JP2007027655A - Radio wave absorber and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio wave absorber from which a sufficient dielectric loss of a high frequency radio wave, in particular 2 to 80 GHz can stably be obtained, which has excellent workability, can easily be formed to an excellent complicated shape, has a light weight and excellent attention to environment, can be suitably used for housings of electronic apparatuses or the like, can be easily manufactured, has high versatility, and can be suitable for industrial manufacturing. <P>SOLUTION: The radio wave absorber has at least one layer containing a thermosetting resin component and a carbon component, the carbon component included in the layer has an average particle diameter of 15 μm or below, the thermosetting resin component has a viscosity of 100 Pa s or below as a raw material in blending of the carbon component, the d002 by X rays of the carbon component is 0.3360 nm or over and 0.3380 nm or below and the crystal size in the axis "a" direction is 20 nm or over. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radio wave absorber, and more particularly to a radio wave absorber that absorbs radio waves having a frequency of 2 to 80 GHz and a method for manufacturing the same.

  In recent years, with the rapid development of IT society, high-speed processing of electronic devices has progressed, and the operating frequency of ICs such as LSIs and microprocessors has increased. In the communication field, high-speed communication networks using optical fibers have been used, and the next generation 2GHz for multimedia mobile communications, 5.8GHz for ETS (Intelligent Transport System) in the field of ITS (Intelligent Transport System), and a driving support road system (AHS) that measures the distance between vehicles and communicates it to the driver In-car radar uses 76 GHz radio waves, and it is expected that the range of high-frequency usage will be further expanded in the future. Radio waves tend to emit noise as the frequency increases. On the other hand, malfunctions occur due to deterioration of the noise environment inside electronic devices due to downsizing and increasing the density of electronic devices. Negative effects are also a problem.

  Such electromagnetic wave blocking materials include an electromagnetic wave blocking body and an electromagnetic wave absorbing body. Generally, a metal material is used for the electromagnetic wave blocking body. For example, in a room where precision equipment that hates electromagnetic waves is installed, A metal plate is used to prevent electromagnetic waves from entering the room. Also, in electronic devices, electromagnetic waves are blocked by using a plastic casing formed by conducting a conductive treatment on the surface or mixing a conductive material into a resin from the viewpoint of freedom of shape and weight reduction.

  In addition, as an electromagnetic wave absorber, a ferrite plate is used, a metal plate is provided with a resistance film made of a conductive loss material having a free space wave impedance value via an insulator, and is backed by a metal plate. There is a material provided with a dielectric loss material or a magnetic loss material. In such an electromagnetic wave absorber, in theory, the electromagnetic wave is partially reflected on the surface of the electromagnetic wave absorber, and the electromagnetic wave entering the absorber is reflected on the metal surface, and this reflected electromagnetic wave is reflected on the surface of the absorber, that is, A part is emitted to the outside at the interface between the absorber and free space, and is reflected again into the absorber. While this reflection is repeated and multiple reflections are made inside, the electromagnetic wave energy is converted into thermal energy, and the electromagnetic wave loses its energy. On the other hand, the electromagnetic wave reflected on the surface of the electromagnetic wave absorber is entered into the absorber and reflected on the surface of the metal surface by setting the thickness of the absorber to a thickness corresponding to λ / 4 of the wavelength of the electromagnetic wave. Reflected electromagnetic waves cause mutual interference with electromagnetic waves that have been partially released from the absorber surface to the outside, and the total energy density of electromagnetic waves reflected from the absorber surface and electromagnetic waves emitted from the inside of the absorber is viewed from free space. 0. As described above, in the electromagnetic wave absorber, the electromagnetic wave can theoretically be subjected to multiple reflection inside the electromagnetic wave absorber, and the energy of the electromagnetic wave can be extinguished by mutual interference of the reflected electromagnetic waves.

