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Description 1, title of the invention
Ultrasonic transducer using polymer piezoelectric film
3. Detailed Description of the Invention The present invention relates to an ultrasonic transducer
using a polymeric piezoelectric film, and more particularly to an ultrasonic transducer having a
polymeric piezoelectric film in which piezoelectricity is imparted only to necessary portions.
Conventional PZT (lead zirconate titanate) * BaTiO3. As shown in FIG. 1, a multi-electrode type
transducer using an inorganic piezoelectric material such as quartz is formed by laminating a
back surface sound absorber 1, a back electrode 29 such as a PZT piezoelectric 39 surface
electrode 4 and a surface protective film 5 The PZT piezoelectric body 3 and the surface
electrode 4 are divided into minute piezoelectric bodies A1TA2HA 31... By the electrical and
acoustic insulator 6. In the process of manufacturing this transducer, a PZT powder is formed
into a desired shape on the back surface sound absorber 1, is sintered at a high temperature, a
high voltage is applied to both ends (poling treatment) to exhibit piezoelectricity, and then
desired. For example, in the case of a sector type, the PZT is cut into strips and separated, and the
insulator 6 is inserted into the groove to be separated. However, since PzT is a ceramic and has
high strength, the number of processing steps increases at the time of polishing and separation,
and there is a great possibility of occurrence of breakage or cracking, and it is restricted by
smoothness and the like. Therefore, when the multi-electrode configuration is refined and
miniaturized, the uniformity as a whole of the transducer, homogeneity 9 yield and large area etc.
are inevitably difficult and inevitably become expensive. The Furthermore, since it is necessary to
prevent crosstalk (leakage), EndPage: 1 except for acoustical and electrical coupling between
adjacent piezoelectric members, the insulator for separation must have a certain width between
the piezoelectric members. There is a limit to miniaturization from this point as well. And this
insulator not only has a property as a buffer (sound absorbing material) for preventing
transmission of vibration to the next minute piezoelectric body, but it is considered to electrically
insulate it as well as as a guard for storage of an electric shield. It is necessary to devise
measures, and from this aspect as well, the production as a whole of the transducer has become
complicated and expensive. SUMMARY OF THE INVENTION The object of the present invention
is to solve the problems of the ultrasonic transducer using such a conventional inorganic
piezoelectric material, and for this reason the present invention relates to a back electrode (this
back electrode is a back reflection A polymer film may be sandwiched between a plate and a
surface electrode, and at least one of the back electrode / back reflector and the surface
electrode may be formed into a desired electrode pattern, and There is provided an ultrasonic
transducer using a polymeric piezoelectric film characterized in that a voltage is applied between
the electrodes to impart piezoelectricity to the polymer film while the two electrodes face each
other. Since the electrode pattern can be easily formed and only the polymer film needs to be
adhered, the fabrication of the entire transducer is easy and inexpensive, and the film thickness
of the polymer film is uniform and homogeneous. Better performance of the Deuter Enables
fabrication of a large-sized transducer because of the large area of the polymer film,
simultaneously imparts piezoelectricity only to the necessary part of the polymer film, and
imparts piezoelectricity to unnecessary parts It is intended to eliminate crosstalk (leakage) by
eliminating the electroacoustic coupling between the portions to which the piezoelectricity is
applied by the portion to which the piezoelectricity is not applied by preventing the
piezoelectricity. It is.
