JP2024021079A - radio wave reflector - Google Patents

Abstract

To provide a radio wave reflector with an excellent workability.SOLUTION: A radio wave reflector 11 including a conductor for reflecting radio waves includes: a conductor layer 16 including a conductor 12; a base material layer 13 including a base material for holding the conductor layer 16; and an adhesive layer 18 including an adhesive material. The adhesive layer 16, the base material layer 13, and the adhesive layer 18 are deposited in that order. The radio wave reflector 11 has a thickness of 400 μm or smaller. Adhesive force which acts between an attachment target object and the adhesive layer 18 when the attachment target layer 18 is attached to the attachment target object is 2 N/25 mm or smaller when the attachment target object is made of glass, a separation angle at a temperature of 23°C is 180 degrees, and a separation rate is 300 mm/min.SELECTED DRAWING: Figure 2

Description

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

In mobile phones and wireless communications, radio waves in a frequency band of approximately 3 GHz or more and 300 GHz or less, called centimeter waves or millimeter waves, are used. Radio waves with such short wavelengths travel in a straight line and are difficult to wrap around even if there are obstacles. Therefore, in order for radio waves to reach a wide range, the surfaces of buildings such as walls, floors, ceilings, and pillars are (hereinafter referred to as "walls, etc.") is provided with a reflective plate. For example, Patent Document 1 proposes a communication system in which a monopole antenna and a metal reflector that reflects radio waves are arranged in an indoor underfloor space. The metal reflector plate diffuses the radio waves emitted from the monopole antenna into the space under the floor, and prevents them from leaking out of the room (building) from the space under the floor or being absorbed by the floor of the building. .

Japanese Patent Application Publication No. 2010-258514

When attaching a reflector to an object such as a wall, a large reflector may be cut to a desired size. Furthermore, if the reflector is tilted or wrinkled during installation, the reflector may be removed from the object and reattached. For this reason, reflectors are required to have good workability.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a radio wave reflector having good workability.

To achieve the above object, the present invention includes the subject matter described in the following sections.

Item 1: A radio wave reflector including a conductor for reflecting radio waves,
comprising a conductive layer containing the conductor, a base material layer containing a base material holding the conductive layer, and an adhesive layer containing an adhesive material,
The conductive layer, the base layer, and the adhesive layer are laminated in this order,
The thickness of the radio wave reflector is 400 μm or less,
When the adhesive layer is attached to the attachment object, the adhesive force that acts between the attachment object and the adhesive layer is such that the attachment object is glass, the peeling angle is 180 degrees, and the peeling speed is 23° C. A radio wave reflector that is 2N/25mm or less at 300mm/min.

Item 2: The radio wave reflector according to item 1, wherein the base layer has a thickness of 100 μm or less and a Young's modulus at 25° C. of 4 GPa or less.

Item 3: further comprising a protective layer containing a protective material for protecting the conductive layer, and an adhesive layer containing an adhesive for bonding the conductive layer and the protective layer,
Item 2. The radio wave reflector according to item 1 or item 2, wherein the protective layer has a thickness of 100 μm or less and a Young's modulus at 25° C. of 4 GPa or less.

Item 4: Items 1 to 3, wherein the conductor has one or more linear shapes and is arranged surrounding an area where there is no conductor, and the areas are arranged periodically at intervals. The radio wave reflector according to any one of the above.

Item 5: Further comprising a release paper for protecting the adhesive layer,
The radio wave reflector according to any one of Items 1 to 4, wherein the conductive layer, the base material layer, the adhesive layer, and the release paper are laminated in this order.

Item 6: The radio wave reflector according to any one of Items 1 to 5, wherein the adhesive force is 0.1 N/25 mm or more.

According to the present invention, a radio wave reflector with good workability can be provided.

FIG. 3 is a diagram for explaining the angular range of reflected waves reflected by a radio wave reflector according to an embodiment of the present invention. FIG. 3 is a cross-sectional view taken along line BB in FIG. 3(B), showing a schematic overall configuration of a radio wave reflector according to an embodiment of the present invention. The overall schematic structure of the radio wave reflector shown in FIG. 2 is shown, in which (A) is a plan view and (B) is an enlarged view of part A in (A). (A) to (E) are plan views of conductors showing other examples of arrangement patterns of conductors. FIG. 7 is a plan view of a conductor showing another example of the arrangement pattern of the conductor. (A) is a plan view showing another example of the arrangement pattern of conductors, and (B) is an enlarged view of portion D in (A). (A) is a plan view showing another example of the arrangement pattern of conductors, and (B) is an enlarged view of portion D in (A). FIG. 7 is a cross-sectional view showing a schematic configuration of a radio wave reflector according to another embodiment. FIG. 7 is a cross-sectional view showing a schematic configuration of a radio wave reflector according to another embodiment. FIG. 7 is a cross-sectional view showing a schematic configuration of a radio wave reflector according to another embodiment. (A) is an explanatory diagram showing an example of application of the building material to a building, and (B) is a plan view showing an example of application of the building material to a room.

(overall structure)
Embodiments of the present invention will be described with reference to the drawings. The radio wave reflector 11 of this embodiment reflects the radio waves output from the radio wave generation source 20, as shown in FIG. The reflected wave is received by the receiving section 21. The radio wave generation 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 that can receive radio waves. The receiving unit 21 according to this embodiment is a communication device having a receiving antenna. Examples of communication devices include smartphones, mobile phones, tablet terminals, notebook PCs, portable game machines, repeaters, radios, televisions, and the like.

The radio wave reflector 11 includes a conductor 12 that reflects radio waves. With the radio wave reflector 11 affixed to a wall or the like in a flat state, radio waves having an incident wave frequency of 3 GHz or more and 5 GHz or less, 25 GHz or more and 30 GHz or less, or 100 GHz or more and 300 GHz or less are reflected on the radio wave reflector 11. The angle of incidence of the incident wave is at least a certain predetermined angle of 15 degrees or more and 75 degrees or less, preferably 45 degrees, and more preferably the whole range of angles of 15 degrees or more and 75 degrees or less. At this time, there is one frequency at which the intensity of the reflected wave when the incident wave is regularly reflected by the radio wave reflector 11 is greater than or equal to -30 dB and less than or equal to 0 dB relative to the incident wave. Preferably, at a frequency of 28.5 GHz, the regular reflection intensity is −30 dB or more and 0 dB or less relative to the incident wave. More preferably, in all frequency bands from 20 GHz to 60 GHz, the normal reflection intensity is -30 dB to 0 dB with respect to the incident wave, and even more preferably, in all frequency bands from 3 GHz to 300 GHz, the normal reflection intensity is -30 dB to 0 dB to the incident wave. In contrast, it is -30 dB or more and 0 dB or less. "Regular reflection intensity" refers to the intensity of reflection of a radio wave, and refers to the intensity of a reflected wave when an incident wave is regularly reflected. "Flat" refers to a state with no irregularities and no curves.

The normal reflection intensity is preferably -25 dB or more and 0 dB or less, 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 with respect to the incident wave. Since the regular reflection intensity is -30 dB or more with respect to the incident wave, the radio wave reflector 11 can reflect the radio waves while keeping the reflection intensity high, and the receiving section 21 can have a strength that is practical for use. Can receive radio waves. In this embodiment, the regular reflection intensity and the reflection intensity are determined based on the distance between the reflection point 11a of the radio wave reflector 11 and the radio wave generation source 20 and the distance between the reflection point 11a of the radio wave reflector 11 and the receiving section 21. This is a value when the distance is 1 m.

To explain with reference to FIG. 1, regular reflection is when a radio wave emitted from a radio wave generation source 20 (transmission antenna) is reflected by a radio wave reflector 11, the angle of incidence θ1 of the incident wave and the reflection of the reflected wave. This means that the angle θ2 is equal. When a radio wave is regularly reflected, the direction of the reflected wave is also called the "regular reflection direction." The incident angle θ1 is the angle formed by the incident wave traveling in the direction of incidence (indicated by arrow A1 in FIG. 1) when the radio wave enters the radio wave reflector 11 and the normal 22 of the reflecting surface of the radio wave reflector 11. It's an angle. The reflection angle θ2 is the angle between the reflected wave traveling in the reflection direction of the reflected wave (indicated by arrow A2 in FIG. 1) and the normal 22 of the reflecting surface. The normal line 22 refers to a straight line that is orthogonal to the tangent (or tangent plane) at the reflection point 11a.

In addition, the radio wave reflector 11 adjusts the receiving angle position of the reflected wave by -15 degrees or more and +15 degrees with respect to the normal reflection direction of the radio wave in a virtual plane including the incident direction of the incident wave and the reflection direction of the reflected wave. It is preferable that the kurtosis of the distribution of the intensity of the reflected wave at each receiving angular position is -0.4 or less when changed in the following angular range α. The kurtosis is more preferably -1.0 or less, still more preferably -1.1 or less, even more preferably -1.2 or less. The lower limit of the kurtosis is not particularly limited, but is usually about -0.5. The virtual plane can also be said to be a plane including the reflection point 11a on the reflection surface of the reflector, the radio wave generation source 20, and the reflected wave reception section 21. Kurtosis is determined with the radio wave reflector 11 being flat.

