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JPWO2016017632

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DESCRIPTION JPWO2016017632
Abstract: An electroacoustic transducer film and an electroacoustic transducer capable of stably
playing high-quality sound with a single diaphragm and capable of widening a reproducible
frequency band are provided. A polymer composite piezoelectric body in which piezoelectric
particles are dispersed in a viscoelastic matrix made of a polymer material having viscoelasticity
at normal temperature, and a pair of electrode pairs laminated on both sides of the polymer
composite piezoelectric body And one or more convex portions formed in a convex shape so as to
protrude to one main surface side.
Electro-acoustic transducer film and electro-acoustic transducer
[0001]
The present invention relates to an electro-acoustic transducer film used for an acoustic device
such as a speaker, and an electro-acoustic transducer using the same.
[0002]
In order to correspond to the thinning of displays such as liquid crystal displays and organic EL
displays, weight reduction and thinning of speakers used for these thin displays are required.
Furthermore, in the flexible display having flexibility, flexibility is also required in order to be
integrated into the flexible display without losing its lightness and flexibility. As such a
lightweight, thin and flexible speaker, it is considered to employ a sheet-like piezoelectric film
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1
having a property of expanding and contracting in response to an applied voltage.
[0003]
For example, Patent Document 1 describes using, as a piezoelectric film, a uniaxially stretched
film of polyvinylidene fluoride (PVDF: Poly Vinyli Dene Fluoride) polarized with a high voltage. In
order to adopt such a piezoelectric film as a speaker, it is necessary to convert the stretching
movement along the film surface into the vibration of the film surface. The conversion from the
stretching movement to the vibration is achieved by holding the piezoelectric film in a curved
state, which enables the piezoelectric film to function as a speaker.
[0004]
However, since a piezoelectric film made of uniaxially stretched PVDF has in-plane anisotropy in
its piezoelectric characteristics, the sound quality is largely different depending on the bending
direction even with the same curvature. Furthermore, since PVDF has a small loss tangent
compared to a general speaker diaphragm such as cone paper, resonance tends to be strong and
frequency characteristics of severe undulations are obtained. Therefore, the amount of change in
sound quality when the lowest resonance frequency changes with the change in curvature also
increases. As described above, it was difficult to reproduce stable sound with a piezoelectric film
made of PVDF.
[0005]
Therefore, the applicant of the present application is a polymer material having visco-elasticity at
ordinary temperature, disclosed in Patent Document 2, as a speaker having flexibility and
capable of stably reproducing high-quality sound. Polymer composite piezoelectric body in which
piezoelectric particles are dispersed in a visco-elastic matrix, a thin film electrode formed on both
sides of the polymer composite piezoelectric body, and a protective layer formed on the surface
of the thin film electrode An acoustic conversion film was proposed.
[0006]
JP 2008-294493 JP 2014-14063 JP
[0007]
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2
The electroacoustic conversion film described in Patent Document 2 is hard against vibrations of
20 to 20 kHz and vibrations of several Hz or less by using the material of the piezoelectric layer
as a polymer material having viscoelasticity at normal temperature. It is possible for it to behave
softly, and has a moderate loss tangent for vibrations of all frequencies below 20 kHz.
Therefore, it is excellent in flexibility and acoustic characteristics, and it is possible to output a
stable voice even if it is deformed, and it is excellent in flexibility and acoustic characteristics, and
it is possible to output a stable sound even if it is deformed.
However, since the electroacoustic conversion film described in Patent Document 2 is a single
diaphragm, it has been found that there is a problem that the reproducible frequency band with
high sound quality and sufficient volume is somewhat narrow.
[0008]
Here, in Patent Document 1, the audio signal is corrected so as to increase or decrease the
amplitude by a predetermined amount for each frequency band, and has a plurality of filters each
provided with a unique correction pattern, according to the degree of curvature of the measured
speaker It is described that one of the filters is selected, the audio signal is corrected by this
filter, and the sound quality such as the frequency characteristic and the volume is improved by
outputting to the speaker. However, in the configuration for correcting the audio signal input to
the speaker, the improvement of the frequency characteristic and the volume is insufficient.
[0009]
An object of the present invention is to solve the problems of the prior art as described above,
and one diaphragm can stably reproduce sound with high sound quality and sufficient volume in
a wide frequency band. An acoustic transducer film and an electroacoustic transducer are
provided.
[0010]
As a result of intensive studies to solve the above problems, the inventors of the present
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3
invention have found that a polymer composite piezoelectric body formed by dispersing
piezoelectric particles in a visco-elastic matrix made of a polymer material having visco-elastic
properties at normal temperature, and a polymer composite A single diaphragm by having at
least one convex portion formed in a convex shape so as to protrude on one main surface side,
having a pair of electrode pairs stacked on both sides of the piezoelectric body. Even in the wide
frequency band, the inventors found that high-quality sound can be stably reproduced at a
sufficient volume, and completed the present invention.
That is, the present invention provides an electroacoustic transducer film and an electroacoustic
transducer having the following configurations.
[0011]
(1) A polymer composite piezoelectric body obtained by dispersing piezoelectric particles in a
viscoelastic matrix made of a polymer material having viscoelasticity at normal temperature, and
a pair of electrode pairs laminated on both sides of the polymer composite piezoelectric body An
electroacoustic transducing film having at least one convex portion formed into a convex shape
so as to protrude on one main surface side. (2) The maximum height d of the convex portion with
respect to the main surface and the maximum length L of the convex portion when viewed from
the direction perpendicular to the main surface satisfy the relationship of d ≦ 0.5 × L (1 The
electroacoustic conversion film as described in 2.). (3) The electroacoustic conversion film
according to (1) or (2), wherein the convex portion is curved in at least one direction. (4) The
electroacoustic conversion according to any one of (1) to (3), wherein the convex portion is
curved in a cross section in one direction perpendicular to the main surface and in a cross
section in the other direction orthogonal to the one direction. the film. (5) The electroacoustic
conversion according to any one of (2) to (4), which has two or more projections, and at least two
of the two or more projections have different surface areas and / or radii of curvature from one
another. the film. (6) The electroacoustic conversion film in any one of (1)-(5) which has a several
electrode pair laminated | stacked according to the formation area of a convex part. (7) The
storage elastic modulus (E ') at a frequency of 1 Hz measured by dynamic viscoelasticity
measurement of the electroacoustic transducer film is 10 to 30 GPa at 0 ° C. and 1 to 10 GPa at
50 ° C. (1) to (6) The electroacoustic conversion film as described in any one of the above. (8)
The electroacoustic conversion film according to any one of (1) to (7), wherein the glass
transition temperature at a frequency of 1 Hz of the polymer material is 0 to 50 ° C. (9) A
maximum value at which the loss tangent (Tan δ) at a frequency of 1 Hz is 0.5 or more as
measured by dynamic viscoelasticity measurement of a polymer material is present in a
temperature range of 0 to 50 ° C. (1) to (8) The electroacoustic conversion film as described in
any one of the above. (10) The electroacoustic converter film according to any one of (1) to (9),
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wherein the polymer material has a cyanoethyl group. (11) The electroacoustic conversion film
according to any one of (1) to (10), wherein the polymer material is cyanoethylated polyvinyl
alcohol. (12) An electro-acoustic transducer comprising the electro-acoustic conversion film
according to any one of (1) to (11) and a support member for supporting the electro-acoustic
conversion film, wherein the support member is an electro-acoustic conversion film An electroacoustic transducer for supporting an electro-acoustic transducer film in a state in which the
main surface is curved. (13) The electroacoustic transducer according to (12), wherein the one or
more convex portions of the electroacoustic transducer film project in the same direction as the
projecting direction of the curvature of the main surface.
(14) The electro-acoustic transducer according to (12), wherein one or more convex portions of
the electro-acoustic transducer film project in a direction opposite to the projecting direction of
the curvature of the main surface. (15) A polymer composite piezoelectric body obtained by
dispersing piezoelectric particles in a viscoelastic matrix made of a polymer material having
viscoelasticity at normal temperature, and a pair of electrode pairs laminated on both sides of the
polymer composite piezoelectric body And a support member for supporting the electroacoustic
conversion film, wherein the electroacoustic conversion film is formed of two or more areas
different in at least one of the area and the radius of curvature. Electro-acoustic transducers
supported. (16) The electro-acoustic transducer according to (15), wherein at least two of the two
or more regions overlap in a direction perpendicular to the main surface of the electro-acoustic
transducer film. (17) The electroacoustic transducer according to (16), wherein one of the two or
more zones is formed by curving the main surface of the electroacoustic transducer film. (18)
The electroacoustic transducer according to any one of (15) to (17), which has three or more
regions, and at least two of which have different areas and / or radii of curvature from one
another. (19) The electroacoustic transducer according to any one of (15) to (18), wherein the
area is curved in at least one direction. (20) The electric field according to any one of (15) to
(19), wherein the region is curved in a cross section in one direction perpendicular to the main
surface of the piezoelectric film and in a cross direction in the other direction orthogonal to the
one direction. Acoustic transducer.
[0012]
According to the electro-acoustic transducer film and the electro-acoustic transducer of the
present invention, it is possible to stably reproduce sound with high sound quality and sufficient
sound volume in a wide frequency band with one diaphragm.
[0013]
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Fig. 1 (A) is a perspective view conceptually showing an example of the electro-acoustic
conversion film of the present invention, and Fig. 1 (B) is a cross-sectional view taken along the
line B-B of Fig. 1 (A). (C) is the CC sectional view taken on the line of FIG. 1 (A).
