JP2016015354A - Electroacoustic conversion film and conduction method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroacoustic conversion film in which thin film electrodes are provided on both surfaces of a dielectric layer and protection layers are provided on both thin film electrodes, the electroacoustic conversion film which enables easy electric conduction between the thin film electrodes and the exterior while protecting the thin film electrodes, and to provide an electric conduction method.SOLUTION: An electroacoustic conversion film 10 includes: a piezoelectric layer 12 which is a piezoelectric sheet-like object forming a dielectric layer (a sheet-like object); an upper thin film electrode 14 formed on one surface of the piezoelectric layer 12; an upper protection layer 16 formed on a surface of the upper thin film electrode 14; a lower thin film electrode 20 formed on a surface of the piezoelectric layer 12 which is opposite to the upper thin film electrode 14; and a lower protection layer 24 formed on a surface of the lower thin film electrode 20. A thin layer part 28 having a film thickness thinner than a surrounding area is provided in at least one side of the protection layer 16.

Description

  The present invention relates to the generation (reproduction) of sound caused by vibration in response to an electric signal and the vibration caused by the sound into an electric signal in various acoustic devices (acoustic equipment) such as pickups used for musical instruments such as speakers, microphones, and guitars. The present invention relates to an electroacoustic conversion film used for conversion. Specifically, the present invention relates to an electroacoustic conversion film that can be easily pulled out when being mounted as a speaker or the like, and an electrical conduction method of the electroacoustic conversion film.

In recent years, research on flexible displays using flexible substrates such as plastics has been advanced.
As a substrate for such a flexible display, for example, Patent Document 1 discloses a flexible display substrate in which a gas barrier layer and a transparent conductive layer are laminated on a transparent plastic film.
A flexible display has superiority in lightness, thinness, flexibility, and the like as compared with a display using a conventional glass substrate, and can be provided on a curved surface such as a cylinder. In addition, since it can be rolled up and stored, it does not impair portability even on a large screen, and has attracted attention as a display device for posting advertisements, PDAs (personal digital assistants) and the like.

When such a flexible display is used as an image display device and a sound generation device that reproduces sound together with an image, such as a television receiver, a speaker that is an acoustic device for generating sound is required.
Here, as a conventional speaker shape, a so-called cone-shaped funnel shape, a spherical dome shape, or the like is common. However, if these speakers are incorporated in the flexible display described above, the lightness and flexibility, which are the advantages of the flexible display, may be impaired. Further, when a speaker is externally attached, carrying and the like are troublesome, and it is difficult to install the speaker on a curved wall, which may impair the beauty.

Under such circumstances, for example, Patent Document 2 discloses that a flexible piezoelectric film in the form of a sheet is employed as a speaker that can be integrated into a flexible display without impairing lightness and flexibility. Yes.
The piezoelectric film is a uniaxially stretched film of polyvinylidene fluoride (PVDF) that is polarized at a high voltage, and has a property of expanding and contracting in response to an applied voltage.

In order to employ a piezoelectric film as a speaker, it is necessary to convert expansion / contraction motion along the film surface into vibration of the film surface. This conversion from expansion / contraction motion to vibration is achieved by holding the piezoelectric film in a curved state, thereby enabling the piezoelectric film to function as a speaker.
It is well known that the minimum resonance frequency f ₀ of the speaker diaphragm is given by the following equation. Here, s is the stiffness (mechanical strength) of the vibration system, and m is the mass.
At this time, since the mechanical stiffness s decreases as the degree of bending of the piezoelectric film, that is, the radius of curvature of the bending portion increases, the minimum resonance frequency f ₀ decreases. That is, the sound quality (volume and frequency characteristics) of the speaker changes depending on the curvature radius of the piezoelectric film.
In order to solve this problem, Patent Document 2 includes a sensor for measuring the degree of bending of the piezoelectric film, and corrects the amplitude by increasing / decreasing the amplitude by a predetermined amount according to the frequency band of the audio signal according to the degree of bending of the piezoelectric film. Enables stable sound output.

By the way, a flexible display with an integrated speaker made of piezoelectric film and rectangular in plan view is gripped in a loosely bent state like a newspaper or magazine for portable use, and the screen display is switched between portrait and landscape. In this case, it is preferable that the image display surface can be curved not only in the vertical direction but also in the horizontal direction.
However, a piezoelectric film made of uniaxially stretched PVDF has in-plane anisotropy in its piezoelectric characteristics, so that the sound quality varies greatly depending on the direction of bending even with the same curvature.
Furthermore, since PVDF has a smaller loss tangent than a general speaker diaphragm such as cone paper, resonance is likely to occur strongly and the frequency characteristics are severely undulated. Accordingly, the amount of change in sound quality when the minimum resonance frequency f ₀ changes with the change in curvature also increases.
As described above, due to the problems inherent in PVDF, it has been difficult for the sound quality correction means disclosed in Patent Document 2 described above to reproduce stable sound.

On the other hand, examples of the sheet-like flexible piezoelectric material having no in-plane anisotropy in piezoelectric characteristics include a polymer composite piezoelectric material in which piezoelectric ceramics are dispersed in a polymer matrix.
In the case of a polymer composite piezoelectric body, since the piezoelectric ceramic is hard but the polymer matrix is soft, energy may be absorbed before the vibration of the piezoelectric ceramic is transmitted to the whole. This is called mechanical vibration energy transmission efficiency. In order to improve this transmission efficiency, it is necessary to harden the polymer composite piezoelectric material. For this purpose, the piezoelectric ceramic is contained in the matrix in a volume fraction of at least 40. It is necessary to put ~ 50% or more.

For example, Non-Patent Document 1 discloses that a polymer composite piezoelectric material obtained by mixing a PZT ceramic powder, which is a piezoelectric material, with PVDF by solvent casting or hot kneading exhibits the flexibility of PVDF and the high piezoelectric properties of PZT ceramics. It is disclosed that both are compatible to some extent.
However, there is a mechanical disadvantage that if the proportion of PZT ceramic is increased in order to increase the piezoelectric characteristics, that is, the transmission efficiency, it becomes hard and brittle.

