Electromagnetic-wave-scattering body

Abstract

The purpose of the present invention is to provide an electromagnetic-wave-scattering body capable of reflecting electromagnetic waves in a wide range of directions. A sheet-form electromagnetic-wave-scattering body 11 according to the present invention comprises an electroconductive layer 16 including a reflection element 12 for reflecting an electromagnetic wave, and a base material layer 13 for supporting the electroconductive layer 16. A plurality of reflection elements 12 are formed on the base material layer 13. The area of at least one of the reflective elements 12 is set to λ2 to 400λ2 as seen from a plane, and the shortest distance L21 between arbitrary points on the edge of adjacent reflective elements 12 is set to 1.1λ or greater, where λ is the wavelength of the electromagnetic wave reflected by the electromagnetic-wave-scattering body 11.

Description

electromagnetic wave scatterer

[0001] The present invention relates to an electromagnetic wave scatterer.

[0002] Mobile phones and wireless communications use electromagnetic waves in the frequency band of approximately 3 GHz to 300 GHz, known as centimeter waves or millimeter waves. Such short-wavelength electromagnetic waves tend to travel in a straight line, and if there is an obstacle between the transmitting antenna and the receiving antenna, the electromagnetic waves have difficulty circumventing the obstacle and reaching the receiving antenna. For this reason, reflectors that reflect electromagnetic waves in a desired direction are installed on the surfaces of buildings, such as the walls, floors, ceilings, and pillars of buildings (hereinafter referred to as "walls, etc."). For example, Patent Document 1 proposes a reflectarray that reflects electromagnetic waves in a predetermined direction.

[0003] JP 2014-045378 A

[0004] However, in the reflectarray described in Patent Document 1, the reflection of electromagnetic waves is limited to one direction, and it is not possible to reflect the waves in a wide direction (beam width).

[0005] An object of the present invention is to provide an electromagnetic wave scatterer that can reflect electromagnetic waves in a wide range of directions.

[0006] To achieve the above object, the present invention includes the following subject matter.

[0007] Item 1: A sheet-like electromagnetic wave scatterer comprising a conductive layer including reflective elements that reflect electromagnetic waves, and a base layer that supports the conductive layer, wherein a plurality of the reflective elements are formed on the base layer, and when the wavelength of the electromagnetic waves reflected by the electromagnetic wave scatterer is λ, the area of ​​at least one of the reflective elements is λ when viewed from above. ２ More than 400λ ２ and the shortest distance between any points on the edge of adjacent reflecting elements is set to 1.1λ or more.

[0008] Item 2: The electromagnetic wave scatterer according to Item 1, having a thickness of 0.05 mm or more and 10 mm or less.

[0009] Item 3: Radar cross section (RCS) is 200λ ２3. The electromagnetic wave scatterer according to item 1 or 2, wherein the 3 dB beam width obtained by subtracting 3 dB from the maximum gain is 1 degree or more.

[0010] Item 4: The electromagnetic wave scatterer according to any one of Items 1 to 3, wherein the conductive layer has a thickness of 0.05 μm or more and 10 μm or less.

[0011] Item 5: The electromagnetic wave scatterer according to any one of Items 1 to 4, further comprising a protective layer on the conductive layer side of the electromagnetic wave scatterer.

[0012] Item 6: The electromagnetic wave scatterer according to Item 5, further comprising an adhesive layer between the protective layer and the conductive layer.

[0013] Item 7: The electromagnetic wave scatterer according to any one of Items 1 to 6, wherein the maximum waviness height Wz of the edge of the reflecting element cross section of the electromagnetic wave scatterer opposite to the base layer is 0.5 mm or more.

[0014] Item 8: The electromagnetic wave scatterer according to any one of Items 1 to 7, which is quadrangular in plan view, with the length of each side being 20 cm or more and 400 cm or less.

[0015] Item 9: The electromagnetic wave scatterer according to any one of Items 1 to 8, wherein the frequency of the electromagnetic wave reflected by the electromagnetic wave scatterer is 3 GHz or more and 300 GHz or less.

[0016] According to the present invention, it is possible to provide an electromagnetic wave scatterer that can reflect electromagnetic waves in a wide range of directions.

[0017] 4(A) is a cross-sectional view showing a schematic configuration of an electromagnetic wave scatterer according to an embodiment of the present invention, and (B) is an enlarged view of part A of (A). It is a plan view showing a schematic configuration of the entire electromagnetic wave scatterer shown in FIG. 1. It is an explanatory diagram of an example of a beam width. It is a modified example of the shape pattern of the conductor of the reflective element. It is a plan view showing an example of an arrangement of a plurality of reflective elements shown in FIG.

