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DESCRIPTION JP2013098724

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DESCRIPTION JP2013098724
An object of the present invention is to provide a piezoelectric device, an ultrasonic probe, and a
method of manufacturing the piezoelectric device, which can deform a membrane efficiently and
largely. An ultrasonic transducer unit 5 as a piezoelectric device in an ultrasonic probe according
to the present invention includes a circular membrane 6 having stacked thin plate-like
piezoelectric members 62, and an electrode. The electrodes are provided in the piezoelectric
member 62 so that a plurality of pairs of first electrodes are provided on the piezoelectric
member 62 so that mutually opposite stresses can be generated as the voltage is applied to the
first region 68 and the second region 69 of the piezoelectric member 62. One electrode 63, 65
and a second electrode 64 are provided. [Selected figure] Figure 5
Piezoelectric device, ultrasonic probe, and method of manufacturing piezoelectric device
[0001]
The present invention relates to a piezoelectric device and an ultrasonic probe used for an
ultrasonic probe, an inkjet printer, and the like, and a method of manufacturing the piezoelectric
device.
[0002]
The ultrasound diagnostic apparatus is characterized by noninvasively observing internal tissue
and observing in real time, so the application to diagnosis is increasing more and more.
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1
As ultrasonic waves of this ultrasonic diagnostic apparatus, for example, a pMUT (Piezoelectric
Micromachined Ultrasonic Transducer) is known which transmits and receives ultrasonic waves
by vibrating a membrane of a unimorph structure in which a piezoelectric member such as PZT
is formed on a substrate in a drum shape. .
[0003]
Such a pMUT ultrasonic probe can broaden the frequency band as compared to one obtained by
dividing bulk PZT by dicing, and can be miniaturized to obtain high resolution and obtain a threedimensional image. It has the advantages of being suitable for two-dimensional arraying of
membranes (oscillators) to be used, and being suitable for application to ultrasound endoscopes
because it can be miniaturized and thinned. In such a pMUT ultrasonic probe, with a onedimensional array of transducers, the image that can be acquired is a tomographic image, and
there is a risk of false negatives due to the operation. Technical skill is required. In order to
alleviate such problems, the need for a two-dimensional array ultrasonic probe capable of
acquiring a three-dimensional image is high.
[0004]
In such an ultrasonic probe, the following energy conversion operation is performed. In
transmission, electrical energy is converted to mechanical energy (vibration of the membrane)
and mechanical energy is converted to acoustic energy (ultrasound). On the other hand,
reception converts acoustic energy (ultrasound) into mechanical energy (vibration of the
membrane) and further converts mechanical energy into electrical energy.
[0005]
Mutual conversion of mechanical energy and acoustic energy is important for acoustic matching,
and it is a point of design to match the effective acoustic impedance of the pMUT to the acoustic
impedance of the living body. Mutual conversion of electrical energy and mechanical energy is
important to enhance the energy conversion efficiency of the membrane configuration including
the piezoelectric member. The piezoelectric member is most efficient to use strain in the same
direction (33 directions) as the direction of the electric field (k index: the electromechanical
coupling coefficient is high in the index indicating the performance of the piezoelectric member).
In the feeler, a configuration using distortion in 33 directions is advantageous. In addition, as
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compared with the configuration in which the electrodes are disposed in the thickness direction
of PZT, the distance between the electrodes can be made relatively large, and the sensitivity at
the time of ultrasonic wave reception (output voltage to unit pressure) can be improved.
[0006]
Patent Document 1 discloses a microminiature shell type converter as a system utilizing such
distortion in 33 directions. This product forms a membrane (arch portion) in which piezoelectric
members (solid electroactive media) are laminated on the inside of two shoulder portions on a
holding substrate, and a pair of electrodes is attached to each shoulder portion to form a
membrane. Form a chamber between the and the holding substrate. Then, a voltage is applied
from the positive electrode along the negative electrode to generate an electric field in the same
direction to induce stress in the same direction in the piezoelectric member to move the
membrane upward or downward in the thickness direction and bend in a curved shape
Transform it.
[0007]
U.S. Pat. No. 6,222,304
[0008]
However, due to the bending deformation of the membrane, the piezoelectric member has a place
where a tensile stress is generated and a place where a compressive stress is generated
depending on the location of the membrane.
Hereinafter, the example shown in FIG. 8 will be described in detail. The film shown in FIG. 8 is a
film in which a film member 101 having a piezoelectric member 102 stacked on a thin plate-like
substrate 101 is held by a holding member 103 and disposed in the inner region of the held
region 106 held. A circular membrane 100 formed of a member 101 is provided. As shown in
FIG. 8 (FIG. 8), a voltage is applied to a pair of electrodes of the first electrode 104 disposed at
the central portion of the membrane 100 and the second electrode 105 disposed on the outer
peripheral side which is the held area 106 side. b) As shown by the alternate long and short dash
line in the figure, when it is bent and deformed downward, tensile stress is generated in the first
region 111 of the membrane 100 on the side of the region to be held 106 of the piezoelectric
member 102. A compressive stress is generated in the second region 112 radially inward of the
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In contrast to the above, when the membrane 100 is bent and deformed upward in FIG. 8B, a
compressive stress is generated in the first region 111 and a tensile stress is generated in the
second region 112. The stress generated in the piezoelectric member due to the bending
deformation in such an electrode configuration inhibits the bending deformation when the
membrane 100 is bent and makes the bending deformation difficult.
[0009]
Therefore, in the case of applying a single electric field (stress application in a single direction) to
the entire piezoelectric member 102 constituting a part of such a membrane 100, the membrane
100 is efficiently used because of the stress that inhibits the above-mentioned bending
deformation. Can not be bent and deformed, making it difficult to increase the displacement of
the membrane 100. As a result, for example, when it is used for an ultrasonic probe, transmission
(sound pressure) can not be increased. Also, for example, when using a sensor that detects
deformation of the membrane due to external pressure by a piezoelectric member, in the case of
one pair of electrodes, stress is generated in the opposite direction in the piezoelectric member
between the pair of electrodes, The charges cancel each other out, the charges can not be
extracted efficiently, and the sensor sensitivity can not be increased. Therefore, for example,
when it uses for an ultrasound probe, reception sensitivity can not be enlarged.
