Window material and method for producing window material

Abstract

To provide a high-productivity window material that functions to reflect or block waves and is capable of enhancing radio wave transmissivity only for radio waves in a specific frequency band, and to provide a method for producing the window material. The window material 1 includes at least one transparent plate 2, a metal layer 3 laminated on at least one transparent plate 2, and at least one metasurface film 4. The metasurface film 4 has a base material 42 attached to the transparent plate 2 or the metal layer 3, and a metal pattern 41 formed on the base material 42.

Description

Window material and method for manufacturing the window material

[0001] The present invention relates to a window material and a method for manufacturing the window material.

[0002] Patent Document 1 discloses a conventional window material (a glass body in Patent Document 1). The glass body in Patent Document 1 has a Low-E film (low emissivity film) formed on the entire surface of one surface of a glass plate. It is known that glass bodies with a Low-E film formed thereon have low transmittance to radio waves over a wide frequency band. For this reason, in Patent Document 1, a portion of the Low-E film is removed by laser processing to form a radio wave-transmitting region.

[0003] Japanese Patent Application Laid-Open No. 2023-113772

[0004] However, when manufacturing a glass body, the process of removing a portion of the Low-E film is not ideal for manufacturability.

[0005] The present invention has been made in consideration of the above circumstances, and aims to provide a window material and a method for manufacturing a window material that has the function of reflecting or blocking radio waves, but can also increase radio wave transmittance only for radio waves in a specific frequency band, and is highly manufacturable.

[0006] To achieve the above object, the present invention includes the following subject matter.

[0007] Item 1. A window material comprising at least one transparent plate, a metal layer laminated on the at least one transparent plate, and at least one metasurface film, wherein the metasurface film has a substrate attached to the transparent plate or the metal layer, and a metal pattern formed on the substrate.

[0008] Item 2. The window material according to Item 1, wherein the at least one transparent plate comprises a plurality of transparent plates arranged at intervals, and at least one of the metasurface films is attached to a transparent plate other than the transparent plate on which the metal layer is laminated.

[0009] Item 3. The window material according to item 1, wherein the at least one transparent plate has a first surface and a second surface opposite to the first surface, the metal layer is laminated on the first surface, and at least one of the metasurface films is attached to the second surface.

[0010] Item 4. The window material according to any one of items 1 to 3, wherein the at least one metasurface film includes a first metasurface film and a second metasurface film, the first metasurface film is for uplink, and the second metasurface film is for downlink.

[0011] Item 5. The window material according to Item 4, wherein the first metasurface film and the second metasurface film are arranged so as not to overlap each other in a plan view seen from a direction perpendicular to the surface of the window material.

[0012] Item 6. The window material according to item 4 or 5, wherein the first metasurface film is provided closer to the interior of a building to which the window material is attached than the second metasurface film.

[0013] Item 7. The window material according to any one of Items 1 to 6, wherein each of the metal patterns is made up of a linear body, and the maximum width of the linear body is 100 μm or less.

[0014] Item 8. The window material according to any one of Items 1 to 7, wherein the metasurface film further includes a protective film covering the metal pattern.

[0015] Item 9. The window material according to Item 8, wherein the protective film contains fluorine.

[0016] Item 10. The window material according to any one of Items 1 to 9, wherein the metal layer is a Low-E film.

[0017] Item 11. The window material according to any one of Items 1 to 9, wherein the metal layer is a heat-shielding film.

[0018] Item 12. A method for manufacturing a window material, comprising attaching a metasurface film comprising a substrate and a metal pattern formed on the substrate to at least one transparent plate on which a metal layer is laminated.

[0019] The window material and the method for manufacturing a window material according to the above aspects of the present invention have the advantage that they can improve radio wave transmittance only for radio waves in a specific frequency band while still having the function of reflecting or blocking radio waves, and can provide a window material and a method for manufacturing a window material that are highly manufacturable.

[0020] FIG. 1 is a cross-sectional view of a window material according to an embodiment. FIG. 2 is a front view of a metasurface film according to an embodiment. FIG. 3 is a cross-sectional view of a metasurface film according to an embodiment. FIG. 4 is a front view of a metasurface film according to Modification 1. FIG. 5 is a cross-sectional view of a window material according to Modification 2. FIG. 6 is a cross-sectional view of a window material according to Modification 3. FIG. 7 is a cross-sectional view of a window material according to Modification 4. FIG. 8 is a cross-sectional view of a window material according to Modification 4. FIGS. 9(A) and (B) are graphs showing the results of evaluation tests.

