Electromagnetic wave reflecting film

Abstract

This invention provides a transparent and flexible electromagnetic wave reflective film. The electromagnetic wave reflective film comprises: a conductive layer for reflecting electromagnetic waves in a predetermined frequency band of 1 GHz to 300 GHz; a first substrate layer supporting the conductive layer; a second substrate layer disposed on the side of the conductive layer opposite to the first substrate layer; and an adhesive layer for bonding the second substrate layer to the conductive layer. The thickness (t3) of the first substrate layer is 1.0 mm or less, and the ratio (t3 / t1) of the thickness of the first substrate layer to the thickness (t1) of the conductive layer is 0.25 or more and 1.0 × 10⁻⁶. 5 the following.

Description

Technical Field

[0001] This invention relates to electromagnetic wave reflective films. Background Technology

[0002] To facilitate various applications such as manufacturing process automation, office work automation, remote operation, AI-based control and management, and autonomous driving, base stations are being deployed in both indoor and outdoor spaces. These spaces include factories, workshops, office buildings, commercial facilities, medical facilities, event venues, highways, and railway lines. Fifth-generation mobile communication systems (hereinafter referred to as "5G") utilize sub-6GHz frequency bands and the 28GHz frequency band classified as millimeter wave bands. The next-generation 6G mobile communication standard is expected to extend to terahertz frequency bands. By using such high-frequency bands, communication bandwidth is expanded, enabling high-volume data communication with low latency.

[0003] 5G radio waves have strong straight-line propagation and are not easily diffracted. Radio waves on roads are blocked by vehicles and structures, while in factories they are blocked by machinery and product racks on production lines, creating blind spots in various locations. These blind spots can be eliminated by installing electromagnetic wave reflecting panels at appropriate locations. A configuration in which electromagnetic wave reflecting devices are arranged along at least a portion of the production line has been proposed (see, for example, Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2021 / 199504 Summary of the Invention

[0007] As electromagnetic wave reflecting panels, metal reflectors made of metal plates such as aluminum and copper are known. Metal reflectors are typically opaque. When installed in roads, factories, office buildings, etc., they can sometimes obstruct the view. Furthermore, if installed on office building windows, they not only hinder lighting but can also sometimes detract from the building's ambiance and aesthetics. Therefore, the use of transparent electromagnetic wave reflecting panels using resin or glass substrates is considered. However, it is difficult to seamlessly adhere a rigid, transparent electromagnetic wave reflecting panel of a certain thickness to existing structures. If adhesives are used to attach rigid electromagnetic wave reflecting panels to structures, air bubbles and air layers easily become trapped between the panel and the structure, making it particularly difficult to apply to curved surfaces. One object of the present invention is to provide a transparent and flexible electromagnetic wave reflecting film.

[0008] In one embodiment, the electromagnetic wave reflecting film comprises:

[0009] The conductive layer reflects electromagnetic waves in a specified frequency band from 1 GHz to 300 GHz.

[0010] The first substrate layer supports the aforementioned conductive layer;

[0011] A second substrate layer is disposed on the side of the conductive layer opposite to the first substrate layer; and

[0012] An adhesive layer is used to bond the second substrate layer to the conductive layer.

[0013] The thickness of the first substrate layer is less than 1.0 mm.

[0014] The ratio of the thickness of the first substrate layer to the thickness of the conductive layer is 0.25 or more and 1.0 × 10⁻⁶. 5 the following.

[0015] Achieving a transparent and flexible electromagnetic wave reflective film. Attached Figure Description

[0016] Figure 1A This is a schematic diagram illustrating an application example of the electromagnetic wave reflective film according to the embodiment.

[0017] Figure 1B This is a schematic diagram illustrating another application example of the electromagnetic wave reflective film according to the embodiment.

[0018] Figure 2 This is a schematic diagram showing the layer structure of the electromagnetic wave reflecting film in the first embodiment.

[0019] Figure 3 It means Figure 2 A schematic diagram illustrating an application example of electromagnetic wave reflective film on window glass.

[0020] Figure 4 This is a schematic diagram showing the layer structure of the electromagnetic wave reflecting film in the second embodiment.

[0021] Figure 5 It means Figure 4 A schematic diagram illustrating an application example of electromagnetic wave reflective film on window glass. Detailed Implementation

[0022] In this embodiment, a conductive layer that reflects electromagnetic waves of a specified frequency band is carried on a transparent, flexible substrate layer, and the surface of the conductive layer is protected by a protective layer via an adhesive layer. By setting the ratio of the thickness t2 of the adhesive layer to the thickness t1 of the conductive layer (t2 / t1) or the ratio of the thickness t3 of the substrate layer to the thickness t1 of the conductive layer (t3 / t1) within an appropriate range, an electromagnetic wave reflective film with a certain degree of reflectivity and transparency is achieved.

[0023] The electromagnetic wave reflective film of the following embodiments will be described with reference to the accompanying drawings. The embodiments described below are examples used to concretize the technical concept of the invention and do not limit the invention to the processes and values ​​described below. In the drawings, sometimes the same symbols are used to denote components with the same function to avoid repetition. Partial substitutions or combinations can be made between different embodiments and configuration examples. Sometimes, the size and positional relationships of the components shown in the drawings are exaggerated for ease of understanding of the invention. When the positional relationship is referred to as "upper" or "lower," unless otherwise specified, it refers to the vertical direction in the stacking direction or film formation direction, not an absolute direction.

