TW202406220A - electromagnetic wave absorber - Google Patents

Abstract

Focusing on the imaginary part of the complex dielectric constant of the dielectric layer used in reflective electromagnetic wave absorbers, the purpose of the present invention is to provide a technology that enables the maintenance of an excellent return loss even if the sheet resistance of the resistive layer is changed. As a consequence, the electromagnetic wave absorber according to the present invention is a laminate comprising a resistive layer, a dielectric layer, and a reflective layer in the indicated sequence. This dielectric layer contains at least one dielectric compound and a resin component and has an imaginary part of the complex dielectric constant of at least 0.5, and the return loss, after a reliability test at 85 DEG C and 85% RH for 700 h, is at least 10 dB. In addition, the real part of the complex dielectric constant of the dielectric layer may be at least 10; the sheet resistance of the resistive layer may be 400 [Omega]/□ to 1000 [Omega]/□; the resistive layer may be a conductive polymer material having a volume resistivity of 8.0*10-5 to 4.0*10-3 [Omega].m; or the thickness of the resistive layer may be 150 nm to 2000 nm.

Description

electromagnetic wave absorber

The present invention relates to an electromagnetic wave absorber.

In recent years, in response to the rapid increase in the amount of information, the increase in speed of mobile objects, autonomous driving, and the practical implementation of IoT (Internet of Things), scanners for communications, radar, and security, etc., that can respond separately The demand is increasing day by day. Along with this, technologies related to high-speed wireless communication methods using next-generation electromagnetic waves utilizing 5G, millimeter waves, and terahertz waves are rapidly advancing.

Products that utilize electromagnetic waves may interfere with electromagnetic waves generated by other electronic devices, causing malfunctions. As a means for preventing this, a reflective electromagnetic wave absorber called a λ/4 type is known. Patent Document 1 discloses a λ/4 type radio wave absorber, which is a laminated body having a resistive film containing molybdenum, a dielectric layer, and a reflective layer in this order as a λ/4 type radio wave absorber. body, and exhibits excellent durability. Patent Document 2 discloses an impedance matching film for a radio wave absorber. The impedance matching film contains metallic elements and non-metallic elements, has a thickness of 10 to 200 nm, and has an oxygen atom content rate of less than 50% based on the atomic number. Therefore, From the perspective of impedance matching, changes in sheet resistance (sheet resistance) can be suppressed when exposed to high temperature environments. [Prior technical literature] [Patent Document]

Patent Document 1: Japanese Patent Application Publication No. 2020-115578 Patent Document 2: Japanese Patent Application Publication No. 2020-167414

[Problem to be solved by the invention]

As the use of electromagnetic wave absorbers expands, the number of cases in which electromagnetic wave absorbers are used in high-temperature and high-humidity environments for long periods of time is also increasing. However, the following problem was discovered: when used in such an environment or during reliability testing, the sheet resistance of the resistive layer contained in the electromagnetic wave absorber changes with the passage of time, resulting in return loss of the electromagnetic wave absorber. The return loss is reduced, and it is recognized that improving the durability performance is an issue. In addition, especially in situations where an electromagnetic wave absorber is installed to stabilize communications indoors, there is the following problem: There are few situations where electromagnetic waves are vertically incident on the electromagnetic wave absorber along the normal direction of the front, and there are cases where the electromagnetic wave absorber is incident at an oblique angle. With the tendency of lower incidence, the value of the sheet resistance that gives good return loss will also change as the angle of incidence changes. There is no disclosure related to this problem or solution in the aforementioned prior patent documents. Therefore, an object of the present invention is to provide a technology that focuses on the imaginary part of the complex permittivity (complex permittivity) of a dielectric layer used in a reflective electromagnetic wave absorber, even if the sheet resistance of the resistive layer changes, or Even when electromagnetic waves are incident obliquely, excellent return loss can be maintained. [Means used to solve problems]

In order to solve the above-mentioned problems, one of the representative electromagnetic wave absorbers of the present invention is a laminated body including a resistive layer, a dielectric layer, and a reflective layer in this order. The dielectric layer contains at least one dielectric compound and a resin. The component, the imaginary part of the complex dielectric constant is 0.5 or more, and the return loss after the reliability test at 85℃, 85%RH, 700h is 10dB or more. [Effects of the invention]

According to the present invention, excellent return loss can be maintained even when the sheet resistance of the resistive layer changes or when electromagnetic waves are incident obliquely. Problems, structures, and effects other than those described above can be understood from the following description of embodiments for implementation.

[Form used to implement the invention]

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the present invention is not limited to this embodiment. In addition, in the description of the drawings, the same parts are indicated by being assigned the same symbols.

＜Electromagnetic wave absorber＞ [First Embodiment A] Hereinafter, the electromagnetic wave absorber according to the first embodiment A will be described. FIG. 1 is a cross-sectional view schematically showing the reflective electromagnetic wave absorber according to the first embodiment. The electromagnetic wave absorber 10 shown in this figure is in the form of a film or a sheet, and is a laminated body including a resistive layer 1, a dielectric layer 2, and a reflective layer 3 in this order. In addition, the overall thickness of the film-like electromagnetic wave absorber 10 is, for example, 24 to 250 μm. On the other hand, the sheet-shaped electromagnetic wave absorber 10 has an overall thickness of, for example, 0.25 to 7.1 mm.

(resistance layer) The resistive layer 1 is a layer that allows electromagnetic waves incident from the outside to reach the dielectric layer 2 . That is, the resistance layer 1 is a layer for impedance matching.

When the electromagnetic wave absorbing system is used in air (impedance: 377Ω/□) and the imaginary part of the complex dielectric constant is a dielectric layer of 0.1 or less, the sheet resistance of the resistive layer 1 is, for example, in order to obtain a response of 10dB or more. The wave loss is set within the range of 200Ω/□ to 800Ω/□. On the other hand, according to this embodiment, by setting the imaginary part of the complex dielectric constant of the dielectric layer to 0.5 or more, the following electromagnetic wave absorber can be obtained: even for 200Ω/□ or more and 1400Ω/□ or less, Especially in the range of 400Ω/□ to 1000Ω/□, high return loss can be obtained, so stable manufacturing can be achieved. Even if the sheet resistance of the resistive layer increases during reliability testing, the amount of return loss remains low. higher than before. Examples of reliability tests here include high-temperature tests, low-temperature tests, high-temperature and high-humidity tests, thermal cycle tests, light irradiation tests, bending tests, and impact tests described in JIS standards, ISO standards, and ASTM standards. Especially in the high-temperature and high-humidity test conducted at 85°C and 85%RH, the sheet resistance increased significantly compared with other tests. Therefore, as will be described later, the present invention can achieve great effects.

Hereinafter, several examples obtained by simulation (described later) will be used for explanation. When the real part of the complex dielectric constant of the dielectric layer 2 at 28 GHz is 2.5 and the imaginary part is 0.5, the response can be obtained by setting the sheet resistance of the resistive layer 1 in the range of, for example, 200 to 1400Ω/□. An electromagnetic wave absorber with a wave loss of 10dB or more. In particular, by setting it within the range of 400 to 600Ω/□, a return loss of more than 20dB can be obtained immediately after manufacturing, and a high return loss of more than 10dB can be maintained even if the sheet resistance of the resistive layer increases due to reliability testing. Wave loss. When the real part of the complex dielectric constant of the dielectric layer 2 at 28 GHz is 10 and the imaginary part is 0.5, the response can be obtained by setting the sheet resistance of the resistive layer 1 in the range of, for example, 200 to 950Ω/□. An electromagnetic wave absorber with a wave loss of 10dB or more. In particular, by setting it within the range of 400 to 550Ω/□, a return loss of more than 20dB can be obtained immediately after manufacturing, and a high return loss of more than 10dB can be maintained even if the sheet resistance of the resistive layer increases due to reliability testing. Wave loss. When the real part of the complex dielectric constant of the dielectric layer 2 at 28 GHz is 10 and the imaginary part is 1.5, the response can be obtained by setting the sheet resistance of the resistive layer 1 in the range of, for example, 200 to 2500Ω/□. An electromagnetic wave absorber with a wave loss of 10dB or more. In particular, by setting it within the range of 450 to 800Ω/□, a return loss of more than 20dB can be obtained immediately after manufacturing, and a high return loss of more than 10dB can be maintained even if the sheet resistance of the resistor layer increases due to reliability testing. Wave loss. When the real part of the complex dielectric constant of the dielectric layer 2 at 28 GHz is 15 and the imaginary part is 1.5, the response can be obtained by setting the sheet resistance of the resistive layer 1 in the range of, for example, 200 to 2000Ω/□. An electromagnetic wave absorber with a wave loss of 10dB or more. In particular, by setting it within the range of 420 to 750Ω/□, a return loss of more than 20dB can be obtained immediately after manufacturing, and a high return loss of more than 10dB can be maintained even if the sheet resistance of the resistor layer increases due to reliability testing. Wave loss.

The inventor used the specific numerical values obtained from the simulation as mentioned above and found that if the sheet resistance R of the resistive layer 1 satisfies Equation 1, an electromagnetic wave absorber with a return loss of 20 dB or more can be obtained. Here, ε' and ε'' are respectively the real part and the imaginary part of the complex dielectric constant in the dielectric layer 2 .

The resistance layer 1 contains conductive inorganic materials and organic materials. Examples of conductive inorganic materials include nanoparticles and nanowires. Examples of materials for nanoparticles and nanowires include indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), carbon nanotubes, graphene, Ag, Al, Au, Pt, Pd, Cu, Co, Cr, In, Ag-Cu, Cu-Au and Ni. Examples of conductive organic materials include polythiophene derivatives, polyacetylene derivatives, polyaniline derivatives, and polypyrrole derivatives. In particular, from the viewpoint of flexibility, film-forming property, stability, and sheet resistance, the resistive layer 1 is preferably a conductive polymer containing polyethylenedioxythiophene (PEDOT). The resistance layer 1 may be a mixture (PEDOT/PSS) containing polyethylenedioxythiophene (PEDOT) and polystyrenesulfonic acid (PSS).

