High frequency diffusion sheet

Abstract

To provide a high frequency diffusion sheet which enables a communication apparatus to satisfactorily receive an electromagnetic wave in a high frequency domain in a case where the communication apparatus is disposed in the vicinity of a front side of a permeation area such as a window part within a building by diffusing the electromagnetic wave while maintaining directivity.SOLUTION: A high frequency diffusion sheet 10 is used for diffusing an electromagnetic wave in a high frequency domain and comprises an electromagnetic wave shield layer 11 having an electromagnetic wave shielding property. The high frequency diffusion sheet includes openings 15 penetrating in a thickness direction of the electromagnetic shield layer. When an average opening width of the openings is defined as W [mm], an average separation distance between the openings is defined as L [mm] and a wavelength of the electromagnetic wave is defined as λ [mm], W / λ and L / λ satisfy the following relational expressions (1) to (3): (1) 1.5<W / λ≤2.7 and 0.4≤L / λ≤3.0, (2) 0.3≤W / λ≤1.5 and 1.3<L / λ≤3.0 and (3) 0.3≤W / λ≤2.7 and 3.0<L / λ≤16.5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a radio frequency diffusion sheet. [Background technology]

[0002] In recent years, as communication devices such as mobile phones, smartphones, tablets, and mobile PCs have become faster and have higher capacities, it has been proposed to use electromagnetic waves (electromagnetic signals) in the high frequency range of 1 GHz or more and 80 GHz or less as the electromagnetic waves to be received by these communication devices (see, for example, Patent Document 1).

[0003] Electromagnetic waves in such high-frequency ranges have a higher degree of directivity (directivity) than those in the low-frequency ranges. Therefore, when electromagnetic waves are received by communication devices inside a building, the electromagnetic waves that pass through areas such as windows that allow electromagnetic waves to pass through are not diffused, resulting in the problem of poor reception of electromagnetic waves inside the building.

[0004] Therefore, when electromagnetic waves pass through a transmission area such as a window, it is desirable that the electromagnetic waves be diffused. For example, when a communication device is located near the front of the transmission area and at a predetermined angle from the linear direction of the electromagnetic waves, it is necessary to diffuse the electromagnetic waves in a predetermined direction while maintaining the directivity. Furthermore, when a communication device is located near the front of the transmission area and at a distance from the transmission area, it is necessary to increase the intensity of the electromagnetic waves by converging the electromagnetic waves while maintaining the directivity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-190920 Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to provide a high-frequency diffusion sheet that can diffuse high-frequency electromagnetic waves while maintaining their directionality, thereby enabling the electromagnetic waves to be received well by communication equipment, for example, when the communication equipment is located near the front of a transmission area such as a window within a building. [Means for solving the problem]

[0007] These objects can be achieved by the present invention as set forth in (1) to (14) below. (1) A high-frequency diffusion sheet is used to diffuse electromagnetic waves in the high-frequency range when the electromagnetic waves pass through the sheet, and includes an electromagnetic wave shielding layer having electromagnetic wave shielding properties, the electromagnetic wave shielding layer is patterned in a plan view of the high-frequency diffusion sheet, and has a plurality of openings penetrating the electromagnetic wave shielding layer in a thickness direction; A high-frequency diffusion sheet characterized in that, when the average opening width of the openings is W [mm], the average distance between adjacent openings is L [mm], and the wavelength of the electromagnetic waves is λ [mm], W / λ and L / λ are within the range of the following relational expression (1), the range of the following relational expression (2), or the range of the following relational expression (3). 1.5 <W / λ≦2.7、および、0.4≦L / λ≦3.0 … (1) 0.3≦W / λ≦1.5 and 1.3 <L / λ≦3.0 … (2) 0.3≦W / λ≦2.7 and 3.0 <L / λ≦16.5 … (3)

[0008] (2) the W / λ and the L / λ are within the range of the relational expression (1) or the range of the relational expression (2); When the electromagnetic waves are transmitted through the high-frequency diffusion sheet and diffused at the opening, the radiation angle θ of the electromagnetic waves diffused with the highest intensity is defined as an inclination angle with respect to the electromagnetic waves traveling straight through the opening without being diffused, The high frequency diffusion sheet according to (1) above, wherein the radiation angle θ is greater than 0° and equal to or less than 30°.

[0009] (3) The high frequency diffusion sheet according to (1) or (2), wherein the opening has a rectangular shape in a plan view.

[0010] (4) The high frequency diffusion sheet according to (1) or (2) above, wherein the openings are arranged in a matrix.

[0011] (5) The high-frequency diffusion sheet according to (1), wherein the plurality of openings are arranged so as to satisfy a point-symmetric relationship with respect to a center of symmetry set in the electromagnetic wave shielding layer.

[0012] (6) The electromagnetic wave shielding layer has an annular opening band penetrating through the layer in the thickness direction, The high frequency diffusion sheet according to (5) above, wherein the plurality of openings are part of the opening band.

[0013] (7) When the radiation angle of the electromagnetic wave radiated with the highest intensity among the electromagnetic waves diffused by the opening is set as an inclination angle with respect to the electromagnetic wave traveling straight without being diffused by the opening, the radiation angle is 20° or less; The high frequency diffusion sheet according to (5) or (6) above, wherein the half-value angle of the electromagnetic waves diffused at the radiation angle is 15° or less.

[0014] (8) The high-frequency diffusion sheet according to any one of (1) to (7), wherein the electromagnetic wave shielding layer shields the electromagnetic waves by reflecting or absorbing the electromagnetic waves.

[0015] (9) The high-frequency diffusion sheet according to any one of (1) to (8), wherein the electromagnetic wave shielding layer is a metal thin film layer or a metal powder-containing adhesive layer containing metal powder and a binder resin.

[0016] (10) The high-frequency diffusion sheet according to any one of (1) to (9), wherein the high-frequency diffusion sheet has a transparent resin film, and the electromagnetic wave shielding layer is bonded to the resin film.

[0017] (11) The high-frequency diffusion sheet according to any one of (1) to (10) above, wherein the high-frequency diffusion sheet is configured to diffuse the electromagnetic waves by diffracting the electromagnetic waves through the openings when the electromagnetic waves pass through the high-frequency diffusion sheet.

[0018] (12) The high-frequency diffusion sheet according to any one of (1) to (11) above, wherein the electromagnetic wave shielding layer has an average thickness T of 0.01 μm or more and 70.0 μm or less.

[0019] (13) The high-frequency diffusion sheet according to any one of (1) to (12) above, wherein the frequency of the electromagnetic waves is 1 GHz or more and 80 GHz or less.