In order to solve this problem, for example, Non-Patent Document 2 discloses an attempt to maintain flexibility by adding fluororubber to PVDF.
This method has a certain effect in terms of flexibility. However, in general, rubber has a very low Young's modulus of 1 to 10 MPa, and therefore, the addition of rubber lowers the hardness of the polymer composite piezoelectric material, resulting in a decrease in vibration energy transmission efficiency.

  Thus, when a conventional polymer composite piezoelectric material is used as a diaphragm for a speaker, a reduction in energy efficiency is inevitable if it is made flexible, and sufficient performance as a speaker for a flexible display is exhibited. I couldn't.

As mentioned above, it is preferable that the polymer composite piezoelectric material used as a speaker for a flexible display 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, a polymer composite piezoelectric body used as a speaker for a flexible display is required to behave hard to vibrations of 20 Hz to 20 kHz and to be soft 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 order to meet this requirement, the present inventors have focused on viscoelastic materials that have a large frequency dispersion in the storage elastic modulus E ′ at around room temperature and at the same time have a maximum value in the loss tangent Tan δ. We studied earnestly to apply. As a result, by using a viscoelastic material, it is hard for vibrations of 20 Hz to 20 kHz, can behave softly for vibrations of several Hz or less, and further for vibrations of all frequencies of 20 kHz or less. An electroacoustic conversion film made of a polymer composite piezoelectric material having an appropriate loss tangent is provided (Patent Document 3).

JP 2000-338901 A JP 2008-294493 A JP 2014-14063 A

Toyoki Kitayama, 1986 Proceedings of the IEICE General Conference, 366 (1971) Seiichi Shirai, Hiroaki Nomura, Toshiro Oga, Takeshi Yamada, Nobuki Oguchi, IEICE Technical Report, 24, 15 (1980)

  The electroacoustic conversion film described in Patent Document 3 is provided with electrode layers for driving on both sides of a polymer composite piezoelectric material, and further has a minimum mechanical strength and good handling properties as a sheet-like material. In order to impart, a protective layer made of a PET (polyethylene terephthalate) film or the like is provided on the surface of the electrode layer.

Such an electroacoustic conversion film is hard for vibrations of 20 Hz to 20 kHz, behaves softly for vibrations of several Hz or less, and has an appropriate loss tangent for vibrations of all frequencies of 20 kHz or less. For this purpose, the product of the thickness of the electrode layer and the Young's modulus needs to be lower than the product of the thickness of the protective layer and the Young's modulus.
However, since the metal material generally used for the electrode layer has a very large Young's modulus compared to the resin material used for the protective layer, the thickness of the electrode layer needs to be made very small accordingly. Specifically, a deposited film having a thickness of 1 μm or less is suitable.

Here, in order to mount the electroacoustic conversion film as a speaker or the like, it is necessary to pull out the electrode layer and connect a wiring here.
However, it is difficult to draw a thin electrode layer such as a vapor deposition film out of the electroacoustic conversion film. Further, if a thin electrode such as a vapor deposition film is exposed to the outside for connection with the wiring and stored in this state, the electrode is oxidized depending on the storage environment, and the conductivity is lowered.

  An object of the present invention is to solve such problems of the prior art, in which thin film electrodes are formed on both surfaces of a dielectric layer made of a polymer piezoelectric composite or the like, and a protection made of a plastic film or the like is formed on both surfaces of the dielectric layer. In the electroacoustic conversion film provided with a layer, the electroacoustic conversion film capable of easily conducting the thin film electrode and an external device while protecting the thin film electrode, and the thin film electrode in the electroacoustic conversion film It is to provide an electrical conduction method.

In order to solve this problem, the electroacoustic conversion film of the present invention includes a dielectric layer,
A thin film electrode formed on both surfaces of the dielectric layer;
A protective layer formed on the surfaces of both thin film electrodes,
Furthermore, the electroacoustic conversion film is characterized in that at least one of the protective layers has a thin layer portion whose thickness is smaller than that of the peripheral portion.

In such an electroacoustic conversion film of the present invention, the thickness of the thin layer portion is preferably 1 to 50% of the thickness of the protective layer on which the thin layer portion is formed.
Moreover, it is preferable that a conductive material is inserted into the concave portion of the protective layer having the thin layer portion.
The conductive material is preferably convex with respect to the surface of the protective layer.
Moreover, it is preferable that a thin layer part has a fracture | rupture part and an electroconductive material is electrically connected with a thin film electrode through a fracture | rupture part.
In addition, it is preferable that a lead wire for electrically connecting the thin film electrode and an external device is connected to the conductive material.
The dielectric layer is preferably 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.
Furthermore, it is preferable that at least one of the protective layers is made of a polymer material.

Further, the conduction method of the electroacoustic conversion film of the present invention includes a dielectric layer, a thin film electrode formed on both surfaces of the dielectric layer, and a protective layer formed on the surfaces of both thin film electrodes. Having an electroacoustic conversion film having a thin layer part in which at least one of the protective layers is thinner than the peripheral part,
The conductive material is inserted into the concave portion of the protective layer having the thin layer portion, and the conductive material inserted into the concave portion is pressed, whereby the protective layer is broken by the conductive material, and the conductive material and the thin film electrode are electrically connected. An electroacoustic conversion film conducting method is provided which is electrically conducting.

In such a conduction method of the electroacoustic conversion film of the present invention, the thickness of the thin layer portion of the electroacoustic conversion film is preferably 1 to 50% of the thickness of the protective layer on which the thin layer portion is formed. .
The conductive material is preferably convex with respect to the surface of the protective layer on which the thin layer portion is formed.
Further, prior to pressing the conductive material inserted into the thin layer portion, it is preferable to connect a lead-out wiring for electrically connecting the thin film electrode and an external device to the conductive material.
Further, the dielectric layer is preferably 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.

