JP2010136368A - Thermoacoustic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoacoustic device, specifically, the thermoacoustic device utilizing a carbon nanotube. <P>SOLUTION: This device includes: a signal device; and a sound wave generator including a carbon nanotube structure. At least a part of the carbon nanotube structure contacts a liquid medium. The carbon nanotube structure converts a signal from the signal device into heat. The density of the liquid medium is converted to generate sounds. The heat capacity of the carbon nanotube structure per unit area is 0 (not including 0) to 2×10<SP>-4</SP>J/cm<SP>2</SP>K. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thermoacoustic apparatus, and more particularly to a thermoacoustic apparatus using carbon nanotubes.

  In general, the acoustic device includes a signal device and a sound wave generator. The signal device transmits a signal to the sound wave generator (for example, a speaker). The speaker can convert an electrical signal into sound as an electroacoustic transducer.

  Depending on the principle of operation, there are various types of speakers such as dynamic speakers, magnetic speakers, electrostatic speakers, and piezoelectric speakers. The various types of speakers all generate sound waves by mechanical vibration, that is, realize electrical-mechanical force-sound conversion. Here, dynamic speakers are widely used.

  Non-Patent Documents 1 and 2 describe thermoacoustic phenomena. The thermoacoustic phenomenon is a phenomenon in which sound and heat are involved, and has two aspects, energy conversion and energy transport. When a signal is transferred to the thermoacoustic device, heat is generated in the thermoacoustic device and propagated to the surrounding medium. Sound waves can be generated due to thermal expansion and pressure waves caused by the propagated heat.

Edward C. WENTE, “The Thermophone”, Phys. 1922, Volume 4, pp. 333-345 William Henry Prece, “On Some Thermal Effects of Electric Currents”, Proc. R. Soc. London. 1879-1880, 30, 408-411 H. D. Arnold, I.D. B. Crandall, “The thermophone as a precision source of sound”, Phys. 1917, Vol. 10, pp. 22-38 Kaili Jiang, Quung Li, Shuushan Fan, “Spinning continuous carbon nanotube yarns”, Nature, 2002, vol. 419, p. 801

Non-Patent Document 3 discloses a thermophone manufactured by a thermoacoustic phenomenon. Referring to FIG. 13, the thermophone 100 includes a platinum piece 102, two clamps 104, and a substrate 106. The platinum piece 102 and the two clamps 104 are installed on the substrate 106. The two clamps 104 are separated by a predetermined distance and are fixed to both ends of the platinum piece 102, respectively. The platinum piece 102 has a thickness of 7 × 10 ⁻⁵ cm. The frequency response range and the sound pressure are related to the heat capacity per unit area of the platinum piece 102. For example, if the heat capacity per unit area is increased, the frequency response range is narrowed and the sound pressure is decreased. However, for a platinum piece having a thickness of 7 × 10 ⁻⁵ cm, the heat capacity per unit area is 2 × 10 ⁻⁴ J / cm ² · K. Since the heat capacity per unit area of the platinum piece is very high, a thermophone using the platinum piece has a problem that sound is very weak when used outdoors.

  In order to solve the above-mentioned problems, the present invention provides a light thermoacoustic apparatus. The thermoacoustic apparatus of the present invention does not depend on a magnetic field and can generate sound without depending on mechanical vibration.

  The apparatus of the present invention includes a signal device and a sound wave generator including a carbon nanotube structure. At least a portion of the carbon nanotube structure is in contact with a liquid medium. The signal from the signal device is converted into heat by the carbon nanotube structure. A sound is generated by changing the density of the liquid medium.

  The apparatus of the present invention includes a signal device and a sound wave generator including a carbon nanotube structure. At least a portion of the carbon nanotube structure is in contact with a liquid medium. When the signal device transfers to the carbon nanotube structure, the carbon nanotube structure generates sound.

  The apparatus of the present invention includes a carbon nanotube structure. The carbon nanotube structure generates sound in a liquid medium by a thermoacoustic principle.

The carbon nanotube structure has a heat capacity per unit area of 0 (not including 0) to 2 × 10 ⁻⁴ J / cm ² · K or less.

The electrical resistivity of the liquid medium is higher than 1 × 10 ⁻² Ω × M.

  The carbon nanotube structure is immersed in the liquid medium.

  The device includes at least two electrodes. The at least two electrodes are separated by a predetermined distance and each is electrically connected to the sound wave generator.