の平均値を

、標準偏差をsとすると尖度は次の式から求められる。 Kurtosis is a statistic that indicates how much the distribution deviates from the normal distribution, and indicates the kurtosis of the peak and the spread of the tail. As shown in FIG. 1, it is assumed that a radio wave output from the radio wave generation source 20 is incident on the radio wave reflector 11 at a predetermined incident angle θ1. The reception angle position i of the receiving unit 21 is set at a predetermined angle increments (for example, 5 degrees) from the normal reflection direction of the radio wave, with the reflection point 11a as the center, from -15 degrees to +15 degrees with respect to the normal reflection direction of the radio wave. The reflection intensity x is measured by moving within the angular range α. The receiving angular position i of the receiving section 21 is located on a circular arc centered on the reflection point 11a. Reflection intensity value at each receiving angle position i

the average value of

, the standard deviation is s, and the kurtosis is calculated from the following formula.

（式１）

(Formula 1)

When the kurtosis is a negative value, it indicates that the intensity data at each angular position has a flatter distribution than the normal distribution, that is, the data is scattered around the average value and the tail of the distribution is widening. The smaller the distribution, 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 becomes small within the angular range α of ±15 degrees with respect to the normal reflection direction of the radio wave.

As shown in FIG. 3, in this embodiment, the radio wave reflector 11 has an overall shape of a square in plan view, and preferably has a length L10 of one side of 20 cm or more and 400 cm or less. Radio waves with a frequency of 3 GHz or more and 300 GHz or less are attenuated by distance, but in order to reflect with sufficient intensity at all points within a practical distance from the radio wave source 20, the length of one side L10 is set to 20 cm or more. It is preferable. Although the upper limit of the length L10 of one side is not particularly limited, it is preferably 400 cm or less from a manufacturing standpoint. 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 be 20 cm or more and 400 cm or less. be done. Alternatively, the shortest distance between a certain vertex and the opposite side or the shortest distance between a certain side and the opposite side may be set to 20 cm or more and 400 cm or less. Further, when 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. When the overall shape of the radio wave reflector 11 is elliptical, the short axis is set to 20 cm or more and 400 cm or less. When the overall shape of the radio wave reflector 11 is fan-shaped, the length of the shorter arc or radius is set to 20 cm or more and 400 cm or less. Furthermore, the overall shape of the radio wave reflector 11 may be a three-dimensional shape such as a cylindrical shape or a conical shape. The overall shape and size of the radio wave reflector 11 is such that it can reflect radio waves with a reflection strength of -30 dB or more relative to the incident wave, and the shape and size are determined by the use of the radio wave reflector 11. is selected as appropriate depending on the aspect.

Although the details will be described later, the radio wave reflector 11 includes at least a conductive layer 16, a base material layer 13 containing a base material holding the conductive layer 16, and an adhesive layer 18 containing an adhesive material. , adhesive layer 18 are laminated in this order. The radio wave reflector 11 may further include an adhesive layer 14 and a protective layer 15, and the protective layer 15, the adhesive layer 14, the conductive layer 16, the base material layer 13, and the adhesive layer 18 may be laminated in this order.

The thickness L1 of the radio wave reflector 11 is set to be 10 μm or more and 400 μm or less. The thickness L1 of the conductive layer radio wave reflector 11 is set to a thickness that allows the radio wave reflector 11 to be cut into any size and shape using cutting means such as a cutter or scissors. Furthermore, the radio wave reflector 11 can have flexibility, and when an external force is applied to the radio wave reflector 11 to curve the radio wave reflector 11, the force is not concentrated on the conductor 12 of the conductive layer 16. First, the thickness is set such that force can be dispersed in the base material layer 13 and the adhesive layer 18. The thickness L1 of the radio wave reflector 11 is the sum of at least the thickness L3 of the conductive layer 16, the thickness L2 of the base material layer 13, and the thickness L13 of the adhesive layer 18. When the radio wave reflector 11 includes the adhesive layer 14 and the protective layer 15, the thickness L1 of the radio wave reflector 11 is the thickness L5 of the protective layer 15, the thickness L4 of the adhesive layer 14, and the thickness L3 of the conductive layer 16. , the sum of the thickness L2 of the base material layer 13 and the thickness L13 of the adhesive layer 18. However, since the thickness L3 of the conductive layer 16 is very thin compared to the thicknesses of other layers, it is not necessary to take the thickness L3 of the conductive layer 16 into consideration when calculating the thickness L1 of the radio wave reflector 11.

Object and adhesive layer 18 when the adhesive layer 18 of the radio wave reflector 11 is attached to the object
The adhesive force at the interface is set to 0.1 N/25 mm or more and 2 N/25 mm or less at 23°C. Adhesive strength is also referred to as peel strength or peel force. Adhesive strength was measured in accordance with JIS K6854-2 using a tensile tester (for example, Tensilon RTC manufactured by Orientech Co., Ltd.) at a peeling angle of 180 degrees, a peeling speed of 300 mm/min, and a room temperature of the place where the measurement was performed. Measured at 23°C. When measuring the adhesive strength, a test piece of the radio wave reflector 11 cut out to a size of 25 mm in length and 150 mm in width is used. The dimensions of the glass object to which the specimen is attached are 50 mm in length in the vertical direction, 100 mm in length in the horizontal direction, and 1 mm in thickness.

The surface resistivity of the radio wave reflector 11 when the radio wave reflector 11 is flat is 0.003Ω/□
Above, 10Ω/□ or less is preferable. Although details will be described later, the surface resistivity is measured as the surface resistivity of the conductor 12. The surface resistivity of the radio wave reflector 11 in a flat state refers to the surface resistivity of the radio wave reflector 11 when the radio wave reflector 11 is placed on a flat mounting surface. A "plane" is a surface in which a straight line connecting any two points on the surface always lies on it.

A peel test is performed on the radio wave reflector 11, and the surface resistivity of the radio wave reflector 11 in a flat state after the peel test is preferably 0.003 Ω/□ or more and 10 Ω/□ or less. That is, the surface resistivity of the radio wave reflector 11 becomes 10Ω/□ or less without being affected by the peel test. The peel test refers to a test in which the radio wave reflector 11 is attached to a window glass to be attached, and after 24 hours, the radio wave reflector 11 is peeled off at a speed of 1 cm/sec.

The surface resistivity of the radio wave reflector 11 means the surface resistance per 1 cm ² (1 cubic centimeter). The surface resistivity can be measured by a four-terminal method in accordance with JIS K6911 by bringing a measurement terminal into contact with the surface of the conductive layer 16 made of the conductor 12. If the conductive layer 16 is not exposed because it is protected with a resin sheet, etc., use a non-contact resistance measuring device (manufactured by Napson Co., Ltd., product name: EC-80P, or an equivalent product) to vortex it. It can be measured by the current method. The surface resistivity of the conductive layer 16 is expressed as the surface resistivity of the radio wave reflector 11.

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 refers to the elastic modulus when a solid is stretched by applying tension in one direction, and is also called tensile elastic modulus or longitudinal elastic modulus, and is defined in JIS K7161-2014. Young's modulus is measured in accordance with JIS K7127-1999. By setting the Young's modulus within the above range, the radio wave reflector 11 becomes easily deformable.

The radio wave reflector 11 may have plasticity. Plasticity refers to the property of being able to deform by applying external pressure and, when deformed beyond the elastic limit by applying pressure, retaining the deformed shape even after the force is removed. All of the synthetic resins constituting the base layer 13, adhesive layer 14, protective layer 15, adhesive layer 18, etc. may have plasticity, or the base layer 13, adhesive layer 14, protective layer 15, adhesive At least one of the layers 18 may be plastic.

The radio wave reflector 11 may have visible light transmittance as a whole, that is, may be transparent. The base material layer 13, the adhesive layer 14, and the protective layer 15 may each be formed of a resin that transmits visible light, and the conductor 12 of the conductive layer 16 is formed to have a thickness that transmits visible light. Good too. Here, "transparent" means that the other side of the radio wave reflector 11 is visible when viewed from one side, and includes semi-transparency, and is not limited to complete transparency with a total light transmittance of 100%. Further, the radio wave reflector 11 may be colored. The radio wave reflector 11 has a total light transmittance of 65% or more under a D65 standard light source, preferably 80% or more, more preferably 85% or more, and still more preferably 90% or more. Total light transmittance refers to the ratio of total transmitted light flux to parallel incident light flux of a test piece, and is measured in accordance with JISK 7375:2008. Note that when measuring the total light transmittance, the radio wave reflector 11 does not include a release paper 19, which will be described later.

