JP2024056339A - Communication wave reflector and method for manufacturing the communication wave reflector - Google Patents

Abstract

The present invention provides a communication wave reflector that enables the realization of a layered structure for improving the reflection performance of radio waves and has particularly high reflection efficiency, and a method for manufacturing the communication wave reflector.
[Solution] The laminate includes at least a metal layer 11, a base layer 13, a metal pattern 14, and a protective layer 15 in this order, the metal pattern 14 being a pattern consisting of a plurality of repeated geometric patterns that are not conductive as a circuit, and an adhesive layer 12 having a thickness of 0.1 to 25 μm is included between the metal layer 11 and the base layer 13.
[Selected Figure] Figure 1

Description

The present invention relates to a communication wave reflector and a method for manufacturing a communication wave reflector.

In recent years, metasurface reflectors have been proposed that can be designed to obtain a desired reflection angle for a given angle of incidence (see, for example, Patent Documents 1 to 3).

JP 2021-048465 A JP 2021-141359 A JP 2021-175054 A

When a normal metal plate is used as a reflector, the metal plate reflects radio waves specularly, limiting the direction of reflection. For this reason, high-frequency radio waves, which tend to travel in a more directional direction than conventional radio waves, have difficulty reaching the terminal if there is an obstruction. Metasurface reflectors have attracted attention as reflectors that can control the direction of the radio wave beam.

The present invention was made in consideration of the above circumstances, and aims to provide a communication wave reflector and a method for manufacturing a communication wave reflector that enables the realization of a layered structure for improving the reflection performance of radio waves and has particularly high reflection efficiency.

The present invention includes the following aspects:

The first aspect of the present invention is a communication wave reflector that is made up of a laminate including at least a metal layer, a base layer, a metal pattern, and a protective layer in this order, the metal pattern being a pattern that is made up of multiple repeated geometric patterns and is not conductive as a circuit, and that includes an adhesive layer having a thickness of 0.1 to 25 μm between the metal layer and the base layer.

A second aspect of the present invention is the communication wave reflector of the first aspect, characterized in that the adhesive layer has a dielectric loss tangent (Df) of 0.02 or less.
A third aspect of the present invention is the communication wave reflector according to the first or second aspect, characterized in that the adhesive layer has a relative dielectric constant (Dk) of 3.0 or less.

The fourth aspect of the present invention is a communication wave reflector according to any one of the first to third aspects, characterized in that the adhesive layer contains an adhesive selected from the group consisting of polyimide resin, maleimide resin, epoxy resin, polyolefin resin, acid-modified polyolefin resin, acrylic resin, and styrene-based elastomer.

The fifth aspect of the present invention is a communication wave reflector according to any one of the first to fourth aspects, characterized in that the base layer is made of a resin selected from the group consisting of polyethylene terephthalate (PET), nylon, polypropylene (PP), polyethylene (PE), polyimide (PI), modified polyimide (MPI), cycloolefin polymer (COP), and liquid crystal polymer (LCP).

The sixth aspect of the present invention is a communication wave reflector according to any one of the first to fifth aspects, characterized in that the metal layer is made of a metal selected from the group consisting of copper, aluminum, and stainless steel.

A seventh aspect of the present invention is a communication wave reflector according to any one of the first to sixth aspects, characterized in that the metal pattern is made of a metal selected from the group consisting of aluminum, copper, gold, and silver.
An eighth aspect of the present invention is a communication wave reflector of any one of the first to seventh aspects, characterized in that the size of each pattern constituting the geometric pattern of the metal pattern is within the range of 0.01 to 8 mm.

The ninth aspect of the present invention is a communication wave reflector according to any one of the first to eighth aspects, characterized in that the protective layer is made of a resin selected from the group consisting of polyethylene resin, polypropylene resin, polybutylene resin, polyester resin, and polyamide resin.

The tenth aspect of the present invention is a method for manufacturing a communication wave reflector according to any one of the first to ninth aspects, characterized in that the laminate is manufactured by roll-to-roll.

The present invention makes it possible to realize a layered structure that improves the reflection performance of radio waves, resulting in a communication wave reflector with particularly high reflection efficiency.

FIG. 2 is an exploded perspective view showing an embodiment of a communication wave reflector. FIG. 2 is a cross-sectional view showing an embodiment of a communication wave reflector. FIG. 11 is a cross-sectional view showing a modified example of a communication wave reflector.