[0020] (14) The high-frequency diffusion sheet according to any one of (1) to (13) above, which is attached to a transparent area of ​​a building where the transmission of the electromagnetic waves is permitted. [Effects of the Invention]

[0021] According to the present invention, when electromagnetic waves in the high-frequency range pass through a high-frequency diffusion sheet, the electromagnetic waves can be diffused at openings in the high-frequency diffusion sheet while maintaining their directivity. Therefore, by attaching a high-frequency diffusion sheet to a transmission area that allows the transmission of electromagnetic waves, such as a window in a building (structure), the electromagnetic waves can be diffused while maintaining their directivity when they pass through the transmission area to which the high-frequency diffusion sheet is attached. Therefore, when communication equipment is located near the front of a transmission area such as a window in a building, the use of this high-frequency diffusion sheet allows for better reception of electromagnetic waves. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a plan view showing a first embodiment of a radio frequency diffusion sheet of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] 1. FIG. 4 is a plan view showing another configuration of the opening in the electromagnetic wave shielding layer of the high-frequency diffusion sheet of FIG. [Figure 4] FIG. 10 is a plan view showing a radio-frequency diffusion sheet according to a second embodiment. [Figure 5] 10 is a table showing simulation results S0, S1, S2, and S3 of the far-field radiation pattern of electromagnetic waves transmitted through a high-frequency diffusion sheet. [Figure 6] 6(a) and 6(b) are plan views showing a high-frequency diffusion sheet according to a third embodiment (FIG. 6(a) is an overall view of the high-frequency diffusion sheet according to the third embodiment, and FIG. 6(b) is a partially enlarged plan view of the high-frequency diffusion sheet located in the area [B] surrounded by the dotted line in FIG. 6(a)). [Figure 7] 7A and 7B are diagrams showing an object used for evaluating the diffraction of electromagnetic waves (FIG. 7A is a plan view, and FIG. 7B is a cross-sectional view taken along line BB in FIG. 7A). [Figure 8] 1 is a scatter diagram in which data on the openings of the high-frequency diffusion sheets of each example and each comparative example are plotted, with L / λ on the horizontal axis and W / λ on the vertical axis. [Figure 9] 1 is a conceptual diagram for explaining a method for measuring the received intensity at a predetermined deflection angle of an electromagnetic wave diffracted and diffused by a subject. DETAILED DESCRIPTION OF THE INVENTION

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The radio frequency diffusion sheet of the present invention will be described in detail below with reference to preferred embodiments shown in the accompanying drawings.

[0024] First Embodiment FIG. 1 is a plan view showing a first embodiment of the radio-frequency diffusion sheet of the present invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. FIG. 3 is a plan view showing another configuration of openings in the electromagnetic wave shielding layer of the radio-frequency diffusion sheet of FIG. 1. In the following description, the front side of the paper in FIGS. 1 and 3 is referred to as "top," the back side of the paper is referred to as "bottom," and the upper side in FIG. 2 is referred to as "top" and the lower side is referred to as "bottom." Furthermore, the up-down direction in FIGS. 1 and 3 and the direction perpendicular to the paper in FIG. 2 are referred to as the Y direction, and the left-right direction in FIGS. 1 to 3 are referred to as the X direction. Furthermore, in each drawing referred to in this specification, dimensions in the left-right direction and / or thickness direction are exaggerated and differ significantly from the actual dimensions.

[0025] The high-frequency diffusion sheet 10 is used to diffuse electromagnetic waves in the high-frequency range and includes an electromagnetic wave shielding layer 11 that has electromagnetic wave shielding properties. The electromagnetic wave shielding layer 11 is patterned when viewed in a plane of the high-frequency diffusion sheet 10 and has openings 15 that penetrate the electromagnetic wave shielding layer 11 in the thickness direction.

[0026] In the present invention, when the average opening width of the openings 15 in this high-frequency diffusion sheet 10 is W [mm], the average distance between adjacent openings 15 is L [mm], and the wavelength of the electromagnetic wave is λ [mm], W / λ and L / λ satisfy the following relational expression (1), (2), or (3):

[0027] 1.5 <W / λ≦2.7、および、0.4≦L / λ≦3.0 … (1) 0.3≦W / λ≦1.5 and 1.3 <L / λ≦3.0 … (2) 0.3≦W / λ≦2.7 and 3.0 <L / λ≦16.5 … (3)

[0028] By configuring the high-frequency diffusion sheet 10 in this manner, i.e., by having openings 15 penetrating the electromagnetic wave shielding layer 11 having electromagnetic wave shielding properties in the thickness direction and further by configuring the openings 15 to satisfy the range of the above-mentioned relational expression (1), the range of the above-mentioned relational expression (2), or the range of the above-mentioned relational expression (3), it is possible to diffuse high-frequency electromagnetic waves while maintaining their directivity when they pass through the high-frequency diffusion sheet 10. Therefore, by attaching the high-frequency diffusion sheet 10 to a transmission area that allows the transmission of electromagnetic waves, such as a window in a building, the high-frequency electromagnetic waves can be diffused by the diffraction at the openings 15 while maintaining their directivity when they pass through the transmission area to which the high-frequency diffusion sheet 10 is attached. Therefore, when a communication device is located near the front of a transmission area such as a window in a building, the electromagnetic waves can be received well by the communication device.

[0029] As described above, the high-frequency diffusion sheet 10 can be directly attached to a window provided in a building (structure), or it can be attached to a curtain, blind, or the like that is placed in correspondence with the window, so that when the electromagnetic waves pass through the window, the high-frequency diffusion sheet 10 can diffuse the electromagnetic waves while maintaining their directionality.

[0030] Hereinafter, a high frequency diffusion sheet 10 having an electromagnetic wave shielding layer 11 with openings 15 will be described.

[0031] In this embodiment, the high frequency diffusion sheet 10 has an electromagnetic wave shielding layer 11 having electromagnetic wave shielding properties and a resin film 12 supporting the electromagnetic wave shielding layer 11, as shown in FIGS.

[0032] <<Resin film>> The resin film 12 is bonded to the electromagnetic wave shielding layer 11 to support the electromagnetic wave shielding layer 11 and is provided in the high frequency diffusion sheet 10 to maintain the stability of its shape as the high frequency diffusion sheet 10, and a transparent resin film is preferably used.

[0033] Examples of this resin film 12 include those primarily made of thermosetting resins such as polyimide resin, polyamide resin, and epoxy resin; polyester-based resins such as polyethylene terephthalate and polyethylene naphthalate; olefin-based resins such as polypropylene and cycloolefin polymer; acrylic resins such as polymethyl methacrylate; and thermoplastic resins such as polycarbonate-based resins, and these are preferably used because they are transparent.

