JP2016099137A - Piezoelectric element, acoustic probe, and photoacoustic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric element whose detection accuracy has been upgraded more greatly than conventional one, an acoustic probe including the piezoelectric element, and a photoacoustic device.SOLUTION: A piezoelectric element 10 includes a piezoelectric substance 11 that receives an acoustic wave and converts the received acoustic wave into a voltage, positive and negative electrodes 12 that sandwich the piezoelectric substance 11, and a shading sound transmission material 13 shields the piezoelectric substance 11, transmits the acoustic wave to such an extent that a piezoelectric effect exerted in the piezoelectric substance 11 due to the acoustic wave can be measured, and suppresses a pyroelectric effect, which is exerted in the piezoelectric substance 11 due to irradiation of light, by attenuating the light.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a piezoelectric element, a sound probe including the piezoelectric element, and a photoacoustic apparatus including the sound probe, and particularly relates to a piezoelectric element, a sound probe, and a photoacoustic apparatus with improved measurement accuracy.

  A piezoelectric element is a passive element that utilizes the piezoelectric effect of a piezoelectric body, and converts a force applied to the piezoelectric body into a voltage or converts a voltage into a force.

  For piezoelectric element applications, vibration applied from the outside is converted into voltage by the piezoelectric effect, and a piezoelectric sensor is distorted by applying a signal voltage to a vibration sensor or an electrode that electrically detects the vibration. A piezoelectric speaker heard as (air vibration) can be mentioned. In addition, it is widely used in power generation circuits, driving devices, gyro sensors, pressure sensors, ink jet printers, and the like.

An example of a device that electrically detects vibration is a photoacoustic device. A “photoacoustic apparatus” is an apparatus that uses a photoacoustic effect. The “photoacoustic effect” is a phenomenon in which molecules that absorb light energy release heat and generate acoustic waves (dense / dense waves) due to volume expansion due to the heat. The generated acoustic waves are detected by a piezoelectric element or the like. Is done.
Conventional photoacoustic devices include a photoacoustic image device that performs image processing based on a photoacoustic signal emitted from a sample by irradiating the sample with light, and an ultrasonic image that obtains an image of the sample by transmitting and receiving ultrasonic waves. There exists an apparatus provided with the apparatus (for example, refer patent document 1). In particular, FIG. 2 describes a conventional photoacoustic image device, and describes a ZnO piezoelectric element as a piezoelectric element (four steps, 19 lines).

Japanese Patent No. 2870888

  Piezoelectric elements used in apparatuses that electrically detect vibrations as described above and analyze their detection amounts are required to have higher detection accuracy. SUMMARY OF THE INVENTION An object of the present invention is to provide a piezoelectric element with higher detection accuracy than the prior art, a sound probe including the piezoelectric element, and a photoacoustic apparatus including the sound probe.

The piezoelectric element 10 according to the first aspect of the present invention for solving the above problems includes a piezoelectric body 11 that receives a sound wave and converts the received sound wave into a voltage as shown in FIG. A positive and negative electrode 12 sandwiching the body 11; a light-blocking sound-transmitting material 13 covering the piezoelectric body 11, transmitting the sound wave to such an extent that the piezoelectric effect generated in the piezoelectric body 11 can be measured by the sound wave, And a light-shielding sound-transmitting material 13 that suppresses the pyroelectric effect generated in the body 11 by attenuating the light.
Note that “the degree to which the piezoelectric effect can be measured” refers to the degree to which the electrical signal of the voltage generated by the piezoelectric effect can be analyzed, and includes the case where the electrical signal is amplified and analyzed. “Attenuation” refers to reflecting, scattering, refraction or absorption of light.
If comprised in this way, in the photoacoustic apparatus which irradiates light to a sample, it can suppress that a piezoelectric material absorbs a thermal energy by irradiation of light, and a pyroelectric effect arises. That is, the piezoelectric element functions as a sensor due to the piezoelectric effect, while the light shielding sound-transmitting material suppresses the irradiation of light to the piezoelectric body and suppresses the generation of the pyroelectric effect on the piezoelectric body. Thereby, it can suppress that the measured value by a piezoelectric effect receives to the influence of a pyroelectric effect. As a result, the measurement accuracy of the piezoelectric element can be improved.

In the piezoelectric element according to the second aspect of the present invention, in the piezoelectric element 10 according to the first aspect of the present invention, the ratio of the sound transmittance to the light transmittance of the light-shielding sound-transmitting material 13 is 0.5 or more. is there.
“Sound transmissivity” refers to the ratio of the sound wave energy received when the light-shielding sound-transmitting material is provided to the sound wave energy received when the light-blocking sound-transmitting material is not provided. “Light transmissivity” refers to the ratio of the light energy received when the light-shielding sound-transmitting material is provided to the light energy received when the light-shielding sound-transmitting material is not provided.
If comprised in this way, light transmittance will become small enough with respect to sound transmittance. That is, the sound wave energy is also slightly lost, but the light energy is also lost. As a result, the piezoelectric effect caused by the sound wave can be measured while effectively suppressing the pyroelectric effect caused by the light irradiation.

In the piezoelectric element according to the third aspect of the present invention, in the piezoelectric element 10 according to the second aspect of the present invention, the acoustic transmission is larger than the light transmission.
With this configuration, since the rate at which sound waves pass through the light-blocking sound-transmitting material is greater than the rate at which light passes through the light-blocking sound-transmitting material, even if there is a loss of sound wave energy due to the light-blocking sound-transmitting material, the loss of light energy Less than. As a result, it is possible to measure the piezoelectric effect caused by sound waves while suppressing the pyroelectric effect caused by light irradiation particularly effectively.

The piezoelectric element according to the fourth aspect of the present invention is the light in which the piezoelectric body 11 has absorbed the irradiated light in the piezoelectric element 10 according to any one of the first to third aspects of the present invention. The sound wave generated by the absorber is received, and the light-shielding sound transmitting material 13 suppresses the pyroelectric effect generated in the piezoelectric body 11 by the light to such an extent that the piezoelectric effect generated in the piezoelectric body 11 by the sound wave can be measured.
With this configuration, the piezoelectric body receives a sound wave emitted from the light absorber irradiated with light, and the light irradiated to the light absorber is irradiated to the piezoelectric body directly or by reflection. However, since the piezoelectric body is covered with the light-blocking sound-transmitting material, light can be blocked (or attenuated). Furthermore, since the light-blocking sound-transmitting material blocks light to such an extent that the piezoelectric effect can be measured, the piezoelectric element including the light-blocking sound-transmitting material can improve the measurement accuracy of the piezoelectric effect.

