TW202422949A - Radio wave reflector - Google Patents

Abstract

The subject of the present invention is to improve the diffusivity when reflecting radio waves. The radio wave reflector 11 of the present invention has a conductive layer 16 having a conductor 12 for reflecting radio waves. The conductor 12 has: a first conductive portion 4, which has a first enclosing portion 41 repeatedly formed at a certain interval, and the first enclosing portion 41 surrounds a first region R1 where the conductor 12 is not formed; and a second conductive portion 5, which includes at least one second enclosing portion 51, and the second enclosing portion 51 surrounds a second region R2 spanning and adjacent to a plurality of first regions R1. When projected onto a projection plane parallel to the conductive layer 16, the first enclosing portion 41 and the second enclosing portion 51 do not have a common portion with each other.

Description

Radio wave reflector

The present invention relates to a radio wave reflector.

In mobile phones and wireless communications, radio waves in the frequency band of about 3 GHz to 300 GHz, called centimeter waves or millimeter waves, are used. Since these short-wavelength radio waves have strong straightness, they are not easy to bend even if there are obstacles. Therefore, in order to make the radio waves reach a wider range, reflectors are installed on the walls, floors, ceilings, columns and other surfaces of buildings (hereinafter referred to as "walls, etc.").

For example, Patent Document 1 describes a communication system that places a monopole antenna and a metal reflector for reflecting radio waves in the space under the floor of a room. The metal reflector diffuses the radio waves output from the monopole antenna to the space under the floor, and prevents the radio waves from leaking from the space under the floor to the outside of the living room (building) or being absorbed by the floor of the building. [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent Application Publication No. 2010-258514

[The problem that the invention wants to solve]

However, the metal reflector described in Patent Document 1 has the following problem: since it is a reflector made of metal alone, the diffusion property when reflecting radio waves is poor. That is, although the metal reflector described in Patent Document 1 can maintain the intensity of radio waves at the position corresponding to the regular reflection, the intensity of radio waves is extremely reduced around the regular reflection.

The purpose of the present invention is to provide a radio wave reflector that can improve the diffusion of radio waves when reflecting them. [Technical means to solve the problem]

In order to achieve the above-mentioned object, the present invention includes the subject matter described in the following items.

Item 1. A radio wave reflector, comprising a conductive layer having a conductor that reflects radio waves, wherein the conductor comprises: a first conductive portion having a first surrounding portion repeatedly formed at a certain interval, the first surrounding portion surrounding a first area where the conductor is not formed; and a second conductive portion comprising at least one second surrounding portion, the second surrounding portion surrounding a second area spanning and adjacent to a plurality of the first areas; and the first surrounding portion and the second surrounding portion do not have a common portion when projected onto a projection plane parallel to the conductive layer.

Item 2. The radio wave reflector as described in Item 1, wherein the perimeter of the first surrounding portion is a length less than the wavelength of the radio wave.

Item 3. The radio wave reflector as described in Item 2, wherein the perimeter of the first surrounding portion is a length that is not more than 5/6 times the wavelength of the radio wave.

Item 4. The radio wave reflector as described in any one of Items 1 to 3, wherein the perimeter of the second surrounding portion is a length less than the wavelength of the radio wave.

Item 5. The radio wave reflector as described in any one of Items 1 to 4, wherein the distance between the centers of gravity of adjacent second regions is at least 0.015 times the wavelength of the radio wave.

Item 6. The radio wave reflector as described in any one of Items 1 to 5, wherein the second region is filled with a dielectric having a relative dielectric constant of 1.5 or more.

Item 7. The radio wave reflector as described in any one of Items 1 to 6, further comprising: a protective layer that protects the conductive layer; and a bonding layer that is disposed between the conductive layer and the protective layer to bond the conductive layer to the protective layer.

Item 8. The radio wave reflector as described in any one of Items 1 to 7, wherein the first conductive portion and the second conductive portion are formed on the same plane.

Item 9. The radio wave reflector as described in any one of Items 1 to 8, wherein the first conductive portion and the second conductive portion are formed at different positions in a direction orthogonal to the conductive layer.

Item 10. The radio wave reflector as described in any one of Items 1 to 9, wherein the line width of at least one of the first surrounding portion and the second surrounding portion is not less than 0.3 μm and not more than 10 μm.

Item 11. The radio wave reflector as described in any one of Items 1 to 10, wherein the thickness of the line of at least one of the first surrounding portion and the second surrounding portion is not less than 0.02 μm and not more than 10 μm. [Effects of the Invention]

The radio wave reflector of the present invention has the advantage of being able to improve the diffusivity when reflecting radio waves.

<Implementation> Hereinafter, the implementation of the present invention will be described with reference to the drawings. As shown in FIG1 , the radio wave reflector 11 of the present embodiment is a sheet-like member capable of reflecting radio waves. The radio wave reflector 11 is configured, for example, to reflect radio waves output from the radio wave generating unit 20. The radio waves reflected by the radio wave reflector 11 are received by the receiving unit 21. As shown in FIG3 , the radio wave reflector 11 is sequentially laminated with a conductive layer 16 including a conductor 12, a bonding layer 14, and a protective layer 15.

The "sheet" mentioned in this specification refers to a shape in which the thickness of the object is less than 10% of the maximum length between the outer edges when viewed from above. When the shape when viewed from above is a rectangle, the "maximum length between the outer edges when viewed from above" means the length of the diagonal. When the shape when viewed from above is a circle, the "maximum length between the outer edges when viewed from above" means the length of the diameter. In this specification, films, foils, thin films, etc. are also included in the "sheet".

The radio wave generator 20 is a device that outputs radio waves. The radio wave generator 20 of this embodiment is a communication device having a transmission antenna, and the transmission antenna can output a wireless signal using radio waves as a medium. Examples of the radio wave generator 20 include: a fixed base station, a mobile phone base station, a radio wave transmitter, a wireless terminal, etc.

The receiving unit 21 is a device capable of receiving radio waves. The receiving unit 21 of this embodiment is a communication device having a receiving antenna. Examples of the receiving unit 21 include: a smart phone, a mobile phone, a tablet terminal, a notebook PC, a portable game console, a repeater, a radio, a television, and the like.

The radio wave reflector 11 of the present embodiment can reflect radio waves, for example, the frequency of the incident wave is in any range of 3 GHz to 5 GHz, 25 GHz to 30 GHz, and 100 GHz to 300 GHz. The "radio wave that can be reflected" mentioned here means having at least one of the following radio waves, the intensity of the outgoing wave of regular reflection (sometimes referred to as "regular reflection intensity") is -30 dB to 0 dB relative to the intensity of any incident wave with an incident angle of 15 degrees to 75 degrees. It is preferred that the regular reflection intensity is -30 dB to 0 dB regardless of which incident wave with an incident angle of 15 degrees to 75 degrees.

More specifically, it is preferred that the regular reflection intensity be -30 dB or more and 0 dB or less with respect to the incident wave at a frequency of 28.5 GHz, and it is more preferred that the regular reflection intensity be -30 dB or more and 0 dB or less with respect to the incident wave in the entire frequency band from 20 GHz to 60 GHz, and it is further preferred that the regular reflection intensity be -30 dB or more and 0 dB or less with respect to the incident wave in the entire frequency band from 3 GHz to 300 GHz.

The regular reflection intensity is preferably smaller than the attenuation of the incident wave. The regular reflection intensity relative to the incident wave is preferably greater than -25 dB and less than 0 dB, more preferably greater than -22 dB and less than 0 dB, further preferably greater than -20 dB and less than 0 dB, and further preferably greater than -15 dB and less than 0 dB.

By making the regular reflection intensity relative to the incident wave greater than -30 dB, the radio wave reflector 11 can reflect radio waves while maintaining the reflection intensity. As a result, the receiving unit 21 can receive radio waves with a practical intensity. The "reflection intensity" and "regular reflection intensity" in this specification refer to the intensity when the distance between the reflection point 11a and the measurement point is 1 m. In addition, the regular reflection intensity is measured in a flat state without bending or folding the radio wave reflector 11.

As shown in FIG. 2 , the radio wave reflector 11 of the present embodiment is a quadrilateral (including a square) in a top view. The length L10 of one side of the radio wave reflector 11 is preferably 20 cm or more, more preferably 100 cm or more, and further preferably 200 cm or more. On the other hand, the upper limit of the length L10 of one side of the radio wave reflector 11 is not particularly limited, and is, for example, 400 cm or less. If the length L10 of one side is 20 cm or more, it is easy to reflect radio waves with sufficient intensity.