  Compared with the prior art, the thermoacoustic device of the present invention has the following advantages. First, since the thermoacoustic device of the present invention includes a carbon nanotube structure, the structure is simpler than that of a conventional speaker, and a light and small size can be realized. Secondly, the thermoacoustic apparatus of the present invention generates a sound wave by heating the carbon nanotube structure, so there is no need to use a magnet. Third, since the carbon nanotube structure has a small heat capacity per unit area, a large specific surface area, and a high heat exchange speed, it can generate sound well in a liquid medium. Fourth, since the carbon nanotube structure is thin, a transparent acoustic device can be manufactured.

It is a schematic diagram of the thermoacoustic apparatus in Example 1 of this invention. It is a scanning electron micrograph of the carbon nanotube film of the fluff structure in Example 1 of this invention. It is a scanning electron micrograph of the carbon nanotube film in which the carbon nanotube in Example 1 of this invention was arranged along the same direction. It is a scanning electron micrograph of the carbon nanotube film in which the carbon nanotubes in Example 1 of the present invention are isotropically arranged. It is a SEM photograph of the carbon nanotube film in Example 1 of the present invention. It is a schematic diagram of the carbon nanotube segment in Example 1 of the present invention. It is a SEM photograph of the carbon nanotube wire in Example 1 of the present invention. It is a SEM photograph of the twisted carbon nanotube wire in Example 1 of the present invention. It is a frequency response curve of the thermoacoustic apparatus in Example 1 of this invention. It is a schematic diagram of the thermoacoustic apparatus in Example 1 of this invention. It is a schematic diagram of the thermoacoustic apparatus in Example 2 of this invention. It is a schematic diagram of the thermoacoustic apparatus in Example 3 of this invention. It is a schematic diagram of the conventional thermophone.

  Embodiments of the present invention will be described below with reference to the drawings.

Example 1
Referring to FIG. 1, the thermoacoustic device 200 of the present invention includes a signal device 210, a sound wave generator 230, and at least two electrodes 220. The at least two electrodes 220 are electrically connected to the sound wave generator 230 so as to be separated from each other by a predetermined distance. The at least two electrodes 220 are electrically connected to the signal device 210, respectively. The signal from the signal device 210 is transferred to the sound wave generator 230 by the at least two electrodes 220. At least a part of the sound wave generator 230 is immersed in the liquid medium 300.

The sound wave generator 230 includes a carbon nanotube structure. Since the carbon nanotube structure has a large specific surface area (for example, 50 m ² / g or more), the area where the carbon nanotube structure contacts the liquid medium 300 is large. The heat capacity per unit area of the carbon nanotube structure is 0 (not including 0) to 2 × 10 ⁻⁴ J / cm ² · K, and preferably 0 (not including 0) to 1.7. × 10 ⁻⁶ J / cm ² · K, and in the present example, it is 1.7 × 10 ⁻⁶ J / cm ² · K. A plurality of carbon nanotubes are uniformly dispersed in the carbon nanotube structure. The plurality of carbon nanotubes are connected by intermolecular force. The plurality of carbon nanotubes are aligned or not aligned in the carbon nanotube structure. According to the arrangement method of the plurality of carbon nanotubes, the carbon nanotube structure is classified into two types, a non-oriented carbon nanotube structure and an oriented carbon nanotube structure. In the non-oriented carbon nanotube structure in this example, the carbon nanotubes are arranged or entangled along different directions. In the oriented carbon nanotube structure, the plurality of carbon nanotubes are arranged along the same direction. Alternatively, in the oriented carbon nanotube structure, when the oriented carbon nanotube structure is divided into two or more regions, a plurality of carbon nanotubes in each region are arranged along the same direction. In this case, the arrangement directions of the carbon nanotubes in different regions are different. The carbon nanotube is a single-walled carbon nanotube, a double-walled carbon nanotube, or a multi-walled carbon nanotube. When the carbon nanotube is a single-walled carbon nanotube, the diameter is set to 0.5 nm to 50 nm. When the carbon nanotube is a double-walled carbon nanotube, the diameter is set to 1 nm to 50 nm. In the case of a nanotube, the diameter is set to 1.5 nm to 50 nm.

  The carbon nanotube structure has a flat plate shape and a thickness of 0.5 nm to 1 mm. The smaller the specific surface area of the carbon nanotube structure, the higher the heat capacity per unit area of the carbon nanotube structure. The higher the heat capacity per unit area of the carbon nanotube structure, the lower the sound pressure of the thermoacoustic device.