FIG. 2 (A) is a top view conceptually showing an example of an electroacoustic transducer using
the electroacoustic transducer film of the present invention, and FIG. 2 (B) is a sectional view
taken along the line B-B in FIG. 2 (A). FIG. 2C is a cross-sectional view of another example of the
electroacoustic transducer. It is a schematic sectional drawing which expands and shows a part
of electroacoustic conversion film shown to FIG. 1 (A). FIGS. 4A to 4E are conceptual diagrams
for explaining the definition of the size of the conversion unit. FIG. 5 (A) is a top view
conceptually showing another example of the electroacoustic transducing film of the present
invention, and FIG. 5 (B) is a cross-sectional view taken along the line B-B of FIG. 5 (A). Fig. 6 (A)
is a top view conceptually showing another example of the electro-acoustic transducer film of the
present invention, and Fig. 6 (B) is a cross-sectional view taken along the line B-B of Fig. 6 (A). It
is sectional drawing which shows notionally another example of the electroacoustic transducing
film of this invention. Fig. 8 (A) is a top view conceptually showing another example of the
electroacoustic transducing film of the present invention, and Fig. 8 (B) is a cross-sectional view
taken along the line B-B of Fig. 8 (A). FIG. 8C is a cross-sectional view taken along the line C-C of
FIG. FIG. 9A to FIG. 9E are conceptual diagrams for describing an example of a method for
producing an electroacoustic conversion film. Fig. 10 (A) is a top view conceptually showing
another example of the electro-acoustic transducer film of the present invention, and Fig. 10 (B)
is a cross-sectional view taken along the line B-B of Fig. 10 (A). FIG. 10C is a cross-sectional view
taken along the line C-C in FIG. Fig. 11 (A) is a top view conceptually showing another example of
the electroacoustic transducing film of the present invention, and Fig. 11 (B) is a cross-sectional
view taken along the line B-B of Fig. 11 (A). FIG.11 (C) is CC sectional view taken on the line of
FIG. 11 (A). 12 (A) is a top view conceptually showing another example of the electroacoustic
transducer film of the present invention, and FIG. 12 (B) is a cross-sectional view taken along the
line B-B of FIG. 12 (A). FIG.12 (C) is CC sectional view taken on the line of FIG. 12 (A). Fig. 13 (A)
is a top view conceptually showing another example of the electro-acoustic transducer film of the
present invention, and Fig. 13 (B) is a cross-sectional view taken along the line B-B of Fig. 13 (A).
FIG.13 (C) is CC sectional view taken on the line of FIG. 13 (A). It is a graph showing the relation
between frequency and sound pressure level.
[0014]
Hereinafter, the electro-acoustic transducer film and the electro-acoustic transducer of the
present invention will be described in detail based on the preferred embodiments shown in the
attached drawings.
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6
[0015]
FIG. 1 (A) shows a perspective view conceptually showing an example of the electroacoustic
transducing film of the present invention, FIG. 1 (B) shows a cross-sectional view taken along the
line B-B of FIG. 1 (A), (C) shows a cross-sectional view taken along the line C-C in FIG.
Moreover, an example of the electroacoustic transducer of this invention which uses the
electroacoustic transducer film of FIG. 1 in FIG. 2 (A) and FIG. 2 (B) is shown notionally. As shown
in FIGS. 2A and 2B, the electroacoustic transducer 80 uses an electroacoustic transducer film
(hereinafter also referred to as a “transducer film”) 10 as a diaphragm.
[0016]
Such an electroacoustic transducer 80 is used as various acoustic devices such as a speaker, a
microphone, and a pickup used for a musical instrument such as a guitar, and an electrical signal
is input to the conversion film 10 to be an electrical signal. Are used to reproduce sound or to
convert the vibration of the conversion film 10 due to the sound into an electrical signal.
[0017]
Here, as shown in FIG. 1 (A), the conversion film 10 of the present invention is formed into a
convex shape so as to protrude to the one main surface side substantially at the center of the one
main surface. The convex portion 10a is formed.
Therefore, as shown in FIG. 2 (B), the electroacoustic transducer 80 using the conversion film 10
converts the first region where the conversion film 10 is composed of the convex portion 10a
formed on the conversion film 10, and The film 10 has a second region consisting of the entire
main surface excluding the convex portion 10a, and the first region and the second region have
different surface areas, and the first region and the second region And has a configuration that is
supported in a curved state with different curvatures. As a result, since it is possible to suitably
differentiate the frequency band that vibrates between the first area and the second area, it is
possible to widen the reproducible frequency band with a single diaphragm without degrading
the sound quality. Can be This point will be described in detail later.
[0018]
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7
First, the electroacoustic conversion film of the present invention will be described. FIG. 3 is a
partial enlarged cross-sectional view of the conversion film 10 shown in FIG. As shown in FIG. 1A
to FIG. 1C and FIG. 3, the conversion film 10 is provided on one surface of the piezoelectric layer
12 which is a sheet-like material having piezoelectricity and the piezoelectric layer 12. The lower
thin film electrode 14 to be stacked, the lower protective layer 18 to be stacked on the lower thin
film electrode 14, the upper thin film electrode 16 to be stacked on the other surface of the
piezoelectric layer 12, and the upper thin film electrode 16 And a convex portion 10a is formed
substantially at the center of the main surface.
[0019]
In the conversion film 10 of the present invention, the piezoelectric layer 12, which is a polymer
composite piezoelectric material, is piezoelectric in a visco-elastic matrix 24 made of a polymer
material having visco-elastic properties at ordinary temperature as schematically shown in FIG. It
is made of a polymer composite piezoelectric material in which body particles 26 are uniformly
dispersed. In the present specification, “normal temperature” refers to a temperature range of
about 0 to 50 ° C. Further, although described later, the piezoelectric layer 12 is preferably
subjected to polarization treatment.
[0020]
The conversion film 10 of the present invention is suitably used as a speaker having flexibility,
such as a speaker for a flexible display. Here, it is preferable that the polymer composite
piezoelectric material (piezoelectric material layer 12) used for the speaker having flexibility has
the following requirements. (I) Flexibility For example, when holding in a loosely bent state in a
document sense like a newspaper or magazine for portable use, constantly receiving a relatively
slow, large bending deformation of several Hz or less from the outside become. At this time, if the
polymer composite piezoelectric body is hard, a large bending stress is generated, and a crack is
generated at the interface between the polymer matrix and the piezoelectric particles, which may
eventually lead to breakage. Therefore, the polymer composite piezoelectric body is required to
have appropriate softness. In addition, if strain energy can be diffused to the outside as heat,
stress can be relaxed. Therefore, it is required that the loss tangent of the polymer composite
piezoelectric body be appropriately large. (Ii) The sound quality speaker vibrates the piezoelectric
particles at a frequency of the audio band of 20 Hz to 20 kHz, and the vibration energy
reproduces the sound by vibrating the entire diaphragm (polymer composite piezoelectric
12-05-2019
8
material) integrally. Ru. Therefore, in order to enhance the transmission efficiency of vibrational
energy, the polymer composite piezoelectric body is required to have an appropriate hardness. In
addition, if the frequency characteristic of the speaker is smooth, the amount of change in sound
quality when the lowest resonance frequency f 0 changes with the change in curvature also
decreases. Therefore, the loss tangent of the polymer composite piezoelectric material is required
to be moderately large.
[0021]
Summarizing the above, it is required that the polymer composite piezoelectric material used for
the speaker having flexibility should be hard for vibrations of 20 Hz to 20 kHz, and be soft for
vibrations of several Hz or less. In addition, the loss tangent of the polymer composite
piezoelectric body is required to be appropriately large for vibrations of all frequencies of 20 kHz
or less.
[0022]
Generally, macromolecular solid has a viscoelastic relaxation mechanism, and large scale
molecular motions decrease storage elastic modulus (Young's modulus) with the increase of
temperature or decrease in frequency (relaxation) or maximum of loss elastic modulus
(absorption) It is observed as Among them, the relaxation caused by the micro brown motion of
molecular chains in the amorphous region is called main dispersion, and a very large relaxation
phenomenon is observed. The temperature at which this main dispersion occurs is the glass
transition point (Tg), and the viscoelastic relaxation mechanism appears most notably. In a
polymer composite piezoelectric material (piezoelectric layer 12), a polymer material having a
glass transition temperature at normal temperature, in other words, a polymer material having
viscoelasticity at normal temperature, is used as a matrix for vibrations of 20 to 20 kHz. A
polymer composite piezoelectric material that is hard and behaves softly for slow vibrations of
several Hz or less is realized. In particular, it is preferable to use a polymer material having a
glass transition temperature at a frequency of 1 Hz at ordinary temperature, that is, 0 to 50 ° C.,
as the matrix of the polymer composite piezoelectric material, in that this behavior suitably
appears. .
[0023]
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9
Various known materials can be used as the polymer material having viscoelasticity at normal
temperature. Preferably, at normal temperature, that is, 0 to 50 ° C., a polymer material having
a maximum value of 0.5 or more of loss tangent Tan δ at a frequency of 1 Hz according to
dynamic viscoelasticity test is used. Thereby, when the polymer composite piezoelectric material
is slowly bent by an external force, stress concentration at the polymer matrix / piezoelectric
particle interface at the maximum bending moment portion is relaxed, and high flexibility can be
expected.
[0024]
Moreover, as for a polymeric material, it is preferable that the storage elastic modulus (E ') in
frequency 1 Hz by dynamic-viscoelasticity measurement is 100 Mpa or more at 0 degreeC, and
10 Mpa or less at 50 degreeC. As a result, the bending moment generated when the polymer
composite piezoelectric material is slowly bent by an external force can be reduced, and at the
same time, it can behave hard against acoustic vibration of 20 Hz to 20 kHz.
[0025]
In addition, it is more preferable that the polymer material has a relative dielectric constant of 10
or more at 25 ° C. Thus, when a voltage is applied to the polymer composite piezoelectric
material, a higher electric field is applied to the piezoelectric particles in the polymer matrix, and
a large amount of deformation can be expected. However, on the other hand, it is also preferable
that the polymer material has a relative dielectric constant of 10 or less at 25 ° C. in
consideration of securing of good moisture resistance and the like.
[0026]
Examples of polymer materials that satisfy such conditions include cyanoethylated polyvinyl
alcohol (cyanoethylated PVA), polyvinyl acetate, polyvinylidene chloride coacrylonitrile,
polystyrene-vinyl polyisoprene block copolymer, polyvinyl methyl ketone, and polybutyl. A
methacrylate etc. are illustrated. Moreover, as these high molecular materials, commercially
available products such as HYBLER 5127 (manufactured by Kuraray Co., Ltd.) can be suitably
used. Among them, it is preferable to use a material having a cyanoethyl group, and it is
particularly preferable to use a cyanoethylated PVA. In addition, only 1 type may be used for
these polymeric materials, and multiple types may be used together (mixing) and using them.
12-05-2019
10
[0027]
The viscoelastic matrix 24 using such a polymeric material having viscoelasticity at normal
temperature may use a plurality of polymeric materials in combination, as necessary. That is, in
addition to the viscoelastic material such as cyanoethylated PVA, other dielectric polymer
materials may be added to the viscoelastic matrix 24 for the purpose of adjusting the dielectric
characteristics and mechanical characteristics. .