  Examples of the dielectric loss material or magnetic loss material used in such an electromagnetic wave absorber include an electromagnetic wave shielding coating material (Patent Document 1) in which graphite powder is mixed in a urethane resin coating material, and at least one of electrostatic interference and electromagnetic interference. A composition capable of forming a conductive protective film on a coating object to be protected from, comprising conductive fine particles and a resin as a binder, wherein the conductive fine particles are metal, metal oxide and carbon Static particles using a conductive resin composition which is a fine particle of one or more materials selected from the group of materials and in which the binder resin can be dissolved and removed with a solvent after the formation of the conductive protective film. A method of protecting against electric interference and electromagnetic interference (Patent Document 2) and a fiber sheet containing synthetic fibers containing conductive powder such as carbon black powder in a layered manner and heat-sealed to each other for radio waves absorption The main component is a radio wave absorber (Patent Document 3) formed with a metal, a radio wave absorber molded body in which a conductive material such as carbon black and an inorganic hollow body powder are bonded with an inorganic adhesive, and sepiolite bonded thereto. An electromagnetic wave absorber (Patent Document 4) provided with a non-combustible sheet or an inorganic coating agent layer made from the above slurry has been reported. In addition, a radio wave absorber (Patent Document 5) in which expanded graphite having an average particle size of 100 to 400 μm is dispersed in a material exhibiting rubber elasticity, or a binder containing no solvent is used. An electromagnetic wave absorber (Patent Document 6) in which expanded graphite having a particle size of 100 to 400 μm is dispersed is known.

  In these radio wave absorbers, those containing a fibrous conductive material have a problem that fibers mixed with the resin are bent or cut, and a uniform dielectric loss cannot be obtained. In addition, as a dielectric loss material or a magnetic loss material, there is room for improvement in terms of weight reduction, environmental impact, and the like, in which a resin or a metal and carbon black or the like is contained in the resin.

In addition, when the resin contains a carbon component such as carbon black or graphite, there is a problem that sufficient dielectric loss cannot be obtained as compared with a resin containing a metal. In order to increase the carbon component content until a sufficient dielectric loss is obtained, if a large amount of the carbon component is added to the resin, the viscosity becomes high and kneading becomes difficult and cannot be easily produced. A radio wave absorber that is easy to manufacture, suitable for industrial manufacture, and capable of stably obtaining a sufficient dielectric loss has not been obtained. In particular, in ETS (automatic toll collection system), it is required to suppress malfunction caused by reflected radio waves with high accuracy, and in particular, sufficient dielectric loss can be stably obtained with respect to high frequencies, and manufacturing is easy. Radio wave absorbers are desired.
JP-A-62-111499 JP 2001-234075 A JP 2004-247720 A JP 2000-82892 A JP 2004-39798 A JP 2004-63578 A

  An object of the present invention is to stably obtain a sufficient dielectric loss with respect to a high frequency, can be easily formed into a complicated shape with excellent workability, is lightweight, excellent in environment, and electronic equipment. Can be suitably used for housings, etc., and sufficient dielectric loss can be stably obtained for radio waves, particularly high frequencies such as 2 to 80 GHz, and is easy to manufacture and highly versatile for industrial manufacture. The object is to provide a suitable electromagnetic wave absorber.

  When a carbon component is used as the conductive material of the radio wave absorber, in the process of kneading the carbon component with the resin component, if the amount of the carbon component added / mixed to the resin component becomes large, the viscosity becomes high, such as shearing force and resin viscosity. Due to the difference in the kneading conditions, the mixed state of the carbon components in the obtained mixture becomes unstable. As a result, the radio wave absorber has changed, and a radio wave absorber capable of obtaining a stable dielectric loss cannot be manufactured. As a result of intensive studies by the inventors, when a thermosetting resin is selected as the resin component, an increase in viscosity at the time of mixing the carbon component and the resin component can be suppressed, and the particle size of the carbon component is 15 μm or less. It has been found that even if it is as small as this, the increase in viscosity of the thermosetting resin component raw material is suppressed, and it is possible to avoid the difficulty of mixing them. If the viscosity of the thermosetting resin component raw material is 100 Pa · s or less when the carbon component is mixed, it is cured even if the mixing conditions such as shearing force and viscosity of the thermosetting resin component raw material are different. It has been found that instability of dielectric loss generated in the thermosetting resin component is suppressed. As long as the average particle diameter of the carbon component is 15 μm or less and the viscosity of the thermosetting resin raw material when the carbon component is mixed with the thermosetting resin component raw material satisfies the condition of 100 Pa · s or less, Even if the mixing conditions such as the viscosity of the curable resin component raw materials are different, the cured thermosetting resin has a sufficiently uniform dielectric loss, and thus a sufficient dielectric loss can be stably obtained in the radio wave absorber. As a result, the present invention has been obtained.

