Electromagnetic wave reflecting plate and electromagnetic wave reflecting device

Abstract

The purpose of the present invention is to provide an electromagnetic wave reflecting plate having high durability against dimensional errors or damage such as cracking, chipping, falling, and detaching of an element pattern.　Thus, this electromagnetic wave reflecting plate is characterized by including a reflection control region composed of a dielectric layer and a plurality of element patterns, and is characterized in that a planar shape of each of the element patterns includes a round corner part or an inverted round corner part. It is preferable that the round corner part includes an arc for which the curvature radius of a curvature circle A thereof has a length that is 1 / 2 or less of a reference length P, in a plan view, and the inverted round corner part includes an arc for which the curvature radius of a curvature circle B thereof has a length that is three times or less of the reference length P, in a plan view. Further, in this electromagnetic wave reflecting plate, a cross-sectional shape of the element pattern may include the round corner part or the inverted round corner part. It is preferable that the round corner part includes an arc for which a curvature radius of a curvature circle C thereof has a length that is 1 / 6 or more of a thickness d of the element pattern, in a cross-sectional view, and the inverted round corner part includes an arc for which a curvature radius of a curvature circle D thereof has a length that is 1 / 6 or more of the thickness d of the element pattern, in a cross-sectional view.

Description

Electromagnetic wave reflector and electromagnetic wave reflector

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

[0002] As various millimeter-wave compatible wireless devices are put into practical use, the occurrence of radio wave dead zones has become a problem. Compared to the increasingly popular VHF and UHF waves, millimeter-wave radio waves are significantly more susceptible to attenuation and have a high degree of directionality. For this reason, millimeter-wave radio waves have difficulty escaping obstacles due to diffraction. Furthermore, as data communication speeds dramatically increase in 5G and 6G wireless communications, the problem of dead zones due to the higher frequency of electromagnetic waves may become more serious. To achieve widespread 5G and 6G communications, the number of base stations must be increased. However, the high cost of increasing base stations makes it difficult to rapidly increase the number of base stations.

[0003] Reflectors that reflect millimeter-wave band radio waves (hereinafter referred to as "millimeter-wave reflectors") or reflectarrays (electromagnetic wave reflectors) have been proposed to eliminate radio wave blind zones. The metasurface reflector described in Patent Document 1 can function as the millimeter-wave reflector. This metasurface reflector (hereinafter also referred to as "electromagnetic wave reflector" or "reflectarray") has multiple reflection units that reflect millimeter waves at a predetermined angle on one side of a planar dielectric, and a metal layer that functions as a ground on the other side. Each reflection unit is composed of multiple metal patterns (hereinafter also referred to as "element patterns") with different shapes. Millimeter waves incident on the surface where the reflection units are provided are reflected by both the individual metal patterns and the metal layer. These reflected waves interfere with each other, resulting in the millimeter waves being reflected with a phase different from that at the time of incidence. Furthermore, interference waves based on different metal patterns have different phases, resulting in secondary interference. Therefore, by appropriately configuring the shape of the multiple metal patterns that make up the reflection units, the reflection direction of the incident millimeter waves can be set to a desired direction. Reflectarrays are also described in Patent Documents 2 to 4.

[0004] Japanese Patent Application Laid-Open No. 2021-48465 International Publication No. 2022 / 163813 Patent No. 7206571 Japanese Patent Application Laid-Open No. 2022-119212

[0005] In principle, electromagnetic wave reflectors can be attached to the interior or exterior surfaces of buildings as relatively large-area building materials, and are expected to efficiently eliminate blind zones. However, there are challenges in manufacturing reflectarrays with element patterns including a cross-shaped (hereinafter also referred to as "cross patch") shape, as described in Patent Document 1, with stable characteristics and a high yield rate. Specifically, because electromagnetic wave reflectors are composed of multiple element patterns with different shapes as described above, when the element patterns are removed using a method such as etching, variations in manufacturing conditions can cause the edges of the element patterns constituting the electromagnetic wave reflector to become rounded (become rounded), or over-etching can occur, resulting in localized thinner or remaining element patterns than expected, resulting in errors in the shape and dimensions of the element patterns. Furthermore, chipping or damage to the edges of the element patterns can cause abnormalities in the element shape. As described above, in the element formation process of an electromagnetic wave reflector, it is inevitable that errors will occur in the shape and dimensions of the element pattern. In the electromagnetic wave reflector of Patent Document 1, if a dimensional error occurs in the design parameters (which in this case correspond to the element pattern shape), the reflection phase in each reflection unit having a cross-shaped element pattern will change significantly from the design value, resulting in a decrease in the reflection intensity in the desired direction.

[0006] Furthermore, reflectarrays generally have a configuration in which an element pattern is formed on a base layer using a conductive layer, and an additional functional layer (hereinafter simply referred to as a "functional layer") such as a protective layer is further laminated on the conductive layer to cover the element pattern. If bubbles are generated around the element pattern during the process of laminating the additional functional layer onto the element pattern, the reflection phase in the cell where the element pattern is located will significantly deviate from the design value. If the number of cells with such defects exceeds a certain percentage, adverse effects such as increased unwanted reflection and reduced reflection intensity in the desired direction will occur. The reflectarrays of Patent Documents 2 and 3 do not even recognize the problem of bubble contamination in the element pattern and the issue of how to suppress it.

[0007] Bubbles are particles formed by enclosing gas that forms inside or on the surface of a liquid or solid, and are covered with a single surfactant layer. Foam is a collection of bubbles, and may be covered with a double surfactant layer. Foam is a general term that includes air bubbles and foam. Bubble particles can take on various shapes, including spheres and ellipsoids. The size of a bubble (bubble diameter) is defined as the length of the longest line segment connecting two points on the bubble's outline (described below).

[0008] The inventors noticed that ultrafine bubbles, which have a diameter of less than 1 μm, are negatively charged in neutral water, so they repel each other and do not combine, whereas microfibers, which have a diameter of approximately 1 μm or more, come into contact with each other and coalesce to form a single larger bubble or foam, which has a more adverse effect on reflection characteristics.

[0009] Although Patent Document 4 is an antenna technology and is in a different technical field from reflectarrays, it describes providing an inclined or curved surface on the side shape of the conductive layer to prevent gaps from occurring between the conductive layer and the additional function layer. However, there is no recognition of the issue of the effect of air bubble size on reflection characteristics, and it is not clear in particular about the side shape of the element pattern aimed at preventing microfiber-sized air bubbles.

[0010] Therefore, an object of the present invention is to provide a technology that improves resistance to factors that cause defects in the manufacturing process of an electromagnetic wave reflector. For example, it is desirable to provide an electromagnetic wave reflector that is highly resistant to damage or dimensional errors such as cracks, chips, detachment, or peeling of the element pattern. It is also desirable to provide a reflectarray that can suppress microfiber-sized bubbles.

[0011] To solve the above problems, a representative electromagnetic wave reflector of the present invention includes a ground layer, a dielectric layer, and an element pattern, the plane or side of which includes a shape that is resistant to factors that cause defects in the manufacturing process, and further includes a reflection control region consisting of a dielectric layer and a plurality of element patterns, and the plane shape of the element pattern may include rounded corners. The element pattern may further include an additional functional layer covering at least the upper surface and the side surface, and the thickness L (μm) of the element pattern satisfies formula (1): 1.0≦L (1). The side surface has a first end connected to the lower surface of the element pattern and a second end connected to the upper surface, and the angle α (°) between a line connecting the first end and the second end in a cross section and a perpendicular line from the second end to the lower surface satisfies formula (2): α≧10 (2). When the side surface is divided into N points at equal intervals in the thickness direction using N obtained from formula (3), the angle βi between a line connecting the (i-1)th point and the i-th point in a cross section and a perpendicular line from the second end to the lower surface satisfies formula (4) for any i. N=[L] (3) βi≧0 (4) (i is an integer satisfying 1≦i≦N+1.)

[0012] According to the present invention, it is possible to improve resistance to factors that cause defects in the manufacturing process of an electromagnetic wave reflector. For example, it is possible to provide an electromagnetic wave reflector that is highly resistant to damage or dimensional errors such as cracking, chipping, falling off, or peeling of the element pattern. It is also possible to provide a reflectarray that can suppress microfiber-sized bubbles, for example. Problems, configurations, and effects other than those described above will become clear from the description of the following embodiments.

[0013] FIG. 1 is a cross-sectional view of a reflectarray. FIG. 2 is a diagram showing an example of the arrangement of a functional layer 15. FIG. 3 is a diagram showing the overall configuration of the reflectarray. FIG. 4 is a diagram showing an example of the arrangement of unit cells according to the direction in which asymmetric reflection is generated. FIG. 5 is a diagram showing an example of the arrangement of unit cells according to the direction in which asymmetric reflection is generated. FIG. 6 is a diagram showing an example of the arrangement of unit cells according to the direction in which asymmetric reflection is generated. FIG. 7 is a diagram showing an example of the shape of an element pattern. FIG. 8 is a diagram showing an example of the shape of an element pattern when viewed in plan. FIG. 9 is an enlarged schematic view of the vicinity of a rounded corner Ar. FIG. 10 is an enlarged schematic view of the vicinity of a rounded corner Br. FIG. 11 is a diagram showing an example of the shape of an element pattern when viewed in cross section. FIG. 12 is an enlarged schematic view of the vicinity of a rounded corner Cr. FIG. 13 is an enlarged schematic view of the vicinity of a rounded corner Dr. FIG. 14 is a graph showing the reflection characteristics of a reflectarray according to Comparative Example A1. FIG. 15 is a graph showing the reflection characteristics of a reflectarray according to Example A1. FIG. 16 is a graph showing the reflection characteristics of the reflectarray according to Example A2. FIG. 17 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A1 and Examples A1 and A2. FIG. 18 is a graph showing the reflection characteristics of the reflectarray according to Comparative Example A2. FIG. 19 is a graph showing the reflection characteristics of the reflectarray according to Example A3. FIG. 20 is a graph showing the reflection characteristics of the reflectarray according to Example A4. FIG. 21 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A2 and Examples A3 and A4. FIG. 22 is a graph showing the reflection characteristics of the reflectarray according to Comparative Example A3. FIG. 23 is a graph showing the reflection characteristics of the reflectarray according to Example A5. FIG. 24 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A3 and Example A5. FIG. 25 is a graph showing the reflection characteristics of the reflectarray according to Comparative Example A4. FIG. 26 is a graph showing the reflection characteristics of the reflectarray according to Example A6. Fig. 27 is a graph showing the reflection characteristics of the reflectarray according to Example A7. Fig. 28 is a graph showing the results of comparing the reflection characteristics of the reflectarray according to Comparative Example A4 with those of Examples A6 and A7. Fig. 29 is a graph showing the reflection characteristics of the reflectarray according to Example A8.FIG. 30 is a graph showing the reflection characteristics of the reflectarray according to Example A9. FIG. 31 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A1 and Examples A8 and A9. FIG. 32 is a graph showing the reflection characteristics of the reflectarray according to Example A10. FIG. 33 is a graph showing the reflection characteristics of the reflectarray according to Example A11. FIG. 34 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A2 and Examples A10 and A11. FIG. 35 is a graph showing the reflection characteristics of the reflectarray according to Example A12. FIG. 36 is a graph showing the reflection characteristics of the reflectarray according to Example A13. FIG. 37 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A3 and Examples A12 and A13. FIG. 38 is a graph showing the reflection characteristics of the reflectarray according to Example A14. FIG. 39 is a graph showing the reflection characteristics of the reflectarray according to Example A15. FIG. 40 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A4 and Examples A14 and A15. FIG. 41 is an example of a schematic diagram showing an enlarged view of the reflection control region. FIG. 42A is a schematic diagram showing an example of a variation in the layer structure of the reflectarray. FIG. 42B is a schematic diagram showing an example of a variation in the layer structure of the reflectarray. FIG. 43 is a photograph of a portion of the element pattern observed from the top surface of the functional layer using an optical microscope. FIG. 44 is a schematic cross-sectional view showing a portion of the basic layer structure of the reflectarray, including the side surface of the element pattern. FIG. 45 is an enlarged schematic diagram of the vicinity of the first side surface of the element pattern. FIG. 46A is a schematic diagram showing an example of the division of the side surface shape of the element pattern and the inclination angles α and βi. FIG. 46B is a schematic diagram showing an example of the division of the side surface shape of the element pattern and the inclination angles α and βi. FIG. 47 is a graph showing the reflection angle and reflection intensity (bistatic RCS) in Examples and Comparative Examples.

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments. In addition, in the description of the drawings, identical parts are denoted by the same reference numerals. When there are multiple components having the same or similar functions, they may be described by using the same reference numerals with different subscripts. Furthermore, when it is not necessary to distinguish between these multiple components, the subscripts may be omitted. The position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc., in order to facilitate understanding of the invention. Therefore, the present disclosure is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

[0015] In the following description, an xyz coordinate system is applied, and the reflectarray is arranged on the xy plane. The terms "plane," "planar view," and "planar shape" refer to a view from the z-axis direction, and the terms "cross section," "cross-sectional view," and "cross-sectional shape" refer to a view cut along the xz or yz plane. Unless otherwise specified, the "surface" of a layer refers to the upper surface (positive side of the z-axis) of the layer parallel to the xy plane, and the "side surface" refers to the outer peripheral surface sandwiched between the upper surface (positive side of the z-axis) and the lower surface (negative side of the z-axis). The distance in the z-axis direction in the xyz coordinate system is sometimes referred to as "thickness." The z-axis direction is also sometimes referred to as the thickness direction.

[0016] (Layer Structure) The layer structure of the reflectarray will be described. Fig. 1 is a cross-sectional view of the reflectarray 1. The reflectarray 1 includes a ground layer 11, a dielectric layer 12, and an element pattern layer 13 (hereinafter also referred to as the "basic structure"). The element pattern layer 13 is a layer having a plurality of element patterns 14 (the element patterns may also be simply referred to as elements). As will be described later, the thickness of the element pattern layer 13 is, for example, 10 nm to 18 µm.

[0017] (Ground Layer) The ground layer 11 is provided to reflect electromagnetic waves that reach the reflect array 1. It is also used to support and protect the dielectric layer 12, which will be described later. The ground layer 11 is made of a conductive material such as an inorganic oxide material, a metal material, or a conductive organic material.