[0021] <Embodiments> Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in Figure 1, a window material 1 according to this embodiment is a double glazing having multiple transparent plates 2. The window material 1 includes multiple transparent plates 2, a metal layer 3, and at least one metasurface film 4. The window material 1 also includes spacers 5 that maintain a distance between the multiple transparent plates 2.

[0022] As shown in Figures 2 and 3, the metasurface film 4 comprises a substrate 42 attached to the transparent plate 2 or the metal layer 3, and a metal pattern 41 formed on the substrate 42.

[0023] Because the window material 1 according to this embodiment is configured in this way, it is possible to increase the radio wave transmittance only for radio waves in a specific frequency band, even if the metal layer 3 reflects or blocks radio waves. Moreover, since it is only necessary to attach the metasurface film 4 to the window material 1 on which the existing metal layer 3 is laminated, the window material 1 can be made highly manufacturable.

[0024] The window material 1 according to this embodiment is used, for example, as window glass in buildings, as well as light-receiving windows in doors, fixed windows in ceilings, floors, etc. Furthermore, the window material 1 according to this embodiment can also be used for windows in automobiles, aircraft, ships, trains, ropeways, etc. in addition to buildings.

[0025] In the window material 1, the specific frequency band of radio waves that can enhance radio wave transmittance is preferably any radio wave in the range of 0.5 GHz to 60 GHz. In this embodiment, the transparent plate 2 is configured to enhance radio wave transmittance in the 5 GHz frequency band (3 GHz to 5 GHz, 25 GHz to 30 GHz). However, there are no particular restrictions on the frequency band in which radio wave transmittance is to be enhanced in the window material 1. The specific frequency band in which radio wave transmittance is to be enhanced can be set to the desired frequency band by changing the shape of the metal pattern 41 in the metasurface film 4.

[0026] (Transparent Plate 2) The transparent plate 2 is a transparent plate material. In this specification, "transparent" means that the light transmittance is 10% or more with respect to the peak wavelength of the light before incidence, preferably 50% or more, and more preferably 80% or more. In other words, "transparent" in this specification also includes "semi-transparent" in which the light transmittance is, for example, about 30% with respect to the peak wavelength of the light before incidence. Furthermore, the transparent plate 2 is not limited to being colorless and transparent, and may be colored.

[0027] The transparent plate 2 according to the present embodiment is preferably a glass plate. Examples of the glass plate include float glass, figured glass, frosted glass, wired glass, and tempered glass. However, examples of the transparent plate 2 include an acrylic plate and a polycarbonate plate in addition to a glass plate.

[0028] There are no particular limitations on the shape of the transparent plate 2. The shape of the transparent plate 2 may be, for example, a rectangular shape in a plan view, a circular shape in a plan view, a pentagonal shape in a plan view, a hexagonal shape in a plan view, an elliptical shape in a plan view, etc. Here, "plan view" means that the main surface of the transparent plate 2 is viewed from a direction perpendicular to the main surface.

[0029] 1, the multiple transparent plates 2 are arranged at regular intervals in the thickness direction of the window material 1. Of the adjacent transparent plates 2, one transparent plate 2 may be referred to as the "first transparent plate 21" and the other transparent plate 2 may be referred to as the "second transparent plate 22."

[0030] A spacer 5 is disposed between the first transparent plate 21 and the second transparent plate 22. The spacer 5 maintains the distance between the two adjacent transparent plates 21, 22. The outer peripheries of the transparent plates 2 are surrounded by a sealing material (not shown), and the space (intermediate layer 6) between the two adjacent transparent plates 21, 22 is formed airtight. The intermediate layer 6 is preferably filled with an insulating gas. Examples of the insulating gas include an inert gas such as argon gas. However, the intermediate layer 6 may also be filled with air. Alternatively, the intermediate layer 6 may be a vacuum.

