Electromagnetic wave reflector

Abstract

To provide an electromagnetic wave reflector that can reflect an electromagnetic wave at a desired angle if an incident angle is any angle while maintaining the electromagnetic wave intensity.SOLUTION: An electromagnetic wave reflector 1 for reflecting an electromagnetic wave having a predetermined wavelength, includes: a substrate 2 in which a plurality of projected parts 31 are provided on a substrate part 23 extending along a virtual plane; and a plurality of conductors 32 which are provided on the plurality of projected parts 31. Each of the plurality of projected parts 31 has an inclined plane 311 which is inclined with respect to the virtual plane and in which the conductors 32 are laminated. A length L6 of each of the conductors 32 in a gradient direction of the inclined plane 311 is less than the predetermined wavelength of the electromagnetic wave.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Conventionally, for wireless communication such as mobile phones, radio waves in a frequency band of about 3 GHz or more and 300 GHz or less, called centimeter waves and millimeter waves, have been used. Such radio waves with short wavelengths have strong directivity and are difficult to bend around obstacles. Therefore, in order to spread such radio waves widely, a reflector is provided on the surface of a building (for example, the surfaces of walls, floors, ceilings, columns, etc.).

[0003] For example, Patent Document 1 describes a communication system in which a monopole antenna and a metal reflector for reflecting radio waves are arranged in an indoor underfloor space. The metal reflector diffuses the radio waves output from the monopole antenna into the underfloor space and prevents the radio waves from leaking from the underfloor space to the outside of the living room (building) or being absorbed by the floor of the building.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since the metal reflector described in Patent Document 1 has a strong reflection intensity of electromagnetic waves in the normal reflection direction, in order to propagate electromagnetic waves to a desired position, it is necessary to set the installation angle based on the same reflection angle as the incident angle, and there is a problem that the constraints during installation are large.

[0006] In addition, there has been a metal reflector capable of partial reflection, but compared with a metal reflector capable of regular reflection, although the intensity of partial reflection is slightly higher, the intensity in the regular reflection direction is still strong and the loss is large, so there is a problem that the intensity in the partial reflection direction tends to be weak.

[0007] An object of the present invention is to provide an electromagnetic wave reflector that can reflect electromagnetic waves at a desired angle while ensuring the electromagnetic wave intensity regardless of the incident angle.

Means for Solving the Problems

[0008] To achieve the above object, the present invention includes the subject matter described in the following items.

[0009] Item 1. An electromagnetic wave reflector that reflects electromagnetic waves of a predetermined wavelength, a base material provided with a plurality of protrusions on a substrate portion extending along a virtual plane, a plurality of conductors provided on the plurality of protrusions, comprising, each of the plurality of protrusions has an inclined surface inclined with respect to the virtual plane and on which the conductor is laminated, each length of the conductor in the gradient direction of the inclined surface is less than the predetermined wavelength, the electromagnetic wave reflector.

[0010] Item 2. The electromagnetic wave reflector according to Item 1, wherein the inclined surfaces of the plurality of protrusions are parallel to each other.

[0011] Item 3. The electromagnetic wave reflector according to Item 1 or Item 2, wherein the angle formed by the virtual plane and the inclined surface is 60° or less.

[0012] Item 4. The electromagnetic wave reflector according to any one of Items 1 to 3, wherein the plurality of protrusions are arranged in a direction perpendicular to the longitudinal direction of the protrusions in a plan view.

[0013] Item 5. The electromagnetic wave reflector according to any one of Items 1 to 4, wherein the protrusion is formed in a right-angled triangular cross-sectional shape including a plane perpendicular to the virtual plane.

[0014] Item 6. The electromagnetic wave reflector according to any one of Items 1 to 5, wherein each of the plurality of protruding portions is formed along a straight line in a plan view.

Advantages of the Invention

[0015] The electromagnetic wave reflector according to the above aspect of the present invention has an advantage that it can reflect electromagnetic waves at a desired angle while ensuring the electromagnetic wave intensity regardless of the incident angle.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0017] <Embodiment> Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The electromagnetic wave reflector 1 according to the present embodiment is a sheet-like member capable of reflecting electromagnetic waves. The electromagnetic wave reflector 1 reflects, for example, electromagnetic waves transmitted from a transmission device, and the electromagnetic waves reflected by the electromagnetic wave reflector 1 are received by a reception device.

[0018] As used herein, the "sheet" means a shape in which the thickness of the object is 10% or less of the maximum length between the outer edges in a plan view. When the shape in the plan view is rectangular, the "maximum length between the outer edges in the plan view" means the length of the diagonal. When the shape in the plan view is circular, the "maximum length between the outer edges in the plan view" means the length of the diameter. In this specification, a film, foil, film, etc. are also included in the "sheet".

