Radio wave reflectors and building materials

Abstract

Provided are: a radio wave reflector that is flexible and reflects radio waves while maintaining the intensity thereof; and a construction material. The radio wave reflector 11 that reflects radio waves is such that: when the radio wave reflector 11 is in a flat state and a radio wave is reflected by the radio wave reflector 11 at an incidence angle of an incident wave of 15-75 degrees, there is at least one frequency at which the intensity of the reflected wave when the incident wave is regularly reflected is -30 dB or greater relative to the intensity of the incident wave; and in relation to a surface resistivity R1 of the radio wave reflector 11 when the radio wave reflector 11 is in a flat state, a change rate of a surface resistivity R2 when the radio wave reflector 11 is in a curved state along a curved surface having a curvature radius of 200 mm is -10% to 10%, inclusive, and the flexural modulus thereof is 0.05-4 GPa.

Description

Technical Field

[0001] The present invention relates to a radio wave reflector for reflecting radio waves and a building material.

Background Art

[0002] In mobile phones and wireless communications, radio waves in the frequency band of about 2 GHz or more and 300 GHz or less are used. Such radio waves with short wavelengths have strong directivity and are difficult to bend around obstacles, so a reflector is used to spread the radio waves over a wide area. For example, Patent Document 1 proposes a communication system in which a monopole antenna and a metal reflector for reflecting radio waves are arranged in an indoor underfloor space. In Patent Document 1, the radio waves radiated from the monopole antenna are diffused in the underfloor space, and leakage of radio waves from the underfloor space to the outside of the living room (building) and absorption of radio waves by the floor of the building are prevented.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A metal reflector for reflecting radio waves is generally composed of a metal plate such as aluminum or copper. It is known that in the case of radio waves with short wavelengths, a metal reflector reflects radio waves with strong intensity in the specular reflection direction, but it is difficult to diffusely reflect them, and it is difficult for radio waves to reach a wide area of space. In order to make radio waves reach a desired range of space, the metal reflector is attached to an installation surface such as a wall or a pillar in a living room at an appropriate angle to reflect the radio waves in a desired direction.

[0005] Because metal reflectors are generally rigid and lack flexibility, they cannot be attached to curved surfaces such as walls or pillars. Furthermore, if the mounting surface is uneven, fine adjustments such as slightly tilting the reflective surface of the metal reflector are impossible, resulting in a significant deviation from the desired angle. Thus, the lack of flexibility in metal reflectors makes it difficult to create an environment conducive to radio wave reflection within living spaces.

[0006] The present invention aims to provide a radio wave reflector and building material that reflect radio waves while maintaining their intensity and is also flexible. [Means for solving the problem]

[0007] To achieve the above objectives, the present invention encompasses the subject matter described in the following sections.

[0008] Item 1. A radio wave reflector that reflects radio waves, With the radio wave reflector in a flattened state, when an incident wave is reflected by the radio wave reflector at an angle of incidence of 15 degrees or more and 75 degrees or less, there exists a frequency at which the intensity of the reflected wave when the incident wave is specularly reflected is -30 dB or more relative to the intensity of the incident wave. The rate of change in the surface resistivity of the radio wave reflector when it is curved along a curved surface with a radius of curvature of 200 mm, compared to the surface resistivity of the radio wave reflector when it is flat, is between -10% and 10%. A radio wave reflector with a bending modulus of elasticity of 0.05 GPa or more and 4 GPa or less.

[0009] Item 2. A radio wave reflector as described in Item 1, wherein the incident wave frequency is any frequency between 2 GHz and 300 GHz.

[0010] Item 3. A radio wave reflector as described in Item 1 or 2, wherein the Young's modulus is 0.01 GPa or more and 80 GPa or less.

[0011] Item 4. The radio wave reflector described in any one of items 1 to 3, wherein the thickness of the radio wave reflector is 0.01 mm or more and 0.5 mm or less.

[0012] Item 5. A radio wave reflector according to any one of items 1 to 4, comprising at least a conductive thin film layer containing a conductor that reflects radio waves, and a substrate layer laminated on the conductive thin film layer and containing a substrate.

[0013] Item 6. A conductive thin film layer containing a conductor that reflects radio waves; a substrate layer laminated on the conductive thin film layer and containing a substrate; a protective layer containing a protective material for protecting the conductive thin film layer; and an adhesive layer containing an adhesive for bonding the conductive thin film layer and the layer containing the protective material. A radio wave reflector according to any one of claims 1 to 5, wherein the substrate layer, the conductive thin film layer, the adhesive layer, and the protective layer are laminated in that order.

[0014] Item 7. The radio wave reflector according to any one of items 1 to 6, wherein the surface resistivity of the radio wave reflector in a flattened state is 0.003 Ω / □ or more and 10 Ω / □ or less.

[0015] Item 8. The radio wave reflector according to Item 6, wherein the protective layer is treated with an anti-glare or anti-reflection coating.

[0016] Section 9. Building materials containing radio wave reflectors as described in any one of sections 1 through 8. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a radio wave reflector that reflects radio waves while maintaining the intensity of the radio waves and is also flexible. [Brief explanation of the drawing]

[0018] [Figure 1] This figure illustrates the angular range of reflected waves reflected by a radio wave reflector according to one embodiment of the present invention. [Figure 2] This is a cross-sectional view along line BB in Figure 3(B), showing the overall schematic configuration of a radio wave reflector according to one embodiment of the present invention. [Figure 3]Fig. 2 shows the overall schematic configuration of the radio wave reflector, where (A) is a plan view and (B) is an enlarged view of part A in (A). [Figure 4] (A)-(E) are plan views of the conductor showing other examples of the conductor arrangement pattern. [Figure 5] It is a plan view of the conductor showing other examples of the conductor arrangement pattern. [Figure 6] It is a plan view of the radio wave reflector showing other examples of the conductor arrangement pattern. [Figure 7] It is a cross-sectional view showing the schematic configuration of the radio wave reflector according to another embodiment. [Figure 8] It is a cross-sectional view showing the schematic configuration of the radio wave reflector according to another embodiment. [Figure 9] (A) is an explanatory view showing an application example of the building material to a building, and (B) is a plan view showing an application example of the building material to the interior of a room. [Figure 10] It is a diagram for explaining a method of evaluating the reflection direction correction property. [Figure 11] It is a diagram for explaining a method of evaluating the concavo-convex followability, where (A) is a side view and (B) is a front view.

Embodiments for Carrying Out the Invention

[0019] (Overall Configuration) Embodiments of the present invention will be described with reference to the drawings. As shown in Fig. 1, the radio wave reflector 11 of the present embodiment reflects radio waves output from the radio wave source 20. The reflected radio waves are received by the receiving unit 21. The radio wave source 20 is a communication device or the like having a transmitting antenna capable of transmitting radio waves. The receiving unit 21 is a device capable of receiving radio waves. The receiving unit 21 according to the present embodiment is a communication device having a receiving antenna. Examples of the communication device include smartphones, mobile phones, tablet terminals, notebook PCs, portable game machines, repeaters, radios, televisions, and the like.

[0020] The radio wave reflector 11 includes a conductor 12 that reflects radio waves. With the radio wave reflector 11 in a flat position, the radio wave reflects the incident wave at at least one predetermined angle, preferably 45 degrees, and more preferably 15 degrees to 75 degrees, where the incident angle of the incident wave is 2 GHz to less than 6 GHz, 6 GHz to less than 20 GHz, 20 GHz to less than 60 GHz, 60 GHz to less than 100 GHz, 100 GHz to less than 150 GHz, or 150 GHz to 300 GHz. At this time, there is at least one frequency at which the intensity of the reflected wave when the incident wave is specularly reflected by the radio wave reflector 11 (hereinafter also referred to as "specular reflection intensity") is -30 dB to 0 dB relative to the incident wave. Preferably, at a frequency of 28.5 GHz, the specular reflection intensity is -30 dB or more and 0 dB or less relative to the incident wave; more preferably, in the entire frequency band from 20 GHz to 60 GHz, the specular reflection intensity is -30 dB or more and 0 dB or less relative to the incident wave; and even more preferably, in the entire frequency band from 2 GHz to 300 GHz, the specular reflection intensity is -30 dB or more and 0 dB or less relative to the incident wave. "Specular reflection intensity" refers to the reflection intensity, which is the intensity of the reflected radio wave, and refers to the intensity of the reflected wave when the incident wave is specularly reflected. "Flat" means a state without irregularities and without curvature, or, if there are irregularities, a state in which the radius of curvature of any point on the surface is 1000 mm or more.

[0021] The specular reflection intensity is preferably -25 dB or more and 0 dB or less relative to the incident wave, more preferably -22 dB or more and 0 dB or less, even more preferably -20 dB or more and 0 dB or less, and even more preferably -15 dB or more and 0 dB or less. When the specular reflection intensity is -30 dB or more relative to the incident wave, the radio wave reflector 11 can reflect radio waves while maintaining a high reflection intensity, and the receiving unit 21 can receive radio waves at a strength that is practical for use. In this embodiment, the specular reflection intensity and reflection intensity are values ​​when the distance between the reflection point 11a of the radio wave reflector 11 and the radio wave source 20 and the distance between the reflection point 11a of the radio wave reflector 11 and the receiving unit 21 is 1 m.

[0022] Referring to Figure 1, specular reflection refers to the condition where, when radio waves emitted from a radio wave source 20 (transmitting antenna) are reflected by a radio wave reflector 11, the angle of incidence θ1 of the incident wave and the angle of reflection θ2 of the reflected wave are equal. The direction of reflection of the reflected wave when radio waves are specularly reflected is also called the "direction of specular reflection." The angle of incidence θ1 is the angle between the incident wave, which travels in the direction of incidence (shown by arrow A1 in Figure 1) when the radio waves enter the radio wave reflector 11, and the normal 22 of the reflecting surface of the radio wave reflector 11. The angle of reflection θ2 is the angle between the reflected wave, which travels in the direction of reflection (shown by arrow A2 in Figure 1), and the normal 22 of the reflecting surface. The normal 22 is a straight line perpendicular to the tangent (or tangent plane) at the reflection point 11a. The intensity of the reflected wave is also referred to as the "reflection intensity" below.

