Electromagnetic wave reflection panel, electromagnetic wave reflection device using same, electromagnetic wave reflection fence, method for manufacturing electromagnetic wave reflection panel, and method for evaluating electromagnetic wave reflection panel
Patent Information
- Application Number
- JP2025541371
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Priority Date
- 2023-08-21
- Filing Date
- 2024-08-01
- Publication Date
- 2025-02-27
Abstract
Description
Electromagnetic wave reflecting panel, electromagnetic wave reflecting device using the same, electromagnetic wave reflecting fence, method for manufacturing an electromagnetic wave reflecting panel, and method for evaluating an electromagnetic wave reflecting panel
[0001] The present invention relates to an electromagnetic wave reflective panel, an electromagnetic wave reflective device using the same, an electromagnetic wave reflective fence, and a method for manufacturing an electromagnetic wave reflective panel.
[0002] Base stations are being increasingly installed in indoor and outdoor facilities to realize various use cases, such as automation of manufacturing processes and office work, remote operation, the introduction of AI (artificial intelligence) control and management, and autonomous driving. Examples of indoor and outdoor facilities include factories, plants, offices, commercial facilities, medical facilities, event venues, highways, and railway tracks. Fifth-generation mobile communication systems (hereinafter referred to as "5G"), which offer high speed, large capacity, low latency, and multiple simultaneous connections, offer a frequency band below 6 GHz called "sub-6" and the 28 GHz band classified as the millimeter wave band. The next-generation 6G mobile communication standard is expected to expand to the terahertz band. Using such high-frequency bands will expand communication bandwidth and enable large-volume data communication with low latency. However, because high-frequency radio waves have a strong tendency to propagate in a straight line and cannot be deflected, measures such as the use of reflectors are required. A configuration has been proposed in which electromagnetic wave reflectors are placed along at least a portion of a factory's production line (see, for example, Patent Document 1).
[0003] International Publication No. 2021 / 199504
[0004] When mounting an electromagnetic wave reflective panel, a flame-retardant resin substrate may be used in consideration of impact resistance, weight, etc. When an electromagnetic wave reflective panel using a resin substrate is used indoors or outdoors, it must meet the long-term durability standards for safety glass specified in JIS R3211, JIS R3213, etc. When an electromagnetic wave reflective panel using a resin substrate is subjected to a heat resistance test specified in the above standards, bubbles and swelling may occur in the panel. The bubbles and swelling may affect the transmittance and visibility of the electromagnetic wave reflective panel.
[0005] An object of the present invention is to provide an electromagnetic wave reflective panel that satisfies long-term durability requirements, an electromagnetic wave reflective device using the same, an electromagnetic wave reflective fence, a method for manufacturing an electromagnetic wave reflective panel, and a method for evaluating an electromagnetic wave reflective panel.
[0006] In one embodiment, the electromagnetic wave reflective panel is an electromagnetic wave reflective panel that reflects electromagnetic waves in a predetermined frequency band of 1 MHz to 300 GHz, and includes a reflective function layer that selectively reflects electromagnetic waves in the predetermined frequency band, and a dielectric resin substrate that supports the reflective function layer. After a durability test in which the electromagnetic wave reflective panel is placed in a constant temperature oven at 40°C to 80°C for 2 hours to 720 hours, or in a constant temperature and high humidity oven at 50°C and 95% humidity for 2 hours to 720 hours, the change in visible light transmittance of the electromagnetic wave reflective panel is 10% or less, and ΔE ＊ ab is less than or equal to 3.0.
[0007] An electromagnetic wave reflective panel that satisfies long-term durability, an electromagnetic wave reflective device that uses the same, an electromagnetic wave reflective fence, a method for manufacturing an electromagnetic wave reflective panel, and a method for evaluating an electromagnetic wave reflective panel are realized.
[0008] FIG. 1 is a schematic diagram of an electromagnetic wave reflecting device using an electromagnetic wave reflecting panel of an embodiment. FIG. 2 is a schematic diagram of an electromagnetic wave reflecting fence in which a plurality of electromagnetic wave reflecting devices are connected. FIG. 3 is a diagram showing an example of a frame for holding an electromagnetic wave reflecting panel. FIG. 4 is a schematic diagram of the layer structure of an electromagnetic wave reflecting panel of an example. FIG. 5 is a schematic diagram of the layer structure of an electromagnetic wave reflecting panel of an example. FIG. 6 is an image showing the appearance of a sample of Example 7 after a durability test. FIG. 7 is an image showing the appearance of a sample of Example 8 after a durability test. FIG. 8 is a diagram summarizing the conditions and measurement results of Examples 1 to 10.
[0009] Electromagnetic wave reflective panels are composed of a laminate of multiple materials. When electromagnetic wave reflective panels using dielectric resin substrates such as polycarbonate or acrylic are subjected to durability tests conforming to the aforementioned standards, bubbles and swelling occur in the panels. Based on the hypothesis that the amount of gas, including moisture, contained in the resin substrate or the adhesion between the resin substrate and the adhesive layer may be related to the bubbles and swelling that occur in the panels, the inventors discovered that long-term durability can be improved by optimizing at least the pre-annealing conditions of the resin substrate. Long-term durability includes heat resistance, moist heat resistance, and light (weather) resistance, but here we focus particularly on heat resistance and moist heat resistance.
[0010] Below, we will explain the electromagnetic wave reflective panel of the embodiment, the electromagnetic wave reflective device using the same, the electromagnetic wave reflective fence, the manufacturing method of the electromagnetic wave reflective panel, and the evaluation method of the electromagnetic wave reflective panel with reference to the drawings. The following embodiments are examples to embody the technical concept of the invention and do not limit the present invention to the following steps and numerical values. In the drawings, components having the same function may be assigned the same reference numerals to avoid redundant description. Partial substitution or combination between different embodiments and configuration examples is possible. The size, positional relationship, etc. of each component shown in each drawing may be exaggerated to make the invention easier to understand. When referring to a positional relationship, "above" or "below" refers to above or below the stacking direction or film formation direction, unless otherwise specified, and is not an absolute direction.
[0011] <Electromagnetic Wave Reflecting Device and Electromagnetic Wave Reflecting Fence> FIG. 1 is a schematic diagram of an electromagnetic wave reflecting device 60 using an electromagnetic wave reflecting panel 10. The electromagnetic wave reflecting panel 10 is manufactured by optimizing the pre-annealing conditions of the dielectric resin substrate used in the electromagnetic wave reflecting panel 10, and maintains transparency or visibility even after long-term durability testing. The surface of the resin substrate may be coated with a hard coat layer or a barrier coat layer. The electromagnetic wave reflecting device 60 includes the electromagnetic wave reflecting panel 10 and a frame 50 that holds the electromagnetic wave reflecting panel 10. In the coordinate system of FIG. 1 , the width or horizontal direction of the electromagnetic wave reflecting panel 10 when the electromagnetic wave reflecting device 60 is installed is defined as the X direction, the height or vertical direction is defined as the Y direction, and the thickness direction is defined as the Z direction.