[0019] The transmitting device is a communication device having a transmitting antenna and can transmit electromagnetic waves. Examples of the transmitting device include a fixed base station, a mobile base station, a radio transmitter, a wireless terminal, etc. The receiving device is a communication device having a receiving antenna and can receive electromagnetic waves. Examples of the communication device include a smartphone, a mobile phone, a tablet terminal, a notebook PC, a portable game machine, a repeater, a radio, a television, etc.

[0020] The electromagnetic wave to be reflected by the electromagnetic wave reflector 1 according to this embodiment (hereinafter, may be referred to as the "electromagnetic wave to be reflected") is, for example, a radio wave (electromagnetic wave with a frequency of 50 Hz or more and 3 THz or less). The frequency of the electromagnetic wave to be reflected preferably belongs to any one of the ranges of 1 GHz or more and 5 GHz or less, 25 GHz or more and 30 GHz or less, and 100 GHz or more and 300 GHz or less. The electromagnetic wave to be reflected is an electromagnetic wave in which the intensity of the outgoing wave (reflected wave) with respect to the incident wave is -30 dB or more and 0 dB or less. In this specification, the intensity of the electromagnetic wave means the intensity when the distance between the reflection point of the electromagnetic wave on the electromagnetic wave reflector 1 and the measurement point is 1 m.

[0021] As shown in FIG. 1, the electromagnetic wave reflector 1 according to this embodiment is a laminate in which a first layer 20 for maintaining the shape of the electromagnetic wave reflector 1, a second layer 30 for reflecting electromagnetic waves, and a third layer 40 for protecting the second layer 30 are laminated in order. The electromagnetic wave reflector 1 according to this embodiment includes a base material 2 having a substrate portion 23 constituting the first layer 20 and a plurality of protrusion portions 31 included in the second layer 30, a conductor 32 included in the second layer, and a coating material 4 constituting the third layer 40. In this embodiment, the conductor 32 is provided on the protrusion portion 31.

[0022] The thickness L1 of the electromagnetic wave reflector 1 is preferably 0.01 mm or more, more preferably 0.05 mm or more, and still more preferably 0.2 mm or more. On the other hand, the upper limit of the thickness L1 of the electromagnetic wave reflector 1 is preferably 0.5 mm or less, more preferably 0.4 mm or less. When the thickness L1 of the electromagnetic wave reflector 1 is 0.01 mm or more, it is possible to maintain strength while having flexibility. When the thickness L1 of the electromagnetic wave reflector 1 is 0.5 mm or less, when the electromagnetic wave reflector 1 is bent, it is difficult to bend, and as a result, stress concentration is less likely to occur in the conductor 32. Here, "bend" means that bending accompanied by plastic deformation occurs in any layer of the electromagnetic wave reflector 1.

[0023] The electromagnetic wave reflector 1 preferably has a longitudinal elastic modulus of 0.01 GPa or more and 80 GPa or less. By setting the longitudinal elastic modulus within the above range, the electromagnetic wave reflector 1 is easily deformed, and the electromagnetic wave reflector 1 can be bent and attached to a curved installation surface without breaking or plastically deforming the electromagnetic wave reflector 1. The longitudinal elastic modulus is measured in accordance with JIS K7127-1999.

[0024] The thickness L2 of the first layer 20 is preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 20 μm or more. On the other hand, as the upper limit value of the thickness L2 of the first layer 20, for example, 500 μm or less is preferable, more preferably 130 μm or less, and still more preferably 100 μm or less.

[0025] The thickness L4 of the second layer 30 is preferably 0.1 μm or more, more preferably 1 μm or more, and still more preferably 1.2 μm or more. On the other hand, as the upper limit value of the thickness L4 of the second layer 30, for example, 100 μm or less is preferable, more preferably 10 μm or less, and still more preferably 5 μm or less.

[0026] The thickness L5 of the third layer 40 is preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 20 μm or more. On the other hand, as the upper limit value of the thickness L5 of the third layer 40, for example, 500 μm or less is preferable, more preferably 130 μm or less, and still more preferably 100 μm or less.

[0027] Hereinafter, each element constituting the electromagnetic wave reflector 1 will be described in more detail. In the following description, the direction in which a plurality of layers overlap is defined as the "vertical direction". Also, when the electromagnetic wave reflector 1 is viewed along the vertical direction, two directions perpendicular to each other are defined as the "longitudinal direction" and the "lateral direction". Also, viewing an object along the vertical direction may be referred to as "plan view". However, these definitions of directions are only used for explanation and do not specify the use. Also, each figure is only a schematic diagram and does not represent an exact scale.

