JP6450014B2 - Electroacoustic conversion film, method for producing electroacoustic conversion film, and electroacoustic transducer - Google Patents

Description

  The present invention relates to an electroacoustic conversion film used for an acoustic device such as a speaker, a manufacturing method thereof, and an electroacoustic transducer.

  In response to the thinning of displays such as liquid crystal displays and organic EL (Electro Luminescence) displays, the speakers used in these thin displays are also required to be light and thin.

  The shape of a conventional speaker is generally a funnel-shaped so-called cone type or a spherical dome shape. However, if such a speaker is incorporated in the above-described thin display, the speaker cannot be sufficiently thinned, and the lightness may be impaired. In addition, when a speaker is externally attached, carrying and the like are troublesome.

  Therefore, as a thin speaker that can be integrated with a thin display or a flexible display without impairing lightness, a piezoelectric film having a sheet-like flexibility and a property of expanding and contracting in response to an applied voltage is used. It has been proposed.

  For example, the applicant of the present application has proposed the electroacoustic conversion film disclosed in Patent Document 1 as a piezoelectric film that is sheet-like, flexible, and can stably reproduce high-quality sound. did. An electroacoustic conversion film disclosed in Patent Document 1 includes a polymer composite piezoelectric material (piezoelectric layer) in which piezoelectric particles are dispersed in a viscoelastic matrix made of a polymer material having viscoelasticity at room temperature, It has a thin film electrode formed on both surfaces of the molecular composite piezoelectric material and a protective layer formed on the surface of the thin film electrode.

Here, such an electroacoustic conversion film converts vibration (sound) and an electric signal by the conversion film itself expanding and contracting in a surface direction and vibrating in a direction perpendicular to the surface in response to an applied voltage. To do. At that time, in order to convert the expansion and contraction in the surface direction of the conversion film into vibration in a direction perpendicular to the surface, it is necessary to hold the conversion film in a curved state.
Therefore, in Patent Document 1, it is described that the viscoelastic support is pressed against the back surface of the conversion film, or the conversion film is curved and supported by applying air pressure in a case sealed with the conversion film. Yes.

  Patent Document 2 describes that a conversion film is curved by hot-pressing a piezoelectric film using PVDF (Poly Vinylidene DiFluoride) as a piezoelectric layer into a dome shape.

JP 2014-14063 A JP 2011-97181 A

However, as described in Patent Document 1, in the configuration in which the viscoelastic support is pressed against the back surface of the conversion film and the conversion film is curved, the viscoelastic support is deformed over time depending on the material and structure of the viscoelastic support. Then, since the amount of bending of the conversion film changes, the sound pressure and sound quality may change. Moreover, since heat dissipation becomes worse and the temperature of the conversion film rises during continuous use, it may lead to discomfort when used as headphones.
In addition, in the configuration where the conversion film is bent by applying air pressure to the case sealed with the conversion film, the pressure in the case changes over time and the amount of bending of the conversion film changes, so the sound pressure and sound quality change. There is a risk that. Moreover, since it is necessary to increase the air density and pressure resistance in the case, the weight and size are increased. Although the pressure change in the case can be suppressed if the pressure is constantly applied, a mechanism such as a compressor is required, which is not practical. Moreover, since air stays in the case, there is a problem in heat dissipation.

Moreover, as described in Patent Document 2, by forming the conversion film itself into a curved dome shape, a viscoelastic support for bending the conversion film, a structure for applying air pressure, and the like are not necessary.
However, according to the study by the present inventors, it has been found that sufficient sound pressure may not be obtained even if the conversion film itself is molded into a dome shape and curved. That is, it has been found that sufficient sound pressure cannot be obtained simply by molding the conversion film into a dome shape.

  An object of the invention is to solve such problems of the prior art, and an electroacoustic conversion film and an electroacoustic conversion that can be reproduced at a sufficient volume, have high heat dissipation, and have little change in sound pressure over time. It is in providing the manufacturing method and electroacoustic transducer of a film.

As a result of intensive studies to solve the above problems, the present inventors have found that a polymer composite piezoelectric material in which piezoelectric particles are dispersed in a viscoelastic matrix made of a polymer material having viscoelasticity at room temperature, and a polymer Two thin-film electrodes laminated on both surfaces of the composite piezoelectric material and two protective layers laminated on the two thin-film electrodes, respectively, are laminated so as to protrude toward one main surface side. The ratio H / Ds between the molding height H of the projection and the minor axis Ds of the projection when viewed from the direction perpendicular to the main surface is 0 <H / Ds ≦ It has been found that the above-mentioned problems can be solved by satisfying 0.15, and the present invention has been completed.
That is, this invention provides the electroacoustic conversion film of the following structures, the manufacturing method of an electroacoustic conversion film, and an electroacoustic transducer.

(1) a polymer composite piezoelectric material obtained by dispersing piezoelectric particles in a viscoelastic matrix made of a polymer material having viscoelasticity at room temperature;
Two thin film electrodes laminated on both sides of a polymer composite piezoelectric material;
Two protective layers stacked on each of the two thin film electrodes;
For at least one of the two thin film electrodes, a colored layer that is formed on the surface layer side of the thin film electrode and covers the thin film electrode is laminated,
It has a convex part formed into a convex shape so as to protrude on one main surface side,
An electroacoustic conversion film in which the ratio H / Ds between the molding height H of the convex portion and the short axis Ds of the convex portion when viewed from a direction perpendicular to the main surface satisfies 0 <H / Ds ≦ 0.15.
(2) The electroacoustic conversion film according to (1), wherein the transmission density of the colored layer is 0.3 or more.
(3) The electroacoustic conversion film according to (1) or (2), wherein the thickness of the colored layer is 1 μm or less.
(4) The electroacoustic conversion film according to any one of (1) to (3), wherein the colored layer has an electrical resistivity of 1 × 10 ⁻⁷ Ωm or less.
(5) The electroacoustic conversion film according to any one of (1) to (4), wherein the electroacoustic conversion film further includes an insulating layer that covers a region where the polymer composite piezoelectric body is exposed to prevent a short circuit.
( 6 ) The electroacoustic conversion film according to any one of (1) to (5), wherein the shape of the convex portion is a part of a sphere or a part of a spheroid.
( 7 ) The protective layer has a hole that penetrates to the electrode layer,
The electroacoustic conversion film according to any one of (1) to ( 6 ) , further including an electrode lead portion that is electrically connected to the electrode layer through the hole portion.
( 8 ) The electroacoustic conversion film as described in ( 7 ) which has 3 or more electrode extraction parts connected to an electrode layer through the hole of a protective layer.
( 9 ) A method for producing an electroacoustic conversion film for producing the electroacoustic conversion film according to any one of (1) to ( 8 ),
A polymer composite piezoelectric material in which piezoelectric particles are dispersed in a viscoelastic matrix made of a polymer material having viscoelasticity at room temperature, two thin film electrodes laminated on both surfaces of the polymer composite piezoelectric material, and two Prepared a laminated body in which two protective layers laminated on each thin film electrode and at least one of the two thin film electrodes are laminated on the surface layer side of the thin film electrode and a colored layer covering the thin film electrode A preparation process to
A method for producing an electroacoustic conversion film, comprising: heating and compression-molding a laminate, and molding a projecting portion protruding toward one main surface.
( 10 ) The electroacoustic conversion film obtained by molding a convex portion according to any one of (1) to ( 8 ),
An electroacoustic transducer having a support member that supports the edge of the convex portion of the electroacoustic transducer film.
( 11 ) The support member has a through hole having the same shape as the shape of the convex portion when viewed from a direction perpendicular to the main surface of the electroacoustic conversion film,
The electroacoustic transducer according to ( 10 ), wherein the edge portion of the convex portion of the electroacoustic conversion film is sandwiched between the two support members.

  According to the present invention as described above, an electroacoustic conversion film that can be reproduced at a sufficient volume, has high heat dissipation, and has a small change in sound pressure over time, a method for producing an electroacoustic conversion film, and an electroacoustic transducer are provided. can do.

It is a perspective view which shows typically an example of the electroacoustic conversion film of this invention. It is the II-II sectional view taken on the line of the electroacoustic conversion film shown in FIG. It is the top view which looked at FIG. 2A from b direction. It is a top view which shows typically another example of the electroacoustic conversion film of this invention. It is sectional drawing which shows typically another example of the electroacoustic conversion film of this invention. It is sectional drawing which shows typically an example of the layer structure of an electrical sound table conversion film. It is sectional drawing which shows typically an example of the layer structure of an electrical sound table conversion film. It is sectional drawing which shows notionally an example of the electroacoustic transducer of this invention. It is a conceptual diagram for demonstrating an example of the preparation methods of an electroacoustic conversion film. It is a conceptual diagram for demonstrating an example of the preparation methods of an electroacoustic conversion film. It is a conceptual diagram for demonstrating an example of the preparation methods of an electroacoustic conversion film. It is a conceptual diagram for demonstrating an example of the preparation methods of an electroacoustic conversion film. It is a conceptual diagram for demonstrating an example of the preparation methods of an electroacoustic conversion film. It is a conceptual diagram for demonstrating an example of the preparation methods of an electroacoustic conversion film. It is a conceptual diagram for demonstrating an example of the preparation methods of an electroacoustic conversion film. It is a schematic sectional drawing of the electroacoustic transducer of a comparative example. It is a schematic sectional drawing of the electroacoustic transducer of a comparative example.

