JP5682762B2 - Piezoelectric device and ultrasonic probe - Google Patents

Description

  The present invention relates to a piezoelectric device and an ultrasonic probe used for an ultrasonic probe, an ink jet printer, and the like.

  The ultrasonic diagnostic apparatus has features such as non-invasive observation of internal tissues and real-time observation, and therefore, the number of applications for diagnosis is increasing. As an ultrasonic wave of this ultrasonic diagnostic apparatus, for example, a pMUT (Piezoelectric Micromachined Ultrasonic Transducer) that transmits and receives ultrasonic waves by vibrating a unimorph diaphragm having a piezoelectric member such as PZT formed on a substrate in a drum shape is known. .

  Such an ultrasonic probe of pMUT can widen the frequency band, can be miniaturized to have a high resolution, and can acquire a three-dimensional image as compared with a bulk PZT divided by dicing. Therefore, it is suitable for two-dimensional arrangement of transducers (cells) for the purpose, and since it can be reduced in size and thickness, it has advantages such as being suitable for application to an ultrasonic endoscope. In such an ultrasonic probe of pMUT, since an image that can be acquired is a tomographic image with a one-dimensional array of transducers, there is a risk of false negatives due to the operation. Engineers' skill is required. In order to alleviate such problems, there is a high need for a two-dimensional array of ultrasonic probes capable of acquiring a three-dimensional image.

  In such an ultrasonic probe, the following energy conversion operation is performed. In transmission, electrical energy is converted into mechanical energy (membrane vibration), and mechanical energy is converted into acoustic energy (ultrasound). On the other hand, in reception, acoustic energy (ultrasound) is converted into mechanical energy (film vibration), and mechanical energy is further converted into electrical energy.

  For mutual conversion between mechanical energy and acoustic energy, acoustic matching is important, and the design point is to match the effective acoustic impedance of the pMUT with the acoustic impedance of the living body. In the mutual conversion between electric energy and mechanical energy, it is important to increase the energy conversion efficiency of the diaphragm structure including the piezoelectric thin film. For the piezoelectric member, it is most efficient to use strain in the same direction (33 directions) as the direction of the electric field (k value: an electromechanical coupling coefficient is high in the index representing the performance of the piezoelectric member). In the touch element, a configuration using distortion in 33 directions is advantageous. Another advantage is that the sensitivity (output voltage with respect to unit pressure) at the time of ultrasonic reception can be improved because the distance between the electrodes can be made relatively large compared to a configuration in which electrodes are arranged in the thickness direction of PZT.

  As a method using such 33-direction distortion, Japanese Patent Application Laid-Open No. H10-228707 discloses an ultra-small shell type converter. This mounts a solid electroactive medium having an arched portion and two shoulder portions on a support substrate, and attaches a pair of electrodes to each shoulder portion to form a chamber between the arch portion and the support substrate. Form. Then, a voltage is applied from the plus electrode along the minus electrode to generate an electric field in the same direction to induce stress in the same direction, and the arch portion is moved upward or downward in the thickness direction to bend.

US Pat. No. 6,222,304

  However, the behavior of the thin plate-like piezoelectric member a using the 33 strain is, for example, in the 33 direction (Z-Z direction) when considering a strain of an arbitrary rectangular cross section as shown in FIG. When expanding, it contracts in the 31 direction (WW direction). Further, in the configuration in which the electric field is generated in a ring shape or a circular shape by the plus electrode b and the minus electrode c as shown in FIG. 13, the distortion in the circumferential direction (31 direction, WW direction) in an arbitrary cross section is Be bound to each other. In such a constrained state, it has been confirmed by simulation that the amount of distortion in the radial direction (Z-Z direction) is reduced by about 25%, and there is a problem in that the characteristics of ultrasonic transmission / reception deteriorate. . A piezoelectric member a shown in FIG. 13 is laminated on a thin plate-like substrate d supported by a support member e. The support member e and the substrate d will be further described later.

  An object of the present invention is to provide a piezoelectric device and an ultrasonic probe capable of improving the performance of transmitting and receiving ultrasonic waves.

In order to solve the above problems, a piezoelectric device according to an aspect of the present invention includes a thin plate-shaped piezoelectric member, a pair of first and second electrodes formed on the piezoelectric member, and the pair of first and second electrodes. A groove formed to include a portion extending along a direction of an electric field generated when a voltage is applied to the second electrode, and the groove is formed between the first electrode and the second electrode. It is characterized by being.

