Radio wave reflector

Abstract

To provide a radio wave reflector that offers good workability, such as replacement. [Solution] The radio wave reflector 10 comprises a first radio wave reflective layer 12 that reflects radio waves at a reflection angle different from the incident angle, a second radio wave reflective layer 13 that reflects all radio waves that have passed through the first radio wave reflective layer 12, a support layer 14 that supports the first radio wave reflective layer 12 and the second radio wave reflective layer 13, and a first adhesive layer 11 for bonding the first radio wave reflective layer 12 and the support layer 14, wherein the first adhesive layer 11 makes the first radio wave reflective layer 12 detachable from the support layer 14.

Description

Technical Field

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

Background Art

[0002] In mobile phones and wireless communications, radio waves in a frequency band of about 3 GHz to 300 GHz, called centimeter waves or millimeter waves, are used. Such radio waves with short wavelengths have high straight-line propagation properties, and if there is an obstacle between the transmitting antenna and the receiving antenna, the radio waves are less likely to diffract, making it difficult for the radio waves to reach the receiving antenna. For this reason, reflectors are provided on the surfaces of structures such as walls, floor surfaces, ceilings, and pillars of buildings (hereinafter referred to as "walls, etc.") in order to deliver radio waves to blind spots where radio waves do not reach.

[0003] When a metal plate made of, for example, aluminum is used as the reflector, the incident angle and reflection angle of the metal plate are constant, so in order to deliver radio waves to a blind spot, the metal plate must be installed at an accurate position and with an accurate mounting angle, which makes installation difficult. For this reason, Patent Document 1 proposes a reflector designed so that the incident angle and reflection angle of radio waves are different. By designing the reflection angle of the reflector according to the angle and position of the wall on which the reflector is installed, the installation of the reflector on a wall or the like is facilitated.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] A radio wave reflector, such as the one described in Patent Document 1, in which the reflection angle can be arbitrarily designed with respect to the incident angle of radio waves, generally has a structure in which three layers—a first radio wave reflection layer, a support layer, and a second radio wave reflection layer—are laminated together as a single unit. The first radio wave reflection layer controls the reflection angle of radio waves to reflect them at a desired angle, while the second radio wave reflection layer causes total internal reflection of the incident radio waves to increase the reflection intensity. The support layer supports the first and second radio wave reflection layers and maintains the distance between them at a distance appropriate for reflecting radio waves.

[0006] Such radio wave reflectors have high radio wave intensity in the designed reflection direction but low reflection intensity in other directions. For this reason, the first radio wave reflecting layer is designed to reflect radio waves in the desired reflection direction depending on the installation location, or multiple radio wave reflectors including first radio wave reflecting layers with different reflection angles are prepared in advance, and the radio wave reflector with the appropriate reflection angle for the installation location is selected.

[0007] However, due to installation errors during the installation of radio wave reflectors, or changes in the layout of the installation site, radio wave reflectors with different reflection angles may be required. However, as mentioned above, radio wave reflectors are heavy because they consist of a support layer with a first and second radio wave reflecting layer bonded to it. This makes replacement work, which involves peeling the radio wave reflector off a wall or other surface and installing a new one, difficult and inefficient.

[0008] This invention has been made in view of the above-mentioned problems, and aims to provide a radio wave reflector that is easy to work with, such as replacement work. [Means for solving the problem]

[0009] To achieve the above objectives, the present invention encompasses the subject matter described in the following sections.

[0010] Item 1: A first radio wave reflection layer that reflects radio waves at a reflection angle different from the incident angle, A second radio wave reflection layer that reflects radio waves that have passed through the first radio wave reflection layer at the same reflection angle as the incident angle, A support layer that supports the first radio wave reflection layer and the second radio wave reflection layer, The first radio wave reflecting layer and the support layer are bonded together by a first adhesive layer, A radio wave reflector in which the first radio wave reflecting layer is detachable from the support layer by the first adhesive layer.

[0011] Item 2: The radio wave reflector according to Item 1, wherein the first adhesive layer is an adhesive sheet.

[0012] Item 3: The radio wave reflector according to item 1 or 2, wherein the first radio wave reflecting layer is a single reflecting layer.

[0013] Section 4: The first radio wave reflection layer includes a plurality of reflection layers with different radio wave reflection angles. Each of the aforementioned reflective layers is peelable, as described in item 1 or 2, for the radio wave reflector.

[0014] Item 5: The radio wave reflector according to any one of items 1 to 4, wherein the first radio wave reflecting layer is flexible.

