plates.

[0208] Through Table 3 and Figure 14 To illustrate the results of the simulation. Figure 14 A graph showing the electromagnetic wave attenuation characteristics corresponding to the proportion of the metal area at 28 GHz in Example 1B is provided. (a) shows the composition of the electromagnetic wave attenuation film, and (b) shows the attenuation characteristics.

[0209] [Table 3]

[0210] W3(mm) 26.10 10.07 6.27 3.58 2.39 1.69 1.20 0.84 0.57 0.34 0.16 Absorption -0.3 -1.4 -3.5 -10.0 -15.0 -23.0 -21.2 -14.0 -10.0 -5.4 -9.9

[0211] When an absorption of 10 dB or more is considered a standard for good attenuation of electromagnetic wave attenuation films, as shown in Table 3 and... Figure 14 As shown, in Example 1B, a good attenuation was obtained when the proportion of metal area was 20% or more.

[0212] (Example 1C)

[0213] Similar to Example 1A, as a dielectric substrate, on one side of a PET film with a thickness (H1) of 50 μm, a dielectric substrate is formed with... Figure 6 The same pattern arrangement was used as a metal plate for the thin-film conductive layer, but its shape was changed to a shape other than a square. Furthermore, an aluminum plate inductor with a thickness (T2) of approximately 2 mm was placed on the other side of the dielectric substrate, and the attenuation characteristics of electromagnetic waves were simulated. Aluminum was used as the metal plate, and the thickness T1 was set to 297.6 nm.

[0214] [Circle]

[0215] Figure 15 A graph illustrating the electromagnetic wave attenuation characteristics when the metal plate is circular in Example 1C. (a) represents the shape of the metal plate, and R1 represents the radius of the circle. (b) represents the electromagnetic wave attenuation characteristics of the plate in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of the II-II lines, where W4 represents the distance between the centers of the circles. (d) The dimensions of R1 and W4 are shown. (e) The attenuation characteristics are shown with frequency as the horizontal axis.

[0216] According to simulation results, it exhibits good attenuation characteristics with an absorption of more than 10dB near 28.8GHz.

[0217] [rectangle]

[0218] Figure 16 A graph illustrating the electromagnetic wave attenuation characteristics of a rectangular metal plate in Example 1C is provided. (a) shows the shape of the metal plate, where W7 represents the length of the long side of the rectangle and W8 represents the length of the short side. (b) shows the shape of the metal plate in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of lines II-II, where W4 represents the distance between the centers of the rectangles. (d) The dimensions of W7, W8, and W4 are shown. (e) The attenuation characteristics are shown with frequency as the horizontal axis.

[0219] According to simulation results, it exhibits good attenuation characteristics with an absorption of more than 10dB near 28.8GHz.

[0220] [hexagon]

[0221] Figure 17 A graph illustrating the electromagnetic wave attenuation characteristics of a hexagonal metal plate in Example 1C is provided. (a) shows the shape of the metal plate, where W9 represents the length of one side of the hexagon. (b) shows the length of the plate passing through the metal plate in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of the II-II lines, where W4 represents the distance between the centers of the hexagons. (d) The dimensions of W9 and W4. (e) The attenuation characteristics with frequency as the horizontal axis.

[0222] According to simulation results, it exhibits good attenuation characteristics with an absorption of more than 10dB near 31GHz.

[0223] [Convex shape]

[0224] Figure 18A graph illustrating the electromagnetic wave attenuation characteristics of a convex metal plate in Embodiment 1C is shown. (a) shows the shape of the metal plate. W10 represents the length of the upper edge of the upper part of the inner protrusion of the convex shape, W11 represents the length of the lower edge of the lower part of the convex shape, W15 represents the length of the side edge of the upper part, and W16 represents the length of the side edge of the lower part. The convex shape is symmetrical about the left and right with respect to the straight line connecting the midpoint of the upper edge of the upper part and the lower edge of the lower part. In addition, the lower edge of the lower part and the left and right sides of the lower part are in contact with the upper edge of the upper part, and the center of the rectangle surrounding the convex shape is taken as the center of this convex shape. (b) shows the shape of the metal plate in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of the II-II lines, where W4 represents the distance between the centers of the convex shapes. (d) The dimensions of W10, W11, W15, W16, and W4 are shown. (d) The attenuation characteristics are shown with frequency as the horizontal axis.

[0225] According to simulation results, it exhibits good attenuation characteristics with an absorption of more than 10dB near 30.6GHz.

[0226] [triangle]

[0227] Figure 19 A graph illustrating the electromagnetic wave attenuation characteristics of a triangular metal plate in Example 1C is provided. (a) shows the shape of the metal plate, where W12 represents the length of one side of the equilateral triangle. (b) shows the length of the metal plate passing through the triangle in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of the II-II lines, where W4 represents the distance between the centers of the triangles. (d) The dimensions of W12 and W4. (e) The attenuation characteristics with frequency as the horizontal axis.

[0228] According to simulation results, it exhibits good attenuation characteristics with an absorption of more than 10dB near 30.2GHz.

[0229] [Cross shape]

[0230] Figure 20 A graph illustrating the electromagnetic wave attenuation characteristics of a cross-shaped metal plate in Embodiment 1C is provided. (a) shows the shape of the metal plate. The cross shape is symmetrical vertically and horizontally, and also symmetrical with respect to a 90-degree rotation. W13 represents the length of the opposite sides of the outer edge of the cross, and W14 represents the length of one side of the square that surrounds the cross shape and contacts the opposite sides of the outer edge. The center of this square is taken as the center of the cross shape. (b) shows the electromagnetic wave attenuation characteristics of the cross-shaped metal plate in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of lines II-II, where W4 represents the distance between the centers of the crosses. (d) The dimensions of W13, W14, and W4 are shown. (d) The attenuation characteristics are shown with frequency as the horizontal axis.

[0231] According to simulation results, it exhibits good attenuation characteristics with an absorption of more than 10dB near 32GHz.

[0232] (Example 1D)

[0233] A square PET film with a thickness of 50 μm and a side length of 14 cm was prepared as the dielectric substrate. A 100 nm thick aluminum thin-film conductive layer was formed on one side of the dielectric substrate using vacuum evaporation. Then, using a mask, the thin-film conductive layer was etched to form a metal plate with certain intervals in both the X and Y coordinates. An aluminum planar inductor was then attached to the other side using an adhesive layer. Simulations were performed using this configuration.