According to this configuration, due to the groove, the distortion in the direction of the electric field is relaxed by the distortion in the direction orthogonal to the direction of the electric field, and the distortion in the direction of the electric field is increased as compared with the case without the groove. Thereby, the displacement of the diaphragm having the piezoelectric member is increased, and the transmission / reception characteristics of the ultrasonic wave can be improved.
In another aspect, in the piezoelectric device, the pair of first and second electrodes are formed apart from each other by a predetermined distance in a direction orthogonal to a thickness direction of the piezoelectric member. It is formed to extend from the first electrode to the second electrode .

  In another aspect, the piezoelectric device further includes a thin plate-like substrate having a unimorph structure with the piezoelectric member, and the substrate is placed on the surface of the substrate in accordance with the distortion of the piezoelectric member due to the voltage application. It is characterized in that it bends and deforms in a thickness direction substantially orthogonal.

  According to this configuration, the substrate can be efficiently bent and deformed by the distortion of the piezoelectric member, and for example, it can be made suitable for an ultrasonic probe that transmits and receives ultrasonic waves.

  In another aspect, in the piezoelectric device, the electrode has a substantially circular shape or a substantially ring shape.

  According to this configuration, an unnecessary vibration mode can be prevented from occurring near the primary resonance frequency (target vibration mode). If the unnecessary vibration mode is in the vicinity of the driving frequency, unnecessary vibration is excited and the pulse waveform may collapse from the designed pulse waveform, which may adversely affect the resolution, but this can be prevented.

  In another aspect, in the piezoelectric device, the groove is formed of a plurality of radially extending members, and the center lines of two grooves adjacent to each other are in the center of 10 ° to 25 °. It is characterized by being arranged side by side in the circumferential direction so as to form a corner.

  According to this configuration, it is possible to further relax the constraint due to the distortion in the direction orthogonal to the direction of the electric field, and to further increase the distortion in the direction of the electric field.

In another aspect, in the piezoelectric device, the pair of first and second electrodes are formed on the surface of the piezoelectric member so as to be separated from each other by a predetermined distance.

According to this configuration, when one element is constituted by a plurality of diaphragms, the arrangement efficiency of the diaphragms in one element can be increased, the effective area of the diaphragm can be increased, and the characteristics of ultrasonic transmission / reception can be improved. In addition, the electrode can be easily pulled out from both sides, and a structure with little loss can be realized.
In another aspect, in the piezoelectric device, the second electrode includes a second electrode main body, and the first electrode includes a first electrode main body disposed inside the second electrode main body. And a connecting portion extending from the first electrode main body portion to the outside of the second electrode main body portion.

  An ultrasonic probe according to an aspect of the present invention includes any one of the above-described piezoelectric devices.

  According to this configuration, the distortion in the direction of the electric field increases due to relaxation of the constraint due to the distortion in the direction orthogonal to the direction of the electric field. Thereby, the displacement of the diaphragm formed using this piezoelectric member increases, and the transmission / reception characteristics of ultrasonic waves can be improved.

  The present invention can provide a piezoelectric device and an ultrasonic probe capable of improving the performance of ultrasonic transmission / reception.

It is a figure which shows the external appearance structure of the ultrasound diagnosing device in embodiment. It is a block diagram which shows the electrical structure of the ultrasonic diagnosing device in embodiment. It is sectional drawing which shows the structure of the ultrasound probe in the ultrasound diagnosing device of embodiment. It is a rear view of the ultrasonic transmission / reception part in an ultrasonic probe. It is the front view which expanded the principal part of the ultrasonic transmission / reception part. FIG. 6 is a sectional view taken along line VI-VI in FIG. 5. It is the VII-VII sectional view taken on the line of FIG. It is a graph which shows the transmission / reception sensitivity of Examples 1-3 and a comparative example. It is a graph which shows the transmission / reception characteristic of Examples 1-6. (A) is the front view which expanded the principal part of the ultrasonic transmission / reception part of other embodiment, (b) is the IX-IX sectional view taken on the line of Fig.10 (a). (A) is the front view to which the principal part of the ultrasonic transmission / reception part of further another embodiment was expanded, (b) is XX sectional drawing of Fig.11 (a). It is the XI-XI sectional view taken on the line of Fig.11 (a). It is explanatory drawing for demonstrating distortion of the piezoelectric member by voltage application.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an external configuration of an embodiment of an ultrasonic diagnostic apparatus having the ultrasonic probe of the present invention. FIG. 2 is a block diagram showing an electrical configuration of an embodiment of an ultrasonic diagnostic apparatus having the ultrasonic probe of the present invention. FIG. 3 is a cross-sectional view showing a configuration of an embodiment of an ultrasonic probe.