  That is, the present invention is a radio wave absorber having at least one layer containing a thermosetting resin and a carbon component, wherein the carbon component contained in the layer has an average particle diameter of 15 μm or less, The electromagnetic wave absorber is characterized in that the curable resin has a viscosity of 100 Pa · s or less as a raw material when the carbon component is mixed. Preferably, the carbon component has an X-ray d002 of 0.3360 nm or more and 0.3. 3380 nm or less, the crystal size in the a-axis direction is 20 nm or more, the layer contains a carbon component in a range of 15 mass% or less, and the layer gradually reduces the carbon component toward the open surface. And the layer has a thickness of 0.01 to 1 times the wavelength of the absorbed radio wave, and the frequency of the radio wave to be absorbed is 2 to 80 GHz, particularly 5.8 GHz. But Masui.

  The method for producing a radio wave absorber according to the present invention, when producing a radio wave absorber containing a thermosetting resin and a carbon component, has a carbon component having an average particle diameter of 15 μm or less and a viscosity of 100 Pa · s or less. And a thermosetting resin raw material is mixed to cure the thermosetting resin raw material. Preferably, as a carbon component, X-ray d002 is 0.3360 nm or more. It is 0.3380 nm or less and the crystal size in the a-axis direction is 20 nm or more, and the radio wave absorber contains a carbon component in a range of 15 mass% or less.

  The radio wave absorber of the present invention can stably obtain a sufficient dielectric loss with respect to high frequency, can be easily molded into a complicated shape with excellent workability, is lightweight, and is environmentally friendly. Preferably, it has high mechanical strength and can be suitably used for electronic equipment casings, etc., easy to manufacture, highly versatile and suitable for industrial manufacturing, especially with sufficient dielectric loss for high frequencies of 2 to 80 GHz Can be obtained stably.

  The radio wave absorber of the present invention is a radio wave absorber having at least one layer containing a thermosetting resin and a carbon component, and the carbon component contained in the layer has an average particle diameter of 15 μm or less. The thermosetting resin is not particularly limited as long as it has a viscosity of 100 Pa · s or less as a raw material at the time of mixing the carbon components.

  Examples of the thermosetting resin used in the radio wave absorber of the present invention include almost all thermosetting resins that are generally known, regardless of homopolymer or copolymer. Specifically, phenol resin, xylene resin, urea resin, melamine resin, unsaturated polyester resin, vinyl ester resin, epoxy resin, silicone resin, diallyl phthalate resin, furan resin, aniline resin, acetone-formaldehyde resin, alkyd resin, etc. The thermosetting resin applied to the radio wave absorber of the present invention is not limited to these, and may be a combination of two or more of these.

  The thermosetting resin has a viscosity of 100 Pa · s or less as a thermosetting resin raw material at the time of mixing a carbon component described later. In the present invention, the thermosetting resin raw material for mixing the carbon component contains a low-condensate / low-polymer or monomer of a thermosetting resin, a solvent / dispersion medium for dissolving / dispersing these, and a viscosity. May be adjusted. When the viscosity of the thermosetting resin raw material in which the carbon component is mixed is 100 Pa · s or less, the carbon component can be easily mixed. The said effect can be acquired more notably that the viscosity of a thermosetting resin raw material is 50 Pa * s or less, and also 30 Pa * s or less.