[0015] Item 6: The radio wave reflector according to any one of items 1 to 5, wherein the first radio wave reflecting layer comprises a conductive layer including a reflective element that reflects radio waves and a substrate layer that supports the conductive layer.

[0016] Item 7: The radio wave reflector according to any one of items 1 to 6, further comprising a second adhesive layer for bonding the second radio wave reflecting layer and the support layer. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a radio wave reflector that offers good workability, such as replacement work. [Brief explanation of the drawing]

[0018] [Figure 1] This is a cross-sectional view of a radio wave reflector according to one embodiment of the present invention. [Figure 2] This is a plan view of the embodiment shown in Figure 1. [Figure 3]It is a cross-sectional view of a radio wave reflector according to another embodiment. [Figure 4] It is a plan view of the embodiment of Figure 3. [Modes for Carrying Out the Invention]

[0019] (Overall Configuration) Embodiments of the present invention will be described with reference to the drawings. A radio wave reflector 10 shown in Figure 1 and Figure 2 includes a first radio wave reflective layer 12 that reflects radio waves at a reflection angle different from the incident angle, a second radio wave reflective layer 13 that reflects radio waves having passed through the first radio wave reflective layer 12 at a reflection angle identical to the incident angle, and a support layer 14 that supports the first radio wave reflective layer 12 and the second radio wave reflective layer 13. The radio wave reflector 10 further includes a first adhesive layer 11 for bonding the first radio wave reflective layer 12 and the support layer 14. In the stacking direction of the radio wave reflector 10, the radio wave reflector 10 is laminated in the order of the first radio wave reflective layer 12, the first adhesive layer 11, the support layer 14, and the second radio wave reflective layer 13.

[0020] In the following description, the vertical direction in Figure 1 is also referred to as the thickness direction or the stacking direction, the side of the first radio wave reflective layer 12 is referred to as the front side or one side, and the side of the second radio wave reflective layer 13 is referred to as the rear side or the other side. Radio waves enter from the first radio wave reflective layer 12 side of the radio wave reflector 10 and are reflected from the first radio wave reflective layer 12 side. Most of the radio waves are reflected by the first radio wave reflective layer 12, but some radio waves pass through the first radio wave reflective layer 12 and the support layer 14 to reach the second radio wave reflective layer 13, are reflected by the second radio wave reflective layer 13, pass through the support layer 14 and the first radio wave reflective layer 12, and exit from the first radio wave reflective layer 12. The radio wave reflector 10 is used with the rear surface of the second radio wave reflective layer 13 attached to a wall or the like.

[0021] (Radio Wave Reflector 10) As shown in Figure 2, the radio wave reflector 10 preferably has a rectangular shape in plan view, with the length of its shorter side being 20 cm or more and 400 cm or less. The radio wave reflector 10 controls radio waves with frequencies of 2 GHz or more and 300 GHz or less. Although radio waves in this frequency band attenuate with distance, in order for the radio wave reflector 10 to reflect radio waves with sufficient intensity, it is preferable that the length of one side of the first radio wave reflecting layer 12 be 20 cm or more. There is no particular upper limit to the length of the side, but from a manufacturing standpoint, 400 cm or less is preferable.

[0022] The overall shape of the radio wave reflector 10 may be a square, or a polygon such as a triangle, pentagon, or hexagon. In this case, the length of the shortest side is set to be between 20 cm and 400 cm. Alternatively, the shortest distance between a vertex and an opposite side, or the shortest distance between a side and an opposite side, may be set to be between 20 cm and 400 cm. If the overall shape of the radio wave reflector 10 is circular, the diameter is set to be between 20 cm and 400 cm. If the overall shape of the radio wave reflector 10 is elliptical, the minor axis is set to be between 20 cm and 400 cm. If the overall shape of the radio wave reflector 10 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 may be a three-dimensional shape such as a cylinder or cone. The shape and size of the radio wave reflector 10 are determined by the shape and size of the first radio wave reflective layer 12, the second radio wave reflective layer 13, and the support layer 14, and are appropriately selected according to the manner in which the radio wave reflector 10 is used.

[0023] (1st adhesive layer 11) The first adhesive layer 11 of the radio wave reflector 10 in this embodiment includes an adhesive that allows the first radio wave reflector 12 to be peeled off from the support layer 14. In addition to allowing the first radio wave reflector 12 to be peeled off from the support layer 14, the adhesive of the first adhesive layer 11 may also allow the first radio wave reflector 12 to be reattached to the support layer 14, i.e., it may be detachable. The first adhesive layer 11 may also include an adhesive that allows the first radio wave reflector 12 to be peeled off from the support layer 14, but does not allow for reattachment.

