Electromagnetic wave reflection device and manufacturing method for electromagnetic wave reflection device

Abstract

Provided are an electromagnetic wave reflection device having desired reflection characteristics, and a manufacturing method for the electromagnetic wave reflection device. This electromagnetic wave reflection device comprises a dielectric layer, a metal ground layer provided on one surface of the dielectric layer, and a plurality of conductive patterns that is provided on the other surface of the dielectric layer and that is designed to constitute an asymmetric reflection region for reflecting an incident electromagnetic wave at a reflection angle different from the incident angle, the electromagnetic wave reflection device configured so that the angle of an edge portion in a cross-sectional shape of each of the plurality of conductive patterns with respect to the dielectric layer is 80° to 100°.

Description

Electromagnetic Wave Reflector and Method for Manufacturing Electromagnetic Wave Reflector

[0001] The present disclosure relates to an electromagnetic wave reflector and a method for manufacturing an electromagnetic wave reflector.

[0002] For the purpose of realizing use cases such as automation of manufacturing processes and office work, remote control, introduction of control and management by AI (Artificial Intelligence), and autonomous driving, indoor base stations in factories, plants, offices, commercial facilities, etc., and outdoor base stations in medical sites, event venues, expressways, railway lines, etc., have been or are being considered for introduction. In the fifth generation (5G) mobile communication system, a frequency band of 6 GHz or less called "sub-6" and a 28 GHz band classified as the millimeter wave band are provided. The next-generation sixth generation (6G) mobile communication system is expected to be extended to the sub-terahertz band. The use of electromagnetic waves in such high-frequency bands greatly expands the communication bandwidth and enables a large amount of data communication with low latency.

[0003] However, since high-frequency electromagnetic waves have strong straightness, when performing mobile communication using high-frequency electromagnetic waves indoors or outdoors, a dead zone where electromagnetic waves cannot reach may occur. In order to eliminate such dead zones, an electromagnetic wave reflector that reflects incident electromagnetic waves is sometimes used.

[0004] As an electromagnetic wave reflector for such purpose, an electromagnetic wave reflector called a metasurface, which is capable of reflecting incident electromagnetic waves at a reflection angle different from the incident angle, is sometimes used. Such a metasurface is realized by forming a plurality of conductive patterns on a dielectric layer that achieve desired reflection characteristics (see, for example, Patent Document 1).

[0005] Japanese Patent No. 7492072

[0006] However, when these conductive patterns are formed by electroplating or etching, variations in manufacturing conditions can cause the edges of the conductive patterns to become rounded or over-etching to occur, resulting in localized variations in the width of the conductive patterns, making them narrower or wider than designed. This can lead to errors in the shape and dimensions of the conductive patterns. When errors occur in the shape and dimensions of the conductive patterns, the reflection characteristics may change from what was designed, potentially preventing the desired reflection characteristics from being achieved.

[0007] The object of this disclosure is to provide an electromagnetic wave reflector having desired reflection characteristics and a method for manufacturing an electromagnetic wave reflector.

[0008] In one aspect of the present disclosure, an electromagnetic wave reflector includes a dielectric layer, a metal ground layer provided on one surface of the dielectric layer, and a plurality of conductive patterns provided on the other surface of the dielectric layer and designed to constitute an asymmetric reflection region that reflects incident electromagnetic waves at a reflection angle different from the angle of incidence, wherein the angles of the edge portions of the cross-sectional shapes of the plurality of conductive patterns with respect to the dielectric layer are 80° or more and 100° or less, respectively.

[0009] In another aspect of the present disclosure, a method for manufacturing an electromagnetic wave reflector comprises the steps of: forming an etching-resistant film on a substrate for making transfer patterns; forming a plurality of conductive patterns designed to constitute an asymmetric reflection region that reflects incident electromagnetic waves at a reflection angle different from the incident angle by immersing the substrate on which the etching-resistant film is formed in a resist removal solution; transferring the plurality of conductive patterns from the substrate to a resin film for transfer; providing an adhesive layer on the surface of the plurality of conductive patterns transferred to the resin film; and forming the asymmetric reflection region by transferring the plurality of conductive patterns from the resin film to the side of a dielectric layer on which a metal ground layer has been formed in advance on one side, using the adhesive layer, wherein an electromagnetic wave reflector is produced configured such that the angles of the edge portions of the cross-sectional shape of the plurality of conductive patterns with respect to the dielectric layer are 80° or more and 100° or less, respectively, by adjusting the immersion time when immersing the substrate on which the etching-resistant film is formed in the resist removal solution.

[0010] According to this disclosure, an electromagnetic wave reflector having desired reflection characteristics and a method for manufacturing an electromagnetic wave reflector are realized.

