JP2012205198A - Thermoacoustic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoacoustic device excellent in high-speed reactivity and having reduced harmonic distortion.SOLUTION: A thermoacoustic device includes a pair of electrodes and a CNT film for connecting between both electrodes and composed of a plurality of long carbon nanotube molecules independent of each other, in which each of the carbon nanotube molecules is electrically connected between both electrodes as a single body. It is preferable that the CNT film is formed in a stripe arrangement. It is preferable that the thermoacoustic device further includes a CNT film for heat dissipation provided in each slit of the CNT film formed in a stripe arrangement.

Description

  The present invention relates to a thermoacoustic apparatus.

  As a device for generating sound waves, a sound wave generating device using mechanical vibration such as an electrodynamic conversion device including a magnet and a coil, a capacitor conversion device, and a conversion device using a piezoelectric material is widely used. In recent years, unlike these sound wave generators, development of sound wave generators (thermoacoustic devices) using a thermoacoustic effect that does not perform mechanical vibration at all has been underway.

  This thermoacoustic apparatus usually includes a heat insulating layer and a heating element layer provided on the surface of the heat insulating layer. In a thermoacoustic apparatus having such a structure, the temperature of the air layer on the surface of the heat generating element layer is changed by applying heat to the heat generating element layer, and sound waves are generated due to the air density due to the temperature change. Is configured to occur. Since such a thermoacoustic apparatus does not involve mechanical vibration, there are advantages such as a wide frequency band, being hardly affected by the surrounding environment, and being relatively easy to miniaturize.

  In this thermoacoustic apparatus, it has been proposed to use carbon nanotubes (hereinafter also referred to as “CNT”) as a heating element for forming a heating element layer in order to increase the efficiency of sound wave generation (Japanese Patent Laid-Open No. 2010-93805). No., JP 2009-268108 A). According to this thermoacoustic apparatus, CNT having a small heat capacity and a large specific surface area are used as a heating element, so that a high-speed temperature change corresponding to an electric signal or the like is possible, and sound waves can be generated satisfactorily. It is said that. However, the thermoacoustic apparatus using CNT as the heating element as described above cannot be said to have sufficient high-speed reactivity, and has a large harmonic distortion, so there is room for improvement for practical use.

JP 2010-93805 A JP 2009-268108 A

  The present invention has been made based on the above-described circumstances, and an object of the present invention is to provide a thermoacoustic apparatus having excellent high-speed reactivity and low harmonic distortion.

  As a result of intensive studies, the present inventors have found that when CNT is used as a heating element, contact resistance occurs at a portion where CNT molecules are connected to each other, and heat generation at this contact portion increases non-uniformity of the heat generation state, and high speed. The inventors have found that it affects the generation of reactivity and harmonic distortion, and has completed the present invention. That is, the presence of a large number of connecting parts between the molecules increases the heat capacity and lowers the high-speed reactivity, and the transient response decreases due to the heat generated by the connecting parts, and harmonic distortion is likely to occur. The headline and improvement of this point led to the completion of the present invention.

The invention made to solve the above problems is
A pair of electrodes;
A thermoacoustic apparatus comprising: a CNT film composed of a plurality of independent long carbon nanotube molecules connecting the two electrodes;
Each of the carbon nanotube molecules is electrically connected between both electrodes as a single unit.

  In the thermoacoustic apparatus, each CNT molecule is electrically connected between both electrodes alone, and the CNT film does not have a connection portion between the CNT molecules. Therefore, according to the thermoacoustic apparatus, the heat capacity of the CNT film is reduced and the high-speed reactivity is excellent. Moreover, according to the thermoacoustic apparatus, since the decrease in transient response due to heat generation from the connection portion between the CNT molecules is suppressed, the generation of harmonic distortion is reduced. Further, according to the thermoacoustic apparatus, the CNT film has a high mechanical strength because the CNT film does not have a connecting portion between molecules.