[0024] The first adhesive layer 11 may be an adhesive sheet. When the first radio wave reflective layer 12 and the support layer 14 are separated, the first adhesive layer 11 may separate from the support layer 14 together with the first radio wave reflective layer 12, or the first adhesive layer 11 may remain on the support layer 14 and only the first radio wave reflective layer 12 may separate. Alternatively, the first adhesive layer 11 may be a viscous liquid such as a gel-like substance, and may be applied to either the rear surface of the first radio wave reflective layer 12, the front surface of the support layer 14, or both. Examples of adhesives for such a first adhesive layer 11 include synthetic resins and rubber adhesive sheets. Examples of synthetic resins include acrylic resins, silicone resins, and polyvinyl alcohol resins.

[0025] The adhesive of the first adhesive layer 11 may, but is not limited to, being removable by the force of the worker's hand during the installation of the radio wave reflector 10. The adhesive of the first adhesive layer 11 may, for example, have such strong adhesive force that it cannot be removed by the worker's hand, but the adhesive force may weaken due to ultraviolet light, allowing it to be removed by the worker. Examples of such first adhesive layers 11 include UV-curable acrylic adhesives, UV-curable rubber adhesives, UV-curable polyurethane adhesives, and UV-sensitive polymer adhesives.

[0026] (1st radio wave reflective layer 12) The first radio wave reflective layer 12 reflects radio waves such that the angle of incidence and the angle of reflection are different. The first radio wave reflective layer 12 includes a base layer and a conductive layer provided on the base layer, although not shown in the figure. A protective layer may be provided on the conductive layer. The protective layer, conductive layer, and base layer are laminated in this order along the front to back of the lamination direction of the radio wave reflector 10. The first radio wave reflective layer 12 is composed of a single sheet-like reflective layer. The first radio wave reflective layer 12 may have a known metamaterial structure.

[0027] The term "sheet-like" includes a film-like shape, and refers to a material where the length in the vertical or horizontal direction on a flat surface is sufficiently long relative to its thickness, for example, the length in the vertical or horizontal direction is 10 times or more the thickness.

[0028] The thickness of the first radio wave reflective layer 12 is preferably set to 1 mm or less. The first radio wave reflective layer 12 may have enough flexibility to be bent by the force of an operator. This makes it easier to peel the first radio wave reflective layer 12 from the support layer 14.

[0029] The conductive layer comprises two or more different types of reflective elements. Each reflective element contains a thin film (sheet-like) of conductor formed in a predetermined shape in a plan view on the upper surface of the substrate layer. The conductive layer is formed by periodically arranging these different types of reflective elements in a row as a single unit on a sheet-like substrate layer. The conductive layer is preferably 5 nm or thicker, and preferably 0.05 μm or more and 10 μm or less. The thickness is set appropriately from the viewpoint of ensuring appropriate radio wave intensity and visible light transmittance. The entire surface of the substrate layer is not covered with reflective elements, and there are parts of the substrate layer where reflective elements are not formed, depending on the shape of the reflective elements. By having a structure that partially transmits visible light in this way, the first radio wave reflective layer 12 is transparent, meaning that one side can be seen from the other side.

[0030] The difference between the phase of the radio wave incident on the reflecting element and the phase of the radio wave reflected by the reflecting element (hereinafter also referred to as the "phase difference" or "phase difference of the reflecting element") is determined according to the shape of the reflecting element, etc. Different types of reflecting elements refer to reflecting elements designed so that the phase difference differs for each type. The first radio wave reflection layer 12 reflects the incident wave incident at the incident angle α1 as a reflected wave at a desired reflection angle α2 that is different from the incident angle α1. The shape and size of each reflecting element, the period of arrangement of multiple reflecting elements, etc. are set so that the reflection angle α2 is the desired angle.

[0031] The conductor may be composed of a metal, metallic compound, or alloy containing free electrons, and is not limited to silver. For example, it may be gold, copper, platinum, aluminum, titanium, silicon, indium tin oxide, and alloys (e.g., alloys containing nickel, chromium, and molybdenum). Examples of alloys 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, and X.

