Reflector

Abstract

A reflector according to one embodiment of the present invention comprises: a dielectric layer having a first surface and a second surface on the opposite side of the first surface; a conductor layer having a plurality of conductor patterns that are disposed at positions separated from each other on the first surface and reflect incident radio waves; a first cover layer that is disposed on the first surface and covers the conductor layer; and a ground layer that is disposed on the second surface of the dielectric layer. The peel strength between the first cover layer and the first surface of the dielectric layer is greater than the peel strength between each conductor pattern and the first surface of the dielectric layer, and the transmittance of the first cover layer with respect to visible light is 20% or less.

Description

Reflector

[0001] The present invention relates to a reflector.

[0002] Using radio waves with high frequencies such as microwaves, millimeter waves, and terahertz waves for wireless communication enables high-speed and large-capacity communication. On the other hand, these high-frequency radio waves have strong straightness. Therefore, obstacles may restrict the propagation path of radio waves. In order to reduce the limitations of communication using high-frequency radio waves, reflectors provided with a plurality of conductor patterns on the radio wave incident surface are used.

[0003] For example, Patent Document 1 discloses a reflector including a dielectric layer, a conductive layer provided on a first surface of the dielectric layer and including a periodic array of a plurality of conductor patterns, a ground layer provided on a second surface opposite to the first surface, and a protective layer covering the conductive layer.

[0004] International Publication No. WO 2023 / 140193

[0005] While many combinations are conceivable for the shape, size, spacing, and the like of the plurality of conductor patterns that reflect incident radio waves, the reflection characteristics of incident radio waves can vary depending on the configuration of the conductor patterns including these combinations. There is a need to conceal information related to the configuration of the plurality of conductor patterns.

[0006] The present invention provides a reflector capable of concealing information related to the configuration of a plurality of conductor patterns.

[0007] A reflector according to one aspect of the present invention includes: a dielectric layer having a first surface and a second surface located on the opposite side of the first surface; a conductor layer having a plurality of conductor patterns each disposed at positions spaced apart from each other on the first surface and reflecting incident radio waves; a first cover layer disposed on the first surface and covering the conductor layer; and a ground layer disposed on the second surface of the dielectric layer, wherein a peel strength between the first cover layer and the first surface of the dielectric layer is greater than a peel strength between each of the conductor patterns and the first surface of the dielectric layer, and a transmittance of the first cover layer for visible light is 20% or less.

[0008] A reflector according to one aspect of the present invention comprises a dielectric layer having a first surface and a second surface opposite to the first surface, a conductor layer having a plurality of conductor patterns that reflect incident radio waves and are arranged at mutually separated positions on the first surface, a first cover layer arranged on the first surface and covering the conductor layer, and a ground layer arranged on the second surface of the dielectric layer, wherein the peel strength between the first cover layer and the first surface of the dielectric layer is greater than the tensile fracture strength of the dielectric layer, and the transmittance of the first cover layer to visible light is 20% or less.

[0009] According to the present invention, it is possible to provide a reflector that can conceal information regarding the configuration of multiple conductor patterns.

[0010] This is a schematic cross-sectional view showing a reflector according to an embodiment. This is a diagram showing an example of a conductor pattern design method. This is a schematic cross-sectional view showing a reflector according to a modified embodiment.

[0011] Embodiments of the present invention will be described in detail below with reference to the drawings. In each drawing, the same reference numerals are used for the same components, and redundant explanations are omitted as appropriate.

[0012] The embodiments shown below illustrate reflectors that embody the technical concept of the present invention, and do not limit the present invention to the embodiments shown below. The dimensions, materials, shapes, relative arrangements, etc. of the components described below are intended to be illustrative, and not to limit the scope of the present invention unless otherwise specified. Furthermore, the size and positional relationships of the components shown in the drawings may be exaggerated to clarify the explanation.

[0013] In the diagrams shown below, directions may be indicated by mutually orthogonal X, Y, and Z axes. The X-axis direction corresponds to the width direction of the reflector according to the embodiment. The Y-axis direction corresponds to the depth direction of the reflector according to the embodiment. The Z-axis direction corresponds to the thickness direction of the reflector according to the embodiment. The direction parallel to the XY plane, which includes the X-axis and Y-axis directions, may be called the in-plane direction. The Z-axis direction may also be called the perpendicular direction or the thickness direction.