  The carbon component used in the radio wave absorber of the present invention has an average particle size of 15 μm or less, preferably 10 μm or less, more preferably 5 μm or less. If the average particle diameter of the carbon component is 15 μm or less, the amount of carbon component used can be reduced, and a stable dielectric loss can be obtained with a small amount of use in the radio wave absorber. If the average particle size is 10 μm or less, and further 5 μm or less, the above effect can be obtained more remarkably.

  As such a carbon component, it is preferable to use graphite having high conductivity and high versatility. Specifically, it is preferable that the following properties are satisfied by X-ray crystal structure analysis. That is, it is preferable that d002 of X-rays is 0.3360 nm or more and 0.3380 nm or less, and the crystal size in the a-axis direction is 20 nm or more. More preferably, the X-ray d002 is 0.3360 nm or more and 0.3370 nm or less, and the crystal size in the a-axis direction is 50 nm or more. By using such carbon, it is possible to obtain a sufficient dielectric loss for a high frequency of 2 to 80 GHz in the radio wave absorber.

  The radio wave absorber of the present invention has at least one layer containing the thermosetting resin and the carbon component. Content of the carbon component in a layer is 15 mass% or less, Preferably it is 10 mass% or less. If the content of the carbon component in the layer is 15% by mass or less, the viscosity does not increase during the production of the layer, the carbon component can be easily mixed, and sufficient dielectric loss can be obtained in the radio wave absorber. Obtainable. If the carbon component content is 10% by mass or less, this effect can be obtained more remarkably.

  Moreover, it is preferable to contain the carbon component in the layer so as to gradually decrease toward the open surface. As the carbon component gradually decreases toward the surface, stable radio wave absorption is performed in the radio wave absorber.

  In addition to the above components, the layer may contain, for example, a curing agent, a stabilizer, a lubricant, a mold release agent, a plasticizer, and the like as long as the functions of these components are not impaired.

  The molded article of the radio wave absorber according to the present invention may have at least one layer as described above, and may have a plurality of layers as a multilayer structure. The thickness of the layer is preferably 0.01 times or more the wavelength of the radio wave to be absorbed because the radio wave absorption performance can be maintained. More preferably, the thickness of the radio wave absorber is 0.02 or more, more preferably 0.03 or more, the wavelength of the target radio wave. With such a thickness, the above effect can be obtained more remarkably. it can. Further, if the thickness is less than 1 times the wavelength of the radio wave to be absorbed, it is lightweight and easy to handle. The thickness of the layer is more preferably 0.8 times or less, and even more preferably 0.5 times or less, with respect to the wavelength of the radio wave to be absorbed. Remarkably can be obtained. Specific examples of the layer thickness include 0.03 mm to 15 cm.

  Such a layer is preferably lined with metal. Any metal may be used, but for example, a metal plate such as iron, nickel, aluminum, zinc, and stainless steel is preferable. The thickness of the metal used for the radio wave absorber may be any thickness, for example, 50 μm to 1 mm.

  The shape of the radio wave absorber of the present invention may be any shape such as an injection molded product, a sheet, a film, a deformed product, a thermoformed product, and a fiber, and can be applied to a casing of an electronic device. It can also be in the form of a sheet such as a plate, sheet, or film.

  In the radio wave absorber of the present invention, the frequency of radio waves to be absorbed can be adjusted by controlling the material of the radio wave absorber, that is, the complex dielectric constant, the thickness, and the layer structure of the material, The frequency of radio waves to be absorbed to which the radio wave absorber of the present invention is applied is preferably 2 to 80 GHz, and particularly preferably 2 to 10 GHz.

  The manufacturing method of the electromagnetic wave absorber of this invention is demonstrated.