The shape of the radio wave reflector 11 is not limited to a quadrilateral, and may be a geometric shape such as a triangle, a pentagon, a hexagon, a circle, an ellipse, or a non-geometric shape. In the radio wave reflector 11, the maximum value of the distance between the ends is preferably 20 cm to 400 cm. The "maximum value of the distance between the ends" refers to the size of the diagonal when the radio wave reflector 11 is a rectangle, the size of the diameter when the radio wave reflector 11 is a circle, and the length of the major axis when the radio wave reflector 11 is an ellipse.

The thickness L1 (FIG. 3) of the radio wave reflector 11 is preferably 0.01 mm or more, more preferably 0.05 mm or more, and further preferably 0.2 mm or more. On the other hand, the upper limit of the thickness L1 of the radio wave reflector 11 is preferably 0.5 mm or less, and more preferably 0.4 mm or less. By making the thickness L1 of the radio wave reflector 11 0.01 mm or more, it is possible to maintain strength while having flexibility. By making the thickness L1 of the radio wave reflector 11 0.5 mm or less, when the radio wave reflector 11 is bent, it is not easy to bend, and as a result, stress concentration is not easy to occur in the conductor 12. The "bending" mentioned here means bending accompanied by plastic deformation in any layer of the radio wave reflector 11.

When the radio wave reflector 11 is subjected to a pencil hardness test, the pencil hardness when the surface load on the protective layer 15 is 500 g is preferably "F" or higher, more preferably "H" or higher, and further preferably "4H" or higher. The "pencil hardness test" described in this specification is a test based on JIS K 5600-5-4 (1999). In addition, "surface load of 500 g" means that if the load applied to the surface during the pencil hardness test is 500 g ± 10 g, it is included therein.

In addition, the radio wave reflector 11 preferably has a decrease rate of adhesion of the protective layer 15 to the adhered layer after the heat and moisture resistance test of 50% or less, more preferably 45% or less, and further preferably 40% or less. The "adhered layer" described in this specification means a layer that directly contacts the target layer. In this embodiment, the adhered layer of the protective layer 15 is the adhesive layer 14. The adhesion is measured by the tensile adhesion strength test according to JIS K 6849 (1994).

The heat and humidity resistance test is a test as follows: the radio wave reflector 11 is placed in a constant temperature and humidity tank adjusted to a temperature of 60°C and a humidity of 95% rh (relative humidity) and left there for 500 hours. The radio wave reflector 11 is then taken out of the constant temperature and humidity tank and left there at room temperature for 4 hours to check changes in properties.

The difference between the intensity of the reflected wave of the radio wave reflector 11 after the heat and humidity resistance test and the intensity of the reflected wave of the radio wave reflector 11 before the heat and humidity resistance test is preferably within 3 dB. At this time, the incident angle θ1 of the incident wave preferably satisfies the above conditions at least at one angle of 15 degrees to 75 degrees, and more preferably satisfies the above conditions at all angles in the angle range of 15 degrees to 75 degrees. At this time, the frequency of the incident wave is preferably 3 GHz to 300 GHz.

In addition, the surface resistivity of the radio wave reflector 11 after the heat and humidity resistance test is preferably 100 Ω/□ or less, more preferably 50 Ω/□ or less, and further preferably 20 Ω/□ or less. By making the surface resistivity after the heat and humidity resistance test 100 Ω/□ or less, the radio wave reflector 11 can be placed in a high temperature and high humidity environment for a long time without damaging the reflection strength, and can maintain the radio wave reflector 11 with practicality.

In addition, the surface resistivity of the radio wave reflector 11 before the heat and moisture resistance test is preferably 0.003 Ω/□ or more and 10 Ω/□ or less, more preferably 0.01 Ω/□ or more and 9 Ω/□ or less, and further preferably 0.02 Ω/□ or more and 8 Ω/□ or less. Furthermore, the surface resistivity in this specification refers to the value measured when the radio wave reflector 11 is placed on a mounting surface composed of a flat surface unless otherwise specified. In this specification, the surface resistivity is measured in accordance with JIS K 6911.

The change rate of the surface resistivity of the radio wave reflector 11 after the heat and humidity test relative to that before the heat and humidity test is preferably 20% or less, more preferably 17% or less, and further preferably 15% or less. When the surface resistivity before the heat and humidity test is set as R1 and the surface resistivity after the heat and humidity test is set as r2, the change rate r can be obtained by r = (R1-r2)/R1×100.

In addition, regarding the radio wave reflector 11, the change rate of the surface resistivity before and after the radio wave reflector 11 is bent along the surface of the member having a curvature radius of 200 mm (also referred to as "the change rate of the surface resistivity when bent") R can be not less than -10% and not more than 10%. The change rate of the surface resistivity when bent R means the ratio of the change in the surface resistivity R2 when the radio wave reflector 11 is bent along the surface of the member having a curvature radius of 200 mm relative to the surface resistivity _R1 of the radio wave reflector 11 when the radio wave reflector ₁₁ is flat. It is obtained from the change rate of the surface resistivity R = ( _R2 - _R1 ) / _R1 × 100.

The reflection intensity of radio waves varies according to the surface resistivity. However, since the change rate R of the surface resistivity when the radio wave reflector 11 is bent is between -10% and 10%, even when the radio wave reflector 11 is bent, sufficient reflection intensity of radio waves can be achieved as in the flat state.

In this specification, surface resistivity means the surface resistance per 1 ^cm2 . The surface resistivity can be measured by the four-terminal method in accordance with JIS K 6911 by bringing the measuring terminal into contact with the surface of the conductive film layer. In addition, when the conductive film layer is not exposed due to protection by a resin sheet or the like, it can be measured by the eddy current method using a non-contact resistance meter (manufactured by Napson Co., Ltd., trade name: EC-80P or its equivalent).

The radio wave reflector 11 is preferably transparent as a whole. That is, the radio wave reflector 11 is preferably transparent. The conductive layer 16, the bonding layer 14 and the protective layer 15 can be formed of a material having visible light transparency and/or a thickness having visible light transparency. "Transparent" here means that an object located on one side of the radio wave reflector 11 can be seen from the other side, and the total light transmittance may not be 100%. "Transparent" includes semi-transparency. In addition, the radio wave reflector 11 can be colored.

The radio wave reflector 11 preferably has a total light transmittance of 70% or more, more preferably 75% or more, and even more preferably 80% or more. In this specification, "total light transmittance" means the transmittance of light from a D65 standard light source. The total light transmittance is measured in accordance with JIS K 7375 (2008).

The bending modulus of the radio wave reflector 11 is preferably not less than 0.05 GPa and not more than 4 GPa. By making the bending modulus within the above range, the radio wave reflector 11 has flexibility, and the radio wave reflector 11 can be bent and attached to a curved surface or a spherical surface without bending or breaking the radio wave reflector 11. The bending modulus is measured in accordance with JIS K7171. In this specification, "flexibility" means the property of being able to bend without breaking or plastic deformation even when a bending force is applied at normal temperature and pressure.

The radio wave reflector 11 preferably has a longitudinal elastic modulus of 0.01 GPa or more and 80 GPa or less. By making the longitudinal elastic modulus within the above range, the radio wave reflector 11 can be easily deformed, and the radio wave reflector 11 can be bent without breaking, so that it can be attached to a curved surface with a curvature radius of 200 mm or more. The longitudinal elastic modulus is measured in accordance with JIS K7127-1999.

The radio wave reflector 11 of this embodiment has at least the flexibility to be attached to a curved surface with a curvature radius of 200 mm or more, and preferably has the flexibility to be attached to a curved surface with a curvature radius of 100 mm or more.

The radio wave reflector 11 may have plasticity. Plasticity means the property that it can be deformed by applying external pressure, and when the deformation exceeds the elastic limit by applying pressure, the deformed shape is maintained even if the force is removed. The conductive layer 16, the bonding layer 14 and the protective layer 15 may all have plasticity, or at least one of the conductive layer 16, the bonding layer 14 and the protective layer 15 may have plasticity.