[0234] The above describes the manufacturing steps of Example 1D according to the second embodiment. The parameters of Example 1D are as follows.

[0235] The width W1 of the metal plates ranges from 2.236 mm to 3.481 mm. Sixteen different types of metal plates, with widths increasing in increments of 0.083 mm, are to be arranged in a 4×4 matrix at 0.1 mm intervals and in the same direction, forming metal plate groups. Multiple such metal plate groups are arranged at 0.1 mm intervals and in the same direction. Furthermore, all metal plate groups are to be identical; that is, the metal plates constituting each metal plate group are identical.

[0236] The distance W3 between adjacent metal plates is 0.1 mm.

[0237] Thickness T1 of the metal plate: 297.6 nm

[0238] The thickness T2 of the planar inductor is approximately 2mm.

[0239] Thickness H1 of dielectric substrate: 50 μm

[0240] In addition, simulations were performed using this configuration to investigate the validity of the attenuation mechanism in the experimental results.

[0241] The electromagnetic wave attenuation films involved in the embodiments excluding planar inductors are all approximately 60 μm thick and weigh approximately 0.02 g, making them thin and lightweight. Therefore, they can be easily attached to components within the frames of mobile phones, automotive radars, etc., where it is desired to suppress the effects of radiated noise caused by electromagnetic waves.

[0242] In the simulation, Examples 1A to 1D all showed good attenuation of electromagnetic waves in the millimeter wave band. Figure 21 The simulation results of Example 1D are shown.

[0243] (A variation of Embodiment 1A in the second embodiment, in which a top coating layer is provided)

[0244] In Embodiment 1A of the second embodiment, an electromagnetic wave attenuation film is produced by applying a top coating 200 manufactured by the following steps to a metal plate using aluminum and with a metal plate thickness T1 set to 298 nm.

[0245] An acrylic resin composition comprising 80 parts by weight of methyl methacrylate monomer and 20 parts by weight of cyclohexyl methacrylate is used as the main component. The solid content of this acrylic resin composition is set at 100 parts by weight. To this composition, 6 parts by weight of a hydroxyphenyltriazine UV absorber (ADK STAB LA-46 manufactured by ADEKA Co., Ltd.), 6 parts by weight of other hydroxyphenyltriazine UV absorbers (Tinuvin 479 manufactured by Ciba Specialty Chemicals Corp.), 3 parts by weight of a benzotriazole UV absorber (Tinuvin 329 manufactured by Ciba Specialty Chemicals Corp.), and 5 parts by weight of a hindered amine free radical supplement (Tinuvin manufactured by Ciba Specialty Chemicals Corp.) are added. 292”), further, a main agent solution with a solid content of 33 parts by mass obtained by adding ethyl acetate solvent for solid content adjustment, and a hexamethylene diisocyanate type curing agent solution with a solid content of 75 parts by mass obtained by adding ethyl acetate solvent for solid content adjustment, are mixed so that the ratio of the main agent solution to the curing agent solution is 10:1 (at this time, the ratio of the number of hydroxyl groups in the main agent solution to the number of isocyanate groups in the curing agent solution is 1:2). The coating solution, with a solid content adjusted to 20 parts by mass by adding ethyl acetate as a solvent, is then coated to a thickness of 6 μm after solvent evaporation, thereby obtaining a top coating 200. The top coating film thickness is 6 μm.

[0246] (Comparative Example 1)

[0247] An electromagnetic wave attenuation film was fabricated according to Example 1A without a top coating.

[0248] In addition, the electromagnetic wave attenuation films obtained in the above modified examples and Comparative Example 1 were pressed onto a stainless steel plate with an adhesive, and exposed to the sun using a solar weather instrument for 10 years, equivalent to outdoor exposure. The surface of the electromagnetic wave attenuation film was then wiped with a cotton cloth, and the residual state of the top coating and the electromagnetic wave attenuation layer, as well as the changes in the monostable RCS attenuation characteristics, were studied.

[0249] As a result, Figure 22 As shown, it can be confirmed that in the modified example, neither the top coating layer nor the electromagnetic wave attenuation layer deteriorated. By forming the top coating layer, impedance matching was achieved, and the monostable RCS attenuation characteristics were improved.

[0250] [35GHz~50GHz]

[0251] (Example 2A)

[0252] For the general theory described in Equation 4, the range of the preferred relationship between the thickness T of the metal plate and the skin depth d, which represents the electromagnetic wave attenuation, can be found in a specific frequency band in the millimeter wave band. This will be explained below.

[0253] The simulations performed in the 35 GHz to 50 GHz frequency band are described. A PET film with a thickness (H1) of 50 μm was used as the dielectric substrate, and a metal plate as a thin-film conductive layer was set on one side of the film at certain intervals in both the X and Y coordinates. Furthermore, an aluminum plate inductor with a thickness (T2) of approximately 2 mm was set on the other side of the dielectric substrate, and simulations were performed.

[0254] For frequencies of 35GHz, 39GHz, 41GHz, 45GHz, and 50GHz, simulations were performed to demonstrate the relationship between the attenuation of electromagnetic waves by each metal type and Ln(T1 / d).

[0255] Through Table 4, Table 5 and Figures 23 to 27 To illustrate the results of the simulation. Figure 23 A graph showing the electromagnetic wave attenuation characteristics at 35 GHz in Example 2A. Figure 24 A graph showing the electromagnetic wave attenuation characteristics at 39 GHz in Example 2A. Figure 25 A graph showing the electromagnetic wave attenuation characteristics at 41 GHz in Example 2A. Figure 26 A graph showing the electromagnetic wave attenuation characteristics at 45 GHz in Example 2A. Figure 27 A graph illustrating the electromagnetic wave attenuation characteristics at 50 GHz in Example 2A is provided. Figures 23-27 In the figure, (a) represents the values ​​of admittance and skin depth, (b) represents the composition of the electromagnetic wave attenuation film, and (c) to (e) represent the attenuation characteristics of silver, copper, and aluminum, respectively. The graph is as follows: the natural logarithm of the normalized value of the metal plate thickness T1 with skin depth d is used as the horizontal axis, and the attenuation in the patterned metal plate with the reflectance of the metal plate of the same area as the dielectric substrate set to 100 (reference) is used as the vertical axis, and the relationship between the two is shown in the figure.

