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Description 1, title of the invention
Acoustic wave focusing transducer using polymer piezoelectric material
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved
acoustic focusing transducer using a polymeric piezoelectric material. For example, PVDF
(polyvinylidene fluoride) is a conventional inorganic piezoelectric material such as PZT (lead
zirconate titanate), BaTiOa + or polymer piezoelectric material whose practical use is in progress
under pressure. An electronic transducer that performs linear scan or sector scan even in an
ultrasonic transducer using a piezoelectric polymer such as PVF (polyvinyl fluoride), pvc
(polyvinyl chloride), pc (polycarbonate) or N-11 In the case of the scan method, for example, a
concentric annular or strip divided piezoelectric body and / or a drive that scans and drives
predetermined electrodes of a transducer formed by using the electrodes as main parts by a
predetermined phase. there were. Further, the principle of the above-mentioned conventional
method and the configuration thereof will be described with reference to FIGS. 1 and 2. That is,
according to the conventional method, as seen in the longitudinal sectional view shown in FIG. 1
and the XX view in FIG. 1 shown in FIG. An electrode layer 2.4 is provided on the surface, and
one of the electrodes (the back electrode 2 in the figure) and the piezoelectric body 6 are
partitioned by the insulator 5 and arranged in a predetermined relationship. Each portion of the
laminate partitioned by the insulator 5 is supported by the back support 1. A1. , A 2 ° BO + B 1
+ B 2 indicate the sections divided concentrically by the insulator 5. In this conventional example,
each concentric ring drawn by the divided piezoelectric member has its radius different from
each other by λ / 2 centering on the focal point 0 when the wavelength of the ultrasonic wave
at the used frequency is λ in principle and ideally 9AI + A2 + Bo, B1 of each piezoelectric body,
which is determined as a part encircled by a circle drawn on the transducer surface by a sphere,
and thus divided into a predetermined relationship. The sound wave generated by selecting the
drive of B2 in a predetermined relationship is used in a state of focusing on focal point 0. That is,
when every other concentric ring shown in the first order brother, for example, ring A and ring
A2 are simultaneously driven, the sound wave from ring A1 and the sound wave from PJA 2 are
at focal point 0 because they are r2rO-λ. Each wavelength is in focus by rl-rQ-λ / 2 when
simultaneously driving adjacent concentric rings, eg, qA1 and ring B1. At 0 you will be weak.
Even in the drive of the adjacent concentric rings A1 + Bl, the phases of the sound waves
reaching the focal point 0 are in phase when driven so that the phases of the respective drive
voltages are in antiphase so that they are mutually constructive. .
Furthermore, at this time, the width of each other is set to A1. A2. Bo、B1. If a stripshaped piezoelectric body having a ratio such as B2 is used, the sound wave is sharp at one point
O, passing through 0 in the figure, parallel to the transducer surface, that is, perpendicular to the
drawing paper in FIG. Can be focused on a straight line. The conventional scanning transducer is
formed by selectively driving the piezoelectric body divided into the predetermined relationship
based on the above configuration and principle with the electrodes subdivided in the same
manner as the piezoelectric body. In the conventional scanning transducer, it has been an
essential requirement to divide and arrange the piezoelectric body and / or the electrode to be
used. However, when an inorganic substance such as PZT (lead zirconate titanate) is used as the
piezoelectric substance, first, the PZT powder is sintered to a desired shape, then it is provided
with piezoelectricity by poling, and is then polished to obtain a support It is necessary to have a
means to divide it into an annular shape to bond it and further to eliminate the adverse effect due
to large size and loss talk between inorganic piezoelectric materials, but this brings about the
precision of machining and the difficulty of micromachining Not only that, there is a high
possibility of causing defects such as two cracks, and the yield is bad. Moreover, it was not easy
to make the thickness of each divided piezoelectric body uniform or to make the characteristics
uniform. As a solution to this point, the present inventors have already separately proposed a
split type transducer using a polymeric piezoelectric film. However, the following non-negligible
manufacturing improvements still remain in the transducer using the above-mentioned polymer
membrane. That is, in order to drive the polymer piezoelectric material with a phase difference, it
was necessary to divide at least the electrodes. In this case, there are large restrictions on wiring
between many and fine electrodes, and lead extraction, so that the number of man-hours is large,
and since these electrodes are difficult to process, the transducer is The production cost was
expensive. SUMMARY OF THE INVENTION The object of the present invention is to solve at once
the above-mentioned drawbacks of the electrode-splitting type in the above-mentioned
conventional scanning transducer, and for this reason the present invention relates to a back
electrode, a polymer piezoelectric material and In the transducer in which the surface electrodes
are laminated, the polymeric piezoelectric material has a concavo-convex shape, and the
difference between adjacent convex portions and concave portions is substantially 1 / 2λ
(where λ is a used frequency) The present invention provides an acoustic wave focusing
transducer made of a polymer piezoelectric material, characterized by satisfying the conditions
equal to the wavelength of the ultrasonic wave in
Embodiments of the present invention will now be described with reference to the drawings. FIG.
