WO2021106930A1 - Piezoelectric element and piezoelectric device - Google Patents

Piezoelectric element and piezoelectric device Download PDF

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Publication number
WO2021106930A1
WO2021106930A1 PCT/JP2020/043815 JP2020043815W WO2021106930A1 WO 2021106930 A1 WO2021106930 A1 WO 2021106930A1 JP 2020043815 W JP2020043815 W JP 2020043815W WO 2021106930 A1 WO2021106930 A1 WO 2021106930A1
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Prior art keywords
piezoelectric
layer
organic protective
piezoelectric element
protective layer
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PCT/JP2020/043815
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French (fr)
Japanese (ja)
Inventor
勝哉 今西
清水　聡
小笠原　健
長瀬　智美
佐藤　寧
野中　一洋
竜夫 田原
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東邦化成株式会社
国立研究開発法人産業技術総合研究所
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Publication of WO2021106930A1 publication Critical patent/WO2021106930A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/16—Measuring force or stress, in general using properties of piezoelectric devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/20—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/30—Piezoelectric or electrostrictive devices with mechanical input and electrical output, e.g. functioning as generators or sensors
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/60—Piezoelectric or electrostrictive devices having a coaxial cable structure
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/85—Piezoelectric or electrostrictive active materials
    • H10N30/853—Ceramic compositions
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/88—Mounts; Supports; Enclosures; Casings