As shown in FIG1 , the radio wave reflector 11 is preferably such that when the receiving angle position of the reflected wave changes within the angle range α of more than -15 degrees and less than +15 degrees relative to the reflected wave A2 of the regular reflection in the virtual plane including the incident wave A1 and the reflected wave, the kurtosis of the distribution of the intensity of the reflected wave at each receiving angle position becomes less than -0.4. The kurtosis is more preferably less than -1.0, further preferably less than -1.1, and further preferably less than -1.2. The lower limit of the kurtosis is not particularly limited, for example, it is greater than -0.5. On the virtual plane, there are the reflection point 11a on the reflection surface of the radio wave reflector 11, the radio wave generation source 20, and the receiving part 21 of the reflected wave. The kurtosis is measured in a state where the radio wave reflector 11 is made into a planar state.

Kurtosis is a statistic that indicates the degree to which a distribution deviates from a normal distribution. It indicates the sharpness of the peak and the spread of the tail. As shown in FIG1 , the radio wave output from the radio wave generating source 20 is incident on the radio wave reflector 11 at an incident angle θ1 and is regularly reflected at an output angle θ2. The receiving angle position i of the receiving unit 21 is moved within an angle range α of -15 degrees to +15 degrees at regular angles (for example, every 5 degrees) with respect to the reflected wave A2 of the regular reflection of the radio wave, with the reflection point 11a as the center. The reflection intensity x is measured. The receiving angle position i of the receiving unit 21 is located on an arc centered on the reflection point 11a. The average value of the reflection intensity x _i (i: 1, 2, ..., n) at each receiving angle position i is set to , when the standard deviation is set to s, the kurtosis can be calculated according to the following formula.

When the kurtosis is a negative value, it indicates that the intensity data at each angle position is flatter than the normal distribution, that is, the data is dispersed near the average value and the tail of the distribution is expanded. The smaller the kurtosis value, the flatter the distribution. In this embodiment, by setting the kurtosis to less than -0.4, the difference in reflection intensity corresponding to the receiving angle position becomes smaller within the angle range α of ±15 degrees relative to the reflected wave of the regular reflection.

The radio wave reflector 11 preferably has a yellowing degree (the difference between the yellowing index after the heat and moisture resistance test and the yellowing index before the heat and moisture resistance test) of 3 or less. The yellowing index is also called yellowness, which means the degree to which the hue shifts from colorless or white to yellow. The yellowing index can be obtained by the method according to JIS K 7373.

The following will describe each layer of the radio wave reflector 11 in more detail. In the following description, the direction in which multiple layers are stacked is defined as the "up-down direction". In addition, when observing the radio wave reflector 11 along the up-down direction, two directions orthogonal to each other are defined as the "longitudinal direction" and the "lateral direction". However, the definition of these directions is only for explanation and is not a specific use. In addition, each figure is only a schematic diagram and does not represent a strict reduction scale.

(Conductive layer 16) The conductive layer 16 is a layer having a conductor 12. The conductive layer 16 includes a substrate 13 and a conductor 12 for reflecting radio waves.

(Substrate 13) The substrate 13 supports the conductor 12. In the present embodiment, the substrate 13 has a quadrilateral shape (more specifically, a square shape) when viewed from above. The thickness of the substrate 13 is uniform over the entire surface. However, the thickness of the substrate 13 may be non-uniform, and may be formed into a three-dimensional shape. Examples of the three-dimensional shape include a wedge shape, a shape having a partially spherical surface, and a shape having a concave-convex shape.

As the substrate 13, for example, synthetic resin, FRP (Fiber Reinforced Plastics), carbon, glass, etc. can be listed. As the synthetic resin, for example, one or more of the group consisting of PET (polyethylene terephthalate), polyethylene, polypropylene, polyvinyl chloride, polystyrene, polymethyl methacrylate, polyester, polyoxymethylene, polyamide, polyphenylene ether, vinylidene chloride, polyvinyl acetate, polyvinyl acetal, AS resin, ABS resin, acrylic resin, fluororesin, nylon resin, polyacetal resin, polycarbonate resin, polyamide resin, and polyurethane resin can be listed. As the substrate, it can also be a composite material of these synthetic resins. The substrate 13 of the present embodiment is composed of a PET sheet.

The thickness L2 of the substrate 13 is preferably 5 μm or more, more preferably 10 μm or more, and further preferably 20 μm or more. On the other hand, the upper limit of the thickness L2 of the substrate 13 is preferably 500 μm or less, more preferably 130 μm or less, and further preferably 100 μm or less.

The substrate 13 is preferably flexible. The longitudinal elastic modulus of the substrate 13 is preferably 0.01 GPa or more, more preferably 1 GPa or more, and further preferably 8 GPa or more. On the other hand, the upper limit of the longitudinal elastic modulus of the substrate 13 is preferably 80 GPa or less, more preferably 30 GPa or less, and further preferably 20 GPa or less.

(Conductor 12) The conductor 12 is a conductor that reflects radio waves. The conductor 12 is formed on the upper surface of the substrate 13. As methods for forming the conductor 12 on the upper surface of the substrate 13, for example, there can be listed: a method of laminating a thin film volume in which the conductor 12 is embedded in a thin film dielectric on the substrate 13; a method of forming a pattern of the conductor 12 on the substrate 13 without using a dielectric. The method of forming the conductor 12 on the upper surface of the substrate 13 will be described in detail below.

The dielectric used here preferably has a relative dielectric constant of 1.5 or more, more preferably 2.5 or more, and further preferably 3 or more. Examples of dielectrics include acrylic resin, PET (polyethylene terephthalate), and a mixture of acrylic acid and air. If the relative dielectric constant is 1.5 or more, the wavelength of the electromagnetic wave in the dielectric is shorter than the wavelength of the electromagnetic wave outside the dielectric, thereby increasing the reflection intensity.

The conductor 12 is made of a conductor. Examples of the conductor 12 include one or more of silver, gold, copper, platinum, aluminum, titanium, polysilicon, indium tin oxide, and alloys (e.g., alloys containing nickel, chromium, and molybdenum). Examples of alloys containing nickel, chromium, and molybdenum include various grades of Herschel alloys B-2, B-3, C-4, C-2000, C-22, C-276, G-30, N, W, and X.

The thickness L3 of the conductor 12 is preferably 20 nm or more, more preferably 30 nm or more, and further preferably 100 nm or more. On the other hand, the upper limit of the thickness L3 of the conductor 12 is preferably 10 μm or less, more preferably 5 μm or less, and further preferably 4 μm or less. If the thickness L3 of the conductor 12 is 20 nm or more, appropriate radio wave intensity can be ensured.

As shown in FIG. 4 (A), the conductor 12 includes a first conductive portion 4 (indicated by a thin line) and a second conductive portion 5 (indicated by a thick solid line). In the conductor 12 of this embodiment, the first conductive portion 4 and the second conductive portion 5 are formed on the same plane. However, as described in the following variation, the first conductive portion 4 and the second conductive portion 5 may be formed at different positions in a direction orthogonal to the conductive layer 16.

Here, a schematic diagram of the conductor 12 for illustrating the present embodiment is shown in FIG4(B). FIG4(B) shows a schematic enlarged diagram of the B portion of FIG4(A). The first conductive portion 4 has a plurality of first surrounding portions 41. As shown in FIG4(B), the first conductive portion 4 is formed by repeatedly forming a plurality of first surrounding portions 41 at a certain interval. Each first surrounding portion 41 surrounds a first region R1 which is a region where the conductor 12 is not formed. The first surrounding portion 41 is composed of a linear conductor. The line width L6 of the first surrounding portion 41 is preferably not less than 0.3 μm and not more than 10 μm, more preferably not less than 0.3 μm and not more than 5 μm, and further preferably not less than 0.4 μm and not more than 1 μm.

The first surrounding portion 41 of the present embodiment is formed as a quadrilateral (more specifically, a square) formed by two parallel first linear bodies 411 and two parallel second linear bodies 412. The first linear body 411 and the second linear body 412 are orthogonal to each other. The first surrounding portion 41 is continuous in the circumferential direction and is not disconnected in the entire circumferential direction. That is, both ends of the two first linear bodies 411 are respectively connected to the adjacent second linear body 412.

In this embodiment, the linear bodies 411 and 412 between adjacent first regions R1 are mutually shared in the adjacent first regions R1. That is, a portion of the first enclosing portion 41 surrounding one first region R1 constitutes a portion of the first enclosing portion 41 surrounding another adjacent first region R1. In this way, in the first conductive portion 4 of this embodiment, a plurality of first enclosing portions 41 are repeatedly formed at a certain interval in the longitudinal direction and the transverse direction, and have a lattice pattern.