The present invention will be described below based on a preferred embodiment with reference to the drawings. These drawings are explanatory diagrams that show the concept, and details such as the shape, dimensions, number, and ratio of each part may differ from the actual ones.

Figures 1 and 2 show an example of a communication wave reflector according to an embodiment. Figure 1 is an exploded perspective view showing the protective layer 15 separated from the base layer 13 and the metal pattern 14. Figure 2 is a cross-sectional view along the thickness direction.

The communication wave reflector 10 of the embodiment is made of a laminate including at least a metal layer 11, an adhesive layer 12, a substrate layer 13, a metal pattern 14, and a protective layer 15 in this order.

The metal pattern 14 is a pattern that consists of multiple repeated geometric patterns and does not form a conductive circuit. Between the metal layer 11 and the base layer 13, an adhesive layer 12 having a thickness of 0.1 to 25 μm is included.

The metal pattern 14 is designed, for example, using technology related to metasurface reflectors, as a pattern consisting of multiple repeated geometric patterns that do not form a conductive circuit. The period, spacing, dimensions, etc. of the metal pattern 14 are determined so as to generate a reflected wave that is directed in the desired direction.

For example, when installing a reflector on the wall of a building, if a metal plate with specular reflection properties is used, the incident and reflected directions must be arranged symmetrically with respect to the normal direction perpendicular to the reflective surface. This places restrictions on the installation of the reflector, and it may be difficult to install it along the wall. In contrast, a metasurface reflector can be installed along the wall, and reflection is possible even if the reflection direction is asymmetric with the incident direction.

The material from which the metal pattern 14 is formed is not particularly limited as long as it is an electrical conductor, but a metal selected from aluminum, copper, gold, and silver is preferred. The metal pattern 14 may be formed using an alloy containing these metals as the main component. From the standpoint of workability and cost, it is preferred that the material of the metal pattern 14 is copper.

The metal pattern 14 may be formed by laminating two or more metal layers on the base layer 13. In this case, it is preferable that at least one of the metal layers is made of a metal selected from aluminum, copper, gold, and silver. Other metal layers include, but are not limited to, nickel, chromium, titanium, tin, or an alloy containing one or more of these.

The geometric pattern of the metal pattern 14 can be a convex polygon (a polygon with no concave angles) such as a square or a rectangle, a concave polygon (a polygon with concave angles) such as a cross, a shape including curves such as a circle or an ellipse, or a shape with an internal gap such as a loop.

It is preferable that the size of each pattern constituting the geometric pattern of the metal pattern 14 is within the range of 0.01 to 8 mm. The size of each pattern is not particularly limited, but may include the diameter, major axis, minor axis, length, width, etc. It is preferable that the minimum and maximum values of the size of each pattern are included in the above-mentioned numerical range.

For example, for frequencies of about 3 to 30 GHz used in fifth generation mobile communication systems (5G), the size of each pattern may be about 6 to 8 mm. For frequencies of 30 to 300 GHz, which are considered millimeter waves, the size of each pattern may be about 1 to 2 mm. For frequencies of over 100 GHz, which are expected to be used in sixth generation mobile communication systems (6G), the size of each pattern may be about 0.01 to 0.2 mm.

The frequency band of the electromagnetic waves reflected by the metal pattern 14 is not particularly limited, but may be a frequency band that propagates through the air and is used for communication. The communication wave reflector 10 may be designed for use in reflecting communication waves such as radio waves, microwaves, millimeter waves, and submillimeter waves. Specific examples of the frequency band may be appropriately set within the range of, for example, 3.0 to 3000 GHz. In particular, it is preferable to design it for use in frequencies of about 3 to 30 GHz used in the fifth generation mobile communication system (5G), or frequencies of 30 to 300 GHz, which are considered millimeter waves.

The method for forming the metal pattern 14 is not particularly limited, but examples include vapor deposition, plating, coating, nanoimprinting, inkjet, photolithography, patterning coating, etc.

When a conductor such as a metal is applied onto the base layer 13, the metal pattern 14 may be formed in a predetermined pattern shape. For example, the desired pattern shape can be obtained by controlling the application pattern, using a resist, a mask, etc., so that the metal material is applied only to predetermined areas.

The metal pattern 14 may be formed by applying a conductor such as a metal to a predetermined area on the base layer 13 and then removing unnecessary portions. For example, the desired pattern shape can be obtained by removing the metal material from areas other than the predetermined area using etching, punching, trimming, etc.