[0024] Figure 1A This is a schematic diagram illustrating an application example of the electromagnetic wave reflective film 10 according to the embodiment. The electromagnetic wave reflective film 10 is applied, for example, to the window glass 3 of a window 1 in a shopping mall or office building. The electromagnetic wave reflective film 10 can be adhered to the entire window glass 3 supported by the window frame 6, or it can be adhered to a portion of the window glass 3 depending on the incident direction of the electromagnetic wave, the desired reflection direction, etc. As described later, the total light transmittance of the electromagnetic wave reflective film 10 is 70% or more, preferably 75% or more, more preferably 80% or more, and even more preferably 85% or more. The absolute value of the reflection attenuation of the electromagnetic wave reflective film 10, based on the measurement method according to JIS R1679, is 1.00 dB or less, preferably 0.50 dB or less. The electromagnetic wave reflective film 10 can effectively reflect electromagnetic waves in a specified frequency band ranging from 1 GHz to 300 GHz without obstructing the view or scenery. The electromagnetic wave reflective film 10 can be applied not only to windows in shopping malls and office buildings, but also to safety fences on production lines, sound barriers on roads, etc.

[0025] Figure 1B This is a schematic diagram illustrating another application example of the electromagnetic wave reflecting film 10. The electromagnetic wave reflecting film 10 can be applied, for example, to structures 2 such as walls and columns in shopping malls or underground malls. The electromagnetic wave reflecting film 10 is flexible overall, allowing it to be installed along the surface of the structure 2 even when the structure 2 has curved surfaces. It can be applied to any location on the structure 2 depending on the incident direction of the electromagnetic wave and the desired reflection direction. Furthermore, as mentioned above, the total light transmittance is 70% or more, thus enabling the presentation of information such as text, still images, and moving images depicted or displayed on the surface of the structure 2. Even when the base station is not in line of sight (LOS) when viewed from the receiving antenna, the electromagnetic wave reflecting film 10 can be used to extend the receiving area of ​​a specified frequency band of radio waves radiated from the base station.

[0026] <First Implementation>

[0027] Figure 2This is a schematic diagram of the layer structure of the electromagnetic wave reflecting film 10 according to the first embodiment. The electromagnetic wave reflecting film 10 has a first substrate layer 11, a conductive layer 13 supported by the first substrate layer 11, a second substrate layer 14 disposed on the side of the conductive layer 13 opposite to the first substrate layer 11, and an adhesive layer 12 for bonding the second substrate layer 14 to the conductive layer 13.

[0028] The first substrate layer 11 is a dielectric transparent flexible film with a thickness "t3" of 1.00 mm or less, preferably 0.70 mm or less, more preferably 0.50 mm or less, and even more preferably 0.10 mm or less. The flexible film is formed from, for example, a transparent and heat-resistant dielectric resin material such as polyethylene terephthalate (PET), polycarbonate (PC), cyclic olefin polymer (COP), polyimide (PI), or fluoropolymer.

[0029] In addition to functioning as a support layer for the conductive layer 13, the first substrate layer 11 can also function as a protective layer for the surface 131 of the conductive layer 13, depending on the incident direction of the electromagnetic wave. For example, when using the second substrate layer 14 as a release layer and adhering the electromagnetic wave reflective film 10 to window glass or structures using the adhesive layer 12, the first substrate layer 11 can serve as a protective layer for one surface 131 of the conductive layer 13.

[0030] The first substrate layer 11 is transparent to visible light and also transparent to electromagnetic waves in a specified frequency band from 1 GHz to 300 GHz, thereby minimizing the attenuation of electromagnetic waves in the aforementioned frequency band incident on the conductive layer 13.

[0031] The conductive layer 13 is formed of a good conductor such as Ag, Cu, Ni, Al, or Pd, or a transparent metal oxide conductor, and can be processed into periodic patterns, mesh patterns, geometric patterns, etc. The conductive layer 13 reflects electromagnetic waves in a specified frequency band from 1 GHz to 300 GHz. Electromagnetic waves in this range include microwaves, millimeter waves, and submillimeter waves. The conductive layer 13 can be formed as a normal reflective surface that mirrors electromagnetic waves in the aforementioned frequency band, or it can be formed as a metasurface that controls the reflection or diffusion of incident electromagnetic waves. Alternatively, it can have both a region with a mirror reflective surface and a region with a metasurface.

[0032] When the conductive layer 13 is formed from an indium oxide-based transparent conductive material containing metal elements such as Sn, Ti, Zn, Zr, Ga, and W, or a metal material with high visible light transmittance such as Ag, the conductive layer 13 can be formed as a solid film on the first substrate layer 11, or as a thin film with a periodic pattern. The conductive layer 13 can be formed from a mesh pattern of metals such as SUS, Al, and Cu. When using a metal mesh pattern, it is preferable to have an aperture ratio of 70% or more such that the total light transmittance is 70% or more. When the conductive layer 13 is formed from Ag or a transparent conductive material, it can be formed on the first substrate layer 11 by sputtering or vacuum evaporation at room temperature. When using a metal mesh, a pre-fabricated metal mesh can be placed on the first substrate layer 11, and an adhesive layer 12 can be coated on the metal mesh. Alternatively, a metal mesh pattern can be formed on the first substrate layer 11 by sputtering or etching.

[0033] When the conductive layer 13 is formed by sputtering or vacuum evaporation, a thin film with a thickness "t1" of 5 nm to 500 nm can be formed. When a metal mesh is used, the thickness t1 of the conductive layer 13 can be several hundred nm to several hundred μm. The surface resistivity of the conductive layer 13 is less than 10.0 Ω / □. When a metal mesh is used, the surface resistivity of the conductive layer 13 can be less than 0.1 Ω / □.

[0034] The adhesive layer 12 is a dielectric adhesive layer capable of bonding the second substrate layer 14 to another surface 132 of the conductive layer 13. For example, thermoplastic resins such as vinyl acetate resin, acrylic resin, cellulose resin, and silicone resin can be used. As the adhesive layer 12, durable and moisture-resistant ethylene-vinyl acetate (EVA) copolymers and cyclic olefin polymers (COP) can be used. The thickness "t2" of the adhesive layer 12 can be appropriately selected between 10 μm and 750 μm depending on the material of the adhesive layer 12, the thickness and weight of the conductive layer 13 and the first substrate layer 11, etc.