The perimeter of the first surrounding portion 41 is preferably less than the wavelength of the target radio wave. However, when the conductor 12 is embedded in a thin film dielectric (i.e., when the first surrounding portion 41 is filled with a dielectric), the perimeter of the first surrounding portion 41 is more preferably less than 5/6 times the wavelength of the target radio wave.

For example, when the circumference of the first enclosure 41 is a length less than the wavelength of the target radio wave, the circumference of the first enclosure 41 can be illustrated as follows. When the incident wave with a frequency in the range of 3 GHz to 5 GHz is the target, the circumference of the first enclosure 41 is preferably 1 cm to 10 cm, more preferably 2 cm to 9 cm, and further preferably 4 cm to 8 cm. Furthermore, when the incident wave with a frequency in the range of 25 GHz to 30 GHz is the target, the circumference of the first enclosure 41 is preferably 1 mm to 12 mm, more preferably 2 mm to 10 mm, and further preferably 5 mm to 8 mm. Furthermore, when the incident wave with a frequency in the range of 100 GHz to 300 GHz is targeted, the circumference of the first surrounding portion 41 is preferably 0.25 mm to 3 mm, more preferably 0.5 mm to 2 mm, and further preferably 0.75 mm to 1 mm.

The second conductive portion 5 has a plurality of second surrounding portions 51. The second surrounding portion 51 surrounds the second region R2 which is a region where the conductor 12 is not formed. The second surrounding portion 51 is formed of a linear conductor. The line width L8 of the second surrounding portion 51 is preferably not less than 0.3 μm and not more than 10 μm, more preferably not less than 0.3 μm and not more than 5 μm, and further preferably not less than 0.4 μm and not more than 1 μm. Furthermore, in FIG. 4 (A) (B), the line width of the second surrounding portion 51 is depicted as being thicker than the line width of the first surrounding portion 41, which is only shown for the sake of convenience of explanation, and is actually formed to have the same width. However, the line width L8 of the second surrounding portion 51 may also be formed to have a width different from the line width L6 of the first surrounding portion 41.

The second enclosing portion 51 may be the same shape and size as the first enclosing portion 41, or may be a different shape or a different size. The second enclosing portion 51 of the present embodiment is formed in the same shape and size as the first enclosing portion 41. The second enclosing portion 51 is formed as a quadrilateral (more specifically, a square) formed by two parallel third linear bodies 511 and two parallel fourth linear bodies 512. The third linear bodies 511 and the fourth linear bodies 512 are orthogonal to each other. The second enclosing portion 51 is continuous in the circumferential direction and is not disconnected in the entire circumferential direction. That is, the two ends of the two third linear bodies 511 are respectively connected to the adjacent fourth linear bodies 512.

The second region R2 surrounded by the second enclosing portion 51 overlaps a portion of the first regions R1 of the adjacent plurality of first enclosing portions 41. That is, the second region R2 spans across the adjacent plurality of first regions R1. In the present embodiment, the second region R2 overlaps with a combination of three first regions R1 adjacent to one first region R1 in the transverse, longitudinal and oblique directions, a total of four first regions R1 (hereinafter sometimes referred to as "four adjacent first regions R1"). The center of gravity of the second region R2 is arranged at a position overlapping with the vertices of the four adjacent first regions R1. Furthermore, the center of gravity of the second region R2 may not be arranged at a position overlapping with the vertices of the four adjacent first regions R1.

The first enclosing portion 41 and the second enclosing portion 51 do not have a common part when projected onto a virtual projection plane parallel to the conductive layer 16. The "not having a common part" in this specification means that the line surrounding the first region R1, the line with width (i.e., the surface), etc. constitute a part of the line, surface, etc. surrounding the second region R2. In this embodiment, when the first enclosing portion 41 and the second enclosing portion 51 are projected onto a virtual projection plane parallel to the conductive layer 16, the linear bodies contained in the first enclosing portion 41 are not linear bodies that are in contact with and parallel to all the linear bodies contained in the second enclosing portion 51. Therefore, when the first surrounding portion 41 and the second surrounding portion 51 are projected onto a virtual projection plane parallel to the conductive layer 16, a situation where a linear body of the first surrounding portion 41 crosses a linear body of the second surrounding portion 51 is included in “having no common portion with each other”.

The second enclosing portion 51 intersects with the first enclosing portion 41 at a plurality of locations (two locations in this example). In this embodiment, the second enclosing portion 51 and the first enclosing portion 41 are electrically connected at the intersection of the second enclosing portion 51 and the first enclosing portion 41, but when the first conductive portion 4 and the second conductive portion 5 are located at different heights, they may not be electrically connected to each other.

When the first conductive portion 4 and the second conductive portion 5 are located at different heights, the minimum distance between the first conductive portion 4 and the second conductive portion 5 is preferably 0.05 μm to 200 μm, more preferably 1 μm to 20 μm, and further preferably 5 μm to 13 μm.

The circumference of the second surrounding portion 51 is preferably less than the wavelength of the target radio wave. However, when the conductor 12 is embedded in a thin film dielectric (i.e., when the second surrounding portion is filled with a dielectric), the circumference of the second surrounding portion 51 is preferably less than 5/6 times the wavelength of the target radio wave.

The distance L9 between the centers of gravity of the adjacent second enclosures 51 is preferably 0.015 times or more of the wavelength of the target radio wave. When the second enclosure 51 is filled with a dielectric, the distance L9 between the centers of gravity is preferably 0.015 times or more of the wavelength of the target radio wave, and when the second enclosure 51 is filled with a dielectric, the distance L9 between the centers of gravity is more preferably 0.019 times or more.

For example, when the distance L9 between the centers of gravity is 0.015 times or more of the wavelength of the target radio wave, the distance L9 between the centers of gravity can be illustrated as follows. When the incident wave with a frequency in the range of 3 GHz to 5 GHz is the target, the distance L9 between the centers of gravity is preferably 0.15 cm to 10 cm, more preferably 0.2 cm to 8 cm, and further preferably 0.3 cm to 5 cm. Furthermore, when the incident wave with a frequency in the range of 25 GHz to 30 GHz is the target, the distance L9 between the centers of gravity is preferably 0.18 mm to 12 mm, more preferably 0.27 mm to 10 mm, and further preferably 0.36 mm to 8 mm. Furthermore, when an incident wave with a frequency in the range of 100 GHz to 300 GHz is targeted, the distance L9 between the centers of gravity is preferably 0.045 mm to 3 mm, more preferably 0.09 mm to 2 mm, and further preferably 0.15 mm to 1 mm.

The adjacent second surrounding parts 51 may be in contact with each other or separated from each other. In this embodiment, the adjacent second surrounding parts 51 are separated from each other.

The maximum length L7 between the edges in the first region R1 is set to be greater than the wavelength of visible light and less than the wavelength of the radio wave reflected by the radio wave reflector 11. The maximum length of the edge of the first region R1 is preferably set to be greater than 2 μm and less than 10 cm, more preferably greater than 20 μm and less than 1 cm, further preferably greater than 25 μm and less than 1 mm, further preferably greater than 30 μm and less than 250 μm. In this way, the maximum length L7 can be greater than the wavelength of visible light and less than the wavelength of the radio wave reflected by the radio wave reflector 11.

The thickness of the substrate 13 dominates the thickness (L2+L3) of the conductive layer 16. The thickness (L2+L3) of the conductive layer 16 is preferably 5.02 μm or more, more preferably 10 μm or more, and further preferably 20 μm or more. On the other hand, the upper limit of the thickness (L2+L3) of the conductive layer is preferably 500.3 μm or less, more preferably 130 μm or less, and further preferably 100 μm or less.

The surface roughness Sa of the conductor 12 is not particularly limited, but is preferably 1 μm to 7 μm, and more preferably 1.03 μm to 6.72 μm. If the surface roughness Sa is within this range, radio waves can be easily diffusely reflected.

The surface roughness Sa is obtained by using the arithmetic mean height of ISO 25178 and is measured in accordance with ISO 25178. The surface roughness Sa of the conductor 12 can be obtained by measuring the surface roughness at a plurality of locations on the surface of the conductor 12 using a laser microscope (product name VK-X1000/1050, manufactured by KEYENCE, or its equivalent) and calculating the average value of the obtained measured values.