The piezoelectric element according to a fifth aspect of the present invention is the piezoelectric element according to any one of the first to fourth aspects of the present invention, wherein the light-shielding sound-transmitting material 13 is a polyvinylidene fluoride resin, It is formed of at least one resin selected from the group consisting of silicon-based resins and epoxy resins, or aluminum.
If comprised in this way, a light-shielding sound-transmitting material can be manufactured with a suitable material.

The piezoelectric element according to the sixth aspect of the present invention is the same as the piezoelectric element 10 according to the fifth aspect of the present invention, wherein the light-blocking sound-transmitting material 13 is formed from the at least one resin, and the light-blocking sound-transmitting material 13 is used. Contains a filler that improves reflection, scattering, refraction or absorption of light, and the filler is granular or powdery talc, mica, silica, alumina, kaolin, ferrite, potassium titanate, titanium oxide, zinc oxide, Iron oxide, magnesium hydroxide, calcium carbonate, nickel carbonate, calcium sulfate, barium sulfate, aluminum hydroxide, glass powder, quartz powder, graphite, inorganic pigment, organic metal salt, other metal oxides, fibrous carbon fiber, glass Fiber, asbestos fiber, silica fiber, alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber It is at least one selected from the group consisting of.
With this configuration, an appropriate filler can be selected as a filler that reflects, scatters, refracts, or absorbs light.

In the piezoelectric element according to the seventh aspect of the present invention, in the piezoelectric element 10 according to the sixth aspect of the present invention, the filler is white.
If comprised in this way, the piezoelectric element provided with the light-shielding sound-transmitting material which attenuates light more can be formed.

The acoustic probe 20 according to the eighth aspect of the present invention includes a piezoelectric element 10 according to any one of the first to seventh aspects of the present invention, as shown in FIG. And a support case 21 to support.
With this configuration, even when a sound wave probe is used in an environment where light is irradiated to the piezoelectric element, the pyroelectric effect due to light irradiation is suppressed, and the voltage based on the piezoelectric effect due to the received sound wave Can be measured more accurately.

The photoacoustic apparatus 50 according to the ninth aspect of the present invention includes, as shown in FIGS. 2 and 3, for example, a light source 31 that emits the light; and light irradiation that irradiates a subject with light emitted from the light source 31. An acoustic probe 20 according to the sixth aspect of the present invention; and a signal processing device 40 that controls these devices and performs signal transmission / reception, recording / analysis, and the like.
Note that the “light irradiator” refers to a portion that delivers light emitted from a light source to a subject in the light source device.
If comprised in this way, a piezoelectric element is equipped with the light-shielding sound-transmitting material manufactured with the material with the high effect of interrupting | blocking light compared with a sound wave. Therefore, even when the light applied to the subject is applied to the piezoelectric element directly or by reflection, the pyroelectric effect caused by the light irradiation can be effectively suppressed. Therefore, the measurement accuracy of the photoacoustic apparatus can be improved.

A photoacoustic apparatus according to a tenth aspect of the present invention is the photoacoustic apparatus according to the ninth aspect of the present invention, wherein a voltage is applied to the piezoelectric element so that the piezoelectric element vibrates and generates a sound wave. A pulse voltage generator; and the piezoelectric element receives a reflected wave of a sound wave generated from the piezoelectric element.
Such a configuration is preferable because the piezoelectric element can transmit and receive sound waves (particularly ultrasonic waves) and can acquire images (particularly ultrasonic images).

The light-shielding sound-transmitting material according to the eleventh aspect of the present invention includes a polyvinylidene fluoride resin; granular or powdered talc, mica, silica, alumina, kaolin, ferrite, potassium titanate, titanium oxide, zinc oxide, and oxide. Iron, magnesium hydroxide, calcium carbonate, nickel carbonate, calcium sulfate, barium sulfate, aluminum hydroxide, glass powder, quartz powder, graphite, inorganic pigments, organic metal salts, other metal oxides, fibrous carbon fibers, glass fibers , Containing at least one filler selected from the group consisting of asbestos fiber, silica fiber, alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, and potassium titanate fiber; Greater than sex.
With this configuration, the rate at which sound waves pass through the light-blocking sound-transmitting material is higher than the rate at which light passes through the light-blocking sound-transmitting material. A light-shielding sound-transmitting material to be lost can be obtained.

The light-blocking sound-transmitting material according to the twelfth aspect of the present invention is the light-blocking sound-transmitting material according to the eleventh aspect of the present invention, wherein the filler is white.
If comprised in this way, the light-shielding sound-transmitting material which attenuates light more can be formed.

  According to the present invention, in a piezoelectric element used in a device that electrically detects vibration, the pyroelectric effect that can occur simultaneously in the piezoelectric body is suppressed. Therefore, the detection accuracy of the element can be improved as compared with the conventional case. In addition, since the acoustic probe and the photoacoustic apparatus provided with the piezoelectric element suppress the pyroelectric effect generated in the piezoelectric element, the measurement accuracy of the probe and the apparatus can be improved.

