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JPS62155700

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DESCRIPTION JPS62155700
[0001]
J. Industrial Field of Application] The present invention relates to an acoustic diaphragm using a
piezoelectric film suitable for use particularly in a microphone. 5 Summary of the Invention] This
invention is an acoustic diaphragm using a piezoelectric film, in particular, by laminating a thin
piezoelectric film having a thickness on which electrode patterns are formed on both sides on a
substrate to constitute an acoustic diaphragm. When used as a microphone, high sensitivity can
be obtained. [Prior Art] An acoustic diaphragm using a conventional piezoelectric film is formed
by laminating and bonding two polarized piezoelectric films together as disclosed in, for example,
Japanese Utility Model Publication No. 54-10918. The piezoelectric film of the present invention
was a bimorph type formed into an accordion shape. That is, as shown in FIG. 8, this type of
conventional acoustic diaphragm laminates and adheres two piezoelectric films 51. 52 different
in polarization direction xl + x 2 and faces each other through the piezoelectric films 51 and 52.
Strip-like electrodes 54 and 55 were provided, and they were configured to be accordion-shaped
as shown in FIG. The electrodes 54 and 55 are arranged so that portions where the strip-like
electrodes face each other and portions where the electrodes do not face alternately occur. As
described above, the electrodes 54 and 55 are arranged such that the short-surface shaped
electrodes alternate between the portions where the electrodes face each other and the portions
where the electrodes do not face each other. It is equivalent to Therefore, when used as a
speaker, the capacitance between the electrodes 54 and 55 can be reduced. The electrodes 54
and 55 may be in the form of a comb, but if the electrodes 54 and 55 are in the form of a comb,
the capacitances generated between the electrodes are connected in parallel, and The
capacitance of the [Problems to be Solved by the Invention] When the above-mentioned
conventional acoustic diaphragm is used as a diaphragm of a speaker, it has a bimorph structure,
and therefore, the tensile force is applied to one of the piezoelectric films 51 or 52. As a result, a
compressive force is generated on the other piezoelectric film 52 or 51, the displacement is
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amplified, and the sensitivity can be increased. However, when it is used as a diaphragm of a
microphone, the diaphragm of the microphone vibrates with sound waves, so whether it is a
bimorph type or a monomorph type, the diaphragm The displacement does not change.
Therefore, when using as a diaphragm of a microphone, it is not necessary to set it as a bimorph
type | mold structure, it may be a monomorph type | mold structure which consists of one
piezoelectric film, and it is desirable that high output voltage is obtained.
Between the electromotive force V of the piezoelectric film and the thickness of the piezoelectric
film, V / F ′ ′ g ++ · 470 ° CF: force + gi +: power generation coefficient, k: beam length. ω:
There is a relationship of angular frequency. Therefore, the smaller the thickness L of the
piezoelectric film, the thicker the electromotive force. The above-described conventional acoustic
diaphragm has a bimorph structure in which piezoelectric films 51. 52 different in polarization
direction are stacked, and electrodes 54 and 55 are opposed to each other via the piezoelectric
films 51 and 52. For this reason, the thickness L of the piezoelectric film is the sum of the
thicknesses of the piezoelectric film 51 and the piezoelectric film 52, the thickness t becomes
large, and there is a problem that a sufficient output voltage can not be obtained. By the way, in a
piezoelectric sensor such as a pyroelectric sensor using a piezoelectric element, there is one in
which a piezoelectric polymer or ceramic is laminated on a thin conductive film. However, in this
type of piezoelectric sensor, a conductive film is used as a substrate, and an electrode is formed
of this "ILM and a film. For this reason, it is impossible to arrange the electrodes so that, for
example, the electrodes are in the form of a strip, and portions in which the electrodes face each
other and portions in which the electrodes do not face alternately occur. Therefore, an object of