[0256] [Table 4]

[0257]

[0258] [Table 5]

[0259] Metal size W1 2.35 2.1 2 1.83 1.63 Intermetal distance W3 1.21 1.08 1 0.94 0.84

[0260] When an absorption of 10 dB or more is considered a standard for good attenuation of electromagnetic wave attenuation films, as shown in Table 4 and... Figures 23 to 27 It is evident that the electromagnetic wave attenuation film satisfying -2.0≤In(T1 / d)≤-0.5 in the frequency band of 35GHz to 50GHz achieved good attenuation.

[0261] It should be noted that the good attenuation characteristic of around 10dB is not limited to the values ​​of the parameters used in Example 2A. Of course, it is expected that it can be achieved in a configuration with a certain width. For example, a good attenuation characteristic of around 10dB can also be expected for a configuration in which the width W1 of the metal plate is 1.7mm to 2.3mm, the distance W3 between adjacent metal plates is 0.9mm to 1.2mm, the thickness H1 of the dielectric substrate is 5μm to 300μm, and the thickness T2 of the planar inductor is 0.5μm to 5mm.

[0262] (Example 2B)

[0263] Similar to Example 2A, a PET film with a thickness (H1) of 50 μm was used as the dielectric substrate. The ratio of the total area of ​​the metal plates serving as the thin-film conductive layer to the total area of ​​the XY plane of the dielectric substrate was adjusted on one side. Furthermore, an aluminum plate inductor with a thickness (T2) of approximately 2 mm was placed on the other side of the dielectric substrate for simulation. Aluminum was used as the metal type, with a width W1 set to 2.0 mm and a thickness T1 set to 149.2 nm. The ratio of the metal area was changed by adjusting the distance W3 between the metal plates.

[0264] Through Table 6 and Figure 28 To illustrate the results of the simulation. Figure 28 A graph showing the electromagnetic wave attenuation characteristics corresponding to the proportion of the metal area at 39 GHz in Example 2B is provided. (a) shows the composition of the electromagnetic wave attenuation film, and (b) shows the attenuation characteristics.

[0265] [Table 6]

[0266] W3(mm) 18.00 6.94 4.32 2.47 1.65 1.16 0.83 0.58 0.39 0.24 0.11 Absorption -0.3 -1.4 -4.3 -10.0 -14.0 -17.8 -19.8 -13.8 -10.0 -10.0 -8.5

[0267] When an absorption of 10 dB or more is considered a standard for good attenuation of electromagnetic wave attenuation films, from Table 6 and... Figure 28 It is shown that in Example 2B, a good attenuation was obtained when the proportion of metal area was 20% or more.

[0268] (Example 2C)

[0269] Similar to Example 2A, a PET film with a thickness (H1) of 50 μm was used as the dielectric substrate, and on one side of it was aligned with... Figure 6 A metal plate with the same pattern arrangement as the thin-film conductive layer was used, but its shape was changed to a shape other than a square. Furthermore, an aluminum plate inductor with a thickness (T2) of approximately 2 mm was placed on the other side of the dielectric substrate, and the attenuation characteristics of electromagnetic waves were simulated. Aluminum was used as the metal in the metal plate, and the thickness T1 was set to 149 nm.

[0270] [Circle]

[0271] Figure 29 A graph illustrating the electromagnetic wave attenuation characteristics when the metal plate is circular in Example 2C. (a) represents the shape of the metal plate, and R1 represents the radius of the circle. (b) represents the electromagnetic wave attenuation characteristics of the plate in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of the II-II lines, where W4 represents the distance between the centers of the circles. (d) The dimensions of R1 and W4 are shown. (e) The attenuation characteristics are shown with frequency as the horizontal axis.

[0272] According to simulation results, it exhibits good attenuation characteristics with an absorption of more than 10dB near 43GHz.

[0273] [rectangle]

[0274] Figure 30 A graph illustrating the electromagnetic wave attenuation characteristics of a rectangular metal plate in Example 2C is provided. (a) shows the shape of the metal plate, where W7 represents the length of the long side of the rectangle and W8 represents the length of the short side. (b) shows the shape of the metal plate in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of lines II-II, where W4 represents the distance between the centers of the rectangles. (d) The dimensions of W7, W8, and W4 are shown. (e) The attenuation characteristics are shown with frequency as the horizontal axis.

[0275] According to simulation results, it exhibits good attenuation characteristics with an absorption of more than 10dB near 39.4GHz.

[0276] [hexagon]

[0277] Figure 31 A graph illustrating the electromagnetic wave attenuation characteristics of a hexagonal metal plate in Example 2C is provided. (a) represents the shape of the metal plate, and W9 represents the length of one side of the hexagon. (b) represents the length of the metal plate passing through the hexagon in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of the II-II lines, where W4 represents the distance between the centers of the hexagons. (d) The dimensions of W9 and W4. (e) The attenuation characteristics with frequency as the horizontal axis.

[0278] According to simulation results, it exhibits good attenuation characteristics with an absorption of more than 10dB near 36GHz.

[0279] [Convex shape]

[0280] Figure 32 A graph illustrating the electromagnetic wave attenuation characteristics of a convex metal plate in Embodiment 2C is shown. (a) shows the shape of the metal plate. W10 represents the length of the upper edge of the inner protrusion of the convex shape, W11 represents the length of the lower edge of the lower part of the convex shape, W15 represents the length of the side edge of the upper part, and W16 represents the length of the side edge of the lower part. The convex shape is symmetrical about the left and right with respect to the straight line connecting the midpoint of the upper edge of the upper part and the lower edge of the lower part. In addition, the lower edge of the lower part and the left and right sides of the lower part are in contact with the upper edge of the upper part, and the center of the rectangle surrounding the convex shape is taken as the center of this convex shape. (b) shows the shape of the metal plate in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of the II-II lines, where W4 represents the distance between the centers of the convex shapes. (d) The dimensions of W10, W11, W15, W16, and W4 are shown. (d) The attenuation characteristics are shown with frequency as the horizontal axis.

[0281] According to simulation results, it exhibits good attenuation characteristics with an absorption of more than 10dB near 35GHz.

[0282] [triangle]

[0283] Figure 33 A graph illustrating the electromagnetic wave attenuation characteristics of a triangular metal plate in Example 2C is provided. (a) shows the shape of the metal plate, where W12 represents the length of one side of the equilateral triangle. (b) shows the length of the metal plate passing through the triangle in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of the II-II lines, where W4 represents the distance between the centers of the triangles. (d) The dimensions of W12 and W4. (e) The attenuation characteristics with frequency as the horizontal axis.