[0010]
An object of the present invention is to provide a piezoelectric device, an ultrasonic probe, and a
method of manufacturing the piezoelectric device, which can deform a membrane efficiently and
largely.
[0011]
A piezoelectric device according to an aspect of the present invention includes a film member in
which piezoelectric members are stacked, a holding member that holds the film member, and a
pair of first and second electrodes that apply a voltage to the piezoelectric member. A
piezoelectric device having a membrane made of a part of the film member formed to be bent
and deformed in a thickness direction when a voltage is applied to the piezoelectric member by
supplying power to the pair of first and second electrodes. The pair of first and second electrodes
are a plurality of sets, and the plurality of sets of the pair of first and second electrodes are
arranged to divide the piezoelectric member in the membrane into a plurality of regions Are
wired in such a manner that mutually opposite stresses in the plurality of regions are generated
when power is supplied to the plurality of pairs of first and second electrodes, respectively. It is
characterized in.
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[0012]
According to this configuration, it is possible to make it difficult to generate a stress that inhibits
the bending deformation of the membrane as compared to the case of a single electrode.
[0013]
For example, when the direction of stress caused by the area is different in bending deformation
of the membrane, a tensile stress is generated in the first area by applying a voltage to the pair of
first and second electrodes, and As a compressive stress is generated in the region, the
piezoelectric member can be distorted and the membrane can be deformed by the distortion.
As a result, it is possible to suppress the generation of stress that inhibits the bending
deformation as compared to the case of a single electrode during the bending deformation of the
membrane, and it is possible to efficiently bend and deform the membrane efficiently.
[0014]
Therefore, for example, when it uses for an ultrasonic probe, transmission sound pressure can be
improved.
Also, for example, when used as a sensor, it is possible to efficiently extract charges from the first
and second electrodes, which can improve sensor sensitivity, for example, when used for an
ultrasonic probe, it is possible to improve reception sensitivity. Since the transmission and
reception characteristics are improved, the diagnostic characteristics are improved.
[0015]
In another aspect, in the piezoelectric device, the plurality of pairs of first and second electrodes
are disposed along a direction substantially perpendicular to a thickness direction of the
piezoelectric member. .
[0016]
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According to this configuration, the membrane can be efficiently deformed as compared with the
configuration in which the electrodes are disposed in the thickness direction of the piezoelectric
member.
Also, since the electrode spacing can be made relatively large as compared with the configuration
in which the electrodes are disposed in the thickness direction of the piezoelectric member, for
example, when used in an ultrasonic probe, the sensitivity at the time of ultrasonic reception
(output voltage relative to unit pressure ) Can be improved.
[0017]
In another aspect, in the piezoelectric device, a part of the plurality of pairs of first and second
electrodes is disposed to include a region in the piezoelectric member in which no stress is
generated in connection with the bending deformation of the membrane. It is characterized by
[0018]
According to this configuration, with the bending deformation of the membrane, the stress state
can be made more appropriate, and the membrane can be deformed more efficiently and largely.
[0019]
In addition, for example, it becomes possible to efficiently collect and take out the charge when
the membrane is deformed due to the ultrasonic wave, and the ultrasonic wave can be measured
more accurately.
[0020]
In another aspect, in the piezoelectric device, the membrane is formed of one having a
substantially circular or substantially rectangular outer peripheral shape, and the held region is
disposed over substantially the entire outer periphery of the membrane. The plurality of pairs of
first and second electrodes are arranged substantially concentrically similar to the outer
periphery of the membrane.
[0021]
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According to this configuration, an unnecessary vibration mode can be prevented from occurring
in the vicinity of the primary resonance frequency (the desired vibration mode).
If the unnecessary vibration mode is near the drive frequency, the unnecessary vibration is
excited and the pulse waveform may be broken from the designed pulse waveform, which may
adversely affect the resolution, but this can be prevented.
[0022]
In another aspect, in the piezoelectric device, the membrane is formed of one having a
substantially rectangular outer peripheral shape, and the held regions are disposed on both ends
in one direction of the membrane, respectively. A plurality of pairs of first and second electrodes
are arranged to be arranged substantially in parallel with each other at one end of the membrane
in one direction.
[0023]
According to this configuration, when one element is constituted by a plurality of membranes,
the arrangement efficiency of the membrane in one element can be increased, the effective area
of the membrane can be enlarged, and for example, the transmission and reception
characteristics of ultrasonic waves can be improved. .
Further, the electrodes can be easily pulled out from both sides, and a structure with less loss can
be realized.
[0024]
In another aspect, in the piezoelectric device, the plurality of sets of first electrodes are
connected in common, and the plurality of sets of second electrodes are connected in common.
[0025]
According to this configuration, the number of lead wires can be reduced, and a voltage can be
applied with a single power supply.
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Therefore, the circuit can be simplified and the cost can be reduced.
[0026]
An ultrasonic probe according to an aspect of the present invention includes the piezoelectric
device described in any of the above.
[0027]
According to this configuration, an appropriate stress state can be obtained when the membrane
is flexed and deformed, and the membrane can be flexed and deformed efficiently.
[0028]
Therefore, for example, when using for an ultrasonic probe, the transmission sound pressure can
be improved, and the reception sensitivity can be improved.
Moreover, for example, when using as a sensor, it is possible to take out electric charge
efficiently, and sensor sensitivity can be improved.