  The method for producing a radio wave absorber according to the present invention includes a carbon component having an average particle diameter of 15 μm or less and a heat having a viscosity of 100 Pa · s or less when producing a radio wave absorber containing a thermosetting resin and a carbon component. If it is the method of hardening a thermosetting resin raw material after mixing with a curable resin raw material, it will not restrict | limit in particular. The carbon component used in the method for producing the radio wave absorber of the present invention is as described above, and the thermosetting resin is a low-condensate / low-polymer of a thermosetting resin, or a monomer, It may contain a solvent / dispersion medium to be dispersed and its viscosity adjusted. These mixings can be performed using a mixer equipped with a general stirrer in which a predetermined amount of a carbon component is blended with the thermosetting resin raw material. The mixing temperature should just be the temperature below the curing temperature of resin, and mixing time can also be performed for desired time, such as 1 minute-1 day. A shearing force for mixing, that is, a shearing amount and a shearing speed can be appropriately selected because the dielectric loss of the radio wave absorber does not become unstable due to the difference.

  After mixing the carbon component and the thermosetting resin raw material, the thermosetting resin raw material is cured and molded. Curing / molding can be carried out by ordinary methods, for example, compression molding, laminate molding, transfer molding, injection molding, low pressure molding, cast molding, etc., and can be obtained by these curing / molding methods. Examples of the radio wave absorber of the present invention include molded articles such as injection molded articles, sheets, films, deformed articles, thermoformed bodies, foamed bodies, and fibers.

  The radio wave absorber of the present invention obtained by such a production method can have a stable dielectric loss in a mixture obtained even if the mixing conditions of the carbon component and the thermosetting resin raw material are different. It is an excellent absorber of 80 GHz radio waves.

Hereinafter, the present invention will be described in more detail with reference to examples.
Various physical properties are measured by the following methods.
(1) Average particle diameter It measured using the Malvern company laser diffraction type particle size distribution analyzer (master sizer). The measurement method and conditions were the standard conditions recommended by Malvern. That is, a sample of a micropartite was dispersed in a small amount of water using a surfactant, charged into the apparatus, and further dispersed by applying ultrasonic waves for 60 seconds while circulating. Thereafter, the ultrasonic irradiation was stopped and measurement was performed to obtain the particle size distribution, and the median value (d ₅₀ ) was taken as the measured value.
(2) X-ray diffraction of graphite Using an X-ray diffraction measurement device, measurement and data processing are performed in accordance with the “Measuring Method of Lattice Constants and Crystallite Size of Artificial Graphite” established by the 117th Committee of the Japan Society for the Promotion of Science. The interplanar spacing d002 and the crystal size La011 were determined.
(3) Dielectric constant A sample having a thickness of 2 to 3 mm is prepared, and a standing wave when a waveguide is made of metal at 5.8 GHz using a rectangular waveguide (47.55 mm × 22.15 mm). The complex dielectric constant was calculated from the ratio of the electric field strength between the node and the antinode, the position of the node, and the ratio of the electric field strength between the node and the antinode of the standing wave when the data was placed in front of the metal plate. Details of the measurement were according to “Material Constant Measurement Method” (p. 45-65, Osamu Hashimoto, Morikita Publishing (2003)).
(4) Radio wave absorption rate Measurement was performed at 1 to 18 GHz using a “lens antenna type oblique incidence type radio wave absorber (radio wave absorbing material) / reflection attenuation measuring device” manufactured by Keycom.
(Preparation of carbon)
[Carbon 1]
10 kg of petroleum coke was pulverized in a dry manner for 4 hours using a ball mill BM50 manufactured by Oshima Tekko Co., Ltd. and then heat treated at 2500 ° C. for 2 hours to obtain carbon particles having an average particle diameter of 10 μm. As a result of X-ray diffraction, the interplanar spacing d002 was 0.3375 nm, and the crystal size in the a-axis direction was 30 nm.
[Carbon 2]
After 10 kg of petroleum coke was pulverized in a dry system for 8 hours using a ball mill BM50 manufactured by Oshima Iron Works, heat treatment was performed at 2800 ° C. for 2 hours to obtain carbon particles having an average particle diameter of 5 μm. As a result of X-ray diffraction, the interplanar spacing d002 was 0.3361 nm and the crystal size in the a-axis direction was 110 nm.
[Carbon 3]
10 kg of petroleum coke was pulverized for 20 minutes in a dry manner using a ball mill BM50 manufactured by Oshima Tekko, and then heat-treated at 2800 ° C. for 2 hours to obtain carbon particles having an average particle size of 30 μm. As a result of X-ray diffraction, the interplanar spacing d002 was 0.3361 nm, and the crystal size in the a-axis direction was 110 nm.
[Carbon 4]
After 10 kg of petroleum coke was dry pulverized for 4 hours using a ball mill BM50 manufactured by Oshima Iron Works, carbon particles having an average particle size of 10 μm were obtained by heat treatment at 1900 ° C. for 2 hours. As a result of X-ray diffraction, the interplanar spacing d002 was 0.3420 nm, and the crystal size in the a-axis direction was 15 nm.
[Example 1]
200 g of the curing agent EPICLON EXB-353 manufactured by the same company was mixed with 1000 g of the epoxy resin EPICLON TSR-960 made by Dainippon Ink to obtain a composition having a viscosity of 89 Pa · s at 25 ° C. This was mixed with 150 g of the above carbon 1 and stirred at 25 ° C. for 10 minutes to obtain a uniform carbon-containing composition. This was poured into a horizontal Teflon frame and cured at 80 ° C. for 10 hours and further at 120 ° C. for 1 hour to obtain a sheet of 30 cm × 30 cm and a thickness of 3.5 mm. The dielectric constant of this sheet was measured. In addition, an aluminum plate having a thickness of 1 mm was disposed on the back surface, and the radio wave absorption performance was measured. Furthermore, using the same material, the stirring after carbon mixing was extended to 1 hour in the same manner, and the dielectric constant and radio wave absorption rate were measured. The dielectric constant measurement results are shown in Table 1, and the radio wave absorption measurement results are shown in FIG.