Embodiments of the present invention will be described below with reference to the drawings. A
first embodiment will be described with reference to FIG. In the figure, CulAJ- + Ag + Au or the
like is vapor deposited or sputtered onto the surface of the support 7 preferably made of bakey),
PMMA (polymethyl methacrylate), glass epoxy or nylon, or the like (an electrode is attached by
attaching a foil or plate). To form a back electrode and back reflector 8 formed into a desired
electrode pattern by ordinary printed circuit board processing technology such as etching or
ruling or other processing technology, and an insulator between the electrode patterns. 9 are
embedded to form four divided electrodes AirA2 + A3r. Poled raw polymer film 100-for example,
PVDF, (polyvinylidene fluoride), a blend of PVDF and PZT, polyvinyl chloride or polyacrylonitrile,
VDF and TV'E, VDF and TrFE, etc. This common polymer is formed by vapor deposition or
sputtering of CulAJ + Ag # Au or the like, or by adhering a foil or plate on the surface of a film
such as a copolymer having as a main component the same, and this polymer The back surface of
the film 10 is adhered onto the back electrode 8 using an adhesive such as epoxy or
cyanoacrylate. Next, the leads 12 from the back electrode 8 are connected, and a high voltage is
applied between the back electrode 8 and the surface electrode 11 to perform poling treatment.
In this poling treatment, piezoelectricity is imparted to the polymer film 16 in the portion
between the electrode pattern of the back electrode 8 and the surface electrode 11, and the
polymer film 14 in the portion between the insulator 9 and the surface electrode 11 is No
piezoelectricity will be imparted. This non-piezoelectric non-imparting portion 14 acts as an
acoustically large mechanical loss and as a 33 ks + = O (or d3s ? ? ds + = 0) K yorida 7 p C
acoustical material) and electrically It acts as a good insulator, so that this non-piezoelectric nonapplication part 14 eliminates the electro-acoustic coupling between the piezo-application parts
13 and prevents crosstalk (leakage). Further, in some cases, the adhesive strength between the
piezoelectric polymer film 10 and the back electrode 8 or the front electrode 11 can be increased
by heating at the time of poling. Also, in the case where a polymeric piezoelectric film having
piezoelectricity applied in advance to the entire film is bonded between the back electrode and
the surface electrode, the step of removing the piezoelectricity of unnecessary portions of the
polymeric piezoelectric film after bonding is adopted. In comparison, the EndPage: 2
manufacturing process is simplified and the cost is reduced.
It goes without saying that the electrode to be patterned is not limited to the back electrode side,
but the front electrode side may be patterned and the back electrode side may be a common
electrode. The second embodiment will be described with reference to FIG. 3. However, in the
second embodiment, both the back and front electrodes have the same pattern. That is, in the
figure, an electrode pattern is formed on a support 7a, and a back electrode (a back reflection
plate) 8a in which the electrodes are divided A ++ A2rAs + by insulator 9a is attached, and a
polymer not subjected to poling treatment is attached thereto. Bond the membrane 10a. Next, the
surface electrode 11a for poling having the same electrode pattern as the back electrode 8a is
put on the insulator 15a, and the back electrode 8a is connected by the lead 12a to perform
poling processing. According to this method, since both the back and front electrodes are formed
in the same opposing electrode pattern, the polymer film 13a between the electrode patterns is
provided with piezoelectricity, and between the insulators 9a and 15a. Piezoelectricity is not
imparted to the polymer film 14a, and the degree of application and non-application of the
piezoelectricity becomes clearer, and in particular, the non-applied portion 14a is not clearly
imparted with the piezoelectricity. After the poling treatment is finished, the poling surface
electrode 11a is removed, and the surface electrodes are uniformly or pattern-wise deposited or
applied onto the poling polymer piezoelectric films 13a and 14a. Form. The operation and effect
of the second embodiment are also similar to those of the first embodiment. FIG. 4 shows a third
embodiment, which in particular shows a self-focusing (Fresnel type) concentric annular planar
transducer. That is, the common back electrode 8b is formed in a disc shape on the cylindrical
support 7b, and a disc-shaped poling untreated polymer film 10b is adhered to this. Next, a
poling surface electrode 11b formed by alternately forming Fresnel ring type concentric annular
electrode patterns Ao + At + A2 +... And insulators B ++ B2 +... Is placed, and poling treatment is
performed between the back surface and both surface electrodes. Piezoelectricity is imparted to
the polymer film 13b of the Ao + AI + 12 +... Portion, and piezoelectricity is not imparted to the
polymer film 14b of the insulator B ++ B2 +. After the poling process is completed, the poling
surface electrode 11b is removed, and a uniform common surface electrode is deposited or
coated on the polymeric piezoelectric films 13b and 14b, and a single electrode is formed
between the surface electrode and the back electrode 8b. When moved, this transducer
immediately acts as a Fresnel type and the sound waves are focused. The functions and effects of
the third embodiment are substantially the same as those of the two embodiments described
above. Furthermore, according to this concentric term type transducer, in the Fresnel type
transducer using a conventional inorganic piezoelectric material. This eliminates the need for the
concentric ring connection, which simplifies the manufacturing process and reduces the cost.