[0029]
In a method of manufacturing a piezoelectric device according to an aspect of the present
invention, a film member in which piezoelectric members are stacked, a holding member that
holds the film member, and a pair of first and second electrodes that apply a voltage to the
piezoelectric member And a membrane made of a part of the membrane member formed to be
bent and deformed in the thickness direction when a voltage is applied to the piezoelectric
member by supplying power to the pair of first and second electrodes. In a method of
manufacturing a piezoelectric device, a plurality of sets of the pair of first and second electrodes
are disposed so as to divide a piezoelectric member in the membrane into a plurality of regions,
and the plurality of pairs of first and second pairs of Wiring is performed such that, when power
is supplied to the two electrodes, stresses in mutually opposite directions are generated in
mutually adjacent regions of the plurality of regions.
[0030]
According to this configuration, it is possible to suppress the generation of stress that inhibits the
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bending deformation as compared to the case of a single electrode during the bending
deformation of the membrane, and to efficiently perform the bending deformation of the
membrane efficiently. It can be manufactured.
[0031]
Therefore, for example, when it uses for an ultrasonic probe, a transmission characteristic
(transmission sound pressure) can be improved and a receiving sensitivity can be improved.
In addition, for example, in the case of using as a sensor, it is possible to efficiently extract
electric charge, and it is possible to obtain a piezoelectric device that can improve sensor
sensitivity.
[0032]
In another aspect, in the method of manufacturing a piezoelectric device, a plurality of pairs of
first and second electrodes are disposed on the piezoelectric member, and the plurality of pairs of
first and second electrodes are disposed. In which the voltage is applied to the two electrodes
with the largest distance to each other to polarize the piezoelectric member, and then the first
electrodes are connected in common and the second electrodes are connected in common. I
assume.
[0033]
According to this configuration, before making the common connection between the first
electrodes and the common connection between the second electrodes, the two electrodes of
which the distance between the pair becomes maximum between the pair of first and second
electrodes. In order to polarize the piezoelectric member by applying a voltage thereto, the
piezoelectric member can be polarized using a plurality of pairs of first and second electrodes.
Therefore, the polarization process can be facilitated.
[0034]
The present invention can provide a piezoelectric device, an ultrasonic probe, and a method of
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manufacturing a piezoelectric device, which can deform a membrane efficiently and largely.
[0035]
It is a figure which shows the external appearance structure of the ultrasound diagnosing device
which has an ultrasound probe of 1st Embodiment.
It is a block diagram which shows the electric constitution of the ultrasound diagnosing device
which has an ultrasound probe of 1st Embodiment.
It is sectional drawing which shows the structure of the ultrasound probe in the ultrasound
diagnosing device of 1st Embodiment.
It is a rear view of the ultrasonic transmission / reception part in the ultrasonic probe of 1st
Embodiment.
(A) is the front view which expanded the principal part of the ultrasonic wave transmission /
reception part in the ultrasonic probe of 1st Embodiment, (b) is a VV sectional view taken on the
line of Fig.5 (a).
(A) is the front view to which the principal part of the ultrasonic wave transmission and reception
part of 2nd Embodiment was expanded, (b) is the VI-VI line sectional view of Drawing 6 (a).
(A) is the front view to which the principal part of the ultrasonic transmission / reception part of
3rd Embodiment was expanded, (b) is the VII-VII sectional view taken on the line of FIG. 7 (a).
It concerns on explanatory drawing of a prior art example, (a) is the top view, (b) is an expanded
sectional view of the principal part.
[0036]
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10
Hereinafter, embodiments of the present invention will be described in detail with reference to
the drawings. FIG. 1 is a view showing an appearance configuration of an ultrasonic diagnostic
apparatus having an ultrasonic probe according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing the electrical configuration of the ultrasonic diagnostic
apparatus having the ultrasonic probe of the first embodiment. FIG. 3 is a cross-sectional view
showing the configuration of the ultrasonic probe of the first embodiment.
[0037]
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 not illustrated living body, and
further uses the first ultrasonic signal. To the ultrasonic probe 2 which is connected via the
ultrasonic probe 2 and the cable 3 to the ultrasonic probe 2 for receiving an ultrasonic wave
(second ultrasonic signal) coming from within the subject based on the By making the ultrasonic
probe 2 transmit the first ultrasonic signal to the subject by transmitting the transmission signal
of the electric signal through 3, and from within the subject received by the ultrasonic probe 2
And an ultrasonic diagnostic apparatus main body 1 for imaging the internal state inside the
subject as an ultrasonic image based on the received signal of the electric signal generated by the
ultrasonic probe 2 according to the second ultrasonic signal that has come. It comprises and is
constituted.
[0038]
The ultrasonic wave coming from the inside of the subject based on the first ultrasonic signal is
not only the reflected wave (echo) in which the first ultrasonic signal is reflected in the subject
due to the mismatch of the acoustic impedance in the subject, for example When an ultrasound
contrast agent (contrast agent) such as microbubbles (microbubbles) is used, there are also
ultrasound waves generated by the microbubbles of the ultrasound contrast agent based on the
first ultrasound signal.
In ultrasound contrast agents, when irradiated with ultrasound, the microbubbles of the
ultrasound contrast agent resonate or resonate, and further collapse and disappear at sound
pressure above a certain threshold. In ultrasound contrast agents, ultrasound is generated by the
resonance of the microbubbles or by the collapse and disappearance of the microbubbles.
[0039]
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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. Is configured.
[0040]
The operation input unit 11 is, for example, a device for inputting data such as a command
instructing start of diagnosis and personal information of the subject, and is, for example, an
operation panel or a keyboard provided with a plurality of input switches.
[0041]
The transmission unit 12 transmits, for example, a control signal from the control unit 16 to the
ultrasound probe 2.
The receiving unit 13 receives, for example, a reception signal sent from the ultrasound probe 2
and outputs the reception signal to the image processing unit 14.
