WO2018181261A1

WO2018181261A1 - Piezoelectric element

Info

Publication number: WO2018181261A1
Application number: PCT/JP2018/012323
Authority: WO
Inventors: 小笠原　健; 川戸　進
Original assignee: 東邦化成株式会社
Priority date: 2017-03-27
Filing date: 2018-03-27
Publication date: 2018-10-04
Also published as: JPWO2018181261A1

Abstract

Provided is a novel piezoelectric element that has a thin and long linear form as a whole, that enables an electrode to be easily taken out, and that can be easily manufactured. The piezoelectric element includes: a core wire which is conductive at least on the surface thereof; and one or more winding wires that are wound on the core wire and that each include a core part which is conductive at least on the surface thereof, and include an organic piezoelectric layer covering the core part, wherein the core wire and each of the core parts of the winding wires function as electrodes with the organic piezoelectric layer interpolated therebetween.

Description

Piezoelectric element

The present invention relates to a piezoelectric element, and more particularly to a piezoelectric element having a generally elongated linear shape that can be referred to as a cable shape or a wire shape.

The piezoelectric element is an element using a piezoelectric body. For example, the piezoelectric element is used as a sensor by utilizing the positive piezoelectric effect of the piezoelectric body (converting an external force applied to the piezoelectric body into a voltage), and the reverse piezoelectric of the piezoelectric body. It is used in various applications as an actuator by utilizing an effect (converting a voltage applied to a piezoelectric body into a force).

Among such piezoelectric elements, a coaxial cable-shaped piezoelectric element is conventionally known as a piezoelectric element having an elongated linear shape as a whole. For example, in Non-Patent Document 1, a PVDF piezo film tape (piezoelectric body) is spirally wound around a core wire (inner conductor), covered with a copper braided wire (outer conductor), and further covered with a polyethylene jacket A piezo cable having the above configuration is disclosed. Patent Document 1 discloses a spirally wound metal inner conductor (the space inside the spiral is filled with a non-hollow material), a continuous piezoelectric polymer layer surrounding the periphery, A piezoelectric coaxial cable is disclosed that is in contact with a molecular layer but consists of an outer conductor separated from an inner conductor. Furthermore, Patent Document 2 discloses a piezoelectric sensor having a coaxial cable shape, which includes an inner conductor, a flexible insulator, an outer conductor including a piezoelectric layer and a metal layer, and a flexible sheath. It is disclosed.

JP 61-71506 A JP 2005-351664 A

However, in the conventional coaxial cable-shaped piezoelectric element, for example, as shown in FIG. 4, an inner conductor 61 and an outer conductor 65 that function as two electrodes sandwiching the piezoelectric layer 63 are arranged coaxially. Therefore, in order to take out these electrodes, the outer conductor 65 is exposed by cutting and peeling the first predetermined distance from the surface of the outer cover 67 of the piezoelectric element 70 to reach the outer conductor 65, and the outer cover 67 of the piezoelectric element 70 is removed. The inner conductor 61 needs to be exposed by cutting and peeling a second predetermined distance from the surface to the inner conductor 61. For this reason, when the wire diameter of the piezoelectric element is reduced, the difference between the first predetermined distance and the second predetermined distance is reduced. Therefore, if the cutting amount in the cross section perpendicular to the axis cannot be controlled very strictly, the piezoelectric element is disposed on the same axis. It becomes difficult to expose the outer conductor and the inner conductor as desired.

Further, in the conventional coaxial cable-shaped piezoelectric element, an outer conductor is disposed so as to cover the piezoelectric layer, and the outer conductor is covered with a copper braided wire (Non-patent Document 1), a conductive polymer. Extrusion or coextrusion molding, application of metal-containing paint (spraying, brushing, dipping, coating, etc.) or vacuum deposition of metal (Patent Document 1), winding of an outer conductor with a piezoelectric layer formed on one side of the metal layer (patent It is formed by the literature 2). The formation of such an outer conductor requires man-hours and is relatively time consuming.

