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DESCRIPTION JPS61184100

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DESCRIPTION JPS61184100
[0001]
FIELD OF THE INVENTION The present invention relates to an ultrasonic probe used in a medical
ultrasonic diagnostic apparatus. 2. Related Art In recent years, ultrasound probes have been
actively used in the field of ultrasound diagnostic apparatuses and the like. As a conventional
ultrasonic probe, for example, a configuration described in Japanese Patent Application LaidOpen No. 55-35654 is known. Hereinafter, a conventional ultrasonic probe will be described with
reference to FIG. A plurality of piezoelectric vibrators 1o1 divided into elongated rectangular
shapes are arranged on the surface of the backing material 102, and the piezoelectric vibrator
101 is provided with an electrode (not shown), and this electrode is an electric terminal (shown
in FIG. Is connected to the drive circuit via An acoustic matching layer 1o3 made of a glass
material having a thickness of 1?4 wavelength is adhered to the surface of the plurality of divided
piezoelectric vibrators 101 by an epoxy adhesive. During this bonding, the epoxy-based adhesive
104 flows sufficiently into the gap formed by the side surfaces of the individual piezoelectric
vibrators 101 and the surface of the backing material 102, and the acoustic matching layer is
formed on the adhesive 104. Glue 103. Thus, the gap between each piezoelectric vibrator 101 is
filled with an epoxy resin adhesive 104 smaller than the value of the acoustic impedance of the
acoustic matching layer 103, and the piezoelectric vibrators 1o1 are acoustically discontinuously
coupled. This is intended to prevent the leakage of acoustic waves (acoustic crosstalk) and to
improve the azimuth resolution of ultrasonic images. The ideal for almost completely preventing
acoustic crosstalk is that the acoustic impedances of the respective piezoelectric vibrators 101
have extremely large differences in the acoustic impedance of the gap. That is, the configuration
in which air with extremely small acoustic impedance intervenes in the gap of the piezoelectric
vibrator 101 is ideal. Some material is filled because it is difficult. For this reason, it is difficult to
almost completely prevent acoustic crosstalk. Therefore, in order to increase the difference in
acoustic impedance of the material filled in the gaps of each piezoelectric vibrator 101 with
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respect to the acoustic impedance of each piezoelectric vibrator 101, the acoustic impedance is
reduced to about 3 X 10 y / d-S to some extent. Under the present circumstances, an epoxy
adhesive is used to reduce acoustic cross). As another method for reducing the acoustic crosstalk,
the gap between each piezoelectric transducer 1 o 1 is filled with a material having a very large
sound attenuation coefficient, and the acoustic crosstalk to the adjacent piezoelectric transducer
101 is made by this filler. It is considered that K is attenuated so as to prevent leakage to the
adjacent piezoelectric vibrator 101.
