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Description 1, title of the invention
Acoustic wave focusing transducer using polymer piezoelectric material
6. Detailed Description of the Invention The present invention relates to an improved acoustic
focusing transducer using a polymeric piezoelectric material. Ultrasonic transducers using
conventional inorganic piezoelectric materials, such as PZT (zirco / lead titanate), BaTiO 3, or
quartz, and recently put into practical use by taking advantage of their flexibility and ease of
processing. Polymer piezoelectrics, such as PVDF (polyvinylidene fluoride), PVF (polyvinyl
chloride LPVC (polyvinyl chloride) + PC (polycarbonate), or a polymer having a piezoelectric
polymer such as N-11. In the case of an electronic scan system which performs linear scan,
sector scan, etc. also in an acoustic wave transducer, for example, a predetermined portion of a
transducer formed mainly of a concentric ring or strip divided piezoelectric body and / or an
electrode is used. The electrodes were driven to scan by shifting the electrodes by a
predetermined phase. 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, in the
conventional method, it is shown in the longitudinal sectional view and FIG. 2 shown in FIG. As
seen from the view in the direction of arrows XX in FIG. 1, the electrode layers 2 and 4 are
provided on the back and surface of the concentric annularly divided piezoelectric material
crucible, and either one of the electrodes (the back electrode in the figure) 2) as well as the
piezoelectric body 3 EndPage: 1 λ, Pa j-principle and ideally, the town with the wavelength of
the ultrasonic wave at the used frequency as λ The ring A + of each piezoelectric body, which is
determined as a part encircled by a circle drawn on the transducer surface by two different
spheres, and thus divided into a predetermined relationship. A sound wave generated by
selecting the drive of A24BQ + BI + B2 in a predetermined relationship has been used in a state
of focusing on the focal point O. That is, when driving every other concentric ring shown in FIG.
1, for example, ring A1 and ring A2 simultaneously, since it is r2-rQ-λ, the sound wave from ring
At and the ring from ring A2 are In the case of simultaneously driving adjacent concentric rings,
for example, rings A1 and 3J] 3 + simultaneously with an adjacent concentric ring, as shown in
FIG. Is rl−−rQ−λ / 2, and each sound wave of 1.8 is destructive at the focal point 0. Further,
also in the drive of the adjacent concentric iAt and B +, when the drive voltages are driven so that
the phases of the drive voltages are opposite to each other, the phases of the sound waves
reaching the focal point O are in phase and are mutually reinforced.
Further, at this time, if strip-shaped piezoelectric members having widths such as AI + A2rBO + Bl
+ B2 in FIG. 1 are used instead of the concentric rings, the sound wave passes through O in the
figure instead of one point 0, It can be focused on a straight line parallel to the transducer
surface, ie, in FIG. 1, perpendicular to the plane of the drawing on which it is written. According
to the above configuration and principle, a conventional scanning transducer is formed by
selectively driving the piezoelectric body partitioned into predetermined relationships with the
electrodes subdivided into the same form as the piezoelectric body. That is, 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. Therefore, when an inorganic substance, such as PZT (/
lead lead titanate), is used as the piezoelectric substance, first, the PZT powder is sintered to a
desired shape, then provided with piezoelectricity by poling, and then polished and adhered to a
support Furthermore, it is necessary to have a means for dividing it into an annular shape, which
not only has the accuracy of machining and the difficulty of performing fine processing, but also
has a high possibility of causing defects, cracks, etc. It 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 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, at least the electrodes need to be divided in order to drive the divided polymer piezoelectric
material with a phase difference. In this case, there are large restrictions on wire connections
between many and fine electrodes, and lead removal, so the number of man-hours for that is
large, and it is difficult to process these electrodes (5). After all, the cost of producing a
transformer was expensive. An object of the present invention is to solve at once the abovementioned drawbacks of the electrode-splitting type in the above-mentioned conventional
scanning transducer, and for the purpose of the present invention, therefore, is a back electrode,
a polymeric piezoelectric material. In the transducer in which the surface electrode and the phase
plate are laminated, the phase plate has a concavo-convex shape, and the depth t of the concave
portion of the phase plate is the wavelength of the sound wave at the working frequency in the
phase plate. And the wavelength of the sound wave at the working frequency in the sound wave
medium is A0. A sound wave focusing transducer comprising a polymer piezoelectric material is
provided as an embodiment of the present invention. Each will be explained while referring to
the drawings.