The electrode to be patterned is not limited to the surface electrode, and the back electrode may
be patterned to share the surface electrode. Although the flat type transducer has been described
above, the fourth embodiment shown in FIG. 5 is a case of a concave type transducer. That is, in
the drawing, a concave back electrode (a back reflection plate) 8c is formed on the concave
portion on the support 7C, and the concave back electrode 8c and the remaining flat support are
formed. The polymer film 10C which is not subjected to poling is adhered, and the surface
electrode 11C comprising a concave part and a flat part is further placed thereon to carry out
poling treatment. As a result, the polymer film i3c of the concave portion facing the back
electrode 8C is provided with piezoelectricity, and the polymer film 14e of the portion away from
the back electrode 8c is not provided with piezoelectricity. The operation and effects of the
fourth embodiment are also similar to those of the first to third embodiments. Although the case
where the front electrode of the piezoelectric body does not have the front additional film has
been described above, for the purpose of adjusting the frequency and protecting the electrode,
for example, a polymer film is coated or adhered on the front of the front electrode. You may
form many. -According to the ultrasonic transducer using the above-mentioned polymer
piezoelectric film of the present invention, an electrode pattern is produced by EndPage: 3
processing technology of the wiring pattern of a normal printed circuit board, Bonding the
polymer film, and then performing poling treatment to impart piezoelectricity only to the
necessary part of the polymer film, and by not imparting piezoelectricity to unnecessary parts,
the manufacturing process of the entire transducer is simplified. By using a polymer film that is
uniform, easy to manufacture, inexpensive and has a uniform, uniform, and large area film
thickness, the transducer can be made large, and the characteristics and performance can be
made good and homogeneous. can do. In particular, by not imparting piezoelectricity to
unnecessary portions of the polymeric piezoelectric film, this non-piezoelectric non-applied
portion has an acoustically large mechanical loss as high as 33 to 2 (or d33-d3). ) Acts as a sound
absorbing material and electrically operates as a good insulator, so that the electro-acoustic
cobbling of the piezoelectricity-imparting part lying on this piezoelectric non-impartioned part is
eliminated and crosstalk is prevented. .
4. Brief description of the drawings Fig. 1 is a longitudinal sectional view of a conventional
ultrasonic transducer using an inorganic piezoelectric material, and Figs. 2 to 5 are ultrasonic
waves having a polymeric piezoelectric film according to the present invention. It is a
longitudinal cross-sectional view which shows 1st thru | or 4th Example of a transducer. 7.7 &,
7b, 7e иии Support, 8.8a, 8b, 8c иии-back electrode and back reflector, 9, 9a и и и insulator, 10 ░ 10a,
10b, 100 и и и high Molecular membrane, 11. lla, Ilb, 11 (! и и и Surface electrode 13, 13, 13b, 13e и и
и Piezoelectricity imparting portion 14, 14, 14a, 14b, 14c и и и non-piezoelectricity imparting
portion, 15a, 15b и и и insulator, Ao + At + A 2 + "и и и division electrode. Attorney Attorney
Nobuyuki Ogawa-Attorney Noguchi Kensuke No. 1 4 Figure 4 ('(55 Figure EndPage: ?
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