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JPS55151894

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DESCRIPTION JPS55151894
Description 1, title of the invention
Scanning ultrasonic transducer using polymer piezoelectric film
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic scan
(scan) ultrasonic transducer such as linear scan and sector scan using a polymeric piezoelectric
film. A conventional ultrasonic transducer of the electronic scan type that performs linear scan or
sector scan using an inorganic piezoelectric material such as PZT (lead zirconate titanate), BaTiOs
or quartz as the piezoelectric material, and explains the process while looking at the
manufacturing process Then, as shown in FIG. 1, the back electrode 2 is formed on the flat
surface of the back sound absorber 1, for example, a PZT powder is formed into a desired shape,
is sintered, and then is subjected to poling treatment to obtain piezoelectricity. After that, the
piezoelectric body 6 is cut and separated by putting kerfs in a strip shape or the like, and then
the divided surface electrodes 4 are formed, and in the grooves between the respective strips,
electrical insulation and acoustic Is filled with an insulator 5 having a dump (sound absorption)
effect as a spacer to form a scanning ultrasonic transducer. In the transducer obtained by such a
process, the piezoelectric body 3 is cracked in the process of baking, or a crack or a defect easily
enters in the process of separating into strips, and it is difficult to improve the yield rate. there
were. Furthermore, it is also difficult to obtain uniformity in the thickness of the piezoelectric
body and uniformity of the poling treatment conditions to make the frequency characteristics
and efficiency etc. of each strip uniform, making the characteristics of each array uniform and It
is not easy to make a large number of aligned arrays, and EndPage: 1. In addition, since each
strip is divided by mechanical processing, there are mechanical restrictions in order to finely
process a uniform strip with a width that is free of defects, and it is expensive to produce a fine
array transducer. And it was difficult. Furthermore, the piezoelectric front electrode has to be
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manufactured integrally, and taking out the lead from such a large number of fine electrodes also
has a great limitation. Furthermore, since PzT and other piezoelectrics have high sound velocity,
the ratio of depth to width of the divided vibration elements is large, crosstalk between elements
is large, and vibration modes other than those required are required. The mode is excited, which
causes the side lobe intensity to increase, resulting in a decrease in resolution and Sha.
Furthermore, ultrasonic transducers using an inorganic piezoelectric material such as PzT,
particularly for ultrasonic diagnosis (for biological use), are based on a mismatch between the
piezoelectric material and water or biological material and 6 acoustic impedances / King
phenomenon or bandwidth Narrowing of the bandwidth caused the degradation of depth
resolution. SUMMARY OF THE INVENTION The object of the present invention is to solve the
problems of such a scanning ultrasonic transducer using a conventional inorganic piezoelectric
material, and for this reason, in the present invention, it is preferable to use In an element having
electrodes which are made of piezoelectric material or polymer piezoelectric film, at least one
side electrode is divided individually with a minute gap in an element having electrodes disposed
opposite to each other through a polymer piezoelectric film, and each electrode is used for
output Alternatively, there is provided a scanning ultrasonic transducer using a polymeric
piezoelectric film in which a lead wire for input is engaged, whereby the manufacturing process
is greatly simplified and the manufacturing cost is low, and the characteristic is easy. An excellent
and homogeneous scanning ultrasonic transducer is obtained.
Embodiments of the present invention will be described below with reference to the drawings. In
FIG. 2 and FIG. 8, the lower surface of the support 7 is formed in a planar shape, and on this
plane, the back surface of many strips AI + A2 + A3r... Which are long in the width direction and
divided in the length direction. Electrode and back reflection plate 8 (in this example, the back
electrode and back reflection plate are combined types, but they may be formed separately) and
insulator B filled in between the strips. ?????? The piezoelectric polymer film 9, the
surface electrode 10, and the surface protective film 11 are similarly laminated in a planar
manner to constitute a scanning-type and planar-type ultrasonic transducer. That is, as the
support 7, for example, Bakelite, PMMA (polymethyl methacrylate), PS (, j- "!! J Styrene), PE
(polyethylene), PET (polyethylene terephthalate), glass epoxy, nylon or other polymers with small
acoustic impedance or inorganic substances are used. The back electrode and back reflection
plate 8 has a lower surface of the support 7 attached with a thin plate made of a conductive
material having a large acoustic impedance, such as Ag + Au + Cu + Fe + Ni, etc., which is used to
process the wiring pattern of the ordinary printed circuit board Using a technology or another
processing technology, and dividing into strips, each divided electrode A1. ?????? ...