[0023] The surface resistivity of the radio wave reflector 11 in a flattened state is between 0.003 Ω / □ and 10 Ω / □. As will be described in detail later, the surface resistivity is measured as the surface resistivity of the conductive thin film layer 16 containing the conductor 12. The surface resistivity of the radio wave reflector 11 in a flattened state refers to the surface resistivity of the radio wave reflector 11 when it is placed on a flat mounting surface. "Flat" means a state without irregularities or curvature, or, if there are irregularities, a state where the radius of curvature of any point on the surface is 1000 mm or more.

[0024] The surface resistivity is 1 cm 2 This refers to the surface resistance per square centimeter. Surface resistivity can be measured by the four-terminal method in accordance with JIS K6911 by bringing the measuring terminals into contact with the surface of the conductive thin film layer 16, which will be described later. If the conductive thin film layer 16 is not exposed due to protection by a resin sheet or the like, it can be measured by the eddy current method using a non-contact resistance meter (manufactured by Napson Corporation, product name: EC-80P, or equivalent).

[0025] The radio wave reflector 11 has a surface resistivity change rate R of -10% or more and 10% or less when bent. The surface resistivity change rate R when bent refers to the ratio of the change in surface resistivity R2 when the radio wave reflector 11 is bent along the surface of a member having a curved surface with a radius of curvature of 200 mm, compared to the surface resistivity R1 of the radio wave reflector 11 when it is flat. The surface resistivity change rate R(%) = (R2-R1) / R1 × 100.

[0026] The reflection intensity of radio waves changes depending on the surface resistivity. However, since the rate of change R of the surface resistivity when the radio wave reflector 11 is curved is between -10% and 10%, sufficient radio wave reflection intensity can be achieved even when the radio wave reflector 11 is curved, just as it is when it is flat.

[0027] The radio wave reflector 11 preferably has a flexural modulus of 0.05 GPa or more and 4 GPa or less. The flexural modulus is a value that indicates how much bending stress it can withstand and is defined in JIS K7171. By keeping the flexural modulus within the above range, the radio wave reflector 11 is flexible and can be bent without breaking, allowing it to be attached to a curved surface with a radius of curvature of 200 mm or more. The flexural modulus is measured in accordance with JIS K7171. Flexibility refers to the property of being flexible under normal temperature and pressure, and being able to deform by bending, flexing, or folding even when force is applied, without shearing or breaking.

[0028] The radio wave reflector 11 preferably has a Young's modulus of 0.01 GPa or more and 80 GPa or less. Young's modulus is the elastic modulus of a solid when tension is applied in one direction and stretched, and is also called the tensile modulus, as defined in JIS K7161-2014. By keeping the Young's modulus within the above range, the radio wave reflector 11 becomes more easily deformable, and can be curved without breaking the radio wave reflector 11, allowing it to be attached to a curved surface with a radius of curvature of 200 mm or more. The Young's modulus is measured in accordance with JIS K7127-1999.

[0029] The radio wave reflector 11 has at least enough flexibility to be attached along a curved surface with a radius of curvature of 200 mm or more, and preferably enough flexibility to be attached along a curved surface with a radius of curvature of 100 mm or more.

[0030] The radio wave reflector 11 may be plastic. Plasticity refers to the property of being able to be deformed by applying external pressure, and retaining the deformed shape even after the force is removed when deformation exceeding the elastic limit is applied by pressurization. All of the synthetic resins constituting the base layer 13, adhesive layer 14, and protective layer 15 may be plastic, or at least one of the base layer 13, adhesive layer 14, and protective layer 15 may be plastic.

[0031] The radio wave reflector 11 has a yellow index of 3 or less, which is the difference between the yellow index after the heat and humidity resistance test and the yellow index before the heat and humidity resistance test. The yellow index, also called the degree of yellowness, refers to the degree to which the hue deviates from colorless or white towards yellow. The yellow index is determined by a method compliant with JIS K7373.

[0032] The heat and humidity resistance test involves leaving the radio wave reflector 11 in a constant temperature and humidity chamber adjusted to a temperature of 60°C and a humidity of 95%RH (relative humidity of 95%) for 500 hours. After that, the radio wave reflector 11 is removed from the constant temperature and humidity chamber and left to stand at room temperature for 4 hours, and then the properties and condition of the radio wave reflector 11 are checked.

[0033] Before and after the heat and humidity resistance test, the radio wave reflector 11 is subjected to specular reflection of incident waves with a frequency of 2 GHz to 300 GHz at a predetermined angle of incidence of 15 degrees to 75 degrees, preferably 45 degrees, and more preferably within the entire range of angles between 15 degrees and 75 degrees. At this time, there exists an incident wave frequency for which the difference between the intensity of the reflected wave of the radio wave reflector 11 after the heat and humidity resistance test and the intensity of the reflected wave of the radio wave reflector 11 before the heat and humidity resistance test is within 3 dB. Preferably, the difference in the intensity of the reflected wave of the radio wave reflector 11 before and after the heat and humidity resistance test is within 3 dB across the entire frequency band from 2 GHz to 300 GHz.

[0034] The radio wave reflector 11 has a surface resistivity change rate r (also called "surface resistivity change rate during the heat and humidity resistance test") of 20% or less before and after the heat and humidity resistance test. The surface resistivity change rate r during the heat and humidity resistance test refers to the ratio of the change in surface resistivity r2 after the heat and humidity resistance test compared to the surface resistivity r1 before the test. The surface resistivity change rate r during the heat and humidity resistance test can be calculated using the following formula: r = (r1 - r2) / r1 × 100

[0035] The reflection intensity of radio waves changes depending on the surface resistivity. However, since the rate of change r of the surface resistivity of the radio wave reflector 11 during the heat and humidity resistance test is 20% or less, the reflection intensity of the radio wave reflector 11 does not decrease significantly even after the heat and humidity resistance test, and sufficient radio wave reflection intensity can be achieved.

[0036] When a pencil hardness test is performed on the radio wave reflector 11, the pencil hardness of the protective layer 15 at a surface load of 500g is preferably "F" or higher, more preferably "H" or higher, and even more preferably "4H" or higher. The "pencil hardness test" as used herein is a test in accordance with JIS K 5600-5-4 (1999). Furthermore, "surface load of 500g" includes any load applied to the surface during the pencil hardness test that is 500g ± 10g. When a pencil hardness test is performed on the protective layer 15, the pencil hardness of the protective layer 15 at a surface load of 500g is also acceptable if it is F or higher.

[0037] Furthermore, after heat and humidity resistance testing, the radio wave reflector 11 preferably has a reduction rate of 50% or less in adhesive strength to the adherend layer in the protective layer 15, more preferably 45% or less, and even more preferably 40% or less. In this specification, "adherend layer" means a layer that is in direct contact with the target layer. In this embodiment, the adherend layer of the protective layer 15 is the adhesive layer 14. The adhesive strength is measured by a tensile adhesive strength test in accordance with JIS K 6849 (1994).

[0038] Furthermore, it is preferable that the radio wave reflector 11 has a kurtosis of -0.4 or less when the receiving angular position of the reflected wave is changed within an angular range α of -15 degrees or more and +15 degrees or less with respect to the specular reflection direction of the radio wave, in a virtual plane that includes the incident direction of the incident wave and the reflection direction of the reflected wave. More preferably, the kurtosis is -1.0 or less, even more preferably -1.1 or less, and even more preferably -1.2 or less. The lower limit of the above kurtosis is not particularly limited, but is usually around -0.5. The virtual plane can also be said to be a plane that includes the reflection point 11a on the reflective surface of the reflector, the radio wave source 20, and the reflected wave receiving section 21. The kurtosis is determined with the radio wave reflector 11 in a flat state.

[0039] Kurtosis is a statistic that represents how much a distribution deviates from a normal distribution, indicating the sharpness of the peak and the breadth of the tail. As shown in Figure 1, assume that radio waves emitted from the radio wave source 20 are incident on the radio wave reflector 11 at a predetermined incident angle θ1. The receiving angular position i of the receiving unit 21 is moved by predetermined angles (for example, 5 degrees each) from the specular reflection direction of the radio waves, centered on the reflection point 11a, within an angular range α of -15 degrees or more and +15 degrees or less relative to the specular reflection direction of the radio waves, and the reflection intensity x is measured. The receiving angular position i of the receiving unit 21 is located on a circular arc centered on the reflection point 11a. Values ​​of the reflection intensity at each receiving angular position i The average value of TIFF0007886865000001.tif8170 TIFF0007886865000002.tif5170, if the standard deviation is s, the kurtosis can be calculated using the following formula.

[0040] TIFF0007886865000003.tif14170 (Formula 1)

[0041] When kurtosis has a negative value, it indicates that the intensity data at each angular position is flatter than a normal distribution; that is, the data is scattered from around the mean and the tails of the distribution are wide. The smaller the kurtosis value, the flatter the distribution. In this embodiment, by setting the kurtosis to -0.4 or less, the difference in reflection intensity depending on the receiving angular position is reduced within an angular range α of ±15 degrees with respect to the specular reflection direction of radio waves.