[0034] Furthermore, the average thickness of the resin film 12 is not particularly limited, but is preferably 0.01 mm or more and 0.40 mm or less, and more preferably 0.10 mm or more and 0.30 mm or less. By setting the average thickness of the resin film 12 within this range, the resin film 12 can reliably support the electromagnetic wave shielding layer 11.

[0035] <<Electromagnetic wave shielding layer>> The electromagnetic wave shielding layer 11 has an opening 15 penetrating through its thickness direction, has a layered overall shape, and is laminated on the resin film 12. In the areas where the opening 15 is not formed, the electromagnetic wave shielding layer 11 has an electromagnetic wave shielding property of suppressing or blocking the transmission of electromagnetic waves, and in the areas where the opening 15 is formed, it has the function of allowing the transmission of electromagnetic waves.

[0036] This electromagnetic wave shielding layer 11 is not particularly limited and may have any form that shields electromagnetic waves in areas where no openings 15 are formed, and examples thereof include a reflective layer that shields (blocks) electromagnetic waves incident on the electromagnetic wave shielding layer 11 by preferentially reflecting them, and an absorbing layer that shields (blocks) electromagnetic waves incident on the electromagnetic wave shielding layer 11 by preferentially absorbing them. Among these, the electromagnetic wave shielding layer 11 is preferably a reflective layer. This allows electromagnetic waves incident on the electromagnetic wave shielding layer 11 to be shielded by preferentially reflecting them, thereby improving the transmittance of electromagnetic waves transmitted through the openings 15.

[0037] As described above, the electromagnetic wave shielding layer 11 may shield electromagnetic waves by either reflecting or absorbing incident electromagnetic waves. In this specification, however, a layer that shields electromagnetic waves mainly by reflection, out of reflection and absorption, is referred to as a reflective layer, and a layer that shields electromagnetic waves mainly by absorption is referred to as an absorbing layer.

[0038] The reflective layer and the absorbing layer will be described below. The reflective layer is a layer that effectively blocks the reflection of electromagnetic waves incident on the reflective layer.

[0039] Examples of the reflective layer include a metal powder-containing adhesive layer, a metal thin film layer, a metal mesh, and a surface treatment of a conductive material such as ITO. These may be used alone or in combination. Among these, it is preferable to use a metal powder-containing adhesive layer and a metal thin film layer. The metal powder-containing adhesive layer and the metal thin film layer are preferably used as the reflective layer because they exhibit excellent electromagnetic wave shielding properties even when their film thickness is set relatively thin.

[0040] The metal powder-containing adhesive layer is composed of metal powder and a binder resin, and examples of the metal powder include gold, silver, copper or silver-coated copper, nickel, etc. Among these, silver is preferably used because of its excellent electromagnetic wave shielding properties.

[0041] The ratio of the metal powder to the binder resin in the metal powder-containing adhesive layer is not particularly limited, but is preferably 40:60 to 95:5 by weight, and more preferably 50:50 to 90:10.

[0042] The metal powder-containing adhesive layer may further contain a flame retardant, a leveling agent, a viscosity adjuster, and the like in addition to the metal powder and binder resin.

[0043] Examples of the metal thin film layer include a vapor-deposited film and a metal foil that are mainly made of the metals listed as the metal powder contained in the metal powder-containing adhesive layer.

[0044] The absorbing layer is a layer that absorbs electromagnetic waves incident on the absorbing layer and advantageously blocks the waves from being converted into thermal energy.

[0045] Examples of this absorption layer include a conductive absorption layer mainly composed of conductive absorption materials such as metal powder and conductive polymer materials, a dielectric absorption layer mainly composed of dielectric absorption materials such as carbon-based materials and conductive polymer materials, and a magnetic absorption layer mainly composed of magnetic absorption materials such as soft magnetic metals. These may be used alone or in combination, and those composed of these main materials and a binder resin are preferably used.

[0046] The conductive absorbing layer absorbs electromagnetic waves by converting electromagnetic energy into thermal energy due to the current that flows inside the material when an electric field is applied. The dielectric absorbing layer absorbs electromagnetic waves by converting electromagnetic waves into thermal energy due to dielectric loss. The magnetic absorbing layer absorbs electromagnetic waves by converting the energy of the electromagnetic waves into heat and consuming it due to magnetic loss such as overcurrent loss, hysteresis loss, and magnetic resonance.

[0047] Examples of conductive absorbing materials include conductive polymers, metal oxides such as ATO, and conductive ceramics.

[0048] Furthermore, examples of conductive polymers include polyacetylene, polypyrrole, PEDOT (poly-ethylenedioxythiophene), PEDOT / PSS, polythiophene, polyaniline, poly(p-phenylene), polyfluorene, polycarbazole, polysilane, and derivatives thereof, and one or more of these can be used in combination. Examples of dielectric absorbing materials include carbon-based materials, conductive polymers, and ceramic materials.

[0049] Examples of carbon-based materials include carbon nanotubes such as single-walled carbon nanotubes and multi-walled carbon nanotubes, carbon nanofibers, CN nanotubes, CN nanofibers, BCN nanotubes, BCN nanofibers, graphene, and carbon such as carbon microcoils, carbon nanocoils, carbon nanohorns, and carbon nanowalls, and one or more of these can be used in combination.

[0050] Examples of ceramic materials include barium titanate, perovskite-type barium calcium titanate zirconate crystal particles, titania, alumina, zirconia, silicon carbide, and aluminum nitride, and one or more of these may be used in combination.

[0051] Further, examples of magnetic absorption materials include soft magnetic metals such as iron, silicon steel, magnetic stainless steel (Fe-Cr-Al-Si alloy), sendust (Fe-Si-Al alloy), permalloy (Fe-Ni alloy), silicon copper (Fe-Cu-Si alloy), Fe-Si alloy, and Fe-Si-B(-Cu-Nb) alloy, and ferrite.

[0052] Furthermore, when the absorbing layer and the absorbing layer contain a binder resin, various resin materials can be used as this binder resin, and are not particularly limited, but examples include thermosetting resins such as epoxy resins, phenolic resins, amino resins, unsaturated polyester resins, and thermosetting elastomers, and thermoplastic resins such as olefin resins, polyamide resins, polyimide resins, acrylic resins, polyester resins, vinyl chloride resins, styrene resins, styrene-based thermoplastic elastomers, and olefin-based thermoplastic elastomers, and one or more of these can be used in combination.

[0053] The average thickness of the reflective layer and the absorbing layer, i.e., the average thickness T of the electromagnetic wave shielding layer 11, is not particularly limited, but is preferably 0.01 μm to 70.0 μm, more preferably 1.0 μm to 70.0 μm, and even more preferably 10.0 μm to 40.0 μm. By setting the average thickness T of the electromagnetic wave shielding layer 11 within this range, it is possible to reliably suppress or block the transmission of electromagnetic waves in areas where the openings 15 are not formed, and therefore it is possible to reliably diffract electromagnetic waves that pass through the openings 15 at the openings 15.