[0028]
Examples of dielectric polymer materials that can be added include polyvinylidene fluoride,
vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene
copolymer, and polyvinylidene fluoride-trifluoroethylene copolymer. And fluorinated polymers
such as polyvinylidene fluoride-tetrafluoroethylene copolymer, vinylidene cyanide-vinyl acetate
copolymer, cyanoethyl cellulose, cyanoethyl hydroxysaccharose, cyanoethyl hydroxycellulose,
cyanoethyl hydroxy pullulan, cyanoethyl methacrylate, cyanoethyl acrylate, cyanoethyl acrylate
Hydroxyethyl cellulose, cyanoethyl amylose, cyanoethyl hydroxypropyl cellulose, cyanoethyl
dihydroxypropyl cellulose, Polymers having cyano group or cyanoethyl group such as noethyl
hydroxypropyl amylose, cyanoethyl polyacrylamide, cyanoethyl polyacrylate, cyanoethyl
pullulan, cyanoethyl polyhydroxy methylene, cyanoethyl glycidol pullulan, cyanoethyl saccharose
and cyanoethyl sorbitol, synthesis of nitrile rubber, chloroprene rubber etc Rubber etc. are
illustrated. Among them, a polymeric material having a cyanoethyl group is suitably used.
Further, the dielectric polymer added in addition to the material having viscoelasticity at normal
temperature such as cyanoethylated PVA in the viscoelastic matrix 24 of the piezoelectric layer
12 is not limited to one type, and plural types are added. It is also good.
[0029]
In addition to dielectric polymers, thermoplastic resins such as vinyl chloride resin, polyethylene,
polystyrene, methacrylic resin, polybutene, isobutylene, phenol resin, urea resin, melamine resin,
for the purpose of adjusting the glass transition point Tg. A thermosetting resin such as alkyd
resin or mica may be added. Furthermore, tackifiers such as rosin esters, rosins, terpenes,
terpene phenols, petroleum resins and the like may be added for the purpose of improving the
tackiness.
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[0030]
The amount of addition of a polymer other than a visco-elastic material such as cyanoethylated
PVA in the visco-elastic matrix 24 of the piezoelectric layer 12 is not particularly limited, but it is
30% by weight or less in the visco-elastic matrix 24 It is preferable to Thereby, the characteristics
of the polymer material to be added can be expressed without impairing the viscoelastic
relaxation mechanism in the viscoelastic matrix 24, so that the dielectric constant can be
increased, the heat resistance can be improved, and the adhesion with the piezoelectric particles
26 and the electrode layer Favorable results can be obtained in terms of improvement and the
like.
[0031]
The piezoelectric particles 26 are made of ceramic particles having a perovskite or wurtzite
crystal structure. Examples of ceramic particles constituting the piezoelectric particles 26 include
lead zirconate titanate (PZT), lead zirconate titanate zirconate (PLZT), barium titanate (BaTiO3),
zinc oxide (ZnO), and titanium. Examples include a solid solution (BFBT) of barium acid and
bismuth ferrite (BiFe3).
[0032]
The particle diameter of such piezoelectric particles 26 may be appropriately selected according
to the size and application of the conversion film 10, but according to the study of the present
inventor, 1 to 10 μm is preferable. By setting the particle diameter of the piezoelectric particles
26 in the above range, preferable results can be obtained in that high piezoelectric
characteristics and flexibility can be compatible.
[0033]
In FIG. 3, the piezoelectric particles 26 in the piezoelectric layer 12 are dispersed in the
viscoelastic matrix 24 with regularity, but the present invention is not limited to this. That is, the
piezoelectric particles 26 in the piezoelectric layer 12 may be irregularly dispersed in the
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12
viscoelastic matrix 24 as long as they are preferably dispersed uniformly.
[0034]
In the conversion film 10 of the present invention, the quantitative ratio of the visco-elastic
matrix 24 to the piezoelectric particles 26 in the piezoelectric layer 12 is the size and thickness
in the plane direction of the conversion film 10, the application of the conversion film 10, the
conversion film 10 It may be set appropriately according to the characteristics required of Here,
according to the study of the present inventor, the volume fraction of the piezoelectric particles
26 in the piezoelectric layer 12 is preferably 30 to 70%, and more preferably 50% or more. It is
more preferable to make it 70%. By setting the ratio of the viscoelastic matrix 24 to the
piezoelectric particles 26 in the above range, preferable results can be obtained in that high
piezoelectric characteristics and flexibility can be compatible.
[0035]
Further, in the conversion film 10 of the present invention, the thickness of the piezoelectric
layer 12 is not particularly limited, depending on the size of the conversion film 10, the
application of the conversion film 10, the characteristics required of the conversion film 10, etc.
It may be set as appropriate. Here, according to the study of the present inventor, the thickness
of the piezoelectric layer 12 is preferably 10 μm to 300 μm, more preferably 20 to 200 μm,
and particularly preferably 30 to 100 μm. By setting the thickness of the piezoelectric layer 12
in the above range, preferable results can be obtained in terms of coexistence of securing of
rigidity and appropriate flexibility. As described above, the piezoelectric layer 12 is preferably
subjected to polarization processing (poling). The polarization process will be described in detail
later.
[0036]
As shown in FIG. 3, in the conversion film 10 of the present invention, the lower thin film
electrode 14 is formed on one surface of such a piezoelectric layer 12, and the lower protective
layer 18 is formed thereon. An upper thin film electrode 16 is formed on the other surface, and
an upper protective layer 20 is formed thereon. Here, the upper thin film electrode 16 and the
lower thin film electrode 14 form an electrode pair. In addition to the layers, the conversion film
10 covers, for example, the upper thin film electrode 16 and an electrode lead-out portion for
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13
drawing out the electrode from the lower thin film electrode 14 and a region where the
piezoelectric layer 12 is exposed. And an insulating layer or the like for preventing a short or the
like.
[0037]
That is, in the conversion film 10, both surfaces of the piezoelectric layer 12 are sandwiched by
the electrode pair, that is, the upper thin film electrode 16 and the lower thin film electrode 14,
and the laminate is sandwiched by the upper protective layer 20 and the lower protective layer
18. The configuration is as follows. Thus, the region held by the upper thin film electrode 16 and
the lower thin film electrode 14 is driven according to the applied voltage.
[0038]
In the conversion film 10, the upper protective layer 20 and the lower protective layer 18 serve
to provide the piezoelectric layer 12 with appropriate rigidity and mechanical strength. That is, in
the conversion film 10 of the present invention, the piezoelectric layer 12 composed of the
viscoelastic matrix 24 and the piezoelectric particles 26 exhibits very excellent flexibility against
slow bending deformation, Depending on the application, rigidity and mechanical strength may
be insufficient. The conversion film 10 is provided with the upper protective layer 20 and the
lower protective layer 18 to compensate for it.
[0039]
The upper protective layer 20 and the lower protective layer 18 are not particularly limited, and
various sheet materials can be used. As an example, various resin films are preferably
exemplified. Among them, polyethylene terephthalate (PET), polypropylene (PP), polystyrene
(PS), polycarbonate (PC), polyphenylene sulfide (PPS), polymethyl methacrylate (PMMA) and the
like because of having excellent mechanical properties and heat resistance. And polyetherimide
(PEI), polyimide (PI), polyethylene naphthalate (PEN), triacetyl cellulose (TAC), and cyclic olefin
resins are preferably used.
[0040]
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14
The thickness of the upper protective layer 20 and the lower protective layer 18 is not
particularly limited. Also, the thicknesses of the upper protective layer 20 and the lower
protective layer 18 are basically the same but may be different. Here, when the rigidity of the
upper protective layer 20 and the lower protective layer 18 is too high, not only the expansion
and contraction of the piezoelectric layer 12 is restrained, but also the flexibility is impaired, so
that the mechanical strength and the sheet-like material are good. The upper protective layer 20
and the lower protective layer 18 are more advantageously thinner, except when handling is
required.
[0041]
According to the study of the present inventor, if the thickness of the upper protective layer 20
and the lower protective layer 18 is not more than twice the thickness of the piezoelectric layer
12, compatibility between securing of rigidity and appropriate flexibility, etc. Favorable results
can be obtained in terms of For example, when the thickness of the piezoelectric layer 12 is 50
μm and the upper protective layer 20 and the lower protective layer 18 are made of PET, the
thickness of the upper protective layer 20 and the lower protective layer 18 is preferably 100
μm or less, more preferably 50 μm or less Among these, 25 μm or less is preferable.
[0042]
In the conversion film 10 of the present invention, an upper thin film electrode (hereinafter also
referred to as an upper electrode) 16 is provided between the piezoelectric layer 12 and the
upper protective layer 20, and an upper thin film electrode is provided between the piezoelectric
layer 12 and the lower protective layer 18. Lower thin film electrodes (hereinafter also referred
to as lower electrodes) 14 are formed respectively. The upper electrode 16 and the lower
electrode 14 are provided to apply an electric field to the conversion film 10 (piezoelectric layer
12).
[0043]
In the present invention, the materials for forming the upper electrode 16 and the lower
electrode 14 are not particularly limited, and various conductors can be used. Specific examples
thereof include carbon, palladium, iron, tin, aluminum, nickel, platinum, gold, silver, copper,
12-05-2019
15
chromium and molybdenum, alloys of these, indium tin oxide and the like. Among them, any of
copper, aluminum, gold, silver, platinum and indium tin oxide is suitably exemplified.
[0044]
Further, the method of forming the upper electrode 16 and the lower electrode 14 is not
particularly limited, and a film formed by vapor deposition (vacuum film forming method) such
as vacuum evaporation or sputtering or film formed by plating, or a foil formed of the above
material Various known methods such as a method of pasting can be used.
[0045]
Above all, a thin film of copper or aluminum formed by vacuum deposition is suitably used as the
upper electrode 16 and the lower electrode 14 because the flexibility of the conversion film 10
can be secured among others.
Among them, a thin film of copper by vacuum evaporation is suitably used. The thickness of the
upper electrode 16 and the lower electrode 14 is not particularly limited. Also, the thicknesses of
the upper electrode 16 and the lower electrode 14 are basically the same but may be different.
[0046]
Here, similarly to the upper protective layer 20 and the lower protective layer 18 described
above, when the rigidity of the upper electrode 16 and the lower electrode 14 is too high, not
only the expansion and contraction of the piezoelectric layer 12 is restricted but also the
flexibility is impaired. Therefore, the upper electrode 16 and the lower electrode 14 are more
advantageous as thin as long as the electrical resistance does not become too high.
[0047]
Here, according to the study of the inventor, if the product of the thickness of the upper
electrode 16 and the lower electrode 14 and the Young's modulus is less than the product of the
thickness of the upper protective layer 20 and the lower protective layer 18 and the Young's
modulus, It is preferable because the flexibility is not greatly impaired.