According to the present invention, the thin layer portion of the protective layer is formed by inserting a conductive material such as silver paste into the thin layer portion formed in the upper protective layer and / or the lower protective layer and pressing the conductive material. It breaks and can electrically conduct an electrically conductive material and a thin film electrode.
Therefore, according to the present invention, the thin film electrode and the external device can be easily electrically connected by connecting the wiring or the like to the conductive material inserted in the thin layer portion. Moreover, even if the electroacoustic conversion film of the present invention is a thin film portion, since the thin film electrode is covered with a protective layer, the thin film electrode does not deteriorate due to oxidation or the like, and is excellent in durability during storage. .

(A) is a top view which shows an example of the electroacoustic conversion film of this invention notionally, (B) is the bb sectional view taken on the line of (A). (A)-(C) are the conceptual diagrams for demonstrating another example of the electroacoustic conversion film shown in FIG. 1 of this invention, and the conduction | electrical_connection method of the electroacoustic conversion film of this invention.

  Hereinafter, the electroacoustic conversion film and the conduction method of the electroacoustic conversion film of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

1A is a plan view conceptually showing an example of an electroacoustic conversion film (hereinafter referred to as a conversion film) of the present invention, and FIG. 1B is a cross-sectional view taken along the line bb of FIG. 1A. FIG.
The (electroacoustic) conversion film 10 shown in FIG. 1 is basically one of a piezoelectric layer 12 that is a piezoelectric sheet-like material that is a dielectric layer (sheet-like material), and one of the piezoelectric layers 12. The upper thin film electrode 14 is formed on the surface (upper surface in the illustrated example), the upper protective layer 16 is formed on the surface of the upper thin film electrode 14, and the upper thin film electrode 14 is formed on the surface opposite to the upper thin film electrode 14. The lower thin film electrode 20 and a lower protective layer 24 formed on the surface (lower surface in the illustrated example) of the lower thin film electrode 20 are configured.
A thin layer portion 28 is formed on the upper protective layer 16, and a thin layer portion 30 is formed on the lower protective layer 24.

  Such a conversion film 10 is used in various acoustic devices (acoustic equipment) such as speakers, microphones, and pickups used for musical instruments such as guitars, to generate (reproduce) sound due to vibration according to electrical signals, It is used to convert the vibration caused by the above into an electrical signal.

  Moreover, in the conversion film 10 of the illustrated example, as a preferred embodiment, the piezoelectric layer 12 has a viscoelastic matrix 34 made of a polymer material having viscoelasticity at room temperature as conceptually shown in FIG. The piezoelectric particles 36 are uniformly dispersed. In this specification, “room temperature” refers to a temperature range of about 0 to 50 ° C.

  As described above, the polymer composite piezoelectric body used for a flexible speaker is required to be hard for vibrations of 20 Hz to 20 kHz and to be soft for 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 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 loss tangent Tanδ at a frequency of 1 Hz in a dynamic viscoelasticity test at room temperature 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 by dynamic viscoelasticity measurement 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. Moreover, as these polymer materials, commercially available products such as Hibler 5127 (manufactured by Kuraray Co., Ltd.) can be suitably used.
In addition, these polymeric materials may use only 1 type, and may use multiple types together (mixed).

The viscoelastic matrix 34 using the polymer material having viscoelasticity at room temperature may use a plurality of polymer materials in combination as necessary.
In other words, in addition to viscoelastic materials such as cyanoethylated PVA, other dielectric polymer materials may be added to the viscoelastic matrix 34 as necessary 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 anoethyl 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, in the viscoelastic matrix 34 of the piezoelectric layer 12, the dielectric polymer material added 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. May be.
In addition to dielectric polymer materials, thermoplastic resins such as vinyl chloride resin, polyethylene, polystyrene, methacrylic resin, polybutene, isobutylene, phenol resin, urea resin are used for the purpose of adjusting the glass transition point (Tg). Further, thermosetting resins such as melamine resin, alkyd resin, and mica may be added.
Furthermore, for the purpose of improving the tackiness, a tackifier such as rosin ester, rosin, terpene, terpene phenol, and petroleum resin may be added.

In the viscoelastic matrix 34 of the piezoelectric layer 12, there is no particular limitation on the addition amount when a polymer other than a viscoelastic material such as cyanoethylated PVA is added, but it is 30% by mass or less in the proportion of the viscoelastic matrix 34. 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 34, so that the dielectric constant is increased, the heat resistance is improved, and the adhesiveness with the piezoelectric particles 36 and the electrode layer is increased. A preferable result can be obtained in terms of improvement.

  In the conversion film 10 of the present invention, as the matrix of the piezoelectric layer (polymer composite piezoelectric body), in addition to the viscoelastic matrix 34, a polymer material used for a known polymer composite piezoelectric body is used. However, various types are available. Specific examples include polyvinylidene fluoride (PVDF), cyanoethylated pullulan, and nylon.

The piezoelectric particles 36 are made of ceramic particles having a perovskite type or wurtzite type crystal structure.
Examples of the ceramic particles constituting the piezoelectric particles 36 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 36 may be appropriately selected according to the size and application of the conversion film 10, but is preferably 1 to 20 μm according to the study of the present inventors.
By setting the particle size of the piezoelectric particles 36 in the above range, a favorable result can be obtained in terms of achieving both high piezoelectric characteristics and flexibility.

In FIG. 1 and the like, the piezoelectric particles 36 in the piezoelectric layer 12 are irregularly dispersed in the viscoelastic matrix 34, but the present invention is not limited to this.
That is, the piezoelectric particles 36 in the piezoelectric layer 12 may be regularly dispersed in the viscoelastic matrix 34 as long as they are preferably dispersed uniformly.

In the conversion film 10 of the present invention, the amount ratio between the viscoelastic matrix 34 and the piezoelectric particles 36 in the piezoelectric layer 12 (polymer composite piezoelectric material) is the size and thickness of the conversion film 10 in the plane direction, the conversion film What is necessary is just to set suitably according to the 10 use, the characteristic requested | required of the conversion film 10, etc.
Here, according to the study of the present inventor, the volume fraction of the piezoelectric particles 36 in the piezoelectric layer 12 is preferably 30 to 70%, particularly preferably 50% or more. 70% is more preferable.
By setting the quantity ratio between the viscoelastic matrix 34 and the piezoelectric particles 36 within the above range, a favorable result can be obtained in terms of achieving both high piezoelectric characteristics and flexibility.