the present invention is to provide an acoustic diaphragm which can obtain high sensitivity
particularly when used as a diaphragm of a microphone. [Means for Solving the Problems] In the
present invention, an acoustic vibration is obtained by laminating one sheet of piezoelectric film
1 having electrode patterns 3.4 formed on both sides on a substrate 7 and forming them in an
accordion shape. It is a board. C) The thickness of the piezoelectric film 1 is sufficiently thin, and
the electrodes 3 and 4 are disposed on both sides of the thin piezoelectric film 1. The
piezoelectric film 1 is laminated on the insulating film 7. Therefore, the thickness of the
piezoelectric film 1 becomes thin and the output voltage becomes high. Therefore, high sound
pressure can be obtained. An embodiment of the present invention will be described below with
reference to the drawings. The diaphragm in one embodiment of the present invention is
configured as shown in FIG. In FIG. 1, 1 is a piezoelectric film. The piezoelectric film 1 is obtained
by imparting piezoelectricity to, for example, a PVDF (polyvinylidene fluoride) film, and when
distortion occurs in the piezoelectric film 1, a voltage is generated accordingly. On one surface of
this piezoelectric film 1, as shown in FIG. 2A, a strip-shaped electrode 3 of 7M number is formed
by aluminum vapor deposition. On the other surface of the piezoelectric film l, as shown in FIG.
2B, a plurality of the plurality of strip-like electrodes 3 formed on one surface of the piezoelectric
film 1 are positioned so that their centers are located respectively. The rectangular electrode 4 is
formed by aluminum vapor deposition.
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Therefore, as shown in FIG. 3, the electrodes W1 and W2 do not face the electrodes 3 and 4
formed on both sides of the piezoelectric film 1, as shown in FIG. The parts and plants are born
alternately. Among the strip-like electrodes 3 formed on one surface of the piezoelectric film 1,
the terminal 5 is led out from the electrode 3 </ b> A formed on one end of the piezoelectric film
1. Among the strip-like electrodes 4 formed on the other surface of the piezoelectric film 1, the
terminal 6 is led out from the electrode 4A formed on the other end of the piezoelectric film l. In
FIG. 1, 7 is an insulating film. The insulating film 7 is made of, for example, a P.sub.V.sub.DF film
having a thickness of 50 .mu.m and not provided with piezoelectricity. A piezoelectric film 1
having electrodes 3 and 4 formed on both sides thereof is laminated on the insulating film 7.
Then, as described above, the diaphragm 8 formed by laminating the piezoelectric films 1 having
the electrodes 3 and 4 formed on the insulating film 7 is bent into an accordion shape as shown
in FIG. It is fixed to 9 and 10. As described above, the diaphragm 8 bent in an accordion shape is
fixed to the frames 9 and 10 to constitute a piezoelectric microphone. When a sound wave is
transmitted to the diaphragm 8 of the piezoelectric microphone configured as described above,
vibration occurs in the diaphragm 8. This vibration causes distortion in the diaphragm 8. When
distortion occurs in the piezoelectric film 1 of the diaphragm 8, a voltage is generated according
to the distortion, and this voltage is taken out from the terminal 5 and the terminal 6. As
described above, as shown in FIG. 3, the portions W1 where the electrodes face each other and
the portions W2 where the electrodes do not face each other alternately occur on the weights 3
and 4 of the piezoelectric film 1. An electrostatic capacitance C is generated at a portion W
where the electrodes face each other. The portion W2 in which the electrodes do not face each
other can be regarded as a connection line connecting the electrostatic capacitance C formed in
this manner. Therefore, the electrodes 3 and 4 are equivalent to connecting the electrostatic
capacitance C in series as shown by the equivalent circuit in FIG. Therefore, from the terminals 5
and 6, a voltage equal to the number obtained by adding the voltage generated from the portion
W where the electrodes 3 and 4 are opposite due to the distortion of the piezoelectric film 1 is
output. The sound wave is transmitted to the diaphragm 8, and the arrow F in FIG. When the
force indicated by is applied, the diaphragm 8 is displaced as shown in FIG. Therefore, one
surface S1 of the diaphragm 8 extends, and the other surface S2 of the diaphragm 8 contracts.