  As shown in FIG. 1, the ultrasonic diagnostic apparatus S in this embodiment transmits an ultrasonic wave (first ultrasonic signal) to a subject such as a living body (not shown) and transmits the ultrasonic wave to the first ultrasonic signal. The ultrasonic probe 2 that receives the ultrasonic wave (second ultrasonic signal) coming from within the subject is connected, and the ultrasonic probe 2 and the cable 3 are connected to each other, and the cable is connected to the ultrasonic probe 2. By transmitting a transmission signal of an electrical signal via 3, the ultrasonic probe 2 is caused to transmit a first ultrasonic signal to the subject, and from within the subject received by the ultrasonic probe 2. An ultrasonic diagnostic apparatus main body 1 that images an internal state of a subject as an ultrasonic image based on a received signal of an electric signal generated by the ultrasonic probe 2 in accordance with the second ultrasonic signal that has come. It is prepared for.

  The ultrasonic waves coming from within the subject based on the first ultrasonic signal are not only reflected waves (echoes) reflected from the first ultrasonic signal in the subject due to acoustic impedance mismatches in the subject, for example, When an ultrasonic contrast agent (contrast agent) such as microbubbles (microbubbles) is used, there is also an ultrasonic wave generated by the microbubbles of the ultrasonic contrast agent based on the first ultrasonic signal. When an ultrasonic contrast agent is irradiated with ultrasonic waves, the microbubbles of the ultrasonic contrast agent resonate or resonate, and further collapse or disappear at a sound pressure above a certain threshold. In the ultrasonic contrast agent, ultrasonic waves are generated by resonance of microbubbles or by collapse or disappearance of microbubbles.

  For example, as shown in FIG. 2, the ultrasonic diagnostic apparatus main body 1 includes an operation input unit 11, a transmission unit 12, a reception unit 13, an image processing unit 14, a display unit 15, and a control unit 16. Configured.

  The operation input unit 11 is, for example, a device for inputting data such as a command for instructing start of diagnosis and personal information of a subject, and is, for example, an operation panel or a keyboard provided with a plurality of input switches.

  For example, the transmission unit 12 transmits a control signal from the control unit 16 to the ultrasound probe 2. For example, the receiving unit 13 receives a reception signal transmitted from the ultrasound probe 2 and outputs the received signal to the image processing unit 14.

  The image processing unit 14 controls the inside of the subject based on a predetermined frequency component in the second ultrasound signal received from the inside of the subject based on the first ultrasound signal received by the receiving unit 13 according to the control of the control unit 16. It is a circuit which forms the image (ultrasonic image) showing the internal state of. Examples of the predetermined frequency component include a fundamental wave component and harmonic components such as a second harmonic component, a third harmonic component, and a fourth harmonic component. The image processing unit 14 may be configured to form an ultrasonic image using a plurality of frequency components. For example, the image processing unit 14 performs processing by the DSP (Digital Signal Processor) that generates an ultrasonic image of the subject based on the output of the receiving unit 13 and the DSP to display the ultrasonic image on the display unit 15. And a digital-analog conversion circuit (DAC circuit) for converting the converted signal from a digital signal to an analog signal. The DSP includes, for example, a B-mode processing circuit, a Doppler processing circuit, a color mode processing circuit, and the like, and can generate so-called B-mode images, Doppler images, and color mode images.

  The display unit 15 is a device that displays an ultrasonic image of the subject generated by the image processing unit 14 under the control of the control unit 16. The display unit 15 is, for example, a display device such as a CRT display, LCD (liquid crystal display), organic EL display, or plasma display, or a printing device such as a printer.