[0014] In the X-axis direction, the direction the arrow is pointing is denoted as the +X side, and the opposite direction is denoted as the -X side. In the Y-axis direction, the direction the arrow is pointing is denoted as the +Y side, and the opposite direction is denoted as the -Y side. In the Z-axis direction, the direction the arrow is pointing is denoted as the +Z side, and the opposite direction is denoted as the -Z side.

[0015] [Embodiment] An example of the configuration of the reflector 1 according to the embodiment will be described with reference to Figures 1 and 2. Figure 1 is a schematic cross-sectional view showing the reflector 1 according to the embodiment. Figure 2 is a diagram showing an example of a design method for the conductor pattern 21.

[0016] The reflector 1 comprises a dielectric layer 10, a conductor layer 20, a first cover layer 30, and a ground layer 40. The conductor layer 20 includes a plurality of conductor patterns 21 and functions as a reflective surface of the reflector 1. This reflective surface is a metasurface that reflects incident radio waves at an angle (absolute value) different from the angle of incidence. The ground layer 40 creates capacitance between the ground layer 40 and each conductor pattern 21, allowing the magnitude of the phase delay to be controlled for each conductor pattern 21.

[0017] In the conductor layer 20, it is preferable that conductor patterns 21 of different sizes are arranged at a predetermined pitch. The size and pitch of the conductor patterns 21 are set according to the desired reflection characteristics. Each of the conductor patterns 21 is sufficiently smaller than the wavelength of the incident radio wave and selectively reflects the incident radio wave in the target frequency band. The phase of reflection is controlled by the conductor patterns 21 and the reflected waves are superimposed to form a reflected beam BM in the desired direction.

[0018] Let λ be the wavelength of the incident radio wave, d be the pitch of the conductor pattern 21, i.e., the distance between the centers of adjacent conductor patterns 21, δ1 and δ2 be the phases of the radio waves reflected by two adjacent conductor patterns 21, and θ be the reflection angle. The phase difference δ1 - δ2 is expressed by equation (1).

[0019] δ1 - δ2 = (2π / λ)d sinθ + 2nπ ... (1) where n is an integer.

[0020] To reflect radio waves in a desired direction using reflector 1, δ1, δ2, and d should be designed so that the desired reflection angle θ is obtained. The reflection angle θ is set to a desired angle between the normal direction (0°) and the horizontal direction (90°) of the reflecting surface of reflector 1, excluding 0° and 90°. In the example shown in Figure 1, the normal direction of the reflecting surface of reflector 1 corresponds to the Z-axis direction.

[0021] The values ​​of δ1 and δ2, which represent the reflection phase, can be controlled and changed by design parameters such as the wavelength λ of the incident radio wave, the size (length × width) and pitch of the conductor pattern 21, and the thickness and relative permittivity of the reflector 1. For example, when designing the length L of the conductor pattern 21 to obtain a desired phase difference, the conductor pattern 21 may be designed by creating the length / phase characteristic graph shown in Figure 2. The length / phase characteristic in Figure 2 is obtained by measuring the reflection pattern of radio waves while changing the length L of the conductor pattern 21, while keeping the design parameters other than length L (mm) fixed, and analyzing the results using 3D electromagnetic field simulation software. As a design parameter other than length, for example, the relative permittivity of the dielectric layer 10 can be fixed to 1.88. However, the relative permittivity of the dielectric layer 10 is not limited to this. The following describes each component of the reflector 1.

[0022] <Dielectric Layer 10> An example of the configuration of the dielectric layer 10 will be described. As shown in Figure 1, the dielectric layer 10 is a plate-shaped member having a first surface 11a on the +Z side and a second surface 11b on the opposite side (-Z side) from the first surface 11a. The dielectric layer 10 has a substantially rectangular shape in plan view, for example. However, the dielectric layer 10 may have other shapes in plan view, such as a substantially circular shape, a substantially elliptical shape, and a substantially polygonal shape other than a rectangle.

[0023] Examples of materials constituting the dielectric layer 10 include polymer materials such as polyethylene resin, polypropylene resin, and polystyrene resin. However, the materials constituting the dielectric layer 10 are not limited to these and may include other materials such as ceramics or glass. Furthermore, the materials constituting the dielectric layer 10 may be composite materials including fluorine-based resin and inorganic porous aggregates. Examples of inorganic porous aggregates include those disclosed in Japan Patent Office Publication No. 2017-171898.

[0024] Examples of fluororesins include polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTEF), tetrafluoroethylene-ethylene copolymer (ETFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), and polyvinylidene fluoride (PVDF), which can be used individually or in combination of two or more. Among these, PTFE is preferred.