Hereinafter, the electroacoustic conversion film, the electroacoustic conversion film manufacturing method, and the electroacoustic transducer of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments.
In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

As will be described later, the electroacoustic conversion film of the present invention is used as a diaphragm of an electroacoustic transducer.
In the electroacoustic transducer, when the electroacoustic conversion film expands in the in-plane direction by applying a voltage to the electroacoustic conversion film, the electroacoustic conversion film absorbs the extension, and the electroacoustic conversion film moves upward (radiation direction of sound). Conversely, when the electroacoustic conversion film contracts in the in-plane direction by applying a voltage to the electroacoustic conversion film, the electroacoustic conversion film moves downward to absorb this contraction. The electroacoustic transducer converts vibration (sound) and an electric signal by vibration caused by repeated expansion and contraction of the electroacoustic conversion film.
Such electroacoustic transducers are used as various acoustic devices such as full-range speakers, tweeters, squawkers, woofers, speakers, headphones, earphone speakers, noise cancellers, microphones, and pickups used in musical instruments such as guitars. It is used to input an electric signal to the electroacoustic conversion film and reproduce the sound by vibration according to the electric signal, or to convert the vibration of the electroacoustic conversion film by receiving the sound wave into an electric signal. It is what is done.

FIG. 1 is a perspective view schematically showing an example of the electroacoustic conversion film of the present invention, FIG. 2A is a cross-sectional view taken along the line II-II of the electroacoustic conversion film of FIG. 1, and FIG. FIG. 4A is a cross-sectional view schematically showing the layer configuration of the electroacoustic conversion film.
As shown in FIG. 4A, an electroacoustic conversion film (hereinafter also referred to as a conversion film) 10 of the present invention is laminated on a piezoelectric layer 12 that is a piezoelectric sheet-like material and one surface of the piezoelectric layer 12. The lower thin film electrode 14, the lower protective layer 18 stacked on the lower thin film electrode 14, the upper thin film electrode 16 stacked on the other surface of the piezoelectric layer 12, and the upper thin film electrode 16. It is a film-like laminate having a layer structure laminated with the upper protective layer 20, and as shown in FIGS. 1, 2A and 2B, a convex portion 10a molded at the center of the film-like laminate is provided. The ratio H between the molding height H of the convex portion 10a (hereinafter also simply referred to as height H) and the short diameter Ds of the convex portion 10a when viewed from the direction perpendicular to the main surface of the conversion film 10 / Ds satisfies 0 <H / Ds ≦ 0.15.

That is, the conversion film 10 has a configuration in which both surfaces of the piezoelectric layer 12 are sandwiched between electrode pairs, that is, the upper thin film electrode 16 and the lower thin film electrode 14, and are further sandwiched between the upper protective layer 20 and the lower protective layer 18. It has a configuration in which a convex portion 10a having a predetermined shape is molded in the laminate.
The region of the piezoelectric layer 12 held by the upper thin film electrode 16 and the lower thin film electrode 14 is driven according to the applied voltage and expands and contracts in the surface direction. At that time, in the region of the convex portion 10a, the expansion and contraction in the surface direction is converted into vibration in a direction perpendicular to the surface, and vibration (sound) and an electric signal are converted.

  In the example shown in FIG. 1, the conversion film 10 has a square shape, and has a convex portion 10 a formed of a part of a sphere with a diameter Ds and a height H at the center. Moreover, the convex part 10a is formed in concave shape, when it sees from the surface on the opposite side to the surface of the side from which the convex part 10a protrudes. That is, it can also be said that the conversion film 10 is obtained by molding a recess.

As described above, in the configuration in which the elastic film is pressed against the back surface of the conversion film and the conversion film is bent, depending on the material and structure of the viscoelastic support, the viscoelastic support is deformed over time, and the amount of bending of the conversion film is increased. Since it changes, there is a risk that the sound pressure and sound quality will change. Moreover, since heat dissipation becomes worse and the temperature of the conversion film rises during continuous use, it may lead to discomfort when used as headphones.
In addition, in the configuration where the conversion film is bent by applying air pressure to the case sealed with the conversion film, the pressure in the case changes over time and the amount of bending of the conversion film changes, so the sound pressure and sound quality change. There is a risk that. Moreover, since it is necessary to increase the air density and pressure resistance in the case, the weight and size are increased. Although the pressure change in the case can be suppressed if the pressure is constantly applied, a mechanism such as a compressor is required, which is not practical. Moreover, since air stays in the case, there is a problem in heat dissipation.

On the other hand, in the present invention, by forming the convex portion 10a on the conversion film 10 in this way, the expansion and contraction in the surface direction of the conversion film is applied to the vibration in the direction perpendicular to the surface when a voltage is applied. A curved state can be created for conversion. Therefore, a member such as an elastic support for bending the conversion film 10 and a mechanism for applying air pressure become unnecessary.
Therefore, the bending amount of the conversion film does not change with time, and the sound pressure and sound quality can be prevented from changing. Moreover, since it can be set as the structure which open | released both surfaces of the conversion film, the heat which generate | occur | produces by driving a conversion film can be thermally radiated efficiently, and heat dissipation can be made high.
In addition, since an elastic support for curving the conversion film 10 or a structure for applying air pressure is not necessary, the conversion film 10 can be reduced in size and thickness.

Here, according to the study by the present inventors, it is not possible to obtain a sufficient sound pressure by simply forming the convex portion on the conversion film, and depending on the shape of the convex portion, a voltage may be applied. It was found that the expansion and contraction in the surface direction of the conversion film may not be efficiently converted into vibration in a direction perpendicular to the surface.
In contrast, in the present invention, the ratio H / Ds between the molding height H of the convex portion and the short axis Ds of the convex portion when viewed from the direction perpendicular to the main surface is 0 <H / Ds ≦ By making the shape satisfying 0.15, even when a pressing force by an elastic support or air pressure is not applied to the conversion film, the expansion and contraction in the surface direction of the conversion film when a voltage is applied is perpendicular to the surface. It is possible to efficiently convert the vibration into a direction, and a sufficient sound pressure can be obtained.

Here, the shape of the convex portion is not particularly limited, but the shape of the convex portion is preferably a part of a sphere or a part of a spheroid, from a direction perpendicular to the main surface of the conversion film. The shape of the convex portion when viewed is not particularly limited, but is preferably a substantially circular shape as shown in FIG. 2B or a substantially elliptical shape as shown in FIG. 3A.
In addition, the shape of the convex portion when viewed in a cross section perpendicular to the main surface of the conversion film is preferably curved as a whole as shown in FIG. 2A, but the top portion is flat as shown in FIG. 3B. It may be molded.
In the following description, a convex portion having a part of a sphere or a part of a spheroid is also referred to as a dome shape.
By making the shape of the convex portion a dome shape, the sound pressure can be further improved, which is preferable.

The ratio H / Ds between the height H of the convex portion and the minor axis Ds of the convex portion is greater than 0 and 0.15 or less, and the upper limit value is 0.1 or less in that the sound pressure can be further improved. Preferably, it is 0.075 or less, more preferably 0.05 or less, and the lower limit is preferably 0.003 or more, and is 0.005 or more. Is more preferable.
Here, the minor axis Ds of the convex part is a diameter when the convex part has a circular shape when viewed from a direction perpendicular to the main surface of the conversion film, and a minor axis when the convex part has an elliptical shape. Yes, in the case of a square shape, it is the length of the short side.

  In addition, when the region of the conversion film where the convex portions are not formed is a marginal portion when viewed from the direction perpendicular to the main surface of the conversion film, the width of the marginal portion is not particularly limited. When configuring the acoustic transducer, the width is preferably such that the edge portion can be suitably held by the support member, preferably 1 mm to 30 mm or less, and more preferably 5 mm to 20 mm.

  In the example shown in FIG. 4A, the layer structure of the conversion film 10 is laminated on the piezoelectric layer 12, the lower thin film electrode 14 stacked on one surface of the piezoelectric layer 12, and the lower thin film electrode 14. Although the lower protective layer 18, the upper thin film electrode 16 stacked on the other surface of the piezoelectric layer 12, and the upper protective layer 20 stacked on the upper thin film electrode 16 are provided, the present invention is not limited thereto. In addition to these layers, for example, an area where the piezoelectric layer 12 is exposed may be covered with an insulating layer for preventing a short circuit, a colored layer for covering a thin film electrode, and the like.