  The control unit 16 includes, for example, a microprocessor, a storage element, and peripheral circuits thereof, and the ultrasonic probe 2, the operation input unit 11, the transmission unit 12, the reception unit 13, the image processing unit 14, and a display. It is a circuit that performs overall control of the ultrasound diagnostic apparatus S by controlling the unit 15 according to the function.

  As shown in FIG. 3, an ultrasonic probe (ultrasonic probe, transducer) 2 is an ultrasonic probe device 4 according to the present invention that is provided in the probe main body 4 and transmits and receives ultrasonic waves. And a sound wave transmitting / receiving unit 5. In the following description, the X direction in FIG. 3 is the front side and the Y direction is the rear side. The same applies to FIGS. 6, 7, 10 (b), 11 (b), (c), and 12 described later.

  The probe body 4 includes a coating layer 41 provided at the front end, a signal processing circuit unit 42 provided on the rear end side, and a backing material disposed between the coating layer 41 and the signal processing circuit unit 42. Layer 43.

  For example, the covering layer 41 is in contact with a living body as a subject and does not give unpleasant feeling in contact, and has an acoustic impedance close to that of the human body in order to achieve acoustic matching with the human body. It is formed from rubber or the like.

  The backing material layer 43 plays a role of attenuating unnecessary vibration generated in the ultrasonic transmission / reception unit 4.

  The signal processing circuit unit 42 is connected to the ultrasonic diagnostic apparatus S via the cable 3 and generates a pulse signal for ultrasonic transmission or processes a received pulse signal.

  Specifically, under the control of the control unit 16, the transmission signal of the electrical signal transmitted from the transmission unit 12 is supplied to cause the ultrasonic transmission / reception unit 5 to generate the first ultrasonic signal. For example, a high voltage pulse generator that generates a high voltage pulse is provided. The drive signal generated by the signal processing circuit unit 42 is a plurality of pulse-like signals in which delay times are individually set appropriately for each of a plurality of diaphragms 6 to be described later, and is supplied to each of the diaphragms 6. . Depending on the plurality of drive signals, the phases of the ultrasonic waves radiated from the diaphragms 6 coincide with each other in a specific direction (specific direction) (or a specific transmission focus point), and the transmission beam forms a main beam in the specific direction. The first ultrasonic signal is generated.

  Further, the signal processing circuit unit 42 receives and processes an electric signal received from the ultrasonic transmission / reception unit 5 under the control of the control unit 16. Then, similarly to the formation of a transmission beam at the time of transmission, a reception beam may be formed at the time of reception by so-called phasing addition. That is, by appropriately setting delay times individually for a plurality of output signals output from the respective diaphragms 6 and adding the delayed output signals, the phase of each output signal is changed to a specific direction (specific direction). ) (Or a specific reception focus point), and a main beam is formed in the specific direction. In such a case, for example, a reception beamformer to which each output signal amplified by the amplifier is input may be provided. The signal processing circuit unit 42 may be provided in the ultrasonic diagnostic apparatus main body 1 and can be changed as appropriate.

  The ultrasonic transmission / reception unit 5 is arranged in a two-dimensional array between the covering layer 41 and the backing material layer 43 of the probe body 4. As shown in FIGS. 4 to 6, the ultrasonic transmission / reception unit 5 of this embodiment includes a substrate (vibrating plate) 61 and a thin plate-like piezoelectric member 62 that is laminated on the front surface of the substrate 61 and has a unimorph structure with the substrate 61. And a pair of plus and minus electrodes 63 and 64 disposed on the front surface side of the piezoelectric member 62, and a support member 8 that supports them.

  In this embodiment, the support member 8 is made of a silicon plate. As shown in FIGS. 4 and 6, the support member 8 is provided with a plurality of circular through holes 81 arranged in the horizontal direction and the vertical direction. Each through hole 81 is formed so as to penetrate from the front surface to the rear surface of the support member 8.

  In this embodiment, the substrate 61 is made of an insulating material such as silicon dioxide (SiO 2) or silicon nitride (SiN) in order to obtain a good potential distribution in PZT, which will be described later. (Thickness of about 2 μm). And this board | substrate 61 is laminated | stacked on the whole front surface of the supporting member 8, and is arrange | positioned so that the through-hole 81 may be covered from the front side.