  The CNT film may be formed in a stripe shape. According to the thermoacoustic apparatus, by forming the CNT film in a stripe shape, the heat dissipation of the film is further increased, and as a result, the high-speed reactivity can be further increased and the generation of harmonic distortion can be further reduced. .

  It is preferable to further include a heat-dissipating CNT film provided in a slit of the CNT film formed in a stripe shape. According to the thermoacoustic apparatus, the CNT film for heat dissipation is alternately arranged in the vicinity of the CNT film, so that the heat dissipation of the CNT film is further improved, and more excellent high-speed reactivity and the ability to reduce harmonic distortion. It can be demonstrated.

  It is preferable to further include a heat insulating layer laminated on the back surface of the CNT film. According to the thermoacoustic apparatus, since the back surface of the CNT film is covered with the heat insulating layer, the generated heat can be prevented from flowing to the back surface side, and the ability to generate sound waves such as high-speed reactivity can be improved. .

  It is good to further provide the heat dissipation layer laminated on the back of the above-mentioned heat insulation layer. According to the thermoacoustic apparatus, by further providing a heat dissipation layer on the back surface of the heat insulating layer, the heat dissipation of the CNT film can be further increased, and as a result, further improvement in high-speed reactivity and reduction in generation of harmonic distortion can be achieved. it can.

  As described above, the thermoacoustic device of the present invention is excellent in high-speed reactivity because each CNT molecule is electrically connected as a single body and there is no connection portion between the CNT molecules in the CNT film. And the harmonic distortion is small. Therefore, the thermoacoustic apparatus of the present invention can be suitably used as a speaker, particularly an ultrasonic speaker.

It is a typical perspective view (a) and a typical side view (b) of a thermoacoustic device concerning a first embodiment of the present invention. It is a typical sectional view of a thermoacoustic device concerning a second embodiment of the present invention. It is a typical top view of a thermoacoustic device concerning a third embodiment of the present invention. It is a schematic plan view of the thermoacoustic apparatus which concerns on other embodiment of this invention. It is a schematic diagram which shows the method of forming the CNT film | membrane of a comparative example. It is a SEM photograph which shows the method of forming the CNT film | membrane of a comparative example. It is a schematic diagram showing the apparatus used for evaluation of an Example. In a reference example, it is a table | surface and a graph which show the resistance value and change rate of a CNT film | membrane when changing a temperature of a CNT film | membrane. In a reference example, it is the table | surface and graph which show the resistance value and change rate of a CNT film | membrane when the temperature of a CNT film | membrane is maintained at 120 degreeC.

<First embodiment>
Hereinafter, embodiments of the thermoacoustic apparatus of the present invention will be described in detail as first to third embodiments and other embodiments.
A thermoacoustic apparatus 1 in FIG. 1 includes a substrate 2, a pair of spacers 3, a CNT film 4, and a pair of electrodes 5.

  The substrate 2 fixes the arrangement state of the CNT film 4 and the like, and protects the back surface of the CNT film 4 and the like.

  The substrate 2 is a rectangular plate-like body in plan view. The size of the substrate 2 is not particularly limited, and can be set as appropriate according to the application of the thermoacoustic apparatus 1. For example, the vertical and horizontal lengths are 1 mm to 10 cm and the thickness is about 0.1 mm to 5 mm. It is.

  The material of the substrate 2 is not particularly limited as long as it has a certain strength, and a metal material such as iron or aluminum, a non-metal material such as glass or synthetic resin, or the like can be used. This substrate 2 may or may not have flexibility. In addition, when the board | substrate 2 has a softness | flexibility, the said thermoacoustic apparatus can expand the range of use as a flexible apparatus.

  The pair of spacers 3 are rectangular plate-like bodies in plan view. The spacers 3 are stacked in parallel with each other on opposite end edges on the surface of the substrate 2. The pair of spacers 3 separates the substrate 2 and the CNT film 4 and thermally insulates the CNT film 4 from the substrate 2.