The present invention has been made in view of the above problems, and is a piezoelectric element having a slender linear shape as a whole, and a novel electrode that can be easily taken out and can be more easily manufactured. An object is to provide a piezoelectric element.

According to the present invention, at least a core wire having a conductive surface,
At least one winding wound around the core wire, the core portion including at least a core portion having a conductive surface and an organic piezoelectric layer covering the core portion, the core wire and the winding There is provided a piezoelectric element in which the core of the wire functions as an electrode having the organic piezoelectric layer interposed between them.

That is, according to the present invention, a winding having at least a core portion having a conductive surface and an organic piezoelectric layer covering the core portion is used, and this winding (may be one or more). Is wound around a core wire having a conductive surface at least on its surface, thereby forming a piezoelectric element. Such a piezoelectric element of the present invention can be a piezoelectric element having an elongated linear shape as a whole. Further, in the piezoelectric element of the present invention, the core wire and the core portion of the winding are not arranged coaxially, and therefore can be exposed separately, and thus the electrode can be easily taken out. Furthermore, the piezoelectric element according to the present invention can be configured by preparing the core wire and the winding and winding the winding around the core wire, and there is no need to form an outer conductor covering the piezoelectric layer. Therefore, it can be manufactured more easily than a conventional piezoelectric element having such an external conductor.

In one aspect of the present invention, the piezoelectric element may include two or more windings.

In one aspect of the present invention, the piezoelectric element may further include a sheath that accommodates the core wire and the at least one winding wound around the core wire.

In the present invention, the organic piezoelectric layer includes polyvinylidene fluoride, a copolymer of vinylidene fluoride and trifluoroethylene, a copolymer of vinylidene fluoride and tetrafluoroethylene, polylactic acid, porous polypropylene, and porous At least one selected from the group consisting of functional polytetrafluoroethylene, and in particular, from a copolymer of vinylidene fluoride and trifluoroethylene and a copolymer of vinylidene fluoride and tetrafluoroethylene. It may contain at least one selected from the group consisting of:

The piezoelectric element of the present invention can be used as either or both of a sensor and an actuator, for example.

According to the present invention, there is provided a novel piezoelectric element that is a piezoelectric element having an elongated linear shape as a whole, in which an electrode can be easily taken out and can be manufactured more easily.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows the piezoelectric element in one embodiment of this invention, Comprising: (a) shows the partial cutaway side view of a piezoelectric element, (b) is sectional drawing along the AA of (a). Show. FIG. 6 shows a schematic side view of a partially cut away piezoelectric element according to another embodiment of the present invention. FIG. 6 shows a schematic side view of a partially cut away piezoelectric element according to another embodiment of the present invention. 1A and 1B are schematic views illustrating a conventional example coaxial cable-shaped piezoelectric element, in which FIG. 1A is a partially cutaway side view of the piezoelectric element, and FIG. 2B is a cross-sectional view taken along line BB in FIG. Indicates. The schematic sectional drawing which cut | disconnected perpendicularly | vertically with respect to the wire direction the strand wire used as a core wire in the Example of this invention is shown. It is a figure explaining the evaluation method of the piezoelectric element produced in the Example of this invention, Comprising: (a) is a schematic perspective view of the state which is not applying external force, (b) is a schematic cross section of the state which is not applying external force FIG. 4C is a schematic sectional view showing a state where an external force is applied.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the attached drawings, electrode terminals are schematically indicated by black circles.

(Embodiment 1)
The present embodiment relates to a piezoelectric element having a configuration in which one winding is wound around a core wire.

Referring to FIG. 1, a piezoelectric element 10 of this embodiment includes a core wire 1 and a single winding 7 wound around the core wire 1, and the winding 7 includes a core portion 3 and the core portion 3. The organic piezoelectric layer 5 is coated. In the piezoelectric element 10, the core wire 1 and the core portion 3 of the winding 7 each function as an electrode having the organic piezoelectric layer 5 interposed therebetween (see FIG. 1B). The piezoelectric element 10 has an elongated linear shape as a whole, which may be referred to as a cable shape or a wire shape, and may be configured to be flexible (bendable) as a whole.

