WO2022196353A1

WO2022196353A1 - Electroacoustic converter

Info

Publication number: WO2022196353A1
Application number: PCT/JP2022/008702
Authority: WO
Inventors: 裕介香川; 輝男芦川
Original assignee: 富士フイルム株式会社
Priority date: 2021-03-19
Filing date: 2022-03-02
Publication date: 2022-09-22
Also published as: JPWO2022196353A1; TW202241146A

Abstract

The present invention addresses the problem of providing an electroacoustic converter in which an acoustic film is affixed to a rollable panel, the electroacoustic converter making it possible to prevent the panel from being scratched by wiring and to output sound having a high sound pressure. The aforementioned problem is solved by having a rollable panel, an acoustic film that causes the panel to vibrate, a rolling shaft for rolling the panel, and flat-plate wiring for connecting the acoustic film and an external device, the flat-plate wiring including a metal foil, and the invention being such that flat-plate wiring having a length of at least 50% of the length of the panel in a direction orthogonal to the rolling shaft is affixed to a region that is no more than 30% of the length of the panel in the axial direction of the rolling shaft from the axial-direction end section of the rolling shaft.

Description

electroacoustic transducer

The present invention relates to a windable electroacoustic transducer.

A technique is known in which sound is output by attaching an acoustic film having a piezoelectric material to a windable panel such as a poster or screen, vibrating the panel with the acoustic film.

For example, in an image projection system, a method is known in which an acoustic film having a piezoelectric material is adhered to the back of a screen on which an image is projected, and sound is output from the screen by vibrating the screen with this acoustic film. there is

As an example, Patent Document 1 discloses a screen surface for displaying an image, an acoustic film (piezoelectric layer) formed on the back surface of the screen, an electrode for supplying power to the acoustic film, and power to be supplied according to an acoustic signal. A screen with a modulating circuit is described.
Patent Document 2 describes a projection screen in which a speaker made of an acoustic film (piezoelectric film) with electrode films laminated on both sides is attached to either the back or front of a sheet-like screen body. It is

JP 2006-339954 A JP 2007-187976 A

By attaching such an acoustic film to the back surface of a panel such as a screen for projection, it is possible to realize various devices that can be wound up and that can output sound with built-in speakers.
A screen having an acoustic film on the back of the projection surface vibrates when the acoustic film expands and contracts, and the vibration of the screen outputs sound. Therefore, on the screen having such an acoustic film, it is as if the sound is being output from the image, and a high sense of realism can be obtained.

Here, in a speaker that outputs sound by attaching an acoustic film to a windable panel such as a screen and vibrating the panel, in order to drive the acoustic film, a driving power is supplied to the acoustic film. Wiring is required.
However, with normal wiring, when the panel is wound, the line pressure of the wiring is applied, and there is a possibility that the panel will be damaged, for example, the shape of the line will be transferred to the surface of the panel.

Further, when outputting sound by vibrating the windable panel with the acoustic film, it is preferable to vibrate the entire panel in order to output sufficient sound. For this purpose, it is necessary to sufficiently support the panel and prevent expansion and contraction of the panel in the plane direction (in-plane direction) of the panel as much as possible.
However, the panel to which the conventional acoustic film is adhered cannot sufficiently suppress expansion and contraction in the surface direction, which causes a decrease in sound pressure.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art. To provide an electroacoustic transducer capable of outputting sound of high sound pressure by preventing damage and suppressing expansion and contraction of a panel in the surface direction.

In order to achieve such an object, the present invention has the following configurations.
[1] A windable panel;
an acoustic film that vibrates the panel;
a winding shaft for winding the panel;
It has flat wiring for connecting the acoustic film and an external device,
The flat wiring includes metal foil, and
Flat wiring with a length of 50% or more of the length of the panel in the direction orthogonal to the winding shaft is within 30% of the length of the panel in the axial direction of the winding shaft from the axial end of the winding shaft an electroacoustic transducer affixed to the area of
[2] The electroacoustic transducer according to [1], wherein the flat wiring is attached to the entire area of the panel in a direction perpendicular to the winding axis.
[3] The electroacoustic transducer according to [1] or [2], wherein the flat wiring is attached to the end of the panel in the axial direction of the winding shaft.
[4] The electroacoustic transducer according to any one of [1] to [3], wherein the lead wire electrically connected to the flat wiring is housed inside the winding shaft.
[5] The electroacoustic transducer according to any one of [1] to [4], having a plurality of acoustic films spaced apart in a direction orthogonal to the winding axis.
[6] The electroacoustic transducer according to any one of [1] to [5], having a fixed shaft fixed to the side of the panel facing the winding shaft.
[7] The electroacoustic transducer according to [6], wherein the lead wire electrically connected to the flat plate wiring is housed inside the fixed shaft.
[8] The acoustic film has a laminate obtained by laminating a plurality of piezoelectric films each having a piezoelectric layer, electrode layers provided on both sides of the piezoelectric layer, and protective layers covering the electrode layers, [1 ] The electroacoustic transducer according to any one of [7].
[9] The electroacoustic transducer according to [8], wherein the piezoelectric layer of the piezoelectric film is a polymeric composite piezoelectric body having piezoelectric particles in a polymeric material.
[10] The electroacoustic transducer according to [9], wherein the polymer material of the polymer composite piezoelectric body is cyanoethylated polyvinyl alcohol.

According to the present invention, in an electroacoustic transducer in which an acoustic film is adhered to a windable panel, damage to the panel due to wiring for driving the acoustic film is prevented, and expansion and contraction of the panel in the plane direction is prevented. can be suppressed to output sound with high sound pressure.

FIG. 1 is a diagram conceptually showing an example of the electroacoustic transducer of the present invention. FIG. 2 is a diagram conceptually showing a side view of the acoustic film. FIG. 3 is a schematic perspective view of an acoustic film. FIG. 4 is a diagram conceptually showing an example of a piezoelectric film that constitutes an acoustic film. FIG. 5 is a conceptual diagram for explaining an example of a method for producing a piezoelectric film. FIG. 6 is a conceptual diagram for explaining an example of a method for producing a piezoelectric film. FIG. 7 is a conceptual diagram for explaining an example of a method for producing a piezoelectric film. FIG. 8 is a conceptual diagram for explaining the electroacoustic transducer of the present invention. FIG. 9 is a diagram conceptually showing another example of the electroacoustic transducer of the present invention. FIG. 10 is a conceptual diagram for explaining an embodiment of the electroacoustic transducer of the invention. FIG. 11 is a conceptual diagram for explaining an embodiment of the electroacoustic transducer of the invention. FIG. 12 is a conceptual diagram for explaining an embodiment of the electroacoustic transducer of the invention. FIG. 13 is a conceptual diagram for explaining an embodiment of the electroacoustic transducer of the invention. FIG. 14 is a conceptual diagram for explaining an embodiment of the electroacoustic transducer of the invention. FIG. 15 is a conceptual diagram for explaining an embodiment of the electroacoustic transducer of the invention. FIG. 16 is a conceptual diagram for explaining an embodiment of the electroacoustic transducer of the invention. FIG. 17 is a conceptual diagram for explaining an embodiment of the electroacoustic transducer of the invention. FIG. 18 is a conceptual diagram for explaining an embodiment of the electroacoustic transducer of the invention. FIG. 19 is a conceptual diagram for explaining a comparative example of the electroacoustic transducer of the invention. FIG. 20 is a conceptual diagram for explaining a comparative example of the electroacoustic transducer of the invention. FIG. 21 is a conceptual diagram for explaining a comparative example of the electroacoustic transducer of the invention.

The electroacoustic transducer of the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.

The description of the constituent elements described below may be made based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.
Also, the drawings shown below are conceptual diagrams for explaining the electroacoustic transducer of the present invention, and the size, thickness, shape, positional relationship, etc. of each member are different from those of the actual product. is different.
In this specification, a numerical range represented by "-" means a range including the numerical values before and after "-" as lower and upper limits.

FIG. 1 conceptually shows an example of the electroacoustic transducer of the present invention.
The electroacoustic transducer 10 shown in FIG. 1 includes a panel 12, two acoustic films 14, a winding shaft 16, a fixed shaft 18, and a plate for electrically connecting the acoustic films 14 and an external device. and a flat plate wiring.
FIG. 1 is a diagram of the electroacoustic transducer 10 viewed from the rear side, that is, the side opposite to the side from which audio is listened to.

In the illustrated electroacoustic transducer 10 , the acoustic film 14 is adhered to one main surface of the panel 12 . The main surface is the maximum surface of the sheet (film, plate, layer), and is usually both sides in the thickness direction.

As will be described in detail later, in the electroacoustic transducer 10, the acoustic film 14 acts as a so-called exciter that vibrates the panel 12 to output sound.
That is, the electroacoustic transducer 10 applies a drive voltage to the acoustic film 14 (piezoelectric film 24 to be described later), so that the acoustic film 14 expands and contracts in the planar direction. The expansion and contraction of the acoustic film 14 in the plane direction bends the panel 12, and as a result, the panel 12 vibrates in the thickness direction. The vibration in the thickness direction causes the panel 12 to output sound. That is, the panel 12 vibrates according to the magnitude of the voltage (driving voltage) applied to the acoustic film 14 and outputs sound according to the driving voltage applied to the acoustic film 14 .
As described above, FIG. 1 is a rear view of the electroacoustic transducer. Therefore, listening to the sound output by the electroacoustic transducer 10 is basically performed on the main surface side of the panel 12 where the acoustic film 14 and the like are not arranged.

In the example shown in FIG. 1, two acoustic films 14 are provided spaced apart in the longitudinal direction of the panel 12 . This corresponds to stereo reproduction of sound, one acoustic film 14 for the right channel and the other acoustic film 14 for the left channel, respectively.
In addition, in the electroacoustic transducer 10 of the present invention, the number of acoustic films 14 is not limited to two, and may be one, or may have three or more acoustic films 14 .

In the illustrated electroacoustic transducer 10 , the acoustic film 14 on the right side of the drawing is connected to two flat-

plate wirings

20 a and 20 b leading to the inside of a cylindrical fixed shaft 18 . Various methods such as conductive adhesive tape, conductive paint, solder, caulking, and connector connection can be used for connection. In this case, it is preferable to use a connecting portion having flexibility.
The flat-plate wiring 20 a is connected to the conductor inside the fixed shaft 18 . This lead wire is connected to a flat plate wiring 20c attached to the upper end of the panel 12 in the drawing. The flat-plate wiring 20c reaches the inside of the cylindrical winding shaft 16 and is connected inside the winding shaft 16 to a conductor in a collective cable 21 for connecting to an external device such as an amplifier.
On the other hand, the flat-plate wiring 20b is connected to the conductor inside the fixed shaft 18 . This conductor wire is connected to a flat plate wiring 20d attached to the lower end of the panel 12 in the figure. The flat-plate wiring 20 d reaches the inside of the cylindrical winding shaft 16 and is connected to the conducting wire in the collective cable 21 inside the winding shaft 16 .
On the other hand, the acoustic film 14 on the left side of the drawing is connected to the flat wiring 20e and the flat wiring 20f leading to the inside of the take-up shaft 16. As shown in FIG.
The flat-plate wiring 20 e is connected to conductors in the cable assembly 21 inside the winding shaft 16 . The flat-plate wiring 20 f is also connected to conductors in the assembly cable 21 inside the winding shaft 16 .