12-05-2019
16
For example, when the upper protective layer 20 and the lower protective layer 18 are a
combination of PET (Young's modulus: about 6.2 GPa) and the upper electrode 16 and the lower
electrode 14 are copper (Young's modulus: about 130 GPa), the upper protective layer 20 When
the thickness of the lower protective layer 18 is 25 μm, the thickness of the upper electrode 16
and the lower electrode 14 is preferably 1.2 μm or less, more preferably 0.3 μm or less, and
particularly preferably 0.1 μm or less.
[0048]
As described above, in the conversion film 10 of the present invention, the upper electrode 16
and the lower electrode 14 sandwich the piezoelectric layer 12 formed by dispersing the
piezoelectric particles 26 in the viscoelastic matrix 24 having viscoelasticity at normal
temperature, Furthermore, the laminate has a configuration in which the upper protective layer
20 and the lower protective layer 18 are sandwiched. It is preferable that such a conversion film
10 has a maximum value at which a loss tangent (Tan δ) at a frequency of 1 Hz determined by
dynamic viscoelasticity measurement is 0.1 or more at normal temperature. Thereby, even if the
conversion film 10 is subjected to a relatively slow, large bending deformation of several Hz or
less from the outside, strain energy can be effectively diffused to the outside as heat, so that the
polymer matrix and the piezoelectric particles It is possible to prevent the occurrence of cracks
at the interface of
[0049]
The conversion film 10 preferably has a storage elastic modulus (E ') at a frequency of 1 Hz
measured by dynamic viscoelasticity measurement of 10 to 30 GPa at 0 ° C and 1 to 10 GPa at
50 ° C. Thereby, conversion film 10 can have large frequency dispersion in storage elastic
modulus (E ') at normal temperature. That is, it is hard for vibrations of 20 Hz to 20 kHz, and can
behave softly for vibrations of several Hz or less.
[0050]
In addition, the conversion film 10 has a product of a thickness and a storage elastic modulus (E
′) at a frequency of 1 Hz measured by dynamic viscoelasticity measurement: 1.0 × 10 6 to 2.0
× 10 6 at 0 ° C. 6> (1.0 E + 06 to 2.0 E + 06) N / m, at 50 ° C. 1.0 × 10 5 <~5> to 1.0 × 10 6
<6> (1.0 E + 05 to 1.0 E + 06) N / m Is preferred. Thereby, appropriate rigidity and mechanical
12-05-2019
17
strength can be provided as long as the conversion film 10 does not lose flexibility and acoustic
characteristics.
[0051]
Furthermore, it is preferable that the conversion film 10 has a loss tangent (Tan δ) at 25 ° C.
and a frequency of 1 kHz in a master curve obtained from dynamic viscoelasticity measurement,
of 0.05 or more. As a result, the frequency characteristics of the speaker using the conversion
film 10 become smooth, and the amount of change in sound quality when the minimum
resonance frequency f 0 changes with the change in curvature of the speaker can be reduced.
[0052]
Here, as described above, the conversion film 10 has a configuration in which one convex portion
10 a is formed in a substantially central portion of the main surface. In the example shown to
FIG. 1 (A)-FIG.1 (C), the convex part 10a is formed in the hemispherical convex surface so that a
part of conversion film 10 may be protruded on one main surface side. That is, the convex part
10a is formed in the hemispherical concave surface, when it sees from the other main surface
side.
[0053]
As described above, by using the conversion film 10 in which the convex portion 10 a is formed
as a diaphragm, in the electroacoustic transducer 80, the conversion film 10 has a first region
including the convex portion 10 a and the conversion film 10. And a second region consisting of
the entire main surface, the surface area being different between the first region and the second
region, and curved with a different radius of curvature between the first region and the second
region Supported in the state. Therefore, the resonance frequency in the first region of the
conversion film 10 is a frequency different from the resonance frequency in the main surface
(second region) of the conversion film 10, so that different vibrations occur in the first region
and the second region. It becomes a characteristic. That is, in the first area and the second area,
the frequency bands where the conversion efficiency of the sound (vibration) and the electric
signal is high are different, and the reproducible frequency bands are different with a sufficient
sound volume. Therefore, as one diaphragm, sound in a wide frequency band can be reproduced
at a sufficient volume.
12-05-2019
18
[0054]
Here, in the present invention, the piezoelectric layer 12 of the conversion film 10 is formed by
dispersing the piezoelectric particles 26 in a visco-elastic matrix 24 made of a polymer material
having visco-elastic properties at normal temperature. Therefore, even in the case where a
plurality of different vibration modes are mixed on a single diaphragm, the vibrations in the
respective vibration modes do not interfere with each other to cause crosstalk. That is, in the
conversion film 10, the vibrations of the first area and the second area do not interfere with each
other, and sounds in different frequency bands can be reproduced well. Therefore, in the
electroacoustic transducer 80 using the conversion film 10 as a diaphragm, high-quality sound in
a wide frequency band can be reproduced at a sufficient volume.
[0055]
There is no particular limitation on the size (surface area), height, curvature, etc. of the convex
portion 10a, and the size, thickness, and conversion film 10 main surface of the conversion film
10 when incorporated in the electroacoustic transducer 80. It may be determined appropriately
according to the curvature radius, the conversion efficiency of the sound and the electric signal
required for the electroacoustic transducer 80, the required frequency band, and the like.
[0056]
Here, the maximum height d of the convex portion 10 a with respect to the main surface of the
conversion film 10 and the maximum length L of the convex portion 10 a when viewed from the
direction perpendicular to the main surface of the conversion film 10 is d ≦ 0. It is preferable to
satisfy the relationship of 5 × L.
For example, as shown in FIG. 1 (A) and FIG. 1 (B), when the shape of the convex portion 10a is
circular when viewed from the direction perpendicular to the main surface of the conversion film,
FIG. As shown in), the diameter is the maximum length L of the protrusion 10a, and the
maximum length L and the maximum height d of the protrusion 10a with respect to the main
surface satisfy the relationship d ≦ 0.5 × L. Is preferred. Here, as the d approaches 0.5 × L, the
resonance frequency becomes higher, and the sound with the higher tone emphasized is
reproduced. In general, high-frequency sound tends to have a high directivity because it has high
rectilinearity, but as shown in FIG. 1 (B), the sound is emitted in all directions by making the
12-05-2019
19
convex portion 10 a hemispherical, so it is ideal. High tweeter can be realized. From the
viewpoint of the resonance frequency and directivity, when the maximum height d of the convex
portion 10 a with respect to the main surface and the maximum length L of the convex portion
10 a are in the high range, 0.3 × L ≦ d ≦ 0. It is preferable to satisfy the relationship of 5 × L,
and in the case of the middle / low range, it is preferable to satisfy the relationship of d ≦ 0.3 ×
L.
[0057]
Here, in the example shown in FIG. 4A, the shape of the convex portion 10a is circular when
viewed from the direction perpendicular to the main surface of the conversion film 10, but the
present invention is not limited thereto. The shape may be various shapes such as a rectangular
shape, a polygonal shape such as a triangular shape, a pentagonal shape, or an elliptical shape. In
addition, it is preferable that the shape of a convex part is a shape with high symmetry, and it is
preferable that it is a regular polygon or circular shape.
[0058]
The definition of the maximum length L of the convex part in each shape of the convex part 10a
is demonstrated using FIG. 4 (B)-FIG.4 (E). As shown to FIG. 4 (B), when the shape of convex part
10a is elliptical, let a major axis be maximum length L of convex part 10a. As shown to FIG. 4C,
when the shape of convex part 10a is quadrangle shape, let the length of the diagonal of convex
part 10a be L maximum length of convex part 10a. As shown in FIG. 4D, when the shape of the
convex portion 10a is a polygon having a quadrangle or more, the longest diagonal among the
diagonals is taken as the maximum length L of the convex portion 10a. As shown in FIG. 4E,
when the shape of the protrusion 10a is a triangle, the longest perpendicular line among the
perpendiculars is taken as the maximum length L of the protrusion 10a.
[0059]
Moreover, although it was set as the structure which has one convex part 10a in the example
shown to FIG. 1 (A), limitation is not carried out to this, It is good also as a structure which has
several convex parts. Fig. 5 (A) is a schematic top view showing another example of the electroacoustic conversion film of the present invention, and Fig. 5 (B) is a cross-sectional view taken
along the line B-B of Fig. 5 (A). As shown in FIGS. 5A and 5B, the conversion film 90 has a total of
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20
eight projections 90a in two rows and four columns arranged at equal intervals in the surface
direction. Similarly to the protrusion 10 a, the protrusion 90 a is a portion formed in a
hemispherical convex shape so as to protrude to the one main surface side, and the surface area,
height, and curvature radius of each protrusion 90 a are the same. is there. By forming the
plurality of convex portions 90 a in this manner, the conversion efficiency in a desired frequency
band can be improved, and the broadband can be made more suitably.
[0060]
Further, when forming a plurality of convex portions, the surface area, height, curvature, etc. of
each convex portion may be different. Fig. 6 (A) is a schematic top view showing another example
of the electro-acoustic conversion film of the present invention, and Fig. 6 (B) is a cross-sectional
view taken along the line B-B of Fig. 6 (A). As shown in FIGS. 6A and 6B, the conversion film 92
has one convex portion 92a substantially at the center in the surface direction, and in the figure,
one convex portion 92b on the right side of the convex portion 92a. And three convex portions
92c on the left side of the convex portion 92a. Each of the convex portions 92a to 92c is a
portion formed in a hemispherical convex shape so as to protrude to one main surface side,
similarly to the convex portion 10a. In addition, the surface area, height, and curvature radius of
each convex portion are different, and the convex portion 92a has a larger surface area, height,
and curvature radius than the convex portion 92b, and the convex portion 92c has a surface
area, height, and curvature than the convex portion 92b. The radius is small. By forming the
convex portions having different sizes in this manner, it is possible to widen the frequency band
that can be efficiently reproduced as different resonance frequencies of the convex portions.
Note that as shown in FIG. 6A, it is sufficient that the curvature radii (resonance frequencies) of
at least two of the plurality of projections are different, and the projections have the same
curvature radius (resonance frequency). May be
[0061]
In the example shown in FIG. 6A, the surface area, height, and radius of curvature of each
protrusion are different, and the resonance frequency of each protrusion is different. However,
the present invention is not limited to this. The resonance frequency may be different in the
convex portion, and the curvature radius of each convex portion may be the same and only the
surface area may be different to make the resonant frequency different, or the surface area of
each convex portion may be the same. The resonance frequencies may be different by changing
only the curvature radius. Moreover, as long as the resonance frequency can be made different, it
is not limited to the configuration in which the shape of the convex portion is made different, for
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21
example, if a protective film is double stuck on part, if mass and stiffness are different for each
region Alternatively, the resonant frequencies may be different.