[0284] According to simulation results, it exhibits good attenuation characteristics with an absorption of more than 10dB near 44.8GHz.

[0285] [Cross shape]

[0286] Figure 34A graph illustrating the electromagnetic wave attenuation characteristics of a cross-shaped metal plate in Embodiment 2C is provided. (a) shows the shape of the metal plate. The cross shape is symmetrical vertically and horizontally, and also symmetrical with respect to a 90-degree rotation. W13 represents the length of the opposite sides of the outer edge of the cross, and W14 represents the length of one side of the square that surrounds the cross shape and contacts the opposite sides of the outer edge. The center of this square is taken as the center of the cross shape. (b) shows the electromagnetic wave attenuation characteristics of the cross-shaped metal plate in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of lines II-II, where W4 represents the distance between the centers of the crosses. (d) The dimensions of W13, W14, and W4 are shown. (d) The attenuation characteristics are shown with frequency as the horizontal axis.

[0287] According to simulation results, it exhibits good attenuation characteristics with an absorption of more than 10dB near 35.8GHz.

[0288] [Example of a ring-shaped variation]

[0289] Figure 35A A graph illustrating the electromagnetic wave attenuation characteristics of the ring-shaped metal plate in Example 2C is shown. (a) shows the shape of the metal plate. W5 represents the length of one side of the outer square, and W6 represents the length of one side of the inner square. The centers of the outer and inner squares coincide, serving as the center of the ring. (b) shows the path through the ring in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of the II-II lines, where W4 represents the distance between the centers of the rings. (d) The dimensions of W5, W6, and W4 are shown. (e) The attenuation characteristics are shown with frequency as the horizontal axis.

[0290] According to the simulation results, a peak in absorption was observed near 42.8 GHz, but no 10 dB attenuation was obtained.

[0291] Therefore, the electromagnetic wave attenuation characteristics were simulated by using a film formed by overlapping two electromagnetic wave attenuation films with the same shape and arrangement. Figure 35B A graph illustrating the electromagnetic wave attenuation characteristics of a modified example in Example 2C where the metal plate is annular and has two overlapping layers of electromagnetic wave attenuation film. (a) shows the structure of the electromagnetic wave attenuation film involved in this modified example. Two overlapping layers Figure 35A The dielectric substrate and metal plate used are shown in Figure 1, and a planar inductor is placed on the lower dielectric substrate. H1 represents the thickness of the upper dielectric substrate, and H2 represents the thickness of the lower dielectric substrate. (b) shows the dimensions of H1 and H2. (c) shows the attenuation characteristics with frequency as the horizontal axis.

[0292] According to simulation results, it exhibits good attenuation characteristics around 44.4 GHz.

[0293] (Example 2D)

[0294] A square PET film with a thickness of 50 μm and a side length of 14 cm was prepared as the dielectric substrate. A 100 nm thick aluminum thin-film conductive layer was formed on one side of the dielectric substrate using vacuum evaporation. Then, using a mask, the thin-film conductive layer was etched to form a metal plate with certain intervals in both the X and Y coordinates. An aluminum planar inductor was then attached to the other side using an adhesive layer. Simulations were performed using this configuration.

[0295] The above describes the manufacturing steps of Embodiment 2D according to the second embodiment. The parameters of Embodiment 2D are as follows.

[0296] The width W1 of the metal plates ranges from 1.519 mm to 2.764 mm. Sixteen different types of metal plates, with widths increasing in increments of 0.083 mm, are to be arranged in a 4×4 matrix at 0.1 mm intervals and in the same direction, forming metal plate groups. Multiple such metal plate groups are arranged at 0.1 mm intervals and in the same direction. Furthermore, all metal plate groups are designed to be identical; that is, the metal plates constituting each metal plate group are identical across all groups.

[0297] The distance W3 between adjacent metal plates is 0.1 mm.

[0298] Metal plate thickness T1: 149nm

[0299] The thickness T2 of the planar inductor is approximately 2mm.

[0300] Thickness H1 of dielectric substrate: 50 μm

[0301] In addition, simulations were performed using this configuration to investigate the validity of the attenuation mechanism in the experimental results.

[0302] The electromagnetic wave attenuation films involved in the embodiments that do not include planar inductors are all approximately 60 μm thick and weigh approximately 0.02 g, making them thin and lightweight. Therefore, they can be easily attached to components such as mobile phones and automotive radars where it is desired to suppress the effects of radiated noise caused by electromagnetic waves.

[0303] In the simulation, Examples 2A to 2D all showed good attenuation of electromagnetic waves in the millimeter wave band. Figure 36 The simulation results of Example 2D are shown.

[0304] (A variation of embodiment 2A in the second implementation involves the provision of a top coating layer)

[0305] In Embodiment 2A of the second embodiment described above, an electromagnetic wave attenuation film is produced by applying a top coating 200 manufactured by the following steps to a metal plate made of aluminum with a metal plate thickness T1 of 153 nm.

[0306] An acrylic resin composition comprising 80 parts by weight of methyl methacrylate monomer and 20 parts by weight of cyclohexyl methacrylate is used as the main component. The solid content of this acrylic resin composition is set at 100 parts by weight. To this composition, 6 parts by weight of a hydroxyphenyltriazine UV absorber (ADK STAB LA-46 manufactured by ADEKA Co., Ltd.), 6 parts by weight of other hydroxyphenyltriazine UV absorbers (Tinuvin 479 manufactured by Ciba Specialty Chemicals Corp.), 3 parts by weight of a benzotriazole UV absorber (Tinuvin 329 manufactured by Ciba Specialty Chemicals Corp.), and 5 parts by weight of a hindered amine free radical supplement (Tinuvin manufactured by Ciba Specialty Chemicals Corp.) are added. 292”), further, a main agent solution with a solid content of 33 parts by mass obtained by adding ethyl acetate solvent for solid content adjustment, and a hexamethylene diisocyanate type curing agent solution with a solid content of 75 parts by mass obtained by adding ethyl acetate solvent for solid content adjustment, are mixed so that the ratio of the main agent solution to the curing agent solution is 10:1 (at this time, the ratio of the number of hydroxyl groups in the main agent solution to the number of isocyanate groups in the curing agent solution is 1:2). The coating solution, with a solid content adjusted to 20 parts by mass by adding ethyl acetate as a solvent, is then coated with a coating solution to achieve a thickness of 6 μm after solvent evaporation, thus obtaining a top coating layer 200. The top coating layer film thickness is 6 μm.