Here, in the present invention, the flat wiring includes metal foil.
Further, in the present invention, the flat wiring having a length of 50% or more of the length of the panel 12 in the direction orthogonal to the winding shaft 16 is wound from the end of the panel 12 in the axial direction of the winding shaft 16. Affixed to an area within 30% of the length of panel 12 in the axial direction of shaft 16 . In the illustrated example, the flat wiring 20c and the flat wiring 20d correspond to this flat wiring.
By having such a configuration, the electroacoustic transducer 10 of the present invention prevents the panel from being damaged by the line pressure of the wiring for driving the acoustic film 14, and prevents the panel 12 from being damaged in the surface direction. It suppresses expansion and contraction and enables sound output of high sound pressure. This point will be described in detail later.

In the electroacoustic transducer 10 of the present invention, the panel 12 is a sheet-like material, and can be rolled up so that it can be repeatedly rolled up from the flat plate shape and returned to the flat plate shape from the rolled state. It is a sheet-like material having a high degree of flexibility.
In the present invention, the panel 12 is not limited, and various sheet-like materials can be used as long as they can be rolled up and can output sound when vibrated by a known exciter. .
Examples include polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyphenylene sulfite (PPS), polymethyl methacrylate (PMMA), polyetherimide (PEI), polyimide (PI), Resin films made of polyethylene naphthalate (PEN), triacetyl cellulose (TAC), cyclic olefin resins, etc., expanded polystyrene, expanded plastics made of expanded styrene, expanded polyethylene, etc. Other paperboard on one or both sides of corrugated paperboard Various corrugated board materials, wood such as plywood, leather materials, photographic printing paper, metal materials such as aluminum, brass and stainless steel, various heat dissipating members, and laminates of these multiple members pasted together A board etc. are illustrated.

In addition, in the electroacoustic transducer 10 of the present invention, as long as it can be wound, organic electroluminescence (OLED (Organic Light Emitting Diode) display, electronic paper, liquid crystal display, micro LED (Light Emitting Diode) display, inorganic electroluminescent display, etc. A display element (display device, display panel) such as a luminescence display and a mini LED display can also be suitably used as the panel 12 .
Furthermore, if the electroacoustic transducer 10 of the present invention can be wound, a screen for projection on which an image is projected from a projector (movie projector) such as a projector to display the image is also suitable as the panel 12. available for
When an image display device or the like is used as the panel 12, the surface opposite to the acoustic film 14 serves as an image display surface (projection surface).

The electroacoustic transducer of the present invention can be obtained by attaching the above-described rollable display element, projection screen, etc. to the rollable panel 12 made of resin film or the like as described above. good.
Also, in the electroacoustic transducer 10 of the present invention, the shape of the panel 12 is basically rectangular, such as rectangular and square. However, the shape of the panel 12 is not limited to being rectangular, and various shapes such as circular, elliptical, and non-rectangular polygonal shapes are available.

As described above, the panel 12 is adhered with the acoustic film 14 . The acoustic film 14 is a so-called exciter that causes the panel 12 to output sound by vibrating the panel 12 .
There are no restrictions on the acoustic film 14, and various types of films that act as exciters (audio exciters) that vibrate the panel 12 to output sound can be used.

Here, the electroacoustic transducer 10 of the present invention is an electroacoustic transducer using rollable panels 12 . Therefore, it is preferable that the acoustic film 14 attached to the panel 12 also has sufficient flexibility to follow the winding of the panel 12 .
Considering this point, the acoustic film 14 is preferably composed of a piezoelectric film having electrode layers provided on both sides of the piezoelectric layer. More preferably, the piezoelectric film further has a protective film that covers the electrode layer and protects the electrode layer and the like.
Further, the acoustic film 14 may have only one layer of piezoelectric film. However, it is preferable to laminate a plurality of layers of piezoelectric films in order to exhibit a sufficient stretching force and bend the panel 12 with a sufficient force to vibrate it.

2 and 3 conceptually show an example of an acoustic film 14 in which such piezoelectric films are laminated.
This acoustic film 14 uses a piezoelectric film 24 having a first electrode layer 28 on one side of a piezoelectric layer 26 and a second electrode layer 30 on the other side. In a preferred embodiment, the piezoelectric film 24 has a first protective layer 32 covering the first electrode layer 28 and a second protective layer 34 covering the second electrode layer 30 .
The illustrated acoustic film 14 is obtained by laminating five layers of the piezoelectric film 24 by folding the piezoelectric film 24 four times. Adjacent laminated piezoelectric films 24 are attached to each other by an adhesive layer 27 .

FIG. 2 is a side view of the acoustic film 14 of the illustrated example, and is a view of the acoustic film 14 viewed from above (or below) in FIG. That is, FIG. 1 is a view of the acoustic film 14 viewed from above in FIG. Accordingly, in the left-hand view of FIG. 1, the acoustic film 14 folds the piezoelectric film 24 in the lateral direction in the drawing. On the other hand, in the drawing on the right side of FIG. 1, the acoustic film 14 is formed by folding the piezoelectric film 24 vertically in the drawing.
FIG. 3 is a schematic perspective view of the acoustic film 14. FIG. In FIG. 3, the piezoelectric film 24 is shown as one layer for simplification of the drawing.

In the electroacoustic transducer 10 of the present invention, the acoustic film 14 in which the piezoelectric films 24 are laminated is not limited to five layers of the piezoelectric films 24 laminated. That is, in the electroacoustic transducer 10 of the present invention, the acoustic film 14 may be formed by laminating the piezoelectric film 24 three times or less, or by folding the piezoelectric film 24 into four or less layers, or by folding the piezoelectric film 24 five times or more. , a laminated structure of six or more layers of piezoelectric films 24 which are folded.
As will be described later, by stacking a plurality of piezoelectric films 24 in this way, it is possible to bend the panel with a greater force than when using one piezoelectric film 24 . In addition, by folding and laminating one piezoelectric film 24, the electrode can be drawn out in one place, and the configuration of the electroacoustic transducer 10 can be simplified.

FIG. 4 conceptually shows an example of the piezoelectric film 24 in a sectional view. In FIG. 4 and the like, hatching is omitted in order to simplify the drawing and clearly show the configuration.
In the following description, unless otherwise specified, "cross section" refers to a cross section in the thickness direction of the piezoelectric film. The thickness direction of the piezoelectric film is the stacking direction of each layer.

The piezoelectric film 24 shown in FIG. 4 includes a piezoelectric layer 26, a first electrode layer 28 laminated on one surface of the piezoelectric layer 26, a first protective layer 32 laminated on the first electrode layer 28, It has a second electrode layer 30 laminated on the other surface of the piezoelectric layer 26 and a second protective layer 34 laminated on the second electrode layer 30 .

In the piezoelectric film 24, the piezoelectric layer 26 is not limited, and various known piezoelectric layers such as a layer made of polyvinylidene fluoride (PVDF) can be used.
In the piezoelectric film 24, the piezoelectric layer 26 is preferably a polymer composite piezoelectric body containing piezoelectric particles 40 in a polymer matrix 38 containing a polymer material, as conceptually shown in FIG. .

Here, the polymer composite piezoelectric body (piezoelectric layer 26) preferably satisfies the following requirements. In the present invention, normal temperature is 0 to 50°C.
(i) Flexibility For example, when gripping a loosely bent state like a document like a newspaper or magazine for portable use, it is constantly subjected to a relatively slow and large bending deformation of several Hz or less from the outside. become. At this time, if the polymer composite piezoelectric material is hard, a correspondingly large bending stress is generated, and cracks occur at the interface between the polymer matrix and the piezoelectric particles, which may eventually lead to destruction. Therefore, the polymer composite piezoelectric body is required to have appropriate softness. Moreover, stress can be relieved if strain energy can be diffused to the outside as heat. Therefore, it is required that the loss tangent of the polymer composite piezoelectric material is appropriately large.
(ii) Sound quality The speaker vibrates piezoelectric particles at frequencies in the audio band of 20 Hz to 20 kHz, and the vibration energy causes the entire panel (polymer composite piezoelectric body) to vibrate as one, thereby reproducing sound. . Therefore, the polymer composite piezoelectric body is required to have appropriate hardness in order to increase the transmission efficiency of vibration energy. Also, if the frequency characteristics of the speaker are smooth, the amount of change in sound quality when the lowest resonance frequency f ₀ changes as the curvature changes becomes small. Therefore, the loss tangent of the polymer composite piezoelectric body is required to be moderately large.

It is well known that the lowest resonance frequency f ₀ of the speaker panel is given by the following formula. where s is the stiffness of the vibration system and m is the mass.

At this time, as the degree of curvature of the piezoelectric film, that is, the radius of curvature of the curved portion increases, the mechanical stiffness s decreases, so the minimum resonance frequency f ₀ decreases. That is, the sound quality (volume and frequency characteristics) of the speaker changes depending on the radius of curvature of the piezoelectric film.

In summary, the polymer composite piezoelectric body is required to behave hard against vibrations of 20 Hz to 20 kHz and softly against vibrations of several Hz or less. Also, the loss tangent of the polymer composite piezoelectric body is required to be moderately large with respect to vibrations of all frequencies of 20 kHz or less.

In general, polymer solids have a viscoelastic relaxation mechanism, and as temperature rises or frequency falls, large-scale molecular motion causes a decrease (relaxation) in storage elastic modulus (Young's modulus) or a maximum loss elastic modulus (absorption). is observed as Among them, the relaxation caused by the micro-Brownian motion of the molecular chains in the amorphous region is called principal dispersion, and a very large relaxation phenomenon is observed. The temperature at which this primary dispersion occurs is the glass transition point (Tg), and the viscoelastic relaxation mechanism appears most prominently.
In the polymer composite piezoelectric body (piezoelectric layer 26), by using a polymer material having a glass transition point at room temperature, in other words, a polymer material having viscoelasticity at room temperature, as a matrix, vibration of 20 Hz to 20 kHz is suppressed. This realizes a polymer composite piezoelectric material that is hard at first and behaves softly with respect to slow vibrations of several Hz or less. In particular, it is preferable to use a polymer material whose glass transition point Tg at a frequency of 1 Hz is at normal temperature for the matrix of the polymer composite piezoelectric material, because this behavior is preferably exhibited.

