WO2007108478A1

WO2007108478A1 - Electromagnetic wave absorbing device and method for controlling electromagnetic wave absorption

Info

Publication number: WO2007108478A1
Application number: PCT/JP2007/055713
Authority: WO
Inventors: Seiji Akita; Yukihiro Fujiyama; Kenichiro Tanaka; Toshikazu Nosaka; Ryota Tomokane; Yoshikazu Nakayama
Original assignee: Osaka Prefectural Government; Osaka Industrial Promotion Organization; Public University Corporation Osaka Prefecture University
Priority date: 2006-03-20
Filing date: 2007-03-20
Publication date: 2007-09-27
Also published as: JPWO2007108478A1; JP5177425B2

Abstract

Disclosed is an electromagnetic wave absorbing device wherein the absorption wavelength range and absorption amount can be varied. This electromagnetic wave absorbing device is characterized in that the space between electrodes is filled with a fluid which contains a conductive carbon having a high aspect ratio. Also disclosed is a method for controlling electromagnetic wave absorption, namely a method for controlling the wavelength range of electromagnetic wave transmitted through the electromagnetic wave absorbing device and/or the absorption amount of electromagnetic wave. This method is characterized in that an electric field is applied between electrodes of the electromagnetic wave absorbing device where a fluid containing a conductive carbon having a high aspect ratio is filled, thereby orienting the conductive carbon in a direction.

Description

Specification

Electromagnetic wave absorber and absorbed electromagnetic wave control method

Technical field

[0001] The present invention relates to a novel electromagnetic wave absorbing device and an absorbed electromagnetic wave controlling method.

Background art

[0002] In recent years, various types of electromagnetic wave absorbing sheets that absorb electromagnetic waves corresponding to each have been provided due to the increase and diversification of communication devices such as mobile phones (Patent Document 1 and the like).

[0003] For example, Patent Document 1 provides a sheet of dielectric loss material containing a specific amount of microcoiled carbon fibers having a specific fiber length.

[0004] However, conventional electromagnetic wave absorbers including the electromagnetic wave absorbing sheet of Patent Document 1 described above have a fixed wavelength range and absorption amount that are fixed in advance. The wavelength range and the amount of absorption cannot be changed. Therefore, there is a problem that when the wavelength range or the like to be absorbed changes, the wavelength range cannot be handled.

[0005] Therefore, it is desired to develop an apparatus capable of controlling the wavelength range and / or absorption amount of electromagnetic waves after manufacture or after installation.

Patent Document 1: Japanese Patent Laid-Open No. 2001-77583

Disclosure of the invention

Problems to be solved by the invention

The main object of the present invention is to provide an apparatus capable of changing the absorption wavelength range and / or absorption amount of electromagnetic waves, and a control method therefor.

Means for solving the problem

[0007] As a result of intensive studies in view of the above prior art, the present inventors have completed the present invention by using an apparatus having a specific structure. That is, the present invention relates to the following apparatus and control method.

[0008] Item 1. An electromagnetic wave absorbing device having a variable absorption wavelength region and / or an absorption amount, wherein a fluid containing conductive carbon having a high aspect ratio is filled between electrodes.

[0009] Item 2. The electromagnetic wave absorption according to Item 1, wherein the conductive carbon has an aspect ratio of 2 or more. Collection device.

[0010] Item 3. The electromagnetic wave absorber according to Item 1 or 2, wherein the conductive carbon is at least one selected from the group consisting of carbon nanocoils, carbon nanotubes, carbon nanofibers, and carbon nanotwists.

[0011] Item 4. The electromagnetic wave absorber according to any of the above items:! To 3, wherein the conductive carbon content is 0.00: to 50 parts by weight with respect to 100 parts by weight of the fluid.

[0012] Item 5. The viscosity of the fluid is:! ~ 100,000cPs (25 ° C)

An electromagnetic wave absorber as described above.