[0018] For example, inorganic oxide materials and metal materials include indium tin oxide (ITO), indium zinc oxide (IZO), zinc aluminum oxide (AZO), gallium zinc oxide (GZO), antimony tin oxide, Ag, Al, Au, Pt, Pd, Cu, Co, Cr, In, Ag—Cu, Cu—Au, and Ni. Nanoparticles or nanowires containing at least one of these materials may also be used. Examples of conductive organic materials include polythiophene derivatives, polyacetylene derivatives, polyaniline derivatives, polypyrrole derivatives, carbon nanotubes, and graphene. Cu and Al are particularly preferred from the standpoints of material cost, conductivity, and film formability. Furthermore, in order to reflect electromagnetic waves, it is desirable that the surface resistance value of the ground layer 11 be 100 Ω / □ or less, and if this condition can be met, inorganic oxide materials such as ITO or organic materials such as a mixture of polyethylenedioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT / PSS) can also be used. By using inorganic oxide materials or organic materials, a transparent reflect array can also be produced.

[0019] The above materials can be used in a continuous film, mesh, punched, or periodic structure. Here, mesh refers to a conductor having a network of holes (openings) on its surface. When the conductor is formed in a mesh shape, the mesh may be rectangular or rhombic. When the mesh is formed in a rectangular shape, the mesh is preferably square. Square meshes provide good design. A random shape formed by a self-assembly method is also acceptable. A random shape can be used to prevent moire. When processing metal into a mesh shape, methods such as punching a metal plate or etching a metal plate can be used. When the ground layer is mesh-shaped or a transparent conductive material is used, the reflect array exhibits visible light transparency, allowing the appearance to be maintained after installation.

[0020] When the ground layer 11 is formed in a mesh shape, the line width of the mesh is preferably 5 μm to 30 μm, more preferably 6 μm to 15 μm. The line spacing of the mesh is preferably 50 μm to 500 μm, more preferably 100 μm to 300 μm. Furthermore, when the wavelength at the operating frequency (hereinafter also referred to as the "design frequency") is λ (m), the line spacing of the mesh is preferably 0.5×λ or less, more preferably 0.1×λ or less, and even more preferably 0.01×λ or less. If the line spacing of the mesh is 0.5×λ or less, the performance of the ground layer 11 can be exhibited. If the line spacing of the mesh is 0.5×λ or more, more electromagnetic waves will pass through the ground layer, thereby reducing the reflection performance of the reflect array. Furthermore, the line spacing of the mesh may be 0.001×λ or more.

[0021] The thickness of the ground layer is, for example, 10 nm to 105 μm. When an inorganic oxide material or a metal material is used for the ground layer 11, the thickness of the ground layer 11 is preferably 18 μm or less, and more preferably 50 nm to 2 μm. A film thickness of 50 nm or more makes it easier to form a uniform film without pinholes, and the ground layer 11 can function more satisfactorily. On the other hand, a film thickness of 2 μm or less can maintain sufficient flexibility and prevent cracks from occurring in the ground layer 11 due to external factors such as bending or pulling. Making the ground layer 11 1 μm or less improves flexibility, making it easier to attach to curved surfaces, etc., and also enables weight reduction.

[0022] When a metal material is used, the ground layer 11 can be formed by a method selected from dry coating such as sputtering or vapor deposition, wet coating such as gravure coating by turning the metal material into ink, or surface treatment such as plating. Alternatively, a rolled metal plate can be used as the ground layer 11. When an inorganic oxide material is used, dry coating can be selected as the method for forming the ground layer 11. When an organic material is used, wet coating can be selected as the method for forming the ground layer 11. The ground layer 11 can also be formed by painting or spraying. When the ground layer is in the form of a thin film formed by plating or vapor deposition, the flexibility of the reflectarray can be improved, which allows it to be used on curved surfaces and to be produced using a roll-to-roll process.

[0023] When the ground layer is in the form of a thin film, its thickness is preferably greater than the skin depth calculated from equation (6) (described later), as with the element pattern. Furthermore, in order to increase the reflection efficiency of electromagnetic waves, it is also important to reduce the loss caused by the ground layer. Therefore, it is preferable that the surface roughness of the ground layer is small.

[0024] When the ground layer has a periodic structure, it can selectively reflect or transmit specific frequencies. For example, when a structure with periodically arranged patch-like conductive patterns is used as the ground layer, it is possible to reflect only specific frequencies, thereby imparting the ability to transmit frequencies other than the operating frequency. Furthermore, when a structure with periodically arranged holes where no conductive material exists is used, it is possible to design a reflect array that asymmetrically reflects the operating frequency while transmitting only specific frequencies.

[0025] In the present disclosure, surface resistance is measured in accordance with JIS-K-7194. The surface resistance measurement method can be appropriately selected from the four-terminal method, two-terminal method, four-probe method, dielectric method, eddy current method, etc. The surface resistance value of the ground layer can be measured using, for example, Loresta GP MCP-T610 (trade name, manufactured by Mitsubishi Chemical Analytech Co., Ltd.).

[0026] (Dielectric Layer) In FIG. 1, the dielectric layer 12 can be made of synthetic resins such as ethylene vinyl acetate copolymer (EVA), vinyl chloride, urethane, acrylic, acrylic urethane, polyolefin, polyethylene, polypropylene, silicone, polyethylene terephthalate, polyester, polystyrene, polyimide, polycarbonate, polyamide, polysulfone, polyethersulfone, polytetrafluoroethylene, cycloolefin polymer, and epoxy, or synthetic rubber materials such as polyisoprene rubber, polystyrene butadiene rubber, polybutadiene rubber, chloroprene rubber, acrylonitrile-butadiene rubber, butadiene rubber, butyl rubber, acrylic rubber, ethylene propylene rubber, and silicone rubber, as the resin component. When the relative dielectric constant is also listed, the following are available: polyethylene (εr = 2.2 to 2.4), polypropylene (εr = 2.0 to 2.6), polystyrene (εr = 2.4 to 2.6), polyvinyl chloride (εr = 2.8 to 8.0), AS resin (εr = 2.6 to 3.1), ABS resin (εr = 2.4 to 4.1), polyethylene terephthalate (εr = 2.9 to 3.0), acrylic resin (εr = 2.7 to 4.5), urethane resin (εr = 4.0 to 7.1), epoxy resin (εr = 2.5 to 6.0), nylon (εr Examples of suitable dielectric constants include polyimide (εr = 3.0 to 5.0), polyimide (εr = 2.4 to 2.7), fluororesin (εr = 2.0 to 2.6), polycarbonate (εr = 2.9 to 8.9), polyphenylene ether (εr = 2.8 to 8.2), polyphenylene sulfide (εr = 3.2 to 4.6), polyvinylidene fluoride (εr = 6.4 to 10.0), polyethylene naphthalate (εr = 2.9), phenolic resin (εr = 3.0 to 12.0), and cycloolefin polymer (εr = 2.3 to 2.5). Here, εr indicates the relative dielectric constant. In particular, polyethylene (PS), polyethylene terephthalate (PET), and cycloolefin polymer (COP) are preferred due to their low cost and versatility. Composite materials may also be used in which glass fiber, synthetic fiber, carbon fiber, nonwoven fabric, or paper is impregnated with these resin components. Examples of composite materials include paper / phenolic resin, paper / epoxy resin, glass / epoxy resin, and glass / fluororesin composite materials.These resin materials and synthetic rubber materials can be used alone or in combination of two or more types. The dielectric layer 12 can be a single layer or multiple layers. The dielectric layer 12 may also be a foam obtained by foaming the above materials. A highly flexible foam is preferably used as the foam. The use of a foam allows air to be contained within the dielectric layer, thereby lowering the dielectric constant.

[0027] In addition to the above materials, the dielectric layer 12 may be composed of a resin component containing a metal compound. The density and dielectric constant of the dielectric layer 12 can be adjusted depending on the type and content of the metal compound in the dielectric layer 12. By including a metal compound in the dielectric layer 12, flame retardancy can be improved and a fire spread prevention effect can be imparted. Examples of metal compounds include barium titanate, titanium oxide, zinc oxide, lead zirconate titanate, strontium tantalate bismuthate, and bismuth ferrite. The metal compound is preferably in the form of a powder (e.g., nanoparticles).

[0028] Another example is the use of a mixture containing resin components or a dielectric compound and a resin component from the viewpoint of adjusting the dielectric constant. The dielectric constant of the mixture can be adjusted depending on the selection of the dielectric compound and its content. The dielectric constant of the mixture can be predicted, for example, using the Maxwell-Garnett law. In a mixture of a dielectric A with a dielectric constant εa and a dielectric B with a dielectric constant εb, when the volume fraction of dielectric A is δa, the dielectric constant εm of the mixture is expressed by the following relational expression (11):

[0029] Examples of the dielectric compound include barium titanate (εr=250 to 20,000), titanium oxide (εr=83 to 183), lead zirconate titanate, strontium tantalate bismuthate, and bismuth ferrite.

[0030] When a transparent dielectric is used, the reflectarray exhibits visible light transmittance, making it possible to maintain the appearance after installation.

[0031] The relative dielectric constant of the dielectric layer 12 is preferably in the range of 1 or more and 20 or less, more preferably in the range of 1 or more and 10 or less, and even more preferably in the range of 2 or more and 4 or less. When the relative dielectric constant is within the above range, it tends to be easier to obtain the desired reflection phase characteristics in the reflectarray 1. Furthermore, the dielectric loss tangent is preferably in the range of 0.00005 or more and 0.01 or less, and more preferably in the range of 0.00005 or more and 0.001 or less. When it is within the above range, a reflectarray 1 with low dielectric loss can be produced.

[0032] The dielectric layer 12 can be formed by, for example, wet coating such as die coating, comma coating, or gravure coating, melt extrusion such as a T-die method or an inflation method, a calendar film forming method, a solution casting method, a heat press method, etc. Alternatively, a co-extrusion method in which a film is formed by extruding a plurality of resins into multiple layers may be used.

[0033] The thickness of the dielectric layer 12 is selected appropriately depending on the design frequency. When the design frequency is 28 GHz, it is preferably 40 μm or more and 250 μm or less, and more preferably 50 μm or more and 200 μm or less. If it is too thin, it becomes difficult to ensure the reflection phase, making design of the reflectarray 1 difficult. On the other hand, if it is too thick, it tends to become difficult to ensure the reflection phase, lose flexibility, and increase the total thickness of the reflectarray 1, making it difficult to save space. For this reason, the thickness of the dielectric layer 12 is preferably 250 μm or less. When the design frequency is 60 GHz, the thickness t of the dielectric layer 12 is preferably 10 μm or more and 250 μm or less. When the design frequency is 100 GHz or more, setting the thickness of the dielectric layer 12 to a few μm or more and 100 μm or less makes it easier to design the reflectarray 1.

[0034] (Element Pattern Layer) The element pattern layer 13 is provided to asymmetrically reflect incident electromagnetic waves and reflect them in a direction different from that of symmetric reflection. The thickness of the element pattern layer 13 is, for example, 10 nm to 105 μm. In consideration of flexibility and film-forming properties, a thinner thickness is preferable as long as it does not affect the function of asymmetrically reflecting electromagnetic waves.

[0035] The element pattern layer 13 preferably has a surface resistance of 100 Ω / □ or less. The material used for the element pattern layer 13 is, for example, a conductive material. The same material as that used for the ground layer 11 can be used as this material. For example, at least one of the ground layer 11 or the element pattern layer 13 can be formed from Cu or Al. Cu has excellent conductivity, which reduces conductor loss. Al has low density, is lightweight, and is inexpensive, allowing for the formation of a lightweight and inexpensive reflect array 1. Furthermore, the thickness of at least one layer can be 1 μm or less. A thickness of 1 μm or less improves flexibility, making it easier to install the reflect array 1 on curved surfaces and achieving weight reduction. A conductive inorganic or organic material may also be formed on the dielectric layer 12. From the perspectives of flexibility, film formability, stability, sheet resistance, and low cost, it is preferable to use a film formed by vapor deposition, as the formation method described below, for the element pattern layer 13. The above materials can be used in a continuous film, mesh, or punched shape.

[0036] The element pattern layer 13 can be formed by forming a conductive material over the entire surface of the dielectric layer 12 to form a continuous film, and then processing the film to form the element pattern layer 13, or by forming the element pattern layer 13 directly on the dielectric layer 12.

[0037] As a method for forming a conductive material as a continuous film over the entire surface of the dielectric layer 12, for metal, dry coating such as sputtering or vapor deposition, plating or gravure coating using metallic ink, wet coating such as die coating, etc. can be selected. Alternatively, a rolled metal plate can be attached to the dielectric layer 12. Similarly, a continuous film can be formed by dry coating for inorganic oxide materials, or wet coating for organic materials. Painting or spraying methods can also be used.

[0038] The element pattern is formed by removing unnecessary portions of the formed continuous film using a removal process such as dry etching, wet etching, or cutting. When removing the element pattern by etching, the edges of the element pattern constituting the reflect array may be rounded (in other words, may become rounded), pinholes may occur, the cross-sectional shape may become forward or reverse tapered, or undercut or overetching may occur. While such shape changes are expected to occur during the etching process, the reflection phase characteristics are acceptable as long as the direction of the main beam of the reflected electromagnetic waves in the basic configuration is within a range of approximately ±5° of the designed reflection angle. Formation by cutting, printing, dry coating, plating, painting, or spraying is also acceptable.

[0039] In addition, methods for directly forming the element pattern layer 13 on the dielectric layer 12 include printing using letterpress printing, lithographic printing, intaglio printing, stencil printing, transfer printing, etc., or masking the dielectric layer 12 except for the element pattern 14 portion with masking tape or masking agent, etc., and then forming the element pattern layer 13 using dry coating, plating, painting, or spraying.

[0040] The cross-sectional shape of the element pattern is preferably a forward tapered shape that widens from the top to the bottom. The forward tapered shape increases the surface area of ​​the element pattern, which increases the adhesion to the functional layer when the functional layer is laminated, as described below, and makes it possible to suppress the inclusion of air bubbles.

[0041] The material of the element pattern may be the same as that of the ground layer, or a different material may be used. For example, at least one of the ground layer and the element pattern may be formed from Cu or Al. Cu has excellent conductivity, which reduces conductor loss. Al has low density, is lightweight, and is inexpensive, allowing for the formation of a lightweight and inexpensive reflect array.

[0042] When the element pattern is mesh-shaped, the line width of the mesh is preferably 5 μm to 30 μm, more preferably 6 μm to 15 μm. The line spacing of the mesh is preferably 50 μm to 500 μm, more preferably 100 μm to 300 μm. Furthermore, when the wavelength at the operating frequency is λ, the line spacing of the mesh is preferably 0.5 × λ or less, more preferably 0.1 × λ or less, and even more preferably 0.01 × λ or less. If the line spacing of the mesh is 0.5 × λ or less, performance can be ensured. If the line spacing of the mesh is 0.5 × λ or more, more electromagnetic waves will pass through the ground layer, thereby reducing the reflection performance of the reflectarray. Furthermore, the line spacing of the mesh may be 0.001 × λ or more. When the element pattern is mesh-shaped or when a transparent conductive material is used, the reflectarray exhibits visible light transparency, allowing the appearance to be maintained after installation.