[0042] The radio wave reflector 11 may be transparent as a whole, i.e., transparent. As will be described in detail later, the radio wave reflector 11 comprises at least a base layer 13 and a conductive thin film layer 16 consisting of a conductor 12, and preferably further comprises an adhesive layer 14 and a protective layer 15. The base layer 13, adhesive layer 14 and protective layer 15 may each be formed of a resin that is transparent to visible light, and the conductor 12 of the conductive thin film layer 16 may be formed to a thickness that is transparent to visible light. Here, "transparent" means that the other side of the radio wave reflector 11 is visible when viewed from one side, and includes translucency, and is not limited to complete transparency with a total light transmittance of 100%. The radio wave reflector 11 may also be colored. The radio wave reflector 11 has a total light transmittance of 65% or more in a D65 standard light source, preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. Total light transmittance refers to the ratio of the total transmitted light flux to the parallel incident light flux of a test specimen, and is measured in accordance with JIS K 7375:2008.

[0043] As shown in Figure 3, in this embodiment, the radio wave reflector 11 preferably has an overall shape that is square in plan view, with a side length L10 of 20 cm or more and 400 cm or less. Although radio waves with frequencies of 2 GHz or more and 300 GHz or less are attenuated with distance, it is preferable that the side length L10 be 20 cm or more in order to reflect with sufficient intensity at all points within a practical distance from the radio wave source 20. There is no particular upper limit to the side length L10, but from a manufacturing standpoint, 400 cm or less is preferable. The overall shape of the radio wave reflector 11 is not limited to a square, but may be a rectangle, or a polygon such as a triangle, pentagon, or hexagon. In this case, the length of the shortest side is set to 20 cm or more and 400 cm or less. Alternatively, the shortest distance between a vertex and the opposite side, or the shortest distance between a side and the opposite side, may be set to 20 cm or more and 400 cm or less. Furthermore, if the overall shape of the radio wave reflector 11 is circular, the diameter is set to 20 cm or more and 400 cm or less. If the overall shape of the radio wave reflector 11 is elliptical, the minor axis is set to be between 20 cm and 400 cm. If the overall shape of the radio wave reflector 11 is sector-shaped, the length of the shorter arc or radius is set to be between 20 cm and 400 cm. Furthermore, the overall shape of the radio wave reflector 11 may be a three-dimensional shape such as cylindrical or conical. The overall shape of the radio wave reflector 11 has a shape and size that can reflect radio waves with a reflection intensity of -30 dB or more relative to the incident wave, and the shape and size are appropriately selected according to the manner in which the radio wave reflector 11 is used.

[0044] The radio wave reflector 11 is preferably set to a thickness L11 of 0.01 mm or more and 0.5 mm or less. The thicknesses of the base layer 13, conductive thin film layer 16, adhesive layer 14, and protective layer 15 are set so that the thickness L11 of the radio wave reflector 11 is 0.5 mm or less. The thickness L11 of the radio wave reflector 11 is set to a thickness that allows the radio wave reflector 11 to be flexible and, when an external force is applied to the radio wave reflector 11 and the radio wave reflector 11 is bent, does not concentrate the force on the conductor 12 of the conductive thin film layer 16, but rather distributes the force to the base layer 13, adhesive layer 14, and protective layer 15.

[0045] The radio wave reflector 11 has at least enough flexibility to be attached along a curved surface with a radius of curvature of 200 mm or more, and preferably enough flexibility to be attached along a curved surface with a radius of curvature of 100 mm or more. The thickness L11 of the radio wave reflector 11 is the sum of the thickness L3 of the conductive thin film layer 16 and the thickness L8 of the base layer 13, or the sum of the thickness L3 of the conductive thin film layer 16, the thickness L8 of the base layer 13, the thickness L4 of the adhesive layer 14, and the thickness L5 of the protective layer 15. However, since the thickness L3 of the conductive thin film layer 16 is very thin compared to the thicknesses L8, L4, and L5 of the base layer 13, adhesive layer 14, and protective layer 15, the thickness L3 of the conductive thin film layer 16 may be ignored when calculating the thickness L11 of the radio wave reflector 11.

[0046] The thickness L11 of the radio wave reflector 11, the thickness L3 of the conductive thin film layer 16, the thickness L8 of the substrate layer 13, the thickness L4 of the adhesive layer 14, and the thickness L5 of the protective layer 15 are determined by measuring multiple arbitrary locations and calculating the average value of the obtained measurements. For measuring thicknesses L11, L3, L8, L4, and L5, for example, a reflectance spectroscopic film thickness analyzer (e.g., F3-CS-NIR, manufactured by Filmetrics Co., Ltd.) is used as a measuring instrument.

[0047] (Structure of the radio wave reflector 11) One embodiment of the radio wave reflector 11 will be described with reference to Figures 2 and 3. The radio wave reflector 11 may have a conductive thin film layer 16 containing a conductor 12, a base layer 13 laminated on the conductive thin film layer 16 and containing a substrate, a protective layer 15 containing a protective material for protecting the conductive thin film layer 16, and an adhesive layer 14 containing an adhesive for bonding the conductive thin film layer 16 and the protective layer 15. Alternatively, the radio wave reflector 11 may also comprise a conductive thin film layer 16 containing a conductor 12 and a resin that maintains the conductor 12 in a sheet shape. At least one of the base layer 13 containing the substrate, the protective layer 15 containing a protective material for protecting the conductive thin film layer 16, and the adhesive layer 14 containing an adhesive for bonding the conductive thin film layer 16 and the protective layer 15 may be made of resin. In the embodiment shown in Figure 2, the radio wave reflector 11 has a conductive thin film layer 16 laminated on the base layer 13, and the adhesive layer 14 and the protective layer 15 are laminated thereon in order.

[0048] In the following explanation, the vertical direction is defined based on Figure 2, and the vertical and horizontal directions are defined based on Figure 3. However, the vertical and vertical directions and vertical and horizontal directions are used for explanatory purposes only and do not define the vertical and vertical directions when the radio wave reflector 11 is used, such as when it is attached to a building. Also, Figures 1 to 11 do not represent the actual scale. Furthermore, in Figure 3(A), the adhesive layer 14 and protective layer 15 are omitted from the illustration for a portion of the radio wave reflector 11.

[0049] (Base material layer 13) In this embodiment, the base layer 13 is formed in a square shape when viewed from above. However, it is not limited to this, and may be rectangular, circular, elliptical, sector-shaped, polygonal, three-dimensional, etc., to match the overall shape of the radio wave reflector 11. A sheet made of synthetic resin is used as the base material for 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. In addition, the thickness L8 of the base layer 13 (length in the vertical direction in Figure 2) is set to 0.13 mm in this embodiment, but it is not limited to this, and can be set appropriately depending on the manner in which the radio wave reflector 11 is used. The base layer 13 may also contain any synthetic resin or other material or any other component in addition to the base material.

[0050] (Conductive thin film layer 16) The conductive thin film layer 16 is preferably formed as a thin film on the upper surface of the substrate layer 13, comprising one or more linear conductors 12. The conductor 12 is preferably composed of, for example, silver (Ag). However, the conductor 12 may be composed of a metal, metal compound, or alloy having free electrons, and is not limited to silver. For example, it may be gold (Au), copper (Cu), platinum (Pt), zinc (Zn), iron (Fe), tin (Sn), lead (Pb), aluminum (Al), cobalt (Co), indium (In), nickel (Ni), chromium (Cr), titanium (Ti), altimon (Sb), bismuth (Bi), thallium (Tl), germanium (Ge), cadmium (Cd), silicon (Si), tungsten (W), molybdenum (Mo), indium tin oxide (ITO), and alloys (for example, alloys containing nickel, chromium, and molybdenum). Examples of alloys containing nickel, chromium, and molybdenum include various grades of Hastelloy such as B-2, B-3, C-4, C-2000, C-22, C-276, G-30, N, W, and X. The conductive thin film layer 16 may also contain any synthetic resin or other material or component in addition to the conductor 12.

[0051] In this embodiment, as shown in Figure 3(B), one or more linear conductors 12 are arranged surrounding multiple regions 12a without conductors 12. That is, the conductors 12 and regions 12a without conductors 12 are arranged periodically at predetermined intervals. The conductors 12 and regions 12a without conductors 12 come together to form a thin film. The interval between adjacent regions 12a without conductors 12 may be equal to the line width L6 of the conductor 12, or it may be greater than the line width L6. Note that "linear" means that the length in the longitudinal direction is 3000 times or more the length in the direction perpendicular to the longitudinal direction. In the example shown in Figure 3(B), the conductors 12 are arranged at equal intervals along the vertical and horizontal directions, and the regions 12a without conductors 12 surrounded by the conductors 12 are square. That is, the regions 12a without conductors 12 are arranged at intervals equal to the line width L6 of the conductors 12. At the intersection where the conductor 12(12A) oriented horizontally and the conductor 12(12B) oriented vertically overlap, the conductors 12A and 12B are electrically conductive. The line width L6 of the conductor 12 is preferably set to 0.05 μm or more and 15 μm or less. The spacing L7 between adjacent conductors 12 along the vertical or horizontal direction (the length of one side of the square area 12a without conductors 12) is set to be greater than the wavelength of visible light and less than the wavelength of radio waves reflected by the radio wave reflector 11, and in this example, it is set to 2 μm or more and 10 cm or less. More preferably 20 μm or more and 1 cm or less, and even more preferably 25 μm or more and 1 mm or less. Even more preferably 30 μm or more and 250 μm or less.

[0052] Furthermore, the thickness (film thickness) L3 of the conductor 12 is preferably such that it is transparent to visible light. The thickness L3 of the conductor 12 is preferably 0.05 μm or more and 10 μm or less. From the viewpoint of ensuring appropriate radio wave intensity, the thickness L3 is preferably 5 nm or more.