[0032] The base layer is transparent, and a conductive layer is formed on its upper surface; it is a sheet-like component. The base layer can be made from materials such as PET (polyethylene terephthalate), FR4 (glass fiber cloth impregnated with epoxy resin and heat-cured to form a sheet), glass, or silicon. Other synthetic resins may also be used as materials. Examples of synthetic resins include one or more selected from the group consisting of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polymethyl methacrylate, polyester, polyformaldehyde, polyamide, polyphenylene ether, polyvinylidene chloride, polyvinyl acetate, polyvinyl acetal, AS resin, ABS resin, acrylic resin, fluororesin, nylon resin, polyacetal resin, polycarbonate resin, polyamide resin, and polyurethane resin.

[0033] One method for providing a conductive layer on a substrate layer is to form a conductive film, then create a pattern by etching, and then extract a conductive thin film with the pattern. Another method involves coating a base film with a lift-off layer with a photosensitive resist, forming a pattern by photolithography, filling the patterned area with a conductor, and then extracting a conductive thin film with the pattern. The manufacturing method is not limited to the above, and in the formation of the reflective element 20, methods such as bonding a metal thin film or depositing metal can be used.

[0034] If a protective layer is provided, it may have the same configuration as the base layer.

[0035] The first radio wave reflective layer 12 may be transparent as a whole. The first radio wave reflective layer 12 has a total light transmittance of 65% or more, preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more, in a D65 standard light source. Total light transmittance refers to the ratio of the total transmitted light flux to the parallel incident light flux of the test piece, and is specified in JIS K7375:2008. The first radio wave reflective layer 12 may be colored as a whole. Note that the base layer and protective layer do not have to be transparent, and the first radio wave reflective layer 12 does not have to be transparent as a whole.

[0036] (Support layer 14) The thickness of the support layer 14 is set appropriately according to the wavelength λ. For example, it is set to 0.1 mm to 6 mm. Specifically, when λ = 10 mm, it is set to 0.1 mm to 1 mm, and when λ = 60 mm, it is set to 0.6 mm to 6 mm. It may also be transparent. The support layer 14 maintains the distance between the first radio wave reflection layer 12 and the second radio wave reflection layer 13 at a distance appropriate for radio wave reflection.

[0037] The support layer 14 is made from materials such as PET (polyethylene terephthalate), FR4 (glass fiber cloth impregnated with epoxy resin and heat-cured to form a sheet), glass, or silicone. Other synthetic resins may also be used as materials. Examples of synthetic resins include one or more selected from the group consisting of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polymethyl methacrylate, polyester, polyformaldehyde, polyamide, polyphenylene ether, polyvinylidene chloride, polyvinyl acetate, polyvinyl acetal, AS resin, ABS resin, acrylic resin, fluororesin, nylon resin, polyacetal resin, polycarbonate resin, polyamide resin, and polyurethane resin.

[0038] (Second radio wave reflective layer 13) The differences between the second radio wave reflection layer 13 and the first radio wave reflection layer 12 will be explained below. The second radio wave reflection layer 13 in this embodiment reflects radio waves that have passed through the first radio wave reflection layer 12. The second radio wave reflection layer 13 controls radio waves differently from the first radio wave reflection layer 12, and is a radio wave reflector 10 that specularly reflects all incident radio waves. Specular reflection means that an incident wave incident at an incident angle α1 is reflected as a reflected wave at the same reflection angle α2 as the incident angle α1. The second radio wave reflection layer 13 may or may not be transparent.

[0039] The second radio wave reflective layer 13 consists of a conductive layer, and the conductive layer may be directly provided on the rear surface of the support layer 14. The conductive layer is provided in the same manner as the conductive layer provided on the substrate layer in the first radio wave reflective layer 12. The second radio wave reflective layer 13 may also consist of a substrate layer and a conductive layer, similar to the first radio wave reflective layer 12. In this case, the substrate layer and the conductive layer are laminated in that order from the front to the rear, and the substrate layer is bonded to the support layer 14 by a second adhesive layer (not shown). The second adhesive layer may be the same adhesive as the first adhesive layer 11, but it may also be an adhesive with sufficient tackiness to prevent the second radio wave reflective layer 13 from being peeled off the support layer 14.

[0040] The conductive layer of the second radio wave reflection layer 13 may have multiple identical reflecting elements. In this case, the shape and size of the reflecting elements are set so that the reflection angle α2 is the same angle as the incident angle α1. The conductive layer may also comprise multiple linear conductors and regions without conductors surrounded by these conductors, with the regions without conductors being periodically arranged at predetermined intervals. Linear means that the length in the longitudinal direction is 3000 times or more the length in the direction perpendicular to the longitudinal direction. The conductors may be arranged in a grid pattern such that the regions without conductors are rectangular. Alternatively, the conductors may be arranged so that the regions without conductors are triangular, polygonal, circular, etc. The configuration of the conductive layer of the second radio wave reflection layer 13 is not limited to the above; any configuration that specularly reflects radio waves is acceptable, and it may be made of metal plates or the like. The other configurations are the same as those of the first radio wave reflection layer 12, so their explanation is omitted.