The core wire 1 only needs to have a conductive surface at least so that it can function as an electrode. The core wire 1 is formed by, for example, covering the surface of a wire made of a conductive material such as a metal wire or an arbitrary linear base material (resin wire, etc.) with a conductive material layer (metal, conductive resin, conductive rubber, etc.). It may be a wire made of Further, the core wire 1 can have an arbitrary cross-sectional shape such as a circle, an ellipse, a rectangle, and a polygon, and may be hollow or solid, such as a single wire, a stranded wire, and a knitted wire. May be. The wire diameter of the core wire 1 (the maximum dimension of the cross section when it has a non-circular cross section, the same applies hereinafter) is not particularly limited, and may vary depending on the material and configuration thereof, but should be selected to be flexible. Is preferred.

The core portion 3 of the winding 7 may be at least a surface conductive so that it can function as an electrode. The material and the configuration of the core part 3 can be applied to the description described above for the core wire 1, but preferably has a smaller wire diameter than the core wire 1.

The organic piezoelectric layer 5 of the winding 7 can be made of any material known as an organic piezoelectric body. The organic piezoelectric body has higher impact resistance and bending resistance than inorganic piezoelectric bodies represented by piezoelectric ceramics such as lead zirconate titanate (PZT), and is suitable for winding around the core wire 1. Examples of the material constituting the organic piezoelectric layer 5 include polyvinylidene fluoride (PVDF), a vinylidene fluoride copolymer (a copolymer of vinylidene fluoride and trifluoroethylene (P (VDF / TrFE)), fluoride, and the like. Permanent dipole type piezoelectric materials such as copolymers of vinylidene and tetrafluoroethylene (including P (VDF / TeFE)), polylactic acid: porous polypropylene (PP), porous polytetrafluoroethylene (PTFE) An electret type piezoelectric material such as: a piezoelectric ceramic particle composite type piezoelectric material in which piezoelectric ceramic particles are dispersed in an organic material such as rubber may be used. Specifically, the organic piezoelectric layer 5 includes at least one selected from the group consisting of PVDF, P (VDF / TrFE), P (VDF / TeFE), polylactic acid, porous PP, and porous PTFE. Can be a thing. Among these, the organic piezoelectric layer 5 preferably contains at least one selected from the group consisting of P (VDF / TrFE) and P (VDF / TeFE). The thickness of the organic piezoelectric layer 5 is not particularly limited, and may vary depending on the material and configuration thereof, but is selected so as to obtain desired piezoelectric characteristics (positive piezoelectric effect and / or reverse piezoelectric effect). Is preferred.

The material forming the organic piezoelectric layer 5 is subjected to a coating process before the core portion 3 is subjected to a treatment necessary for expressing the piezoelectricity, for example, stretching and / or polarization treatment, depending on the material actually used. It can be applied at any suitable time during and after.

For example, when PVDF is used as the material forming the organic piezoelectric layer 5, the winding 7 can be manufactured as follows. PVDF can take three types of crystal structures, α, β, and γ. Usually, it can be the most stable α type in terms of energy, but PVDF containing many α type crystal structures is uniaxially stretched, for example. Thus, it can be converted into PVDF containing a lot of β-type crystal structure. PVDF containing a lot of β-type crystal structure exhibits ferroelectricity, and when subjected to polarization treatment, the dipoles are aligned and exhibit piezoelectricity. Therefore, PVDF is extrusion-coated around the core 3, the PVDF layer covering the core 3 and the periphery thereof is stretched together, and then subjected to a polarization treatment such as corona discharge, thereby exhibiting piezoelectricity. As a result, a winding 7 in which the core 3 is covered with an organic piezoelectric layer (more specifically, a PVDF layer) 5 can be obtained. In this case, the material and / or structure of the core portion 3 can be appropriately selected so as to sufficiently withstand the stretching. Alternatively, a PVDF layer exhibiting piezoelectricity can be obtained by wrapping a stretched PVDF film formed by uniaxially stretching a PVDF film around the core 3 and then subjecting it to a polarization treatment such as corona discharge. As a result, a winding 7 in which the core 3 is covered with an organic piezoelectric layer (more specifically, a PVDF layer) 5 can be obtained.