FIG. 3 is a longitudinal sectional view of one embodiment of the transducer according to the
present invention, in which 1 is a support, which comprises PMMA (polymethyl meta (6)
EndPage: 2 clear), nylon, epoxy resin, etc. . 2 is a back electrode / back reflector, 5 is a polymeric
piezoelectric material, 4 is a surface electrode, and 5 is a surface phase plate. The surface
electrode 4 is formed on the polymeric piezoelectric material by a method such as vapor
deposition of Cu, AA or the like, Ag paste application or the like. The back electrode 2 may be
formed separately between the support 1 and the piezoelectric polymer or between the support
1 and the back reflection plate 20 without being used as the back reflection plate. With such a
configuration, the polymeric piezoelectric material is fixed to a flat surface, which makes it easy
to fix, and hence the fixing strength is also high. That is, according to the present invention, since
the focusing property of the sound wave is given by the specific shape of the surface phase plate,
the polymer piezoelectric material or the electrode is processed to be uneven or minutely divided
to change the phase. The operation such as driving is not required at all, and it is sufficient to
merely apply a driving voltage between the back electrode and the surface electrode. Such a
surface phase plate 5 constituting the feature of the present invention is obtained 5a, 5b in a
predetermined relationship in accordance with the same idea as in FIG. Concentric annular
portions of Japanese Patent Application Laid-Open No. 56-42493 <3 ′ ′ 15c, 5d,... Are
positioned on the surface electrode with a concavo-convex shape having a predetermined
relationship with each other. The depth t of the recess is formed to substantially correspond to
an acoustic wave difference of 1⁄2 of the wavelength λ of the ultrasonic wave at the use
frequency. With such a configuration, the sound wave can be focused on the focal point O in the
figure. Here, assuming that the depth of the concave portion is λ, the wavelength of the sound
wave at the working frequency of the t 2 phase plate is λ, and the wave 1 λ · λ 0 length of the
frequency in the sound wave medium is λ 0. By satisfying the relationship of + -2 ° 1, the path
difference of the sound waves on the adjacent uneven surfaces creates a phase difference
corresponding to λ / 2, that is, π. The asperities in the phase plate can be easily produced by a
conventional technique, such as molding plastic such as PMMA, nylon, epoxy resin or the like
with a mold or scraping it from these blocks. The polymeric piezoelectric body has an acoustic
impedance close to that of the phase plate made of the above-mentioned material, and the
reflection loss due to the addition of the phase plate is small, and the decrease in efficiency is
small. On the other hand, inorganic piezoelectrics, such as PZT, have high acoustic impedance
and generally have a large difference in acoustic impedance from water used as a sound wave
medium. Therefore, depending on the material of the phase plate used, the piezoelectric body
and the phase plate At the boundaries between the phase plate and the water, reflections become
dogs, causing a drop in efficiency.
Therefore, when the conventional inorganic piezoelectric material is used, the material of the
phase plate is limited. FIG. 4 is a longitudinal cross-sectional view of another embodiment of the
transducer according to the present invention, and the reference numerals in the drawing are the
same as the reference numerals in FIG. Here, the surface phase plate 5 is 5'a, 5'b, 5'c, 5'd in
accordance with the same idea as in FIG. Each ring 5'a, 5'b. 5'c, 5'd... Are not rectangular
asperities, but are arranged with curvatures designed so that the respective sound waves are
completely in phase at the focal point O in the figure. This curvature is set as follows. That is,
when the ultrasonic wavelength λ at the operating frequency in the phase plate and the
wavelength λo ′ ′ in the acoustic wave medium, the depth t is set by selecting the relationship
of t (9). At the boundary between the i-th ring 5'i and the i + 1'th ring 5'i + 1, the phase plate has
a recess depth t in the range of 5'i + 1, and the phase plate has a greater thickness, 5'i + 1. The
thickness at the boundary between the and 5'i + 2 is equal to the thickness at the boundary
between the 5 "i and the E'i + i and the thickness at the boundary between the 5'i and the 5'i + 1.
The phase plate surface of each ring is smooth if the thickness change of the phase plate within
the boundary of each ring is determined so that the paths to the focal point O of the sound wave
from each point in each ring are all equal. Although the curve should be drawn, even if it is
approximated by a straight line, the focusing of the sound wave is much improved as compared
with the case of providing the rectangular asperity. Next, the present invention will be described
in more specific (1D) EndPage: 3 by giving examples. Embodiment FIG. 5 is a longitudinal crosssectional view of still another embodiment of the transducer according to the present invention.