between electrical insulators B1 ░ (5) B2. ??? , To flatten the back electrode and back
reflection plate 8. On top of this, for example, PVDF (polyvinylidene fluoride), a blend of PVDF
and PZT, polyvinyl fluoride, polyacrylonitrile, a copolymer mainly composed of vinylidene
fluoride such as VDF and TFE, VDF and TrFE, etc. A high voltage is applied to the polymer film at
a predetermined temperature (referred to as poling treatment). Polymer piezoelectric film 9 to
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which piezoelectricity has been imparted by an adhesive agent, and then, on this polymer
piezoelectric film 9 by a method such as vapor deposition, plating or a method such as adhesion
of a thin film. , Form a common and uniform surface electrode 10. The surface protective film 11
is formed by applying PET, enamel, epoxy, polyester, nylon or the like, or adhering a polymer
film of these, and the function and effect of the protection of the surface electrode 10 and the
adjustment of the resonance frequency are necessary. Although it adds, it does not necessarily
have to be provided. In addition, the support 7 may be omitted if the back electrode / back
reflector 8 has sufficient strength and rigidity and only the function as a support is (6) EndPage:
2 it can.
Also, the back electrode and the reflector do not necessarily have to be the same, and in some
cases the back reflector can be eliminated. A lead extraction portion is provided at the end of
each strip A1rA2 + A3,... Of the back electrode 8, and a voltage is independently applied to each
strip to enable driving. The back electrode 8 doubles as a back reflection plate, but of course the
electrode may be formed as an electrode, and the reflection plate may be formed as a reflection
plate. For example, the back reflection plate is an insulating material having a large acoustic
impedance, such as a ceramic plate In this case, the divided electrodes can be easily formed on
the reflection plate by a method such as etching. The thickness of the back reflector may be set
to a quarter wavelength of the operating frequency or may be less than that, and may be set to a
desired thickness according to the design purpose or the purpose of use. In the above
embodiment, Although the case where the 'back electrode 8 side is divided and the front
electrode 10 side is a common electrode has been described, the front electrode side may be
divided and the back electrode side may be a common electrode. According to the abovedescribed structure, in this embodiment, a large number of strip-shaped vibrators T1rT2 + T3r...
Are formed by the split strip of one electrode, the other common electrode and the polymer
piezoelectric film therebetween. Be done. Now, as shown in FIG. 4, each of n transducers T1 + T2
+ T5 + ". Multidot.rTml". + Tn (where m (n) are linearly arranged), switch and / or phase control
(delay) element S1. ??? ??? ???? , Sn are connected, and m oscillators (T1 ░ T2, T3,-,
Tm) + (T2 + T3 rT4 r-) are connected. When Tm + 1), = иии ? (Tn?m + 1, Tn?m + 2, Tn = m + 3
?,..., Tn) are sequentially driven, the ultrasonic waves generated from the transducer are
spatially distributed in the transducer array direction The direction of travel of the electron linear
wave scanned (scanned) is the alignment direction of the transducers T1 to Tn or the normal
direction perpendicular to the alignment surface, but the phase of the drive of the phase control
elements S,. By sequentially delaying, the traveling direction of the composite wave can be a
direction having a desired angle with respect to the normal, that is, an electronic sector (sector)
scan. Next, a specific embodiment will be described. In FIGS. 5 and 6, the support 7 made of glass
epoxy (50 О 10 ? Ky / rr in acoustic impedance Z? A copper foil (50 ?m thick) as a back
electrode and back reflector 8 is bonded to the minimum thickness of 2 m) and etched using a
photopolymer (photoresist) to a thickness of 10111111 (thickness) A strip of .times..alpha.4wn
(width) is arranged with a gap of .alpha.l + mn (thus pitch .alpha.5 mm) for 82 electrodes A4.