1 is a schematic diagram illustrating a layer configuration of a piezoelectric element 10. 1 is a schematic view of a photoacoustic apparatus 50 including a sonic probe 20. It is the schematic of the apparatus used for the measurement of a photoacoustic wave. It is the schematic of the apparatus used for the measurement of the change of a pyroelectric signal for verifying light-shielding property (it may be called light transmittance). (A) is a graph which shows the ratio of the pyroelectric signal intensity | strength of each Example with respect to the reference example 1 (No Cover) in the case of no time direction mask. (B) is a graph showing the pyroelectric signal suppression ratio with the time direction mask, that is, the ratio of the pyroelectric signal intensity of each example to Reference Example 1 (No Cover). (A) is a graph which shows a pyroelectric signal half value width (microsecond). (B) is a graph showing the rate of change of the half-value width of the pyroelectric signal, that is, the ratio of the half-value width of the pyroelectric signal of each example to Reference Example 1 (No Cover). It is an illustration of a pyroelectric signal waveform (Reference Example 1 (No Cover)). It is a signal waveform of the reference example 1 (No Cover). (A) is a signal waveform displayed on a long time scale. (B) is a signal waveform displayed on a short time scale. It is a signal waveform of Example 1 (FILM-1). (A) is a signal waveform displayed on a long time scale. (B) is a signal waveform displayed on a short time scale. It is a signal waveform of Example 2 (FILM-2). (A) is a signal waveform displayed on a long time scale. (B) is a signal waveform displayed on a short time scale. It is a signal waveform of Example 3 (FT-50Y). (A) is a signal waveform displayed on a long time scale. (B) is a signal waveform displayed on a short time scale. It is a signal waveform of Example 4 (FILM-3). (A) is a signal waveform displayed on a long time scale. (B) is a signal waveform displayed on a short time scale. It is a signal waveform of Example 5 (Al-film). (A) is a signal waveform displayed on a long time scale. (B) is a signal waveform displayed on a short time scale. It is a signal waveform of Example 6 (Al20micrometer). (A) is a signal waveform displayed on a long time scale. (B) is a signal waveform displayed on a short time scale. It is a signal waveform of Example 7 (Black Epoxy). (A) is a signal waveform displayed on a long time scale. (B) is a signal waveform displayed on a short time scale. It is a signal waveform of Example 8 (White Silicone). (A) is a signal waveform displayed on a long time scale. (B) is a signal waveform displayed on a short time scale. It is the schematic of the apparatus used for the measurement of the change of an acoustic signal for verifying sound permeability (it may be called sound permeability). It is a graph which shows the acoustic signal attenuation factor (signal amplitude transmittance | permeability) of each Example with respect to the reference example 1 (No Cover). It is a graph which shows the arrival time of an acoustic signal. It is a signal waveform of the reference example 1 (No Cover). (A) is a time waveform. (B) is a frequency spectrum. It is a signal waveform of Example 1 (FILM-1). (A) is a time waveform. (B) is a frequency spectrum. It is a signal waveform of Example 2 (FILM-2). (A) is a time waveform. (B) is a frequency spectrum. It is a signal waveform of Example 3 (FT-50Y). (A) is a time waveform. (B) is a frequency spectrum. It is a signal waveform of Example 4 (FILM-3). (A) is a time waveform. (B) is a frequency spectrum. It is a signal waveform of Example 5 (Al-film). (A) is a time waveform. (B) is a frequency spectrum. It is a signal waveform of Example 6 (Al20micrometer). (A) is a time waveform. (B) is a frequency spectrum. It is a signal waveform of Example 7 (Black Epoxy). (A) is a time waveform. (B) is a frequency spectrum. It is a signal waveform of Example 8 (White Silicone). (A) is a time waveform. (B) is a frequency spectrum. The signal waveform derived from the blood vessel of a rabbit at the time of using Example 4 (FILM-3) is shown. The signal waveform derived from the blood vessel of a rabbit at the time of using Example 8 (White Silicone) is shown. It is a block diagram of the apparatus used by the animal experiment.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same or similar reference numerals, and redundant description is omitted. Further, the present invention is not limited to the following embodiment.

A piezoelectric body is a dielectric that generates polarization (and voltage) when stress is applied. Conversely, stress and deformation occur when voltage is applied. Among piezoelectric bodies, those that spontaneously polarize without applying an electric field from the outside are called pyroelectric bodies. The pyroelectric material has a property that dielectric polarization (and electromotive force caused by it) occurs in response to a minute temperature change.
Among the applications of piezoelectric elements using piezoelectric materials, vibrations applied from the outside are converted into voltages by the piezoelectric effect, and vibrations are electrically detected, and precise measurement and analysis are performed based on the detected signals. There are a variety of devices. In the measurement using such a piezoelectric element, the present inventors may have a pyroelectric effect on the piezoelectric body simultaneously with the piezoelectric effect, and the detected signal may be affected by the pyroelectric effect, and the measurement may not be accurate. I found out. In addition, it has been found that if the piezoelectric element is configured so as to suppress the pyroelectric effect generated in the piezoelectric body, the measurement accuracy of the apparatus using the element can be greatly improved, and the present invention has been completed.

[Piezoelectric element]
A piezoelectric element according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a longitudinal sectional view showing a section in a direction perpendicular to the thickness of the piezoelectric element 10. As shown in FIG. 1, a piezoelectric element 10 includes a piezoelectric body 11, current collecting electrodes 12 (positive and negative electrodes) sandwiching the piezoelectric body 11 from above and below, a protective film 13 as a light-shielding sound-transmitting material, and a lead-out cable 14 is comprised. In addition, the thickness of each layer shown in FIG. 1 is exaggerated, and does not show the actual thickness. The protective film 13 also functions as a film that covers and protects one surface of the electrode 12.
In addition, it is preferable that the protective film 13 is provided in the surface side (for example, single side | surface or both surfaces) on which the piezoelectric material 11 passively vibrates vibrations, such as a sound wave. That is, it is preferable that the protective film 13 is disposed so as to block light from irradiating the piezoelectric body 11 directly or by reflection. Therefore, the protective film 13 may be laminated on the piezoelectric body 11 via the electrode 12 or may be disposed apart from the piezoelectric body.

Piezoelectric body The piezoelectric body 11 can be a piezoelectric polymer film. The piezoelectric polymer film can be obtained by preparing a film from a polymer melt or solution and subjecting it to a polarization treatment. Specifically, it is not particularly limited, such as a vinylidene fluoride polymer and a vinylidene cyanide copolymer, and a known piezoelectric polymer can be used. Piezoelectric polymers are flexible and easy to process, are lightweight, and can be molded thinly. Among these, a polyvinylidene fluoride (PVDF) uniaxially stretched film and a vinylidene fluoride-trifluoroethylene copolymer (P (VDF-TrFE)) film are preferable. A polyvinylidene fluoride uniaxially stretched film can be obtained by subjecting polyvinylidene fluoride to uniaxial stretching and then a polarization treatment. The vinylidene fluoride-trifluoroethylene copolymer film is mainly composed of vinylidene fluoride (that is, contains 50% by weight or more), and is polarized without stretching the vinylidene fluoride-trifluoroethylene copolymer. It can be obtained by processing. Both films are easy to process into an arbitrary area, can be thinly formed, and are suitable for industrial production. In addition, since the vinylidene fluoride-trifluoroethylene copolymer film can be produced without undergoing a stretching process such as uniaxial stretching, shrinkage caused by stretching can be suppressed.

The piezoelectric body 11 may be a piezoelectric ceramic. Piezoelectric ceramics are polycrystalline ceramics obtained by baking high-temperature powders such as barium titanate (BaTiO ₃ ), lead zirconate titanate (PZT), and lead titanate (PbTiO ₃ ) at high temperatures. Is obtained by polarization treatment. The piezoelectric body 11 may be a piezoelectric body using zinc oxide (ZnO), single crystal quartz, or lithium niobate as a main material.

-Electrode The electrode 12 can be a metal electrode such as platinum (Pt) or gold (Au), or a carbon electrode.