[0025] It is preferable that the fluororesin is "fibrillated (structured into a fibrous form)". The fibrillated fluororesin may hereafter be referred to as "fibril made of fluororesin" or "fibril of fluororesin". It is more preferable that the fibrillated fibers are oriented not only in one direction but in multiple directions. It is also particularly preferable that the fibrils of the fluororesin and inorganic fine particle aggregates are linked to form a "three-dimensional fine network structure". When the fibrils of the fluororesin and inorganic fine particle aggregates are linked to form a three-dimensional fine network structure, excellent mechanical strength and dimensional stability can be ensured as a composite material. Furthermore, the fibrillation of the fluororesin can be promoted, for example, by applying shear force, but more specifically, it is preferable to carry it out by multi-stage rolling. Furthermore, it is preferable to carry out the three-dimensional fine network structure by multi-stage rolling in opposite directions. Note that "inorganic fine particle aggregates" are an example of inorganic porous aggregates.

[0026] If the dielectric layer 10 includes, for example, fibrils of a fluororesin and aggregates of inorganic fine particles, the dielectric layer 10 has a porosity shown in formula (1). The porosity is a value calculated by measuring the bulk density and true density of the material that forms the void-encapsulating layer and substituting them into formula (1).

[0027] Porosity [%] = (1 - (bulk density [g / cm³] of the material containing fibrils and inorganic fine particle aggregates of fluororesin) ３ ] / True density of materials containing fibrils and inorganic fine particle aggregates of fluororesin [g / cm³ ３ ])) × 100 ... (1)

[0028] The porosity of the dielectric layer 10 is preferably 30% or more, more preferably 35% or more, even more preferably 40% or more, even more preferably 45% or more, and particularly preferably 50% or more. Furthermore, the porosity of the dielectric layer 10 is preferably 80% or less, and more preferably 70% or less. When the porosity of the dielectric layer 10 is within the above range, good properties such as dielectric constant and expansion coefficient can be ensured as a composite material.

[0029] The relative permittivity of the dielectric layer 10 is not particularly limited. For example, the relative permittivity of the dielectric layer 10 is preferably 1.5 to 5.0. By setting the relative permittivity of the dielectric layer 10 to 1.5 to 5.0, the range of the reflected beam BM can be increased. Alternatively, the relative permittivity of the dielectric layer 10 is preferably 1.5 to 2.0. By setting the relative permittivity of the dielectric layer 10 to 1.5 to 2.0, the range of the reflected beam BM can be further increased. However, the relative permittivity of the dielectric layer 10 is not limited to these values.

[0030] The thickness of the dielectric layer 10 is not particularly limited, but is preferably 0.1 mm to 1.5 mm. By setting the thickness of the dielectric layer 10 within this range, the propagation distance of the reflected beam BM can be increased. Furthermore, by setting the thickness of the dielectric layer 10 within this range, robustness can be improved.

[0031] As will be explained separately, a plurality of conductor patterns 21 of the conductor layer 20 and a first cover layer 30 are arranged on the first surface 11a of the dielectric layer 10. By adjusting the arithmetic mean roughness (Ra) of the first surface 11a of the dielectric layer 10, the peel strength between each conductor pattern 21 and the first surface 11a of the dielectric layer 10, and the peel strength between the first cover layer 30 and the first surface 11a of the dielectric layer 10 can be changed. An example of the range of arithmetic mean roughness (Ra) of the first surface 11a of the dielectric layer 10 is 100 nm or more and 1000 nm or less. However, the arithmetic mean roughness (Ra) of the first surface 11a of the dielectric layer 10 is not limited to this.

[0032] <Conducting Layer 20> An example of the configuration of the conducting layer 20 will be described. As shown in Figure 1, the conducting layer 20 has a plurality of conducting patterns 21. Each of the plurality of conducting patterns 21 is arranged at a distance from each other on the first surface 11a of the dielectric layer 10. In the example shown in Figure 1, the conducting layer 20 has three conducting patterns 21. However, the number of conducting patterns 21 in the conducting layer 20 is not limited to three.

[0033] The incident surface to which the radio waves incident on the reflector 1 enter is formed by the +Z-side surface (surface) of each of the multiple conductor patterns 21 and the first surface 11a of the dielectric layer 10. Here, the incident radio waves incident on the reflector 1 are reflected by each of the multiple conductor patterns 21. That is, multiple reflected waves are generated, each reflected by a different conductor pattern 21. When these multiple reflected waves are combined, a reflected beam BM is emitted from the reflector 1.