By setting the conductor to a shape composed of the first conductive part 4 and the second conductive part 5, the diffusion of radio waves can be improved. One of the reasons is that by combining the first conductive part 4 and the second conductive part 5, a portion with a relatively small opening area (first opening A1) and a portion larger than the first opening (second opening A2) are formed as shown in FIG4 (C). The reason is that the reflection angle of the radio wave reflected to the conductor 12 forming the first opening A1 and the radio wave reflected to the conductor 12 forming the second opening A2 is slightly different, so the reflection of the reflection surface is slightly uneven, and the portion with a stronger regular reflection intensity is expanded. It is believed that the diffusion of radio waves is improved by this.

The "radio wave diffusivity" described in this manual means that the difference between the regular reflection intensity and the radio wave intensity around the regular reflection falls within a certain range. The radio wave intensity around the regular reflection includes, for example, the radio wave intensity at a position of ±15° when the regular reflection is set to 0°. When the absolute value of the difference between the regular reflection intensity and the radio wave intensity around the regular reflection is small, it can be evaluated that the radio wave diffusivity is high. The "certain range" mentioned here is preferably 5 dB, more preferably 4.5 dB, and even more preferably 4 dB.

(Method for Forming Conductor 12) Next, a method for forming conductor 12 will be described. The method described below is merely an example for explaining the method for forming conductor 12.

(1) Method for forming a pattern of the conductor 12 on the substrate 13 As shown in FIG5(A), a photoresist 61 is applied on the substrate 13. Then, the photoresist 61 is covered with a mask (not shown) having a pattern of the conductor 12 formed thereon, and is exposed by irradiating ultraviolet rays (FIG5(B)), and the photosensitive portion 62 is removed by a developer.

Next, as shown in FIG5(C), metal 63 is partially evaporated after removing the photoresist 61, and as shown in FIG5(D), the photoresist 61 is removed to form a pattern of the conductor 12 on the substrate 13. In this case, the mask is preferably formed with a pattern composed of the first conductive portion 4 and the second conductive portion 5.

Furthermore, here, although the positive photolithography method is used as an example for explanation, the negative photolithography method may also be used.

(2) Method of Laminating a Thin Film on the Substrate 13 As a method different from the method of directly forming the conductive body 12 including the first conductive portion 4 and the second conductive portion 5 on the substrate 13, there can be cited a method of laminating a thin film on the substrate 13. The thin film can be formed, for example, by the method shown in Figs. 6(A) to (E).

First, as shown in FIG6(A), a mold 7 is prepared in which a pattern corresponding to the first conductive portion 4 is formed in the form of protrusions 71. In this embodiment, the protrusions 71 are formed in a grid shape in a plan view. Then, the substrate 13 is arranged so as to face the mold 7.

Next, as shown in FIG6(B), a dielectric 8 is filled between the mold 7 and the substrate 13. The dielectric 8 is preferably a photocurable resin. Then, the filled dielectric 8 is cured, and the mold 7 is removed from the dielectric 8 (FIG6(C)).

Next, as shown in FIG. 6(D) , the dielectric 8 is electrolessly plated, and the formed recess 81 is filled with the metal 63 .

Then, regarding the second conductive portion 5, a mold having a pattern corresponding to the second conductive portion 5 formed in the form of a convex portion is used to perform the sequence of FIG. 6 (A) to (D) to form the second conductive portion 5. Then, the second conductive portion 5 is peeled off from the substrate 13. The thin film body including the second conductive portion 5 peeled off from the substrate 13 is superimposed on one surface of the first conductive portion 4 produced in FIG. 6 (D), thereby forming a conductive layer 16 having the first conductive portion 4 and the second conductive portion 5.

Furthermore, here, the thin film body including the second conductive part 5 is overlapped on the first conductive part, for example, the thin film body including the second conductive part may be overlapped on the substrate 13 of the first conductive part 4. That is, the first conductive part 4 and the second conductive part 5 may be located on both sides with the substrate 13 interposed therebetween. In short, as long as the pattern of the conductive body 12 including the first conductive part 4 and the second conductive part 5 can be formed when projected onto a projection plane parallel to the conductive layer 16.

(Variations of the Pattern of the Conductor 12) The pattern of the conductor 12 is not limited to the lattice pattern of the embodiment, and may be, for example, the pattern shown in FIGS. 7(A) to (E).

In a variation, the conductor 12 may be a pattern as shown in FIG. 7 (A). The first conductive portion 4 is formed in a brick-like shape, and the second conductive portion 5 is formed in a triangle or an inverted triangle. In the first conductive portion 4, a plurality of first surrounding portions 41 are arranged in a straight line in the horizontal direction. In addition, in the first conductive portion 4, adjacent first surrounding portions 41 are staggered in the vertical direction. That is, a plurality of first surrounding portions 41 are repeatedly formed at a certain interval in the vertical direction and the horizontal direction (i.e., in the direction orthogonal to each side).

The second surrounding portion 51 includes a triangular second surrounding portion 51a and an inverted triangular second surrounding portion 51b. The second region R2 spans over three adjacent first regions R1.

In a variation, the conductor 12 may be a pattern as shown in FIG. 7 (B). The first enclosing portion 41 of the first conductive portion 4 is formed into a triangle, and the second enclosing portion 51 of the second conductive portion 5 is formed into a circle. In this variation, the first enclosing portion 41 has a first enclosing portion 41a in the shape of a triangle and a first enclosing portion 41b in the shape of an inverted triangle. The first enclosing portion 41a and the first enclosing portion 41b are alternately arranged in a direction perpendicular to each side. In this way, the first conductive portion 4 may have a mixture of first enclosing portions 41a and 41b of different shapes. However, the first enclosing portions 41 having the same shape are repeatedly formed at a certain interval in a direction perpendicular to each side.

The second conductive portion 5 has a plurality of circular second surrounding portions 51. Each second surrounding portion 51 surrounds the second region R2. The second region R2 extends over a portion of the six adjacent first regions R1.

Furthermore, the first surrounding portion 41 is an equilateral triangle, for example, it may also be an isosceles triangle or a triangle with three sides of different lengths.

In a variation, the conductor 12 may be in a pattern as shown in Fig. 7(C). The first surrounding portion 41 of the first conductive portion 4 is formed in a regular hexagon. In the first conductive portion 4, a plurality of first surrounding portions 41 are repeatedly formed at a certain interval in a direction perpendicular to each side.

The second conductive portion 5 has a plurality of second surrounding portions 51. The second surrounding portion 51 is formed in a hexagonal shape, which is the same shape as the first surrounding portion 41. However, the plurality of second surrounding portions 51 are formed in a shape obtained by rotating the first conductive portion 4 by 90° with the centroid of a certain first surrounding portion 41 as the center. Such a second region R2 also spans over the plurality of adjacent first regions R1.

In a variation, the conductor 12 may be a pattern as shown in FIG. 7 (D). In this variation, the first enclosing portion 41 includes a circular first enclosing portion 41a and substantially triangular first enclosing portions 41b and 41c whose sides are formed by arcs. Each of the first enclosing portions 41a, 41b, and 41c surrounds the first region R1. In the first conductive portion 4, each of the plurality of first enclosing portions 41a, 41b, and 41c is repeatedly formed at a certain interval in the longitudinal and transverse directions.

The second conductive portion 5 has a plurality of second surrounding portions 51. In this variation, the second surrounding portion 51 has a circular first surrounding portion 51a and substantially triangular second surrounding portions 51b and 51c whose sides are formed by arcs. The second conductive portion 5 is formed into a shape obtained by rotating the first conductive portion 4 by 90° with the centroid of one first surrounding portion 41 as the center. Such a second region R2 also spans over a plurality of adjacent first regions R1.

In a variation, the conductor 12 may be a pattern as shown in FIG. 7 (E). In this variation, the first conductive portion 4 is formed in a lattice shape, and the second conductive portion 5 is formed in a circular shape. In the first conductive portion 4, a plurality of first surrounding portions 41 are arranged in the longitudinal and transverse directions. The plurality of first surrounding portions 41 are repeatedly formed at a certain interval in the longitudinal and transverse directions.

The second conductive portion 5 has a plurality of circular second enclosing portions 51. Each second enclosing portion 51 encloses a second region R2. The second region R2 spans a portion of the four adjacent first regions R1. The centers of the plurality of second enclosing portions 51 are all located at the corners of the first enclosing portion 41 (the intersection of the grids of the first conductive portion 4). The adjacent second enclosing portions 51 have a contact point, but do not have a common portion with each other.