The sheet resistance value of the resistive layer 1 is calculated by assuming that the volume resistivity of the conductive material is ρ (Ω·m) and the thickness of the conductive material is t (m). t is given. Therefore, it can be appropriately set by selecting conductive inorganic materials and organic materials and adjusting the film thickness. When the resistance layer 1 is made of an inorganic material, the thickness (film thickness) of the resistance layer 1 is preferably in the range of 0.1 nm to 100 nm, more preferably in the range of 1 nm to 50 nm. When the film thickness is 0.1 nm or more, a uniform film can be easily formed, and the function as the resistive layer 1 tends to be more fully exerted. On the other hand, if the film thickness is 100 nm or less, sufficient flexibility can be maintained, and cracks can be more reliably prevented from occurring in the film due to external factors such as bending and stretching after film formation. Suppresses the tendency of damage and shrinkage of the substrate due to heat. When the resistance layer 1 is made of an organic material, the thickness (film thickness) of the resistance layer 1 is preferably in the range of 0.1 to 2.0 μm. Especially when the sheet resistance range is 450Ω/□ or more, the volume resistivity is set to 8.0×10 ^-5 to 4.0×10 ^-3 Ω. m, the film thickness can also be set to 0.15 to 0.5 μm, or even 0.15 to 0.2 μm, which can suppress the change in sheet resistance during reliability testing and obtain an electromagnetic wave absorber with a return loss of 10 dB or more. On the other hand, if the film thickness is 2.0 μm or less, sufficient flexibility can be maintained, and cracks in the film due to external factors such as bending and stretching after film formation can be more reliably prevented. tendency.

Examples of film forming methods include dry coating methods and wet coating methods.

Dry coating methods mainly include: vacuum evaporation using resistance heating, induction heating, ion beam (EB), sputtering, etc. The resistance heating method forms a film by placing the material in a ceramic crucible, applying a voltage to a heater surrounding the crucible to cause current to flow, and heating the crucible in a vacuum to cause the inorganic material to pass through the opening. Evaporates and adheres to the substrate. The film production speed is adjusted by controlling the distance between the material and the substrate, the voltage and current applied to the heater, and in the case of batch film production, the film is controlled by controlling the film production time with the opening and closing time of the shutter. Thickness. In the case of roll film forming, the film thickness is controlled by controlling the film forming time with linear speed and the like. Ion beams are used to form films by flowing current into a filament in a vacuum to release electrons, and using an electromagnetic lens to directly irradiate the released electrons onto the material, thereby heating and evaporating the inorganic material. , making it adhere to the substrate. Used for inorganic materials that require a huge amount of heat to evaporate and when a high film formation rate is required. The distance between the material and the substrate is controlled, the amount of electrons generated from the filament is controlled by current, and the irradiation position and range (aperture) of the material are controlled by the electromagnetic lens. The film production speed is adjusted, and the same gate opening and closing time and linear speed are controlled as mentioned above. Film time, control film thickness. The sputtering method forms a film by introducing a rare gas, mainly Ar, etc. onto a target made of an inorganic material, applying a voltage to plasmaize the Ar, and using the voltage to plasmaize the Ar. Ar accelerates and collides with the target, thereby physically sputtering the material and attaching it to the substrate. If the sputtering method is used, films of inorganic materials that cannot be formed by vacuum evaporation can sometimes be formed. The distance between the target and the substrate, the electric power applied to the target, and the Ar gas pressure are controlled to adjust the film forming speed. The film forming time is controlled by the same gate opening and closing time and linear speed as described above, and the film thickness is controlled. It is mainly used when forming films of inorganic materials.

The wet coating method is a method that mainly applies materials to a substrate. Materials that are solid at normal temperatures and pressures are converted into ink by dissolving or dispersing in a suitable solvent. After coating, the solvent is removed by drying. And make film. Examples of coating methods include die coating, microgravure coating, rod gravure coating, gravure coating, and the like. If the solid content of the ink and die coating are the same, the gap between the die opening, the base material, and the coating machine nozzle is controlled, and the ink is applied to the base material and dried to control the film. If the solid content of the ink is the same as that of microgravure coating, rod gravure coating, or gravure coating, then the number of lines, depth, and plate rotation ratio of the plate are controlled, and the ink is applied to the base material and The film is formed by drying to control the film thickness. It is mainly used when organic materials and some inorganic dispersed materials are formed into films.

The sheet resistance value of the resistive layer 1 can be measured using, for example, LORESTA-GP MCP-T610 (trade name, manufactured by Mitsubishi Chemical Analytech Co., Ltd.).

(Dielectric layer) The dielectric layer 2 is a layer that adjusts the phase in order to cancel the incident electromagnetic wave and the reflected electromagnetic wave through interference. Simply put, the thickness and the like of the dielectric layer 2 are set so as to satisfy the conditions expressed by the following formula. d=λ/(4(ε') ^1/2 ) where λ represents the wavelength of the electromagnetic wave to be suppressed (unit: m), ε' represents the real part of the complex dielectric constant of the material constituting the dielectric layer 2, d represents the thickness of the dielectric layer 2 (unit: m). The return loss can be obtained by the phase difference π between the incident electromagnetic wave and the reflected electromagnetic wave.

The dielectric layer 2 is composed of a resin composition having an imaginary part of the complex dielectric constant higher than 0.5 at a frequency that can best absorb electromagnetic waves. By having the imaginary part of the dielectric layer 2 higher than 0.5, as described above, the sheet resistance range of the resistive layer required to obtain a high return loss can be sufficiently expanded, and stable manufacturing can be achieved, even if It is an electromagnetic wave absorber in which the sheet resistance of the resistive layer increases during reliability testing and the amount of return loss is also higher than before. In particular, even if the real part of the complex dielectric constant is set to 10 or more in order to make the dielectric layer 2 thinner, the sheet resistance range of the resistive layer required to obtain a high return loss can be sufficiently expanded to obtain An electromagnetic wave absorber that can be manufactured stably and has a higher return loss than before even if the sheet resistance of the resistive layer increases during reliability testing.

The inventor found that when the real part of the complex dielectric constant is constant, if the imaginary part increases, the upper limit of the sheet resistance required to obtain a return loss of 10 dB tends to increase. On the other hand, if the complex dielectric constant The imaginary part of is constant and the real part increases, the upper limit of the chip resistance required to obtain a return loss of 10dB tends to decrease. According to this, the upper limit of the real part of the resin composition is about 15. However, by setting the imaginary part of the complex dielectric constant to 0.5 or more, compared with the case of 0, it is possible to make the return loss required to obtain a return loss of 10 dB. The upper limit of the chip resistance is increased by more than 10%. Even if the chip resistance changes after the environmental test of 85°C and 85%RH, the reduction in return loss can be effectively suppressed.

When the imaginary part of the complex dielectric constant of the dielectric layer 2 is 0.5 or more, a compound with high resistivity that cannot be used due to high resistivity can be used for the resistive layer. For example, aluminum zinc oxide (AZO), gallium-doped zinc oxide (GZO), antimony-doped tin oxide (ATO), etc. can be used instead of indium tin oxide (ITO) and indium zinc oxide (IZO) which have excellent conductivity. ). By using indium-free materials, there are advantages of reduced environmental load and cost reduction.

The resin composition constituting the dielectric layer 2 contains at least one dielectric compound and a resin component. The imaginary part and the real part of the complex dielectric constant of the dielectric layer 2 can be adjusted according to the selection and content of the dielectric compound in the resin composition. The content of the dielectric compound is preferably 10 to 300 parts by volume, more preferably 25 to 100 parts by volume relative to 100 parts by volume of the resin composition. The content of the dielectric compound is preferably 10 to 900 parts by mass, more preferably 25 to 100 parts by mass relative to 100 parts by mass of the resin composition. When the content of the dielectric compound in the resin composition is equal to or greater than the lower limit, the imaginary part of the complex dielectric constant of the dielectric layer 2 tends to be equal to or greater than 0.5. By increasing the blending ratio, the imaginary part of the complex dielectric constant of the dielectric layer 2 can be increased. The imaginary part of the complex permittivity increases. On the other hand, when the value is less than the upper limit, the dielectric layer 2 tends to be efficiently produced by a wet coating method or extrusion molding. For example, when the resin composition is urethane and the dielectric compound is barium titanate, the barium titanate is 22 parts by volume relative to 100 parts by volume of urethane, that is, When the barium titanate is 132 parts by mass relative to 100 parts by mass of urethane, the imaginary part of the complex dielectric constant becomes 0.5. In addition, when the barium titanate is 30 parts by volume relative to 100 parts by volume of urethane, that is, the barium titanate is 180 parts by mass relative to 100 parts by mass of urethane, the complex dielectric constant The imaginary part becomes 1.0. In addition, when the barium titanate is 35 parts by volume relative to 100 parts by volume of urethane, that is, the barium titanate is 210 parts by mass relative to 100 parts by mass of urethane, the complex dielectric constant The imaginary part becomes 1.5. In addition, by increasing the content of the dielectric compound, the burning resistance can also be increased.

Examples of the dielectric compound include barium titanate (BaTiO ₃ ), neodymium barium titanate (Ba ₃ Nd _9.3 Ti ₁₈ O ₅₄ ), titanium oxide (TiO ₂ ), zinc oxide (ZnO), and silicate Metal compounds such as (Mg ₂ SiO ₄ ), aluminum oxide (Al ₂ O ₃ ), magnesium barium niobate (Ba(Mg _1/3 Nb _2/3 )O ₃ ), and carbon. In particular, barium titanate and carbon are preferable because they can significantly increase the imaginary part of the complex dielectric constant. In addition, a metal compound and carbon may be mixed. By mixing, in addition to increasing the imaginary part of the complex dielectric constant, the resistance to burnout can also be improved.

The dielectric compound is preferably in the form of powder (for example, nanoparticles). If the particle shape is 0.3 to 1 μm, large real and imaginary parts of the complex dielectric constant can be obtained, and the shape of the film can be maintained without cracking even if the content is increased. Wet coating methods or extrusion molding can be used efficiently. The dielectric layer 2 is produced.

Examples of the resin component include acrylic resin, urethane resin, methacrylic resin, silicone resin, polycarbonate, epoxy resin, glycerin phthalate resin (glyptal resin), and polyvinyl chloride. , polyethylene formaldehyde, phenol resin, urea resin and polychloroprene resin. The higher the solubility parameter (SP value) of the resin component, the greater the imaginary part of the complex dielectric constant can be increased when the dielectric compound is mixed. The SP value of the resin component for making the imaginary part of the complex dielectric constant of the dielectric compound 0.5 or more is preferably 8 or more, more preferably 9 or more, and still more preferably 10 or more. The real part of the complex dielectric constant of the resin component is preferably 2.5 to 9.5, more preferably 3.5 to 9.5, still more preferably 5.0 to 9.5.