[0011] This figure shows an example of an electromagnetic wave reflecting device according to an embodiment. This figure shows another example of an electromagnetic wave reflecting device according to an embodiment. This figure shows an example of the layer structure of an electromagnetic wave reflecting panel. This figure shows an example of the conductive pattern of an electromagnetic wave reflecting panel. Figures (A) to (C) are diagrams illustrating the shape of the conductive pattern. Figures (A) to (C) show an example of the manufacturing process of an electromagnetic wave reflecting panel according to an embodiment. Figures (A) to (C) show an example of the manufacturing process of an electromagnetic wave reflecting panel according to an embodiment. This figure shows an example of the manufacturing process of an electromagnetic wave reflecting panel according to an embodiment. This figure shows another example of the layer structure of an electromagnetic wave reflecting panel. This figure shows another example of the layer structure of an electromagnetic wave reflecting panel.

[0012] Hereinafter, one aspect of this disclosure will be described, mainly with reference to Figures 1 to 10. Note that the drawings used in the following description are all schematic, and the dimensional relationships and ratios of the elements shown in the drawings do not necessarily correspond to reality. Furthermore, the dimensional relationships and ratios of the elements do not necessarily correspond between multiple drawings. Elements that are substantially the same as those described in multiple drawings will be given the same reference numeral, and their descriptions will be omitted. Also, this disclosure is not limited in any way to the following embodiments, and can be implemented with appropriate modifications within the scope of this disclosure.

[0013] First, an overview of the electromagnetic wave reflecting device according to this embodiment will be described with reference to Figures 1 and 2.

[0014] Figure 1 shows an example of an electromagnetic wave reflecting device 10 according to this embodiment. The electromagnetic wave reflecting device 10 has an electromagnetic wave reflecting panel 20 and a frame 30 that holds the electromagnetic wave reflecting panel 20. The electromagnetic wave reflecting panel 20 reflects radio waves in a desired band selected from a frequency band of 1 GHz to 300 GHz, for example, from 1 GHz to 170 GHz, and includes a metasurface on at least a portion of the reflective surface, in which the reflection angle and reflection efficiency are controlled.

[0015] Metasurfaces are formed using periodic patterns, mesh patterns, or geometric patterns designed according to the desired reflection mode and frequency band, and their reflective properties, including reflection angle and reflection efficiency, are controlled. The patterns forming the metasurface are made of good conductors such as metals or conductive films that are transparent to visible light. Control of the reflection angle includes achieving non-specular reflection, which reflects in a direction different from the angle of incidence, and controlling the direction of diffusion.

[0016] The electromagnetic wave reflective panel 20 may include a specular reflective surface in at least part of it. The specular reflective surface reflects incident electromagnetic waves in the same direction as the angle of incidence. Depending on the location and environment in which the electromagnetic wave reflective device 10 is installed, the reflective surface of the electromagnetic wave reflective panel 20 may be a mixture of specular and non-specular reflective surfaces. In other words, the electromagnetic wave reflective panel 20 is configured to have an asymmetrical reflective region that reflects incident electromagnetic waves at a reflection angle different from the angle of incidence.

[0017] The frame 30 consists of a side frame 31 that holds two sides along the height direction when the electromagnetic wave reflective panel 20 is installed, a top frame 32 that holds the upper end of the electromagnetic wave reflective panel 20, and a bottom frame 33 that holds the lower end of the electromagnetic wave reflective panel 20. In other words, the frame 30 is configured to hold the entire circumference of the electromagnetic wave reflective panel 20 with the side frame 31, the top frame 32, and the bottom frame 33. As the frame 30, a frame made of aluminum, for example, which is easy to process and has high strength, can be used. In addition, legs 34 that support the side frame 31 are provided at the lower end of the side frame 31. As shown in Figure 1, it is desirable to provide legs 34 when the electromagnetic wave reflective device 10 is to stand on its own on the installation surface, but the legs 34 are not essential. Casters may be provided on the legs 34 to make it movable, or the electromagnetic wave reflective panel 20 may be installed on a wall or suspended from the ceiling without legs 34.

[0018] Figure 2 shows an example of an electromagnetic wave reflective fence 100 formed by connecting the electromagnetic wave reflectors 10 shown in Figure 1. In Figure 2, the electromagnetic wave reflective fence 100 is constructed by connecting multiple electromagnetic wave reflectors 10-1, 10-2, and 10-3 (hereinafter sometimes referred to as electromagnetic wave reflectors 10), but there is no particular limit to the number of electromagnetic wave reflectors 10 that are connected. Electromagnetic wave reflectors 10-1, 10-2, and 10-3 each have electromagnetic wave reflective panels 20-1, 20-2, and 20-3 (hereinafter sometimes referred to as electromagnetic wave reflective panels 20). By holding adjacent electromagnetic wave reflective panels 20 together with a single side frame 31, an electromagnetic wave reflective fence 100 connected in the lateral direction can be obtained.

