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JPWO2016208385

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DESCRIPTION JPWO2016208385
Abstract: Provided are an electroacoustic transducer film and an electroacoustic transducer that
can be reproduced at a sufficient volume and can prevent appearance defects. A polymer
composite piezoelectric body formed by dispersing piezoelectric particles in a viscoelastic matrix
made of a polymer material having viscoelasticity at normal temperature, and a lower thin film
electrode laminated on one main surface of the polymer composite piezoelectric body; The lower
protective layer laminated on the lower thin film electrode, the upper thin film electrode
laminated on the other principal surface of the polymer composite piezoelectric material, the
upper protective layer laminated on the upper thin film electrode, and the upper thin film
electrode It has a colored layer laminated on at least one of the surface side and the surface side
of the lower thin film electrode.
Electro-acoustic transducer film and electro-acoustic transducer
[0001]
The present invention relates to an electro-acoustic transducer film and an electro-acoustic
transducer used for an acoustic device such as a speaker.
[0002]
In response to the thinning of displays such as liquid crystal displays and organic EL (Electro
Luminescence) displays, weight reduction and thinning of speakers used in these thin displays
are required.
[0003]
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1
The shape of a conventional speaker is generally a funnel-shaped so-called cone shape, a
spherical dome shape or the like.
However, if such a speaker is to be incorporated in the above-described thin display, it can not be
made sufficiently thin, and there is a possibility that the lightness may be impaired.
In addition, when the speaker is externally attached, carrying and the like is troublesome.
[0004]
Therefore, as a thin speaker that can be integrated with a thin display or a flexible display
without loss of lightness, a sheet-like flexible flexible film is used, which uses a piezoelectric film
that has the property of expanding and contracting in response to an applied voltage. It has been
proposed.
[0005]
For example, the applicant of the present application proposes the electroacoustic transducing
film disclosed in Patent Document 1 as a piezoelectric film which is sheet-like, flexible, and
capable of stably reproducing high-quality sound. did.
The electroacoustic conversion film disclosed in Patent Document 1 comprises a polymer
composite piezoelectric body (piezoelectric body layer) formed by dispersing piezoelectric body
particles in a viscoelastic matrix made of a polymer material having viscoelasticity at normal
temperature. It has a thin film electrode formed on both sides of a molecular composite
piezoelectric material and a protective layer formed on the surface of the thin film electrode.
[0006]
JP, 2014-14063, A
[0007]
11-05-2019
2
Here, in such an electroacoustic conversion film, in response to an applied voltage, the
conversion film itself expands and contracts in a plane direction, and vibrates in a direction
perpendicular to the plane to convert vibration (sound) and an electric signal. It is
Therefore, in order to further improve the sound pressure, it is necessary to make the conversion
film thinner and to make the response high. In the conversion film, since the thin film electrode is
very thin, the thickness of the conversion film is substantially determined by the thickness of the
piezoelectric layer and the thickness of the protective layer, but in order to develop sufficient
piezoelectricity, the piezoelectric The thickness of the layer is required to some extent. Therefore,
in order to further improve the sound pressure, it is conceivable to reduce the thickness of the
conversion film by reducing the thickness of the protective layer.
[0008]
By the way, as a thin film electrode of such a conversion film, a copper electrode is mainly used
from a viewpoint of electroconductivity, flexibility, etc. However, when a copper electrode is used
as a thin film electrode, it rusts over time, causing a problem that appearance defects occur. In
order to prevent appearance defects due to such rusting, it is conceivable to provide gas barrier
properties to the protective layer to suppress rusting, but as described above, to improve the
sound pressure, the protective layer is made thinner As it is necessary, it is difficult to impart
sufficient gas barrier properties to a thin protective layer.
[0009]
Moreover, it is possible to make the rust of a thin film electrode not distinguishable from the
outside by coloring a protective layer. However, as described above, when the protective layer is
made thin to improve the sound pressure, it becomes difficult to sufficiently color, so the
appearance also becomes poor.
[0010]
An object of the present invention is to solve the problems of the prior art, and to provide an
electroacoustic transducer film and an electroacoustic transducer that can be reproduced at a
sufficient volume and can prevent appearance defects. .
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3
[0011]
As a result of intensive studies to solve the above problems, the present inventors 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 A lower thin film electrode stacked on one main surface of the
composite piezoelectric body, a lower protective layer stacked on the lower thin film electrode,
an upper thin film electrode stacked on the other main surface of the polymer composite
piezoelectric body, and an upper portion It is found that the above problem can be solved by
having the upper protective layer laminated on the thin film electrode and the colored layer
laminated on at least one of the surface layer side of the upper thin film electrode and the
surface layer side of the lower thin film electrode. , Completed the present invention.
That is, the present invention provides an electroacoustic transducer having the following
configuration.
[0012]
(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 lower thin film laminated on one main surface of the polymer composite
piezoelectric body An electrode, a lower protective layer laminated on the lower thin film
electrode, an upper thin film electrode laminated on the other main surface of the polymer
composite piezoelectric material, an upper protective layer laminated on the upper thin film
electrode, and an upper thin film An electroacoustic transducing film having a colored layer
laminated on at least one of a surface side of an electrode and a surface side of a lower thin film
electrode. (2) The electroacoustic conversion film according to (1), wherein a colored layer is
laminated on at least one of between the upper thin film electrode and the upper protective layer
and between the lower thin film electrode and the lower protective layer. (3) The electroacoustic
transducing film according to (1) or (2), wherein the colored layer is laminated on both main
surface sides of the polymer composite piezoelectric material. (4) The electroacoustic conversion
film in any one of (1)-(3) whose transmission density of a colored layer is 0.3 or more. (5) The
electroacoustic conversion film according to any one of (1) to (4), wherein the thickness of the
colored layer is 40 nm or less. (6) The electroacoustic conversion film according to any one of (1)
to (5), wherein the electrical resistivity of the colored layer is 1 × 10 <−7> Ωm or less. (7) The
electroacoustic conversion film in any one of (1)-(6) in which a colored layer consists of metals.
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4
(8) The electroacoustic conversion film according to any one of (1) to (7), wherein the colored
layer is made of nickel. (9) The electroacoustic conversion film according to any one of (1) to (8),
wherein the polymer material has a cyanoethyl group. The electroacoustic transducer which has
an electroacoustic conversion film in any one of (10) (1)-(9).
[0013]
According to the present invention, it is possible to provide an electroacoustic transducer film
and an electroacoustic transducer that can be reproduced at a sufficient volume and can prevent
appearance defects.
[0014]
It is sectional drawing which shows typically an example of the electroacoustic transducing film
of this invention.