FIG. 4B is a cross-sectional view conceptually showing the layer structure of the conversion film 10 having a colored layer.
The layer structure of the conversion film shown in FIG. 4B includes a piezoelectric layer 12, a lower thin film electrode 14 stacked on one surface of the piezoelectric layer 12, a lower colored layer 21 stacked on the lower thin film electrode 14, The lower protective layer 18 laminated on the lower colored layer 21, the upper thin film electrode 16 laminated on the other surface of the piezoelectric layer 12, the upper colored layer 22 laminated on the upper thin film electrode 16, and the upper colored And an upper protective layer 20 stacked on the layer 22.
By having the upper colored layer 22 and the lower colored layer 21, the rust of the upper thin film electrode 16 and the lower thin film electrode 14 can be made invisible from the outside.

  Moreover, the conversion film 10 may have an electrode lead-out portion that pulls out the electrodes from the upper thin film electrode 16 and the lower thin film electrode 14.

There is no particular limitation on the electrode lead-out part, and the thin film electrode and the protective layer may be provided with a protruding portion outside the surface of the piezoelectric layer, or a part of the protective layer may be removed. A hole portion may be formed, and a conductive material such as a silver paste may be inserted into the hole portion to electrically connect the conductive material and the thin film electrode to form an electrode lead portion.
A configuration in which a hole is formed in the protective layer and a conductive material is inserted into the hole to form an electrode lead-out portion is preferable in terms of easy formation and miniaturization.
In each thin film electrode, the number of electrode lead portions is not limited to one, and may include two or more electrode lead portions. In particular, in the case of a configuration in which a part of the protective layer is removed and a conductive material is inserted into the hole portion to form an electrode lead portion, energization can be ensured more reliably and the contact area with the conductive material can be increased. Thus, it is preferable to have a total of 3 or more electrode lead portions in terms of reducing the electrical resistance and reducing the amount of heat generated.

  Hereinafter, each layer of the conversion film will be described in detail.

In the conversion film 10, the piezoelectric layer 12, which is a polymer composite piezoelectric body, has piezoelectric particles 26 in a viscoelastic matrix 24 made of a polymer material having viscoelasticity at room temperature as conceptually shown in FIG. 4A. It is made of a polymer composite piezoelectric material that is uniformly dispersed. In this specification, “room temperature” refers to a temperature range of about 0 to 50 ° C.
As will be described later, the piezoelectric layer 12 is preferably polarized.

Here, the polymer composite piezoelectric material (piezoelectric layer 12) preferably has the following requirements.
(I) Flexibility For example, when gripping in a loosely bent state like a newspaper or a magazine for portable use, it is constantly subject 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 large bending stress is generated, and a crack is generated at the interface between the polymer matrix and the piezoelectric particles, which may eventually lead to destruction. Accordingly, the polymer composite piezoelectric body is required to have an appropriate softness. Further, if the strain energy can be diffused to the outside as heat, the stress can be relaxed. Accordingly, it is required that the loss tangent of the polymer composite piezoelectric material is appropriately large.
(Ii) Sound quality The speaker vibrates the piezoelectric particles at an audio band frequency of 20 Hz to 20 kHz, and the vibration plate (polymer composite piezoelectric body) vibrates as a whole by the vibration energy, so that sound is reproduced. The Accordingly, in order to increase the transmission efficiency of vibration energy, the polymer composite piezoelectric body is required to have an appropriate hardness. Further, if the frequency characteristic of the speaker is smooth, the amount of change in the sound quality when the lowest resonance frequency f ₀ with the change in the curvature is changed becomes small. Therefore, the loss tangent of the polymer composite piezoelectric material is required to be moderately large.

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

In general, polymer solids have a viscoelastic relaxation mechanism, and as the temperature increases or the frequency decreases, large-scale molecular motion decreases (relaxes) the storage elastic modulus (Young's modulus) or maximizes the loss elastic modulus (absorption). As observed. Among them, the relaxation caused by the micro Brownian motion of the molecular chain in the amorphous region is called main dispersion, and a very large relaxation phenomenon is observed. The temperature at which this main dispersion occurs is the glass transition point (Tg), and the viscoelastic relaxation mechanism appears most remarkably.
In the polymer composite piezoelectric material (piezoelectric layer 12), a polymer material having a glass transition point at room temperature, in other words, a polymer material having viscoelasticity at room temperature is used for a vibration at 20 Hz to 20 kHz. A polymer composite piezoelectric material that is hard and softly behaves with respect to slow vibrations of several Hz or less is realized. In particular, a polymer material having a glass transition temperature at a frequency of 1 Hz at room temperature, that is, 0 to 50 ° C., is preferably used for the matrix of the polymer composite piezoelectric material in terms of suitably exhibiting this behavior.

Various known materials can be used as the polymer material having viscoelasticity at room temperature. Preferably, a polymer material having a maximum value of a loss tangent Tanδ at a frequency of 1 Hz in a dynamic viscoelasticity test at room temperature, that is, 0 to 50 ° C., is 0.5 or more.
As a result, when the polymer composite piezoelectric body is slowly bent by an external force, the stress concentration at the polymer matrix / piezoelectric particle interface at the maximum bending moment portion is alleviated, and high flexibility can be expected.

The polymer material preferably has a storage elastic modulus (E ′) at a frequency of 1 Hz as measured by dynamic viscoelasticity of 100 MPa or more at 0 ° C. and 10 MPa or less at 50 ° C.
As a result, the bending moment generated when the polymer composite piezoelectric body is bent slowly by an external force can be reduced, and at the same time, it can behave hard against an acoustic vibration of 20 Hz to 20 kHz.

Further, it is more preferable that the polymer material has a relative 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 that a large amount of deformation can be expected.
However, in consideration of ensuring good moisture resistance, the polymer material preferably has a relative dielectric constant of 10 or less at 25 ° C.

Polymer materials satisfying such conditions include cyanoethylated polyvinyl alcohol (cyanoethylated PVA), polyvinyl acetate, polyvinylidene chloride core acrylonitrile, polystyrene-vinyl polyisoprene block copolymer, polyvinyl methyl ketone, and polybutyl. Examples include methacrylate.
Besides these, polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride-trifluoroethylene copolymer, and polyvinylidene fluoride-tetrafluoroethylene copolymer. Fluoropolymers such as polymers, vinylidene cyanide-vinyl acetate copolymer, cyanoethyl cellulose, cyanoethyl hydroxy saccharose, cyanoethyl hydroxy cellulose, cyanoethyl hydroxy pullulan, cyanoethyl methacrylate, cyanoethyl acrylate, cyanoethyl hydroxyethyl cellulose, cyanoethyl amylose, cyanoethyl hydroxypropyl Cellulose, cyanoethyl dihydroxypropyl cellulose, cyanoethyl hydroxypropyl amino Cyanoethyl polyacrylamide, cyanoethyl polyacrylate, cyanoethyl pullulan, cyanoethyl polyhydroxymethylene, cyanoethyl glycidol pullulan, cyano group such as cyanoethyl saccharose and cyanoethyl sorbitol, polymers having cyanoethyl group, synthetic rubbers such as nitrile rubber and chloroprene rubber Examples thereof include a polymer material having a cyanoethyl group.
Moreover, as these polymer materials, commercially available products such as Hibler 5127 (manufactured by Kuraray Co., Ltd.) can also be suitably used. Among these, it is preferable to use a material having a cyanoethyl group, and it is particularly preferable to use cyanoethylated PVA.
In addition, these polymeric materials may use only 1 type, and may use multiple types together (mixed).

The viscoelastic matrix 24 using the polymer material having viscoelasticity at room temperature may use a plurality of polymer materials in combination as necessary.
That is, other dielectric polymer materials may be added to the viscoelastic matrix 24 as needed in addition to viscoelastic materials such as cyanoethylated PVA for the purpose of adjusting dielectric properties and mechanical properties. .

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. Fluorine polymers such as polyvinylidene fluoride-tetrafluoroethylene copolymer, vinylidene cyanide-vinyl acetate copolymer, cyanoethyl cellulose, cyanoethyl hydroxy saccharose, cyanoethyl hydroxy cellulose, cyanoethyl hydroxy pullulan, cyanoethyl methacrylate, cyanoethyl acrylate, cyanoethyl Hydroxyethyl cellulose, cyanoethyl amylose, cyanoethyl hydroxypropyl cellulose, cyanoethyl dihydroxypropyl cellulose, Synthesis of polymers having cyano groups or cyanoethyl groups, such as noethyl hydroxypropyl amylose, cyanoethyl polyacrylamide, cyanoethyl polyacrylate, cyanoethyl pullulan, cyanoethyl polyhydroxymethylene, cyanoethyl glycidol pullulan, cyanoethyl saccharose and cyanoethyl sorbitol, nitrile rubber, chloroprene rubber, etc. Examples thereof include rubber.
Among these, a polymer material having a cyanoethyl group is preferably used.
In addition, the dielectric polymer added to the viscoelastic matrix 24 of the piezoelectric layer 12 in addition to the material having viscoelasticity at room temperature such as cyanoethylated PVA is not limited to one type, and a plurality of types are added. Also good.