[0042]
Under the control of the control unit 16, the image processing unit 14 controls the inside of the
object based on a predetermined frequency component of the second ultrasonic signal received
from within the object based on the first ultrasonic signal received by the receiving unit 13. It is a
circuit which forms the image (ultrasound 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
ultrasound image using a plurality of frequency components. The image processing unit 14
processes, for example, a DSP (Digital Signal Processor) that generates an ultrasound image of
the subject based on the output of the receiving unit 13, and the DSP to display the ultrasound
image on the display unit 15. A digital-to-analog conversion circuit (DAC circuit) or the like that
converts a digital signal to an analog signal is included. The DSP includes, for example, a B mode
processing circuit, a Doppler processing circuit, a color mode processing circuit, and the like, and
is capable of generating so-called B mode images, Doppler images, and color mode images.
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[0043]
The display unit 15 is a device that displays the 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, an LCD (liquid crystal display), an organic EL
display, a plasma display, or a printing device such as a printer.
[0044]
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 the display It is a circuit that performs
overall control of the ultrasonic diagnostic apparatus S by controlling the unit 15 according to
the function.
[0045]
As shown in FIG. 3, the ultrasonic probe (ultrasonic probe, transducer) 2 is provided on the probe
main body 4 and the probe main body 4 to transmit and receive ultrasonic waves. And).
The X direction in FIG. 3 will be described as the front side, and the Y direction as the rear side.
The same applies to FIG. 5 (b), FIG. 6 (b), FIG. 7 (b) and FIG. 8 (b) described later.
[0046]
The probe main body 4 includes a cover layer 41 provided at the front end, a signal processing
circuit unit 42 provided at the rear end side, and a backing material provided between the cover
layer 41 and the signal processing circuit unit 42. And a layer 43.
[0047]
The covering layer 41 abuts against, for example, a living body as a subject at the time of
diagnosis, and does not give discomfort at the time of the aiding, and silicone having an acoustic
impedance close to that of the human body for acoustic matching with the human body. It is
formed of rubber or the like.
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[0048]
The backing material layer 43 plays a role of, for example, damping unnecessary vibration
generated in the ultrasonic transmitting and receiving unit 5.
[0049]
The signal processing circuit unit 42 is connected to the ultrasonic diagnostic apparatus S via the
cable 3 and performs generation of a pulse signal for ultrasonic transmission, processing of a
reception pulse signal, and the like.
[0050]
Specifically, under the control of the control unit 16, the transmission signal of the electric signal
sent from the transmission unit 12 is supplied to cause the ultrasonic transmission / reception
unit 5 to generate a first ultrasonic signal.
For example, it comprises a high voltage pulse generator etc. which generate a pulse of high
voltage.
The drive signal generated by the signal processing circuit unit 42 is a plurality of pulse-like
signals whose delay times are individually set appropriately for each of a plurality of membranes
6 (see FIG. 5) described later. It is supplied to each.
The transmission beam in which the phases of the ultrasonic waves emitted from the respective
membranes 6 coincide with each other in a specific direction (specific direction) (or a specific
transmission focus point) depending on the plurality of drive signals and form the main beam in
that specific direction. Generating a first ultrasound signal of
[0051]
Further, the signal processing circuit unit 42 receives and processes the received signal of the
electric signal from the ultrasonic wave transmitting / receiving unit 5 according to the control of
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the control unit 16.
Then, similarly to the formation of the transmission beam at the time of transmission, the
reception beam may be formed by so-called phasing addition at the time of reception. That is, the
delay time is individually set appropriately for a plurality of output signals output from each of
the membranes 6, and the phase of each output signal is in a specific direction (specific direction)
by adding the plurality of delayed output signals. Alternatively, they coincide at a particular
reception focus point, and the main beam is formed in that particular direction. In such a case,
for example, a reception beam former 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.
[0052]
The ultrasonic transmitting and receiving unit 5 is disposed between the covering layer 41 of the
probe main body 4 and the backing material layer 43. As shown in FIGS. 4 and 5, the ultrasonic
transmitting / receiving unit 5 of this embodiment includes a plurality of membranes 6 and a
plurality of pairs (two pairs in this embodiment) of pair of plus electrodes (two in this
embodiment) provided on each membrane 6. (1) Electrodes 63 and 65, a ground electrode
(second electrode) 64, and a holding member 8 holding the membrane 6.
[0053]
The holding member 8 in this embodiment is formed of a plate made of silicon. As shown in FIG.
4, the holding member 8 is provided with a plurality of circular through holes 81 arranged in the
left-right direction and the up-down direction. Each through hole 81 is formed to penetrate from
the front surface to the rear surface of the holding member 8 as shown in FIG.
[0054]
Each membrane 6 is formed on the front side of each through hole 81 by a part of the membrane
member 60. Specifically, the film member 60 includes a substrate (diaphragm) 61 and a thin
plate-like piezoelectric member 62 laminated on the front surface of the substrate 61 and having
a unimorph structure.
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[0055]
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 the laterdescribed PZT, and is in the form of a thin plate (in this embodiment) It has a thickness of about
2 μm.
[0056]
The substrate 61 is held so as to be laminated and bonded to the entire front surface of the
holding member 8 and disposed so as to cover the through holes 81 from the front side.
[0057]
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 one composed of PZT, and for example, the
piezoelectric member may be made of quartz, lithium niobate (LiNbO3), potassium niobate
tantalate (K (Ta, Nb) O3), barium titanate It may be made of BaTiO 3), lithium tantalate (LiTaO 3),
strontium titanate (SrTiO 3), PZN-PT, PMN-PT or the like, and can be appropriately modified.
[0058]
Further, the piezoelectric member 62 of this embodiment is formed of a disc-like member slightly
larger than the through hole 81 of the holding member 8 and having a thickness of about 2 μm.
[0059]
The piezoelectric members 62 are laminated and held on the front surface of the substrate 61 on
the front side of the through holes 81.
[0060]
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In this manner, the membrane member 60 is held on the entire front surface of the holding
member 8 including the peripheral edge of the through hole 81, and the membrane 6 is located
in the radially inner region (inner region) of the held region 60a. It is formed so that it may be
enclosed by the holding area 60a circularly.