The resin composition preferably has adhesive properties. Thereby, the dielectric layer 2 can be efficiently attached to the surface of the reflective layer 3 . Examples of such materials include silicone adhesives, acrylic adhesives, and urethane adhesives. These materials may be used as the resin component, and an adhesive layer composed of these materials may be formed on at least one side of the dielectric layer 2 . The adhesion force of the resin composition itself or the adhesive layer to the stainless steel 304 steel plate is preferably 1.0N/25mm or more, and can also be 3.0~10.0N/25mm or 10.0~15.0N/25mm.

(reflective layer) The reflective layer 3 is a layer for reflecting electromagnetic waves incident from the dielectric layer 2 so that the electromagnetic waves reach the dielectric layer 2 . The thickness of the reflective layer 3 is, for example, 0.1 nm to 1 mm, and may be a film of 0.1 nm to 10 μm, a foil of 0.01 to 0.2 mm, or a plate of 0.2 mm to 1 mm.

The reflective layer 3 contains conductive inorganic materials and organic materials. Examples of conductive inorganic materials include nanoparticles and nanowires. Examples of materials for nanoparticles and nanowires include indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), carbon nanotubes, graphene, Ag, Al, Au, Pt, Pd, Cu, Co, Cr, In, Ag-Cu, Cu-Au and Ni. Examples of conductive organic materials include polythiophene derivatives, polyacetylene derivatives, polyaniline derivatives, and polypyrrole derivatives. In addition, a conductive inorganic material or organic material can be formed into a film on the base material. In particular, from the viewpoints of flexibility, film-forming properties, stability, sheet resistance, and low cost, it is preferable to use a laminated film including a PET film and an aluminum layer vapor-deposited on the surface (Al vapor-deposited PET film ) as a reflective layer. The sheet resistance of the reflective layer 3 may be 100Ω/□ or less.

The maximum return loss of the electromagnetic wave absorber 10 may be 10 dB or more, 20 bB or more, or 30 dB or more.

[First Embodiment B] Hereinafter, the electromagnetic wave absorber according to the first embodiment B will be described. Matters not described below are the same as those of the electromagnetic wave absorber of the first embodiment A as long as there is no inconsistency. In this embodiment, the normal direction from the surface of the electromagnetic wave incident side toward the air (outside) in the electromagnetic wave absorber is used as the reference line, and the angle formed by the incident direction of the incident wave is called the incident angle (°). The angle formed by the reflection direction of the reflected wave is called the reflection angle (°). Unless otherwise specified, clockwise rotation from the aforementioned reference line is the positive direction, and counterclockwise rotation is the negative direction. For a given electromagnetic wave, the angle of incidence and angle of reflection are equal.

When the electromagnetic wave absorbing system is used in air (impedance: 377Ω/□) and the imaginary part of the complex dielectric constant is a dielectric layer of 0.1 or less, the sheet resistance of the resistive layer 1 is, for example, in order to obtain a response of 10dB or more. The wave loss amount is set within the range of 200Ω/□ or more and 800Ω/□ or less. On the other hand, according to this embodiment, the following electromagnetic wave absorber is obtained by setting the real part of the complex dielectric constant of the dielectric layer to 10 or more and 15 or less and setting the imaginary part to 1.0 or more and 1.5 or less. : Even in the range of 600Ω/□ or more and 2500Ω/□ or less, high return loss can be obtained for the incident angle/reflection angle of 30° to 70°, so stable manufacturing can be achieved, and even after reliability testing The sheet resistance of the international resistive layer increases, and the return loss is also higher than before. Examples of reliability tests here include high-temperature tests, low-temperature tests, high-temperature and high-humidity tests, thermal cycle tests, light irradiation tests, bending tests, and impact tests described in JIS standards, ISO standards, and ASTM standards. Especially in the high-temperature and high-humidity test conducted at 85°C and 85%RH, the sheet resistance increased significantly compared with other tests.

The inventor used specific numerical values obtained from the simulation described below and found that if the sheet resistance R of the resistive layer 1 satisfies Equation 2, an electromagnetic wave absorber with a return loss of 25 dB or more can be obtained. Here, ε' is the imaginary part of the complex dielectric constant in the dielectric layer 2, and θ (°) is the incident angle/reflection angle.

The inventor found the following tendency: as will be described later, if the real part of the sheet resistance of the resistive layer and the complex dielectric constant of the dielectric layer is made constant and the imaginary part is increased, then at a given incident angle/reflection angle The amount of return loss increases roughly. This discovery enables designs that maintain good return loss characteristics under oblique incidence by focusing on the imaginary part even when the sheet resistance changes.

In this embodiment, the real part of the complex dielectric constant of the resin component constituting the dielectric layer 2 is 10 to 15, preferably 10 to 12, more preferably 12 to 13, still more preferably 13 to 15.

[Second Embodiment] Hereinafter, the electromagnetic wave absorber according to the second embodiment will be described. Matters not described below are the same as those of the electromagnetic wave absorber of the first embodiment as long as there is no inconsistency. FIG. 2 is a cross-sectional view schematically showing a reflective electromagnetic wave absorber according to the second embodiment. The electromagnetic wave absorber 20 shown in this figure is a laminated body including a protective layer 4, a resistive layer 1, a dielectric layer 2, and a reflective layer 3 in this order.

(Protective layer 4) Examples of the protective layer 4 include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyamides such as nylon; polypropylene and cyclic Polyolefins such as olefins; polycarbonate; and cellulose triacetate, ethylene tetrafluoroethylene; fluororesins such as polychlorotetrafluoroethylene, polytetrafluoroethylene, etc., but are not limited thereto. The protective layer 4 is preferably a polyester film, a polyamide film or a polyolefin film, more preferably a polyester film or a polyamide film, and still more preferably a polyethylene terephthalate (PET film). PET film is ideal from the viewpoint of processability and adhesion. In addition, the PET film is preferably a biaxially stretched PET film from the viewpoint of gas barrier properties. A barrier film in which a coating film or a vapor-deposited film is further formed on the PET film may be used.

The thickness of the protective layer 4 may be, for example, 11 to 13 μm, 49 to 51 μm, 74 to 76 μm, or 95 to 110 μm.

The resistive layer 1 may be formed on the protective layer 4, the protective layer 4 may be located on the outermost surface, or the resistive layer 1 may be located on the outermost surface. If the protective layer 4 is located on the outermost surface, the increase in the sheet resistance of the resistive layer 1 caused by external environments such as water vapor and oxygen can be suppressed.

On the surface of the protective layer 4, a design having wood grain, tiles, etc. may be formed.

The electromagnetic wave absorbers of the first and second embodiments have been described in detail above. However, the present invention is not limited to the above embodiments. For example, in the electromagnetic wave absorber 20 , a base layer may be provided between the protective layer 4 and the resistive layer 1 . Thereby, in the electromagnetic wave absorber, the adhesion between the protective layer and the resistive layer is improved, and the coating properties of the protective layer tend to be improved. Furthermore, in the electromagnetic wave absorber 20 , a topcoat layer may be provided on the surface of the protective layer 4 opposite to the surface in contact with the resistive layer 1 . Thereby, migration tends to be suppressed, and the protective layer 4 can be protected.

[Third Embodiment] Hereinafter, the electromagnetic wave absorber according to the third embodiment will be described. Matters not described below are the same as those of the electromagnetic wave absorbers of the first and second embodiments as long as there is no inconsistency. FIG. 3 is a cross-sectional view schematically showing a reflective electromagnetic wave absorber according to the third embodiment. The electromagnetic wave absorber 30 shown in this figure is a laminated body including a protective layer 4, a resistive layer 1, a barrier bonding layer 5, a barrier layer 6, a dielectric layer 2, and a reflective layer 3 in this order. By providing the barrier adhesive layer 5 and the barrier layer 6, the increase in resistance of the resistive layer 1 caused by the dielectric layer 2 is suppressed, and an electromagnetic wave absorber with a large return loss and a wide band width is obtained.

(barrier bonding layer) The barrier adhesion layer 5 is a layer for tightly contacting the resistive layer 1 with the barrier layer 6 without increasing the resistance of the resistive layer 1 .

The thickness of the barrier adhesive layer 5 is preferably set appropriately based on the absorption frequency and adhesion force. That is, it is preferably 0.5 μm or more and 100 μm or less, and more preferably 3 μm or more and 25 μm or less. If the thickness is 0.5 μm or more, sufficient adhesion can be obtained, and if the thickness is 100 μm or less, the total thickness of the electromagnetic wave absorber can be reduced.

Examples of the barrier adhesive layer 5 include: acrylic adhesives or adhesives, polysiloxane adhesives or adhesives, polyolefin adhesives or adhesives, urethane adhesives or adhesives, or Polyvinyl ether adhesive or adhesive, etc. Among them, the polysiloxane-based adhesive is preferred because it has high transparency and resistance to moisture and heat, does not reduce the adhesion force even under reliability tests, and has a small increase in resistance of the resistive layer 1 . The sheet resistance value of the barrier adhesive layer 5 is preferably sufficiently high, for example, 1.0×10 ⁶ Ω/□ or more. When the sheet resistance value of the barrier adhesive layer 5 is 1.0×10 ⁶ Ω/□ or more, the electromagnetic waves incident from the resistive layer 1 can be suppressed from being reflected on the surface of the barrier adhesive layer 5 .

(Barrier layer) The barrier layer 6 is a layer for suppressing an increase in the resistance of the resistive layer 1 caused by the dielectric layer 2 . The sheet resistance value of the barrier layer 6 is preferably high enough, for example, 1.0×10 ⁶ Ω/□ or more. When the sheet resistance value of the barrier layer 6 is 1.0×10 ⁶ Ω/□ or more, the electromagnetic waves incident from the resistive layer 1 can be suppressed from being reflected on the surface of the barrier layer 6 .

The oxygen permeability of the barrier layer 6 is preferably 4.0×10 ² cc/m ² . day. atm or less, preferably 1.0×10 ¹ cc/m ² ． day. atm or less, preferably 1.0×10 ^-1 cc/m ² ． day. below atm. The oxygen permeability means a value measured under the conditions of a temperature of 30° C. and a relative humidity of 70% according to the method described in JIS K7126-2.