[0012] The electromagnetic wave reflective panel 10 has a reflective functional layer, as described below, and reflects radio waves in a desired band selected from a frequency band of 1 MHz to 300 GHz. The band of radio waves reflected by the electromagnetic wave reflective panel 10 is preferably a desired band selected from a frequency band of 1 GHz to 300 GHz. The electromagnetic wave reflective panel 10 selectively reflects electromagnetic waves in a specific frequency band while being transparent to visible light. At least a portion of the reflective surface 105 of the electromagnetic wave reflective panel 10 may include a metasurface with controlled reflection angle and reflection efficiency. The metasurface is formed using a periodic pattern, mesh pattern, geometric pattern, or the like designed according to the desired reflection mode and frequency band, and its reflection characteristics, such as reflection angle and reflection efficiency, are controlled. Control of the reflection angle includes forming non-specular reflections where the angle of incidence and the angle of reflection differ, and controlling the direction of diffusion. The reflective surface 105 of the electromagnetic wave reflective panel 10 may be formed from a good conductor such as a metal or a transparent conductive film.
[0013] The electromagnetic wave reflecting panel 10 has at least a specular reflecting surface. The specular reflecting surface reflects incident electromagnetic waves in the same direction as the angle of incidence. Depending on the location and environment in which the electromagnetic wave reflecting device 60 is installed, the electromagnetic wave reflecting panel 10 may have a mixture of specular and non-specular reflecting surfaces. The specular reflecting surface may be formed of a metal mesh or a metal film with an opening pattern smaller than the wavelength of the electromagnetic waves to be reflected.
[0014] The frame 50 holds two sides along the height direction of the electromagnetic wave reflecting panel 10 when it is installed. In addition to the frame 50, a top frame 57 that holds the upper end of the electromagnetic wave reflecting panel 10 and a bottom frame 58 that holds the lower end may be provided. In this case, the frame 50, the top frame 57, and the bottom frame 58 constitute a frame that holds the entire periphery of the electromagnetic wave reflecting panel 10. The frame 50 may be called a "side frame" based on its positional relationship with the top frame 57 and the bottom frame 58.
[0015] The electromagnetic wave reflecting device 60 may have legs 56 that support the frame 50. As shown in Fig. 1, it is desirable to provide the legs 56 when the electromagnetic wave reflecting device 60 is to be freestanding on an installation surface, but the legs 56 are not essential. Casters may be provided on the legs 56 to make the device mobile, or the electromagnetic wave reflecting panel 10 may be installed on a wall surface without the legs 56, or may be hung from a ceiling or support.
[0016] Fig. 2 is a schematic diagram of an electromagnetic wave reflecting fence 100 in which electromagnetic wave reflecting devices 60-1, 60-2, and 60-3 are connected together. In Fig. 2, three electromagnetic wave reflecting devices 60-1, 60-2, and 60-3 (hereinafter, sometimes collectively referred to as "electromagnetic wave reflecting devices 60") are connected together to form the electromagnetic wave reflecting fence 100, but there is no particular limit to the number of electromagnetic wave reflecting devices 60 that can be connected together.
[0017] The electromagnetic wave reflecting devices 60-1, 60-2, and 60-3 each have an electromagnetic wave reflecting panel 10-1, 10-2, and 10-3, respectively. Adjacent electromagnetic wave reflecting panels are held together by a frame 50 to obtain an electromagnetic wave reflecting fence 100 connected in the X direction. Each of the electromagnetic wave reflecting panels 10-1, 10-2, and 10-3 (hereinafter sometimes collectively referred to as the "electromagnetic wave reflecting panel 10") has optimized pre-annealing conditions for the resin substrate, and retains transparency or good visibility even after long-term durability testing.
[0018] 3 shows an example of the configuration of a cross section of the frame 50 parallel to the XZ plane. The frame 50 has a conductive main body 500 and slits 51-1 and 51-2 formed on both sides of the main body 500 in the width direction (X direction). Spaces 52-1 and 52-2 communicating with the slits 51-1 and 51-2, and grooves 53-1 and 53-2 are formed inside the main body 500. The edge of the electromagnetic wave reflecting panel 10-1 is inserted into the slit 51-1, passes through the space 52-1, and is held in the groove 53-1. Similarly, the edge of the electromagnetic wave reflecting panel 10-2 is inserted into the slit 51-2, passes through the space 52-2, and is held in the groove 53-2. Although the spaces 52-1 and 52-2 are not essential, providing the spaces 52-1 and 52-2 makes it possible to reduce the weight of the main body 500 of the frame 50 and to provide more room for the holding angle of the electromagnetic wave reflecting panels 10-1 and 10-2.
[0019] The electromagnetic wave reflecting panels 10-1 and 10-2 are inserted into the grooves 53-1 and 53-2 through the slits 51-1 and 51-2, thereby stably holding the adjacent electromagnetic wave reflecting panels 10-1 and 10-2 and assembling the electromagnetic wave reflecting fence 100. A portion of the main body 500 may be formed from a non-conductive material. A non-conductive cover 501 made of resin or the like may be provided on the outer surface of the main body 500, but the cover 501 is not essential. If the cover 501 is provided, the cover 501 can function as a protective member that protects the frame 50.
[0020] FIG. 4 shows an example of the layer structure of the electromagnetic wave reflection panel 10. This layer structure is the structure in the thickness (Z) direction of the electromagnetic wave reflection panel 10. The electromagnetic wave reflection panel 10 includes a reflection function layer 11 and resin substrates 14 and 15 bonded to both sides of the reflection function layer 11 by adhesive layers 12 and 13. The reflection function layer 11 is formed of a conductive material and forms a reflective surface that reflects electromagnetic waves in a specific frequency band selected from 1 MHz to 300 GHz. Materials that can be used for the reflection function layer 11 include stainless steel, mild steel, copper, copper oxide, nickel, nickel oxide, gold, silver, aluminum, and combinations thereof. The reflection function layer 11 may be a conductive layer with a predetermined opening pattern. The opening pattern may be through holes such as rectangular, circular, elliptical, or polygonal, or may be a mesh opening. The reflection function layer 11 may be formed with a periodic opening pattern to enhance the reflection selectivity for specific frequencies.
[0021] The resin substrates 14 and 15 are formed of a dielectric transparent resin such as polycarbonate, flame-retardant acrylic, cycloolefin polymer (COP), polyethylene terephthalate (PET), or fluororesin. When the electromagnetic wave reflective panel 10 is used on a production line or indoors or outdoors, it is desirable for the electromagnetic wave reflective panel 10 to have a certain degree of strength (impact resistance) as well as transparency or visibility. In order to make the total weight of the electromagnetic wave reflective panel 10 as light as possible while maintaining the strength of the electromagnetic wave reflective panel 10, the thickness of the resin substrates 14 and 15 is appropriately selected from the range of 1.0 mm to 10.0 mm.