[0019] <Layer Structure of Electromagnetic Wave Reflecting Panel> Figure 3 shows an example of the layer structure of the electromagnetic wave reflecting panel 20. The stacking direction is the thickness direction of the electromagnetic wave reflecting panel 20. The electromagnetic wave reflecting panel 20 has a dielectric layer 14, a conductive pattern 15 formed on one surface (front surface 141) of the dielectric layer 14, and a metal ground layer 13 formed on the other surface (back surface 142) of the dielectric layer 14. The conductive pattern 15 is composed of a plurality of conductive strips 151, which are plurality of conductive patterns. Each conductive strip 151 is bonded to the surface 141 of the dielectric layer 14 with an adhesive layer 108.

[0020] The dielectric layer 14 has a relative permittivity and dielectric loss tangent suitable for achieving the target reflective properties, and is a transparent material in the visible light range. As the dielectric layer 14, insulating polymer films such as polycarbonate, cycloolefin polymer (COP), polyethylene terephthalate (PET), and fluororesin can be used. The thickness of the dielectric layer 14 is, for example, 0.3 mm to 1.0 mm, preferably 0.5 mm to 0.9 mm.

[0021] In this specification, numerical ranges such as "0.3 mm to 1.0 mm" mean that the lower and upper limits are included within that range. Therefore, for example, "0.3 mm to 1.0 mm" means "0.3 mm or more and 1.0 mm or less." The same applies to other numerical ranges.

[0022] The conductive pattern 15 forms the reflective surface of the electromagnetic wave reflection panel 20. The reflective surface formed by the conductive pattern 15 includes a metasurface whose reflection characteristics are artificially controlled. In other words, the reflective surface formed by the conductive pattern 15 is designed to constitute an asymmetric reflection region that reflects incident electromagnetic waves at a reflection angle different from the incident angle. For example, the conductive pattern 15 is designed so that the power reflection efficiency of the reflected wave reflected by the asymmetric reflection region relative to the incident wave is 60% or more. Each conductive strip 151 of the conductive pattern 15 is made of a good conductor such as Cu, Ni, or Ag. The thickness of each conductive strip 151 is, for example, 0.010 mm to 0.050 mm.

[0023] The adhesive layer 108 is a material that can support and fix each conductive strip 151 to the dielectric layer 14. For example, thermoplastic resins such as vinyl acetate resin, acrylic resin, cellulose resin, and silicone resin can be used as the adhesive layer 108. The thickness of the adhesive layer 108 is, for example, 0.010 mm to 0.015 mm. By bonding each conductive strip 151 with the adhesive layer 108 instead of applying the adhesive layer 108 to the entire surface 141 of the dielectric layer 14, the influence of the adhesive layer 108 on the dielectric layer 14 can be minimized.

[0024] The metal ground layer 13 is formed of, for example, an Ag-based multilayer film.

[0025] Figure 4 is a schematic diagram of the conductive pattern 15 transferred to the surface 141 of the dielectric layer 14, and is a view of the electromagnetic wave reflection panel 20 shown in Figure 3 from the reflection side. Each conductive strip 151 is bonded to the surface 141 with an adhesive layer 108 as described above.

[0026] The conductive pattern 15 includes, for example, a unit cell (also called a "supercell") 210 formed by five conductive strips 151 of different shapes and sizes. These unit cells 210 are repeatedly arranged in the transverse and longitudinal directions of the dielectric layer 14 to form a periodic arrangement of the conductive pattern 15. The area occupancy rate of the conductive pattern 15 on the surface 141 of the dielectric layer 14 is, for example, 10.0% to 45.0%. The conductive pattern 15 formed by the repetition of the unit cells 210 forms a reflective surface that reflects electromagnetic waves in a desired frequency band, such as 1 GHz to 300 GHz, or 1 GHz to 170 GHz, in a desired direction. The conductive pattern 15 forms a metasurface that, for example, reflects incident electromagnetic waves at an angle different from the angle of incidence, or scatters them in a desired direction.

[0027] The six conductive strips 151 are of equal width and different lengths, but their central axes are aligned. The central axis passing through the center of each conductive strip 151 coincides with the longitudinal axis of the unit cell 210. The spacing between adjacent conductive strips 151 in the width direction is constant. The shape and size of the six conductive strips 151 control the phase of reflection, and the superposition of the reflected waves reflects electromagnetic waves in the desired direction.

[0028] Figure 5(A) is a view of the conductive strip 151 from the reflective surface side, and Figures 5(B) and 5(C) are examples of cross-sectional views along line A-A in Figure 5(A).