[0018] (Overall Configuration of Electromagnetic Wave Scatterer 11) An embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1(A), the electromagnetic wave scatterer 11 of the present invention includes a conductive layer 16 including reflecting elements 12 that reflect electromagnetic waves, and a base layer 13 that supports the conductive layer 16. In this embodiment, the electromagnetic wave scatterer 11 further includes a protective layer 15 that protects the conductive layer 16, and an adhesive layer 14 that bonds the conductive layer 16 and the protective layer 15, and is laminated in the order of the base layer 13, the conductive layer 16, the adhesive layer 14, and the protective layer 15. Details of each layer will be described later. In FIG. 2(A), the adhesive layer 14 and the protective layer 15 are not shown in part of the electromagnetic wave scatterer 11.

[0019] In the following description, the direction in which each layer is stacked is defined as the up-down direction, and the up-down direction of the electromagnetic wave scatterer 11 corresponds to the up-down direction in Fig. 1. Furthermore, the vertical and horizontal directions are defined based on Fig. 2 and Fig. 4. The up-down direction and vertical and horizontal directions are used for the purpose of explanation, and do not define the up-down direction and vertical and horizontal directions when the electromagnetic wave scatterer 11 is used, for example, when attached to a building or the like. Furthermore, the drawings are not shown to actual scale.

[0020] When the electromagnetic wave scatterer 11 is attached flat to a wall or the like, the electromagnetic wave scatterer 11 reflects electromagnetic waves having incident frequencies of 3 GHz to 5 GHz, 25 GHz to 30 GHz, or 100 GHz to 300 GHz.

[0021] The electromagnetic wave scatterer 11 is sheet-shaped. In this specification, "sheet" refers to a shape in which the thickness of the object is 10% or less of the maximum length between the outer edges in a planar view. When the shape in a planar view is rectangular, the "maximum length between the outer edges in a planar view" refers to the length of the diagonal. When the shape in a planar view is circular, the "maximum length between the outer edges in a planar view" refers to the length of the diameter. In this specification, membranes, foils, films, etc. are also included in the term "sheet."

[0022] The electromagnetic wave scatterer 11 according to this embodiment is quadrilateral (including square and rectangle) in plan view, and is square in the embodiment shown in Fig. 2. The length L10 of one side of the electromagnetic wave scatterer 11 is, for example, preferably 20 cm or more, more preferably 100 cm or more, and even more preferably 200 cm or more. On the other hand, there is no particular upper limit to the length L10 of one side of the electromagnetic wave scatterer 11, but it is, for example, 400 cm or less. When the length L10 of one side is 20 cm or more, electromagnetic waves are likely to be reflected with sufficient intensity.

[0023] The thickness L1 of the electromagnetic wave scatterer 11 is preferably 0.05 mm or more and 10 mm or less, and more preferably 0.08 mm or more and 1.00 mm or less. When the thickness L1 of the electromagnetic wave scatterer 11 is 0.05 mm or more, it is possible to maintain strength while maintaining flexibility. When the thickness L1 of the electromagnetic wave scatterer 11 is 10 mm or less, it is possible to make the electromagnetic wave scatterer 11 thin and, when curved, it is less likely to bend, and as a result, stress concentration is less likely to occur in the reflecting element 12. Here, "bending" refers to bending accompanied by plastic deformation in any of the layers of the electromagnetic wave scatterer 11.

[0024] (Conductive layer 16) As shown in Fig. 2, the plurality of reflective elements 12 of the conductive layer 16 of the electromagnetic wave scatterer 11 are thin-film conductors formed on the upper surface of the base layer 13. The reflective elements 12 of the conductive layer 16 are formed in a square shape in a plan view, and in the example of Fig. 2, a total of four reflective elements 12 each having a square shape in a plan view are arranged on the upper surface of one base layer 13, two vertically and two horizontally.

[0025] The area of ​​at least one reflecting element 12 in a plan view is λ, where λ is the wavelength of the electromagnetic wave incident on the electromagnetic wave scatterer 11 and reflected by the electromagnetic wave scatterer 11. ２ More than 400λ ２ The area of ​​all the reflective elements is set to λ × λ or more and 400 × λ × λ or less. ２ More than 400λ ２The shortest distance L21 between any points on the edge of adjacent reflecting elements 12 is set to 1.1λ or more and 3λ or less, and more preferably 1.2λ or more and 2.7λ or less. In the example of Fig. 2, the shortest distance L21 is the minimum value of the distance between any points on adjacent reflecting elements 12 (conductors).