3 is a longitudinal sectional view of an embodiment of the acoustic focusing transducer
according to the present invention, in which the concentric annular portions 2a, 2b, 2c and 2d
are formed on the upper surface of the support 1 so as to be uneven. A back electrode / reflector
2 of a proper shape is laminated, and further, the polymer piezoelectric film 3 and the surface
electrode 4 are in close contact with the irregularities of the back electrode / reflector EndPage:
2 To make the difference between the convex and concave parts of the back electrode /
reflecting plate which forms the base of the above, that is, the difference between the symbols T
and 8 in the figure, substantially be half the acoustic wavelength λ at the operating frequency.
Set In this way, the difference in the distance to the focal point O of the adjacent rings is λ / 2 +
λ / 2 × 2λ, and as a result, the wavelength shifts. Therefore, in the present invention having
the above configuration, even if the electrodes are driven in phase, the focal point O strengthens
the sound wave, which is another configuration of the conventional scanning transducer, that is,
@ Finally, the same effect can be obtained as driving in the opposite phase through adjacent
electrodes which are separated from each other and have complicated connections, and in the
present invention, the electrodes are It has an extremely advantageous advantage in terms of
construction that it can be a series without dividing. In addition, as the support body 1, polymers
with small acoustic impedances, such as PMMA (polymethyl methacrylate), PUT (polyethylene te
f7) left-late, nylon, an epoxy resin, etc., are used. The back electrode / reflecting plate type may
use thin film metal such as Cu, A7 or the like, and the electrode and the reflecting plate may be
separately formed. The scooped surface electrode 4 is a polymeric piezoelectric body 6, for
example, the aforementioned PVDF or PVF. pvc and N-11, etc. (7) on H / l / A, A, e. It forms by
methods, such as vapor deposition, such as Cu and Ay-, application ¦ coating of Ay- paste
(conductive paste). FIG. 4 shows a longitudinal sectional view of another embodiment of the
present invention, and the reference numerals 1.2 and 3.4 in the drawing are the same as those
in FIG. Here, a support 1. Back electrode and reflector 2. It comprises a polymeric piezoelectric
body 6 ° and a surface electrode 4. Here, instead of providing the back reflector 2 with
rectangular asperities, the asperities of the back reflector are designed so that the phases of the
sound waves from the respective concentric rings at the focal point O are more completely
matched. The shape is determined, as shown in the figure, as a part of a concentric sphere whose
radius is different by half of the wavelength λ of the used frequency around the focal point O.