[0022] The resin substrates 14 and 15 are pre-annealed under predetermined conditions to reduce the amount of moisture contained therein before lamination with the reflective functional layer 11 using the adhesive layers 12 and 13. As described below, the resin substrates 14 or 15 may be coated on their surfaces. The adhesive layers 12 and 13 are dielectric adhesive layers, and may be made of ethylene vinyl acetate (EVA), COP, UV-curable resin, thermosetting resin, thermoplastic resin, etc. UV-curable resins may include urethane-based resin, acrylic-based resin, silicone-based resin, epoxy resin, urethane acrylate, etc. The adhesive layers 12 and 13 may be made of the same or different materials. However, it is desirable for them to be made of the same material so that the front and back surfaces of the electromagnetic wave reflective panel 10 can be used with the same reflective properties from either direction without distinguishing between them.
[0023] The dielectric constant and dielectric loss tangent of the material of the adhesive layers 12 and 13 are set within appropriate ranges to suppress a decrease in reflection efficiency. For example, the dielectric constant of the adhesive layers 12 and 13 is 2.0 or more and less than 3.0, and the dielectric loss tangent is 0.0001 or more and less than 0.1000. If the dielectric constant of the adhesive layers 12 and 13 is 3.0 or more, there is a risk of increased loss at high frequencies. If the dielectric loss tangent of the adhesive layers 12 and 13 is 0.1000 or more, there is a risk of increased loss of electrical energy in the resin film.
[0024] The electromagnetic wave reflecting panel 10 having such a laminated structure uses resin substrates 14, 15 that have been pre-annealed under predetermined conditions, and even after a durability test in a constant temperature bath at 80°C for up to 720 hours, the absolute value of the change in transmittance is within 10.0%, preferably within 5%, more preferably within 2.5%, and even more preferably within 1.0%. In addition, the color difference (ΔE ＊ ab) is 3.0 or less, preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.0 or less. In addition, the change in transmittance after a durability test in which the film is placed in a constant temperature and humidity chamber at 50°C and 95% for up to 720 hours is 10.0% or less, preferably 5.0% or less, and more preferably 2.5% or less in absolute value. ＊ab) is 3.0 or less, preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.0 or less.
[0025] Based on the layer structure of FIG. 4, the conditions (temperature and time) of the pre-annealing of the resin substrate are changed, and the change in visible light transmittance and color difference (ΔE ＊ ab) is measured.
[0026] The method for evaluating an electromagnetic wave reflective panel according to the present disclosure is a method for evaluating an electromagnetic wave reflective panel that reflects electromagnetic waves in a predetermined frequency band of 1 MHz or more and 300 GHz or less, the electromagnetic wave reflective panel having a reflective function layer that selectively reflects electromagnetic waves in the predetermined frequency band and a dielectric resin substrate that supports the reflective function layer, and the electromagnetic wave reflective panel is subjected to a durability test in which the electromagnetic wave reflective panel is placed in a constant temperature oven at 40°C to 80°C for 2 hours to 720 hours, or in a constant temperature and high humidity oven at 50°C and 95% humidity for 2 hours to 720 hours, after which a change in visible light transmittance of the electromagnetic wave reflective panel is 10% or less, and ΔE ＊ This is an evaluation method that evaluates whether ab is 3.0 or less.
[0027] In Examples 1 to 6, 9 and 10, and 12 and 13 described below, the durability test involved placing the prepared sample in a thermostatic chamber at 40°C to 80°C for 2 to 720 hours. Specifically, the sample was placed in a thermostatic chamber at a temperature selected from the group consisting of 40°C, 50°C, 60°C, 70°C, and 80°C. In Examples 7 and 8, the durability test involved placing the prepared sample in a thermostatic chamber at 50°C and 95% humidity for 2 to 720 hours. The materials and thicknesses of the reflective functional layer 11 and adhesive layers 12 and 13 constituting the electromagnetic wave reflective panel were uniform, and the materials and sizes of the resin substrates 14 and 15 were uniform. A 100 μm-thick stainless steel mesh was used as the reflective functional layer 11, and 400 μm-thick ethylene vinyl acetate (EVA) layers were used as the adhesive layers 12 and 13. The resin substrates 14 and 15 are polycarbonate (PC) sheets measuring 1.0 m in length, 2.0 m in width, and 2.0 mm in thickness.
[0028] [Example 1] Example 1 corresponds to Example 1. Prior to lamination of the electromagnetic wave reflective panel having the layer structure shown in Figure 4, a PC sheet measuring 1.0 m in length, 2.0 m in width, and 2.0 mm in thickness was pre-annealed at 80°C for 20.0 hours. The moisture content of the PC sheet was measured using a moisture meter before and after pre-annealing. The moisture content of the PC sheet before pre-annealing was 3500 ppm, and the moisture content of the PC sheet after pre-annealing at 80°C for 20 hours was 1650 ppm. Pre-annealing reduced the moisture content of the PC sheet by 52.9%. One hour after removing the PC sheet from the pre-annealing thermostatic chamber, lamination was performed to produce the electromagnetic wave reflective panel. In the lamination process, 400 μm-thick EVA was applied to both sides of a 100 μm-thick stainless steel mesh, and the pre-annealed PC sheet was bonded to the laminate, followed by a pressure treatment at 80°C for 20 minutes. This lamination process resulted in an electromagnetic wave reflective panel.
[0029] A 300 mm x 300 mm sample was cut out from the prepared electromagnetic wave reflective panel. In accordance with the test method of JIS R3212, the sample was cut out so that one side of the sample coincided with the upper side of the electromagnetic wave reflective panel. The cut out sample was placed in a thermostatic chamber at 80°C and subjected to a 240-hour durability test (A) and a 720-hour durability test (B). After each durability test, the appearance of the sample was observed, and the visible light transmittance and ΔE were measured using an optical measuring instrument (spectrophotometer) manufactured by Shimadzu Corporation. ＊ The change (difference) from the visible light transmittance measured on the remaining electromagnetic wave reflection panel from which the sample was cut out is calculated. As a result of visual observation, no bubbles, peeling, or swelling occurred in the samples in either test A or B. The change in visible light transmittance was -0.5% after 240 hours, ΔE ＊ ab is 0.7. The change in visible light transmittance after 720 hours is -0.7%, ΔE ＊ ab is 1.5.
[0030] [Example 2] Example 2 is Example 2. The same PC sheet as in Example 1, measuring 1.0 m in length, 2.0 m in width, and 2.0 mm in thickness, was subjected to pre-annealing at 120°C for 2.5 hours. The moisture content of the PC sheet was measured using a moisture meter before and after pre-annealing. The moisture content of the PC sheet before pre-annealing was 3550 ppm, and the moisture content of the PC sheet after pre-annealing at 120°C for 2.5 hours was 1350 ppm. Pre-annealing reduced the moisture content in the PC sheet by 62.0%. One hour after removing the PC sheet from the thermostatic oven used for pre-annealing, an electromagnetic wave reflective panel was fabricated by performing the same lamination process as in Example 1. A 300 mm x 300 mm sample was cut from the fabricated electromagnetic wave reflective panel and subjected to a 240-hour durability test (A) and a 720-hour durability test (B) in an 80°C thermostatic oven. After each durability test, the sample's appearance was observed, and the visible light transmittance and ΔE ＊ The change (difference) from the visible light transmittance measured on the remaining electromagnetic wave reflection panel from which the sample was cut out is calculated. As a result of visual observation, no bubbles, peeling, or swelling occurred in the samples in either test A or B. The change in visible light transmittance after 240 hours was -0.6%, ΔE ＊ ab is 1.0. The change in visible light transmittance after 720 hours is -0.9%, ΔE ＊ ab is 1.4.