The polymer material that forms the polymer matrix 38 preferably has a maximum loss tangent Tan δ of 0.5 or more at a frequency of 1 Hz in a dynamic viscoelasticity test at room temperature.
As a result, when the polymer composite piezoelectric body is slowly bent by an external force, stress concentration at the polymer matrix/piezoelectric particle interface at the maximum bending moment portion is alleviated, and high flexibility can be expected.

In addition, it is preferable that the storage elastic modulus (E') at a frequency of 1 Hz measured by dynamic viscoelasticity measurement of the polymer material forming the polymer matrix 38 is 100 MPa or more at 0°C and 10 MPa or less at 50°C.
As a result, the bending moment generated when the polymeric composite piezoelectric body is slowly bent by an external force can be reduced, and at the same time, it can behave rigidly against acoustic vibrations of 20 Hz to 20 kHz.

Further, it is more preferable that the polymer material that forms the polymer matrix 38 has a dielectric constant of 10 or more at 25°C. As a result, 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, so a large amount of deformation can be expected.
On the other hand, however, in consideration of ensuring good moisture resistance and the like, it is also suitable for the polymer material to have a dielectric constant of 10 or less at 25°C.

Polymer materials that satisfy these conditions include cyanoethylated polyvinyl alcohol (cyanoethylated PVA), polyvinyl acetate, polyvinylidene chloride core acrylonitrile, polystyrene-vinylpolyisoprene block copolymer, polyvinylmethylketone, and polybutyl. Methacrylate and the like are preferably exemplified.
Commercially available products such as Hybler 5127 (manufactured by Kuraray Co., Ltd.) can also be suitably used as these polymer materials.

As the polymer material constituting the polymer matrix 38, it is preferable to use a polymer material having a cyanoethyl group, and it is particularly preferable to use cyanoethylated PVA. That is, in the piezoelectric film 24, the piezoelectric layer 26 preferably uses a polymer material having a cyanoethyl group as the polymer matrix 38, and more preferably uses cyanoethylated PVA.
In the following description, the above-mentioned polymeric materials represented by cyanoethylated PVA are collectively referred to as "polymeric materials having viscoelasticity at room temperature".

These polymer materials having viscoelasticity at room temperature may be used alone or in combination (mixed).

In the piezoelectric film 24, the polymer matrix 38 of the piezoelectric layer 26 may be made of a plurality of polymer materials, if necessary.
That is, for the polymer matrix 38 constituting the polymer composite piezoelectric body, in addition to the above-described polymer material having viscoelasticity at room temperature, other materials may be used as necessary for the purpose of adjusting dielectric properties and mechanical properties. dielectric polymer material may be added.

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 fluorine-based polymers such as polyvinylidene fluoride-tetrafluoroethylene copolymer, vinylidene cyanide-vinyl acetate copolymer, cyanoethylcellulose, cyanoethylhydroxysaccharose, cyanoethylhydroxycellulose, cyanoethylhydroxypullulan, cyanoethylmethacrylate, cyanoethylacrylate, cyanoethyl Cyano groups such as hydroxyethylcellulose, cyanoethylamylose, cyanoethylhydroxypropylcellulose, cyanoethyldihydroxypropylcellulose, cyanoethylhydroxypropylamylose, cyanoethylpolyacrylamide, cyanoethylpolyacrylate, cyanoethylpullulan, cyanoethylpolyhydroxymethylene, cyanoethylglycidolpullulan, cyanoethylsaccharose and cyanoethylsorbitol. Alternatively, polymers having cyanoethyl groups, and synthetic rubbers such as nitrile rubbers and chloroprene rubbers are exemplified.
Among them, polymer materials having cyanoethyl groups are preferably used.
Moreover, in the polymer matrix 38 of the piezoelectric layer 26, these dielectric polymer materials are not limited to one type, and a plurality of types may be added.

In addition to dielectric polymer materials, thermoplastic resins such as vinyl chloride resins, polyethylene, polystyrene, methacrylic resins, polybutene and isobutylene, and phenolic resins are used for the purpose of adjusting the glass transition point Tg of the polymer matrix 38. , thermosetting resins such as urea resins, melamine resins, alkyd resins and mica may be added.
Furthermore, a tackifier such as rosin ester, rosin, terpene, terpene phenol, and petroleum resin may be added for the purpose of improving adhesiveness.

In the polymer matrix 38 of the piezoelectric layer 26, the addition amount of the polymer material other than the polymer material having viscoelasticity at room temperature is not limited, but the proportion of the polymer matrix 38 is 30% by mass. It is preferable to:
As a result, the characteristics of the polymer material to be added can be expressed without impairing the viscoelastic relaxation mechanism in the polymer matrix 38, so that the dielectric constant can be increased, the heat resistance can be improved, and the adhesion between the piezoelectric particles 40 and the electrode layer can be improved. Favorable results can be obtained in terms of improvement and the like.

The polymer composite piezoelectric material that forms the piezoelectric layer 26 contains piezoelectric particles 40 in such a polymer matrix. The piezoelectric particles 40 are dispersed in a polymer matrix, preferably uniformly (substantially uniformly).
The piezoelectric particles 40 are preferably ceramic particles having a perovskite or wurtzite crystal structure.
Examples of ceramic particles constituting the piezoelectric particles 40 include lead zirconate titanate (PZT), lead zirconate lanthanate titanate (PLZT), barium titanate (BaTiO ₃ ), zinc oxide (ZnO), and A solid solution (BFBT) of barium titanate and bismuth ferrite (BiFe ₃ ) is exemplified.

The particle size of the piezoelectric particles 40 may be appropriately selected according to the size and application of the piezoelectric film 24 . The particle size of the piezoelectric particles 40 is preferably 1 to 10 μm.
By setting the particle size of the piezoelectric particles 40 within the above range, favorable results can be obtained in terms of achieving both high piezoelectric characteristics and flexibility.

In the piezoelectric film 24, the quantitative ratio of the polymer matrix 38 and the piezoelectric particles 40 in the piezoelectric layer 26 is required for the size and thickness of the piezoelectric film 24 in the plane direction, the application of the piezoelectric film 24, and the piezoelectric film 24. It may be set as appropriate according to the characteristics of the device.
The volume fraction of the piezoelectric particles 40 in the piezoelectric layer 26 is preferably 30-80%, more preferably 50-80%.
By setting the amount ratio between the polymer matrix 38 and the piezoelectric particles 40 within the above range, favorable results can be obtained in terms of achieving both high piezoelectric characteristics and flexibility.

In the piezoelectric film 24, the thickness of the piezoelectric layer 26 is not limited, and can be appropriately set according to the size of the piezoelectric film 24, the application of the piezoelectric film 24, the properties required of the piezoelectric film 24, and the like. good.
The thickness of the piezoelectric layer 26 is preferably 8-300 μm, more preferably 8-200 μm, still more preferably 10-150 μm, particularly preferably 15-100 μm.
By setting the thickness of the piezoelectric layer 26 within the above range, favorable results can be obtained in terms of ensuring both rigidity and appropriate flexibility.

The piezoelectric layer 26 is preferably polarized (poled) in the thickness direction. The polarization treatment will be detailed later.

In the piezoelectric film 24, the piezoelectric layer 26 is a polymer composite including piezoelectric particles 40 in a polymer matrix 38 made of a polymer material having viscoelasticity at room temperature, such as cyanoethylated PVA, as described above. There is no limitation to piezoelectric bodies.
That is, in the piezoelectric film 24 , various known piezoelectric layers can be used for the piezoelectric layer 26 .

As an example, a high-performance dielectric material containing similar piezoelectric particles 40 in a matrix containing a dielectric polymer material such as the polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene copolymer, and vinylidene fluoride-trifluoroethylene copolymer described above may be used. Molecular composite piezoelectric material, piezoelectric layer made of polyvinylidene fluoride, piezoelectric layer made of fluorine resin other than polyvinylidene fluoride, piezoelectric layer made by laminating a film made of poly-L-lactic acid and a film made of poly-D-lactic acid, etc. is also available.
However, as described above, the panel 12 is hard against vibrations of 20 Hz to 20 kHz and behaves softly against slow vibrations of several Hz or less. In terms of obtaining an acoustic film 14 that suitably follows the sound, a polymer composite piezoelectric material containing piezoelectric particles 40 in a polymer matrix 38 made of a polymer material having viscoelasticity at room temperature, such as cyanoethylated PVA, is used. A body is suitably used as the piezoelectric layer 26 .

The piezoelectric film 24 shown in FIG. 4 has the second electrode layer 30 on one surface of the piezoelectric layer 26, the second protective layer 34 on the surface of the second electrode layer 30, and the piezoelectric layer 26 has a first electrode layer 28 on the other surface thereof, and has a first protective layer 32 on the surface of the first electrode layer 28 . In the piezoelectric film 24, the first electrode layer 28 and the second electrode layer 30 form an electrode pair.
In other words, in the laminated film that constitutes the piezoelectric film 24, both surfaces of the piezoelectric layer 26 are sandwiched between electrode pairs, that is, the first electrode layer 28 and the second electrode layer 30, and the first protective layer 32 and the second electrode layer 30 are sandwiched between the electrode pairs. It has a configuration sandwiched between protective layers 34 .
Thus, the regions sandwiched by the first electrode layer 28 and the second electrode layer 30 are driven according to the applied voltage.

In addition, in the present invention, the terms “first” and “second” in the first electrode layer 28 and the second electrode layer 30 are used for the sake of convenience in describing the piezoelectric film 24 .
Therefore, the first and second in the piezoelectric film 24 have no technical significance and are irrelevant to the actual usage conditions.

In addition to these layers, the piezoelectric film 24 includes, for example, an adhesive layer for attaching the electrode layer and the piezoelectric layer 26 and an adhesive layer for attaching the electrode layer and the protective layer. may have.
The adhesive may be an adhesive or an adhesive. Also, as the adhesive, a polymer material obtained by removing the piezoelectric particles 40 from the piezoelectric layer 26, ie, the same material as the polymer matrix 38, can be suitably used. The adhesive layer may be provided on both the first electrode layer 28 side and the second electrode layer 30 side, or may be provided on only one of the first electrode layer 28 side and the second electrode layer 30 side. good.

In the piezoelectric film 24, the first protective layer 32 and the second protective layer 34 cover the first electrode layer 28 and the second electrode layer 30, and provide the piezoelectric layer 26 with appropriate rigidity and mechanical strength. is responsible for That is, in the piezoelectric film 24, the piezoelectric layer 26 containing the polymer matrix 38 and the piezoelectric particles 40 exhibits excellent flexibility against slow bending deformation. , rigidity and mechanical strength may be insufficient. The piezoelectric film 24 is provided with a first protective layer 32 and a second protective layer 34 to compensate.
The first protective layer 32 and the second protective layer 34 have the same configuration, except for the arrangement position. Therefore, in the following description, when there is no need to distinguish between the first protective layer 32 and the second protective layer 34, both members are collectively referred to as protective layers.