As described above, in order to prevent acoustic crosstalk, desirable characteristics of the
material filling the gap of the piezoelectric vibrator 1 o 1 are: 0) a large difference from the
acoustic impedance of the piezoelectric vibrator, that is, a small acoustic impedance value (2) The
sound wave attenuation coefficient is large. However, when an epoxy-based adhesive is used as a
material for filling the gaps of the piezoelectric vibrator 101, it is possible to use a piezoelectric
vibrator 101 in which a plurality of acoustic matching layers 103 made of glass material are
arranged. Although there is an advantage in the manufacturing process that the epoxy adhesive
can be filled in the gap of the piezoelectric vibrator 1 o 1 at the same time as bonding, it is
insufficient to prevent acoustic crosstalk between the piezoelectric vibrators 101. That is, the
acoustic impedance of the piezoelectric vibrator 101 (generally, 20 О 10 5 to 36 О 10 5 / ad
?S in the case of a piezoelectric ceramic vibrator such as PZT). However, the transmission
coefficient relating to the acoustic and loss-talk of the epoxy adhesive from the piezoelectric
vibrator 101 is approximately 15 to 26%. In addition, since the sound attenuation coefficient of
the epoxy adhesive is as small as about 1 dB / m at 3.0 M lz, the transmitted sound (cross talk)
can hardly be attenuated, and the adjacent piezoelectric vibrator 101 is obtained. It will
propagate. Therefore, there is a problem that it is impossible to form a predetermined ultrasonic
beam batan, and the characteristics such as the azimuth resolution required for the image quality
of the ultrasonic image deteriorate. Therefore, in order to solve the above-mentioned problems,
the present invention intends to provide an ultrasonic probe which can eliminate acoustic
crosstalk and prevent characteristic deterioration such as azimuth resolution of an ultrasonic
image. It is a thing. Means for solving the problems and technical means of the present invention
for solving the above problems comprise a piezoelectric vibrator, a back load material provided
on one side of the piezoelectric vibrator, and the piezoelectric vibration. And one or more
acoustic matching layers provided on the other surface side of the element, and at least the
piezoelectric vibrator is divided into a plurality of parts, and metal powder or metal powder or a
base material such as a rubber material or synthetic resin in the gap thereof. It is filled with filler
such as powder of insulating powder or the like and micro balloon mixed. Operation With the
above construction, according to the present invention, the material for filling the gap between
the piezoelectric vibrators can be arbitrarily selected in the range of smaller acoustic impedance
compared with the conventional epoxy adhesive, and the sound attenuation The coefficient is
also as large as 35 times or more. Therefore, the difference between the acoustic impedances of
the piezoelectric vibrator and the filling material can be increased, and the acoustic crosstalk to
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the adjacent piezoelectric vibrator can be reduced.
In addition, even if there is a slight amount of acoustic crosstalk, the sound attenuation
coefficient of the filling material is large and can be attenuated by this filling material.
Embodiments Hereinafter, one embodiment of the present invention will be described in detail
with reference to the drawings. FIG. 1 is a cross-sectional view of the ultrasonic probe of the
present invention. The piezoelectric vibrator 1 has electrodes (not shown) on both sides, and an
electrical terminal is taken out from one of the electrodes. The back load material 2 is poured
into one surface of the piezoelectric vibrator 1 or is provided by means such as adhesion. The
piezoelectric vibrator 1 is divided into a plurality of parts by machining or the like. Fillers 3 are
filled in the gaps between the piezoelectric vibrators 1 and two acoustic matching layers 4 and 6
are provided on the other surface of the piezoelectric vibrator 1 by means such as pouring or
bonding. In addition, the acoustic lens 6 is provided on the acoustic matching layer 5 as needed.
The filler 3 filled in the gap of the piezoelectric vibrator 10 is a rubber material mixed with two
types of powder such as metal powder or insulating powder and micro balloon. For example,
when silicone rubber is used as a rubber material, and tungsten powder and plastic
microballoons are mixed by 200% and 1.5% respectively by weight ratio to silicon rubber of a
base material to produce filler 3, acoustical material is produced. The impedance is 1606 О
10551 / dS, and the sound attenuation coefficient is about 40 dB / m at 3 MHz. As described
above, due to the difference in acoustic impedance between the adjacent piezoelectric vibrator 1
and the acoustic impedance therebetween, the propagation of the sound wave to the adjacent
piezoelectric vibrator 1 can be prevented, and the crossover can be reduced. As in the case of
using the filler 3 with an acoustic impedance of 1.06 О 1 d and an ff 1-8, while using a ceramic
material of PZT having an acoustic impedance of 20 О 10 to 35 О 10 и A и S as the piezoelectric
vibrator 1 The acoustic transmission coefficient of the piezoelectric vibrator 1 and the filler 3 is
approximately 6 to 10%, and is 15 to 26% when the conventional epoxy adhesive is used as the
filler. It is clear that the acoustic crosstalk can be reduced significantly according to the example.