Further, in the conversion film 10 of the present invention, the thickness of the piezoelectric layer 12 is not particularly limited, depending on the size of the conversion film 10, the use of the conversion film 10, the characteristics required for the conversion film 10, etc. What is necessary is just to set suitably.
Here, according to the study of the present inventor, the thickness of the piezoelectric layer 12 is preferably 10 to 200 μm, particularly preferably 15 to 100 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 subjected to polarization treatment (polling).

In the conversion film of the present invention, the dielectric layer is a polymer composite piezoelectric material obtained by dispersing piezoelectric particles 36 in a viscoelastic matrix 34 made of a polymer material having viscoelasticity at room temperature. In addition, various known dielectric layers (sheet-like materials) can be used.
Specifically, a piezoelectric film made of polyvinylidene fluoride is generally used. A layer made of a fluororesin other than polyvinylidene fluoride, or a laminated film of a film made of poly L lactic acid and a film made of poly D lactic acid can also be used as the dielectric layer.
However, as described above, it is hard for vibrations of 20 Hz to 20 kHz, can behave softly for slow vibrations of several Hz or less, can obtain excellent acoustic characteristics, and has excellent flexibility. Thus, the polymer composite piezoelectric material obtained by dispersing the piezoelectric particles 36 in the viscoelastic matrix 34 as shown in the drawing is suitably used as a dielectric layer.

As shown in FIG. 1 (B), the conversion film 10 of the present invention has an upper thin film electrode 14 formed on one surface of such a piezoelectric layer 12, and an upper protective layer 16 formed on the surface thereof. The lower thin-film electrode 20 is formed on the other surface of 12, and the lower protective layer 24 is formed on the surface thereof.
That is, the conversion film 10 has a configuration in which the piezoelectric layer 12 is sandwiched between the upper thin film electrode 14 and the lower thin film electrode 20, and this laminate is sandwiched between the upper protective layer 16 and the lower protective layer 24.

  In the conversion film 10, the upper protective layer 16 and the lower protective layer 24 have a role of imparting appropriate rigidity and mechanical strength to the piezoelectric layer 12. That is, in the conversion film 10 of the present invention, the piezoelectric layer 12 (polymer composite piezoelectric body) composed of the viscoelastic matrix 34 and the piezoelectric particles 36 is very excellent for slow bending deformation. While exhibiting flexibility, depending on the application, rigidity and mechanical strength may be insufficient. The conversion film 10 is provided with an upper protective layer 16 and a lower protective layer 24 to supplement it.

  Here, in the conversion film 10 of the present invention, a thin layer portion 28 is formed on the upper protective layer 16, and a thin layer portion 30 is formed on the lower protective layer 24. The thin layer portion 28 and the thin layer portion 30 will be described in detail later.

  The upper protective layer 16 and the lower protective layer 24 are not particularly limited, and various sheet materials can be used. As an example, films (resin films / plastic films) made of various polymer materials are preferable. Is done. 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), polyethylene naphthalate (PEN), triacetyl cellulose (TAC), and a cyclic olefin resin are preferably used.

The thicknesses of the upper protective layer 16 and the lower protective layer 24 are not particularly limited. The thicknesses of the upper protective layer 16 and the lower protective layer 24 are basically the same, but may be different.
Here, if the rigidity of the upper protective layer 16 and the lower protective layer 24 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 where handling is required, the upper protective layer 16 and the lower protective layer 24 are more advantageous as they are thinner.

  If the upper protective layer 16 and the lower protective layer 24 are very thin and have poor handling properties, the upper protective layer 16 and / or the lower protective layer 24 with a detachable separator (support) may be used. . Examples of the separator include a PET film having a thickness of about 25 to 100 μm.

According to the study of the present inventor, if the thickness of the upper protective layer 16 and the lower protective layer 24 is not more than twice the thickness of the piezoelectric layer 12, it is possible to ensure both rigidity and appropriate flexibility. In this respect, preferable results can be obtained.
For example, when the thickness of the piezoelectric layer 12 is 50 μm and the upper protective layer 16 and the lower protective layer 24 are made of PET, the thickness of the upper protective layer 16 and the lower protective layer 24 is preferably 100 μm or less, more preferably 50 μm or less. In particular, the thickness is preferably 25 μm or less.

In the conversion film 10 of the present invention, an upper thin film electrode 14 (hereinafter also referred to as an upper electrode 14) is interposed between the piezoelectric layer 12 and the lower protective layer 24 between the piezoelectric layer 12 and the upper protective layer 16. The lower thin film electrode 20 (hereinafter also referred to as the lower electrode 20) is formed.
The upper electrode 14 and the lower electrode 20 are provided to apply an electric field to the conversion film 10 (piezoelectric layer 12).

  In the present invention, the material for forming the upper electrode 14 and the lower electrode 20 is not particularly limited, and various conductors can be used. Specific examples include carbon, palladium, iron, tin, aluminum, nickel, platinum, gold, silver, copper, chromium and molybdenum, alloys thereof, indium tin oxide, and the like. Among these, any one of copper, aluminum, gold, silver, platinum, and indium tin oxide is preferably exemplified.

  Further, the method for forming the upper electrode 14 and the lower electrode 20 is not particularly limited, and a film formed by a vapor deposition method (vacuum film forming method) such as vacuum vapor deposition or sputtering, plating, or a foil formed of the above material. Various known methods such as a method of sticking can be used.

In particular, a thin film of copper or aluminum formed by vacuum vapor deposition is suitably used as the upper electrode 14 and the lower electrode 20 because 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 thickness of the upper electrode 14 and the lower electrode 20 is not particularly limited. The thicknesses of the upper electrode 14 and the lower electrode 20 are basically the same, but may be different.

  Here, similarly to the upper protective layer 16 and the lower protective layer 24 described above, if the rigidity of the upper electrode 14 and the lower electrode 20 is too high, not only the expansion and contraction of the piezoelectric layer 12 is restricted, but also the flexibility is impaired. . Therefore, it is more advantageous that the upper electrode 14 and the lower electrode 20 are thinner as long as the electric resistance is not excessively high.