[0043] When the element pattern is in the form of a thin film, adhesion with the additional function layer and the adhesion improving layer is improved, and the flexibility of the reflectarray can be improved, thereby enabling use on curved surfaces and roll-to-roll production processes. When the element is formed as a thin film, its thickness is preferably greater than the skin depth calculated from the known formula (6), where d is the skin depth, ω is the angular frequency, μ is the magnetic permeability of the material, and σ is the electrical conductivity of the material.

[0044] Furthermore, in order to increase the reflection efficiency of electromagnetic waves, it is necessary to reduce loss due to the element pattern, and therefore it is preferable that the surface roughness of the element pattern is small.

[0045] (Functional Layer) (Addition of Function) Functions can be added to the reflectarray as needed. Examples of functions that can be added include anti-degradation properties, design properties, protection / scratch resistance, waterproof properties, gas / water vapor barrier properties, flame retardancy, non-combustibility, self-extinguishing properties, weather resistance, stain resistance, antibacterial / antiviral properties, chemical resistance, deodorizing properties, and adhesive / adhesive properties. One of these functions may be added, or a combination of multiple functions may be added. The thickness of the additional functional layer is, for example, 5 μm or more and 6 mm or less.

[0046] As a method for adding a function, a functional layer, which is a layer having a function described below, may be added to the reflectarray, or a material that imparts a function may be mixed when forming the dielectric layer 12. In addition, the reflectarray may be subjected to a coating process or the like using a material having a function.

[0047] Methods for laminating a sheet-like additional functional layer include bonding using lamination, extrusion lamination, etc., and methods for applying a liquid additional functional layer include, but are not limited to, printing, coating, dry lamination, wet lamination, etc. Furthermore, if the additional functional layer does not have tackiness or adhesiveness, there is a method for adhering it to the reflectarray using an adhesion improving layer (adhesive).

[0048] Depending on the purpose, the functional layer can be formed on at least one of the element pattern layer 13, the ground layer 11, and the dielectric layer 12. The functional layer can be formed on the entire surface of the element pattern layer 13, the ground layer 11, or the dielectric layer 12, or it can be formed on only a part of any of the layers.

[0049] FIG. 2 is a diagram showing an example of the arrangement of the functional layer 15. The lamination method on the element pattern layer 13 side may be such that the functional layer 15 fills the gaps between the plurality of element patterns 14, as in the reflectarray 2a ( FIG. 2( a) ), or such that the functional layer 15 contacts the upper surfaces of the element patterns 14 while maintaining the gaps between the plurality of element patterns 14, as in the reflectarray 2b ( FIG. 2( b) ), or such that the functional layer 15 does not contact the upper surfaces of the element patterns 14, as in the reflectarray 2c ( FIG. 2( c) ). Note that when the reflectarrays 2a to 2c have a common configuration excluding the functional layer 15, the reflectarrays 2a to 2c each have different reflection characteristics. Therefore, it is possible to change the characteristics of the reflectarray by changing the lamination method of the functional layer 15.

[0050] (Examples of Functions) Weather Resistance Possible causes of deterioration of reflectarrays include oxidation due to exposure to the atmosphere, absorption of water vapor, and alteration due to light (ultraviolet rays) such as sunlight. In order to prevent deterioration due to oxygen and water vapor, it is possible to provide a layer with excellent gas barrier properties, such as a barrier film, on the surface of the reflectarray. In addition, to prevent deterioration due to oxygen in particular, it is necessary for the oxygen permeability of the functional layer to be 500 cc / m ２ It is preferable that the barrier strength is 1 / 4 atm / day or less. If this condition can be met, films may be laminated, or an overcoat layer may be applied by dry coating or wet coating. These layers may be single layers, or multiple layers may be combined or laminated. Examples of barrier films include simple films such as ethylene-vinyl alcohol copolymer resins, co-extruded multilayer nylon (Ny) films, and wet-coated films such as polyvinylidene chloride (PVDC)-coated and polyvinyl alcohol (PVA)-coated films.

[0051] In addition, to prevent deterioration of the dielectric layer 12, an antioxidant, a deterioration inhibitor, or an antioxidant material may be added when forming the dielectric layer 12. Similarly, to prevent deterioration due to water vapor, a material having a water vapor permeability of 300 g / m ２ It is preferable to provide a layer having a luminance of 1000 nm or less. To protect against light from sunlight, etc., it is possible to provide a film having UV-cutting properties or a layer having light-shielding properties. In addition, an ultraviolet scattering agent, an ultraviolet absorber, or a light stabilizer may be added. Examples of UV-cutting films include vinyl chloride resins and polyolefin resins.

[0052] Design When a reflectarray is installed on the exterior or interior of a building, for example, it may be possible to impart a design to it so that it blends in with the space. Specifically, the design can be imparted by attaching a designed sheet material to the reflectarray using an adhesive, or by fusing and attaching a sheet material to the reflectarray by applying heat and pressure. Examples of such decorative sheets include a decorative sheet in which a printed pattern and an embossed surface pattern are harmonized by laminating a base sheet, a base pattern layer, and a transparent thermoplastic resin layer in this order, and a decorative sheet in which a color similar to that of real wood or stone is achieved by laminating a pattern layer, a transparent resin layer, and a surface protection layer in this order.

[0053] Examples of materials include polyester-based materials such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), and olefin-based materials such as polyethylene, polypropylene, polystyrene, cycloolefin polymers, and cycloolefin copolymers.

[0054] In a plan view of the reflect array 1, the functional layer 15 covers the element pattern layer 13. Therefore, by configuring the functional layer 15 in a predetermined manner, the element pattern layer 13 can be made invisible, improving the appearance. There are no particular limitations on the specific manner in which the element pattern layer 13 can be made invisible, and examples include the following: - The functional layer is made opaque by containing a pigment or dye. - An opaque printed layer is provided on at least one surface of the functional layer. - A porous film with a large number of pores is used as the functional layer, causing diffuse reflection of incident light. - At least one surface of the functional layer is roughened by sandblasting, transfer printing, etc., causing diffuse reflection of incident light on the roughened surface. For example, a surface haze of 70% or more can make the element pattern layer sufficiently invisible.

[0055] The above-described embodiments may be combined as appropriate. For example, by using a film having a porous structure as the functional layer 15 and further providing an opaque wood-grain printed layer, the reflect array 1 can be configured as soft-touch wood-grain wallpaper. Furthermore, even if the coloring or diffuse reflection of the functional layer 15 is not sufficient alone to completely obscure the element pattern layer 13, there is no problem as long as it becomes obscured when multiple functional layers are stacked. Note that if the functional layer 15 is already opaque, it is of course sufficient to use it as is.

[0056] Protection and scratch resistance Protection and scratch resistance refers to the function of preventing scratches on the reflectarray and preventing deterioration of the reflectarray itself. Methods of imparting such functions include coating the reflectarray to increase its surface hardness or laminating a hard coat film. Evaluation of protection and scratch resistance is carried out using a pencil hardness test based on JIS K5600-5-4, and it is preferable that the hardness is H or higher. In addition, the protection and scratch resistance is measured using steel wool (#0000) with a load of 1,000 gf / cm ２ It is preferable that when rubbed with a material, scratches do not occur up to 1000 reciprocating strokes. Examples of synthetic resins include polyethylene terephthalate, cycloolefin polymer, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polymethyl methacrylate, polyester, polyformaldehyde, polyamide, polyphenylene ether, vinylidene chloride, polyvinyl acetate, polyvinyl acetal, AS resin, ABS resin, acrylic resin, fluororesin, nylon resin, polyacetal resin, polycarbonate resin, polyamide resin, and polyurethane resin.

[0057] Flame Retardant, Non-Flame Resistant, and Self-Extinguishing Properties Flame retardant and non-flammable properties can be imparted to a reflectarray by layering non-flammable, quasi-non-flammable, or flame-retardant materials certified as fire-resistant under the Building Standards Act. Examples include flame-retardant fibers, flame-retardant plastics, non-flammable paints, and flame-retardant paints. Flame-retardant fibers include halogen-based compounds, phosphorus-based compounds, vinylon fibers, polyetherimide fibers, aramid fibers, polyester fibers, and vinylon fibers. Flame-retardant plastics include plastic materials to which halogen-based, phosphorus-based, or inorganic flame retardants such as aluminum hydroxide and magnesium hydroxide have been added. Self-extinguishing materials include nylon, polycarbonate, and vinyl chloride. These materials can be layered or mixed when forming the dielectric layer 12. Flame-retardant plastics and fibers can also be used directly as the material for the dielectric layer 12.

[0058] Antifouling, antibacterial, and antiviral properties One method of imparting antifouling properties to a reflectarray is to laminate or coat it with a hydrophilic or water-repellent substrate. Photocatalytic materials, silica-based materials, and the like can be used as hydrophilic materials. Fluororesin-based, silicone-based, and other materials can be used as water-repellent materials. Photocatalytic materials, chlorine-based materials, organic materials containing cationic polymers, and materials containing metals such as silver and zinc can be used as antibacterial and antiviral materials. These materials can be formed as films by laminating them or using them in coating processes, or by mixing them when forming the dielectric layer 12, for example.

[0059] (Adhesion Improvement Layer) The adhesion improvement layer is a layer with adhesive strength that bonds layers together. The adhesion improvement layer may be composed of two or more layers or a combination of multiple materials. In this embodiment, the adhesion improvement layer bonds the ground layer and the dielectric layer, or the dielectric layer and the element pattern, or the dielectric layer, the element pattern, and the additional function layer, and is composed of an adhesive. The adhesive may be a water-dispersion adhesive, a solution-based adhesive, a solventless adhesive, or a solid-based adhesive. Examples of adhesives include epoxy resin-based adhesives, polyvinyl acetate-based adhesives, nitrile rubber-based adhesives, phenolic resin-based adhesives, vinyl acetate-based adhesives, chloroprene rubber-based adhesives, acrylic resin-based adhesives, polyvinyl alcohol resin-based adhesives, silicone rubber-based adhesives, styrene-butadiene rubber-based adhesives, and urethane-based adhesives. In addition to the adhesive, the adhesion improvement layer may also contain any synthetic resin or other substance or any other component. The thickness of the adhesion improvement layer is, for example, 5 μm to 500 μm.

[0060] If the additional functional layer does not have adhesiveness or tackiness, it can be attached to the reflectarray using an adhesion improving layer. The functional layer is a general term that includes single or multiple additional functional layers, single or multiple adhesion improving layers, or layers in which single or multiple additional functional layers and adhesion improving layers are stacked.

[0061] (Installation layer) The installation layer is a layer used to fix the reflectarray to the support. For example, an adhesive layer, a sticky layer, or a magnet can be used if the support is made of metal. When a magnet is used, the position and angle of the reflectarray can be easily changed. In addition, by arranging a bonding material such as adhesive or mortar in layers, it can be attached to the interior or exterior wall of a building.

[0062] (Support) The reflectarray is installed on a support. The support may be a newly installed panel or pole, or an existing sign, wall, ceiling, etc. It is also possible to use such a support. The support preferably has a mechanism that can adjust the angle of the reflectarray in the vertical or horizontal direction, and more preferably has a mechanism that can move the position of the reflectarray up, down, left, and right. The reflectarray is installed on the support and used as a reflectarray device.

[0063] (Element Pattern Configuration) An example of the element pattern configuration of the reflectarray 1 will be described with reference to FIG. 3. FIG. 3 is a diagram showing the overall configuration of the reflectarray 1. The reflectarray 1 is made up of an array of multiple reflection control regions 4, each configured by arranging unit cells 3 having element patterns 14 (14a to 14c) of different shapes. Element patterns 14a to 14c are each arranged in the unit cell 3, and the phase can be controlled by the dimensions of the element pattern 14. The number of unit cells 3 that make up the reflection control region 4 can be any number, as long as it is two or more.

[0064] (Reflection Control Region) The reflectarray 1 includes at least one reflection control region. The properties of the reflectarray can be changed by changing the arrangement of the reflection control regions. For example, when electromagnetic waves of a certain wavelength are incident at a certain incident angle, it is possible to impart the reflectarray with the property of reflecting in a single direction by periodically arranging reflection control regions with a common reflection direction. Furthermore, when electromagnetic waves of a certain wavelength are incident at a certain incident angle, it is possible to impart the reflectarray with the property of scattering the electromagnetic waves in multiple directions by configuring a reflectarray with reflection control regions each with a different reflection direction. Furthermore, it is possible to impart the property of concentrating electromagnetic waves at a specific location by shifting the reflection direction for each reflection control region by a predetermined angle. The frequency expected to be applied to the reflectarray during design is hereinafter referred to as the "operating frequency." The size Lx of the reflection control area in the x-axis direction is determined, for example, by equation (7), where λ is the wavelength of the operating frequency, θix is ​​the x-axis component of the angle of incidence of the electromagnetic wave incident on the reflection control area, and θrx is the x-axis component of the angle of reflection of the electromagnetic wave reflected from the reflection control area. When θix ≠ −θrx,

[0065] (Unit Cell) The reflection control area is divided into n equal sections along the x-axis in the yz plane, and the sections, each having a length equal to the length in the y-axis direction, are defined as unit cell 1, unit cell 2, ..., unit cell n along the positive direction of the x-axis. Here, n is an integer greater than or equal to 2, and the size of each unit cell in the x-axis and y-axis directions is Lx / n. The unit cells reflect incident radio waves with a predetermined phase difference. Within the reflection control area, each unit cell exhibits a different reflection phase, resulting in an inclined reflected wavefront, resulting in asymmetric reflection, which is different from symmetric reflection. Figures 4 to 6 show examples of unit cell arrangements according to the direction in which asymmetric reflection is to occur. When asymmetric reflection is to be performed only along the x-axis direction (Figure 4(a)), unit cells exhibiting different reflection phases are arranged along the x-axis direction in the reflection control area (Figure 4(b)). In this case, identical unit cells are arranged at arbitrary intervals along the y-axis direction of the reflection control area.

[0066] Similarly, when asymmetric reflection is performed only along the y-axis direction (FIG. 5A), unit cells exhibiting different reflection phases are arranged along the y-axis direction in the reflection control region (FIG. 5B). In this case, identical unit cells are arranged at arbitrary intervals along the x-axis direction of the reflection control region.

[0067] When unit cells exhibiting different reflection phases along both the x-axis and y-axis directions are arranged in the reflection control region (FIG. 6(b)), both the x-axis and y-axis components of the incident wave are reflected asymmetrically, and therefore the x-axis and y-axis components of the reflected wave are different from those of the incident wave (FIG. 6(a)).