[0028] In addition, in this specification, "parallel" includes not only the case where two straight lines, planes, etc. (hereinafter, straight lines, etc.) do not intersect even when extended, but also the case where the angle formed by two straight lines, etc. intersects within a range of 10° or less. Also, "orthogonal" means the case where two straight lines, etc. intersect within a range of 90° ± 10°. However, even if two straight lines, etc. do not directly intersect, if they intersect when extended, they are included in "orthogonal".

[0029] (Base material 2) The base material 2 supports the conductor 32. As shown in FIG. 1(B), the base material 2 includes a substrate portion 23 constituting the first layer 20 and a plurality of ridge portions 31 provided on the substrate portion 23. In the present embodiment, the substrate portion 23 and the plurality of ridge portions 31 are integrally formed, but those configured separately may be joined by adhesion or the like.

[0030] The substrate portion 23 is a flat plate-shaped portion extending along a virtual plane. Here, the virtual plane is a virtual plane parallel to the vertical direction and the horizontal direction. The substrate portion 23 has a first surface 21 and a second surface 22 on the side opposite to the first surface 21. The first surface 21 constitutes one surface of the electromagnetic wave reflector 1. The second surface 22 is a virtual boundary surface between the substrate portion 23 and the ridge portion 31 and does not actually appear in the base material 2. The first surface 21 and the second surface 22 are parallel to the virtual plane.

[0031] The plurality of ridge portions 31 are provided on the second surface 22 of the substrate portion 23. Each ridge portion 31 has an inclined surface 311 that is inclined with respect to the virtual plane. The inclined surface 311 is a plane. However, the plane referred to in this specification may have fine irregularities and includes the case where the flatness is 1 μm or less. The flatness is measured in accordance with JIS B 0621-1984.

[0032] The angle α formed by the inclined surface 311 and the virtual plane is preferably 60° or less, more preferably 55° or less, and even more preferably 50° or less. On the other hand, the lower limit value of the angle α is preferably more than 0°, more preferably 10° or more. The angle of the conductor 32 is determined according to the magnitude of the angle α formed by the virtual plane and the inclined surface 311.

[0033] As long as each ridge portion 31 has at least one inclined surface 311, the cross-sectional shape is not particularly limited. The ridge portion 31 according to the present embodiment has a cross-sectional right triangle including a plane orthogonal to the second surface 22. However, for example, with respect to the angle corresponding to the right vertex, it may have a cross-sectional triangular shape with an obtuse angle or a cross-sectional triangular shape with an acute angle. Also, the surface other than the inclined surface 311 may be a curved surface.

[0034] As shown in Fig. 2, each rib portion 31 extends in the longitudinal direction in a plan view. In the present embodiment, each rib portion 31 is formed along a straight line. Each rib portion 31 is formed over the entire longitudinal length of the electromagnetic wave reflector 1. By being configured in this way, it is easy to control the direction of the emitted wave (reflected wave). However, the rib portion 31 does not necessarily have to be formed over the entire length of the electromagnetic wave reflector 1, and for example, it may be formed only on a part of the longitudinal direction of the electromagnetic wave reflector 1.

[0035] The plurality of rib portions 31 are arranged side by side in the lateral direction. The plurality of rib portions 31 are parallel to each other. The cross-sectional shapes of the plurality of rib portions 31 are the same shape, and it is preferable that all the inclined surfaces 311 are parallel to each other and face in the same direction. By being configured in this way, the intensity loss of the reflected wave of the electromagnetic wave reflector 1 can be reduced.

[0036] As shown in Fig. 1, it is preferable that adjacent rib portions 31 are formed continuously. "Adjacent rib portions 31 are formed continuously" means that a part of one rib portion 31 is connected to the other rib portion 31, and the second surface 22 of the substrate portion 23 does not appear between the adjacent rib portions 31 and they are connected. Thereby, the pitch distance between the plurality of rib portions 31 can be made as short as possible.

[0037] Note that the rib portion 31 only needs to extend in one direction and does not necessarily have to be formed along a straight line. The plurality of rib portions 31 adjacent to each other in the direction orthogonal to the longitudinal direction of the rib portion 31 may be formed in an arc shape in a plan view, a wave shape in a plan view, etc., as long as they are parallel to each other.

[0038] As shown in Fig. 2, the shape of the base material 2 is, for example, a quadrangular shape (more specifically, a square shape). There is no particular limitation on the outer shape of the base material 2, and for example, it may be a triangular shape, a pentagonal shape, a hexagonal shape, a circular shape, an elliptical shape, etc.