Resin or metal used for light-blocking sound-transmitting material The protective film 13 as the light-blocking sound-transmitting material is formed of at least one resin selected from the group consisting of polyvinylidene fluoride resin, silicon resin, and epoxy resin, or aluminum Is done.
Polyvinylidene fluoride resins include homopolymers of vinylidene fluoride (that is, polyvinylidene fluoride; PVDF), and copolymerization of vinylidene fluoride and other copolymerizable monomers having vinylidene fluoride as the main structural unit. Coalescence can be mentioned. As the copolymer with vinylidene fluoride, a vinylidene fluoride-hexafluoropropylene copolymer, a vinylidene fluoride-tetrafluoroethylene copolymer, or a vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer is suitable. It is mentioned as a thing. These polyvinylidene fluoride resins can be used alone or in combination of two or more. Among the polyvinylidene fluoride resins, PVDF which is a homopolymer of vinylidene fluoride is preferable from the viewpoint of contamination resistance, ozone resistance, and solvent resistance. From the viewpoint of flexibility and tear strength, it is preferable to use a vinylidene fluoride copolymer having vinylidene fluoride as a main structural unit alone or blended with PVDF. In order to improve adhesiveness, a vinylidene fluoride copolymer into which a functional group is introduced is preferably used. Note that it is preferable to use the same material for the light-shielding sound-transmitting material and the piezoelectric material so that the light-shielding sound-transmitting material and the piezoelectric material are made of PVDF because impedances can be made uniform.
A typical example of the silicon-based resin is dimethylpolysiloxane, and silicone rubber can also be used.
A representative example of the epoxy resin is a bisphenol A type epoxy resin.
Aluminum may be an aluminum foil or an aluminum vapor deposition film. An aluminum vapor deposition film is preferable because the thickness of aluminum can be easily changed and vapor deposition can be performed uniformly.

-Filler used for light-blocking sound-transmitting material The protective film 13 as the light-blocking sound-transmitting material may contain a filler that improves reflection, scattering, refraction, or absorption of light.
As filler, granular or powdered talc, mica, silica, alumina, kaolin, ferrite, potassium titanate, titanium oxide, zinc oxide, iron oxide, magnesium hydroxide, calcium carbonate, nickel carbonate, calcium sulfate, barium sulfate, Aluminum hydroxide, glass powder, quartz powder, graphite, inorganic pigment, organic metal salt, other metal oxides, carbon, fibrous carbon fiber, glass fiber, asbestos fiber, silica fiber, alumina fiber, zirconia fiber, boron nitride fiber And at least one filler selected from the group consisting of silicon nitride fiber, boron fiber, and potassium titanate fiber.
In particular, a white filler that improves reflection, scattering, refraction, or absorption of light is preferable.

The filler is preferably contained in an amount of 1 to 55 parts by weight, more preferably 2 to 50 parts by weight, and still more preferably 3 to 45 parts by weight with respect to 100 parts by weight of the resin forming the protective film 13 as the light-shielding sound-transmitting material. Part contained. When the amount is 1 part by weight or more, the effect of light reflection, scattering, refraction or absorption can be sufficiently obtained, and when it is 55 parts by weight or less, the resin and the filler can be easily kneaded.
The average particle size of the filler is in the range of 0.1 to 10 μm, preferably in the range of 0.2 to 6 μm. The average particle size of the filler is preferably 1.5 times or less, more preferably 0.8 times or less with respect to the film thickness in consideration of the mechanical strength of the protective film 13 to be obtained. When the thickness is 0.1 μm or more, the effect of light reflection, scattering, refraction, or absorption can be sufficiently obtained, and when the thickness is 10 μm or less, the thickness of the film can be sufficiently reduced.
The “average particle size” means the particle size at an integrated value of 50% in the particle size distribution obtained by the laser diffraction / scattering method.

  The protective film 13 as the light-shielding sound-transmitting material can be manufactured from a resin and a filler by a known method. That is, after a composition is obtained from a resin and a filler by a roll, a brabender, a kneading extruder, etc., it may be formed into a film by press, T-die, melt extrusion film formation by an inflation method, or the like.

  The protective film 13 functions as a light shielding sound transmitting material. That is, by covering the light that irradiates the piezoelectric body 11 with the protective film 13, the transmission of light is more blocked than the transmission of sound waves. As a result, although the piezoelectric effect is generated in the piezoelectric body 11, it is possible to suppress the pyroelectric effect from being generated in the piezoelectric body 11 that has absorbed the thermal energy by light irradiation. Thus, although the vibration to be passive is a sound wave, when the piezoelectric element is used in an environment that is affected by light irradiation, the piezoelectric body 11 is covered with the protective film 13 that functions as a light-blocking sound-transmitting material. The pyroelectric effect can be suppressed and the measurement accuracy due to the piezoelectric effect can be increased.

When the piezoelectric material is covered with the light-shielding sound-transmitting material, the received sound wave is slightly attenuated. However, the light-shielding sound-transmitting material used in the present application transmits sound waves to such an extent that the piezoelectric effect generated in the piezoelectric body can be measured. On the other hand, the transmission of light is further blocked to suppress the pyroelectric effect. The ratio of sound transmittance to light transmittance of the light-shielding sound-transmitting material is preferably 0.5 or more, more preferably 0.8 or more, still more preferably 1.0 or more, and particularly preferably 1.4 or more. It is.
“Sound transmissivity” refers to the ratio of the sound wave energy received when the light-shielding sound-transmitting material is provided to the sound wave energy received when the light-blocking sound-transmitting material is not provided. “Light transmissivity” refers to the ratio of the light energy received when the light-shielding sound-transmitting material is provided to the light energy received when the light-shielding sound-transmitting material is not provided. The “ratio of sound transmission to light transmission” refers to a value obtained by dividing “acoustic transmission” by “light transmission”.
Sound permeability = received sound wave (with light-blocking sound-transmitting material) / received sound wave (without light-blocking sound-transmitting material)
Light transmission = received light (with light shielding sound transmitting material) / received light (without light shielding sound transmitting material)
For example, when the sound wave is attenuated by 50% and the light is attenuated by 50% by the light-shielding sound-transmitting material, it is considered that both transmit 50%. Therefore, the “ratio of sound transmittance to light transmittance” is 0.5 / 0.5 = 1. When the “ratio of sound transmittance to light transmittance” is 0.5 or more, the light-shielding sound-transmitting material of the present application can suppress the pyroelectric effect and sufficiently improve the measurement accuracy due to the piezoelectric effect.