[0068] (Distribution of reflection phase and impedance within reflection control area) The distribution of reflection phase within the reflection control area is determined, for example, according to the well-known formula (8). Here, the wavelength of the operating frequency is λ (m), the x-axis component of the incident angle of the radio wave incident on the reflection control area is θix, the x-axis component of the reflection angle of the radio wave reflected from the reflection control area is θrx, and the reflection phases at arbitrary coordinates x1 and x2 within the reflection control area are φx1 and φx2, respectively.

[0069] As another guideline, not only the reflection phase but also the surface impedance can be allocated within the reflection control area, in which case the distribution of the surface impedance can be expressed by, for example, the well-known formulas (9), (10), and (11), where Zs is the surface impedance and η1 is the impedance of the incident wave.

[0070] After the reflection phase is calculated by the above method, the shape of the element pattern is changed so as to satisfy the reflection phase in each unit cell, and a simulation is performed to optimize the shape of the element pattern. When an electromagnetic wave is incident on the element pattern, the relationship between the shape of the element pattern and the reflection phase can be calculated by a simulation using, for example, an electromagnetic analysis tool (High Frequency Structure Simulator: HFSS) or the like.

[0071] (Element Pattern Shape) Examples of element pattern shapes include, but are not limited to, a cross patch. FIG. 7 is a diagram showing an example of an element pattern shape. As shown in FIG. 7, a reflect array may be formed using an element pattern of any shape that reflects radio waves, such as a continuous film, a mesh, or a punched shape. For example, instead of a cross patch ( FIG. 7( a)), a cube patch ( FIG. 7( b)), a cylindrical patch ( FIG. 7( c)), a triangular prism patch ( FIG. 7( d)), a Jerusalem cross patch ( FIG. 7( e)), a plurality of parallel conductive patterns ( FIG. 7( f)), a ring-shaped conductive pattern ( FIG. 7( g)), or an element pattern ( FIG. 7( h)) that combines a plurality of these may be used. Furthermore, the structure may be a Jerusalem structure as shown in black in Figure 7, a structure in which rings are arranged around a Jerusalem structure, a patch structure, a rectangular structure, a loop structure, a polygonal structure, a structure combining multiple polygons, a star structure, a fan structure, a structure combining a circle and a polygon, a structure in which a polygon is removed from a circle, a structure in which a polygon or a circle is removed from a polygon, a crescent structure, or the like.

[0072] A case where the element pattern is a cross patch will be described. A cross patch refers to a shape in which two rectangular patches intersect at right angles in the xy plane. The length of the element pattern of the cross patch is referred to as the element length, and the width of the element pattern of the cross patch is referred to as the element width. The reflection phase of the unit cell is controlled by varying either the element length or the element width, or both. When the element length is fixed, it is desirable to set the element length value as large as possible within the unit cell. By setting it large, it becomes easier to obtain desired reflection phase characteristics. Furthermore, when the element width is fixed, it is desirable to set the element width value as large as possible within the unit cell. Setting the element width value large reduces the slope of the reflection phase, thereby improving processing accuracy during processing. Note that the element length is not limited to being set for a cross patch element pattern, but can also be set for element patterns having other shapes. Furthermore, the element length can be set to a common length within the reflection control region, or different lengths can be set for each element pattern included in the reflection control region.

[0073] [Embodiment A-1] Embodiment A-1 will be further described, focusing on its characteristic features. <Planar View> FIG. 8 is a diagram showing an example of the shape of an element pattern when viewed in a plan view. The element pattern 14 is a cross patch formed by intersecting two square patches: a square patch having an element width wx, which is the width in the x-axis direction, and an element length ly, which is the length in the y-axis direction, in the xy plane, as shown in FIG. 8(a), and a square patch having an element width wy, which is the width in the y-axis direction, and an element length lx, which is the length in the x-axis direction. The cross patch also has corners A and corners B. Here, the corners refer to the apexes of the square patches that form the element pattern, and the corners refer to the intersections where the sides of the square patches intersect.

[0074] 8(b) shows the element pattern shape of the cross patch according to this embodiment, and has corners (hereinafter referred to as "rounded corners") Ar and corners (hereinafter referred to as "rounded corners") Br that are rounded at the portions corresponding to corners A and B in FIG. 8(a). The figure shows examples of rounding by arcs with radii of curvature R1 and R2. The cross patch shown in FIG. 8 has a total of eight corners and rounded corners, and four corners and rounded corners. However, this disclosure will mainly describe the corners and rounded corners and corners and rounded corners in the areas surrounded by dotted circles in FIG. 8, and similar descriptions of other areas will be omitted.

[0075] (Rounded Corner Ar) Figure 9 is an enlarged schematic diagram of the vicinity of the rounded corner Ar. In the cross patch, the portion protruding in the positive y-axis direction from the imaginary line K formed by connecting the positive y-axis sides extending parallel to the x-axis from the intersection region is referred to as the arm portion 16. Similarly, the portion protruding in the negative y-axis direction from the imaginary line K formed by connecting the negative y-axis sides extending parallel to the x-axis, the portion protruding in the positive x-axis direction from the imaginary line K formed by connecting the positive x-axis sides extending parallel to the y-axis, and the portion protruding in the negative x-axis direction from the imaginary line K formed by connecting the negative x-axis sides extending parallel to the y-axis are also arm portion 16. In Figure 9, the element width wx, which is the width of the element pattern in the x-axis direction, and the length py of the center line of the arm portion 16 protruding in the y-axis direction are compared, and the shorter of these lengths is defined as P (in the example of Figure 9, wx < py, so wx = P). Similarly, the element width wy, which is the width in the y-axis direction, is compared with the length px of the center line of the arm portion 16 protruding in the x-axis direction, and the shorter length is defined as P. When comparing the element width and center line length of a given arm portion 16 in this manner, the shorter length P is referred to as the reference length P. However, when referring to the element width in the element pattern of FIG. 4( b), it refers to the width in the x-axis direction and the width in the y-axis direction at the portion where the opposing sides of the arm portion, excluding the rounded corners, are parallel to each other. Furthermore, py is calculated as (ly - wy) / 2, and px is calculated as (lx - wx) / 2. Furthermore, the intersection where the sides of the arm portion 16 parallel to the x-axis direction or the y-axis direction intersect in the direction of the rounded corner Ar is defined as the reference intersection point sx, and the straight line passing through sx and extending in the direction of half the intersection angle (in FIG. 9, a direction inclined at 45° with respect to the sides of the arm portion 16 parallel to the x-axis direction or the y-axis direction) is defined as the reference line S.

[0076] In this embodiment, the roundness of the rounded corner portion Ar in plan view preferably includes an arc of a circle of curvature with a radius of curvature R1 of 1 / 2 or less of the reference length P. Furthermore, it is preferable that the curve includes an arc of a circle of curvature whose center of curvature is located within a range of P / 2 × √2 or less from the reference intersection point sx on the reference straight line S toward the inside of the element. If the radius of curvature is 1 / 2 or more, the tip of the element may have a sharp shape, which may make the element pattern prone to cracking, chipping, falling off, or peeling.

[0077] 10 is an enlarged schematic diagram of the vicinity of the rounded corner Br. The intersection point where the sides of adjacent arm portions 16 parallel to the x-axis direction and the y-axis direction intersect in the direction of the rounded corner Br is defined as a reference intersection point tx, and a straight line passing through tx and extending in a direction that is half the intersection angle (in FIG. 6 , a direction inclined at 45° with respect to the sides of arm portions 16 parallel to the x-axis direction or the y-axis direction) is defined as a reference line T.

[0078] In the present embodiment, the roundness of rounded corner portion Br in plan view may be such that it includes an arc of a circle whose radius of curvature R2 is no greater than three times the reference length P. Preferably, radius of curvature R2 includes an arc of a circle whose length is no greater than three times the reference length P of unit cell 3 having the shortest reference length P in reflection control region 4. Preferably, the center of curvature is a curve including an arc of a circle whose center of curvature is located within a range of 3P × √2 or less on reference line T from reference intersection point tx toward the outside of the element.

[0079] [Embodiment A-2] Next, embodiment A-2 will be further described, focusing on its characteristic features. <Cross-Sectional View> Figure 11 is a diagram showing an example of the shape of an element pattern when viewed in cross section. As shown in Figure 11(a), a cross patch, which is an example of an element pattern, has a corner C and a corner D. Here, the corner refers to the apex of the side of the rectangular cross-sectional shape that does not come into contact with the surface of the dielectric layer, and the corner refers to the apex of the side that comes into contact with the surface of the dielectric layer.

[0080] 11(b) shows the element pattern shape of the cross patch according to this embodiment, with rounded corners Cr and Dr, which are rounded at the portions corresponding to corners A and B in FIG. 11(a). The figure shows an example of rounding by arcs with radii of curvature R3 and R4. The cross patch shown in FIG. 11 has a total of two corners and two rounded corners, and two corners and two rounded corners. However, this disclosure will mainly describe the corners and rounded corners and corners and rounded corners in the areas surrounded by dotted circles in FIG. 7, and similar descriptions for other areas will be omitted.

[0081] 12 is an enlarged schematic diagram of the vicinity of the rounded corner Cr. The intersection point at which a side perpendicular to the surface of the dielectric layer and a side parallel to the surface on the side not in contact with the surface of the dielectric layer intersect in the direction of the rounded corner Cr in the cross section of the element pattern is defined as a reference intersection point ux, and a straight line passing through ux and extending in a direction that is half the intersection angle (in FIG. 12 , a direction inclined at 45° with respect to a side parallel to the x-axis or z-axis direction of the cross section) is defined as a reference line U.

[0082] In this embodiment, the roundness of the rounded corner Cr when viewed in cross section preferably includes an arc of a circle of curvature whose radius of curvature R3 is equal to or greater than 1 / 6 of the thickness d of the element pattern. Furthermore, it is preferable that the curve includes an arc of a circle of curvature whose center of curvature is located within a range of d / 6 × √2 or greater from the reference intersection point ux along the reference line U toward the surface of the dielectric layer. If the radius of curvature is equal to or less than d / 6, the tip of the rounded corner when viewed in cross section may become sharp, making the element pattern prone to cracking, chipping, detachment, or peeling. Furthermore, the gentle corners of the element pattern when viewed in cross section make it less likely for air bubbles to be trapped between the element pattern and the dielectric layer 12 or functional layer 15 when a functional layer is laminated on the element pattern layer 13 side. This is expected to improve adhesion with the functional layer 15 and suppress the increase in unwanted reflection due to air bubbles and the deterioration of reflection performance in the desired direction.

[0083] 13 is an enlarged schematic diagram of the vicinity of the rounded corner Dr. The intersection point where the surface of the dielectric layer intersects with the side end of the element pattern in the cross section of the element pattern is defined as a reference intersection point vx, and the normal to the surface of the dielectric layer that passes through vx is defined as a reference straight line V.

[0084] In this embodiment, the roundness of the rounded corners Dr when viewed in cross section preferably includes an arc of a circle of curvature whose radius of curvature R4 is 1 / 6 or more of the thickness d of the element pattern. Furthermore, it is preferable that the curve includes an arc of a circle of curvature whose center of curvature is located within a range of d / 6 or more from the reference intersection point vx along the reference line V toward the surface of the element pattern. A radius of curvature of d / 6 or less may cause the element pattern to get caught on the step at the corner when viewed in cross section, making it difficult to slide, resulting in a shape that is prone to cracking, chipping, falling off, or peeling. Furthermore, the gentle corners of the element pattern when viewed in cross section make it less likely for air bubbles to be trapped between the element pattern and the dielectric layer 12 or functional layer 15 when a functional layer is laminated on the element pattern layer 13 side. This is expected to improve adhesion with the functional layer 15 and suppress the increase in unwanted reflection due to the inclusion of air bubbles and the deterioration of reflection performance in the desired direction.

[0085] <Actions and Effects> As described above in embodiments A-1 and A-2, by rounding the corners and edges of the element pattern in advance, variations in reflection characteristics due to dimensional errors caused by variations in manufacturing conditions are reduced. In addition, durability against damage such as cracking, chipping, falling off, and peeling of the elements during the manufacturing process is improved, making it easier to handle and transport the product. Furthermore, effects such as making the functional layer 15 laminated on the element pattern layer 13 side less susceptible to damage can be expected.

[0086] In the above-described embodiment, durability is improved by rounding the corners and / or corners that exist in a cross patch structure where two square patches intersect, but the structure is not limited to a cross patch structure as long as the original element pattern structure has corners and / or corners.

[0087] (Manufacturing Method) The main manufacturing method for the basic configuration of a reflectarray is to form an element pattern by cutting or etching a copper-clad laminate used in printed circuit boards, etc., or a dielectric layer on one or both sides of which a metal film is formed by dry coating using a vapor deposition method or sputtering method, plating process, wet coating, etc. Specifically, a copper-clad laminate is formed by laminating copper foil to an insulator, for example, a substrate such as glass cloth impregnated with a resin such as epoxy. The copper-clad laminate has a plate-like shape, and copper foil is laminated to both sides of the plate-like insulator. The copper foil on one side serves as the element pattern layer 13, and the copper foil on the other side serves as the ground layer 11. The insulator corresponds to the dielectric layer 12. When metal films are formed on both sides of the dielectric, the element pattern layer 13 is formed from one metal film, and the other metal film is used as the ground layer 11. The dielectric serves as the dielectric layer 12.

[0088] The element pattern in plan view can be produced by using a photomask in which an element pattern with a radius of curvature R is formed at the corners and / or edges of the element pattern. Furthermore, a method for forming an element pattern with a radius of curvature R at the corners and / or edges of the element pattern in a cross-sectional view can be achieved by adjusting a combination of factors such as the type and concentration of the etching solution, temperature, solution agitation, etching time, and the type and thickness of the resist. By adjusting these factors, the etching rate in the depth direction and the side etching rate can be optimized. The etching solution can be selected from copper chloride solution, ferric chloride solution, alkaline etching solution, etc. In general, acidic etching solutions such as copper chloride solution and ferric chloride solution have high etching directionality in the depth direction.

[0089] Generally, in the case of cutting, the dimensional error of the element pattern is about ±100 μm, and in the case of etching, the dimensional error of the element pattern is about ±50 μm.

[0090] Other manufacturing methods include directly forming the element pattern and ground layer on the dielectric layer, printing using letterpress printing, lithographic printing, intaglio printing, stencil printing, transfer printing, etc., or masking the dielectric layer except for the element pattern area with masking tape or a masking agent, and then forming the element pattern using dry coating, plating, painting, or spraying.

[0091] Other layers (functional layers 15 such as protective layers, adhesive layers, and design layers) can be laminated onto the basic structure by lamination, printing / coating, or extrusion molding. Examples of lamination include, but are not limited to, dry lamination, wet lamination, thermal lamination, and extrusion lamination.