Here, according to the study of the present inventors, if the product of the thickness of the upper electrode 14 and the lower electrode 20 and the Young's modulus is less than the product of the thickness of the upper protective layer 16 and the lower protective layer 24 and the Young's modulus, This is preferable because flexibility is not greatly impaired.
For example, when the upper protective layer 16 and the lower protective layer 24 are a combination of PET (Young's modulus: about 6.2 GPa) and the upper electrode 14 and the lower electrode 20 are made of copper (Young's modulus: about 130 GPa), the upper protective layer 16 Assuming that the thickness of the lower protective layer 24 is 25 μm, the thickness of the upper electrode 14 and the lower electrode 20 is preferably 1.2 μm or less, more preferably 0.3 μm or less, and particularly preferably 0.1 μm or less.

Further, the upper electrode 14 and / or the lower electrode 20 are not necessarily formed corresponding to the entire surface of the piezoelectric layer 12 (the upper protective layer 16 and / or the lower protective layer 24).
That is, at least one of the upper electrode 14 and the lower electrode 20 may be smaller than the piezoelectric layer 12, for example, and the piezoelectric layer 12 and the protective layer may be in direct contact with each other at the periphery of the conversion film 10. .

The conversion film 10 in the illustrated example has a piezoelectric layer 12 in which piezoelectric particles 36 are dispersed in a viscoelastic matrix 34 having viscoelasticity at room temperature, and the piezoelectric layer 12 is formed on the upper electrode 14 as a preferred embodiment. And the lower electrode 20 is sandwiched between the upper protective layer 16 and the lower protective layer 24.
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.

  As shown in FIGS. 1A and 1B, a thin layer portion 28 is formed in the upper protective layer 16. In addition, a thin layer portion 30 is formed in the lower protective layer 24.

It should be noted that the thin layer portion 28 of the upper protective layer 16 and the thin layer portion 30 of the lower protective layer 24 are different only in the protective layer formed, and there is no other difference.
Therefore, in the following description, the thin layer portion 28 of the upper protective layer 16 is representative unless the thin layer portion 28 of the upper protective layer 16 and the thin layer portion 30 of the lower protective layer 24 need to be described separately. An explanation will be given as an example. That is, the upper electrode 14 can be read as the lower electrode 20, the upper protective layer 16 can be read as the lower protective layer 24, and the thin layer portion 28 can be read as the thin layer portion 30.

As shown in FIGS. 1B and 2A, the thin layer portion 28 is formed by removing a part of the upper protective layer 16 to form a concave portion 28a (a concave portion 30a corresponding to the thin layer portion 30). Thus, a part of the upper protective layer 16 is thinned.
In the conversion film 10 of the present invention, since the upper protective layer 16 has the thin layer portion 28, the upper electrode 14 and the outside can be easily electrically connected while protecting the upper electrode 14. Yes.

As described above, since the upper electrode 14 is a very thin metal layer formed by vapor deposition or the like, it is very difficult to draw it out of the surface of the conversion film 10.
On the other hand, a part of the upper protective layer 16 may be completely removed, and the upper electrode 14 may be exposed in the surface of the conversion film 10 to be electrically connected to the upper electrode 14 from here. However, since the upper electrode 14 is a very thin metal layer, in the state of being exposed to the outside, it is easily oxidized depending on the storage environment, the conductivity is lowered, and the conversion film cannot be driven properly. End up.

On the other hand, the conversion film 10 of the present invention has a thin layer portion 28 formed by partially thinning the upper protective layer 16 in the upper protective layer 16. Therefore, the upper protective layer 16 can be easily broken by inserting a conductive material such as silver paste into the thin layer portion 28 and pressing the conductive material, and the conductive material and the thin film can be broken by breaking the thin layer portion of the protective layer. The electrode can be electrically connected.
Therefore, according to the present invention, the thin film electrode and the external device can be easily electrically connected by connecting the wiring or the like to the conductive material inserted in the thin layer portion. Moreover, since the thin film electrode is entirely covered with the protective layer, the electroacoustic conversion film of the present invention does not deteriorate due to oxidation or the like, and is excellent in durability during storage.

The thin layer portion 28 may be formed by thinning the upper protective layer 16 by forming a hole that does not penetrate the upper protective layer 16 in at least a part of the upper protective layer 16.
Here, according to the study by the present inventors, the thickness t of the thin layer portion 28 is preferably 1 to 50% of the thickness T of the upper protective layer 16 and is 1.5 to 25%. Is more preferable (see FIG. 2A).
That is, when the thickness of the upper protective layer 16 is 3 to 5 μm, the thickness of the thin layer portion 28 is preferably 0.05 to 1.5 μm.

By setting the thickness t of the thin layer portion 28 to 1% or more of the thickness T of the upper protective layer 16, the protective effect of the upper electrode 14 by the upper protective layer 16 in the thin layer portion 28 can be ensured, This is preferable in that oxidation of the upper electrode 14 can be prevented and damage to the upper electrode 14 can be prevented.
Further, by setting the thickness t of the thin layer portion 28 to 50% or less of the thickness T of the upper protective layer 16, it becomes possible to reliably break the thin layer portion 28 with a conductive material described later. This is preferable.

The size in the surface direction of the thin layer portion 28, that is, the size of the recess 28 a of the upper protective layer 16 in which the thin layer portion 28 is formed is the size in the surface direction of the conversion film 10 and the thickness of the upper protective layer 16. What is necessary is just to set suitably according to the shape of the surface direction of the conversion film 10, etc.
The concave portion 28a of the upper protective layer 16 where the thin layer portion 28 is formed is not necessarily the same in size and shape on the surface side of the upper protective layer 16 and in size and shape on the bottom surface side (that is, the thin layer portion 28). There is no need to do it.