[0026] 2, the edge of each reflective element 12 that runs along the edge of the base layer 13 is located more inward than the edge of the base layer 13, but the edge of each reflective element 12 that runs along the edge of the base layer 13 may be located in the same position as the edge of the base layer 13. The conductor of each reflective element 12 is preferably made of, for example, silver.

[0027] Furthermore, the thickness L3 of the conductive layer 16, i.e., the thickness (film thickness) L3 of the conductor of the reflective element 12, is preferably thick enough to transmit visible light. The thickness L3 of the reflective element 12 is preferably 0.05 μm or more and 10 μm or less. From the viewpoint of ensuring appropriate electromagnetic wave intensity, the thickness L3 is preferably 5 nm or more. Note that, as will be described later, if the upper or lower surface of the reflective element 12 includes a curved surface and the thickness L3 is not constant, it is preferable that the average value of the thickness L3 be in the above range.

[0028] (Maximum waviness height Wz) If the protective layer 15 side of the laminated electromagnetic wave scatterer 11 is defined as the upper side and the base layer 13 side as the lower side, in this embodiment, as shown in FIG. 1B , the upper or lower surface of the reflective element 12 includes a curved surface. That is, in any cross section along the thickness direction of the electromagnetic wave scatterer 11, the upper edge of the cross section of the reflective element 12 of the conductive layer 16 is a curve with vertical irregularities. The maximum waviness height Wz of this curve (cross-sectional curve) is set to 0.5 mm or more. The maximum waviness height Wz is defined in JIS B0601:2013. In this embodiment, since the reflective element 12 is a thin-film conductor, the upper edge of the cross section of the conductor is set to be the cross-sectional curve.

[0029] 1(B), the upper edge of the cross section of the reflective element 12 of the conductive layer 16 is curved, and the thickness L3 of the reflective element 12 is not uniform. However, a reflective element 12 may be used in which the upper and lower surfaces of the reflective element 12 have the same curved surface and the thickness L3 at any point in a plan view is uniform. In this case, it is preferable to form the upper surface of the base layer 13 as a curved surface corresponding to the lower surface of the reflective element 12. The reflective element 12 is formed on the upper surface of the base layer 13 so that the curved surfaces of the upper surface of the base layer 13 and the lower surface of the reflective element 12 fit together.

[0030] (Reflection Performance of Electromagnetic Wave Scatterer 11) The electromagnetic wave scatterer 11 has a radar cross section (RCS) of 200λ. ２ (200 × λ × λ) mm ２ (square millimeters) or more. Radar cross section is a measure of the ability of a material to reflect electromagnetic waves in the direction of an antenna when irradiated by a radar, and is a function of the geometric cross section, reflectivity, and directivity. Radar cross section is expressed as the area of ​​an isotropic reflector (the cross section of a sphere made of a perfect conductor) that can reflect electromagnetic waves of equal strength to the reflected wave.

[0031] The electromagnetic wave scatterer 11 has a 3 dB beam width (also simply referred to as "beam width") of 1 degree or more, which is 3 dB less than the maximum gain of the reflected wave when the electromagnetic wave is reflected. The beam width refers to the angle between two directions B, including direction A, when direction A in which the reflection intensity of the electromagnetic wave is maximum (maximum gain) and two directions B in which the reflection intensity of the electromagnetic wave is 3 dB lower than the maximum gain are on the same plane (see FIG. 3). In this case, the magnitude of the beam width is expressed as an angle. The direction in which the maximum gain occurs (reflection angle) may coincide with the direction of specular reflection, but it does not have to coincide with the direction of specular reflection.

[0032] Figure 3 is an explanatory diagram of an example of beam width. The horizontal axis represents the reflection direction of the electromagnetic wave in degrees, with the direction in which the reflection intensity of the reflected wave has the maximum gain being an angle of 0 degrees. The vertical axis represents the reflection intensity of the electromagnetic wave. In the example of Figure 3, the angle in the direction in which the maximum gain is 11.47 dB is 0 degrees. The angles at which the reflection intensity is greater than 8.47 dB (3 dB less than 11.47 dB) are between -0.9 degrees and 0.89 degrees, and the beam width is 1.79 degrees.

[0033] By setting the maximum waviness height Wz of the cross-sectional curve of the reflective elements 12 of the conductive layer 16 to 0.5 mm or more, the electromagnetic wave scatterer 11 can scatter electromagnetic waves with a wide beam width. It is known that conventional electromagnetic wave scatterers have a smaller beam width as their overall size increases. However, the electromagnetic wave scatterer 11 of this embodiment has a larger beam width than conventional electromagnetic wave scatterers of the same size, allowing the electromagnetic waves to be scattered over a wider area.