The substrate layer 13 is a member that serves as the substrate for the metal pattern 14. The substrate layer 13 is preferably formed from an electrical insulator such as resin, glass, or ceramics. From the viewpoint of ease of handling, it is preferable to use a resin material such as a resin film, resin sheet, or resin plate for the substrate layer 13.

The resin material used for the base layer 13 may be a thermoplastic resin, a thermosetting resin, a photocurable resin, etc. The thermoplastic resin used for the base layer 13 may be an aromatic or aliphatic polyester resin, an aromatic or aliphatic polyamide resin, a cyclic or non-cyclic polyolefin resin, an aromatic or aliphatic polyamide resin, an aromatic or aliphatic polyimide resin, etc.

The base layer 13 is preferably made of a resin selected from the group consisting of polyethylene terephthalate (PET), nylon, polypropylene (PP), polyethylene (PE), polyimide (PI), modified polyimide (MPI), cycloolefin polymer (COP), and liquid crystal polymer (LCP). Mixtures, copolymers, modified resins, etc. that contain these resins as the main components may also be used for the base layer 13.

From a cost perspective, the base layer 13 may be formed using a general-purpose resin such as polyethylene terephthalate (PET), polypropylene (PP), or polyethylene (PE).

From the viewpoint of low dielectric constant for high-frequency signals, the base layer 13 may be formed using polyethylene (PE), cycloolefin polymer (COP), liquid crystal polymer (LCP), etc. This can suppress loss of high-frequency signals and further increase reflection efficiency.

The thickness of the base layer 13 is not particularly limited, but may be approximately 50 to 500 μm, and is more preferably approximately 100 to 300 μm.

The optical properties of the substrate layer 13 in the visible light region are not particularly limited, but it is preferable that the substrate layer 13 is transparent, since this improves workability in forming and inspecting the metal pattern 14. The substrate layer 13 may be in direct contact with the metal pattern 14, or another layer may be interposed between the substrate layer 13 and the metal pattern 14.

The substrate layer 13 may be composed of one layer of material, or may be composed of two or more layers of material. The laminated structure of the substrate layer 13 and the metal pattern 14 may be repeated two or more times in the thickness direction of the laminate.

Although not specifically shown, the communication wave reflector 10 may be, for example, a laminate including a metal layer 11, an adhesive layer 12, a substrate layer 13, a first metal pattern 14, a substrate layer 13, a second metal pattern 14, and a protective layer 15 in this order. The first metal pattern 14 and the second metal pattern 14 may have reflection characteristics for different frequencies. An adhesive layer 12 may be provided between the first metal pattern 14 and the substrate layer 13.

The metal layer 11 is used as a ground layer to eliminate radio waves that have passed through the metal pattern 14. The base layer 13 provides electrical insulation between the metal layer 11 and the metal pattern 14. For the laminate to become a metasurface reflector, it is preferable that it contains at least the metal layer 11, the base layer 13, and the metal pattern 14 in this order.

The material forming the metal layer 11 is not particularly limited as long as it is an electrical conductor, but a metal selected from copper, aluminum, and stainless steel is preferable. The metal layer 11 may be formed using an alloy containing these metals as the main component.

The method for forming the metal layer 11 is not particularly limited, but examples include vapor deposition, plating, coating, nanoimprinting, inkjet, and attaching metal foil. The metal layer 11 does not need to have a pattern shape consisting of multiple repeated geometric patterns, such as the metal pattern 14.

The metal layer 11 may be uniformly continuous and solid on the surface of the base layer 13 opposite to the side on which the metal pattern 14 is laminated. From the viewpoint of productivity, it is preferable that the metal layer 11 is made of metal foil.

The metal foil used for the metal layer 11 is preferably a metal foil selected from copper foil, aluminum foil, and stainless steel foil. The metal layer 11 may be formed using an alloy foil whose main component is copper, aluminum, or stainless steel.

In the embodiment, an adhesive layer 12 is included between the metal layer 11 and the base layer 13. This improves the adhesion between the metal layer 11 and the base layer 13, and increases the reflection efficiency of the metal pattern 14. In addition, productivity can be improved when laminating the metal layer 11 and the base layer 13.

The adhesive layer 12 is laminated between the metal layer 11 and the base layer 13. The adhesive layer 12 may be in direct contact with the metal layer 11, or another layer may be interposed between the adhesive layer 12 and the metal layer 11. The adhesive layer 12 may be in direct contact with the base layer 13, or another layer may be interposed between the adhesive layer 12 and the base layer 13.