[0053] The surface roughness Sa of the conductive thin film layer 16 is not particularly limited, but is preferably 1 μm or more and 7 μm or less, and more preferably 1.03 μm or more and 6.72 μm or less. A surface roughness Sa within this range makes it easier to diffusely reflect radio waves.

[0054] The surface roughness Sa is determined by the arithmetic mean height according to ISO 25178 and measured in accordance with ISO 25178. The surface roughness Sa of the conductive thin film layer 16 can be determined by measuring the surface roughness at multiple locations on the surface of the conductive thin film layer 16 using a laser microscope (product name VK-X1000 / 1050, manufactured by Keyence Corporation, or equivalent) and calculating the average value of the obtained measurements. In some cases, the conductor 12 and the substrate layer 13 may also be measured. In this embodiment, there are multiple conductors 12, and the surface roughness is measured at multiple locations on each conductor 12, and the average value of these measurements is taken as the surface roughness Sa of the conductive thin film layer 16.

[0055] The conductive thin film layer 16 preferably has a coverage rate of 1% to 50%, and more preferably 1% to 10%. Coverage rate refers to the ratio of the area occupied by the conductor 12 per unit area in a plan view. In the embodiments shown in Figures 2 and 3, it refers to the ratio of the area of ​​the conductor 12 in a plan view to the area of ​​the substrate layer 13 in a plan view. Coverage rate can also be said to be the area of ​​the substrate layer 13 covered by the conductor 12 relative to the area of ​​the substrate layer 13 in a plan view. Coverage rate is measured using a scanning electron microscope (SEM), transmission electron microscope (TEM), optical microscope, etc.

[0056] In the arrangement of conductors 12 shown in Figure 3(B), the shape of the region 12a without conductors 12 is square. However, for example, the spacing between adjacent laterally extending conductors 12A and the spacing between adjacent vertically extending conductors 12B may be different, and the shape of the region 12a without conductors 12 may be rectangular. Furthermore, the conductors 12 may be arranged in the arrangement patterns shown in Figures 4(A) to (E). In Figure 4(A), multiple conductors 12A are arranged laterally and vertically with predetermined spacings, and multiple vertically extending conductors 12B are arranged in a staggered pattern between vertically adjacent conductors 12A. A staggered arrangement refers to a state in which multiple conductors 12B extending in the vertical direction are arranged horizontally at predetermined intervals, and the multiple conductors 12B forming one row are located between the multiple conductors 12B forming the adjacent row in the vertical direction of that row, and the conductors 12B in skipped rows are arranged in a straight line. In Figure 4(B), the conductor 12A extends horizontally, and the conductors 12B and 12C extend along diagonal directions that are symmetrically tilted with respect to the horizontal direction, and the conductors 12B and 12C intersect each other on the conductor 12A. As a result, the shape of the region 12a without conductors 12 is an equilateral triangle. Note that the shape of the region 12a without conductors 12 may not be an equilateral triangle, but an isosceles triangle or a triangle with three sides of different lengths. In Figure 4(C), hexagonal regions 12a without conductors 12, surrounded by linear conductors 12, are periodically arranged. In Figure 4(D), pentagonal regions 12a without conductors 12, surrounded by linear conductors 12, are periodically arranged. In Figure 4(E), circular regions 12a without conductors 12, surrounded by linear conductors 12, are periodically arranged. Note that Figures 4(A) to (E) only show the conductors 12.

[0057] Examples of methods for manufacturing the conductive thin film layer 16 having the arrangement patterns shown in Figures 3(B) and 4 include the following: a method in which a conductive film is formed, a pattern is formed by etching, and the conductive thin film having the pattern is removed; a method in which a photosensitive resist is coated onto a base film having a lift-off layer, a pattern is formed by photolithography, a conductor is filled into the patterned area, and then the conductive thin film having the pattern is removed. However, the manufacturing method is not limited to the above, and in forming the conductive thin film layer 16, methods such as bonding a metal thin film or depositing metal can be used.

[0058] (Other embodiments of the conductive thin film layer 16) Figure 5 shows another embodiment of the conductive thin film layer 16. In the embodiment of Figure 5, a plurality of conductors 12 are periodically arranged on the upper surface of the substrate layer 13 in a sheet shape (thin film). In this embodiment, circular conductors 12 are used in a plan view. The diameter L1 and the shortest distance (spacing) L2 between adjacent conductors 12 are set according to the frequency band of the radio waves to be reflected. In this embodiment, in particular, it is set to reflect radio waves in the frequency band of 20 GHz or more and 300 GHz or less, which is related to the fifth-generation mobile communication system (5G). However, it is not limited to this, and the diameter L1 and spacing L2 may be set so that the conductors 12 reflect radio waves with frequencies of 2 GHz or more and 300 GHz or less. The diameter L1 of each conductor 12 may be 0.7 mm or more and 800 mm or less, and the spacing L2 may be 1 μm or more and 1000 μm or less. The number of conductors 12 is set appropriately according to the size (area) of the substrate layer 13. A sheet shape refers to a shape in which the length in the longitudinal direction is approximately the same as, or less than 3000 times, the length in the direction perpendicular to the longitudinal direction.

[0059] The shape of the conductor 12 is not limited to a circle, but may be any shape. Preferably, the shape is such that the sides of one conductor 12 are parallel to the sides of adjacent conductors 12, and the spacing between a given conductor 12 and all adjacent conductors 12 is equal, allowing for periodic arrangement. For example, it may be a square, rectangle, triangle, hexagon, etc. In this case, the length of the shortest side of the conductor 12, the shortest distance between a vertex of the conductor 12 and the opposite side, or the shortest distance between a certain side and the opposite side may be set to 0.005 μm or more and 100 mm or less. More preferably, it may be set to 0.1 μm or more and 1000 μm or less. The other configurations and operations are the same as those of the embodiments shown in Figures 2 and 3, so detailed explanations are omitted by using the same reference numerals for corresponding components.

[0060] (Other embodiments of the conductive thin film layer 16) The conductive thin film layer 16 may have, for example, a metamaterial structure. The metamaterial structure consists of sheet-shaped conductors 12, which are dielectrics, arranged periodically in equal proportions. This periodic arrangement structure gives it a negative dielectric constant and reflects radio waves belonging to a specific frequency band determined based on the periodic interval. The shape of each conductor 12 is not limited and may be the shape described above, but for example, as shown in Figure 6, each conductor 12 may be square-shaped. The length of one side L12 and the spacing L13 between adjacent conductors 12 may be set so that the conductors 12 reflect radio waves with frequencies of 2 GHz or more and 300 GHz or less. In this case, the length of one side L12 of the conductor 12 may be 0.7 mm or more and 800 mm or less, and the spacing L13 may be 1 μm or more and 1000 μm or less. The thickness L3 of the conductor 12 is preferably 350 nm (0.35 μm) or less, more preferably 100 nm or less, and even more preferably 50 nm or less. The number of conductors 12 is appropriately set according to the size (area) of the substrate layer 13. In one example, four conductors 12 may be formed on the substrate layer 13, two vertically and two horizontally, according to the size of the substrate layer 13. In this case, the length L12 of one side of each conductor 12 is 77.460 mm, the spacing L13 between adjacent conductors 12 is 100 μm, and the thickness L3 is set to 350 nm (0.35 μm) or less. The conductive thin film layer 16 is not limited to a metamaterial structure and may be a metal nanowire laminate, multilayer graphene, or partially exfoliated graphite. In addition to conductors, the conductive thin film layer 16 may also contain any synthetic resin or other material or component.

[0061] (adhesive layer 14) The adhesive layer 14 adheres the protective layer 15 to the base layer 13 and the conductive thin film layer 16, and is composed of an adhesive. The adhesive layer 14 has a size corresponding to the base layer 13 in a plan view. As the adhesive for the adhesive layer 14, adhesive sheets made of synthetic resin or rubber are used. Examples of synthetic resins include acrylic resin, silicone resin, and polyvinyl alcohol resin. The thickness L4 of the adhesive layer 14 is preferably set to 5 μm or more and 500 μm or less. In addition to the adhesive, the adhesive layer 14 may also contain any synthetic resin or other substance or any component.

[0062] The adhesive layer 14 is preferably made of a synthetic resin material with a dielectric loss tangent (tanδ) of 0.018 or less. A lower dielectric loss tangent is preferable, but it is usually 0.0001 or higher. The dielectric loss tangent represents the degree of electrical energy loss within the dielectric material; materials with a larger dielectric loss tangent result in greater electrical energy loss. By using an adhesive layer 14 with a dielectric loss tangent of 0.018 or less, the loss of electrical energy of radio waves in the radio wave reflector 11 is reduced, and the reflection intensity can be increased.

[0063] Furthermore, it is preferable that the synthetic resin material of the adhesive layer 14 has a relative permittivity that changes depending on the frequency of the electric field. Relative permittivity is the ratio of the permittivity of the medium (synthetic resin material in this embodiment) to the permittivity of vacuum. By changing the relative permittivity in response to the electric field, the intensity of reflected waves at electric fields of specific frequencies can be increased. It is preferable that the relative permittivity changes between 1.5 and 7. More preferably, it is preferable that it changes between 1.8 and 6.5. The inductive loss tangent and relative permittivity are measured using a measuring device (for example, Toyo Technica, model TTPX tabletop cryogenic prober, material impedance analyzer MIA-5M) by known methods (for example, cavity resonator method, coaxial resonator method).

[0064] Furthermore, not only the adhesive layer 14, but also the synthetic resin materials constituting the base layer 13 and the protective layer 15 may have a dielectric loss tangent of 0.018 or less, and their relative permittivity may change depending on the electric field.

[0065] (Protective layer 15) The protective layer 15 has a size corresponding to the base layer 13 in a plan view and protects the conductor 12, and is composed of a protective material. A sheet (film) made of synthetic resin is used as the protective material for 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 synthetic resin or other substance or any component.