  The negative electrode 64 (second electrode) is made of gold, platinum, or the like, and includes a plurality of substantially ring-shaped negative electrode main body portions 64 a each having a diameter slightly larger than that of the through hole 81. (Shown in FIGS. 5 and 6). As shown in FIGS. 5 and 6, each negative electrode main body 64 a is disposed so as to be concentric with the through hole 81 and surround the through hole 81.

  The plus electrode 63 (first electrode) is made of gold, platinum, or the like, and includes a plurality of plus electrode body portions 63a corresponding to the minus electrode body portions 64a (shown in FIGS. 5 and 6). As shown in FIGS. 5 and 6, each positive electrode main body 63 a is formed to have a smaller diameter than the negative electrode main body 64 a and is concentrically arranged on the inner side of the negative electrode main body 64 a. Thereby, an electric field is generated in the radial direction from the positive electrode main body portion 63a to the negative electrode main body portion 64a in accordance with the voltage application, and the ring is defined by the positive electrode main body portion 63a and the negative electrode main body portion 64a. The region 65 is an electric field region.

  The piezoelectric member 62 is made of a piezoelectric material. In this embodiment, the piezoelectric member 62 is made of PZT. The piezoelectric member 62 is not limited to PZT. For example, the piezoelectric member may be made of quartz, lithium niobate (LiNbO3), potassium niobate tantalate (K (Ta, Nb) O3), barium titanate ( BaTiO3), lithium tantalate (LiTaO3), strontium titanate (SrTiO3), PZN-PT, PMN-PT, and the like can also be appropriately changed.

  Further, the thickness of the piezoelectric member 62 of this embodiment is about 2 μm. The piezoelectric member 62 includes a plurality (16 in this embodiment) of grooves 7. Each groove 7 is formed so as to extend from the front surface to the rear surface so as to extend from the positive electrode main body portion 63a to the negative electrode main body portion 64a in the ring-shaped region portion 65 in the radial direction that is the direction of the electric field. .

  In this embodiment, the center lines 71 of the two grooves 7 adjacent to each other are arranged side by side in the circumferential direction at a pitch that forms a central angle θ of 10 ° to 25 °. The center line 71 is a line extending in the radial direction from the center O of the ring-shaped region 65 in plan view so as to divide the groove 7 into two.

  In this embodiment, the groove 7 is formed so as to gradually widen from the inner diameter side to the outer diameter side, the width on the inner diameter side is about 1 μm, and the width on the outer diameter side is about 2 μm. The width and shape of the groove 7 are not limited to those in this form, and may be appropriately changed, for example, those having the same width from the inner diameter to the outer diameter.

  The piezoelectric member 62 is stacked on the front surface of the substrate 61, and thus, the substrate 61 includes a circular cell centering on the center O of the ring-shaped region portion 65 in a portion corresponding to each through hole 81. A thin film diaphragm (vibrator) 6 having a unimorph structure is formed.

  Further, in this embodiment, as shown in FIG. 5, the four diaphragms 6 are commonly connected as one element 66 (four surrounded by a two-dot chain line in FIG. 5) and configured to operate in synchronization. A plurality of elements 66 are two-dimensionally arranged on the left, right, and top.

  More specifically, the negative electrode main body portions 64a arranged for each of the four diaphragms 6 are connected to each other through a cell connecting portion 64b shown in FIG.

  Further, the positive electrode main body 63a is arranged so that the four diaphragms 6 are connected to each other through the cell connecting portion 63b shown in FIG. 5A so that the four diaphragms can be energized. The elements 66 are connected to each other by an element extending portion (not shown) extending from each of the six elements 6.

  In this embodiment, the ultrasonic transmission / reception unit 5 configured as described above is formed as follows.

  A substrate 61 is formed on the front surface of the support member 8 by a method such as thermal oxidation, sputtering, or CVD.

  Then, the piezoelectric member 62 is formed on the front surface of the substrate 61 by a method such as sputtering or sol-gel. In order to improve the characteristics (film quality) of the PZT that constitutes the piezoelectric member 62, a method of forming a seed layer such as an oxide under the PZT can be used.

  The electrode is patterned using photolithography by etching, lift-off, or the like. The central side portion of the inner plus electrode 63 and the groove 7 in the piezoelectric member 62 are removed by etching. The through hole 81 of the support member 8 is also processed and removed by etching to form the diaphragm 6.