[0031] The first transparent plate 21 has a first surface 211 and a second surface 212. Similarly, the second transparent plate 22 has a first surface 221 and a second surface 222. The first surfaces 211 and 221 are one of the surfaces (main surfaces) in the thickness direction of the transparent plate 2. The second surfaces 212 and 222 are main surfaces opposite the first surfaces 211 and 221. In this embodiment, the first surfaces 211 and 221 refer to surfaces of adjacent transparent plates 2 that face each other (inner surfaces in the thickness direction of the window material 1), and the second surfaces 212 and 222 refer to outer surfaces of the window material 1.

[0032] The window material 1 in this embodiment is a double-pane glass made up of two transparent plates 2, but it may also be a triple-pane glass made up of three transparent plates 2, or it may be made up of four or more transparent plates 2.

[0033] (Metal Layer 3) The metal layer 3 is laminated on the transparent plate 2 to improve the heat insulating properties of the window material 1. The metal layer 3 is preferably a Low-E film. There are no particular limitations on the Low-E film, and examples thereof include a film in which a transparent dielectric layer, an infrared reflective layer, and a transparent dielectric layer are laminated in this order. Examples of the transparent dielectric layer include metal oxides (e.g., zinc oxide, tin oxide) and metal nitrides. Examples of the infrared reflective layer include metal films (e.g., silver), semiconductor films, etc.

[0034] The metal layer 3 may be laminated on any one of the plurality of transparent plates 2. In this embodiment, the metal layer 3 is laminated on the first surface 211 of the first transparent plate 21. The metal layer 3 is laminated over the entire surface of the first surface 211 of the transparent plate 2. The metal layer 3 is laminated on the transparent plate 2 by, for example, coating, vapor deposition, adhesion, welding, or the like.

[0035] (Metasurface film 4) The metasurface film 4 is attached to the transparent plate 2 or the metal layer 3. By attaching the metasurface film 4 to the transparent plate 2 or the metal layer 3, the radio wave transmittance of the window material 1 can be increased in a specific frequency band of radio waves. As shown in FIG. 2, the metasurface film 4 is formed by laminating a substrate 42, multiple metal patterns 41, and a protective film 44 in this order. The metasurface film 4 of this embodiment is attached to the second surface 212 of the first transparent plate 21. The metasurface film 4 may cover the entire surface of the transparent plate 2, or may be attached to only a portion of the entire surface.

[0036] (Substrate 42) The substrate 42 supports a plurality of metal patterns 41. In this embodiment, the substrate 42 is transparent. The substrate 42 is attached to the transparent plate 2 or the metal layer 3. An adhesive layer (hereinafter referred to as the first adhesive layer 45) is provided on the surface of the substrate 42 opposite the metal pattern 41. The first adhesive layer 45 preferably has a large number of capsules filled with adhesive before bonding, and is structured so that, upon application of pressure from the substrate 42 toward the transparent plate 2 or the metal layer 3, the capsules rupture to allow bonding. However, the first adhesive layer 45 may be an adhesive applied without being filled into capsules. Examples of adhesives include synthetic resins such as acrylic resin, silicone resin, and polyvinyl alcohol resin.

[0037] In this embodiment, the outer shape of the substrate 42 is quadrangular (more specifically, square) in plan view, as shown in Fig. 2. However, there are no particular limitations on the shape of the substrate 42, and examples include a polygon, a circle, an ellipse, a star, a heart, and the like. The thickness of the substrate 42 is uniform over the entire surface. However, the thickness of the substrate 42 does not have to be uniform.

[0038] Examples of the substrate 42 include synthetic resin, fiber reinforced plastics (FRP), carbon, and glass. Examples of the synthetic resin include one or more selected from the group consisting of PET (polyethylene terephthalate), 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. The substrate 42 may be a composite material of these synthetic resins. The substrate 42 according to this embodiment is made of a PET film.

[0039] The thickness of the substrate 42 is, for example, preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more. On the other hand, the upper limit of the thickness of the substrate 42 is, for example, preferably 500 μm or less, more preferably 130 μm or less, and even more preferably 100 μm or less.