  The size of the spacer 3 is not particularly limited and can be appropriately set according to the size of the substrate 2 or the like. For example, the length is about the same as the length of one side of the substrate 2 and the width is about 1 mm to 1 cm. The thickness is about 0.05 mm to 3 mm.

  The material of the spacer 3 is not particularly limited, and metals, metal oxides, other inorganic substances, synthetic resins, and the like can be used. However, in order to improve the thermal insulation of the CNT film 4, glass, silicon, synthetic resin A material with low thermal conductivity such as is preferable. In addition, when the spacer 3 is formed from electroconductive materials, such as a metal, the spacer 3 can also be functioned as an electrode. In addition, an adhesive or a pressure-sensitive adhesive can be used as the spacer 3, and in this case, it is easy to fix the CNT film 4 during production.

  The CNT film 4 is constructed between the spacers 3. The pair of electrodes 5 has a strip shape, and is superimposed on the surfaces of the pair of spacers 3 so as to sandwich the end of the CNT film 4. That is, the CNT film 4 connects both electrodes 5.

  The CNT film 4 is composed of a plurality of independent long CNT molecules 6. Each CNT molecule 6 is electrically connected between both electrodes 5 by itself. Specifically, each CNT molecule 6 is arranged in the opposing direction of both electrodes 5, that is, substantially perpendicular to both electrodes 5. In the thermoacoustic apparatus 1, since the CNT molecules 6 are arranged in this way, there is no contact portion between the end portions of the CNT molecules 6 or a portion where the CNT molecules 6 are randomly overlapped. Therefore, according to the thermoacoustic apparatus 1, the heat capacity of the CNT film 4 is reduced and the high-speed reactivity is excellent.

  In addition, since the CNT film 4 has no connection portion between the CNT molecules 6 as described above, the thermoacoustic apparatus 1 suppresses a decrease in transient response due to heat generated from the connection portion between the CNT molecules 6. It has been. Therefore, according to the thermoacoustic apparatus 1, generation of harmonic distortion is reduced. Furthermore, according to the thermoacoustic apparatus 1, the CNT film 4 has high mechanical strength because the CNT film 4 does not have a connection portion between the CNT molecules 6 as described above.

  The lower limit of the opposing direction length of the electrodes 5 of the CNT film 4 is preferably 1 mm, more preferably 1.5 mm, and particularly preferably 2 mm. On the other hand, the upper limit of the length of the CNT film 4 is preferably 10 mm, and more preferably 6 mm. Note that the length of the CNT film 4 is the length of each independent CNT molecule forming the CNT film 4. When this length of the CNT film 4 is less than the lower limit, it may be difficult to convert the generated heat into sound waves. Conversely, when the length of the CNT film 4 exceeds the upper limit, it is difficult to produce such CNT molecules.

  The lower limit of the average thickness of the CNT film 4 is preferably 0.05 μm, and more preferably 0.1 μm. On the other hand, the upper limit of the average thickness of the CNT film 4 is preferably 100 μm, and more preferably 20 μm. When the average thickness of the CNT film 4 is less than the above lower limit, it may be difficult to form such a thin film. On the other hand, when the average thickness of the CNT film 4 exceeds the above upper limit, the heat dissipation of the CNT film 4 may be reduced, and the high-speed reactivity and the ability to suppress harmonic distortion may be reduced.

  Note that the CNT film 4 preferably has a single-layer structure in which CNT molecules are arranged substantially in parallel in a planar shape. By adopting a single layer structure, the surface area of the CNT film 4 is expanded. As a result, the heat capacity of the CNT film 4 is reduced, and the high-speed reactivity of the thermoacoustic device 1 can be further increased.

