JPS58156295

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DESCRIPTION JPS58156295
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
array transducer type piezoelectric transducer and a method of manufacturing the same, and
such a piezoelectric transducer is used, for example, as a transducer of an ultrasonic diagnostic
equipment case. . [Description of the Prior Art] Conventionally, a nine-array transducer type
piezoelectric transducer is known in which a large number of electroacoustic transducer
elements are arranged, but this one incorporates a large number of piezoelectric elements each
of which is an independent element. The production process is complicated and time-consuming.
In addition, since these piezoelectric elements have a structure in which uniform materials are
uniformly polarized, the frequency characteristics are band-limited as shown in FIG. 1 having
frequency portions where the sensitivity is zero. It is very inconvenient for practical use. As a
vibrator that solves this problem, there is known a van der pauw structure, that is, a vibrator
having a structure in which the strength of the polarization immediately below the stripe
electrode decreases and converges to zero as the depth goes back. However, this vibrator needs
to use a pair of stripe electrodes as its element unit, and each stripe electrode can not be used as
an independent element one by one, and furthermore, the width of the element is polarized. It is
inconvenient because the degree of freedom is limited with respect to the depth of distribution.
In addition, as a vibrator of the next structure, which is similar to the Van dsr paww structure,
there is a vibrator made of a multi-layer piezoelectric material, but this requires a dedicated
piezoelectric plate and can not use a general-purpose material. Is too complicated. OBJECTS OF
THE INVENTION The present invention has the structure of Van dar pauw whose impulse
response is a single pulse with a broad spectrum, and each of the stripe electrodes is one of each
of the sufficiently independent acoustical elements. An object of the present invention is to
provide a piezoelectric transducer of an array transducer shop having a fine pitch, and a
manufacturing method capable of easily manufacturing such a piezoelectric transducer.
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SUMMARY OF THE INVENTION The piezoelectric transducer of the present invention forms a
plurality of drive electrodes on one side of a plate-like piezoelectric material, forms a counter
electrode on the other side, and polarizes the piezoelectric material directly below this drive
electrode. Is characterized in that it gradually decreases in the direction of the shortest distance
from the drive electrode to the counter electrode. Further, in the manufacturing method of the
present invention, the first step of arranging a plurality of drive electrodes of one WJK of the
plate-like piezoelectric material and the voltages applied to the adjacent drive electrodes have
mutually opposite polarities. A second step of applying a polarization application voltage to the
drive electrode and a third step of providing a counter electrode on the other surface of the platelike piezoelectric material are characterized.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described
below based on the drawings. FIG. 2 is a side cross-sectional view of the first embodiment
piezoelectric transducer of the present invention manufactured using the manufacturing method
of the present invention. In the figure, reference numeral 1 denotes a piezoelectric plate, which is
made of a piezoelectric seranck material such as pzT (diA, core f fi 7 lead acid: Pb (Zr, Ti) 05),
PbNb 204 (lead meta niobate), or the like. On one surface of the piezoelectric plate 1, a plurality
of stripe electrodes 2. , 2bx 2 °... 2n are arranged at equal intervals of the pitch interval P. This
stripe electrode 2. . It is desirable that the width W of 2b,..., 2n be approximately 2 P. Lead wires
諷, 3b,..., 3n are connected to the respective stripe electrodes 2a, 2b,. Further, on the other
surface, the counter electrode 4 is attached to the entire surface, and the counter electrode 4t is
grounded. The strength of the polarization of the piezoelectric plate 10 immediately below each
stripe electrode 2IL% 2bs... 2n is, as shown by the self line 2 in FIG. . 2b... 2n, it gradually
decreases in the direction to reach the counter electrode 4 through the shortest distance, and
converges to almost zero in the vicinity of the counter electrode 4. Further, the polarity of the
polarization is in the vertical direction in FIG. 2 and is alternately reversed for every adjacent
stripe electrode. The ratio P / l of the pitch interval P between the stripe electrodes 2 &, 2b, ..., 2n
to the thickness t of the piezoelectric plate 1 is approximately one. When the piezoelectric
transducer is configured as described above, as shown in FIG. 4, the point of sensitivity zero is
absent in the frequency t & characteristic, and it is possible to obtain a vibrator having a wide
spectrum and a good impulse response. As a method of using this piezoelectric transducer, a case
where it is used for a transducer linear scan or a sector scan of an ultrasonic diagnostic
apparatus will be described. In this case, each stripe electrode 2a, 2b,..., 2n is treated as an
independent element with respect to the counter electrode 4, and the counter electrode 4 and
each stripe electrode 2aq 2b,. Send and receive signals with% 2n. The polarization polarity of
each element is alternately reversed, but the processing becomes complicated if transmission
pulses of both polarities are generated, so the stripe electrodes have an odd number of 2a12 °,
...--, 2n Only one of s or even-numbered 2 kl, 2 (L,..., 21 El is used.
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Since the polarization is alternately reversed in this manner, it is advantageous to cancel the
common mode noise of the circuit including the probe. In order to simplify the polarity inversion
of the received wave, all the stripe electrodes 2a and 2kls-12n are used. FIG. 5 is a side sectional
view of a second embodiment piezoelectric transducer of the present invention. In this converter,
grooves 111% lb... It has increased in sex. On the stripe electrodes 2 &, 2b%,..., 2n, a loadmatching layer consisting of a quartz glass layer 5 and a triacetylcellulose layer 6 is provided,
and a silicone rubber lens 7 is attached thereon. In addition, the backing material 8 is scattered
on the opposite electric charge 1ii 4011. With such a configuration, it is possible to improve the
matching with the sputum specimen as it can remove the unwanted vibration. Next, a method of
manufacturing the above-described piezoelectric transducer will be described. As shown in FIG.