When another layer is interposed between the adhesive layer 12 and the metal layer 11 or the substrate layer 13, it is preferable that the other layer does not interfere with the adhesive strength of the adhesive layer 12, and may be a layer that improves the adhesive strength of the adhesive layer 12. Examples of the other layer include, but are not limited to, a surface treatment layer, an anti-blocking layer, a natural oxide film, etc.

The adhesive layer 12 is preferably formed from an adhesive that bonds the metal layer 11 and the base layer 13. In this case, the adhesive layer 12 may be adhered to at least a portion of the metal layer 11. Furthermore, the adhesive layer 12 may be adhered to at least a portion of the base layer 13.

The adhesive used in the adhesive layer 12 is not particularly limited, but preferably includes an adhesive selected from polyimide resin, maleimide resin, epoxy resin, polyolefin resin, acid-modified polyolefin resin, acrylic resin, and styrene-based elastomer. Modified polyphenylene resin such as modified polyphenylene ether (m-PPE) may also be used as the adhesive.

The adhesive layer 12 may contain one type of adhesive, or may contain two or more types of adhesive. It is preferable to use an adhesive that has both adhesion to metals and adhesion to resins for the adhesive layer 12.

The thickness of the adhesive layer 12 is preferably within the range of 0.1 to 25 μm, more preferably 0.5 to 10 μm, and even more preferably 1 to 5 μm. If the adhesive layer 12 is too thin, the adhesion between the metal layer 11 and the base layer 13 may decrease. The adhesive layer 12 is preferably formed with a uniform thickness. If the adhesive layer 12 is too thick, the radio wave reflectivity may decrease.

The adhesive layer 12 preferably has excellent dielectric properties with respect to radio waves in the band requiring reflection. The dielectric tangent (Df) of the adhesive layer 12 is preferably 0.02 or less. The relative dielectric constant (Dk) of the adhesive layer 12 is preferably 3.0 or less.

When the difference in the dielectric tangent (Df) between the adhesive layer 12 and the base material layer 13 or the difference in the relative dielectric constant (Dk) between the adhesive layer 12 and the base material layer 13 is small, it is considered that the interface between the adhesive layer 12 and the base material layer 13 is less likely to adversely affect radio waves, and the reflectance is also improved.
The difference between the dielectric tangent (Df) of the adhesive layer 12 and the dielectric tangent (Df) of the base layer 13 is preferably 0.005 or less, more preferably 0.001 or less, and particularly preferably 0.0005 or less.
The difference between the relative dielectric constant (Dk) of the adhesive layer 12 and the relative dielectric constant (Dk) of the base material layer 13 is preferably 0.6 or less, and more preferably 0.3 or less.

When the dielectric loss tangent (Df) and the relative dielectric constant (Dk) depend on the frequency, these values may be measured at the design frequency reflected by the communication wave reflector 10. As a representative example of measuring the dielectric properties at high frequencies, the value of Df or Dk may be measured by selecting a specific frequency such as 1 MHz, 10 GHz, or 30 GHz.

When the communication wave reflector 10 has a metal pattern 14 on the outermost surface, the pattern may be chipped due to contact or static electricity, and therefore the communication wave reflector 10 may be installed outdoors. To protect the metal pattern 14, the communication wave reflector 10 preferably has a protective layer 15 on the surface of the base layer 13 on which the metal pattern 14 is laminated. From the viewpoint of ease of handling, the protective layer 15 is preferably made of a resin material such as a resin film, resin sheet, or resin plate.

By laminating the protective layer 15 on the metal pattern 14, the durability of the communication wave reflector 10 is improved, and the weather resistance is improved.
The protective layer 15 has the advantage that the metal pattern 14 is not chipped when the communication wave reflector 10 is manufactured or wound into a roll for transportation.
Furthermore, when installing the communication wave reflector 10 of the embodiment, a protective member such as decorative board, wallpaper, flooring, wood, or board can be installed on the surface side of the protective layer 15 as a separate member from the communication wave reflector 10.

The resin material used for the protective layer 15 may be a thermoplastic resin, a thermosetting resin, a photocurable resin, etc. The thermoplastic resin used for the protective layer 15 may be an aromatic or aliphatic polyester resin, an aromatic or aliphatic polyamide resin, a cyclic or acyclic polyolefin resin, an aromatic or aliphatic polyamide resin, an aromatic or aliphatic polyimide resin, etc.