  The lower limit of the impedance of the CNT film 4 is preferably 1Ω, and more preferably 5Ω. On the other hand, the upper limit of this impedance is preferably 1,000Ω, and more preferably 100Ω. If the impedance of the CNT film 4 is less than the lower limit, current may easily flow and may ignite and burn. On the other hand, when this impedance exceeds the upper limit, current does not flow easily, heat is not generated easily, and no sound is generated, and a high voltage is required when current is to flow.

  As the CNT molecules constituting the CNT film 4, either single-walled single-wall nanotubes (SWNT) or multi-walled multi-wall nanotubes (MWNT) can be used. MWNT having a diameter of 1.5 nm or more and 100 nm or less is more preferable.

  Note that the CNT molecules are those in which the individual molecules are independent and unspun. By using such independent CNT molecules, the uniformity of the CNT film 4 is increased and the surface area is increased. Therefore, the temperature change rate of the CNT film 4 is high, and the high-speed reactivity can be further increased.

  The CNT (molecule) can be produced by a known method, for example, by a CVD method, an arc method, a laser ablation method, a DIPS method, a CoMoCAT method, or the like. Among these, it is preferable to produce by a CVD method using iron as a catalyst and a substrate and ethylene gas from the point that CNT (MWNT) having a desired size can be efficiently obtained. In this case, a CNT molecule crystal having a desired length which is grown in a vertical orientation on an iron or nickel thin film as a catalyst formed on a quartz glass substrate or a silicon substrate with an oxide film can be obtained.

  The material of the pair of electrodes 5 is not particularly limited as long as it has conductivity. For example, a conductive adhesive containing silver particles can be used. The pair of electrodes 5 energize the CNT film 4 to generate heat.

  In the thermoacoustic apparatus 1, the CNT film 4 generates heat by applying an alternating signal voltage to the pair of electrodes 5. Due to this heat generation, a temperature change of the air layer on the surface of the CNT film 4 occurs, and sound waves are generated due to air density due to this temperature change. In the thermoacoustic apparatus 1, each CNT molecule 6 is electrically connected between the electrodes 5 as a single unit, and thus has excellent high-speed reactivity and low harmonic distortion. Therefore, the thermoacoustic apparatus 1 can be suitably used as a speaker, particularly an ultrasonic speaker.

(Production method)
The thermoacoustic apparatus 1 can be suitably manufactured by the following method, for example. A pressure-sensitive adhesive is laminated on both ends of the surface of the substrate 2 to form a pair of spacers 3. CNT molecules are bridged between the spacers 3 to form a CNT film 4. Specifically, for example, the above-described vertically aligned CNT molecules are peeled off from a substrate on which iron or nickel is formed as a catalyst, and the CNT molecules are fixed between the adhesives as the spacers 3 to thereby form the CNT film 4. Can be formed. Thereafter, a pair of electrodes 5 is formed by laminating a conductive adhesive on both end edges (spacer 3) of the CNT film 4, and the thermoacoustic device 1 can be obtained.

  In the above process, after the vertically aligned CNT molecules are peeled off from the iron substrate, a solvent such as isopropyl alcohol is sprayed on or immersed in a bundle of CNTs composed of a plurality of CNT molecules. A dried product may be used as the CNT film. Through such a process, the bundle of CNTs shrinks. Such a bundle of shrinked CNTs has little resistance change with time in a high-temperature environment, and when used as a CNT film, the high-speed reactivity of the resulting thermoacoustic device and the ability to suppress the occurrence of harmonic distortion are further improved. To do.

<Second embodiment>
The thermoacoustic device 11 in FIG. 2 includes a CNT film 4, a pair of electrodes 5, a heat insulating layer 7, and a heat dissipation layer 8. The CNT film 4 and the pair of electrodes 5 are the same as those provided in the thermoacoustic apparatus 1 of FIG.

  The heat insulating layer 7 is laminated on the back surface of the CNT film 4. According to the thermoacoustic device 11, since the back surface of the CNT film 4 is covered with the heat insulating layer 7, the generated heat is prevented from flowing to the back surface side, and the sound wave generation capability such as high-speed reactivity is increased. be able to.