  Examples of the carbon nanotube structure of the present invention include the following (1) to (4).

(1) Fluff-structured carbon nanotube film The carbon nanotube structure includes at least one carbon nanotube film. The carbon nanotube film is a fluffed carbon nanotube film. Referring to FIG. 2, in the single carbon nanotube film, a plurality of carbon nanotubes are entangled and isotropically arranged. In the carbon nanotube structure, the plurality of carbon nanotubes are uniformly distributed. The plurality of carbon nanotubes are arranged without being oriented. The length of the single carbon nanotube is 100 nm or more, and preferably 100 nm to 10 cm. The carbon nanotube structure is formed in the shape of a self-supporting thin film. Here, the self-supporting structure is a form in which the carbon nanotube structure can be used independently without using a support material. The plurality of carbon nanotubes are close to each other by intermolecular force and entangled with each other to form a carbon nanotube net. The plurality of carbon nanotubes are arranged without being oriented to form many minute holes. Here, the diameter of the single minute hole is 10 μm or less. Since the carbon nanotubes in the carbon nanotube structure are arranged so as to be entangled with each other, the carbon nanotube structure is excellent in flexibility and can be formed to be bent into an arbitrary shape. Depending on the application, the length and width of the carbon nanotube structure can be adjusted. The carbon nanotube structure has a thickness of 0.5 nm to 1 mm.

  The method for producing the carbon nanotube film includes the following steps.

  In the first step, a carbon nanotube raw material (a carbon nanotube used as a raw material of a fluff structure carbon nanotube film) is provided.

  The carbon nanotubes are peeled from the substrate with a tool such as a knife to form a carbon nanotube raw material. The carbon nanotubes are intertwined with each other to some extent. In the carbon nanotube raw material, the carbon nanotube has a length of 100 micrometers or more, preferably 10 micrometers or more.

  In the second step, the carbon nanotube raw material is immersed in a solvent, and the carbon nanotube raw material is processed to form a fluffy carbon nanotube structure.

    After the carbon nanotube raw material is immersed in the solvent, the carbon nanotube is formed into a fluff structure by a method such as ultrasonic dispersion, high-strength stirring, or vibration. The solvent is water or a volatile organic solvent. Treatment is performed for 10 to 30 minutes with respect to the solvent containing carbon nanotubes by an ultrasonic dispersion method. Since the carbon nanotube has a large specific surface area and a large intermolecular force is generated between the carbon nanotubes, the carbon nanotubes are entangled and formed into a fluff structure.

  In the third step, the solution containing the fluff structure carbon nanotube structure is filtered to take out the final fluff structure carbon nanotube structure.

  First, provide a funnel with filter paper. When the solvent containing the fluffy carbon nanotube structure is applied to the funnel on which the filter paper is placed and then left standing for a while to dry, the fluffy carbon nanotube structure is separated. Referring to FIG. 2, the carbon nanotubes in the carbon nanotube structure having the fluff structure are intertwined to form an irregular fluff structure.

  The separated fluff structure carbon nanotube structure is placed in a container, the fluff structure carbon nanotube structure is expanded into a predetermined shape, and a predetermined pressure is applied to the expanded fluff structure carbon nanotube structure, When the solvent remaining in the fluffy carbon nanotube structure is heated or the solvent spontaneously evaporates, a fluffy carbon nanotube film is formed.

  The thickness and surface density of the fluffy carbon nanotube film can be controlled by the area where the fluffy carbon nanotube structure is developed. That is, the fluff-structured carbon nanotube structure having a certain volume has a smaller thickness and areal density of the fluff-structured carbon nanotube film as the developed area increases.

  In addition, a carbon nanotube film having a fluff structure is formed using a microporous film and an air pump funnel. Specifically, a microporous membrane and an air pump funnel are provided, and the solvent containing the fluff-structured carbon nanotube structure is passed through the microporous membrane to the air pump funnel, and then extracted to the air pump funnel and dried. As a result, a carbon nanotube film having a fluff structure is formed. The microporous film has a smooth surface. In the microporous membrane, the diameter of a single micropore is 0.22 micrometers. Since the microporous membrane has a smooth surface, the carbon nanotube film can be easily peeled off from the microporous membrane. Furthermore, since the air pump is used to apply air pressure to the carbon nanotube film having the fluff structure, a carbon nanotube film having a uniform fluff structure can be formed.