[0041] The radio wave reflector 10 is manufactured as follows. First, a first sheet is manufactured in which a support layer 14 and a second radio wave reflecting layer 13 are integrally formed. Next, a second sheet is manufactured in which a first adhesive layer 11 is provided on the first radio wave reflecting layer 12. Then, the first sheet is attached to the front surface of the support layer 14 of the second sheet using the first adhesive layer 11.

[0042] According to the above configuration, the first radio wave reflecting layer 12 and the support layer 14 are bonded together by the first adhesive layer 11 and are removable. Therefore, if it is necessary to change the radio wave reflection angle due to installation errors, design errors, or layout changes during the installation of the radio wave reflector 10, instead of replacing the entire radio wave reflector 10, only the first radio wave reflecting layer 12 can be removed and a new first radio wave reflecting layer 12 can be attached. In this way, it is not necessary to replace the heavy support layer 14 or the second radio wave reflecting layer 13, and only the first radio wave reflecting layer 12, which is lighter than the support layer 14, needs to be replaced, thus improving work efficiency.

[0043] (Other embodiments) Figures 3 and 4 show other embodiments. In the embodiment of Figure 3, the first radio wave reflective layer 12 includes a plurality of reflective layers 12A to 12C (three in the example of Figures 3 and 4), and first adhesive layers 11A to 11C are provided on the rear surfaces of each of the reflective layers 12A to 12C. These reflective layers 12A to 12C are arranged in a continuous line on the front surface of the support layer 14 by the first adhesive layers 11A to 11C. Each of the reflective layers 12A to 12C has a different radio wave reflection angle. The worker can peel off each of the reflective layers 12A to 12C together with the first adhesive layers 11A to 11C. That is, it is possible to peel off only one or two of the reflective layers 12A to 12C, or to peel off all of them. In this way, partial replacement of the first radio wave reflective layer 12 is possible. Note that the first adhesive layers 11A to 11C may not be peeled off, and only the reflective layers 12A to 12C may be peelable.

[0044] The dimensions, materials, shapes, and relative arrangements of 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. Expressions indicating that things are equal, such as "in a certain direction," "along a certain direction," "same," "identical," "equal," and "homogeneous," should not only indicate strictly equal states, but also states where tolerances or differences exist to the extent that the same function can be achieved. Expressions indicating triangular, quadrilateral, and circular shapes should not only indicate shapes in a geometrically precise sense, but also include shapes with concave and concave parts, chamfered parts, etc., to the extent that the same effect can be achieved. Expressions such as "equipped with," "include," or "possess" a single component are not exclusive expressions that exclude the existence of other components. "Parallel" and "orthogonal" mean substantially "parallel" and "orthogonal," and include not only strictly "parallel" and "orthogonal" states, but also states that include errors of a few degrees. [Explanation of Symbols]

[0045] 10 Radio wave reflectors 11(11A~11C) 1st adhesive layer 12 1st radio wave reflective layer 13 Second radio wave reflective layer 14 Support layer

Claims

1. A first radio wave reflection layer that reflects radio waves at a reflection angle different from the incidence angle, A second radio wave reflection layer that reflects radio waves that have passed through the first radio wave reflection layer at the same reflection angle as the incident angle, A support layer that supports the first radio wave reflection layer and the second radio wave reflection layer, The device comprises a first adhesive layer for bonding the first radio wave reflective layer and the support layer, A radio wave reflector wherein the first radio wave reflecting layer is detachable from the support layer by the first adhesive layer.

2. The radio wave reflector according to claim 1, wherein the first adhesive layer is an adhesive sheet.

3. The radio wave reflector according to claim 1, wherein the first radio wave reflecting layer is a single reflecting layer.

4. The aforementioned first radio wave reflection layer includes a plurality of reflection layers with different radio wave reflection angles, Each of the reflective layers is peelable, as described in claim 1, for the radio wave reflector.

5. The radio wave reflector according to claim 1, wherein the first radio wave reflecting layer is flexible.

6. The radio wave reflector according to claim 1, wherein the first radio wave reflecting layer comprises a conductive layer including a reflective element that reflects radio waves, and a substrate layer that supports the conductive layer.

7. The radio wave reflector according to claim 1, further comprising a second adhesive layer for bonding the second radio wave reflecting layer and the support layer.

Images