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BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an ultrasonic light deflection or modulator
using a piezoelectric polymer film (poled polyvinylidene fluoride) as an ultrasonic transducer and
water as an acousto-optic material. FIG. 2 shows an ultrasonic delay line in which the
piezoelectric polymer film is used as an electroacoustic transducer (ultrasonic transmitter and
receiver). FIG. 3 shows the relationship between the total insertion loss of the ultrasonic delay
line having the structure of FIG. 2 and the frequency.
[Detailed description of the invention] This invention is high performance 111! The present
invention relates to an electroacoustic functional device which is easily manufactured and
processed and which uses a novel acoustic transducer. In the field of polymer research in recent
years, various applications have been made to use polymer materials as functional materials of
electronics, and some of them have been successful. The inventors of the present invention have
conducted deep researches on polymer pressure tit, and as a result, the piezoelectric polymer
film can be practically used as an electroacoustic transducer in which thickness stretching
vibration is given as 1- / s1pig30- □□□ J We have found that we have sufficient pressure and
electromechanical couplings, and we have found that this transmutation probe can operate in the
poetic frequency domain, and reached the present invention. In the present invention, the
present invention is an electroacoustic fIk device in which a piezoelectric e'-ring polymer film
made of 7e-ring is brought into contact with or propagating to a sound wave propagation
medium material. I have vc2. An electroacoustic 41-hyde device in which the piezoelectric
polymer film is driven to resonate under thickness stretching vibration is defined as a gist.
Because this pressure 11L product molecular gland has advantages such as ease of processing,
oJ flexibility and large surface area. It is obvious that it can replace -S in electric keying elements
made of piezoelectric single crystals and piezoelectric ceramics that are being used efficiently,
and that it can be applied to fields not possible with these as well. became. According to a recent
study, a kind of synthetic polymer film is stretched, and a direct current high electric field is
applied thereto and kept for a time at high temperature, and then it is cooled to room
temperature while applying an electric field of 9 parts. "After that, excluding the direct current
high electric field (this operation is a symmetry 2-31-----------------------which belongs to a 19 mm 2
fish school called touring) ~----------J 'j It has been clarified that it becomes a definite piezoelectric
material (applied physics 381133 (19691, Japan, J, Appl. Phys, 8975 (196911 °, a typical
polymer being polyvinylidene fluoride (PVDFl). According to the research of the present
inventors. In order to obtain a piezoelectric polymer film, a stretching operation is not necessarily
required, and a piezoelectric polymer film can also be obtained by "rolling" a non-stretching
group. The inventors of the present invention have also obtained a piezoelectric i polymer film by
mailing polyacrylonitrile (PAN). A piezoelectric film can also be obtained by forming a film in
which a powder of a ferroelectric, for example, a powder of lead zirconate, is mixed with a
In the present invention, the piezoelectric film mixed with the inorganic powder in this way is
also called a piezoelectric polymer film. Piezoelectric constants which are expected to be not zero
of these piezoelectric polymer films 1t obtained by O O mailing, for example, piezoelectric strain
trains are d 31. a32. a33. als. a24である。 Of these, the first three are of practical interest 6-).