The radio wave reflector 11 also has a rate of change in surface resistivity before and after the radio wave reflector 11 is curved along the surface of a member having a curved surface with a radius of curvature of 200 mm (“rate of change in surface resistivity during bending”). ) R may be -10% or more and 10% or less. The rate of change R in the surface resistivity when curved is defined as the rate of change R of the surface resistivity when the radio wave reflector 11 is flat, compared to the surface resistivity R1 of the radio wave reflector 11 when the radio wave reflector 11 is flat. This refers to the rate at which the surface resistivity R2 changes when the surface is curved along the surface. The rate of change in surface resistivity is determined by R (%)=(R2-R1)/R1×100.

The reflected strength of radio waves changes depending on the surface resistivity. However, since the rate of change R in surface resistivity when the radio wave reflector 11 is curved is -10% or more and 10% or less, even if the radio wave reflector 11 is curved, it is as good as when it is flat. It is possible to achieve a reflection strength of radio waves.

It is preferable that the radio wave reflector 11 has a bending elastic modulus of 0.05 GPa or more and 4 GPa or less. The bending elastic modulus is a value indicating how much bending stress can be withstood, and is defined in JIS K7171. By setting the bending elastic modulus within the above range, the radio wave reflector 11 has flexibility, and the radio wave reflector 11 can be curved without breaking the radio wave reflector 11 to form a curved surface with a radius of curvature of 200 mm or more. can be pasted on. Flexural modulus is measured in accordance with JIS K7171. Flexibility refers to the property of having flexibility at room temperature and normal pressure, and allowing deformation such as bending, bending, bending, etc., without shearing or breaking even when force is applied.

The radio wave reflector 11 has at least a degree of flexibility that allows it to be attached along a curved surface with a radius of curvature of 200 mm or more, preferably a degree that allows it to be attached along a curved surface with a radius of curvature of 100 mm or more. It may have flexibility.

In the radio wave reflector 11, it is preferable that the difference between the yellow index after the heat and humidity test and the yellow index before the heat and humidity test is 3 or less. Yellow index is also called yellowness and refers to the degree to which the hue deviates from colorless or white toward yellow. The yellow index is determined by a method based on JISK7373:2006. The difference in yellow index is an index for evaluating yellowing, which is one of the deterioration phenomena of the radio wave reflector 11, and the smaller the difference in yellow index, the smaller the deterioration. The yellow index is determined using the XYZ color system defined by CIE (Commission Internationale de l'Eclairage).

In the heat and humidity resistance test, the radio wave reflector 11 was left in a constant temperature and humidity chamber adjusted to a temperature of 60°C and a humidity of 95% RH (relative humidity is 95%) for 500 hours, and then the radio wave reflector 11 was removed from the constant temperature and humidity chamber. This is a test to check the properties and condition of the radio wave reflector 11 after taking it out and leaving it at room temperature for 4 hours.

The radio wave reflector 11 before and after the heat resistance and humidity resistance test regularly reflects incident waves with a frequency of 3 GHz or more and 300 GHz or less. At this time, at a certain angle of incidence, the difference between the intensity of the reflected wave of the radio wave reflector 11 after the heat resistance and humidity resistance test and the intensity of the reflected wave of the radio wave reflector 11 before the heat resistance and humidity resistance test is within 3 dB. Preferably, at least one wave frequency is present. Preferably, in all frequency bands from 3 GHz to 300 GHz, the difference in the intensity of the reflected waves of the radio wave reflector 11 before and after the heat and humidity test is preferably within 3 dB. It is preferable that at least one angle of incidence of the incident wave exists in the range of 15 degrees or more and 75 degrees or less, such that the difference in the intensity of the reflected wave of the radio wave reflector 11 before and after the heat and humidity test is within 3 dB, and 45 degrees is preferable. More preferably, the entire angle range is 15 degrees or more and 75 degrees or less.

The radio wave reflector 11 has a rate of change r in surface resistivity before and after the heat and humidity test (also referred to as "rate of change in surface resistivity during the heat and humidity test") of 20% or less. The rate of change r in surface resistivity during the heat and humidity test is the rate at which the surface resistivity r2 after the heat and humidity test changes with respect to the surface resistivity r1 before the heat and humidity test. The rate of change r in surface resistivity during the heat and humidity resistance test is determined by the following formula. r=(r1-r2)/r1×100

The reflected strength of radio waves changes depending on the surface resistivity. However, since the rate of change r in the surface resistivity of the radio wave reflector 11 during the heat resistance and humidity resistance test is 20% or less, the reflection strength of the radio wave reflector 11 does not decrease significantly even after the heat resistance and humidity resistance test, and the radio wave reflector 11 has sufficient It is possible to achieve the reflected strength of radio waves.

When the radio wave reflector 11 is subjected to a pencil hardness test, the pencil hardness at a surface load of 500 g to the protective layer 15 is preferably "F" or higher, more preferably "H" or higher, and Preferably it is "4H" or more. The "pencil hardness test" herein refers to the JIS
This is a test based on K 5600-5-4 (1999). Moreover, "surface load of 500 g" is included if the load applied to the surface during the pencil hardness test is 500 g±10 g. When the protective layer is subjected to a pencil hardness test, the pencil hardness at a surface load of 500 g to the protective layer may be F or more.

In addition, after the radio wave reflector 11 is subjected to a heat and humidity resistance test, the reduction rate of the adhesive strength of the protective layer 15 to the adherend layer is preferably 50% or less, more preferably 45% or less, and Preferably it is 40% or less. The term "adhered layer" as used herein means a layer that is in direct contact with the target layer. The adherent layer of the protective layer 15 is the adhesive layer 14 in this embodiment. The adhesive strength is measured by a tensile adhesive strength test based on JIS K 6849 (1994).

(Structure of radio wave reflector 11)
One embodiment of the radio wave reflector 11 will be described using FIGS. 2 and 3. The radio wave reflector 11 includes a conductive layer 16 including a conductor 12, and a resin that keeps the conductor 12 in a sheet shape. The sheet shape means a shape that has a wide area and has a length in the thickness direction that is sufficiently shorter than the length in the vertical and horizontal directions when viewed from the plane. The resin has a base material layer 13 containing a base material and an adhesive layer 18. The resin may further include a protective layer 15 containing a protective material for protecting the conductive layer 16 and an adhesive layer 14 containing an adhesive for bonding the conductive layer 16 and the protective layer 15. . In the embodiment shown in FIG. 2, the radio wave reflector 11 includes an adhesive layer 18 provided below the base layer 13, a conductive layer 16 laminated on the base layer 13, and an adhesive layer 16 on the conductive layer 16. Layer 14 and protective layer 15 are laminated in this order.

In the following explanation, the vertical direction is defined based on FIG. 2, and the vertical and horizontal directions are defined based on FIG. It does not specify the vertical or horizontal directions when used, such as when attaching to objects. Further, FIGS. 1 to 11 do not show actual scales. Further, in FIG. 3A, illustration of the adhesive layer 14 and the protective layer 15 is omitted in a part of the radio wave reflector 11.

(Base material layer 13)
In this embodiment, the base material layer 13 has a square outer shape in plan view. However, the shape is not limited to this, and may be a rectangle, circle, ellipse, fan shape, polygon, three-dimensional shape, etc. depending on the overall shape of the radio wave reflector 11. As the base material which is the base material layer 13, a synthetic resin sheet is used. Examples of synthetic resins include PET (polyethylene terephthalate), polyethylene, polypropylene, polyvinyl chloride, polystyrene, polymethyl methacrylate, polyester, polyformaldehyde, polyamide, polyphenylene ether, vinylidene chloride, polyvinyl acetate, polyvinyl acetal, and AS resin. , ABS resin, acrylic resin, fluororesin, nylon resin, polyacetal resin, polycarbonate resin, polyamide resin, and polyurethane resin.

In this embodiment, the thickness L2 (length in the vertical direction in FIG. 2) of the base material layer 13 is formed uniformly, and the thickness L2 is preferably 25 μm or more and 200 μm or less, but is not limited to this. Rather, it is set as appropriate depending on the manner in which the radio wave reflector 11 is used. Further, the thickness may not be uniform; for example, it may be formed into a wedge shape, a partially spherical surface, or a three-dimensional shape having an uneven shape.

The base material layer 13 preferably has a Young's modulus at 25° C. of 1 GPa or more and 4 GPa or less. By setting the Young's modulus of the base material layer 13 within the above range, the radio wave reflector 11 has flexibility, and when the radio wave reflector 11 attached to an object such as a wall is peeled off, the radio wave reflection is prevented. The body 11 is difficult to break. In addition to the base material, the base material layer 13 may contain a substance such as an arbitrary synthetic resin or an arbitrary member.