It is a conceptual diagram for demonstrating an example of the preparation methods of an
electroacoustic transducer film. It is a conceptual diagram for demonstrating an example of the
preparation methods of an electroacoustic transducer film. It is a conceptual diagram for
demonstrating an example of the preparation methods of an electroacoustic transducer film. It is
a conceptual diagram for demonstrating an example of the preparation methods of an
electroacoustic transducer film. It is a conceptual diagram for demonstrating an example of the
preparation methods of an electroacoustic transducer film. It is sectional drawing which
represents typically an example of the electroacoustic transducer of this invention. It is a top
view of FIG. 3A. It is sectional drawing for demonstrating the structure of an electroacoustic
transducer. It is sectional drawing which shows notionally another example of the electroacoustic
transducer of this invention. It is sectional drawing for demonstrating another example of the
electroacoustic transducer of this invention. It is sectional drawing for demonstrating another
example of the electroacoustic transducer of this invention. It is sectional drawing for
demonstrating another example of the electroacoustic transducer of this invention. It is sectional
drawing for demonstrating another example of the electroacoustic transducing film of this
invention. It is sectional drawing which shows an example of an electroacoustic transducer using
the electroacoustic transducing film of FIG. 6A.
[0015]
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5
Hereinafter, the electro-acoustic transducer film and the electro-acoustic transducer of the
present invention will be described in detail based on preferred embodiments shown in the
accompanying drawings. Although the description of the configuration requirements described
below may be made based on the representative embodiments of the present invention, the
present invention is not limited to such embodiments. In addition, in this specification, the
numerical range represented using "-" means the range which includes the numerical value
described before and after "-" as a lower limit and an upper limit.
[0016]
The electro-acoustic conversion film of the present invention is used as a diaphragm of an
electro-acoustic transducer as described later. In the electroacoustic transducer, when the
electroacoustic transducing film is stretched in the in-plane direction by voltage application to
the electroacoustic transducer film, the electroacoustic transducing film is above (sound radiation
direction) to absorb the stretched portion. When the electroacoustic transducing film is
contracted in the in-plane direction by voltage application to the electroacoustic transducing film,
the electroacoustic transducing film is directed downward (case side) to absorb the contraction.
Moving. The electro-acoustic transducer converts the vibration (sound) and the electrical signal
by vibration due to the repetition of expansion and contraction of the electro-acoustic transducer
film, and inputs the electrical signal to the electro-acoustic transducer film and responds to the
electrical signal. It is used for reproducing the sound by vibration, converting the vibration of the
electro-acoustic conversion film by receiving the sound wave into an electric signal, imparting a
tactile sensation by the vibration, and transporting the object. Specifically, various acoustic
devices such as full-range speakers, speakers such as tweeters, squawkers and woofers, speakers
for headphones, noise cancelers, microphones, and pickups used for musical instruments such as
guitars can be mentioned. In addition, since the electroacoustic conversion film of the present
invention is a nonmagnetic material, it can be suitably used as a noise canceller among MRI noise
cancellers. In addition, the above electroacoustic transducers are thin, light and bendable,
wearable products such as hats, mufflers and clothes, flat displays such as TVs and digital
signage, ceilings of buildings and cars, curtains, umbrellas, wallpapers, windows, beds, etc. Are
preferably used.
[0017]
FIG. 1 is a cross-sectional view schematically showing an example of the electroacoustic
transducer film of the present invention. As shown in FIG. 1, the electroacoustic conversion film
(hereinafter also referred to as conversion film) 10 of the present invention is laminated on one
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6
surface of a piezoelectric layer 12 which is a sheet-like material having piezoelectricity, and the
piezoelectric layer 12. The lower thin film electrode 14, the lower colored layer 21 stacked on
the lower thin film electrode 14, the lower protective layer 18 stacked on the lower colored layer
21, and the other surface of the piezoelectric layer 12 An upper thin film electrode 16, an upper
colored layer 22 stacked on the upper thin film electrode 16, and an upper protective layer 20
stacked on the upper colored layer 22 are provided.
[0018]
In the conversion film 10, the piezoelectric layer 12 which is a polymer composite piezoelectric
body is formed of piezoelectric particles 26 in a visco-elastic matrix 24 made of a polymer
material having visco-elastic properties at normal temperature as schematically shown in FIG.
The polymer composite piezoelectric material is obtained by uniformly dispersing 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.
[0019]
Here, the polymer composite piezoelectric material (piezoelectric material layer 12) is preferably
provided with the following requirements. (I) Flexibility For example, when holding in a loosely
flexed state like a document or magazine in a document sense for portable use, to be subjected to
relatively slow, large bending deformation of several Hz or less from outside constantly 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) Sound quality
The 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 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 f0 changes with the
change in curvature also decreases. Therefore, the loss tangent of the polymer composite
piezoelectric material is required to be moderately large.
11-05-2019
7
[0020]
In summary, the polymer composite piezoelectric body is required to be hard against vibrations
of 20 Hz to 20 kHz and to behave softly against 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.
[0021]
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 the
polymer composite piezoelectric material (piezoelectric layer 12), by using a polymer material
having a glass transition temperature at normal temperature, in other words, a polymer material
having viscoelasticity at normal temperature as a matrix, against vibration of 20 Hz 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. .
[0022]
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.
11-05-2019
8
[0023]
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.
[0024]
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.
[0025]
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.
[0026]
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
11-05-2019
9
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. .
[0027]
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.
[0028]
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.
[0029]
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
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10
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.
[0030]
Further, in order to increase the dielectric constant of the piezoelectric layer 12, dielectric
particles may be added to the viscoelastic matrix. The dielectric particles are made of particles
having a high relative dielectric constant of 80 or more at 25 ° C. As dielectric particles, for
example, lead zirconate titanate (PZT), barium titanate (BaTiO3), titanium oxide (TiO2), strontium
titanate (SrTiO3), lead zirconate titanate zirconate (PLZT), zinc oxide (ZnO), a solid solution
(BFBT) of barium titanate and bismuth ferrite (BiFeO3), etc. are exemplified. Among them, barium
titanate (BaTiO3) is preferably used as the dielectric particles in view of having a high relative
dielectric constant.
[0031]
The dielectric particles preferably have an average particle size of 0.5 μm or less. The volume
fraction of the dielectric particles is preferably 5 to 45%, more preferably 10 to 30%, and
particularly preferably 20 to 30% of the total volume of the viscoelastic matrix and the dielectric
particles.
[0032]
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).
[0033]
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11
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.
[0034]
Although the piezoelectric particles 26 in the piezoelectric layer 12 are dispersed uniformly and
regularly in the viscoelastic matrix 24 in FIG. 1, 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
viscoelastic matrix 24 as long as they are preferably dispersed uniformly.