Also, for example, when a vinylidene fluoride copolymer is used as a material for the organic piezoelectric layer 5, the winding 7 can be manufactured as follows. Vinylidene fluoride-based copolymers, particularly P (VDF / TrFE) and P (VDF / TeFE) may contain more β-type crystal structure than PVDF. Therefore, the vinylidene fluoride copolymer can easily produce the winding 7 in which the core 3 is covered with the organic piezoelectric layer 5 only by performing a polarization treatment without stretching. Specifically, the winding 7 can be produced by the following solvent coating method or melt extrusion method.

In the solvent coating method, first, a resin liquid in which a vinylidene fluoride copolymer is dissolved or dispersed in a solvent is prepared, this resin liquid is applied (for example, applied) to the surface of the core portion 3, and this is heated. By substantially removing the solvent to obtain a vinylidene fluoride copolymer layer, and then subjecting to a polarization treatment such as corona discharge, a vinylidene fluoride copolymer layer exhibiting piezoelectricity can be obtained. As a result, a winding 7 in which the core 3 is covered with an organic piezoelectric layer (more specifically, a vinylidene fluoride copolymer layer) 5 can be obtained. Examples of the solvent include ketone solvents (eg, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), acetone, diethyl ketone, dipropyl ketone), ester solvents (eg, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl lactate). ), Ether solvents (eg tetrahydrofuran, methyltetrahydrofuran, dioxane), amide solvents (eg dimethylformamide (DMF), dimethylacetamide), pyrrolidone solvents (eg N-methylpyrrolidone) and the like. The heating temperature may vary depending on the solvent used, but may be, for example, 80 to 180 ° C.

In the melt extrusion method, first, for example, a pellet-like vinylidene fluoride copolymer is heated and melted to obtain a molten resin. The heating temperature may be not less than the melting point of the vinylidene fluoride copolymer to be used, and may be 120 to 250 ° C., for example. This molten resin is applied to the surface of the core portion 3 (for example, extrusion coated around it) to obtain a vinylidene fluoride copolymer layer, and then subjected to a polarization treatment such as corona discharge, thereby exhibiting piezoelectricity. A vinylidene fluoride copolymer layer can be obtained, and as a result, a winding 7 in which the core 3 is coated with an organic piezoelectric layer (more specifically, a vinylidene fluoride copolymer layer) 5 can be obtained. it can.

The method for forming the organic piezoelectric layer 5 using these vinylidene fluoride copolymers can be preferably carried out particularly when the core 3 has a small wire diameter. For example, the core 3 has a wire diameter of 1 mm or less, typically 0.5 mm or less, and may be approximately 0.008 mm or more. In these methods, the thickness of the organic piezoelectric layer (more specifically, the vinylidene fluoride copolymer layer) 5 can be 2 μm or more and 200 μm or less, for example, 10 μm or more and 50 μm or less.

The organic piezoelectric layer 5 using PVDF and / or vinylidene fluoride copolymer is preferable because it exhibits high heat resistance of, for example, 85 ° C. or higher. The molecular weight of PVDF and vinylidene fluoride copolymer is not particularly limited, and may be, for example, 10,000 to 1,000,000 in terms of number average molecular weight. The vinylidene fluoride copolymer is a copolymer of vinylidene fluoride and one or more fluorine-based monomers copolymerizable with vinylidene fluoride (hereinafter also simply referred to as other fluorine-based monomers). . The other fluorine-based monomer can be one or both of trifluoroethylene and tetrafluoroethylene. In the vinylidene fluoride copolymer, the unit derived from vinylidene fluoride can be 50 mol% or more, preferably 60 mol% or more, derived from other fluorine-based monomers and vinylidene fluoride. The molar ratio with the unit to be can be within the range of 5:95 to 36:64, preferably within the range of 15:85 to 25:75, more preferably within the range of 18:82 to 22:78. .