Here, the two-fold symmetry axis (normal to the film surface) is selected as the two axes, and the
intersection line t between the two mirror surfaces and the film surface is respectively selected as
the X-Y axis (in the case of -axis stretching film, X axis). A31 = a32. It is di5 two d24. All
conventional studies on piezoelectric surface molecular films obtained from 9 conventional /phosphorus are as described in d 31. Nothing has been known about a33 (e63.g33 etc.) and the
properties involved therein, as was done for a32 (or the corresponding gf numbers or 0's). The
present inventors have developed a method of quasi-statically measuring a33 of a piezoelectric
high-molecular-weight has-pole film obtained in the low-frequency region, as well as devising the
“L ': F method, It is used to measure the piezoelectric constant of substances. The electrical
frequency characteristics in the vicinity of the resonance frequency of the no-load piezoelectric
vibrator are analyzed to obtain a piezoelectric equation. The so-called dynamic measurement
method (proc, Ko, R, B, 45355 (19b711 is applied to a piezoelectric polymer film (thickness
stretch oscillator) for the first time). 4-33)----was successful in obtaining the piezoelectric
numbers in high frequency chain acid. Table 1 exemplifies a biaxially stretched PVDF d-t4 film
obtained by dynamic measurement at room temperature and using piezoelectric constants at
room temperature (value at 24 MHz). Table 1 Piezoelectric polymer (piezoelectric constant of
longitudinal velocity of PVDFI-film VV 2.565 x 10 Sm / sea elastic stiffness constant 0 treasure
s1-18 x 10 IN / m2 density ρ 1.79 x 10 'lcg / m2 frequency constant fc1.28 x 10' H2 -M
acoustic intensivity Z / 4.59 x 10 'kg / m2 * sθC electromechanical coupling constant ktO, 11
piezoelectric stress constant essz 9x10-50 / m2 mechanical Q-factor QM 9.5 dielectric constant
ε3 / ε. 511 condition 0 condition 5 condition f7-status 1 electric "VDF [O electrical-<p town
mechanical coupling constant ki = e3. /(。 (P3 · treasure) (high-frequency area)-(-10 'H2) te is
always 0.10-0.14 te. Mechanical Q value (QMI is around 10). (C-3 is elastic compliance, ε! Is the
dielectric constant 10 SN is the pressure 5-34--1? .
Force constant). In low humidity, kt is close to 1 厘 of normal temperature. QM increases (QM =
70 at -10 C 1 C). As described above, it is extremely significant in practice that the number kt of
the piezoelectric polymer film without the coupling of the thickness expansion and reduction
oscillation is equivalent to that of the crystal. A small QM makes insertion loss fat and one of the
drawbacks, but conversely works in a wide frequency band! It can also be said that it has the
advantage of being used as an air acoustic transducer. In addition, since the dielectric constant is
small, it has a high voltage output coefficient g63. Therefore, it becomes a receiver with high
sensitivity of longitudinal elastic waves. Furthermore, the thickness of the film can be made
extremely uniform over a large area, so it is directional. Not only can pure longitudinal acoustic
waves be generated, for example, it is also possible to produce an integrated electroacoustic
transducer in which a matrix-like electrographic image is provided on the film surface.
Furthermore, since it is flexible, it is excellent in impact resistance in the place where it is lacking
in the electroacoustic transducer of the inorganic piezoelectric material, and does not require
careful attention in processing and handling. Also, six piezoelectric layers can be easily viewed on
an object having a curved surface. 6-- When utilizing the characteristics of such a piezoelectric
polymer film. Elliptical electroacoustic functional devices can be created. For example, an
ultrasonic light deflection or light modulator, an ultrasonic delaying edge, a solid ultrasonic
memory, reception of sound waves in solid or liquid and a receiver of vibration of an object such
as a @ signal or a 磯, etc. These are generally defined as a device in which a piezoelectric polymer
provided with an appropriate electrode is used as an electroacoustic transducer for longitudinal
acoustic waves, and this is densely bonded or adhered to a propagation medium of acoustic
waves to be incident or received. Here, the electroacoustic transducer for longitudinal wave
sound uses thickness expansion and contraction vibration of a piezoelectric film or a
piezoelectric plate "[Th1ckness extssional mode 1]. That is, it means an electroacoustic
transducer using a piezoelectric phenomenon such as a33 or e66 ° g33 corresponding thereto.
Here, the sound-wave propagation medium may be two or more types of objects, and a plurality
of electroacoustic transducers may be used, and may be used together with one element other
than the piezoelectric polymer film. I get a reed. Electric 7-6: 36--! Using a piezoelectric polymer
film according to the present invention below. An embodiment of the acoustic functional device
will be specifically described. Example 1 A 50-μm-thick biaxially-abrasive PVDF membrane
made of fish with aluminum on both sides is sandwiched between two aluminum foils. The
aluminum foil was heated to 130 ° C. in an oven while applying a voltage of 2400 V as an
electrode, and after 2 hours, it was gradually cooled to room temperature to remove the voltage.