[0066] The protective layer 15 may have an anti-glare treatment or anti-reflection treatment applied to at least one of the top surface (outer surface) and bottom surface (surface in contact with the adhesive layer 14) of a synthetic resin film, as shown in Figure 2.

[0067] Anti-glare treatment (also called "AG treatment" or "non-glare treatment") refers to a treatment that forms an uneven surface on at least one surface of the protective layer 15, scattering light and suppressing reflections of light sources such as illumination onto the protective layer 15. Methods for applying anti-glare treatment include, for example, applying a binder resin containing dispersed fine particles to the surface of the film. Known methods such as sandblasting and chemical etching may also be used.

[0068] Anti-reflection treatment (also called "AR treatment") is a process in which an anti-reflective coating is formed on at least one surface of a film, and the reflected light reflected from the surface of the anti-reflective coating and the reflected light reflected from the interface between the anti-reflective coating and the film are attenuated by interference, thereby suppressing reflections of light sources such as illumination. The anti-reflective coating may be a single layer, or it may be made by alternately laminating thin films with different refractive indices, and known anti-reflective coatings can be used.

[0069] The protective layer 15 may be a film made of synthetic resin with an anti-glare or anti-reflection film attached to one or both sides of it.

[0070] The protective layer 15 has a moisture permeability of 20 g / m² at a temperature of 40°C and a humidity of 90% rh (relative humidity). 2 Preferably, it is 24 hours or less, and more preferably 16 g / m² 2 • Less than 24 hours, and more preferably 12 g / m² 2 • Less than 24 hours, and more preferably 10 g / m² 2 • Less than 24 hours. The moisture permeability of protective layer 15 at a temperature of 40°C and a humidity of 90%rh (relative humidity) is 20 g / m². 2 If the duration is 24 hours or less, the conductive thin film layer 16 is less likely to corrode, and the surface resistivity of the conductive thin film layer 16 is less likely to increase, which is an advantage. The term "water vapor permeability" as used herein is measured by a test method compliant with JIS Z 0208 (1976).

[0071] (Other embodiments) Figure 7 shows another embodiment of the present invention. The radio wave reflector 11 shown in Figure 7 is formed by laminating conductive materials 12A and 12B in two layers vertically using resin substrate layers 13A and 13B. Each conductive material 12A formed on the substrate layer 13A and each conductive material 12B formed on the substrate layer 13B are aligned and laminated so as to overlap when viewed from above. Note that the arrangement patterns of the conductive thin film layers 16A and 16B in Figure 7 do not necessarily have to overlap when viewed from above, and the conductive thin film layers 16A and 16B may be formed in different arrangement patterns. The lower surface of the substrate layer 13B is attached to the conductive material 12A by adhesive layer 14A, and a protective layer 15 is attached to the conductive material 12B by adhesive layer 14B. In this embodiment, the Young's modulus is preferably 0.01 GPa or more and 80 GPa or less, and the thickness of the radio wave reflector is preferably 0.01 mm or more and 0.5 mm or less. The total light transmittance of the radio wave reflector 11 is 70%.

[0072] Radio waves incident on the radio wave reflector 11 are reflected by the first layer of conductor 12B, but some pass through the conductor 12B without being reflected. These radio waves that pass through the conductor 12B are reflected by the second layer of conductor 12A. In this way, by stacking multiple layers of conductor 12 in the vertical direction, radio waves that have passed through the upper layer of conductor 12B can be reflected by the lower layer of conductor 12A, and the reflection intensity of the radio wave reflector 11 can be kept higher compared to when there is only one layer of conductor 12. In addition, the kurtosis of the distribution of reflection intensity in the angular range α of ±15 degrees with respect to the specular reflection direction of the radio waves can be further reduced, and the difference in reflection intensity depending on the angular position within the angular range α becomes smaller. Furthermore, since two adhesive layers 14A and 14B are used, the dielectric loss tangent value becomes even smaller than in the embodiment shown in Figure 2, and the reflection intensity can be kept even higher. The other configurations and operations are the same as in the embodiments shown in Figures 2 and 3, so detailed explanations are omitted by assigning the same reference numerals to the corresponding components.

[0073] In the embodiment shown in Figure 7, the conductor 12 formed on the base layer 13 is laminated in two layers, but it may be laminated in three or more layers. Increasing the number of laminated conductors 12 increases the reflectivity, but the overall thickness of the radio wave reflector 11 increases, reducing its flexibility and visible light transmittance. For this reason, the number of laminates should be set appropriately according to the intended use, for example, by increasing the number of laminates when the radio wave reflector 11 is to be installed in a location where flexibility or transparency is not particularly required.

[0074] (Other embodiments) Figure 8 shows another embodiment of the radio wave reflector 11. In the embodiment of Figure 8, a conductive thin film layer 16 and a substrate layer 13 are provided, which are composed of a plurality of linear conductors 12, similar to the embodiments shown in Figures 2 and 3, but the adhesive layer 14 and protective layer 15 are not provided. In this embodiment, the flexural modulus is preferably 0.05 GPa or more and 4 GPa or less, the Young's modulus is preferably 0.01 GPa or more and 80 GPa or less, and the thickness of the radio wave reflector is preferably 0.01 mm or more and 0.5 mm or less. The total light transmittance of the radio wave reflector 11 is 70%. The other configurations and operations are the same as in the embodiments shown in Figures 2 and 3, so detailed explanations are omitted by assigning the same reference numerals to the corresponding components.

[0075] In the embodiment shown in Figure 8, the conductive thin film layer 16 is composed of a plurality of linear conductors 12. However, the conductive thin film layer 16 is not limited to this embodiment. For example, a single sheet-shaped dielectric conductor 12 may be formed in a square shape over substantially the entire upper surface of the substrate layer 13. In this case, the coverage rate is defined as the ratio of the area occupied by the conductor 12 per unit area in the portion of the substrate layer 13 on which the conductive thin film layer 16 is provided, and the coverage rate is 100%. Note that in a plan view, the size of the conductor 12 is slightly smaller than the size of the substrate layer 13, and the conductor 12 does not have to be formed in a region close to the side edge of the substrate layer 13.

[0076] Furthermore, the conductive thin film layer 16 in the embodiment shown in Figure 8 may be formed by periodically arranging multiple sheet-like conductors 12 in an equal arrangement, similar to the conductive thin film layer 16 in the embodiment shown in Figure 6. In this case, the multiple conductors 12 are arranged at predetermined intervals across substantially the entire upper surface of the substrate layer 13. The shape of the conductors 12 may be square, circular, rectangular, triangular, polygonal, or the like. The conductive thin film layer 16 may have a metamaterial structure and may be a metal nanowire laminate, multilayer graphene, or partially exfoliated graphite.

[0077] (use) Any of the above-mentioned radio wave reflectors 11 may be included in the building material 30. The building material 30 can be installed inside a building, for example, as shown in Figure 9(A), as decorative materials 30A such as walls, ceilings, and floors in rooms and corridors, wallpaper for partitions, posters, etc., and decorative materials 30B such as transparent seals for light fixtures. By attaching decorative materials 30A and 30B containing the radio wave reflector 11 to the wall surface 31 or light fixture cover 32, radio waves that enter the room from outside through windows 33, etc., are reflected by the decorative materials 30A and 30B installed on the wall surface 31 or light fixture cover 32. As a result, radio waves can reach a wider area of ​​the indoor space S, improving the convenience of radio wave reception.

[0078] Furthermore, the radio wave reflector 11 may be formed as a component made of a non-conductive material such as resin, or as being held inside a building material. For example, the wall surface 31 or the light fixture cover 32 itself, which are building materials 30, may be composed of the radio wave reflector 11. Moreover, the building material 30 is not limited to interior walls or light fixture covers, but may also be partitions, columns, lintels, exterior walls of buildings, windows, etc. For example, Figure 9(B) is a view of the interior from a plan view, and the building material 30, which is the radio wave reflector 11, is formed as a corner column 30C with a curved surface at the corner of the room. Radio waves entering from the window 33 are reflected by the corner column 30C, allowing the radio waves to reach a wider area of ​​the interior space S. Note that Figures 9(A) and 9(B) show examples of the application of the building material 30 and do not show the actual range of radio wave reflection.

[0079] (Evaluation test) Examples 1 to 9 were prepared as radio wave reflectors 11, and evaluation tests were conducted on Examples 1 to 9 and Comparative Examples 1 to 4 regarding their ability to correct the reflection direction and follow surface irregularities. However, the radio wave reflector 11 of the present invention is not limited to Examples 1 to 9.

[0080] (Description of Examples and Comparative Examples) Table 1 shows the details of Examples 1-9 and Comparative Examples 1-4, as well as the results of their evaluation tests. In Table 1, Examples 1-9 and Comparative Examples 1-4 have one of the following configurations for the radio wave reflector: "Configuration A" to "Configuration D" or "Metal Plate". "Configuration A" is a configuration in which a base layer 13, a conductive thin film layer 16 (conductor 12), an adhesive layer 14, and a protective layer 15 are laminated in order, as shown in the embodiments in Figures 2 and 3. A synthetic resin material sheet made of PET (Toray Industries, Ltd., Lumirror 50T60; product number #125-U34 when the thickness of the base layer 13 and protective layer 15 is 0.13 mm, product number #188-U34 when the thickness is 0.19 mm) was used for the base layer 13 and protective layer 15.

[0081] "Configuration B" is a configuration in which a conductive thin film layer 16 (conductor 12) is laminated on a base layer 13, as shown in the embodiment in Figure 8. A synthetic resin material sheet made of PTFE (fluororesin) (TOMBP No. 9000 manufactured by Nichias Corporation) was used as the base layer 13.