6, first, stripe electrodes 2a, 2b,...% 2n are arranged at a pitch interval P on one surface of the
piezoelectric plate 1. As shown in FIG. Assuming that the thickness of the piezoelectric plate 1 is
t, the value of P / l is preferably α1 to 10 °, particularly I15 or 2 in this embodiment. lζ1.
Next, odd-numbered stripe electrodes 21.2 °,..., 2n are collectively used as a positive voltage
power source, and even-numbered stripe electrodes 2b, 2d,. Then, the polarization application
voltage is applied such that the voltage application to the adjacent stripe electrodes is opposite in
polarity to each other by being connected to the negative voltage power supply. Then, as shown
in FIG. 7, inside the piezoelectric plate 1, an electric field indicated by an arrow (A) is generated
from the positive voltage side stripe electrode to the negative voltage side stripe electrode. This
electric field is strongest immediately below the stripe electrodes 2 &, 2b, ..., 2n, and becomes
approximately zero in the vicinity of the counter electrode 4 by appropriately selecting the
polarization application voltage. The strength of the applied polarization gradually decreases in
the direction from the stripe electrodes 1j2a, 2b,... -12n to the counter electrode 4 as shown by
the line (a) in FIG. It converges to almost zero near the electrode 4. The polarity of the
polarization is the vertical direction in FIG. 6, and it becomes a book in which the adjacent stripe
electrodes 2a, 2b,... The dotted line (b) in FIG. 7 is an equipotential line.
After the application of the polarization to the piezoelectric plate 1 is completed, the counter
electrode 4 is deposited on the entire surface of the piezoelectric plate 1 to form a piezoelectric
transducer. As in the example shown in FIG. 5, in the case of forming a groove between the stripe
electrodes, piezoelectric [1 is polarized. If it is done before that, it will not be possible to obtain
the Van dlr pauW structure, since the key distribution is not obtained as described above. When
the application of the polarization voltage is performed in the relationship of P)) t, the electric
field has only a component that mostly points in the horizontal direction between the stripe
electrodes, and it is polarized in the horizontal direction where it is not useful. If this is done, a
satisfactory Van der pauw structure can not be obtained immediately below the stripe electrode,
which is undesirable. The dotted line 2 in FIG. 3 shows the polarization distribution in this case.
The polarization distribution is such that the strength of the polarization converges to zero inside
the piezoelectric plate l, as indicated by the dotted line 6 of the third WJ, when P ((t, (t). In this
case, it is possible to obtain a Van der pauw structure, but it is difficult to make each stripe
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electrode 21L, 2b,... The reason why it is desirable to deposit the counter electrode 4 after the
application of the polarization voltage is as follows. That is, if the counter electrode 4 is first
deposited, even if a polarization application voltage is applied, the electric field and electric lines
of force in the piezoelectric plate 1 are called to the side where the counter electrode 4 exists,
and the stripe electrode k , 2b, ..., 2n and the counter electrode 4 produce a uniform electric
field distribution, and the Van der pauw structure is such that the polarization strength gradually
converges toward zero near the counter electrode 4 I will not get it. Even if P << t, even if the
counter electrode 4 is deposited first, there is almost no effect, but in this case, as described
above, each stripe electrode is made an independent element. I'm getting ugly. Therefore,
whether or not the counter electrode 4 is to be deposited first needs to be reconsidered based on
the above-mentioned problems and the P / l ratio. [Description of application example] The
piezoelectric material used for the piezoelectric transducer of the present invention is not limited
to the one shown in the present embodiment, and any so-called high voltage voltage electric
material may be used. In addition, an embodiment for mounting the piezoelectric transducer of
the present invention on a probe or the like, that is, a matching structure of acoustic impedance,
a processing shape of a piezoelectric plate, a shape of driving and counter electrodes, and an
arrangement position thereof are described in this embodiment. Of course, it is not limited.
[Description of Effects] As described above, according to the present invention, the piezoelectric
element of the array transducer lid having the Vand @ r plLuW structure and in which the stripe
electrode cans are sufficiently Kfi erected is an acoustic element. A transducer can be obtained.
Such a piezoelectric transducer is excellent in the impulse response that can satisfactorily
generate a single pulse having a wide band 斌 spectrum, and its practical value is extremely
excellent. Further, according to the manufacturing method of the present invention, the
complicated process of incorporating a large number of piezoelectric elements as in the
conventional array transducer is not required, and the above-mentioned piezoelectric transducer
can be manufactured extremely easily. . Furthermore, since a general-purpose piezoelectric
material is sufficient, the manufacturing cost is low.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a peripheral liquid number characteristic of the conventional piezoelectric transducer.
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FIG. 2 is a top sectional view of the piezoelectric transducer according to the first embodiment of
the present invention. FIG. 3 is a distribution diagram of polarization strength in the piezoelectric
plate. FIG. 4 is a frequency characteristic diagram of the piezoelectric transducer of the present
invention. FIG. 5 is a cross-sectional view of a piezoelectric transducer according to a second
embodiment of the present invention. FIG. 6 is a view for explaining the manufacturing method
of the present invention. FIG. 7 is a view for explaining the electric field distribution in the
piezoelectric plate. 1--Piezoelectric plate, 2 ... stripe electrode, 4 ... counter electrode. Patent
Assignee Yokogawa Electric Mfg. Co., Ltd. Attorney Attorney Ide Tadashi Takashi 3 (21 40
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