[0031] [Example 3] Example 3 is Example 3. A PC sheet having the same length as Example 1, 1.0 m in length, 2.0 m in width, and 2.0 mm in thickness, is subjected to pre-annealing at 110°C for 10.0 hours. The moisture content of the PC sheet is measured using a moisture meter before and after pre-annealing. The moisture content of the PC sheet before pre-annealing is 3530 ppm, and the moisture content of the PC sheet after pre-annealing at 110°C for 10 hours is 1450 ppm. The moisture content of the PC sheet is reduced by 58.9% by pre-annealing. 1.0 hour after removing the PC sheet from the thermostatic oven used for pre-annealing, an electromagnetic wave reflective panel is fabricated by performing the same lamination process as in Example 1. A 300 mm x 300 mm sample is cut from the fabricated electromagnetic wave reflective panel and subjected to a durability test for 720 hours in a thermostatic oven at 80°C. After the durability test, the appearance of the sample is observed, and the visible light transmittance and ΔE ＊ab is measured. The change (difference) from the visible light transmittance measured on the remaining electromagnetic wave reflection panel from which the sample was cut out is calculated. As a result of visual observation, no bubbles, peeling, or swelling occurred in the sample, and the change in visible light transmittance was -0.4%, ΔE ＊ ab is 0.4.
[0032] In the following Examples 4 to 6, a hard coat is applied to the surface of the resin substrate. FIG. 5 shows the layer structure of the electromagnetic wave reflective panel 10A produced in Examples 4 to 6. The basic layer structure is the same as that shown in FIG. 4, with resin substrates 14 and 15 bonded to both sides of the reflective function layer 11 via adhesive layers 12 and 13. Each of the resin substrates 14 and 15 has a hard coat layer 17 on at least the surface that contacts the adhesive layers 12 and 13. In the example shown in FIG. 5, each of the resin substrates 14 and 15 has a hard coat layer 17 on both sides. The hard coat layer 17 on the surface that contacts the adhesive layers 12 and 13 prevents moisture from penetrating from the adhesive layers 12 and 13 into the resin substrate. The hard coat layer 17 on the surface of the resin substrate 14 or 15 opposite the surface that contacts the adhesive layer 12 or 13 becomes the outermost layer of the electromagnetic wave reflective panel 10A. This outermost hard coat layer 17 prevents moisture from entering the resin substrates 14 and 15 from the external environment and also functions as a protective layer for the electromagnetic wave reflecting panel 10A. In Examples 4 to 6, the type of hard coat was changed and durability tests similar to those in Examples 1 to 3 were conducted.
[0033] [Example 4] Example 4 is Example 4. A hard coat layer 17 is formed on both sides of a PC sheet having the same dimensions as Example 1, 1.0 m in length, 2.0 m in width, and 2.0 mm in thickness. An 8 μm-thick urethane acrylate coating is formed as the hard coat layer 17. The PC sheet having the urethane acrylate hard coat layer 17 on both sides is pre-annealed at 120°C for 2.5 hours. The moisture content of the PC sheet is measured using a moisture meter before and after pre-annealing. The moisture content of the PC sheet before pre-annealing is 3520 ppm, and the moisture content of the PC sheet after pre-annealing is 1300 ppm. The moisture content of the hard-coated PC sheet is reduced by 63.1% by pre-annealing. One hour after removing the hard-coated PC sheet from the thermostatic chamber used for pre-annealing, the same lamination process as Example 1 is performed to produce an electromagnetic wave reflecting panel 10A. In this case, the hard coat layer 17 is bonded to the adhesive layers 12 and 13. A sample of 300 mm x 300 mm was cut out from the manufactured electromagnetic wave reflecting panel 10A, and a durability test was carried out for 720 hours in a thermostatic chamber at 80°C. After the durability test, the appearance of the sample was observed, and the visible light transmittance and ΔE ＊ ab is measured. The change (difference) from the visible light transmittance measured on the remaining electromagnetic wave reflection panel from which the sample was cut out is calculated. As a result of visual observation, no bubbles, peeling, or swelling occurred in the sample, and the change in visible light transmittance was -0.5%, ΔE ＊ ab is 0.4.
[0034] [Example 5] Example 5 is Example 5. The same urethane acrylate-based hard coat layer 17 as in Example 4 was applied to both sides of a PC sheet having the same layer structure as Example 4, measuring 1.0 m in length, 2.0 m in width, and 2.0 mm in thickness. This hard-coated PC sheet was pre-annealed at 120°C for 2.5 hours. The hard-coated PC sheet was removed from the thermostatic chamber used for pre-annealing and left in an environment for 5.0 hours. The same lamination process as in Example 4 was then performed to produce an electromagnetic wave reflecting panel 10A. The moisture content of the PC sheet before pre-annealing was 3510 ppm, the moisture content of the PC sheet immediately after pre-annealing was 1320 ppm (a 62.4% decrease), and the moisture content of the PC sheet after leaving it in the environment for 5.0 hours was 2080 ppm. Even after leaving it in the environment for 5.0 hours, the moisture content in the PC sheet was 40.7% lower than before pre-annealing. A sample of 300 mm x 300 mm was cut out from the manufactured electromagnetic wave reflecting panel 10A, and a durability test was carried out for 720 hours in a thermostatic chamber at 80°C. After the durability test, the appearance of the sample was observed, and the visible light transmittance and ΔE ＊ ab is measured. The change (difference) from the visible light transmittance measured on the remaining electromagnetic wave reflection panel from which the sample was cut out is calculated. As a result of visual observation, no bubbles, peeling, or swelling occurred in the sample, and the change in visible light transmittance was -0.5%, ΔE ＊ ab is 0.5.
[0035] The PC sheet of Example 5, like Example 4, has a sufficiently reduced moisture content even when pre-annealing is performed for a short period of 2 hours at 90° C. Furthermore, since the PC sheet has hard coat layers 17 on both sides, even if it is left in the environment for 5 hours after pre-annealing until the start of lamination processing, the penetration of moisture into the resin substrate is suppressed, and the change in transmittance, ΔE ＊ Both a and b are small.
[0036] [Example 6] Example 6 is Example 6. A different type of hard coat layer 17 was provided with the same layer structure as Example 5. A 5 μm-thick silicone-based hard coat layer 17 was provided on both sides of a 1.0 m long, 2.0 m wide, and 2.0 mm thick PC sheet. This hard-coated PC sheet was then pre-annealed at 120°C for 2.5 hours. The hard-coated PC sheet was removed from the pre-annealing thermostatic chamber and left in the environment for 5.0 hours. The same lamination process as in Examples 4 and 5 was then performed to produce an electromagnetic wave reflecting panel 10A. The moisture content of the PC sheet before pre-annealing was 3500 ppm. The moisture content of the PC sheet immediately after pre-annealing was 1350 ppm (a 61.4% decrease). After leaving the PC sheet in the environment for 5.0 hours, the moisture content of the PC sheet was 2020 ppm. Even after leaving the PC sheet in the environment for 5.0 hours, the moisture content in the PC sheet was 42.2% less than before pre-annealing.