[0034] In the example shown in Figure 1, the multiple conductor patterns 21 are arranged along the X-axis direction. However, the arrangement direction of the multiple conductor patterns 21 is not limited to the X-axis direction. For example, the multiple conductor patterns 21 may be arranged in a matrix along both the X-axis and Y-axis directions. Alternatively, the multiple conductor patterns 21 may be arranged in a direction different from the X-axis or Y-axis direction.

[0035] Each of the multiple conductor patterns 21 may have a shape known as a cross dipole, in which, in a plan view, a strip-shaped pattern along the X-axis intersects with another strip-shaped pattern along the Y-axis. However, the shape of the conductor pattern 21 is not limited to a cross dipole. Examples of other shapes for the conductor pattern 21 include shapes that are approximately circular, approximately elliptical, or approximately rectangular in a plan view. Furthermore, the shape of the conductor pattern 21 may be different from these.

[0036] Examples of materials that constitute each of the multiple conductor patterns 21 include metals such as titanium, silicon, niobium, indium, zinc, tin, gold, silver, copper, aluminum, cobalt, chromium, nickel, lead, iron, palladium, platinum, tungsten, zirconium, tantalum, and hafnium; and conductive metal oxides such as ITO (indium and tin oxide), zinc oxide, and tin oxide. Furthermore, materials containing two or more of these metals or metal oxides, or alloys with these metals as the main component, are also acceptable.

[0037] By changing the thickness of each conductor pattern 21, the peel strength between each conductor pattern 21 and the first surface 11a of the dielectric layer 10 can be changed. From the viewpoint of both preventing the conductor pattern 21 from peeling off when using the reflector 1 and concealing the conductor pattern 21 when the first cover layer 30 is peeled off from the dielectric layer 10, it is preferable that the peel strength between each conductor pattern 21 and the first surface 11a of the dielectric layer 10 be greater than the tensile fracture strength of the dielectric layer 10. For example, when the dielectric layer 10 is made of a resin material mainly composed of fluororesin (an example in which fibrils of fluororesin are included), the peel strength between each conductor pattern 21 and the first surface 11a of the dielectric layer 10 is preferably 0.5 N / mm or more, more preferably 0.6 N / mm or more, and even more preferably 0.7 N / mm or more. The thickness of each conductor pattern 21 is, for example, 5 μm or more and 50 μm or less. However, the thickness of each conductor pattern 21 is not limited to this. In this specification, "tensile fracture strength" refers to the value measured as the external force (in N / mm) at which the test specimen was subjected to peel strength testing, for example, in accordance with JIS C 6481:1996 Test Method for Copper-Clad Laminates for Printed Wiring Boards, using only the dielectric layer 10 as the test specimen, and when the test specimen was subjected to peeling, fracturing, or other damage.

[0038] <First Cover Layer 30> The first cover layer 30 is placed on the first surface 11a of the dielectric layer 10 and covers the conductor layer 20. Specifically, the first cover layer 30 covers all of the conductor patterns 21 of the conductor layer 20 at once. By covering all of the conductor patterns 21 with the first cover layer 30 at once, corrosion of the conductor patterns 21 can be reduced. In addition, the durability of the reflector 1 can be improved.

[0039] As shown in Figure 1, the portion of the first cover layer 30 that fills the gap between adjacent conductor patterns 21 is in contact with the first surface 11a of the dielectric layer 10. In addition, the portion of the first cover layer 30 that is placed on the conductor pattern 21 is in contact with the upper surface of the conductor pattern 21.

[0040] The first cover layer 30 is transparent to incident radio waves incident on the reflector 1 and to the reflected beam BM reflected by the conductor layer 20. Here, "transparent" to incident radio waves and reflected beam BM means having a transmittance of 60% or more, preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more, with respect to the incident radio waves and reflected beam BM.

[0041] The first cover layer 30 includes, for example, a resin material. Among these, epoxy resins, urethane resins, and acrylic resins are preferred, as they can be directly coated onto the dielectric layer 10 and the conductor layer 20 using methods such as dip coating and spin coating. By using epoxy resins, urethane resins, and acrylic resins as the resin material included in the first cover layer 30, the first cover layer 30 can be easily placed on the dielectric layer 10 and the conductor layer 20, thereby reducing manufacturing costs. From the viewpoint of improving the peel strength between the first cover layer 30 and the first surface 11a of the dielectric layer 10, epoxy resins are particularly preferred.