[Example 2]
Asahi Denka Epoxy Resin (Adeka Resin EP-4010S) 1000 g was mixed with 150 g of the curing agent EH-455 manufactured by the same company at room temperature to obtain a composition having a viscosity of 42 Pa · s at 25 ° C. 90 g of the above carbon 2 was mixed with this and stirred at 25 ° C. for 50 minutes to obtain a uniform carbon-containing composition. This was poured into a horizontal Teflon frame and cured at 80 ° C. for 10 hours and further at 120 ° C. for 1 hour to obtain a sheet of 30 cm × 30 cm and a thickness of 4.0 mm. The dielectric constant of this sheet was measured. In addition, an aluminum plate having a thickness of 1 mm was disposed on the back surface, and the radio wave absorption performance was measured. Furthermore, using the same material, the stirring after carbon mixing was extended to 1 hour in the same manner, and the dielectric constant and radio wave absorption rate were measured. The measurement results of the dielectric constant are shown in Table 2, and the radio wave absorption measurement results are shown in FIG.

[Example 3]
120 g of the above carbon 3 was mixed with 1000 g of Dainippon Ink Phenol Resin 1196 (viscosity 11 Pa · s at 25 ° C.) and stirred at 25 ° C. for 10 minutes to obtain a uniform carbon-containing composition. This was poured into a horizontal Teflon frame and cured at 80 ° C. for 10 hours and further at 160 ° C. for 1 hour to obtain a sheet of 30 cm × 30 cm and a thickness of 3.7 mm. The dielectric constant of this sheet was measured. In addition, an aluminum plate having a thickness of 1 mm was disposed on the back surface, and the radio wave absorption performance was measured. Furthermore, using the same material, the stirring after carbon mixing was extended to 1 hour in the same manner, and the dielectric constant and radio wave absorption rate were measured. The measurement results of the dielectric constant are shown in Table 3, and the radio wave absorption measurement results are shown in FIG.