[0062]
Moreover, in the example shown to FIG. 1 (A), although the shape of the convex part was made
into the hemispherical convex surface, it is not limited to this, Like the convex part 94a of the
conversion film 94 shown in FIG. It may be convex. Alternatively, the convex portion may be a
convex surface such as an elliptical shape, a sine wave shape, a rounded rectangular shape, a
honeycomb shape, etc. The convex surface curved in a shape represented by a part of these
shapes, a part of these shapes It may be a curved convex surface.
[0063]
Moreover, in the example shown to FIG. 5 (A) and FIG. 6 (A), although the several convex part
was arrange | positioned in the position where the surface direction of the main surface of
conversion film differs, it is not limited to this. It is good also as composition which arranges a
convex part from which a difference etc. differ in a surface direction overlap. That is, it is good
also as composition which the convex part from which a curvature radius etc. differs differs in
the direction perpendicular to the principal surface of conversion film.
[0064]
Fig. 8 (A) is a top view conceptually showing another example of the conversion film of the
present invention, and Fig. 8 (B) is a cross-sectional view taken along the line B-B of Fig. 8 (A). (C)
is CC sectional view taken on the line of FIG. 8 (A). As shown to FIG. 8 (A)-FIG. 8 (C), the
conversion film 102 has the convex part 102a and the convex part 102b larger than the convex
part 102a in the approximate center of the surface direction. The convex portion 102 a is a
convex surface formed by curving a rectangular region substantially at the center of the main
surface of the conversion film 102 in the horizontal direction and the vertical direction in the
drawing. The convex portion 102b is a convex surface formed by curving a rectangular area
larger than the convex portion 102a in the horizontal direction and the vertical direction in the
figure at a position where the center coincides with the convex portion 102a in the surface
direction of the main surface. is there. As shown to FIG. 8 (B) and FIG. 8 (C), the curvature radius
of the convex part 102b is larger than the curvature radius of the convex part 102a. Further, the
12-05-2019
22
surface area of the convex portion 102 b is larger than the surface area of the convex portion
102 a. As described above, even in the case where the plurality of projections overlap in the
direction perpendicular to the main surface of the conversion film, it is possible to efficiently
reproduce the frequency band where the resonance frequencies of the projections are different.
More broadband can be achieved.
[0065]
In the example shown in FIG. 8A, the convex portion is curved in a cross section in one direction
perpendicular to the main surface of the conversion film and in a cross direction in the other
direction orthogonal to the one direction. There may be a configuration in which only one
direction is curved. In the present invention, the piezoelectric layer 12 is a polymer composite
piezoelectric formed by dispersing piezoelectric particles in a visco-elastic matrix made of a
polymer material having visco-elastic properties at normal temperature. Therefore, since the
piezoelectric layer 12 has no in-plane anisotropy in piezoelectric characteristics, it can function
as a diaphragm regardless of which direction the conversion film 10 is curved. Therefore, the
band can be more suitably broadened without changing the sound quality by curving the cross
section in one direction perpendicular to the main surface of the conversion film and in the other
direction orthogonal to this one direction, The speaker structure using this conversion film can
be easily simplified and reduced in weight.
[0066]
Hereinafter, with reference to FIG. 9 (A)-FIG.9 (E), an example of the manufacturing method of
the conversion film 10 is demonstrated.
[0067]
First, as shown in FIG. 9A, the sheet-like material 11a in which the lower electrode 14 is formed
on the lower protective layer 18 is prepared.
The sheet-like material 11 a may be manufactured by forming a copper thin film or the like as
the lower electrode 14 on the surface of the lower protective layer 18 by vacuum deposition,
sputtering, plating or the like. When the lower protective layer 18 is very thin and handling is
poor, the lower protective layer 18 with a separator (temporary support) may be used as needed.
In addition, PET etc. of 25-100 micrometers in thickness can be used as a separator. Note that
12-05-2019
23
the separator may be removed immediately after the side surface insulating layer, the second
protective layer, and the like are formed after thermocompression bonding of the thin film
electrode and the protective layer.
[0068]
On the other hand, a polymer material (hereinafter, also referred to as a visco-elastic material)
having visco-elastic properties such as cyanoethylated PVA (hereinafter referred to as viscoelastic material) is dissolved in an organic solvent, and piezoelectric particles 26 such as PZT
particles are further added and stirred. To prepare a paint that is dispersed. There is no
particular limitation on the organic solvent, and various organic solvents such as
dimethylformamide (DMF), methyl ethyl ketone and cyclohexanone can be used. Once the sheet
11a is prepared and the paint is prepared, the paint is cast (coated) on the sheet and the organic
solvent is evaporated to dryness. As a result, as shown in FIG. 9B, the lower electrode 14 is
formed on the lower protective layer 18, and the laminate 11b is formed by forming the
piezoelectric layer 12 on the lower electrode 14.
[0069]
There is no particular limitation on the method of casting the paint, and all known methods
(coating apparatus) such as a slide coater and a doctor knife can be used. Alternatively, if the
visco-elastic material is a heat-meltable material such as cyanoethylated PVA, the visco-elastic
material is heat-melted to prepare a melt formed by adding / dispersing the piezoelectric
particles 26 thereto. The lower electrode 14 is provided on the lower protective layer 18 as
shown in FIG. 9B by extruding in a sheet form on the sheet 11a shown in FIG. 9A by molding or
the like and cooling. Alternatively, the laminate 11 b formed by forming the piezoelectric layer
12 on the lower electrode 14 may be manufactured.
[0070]
As described above, in the conversion film 10 of the present invention, a polymeric piezoelectric
material such as PVDF may be added to the viscoelastic matrix 24 in addition to the viscoelastic
material such as cyanoethylated PVA. When adding these polymeric piezoelectric materials to the
viscoelastic matrix 24, the polymeric piezoelectric materials added to the above-mentioned paint
may be dissolved. Alternatively, the polymer piezoelectric material to be added may be added to
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24
the heat-melted viscoelastic material and heat-melted. Once the laminate 11b having the lower
electrode 14 on the lower protective layer 18 and the piezoelectric layer 12 formed on the lower
electrode 14 is produced, preferably, the polarization process (poling) of the piezoelectric layer
12 is performed. Do.
[0071]
There is no particular limitation on the method of polarization treatment of the piezoelectric
layer 12, and a known method can be used. As a preferable polarization method, the methods
shown in FIG. 9 (C) and FIG. 9 (D) are exemplified.
[0072]
In this method, as shown in FIGS. 9 (C) and 9 (D), a gap g is opened by, for example, 1 mm on the
upper surface 12a of the piezoelectric layer 12 of the laminated body 11b, A possible rod-like or
wire-like corona electrode 30 is provided. Then, the corona electrode 30 and the lower electrode
14 are connected to a DC power supply 32. Further, a heating means for heating and holding the
laminate 11b, for example, a hot plate is prepared.
[0073]
Then, while heating and holding the piezoelectric layer 12 at a temperature of 100 ° C., for
example, by heating means, between the DC power source 32 and the lower electrode 14 and the
corona electrode 30, several kV, for example, 6 kV A direct current voltage is applied to cause
corona discharge. Further, while maintaining the gap g, the corona electrode 30 is moved
(scanned) along the upper surface 12 a of the piezoelectric layer 12 to polarize the piezoelectric
layer 12.
[0074]
In the polarization treatment using such corona discharge (hereinafter, also referred to as a
corona poling treatment for convenience, for convenience), the movement of the corona
electrode 30 may be performed using a known rod-like moving means. Further, in the corona
12-05-2019
25
poling treatment, the method of moving the corona electrode 30 is not limited. That is, a moving
mechanism may be provided to fix the corona electrode 30 and move the stacked body 11b, and
the stacked body 11b may be moved for polarization processing. Also for the movement of the
laminate 11b, a known sheet moving means may be used. Furthermore, the number of corona
electrodes 30 is not limited to one, and a plurality of corona electrodes 30 may be used to
perform corona poling treatment. Further, the polarization process is not limited to the corona
poling process, and a normal electric field poling in which a direct current electric field is directly
applied to an object to be subjected to the polarization process can also be used. However, when
performing this normal electric field poling, it is necessary to form the upper electrode 16 before
the polarization processing. A calendar process may be applied to smooth the surface of the
piezoelectric layer 12 using a heating roller or the like before the polarization process. By
performing this calendering process, the thermocompression bonding process described later
can be smoothly performed.
[0075]
Thus, while the polarization process of the piezoelectric material layer 12 of the laminated body
11b is performed, the sheet-like article 11c in which the upper electrode 16 is formed on the
upper protective layer 20 is prepared. The sheet-like material 11 c may be manufactured by
forming a copper thin film or the like as the upper electrode 16 on the surface of the upper
protective layer 20 by vacuum deposition, sputtering, plating or the like. Next, as shown in FIG.
9E, the sheet-like material 11c is laminated on the laminate 11b after the polarization treatment
of the piezoelectric layer 12 is finished, with the upper electrode 16 facing the piezoelectric layer
12. Further, the laminated body of the laminated body 11b and the sheet-like material 11c is
thermocompression-bonded by a heating press device, a heating roller pair, etc. so as to
sandwich the upper protective layer 20 and the lower protective layer 18 to obtain a conversion
film. Make.
[0076]
Next, the produced conversion film is processed to form a convex portion 10a as shown in FIG. 1
(A). There is no limitation in particular as a formation method of a convex part, The processing
method of various well-known resin films can be utilized. For example, the convex portion 10 a
can be formed by a forming method such as a vacuum pressure molding method or embossing.
Thus, the conversion film 10 of the present invention having the convex portion 10a is produced.
12-05-2019
26
[0077]
Next, the electro-acoustic transducer of the present invention using the conversion film 10 will
be described. FIG. 2A is a top view showing an example of the electro-acoustic transducer of the
present invention, and FIG. 2B is a cross-sectional view taken along the line B-B of FIG. As shown
in FIGS. 2A and 2B, the electroacoustic transducer 80 has a conversion film 10, a case 82, a
frame 84, and a viscoelastic support 86.