[0040] The substrate 42 preferably has flexibility. The modulus of longitudinal elasticity of the substrate 42 is, for example, preferably 0.01 GPa or more, more preferably 1 GPa or more, and even more preferably 8 GPa or more. On the other hand, the upper limit of the modulus of longitudinal elasticity of the substrate 42 is, for example, preferably 80 GPa or less, more preferably 30 GPa or less, and even more preferably 20 GPa or less.

[0041] (Metal Pattern 41) The metal pattern is a metal microstructure having a structure finer than the wavelength of the target radio wave (electromagnetic wave). The metal pattern corresponds to a split ring resonator in a metasurface (metamaterial) and is also called a split ring resonator (SRR). In this specification, the metal pattern may be referred to as a "split ring resonator portion."

[0042] The metal pattern 41 is made of a conductor and is formed on a substrate 42. Methods for forming the metal pattern 41 on the substrate 42 include, for example, laminating a thin film formed by embedding the metal pattern 41 in a thin-film dielectric on the substrate 42, or forming the metal pattern 41 on the substrate 42 without using a dielectric.

[0043] Examples of conductors constituting the metal pattern 41 include one or more of silver, gold, copper, platinum, aluminum, titanium, silicone, indium tin oxide, and alloys (e.g., alloys containing nickel, chromium, and molybdenum). Examples of alloys containing nickel, chromium, and molybdenum include various grades of Hastelloy B-2, B-3, C-4, C-2000, C-22, C-276, G-30, N, W, and X.

[0044] The thickness of the metal pattern 41 is preferably 10 nm or more, more preferably 30 nm or more, and even more preferably 100 nm or more. On the other hand, the upper limit of the thickness of the metal pattern 41 is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 4 μm or less. When the thickness of the metal pattern 41 is 10 nm or more, appropriate radio wave strength can be ensured.

[0045] The shape of the metal pattern 41 may be various depending on the desired frequency band of radio waves for which radio wave permeability is to be increased, but in this embodiment, the pattern shown in Fig. 2 will be described as an example. By adjusting the metal pattern 41 and the size of the metal pattern 41 in this embodiment, it is possible to increase the radio wave permeability of radio waves in a desired frequency band.

[0046] As shown in FIG. 2 , the metal pattern 41 is composed of a plurality of linear bodies. The linear bodies extend thinly. In the present embodiment, each linear body is straight. The metal pattern 41 according to the present embodiment is composed of a pair of first vertical portions 411, a pair of first horizontal portions 412, a pair of second vertical portions 413, and a pair of second horizontal portions 414 as linear bodies. The metal pattern 41 according to the present embodiment is composed of a single shape in which a plurality of linear bodies are connected, and is separated from adjacent metal patterns 41 without contacting them.

[0047] The first vertical portion 411 and the first horizontal portion 412 are connected to form a rectangular frame. The second vertical portion 413 protrudes inward from the center of the first horizontal portion 412 in the longitudinal direction within the area surrounded by the first vertical portion 411 and the first horizontal portion 412. The second horizontal portion 414 is parallel to the first horizontal portion 412 and connected to the inner end of the second vertical portion 413. The second horizontal portions 414 are spaced apart and parallel to each other. The second horizontal portions 414 are also spaced apart from the first vertical portion 411.

[0048] The maximum width of the linear body of the metal pattern 41 configured as described above is preferably 2 mm or less. On the other hand, the maximum width of the linear body of the metal pattern 41 is preferably 10 μm or more. When the maximum width of the linear body is 2 mm or less, the degree of freedom in designing the metal pattern 41 can be improved. When the maximum width of the linear body is 10 μm or more, the productivity of the metal pattern can be maintained while suppressing costs. The width of the linear body means the dimension (thickness) in the direction perpendicular to the longitudinal direction of the linear body.

[0049] The metal pattern 41 preferably has a relative dielectric constant of 7 or more. On the other hand, the upper limit of the relative dielectric constant is preferably 10,000 or less.

[0050] Furthermore, the metal pattern 41 is preferably a rotationally symmetric figure. The metal pattern according to this embodiment is a two-fold symmetric figure. The metal pattern may also be a three-fold, four-fold, or five-fold symmetric figure.

[0051] (Protective Film 44) The protective film 44 can protect the metal patterns 41 by covering the multiple metal patterns 41. The protective film 44 has a size corresponding to the substrate 42 in a plan view. Examples of the protective film 44 include films made of synthetic resins. Examples of synthetic resins include one or more selected from the group consisting of PET (polyethylene terephthalate), COP (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.