  The material for forming the heat insulating layer 7 is not particularly limited as long as it has heat insulating properties, but a porous material is preferably used in order to exhibit excellent heat insulating properties. In addition, it is preferable to use a material having electrical insulation in order to prevent current from flowing to the heat insulating layer 7 side.

  Examples of such materials include glass, zeolite, alumina, silica, ceramics, other metal oxides, engineering plastics, carbon materials (carbon, silicon carbide, titanium carbide, etc.), nitrogen materials (silicon nitride, etc.), surface Can be a porous metal coated with an insulating material such as oxide.

  As the silica, for example, silica aerogel obtained by drying a hydrated gel obtained from a mixed reaction of tetramethyl orthosilicate (TMOS), aqueous ammonia and ethanol using a supercritical drying method is preferable. This silica airgel can exhibit particularly excellent heat insulation.

  As the engineering plastic, the heat resistance temperature of polyimide (PI), polyphenylene sulfide (PPS), polyetherimide (PEI), polyetheretherketone (PEEK), fluororesin, etc. is 150 ° C. or higher, preferably 200 ° C. or higher. Resins are preferred.

  The thermal conductivity at 25 ° C. of the material forming the heat insulating layer 7 is preferably 0.1 W / mK or less, more preferably 0.06 W / mK or less, and particularly preferably 0.03 W / mK or less. The thermal conductivity can be measured by the flash method described in JIS-R1611 (2010).

  As a minimum of the porosity of heat insulation layer 7, 50 volume% is preferred, 80 volume% is more preferred, and 90 volume% is still more preferred. When the heat insulation layer 7 has such a porosity, the heat insulation performance can be effectively exhibited. The upper limit of the porosity of the heat insulating layer 7 is preferably 99% by volume and more preferably 97% by volume in order to suppress a decrease in strength. The porosity can be calculated by the Archimedes method.

  Moreover, as a minimum of the average diameter of the hole of the heat insulation layer 7, 5 nm is preferable and 10 nm is more preferable. On the other hand, the upper limit of the average diameter of the holes of the heat insulating layer 7 is preferably 1,000 nm, and more preferably 200 nm. When the average diameter of the holes is less than 5 nm, sufficient heat insulating properties may not be exhibited. On the other hand, when the average diameter of the holes exceeds 1,000 nm, the strength may decrease.

  As an average thickness of the heat insulation layer 7, it can be 0.1 mm or more and 3 mm or less, for example. When the average thickness of the heat insulation layer 7 is less than the said minimum, there exists a possibility that heat insulation and intensity | strength may fall. On the contrary, when the average thickness of the heat insulation layer 7 exceeds the said upper limit, there exists a possibility that the heat dissipation of the heat insulation layer 7 may fall.

  The heat radiation layer 8 is laminated on the back surface of the heat insulation layer 7. According to the thermoacoustic device 11, the heat dissipation layer 8 is further provided on the back surface of the heat insulation layer 7, thereby further improving the heat dissipation of the CNT film 4, and as a result, further improving high-speed reactivity and reducing the generation of harmonic distortion. Can be achieved.

  The material of the heat dissipation layer 8 is not particularly limited, and examples thereof include metals, metal oxides, metal nitrides, resin materials in which these powders are mixed, etc., but metals having high thermal conductivity such as copper and aluminum. Is preferred. The thickness of the heat dissipation layer 8 is not particularly limited and is, for example, about 100 nm to 1 mm. In order to increase the surface area and enhance the heat dissipation, an uneven shape or the like may be formed on the back surface of the heat dissipation layer 8 (the surface not in contact with the heat insulating layer 7).