[0035]
In the conversion film 10, the ratio of the visco-elastic matrix 24 to the piezoelectric particles 26
in the piezoelectric layer 12 is required for the size and thickness in the plane direction of the
conversion film 10, the application of the conversion film 10, and the conversion film 10
Depending on the characteristics of the 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.
[0036]
In the conversion film 10, the thickness of the piezoelectric layer 12 is not particularly limited,
and is appropriately set according to the size of the conversion film 10, the application of the
conversion film 10, the characteristics required of the conversion film 10, etc. do it. Here,
according to the study of the present inventor, the thickness of the piezoelectric layer 12 is
preferably 8 to 300 μm, more preferably 8 to 40 μm, still more preferably 10 to 35 μm, and
particularly preferably 15 to 25 μm. By setting the thickness of the piezoelectric layer 12 in the
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12
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.
[0037]
As shown in FIG. 1, 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 colored
layer 21 is formed on the lower thin film electrode 14 The lower protective layer 18 is formed on
the colored layer 21, and the upper thin film electrode 16 is formed on the other surface of the
piezoelectric layer 12, and the upper colored layer 22 is formed on the upper thin film electrode
16. The upper protective layer 20 is formed on the colored layer 22. 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 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.
[0038]
A thin film electrode and a protective layer may be provided with a projecting portion at the
outside in the surface direction of the piezoelectric layer as an electrode lead-out part, or a part
of the protective layer is removed to form a hole. Alternatively, a conductive material such as
silver paste may be inserted into the hole to electrically conduct the conductive material and the
thin film electrode to form an electrode lead-out portion. In each thin film electrode, the number
of electrode lead portions is not limited to one, and two or more electrode lead portions may be
provided. In particular, in the case of a configuration in which a conductive material is inserted
into the hole to remove a part of the protective layer to form an electrode lead-out part, three or
more electrode lead-out parts are provided to ensure electric conduction more reliably.
preferable.
[0039]
That is, the conversion film 10 sandwiches both surfaces of the piezoelectric layer 12 with an
electrode pair, that is, the upper thin film electrode 16 and the lower thin film electrode 14, and
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13
sandwiches the laminate between the upper colored layer 22 and the lower colored layer 21.
Further, it has a configuration in which it is sandwiched by the upper protective layer 20 and the
lower protective layer 18. 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.
[0040]
In the conversion film 10, the upper protective layer 20 and the lower protective layer 18 serve
to cover the upper thin film electrode 16 and the lower thin film electrode 14 and 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.
[0041]
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), polyamide (PA), polyethylene naphthalate (PEN), triacetyl cellulose (TAC),
and cyclic olefin resins are preferably used.
[0042]
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
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14
required. According to the study of the present inventor, the thickness of the upper protective
layer 20 and the lower protective layer 18 is preferably 50 μm or less, more preferably 25 μm
or less, and particularly preferably 10 μm or less.
[0043]
In the conversion film 10, 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 a lower thin film electrode is provided between the piezoelectric layer 12 and the lower
protective layer 18. (Hereinafter, it is also called a lower electrode) 14 is 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).
[0044]
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. Specifically,
carbon, palladium, iron, tin, aluminum, nickel, platinum, gold, silver, copper, chromium and
molybdenum or the like, alloys thereof, indium tin oxide, PEDOT / PPS
(polyethylenedioxythiophene-polystyrene sulfone) Examples thereof include conductive polymers
such as acids). Among them, any of copper, aluminum, gold, silver, platinum and indium tin oxide
is suitably exemplified, and copper is more preferable in terms of conductivity, cost and
flexibility.
[0045]
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 sticking and a method of applying can be
used.
[0046]
Above all, a thin film of copper or aluminum formed by vacuum deposition is suitably used as the
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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.
[0047]
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. According to
the study of the present inventor, 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]
In the conversion film 10, the upper colored layer 22 is formed between the upper electrode 16
and the upper protective layer 20, and the lower colored layer 21 is formed between the lower
electrode 14 and the lower protective layer 18. The upper colored layer 22 and the lower colored
layer 21 are for making the rust of the upper electrode 16 and the lower electrode 14 invisible
from the outside.
[0049]
The transmission density of the upper colored layer 22 and the lower colored layer 21 is
preferably 0.3 or more from the viewpoint of making the rusting of the upper electrode 16 and
the lower electrode 14 invisible from the outside, the value is preferably 0.3 or more. Is more
preferable. The transmission density is an optical density measured as a ratio of transmitted light
to incident light, and the transmittance at a transmission density of 0.3 is about 50%, and the
transmittance at a transmission density of 0.5 Is about 30%.
11-05-2019
16
[0050]
Similarly to the upper protective layer 20 and the lower protective layer 18 described above, and
the upper electrode 16 and the lower electrode 14, when the rigidity of the upper colored layer
22 and the lower colored layer 21 is too high, expansion and contraction of the piezoelectric
layer 12 are caused. The upper colored layer 22 and the lower colored layer 21 are
advantageously thinner as long as the transmission density does not become too low, since not
only restraint but also flexibility is lost. According to the study of the present inventor, the
thickness of the upper colored layer 22 and the lower colored layer 21 is preferably 1 μm or
less, more preferably 100 nm or less, and particularly preferably 40 nm or less.
[0051]
The upper colored layer 22 and the lower colored layer 21 preferably have a low electrical
resistivity, and preferably 1 × 10 <−7> Ωm or less. In the conversion film 10, as a method of
drawing out the electrodes from the upper electrode 16 and the lower electrode 14, a part of the
protective layer is removed to form a hole, and a conductive material such as silver paste is
formed in the hole. There is a method of inserting and electrically conducting a conductive
material and a thin film electrode to form an electrode lead-out portion. In the case where the
electrode lead-out portion is formed by such a method, if the electrical resistivity of the upper
colored layer 22 and the lower colored layer 21 is high, the conductive material and the thin film
electrode can be formed only by removing a part of the protective layer. Since electrical
conduction can not be achieved, it is necessary to remove the upper colored layer 22 and the
lower colored layer 21 at the positions of the holes, which results in poor productivity. Therefore,
by lowering the electrical resistivity of the upper colored layer 22 and the lower colored layer
21, the conductive material and the thin film electrode can be electrically isolated without
removing the upper colored layer 22 and the lower colored layer 21 at the position of the hole. It
is preferable because it can be conducted.