The water vapor permeability of the barrier layer 6 is preferably 1.0×10 ² g/m ² . day or less, preferably 1.0×10 ¹ g/m ² . day or less, preferably 2.0×10 ^-1 g/m ² . day or less. The water vapor permeability means a value measured under the conditions of a temperature of 40° C. and a relative humidity of 90% according to the method described in JIS K7129B.

The thickness of the barrier layer 6 is preferably set appropriately based on the absorption frequency, oxygen permeability, and water vapor permeability, and is preferably 3 μm or more and 100 μm or less, more preferably 5 μm or more and 25 μm or less. If the thickness is 3 μm or more, processing is easy, and if the thickness is 100 μm or less, the total thickness of the electromagnetic wave suppressor can be reduced. In addition, the barrier layer 6 may contain additives such as antistatic agents, ultraviolet absorbers, plasticizers, and lubricants as necessary. The surface of the barrier layer can be subjected to surface treatment such as corona treatment, flame treatment, and plasma treatment.

Examples of the barrier layer 6 include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyamides such as nylon; polypropylene and cyclic olefins; and the like. Polyolefin; polycarbonate; and cellulose triacetate, etc., but are not limited to these. The barrier layer 6 is preferably a polyester film, a polyamide film or a polyolefin film, more preferably a polyester film or a polyamide film, and still more preferably a polyethylene terephthalate (PET film). PET film is ideal from the viewpoint of processability and adhesion. In addition, the PET film is preferably a biaxially stretched PET film from the viewpoint of gas barrier properties.

The barrier layer 6 may be a laminated structure including a vapor deposition layer and a barrier coating layer on a base film, and the base film is made of polyethylene terephthalate, polybutylene terephthalate, and polynaphthalene. Polyesters such as ethylene formate; polyamides such as nylon; polyolefins such as polypropylene and cyclic olefins; polycarbonate; and cellulose triacetate, etc. The barrier coating layer is provided to cover the vapor deposition layer. The barrier coating layer is provided to prevent various secondary damages in subsequent steps and to provide high barrier properties. The thickness of the barrier coating layer is preferably 50 to 2000 nm, more preferably 100 to 1000 nm. If the thickness of the barrier coating layer is 50 nm or more, film formation tends to be easier, while on the other hand, if the thickness is 2000 nm or less, cracking or curling tends to be suppressed.

The barrier coating may contain siloxane linkages. The compound containing a siloxane bond is preferably formed by reacting a silanol group using a silane compound, for example. Examples of such silane compounds include compounds represented by the following formula 3. R1 _n (OR2) _4-n Si...(Formula 3) [In the formula, n represents an integer of 0 to 3, and R1 and R2 each independently represent a hydrocarbon group, preferably an alkyl group having 1 to 4 carbon atoms. ] Examples of the compound represented by the above formula 3 include: tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, methyltrimethoxysilane, methyl Triethoxysilane, dimethyldimethoxysilane, and dimethyldiethoxysilane, etc. Nitrogen-containing polysilazanes may also be used.

For the barrier coating layer, materials made from precursors containing other metal atoms can be used. Examples of compounds containing Ti atoms include compounds represented by the following formula 4. R1 _n (OR2) _4-n Ti...(Formula 4) [In the formula, n represents an integer of 0 to 3, and R1 and R2 each independently represent a hydrocarbon group, preferably an alkyl group having 1 to 4 carbon atoms. ] Examples of the compound represented by the above formula 4 include titanium tetramethoxide, titanium tetraethoxide, titanium tetraisopropoxide, and titanium tetrabutoxide.

Examples of compounds containing Al atoms include compounds represented by the following formula 5. R1 _m (OR2) _3-m Al...(Formula 5) [In the formula, m represents an integer of 0 to 2, and R1 and R2 each independently represent a hydrocarbon group, preferably an alkyl group having 1 to 4 carbon atoms. ] Examples of the compound represented by the above formula 5 include aluminum trimethoxide, aluminum triethoxide, aluminum triisopropoxide, aluminum tributoxide, and the like.

Examples of compounds containing Zr atoms include compounds represented by the following formula 6. R1 _n (OR2) _4-n Zr...(Formula 6) [In the formula, n represents an integer of 0 to 3, and R1 and R2 each independently represent a hydrocarbon group, preferably an alkyl group having 1 to 4 carbon atoms. ] Examples of the compound represented by the above formula 6 include zirconium tetramethoxide, zirconium tetraethoxide, zirconium tetraisopropoxide, and zirconium tetrabutoxide.

Barrier coatings can also form in the atmosphere. When forming a barrier coating layer in the atmosphere, for example, a compound containing chlorine such as a polar compound such as polyvinyl alcohol, polyvinylpyrrolidone, ethylene vinyl alcohol, or polyvinylidene chloride can be used. , and a coating liquid containing a compound containing Si atoms, a compound containing Ti atoms, a compound containing Al atoms, a compound containing Zr atoms, etc., is applied on the vapor deposition layer, and dried and hardened to form. Specific examples of the application method of the coating liquid when forming the barrier coating layer in the atmosphere include gravure coaters, dip coaters, reverse roll coaters, wire bar coaters, die coaters, and the like. coating method. The above-mentioned coating liquid is hardened after application. The curing method is not particularly limited, and examples thereof include ultraviolet curing and thermal curing. In the case of ultraviolet curing, the coating liquid may contain a polymerization initiator and a compound having a double bond. In addition, it can be heated and aged as needed.

As another method of forming a barrier coating layer in the atmosphere, the following method can also be used: particles of inorganic oxides such as magnesium, calcium, zinc, aluminum, silicon, titanium, zirconium, etc. are allowed to pass through each other. The reaction product obtained by dehydration and condensation of phosphorus atoms of the phosphorus compound serves as a barrier coating layer. Specifically, functional groups (for example, hydroxyl groups) present on the surface of the inorganic oxide, and sites of the phosphorus compound that can react with the inorganic oxide (for example, halogen atoms directly bonded to phosphorus atoms, halogen atoms directly bonded to phosphorus atoms, The bonded oxygen atoms) produce a condensation reaction and bond. The reaction product can be obtained, for example, by applying a coating liquid containing an inorganic oxide and a phosphorus compound to the surface of the vapor deposition layer, and subjecting the formed coating film to heat treatment so that particles of the inorganic oxide can penetrate each other. Derived from phosphorus atom bonding in phosphorus compounds. The lower limit of the heat treatment temperature is 110°C or higher, preferably 120°C or higher, more preferably 140°C or higher, still more preferably 170°C or higher. If the heat treatment temperature is low, it becomes difficult to obtain a sufficient reaction rate, which causes a decrease in productivity. The preferable upper limit of the heat treatment temperature varies depending on the type of base material, etc., but is 220°C or lower, preferably 190°C or lower. The heat treatment can be performed in the air, in a nitrogen atmosphere, or in an argon atmosphere, or the like.

When the barrier coating layer is formed in the atmosphere, the coating liquid may further contain a resin as long as aggregation or the like does not occur. Specific examples of the resin include acrylic resin, polyester resin, and the like. The coating liquid preferably contains a resin that has high compatibility with other materials in the coating liquid among these resins. The above-mentioned coating liquid may further contain fillers, leveling agents, defoaming agents, ultraviolet absorbers, antioxidants, silane coupling agents, titanium chelating agents, etc. as needed.

[Fourth Embodiment] Hereinafter, the electromagnetic wave absorber according to the fourth embodiment will be described. Matters not described below are the same as those of the electromagnetic wave absorbers of the first to third embodiments as long as there is no inconsistency. FIG. 4 is a cross-sectional view schematically showing a reflective electromagnetic wave absorber according to the fourth embodiment. The electromagnetic wave absorber 40 shown in this figure is a laminated body including a protective layer 4, a resistive layer 1, a barrier adhesive layer 5, a barrier layer 6, an adhesive layer 7, a dielectric layer 2, an adhesive layer 7, and a reflective layer 3 in this order. .

(adhering layer) The subsequent layer 7 is a layer used to closely connect the barrier layer 6 and the reflective layer 3 when it has no adhesiveness or adhesion to the dielectric layer 2 .

The thickness of the subsequent layer 7 can be appropriately set based on the absorption frequency and adhesion force. That is, it is preferably 0.5 μm or more and 100 μm or less, and more preferably 3 μm or more and 25 μm or less. If the thickness is 0.5 μm or more, sufficient adhesion can be obtained, and if the thickness is 100 μm or less, the total thickness of the electromagnetic wave suppressor can be reduced.

Examples of the adhesive layer 7 include: acrylic adhesives or adhesives, epoxy adhesives or adhesives, polysiloxane adhesives or adhesives, polyolefin adhesives or adhesives, urethane adhesives, etc. Adhesives or adhesives, or polyvinyl ether adhesives or adhesives, etc.

＜Manufacturing method of electromagnetic wave absorber＞ [First Embodiment] Hereinafter, a method of manufacturing the electromagnetic wave absorber 10 according to the first embodiment will be described. The manufacturing method of this embodiment includes the step of forming the dielectric layer 2 by extruding a composition containing a thermoplastic resin in a molten state.

The method of forming the resistive layer 1 is preferably appropriately selected according to the material constituting the resistive layer 1 . For example, if the material is an organic material, a wet coating method is preferred, and if the material is an inorganic material, a dry coating method is preferred. Examples of the wet coating method include a die coater, a microgravure coater, a contact reverse roll coater, and a lip die coater. Examples of the dry coating method include resistance heating evaporation, ion beam (EB) method, and sputtering method. The resistance layer 1 may be directly formed on the surface of the dielectric layer 2 .

As the thermoplastic resin, a thermoplastic resin may be used among the resins exemplified as the organic materials constituting the dielectric layer 2 .

The electromagnetic wave absorber 10 can be manufactured by laminating the resistive layer 1 and the reflective layer 3 using the dielectric layer 2, or by laminating a laminate including the resistive layer 1 and the dielectric layer 2, and the reflective layer 3. The dielectric layer 2 and the reflective layer 3 of the laminated body are bonded so as to face each other and are manufactured.

[Second Embodiment] Hereinafter, a method for manufacturing the electromagnetic wave absorber 20 according to the second embodiment will be described. Matters not described below are the same as the manufacturing method of the electromagnetic wave absorber 10 of the first embodiment as long as there is no inconsistency.

The method of forming the resistive layer 1 is preferably appropriately selected according to the material constituting the resistive layer 1 . For example, if the material is an organic material, a wet coating method is preferred, and if the material is an inorganic material, a dry coating method is preferred. Examples of the wet coating method include a die coater, a microgravure coater, a contact reverse roll coater, and a lip die coater. Examples of the dry coating method include resistance heating evaporation, ion beam (EB) method, and sputtering method. The resistance layer 1 may be directly formed on the surface of the protective layer 4 .