If the formation position of the thin layer part 28 is also suitably set according to the size of the surface direction of the conversion film 10, the shape of the surface direction of the conversion film 10, the configuration of the apparatus and equipment where the conversion film 10 is used, Good. However, since the thin layer portion 28 serves as a lead portion for wiring from the upper electrode 14, it is preferably formed outside the effective region of the conversion film 10.
Further, the number of the thin layer portions 28 may be plural in addition to one in the illustrated example.

  Further, as the shape of the thin layer portion 28 in the surface direction, various shapes such as a triangle such as a triangle and a quadrangle, an ellipse, and an indefinite shape can be used in addition to the circular shape in the illustrated example.

The conversion film 10 in the illustrated example has thin layer portions in both the upper protective layer 16 and the lower protective layer 24.
However, the conversion film of the present invention may have a thin layer portion in only one of the upper protective layer 16 and the lower protective layer 24 depending on the application, shape, and the like.

What is necessary is just to produce the conversion film 10 by a well-known method. The following method is illustrated as an example.
First, a sheet-like material in which the lower electrode 20 is formed on the lower protective layer 24 is prepared. In addition, a polymer material having viscoelasticity at room temperature (hereinafter also referred to as viscoelastic material) such as cyanoethylated PVA is dissolved in an organic solvent, and further, piezoelectric particles 36 such as PZT particles are added and stirred. A dispersed paint is prepared.
The prepared paint is applied to the lower electrode 20 of the sheet-like material and dried to form the piezoelectric layer 12.
Next, the polarization treatment of the piezoelectric layer 12 is preferably performed. The polarization process may be performed by a known method such as a corona polling process using corona discharge using a corona electrode or an electric field poling in which a direct current electric field is directly applied to an object to be polarized.
Further, a sheet-like material in which the upper electrode 14 is formed on the upper protective layer 16 is prepared. This sheet-like material may be the same as the aforementioned sheet-like material in which the lower electrode 20 is formed on the lower protective layer 24.
The sheet-like material is laminated on the piezoelectric layer 12 with the upper electrode 14 facing, and the upper protective layer 16 and the lower protective layer 24 are sandwiched and thermocompression bonded with a heating press device, a heating roller pair, or the like, Let it be a conversion film.

Here, the thin layer portion 28 may be formed after the conversion film is produced, or may be formed at the stage of a sheet-like material in which the upper electrode 14 is formed on the upper protective layer 16, or Alternatively, the upper protective layer 16 may be formed in a single state.
In particular, it is preferable to form the thin layer portion 28 after producing the conversion film in terms of easy handling when forming the thin layer portion 28.

Various methods can be used as the method for forming the thin layer portion 28 depending on the material for forming the upper protective layer 16.
As an example, a method of forming the thin layer portion 28 by removing the upper protective layer 16 by burning (ablation) with a laser beam such as a laser beam having a wavelength of 10.6 μm by a carbon dioxide gas laser is exemplified. For example, the thin layer portion 28 may be formed at a desired position in the upper protective layer 16 by scanning the formation position of the thin layer portion 28 in the upper protective layer 16 with a laser beam. In this case, the thin layer portion 28 having a desired thickness can be formed by adjusting the intensity of the laser beam, the scanning speed (that is, the processing time by the laser beam), and the like.
Moreover, the method of forming the thin layer part 28 by melt | dissolving the upper protective layer 16 using an organic solvent can also be utilized. For example, when the upper protective layer 16 is PET, the thin layer portion 28 can be formed using hexafluoroisopropanol. In the case of using a solvent, the thin layer portion 28 may be formed at a desired position by using a mask or the like as in etching in photolithography or the like. In this case, the thin layer portion 28 having a desired thickness can be formed by adjusting the processing time and the concentration of the organic solvent.
Further, the thin layer portion 28 may be formed by a mechanical method such as drilling by grinding. In this case, the thin layer portion 28 having a desired thickness can be formed by adjusting the processing strength and the like.

  Alternatively, a sheet-like material having the same thickness as the target thin-layer portion 28 is prepared, and a sheet-like material having a through-hole that becomes the thin-layer portion 28 is laminated and bonded to the sheet-like material. Thus, a method of manufacturing the upper protective layer 16 having the thin layer portion 28 can also be used.

Hereinafter, with reference to FIG. 2 (A)-FIG.2 (C), the usage method of the conversion film 10 and an example of the conduction | electrical_connection method of this invention are demonstrated.
First, as shown in FIGS. 2A and 2B, the conductive material 40 is inserted into the recess 28 a of the upper protective layer 16 of the conversion film 10. Furthermore, if necessary, a lead wiring 42 for electrically connecting an external device and the upper electrode 14 is connected to the conductive material 40.

  As will be described later, the conductive material 40 is for breaking the thin layer portion 28 and being electrically connected to the upper electrode 14 to electrically connect the upper electrode 14 and the lead wiring 42.

In the conversion film 10 of the present invention, as the conductive material 40, various types of conductive materials that can be inserted into the recesses 28a can be used.
Specifically, a type in which metal particles such as silver, copper, and gold are dispersed in a binder made of a thermosetting resin such as epoxy resin and polyimide, and a binder made of a resin that cures at about room temperature such as an acrylic resin. Dispersed types of metal pastes, metal pastes of a type heat-cured with a complex metal, metal tapes such as copper foil tapes, and concave portions 28a formed with sharp convex portions (can be plural) at one end An insertable metal member is exemplified.
Among these, the metal paste is a conductive material in that it can be suitably broken by pressing the thin layer portion 28 to be described later, and the electrical connection between the broken thin layer portion 28 and the upper electrode 14 can be ensured. 40 is preferably exemplified.

Also, as shown in FIG. 2B, the conductive material 40 is inserted into the recess 28a so as to be convex with respect to the upper surface of the upper protective layer 16, that is, so as to rise from the surface of the upper protective layer 16. It is preferable to do this.
Thereby, it becomes possible to perform the fracture | rupture of the thin layer part 28 by the press of the electrically-conductive material 40 mentioned later more easily and reliably.
The degree of protrusion of the conductive material 40 with respect to the upper surface of the upper protective layer 16 is appropriately set to a height at which the thin layer portion 28 can be broken by the conductive material 40 according to the thickness, strength, etc. of the thin layer portion 28. That's fine.

