WO2010143380A1 - 音波発生器とその製造方法ならびに音波発生器を用いた音波発生方法 - Google Patents
音波発生器とその製造方法ならびに音波発生器を用いた音波発生方法 Download PDFInfo
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- WO2010143380A1 WO2010143380A1 PCT/JP2010/003709 JP2010003709W WO2010143380A1 WO 2010143380 A1 WO2010143380 A1 WO 2010143380A1 JP 2010003709 W JP2010003709 W JP 2010003709W WO 2010143380 A1 WO2010143380 A1 WO 2010143380A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R23/00—Transducers other than those covered by groups H04R9/00 - H04R21/00
- H04R23/002—Transducers other than those covered by groups H04R9/00 - H04R21/00 using electrothermic-effect transducer
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- the present invention relates to a thermal excitation type sound wave generator, a manufacturing method thereof, and a sound wave generation method using the sound wave generator.
- various sound wave generators are known. Except for some special sound wave generators, most of them generate sound waves by converting the mechanical vibration of the vibration part into the vibration of a medium (for example, air). However, in the sound wave generator using mechanical vibration, since the vibration part has a specific resonance frequency, the frequency band of the generated sound wave is narrow. In addition to this, since the resonance frequency changes depending on the size of the vibration part, it is difficult to miniaturize and make an array while maintaining the frequency characteristics.
- Non-Patent Document 1 is a combination of a base layer having a relatively high thermal conductivity (p-type crystalline Si layer) and a heat insulating layer having a relatively low thermal conductivity (microporous Si layer). Disclosed is a sound wave generator in which an Al (aluminum) thin film sandwiching a heat insulating layer is further disposed.
- Non-Patent Document 2 is a combination of a base layer having a relatively high thermal conductivity (single crystal Si layer) and a heat insulating layer having a relatively low thermal conductivity (porous nanocrystalline Si layer). Disclosed is a sound wave generator in which a W (tungsten) thin film sandwiching a heat insulating layer is further disposed.
- Non-Patent Documents 1 and 2 When electric power containing an AC component is supplied to an Al thin film or a W thin film, the temperature of the thin film periodically changes due to Joule heat; Because the thermal conductivity of the layer is small, it is transmitted to the air in contact with the thin film without escaping to the base layer side; periodic temperature changes transmitted to the air induce periodic changes in the air density and sound waves Is generated.
- a heat-induced sound wave generator can generate sound waves without mechanical vibration. Therefore, the frequency band of the generated sound wave is wide. In addition to this, miniaturization and arraying are relatively easy.
- Patent Document 1 discloses that in a thermally excited sound wave generator, application of heat by a pulse current is preferable for increasing the power of the generated sound wave. Patent Document 1 further discloses a heat insulating layer having protrusions on the surface.
- Patent Document 2 discloses a technique in which a current obtained by superimposing a direct current on an alternating current is applied to a thermal excitation type sound wave generator.
- Patent Document 2 describes a sound wave generator in which the base layer is a single crystal Si substrate and the heat insulating layer is a porous Si layer.
- Patent Document 3 discloses a sound wave generator including a heat insulating layer (nanocrystalline Si layer) obtained by anodizing treatment and supercritical drying. Patent Document 3 further describes that the smaller the ratio of ⁇ C of the heat insulating layer to the thermal property value ⁇ C ( ⁇ : thermal conductivity, C: heat capacity) of the base layer, the larger the sound pressure that is output, and the porosity of the heat insulating layer. The higher the value, the smaller the ⁇ C of the layer, and the fact that a nanocrystalline Si layer having a porosity of 75% or more is preferable as the heat insulating layer.
- Patent Document 4 the ratio of ⁇ C of the heat insulating layer to ⁇ C of the base layer ⁇ I C I / ⁇ S C S (I: heat insulating layer, S: base layer) satisfies the formula 1/100 ⁇ ⁇ I C I / ⁇ S C S Disclosed is a sound wave generator that satisfies and satisfies the formula ⁇ S C S ⁇ 100 ⁇ 10 6 .
- the technology of Patent Document 4 is based on the technical idea of combining a base layer and a heat insulating layer so that the thermal contrast between the base layer and the heat insulating layer represented by the formula ⁇ I C I / ⁇ S C S exceeds 1: 100, and a high ⁇ C.
- Patent Document 4 Based on the technical idea of selecting a base layer having Patent Document 4 describes silicon, copper and SiO 2 as materials constituting the base layer, and porous silicon, polyimide, SiO 2 , Al 2 O 3 and polystyrene foam as materials constituting the heat insulating layer, respectively. .
- the most preferable combination of the base layer and the heat insulating layer in Patent Document 4 is a combination of a base layer made of silicon and a heat insulating layer made of porous silicon.
- the sound pressure output from the sound wave generator is determined by the thermal contrast ⁇ I C I / ⁇ S C S between the base layer and the heat insulating layer and ⁇ C of the base layer.
- the output characteristics of the sound wave generator are not simply determined only by the thermal characteristics of the base layer and the heat insulating layer. In a minute structure such as a sound wave generator, it is estimated that heat transfer and dissipation proceed through a very complicated process.
- the present invention provides a sound wave generator that is superior in output characteristics than the conventional one based on a combination of a base layer and a heat insulating layer that cannot be predicted by conventional techniques.
- the sound wave generator according to the present invention includes a base layer, a heat insulating layer disposed on the base layer, and a heat pulse source that applies a heat pulse to the heat insulating layer.
- the base layer is made of graphite or sapphire.
- the heat insulating layer is composed of crystalline fine particles containing silicon or germanium.
- the method for manufacturing a sound wave generator according to the present invention is a method for manufacturing the sound wave generator according to the present invention, and includes the following first step and second step.
- the first step is to form a coating film of a solution in which crystalline fine particles containing silicon or germanium are dispersed on a base layer composed of graphite or sapphire, and heat-treating the formed coating film; Forming a heat insulating layer to be constructed on the base layer;
- the second step is a step of providing a heat pulse source for applying a heat pulse to the heat insulating layer.
- the sound wave generation method of the present invention is a sound wave generation method using a sound wave generator.
- the sound wave generator includes a base layer, a heat insulating layer disposed on the base layer, and a heat pulse source that applies a heat pulse to the heat insulating layer.
- the base layer is made of graphite or sapphire.
- the heat insulating layer is composed of crystalline fine particles containing silicon or germanium.
- the method includes the step of generating a sound wave by applying a heat pulse to the heat insulating layer by the heat pulse source.
- the present invention realizes a sound wave generator that has better output characteristics than conventional ones.
- FIG. 1 It is a schematic diagram which shows an example of a structure of the object detection sensor using the sound wave generator of this invention. It is a schematic diagram which shows an example of the nondestructive inspection method of a wall surface which applied the sound wave generator of this invention. It is a schematic diagram which shows another example of the nondestructive inspection method of a wall surface which applied the sound wave generator of this invention. It is a flowchart which shows an example of the manufacturing method of the sound wave generator of this invention. It is a flowchart which shows another example of the manufacturing method of the sound wave generator of this invention. It is a figure which shows the evaluation result of the particle size distribution with respect to the silicon fine particle used in Example 1.
- FIG. 1 It is a schematic diagram which shows an example of a structure of the object detection sensor using the sound wave generator of this invention. It is a schematic diagram which shows an example of the nondestructive inspection method of a wall surface which applied the sound wave generator of this invention. It is a schematic diagram which shows another example of the nondestructive inspection
- FIG. 2 is a diagram showing a scanning electron microscope (SEM) image of a cross section of a heat insulating layer produced in Example 1.
- FIG. It is a figure which shows typically the cross section shown by FIG. 12A.
- 4 is a diagram showing an SEM image of a joint portion between fine particles in the heat insulating layer produced in Example 1.
- FIG. It is the figure which expanded the inside of the frame in FIG. 13A. It is a figure which shows typically the state of joining of microparticles
- FIG. It is a schematic diagram for demonstrating the measurement system which evaluates the sound wave generator produced in the Example. It is a figure which shows the output characteristic of the sound wave generator (Example 1-1) of this invention produced in Example 1.
