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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
appropriate acoustic wave probe suitable as a sensor portion of an ultrasonic imaging apparatus
such as an ultrasonic diagnostic apparatus or an ultrasonic flaw detector. BACKGROUND OF THE
INVENTION An acoustic matching layer is a layer provided between a medium and an electrical /
acoustic conversion material having acoustic impedance different from that of the medium in
order to improve the acoustic matching between the medium and the medium. In the
conventional probe for an ultrasonic diagnostic apparatus, as the material of the acoustic
matching layer, one mainly composed of an epoxy resin is widely used, but with the epoxy resin
alone, the acoustic impedance is small as a matching layer material. Since the specific gravity is
too high (~3 × 102 kg / M−3 ec), as shown in JP-A-58-94839, the specific gravity is increased
by mixing the metal powder or the metal oxide powder, etc. I was getting the impedance.
However, when the demand for high frequency in ultrasound probes increases and high
matching layer material is required, the conventional acoustic matching layer with an essentially
nonuniform structure is necessarily optimal. It will be gone. OBJECTS OF THE INVENTION The
object of the present invention is to solve the above-mentioned problems of the conventional
acoustic matching layer and to provide an acoustic matching layer material suitable for high
frequency. [Summary of the Invention] In order to realize such an object, in the present
invention, it is proposed to use a material having methylol-melamine resin as a main component
as an acoustic matching layer material. The methylol-melamine resin has the feature of good
molding processability of a polymeric material, and at the same time has a high speed of sound
as a polymeric material. (Longitudinal wave velocity of about 3300 m / sec) Since it has such
high longitudinal wave velocity, its acoustic impedance is as high as 5 × 10 'kglrd · sec As an
acoustic matching layer material between them, it can be used without mixture. The invention
will now be described in more detail with reference to the following examples. An example of the
present invention applied to an arrayed transducer type ultrasonic probe is shown in FIG. 1. An
ultrasonic wave emerging from the arrayed transducer 1 made of piezoelectric ceramics or the
like to the front surface is an acoustic wave made of methylol-melamine resin. The ultrasonic
waves that propagate through the matching layer 2 to a medium such as water or a human body
and come out to the back are braked by the back damping material 3. Unlike a conventional
acoustic matching layer, it is a matching layer formed without mixing materials with different
acoustic properties, so it has low scattering and attenuation for high-frequency ultrasonic waves,
and excellent acoustic characteristics. To be realized.
Another embodiment of the present invention is shown in FIG. Since the acoustic matching layer
of the present invention has a high sound velocity as compared with the conventional matching
layer, as shown in FIG. 1, when the integral matching layer is structured, the mechanical coupling
via the matching layer is adjacent. It may occur between transducer elements, which may impair
the characteristics of the array transducer as a whole. This problem can be solved by adopting a
structure in which the matching layer is divided in the same manner as the vibrator as shown in
FIG. An example of the structure when the present invention is applied to a monolithic array type
ultrasound probe is shown in FIG. In the case of monolithic arrays, the following advantages
occur in addition to the already mentioned advantages of the invention. The cross-sectional
structure of the monolithic type probe is shown in FIG. 4. As apparent from the figure, the
resonant frequency fr of the plate-like piezoelectric material is determined by the angle θ
between the propagation direction of the partial wave and the normal to the plate. Different,
where C is the speed of sound of longitudinal waves in the piezoelectric body, and T is the
thickness. Therefore, the acoustic matching condition is different depending on the angle θ, and
in general, the acoustic matching can be achieved only for a certain angle θ. However, according
to the present invention, the speed of sound of the matching layer is approximately equal to that
of the plate-like piezoelectric material. Can be acoustically matched simultaneously for all angles
.theta., Providing an acoustically matched layer that is ideal for monolithic arrays. As described
above, according to the present invention, an ultrasonic probe having excellent acoustic
characteristics even at high frequencies can be realized, and a monolithic array type having
excellent acoustic characteristics can be realized. An ultrasound probe can be realized, and the
effect is extremely large. Although the present invention has been described by taking the
arrayed transducer type ultrasonic probe as an example for one or more, the scope of the present
invention is not limited to this and extends to a single transducer type probe. Needless to say.
Brief description of the drawings
FIG. 1 is a view of an example of a probe embodying the present invention, FIG. 2 is a view of an
embodiment of the present invention having a split matching layer, and FIG. 3 is an example of
the present invention implemented in a monolithic array. FIG. 4 is an explanatory view of a
partial wave propagating from the probe of FIG. 3 into the medium.
Explanation of symbols 1 ... piezoelectric body 2 ... acoustic matching layer 3 ... back surface
damping material. Restraint Figure Figure 3 Figure 4
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description, jps61234199
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