[0054] As shown in FIGS. 1 and 2, the opening 15 is a through-hole provided so as to penetrate the electromagnetic wave shielding layer 11 in the thickness direction.

[0055] In the present invention, when the average opening width of the openings 15 in the high-frequency diffusion sheet 10 is W [mm], the average distance between adjacent openings 15 is L [mm], and the wavelength of the electromagnetic wave is λ [mm], W / λ and L / λ satisfy the following relational expression (1), (2), or (3):

[0056] 1.5 <W / λ≦2.7、および、0.4≦L / λ≦3.0 … (1) 0.3≦W / λ≦1.5 and 1.3 <L / λ≦3.0 … (2) 0.3≦W / λ≦2.7 and 3.0 <L / λ≦16.5 … (3)

[0057] As described above, in the present invention, not only the average opening width W [mm] of the openings 15 as through holes formed in the electromagnetic wave shielding layer 11 but also the average separation distance L [mm] between adjacent openings 15 are set. Specifically, W / λ and L / λ, which represent the ratio of the wavelength λ [mm] of the electromagnetic wave, are set within the ranges of the above-mentioned relational expression (1), the ranges of the above-mentioned relational expression (2), or the ranges of the above-mentioned relational expression (3). As a result, when, for example, electromagnetic waves (plane waves WA) in the high frequency range (frequency: approximately 1 GHz or more and 80 GHz or less) are incident on the electromagnetic wave shielding layer 11 and pass through the electromagnetic wave shielding layer 11 via the openings 15, the electromagnetic waves can be diffused while maintaining their directivity. Therefore, by attaching the high frequency diffusion sheet 10 to a transmission area where electromagnetic waves are permitted to pass, such as a window in a building, the electromagnetic waves in the high frequency range can be diffused at the openings 15 by the diffraction while maintaining their directivity when they pass through the transmission area to which the high frequency diffusion sheet 10 is attached. Therefore, when a communication device is placed near the front of a transmission area such as a window in a building, the electromagnetic waves can be received well by the communication device (see FIG. 2). Furthermore, interference between the electromagnetic waves emerging from the openings 15 allows the waves to be diffused evenly while maintaining their directivity. This allows the electromagnetic wave shielding layer 11 to diffract electromagnetic waves in the high frequency range evenly. This allows the electromagnetic waves passing through the high frequency diffusion sheet 10 to be deflected at a predetermined angle.

[0058] The number of openings 15 having such a configuration is not limited as long as a plurality (two or more) of them are provided in the electromagnetic wave shielding layer 11. In this embodiment, as shown in FIG. 1, nine rows are arranged at equal intervals along the X direction (the short side direction of the openings 15) and three rows are arranged at equal intervals along the Y direction (the long side direction of the openings 15), for a total of 27 (plural) openings.

[0059] Also, in FIG. 1, the separation distance L between the adjacent openings 15 in the X direction is the same for each other. Further, each of the openings 15 shown in FIG. 1 has an elongated shape, that is, a rectangular shape, extending linearly along the Y direction (the longitudinal direction of the opening 15), and the lengths are the same for each other, and the widths W are also the same for each other.

[0060] Here, in order to diffuse the electromagnetic wave with excellent directivity as described above, it is sufficient that W / λ and L / λ satisfy within the range of the relational expression (1), within the range of the relational expression (2), or within the range of the relational expression (3).

[0061] Among these, when satisfying within the range of the relational expression (1), it is preferably within the range of 1.7 < W / λ ≤ 2.7 and 0.4 ≤ L / λ ≤ 2.9, and more preferably within the range of 1.7 < W / λ ≤ 2.0 and 0.4 ≤ L / λ ≤ 1.9, or within the range of 2.6 < W / λ ≤ 2.7 and 0.4 ≤ L / λ ≤ 2.8.

[0062] Also, when satisfying within the range of the relational expression (2), it is preferably within the range of 0.4 ≤ W / λ ≤ 1.2 and 1.3 < L / λ ≤ 1.9, and more preferably within the range of 0.8 ≤ W / λ ≤ 1.1 and 1.3 < L / λ ≤ 1.6.

[0063] Furthermore, when satisfying within the range of the relational expression (3), it is preferably within the range of 0.5 ≤ W / λ ≤ 2.7 and 4.0 ≤ L / λ ≤ 16.5, and more preferably within the range of 0.8 ≤ W / λ ≤ 2.4 and 5.0 ≤ L / λ ≤ 15.5.

[0064] Thereby, the above effects can be more significantly exhibited. Also, the electromagnetic wave can be transmitted through the high-frequency diffusion sheet 10 with a high transmittance as described later, that is, excellent permeability.

[0065] 1, it is particularly preferable that W / λ and L / λ are within the range of the relational expression (1) or the range of the relational expression (2). In this case, the degree of diffusion of the electromagnetic waves diffused at the openings 15 of the high-frequency diffusion sheet 10 is preferably set as follows: That is, when the radiation angle θ of the electromagnetic waves diffused at the openings 15 with the highest intensity is defined as the inclination angle with respect to the electromagnetic waves that travel straight through the openings 15 without being diffused (see FIG. 2), the radiation angle θ is preferably greater than 0° and less than 30°, and more preferably greater than 10° and less than 25°. This means that the electromagnetic waves are diffused at the openings 15 while maintaining their directionality (straight propagation). Note that, in this specification, the term "diffused electromagnetic waves" refers to electromagnetic waves excluding the electromagnetic waves that travel straight through the openings 15 without being diffused (electromagnetic waves that pass through the high-frequency diffusion sheet 10 in a direction perpendicular to the openings 15). In other words, the term "diffusion" in this specification not only means to widen, but also includes the meaning of deflection that changes the propagation direction, and the meaning of focusing by changing the propagation direction.

[0066] Furthermore, it is preferable that the electromagnetic waves diffused at the openings 15 while passing through the high frequency diffusion sheet 10 have high transmittance, and specifically, the transmittance of the electromagnetic waves is preferably 30% or more, and more preferably 50% or more. This means that the electromagnetic waves are diffused at the openings 15 while maintaining their directionality, and are transmitted through the high frequency diffusion sheet 10 with excellent transmittance.