<Third embodiment>
3 includes a substrate 2, a pair of spacers 3, a CNT film 24, a radiating CNT film 9, and a pair of electrodes 25. Since the board | substrate 2 and the spacer 3 are the same as that of the thermoacoustic apparatus 1 of FIG. 1, description is abbreviate | omitted.

  The CNT film 24 is installed between the spacers 3 and connects the electrodes 25 together. The CNT film 24 is formed in a stripe shape. That is, a plurality of strip-like CNT films 24 are formed in parallel and spaced apart. According to the thermoacoustic device 21, by forming the CNT film 24 in a stripe shape and having a plurality of slits, the heat dissipation of the CNT film 24 is further enhanced, and as a result, the high-speed reactivity is further enhanced. The generation of harmonic distortion can be further reduced.

  The width of each of the CNT films 24 formed in a stripe shape is not particularly limited, but is, for example, about 0.1 μm or more and 100 μm or less. The CNT film 24 is the same as the CNT film 4 provided in the thermoacoustic device 1 of FIG. 1 except that the CNT film 24 is formed in a stripe shape.

  The heat-dissipating CNT film 9 has a strip shape and is provided in each slit of the CNT film 24. That is, the strip-shaped CNT films 24 and the strip-shaped heat-dissipating CNT films 9 are alternately arranged in a planar shape. The adjacent CNT films 24 and the heat-dissipating CNT films 9 may be in contact with each other or may be separated from each other. The heat-dissipating CNT film 9 is composed of CNT molecules arranged in the facing direction of the spacer 3 like the CNT film 24, but both ends are not in contact with the electrode 25. That is, the heat-dissipating CNT film 9 does not generate heat.

  A pair of electrodes 25 are laminated on the surface of each spacer 3 via both ends of the CNT film 24. However, the electrode 25 is not in contact with the heat-dissipating CNT film 9. The pair of electrodes 25 energize the CNT film 24 to generate heat.

  According to the thermoacoustic device 21, the heat dissipation CNT films 9 are alternately arranged in the vicinity of the CNT film 24 in this manner, so that the heat dissipation of the CNT film 24 is further enhanced, and more excellent high-speed reactivity and The ability to reduce harmonic distortion can be exhibited.

<Other embodiments>
The thermoacoustic apparatus of the present invention is not limited to the above embodiment. For example, as in the thermoacoustic device 31 in FIG. 4A, each CNT molecule forming the CNT film 34 may not be arranged perpendicular to the pair of electrodes 5. Further, like the thermoacoustic device 41 in FIG. 4B, the CNT film 44 may be formed from CNT molecules bent on the electrode 5. Furthermore, the pair of electrodes 55 need not be provided in parallel as in the thermoacoustic device 51 of FIG. Moreover, in the thermoacoustic apparatus 1 of FIG. 1, even if there is no spacer 3, the thermoacoustic apparatus of this invention can be comprised.

  In any of the thermoacoustic apparatuses described above, each CNT molecule is electrically connected between both electrodes as a single unit, so that high-speed reactivity is excellent and generation of harmonic distortion is reduced.

  Furthermore, the heat insulating material may be provided not only on the back surface of the CNT film as a heat insulating layer but also on the side surface side or the front surface side of the CNT film. In this way, by surrounding the CNT film with a heat insulating material, or by adopting a structure in which the CNT film is disposed inside the heat insulating material, the heat insulating property of the CNT film can be improved and the high-speed reactivity of the thermoacoustic apparatus can be further improved. .

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

[Example]
A substrate having a size of 60 mm in length, 60 mm in width, and 0.5 mm in thickness was prepared. Two double-sided tapes (spacers) were affixed in parallel on the surface of the substrate with an interval of slightly less than 2 mm. Vertically oriented CNT (MWNT: length 2 mm, average diameter 25 nm) was peeled off from the side surface on a substrate in which iron was deposited as a catalyst on quartz glass, and was stuck so as to be bridged between the double-sided tapes to form a CNT film. .