[0039] Examples of the base material 2 include synthetic resins, FRP (Fiber Reinforced Plastics), carbon, glass, etc. Examples of the synthetic resin 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. The base material 2 may be a composite material of these synthetic resins. The base material 2 according to the present embodiment is composed of a PET sheet.

[0040] The base material 2 may have flexibility. As the longitudinal elastic modulus of the base material 2, for example, 0.01 GPa or more is preferable, more preferably 1 GPa or more, and still more preferably 8 GPa or more. On the other hand, as the upper limit of the longitudinal elastic modulus of the base material 2, for example, 80 GPa or less is preferable, more preferably 30 GPa or less, and still more preferably 20 GPa or less.

[0041] The base material 2 may have visible light transmissivity. That is, the base material 2 may be transparent. Thereby, even if the installation surface is, for example, window glass or the like, the electromagnetic wave reflector 1 can be installed without being conspicuous. "Transparent" as used in this specification means that the light transmittance may be 10% or more with respect to the peak wavelength of the light before incidence, preferably 50% or more, and more preferably 80% or more. That is, "semi-transparent" with a light transmittance of, for example, about 30% with respect to the peak wavelength of the light before incidence is also included in "transparent" as used in this specification. Further, the base material 2 is not limited to colorless and transparent, and may be colored.

[0042] (Conductor 32) The conductor 32 reflects electromagnetic waves. The conductor 32 is provided on the inclined surface 311 of the ridge portion 31. As a method of forming the conductor 32 on the inclined surface 311, for example, there are a method of laminating a conductor 32 in which a conductor is embedded in a thin-film dielectric on the inclined surface 311, and a method of forming a conductor on the inclined surface 311 without using a dielectric. The dielectric used here preferably has a relative permittivity of 1.5 or more, more preferably 2.5 or more, and still more preferably 3 or more. Examples of the dielectric include acrylic resin, PET (polyethylene terephthalate), a mixture of acrylic and air, and the like. When the relative permittivity is 1.5 or more, the wavelength of the electromagnetic wave in the dielectric becomes shorter than the wavelength of the electromagnetic wave outside the dielectric, so that the reflection intensity can be increased.

[0043] Examples of the conductor include one or more of silver, gold, copper, platinum, aluminum, titanium, silicon, indium tin oxide, and alloys (for example, alloys containing nickel, chromium, and molybdenum). Examples of the alloy containing nickel, chromium, and molybdenum include various grades such as Hastelloy B-2, B-3, C-4, C-2000, C-22, C-276, G-30, N, W, X, etc.

[0044] The thickness of the conductor 32 is preferably 20 nm or more, more preferably 30 nm or more, and still more preferably 100 nm or more. On the other hand, the upper limit value of the thickness of the conductor 32 is preferably 10 μm or less, more preferably 5 μm or less, and still more preferably 4 μm or less. When the thickness of the conductor 32 is 20 nm or more, an appropriate electromagnetic wave intensity can be ensured.

[0045] The conductors 32 provided on each of the adjacent ridge portions 31 are electrically insulated from each other. In the present embodiment, the adjacent conductors 32 are separated via one surface of the ridge portion 31 and are not electrically connected.

[0046] The conductor of each conductor 32 is a metal microstructure having a structure finer than the wavelength of the electromagnetic wave to be reflected, and has a metasurface structure. That is, the maximum width of the non-conductor portion in the conductor 32 is shorter than the wavelength of the electromagnetic wave to be reflected.

[0047] As shown in FIG. 3, the conductor has a plurality of resonators 321 formed repeatedly. In the conductor 32, a pattern is formed by periodically forming a plurality of resonators 321. The resonator 321 means the minimum unit on the metasurface. The resonator 321 is formed in a frame shape and can take various shapes such as a ring shape, a triangular shape, a quadrangular shape, and a pentagonal shape.

[0048] Here, FIGS. 3(A) to (F) illustrate the pattern of the conductor of the conductor 32. In the following description, in FIG. 3, the vertical direction is referred to as the "longitudinal direction" and the horizontal direction is referred to as the "lateral direction" for explanation.

[0049] In the example shown in FIG. 3(A), the resonator 321 is quadrangular. A plurality of resonators 321 are periodically formed in the longitudinal direction and the lateral direction. Each resonator 321 is composed of a plurality (four) of linear bodies 322. Each linear body 322 is linear and extends thinly. The adjacent end portions of adjacent linear bodies 322 are electrically connected. Thereby, the pattern of the conductor is formed in a lattice shape.