It is preferable that the protective layer 15 is made of a resin selected from the group consisting of polyolefin resins (e.g., polyethylene resins, polypropylene resins, polybutylene resins), polyester resins, and polyamide resins. Mixtures, copolymers, modified resins, etc. that contain these resins as the main components may also be used for the protective layer 15.

The thickness of the protective layer 15 is not particularly limited, but may be about 20 to 200 μm. The protective layer 15 may be made of one layer of material, or may be made of two or more layers of material. Although not specifically shown, when the protective layer 15 is made of two or more layers of material, each layer may have a different function.

From the viewpoint of cost, the protective layer 15 may be formed using a single-layer film of a general-purpose resin such as polyethylene terephthalate (PET), polypropylene (PP), or polyethylene (PE). Alternatively, the protective layer 15 may be made of multiple layers by using such a single-layer film as a support and layering appropriate functional layers by coating or laminating.

The protective layer 15 may be a material that is thermocompression bondable to the base layer 13 having the metal pattern 14. For example, if a polyolefin resin such as polyethylene (PE) or polypropylene (PP) is used as the base layer 13, the protective layer 15 may also be made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP).

When both the base layer 13 and the protective layer 15 are made of polyethylene (PE), the protective layer 15 can be well adhered by thermocompression bonding of the area where the base layer 13 and the protective layer 15 contact each other, even if the metal pattern 14 is interposed. Similarly, when both the base layer 13 and the protective layer 15 are made of polypropylene (PP), the protective layer 15 can be well adhered by thermocompression bonding.

When laminating the protective layer 15 onto the base layer 13 having the metal pattern 14 by thermocompression bonding, it is preferable to apply pressure using a member made of a flexible material such as a rubber plate, rubber stand, or rubber roll. This allows for uniform pressure to be applied even if there are irregularities on the base layer 13 due to the metal pattern 14. If a pair of rubber rolls is used as the pressure member and the material to be thermocompression bonded is passed between them, long materials can be processed efficiently.

When the protective layer 15 is thermocompression bonded to the base layer 13, it is preferable to process the material including at least the base layer 13, the metal pattern 14, and the protective layer 15. When the metal layer 11 is adhered to the base layer 13 before the thermocompression bonding, it is preferable to thermocompress the material including the metal layer 11 to the metal pattern 14 and the protective layer 15.

The protective layer 15 may be adhered to the base layer 13 having the metal pattern 14 using an adhesive or pressure-sensitive adhesive. When the support of the protective layer 15 is composed of a resin film, an adhesive layer made of the adhesive or pressure-sensitive adhesive is formed in a layer shape on the side facing the base layer 13.

The adhesive or pressure sensitive adhesive used to adhere the protective layer 15 is not particularly limited, but may include an adhesive selected from the group consisting of polyimide resin, maleimide resin, epoxy resin, polyolefin resin, acid-modified polyolefin resin, acrylic resin, and styrene-based elastomer.

For example, the protective layer 15 may be adhered using an acrylic adhesive that has excellent conformability to uneven surfaces. This allows for uniform adhesion even if the base layer 13 has uneven surfaces due to the metal pattern 14.

The protective layer 15 may have a hard coat layer. The material of the hard coat layer is not particularly limited, but a resin composition that is cured by heat curing, photocuring, or the like may be used. Examples of resins used in the hard coat layer include acrylic resins, fluororesins, and silicone resins.

When the support of the protective layer 15 is composed of a resin film, the hard coat layer is preferably formed on the outer surface opposite the base layer 13. When a resin film is interposed between the hard coat layer of the protective layer 15 and the metal pattern 14, the resin film functions as a buffer layer, thereby preventing an external force acting on the hard coat layer from being directly applied to the metal pattern 14.

The protective layer 15 may have one or more layers containing a weather resistance improver such as an ultraviolet absorber, an infrared absorber, or an antioxidant. For example, a weather resistance improver may be added to the support film, a weather resistance improver may be added to the adhesive layer, or a weather resistance improver may be added to the hard coat layer.

The protective layer 15 may have an antistatic layer containing an antistatic agent such as conductive particles, an ionic compound, a surfactant, or a conductive polymer.
The conductive particles used in the antistatic layer are not particularly limited, but examples thereof include metal particles such as copper, aluminum, and tin, and carbon particles.

The ionic compound used in the antistatic layer is not particularly limited, but examples thereof include metal salts such as alkali metal salts; organic or inorganic onium salts such as ammonium salts, pyridinium salts, phosphonium salts, and sulfonium salts; and ionic liquids.
The surfactant used in the antistatic layer is not particularly limited, but examples thereof include cationic surfactants, nonionic surfactants, and amphoteric surfactants.