[0092] When a large-sized reflectarray is required, a single reflectarray may be configured by arranging a plurality of reflectarrays.

[0093] [Examples] Examples A1 to A15 and Comparative Examples A1 to A4 are described below. Regarding Examples A1 to A7, we will first describe a comparative example having a cross patch element pattern shape, and then explain an example in which the corners of the cross patch are rounded with radii of curvature R1 and R2. Furthermore, we will explain Examples A8 to A15 in which the corners of the cross section are rounded with a radius of curvature R3.

[0094] (Comparative Example A1) A 300 mm square copper-clad laminate (ELC-4762 manufactured by Sumitomo Bakelite Co., Ltd.) was prepared, with copper foil provided on both sides of the dielectric. The dielectric 12 was glass / epoxy resin (thickness: 1.564 mm). The copper foil, which served as the base layer 11 and the element pattern layer 13, was 18 μm thick, for a total thickness of 1.6 mm. Photoresist layers were formed on both sides of the copper-clad laminate, and the photoresist layer on one side was exposed through a photomask with a predetermined element pattern. The photoresist layer was developed and etched to form the element pattern layer 13, resulting in a reflectarray. The conductivity of copper was 5.8 × 10 siemens / m, the relative dielectric constant of the dielectric layer 12 was 4.5, and the dielectric loss tangent tanδ was 0.014.

[0095] The operating frequency was set to 4.85 GHz, the target reflection characteristics (desired reflection characteristics) were set to θix = −60°, θrx = 0°, and θiy = θry = 0°, and the size Lx of reflection control area 4 in the x-axis direction was determined to be 71.376 mm using equation (1).

[0096] The number of divisions of reflection control region 4 was set to 3, and the size of the unit cell in the x-axis and y-axis directions was set to 23.792 mm. The shape of the element was a cross patch in which two square patches intersected at right angles in the xy plane. Here, the only difference between elements in the reflection control region was the element width; specifically, the element width was a variable, and the element length within the same element was set to 15.000 mm.

[0097] First, the reflection phase of the unit cell relative to the element width was analyzed using finite element analysis software (HFSS) from Ansys. Next, based on the analysis results of the unit cell, the element width of each unit cell was determined so as to conform to the impedance distribution of Equation (10).

[0098] The reflectarray 1 had 4 x 12 reflection control areas 4 arranged in the x-axis and y-axis directions, and its size in the xy plane was 285.504 mm square. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto the reflectarray 1 at θix = -60° and θiy = 0°.

[0099] Figure 14 is a graph showing the reflection characteristics of the reflectarray according to comparative example A1. In Figure 14, the horizontal axis represents the reflection angle θx, and the vertical axis represents RCS (radar cross section). RCS is a value that essentially corresponds to the intensity of the reflected radio wave. In this reflectarray 1, radio waves incident at θix = -60° were reflected in the desired direction of θiy = 0°, and the RCS was 7.022 dBsm. In the following description of the drawings, the corners of the rectangle will be represented as R = 0 mm.

[0100] (Example A1) A reflectarray was fabricated that was similar to the reflectarray described in Comparative Example A1 except for the element pattern shape. The element pattern shape differed only in the corners and corners of each element pattern in the reflection control region 4 in a planar view. Specifically, the corners and corners of each cross-shaped element pattern were rounded with a radius of curvature (R1 and R2) of 0.6 mm. In each element pattern, R1 was 1 / 2 or less of the reference length P, and R2 was 3 times or less of the reference length P. FIG. 15 is a graph showing the reflection characteristics of the reflectarray according to Example A1. An electromagnetic wave incident at θix = -60° was reflected in the desired direction of θrx = 0°, and the RCS was 6.992 dBsm.

[0101] 17 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A1 and Example A1. The change in RCS due to the presence or absence of rounded radii of curvature at the corners and corners of each cross-shaped element pattern was −0.030 dBsm, and compared to the reflectarray described in Comparative Example A1, the presence or absence of rounded radii of curvature at the corners and corners did not affect the reflection characteristics, and it is expected that the reflection characteristics will be stable.

[0102] (Example A2) A reflectarray was fabricated that was similar to the reflectarray described in Comparative Example A1 except for the element pattern shape. The element pattern shape differed only in the corners and corners of each element pattern in the reflection control region 4 in a planar view. Specifically, the corners of each cross-shaped element pattern were rounded with a radius of curvature (R1) of 0.6 mm and a radius of curvature (R2) of 3.0 mm. In each element pattern, R1 was equal to or less than half the reference length P, and R2 was equal to or less than three times the reference length P. FIG. 16 is a graph showing the reflection characteristics of the reflectarray according to Example A2. An electromagnetic wave incident at θix = -60° was reflected in the desired direction of θrx = 0°, and the RCS was 7.165 dBsm.

[0103] 17 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A1 and Example A2. The change in RCS due to the presence or absence of rounded radii of curvature at the corners and corners of each cross-shaped element pattern was 0.143 dBsm, and compared to the reflectarray described in Comparative Example A1, the presence or absence of rounded radii of curvature at the corners and corners did not affect the reflection characteristics, and it is expected that the reflection characteristics will be stable.

[0104] (Comparative Example A2) A 300 mm square copper-clad laminate (CGP-500 manufactured by Chukoh Chemical Industry Co., Ltd.) with copper foil on both sides of the dielectric was prepared. The dielectric 12 was a fluororesin-impregnated glass cloth (thickness 764 μm), and the copper foil, which served as the base layer for the ground layer 11 and the element pattern layer 13, was 18 μm thick, for a total thickness of 0.8 mm. Photoresist layers were formed on both sides of the copper-clad laminate, and the photoresist layer on one side was exposed through a photomask with a predetermined element pattern. The photoresist layer was developed and etched to form the element pattern layer 13, producing a reflectarray. The conductivity of copper was 5.8 × 10 siemens / m, the relative dielectric constant of the dielectric layer 12 was 2.6, and the dielectric loss tangent tanδ was 0.0025.

[0105] The operating frequency was set to 27.2 GHz, the target reflection characteristics (desired reflection characteristics) were set to θix = -33°, θrx = 0°, θiy = θry = 0°, and the size Lx of reflection control area 4 in the x-axis direction was determined to be 20.238 mm using equation (1).

[0106] The number of divisions of reflection control region 4 was set to 3, and the size of the unit cell in the x-axis and y-axis directions was set to 6.746 mm. The shape of the element was a cross patch in which two square patches intersected at right angles in the xy plane. Here, the only difference between elements in the reflection control region was the element width; specifically, the element width was a variable, and the element length within the same element was set to 3.250 mm.

[0107] First, the reflection phase of the unit cell relative to the element width was analyzed using finite element analysis software (HFSS) from Ansys. Next, based on the analysis results of the unit cell, the element width of each unit cell was determined so as to conform to the impedance distribution of equation (4).

[0108] The reflectarray 1 had 3 x 9 reflection control areas 4 arranged in the x-axis and y-axis directions, and its size in the xy plane was 60.714 mm square. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto the reflectarray 1 at θix = -33° and θiy = 0°.

[0109] Fig. 18 is a graph showing the reflection characteristics of the reflectarray according to Comparative Example A2. In Fig. 18, the horizontal axis represents the reflection angle θx, and the vertical axis represents the RCS (radar cross section). The RCS is a value that substantially corresponds to the intensity of the reflected radio wave. In this reflectarray 1, the radio wave incident at θix = -33° was reflected in the desired direction of θiy = 0°, and the RCS was 0.259 dBsm.

[0110] (Example A3) A reflectarray was fabricated that was similar to the reflectarray described in Comparative Example A2 except for the element pattern shape. The element pattern shape differed only in the corners and corners of each element pattern in the reflection control region 4 in a planar view. Specifically, the corners and corners of each cross-shaped element pattern were rounded with a radius of curvature (R1 and R2) of 0.05 mm. In each element pattern, R1 was equal to or less than half the reference length P, and R2 was equal to or less than three times the reference length P. FIG. 19 is a graph showing the reflection characteristics of the reflectarray according to Example A3. An electromagnetic wave incident at θix = -33° was reflected in the desired direction of θrx = 0°, and the RCS was 0.269 dBsm.

[0111] 21 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A2 and Example A3. The change in RCS due to the presence or absence of rounded radii of curvature at the corners and edges of each cross-shaped element pattern was 0.010 dBsm, and compared to the reflectarray described in Comparative Example A2, the presence or absence of rounded radii of curvature at the corners and edges of the elements did not affect the reflection characteristics, and it is expected that the reflection characteristics will be stable.

[0112] (Example A4) A reflectarray was fabricated that was similar to the reflectarray described in Comparative Example A2 except for the element pattern shape. The element pattern shape differed only in the corners and corners of each element pattern in the reflection control region 4 in a planar view. Specifically, the corners of each cross-shaped element pattern were rounded with a radius of curvature (R1) of 0.05 mm and a radius of curvature (R2) of 0.25 mm. In each element pattern, R1 was equal to or less than half the reference length P, and R2 was equal to or less than three times the reference length P. FIG. 20 is a graph showing the reflection characteristics of the reflectarray according to Example A4. An electromagnetic wave incident at θix = -33° was reflected in the desired direction of θrx = 0°, and the RCS was 0.274 dBsm.

[0113] 21 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A2 and Example A4. The change in RCS due to the presence or absence of rounded radii of curvature at the corners and corners of each cross-shaped element pattern was 0.015 dBsm, and compared to the reflectarray described in Comparative Example A2, the presence or absence of rounded radii of curvature at the corners and corners did not affect the reflection characteristics, and it is expected that the reflection characteristics will be stable.

[0114] (Comparative Example A3) A 300 mm square copper-clad laminate (CGP-500 manufactured by Chukoh Chemical Industry Co., Ltd.) was prepared, with copper foil provided on both sides of the dielectric. The dielectric 12 was a fluororesin-impregnated glass cloth (thickness 764 μm). The copper foil, which was the base layer of the ground layer 11 and the element pattern layer 13, was each 18 μm thick, for a total thickness of 0.8 mm. Photoresist layers were formed on both sides of the copper-clad laminate, and the photoresist layer on one side was exposed through a photomask with a predetermined element pattern. The photoresist layer was developed and etched to form the element pattern layer 13, thereby producing a reflectarray. The conductivity of copper was 5.8 × 10 siemens / m, the relative dielectric constant of the dielectric layer 12 was 2.6, and the dielectric loss tangent tanδ was 0.0025.

[0115] The operating frequency was set to 28.0 GHz, the target reflection characteristics (desired reflection characteristics) were set to θix = 0°, θrx = 45°, and θiy = θry = 0°, and the size Lx of reflection control area 4 in the x-axis direction was determined to be 15.1524 mm using equation (7).

[0116] The number of divisions of reflection control region 4 was set to 3, and the size of the unit cell in the x-axis direction and the y-axis direction was set to 5.0508 mm. The shape of the element was a cross patch in which two square patches were orthogonal to each other in the xy plane.

[0117] First, the reflection phase of the unit cell relative to the element width was analyzed using finite element analysis software (HFSS) manufactured by Ansys. The element length and element width were changed and an automatic analysis was performed to achieve the target reflection characteristics, thereby determining the element length and element width of elements 14a, 14b, and 14c.

[0118] The reflectarray 1 had 4 x 12 reflection control areas 4 arranged in the x-axis and y-axis directions, and its size in the xy plane was 60.6096 mm square. The reflection characteristics when polarized waves parallel to the y-axis were irradiated onto the reflectarray 1 at θix = 0° and θiy = 45° were analyzed using HFSS.

[0119] Fig. 22 is a graph showing the reflection characteristics of the reflectarray according to Comparative Example A3. In Fig. 22, the horizontal axis represents the reflection angle θx, and the vertical axis represents the RCS (radar cross section). The RCS is a value that substantially corresponds to the intensity of the reflected radio wave. In this reflectarray 1, the radio wave incident at θix = 0° was reflected in the desired direction of θiy = 45°, and the RCS was -0.712 dBsm.

[0120] Example A5 A reflectarray similar to the reflectarray described in Comparative Example A3 was fabricated except for the element pattern shape. The element pattern shape differed only in the corners and corners of each element pattern in the reflection control region 4 in a planar view. Specifically, each cross-shaped element pattern had a rounded shape with a radius of curvature of 0.035 mm at the corners of element 14a, 0.091 mm at the corners of element 14a, 0.041 mm at the corners of element 14b, 0.062 mm at the corners of element 14b, 0.039 mm at the corners of element 14c, and 0.061 mm at the corners of element 14c. In each element pattern, R1 was equal to or less than half the reference length P, and R2 was equal to or less than three times the reference length P. FIG. 23 is a graph showing the reflection characteristics of the reflectarray according to Example A5. An electromagnetic wave incident at θix = 0° was reflected in the desired direction of θrx = 45°, and the RCS was −0.738 dBsm.

[0121] 24 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A3 and Example A5. The change in RCS due to the presence or absence of rounded radii of curvature at the corners and edges of each cross-shaped element pattern was −0.027 dBsm, and compared to the reflectarray described in Comparative Example A3, the presence or absence of rounded radii of curvature at the corners and edges of the elements did not affect the reflection characteristics, and it is expected that the reflection characteristics will be stable.

[0122] (Comparative Example A4) A 300 mm square copper-clad laminate (CGP-500 manufactured by Chukoh Chemical Industry Co., Ltd.) with copper foil on both sides of the dielectric was prepared. The dielectric 12 was a fluororesin-impregnated glass cloth (thickness 764 μm), and the copper foil, which served as the base layer for the ground layer 11 and the element pattern layer 13, was 18 μm thick, for a total thickness of 0.8 mm. Photoresist layers were formed on both sides of the copper-clad laminate, and the photoresist layer on one side was exposed through a photomask with a predetermined element pattern. The photoresist layer was developed and etched to form the element pattern layer 13, resulting in a reflectarray. The conductivity of copper was 5.8 × 10 siemens / m, the relative permittivity of the dielectric layer 12 was 2.6, and the dielectric loss tangent tanδ was 0.0025.

[0123] The operating frequency was set to 60.0 GHz, the target reflection characteristics (desired reflection characteristics) were set to θix = 0°, θrx = 45°, and θiy = θry = 0°, and the size Lx of the reflection control area 4 in the x-axis direction was determined to be 7.065 mm using equation (1).

[0124] The number of divisions of reflection control region 4 was set to 3, and the size of the unit cell in the x-axis direction and the y-axis direction was set to 2.355 mm. The shape of the element was a cross patch in which two square patches intersected at right angles in the xy plane. Here, the elements in the reflection control region differed only in element width; specifically, the element width was a variable, and the element length within the same element was set to 1.700 mm.