That is, the outer periphery 60 b of the membrane 6 partitioned in the held region 60 a has the
same shape as the through hole 81 and has a circular shape concentric with the through hole 81.
[0061]
In this embodiment, the electrodes are a first pair of first pair of plus electrodes 63 and a first
and second pair of ground electrodes 64, and a second pair of second pair of plus electrodes 65
and a first pair. And a second set of ground electrodes 64.
And while these electrodes 63, 64, 65 are arrange | positioned so that the piezoelectric member
62 in a membrane may be divided into multiple (two in this embodiment) area | region, when
they are each electrically fed, the said, It is wired so that the mutually opposing stress is
generated in the mutually adjacent areas in the plurality of areas. Details will be described below.
[0062]
These electrodes 63, 64, 65 are arranged in the same configuration on the piezoelectric member
62 of each membrane 6. Therefore, hereinafter, one disposed on the piezoelectric member 62 of
one membrane 6 will be described based on FIG. In this embodiment, these electrodes 63, 64, 65
are made of gold, platinum or the like. Further, the first and second set ground electrodes 64 are
configured to double as the first set ground electrode and the second set ground electrode.
[0063]
The first pair of positive electrodes 63 has a substantially ring shape in plan view over
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substantially the entire outer periphery of the front surface of the piezoelectric member 62, that
is, the front side of the peripheral edge of the through hole 81 in the held area 60a. Are located
in On the other hand, the second pair of positive electrodes 65 is disposed at the center of the
front surface of the piezoelectric member 62 so as to have a circular shape in plan view.
[0064]
In addition, the ground electrode 64 for the first and second sets extends substantially all around
between the first set plus electrode main portion 63a and the second set plus electrode main
portion 65a in the radial direction of the piezoelectric member 62. It is disposed to be adjacent to
each of the first pair plus electrode main portion 63a and the second pair plus electrode main
portion 65a in a substantially ring shape in plan view.
[0065]
In this embodiment, the ground electrode 64 for the first and second sets is a region 7 in the
piezoelectric member 62 in which no stress is generated due to the bending deformation of the
membrane 6, that is, the piezoelectric member 62 deformed in bending when the membrane 6 is
bent. The inflection point is formed by connecting the inflection points of the deflection curve in
the cross-sectional shape over the entire circumference.
[0066]
Note that the first and second sets of ground electrodes 64 are not limited to those in a
configuration in which the whole is disposed in the above-described area 7, and for example, all
or part of the first and second sets of ground electrodes 64 It may be disposed near 7 and can be
changed as appropriate.
Further, in this embodiment, the region 7 is determined by simulation, and the first and second
sets of ground electrodes 64 are disposed based thereon.
[0067]
Further, the first pair of plus electrodes 63, the second pair of plus electrodes 65, and the first
and second pair of ground electrodes 64 are concentrically arranged in a similar shape with the
outer periphery 60b of the membrane 6.
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[0068]
In this manner, the piezoelectric member 62 in the membrane 6 is held by the holding region 60
a in the radial direction by the first pair plus electrode 63, the second pair plus electrode 65, and
the first and second pair ground electrodes 64. It is divided into two (plurality) regions of a first
region 68 on the side (radially outer side) and a second region 69 including a central portion on
the inner peripheral side (radially inner side) than the first region 68.
[0069]
Further, the first pair of plus electrodes 63 and the second pair of plus electrodes 65 are
connected in common so as to be conductive via the plus electrode connection wiring 66
connected to each of them.
[0070]
Further, in this embodiment, as shown in FIG. 4, the plurality of membranes 6 formed as
described above are common to the four membranes 6 as one element 66 (four surrounded by
the two-dot chain line in FIG. 4). A plurality of elements 66 are arranged two-dimensionally in the
left, right, upper, and lower directions so as to be connected and operated in synchronization.
[0071]
More specifically, the first and second sets of ground electrodes 64 provided for each of the four
membranes 6 are mutually connected via the ground electrode connection wiring 67 shown in
FIG. ing.
[0072]
Further, the first set of plus electrodes 63 and the second set of plus electrodes 65, which are
disposed for each of the four membranes 6, are mutually connected via the plus electrode
connection wiring 66 so as to be able to be energized. A plurality of elements 66 are connected
by element connection wiring (not shown) extended from each one element 66 consisting of the
four membranes 6.
[0073]
Then, when the electrodes 63, 64, 65 arranged as described above are supplied with power,
respectively, stress in the opposite direction is generated in the first region 68 and the second
region 69 in the piezoelectric member.
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[0074]
The ultrasonic transmitting and receiving unit 5 configured as described above is formed as
follows in this embodiment.
[0075]
A substrate 61 is formed on the front surface of the holding member 8 by a method such as
thermal oxidation, sputtering, or CVD.
[0076]
Then, the piezoelectric material constituting the piezoelectric member 62 is laminated on the
front surface of the substrate 61 by a method such as sputtering or sol-gel.
Incidentally, in order to improve the characteristics (film quality) of PZT which is a piezoelectric
material constituting the piezoelectric member 62, a method of forming a seed layer of oxide or
the like under the PZT can also be taken.
[0077]
Also, the first set of plus electrodes 63, the second set of plus electrodes 65, and the first and
second sets of ground electrodes 64 are patterned using photolithography by etching or lift-off,
and the piezoelectric material is etched by etching. The piezoelectric member 62 is formed by
patterning using photolithography.
Also, the through hole 81 of the holding member 8 is processed by etching, whereby the
membrane 6 is formed on the front side of the through hole 81.
[0078]
Further, the positive electrode connection wiring 66 is formed, and the first pair of positive
electrodes 63 and the second pair of positive electrodes 65 are commonly connected.
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However, in this embodiment, prior to the formation of the positive electrode connection wiring
66, a number V / um or more is set between the first pair plus electrode 63 on the outer
peripheral side and the second pair plus electrode 65 on the center side. A voltage is applied so
that an electric field is applied, and polarization processing is performed on the entire
piezoelectric member 62 so that the charge direction is a single direction P from the center
outward in the radial direction.