- FIG. 6 is a view showing an SEM image of a cross section of a heat insulating layer produced in Example 3.
- FIG. 6 is a view showing an SEM image of a cross section of a heat insulating layer produced in Example 3.
- FIG. 6 is a view showing an SEM image of a cross section of a heat insulating layer produced in Example 3.
- FIG. 19 is a diagram schematically showing a cross section shown in FIGS. 18A to 18C.
- FIG. 6 is a perspective view schematically showing a sound wave generator of the present invention produced in Example 4.
- FIG. 1 shows an example of a sound wave generator of the present invention.
- a sound wave generator 1 (1A) shown in FIG. 1 includes a base layer 11, a heat insulating layer 12, and a heat pulse source 13.
- the base layer 11 is disposed on the heat insulating layer 12 so as to be in contact with the heat insulating layer 12.
- the base layer 11 is made of graphite or sapphire.
- the heat insulating layer 12 is composed of crystalline fine particles containing silicon or crystalline fine particles containing germanium.
- the heat pulse source 13 is disposed so that the heat pulse 14 can be applied to the surface of the heat insulating layer 12 opposite to the surface on the base layer 11 side.
- the heat pulse 14 When the heat pulse 14 is applied from the heat pulse source 13 to the heat insulation layer 12 in the sound wave generator 1A, most of the heat energy given to the heat insulation layer 12 by the AC component of the heat pulse 14 is in contact with the heat insulation layer 12. (For example, air). At this time, the thermal energy transmitted to the medium changes over time according to the waveform of the AC component. For this reason, the density of the medium in the vicinity of the heat insulating layer 12 changes with time, and sound waves 15 are generated. Except for the heat pulse 14 having a sinusoidal waveform, the heat pulse 14 generally includes an AC component and a DC component. The heat energy given to the heat insulation layer 12 by the direct current component of the heat pulse 14 does not change with time, and thus does not contribute to the generation of the sound wave 15. The thermal energy moves from the heat insulating layer 12 to the base layer 11 and is removed from the heat insulating layer 12. The change in the density of the medium in the vicinity of the heat insulating layer 12 caused by the application of the heat pulse 14 may or may not be periodic.
- the sound wave generator of the present invention is a combination of the base layer 11 and the heat insulating layer 12 made of a specific material, and is suitable for such heat-induced sound wave generation by an unprecedented combination. A state of heat flow is achieved.
- the output characteristics of the sound wave generator of the present invention are higher than those of the conventional sound wave generator.
- the base layer 11 is a layer made of graphite or sapphire. As long as the effects of the present invention are obtained, the base layer 11 may contain a material other than graphite or sapphire.
- the base layer 11 is typically a layer whose surface in contact with the heat insulating layer 12 is formed of graphite or sapphire.
- the shape of the base layer 11 is not limited.
- the shape of the base layer 11 is arbitrarily selected according to the use of the sound wave generator 1 of the present invention.
- the base layer 11 is typically a sheet, but may have a three-dimensional shape.
- a specific example of the three-dimensional shape is a shape in which the surface in contact with the heat insulating layer 12 is a paraboloid as shown in Example 4.
- the heat insulating layer 12 is composed of crystalline fine particles containing silicon or crystalline fine particles containing germanium.
- the fine particles are typically silicon crystal fine particles or germanium crystal fine particles.
- the heat insulation layer 12 may contain materials other than the said microparticles
- the material includes, for example, particles made of other materials; particles made of silicon or germanium crystals but larger in size; particles containing silicon or germanium amorphous; particles containing silicon or germanium oxide; and these Any material present between each particle.
- the “fine particles” in the present specification typically have an average particle diameter of 10 nm to 0.5 ⁇ m.
- the average particle diameter of the fine particles is a median value of the particle size distribution of the fine particles in the heat insulating layer 12.
- the particle size distribution of the fine particles can be evaluated by image analysis of the heat insulating layer 12 using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).
- SEM scanning electron microscope
- TEM transmission electron microscope
- the “particle size of the fine particles” measured in the evaluation of the particle size distribution is defined by the long side of a quadrangle that circumscribes the cross-sectional shape and has the smallest area. When the fine particles are spherical, the particle diameter of the fine particles is equal to the diameter of the sphere.
- the fine particles in the heat insulating layer 12 have a particle size distribution in the range of D10 (particle size with cumulative distribution of 10%) to D90 (particle size with cumulative distribution of 90%) in the range of 10 nm to 0.5 ⁇ m. Preferably there is.
- Crystal fine particles are fine particles whose diffraction peaks or spectral peaks peculiar to silicon crystals or germanium crystals are measured by wide-angle X-ray diffraction (WAXD) measurement or Raman spectroscopic measurement.
- WAXD wide-angle X-ray diffraction
- the shape of crystalline fine particles containing silicon or germanium constituting the heat insulating layer 12 (hereinafter also simply referred to as “fine particles”) is not limited.
- the fine particles are, for example, scaly or spherical.
- the shape of the fine particles can be confirmed by image analysis of the heat insulating layer 12 by SEM or TEM.
- primary particles of fine particles and secondary particles in which the primary particles are aggregated are mixed.
- the secondary particles have different particle sizes, they often have the same shape as the primary particles. Examples of secondary particles of fine particles are shown in FIGS.
- the primary particles 51 are scaly
- the secondary particles 52 in which the primary particles 51 are aggregated are also scaly reflecting the shape of the primary particles 51.
- the primary particles 53 are spherical
- the secondary particles 54 in which the primary particles 53 are aggregated are also spherical, reflecting the shape of the primary particles 53.
- the state in which primary particles and secondary particles in the heat insulating layer 12 are mixed, the ratio of the primary particles and the secondary particles in the heat insulating layer 12, and the shape of the secondary particles are analyzed by image analysis of the heat insulating layer 12 by SEM or TEM. Can be confirmed.
- the average particle diameter of both the primary particles and the secondary particles is typically 10 nm to 0.5 ⁇ m. In this case, it is preferable that D10 to D90 in the particle size distribution of both the primary particles and the secondary particles are in the range of 10 nm to 0.5 ⁇ m.
- the structure of the heat insulating layer 12 is not limited as long as it is composed of crystalline fine particles containing silicon or germanium and is disposed on a base layer composed of graphite or sapphire.
- FIG. 12A shows an SEM image of a cross section of the heat insulating layer 12 made of scale-like fine particles prepared in Example 1, and
- FIG. 12B shows a diagram schematically showing the cross section.
- FIGS. 18A to 18C show SEM images of the cross section of the heat insulating layer 12 made of spherical fine particles produced in Example 3, and
- FIG. 18D shows a diagram schematically showing the cross section.
- the heat insulating layer 12 preferably has a structure in which the fine particles are deposited and stacked so that the fine particles include innumerable pores between the fine particles.
- the heat insulating layer 12 has a porous structure in which fine particles are randomly stacked rather than closest packing.
- the state of heat flow in the heat insulating layer 12 and the state of heat flow between the heat insulating layer 12 and the base layer 11 are suitable for the generation of the sound wave 15, and the output characteristics of the sound wave generator 1 are further improved.
- the ratio of the included holes varies depending on the portion of the heat insulating layer 12.
- the lower layer portion of the heat insulating layer 12 (the portion on the base layer 11 side in the heat insulating layer 12) is included in the pores included in the upper layer portion (the portion of the heat insulating layer 12 opposite to the base layer 11).
- the percentage of is high. That is, the heat insulating layer 12 has a gradient of fine particle density in the thickness direction that gradually decreases from the base layer 11 side.
- the heat insulating layer 12 preferably has such a structure. In this case, the state of heat flow in the heat insulating layer 12 and the state of heat flow between the heat insulating layer 12 and the base layer 11 are suitable for the generation of the sound wave 15, and the output characteristics of the sound wave generator 1 are further improved.