Examples of the cationic surfactant include compounds having a cationic functional group, such as an ammonium group (R ₃ N ⁺ --), a phosphonium group (R ₃ P ⁺ --), or a sulfonium group (R ₂ S ⁺ --), which may be substituted with an organic group R such as an alkyl group.
Examples of anionic surfactants include compounds having an anionic functional group such as a sulfonate group (-SO ₃ ^- ), a sulfate group (-OSO ₃ ^- ), a phosphate group (-OPO ₃ ^2- ), a phosphonate group (-PO ₃ ^2- ), or a carboxylate group (-COO ^- ).

Examples of the nonionic surfactant include compounds having a nonionic functional group, such as amino alcohols, glycerin, and polyethylene glycols.
Amphoteric surfactants include compounds having a cationic functional group and an anionic functional group in the same molecule.

The conductive polymer used in the antistatic layer may be a polymer compound having at least one of the above-mentioned cationic functional groups, anionic functional groups, and nonionic functional groups.

The antistatic layer is preferably formed on the outer surface of the protective layer 15 opposite the base layer 13 so as not to come into contact with the metal pattern 14. The antistatic layer may be formed in an intermediate layer of the protective layer 15, or an antistatic agent may be kneaded into the resin layer contained in the protective layer 15.

The antistatic layer may contain one or more types of antistatic agents. The antistatic layer may contain a binder resin. There are no particular limitations on the binder resin, but it is preferable to use a resin that has a high affinity with the antistatic agent, such as an acrylic resin, a fluororesin, a silicone resin, a polyimide resin, a maleimide resin, or an epoxy resin.

Figure 3 shows an example of a modified communication wave reflector 20. The communication wave reflector 20 can be the same as the communication wave reflector 10 of the above-mentioned embodiment, except that it includes an adhesive layer 16 between the base layer 13 and the metal pattern 14.

The metal layer 11, adhesive layer 12, base layer 13, metal pattern 14, and protective layer 15 contained in the communication wave reflector 20 may be given the same reference numerals, and duplicate descriptions may be omitted.

The adhesion layer 16 may be formed from an adhesive that bonds the metal pattern 14 and the base layer 13. In this case, the adhesion layer 16 may be adhered to at least a portion of the metal pattern 14. Furthermore, the adhesion layer 16 may be adhered to at least a portion of the base layer 13.

The adhesive used in the adhesion layer 16 is not particularly limited, but preferably includes an adhesive selected from polyimide resin, maleimide resin, epoxy resin, polyolefin resin, acid-modified polyolefin resin, acrylic resin, and styrene-based elastomer. Modified polyphenylene resin such as modified polyphenylene ether (m-PPE) may be used in the adhesion layer 16.

The adhesion layer 16 may contain one type of adhesive, or may contain two or more types of adhesive. It is preferable to use an adhesive that has both adhesion to metals and adhesion to resins for the adhesion layer 16.

The thickness of the adhesion layer 16 is not particularly limited, but is preferably within the range of 0.1 to 25 μm, more preferably 0.5 to 10 μm, and even more preferably 1 to 5 μm.

The adhesive layer 16 preferably has excellent dielectric properties with respect to radio waves in the band requiring reflection. The dielectric tangent (Df) of the adhesive layer 16 is preferably 0.02 or less. The relative dielectric constant (Dk) of the adhesive layer 16 is preferably 3.0 or less.

It is preferable to manufacture the communication wave reflectors 10 and 20 as a laminate by roll-to-roll. For example, the communication wave reflectors 10 and 20 may be manufactured by transporting the base layer 13, such as a resin film or resin sheet, by roll-to-roll and laminating other layers on the base layer 13 in an appropriate order.

When producing the laminate, the metal layer 11 may be laminated on one side of the base layer 13 via the adhesive layer 12, the metal pattern 14 may be formed, and then the protective layer 15 may be laminated.
The metal pattern 14 may be formed on one side of the base layer 13 , and then a protective layer 15 may be laminated thereon, and then a metal layer 11 may be laminated on the opposite side of the base layer 13 via an adhesive layer 12 .
The metal pattern 14 may be formed on one side of the base layer 13 , and the metal layer 11 may be laminated on the opposite side via the adhesive layer 12 , and then the protective layer 15 may be laminated on the metal pattern 14 .