[0035] The second substrate layer 14 can be used as a release layer. Before the electromagnetic wave reflective film 10 is adhered to the object, the second substrate layer 14 is attached to the conductive layer 13 via the adhesive layer 12. When adhering the electromagnetic wave reflective film 10 to window glass or structures, the second substrate layer 14 can be peeled off, and the electromagnetic wave reflective film 10 can be adhered to the object using the adhesive layer 12. The adhesive layer 12 is a re-peelable or reprocessable adhesive.

[0036] Figure 3 It means Figure 2This is a schematic diagram illustrating an application example of the electromagnetic wave reflective film 10 on a window glass 3. The electromagnetic wave reflective film 10, with the second substrate layer 14 peeled off, is adhered to the surface of the window glass 3 supported by the window frame 6 via an adhesive layer 12. The electromagnetic wave reflective film 10 can be adhered from the indoor 4 side or the outdoor 5 side. In locations such as offices or shopping malls where small wireless base stations are installed indoors 4, the electromagnetic wave reflective film 10 can be adhered from the indoor 4 side. In this case, the electromagnetic waves W radiated from the antenna of the base station installed indoors 4... EM The electromagnetic wave is reflected to the indoor 4 side by the conductive layer 13 of the electromagnetic wave reflective film 10, which can reduce the blind spot in the indoor 4.

[0037] When the window glass 3 and the adhesive layer 12 are transmissive to electromagnetic waves of 1GHz to 300GHz, and the conductive layer 13 has the function of reflecting the frequency band used for wireless communication in the outdoor 5, the conductive layer 13 disposed on the indoor 4 side also functions as a reflective film for electromagnetic waves incident from the outdoor 5. In this case, the blind spot of the outdoor 5 can also be reduced.

[0038] When the electromagnetic wave reflective film 10 is adhered from the outdoor side 5, the first substrate layer 11 can function as a protective layer, possessing impact resistance or durability. As a protective substrate layer, polycarbonate film, PET film, COP film, etc., with a thickness of 0.025mm to 1.0mm can be used. A hard coating that provides UV protection and scratch resistance can be provided on both sides or any one side of the first substrate layer 11.

[0039] The relative permittivity and dielectric loss tangent of the first substrate layer 11 and the adhesive layer 12 are appropriately selected as a whole in order to give the electromagnetic wave reflecting film 10 the desired reflection characteristics. The non-dielectric constant of the dielectric portion, excluding the conductive layer 13, is, for example, 2.0 to 3.0, and the dielectric loss tangent is 0.0001 or more and less than 0.1000. Flexible films with a relative permittivity less than 2.0 are currently difficult to obtain. If the relative permittivity exceeds 3.0, there is a risk of increased loss, especially at high frequencies. The same applies to the dielectric loss tangent. Flexible films with a dielectric loss tangent less than 0.0001 are difficult to obtain, and if the dielectric loss tangent is 0.1000 or more, the internal power loss of the electromagnetic wave reflecting film 10 increases.

[0040] By optimizing the ratio (t3 / t1) of the thickness t3 of the first substrate layer 11 to the thickness t1 of the conductive layer 13, or the ratio (t2 / t1) of the thickness t2 of the adhesive layer 12 to the thickness t1 of the conductive layer 13, a transparent and flexible electromagnetic wave reflective film 10 can be obtained. The optimal ranges for t3 / t1 and t2 / t1 are described later.

[0041] <Second Implementation>

[0042] Figure 4 This is a schematic diagram of the layer structure of the electromagnetic wave reflecting film 20 according to the second embodiment. The electromagnetic wave reflecting film 20 has a first substrate layer 21, a conductive layer 23 supported by the first substrate layer 21, a second substrate layer 24 disposed on the side of the conductive layer 23 opposite to the first substrate layer 21, and an adhesive layer 22 for bonding the second substrate layer 24 to the conductive layer 23. The electromagnetic wave reflecting film 20 also has a third substrate layer 27 bonded by the second adhesive layer 26 on the side 212 of the first substrate layer 21 opposite to the side 211 supporting the conductive layer 23.

[0043] The first substrate layer 21 is a dielectric transparent flexible film with a thickness "t3" of 1.00 mm or less, preferably 0.70 mm or less, more preferably 0.50 mm or less, and even more preferably 0.10 mm or less. The flexible film, like in the first embodiment, is formed from a transparent and heat-resistant dielectric resin material such as PET, PC, COP, PI, or fluoropolymer.

[0044] In addition to functioning as a support layer for the conductive layer 23, the first substrate layer 21 also functions as an adhesive surface for the window glass and structures. For example, when the third substrate layer 27 is used as a release layer and the electromagnetic wave reflective film 20 is adhered to the window glass and structures using the second adhesive layer 26, the surface 212 of the first substrate layer 21 becomes the adhesive surface for the window glass and structures.

[0045] The conductive layer 23 is formed of a good conductor such as Ag, Cu, Ni, Al, or Pd, or a transparent metal oxide conductor, and can be processed into periodic patterns, mesh patterns, geometric patterns, etc. The conductive layer 23 reflects electromagnetic waves in a specified frequency band from 1 GHz to 300 GHz. This range of electromagnetic waves includes microwaves, millimeter waves, and submillimeter waves. The conductive layer 23 can be formed as a normal reflective surface that specularly reflects electromagnetic waves in the aforementioned frequency band, or it can be formed as a metasurface that controls the reflection or diffusion of incident electromagnetic waves. The material, formation method, surface resistivity, and thickness "t1" of the conductive layer 23 are the same as those of the conductive layer 13 in the first embodiment.