[0082] "Configuration C" is a configuration in which a conductive thin film layer 16 (conductor 12) is laminated on a substrate layer 13, as shown in the embodiment in Figure 8, and thin film glass (G-Leaf manufactured by Nippon Electric Glass Co., Ltd.) is used as the substrate layer 13.

[0083] Configuration D, as shown in the embodiments in Figures 2 and 3, is a configuration in which a base layer 13, a conductive thin film layer 16 (conductor 12), an adhesive layer 14, and a protective layer 15 are laminated in that order. The base layer 13 is different from that of Configuration A; in Configuration D, a synthetic resin material sheet made of PEEK (polyether ether ketone) (Midfil NS manufactured by Kurabo Industries Ltd.) is used as the base layer 13. The other components are the same as those of Configuration A.

[0084] A "metal plate" is composed of a single metal plate.

[0085] Table 1 shows the arrangement patterns of the conductors 12 in the conductive thin film layer 16 as "linked type" and "isolated type". The "linked type" is, as shown in Figures 3(B) and 4, in which one or more linear conductors 12 are arranged surrounding multiple areas 12a without conductors 12; that is, the conductors 12 and areas 12a without conductors 12 are arranged periodically at predetermined intervals. The "isolated type" is, as shown in Figure 5 or 6, in which sheet-shaped conductors 12 are arranged periodically.

[0086] Table 1 shows the shapes of the arrangement patterns of the conductors 12 as "staggered," "grid," and "circular." "Staggered" is the case when the arrangement pattern of the conductors 12 is "connected," and as shown in Figure 4(A), the conductors 12 are arranged in a staggered shape. "Grid" is the case when the arrangement pattern of the conductors 12 is "connected," and as shown in Figure 3(B), the conductors 12 are arranged at equal intervals along the vertical and horizontal directions. "Circular" is the case when the arrangement pattern of the conductors 12 is "isolated," and as shown in Figure 5, the shape of each conductor 12 is circular.

[0087] Table 1 indicates that the adhesives used in the adhesive layer 14 are "rubber-based" and "acrylic-based." "Rubber-based" refers to a rubber-based adhesive. The rubber-based adhesive was obtained by the following method: In a reaction vessel equipped with a cooling tube, nitrogen inlet tube, thermometer, dropping funnel, and stirring device, 100 parts by weight of 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 synthetic resin (manufactured by Mitsui Chemicals, Inc., FMR-0150), 20 parts by weight of softener (manufactured by JX Nippon Oil & Energy Corporation, LV-100), 0.5 parts by weight of antioxidant (manufactured by ADEKA Corporation, ADEKA Stab AO-330), and 150 parts by weight of toluene were charged and stirred at 40°C for 5 hours. This mixture was then applied to the protective layer 15 and dried. This obtained a rubber-based adhesive.

[0088] "Acrylic" refers to an acrylic adhesive. The acrylic adhesive was obtained by the following method: 40 parts by mass of monofunctional long-chain urethane acrylate (AGC PEM-X264, molecular weight 10000) and 60 parts by mass of acrylic monomer (35 parts by mass of 2-ethylhexyl acrylate (2EHA), 10 parts by mass of cyclohexyl acrylate (CHA), 10 parts by mass of 2-hydroxyethyl acrylate (2HEA), and 5 parts by mass of dimethylacrylamide (DMAA)) were mixed and stirred. To the obtained (meth)acrylic acid ester copolymer solution, 0.5 parts by mass of a crosslinking agent (1,6-hexanediol diacrylate (A-HD-N, manufactured by Shin-Nakamura Chemical Co., Ltd.)) and a photopolymerization initiator (Omnirad651 (manufactured by IGM Japan LLC)) were added per 100 parts by mass of the solid content of the (meth)acrylic acid ester copolymer, and the mixture was stirred and degassed under vacuum. This yielded an acrylic adhesive.

[0089] Furthermore, the adhesive layer 14 has a dielectric loss tangent of 0.002, which is 0.018 or less.

[0090] (Description of Examples and Comparative Examples) The radio wave reflector 11 created as Example 1 has the configuration of "Configuration A". The radio wave reflector 11 has a square planar shape, with a side length L10 of 100 cm and a thickness L11 of 0.4 mm. The radio wave reflection intensity in a flat state ("Specular reflection intensity at 28.5 GHz in a flat state" in Table 1) is -24 dB, the Young's modulus is 0.08 GPa, the flexural modulus is 2.2 GPa, the surface resistivity is 1.7 Ω / □, and the rate of change R of surface resistivity when curved is 4.3%. The total light transmittance of the radio wave reflector 11 is 89%. The thickness L8 of the substrate layer 13 is 0.13 mm. The arrangement pattern of the conductors 12 in the conductive thin film layer 16 is linked, and the shape of the arrangement pattern is staggered. The line width L6 of the conductor 12 is 400 nm, the thickness L3 of the conductor 12 is 0.4 μm, and the spacing L7 between adjacent conductors 12 is 100 μm (tolerance ±10 μm; the same applies hereafter). The conductor 12 is a thin metal film made of silver (Ag). The surface roughness Sa of the conductive thin film layer 16 is 1.1 μm, and the coverage is 0.80%. The adhesive layer 14 is rubber-based, the thickness L4 of the adhesive layer 14 is 0.04 mm, and the thickness L5 of the protective layer 15 is 0.13 mm.

[0091] The manufacturing method for the radio wave reflector 11 of Example 1 will now be described. First, the conductor 12 is formed on the substrate layer 13. A core layer of 0.01 μm to 3 μm in thickness is formed on one surface of a copper foil with a thickness of 5 μm to 200 μm, which has sufficient strength as a metal layer, by electrolytic or electroless plating. Then, a conductive thin film layer 16 in a predetermined arrangement pattern is formed on the surface of the core layer by electrolytic or electroless plating. Next, the entire conductive thin film layer 16 is covered with the substrate layer 13. An adhesive is pre-applied to the substrate layer 13. Then, the copper foil and core layer are etched off. As a result, the conductor 12 is formed on the substrate layer 13.

[0092] Then, the protective layer 15 is attached to the side of the conductor 12 opposite to the base layer 13 using the adhesive layer 14. The protective layer 15 is attached to the conductor 12 of the base layer 13 using the adhesive layer 14, taking care not to include air bubbles. This completes the manufacture of the radio wave reflector 11.

[0093] The radio wave reflector 11 created as Example 2 has the configuration of "Configuration B" and does not have an adhesive layer 14 or a protective layer 15. The thickness L11 of the radio wave reflector 11 is 0.08 mm. The radio wave reflection intensity in a flat state is -23 dB, the Young's modulus is 0.5 GPa, the flexural modulus is 0.6 GPa, the surface resistivity is 1.4 Ω / □, and the rate of change R of surface resistivity when curved is 2.8%. The total light transmittance of the radio wave reflector 11 is 0.1%. The thickness L8 of the base layer 13 is 0.08 mm. The arrangement pattern of the conductors 12 in the conductive thin film layer 16, the shape of the arrangement pattern, the line width L6, the thickness L3, the spacing L7 between adjacent conductors 12, the material of the conductors, and other configurations are the same as in Example 1. The radio wave reflector 11 of Example 2 is manufactured in the same way as in Example 1, but the adhesive layer 14 and protective layer 15 are not provided.

[0094] The radio wave reflector 11 created as Example 3 has the same "Configuration A" configuration as Example 1. The thickness L11 of the radio wave reflector 11 is 0.5 mm. The radio wave reflection intensity in a flat state is -25 dB, the Young's modulus is 0.08 GPa, the flexural modulus is 2.2 GPa, the surface resistivity is 1.5 Ω / □, and the rate of change R of surface resistivity when curved is 9.8%. The total light transmittance of the radio wave reflector 11 is 87%. The thickness L8 of the base layer 13 is 0.19 mm. The adhesive layer 14 is rubber-based, with a thickness L4 of 0.12 mm and a thickness L5 of 0.19 mm for the protective layer 15. The arrangement pattern of the conductors 12 in the conductive thin film layer 16, the shape of the arrangement pattern, the line width L6, the thickness L3, the spacing L7 between adjacent conductors 12, the material of the conductors, and other configurations are the same as in Example 1.

[0095] The radio wave reflector 11 created as Example 4 has the configuration of "Configuration C" and does not have an adhesive layer 14 or a protective layer 15. The thickness L11 of the radio wave reflector 11 is 0.05 mm. The radio wave reflection intensity in a flat state is -26 dB, the Young's modulus is 70 GPa, the flexural modulus is 0.05 GPa, the surface resistivity is 3.8 Ω / □, and the rate of change R of surface resistivity when curved is 3.9%. The total light transmittance of the radio wave reflector 11 is 90%. The thickness L8 of the base layer 13 is 0.05 mm. The arrangement pattern of the conductors 12 in the conductive thin film layer 16 is linked, and the shape of the arrangement pattern is grid-like. The line width L6, thickness L3, spacing L7 between adjacent conductors 12, conductor material, and other configurations are the same as in Example 1. The radio wave reflector 11 of Example 4 is manufactured in the same way as in Example 1, but the adhesive layer 14 and protective layer 15 are not provided.

[0096] The radio wave reflector 11 created as Example 5 has the configuration of "Configuration D". The thickness L11 of the radio wave reflector 11 is 0.5 mm. The radio wave reflection intensity in a flat state is -25 dB, the Young's modulus is 0.1 GPa, the flexural modulus is 3.7 GPa, the surface resistivity is 2.1 Ω / □, and the rate of change R of surface resistivity when curved is 9.5%. The total light transmittance of the radio wave reflector 11 is 0.1%. The thickness L8 of the base layer 13 is 0.25 mm. The arrangement pattern of the conductors 12 in the conductive thin film layer 16 is linked, and the shape of the arrangement pattern is grid-like. The adhesive layer 14 is rubber-based, the thickness L4 of the adhesive layer 14 is 0.06 mm, and the thickness L5 of the protective layer 15 is 0.19 mm. The line width L6, thickness L3 of the conductors 12, the spacing L7 between adjacent conductors 12, the material of the conductors, and other configurations are the same as in Example 1.