[0029] As shown in Figure 5(A), the conductive strip 151 is formed, for example, in a rectangular shape and has hollowed-out sections 1511 on the inside with rounded corners. Having the hollowed-out sections 1511 improves the transparency of the electromagnetic wave reflection panel 20. Furthermore, by making the corners of the hollowed-out sections 1511 rounded, current can flow more easily through the corners, thereby improving the reflection efficiency.

[0030] Furthermore, as shown in Figures 5(B) and 5(C), the angle θ of the edge portion of the conductive strip 151 with respect to the dielectric layer 14 is configured to be 80° to 100°, respectively. In other words, the edge portion of the conductive strip 151 does not have an R shape. When the conductive strip 151 is formed by electroplating or etching, the edge portion of the conductive strip 151 may be rounded, or the width of the conductive pattern may become narrower or wider locally than the designed width. In this way, if there are dimensional errors in the shape of the conductive strip 151, the reflection characteristics may change from those designed, and the desired reflection characteristics may not be obtained.

[0031] In this embodiment, in the manufacturing process of the electromagnetic wave reflective panel 20 described later, an etching-resistant film is formed on a substrate for transfer pattern fabrication, and the immersion time when immersing the substrate with the etching-resistant film in the resist removal solution is adjusted. This makes the angle θ of the edge portion of the cross-sectional shape of the conductive strip 151 with respect to the dielectric layer 14 80° or more and 100° or less, respectively. By making the angle θ of the edge portion of the cross-sectional shape of the conductive strip 151 with respect to the dielectric layer 14 80° or more and 100° or less, the conductive strip 151 can have the desired reflection characteristics even when it is formed by electroplating or etching, and the power reflection efficiency can be made, for example, 60% or more.

[0032] The etching-resistant film is selected from the group consisting of, for example, plating resist, copper foil laminate, and aluminum foil laminate. The resist removal solution is, for example, a plating solution, an etching solution, etc.

[0033] The following explanation uses an example where a substrate with a plating resist formed on it is immersed in a plating solution as an etching-resistant film. However, the same method can be applied when a substrate laminated with copper foil or aluminum foil as an etching-resistant film is immersed in an etching solution.

[0034] <Manufacturing process of electromagnetic wave reflective panel> Figures 6 to 8 show the manufacturing process of the electromagnetic wave reflective panel 20.

[0035] In Figure 6(A), a conductive pattern 15 composed of multiple conductive strips 151 is formed on a substrate 101 for transfer pattern fabrication. For example, a stainless steel (SUS) substrate for plating growth is used as the substrate 101 for transfer pattern fabrication, but the example is not limited to this. Other substrates used in other metal growth methods may be used. First, a plating resist 154, which is an etching-resistant film, is formed on the surface of the substrate 101 by screen printing or the like. At this time, the plating resist 154 is also formed in the portions corresponding to the hollowed-out sections 1511 of the conductive strips 151. Therefore, the plating resist 154 has an opening pattern corresponding to the pattern of the conductive strips 151. The substrate 101 with the plating resist 154 formed on it is immersed in a plating solution, and the conductive pattern 15 is formed by electroplating. The conductive pattern 15 is then grown to a thickness of 0.010 mm to 0.050 mm. After the conductive pattern 15 is formed on the substrate 101, the plating resist 154 is removed with the plating solution. At this time, the immersion time when immersing the substrate 101 on which the plating resist 154 is formed in the plating solution is adjusted to an immersion time corresponding to the plating resist 154, so that the angle θ of the edge portion of the cross-sectional shape of the conductive strip 151 with respect to the dielectric layer 14 is 80° or more and 100° or less, respectively.

[0036] In Figure 6(B), a transfer resin film 105 is bonded to the conductive pattern 15 on the substrate 101. A PET film with a UV release adhesive 106 can be used as the transfer resin film 105. Generally, a PET film with a thickness of 0.050 mm to 0.100 mm is used as the transfer film, but in this embodiment, the thickness of the transfer resin film 105 is reduced to 0.010 mm to 0.030 mm, preferably 0.015 mm to 0.025 mm. If the thickness of the resin film 105 is less than 0.010 mm, it becomes difficult to stably support the transferred conductive pattern 15, and conversely, it can cause the conductive strip 151 to peel off. If the thickness of the resin film 105 is more than 0.030 mm, it becomes difficult to peel only the resin film 105 from the dielectric layer 14 when transferring the conductive pattern 15 to the dielectric layer 14 used in the electromagnetic wave reflection panel 20 in a later process.

[0037] In Figure 6(C), the substrate 101 for plating growth is removed. Generally, the surface of a SUS substrate is passivated, and the adhesion of the plating metal to the SUS substrate is low. The conductive pattern 15 is transferred from the substrate 101 to the transfer resin film 105 using a UV release adhesive 106.