(Adhesive layer 18)
The adhesive layer 18 includes an adhesive material and is provided on the lower surface of the base layer 13 to attach the radio wave reflector 11 to an object. The adhesive layer 18 may be provided on the entire lower surface of the base material layer 13 or may be provided only on a part of the lower surface of the base material layer 13. The radio wave reflector 11 has reworkability due to the adhesive layer 18. Reworkability is also referred to as re-peelability, and refers to a property that allows the radio wave reflector 11 to be peeled off without destroying the attachment target after it has been attached to the attachment target. As the adhesive material for the adhesive layer 18, for example, an adhesive material such as acrylic resin, rubber-based resin, silicone resin, etc. to which a resin for adjusting adhesive force such as a chemical crosslinking agent is added is used, but is not limited thereto. isn't it. The adhesive force of the radio wave reflector 11 described above is generated by the adhesive layer 18. The thickness L13 of the adhesive layer 18 is preferably 10 μm or more and 100 μm or less. Note that, in addition to the adhesive material, the adhesive layer 18 may contain a substance such as an arbitrary synthetic resin or an arbitrary member.

(Conductive layer 16)
In the conductive layer 16, it is preferable that one or more linear conductors 12 are formed as a thin film on the upper surface of the base layer 13. The conductor 12 is preferably made of silver (Ag), for example. The conductor 12 may be made of a metal, a metal compound, or an alloy having free electrons, and is not limited to silver; for example, gold, copper, platinum, aluminum, titanium, silicone, indium tin oxide, and alloys ( For example, it may be an alloy containing nickel, chromium, and molybdenum). Examples of alloys containing nickel, chromium, and molybdenum include Hastelloy B-2, B-3, C-4, C-2000, C-22, C-276, G-30, N, W, and X. Various grades can be mentioned.

In this embodiment, as shown in FIG. 3(B), one or more linear conductors 12 are arranged surrounding a region 12a where there are no conductors 12. That is, the conductive layer 16 has conductors 12 and regions 12a without conductors 12 arranged periodically 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. In the example shown in FIG. 3(B), a plurality of first linear bodies 12A and a plurality of second linear bodies 12B constituting the conductor 12 are arranged at regular intervals along the vertical and horizontal directions. The area surrounded by the two adjacent first linear bodies 12A and the two adjacent second linear bodies 12B is the area 12a where there is no conductor 12. The area 12a without the conductor 12 has the same square shape. In other words, a plurality of regions 12a without the conductor 12 are arranged in the vertical and horizontal directions at intervals of the line width L6 of the conductor 12. The first linear body 12A and the second linear body 12B are electrically conductive at the intersection where the first linear body 12A along the horizontal direction and the second linear body 12B along the vertical direction overlap. are doing. The line width L6 of the conductor 12 is 0.0
It is preferable to set the thickness to 5 μm or more and 15 μm or less. The distance L7 between adjacent conductors 12 in the vertical or horizontal direction (the length of one side of the square area 12a without conductors 12) is larger than the wavelength of visible light, and the distance L7 between adjacent conductors 12 is larger than the wavelength of visible light, which is reflected by the radio wave reflector 11. In this example, the wavelength is set to be smaller than the wavelength of the radio waves transmitted, and in this example, it is set to 2 μm or more and 10 cm or less. More preferably, it is 20 μm or more and 1 cm or less, and even more preferably 25 μm or more and 1 mm or less. More preferably, it is 30 μm or more and 250 μm or less. If the region 12a without the conductor 12 is not square, the maximum length of any two points at the ends of the region 12a without the conductor 12 is set to the above length. Further, the region 12a where there is no conductor 12 may be filled with an adhesive of the adhesive layer 14.

Further, the thickness L3 of the conductive layer 16, that is, the thickness (film thickness) L3 of the conductor 12 is preferably a thickness that allows visible light transmission. The thickness L3 of the conductor 12 is preferably 0.05 μm or more and 10 μm or less. The thickness L3 is preferably 5 nm or more from the viewpoint of ensuring appropriate radio wave intensity.

The coverage of the conductive layer 16 is preferably 1% or more and 50% or less, more preferably 1% or more and 10% or less. The conductor coverage refers to the ratio of the area occupied by the conductor 12 per unit area in plan view. The coverage can also be said to be the ratio of the area of the base layer 13 covered by the conductor 12 to the area of the base layer 13 in plan view. As in the embodiment shown in FIGS. 2 and 3, when the conductive layer 16 is not provided at the peripheral edge of the base layer 13 but is provided inside the edge of the base layer 13, The coverage rate refers to the ratio of the area occupied by the conductor 12 per unit area in the region where the conductive layer 16 is provided on the upper surface of the base layer 13 in plan view. The area where the conductive layer 16 is provided is the area obtained by excluding the peripheral edge of the base layer 13 (the area between the edge of the base layer 13 and the conductive layer 16) from the upper surface area of the base layer 13. Become. The coverage rate is measured using a scanning electron microscope (SEM), a transmission electron microscope (TEM), an optical microscope, or the like.

Although the surface roughness Sa of the conductor 12 is not particularly limited, it 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. When the surface roughness Sa is within this range, radio waves can be easily diffused and reflected.

The surface roughness Sa is determined by the arithmetic mean height of ISO 25178 and is measured in accordance with ISO 25178. Using a laser microscope (product name VK-X1000/1050, manufactured by Keyence Corporation, or equivalent product), measure the surface roughness at multiple locations on the surface of the conductor 12, and calculate the average value of the obtained measurement values. By calculation, the surface roughness Sa of the conductor 12 can be determined. Note that the conductor 12 and the base material layer 13 may be measured. In this embodiment, a plurality of conductors 12 are provided, and the surface roughness of each conductor 12 is measured at a plurality of locations, and the average value of the measured values is taken as the surface roughness Sa of the conductor 12. .

In the arrangement of the conductors 12 shown in FIG. 3B, the shape of the region 12a without the conductor 12 is square, but for example, the spacing between the adjacent conductors 12A extending in the horizontal direction and the distance between the adjacent conductors 12A in the vertical direction The spacing between the conductors 12B extending in the direction may be different, and the shape of the region 12a without the conductor 12 may be rectangular.

Furthermore, the conductors 12 may be arranged in the arrangement patterns shown in FIGS. 4(A) to 4(E). In FIG. 4A, the conductors 12 are arranged in a brick-laying pattern. A plurality of first linear bodies 12A are arranged along the horizontal direction and at predetermined intervals in the vertical direction, and between the first linear bodies 12A adjacent to each other in the vertical direction, a plurality of first linear bodies 12A extending in the vertical direction are arranged. The second linear bodies 12B are arranged in a staggered manner. A staggered pattern means that a plurality of second linear bodies 12B extending in the vertical direction are arranged at a predetermined interval in the horizontal direction, and a plurality of second linear bodies 12B forming one row are arranged in this row. is located between a plurality of second linear bodies 12B forming adjacent rows in the vertical direction, and the second linear bodies 12B in every row are arranged in a straight line. say. The area 12a without the conductor 12 is an area surrounded by two adjacent first linear bodies 12A and two adjacent second linear bodies 12B.

In FIG. 4(B), the conductors 12 are arranged so that the plurality of regions without the conductors 12 are triangular. The plurality of regions without the conductor 12 include a plurality of triangular first regions 12a and a plurality of inverted triangular second regions 12b. The first region 12a and the second region 12b are arranged at regular intervals in the horizontal and vertical directions, and the second region 12b is arranged between adjacent first regions 12a. . Each of the first region 12a and the second region 12b is a region surrounded by each of the first to third linear bodies 12A to 12C. The first linear body 12A is arranged along the lateral direction, the second linear body 12B is arranged along the direction obliquely inclined with respect to the first linear body 12A, and the third linear body 12B The body 12C is arranged along a direction symmetrical to the second linear body 12B with respect to the first linear body 12A.

Although each of the regions 12a and 12b is an equilateral triangle in FIG. 4B, it may be an isosceles triangle or a triangle whose three sides have different lengths.

In FIG. 4C, the conductors 12 are arranged to surround a regular hexagonal region 12a where no conductors 12 are present. The regions 12a without the conductor 12 are arranged continuously in the vertical direction at intervals of the line width L6 of the conductor 12, and a plurality of these rows are arranged in the horizontal direction. A region 12a without a conductor 12 in an adjacent row in the horizontal direction is arranged between regions 12a without a conductor 12 adjacent in the vertical direction.

In FIG. 4(D), there is a region without a plurality of types of conductors 12 having different shapes. The region without the conductor 12 includes a first region 12a in the shape of a regular pentagon surrounded by the linear conductor 12, a second region 12b in the shape of an inverted regular pentagon, and a third region 12c in the shape of a rhombus. The first region 12a to the third region 12c are arranged at regular intervals in the horizontal and vertical directions, respectively. Specifically, the first region 12a and the second region 12b are arranged adjacent to each other in the vertical direction with an interval equal to the line width L6 of the conductor 12. The pairs of regions 12b and 12b are arranged horizontally and periodically. The third region 12c is arranged between a pair of the first region 12a and the second region 12b that are adjacent in the horizontal direction. The shapes formed by the first region 12a, the second region 12b, and the third region 12c are arranged at the same period.