[0046] The adhesive layer 22 is a dielectric adhesive layer capable of bonding the second substrate layer 24 to the conductive layer 23. For example, thermoplastic resins such as vinyl acetate resin, acrylic resin, cellulose resin, and silicone resin can be used. As the adhesive layer 22, durable and moisture-resistant ethylene-vinyl acetate (EVA) copolymers and cyclic olefin polymers (COP) can be used. The thickness "t2" of the adhesive layer 22 can be appropriately selected between 10 μm and 750 μm, depending on the material of the adhesive layer 22, the thickness of the conductive layer 23, and the second substrate layer 24.

[0047] The second substrate layer 24 is transparent to visible light and also transparent to electromagnetic waves in a specified frequency band from 1 GHz to 300 GHz, minimizing the attenuation of electromagnetic waves in the aforementioned frequency band incident on the conductive layer 23. The second substrate layer 24 functions as a protective layer. A hard coating for scratch resistance or UV protection can be applied to either or both sides of the second substrate layer 24.

[0048] The third substrate layer 27 serves as a release layer. Before the electromagnetic wave reflective film 20 is adhered to the object, the third substrate layer 27 is attached to the surface 212 of the first substrate layer 21 via the second adhesive layer 26. When the electromagnetic wave reflective film 20 is adhered to window glass or a structure, the third substrate layer 27 can be peeled off, and the second adhesive layer 26 can be used for adhesion.

[0049] Figure 5 It means Figure 4 A schematic diagram illustrating an application example of the electromagnetic wave reflective film 20 on a window glass 3. The electromagnetic wave reflective film 20, with the third substrate layer 27 peeled off, is adhered to the surface of the window glass 3 supported by the window frame 6 via a second adhesive layer 26. The second adhesive layer 26 supports the entire electromagnetic wave reflective film 20 on the window glass 3, and is therefore preferably thicker than the adhesive layer 22, or has a higher adhesion than the adhesive layer 22. The electromagnetic wave reflective film 20 can be adhered from either the indoor 4th side or the outdoor 5th side. When the electromagnetic wave reflective film 20 is disposed on the indoor 4th side, the electromagnetic wave W incident from the indoor 4th side... EM The electromagnetic wave is reflected to the indoor side 4 by the conductive layer 23 of the electromagnetic wave reflective film 20, reducing the blind spot in the indoor 4.

[0050] When the window glass 3, the second adhesive layer 26, and the first substrate layer 21 are transmissive to electromagnetic waves of 1GHz to 300GHz, and the conductive layer 23 has the function of reflecting the frequency band used for wireless communication in the outdoor area 5, the conductive layer 23 also functions as a reflective film for electromagnetic waves incident from the outdoor area 5. In this case, the blind spot of the outdoor area 5 can be reduced.

[0051] When the electromagnetic wave reflective film 20 is adhered from the outdoor side 5, the second substrate layer 24 can function as a protective layer, possessing impact resistance or durability. As the protective substrate layer, PC film, PET film, COP film, etc., with a thickness of 0.025mm to 1.0mm can be used. A hard coating for UV protection and scratch resistance can be provided on both sides or one side of the second substrate layer 24.

[0052] The relative permittivity and dielectric loss tangent of the first substrate layer 21, the second substrate layer 24, the adhesive layer 22, and the second adhesive layer 26 are appropriately selected as a whole in order to give the electromagnetic wave reflecting film 20 the desired reflection characteristics. The non-dielectric constant of the dielectric portion, excluding the conductive layer 23, is, for example, 2.0 to 3.0, similar to the first embodiment, and the dielectric loss tangent is 0.0001 or more and less than 0.1000. Flexible films with a relative permittivity less than 2.0 are currently difficult to obtain. If the relative permittivity exceeds 3.0, there is a risk of increased loss, especially at high frequencies. The same applies to the dielectric loss tangent. Flexible films with a dielectric loss tangent less than 0.0001 are difficult to obtain, and if the dielectric loss tangent is 0.1000 or more, the internal power loss of the electromagnetic wave reflecting film 20 increases.

[0053] By optimizing the ratio (t3 / t1) of the thickness t3 of the first substrate layer 21 to the thickness t1 of the conductive layer 23, or the ratio (t2 / t1) of the thickness t2 of the adhesive layer 22 to the thickness t1 of the conductive layer 23, a transparent and flexible electromagnetic wave reflective film 20 can be obtained. The optimal ranges for t3 / t1 and t2 / t1 are described later.

[0054] <Characteristic Evaluation>

[0055] The following describes the fabrication of an electromagnetic wave reflective film sample, measuring its total light transmittance and reflection attenuation. The sample has the layered structure of the electromagnetic wave reflective film 10 of the first embodiment. Total light transmittance was measured using a UV-Vis-IR spectrophotometer manufactured by Shimadzu Corporation. Reflection attenuation was measured according to JIS R1679. Specifically, reflection attenuation was measured when a 28.0 GHz plane wave was incident at an angle of 0°. The material and thickness t3 of the first substrate layer 11, the material and thickness t1 of the conductive layer 13, and the thickness t2 of the adhesive layer 12 were varied. An acrylic adhesive with re-peelability was used as the adhesive layer 12. A sample achieving a total light transmittance of 70% or more and a reflection attenuation (absolute value) of 1.0 dB or less was used as an example sample, while samples that did not meet one or both of the above-mentioned total light transmittance and reflection attenuation were used as comparative examples. It should be noted that the total light transmittance and reflection attenuation were measured with the second substrate layer 14, which serves as the release layer, included. The type and thickness of the second substrate layer 14 were set to optimize the total light transmittance and reflection attenuation for the layer composition of each sample.