[0307] (Comparative Example 1)

[0308] An electromagnetic wave attenuation film was fabricated according to Example 2A without a top coating.

[0309] In addition, the electromagnetic wave attenuation films obtained in the above modified examples and Comparative Example 1 were pressed onto a stainless steel plate with an adhesive, and exposed to the sun using a solar weather instrument for 10 years, equivalent to outdoor exposure. The surface of the electromagnetic wave attenuation film was then wiped with a cotton cloth, and the residual state of the top coating and the electromagnetic wave attenuation layer, as well as the changes in the monostable RCS attenuation characteristics, were studied.

[0310] As a result, Figure 37 As shown, it can be confirmed that in the modified example, neither the top coating layer nor the electromagnetic wave attenuation layer deteriorated. By forming the top coating layer, impedance matching was achieved, and the monostable RCS attenuation characteristics were improved.

[0311] [57GHz~90GHz]

[0312] (Example 3A)

[0313] For the general theory described in Equation 4, the range of the preferred relationship between the thickness T of the metal plate representing electromagnetic wave attenuation and the skin depth d can be found in a specific frequency band in the millimeter wave band. This will be explained below.

[0314] The simulations performed in the 57 GHz to 90 GHz frequency band are described. A PET film with a thickness (H1) of 50 μm was used as the dielectric substrate, and a metal plate as a thin-film conductive layer was set on one side of the film at certain intervals in both the X and Y coordinates. Furthermore, an aluminum plate inductor with a thickness (T2) of approximately 2 mm was set on the other side of the dielectric substrate, and simulations were performed.

[0315] For frequencies of 57GHz, 66GHz, 71GHz, 81GHz, 86GHz, and 90GHz, the relationship between electromagnetic wave attenuation and In(T1 / d) was simulated according to each metal type.

[0316] Through Tables 7 and 8, and Figures 38 to 43 To illustrate the results of the simulation. Figure 38 A graph showing the electromagnetic wave attenuation characteristics at 57 GHz in Example 3A. Figure 39 A graph showing the electromagnetic wave attenuation characteristics at 66 GHz in Example 3A. Figure 40 A graph showing the electromagnetic wave attenuation characteristics at 71 GHz in Example 3A. Figure 41 A graph showing the electromagnetic wave attenuation characteristics at 81 GHz in Example 3A. Figure 42 A graph showing the electromagnetic wave attenuation characteristics at 86 GHz in Example 3A. Figure 43 A graph illustrating the electromagnetic wave attenuation characteristics at 90 GHz in Example 3A is provided. Figures 38-43 In the figure, (a) represents the values ​​of admittance and skin depth, (b) represents the composition of the electromagnetic wave attenuation film, and (c) to (e) represent the attenuation characteristics of silver, copper, and aluminum, respectively. The graph is as follows: the natural logarithm of the normalized value of the metal plate thickness T1 with skin depth d is used as the horizontal axis, and the attenuation in the patterned metal plate with the reflectance of the metal plate of the same area as the dielectric substrate set to 100 (reference) is used as the vertical axis, and the relationship between the two is shown in the figure.

[0317] [Table 7]

[0318]

[0319]

[0320] [Table 8]

[0321]

[0322] When an absorption of 10 dB or more is considered a standard for good attenuation of electromagnetic wave attenuation films, as shown in Table 7 and... Figures 38 to 43 It is evident that the electromagnetic wave attenuation film satisfying -2.5≤ln(T1 / d)≤-1.0 achieves good attenuation in the frequency band of 57GHz to 90GHz.

[0323] It should be noted that the good attenuation characteristics of around 10dB are not limited to the values ​​of the parameters used in Example 3A. Of course, it is expected that they can be achieved in configurations with a certain width. For example, a good attenuation characteristic of around 10dB can also be expected for a configuration in which the width W1 of the metal plate is 0.9mm to 1.4mm, the distance W3 between adjacent metal plates is 0.5mm to 0.7mm, the thickness H1 of the dielectric substrate is 5μm to 300μm, and the thickness T2 of the planar inductor is 0.5μm to 5mm.

[0324] (Example 3B)

[0325] Similar to Example 3A, a PET film with a thickness (H1) of 50 μm was used as the dielectric substrate. The ratio of the total area of ​​the metal plates serving as the thin-film conductive layer to the total area of ​​the XY plane of the dielectric substrate was adjusted on one side. Furthermore, an aluminum plate inductor with a thickness (T2) of approximately 2 mm was placed on the other side of the dielectric substrate for simulation. Aluminum was used as the metal type, with a width W1 set to 1.0 mm and a thickness T1 set to 80 nm. The ratio of the metal area was changed by adjusting the distance W3 between the metal plates.

[0326] Through Table 9 and Figure 44 To illustrate the results of the simulation. Figure 44 A graph showing the electromagnetic wave attenuation characteristics corresponding to the proportion of the metal area at 81 GHz in Example 3B is provided. (a) shows the composition of the electromagnetic wave attenuation film, and (b) shows the attenuation characteristics.

[0327] [Table 9]

[0328]

[0329] When an absorption of 10 dB or more is considered a standard for good attenuation of electromagnetic wave attenuation films, from Table 9 and... Figure 44 It is shown that in Example 3B, a good attenuation was achieved when the metal area ratio was around 10-40%.

[0330] (Example 3C)

[0331] Similar to Example 3A, a PET film with a thickness (H1) of 50 μm was used as the dielectric substrate, and on one side of it was aligned with... Figure 6 The same pattern arrangement was used as a metal plate for the thin-film conductive layer, but its shape was changed to a shape other than a square. Furthermore, an aluminum plate inductor with a thickness (T2) of approximately 2 mm was placed on the other side of the dielectric substrate, and the attenuation characteristics of electromagnetic waves were simulated. Aluminum was used as the metal for the plate, and the thickness T1 was set to 80 nm.

[0332] [rectangle]

[0333] Figure 45 A graph illustrating the electromagnetic wave attenuation characteristics of a rectangular metal plate in Example 3C is provided. (a) shows the shape of the metal plate, where W7 represents the length of the long side of the rectangle and W8 represents the length of the short side. (b) shows the shape of the metal plate in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of lines II-II, where W4 represents the distance between the centers of the rectangles. (d) The dimensions of W7, W8, and W4 are shown. (e) The attenuation characteristics are shown with frequency as the horizontal axis.