In addition to dielectric polymers, for the purpose of adjusting the glass transition point Tg, thermoplastic resins such as vinyl chloride resin, polyethylene, polystyrene, methacrylic resin, polybutene, isobutylene, phenol resin, urea resin, melamine resin, Thermosetting resins such as alkyd resins and mica may be added.
Furthermore, for the purpose of improving the tackiness, a tackifier such as rosin ester, rosin, terpene, terpene phenol, petroleum resin, etc. may be added.

In the viscoelastic matrix 24 of the piezoelectric layer 12, there is no particular limitation on the amount of addition of a polymer other than a viscoelastic material such as cyanoethylated PVA, but it is 30% by weight or less in the proportion of the viscoelastic matrix 24. Is preferable.
As a result, the characteristics of the polymer material to be added can be expressed without impairing the viscoelastic relaxation mechanism in the viscoelastic matrix 24, so that the dielectric constant is increased, the heat resistance is improved, and the adhesiveness to the piezoelectric particles 26 and the electrode layer is increased. A preferable result can be obtained in terms of improvement.

In order to increase the dielectric constant of the piezoelectric layer 12, dielectric particles may be added to the viscoelastic matrix.
The dielectric particles are particles having a high relative dielectric constant of 80 or more at 25 ° C.
Examples of the dielectric particles include lead zirconate titanate (PZT), barium titanate (BaTiO ₃ ), titanium oxide (TiO ₂ ), strontium titanate (SrTiO ₃ ), and lead lanthanum zirconate titanate (PLZT). Examples thereof include zinc oxide (ZnO), solid solution (BFBT) of barium titanate and bismuth ferrite (BiFeO ₃ ), and the like. Especially, it is preferable to use barium titanate (BaTiO ₃ ) as the dielectric particles in terms of having a high relative dielectric constant.

The dielectric particles preferably have an average particle size of 0.5 μm or less.
The volume fraction of the dielectric particles relative to the total volume of the viscoelastic matrix and the dielectric particles is preferably 5 to 45%, more preferably 10 to 30%, and particularly preferably 20 to 30%.

The piezoelectric particles 26 are made of ceramic particles having a perovskite type or wurtzite type crystal structure.
Examples of the ceramic particles constituting the piezoelectric particles 26 include lead zirconate titanate (PZT), lead lanthanum zirconate titanate (PLZT), barium titanate (BaTiO ₃ ), zinc oxide (ZnO), and Examples thereof include a solid solution (BFBT) of barium titanate and bismuth ferrite (BiFe ₃ ).

The particle size of the piezoelectric particles 26 may be appropriately selected according to the size and application of the conversion film 10, but is preferably 1 to 10 μm according to the study of the present inventors.
By setting the particle size of the piezoelectric particles 26 within the above range, a favorable result can be obtained in terms of achieving both high piezoelectric characteristics and flexibility.

In FIG. 1, the piezoelectric particles 26 in the piezoelectric layer 12 are uniformly and regularly dispersed in the viscoelastic matrix 24, but the present invention is not limited to this.
That is, the piezoelectric particles 26 in the piezoelectric layer 12 may be irregularly dispersed in the viscoelastic matrix 24 as long as it is preferably dispersed uniformly.

In the conversion film 10, the quantity ratio between the viscoelastic matrix 24 and the piezoelectric particles 26 in the piezoelectric layer 12 is required for the size and thickness of the conversion film 10 in the surface direction, the use of the conversion film 10, and the conversion film 10. What is necessary is just to set suitably according to the characteristic etc. to be.
Here, according to the study of the present inventor, the volume fraction of the piezoelectric particles 26 in the piezoelectric layer 12 is preferably 30 to 70%, particularly preferably 50% or more, and therefore 50 to 50%. 70% is more preferable.
By setting the quantity ratio between the viscoelastic matrix 24 and the piezoelectric particles 26 within the above range, a favorable result can be obtained in that high piezoelectric characteristics and flexibility can be achieved.

Further, in the conversion film 10, the thickness of the piezoelectric layer 12 is not particularly limited, and is appropriately set according to the size of the conversion film 10, the use of the conversion film 10, the characteristics required for the conversion film 10, and the like. do it.
Here, according to the study by the present inventors, the thickness of the piezoelectric layer 12 is preferably 8 to 300 μm, more preferably 8 to 40 μm, further preferably 10 to 35 μm, and particularly preferably 15 to 25 μm.
By setting the thickness of the piezoelectric layer 12 in the above range, a preferable result can be obtained in terms of ensuring both rigidity and appropriate flexibility.
The piezoelectric layer 12 is preferably polarized (polled) as described above. The polarization process will be described in detail later.

  In the conversion film 10, the upper protective layer 20 and the lower protective layer 18 cover and protect the upper thin film electrode 16 and the lower thin film electrode 14, and also provide the piezoelectric layer 12 with appropriate rigidity and mechanical strength. I'm in charge. That is, in the conversion film 10 of the present invention, the piezoelectric layer 12 composed of the viscoelastic matrix 24 and the piezoelectric particles 26 exhibits very excellent flexibility against slow bending deformation, Depending on the application, rigidity and mechanical strength may be insufficient. The conversion film 10 is provided with an upper protective layer 20 and a lower protective layer 18 to supplement it.

  The upper protective layer 20 and the lower protective layer 18 are not particularly limited, and various sheet materials can be used. As an example, various resin films are preferably exemplified. Among them, polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyphenylene sulfite (PPS), polymethyl methacrylate (PMMA) due to excellent mechanical properties and heat resistance. ), Polyetherimide (PEI), polyimide (PI), polyamide (PA), polyethylene naphthalate (PEN), triacetylcellulose (TAC), and cyclic olefin-based resin are preferably used.

The thickness of the upper protective layer 20 and the lower protective layer 18 is not particularly limited. The thicknesses of the upper protective layer 20 and the lower protective layer 18 are basically the same, but may be different.
Here, if the rigidity of the upper protective layer 20 and the lower protective layer 18 is too high, not only the expansion and contraction of the piezoelectric layer 12 is restricted, but also the flexibility is impaired, so that the mechanical strength and the sheet-like material are good. Except when handling is required, the upper protective layer 20 and the lower protective layer 18 are more advantageous as they are thinner.
According to the study of the present inventor, the thicknesses of the upper protective layer 20 and the lower protective layer 18 are preferably 50 μm or less, more preferably 25 μm or less, and particularly preferably 10 μm or less.

In the conversion film 10, an upper thin film electrode (hereinafter also referred to as an upper electrode) 16 is provided between the piezoelectric layer 12 and the upper protective layer 20, and a lower thin film electrode is provided between the piezoelectric layer 12 and the lower protective layer 18. (Hereinafter also referred to as a lower electrode) 14 are formed.
The upper electrode 16 and the lower electrode 14 are provided for applying an electric field to the conversion film 10 (piezoelectric layer 12).

  In the present invention, the material for forming the upper electrode 16 and the lower electrode 14 is not particularly limited, and various conductors can be used. Specifically, carbon, palladium, iron, tin, aluminum, nickel, platinum, gold, silver, copper, chromium, molybdenum and the like, alloys thereof, indium tin oxide, PEDOT / PPS (polyethylenedioxythiophene-polystyrenesulfone) Examples thereof include conductive polymers such as (acid). Among these, any of copper, aluminum, gold, silver, platinum, and indium tin oxide is preferably exemplified, and copper is more preferable from the viewpoint of conductivity, cost, flexibility, and the like.

  Also, the method for forming the upper electrode 16 and the lower electrode 14 is not particularly limited, and a vapor deposition method (vacuum film forming method) such as vacuum vapor deposition or sputtering, film formation by plating, or a foil formed of the above materials. Various known methods such as a method of sticking and a method of applying can be used.

In particular, a thin film of copper or aluminum formed by vacuum vapor deposition is preferably used as the upper electrode 16 and the lower electrode 14 because, for example, the flexibility of the conversion film 10 can be ensured. Among these, a copper thin film formed by vacuum deposition is particularly preferably used.
The thicknesses of the upper electrode 16 and the lower electrode 14 are not particularly limited. The thicknesses of the upper electrode 16 and the lower electrode 14 are basically the same, but may be different.