For example, when polylactic acid is used as a material for the organic piezoelectric layer 5, the winding 7 can be manufactured as follows. There are L-form and D-form in polylactic acid, and L-type polylactic acid (PLLA) is generally available as polylactic acid. It is known that PLLA exhibits piezoelectricity by uniaxially stretching. In this case, no polarization treatment is necessary. Therefore, a PLLA layer exhibiting piezoelectricity can be obtained by extrusion-coating PLLA around the core 3 and stretching the PLLA layer covering the core 3 and its periphery together. As a result, the core 3 Can be obtained by covering the substrate with an organic piezoelectric layer (more specifically, PLLA layer) 5. In this case, the material and / or structure of the core portion 3 can be appropriately selected so as to sufficiently withstand the stretching. Alternatively, a PVDF layer exhibiting piezoelectricity can be obtained by wrapping a stretched PLLA film formed by uniaxially stretching a PLLA film around the core portion 3, and as a result, the core portion 3 is made of an organic piezoelectric layer (more Specifically, the winding 7 coated with the PLLA layer 5 can be obtained.

For example, when porous PP or porous PTFE is used as a material for the organic piezoelectric layer 5, the winding 7 can be manufactured as follows. It is known that porous PP and porous PTFE can be obtained by stretching PP and PTFE, respectively, and exhibit piezoelectricity by applying a polarization treatment thereto. Therefore, a porous PP film or a porous PTFE film formed by stretching a PP film or a PTFE film is wrapped around the core 3 and then subjected to a polarization treatment such as corona discharge, for example, to exhibit a piezoelectric property. As a result, a winding 7 in which the core 3 is covered with an organic piezoelectric layer (more specifically, a porous PP layer or a porous PTFE layer) 5 can be obtained. Can do.

However, it should be noted that the winding 7 is not limited to the above example, and can be manufactured by any appropriate method as long as the core 3 can be covered with the organic piezoelectric layer 5. In addition, the material forming the organic piezoelectric layer 5 is not limited to the materials described in detail above, and may include any appropriate other component (for example, an additive such as piezoelectric ceramics) in a relatively small amount. Alternatively, other known organic materials exhibiting piezoelectricity may be used.

The piezoelectric element 10 of the present embodiment is configured by winding the single winding 7 as described above around the core wire 1 as described above. The winding method is not particularly limited as long as the organic piezoelectric layer 5 is disposed between the core wire 1 and the core portion 3 (preferably in close contact with the core wire and the organic piezoelectric layer). For example, as shown in FIG. 1, the winding 7 can be wound around the core wire 1 in a spiral shape, preferably without a gap between adjacent windings 7.

As described above, the piezoelectric element 10 of the present embodiment can be obtained. The piezoelectric element 10 of the present embodiment can expose the core wire 1 (more specifically, the conductive portion) by removing (for example, unwinding) the winding 7, and only the winding 7 (for example, unwinding). The core portion 3 (more specifically, the conductive portion) can be exposed by cutting and peeling the portion) by a distance reaching the core portion 3 from the surface of the organic piezoelectric layer 5. For this reason, regardless of the wire diameter of the piezoelectric element 10, the core wire 1 and the core portion 3 can be separately exposed as desired, so that the electrodes can be easily taken out (in the figure, the electrode terminals are indicated by black circles). Shown schematically).

The piezoelectric element 10 according to the present embodiment does not need to form an outer conductor that covers the organic piezoelectric layer 5 and can be manufactured more easily than a conventional piezoelectric element having such an outer conductor.