[0079]
After the polarization process, the positive electrode connection wiring 66 is formed of platinum,
gold or the like by film formation, patterning, or wire bonding, and the first pair of positive
electrodes 63 and the second pair of positive electrodes 65 are formed. And common connection.
[0080]
Thus, if the polarization process of the piezoelectric member 62 is performed, the polarization
process of the piezoelectric member 62 can be performed using the first pair plus electrode 63
and the second pair plus electrode 65 before common connection. , Polarization processing can
be easily performed.
[0081]
In the case of diagnosis by the ultrasonic diagnostic apparatus S having the ultrasonic probe
configured as described above, for example, when an instruction to start diagnosis is input from
the operation input unit 11, signal processing is performed according to the control of the
control unit 16. The circuit unit 42 generates a pulse signal for ultrasonic wave transmission.
[0082]
The generated pulse signal has a pulse voltage with a predetermined delay time for each of the
elements 66 of the plurality of (four) membranes 6 of the ultrasonic wave transmitting /
receiving unit 5, the first set of plus electrodes 63 and the first and second sets of And between
the second pair of positive electrodes 65 and the first and second pair of ground electrodes 64 in
the radial direction perpendicular to the thickness direction of the piezoelectric member 62.
Generate an electric field.
[0083]
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Due to this electric field, a radial pulling stress is generated in the first region 68 between the
first pair plus electrode 63 and the first and second pair grounding electrodes 64 in each
piezoelectric member 62, and the tensile stress causes the first region 68 to The piezoelectric
member 62 in the first region 68 is distorted so as to extend in the radial direction.
Further, the second region 69 between the first and second sets of ground electrodes 64 and the
second set of plus electrodes 65 in the piezoelectric member 62 is stressed in the opposite
direction to the above, that is, compressed in the radial direction. Stress is generated, and the
compressive stress causes the piezoelectric member 62 in the second region 69 to be distorted
so as to contract in the radial direction.
[0084]
Due to the distortion of each piezoelectric member 62, each membrane 6 is bent and deformed in
a drum shape on the front side in the front-rear direction which is the thickness direction.
Thereby, each membrane 6 can be deformed efficiently and largely.
[0085]
Further, in this embodiment, since the first and second sets of ground electrodes 64 are disposed
in the area 7 where the stress associated with the bending deformation of the membrane 6 in the
piezoelectric member 62 does not occur, the efficiency is further enhanced for each area. Stress
can be generated well, and each membrane 6 can be deformed more efficiently and largely.
[0086]
Then, the membrane 6 is bent and deformed, and a vibration corresponding to the resonance
characteristic (resonance frequency and attenuation characteristic) is excited, and a pulse-like
ultrasonic wave is transmitted into the living body.
By shifting the phase of each element 66 of the array by a predetermined amount, the ultrasonic
beam is focused and steered (or directed) to scan a necessary region in a three-dimensional
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manner.
In the living body, the ultrasonic wave is transmitted while being attenuated, and reflection
occurs at a portion where a difference in acoustic impedance occurs, and is returned to the
ultrasonic probe 2.
[0087]
Each membrane 6 is vibrated by the returned ultrasonic waves, and electric charges are
generated in accordance with the distortion of the piezoelectric member 62 accompanying it. In
this case also, the first region 68 and the second region 69 of the piezoelectric member 62 of the
membrane 6 are reversed. Distortion in the direction occurs.
Therefore, for example, in the case where a pair of electrodes are disposed at the central portion
and the outer peripheral portion as in the conventional one shown in FIG. 8, charges generated
with tensile strain and compressive strain are generated in those electrodes. The charge is
generated in such a manner that the charge with the
[0088]
However, in this embodiment, since the ground electrode 64 for the first and second sets is
disposed in the area 7 where the stress associated with the bending deformation of the
membrane 6 in the piezoelectric member 62 does not occur, the first area 68 and the second
area 68 A charge due to each distortion with the region 69 can be efficiently generated in the
first and second sets of ground electrodes 64, and ultrasonic waves can be measured efficiently
and accurately.
[0089]
Then, it is processed by the signal processing circuit unit 42 and output to the image processing
unit 14, and the image processing unit 14 controls the control unit 16 based on the received
signal received to determine the object by the time from transmission to reception. The direction
of the subject is detected by the time difference between the elements, respectively, and the
ultrasonic image of the subject is generated.
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Furthermore, in the image processing unit 14, harmonic components are extracted from the
received signal by the filter method, and an ultrasonic image of the internal state inside the
object is generated using harmonic imaging technology based on the extracted harmonic
components. Ru.
Further, for example, in the image processing unit 14, harmonic components are extracted from
the received signal by the phase inversion method (pulse inversion method), and the inside of the
object is extracted using harmonic imaging technology based on the extracted harmonic
components. An ultrasound image of the condition is generated.
Then, the display unit 15 displays the ultrasonic image of the subject generated by the image
processing unit 14 under the control of the control unit 16.
[0090]
Next, an ultrasound probe according to a second embodiment will be described based on FIG.
The ultrasonic transmitting and receiving unit 205 in the ultrasonic probe according to the
second embodiment also has a plurality of membranes 206 (only one is shown in FIG. 6) as in the
first embodiment. A plurality of (two in this second embodiment) pairs of plus electrodes (first
electrodes) 263 and 265, a ground electrode (second electrode) 264, and a membrane 206
provided on the piezoelectric member 262 of each membrane 206 And a holding member 208
held.
[0091]
However, the through hole 281 of the holding member 208 in the second embodiment is formed
in a rectangular shape in a plan view.
[0092]
Further, the substrate 261 in the film member 260 consisting of the substrate 261 and the
piezoelectric member 262 is attached to the entire front surface including the periphery of the
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through hole 281 in the holding member 208, and extends over the entire periphery of the
membrane 206. The holding area 260a is disposed, and the membrane 206 is surrounded by the
holding area 260a in a rectangular shape, and is formed in a rectangular shape on the inner
peripheral side (inner area) of the holding area 260a.