[0067] Although the shape of each opening 15 is rectangular, i.e., linear, in a plan view, it is not limited thereto as long as it satisfies the range of relational formula (1), the range of relational formula (2), or the range of relational formula (3). Other shapes of opening 15 include, for example, a circular shape as shown in FIG. 3 , as well as shapes with curved portions such as an S-shape, a U-shape, a semicircular shape, or a wavy shape, and shapes with corners such as a V-shape, an X-shape, an L-shape, an H-shape, a T-shape, a W-shape, and a C-shape. When opening 15 has a circular shape as shown in FIG. 3 in a plan view, the diameter D of the circle corresponds to the width W of opening 15 when opening 15 has a rectangular shape. Furthermore, the shortest distance between adjacent circles can be treated as the separation distance L between adjacent openings 15 in the X direction when openings 15 have a rectangular shape.

[0068] In addition, in this embodiment, the openings 15 are described as having the same shape and are formed at equal intervals in the electromagnetic wave shielding layer 11, but this is not limited to this, and each opening 15 may have a different shape from each other.

[0069] In addition, in FIG. 1 , the multiple openings 15 are arranged in a matrix. The matrix refers to an arrangement pattern that includes an arrangement along an X-axis and an arrangement along a Y-axis that are orthogonal to each other. By arranging the multiple openings 15 in such an arrangement pattern, electromagnetic waves can be diffracted and interfered in a specific direction. This makes it possible to realize a high-frequency diffusion sheet 10 that can deflect electromagnetic waves at a predetermined deflection angle in the X-axis. As a result, it is possible to realize a high-frequency diffusion sheet 10 that can deflect electromagnetic waves and improve the reception environment, even in places where the radio wave source cannot be directly seen.

[0070] Furthermore, the separation distance L affects the diffraction of electromagnetic waves in the X direction. That is, in the example shown in Fig. 1, when a line parallel to the X axis is drawn, the average opening width W and the average separation distance L are determined based on the width of the openings 15 measured on the line and the separation distance between adjacent openings 15. In the high-frequency diffusion sheet 10, the average opening width W and the average separation distance L determined in this manner are required to fall within the ranges of the above-mentioned relational expressions (1) to (3). Note that, as long as the openings 15 are separated on the line, the openings 15 that are separated on the line may be connected at a location other than the line.

[0071] 1, the separation distance L between adjacent openings 15 in the X direction is the same, but may be different within the range of the relational expressions (1) to (3). In this case, the high-frequency diffusion sheet 10 can diffuse a plurality of electromagnetic wave wavelengths. In other words, it is possible to realize a high-frequency diffusion sheet 10 that can diffuse a plurality of electromagnetic wave wavelengths.

[0072] <<Adhesive layer>> The high-frequency diffusion sheet 10 may also include an adhesive layer laminated on the surface of the resin film 12 opposite to the electromagnetic wave shielding layer 11. This allows the high-frequency diffusion sheet 10 to be easily attached to a transparent area that allows the transmission of electromagnetic waves, such as a window in a building (structure).

[0073] This adhesive layer is not particularly limited, but is preferably made of, for example, an adhesive that is primarily made of at least one type of adhesive selected from the group consisting of acrylic adhesives, silicone adhesives, and rubber adhesives.

[0074] Examples of acrylic adhesives include resins composed of (meth)acrylic acid and esters thereof, copolymers of (meth)acrylic acid and esters thereof with unsaturated monomers copolymerizable therewith (e.g., vinyl acetate, styrene, acrylonitrile, etc.), etc. Also included are mixtures of two or more of these resins.

[0075] Examples of rubber-based adhesives include natural rubber-based, isoprene rubber-based, styrene-butadiene-based, reclaimed rubber-based, and polyisobutylene-based adhesives, as well as those primarily composed of block copolymers containing rubber such as styrene-isoprene-styrene and styrene-butadiene-styrene.

[0076] Furthermore, examples of silicone-based adhesives include dimethylsiloxane-based and diphenylsiloxane-based adhesives.

[0077] Furthermore, the adhesive layer may contain various additives, such as plasticizers, tackifiers, thickeners, fillers, antioxidants, preservatives, anti-mold agents, dyes, and pigments, as needed.

[0078] In this embodiment, the high-frequency diffusion sheet 10 has been described as having one resin film 12 on one side of the electromagnetic wave shielding layer 11, but this is not limited to this, and the resin film 12 may be provided on both one side and the other side of the electromagnetic wave shielding layer 11, or the formation of the resin film 12 may be omitted.

[0079] The high frequency diffusion sheet 10 may further include an intermediate layer or the like between the electromagnetic wave shielding layer 11 and the resin film 12 and / or between the resin film 12 and the adhesive layer.

[0080] Second Embodiment Next, a second embodiment of the radio frequency diffusion sheet of the present invention will be described.

[0081] FIG. 4 is a plan view showing a radio frequency diffusion sheet according to the second embodiment. The second embodiment will be described below, focusing on the differences from the first embodiment, and the description of the similarities will be omitted. Note that in Fig. 4, the same components as those in the first embodiment are denoted by the same reference numerals.

[0082] In the second embodiment, the plurality of openings 15 are arranged so as to satisfy a point-symmetric relationship with respect to a center of symmetry O set in the electromagnetic wave shielding layer 11. Specifically, the high-frequency diffusion sheet 10 shown in Fig. 4 has an opening band 14 that penetrates the electromagnetic wave shielding layer 11, which has electromagnetic wave shielding properties, in the thickness direction and has a circular ring shape in a plan view. The center of this opening band 14 is the center of symmetry O described above.

[0083] Also, in Fig. 4, a straight line S parallel to the X-axis is drawn. This straight line S passes through the opening band 14, and therefore two openings 15 exist on the straight line S. Therefore, the average opening width W and the average separation distance L can be determined based on the widths of the two openings 15 and the separation distance between the two openings 15 shown in Fig. 4. In the high-frequency diffusion sheet 10 shown in Fig. 4, the average opening width W and the average separation distance L determined in this manner fall within the ranges of the relational expressions (1) to (3).

[0084] The two openings 15 of the high-frequency diffusion sheet 10 shown in Fig. 4 are part of a circular opening band 14. With this configuration, electromagnetic waves passing through the two openings 15 are diffracted so as to converge and also interfere with each other. This narrows the radiation angle of the electromagnetic waves, and increases the intensity of the electromagnetic waves on the transmission axis of the electromagnetic waves passing through the center of symmetry O (on a straight line that passes through the center of symmetry O and is perpendicular to both the X-axis and Y-axis).

[0085] Furthermore, the radiation angle θ of the electromagnetic wave radiated with the highest intensity among the electromagnetic waves diffused at opening 15 is defined as the inclination angle with respect to the electromagnetic wave traveling straight through opening 15 without being diffused. In this case, radiation angle θ is preferably 20° or less, and more preferably 10° or less. Furthermore, the half-value angle φ of the electromagnetic wave diffused at radiation angle θ is preferably 15° or less.

[0086] This configuration effectively concentrates electromagnetic waves and increases the strength of the electromagnetic waves reaching a specific location, thereby improving the electromagnetic wave reception and relay environments in receivers and repeaters, for example.