[0052]
In the present invention, the material for forming the upper colored layer 22 and the lower
colored layer 21 is not particularly limited as long as it satisfies the above transmission density
and does not change color due to rusting or the like. Specifically, as materials for forming the
11-05-2019
17
upper colored layer 22 and the lower colored layer 21, metals such as nickel, titanium,
aluminum, gold and platinum, and inorganic materials such as carbon black (CB), titanium oxide,
zinc oxide and barium sulfate Examples thereof include pigments, organic pigments of
quinacridone type, azo type, benzimidazolone type, phthalocyanine type, and anthraquinone type,
and members having a light scattering property having holes inside. It is preferable to use a
metal as a formation material of the upper colored layer 22 and the lower colored layer 21 from
the viewpoint of the above-mentioned transmission density, thickness, and electric resistivity, and
among them, nickel is more preferable. Moreover, it is preferable to use various pigments as the
upper colored layer 22 and the lower colored layer 21 from the viewpoint of the designability
that the converted film can be colored in various colors.
[0053]
The method of forming the upper colored layer 22 and the lower colored layer 21 is not
particularly limited, and may be formed by various known methods according to the abovementioned materials. For example, in the case of using a metal as a material for forming the
colored layer, a film formed by vapor deposition (vacuum film forming method) such as vacuum
evaporation or sputtering or plating, or a foil formed of the above material is attached Methods
etc. are available. It is more preferable to form by vacuum evaporation from the point which can
be formed thinner. Moreover, when using a pigment as a formation material of a colored layer,
the apply ¦ coating method, printing, etc. can be utilized. Also, a method of transferring a
previously formed colored layer can be used.
[0054]
In the illustrated example, the upper colored layer 22 and the lower colored layer 21 are formed
between the upper electrode 16 and the upper protective layer 20 and between the lower
electrode 14 and the lower protective layer 18, respectively. However, the present invention is
not limited to this, as long as it is formed on the surface side with respect to the upper electrode
16 and on the surface side with respect to the lower electrode 14. That is, for example, the upper
electrode 16, the upper protective layer 20, and the upper colored layer 22 are sequentially
formed on one surface of the piezoelectric layer 12, and the lower electrode 14 and the lower
protective layer 18 are formed on the other surface of the piezoelectric layer 12. The lower
colored layer 21 may be formed in this order.
[0055]
11-05-2019
18
In the illustrated example, although the colored layer is provided on each of the upper electrode
16 side and the lower electrode 14 side, the present invention is not limited to this, and a colored
layer is provided on at least one side. It may be In this case, it is preferable to have a colored
layer on the side to be viewed (the side facing the outside of the device) when incorporated into
the electroacoustic transducer. In addition to the thin film electrode, the protective layer, the
colored layer and the like described above, the conversion film of the present invention may
include functional layers such as an adhesion imparting layer and an antioxidant layer.
[0056]
As described above, the conversion film 10 sandwiches the piezoelectric layer 12 formed by
dispersing the piezoelectric particles 26 in the visco-elastic matrix 24 having visco-elastic
properties at normal temperature, with the upper electrode 16 and the lower electrode 14, and
further The laminate is sandwiched between the upper colored layer 22 and the lower colored
layer 21, and further, 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
[0057]
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.
[0058]
In addition, the conversion film 10 has a product of a thickness and a storage elastic modulus (E
11-05-2019
19
′) at a frequency of 1 Hz according to dynamic viscoelasticity measurement, which is 1.0 × 10
<6> to 2.0 × 10 <0 at 0 ° C. 6> (1.0E + 06 to 2.0E + 06) N / m at 50 ° C. 1.0 × 10 <5> to 1.0
× 10 <6> (1.0E + 05 to 1.0E + 06) N / m Is preferred. Thereby, appropriate rigidity and
mechanical strength can be provided as long as the conversion film 10 does not lose flexibility
and acoustic characteristics.
[0059]
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 lowest resonance
frequency f0 changes with the change in curvature of the speaker can be reduced.
[0060]
Hereinafter, with reference to FIG. 2A-FIG. 2E, an example of the manufacturing method of the
conversion film 10 is demonstrated.
[0061]
First, as shown in FIG. 2A, the lower colored layer 21 is formed on the lower protective layer 18,
and the sheet 11a having the lower electrode 14 formed on the lower colored layer 21 is
prepared.
The sheet-like material 11 a has the lower colored layer 21 formed on the surface of the lower
protective layer 18 by vacuum deposition, sputtering, plating, coating, printing or the like, and
then on the surface of the lower colored layer 21 formed, A copper thin film or the like may be
formed as the lower electrode 14 by vacuum evaporation, 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 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.
11-05-2019
20
[0062]
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. Thereby, as shown in FIG. 2B, the lower colored layer 21 is
provided on the lower protective layer 18, the lower electrode 14 is provided on the lower
colored layer 21, and the piezoelectric layer 12 is provided on the lower electrode 14. The
laminated body 11b formed is produced.
[0063]
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 laminate 11b as shown in FIG. 2B may be produced by extruding in a
sheet form on the sheet-like material 11a shown in FIG. 2A by molding or the like and cooling.
[0064]
As described above, in the conversion film 10, in addition to the viscoelastic material such as
cyanoethylated PVA, a polymeric piezoelectric material such as PVDF may be added to the
viscoelastic matrix 24. 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 the heatmelted viscoelastic material and heat-melted. Once the laminated body 11 b having the lower
colored layer 21 and 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
of the piezoelectric layer 12 is Perform processing (polling).
11-05-2019
21
[0065]
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 FIGS. 2C and 2D are exemplified.
[0066]
In this method, as shown in FIGS. 2C and 2D, a bar or wire shape movable along the upper
surface 12a with a gap g of, for example, 1 mm on the upper surface 12a of the piezoelectric
layer 12 of the laminate 11b. The 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.
[0067]
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.
[0068]
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
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
11-05-2019
22
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.
[0069]
Thus, while the polarization process of the piezoelectric material layer 12 of the laminated body
11b is performed, the sheet in which the upper colored layer 22 is formed on the upper
protective layer 20 and the upper electrode 16 is formed on the upper colored layer 22 The
article 11c is prepared. The sheet-like material 11c has the upper colored layer 22 formed on the
surface of the upper protective layer 20 by vacuum deposition, sputtering, plating, coating,
printing, etc., and then on the surface of the upper colored layer 22 formed, A copper thin film or
the like may be formed as the upper electrode 16 by vacuum deposition, sputtering, plating or
the like. Next, as shown in FIG. 2E, the sheet-like material 11c is laminated on the laminate 11b
in which 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 or the like so as to sandwich the upper protective layer 20 and the lower
protective layer 18 to convert the conversion film 10 Can be made.
[0070]
Next, an electroacoustic transducer using the electroacoustic transducer film of the present
invention will be described with reference to FIGS. 3A to 3C. FIG. 3A is a cross-sectional view
conceptually showing the electroacoustic transducer 40, and FIG. 3B is a front view. That is, FIG.