[0038] In Figure 7(A), an adhesive layer 108 is formed on the entire surface of the resin film 105 on which the conductive pattern 15 is supported, by screen printing or the like. As the adhesive layer 108 applied to the surface of the conductive pattern 15, for example, a pressure-sensitive adhesive can be used. The adhesive layer 108 is applied to a thickness of, for example, 0.010 mm to 0.015 mm.

[0039] In Figure 7(B), a release film 109 is attached to the surface of the adhesive layer 108. The release film 109 is a film that protects the conductive pattern 15 and the adhesive layer 108 until the next step. If the conductive pattern 15 is transferred to the dielectric layer 14 immediately after the formation of the adhesive layer 108, the step in Figure 7(B) may be omitted.

[0040] In Figure 7(C), the release film 109 is removed, and the surface 141 of the dielectric layer 14, which has a metal ground layer 13 already formed on its back surface 142, is placed on top of the surface of the adhesive layer 108. The dielectric layer 14 is, for example, a polycarbonate film with a thickness of 0.3 mm to 1.0 mm, preferably 0.5 mm to 0.9 mm. The metal ground layer 13 is, for example, an Ag-based multilayer film.

[0041] In Figure 8, ultraviolet light is irradiated from the back surface of the transfer resin film 105 to peel off the resin film 105. As shown in Figure 8, in the manufacturing method of this embodiment, the conductive strip 151 of the conductive pattern 15 is transferred to the surface 141 of the dielectric layer 14 by the adhesive layer 108.

[0042] Next, a modified example of the electromagnetic wave reflective panel 20 described above will be explained. In the modified example, elements that are substantially the same as those described above will be denoted by the same reference numerals, and their explanations will be omitted.

[0043] (Modification 1) Figure 9 shows an electromagnetic wave reflective panel 20A. The electromagnetic wave reflective panel 20A has a dielectric layer 14, a conductive pattern 15 provided on one surface (front surface 141) of the dielectric layer 14, a metal ground layer 13 provided on the other surface (back surface 142) of the dielectric layer 14, a first intermediate layer 16 covering the conductive pattern 15, a second intermediate layer 12 covering the metal ground layer 13, a first dielectric substrate 17 covering the first intermediate layer 16, and a second dielectric substrate 11 covering the second intermediate layer 12. That is, the first dielectric substrate 17 is bonded to the front surface 141 of the dielectric layer 14 on which the conductive pattern 15 is formed by the first intermediate layer 16, and the second dielectric substrate 11 is bonded to the metal ground layer 13 on the back surface 142 by the second intermediate layer 12.

[0044] That is, similar to the electromagnetic wave reflection panel 20 shown in FIG. 1, in the electromagnetic wave reflection panel 20A, a conductive pattern 15 is formed of a plurality of conductive strips 151, and each conductive strip 151 is adhered to a surface 141 of a dielectric layer 14 via an adhesive layer 108. A first intermediate layer 16 covering the conductive pattern 15 is an adhesive film, and a first dielectric substrate 17 is bonded to the first intermediate layer 16. A second intermediate layer 12 covering a metal ground layer 13 is an adhesive film, and a second dielectric substrate 11 is bonded to the second intermediate layer 12.

[0045] The first intermediate layer 16 protects the surface of the conductive pattern 15 and is used for bonding the first dielectric substrate 17. The first intermediate layer 16 is made of a material having durability and moisture resistance. For the first intermediate layer 16, for example, ethylene-vinyl acetate (EVA) copolymer, cycloolefin polymer (COP) or the like can be used. The thickness of the first intermediate layer 16 is, for example, 0.010 mm to 0.400 mm.

[0046] The first dielectric substrate 17, which serves as the outermost layer of the electromagnetic wave reflection panel 20A, is preferably formed of a material excellent in impact resistance, durability and transparency. For the first dielectric substrate 17, for example, polycarbonate, acrylic resin, PET or the like can be used. The thickness of the first dielectric substrate 17 is, for example, 1.0 mm to 10.0 mm.

[0047] The second intermediate layer 12 covering the metal ground layer 13 protects the surface of the metal ground layer 13 and is used for bonding the second dielectric substrate 11. The second intermediate layer 12 is made of a material having durability and moisture resistance. For the second intermediate layer 12, for example, EVA, COP or the like can be used. The thickness of the second intermediate layer 12 is, for example, 0.010 mm to 0.400 mm.

[0048] The second dielectric substrate 11, which serves as the outermost layer of the electromagnetic wave reflection panel 20A, is preferably formed of a material excellent in impact resistance, durability and transparency. For the second dielectric substrate 11, for example, polycarbonate, acrylic resin, PET or the like can be used. The thickness of the second dielectric substrate 11 is, for example, 1.0 mm to 10.0 mm.

