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JPS60247399

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DESCRIPTION JPS60247399
[0001]
TECHNICAL FIELD OF THE INVENTION The present invention relates to an ultrasonic acoustic
lens provided in an ultrasonic probe. Technical Background of the Invention and Problems
Thereof An ultrasonic probe is shown in FIG. 1 shows a piezoelectric actuator capable of
converting an electric signal into an ultrasonic wave or an ultrasonic wave into an electric signal,
2 is a sound absorbing material bonded to the rear surface of the piezoelectric vibrator 1, 3 is an
efficient transmitting / receiving of ultrasonic waves. And an ultrasonic acoustic lens 4 for
focusing the ultrasonic wave. By the way, in the ultrasonic acoustic lens 4, in order to prevent
multiple reflection in the ultrasonic acoustic lens 4, the acoustic impedance Z is matched to the
living body (Z = 1.5 to 1.6 × 1 ′ ′ 06 Kg / m 2 · S) In addition, it is desirable that the
attenuation factor of the ultrasonic waves be low in order to improve the S / N. However, a
conventional ultrasonic acoustic lens formed by vulcanizing and molding a silicone raw rubber
after filling it with silica powder of about 0.01 to 5 μm and silica powder of about 1 to 10 μm It
is difficult to obtain the desired S / N because the attenuation factor of ultrasonic waves is large
when the acoustic impedance is matched to the living body or water. Because the acoustic
impedance and the attenuation of the ultrasonic wave are approximately proportional to each
other, for example, between the fillers in the acoustic impedance matching range of FIG. 5-5 is in
the range of FIG. Is a large value as shown in FIG. 3-7. SUMMARY OF THE INVENTION The
present invention has been made in view of the above circumstances, and it is an object of the
present invention to provide a low attenuation ultrasonic sound pipe lens. [Summary of the
Invention] The summary of the present invention for achieving the above object is an ultrasonic
acoustic lens comprising a raw silicone rubber filled with one or more fillers, wherein at least one
of the fillers has an acoustic impedance of 12 × 106 Kg. / M 2 · S or less. [Embodiments of the
Invention] Hereinafter, embodiments of the present invention will be described. The acoustic
impedance of silicone rubber is usually 1, 0 x 106 Ky / m2-sr, cl: (7) silicone rubber filled with an
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acoustic impedance 7 filler of 12X106 to 9 / m2 · S or less The acoustic impedance Z of the
whole silicone rubber is adjusted to 1.25 × 10 6 to 1.5 × 10 6 / (y / m 2 −s). Here, as the filler
having the acoustic impedance Z of 12 × 10 6 Ky / m 2 · S or less, for example, carbon random
(silicon carbide brane, −3-3, 1 × 10 3 Ny / m 3. V = 3, 300 m / s).
Z = I Qxl 06 Kg / m2-s), carbon (ρ = 1.8 × 10 3 Kg / m 3, v = 4000 m / s). Z = 7 x 10 6 Ky / m
2-s, Tare 0 (lJ fluorinated ethylene, ρ-2, 3, x 10 3 Ky / m 3). V = 1400 m / S, Z = 3 × 106 K9 /
m2-8) and the like. For example, an ultrasonic sound tube lens (first example lens) formed by
filling 11% and 35% of carbon black having particle diameter of about 0.01 to 0.1 μm and
carbon random of about 1 μm on a weight ratio, respectively. According to the measurement of
the inventors of the present invention, the attenuation factor α of the ultrasonic wave (f = 5.0
MHz) is 2.8 dB / mm at the acoustic impedance Z = 1.35 × 10 6 Ky / m 2 -s. Also, in the case of
an ultrasonic acoustic lens (lens of the second embodiment) formed by filling approximately 12%
and 29% by weight of fumed silica having a particle size of 1 μm or less and carbon random
having a particle size of 1 μm or less, respectively. The attenuation factor α of the ultrasonic
wave (f = 5.0 MHz) was α−2,5 dB / mm at an impedance Z = 1.33 × 10 6 Kg / m 2 · s. On the
other hand, a conventional ultrasonic acoustic lens (first prior art lens) is prepared by filling
approximately 24% and 29% respectively by weight ratio of fumed silica having a particle size of
about 0.02μ and quartz powder having a particle size of about 2μ. In an acoustic impedance Z
= 1.40 × 1061c9 / m2-6, the attenuation factor α of ultrasonic waves (f = 5.0 MHz) was α−3,
7 dB / mm. In addition, the conventional ultrasonic acoustic lens (second prior art lens) is
prepared by filling approximately 24% and 18% by weight ratio of fumed silica having a particle
size of about 0.02μ and quartz powder having a particle size of about 2μ. In the acoustic
impedance 7-128 Ny / m 2 -s, the attenuation factor α of ultrasonic waves (f = 5.0 MH 2) was
α-2, 8 dB / mm. The above measurement results are shown in FIG. This figure shows the first
and second conventional lenses and the first. The actual measurement values of the second
conventional lens are plotted on the same characteristic diagram, and the mark .beta. Represents
the first example lens, the mark 8 'represents the second example lens, and the x mark 9
represents the first example. A conventional example lens, and an x mark 9- indicate the
measurement points of the second conventional example lens. As described above, as the
characteristics of the ultrasonic acoustic lens, the smaller the attenuation factor of the ultrasonic
wave with respect to the same acoustic impedance, the better. Therefore, in FIG. 4, it is better to
plot in the lower right, and the first and second example lenses are the same as the first and
second ones. It can be said that the attenuation factor of ultrasonic waves is smaller than that of
the i2 conventional lens.
The reason why the attenuation of ultrasonic waves can be reduced compared to the prior art by
filling a filler having an acoustic impedance of 12 × 10 'Kg / m 2 · S or less is as follows. That is,
although the silica-based material is conventionally used as the filler, the acoustic impedance of
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this silica-based material is 15 × 10 6 Kg / rn 2 · S, and the Sess filler is matched to the acoustic
impedance Z of silicon green rubber Z = 1.0 × 10 6 Ky / m 2 -s Scattering of sound waves by the
For this reason, even if the amount of filler is small, the attenuation factor of the ultrasonic wave
will be relatively large. Therefore, the inclusion of a filler having an acoustic impedance of 12 ×
10 6 Ng / ml · S or less improves the attenuation factor of ultrasonic waves. It is needless to say
that the present invention is not limited to the above embodiment, and modifications can be
made as appropriate within the scope of the present invention. [Effects of the Invention
According to the invention described above, according to the invention, by using a filler having
an acoustic impedance of 12 × 10 6 Kg / m 2 · S or less, the attenuation factor of ultrasonic
waves can be reduced, so that ultrasonic acoustic waves with low attenuation are obtained. A lens
can be provided.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is an explanatory view showing the structure of an ultrasonic probe having an ultrasonic
acoustic lens, FIGS. 2 and 3 are characteristic diagrams showing the characteristics of a
conventional ultrasonic lens, and FIG. It is a characteristic view for comparing the characteristic
of the ultrasonic acoustic lens which is an example of the present invention with a conventional
example.
4 ... acoustic lens. Agent Patent attorney Masayoshi Misawa Figure 1 Figure 1
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