  When the carbon nanotube structure includes only one carbon nanotube film, both ends of the carbon nanotubes in the carbon nanotube film are electrically connected to the at least two electrodes 220, respectively. When the carbon nanotube structure includes a plurality of stacked carbon nanotube films, an angle α formed by the carbon nanotubes between adjacent carbon nanotube films is 0 ° to 90 °. Both ends of the carbon nanotubes in the at least one carbon nanotube film are electrically connected to the at least two electrodes 220, respectively.

(2) Precise carbon nanotube film The carbon nanotube structure includes at least one carbon nanotube film. This carbon nanotube film is a pressed carbon nanotube film. The plurality of carbon nanotubes in the single carbon nanotube film are arranged isotropically, arranged along a predetermined direction, or arranged along a plurality of different directions. The carbon nanotube film has a sheet-like self-standing structure formed by pressing the carbon nanotube array by applying a predetermined pressure by using a pushing tool and then depressing the carbon nanotube array with the pressure. is there. The arrangement direction of the carbon nanotubes in the carbon nanotube film is determined by the shape of the pushing device and the pushing direction of the carbon nanotube array.

  Referring to FIG. 4, the carbon nanotubes in a single carbon nanotube film are arranged without being oriented. The carbon nanotube film includes a plurality of carbon nanotubes arranged isotropically. Adjacent carbon nanotubes attract each other by intermolecular force and connect. The carbon nanotube structure has planar isotropy. The carbon nanotube film is formed by pressing the carbon nanotube array along a direction perpendicular to the substrate on which the carbon nanotube array is grown using a pressing device having a flat surface.

  Referring to FIG. 3, the carbon nanotubes in a single carbon nanotube film are aligned and arranged. The carbon nanotube film includes a plurality of carbon nanotubes arranged along the same direction. When the carbon nanotube array is simultaneously pressed along the same direction using a pressing device having a roller shape, a carbon nanotube film including carbon nanotubes arranged in the same direction is formed. In addition, when the carbon nanotube array is simultaneously pressed along different directions using a pressing device having a roller shape, a carbon nanotube film including carbon nanotubes arranged in a selective direction along the different directions Is formed.

  The degree of inclination of the carbon nanotubes in the carbon nanotube film is related to the pressure applied to the carbon nanotube array. The carbon nanotubes in the carbon nanotube film and the surface of the carbon nanotube film form an angle α, and the angle α is not less than 0 ° and not more than 15 °. Preferably, the carbon nanotubes in the carbon nanotube film are parallel to the surface of the carbon nanotube film. The greater the pressure, the greater the degree of tilt. The thickness of the carbon nanotube film is related to the height of the carbon nanotube array and the pressure applied to the carbon nanotube array. That is, as the height of the carbon nanotube array increases and the pressure applied to the carbon nanotube array decreases, the thickness of the carbon nanotube film increases. On the contrary, as the height of the carbon nanotube array becomes smaller and as the pressure applied to the carbon nanotube array becomes larger, the thickness of the carbon nanotube film becomes smaller.

(3) Drone-structured carbon nanotube film The carbon nanotube structure includes at least one carbon nanotube film 143a shown in FIG. This carbon nanotube film is a drone structure carbon nanotube film. The carbon nanotube film 143a is obtained by pulling out from a super aligned carbon nanotube array (see Non-Patent Document 4). In the single carbon nanotube film, a plurality of carbon nanotubes are connected to each other along the same direction. That is, the single carbon nanotube film 143a includes a plurality of carbon nanotubes whose end portions in the length direction are connected to each other by intermolecular force. 5 and 6, the single carbon nanotube film 143a includes a plurality of carbon nanotube segments 143b. The plurality of carbon nanotube segments 143b are connected to each other by an intermolecular force along the length direction. Each carbon nanotube segment 143b includes a plurality of carbon nanotubes 145 connected in parallel to each other by intermolecular force. In the single carbon nanotube segment 143b, the plurality of carbon nanotubes 145 have the same length. By soaking the carbon nanotube film 143a in an organic solvent, the toughness and mechanical strength of the carbon nanotube film 143a can be increased. Since the heat capacity per unit area of the carbon nanotube film immersed in the organic solvent is lowered, the thermoacoustic effect can be enhanced. The carbon nanotube film 143a has a width of 100 μm to 10 cm and a thickness of 0.5 nm to 100 μm.