[0125] First, the reflection phase of the unit cell relative to the element width was analyzed using finite element analysis software (HFSS) from Ansys. Next, based on the analysis results of the unit cell, the element width of each unit cell was determined so as to conform to the impedance distribution of equation (4).

[0126] The reflectarray 1 had 9 x 18 reflection control areas 4 arranged in the x-axis and y-axis directions, and its size in the xy plane was 63.585 x 42.390 mm. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto the reflectarray 1 at θix = 0° and θiy = 45°.

[0127] Fig. 25 is a graph showing the reflection characteristics of the reflectarray according to comparative example A4. The horizontal axis of Fig. 25 represents the reflection angle θx, and the vertical axis represents the RCS (radar cross section). The RCS is a value that essentially corresponds to the intensity of the reflected radio wave. In this reflectarray 1, the radio wave incident at θix = 0° was reflected in the desired direction of θiy = 45°, and the RCS was 3.915 dBsm.

[0128] (Example A6) A reflectarray was fabricated that was similar to the reflectarray described in Comparative Example A4 except for the element pattern shape. The element pattern shape differed only in the corners and corners of each element pattern in the reflection control region 4 in a planar view. Specifically, the corners and corners of each cross-shaped element pattern were rounded with a radius of curvature (R1 and R2) of 0.07 mm. In each element pattern, R1 was 1 / 2 or less of the reference length P, and R2 was 3 times or less of the reference length P. Figure 26 is a graph showing the reflection characteristics of the reflectarray according to Example A6. An electromagnetic wave incident at θix = 0° was reflected in the desired θrx = 45° direction, with an RCS of 3.866 dBsm.

[0129] 28 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A4 and Example A6. The change in RCS due to the presence or absence of rounded radii of curvature at the corners and edges of each cross-shaped element pattern was −0.050 dBsm, and compared to the reflectarray described in Comparative Example A4, the presence or absence of rounded radii of curvature at the corners and edges of the elements did not affect the reflection characteristics, and it is expected that the reflection characteristics will be stable.

[0130] (Example A7) A reflectarray was fabricated that was similar to the reflectarray described in Comparative Example A4 except for the element pattern shape. The element pattern shape differed only in the corners and corners of each element pattern in the reflection control region 4 in a planar view. Specifically, the corners of each cross-shaped element pattern were rounded with a radius of curvature (R1) of 0.07 mm and a radius of curvature (R2) of 0.35 mm. In each element pattern, R1 was 1 / 2 or less of the reference length P, and R2 was 3 times or less of the reference length P. FIG. 27 is a graph showing the reflection characteristics of the reflectarray according to Example A7. An electromagnetic wave incident at θix = 0° was reflected in the desired direction of θrx = 45°, and the RCS was 3.641 dBsm.

[0131] 28 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A4 and Example A7. The change in RCS due to the presence or absence of rounded radii of curvature at the corners and corners of each cross-shaped element pattern was −0.274 dBsm, and compared to the reflectarray described in Comparative Example A4, the presence or absence of rounded radii of curvature at the corners and corners did not affect the reflection characteristics, and it is expected that the reflection characteristics will be stable.

[0132] (Example A8) A reflectarray was fabricated that was similar to the reflectarray described in Comparative Example A1 except for the element pattern shape. The element pattern shape differed only in the corners and corners of each element pattern in the planar view of the element in the reflection control region 4, and in the corners of the element cross section (the intersections of the element surface and the element side). Specifically, the corners and corners of each cross-shaped element pattern were rounded with a radius of curvature (R1 and R2) of 0.6 mm, and the corners of the element cross section of each cross-shaped element pattern (the intersections of the element surface and the element side) were rounded with a radius of curvature (R3) of 3.6 μm. In each element pattern, R1 was ½ or less of the reference length P, R2 was 3 times or less of the reference length P, and R3 was ⅙ or more of the thickness d of the element pattern. Figure 29 is a graph showing the reflection characteristics of the reflectarray according to Example A8. An electromagnetic wave incident at θix = -60° was reflected in the desired direction of θrx = 0°, and the RCS was 7.008 dBsm.

[0133] 31 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A1 and Example A8. The change in RCS due to the presence or absence of rounding of the radius of curvature at the corners and nooks of the elements in a planar view and at the corners of the element cross section for each cross-shaped element pattern was -0.015 dBsm, and compared to the reflectarray described in Comparative Example A1, the presence or absence of rounding of the radius of curvature at the corners and nooks of the elements and at the corners of the element cross section (the intersections of the element surface and element side surface) does not affect the reflection characteristics, and stable reflection characteristics are expected.

[0134] (Example A9) A reflectarray was fabricated that was similar to the reflectarray described in Comparative Example A1 except for the element pattern shape. The element pattern shape differed only in the corners and corners of each element pattern in the planar view of the element in the reflection control region 4, and in the corners of the element cross section (the intersections of the element surface and the element side). Specifically, the corners and corners of each cross-shaped element pattern were rounded with a radius of curvature (R1 and R2) of 0.6 mm, and the corners of the element cross section of each cross-shaped element pattern (the intersections of the element surface and the element side) were rounded with a radius of curvature (R3) of 54 μm. In each element pattern, R1 was ½ or less of the reference length P, R2 was 3 times or less of the reference length P, and R3 was ⅙ or more of the thickness d of the element pattern. Figure 30 is a graph showing the reflection characteristics of the reflectarray according to Example A9. An electromagnetic wave incident at θix = -60° was reflected in the desired direction of θrx = 0°, and the RCS was 7.027 dBsm.

[0135] 31 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A1 and Example A9. The change in RCS due to the presence or absence of rounding of the radius of curvature at the corners and nooks of the elements in a planar view and at the corners of the element cross section of each cross-shaped element pattern was 0.005 dBsm, and compared to the reflectarray described in Comparative Example A1, the presence or absence of rounding of the radius of curvature at the corners and nooks of the elements and the corners of the element cross section (the intersections of the element surface and element side surface) does not affect the reflection characteristics, and stable reflection characteristics are expected.

[0136] (Example A10) A reflectarray was fabricated that was similar to the reflectarray described in Comparative Example A2 except for the element pattern shape. The element pattern shape differed only in the corners and corners of each element pattern in the reflection control region 4 in a planar view and in the corners of the element cross section (the intersections of the element surface and the element side surface). Specifically, the corners and corners of each cross-shaped element pattern were rounded with a radius of curvature (R1 and R2) of 0.05 mm, and the corners of the element cross section of each cross-shaped element pattern (the intersections of the element surface and the element side surface) were rounded with a radius of curvature (R3) of 3.6 μm. In each element pattern, R1 was ½ or less of the reference length P, R2 was 3 times or less of the reference length P, and R3 was ⅙ or more of the thickness d of the element pattern. FIG. 32 is a graph showing the reflection characteristics of the reflectarray according to Example A10. An electromagnetic wave incident at θix=-33° was reflected in the desired direction of θrx=0°, and the RCS was 0.268 dBsm.

[0137] 34 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A2 and Example A10. The change in RCS due to the presence or absence of rounding of the radius of curvature at the corners and nooks in a plan view of the elements of each cross-shaped element pattern and at the corners of the element cross section was 0.009 dBsm, and compared to the reflectarray described in Comparative Example A2, the presence or absence of rounding of the radius of curvature at the corners and nooks of the elements and at the corners of the element cross section (the intersections of the element surface and element side surface) does not affect the reflection characteristics, and stable reflection characteristics are expected.

[0138] (Example A11) A reflectarray was fabricated that was similar to the reflectarray described in Comparative Example A2 except for the element pattern shape. The element pattern shape differed only in the corners and corners of each element pattern in the planar view of the element in the reflection control region 4, and in the corners of the element cross section (the intersections of the element surface and the element side). Specifically, the corners and corners of each cross-shaped element pattern were rounded with a radius of curvature (R1 and R2) of 0.05 mm, and the corners of the element cross section of each cross-shaped element pattern (the intersections of the element surface and the element side) were rounded with a radius of curvature (R3) of 54 μm. In each element pattern, R1 was ½ or less of the reference length P, R2 was 3 times or less of the reference length P, and R3 was ⅙ or more of the thickness d of the element pattern. Figure 33 is a graph showing the reflection characteristics of the reflectarray according to Example A11. An electromagnetic wave incident at θix = -33° was reflected in the desired direction of θrx = 0°, and the RCS was 0.280 dBsm.

[0139] 34 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A2 and Example A11. The change in RCS due to the presence or absence of rounding of the radius of curvature at the corners and nooks in a plan view of the elements of each cross-shaped element pattern and at the corners of the element cross section was 0.021 dBsm, and compared to the reflectarray described in Comparative Example A2, the presence or absence of rounding of the radius of curvature at the corners and nooks of the elements and at the corners of the element cross section (the intersections of the element surface and element side surface) does not affect the reflection characteristics, and stable reflection characteristics are expected.

[0140] (Example A12) A reflectarray was produced that was similar to the reflectarray described in Comparative Example A3 except for the element pattern shape. The element pattern shape was such that only the corners and corners in a planar view of the elements of each element pattern in reflection control region 4 and the corners of the element cross section (intersections of the element surface and element side surface) were different, and specifically, in each cross-shaped element pattern, the corners of element 14a had a radius of curvature of 0.035 mm, the corners of element 14a had a radius of curvature of 0.091 mm, the corners of element 14b had a radius of curvature of 0.041 mm, the corners of element 14b had a radius of curvature of 0.062 mm, the corners of element 14c had a radius of curvature of 0.039 mm, and the corners of element 14c had a radius of curvature of 0.061 mm, and the corners of the element cross section of each cross-shaped element pattern were rounded with a radius of curvature (R3) of 3.6 μm. In each element pattern, R1 is 1 / 2 or less of the reference length P, R2 is 3 times or less of the reference length P, and R3 is 1 / 6 or more of the thickness d of the element pattern. Fig. 35 is a graph showing the reflection characteristics of the reflectarray according to Example A12. An electromagnetic wave incident at θix = 0° was reflected in the desired direction of θrx = 45°, and the RCS was -0.753 dBsm.

[0141] 37 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A3 and Example A12. The change in RCS due to the presence or absence of rounding of the radius of curvature at the corners and nooks in a plan view of the elements of each cross-shaped element pattern and at the corners of the element cross section was -0.041 dBsm, and compared to the reflectarray described in Comparative Example A3, the presence or absence of rounding of the radius of curvature at the corners and nooks of the elements and at the corners of the element cross section (the intersections of the element surface and element side surface) does not affect the reflection characteristics, and stable reflection characteristics are expected.

[0142] (Example A13) A reflectarray was produced that was similar to the reflectarray described in Comparative Example A3 except for the element pattern shape. The element pattern shape was such that only the corners and corners in a planar view of the elements of each element pattern in reflection control region 4 and the corners of the element cross section (intersections of the element surface and element side surface) were different. Specifically, in each cross-shaped element pattern, the corners of element 14a had a radius of curvature of 0.035 mm, the corners of element 14a had a radius of curvature of 0.091 mm, the corners of element 14b had a radius of curvature of 0.041 mm, the corners of element 14b had a radius of curvature of 0.062 mm, the corners of element 14c had a radius of curvature of 0.039 mm, and the corners of element 14c had a radius of curvature of 0.061 mm, and the corners of the element cross section of each cross-shaped element pattern were rounded with a radius of curvature (R3) of 54 μm. In each element pattern, R1 is 1 / 2 or less of the reference length P, R2 is 3 times or less of the reference length P, and R3 is 1 / 6 or more of the thickness d of the element pattern. Fig. 36 is a graph showing the reflection characteristics of the reflectarray according to Example A13. An electromagnetic wave incident at θix = 0° was reflected in the desired direction of θrx = 45°, and the RCS was -0.697 dBsm.

[0143] 37 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A3 and Example A13. The change in RCS due to the presence or absence of rounding of the radius of curvature at the corners and nooks in a plan view of the elements of each cross-shaped element pattern and at the corners of the element cross section was 0.014 dBsm, and compared to the reflectarray described in Comparative Example A3, the presence or absence of rounding of the radius of curvature at the corners and nooks of the elements and at the corners of the element cross section (the intersections of the element surface and element side surface) does not affect the reflection characteristics, and stable reflection characteristics are expected.

[0144] (Example A14) A reflectarray was fabricated that was similar to the reflectarray described in Comparative Example A4 except for the element pattern shape. The element pattern shape differed only in the corners and corners of each element pattern in the planar view of the element in the reflection control region 4, and in the corners of the element cross section (the intersections of the element surface and the element side surface). Specifically, the corners and corners of each cross-shaped element pattern were rounded with a radius of curvature (R1 and R2) of 0.07 mm, and the corners of the element cross section of each cross-shaped element pattern (the intersections of the element surface and the element side surface) were rounded with a radius of curvature (R3) of 3.6 μm. In each element pattern, R1 was ½ or less of the reference length P, R2 was 3 times or less of the reference length P, and R3 was ⅙ or more of the thickness d of the element pattern. FIG. 38 is a graph showing the reflection characteristics of the reflectarray according to Example A14. An electromagnetic wave incident at θix = 0° was reflected in the desired direction of θrx = 45°, and the RCS was 3.841 dBsm.

[0145] 40 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A4 and Example A14. The change in RCS due to the presence or absence of rounding of the radius of curvature at the corners and nooks in a plan view of the elements of each cross-shaped element pattern and at the corners of the element cross section was -0.074 dBsm, and compared to the reflectarray described in Comparative Example A4, the presence or absence of rounding of the radius of curvature at the corners and nooks of the elements and at the corners of the element cross section (the intersections of the element surface and element side surface) does not affect the reflection characteristics, and stable reflection characteristics are expected.

[0146] (Example A15) A reflectarray was fabricated that was similar to the reflectarray described in Comparative Example A4 except for the element pattern shape. The element pattern shape differed only in the corners and corners of each element pattern in the planar view of the element in the reflection control region 4, and in the corners of the element cross section (the intersections of the element surface and the element side surface). Specifically, the corners and corners of each cross-shaped element pattern were rounded with a radius of curvature (R1 and R2) of 0.07 mm, and the corners of the element cross section of each cross-shaped element pattern (the intersections of the element surface and the element side surface) were rounded with a radius of curvature (R3) of 54 μm. In each element pattern, R1 was ½ or less of the reference length P, R2 was 3 times or less of the reference length P, and R3 was ⅙ or more of the thickness d of the element pattern. FIG. 39 is a graph showing the reflection characteristics of the reflectarray according to Example A15. An electromagnetic wave incident at θix = 0° was reflected in the desired direction of θrx = 45°, and the RCS was 3.793 dBsm.