[0087] The high-frequency diffusion sheet 10 may have two or more aperture zones 14. In this case, the two or more aperture zones 14 are all arranged concentrically around the center of symmetry O. This makes it possible to increase the intensity of the concentrated electromagnetic waves and further narrow the radiation angle of the concentrated electromagnetic waves compared to when there is only one aperture zone 14. Furthermore, the wavelength range of electromagnetic waves for which such effects can be obtained can be increased to two or more. In other words, it is possible to realize a high-frequency diffusion sheet 10 that can obtain the above effects for electromagnetic waves of various wavelengths.

[0088] Figure 5 is a table showing simulation results S0, S1, S2, and S3 of the far-field radiation pattern of electromagnetic waves transmitted through a radio-frequency diffusion sheet. The table in Figure 5 compares simulation results S1, S2, and S3 when three types of radio-frequency diffusion sheets with different average opening widths W and average separation distances L are used, with simulation result S0 when no radio-frequency diffusion sheet is used. The simulation results S0, S1, S2, and S3 include a graph showing the angular characteristics of the electromagnetic waves in the far field and the half-value angle of the main beam included in this graph.

[0089] In the simulation shown in FIG. 5, the high-frequency diffusion sheet 10 having the annular opening band 14 shown in FIG. 4 is used.

[0090] As can be seen from the simulation result S0 shown in Figure 5, when a radio frequency diffusion sheet is not used, an electromagnetic wave having a main beam with a wide half-value angle (half-value angle is 60°) is output from the radio wave source. When an electromagnetic wave with such angular characteristics passes through a radio frequency diffusion sheet, the angular characteristics shown in the simulation results S1, S2, and S3 are obtained. In all of the simulation results S1, S2, and S3, the spread of the electromagnetic wave is suppressed (it is concentrated) compared to the simulation result S0.

[0091] The main beam of the electromagnetic waves that pass through the high-frequency diffusion sheet extends linearly along the line where the radiation angle θ is 0°. In other words, the radiation angle of the electromagnetic waves is narrowed. The radiation angle θ estimated from the angle characteristics graph is 10° or less.

[0092] Furthermore, the half-value angle of the main beam of the electromagnetic waves that pass through the high-frequency diffusion sheet is kept to 15° or less. The half-value angle is the width of the angular range between the angle at which the gain is at its maximum and the angle at which the strength is halved.

[0093] Furthermore, the intensities of these main beams are greater than the intensities of the electromagnetic waves when no high frequency diffusion sheet is used.

[0094] Therefore, the simulation results S1, S2, and S3 shown in FIG. 5 support the idea that by using the high-frequency diffusion sheet 10 shown in FIG. 4, electromagnetic waves can be diffracted in a concentrated manner and the intensity of the electromagnetic waves can be increased.

[0095] Third Embodiment Next, a third embodiment of the radio frequency diffusion sheet of the present invention will be described.

[0096] Fig. 6 is a plan view showing a radio-frequency diffusion sheet according to a third embodiment, in which Fig. 6(a) is an overall view of the radio-frequency diffusion sheet according to the third embodiment, and Fig. 6(b) is an enlarged partial plan view of the radio-frequency diffusion sheet located in an area [B] surrounded by a dotted line in Fig. 6(a).

[0097] The following description of the radio frequency diffusion sheet 10 of the third embodiment will focus on the differences from the radio frequency diffusion sheet 10 of the first embodiment, and will omit a description of similar points. Note that in Fig. 6, the same reference numerals are used to designate the same components as those of the first embodiment.

[0098] The radio frequency diffusion sheet 10 shown in FIG. 6 is the same as the radio frequency diffusion sheet 10 of the first embodiment shown in FIG. 1, except that the configuration of the electromagnetic wave shielding layer 11 provided in the radio frequency diffusion sheet 10 is different.

[0099] That is, in the high-frequency diffusion sheet 10 of the third embodiment, the electromagnetic wave shielding layer 11 has a plurality of through holes 16 formed with a smaller size than the openings 15 and penetrating through the thickness direction of the electromagnetic wave shielding layer 11 in areas where the openings 15 are not formed, i.e., areas where the transmission of electromagnetic waves is suppressed or blocked.

[0100] Here, as mentioned above, the high-frequency diffusion sheet 10 is used by being attached to a transparent area where electromagnetic waves are allowed to pass, such as a window provided in a building (structure), and transparency may be required in such a transparent area.

[0101] In the high-frequency diffusion sheet 10, the electromagnetic wave shielding layer 11 contains a material that exhibits electromagnetic wave blocking properties as a main material in order to suppress or block the transmission of electromagnetic waves in areas where the openings 15 are not formed, but this material that exhibits electromagnetic wave blocking properties may be translucent or opaque.

[0102] Therefore, even if the electromagnetic wave shielding layer 11 contains a material that exhibits translucency or opacity, in order to impart transparency to the high-frequency diffusion sheet 10, in this embodiment, the electromagnetic wave shielding layer 11 has a plurality of through holes 16 that penetrate through the thickness direction in areas where no openings 15 are formed, and are smaller in size than the openings 15. This allows visible light to pass through the through holes 16 even if the electromagnetic wave shielding layer 11 contains a material that exhibits translucency or opacity, so that transparency can be reliably imparted to the electromagnetic wave shielding layer 11, i.e., the high-frequency diffusion sheet 10.

[0103] The through holes 16 may have any shape and size as long as they are smaller than the openings 15 so as to suppress the transmission of electromagnetic waves while allowing the transmission of visible light. However, when the through holes 16 are square-shaped as shown in FIG. 6(b), the width Wh of the through holes 16 is preferably approximately 50 μm or more and less than 1000 μm, and more preferably approximately 100 μm or more and 250 μm or less. In this case, the spacing Lh between the through holes 16 is preferably approximately 10 μm or more and 150 μm or less, and more preferably approximately 30 μm or more and 75 μm or less. By setting the width Wh and spacing Lh within the above ranges for the square-shaped through holes 16, the through holes 16 can be reliably configured to suppress the transmission of electromagnetic waves while allowing the transmission of visible light.

[0104] The through holes 16 shown in FIG. 6(b) are each square-shaped in plan view, but may also be shaped in other shapes, such as S-shape, U-shape, circle, semicircle, or wave-shaped curved portions, or straight, V-shape, X-shape, L-shape, H-shape, T-shape, W-shape, or U-shape with corners.

[0105] Furthermore, in this embodiment, the through holes 16 are described as having the same shape and being formed at equal intervals in the electromagnetic wave shielding layer 11, but this is not limited to this, and the through holes 16 may have different shapes from each other, or may be arranged randomly in the electromagnetic wave shielding layer 11.