[0013] Item 6. A method for controlling the wavelength range and / or amount of absorption of electromagnetic waves that pass through an electromagnetic wave absorber, wherein a fluid containing conductive carbon having a high aspect ratio is filled between electrodes. Orienting the conductive carbon by applying an electric field between the electrodes of the electromagnetic wave absorber;

A method for controlling absorbed electromagnetic waves.

[0014] Item 7. The method of controlling an absorbed electromagnetic wave according to Item 6, wherein the electromagnetic wave is an electromagnetic wave having a wavelength range equal to or greater than a microwave.

[0015] Item 8. The absorbed electromagnetic wave control method according to Item 6, wherein the electromagnetic wave is an electromagnetic wave having a wavelength region equal to or less than an infrared ray.

Item 9. A method for controlling a wavelength region and / or an absorption amount of an electromagnetic wave transmitted through an electromagnetic wave absorber,

(9) The orientation state of the conductive carbon is changed by applying a flow, vibration or heat to the fluid containing the conductive carbon oriented by the method according to any one of (6) to (8) above. To absorb absorbed electromagnetic waves.

[0017] The electromagnetic wave absorber (also referred to as "electromagnetic wave modulator") of the present invention is characterized in that a fluid containing conductive carbon having a high aspect ratio is filled between electrodes.

[0018] As the conductive carbon having a high aspect ratio, for example, carbon micro tubes having a diameter of less than lxm, such as carbon nanotubes, strong carbon nanofibers, carbon nanocoils, carbon nanotwist, etc. A coil etc. are also mentioned. Of these, carbon nanotubes, carbon nanotubes, At least one of bon nanofibers, carbon nanocoils, and carbon nanotwists is preferred, and carbon nanocoils are most preferred.

[0019] The aspect ratio (fiber length / fiber diameter) of the conductive carbon is not limited. For example, the average ratio is 2 or more, and preferably about 10 to 5000000 on average.

[0020] The fiber length of the conductive carbon is not limited, and may be appropriately determined from a wide range such as an average of about 50 nm to about 1 mm. The fiber diameter (diameter) is not limited, but is preferably 1 nm or more and less than 1 μm on average.

[0021] When the conductive carbon has a coil shape, that is, a carbon nanocoil or carbon nanotwist, the coil length is preferably about 50 nm to lmm on average, more preferably 0.5 xm to 100 xm on average. Degree. The coil diameter (diameter) is preferably about lOnm to about 10 μm, more preferably about 50 nm or more and less than 1 μm.

[0022] The fluid containing the conductive carbon is not particularly limited as long as it has fluidity and can disperse the conductive carbon. For example, water; monovalent or polyvalent alcoholones such as isopropyl alcohol, ethanol, glycerin, ethylene glycol, polyethylene glycol, sorbitol; organic solvents such as benzene, hexane, chloroform, acetone, and the like.

[0023] In the present invention, a substance that has fluidity when heated (for example, about 60 to 250 ° C) is also included in the fluid. As such a fluid, for example, a thermoplastic resin and the like can be preferably cited. Specific examples include styrene resin, acrylic resin, (meth) acrylic resin, polyvinyl alcohol (PVA), polyethylene (PE), polypropylene (PP), and the like. In addition, norafine, cocoons, oligomers and the like are also included. By using such a resin as a fluid, for example, the fluid is heated to about 60 to 250 ° C. to make the fluid fluid, and then an electric field is applied to orient the conductive carbon. The orientation state can be maintained by returning the temperature to room temperature and losing the fluidity of the fluid. Furthermore, it can be heated again to have fluidity, and then an electric field can be applied to bring the conductive carbon into a new orientation state again.

[0024] A substance having fluidity by flowing an electric current such as liquid crystal is also included in the fluid of the present invention. [0025] These fluids may be used alone or in combination of two or more.

In the present invention, among these fluids, alcohol and thermoplastic resin are particularly preferable.

[0027] The fluid contains polycyclic aromatic compounds such as anthracene, pyrene and porphyrin; polymer compounds such as carboxymethyl cellulose, gelatin, polycarbonate and polyimide; and various additives such as surfactants. It ’s okay.