[0078]
The case 82 is a thin square cylindrical case which is formed of plastic or the like and which is
open on one side. In the electroacoustic transducer using the conversion film of the present
invention, the case 82 is not limited to a square cylinder, and various shapes of casings such as a
cylinder or a square cylinder having a rectangular bottom can be used. It is. The frame 84 is a
plate having an opening at the center and having the same shape as the upper end surface (open
surface side) of the case 82. Furthermore, the visco-elastic support 86 has appropriate viscosity
and elasticity, supports the conversion film 10, and does not waste the expansion and contraction
motion of the conversion film by providing a constant mechanical bias anywhere in the
piezoelectric film. It is for conversion into back and forth movement (movement in the direction
perpendicular to the plane of the film). As an example, nonwoven fabric such as wool felt, wool
felt including rayon and PET, glass wool, foam material such as polyurethane (foam plastic), a
plurality of sheets of paper, paint, etc. are exemplified. In the illustrated example, the viscoelastic
support 86 is in the form of a square pole having a bottom shape substantially equal to the
bottom surface of the case 82. The viscoelastic support 86 has a convex portion one size larger
than the convex portion 10 a at a position corresponding to the convex portion 10 a of the
conversion film 10, and the viscoelastic support body 86 is disposed also in the convex portion
10 a It may be configured to Alternatively, as in the electroacoustic transducer 80b shown in FIG.
2C, the inside of the convex portion 10a may be configured as a cavity. The specific gravity of the
viscoelastic support 86 is not particularly limited, and may be appropriately selected according
to the type of the viscoelastic support. As an example, when using a felt as a visco-elastic support,
50-500 kg / m <3> is preferable and, as for specific gravity, 100-300 kg / m <3> is more
preferable. When glass wool is used as the viscoelastic support, the specific gravity is preferably
10 to 100 kg / m <3>.
[0079]
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In the electroacoustic transducer 80, the visco-elastic support 86 is accommodated in the case
82, the case 82 and the visco-elastic support 86 are covered by the conversion film 10, and the
case around the conversion film 10 is formed by the frame 84. The frame 84 is fixed to the case
82 in contact with the upper end surface of the frame 82. The method for fixing the frame to the
case 82 is not particularly limited, and various known methods such as a method using a screw
or a bolt and a nut, and a method using a fixing jig can be used.
[0080]
Here, in the electroacoustic transducer 80, the height (thickness) of the viscoelastic support 86 is
larger than the height of the inner surface of the case 82. That is, in a state before the conversion
film 10 and the frame 84 are fixed, the viscoelastic support 86 is in a state of protruding beyond
the upper surface of the case 82. Therefore, in the electro-acoustic transducer 80, the viscoelastic support 86 is pressed downward by the conversion film 10 and held in a thinner state as
it gets closer to the peripheral portion of the visco-elastic support 86. That is, the main surface of
the conversion film 10 is held in a curved state. Under the present circumstances, it is preferable
to press the whole surface of the viscoelastic support body 86 in the surface direction of the
conversion film 10, and to make thickness thin entirely. That is, it is preferable that the entire
surface of the conversion film 10 be pressed and supported by the viscoelastic support 86.
[0081]
In the electroacoustic transducer 80, the pressing force of the visco-elastic support 86 by the
conversion film 10 is not particularly limited, but the surface pressure at a position where the
surface pressure is low is 0.005 to 1.0 MPa, particularly 0.02 It is preferable to set it as about 0.2MPa. The height difference of the conversion film 10 incorporated in the electroacoustic
transducer 80, and in the illustrated example, the distance between the nearest place and the
farthest place to the bottom of the frame 84 is not particularly limited, but a thin flat speaker Is
preferably about 1 to 50 mm, particularly about 5 to 20 mm in that sufficient conversion of the
conversion film 10 up and down is possible. In addition, the thickness of the viscoelastic support
86 is not particularly limited, but the thickness before being pressed is preferably 1 to 100 mm,
particularly 10 to 50 mm.
[0082]
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28
In such an electro-acoustic transducer 80, when the conversion film 10 is stretched in the inplane direction by voltage application to the piezoelectric layer 12, the conversion film 10 is
exposed to the upper side (sound emission to absorb the stretching component). Direction).
Conversely, when the conversion film 10 contracts in the in-plane direction by voltage
application to the piezoelectric layer 12, the conversion film 10 moves downward (to the case 82
side) to absorb the contraction. When the electroacoustic transducer 80 is used as a speaker,
sound is generated by the vibration due to the repetition of expansion and contraction of the
conversion film 10.
[0083]
In the electroacoustic transducer 80, the visco-elastic support 86 is compressed in the thickness
direction as it approaches the frame 84. However, the static visco-elastic effect (stress relaxation)
makes it possible to machine anywhere on the piezoelectric film 10 Bias can be kept constant. As
a result, since the expansion and contraction movement of the piezoelectric film 10 is converted
to the back and forth movement without wasting, a thin, sufficient sound volume can be
obtained, and the planar electroacoustic transducer 80 excellent in acoustic characteristics can
be obtained.
[0084]
Here, as described above, the conversion film 10 used as the diaphragm has the convex portion
10 a formed. Therefore, the conversion film 10 incorporated in the electroacoustic transducer 80
has a second area formed by curving the entire main surface, a smaller surface area than the
second area, and a radius of curvature different from that of the second area. It is supported in a
state of having a first region composed of a curved convex portion 10a. Therefore, the resonance
frequency in the main surface (second region) of the conversion film 10 and the resonance
frequency in the first region are different frequencies, and the first region and the second region
have different vibration characteristics. That is, in the first area and the second area, the
frequency bands where the conversion efficiency of the sound (vibration) and the electric signal
is high are different, and the reproducible frequency bands are different with a sufficient sound
volume. Therefore, as one diaphragm, sound in a wide frequency band can be reproduced at a
sufficient volume.
[0085]
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29
In addition, the conversion film 10 incorporated in the electroacoustic transducer 80 is held in a
state in which the first region and the second region overlap in the direction perpendicular to the
main surface of the conversion film. Here, in general, in the case of having a plurality of
diaphragms (speakers), if the distance from each speaker to the viewer is the same, the phase of
the sound reproduced from each speaker is matched, and the sound image is improved, When
the distance from each speaker to the viewer is different, the phase of the sound reproduced
from each speaker is shifted, and the sounds of the overlapping frequencies cancel each other
out, and the sound of that frequency is lost and the connection becomes a bad sound, The sound
may fade and the sound may be worse. On the other hand, in the electroacoustic transducer 80,
by having a configuration in which the regions having different vibration characteristics overlap
in the direction perpendicular to the main surface, the sound of the frequency band mainly
generated from the first region, The sound of the frequency band mainly generated from the
second area is reproduced from the same position. Thereby, an excellent sound image can be
realized.
[0086]
In the present invention, when the conversion film is incorporated into the electroacoustic
transducer, the direction perpendicular to the main surface of the conversion film is a straight
line connecting the boundary between the area where the conversion film vibrates and the area
where it is fixed. It is the direction perpendicular to the enclosed surface. For example, in the case
of fixing the periphery of the conversion film with a frame, it is a direction perpendicular to the
plane surrounded by the boundary between the region fixed by the frame and the vibrating
region inside the frame. .
[0087]
Here, although the electroacoustic transducer 80 of the illustrated example presses the entire
peripheral area of the conversion film 10 to the case 82, that is, the viscoelastic support 86 by
the frame 84, the present invention is not limited to this. That is, the electroacoustic transducer
using the conversion film 10 does not have the frame 84, and for example, supports the
conversion film 10 in a viscoelastic manner by screws, bolt nuts, jigs, etc. at four corners of the
case 82. It is also possible to use a configuration in which the upper surface of the body 86 is
pressed / fixed. In addition, an O-ring or the like may be interposed between the case 82 and the
conversion film 10. By having such a configuration, a damper effect can be provided, and
12-05-2019
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transmission of vibration of the conversion film 10 to the case 82 can be prevented, and more
excellent acoustic characteristics can be obtained.
[0088]
Further, the electroacoustic transducer using the conversion film 10 may be configured to have a
support plate on which the visco-elastic support 86 is placed, instead of the case 82
accommodating the visco-elastic support 86. That is, the visco-elastic support 86 is placed on a
rigid support plate, the visco-elastic support 86 is covered, the conversion film 10 is placed, and
the same frame 84 as above is placed on the periphery of the conversion film 10. It is also
possible to use a configuration in which the visco-elastic support 86 is pressed by the conversion
film 10 together with the frame 84 by fixing the frame 84 to the support plate with a screw or
the like to bend the conversion film 10 It is. Also, even in a configuration without such a case 82,
the conversion film 10 may be held in a state where the viscoelastic support 86 is pressed and
thinned with a screw or the like without using the frame 84. The vibration of the conversion film
10 may be further amplified by using various diaphragms such as polystyrene, foamed PET, or
carbon fiber as the material of the support plate.
[0089]
Furthermore, the electro-acoustic transducer using the conversion film 10 is not limited to the
configuration for pressing the periphery, for example, a location other than the periphery of the
laminate of the visco-elastic support 86 and the conversion film 10 by some means A
configuration in which at least a part of the conversion film 10 is held in a curved state by
pressing can also be used. Alternatively, a resin film may be attached to the conversion film 10 to
apply (hold) tension. A flexible speaker can be obtained by being configured to be held by a resin
film and can be held in a curved state. Alternatively, the conversion film 10 may be stretched on
a curved frame.
[0090]
Further, the electroacoustic transducer of the present invention is not limited to the
configuration using the viscoelastic support 86. For example, as the case, using an airtight
material having the same shape as the case 82, the open end of the case is covered with the
conversion film 10 and closed, and a gas is introduced into the case to apply pressure to the
12-05-2019
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conversion film 10 It may be configured to be held in a convexly bulging state.
[0091]
If pressure is applied to the inside, distortion components increase due to the influence of the air
spring, and the sound quality may be degraded. On the other hand, in the case of a structure in
which the conversion film 10 is supported by a visco-elastic support such as glass wool or felt,
since viscosity is given, it is preferable without an increase in distortion component. Also, the
case may be filled with gas other than gas, and magnetic fluid and paint can be used as long as
appropriate viscosity can be given. Further, the configuration using the viscoelastic support 86
and the configuration applying pressure inside may be combined. In addition, the surface
pressure applied to the conversion film 10 may be made different by changing the pressure of
the viscoelastic support 86 or the inside for each region. As a result, the stiffness of the
conversion film 10 can be controlled to control the resonance frequency for each region, and the
bandwidth can be made more preferable.
[0092]
Next, an electroacoustic transducer using a conversion film having a plurality of convex portions
overlapping in a direction perpendicular to the main surface will be described with reference to
FIGS. 10 (A) to 10 (C). In addition, the electroacoustic transducer 100 shown to FIG. 10 (A)FIG.10 (C) is replaced with the conversion film 10, and except using the conversion film 102
shown to FIG. 8 (A), an electroacoustic transducer 80 is used. The same parts as those in the
above are denoted by the same reference numerals, and different parts will be mainly described
in the following description.