There are no restrictions on the protective layer, and various sheet-like materials can be used, and various resin films are suitable examples. Among them, polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyphenylene sulfite (PPS), polymethyl methacrylate (PMMA), due to their excellent mechanical properties and heat resistance. ), polyetherimide (PEI), polyimide (PI), polyamide (PA), polyethylene naphthalate (PEN), triacetyl cellulose (TAC), and resin films made of cyclic olefin resins are preferably used. .

The thickness of the protective layer is also not limited. Also, the thicknesses of the first protective layer 32 and the second protective layer 34 are basically the same, but may be different.
If the rigidity of the protective layer is too high, it not only restricts expansion and contraction of the piezoelectric layer 26, but also impairs its flexibility. Therefore, the thinner the protective layer, the better, except when mechanical strength and good handling properties as a sheet are required.

If the thickness of each of the first protective layer 32 and the second protective layer 34 is not more than twice the thickness of the piezoelectric layer 26, favorable results can be achieved in terms of ensuring both rigidity and appropriate flexibility. is obtained.
For example, when the thickness of the piezoelectric layer 26 is 50 μm and the first protective layer 32 and the second protective layer 34 are made of PET, the thicknesses of the first protective layer 32 and the second protective layer 34 are each preferably 100 μm or less. , 50 μm or less, and particularly preferably 25 μm or less.

In addition, in this invention, the 1st protective layer 32 and the 2nd protective layer 34 are provided as a preferable aspect, and are not essential components. That is, in the electroacoustic transducer of the present invention, the piezoelectric film may have only the first protective layer 32 or only the second protective layer 34. It can be something you don't.
However, considering the strength of the piezoelectric film 24, handleability, protection of the electrode layer, etc., the piezoelectric film preferably has both the first protective layer 32 and the second protective layer 34 as shown in the figure.

In the piezoelectric film 24, a first electrode layer 28 is provided between the piezoelectric layer 26 and the first protective layer 32, and a second electrode layer 30 is provided between the piezoelectric layer 26 and the second protective layer 34. It is formed. The first electrode layer 28 and the second electrode layer 30 are provided for applying an electric field to the piezoelectric film 24 (piezoelectric layer 26).

The first electrode layer 28 and the second electrode layer 30 are basically the same except for their positions. Therefore, in the following description, when there is no need to distinguish between the first electrode layer 28 and the second electrode layer 30, both members are collectively referred to as electrode layers.

In the piezoelectric film, the material for forming the electrode layer is not limited, and various conductors can be used. Specifically, carbon, palladium, iron, tin, aluminum, nickel, platinum, gold, silver, copper, chromium, molybdenum, alloys thereof, indium tin oxide, and PEDOT/PPS (polyethylenedioxythiophene-polystyrenesulfone Acid) and other conductive polymers are exemplified.
Among them, copper, aluminum, gold, silver, platinum, and indium tin oxide are preferred. Among them, copper is more preferable from the viewpoint of conductivity, cost, flexibility, and the like.

In addition, the method of forming the electrode layer is not limited, and a vapor phase deposition method (vacuum film formation method) such as vacuum deposition and sputtering, a method of forming a film by plating, a method of attaching a foil formed of the above materials, a coating method, or the like. Various known methods such as the method of
Among them, a thin film of copper or aluminum formed by vacuum deposition is particularly preferably used as the electrode layer because the flexibility of the piezoelectric film 24 can be ensured. Among them, a copper thin film formed by vacuum deposition is particularly preferably used.

The thicknesses of the first electrode layer 28 and the second electrode layer 30 are not limited. Also, the thicknesses of the first electrode layer 28 and the second electrode layer 30 are basically the same, but may be different.
Here, as with the protective layer described above, if the rigidity of the electrode layer is too high, not only will the expansion and contraction of the piezoelectric layer 26 be restricted, but also the flexibility will be impaired. Therefore, the thinner the electrode layer, the better, as long as the electrical resistance does not become too high.

In the piezoelectric film 24, if the product of the thickness of the electrode layer and the Young's modulus is less than the product of the thickness of the protective layer and the Young's modulus, the flexibility is not greatly impaired, which is preferable.
As an example, the case where the protective layer is PET and the electrode layer is copper will be described. In this case, PET has a Young's modulus of about 6.2 GPa and copper has a Young's modulus of about 130 GPa. Therefore, in this case, if the thickness of the protective layer is 25 μm, the thickness of the electrode layer is preferably 1.2 μm or less, more preferably 0.3 μm or less, and even more preferably 0.1 μm or less.

The piezoelectric film 24 has a structure in which a piezoelectric layer 26 is sandwiched between a first electrode layer 28 and a second electrode layer 30, and this laminated body is sandwiched between a first protective layer 32 and a second protective layer .
Such a piezoelectric film 24 preferably has a maximum value of 0.1 or more in the loss tangent (Tan δ) at a frequency of 1 Hz by dynamic viscoelasticity measurement at room temperature.
As a result, even if the piezoelectric film 24 receives a relatively slow and large bending deformation of several Hz or less from the outside, the strain energy can be effectively diffused to the outside as heat. It is possible to prevent cracks from occurring at the interface of

The piezoelectric film 24 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.
This allows the piezoelectric film 24 to have a large frequency dispersion in the storage modulus (E') at room temperature. That is, it can act hard against vibrations of 20 Hz to 20 kHz and soft against vibrations of several Hz or less.

In addition, the piezoelectric film 24 has a product of thickness and storage elastic modulus (E′) at a frequency of 1 Hz measured by dynamic viscoelasticity measurement of 1.0×10 ⁶ to 2.0×10 ⁶ N/m at 0° C. , 1.0×10 ⁵ to 1.0×10 ⁶ N/m at 50°C.
As a result, the piezoelectric film 24 can have appropriate rigidity and mechanical strength within a range that does not impair flexibility and acoustic properties.

Furthermore, the piezoelectric film 24 preferably has a loss tangent (Tan δ) of 0.05 or more at 25° C. and a frequency of 1 kHz in a master curve obtained from dynamic viscoelasticity measurement.

An example of a method for manufacturing the piezoelectric film 24 will be described below with reference to FIGS. 5 to 7. FIG.
First, a laminate 42b conceptually shown in FIG. 5 is prepared in which the second electrode layer 30 is formed on the surface of the second protective layer 34 . Furthermore, a laminated body 42a conceptually shown in FIG. 7 is prepared in which the first electrode layer 28 is formed on the surface of the first protective layer 32. Next, as shown in FIG.

The laminate 42b may be produced by forming a copper thin film or the like as the second electrode layer 30 on the surface of the second protective layer 34 by vacuum deposition, sputtering, plating, or the like. Similarly, the laminate 42a may be produced by forming a copper thin film or the like as the first electrode layer 28 on the surface of the first protective layer 32 by vacuum deposition, sputtering, plating, or the like.
Alternatively, a commercially available sheet having a copper thin film or the like formed on a protective layer may be used as the laminated body 42b and/or the laminated body 42a.
The laminate 42b and the laminate 42a may be the same or different.

In addition, when the protective layer is very thin and the handling property is poor, a protective layer with a separator (temporary support) may be used as necessary. As the separator, PET or the like having a thickness of 25 to 100 μm can be used. The separator may be removed after the electrode layer and protective layer are thermocompression bonded.

Next, as conceptually shown in FIG. 6, the piezoelectric layer 26 is formed on the second electrode layer 30 of the laminate 42b, and the piezoelectric laminate 46 is formed by laminating the laminate 42b and the piezoelectric layer 26. make.

The piezoelectric layer 26 may be formed by a known method suitable for the piezoelectric layer 26 .
For example, a piezoelectric layer (polymer composite piezoelectric layer) in which piezoelectric particles 40 are dispersed in a polymer matrix 38 shown in FIG. 4 is manufactured as follows.
First, a polymer material such as cyanoethylated PVA is dissolved in an organic solvent, and piezoelectric particles 40 such as PZT particles are added and stirred to prepare a paint. Organic solvents are not limited, and various organic solvents such as dimethylformamide (DMF), methyl ethyl ketone, and cyclohexanone can be used.
After the laminate 42b is prepared and the paint is prepared, the paint is cast (applied) to the laminate 42b and dried by evaporating the organic solvent. As a result, as shown in FIG. 6, a piezoelectric laminate 46 having the second electrode layer 30 on the second protective layer 34 and the piezoelectric layer 26 laminated on the second electrode layer 30 is produced. do.

There are no restrictions on the method of casting the coating material, and known methods (coating equipment) such as bar coaters, slide coaters and doctor knives can all be used.
Alternatively, if the polymer material is heat-meltable, the polymer material is heat-melted and the piezoelectric particles 40 are added to prepare a melted material, which is then extruded or otherwise laminated as shown in FIG. A piezoelectric laminate 46 as shown in FIG. 7 may be produced by extruding a sheet onto the body 42b and cooling.

As described above, in the piezoelectric film 24, the polymer matrix 38 may be added with a polymer piezoelectric material such as PVDF, in addition to the polymer material having viscoelasticity at room temperature.
When these polymeric piezoelectric materials are added to the polymeric matrix 38, the polymeric piezoelectric materials to be added to the paint may be dissolved. Alternatively, the polymer piezoelectric material to be added may be added to a polymer material that has been melted by heating and has viscoelasticity at room temperature, and then melted by heating.

After the piezoelectric layer 26 is formed, it may be calendered, if desired. Calendering may be performed once or multiple times.
As is well known, calendering is a process in which a surface to be treated is heated and pressed by a hot press, hot rollers, or the like to flatten the surface.

Further, the piezoelectric layer 26 of the piezoelectric laminate 46 having the second electrode layer 30 on the second protective layer 34 and the piezoelectric layer 26 formed on the second electrode layer 30 is subjected to a polarization treatment ( polling).
The method of polarization treatment of the piezoelectric layer 26 is not limited, and known methods can be used. For example, electric field poling, in which a DC electric field is directly applied to an object to be polarized, is exemplified. When electric field poling is performed, the first electrode layer 28 may be formed before the polarization treatment, and the electric field poling treatment may be performed using the first electrode layer 28 and the second electrode layer 30. .
Further, when the piezoelectric film 24 is manufactured, the polarization treatment is performed not in the surface direction of the piezoelectric layer 26 but in the thickness direction.

Next, as conceptually shown in FIG. 7, the previously prepared laminate 42 a is laminated on the piezoelectric layer 26 side of the piezoelectric laminate 46 with the first electrode layer 28 facing the piezoelectric layer 26 .
Further, this laminate is thermocompression bonded using a heat press device, a heating roller, etc., with the first protective layer 32 and the second protective layer 34 sandwiched between them, thereby forming the piezoelectric laminate 46 and the laminate 42a. to paste together.
As a result, the piezoelectric layer 26, the first electrode layer 28 and the second electrode layer 30 provided on both surfaces of the piezoelectric layer 26, and the first protective layer 32 and the second protective layer 34 formed on the surface of the electrode layer A piezoelectric film 24 made of

The piezoelectric film 24 produced by such a production process is polarized not in the plane direction but in the thickness direction, and excellent piezoelectric properties can be obtained without stretching after the polarization treatment. Therefore, the piezoelectric film 24 has no in-plane anisotropy in piezoelectric properties, and expands and contracts isotropically in all directions in the plane direction when a drive voltage is applied.