The piezoelectric strain constant obtained by applying the alternating force of 110 H 2 to this
film and measuring the amount of alternating charge generated on the film quasi-statically is d
31 = 6.9 × 10 −12 C / N, d 32 = 3.6 × 10 −120 / N, d63 = 22.8 x 10-"O / N data. In addition,
a thickness expansion and contraction free vibrator was made of this film, and it was measured
by a dynamic measurement method. The piezoacoustic constants around 24 MHz are shown in
Table 1. An optical deflector was produced using this piezoelectric polymer film as an ultrasonic
transducer and water as an acousto-optic material (FIG. 1). That is, gold deposition 6 was
performed on one side 2 of the parallel square prism type transparent quartz cell 1 and two sides
2 were cut out from the above-described needle-ring film. A 10 mm x 10 mm piezoelectric film 4
on which aluminum was deposited is bonded by an epoxy resin. When the cell 1 was filled with
water and a high frequency voltage of f-10 to 30 MH 2 was applied to the piezoelectric film 4
through the electrode leads 5 and 6, an ultrasonic wave was generated from the piezoelectric
film 4 and was temporarily borrowed into water. When H.theta.-Ne laser beam 7 (.lambda.-0.63
.mu.m) is incident almost perpendicularly to the traveling direction of the ultrasonic waves, a part
of the incident laser light 7 (.lambda. = N.lambda.f / v (n =. ± .1) due to the ultrasonic waves.
Polarized by an angle given by ± 2... V is the speed of sound in water. The intensity of the
polarized light with respect to the incident light becomes maximum when the angle of the wave
front of the ultrasonic wave and the incident light becomes 1/2 of θ given by the above
equation. If a high frequency pulse of 80 v (pulse width 8 μsacl is applied to the piezoelectric
film 4 so as to satisfy this condition for 'n = 1, the intensity of polarized light to the intensity of
incident light (intensity of polarized light of all orders The percentage of the sum) (deflection
efficiency) was 95% at 25 MHz. The deflection efficiencies at both IDMH2 and 30 MHz were
approximately 50%. Therefore, in this case, the light not deflected (n-01 received 95% of 5 @
modulation by an ultrasonic pulse 9-38 S 'of 25 MH 2). Conducted gold deposition on both sides
of a 22 mm thick quartz crow block with two half faces facing each other, and two piezoelectric
PVDF films (areas 10 mm x 10 mm Contact with epoxy resin (Fig. 2). An ultrasonic delay line was
created in which the piezoelectric film 10 in contact with the surface A of the quartz glass block
9 was a speaker of ultrasonic waves, and the piezoelectric d11 in contact with the surface B was
a receiver of ultrasonic waves. When a% frequency pulse (pulse l @ 1μ5ecl ヲ is applied to the
piezoelectric film 10, an ultrasonic pulse is generated, and a high frequency voltage A peak pulse
is generated from the piezoelectric film 11 at a delay 1-11 'at fI 3.75μ day θC. .
In the figure, reference numeral 12 denotes a # -4 vapor deposition film t15, which is A / vapor
deposition film, and 14.15, a light exposure. The ratio of input voltage to output voltage was
approximately 40 dB in the range of 15 to 60 MH2. FIG. 6 shows the measurement of the
frequency characteristics of the total insertion loss of this ultrasonic delay @ purple. Examples
610-39) Unstretched PVDF was stretched to 4 times at 70 ° C. to obtain a 120 μm-thick @ stretching. Aluminum fish scraps were applied to both sides of this, and in order to prevent
corona discharge, a film of Nico was immersed in silicone oil at 160 ° C., and a voltage of 4.2 kV
was applied to perform coating. The piezoelectric strain constant of the obtained film is d31 =
20.8 × 10− ′ ′ at 110 · JH2 and gH. d52=1.33x10−120/N、
d55=25.6xl0−”O/Nであった。 It was obtained from the dynamic measurement
method of thickness expansion ring oscillator. The piezoacoustic constant at room temperature
around 10 MH 2 is kt = 0.12. θ5. =8.5X10−2C/m2. QM = 11 and the number of
frequency stations fc = 1.25 KH2'n "t '. The piezoelectric film (area 5-mm x 7 mm) obtained
above at "@" is bonded to an ultrasonic delay glass (DL-1 made by Hoya Glass) with an epoxy
resin as an ultrasonic wave transmitter and receiver, respectively, A supersonic f pulse generated
by applying a high frequency pulse to a seeko was received by the receiver. A delay time of 47
μSθC was obtained with a delay circuit with an effective length of 188 mm. The total insertion
loss was 50 clB at 11-40 l center frequency (about 10 MH2). Also, the insertion loss was constant
in the range of ± 2 dB from 6 MHz to 15 MHz. The parasitic output was less than 120 dB of the
output signal. By using a piezoelectric PVDF film having a thickness of 280 μm, an ultrasonic
transducer having a center frequency of 4.4 MH 2 can be obtained. By bonding this to the above
delay glass having an effective length of 280 mm, it is possible to obtain an ultrasonic wave delay
for television receiver having a delay time of 64 μsec and which can be used in a wide band.