[0049] By covering the conductive pattern 15 with the first intermediate layer 16 and bonding the first dielectric substrate 17, the intrusion of moisture and air to the surface of the conductive pattern 15 is suppressed, and the surface deterioration of each conductive strip 151 is suppressed. By covering the metal ground layer 13 with the second intermediate layer 12 and bonding the second dielectric substrate 11, the intrusion of moisture and air to the surface of the metal ground layer 13 is suppressed, and the surface deterioration of the metal ground layer 13 is suppressed. Thereby, the capacitance between the metal ground layer 13 and the conductive pattern 15 is maintained constant, and the designed magnitude of phase delay can be maintained.

[0050] (Modification 2) FIG. 10 shows an electromagnetic wave reflection panel 20B. In the electromagnetic wave reflection panel 20B, a hard coat 19 is provided between the back surface 142 of the dielectric layer 14 and the metal ground layer 13. The hard coat 19 prevents environmental factors that affect the reflection characteristics of the electromagnetic wave reflection panel 20B and aged deterioration, such as, for example, an abrasion-resistant hard coat that suppresses aged scratching of the dielectric layer 14, a water-repellent or waterproof hard coat that suppresses moisture intrusion, and an ultraviolet protection hard coat that suppresses ultraviolet absorption. The hard coat 19 may be provided between the back surface 142 of the dielectric layer 14 and the metal ground layer 13 of the electromagnetic wave reflection panel 20 in FIG. 3. Alternatively, it may be provided on the surface of at least one of the first dielectric substrate 17 and the second dielectric substrate 11 that are outermost layers of the electromagnetic wave reflection panel 20A.

[0051] Examples will be described below.

[0052] For the electromagnetic wave reflective panels of Examples 1 to 8, a 0.36 mm thick metal ground layer containing silver was provided on one side of a 0.7 mm thick polycarbonate film, and on the other side of the polycarbonate film, a 0.03 mm thick Ni pattern was fabricated at a different angle to the polycarbonate film via an adhesive layer with the same area occupancy as the conductive pattern and a thickness of 0.01 mm. The Ni pattern was then transferred to a 0.025 mm thick PET film with UV release adhesive, and adhesive was applied to the surface of the Ni pattern transferred to the PET film to a thickness of 0.015 mm. Subsequently, the Ni pattern on the PET film was transferred to a polycarbonate film with the metal ground layer. Then, a 2 mm thick polycarbonate film was bonded to the metal ground layer and the Ni pattern via an adhesive layer with a thickness of 400 μm to fabricate the electromagnetic wave reflective panels of Examples 1 to 8. In other words, in the electromagnetic wave reflective panels of Examples 1 to 8, patterns of plating resist with different thicknesses (heights) were formed on a SUS substrate, and Ni patterns were fabricated by adjusting the immersion time in the plating solution by electroplating. For the electromagnetic wave reflective panels of Examples 1 to 8, the occupancy rate of the Ni pattern on the polycarbonate film was set to 15.4%, and the transmittance of the layer structure was set to 55.5%.

[0053] For evaluation, general-purpose 3D electromagnetic field simulation software was used. The size of the analysis space was set to 83.9 mm x 192.6 mm x 3.7 mm, and the boundary conditions were set to a design in which radio wave absorbers were placed around the analysis space. Furthermore, as the electromagnetic wave reflection panels in Examples 1 to 8, a model was used in which unit cells formed by regularly arranged Ni patterns were arranged in 6 x 36 directions in the x and y axes. Then, plane waves were reflected by the layer configuration models of the electromagnetic wave reflection panels in Examples 1 to 8, and the scattering cross-section was analyzed as the reflection characteristic, and the power reflection efficiency was calculated from the reflection angle and gain (dB) value corresponding to the desired incident angle. In the case of a metasurface having an asymmetric reflection region that reflects at a reflection angle different from the incident angle, as in this embodiment, the calculated power reflection efficiency is corrected by a correction value corresponding to the incident angle. In Examples 1 to 8, the power reflection efficiency was evaluated after correcting the power reflection efficiency, which was calculated from the gain value of -11.192 dB at the 50° RCS plot when a radio wave incident at an incident angle of 0° is reflected at a reflection angle of 50°, with a correction value of 0.7826.

[0054] <Example 1> Example 1 is the first embodiment. In the first embodiment, a plating resist was formed to the same height as the target height of the Ni pattern (i.e., 1.0 times the target height of the Ni pattern, which was 0.03 mm thick). The immersion time of the SUS substrate on which the plating resist was formed in the plating solution was 45 minutes. At this time, the angle θ of the edge portion with respect to the bottom surface in the cross-sectional shape of the Ni pattern formed was 90°, and the power reflection efficiency was 72.0%.