[0097] The radio wave reflector 11 prepared as Example 6 has the configuration of "Configuration A". The radio wave reflection intensity in a flat state is -27 dB, the Young's modulus is 0.08 GPa, the flexural modulus is 2.2 GPa, the surface resistivity is 0.003 Ω / □, and the rate of change R of surface resistivity when bent is 1.1%. The total light transmittance of the radio wave reflector 11 is 80%. The arrangement pattern of the conductors 12 in the conductive thin film layer 16 is isolated, and the shape of the arrangement pattern is circular. The thickness L3 of the conductor 12 is 0.5 μm, the diameter L1 of the conductor 12 is 1000 μm, and the spacing L2 between adjacent conductors 12 is 10 μm (tolerance ±10 μm; the same applies hereafter). The surface roughness Sa of the conductive thin film layer 16 is 2.3 μm, and the coverage is 23%. The other configurations are the same as in Example 1.

[0098] The manufacturing methods for the radio wave reflectors 11 of Examples 6, 7 and Comparative Example 3 will now be described. First, the conductor 12 is formed on the substrate layer 13. In the manufacturing of Examples 6, 7 and Comparative Example 3, a roll-to-roll sputtering apparatus is used. A target containing metal (e.g., silver) is attached to the cathode provided in the deposition chamber of the sputtering apparatus. An earth shield is provided with a size such that 5% of the cathode is hidden. The deposition chamber of the sputtering apparatus is evacuated by a vacuum pump, for example, 3.0 × 10⁻⁶ -4 The pressure is reduced to Pa, and argon gas, for example, is supplied at a predetermined flow rate (100 sccm). In this state, the substrate layer 13 is transported below the cathode at a transport speed of 0.1 m / min and a tension of 100 N. Pulse power of 5 kW is supplied from a bipolar power supply connected to the cathode, causing metal to be ejected from the target and deposited on the surface of the substrate layer 13, thereby forming a thin metal film. A mask is formed on the surface of the thin metal film in the shape of a conductor 12 arrangement pattern by photolithography. Then, the unmasked portions of the thin metal film are removed with a chemical. Next, the mask portions are removed to form the conductor 12. As a result, a conductive thin film layer 16 having multiple conductors 12 is formed on the substrate layer 13.

[0099] The evaluation of whether a metal thin film has been formed to the desired thickness can be performed, for example, by the following procedure. For example, an indenter (HYSITRON, TI950) is used to create indentations that penetrate the metal thin film at predetermined locations (approximately 30 locations in this embodiment). A laser microscope (KEYENCE, VK-X1000 / 1050) is used to measure the thickness of the metal thin film from the gaps created by the indentations. The average film thickness and standard deviation are determined from the approximately 30 measurement values, and it is evaluated whether the average film thickness is the desired thickness L3 (e.g., 50 nm) and whether the variation in the measurement values ​​is within the desired range (e.g., standard deviation within 5).

[0100] Then, the protective layer 15 is attached to the conductor 12 using the adhesive layer 14. The protective layer 15 is attached to the conductor 12 of the base layer 13 using the adhesive layer 14, taking care not to include any air bubbles. This completes the production of the radio wave reflector 11.

[0101] The radio wave reflector 11 prepared as Example 7 has the configuration of "Configuration A". The radio wave reflection intensity in a flat state is -29 dB, the Young's modulus is 0.08 GPa, the flexural modulus is 2.2 GPa, the surface resistivity is 9.8 Ω / □, and the rate of change R of surface resistivity when bent is 1.2%. The total light transmittance of the radio wave reflector 11 is 79%. The arrangement pattern of the conductors 12 in the conductive thin film layer 16 is isolated, and the shape of the arrangement pattern is circular. The thickness L3 of the conductor 12 is 0.04 μm, the diameter L1 of the conductor 12 is 1000 μm, and the spacing L2 between adjacent conductors 12 is 10 μm. The conductor 12 is a metal thin film made of titanium. The surface roughness Sa of the conductive thin film layer 16 is 3.1 μm, and the coverage is 23%. The other configurations are the same as in Example 1.

[0102] The radio wave reflector 11 prepared as Example 8 has the configuration of "Configuration D". The bending modulus is 3.9 GPa, and the rate of change R of surface resistivity during bending is 9.6%. The other configurations are the same as in Example 5.

[0103] The radio wave reflector 11 prepared as Example 9 has an acrylic adhesive layer 14. The other components are the same as in Example 3.

[0104] The radio wave reflector prepared as Comparative Example 1 is a single metal plate made of aluminum with a thickness of 0.5 mm. In a flat state, the radio wave reflection intensity is -24 dB, the Young's modulus is 70 GPa, the flexural modulus is 71 GPa, the surface resistivity is 0.00005 Ω / □, and the rate of change R of surface resistivity when curved is 0.1%. The total light transmittance of radio wave reflector 11 is 0%, and the surface roughness Sa is 1.06 μm.

[0105] The radio wave reflector prepared as Comparative Example 2 has the configuration of "Configuration B" and does not have an adhesive layer 14 or a protective layer 15. The thickness L11 of the radio wave reflector 11 is 0.6 mm. In a flat state, the radio wave reflection intensity is -23 dB, the Young's modulus is 0.5 GPa, the flexural modulus is 0.6 GPa, and the surface resistivity is 1.4 Ω / □. The surface resistivity when the radio wave reflector is curved along a curved surface with a radius of curvature of 200 mm could not be measured because the radio wave reflector 11 was damaged during the bending process, and the rate of change R of the surface resistance could not be measured. The total light transmittance of the radio wave reflector 11 is 0%. The thickness L8 of the base layer 13 is 0.6 mm. The arrangement pattern of the conductors 12 in the conductive thin film layer 16, the shape of the arrangement pattern, the line width L6, the thickness L3, the spacing L7 between adjacent conductors 12, the material of the conductors, and other configurations are the same as in Example 1. The radio wave reflector 11 of Comparative Example 2 is manufactured in the same manner as in Example 1, but the adhesive layer 14 and protective layer 15 are not provided, and the thickness of the base material layer 13 is set to be larger compared to Example 2.

[0106] The radio wave reflector prepared as Comparative Example 3 has the configuration of "Configuration A". In a flat state, the radio wave reflection intensity is -38 dB, the Young's modulus is 0.08 GPa, the flexural modulus is 2.2 GPa, the surface resistivity is 20.5 Ω / □, and the rate of change R of the surface resistivity is 0.6%. The total light transmittance of the radio wave reflector 11 is 80%. The arrangement pattern of the conductors 12 in the conductive thin film layer 16 is isolated, and the shape of the arrangement pattern is circular. The thickness L3 of the conductor 12 is 0.02 μm, the diameter L1 of the conductor 12 is 1000 nm, and the spacing L2 between adjacent conductors 12 is 10 μm. The conductor 12 is a metal thin film made of titanium. The surface roughness Sa of the conductive thin film layer 16 is 2.6 μm, and the coverage is 23%. The other configurations are the same as in Example 1.

[0107] The radio wave reflector prepared as Comparative Example 4 has the configuration of "Configuration D". In a flat state, the radio wave reflection intensity is -31 dB, the Young's modulus is 0.8 GPa, the flexural modulus is 4.2 GPa, and the rate of change R of surface resistivity is 13%. The total light transmittance of the radio wave reflector 11 is 80%. The other configurations are the same as in Example 5.

[0108] (Measurement of reflectivity) The intensity of reflected waves from Examples 1-9 and Comparative Examples 1-4 (collectively referred to as "samples"), which were the objects to be measured, was measured according to the method for measuring the amount of reflection described in JIS R1679:2007, using the following procedure. The samples were placed flat on a sample stand, and the transmitting and receiving antennas were positioned according to the incident angle θ1 and reflection angle θ2 of the radio waves (θ1, θ2 = 45 degrees). The distance between the sample and the receiving antenna and the distance between the sample and the transmitting antenna were set to 1 m. A continuously changing radio wave with a frequency of 3 to 300 GHz was output from the transmitting antenna, and the amount of reflection (reflection intensity) to the radio wave was measured. The amount of reflection at a frequency of 28.5 GHz and the frequency band in which the amount of reflection was -30 dB or higher were determined.

[0109] First, a reference metal plate (aluminum A1050 plate, 3 mm thick) was placed on the sample stand, and the received level was measured and recorded using a scalar network analyzer. At this time, the coaxial cables of the receiving antenna and transmitting antenna were directly connected using the scalar network analyzer, and the signal level at each frequency was set to 0 for calibration. After that, the apparatus was reconfigured and measurements were performed again. The reference metal plate was removed from the sample stand, the sample was placed on the sample stand, and the received level was measured and recorded. The amount of reflection in the specular reflection direction of the radio wave reflector 11 being measured was determined by subtracting the received level of the reference metal plate from the measured received level. The same measurement was repeated for each sample. When the radio wave frequency was 10 GHz or less, the first Fresnel radius of the rectangular horn antenna was taken into consideration, and a plane wave was irradiated onto the sample using a millimeter-wave lens as appropriate.

[0110] (Measurement of surface resistivity, calculation of the rate of change R of surface resistivity) The surface resistivity R1 of the radio wave reflector 11 in a flattened state was measured in accordance with the four-terminal method specified in JIS K7194:1994 by bringing the measuring terminals into contact with the surface of the conductive thin film layer 16 made of the conductor 12. If the conductive thin film layer 16 was not exposed and protected by a resin sheet or the like, it was measured using the eddy current method with a non-contact resistance meter (Napson Corporation, product name: EC-80P, or equivalent). The surface resistivity of the conductive thin film layer 16 is shown as the surface resistivity of the radio wave reflector 11.