In FIG. 4E, there is a region without a plurality of types of conductors 12 having different shapes. The regions without the conductor 12 include a circular first region 12a surrounded by the linear conductors 12, a substantially triangular second region 12b, and a substantially inverted triangular third region 12c. It is equipped with The first to third regions 12a to 12c are arranged periodically at regular intervals in the vertical and horizontal directions, respectively. The first regions 12a are arranged horizontally and periodically at intervals of the line width L6 of the conductor 12 so as to be continuous. Rows of such first regions 12a are arranged continuously in the vertical direction, and vertically adjacent first regions 12a are arranged between horizontally adjacent first regions 12a. .

Note that FIGS. 4A to 4E only illustrate the conductor 12. The other structure of the conductor 12 is the same as that in FIG. 3(B).

As a method for manufacturing the conductive layer 16 having the arrangement patterns shown in FIGS. 3(B) and 4, for example, there is a method in which a conductive film is formed, a pattern is formed by etching, and a conductive thin film body having the pattern is taken out. . Also,
Examples include a method in which a photosensitive resist is coated on a base film provided with a lift-off layer, a pattern is formed by photolithography, the patterned portion is filled with a conductor, and then a conductive thin film body having a pattern is taken out. Note that the manufacturing method is not limited to the above, and examples of forming the conductive layer 16 include a method of bonding a metal thin film, a method of vapor depositing a metal, and the like.

(Other embodiments of conductive layer 16)
The conductive layer 16 may have a metamaterial structure, for example. A metamaterial structure is one in which sheet-shaped conductors 12, which are dielectric materials, are arranged periodically and equally, and this periodic arrangement structure has a negative dielectric constant, and a specific frequency band determined based on the periodic interval. reflects radio waves belonging to The shape of each conductor 12 is not limited and may be the above-mentioned shape, but for example, as shown in FIG. 5, each conductor 12 may have a square shape. The length L20 of one side and the interval L21 between adjacent conductors 12 may be set so that the conductors 12 reflect radio waves having a frequency of 3 GHz or more and 300 GHz or less. In this case, the length L20 of one side of the conductor 12 may be 0.7 mm or more and 800 mm or less, and the interval L21 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 base material layer 13. In one example, the conductors 12 may be formed in a total of four, two vertically and two horizontally, on the base layer 13 according to the size of the base layer 13. In this case, the length L20 of one side of each conductor 12 is set to 77.460 mm, the interval L21 between adjacent conductors 12 is set to 100 μm, and the thickness L3 is set to 350 nm (0.35 μm) or less. The conductive layer 16 is not limited to a metamaterial structure, and may be any one of a metal nanowire laminated film, multilayer graphene, or partially exfoliated graphite.

(Other embodiments of conductive layer 16)
The conductor 12 may have a form as shown in FIG. 6, for example. The conductor 12 is formed in a pattern such that a first conductive part 62 including a plurality of first enclosing parts 61 and a second conductive part 64 including a plurality of second enclosing parts 63 overlap. There is. The first enclosing part 61 and the second enclosing part 63 do not have a shared portion with each other when projected onto a projection plane parallel to the conductive layer.

In the first conductive part 62, the first surrounding part 61 surrounding the first region AR1 where the conductor 12 is not formed is repeatedly formed at a constant pitch. Although the first conductive portion 62 is formed in a lattice shape here, it may be formed in a pentagonal shape, a hexagonal shape, a circular shape, or the like.

In the second conductive portion 64, a second enclosing portion 63 surrounding a fourth region AR4, which is a region where the conductor 12 is not formed, is repeatedly formed at a constant pitch. The fourth region AR4 is formed so as to span the plurality of adjacent first regions AR1. The second conductive part 64 may be located on the same plane as the first conductive part 62, or may be located on a different plane. That is, the second conductive part 64 may or may not be electrically connected to the first conductive part 62. Further, although adjacent second conductive parts 64 are separated from each other, they may be in contact with each other. Although the second conductive portion 64 is formed in a rectangular shape, it may be formed in a pentagonal shape, a hexagonal shape, or the like.

According to this conductor 12, the diffusibility of radio waves can be improved. "Radio wave diffusivity" here means that the difference between the regular reflection intensity and the radio wave intensity around the regular reflection falls within a certain range.

(Other embodiments of conductive layer 16)
The conductor 12 may have a form as shown in FIG. 7, for example. The embodiment in FIG. 7 is different from the embodiment in FIG. 6 in the shape of the second conductive portion 64 (second enclosing portion 63), and the second enclosing portion 63 is circular. The center point of the second enclosing part 63 is arranged so as to overlap with the intersection of the first conductive parts 62 formed in a lattice shape, and the diameter of the second enclosing part 63 is equal to pitch. That is, adjacent second enclosing parts 63 are in contact with each other. Note that adjacent second enclosing portions 63 may be separated from each other. Since the other configurations are similar to the embodiment shown in FIG. 6, corresponding configurations are given the same reference numerals and description thereof will be omitted.

In this manner, by having the circular second enclosing portion 63, the influence of the direction of incidence on the radio wave reflector 11 on the reflection intensity can be reduced in plan view. In other words, in this case, no matter which direction the radio waves are incident on the radio wave reflector 11 from in plan view, variations in diffusivity depending on the direction of incidence can be reduced.

(Adhesive layer 14)
The adhesive layer 14 adheres the protective layer 15 onto the base layer 13 and the conductive layer 16, and is made of an adhesive. Adhesive layer 14 has a size corresponding to base material layer 13 in plan view. As the adhesive material for the adhesive layer 14, a synthetic resin or rubber adhesive sheet is used. Examples of the synthetic resin 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. Note that, in addition to the adhesive, the adhesive layer 14 may contain a substance such as an arbitrary synthetic resin or an arbitrary member.

The adhesive layer 14 is preferably made of a synthetic resin material having a dielectric loss tangent (tan δ) of 0.018 or less. The lower the dielectric loss tangent, the better, but it is usually 0.0001 or more. The dielectric loss tangent represents the degree of electrical energy loss within a dielectric, and the larger the dielectric loss tangent of a material, the greater the electrical energy loss. By using the adhesive layer 14 having a dielectric loss tangent of 0.018 or less, the loss of electric energy of the radio wave in the radio wave reflector 11 is reduced, and the reflection intensity can be made stronger.

Further, it is preferable that the synthetic resin material of the adhesive layer 14 has a dielectric constant that changes depending on the frequency of the electric field. The relative permittivity is the ratio of the permittivity of a medium (synthetic resin material in this embodiment) to the permittivity of a vacuum. By changing the dielectric constant according to the electric field, it is possible to increase the intensity of reflected waves in the electric field of a specific frequency. The dielectric constant preferably varies between 1.5 and 7. More preferably, it varies between 1.8 or more and 6.5 or less. The inductive tangent and relative permittivity are measured using a measuring device (for example, Toyo Technica, model number TTPX Table Top Cryogenic Prober, Material Impedance Analyzer MIA-5M) using a known method (for example, cavity resonator method, coaxial resonator method). It is measured by

Note that the synthetic resin material constituting not only the adhesive layer 14 but also the base layer 13 and the protective layer 15 may have a dielectric loss tangent of 0.018 or less, and the relative dielectric constant changes depending on the electric field. It may be something.

Further, the adhesive layer 14 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, still more preferably 90 mgKOH/g or more. It is. On the other hand, the upper limit of the hydroxyl value of the adhesive layer 14 is preferably 120 mgKOH/g or less. When the hydroxyl value of the adhesive layer 14 is 5 mgKOH/g or more, there is an advantage that the adhesive layer 14 is difficult to foam and/or whiten in a high temperature and high humidity environment. In this specification, the hydroxyl value is measured by a test method based on JIS K 1557.

Further, the acid value of the adhesive layer 14 is preferably 50 mgKOH/g or less, more preferably 45 mgKOH/g or less, still more preferably 30 mgKOH/g or less, still more preferably 10 mgKOH/g or less. It is. On the other hand, the lower limit of the acid value of the adhesive layer 14 is preferably 0.1 mgKOH/g or more. When the acid value of the adhesive layer 14 is 50 mgKOH/g or less, the conductor 12 can be prevented from corroding, and the stability of radio wave reflection properties over time can be increased. In this specification, the acid value is measured by a test method based on JIS K 2501.

The adhesive layer 14 preferably does not contain an ultraviolet inhibitor. When the adhesive layer 14 does not contain an ultraviolet inhibitor, there is an advantage that the adhesive layer 14 can be easily adjusted to be colorless and transparent. Here, "not containing" includes not only the case where the ultraviolet inhibitor is not contained at all, but also the case where the adhesive layer 14 contains a small amount that does not impair the colorless transparency. Ultraviolet inhibitors absorb or scatter ultraviolet rays to prevent entry of ultraviolet rays, and include ultraviolet absorbers and ultraviolet scattering agents.