On a cylindrical support 1 made of PMMA with a diameter of 20 mm, a lead wire is attached in
advance to the center, and a 150 μm-thick Cu plate is taken from the small hole in the center of
the PMMA cylinder and taken to the back. It bonds as a back electrode and back reflection plate
2. On the Cu plate, a PVDF piezoelectric film 3 with a thickness of 9 D μm, which was subjected
to poling treatment at 120 ° C. and an electric field of 10 ′ V / crn for 1 hour, was adhered
with 7 annoacrylate. The surface electrode 4 used the AI vapor deposition electrode at the time
of poling as it was, and the lead 6 was taken through a 60 μm Cu foil from the surface end. On
the surface of this laminate, a retardation plate 5 made of PMMA with a thickness of 1.5 and M1
having a surface unevenness of 300 μm was adhered by cyanoacrylate by means of a ruling.
The radius of the circle (convex part 5a) at the center of the phase plate is 6.9 + II + 11 ° The
part that works as a phase plate including this consists of 5 concentric rings and its diameter is
between 17 In order to protect the phase plate is to have a diameter of 20 cabinets.
When the transducer produced in this manner was driven in water at 5 MHz on the entire
surface, it was confirmed that the sound wave was concentrated and emitted at the front surface
5α of the transducer. The transducer according to the present invention is easy to bond since
each layer is bonded in a plane, and therefore, a support, a back electrode / reflecting plate, a
polymeric piezoelectric material. A strong and homogeneous adhesive strength between the
surface electrode and the phase plate is obtained. Moreover, according to the present invention,
since the focusing property of the sound wave is due to the effect of the surface phase plate, it is
not necessary to perform operations such as driving the piezoelectric body or the electrode
unevenly, dividing it into small parts and changing the phase. The configuration is extremely
simple as compared with the conventional scanning transducer, such as merely applying a drive
voltage between the back electrode and the surface electrode. Therefore, it can be realized as an
acoustic focusing transducer whose production cost is low, easy to operate, easy to operate, and
uniform in quality.
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,
and FIGS. Fig. 2 shows a longitudinal section of a respectively different embodiment of an
acoustic wave focusing transducer according to the invention. Explanation of symbols in the
figure 1; support 2: back electrode 3; polymer piezoelectric ˜; surface surface electrode 5 (16)
EndPage: 4v 3 figure procedure 1 54, 12.19 Showa Date Secretary General殿 (investigator code
& code) 1 Display of the case 1959 patent application number 116655 2 name of the invention
2 name of the invention sound wave focusing type transducer using polymer piezoelectric body 6
person with correction case Related patent applicant
Acoustic wave focusing transducer using polymer piezoelectric material
Address Tokyo, Chuo-ku, Nihonbashi zJ 2-chome 2 Kaji name (Lo 15) East Japan 4 correction
instructions Date of voluntary 5 corrections Number of inventions to be increased by correction
6 detailed description of the invention as well as
As described in the attached sheet of each column 7 correction of "the brief description of the
drawings" EndPage: 5 in the specification (1) page 2 page 5. Line 6 to or correct N-11 J as or
nylon 11 . (2) On page 2, line 10, "Piezoelectric and / or" are corrected as "Piezoelectric and".
(5) page 2 line 12 (4) page 3 line 7 "correct the ultrasonic wave J at the operating frequency to"
the ultrasonic wave in the propagation medium at the operating frequency ". (5) Correct the page
3, line 14 focus on focus 0 on U focus 0 0 (6) Page 4 lines 16 to 17 conventional
scanning type F Correct 0 (7) page 4 line 18 Conventional scanning transducer to
conventional focusing or scanning transducer ((8) page 4 line 19 Correct the FIIE current
collector and / or spring as "piezoelectric and". (9) On page 5, line 5, "Furthermore, this is
annularly corrected" to "Further, this is annularly or strip-likely". (10) On page 6, line 4, "The
above-mentioned conventional scanning transformer" is corrected as "the above-mentioned
conventional focusing or scanning transformer". (11) On page 7, line 7, "Or, with the support 1"
is corrected as "or with the polymer pressure 'sulphate 6". (12) On page 10, line 8, "E'i + IJ is
corrected to 5'i + IJ." (16) Insert the following sentence between page 13, lines 1 and 2. F As
described in the present description, it goes without saying that the principle and structure of the
phase plate used in the acoustic focusing type according to the present invention can be easily
applied to a scanning transducer, and the function and effect by this are all different Needless to
say, there is no such thing. (14) On page 13, line 6, "Conventional scanning type" is corrected to
"conventional acoustic focusing type". 6−EndPage: 6
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