[0106] The high frequency diffusion sheet 10 of the third embodiment also provides the same effects as those of the first embodiment. The dimensions of each part are the same as those of the high-frequency diffusion sheet 10 of the first embodiment.

[0107] In the high-frequency diffusion sheet 10 of the third embodiment having the through-holes 16 configured as described above, the light transmittance of visible light in the wavelength range of 300 nm to 800 nm is preferably 70% to 100%, and more preferably 90% to 100%. This allows the high-frequency diffusion sheet 10 to have excellent light translucency, and when the high-frequency diffusion sheet 10 is attached to a window, it is possible to effectively suppress or prevent a decrease in the efficiency of light capture into the building (structure) through the window. The light transmittance can be measured, for example, using an ultraviolet-visible spectrophotometer.

[0108] Although the high frequency diffusion sheet of the present invention has been described above, the present invention is not limited to this.

[0109] For example, in the high frequency diffusion sheet of the present invention, each component can be replaced with any component that can exert the same function, or any component can be added. [Example]

[0110] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples in any way.

[0111] 1. Preparation of film, etc. <Metal foil laminated resin film> An aluminum foil-PET substrate laminate was prepared as a metal foil laminated resin film by bonding an aluminum foil with an average thickness of 12 μm onto a PET substrate (resin film 12) with an average thickness of 0.1 mm using an acrylic adhesive.

[0112] <Frame> 7A and 7B are diagrams showing an object 150 used for evaluating the diffraction of electromagnetic waves, in which Fig. 7A is a plan view of the object 150, and Fig. 7B is a cross-sectional view taken along line BB in Fig. 7A.

[0113] For the subject 150 shown in Fig. 7, two frames 100 were prepared as frames 100 that do not allow the transmission of electromagnetic waves, one made of aluminum plate with a square outer shape and inner opening, outer dimensions: 200 mm x 200 mm, inner opening size: 100 mm x 100 mm, and the other made of aluminum plate with an outer shape: 200 mm x 200 mm, inner opening size: 150 mm x 150 mm. Fig. 7 shows a high frequency diffusion sheet 10 with four rectangular openings as an example.

[0114] 2. Fabrication of High-Frequency Diffusion Sheet (Sample No. 1A) The prepared metal foil laminated resin film (aluminum foil-PET substrate laminate) was cut to a size of 100 mm x 100 mm. Next, the aluminum foil included in the cut metal foil laminated resin film was irradiated with laser light to form openings 15 (slits) in the aluminum foil that met the conditions such as the shape shown in Table 1. In this way, a high-frequency diffusion sheet 10 (sample No. 1A) was produced, which had a patterned electromagnetic wave shielding layer 11 provided on a resin film 12.

[0115] (Sample No. 2A~29A) High-frequency diffusion sheets 10 of Samples Nos. 2A to 29A were produced in the same manner as Sample No. 1A, except that the conditions such as the shape of the openings 15 formed in the aluminum foil were changed as shown in Table 1 or Table 2.

[0116] (Sample No. 1B) The prepared metal foil laminated resin film (aluminum foil-PET substrate laminate) was cut to a size of 150 mm x 150 mm. Next, the aluminum foil included in the cut metal foil laminated resin film was irradiated with laser light to form openings 15 (slits) in the aluminum foil that met the conditions such as shape shown in Table 3. In this way, a high-frequency diffusion sheet 10 (sample No. 1B) was produced, which had a patterned electromagnetic wave shielding layer 11 provided on a resin film 12.

[0117] (Sample No. 2B~26B) High-frequency diffusion sheets 10 of Samples Nos. 2B to 26B were produced in the same manner as Sample No. 1B, except that the shape of the openings 15 formed in the aluminum foil was changed as shown in Table 3 or Table 4.

[0118] (Sample No. 1C) The prepared metal foil laminated resin film (aluminum foil-PET substrate laminate) was cut to a size of 300 mm x 300 mm. Next, the aluminum foil included in the cut metal foil laminated resin film was irradiated with laser light to form an aperture band 14 in the aluminum foil, including an aperture 15, having the shape shown in Table 5. This produced a high-frequency diffusion sheet 10 (Sample No. 1C) comprising a resin film 12 and a patterned electromagnetic wave shielding layer 11.

[0119] (Sample No. 2C~10C) Except for changing the shape of the openings 15 formed in the aluminum foil as shown in Table 5, the radio frequency diffusion sheets 10 of Samples 2C to 10C were produced in the same manner as Sample No. 1C.

[0120] In Tables 1 to 5, among the high frequency diffusion sheets of each sample number, those that correspond to the present invention are designated as "Examples," and those that do not correspond to the present invention are designated as "Comparative Examples."

[0121] Furthermore, for the radio-frequency diffusion sheets of each example and each comparative example, the graph shown in Fig. 8 was created based on the relationship between the ratio (L / λ) of the distance L between the openings to the wavelength λ of the electromagnetic wave and the ratio (W / λ) of the width W of the opening to the wavelength λ of the electromagnetic wave. Fig. 8 is a scatter plot in which data on the openings of the radio-frequency diffusion sheets of each example and each comparative example are plotted, with L / λ on the horizontal axis and W / λ on the vertical axis. Note that Fig. 8 also shows the ranges of L / λ and W / λ expressed by the above-mentioned relational expressions (1), (2), and (3).

[0122] 3. Evaluation <Measurement of radiation angle θ> First, the high-frequency diffusion sheet 10 of each sample number was attached to a frame 100 having an inner opening corresponding to the size of the sheet, thereby obtaining a test object 150 shown in FIG. 7 for confirming the diffraction and diffusion of electromagnetic waves.

[0123] Next, as shown in FIG. 9, a receiver 20 was placed to measure the electromagnetic waves transmitted through the test object 150. FIG. 9 is a conceptual diagram illustrating a method for measuring the reception intensity at a predetermined deflection angle α of the electromagnetic waves diffracted and diffused by the test object 150. In the method shown in FIG. 9, electromagnetic waves (plane waves WA) having the frequencies shown in Tables 1 to 5 were incident on the high-frequency diffusion sheet 10 of each sample number. The receiver 20 was placed 200 mm away from the center position of the high-frequency diffusion sheet 10, and the reception intensity was measured while changing the deflection angle α of the electromagnetic waves (the angle of the receiver 20 relative to the linear propagation direction of the electromagnetic waves) from 0° to 90°. The deflection angle α of the electromagnetic wave diffused with the highest intensity at the opening 15 was measured, and this was defined as the radiation angle θ [°]. The measurement results are shown in Tables 1 to 5. When measuring the radiation angle θ for the high-frequency diffusion sheet 10 shown in FIG. 4, the distance from the radio wave source to the high-frequency diffusion sheet 10 was set to the value shown in Table 5.