The extension and contraction of the diaphragm 8 at this time become so thick that the distances
+41 + and 12 from the center M of the diaphragm 8 become longer.
The piezoelectric film 1 is stacked on the diaphragm 8 and the insulating film 7, and the
thickness of the piezoelectric film 1 is sufficiently thin relative to the thickness of the insulating
film 7. For this reason, when the diaphragm 8 is deformed, the piezoelectric film l is largely
distorted, and the piezoelectric film 1 receives a large stress. In addition, the smaller the
thickness of the piezoelectric film l, the higher the electromotive voltage, and the higher the
piezoelectric voltage, piezoelectric), the thickness L of the illumination 1 and the electromotive
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voltage of the piezoelectric film l. There is a relationship of / ωt. The piezoelectric film 1 is
sufficiently thin. Therefore, the output voltage is high. As described above, in the diaphragm 8,
the thickness of the piezoelectric film 1 is sufficiently thin with respect to the thickness of the
insulating film 7, and the portion W1 in which the electrode faces the piezoelectric film 1 and the
portion W2 in which the electrode does not face alternately occur. The electrodes 3 and 4 are
arranged on the Therefore, the output voltages from the terminals 5 and 6 become very high
voltages. In the above-described embodiment, a PVDF film not provided with piezoelectricity is
used as the insulating film 7 to be a base, and a PVDF film provided with piezoelectricity as the
piezoelectric film 1 is used to & Iam! The piezoelectric film 1 is laminated and adhered to the film
7. However, if the ion plating method or plasma CVD is used, the piezoelectric film 1 can be
formed into a thin film shape, the output voltage can be further increased, and the sensitivity is
increased. it can. For example, an electrode pattern is aluminum-deposited on one side of a 15
μm thick polyester film with a diaphragm 8 formed thereon, and this polyester film has a strip
shape of ion play number? ? ii4 is formed by aluminum base. Therefore, as shown in FIG. 3, the
electrodes fi 3 and 4 formed on both sides of the piezoelectric film 1 alternately have a portion in
which the electrodes indicated by Wl face each other and a portion in which the electrodes
indicated by W2 do not face each other. It occurs. Among the strip-like electrodes 3 formed on
one surface of the piezoelectric film 1, the terminal 5 is led out from the electrode 3 </ b> A
formed on one end of the piezoelectric film 1. Among the strip-like electrodes 4 formed on the
other surface of the piezoelectric film 1, the terminal 6 is derived from the electrode 4 </ b> A
formed on the other end of the piezoelectric film 1. In FIG. 1, 7 is an insulating film. The
insulating film 7 is made of, for example, a PVDF film having a thickness of 50 μm and not
provided with piezoelectricity. A piezoelectric film 1 having electrodes 3 and 4 formed on both
sides thereof is laminated on the insulating film 7. Then, as described above, the diaphragm 8
formed by laminating the piezoelectric films 1 having the electrodes 3 and 4 formed on the
insulating film 7 is bent into an accordion shape as shown in FIG. It is fixed to 9 and 1O.
As described above, the diaphragm 8 bent in an accordion shape is fixed to the frames 9 and 10
to constitute a piezoelectric microphone. When a sound wave is transmitted to the diaphragm 8
of the piezoelectric microphone configured as described above, vibration occurs in the
diaphragm 8. This vibration causes distortion in the diaphragm 8. When distortion occurs in the
piezoelectric film 1 of the diaphragm 8, a voltage is generated according to the distortion, and
this voltage is taken out from the terminal 5 and the terminal 6. As described above, in the
electrodes 3 and 4 of the piezoelectric film 1, as shown in FIG. 3, the portions W1 facing the
electrodes and the portions W2 not facing the electrodes alternately occur. An electrostatic
capacitance C is generated at a portion W where the electrodes face each other. And the part W2
which an electrode does not oppose can be regarded as a connecting wire which connects the
electrostatic capacitance C formed in this way. Therefore, the electrodes 3 and 4 are equivalent
to connecting the electrostatic capacitance C in series as shown by the equivalent circuit in FIG.