[0050] In the example shown in FIG. 3(B), the resonator 321 is quadrangular. Each resonator 321 is the same as the example of FIG. 3(A). However, the resonators 321 adjacent in the longitudinal direction are shifted by 1 / 2 of the lateral width of the resonator 321 in the lateral direction. Thereby, the pattern of the conductor is formed in a brickwork shape.

[0051] In the example shown in FIG. 3(C), the resonance part 321 is triangular. A plurality of resonance parts 321 are formed periodically in the horizontal direction. The resonance parts 321 adjacent in the vertical direction are formed at positions intermediate between a pair of adjacent resonance parts 321 in the horizontal direction. Each resonance part 321 is composed of a plurality (three) of linear bodies 322. Each linear body 322 is linear and extends thinly. The adjacent end portions of adjacent linear bodies 322 are electrically connected.

[0052] In the example shown in FIG. 3(D), the resonance part 321 is hexagonal. A plurality of resonance parts 321 are formed periodically in the vertical and horizontal directions. Each resonance part 321 is composed of a plurality (six) of linear bodies 322. Each linear body 322 is linear and extends thinly. The adjacent end portions of adjacent linear bodies 322 are electrically connected.

[0053] In the example shown in FIG. 3(E), the resonance part 321 has a shape composed of two adjacent pentagons in the vertical direction. A plurality of resonance parts 321 are formed periodically in the vertical and horizontal directions. Each resonance part 321 is composed of a plurality (nine) of linear bodies 322. Each linear body 322 is linear and extends thinly. The adjacent end portions of adjacent linear bodies 322 are electrically connected.

[0054] In the example shown in FIG. 3(F), the resonance part 321 is ring-shaped. A plurality of resonance parts 321 are formed periodically in the vertical and horizontal directions. Each resonance part 321 is composed of one thinly extending linear body 322.

[0055] The line width of each linear body 322 of the conductor 32 formed in this way is preferably 0.3 μm or more and 10 μm or less, more preferably 0.3 μm or more and 5 μm or less, and still more preferably 0.4 μm or more and 1 μm or less.

[0056] Thus, since the conductor 32 has a pattern in which a plurality of resonance parts 321 formed in a frame shape are periodically formed, it can reflect electromagnetic waves while having translucency.

[0057] Here, the electromagnetic wave incident on the conductor 32 is emitted from the conductor 32 at an emission angle equal to the incident angle. At this time, the emitted waves reflected by the conductor 32 on the plurality of protrusions 31 form a wavefront according to the Huygens' principle. When this is regarded as the wavefront reflected by the second layer 30, the wavefront does not move along the wavefront that is emitted at the same emission angle as the incident wave (the wavefront moving along the specular reflection direction), but advances in a direction having an angle with respect to the specular reflection direction. That is, the electromagnetic wave reflector 1 according to the present embodiment can suppress the intensity of the emitted wave at the position of specular reflection with respect to the incident wave and improve the intensity of the obliquely reflected electromagnetic wave for the electromagnetic wave reflected by the second layer 30. The "position of specular reflection" as used herein means the position on the emitted wave having a reflection angle equal to the incident angle.

[0058] Further, the length L6 of the conductor 32 in the gradient direction of the inclined surface 311 of the protrusion 31 is set to be less than the wavelength of the electromagnetic wave to be reflected. Since the frequency of the electromagnetic wave to be reflected in the present embodiment belongs to the range of 1 GHz or more and 300 GHz or less, the wavelength of the electromagnetic wave to be reflected is 1 mm or more and 300 mm or less. When making the length L6 correspond to the electromagnetic waves in all frequency bands within this range, the length L6 may be set to be less than the wavelength corresponding to the maximum frequency in the frequency band of the electromagnetic wave to be reflected. Therefore, when corresponding to all of the electromagnetic waves in the frequency band of 1 GHz or more and 300 GHz or less, the length L6 is set to be less than 1 mm. The lower limit of the length L6 is not particularly limited, but is preferably set to 100 nm or more.

[0059] If the length L6 of the conductor 32 in the gradient direction of the inclined surface 311 of the protruding portion 31 is equal to or greater than the wavelength of the electromagnetic wave to be reflected, it may affect the reflection intensity. However, in the electromagnetic wave reflector 1 according to the present embodiment, the length L6 of the conductor 32 is set to be less than the wavelength of the electromagnetic wave in the highest frequency band among the electromagnetic waves to be reflected (that is, less than 1 mm). Therefore, according to the electromagnetic wave reflector 1 according to the present embodiment, for electromagnetic waves in the frequency band of 300 GHz or less, regardless of the frequency of the radio wave, it is possible to perform partial reflection without being affected by the length L6 of the conductor 32, and the electromagnetic wave reflector 1 with low frequency dependence can be obtained.