Here, similarly to the upper protective layer 20 and the lower protective layer 18 described above, if the rigidity of the upper electrode 16 and the lower electrode 14 is too high, not only the expansion and contraction of the piezoelectric layer 12 is restricted, but also the flexibility is impaired. For this reason, the upper electrode 16 and the lower electrode 14 are more advantageous as they are thinner as long as the electric resistance is not excessively high.
According to the study of the present inventor, the thicknesses of the upper electrode 16 and the lower electrode 14 are preferably 1.2 μm or less, more preferably 0.3 μm or less, and particularly preferably 0.1 μm or less.

As described above, in the conversion film 10, the upper colored layer 22 is formed between the upper electrode 16 and the upper protective layer 20, and the lower colored layer 21 is formed between the lower electrode 14 and the lower protective layer 18, respectively. It may be.
The upper colored layer 22 and the lower colored layer 21 are for preventing the rust of the upper electrode 16 and the lower electrode 14 from being visible from the outside.

From the viewpoint of preventing the rust of the upper electrode 16 and the lower electrode 14 from being visually recognized from the outside, the transmission density of the upper colored layer 22 and the lower colored layer 21 is preferably 0.3 or more, more preferably 0.5 or more. Is more preferable.
The transmission density is an optical density measured as a ratio of the transmitted light to the incident light. The transmittance when the transmission density is 0.3 is about 50%, and the transmittance when the transmission density is 0.5. Is about 30%.

Similarly to the upper protective layer 20 and the lower protective layer 18, and the upper electrode 16 and the lower electrode 14, if the rigidity of the upper colored layer 22 and the lower colored layer 21 is too high, the piezoelectric layer 12 expands and contracts. Since the upper colored layer 22 and the lower colored layer 21 are not limited to be restricted, the upper colored layer 22 and the lower colored layer 21 are more advantageous as long as the transmission density is not too low.
According to the study of the present inventors, the thickness of the upper colored layer 22 and the lower colored layer 21 is preferably 1 μm or less, more preferably 100 nm or less, and particularly preferably 40 nm or less.

Further, the upper colored layer 22 and the lower colored layer 21 preferably have a low electrical resistivity, preferably 1 × 10 ⁻⁷ Ωm or less.
In the conversion film 10, as one method of drawing out the electrodes from the upper electrode 16 and the lower electrode 14, a hole is formed by removing a part of the protective layer, and a conductive material such as silver paste is formed in the hole. There is a method of forming an electrode lead portion by inserting and electrically conducting a conductive material and a thin film electrode. When the electrode lead-out portion is formed by such a method, if the electrical resistivity of the upper colored layer 22 and the lower colored layer 21 is high, the conductive material and the thin-film electrode can be removed only by removing a part of the protective layer. Since it cannot conduct electrically, it becomes necessary to remove the upper colored layer 22 and the lower colored layer 21 at the positions of the holes, resulting in poor productivity.
Therefore, by reducing the electrical resistivity of the upper colored layer 22 and the lower colored layer 21, the conductive material and the thin film electrode can be electrically connected without removing the upper colored layer 22 and the lower colored layer 21 at the positions of the holes. Can be conducted.

In the present invention, the material for forming the upper colored layer 22 and the lower colored layer 21 is not particularly limited as long as it satisfies the above transmission density and does not change color due to rust or the like.
Specifically, the material for forming the upper colored layer 22 and the lower colored layer 21 includes metals such as nickel, titanium, aluminum, gold, platinum, and chromium, carbon black (CB), titanium oxide, zinc oxide, barium sulfate, and the like. And inorganic pigments, quinacridone-based, azo-based, benzimidazolone-based, phthalocyanine-based, anthraquinone-based organic pigments, light-scattering members having pores therein, and the like.
From the viewpoint of the above-mentioned transmission density, thickness, and electrical resistivity, it is preferable to use a metal as the material for forming the upper colored layer 22 and the lower colored layer 21, and among these, nickel is more preferable.
Moreover, from the viewpoint of designability that the conversion film can be colored in various colors, it is preferable to use various pigments as the upper colored layer 22 and the lower colored layer 21.

Moreover, there is no limitation in particular in the formation method of the upper colored layer 22 and the lower colored layer 21, What is necessary is just to form by various well-known methods according to the said material.
For example, when a metal is used as a coloring layer forming material, a vapor deposition method (vacuum film forming method) such as vacuum evaporation or sputtering, film formation by plating, or a foil formed of the above material is attached. Methods etc. are available. It is more preferable to form by vacuum deposition from the point that it can be formed thinner.
In addition, when a pigment is used as the coloring layer forming material, a coating method, printing, or the like can be used.
A method of transferring a colored layer formed in advance can also be used.

  In the illustrated example, the upper colored layer 22 and the lower colored layer 21 are formed between the upper electrode 16 and the upper protective layer 20 and between the lower electrode 14 and the lower protective layer 18, respectively. However, the present invention is not limited to this, and any structure may be used as long as it is formed on the surface layer side with respect to the upper electrode 16 and on the surface layer side with respect to the lower electrode 14. That is, for example, the upper electrode 16, the upper protective layer 20, and the upper colored layer 22 are formed in this order on one surface of the piezoelectric layer 12, and the lower electrode 14 and the lower protective layer 18 are formed on the other surface of the piezoelectric layer 12. The lower colored layer 21 may be formed in this order.

In the illustrated example, each of the upper electrode 16 side and the lower electrode 14 side has a colored layer. However, the present invention is not limited to this, and the colored layer is provided on at least one side. It may be. In this case, when incorporated in the electroacoustic transducer, it is preferable to have a colored layer on the surface that is visually recognized (the surface facing the outside of the device).
Moreover, the conversion film of this invention may contain functional layers, such as a contact | adherence provision layer and an antioxidant layer, in addition to the above-mentioned thin film electrode, a protective layer, a colored layer, and the like.

As described above, the conversion film 10 includes at least the piezoelectric layer 12 in which the piezoelectric particles 26 are dispersed in the viscoelastic matrix 24 having viscoelasticity at room temperature, and is sandwiched between the upper electrode 16 and the lower electrode 14. The body has a layer structure in which an upper protective layer 20 and a lower protective layer 18 are sandwiched.
Such a conversion film 10 preferably has a maximum value at room temperature at which the loss tangent (Tanδ) at a frequency of 1 Hz as measured by dynamic viscoelasticity measurement is 0.1 or more.
Thereby, even if the conversion film 10 is subjected to 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, so that the polymer matrix and the piezoelectric particles It is possible to prevent cracks from occurring at the interface.

The conversion film 10 preferably has a storage elastic modulus (E ′) at a frequency of 1 Hz as measured by dynamic viscoelasticity of 10 to 30 GPa at 0 ° C. and 1 to 10 GPa at 50 ° C.
Thereby, the conversion film 10 can have a large frequency dispersion in the storage elastic modulus (E ′) at room temperature. That is, it can behave hard for vibrations of 20 Hz to 20 kHz and soft for vibrations of several Hz or less.

The conversion film 10 thickness and the product of the storage modulus at a frequency 1 Hz (E ') by dynamic viscoelasticity ^{measurement, 1.0 × 10 6 ~2.0 × 10} 6 (1 at 0 ° C.. 0E + 06 to 2.0E + 06) N / m, preferably 1.0 × 10 ^{5 to} 1.0 × 10 ⁶ (1.0E + 05 to 1.0E + 06) N / m at 50 ° C.
Thereby, in the range which does not impair flexibility and an acoustic characteristic, the conversion film 10 can be equipped with moderate rigidity and mechanical strength.

Furthermore, the conversion film 10 preferably has a loss tangent (Tan δ) at 25 ° C. and a frequency of 1 kHz in a master curve obtained from dynamic viscoelasticity measurement of 0.05 or more.
Thus, the conversion frequency characteristic of the loudspeaker using the film 10 becomes smooth, can vary the amount of sound is also small when the lowest resonance frequency f ₀ with the change in the curvature of the speaker has changed.

Next, an electroacoustic transducer using the electroacoustic transducer film of the present invention will be described with reference to FIG.
FIG. 5 is a sectional view conceptually showing an example of the electroacoustic transducer of the present invention.
The electroacoustic transducer 60 shown in FIG. 5 uses the conversion film 10 as a diaphragm.

  In the electroacoustic transducer 60, when the conversion film 10 expands in the in-plane direction by applying a voltage to the conversion film 10, the conversion film 10 moves upward (in the protruding direction of the convex portion) to absorb this extension. On the contrary, when the conversion film 10 contracts in the in-plane direction by applying a voltage to the conversion film 10, the conversion film 10 is moved downward (on the side opposite to the protruding direction of the convex portion) to absorb this contraction. Direction). The electroacoustic transducer 60 converts vibration (sound) and an electric signal by vibration caused by repeated expansion and contraction of the conversion film 10.