[0028] The fluidity of the fluid is such that the viscosity at 25 ° C is usually about lcPs ~:! OOOOOOcPs, preferably about 2cPs ~:! OOOOcPs. By setting this range, the dispersion and orientation state of the conductive carbon can be controlled more easily. Note that a substance that has fluidity when heated or when an electric current is passed may have a viscosity in the above-mentioned range when heated (for example, 60 to 250 ° C.) or when energized. In the present invention, the viscosity is measured by a viscosity measuring device.

[0029] In terms of electromagnetic wave permeability, the fluid is preferably an insulator, and usually has a relative dielectric constant of about! -200 (normal temperature 25 ° C).

[0030] The content of the conductive carbon in the fluid is a force that is appropriately determined according to the type of conductive carbon, the type of fluid, the viscosity, etc. For example, 0.0001 to 50 weights per 100 parts by weight of the fluid About 0.1 part, preferably about 0.01 to 30 parts by weight.

[0031] Known or commercially available electrodes can be used. Examples of the material include gold, white gold, silver, copper, ano-remium, titanium, nickel, chromium, cobalt, indium, tin, zinc and other metals or alloys thereof, IT〇 (Indium Tin Oxide), IZ 〇 (In O—Zn

twenty three

0), oxides such as SnO, and carbon can also be used.

2

[0032] The shape of the electrode may be a thin line or a thin film. Also, it may be a comb-shaped electrode with a plurality of fine wires arranged in parallel.

[0033] When the electrode is made into a thin film, the electromagnetic resistance must be transmitted through the thin film electrode (see Fig. 1 to be described later), so the surface resistance of the electrode is a free space radio wave impedance (about 377 Ω) Just make it bigger. Generally, it may be about 400 Ω or more, preferably about 1000 Ω or more, more preferably about 3000 Ω or more. The upper limit is not limited, but for example, '100000 Ω'. [0034] In the case of a comb-shaped electrode, the electromagnetic wave impedance is not particularly limited because electromagnetic waves are transmitted through the substrate between the electrodes.

[0035] The substrate is not limited as long as it is a material that can transmit electromagnetic waves, and examples thereof include a glass substrate, a stone substrate, a plastic substrate, and a ceramic substrate.

[0036] The area of the substrate and the electrodes, the distance between the electrodes, and the like may be appropriately determined according to the content of the conductive carbon in the fluid, the strength of the electric field, and the like.

[0037] The power source connected to the electrode is not limited, and a known or commercially available power source can be used.

[0038] A typical example of the electromagnetic wave absorber of the present invention in which at least one selected from the group consisting of an absorption wavelength region and an absorption amount is variable is given as follows:

i) As shown in FIG. 1, two thin film electrodes laminated on a substrate are arranged so as to face each other, and a fluid containing conductive carbon having a high aspect ratio is filled between the two electrodes. Equipment,

ii) As shown in FIG. 2, two sets of comb electrodes stacked on the substrate are arranged so that the respective thin wire electrodes constituting the comb electrodes facing each other are parallel, and the two sets of comb electrodes are arranged between the two sets of comb electrodes. A device filled with a fluid containing conductive carbon having a high aspect ratio,

iii) As shown in FIG. 3, two sets of comb-shaped electrodes stacked on the substrate are arranged so that each thin wire electrode of the facing comb-shaped electrodes is vertical (relationship of twist), and has a high aspect ratio Examples thereof include an apparatus filled with a fluid containing conductive carbon.

In particular, in the apparatus shown in FIGS. 1 to 3, when the transmitted electromagnetic wave is visible light, a transparent substrate may be used. In this case, in FIG. 1, the thin film electrode is also a transparent electrode, that is, ΙΤΟ, ΙΖ〇 etc.

[0040] In order to redisperse the oriented conductive carbon (in an unoriented state), a dispersing device may be provided between the electrodes or between the electrodes. Specifically, if a known or commercially available flow / vibration device (for example, liquid feed pump, stirrer, sonic device, etc.), heating device (electric heater, infrared lamp, halogen lamp, etc.) is installed between the electrodes. Good.