As described above, the illustrated acoustic film 14 is obtained by laminating five layers of piezoelectric films by folding the piezoelectric film 24 four times. In addition, the piezoelectric films 24 that are laminated and adjacent to each other are adhered to each other by an adhesion layer 27 as a preferred embodiment.

In the present invention, as the adhesive layer 27, various known adhesive agents (adhesive materials) can be used as long as the adjacent piezoelectric films 24 can be attached.
Therefore, the sticking layer 27 may be a layer made of an adhesive (adhesive material), a layer made of an adhesive (adhesive material), or a layer made of a material having characteristics of both an adhesive and an adhesive. The adhesive layer 27 may be formed by applying an adhesive having fluidity such as a liquid, or may be formed using a sheet-like adhesive such as a double-sided tape. Note that the adhesive is a sticking agent that has fluidity at the time of bonding and then becomes solid. The pressure-sensitive adhesive is a gel-like (rubber-like) soft solid that is adhered to each other and does not change its gel-like state afterward.
Here, the acoustic film 14 is an exciter, and the acoustic film 14 is expanded and contracted by expanding and contracting a plurality of laminated piezoelectric films 24, for example, vibrating the panel 12 as described later to output sound. . Therefore, in the acoustic film 14, it is preferable that the expansion and contraction of each piezoelectric film 24 is directly transmitted. If a viscous substance that relaxes vibration exists between the piezoelectric films 24, the transmission efficiency of the expansion/contraction energy of the piezoelectric films 24 is lowered, and the driving efficiency of the acoustic film 14 is lowered.
Considering this point, the sticking layer 27 is preferably an adhesive layer made of an adhesive that provides a solid and hard sticking layer 27 rather than a sticky layer made of an adhesive. Specifically, a more preferable adhesive layer 27 is an adhesive layer made of a thermoplastic type adhesive such as a polyester adhesive and a styrene-butadiene rubber (SBR) adhesive.
Adhesion, unlike sticking, is useful in seeking high adhesion temperatures. Further, a thermoplastic type adhesive is suitable because it has "relatively low temperature, short time, and strong adhesion".

In the acoustic film 14, the thickness of the adhesive layer 27 is not limited, and a thickness capable of exhibiting sufficient adhesive force may be appropriately set according to the material forming the adhesive layer 27.
Here, the thinner the adhesive layer 27 of the acoustic film 14 is, the higher the effect of transmitting the expansion/contraction energy (vibration energy) of the piezoelectric layer 26 can be and the higher the energy efficiency can be. Also, if the adhesive layer 27 is thick and rigid, it may restrict the expansion and contraction of the piezoelectric film 24 .
Considering this point, the adhesive layer 27 is preferably thinner than the piezoelectric layer 26 . That is, in the acoustic film 14, the adhesive layer 27 is preferably hard and thin. Specifically, the thickness of the adhesion layer 27 after adhesion is preferably 0.1 to 50 μm, more preferably 0.1 to 30 μm, even more preferably 0.1 to 10 μm.

In addition, in the acoustic film 14 constituting the electroacoustic transducer 10 of the present invention, the adhesive layer 27 is provided as a preferred embodiment and is not an essential component.
However, if the adhesive layer 27 is not provided, the piezoelectric films 24 may bend in opposite directions to form voids, which may reduce the driving efficiency of the acoustic film.
In consideration of this point, when the piezoelectric element constituting the electroacoustic transducer of the present invention is configured by laminating a plurality of piezoelectric films 24, adjacent piezoelectric films 24 are arranged like the acoustic film 14 in the illustrated example. It is preferable to have an adhesive layer 27 that sticks them together.

In addition, in the electroacoustic transducer of the present invention, the acoustic film is not limited to one in which a plurality of layers of the piezoelectric film 24 are laminated by folding the piezoelectric film 24 .
For example, the acoustic film may be obtained by laminating a plurality of cut sheet-like piezoelectric films 24 and preferably adhering adjacent piezoelectric films with an adhesive layer 27 . In this case, the number of layers to be laminated is not limited, as in the case of the acoustic film 14 in which the piezoelectric films 24 are laminated by folding. When a plurality of cut sheet-like piezoelectric films 24 are laminated to form an acoustic film, for example, the piezoelectric film 24 having a protective layer and the piezoelectric film 24 having no protective layer are laminated. The acoustic film may be configured by laminating different piezoelectric films such as.
Alternatively, the acoustic film may be composed of one piezoelectric film 24 as long as the elastic force sufficient for vibrating the panel 12 can be obtained.

The piezoelectric film 24 of the acoustic film 14 is connected with a first extraction electrode 24a and a second extraction electrode 24b for electrical connection with an external device such as a power supply. A flat wiring 20a for connection with an external device is connected to the first extraction electrode 24a, and a flat wiring 20b for connection with an external device is connected to the second extraction electrode 24b.
The first extraction electrode 24 a is an electrode electrically extracted from the first electrode layer 28 , and the second extraction electrode 24 b is an electrode electrically extracted from the second electrode layer 30 . In the following description, when there is no need to distinguish between the first extraction electrode 24a and the second extraction electrode 24b, they will simply be referred to as extraction electrodes.
In the example shown in FIG. 1, in the acoustic film 14 on the right side of the drawing, the flat wiring 20a is connected to the first extraction electrode 24a, and the flat wiring 20b is connected to the second extraction electrode 24b. In the acoustic film 14 on the left side of the drawing, the flat wiring 20e is connected to the first extraction electrode 24a, and the flat wiring 20f is connected to the second extraction electrode 24b.

In the electroacoustic transducer 10 of the present invention, there are no restrictions on the method of connecting the electrode layer of the acoustic film 14 (piezoelectric film 24) and the extraction electrodes, and various methods can be used.
In the illustrated example, as an example, a sheet-like extraction electrode is inserted between the electrode layer and the piezoelectric layer, and wiring is connected to this extraction electrode. Note that the extraction electrode may be inserted between the electrode layer and the protective layer.
Another method is to form a through hole in the protective layer, provide an electrode connection member formed of a metal paste such as silver paste so as to fill the through hole, and provide a lead electrode in this electrode connection member. Alternatively, wiring may be inserted directly between the electrode layer and the piezoelectric layer or between the electrode layer and the protective layer to connect the extraction electrode to the electrode layer. As another method, a method is exemplified in which a part of the protective layer and the electrode layer is protruded from the piezoelectric layer in the plane direction, and the lead electrode is connected to the protruded electrode layer. The extraction electrode and the electrode layer may be connected by a known method such as a method using a metal paste such as silver paste, a method using solder, or a method using a conductive adhesive.
Examples of suitable methods for extracting electrodes include the method described in Japanese Patent Application Laid-Open No. 2014-209724 and the method described in Japanese Patent Application Laid-Open No. 2016-015354.

The acoustic film 14 is attached to the panel 12 by an adhesive layer (not shown).
In the present invention, various known adhesive layers can be used as long as they can adhere the panel 12 and the acoustic film 14 (piezoelectric film 24) together.
Therefore, the adhesive layer may be a layer made of an adhesive, a layer made of a pressure-sensitive adhesive, or a layer made of a material having the characteristics of both an adhesive and a pressure-sensitive adhesive. The adhesive layer may be formed by applying an adhesive having fluidity such as a liquid, or may be formed using a sheet-like adhesive such as a double-sided tape.
Here, in the electroacoustic transducer 10 of the present invention, the acoustic film 14 is expanded and contracted by expanding and contracting a plurality of laminated piezoelectric films 24, and the expansion and contraction of the acoustic film 14 bends and vibrates the panel 12, output sound. Therefore, in the electroacoustic transducer 10 of the present invention, it is preferable that the expansion and contraction of the acoustic film 14 be directly transmitted to the panel 12 . If there is a viscous substance that reduces vibrations between the panel 12 and the acoustic film 14, the efficiency of transmission of the expansion and contraction energy of the acoustic film 14 to the panel 12 will be low. drive efficiency is reduced.
Considering this point, the sticking layer is preferably an adhesive layer made of an adhesive that provides a solid and hard sticking layer rather than a sticking layer made of an adhesive. More preferred adhesive layers are specifically exemplified by adhesive layers made of thermoplastic adhesives such as polyester adhesives and styrene-butadiene rubber (SBR) adhesives.
Adhesion, unlike sticking, is useful in seeking high adhesion temperatures. Further, a thermoplastic type adhesive is suitable because it has "relatively low temperature, short time, and strong adhesion".

In the electroacoustic transducer 10 of the present invention, there is no limitation on the thickness of the adhesion layer that adheres the panel 12 and the acoustic film 14, and sufficient adhesion strength is exhibited according to the material forming the adhesion layer 27. A possible thickness may be set as appropriate.
Here, in the electroacoustic transducer 10 of the illustrated example, the thinner the adhesive layer, the higher the effect of transmitting the stretching energy (vibrational energy) of the piezoelectric layer 26, and the higher the energy efficiency. Also, if the adhesive layer is thick and rigid, it may restrict expansion and contraction of the acoustic film 14 .
Considering this point, it is preferable that the adhesive layer is thin.
Specifically, the thickness of the adhesive layer that adheres the panel 12 and the acoustic film 14 is preferably 10 to 1000 μm, more preferably 30 to 500 μm, even more preferably 50 to 300 μm after adhesion. .

In the illustrated electroacoustic transducer 10 , the piezoelectric film 24 is formed by sandwiching the piezoelectric layer 26 between the first electrode layer 28 and the second electrode layer 30 .
Piezoelectric layer 26 preferably has piezoelectric particles 40 in a polymer matrix 38 . Preferably, piezoelectric layer 26 comprises piezoelectric particles 40 dispersed in polymer matrix 38 .

When a voltage is applied to the second electrode layer 30 and the first electrode layer 28 of the piezoelectric film 24 having such a piezoelectric layer 26, the piezoelectric particles 40 expand and contract in the polarization direction according to the applied voltage. As a result, the piezoelectric film 24 (piezoelectric layer 26) shrinks in the thickness direction. At the same time, due to the Poisson's ratio, the piezoelectric film 24 expands and contracts in the plane direction as well.
This expansion and contraction is about 0.01 to 0.1%.
As described above, the thickness of the piezoelectric layer 26 is preferably about 10-300 μm. Therefore, the expansion and contraction in the thickness direction is as small as about 0.3 μm at maximum.
On the other hand, the piezoelectric film 24, that is, the piezoelectric layer 26, has a size much larger than its thickness in the planar direction. Therefore, for example, if the length of the piezoelectric film 24 is 20 cm, the piezoelectric film 24 expands and contracts by about 0.2 mm at the maximum due to the application of voltage.