The range in which the same concentric sphere is used is separated in the same way as the
concentric ring in the case of FIG. For example, in the case of a sphere of radius ro, the sphere of
radius r,) is from the position at which the transducer surface S is cut to the position at which the
sphere of radius r6 + λ / 2 is to cut the transducer surface S. In an ultrasonic transducer having
such a configuration, the phase of the sound wave at the focal point is completely in phase, and
the focusing of the acoustic wave energy at the focal point is much improved as compared with
the case of the rectangular asperity. Ru. However, producing a perfect sphere on the back
electrode / reflector with sufficient accuracy involves processing difficulties, so in practice it may
be approximated by saw-toothed irregularities instead of spheres. Good. This shape can be
manufactured without difficulty by existing technology such as ruling. Even with such an
approximation, the focusability of the sound wave to the focal point 0 is much higher than when
the rectangular asperity is used, and the longitudinal cross-sectional view in FIG. As shown in the
figure, by giving a rounded shape and a rounded shape (cJ nori, the change of the surface
becomes gentler than in the case of the concave and convex portions of a rectangle, so adhesion
of the polymer piezoelectric film becomes easy and the adhesion strength becomes Benefits can
also be obtained. Next, the present invention will be further described with reference to a specific
example. EXAMPLE FIG. 6 is a longitudinal sectional view of an embodiment of the type shown in
FIG. 3 of an acoustic focusing transducer according to the present invention. After bonding a Cu
plate, which will be described in detail later, as a back electrode and reflector 2 to the PMMA
support 1 (acoustic impedance Z key, 2 × 10 6 My / ln 2 · S) in the figure, using an epoxy resin,
poling is performed thereon. The 90 [mu] m thick uniaxially stretched PVDF piezoelectric film
treated (120 [deg.] C., 1 hour in an electric field of ID 6 V / cm) was adhered with a
cyanoacrylate adhesive. The surface electrode 4 was taken. Furthermore, PET with a thickness of
15 μm was adhered to the entire surface of the AA vapor-deposited electrode, to form a surface
protection EndPage: 3 film 6. The Cu plate used for the back electrode / reflecting plate 2 of the
present embodiment is formed by etching a Cu plate having a diameter of 17 μm and a
thickness of 300 μm and having an unevenness of 150 μm. Central circle B. The radius of the
(convex part) is 3.9 vfL, and it is a Cu plate consisting of five concentric rings including this.
When the transducer having such a configuration was simultaneously driven on the entire
surface at a frequency of 5 MHz, it was confirmed that the sound wave was emitted in a state of
being focused on one point on the front face of the transducer (the sound medium was a stroke).
Moreover, according to the present embodiment, since the back electrode 2 is not a divided type
as in the prior art but an integral electrode, the driving method of the conventional transducer,
that is, the divided and arranged annular electrodes is electrically When driving, every other
concentric ring is driven simultaneously at one time, or different from the case where adjacent
concentric rings are driven in reverse phase with each other, the electrodes are divided as
described above, and There is no need to connect the rings, and there is no need to arrange
adjacent rings in reverse phase.
According to the present invention, it is only necessary to apply a four-axis ginseng voltage
between the front and back electrodes. For this reason, compared with the conventional scanning
transducer, its production is easier, and the variation of the performance characteristics of each
item is less, so it goes without saying that the transducer of uniform quality can be made
inexpensive. It became possible to offer. Supplementally, providing such a concavoconvex on the
reflector is easily realized using conventional techniques such as etching and ruling, and when
bonding a piezoelectric body on an electrode having such a concavo-convex structure, polymer
piezoelectric Since the body is rich in flexibility and flexibility with conventional inorganic
piezoelectric bodies such as PZT, it is easy to bond along the irregularities of the electrode, and a
film with uniform thickness and piezoelectricity It is also easy to do.
4. Brief description of the drawings. FIG. 1 is a longitudinal sectional view of a conventional
scanning ultrasonic transducer, FIG. 2 is a view as seen in the direction of arrows XX in FIG. 1,
FIG. Explanatory drawing of the code ¦ symbol in 0 which shows the longitudinal cross-sectional
view of each another embodiment of the sound wave focusing type ¦ mold transducer using the
polymeric piezoelectric film by this invention 1: Support body 2: Back electrode 6: Surface
protection film patent application Person East Ltd. EndPage: 4 Procedure Amendment 54.12.14
° Showa Date Secretary General of Patent Office (Investigator's Office Code A) 1, Display of Case
Showa Patent Application No. 116654 No. 2, Invention Name 2, Name of invention Sound wave
focusing type transducer 6 using polymer piezoelectric material, Related patent applicant for
correction case
2, the title of the invention