[0041] Since the present invention employs the above-described structure, by passing an electric current through the electrodes and generating an electric field between the electrodes, the conductive carbon between the electrodes is oriented at a desired angle and transmitted between the electrodes. The absorption wavelength range and / or absorption amount (transmittance or reflectance) of the electromagnetic wave can be changed.

The orientation of the present invention means that individual conductive carbons are arranged in a specific direction, and includes not only uniaxial orientation but also plane orientation.

[0043] The electromagnetic wave absorbed by the device of the present invention can absorb light in a wide wavelength range of about 200 nm to 300 mm. Specifically, microwaves (about 300 mm to 10 mm, about 1 GHz to about 30 GHz), Millimeter wave (10 mm to: about 1 mm, 30 GHz to about 300 GHz), terahertz wave (lmm to: about 10 zm, about 0.3 THz to about 30 THz), infrared light (about 100 μm to about 800 nm), visible light (830 nm ˜360 nm) and ultraviolet light (400 nm˜: about 14 nm).

[0044] Among these, particularly for visible light and ultraviolet light, by changing the amount of absorption (transmittance or reflectivity), a switch function (on / off function of light absorption typified by an optical shutter or the like) is achieved. Since it can exhibit suitably, it can be used suitably as an electromagnetic wave absorber.

[0045] In microwaves, millimeter waves, terahertz waves, infrared rays, etc., in addition to the above-mentioned absorption amount, the absorption wavelength region can be changed in a multi-step (stepwise) manner. The function (the function of changing the absorption wavelength range in multiple stages) and the modulation function (the function of changing the electromagnetic wave transmittance (or reflectivity) or polarization plane (or polarization component) in multiple stages) can also be suitably exhibited. Therefore, it can be suitably used not only as an electromagnetic wave absorber but also as a variable wavelength electromagnetic wave absorber.

[0046] 2. Control method

The method according to the first aspect of the present invention is a method for controlling the wavelength range and / or absorption amount of electromagnetic waves that pass through an electromagnetic wave absorber, and a fluid containing conductive carbon having a high aspect ratio is filled between electrodes. The conductive carbon is oriented by applying an electric field between the electrodes of the electromagnetic wave absorbing device.

[0047] As the electromagnetic wave absorber, the electromagnetic wave absorber having the variable absorption wavelength range and / or absorption amount according to the present invention described above is used.

[0048] Hereinafter, a preferable method will be described using the above-described typical electromagnetic wave absorber.

[0049] i) A field of an apparatus in which two thin film electrodes laminated on a substrate are arranged so as to face each other, and a fluid containing conductive carbon having a high aspect ratio is filled between the two electrodes. Together

As shown in FIG. 4, when an AC voltage is applied to a bipolar electrode, the conductive carbon in the fluid is oriented in a direction perpendicular to the plane of the electrode substrate. Note that, by appropriately adjusting the voltage, the angle of the conductive carbon until it is oriented in the vertical direction can be appropriately adjusted. By these, it is possible to control the wavelength range and Z or the amount of absorption of electromagnetic waves transmitted between the electrodes of the device.

[0050] To explain this mechanism in detail, for example, when carbon nanocoils are used as conductive carbon, carbon nanocoils are dispersed when carbon nanocoils are unoriented (the orientation is irregular shell IJ). The dielectric anisotropy of the fluid is averaged and is isotropic as a whole. On the other hand, when an AC voltage is applied between the transparent electrodes, the carbon nanocoils in the fluid are oriented perpendicular to the transparent electrodes. When carbon nanocoils are in an oriented state, dielectric anisotropy develops, the dielectric constant and dielectric loss for an electric field perpendicular to the orientation direction decrease, and the dielectric constant and dielectric loss for an electric field parallel to the orientation direction increase. . Since the electric field of the electromagnetic wave incident perpendicularly to this device is perpendicular to the orientation direction of the carbon nanocoil, the absorption peak frequency of the electromagnetic wave increases as the dielectric constant decreases, and the transmission loss of the electromagnetic wave decreases as the dielectric loss decreases. In addition, when the wavelength of the incident electromagnetic wave is smaller than the size of the carbon nanocoil, the transmittance (transmittance) increases due to the reduction of the geometric optical shielding area.

