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JPS55151895

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DESCRIPTION JPS55151895
Description 1, title of the invention
Variable Focus Ultrasonic Transducer Using Polymer Piezoelectric Film
3. Detailed description of the invention For the user. Conventionally, in the case of an electronic
transducer using an inorganic transducer such as PZT (lead zirconate titanate), BaTiOs, or quartz
as a piezoelectric material, in the case of an electronic scan method that performs linear scan,
sector scan, etc. Focusing can be performed by delaying the electrical drive pulse, but focusing in
the direction orthogonal to the scan direction may be performed by processing the wave front
into a concave surface, or performing focusing using an acoustic lens, etc. It was That is, a linear
array type ultrasonic transducer using a conventional inorganic piezoelectric material as shown
in FIG. 1 as an example of the conventional method has a back electrode 2. The PZT piezoelectric
body 39 is formed by laminating surface electrodes 4, and the laminated body is divided by the
insulators 5 in a strip shape along one direction and divided and arranged, and electrically in the
direction of the divided piezoelectric bodies A1 + A2 + Asl. The drive pulse is delayed to perform
linear scan or sector scan. Although this conventional transducer can scan, it has not been
possible to change the focus because it is not possible to bend the piezoelectric in the direction
orthogonal to it. Further, the transducer using the conventional inorganic piezoelectric material
shown in FIG. 2 forms the back surface sound absorber 1a + the back electrode 2a and the PZT
pressure integrated 3a + surface electrode 4a in a planar shape, and the electrodes 2a and 4a and
the piezoelectric body 3a. Is divided by the insulator 5a in the scan direction, and the acoustic
lens 6 having a curvature radius in the direction orthogonal to the scan direction is attached to
the surface of the surface electrode EndPage: 14a. Although this transducer can also scan,
focusing in the direction orthogonal to this can be made constant by the curvature of the acoustic
lens 6 and can not be made variable. When manufacturing a transducer using such two
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conventional inorganic piezoelectric materials, powder such as PZT is formed into a desired
shape on the back surface sound absorber 1, sintered, and then subjected to poling treatment to
obtain piezoelectric material. The piezoelectric material is separated into strips and separated to
form electrodes on the surface side, and an electrical insulator and acoustically dump between
the strips of each piezoelectric material. Fill and shape materials that have an effect. In addition
to having to go through such complicated and time-consuming steps, it is not easy to obtain
desired dimensional accuracy, and in the step of baking, the piezoelectric material is easily
cracked, and it is further cut into strips 9 In the separation step, cracks and defects easily occur,
and it is generally difficult to improve the yield. Furthermore, it is also difficult to obtain
uniformity in the thickness of the piezoelectric body to make the frequency characteristics and
efficiency etc. of each strip of the piezoelectric body uniform, and uniformization of the poling
conditions, and to make the characteristics of each array uniform. It was not easy to produce a
large number of arrays with uniform characteristics.
In addition, since mechanical separation is performed on each strip, there are mechanical
restrictions in order to finely process a uniform strip during division without defects, and it is
difficult to manufacture a fine array transducer. It was expensive. Also, when using the acoustic
lens shown in FIG. 2, there is a limit to the improvement of focusing by this acoustic lens, or any
restriction on the material for preventing the generation of noise or the reduction of efficiency
due to reflection from the boundary surface. There was a problem. An object of the present
invention is to solve various problems of such a transducer using a conventional inorganic
piezoelectric material, and therefore, in the present invention, in place of the conventional
inorganic piezoelectric material, flexibility is provided. The piezoelectric body is divided and
scanned along one direction by using a polymer piezoelectric film having at the same time, the
piezoelectric body is bent in a direction orthogonal to this, the acoustic wave is focused, and the
curvature of this bending is By providing a variable means to make the focus of focus variable,
and also take advantage of the various excellent properties of the polymeric piezoelectric film, an
easy-to-fabricate, uniform property, inexpensive transducer It is provided. Embodiments of the
invention are described below with reference to the drawings. Cow explaining the first
embodiment with FIG. The back electrode 8 (in this example, this electrode also functions as a
back reflector), the polymer piezoelectric film 99 surface electrode 10 is laminated, and flexibility
is given to the entire lamination, and in one direction , And the scan direction orthogonal to this
is linear, and the surface electrode 10 is divided into a large number of strips A ++ A2 + As +. The
support 7 is, for example, silicone rubber or other rubber-like substance 4 which is a flexible or
elastic material, and the polymeric piezoelectric film 9 is, for example, PVDF (polyvinylidene
fluoride ') It comprises a polymer of VDF and TFE, a copolymer of VDF and TrFE, a blend of PVDF
and PZT, or a polymer containing a cyan group such as polyacrylonitrile. The surface electrode
10 is formed by depositing or sputtering AJtCulAglAu or the like on the surface of the polymeric
piezoelectric film 9 and adhering a foil or plate or applying an Ag paste, while the back electrode
8 is made of, for example, phosphor bronze Material that has a high acoustic impedance, and the
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back surface of the polymer piezoelectric film 9 on the surface of this back electrode 8 with an
adhesive such as epoxy or cyanoacrylate. Glue. The back electrode 8 may be formed by vapor
deposition, sputtering, or adhesion of a foil or a plate when the support 7 is flexible 9 elasticity.