- the heat insulating layer 12 shown in FIGS. 12A, 12B, and 18A-D has a structure having fine particles having a relatively large particle size in the lower layer portion and fine particles having a relatively small particle size in the upper layer portion.
- the heat insulating layer 12 has a gradient of the particle diameter of the fine particles that gradually decreases from the base layer 11 side in the thickness direction.
- the heat insulating layer 12 preferably has such a structure. In this case, the state of heat flow in the heat insulating layer 12 and the state of heat flow between the heat insulating layer 12 and the base layer 11 are suitable for the generation of the sound wave 15, and the output characteristics of the sound wave generator 1 are further improved.
- the heat insulating layer 12 has a fine particle density and a particle size gradient gradually decreasing in the thickness direction from the base layer 11 side.
- the sound wave generator 1 of the present invention having such a heat insulating layer 12 can be manufactured, for example, by the manufacturing method of the present invention.
- the fine particles are bonded to each other at their minute portions.
- an oxide film is formed at a portion where the fine particles are joined, and the fine particles are joined via the oxide film.
- the state of the heat flow in the heat insulating layer 12 and the state of the heat flow between the heat insulating layer 12 and the base layer 11 are more suitable for the generation of the sound wave 15, and the output characteristics of the sound wave generator 1 are further improved.
- the oxide film is made of, for example, SiO 2 .
- germanium for example, GeO 2 is used .
- the portion where the oxide film is formed in the fine particles extends over a length of about 2 to 10 nm, for example.
- the oxide film may be formed by natural oxidation or may be formed by an active oxidation method such as plasma oxidation or radical oxidation.
- the thickness of the heat insulation layer 12 needs to be at least enough to prevent the generation of the sound wave 15 due to a thermal short circuit between the base layer 11 and the heat pulse source 13.
- the thickness of the heat insulating layer 12 is preferably 10 nm to 50 ⁇ m, and more preferably 50 nm to 10 ⁇ m.
- the structure of the heat pulse source 13 and the arrangement of the heat pulse source 13 in the sound wave generator of the present invention are not limited as long as the heat pulse can be applied to the heat insulating layer 12.
- the laminated body of the base layer 11 and the heat insulation layer 12 and the heat pulse source 13 are separately arranged.
- the heat pulse source 13 is usually arranged so that the heat pulse 14 can be applied to the heat insulating layer 12 from the surface of the heat insulating layer 12 opposite to the surface on the base layer 11 side.
- the heat insulating layer can be arranged so that the heat pulse 14 can be applied to the heat insulating layer 12 from the surface on the base layer 11 side in FIG.
- the heat pulse source 13 includes, for example, a laser irradiation device or an infrared irradiation device.
- the laser is, for example, a pulse laser.
- the heat insulating layer 12 is made of a material that generates heat by the laser or infrared rays.
- the heat pulse source 13 includes, for example, a heat pulse generation layer (heat generation layer) that applies a heat pulse to the heat insulating layer 12 disposed on the surface of the heat insulating layer 12 opposite to the surface on the base layer 11 side.
- FIG. 4 shows a sound wave generator 1 (1B) of the present invention having such a configuration.
- the sound wave generator 1 ⁇ / b> B shown in FIG. 4 includes such a heat pulse generation layer 16.
- the heat pulse generation layer 16 is integrated with the base layer 11 and the heat insulating layer 12.
- the sound wave generator 1B including the heat pulse generation layer 16 has a higher efficiency of heat applied to the heat insulation layer 12 by the heat pulse source 13 than the sound wave generator 1A shown in FIG.
- the heat pulse generation layer 16 is a layer that generates a heat pulse by, for example, laser or infrared energy irradiated from a laser irradiation device or an infrared irradiation device provided in the heat pulse source 13.
- a heat pulse generation layer 16 is made of a material that generates heat by laser or infrared rays.
- the heat pulse generation layer 16 is, for example, an electrothermal layer that generates a heat pulse by a pulse current or a pulse voltage (hereinafter, both may be collectively referred to as “power pulse”) supplied to the layer.
- the heat pulse source 13 further includes power supply lines 17 ⁇ / b> A and 17 ⁇ / b> B for supplying power pulses to the heat pulse generation layer (electric heat layer) 16. May be. Since the sound wave generator 1 ⁇ / b> C including such a heat pulse source 13 can control the generation of the sound wave 15 by controlling the power pulse supplied to the heat pulse generation layer 16, it has excellent control characteristics. In addition to this, the efficiency of heat applied to the heat insulating layer 12 is high, and the sound wave output characteristics are further improved.
- the heat pulse generation layer 16 that generates a heat pulse by a power pulse is made of a resistance material that can generate a desired heat generation by applying power.
- the material is, for example, a carbon material. More specifically, for example, a carbon material obtained by heat-treating an organic material.
- the electrical resistivity of the material is preferably 10 ⁇ / square to 10 k ⁇ / square.
- the thickness of the heat pulse generation layer 16 is not particularly limited.
- the power supply lines 17A and 17B are usually made of a conductive material.
- the specific shape of the heat pulse generation layer 16 in the heat pulse source 13, the shape of the power supply lines 17A and 17B, and the state of electrical connection between the heat pulse generation layer 16 and the power supply lines 17A and 17B are not particularly limited. .
- the heat insulating layer 12 When the heat insulating layer 12 has an electrical resistivity that can function as an electric heating layer by supplying power pulses, the heat insulating layer 12 may function as both a heat insulating layer and a heat pulse generating layer.
- a sound wave generator of the present invention having such a heat insulating layer 12 is shown in FIG.
- the electrode supply lines 17 ⁇ / b> A and 17 ⁇ / b> B are electrically connected to the heat insulation layer 12, and the heat insulation layer 12 also functions as the heat pulse generation layer 16.
- Such a heat insulating layer 12 is composed of, for example, crystalline fine particles containing germanium that has been subjected to heat treatment in a specific temperature range.
- the heat pulse source includes a heat pulse generation layer (heat generation layer) disposed on a surface of the heat insulation layer opposite to the surface on the base layer side, and the heat pulse generation layer supplies power pulses supplied to the layer.
- the sound wave generator according to the present invention which is an electrothermal layer that generates heat pulses by means of an output factor (unit: 0.1 Pa / W or more, further 0.2 Pa / W or more, 0.5 Pa / W or more, depending on its configuration. Output sound pressure per applied power).
- an output factor unit: 0.1 Pa / W or more, further 0.2 Pa / W or more, 0.5 Pa / W or more, depending on its configuration. Output sound pressure per applied power.
- Such a high output factor realizes the use of the sound wave generator of the present invention as an ultrasonic sound source for detecting an object, particularly a small-sized and power saving (for example, driving power of 1 W or less).
- an ultrasonic wave is irradiated to an object separated from several tens of centimeters to several m, and the reflected sound wave is detected by a high sensitivity microphone, and the distance and position of the object are determined.
- An object detection sensor to detect is realized.
- An object detection sensor 101 shown in FIG. 7 includes a sound wave generator 1 according to the present invention, a drive circuit 102 that supplies power pulses to the sound wave generator 1, a sound collecting microphone 103, and an output signal amplifier 104 connected to the sound collecting microphone 103. , An A / D converter 105 and an arithmetic unit 106 are provided.
- the driving circuit 102 applies a power pulse to the sound wave generator 1 to generate a sound wave 15 from the sound wave generator 1.
- the sound wave 15 is preferably an ultrasonic wave.
- the sound wave 15 transmitted from the sound wave generator 1 is reflected by the object 107, and the reflected wave 108 returns to the object detection sensor 101.
- the reflected wave 108 is converted into an electric signal by the sound collecting microphone 103.
- the electric signal passes through the output signal amplifier 104 and the A / D converter 105 and is then processed by the arithmetic unit 106 to measure the distance and position of the object 107 with respect to the object detection sensor 101.
- the output characteristics of the sound wave generator 1 of the present invention are high, and therefore the object detection sensor 101 has high sensitivity.