[0051] ii) Two sets of comb-shaped electrodes stacked on the substrate are arranged so that the respective electrodes constituting the facing comb-shaped electrodes are parallel to each other, and a high aspect ratio is provided between the two sets of comb-shaped electrodes. In the case of a device filled with a fluid containing conductive carbon

As shown in FIG. 5, when an alternating voltage is applied to the comb electrode, the conductive carbon in the fluid is perpendicular to the thin wire electrode between each thin wire electrode constituting the comb electrode, and Oriented to be parallel to the electrode substrate. Note that, by appropriately adjusting the voltage, the angle of the conductive carbon until it is vertically aligned can be appropriately adjusted. Thus, it is possible to control the wavelength range and / or the amount of absorption of electromagnetic waves transmitted between the electrodes of the device.

[0052] This mechanism will be described in detail. Electromagnetic waves incident perpendicularly to this device can be considered by dividing them into a polarization component whose electric field is parallel to the comb teeth and a polarization component whose electric field is perpendicular to the comb electrodes. For the polarization component whose electric field is parallel to the comb electrode, an increase in dielectric constant and an increase in dielectric loss cause a decrease in absorption peak frequency and an increase in transmission loss. [0053] With respect to the polarization component in which the electric field is perpendicular to the comb electrode, a decrease in dielectric constant and a decrease in dielectric loss cause an increase in absorption peak frequency and a decrease in transmission loss. In addition, when the wavelength of the incident electromagnetic wave is smaller than the size of the carbon nanocoil, the transmittance (transmittance) increases due to the increase of the geometric optical shielding area.

[0054] iii) Two sets of comb-shaped electrodes laminated on the substrate are arranged so that each of the opposing comb-shaped electrodes is vertical (twisted relationship), and conductive carbon having a high aspect ratio is disposed. In the case of equipment filled with fluid

a) When a voltage is applied to the upper and lower comb electrodes, the conductive carbon is oriented perpendicular to the electrode substrate plane (in the Z direction) as shown in FIG.

b) When a voltage is applied only to the upper comb electrode, the conductive carbon is oriented in the Y direction between the thin wire electrodes of the upper comb electrode as shown in FIG.

c) When a voltage is applied only to the lower comb electrode, the conductive carbon is oriented in the X direction between the thin wire electrodes of the lower comb electrode, as shown in FIG.

[0055] By appropriately adjusting the voltage, the angle of the conductive carbon until it is vertically aligned can be appropriately adjusted. By these, it is possible to control the wavelength region and / or the amount of absorption (transmittance or reflectance) of the electromagnetic wave transmitted between the electrodes of the device. These mechanisms are the same as described above. From the above method, an optimal control method may be taken according to the use and purpose of the final product.

[0056] In particular, when the electromagnetic waves are visible light and ultraviolet light, the conductive carbon is oriented by the above-described method to change the absorption amount (transmittance or reflectance) of the electromagnetic waves, so that the switch function (light It effectively plays a role as a light absorption on / off function represented by a shutter.

[0057] When the electromagnetic waves are microwaves, millimeter waves, terahertz waves, infrared rays, or the like, the conductive carbon is oriented by the above method, so that in addition to the above-mentioned absorption amount, the absorption wavelength range and the like are multistage. Switchable function, variable wavelength function (function to change absorption wavelength range in multiple stages) and modulation function (function to change electromagnetic wave transmittance (or reflectivity) in multiple stages) Can also be suitably exhibited.

[0058] Voltage, application time, etc. are the distance between the electrodes in addition to the conductive carbon, fluid, type of the above device By appropriately changing the voltage, the application time, etc. as appropriate according to the above, it is possible to appropriately adjust the degree of orientation of the conductive carbon, and hence the absorption wavelength range and / or absorption amount of the electromagnetic wave.