Furthermore, the sound attenuation coefficient of the filler 3 of the above embodiment is 40 dB /
w at 3 MHz, which is about 40 times larger than the sound attenuation coefficient 1 dB / a of the
filler using the conventional epoxy adhesive. The transmission coefficient of 6 to 10%, which
causes acoustic crosstalk, can be almost completely attenuated by the filler 3. Therefore, it is
possible to substantially eliminate acoustic crosstalk between the adjacent piezoelectric
transducers 1 by using the filler 3 of the embodiment, and an ultrasonic image with high azimuth
resolution can be obtained.
The acoustic impedance and the sound attenuation coefficient are 0.7 X 10 L 4 when mixing
tungsten powder with silicon rubber as the base material and mixing tungsten powder with
silicon rubber at 100% and plastic microballoon at 2%. The acoustic impedance and the sound
attenuation coefficient are 2 О 1 o 5 P / in the case where S and 50 dB / wm (3 MHz), tungsten
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powder and plastic microballoon are mixed at 400 wt% and 0.8 wt% respectively with respect to
silicon rubber. The value is d?E3, 35 dB / a. As described above, the sound attenuation
coefficient is 35 to 5 odB / + w, and the acoustic impedance is 0.7 О 10 5 to 2 О 10 5 g / d ?
by changing the mixing amount of the tungsten powder and the plastic micro balloon
respectively to silicon rubber. The filler 3 in the range of 3 can be obtained, and in the present
invention, it may be appropriately selected within this range. In the above embodiment, although
the case of using silicone rubber as the base material of the filler 3 has been described, it is also
possible to use urethane rubber, butyl rubber, neoprene rubber, epoxy resin of synthetic resin,
urethane resin, etc. What can be done is clear from their properties. In the above embodiment,
the case of using tungsten powder as powder such as metal powder or insulating powder has
been described, but in addition to this, tantalum powder, ferrite powder, zinc powder, silicon
carbide powder, tungsten carbide powder It is apparent from their properties that iron powder,
etc. can be used. Of course, it is also clear that two or more of these metal powders or insulating
powders can be used. It is also possible to divide the acoustic matching layer 4 on the side of the
piezoelectric vibrator 1 in the above embodiment into a plurality of pieces together with the
piezoelectric vibrator, and to fill the gap with the filler 3 similarly to the piezoelectric vibrator 1.
Furthermore, in the above embodiment, the so-called array type ultrasonic probe in which the
piezoelectric vibrators 1 are linearly arranged is described, but in the present invention, in
addition to this, the piezoelectric vibrators are arranged in an arc. Alternatively, it can be applied
to various types such as arranging in two dimensions or arranging in a ring. Effects of the
Invention As is apparent from the above description, according to the present invention, a
piezoelectric vibrator, a back load material provided on one side of the piezoelectric vibrator, and
the other side of the piezoelectric vibrator are provided. And one or more acoustic matching
layers, wherein at least the piezoelectric vibrator is divided into a plurality of parts, and a matrix
material such as a rubber material or a synthetic resin or the like in the gaps thereof and a
powder such as metal powder or insulating powder The micro balloon is filled with the mixed
filler.
As described above, since the acoustic impedance of the filler is small, the difference from the
acoustic impedance of the piezoelectric vibrator is large, and the acoustic wave attenuation
coefficient is also large. It can be made extremely small. Therefore, it becomes possible to form a
predetermined ultrasonic beam pattern, to improve the characteristic of the azimuth resolution
required for ultrasonic image quality, and to obtain an ultrasonic probe having high-resolution
characteristics. it can.
[0002]
Brief description of the drawings
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[0003]
FIG. 1 is a cross-sectional view showing one embodiment of the ultrasonic probe of the present
invention, and FIG. 2 is a cross-sectional view of a conventional ultrasonic probe.
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agent Attorney Nakao Toshio Other 1 person Figure 1
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