[0037] A sample of 300 mm x 300 mm was cut out from the manufactured electromagnetic wave reflecting panel 10A, and a durability test was carried out for 720 hours in a thermostatic chamber at 80°C. After the durability test, the appearance of the sample was observed, and the visible light transmittance and ΔE ＊ ab is measured. The change (difference) from the visible light transmittance measured on the remaining electromagnetic wave reflection panel from which the sample was cut out is calculated. As a result of visual observation, no bubbles, peeling, or swelling occurred in the sample, and the change in visible light transmittance was -0.3%, ΔE ＊ ab is 0.3. By providing the silicone-based hard coat layer 17 on both sides of the PC sheet, the visible light transmittance and color are more stable than in Example 5, and durability is improved.
[0038] [Example 7] Example 7 is Example 7. The durability test conditions were changed. Prior to lamination of the electromagnetic wave reflective panel having the layer structure of Figure 4, a PC sheet measuring 1.0 m in length, 2.0 m in width, and 2.0 mm in thickness was pre-annealed at 80°C for 20.0 hours. The moisture content of the PC sheet was measured using a moisture meter before and after pre-annealing. The moisture content of the PC sheet before pre-annealing was 3500 ppm, and the moisture content of the PC sheet after pre-annealing at 80°C for 20 hours was 1650 ppm. Pre-annealing reduced the moisture content of the PC sheet by 52.9%. One hour after removing the PC sheet from the pre-annealing thermostatic chamber, lamination was performed to produce an electromagnetic wave reflective panel. In the lamination process, 400 μm-thick EVA was applied to both sides of a 100 μm-thick stainless steel mesh, and the pre-annealed PC sheet was bonded, followed by pressure treatment at 80°C for 20 minutes. This lamination process results in an electromagnetic wave reflective panel.
[0039] A 300 mm x 300 mm sample is cut out from the prepared electromagnetic wave reflective panel. In accordance with the test method of JIS R3212, the sample is cut out so that one side of the sample coincides with the upper side of the electromagnetic wave reflective panel. The cut out sample is placed in a constant temperature and humidity chamber at 50°C and 95% humidity, and a durability test is performed for 240 hours. After the durability test, the appearance of the sample is observed, and the visible light transmittance and ΔE are measured using an optical measuring instrument (spectrophotometer) manufactured by Shimadzu Corporation. ＊ ab is measured. The change (difference) from the visible light transmittance measured on the remaining electromagnetic wave reflection panel from which the sample was cut out is calculated. As a result of visual observation, no bubbles, peeling, or swelling occurred in the sample, and the change in visible light transmittance was -2.0%, ΔE ＊ ab is 0.5.
[0040] [Example 8] Example 8 is Example 8. In Example 8, the time of insertion into the thermo-hygrostat chamber is changed. Prior to lamination of the electromagnetic wave reflection panel having the layer structure of Figure 4, a PC sheet measuring 1.0 m in length, 2.0 m in width, and 2.0 mm in thickness is pre-annealed at 80°C for 20.0 hours. The moisture content of the PC sheet is measured using a moisture meter before and after pre-annealing. The moisture content of the PC sheet before pre-annealing is 3500 ppm, and the moisture content of the PC sheet after pre-annealing at 80°C for 20 hours is 1650 ppm. Pre-annealing reduced the moisture content of the PC sheet by 52.9%. One hour after removing the PC sheet from the thermo-hygrostat chamber for pre-annealing, lamination is performed to produce an electromagnetic wave reflection panel. In the lamination process, 400 μm-thick EVA is applied to both sides of a 100 μm-thick stainless steel mesh, and the pre-annealed PC sheet is bonded to the laminate, followed by pressure treatment at 80°C for 20 minutes. This lamination process results in an electromagnetic wave reflective panel.
[0041] A 300 mm x 300 mm sample is cut out from the prepared electromagnetic wave reflective panel. In accordance with the test method of JIS R3212, the sample is cut out so that one side of the sample coincides with the upper side of the electromagnetic wave reflective panel. The cut out sample is placed in a constant temperature and humidity chamber at 50°C and 95% humidity, and a durability test is performed for 720 hours. After the durability test, the appearance of the sample is observed, and the visible light transmittance and ΔE are measured using an optical measuring instrument (spectrophotometer) manufactured by Shimadzu Corporation. ＊ ab is measured. The change (difference) from the visible light transmittance measured on the remaining electromagnetic wave reflection panel from which the sample was cut out is calculated. As a result of visual observation, no bubbles, peeling, or swelling occurred in the sample, and the change in visible light transmittance was -0.5%, ΔE ＊ ab is 0.7.
[0042] [Example 9] Example 9 is Example 9. In Example 9, the time of insertion into the thermo-hygrostat chamber is changed. Prior to lamination of the electromagnetic wave reflective panel having the layer structure of Figure 4, a PC sheet measuring 1.0 m in length, 2.0 m in width, and 2.0 mm in thickness is pre-annealed at 120°C for 5.0 hours. The moisture content of the PC sheet is measured using a moisture meter before and after pre-annealing. The moisture content of the PC sheet before pre-annealing is 3500 ppm, and the moisture content of the PC sheet after pre-annealing at 120°C for 5 hours is 1150 ppm (a 67.1% decrease). One hour after removing the PC sheet from the pre-annealing thermostat chamber, lamination is performed to produce an electromagnetic wave reflective panel. In the lamination process, 400 μm-thick EVA is applied to both sides of a 100 μm-thick stainless steel mesh, and the pre-annealed PC sheet is bonded to the laminate, followed by a 20-minute pressure treatment at 80°C. This lamination process results in an electromagnetic wave reflective panel.
[0043] A 300 mm x 300 mm sample was cut out from the prepared electromagnetic wave reflective panel. According to the test method of JIS R3212, the sample was cut out so that one side of the sample coincided with the top side of the electromagnetic wave reflective panel. The cut-out 40°C sample, the cut-out 50°C sample, and the cut-out 60°C sample were placed in thermostatic chambers at 40°C, 50°C, and 60°C, respectively, and a 240-hour durability test (A) and a 720-hour durability test (B) were performed. After the durability test, the appearance of the sample was observed, and the visible light transmittance and ΔE were measured using an optical measuring instrument (spectrophotometer) manufactured by Shimadzu Corporation. ＊ ab is measured. The change (difference) from the visible light transmittance measured on the remaining electromagnetic wave reflection panel from which the sample was cut out is calculated. As a result of visual observation, no bubbles, peeling, or swelling occurred in the sample, and the change in visible light transmittance after 240 hours was -0.1% at 40°C, -0.2% at 50°C, and -0.2% at 60°C. ΔE ＊ ab was 0.1 at 40°C, 0.3 at 50°C, and 0.5 at 60°C. After 720 hours, ab was -0.1% at 40°C, -0.1% at 50°C, and +1.0% at 60°C. ΔE ＊ ab is 0.1 at 40°C, 0.2 at 50°C, and 0.6 at 60°C.