[0334] According to simulation results, it exhibits good attenuation characteristics with an absorption of more than 10dB near 82.8GHz.

[0335] [hexagon]

[0336] Figure 46 A graph illustrating the electromagnetic wave attenuation characteristics of a hexagonal metal plate in Example 3C is provided. (a) shows the shape of the metal plate, where W9 represents the length of one side of the hexagon. (b) shows the length of the metal plate passing through the hexagon in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of the II-II lines, where W4 represents the distance between the centers of the hexagons. (d) The dimensions of W9 and W4. (e) The attenuation characteristics with frequency as the horizontal axis.

[0337] According to simulation results, it exhibits good attenuation characteristics with an absorption of more than 10dB near 71.2GHz.

[0338] [Convex shape]

[0339] Figure 47A graph illustrating the electromagnetic wave attenuation characteristics of a convex metal plate in Embodiment 3C is provided. (a) shows the shape of the metal plate. W10 represents the length of the upper edge of the inner protrusion of the convex shape, W11 represents the length of the lower edge of the lower part of the convex shape, W15 represents the length of the side edge of the upper part, and W16 represents the length of the side edge of the lower part. The convex shape is symmetrical about the left and right with respect to the straight line connecting the midpoint of the upper edge of the upper part and the lower edge of the lower part. Furthermore, the lower edge of the lower part and the left and right sides of the lower part are brought into contact with the upper edge of the upper part, and the center of the rectangle surrounding the convex shape is taken as the center of this convex shape. (b) shows the shape of the metal plate in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of the II-II lines, where W4 represents the distance between the centers of the convex shapes. (d) The dimensions of W10, W11, W15, W16, and W4 are shown. (d) The attenuation characteristics are shown with frequency as the horizontal axis.

[0340] According to simulation results, it exhibits good attenuation characteristics with an absorption of more than 10dB near 87GHz.

[0341] [triangle]

[0342] Figure 48 A graph illustrating the electromagnetic wave attenuation characteristics of a triangular metal plate in Embodiment 3C is provided. (a) represents the shape of the metal plate, where W12 represents the length of one side of the equilateral triangle. (b) represents the length of the metal plate passing through the triangle in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of the II-II lines, where W4 represents the distance between the centers of the triangles. (d) The dimensions of W12 and W4. (e) The attenuation characteristics with frequency as the horizontal axis.

[0343] According to simulation results, it exhibits good attenuation characteristics with an absorption of more than 10dB near 80.8GHz.

[0344] [Cross shape]

[0345] Figure 49 A graph illustrating the electromagnetic wave attenuation characteristics of a cross-shaped metal plate in Embodiment 3C is provided. (a) shows the shape of the metal plate. The cross shape is symmetrical vertically and horizontally, and also symmetrical with respect to a 90-degree rotation. W13 represents the length of the opposite sides of the outer edge of the cross, and W14 represents the length of one side of the square that surrounds the cross shape and contacts the opposite sides of the outer edge. The center of this square is taken as the center of the cross shape. (b) shows the electromagnetic wave attenuation characteristics of the cross-shaped metal plate in this embodiment. Figure 6 (c) A magnified view of the area near the arrangement pattern of lines II-II, where W4 represents the distance between the centers of the crosses. (d) The dimensions of W13, W14, and W4 are shown. (d) The attenuation characteristics are shown with frequency as the horizontal axis.

[0346] According to simulation results, it exhibits good attenuation characteristics with an absorption of more than 10dB near 90GHz.

[0347] (Example 3D)

[0348] A square PET film with a thickness of 50 μm and a side length of 14 cm was prepared as the dielectric substrate. A 100 nm thick aluminum thin-film conductive layer was formed on one side of the dielectric substrate using vacuum evaporation. Then, using a mask, the thin-film conductive layer was etched to form a metal plate with certain intervals in both the X and Y coordinates. An aluminum planar inductor was then attached to the other side using an adhesive layer. Simulations were performed using this configuration.

[0349] The above describes the manufacturing steps of Embodiment 3D according to the second embodiment. The parameters of Embodiment 3D are as follows.

[0350] The width W1 of the metal plates ranges from 0.9 mm to 1.0245 mm. Sixteen different types of metal plates, with widths increasing in increments of 0.0083 mm, are to be arranged in a 4×4 matrix with equal intervals of 0.1 mm and in the same direction, forming metal plate groups. Multiple such metal plate groups are arranged with 0.1 mm intervals and in the same direction. Furthermore, all metal plate groups are to be identical; that is, the metal plates constituting each metal plate group are identical.

[0351] The distance W3 between adjacent metal plates is 0.1 mm.

[0352] The thickness of the metal plate, T1, is 80 nm.

[0353] The thickness T2 of the planar inductor is approximately 2mm.

[0354] Thickness H1 of dielectric substrate: 50 μm

[0355] In addition, simulations were performed using this configuration to investigate the validity of the attenuation mechanism in the experimental results.

[0356] The electromagnetic wave attenuation films involved in the embodiments that do not include planar inductors are all approximately 60 μm thick and weigh approximately 0.02 g, making them thin and lightweight. Therefore, they can be easily attached to components such as mobile phones and automotive radars where it is desired to suppress the effects of radiated noise caused by electromagnetic waves.

[0357] In simulations, Examples 3A through 3D all exhibited good attenuation of electromagnetic waves in the millimeter-wave band. Furthermore, the attenuation rate was obtained in actual measurements, confirming the effectiveness of this configuration. Although there are differences from experimental results that are believed to be based on factors other than attenuation, such as various parameters in the simulations and Maxwell's equations, the same attenuation tendency was observed, therefore the mechanism in the embodiments of the present invention is considered appropriate. Additionally, although there are differences in the attenuation rate between simulations and actual measurements, the same tendency was obtained, indicating that the attenuation center frequency can be appropriately set.

[0358] Figure 50 and Figure 51 The monostable RCS decay characteristics in the simulation and measured results of Examples 3A and 3D are shown respectively. In Example 3A, aluminum with a metal plate width W1 of 1.0 mm, a distance W3 between adjacent metal plates of 0.5 mm, and a metal plate thickness T1 of 100 nm was used. It should be noted that the measured steps are as follows.

[0359] Two identical metal plates were prepared. The electromagnetic wave attenuation films of each embodiment were adhered to one of the metal plates in a completely covering manner. In an anechoic chamber, electromagnetic waves were irradiated onto both the metal plate with the attenuation film and the unattached metal plate. The amount of reflected electromagnetic waves was measured using a network analyzer (KEYSIGHT Model E5071C). The reflection amount of the metal plate without the attenuation film was set to 100 (reference), and the monostable RCS attenuation was evaluated.