  As the lead-out wiring 42, various known wirings that can be used for wiring that electrically connects an electrode or the like to an external device, such as a metal foil such as a copper foil and various metal wirings, can be used.

Next, as shown by an arrow in FIG. 2C, the conductive material 40 is pressed toward the piezoelectric layer 12. By pressing the conductive material 40, the thin layer portion 28 is pressed by the conductive material 40 and is broken. In FIG. 2C, the broken thin layer portion 28 is omitted in order to simplify the drawing.
The upper electrode 14 and the conductive material 40 are brought into contact with each other by the breakage of the thin layer portion 28 due to the pressing of the conductive material 40, and the upper electrode 14 and the conductive material 40 are electrically connected. Further, due to the conduction between the upper electrode 14 and the conductive material 40, the upper electrode 14 and the lead wiring 42 are electrically connected.
Therefore, by connecting an amplifier or the like for driving the conversion film 10 to the lead-out wiring 42, the conversion film 10 can be driven as a flexible film speaker or the like. Further, by connecting an amplifier or the like for amplifying an electric signal to the lead wiring 42, the conversion film 10 can be used as a flexible microphone or a flexible pickup used for a musical instrument such as a guitar. Can be used.

The operator may press the conductive material 40 for breaking the thin layer portion 28 using a finger, a jig, or the like.
Alternatively, the conversion film 10 is usually incorporated into a cover, a display, an acoustic system, etc. and packaged for use. Therefore, by adjusting the formation position of the thin layer portion 28 and the like, pressing of the conductive material 40 for breaking the thin layer portion 28 may be performed simultaneously with the packaging.

  As mentioned above, although the electroacoustic conversion film of this invention and the conduction | electrical_connection method of an acoustic conversion film 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, various improvement and change Of course, you may do this.

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

[Example 1]
Cyanoethylated PVA (CR-V manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved in dimethylformamide (DMF) 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 ・ ・ ・ ・ ・ ・ 300 parts by mass ・ Cyanoethylated PVA ・ ・ ・ ・ ・ ・ 30 parts by mass ・ DMF ・ ・ ・ ・ ・ ・ 70 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 5 μm.

On the other hand, a sheet-like material was prepared by vacuum-depositing a 0.1 μm thick copper thin film to be the lower electrode 20 on a 4 μm thick PET film to be the lower protective layer 24.
The size of the sheet was 210 × 300 mm (A4 size).

On the sheet-like lower electrode 20 (copper deposited thin film), 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 40 micrometers.
Next, the DMF was evaporated by heating and drying the product obtained by applying the paint on the sheet-like material on a 120 ° C. hot plate. As a result, the piezoelectric layer 12 having a thickness of 40 μm was formed on the lower electrode 20.

  The piezoelectric layer 12 was polarized by corona poling using a corona electrode. In the polarization treatment, the temperature of the piezoelectric layer 12 is set to 100 ° C., and a DC voltage of 6 kV is applied between the lower electrode 20 and the corona electrode to generate corona discharge. Was performed by scanning.

Further, a sheet-like material similar to the above was prepared by vacuum-depositing a 0.1 μm thick copper thin film to be the upper electrode 14 on a 4 μm thick PET film to be the upper protective layer 16.
The sheet-like material was laminated on the piezoelectric layer 12 subjected to the polarization treatment with the upper electrode 14 (copper thin film side) facing the piezoelectric layer 12.
Next, the laminated body is thermocompression bonded at 120 ° C. using a laminator device so that the upper protective layer 16 and the lower protective layer 24 are sandwiched, thereby bonding the piezoelectric body layer 12 to the lower electrode 20 and the upper electrode 14. Thus, a conversion film was produced.

By scanning the upper protective layer 16 of this conversion film with a laser beam having a wavelength of 10.6 μm by a carbon dioxide laser, a circular recess 28a having a diameter of 3 mm is formed to form a thin layer 28, and the recess 30a and the thin layer Except not having the part 30, the conversion film 10 shown to FIG. 1 (A) and FIG. 1 (B) was produced.
The thickness t of the thin layer portion 28 was 1.3% of the thickness T (4 μm) of the upper protective layer 16.

A silver paste (D-362, manufactured by Fujikura Kasei Co., Ltd.) was inserted as the conductive material 40 into the formed recess 28a. Note that the conductive material 40 was inserted into the recess 28 a so as to rise above the surface of the upper protective layer 16.
Furthermore, the leading end portion of a copper foil having a thickness of 0.5 mm, a width of 5 mm, and a length of 50 mm was inserted into the conductive material 40 as the lead wiring 42.
Next, the conductive material 40 (silver paste) was dried at 25 ° C. for 10 minutes to obtain a conversion film shown in FIG.

[Examples 2 to 4]
The thickness t of the thin layer portion 28 was 2.5% of the thickness T (4 μm) of the upper protective layer 16 (Example 2),
The thickness t of the thin layer portion 28 was 25% of the thickness T (4 μm) of the upper protective layer 16 (Example 3),
The thickness t of the thin layer portion 28 was 38% of the thickness T (4 μm) of the upper protective layer 16 (Example 4),
In the same manner as in Example 1, a conversion film shown in FIG.
Note that the thickness of the thin layer portion 28 was adjusted by changing the output of the carbon dioxide laser. In this regard, the other examples are the same.

[Example 5]
Example 1 is the same as Example 1 except that the thickness T of the upper protective layer 16 is 5 μm and the thickness t of the thin layer part 28 is 2% of the thickness T of the upper protective layer 16. Similarly, a conversion film shown in FIG. 2 (B) was produced.
[Example 6]
Example 1 is the same as Example 1 except that the thickness T of the upper protective layer 16 is 3 μm and the thickness t of the thin layer part 28 is 3.3% of the thickness T of the upper protective layer 16. In the same manner as in Example 1, a conversion film shown in FIG.

[Example 7]
A conversion film shown in FIG. 2B was produced in the same manner as in Example 1 except that the thickness t of the thin layer portion 28 was set to 75% of the thickness T (4 μm) of the upper protective layer 16.