  Further, in order to align the polarization direction of the piezoelectric member 62 with the direction of the electric field, the electric connection is performed, and then an electric field of several V / μm or more is applied between the inner plus electrode 63 and the outer minus electrode 64 to perform the polarization treatment. Do.

  When diagnosing with the ultrasonic diagnostic apparatus S configured as described above, for example, when an instruction to start diagnosis is input from the operation input unit 11, the signal processing circuit unit 42 performs ultrasonic transmission according to the control of the control unit 16. A trusted pulse signal is generated.

  The generated pulse signal applies a pulse voltage to the ring-shaped region 65 in the radial direction with a predetermined delay time for each element 66 of the plurality of diaphragms 6 of the ultrasonic transmission / reception unit 5.

  Accordingly, the piezoelectric member 62 of the diaphragm 6 is distorted in the radial direction, and the substrate 61 of the diaphragm 6 is bent and deformed in the thickness direction (XY direction in FIG. 6) due to the radial distortion. At this time, since the piezoelectric member 62 includes the plurality of grooves 7 extending in the radial direction, the piezoelectric member 62 is less likely to be restrained by distortion in the circumferential direction orthogonal to the radial direction, and can be efficiently distorted in the radial direction.

  The diaphragm 6 vibrates in a drum shape by the bending deformation of the substrate 61 accompanying the distortion of the piezoelectric member 62 in the radial direction. Due to this vibration, the diaphragm 6 radiates the first ultrasonic signal in the front-rear direction in the thickness direction of the diaphragm 6. In addition, by providing a time difference between the elements of the diaphragm 6 and transmitting a pulse voltage, the ultrasonic wave can be focused in a predetermined distance and direction.

  The first ultrasonic signal radiated from the diaphragm 6 toward the front coating layer 25 is radiated through the coating layer 25. When the covering layer 25 is in contact with the subject, for example, the first ultrasound signal is transmitted from the ultrasound probe 2 to the subject. Note that the first ultrasonic signal radiated rearward from the diaphragm 6 is attenuated by the backing material layer 43.

  Note that the ultrasound probe 2 may be used in contact with the surface of the subject, or may be used by being inserted into the subject, for example, being inserted into a body cavity of a living body. .

The ultrasonic wave transmitted to the subject is reflected at one or a plurality of boundary surfaces having different acoustic impedances inside the subject, and becomes a reflected wave of the ultrasonic wave. Alternatively, when the ultrasound contrast agent is injected into the subject, ultrasound is generated by the ultrasound contrast agent due to the first ultrasound signal. This ultrasonic wave includes not only the frequency (fundamental fundamental frequency) component of the transmitted first ultrasonic signal but also a harmonic frequency component that is an integral multiple of the fundamental frequency. For example, second harmonic components such as twice, three times, and four times the fundamental frequency, third harmonic components, and fourth harmonic components are also included. This ultrasonic wave is received by the ultrasonic probe 2.

  More specifically, this ultrasonic wave is received by the diaphragm 6 through the coating layer 25, mechanical vibrations are converted into electric signals, received as received signals, processed by the signal processing circuit unit 42, and image It is output to the processing unit 14.

  Then, under the control of the control unit 16, the image processing unit 14 determines the distance to the subject based on the time from transmission to reception based on the received reception signal, and the direction of the subject due to the time difference between the elements. An ultrasonic image of the subject is detected and generated. Further, the image processing unit 14 extracts a harmonic component from the received signal by a filtering method, and generates an ultrasonic image of the internal state inside the subject using a harmonic imaging technique based on the extracted harmonic component. The Further, for example, the image processing unit 14 extracts a harmonic component from the received signal by the phase inversion method (pulse inversion method), and uses the harmonic imaging technique based on the extracted harmonic component to inside the subject. An ultrasound image of the state is generated. The display unit 15 displays the ultrasound image of the subject generated by the image processing unit 14 under the control of the control unit 16.

  Next, a simulation for verifying the effect of the groove 7 in the piezoelectric member 62 was performed, which will be described below. In this simulation, three types of piezoelectric members of Examples 1 to 3 in which the grooves are arranged so that the center angles θ (see FIG. 5) of the center lines 71 serving as the pitch of the grooves 7 are different from each other, and the groove 7 as a comparative example. A piezoelectric member that does not have a structure was manufactured and evaluated. In Example 1, the central angle θ is 15 °, and in Example 2, the central angle θ is 30 °. In Example 3, the central angle θ is 45 °.