Clamping is fixed by holding frames 11 and 12, and both ends of each strip A1 + A2 + As + of the
surface electrode 10 are connected via a conductive EndPage: dual conelter 13. On the other
hand, the back electrode 8 is connected by the through hole 14 in the support 7.
On the other hand, the holding frame 11 is appropriately fixed, and one end of a solenoid
actuator 15 is fixed to the other holding frame 12, and this actuator 15 excites the drive coil 17
by the solenoid drive power supply 16 in the direction of arrow B-C in the figure. The other
holding frame 12 is moved in a direction toward or away from the other holding frame 11 which
has been moved and fixed, thereby changing the curvature of the transducer and orthogonal to
the scanning direction Change the focus position (focal depth) of the sound wave in the direction.
A displacement amount detector 18 for detecting the amount of movement of the actuator 15 is
attached to the other end of the actuator 15. The drive power source 16 is controlled by the
detector 18 to arbitrarily set the curvature of the transducer. Furthermore, if the phase shift of
each strip A ++ A2 + As +... In the array (scan) direction is also controlled according to the output
of this detector 18, the focus position in the scan direction can also be changed. And the phase
shift in the array direction are controlled in synchronization with each other. The back electrode
8 (This electrode also functions as a back reflection plate, but a back reflection plate may be
separately provided separately) The support 7 may be omitted if it is formed of a material having
the flexibility and appropriate strength. Further, although the surface side of the surface
electrode 10 is exposed, a suitable protective film may be attached. Furthermore, the electrode
pattern is not limited to the surface electrode 10 side, and the back electrode 8 side may be
divided. The second embodiment will be described with reference to FIG. 4. The support 7a, the
back electrode / back reflector 8a + the polymeric piezoelectric film 9a + the surface electrode
10a and the surface protective film 19 (which may not be provided). 1) The first embodiment is
stacked in the same manner as in the first embodiment, the end portions are fixed by the holding
frames 11a and 12a, and each strip of the divided surface electrodes 10a is connected by the
conductive connector 13a for lead extraction. One end of the actuator 15a is fixed to the back
surface of the support 7a, the solenoid drive power supply 16a is controlled by the displacement
amount detector 18a, the drive coil 17a is excited, and the actuator 15a is moved in the B-C
direction. Select curvature arbitrarily. The operation and effects of the second embodiment are
the same as those of the first embodiment, and the other various technical ideas described in the
first embodiment can be applied to the second embodiment as they are. . The third embodiment
will be described with reference to FIG. 5. As in the two embodiments described above, the
support 7b, the back electrode and back reflector 6b, the piezoelectric polymer film 9b, the
surface electrode 10b, and the surface protection film 19b And the end portions are fixed by
holding frames 11b and 12b, and wire connection is performed by a conductive connector 13b
to constitute a transducer, and at the back side of the support 7b, the holding frames 11b and
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12b are airtight. The holding surface 20 is fixed, and the inside of the holding surface 20 can be
pressurized and depressurized through the pipe 21.