[0034] (Evaluation Test) Examples 1 and 2 were prepared as the electromagnetic wave scatterer 11, and an evaluation test was conducted on the electromagnetic wave reflection intensity for Examples 1 and 2 and Comparative Example 1. However, the electromagnetic wave scatterer 11 of the present invention is not limited to Examples 1 and 2. Table 1 shows the configurations and evaluation results of Examples 1 and 2 and Comparative Example 1.

[0035] (Explanation of Examples and Comparative Examples) (Example 1) The configuration of the electromagnetic wave scatterer 11 created as Example 1 is as follows. In Example 1, a total of 49 square reflective elements 12 of the same shape are arranged in 7 rows and 7 columns. Thickness of the electromagnetic wave scatterer 11: 3 mm Maximum waviness height Wz of the reflective elements 12: 0 mm Number of reflective elements 12: 49 Area of ​​each reflective element 12 as viewed from the plane: 400 mm ２ (square millimeters) (length of one side of each reflecting element 12 L20: 20 mm) Area of ​​the electromagnetic wave scatterer 11 as viewed from the plane: 42,436 mm ２ (square millimeters) Shortest distance L21 between reflective elements 12: 11 mm Electromagnetic wave frequency: 30 GHz Wavelength: 10 mm

[0036] (Example 2) The electromagnetic wave scatterer 11 created as Example 2 has the following configuration. Example 2 differs from Example 1 in the maximum waviness height Wz, the number and area of ​​the reflective elements 12, and the area of ​​the electromagnetic wave scatterer 11. In Example 2, a total of four square reflective elements 12 are arranged in two rows and two columns. Thickness of electromagnetic wave scatterer 11: 3 mm Maximum waviness height Wz of reflective elements 12: 0.5 mm Number of reflective elements 12: 4 Area of ​​each reflective element 12 as viewed from the plane: 40,000 mm ２ (square millimeters) (length of one side of each reflecting element 12 L20: 200 mm) Area of ​​the electromagnetic wave scatterer 11 as seen from the plane: 168,921 mm ２ (square millimeters) Shortest distance L21 between reflective elements 12: 11 mm Electromagnetic wave frequency: 30 GHz Wavelength: 10 mm

[0037] (Comparative Example 1) The electromagnetic wave scatterer 11 produced as Comparative Example 1 has the following configuration. Comparative Example 1 differs from Example 1 in the number of reflective elements 12, the area of ​​the reflective elements 11, and the area of ​​the electromagnetic wave scatterer 11 as viewed from above. Thickness of the electromagnetic wave scatterer 11: 3 mm Maximum waviness height Wz of the reflective elements 12: 0 mm Number of reflective elements 12: 1 Area of ​​the reflective element 12 as viewed from above: 40,000 mm ２ (square millimeters) Planar area of ​​the electromagnetic wave scatterer 11: 40,000 mm ２ (square millimeters) Shortest distance L21 between the reflective elements 12: Not specified because there is only one reflective element 12 (shown as "-" in Table 1) Electromagnetic wave frequency: 30 GHz Wavelength: 10 mm

[0038]

[0039] (Configuration common to Examples 1 and 2 and Comparative Example 1) Planar shape of electromagnetic wave scatterer 11: square shape Length of one side of electromagnetic wave scatterer 11 L10: 200 mm

[0040] Material of base layer 13: Synthetic resin material sheet made of PET (Lumirror 50T60, manufactured by Toray Industries, Inc.) Thickness L2 of base layer 13: 0.13 mm

[0041] Planar shape of the reflective elements 12 of the conductive layer 16: square Material of the reflective elements 12 of the conductive layer 16: metal thin film made of copper (Cu) Thickness (film thickness) L3 of the conductive layer 16: 7 μm

[0042] Material of adhesive layer 14: Rubber-based adhesive (a reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer, a dropping funnel and a stirrer was charged with 100 parts by weight of a rubber-based polymer (a mixture of 50% by mass of styrene-(ethylene-propylene)-styrene type block copolymer and 50% by mass of styrene-(ethylene-propylene) type block copolymer, styrene content 15%, weight average molecular weight 130,000), 40 parts by weight of a synthetic resin (manufactured by Mitsui Chemicals, Inc., FMR-0150), 20 parts by weight of a softener (manufactured by JX Nippon Oil & Energy Corporation, LV-100), 0.5 parts by weight of an antioxidant (manufactured by ADEKA Corporation, Adekastab AO-330) and 150 parts by weight of toluene, and stirred at 40 ° C. for 5 hours). Thickness L4 of adhesive layer 14: 0.05 mm

[0043] Material of protective layer 15: Synthetic resin sheet made of PET (Lumirror 50T60, manufactured by Toray Industries, Inc.) Thickness L5 of protective layer 15: 0.13 mm