In the variation examples of FIG. 7 (B), FIG. 7 (D) and FIG. 7 (E), at least one of the first surrounding portion 41 and the second surrounding portion 51 is circular. If at least one of the first surrounding portion 41 and the second surrounding portion 51 is circular, the effect of the incident direction on the reflection intensity of the radio wave reflector 11 in a plan view can be reduced. In other words, in this case, regardless of the direction from which the radio wave is incident on the radio wave reflector 11 in a plan view, the change in diffusivity corresponding to the incident direction can be reduced.

(Adhesive layer 14) The adhesive layer 14 is provided between the conductive layer 16 and the protective layer 15 to connect the conductive layer 16 and the protective layer 15. The adhesive layer 14 is preferably provided over the entire surface between the conductive layer 16 and the protective layer 15, but may be provided only in a portion between the conductive layer 16 and the protective layer 15. Examples of the adhesive layer 14 include synthetic resins, rubber adhesive sheets, and the like. Examples of synthetic resins include acrylic resins, silicone resins, and polyvinyl alcohol resins. The adhesive layer 14 may be formed by filling a fluid adhesive between the conductive layer and the protective layer and curing the adhesive, or an adhesive sheet having an adhesive surface may be disposed between the conductive layer 16 and the protective layer 15 .

The thickness L4 of the bonding layer 14 is preferably 2 μm or more, more preferably 5 μm or more, and further preferably 10 μm or more. The upper limit of the thickness L4 of the bonding layer 14 is preferably 250 μm or less, more preferably 150 μm or less, and further preferably 100 μm or less.

Furthermore, the hydroxyl value of the bonding layer 14 is preferably 5 mgKOH/g or more, more preferably 8 mgKOH/g or more, further preferably 30 mgKOH/g or more, further preferably 90 mgKOH/g or more. On the other hand, the upper limit of the hydroxyl value of the bonding layer 14 is preferably 120 mgKOH/g or less. If the hydroxyl value of the bonding layer 14 is 5 mgKOH/g or more, there is an advantage that the bonding layer 14 is not easy to foam and/or turn white in a high temperature and high humidity environment. In this specification, the hydroxyl value is measured by the test method based on JIS K 1557.

Furthermore, the acid value of the bonding layer 14 is preferably 50 mgKOH/g or less, more preferably 45 mgKOH/g or less, further preferably 30 mgKOH/g or less, further preferably 10 mgKOH/g or less. On the other hand, the lower limit of the acid value of the bonding layer 14 is preferably 0.1 mgKOH/g or more. If the acid value of the bonding layer 14 is 50 mgKOH/g or less, corrosion of the conductor 12 can be prevented, and the stability of radio wave reflectivity over time can be improved. In this specification, the acid value is measured by the test method based on JIS K 2501.

The bonding layer 14 preferably does not contain an ultraviolet absorber. If the bonding layer 14 does not contain an ultraviolet absorber, it is easy to adjust the bonding layer 14 to be colorless and transparent. Here, "does not contain" includes not only the case where the bonding layer 14 does not contain an ultraviolet absorber at all, but also includes the case where the bonding layer 14 contains a small amount to the extent that the colorless and transparent bonding layer is not damaged.

The bonding layer 14 is preferably made of a material having a dielectric loss tangent (tanδ) of 0.018 or less. The lower the dielectric loss tangent, the better. As the lower limit of the dielectric loss tangent, for example, 0.0001 or more can be listed. By using the bonding layer 14 having a dielectric loss tangent of 0.018 or less, the electric energy loss of the radio wave in the radio wave reflector 11 is reduced, and the reflection intensity can be further enhanced.

Furthermore, the synthetic resin material of the next layer 14 is preferably one whose relative dielectric constant changes according to the frequency of the electric field. The relative dielectric constant refers to the ratio of the dielectric constant of the medium (synthetic resin material in this embodiment) to the dielectric constant of a vacuum. By making the relative dielectric constant change according to the electric field, the intensity of the reflected wave in the electric field of a specific frequency can be increased. The relative dielectric constant preferably changes between 1.5 and 7, and more preferably changes between 1.8 and 6.5.

(Protective layer 15) The protective layer 15 covers at least one side of the conductive layer 16 to protect the conductive layer 16. The protective layer 15 of this embodiment has a size corresponding to the base material 13 in a plan view. Examples of the protective layer 15 include a sheet (film) made of a synthetic resin. Examples of the synthetic resin include PET (polyethylene terephthalate), COP (cycloolefin polymer), polyethylene, polypropylene, polyvinyl chloride, polystyrene, polymethyl methacrylate, polyester, polyoxymethylene, polyamide, polyphenylene ether, vinylidene chloride, polyvinyl acetate, polyvinyl acetal, AS resin, ABS resin, acrylic resin, fluororesin, nylon resin, polyacetal resin, polycarbonate resin, polyamide resin, and polyurethane resin.

The thickness L5 of the protective layer 15 is preferably 20 μm or more, more preferably 38 μm or more, and further preferably 50 μm or more. On the other hand, the upper limit of the thickness L5 of the protective layer 15 is preferably 200 μm or less, and more preferably 150 μm or less.

When only the protective layer 15 is subjected to a pencil hardness test, the pencil hardness of the protective layer 15 with a surface load of 500 g is preferably "4B" or higher, more preferably "B" or higher, and further preferably "F" or higher. If the pencil hardness of only the protective layer 15 is "4B" or higher, the conductor 12 can be protected. Furthermore, if the pencil hardness of only the protective layer 15 is "F" or higher, the conductor 12 can be protected more firmly.

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, further preferably 12 g/m ²・24 h or less, further preferably 10 g/m ²・24 h or less. If 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 not easily corroded and the surface resistivity of the conductive layer 16 is not easily increased. The "moisture permeability" described in this specification is measured by the test method based on JIS Z 0208 (1976).

The protective layer 15 is preferably flexible. The longitudinal elastic modulus of the protective layer 15 is preferably 0.01 GPa or more, more preferably 1 GPa or more, and further preferably 8 GPa or more. On the other hand, the upper limit of the longitudinal elastic modulus of the protective layer 15 is preferably 80 GPa or less, more preferably 30 GPa or less, and further preferably 20 GPa or less.

The protective layer 15 may be subjected to an anti-glare treatment or an anti-reflection treatment. For example, when the protective layer 15 is formed of a film, at least one of the upper surface (surface) and the lower surface (the surface opposite to the bonding layer 14) of the film may be subjected to an anti-glare treatment or an anti-reflection treatment.

The anti-glare treatment means a treatment in which a concave-convex shape is formed on at least one surface of the protective layer 15 to scatter light and suppress the reflection of the light source such as lighting into the protective layer 15. Examples of methods for implementing the anti-glare treatment include a method of applying a binder resin in which fine particles are dispersed on the surface of the film, sandblasting, chemical etching, and the like.

The anti-reflection treatment means the following treatment: an anti-reflection film is formed on at least one side of the protective layer 15, and the reflected light reflected from the surface of the anti-reflection film and the reflected light reflected from the interface between the anti-reflection film and the thin film are attenuated by interference, thereby suppressing the reflection of the light source such as the lighting. The anti-reflection film can be a single layer or a film formed by alternately stacking thin films with different refractive indices.

The protective layer 15 may also be formed by attaching an anti-glare or anti-reflection film to one or both sides of a synthetic resin film.

(Usage) The radio wave reflector 11 of the above-mentioned embodiment can be used as, for example, interior paper or decorative material. The inner layer paper is a paper material installed on the inner surface of the interior material. Examples of interior materials include: inner walls, ceilings, partitions, floor materials, etc. Examples of decorative materials include: posters, decorative stickers, stained glass style stickers, etc. Examples of decorative materials include: wall materials, floor materials, doors, lighting covers, door lintels, columns, televisions, table tops, etc. FIG. 8 shows an example in which a poster as decorative material 30A is installed on a wall, and decorative material 30B is installed on a lighting cover.

By installing the decorative materials 30A and 30B including the radio wave reflector 11 on indoor equipment or building materials, the radio waves entering the room from the outside through the window 33 are reflected at the decorative materials 30A and 30B. In this way, the radio waves reach a wider range of the indoor space S, and the convenience of radio wave reception is improved.