[0042] The resin material included in the first cover layer 30 is not limited to epoxy resin, urethane resin, or acrylic resin. Examples of resin materials other than epoxy resin, urethane resin, and acrylic resin include polyimide resin, acrylic resin, vinylester resin, and phenolic resin. In the case of polyimide resin, vinylester resin, and phenolic resin, it may not be possible to directly coat them onto the dielectric layer 10 and the conductor layer 20. Therefore, the first cover layer 30, which has been pre-processed into a sheet, may be bonded onto the dielectric layer 10 and the conductor layer 20. In this case, the first cover layer 30 may have a configuration that includes a base material containing polyimide resin, rubber-based resin, or silicone resin, and an adhesive layer disposed on the lower surface of the base material and in contact with the dielectric layer 10 and the conductor layer 20. Examples of materials constituting the adhesive layer include acrylic resin, urethane resin, and silicone resin.

[0043] The transmittance of the first cover layer 30 to visible light is 20% or less. Further, the transmittance of the first cover layer 30 to visible light is more preferably 10% or less, and still more preferably 5% or less. When the transmittance of the first cover layer 30 to visible light is 20% or less, the possibility that configurations related to the shapes, sizes, intervals and the like of the plurality of conductor patterns 21 are visually recognized from the outside can be reduced.

[0044] In order to set the transmittance of the first cover layer 30 to visible light to 20% or less, the first cover layer 30 may have light absorbability or may have light reflectivity. Further, in order to set the transmittance of the first cover layer 30 to visible light to 20% or less, the first cover layer 30 may contain a colored filler. Examples of the color of the colored filler include black, white, red, blue, yellow, green, orange, brown, and purple. From the viewpoint of reducing transmittance, black and white are preferable as examples of the color of the colored filler.

[0045] Examples of the colored filler in the first cover layer 30 include hard carbon, soft carbon, activated carbon, carbon black, carbon nanotubes, cobalt-based pigments, iron-based pigments, chromium-based pigments, titanium-based pigments, vanadium-based pigments, zirconium-based pigments, molybdenum-based pigments, ruthenium-based pigments, platinum-based pigments, ITO (Indium Tin Oxide)-based pigments, ATO (antimony-doped tin oxide), carbon black, aniline black, titanium black, inorganic pigment hematite, perylene black, aluminum-based pigments, cyanine-based pigments, merocyanine-based pigments, croconium-based pigments, squarium-based pigments, azulenium-based pigments, polymethine-based pigments, naphthoquinone-based pigments, pyrylium-based pigments, phthalocyanine-based pigments, naphthalocyanine-based pigments, naphtholactam-based pigments, azo-based pigments, condensed azo-based pigments, and indigo-based pigments.

[0046] The content of the colored filler in the first cover layer 30 is preferably 5% by weight or more and 40% by weight or less. More preferably, the content of the colored filler in the first cover layer 30 is 7% by weight or more and 30% by weight or less, and even more preferably 10% by weight or more and 25% by weight or less. By having a colored filler content of 5% by weight or more and 40% by weight or less in the first cover layer 30, it is possible to reduce the transmittance of the first cover layer 30 to visible light while ensuring the strength of the first cover layer 30. On the other hand, if the content of the colored filler in the first cover layer 30 is less than 5% by weight, the effect of reducing the transmittance of the first cover layer 30 to visible light may be reduced. Also, if the content of the colored filler in the first cover layer 30 exceeds 40% by weight, it may become impossible to ensure the strength of the first cover layer 30.