[0044] (Measurement of Reflection Intensity (Maximum Gain) and Calculation of Beam Width) The intensity of the reflected waves from the measurement targets, Examples 1 and 2, and Comparative Example 1 (collectively referred to as "samples"), was measured using a cylindrical near-field far-field conversion radar cross section (RCS) measurement system (model number RCS03) provided by KEYCOM Corporation. In this system, two probe antennas (hereinafter referred to as "transmitting antenna" and "receiving antenna") constituting the transmitter and receiver are mounted vertically on the same support base. The sample is attached to a rotation table. The distance between the transmitting antenna and the receiving antenna and the sample is set to 2000 mm. The direction in which the transmitting antenna transmits electromagnetic waves to the sample is the same as the direction in which the receiving antenna receives reflected waves from the sample. The transmitting antenna and the receiving antenna are connected to a vector network analyzer, computer, etc.

[0045] The orientation of the sample relative to the probe antenna is adjusted using a rotating table so that the incident angle is a predetermined angle. The predetermined incident angles are from 0 degrees to 60 degrees in 0.1 degree increments. At each incident angle, an electromagnetic wave with a frequency of 30 GHz and an intensity of 0.1 mW is output from the transmitter, and the reflection intensity of the reflected wave reflected by the sample is measured by the receiver. That is, the receiver measures the reflection intensity of the reflected wave at successively different reflection angles. The maximum value of the measured reflection intensity is defined as the maximum gain. The reflection angle of the reflected wave resulting in the maximum gain is defined as 0 degrees, and the angle between the two directions where the reflection intensity of the electromagnetic wave is 3 dB lower than the maximum gain is defined as the beam width. In calculating the beam width, the direction of the reflected wave resulting in the maximum gain and the two directions where the reflection intensity is 3 dB lower than the maximum gain are assumed to be on the same plane.

[0046] (Evaluation) We evaluated whether electromagnetic waves of sufficient strength reached the receiving antenna. ２ (mm ２ ) or more (in this evaluation test, the radar cross section is 20,000 mm ２ The case where all of the following conditions were met was evaluated as "○", and the case where any one of them was not met was evaluated as "×".

[0047] In Example 1, the maximum gain is 5.8 dB, the beam width is 1 degree, and the radar cross section is 2,452,000 mm ２ In Example 2, the maximum gain was 23.6 dB, the beam width was 1.72 degrees, and the radar cross section was 4,038,800 mm ２ On the other hand, in Comparative Example 1, the beam width was 0.7 degrees, and the electromagnetic waves did not reach the receiving antenna with sufficient strength, so it was evaluated as "x."

[0048] (Modifications of Electromagnetic Wave Scatterer 11) The shape of the electromagnetic wave scatterer 11 is not limited to a rectangle, and may be a geometric shape such as a triangle, pentagon, hexagon, circle, or ellipse, or a non-geometric shape. In the electromagnetic wave scatterer 11, it is preferable that the maximum dimension of the distance between the edges is 20 cm or more and 400 cm or less. The "maximum dimension of the distance between the edges" refers to the diagonal dimension if the electromagnetic wave scatterer 11 is rectangular, refers to the diameter dimension if the electromagnetic wave scatterer 11 is circular, and refers to the length of the major axis if the electromagnetic wave scatterer 11 is elliptical.

[0049] (Modifications of Conductive Layer 16) The conductor of the reflective element 12 of the conductive layer 16 may be made of a metal, metal compound, or alloy having free electrons, and is not limited to silver, but may also be, for example, gold, copper, platinum, aluminum, titanium, silicone, indium tin oxide, or an alloy (for example, an alloy containing nickel, chromium, and molybdenum), etc. Examples of alloys containing nickel, chromium, and molybdenum include various grades of Hastelloy B-2, B-3, C-4, C-2000, C-22, C-276, G-30, N, W, X, etc.

[0050] In the embodiment of Figure 2, the shape (pattern) of the conductor of each reflective element 12 in the conductive layer 16 is all the same shape, size, and material, but it may include multiple different shapes, and the sizes and materials may be different.

[0051] The shape (pattern) of the conductive layer 16 when viewed from the plane of the reflective element 12 may be any geometric shape, such as a triangle, a pentagon, a hexagon, a circle, or an ellipse.

[0052] Furthermore, as shown in Figures 4(A) to 4(F), each reflective element 12 of the conductive layer 16 may be one or more linear conductors formed as a thin film on the upper surface of the base layer 13. Figures 4(A) to 4(F) are diagrams showing part B of Figure 2. In these examples, one or more linear conductors 12A to 12C constituting the conductor are arranged surrounding multiple conductor-free regions 12a. In other words, the reflective element 12 is composed of conductors and conductor-free regions 12a periodically arranged at predetermined intervals. "Linear" means that the longitudinal length is 3000 times or more the length in the direction perpendicular to the longitudinal direction.