Therefore, in this embodiment, the outer periphery 260 b of the membrane 206 divided and
formed in the held area 260 a is formed in a rectangular shape that matches the through hole
281.
[0093]
The piezoelectric member 262 is formed in a rectangular shape slightly larger than the through
hole 281, and is held so as to be stacked on the front surface of the substrate 261 on the front
side of the through hole 281.
[0094]
The first pair of positive electrodes 263 is disposed to form a square shape in plan view over
substantially the entire outer periphery of the front surface of the piezoelectric member 262.
On the other hand, the second pair of positive electrodes 265 is disposed at the center of the
front surface of the piezoelectric member 262 so as to form a square shape in plan view.
[0095]
In addition, the ground electrode 264 for the first and second sets is substantially rectangular in
plan view over substantially the entire periphery between the first electrode 263 for the first
electrode and the second electrode 250 for the second electrode in the piezoelectric member
262. It is arranged as it is.
[0096]
Also in the second embodiment, the ground electrode 264 for the first and second sets is
disposed in a region where the stress associated with the bending deformation of the membrane
206 in the piezoelectric member 262 does not occur.
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[0097]
Further, the first set of plus electrodes 263, the second set of plus electrodes 265, and the first
and second sets of ground electrodes 264 are disposed concentrically with the outer periphery
260b of the membrane 206 and have a similar shape. ing.
The other configuration is the same as that of the first embodiment.
[0098]
The first pair of positive electrodes 263 and the second pair of positive electrodes 265 are
connected in common via the positive electrode connection wiring 266, but also in this second
embodiment, they are formed on the positive electrode connection wiring 266. Voltage (prior to
common connection), a voltage is applied between the first pair of positive electrodes 263 and
the second pair of positive electrodes 265 so that an electric field of several V / um or more is
applied to the piezoelectric member 262 In the whole, the electric charge direction is polarized in
a single direction P radially outward from the center.
[0099]
Also in the second embodiment configured in this way, between the first pair of positive
electrodes 263 and the first and second pair of ground electrodes 264, and the second pair of
positive electrodes 265 and the first and second pairs of first electrodes. When a voltage is
applied between the pair of ground electrodes 264, an electric field is generated in the direction
perpendicular to the thickness direction of the piezoelectric member 262.
[0100]
Due to this electric field, a tensile stress is generated in the direction perpendicular to the
thickness direction in the first region 268 between the first pair of positive electrodes 263 and
the first and second pairs of ground electrodes 264 in each piezoelectric member 262. The
tensile stress distorts the piezoelectric member 262 in the first region 268 to stretch.
On the other hand, the second region 269 between the second pair of positive electrodes 265 of
the piezoelectric member 262 and the first and second pair of ground electrodes 264 has a
stress in the opposite direction to the above, that is, perpendicular to the thickness direction. A
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compressive stress is generated in the direction, and the compressive stress distorts the
piezoelectric member 262 in the second region 269 so as to contract.
[0101]
Due to the strain of each piezoelectric member 262, each membrane 206 is bent and deformed
to the front side in the front-rear direction which is the thickness direction.
Thereby, each membrane 206 can be efficiently and largely deformed.
[0102]
In addition, since the ground electrode 264 for the first and second sets is disposed in a region
where the stress due to the bending deformation of the membrane 206 in the piezoelectric
member 262 does not occur, an appropriate stress can be generated for each region. Each
membrane 206 can be deformed more efficiently and largely.
[0103]
When the membranes 206 are vibrated by the ultrasonic waves returned from the body, the
ground electrode 264 for the first and second sets is disposed in a region in the piezoelectric
member 262 where no stress is generated due to the bending deformation of the membrane 206,
Charges due to distortions of the first region 268 and the second region 269 can be efficiently
generated and extracted in the first and second set ground electrodes 264, and ultrasonic waves
can be measured efficiently and accurately.
[0104]
Next, an ultrasound probe according to a third embodiment will be described based on FIG.
The ultrasonic transmitting and receiving unit 305 in the ultrasonic probe according to the third
embodiment also has a plurality of membranes 306 (only one is shown in FIG. 7) as in the first
embodiment. A plurality of pairs (two pairs in the third embodiment) of pairs of plus electrodes
(first electrodes) 363 and 365, ground electrodes (second electrodes) 364a and 364b provided
on the piezoelectric member 362 of each membrane 306, and membranes And a holding
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member 308 which holds 306.
[0105]
The through hole 381 of the holding member 308 in the third embodiment is formed in a
rectangular shape in a plan view.
[0106]
Further, the substrate 361 in the film member 360 consisting of the substrate 361 and the
piezoelectric member 362 is bonded to the entire front surface including both end edges in the
lateral direction (one direction) which is the longitudinal direction of the through hole 381 in the
holding member 308 While being held, it is separated and opened by slit-like notches 361
provided along both end edges in the vertical direction (the other direction) which is the width
direction of the through hole 381.
[0107]
The piezoelectric member 362 is formed in a rectangular shape that is narrower than the
through hole 381 and whose left and right lengths are slightly longer than the through hole 381,
and is laminated and bonded to the front surface of the substrate 361 on the front side of the
through hole 381. It is held as it is.
[0108]
Therefore, in the third embodiment, the holding regions 360 are disposed on the left and right
ends of the membrane 306, respectively, and the left outer circumference 360c and the right
outer circumference 360d of the membrane 306 are linearly arranged. The membrane 306 is
formed in parallel, and the outer periphery of the membrane 306 is rectangular (rectangular) in a
plan view slightly narrower than the through hole 381.
[0109]
In the third embodiment, the electrodes are a first set of a pair of first plus electrodes 363 and a
first pair of ground electrodes 364a, and a second set of second pairs of plus electrodes 365 and
a second set. And a ground electrode 364b.