  The carbon nanotube structure may include a plurality of stacked carbon nanotube films. In this case, the adjacent carbon nanotube films are bonded by intermolecular force. The carbon nanotubes in the adjacent carbon nanotube films intersect each other at an angle of 0 ° to 90 °. When the carbon nanotubes in the adjacent carbon nanotube films intersect at an angle of 0 ° or more, a plurality of micropores are formed in the carbon nanotube structure. Alternatively, the plurality of carbon nanotube films may be juxtaposed without gaps. When the carbon nanotube structure having a plurality of micropores is immersed in a liquid medium and then dried, the carbon nanotube structure contracts due to the surface tension of the liquid medium 300. It is difficult to let

  When the carbon nanotube structure is formed by laminating sixteen carbon nanotube films, the sound generator 230 has high light transmittance, so that the sound generator 230 can be used for the transparent thermoacoustic device 200. .

  The method for manufacturing the carbon nanotube film includes the following steps.

  In the first step, a carbon nanotube array is provided. The carbon nanotube array is a super aligned carbon nanotube array (see Superaligned array of carbon nanotubes, Non-Patent Document 4), and a chemical vapor deposition method is employed as a method of manufacturing the super aligned carbon nanotube array. The manufacturing method includes the following steps. In step (a), a flat substrate is provided, and the substrate is any one of a P-type silicon substrate, an N-type silicon substrate, and a silicon substrate on which an oxide layer is formed. In this embodiment, it is preferable to select a 4-inch silicon substrate. In step (b), a catalyst layer is uniformly formed on the surface of the substrate. The material of the catalyst layer is any one of iron, cobalt, nickel and two or more alloys thereof. In step (c), the substrate on which the catalyst layer has been formed is annealed with air at 700 ° C. to 900 ° C. for 30 minutes to 90 minutes. In step (d), the annealed substrate is placed in a reaction furnace, heated with a protective gas at a temperature of 500 ° C. to 740 ° C., and then a carbon-containing gas is introduced to react for 5 to 30 minutes. Then, a super aligned carbon nanotube array (Superaligned array of carbon nanotubes, Non-Patent Document 4) can be grown. The carbon nanotube array has a height of 100 micrometers or more. The carbon nanotube array is composed of a plurality of carbon nanotubes that grow parallel to each other and perpendicular to the substrate. Since the carbon nanotubes are long, the carbon nanotubes are partially entangled with each other. By controlling the growth conditions, the carbon nanotube array does not contain impurities such as amorphous carbon and remaining metal particles as a catalyst.

  In this embodiment, as the gas containing carbon, for example, active hydrocarbons such as acetylene, ethylene, and methane are selected, and it is preferable to select ethylene. The protective gas is nitrogen gas or inert gas, preferably argon gas.

  The carbon nanotube array provided from this example is not limited to being manufactured by the above-described manufacturing method, and may be manufactured by an arc discharge method or a laser evaporation method.

  In the second step, at least one carbon nanotube film is stretched from the carbon nanotube array. First, using a tool such as tweezers, a plurality of carbon nanotube ends are provided. For example, a plurality of carbon nanotube ends are used by using a tape having a certain width. Next, the plurality of carbon nanotubes are pulled out at a predetermined speed to form a continuous carbon nanotube film composed of a plurality of carbon nanotube segments.

  In the step of drawing out the plurality of carbon nanotubes, when the plurality of carbon nanotubes are detached from the base material, the carbon nanotube segments are joined to each other by an intermolecular force to form a continuous carbon nanotube film. .

(4) Carbon nanotube wire The carbon nanotube structure includes at least one carbon nanotube wire. The heat capacity of one carbon nanotube wire is 0 (not including 0) to 2 × 10 ⁻⁴ J / cm ² · K, and preferably 5 × 10 ⁻⁵ J / cm ² · K. The diameter of one carbon nanotube wire is 4.5 nm to 1 cm. Referring to FIG. 7, the carbon nanotube wire is composed of a plurality of carbon nanotubes connected by intermolecular force. In this case, one carbon nanotube wire (non-twisted carbon nanotube wire) includes a plurality of carbon nanotube segments (not shown) in which ends are connected. The carbon nanotube segments have the same length and width. Further, a plurality of carbon nanotubes having the same length are arranged in parallel in each of the carbon nanotube segments. The plurality of carbon nanotubes are arranged parallel to the central axis of the carbon nanotube wire. In this case, the diameter of one carbon nanotube wire is 1 μm to 1 cm. Referring to FIG. 8, the carbon nanotube wire can be twisted to form a twisted carbon nanotube wire. Here, the plurality of carbon nanotubes are arranged in a spiral shape around the central axis of the carbon nanotube wire. In this case, the diameter of one carbon nanotube wire is 1 μm to 1 cm. The carbon nanotube structure is made of any one of the non-twisted carbon nanotube wire, the twisted carbon nanotube wire, or a combination thereof.