As described above, the acoustic film 14 is formed by laminating five layers of the piezoelectric film 24 by folding. An acoustic film 14 is attached to the panel 12 by an adhesive layer.
As the piezoelectric film 24 expands and contracts, the acoustic film 14 expands and contracts in the same direction. The expansion and contraction of the acoustic film 14 bends the panel 12, and as a result, the panel 12 vibrates in the thickness direction.
The vibration in the thickness direction causes the panel 12 to output sound. That is, the panel 12 vibrates according to the magnitude of the voltage (driving voltage) applied to the piezoelectric film 24 and outputs sound according to the driving voltage applied to the piezoelectric film 24 .

As described above, the illustrated acoustic film 14 is obtained by laminating five such piezoelectric films 24 . In the illustrated acoustic film 14 , as a preferred embodiment, the adjacent piezoelectric films 24 are adhered to each other with the adhesion layer 27 .
Therefore, even if the rigidity of each piezoelectric film 24 is low and the expansion/contraction force is small, the lamination of the piezoelectric films 24 increases the rigidity and the expansion/contraction force of the acoustic film 14 . As a result, even if the panel 12 has a certain degree of rigidity, the acoustic film 14 can sufficiently flex the panel 12 with a large force and sufficiently vibrate the panel 12 in the thickness direction. Audio can be output.

Moreover, as described above, in the piezoelectric film 24 constituting the acoustic film 14, the preferable thickness of the piezoelectric layer 26 is about 300 μm at maximum. Moreover, the piezoelectric film 24 using the piezoelectric layer 26, which is a composite piezoelectric polymer, has very good flexibility.
Therefore, the acoustic film 14 is very thin and has good flexibility even if it is made by laminating a plurality of layers (five layers in the illustrated example) of the piezoelectric films 24 . Therefore, by using the acoustic film 14 made of such a piezoelectric film 24, the acoustic film 14 suitably follows the winding of the panel 12 when the panel 12 is wound. As a result, the electroacoustic transducer 10 provided with the acoustic film 14 made of the piezoelectric film 24 can be suitably wound.

As described above, in the electroacoustic transducer 10 of the present invention, the panel 12 is flexible and rollable.
In the example shown in FIG. 1, a winding shaft 16 is fixed to one side (right side in the drawing) of the panel 12 in the longitudinal direction. The panel 12 (electroacoustic transducer 10) is wound around the winding shaft 16 when not in use.

The winding shaft 16 is not limited, and various rod-shaped objects such as resin rods and metal rods can be used as long as the panel 12 can be wound. In order to smoothly wind the panel 12, the winding shaft 16 is preferably cylindrical or columnar.
In the illustrated example, the winding shaft 16 has a cylindrical shape, and includes a conductor wire for connecting the flat wiring 20c and the assembly cable 21, a conductor wire for connecting the flat wiring 20d and the assembly cable 21, and a flat wiring 20e and the assembly cable. 21, a conductor wire for connecting the flat wiring 20f and the collective cable 21, and the like are accommodated as appropriate.
Various known conductors (lead wires, electric wires, wires) can be used as the conductors connected to the flat-plate wirings of the present invention such as the flat-

plate wirings

20c and 20d. Alternatively, a flat wiring similar to the flat wiring 20c or the like may be used as the conducting wire.

Moreover, as a preferred embodiment, the winding shaft 16 is attached to the panel 12 so as to fix the entire length of one side. That is, one side of the panel 12 is fixed and restrained to the winding shaft 16 . The panel 12 may be detachably fixed to the winding shaft 16, or may be fixed in a non-detachable manner.
The method for fixing the edge of the panel 12 to the take-up shaft 16 is not limited, and various known methods for fixing the sheet-like material to the rod-like material can be used. Examples include a method using an adhesive, a method using Velcro (registered trademark), a method using clasps such as hooks and snaps, a method by clamping using a flat plate and a screw, and a hollow round bar with a split. Various known methods such as a sandwiching method can be used.

In the example shown in FIG. 1, a fixed shaft 18 is provided as a preferred embodiment on the side of the panel 12 facing the winding shaft 16 side.
The fixed shaft 18 is also not limited, and various rod-shaped objects such as resin rods and metal rods can be used. Since the fixed shaft 18 does not take up the panel 12, it can be preferably used in the form of a rectangular cylinder or prism.
In the illustrated example, the fixed shaft 18 has a cylindrical shape, and accommodates a conductor wire for connecting the flat-plate wiring 20a and the flat-plate wiring 20c and a conductor wire for connecting the flat-plate wiring 20b and the flat-plate wiring 20d. be done.

In addition, the fixed shaft 18 is preferably attached to the panel 12 so as to fix the entire length of one side. That is, the side of the panel 12 facing the take-up shaft 16 side is fixed and constrained by the fixed shaft 18 . Therefore, the short sides of the panel 12 are fixed by the winding shaft 16 and the fixed shaft 18, and expansion and contraction are restrained.
The method for fixing the edge of the panel 12 to the fixing shaft 18 is not limited, and various known methods for fixing the sheet-like object to the rod-like object can be used. As an example, the method mentioned above for the winding shaft 16 is exemplified.

The electroacoustic transducer 10 of the present invention has flat wiring containing metal foil as wiring for connecting the acoustic film 14 and an external device.

In the electroacoustic transducer 10 of the illustrated example, the acoustic film 14 on the right side of the figure has a first lead-out electrode 24a connected to the flat wiring 20a leading to the inside of the fixed shaft 18, and a second lead-out electrode 24b connected to the inside of the fixed shaft 18. are connected to the flat-plate wirings 20b.
The flat-plate wiring 20 a is connected to the conductor inside the fixed shaft 18 . This lead wire is connected to a flat plate wiring 20c attached to the upper end of the panel 12 in the drawing. The flat-plate wiring 20c reaches the inside of the cylindrical winding shaft 16 and is connected inside the winding shaft 16 to a conductor in a collective cable 21 for connecting to an external device such as an amplifier.

On the other hand, the flat-plate wiring 20b is connected to the conductor inside the fixed shaft 18 . This conductor wire is connected to a flat plate wiring 20d attached to the lower end of the panel 12 in the drawing. The flat-plate wiring 20 d reaches the inside of the cylindrical winding shaft 16 and is connected to the conducting wire in the collective cable 21 inside the winding shaft 16 .
In addition, inside the fixed shaft 18, the flat-plate wiring and the wiring of the assembly cable 21 may be connected via a conducting wire, if necessary. In this regard, the same applies to the acoustic film 14 on the left side of the drawing shown below.

In the acoustic film 14 on the left side of the figure, the first extraction electrode 24 is connected to the flat wiring 20e leading to the inside of the winding shaft 16, and the second extraction electrode 24b is connected to the flat wiring 20f leading to the inside of the winding shaft 16. Connected.
The flat-plate wiring 20 e is connected to conductors in the cable assembly 21 inside the winding shaft 16 . The flat-plate wiring 20 f is also connected to conductors in the assembly cable 21 inside the winding shaft 16 .

In the electroacoustic transducer 10 of the present invention, the conductors (wirings) not inserted into the winding shaft 16 and the fixed shaft 18, that is, the wirings in contact with the wound surface of the panel 12 are all flat wirings. is.
Further, the flat-plate wiring that is not inserted into the winding shaft 16 and the fixed shaft 18 is basically adhered to the panel 12 .

As described above, flat wiring includes metal foil.
In the present invention, the metal foil is a plate-shaped metal object having a thickness of 100 μm or less.
There is no lower limit to the thickness of the metal foil, and the thickness may be any thickness that provides sufficient conductivity depending on the material forming the metal foil. The thickness of the metal foil is preferably 10 μm or more in consideration of the conductivity and ability of the flat wiring to constrain the panel 12, which will be described later.

In the electroacoustic transducer 10 of the present invention, the flat wiring having a length of 50% or more of the length of the panel 12 in the direction orthogonal to the winding shaft 16 is wound from the end of the winding shaft 16 in the axial direction. The area within 30% of the length of the panel 12 in the axial direction of the mandrel 16 is adhered. In other words, in the present invention, the flat wiring having a length of 50% or more of the length of the panel 12 in the winding direction is extended from the end in the direction perpendicular to the winding direction to the panel in the direction perpendicular to the winding direction. An area within 30% of the length of 12 is applied.
Specifically, as conceptually shown in FIG. It is adhered to a hatched width [Lb×(3/10)] area within 30% of the length Lb of the panel 12 in the axial direction of the winding shaft 16 from the end.
In the electroacoustic transducer 10 of the present invention having such a configuration, in the electroacoustic transducer in which the acoustic film 14 is adhered to the panel 12 that can be wound, the wiring for driving the acoustic film 14 can be used to drive the panel. 12 is prevented from being damaged and expansion and contraction of the panel 12 in the plane direction is suppressed, thereby enabling output of sound with high sound pressure.

In the following description, the direction perpendicular to the winding shaft 16, that is, the direction of the length La in FIG. 8 is also referred to as the "winding direction" for convenience. Further, the axial direction of the winding shaft 16, that is, the direction of the length Lb in FIG. 8 is also referred to as the "axial direction" for convenience.
Further, in the following description, the length of the panel 12 in the winding direction, that is, the length La in FIG. 8 is also simply referred to as "the length in the winding direction". Further, the length of the panel 12 in the axial direction, that is, the length Lb in FIG. 8 is also simply referred to as the "axial length".

As described above, for example, a windable image display device, a projection screen, or a windable panel 12 such as a flexible resin film is adhered to the acoustic film 14 having a piezoelectric body, thereby forming a panel. 12 can be vibrated to output sound.
Sound output at this time is performed by vibrating the panel 12 in the thickness direction by expanding and contracting the acoustic film 14 in the plane direction to bend the panel 12 as described above.

Here, in order to drive the acoustic film 14, it is necessary to connect a lead wire for supplying driving power to the acoustic film 14. FIG.
However, in the conventional electroacoustic transducer, when the panel 12 is rolled up, the panel 12 is subjected to the line pressure of the string-like conducting wire. As a result, the panel 12 may be damaged, for example, the shape of the conductor may be transferred to the surface.

Sound output from the panel 12 using the acoustic film 14 is performed by vibrating the panel 12 by bending the panel 12 due to expansion and contraction of the acoustic film 14 . Therefore, in order to vibrate the panel 12 efficiently, it is necessary to suppress the expansion and contraction (deformation) of the panel 12 in the plane direction so that the expansion and contraction of the acoustic film 14 does not cause the panel 12 to expand and contract together.
However, in the conventional electroacoustic transducer in which the panel 12 can be wound, one side of the panel 12 in the axial direction is fixed by the winding shaft 16 to suppress expansion and contraction, but the winding direction is not fixed. not Therefore, the winding direction of the panel 12 expands and contracts together with the acoustic film 14 when the acoustic film 14 expands and contracts. As a result, the panel 12 cannot be entirely vibrated, resulting in a low sound pressure.