[0147] 40 is a graph showing the results of comparing the reflection characteristics of the reflectarrays according to Comparative Example A4 and Example A15. The change in RCS due to the presence or absence of rounding of the radius of curvature at the corners and nooks in a plan view of the elements of each cross-shaped element pattern and at the corners of the element cross section was -0.123 dBsm, and compared to the reflectarray described in Comparative Example A4, the presence or absence of rounding of the radius of curvature at the corners and nooks of the elements and at the corners of the element cross section (the intersections of the element surface and element side surface) does not affect the reflection characteristics, and stable reflection characteristics are expected.

[0148] <Evaluation> The configuration data and reflection characteristic results of the reflectarrays used in the above-mentioned Examples and Comparative Examples are summarized in Table A1 for Examples A1 to A7 and Comparative Examples A1 to A4, and in Table A2 for Examples A8 to A15. The radius of curvature of each element is the average value of values ​​measured at 10 points.

[0149] (Abrasion test evaluation) Using a Gakushin-type abrasion fastness tester (AB-301, manufactured by Tester Sangyo Co., Ltd.), the element pattern layer surfaces of the reflectarrays of Examples A1 to A15 and Comparative Examples A1 to A4 were subjected to an abrasion resistance test under the following conditions to evaluate durability. The evaluation results are summarized in Tables A1 and A2. Evaluation environment conditions: 25°C, 60% RH Friction element: cotton (the friction element was attached and fixed to the tip (2 cm x 2 cm) of the friction element of the tester that comes into contact with the element pattern layer surface of the reflectarray so as not to move) Contact area of ​​friction element tip: 1 cm x 1 cm Reciprocating distance: 120 mm Reciprocating speed: 30 c / min Load: 400 g / cm ２ Number of round trips: 100

[0150] After rubbing, the reflectarrays were observed under a microscope to evaluate the presence or absence of scratches and caught fibers at the rubbed areas. The results are shown in Tables A1 and A2. In the reflectarrays of Comparative Examples A1 to A4, the element surfaces were scratched and many of the cotton fibers of the friction element were caught on the elements, whereas in the reflectarrays of Examples A1 to A15, in which the elements were rounded, the element surfaces were not scratched and the cotton fibers of the friction element were not caught on the elements. Therefore, by rounding the corners and edges of the elements of each element pattern in reflection control region 4 and the corners of the element cross section (the intersections between the element surface and the element side surface) as part of the element pattern shape, factors that lead to damage such as cracking, chipping, detachment, and peeling of the elements can be suppressed. Furthermore, it was found that including such rounded corners and edges in the element pattern shape does not affect the reflection characteristics and allows stable reflection characteristics to be obtained.

[0151] [Embodiment B] Embodiment B will be further described, focusing on its characteristic features. In the following description, the reflectarray is assumed to be a simple rectangle, with each side of the reflectarray parallel to the x-axis and y-axis, respectively. The ground layer, dielectric layer, element pattern, and functional layer are stacked in this order along the positive direction of the z-axis. The term "surface" can refer not only to the surface of a plate-shaped member but also to the interface of a layer contained in the plate-shaped member that is approximately parallel to the surface of the plate-shaped member. Furthermore, the terms "upper surface" and "lower surface" refer to the surfaces shown at the top or bottom of a drawing of a plate-shaped member or a layer contained in the plate-shaped member. "Up" refers to the positive direction of the z-axis, and "down" refers to the negative direction of the z-axis. The "upper surface" and "lower surface" may also be referred to with numbers such as "first surface" and "second surface." The term "tapered" refers to the shape of a side surface, which indicates that all of the side surfaces of the structure are inclined. Furthermore, when the shape of the side surface is described as being forward tapered, this means that all of the side surfaces of the structure are inclined so as to be displaced outward from the top surface to the bottom surface.

[0152] FIG. 41 is an example of a schematic diagram showing an enlarged reflection control region portion. FIG. 41(a) is a perspective view of the reflection control region, FIG. 41(b) is a cross-sectional view of the reflection control region in the xz plane cut by the y direction Uy / 2, and FIG. 41(c) is a cross-sectional view of an arbitrary unit cell of the reflection control region in the yz plane cut by the x direction Ux / 2. An element pattern 100 having an element side surface 500 is formed on one xy plane of the dielectric layer 200, and a ground layer 300 is formed on the other xy plane. An additional function layer 400 is formed so as to cover the entire element pattern 100 including the element side surface 500. When the unit cells are formed by dividing the reflection control region into n equal parts along a predetermined direction, Ux is Lx / n, where n is an integer equal to or greater than 2 (in the example of FIG. 41, three square unit cells 100 each having a long side in the x-axis direction divided into thirds are formed). １ , 100 ２ , 100 ３ The reflection control area is made up of ().

[0153] (Variations in Layer Structure) Figures 42A and 42B (hereinafter collectively referred to as Figure 42 for convenience) are schematic diagrams showing examples of variations in the layer structure of a reflectarray. However, the layer structure is not limited to this example. Figure 42(a) shows a configuration in which an additional function layer 400 is laminated on the top surface of a configuration in which a ground layer 300, a dielectric layer 200, and element patterns 100 are laminated (hereinafter referred to as the "basic configuration"), and adjacent element patterns 100 are connected by an additional function layer 400 having a groove formed therein. Figure 42(b) shows a configuration similar to Figure 42(a) except that a gap is formed between adjacent element patterns 100 where no additional function layer 400 is present. Figure 42(c) shows a configuration in which the additional function layer 400 is uniformly laminated on the top and bottom surfaces of the basic configuration. Figure 42(d) shows a configuration in which the additional function layer 400 is uniformly laminated so as to cover not only the top and bottom surfaces of the basic configuration but also the side surfaces.

[0154] Figure 42(e) shows an embodiment in which an adhesion improving layer 600 and an additional function layer 400 are uniformly laminated on the upper surface of the basic structure. Figure 42(f) shows an embodiment similar to Figure 42(e) except that a gap is formed between adjacent element patterns 100 where neither the additional function layer 400 nor the adhesion improving layer 600 is present. Figure 42(g) shows an embodiment in which an adhesion improving layer 600 and an additional function layer 400 are uniformly laminated on the upper and lower surfaces of the basic structure. Figure 42(h) shows an embodiment in which an additional function layer 400 is uniformly laminated on the upper surface of the basic structure, and an adhesion improving layer 600 is further laminated between the dielectric layer 200 and the element pattern 100, and between the dielectric layer 200 and the ground layer 300.

[0155] (Air bubble inclusion) When a functional layer is laminated on a reflectarray of basic configuration, the functional layer may contain multiple bubbles. However, fewer bubbles are preferable because they adversely affect the appearance of the reflectarray and the reflector performance. In particular, bubbles on the side of the element pattern change the reflection phase in the unit cell, causing adverse effects such as increased unwanted reflection and reduced reflection intensity in the desired direction, so it is strongly desired to suppress their occurrence. Furthermore, the larger the bubble diameter relative to the wavelength of the radio wave, the greater the adverse effects. From the above perspective, when using radio waves in the 1 GHz to 300 GHz band, for example, it is preferable that the bubble diameter of the bubbles on the side of the element be less than 100 μm.

[0156] For example, for 100 randomly selected element patterns on a reflect array, it is preferable that there are fewer than 5 element patterns with bubbles on their sides that have a bubble diameter of 100 μm or more, more preferably fewer than 3, and even more preferably zero.

[0157] Figure 43 is a photograph of a portion of the element pattern observed from the top surface of the functional layer using an optical microscope. If a transparent or semitransparent adhesion improving layer and an opaque additional functional layer are present on the top surface of the element pattern, the additional functional layer is removed by peeling, scraping, dissolving, or the like while leaving the adhesion improving layer in place, and the entire periphery of the element pattern is observed from the top surface of the adhesion improving layer using an optical microscope. If the element pattern cannot be observed using the above method, the reflect array is cut in the thickness direction, and the cross section of the element pattern is observed using an optical microscope. In Figure 43, the presence of bubbles is observed above the side surface 500 of the element pattern.

[0158] When measuring bubble diameters in a reflectarray with a functional layer, the bubble diameter is determined by observing the entire circumference or cross section of the element pattern using an optical microscope at a magnification of 50 to 400 times. The magnification for the entire circumference observation is set arbitrarily, and the magnification for the cross section observation is set so that the top and bottom surfaces of the element pattern are simultaneously displayed on one screen. When measuring bubble diameters, only bubbles that can be clearly observed in their entirety from the observation image are measured, and the longest line segment connecting two points on the bubble's outline is measured as the bubble diameter. When actually measuring, the above-described bubble detection and bubble diameter measurement can be performed on randomly selected element patterns (e.g., 100) on the reflectarray.

[0159] (Suppression of Air Bubbles) Next, a configuration for efficiently suppressing the generation of air bubbles of microfine bubble size will be described. Fig. 44 is a schematic cross-sectional view showing a part of the basic layer configuration of a reflectarray including the side surface of the element pattern 1. However, it goes without saying that the following description is not limited to the layer configuration of Fig. 44, and can also be applied to the layer configuration shown in Fig. 42 and other layer configurations within the scope of the object of the present invention.

[0160] The layer configuration of Figure 44 includes a ground layer 300 including a first surface and a second surface located opposite the first surface, a dielectric layer 200 including a third surface opposite the second surface and a fourth surface located opposite the third surface, an element pattern 100 including a fifth surface opposite the fourth surface, a sixth surface located opposite the fifth surface, and an element pattern side surface 500 (first side surface) located between the fifth and sixth surfaces, and an additional function layer 400 covering the sixth surface and the first side surface, and the first side surface includes a first end connected to the fifth surface, a second end connected to the sixth surface, and an intermediate point therebetween.

[0161] 45 is an enlarged schematic diagram of the vicinity of the first side surface of the element pattern 100. The thickness L (μm) of the element pattern 100 satisfies the following formula (1): 1.0≦L (1) It is believed that the occurrence of microfables with bubble diameters of approximately 1 μm or larger becomes a problem when the thickness L satisfies formula (1), and therefore, the provision of formula (1) enables a configuration that is more specialized for suppressing microfables.

[0162] Furthermore, the angle (general tilt angle) α (°) between the line connecting the first end and the second end and the perpendicular line from the second end to the fifth surface is specified to satisfy the following formula (2): α≧10 (2) This results in an overall configuration in which the side surfaces of the element pattern 1 expand so as to be displaced outward from the upper surface (sixth surface) to the lower surface (fifth surface).

[0163] Next, the side of the element pattern 1 is divided at N points at equal intervals in the thickness direction using N calculated from the following formula (3), with the division point closest to the second end being the first point and the division point closest to the first end being the Nth point: N = [L] (3) (N = 1, 2, ...) where N is the maximum integer value not exceeding L (μm).

[0164] The angle (point inclination angle) βi (°) between the line connecting the (i-1)th point and the ith point and the perpendicular line from the second end to the bottom surface is specified to satisfy the following formula (4) for any i (i = 1 to N+1): βi ≧ 0 (4) (i is an integer that satisfies 1≦i≦N+1, where the 0th point corresponds to the second end and the N+1th point corresponds to the first end.)

[0165] 46A and 46B (hereinafter collectively referred to as FIG. 46 for convenience) are schematic diagrams showing examples of the division of the side shape of the element pattern and the inclination angles α and βi. FIG. 46(a) shows α when formula (1) is not satisfied and N = 0 (La < 1.0). For thicknesses where La is less than 1.0 μm, if α ≧ 10, it is considered that even if the first side has any shape, there is almost no risk of microfudge-sized bubbles being generated by entrapment of an air layer.

[0166] 46(b) shows β1 when N = 1 (1.0≦Lb<2.0). If the conditions of the general inclination angle α≧10 and the point inclination angles β1 and β2≧0 are satisfied, it is considered that there is almost no possibility of microfubble-sized bubbles being generated by entraining air layers, even if the two divided sections of the first side surface have any shape.

[0167] 46(c) shows β2 when N = 2 (2.0≦Lc<3.0). If the conditions of the general inclination angle α≧10 and the point inclination angles β1 to β3≧0 are satisfied, it is considered that there is almost no possibility of microfubble-sized bubbles being generated by entraining air layers, even if each of the three divided sections of the first side surface has an arbitrary shape.

[0168] Figure 46(d) shows β3 when N = 3 (3.0 ≦ Ld < 4.0). If the conditions of the general inclination angle α ≧ 10 and the point inclination angles β1 to β4 ≧ 0 are satisfied, it is considered that there is almost no possibility of microfubble-sized bubbles being generated by entraining air layers, even if each of the four divided sections of the first side surface has an arbitrary shape.

[0169] In this way, when the thickness of element pattern 1 satisfies formula (1), if the conditions of formulas (2) and (4) are satisfied in the N+1 divided sections scaled to approximately 1 μm size according to formula (3) depending on the thickness, even if each of the N+1 divided sections on the first side surface has an arbitrary shape, there will be no depressions into which bubbles larger than microfables can enter, making it possible to suppress the generation of bubbles. Therefore, the growth of numerous bubbles with diameters of 100 μm or larger can also be efficiently suppressed.

[0170] [Examples] Examples and comparative examples will be described. Table B1 shows the specifications of the configuration of the reflectarray used. Fig. 47 is a graph showing the reflection angle and reflection intensity (bistatic RCS) in the examples and comparative examples.

[0171] (Example B1) A reflectarray was constructed by laminating an additional functional layer 0.098 mm thick on the element pattern side of a basic configuration using 0.018 mm thick (L = 18 μm) copper for the element pattern and ground layer, and a 0.764 mm thick glass / fluororesin composite material for the dielectric. However, the conductivity of the copper was 5.8 × 10 siemens / m, the real part of the dielectric constant of the dielectric was 2.6, tan δ was 0.0025, and the real part of the dielectric constant of the additional functional layer was 2.70, tan δ was 0.0060.

[0172] The operating frequency was set to 27.2 GHz, the target reflection characteristics were set to θi = 33° and θr = 0°, and the x-axis size Lx of the reflection control area was determined to be 20.238 mm using equation (7). The number of divisions of the reflection control area was set to 3, and the x-axis and y-axis sizes of the unit cell were set to 6.746 mm. The element shape was a cross patch in which two square patches were orthogonal to each other in the xy plane. Here, the element lengths of each element pattern within the reflection control area were the same, and only the element widths differed. The reflect array was arranged with 81 unit cells in a 9 x 9 arrangement in the x-axis and y-axis directions, and the size in the xy plane was 60.714 mm square.

[0173] The general tilt angle of all element patterns was α = 10°, and the side shape was a uniform plane (point tilt angles β1 to β19 = 10°) (β1 to β19 are sometimes collectively referred to as simply β), and a 0.1 mm air layer was inserted on the side of the element pattern in four unit cells. The reflection characteristics when polarized waves parallel to the y axis were irradiated onto the reflectarray at θix = 33° and θiy = 0° were analyzed using HFSS.