  In the simulation, a piezoelectric device having the piezoelectric member and a model in which an acoustic medium (water) is arranged in the ultrasonic radiation direction is created, and the generated sound pressure Pout [Pa] with respect to the input voltage Vin [V] at the time of transmission is received. The voltage Vout [V] generated with respect to the sound pressure Pin [Pa] received by the piezoelectric device at each time is obtained for each frequency by simulation. From the result, the output voltage Vout / Vin (with respect to the input voltage) The voltage output by the returned ultrasonic wave) was determined by decibel (dB) conversion.

  The result is shown in FIG. The sensitivity in FIG. 8 is normalized by the peak value of the comparative example having no groove.

  Further, when evaluated with the overall performance index (sensitivity + frequency band) of the ultrasonic probe from the frequency characteristics of FIG. 8, it is 2.2 dB in the first embodiment and 2.2 dB in the second embodiment compared to the comparative example. 1.8 dB, and in Example 3, it was 1.7 dB, respectively. Here, for example, as shown for the data of the comparative example in FIG. 8, the performance index is obtained by converting the frequency bandwidth BW obtained by dividing the frequency width fbw that is −6 dB from the peak value by the center frequency fc into dB, and fc This is the sum (transmission / reception characteristics) shown in FIG.

  As described above, in all of Examples 1 to 3, the performance index (transmission / reception characteristics) was larger than that of the comparative example, and the effect of the groove was confirmed.

  In addition, a simulation for verifying the effect of the central angle of the groove 7 in the piezoelectric member 62 was performed and will be described below.

  In this simulation, in addition to Examples 1 to 3, Example 4 has the central angle θ of 10 °, Example 5 has the central angle θ of 20 °, and Example 6 has the central angle θ. Each of which is 25 °. And about those Examples 1-6, the transmission / reception characteristic (sensitivity + frequency band) used as the said performance index was computed.

  As a result, as shown in FIG. 9, the value of the transmission / reception characteristics is particularly large when the central angle θ is in the range of 10 ° to 25 °, and the transmission / reception characteristics can be further improved. Therefore, it is particularly preferable to dispose the plurality of grooves 7 in the circumferential direction so that the center angle θ between the center lines 71 serving as the pitch of the grooves 7 is 10 ° to 25 °.

  In the above-described embodiment, the piezoelectric member 62 is formed larger than the through hole 81, but is not limited to this configuration and can be changed as appropriate.

  For example, as shown in FIGS. 10A and 10B, the piezoelectric member 162 is formed of a circular shape smaller than the through hole 181, and the plus electrode main body portion 163 a of the plus electrode 163 is formed at the center of the piezoelectric member 162. The negative electrode main body 164a of the negative electrode 164 is provided on the outer peripheral side of the piezoelectric member 162.

  As the voltage is applied, an electric field is generated in the radial direction from the plus electrode body 163a of the plus electrode 163 to the minus electrode body 164a side of the minus electrode 164, and the plus electrode body 163a and the minus electrode body 64a. The circular region portion 165 partitioned and formed into an electric field region.

  In the above embodiment, the positive electrode main body portion of the positive electrode and the negative electrode main body portion of the negative electrode form the electric field region in the ring-shaped region portion or the circular region portion. The region may be formed in a rectangular region and can be changed as appropriate.

  Specifically, for example, as shown in FIGS. 11 and 12, the plus electrode 263 has a rectangular plus electrode main body portion 263 a linearly extending along the width direction at the left end (one end) of the piezoelectric member 262. I have. The negative electrode 264 is a rectangular negative electrode main body 264a extending in parallel with the positive electrode main body 263a at the right end (the other end) of the piezoelectric member 262 spaced apart from the positive electrode main body 263a by a predetermined distance. It has.

  The piezoelectric member 262 is formed of a rectangular shape that is slightly smaller than the through hole 281 of the support member 208. In addition, a plurality of grooves 207 extending in the longitudinal direction are provided between the plus electrode body 263a and the minus electrode body 264a.