The surface side of the transducer is usually in contact with an ultrasonic wave propagation
medium such as water, for example, and the surface side is usually at 1 atm. Therefore, a
pressure difference occurs between pressurizing and depressurizing the inside of the holding
surface 2 o and between the surface side, and reducing the curvature radius of the piezoelectric
body by depressurizing and enlarging the curvature radius of pressurizing. The curvature can be
arbitrarily selected by controlling the pressure in the holding surface 2o. Referring to FIG. 6, the
fourth embodiment will be described. A support 7C + back electrode / back reflector 8e (not
necessarily used in combination but may be provided independently in some cases), polymeric
piezoelectric film 9ct surface electrode 10e and surface A protective film 19c (which may not be
provided) is laminated in the same manner as in the first embodiment, the end portions thereof
are fixed by holding frames 110 and 12e, and each strip of divided surface electrode 1oc is used
for lead extraction. Make a wire connection to the conductive connector 13e. On the back side of
the support 7c, the airtight holding surface 20c is fixed to the holding frame 11e, and one
holding frame 12C is movable in the B-C direction in the figure while maintaining airtightness
with the holding surface 20c. EndPage: 3 through the pipe 21c allows the inside of the holding
surface 20e to be pressurized and decompressed. Furthermore, one end of the actuator 150 is
fixed to the holding frame 12C, the solenoid drive power supply 16C is controlled by the
displacement detector 18C, and the drive coil 17C is excited to make the actuator 15C movable
in the B-C direction. The surface side of the transducer is usually in contact with an ultrasonic
wave propagation medium such as water, for example, and the surface side is usually at 1 atm.
Therefore, by holding and depressurizing the inside of the holding box 2 (C, a pressure difference
is generated between the surface side and the pressure side, and by pressurizing, the radius of
curvature can be reduced, and the pressure can be reduced. , The radius of curvature can be
reduced. Therefore, by setting the inside of the holding surface 20e to a desired pressure via the
pipe 21e, setting the curvature of the transducer, and then moving the actuator 15C in the B-C
direction, the curvature of the transducer is set. Can be set arbitrarily. By this method, it is also
possible to set the value of the average of the desired curvature by the pressure inside the
holding surface 20C, and then to control the curvature more finely by the actuator. In this
embodiment, the support 7C is not necessarily required, and may not be necessary in some cases.
Furthermore, the back electrode 8C does not necessarily have to be elastic. It is sufficient that the
back electrode 8C is sufficiently flexible and its curvature can be changed by the pressure
difference in this embodiment. The operation and effects of the fourth embodiment are the same
as those of the first embodiment, and the technical ideas of the other various types shown in the
first embodiment are also applied to the fourth embodiment as they are.
According to the variable-focus-type ultrasonic transducer using the polymeric piezoelectric film
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of the present invention described above, the back electrode, the polymeric piezoelectric film and
the surface electrode are flexibly laminated, and the lamination is performed in one direction. It
is formed in a curved shape with a curvature along it, and is moved by an actuator that moves by
exciting the coil, or by pressurizing or depressurizing the airtight chamber on the back side of
the back electrode. Since the curvature of V is made variable, the curvature can be set
appropriately to select the focus position (or focus) arbitrarily, and the selection of the focus
position can be performed independently of the scan or in synchronization with the scan. . Such
variable focusing position is achieved by using a polymer piezoelectric film having flexibility and
a constant film thickness and uniform characteristics as a piezoelectric material, Furthermore, by
using this polymer piezoelectric film, division of the electrodes can be performed by simple
techniques such as evaporation, paste application, etching, and ruling, and the piezoelectric film
can be simply adhered by an adhesive. It is easy to manufacture the entire transducer, is
inexpensive, and is excellent in piezoelectric characteristics and degradation characteristics as a
transducer.
4. Brief description of the drawings FIGS. 1 and 2 are perspective views showing a conventional
inorganic piezoelectric transducer, and FIGS. 3 to 5 show polymer piezoelectric films according
to the present invention. FIG. 3 is a perspective view showing the first embodiment, FIG. 4 is a
longitudinal sectional view showing the second embodiment, and FIG. 5 is the third embodiment.
A longitudinal sectional view showing an example, and FIG. 6 is a longitudinal sectional view
showing a fourth embodiment. 7.7a, 7b: support, 8.8 &, 8b: back electrode and back reflector, 9.9
&, 9b: polymeric piezoelectric film, 10 ° 10a, 10b: surface electrode, 11.11 &, 11b, 12.12 &.
12b: Holding frame 15, 15a: Solenoid actuator 16, 16a: Solenoid drive power supply, 17 ° 17a ':
Drive coil, ta, t8a: Displacement amount detector, 201 .. Holding box, 21 ... pipe, At + A 2 + A 3 +
... short strip. Attorney Attorney Nobuyuki Ogawa-Attorney Noguchi Kensuke EndPage: 4
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