Therefore, from the terminals 5 and 6, a voltage equal to the number obtained by adding the
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number of voltages generated from the portion WI where the electrodes 3 and 4 are paired due
to the distortion of the piezoelectric film 1 is outputted. When a sound wave is transmitted to the
diaphragm 8 and a force shown by an arrow F0 in FIG. 6 is applied to the diaphragm 8, the
diaphragm 8 is displaced as shown in FIG. Therefore, one surface S of the diaphragm 8 is
extended, and the other surface S2 of the diaphragm 8 is contracted. The extension and
contraction of the diaphragm 8 at this time is the distance from the center M of the diaphragm 8!
, And e2 becomes thicker (becomes longer). The diaphragm 8 is configured by laminating the
piezoelectric film 1 on the insulating film 7, and the thickness of the piezoelectric film 1 is
sufficiently thin relative to the thickness of the insulating film 7. For this reason, when the
diaphragm 8 is deformed, the piezoelectric film l is largely distorted, and the piezoelectric film 1
receives a large stress. Further, the piezoelectric film 1 has a thin thickness, and the voltage is
high (, piezoelectric), and the relationship of V / F processing gx + · l / ωt is between the
thickness L of the film 1 and the electromotive voltage of the piezoelectric film l. is there. The
piezoelectric film 1 is sufficiently thin. Therefore, the output voltage is high. As described above,
in the diaphragm 8, the thickness of the piezoelectric film 1 is sufficiently thin with respect to the
thickness of the insulating film 7, and the portion W1 in which the electrode faces the
piezoelectric film 1 and the portion W2 in which the electrode does not face alternately occur.
The electrodes 3 and 4 are arranged on the Therefore, the output voltages from the terminals 5
and 6 become very high voltages. In the above-described embodiment, a PVDF film not provided
with piezoelectricity is used as the insulating film 7 as a substrate, a PVDF film provided with
piezoelectricity as the piezoelectric film 1, and the piezoelectric film 1 is used as the insulating
film 7. Although lamination is made to adhere, if the ion plating method or plasma CVD is used,
the piezoelectric film 1 can be formed into a thin film, the output voltage can be further
increased, and the sensitivity can be increased.
For example, an electrode pattern is aluminum-deposited on one side of a 15 μm thick polyester
film of diaphragm 8 and this polyester film is ion pre-FIG. 1, FIG. 2, FIG. -J----14 "to the eyebrow
of the eyebrow (I δ In In j j-Fig 5 it, t IJ 欠 /) イ i i) 議 議 Y 刀-5-5. 夕 ・ ・ ・ 20 50 100 200
500 1 K 2 K 5 to IOK 20 for 21 I comparison H 2 945, 11 meat meat ff 1 ·] 12] Fig. 7 m Aw-J itl
A 161 ff] Fig. 8 4 4 [ Fig. 9 Procedure correction amount date Fig. 9 Procedure correction date
August 15, 1986 Secretary General of Patent Office Black 1) Akio Hall 1, display of case Showa
6019 patent application No. 295294 2, title of the invention Acoustic diaphragm 3, correction
Relationship with the case to do patent applicant address for concave parts for Tokyo parts 6chome 7-35 name (218) Sony Corporation Representative Director Norio Oga 4; agent address 148, Higashi-Ikebukuro, Toshima-ku, Tokyo 10 No. 6, object of correction Drawing 7, contents of
correction In the drawing, correct FIG. 9 as shown in the attached drawing. 芝 イ row 9
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