3A is a cross-sectional view taken along line aa of FIG. 3B. The electroacoustic transducer 40
uses the conversion film 10 as a diaphragm.
[0071]
When the conversion film 10 stretches in the in-plane direction by applying a voltage to the
11-05-2019
23
conversion film 10, the electroacoustic transducer 40 moves the conversion film 10 upward (the
radiation direction of the sound) to absorb the stretching component. Conversely, when the
conversion film 10 contracts in the in-plane direction by voltage application to the conversion
film 10, the conversion film 10 moves downward (case 42 side) to absorb the contraction. The
electro-acoustic transducer 40 converts the vibration (sound) and the electric signal by the
vibration caused by the repetition of the expansion and contraction of the conversion film 10.
[0072]
The electroacoustic transducer 40 is configured to include the conversion film 10, the case 42,
the viscoelastic support 46, and the pressing member 48.
[0073]
The case 42 is a holding member that holds the conversion film 10 and the visco-elastic support
46 together with the pressing member 48, and is a box-shaped case that is formed of plastic,
metal, wood, or the like and is open on one side.
As shown in the figure, the case 42 has a thin hexahedron shape, and one of the largest surfaces
is an open surface. Also, the open part is a square. The case 42 accommodates the visco-elastic
support 46 therein.
[0074]
The viscoelastic support 46 has appropriate viscosity and elasticity, holds the conversion film 10
in a curved state, and stretches the conversion film 10 by applying a constant mechanical bias
anywhere on the conversion film 10 It is for converting motion into forward and backward
motion (motion in the direction perpendicular to the surface of the conversion film) without
waste. In the illustrated example, the viscoelastic support 46 is in the form of a square pole
having a bottom shape substantially equal to the bottom surface of the case 42. Also, the height
of the visco-elastic support 46 is larger than the depth of the case 42.
[0075]
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24
The material of the viscoelastic support 46 is not particularly limited as long as it has
appropriate viscosity and elasticity, and does not prevent the vibration of the piezoelectric film
and deforms suitably. For example, nonwoven fabric such as wool felt, wool felt including rayon
and PET, glass wool, foam material such as polyurethane (foam plastic), polyester wool, multiple
sheets of paper, magnetic fluid, paint, etc. It is illustrated. The specific gravity of the viscoelastic
support 46 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>.
[0076]
The pressing member 48 is for supporting the conversion film 10 in a state where it is pressed
against the viscoelastic support 46, and is formed of plastic, metal, wood or the like, and is a
square plate having an opening at the center. Like members. The pressing member 48 has the
same shape as the open surface of the case 42, and the shape of the opening is a square shape
similar to the open portion of the case 42.
[0077]
In the electroacoustic transducer 40, the visco-elastic support 46 is accommodated in the case
42, the case 42 and the visco-elastic support 46 are covered by the conversion film 10, and the
case 42 is surrounded by the pressing member 48. The pressing member 48 is fixed to the case
42 in a state of being in contact with the open surface of the case. The method for fixing the
pressing member 48 to the case 42 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.
[0078]
In the electroacoustic transducer 40, the height (thickness) of the viscoelastic support 46 is
larger than the height of the inner surface of the case 42. That is, in the state before the
conversion film 10 and the pressing member 48 are fixed, the visco-elastic support 46 protrudes
from the upper surface of the case 42 (see FIG. 3C). Therefore, in the electroacoustic transducer
40, the viscoelastic support 46 is held by the conversion film 10 so as to be pressed downward
11-05-2019
25
by the conversion film 10 as it gets closer to the peripheral portion of the viscoelastic support 46
in a state where the thickness becomes thinner. That is, at least a part of the main surface of the
conversion film 10 is held in a curved state. Thereby, a curved part is formed in at least one part
of the conversion film 10. In the electroacoustic transducer 40, this curved portion is a vibrating
surface. In the following description, the curved portion is also referred to as a vibrating surface.
Under the present circumstances, it is preferable to press the whole surface of the visco-elastic
support 46 in the surface direction of the conversion film 10, and to make thickness whole thin.
That is, it is preferable that the entire surface of the conversion film 10 be pressed and supported
by the viscoelastic support 46. In addition, it is preferable that the curvature of the curved
portion formed in this manner gradually changes from the center toward the peripheral portion.
As a result, the resonance frequency can be dispersed and the frequency band can be further
increased.
[0079]
In the electroacoustic transducer 40, the viscoelastic support 46 is compressed in the thickness
direction as it approaches the pressing member 48. However, due to the static viscoelastic effect
(stress relaxation), which place of the conversion film 10 But mechanical bias can be kept
constant. As a result, since the expansion and contraction movement of the conversion film 10 is
converted to the back and forth movement without wasting, a thin, sufficient volume can be
obtained, and the planar electroacoustic transducer 40 excellent in acoustic characteristics can
be obtained.
[0080]
In the electro-acoustic transducer 40 with such a configuration, a region of the conversion film
10 corresponding to the opening of the pressing member 48 is a curved portion that actually
vibrates. That is, the pressing member 48 is a portion that defines the curved portion. An
electroacoustic conversion unit using a conversion film having piezoelectricity can easily make
the relative size of the diaphragm to the size of the whole unit larger than that of a cone speaker
in which the diaphragm generally has a circular shape. Is easy to Moreover, from the said
viewpoint, 20 mm or less is preferable and, as for the width ¦ variety of the edge part of the press
member 48, 1 mm-10 mm are preferable.
[0081]
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26
Moreover, it is preferable that the surface by the side of the conversion film 10 of the
electroacoustic transducer 40 and a curved part are similar. That is, it is preferable that the outer
shape of the pressing member 48 and the shape of the opening be similar.
[0082]
In the electroacoustic transducer 40, the pressing force of the visco-elastic support 46 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. In addition, the thickness of the viscoelastic support 46 is not particularly limited, but
the thickness before pressed is preferably 1 to 100 mm, particularly 10 to 50 mm.
[0083]
In the illustrated example, the viscoelastic support 46 having viscoelasticity is used. However, the
present invention is not limited to this, as long as the elastic support having at least elasticity is
used. For example, instead of the viscoelastic support 46, an elastic support having elasticity may
be provided. Examples of the elastic support include natural rubber and various synthetic
rubbers.
[0084]
Here, although the electroacoustic transducer 40 shown to FIG. 3A is pressing the peripheral
region of the conversion film 10 on the case 42 by the press member 48, this invention is not
limited to this. That is, the electroacoustic transducer using the conversion film 10 does not have
the pressing member 48, for example, at four corners of the case 42, the conversion film 10 is
formed of the case 42 by screws, bolts, nuts and jigs. A configuration in which pressing / fixing
to the upper surface is also available. In addition, an O-ring or the like may be interposed
between the case 42 and the conversion film 10. By having such a configuration, a damper effect
can be provided, and transmission of vibration of the conversion film 10 to the case 42 can be
prevented, and more excellent acoustic characteristics can be obtained.