[0052] The protective film 44 preferably contains fluorine. The protective film 44 containing fluorine can prevent transmission of ultraviolet rays, and therefore can protect the plurality of metal patterns 41 from ultraviolet rays.

[0053] The thickness of the protective film 44 is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more. On the other hand, the upper limit of the thickness of the protective film 44 is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 25 μm or less.

[0054] The protective film 44 is adhered to the substrate 42 via an adhesive layer (hereinafter referred to as the second adhesive layer 43). The second adhesive layer 43 may be made of, for example, a synthetic resin or a rubber adhesive sheet. Examples of the synthetic resin include an acrylic resin, a silicone resin, and a polyvinyl alcohol resin.

[0055] <Modifications> The above embodiment is merely one of various embodiments of the present invention. The embodiment can be modified in various ways depending on the design, etc., as long as the object of the present invention can be achieved. Modifications of the embodiment are listed below. The modifications described below can be applied in appropriate combinations.

[0056] (Variation 1) The metal pattern 41 may be, for example, as shown in Fig. 4. As shown in Fig. 4, the metal pattern 41 includes a split ring resonator and an enclosing portion 415. The split ring resonator has the same shape as the metal pattern 41 of the above embodiment, so it is denoted by the same reference numeral and description thereof will be omitted.

[0057] The surrounding portion 415 surrounds the split-ring resonator. In this modification, the surrounding portion 415 is rectangular, but may be, for example, circular, elliptical, pentagonal, or hexagonal. It is preferable that the surrounding portion 415 is continuous in the circumferential direction without being divided. However, the surrounding portion 415 may be partially divided.

[0058] It is preferable that the minimum distance between the first vertical portion 411 of the split ring resonator and the surrounding portion 415 is the same as the minimum distance between the first horizontal portion 412 of the split ring resonator and the surrounding portion 415. Here, "the same" means that the minimum distance falls within a range of 3% of the larger of the vertical dimension and horizontal dimension of the metal pattern 41.

[0059] In this way, by forming the metal pattern 41 in a shape in which the integrally connected split ring resonator portions are surrounded by the surrounding portion 415, it is possible to increase the radio wave transparency for radio waves in two specific frequency bands.

[0060] (Variation 2) In the above embodiment, multiple transparent plates 2 were provided, but as shown in Fig. 5, the window material 1 may have only one transparent plate 2. As shown in Fig. 5, a metal layer 3 is laminated on a first surface 211 of the transparent plate 2. A metasurface film 4 is attached to the metal layer 3. Note that the metasurface film 4 may also be attached to a second surface 212 on which no metal layer 3 is provided.

[0061] Furthermore, the metal layer 3 is not limited to a Low-E film and may be a heat-shielding film. When the metal layer 3 is a heat-shielding film, it may be attached to the first surface 211 or the second surface 212 of the transparent plate 2, for example, after the window material 1 is installed in the window frame.

[0062] (Variant 3) In the above embodiment, the metasurface film 4 was attached to a transparent plate 2 (first transparent plate 21) on which a metal layer 3 was laminated, but as shown in Figure 6, it may also be attached to a transparent plate 2 (second transparent plate 22) other than the transparent plate 2 on which the metal layer 3 was laminated.

[0063] The distance between the metasurface film 4 and the metal layer 3 is preferably 110 mm or less, more preferably 30 mm or less, and even more preferably 10 mm or less. On the other hand, the lower limit of the distance between the metasurface film 4 and the metal layer 3 may be 0 mm. That is, the metasurface film 4 may be directly bonded to the metal layer 3 (see FIG. 5).

[0064] (Variant 4) In the above embodiment, the uses of the multiple metasurface films 4 are not specified, but the metasurface film 4 may include a first metasurface film 4A and a second metasurface film 4B. The first metasurface film 4A is for uplink (for transmission from the terminal to the base station), and the second metasurface film 4B is for downlink (for transmission from the base station to the terminal). The first metasurface film 4A and the second metasurface film 4B may have the same structure, but it is preferable that the spacing of the metal patterns 41, for example, be different.