  When a polyvinylidene fluoride (PVDF) uniaxially stretched film or a vinylidene fluoride-trifluoroethylene copolymer (P (VDF-TrFE)) film is used for the piezoelectric body 11 constituting the piezoelectric element 10, the thickness is, for example, It is about 20-55 micrometers. When a carbon electrode is used as the electrode 12 for current collection, the thickness of the carbon electrode deposited on both sides of the polymer film is about 1 μm. The thickness of the protective film 13 attached to one surface of the carbon electrode is about several tens of μm. Therefore, the total thickness of the piezoelectric element 10 including the protective film 13 is about 100 μm or less, and is thin and lightweight. The thicknesses of the piezoelectric body 11, the carbon electrode 12, and the protective film 13 may be changed as appropriate, such as a uniaxially stretched polyvinylidene fluoride (PVDF) film or a vinylidene fluoride-3 fluoroethylene copolymer (P (VDF− TrFE)) It is also possible to further reduce the thickness of the film. For example, the thickness of the protective film 13 as the light-shielding sound-transmitting material is appropriately changed depending on the material of the film and the average particle diameter when a filler is included. For example, it is 1-1000 micrometers, Preferably it is 10-500 micrometers. In aluminum foil, in order to suppress the pyroelectric effect more, 15-30 micrometers is preferable, More preferably, it is 20-25 micrometers.

  The piezoelectric element 10 according to the first embodiment of the present invention is configured to block light applied to the piezoelectric body 11 in order to suppress the pyroelectric effect generated in the piezoelectric body 11. However, the factor causing the pyroelectric effect in the piezoelectric body is not limited to light. Therefore, depending on the environment in which the piezoelectric element is used, the detection of the voltage generated by the piezoelectric effect can be made more accurate by reducing the factors causing the pyroelectric effect, such as thermal energy, using a protective film (such as a heat insulating material). The accuracy of the apparatus using such a piezoelectric element can be further increased.

[Sound probe]
With reference to FIG. 2, the acoustic probe 20 which concerns on the 2nd Embodiment of this invention is demonstrated. The acoustic probe 20 includes the piezoelectric element 10 according to the first embodiment. The sound wave received by the piezoelectric body 11 is converted into a voltage and sent as an electrical signal from the electrode 12 to the connector 22 via the lead cable 14. Further, it is sent to the signal processing device 40 included in the photoacoustic device 50 for analysis and processing. The shape of the support case 21 that supports the piezoelectric element is not limited. The shape may be easily gripped during measurement. The “sonic probe” includes a hydrophone.

[Photoacoustic device]
A photoacoustic apparatus 50 according to a third embodiment of the present invention will be described with reference to FIGS. The photoacoustic apparatus 50 analyzes and diagnoses optical characteristics in a subject (for example, a living body). The photoacoustic apparatus 50 includes a sonic probe 20, a light source device 30, and a signal processing device 40. The light source device 30 includes a light source 31 that emits light and a light irradiation unit that irradiates a subject with light emitted from the light source 31. The light irradiation unit may be configured to irradiate the subject with light. For example, the light irradiation unit may include a light chopper that chops light into intermittent light at a predetermined frequency, a condensing lens, and an optical fiber that propagates light. When used, a mirror may be provided. Furthermore, you may provide the spectrometer and wavelength variable drive device for setting light to a single wavelength. The signal processing device 40 may be any device that can analyze and diagnose the electrical signal sent from the acoustic probe 20, and includes, for example, a signal processor 41, a personal computer 42, a pulse generator 43, and the like as shown in FIG. It may be a group of devices.
The light that has entered the subject is absorbed by the light absorber present in the subject. The light absorber emits ultrasonic waves (acoustic waves) by absorbing light. The acoustic probe 20 receives an acoustic wave generated by the light absorber. The received acoustic wave is converted into a voltage by a piezoelectric element included in the ultrasonic probe and sent as an electric signal to the signal processing device 40, where recording, analysis, diagnosis, image processing, and the like are performed. The image processing signal is sent to an image display device (not shown) and displayed as an image. Note that the signal processing device 40 may include an amplifier (amplifier). When the electrical signal obtained from the piezoelectric element is small, it is preferable to amplify the strength of the electrical signal using this amplifier.
Further, although there is one sensor 20a (one embodiment of the sonic probe 20) in FIG. 3, a plurality of sensors may be provided and the subject may be measured from a plurality of locations.
In the photoacoustic apparatus 50, the acoustic probe 20, the light source apparatus 30, and the signal processing apparatus 40 may be individually configured or may be configured integrally. Further, only the light source device 30 may be individually configured, and the other may be configured integrally. Thus, the configuration of the apparatus may be changed as appropriate.
In addition, it is preferable to use an acoustic impedance matching material for suppressing reflection of sound waves between the sound wave probe 20 and the subject. For example, since the acoustic impedance of air is much smaller than that of living tissue as a subject, if air is interposed between the acoustic probe 20 and the subject, the sound wave cannot enter the inside and is reflected on the subject surface. End up. Therefore, a substance close to the acoustic impedance of the living body (acoustic impedance matching material) is interposed to eliminate air and make it easier for sound waves to enter. With the acoustic impedance matching material, it is possible to acquire data under conditions that are not affected by the reflection of sound waves and do not affect the frequency characteristic evaluation.

The signal processing device 40 analyzes the obtained electrical signal. Thereby, the distribution information of the optical characteristic value of the subject can be obtained. For example, the position and size of the light absorber can be known based on the electrical signal. Alternatively, a distribution of optical characteristic values such as a light absorption coefficient or a light energy deposition amount distribution may be calculated.
The signal processing device 40 stores the change in the intensity of the electrical signal (that is, the intensity of the ultrasonic wave) obtained with the passage of time, and converts the change into the optical characteristic value distribution data by the arithmetic means included in the signal processing device 40. It may be one that can be converted. For example, an oscilloscope and a computer capable of data analysis may be combined.

The light source 31 is preferably a laser beam. Examples of the laser light include a solid laser, a liquid (pigment) laser, a gas laser, a semiconductor laser, and a wavelength conversion laser using a non-linear element. Alternatively, the light source 31 may be optical parametric oscillation, laser diode (LD) excitation, or light emitting diode (LED). Alternatively, a continuous spectrum light source such as a halogen lamp, a glow bar, an incandescent carbon rod, a xenon lamp, a mercury lamp, a mercury xenon lamp, or a flash lamp may be used. Or, it may be non-interfering light among normal light. The wavelength of light emitted from the light source is not particularly limited, and may be a visible light region, an ultraviolet light region, an infrared light region, or the like. In addition, it is preferable to make continuous light into intermittent light from providing an optical chopper.
When laser light is used, there is an advantage that light can be concentrated on the measurement target portion. When a light emitting diode (LED) is used, the power consumption is low and the energy saving effect is high.