[0085]
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27
In addition, the electroacoustic transducer using the conversion film 10 may not have the case
42 for housing the viscoelastic support 46. That is, as a cross-sectional view of the electroacoustic transducer 50 shown in FIG. 4, the visco-elastic support 46 is placed on the rigid
support plate 52, as schematically shown as an example thereof. And the conversion film 10 is
placed, and the same pressing member 48 as described above is placed on the periphery. Next, a
configuration in which the visco-elastic support 46 is pressed together with the pressing member
48 by fixing the pressing member 48 to the support plate 52 with the screw 54 can also be used.
The size of the support plate 52 may be larger than that of the visco-elastic support 46.
Furthermore, as the material of the support plate 52, various diaphragms such as polystyrene,
foamed PET, or carbon fiber can be used to obtain electricity. The effect of further amplifying the
vibration of the acoustic transducer can also be expected.
[0086]
Furthermore, the electro-acoustic transducer is not limited to the configuration for pressing the
periphery, for example, a configuration in which the center of the laminate of the viscoelastic
support 46 and the conversion film 10 is pressed by some means is also available. is there. That
is, as long as the electroacoustic transducer is configured to be held in a curved state of the
conversion film 10, various configurations can be used. Alternatively, the conversion film 10 may
be attached to a resin film to apply tension (curve). 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.
[0087]
In the example shown in FIGS. 3A and 3B, the conversion film 10 is pressed against the
viscoelastic support 46 and supported using the pressing member 48, but the invention is not
limited thereto. For example, the case 42 The end of the conversion film may be fixed on the
back surface side of the case 42 using the conversion film 10 larger than the opening surface of
the above. That is, the case 42 and the visco-elastic support 46 disposed in the case 42 are
covered with the conversion film 10 larger than the opening surface of the case 42, and the end
of the conversion film 10 is pulled to the back side of the case 42. Alternatively, the conversion
film 10 may be pressed against the viscoelastic support 46 to apply tension to be curved, and the
end of the conversion film may be fixed on the back side of the case 42.
11-05-2019
28
[0088]
Alternatively, using an airtight case, cover the open end of the case with a conversion film to
close it, introduce a gas into the case, apply pressure to the conversion film, and hold it in a
convexly expanded state It may be
[0089]
For example, an electroacoustic transducer 56 shown in FIG. 5C is illustrated.
First, as shown in FIG. 5A, the electro-acoustic transducer 56 uses a similar airtight case 42, and
a pipe 42a for introducing air into the case 42 is provided. An O-ring 57 is provided on the upper
surface of the open end of the case 42, and the O-ring 57 is covered with the conversion film 10
so as to close the open surface of the case 42.
[0090]
Next, as shown in FIG. 5B, a frame-like presser lid 58 having a substantially L-shaped cross
section having an inner periphery substantially the same as the outer periphery of the case 42 is
fitted to the outer periphery of the case 42 (FIG. 5B In (C), the O-ring 57 is omitted). Thereby, the
conversion film 10 is pressed and fixed to the case 42, and the inside of the case 42 is airtightly
closed by the conversion film 10.
[0091]
Furthermore, as shown in FIG. 5C, air is introduced from the pipe 42a into the case 42 (the
closed space by the case 42 and the conversion film 10), and pressure is applied to the
conversion film 10 to expand in a convex shape. , Hold the electro-acoustic transducer 56. The
pressure in the case 42 is not limited, as long as the conversion film 10 bulges outward in a
convex shape, as long as the pressure is equal to or higher than the atmospheric pressure. The
pipe 42a may be fixed or detachable. When the pipe 42a is removed, it is natural that the pipe
attaching / detaching portion is closed airtight.
11-05-2019
29
[0092]
Moreover, in the electroacoustic transducer 40 shown to FIG. 3A, the conversion film 10 is
pressed by the viscoelastic support body 46, and the main surface is hold ¦ maintained in the
convexly curved state. Thus, there is no limitation in particular in the structure which hold ¦
maintains the conversion film 10 in the curved state. For example, as shown to FIG. 6A, you may
shape ¦ mold conversion film 10 itself in convex shape or concave shape previously. At that time,
the entire conversion film 10 may be formed into a convex shape or a concave shape, or a part of
the conversion film may be formed into a convex portion (concave portion). There is no
particular limitation on the method for molding the convex portion, and various known methods
for processing a resin film can be used. For example, the convex portion (concave portion) can be
formed by a forming method such as vacuum pressure molding, embossing, or the like. Thus, by
forming a convex part in the conversion film itself, it is preferable at the point which can prevent
that a viscoelastic support deform ¦ transforms with time and air escapes and a sound pressure
changes.
[0093]
Moreover, when forming a convex part in a conversion film in this way, although there is no
limitation in particular in the shape of a convex part, the shape of a convex part is a part of
spherical body, or a part of spheroid The shape of the projections when viewed in the direction
perpendicular to the main surface of the conversion film is preferably a substantially circular
shape or a substantially elliptical shape. At that time, the ratio H / D of the height H of the convex
portion to the diameter of the convex portion (the minor axis in the case of an ellipse, the length
of the minor side in the case of a rectangle) D is greater than 0 and 0.15 or less Is more
preferably 0.003 or more and 0.15 or less, and particularly preferably 0.005 or more and 0.10
or less. The sound pressure can be further improved by setting the ratio H / D of the height H of
the convex portion to the diameter D of the convex portion in this range.
[0094]
Moreover, when incorporating the conversion film which has a convex part in this way in an
electroacoustic transducer, it is preferable to press and fix the periphery of a convex part by a
press member. That is, it is preferable that the shape of the convex part when it sees from the
direction perpendicular ¦ vertical to the main surface of the conversion film, and the shape of the
opening part of a press member are substantially the same. Also, for example, as in the
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30
electroacoustic transducer 60 shown in FIG. 6B, the peripheral edge portion of the convex
portion of the conversion film 10 may be held by two pressing members 48 to support the
conversion film in a vibratable manner. Moreover, when incorporating the conversion film which
has a convex part in an electroacoustic transducer, a convex part may be arrange ¦ positioned
facing outward, and a convex part may be faced inside (namely, concave part may be faced
outward) and arrange ¦ positioned. You may
[0095]
Further, since the conversion film having the convex portion is formed in a convex shape itself,
there is no need for a viscoelastic support for bending the conversion film or a configuration for
applying pressure to the inside of the case. You may use in combination.