- the application of the sound wave generator of the present invention is not limited to the object detection sensor, and can be applied to any conventional device including a sound wave generator.
- FIG. 8A shows an example of a non-destructive inspection method for a wall surface to which the sound wave generator of the present invention is applied.
- the base layer (not shown) and the heat insulating layer 12 are arranged so as to be in contact with the inspection target surface of the wall surface 111.
- the heat insulating layer 12 is exposed, and the base layer is sandwiched between the wall surface 111 and the heat insulating layer 12.
- Such a base layer can be formed, for example, by laminating graphite sheets on the inspection target surface of the wall surface 111.
- the heat insulating layer 12 on the base layer can be formed, for example, by attaching a separately formed heat insulating layer 12 to the base layer.
- a heat pulse is applied to the heat insulation layer 12 from the unit 112 provided with a heat pulse source and a sound wave detection part.
- the heat pulse is applied to the heat insulating layer 12 by, for example, laser, infrared, or microwave. With the application of the heat pulse, the heat insulating layer 12 emits a sound wave 15, and the transmitted sound wave 15 is measured by the sound wave detection unit of the unit 112.
- the sound wave 15 includes information on the surface and the inside of the wall surface 111.
- the information includes, for example, the history of the wall surface 111, the structure of the material constituting the wall surface 111, and the scratches present on the wall surface 111.
- the shape of the wall surface 111 is not limited, and may be, for example, the shape shown in FIG. 8B.
- the configuration shown in FIG. 8B is the same as the configuration shown in FIG. 8A except that the shape of the wall surface 111 is different.
- Patent Literature 3 Patent No. 3845077
- Literature 4 Patent No. 3808493
- the material having the highest ⁇ C among the materials listed in Table 1 is optimal as the base layer. It becomes. That is, according to the technique, diamond is the most suitable base layer, graphite having a lower ⁇ C than diamond is inferior to diamond, and sapphire having a much lower ⁇ C is unsuitable as a base layer.
- the base layer composed of sapphire or graphite is much higher than the base layer of diamond.
- a sound wave generator having output characteristics is realized.
- output characteristics are higher when a sapphire base layer having a relatively low ⁇ C is used than when a graphite base layer having a relatively high ⁇ C is used.
- Such a sound wave generator of the present invention is not derived from conventional techniques including those disclosed in Patent Documents 3 and 4.
- the present inventors have the interface between the graphite or sapphire constituting the base layer and the crystalline fine particles containing silicon or germanium constituting the heat insulating layer to generate heat-excited sound waves. Estimate that it is in a suitable state. As in the sound wave generator of the present invention, in a heat insulating layer composed of nanometer-sized fine particles, the state of heat flow in the layer is very complicated. Whether such a complicated heat flow state is actually suitable for the generation of thermally excited sound waves is not determined solely by the thermal property value ⁇ C of the layer and the thermal contrast between the layer and the base layer.
- the state of heat flow is suitable for the generation of thermally excited sound waves is considered to depend on the state of bonding between the fine particles constituting the heat insulating layer and the state of bonding between the fine particles and the base layer.
- the fine particles constituting the heat insulating layer and the fine particles and the base layer are bonded to each other through the oxide film (SiO 2 or GeO 2 film). There is a possibility that a heat flow state more suitable for the generation of sound waves is realized.
- the bonding between the fine particles constituting the heat insulating layer and the base layer is as follows.
- the surface energy ⁇ E of the material is proportional to the difference in electronegativity ( ⁇ ) of each element constituting the material.
- the ⁇ between Si—O of the silicon oxide film is 1.54.
- the ⁇ between Ge—O of the germanium oxide film is 1.43.
- ⁇ between sapphire Al—O is 1.83, which is larger than ⁇ between Si—O and Ge—O.
- the bonding between the fine particles constituting the heat insulating layer and the base layer is as follows.
- C—H bonds and C—OH bonds on the surface of graphite CH bonds and C—OH bonds are mainly found at the grain boundaries of graphite).
- the van der Waals force acting between the fine particles and the base layer is strengthened by reducing the distance between the fine particles and the base layer due to the strong bonding.
- This improved van der Waals force itself also promotes the formation of a strong bond between the particulate and the base layer. Thereby, it is considered that a state of hot particles suitable for the generation of thermally excited sound waves is realized between the base layer and the heat insulating layer.
- the thermal property value ⁇ C of sapphire is smaller than the thermal property value ⁇ C of silicon and germanium, but the relationship between the thermal conductivity of the base layer and the heat insulating layer in the sound generator of the present invention is the same as that of the conventional sound generator. Similarly, it is preferable that the thermal conductivity of the base layer is relatively high and the thermal conductivity of the heat insulating layer is relatively low. This relationship is based on the fact that the heat insulating layer is composed of fine particles.
- FIG. 9 shows an example of the production method of the present invention.
- a base layer and a first ink are prepared.
- the base layer is made of graphite or sapphire.
- the first ink is a solution in which crystalline fine particles containing silicon or germanium are dispersed, and is used to form a heat insulating layer on the base layer.
- the average particle size of the crystalline fine particles is typically 10 nm to 0.5 ⁇ m.
- D10 to D90 in the particle size distribution of the fine particles are in the range of 10 nm to 0.5 ⁇ m.
- the fine particles can be obtained, for example, by pulverizing silicon crystals or germanium crystals, preferably single crystals.
- the solvent of the first ink is not limited, but is typically an organic solvent.
- the solvent is preferably at least one selected from acetone, ethanol, methanol, benzene, hexane, pentane and isopropyl alcohol (IPA), and IPA is particularly preferable.
- These solvents have low surface tension and high wettability to the surface of the base layer composed of graphite or sapphire.
- a solvent with high wettability the state of heat flow between the base layer and the heat insulating layer formed from the first ink is suitable for the generation of heat-induced sound waves.
- the C—H bond and C—OH bond present on the surface of the base layer made of graphite contribute to the improvement of wettability between the base layer and the first ink.
- the first ink is applied to the surface of the base layer, and a coating film of the first ink is formed on the surface of the base layer.
- the formation method of a coating film is not specifically limited, For example, a spin coat method and the die coat method are applicable.
- the heat treatment temperature is adjusted according to the type of fine particles contained in the first ink.
- the heat treatment temperature is preferably 550 to 900 ° C.
- the heat treatment temperature is preferably 250 to 600 ° C.
- the heat treatment method is not particularly limited, and for example, the entire base layer and coating film may be accommodated in a furnace maintained at the heat treatment temperature.
- the heat treatment may include two or more heat treatment steps having different heat treatment temperatures and / or heat treatment atmospheres.
- a heat pulse source is provided so that a heat pulse can be applied to the heat insulating layer (second step).
- the sound wave generator of the present invention is manufactured. What is necessary is just to provide a heat pulse source so that a heat pulse can be applied to the said heat insulation layer from the surface on the opposite side to the base layer side in a heat insulation layer, for example.
- the heat pulse source in the sound wave generator of the present invention includes a heat pulse generation layer (heat generation layer) that applies a heat pulse to the heat insulation layer, disposed on the surface of the heat insulation layer opposite to the base layer side surface,
- the second step may be the following step A.
- step A a coating film of a precursor solution (second ink) that becomes a carbon material is formed by heat treatment on the surface of the heat insulating layer formed in the first step opposite to the base layer side, and the coating film thus formed is formed. Is heat-treated to form a heat pulse generating layer.
- FIG. 10 An example of the manufacturing method of the present invention including such a second step is shown in FIG.
- the method shown in FIG. 10 is the same as the method shown in FIG. 9 until a laminate of the base layer and the heat insulating layer is obtained.
- the second ink is applied to the surface of the formed heat insulating layer, and a coating film of the second ink is formed on the surface of the heat insulating layer.
- the formation method of a coating film is not specifically limited, For example, a spin coat method and the die coat method are applicable.