[0124] <Measurement of radio wave intensity ratio at radiation angle θ> The received intensity of the electromagnetic wave at the above radiation angle θ [°] was measured. Next, the ratio of the measured received intensity to the received intensity when the high-frequency diffusion sheet 10 was not placed was calculated, and this was designated as the "radio field intensity ratio at radiation angle θ." This radio field intensity ratio serves as an index that quantitatively represents the directivity of the electromagnetic wave deflected at the radiation angle θ. The obtained radio field intensity ratio was then evaluated in accordance with the following evaluation criteria. The evaluation results are shown in Tables 1 to 4.

[0125] A: The radio wave intensity ratio is 100 times or more. B: The radio wave intensity ratio is 30 times or more but less than 100 times. C: The radio wave intensity ratio is 10 times or more but less than 30 times. D: The radio wave intensity ratio is less than 10 times

[0126] [Table 1]

[0127] [Table 2]

[0128] [Table 3]

[0129] [Table 4]

[0130] <Measurement of half-value angle φ> The half-value angle φ was measured for the electromagnetic waves that passed through the high-frequency diffusion sheets 10 of Samples 1C to 10C. Table 5 shows the measurement results.

[0131] [Table 5]

[0132] It was found that the radio wave intensity ratio at a given radiation angle θ was higher for the high-frequency diffusion sheets of the examples shown in Tables 1 to 4 than for the high-frequency diffusion sheets of the comparative examples. Furthermore, as shown in Fig. 8, it was found that examples that exhibit the above-mentioned effects could be obtained by setting L / λ and W / λ within the given ranges.

[0133] Furthermore, the high-frequency diffusion sheets of the examples shown in Table 5 were able to concentrate electromagnetic waves at a predetermined radiation angle θ. The half-value angle of the electromagnetic waves at this time was sufficiently smaller than the half-value angle before concentration. Furthermore, referring to the simulation results shown in FIG. 5, it was found that the intensity of the electromagnetic waves can be increased by concentrating the electromagnetic waves. Furthermore, as shown in FIG. 8, it was confirmed that examples that exhibit the above-mentioned effects can be obtained by setting L / λ and W / λ within the predetermined ranges.

[0134] From the above, it has been confirmed that by having an opening 15 in which W / λ and L / λ are within a predetermined range, it is possible to deflect electromagnetic waves to a predetermined radiation angle θ and realize a high-frequency diffusion sheet with high directionality. [Explanation of symbols]

[0135] 10 High frequency diffusion sheet 11 Electromagnetic shielding layer 12 Resin film 14 Opening Zone 15 Opening 16 through holes 20 Receiver 100 frame 150 subjects D diameter L separation distance Lh separation distance O center S straight line S0 Simulation Results S1 Simulation results S2 Simulation results S3 Simulation results T average thickness W width Wh width WA plane wave θ radiation angle α deflection angle

Claims

1. A high-frequency diffusion sheet is used to diffuse electromagnetic waves in a high-frequency region when the electromagnetic waves pass through the sheet, and includes an electromagnetic wave shielding layer having electromagnetic wave shielding properties, the electromagnetic wave shielding layer is patterned in a plan view of the high-frequency diffusion sheet, and has a plurality of openings penetrating the electromagnetic wave shielding layer in a thickness direction; a high-frequency diffusion sheet, characterized in that, when the average opening width of the openings is W [mm], the average distance between adjacent openings is L [mm], and the wavelength of the electromagnetic wave is λ [mm], W / λ and L / λ are within the range of the following relational expression (1), the range of the following relational expression (2), or the range of the following relational expression (3): 1.5<W / λ≦2.7 and 0.4≦L / λ≦3.0 (1) 0.3≦W / λ≦1.5, and 1.3<L / λ≦3.0 (2) 0.3≦W / λ≦2.7, and 3.0<L / λ≦16.5 (3)

2. the W / λ and the L / λ are within the range of the relational expression (1) or the range of the relational expression (2), When the electromagnetic waves are transmitted through the high-frequency diffusion sheet and diffused at the opening, the radiation angle θ of the electromagnetic waves diffused with the highest intensity is defined as an inclination angle with respect to the electromagnetic waves traveling straight through the opening without being diffused, The radio frequency diffusion sheet according to claim 1 , wherein the radiation angle θ is greater than 0° and is equal to or smaller than 30°.

3. The radio frequency diffusion sheet according to claim 1 , wherein the opening has a rectangular shape in a plan view.

4. 3. The radio frequency diffusion sheet according to claim 1, wherein the plurality of openings are arranged in a matrix.

5. The radio frequency diffusion sheet according to claim 1 , wherein the plurality of openings are arranged so as to satisfy a point-symmetric relationship with respect to a center of symmetry set in the electromagnetic wave shielding layer.

6. a circular opening zone penetrating the electromagnetic wave shielding layer in the thickness direction, The radio frequency diffusion sheet according to claim 5 , wherein the plurality of openings are part of the opening band.

7. When the radiation angle of the electromagnetic wave radiated with the highest intensity among the electromagnetic waves diffused by the opening is defined as an inclination angle with respect to the electromagnetic wave traveling straight without being diffused by the opening, the radiation angle is 20° or less; 7. The radio frequency diffusion sheet according to claim 5, wherein the half-value angle of the electromagnetic waves diffused at the radiation angle is 15 degrees or less.

8. The high frequency diffusion sheet according to claim 1 , wherein the electromagnetic wave shielding layer shields the electromagnetic waves by reflecting or absorbing the electromagnetic waves.

9. 2. The radio frequency diffusion sheet according to claim 1, wherein the electromagnetic wave shielding layer is a metal thin film layer or a metal powder-containing adhesive layer containing metal powder and a binder resin.

10. 2. The radio frequency diffusion sheet according to claim 1, wherein the radio frequency diffusion sheet comprises a transparent resin film, and the electromagnetic wave shielding layer is bonded to the resin film.

11. The high-frequency diffusion sheet according to claim 1 , wherein the high-frequency diffusion sheet is configured to diffuse the electromagnetic waves by diffracting the electromagnetic waves through the openings when the electromagnetic waves pass through the high-frequency diffusion sheet.

12. 2. The radio frequency diffusion sheet according to claim 1, wherein the electromagnetic wave shielding layer has an average thickness T of 0.01 [mu]m or more and 70.0 [mu]m or less.

13. 2. The high frequency diffusion sheet according to claim 1, wherein the frequency of the electromagnetic waves is in the range of 1 GHz to 80 GHz.

14. The high frequency diffusion sheet according to claim 1 , which is attached to a transmission area of ​​a building where the transmission of the electromagnetic waves is permitted.

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