Roll-to-roll lamination processes include one or more of the following: lamination, coating, thermocompression bonding, vapor deposition, plating, coating, nanoimprinting, inkjet, photolithography, and patterning coating.

For example, the metal layer 11 may be formed by laminating the metal foil of the metal layer 11 to the base layer 13, which is transported by roll-to-roll, via the adhesive layer 12. The adhesive layer 12 can be formed by applying an adhesive to at least one of the base layer 13 or the metal layer 11.

The metal pattern 14 may be laminated on the substrate layer 13 transported by roll-to-roll, for example, by vapor deposition, plating, coating, nanoimprinting, inkjet, photolithography, patterning coating, or the like.

For the protective layer 15, for example, a resin film or resin sheet of the protective layer 15 may be laminated to the base layer 13 transported by roll-to-roll, using thermocompression, adhesive, pressure sensitive adhesive, etc.

When the adhesive, conductive material, etc. are laminated by coating, an appropriate coating device can be used for coating. Coating devices are not particularly limited, but include gravure coaters, knife coaters, reverse coaters, bar coaters, spray coaters, spin coaters, die coaters, slit coaters, roll coaters, dip coaters, etc.

The material used for coating may be solvent-free or may be a solution or dispersion containing a solvent. Examples of solvents include alcohol-based solvents such as methanol, ethanol, and 2-propanol; ketone-based solvents such as acetone and methyl ethyl ketone; glycol ether-based solvents such as 2-methoxyethanol and dimethoxyethane; ester-based solvents such as ethyl acetate; aromatic solvents such as toluene and xylene; and amide-based solvents such as dimethylformamide and N-methylpyrrolidone. The solvent may be one type or a mixture of two or more types.

The communication wave reflectors 10 and 20 of the embodiment may be in the form of a flexible film or sheet, or may be in the form of a plate that has rigidity when cut to a certain size. If the communication wave reflectors 10 and 20 have rigidity, it becomes easier to align the incident direction with the reflection direction when installing them on a wall surface, etc.

If the communication wave reflectors 10 and 20 are flexible, they can be wound up in a roll even if they are long, making them easy to transport and store. When installing the flexible communication wave reflectors 10 and 20 on a wall surface or the like, the normal direction may be fixed by attaching them to a support plate such as a metal plate or a resin plate.

The present invention has been described above based on a preferred embodiment, but the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the present invention. Modifications include addition, substitution, omission, and other changes to components in each embodiment.

The present invention will now be described in detail with reference to examples.

Using the materials shown in Table 1 for "metal layer,""adhesivelayer,""substratelayer,""metalpattern," and "protective layer," laminates were produced as shown in "lamination method," to obtain communication wave reflectors of Examples 1 to 12 and Comparative Examples 1 to 4.
The obtained communication wave reflector was evaluated for "reflectance,""floating," and "weather resistance."

The types of materials used in the metal layers are indicated using the following abbreviations.
Al foil: aluminum foil Cu foil: copper foil Cu plating: copper plating

The types of adhesives used in the adhesive layers are indicated using the following abbreviations.
AP: Acid-modified polyolefin resin EP: Epoxy resin IM: Imide-based adhesive MI: Maleimide resin PE: Polyethylene resin UR: Urethane-based adhesive

The types of resins used in the base layer are indicated using the following abbreviations.
COP: Cycloolefin polymer PE: Polyethylene PI: Polyimide

The methods for forming metal patterns and the types of metals are indicated using the following abbreviations.
Ph: Photolithography Cu: Copper

The types of materials used in the protective layers are indicated by the following abbreviations.
PE: polyethylene SPF: surface protection film (laminate of adhesive layer + resin film)

When the protective layer has an antistatic layer, it is marked as having antistatic properties in Table 1. When having antistatic properties, the antistatic layer is laminated on the side farther from the base layer and the metal pattern. For example, when polyethylene has antistatic properties, the protective layer is made up of polyethylene + antistatic layer. Also, when the surface protective film has antistatic properties, the protective layer is made up of adhesive layer + resin film + antistatic layer.

When the protective layer has two or more layers, the thickness of the protective layer is indicated by connecting the thickness (μm) of each layer with a plus sign (+) in order from the side closest to the base layer and metal pattern.

The lamination method was indicated using the following abbreviations.
RTR: Roll-to-roll stacking Sheet: Made from sheets

The "reflectance" was evaluated by measuring the reflectance (%) of the sample before conducting the durability test described below, n=10.

