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Description 1, title of the invention
Piezoelectric type electroacoustic transducer
3. Detailed Description of the Invention The present invention relates to a piezoelectric
electroacoustic transducer having a thickness suitable for an ultrasonic wave receiver etc. In
particular, transmission and / or reception of ultrasonic waves in a liquid phase such as water
The present invention relates to the structure of an in-liquid ultrasonic transducer in which a
sheet-like polymer piezoelectric material used for waves is used as a transducer. In order to use
the piezoelectricity (d, 5) in the thickness direction of the polymeric piezoelectric material, one
surface of the polymeric piezoelectric material is lined with a large blue object having a large
elastic modulus and mass from this polymeric piezoelectric material, and the opposite surface
Japanese Patent Publication No. 51-26459 proposes an air-permeable acoustic transducer
having a pressure acting surface on the side, and particularly a high g degree in a high frequency
region. This transducer is an ultrasonic flaw detector, an ultrasonic diagnostic device, an
ultrasonic microscope, etc., and an ultrasonic wave receiver that transmits ultrasonic waves in
water or receives ultrasonic waves from water. It is also used as a wave. However, the invention
according to JP-B-51-23439 is based on experiments conducted under the conditions in the
atmosphere, and it is desirable to line the object with a substance having a larger elastic modulus
and mass than the piezoelectric in the atmosphere. It is only possible to sit at a much higher
power or sensitivity than this. Therefore, it has not been asked whether the same effect can be
obtained, especially when using one dose in water. According to the inventor's research, for
transmission and reception of ultrasonic waves in the water, an air gap is provided on the back
surface of the sheet-like polymeric piezoelectric element, and the base is directly adhered to the
entire back surface even when the element and the base are not directly adhered. Not only does
EndPage: 1 have higher transmission / reception efficiency than the ultrasonic transmitterreceiver of Japanese Patent Publication No. 51-23439, but the peak wavelength becomes broad
if there is a gap in the back direction, It has been found to be a useful ultrasonic transducer that
can be used for transmission and reception in a wide wavelength range. As well known, the
shorter the wavelength of the ultrasonic wave used in the ultrasonic imaging apparatus, the
better the resolution of the obtained image, but the greater the reduction of the sound wave in
the medium or the subject, the depth of the part to be imaged and Depending on the composition
etc., ultrasonic waves of appropriate wavelength are used conveniently. Also, in some cases, the
resolution of one image is increased by changing the wavelength of ultrasonic waves used for a
portable image and sweeping. When converting or extracting these wavelengths, it is extremely
advantageous to obtain high transmission power or reception feeling in a wide wavelength range.
According to the present invention, the peripheral portion of the back surface of the sheet-like
polymeric piezoelectric element with electrodes attached on both sides and the substrate are
adhered to each other, and the adhesion is carried out. In the process, a sealed space is formed
between the polymeric piezoelectric element and the substrate, and at least the surface side of
the polymeric piezoelectric element is covered with an insulator film. Piezoelectric type!
It relates to the air acoustic transducer. According to this configuration, the conversion efficiency
is the same, and the peak wavelength range of the specific imaging motion is broad, so that the
ultrasonic wave receiver used in this solution becomes 'tE'. Hereinafter, an embodiment in which
the present invention is applied to a submerged ultrasonic transducer will be described with
reference to the drawings. According to the example shown in FIG. 1, in the polymer pressuresensitive element fil consisting of a sheet-like polyvinylidene fluoride film having Nf + 21 + 21 ′
such as Ni, All, etc. on both sides, the peripheral portion of the side of one side is It is fixed to a
substrate (3) such as metal or plastic by an adhesive (4). In this figure, the base (3) has a hollow
central section [L! Although it is J-shaped, a flat substrate (3) may be used as in the 21st
embodiment, and the element (1) and the substrate (3) may be joined via a frame-like spacer αIf.
Alternatively, the frame plate may be attached 1 to the four side surfaces of the bottom plate, and
the element (1) may be adhered to the frame plate to form a suspended or t1 cylindrical shape. In
any case, the back surface of the high-polymer piezoelectric element + IJ (this air gap (5) may be
formed). This sky 1! J + 5J is a sealed space so that water does not enter when immersed in
liquid. The shape of the air gap may be any shape such as a square, a circle, or an oval. Also, the
thickness of the air gap is not particularly limited, but if the ultrasonic transducer is immersed in
liquid, the thickness of the element (1) is such that it is shouted by water pressure and does not
contact the back substrate (3). Good. If the element fi + has a large area and the central part
thereof is easily indented, as shown in FIG. 2, in the space 11fIl) I, for example, a flexible material
such as foam rubber, polyurethane foam or a hollow bag. Spacer 0 υ ヲ 1111! One or more
arrangements, direct contact between the element (1) and the substrate (3) can be prevented.
Also, in FIG. 1, the entire surface is covered with a water-resistant insulation coating (6), but this
coating is only the surface on the piezoelectric sheet element fil side as shown in FIG. (れていて
もよい。 In FIG. 1, an electrode +21 (arrangement # 171 + 7 from 21 is taken out, and
connected to a high frequency power supply (8) and a signal processing circuit (not shown)
through an amplifier (91), for example). The gate in this figure is of the type that switches
between sending and receiving ultrasonic waves alternately, but if dedicated for sending or
receiving, 18+: l): One of (9) Is omitted. Although not shown in the example of FIG. 2, a circuit
configuration similar to that of FIG. 1 may be employed.