  The electroacoustic transducer 60 includes the conversion film 10 and two support members 48.

As shown in FIG. 5, the two support members 48 sandwich and support the edge portion of the convex portion 10 a of the conversion film 10.
The support member 48 is a plate-like member that is formed of plastic, metal, wood, or the like and has a through hole in the center. The shape of the through hole is substantially the same as the shape of the convex portion 10a when viewed from the direction perpendicular to the main surface of the conversion film 10, and is a circular shape having a diameter Ds in the illustrated example.

As shown in the figure, the position of the convex portion 10a of the conversion film 10 and the penetration of the support member 48 when viewed from a direction perpendicular to the main surface of the conversion film 10 using two such support members 48. By aligning the positions of the holes and holding the conversion film 10 between the two support members 48, the entire periphery of the edge of the convex portion 10 a of the conversion film 10 is held and supported.
The method for fixing the two support members 48 is not particularly limited, and various known methods such as a method using screws and bolts and nuts and a method using a fixing jig can be used.

In the electroacoustic transducer 60 having such a configuration, the convex portion 10a of the conversion film 10 is a region that actually vibrates. In this way, by supporting (fixing) the peripheral portion of the convex portion 10a that is a vibrating region with the two support members 48, the expansion and contraction in the surface direction of the conversion film is transmitted to a region other than the convex portion 10a. And the vibration of the convex portion 10a can be efficiently performed.
In addition, since an elastic support for curving the conversion film 10 and a structure for applying air pressure are unnecessary, a structure in which both surfaces of the conversion film 10 are open can be used. Therefore, the heat generated by driving the conversion film 10 can be efficiently dissipated, and the heat dissipation can be enhanced.
In addition, since an elastic support for bending the conversion film 10 and a structure for applying air pressure are unnecessary, the elastic support is deformed over time, or the air pressure changes to change the amount of bending of the conversion film. Therefore, sound pressure and sound quality do not change over time, and durability against changes over time can be increased.
In addition, since an elastic support for curving the conversion film 10 or a structure for applying air pressure is not necessary, the conversion film 10 can be reduced in size and thickness.

The width of the edge portion of the support member 48 is not particularly limited as long as the width of the edge portion of the conversion film 10 can be suitably supported, but is preferably 20 mm or less, and preferably 1 mm to 10 mm.
In the illustrated example, the two support members 48 are configured to sandwich the entire periphery of the edge portion of the convex portion 10a of the conversion film 10, but this is not a limitation, and at least a part of the edge portion is not limited thereto. It is good also as a structure which clamps and supports an area | region.

In addition, when a conversion film having a convex portion is incorporated in an electroacoustic transducer, the convex portion may be arranged outward, and the convex portion is arranged inward (that is, the concave portion is directed outward). May be.
Moreover, since the conversion film having a convex part is formed in a convex shape, a viscoelastic support for curving the conversion film and a structure for applying pressure to the inside of the case are not necessary. You may use it in combination.

Next, an example of the manufacturing method of the conversion film of this invention is demonstrated with reference to FIG. 6A-FIG. 6E and FIG. 7A-FIG. 7B.
The manufacturing method of the conversion film of the present invention includes a polymer composite piezoelectric material in which piezoelectric particles are dispersed in a viscoelastic matrix made of a polymer material having viscoelasticity at room temperature, and laminated on both surfaces of the polymer composite piezoelectric material. A preparation step of preparing a laminate formed by laminating the two thin film electrodes and two protective layers laminated on the two thin film electrodes,
The laminate is heated and compression molded, and a method for producing an electroacoustic conversion film including a molding step of molding a convex portion protruding toward one main surface side.

The laminated body prepared in the preparation process is manufactured as follows as an example.
First, as shown in FIG. 6A, a sheet-like object 11a in which the lower electrode 14 is formed on the lower protective layer 18 is prepared. The sheet-like material 11a may be produced by forming a copper thin film or the like as the lower electrode 14 on the surface of the lower protective layer 18 by vacuum deposition, sputtering, plating, or the like.
When the lower protective layer 18 is very thin and handling properties are poor, the lower protective layer 18 with a separator (temporary support) may be used as necessary. In addition, as a separator, 25-100 micrometers thick PET etc. can be used. In addition, what is necessary is just to remove a separator just before forming a side surface insulating layer, a 2nd protective layer, etc. after thermocompression bonding of a thin film electrode and a protective layer.

On the other hand, a polymer material having viscoelasticity (hereinafter also referred to as viscoelastic material) such as cyanoethylated PVA is dissolved in an organic solvent, and piezoelectric particles 26 such as PZT particles are added and stirred. A paint is prepared which is dispersed. The organic solvent is not particularly limited, and various organic solvents such as dimethylformamide (DMF), methyl ethyl ketone, and cyclohexanone can be used.
When the aforementioned sheet-like material 11a is prepared and a paint is prepared, this paint is cast (applied) on the sheet-like material 11a, and the organic solvent is evaporated and dried. As a result, as shown in FIG. 6B, the first stacked body 11b having the lower electrode 14 on the lower protective layer 18 and the piezoelectric layer 12 formed on the lower electrode 14 is manufactured.

The coating casting method is not particularly limited, and all known methods (coating apparatuses) such as a slide coater and a doctor knife can be used.
Alternatively, if the viscoelastic material is a material that can be heated and melted, such as cyanoethylated PVA, the viscoelastic material is heated and melted, and a melt obtained by adding / dispersing the piezoelectric particles 26 is prepared and extruded. The first laminated body 11b as shown in FIG. 6B may be produced by extruding the sheet-like material 11a shown in FIG.

As described above, in the conversion film 10, a polymer piezoelectric material such as PVDF may be added to the viscoelastic matrix 24 in addition to a viscoelastic material such as cyanoethylated PVA.
When these polymer piezoelectric materials are added to the viscoelastic matrix 24, the polymer piezoelectric material added to the paint may be dissolved. Alternatively, the polymer piezoelectric material to be added may be added to the heat-melted viscoelastic material and heat-melted.
When the first laminated body 11b having the lower electrode 14 on the lower protective layer 18 and the piezoelectric layer 12 formed on the lower electrode 14 is manufactured, it is preferable that the piezoelectric layer 12 be subjected to polarization treatment (polling). )I do.

The method for polarization treatment of the piezoelectric layer 12 is not particularly limited, and a known method can be used.
As a preferable method of polarization treatment, the method shown in FIGS. 6C and 6D is exemplified.

In this method, as shown in FIGS. 6C and 6D, on the upper surface 12a of the piezoelectric layer 12 of the first laminated body 11b, a gap g is formed, for example, by 1 mm, or a rod-shaped or movable along the upper surface 12a. A wire-shaped corona electrode 30 is provided. The corona electrode 30 and the lower electrode 14 are connected to a DC power source 32.
Furthermore, a heating means for heating and holding the first stacked body 11b, for example, a hot plate is prepared.

  Then, the piezoelectric layer 12 is heated and held at, for example, a temperature of 100 ° C. by a heating means, and a direct current of several kV, for example, 6 kV, is connected between the lower electrode 14 and the corona electrode 30 from the DC power source 32. A voltage is applied to cause corona discharge. Further, the corona electrode 30 is moved (scanned) along the upper surface 12a of the piezoelectric layer 12 while maintaining the gap g, and the piezoelectric layer 12 is polarized.

In such polarization treatment using corona discharge (hereinafter also referred to as corona poling treatment for convenience), the corona electrode 30 may be moved by using a known rod-like moving means.
In the corona poling process, the method for moving the corona electrode 30 is not limited. That is, the corona electrode 30 may be fixed and a moving mechanism for moving the first stacked body 11b may be provided, and the first stacked body 11b may be moved to perform the polarization treatment. The movement of the first laminated body 11b may be performed by using a known sheet-like moving means.
Furthermore, the number of corona electrodes 30 is not limited to one, and a plurality of corona electrodes 30 may be used to perform corona poling treatment.
Further, the polarization process is not limited to the corona polling process, and normal electric field poling in which a direct current electric field is directly applied to a target to be polarized can also be used. However, when performing this normal electric field poling, it is necessary to form the upper electrode 16 before the polarization treatment.
In addition, you may perform the calendar process which smoothes the surface of the piezoelectric material layer 12 using a heating roller etc. before this polarization process. By applying this calendar process, the thermocompression bonding process described later can be performed smoothly.