[0053] In this way, when the reflective element 12 is composed of conductors and regions 12a without conductors, the area of ​​the reflective element 12 as viewed from the plane is the sum of the area of ​​the conductors and the area of ​​the regions 12a without conductors surrounded by the conductors. Figure 5 shows an example in which each reflective element 12 includes conductors (first and second linear bodies 12A, 12B) as shown in Figure 4(A) and regions 12a without conductors. In Figure 5, the area of ​​the reflective element 12 as viewed from the plane is the sum of the area of ​​the conductors (first and second linear bodies 12A, 12B) and the area of ​​the regions 12a without conductors surrounded by the conductors (first and second linear bodies 12A, 12B) (the areas colored light gray in Figure 5).

[0054] In this case, the shortest distance L21 between any points on the edge of adjacent reflecting elements 12 is the shortest value of the distance between any point on the conductor of one reflecting element 12 and any point on the conductor of the adjacent reflecting element 12. In Figure 5, the shortest distance L21 is the distance between the ends of the linear bodies 12A and 12B of adjacent reflecting elements 12.

[0055] In the example shown in FIG. 4A , a plurality of first linear bodies 12A and a plurality of second linear bodies 12B constituting the conductor are arranged at equal intervals along the vertical and horizontal directions of FIG. 4A , and the area surrounded by two adjacent first linear bodies 12A and two adjacent second linear bodies 12B is a region 12a without conductors. The regions 12a without conductors are squares of the same shape. In other words, a plurality of regions 12a without conductors are arranged in the vertical and horizontal directions at intervals equal to the line width L6 of the linear bodies 12A and 12B. Electrical conduction occurs between the first linear body 12A extending horizontally and the second linear body 12B extending vertically at the intersections where they overlap. The line width L6 of the linear bodies 12A, 12B is preferably set to 0.05 μm or more and 15 μm or less. The distance L7 between adjacent linear bodies 12A, 12B in the vertical or horizontal direction (the length of one side of the square conductor-free region 12a) is set to be greater than the wavelength of visible light and smaller than the wavelength of the electromagnetic wave reflected by the electromagnetic wave scatterer 11. In this example, it is set to 2 μm or more and 10 cm or less. More preferably, it is set to 20 μm or more and 1 cm or less, and even more preferably, it is set to 25 μm or more and 1 mm or less. Even more preferably, it is set to 30 μm or more and 250 μm or less. If the conductor-free region 12a is not square, the maximum length between any two points on the ends of the conductor-free region 12a is set to the above-mentioned length. The conductor-free region 12a may also be filled with the adhesive of the adhesive layer 14.

[0056] In the arrangement of conductors shown in Figure 4 (A), the shape of the conductor-free area 12a is square, but for example, the spacing between adjacent horizontally extending linear bodies 12A and the spacing between adjacent vertically extending linear bodies 12B may be different, and the conductor-free area 12a may be rectangular.

[0057] The reflective elements 12 may also be arranged in the arrangement patterns shown in Figures 4(B) to 4(F). In Figure 4(B), the conductors are arranged in a brickwork pattern. A plurality of first linear bodies 12A are arranged horizontally and vertically at predetermined intervals, and a plurality of second linear bodies 12B extending vertically are arranged in a staggered pattern between adjacent first linear bodies 12A in the vertical direction. The staggered pattern refers to a state in which a plurality of second linear bodies 12B extending vertically are arranged horizontally at predetermined intervals, a plurality of second linear bodies 12B forming one row are located between a plurality of second linear bodies 12B forming a row adjacent to this row in the vertical direction, and the second linear bodies 12B in every other row are arranged in a straight line. The region 12a without conductors is a region surrounded by two adjacent first linear bodies 12A and two adjacent second linear bodies 12B.

[0058] In FIG. 4C , the linear bodies 12A to 12C are arranged so that the multiple regions without conductors form a triangular shape. The multiple regions without conductors include multiple triangular first regions 12a and multiple inverted triangular second regions 12b. The first regions 12a and the second regions 12b are arranged at regular intervals in the horizontal and vertical directions, respectively, and the second regions 12b are arranged between adjacent first regions 12a. Each of the first regions 12a and the second regions 12b is an area surrounded by the first to third linear bodies 12A to 12C. The first linear body 12A is arranged in the horizontal direction, the second linear body 12B is arranged in a direction oblique to the first linear body 12A, and the third linear body 12C is arranged in a direction symmetrical to the second linear body 12B with respect to the first linear body 12A.