On the other hand, in the electroacoustic transducer 10 of the present invention, as described above, the flat wiring whose length is 50% or more of the length in the winding direction extends from the end in the axial direction to the length in the axial direction. is attached to an area within 30% of the
A flat-plate wiring is a wiring containing metal foil, that is, a strip-shaped wiring. Therefore, even if the panel 12 is wound, a strong linear pressure is not applied to the panel 12 unlike a normal cord-like conductor. Therefore, the electroacoustic transducer 10 of the present invention can prevent damage to the panel 12 such as the shape of the flat wiring being transferred to the surface even when the panel 12 is wound.

Further, the electroacoustic transducer 10 of the present invention has a length of 50% or more of the length in the winding direction (length La) in the vicinity of the end portion in the axial direction of the panel 12 . Here, flat wiring is wiring containing metal foil.
Therefore, the expansion and contraction of the panel 12 in the axial direction can be prevented by the winding shaft 16, and the expansion and contraction of the panel 12 in the winding direction can be suppressed by the flat wiring, which is wiring including metal foil. In the example shown in FIG. 1, expansion and contraction of the panel 12 in the winding direction can be suppressed by the flat wiring 20c and the flat wiring 20d.
Therefore, according to the electroacoustic transducer 10 of the present invention, expansion and contraction of the panel 12 can be prevented in both the winding direction and the axial direction. As a result, the expansion and contraction of the acoustic film 14 allows the entire panel 12 to vibrate in the thickness direction, that is, the acoustic film 14 efficiently vibrates the entire surface of the panel 12 to output sound with high sound pressure. .

Moreover, in the illustrated electroacoustic transducer 10, the side of the panel 12 facing the take-up shaft 16 is fixed by the fixed shaft 18 as a preferred embodiment.
Therefore, expansion and contraction of the panel 12 in the axial direction can be prevented at both ends in the winding direction by the winding shaft 16 and the fixed shaft 18, and the entire surface of the panel 12 can be vibrated with higher efficiency.

In the electroacoustic transducer 10 of the present invention, the flat wiring of 50% or more of the length in the winding direction should be attached to the area within 30% of the length in the axial direction from the end in the axial direction. Just do it. In other words, in the electroacoustic transducer 10 of the present invention, the flat wiring of 0.5 La or more in FIG. It is sufficient if it is attached.
The length of the flat wiring attached to this region is preferably 60% or more, more preferably 80% or more, of the length in the winding direction (the length of the panel 12). As in the illustrated example, it is more preferable that the flat wiring is adhered over the entire area (substantially the entire area) in the winding direction. It should be noted that "over the entire winding direction" means not only covering the entire winding direction of the panel 12, but also until it abuts on the winding shaft 16 or further the fixed shaft 18, and as in the illustrated example. Including up to the interior of the shaft 16 or even the fixed shaft 18 .

Also, the area where the flat wiring is attached that is 50% or more of the length in the winding direction is within 30% of the length in the axial direction (the length of the panel 12) from the end in the axial direction. Just do it. However, the closer the flat-plate wiring is to the end in the axial direction, the more preferably the expansion and contraction of the panel 12 can be suppressed. Considering this point, it is preferable to attach the flat-plate wiring having a length of 50% or more of the length in the winding direction, preferably within 20% of the length in the axial direction, more preferably within 10%. More preferably, it is attached to the axial ends, as shown.
Here, the acoustic film 14 has a first electrode layer 28 and a second electrode layer 30 . Therefore, two flat wirings can be provided so as to be connected to each electrode layer. In the present invention, two flat plate electrodes having a length of 50% or more of the length in the winding direction may be attached to a region within 30% of the length in the axial direction from one end in the axial direction. . However, it is more preferable to prevent expansion and contraction of the panel 12 in the winding direction. is preferably applied to the area of

In the electroacoustic transducer 10 of the present invention, the flat wiring of 50% or more of the length in the winding direction, which is attached to the region within 30% of the length in the axial direction from the end in the axial direction, is shown in FIG. is not restricted to being parallel to the edge of the panel 12, as shown in FIG.
That is, as shown in an embodiment described later, the flat wiring attached to the region within 30% of the length in the axial direction from the end in the axial direction may be inclined with respect to the edge of the panel. Moreover, in a region within 30% of the length in the axial direction from the end in the axial direction, the flat wiring parallel to the edge of the panel 12 and the flat wiring inclined with respect to the edge of the panel 12 are mixed. may
The flat-plate wiring attached to the area within 30% of the length in the axial direction from the end in the axial direction may have a curved portion, but the shape is straight or a combination of straight lines. is preferred. Furthermore, it is preferable that the flat wiring attached to the area within 30% of the length in the axial direction from the end in the axial direction has a linear portion of 50% or more of the length in the winding direction.

As described above, flat wiring includes metal foil.
There are no restrictions on the metal foil, and various known metal foils can be used as long as they are made of conductive metal. In addition, an alloy is included in the metal used as metal foil.
Examples include aluminum foil, copper foil, nickel foil, gold foil, silver foil, and tin foil.

Various types of flat wiring can be used as long as they contain metal foil.
Examples thereof include a metal foil, a metal tape obtained by providing an adhesive layer on a metal foil, an FPC (Flexible printed circuits) wiring board (FPC substrate, FPC wiring), and the like.
Commercially available products of these flat-plate wirings are also suitable for use.

The method of adhering the flat wiring to the panel 12 is also not limited, and various known methods can be used.
Examples include a method using an adhesive, a method using an adhesive tape such as a polyimide tape, a method using a double-sided tape, a method using a hot-melt sheet or the like to heat and press, and direct vacuum deposition of copper or the like onto the panel. and the like are exemplified.

In the example shown in FIG. 1, the longitudinal direction of the rectangular panel 12 is the winding direction, that is, the direction perpendicular to the winding shaft 16, and the lateral direction is the axial direction of the winding shaft 16. is not restricted to
That is, in the electroacoustic transducer of the present invention, as conceptually shown in FIG. 9, the transverse direction of a rectangular panel 12 is the winding direction, i.e., the direction orthogonal to the winding axis 16, and the longitudinal direction is the winding axis. 16 axial directions. Therefore, in this case, the flat wiring 20g and the flat wiring 20h of 50% or more of the length in the winding direction, that is, the short side, are arranged in the axial direction corresponding to both ends of the panel 12 in the longitudinal direction, that is, the short side. The area within 30% of the length in the axial or longitudinal direction from the ends is adhered.

Although the electroacoustic transducer of the present invention has been described in detail above, the present invention is not limited to the above examples, and various improvements and changes may be made without departing from the gist of the present invention. , of course.

Hereinafter, the present invention will be described in more detail by giving specific examples of the present invention. The present invention is not limited to this example, and the materials, amounts used, proportions, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. can.

[Preparation of piezoelectric film]
A piezoelectric film was produced by the method shown in FIGS.
First, cyanoethylated PVA (CR-V, manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved in dimethylformamide (DMF) at the following compositional ratio. After that, PZT particles as piezoelectric particles were added to this solution at the following composition ratio, and the mixture was stirred with a propeller mixer (rotation speed: 2000 rpm) to prepare a paint for forming a piezoelectric layer.
・PZT particles・・・・・・・・・・300 parts by mass ・Cyanoethylated PVA・・・・・・・・30 parts by mass ・DMF・・・・・・・・・・・・70 parts by mass The PZT particles are composed of powders of Pb oxide, Zr oxide and Ti oxide, which are the main components, so that Zr = 0.52 mol and Ti = 0.48 mol with respect to Pb = 1 mol. Mixed powder obtained by wet-mixing in a ball mill was fired at 800° C. for 5 hours and then pulverized.

On the other hand, a sheet-like material was prepared by vacuum-depositing a copper thin film with a thickness of 0.1 μm on a PET film with a thickness of 4 μm. That is, in this example, the first electrode layer and the second electrode layer are 0.1 m-thick copper-evaporated thin films, and the first protective layer and the second protective layer are 4 μm-thick PET films.
Using a slide coater, the previously prepared paint for forming the piezoelectric layer was applied onto the second electrode layer (copper-deposited thin film) of the sheet-like material. The paint was applied so that the thickness of the coating film after drying was 40 μm.
Next, the sheet-like material coated with the paint was dried by heating on a hot plate at 120° C. to evaporate the DMF. As a result, a laminate having a second electrode layer made of copper on a second protective layer made of PET and a piezoelectric layer (polymer composite piezoelectric layer) having a thickness of 30 μm thereon was produced. .

The produced piezoelectric layer was subjected to polarization treatment in the thickness direction.

A sheet-like product obtained by vapor-depositing the same thin film on a PET film was laminated with the first electrode layer (copper thin film side) facing the piezoelectric layer on the laminate in which the piezoelectric layer had been subjected to the polarization treatment.
Next, the laminate of the laminate and the sheet-like material is thermocompressed at a temperature of 120° C. using a laminator device to adhere and adhere the composite piezoelectric body and the first electrode layer, as shown in FIG. A piezoelectric film as shown in was produced.

This piezoelectric film was cut into strips with a width of 180 mm, and folded four times so that the length in the folding direction was 70 mm. Therefore, this acoustic film has a planar shape of 180×70 mm when viewed from the stacking direction.
The piezoelectric films adjacent to each other in the stacking direction were attached using an adhesive (TSU0041SI, manufactured by Toyochem Co., Ltd.).
As shown in FIGS. 2 and 3, the produced acoustic film was fixed by inserting the first extraction electrode between the first protective layer and the first electrode layer at one end in the longitudinal direction of the piezoelectric film. Furthermore, the second extraction electrode was inserted and fixed between the second protective layer and the second electrode layer. A copper foil having a thickness of 35 μm, a length of 25 mm, and a width of 15 mm was used as the extraction electrode.

[Example 1]
As a panel, a polypropylene flat plate having a thickness of 0.2 mm and a size of 700×500 mm was prepared. This panel can be easily rolled up by a person.
Two sheets of the produced acoustic film were adhered to one surface of the panel. As conceptually shown in FIG. 10, the acoustic film has the longitudinal direction (direction of 180 mm) aligned with the width direction (direction of 500 mm) of the panel, the center of the width direction of the panel, and the width of the panel. In the vicinity of the ends in the longitudinal direction, the extraction electrodes were attached facing outward.
A double-sided tape was used to attach the acoustic film to the panel.