[0047] The peel strength between the first cover layer 30 and the first surface 11a of the dielectric layer 10 is greater than the peel strength between each conductor pattern 21 and the first surface 11a of the dielectric layer 10. Since the first cover layer 30 covers all the conductor patterns 21 of the conductor layer 20 together, when the first cover layer 30 is peeled off from the first surface 11a of the dielectric layer 10, some or all of the conductor patterns 21 peel off from the first surface 11a of the dielectric layer 10 together with the first cover layer 30. As a result, either a part of the conductor pattern 21 remains on the first surface 11a of the dielectric layer 10 without retaining its original shape, or the entire conductor pattern 21 does not remain on the first surface 11a of the dielectric layer 10. Consequently, even if the first cover layer 30 is peeled off by an external force, the possibility of information regarding the configuration of the multiple conductor patterns 21 arranged on the first surface 11a of the dielectric layer 10 being recognized can be reduced. In other words, information regarding the configuration of the multiple conductor patterns 21 can be kept confidential. Preferably, the peel strength between the first cover layer 30 and the first surface 11a of the dielectric layer 10 is greater than the tensile fracture strength of the dielectric layer 10. For example, when the dielectric layer 10 is composed of a resin material mainly composed of fluororesin, the peel strength between the first cover layer 30 and the first surface 11a of the dielectric layer 10 is preferably 0.5 N / mm or more, more preferably 0.7 N / mm or more, and even more preferably 0.9 N / mm or more. In this way, when the first cover layer 30 is peeled from the dielectric layer 10, even if the peel strength of the adhesion surface 25 between each conductor pattern 21 and the first cover layer 30 is less than the peel strength between the first cover layer 30 and the first surface 11a of the dielectric layer 10, the surface of the dielectric layer 10 is destroyed and becomes a peeled layer containing each conductor pattern 21. In other words, the conductive layer 20 located between the first cover layer 30 and the dielectric layer 10 is difficult to see even when the surface of the dielectric layer 10 is examined after the peeling layer and the first cover layer 30 have been peeled off, thus concealing information regarding the configuration of the multiple conductive patterns 21. In this specification, "peel strength" can be measured using the "peel strength" test method conforming to JIS C 6481:1996 Test Method for Copper-Clad Laminates for Printed Wiring Boards. In the following description, the "peel strength" test and the peel strength test may be collectively referred to as the "peel strength test."In addition, it is more preferable that the transmittance of the first cover layer 30 for visible light is 20% or less, for concealing information related to the configuration of the plurality of conductor patterns 21.

[0048] The thickness of the first cover layer 30 is preferably 10 µm or more and 50 µm or less. Further, the thickness of the first cover layer 30 is more preferably 12 µm or more and 40 µm or less, and still more preferably 15 µm or more and 30 µm or less. When the thickness of the first cover layer 30 is 15 µm or more and 30 µm or less, the peel strength between the first cover layer 30 and the first surface 11a of the dielectric layer 10 can be improved.

[0049] In order to make the peel strength between the first cover layer 30 and the first surface 11a of the dielectric layer 10 greater than the peel strength between each conductor pattern 21 and the first surface 11a of the dielectric layer 10, it is preferable that the thickness of the first cover layer 30 is made larger than the thickness of the conductor pattern 21, and the difference in thickness between the first cover layer 30 and the conductor pattern 21 is set to 1 µm or more and 45 µm or less. Further, the difference in thickness between the first cover layer 30 and the conductor pattern 21 is more preferably 3 µm or more and 30 µm or less, and still more preferably 5 µm or more and 15 µm or less.

[0050] It is preferable that the contact area between the first cover layer 30 and the first surface 11a of the dielectric layer 10 is larger than the contact area between each conductor pattern 21 and the first surface 11a of the dielectric layer 10. For example, it is preferable that the contact area between the first cover layer 30 and the first surface 11a of the dielectric layer 10 is larger than the contact area between the conductor pattern 21 having the largest area in plan view among the plurality of conductor patterns 21 and the first surface 11a of the dielectric layer 10. When the contact area between the first cover layer 30 and the first surface 11a of the dielectric layer 10 is larger than the contact area between each conductor pattern 21 and the first surface 11a of the dielectric layer 10, the peel strength between the first cover layer 30 and the first surface 11a of the dielectric layer 10 can be further improved. Thereby, when the first cover layer 30 is peeled from the first surface 11a of the dielectric layer 10, the possibility that the conductor pattern 21 remains on the first surface 11a of the dielectric layer 10 can be further reduced. As a result, information related to the configuration of the plurality of conductor patterns can be concealed.

[0051] <Ground Layer 40> An example of the configuration of the ground layer 40 will be described. The ground layer 40 is a conductive layer placed on the second surface 11b of the dielectric layer 10. In the example shown in Figure 1, the ground layer 40 is provided over the entire second surface 11b of the dielectric layer 10. However, the ground layer 40 may be provided on only a part of the second surface 11b of the dielectric layer 10.

[0052] Examples of materials constituting the ground layer 40 include metals such as titanium, silicon, niobium, indium, zinc, tin, gold, silver, copper, aluminum, cobalt, chromium, nickel, lead, iron, palladium, platinum, tungsten, zirconium, tantalum, and hafnium; and conductive metal oxides such as ITO, zinc oxide, and tin oxide. The ground layer 40 may also contain two or more of these metals or metal oxides, or it may be an alloy in which these metals are the main component.

[0053] <Examples> Next, the reflector 1 will be described in more detail using examples. However, the reflector 1 is not limited to the following examples.