- the second ink is not limited as long as a heat pulse generation layer composed of a carbon material is formed by heat treatment, and typically contains an organic component such as turpentine oil or butyl acetate.
- the whole is heat-treated at 100 to 1000 ° C. to form a heat pulse generating layer from the second ink coating film.
- the sound wave generator of this invention provided with a base layer, a heat insulation layer, and a heat pulse generation layer is manufactured.
- the heat treatment temperature is adjusted according to the type of components contained in the second ink.
- the heat treatment may include two or more heat treatment steps having different heat treatment temperatures and / or heat treatment atmospheres.
- the heat treatment method is not particularly limited.
- the entire base layer, heat insulating layer, and second ink coating film may be accommodated in a furnace maintained at the heat treatment temperature.
- the heat pulse generation layer formed by application of the second ink and heat treatment is made of a tar-like material containing a carbon material such as carbon black. Since the material is excellent in heat resistance, it exhibits a stable function of the heat pulse generation layer when the sound wave generator of the present invention is operated. In addition, as the time of use as the heat generating layer elapses, the amount of nitrogen and oxygen contained immediately after formation gradually decreases, and the heat pulse generation layer becomes more stable. This decrease in the amount of nitrogen and oxygen is confirmed by energy dispersive X-ray spectroscopy (EDX).
- EDX energy dispersive X-ray spectroscopy
- the heat pulse generation layer preferably functions as a heat pulse generation layer by applying a power pulse to the layer, that is, an electrothermal layer.
- the sound wave generation method of the present invention is a method of generating sound waves using the above-described sound wave generator of the present invention. Specifically, in the sound wave generator of the present invention, a heat pulse is applied to the heat insulation layer by a heat pulse source to generate sound waves.
- the configuration of the sound wave generator is as described above.
- the heat pulse source includes a heat pulse generation layer that is disposed on a surface of the heat insulation layer opposite to the surface on the base layer side and that applies the heat pulse to the heat insulation layer.
- a heat pulse is applied to the heat insulation layer by the heat pulse generation layer to generate sound waves.
- the heat pulse generation layer is an electric heating layer that generates a heat pulse by a pulse current or a pulse voltage supplied to the layer, and the heat pulse source supplies electric power that supplies the pulse current or pulse voltage to the electric heating layer. It is preferable to further provide a supply line. At this time, a pulse current or a pulse voltage is supplied to the electric heating layer through the power supply line to generate a heat pulse in the layer. Then, the generated heat pulse is applied to the heat insulating layer to generate sound waves.
- the sound wave generation method of the present invention can be widely applied to conventional devices and methods using sound waves.
- Example 1 In Example 1, a sound wave generator having a heat insulating layer composed of crystalline silicon fine particles was produced. And the material which comprises a base layer was changed and it verified about the combination of a heat insulation layer and a base layer. In addition to this, a sound wave generator having a heat insulating layer composed of crystalline TiO 2 (titanium oxide) fine particles was produced, and similar verification was performed.
- the sound wave generator used for the verification was manufactured as follows according to the manufacturing method shown in FIG. First, four types of base layers made of graphite, sapphire, diamond or silicon were prepared. As the graphite, EYGS091203 manufactured by Panasonic Corporation was used. The thickness of the graphite base layer was 200 ⁇ m, and the thickness of the remaining three base layers was 500 ⁇ m. Next, a dispersion of crystalline silicon fine particles or a dispersion of crystalline TiO 2 fine particles was applied to the surface of the base layer by spin coating to form a coating film of the dispersion.
- the spin coating was performed in an airtight container kept in an air atmosphere and at room temperature (25 ° C.), and the conditions were 5 seconds at a rotational speed of 500 rpm and 60 seconds at 8000 rpm.
- the base layer with the coating film formed on the surface is heated at 100 ° C. under a nitrogen flow to dry the coating film, and then is heated at 800 ° C. (in the case of silicon fine particles) under a hydrogen flow or 500 ° C. (TiO 2 under an argon flow).
- a heat treatment was further performed to obtain a laminate in which the base layer and the heat insulating layer composed of the silicon fine particles or the TiO 2 fine particles were integrated. Heating at 100 ° C.
- the dispersion of silicon fine particles As the dispersion of silicon fine particles, a scale-like IPA dispersion of crystalline silicon fine particles (the content of silicon fine particles is 8.5% by weight, manufactured by Primet Precision Materials, Inc.) was used. .
- the silicon fine particles may be referred to as “Si (Lot # 1)”.
- TiO 2 fine particle dispersion a spherical crystalline TiO 2 fine particle IPA dispersion (the content of TiO 2 fine particles was 15.4% by weight, manufactured by CI Kasei Co., Ltd.) was used.
- the TiO 2 fine particles may be referred to as “TiO 2 (Lot # 1)”.
- the particle size distribution of the silicon fine particles in the dispersion was evaluated by a particle size distribution meter.
- the particle size distribution of silicon fine particles had a maximum value in the range of 8 nm (D10) to 156 nm (D90), and the median value of the particle size distribution as an example was 57 nm.
- the particle size distribution of silicon fine particles has a maximum value in the range of 100 nm (D10) to 300 nm (D90), and the median value of the particle size distribution as an example is 167 nm. there were.
- the particle size analysis by a general particle size distribution analyzer is performed by a spherical particle model, and does not depend on whether it is an ultrasonic method or a laser diffraction / scattering method.
- the particle size distribution is estimated by the scattering cross section of the laser light. For this reason, it is considered that the measured value by the laser diffraction scattering method is larger than the measured value by the ultrasonic method for particles having a flat shape such as scale-like particles. Therefore, in this embodiment, the heat insulating layer including silicon fine particles is analyzed by image analysis of a scanning electron microscope (SEM) image of the cross section of the formed heat insulating layer (the cross section perpendicular to the main surface of the layer). And the structure of the heat insulating layer were also evaluated.
- SEM scanning electron microscope
- the shape and particle size distribution of the silicon fine particles (Si (Lot # 1)) and TiO 2 fine particles (TiO 2 (Lot # 1)) in the heat insulation layer produced above were evaluated by image analysis of the SEM image.
- D10 was 50 nm
- D90 was 254 nm
- the median was about 115 nm.
- the evaluation results of the particle size distribution for silicon fine particles (Si (Lot # 1)) are shown in FIG.
- the TiO 2 fine particles were spherical, and D10 in the particle size distribution was 20 nm, D90 was 100 nm, and the median was 40 nm.
- the median value was 36 nm.
- Each fine particle in the produced heat insulating layer is in a state in which primary particles and secondary particles in which primary particles are aggregated are mixed, by observation using a high-resolution SEM or transmission electron microscope (TEM), confirmed.
- the particle size distribution obtained by image analysis of the SEM image is a particle size distribution including both primary particles and secondary particles because all the fine particles constituting the heat insulating layer cannot be classified into primary particles and secondary particles. is there.
- the heat insulating layer composed of silicon fine particles has a unique structure shown in FIGS. 12A and 12B.
- the structure had the following specific features: a large amount of relatively large fine particles were distributed in the lower layer portion (the portion on the base layer 11 side) of the heat insulating layer 12, and the upper layer portion (the portion on the side opposite to the base layer 11). ) A large number of relatively small fine particles were distributed; the fine particles in the lower layer portion were mainly the secondary particles 52 in which the primary particles 51 were aggregated, and the particles in the upper layer portion were mainly the primary particles 51 and the relatively small particles. It was a small secondary particle 52; each adjacent fine particle was bonded to each other by a bonding portion having a very small area.
- FIG. 13B is an enlarged view of a portion indicated by a frame in FIG. 13A.
- the porosity of the layer was evaluated by performing RBS (Rutherford backscattering) analysis while etching the layer from the upper layer portion of the heat insulation layer thus prepared.
- RBS Rutherford backscattering
- the scattering cross section of the heat insulating layer is estimated, whereby the porosity of the layer can be calculated.
- the porosity of the heat insulating layer was about 50% in the uppermost layer portion and about 90% in the lowermost layer portion, and had a tendency to gradually increase from the uppermost layer portion toward the lowermost layer portion.