As conceptually shown in FIG. 10, a metal tape having a width of 15 mm and a metal foil (copper foil) thickness of 25 μm was attached to both ends of the panel in the longitudinal direction over the entire length. In FIG. 10, the metal tape is indicated by a thick line.
A short metal tape was connected to the first lead-out electrode of the acoustic film on the right side of the figure, and this metal tape was connected to the right end of the metal tape on the upper side of the figure with a string-like conductive wire. Similarly, a short metal tape was connected to the second lead-out electrode of the acoustic film on the right side of the figure, and this metal tape and the right end of the metal tape on the bottom side of the figure were connected with a string-like conductive wire.
In addition, the end of the metal tape on the left side in the drawing was connected to the lead wire of the collective cable for connecting to the external power source.
The metal tape is flat wiring in the present invention.

A short metal tape was connected to the first lead-out electrode of the acoustic film on the left side of the figure, and this metal tape was connected to a conductor wire of an assembly cable for connecting to an external power source.
Similarly, a short metal tape was connected to the second lead-out electrode of the acoustic film on the left side of the drawing, and this metal tape was connected to a conductor wire of an assembly cable for connecting to an external power supply.

10 to 21, in order to simplify the drawings and make the configuration easier to understand, for the sake of convenience, an assembly cable, a metal tape (flat wiring) passing through the same area, and a cord-like conductor wire passing through the same area (lead wire), etc. are indicated by a single line.
However, it goes without saying that each of the flat-plate wirings and conductors connected to the individual extraction electrodes are independent of each other and insulated from each other.

A cylinder (cylinder) made of Duracon with a diameter of 40 mm was prepared as a winding shaft. The entire short side of the panel on the left side in the figure was fixed to this winding shaft. The collective cable was housed inside the winding shaft (see FIG. 1).
As a fixed shaft, a cylinder (cylinder) made of Duracon and having a diameter of 40 mm was prepared. The entire short side of the panel on the right side in the drawing was fixed to this fixed shaft. A string-like conductor was accommodated inside the fixed shaft.
In order to clearly show the configuration of the electroacoustic transducer, FIGS. 10 to 21 omit the illustration of the winding shaft and the fixed shaft.
Thus, an electroacoustic transducer as shown in FIG. 1 was produced.

[Example 2]
As conceptually shown in FIG. 11, the right half (350 mm) of the metal tape at both ends in the width direction of the panel was positioned 160 mm from the end in the width direction. An electroacoustic transducer was similarly produced.
[Example 3]
As conceptually shown in FIG. 12, an electroacoustic transducer was produced in the same manner as in Example 1, except that the metal tapes at both ends in the lateral direction of the panel were positioned 150 mm from the ends in the lateral direction. .
[Example 4]
As conceptually shown in FIG. 13, the right half (350 mm) of the metal tape at both ends in the panel width direction is positioned 160 mm from the width direction end, and the left half in the diagram is , an electroacoustic transducer was produced in the same manner as in Example 1, except that the position was 150 mm from the end in the lateral direction.

[Example 5]
As conceptually shown in FIG. 14, the metal tapes are placed on both ends of the panel in the transverse direction so that the ends on the right side in the figure are positioned 150 mm from the ends of the panel in the transverse direction. An electroacoustic transducer was produced in the same manner as in Example 1, except that the long side of the panel was oblique.
[Example 6]
As conceptually shown in FIG. 15, the metal tapes are placed on both ends of the panel in the widthwise direction so that the ends on the left side of the drawing are positioned 150 mm from the widthwise end of the panel. An electroacoustic transducer was produced in the same manner as in Example 1, except that the long side of the panel was oblique.
[Example 7]
As conceptually shown in FIG. 16, the right half of the metal tapes at both ends in the panel width direction are positioned 160 mm from the panel width direction ends. An electroacoustic transducer was produced in the same manner as in Example 1, except that the metal tape was slanted with respect to the long side of the panel so as to connect the left corner of the panel to the corner of the panel.
[Example 8]
As conceptually shown in FIG. 17, the metal tapes at both ends in the widthwise direction of the panel are placed at a position 160 mm from the widthwise end of the panel, and the metal tape ends An electroacoustic transducer was produced in the same manner as in Example 1, except that the metal tape was slanted with respect to the long side of the panel so as to connect the edge and the right corner of the panel in the figure.

[Example 9]
As conceptually shown in FIG. 18, an electroacoustic transducer was produced in the same manner as in Example 1, except that four acoustic films were attached near the corners of the panel.

[Example 10]
An electroacoustic transducer was produced in the same manner as in Example 1, except that a metal foil having a thickness of 25 μm was adhered to the panel with a polyimide tape instead of the metal tape.
[Example 11]
An electroacoustic transducer was produced in the same manner as in Example 1, except that FPC wiring having a metal foil with a thickness of 25 μm was adhered to the panel with a polyimide tape instead of the metal tape.

[Comparative Example 1]
As conceptually shown in FIG. 19, an electroacoustic transducer was produced in the same manner as in Example 1, except that the metal tapes at both ends in the lateral direction of the panel were positioned 160 mm from the ends in the lateral direction. .
[Comparative Example 2]
As conceptually shown in FIG. 20, 400 mm on the right side of the metal tape at both ends of the panel in the transverse direction was positioned 160 mm from the ends in the transverse direction, in the same manner as in Example 1. An electroacoustic transducer was fabricated.

[Comparative Example 3]
As conceptually shown in FIG. 21, the electroacoustic transducer was performed in the same manner as in Example 1, except that the extraction electrode of the acoustic film on the right side of the figure was directed inward, and the metal tape was positioned at the center of the panel in the lateral direction. I made a vessel.

[Comparative Example 4]
An electroacoustic transducer was produced in the same manner as in Example 1, except that a flat cable with a wire diameter of 1 mm was used instead of the metal tape and adhered to the panel with a polyimide tape.
[Comparative Example 5]
An electroacoustic transducer was produced in the same manner as in Example 1, except that a VCT (Vinyl Cab Tire) cable with a wire diameter of 3 mm was used instead of the metal tape, and the cable was attached to the panel with a polyimide tape.

[Comparative Example 6]
An electroacoustic transducer was fabricated in the same manner as in Example 1, except that FPC wiring having a metal foil with a thickness of 25 μm was used instead of the metal tape, and the FPC wiring was not adhered to the panel.

[evaluation]
The produced electroacoustic transducers were evaluated as follows.
<Sound pressure>
The sound pressure was measured using a sound level meter at a distance of 1 m from the panel and at the central position in the longitudinal and lateral directions.
In measuring the sound pressure, pink noise of 500 to 20 kHz was input by a constant current amplifier. The voltage was adjusted to give a 20 Vrms input at 1 kHz. The sound pressure level of Example 9 was evaluated as 5 out of 5, and the evaluation was lowered by 1 for each 1 dB decrease in sound pressure.

<Windability>
The panel was wound up on a winding shaft and left for one day. After that, the panel was unfolded and the presence or absence of wrinkles and folds was visually confirmed.
A when no wrinkles and folds can be confirmed,
A case where wrinkles and folds could be confirmed was evaluated as B.
<Image>
The panel was wound up on a winding shaft and left for one day. After that, the panel was spread out, and the presence or absence of wiring reflection was visually evaluated.
If the wiring image cannot be confirmed, A,
A case in which the image of the wiring could be confirmed was evaluated as B.
Results are shown in the table below.

As mentioned above, the size of the panel is 700×500 mm, in this example the winding direction is 700 mm and the axial direction is 500 mm.
As shown in Table 1, flat wiring using metal foil is used, and flat wiring of 50% or more (350 mm or more) of the length in the winding direction of the panel is extended from the end in the axial direction of the panel. All of the electroacoustic transducers of the present invention attached to a region within 30% (within 150 mm) of the length in the axial direction have high sound pressure, good windability of the panel, and can be easily attached to the panel. There is no picture of wiring.
As shown in Examples 2 and 3, the longer the flat wiring attached within 30% of the axial length of the panel from the axial end of the panel, the longer the axial end. The closer to , the higher the sound pressure. In particular, as shown in Example 1, a higher sound pressure can be obtained by providing flat-plate wiring over the entire length in the winding direction at the ends in the axial direction.

On the other hand, the flat wiring of 50% or more of the length in the winding direction of the panel is not attached to the area within 30% of the length in the axial direction of the panel from the end of the panel in the axial direction. The electroacoustic transducers of Comparative Examples 1 to 3 and the electroacoustic transducer of Comparative Example 6 in which the flat wiring was not adhered to the panel had low sound pressure.
In addition, in Comparative Example 4 using a flat cable instead of the flat wiring, the wiring is reflected on the panel. Furthermore, in Comparative Example 5, in which a VCT cable was used instead of the flat wiring, wrinkles occurred, resulting in poor windability, and the wiring also appeared on the panel.
From the above results, the effect of the present invention is clear.

It can be suitably used for various purposes as a rollable image display device.

REFERENCE SIGNS LIST 10 Electroacoustic transducer 12 Panel 14 Acoustic film 16 Winding shaft 18

Fixed shaft

20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h Flat wiring 21 Collective cable 24 Piezoelectric film 24a First extraction electrode 24b Second extraction electrode 26 piezoelectric layer 28 first electrode layer 30 second electrode layer 32 first protective layer 34 second protective layer 38 polymer matrix 40

piezoelectric particles

42a, 42b laminate 46 piezoelectric laminate

Claims

a rollable panel,
an acoustic film for vibrating the panel;
a winding shaft for winding the panel;
A flat wiring for connecting the acoustic film and an external device,
The flat wiring includes a metal foil, and
The flat wiring having a length of 50% or more of the length of the panel in the direction orthogonal to the winding shaft extends from the end in the axial direction of the winding shaft to the length of the panel in the axial direction of the winding shaft. An electroacoustic transducer that is attached to an area within 30% of its length.
The electroacoustic transducer according to claim 1, wherein the flat wiring is attached to the entire area of the panel in a direction orthogonal to the winding axis.
The electroacoustic transducer according to claim 1 or 2, wherein the flat wiring is attached to the end of the panel in the axial direction of the winding shaft.
The electroacoustic transducer according to any one of claims 1 to 3, wherein a conductor electrically connected to said flat wiring is accommodated inside said winding shaft.
The electroacoustic transducer according to any one of claims 1 to 4, having a plurality of said acoustic films spaced apart in a direction orthogonal to said winding axis.
The electroacoustic transducer according to any one of claims 1 to 5, having a fixed shaft fixed to a side of the panel facing the winding shaft.
The electroacoustic transducer according to claim 6, wherein a conductor electrically connected to said flat wiring is accommodated inside said fixed shaft.
2. The acoustic film has a laminated body in which a plurality of piezoelectric films each having a piezoelectric layer, electrode layers provided on both sides of the piezoelectric layer, and protective layers covering the electrode layers are laminated. 8. The electroacoustic transducer according to any one of 1 to 7.
The electroacoustic transducer according to claim 8, wherein the piezoelectric layer of the piezoelectric film is a polymeric composite piezoelectric body having piezoelectric particles in a polymeric material.
10. The electroacoustic transducer of claim 9, wherein the polymer material of the polymer composite piezoelectric body is cyanoethylated polyvinyl alcohol.