[0111] The surface resistivity R2 of the radio wave reflector 11 when it is curved along a curved surface with a radius of curvature of 200 mm is measured as follows: A column member having a circular or semicircular cross-section with a radius of 200 mm is prepared, and the sample is curved and fixed along the outer surface of the column member. Then, the surface resistivity R2 is measured in accordance with the four-terminal method described above. The rate of change R of the surface resistivity during curvature is calculated as R(%) = (R2-R1) / R1 × 100.

[0112] In cases where the arrangement pattern of the conductive thin film layer 16 is linked, as in Examples 1-5 and Comparative Example 2, or where it consists of a single metal plate, as in Comparative Example 1, the entire conductive thin film layer 16, i.e., 20 arbitrary points on the multiple conductive elements 12 constituting the conductive thin film layer 16, were used as measurement targets, and the arithmetic mean of the obtained values ​​was taken as the surface resistivity R1 and R2. In cases where the arrangement pattern of the conductive elements 12 is isolated, as in Examples 6, 7, and Comparative Example 3, 20 arbitrary points on the multiple conductive elements 12 were used as measurement targets, and the arithmetic mean of the obtained values ​​was taken as the surface resistivity R1 and R2. In Examples 6, 7, and Comparative Example 3, the shape of each conductive element 12 in plan view is circular with a diameter of 1000 nm, and each conductive element 12 was used as the measurement target for surface resistivity R1 and R2. However, when the area of ​​each conductive element 12 in plan view is several centimeters square meter, the entire conductive thin film layer 16 is used as the measurement target for surface resistivity R1 and R2.

[0113] (Measurement of bending modulus and Young's modulus) The flexural modulus is measured according to the method conforming to JIS K7171, and the Young's modulus is measured according to the method conforming to JIS K7127-1999.

[0114] (Evaluation metrics) Two evaluation indicators were established: reflection direction correction capability and surface conformability. Reflection direction correction capability evaluates whether the radio wave reflector 11 can reflect radio waves in a direction with a practically usable reflection intensity when it is desired to reflect radio waves in a direction rotated by a certain angle around the reflection point relative to the specular reflection direction, by bending and installing the radio wave reflector 11.

[0115] The method for evaluating the reflection direction correction capability is as follows. As shown in Figure 10, the radio wave reflector 11 is placed on a flat, horizontally parallel mounting surface 42, and the radio wave reflector 11 is bent along a line (center line) passing through the center points of opposite sides of a square. The bending angle θ3 between the mounting surface 42 and the reflective surface of the radio wave reflector 11 is set to 10 degrees. The transmitting antenna 40 is set such that the incidence angle θ1 of the incident wave is 60 degrees when a point on the center line of the radio wave reflector 11 is taken as the reflection point 11a. The distance between the reflection point 11a and the transmitting antenna 40 is set to 5m. The installation position of the receiving antenna 41, which is the receiving unit 21, is set to the position with a clockwise rotation angle θ4 in Figure 10 when the normal 22 is set to 0 degrees, and the rotation angle θ4 is set to 50 degrees. In other words, the receiving antenna 41 is positioned so that it is close to the normal 22 by a rotation angle of 10 degrees around the reflection point 11a from the specular reflection direction (arrow A3) when the radio wave reflector 11 is installed flat on the installation surface 42. The distance between the reflection point 11a and the receiving antenna 41 is set to 5m.

[0116] A radio wave with a frequency of 28 GHz was emitted from the transmitting antenna 40, and the amount of reflection (reflection intensity) was measured at the receiving antenna 41. The method for measuring the reflection intensity was the same as the method described above. The received signal strength of the radio wave at the receiving antenna 41 was evaluated as "○" if it was -30 dB or higher, and as "×" if it was less than -30 dB.

[0117] The method for evaluating the ability to follow uneven surfaces is as follows. As shown in Figure 11, a test stand 43 was prepared having a protrusion 43b projecting upward from the upper surface of a plate-like portion 43a. The protrusion 43b has a semi-cylindrical cross-sectional shape with a semicircular shape (a curved surface with a radius of curvature of 200 mm) and a radius of 200 mm. The test stand 43 is transparent as a whole, and the total light transmittance at the longest point in the vertical direction in the side view of the test stand 43 shown in Figure 11 is 75%. An image capturing device 44, such as a camera, is placed below the test stand 33.

[0118] The substrate layer 13 of the radio wave reflector 11 is attached to the surface of the protrusion 43b of the test stand 43 using adhesive (PPX manufactured by Cemedyne Co., Ltd.), and the conductor 12 passing through the test stand 43 is photographed using an image capture device 44. The obtained images are analyzed by computer using image processing software (AVizo manufactured by THERMO FISHER SCIENTIFIC). In the analysis, the area where the radio wave reflector 11 and the protrusion 43b of the test stand 43 overlap (i.e., the area of ​​the radio wave reflector 11) and the area of ​​air bubbles existing between the surface of the protrusion 43b of the test stand 43 and the radio wave reflector 11 are determined, and the area in which the radio wave reflector 11 is in close contact with the protrusion 43b by the adhesive is calculated by subtracting the area of ​​air bubbles from the area of ​​the radio wave reflector 11. If the ratio of the area in close contact with the protrusion 43b to the area of ​​the radio wave reflector 11 is 90% or more, it is evaluated as "○", and if it is less than 90%, it is evaluated as "×". "Adhesion" means that adhesive exists between the surface of the protrusion 43b and the radio wave reflector 11, but no air bubbles are present.

[0119] (Evaluation results) Table 1 shows the evaluation results. In all of Examples 1 to 9, the specular reflection intensity of the radio wave reflector 11 in a flat state was -30 dB or higher, and the reflection direction correction ability was rated "○" and the surface conformability was rated "○". On the other hand, Comparative Example 1 was made of an aluminum plate, and although the specular reflection intensity was greater than -30 dB and the reflection direction correction ability was rated "○", it could not be bent and the surface conformability was rated "×". Comparative Example 2 had a larger thickness of the base material layer 13 compared to Example 2, and although the specular reflection intensity was greater than -30 dB, the reflection direction correction ability was rated "×", and it could not be bent and the surface conformability was rated "×". Comparative Example 3 had a smaller thickness L3 of the conductor 12 compared to Example 7, and sufficient specular reflection intensity could not be secured, so the reflection direction correction ability was rated "×". Comparative Example 4 had a larger bending modulus compared to Example 5, and it could not be bent, so the surface conformability was rated "×".

[0120] [Table 1]

[0121] 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 of the invention. The dimensions, materials, shapes, relative arrangements, etc. of the components described or shown in the drawings as embodiments are not intended to limit the scope of the present invention, but are merely illustrative examples. In this specification, "parallel" includes not only cases where two lines, edges, planes, etc. do not intersect even when extended, but also cases where the angles formed by the two lines, edges, planes, etc. intersect within a range of 10° or less. [Explanation of Symbols]

[0122] 11. Radio wave reflector 11a Reflection point 12, 12A, 12B conductors 13, 13A, 13B base material layer 14, 14A, 14B adhesive layer 15 Protective layer 16 Conductive thin film layer 20 Radio wave sources 21 Receiving unit 30, 30A, 30B, 30C Building materials L1 Diameter of the conductor L2: Distance between adjacent conductors L3 Thickness of the conductor L4 thickness of the adhesive layer L5 Protective layer thickness L6 Conductor line width L7 Distance between adjacent conductors L8 substrate layer thickness L10 Length of one side of the radio wave reflector L11 Thickness of the radio wave reflector R - Rate of change of surface resistivity during curvature R1, R2 surface resistivity

Claims

1. A radio wave reflector that reflects radio waves, With the radio wave reflector in a flattened state, when radio waves are reflected by the radio wave reflector at an incident angle of 15 degrees or more and 75 degrees or less, there exists a frequency at which the intensity of the reflected wave when the incident wave is specularly reflected is -30 dB or more relative to the intensity of the incident wave. The rate of change in the surface resistivity of the radio wave reflector when it is curved along a curved surface with a radius of curvature of 200 mm, compared to the surface resistivity of the radio wave reflector when it is flat, is -10% or more and 10% or less. A radio wave reflector having a bending modulus of 0.05 GPa or more and 4 GPa or less.

2. The radio wave reflector according to claim 1, wherein the frequency of the incident wave is any frequency between 2 GHz and 300 GHz.

3. The radio wave reflector according to claim 1, wherein the Young's modulus is 0.01 GPa or more and 80 GPa or less.

4. The radio wave reflector according to claim 1, wherein the thickness of the radio wave reflector is 0.01 mm or more and 0.5 mm or less.

5. The radio wave reflector according to claim 1, comprising at least a conductive thin film layer containing a conductor that reflects radio waves, and a substrate layer laminated on the conductive thin film layer and containing a substrate.

6. The conductive thin film layer, the substrate layer, a protective layer including a protective material for protecting the conductive thin film layer, and an adhesive layer including an adhesive for bonding the conductive thin film layer and the layer including the protective material, The radio wave reflector according to claim 5, wherein the substrate layer, the conductive thin film layer, the adhesive layer, and the protective layer are laminated in that order.

7. The radio wave reflector according to claim 1, wherein the surface resistivity of the radio wave reflector in a flattened state is 0.003 Ω / □ or more and 10 Ω / □ or less.

8. The radio wave reflector according to claim 6, wherein the protective layer is subjected to an anti-glare treatment or an anti-reflection treatment.

9. A building material comprising a radio wave reflector according to any one of claims 1 to 8.

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