Thus, while performing the polarization process of the piezoelectric layer 12 of the first laminated body 11b, the sheet-like object 11c in which the upper electrode 16 is formed on the upper protective layer 20 is prepared. The sheet-like material 11c may be manufactured by forming a copper thin film or the like as the upper electrode 16 on the surface of the upper protective layer 20 by vacuum deposition, sputtering, plating, or the like.
Next, as illustrated in FIG. 6E, the upper electrode 16 is directed toward the piezoelectric layer 12, and the sheet-like material 11 c is stacked on the first stacked body 11 b that has finished the polarization treatment of the piezoelectric layer 12.
Further, the laminated body of the first laminated body 11b and the sheet-like material 11c is subjected to thermocompression bonding with a heating press device, a heating roller pair or the like so as to sandwich the upper protective layer 20 and the lower protective layer 18, A two-layered product 11d is produced.
In addition, the 2nd laminated body 11d is a laminated body prepared by a preparatory process in this invention.

Next, in the molding step, the produced second laminated body 11d is heated and compression-molded, and the convex portion 10a protruding to one main surface side of the conversion film 10 (second laminated body 11d) is molded.
The method for heat compression molding is not particularly limited, and various known resin film processing methods can be used. As an example, as shown in FIGS. 7A and 7B, by using a molding apparatus having molds 70a and 70b having a shape corresponding to the shape of the convex portion 10a to be molded, the second laminate 11d is heat compression molded. The convex portion 10a having a desired shape can be molded.

  As mentioned above, although the electroacoustic conversion film of this invention, the manufacturing method of an electroacoustic conversion film, and the electroacoustic transducer were demonstrated in detail, this invention is not limited to the above-mentioned example, In the range which does not deviate from the summary of this invention. Of course, various improvements and changes may be made.

  Hereinafter, specific examples of the present invention will be given to explain the present invention in more detail.

[Example 1]
The conversion film 10 shown in FIG. 1 was produced by the method shown in FIGS. 6A to 6E and FIGS. 7A to 7B.
First, cyanoethylated PVA (CR-V manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved in methyl ethyl ketone (MEK) at the following composition ratio. Thereafter, PZT particles were added to the solution at the following composition ratio and dispersed with a propeller mixer (rotation speed: 2000 rpm) to prepare a coating material for forming the piezoelectric layer 12.
・ PZT particles ・ ・ ・ ・ ・ ・ 1000 parts by mass ・ Cyanoethylated PVA ・ ・ ・ ・ ・ ・ 100 parts by mass ・ MEK ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 600 parts by mass The PZT particles used were obtained by sintering a commercially available PZT raw material powder at 1000 to 1200 ° C. and then crushing and classifying the PZT particles so as to have an average particle size of 3.5 μm.

On the other hand, sheet-like materials 11a and 11c were prepared by vacuum-depositing a 0.1 μm-thick copper thin film on a 4 μm-thick PET film by vacuum deposition. That is, in this example, the upper electrode 16 and the lower electrode 14 are copper-deposited thin films having a thickness of 0.1 μm, and the upper protective layer 20 and the lower protective layer 18 are PET films having a thickness of 4 μm.
In order to obtain good handling during the process, a PET film with a 50 μm thick separator (temporary support PET) was used, and the separator of each protective layer was removed after thermocompression of the sheet-like material 11c. It was.

On the lower electrode 14 (copper deposited thin film) of the sheet-like material 11a, a paint for forming the piezoelectric layer 12 prepared previously was applied using a slide coater. In addition, the coating material was apply | coated so that the film thickness of the coating film after drying might be set to 20 micrometers.
Next, the MEK was evaporated by heating and drying the sheet with the paint applied on the sheet 11a in an oven at 120 ° C. Thus, the first laminated body 11b having the copper lower electrode 14 on the lower protective layer 18 made of PET and the piezoelectric layer 12 (piezoelectric layer) having a thickness of 20 μm formed thereon is formed. Was made.

  The piezoelectric layer 12 of the laminate 11b was subjected to polarization treatment by the above-described corona poling shown in FIGS. 6C and 6D. The polarization treatment was performed by setting the temperature of the piezoelectric layer 12 to 100 ° C. and applying a DC voltage of 6 kV between the lower electrode 14 and the corona electrode 30 to cause corona discharge.

A mixture of cyanoethylated pullulan and cyanoethylated PVA (CR-M manufactured by Shin-Etsu Chemical Co., Ltd.) is 0.3 μm on the upper electrode 16 (copper thin film side) on the first laminated body 11b subjected to the polarization treatment. The sheet-like material 11c was laminated so that the coated surface applied to the piezoelectric material layer 12 faced.
Next, the laminated body of the first laminated body 11b and the sheet-like material 11c is thermocompression bonded at 120 ° C. using a laminator device to bond the piezoelectric body layer 12, the upper electrode 16 and the lower electrode 14 to each other. A two-layered body 11d was produced.

Next, the produced second laminated body 11d is cut into a size of 50 mm × 50 mm, and a hot press apparatus (with a mold having a shape corresponding to the shape of the convex portion 10a to be molded, as shown in FIGS. 7A and 7B, is used. The electroacoustic conversion film 10 was produced by molding into a shape having a convex portion 10a as shown in FIG. 1 by a heat compression molding method using AH-2003) manufactured by ASONE.
The shape of the convex part 10a was made into the shape which consists of a part of sphere. Moreover, the short diameter Ds of the convex part 10a when it sees from the direction perpendicular | vertical to the main surface of the conversion film 10 was 40 mm, and height was 0.5 mm. That is, the ratio H / Ds between the height H of the convex portion and the minor axis Ds was set to 0.01.

  In each of the upper protective layer 20 side and the lower protective layer 18 side of the produced conversion film 10, a part of the protective layer is removed by cutting to form a hole, and a conductive material such as silver paste is formed in the hole. The conductive material and the thin film electrode were electrically connected to form an electrode lead portion.

An electroacoustic transducer 60 as shown in FIG. 5 was produced by sandwiching the edge portion of the produced conversion film 10 with two support members 48.
The support member 48 is a plate-like member having a through hole in the center and made of acrylic. The outer shape is 50 mm × 50 mm, the size of the through hole is a circle of φ40 mm, and the thickness is 3 mm.

[Examples 2 to 6]
The electroacoustic conversion film 10 and the electroacoustics were the same as in Example 1 except that the height H of the convex portion 10a and the ratio H / Ds of the height H to the minor axis Ds were changed to the values shown in Table 1, respectively. A transducer 60 was produced.

[Examples 7 to 9]
An electroacoustic conversion film 10 and an electroacoustic transducer 60 were produced in the same manner as in Example 3 except that the thicknesses of the upper protective layer 20 and the lower protective layer 18 were changed as shown in Table 1 below.

[Example 10]
Example 2 was performed except that the two support members 48 were not provided. That is, the below-mentioned evaluation was performed with the electroacoustic conversion film 10 alone.

[Example 11]
The electroacoustic transducer film 10 and the electroacoustic transducer 60 were produced in the same manner as in Example 3 except that the shape of the convex portion 10a was molded into a shape having a flat top as shown in FIG. 3A.

[Example 12]
An electroacoustic conversion film 10 and an electroacoustic transducer 60 were produced in the same manner as in Example 3 except that the electrode lead-out portions were provided at two locations on each of the upper protective layer 20 side and the lower protective layer 18 side.

[Example 13]
The electroacoustic conversion film 10 and the electroacoustic transducer 60 were produced in the same manner as in Example 3 except that a polyamide film having a thickness of 4 μm was used as the upper protective layer 20 and the lower protective layer 18.

[Example 14]
As the sheet-like materials 11a and 11c, a nickel thin film having a thickness of 20 nm was formed on a PET film having a thickness of 4 μm by vacuum deposition, and a copper thin film having a thickness of 0.1 μm was further vacuum deposited on the nickel thin film. An electroacoustic conversion film 10 and an electroacoustic transducer 60 were produced in the same manner as in Example 3 except that those were used.
That is, in the conversion film (second laminate) of Example 15, the lower electrode 14, the lower colored layer 21, and the lower protective layer 18 are laminated in this order on one surface of the piezoelectric layer 12, as shown in FIG. 4B. The upper electrode 16, the upper colored layer 22, and the upper protective layer 20 are stacked in this order on the other surface of the piezoelectric layer 12.

[Comparative Example 1]
The electroacoustic conversion film and the electroacoustic transducer were obtained in the same manner as in Example 1 except that the height H of the convex portion was 8 mm and the ratio H / Ds of the height H to the minor axis Ds was 0.2. Produced.

[Comparative Example 2]
An electroacoustic conversion film was produced in the same manner as in Example 1 except that the convex portions were not formed. That is, the second laminate before molding the convex portions was used as the conversion film 102.
Using this conversion film 102, an electroacoustic transducer 100 as shown in FIG. 8A was produced.