[0093]
Fig. 10 (A) is a top view conceptually showing another example of the electroacoustic transducer
of the present invention, and Fig. 10 (B) is a cross-sectional view taken along the line B-B of Fig.
10 (A). FIG. 10C is a cross-sectional view taken along the line C-C in FIG. As shown in FIG. 10A,
the electroacoustic transducer 100 has a conversion film 102, a case 82, a frame 84, and a
viscoelastic support 86.
12-05-2019
32
[0094]
As shown in the figure, the conversion film 102 is supported with the main surface being curved.
Here, as shown to FIG. 8 (B), the conversion film 102 has two convex parts which differ in a
curvature radius which overlap in the direction perpendicular | vertical to the main surface of
conversion film. Therefore, in the electroacoustic transducer 100 using the conversion film 102,
the conversion film 102 includes a first region formed of the convex portion 102a, a second
region formed of the convex portion 102b, the convex portion 102a of the main surface, and the
convex portion. A third region formed of a region other than the portion 102b overlaps in a
direction perpendicular to the main surface, and each has a different surface area and is
supported in a curved state with a different radius of curvature. Therefore, since each region has
different vibration characteristics, sound of a wider frequency band can be reproduced at a
sufficient volume with one diaphragm, and a good sound image can be realized.
[0095]
Further, in the electroacoustic transducer 100 shown in FIG. 10A, each region is curved in a
cross section of a predetermined one direction perpendicular to the main surface of the
conversion film and a cross section in the other direction orthogonal to this one direction.
However, the present invention is not limited thereto. Fig. 11 (A) is a top view conceptually
showing another example of the electroacoustic transducer of the present invention, and Fig. 11
(B) is a cross-sectional view taken along the line B-B of Fig. 11 (A). FIG.11 (C) is CC sectional view
taken on the line of FIG. 11 (A). As shown in FIGS. 11A to 11C, the electroacoustic transducer
110 has a conversion film 112, a case 82, a frame 116, and a viscoelastic support 86.
[0096]
The frame 116 is a rod-like member having a rectangular cross section and elongated in the
vertical direction in FIG. 11A, and fixed to the edge of the opening surface of the case 82 so that
both end portions of the conversion film 112 can Fix it. On the other hand, both ends in the
vertical direction in the drawing of the conversion film 112 are not fixed. That is, the conversion
film 112 has a width substantially equal to the inside of the case 82 in the vertical direction in
FIG. 11A, and both ends in the left and right direction are fixed to the case 82 by the frame 116
and supported There is. Therefore, as shown in FIG. 11 (B), the conversion film 112 is supported
in a state in which the main surface is curved in the left-right direction in FIG. 11 (A). On the
other hand, in the vertical direction, as shown in FIG. 11C, it is not curved and supported in a flat
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state.
[0097]
Moreover, as shown to FIG. 11 (B), the conversion film 112 has three surface areas which have
different surface areas in the left-right direction, and curve with a different curvature radius. The
first area 112a is an area which is curved at a substantially central portion with the smallest
radius of curvature. The second area 112b is an area which is curved with a larger radius of
curvature than the first area 112a, and whose center is coincident with the first area 112a, which
is slightly larger than the first area 112a. The third area 112 c is an area other than the first area
112 a and the second area 112 b that is curved with a curvature radius larger than that of the
second area 112 b. These three regions are formed to overlap in the direction perpendicular to
the main surface of the conversion film.
[0098]
As described above, the conversion film may be curved only in a cross section in one direction
perpendicular to the main surface of the conversion film. In such a configuration, a convex
portion corresponding to the first region 112 a and a convex portion corresponding to the
second region 112 b are formed in advance on the conversion film 112, and the main surface of
the conversion film 112 is curved. Can be formed by being incorporated in the electroacoustic
transducer 110. In the present invention, the piezoelectric layer 12 is a polymer composite
piezoelectric formed by dispersing piezoelectric particles in a visco-elastic matrix made of a
polymer material having visco-elastic properties at normal temperature. Such a piezoelectric
layer 12 has no in-plane anisotropy in piezoelectric characteristics, and therefore, the conversion
film 10 can function as a diaphragm regardless of the direction in which the conversion film 10
is curved. Therefore, it is preferable to make a cross section in one direction perpendicular to the
main surface of the conversion film and a cross section in the other direction orthogonal to this
one direction, from the viewpoint of wide band, high sound quality, high efficiency, etc. More
preferably, it is curved in all directions.
[0099]
Further, in the example shown in FIG. 2B and the like, the regions curved with different curvature
radius are arranged to overlap in the direction perpendicular to the main surface, but the present
invention is not limited to this, and different curvatures It is good also as composition which
arranges a field which curves by a radius in a different position of surface direction of a principal
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surface.
[0100]
12 (A) is a top view conceptually showing another example of the electroacoustic transducer of
the present invention, and FIG. 12 (B) is a cross-sectional view taken along the line B-B of FIG. 12
(A). FIG.12 (C) is CC sectional view taken on the line of FIG. 12 (A).
As shown in FIGS. 12A to 12C, the electroacoustic transducer 120 has a conversion film 122, a
case 82, a frame 124, and a viscoelastic support 86. As shown in the figure, in the
electroacoustic transducer 120, the conversion film 122 has three surface areas which are
different in surface area and curved with different curvature radii, and which are formed at
different positions in the plane direction. In the following description, formation of regions at
different positions in the surface direction is also referred to as formation in parallel.
[0101]
The frame body 124 has an outer frame portion 124 a corresponding to the edge of the opening
surface of the case 82, and two frame portions 124 b arranged at positions corresponding to
boundaries between the respective regions of the conversion film 122. In other words, the frame
124 is a member having three openings corresponding to the respective regions of the
conversion film 122. The frame 124 is fixed to the edge of the opening surface of the case 82 to
fix the peripheral portion of the conversion film 122 and the boundary portion of each region.
[0102]
The conversion film 122 covers the visco-elastic support 86 disposed in the case 82 and is
supported by the frame 124 while pressing the visco-elastic support 86. Accordingly, in the
conversion film 122, the peripheral portion corresponding to the outer frame portion 124a of
the frame 124 and the portion corresponding to the two frame portions 124b are fixed, and as
shown in FIG. In parallel, three regions are formed. As shown in FIG. 12B, in the left-right
direction of FIG. 12A, the three areas have different surface areas, and are curved with different
radii of curvature. That is, the conversion film 122 is the largest area, and the first area 122a
curved with the largest radius of curvature, and the second area 122b curved with a smaller
12-05-2019
35
radius of curvature than the first area 122a, and It is supported in the form of a small area and a
third area 122c which is curved with the smallest radius of curvature. In addition, as shown to
FIG. 12C, the conversion film 122 is curving also in the up-down direction of FIG. 12 (A).
[0103]
As described above, even in the case where the curved regions with different radius of curvature
are formed in parallel, the vibration characteristics of each region are different, so the sound in a
wider frequency band is reproduced with a sufficient volume by one diaphragm. be able to.
[0104]
In addition, also in the case of the configuration in which the curved regions with different radius
of curvature are formed in parallel, the bending direction of each region is orthogonal to the
cross section of a predetermined one direction perpendicular to the main surface of the
conversion film The conversion film is not limited to a configuration that is curved in the cross
section in the other direction, but may be configured to be curved only in a cross section in one
direction perpendicular to the main surface.
[0105]
FIG. 13A is a top view conceptually showing another example of the electroacoustic transducer of
the present invention, and FIG. 13B is a cross-sectional view taken along the line B-B of FIG.
FIG.13 (C) is CC sectional view taken on the line of FIG. 13 (A).
As shown in FIGS. 13A to 13C, the electroacoustic transducer 130 includes a conversion film
132, a case 82, two frames 134a, two frames 134b, and a visco-elastic support 86. Have.
As shown in the figure, the electro-acoustic transducer 130 is one in which three areas having
different surface areas and being curved with different radii of curvature are formed in parallel.
[0106]
The frame 134a is a rod-like member having a rectangular cross section and elongated in the
vertical direction in FIG. 13A, and is fixed to the edge of the opening surface of the case 82 so
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that both end portions of the conversion film 132 in the left and right direction Fix it. Also, the
frame 134 b has the same shape as the frame 134 a, is disposed at a position corresponding to
the boundary of each area of the conversion film 132, and is fixed to the case 82.
[0107]
On the other hand, both ends of the conversion film 132 in the vertical direction in the drawing
are not fixed. That is, the conversion film 132 has a width substantially equal to the inside of the
case 82 in the vertical direction in FIG. 13A, and both ends in the horizontal direction are fixed to
the case 82 by the frame 134a and supported. There is. Accordingly, as shown in FIG. 13B, the
conversion film 132 is supported in a curved state in the respective regions of the conversion
film 132 in the left-right direction in FIG. 13A. On the other hand, in the vertical direction, as
shown in FIG. 13C, it is not curved and supported in a flat state.
[0108]
Further, as shown in FIG. 13B, in the conversion film 132, three regions are formed in parallel in
the left-right direction by the two frames 134b. That is, the conversion film 132 is the largest
area, and the first area 132a curved with the largest radius of curvature, and the second area
132b curved with a smaller radius of curvature than the first area 132a, and It is supported in
the form of a small area and a third area 132c which is curved with the smallest radius of
curvature.
[0109]
As described above, even when areas having different surface areas and curved with different
curvature radii are formed in parallel, the conversion film may be curved only in a cross section
in one direction perpendicular to the main surface.
[0110]
Moreover, although it was set as the structure which arrange | positions the convex part 10a
formed in the conversion film 10 toward the outer side in the example shown to FIG. 2 (B), this
invention is not limited to this, The convex part 10a is inside. It is good also as composition
arranged towards.
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That is, in the electroacoustic transducer, the conversion film may be configured to have a
concavely curved region. The sound generated from the concavely curved region is 180 ° out of
phase with the sound generated from the main surface, so the phase of the input signal of the
sound of the frequency band mainly generated from this concavely curved region It is preferable
to adjust the input signal so that the phase of the generated sound is matched, shifting the input
signal of the other frequency bands.