[0065] It is preferable that the first metasurface film 4A and the second metasurface film 4B are arranged so that they do not overlap each other when viewed in a planar view perpendicular to the surface of the window material, and it is preferable that the first metasurface film 4A be positioned closer to the interior of the building to which the window material is attached than the second metasurface film 4B.

[0066] Specific examples are shown in Figures 7 and 8. In Figures 7 and 8, the right side of the window material 1 is the interior side of the building.

[0067] 7, the window material 1 includes two transparent plates 2 (a first transparent plate 21 and a second transparent plate 22), a metal layer 3, a plurality of metasurface films 4, and a spacer 5, and the metal layer 3 is laminated on the first surface 211 of the first transparent plate 21. That is, the structures of the transparent plate 2, the metal layer 3, and the spacer 5 are the same as those in FIGS.

[0068] Of the metasurface films 4, the first metasurface film 4A is attached to the second surface 222 of the second transparent plate 22 on the inside side of the building, and the second metasurface film 4B is attached to the second surface 212 of the first transparent plate 21 on the outside side of the building. Furthermore, the first metasurface film 4A and the second metasurface film 4B are arranged so as not to overlap each other in a planar view seen from a direction D1 perpendicular to the surface of the window material 1.

[0069] In addition, when the first metasurface film 4A is attached to the second surface 222 of the second transparent plate 22, the second metasurface film 4B may be attached to the metal layer 3 or the first surface 221 of the second transparent plate 22. In addition, when the second metasurface film 4B is attached to the second surface 212 of the first transparent plate 21, the first metasurface film 4A may be attached to the metal layer 3 or the first surface 221 of the second transparent plate 22. Alternatively, the first metasurface film 4A may be attached to the first surface 221 of the second transparent plate 22, and the second metasurface film 4B may be attached to the metal layer 3.

[0070] 8, the window material 1 comprises one transparent plate 2, a metal layer 3, and multiple metasurface films 4, and the metal layer 3 is laminated on the first surface 221 of the transparent plate 2. That is, the structures of the transparent plate 2 and the metal layer 3 are the same as those in FIG.

[0071] Of the metasurface films 4, the first metasurface film 4A is attached to the metal layer 3, and the second metasurface film 4B is attached to the second surface 212 of the transparent plate 2. Furthermore, the first metasurface film 4A and the second metasurface film 4B are arranged so as not to overlap each other in a planar view seen from a direction D1 perpendicular to the surface of the window material 1.

[0072] 7 and 8, the first metasurface film 4A is provided closer to the interior of the building than the second metasurface film 4B, and the first metasurface film 4A and the second metasurface film 4B are arranged so as not to overlap each other in a plan view seen from the direction D1 perpendicular to the surface of the window material 1. This allows both uplink radio waves and downlink radio waves to pass through efficiently.

[0073] In addition, in Figures 7 and 8, the first metasurface film 4A and the second metasurface film 4B may partially overlap when viewed in a planar view from direction D1.

[0074] <Examples> Tests were conducted to confirm the effects of the window material according to the present invention. Test pieces for the examples and comparative examples 2 to 4 were prepared for the window material, and evaluation tests were conducted using the following methods. Note that the test for comparative example 1 was conducted without a test piece. However, the window material of the present invention is not limited to the examples.

[0075] (Example) The metasurface film of the example is the same as metasurface film 4 of the embodiment. For the metasurface film of the example, a pattern with a thickness of 1.8 μm was formed on a 0.1 mm thick PET film (substrate). Copper was used for the pattern. Two pieces of glass manufactured by YKK AP were used as the transparent plates used in the example. Each piece of glass was 6 mm thick, and the gap between the two adjacent pieces of glass was 12 mm. A Low-E film was laminated as a metal layer on the inside of one of the two pieces of glass.

[0076] (Comparative Example 2) The test piece for Comparative Example 2 used two transparent plates without a metal layer. As in the example, two pieces of glass manufactured by YKK AP were used as the transparent plates. Each piece of glass was 6 mm thick, and the gap between the two adjacent pieces of glass was 12 mm. No metasurface film was attached.