[0059] In FIG. 4C, the shape of each of the regions 12a and 12b is an equilateral triangle, but it may be an isosceles triangle or a triangle with three sides of different lengths.

[0060] 4(D), linear bodies 12A are arranged surrounding regular hexagonal regions 12a without conductors. The regions 12a without conductors are arranged consecutively in the vertical direction at intervals of the line width L6 of the linear bodies 12A, and multiple such rows are arranged in the horizontal direction. Between adjacent regions 12a without conductors in the vertical direction, adjacent rows of regions 12a without conductors are arranged.

[0061] In FIG. 4(E), the conductive film has multiple types of non-conductor regions with different shapes. The non-conductor regions include a first region 12a in the shape of a regular pentagon surrounded by the linear body 12A, a second region 12b in the shape of an inverted regular pentagon, and a third region 12c in the shape of a rhombus. The first region 12a to the third region 12c are arranged at regular intervals in the horizontal and vertical directions. Specifically, the first region 12a and the second region 12b are arranged adjacent to each other in the vertical direction with a gap equal to the line width L6 of the linear body 12A. Pairs of the first region 12a and the second region 12b are arranged periodically in the horizontal direction. The third region 12c is arranged between pairs of the first region 12a and the second region 12b adjacent to each other in the horizontal direction. The shapes formed by the first region 12a, the second region 12b, and the third region 12c are arranged at the same period.

[0062] In Figure 4(F), there are multiple types of conductor-free regions with different shapes. The conductor-free regions include a circular first region 12a surrounded by the linear body 12A, a substantially triangular second region 12b, and a substantially inverted triangular third region 12c. The first to third regions 12a to 12c are periodically arranged at regular intervals in the vertical and horizontal directions. The first regions 12a are periodically arranged in a row in the horizontal direction so as to be consecutive with an interval of the line width L6 of the linear body 12A. Rows of such first regions 12a are continuously arranged in the vertical direction, and adjacent first regions 12a in the vertical direction are arranged between adjacent first regions 12a in the horizontal direction.

[0063] 4A to 4F only show the conductors of the reflecting element 12.

[0064] The conductive layer 16 can be manufactured, for example, by forming a conductive film, forming a pattern by etching, and then extracting a conductive thin film having the pattern. Another example is a method in which a photosensitive resist is applied to a base film having a lift-off layer, a pattern is formed by photolithography, the patterned portion is filled with a conductor, and then the conductive thin film having the pattern is extracted. The manufacturing method is not limited to the above, and examples of the formation of the conductive layer 16 include a method of adhering a metal thin film and a method of vapor-depositing a metal.

[0065] (Configuration of Other Layers of Electromagnetic Wave Scatterer 11) (Base Layer 13) In this embodiment, the base layer 13 has an outer shape that is square in a plan view. However, the shape is not limited to this and may be rectangular, circular, elliptical, sector-shaped, polygonal, three-dimensional, or the like, depending on the overall shape of the electromagnetic wave scatterer 11. A synthetic resin sheet is used as the base material that is the base layer 13. Examples of synthetic resins include one or more selected from the group consisting of PET (polyethylene terephthalate), polyethylene, polypropylene, polyvinyl chloride, polystyrene, polymethyl methacrylate, polyester, polyformaldehyde, polyamide, polyphenylene ether, vinylidene chloride, polyvinyl acetate, polyvinyl acetal, AS resin, ABS resin, acrylic resin, fluororesin, nylon resin, polyacetal resin, polycarbonate resin, polyamide resin, and polyurethane resin.

[0066] In this embodiment, the thickness L2 (length in the vertical direction in FIG. 1 ) of the base layer 13 is uniform and set to 0.13 mm, but the thickness L2 is not limited to this and may be set appropriately depending on the manner in which the electromagnetic wave scatterer 11 is used. The thickness does not have to be uniform, and may be formed, for example, in a wedge shape, or in a three-dimensional shape having a partially spherical surface or an uneven shape. The base layer 13 may contain, in addition to the base material, any substance such as a synthetic resin or any other material.

[0067] (Adhesive layer 14) The adhesive layer 14 adheres the protective layer 15 onto the base material layer 13 and the conductive layer 16, and is made of an adhesive. The adhesive layer 14 has a size corresponding to the base material layer 13 in a plan view. A pressure-sensitive adhesive sheet made of synthetic resin or rubber is used as the adhesive that forms the adhesive layer 14. Examples of synthetic resins include acrylic resin, silicone resin, and polyvinyl alcohol resin.