- the wide-angle X-ray diffraction (WAXD) profile and the Raman spectroscopic profile were evaluated with respect to the produced heat insulation layer.
- WAXD wide-angle X-ray diffraction
- Raman spectroscopic profile a peak was confirmed at the position where the Raman shift was 522 cm ⁇ 1 .
- the WAXD profile of the heat insulating layer composed of TiO 2 fine particles diffraction peaks are present at diffraction angles 2 ⁇ of 25.3 °, 37.8 °, 48.1 °, 55.1 ° and 75.0 °. confirmed. These diffraction peaks are unique to TiO 2 crystals. That is, it was confirmed that the produced heat insulating layer was composed of crystalline silicon fine particles or crystalline TiO 2 fine particles.
- a precursor solution in which turpentine oil, butyl acetate and ethyl acetate are mixed at a weight ratio of 6: 3: 1 is applied to the exposed surface of the heat insulating layer in the prepared laminate by spin coating, and the precursor solution The coating film was formed.
- the spin coating conditions were the same as those for spin coating a dispersion of silicon fine particles or TiO 2 fine particles on the surface of the base layer.
- the laminate on which the coating film is formed is heated at 120 ° C. under a nitrogen flow to dry the coating film, and then 800 ° C. (in the case of a heat insulating layer composed of silicon fine particles) or 500 ° C. under an argon flow.
- a pair of Pt (platinum) electrodes for applying a power pulse to the heat generating layer was provided on the heat generating layer in the produced laminate by a sputtering method, thereby obtaining a sound wave generator.
- One of the electrodes has a strip shape with a thickness of 0.3 ⁇ m, a width of 1 mm, and a length of 10 mm. The distance between the pair of electrodes was adjusted between 1 and 20 mm, typically 5 mm.
- the electrode for applying the power pulse to the heat generating layer is not limited to Pt, and can be composed of any conductive material.
- Table 2 below shows the configuration of the produced sound wave generator.
- the numerical value in the parenthesis in each column of Table 2 is the thickness of each layer.
- the system shown in FIG. 14 includes a sound generation unit 221 including a sound wave generator 200 and a sound collection unit 222 that collects and analyzes the sound wave 213 emitted from the sound wave generator 200.
- the sound generator 221 further includes a signal generator 210, an input signal amplifier 211, and a waveform measuring device 212.
- the signal generator 210 and the input signal amplifier 211 are connected to the sound wave generator 200 and apply power pulses for sound wave output to the heat generation layer of the sound wave generator 200.
- the waveform of the applied power pulse is measured by the waveform measuring device 212.
- the sound collection unit 222 includes a sound collection microphone 214, an output signal amplifier 215, a filter (noise filter) 216, and a waveform measuring instrument 217.
- the sound wave 213 transmitted from the sound wave generator 200 is converted into an electric signal by the sound collecting microphone 214.
- the signal is measured by the waveform measuring instrument 217 after passing through the output signal amplifier 215 and the filter 216.
- the output characteristics of the sound wave generator were evaluated according to the description in Non-Patent Document 2, with the distance between the sound wave generator 200 and the sound collecting microphone 214 being 5 mm.
- 4939 manufactured by B & K was used for the sound collecting microphone 214.
- FIG. 15 shows the evaluation results for Example 1-1.
- the upper part of FIG. 15 shows the waveform of the power pulse applied to the heat generating layer of Example 1-1.
- the lower part shows the waveform of the sound wave generated by the sound wave generator as the sound pressure waveform.
- the horizontal axis is the elapsed time from the start of application of the power pulse.
- by applying a power pulse having a rectangular waveform it was confirmed that an impulse sound wave having a frequency corresponding to the modulation was transmitted.
- the frequency was about 100 kHz (the half width of the pulse was about 10 ⁇ sec). Sound waves were emitted when a large modulation bias such as the rising and falling of a rectangular pulse was applied.
- no sound wave was emitted when a steady bias was applied. This indicates that the mechanism of sound wave generation in Example 1-1 is based on heat-induced sound wave generation in which sound waves are generated by the alternating current component of the applied heat pulse.
- Example 1-1 the change in the maximum sound pressure of the sound wave transmitted from Example 1-1 when the maximum value of the power pulse applied to the heat generation layer of Example 1-1 was changed was measured.
- the measurement results are shown in FIG.
- the horizontal axis in FIG. 16 represents the applied power to Example 1-1.
- the maximum sound pressure of the sound wave transmitted from Example 1-1 was proportional to the applied power.
- the maximum sound pressure of a transmitted sound wave is proportional to the applied “voltage”.
- the maximum sound pressure of a transmitted sound wave is proportional to the applied “power”, that is, the square of the applied voltage.
- the maximum sound pressure of the transmitted sound wave is proportional to the applied power. This is because the sound wave generation mechanism in Example 1-1 is a heat-induced type. It is based on the generation of sound waves.
- the same evaluation was performed by changing the frequency of the applied power pulse in the range of 1 kHz to 100 kHz. Irrespective of the frequency of the power pulse, the transmission of an impulse sound wave having a frequency corresponding to the frequency could be confirmed.
- the upper limit of the band of the sound collecting microphone of the measurement system is 100 kHz, the transmission of sound waves up to a frequency of 100 kHz was measured. However, generation of sound waves having a higher frequency can be sufficiently expected.
- Example 1-2 the same waveform was obtained although the maximum value of the output sound pressure was different.
- Table 3 below shows the sound pressure of sound waves (output sound pressure per unit applied power) transmitted by each of the examples and comparative examples shown in Table 2.
- the output characteristics of the transmitted sound wave were evaluated by changing the thickness of the heat insulating layer. It was confirmed that the thickness of the heat insulating layer is preferably 10 nm or more and less than 50 ⁇ m, and more preferably 50 nm or more and 10 ⁇ m or less.
- Comparative Examples 1-B to 1-F the output characteristics of the transmitted sound waves were evaluated by changing the thickness of the heat insulating layer. Even when the thickness of the heat insulating layer was changed, the situation in which sound waves were hardly transmitted was not changed.
- Example 2 In Example 2, a sound wave generator having a heat insulating layer composed of crystalline germanium fine particles was produced. And the material which comprises a base layer was changed and it verified about the combination of a heat insulation layer and a base layer.
- the sound wave generator used for the verification used a dispersion of crystalline germanium fine particles instead of a dispersion of crystalline silicon fine particles, and the temperature of the heat treatment was changed from 800 ° C. for silicon fine particles to 400 ° C. Except what was done, it produced similarly to each Example in Example 1, and a comparative example.
- germanium fine particles As a dispersion of germanium fine particles, an IPA dispersion of scaly crystalline germanium fine particles (germanium fine particle content: 8.6% by weight, manufactured by Primet Precision Material Co., Ltd.) was used. In this embodiment, the germanium fine particles may be referred to as “Ge (Lot # 1)”.
- the shape and particle size distribution of the germanium fine particles (Ge (Lot # 1)) in the produced heat insulating layer were evaluated by image analysis of SEM images.
- the germanium fine particles were scaly, and D10 in the particle size distribution was 42 nm, D90 was 200 nm, and the median was 95 nm.
- D10 was 4 nm
- D90 was 125 nm
- the median was 40 nm.
- the heat insulating layer composed of the germanium fine particles has a unique structure similar to the heat insulating layer composed of the silicon fine particles in Example 1 (see FIG. 12B). confirmed.
- the structure had the following specific features: a lot of relatively large fine particles were distributed in the lower layer part (base layer side part) of the heat insulation layer, and compared with the upper layer part (part opposite to the base layer). Many fine particles were distributed; the fine particles in the lower layer were mainly secondary particles in which the primary particles were aggregated, and the particles in the upper layer were mainly the primary particles and relatively small secondary particles. Each adjacent fine particle was bonded to each other by a bonding portion having a very small area.