[0060] (Coating material 4) The coating material 4 covers the conductor 32 and protects the conductor 32. The coating material 4 constitutes the third layer 40. The coating material 4 has a size corresponding to the base material 2 in a plan view. Examples of the coating material 4 include a sheet (film) made of synthetic resin. Examples of the synthetic resin 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.

[0061] The coating material 4 preferably has flexibility. As the longitudinal elastic modulus of the coating material 4, for example, 0.01 GPa or more is preferable, more preferably 1 GPa or more, and still more preferably 8 GPa or more. On the other hand, as the upper limit of the longitudinal elastic modulus of the coating material 4, for example, 80 GPa or less is preferable, more preferably 30 GPa or less, and still more preferably 20 GPa or less.

[0062] The coating material 4 is fixed to the base material 2 and the conductor 32 by an adhesive 33.

[0063] Adhesive 33 The adhesive 33 is provided between the conductor 32 and the coating material 4, and adheres the base material 2 and the conductor 32 to the coating material 4. The adhesive 33 is preferably filled between adjacent ridge portions 31. Thereby, the thickness of the electromagnetic wave reflector 1 can be reduced.

[0064] Examples of the adhesive 33 include synthetic resins and rubber-based adhesive sheets. Examples of the synthetic resin include acrylic resins, silicone resins, polyvinyl alcohol resins, and the like.

[0065] Also, the adhesive 33 preferably has a hydroxyl value of 5 mgKOH / g or more, more preferably 8 mgKOH / g or more, still more preferably 30 mgKOH / g or more, and still more preferably 90 mgKOH / g or more. On the other hand, the upper limit of the hydroxyl value of the adhesive 33 is preferably 120 mgKOH / g or less. When the hydroxyl value of the adhesive 33 is 5 mgKOH / g or more, there is an advantage that the adhesive 33 is less likely to foam and / or turn white in a high-temperature and high-humidity environment. In this specification, the hydroxyl value is measured by a test method conforming to JIS K 1557.

[0066] Also, the acid value of the adhesive 33 is preferably 50 mgKOH / g or less, more preferably 45 mgKOH / g or less, still more preferably 30 mgKOH / g or less, and still more preferably 10 mgKOH / g or less. On the other hand, the lower limit of the acid value of the adhesive 33 is preferably 0.1 mgKOH / g or more. When the acid value of the adhesive 33 is 50 mgKOH / g or less, corrosion of the conductor can be prevented, and the temporal stability of the radio wave reflectivity can be enhanced. In this specification, the acid value is measured by a test method conforming to JIS K 2501.

[0067] The adhesive 33 preferably does not contain an ultraviolet absorber. If the adhesive 33 does not contain an ultraviolet absorber, there is an advantage that it is easy to adjust the adhesive 33 to be colorless and transparent. Here, "does not contain" includes not only the case where it does not contain any ultraviolet absorber, but also the case where the adhesive 33 contains a small amount that does not impair the colorless and transparent state.

[0068] For the adhesive 33, it is preferable to use a material having a dielectric loss tangent (tanδ) of 0.018 or less. The lower the value of the dielectric loss tangent, the more preferable. Examples of the lower limit value of the dielectric loss tangent include 0.0001 or more. By using the adhesive 33 having a dielectric loss tangent of 0.018 or less, the loss of the electric energy of the radio wave in the electromagnetic wave reflector 1 is reduced, and the reflection intensity can be made stronger.

[0069] (Overall) The electromagnetic wave reflector 1 configured as described above preferably has visible light transmissivity as a whole. The electromagnetic wave reflector 1 preferably has a total light transmittance of 70% or more, more preferably 75% or more, and still more preferably 80% or more. In this specification, the "total light transmittance" means the transmittance of light rays from a D65 standard light source. The total light transmittance is measured in accordance with JIS K 7375 (2008).

[0070] The electromagnetic wave reflector 1 may have plasticity. Plasticity means the property that it can be deformed by applying an external pressure, and when a deformation exceeding the elastic limit is given by pressurization, it retains the deformed shape even after the force is removed. The base material 2 and the coating material 4 may have plasticity, or either one of the base material 2 and the coating material 4 may have plasticity.