[0054] Examples 1 and 2 were prepared, each comprising a dielectric layer 10, a conductor layer 20, a first cover layer 30, and a ground layer 40, respectively. Peel strength tests were then performed on the first cover layer 30 and the conductor pattern 21, respectively. The peel strength tests were performed using a tensile and compression testing machine.

[0055] (Example 1) - Thickness of conductor pattern 21: 9 μm - Material of conductor pattern 21: copper - Thickness of first cover layer 30: 28 μm - Material of first cover layer 30 (main component): epoxy resin - Coloring filler of first cover layer 30: carbon black (Example 2) - Thickness of conductor pattern 21: 9 μm - Material of conductor pattern 21: copper - Thickness of first cover layer 30: 16 μm - Material of first cover layer 30 (main component): epoxy resin - Coloring filler of first cover layer 30: carbon black

[0056] In Examples 1 and 2, the configurations other than those described above were the same. Also, the first cover layer 30 in Examples 1 and 2 does not include an adhesive layer. The measurement results for the peel strength test are shown in Table 1 below. Here, "peel strength of the first cover layer" in Table 1 refers to the peel strength between the first cover layer 30 and the first surface 11a of the dielectric layer 10. Also, "peel strength of the conductor pattern" refers to the peel strength between the conductor pattern 21 and the first surface 11a of the dielectric layer 10. The peel strength of the first cover layer 30 and the peel strength of the conductor pattern 21 are the arithmetic mean of the measured values ​​at any five points in the surface. Note that "transmittance to visible light" refers to the transmittance of the first cover layer 30 to visible light (white light source with wavelengths of 380 nm to 780 nm). The transmittance to visible light was measured using a visible light transmittance meter (manufactured by Epson Corporation).

[0057]

[0058] As shown in Table 1, in Examples 1 and 2, it was confirmed that the peel strength between the first cover layer 30 and the first surface 11a of the dielectric layer 10 was greater than the peel strength between the conductor pattern 21 and the first surface 11a of the dielectric layer 10. Furthermore, in Example 1, where the thickness difference between the first cover layer 30 and the conductor pattern 21 was large, it was confirmed that the peel strength between the first cover layer 30 and the first surface 11a of the dielectric layer 10 was greater than in Example 2.

[0059] [Modified Version] Next, a modified version of the reflector 1A of the embodiment will be described with reference to Figure 3. Figure 3 is a schematic cross-sectional view showing a modified version of the reflector 1A of the embodiment. In the modified version, the same reference numerals are used for components similar to those in the embodiment, and their descriptions are omitted as appropriate.

[0060] As shown in Figure 3, the reflector 1A further comprises a second cover layer 50. The second cover layer 50 is positioned on the surface 41 of the ground layer 40 opposite to the dielectric layer 10 side. The second cover layer 50 covers the ground layer 40. By covering the ground layer 40 with the second cover layer 50, corrosion of the ground layer 40 can be reduced. Furthermore, since the first cover layer 30 and the second cover layer 50 sandwich the laminate including the dielectric layer 10, the conductor layer 20, and the ground layer 40, the durability of the reflector 1A can be further improved.

[0061] The second cover layer 50 includes, for example, a resin material. The resin material in the second cover layer 50 may be the same as that exemplified as the resin material in the first cover layer 30. In addition, to reduce the transmittance of the second cover layer 50 to visible light, the second cover layer 50 may include a colored filler. The colored filler in the second cover layer 50 may be the same as that exemplified as the colored filler in the first cover layer 30.

[0062] The thickness difference between the second cover layer 50 and the first cover layer 30 is preferably 1000 μm or less. By having a thickness difference of 1000 μm or less between the second cover layer 50 and the first cover layer 30, the warping of the reflector 1A can be reduced.

[0063] Examples of the present invention are as follows:

[0064] <1> A reflector comprising: a dielectric layer having a first surface and a second surface opposite to the first surface; a conductor layer having a plurality of conductor patterns arranged at mutually separated positions on the first surface and reflecting incident radio waves; a first cover layer arranged on the first surface and covering the conductor layer; and a ground layer arranged on the second surface of the dielectric layer, wherein the peel strength between the first cover layer and the first surface of the dielectric layer is greater than the peel strength between each of the conductor patterns and the first surface of the dielectric layer, and the transmittance of the first cover layer to visible light is 20% or less.

[0065] <2> The reflector according to <1>, wherein the peel strength between each of the conductor patterns and the first surface of the dielectric layer is greater than the tensile fracture strength of the dielectric layer.