The dielectric layer 2 is formed by wet coating. Wet coating can be performed by applying a dispersion liquid in which the material constituting the dielectric layer 2 is dispersed onto a base material to form a coating film, and drying the coating film. Examples of wet coating methods include gravure coating, roll coating, die coating, comma coating, blade coating, etc., and include an operation system such as application of a dispersion liquid and drying of a coating film. In view of the tendency to form a dielectric layer with a sufficient thickness at one time, notch wheel coating, blade coating, and roller coating are preferred. The dielectric layer 2 may be directly formed on the surface of the resistance layer 1 , may be directly formed on the surface of the reflective layer 3 , or may be temporarily formed on a material that has release properties for the material used for the dielectric layer 2 . After applying the release film on the surface, the dielectric layer 2 and the reflective layer 3 are bonded together by a lamination method, the release film is peeled off, and the resistive layer 1 formed on the surface of the protective layer 4 is bonded together.

In wet coating, the operations of applying the dispersion liquid and drying the coating film may be performed only once or a plurality of times.

[Third Embodiment] Hereinafter, a method for manufacturing the electromagnetic wave absorber 30 according to the third embodiment will be described. Matters not described below are the same as the manufacturing methods of the electromagnetic wave absorbers 10 and 20 of the first and second embodiments as long as there is no inconsistency. The manufacturing method of this embodiment includes the step of forming the dielectric layer 2 by wet coating.

The resistive layer 1 and the barrier layer 6 produced in the same manner as in the first embodiment are bonded together with the barrier adhesive layer 5 . The laminating method is, for example, the following method: a dry lamination method in which the resistive layer 1 is directly bonded to the barrier adhesive layer 5 using a lamination roller. The barrier adhesive layer 5 is applied to the surface of the barrier layer 6 by gravure coating or roller coating. It is formed by coating and drying the coating film using wet coating methods such as die coating, notch wheel coating, and blade coating; or it is a release film formed of polysiloxane or fluororesin by the aforementioned dry lamination method. After being temporarily bonded to one side, the release film is peeled off, and the resistive layer 1 is bonded to the barrier adhesive layer 5 by lamination.

In addition, on the reflective layer 3, the dielectric layer 2 having adhesiveness and adhesiveness is bonded to the barrier layer of the laminate including the resistive layer 1, the barrier adhesive layer 5, and the barrier layer 6 in this order using the same dry lamination method. On level 6.

[Fourth Embodiment] Hereinafter, a method for manufacturing the electromagnetic wave absorber 40 according to the fourth embodiment will be described. Matters not described below are the same as the manufacturing methods of the electromagnetic wave absorbers 10, 20, and 30 of the first to third embodiments as long as there is no inconsistency. The manufacturing method of this embodiment includes the step of forming the dielectric layer 2 by extruding a composition containing a thermoplastic resin in a molten state.

The reflective layer 3 is coated using a wet coating method such as gravure coating, roller coating, die coating, notched wheel coating, or blade coating, and the coating film is dried to form the adhesive layer 7, which is then laminated using a dry lamination method. The dielectric layer 2 is produced in the same manner as in the first embodiment.

Next, on the surface of the barrier layer 6, which is a laminate including the resistive layer 1, the barrier adhesive layer 5, and the barrier layer 6, which is produced in the same manner as in the third embodiment, gravure coating, roller coating, die coating, and die coating are performed. The adhesive layer 7 is formed by applying wet coating methods such as angle wheel coating and knife coating and drying the coating film, and laminating a laminate including the dielectric layer 2, the adhesive layer 7, and the reflective layer 3 in this order by a dry lamination method. The surface of the dielectric layer 2 of the body.

<Example> Hereinafter, description will be given based on Examples and Comparative Examples. First, among the first to fourth embodiments, Examples A1 to A22 and Comparative Examples A1 to A4 concerning the first embodiment A (hereinafter referred to as “the first embodiment A”) will be described. , explained using Table 1 and Figures 5 to 30. Next, among the first to fourth embodiments, Examples B1 to B16 and Comparative Examples B1 to B3 concerning the first embodiment B (hereinafter referred to as “the first embodiment B”) will be described. , explained using Table 2 and Figures 31 to 49. In addition, the present invention is not limited to the following examples.

[About first embodiment A] First, the components and manufacturing methods of each component used in Examples A15, A19, A21, and Comparative Example A1 in which return loss characteristics were actually measured will be described. [protective layer] PET film (thickness: 50 μm, manufactured by Toray Co., Ltd., trade name "Lumirror S10") [Resistive layer] Mixture of polyethylenedioxythiophene (PEDOT) and polystyrenesulfonic acid (PSS) (PEDOT/PSS) (manufactured by Nagase Chemtex Co., Ltd.) [Barrier bonding layer] Polysilicone adhesive (trade name "KR-3700" "CAT-PL-50T" manufactured by Shin-Etsu Chemical Industry Co., Ltd.) [barrier layer] Barrier film (trade name "GL-RD" manufactured by Toppan Printing Co., Ltd.) [Dielectric layer] Acrylic adhesive (trade name "OC-3405" "K-341", manufactured by Saiden Chemical Co., Ltd.) Urethane resin (trade name "C60A" manufactured by BASF Corporation) Barium titanate nanoparticles (manufactured by Sakai Chemical Industry Co., Ltd., average primary particle size: 100 nm) [Adhering layer] Epoxy urethane adhesive (trade name "AD-393" "CAT-EP5" manufactured by Toyo Ink Co., Ltd.) [Reflective layer] Al evaporated PET film (thickness of evaporated layer: 30nm, overall thickness: 12μm)

(Example A15) The surface of the PET film (protective layer) was coated with a PEDOT/PSS resistive layer (thickness: 500 nm) using a bar coater No. 30 with a solid content of 1.3 wt%, and then dried in an oven set to 120°C for 1 minute. The first layered body. Next, on the surface of the barrier film (barrier layer), KR-3700, CAT-PL-50T, and toluene solvent were mixed and stirred so that the mass-based mixing ratio became 40:0.2:60 to obtain a poly(polymer) with a solid content of 20 wt%. Silicone adhesive. After applying the polysiloxane adhesive produced using a bar coater No. 34, it was dried in an oven set to 130°C for 1 minute to form a barrier adhesive layer (thickness: 10 μm), and then the lamination temperature was set to 40°C. A laminator with a pressure of 0.4 MPa and a speed of 1 m/min was used to laminate the first laminated body to obtain a second laminated body.

Next, the dielectric layer is obtained by the following method. Barium titanate nanoparticles, OC-3405, K-341, and a toluene solvent were mixed and stirred in a mass-based mixing ratio of 57:28:1:15 to obtain an acrylic adhesive with a solid content of 74%. Use the acrylic adhesive produced in this way, a separator film (trade name "TN-100", produced by Toyobo), a shim tape (thickness: 300 μm), and an applicator (200 μm). gap), apply as follows. A caulk strip is provided between the release surface of the release film and the base surface of the applicator. By following this operation, the distance between the release surface of the release film and the knife part of the applicator during application will always be an average of 500 μm. The acrylic adhesive solution is dropped into the gap between the release surface of the release film and the applicator, and the applicator is scanned while applying the applicator with the base surface of the applicator in contact with the gap-filling tape. After drying in an oven for 2 minutes, drying in an oven set to 80°C for 2 minutes, and drying in an oven set to 120°C for 2 minutes to form a film, the layer was set to a lamination temperature of 60°C, a pressure of 0.4MPa, and a speed of 1m/min. A pressing device is used to bond the film forming surfaces to each other to obtain a dielectric layer.

After peeling off one isolation film of the dielectric layer obtained in this way, the Al vapor-deposited PET film (reflective layer) was bonded using a laminating device set to a laminating temperature of 40°C, a pressure of 0.4MPa, and a speed of 1m/min. After peeling off the other separator, the second laminated body was bonded using a laminating device in the same manner. After lamination, aging treatment was performed in an aging room at 50° C. for 3 days, and an electromagnetic wave absorber having the same layer structure as the electromagnetic wave absorber shown in FIG. 3 was obtained.

(Example A19) An electromagnetic wave absorber was obtained in the same manner as in Example A15, except that the following method was used to laminate the dielectric layer and its upper and lower layers. Barium titanate nanoparticles and urethane resin pellets C60A were mixed and stirred at a mass-based mixing ratio of 70:30. The resulting mixed pellets were put into an extruder and melted and kneaded at 100°C. And extruded into rod shape, cooled and cut into pellets to make masterbatch. The masterbatch obtained in this way was calendered using a calendering machine set to a calender roll temperature of 140° C. and a gap between the rolls of 390 μm to obtain a molded sheet. A molded sheet rolled in the same manner is laminated on the molded sheet produced in this manner to obtain a dielectric layer.

Next, AD-393, CAT-EP5, and IPA solvent were mixed and stirred so that the mass-based mixing ratio became 44:3:53 to obtain an epoxy urethane adhesive with a solid content of 25 wt%. The prepared epoxy urethane adhesive was dropped on the PET surface of the Al vapor-deposited PET film (reflective layer), applied using a bar coater No. 34, and then dried in an oven set to 130°C for 1 minute. After forming the adhesive layer (thickness: 8 μm), the laminator was bonded to the dielectric layer using a laminator set to a lamination temperature of 40° C., a pressure of 0.4 MPa, and a speed of 1 m/min to obtain a third laminated body.

Similarly, the epoxy urethane adhesive was dropped on the surface of the barrier film of the second laminated body, applied using a bar coater No. 70, and then dried in an oven set at 130° C. for 1 minute to form an adhesive layer. (Thickness: 18 μm), the laminator was bonded to the dielectric layer of the third dielectric using a laminator set to a lamination temperature of 40° C., a pressure of 0.4 MPa, and a speed of 1 m/min.

(Example A21) An electromagnetic wave absorber was obtained in the same manner as in Example A19 except that the gap between the calender rolls was set to 270 μm.

(Comparative example A1) The surface of the PET film (protective layer) was coated with a PEDOT/PSS resistive layer (thickness: 500 nm) using a bar coater No. 30 with a solid content of 1.3 wt%, and then dried in an oven set to 120°C for 1 minute. The first layered body.