[0071] (Usage method) The electromagnetic wave reflector 1 according to the embodiment is used, for example, as interior paper or a decorative material. The inner layer paper is a paper material attached to the inner surface of the interior material. Examples of the interior material include an inner wall, a ceiling board, a partition, a floor material, and the like. Examples of the decorative material include a poster, a decorative sticker, a stained glass-like sticker, and the like. Examples of the decorative material include a wall material, a floor material, a door, a lighting cover, a lattice, a pillar, a television, a table top board, and the like.

[0072] Further, the electromagnetic wave reflector 1 may be used, for example, for the printed paper of a plywood. In this case, using the plywood including the electromagnetic wave reflector 1, a door, a wall surface, a partition, an outer wall material, a roof, a ceiling board, a floor material, a skirting board, and the like may be configured.

[0073] Here, in the incident direction of the electromagnetic wave, assuming that the direction having a component parallel to the virtual plane is the "incident azimuth", it is preferable that the electromagnetic wave reflector 1 be installed within a range where the angle formed by the incident azimuth and the lateral direction is 0° or more and less than 90°. More preferably, the electromagnetic wave reflector 1 is installed such that the incident azimuth is parallel to the lateral direction.

[0074] <Modification Example> The above embodiment is merely one of various embodiments of the present invention. The embodiment can be variously modified according to design and the like as long as the object of the present invention can be achieved. Hereinafter, modification examples of the embodiment will be listed. The modification examples described below can be applied in appropriate combinations.

[0075] In the above embodiment, the base material 2 has the ridge portion 31 having a right-angled triangular cross section, but the ridge portion 31 may have, for example, a shape as shown in FIG. 4(A). The ridge portion 31 is formed in an isosceles triangle shape.

[0076] Further, as shown in FIG. 4(B), one of the vertices of the ridge portion 31 in contact with the second surface 22 of the substrate portion 23 may be an obtuse angle. In this case, in a plan view, a part of the adjacent conductors 32 overlaps. Further, the ridge portion 31 is composed of a member different from the substrate portion 23, and after providing the conductor 32 on the ridge portion 31, it is joined to the substrate portion 23 by adhesion or the like.

[0077] In the above embodiment, the coating material 4 and the adhesive 33 are provided. However, as the electromagnetic wave reflector 1, the coating material 4 and the adhesive 33 may not be provided.

[0078] <Test> A simulation test for effect confirmation was conducted using the electromagnetic wave reflector 1 described in the above embodiment. However, the electromagnetic wave reflector 1 of the present invention is not limited thereto.

[0079] (Reflection direction control) Using the electromagnetic wave reflector 1 according to the above embodiment, the electromagnetic wave reflectors 1 of Examples 1 and 2 were fabricated. However, the angle α formed between the virtual plane and the inclined surface 311 in the protruding strip portion 31 was set to 30° in Example 1 and 60° in Example 2. The length L6 of the conductor in the gradient direction of the inclined surface 311 of the protruding strip portion 31 was set to 0.001 mm in both cases.

[0080] The measurement results of the reflected wave when electromagnetic waves were incident on the electromagnetic wave reflector 1 of Example 1 at an incident angle of 0° are shown in Fig. 5(A), and the measurement results of the reflected wave when electromagnetic waves were incident on the electromagnetic wave reflector 1 of Example 1 at an incident angle of 30° are shown in Fig. 5(B). Also, the measurement results of the reflected wave when electromagnetic waves were incident on the electromagnetic wave reflector 1 of Example 2 at an incident angle of 0° are shown in Fig. 5(C). The frequency of the electromagnetic waves is 300 GHz (wavelength λ = 1 mm). In the graphs of Figs. 5(A) to (C), the vertical axis represents the voltage (pV) indicating the intensity of the electromagnetic waves, and the horizontal axis represents the reflection angle with respect to the normal of the second layer 30.

[0081] As can be seen from Figs. 5(A) and (B), even when the incident angle of the electromagnetic waves is different, there is not much influence on the electromagnetic wave intensity. Therefore, according to the electromagnetic wave reflector 1 according to the present embodiment, it is verified that reflection can be achieved regardless of the magnitude of the incident angle of the electromagnetic waves. Also, it is verified that reflection can be achieved even when the angle α formed by the inclined surface 311 of the protruding strip portion 31 is changed. As a result, according to the electromagnetic wave reflector 1 according to the present embodiment, it is found that the electromagnetic waves can be reflected at a desired angle while ensuring the electromagnetic wave intensity at any incident angle.

[0082] (Frequency independence) For the electromagnetic wave reflector 1 of Example 1, an electromagnetic wave with a frequency of 300 GHz (wavelength λ = 1 mm) and an electromagnetic wave with a frequency of 30 GHz (wavelength λ = 1 mm) were each incident with an incident angle of 0°, and the intensity of the reflected wave was measured.