[Comparative Example 1]
A radio wave absorber was prepared in the same manner as in Example 2 except that carbon 4 was used instead of carbon 2 as carbon to be used, and dielectric constant and radio wave absorption were measured. The dielectric constant measurement results are shown in Table 4, and the radio wave absorption measurement results are shown in FIG.

From the results, it was found that the radio wave absorber of Comparative Example 1 did not have radio wave absorption performance.
[Comparative Example 2]
A radio wave absorber was prepared in the same manner as in Example 1 except that the amount of carbon 1 used was 350 g, and the dielectric constant and radio wave absorption were measured. The measurement results of the dielectric constant are shown in Table 5, and the radio wave absorption measurement results are shown in FIG.

From the results, it was found that the radio wave absorber of Comparative Example 2 did not have radio wave absorption performance.
[Comparative Example 3]
After mixing the resin and the curing agent, stirring was performed at 30 ° C., and a radio wave absorber was prepared in the same manner as in Example 1 except that carbon was added after the composition viscosity reached 200 Pa · s. Radio wave absorption was measured. Table 6 shows the dielectric constant measurement results, and FIG. 6 shows the radio wave absorption measurement results.

From the results, it was found that the radio wave absorber of Comparative Example 3 had unstable radio wave absorption performance.

It is a figure which shows the electromagnetic wave absorption factor of Example 1 of the electromagnetic wave absorber of this invention. It is a figure which shows the electromagnetic wave absorption factor of Example 2 of the electromagnetic wave absorber of this invention. It is a figure which shows the electromagnetic wave absorptivity of Example 3 of the electromagnetic wave absorber of this invention. It is a figure which shows the electromagnetic wave absorption factor of the comparative example 1 of an electromagnetic wave absorber. It is a figure which shows the electromagnetic wave absorption factor of the comparative example 2 of an electromagnetic wave absorber. It is a figure which shows the electromagnetic wave absorption factor of the comparative example 3 of an electromagnetic wave absorber.

Claims (10)

  A radio wave absorber having at least one layer containing a thermosetting resin and a carbon component, wherein the carbon component contained in the layer has an average particle diameter of 15 μm or less, and the thermosetting resin is carbon A radio wave absorber characterized by having a viscosity of 100 Pa · s or less as a raw material when mixing components.   2. The radio wave absorber according to claim 1, wherein the carbon component has an x-ray d002 of 0.3360 nm or more and 0.3380 nm or less and a crystal size in the a-axis direction of 20 nm or more.   The radio wave absorber according to claim 1 or 2, wherein the layer contains a carbon component in a range of 15 mass% or less.   The radio wave absorber according to any one of claims 1 to 3, wherein the layer contains a carbon component so as to gradually decrease toward the open surface.   The radio wave absorber according to any one of claims 1 to 4, wherein the layer has a thickness of 0.01 to 1 times the wavelength of the absorbed radio wave.   The radio wave absorber according to any one of claims 1 to 5, wherein the frequency of the radio wave to be absorbed is 2 to 80 GHz.   The radio wave absorber according to claim 6, wherein the frequency of the radio wave to be absorbed is 5.8 GHz.   When producing a radio wave absorber containing a thermosetting resin and a carbon component, a carbon component having an average particle size of 15 μm or less and a thermosetting resin raw material having a viscosity of 100 Pa · s or less are mixed and thermoset. A method for manufacturing a radio wave absorber, comprising curing a resin material.   9. The radio wave absorber according to claim 8, wherein a carbon component having an x-ray d002 of 0.3360 nm or more and 0.3380 nm or less and a crystal size in the a-axis direction of 20 nm or more is used. Manufacturing method.   The method for producing a radio wave absorber according to claim 8 or 9, wherein the radio wave absorber contains a carbon component in a range of 15 mass% or less.

Images