[0068] The thickness L4 of the adhesive layer 14 is the distance between the upper surface of the conductive layer 16 and the lower surface of the protective layer 15, and is set to 150 μm in this embodiment, but is not limited to this. The adhesive of the adhesive layer 14 may be filled in the non-conductor region 12 a of the conductive layer 16 or the peripheral edge of the base layer 13 (the portion between the edge of the base layer 13 and the conductive layer 16). Note that the adhesive layer 14 may contain, in addition to the adhesive, any substance such as a synthetic resin or any other material.

[0069] (Protective Layer 15) The protective layer 15 has a size corresponding to the base layer 13 in a plan view, protects the reflective element 12, and is composed of a protective material. A synthetic resin sheet (film) is used as the protective material of the protective layer 15. Examples of synthetic resins include one or more selected from the group consisting of PET (polyethylene terephthalate), COP (cycloolefin polymer), polyethylene, polypropylene, polyvinyl chloride, polystyrene, polymethyl methacrylate, polyester, polyformaldehyde, polyamide, polyphenylene ether, vinylidene chloride, polyvinyl acetate, polyvinyl acetal, AS resin, ABS resin, acrylic resin, fluororesin, nylon resin, polyacetal resin, polycarbonate resin, polyamide resin, and polyurethane resin. The thickness L5 of the protective layer 15 is preferably set to 0.02 mm or more and 0.30 mm or less. In addition to the protective material, the protective layer 15 may also contain any other substance such as a synthetic resin or any other material.

[0070] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit and scope of the present invention. The dimensions, materials, shapes, and relative arrangements of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention. For example, expressions expressing relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such arrangements, but also express relative displacements with a tolerance or angle or distance to the extent that the same function is obtained. For example, expressions expressing the equality of things, such as "same," "equal," and "homogeneous," not only express strict equality, but also express tolerance or differences to the extent that the same function is obtained. For example, expressions expressing shapes such as a square or cylindrical shape not only express shapes such as a square or cylindrical shape in the strict geometric sense, but also express shapes including concave and convex portions, chamfered portions, etc., to the extent that the same effect is obtained. The expressions "comprise," "include," "have," "includes," or "have" one component are not exclusive expressions that exclude the presence of other components. In addition, expressions that include "approximately," such as "approximately parallel" or "approximately perpendicular," are sometimes used. For example, "approximately parallel" means that the component is essentially "parallel," and does not mean a strictly "parallel" state, but also includes an error of a few degrees. The same applies to other expressions that include "approximately." In addition, expressions that include "... part," such as "end portion," are sometimes used. For example, "end portion" means a portion having a certain range that includes the "end." The same applies to other expressions that include "... part."

[0071] 11 Electromagnetic wave scatterer 12 Conductor 13 Base layer 14 Adhesive layer 15 Protective layer 16 Conductive layer λ Wavelength L21 Shortest distance between any points on the edge of the conductive layer Wz Maximum height waviness

Claims

1. A sheet-like electromagnetic wave scatterer comprising a conductive layer including reflective elements that reflect electromagnetic waves, and a base layer that supports the conductive layer, wherein the reflective elements are formed in a plurality of layers on the base layer, and the area of ​​at least one of the reflective elements, as viewed from a plane, is λ, where λ is the wavelength of the electromagnetic waves reflected by the electromagnetic wave scatterer. ２ More than 400 λ ２ The electromagnetic wave scatterer according to claim 1, wherein the shortest distance between any points on the edge of adjacent reflecting elements is set to 1.1 λ or more.

2. The electromagnetic wave scatterer according to claim 1, having a thickness of 0.05 mm or more and 10 mm or less.

3. Radar cross section (RCS) of 200 λ ２ 3. The electromagnetic wave scatterer according to claim 1 or 2, wherein a 3 dB beam width, which is 3 dB less than the maximum gain, is 1 degree or more.

4. The electromagnetic wave scatterer according to claim 1, wherein the conductive layer has a thickness of 0.05 μm or more and 10 μm or less.

5. The electromagnetic wave scatterer according to claim 1, further comprising a protective layer on the surface of the electromagnetic wave scatterer facing the conductive layer.

6. The electromagnetic wave scatterer according to claim 5, further comprising an adhesive layer between the protective layer and the conductive layer.

7. The electromagnetic wave scatterer according to claim 1, wherein the maximum waviness height Wz of the edge of the electromagnetic wave scatterer opposite the base layer of the cross section of the reflecting element is 0.5 mm or more.

8. The electromagnetic wave scatterer according to claim 1, which is quadrangular in plan view, with each side having a length of 20 cm or more and 400 cm or less.

9. The electromagnetic wave scatterer according to claim 1, wherein the frequency of the electromagnetic wave reflected by said electromagnetic wave scatterer is 3 GHz or more and 300 GHz or less.

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