[0044] [Example 10] Example 10 is Example 10. In Example 10, the time of insertion into the thermo-hygrostat chamber is changed. Prior to lamination of the electromagnetic wave reflective panel having the layer structure of FIG. 4, a PC sheet measuring 1.0 m in length, 2.0 m in width, and 2.0 mm in thickness is pre-annealed at 120°C for 5.0 hours. The moisture content of the PC sheet is measured using a moisture meter before and after pre-annealing. The moisture content of the PC sheet before pre-annealing is 3510 ppm, and the moisture content of the PC sheet after pre-annealing at 120°C for 5 hours is 1140 ppm (a 67.5% reduction). One hour after removing the PC sheet from the thermostatic chamber used for pre-annealing, lamination is performed to produce an electromagnetic wave reflective panel. In the lamination process, 400 μm thick EVA is applied to both sides of a 100 μm thick stainless steel mesh, and the pre-annealed PC sheet is bonded to the laminate, followed by pressure treatment at 80°C for 20 minutes. This lamination process results in an electromagnetic wave reflective panel.
[0045] A 300 mm x 300 mm sample is cut out from the prepared electromagnetic wave reflective panel. In accordance with the test method of JIS R3212, the sample is cut out so that one side of the sample coincides with the upper side of the electromagnetic wave reflective panel. The cut out sample is placed in a thermostatic chamber at 70°C and a durability test is performed for 48 hours. After the durability test, the appearance of the sample is observed, and the visible light transmittance and ΔE are measured using an optical measuring instrument (spectrophotometer) manufactured by Shimadzu Corporation. ＊ ab is measured. The change (difference) from the visible light transmittance measured on the remaining electromagnetic wave reflection panel from which the sample was cut out is calculated. As a result of visual observation, no bubbles, peeling, or swelling occurred in the sample, and the change in visible light transmittance was +0.3%, ΔE ＊ ab is 0.5.
[0046] [Example 11] Example 11 is Example 11. In Example 11, a different PC sheet is used. A 0.2 μm barrier coating layer with low water vapor and oxygen permeability is provided on the surface of the PC sheet. Prior to lamination of the electromagnetic wave reflective panel having the layer structure shown in FIG. 4, a PC sheet measuring 1.0 m in length, 2.0 m in width, and 2.0 mm in thickness is pre-annealed at 80°C for 5.0 hours. The moisture content of the PC sheet is measured using a moisture meter before and after pre-annealing. The moisture content of the PC sheet before pre-annealing is 3510 ppm, and the moisture content of the PC sheet after pre-annealing at 80°C for 5 hours is 1150 ppm (a 67.5% decrease). One hour after removing the PC sheet from the pre-annealing thermostatic chamber, lamination is performed to produce the electromagnetic wave reflective panel. In the lamination process, 400 μm thick EVA is applied to both sides of a 100 μm thick stainless steel mesh, and a pre-annealed PC sheet is bonded to it, followed by a pressure treatment at 80° C. for 20 minutes. This lamination process results in an electromagnetic wave reflective panel.
[0047] A 300 mm x 300 mm sample is cut out from the prepared electromagnetic wave reflective panel. In accordance with the test method of JIS R3212, the sample is cut out so that one side of the sample coincides with the upper side of the electromagnetic wave reflective panel. The cut out sample is placed in a thermostatic chamber at 70°C and a durability test is performed for 720 hours. After the durability test, the appearance of the sample is observed, and the visible light transmittance and ΔE are measured using an optical measuring instrument (spectrophotometer) manufactured by Shimadzu Corporation. ＊ ab is measured. The change (difference) from the visible light transmittance measured on the remaining electromagnetic wave reflection panel from which the sample was cut out is calculated. As a result of visual observation, no bubbles, peeling, or swelling occurred in the sample, and the change in visible light transmittance was -0.5%, ΔE ＊ ab is 0.8.
[0048] Example 12 Example 12 is Comparative Example 1. In Example 12, an electromagnetic wave reflective panel 10 having the layer structure shown in FIG. 4 was fabricated using the same PC sheet as in Example 1. The PC sheet did not have a hard coat layer 17. Prior to lamination, the PC sheet was pre-annealed at 80°C for 20.0 hours. 25.0 hours after removing the PC sheet from the pre-annealing thermostatic chamber, the same lamination process as in Example 1 was performed to fabricate the electromagnetic wave reflective panel 10. The moisture content of the PC sheet before pre-annealing was 3510 ppm, the moisture content of the PC sheet immediately after pre-annealing was 1600 ppm, and the moisture content of the PC sheet after leaving it in the environment for 25.0 hours was 3500 ppm. The moisture content of the PC sheet decreased by 54.4% due to pre-annealing, but by leaving it in the environment for 25.0 hours without a hard coat, the moisture content returned to the moisture content before pre-annealing. A sample of 300 mm x 300 mm was cut out from the produced electromagnetic wave reflecting panel 10 and subjected to a durability test for 720 hours in a thermostatic chamber at 80° C. After the durability test, the appearance of the sample was observed and it was found that bubbles had occurred all over the surface.
[0049] FIG. 6 is an external view of the sample of Example 12 (Comparative Example 1) after the durability test. Air bubbles are clearly visible in the upper left area of the figure. Although it is difficult to see in the image due to the lighting conditions, fine air bubbles have occurred throughout the sample. This is thought to be because, although the moisture contained in the PC sheet was removed to some extent by pre-annealing, the sample was left for 24 hours before the lamination process began, allowing moisture from the air to penetrate. The change in visible light transmittance of the sample after the durability test was -19.7%, and ΔE ＊ ab is 12.1. Because bubbles have appeared all over the panel, visibility is insufficient and the panel cannot be used as a product.
[0050] Example 13 is Comparative Example 2. In Example 13, an electromagnetic wave reflective panel 10 having the layer structure shown in FIG. 4 was fabricated using the same PC sheet as in Example 1. The PC sheet did not have a hard coat layer 17. Prior to lamination, the PC sheet was pre-annealed at 70°C for 20.0 hours. One hour after removing the PC sheet from the thermostatic oven for pre-annealing, the electromagnetic wave reflective panel 10 was fabricated using the same lamination process as in Example 1. The moisture content of the PC sheet before pre-annealing was 3520 ppm, and the moisture content of the PC sheet immediately after pre-annealing was 2145 ppm (a 39.0% decrease). A 300 mm x 300 mm sample was cut from the fabricated electromagnetic wave reflective panel 10 and subjected to a 720-hour durability test in a thermostatic oven at 80°C. After the durability test, the sample's appearance was observed, revealing bubbles throughout the panel and long ridges in several locations.