  The method of forming the carbon nanotube wire uses a carbon nanotube film drawn from a carbon nanotube array. There are the following three methods for forming the carbon nanotube wire. In the first type, the carbon nanotube film is cut with a predetermined width along the longitudinal direction of the carbon nanotube in the carbon nanotube film to form a carbon nanotube wire. In the second type, the carbon nanotube film can be formed by immersing the carbon nanotube film in an organic solvent and shrinking the carbon nanotube film. In the third type, the carbon nanotube film is machined (for example, a spinning process) to form a twisted carbon nanotube wire. More specifically, first, the carbon nanotube film is fixed to a spinning device. Next, the spinning device is operated to rotate the carbon nanotube film to form a twisted carbon nanotube wire.

  When the carbon nanotube structure includes a plurality of carbon nanotube wires, the plurality of carbon nanotube wires may be arranged in parallel, cross-woven, or twisted.

  As shown in FIG. 1, the sound wave generator 230 of the present embodiment includes a carbon nanotube structure. The carbon nanotube structure includes a carbon nanotube film. In the carbon nanotube film, the carbon nanotubes are arranged along the same direction. The sound wave generator 230 has a length of 3 cm, a width of 3 cm, and a thickness of 50 nm. When the sound wave generator 230 is thin (thickness is 10 μm or less), the sound wave generator 230 has excellent transparency. Therefore, by using the transparent sound wave generator 230, a transparent thermoacoustic device can be manufactured. The transparent thermoacoustic device can be installed on the surface of a mobile phone or LCD, for example. Or the said transparent thermoacoustic apparatus can be affixed on the surface of a picture. By using the transparent sound wave generator 230, the thermoacoustic apparatus is excellent in that it is small and light.

  In this embodiment, at least the electrode 220 includes a first electrode 220a and a second electrode 220b. The first electrode 220a and the second electrode 220b are made of a conductive material of metal, conductive adhesive, carbon nanotube, or ITO. In the present embodiment, the first electrode 220a and the second electrode 220b are rod-shaped metal electrodes. The sound wave generator 230 is electrically connected to the first electrode 220a and the second electrode 220b, respectively. The sound wave generator 230 can be supported by the first electrode 220a and the second electrode 220b. Using a conductive wire, the first electrode 220a and the second electrode 220b are electrically connected to both ends of the signal device 210 to form a signal loop. When the signal device 210 emits electromagnetic waves or light, the signal may be directly transmitted from the signal device 210 to the sound wave generator 230 without using the first electrode 220a and the second electrode 220b. it can. Since the carbon nanotube structure used for the sound wave generator 230 has adhesiveness, the sound wave generator 230 can be directly bonded to the first electrode 220a and the second electrode 220b.

  In order to satisfactorily electrically connect the first electrode 220a or the second electrode 220b and the sound wave generator 230, electrical conductivity is provided between the first electrode 220a or the second electrode 220b and the sound wave generator 230. An adhesive layer (not shown) can also be installed. The conductive adhesive layer may be installed on the surface of the sound wave generator 230. The conductive adhesive layer is made of a silver paste.

  The signal device 210 is one of an electric signal device, a direct current pulse signal device, an alternating current device, and an electromagnetic wave signal device (for example, an optical signal device, a laser). The signal transferred from the signal device 210 to the sound wave generator 230 is, for example, an electromagnetic wave (for example, an optical signal), an electrical signal (for example, an alternating current, a direct current pulsation signal, an audio electrical signal) or a mixed signal thereof. is there. The signal is received by the carbon nanotube structure and emitted as heat. Since the pressure intensity of the surrounding medium (environment) changes due to the radiation of heat, a detectable signal can be generated. When the thermoacoustic device 200 is used as a speaker, the input signal is an AC electric signal or an audio electric signal. When the thermoacoustic apparatus 200 is used as a photoacoustic spectrum device, the input signal is an optical signal. In this embodiment, the signal device 210 is a photoacoustic spectrum device, and the input signal is an optical signal.