  The light from the light source 31 propagates to the subject through the optical fiber and is irradiated on the subject. Light travels through the subject while being transmitted, scattered and reflected. If an optical fiber is used, light scattering can be suppressed and efficient irradiation is possible. In addition, since the optical fiber is flexible, the light can be moved and applied freely to the examination location of the subject regardless of the installation position of the light source. The optical fiber may be formed by a single optical fiber or a bundle of a plurality of optical fibers. Note that light may be propagated in the air instead of the optical fiber.

The photoacoustic apparatus 50 may further include a pulse voltage generator (not shown). By sending the pulse signal generated by the pulse voltage generator to the piezoelectric body 11 provided in the sonic probe 20, the piezoelectric body 11 vibrates and ultrasonic waves are generated. The piezoelectric body 11 further receives the reflected ultrasonic wave and performs recording, analysis, diagnosis, image processing, and the like. The image processing signal is sent to an image display device (not shown) and displayed as an image.
Such a configuration is preferable because an image based on an acoustic wave and an image based on a transmission / reception wave of an ultrasonic wave of the same subject can be displayed side by side on the image display device or displayed in a superimposed manner.

The photoacoustic apparatus of the present application may irradiate the subject with light from a position facing the wave receiving surface of the piezoelectric element 10. Even when the irradiated light is transmitted directly through the subject and directly enters the piezoelectric element of the acoustic probe, since the light shielding sound transmitting material is provided, the pyroelectric effect generated in the piezoelectric body due to the light irradiation is further suppressed. be able to. Therefore, the photoacoustic apparatus can measure with higher accuracy. In addition, with such a configuration, light is emitted from a position facing the wave receiving surface of the piezoelectric element with the subject interposed therebetween, so measurement is possible even when the subject is small and the light source device and the acoustic probe cannot be arranged side by side. Is possible.
Further, the light irradiation may be performed on the subject from a position that is aligned with the wave receiving surface of the piezoelectric element 10. Even when the irradiated light is reflected inside the subject and is incident on the piezoelectric element of the sound wave probe, since the light-shielding sound-transmitting material is provided, the pyroelectric effect generated in the piezoelectric body due to light irradiation is further suppressed. Can do. Therefore, the photoacoustic apparatus can measure with higher accuracy. Also, with such a configuration, light is emitted from a position aligned with the wave receiving surface of the piezoelectric element, so that the light does not directly enter the acoustic probe, and the effect of improving the measurement accuracy of the photoacoustic apparatus is high. .

  The photoacoustic apparatus of the present application with improved detection accuracy is effective, for example, for detecting defects in semiconductor manufacturing processes, measuring absorption spectra of opaque substances, and detecting imaging images inside solids. In the medical field, it is also effective to obtain image information inside the living body using the photoacoustic effect.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the contents described in the following examples.

In the following examples, regarding a protective film as a light shielding sound-transmitting material,
(1) Changes in pyroelectric signal due to application of protective film (shading sound transmission material) (2) Changes in acoustic signal due to application of protection film (light transmission sound transmission material) (3) In animal experiments A measurement waveform is shown.
The protective film evaluated whether to suppress pyroelectricity and to transmit acoustic waves. In the acoustic wave evaluation experiment, it is considered that there is no need to consider pyroelectricity because a setup that can accurately grasp the acoustic signal and does not produce a pyroelectric signal is used.

・ＦＩＬＭ−１：試作多層フィルム＝ＰＶＤＦ層４μｍ、ＰＭＭＡ層４６μｍ（フィラー４重量％＝酸化チタン＋ＣＢ）
・ＦＩＬＭ−２：試作多層フィルム＝ＰＶＤＦ層４μｍ、ＰＭＭＡ層４６μｍ（フィラー７重量％＝酸化チタン）
・ＦＴ−５０Ｙ：（株）クレハ製、ＫＦＣフィルム＝ＰＶＤＦ層４μｍ、ＰＭＭＡ層４６μｍ
・ＦＩＬＭ−３：試作単層フィルム＝（ＰＶＤＦ＋ＰＭＭＡ＋フィラー）ブレンド系フィルム、厚み２０μｍ、フィラー３０重量％＝酸化チタン（粒径０．２μｍ）
・Ａｌ−ＦＩＬＭ：アルミ蒸着Ｐ（ＶＤＦ−ＴｒＦＥ）フィルム４０μｍ
・Ａｌ ２０μｍ
・Ｂｌａｃｋ Ｅｐｏｘｙ
・Ｗｈｉｔｅ Ｓｉｌｉｃｏｎｅ Details of the protective film are shown below.

FILM-1: prototype multilayer film = PVDF layer 4 μm, PMMA layer 46 μm (filler 4% by weight = titanium oxide + CB)
FILM-2: prototype multilayer film = PVDF layer 4 μm, PMMA layer 46 μm (7 wt% filler = titanium oxide)
FT-50Y: Kureha Co., Ltd., KFC film = PVDF layer 4 μm, PMMA layer 46 μm
FILM-3: prototype monolayer film = (PVDF + PMMA + filler) blend film, thickness 20 μm, filler 30% by weight = titanium oxide (particle size 0.2 μm)
・ Al-FILM: Aluminum vapor deposition P (VDF-TrFE) film 40 μm
・ Al 20μm
・ Black Epoxy
・ White Silicone

As the sensor shown in FIG. 4 and FIG. 17, a probe: C (acoustic probe) having the following characteristics was used.
・ Clear rubber coat (Reference Example 1: Used for No Cover)
・ Outer cylinder diameter: 5.5 mm (effective element diameter measurement is about 4 mm)
Sensor area: 19.62 mm ²
・ Sensor thickness: 55μm
・ Case length: 10cm
・ Signal wire diameter: 2.6 mm
・ Signal line length: 4cm
-Coaxial cable with a length of 50cm to connect to the amplifier

(1) Change in pyroelectric signal due to application of protective film FIG. 4 shows a schematic diagram of a measuring apparatus used for measuring the change in pyroelectric signal in order to verify the light shielding property (light transmittance).
A second harmonic Q-switched Nd: YAG laser was used as the light source.
・ Wavelength: 532nm
-Beam diameter: 3.25mm
・ Energy: 100μJ / pulse
(Approximate to flat top, fluence 1.10 mJ / cm ² )
・ Slide glass (FF-004, manufactured by Matsunami Glass Industry Co., Ltd.)
Optical fiber: 400 μm, NA 0.48 (M40L02, manufactured by Thorlabs)
Collimator: f = 11 mm, NA 0.25 (47221, manufactured by Edmund Optics)
A water tank containing deaerated water was used as a simulated subject. The size of the water tank is 23 × 17 × 7.5 cm.
A hole of about φ10 mm was drilled on the bottom of a 35 mm dish, a double-sided tape was attached around the hole, and a protective film was attached (no double-sided tape interposed between the protective film and the probe). The dish was fixed with the lens holder, and the probe was moved up and down on the z stage and fixed to the protective film.