[0055] <Example 2> Example 2 is the second embodiment. In the second embodiment, a plating resist was formed with a height 1.1 times the target height of the Ni pattern (thickness 0.03 mm). The immersion time when the SUS substrate on which the plating resist was formed was set to 45 minutes. At this time, the angle θ of the edge portion with respect to the bottom surface in the cross-sectional shape of the Ni pattern formed was 85°, and the power reflection efficiency was 70.2%.

[0056] <Example 3> Example 3 is the third embodiment. In the third embodiment, a plating resist was formed with a height 1.2 times the target height of the Ni pattern (thickness 0.03 mm). The immersion time when the SUS substrate on which the plating resist was formed was set to 40 minutes. At this time, the angle θ of the edge portion with respect to the bottom surface in the cross-sectional shape of the Ni pattern formed was 80°, and the power reflection efficiency was 69.6%.

[0057] <Example 4> Example 4 is the fourth embodiment. In the fourth embodiment, a plating resist was formed with a height 0.9 times the target height of the Ni pattern (thickness 0.03 mm). The immersion time of the SUS substrate on which the plating resist was formed in the plating solution was set to 45 minutes. At this time, the angle θ of the edge portion with respect to the bottom surface in the cross-sectional shape of the Ni pattern formed was 95°, and the power reflection efficiency was 69.6%.

[0058] <Example 5> Example 5 is Example 5. In Example 5, a plating resist was formed with a height of 0.8 times the target height of the Ni pattern (thickness 0.03 mm). The immersion time when the SUS substrate on which the plating resist was formed was set to 50 minutes. At this time, the angle θ of the edge portion with respect to the bottom surface in the cross-sectional shape of the Ni pattern formed was 100°, and the power reflection efficiency was 68.2%.

[0059] <Example 6> Example 6 is Comparative Example 1. In Comparative Example 1, a plating resist was formed with a height 0.85 times the target height of the Ni pattern (thickness 0.03 mm). The immersion time of the SUS substrate on which the plating resist was formed in the plating solution was set to 60 minutes. At this time, the angle θ of the edge portion with respect to the bottom surface in the cross-sectional shape of the Ni pattern formed was 110°, and the power reflection efficiency was 58.6%.

[0060] <Example 7> Example 7 is Comparative Example 2. In Comparative Example 2, a plating resist was formed with a height of 0.75 times the target height of the Ni pattern (thickness 0.03 mm). The immersion time when the SUS substrate on which the plating resist was formed was set to 65 minutes. At this time, the angle θ of the edge portion with respect to the bottom surface in the cross-sectional shape of the Ni pattern formed was 115°, and the power reflection efficiency was 57.9%.

[0061] <Example 8> Example 8 is Comparative Example 3. In Comparative Example 3, a plating resist was formed with a height 1.3 times the target height of the Ni pattern (thickness 0.03 mm). The immersion time when the SUS substrate on which the plating resist was formed was set to 45 minutes. At this time, the angle θ of the edge portion with respect to the bottom surface in the cross-sectional shape of the Ni pattern formed was 75°, and the power reflection efficiency was 57.8%.

[0062] Table 1 shows the height of the plating resist relative to the target height of the Ni pattern, the immersion time in the plating solution, the angle of the edge portion of the Ni pattern with respect to the bottom surface, and the evaluation results of the power reflection efficiency for the electromagnetic wave reflective panels of Examples 1 to 8 described above.

[0063]

[0064] As shown in Table 1, it was confirmed that the angle of the conductive pattern's edge relative to the bottom surface can be controlled by adjusting the height of the plating resist and / or the immersion time in the plating solution. Furthermore, it was confirmed that by setting the angle of the conductive pattern's edge relative to the bottom surface to 80° or more and 100° or less, a desired electromagnetic wave reflection characteristic, such as a power reflection efficiency of 60% or more, can be obtained.

[0065] The embodiments and modifications described above can be used in combination as appropriate.

[0066] [Note] Preferred forms of this disclosure are noted below.

[0067] (Note 1) An electromagnetic wave reflector comprising: a dielectric layer; a metal ground layer provided on one surface of the dielectric layer; and a plurality of conductive patterns provided on the other surface of the dielectric layer, designed to constitute an asymmetric reflection region that reflects incident electromagnetic waves at a reflection angle different from the angle of incidence, wherein the angles of the edge portions of the cross-sectional shapes of the plurality of conductive patterns with respect to the dielectric layer are 80° or more and 100° or less, respectively.

[0068] (Note 2) The electromagnetic wave reflecting device described in Note 1, wherein the power reflection efficiency of the reflected wave reflected by the asymmetric reflection region relative to the incident wave is 60% or more.

[0069] (Note 3) An electromagnetic wave reflecting device according to Note 1 or Note 2, further comprising: a first intermediate layer covering the plurality of conductive patterns; a first dielectric substrate connected to the plurality of conductive patterns by the first intermediate layer; a second intermediate layer covering the metal ground layer; and a second dielectric substrate connected to the metal ground layer by the second intermediate layer.