The piezoelectric element 10 of this embodiment can be used as various sensors and / or actuators. The piezoelectric element 10 of this embodiment has high impact resistance and bending resistance, is flexible, and can be arranged along an arbitrary shape.

The piezoelectric element 10 of the present embodiment can be used as a sensor using the positive piezoelectric effect of a piezoelectric body. The piezoelectric element 10 is attached to and / or embedded in a detection target object, for example, as a pressure-sensitive sensor capable of detecting an external force applied to the piezoelectric element 10 or a detection target. It can be used as a sensor for detecting internal fatigue of an object. Further, a knitted fabric or a woven fabric can be formed using a plurality of piezoelectric elements 10 and used as a fibrous piezoelectric sensor or a vibration power generation element. In addition, for example, a security sensor, a care / monitoring sensor, an impact sensor, a wearable sensor, a biological signal sensor (respiration / pulse), a vehicle pinching prevention sensor, a vehicle bumper collision sensor, a vehicle air flow sensor, a weather detection sensor ( Rain / snow), underwater acoustic sensor, robot tactile sensor, medical device tactile sensor, fiber sheet pressure distribution sensor, environmental vibration power generation wire, and the like.

The piezoelectric element 10 of the present embodiment can be used as an actuator using the inverse piezoelectric effect of the piezoelectric body instead of / in addition to the above. The piezoelectric element 10 can be used, for example, as an actuator that excites vibration when a driving voltage is applied to the piezoelectric element 10, and can also be used as an actuator drive sensor that uses the vibration as a sensor. In addition, it can be used for various applications such as a robot joint drive actuator, an artificial muscle actuator, a medical device operation wire drive actuator, a fiberscope drive actuator, an ultrasonic motor, and a piezoelectric motor.

(Embodiment 2)
The present embodiment relates to a piezoelectric element having a configuration in which two or more windings are wound around a core wire. Hereinafter, unless otherwise specified, the description described in the first embodiment can be similarly applied to the present embodiment.

Referring to FIG. 2, the piezoelectric element 13 of the present embodiment includes a core wire 1 and two or more windings wound around the core wire 1, and each winding covers a core portion and the core portion. It has an organic piezoelectric layer. FIG. 2 exemplarily shows three

windings

7a, 7b, and 7c (typically, the winding 7a has a core portion 3a and an organic piezoelectric layer 5a that covers the core portion 3a. However, the present invention is not limited to this, and can be suitably used within the range of 2 to 100, particularly 2 to 20, for example. In the piezoelectric element 13, the core wire and the core portion of each winding function as an electrode with an organic piezoelectric layer interposed therebetween, and the core portion of these windings with respect to the core wire electrode, It can function as a different counter electrode for each winding. Such a piezoelectric element 13 may be referred to as a cable shape, a wire shape, or the like, and has an elongated linear shape as a whole, and may be configured to be flexible (bendable) as a whole.

The piezoelectric element 13 of the present embodiment is configured by winding the above-described two or

more windings

7a, 7b and the like around the core wire 1. The winding method is not particularly limited as long as the organic piezoelectric layer is disposed between the core wire and the core portion of each winding (preferably the core wire and the organic piezoelectric layer are in close contact). For example, as shown in FIG. 2, two or more windings can be spirally wound around the core wire 1 in parallel with each other, preferably without a gap between adjacent windings.

As described above, the piezoelectric element 13 of the present embodiment can be obtained. The piezoelectric element 13 of the present embodiment can achieve the same effects as the piezoelectric element described in the first embodiment.

In addition, in the piezoelectric element 13 of the present embodiment, the core part of two or more windings can function as a different counter electrode for each winding with respect to the core wire electrode. For example, as shown in FIG. When these core electrodes are taken out at the same terminal (in the figure, the electrode terminal is schematically indicated by a black circle), even if one of the two or more windings is disconnected, it is not disconnected. Since the winding can still perform the same function, it is possible to prevent the entire piezoelectric element 13 from failing.