[0111]
Moreover, in the example shown to FIG. 2 (B), although the conversion film 10 set it as the
structure which hold | maintains a piezoelectric material layer by one electrode pair, this
invention is not limited to this, It curves by a different curvature radius For each region, it may be
held by an electrode pair of a size corresponding to this region. At that time, one of the
electrodes may be used as a common electrode. That is, only the other electrode may be an
electrode of a size corresponding to each region. In addition, when the electrode pair is divided
for each region in this way, the same signal may be input to each electrode pair, or a signal in a
frequency band that can be suitably reproduced may be input for each region. It is also good. In
the present invention, the piezoelectric layer 12 is a polymer composite piezoelectric formed by
dispersing piezoelectric particles in a visco-elastic matrix made of a polymer material having
visco-elastic properties at normal temperature. Therefore, the internal loss (loss tangent tan δ) is
large near the frequency of 0 Hz, and the sound velocity is small because the storage elastic
modulus E ′ is small. Therefore, it is possible to prevent the propagation of vibration between
the regions. Therefore, even when signals different from one another are input to each area and
reproduced, the sound can be suitably reproduced in each area without the vibrations of the
areas interfering with each other.
[0112]
Further, when driving the electro-acoustic transducer of the present invention as a speaker, the
signal level to be input may be corrected for each frequency band according to the frequency
characteristics of the conversion film.
[0113]
The electroacoustic conversion film and the electroacoustic transducer of the present invention
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can be suitably used as a speaker in combination with a flexible display such as an organic EL
display.
Also, the electro-acoustic transducer film and the electro-acoustic transducer of the present
invention may be combined with a screen for a projector. Such a configuration can improve the
design and entertainability of the converted film. Further, by integrating the conversion film as a
speaker with the screen or the flexible display, sound can be reproduced from the direction in
which the image is displayed, and the sense of reality can be improved. In addition, since the
projector screen is flexible, it can have a curvature. By giving the curvature to the image display
surface, the distance from the observer to the screen can be made substantially uniform between
the center and the edge of the screen, and the sense of reality can be improved. In addition, when
the curvature is given to the image display surface as described above, distortion occurs in the
projected image. Therefore, it is preferable to perform image processing on data of an image to
be projected so as to reduce distortion in accordance with the curvature of the image display
surface.
[0114]
Although the electro-acoustic transducer film and the electro-acoustic transducer of the present
invention have been described above in detail, the present invention is not limited to the abovedescribed example, and various improvements and modifications can be made without departing
from the scope of the present invention. Of course it is good.
[0115]
Hereinafter, the present invention will be described in more detail by way of specific examples of
the present invention.
[0116]
Example 1 The conversion film 10 of the present invention shown in FIG. 1 was produced by the
method shown in FIGS. 9 (A) to 9 (E) described above.
First, cyanoethylated PVA (CR-V, manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved in
dimethylformamide (DMF) at the following composition ratio.
12-05-2019
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Thereafter, PZT particles were added to this solution at the following composition ratio, and
dispersed by a propeller mixer (rotation speed: 2000 rpm) to prepare a paint for forming the
piezoelectric layer 12. · · · · · · · · · · · · · PZT particles · · · · · · · · · · · 300 parts by weight ·
cyanoethylated PVA · · · · · · · · · · 30 parts by weight · DMF · · · · · · · · · · · · · · 70 The PZT particles
were obtained by sintering a commercially available PZT raw material powder at 1000 to 1200
° C., and then crushing and classifying this to an average particle diameter of 5 μm.
[0117]
On the other hand, sheet-like materials 11 a and 11 c were prepared by vacuum-depositing a 0.1
μm thick copper thin film on a 4 μm thick PET film. That is, in this example, the upper
electrode 16 and the lower electrode 14 are a copper-deposited thin film having a thickness of
0.1 m, and the upper protective layer 20 and the lower protective layer 18 are a PET film having
a thickness of 4 μm. In addition, in order to obtain good handling during the process, a PET film
with a 50 μm thick separator (temporary support PET) is used, and after the
thermocompression bonding of the thin film electrode and the protective layer, the separator of
each protective layer is I removed it.
[0118]
A paint for forming the previously prepared piezoelectric layer 12 was applied on the lower
electrode 14 (copper vapor deposited thin film) of the sheet 11 a using a slide coater. The paint
was applied such that the thickness of the coating after drying was 40 μm. Then, the paint was
applied onto the sheet 11a, and dried by heating on a hot plate at 120 ° C. to evaporate the
DMF. As a result, a laminate 11 b was produced, which had the lower electrode 14 made of
copper on the lower protective layer 18 made of PET, and the piezoelectric layer 12
(piezoelectric layer) having a thickness of 40 μm formed thereon. .
[0119]
The piezoelectric layer 12 of the laminate 11b was subjected to polarization treatment by the
above-mentioned corona poling shown in FIGS. 9 (C) and 9 (D). The polarization treatment was
performed by setting the temperature of the piezoelectric layer 12 to 100 ° C. and applying a
DC voltage of 6 kV between the lower electrode 14 and the corona electrode 30 to cause corona
discharge.
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[0120]
The sheet-like material 11 c was laminated on the polarization-processed laminate 11 b with the
upper electrode 16 (copper thin film side) facing the piezoelectric layer 12. Next, the laminate of
the laminate 11b and the sheet 11c is thermocompression-bonded at 120 ° C. using a laminator
device to bond the piezoelectric layer 12 to the upper electrode 16 and the lower electrode 14 so
as to be flat. A conversion film was made.
[0121]
Next, the convex part 10a was formed in the produced flat conversion film. The convex portion
10 a had a diameter (cord length) of 60 mm, a radius of curvature of 30 mm, and was formed by
vacuum pressure molding to produce a conversion film 10.
[0122]
As shown in FIG. 2C, the produced conversion film 10 was incorporated into a case 82 to
produce an electroacoustic transducer 80 as a speaker. The case 82 is a box-shaped container
whose one side is open, and a plastic rectangular container having a size of 200 × 290 mm at an
opening and a depth of 9 mm was used. Further, in the case 82, the viscoelastic support 86 is
disposed. The viscoelastic support 86 is glass wool having a height of 25 mm and a density of 32
kg / m <3> before assembly. The conversion film 10 is disposed so as to cover the openings of
the viscoelastic support 86 and the case 82, and the peripheral portion is fixed by the frame 84,
and the conversion film 10 is given appropriate tension and curvature by the viscoelastic support
86. . In addition, the inside of the convex portion 10a was hollow and was at atmospheric
pressure.
[0123]
Example 2 As Example 2, an electroacoustic transducer in which two regions are formed in
parallel, that is, an electroacoustic transducer having two curved regions with different radius of
curvature in FIG. 12A is manufactured. did. Example 2 is the same as Example 1, except that the
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size of the first area is 200 mm × 200 mm, the radius of curvature is 600 mm, the size of the
second area is 200 mm × 60 mm, and the radius of curvature is 30 mm. did.
[0124]
Comparative Example 1 An electroacoustic transducer was produced in the same manner as in
Example 1 except that a flat conversion film was used. That is, it was set as the electroacoustic
transducer which curved the whole main surface of the conversion film uniformly.
[0125]
Comparative Example 2 The entire main surface of a conversion film is formed using a
conversion film produced by vacuum evaporation of the upper electrode and the lower electrode
using a commercially available 50 μm thick PVDF as a speaker diaphragm. An electroacoustic
transducer was produced in the same manner as in Example 1 except that it was uniformly
curved.
[0126]
Comparative Example 3 An electroacoustic transducer was produced in the same manner as in
Example 2 except that the same conversion film as in Comparative Example 2 was used.
[0127]
[Evaluation] <Frequency band> The sound pressure level-frequency characteristics of the
manufactured speaker were measured by sine wave sweep measurement using a constant
current type power amplifier.
The measurement microphone was placed at a position 50 cm immediately above the center of
the speaker.
The width of the frequency band was determined from the measurement results of the sound
pressure level-frequency characteristics. Specifically, the frequency range in which the frequency
response of the speaker does not decrease by 10 dB or more from the average sound pressure
level in the rated frequency range was determined.
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[0128]
<Distortion> Next, the magnitude of the second harmonic or third harmonic component when a 1
kHz sine wave (voltage 10 Vo-p) is applied to the speaker, ie, the second harmonic to the sound
pressure level of 1 kHz Or the ratio of the sound pressure level of the third harmonic component
was measured.
[0129]
<Sound image> Using a speaker, five commercially available music CDs were reproduced to
evaluate the sound image.
Two speakers were arranged 1 m apart on the left and right, and viewed and evaluated at a
position 0.87 m away from the center of the two speakers, that is, at the apex of an equilateral
triangle with one side connecting the left and right speakers. . The evaluation was performed by a
sensory evaluation by 20 ordinary people, and the case where the number of persons who
evaluated the sound image as equal or higher compared to a normal 2-way cone type speaker
(Brilon 2 made by Audio Physic) was regarded as evaluation A. The case of 10 or more and less
than 15 was regarded as evaluation B, and the case of less than 10 as evaluation C. The
evaluation results are shown in Table 1. Further, FIG. 14 shows an example of the measurement
result of the measured sound pressure level-frequency characteristic. In FIG. 14, the result of
Example 1 is indicated by a solid line, and the result of Comparative Example 1 is indicated by a
broken line.
[0130]
[0131]
From Table 1, a polymer composite piezoelectric body formed by dispersing piezoelectric
particles in a viscoelastic matrix made of a polymer material having viscoelastic properties at
normal temperature, and a pair of electrode pairs laminated on both sides of the polymer
composite piezoelectric body In Example 1 and Example 2 in which the conversion film having
the above-described structure is supported by forming two or more regions in which at least one
of the surface area and the curvature radius differs, sufficient sound is obtained as compared
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with Comparative Examples 1 to 3. It can be seen that the frequency band having the pressure
level is wide and distortion is also small.
In particular, it can be understood from the comparison between Example 1 and Comparative
Example 1 and FIG. 14 that the frequency band having a sufficient sound pressure level is
broadened by forming two or more regions having different curvature radii in the conversion
film. . Further, it can be understood from the comparison between Example 1 and Example 2 that
the sound image is improved by arranging two or more regions different in radius of curvature in
the direction perpendicular to the main surface. From the above results, the effects of the present
invention are clear.
[0132]
10, 90, 92, 94, 102, 112, 122, 132 Electro-acoustic conversion films 10a, 90a, 92a, 92b, 94a,
102a, 102b, convex portions 11a, 11c sheet-like material 11b laminated body 12 piezoelectric
layer 14 lower portion Electrode 16 Upper electrode 18 Lower protective layer 20 Upper
protective layer 24 Viscoelastic matrix 26 Piezoelectric particles 30 Corona electrode 32 DC
power supplies 80, 80b, 100, 110, 120, 130 Electroacoustic transducers 82 Case 84, 124 Frame
86, 86b Viscoelastic support 112a, 122a, 132a first area 112b, 122b, 132b second area 112c,
122c, 132c third area 116, 134a, 134b frame 124a outer frame portion 124b frame portion
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