EXAMPLE 4 Poly (vinylidene fluoride) dissolved in dimethylformamide was cast on a 20 mmthick parallel quartz glass plate with one surface plated, and the solvent was evaporated to form
a PVDF film having a thickness of about 60 μm. An electrode with a diameter of 10 mm was
produced on this membrane surface as AJ steaming waste. A voltage of 150 V was applied
between a silver vapor deposition electrode on quartz glass and an A4 electrode on PVDF, and
10-ring was performed at 120 ° C. for 2 hours. The obtained piezoelectric film is used as an
ultrasonic transducer (for common use) for transmission and reception, and this is 10 MH2 to 50
MH2 high-perimeter i harsu (halus width 0.5 μ12-41)----------- When 8θC was added, an
exponentially decaying pulse echo train was observed over a long time (1 msec at 20 MHz or
Instead of quartz glass, an ultrasonic pulse is generated using a piezoelectric pvDpi similarly
prepared on a polymethyl methacrylate plate as an ultrasonic transducer, and the distance
between ultrasonic echo trains observed by the same transducer is attenuated from the amount
of attenuation The velocity of sound and absorption coefficient of polymethyl methacrylate could
be measured. Example 5 A film having a diameter of 18 was cut out from the piezoelectric film
obtained in Example 2, and this was used as a conductive sheet of 2 sheets of glass (Nesa glass).
From the top of these two Nesa plates, I tightened with two more gold plates. When a voltage (60
V) at a frequency of IIH 2 -10 KH 2-was applied to the Nesa glass conductive electrode, an
audible sound was generated. Also, when the voltage signal generated on the Nesa glass plate on
a complex vibrating object is put into a frequency analyzer. A frequency spectrum was obtained
with the full upper limit of SKH2. It has been reported that the piezoelectric polymer film mixed
with PVDF KPZT produces an audible sound by means of 15-42->-(Toyoki Kitayama, Hisashi Oga
Department, Proceedings of the Federation of Electrical and Electronical Society of Japan 140
(19711, Oga In the front, Acoustical Society 2-3-20 (1972) 3 ° In this case, the audible sound is
generated by a bimorph-type film in which two piezoelectric films are crimped in opposite
directions of polarization. . The vibration of the gland resulting from a31 (= a32) is used. The
generation of the audible sound described above in the fifth embodiment is completely due to the
thickness stretching vibration of the film caused by a33. Example 6 A circular film of diameter 5
was cut out from the piezoelectric PVDF membrane obtained in Example 6, and this was adhered
to the cut surface of a brass cylinder. Provide a lead wire with conductive paste on the top of this
circular piezoelectric film to make an ultrasonic wave receiver. The piezoelectric film and the lead
wire were coated with silicone resin to make it water resistant. Ultrasonic waves of 2 MHz were
generated from a PZT ultrasonic transducer in a water tank, and ultrasonic waves in water were
received by the above-mentioned piezoelectric polymer membrane ultrasonic receiver at a
position 50 ff away from the ultrasonic wave. 14-43) The output signal could be obtained with a
good S / N ratio. Example 7 An ultrasonic receiver comprising a two-dimensional array of
piezoelectric polymer film ultrasonic transducer elements in which 10 pieces of substitution of 3
mm in diameter are arranged in a ridge line on 10 mm x b 0 mm 1 Were prepared in the same
manner as in Example 6. The array was placed in the same water tank as in Example 6 and the @
sign from 10 electrodes was switched and written on a cathode ray tube, and the output signal
was:-ultrasonic wave of an object placed in front of a dimensional array I reproduced the shadow.