Furthermore, the radio wave reflector 11 is not limited to being used as wallpaper, and can also be used as printed paper for printing plywood. In this case, the plywood including the radio wave reflector 11 can be used to form doors, walls, partitions, exterior wall materials, roofs, ceilings, floor panels, baseboards, etc.

Furthermore, the radio wave reflector 11 is not limited to a flat plate, but can also be a spherical surface. For example, FIG8 (B) is a diagram obtained by observing the interior of a room from a top view. The building material 30 having the radio wave reflector 11 on the surface is a spherical corner column 30C at the corner of the house. The radio waves entering from the window 33 are reflected at the corner column 30C, and the radio waves are expanded in a wider range in the indoor space S. Furthermore, FIG8 (A) and FIG8 (B) are only schematic diagrams showing the outgoing waves, and do not represent the actual reflection range of the radio waves.

<Evaluation Test> Regarding the radio wave reflector 11, Examples 1 to 3 and Comparative Examples 1 and 2 were prepared and a diffusion evaluation test was performed. However, the radio wave reflector 11 of the present invention is not limited to Examples 1 to 3.

(Explanation of Examples and Comparative Examples) In Examples 1 to 3 and Comparative Examples 1 and 2, test pieces were prepared in the following manner. 1 part of a crosslinking agent was added to 100 parts of the following adhesive, and the mixture was stirred for 3 minutes to obtain an adhesive composition. Then, a protective layer was laid on a coating table, the adhesive composition was dripped, and a coating machine adjusted to a thickness of 25 μm was started to obtain an adhesive layer. It was dried at a temperature of 110°C for 5 minutes, and then heated and aged at 40°C for 48 hours to obtain a protective layer and an adhesive layer of the test piece.

Then, the conductive layer under the following conditions, the protective layer and the adhesive layer prepared above were vacuum-laminated at 40° C. for 6 minutes to obtain a test piece.

(1) Example 1 As Example 1, the conditions for the conductive layer of the test piece were as follows.・First conductive part Shape of the first surrounding part: quadrilateral (square) Line width of the first surrounding part: 2 μm Line thickness of the first surrounding part: 1 μm Outer perimeter of the first surrounding part: 0.8 mm Ratio of the length of the outer perimeter to the wavelength: 0.08 Dielectric: acrylic resin Relative dielectric constant: 3.1 ・Second conductive part Shape of the second surrounding part: quadrilateral (square) Line width of the second surrounding part: 2 μm Line thickness of the second surrounding part: 1 μm Distance between centers of gravity: 2.63 mm Ratio of the distance between centers of gravity to the wavelength: 0.263 Structure of the first conductive part and the second conductive part: single layer The pattern of the conductive body of Example 1 is shown in FIG. 10 . Furthermore, in the drawing, the thickness of the line of the first enclosing part and the second enclosing part is set to different thicknesses, but the values are the same as above.

(2) Example 2 As Example 2, the conditions for the conductive layer of the above-mentioned test piece were as follows.・1st conductive part Shape of the 1st surrounding part: quadrilateral (square) Line width of the 1st surrounding part: 1 μm Line thickness of the 1st surrounding part: 1 μm Outer perimeter of the 1st surrounding part: 1 mm Ratio of the length of the outer perimeter to the wavelength: 0.1 Dielectric: acrylic resin Relative dielectric constant: 3.1 ・2nd conductive part Shape of the 2nd surrounding part: quadrilateral (square) Line width of the 2nd surrounding part: 1 μm Line thickness of the 2nd surrounding part: 1 μm Distance between centers of gravity: 0.5 mm Ratio of the distance between centers of gravity to the wavelength: 0.05 Structure of the 1st conductive part and the 2nd conductive part: single layer The pattern of the conductive body of Example 2 is shown in FIG11. FIG11 shows a projection of the 1st conductive part and the 2nd conductive part. Furthermore, in the drawing, the thickness of the line of the first enclosing part and the second enclosing part is set to different thicknesses, but the values are the same as above.

(3) Example 3 As Example 3, the conditions for the conductive layer of the test piece were as follows.・The first conductive part The shape of the first surrounding part: quadrilateral (square) The line width of the first surrounding part: 1 μm The thickness of the line of the first surrounding part: 1 μm The outer perimeter of the first surrounding part: 1 mm The ratio of the length of the outer perimeter to the wavelength: 0.1 Dielectric: acrylic resin Relative dielectric constant: 3.1 ・The second conductive part The shape of the second surrounding part: quadrilateral (square) The line width of the second surrounding part: 1 μm The thickness of the line of the second surrounding part: 1 μm The distance between the centers of gravity: 0.5 mm The ratio of the distance between the centers of gravity to the wavelength: 0.05 Structure of the first conductive part and the second conductive part: multilayer The pattern of the conductive body of Example 3 is the same as that of Figure 11. However, in the third embodiment, the first conductive portion and the second conductive portion are formed in different layers.

(4) Example 4 As Example 4, the conditions for the conductive layer of the test piece were as follows.・The first conductive part The shape of the first surrounding part: quadrilateral (square) The line width of the first surrounding part: 1.5 μm The thickness of the line of the first surrounding part: 1.1 μm The outer perimeter of the first surrounding part: 0.0985 mm The ratio of the length of the outer perimeter to the wavelength: 0.00985 Dielectric: acrylic resin Relative dielectric constant: 3.1 ・The second conductive part The shape of the second surrounding part: circle The line width of the second surrounding part: 1.5 μm The thickness of the line of the second surrounding part: 1.1 μm The distance between the centers of gravity: 0.0985 mm The ratio of the distance between the centers of gravity to the wavelength: 0.00985 Structure of the first conductive part and the second conductive part: single layer The pattern of the conductive body of Example 3 is the same as that of Figure 7 (E). Furthermore, in the drawing, the thickness of the line of the first enclosing part and the second enclosing part is set to different thicknesses, but the values are the same as above.

(4) Comparative Example 1 As Comparative Example 1, the conditions for the conductive layer of the test piece were as follows: A surface-polished aluminum plate (A1050) was used.

(5) Comparative Example 2 As Comparative Example 2, the conditions for the conductive layer of the above test piece are as follows. ・1st conductive part Shape of the 1st surrounding part: quadrilateral Line width of the 1st surrounding part: 2 μm Line thickness of the 1st surrounding part: 1 μm Outer perimeter of the 1st surrounding part: 0.8 mm Ratio of the length of the outer perimeter to the wavelength: 0.08 Dielectric: acrylic resin Relative dielectric constant: 3.1 ・2nd conductive part: None

(Evaluation method) The test pieces of Examples 1 to 3 and Comparative Examples 1 and 2 were made to reflect radio waves with a frequency of 30 GHz (wavelength 10 mm), and the regular reflection intensity and the reflection intensity at the position of ±15° when the regular reflection was set to 0° were measured. In order to evaluate the diffusibility, the difference between the reflection intensity of the regular reflection and the reflection intensity at the position of ±15° when the regular reflection was set to 0° was 5 dB or less was evaluated as "○", and the difference greater than 5 dB was evaluated as "×".

(Test results) The test results are shown in Table 1. [Table 1] Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 Comparison Example 1 Comparison Example 2 First conductive part have have have have without have Enclosed Section 1 Shape square square square square - square Line width (μm) 2 1 1 1.5 - 2 Line thickness(μm) 1 1 1 1.1 - 1 Outer circumference (mm) 0.8 1 1 0.0985 - 1 Ratio of circumference to wavelength 0.08 0.1 0.1 0.00985 0.1 Dielectric Acrylic resin Acrylic resin Acrylic resin Acrylic resin Acrylic resin Relative permittivity of dielectrics 3.1 3.1 3.1 3.1 3.1 Second conductive part have have have have - without Second enclosure Shape square square square Circle - - Line width (μm) 2 1 1 1.5 - - Line thickness(μm) 1 1 1 1.1 - - Center of gravity distance (mm) 2.63 0.5 0.5 0.0985 - Ratio of distance between centers of gravity to wavelength 0.263 0.05 0.05 0.00985 Single layer/multi-layer of conductor Single layer Single layer Multi-layer Single layer Single layer Normal reflected radio wave intensity (dB) -19 -20 -20 -16 -20 -20 ±15 degree reflection intensity (dB) -twenty three -twenty four -twenty three -twenty one -28 -26 Diffusion ○ ○ ○ ○ × ×

As can be seen from Table 1, the evaluation of the diffusivity of Examples 1 to 4 is "○", while that of Comparative Examples 1 and 2 is "×". It can be seen that in Examples 1 to 4, the reflection intensity is not much attenuated even at the position of ±15° relative to the normal reflection. Thus, by providing the second conductive part as in Examples 1 to 4, a radio wave reflector 11 with high diffusivity can be obtained.