[0066] <3> The reflector according to <1> or <2>, wherein the contact area between the first cover layer and the first surface of the dielectric layer is greater than the contact area between each conductor pattern and the first surface of the dielectric layer.

[0067] <4> The reflector according to any one of <1> to <3>, further comprising a second cover layer disposed on the side of the ground layer opposite to the dielectric layer side.

[0068] <5> The reflector according to any one of <1> to <4>, wherein the first cover layer contains an epoxy resin.

[0069] <6> The reflector according to any one of <1> to <5>, wherein the dielectric layer comprises fibrils of a fluororesin and an inorganic porous aggregate.

[0070] <7> A reflector comprising: a dielectric layer having a first surface and a second surface opposite to the first surface; a conductor layer having a plurality of conductor patterns that reflect incident radio waves and are arranged at mutually separated positions on the first surface; a first cover layer arranged on the first surface and covering the conductor layer; and a ground layer arranged on the second surface of the dielectric layer, wherein the peel strength between the first cover layer and the first surface of the dielectric layer is greater than the tensile fracture strength of the dielectric layer, and the transmittance of the first cover layer to visible light is 20% or less.

[0071] <8> The reflector according to <7>, wherein the contact area between the first cover layer and the first surface of the dielectric layer is greater than the contact area between each of the conductor patterns and the first surface of the dielectric layer.

[0072] <9> The reflector according to <7> or <8>, further comprising a second cover layer disposed on the side of the ground layer opposite to the dielectric layer side.

[0073] <10> The reflector according to any one of <7> to <9>, wherein the first cover layer contains an epoxy resin.

[0074] <11> The reflector according to any one of <7> to <10>, wherein the dielectric layer comprises fibrils of a fluororesin and an inorganic porous aggregate.

[0075] This application claims priority based on Japanese Patent Application No. 2025-031723, filed on 28 February 2025, which is incorporated herein by reference to the entire contents of Japanese Patent Application No. 2025-031723.

[0076] 1, 1A Reflector 10 Dielectric layer 11a First surface 11b Second surface 20 Conductor layer 21 Conductor pattern 30 First cover layer 40 Ground layer 50 Second cover layer

Claims

1. A reflector comprising: a dielectric layer having a first surface and a second surface opposite to the first surface; a conductor layer having a plurality of conductor patterns arranged at mutually separated positions on the first surface and reflecting incident radio waves; a first cover layer arranged on the first surface and covering the conductor layer; and a ground layer arranged on the second surface of the dielectric layer, wherein the peel strength between the first cover layer and the first surface of the dielectric layer is greater than the peel strength between each of the conductor patterns and the first surface of the dielectric layer, and the transmittance of the first cover layer to visible light is 20% or less.

2. The peel strength between each of the conductor patterns and the first surface of the dielectric layer is greater than the tensile fracture strength of the dielectric layer, as described in claim 1.

3. The reflector according to claim 1 or claim 2, wherein the contact area between the first cover layer and the first surface of the dielectric layer is greater than the contact area between each of the conductor patterns and the first surface of the dielectric layer.

4. The reflector according to claim 1 or claim 2, further comprising a second cover layer disposed on the side of the ground layer opposite to the dielectric layer side.

5. The reflector according to claim 1 or claim 2, wherein the first cover layer comprises an epoxy resin.

6. The reflector according to claim 1 or claim 2, wherein the dielectric layer comprises fibrils of a fluororesin and an inorganic porous aggregate.

7. A reflector comprising: a dielectric layer having a first surface and a second surface opposite to the first surface; a conductor layer having a plurality of conductor patterns that reflect incident radio waves and are arranged at mutually separated positions on the first surface; a first cover layer arranged on the first surface and covering the conductor layer; and a ground layer arranged on the second surface of the dielectric layer, wherein the peel strength between the first cover layer and the first surface of the dielectric layer is greater than the tensile fracture strength of the dielectric layer, and the transmittance of the first cover layer to visible light is 20% or less.

8. The reflector according to claim 7, wherein the contact area between the first cover layer and the first surface of the dielectric layer is greater than the contact area between each of the conductor patterns and the first surface of the dielectric layer.

9. The reflector according to claim 7 or claim 8, further comprising a second cover layer disposed on the side of the ground layer opposite to the dielectric layer side.

10. The reflector according to claim 7 or claim 8, wherein the first cover layer comprises an epoxy resin.

11. The reflector according to claim 7 or claim 8, wherein the dielectric layer comprises fibrils of a fluororesin and an inorganic porous aggregate.

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