(Protective layer 15)
The protective layer 15 has a size corresponding to the base material layer 13 in plan view, protects the conductor 12, and is made of a protective material. As the protective material that is the protective layer 15, a synthetic resin sheet (film) is used. Examples of synthetic resins include PET (polyethylene terephthalate), COP (cycloolefin polymer), polyethylene, polypropylene, polyvinyl chloride, polystyrene, polymethyl methacrylate, polyester, polyformaldehyde, polyamide, polyphenylene ether, vinylidene chloride, and 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 10 μm or more and 200 μm or less, but is not limited thereto and is appropriately set according to the usage mode of the radio wave reflector 11. Further, it is preferable that the protective layer 15 has a Young's modulus at 25° C. of 1 GPa or more and 4 GPa or less. By setting the Young's modulus of the protective layer 15 within the above range, the radio wave reflector 11 has flexibility, and when the radio wave reflector 11 affixed to the object to be attached is peeled off, the radio wave reflector 11 does not break. It's hard to do. In addition to the protective material, the protective layer 15 may contain any material such as an arbitrary synthetic resin or any other member.

The moisture permeability of the protective layer 15 at a temperature of 40° C. and a humidity of 90% rh (relative humidity) is preferably 20 g/m ² ·24 h or less, more preferably 16 g/m ² ·24 h or less, More preferably, it is 12 g/m ² ·24 h or less, and still more preferably 10 g/m ² ·24 h or less. When the moisture permeability of the protective layer 15 at a temperature of 40° C. and a humidity of 90% rh (relative humidity) is 20 g/m ² · 24 h or less, the conductive layer 16 is less likely to corrode and the surface resistivity of the conductive layer 16 increases. It has the advantage of being difficult to do. "Moisture permeability" as used herein is measured by a test method based on JIS Z 0208 (1976).

(Other embodiments)
FIG. 8 shows another embodiment of the invention. The radio wave reflector 11 shown in FIG. 8 may have a plurality of conductive layers 16A, 16B in the vertical direction by base layers 13A, 13B in which the conductors 12A, 12B are made of resin. Each conductor 12 of the conductive layer 16A formed on the base material layer 13A and each conductor 12 of the conductive layer 16B formed on the base material layer 13B are aligned and stacked so as to overlap when viewed from a plane. ing. Note that the arrangement patterns of the conductive layers 16A and 16B in FIG. 8 do not need to overlap in plan view, and the conductive layers 16A and 16B may be formed with different arrangement patterns. The lower surface of the base layer 13B is pasted onto the conductive layer 16A with an adhesive layer 14A, and the protective layer 15 is pasted onto the conductive layer 16B with an adhesive layer 14B.

In this embodiment, the Young's modulus of the radio wave reflector 11 is preferably 0.01 GPa or more and 80 GPa or less, and the thickness L1 of the radio wave reflector 11 is preferably 10 μm or more and 400 μm or less.

The radio waves incident on the radio wave reflector 11 are reflected by the conductor 12 of the first conductive layer 16B, but some of the radio waves are not reflected by the conductive layer 16B and pass through the conductive layer 16B. The radio waves that have passed through this conductive layer 16B are reflected by the second conductive layer 16A. In this way, by stacking a plurality of conductors 12 in the vertical direction, the radio waves that have passed through the upper conductive layer 16B can be reflected by the lower conductive layer 16A, and the reflection intensity of the radio wave reflector 11 is reduced by the conductor 12. can be kept larger than in the case of only one layer. Moreover, the kurtosis of the distribution of reflection intensity in the angular range α of ±15 degrees with respect to the normal reflection direction of radio waves can be further reduced, and the difference in reflection intensity depending on the angular position within the angular range α is reduced. Furthermore, since two adhesive layers 14A and 14B are used, the value of the dielectric loss tangent becomes even smaller than the embodiment shown in FIG. 2, and the reflection intensity can be kept even higher. Other configurations and operations are similar to those of the embodiment shown in FIGS. 2 and 3, so corresponding configurations are given the same reference numerals and detailed explanations will be omitted.

In the embodiment of FIG. 8, the conductors 12 formed on the base material layer 13 are laminated in two layers, but three or more layers may be laminated. As the number of laminated conductors 12 increases, the reflection intensity increases, but since the overall thickness of the radio wave reflector 11 increases, flexibility decreases, and visible light transmittance also decreases. Therefore, when the radio wave reflector 11 is provided in a place where flexibility and transparency are not particularly required, the number of laminated layers is increased, and the number of laminated layers is appropriately set depending on the intended use.

(Other embodiments)
FIG. 9 shows another embodiment of the radio wave reflector 11. The embodiment of FIG. 9 includes a conductive layer 16 and a base material layer 13 made up of a plurality of linear conductors 12 similar to the embodiments shown in FIGS. 2 and 3, and includes an adhesive layer 14 and a protective layer. 15. In this embodiment, the Young's modulus is preferably 0.01 GPa or more and 80 GPa or less, and the thickness L1 of the radio wave reflector 11 is preferably 10 μm or more and 400 μm or less. Other configurations and operations are similar to those of the embodiment shown in FIGS. 2 and 3, so corresponding configurations are given the same reference numerals and detailed explanations will be omitted.

In the embodiments shown in FIGS. 2 to 9, the conductive layer 16 is composed of a plurality of linear conductors 12, but the conductive layer 16 is not limited to the embodiments shown in FIGS. 2 to 9, and for example, A single sheet-shaped conductor 12 that is a dielectric material may be formed in a square shape over substantially the entire upper surface of the base material layer 13. In this case, the coverage is defined as the ratio of the area occupied by the conductor 12 per unit area in the portion of the base layer 13 where the conductive layer 16 is provided, and the coverage is 100%. Note that the size of the conductor 12 may be one size smaller than the size of the base layer 13 in a plan view, and the conductor 12 may not be formed in a region close to the side edge of the base layer 13.

Further, the conductive layer 16 of the embodiment shown in FIG. 9 may be formed by periodically arranging a plurality of sheet-like conductors 12 in the same manner as the conductive layer 16 of the embodiment shown in FIG. good. In this case, the plurality of conductors 12 are arranged on substantially the entire upper surface of the base material layer 13 at predetermined intervals. Furthermore, the shape of the conductor 12 may be square, circular, rectangular, triangular, polygonal, or the like. The conductive layer 16 may have a metamaterial structure, and may be made of a metal nanowire stack, multilayer graphene, or partially exfoliated graphite.

(Other embodiments)
In the embodiments shown in FIGS. 2 to 9, a release paper 19 may be further provided on the lower surface of the adhesive layer 18. The release paper 19 is used to protect the adhesive layer 18 from reducing adhesive strength due to dust, dirt, etc. adhering to the adhesive layer 18, and the radio wave reflector 11 is attached to the object to be attached. removed at the time. The release paper 19 is, for example, paper whose surface has been subjected to release processing. FIG. 10 shows a radio wave reflector 11 in which a release paper 19 is further attached to the embodiment shown in FIG. The release paper 19 has an area that covers at least the adhesive layer 18 when viewed from above, and the thickness L14 is preferably 10 μm or more and 50 μm or less.

(use)
Any of the above-mentioned radio wave reflectors 11 may be used by being attached to surfaces such as walls, partitions, pillars, lintels, outer walls of buildings, windows, etc., using an adhesive or the like. Moreover, the radio wave reflector 11 may be included in the building material 30 and used. For example, as shown in FIG. 11A, the building materials 30 include decorative materials 30A such as walls, ceilings, and floors in rooms and hallways, wallpaper for partitions, posters, etc., and decorative materials such as transparent stickers for light covers. 30B, which can be installed inside a building. By attaching the decorative materials 30A and 30B containing the radio wave reflector 11 to the wall surface 31 and the light cover 32, the decorative material provided on the wall surface 31 and the light cover 32 can prevent radio waves that have entered the room from outside through the window 33 etc. It is reflected by 30A and 30B. This allows the radio waves to reach a wider area of the indoor space S, improving the convenience of receiving radio waves.

Further, the radio wave reflector 11 may be formed as a member made of a non-conductive material such as resin or held inside a building material. For example, the wall surface 31 itself or the light cover 32 itself, which is the building material 30, may be composed of the radio wave reflector 11. Further, the building material 30 is not limited to an indoor wall or a light cover, but may be, for example, a partition, a pillar, a lintel, an outer wall of a building, a window, etc. For example, FIG. 11(B) is a plan view of the room, and the building material 30 that is the radio wave reflector 11 is formed as a corner post 30C having a curved surface at the corner of the room. Radio waves entering through the window 33 are reflected by the corner post 30C, and the radio waves reach a wider area of the indoor space S. Note that FIGS. 11(A) and 11(B) show examples of application of the building material 30, and do not show the actual range of radio wave reflection.