図５（ａ）に時間方向マスクなしの場合の、参考例１（No Cover）に対する各実施例の焦電信号強度の比を示す。図５（ｂ）に時間方向マスクありの場合の、参考例１（No Cover）に対する各実施例の焦電信号強度の比、すなわち本願の光透過性を示す。 The pyroelectric signal intensity measurement results are shown below.
No time mask: The maximum value of the pyroelectric signal detected immediately after laser irradiation and generated by light absorption by the protective film.
With time mask: Maximum value of pyroelectric signal from the subject. In this embodiment, a value obtained by applying a time mask so as to extract only the maximum value between 2 to 30 μs after laser irradiation in order to eliminate electromagnetic noise.

FIG. 5A shows the ratio of the pyroelectric signal intensity of each example with respect to Reference Example 1 (No Cover) when there is no time direction mask. FIG. 5B shows the ratio of the pyroelectric signal intensity of each example with respect to Reference Example 1 (No Cover) when the time direction mask is provided, that is, the light transmittance of the present application.

FIG. 6A shows the pyroelectric signal half-value width (μs). FIG. 6B shows the change rate of the pyroelectric signal half-value width, that is, the ratio of the pyroelectric signal half-value width of each example to Reference Example 1 (No Cover).
It should be noted that aluminum (Examples 5 and 6) and black film (Example 7) could not be measured at half-width because the intensity of the pyroelectric signal was small. White silicone (Example 8) has a half width of about 5% smaller than that of Reference Example 1 (No Cover).

Next, a signal waveform analysis method will be described with reference to FIG. FIG. 7 shows the waveform of Reference Example 1 (No Cover).
As the light transmittance of the present application, the pyroelectric signal suppression ratio was determined as follows.
[1] In order to remove the influence of the output signal offset (several mV), the average voltage of the signal observed before light irradiation is calculated, and the difference is taken from the raw waveform.
[2] Divide the raw waveform by the energy value monitored simultaneously at the time of signal measurement in order to eliminate the influence of fluctuations in laser pulse energy.
[3] The maximum voltage is calculated from the signal waveform.
[4] A ratio to [3] measured under the condition without a cover film is defined as a pyroelectric signal suppression ratio (light transmittance).
Note that the addition average was 16 times, the sampling frequency was 100 MHz, and the data capture time was 2 ms. Moreover, the limit (maximum value about 3V) which is saturated in the state without a cover film was set.
8 to 16 show signal waveforms of Reference Example 1 and Examples 1 to 8. FIG. FIG. 8A shows a signal waveform displayed on a long time scale. FIG. 8B shows a signal waveform displayed on a short time scale. The same applies to FIGS.

(2) Change in acoustic signal due to application of protective film FIG. 17 shows a schematic diagram of a measuring apparatus used for measuring change in acoustic signal for verifying sound permeability (acoustic permeability).
A second harmonic Q-switched Nd: YAG laser was used as the light source.
・ Energy: 40μJ / pulse
(Condensed by a convex lens of f = 250 mm and aligned so that the silicone rubber surface is focused. Lens: KPX109, manufactured by Newport Corp., mirror: TFM-25C05-532, manufactured by Sigma Kogyo Co., Ltd.)
・ An incident angle to the water surface: 16.9 °
A 1 L beaker containing deaerated water was used as a simulated subject. A 1 L beaker has an inner diameter of 10.5 cm and a depth of 14.5 cm.
Silicone rubber (high μa) was used as a light absorber that exists in the pseudo specimen and absorbs light to generate sound waves. Silicone rubber was prepared by mixing 80 ml of a solution in which the main component of silicone two-component RTV rubber (KE-1283-A / B, manufactured by Shin-Etsu Chemical Co., Ltd.) and a curing agent at a weight ratio of 1: 1 was 90 mm in diameter. It was poured into a 15 mm high Petri dish (3020-100, IWAKI) and allowed to stand for 48 hours in a room temperature environment and cured.

図１８に参考例１（No Cover）に対する各実施例の信号減衰率（信号振幅透過率）、すなわち本願の音響透過性を示す。 The measurement result of the acoustic signal intensity is shown below.

FIG. 18 shows the signal attenuation rate (signal amplitude transmittance) of each example with respect to Reference Example 1 (No Cover), that is, the sound transmittance of the present application.

FIG. 19 shows the arrival time of the signal.
Since silicone (Example 8) has a slower sound speed than water, the signal arrival time is delayed.
Epoxy (Example 7) has a faster sound speed than water, so the signal arrival time is faster.
Regarding other materials, since the thickness is as thin as 10 μm, the propagation time change is almost negligible.

Next, a signal waveform analysis method will be described with reference to FIG. 20A is a time waveform of Reference Example 1 (No Cover), and FIG. 20B is a frequency spectrum of Reference Example 1.
As the sound transmission of the present application, the acoustic wave attenuation characteristics were determined as follows.
[1] In order to remove the influence of fluctuations in laser pulse energy, the raw waveform is divided by the energy value monitored simultaneously during signal measurement.
[2] Data in a time range of 99 to 103 μs is extracted from the received signal waveform and subjected to FFT to calculate a spectrum.
[3] A ratio to [2] measured under the condition without a cover film is defined as acoustic wave attenuation characteristics (acoustic permeability).
Note that the addition average was 16 times, the sampling frequency was 2 GHz, and the data capture time was 200 μs.
21 to 28 show signal waveforms of the first to eighth embodiments. FIG. 21A shows a time waveform. FIG. 21B shows a frequency spectrum. The same applies to FIGS.

図１８に示すように、実施例１〜４（フィルム系の素材）は８０％以上の透過率が得られ、最も透過率が高い。実施例５〜８は、実施例１〜４と比べると透過率は下がるが、図５に示すように光を遮断する効果が極めて高く（すなわち光透過性が小さい）、遮光透音剤として有効である。

As shown in FIG. 18, Examples 1 to 4 (film-based materials) have a transmittance of 80% or more, and the highest transmittance. In Examples 5 to 8, the transmittance is lower than in Examples 1 to 4, but the effect of blocking light is extremely high (that is, the light transmittance is small) as shown in FIG. It is.