  In this embodiment, the grooves 207 are arranged with a groove width of about 1 μm and a pitch interval of about 10 μm. Note that the groove width or pitch interval is not limited to this, and can be changed as appropriate.

  As the voltage is applied, an electric field is generated in the rectangular region 265 formed between the positive electrode main body 263a and the negative electrode main body 264a, so that the rectangular region 265 becomes an electric field region. The member 262 is distorted in the longitudinal direction from the positive electrode main body 263a to the negative electrode main body 264a, and the substrate 261 of the diaphragm 206 is bent and deformed in the thickness direction (XY direction) due to the longitudinal distortion of the piezoelectric member 262. To do.

  At this time, the plurality of grooves 207 in which the piezoelectric member 262 extends in the longitudinal direction makes it difficult for the strain in the longitudinal direction of the piezoelectric member 262 to be restrained by the strain in the width direction, and can be efficiently distorted in the longitudinal direction.

  As described above, when the electric field region is formed in the rectangular region 265, for example, as described above, four diaphragms including piezoelectric members constitute one element (portion surrounded by a two-dot chain line in FIG. 5). The arrangement efficiency of the diaphragm in one element can be increased, the effective area of the diaphragm can be increased, and the transmission / reception characteristics of ultrasonic waves can be improved. Further, the plus electrode 263 and the minus electrode 264 can be easily pulled out from both sides, and a structure with little loss can be achieved.

  Moreover, in the said embodiment, although the groove | channel is formed so that a piezoelectric member may be penetrated from a front surface to a back surface, it is not restricted to the thing of this form, It can change suitably. For example, the groove may be formed with a predetermined depth from the front surface of the piezoelectric member. However, if the groove is formed so as to penetrate the piezoelectric member from the front surface to the rear surface, it is preferable in that the restriction due to the distortion in the direction orthogonal to the electric field direction can be easily relaxed and the distortion in the electric field direction can be easily increased. .

  In the above embodiment, the piezoelectric device of the present invention is used as an ultrasonic transmission / reception unit of an ultrasonic probe. However, the piezoelectric device is not limited to the form used for an ultrasonic probe, and for example, ink for an inkjet printer. It can also be used for a discharge head and can be changed as appropriate.

1 Ultrasonic Diagnostic Equipment 2 Ultrasonic Probe 5 Ultrasonic Transceiver (Piezoelectric Device)
6 Diaphragm 7 Groove 61 Substrate 62 Piezoelectric member 63 Positive electrode 64 Negative electrode S Ultrasonic diagnostic apparatus

Claims (8)

A thin plate-like piezoelectric member, a pair of first and second electrodes formed on the piezoelectric member, and an electric field generated when a voltage is applied to the pair of first and second electrodes. A groove formed to include the extended portion ;
The piezoelectric device is characterized in that the groove is formed between the first electrode and the second electrode . The pair of first and second electrodes are formed apart from each other by a predetermined distance in a direction orthogonal to the thickness direction of the piezoelectric member,
The piezoelectric device according to claim 1 , wherein the groove is formed to extend from the first electrode to the second electrode . Further comprising a thin plate-like substrate that adopts a unimorph structure with the piezoelectric member,
3. The piezoelectric device according to claim 1 , wherein the substrate is bent and deformed in a thickness direction substantially orthogonal to a surface of the substrate in accordance with distortion of the piezoelectric member due to the voltage application . The piezoelectric device according to any one of claims 1 to 3, wherein the pair of first and second electrodes have a substantially circular shape or a substantially ring shape . The grooves are composed of a plurality of radially extending grooves, and are arranged side by side in the circumferential direction so that the center lines of two grooves adjacent to each other form a central angle of 10 ° to 25 °. the piezoelectric device according to claim 4, characterized in that is. First and second electrodes of said pair of piezoelectric device according to any one of claims 1 to 5, characterized in that it is spaced apart by a predetermined distance on a surface of said piezoelectric member . The second electrode includes a second electrode main body,
  The first electrode includes a first electrode main body disposed inside the second electrode main body, and a connecting portion extending from the first electrode main body to the outside of the second electrode main body. The piezoelectric device according to claim 1, wherein the piezoelectric device is a piezoelectric device. The ultrasonic probe provided with the piezoelectric device as described in any one of Claims 1-7.

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