[0096]
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.
[0097]
Hereinafter, the present invention will be described in more detail by way of specific examples of
the present invention.
[0098]
Example 1 The conversion film 10 shown in FIG. 1 was produced by the method shown in FIGS.
2A to 2E described above.
First, cyanoethylated PVA (CR-V, manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved in
methyl ethyl ketone (MEK) at the following composition ratio.
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.
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・ PZT particles ································································································· 600 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 3.5 μm.
[0099]
On the other hand, a sheet-like material 11a formed by vacuum depositing a 20 nm thick nickel
thin film on a 4 μm thick PET film and further vacuum depositing a 0.1 μm thick copper thin
film on the nickel thin film And 11c were prepared. That is, in the present example, the upper
electrode 16 and the lower electrode 14 are copper-deposited thin films having a thickness of
0.1 μm, and the upper colored layer 22 and the lower colored layer 21 are nickel-deposited thin
films having a thickness of 20 nm. The protective layer 20 and the lower protective layer 18
become a PET film with a thickness of 4 μm. In addition, in order to obtain good handling during
the process, the one with a 50 μm-thick separator (temporary support PET) is used as the PET
film, and the separator of each protective layer is removed after the thermocompression bonding
of the sheet 11c. The
[0100]
Here, the electrical resistivity of nickel which is a colored layer is 7 × 10 <−7> Ωm. In addition,
when a nickel thin film is formed on a PET film before forming a copper thin film, the
transmission density is measured by a transmission densitometer (X-Rite 310 manufactured by
X-Rite), and the transmission density is 0.6. The
[0101]
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. Subsequently, what
applied the paint on the sheet-like object 11a was heated and dried in an oven at 120 ° C. to
evaporate MEK. Thus, the lower colored layer 21 made of nickel is provided on the lower
protective layer 18 made of PET, and the lower electrode 14 made of copper is provided on the
lower colored layer 21, and the thickness is 40 μm thereon. The laminated body 11b formed by
forming the piezoelectric layer 12 (piezoelectric layer) of the above was produced.
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[0102]
The piezoelectric layer 12 of the laminate 11b was subjected to polarization treatment by the
aforementioned corona poling shown in FIGS. 2C and 2D. 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.
[0103]
A mixture of cyanoethylated pullulan and cyanoethylated PVA (CR-M, manufactured by Shin-Etsu
Chemical Co., Ltd.) was applied to 0.3 μm on the upper electrode 16 (copper thin film side) on
the polarized laminate 11b. The sheet-like material 11 c was laminated with the application
surface directed to 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 to convert the film
10 was produced.
[0104]
The produced conversion film 10 was incorporated into a case 42 to produce an electroacoustic
transducer 40. The case 42 is a box-shaped container whose one side is open, and a plastic
rectangular container having a size of 172 × 302 mm at an opening and a depth of 9 mm was
used. Further, in the case 42, the visco-elastic support 46 is disposed. The viscoelastic support 46
was glass wool having a height of 40 mm and a density of 16 kg / m <3> before assembly. The
conversion film 10 is disposed so as to cover the openings of the viscoelastic support 46 and the
case 42, and the peripheral portion is fixed by the pressing member 48, and the conversion film
10 is given appropriate tension and curvature by the viscoelastic support 46. The electroacoustic
transducer 40 was manufactured. Thereby, the conversion film 10 was bent in a convex shape
like a convex lens.
[0105]
[Examples 2 to 6] The electroacoustic conversion film 10 and the electroacoustic transducer 40
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were produced in the same manner as in Example 1 except that the thickness of the piezoelectric
layer 12 was changed as shown in Table 1 below.
[0106]
Example 7 An electroacoustic transducer film 10 and an electroacoustic transducer are prepared
in the same manner as in Example 3 except that the piezoelectric layer 12 is formed using the
following as a paint for forming the piezoelectric layer 12. 40 was produced.
························································································
· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ... 600 parts by mass Further,
as the BaTiO 3 particles, BT-05 (manufactured by Sakai Chemical Co., Ltd., average particle
diameter 0.5 μm) was used.
[0107]
[Examples 8 to 10] The electroacoustic conversion film 10 and the electroacoustic transducer 40
were produced in the same manner as in Example 3 except that the thickness of the colored layer
was changed as shown in Table 1 below.
[0108]
[Example 11] A nickel thin film having a thickness of 20 nm is formed by vacuum evaporation on
one side of a PET film having a thickness of 4 μm as sheet-like materials 11a and 11c, and a
thickness of 0.1 μm is formed on the other side. An electroacoustic transducer film 10 and an
electroacoustic transducer 40 were produced in the same manner as in Example 3, except that a
copper thin film was vacuum deposited.
That is, the electroacoustic conversion film 10 of Example 11 is laminated in the order of the
lower electrode 14, the lower protective layer 18 as a support, and the lower colored layer 21 on
one surface of the piezoelectric layer 12, and the piezoelectric layer An upper electrode 16, an
upper protective layer 20 as a support, and an upper colored layer 22 are stacked in this order
on the other surface of the substrate 12. In the item of stacking order in Table 1, A is a
configuration in which the thin film electrode, the colored layer and the protective layer are
stacked in order from the piezoelectric layer 12 side, and the thin film electrode from the
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piezoelectric layer 12 side A configuration in which the layer and the colored layer are stacked in
this order is referred to as "B".
[0109]
Example 12 An electroacoustic transducer film 10 and an electroacoustic transducer 40 are
prepared in the same manner as in Example 3, except that the colored layer is formed by a
coating method using the following as a paint for forming a colored layer. Was produced.
······························································································································ Cross-linking agent
···································· 240 mass parts carbon black water dispersion MF-5630 black (made by
Dainichi Seika Kogyo Co., Ltd.), acrylic resin water dispersion Julimer ET-410 (Toagosei Co., Ltd.)
Epocross WS-700 (manufactured by Nippon Shokubai Co., Ltd.) was used as the crosslinking
agent. CB in Table 1 is carbon black.
[0110]
[Examples 13 to 15] The electroacoustic transducer film 10 and the electroacoustic transducer
40 were produced in the same manner as in Example 3 except that the forming material and
thickness of the colored layer were changed as shown in Table 1 below. .
[0111]
Example 16 The electroacoustic transducer film 10 produced in the same manner as in Example
3 is molded into a shape having a convex portion as shown in FIG. Made.