(Embodiment 3)
The present embodiment relates to a piezoelectric element having a configuration in which one or two or more windings are wound around a core wire and further housed in a sheath. Hereinafter, unless otherwise specified, the description described in the first and second embodiments can be similarly applied to the present embodiment.

Referring to FIG. 3, the piezoelectric element 15 of the present embodiment further includes a sheath 9 that houses the core wire 1 and at least one winding 7 wound around the core wire 1. In FIG. 3, one winding 7 is exemplarily shown, but the present invention is not limited to this, and may include two or more windings as described in detail in the second embodiment. The cross-sectional shape of the sheath 9 is not particularly limited, but may be appropriately selected according to the shapes of the core wire 1 and the winding 7 to be accommodated.

The sheath 9 is preferably flexible. The material, thickness, and the like of the sheath 9 can be appropriately selected according to the use desired for the piezoelectric element 15. For example, a material exhibiting characteristics such as electrical insulation, waterproofness, and weather resistance can be used. The internal space of the sheath 9 (the space between the inner wall surface of the sheath 9 and the core wire 1 and the winding 7 wound around the core 9) may be a cavity, but may be filled with any appropriate material. .

Although the three embodiments of the present invention have been described in detail above, various modifications can be made to these embodiments.

Example 1
A piezoelectric element having the configuration detailed in Embodiment 1 with reference to FIG. 1 was produced as follows.

As the core wire 1, a single wire having a diameter of 0.5 mm made of SUS304 (JIS G 4309) was used.

As the core 3 of the winding 7, a single wire (manufactured by Nippon Steel & Sumikin SG Wire Co., Ltd.) having a diameter of 0.07 mm made of a high-strength piano wire with a brass plating on its surface was used. The core 3 was covered with a copolymer of vinylidene fluoride and tetrafluoroethylene and subjected to polarization treatment to form an organic piezoelectric layer 5, thereby preparing a winding 7. In this winding 7, the thickness of the organic piezoelectric layer 5 was about 30 to 35 μm, and the diameter of the winding 7 was about 0.13 to 0.14 mm.

The winding 7 prepared above was spirally wound around the core wire 1 as shown in FIG. 1 without any gap between the adjacent windings 7, thereby producing the piezoelectric element 10.

(Example 2)
As core wire 1, the same procedure as in Example 1 was used except that a twisted wire having a diameter of 0.4 mm formed by twisting 19 strands having a diameter of 0.08 mm made of SUS304 (JIS G 4309) was used. A piezoelectric element was produced. FIG. 5 shows a schematic cross-sectional view of a stranded wire used as a core wire cut perpendicularly to the line direction. The twisted wires are arranged so that six strands E are arranged uniformly around the central strand E while rotating concentrically along the linear direction, and 12 strands around the strands. E is arranged so as to rotate evenly and concentrically along the linear direction, and the diameter of the stranded wire corresponds to the diameter of the virtual circular cross-sectional area shown in FIG.

(Example 3)
Except that the core wire 1 is made of conductive fibers (diameter, 70d / 34f, where d is denier and f is the number of filaments) made of nylon thread with silver plating on the surface. In the same manner as in Example 1, a piezoelectric element was produced.

(Evaluation)
For each piezoelectric element produced in Examples 1 to 3, whether or not it can actually function as a piezoelectric element, more specifically, whether or not a voltage can be generated when released after applying a pressing force as an external force is described below. Evaluated according to.

As shown in FIGS. 6 (a) and 6 (b), along the upper surface center line of the ceramic plate 21 between the two ceramic plates 21, 23 (all 5 cm long, 5 cm wide and 1 cm thick). The piezoelectric element 10 was disposed so as to extend. Electrodes were taken out from the core wire 1 of the piezoelectric element 10 and the core portion 3 of the winding 7 (both not shown in FIG. 6) and connected to a charge amplifier (not shown). The charge amplifier is not particularly limited as long as it can convert the electric charge from the piezoelectric element 10 into a voltage. For example, a charge amplifier MODEL-4001B-50 (manufactured by Showa Keiki Co., Ltd.) can be used. The evaluation system was configured so that the voltage generated by the charge amplifier could be measured over time with an oscilloscope (not shown) connected to the charge amplifier.