[0056] <Example 1>

[0057] Example 1 is Example 1. In Example 1, a PET film with a length of 0.5m, a width of 0.5m, and a thickness (t3) of 0.188mm was used as the first substrate layer 11. A conductive layer 13 was formed on the PET film by sputtering at room temperature to form an Ag film with a thickness (t1) of 0.360μm (360nm). The surface resistivity of the Ag film was 1.0Ω / □. An adhesive with a thickness (t2) of 0.025mm was coated on the surface of the Ag film to form an adhesive layer 12. A PET film with a thickness of 0.150mm was bonded to the conductive layer 13 as the second substrate layer 14 through the adhesive layer 12. The total thickness of the conductive layer 13, the adhesive layer 12, and the first substrate layer 11 (Tsum = t1 + t2 + t3) was 213.4μm.

[0058] The ratio (t3 / t1) of the thickness t3 of the first substrate layer 11 to the thickness t1 of the conductive layer 13 is 5.2 × 10⁻⁶. 2 The ratio (t2 / t1) of the thickness t2 of the adhesive layer 12 to the thickness t1 of the conductive layer 13 is 6.9 × 10⁻⁶. The ratio (t1 / Tsum) of the thickness t1 of the conductive layer 13 to Tsum(t1 + t2 + t3) is 1.7 × 10⁻⁶. －3 The total light transmittance of the sample was 90.4%, and the reflection attenuation, measured according to JIS R1679, was -0.05 dB. The sample in Example 1 exhibited high transparency and low reflection attenuation.

[0059] <Example 2>

[0060] Example 2 is Example 2. In Example 2, a PET film with a length of 0.5m, a width of 0.5m, and a thickness (t3) of 0.350mm was used as the first substrate layer 11. A conductive layer 13 was formed on the PET film by sputtering at room temperature to form an Ag film with a thickness (t1) of 0.050μm (50nm). The surface resistivity of the Ag film was 5.0Ω / □. An adhesive with a thickness (t2) of 0.025mm was coated on the surface of the Ag film to form an adhesive layer 12. A PET film with a thickness of 0.150mm was bonded to the conductive layer 13 as the second substrate layer 14 through the adhesive layer 12. The total thickness of the conductive layer 13, the adhesive layer 12, and the first substrate layer 11 (Tsum = t1 + t2 + t3) was 375.1μm.

[0061] The ratio (t3 / t1) of the thickness t3 of the first substrate layer 11 to the thickness t1 of the conductive layer 13 is 7.0 × 10⁻⁶. 3 The ratio (t2 / t1) of the thickness t2 of the adhesive layer 12 to the thickness t1 of the conductive layer 13 is 5.0 × 10⁻⁶. 2 The ratio (t1 / Tsum) of the thickness t1 of conductive layer 13 to Tsum(t1+t2+t3) is 1.3×10⁻⁶.－4 The total light transmittance of the sample was 95.3%, and the reflection attenuation, measured according to JIS R1679, was -0.15 dB. The sample in Example 2 exhibited high transparency and low reflection attenuation.

[0062] <Example 3>

[0063] Example 3 is Example 3. In Example 3, a PET film with a length of 0.5m, a width of 0.5m, and a thickness (t3) of 0.025mm was used as the first substrate layer 11. A conductive layer 13 was formed on the PET film by sputtering at room temperature to form an ITO film with a thickness (t1) of 0.500μm (500nm). The surface resistivity of the ITO film was 5.0Ω / □. An adhesive with a thickness (t2) of 0.010mm was coated on the surface of the ITO film to form an adhesive layer 12. A PET film with a thickness of 0.150mm was bonded to the conductive layer 13 as the second substrate layer 14 through the adhesive layer 12. The total thickness of the conductive layer 13, the adhesive layer 12, and the first substrate layer 11 (Tsum = t1 + t2 + t3) was 35.5μm.

[0064] The ratio (t3 / t1) of the thickness t3 of the first substrate layer 11 to the thickness t1 of the conductive layer 13 is 5.0 × 10⁻⁶. The ratio (t2 / t1) of the thickness t2 of the adhesive layer 12 to the thickness t1 of the conductive layer 13 is 2.0 × 10⁻⁶. The ratio (t1 / Tsum) of the thickness t1 of the conductive layer 13 to Tsum(t1 + t2 + t3) is 1.0 × 10⁻⁶. －2 The total light transmittance of the sample was 87.0%, and the reflection attenuation, measured according to JIS R1679, was -0.02 dB. The sample in Example 3 exhibited high transparency and low reflection attenuation.

[0065] <Example 4>

[0066] Example 4 is Example 4. In Example 4, a PET film with a length of 0.5m, a width of 0.5m, and a thickness (t3) of 0.500mm was used as the first substrate layer 11. A conductive layer 13 was formed on the PET film by sputtering at room temperature to form an ITO film with a thickness (t1) of 0.005μm (5nm). The surface resistivity of the ITO film was 10.0Ω / □. An adhesive with a thickness (t2) of 0.750mm was coated on the surface of the ITO film to form an adhesive layer 12. A PET film with a thickness of 0.150mm was bonded to the conductive layer 13 as the second substrate layer 14 through the adhesive layer 12. The total thickness of the conductive layer 13, the adhesive layer 12, and the first substrate layer 11 (Tsum = t1 + t2 + t3) was 1250.0μm.

[0067] The ratio (t3 / t1) of the thickness t3 of the first substrate layer 11 to the thickness t1 of the conductive layer 13 is 1.0 × 10⁻⁶. 5 The ratio (t2 / t1) of the thickness t2 of the adhesive layer 12 to the thickness t1 of the conductive layer 13 is 1.5 × 10⁻⁶. 5 The ratio (t1 / Tsum) of the thickness t1 of conductive layer 13 to Tsum(t1+t2+t3) is 4.0×10⁻⁶. －6 The total light transmittance of the sample was 85.2%, and the reflection attenuation, measured according to JIS R1679, was -0.03 dB. The sample in Example 4 exhibited high transparency and low reflection attenuation.