[0083] Fig. 6(A) shows the measurement results of the reflected wave when an electromagnetic wave with a frequency of 300 GHz is incident at an incident angle of 0°, and Fig. 6(B) shows the measurement results of the reflected wave when an electromagnetic wave with a frequency of 30 GHz is incident at an incident angle of 0°. The graphs in Figs. 6(A) and 6(B) have the voltage (pV) indicating the intensity of the electromagnetic wave on the vertical axis and the reflection angle with respect to the normal of the second layer 30 on the horizontal axis.

[0084] As can be seen from Figs. 6(A) and 6(B), even when the frequency of the electromagnetic wave is different, the intensity of the reflected wave shows the same behavior. Therefore, it was found that the reflection performance of the electromagnetic wave reflector 1 of this embodiment does not depend on the frequency.

[0085] (Critical point of the length L6 of the conductor) Using the electromagnetic wave reflector 1 according to the above embodiment, electromagnetic wave reflectors of Examples 3 - 14 and Comparative Example 1 were fabricated. The electromagnetic wave reflectors of Examples 3 - 14 and Comparative Example 1 had the angle α formed by the protruding strip portion 31 set to 30°. Also, for Example 3 - 13 and Comparative Example 1, the length L6 of the conductor in the gradient direction of the inclined surface 311 of the protruding strip portion 31 was set as follows. Example 3: 0.01 mm, Example 4: 0.02 mm, Example 5: 0.04 mm, Example 6: 0.08 mm, Example 7: 0.016 mm, Example 8: 0.032 mm, Example 9: 0.064 mm, Example 10: 0.1 mm, Example 11: 0.1 mm, Example 12: 0.128 mm, Example 13: 0.256 mm, Example 14: 0.512 mm, Comparative Example 1: 1 mm

[0086] The results of measuring the intensity of the reflected wave when electromagnetic waves of 300 GHz (wavelength λ = 1 mm) were incident on the electromagnetic wave reflector of Example 3-14 and Comparative Example 1 at an incident angle of 0° are shown in FIGS. 7(A) to (C). Although there are some cases where the length L6 overlaps among the examples, they are described as different examples in the graph for easy comparative study. In FIGS. 7(A), (B), and (C), the radio wave intensities are compared in different ranges for easy viewing.

[0087] As shown in FIGS. 7(A) to (C), although the wavelength of the electromagnetic wave is 1 mm, the length L6 of the conductor in Example 3-14 is less than 1 mm, so the intensity of the reflected wave shows the same behavior. On the other hand, in Comparative Example 1, the length L6 of the conductor is 1 mm, which is the same as the wavelength of the electromagnetic wave of 1 mm, and there is an angle at which the intensity of the reflected wave cannot be obtained. From this, it was found that when the length L6 of the conductor is less than the wavelength of the electromagnetic wave to be reflected, the electromagnetic wave can be reflected at a desired angle while ensuring the radio wave intensity.

Explanation of Symbols

[0088] 1 Electromagnetic wave reflector 20 First layer 30 Second layer 40 Third layer 2 Substrate 21 First surface 22 Second surface 23 Substrate part 31 Protrusion 311 Inclined surface 32 Conductor 321 Resonant part 322 Linear body 33 Adhesive 4 Coating material L6 Length of the conductor in the gradient direction of the inclined surface

Claims

1. An electromagnetic wave reflector that reflects electromagnetic waves of a predetermined wavelength, A base material having a base portion extending along an imaginary plane and having a plurality of protrusions provided on the base portion; A plurality of conductors provided on the plurality of protrusions; Equipped with Each of the plurality of protrusions has an inclined surface that is inclined with respect to the imaginary plane and on which the conductor is laminated, a length of each of the conductors in a gradient direction of the inclined surface is less than the predetermined wavelength; Electromagnetic wave reflector.

2. The inclined surfaces of the plurality of protrusions are parallel to each other.

2. The electromagnetic wave reflector according to claim 1.

3. The angle between the virtual plane and the inclined surface is 60° or less.

3. The electromagnetic wave reflector according to claim 1 or 2.

4. The plurality of protrusions are arranged in a direction perpendicular to the longitudinal direction of the protrusions in a plan view.

3. The electromagnetic wave reflector according to claim 1 or 2.

5. The protrusion portion is formed in a cross section having a right-angled triangular shape including a plane perpendicular to the imaginary plane.

3. The electromagnetic wave reflector according to claim 1 or 2.

6. Each of the plurality of protrusions is formed along a straight line in a plan view.

3. The electromagnetic wave reflector according to claim 1 or 2.

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