[0051] Figure 7 is an external view of the sample of Example 13 (Comparative Example 2) after a durability test. Numerous elongated, undulating air layers are observed in the lower half of the image. Although difficult to see in the image due to lighting conditions, air bubbles are also present throughout the sample. It is believed that the elongated, undulating bubbles grow as nearby bubbles fuse together. The pre-annealing temperature for the PC sheet was low, which likely prevented sufficient moisture removal from the PC sheet. The lamination process began one hour after the PC sheet was removed from the pre-annealing thermostatic chamber, limiting moisture penetration from the environment into the PC sheet. However, compared to Example 1, the pre-annealing temperature was low, resulting in insufficient adhesion between the PC sheet and the adhesive layer after lamination. It is believed that the moisture remaining in the PC sheet during pre-annealing evaporated and fused during the durability test, resulting in the elongated, undulating bubbles. The change in visible light transmittance of the sample after the durability test was -19.9%, ΔE ＊ The ab is 12.2. Visibility is insufficient due to undulations and bubbles on the panel surface, and the product cannot be used.
[0052] FIG. 8 summarizes the conditions and measurement results for Examples 1 to 13. The measurement results for Examples 1 to 13 lead to the following: (a) The change in visible light transmittance of the electromagnetic wave reflective panel after a durability test for up to 720 hours in a thermostatic chamber at 80°C is within 10.0% in absolute value, preferably within 5%, more preferably within 2.5%, and even more preferably within 1.0%. The change in visible light transmittance of the electromagnetic wave reflective panel after a durability test for up to 720 hours in a thermostatic chamber at 50°C and 95% humidity is within 10.0% in absolute value, preferably within 5%, and more preferably within 2.5%. (b) The color difference (ΔE ＊ ab) is 3.0 or less, preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.0 or less. (c) Prior to lamination of the electromagnetic wave reflective panel, pre-annealing the resin substrate to be used at a temperature higher than 70°C but lower than the heat-resistant temperature of the resin substrate reduces the moisture content of the resin substrate by 35% or more, thereby suppressing the generation of bubbles even after durability testing. (c) By providing a hard coat layer on the surface of the resin substrate of the electromagnetic wave reflective panel, moisture penetration into the resin substrate is suppressed, making it easier to satisfy the above condition (a) or (b). (e) The pre-annealing time does not necessarily have to be long; annealing for a short period of time at a relatively high temperature within the heat-resistant temperature range may be performed. (f) When a hard coat layer or a barrier coat layer is provided on the resin substrate, moisture penetration can be suppressed even if the lamination process is initiated after the substrate is removed from the pre-annealing thermostatic chamber and left in an environment for a relatively long period of time. On the other hand, when a resin substrate not provided with a hard coat layer or a barrier coat layer is used, it is desirable to carry out the lamination treatment within a predetermined time, for example, within 24 hours, preferably within several hours, more preferably within one hour, after removal from the constant temperature bath for preliminary annealing.
[0053] In the case of the PC sheet used in Examples 1 to 11, pre-annealing is performed, for example, at a temperature higher than 70°C and not higher than 130°C. When flame-retardant acrylic is used as a dielectric resin substrate, pre-annealing at a temperature higher than 70°C and not higher than 120°C, for example, removes gases containing moisture and the like contained in the acrylic sheet, and prevents the generation of bubbles even after durability tests of 2 to 720 hours in thermostatic chambers at 60°C, 70°C, and 80°C, or after durability tests of 2 to 720 hours in a thermostatic chamber at 50°C and 95% humidity. A hard coat layer or barrier coat layer may be applied to at least the surface of the acrylic sheet that contacts the adhesive layer to prevent the penetration of gases containing moisture and the like from the adhesive layer into the acrylic sheet. When COP or fiber-reinforced PET is used as the dielectric resin substrate, pre-annealing may also be performed at a temperature higher than 70°C and not higher than 150°C. When a resin material with a higher heat resistance temperature is used, the pre-annealing may be performed at a temperature higher than 70°C and not higher than 180°C, for example.
[0054] For the hard coat layer 17, an ultraviolet (UV) curable coating agent other than a urethane acrylate-based one may be used. As a UV curable coating agent that is easy to spread and hardens in a short time, an epoxy acrylate-based, polyester acrylate-based, or other UV curable coating agent may be used. In addition to a silicone-based coating agent, a fluorine-based coating agent may also be used. For the barrier coat layer, a fluororesin, PVA, or an ethylene-vinyl alcohol copolymer polyvinylidene chloride may be used as the coating agent, or a film-like coating on a transferable resin film may be used.
[0055] When a hard coat layer or a barrier coat layer is not applied to the resin substrate, a method for manufacturing an electromagnetic wave reflective panel includes: pre-annealing a dielectric resin substrate at a temperature higher than 70°C and within the heat resistance temperature range of the resin substrate; bonding the pre-annealed resin substrate to a reflective functional layer within a predetermined time, for example, within 24 hours, preferably within several hours, and more preferably within 1 hour, from the end of the pre-annealing to produce an electromagnetic wave reflective panel; and reducing the amount of gas containing moisture and the like contained in the resin substrate by 35% or more, preferably 40% or more, by the pre-annealing. This method removes gas containing moisture and the like contained in the resin substrate, and can suppress the generation of bubbles, peeling, and swelling even after a durability test of up to 720 hours in an 80°C constant temperature chamber or a 50°C / 95% constant temperature / humidity chamber.
[0056] When a hard coat layer or a barrier coat layer is applied to a resin substrate, a method for producing an electromagnetic wave reflective panel includes forming a hard coat layer or a barrier coat layer on at least one surface of a dielectric resin substrate, pre-annealing the resin substrate having the hard coat layer or the barrier coat layer at a temperature higher than 70°C and within the heat resistance temperature range of the resin substrate, and bonding the surface of the pre-annealed resin substrate on which the hard coat layer or the barrier coat layer has been formed to a reflective function layer to produce an electromagnetic wave reflective panel. In this method, the hard coat layer or the barrier coat layer prevents penetration of gases containing moisture and the like into the resin substrate, and can suppress the generation of bubbles, peeling, and swelling even after a durability test of up to 720 hours in an 80°C constant temperature oven or a 50°C constant temperature and humidity oven of 95% humidity.
[0057] This international application claims priority based on Japanese Patent Application No. 2023-134113, filed on August 21, 2023, the entire contents of which are incorporated herein by reference.