Next, OC-3405, K-341, and toluene solvent were mixed and stirred so that the mass-based mixing ratio became 73:2:25 to obtain an acrylic adhesive with a solid content of 45%. Use the acrylic adhesive produced in this way, a release film (trade name "TN-100", manufactured by Toyobo), a gap filling tape (thickness: 300 μm), and an applicator (200 μm gap) to apply in the following manner. A caulk strip is provided between the release surface of the release film and the base surface of the applicator. By following this operation, the distance between the release surface of the release film and the knife part of the applicator during application will always be an average of 500 μm. The acrylic adhesive solution is dropped into the gap between the release surface of the release film and the applicator, and the applicator is scanned while applying the applicator with the base surface of the applicator in contact with the gap-filling tape. After drying in an oven for 2 minutes, drying in an oven set to 80°C for 2 minutes, and drying in an oven set to 120°C for 2 minutes to form a film, the layer was set to a lamination temperature of 60°C, a pressure of 0.4MPa, and a speed of 1m/min. A pressing device is used to bond the film forming surfaces to each other to obtain a dielectric layer.

After peeling off one isolation film of the dielectric layer obtained in this way, the PET film (reflective layer) was vapor-deposited with Al using a laminating device set to a lamination temperature of 40°C, a pressure of 0.4 MPa, and a speed of 1 m/min. The Al vapor-deposited surface was bonded, and after peeling off the other separator, it was bonded to the PEDOT/PSS of the first laminated body using a laminating device in the same manner. In addition, in the comparative example, the bonding surface of the dielectric layer and the reflective layer is the Al vapor deposition layer, but they may be bonded together such that PET serves as the bonding surface in the same manner as in the embodiment. Either situation will not affect the reliability test.

<Measurement of protective layer thickness> The thickness of the protective layer was measured in accordance with JIS B 7503:2011 using THICKNESS GAUG (manufactured by Mitsutoyo Co., Ltd.).

<Measurement of complex dielectric constant of protective layer> The complex dielectric constant of the protective layer was measured by the frequency variation method using a vector network analyzer (Keysight PNA N5222B 10MHz-43.5GHz, Virginia Diodes Inc, WR12 55-95GHz). The real part of the complex dielectric constant of the protective layer is 2.95 and the imaginary part is 0.003.

<Measurement of complex dielectric constant of dielectric layer> The complex dielectric constant of the dielectric layer is measured by the frequency variation method using a vector network analyzer (Keysight PNA N5222B 10MHz-26.5GHz, Virginia Diodes Inc, WR12 55-95GHz). The complex dielectric constants of the dielectric layers are shown in Table 1.

<Measurement of return loss characteristics> The return loss amount of the electromagnetic wave absorber obtained in each Example and Comparative Example was measured using the following apparatus. Vector network analyzer (Keysight PNA N5222B 10MHz-26.5GHz, Virginia Diodes Inc, WR12 55-95GHz) A high-frequency network analyzer (manufactured by Agilent Technology, E8362C) irradiates millimeter waves from an antenna that transmits signals to an electromagnetic wave absorber, measures the intensity of the millimeter waves that are reflected by the electromagnetic wave absorber and enters the antenna that receives signals, and calculates the loss. Amount (dB).

＜High temperature and high humidity test＞ The electromagnetic wave absorber obtained in each of the Examples and Comparative Examples was placed in the following apparatus, and was taken out after 1000 hours. After returning to room temperature, the sheet resistance and return loss characteristics were measured. Thermostat and humidistat (manufactured by ESPEC, RP-4J)

<Simulation of return loss characteristics> Regarding Examples A1 to A14, A16 to A18, A20, A22, and Comparative Examples A2 to A4, the return loss characteristics were derived through simulation, and the influence of the imaginary part of the complex dielectric constant of the dielectric layer on the return loss characteristics was evaluated. . The simulation soft system uses the theory and algorithm based on deriving the return loss characteristics of λ/4 type radio wave absorbers ("Introduction to Radio Wave Absorbers", Shu Hashimoto, Morikita Publishing, 1997, refer to pp. 58~62, 128~ 134 pages) built-in software. The simulation system sets the layer structure in order from the incident side of the electromagnetic wave to a protective layer, a resistance layer, a barrier adhesive layer, a barrier layer, an adhesive layer, a dielectric layer, an adhesive layer, and a reflective layer (support PET, Al evaporated layer ( Short circuit)), each layer is produced by the same method as the above-mentioned manufacturing method. According to this operation, the actual measurement results of the complex dielectric constant and thickness of the protective layer, the actual measurement results of the sheet resistance of the resistive layer, the thickness of the barrier layer and the actual measurement results, the thickness of the barrier layer and the actual measurement results, the thickness of the adhesive layer and the actual measurement results , the actual measurement results of the thickness and complex dielectric constant of the dielectric layer, the actual measurement results of the thickness and complex dielectric constant of the connecting layer, and the actual measurement results of the thickness and complex dielectric constant of the reflective layer are used as the set values. After conducting reliability tests at 85°C and 85%RH for 700h and 1000h, a structure without a reflective layer was prepared, and the actual measurement result of the sheet resistance of the resistive layer measured with a non-contact resistance meter was used as the set value.

<Characteristic evaluation> Regarding the Examples and Comparative Examples, the results of actual measurement and simulation evaluation of the return loss characteristics are shown in Table 1 and Figures 5 to 30. The return loss characteristics represent the frequency (GHz) and the maximum loss amount when the return loss amount reaches the maximum based on the values obtained when the electromagnetic wave absorber is first produced (initial stage) and after the reliability test (85°C 85%RH 700h and 1000h). (dB). [Table 1] Example/Comparative Example constitute Reflection attenuation characteristics resistive layer protective layer resistive layer Barrier bonding layer Barrier layer (PET/barrier layer) Next layer dielectric layer Next layer Reflective layer (PET/Al evaporated layer) Frequency(GHz) Maximum reflection attenuation (dB) 85℃85%RH thickness complex permittivity Chip resistor thickness Volume resistivity complex permittivity thickness complex permittivity thickness Next layer complex permittivity thickness complex permittivity thickness complex permittivity thickness Next layer complex permittivity thickness at maximum reflection Early stage sim/actual measurement 85℃85%RH sim/actual measurement 85℃85%RH sim/actual measurement Chip resistance (Ω/□) μm Ω/□ nm Ω・m μm μm joint surface μm μm μm joint surface μm Attenuation 700h 1000h 700h 1000h sim/actual measurement Example A1 50 2.95-0j 354 107 3.80E-05 3.1-0j 10 2.95-0j 12 barrier layer - - 9.3-0.74j 388.4 - - PET 2.95-0j 12 58.6 20 sim 17 sim 10 sim 810 1062 Actual measurement Example A2 ↑ ↑ 450 84 ↑ ↑ ↑ ↑ ↑ ↑ - - ↑ ↑ - - ↑ ↑ ↑ 58.8 53 ↑ 13 ↑ 8 ↑ 1013 1350 ↑ Example A3 ↑ ↑ 534 71 ↑ ↑ ↑ ↑ ↑ ↑ - - ↑ ↑ - - ↑ ↑ ↑ 59.0 twenty three ↑ 10 ↑ 8 ↑ 1100 1602 ↑ Example A4 ↑ ↑ 354 107 ↑ ↑ ↑ ↑ ↑ ↑ - - 9.3-1.45j ↑ - - ↑ ↑ ↑ 58.4 16 ↑ 20 ↑ 15 ↑ 810 1062 ↑ Example A5 ↑ ↑ 450 84 ↑ ↑ ↑ ↑ ↑ ↑ - - ↑ ↑ - - ↑ ↑ ↑ 58.7 twenty two ↑ 13 ↑ 13 ↑ 1013 1350 ↑ Example A6 ↑ ↑ 534 71 ↑ ↑ ↑ ↑ ↑ ↑ - - ↑ ↑ - - ↑ ↑ ↑ 58.9 34 ↑ 11 ↑ 12 ↑ 1100 1602 ↑ Example A7 ↑ ↑ 354 107 ↑ ↑ ↑ ↑ ↑ ↑ 2.95-0j 8 11.7-1.19j 754 2.95-0j 8 ↑ ↑ ↑ 28.6 17 ↑ 15 ↑ 13 ↑ 810 1062 ↑ Example A8 ↑ ↑ 450 84 ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ 28.2 26 ↑ 12 ↑ 11 ↑ 1013 1350 ↑ Example A9 ↑ ↑ 534 71 ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ 28.2 37 ↑ 11 ↑ 10 ↑ 1100 1602 ↑ Example A10 ↑ ↑ 354 480 1.70E-04 ↑ ↑ ↑ ↑ ↑ - - 9.3-0.74j 388.4 - - ↑ ↑ ↑ 58.6 20 ↑ 19 ↑ 35 ↑ 389 471 ↑ Example A11 ↑ ↑ 450 378 ↑ ↑ ↑ ↑ ↑ ↑ - - ↑ ↑ - - ↑ ↑ ↑ 58.8 53 ↑ 30 ↑ 19 ↑ 495 599 ↑ Example A12 ↑ ↑ 534 318 ↑ ↑ ↑ ↑ ↑ ↑ - - ↑ ↑ - - ↑ ↑ ↑ 59.0 twenty three ↑ 25 ↑ 15 ↑ 587 710 ↑ Example A13 ↑ ↑ 354 480 ↑ ↑ ↑ ↑ ↑ ↑ - - 9.3-1.45j ↑ - - ↑ ↑ ↑ 58.4 16 ↑ 15 ↑ twenty four ↑ 389 471 ↑ Example A14 ↑ ↑ 450 378 ↑ ↑ ↑ ↑ ↑ ↑ - - ↑ ↑ - - ↑ ↑ ↑ 58.7 twenty two ↑ twenty two ↑ 35 ↑ 495 599 ↑ Example A15 ↑ ↑ 539 318 ↑ ↑ ↑ ↑ ↑ ↑ - - ↑ ↑ - - ↑ ↑ ↑ 58.9 34 Actual measurement - - twenty three ↑ 593 710 ↑ Example A16 ↑ ↑ 555 318 ↑ ↑ ↑ ↑ ↑ ↑ - - ↑ ↑ - - ↑ ↑ ↑ 58.9 34 sim 40 sim twenty three ↑ 611 710 ↑ Example A17 ↑ ↑ 354 480 ↑ ↑ ↑ ↑ ↑ ↑ 2.95-0j 8 11.7-1.19j 754 2.95-0j 8 ↑ ↑ ↑ 28.6 17 ↑ 20 ↑ 30 ↑ 389 471 ↑ Example A18 ↑ ↑ 450 378 ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ 28.2 26 ↑ 34 ↑ 25 ↑ 495 599 ↑ Example A19 ↑ ↑ 534 318 ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ 28.2 37 Actual measurement - - 19 ↑ 587 710 ↑ Example A20 ↑ ↑ 534 318 ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ 28.2 37 sim 35 sim 19 ↑ 587 710 ↑ Example A21 ↑ ↑ 534 263 ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ 10.3-1.45j 263 ↑ ↑ ↑ ↑ ↑ 75.5 43 Actual measurement - - 20 Actual measurement 587 714 ↑ Example A22 ↑ ↑ 534 263 ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ 75.6 35 sim 38 sim twenty one sim 587 714 ↑ Comparative example A1 ↑ ↑ 354 107 3.80E-05 - - - - - - 3-0.01j 500 - - Al evaporated layer (↑) (↑) 79.3 36 Actual measurement 9 Actual measurement 6 ↑ 797 1062 ↑ Comparative example A2 ↑ ↑ 354 107 ↑ - - - - - - ↑ ↑ - - ↑ (↑) (↑) 80.1 32 sim 9 sim 6 ↑ 797 1062 ↑ Comparative example A3 ↑ ↑ 450 84 ↑ - - - - - - ↑ ↑ - - ↑ (↑) (↑) 80.1 20 ↑ 5 ↑ 5 ↑ 1013 1350 ↑ Comparative example A4 ↑ ↑ 534 71 ↑ - - - - - - ↑ ↑ - - ↑ (↑) (↑) 80.0 15 ↑ 5 ↑ 4 ↑ 1202 1602 ↑ ↑ means the same as above. In addition, (↑) indicates a numerical value that has no influence on the actual measurement or simulation of the reflection attenuation amount.