[0068] <Example 5>

[0069] Example 5 is Example 5. In Example 5, a PC film with a length of 0.5m, a width of 0.5m, and a thickness (t3) of 1.000mm was used as the first substrate layer 11. A conductive layer 13 was formed on the PC film by sputtering at room temperature to form an Ag film with a thickness (t1) of 0.010μm (10nm). The surface resistivity of the Ag film was 10.0Ω / □. An adhesive with a thickness (t2) of 0.025mm was coated on the surface of the Ag film to form an adhesive layer 12. A PC film with a thickness of 0.100mm was bonded to the conductive layer 13 as the second substrate layer 14 through the adhesive layer 12. The total thickness of the conductive layer 13, the adhesive layer 12, and the first substrate layer 11 (Tsum = t1 + t2 + t3) was 1025.0μm.

[0070] The ratio (t3 / t1) of the thickness t3 of the first substrate layer 11 to the thickness t1 of the conductive layer 13 is 1.0 × 10⁻⁶. 5 The ratio (t2 / t1) of the thickness t2 of the adhesive layer 12 to the thickness t1 of the conductive layer 13 is 2.5 × 10⁻⁶. 3 The ratio (t1 / Tsum) of the thickness t1 of conductive layer 13 to Tsum(t1+t2+t3) is 1.0×10⁻⁶. －4 The total light transmittance of the sample was 95.3%, and the reflection attenuation, measured according to JIS R1679, was -0.15 dB. The sample in Example 5 exhibited high transparency and low reflection attenuation.

[0071] <Example 6>

[0072] Example 6 is Example 6. In Example 6, a PET film with a length of 0.5m, a width of 0.5m, and a thickness (t3) of 1.000mm was used as the first substrate layer 11. A conductive layer 13 was formed by depositing a SUS mesh with a thickness (t1) of 200μm on the PET film. The surface resistivity of the SUS mesh was 0.03Ω / □. An adhesive with a thickness (t2) of 0.200mm was coated on the surface of the SUS mesh to form an adhesive layer 12. A PET film with a thickness of 0.100mm was bonded to the conductive layer 13 as the second substrate layer 14 through the adhesive layer 12. The total thickness of the conductive layer 13, the adhesive layer 12, and the first substrate layer 11 (Tsum = t1 + t2 + t3) was 1400.0μm.

[0073] The ratio (t3 / t1) of the thickness t3 of the first substrate layer 11 to the thickness t1 of the conductive layer 13 is 5.0. The ratio (t2 / t1) of the thickness t2 of the adhesive layer 12 to the thickness t1 of the conductive layer 13 is 1.0. The ratio (t1 / Tsum) of the thickness t1 of the conductive layer 13 to Tsum(t1+t2+t3) is 1.4×10⁻⁶. －1 The total light transmittance of the sample was 72.3%, and the reflection attenuation, measured according to JIS R 1679, was -0.23 dB. The transparency of the sample in Example 6 was within the permissible range, and the reflection attenuation was small.

[0074] <Example 7>

[0075] Example 7 is Example 7. In Example 7, a PET film with a length of 0.5m, a width of 0.5m, and a thickness (t3) of 0.025mm was used as the first substrate layer 11. A conductive layer 13 was formed by depositing a SUS mesh with a thickness (t1) of 100μm on the PET film. The surface resistivity of the SUS mesh was 0.03Ω / □. An adhesive with a thickness (t2) of 0.200mm was coated on the surface of the SUS mesh to form an adhesive layer 12. A PET film with a double-sided hard coating and a thickness of 0.100mm was bonded to the conductive layer 13 as the second substrate layer 14 through the adhesive layer 12. The total thickness (Tsum = t1 + t2 + t3) of the conductive layer 13, adhesive layer 12, and first substrate layer 11 was 325.0μm.

[0076] The ratio (t3 / t1) of the thickness t3 of the first substrate layer 11 to the thickness t1 of the conductive layer 13 is 2.5 × 10⁻⁶. -1 The ratio (t2 / t1) of the thickness t2 of the adhesive layer 12 to the thickness t1 of the conductive layer 13 is 2.0. The ratio (t1 / Tsum) of the thickness t1 of the conductive layer 13 to Tsum(t1+t2+t3) is 3.1×10⁻⁶. －1The total light transmittance of the sample was 70.3%, and the reflection attenuation, measured according to JIS R1679, was -0.23 dB. The transparency of the sample in Example 7 was within the allowable range, and the reflection attenuation was small.

[0077] <Example 8>

[0078] Example 8 is Example 8. In Example 8, a PC film with a double-sided hard coating, measuring 0.7m in length and 0.7m in width, and with a thickness (t3) of 0.700mm, was used as the first substrate layer 11. A conductive layer 13 was formed on this PC film with a double-sided hard coating by forming an Ag film with a thickness (t1) of 0.360μm (360nm). The surface resistivity of the conductive layer 13 was 1.0Ω / □. An adhesive with a thickness (t2) of 0.400mm was coated on the surface of the conductive layer 13 of the Ag film to form an adhesive layer 12. A PET film with a thickness of 0.100mm was bonded to the conductive layer 13 as the second substrate layer 14 through the adhesive layer 12. The total thickness of the conductive layer 13, the adhesive layer 12, and the first substrate layer 11 (Tsum = t1 + t2 + t3) was 1100.4μm.