(3) Measurement waveform in animal experiment The blood oxygen saturation of rabbit arterial blood was measured by the principle of pulse oximeter, but the measurement result was not stable.
On the other hand, the blood vessel position was confirmed by ultrasonic echo. A blood vessel having a depth of 6 to 7 mm could be detected from the body surface. The position of the probe when the blood vessel was visible was marked, and the blood vessel-derived signal was measured with an apparatus having the configuration shown in FIG. 31 in accordance with the position where the photoacoustic probe was marked using an arm with a high degree of freedom.
The irradiated laser light is as follows. An optical fiber was used for irradiation.
・ Light wavelength: 756,770,798nm
・ Energy: 4-5mJ / pulse
・ Pulse width: 8ns

Protective film: FILM-3 (Example 4)
FIG. 29 shows a signal waveform derived from a rabbit blood vessel when FILM-3 is used. The photoacoustic signal derived from blood vessels could be clearly detected within 10 to 12 μs without the photoacoustic signal being hidden by the pyroelectric voltage.
As shown in FIG. 7, the waveform indicating the pyroelectric voltage gradually decreases after a rapid rise. That is, the photoacoustic signal is most affected by the pyroelectric voltage at an earlier stage of elapsed time. Therefore, measurement in a particularly shallow region can be performed more accurately by the light-shielding sound-transmitting material of the present application.
Protective film: White Silicone (Example 8)
FIG. 30 shows a signal waveform (wavelength: 756 nm, energy: 4 mJ) derived from a rabbit blood vessel when White Silicone according to the same method is used. The photoacoustic signal derived from the blood vessel could be clearly detected in 8 to 10 μs without the photoacoustic signal being hidden by the pyroelectric voltage. 30 and 29, the positive and negative polarities are reversed depending on the sensor characteristics.
The sonagel layer in FIGS. 29 and 30 is a signal derived from a sonagel (trade name: Sonagel, manufactured by Takiron Co., Ltd., dimensions: 200 × 100 × 10 mm) disposed between the probe and the body surface. Sonagel is used for the purpose of increasing the distance between the probe and the body surface so that the light spreads. When the ultrasonic gel is applied thickly, bubbles enter into the gel and the scattering and reflection of ultrasonic waves by the bubbles cause artifacts, but sona gel is preferable because it is solid and does not contain bubbles.

DESCRIPTION OF SYMBOLS 10 Piezoelectric element 11 Piezoelectric body 12 Electrode, carbon electrode 13 Light-shielding sound-transmitting material, protective film 14 Lead-out cable 20 Sound wave probe 20a Sensor 21 Support case 22 Connector 30 Light source device 31 Light source, laser light source 32a Lens 32b Lens 33 Mirror 40 Signal processing device 41 Signal Processor 42 Personal Computer (PC)
43 Pulse generator 50 Photoacoustic apparatus 101 Silicone rubber 102 Water tank 103 Beaker 104 Deaerated water 105 Optical fiber 106 Collimator 107 Slide glass

Claims (12)

A piezoelectric body that receives sound waves and converts the received sound waves into voltage;
Positive and negative electrodes sandwiching the piezoelectric body;
A light-blocking sound-transmitting material covering the piezoelectric body, wherein the sound wave is transmitted to such an extent that the piezoelectric effect generated in the piezoelectric body can be measured by the sound wave, and the pyroelectric effect generated in the piezoelectric body by light irradiation is transmitted to the light A light-shielding sound-transmitting material that is suppressed by attenuating
Piezoelectric element. The ratio of sound transmittance to light transmittance of the light-shielding sound-transmitting material is 0.5 or more.
The piezoelectric element according to claim 1. The sound transmission is greater than the light transmission;
The piezoelectric element according to claim 2. The piezoelectric body receives the sound wave generated by the light absorber that has absorbed the irradiated light,
The light-shielding sound-transmitting material suppresses the pyroelectric effect generated in the piezoelectric body by the light to such an extent that the piezoelectric effect generated in the piezoelectric body by the sound wave can be measured.
The piezoelectric element according to any one of claims 1 to 3. The light-shielding sound-transmitting material is formed of at least one resin selected from the group consisting of polyvinylidene fluoride resin, silicon resin, and epoxy resin, or aluminum.
The piezoelectric element according to any one of claims 1 to 4. The light-shielding sound-transmitting material is formed of the at least one resin;
The light-shielding sound-transmitting material contains a filler that improves reflection, scattering, refraction, or absorption of light,
The filler is granular or powdery talc, mica, silica, alumina, kaolin, ferrite, potassium titanate, titanium oxide, zinc oxide, iron oxide, magnesium hydroxide, calcium carbonate, nickel carbonate, calcium sulfate, barium sulfate, Aluminum hydroxide, glass powder, quartz powder, graphite, inorganic pigment, organic metal salt, other metal oxides, fibrous carbon fiber, glass fiber, asbestos fiber, silica fiber, alumina fiber, zirconia fiber, boron nitride fiber, nitriding It is at least one selected from the group consisting of silicon fiber, boron fiber, potassium titanate fiber,
The piezoelectric element according to claim 5. The filler is white;
The piezoelectric element according to claim 6. A piezoelectric element according to any one of claims 1 to 7;
A support case for supporting the piezoelectric element;
Acoustic probe. A light source that emits the light;
A light irradiation unit that irradiates the subject with light emitted from the light source;
An acoustic probe according to claim 8;
A signal processing device for processing a voltage signal from the piezoelectric element;
Photoacoustic device. A pulse voltage generator for applying a voltage to the piezoelectric element so that the piezoelectric element vibrates and generates a sound wave;
The piezoelectric element receives a reflected wave of a sound wave generated from the piezoelectric element;
The photoacoustic apparatus according to claim 9. A polyvinylidene fluoride resin;
Granular or powdery talc, mica, silica, alumina, kaolin, ferrite, potassium titanate, titanium oxide, zinc oxide, iron oxide, magnesium hydroxide, calcium carbonate, nickel carbonate, calcium sulfate, barium sulfate, aluminum hydroxide, Glass powder, quartz powder, graphite, inorganic pigment, organic metal salt, other metal oxides, fibrous carbon fiber, glass fiber, asbestos fiber, silica fiber, alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron Containing at least one filler selected from the group consisting of fibers and potassium titanate fibers;
Sound transmission is greater than light transmission,
Shading sound-transmitting material. The filler is white;
The light-shielding sound-transmitting material according to claim 11.

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