FIG. 5 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A1. Figure 5(a) shows the initial characteristics, and Figure 5(b) shows the characteristics of a person who performed a reliability test at 85°C and 85%RH for 1000 hours. Figures 6 to 26 relate to Examples A2 to A22, and are the same as Example A1, so description is omitted. In addition, FIG. 27 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Comparative Example A1. Figure 27(a) shows the initial characteristics, and Figure 27(b) shows the characteristics of a person who performed a reliability test at 85°C and 85%RH for 1000 hours. Figures 28 to 30 relate to Comparative Examples A2 to A4, and are the same as Comparative Example A1, so description will be omitted. It can be seen from the examples and comparative examples that for electromagnetic wave absorbers in which the imaginary part of the complex dielectric constant of the dielectric layer is 0.5 or more, the sheet resistance value increases even after a reliability test at 85°C and 85%RH for 700 hours. Under the circumstances, the return loss is still maintained at a good characteristic of more than 10dB. In addition, even when the reliability test was performed at 85°C and 85%RH for 1000 hours, most of the examples still showed good characteristics with a return loss of 10 dB or more.

[About first embodiment B] <Simulation of return loss characteristics> Regarding Examples B1 to B16 and Comparative Examples B1 to B3, the return loss characteristics were derived through simulation, and the influence of the imaginary part of the complex dielectric constant of the dielectric layer on the return loss characteristics was evaluated. The simulation soft system uses the theory and algorithm based on deriving the return loss characteristics of λ/4 type radio wave absorbers ("Introduction to Radio Wave Absorbers", Shu Hashimoto, Morikita Publishing, 1997, refer to pp. 58~62, 128~ 134 pages) built-in software. The simulation system sets the layer structure in order from the incident side of the electromagnetic wave to a protective layer, a resistance layer, a barrier adhesive layer, a barrier layer, an adhesive layer, a dielectric layer, an adhesive layer, and a reflective layer (support PET, Al evaporated layer ( short circuit)).

<Characteristics evaluation> Regarding the Examples and Comparative Examples, the thickness of each layer of the laminate constituting the electromagnetic wave absorber, the set values of the complex dielectric constant, the incident/reflection angle, and the simulation evaluation results of the return loss characteristics are shown in the table. 2. The return loss characteristics represent the frequency (GHz) and the maximum loss (dB) at which the return loss reaches the maximum using the values when the electromagnetic wave absorber is first produced (initial stage). [Table 2] Example/Comparative Example constitute Reflection attenuation characteristics protective layer resistive layer Barrier bonding layer barrier layer Next layer dielectric layer Next layer Reflective layer (support: PET) Incident/reflection angle Frequency(GHz) Maximum reflection attenuation (dB) thickness complex permittivity Chip resistor complex permittivity thickness complex permittivity thickness complex permittivity thickness complex permittivity thickness complex permittivity thickness complex permittivity thickness ° at maximum reflection Early stage sim/actual measurement μm Ω/□ μm μm μm real part imaginary part μm μm μm Attenuation Example B1 98 2.7-0j 600 3.1-0j 10 2.95-0j 12 2.95-0j 18 10 1.0 760 2.95-0j 18 2.95-0j 12 30 29.0 39.1 sim Example B2 ↑ ↑ 800 ↑ ↑ ↑ ↑ ↑ ↑ 10 1.0 760 ↑ ↑ ↑ ↑ 45 28.8 36.3 ↑ Example B3 ↑ ↑ 1500 ↑ ↑ ↑ ↑ ↑ ↑ 10 1.0 760 ↑ ↑ ↑ ↑ 62 28.8 46.2 ↑ Example B4 ↑ ↑ 2500 ↑ ↑ ↑ ↑ ↑ ↑ 10 1.0 760 ↑ ↑ ↑ ↑ 70 28.8 28.4 ↑ Example B5 ↑ ↑ 600 ↑ ↑ ↑ ↑ ↑ ↑ 10 1.5 760 ↑ ↑ ↑ ↑ 30 29.0 25.4 ↑ Example B6 ↑ ↑ 800 ↑ ↑ ↑ ↑ ↑ ↑ 10 1.5 760 ↑ ↑ ↑ ↑ 40 29.0 31.8 ↑ Example B7 ↑ ↑ 1500 ↑ ↑ ↑ ↑ ↑ ↑ 10 1.5 760 ↑ ↑ ↑ ↑ 55 28.8 39.8 ↑ Example B8 ↑ ↑ 2500 ↑ ↑ ↑ ↑ ↑ ↑ 10 1.5 760 ↑ ↑ ↑ ↑ 60 28.8 32.4 ↑ Example B9 ↑ ↑ 600 ↑ ↑ ↑ ↑ ↑ ↑ 15 1 640 ↑ ↑ ↑ ↑ 40 29.8 30.5 ↑ Example B10 ↑ ↑ 800 ↑ ↑ ↑ ↑ ↑ ↑ 15 1 640 ↑ ↑ ↑ ↑ 50 28.0 38.3 ↑ Example B11 ↑ ↑ 1500 ↑ ↑ ↑ ↑ ↑ ↑ 15 1 640 ↑ ↑ ↑ ↑ 65 27.8 34.7 ↑ Example B12 ↑ ↑ 2500 ↑ ↑ ↑ ↑ ↑ ↑ 15 0.5 640 ↑ ↑ ↑ ↑ 70 27.8 34.2 ↑ Example B13 ↑ ↑ 600 ↑ ↑ ↑ ↑ ↑ ↑ 15 1.5 640 ↑ ↑ ↑ ↑ 30 28.0 32.7 ↑ Example B14 ↑ ↑ 800 ↑ ↑ ↑ ↑ ↑ ↑ 15 1.5 640 ↑ ↑ ↑ ↑ 40 28.0 38.1 ↑ Example B15 ↑ ↑ 1500 ↑ ↑ ↑ ↑ ↑ ↑ 15 1.5 640 ↑ ↑ ↑ ↑ 60 28.0 29.9 ↑ Example B16 ↑ ↑ 2500 ↑ ↑ ↑ ↑ ↑ ↑ 15 1.5 640 ↑ ↑ ↑ ↑ 65 27.8 33.4 ↑ Comparative example B1 ↑ ↑ 500 ↑ ↑ ↑ ↑ ↑ ↑ 10 1 760 ↑ ↑ ↑ ↑ 30 28.8 24.6 ↑ Comparative example B2 ↑ ↑ 600 ↑ ↑ ↑ ↑ ↑ ↑ 2.5 1.5 760 ↑ ↑ ↑ ↑ 30 27.2 15.2 ↑ Comparative example B3 ↑ ↑ 3000 ↑ ↑ ↑ ↑ ↑ ↑ 15 1.5 640 ↑ ↑ ↑ ↑ 70 27.8 22.3 ↑ ↑ means the same as above.

FIG. 31 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example B1. 32 to 46 relate to Embodiments B2 to B16 and are the same as Embodiment B1, so the description will be omitted. In addition, FIG. 47 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Comparative Example B1. Figures 48 and 49 relate to Comparative Examples B2 and B3, and are the same as Comparative Example B1, so description is omitted. It can be seen from the examples and comparative examples that the real part of the complex dielectric constant of the dielectric layer is 10 or more and 15 or less, the imaginary part is 1.0 or more and 1.5 or less, and the sheet resistance range of the resistive layer is 600Ω/□ or more and 2500Ω/□ or less. The electromagnetic wave absorber has been found to have excellent characteristics such that the return loss of electromagnetic waves at an incident/reflection angle of 30° to 70° is 25dB or more.

The influence of the imaginary part of the complex dielectric constant of the dielectric layer on the return loss characteristics will be explained using the simulations of Embodiment B12 and Embodiment B16 as examples. FIG. 50 is a graph showing the relationship between the imaginary part of the complex dielectric constant of the dielectric layer and the amount of return loss. Figure 50(a) shows that when the horizontal axis is frequency and the vertical axis is incident/reflection angle, the sheet resistance of the resistive layer is 2500Ω/□, the real part of the complex dielectric constant of the dielectric layer is 15, and the imaginary part A graph showing the contours of the return loss of electromagnetic waves when the value is 0.5. FIG. 50(b) is a graph showing the same return loss characteristics when the imaginary part is set to 1.5. It was found that when the imaginary part increases, the height of the contour line of the return loss amount generally increases and the base tends to expand. That is, it is found that the return loss amount at a given incident angle/reflection angle generally increases, and the range of the incident angle/reflection angle at which a given return loss amount is obtained tends to expand substantially.