[Example 8]
The silver paste used as the conductive material 40 is changed (SSF-1511, manufactured by Sanwa Chemical Industry Co., Ltd.), and the conductive material is dried at 150 ° C. for 5 minutes. A conversion film shown in FIG.
That is, in this example, the thickness of the thin layer portion 28 with respect to the thickness T (4 μm) of the upper protective layer 16 is 2.5%.

[Example 9]
A conversion film shown in FIG. 2B was produced in the same manner as in Example 1 except that the conductive material 40 was changed to a copper foil tape and a copper foil tape was attached so as to close the recess 28a.

[Comparative Example 1]
2 (B) except that a concave portion from which the upper protective layer 16 was completely removed was formed and a portion where the upper electrode 14 was exposed at a position corresponding to the thin layer portion 28 was formed. The conversion film shown in FIG.
That is, in this example, the thickness of the thin layer portion 28 with respect to the thickness T (4 μm) of the upper protective layer 16 is 0%.
[Comparative Example 2]
A conversion film shown in FIG. 2B was produced in the same manner as in Example 1 except that the thin layer portion 28, that is, the concave portion 28a was not formed.
That is, in this example, the thickness of the thin layer portion 28 with respect to the thickness T (4 μm) of the upper protective layer 16 is 100%.

[Evaluation]
For the conversion films of Examples 1 to 9 and Comparative Examples 1 and 2 produced in this manner, the conduction resistance at 50% relative humidity at 25 ° C. immediately after production and the relative humidity 90 at 45 ° C. The conduction resistance after 24 hours exposure (after exposure) was measured.
The conductive resistance was measured by pressing the conductive material 40 with a load of 0.1 N to break the thin layer portion 28 and measuring the electrical resistance between the lead-out wiring 42 and the upper electrode 14.
The results are shown in the table below.
The table below also shows the amount of increase in conduction resistance immediately after fabrication and after exposure ("after exposure / just after creation").

As shown in the above table, the conversion films of Examples 1 to 6 and Examples 8 and 9 can be suitably electrically conducted by breaking the thin layer portion 28 due to the pressing of the conductive material 40, Even after exposure to a high temperature and high humidity environment, the conduction resistance is the same as that immediately after fabrication.
In Example 7 in which the thickness of the thin layer portion 28 is 75% thicker than that of the upper protective layer 16, the conduction resistance is large but the conduction is conducted, and further, after being exposed to a high-temperature and high-humidity environment. However, the conduction resistance is the same as that immediately after fabrication.
On the other hand, Comparative Example 1 in which the upper electrode 14 is exposed without leaving the thin layer portion 28 has a low resistance value immediately after fabrication, but the energization resistance is about 6.3 times after exposure to a high-temperature and high-humidity environment. And has increased significantly. Therefore, depending on the storage environment and the storage time, there is a possibility that the upper electrode 14 is not electrically connected due to oxidation.
Further, Comparative Example 2 in which the thin layer portion 28 was not formed did not conduct even when the conductive material 40 was pressed (insulated state).
From the above results, the effects of the present invention are clear.

  The present invention can be suitably used for manufacturing pickups used for musical instruments such as flexible speakers, microphones, and guitars.

DESCRIPTION OF SYMBOLS 10 (electroacoustic) conversion film 12 Piezoelectric layer 14 Upper (thin film) electrode 16 Upper protective layer 20 Lower (thin film) electrode 24 Lower protective layer 28,30 Thin layer part 28a, 30a Recessed part 34 Viscoelastic matrix 36 Piezoelectric particle 40 Conductive material 42 Lead wiring

Claims (13)

A dielectric layer;
Thin film electrodes formed on both surfaces of the dielectric layer;
A protective layer formed on the surfaces of both the thin film electrodes,
Furthermore, at least one of the protective layers has a thin layer part whose film thickness is thinner than the peripheral part.   The electroacoustic conversion film according to claim 1, wherein the thickness of the thin layer portion is 1 to 50% of the thickness of the protective layer on which the thin layer portion is formed.   The electroacoustic conversion film according to claim 1 or 2, wherein a conductive material is inserted into a concave portion of the protective layer having the thin layer portion.   The electroacoustic conversion film according to claim 3, wherein the conductive material is convex with respect to the surface of the protective layer.   The electroacoustic conversion film according to claim 3 or 4, wherein the thin layer portion has a fracture portion, and the conductive material is electrically connected to the thin film electrode through the fracture portion.   The electroacoustic conversion film according to claim 3, wherein a lead wiring for electrically connecting the thin film electrode and an external device is connected to the conductive material.   7. The polymer composite piezoelectric material according to claim 1, wherein the dielectric layer is 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. The electroacoustic conversion film as described.   The electroacoustic conversion film according to claim 1, wherein at least one of the protective layers is made of a polymer material. A dielectric layer; a thin film electrode formed on both surfaces of the dielectric layer; and a protective layer formed on the surface of both thin film electrodes, wherein at least one of the protective layers is a peripheral layer. Of the electroacoustic conversion film having a thin layer part whose film thickness is thinner than the part,
By inserting a conductive material into the recess of the protective layer having the thin layer portion and pressing the conductive material inserted into the recess, the protective layer is broken by the conductive material, and the conductive material and the thin film A method for conducting an electroacoustic conversion film, comprising electrically conducting an electrode.   The conduction method of the electroacoustic conversion film according to claim 9, wherein the thickness of the thin layer portion of the electroacoustic conversion film is 1 to 50% of the thickness of the protective layer on which the thin layer portion is formed.   The conduction method of the electroacoustic conversion film according to claim 9 or 10, wherein the conductive material is convex with respect to a surface of the protective layer on which the thin layer portion is formed.   The lead wiring for electrically connecting the thin film electrode and an external device is connected to the conductive material prior to pressing of the conductive material inserted into the thin layer portion. The conduction | electrical_connection method of the electroacoustic conversion film of description.   13. The polymer composite piezoelectric material according to claim 9, wherein the dielectric layer is 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. The conduction method of the electroacoustic conversion film as described.