[0079] The ratio (t3 / t1) of the thickness t3 of the first substrate layer 11 to the thickness t1 of the conductive layer 13 is 1.9 × 10⁻⁶. 3 The ratio (t2 / t1) of the thickness t2 of the adhesive layer 12 to the thickness t1 of the conductive layer 13 is 1.1 × 10⁻⁶. 3 The ratio (t1 / Tsum) of the thickness t1 of conductive layer 13 to Tsum(t1+t2+t3) is 3.3×10⁻⁶. －4 The total light transmittance of the sample was 75.2%, and the reflection attenuation, measured according to JIS R1679, was -0.98 dB. The transparency of the sample in Example 8 was within the permissible range, and the reflection attenuation was small.

[0080] <Example 9>

[0081] Example 9 is Comparative Example 1. In Comparative Example 1, a PET film with a length of 0.5 m, a width of 0.5 m, and a thickness (t3) of 0.025 mm was used as the first substrate layer 11. A conductive layer 13 was formed by depositing a SUS mesh with a thickness (t1) of 0.200 mm on the PET film. The surface resistivity of the SUS mesh was 0.01 Ω / □. An adhesive with a thickness (t2) of 0.40 mm was coated on the surface of the SUS mesh to form an adhesive layer 12. A PET film with a thickness of 0.150 mm was bonded to the conductive layer 13 as the second substrate layer 14 through the adhesive layer 12. The total thickness of the conductive layer 13, the adhesive layer 12, and the first substrate layer 11 (Tsum = t1 + t2 + t3) was 625.0 μm.

[0082] The ratio (t3 / t1) of the thickness t3 of the first substrate layer 11 to the thickness t1 of the conductive layer 13 is 1.3 × 10⁻⁶. -1 The ratio (t2 / t1) of the thickness t2 of the adhesive layer 12 to the thickness t1 of the conductive layer 13 is 2.0. The ratio (t1 / Tsum) of the thickness t1 of the conductive layer 13 to Tsum(t1+t2+t3) is 3.2×10⁻⁶. －1 The total light transmittance of the sample was 85.2%, and the reflection attenuation, measured according to JIS R1679, was -1.02 dB. The sample in Example 9 had high transparency, but its reflection attenuation exceeded the permissible range, therefore it could not be used as a product.

[0083] <Example 10>

[0084] Example 10 is Comparative Example 2. In Comparative Example 2, a PET film with a length of 0.5 m, a width of 0.5 m, and a thickness (t3) of 0.025 mm was used as the first substrate layer 11. A conductive layer 13 was formed by depositing a SUS mesh with a thickness (t1) of 0.100 mm on the PET film. The surface resistivity of the SUS mesh was 0.03 Ω / □. An adhesive with a thickness (t2) of 0.025 mm was coated on the surface of the SUS mesh to form an adhesive layer 12. A PET film with a thickness of 0.150 mm was bonded to the conductive layer 13 as the second substrate layer 14 through the adhesive layer 12. The total thickness of the conductive layer 13, the adhesive layer 12, and the first substrate layer 11 (Tsum = t1 + t2 + t3) was 150.0 μm.

[0085] The ratio (t3 / t1) of the thickness t3 of the first substrate layer 11 to the thickness t1 of the conductive layer 13 is 2.5 × 10⁻⁶. -1 The ratio (t2 / t1) of the thickness t2 of the adhesive layer 12 to the thickness t1 of the conductive layer 13 is 2.5 × 10⁻⁶. -1 The ratio (t1 / Tsum) of the thickness t1 of conductive layer 13 to Tsum(t1+t2+t3) is 6.6×10. －1 The metal mesh had an opening ratio of 69.5%, and the total light transmittance of the sample was 62.3%. The reflection attenuation, measured according to JIS R1679, was -0.32 dB. The sample in Example 10 had low reflection attenuation but insufficient transparency, therefore it could not be used as a product.

[0086] Table 1 shows the characteristic parameters and measurement results of samples from Examples 1 to 10.

[0087]

[0088] The following content is derived from the results of Examples 1 to 10.

[0089] (1) In order to give the electromagnetic wave reflective film sufficient flexibility, the thickness of the first substrate layer is preferably less than 1.0 mm.

[0090] (2) In order to have sufficient reflective properties, the surface resistivity of the conductive layer is preferably 10.0 Ω / □ or less.

[0091] (3) From the perspective of transparency, the total light transmittance of the electromagnetic wave reflective film is preferably above 70%.

[0092] (4) From the perspective of reflection efficiency, the reflection attenuation (absolute value) of the electromagnetic wave reflective film is preferably below 1.00dB.

[0093] (5) The ratio (t3 / t1) of the thickness t3 of the first substrate layer 11 to the thickness t1 of the conductive layer 13 is preferably 0.25 or more and 1.0 × 10⁻⁶. 5 If the thickness of the first substrate layer 11 is insufficient compared to the thickness of the conductive layer 13, the conductive layer 13 cannot be stably supported, and there is a risk that the conductive layer 13 will become distorted or uneven, resulting in reflection loss.

[0094] (6) The ratio (t2 / t1) of the thickness t2 of the adhesive layer 12 to the thickness t1 of the conductive layer 13 is preferably 1.0 or more and 1.5 × 10⁻⁶. 5 If the thickness of the adhesive layer 12 is insufficient compared to the thickness of the conductive layer 13, there is a risk of bubbles or reduced transparency being introduced between the object to which the electromagnetic wave reflective film 10 is applied and the adhesive layer 12, or between the adhesive layer 12 and the conductive layer 13.

[0095] (7) Preferably, the electromagnetic wave reflective film 10 is made in a range where the total thickness Tsum of the conductive layer 13 (t1), the adhesive layer 12 (t2), and the first substrate layer 11 (t3) is 30 μm or more and 1500 μm or less, and the ratio of the thickness of the conductive layer 13 to Tsum (t1 / Tsum) is preferably less than 1 / 3.

[0096] By having the above-described structure, a transparent electromagnetic wave reflective film with excellent reflective properties is achieved.