[0059] If the fluid between the electrodes of the device is a resin, depending on the type of the resin, there is a case where the conductive carbon does not orient at normal temperature and there is no fluidity. In this case, after imparting fluidity to the resin by heating, an electric field may be applied to orient the conductive carbon. By using as the fluid a resin that does not have fluidity at room temperature but will become fluid by heating, change the absorption wavelength range and Z or amount of absorbed electromagnetic waves after installation. At the same time, it is possible to provide an electromagnetic wave absorber that can firmly stabilize the orientation of the conductive carbon at room temperature.

[0060] The method of the second aspect of the present invention is a method for controlling the wavelength range and Z or the amount of absorption of electromagnetic waves that pass through the electromagnetic wave absorber, and is a high-space orientation oriented by the method of the first invention. The oriented conductive carbon is dispersed by applying a flow, vibration, or heat to a fluid containing the conductive carbon having a ratio of 1 to 5. Thereby, the orientation state of the conductive carbon once oriented can be changed.

[0061] Specific examples include a method of flowing a fluid with a liquid feed pump, a method of vibrating the fluid with an ultrasonic device, a method of stirring the fluid with a stirrer, a method of heating the fluid with an electric heater, etc. In addition, a method of indirectly flowing, vibrating, stirring, and heating the fluid by vibrating or heating the electrode can be used. When the fluid is a resin that does not have fluidity at room temperature, the above method may be adopted after the fluidity is provided by heating the resin.

The invention's effect

[0062] Since the electromagnetic wave absorber of the present invention has a structure in which a fluid containing conductive carbon having a high aspect ratio is filled between electrodes, the electromagnetic wave absorption wavelength range and Z or the amount of absorption can be adjusted. . For this reason, the absorption wavelength region and / or the amount of absorption can be appropriately changed after production or after installation at a desired location, and can be used for various applications.

[0063] Further, according to the control method of the present invention, the absorption wavelength region and / or the amount of absorption of electromagnetic waves can be adjusted by adjusting the electric field (voltage, etc.). BEST MODE FOR CARRYING OUT THE INVENTION

[0064] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to the following examples.

[0065] Example 1

A dispersion in which carbon nanocoils were dispersed in an isopropyl alcohol solution (viscosity at 25 ° C .: 2 cPs) was prepared. The average coil length of the nanocoils in the dispersion was 1 to 40 μΐη, and the concentration of the carbon nanocoils in the dispersion was 0.0127 wt%.

[0066] An electrode device (for horizontal orientation) was fabricated by arranging two thin wire electrodes (copper wires) in parallel at 0.9 mm intervals. The electromagnetic wave absorbing device of Example 1 was manufactured by filling the dispersion between the two electrodes. An electric field with a frequency of 100 kHz and an electric field strength of 63 kV / m was applied to this device for 1 minute.

[0067] Fig. 9 shows the results of observation with an optical microscope before and after electric field application.

[0068] When the transmitted light quantity of the fluid between the electrodes before and after the application of the electric field was measured, a change of 0.91% occurred. As a result, it was found that there was a switch function.

[0069] A white LED (manufactured by Nichia Corporation, model number: NSPW500CS) was used as the light source. The rate of change in the amount of transmitted light was determined as follows.

[0070] A small CCD camera (Logitech Q Cam Pro 4 000) that can be directly connected to a personal computer is attached to the eyepiece of a bright-field microscope (Olympus), and the state of electrophoresis (orientation) is colored by collimated photography. Recorded as moving images. Color still images before and after the alignment were extracted from the recorded moving images, and the average luminance of all pixels in the region where the alignment of the carbon nanocoils between the electrodes occurred was calculated.

[0071] The luminance (Y) was calculated using the following equation using the level (0 to 255) force of each component of red (R), green (G), and blue (B) of one pixel.

[0072] Y = 0.29891 X R + 0. 58661 X G + 0. 11448 X B

The rate of change between the average value of the luminance after orientation calculated by the above formula and the average value of the luminance before orientation was defined as the change rate of the transmitted light amount.