An electroacoustic transducer 100 shown in FIG. 8A includes a case 104 having a thin cylindrical shape and one of the largest surfaces being an open surface, an elastic support 106 accommodated in the case 104, an open surface of the case 104, and an elastic support. A conversion film 102 that covers the body 106, and a pressing member 108 that is a circular plate-like member having an opening in the center that fixes the periphery of the conversion film 102 in contact with the open surface of the case 104. Have
The case 104 is a cylindrical container with one open surface, and a plastic container having an outer size of 50 mm × 50 mm, a height of 6 mm, an opening size of φ40 mm, and a depth of 3 mm was used.
The elastic support 106 was made of felt having a size of 40 mm, a height of 10 mm before assembly, and a density of 250 kg / m ³ .
As the pressing member 108, an acrylic plate-like member having an opening size of 40 mm and a thickness of 3 mm was used.
As shown in FIG. 8A, the conversion film 102 is curved and held in a convex shape by the elastic support 106. The bending height was 2 mm.

[Comparative Example 3]
It was the same as Comparative Example 2 except that an electroacoustic transducer 110 as shown in FIG.
That is, the 2nd laminated body before shape | molding a convex part was used as the conversion film 102. FIG.

The electroacoustic transducer 110 shown in FIG. 8B includes an airtight case 104, a pipe 104 a for introducing air into the case 104, a conversion film 102 that covers the open surface of the case 104, and a case 104. And a holding lid 112 fitted to the outer periphery.
The presser lid 112 is a frame-like member having a substantially L-shaped cross section having an inner periphery substantially the same as the outer periphery of the case 104, and is fitted to the outer periphery of the case 104.
The conversion film 102 is pressed and fixed to the open surface of the case 104, and the inside of the case 104 is hermetically closed by the conversion film 102. Further, air is introduced from the pipe 104a into the case 104 (closed space formed by the case 104 and the conversion film 102), pressure is applied to the conversion film 102, and the convex height is increased, so that the bending height becomes 2 mm. The electroacoustic transducer 110 was held.

[Comparative Example 4]
A commercially available PVDF (Poly Vinylidene DiFluoride) with a thickness of 20 μm was used as a piezoelectric layer, and a conversion film was molded using a laminate in which the upper electrode and the lower electrode were formed on both sides of the PVDF by vacuum vapor deposition as a second laminate. Except for the above, an electroacoustic conversion film and an electroacoustic transducer were produced in the same manner as in Example 3.

[Evaluation]
The sound pressure level, heat dissipation, and change with time of the electroacoustic transducers produced in each example and comparative example were evaluated.

<Sound pressure level>
The sound pressure level of the produced electroacoustic transducer was measured.
Specifically, a microphone is disposed at a position 0.1 m away from the center of the conversion film of the electroacoustic transducer, and a sign of 1 kHz, 10 V _0-P is provided between the upper electrode and the lower electrode of the conversion film. A wave was input and the sound pressure level was measured.
The following evaluation was made based on the sound pressure level.
A: 65 dB or more B: 60 dB or more and less than 65 dB C: 55 dB or more and less than 60 dB D: 50 dB or more and less than 55 dB E: less than 50 dB

<Heat dissipation>
The heat dissipation of the produced electroacoustic transducer was evaluated as follows.
First, a 10 kHz, 20 V _0-P sine wave was input for 15 minutes between the upper electrode and the lower electrode of the conversion film of the electroacoustic transducer in an environment at room temperature of 25 ° C.
After continuous driving for 15 minutes, the surface temperature of the conversion film was measured and evaluated according to the following criteria.
A: Room temperature + less than 1.5 ° C B: Room temperature + 1.5 ° C or more and room temperature + less than 3.0 ° C C: Room temperature + 3.0 ° C or more and room temperature + 5.0 ° C
D: Room temperature + 5.0 ° C or higher

<Change over time>
The produced electroacoustic transducer is left in an environment of a temperature of 23 ° C. and a humidity of 50% RH for 2 weeks, and then the sound pressure level is measured in the same manner as described above, and is evaluated as follows based on the amount of change in the sound pressure level. did.
A: Less than ± 1.0 dB B: ± 1.0 dB or more The evaluation results are shown in Table 1.

From the results shown in Table 1, Examples 1 to 15 of the electroacoustic conversion film of the present invention are good in parallel with all of sound pressure level, heat resistance, and durability against changes over time, as compared with Comparative Examples 1 to 4. You can see that
In addition, it is understood from the comparison between Examples 1 to 6 and Comparative Example 1 that the lower the height of the convex portion, the better the sound pressure level is improved, and the ratio H / Ds of the minor axis Ds to the height H is 0. .15 or less, 0.1 or less is preferable, 0.075 or less is more preferable, and 0.005 or less is particularly preferable.

Moreover, it turns out that efficiency increases and the sound pressure level improves by fixing the edge part of the convex part of a conversion film from the comparison of Example 3 and Example 10.
Further, it can be seen from the comparison between Example 3 and Example 11 that it is preferable to provide a hole in the protective layer and to provide an electrode lead-out part through this hole, thereby reducing the size.
Further, it is understood from the comparison between Example 3 and Example 12 that the sound pressure level can be improved by making the shape of the convex portion a dome shape.
Further, it can be seen from the comparison between Example 3 and Example 13 that by increasing the number of electrode lead-out portions, the area for electrical connection can be increased and the electrical resistance can be reduced, so that the amount of heat generation can be reduced, which is preferable.
From the above results, the effect of the present invention is clear.

DESCRIPTION OF SYMBOLS 10, 102 Electroacoustic conversion film 10a Convex part 11a, 11c Sheet-like material 11b 1st laminated body 11d 2nd laminated body 12 Piezoelectric layer 14 Lower thin film electrode 16 Upper thin film electrode 18 Lower protective layer 20 Upper protective layer 21 Lower colored layer 22 Upper colored layer 24 Viscoelastic matrix 26 Piezoelectric particle 30 Corona electrode 32 DC power supply 48 Support member 60, 100, 110 Electroacoustic transducer 70a, 70b Mold 104 Case 104a Pipe 106 Elastic support body 108 Pressing member 112 Holding lid

Claims (11)

A polymer composite piezoelectric material obtained by dispersing piezoelectric particles in a viscoelastic matrix made of a polymer material having viscoelasticity at room temperature;
Two thin film electrodes laminated on both surfaces of the polymer composite piezoelectric body;
Two protective layers stacked on each of the two thin film electrodes;
About at least one of the two thin film electrodes, a colored layer that is formed on the surface layer side of the thin film electrode and covers the thin film electrode is laminated,
It has a convex part formed into a convex shape so as to protrude on one main surface side,
The ratio H / Ds between the molding height H of the convex portion and the minor axis Ds of the convex portion when viewed from the direction perpendicular to the main surface satisfies 0 <H / Ds ≦ 0.15. An electroacoustic conversion film.   The electroacoustic conversion film according to claim 1, wherein a transmission density of the colored layer is 0.3 or more.   The electroacoustic conversion film according to claim 1 or 2, wherein the colored layer has a thickness of 1 µm or less.   The electrical resistivity of the colored layer is 1 × 10 ^-7 The electroacoustic conversion film according to any one of claims 1 to 3, which is Ωm or less. The electroacoustic conversion film according to any one of claims 1 to 4, further comprising an insulating layer that covers a region where the polymer composite piezoelectric body is exposed and prevents a short circuit. The electroacoustic conversion film according to any one of claims 1 to 5, wherein a shape of the convex portion is a part of a sphere or a part of a spheroid. The protective layer has a hole penetrating to the electrode layer;
The electroacoustic conversion film as described in any one of Claims 1-6 which has an electrode extraction part electrically connected to the said electrode layer through the said hole part. The electroacoustic conversion film of Claim 7 which has 3 or more of said electrode extraction parts connected to the said electrode layer through the said hole part of the said protective layer. It is the manufacturing method of the electroacoustic conversion film which manufactures the electroacoustic conversion film as described in any one of Claims 1-8 ,
A polymer composite piezoelectric material in which piezoelectric particles are dispersed in a viscoelastic matrix made of a polymer material having viscoelasticity at room temperature, two thin film electrodes laminated on both surfaces of the polymer composite piezoelectric material, and 2 Two protective layers laminated on each of the two thin film electrodes, and at least one of the two thin film electrodes are laminated on the surface layer side of the thin film electrode, and a colored layer covering the thin film electrode is laminated. A preparation step of preparing a laminate,
A method for producing an electroacoustic conversion film, comprising: heating and compression-molding the laminate, and molding a projecting portion protruding toward one main surface. An electroacoustic conversion film obtained by molding a convex portion according to any one of claims 1 to 8 ,
The electroacoustic transducer which has a supporting member which supports the edge part of the said convex part of the said electroacoustic conversion film. The support member has a through-hole having the same shape as the convex portion when viewed from a direction perpendicular to the main surface of the electroacoustic conversion film,
The electroacoustic transducer according to claim 10 , wherein the two support members sandwich the edge portion of the convex portion of the electroacoustic conversion film.