[0070] (Note 4) An electromagnetic wave reflecting device according to any one of Notes 1 to 3, wherein the area occupancy rate of the plurality of conductive patterns on the other surface of the dielectric layer is 10.0% or more and 45.0% or less.

[0071] (Note 5) A method for manufacturing an electromagnetic wave reflector, comprising the steps of: forming an etching-resistant film on a substrate for making a transfer pattern; forming a plurality of conductive patterns designed to constitute an asymmetric reflection region that reflects incident electromagnetic waves at a reflection angle different from the incident angle by immersing the substrate on which the etching-resistant film is formed in a resist removal solution; transferring the plurality of conductive patterns from the substrate to a transfer resin film; providing an adhesive layer on the surface of the plurality of conductive patterns transferred to the resin film; and forming the asymmetric reflection region by transferring the plurality of conductive patterns from the resin film to the side of a dielectric layer on which a metal ground layer has been formed in advance on one side, using the adhesive layer, wherein the immersion time when immersing the substrate on which the etching-resistant film is formed in the resist removal solution is adjusted so that the angles of the edge portions of the cross-sectional shape of the plurality of conductive patterns with respect to the dielectric layer are 80° or more and 100° or less, respectively, to produce an electromagnetic wave reflector.

[0072] (Note 6) The method for manufacturing an electromagnetic wave reflector according to Note 5, wherein the etching-resistant film is selected from the group consisting of a plating resist, a copper foil laminate, and an aluminum foil laminate.

[0073] This application claims priority based on Japanese Patent Application No. 2025-29954, filed on 27 February 2025, and incorporates all of its disclosures herein.

[0074] 10 Electromagnetic wave reflector 11 Second dielectric substrate 12 Second intermediate layer 13 Metal ground layer 14 Dielectric layer 15 Conductive pattern 16 First intermediate layer 17 First dielectric substrate 19 Hard coat 20, 20A, 20B Electromagnetic wave reflecting panel 30 Frame 31 Side frame 32 Top frame 33 Bottom frame 34 Legs 100 Electromagnetic wave reflecting fence 101 Substrate 105 Resin film 106 Release adhesive 108 Adhesive layer 109 Release film 151 Conductive strip 154 ​​Plating resist 210 Unit cell

Claims

1. An electromagnetic wave reflector comprising: a dielectric layer; a metal ground layer provided on one surface of the dielectric layer; and a plurality of conductive patterns provided on the other surface of the dielectric layer, designed to constitute an asymmetric reflection region that reflects incident electromagnetic waves at a reflection angle different from the angle of incidence, wherein the angles of the edge portions of the cross-sectional shapes of the plurality of conductive patterns with respect to the dielectric layer are 80° or more and 100° or less, respectively.

2. The electromagnetic wave reflecting device according to claim 1, wherein the power reflection efficiency of the reflected wave reflected by the asymmetric reflection region with respect to the incident wave is 60% or more.

3. The electromagnetic wave reflecting device according to claim 1, further comprising: a first intermediate layer covering the plurality of conductive patterns; a first dielectric substrate connected to the plurality of conductive patterns by the first intermediate layer; a second intermediate layer covering the metal ground layer; and a second dielectric substrate connected to the metal ground layer by the second intermediate layer.

4. The electromagnetic wave reflecting device according to claim 1, wherein the area occupancy rate of the plurality of conductive patterns on the other surface of the dielectric layer is 10.0% or more and 45.0% or less.

5. A method for manufacturing an electromagnetic wave reflector, comprising the steps of: forming an etching-resistant film on a substrate for creating a transfer pattern; immersing the substrate on which the etching-resistant film is formed in a resist removal solution to form a plurality of conductive patterns designed to constitute an asymmetric reflection region that reflects incident electromagnetic waves at a reflection angle different from the incident angle; transferring the plurality of conductive patterns from the substrate to a transfer resin film; providing an adhesive layer on the surface of the plurality of conductive patterns transferred to the resin film; and forming the asymmetric reflection region by transferring the plurality of conductive patterns from the resin film to the side of a dielectric layer on which a metal ground layer has been formed in advance on one side, using the adhesive layer, wherein the immersion time when immersing the substrate on which the etching-resistant film is formed in the resist removal solution is adjusted so that the angles of the edge portions of the cross-sectional shape of the plurality of conductive patterns with respect to the dielectric layer are 80° or more and 100° or less, respectively, to produce an electromagnetic wave reflector.

6. The method for manufacturing an electromagnetic wave reflector according to claim 5, wherein the etching-resistant film is selected from the group consisting of a plating resist, a copper foil laminate, and an aluminum foil laminate.

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