  The installation of the first electrode 220a and the second electrode 220b is selective with respect to the different types of the signal device 210. For example, when the signal from the signal device 210 is an electromagnetic wave or light, the signal device 210 does not use the first electrode 220a and the second electrode 220b, and directly transfers the signal to the sound wave generator 230. be able to.

  The sound wave generator 230 can operate in the liquid medium 300. When a signal (eg, an electrical signal) is transmitted to the carbon nanotube structure in the sound wave generator 230 of the signal device 210, the carbon nanotube structure in the sound wave generator 230 generates heat. In the signal device 210, the carbon nanotube structure of the sound wave generator 230 includes a plurality of carbon nanotubes, and the heat capacity of the unit area is small. Therefore, the temperature wave generated in the sound wave generator 230 is quickly generated in the liquid medium 300. Is diffused. When a signal (for example, an electric signal) is transferred to the carbon nanotube structure of the sound wave generator 230, heat is generated in the carbon nanotube structure according to signal intensity and / or signal. Due to the heat generated in the sound wave generator 230, the liquid medium 300 is thermally expanded and its density is changed. Accordingly, sound is generated by diffusion of temperature waves generated by the sound wave generator 230.

In order to maintain the electro-thermal conversion rate of the sonic generator 230, the electrical resistivity of the liquid medium 300 is higher than the resistivity of the sonic generator 230 (eg, higher than 1 × 10 ⁻² Ω × M). ) It is preferable to set. The liquid medium 300 is a non-electrolyte solution, pure water, seawater, an organic solvent, or a mixture thereof. When the liquid medium 300 is pure water having an electric resistivity of 1.5 × 10 ⁷ Ω × M, the specific heat capacity of pure water is high, so that the heat generated by the sound wave generator 230 is quickly generated. Is diffused.

  FIG. 9 is a frequency response curve of the thermoacoustic apparatus 200 according to the first embodiment of the present invention. The carbon nanotube structure in the thermoacoustic device 200 includes a 16-layer drone structure carbon nanotube film. The carbon nanotubes in the adjacent carbon nanotube films are crossed at 0 °. The carbon nanotube structure is immersed in pure water having a depth of 0.1 cm. AC electric signals of 40 V, 50 V, and 60 V are applied to the carbon nanotube structure, respectively. In order to detect the performance of the thermoacoustic apparatus 200, the microphone is separated from the sound wave generator 230 at a distance of 5 cm and opposed to one side of the sound wave generator 230. From FIG. 9, it can be understood that the frequency response range of the thermoacoustic device 200 is wide and the sound pressure level is high in pure water. For example, the sound pressure level of the thermoacoustic device 200 can reach about 95 dB. The frequency response range of the thermoacoustic apparatus 200 is 1 Hz to 100 KHz.

(Example 2)
Referring to FIG. 10, the thermoacoustic device 400 of the present embodiment includes a signal device 410, a sound wave generator 430, a first electrode 420a, a second electrode 420b, a third electrode 420c, and a fourth electrode 420d. ,including. The configuration, characteristics, and functions of the thermoacoustic apparatus 400 of this embodiment are the same as those of the thermoacoustic apparatus 200 of the first embodiment. The difference between the present embodiment and the first embodiment is that the thermoacoustic apparatus 400 of the present embodiment includes four electrodes (first electrode 420a, second electrode 420b, third electrode 420c, and fourth electrode 420d). is there. The four electrodes have a rod shape and are separated from each other by a predetermined distance. The sound wave generator 430 is electrically connected to the four electrodes 420 so as to surround the four electrodes 420. Further, the first electrode 420a and the third electrode 420c are electrically connected in parallel to one end of the signal device 410 through a first conductive line (not shown). The second electrode 420b and the fourth electrode 420d are electrically connected in parallel to the other end of the signal device 410 through a second conductive line (not shown). Since the electrodes are connected in parallel to the signal device 410, the voltage applied to the thermoacoustic device 400 is low.

  The four electrodes may be installed on the same plane. In this case, the thermoacoustic apparatus 400 can be provided with a plurality of electrodes without being limited to the four electrodes.