[0058] Although the embodiments of the present disclosure have been described above, the present disclosure may also include the following configurations: (Item 1) An electromagnetic wave reflective panel is an electromagnetic wave reflective panel that reflects electromagnetic waves in a predetermined frequency band of 1 MHz to 300 GHz, and includes a reflective functional layer that selectively reflects electromagnetic waves in the predetermined frequency band and a dielectric resin substrate that supports the reflective functional layer, and after a durability test in which the electromagnetic wave reflective panel is placed in a constant temperature oven at 40°C to 80°C for 2 hours to 720 hours, or in a constant temperature and high humidity oven at 50°C and 95% humidity for 2 hours to 720 hours, the change in visible light transmittance of the electromagnetic wave reflective panel is 10% or less, and ΔE ＊ ab is 3.0 or less. (Item 2) The electromagnetic wave reflective panel according to Item 1, wherein the change in the visible light transmittance of the electromagnetic wave reflective panel after the durability test is 5.0% or less, preferably 2.5% or less. (Item 3) The ΔE ＊Item 1 or 2, wherein ab is 2.0 or less, preferably 1.5 or less. (Item 4) The electromagnetic wave reflective panel according to any one of Items 1 to 3, comprising an adhesive layer provided between the resin substrate and the reflective function layer, wherein the resin substrate has a hard coat layer or a barrier coat layer on the surface in contact with the adhesive layer. (Item 5) The electromagnetic wave reflective panel according to any one of Items 1 to 3, wherein the resin substrate has a hard coat layer or a barrier coat layer on both surfaces. (Item 6) The electromagnetic wave reflective panel according to any one of Items 1 to 5, wherein the resin substrate includes a first resin substrate and a second resin substrate sandwiching the reflective function layer therebetween, wherein the first resin substrate and the second resin substrate are bonded to both surfaces of the reflective function layer. (Item 7) An electromagnetic wave reflective device comprising: the electromagnetic wave reflective panel according to any one of Items 1 to 6; and a frame that holds the electromagnetic wave reflective panel. (Item 8) An electromagnetic wave reflective fence, comprising a plurality of electromagnetic wave reflective devices according to Item 7 connected by the frame. (Item 9) A method for manufacturing an electromagnetic wave reflective panel, comprising: performing pre-annealing on a dielectric resin substrate at a temperature higher than 70°C and within the heat resistance temperature range of the resin substrate; bonding the pre-annealed resin substrate and a reflective function layer together within a predetermined time from the end of the pre-annealing to manufacture an electromagnetic wave reflective panel; and reducing the amount of gas containing moisture contained in the resin substrate by 35% or more by the pre-annealing. (Item 10) A method for manufacturing an electromagnetic wave reflective panel, comprising: forming a hard coat layer or a barrier coat layer on at least one surface of a dielectric resin substrate; performing pre-annealing on the resin substrate having the hard coat layer or the barrier coat layer at a temperature higher than 70°C and within the heat resistance temperature range of the resin substrate; and bonding the surface of the pre-annealed resin substrate on which the hard coat layer or the barrier coat layer is formed to a reflective function layer to manufacture an electromagnetic wave reflective panel.(Item 11) A method for evaluating an electromagnetic wave reflective panel that reflects electromagnetic waves in a predetermined frequency band of 1 MHz or more and 300 GHz or less, wherein the electromagnetic wave reflective panel has a reflective function layer that selectively reflects electromagnetic waves in the predetermined frequency band, and a dielectric resin substrate that supports the reflective function layer, and after a durability test in which the electromagnetic wave reflective panel is placed in a constant temperature oven at 40°C to 80°C for 2 hours to 720 hours, or in a constant temperature and high humidity oven at 50°C and 95% humidity for 2 hours to 720 hours, the change in visible light transmittance of the electromagnetic wave reflective panel is 10% or less, and ΔE ＊ An evaluation method for electromagnetic wave reflective panels that evaluates whether ab is 3.0 or less.
[0059] 10, 10A, 10-1, 10-2, 10-3 Electromagnetic wave reflecting panel 11 Reflecting function layer 12, 13 Adhesive layer 14, 15 Resin substrate 50 Frame (side frame) 57 Top frame 58 Bottom frame 60, 60-1, 60-2, 60-3 Electromagnetic wave reflecting device 100 Electromagnetic wave reflecting fence
Claims
1. An electromagnetic wave reflection panel that reflects electromagnetic waves in a predetermined frequency band of 1 MHz to 300 GHz, comprising: a reflection function layer that selectively reflects electromagnetic waves in the predetermined frequency band; and a dielectric resin substrate that supports the reflection function layer; and after a durability test in which the electromagnetic wave reflection panel is placed in a constant temperature chamber at 40°C to 80°C for 2 to 720 hours, or in a constant temperature and humidity chamber at 50°C and 95% for 2 to 720 hours, the change in visible light transmittance of the electromagnetic wave reflection panel is 10% or less, and ΔE ＊ An electromagnetic wave reflective panel with ab below 3.
0.
2. The electromagnetic wave reflective panel according to claim 1, wherein the visible light transmittance of the electromagnetic wave reflective panel changes by 5.0% or less, preferably 2.5% or less after the durability test.
3. ΔE of the electromagnetic wave reflective panel after the durability test ＊ 2. The electromagnetic wave reflecting panel according to claim 1, wherein ab is equal to or smaller than 2.0, preferably equal to or smaller than 1.
5.
4. An electromagnetic wave reflecting panel as described in claim 1, further comprising an adhesive layer provided between the resin substrate and the reflective function layer, the resin substrate having a hard coat layer or a barrier coat layer on the surface in contact with the adhesive layer.
5. The electromagnetic wave reflecting panel according to claim 1, wherein the resin substrate has a hard coat layer or a barrier coat layer on both sides.
6. An electromagnetic wave reflecting panel as described in claim 1, wherein the resin substrate includes a first resin substrate and a second resin substrate sandwiching the reflective functional layer therebetween, and the first resin substrate and the second resin substrate are bonded to both sides of the reflective functional layer.
7. An electromagnetic wave reflecting device comprising: an electromagnetic wave reflecting panel according to any one of claims 1 to 6; and a frame for holding the electromagnetic wave reflecting panel.
8. An electromagnetic wave reflecting fence comprising a plurality of electromagnetic wave reflecting devices according to claim 7 connected by the frame.
9. A method for manufacturing an electromagnetic wave reflective panel, comprising: performing pre-annealing on a dielectric resin substrate at a temperature higher than 70°C and within the heat resistance temperature range of the resin substrate; bonding the pre-annealed resin substrate and a reflective function layer together to produce an electromagnetic wave reflective panel within a predetermined time from the end of the pre-annealing; and reducing the amount of moisture-containing gas contained in the resin substrate by 35% or more through the pre-annealing.
10. A method for manufacturing an electromagnetic wave reflective panel, comprising forming a hard coat layer or a barrier coat layer on at least one surface of a dielectric resin substrate, subjecting the resin substrate having the hard coat layer or the barrier coat layer to pre-annealing at a temperature higher than 70°C and within the heat resistance temperature range of the resin substrate, and bonding the surface of the resin substrate having the hard coat layer or the barrier coat layer formed thereon to a reflective function layer to produce an electromagnetic wave reflective panel.
11. A method for evaluating an electromagnetic wave reflective panel that reflects electromagnetic waves in a predetermined frequency band of 1 MHz to 300 GHz, the electromagnetic wave reflective panel having a reflective functional layer that selectively reflects electromagnetic waves in the predetermined frequency band, and a dielectric resin substrate that supports the reflective functional layer, the electromagnetic wave reflective panel being subjected to a durability test in which the electromagnetic wave reflective panel is placed in a constant temperature chamber at 40°C to 80°C for 2 to 720 hours, or in a constant temperature and humidity chamber at 50°C and 95% for 2 to 720 hours, after which the change in visible light transmittance of the electromagnetic wave reflective panel is 10% or less, and ΔE ＊ A method for evaluating electromagnetic wave reflective panels to evaluate whether ab is 3.0 or less.