According to the ultrasonic transducer described above, the gas such as the back face f ′ ′ of
the sheet-like polymer piezoelectric element (1), + 常 and 孕 is tightly sealed in the air space
“M” +51. There is. The molecular piezoelectric element +1) has an acoustic impedance similar
to that of a liquid such as water, but the difference in acoustic impedance is large between that of
a liquid such as air and the like. Therefore, when used as a transmitter, for example, in a liquid,
the signal wave is largely reflected at the interface with the high resistance vacancy, and is
transmitted a lot in the liquid phase with low resistance. The rate rookie efficiency is high. Also in
the case of wave reception, although the resistance when entering from the liquid phase is small,
the eight piles when entering the gas phase (ie, air phase) are large, so the sound wave can not
pass through the element (1). Most of the energy is consumed in the element EndPage: 2, and the
energy efficiency of the received wave becomes a light. However, when this transducer is used in
the atmosphere, there is no difference between the acoustic impedances on both sides of the
pressure-acid element (1), and therefore the efficiency of high transmission and reception is
considered to be (4). Furthermore, according to the inventors of the present invention, according
to the inventors of the present invention, the molecular piezoelectric material fi) has a very broad
peak wavelength of the natural vibration, and as described above, when the back surface is gas
phase φ, this natural vibration is the back surface. Because it is not affected, its transmission or
reception efficiency can be kept near peak over a wide wavelength range. However, it is
recognized that the peak of the intrinsic imaging wavelength is extremely sharp when the
polymer piezoelectric sheet (the entire back surface of the polymer sheet 11 is fixed to the
substrate as in the prior art), a wavelength having an efficiency close to the peak wavelength It is
recognized that the range is narrowed significantly 7). As described above, the ultrasonic
transducer according to the present embodiment is particularly an ultrasonic flaw detector of a
type that performs ultrasonic wave transmission and reception in liquid, an ultrasonic flaw
detector, and an ultrasonic wave g! , Φ, etc. are extremely useful as transducers. Next, specific
911 of the present embodiment will be described. A screen of a nickel 岨 pole (a 660 μm thick
polyvinylidene fluoride piezoelectric film (11 having a size of 50 m × 80 square) having 2 r 121
'was cut on a specific example screen. Then, this film is pasted with an epoxy adhesive (4) on a
Bakelite substrate (3) with a thickness of 20M1 and a size of 50 am x 80 with a recess of 5 m +
deep x 40 + wx 70 sa + deep at the center As shown in the figure (the film tl), the electroacoustic
transducer having the intercity seal (54) was placed on the back side. On the other hand, in
Comparative Example 1, a polyvinylidene fluoride electroconductive film of the same shape was
attached to a flat Bakelite 4 plate having a thickness of 20 M1 and a size of 50 s + x 80 m +
without a recess to produce an electroacoustic transducer of the same type.
Using these samples, the conversion efficiency was measured as shown in FIG. In FIG. 6, 6z is a
sample, (13) is a BP radiographer (Model 6600 made by Matic Corporation), and (14 is an
attenuator. In addition, (I 51 is an underwater sound receiver (hydrophone) for determining the
ultrasonic wave output Sakai City 11; the wave receiving surface of this underwater sound
receiver is located by buying a distance of 30 # III above the Tateshina surface ing. The water
receiver (the output from 19 is transmitted to the oranscope Uη through the amplifier ae. The
bet is a water tank. Measure the output of the RF speaker 03 at a constant 700VP-P, and adjust
the attenuator (14) so that the output of the water receiver (15 always shows a constant value). It
goes without saying that the value of the attenuator (I4) with respect to the above is probed, and
the larger the linearity of the attenuator, the smaller the voltage of the burner applied to the
sample, which means that the efficiency of the abrasive is higher. The results are shown in FIG.
4). The curve iA is the sample according to this example, and the curve B is the value of the
comparative example. As is apparent from this example, the value l of the attenuator at the
maximum efficiency (frequency fB) of the comparative example is about 26.5 dB, but the
maximum efficiency of the sample according to this example (number # f, L) 4 The value in this
case is about 26.5 dB, and particularly in the vicinity of the frequency fA, the efficiency is as high
as 6 to 7 dB. Moreover, the high performance factor 5 is held in a wide frequency (wavelength)
range, which is advantageous. The examples described above are based on the technical idea of
the present invention (X can be further modified.
4. Brief description of the drawings The drawings show an embodiment in which the present
invention is applied to ultrasonic wave transmission / reception in water, and FIG. 1 is a sectional
view of an example of the ultrasonic wave transmitter-receiver, and FIG. Fig. 6 is a schematic
view showing a method of measuring the conversion efficiency, and Fig. 4 is a graph showing the
measurement results. Fig. 6 is a graph showing the measurement results of another ultrasonic
transducer. G), +11......... Polymer piezoelectric element (2 × 2)... 'Electrode (3). · · · · · · · · · · · · · · · · ·
· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Sealed space (6) · · · · · · · · · · · · · insulator coating LIOXili · ·
............ It is a spacer. Atsushi Yasushi Katsuhiro Saka Matsuda EndPage: 3
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