The

ceramic plates

21 and 23 and the piezoelectric element 10 arranged as described above were set in a precision universal testing machine (manufactured by Shimadzu Corporation, Autograph AGS-500X, load cell 50N). While setting the capacitance of the charge amplifier as shown in Table 1 and measuring the voltage with an oscilloscope, using a precision universal testing machine, the piezoelectric element 10 disposed on the ceramic plate 21 was placed on a portion over a length of 5 cm. On the other hand (see FIGS. 6A and 6B), the ceramic plate 23 is lowered and deformed by applying a pressing force (compression load) of 5 N (see FIG. 6C, the load is schematically shown by an arrow). The compression load 5N is constant and maintained for a while, and then the ceramic plate 23 is lifted and released (see FIGS. 6A and 6B). When measuring the voltage over time with an oscilloscope, a pressure of 5N is applied to the piezoelectric element 10 and when it becomes stable, it shows an almost constant voltage value. After that, when it is released, a voltage is generated and the voltage value increases rapidly. After that, the increased voltage value was maintained and shown substantially. In this case, when released from the pressing force, a charge is generated in the piezoelectric element 10, the charge is input to the charge amplifier, and a voltage is output from the charge amplifier. The voltage value in the stable state was set to 0 V, and the increased voltage value observed when released and thereafter was measured as “generated voltage”. The results are also shown in Table 1.

As understood from Table 1, in any of the piezoelectric elements of Examples 1 to 3, a voltage can be generated when released after applying a pressing force as an external force, and thus can actually function as a piezoelectric element. It was confirmed.

The piezoelectric element of the present invention can be used as various sensors and / or actuators. Although not limiting the present invention, the piezoelectric element of the present invention is flexible and can be arranged along an arbitrary shape. For example, it can detect when an external force is applied to the piezoelectric element. It can be used as a possible pressure-sensitive sensor or the like.

This application claims priority based on Japanese Patent Application No. 2017-061702 filed on Mar. 27, 2017, the entire contents of which are incorporated herein by reference.

1 Core wire 3,

3a Core portion

5, 5a Organic

piezoelectric layer

7, 7a, 7b, 7c Winding 9

Sheath

10, 13, 15 Piezoelectric element

E Elementary wire

21, 23 Ceramic plate 61 Internal conductor 63 Piezoelectric layer 65 External conductor 67 Jacket 70 Piezoelectric element

Claims

A core wire having at least a conductive surface;
At least one winding wound around the core wire, the core portion including at least a conductive core portion and an organic piezoelectric layer covering the core portion, the core wire and the winding The piezoelectric element in which the core portion of the wire functions as an electrode having the organic piezoelectric layer interposed between them.
The piezoelectric element according to claim 1, comprising two or more windings.
3. The piezoelectric element according to claim 1 or 2, further comprising a sheath that accommodates the core wire and the at least one winding wound around the core wire.
The organic piezoelectric layer is composed of polyvinylidene fluoride, a copolymer of vinylidene fluoride and trifluoroethylene, a copolymer of vinylidene fluoride and tetrafluoroethylene, polylactic acid, porous polypropylene, and porous polytetrafluoroethylene. The piezoelectric element according to any one of claims 1 to 3, comprising at least one selected from the group consisting of:
The organic piezoelectric layer includes at least one selected from the group consisting of a copolymer of vinylidene fluoride and trifluoroethylene and a copolymer of vinylidene fluoride and tetrafluoroethylene. Piezoelectric element.
The piezoelectric element according to any one of claims 1 to 5, which is used as one or both of a sensor and an actuator.