To evaluate "floating," samples were cut into 10 cm squares and placed in a thermo-hygrostat set at high temperature and humidity conditions of 40°C and 90% RH for 100 hours as a durability (weather resistance) test. After removing the samples from the thermo-hygrostat, the samples were visually inspected for the occurrence of floating and rated according to the following criteria.

⊚: No lifting occurred within the surface.
◯: Although some deterioration in flatness was observed, no floating occurred within the surface.
Δ: Lifting or peeling was observed between any of the layers within the plane.
×: Severe peeling was observed between any of the layers within the surface.

To evaluate "weatherability," samples cut into 10 cm squares were placed in a thermo-hygrostat chamber set at high temperature and humidity conditions of 40°C and 90% RH for 100 hours as a durability (weatherability) test, and the samples were then taken out of the chamber and the reflectance (%) was measured (n=10). The degree of deterioration in reflectance was used to evaluate the sample according to the following criteria.

⊚: No deterioration in reflectance was observed after the durability evaluation.
A: The deterioration of the reflectance after the durability evaluation was less than 10%.
Δ: The deterioration of the reflectance after the durability evaluation was 10% or more and less than 30%.
x: The reflectance after the durability evaluation was deteriorated by 30% or more.

The above results are summarized in Table 1.

As shown in Table 1, in Examples 1 to 12, which included an adhesive layer with a thickness of 0.1 to 25 μm between the metal layer and the substrate layer, communication wave reflectors with high reflection efficiency were obtained.

In Comparative Example 1, in which the metal foil was laminated using an adhesive layer having a thickness of 0.04 μm, the reflection efficiency of the communication wave reflector was low, and lifting occurred under high temperature and high humidity conditions.
In comparison example 2, in which metal foil was laminated without using an adhesive layer, the reflection efficiency of the communication wave reflector was low, lifting occurred under high temperature and high humidity conditions, and the reflectivity also deteriorated after being left under high temperature and high humidity conditions.

In Comparative Example 3, in which the metal layer was laminated by plating without using an adhesive layer, the reflection efficiency of the communication wave reflector was low, and the reflectance also deteriorated after being left under high temperature and high humidity conditions.
In Comparative Example 4, which was produced without using a protective layer, the reflection efficiency of the communication wave reflector was low, lifting occurred under high temperature and high humidity conditions, and the reflectance also deteriorated after being left under high temperature and high humidity conditions.

10, 20... communication wave reflector, 11... metal layer, 12... adhesive layer, 13... substrate layer, 14... metal pattern, 15... protective layer, 16... adhesion layer.

Claims (10)

The laminate includes at least a metal layer, a base layer, a metal pattern, and a protective layer in this order.
The metal pattern is a pattern that is made up of a plurality of repeated geometric patterns and is not electrically connected as a circuit,
A communication wave reflector comprising an adhesive layer having a thickness of 0.1 to 25 μm between the metal layer and the base layer. The communication wave reflector according to claim 1, characterized in that the dielectric tangent (Df) of the adhesive layer is 0.02 or less. The communication wave reflector according to claim 1, characterized in that the relative dielectric constant (Dk) of the adhesive layer is 3.0 or less. The communication wave reflector according to claim 1, characterized in that the adhesive layer contains an adhesive selected from the group consisting of polyimide resin, maleimide resin, epoxy resin, polyolefin resin, acid-modified polyolefin resin, acrylic resin, and styrene-based elastomer. The communication wave reflector according to claim 1, characterized in that the base layer is made of a resin selected from the group consisting of polyethylene terephthalate (PET), nylon, polypropylene (PP), polyethylene (PE), polyimide (PI), modified polyimide (MPI), cycloolefin polymer (COP), and liquid crystal polymer (LCP). The communication wave reflector according to claim 1, characterized in that the metal layer is made of a metal selected from the group consisting of copper, aluminum, and stainless steel. The communication wave reflector according to claim 1, characterized in that the metal pattern is made of a metal selected from the group consisting of aluminum, copper, gold, and silver. The communication wave reflector according to claim 1, characterized in that the size of each pattern constituting the geometric pattern of the metal pattern is within the range of 0.01 to 8 mm. The communication wave reflector according to claim 1, characterized in that the protective layer is made of a resin selected from the group consisting of polyethylene resin, polypropylene resin, polybutylene resin, polyester resin, and polyamide resin. A method for producing a communication wave reflector according to any one of claims 1 to 9,
A method for producing a communication wave reflector, comprising the steps of: producing the laminate by roll-to-roll processing.

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