(Example 3)
Referring to FIG. 11, the thermoacoustic device 500 of the present embodiment includes a signal device 510, a sound wave generator 530, a first electrode 520a, and a second electrode 520b. The configuration, characteristics, and functions of the thermoacoustic apparatus 500 of this embodiment are the same as those of the thermoacoustic apparatus 200 of the first embodiment. The difference between the present embodiment and the first embodiment is that the thermoacoustic apparatus 500 of the present embodiment includes a support 540. The sound wave generator 530 is installed on the surface of the support 540. The shape of the support 540 is determined according to the shape of the sound wave generator 530. The support 540 has a flat surface and / or a curved surface. The support 540 is one of a screen, a wall, a desk, and a display. The sound wave generator 530 may be in contact with the support 540.

  The support 540 is made of a hard material such as diamond, glass, or quartz, or a flexible material such as plastic, resin, or fabric. The support 540 has thermal insulation and cannot absorb the heat generated by the sound wave generator 530. Furthermore, it is preferable that a surface on which the support 540 and the sound wave generator 530 are in contact is provided roughly. As a result, the area where the sound wave generator 530 contacts the surrounding liquid medium can be increased. Since the carbon nanotube structure has a large specific surface area, the sound wave generator 530 can be directly bonded to the support 540.

  In order to connect the sound wave generator 530 and the support body 540 well, an adhesive layer (not shown) may be installed between the sound wave generator 530 and the support body 540. The adhesive layer may be disposed on the surface of the sound wave generator 530. In this embodiment, the conductive adhesive layer is made of a silver paste.

  The first electrode 520 a and the second electrode 520 b are installed on the same surface of the sound wave generator 530, or are respectively installed on opposing surfaces of the sound wave generator 530. The thermoacoustic device 500 can be provided with a plurality of electrodes without being limited to the two electrodes. The signal device 510 is connected to the sound wave generator 530 by a conductive wire (not shown).

Example 4
Referring to FIG. 12, the configuration, characteristics, and functions of the thermoacoustic apparatus of the present embodiment are the same as those of the thermoacoustic apparatus 500 of the third embodiment. The difference between the present embodiment and the third embodiment is that a part of the sound wave generator 530 is installed on the support body 540 to form a sound collection space from the sound wave generator 530 and the support body 540. That is. The space is a closed space or an open space. The support 540 is V-shaped, U-shaped or L-shaped. The thermoacoustic device 500 may include two or more supports 540. The support 540 is one of wood, plastic, metal, and glass. Referring to FIG. 12, in the present embodiment, the support 540 is L-shaped, and the sound wave generator 530 extends from the first end of the support 540 to the second end. In addition, a space for collecting sound can be formed from the support 540. The first electrode 520 a and the second electrode 520 b are installed on the surface of the sound wave generator 530 and are electrically connected to the signal device 510. Thereby, since the sound generated from the sound wave generator 530 is reflected by the inner wall of the support 540, the acoustic function of the thermoacoustic device 50 can be enhanced.

DESCRIPTION OF SYMBOLS 100 Thermophone 102 Platinum piece 104 Clamp 143a Carbon nanotube film 143b Carbon nanotube segment 145 Carbon nanotube 200 Thermoacoustic device 210 Signal device 220 Electrode 220a First electrode 220b Second electrode 230 Sound wave generator 400 Thermoacoustic device 410 Signal device 420 Electrode 420a First One electrode 420b Second electrode 420c Third electrode 420d Fourth electrode 430 Sound wave generator 500 Thermoacoustic device 510 Signal device 520 Electrode 520a First electrode 520b Second electrode 530 Sound wave generator 540 Support

Claims (6)

A signal device and a sound wave generator including a carbon nanotube structure,
At least a portion of the carbon nanotube structure is in contact with a liquid medium;
By the carbon nanotube structure, the signal from the signal device is converted into heat,
A thermoacoustic apparatus that generates sound by converting the density of the liquid medium. Including carbon nanotube structures,
A thermoacoustic apparatus, wherein the carbon nanotube structure generates sound by a thermoacoustic principle in a liquid medium. 3. The thermoacoustic according to claim 1, wherein the carbon nanotube structure has a heat capacity per unit area of 0 (not including 0) to 2 × 10 ⁻⁴ J / cm ² · K or less. apparatus. The thermoacoustic device according to any one of claims 1 to 3, wherein the electric resistivity of the liquid medium is higher than 1 x ^10-2 Ω x M.   The thermoacoustic device according to any one of claims 1 to 4, wherein the carbon nanotube structure is immersed in the liquid medium. The device comprises at least two electrodes;
The thermoacoustic apparatus according to any one of claims 1 to 5, wherein the at least two electrodes are separated by a predetermined distance and are electrically connected to the sound wave generator, respectively.