[0360] (A variation of embodiment 3A in the second embodiment, in which a top coating layer is provided)

[0361] In Embodiment 3A of the second embodiment, an electromagnetic wave attenuation film is produced by applying a top coating 200 manufactured by the following steps to a metal plate made of aluminum with a thickness T1 of 80 nm.

[0362] An acrylic resin composition comprising 80 parts by weight of methyl methacrylate monomer and 20 parts by weight of cyclohexyl methacrylate is used as the main component. The solid content of this acrylic resin composition is set at 100 parts by weight. To this composition, 6 parts by weight of a hydroxyphenyltriazine UV absorber (ADK STAB LA-46 manufactured by ADEKA Co., Ltd.), 6 parts by weight of other hydroxyphenyltriazine UV absorbers (Tinuvin 479 manufactured by Ciba Specialty Chemicals Corp.), 3 parts by weight of a benzotriazole UV absorber (Tinuvin 329 manufactured by Ciba Specialty Chemicals Corp.), and 5 parts by weight of a hindered amine free radical supplement (Tinuvin manufactured by Ciba Specialty Chemicals Corp.) are added. 292”), further, a main agent solution with a solid content of 33 parts by mass obtained by adding ethyl acetate solvent for solid component adjustment, and a hexamethylene diisocyanate type curing agent solution with a solid content of 75 parts by mass obtained by adding ethyl acetate solvent for solid component adjustment, are mixed so that the ratio of the main agent solution to the curing agent solution is 10:1 (at this time, the ratio of the number of hydroxyl groups in the main agent solution to the number of isocyanate groups in the curing agent solution is 1:2). The coating solution, with a solid content of 20 parts by mass adjusted by adding ethyl acetate as a solvent, is then coated to a thickness of 6 μm after solvent evaporation, thereby obtaining a top coating 200. The top coating film thickness is 6 μm.

[0363] (Comparative Example 1)

[0364] An electromagnetic wave attenuation film was fabricated according to Example 3A without a top coating layer.

[0365] In addition, the electromagnetic wave attenuation films obtained in the above modified examples and Comparative Example 1 were pressed onto a stainless steel plate with an adhesive, and exposed to the sun using a solar weather instrument for 10 years, equivalent to outdoor exposure. The surface of the electromagnetic wave attenuation film was then wiped with a cotton cloth, and the residual state of the top coating and the electromagnetic wave attenuation layer, as well as the changes in the monostable RCS attenuation characteristics, were studied.

[0366] As a result, Figure 52 As shown, it can be confirmed that in the modified example, neither the top coating layer nor the electromagnetic wave attenuation layer deteriorated. By forming the top coating layer, impedance matching was achieved, and the monostable RCS attenuation characteristics were improved.

[0367] The various embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the specific configuration is not limited to these embodiments, and also includes changes and combinations of configurations without departing from the spirit of the present invention. Some changes are exemplified below, but these are not exhaustive, and other changes may also be included. These changes may also be appropriately combined in two or more ways.

[0368] In the first embodiment, the methods used in the second embodiment, such as frequency bands and metal plates, can be appropriately used.

[0369] In the first embodiment, the metal layer in the second region can be omitted, and only a metal plate is formed.

[0370] In this invention, the planar inductor is not limited to being formed on the entire back side. For example, multiple metal plates can be arranged in the same manner as the front side, or they can be formed in a grid pattern.

[0371] In this invention, the shape of the metal plate is not limited to a square, but can be set to various shapes such as polygons other than circles (including ellipses), squares, polygons with rounded corners, and irregular shapes.

[0372] The total area of ​​the metal plate should preferably account for more than 20% of the projected area.

[0373] In this way, electromagnetic waves can be effectively attenuated.

[0374] The electromagnetic wave attenuation film of this invention can be used by stacking multiple layers. By making the structural parameters of the stacked layers different, the attenuation can be adjusted in more detail.

[0375] In the first embodiment, the elevation difference between the first region and the second region can be reversed. In this case, the metal plate is in a relatively higher position, and the support cage is in a relatively lower position.

[0376] In the electromagnetic wave attenuation film of the present invention, it can be configured without a planar inductor on the back side. For example, if the object to be bonded to the back side is metal, the second and third mechanisms can be performed without any problems by bonding to the metal surface of the object, even without a planar inductor. In this case, it is sufficient to have an adhesive layer or other bonding layer on the back side that can be bonded to the object.

[0377] In the electromagnetic wave attenuation film of this invention, parameters such as structural period and metal plate dimensions do not need to be completely consistent in all parts. For example, even if the above parameters vary within the tolerance range (approximately 5%) during the manufacturing process, they are still included in the "same shape and same size" in this invention. Furthermore, the "value within a predetermined range" can be a range of values ​​with regularity. This regularity can be a Gaussian distribution, a binomial distribution, a random or quasi-random distribution with equal frequencies within a certain region, or a tolerance range during the manufacturing process.

[0378] The support cage can be composed of multiple conductive segments arranged with gaps between them. The gaps can be set to less than 1 / 10 of the wavelength of the electromagnetic wave to be captured. In other words, the support cage can be composed of multiple conductive segments.

[0379] In the electromagnetic wave attenuation film of the present invention, a release layer may be provided on a support substrate, and then the electromagnetic wave attenuation film of the first embodiment and the second embodiment may be provided, and an adhesive / adhesive may be provided as a transfer foil.

[0380] Specifically, a release layer is applied to a support substrate and dried, and then a base layer is formed. In the configuration of the first embodiment, the base layer is given an uneven surface, and a thin-film conductive layer is formed by vapor deposition. Then, the thin-film conductive layer formed on the side of the second region is removed, and a layer serving as a dielectric substrate is formed. By sequentially stacking a planar inductor and an adhesive on the dielectric substrate, a transfer foil can be formed. In the configuration of the second embodiment, a thin-film conductive layer is formed on the base layer, and a mask layer is printed in the shape of a metal plate according to a pattern. Then, excess thin-film conductive layer is removed by etching, thereby forming a metal plate. Furthermore, by sequentially stacking a dielectric substrate, a planar inductor, and an adhesive, a transfer foil can be formed. When transferring to a metal frame or the like, the planar inductor layer can be omitted.