Example 8 An unstretched polyacrylonitrile membrane was pressed at a rate of F 15 times in hot
water at 95 ° C. to obtain a uniaxially stretched membrane with a thickness of 70 μm. Both
sides were steamed Al, voltage applied 1400 V, held at 180 ° C. for 0.5 h, gradually cooled to
room temperature and then the voltage was removed. A piezoelectric film was obtained by this
tooling 1'-. The piezoelectric strain constant at 110H2 is d31 = 0.8 x ID-"C!" At room
temperature. /N、d32=0.1xl0−12c/N、d33=1.8x10−12C!
/Nであった。 The piezoelectric PAN film is used as an ultrasonic transducer. An ultrasonic
delay line having the same structure as in Example 2 is created. When a high frequency pulse
was applied to the first piezoelectric film, a good delayed signal of S / H could be obtained from
the second piezoelectric film. ! Lead di-conate (PZT 15 Ji conquest powder 06I! Against MIJ 9 宕 ·
−) Pv DF 1, P The mixture was mixed well and mixed well at a temperature of 1 鍔 W or more
above the melting temperature of PVDF, and then a film having a thickness of 100 μm was
obtained by a melt film-forming method. The aluminum foil was used as an electrode, and a
voltage of 1 GOOV was applied perpendicularly to the film surface to carry out body mailing at
70 ° C. for 10 hours. The piezoelectric strain enrichment constant of the obtained piezoelectric
film was d31 = d32 = 5 × 10−120 / N, (L53−22 × 10 ′ ′ ′ ′ ′ ′ 207 N. An experiment
was conducted according to Examples 1, 2.5, and 5.6 using this piezoelectric polymer film as an
electroacoustic transducer, and as a result, similar results were obtained in all cases. Although
the above embodiments 1 to 9 show some examples of the electro-acoustic function device using
the electro-acoustic transducer using thickness expansion and contraction of the piezoelectric
polymer film, the mochi 16-45 y, y , + 蒙 It is not limited to this. To mailing, 3. In addition to
those already mentioned as polymers that become piezoelectric according to '$ tiho 1', polyvinyl
fluoride and polyvinyl chloride. Polyvinylidene chloride, nylon 11. Alternatively, a copolymer
containing this as a main component is known. In addition to polyacrylonitrile described in 1-- as
a polymer containing no end group, the present inventors have found that polyacrylonitrile and
copolymers of acrylonitrile and vinylpolyidene chloride also have a good effect by mailing. It has
been found that it becomes a piezoelectric body. The inventors of the present invention found
that +133 of these polymer piezoelectric films has 1 to 5 times as large as a31, and furthermore,
these piezoelectric films are used as electroacoustic transducers using thickness expansion and
contraction of the films. I found it to work. According to the point of view of the present
inventors, the polymer is!
-In order to have high piezoelectricity by ring ing, (1) there is no center of symmetry in the
crystal structure, (2) including polar groups with large dipolar efficiency in the unit Yuko circle,
(3) high temperature The molecules are easy to move and easy to reorient under an electric field.
である。 PVDF or PAN, or a mixture of polymer and pressed 17-4G ceramic ceramic powder
satisfies these conditions. The polyamide having an even number of carbon atoms in the main
chain and the isotactic PAN obtained by a special polymerization method are different from the
polyamide having an odd number of carbon atoms in the main chain and PAN (atactic) obtained
by a general polymerization method The large piezoelectricity is not raw due to the ring. This is
because the former polymer does not satisfy the conditions of il + and +21. Since the crystal
structure of polyvinyl chloride belongs to mmnzi, it is believed that the piezoelectricity is not due
to the crystal part but to the molecular orientation due to the mail field of the amorphous part
due to the シ ji ji jiβ. In this case, the piezoelectricity is expected to disappear at the disclosed
glass transition temperature of the micro-brown motion of the amorphous part, which is
consistent with the experimental facts of the present inventors. In PVDF or PAN obtained by a
conventional polymerization method, it is considered that microcrystals oriented at high
temperature and high electric field mainly give large piezoelectricity. In the future, crystalline 18471, y, 2 piezoelectric polymers with larger electromechanical coupling constants have been
developed, and it is believed that electroacoustic devices that use polymers as functional
materials will be actively used. . Although in the embodiment of the present invention 9 an
example of the operation of the polymer piezoelectric film and the electroacoustic transducer is
shown as an example of -530 MHz, one inventor has observed an operation of up to 120 MH2.
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