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??? ... ?52? was made, and the end of each electrode was plated with C4 to C5 ░ through
holes and connected to the same <82 wiring parts formed by etching on the back of the support
7 . A PVDF ? piezoelectric film 9 (about 12 mm in width, about 20+ m in length and about 20
mm in length), which has been poled to a 70 ?m thick uniaxially stretched PVDF film, is
adhesively bonded with an epoxy resin. Many were formed by vapor deposition, and this was also
processed through-hole G. A 100 ?m-thick PET film is further adhered to the entire surface as a
surface (9) protective film 11 with cyanoacrylate, and the wiring portion on the back surface side
of the support 7 is covered and reinforced with a glass epoxy resin. The side portions of the film
11 and the support 7 were also coated with an epoxy resin and made water resistant to prepare a
transducer. The transducer is housed in a watertight metal casing, and the terminal portions C4,
C2 ░,..., C32 of the electrodes of the respective transducers are connected in parallel, and
ultrasonic waves are radiated from the surface of the surface protective film 11 into water. FIG. 7
shows a graph comparing the calculation result of the frequency characteristic of the conversion
loss TLf and the measurement result when the conversion loss TLf is obtained. Here, assuming
that the electrical energy input to the transducer is the output energy of the ultrasonic wave
forward of PT1 as PAi, the loss TLf is defined as TLf = ?10 # g (PAf / PT). As apparent from the
figure, the calculation result (X) and the actual measurement result (Y) coincide with each other
at 05 MHz or less, about 45 MHz and 10 MHz at the resonance frequency f, and the conversion
loss TLf also agrees within 4 dB. / Ln) EndPage: 3 Furthermore, cut off the lead wires of each
electrode, insert a delay circuit consisting of a high frequency coil and a capacitor between the
power source and each electrode lead for the purpose of electrical impedance matching and
delay, When the phase applied to the electrodes was sequentially delayed and all excitation was
performed with a high frequency pulse of 5 MHz and 1.5 ?S, it was confirmed that ultrasonic
waves were emitted in the deflected direction. Sector scan was possible by varying and
controlling the delay time of the voltage applied to each vibrator. According to the abovedescribed scanning ultrasonic transducer using the polymeric piezoelectric film of the present
invention described above, when arranging a large number of transducers in the scanning
direction and connecting each transducer, either of the surface electrode or the back electrode is
used. Alternatively, the back electrode is preferably divided into a plurality of desired shapes and
fine shapes easily using etching or ruling, which is a processing technology of a wiring pattern of
a normal printed circuit board, Since the polymer piezoelectric film provided with the above may
be simply adhered using an adhesive, the number of manufacturing steps of the scanning
ultrasonic transducer is small, so that the manufacture is easy and the cost is low.
Moreover, since the thickness of the polymer piezoelectric film can be made uniform and the
poling conditions can be made uniform, the characteristics of each transducer of the transducer
can be made uniform, and a large number of fine and large number of transducers with uniform
characteristics can be obtained. It can be formed into an array, and the piezoelectric film itself
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does not require any cutting or other mechanical processing, a large area single film can be used
as it is, so a large area transducer can be fabricated and continuous Even with the use of the
above-mentioned film, crosstalk between the respective transducers hardly occurs. Furthermore,
lead removal from each split electrode is easy, and wire connection is easy, which also makes it
possible to simplify the fabrication and reduce the cost.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an essential part of a
conventional scanning type ultrasonic transducer using an inorganic piezoelectric material, and
FIGS. 2 to 7 use a polymer piezoelectric film according to the present invention. 2 shows an
embodiment and an example of the scanning type ultrasonic transducer which was used, FIG. 2 is
a longitudinal sectional front view of the embodiment, FIG. 8 is a sectional side view along the
line OLm in FIG. 2, and FIG. Fig. 5 is a longitudinal sectional front view showing an example
embodying the above embodiment, Fig. 6 is a plan view of the main part of Fig. 5, and Fig. 7 is a
conversion loss according to the above example Is a graph comparing the calculation result of
the frequency characteristic of and the measurement result. DESCRIPTION OF SYMBOLS 7 ...
Support body, 8 ... back surface electrode back reflection plate, 9 ... Polymer piezoelectric film, 10
... Surface electrode, 11 ... Surface protective film, AI + A2 + A3 + ... split electrode, B1 , B2rB3. ...
Insulator, T, ~ Tn ... Vibrator, 81 ~ Sn ... Switch and / or phase control (delay) element. Attorney
Attorney Attorney Ogawa-Attorney Noguchi Kensuke (18) Figure 2 EndPage: 4 Figure 4 Figure 5
EndPage: ?
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