[0073] Example 2 <Example of vertical alignment of nanocoil by electric field>

A dispersion in which carbon nanocoils were dispersed in an isopropyl alcohol solution (viscosity at 25 ° C .: 2 cPs) was used. The coil length of carbon nanocoils in the dispersion was 1-40 μm, and the concentration of nanocoils in the dispersion was 0.006% by weight.

[0074] An electrode device (vertically opposed) is formed by placing two ITO glass substrates on which ITO electrodes (manufactured by Sanyo Vacuum Industry Co., Ltd.) are laminated on a glass substrate at an interval of 0.22 mm so that the ITO layer is on the inside. For measurement). The electromagnetic wave absorber of Example 2 was manufactured by filling the electrode device with the dispersion. An electric field with a frequency of 1 kHz and an electric field strength of 256 kVZm was applied for 1 minute.

[0075] Fig. 10 shows the results of observation with an optical microscope.

[0076] When the amount of transmitted light of the fluid between the electrodes before and after the application of the electric field was measured, a change of 8% occurred. As a result, it was found that there was a switch function.

[0077] Example 3

A dispersion liquid in which carbon nanocoils were dispersed in a glycerin solution (viscosity at 25 ° C .: 800 cPs) was prepared. The coil length of the carbon nanocoil in the dispersion was 1 to 40 / im, and the concentration of the nanocoil in the dispersion was 0.006% by weight. The electromagnetic wave absorbing device of Example 3 was manufactured by filling the electrode device manufactured in Example 1 with the above dispersion. An electric field with a frequency of 1 kHz and an electric field strength of 63 kV / m was applied to this device.

FIG. 11 shows the results of observation with an optical microscope before and after the application of an electric field.

[0079] When the amount of transmitted light between the electrodes before and after the application of the electric field was measured, a change of 0.7% occurred. As a result, it was found that there was a switch function.

[0080] Example 4

A coil-containing resin was prepared by dispersing 0.05% by weight of carbon nanocoils in an acrylic ultraviolet curable resin (TESK, model number A-1836, viscosity 1 OcPs at 25 ° C.). Two ITO glass substrates (22mm X 33mm) with I TO electrodes (manufactured by Sanyo Vacuum Industries Co., Ltd.) laminated on a glass substrate so that the IT ○ layer is on the inside and the electrode spacing is 0.5mm. Cells were prepared by placing them in parallel and fixing them with a spacer. Coil-containing resin in cell The electromagnetic wave absorbing device of the present invention was produced by filling 0.4 g of the solution.

[0081] Carbon nanocoils in the obtained electromagnetic wave absorber were oriented, and the complex dielectric constant before and after the orientation was measured. Figure 12 shows the measurement circuit.

[0082] First, an AC voltage (voltage 20V, frequency 100kHz) was applied to the electromagnetic wave absorber immediately after filling the cell with the coil-containing resin, and orientation was performed using a two-phenomenon oscilloscope (Tektronix Corp., model number TDS3024B). The previous cell impedance Z and the phase difference φ between the voltage waveform and the current waveform were measured. The measurement results were an impedance Z of 54.3 kΩ and a phase difference φ of -78.2 °. From this result, the complex dielectric constant ε before orientation was calculated to be 2.23-jO.466.

Next, the applied voltage was increased and a 200 V AC voltage (frequency: 100 kHz) was applied to the electromagnetic wave absorbing device, so that the carbon nanocoils in the device were oriented perpendicular to the electrode plane.

[0084] After that, the applied voltage was lowered, an AC voltage of 20 V (frequency 100 kHz) was applied, and the cell impedance Z ′ after orientation and the voltage waveform were measured using a two-phenomenon oscilloscope (Tektronix, model number TDS3024B). The phase difference φ with respect to the current waveform was measured. The measurement results were impedance Z of 48. Ok Ω and phase difference φ force S—77.9 °. From this result, the complex dielectric constant ε after orientation was calculated to be 2.53-jO.527.

[0085] Because of this, the complex relative permittivity after orientation was larger for both the imaginary part and the real part than the complex relative permittivity before orientation. Thereby, it was found that the electromagnetic wave absorption device of the present invention can change the electromagnetic wave absorption characteristics (absorption wavelength region and absorption amount).