(Evaluation test)
Examples 1 to 4 were created as the radio wave reflector 11, and evaluation tests were conducted on cutting properties, rework properties (repeel properties), and surface resistivity before and after the peel test for Examples 1 to 4 and Comparative Examples 1 and 2. I did it. However, the radio wave reflector 11 of the present invention is not limited to Examples 1 to 4. Table 1 shows the structures and evaluation results of Examples 1 to 4 and Comparative Examples 1 and 2.

(Explanation of Examples and Comparative Examples)
(Example 1)
The radio wave reflector 11 created as Example 1 has the configuration of the embodiment shown in FIG. 10, that is, the radio wave reflector 11 has a configuration in which a release paper 19 is provided in the embodiment shown in FIGS. 2 and 3. The radio wave reflector 11 had a square planar shape, the length L10 of one side was 20 cm, and the thickness L1 of the radio wave reflector 11 was 200 μm. The thickness L1 of the radio wave reflector 11 is the same as the thickness L5 of the protective layer 15, the thickness L4 of the adhesive layer 14, the thickness L3 of the conductive layer 16, the thickness L2 of the base layer 13, the thickness L13 of the adhesive layer 18, and the release paper 19. is the total thickness L14. However, since the thickness L3 of the conductive layer 16 is very thin compared to the thicknesses of other layers, the thickness L3 of the conductive layer 16 is not taken into account in the thickness L1 of the radio wave reflector 11. The radio wave reflector 11 has a radio wave reflection strength of -30 dB or more in a frequency band of 3 GHz or more and 300 GHz or less. Further, the radio wave reflector 11 has a maximum value of radio wave reflection intensity (hereinafter also referred to as "maximum value of radio wave reflection intensity") of -20 dB when an incident wave with a frequency of 3 GHz or more and 300 GHz or less is reflected.

The adhesive used as the adhesive layer 18 was prepared by mixing 2.0 parts by weight (solid content) of Coronate L45K as a chemical cross-linking agent with 100 parts by weight (solid content) of model number SK Dyne 1604N manufactured by Soken Kagaku Co., Ltd. After coating on the mold PET, the solvent was dried and removed to give the desired thickness. The thickness L13 of the adhesive layer 18 is 25 μm, and the adhesive force is 0.8 N/25 mm. The adhesive layer 18 was laminated on the entire lower surface of the base layer 13.

A synthetic resin material sheet made of PET (Lumirror 50T60, manufactured by Toray Industries, Inc.) was used as the base layer 13, and the thickness L2 of the base layer 13 was 50 μm. The Young's modulus of the base material layer 13 is 3.8 GPa.

The conductor 12 of the conductive layer 16 is a linear metal thin film made of silver (Ag), and has a thickness (film thickness) L3 of 500 nm, a line width L6 of 0.5 μm, and a length L7 between adjacent conductors 12. was set to 60 μm. The surface resistivity of the conductive layer 16 is 1.7Ω/□, and the conductor coverage is 3.3%.

As the adhesive layer 14, a rubber adhesive was used. Specifically, the adhesive layer 14 is made of rubber-based polymer (styrene-(ethylene-propylene)-styrene type block copolymer 50) in a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer, a dropping funnel, and a stirring device. % by mass and 50% by mass of styrene-(ethylene-propylene) type block copolymer, styrene content 15%, weight average molecular weight 130,000) 100 parts by weight, synthetic resin (manufactured by Mitsui Chemicals, FMR-0150) 40 parts by weight, 20 parts by weight of a softener (manufactured by JX Nippon Oil & Energy Corporation, LV-100), 0.5 parts by weight of an antioxidant (manufactured by ADEKA, ADEKA STAB AO-330), and 150 parts by weight of toluene. The mixture was stirred at ℃ for 5 hours. The thickness L4 of the adhesive layer 14 was 50 μm.

A synthetic resin sheet made of PET as the protective layer 15 (manufactured by Toray Industries, Lumirror 50T60)
was used. The thickness L5 of the protective layer 15 was 50 μm. The Young's modulus of the protective layer 15 is 4.0 GPa.

In addition, the thickness L1 of the radio wave reflector 11, the thickness L3 of the conductive layer 16, the thickness L2 of the base material layer 13, the thickness L4 of the adhesive layer 14, the thickness L5 of the protective layer 15, the thickness L13 of the adhesive layer 18, and the thickness of the release paper 19. Thickness L14 was determined by measuring at a plurality of arbitrary locations and calculating the average value of the obtained measurement values. The thicknesses L1 to L5, L13, and L14 are measured at the time of manufacturing the radio wave reflector 11, and a reflectance spectroscopic film thickness measuring device (for example, F3-CS-NIR manufactured by Filmetrics Co., Ltd.) is used as the measuring instrument. Ta.

As the release paper 19, SP3000 manufactured by Toyo Cross Co., Ltd. was used. The thickness L14 of the release paper 19 was 25 μm.

A method of manufacturing the radio wave reflector 11 of Example 1 will be described. First, the conductor 12 is formed on the base material layer 13. A core layer of 0.01 μm or more and 3 μm or less is formed by a method such as electrolytic or electroless plating on one surface of a copper foil having a thickness of 5 μm or more and 200 μm or less and having sufficient strength as a metal layer. Then, a conductive layer 16 having a predetermined arrangement pattern is formed on the surface of the core layer by a method such as electrolytic or electroless plating. Next, the entire conductive layer 16 is covered with the base material layer 13. An adhesive is applied to the base layer 13 in advance. Then, the copper foil and core layer are removed by etching. As a result, the conductor 12 is formed on the base material layer 13.

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 . A protective layer 15 is pasted onto the conductor 12 of the base layer 13 using the adhesive layer 14 to prevent air bubbles from entering. An adhesive layer 18 is applied to the surface of the base layer 13 opposite to the surface on which the conductor 12 is provided. A release paper 19 for protecting the adhesive layer 18 is placed over the entire surface of the adhesive layer 18. In this way, the radio wave reflector 11 is manufactured.

(Example 2)
Regarding the radio wave reflector 11 created as Example 2, only the points different from Example 1 will be described.
The adhesive material used as the adhesive layer 18 is a resin obtained by copolymerizing hydroxyethyl acrylate (HEA) and ethyl acrylate (EA) at a ratio of 20:80 (mole ratio), and 100 parts by weight (solid content) of a chemical crosslinking agent. 2.0 parts by weight (solid content) of Coronate L45K manufactured by Soken Kagaku Co., Ltd. was blended, and after coating on the release PET, the solvent was dried and removed to give the desired thickness. The adhesive force is 1.2N/25mm. The other configurations are the same as in the first embodiment.

(Example 3)
Regarding the radio wave reflector 11 created as Example 2, only the points different from Example 1 will be described. The thickness L1 of the radio wave reflector 11 was set to 230 μm. The adhesive force is 0.9N/25mm. As the base layer 13 and the protective layer 15, a synthetic resin material sheet made of soft vinyl chloride (manufactured by Okamoto Co., Ltd., transparent general-use PVC film) was used. The thickness L2 of the base material layer 13 is 80 μm. In Table 1, soft vinyl chloride is described as "soft vinyl chloride." The Young's modulus of the base layer 13 and the protective layer 15 is 2.8 GPa. The other configurations are the same as in the first embodiment.

(Example 4)
Regarding the radio wave reflector 11 created as Example 4, only the points different from Example 1 will be described. The thickness L3 of the conductive layer 16 (that is, the thickness of the conductor 12) was set to 1000 nm (1 μm). As the adhesive layer 14, an acrylic adhesive was used. The acrylic adhesive used in Example 4 was made of adhesive 2980 (manufactured by Soken Kagaku) with an acid value of 0.5 mgKOH/g and a hydroxyl value of 95 mgKOH/g, and an isocyanate-based crosslinking agent of L-45K (manufactured by Soken Kagaku). It is a mixture. The other configurations are the same as in the first embodiment.

(Comparative example 1)
The radio wave reflector 11 prepared as Comparative Example 1 has an adhesive strength of 2.2 N/25 mm. The other configurations are the same as in the first embodiment.

(Comparative example 2)
The radio wave reflector 11 created as Comparative Example 2 had a thickness L1 of 475 μm. The thickness L13 of the adhesive layer 18 is 100 μm, and the adhesive force is 1.2 N/25 mm. The thickness L2 of the base material layer 13 is 125 μm, the thickness L4 of the adhesive layer 14 is 100 μm, and the thickness L5 of the protective layer 15 is 125 μm. The other configurations are the same as in the first embodiment.

(Measurement of reflection intensity)
The intensity of the reflected waves of the measurement objects Examples 1 to 4 and Comparative Examples 1 and 2 (also collectively referred to as "samples") was measured in accordance with the method for measuring the amount of reflection described in JISR1679:2007. , was performed using the following steps. The sample was placed flat on a sample mount, and a transmitting antenna and a receiving antenna were placed in accordance with the incident angle θ1 and reflection angle θ2 (θ1, θ2 = 45 degrees) of the radio waves. The distance between the sample and the receiving antenna and the distance between the sample and the transmitting antenna were 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) of the radio wave was measured. The amount of reflection at a frequency of 28.5 GHz and the frequency band where the amount of reflection is -30 dB or more were determined.