The shape of the convex portion was a shape consisting of a part of a sphere. Moreover, when it
saw from the direction perpendicular ¦ vertical to the main surface of the conversion film 10,
diameter D of the convex part was 40 mm, and height was 0.5 mm. That is, the ratio H / D of the
height H to the diameter D of the convex portion is 0.01. The edge part of the produced
conversion film 10 was sandwiched by two pressing members 48 to produce an electroacoustic
transducer 60 as shown in FIG. 6B. Here, a sine wave of 1 kHz, 0.5 V 0 -P was input to the
electroacoustic transducer 60, and the amplitude of the central portion of the conversion film
was measured by a laser Doppler vibrometer, and it was 30 nm.
[0112]
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[Examples 17 and 18] Except that the height H of the convex portion is changed to 4 mm and 6
mm, respectively, and the ratio H / D of the height H to the diameter D is set to 0.10 and 0.15,
respectively, In the same manner as in Example 16, an electroacoustic transducer film 10 and an
electroacoustic transducer 60 were produced. Moreover, when the amplitude of the center part
of the conversion film was measured in the same manner as in Example 16, the amplitudes were
22 nm and 17 nm, respectively.
[0113]
Comparative Example 1 An electroacoustic transducer film and an electroacoustic transducer
were produced in the same manner as in Example 3 except that the colored layer was not
provided.
[0114]
Comparative Example 2 An electroacoustic transducing film and an electroacoustic transducer
were produced in the same manner as in Example 3 except that the thickness of the protective
layer was set to 20 μm and no colored layer was provided.
[0115]
Comparative Example 3 An electroacoustic transducer film and an electroacoustic transducer
were produced in the same manner as in Example 18 except that the colored layer was not
provided.
[0116]
[Evaluation] <Appearance> After leaving the produced electroacoustic conversion film in an
environment of temperature 70 ° C. and humidity 80% RH for 150 hours, the appearance is
visually observed, and the appearance change due to rust of the thin film electrode is visually
recognized It was evaluated whether or not
A: No change B: Rust is slightly visible C: Rust is present
[0117]
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<Scratch resistance> The surface of the produced electroacoustic conversion film was rubbed
with steel wool (# 0000), load 500 g, speed 1000 mm / min, 10 reciprocations with a continuous
load type scratch strength tester (HEIDON-18S) After rubbing, it was evaluated whether the thin
film electrode was visible or not.
A: not visible at all B: slightly visible C: visible
[0118]
<Adhesiveness> The tape peeling test was implemented with respect to the produced sheet-like
article 10a.
Specifically, a razor was used on the surface on the thin film electrode side of the sheet-like
material 10a, and 11 pieces of scratches were made in each of the vertical and horizontal
directions at intervals of 1 mm. On top of that, mylar tape of width 20 mm was applied and
peeled off quickly in the 90 ° direction. After peeling, the number of peeled squares was
counted and evaluated according to the following evaluation criteria. A: Residual area rate of 50%
or more B: Residual area rate of 25% to less than 50% C: Residual area rate of less than 25%
[0119]
<Sound pressure> (Examples 1-15, comparative examples 1 and 2) The sound pressure level of
the produced electroacoustic transducer was measured. Specifically, a microphone is disposed at
a distance of 0.5 m toward the center of the conversion film of the electroacoustic transducer,
and 1 kHz, 10 V 0 -P between the upper electrode and the lower electrode of the electroacoustic
transducer. The sound pressure level was measured by inputting a sine wave. Based on the
difference with the sound pressure level of the comparative example 1, it evaluated as follows. A:
+1.0 dB or more B: +1.0 dB or less-0.5 dB or more C:-0.5 dB or less-1.5 dB or more D:-1.5 dB or
less-3.0 dB or more E:-3.0 dB or less Evaluation result Is shown in Table 1.
[0120]
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(Examples 16 to 18, Comparative Example 3) The sound pressure level of the produced
electroacoustic transducer was measured. Specifically, a microphone is placed at a distance of 0.1
m toward the center of the conversion film of the electroacoustic transducer, and 1 kHz, 10 V 0 P between the upper electrode and the lower electrode of the electroacoustic transducer The
sound pressure level was measured by inputting a sine wave. Based on the difference with the
sound pressure level of the comparative example 3, it evaluated as follows. A: +1.0 dB or more B:
+1.0 dB or less-0.5 dB or more C:-0.5 dB or less-1.5 dB or more D:-1.5 dB or less-3.0 dB or more
E:-3.0 dB or less Evaluation result Is shown in Table 2.
[0121]
[0122]
[0123]
From Tables 1 and 2, it is understood that in Examples 1 to 18 of the electroacoustic conversion
film of the present invention, a change in the appearance due to rust of the thin film electrode is
less visible than in Comparative Examples 1 to 3.
Moreover, it turns out that Example 1-18 of the electroacoustic transducer using the
electroacoustic conversion film of this invention becomes high [sound pressure] compared with
Comparative Examples 1-3.
[0124]
Further, from the comparison of Examples 1 to 6, it is understood that the thickness of the
piezoelectric layer is preferably 8 μm to 40 μm, more preferably 10 μm to 35 μm, and
particularly preferably 15 μm to 25 μm.
Further, from the comparison between Example 3 and Example 7, it is understood that it is
preferable to add dielectric particles to the viscoelastic matrix of the piezoelectric layer.
Moreover, it turns out that 5 nm-40 nm are preferable and, as for the thickness of a colored
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layer, 15 nm-25 nm are more preferable from contrast of Example 3 and Examples 8-10.
[0125]
Further, from the comparison between Example 3 and Example 11, in the configuration in which
the colored layer is disposed outside the protective layer, the colored layer may be scraped off
and the inside (thin film electrode) may be visually recognized. It can be seen that the layer is
preferably arranged between the protective layer and the thin film electrode. Further, it is
understood from the comparison of Example 3 and Examples 12 to 15 that the material for
forming the colored layer is preferably a metal, and in particular, nickel, aluminum and gold are
preferable.
[0126]
Moreover, it turns out that a sound pressure can be improved more by shape ¦ molding an
electroacoustic conversion film in the shape which has a convex part from contrast of Example 3
and Examples 16-18. At that time, it is understood that the ratio H / D of the height H of the
convex portion to the diameter D is preferably more than 0 and 0.15 or less, and more preferably
0.003 or more and 0.10 or less. From the above results, the effects of the present invention are
clear.
[0127]
DESCRIPTION OF SYMBOLS 10 electroacoustic conversion film 11a, 11c sheet-like material 11b
laminated body 12 piezoelectric material layer 14 lower thin film electrode 16 upper thin film
electrode 18 lower protective layer 20 upper protective layer 21 lower colored layer 22 upper
colored layer 24 viscoelastic matrix 26 piezoelectric particles Reference Signs List 30 corona
electrode 32 direct current power supply 40, 50, 60 electroacoustic transducer 42 case 46 viscoelastic support 48 pressing member 52 support plate 54 screw 57 O ring 58 pressing cover
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