  The size of this CNT film was 2 mm wide and 50 mm long. In this lateral direction, CNT molecules having a length of 2 mm are arranged. The thickness of the CNT film was 0.05 μm to 0.5 μm as measured by SEM.

  On the double-sided tape, a copper wire adhesive containing silver particles was laminated via both ends of CNT molecules to form a pair of electrodes, and a thermoacoustic device of an example was obtained.

[Comparative example]
As shown in FIG. 5, the vertically aligned CNTs 102 were pulled out from the side surface on a substrate 101 in which iron was deposited on quartz glass as a catalyst to form a CNT bundle 104 in which there were many portions 103 where CNT molecules were connected. Except that this CNT bundle was used as the CNT film, the same operation as in the example was performed to obtain a thermoacoustic device of a comparative example. FIG. 6 shows an SEM photograph in a state where the CNTs are pulled out from the substrate.

[Evaluation]
The apparatus of FIG. 7 was assembled, and the thermoacoustic apparatuses of Examples and Comparative Examples were evaluated. The input signals were Vdc = 10V and Vp−p = 10V. The sound pressure when using the generated thermoacoustic apparatus of the example with respect to the input of a sine wave with a frequency of 10 kHz was about 1.7 times larger than that of the comparative example.

[Reference example]
Temperature of (1) CNT bundle as CNT film, (2) Shrinked CNT bundle (CNT bundle (S)), (3) Carbon fiber (CF) and (4) Spinned CNT (CNT spinning) as a comparison The resistance change rate with respect to the change was measured. In addition, the CNT bundle of (1) is the CNT film | membrane in the said Example. The CNT bundle (S) of (2) is obtained by spraying isopropyl alcohol on the CNT bundle of (1) and then drying. The CF of (3) is a trading card T700 manufactured by Toray. The CNT spinning of (4) is the CNT film in the comparative example.

  In the measurement, each CNT film (CNT bundle or the like) was placed on a hot plate to change the temperature, and the resistance at each temperature was measured using a digital multimeter. FIG. 8 shows the resistance value and the change rate of the resistance value for each temperature. FIG. 9 shows the resistance value and the rate of change of the resistance value when the temperature is held at 120 ° C. for 20 minutes in (2) CNT bundle (S), (3) CF, and (4) CNT spinning.

  As shown in FIG. 8, it can be seen that (1) the CNT bundle and (2) the CNT bundle (S) have the same rate of change in resistance at the time of temperature rise and at the time of high temperature, and are suitable as thermoacoustic films. In addition, as shown in FIG. 9, it can be seen that CNT (S) is stable with a small change in resistance over time in a high temperature environment as compared with a CNT bundle.

  The thermoacoustic apparatus of the present invention can be suitably used as a speaker, particularly an ultrasonic speaker.

DESCRIPTION OF SYMBOLS 1, 11, 21, 31, 41, 51 Thermoacoustic apparatus 2 Substrate 3 Spacer 4, 24, 34, 44 CNT film 5, 25, 55 Electrode 6 CNT molecule 7 Heat insulation layer 8 Heat radiation layer 9 CNT film for heat radiation

Claims (5)

A pair of electrodes;
A thermoacoustic apparatus comprising: a CNT film composed of a plurality of independent long carbon nanotube molecules connecting the two electrodes;
A thermoacoustic apparatus, wherein each of the carbon nanotube molecules is electrically connected between both electrodes as a single unit.   The thermoacoustic device according to claim 1, wherein the CNT film is formed in a stripe shape.   The thermoacoustic device according to claim 2, further comprising a heat-dissipating CNT film provided in a slit of the CNT film formed in a stripe shape.   The thermoacoustic device according to claim 1, 2 or 3, further comprising a heat insulating layer laminated on the back surface of the CNT film.   The thermoacoustic apparatus of Claim 4 further provided with the thermal radiation layer laminated | stacked on the back surface of the said heat insulation layer.