First, a reference metal plate (aluminum A1050 plate, thickness 3 mm) was placed on a sample mount, and the reception level was measured and recorded using a scalar network analyzer. At this time, the coaxial cables of the receiving antenna and the transmitting antenna were directly connected using a scalar network analyzer, and the signal level at each frequency was set to 0 for calibration. Thereafter, the device was configured again and measurements were taken. The reference metal plate was removed from the sample mount, the sample was placed on the sample mount, and the reception level was measured and recorded. The reception level of the reference metal plate was subtracted from the measured reception level to determine the amount of reflection in the normal reflection direction of the radio wave reflector 11 to be measured. Similar measurements were repeated for each sample. Note that when the frequency of the radio wave was 10 GHz or less, the sample was irradiated with a plane wave using a millimeter wave lens as appropriate, taking into account the first Fresnel radius of the rectangular horn antenna.

(Measurement of surface resistivity)
The surface resistivity of the radio wave reflector 11 was measured by the eddy current method using a non-contact resistance measuring device (manufactured by Napson Corporation, trade name: EC-80P, or its equivalent). The surface resistivity of the conductive layer 16 is expressed as the surface resistivity of the radio wave reflector 11.

(Measurement of Young's modulus)
Young's modulus was measured according to JIS K7127-1999.

(evaluation index)
In order to evaluate the workability of the radio wave reflector 11, three evaluation indicators were set: cutting performance, reworkability (repeelability), and comparison of surface resistivity before and after the peel test.

(cutting performance)
Cutting performance is an evaluation of the ease with which the radio wave reflector 11 can be cut into a desired shape. The radio wave reflector 11 was spread on the cutter mat, a ruler was placed, and a cutter (manufactured by NT Corporation, model number PMGL-EVO2R) was used to cut along the ruler. The case where the operator could cut the radio wave reflector 11 without resistance was evaluated as "○", and the case where the operator felt resistance and could not cut smoothly was evaluated as "x".

(Reworkability)
Reworkability (repeelability) is to evaluate whether the radio wave reflector 11 attached to the object to be attached can be peeled off from the object to be attached. The procedure for the peel test is shown below. The release paper 19 is peeled off from the radio wave reflector 11, and the adhesive layer 18 is attached to a window glass, which is an object to be attached, using a rubber roller. After 24 hours had passed, an operator peeled off the radio wave reflector 11 at a speed of 1 cm/sec. When the operator can peel off the radio wave reflector 11 without leaving almost any adhesive layer 18 on the object to be attached, that is, more than 90% of the adhesive layer 18 of the radio wave reflector 11 is removed together with the radio wave reflector 11. A case where the film peeled off was evaluated as "○". In cases other than "○", for example, if less than 10% of the adhesive layer 18 remains on the object to be attached, even if the operator attempts to peel off the radio wave reflector 11 from the object to be attached with normal force. , cases where the adhesive layer 18 could not be completely peeled off due to the adhesive force, or cases where the radio wave reflector 11 was damaged when attempting to peel it off were evaluated as "x".

(Surface resistivity before and after peeling test)
Surface resistivity was measured before and after the peel test for reworkability described above. Before the peel test, the surface resistivity was measured with the radio wave reflector 11 having the release paper 19 in a flat state before being attached to a window glass. After the peel test, the radio wave reflector 11 peeled from the window glass was kept flat and its surface resistivity was measured. The radio wave reflector 11 after the peel test was not provided with the release paper 19. When the surface resistivity was 10Ω/□ or less, it was evaluated as “○”, and when it was larger than 10Ω/□, it was evaluated as “×”. If the surface resistivity is 10Ω/□ or less, it means that the radio wave reflector 11 has sufficient reflection strength for use.

(Evaluation results)
Table 1 shows the evaluation results. In all Examples 1 to 4, the cutting properties were evaluated as "○" and were good. Moreover, the reworkability was evaluated as "○", and the radio wave reflector 11 could be peeled off from the window glass. In addition, the surface resistivity was evaluated as "○" before and after the peel test, and the surface resistivity did not exceed 10Ω/□, and the radio wave reflector 11 had a reflection strength that was sufficient to withstand use before and after the peel test. has. As described above, in Examples 1 to 4, the workability was good.

On the other hand, in Comparative Example 1, the adhesive force of the adhesive layer 18 is greater than in Examples 1 to 4, and when the radio wave reflector 11 of Comparative Example 1 is peeled off from the window glass, a part of the adhesive layer 18 is attached to the window glass. Therefore, the reworkability was evaluated as "x". The surface resistivity of the radio wave reflector 11 after the peel test was 55Ω/□, which exceeded 10Ω/□, so it was evaluated as “x”. In Comparative Example 2, the thicknesses L13, L2, L4, and L5 of the adhesive layer 18, base material layer 13, adhesive layer 14, and protective layer 15 are larger than those of Examples 1 to 4, and the thickness L1 of the radio wave reflector 11 as a whole is larger. It got bigger. Therefore, the cutting property was evaluated as "x".

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various changes can be made without departing from the spirit of the present invention. The dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments or shown in the drawings are not intended to limit the scope of the invention thereto, and are merely illustrative examples. For example, expressions expressing relative or absolute positioning such as "in a certain direction,""along a certain direction,""parallel,""orthogonal,""centered,""concentric," or "coaxial" are strictly In addition to representing such an arrangement, it also represents a state in which they are relatively displaced with a tolerance or an angle or distance that allows the same function to be obtained. For example, expressions such as "same,""equal," and "homogeneous" that indicate that things are in an equal state do not only mean that things are exactly equal, but also have tolerances or differences in the degree to which the same function can be obtained. It also represents the existing state. For example, expressions expressing shapes such as squares and cylinders do not only refer to shapes such as squares and cylinders in a strict geometric sense, but also include uneven parts and chamfers to the extent that the same effect can be obtained. Shapes including parts, etc. shall also be expressed. The expressions "comprising,""comprising,""comprising,""containing," or "having" one component are not exclusive expressions that exclude the presence of other components.

In this specification, expressions accompanied by "approximately" such as "approximately parallel" or "approximately perpendicular" may be used. For example, "substantially parallel" means substantially "parallel", and includes not only a strictly "parallel" state but also an error of several degrees. The same applies to other expressions accompanied by "abbreviation".

Further, in this specification, expressions such as "end" and "end" are used that are distinguished by the presence or absence of "...part". For example, "edge" means the end part of an object, while "edge" means an area having a certain range that includes the "edge." Any point within a certain range that includes the edge is considered to be an "edge." The same applies to other expressions accompanied by "...part".

11 Radio wave reflector 11a Reflection points 12, 12A, 12B Conductor 13, 13A, 13B Base layer 14, 14A, 14B Adhesive layer 15 Protective layer 16 Conductive layer 18 Adhesive layer 19 Release paper 20 Radio wave source 21 Receiving section 30, 30A, 30B, 30C Building material L1 Thickness of radio wave reflector L2 Thickness of base layer L3 Thickness of conductor L4 Thickness of adhesive layer L5 Thickness of protective layer L6 Line width of conductor L7 Distance between adjacent conductors L10 Length of one side of radio wave reflector L13 Thickness of adhesive layer L14 Thickness of release paper

Claims (6)

A radio wave reflector including a conductor for reflecting radio waves,
comprising a conductive layer containing the conductor, a base material layer containing a base material holding the conductive layer, and an adhesive layer containing an adhesive material,
The conductive layer, the base layer, and the adhesive layer are laminated in this order,
The thickness of the radio wave reflector is 400 μm or less,
When the adhesive layer is attached to the attachment object, the adhesive force that acts between the attachment object and the adhesive layer is such that the attachment object is glass, the peeling angle is 180 degrees, and the peeling speed is 23° C. A radio wave reflector that is 2N/25mm or less at 300mm/min. The radio wave reflector according to claim 1, wherein the base material layer has a thickness of 100 μm or less and a Young's modulus at 25° C. of 4 GPa or less. further comprising a protective layer containing a protective material for protecting the conductive layer, and an adhesive layer containing an adhesive for bonding the conductive layer and the protective layer,
The radio wave reflector according to claim 1, wherein the protective layer has a thickness of 100 μm or less and a Young's modulus at 25° C. of 4 GPa or less. The conductor has one or more linear shapes and is arranged surrounding an area where there is no conductor,
The radio wave reflector according to claim 1, wherein the regions are periodically arranged at intervals. Further comprising a release paper for protecting the adhesive layer,
The radio wave reflector according to claim 1, wherein the conductive layer, the base material layer, the adhesive layer, and the release paper are laminated in this order. The radio wave reflector according to claim 1, wherein the adhesive force is 0.1 N/25 mm or more.

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