[0381] By forming it as a transfer foil, it can be further thinned, and its conformability can be further improved. Even complex shapes can be transferred, thereby expanding the application range of the electromagnetic wave attenuation film of the present invention.

[0382] Based on the above-described implementation methods and modifications, the notes described below can be derived.

[0383] [Postscript 1]

[0384] An electromagnetic wave attenuation film, comprising:

[0385] Dielectric substrate with front and back sides,

[0386] The thin film conductive layer disposed on the front, and

[0387] A planar inductor or bonding layer disposed on the back side,

[0388] The thin-film conductive layer comprises multiple metal plates.

[0389] The thickness T of the metal plate is less than 1000 nm.

[0390] [Postscript 2]

[0391] An electromagnetic wave attenuation film, comprising:

[0392] Dielectric substrate with front and back sides,

[0393] The thin film conductive layer disposed on the front, and

[0394] A planar inductor or bonding layer disposed on the back side,

[0395] The thin-film conductive layer comprises multiple metal plates.

[0396] When the thickness of the metal plate is set to T and the skin depth is set to d, the following equation (2) is satisfied.

[0397] -2≤ln(T / d)≤0…(2).

[0398] [Postscript 3]

[0399] An electromagnetic wave attenuation film, comprising:

[0400] Dielectric substrate with front and back sides,

[0401] The thin film conductive layer disposed on the front, and

[0402] A planar inductor or bonding layer disposed on the back side,

[0403] The thin-film conductive layer comprises multiple metal plates.

[0404] The dielectric layer has an uneven surface on the front, consisting of a first region with a relatively low recessed portion and a second region with a relatively high recessed portion.

[0405] The first region is discretely configured.

[0406] The second region is configured among multiple first regions.

[0407] The metal plate is disposed in the first region.

[0408] When the thickness of the metal plate is set as T and the skin depth is set as d, the following equation (2) is satisfied.

[0409] -2≤ln(T / d)≤0…(2).

[0410] [Postscript 4]

[0411] An electromagnetic wave attenuation film, comprising:

[0412] Dielectric substrate with front and back sides,

[0413] The thin film conductive layer disposed on the front, and

[0414] A planar inductor or bonding layer disposed on the back side,

[0415] The dielectric layer has an uneven surface on the front, consisting of a first region with a relatively low recessed portion and a second region with a relatively high recessed portion.

[0416] The thin-film conductive layer includes a plurality of metal plates disposed in the first region and a support cage disposed in the second region.

[0417] The first region is discretely configured.

[0418] The second region is configured among multiple first regions.

[0419] In the above embodiments, the attenuation of electromagnetic waves was studied; however, it is known that a conductor that attenuates specific electromagnetic waves can be used as an antenna for receiving electromagnetic waves. Therefore, the above embodiments can also be used as receiving antennas. Furthermore, in the above embodiments, quanta with zero momentum in a two-dimensional system are captured, so it is considered that they can also be used as elements for data computation and recording in the quantum state of a metal plate.

[0420] As described above, in the embodiments of the present invention, the interaction mechanism with electromagnetic waves is different from that in the prior art. Therefore, products exhibiting the same mechanism should be considered to have substantially used the embodiments of the present invention.

[0421] Explanation of symbols

[0422] 1.61 Electromagnetic wave attenuation film

[0423] 10, 62 Dielectric substrate

[0424] Before 10a and 62a

[0425] 10b, 62b back

[0426] 30 Thin film conductive layer

[0427] 30A metal sheet

[0428] 50 Flat Panel Inductor

[0429] 200 top coating

[0430] 121 First District

[0431] 122 Second Area

Claims

1. An electromagnetic wave attenuation film, used in millimeter wave frequency bands of 27GHz–34GHz, 35GHz–50GHz, or 57GHz–90GHz, comprising: Dielectric substrate with front and back sides, The thin film conductive layer disposed on the front, and The planar inductor is configured on the back side. The dielectric substrate has an uneven surface on its front side, consisting of a first region with a relatively low recessed portion and a second region with a relatively high recessed portion. The thin-film conductive layer includes a plurality of metal plates disposed in the first region and a support cage disposed in the second region. The first region is discretely configured. The second region is configured among multiple first regions. The conductive film layer is absent on the sides of the second region, which extends upwards from the first region, thus exposing the dielectric substrate. The thickness of the dielectric substrate is between 5 μm and 100 μm.

2. The electromagnetic wave attenuation film according to claim 1, used in the frequency band of 27GHz to 34GHz, wherein, When the thickness of the metal plate is set as T and the skin depth is set as d, the following equation (1) is satisfied. -1.0 ≤ln(T / d) ≤ 0.0…(1).

3. The electromagnetic wave attenuation film according to claim 1, used in the frequency band of 35GHz to 50GHz, wherein, When the thickness of the metal plate is set as T and the skin depth is set as d, the following equation (2) is satisfied. -2.0 ≤ln(T / d) ≤ -0.5…(2).

4. The electromagnetic wave attenuation film according to claim 1, used in the frequency band of 57GHz to 90GHz, wherein, When the thickness of the metal plate is set as T and the skin depth is set as d, the following equation (3) is satisfied. -2.5 ≤ln(T / d) ≤ -1.0…(3).

5. The electromagnetic wave attenuation film according to any one of claims 1 to 4, wherein, The thin-film conductive layer and the planar inductor are separated in the thickness direction of the dielectric substrate.

6. The electromagnetic wave attenuation film according to any one of claims 1 to 4, wherein it comprises an adhesive layer in place of the planar inductor.

7. The electromagnetic wave attenuation film according to any one of claims 1 to 4, wherein, The metal plate has a pair of opposite edges.

8. The electromagnetic wave attenuation film according to claim 7, wherein, The length of a pair of opposite sides of the metal plate is more than 0.25 mm and less than 4 mm.

9. The electromagnetic wave attenuation film according to any one of claims 1 to 4, characterized in that, A top coating layer is provided on the thin film conductive layer.

10. The electromagnetic wave attenuation film according to claim 9, characterized in that, The top coating layer and the air layer through which electromagnetic waves propagate are configured to be impedance matched.

11. The electromagnetic wave attenuation film according to any one of claims 1 to 4, wherein, The metal plate is made of any one of silver, copper, or aluminum.

12. The electromagnetic wave attenuation film according to any one of claims 1 to 4, wherein, Multiple metal plates of the same shape and size are arranged at a predetermined distance.

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