[0077] (Comparative Example 3) The test piece for Comparative Example 3 used two transparent plates made of glass manufactured by YKK AP Corporation, as in the example. Each glass was 6 mm thick, and the gap between the two adjacent glasses was 12 mm. A Low-E film was laminated as a metal layer on the inside of one of the two glasses. No metasurface film was attached.

[0078] (Comparative Example 4) For the test piece of Comparative Example 4, two pieces of glass manufactured by YKK AP Corporation were used as two transparent plates, as in the example. Each piece of glass was 6 mm thick, and the gap between the two adjacent pieces of glass was 12 mm. Copper foil was laminated as a metal layer on the inside of one of the two pieces of glass. No metasurface film was attached.

[0079] (Test method) In an anechoic chamber, a network analyzer (Keysight PNA E8363C) was connected to a transmitter and a receiver (FT-RF HA-0218G-NF) with an RF cable. The transmitter and receiver were installed so that the distance between the antennas was 60 cm, and a test piece was placed at the center of the transmitter and receiver, and measurements were performed.

[0080] The frequency was changed from 2 GHz to 6 GHz, and the strength of the radio waves received by the receiver was measured at each frequency.

[0081] The test results are shown in Figures 9(A) and 9(B). Figure 9(A) shows the results when the transmitter was placed facing the metasurface film, and Figure 9(B) shows the results when the receiver was placed facing the metasurface film.

[0082] As can be seen by comparing Comparative Example 2 with Comparative Examples 3 and 4, radio waves passing through the transparent plate having a metal layer are largely blocked over the entire frequency range from 2 GHz to 6 GHz. On the other hand, by comparing the Example with Comparative Example 3, it can be seen that radio waves are relatively easily transmitted through the transparent plate in a specific frequency band (a range of approximately 5.5 GHz or higher).

[0083] This shows that even if a metal layer is present, by attaching a metasurface film, it is possible to increase the radio wave transmittance for only a specific frequency band of radio waves.

[0084] 9A and 9B, the graphs of the examples show a downwardly concave valley (near 5.2 GHz). It is known that this valley is caused by the metal pattern, and the position of the valley can be adjusted appropriately by changing the shape and / or size of the metal pattern.

[0085] REFERENCE SIGNS LIST 1 window material 2 transparent plate 21 first transparent plate 211 first surface 212 second surface 22 second transparent plate 221 first surface 222 second surface 3 metal layer 4 metasurface film 4A first metasurface film 4B second metasurface film 41 metal pattern 42 substrate 44 protective film

Claims

1. A window material comprising: at least one transparent plate; a metal layer laminated on the at least one transparent plate; and at least one metasurface film, wherein the metasurface film has a substrate attached to the transparent plate or the metal layer; and a metal pattern formed on the substrate.

2. The window material described in claim 1, wherein the at least one transparent plate comprises a plurality of transparent plates arranged at intervals, and at least one of the metasurface films is attached to a transparent plate other than the transparent plate on which the metal layer is laminated.

3. The window material of claim 1, wherein the at least one transparent plate has a first surface and a second surface opposite the first surface, the metal layer is laminated to the first surface, and at least one of the metasurface films is attached to the second surface.

4. A window material described in any one of claims 1 to 3, comprising a first metasurface film and a second metasurface film as the at least one metasurface film, the first metasurface film being for uplink, and the second metasurface film being for downlink.

5. The window material described in claim 4, wherein the first metasurface film and the second metasurface film are arranged so as not to overlap each other in a planar view seen in a direction perpendicular to the surface of the window material.

6. The window material described in claim 4, wherein the first metasurface film is arranged on the interior side of the building to which the window material is attached relative to the second metasurface film.

7. The window material according to any one of claims 1 to 6, wherein each of the metal patterns is composed of a linear body, and the maximum width of the linear body is 100 μm or less.

8. A window material described in any one of claims 1 to 6, wherein the metasurface film further has a protective film covering the metal pattern.

9. The window material according to claim 8, wherein the protective film comprises fluorine.

10. The window material according to claim 1, wherein the metal layer is a Low-E film.

11. The window material of claim 1, wherein the metal layer is a heat insulating film.

12. A method for manufacturing a window material, comprising attaching a metasurface film comprising a substrate and a metal pattern formed on the substrate to at least one transparent plate having a metal layer laminated thereon.

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