[0110]
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The first pair of positive electrodes 363 is linearly arranged in parallel with the left outer
circumference 360 c of the membrane 306 with a predetermined width over substantially the
entire width of the left end edge of the front surface of the piezoelectric member 362.
The first pair of ground electrodes 364a is parallel to the first pair of positive electrodes 363 (the
left end side outer periphery 360c of the membrane 306) with a predetermined width at a
position closer to the left than the center line in the left and right direction on the front surface
of the piezoelectric member 362 It is arranged in a straight line.
[0111]
The second pair of positive electrodes 365 is linearly disposed in parallel with the right end side
outer periphery 360 d of the membrane 306 at a position on the front side of the front surface of
the piezoelectric member 362 at a position closer to the right than the center line in the left and
right direction. .
The second set of ground electrodes 364b is substantially straight over the right end periphery
360d (second set of positive electrodes 365) of the membrane 306 with a predetermined width
over substantially the entire width of the right end of the front surface of the piezoelectric
member 362 Are located in
[0112]
Therefore, in the third embodiment, the piezoelectric member 362 in the membrane 306 is
provided with the first region 368a between the first pair of positive electrodes 363 and the first
pair of ground electrodes 364a, and the second pair of positive electrodes is formed. A third
region 368b is formed between the first set ground electrode 364b and the second set ground
electrode 364b, and the first region 368a and the second set positive electrode 365 are formed
between the first set ground electrode 364a and the second set plus electrode 365. A second
region 369 is formed adjacent to each of the three regions 368b.
[0113]
Also in the third embodiment, the first set ground electrode 364a and the second set plus
electrode 365 are disposed in the area 307 where no stress is generated in the piezoelectric
member 362 due to the bending deformation of the membrane 306. There is.
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[0114]
Then, the first pair of ground electrodes 364a and the second pair of ground electrodes 364b are
connected via the first pair of positive electrodes 363 and the second pair of positive electrodes
365 via the positive electrode connection wire 366. First pair plus electrodes 363 that are
commonly connected via 367 but prior to formation of their connection wires 366 and 367
(prior to common connection), the distance between the electrodes is maximum. A voltage is
applied between the second pair of ground electrodes 364b so that an electric field of several V /
um or more is applied, and the direction of the charge becomes a single direction P from right to
left in the entire piezoelectric member 362 Perform the polarization process.
The other configuration is the same as that of the first embodiment.
[0115]
In the third embodiment configured as described above, between the first pair of positive
electrodes 363 and the first pair of ground electrodes 364a, between the second pair of positive
electrodes 265 and the second pair of ground electrodes 264b. When a voltage is applied
between the second pair of positive electrodes 265 and the first pair of ground electrodes 364a,
an electric field is generated in the direction perpendicular to the thickness direction of the
piezoelectric member 362.
[0116]
The electric field causes tensile stress in the direction perpendicular to the thickness direction in
the first region 368a and the third region 368b of the piezoelectric member 362, and the tensile
stress extends the first region 368a and the third region 368b of the piezoelectric member 362
As distorted.
On the other hand, in the second region 369 of the piezoelectric member 362, a compressive
stress is generated in a direction opposite to the above, that is, in a direction perpendicular to the
thickness direction, and the piezoelectric member 362 in the second region 369 is contracted by
the compressive stress. Distort.
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[0117]
Due to the distortion of each piezoelectric member 362, each membrane 306 is bent and
deformed to the front side in the front-rear direction which is the thickness direction.
Then, more appropriate stress can be generated in each area, and thereby, each membrane 306
can be efficiently and largely deformed.
[0118]
In addition, since the first set ground electrode 364a and the second set positive electrode 365
are disposed in the area 307 where the stress caused by the bending deformation of the
membrane 306 in the piezoelectric member 362 does not occur, the optimum stress distribution
is obtained. As a result, each membrane 306 can be deformed more efficiently and greatly.
[0119]
Also, for example, when each membrane 306 is vibrated by ultrasonic waves returned from the
body, charges due to distortion of the first region 368a, the second region 369, and the third
region 368b can be used as the first pair of ground electrodes 364a and the second pair. It can
be efficiently generated and taken out with the positive electrode for positive electrode 365, and
ultrasonic waves can be measured efficiently and accurately.
[0120]
By arranging the electrodes at both ends in the left-right direction of the piezoelectric member
(membrane), as described above, the four membranes including the piezoelectric member
constitute one element (a portion surrounded by a two-dot chain line in FIG. 5) In the case of the
configuration, the arrangement efficiency of the membrane in one element can be increased, the
effective area of the membrane can be increased, and the characteristics of transmission and
reception of ultrasonic waves can be improved.
Also, the positive electrode and the ground electrode can be easily pulled out from both sides,
and a structure with less loss can be made.
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[0121]
In the above embodiment, two pairs of electrodes are disposed. However, the present invention is
not limited to this embodiment, and can be changed as appropriate.
For example, when the membrane is bent and deformed so that the bending curve in the crosssectional shape draws an n-order curve (n is 3 or more), three or more pairs of electrodes may be
provided in the piezoelectric member.
In that case, it is preferable to dispose the electrodes in each of the plurality of inflection
sections.
[0122]
Further, in the above embodiment, the piezoelectric device of the present invention is used as the
ultrasonic wave transmitting and receiving unit of the ultrasonic probe, but the piezoelectric
device is not limited to the form used for the ultrasonic probe. It can also be used as a sensor for
an ink discharge actuator of a discharge head, a microphone, etc., and can be appropriately
changed.
[0123]
DESCRIPTION OF SYMBOLS 1 ultrasound diagnostic apparatus main body 2 ultrasound probe 5,
205, 305 ultrasound transmission / reception part (piezoelectric device) 6, 206, 306 Membrane
61, 261, 361 board | substrate 62, 262, 362 Piezoelectric member 63, 65, 263, 265, 363, 365
plus electrodes (first electrode) 64, 264, 364a, 364b ground electrodes (second electrode) S
ultrasonic diagnostic apparatus
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