[0097] The above disclosure includes the following components.

[0098] (Project 1)

[0099] An electromagnetic wave reflective film, comprising:

[0100] The conductive layer reflects electromagnetic waves in a specified frequency band from 1 GHz to 300 GHz.

[0101] The first substrate layer supports the aforementioned conductive layer;

[0102] A second substrate layer is disposed on the side of the conductive layer opposite to the first substrate layer; and

[0103] An adhesive layer is used to bond the second substrate layer to the conductive layer.

[0104] The thickness of the first substrate layer is less than 1.0 mm.

[0105] The ratio of the thickness of the first substrate layer to the thickness of the conductive layer is 0.25 or more and 1.0 × 10⁻⁶. 5 the following.

[0106] (Project 2)

[0107] According to the electromagnetic wave reflective film described in Project 1, the ratio of the thickness of the adhesive layer to the thickness of the conductive layer is 1.0 or more and 1.5 × 10⁻⁶. 5 the following.

[0108] (Project 3)

[0109] According to the electromagnetic wave reflective film of Project 1 or 2, the surface resistivity of the conductive layer is less than 10.0 Ω / □.

[0110] (Project 4)

[0111] The electromagnetic wave reflective film according to any one of items 1 to 3, wherein the conductive layer is an Ag thin film or a transparent conductive film of a metal oxide, and the thickness of the conductive layer is 5 nm to 1000 nm.

[0112] (Project 5)

[0113] The electromagnetic wave reflecting film according to any one of items 1 to 3, wherein the conductive layer has a metal mesh, and the opening ratio of the metal mesh is 70% or more.

[0114] (Project 6)

[0115] According to the electromagnetic wave reflecting film of item 5, the surface resistivity of the metal mesh is less than 1.0 Ω / □.

[0116] (Project 7)

[0117] According to any one of items 1 to 6, the electromagnetic wave reflecting film wherein the combined thickness of the first substrate layer, the conductive layer, and the adhesive layer is 30 μm or more and 1500 μm or less.

[0118] The ratio of the thickness of the conductive layer to the total thickness is less than 1 / 3.

[0119] (Project 8)

[0120] The electromagnetic wave reflecting film according to any one of items 1 to 7, wherein it has:

[0121] A second adhesive layer is disposed on the side of the first substrate layer opposite to the conductive layer; and

[0122] The third substrate layer is bonded to the first substrate layer via the second adhesive layer.

[0123] (Project 9)

[0124] According to the electromagnetic wave reflective film of item 8, the second adhesive layer is thicker or has stronger adhesion than the adhesive layer described above.

[0125] (Project 10)

[0126] The electromagnetic wave reflective film according to any one of items 1 to 7, wherein a hard coating is applied to both or any one of the first substrate layers.

[0127] (Project 11)

[0128] According to item 8 or 9, the electromagnetic wave reflective film is provided with a hard coating on both or either side of the second substrate layer.

[0129] It should be noted that this international application claims priority based on Japanese Patent Application No. 2023-190975, filed on November 8, 2023, the entire contents of which are incorporated herein by reference.

[0130] Symbol Explanation

[0131] 10, 20 Electromagnetic wave reflective film

[0132] 11, 21 First substrate layer

[0133] 12, 22 Adhesive Layers

[0134] 13, 23 conductive layers

[0135] 14, 24 Second substrate layer

[0136] 26 Second adhesive layer

[0137] 27 Third substrate layer

Claims

1. An electromagnetic wave reflective film, comprising: The conductive layer reflects electromagnetic waves in a specified frequency band from 1 GHz to 300 GHz. A first substrate layer supports the conductive layer; The second substrate layer is disposed on the side of the conductive layer opposite to the first substrate layer; as well as An adhesive layer is used to bond the second substrate layer to the conductive layer. The thickness of the first substrate layer is less than 1.0 mm. The ratio of the thickness of the first substrate layer to the thickness of the conductive layer is 0.25 or more and 1.0 × 10⁻⁶. 5 the following.

2. The electromagnetic wave reflecting film according to claim 1, wherein, The ratio of the thickness of the adhesive layer to the thickness of the conductive layer is 1.0 or more and 1.5 × 10⁻⁶. 5 the following.

3. The electromagnetic wave reflecting film according to claim 1, wherein, The surface resistivity of the conductive layer is less than 10.0 Ω / □.

4. The electromagnetic wave reflecting film according to claim 1, wherein, The conductive layer is an Ag thin film or a transparent conductive film of a metal oxide, and the thickness of the conductive layer is 5 nm to 1000 nm.

5. The electromagnetic wave reflecting film according to claim 1, wherein, The conductive layer has a metal mesh with an opening ratio of 70% or more.

6. The electromagnetic wave reflecting film according to claim 5, wherein, The surface resistivity of the metal mesh is less than 1.0 Ω / □.

7. The electromagnetic wave reflecting film according to claim 1, wherein, The combined thickness of the first substrate layer, the conductive layer, and the adhesive layer is 30 μm or more and 1500 μm or less. The ratio of the thickness of the conductive layer to the total thickness is less than 1 / 3.

8. The electromagnetic wave reflecting film according to claim 1, wherein, have: The second adhesive layer is disposed on the side of the first substrate layer opposite to the conductive layer; as well as The third substrate layer is bonded to the first substrate layer via the second adhesive layer.

9. The electromagnetic wave reflecting film according to claim 8, wherein, The second adhesive layer is thicker or has stronger adhesion than the first adhesive layer.

10. The electromagnetic wave reflecting film according to claim 1, wherein, A hard coating is applied to either or both sides of the first substrate layer.

11. The electromagnetic wave reflecting film according to claim 8, wherein, A hard coating is applied to either or both sides of the second substrate layer.

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