[0174] The reflection characteristics of the reflectarray in the xz plane are shown in Table B1. The radio wave incident at θi = 33° was reflected in the desired direction of θr = 0°, with an RCS of 0.22 dBsm. The relationship between the reflection angle and the reflection intensity is shown in Figure 47.

[0175] (Example B2) In a reflectarray similar to that in Example B1, the general tilt angle α of all element patterns was 15°, and the side surface shape was a uniform plane (point tilt angles β1 to β19 = 15°), and an air layer of 0.1 mm was inserted on the side surface of the element pattern in two unit cells. The reflection characteristics when polarized waves parallel to the y-axis were irradiated onto the reflectarray at θix = 33° and θiy = 0° were analyzed using HFSS.

[0176] The reflection characteristics of the reflectarray in the xz plane are shown in Table B1. The radio wave incident at θi = 33° was reflected in the desired direction of θr = 0°, with an RCS of 0.23 dBsm. The relationship between the reflection angle and the reflection intensity is shown in Figure 47.

[0177] (Example B3) In a reflectarray similar to Example B1, the general tilt angle α of all element patterns was 30°, and the side surface shape was a uniform plane (point tilt angles β1 to β19 = 30°), and a 0.1 mm air layer was inserted on the side surface of the element pattern in 0 unit cells (no air bubbles). The reflection characteristics when polarized waves parallel to the y-axis were irradiated onto the reflectarray at θix = 33° and θiy = 0° were analyzed using HFSS.

[0178] The reflection characteristics of the reflectarray in the xz plane are shown in Table B1. The radio wave incident at θi = 33° was reflected in the desired direction of θr = 0°, with an RCS of 0.25 dBsm. The relationship between the reflection angle and the reflection intensity is shown in Figure 47.

[0179] Comparative Example B1 In a reflectarray similar to that in Example B1, the general tilt angle α of all element patterns was 0°, the side surface shape was a uniform plane, and an air layer of 0.1 mm was inserted on the side surface of the element pattern in 27 unit cells. The reflection characteristics when polarized waves parallel to the y-axis were irradiated onto the reflectarray at θix = 33° and θiy = 0° were analyzed using HFSS.

[0180] The reflection characteristics of the reflectarray in the xz plane are shown in Table B1. The radio wave incident at θi = 33° was reflected in the desired direction of θr = 0°, with an RCS of -1.2 dBsm. The relationship between the reflection angle and the reflection intensity is shown in Figure 47.

[0181] Comparative Example B2 In a reflectarray similar to that in Example B1, the general tilt angle α of all element patterns was 0°, the side surface shape was a uniform plane, and an air layer of 0.1 mm was inserted on the side surface of the element pattern in 27 unit cells. The reflection characteristics when polarized waves parallel to the y-axis were irradiated onto the reflectarray at θix=33° and θiy=0° were analyzed using HFSS.

[0182] The reflection characteristics of the reflectarray in the xz plane are shown in Table B1. The radio wave incident at θi = 33° was reflected in the desired direction of θr = 0°, with an RCS of -1.18 dBsm. The relationship between the reflection angle and the reflection intensity is shown in Figure 47.

[0183] Comparative Example B3 In a reflectarray similar to that in Example B1, the general tilt angle α of all element patterns was 0°, the side surface shape was a uniform plane, and an air layer of 0.1 mm was inserted on the side surface of the element pattern in eight unit cells. The reflection characteristics when polarized waves parallel to the y-axis were irradiated onto the reflectarray at θix=33° and θiy=0° were analyzed using HFSS.

[0184] The reflection characteristics of the reflectarray in the xz plane are shown in Table B1. The radio wave incident at θi = 33° was reflected in the desired direction of θr = 0°, with an RCS of -1.06 dBsm. The relationship between the reflection angle and the reflection intensity is shown in Figure 47.

[0185] In Example B1, four bubbles were trapped in the element pattern at an inclination angle of α / β = 10°, in Example B2, two bubbles were trapped at an inclination angle of α / β = 15°, and in Example B3, zero bubbles were trapped at an inclination angle of α / β = 30°, demonstrating good reflection intensity and suppression of unwanted reflection. Meanwhile, in Comparative Examples B1 to B3, the inclination angle α / β = 0° was observed, with 27 bubbles trapped in the element pattern in Comparative Example B1, 27 bubbles in Comparative Example B2, and eight bubbles in Comparative Example B3, resulting in unwanted reflection to the back side of the reflector. When the number of bubbles trapped in the element pattern exceeds a certain number (four), unwanted reflection to the back side of the reflector increases, and the RCS in the desired reflection angle θr = 0° direction decreases. It is believed that by providing an inclination angle on the side of the element pattern that displaces the general inclination angle α or the point inclination angle βi outward, it is possible to reduce the intrusion of bubbles between the additional function layer and the side of the element pattern, thereby suppressing unwanted reflection.

[0186] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention. Different embodiments can also be combined. Furthermore, by providing an electromagnetic wave reflecting plate on the support body to form an electromagnetic wave reflecting device, the convenience of installation and movement can be improved.

[0187] The following are some non-limiting aspects of the present invention. (Aspect 1) An electromagnetic wave reflector comprising a ground layer, a dielectric layer, and an element pattern, wherein the plane or side of the element pattern includes a shape that is resistant to factors that cause defects in the manufacturing process. (Aspect 2) The electromagnetic wave reflector according to Aspect 1, including a reflection control region consisting of the dielectric layer and a plurality of the element patterns, wherein the plane shape of the element pattern includes rounded corners or rounded corners. (Aspect 3) The electromagnetic wave reflector according to Aspect 2, wherein the rounded corners, when viewed in plan, include an arc of a circle of curvature whose radius of curvature R1 is equal to or less than half the reference length P, and the rounded corners, when viewed in plan, include an arc of a circle of curvature whose radius of curvature R2 is equal to or less than three times the reference length P. (Aspect 4) The electromagnetic wave reflector according to Aspect 3, characterized in that the rounding of the rounded corner portion includes an arc of the circle of curvature whose center of curvature is located within a range of P / 2×√2 or less from the reference intersection point sx on the reference line S toward the inside of the element in plan view, and the rounding of the rounded corner portion includes an arc of the circle of curvature whose center of curvature is located within a range of 3P×√2 or less from the reference intersection point tx on the reference line T toward the outside of the element in plan view. (Aspect 5) The electromagnetic wave reflector according to any one of Aspects 1 to 4, characterized in that it includes a reflection control region consisting of the dielectric layer and a plurality of the element patterns, and the cross-sectional shape of the element patterns includes a rounded corner portion or a rounded corner portion. (Aspect 6) The electromagnetic wave reflector according to Aspect 5, characterized in that the rounding of the rounded corners, when viewed in cross section, includes an arc of a circle of curvature whose radius of curvature R3 is equal to or greater than 1 / 6 of the thickness d of the element pattern, and the rounding of the rounded corners, when viewed in cross section, includes an arc of a circle of curvature whose radius of curvature R4 is equal to or greater than 1 / 6 of the thickness d of the element pattern. (Aspect 7) The electromagnetic wave reflector according to Aspect 6, characterized in that the rounding of the rounded corners, when viewed in cross section, includes an arc of the circle of curvature whose center of curvature is located within a range of d / 6 × √2 or more from the reference intersection point ux along the reference line U toward the surface of the dielectric layer, and the rounding of the rounded corners, when viewed in cross section, includes an arc of the circle of curvature whose center of curvature is located within a range of d / 6 or more from the reference intersection point vx along the reference line V toward the surface of the element pattern.(Embodiment 8) The electromagnetic wave reflector according to any one of embodiments 1 to 7, further comprising a functional layer disposed so as to cover the element pattern. (Aspect 9) An electromagnetic wave reflector according to any one of Aspects 1 to 7, comprising an additional functional layer covering at least the top and side surfaces of the element pattern, wherein a thickness L (μm) of the element pattern satisfies the following formula (1): 1.0≦L (1); the side surfaces have a first end connected to the bottom surface of the element pattern and a second end connected to the top surface, wherein an angle α (°) between a straight line connecting the first end and the second end and a perpendicular line from the second end to the bottom surface in a cross section satisfies the following formula (2): α≧10 (2); and wherein the side surfaces are divided at N points at equal intervals in the thickness direction using N calculated from the following formula (3), and the division point closest to the second end is defined as the first point and the division point closest to the first end is defined as the Nth point, an angle βi between a straight line connecting point (i-1) and point i in the cross section and a perpendicular line from the second end to the bottom surface satisfies the following formula (4) for any i (i = 1 to N+1). N=[L] (3) (N=1, 2, ...) βi≧0 (4) (i is an integer satisfying 1≦i≦N+1, where the 0th point corresponds to the second end and the N+1th point corresponds to the first end.) (Aspect 10) The electromagnetic wave reflector according to any one of Aspects 1 to 9, wherein the element pattern includes a cross patch in which two square patches intersect at right angles. (Aspect 11) The electromagnetic wave reflector according to any one of Aspects 1 to 9, wherein the element pattern consists of a cross patch and a ring surrounding the cross patch. (Aspect 12) The electromagnetic wave reflector according to any one of Aspects 1 to 9, wherein the element pattern consists of a Jerusalem cross shape. (Aspect 13) The electromagnetic wave reflector according to any one of Aspects 8 to 12, wherein the functional layer has a porous structure. (Aspect 14) The electromagnetic wave reflector according to any one of Aspects 8 to 13, wherein the surface haze of the functional layer is 70% or more. (Aspect 15) The electromagnetic wave reflector according to any one of Aspects 8 to 14, wherein the functional layer is formed so as to achieve impedance matching with an air layer through which radio waves propagate.(Aspect 16) The electromagnetic wave reflector according to any one of Aspects 1 to 15, further comprising an adhesion improving layer. (Aspect 17) An electromagnetic wave reflecting device comprising the electromagnetic wave reflector according to any one of Aspects 1 to 16 provided on a support.

[0188] REFERENCE SIGNS LIST 1...reflectarray, 2...reflectarray with laminated functional layers, 3...unit cell, 4...reflection control area, 11, 300...ground layer, 12, 200...dielectric layer, 13...element pattern layer, 14, 100...element pattern, 15, 400...functional layer, 16...arm portion, 500...side surface of element pattern, 600...adhesion improving layer

Claims

1. An electromagnetic wave reflector comprising a ground layer, a dielectric layer, and an element pattern, the plane or side of the element pattern including a shape that is resistant to factors that cause defects in the manufacturing process.

2. The electromagnetic wave reflector according to claim 1, comprising a reflection control region consisting of the dielectric layer and a plurality of the element patterns, the planar shape of the element patterns including rounded corners or edges.

3. The electromagnetic wave reflector according to claim 2, wherein the roundness of the rounded corner portion, when viewed in a plane, includes an arc of a circle of curvature whose radius of curvature R1 is equal to or less than 1 / 2 the reference length P, and the roundness of the rounded corner portion, when viewed in a plane, includes an arc of a circle of curvature whose radius of curvature R2 is equal to or less than 3 times the reference length P.

4. The electromagnetic wave reflector of claim 3, wherein the roundness of the rounded corner portion includes an arc of the circle of curvature whose center of curvature is located within a range of P / 2 x √2 or less from the reference intersection point sx along the reference line S toward the inside of the element when viewed in a plane, and the roundness of the rounded corner portion includes an arc of the circle of curvature whose center of curvature is located within a range of 3P x √2 or less from the reference intersection point tx along the reference line T toward the outside of the element when viewed in a plane.

5. The electromagnetic wave reflector according to claim 1, comprising a reflection control region consisting of said dielectric layer and a plurality of said element patterns, wherein the cross-sectional shape of said element patterns includes a rounded corner portion or a rounded end portion.

6. The electromagnetic wave reflector according to claim 5, wherein the roundness of the rounded corner portion, when viewed in cross section, includes an arc of a circle of curvature whose radius of curvature R3 is greater than or equal to 1 / 6 of the thickness d of the element pattern, and the roundness of the rounded corner portion, when viewed in cross section, includes an arc of a circle of curvature whose radius of curvature R4 is greater than or equal to 1 / 6 of the thickness d of the element pattern.

7. The electromagnetic wave reflector of claim 6, wherein the roundness of the rounded corner portion includes an arc of the circle of curvature whose center of curvature is located within a range of d / 6 × √2 or more from the reference intersection point ux along a reference line U in the direction of the surface of the dielectric layer when viewed in cross section, and the roundness of the rounded corner portion includes an arc of the circle of curvature whose center of curvature is located within a range of d / 6 or more from the reference intersection point vx along a reference line V in the direction of the surface of the element pattern when viewed in cross section.

8. The electromagnetic wave reflector according to claim 1, further comprising a functional layer disposed so as to cover said element pattern.

9. The electromagnetic wave reflector according to claim 1, further comprising an additional functional layer covering at least an upper surface and a side surface of the element pattern, wherein a thickness L (μm) of the element pattern satisfies the following formula (1): 1.0≦L (1); the side surface has a first end connected to a lower surface of the element pattern and a second end connected to the upper surface, and an angle α (°) between a straight line connecting the first end and the second end in a cross section and a perpendicular line from the second end to the lower surface satisfies the following formula (2): α≧10 (2); and when the side surface is divided at N points at equal intervals in the thickness direction using N obtained from the following formula (3), and the division point closest to the second end is the first point and the division point closest to the first end is the Nth point, an angle βi between a straight line connecting point (i-1) and point i in a cross section and a perpendicular line from the second end to the lower surface satisfies the following formula (4) for any i (i = 1 to N + 1). N=[L] (3) (N=1, 2,...) βi≧0 (4) (i is an integer satisfying 1≦i≦N+1, where the 0th point corresponds to the second end and the N+1th point corresponds to the first end.) 10. An electromagnetic wave reflector according to any one of claims 1 to 9, wherein the element pattern includes a cross patch in which two rectangular patches are perpendicular to each other.

11. The electromagnetic wave reflector according to any one of claims 1 to 9, wherein the element pattern comprises a cross patch and a circular ring surrounding the cross patch.

12. The electromagnetic wave reflector according to any one of claims 1 to 9, wherein the element pattern is in the shape of a Jerusalem cross.

13. The electromagnetic wave reflector according to claim 8 or 9, wherein the functional layer has a porous structure.

14. The electromagnetic wave reflector according to claim 8 or 9, wherein the functional layer is formed so as to achieve impedance matching with the air layer through which the radio waves propagate.

15. An electromagnetic wave reflecting device comprising an electromagnetic wave reflecting plate according to any one of claims 1 to 9 provided on a support.

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