[0086] Comparative Example 1

A dispersion was prepared by dispersing carbon black (average particle size 25 nm, manufactured by Tokai Carbon Co., Ltd., “Conductive Talker Black # 5500”) in an isopropyl alcohol solution (viscosity at 25 ° C .: 2 cPs). The concentration of carbon black in the dispersion was 0.0127% by weight.

[0087] An electrode device (for horizontal orientation) was fabricated by arranging two thin wire electrodes (copper wires) in parallel at 0.9 mm intervals. The device of Comparative Example 1 was manufactured by filling the dispersion between the two electrodes. [0088] An electric field having a frequency of 100 kHz and an electric field strength of 63 kV / m was applied to this apparatus for 1 minute. When the amount of transmitted light between the electrodes before and after the application of the electric field was measured, no change occurred. As a result, the switch function was not demonstrated.

Brief Description of Drawings

[0089] FIG. 1 shows an example of an electromagnetic wave absorber according to the present invention.

FIG. 2 shows an example of an electromagnetic wave absorber according to the present invention.

FIG. 3 shows an example of an electromagnetic wave absorber according to the present invention.

FIG. 4 shows an example of the mechanism of the electromagnetic wave control method of the present invention.

FIG. 5 shows an example of the mechanism of the electromagnetic wave control method of the present invention.

FIG. 6 shows an example of the mechanism of the electromagnetic wave control method of the present invention.

FIG. 7 shows an example of the mechanism of the electromagnetic wave control method of the present invention.

FIG. 8 shows an example of the mechanism of the electromagnetic wave control method of the present invention.

[FIG. 9] FIG. 9 shows the observation results of the electromagnetic wave absorbing device of Example 1 before and after application of an electric field.

FIG. 10 shows the observation results before and after applying the electric field in the electromagnetic wave absorber of Example 2. FIG.

[FIG. 11] FIG. 11 shows the observation results of the electromagnetic wave absorbing device of Example 3 before and after application of an electric field. 12] FIG. 12 shows a measurement circuit of the variable wavelength electromagnetic wave absorber used in the fourth embodiment.

Claims

The scope of the claims

[1] An electromagnetic wave absorber having a variable absorption wavelength range and / or absorption amount, which is formed by filling a fluid containing conductive carbon having a high aspect ratio between electrodes.

[2] The electromagnetic wave absorber according to claim 1, wherein the conductive carbon has an aspect ratio of 2 or more.

[3] The electromagnetic wave absorber according to claim 1, wherein the conductive carbon is at least one selected from the group consisting of carbon nanocoils, carbon nanotubes, carbon nanofibers, and carbon nanotwists.

[4] The conductive carbon content is 0.001 to 50 parts by weight per 100 parts by weight of the fluid.

The electromagnetic wave absorber according to claim 1.

[5] The electromagnetic wave absorber according to claim 1, wherein the fluid has a viscosity of:! To 100,000 cPs (25 ° C).

[6] A method for controlling the wavelength range and / or amount of absorption of electromagnetic waves transmitted through an electromagnetic wave absorber.

Orienting the conductive carbon by applying an electric field between the electrodes of an electromagnetic wave absorber in which a fluid containing conductive carbon having a high aspect ratio is filled between the electrodes.

A method for controlling absorbed electromagnetic waves.

7. The absorbed electromagnetic wave control method according to claim 6, wherein the electromagnetic wave is an electromagnetic wave having a wavelength range equal to or greater than a microwave.

8. The absorbed electromagnetic wave control method according to claim 6, wherein the electromagnetic wave is an electromagnetic wave having a wavelength range equal to or less than infrared.

[9] A method for controlling the wavelength range and / or amount of absorption of electromagnetic waves transmitted through an electromagnetic wave absorbing device,

Changing the orientation state of the conductive carbon by applying a flow, vibration or heat to the fluid containing the conductive carbon oriented by the method according to claim 6;

A method for controlling absorbed electromagnetic waves.