In addition, regarding the intensity of the radio wave of the regular reflection, Example 4 remains at -16, while Example 2-3 is -20. The reason is considered to be that since the line width of Example 4 is 1.5 μm and the outer perimeter is 0.0985 mm, while the line width of Example 2-3 is 1 μm and the outer perimeter is 1 mm, the higher the ratio of the conductor to the entire reflection surface, the smaller the attenuation of the intensity of the radio wave of the regular reflection. Thus, according to Example 4, while maintaining the transparency as a radio wave reflector, the radio wave reflection intensity is maintained at a higher level, and a higher diffusivity can be obtained.

<Variations> The above-mentioned implementation is only one of various implementations of the present invention. As long as the purpose of the present invention can be achieved, the implementation can be variously modified according to the design, etc. The following lists the variations of the implementation. The variations described below can be appropriately combined and applied.

(1) Modification 1 As shown in FIG. 9 , the radio wave reflector 11 may be formed by stacking a plurality of layers in the vertical direction. For example, another conductive layer 16B is connected to the conductive layer 16A via the bonding layer 14A, and a protective layer 15 is connected to the conductive layer 16B via the bonding layer 14B. The conductive layer 16A includes a substrate 13A and a conductor 12A in the same manner as in the embodiment. The conductive layer 16B includes a substrate 13B and a conductor 12B in the same manner.

Furthermore, the number of the conductors 12 formed on the conductive layer 16 may be three or more. If the number of the conductors 12 is increased, the reflection intensity increases, but since the thickness of the radio wave reflector 11 increases, the flexibility decreases, and the visible light transmittance also decreases. Therefore, when the radio wave reflector 11 is provided at a location where flexibility or transparency is not required, the number of layers may be appropriately set according to the intended use, such as increasing the number of layers.

(2) Others In the above-mentioned embodiment, the radio wave reflector 11 is formed in a sheet shape, but the present invention is not limited thereto, and may be in a plate shape, block shape, spherical shape, box shape, etc. Furthermore, the object on which the radio wave reflector 11 is installed is not limited to building materials, and may be electrical appliances, building structures, cars, trains, airplanes, etc.

In the above embodiment, the radio wave reflector 11 has the bonding layer 14 between the conductive layer 16 and the protective layer 15, but if the protective layer 15 has self-bonding force, the bonding layer 14 may be omitted. In addition, the protective layer 15 may be fixed to the conductive layer 16 by sealing the outer edge with a sealing material without relying on the bonding layer 14. Furthermore, the protective layer 15 does not necessarily need to be fixed to the conductive layer 16.

One embodiment of the present invention has been described above, but the present invention is not limited to the above-mentioned embodiment, and various changes can be made within the scope of the subject matter of the present invention. The dimensions, materials, shapes, relative configurations, etc. of the components recorded as embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples. For example, expressions such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" that indicate relative or absolute configurations not only strictly indicate such configurations, but also indicate a state in which displacement occurs relative to each other at an angle or distance that is within a tolerance or a degree that enables 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 indicate a strictly equal state, but also indicate a state in which there is a tolerance or a difference in the degree to which the same function can be obtained. For example, expressions such as quadrilateral or cylinder that indicate shapes do not only indicate shapes such as quadrilateral or cylinder in the strict sense of geometry, but also indicate shapes that include concave and convex parts or chamfered parts within the scope of being able to obtain the same effect. The expression "includes", "contains", "has", "includes" or "has" a constituent element is not an exclusive expression that excludes the existence of other constituent elements.

In this specification, sometimes, expressions accompanied by "approximately" are used, such as "approximately parallel" or "approximately orthogonal". For example, "approximately parallel" means substantially "parallel", not only the state of strict "parallelism", but also means including errors of several degrees. The same applies to other expressions accompanied by "approximately".

In addition, in this specification, expressions such as "end" and "end" are distinguished by the presence or absence of "part". For example, "end" means the end of an object, and "end" means a region with a certain range including the "end". Any point within a certain range including the end is considered an "end". The same applies to other expressions accompanied by "part".

11: Radio wave reflector 12: Conductor 14: Adhesive layer 15: Protective layer 16: Conductive layer 4: 1st conductive part 41: 1st surrounding part 5: 2nd conductive part 51: 2nd surrounding part R1: 1st region R2: 2nd region

[Fig. 1] is a schematic diagram for explaining the angle range of the reflected wave reflected by the radio wave reflector of the embodiment. [Fig. 2] is a schematic plan view of the radio wave reflector of the embodiment. [Fig. 3] is a schematic cross-sectional view of the C-C line of Fig. 2. [Fig. 4] Fig. 4 (A) is an enlarged view of the A part of Fig. 2. Fig. 4 (B) is a schematic enlarged view of the B part of Fig. 4 (A). Fig. 4 (C) is a schematic diagram for explaining the diffusivity of radio waves. [Fig. 5] (A) to (D) are schematic diagrams for explaining the manufacturing steps of the conductor. [Fig. 6] (A) to (E) are schematic diagrams for explaining another manufacturing step of the conductor. [Fig. 7] (A) to (E) are schematic plan views showing a variation of the configuration pattern of the conductor. FIG. 8 (A) of FIG. 8 is an explanatory diagram showing an example of use of the radio wave reflector of the embodiment. FIG. 8 (B) is a schematic plan view showing an example of indoor application of the building material. FIG. 9 is a schematic cross-sectional view of a radio wave reflector of a variation. FIG. 10 is a schematic plan view showing a pattern of the conductor of the embodiment 1. FIG. 11 is a schematic plan view showing a pattern of the conductor of the embodiments 2 and 3.

4: First conductive part

5: Second conductive part

12: Conductor

41: The first encirclement

51: Second encirclement

411: 1st linear body

412: Second linear body

511: The third linear body

512: 4th linear body

A1: Opening 1

A2: 2nd opening

R1: Area 1

R2: Area 2

L6: Line width of the first enclosing part

L7: Maximum length between edges in region 1

L8: Line width of the second enclosing part

L9: The distance between the centers of gravity of the adjacent second enclosures

Claims (11)

A radio wave reflector, which has a conductive layer having a conductor that reflects radio waves, wherein the conductor has: a first conductive portion having first surrounding portions repeatedly formed at a certain interval, the first surrounding portion surrounding a first area where the conductor is not formed and being composed of a conductor; and a second conductive portion including at least one second surrounding portion, the second surrounding portion surrounding a second area spanning over a plurality of adjacent first areas and being composed of a conductor; and the first surrounding portion and the second surrounding portion have no common parts when projected onto a projection plane parallel to the conductive layer. As for the radio wave reflector of claim 1, the perimeter of the above-mentioned first surrounding portion is a length less than the wavelength of the above-mentioned radio wave. As for the radio wave reflector of claim 2, wherein the perimeter of the above-mentioned first surrounding portion is a length that is less than 5/6 times the wavelength of the above-mentioned radio wave. As for the radio wave reflector of claim 1, the perimeter of the above-mentioned second surrounding portion is a length less than the wavelength of the above-mentioned radio wave. A radio wave reflector as claimed in claim 1, wherein the distance between the centers of gravity of adjacent second regions is at least 0.015 times the wavelength of the radio wave. As for the radio wave reflector of claim 1, wherein the second region is filled with a dielectric having a relative dielectric constant of 1.5 or more. The radio wave reflector of claim 1 further comprises: a protective layer that protects the conductive layer; and a bonding layer that is disposed between the conductive layer and the protective layer to bond the conductive layer to the protective layer. The radio wave reflector of claim 1, wherein the first conductive portion and the second conductive portion are formed on the same plane. The radio wave reflector of claim 1, wherein the first conductive portion and the second conductive portion are formed at different positions in a direction orthogonal to the conductive layer. The radio wave reflector of claim 1, wherein the line width of at least one of the first surrounding portion and the second surrounding portion is not less than 0.3 μm and not more than 10 μm. The radio wave reflector of claim 1, wherein the thickness of the line of at least one of the first surrounding portion and the second surrounding portion is not less than 0.02 μm and not more than 10 μm.

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