Furthermore, the inventor used specific numerical values obtained from the simulation results based on the embodiments and found that if the sheet resistance R of the resistive layer satisfies Equation 2, an electromagnetic wave absorber with a return loss of 25 dB or more can be obtained. Here, ε' is the imaginary part of the complex dielectric constant in the dielectric layer, and θ (°) is the incident angle/reflection angle.

＜Application examples＞ The electromagnetic wave absorbers 10, 20, 30, and 40 of the first to fourth embodiments can be applied to various articles. Specific examples of the articles include building decoration materials (for example, mirror decorative panels, floor sheets, and decorative films), and industrial materials (for example, road surface components, traffic guardrails, road signs, and soundproof walls). By applying the electromagnetic wave absorbers 10, 20, 30, and 40 of the first to fourth embodiments to building decoration materials, for example, high-speed wireless communications using electromagnetic waves such as 5G and 6G can be used in office buildings and condominiums. Even under such circumstances, the original communication speed of 5G and 6G can be maintained by achieving good return loss. Specifically, if it is a room having at least a part of the inner wall covered with the aforementioned building decoration materials including the electromagnetic wave absorbers 10, 20, 30, and 40 of the first embodiment A, and a transmitter arranged in the aforementioned room, If you install the communication stable room of the device, you can expect related effects. In addition, the same effect can be expected from a system including the communication stable room and a wireless communication device arranged in the communication stable room. Similarly, if it is a room having at least a part of the inner wall covered with the aforementioned building decoration material including the electromagnetic wave absorbers 10, 20, 30, 40 of the first embodiment B, and a transmitter arranged in the aforementioned room , and if the angle between the surface normal of the building decoration material and the electromagnetic wave incident from the transmitter is 30° to 60° in a stable communication room, the relevant effects can be expected. However, the surface of the building decoration material that receives the incident wave in the aforementioned angle range may be partially present. In addition, if it is a system including the communication stable room and the wireless communication device arranged in the communication stable room, the same effect can be expected, and at the same time, only direct waves can be received, and a stable system with a high S/N ratio can be constructed. . Furthermore, it is also possible to provide a communication stable space that can achieve a good return loss in the space formed by the communication stable room or the system. In addition, for example, by applying the electromagnetic wave absorbers 10, 20, 30, and 40 of the first to fifth embodiments to industrial materials, the scattering and noise of electromagnetic waves can be suppressed, which can contribute to improving the performance of autonomous driving. safety.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications and combinations of embodiments can be made without departing from the gist of the present invention.

The following describes items that can form the content of the present invention, but is not limited thereto. (Item 1) An electromagnetic wave absorber, which is a laminated body including a resistive layer, a dielectric layer, and a reflective layer in this order. The dielectric layer contains at least one dielectric compound and a resin component, and has a complex dielectric constant. The imaginary part is above 0.5. (Item 2) For example, the electromagnetic wave absorber of Item 1 has a return loss of more than 10dB after a reliability test at 85°C, 85%RH, and 700 hours. (Item 3) The electromagnetic wave absorber of Item 1 or 2, wherein the real part of the complex dielectric constant of the dielectric layer is 10 or more. (Item 4) The electromagnetic wave absorber according to any one of Items 1 to 3, wherein the sheet resistance of the resistive layer is 400Ω/□ or more and 1000Ω/□ or less. (Item 5) The electromagnetic wave absorber according to any one of Items 1 to 4, wherein the volume resistivity of the resistive layer is 8.0×10 ^-5 to 4.0×10 ^-3 Ω. m conductive polymer material. (Item 6) The electromagnetic wave absorber according to any one of Items 1 to 5, wherein the thickness of the resistive layer is 150 nm to 2000 nm. (Item 7) The electromagnetic wave absorber according to any one of Items 1 to 6, wherein the sheet resistance R (Ω/□) of the resistive layer, the real part ε' and the imaginary part of the complex dielectric constant of the dielectric layer ε'' is the relationship of Equation 1. (Item 8) An electromagnetic wave absorber according to any one of Items 1 to 7, in which the return loss after a reliability test at 85°C and 85%RH for 1000h is more than 10dB. (Item 9) The electromagnetic wave absorber according to any one of Items 1 to 8, wherein the real part of the complex dielectric constant of the dielectric layer is 10 to 15 and the imaginary part is 1.0 to 1.5, and the resistive layer is The resistance is 600Ω/□ or more and 2500Ω/□ or less, and the return loss of electromagnetic waves with a reflection angle θ of 30° to 70° is 25dB or more. (Item 10) The electromagnetic wave absorber of Item 9, wherein the sheet resistance R (Ω/□) of the resistive layer, the imaginary part ε'' of the complex dielectric constant of the dielectric layer, and the reflection angle θ (°) is the relationship of Equation 2. (Item 11) The electromagnetic wave absorber according to any one of Items 1 to 10, wherein the laminated body includes the resistance layer, the barrier bonding layer, the barrier layer, the dielectric layer, and the reflection layer in this order. (Item 12) The electromagnetic wave absorber of Item 11, wherein the laminated body includes the resistance layer, the barrier adhesive layer, the barrier layer, the adhesive layer, the dielectric layer, the adhesive layer, and the reflective layer in this order. (Item 13) A building decoration material equipped with the electromagnetic wave absorber according to any one of claims 1 to 12. (Item 14) A communication stable room including a room in which at least part of the inner wall is covered with the architectural decoration material of Item 13, and a transmitter arranged in the room. (Item 15) A system including the communication stable room according to Item 14, and a wireless communication device arranged in the communication stable room.

1:Resistance layer 2: Dielectric layer 3: Reflective layer 4: Protective layer 5: Barrier bonding layer 6: Barrier layer 7: Next layer 10,20,30,40: Electromagnetic wave absorber

FIG. 1 is a cross-sectional view schematically showing the reflective electromagnetic wave absorber according to the first embodiment. FIG. 2 is a cross-sectional view schematically showing a reflective electromagnetic wave absorber according to the second embodiment. FIG. 3 is a cross-sectional view schematically showing a reflective electromagnetic wave absorber according to the third embodiment. FIG. 4 is a cross-sectional view schematically showing a reflective electromagnetic wave absorber according to the fourth embodiment. FIG. 5 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A1. FIG. 6 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A2. FIG. 7 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A3. FIG. 8 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A4. FIG. 9 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A5. FIG. 10 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A6. FIG. 11 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A7. FIG. 12 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A8. FIG. 13 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A9. FIG. 14 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A10. FIG. 15 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A11. FIG. 16 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A12. FIG. 17 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A13. FIG. 18 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A14. FIG. 19 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A15. FIG. 20 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A16. FIG. 21 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A17. FIG. 22 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A18. FIG. 23 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A19. FIG. 24 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A20. FIG. 25 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A21. FIG. 26 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example A22. FIG. 27 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Comparative Example A1. FIG. 28 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Comparative Example A2. FIG. 29 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Comparative Example A3. FIG. 30 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Comparative Example A4. FIG. 31 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example B1. FIG. 32 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example B2. FIG. 33 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example B3. FIG. 34 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example B4. FIG. 35 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example B5. FIG. 36 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example B6. FIG. 37 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example B7. FIG. 38 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example B8. FIG. 39 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example B9. FIG. 40 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example B10. FIG. 41 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example B11. FIG. 42 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example B12. FIG. 43 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example B13. FIG. 44 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example B14. FIG. 45 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example B15. FIG. 46 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Example B16. FIG. 47 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Comparative Example B1. FIG. 48 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Comparative Example B2. FIG. 49 is a graph showing the return loss characteristics of the electromagnetic wave absorber of Comparative Example B3. FIG. 50 is a graph showing the relationship between the imaginary part of the complex dielectric constant of the dielectric layer and the amount of return loss.

without.

Claims (15)

An electromagnetic wave absorber, which is a laminate having a resistive layer, a dielectric layer, and a reflective layer in this order. The dielectric layer contains at least one dielectric compound and a resin component, and has a complex permittivity. The imaginary part is above 0.5. For example, the electromagnetic wave absorber in claim 1 has a return loss of more than 10dB after a reliability test at 85°C, 85%RH, and 700 hours. The electromagnetic wave absorber of claim 2, wherein the real part of the complex dielectric constant of the dielectric layer is 10 or more. For example, the electromagnetic wave absorber of claim 2 or 3, wherein the sheet resistance of the resistive layer is 400Ω/□ or more and 1000Ω/□ or less. For the electromagnetic wave absorber of claim 2 or 3, the volume resistivity of the resistive layer is 8.0×10 ^-5 ~ 4.0×10 ^-3 Ω. m conductive polymer material. The electromagnetic wave absorber of claim 2 or 3, wherein the thickness of the resistive layer is 150nm~2000nm. The electromagnetic wave absorber of claim 2 or 3, wherein the sheet resistance R (Ω/□) of the resistive layer, the real part ε' and the imaginary part ε'' of the complex dielectric constant of the dielectric layer are expressed by Equation 1 relation, . For example, the electromagnetic wave absorber of claim 2 has a return loss of more than 10dB after a reliability test at 85°C and 85%RH for 1000h. The electromagnetic wave absorber of claim 1, wherein the real part of the complex dielectric constant of the dielectric layer is 10 or more and 15 or less, the imaginary part is 1.0 or more and 1.5 or less, and the sheet resistance of the resistive layer is 600Ω/□ or more and 2500Ω/□ Hereinafter, the return loss of electromagnetic waves with a reflection angle θ of 30° to 70° is 25dB or more. The electromagnetic wave absorber of claim 9, wherein the sheet resistance R (Ω/□) of the resistive layer, the imaginary part ε'' of the complex dielectric constant of the dielectric layer, and the reflection angle θ (°) are expressed by Equation 2 relationship, . The electromagnetic wave absorber of claim 2 or 9, wherein the laminated body includes the resistive layer, the barrier bonding layer, the barrier layer, the dielectric layer, and the reflective layer in this order. The electromagnetic wave absorber of claim 11, wherein the laminated body includes the resistive layer, the barrier adhesive layer, the barrier layer, the adhesive layer, the dielectric layer, the adhesive layer, and the reflective layer in this order. A building decoration material, which is provided with the electromagnetic wave absorber according to any one of claims 1 to 3 and 8 to 10. A communication stable room including a room in which at least a part of the inner wall is covered with the architectural decoration material according to claim 13, and a transmitter arranged in the room. A system provided with the communication stable room according to claim 14, and a wireless communication device arranged in the communication stable room.