- the porosity of the heat insulating layer was about 50% in the uppermost layer portion and about 90% in the lowermost layer portion, and had a tendency to gradually increase from the uppermost layer portion toward the lowermost layer portion.
- the WAXD profile and the Raman spectroscopic profile were evaluated with respect to the produced heat insulation layer.
- diffraction angles 2 ⁇ are positions at 27.3 °, 45.3 °, 53.7 °, 66.0 °, 72.8 ° and 83.7 °.
- a diffraction peak was confirmed at 1 and a peak was confirmed at the position where the Raman shift was 297 cm ⁇ 1 in the Raman spectroscopic profile.
- These diffraction peaks and Raman shifts are peaks and shifts unique to germanium crystals. That is, it was confirmed that the produced heat insulating layer was composed of crystalline germanium fine particles.
- Table 4 shows the configuration of the produced sound wave generator.
- the numerical value in the parenthesis in each column of Table 4 is the thickness of each layer.
- Example 2-3 the heat generating layer composed of the carbon material was not formed, and the heat insulating layer composed of the germanium fine particles was allowed to function as the heat generating layer.
- the heat insulating layer exhibits a sheet resistance suitable for the heat generating layer because the germanium fine particles exhibit conductivity by heat treatment at 400 to 600 ° C.
- the expression of conductivity is presumed to be due to the fact that GeO 2 between germanium fine particles tends to become GeO x (1 ⁇ x ⁇ 2) due to its deliquescence, and a conductive path is formed between the fine particles.
- the distance between the sound wave generator and the sound collecting microphone was 5 mm.
- Example 2-1 to 2-3 although the maximum value of the output sound pressure is different, the same result as in Example 1-1 was obtained. For example, in the same manner as in Example 1-1, by applying a power pulse having a rectangular wave waveform, it was confirmed that an impulse sound wave having a frequency corresponding to the modulation was transmitted. Further, for example, in Examples 2-1 to 2-3, the maximum sound pressure of the transmitted sound wave was proportional to the applied power. These indicate that the sound wave generation mechanism in Examples 2-1 to 2-3 is based on heat-induced sound wave generation.
- Table 5 below shows sound pressures of sound waves (output sound pressure per unit applied power) transmitted from the respective examples and comparative examples shown in Table 4.
- Example 2-2 and 2-3 when sapphire having a thermophysical value ⁇ C significantly smaller than that of diamond (Comparative Example 2-A) is used for the base layer (Examples 2-2 and 2-3), high output characteristics are obtained. It was realized. In Examples 2-2 and 2-3, the output characteristics of Example 2-2 were higher. Similar high output characteristics were realized when graphite was used for the base layer (Example 2-1). This high output characteristic is achieved for the first time in this example by finding that a combination of a base layer composed of sapphire or graphite and a heat insulating layer composed of crystalline germanium fine particles is optimal. It was done. Based on the conventional sound wave generator that discloses a technique for increasing the thermal contrast between the base layer and the heat insulating layer as much as possible and the technical idea thereof, those skilled in the art can never expect and realize the result of this embodiment. It was.
- the heat insulating layer composed of the germanium fine particles subjected to the heat treatment in a specific temperature range also functions as a heat pulse source (heat pulse generating layer) by applying a power pulse.
- the output characteristics of the transmitted sound wave were evaluated by changing the thickness of the heat insulating layer. It was confirmed that the thickness of the heat insulating layer is preferably 10 nm or more and less than 50 ⁇ m, and more preferably 50 nm or more and 10 ⁇ m or less.
- Example 3 a sound wave generator having a heat insulating layer made of crystalline silicon fine particles having a shape different from that of Example 1 was produced. And the material which comprises a base layer was changed and it verified about the combination of a heat insulation layer and a base layer.
- the sound wave generator used for the verification was produced in the same manner as in each example and comparative example in Example 1 except that the dispersion of silicon fine particles was different.
- silicon fine particles As the dispersion of silicon fine particles, spherical IPA dispersion of crystalline silicon fine particles (the content of silicon fine particles was 5% by weight, manufactured by EMPA) was used.
- the silicon fine particles may be referred to as “Si (Lot # 2)”.
- the shape and particle size distribution of the silicon fine particles (Si (Lot # 2)) in the produced heat insulating layer were evaluated by image analysis of the SEM image.
- the silicon fine particles were spherical, and D10 in the particle size distribution was 19 nm, D90 was 68 nm, and the median was 32 nm.
- the evaluation results of the particle size distribution for silicon fine particles (Si (Lot # 2)) are shown in FIG.
- D10 was 10 nm
- D90 was 100 nm
- the median was 20 nm.
- the heat insulation layer composed of silicon fine particles has a unique structure shown in FIGS. 18A to 18D.
- the structure had the following specific features: a large amount of relatively large fine particles were distributed in the lower layer portion (the portion on the base layer 11 side) of the heat insulating layer 12, and the upper layer portion (the portion on the side opposite to the base layer 11). ) A large number of relatively small fine particles were distributed; the fine particles in the lower layer portion were mainly secondary particles 54 in which the primary particles 53 were aggregated, and the particles in the upper layer portion were mainly the primary particles 53 and the relatively small particles. Small secondary particles 54; each adjacent fine particle was bonded to each other by a bonding portion having a very small area.
- the porosity of the heat insulating layer is about 50% in the uppermost layer portion and about 90% in the lowermost layer portion, and the porosity tends to gradually increase from the uppermost layer portion toward the lowermost layer portion. It was.
- the WAXD profile and the Raman spectroscopic profile were evaluated with respect to the produced heat insulation layer.
- the WAXD profile of the heat insulation layer composed of silicon fine particles diffraction peaks were confirmed at positions where the diffraction angle 2 ⁇ was 28.5 °, 47.3 °, 56.1 °, etc., and the Raman shift in the Raman spectroscopic profile A peak was confirmed at a position of 522 cm ⁇ 1 .
- These diffraction peaks and Raman shifts are peaks and shifts unique to silicon crystals. That is, it was confirmed that the produced heat insulating layer was composed of crystalline silicon fine particles.
- Table 6 below shows the configuration of the produced sound wave generator.
- the numerical value in the parenthesis in each column of Table 6 is the thickness of each layer.
- the distance between the sound wave generator and the sound collecting microphone was 5 mm.
- Example 3-1 and 3-2 although the maximum value of the output sound pressure is different, the same result as in Example 1-1 was obtained. For example, in the same manner as in Example 1-1, by applying a power pulse having a rectangular wave waveform, it was confirmed that an impulse sound wave having a frequency corresponding to the modulation was transmitted. Further, for example, in Examples 3-1 and 3-2, the maximum sound pressure of the transmitted sound wave was proportional to the applied power. These indicate that the sound wave generation mechanism in Examples 3-1 and 3-2 is based on heat-induced sound wave generation.
- Table 7 below shows sound pressures of sound waves (output sound pressures per unit applied power) transmitted by the respective examples and comparative examples shown in Table 6.
- Example 3-2 when sapphire having a thermophysical value ⁇ C significantly smaller than that of diamond (Comparative Example 3-A) and silicon (Comparative Example 3-B) was used for the base layer (Example 3-2) Realized high output characteristics. Even when graphite (Example 3-1) was used for the base layer, high output characteristics were realized. The output characteristics of Example 3-2 using sapphire as the base layer were much higher than those of Example 3-1 using graphite as the base layer. This high output characteristic was achieved for the first time by finding that the combination of a base layer composed of sapphire or graphite and a heat insulating layer composed of silicon fine particles was optimal in this example. Based on the conventional sound wave generator that discloses a technique for increasing the thermal contrast between the base layer and the heat insulating layer as much as possible and the technical idea thereof, those skilled in the art can never expect and realize the result of this embodiment. It was.
- Example 4 In Example 4, a sound wave generator having the same base layer and heat insulating layer combination as in Example 1-1 and having a parabolic surface shape for transmitting sound waves was produced, and its output characteristics were verified.
- the sound wave generator used for verification was produced in the same manner as in Example 1-1 except that the shape of the surface on which the heat insulating layer in the graphite base layer was arranged was changed from a flat surface to a parabolic surface.
- the graphite base layer is formed by laminating two or more flexible graphite sheets (thickness 50 ⁇ m to 1 mm, typically 100 ⁇ m) on the paraboloid in the mold in which the paraboloid is formed, The laminate of sheets and the mold were formed separately.
- the diameter of the graphite base layer was 20 mm.
- One Pt electrode for applying a power pulse to the heat generating layer is arranged in a ring shape (1 mm width) at the peripheral edge of the heat generating layer, and the other is arranged in a circle having a diameter of 3 mm at the center of the heat generating layer. did.
- the produced sound wave generator 300 is shown in FIG. In FIG. 19, reference numeral 11 is a base layer, reference numeral 16 is a heat generating layer, and reference numeral 301 is an electrode.
- the heat insulating layer is sandwiched between the base layer 11 and the heat generating layer 16.
- the sound collecting microphone was moved on the central axis of the sound wave transmission surface of the sound wave generator so as to gradually move away from the transmission surface.
- the distance between the transmission surface and the sound collecting microphone was 7 mm, the largest output sound pressure was obtained. This indicates that a sound collection type sound wave generator can be realized by using the transmitting surface as a paraboloid.
- Example 1-1 it was confirmed that an impulse-like sound wave having a frequency corresponding to the modulation was transmitted by applying a power pulse having a rectangular waveform. According to Example 4, it was confirmed that the sound wave generator which has the shape of the transmission surface of various sound waves was fully implement
- the sound wave generator of the present invention Since the sound wave generator of the present invention has a high degree of freedom in shape and can be formed by drying and heat treatment of a coating film, it can be applied to various electronic devices.
- the sound wave generator of the present invention can be applied to various applications such as a sound source (ultrasonic sound source) directly provided on a three-dimensional object, a speaker, and an actuator.
Abstract
Description
図1は、本発明の音波発生器の一例を示す。図1に示される音波発生器1(1A)は、基層11、断熱層12および熱パルス源13を備える。基層11は、断熱層12と接するように、断熱層12上に配置されている。基層11は、グラファイトまたはサファイヤにより構成される。断熱層12は、シリコンを含む結晶性の微粒子、またはゲルマニウムを含む結晶性の微粒子により構成される。熱パルス源13は、断熱層12における基層11側の面とは反対側の面に熱パルス14を印加し得るように配置されている。
図9に、本発明の製造方法の一例を示す。図9に示される製造方法では、最初に、基層および第1のインクが準備される。基層は、グラファイトまたはサファイヤにより構成される。第1のインクは、シリコンまたはゲルマニウムを含む結晶性の微粒子が分散した溶液であり、基層上に断熱層を形成するために用いられる。
本発明の音波発生方法は、上述した本発明の音波発生器を用いて音波を発生する方法である。具体的には、本発明の音波発生器において、熱パルス源によって断熱層に熱パルスを印加して音波を発生させる。
実施例1では、結晶性のシリコン微粒子により構成される断熱層を有する音波発生器を作製した。そして、基層を構成する材料を変えて、断熱層と基層との組み合わせについて検証した。これに加えて、結晶性のTiO2(酸化チタン)微粒子により構成される断熱層を有する音波発生器を作製し、同様の検証を実施した。
実施例2では、結晶性のゲルマニウム微粒子により構成される断熱層を有する音波発生器を作製した。そして、基層を構成する材料を変えて、断熱層と基層との組み合わせについて検証した。
実施例3では、実施例1とは異なる形状を有する、結晶性のシリコン微粒子により構成される断熱層を有する音波発生器を作製した。そして、基層を構成する材料を変えて、断熱層と基層との組み合わせについて検証した。
実施例4では、実施例1-1と同じ基層および断熱層の組み合わせを有するとともに、音波を発信する面の形状が放物面である音波発生器を作製し、その出力特性を検証した。
Claims (10)
- 基層と、前記基層上に配置された断熱層と、前記断熱層に熱パルスを印加する熱パルス源と、を備え、
前記基層が、グラファイトまたはサファイヤにより構成され、
前記断熱層が、シリコンまたはゲルマニウムを含む結晶性の微粒子により構成される、音波発生器。 - 前記熱パルス源が、
前記断熱層における前記基層側の面とは反対側の面上に配置された、前記断熱層に熱パルスを印加する熱パルス発生層を備える請求項1に記載の音波発生器。 - 前記熱パルス発生層が、当該層に供給されるパルス電流またはパルス電圧によって熱パルスを発生する電熱層であり、
前記熱パルス源が、前記電熱層に前記パルス電流またはパルス電圧を供給する電力供給ラインをさらに備える請求項2に記載の音波発生器。 - 前記熱パルス発生層が、炭素材料により構成される請求項2に記載の音波発生器。
- 前記断熱層における前記微粒子の粒度分布の中央値が、10nm~0.5μmである請求項1に記載の音波発生器。
- 請求項1に記載の音波発生器の製造方法であって、
グラファイトまたはサファイヤにより構成される基層上にシリコンまたはゲルマニウムを含む結晶性の微粒子が分散した溶液の塗布膜を形成し、前記形成された塗布膜を熱処理して、前記微粒子により構成される断熱層を前記基層上に形成する第1工程と、
前記断熱層に熱パルスを印加する熱パルス源を設ける第2工程と、を含む音波発生器の製造方法。 - 前記熱パルス源が、前記断熱層における前記基層側の面とは反対側の面上に配置された、前記断熱層に熱パルスを印加する熱パルス発生層を備え、
前記熱パルス発生層は、炭素材料により構成され、
前記第2工程が、
前記第1工程において形成した前記断熱層における前記基層側とは反対側の面上に、熱処理によって炭素材料となる前駆体溶液の塗布膜を形成し、前記形成した塗布膜を熱処理して、前記熱パルス発生層を形成する工程である請求項6に記載の音波発生器の製造方法。 - 音波発生器を用いた音波発生方法であって、
前記音波発生器は、基層と、前記基層上に配置された断熱層と、前記断熱層に熱パルスを印加する熱パルス源と、を備え、
前記基層が、グラファイトまたはサファイヤにより構成され、
前記断熱層が、シリコンまたはゲルマニウムを含む結晶性の微粒子により構成され、
前記熱パルス源によって前記断熱層に熱パルスを印加して音波を発生させる工程を含む、音波発生方法。 - 前記熱パルス源が、前記断熱層における前記基層側の面とは反対側の面上に配置された、前記断熱層に熱パルスを印加する熱パルス発生層を備え、
前記工程が、前記熱パルス発生層によって前記断熱層に熱パルスを印加して音波を発生させる工程である請求項8に記載の音波発生方法。 - 前記熱パルス発生層が、当該層に供給されるパルス電流またはパルス電圧によって熱パルスを発生する電熱層であり、
前記熱パルス源が、前記電熱層に前記パルス電流またはパルス電圧を供給する電力供給ラインをさらに備え、
前記工程が、前記電力供給ラインを介して前記電熱層に前記パルス電流またはパルス電圧を供給することで当該層において熱パルスを発生させ、発生した熱パルスを前記断熱層に印加して音波を発生させる工程である請求項9に記載の音波発生方法。
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JP2004153797A (ja) * | 2002-09-30 | 2004-05-27 | Matsushita Electric Works Ltd | 超音波発生装置および照明器具 |
WO2004077881A1 (ja) * | 2003-02-28 | 2004-09-10 | Tokyo University Of Agriculture And Technology Tlo Co., Ltd. | 熱励起音波発生装置 |
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WO2004077881A1 (ja) * | 2003-02-28 | 2004-09-10 | Tokyo University Of Agriculture And Technology Tlo Co., Ltd. | 熱励起音波発生装置 |
JP2005073197A (ja) * | 2003-08-28 | 2005-03-17 | Nokodai Tlo Kk | 音波発生装置とその製造方法 |
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