Definitions

  • the present invention relates to a piezoelectric element, and more particularly to a piezoelectric element having an elongated linear shape as a whole, which may be referred to as a cable shape or a wire shape.
  • the present invention also relates to a piezoelectric device including such a piezoelectric element.
  • the piezoelectric element is an element using a piezoelectric body.
  • it can be 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 inverse piezoelectric of the piezoelectric body. It is used in piezoelectric devices for various purposes as an actuator by utilizing the effect (converting the voltage applied to the piezoelectric body into force).
  • Piezoelectric materials can be roughly classified into inorganic piezoelectric materials represented by piezoelectric ceramics and organic piezoelectric materials represented by piezoelectric polymers.
  • the inorganic piezoelectric material is harder than the organic piezoelectric material, and the organic piezoelectric material can be flexible.
  • a piezoelectric element using an inorganic piezoelectric material made of piezoelectric ceramics is usually configured in a planar form (for example, as a planar sensor) (see Patent Document 1).
  • a piezoelectric element having an elongated linear shape as a whole which may be referred to as a cable shape or a wire shape
  • a flexible organic piezoelectric material may be used so as to have flexibility (bendability).
  • inorganic piezoelectrics can be stable even when exposed to high temperatures and have a higher heat resistant temperature than organic piezoelectrics.
  • the present inventors have applied an inorganic piezoelectric material to a piezoelectric element in order to realize a novel piezoelectric element having an elongated linear shape as a whole, flexibility, and high heat resistance.
  • the flexible piezoelectric element is formed of a core wire (inner electrode) having a conductive surface, an inorganic piezoelectric layer covering the core wire, and a conductor layer (outer electrode) covering the inorganic piezoelectric layer. Then, there is a problem that the piezoelectric response may not be exhibited, the sensor cannot measure the piezoelectric output according to the time change of the external force, and the actuator cannot bring about the deformation according to the time change of the voltage. There was found.
  • the present invention provides a novel piezoelectric element having an elongated linear shape as a whole, flexibility, and high heat resistance, and which exhibits sufficient piezoelectric responsiveness.
  • Another object of the present invention is to provide a piezoelectric device including such a piezoelectric element.
  • the core wire having a conductive surface, the inorganic piezoelectric layer covering the core wire, the organic protective layer covering the inorganic piezoelectric layer, and the organic protective layer are coated.
  • the organic protective layer includes a conductor layer and has a thickness of 0.1 to 100 ⁇ m, and the core wire and the conductor layer are interposed between the inorganic piezoelectric layer and the organic protective layer. Piezoelectric elements are provided that each function as an inserted electrode.
  • a piezoelectric device including the above-mentioned piezoelectric element of the present invention is provided.
  • the piezoelectric element of the present invention has a core wire (inner electrode) having a conductive surface, an inorganic piezoelectric layer covering the core wire, an organic protective layer covering the inorganic piezoelectric layer, and a conductor covering the organic protective layer. It is configured to include a layer (outer electrode), which provides a novel piezoelectric element having an elongated linear shape as a whole and having flexibility. According to the piezoelectric element of the present invention, the inorganic piezoelectric layer is covered with an organic protective layer having a thickness of 0.1 to 100 ⁇ m to protect the inorganic piezoelectric layer, whereby the piezoelectric responsiveness can be sufficiently exhibited.
  • an inorganic piezoelectric layer is used, and the organic protective layer can be freely selected from organic materials having electrical insulation, so that a piezoelectric element having high heat resistance can be used. It can be realized. Further, a piezoelectric device including the piezoelectric element of the present invention is also provided.
  • the piezoelectric element 10 of the present embodiment includes a core wire 1 having a conductive surface, an inorganic piezoelectric layer 3 covering the core wire 1, and an organic protective layer 5 covering the inorganic piezoelectric layer 3. And a conductor layer 7 that covers the organic protective layer 5.
  • the organic protective layer 5 has a thickness of 0.1 to 100 ⁇ m.
  • the core wire 1 and the conductor layer 7 function as electrodes (inner electrode and outer electrode) in which the inorganic piezoelectric layer 3 and the organic protective layer 5 are interposed between them (see FIG. 1 (b)).
  • the piezoelectric element 10 may further include an insulator layer (sheath) 9 that covers the conductor layer 7.
  • 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 is configured to have flexibility (bendability) as a whole piezoelectric element.
  • "flexible” means, in other words, flexible.
  • the core wire 1 may have at least a conductive surface so that it can function as an electrode (inner electrode).
  • the core wire 1 has a conductive material layer on the surface of, for example, a metal wire, a wire made of an arbitrary conductive material (metal, a composite of metal and ceramics, etc.), or an arbitrary linear base material (heat-resistant resin wire, etc.). It may be a wire rod coated with (metal, conductive heat-resistant resin, conductive heat-resistant rubber, etc.).
  • the core wire 1 may have substantially any cross-sectional shape such as a circle, an ellipse, a rectangle, a polygon, and may be hollow or solid, and may be a single wire, a stranded wire, a braided wire, or the like. You may. Further, two or more kinds of these wire rods may be used in combination.
  • the entire surface of the core wire 1 is conductive, but a part of the surface of the core wire 1 (for example, 20% or less, preferably 10% or less, more preferably 5% or less of the total surface area) is not conductive. You may.
  • the core wire 1 is formed by wrapping a tape made of a conductive material on the surface of a non-conductive linear base material, a gap exists between the edges of the wound tape, and the gap is non-conductive. The linear base material may be exposed.
  • the external cross-sectional dimension of the core wire 1 (the maximum dimension of the cross section perpendicular to the line direction, the wire diameter when having a circular cross section, the same applies hereinafter) is not particularly limited, but the core wire 1 itself is flexible. Be selected.
  • the inorganic piezoelectric layer 3 that covers the core wire 1 is made of piezoelectric ceramics and does not contain resin.
  • the piezoelectric ceramic may be one kind of piezoelectric ceramic, but may be a mixture of two or more kinds of piezoelectric ceramics.
  • the term "consisting of (material)” means that it may be substantially composed of the material, and that there may be a substance that can inevitably be mixed and / or remain. means.
  • the solvent, stabilizer, or the like used as a raw material for forming the inorganic piezoelectric layer (for example, the first solution described later) may remain in the inorganic piezoelectric layer 3.
  • Piezoelectric ceramics have high heat resistance because they are inorganic materials.
  • the inorganic piezoelectric layer 3 is particularly preferably made of piezoelectric ceramics having a wurtzite crystal structure. It is known that a substance (compound) having a wurtzite crystal structure exhibits piezoelectricity by aligning its crystal orientation in the c-axis direction and further controlling the degree of dipole orientation (see Patent Document 1). .. Therefore, the piezoelectric element 10 can be manufactured without requiring the polarization treatment step required in the manufacture of the piezoelectric polymer (for example, polyvinylidene fluoride).
  • the piezoelectric ceramic having a wurtzite type crystal structure is at least one selected from the group consisting of ZnO, ZnS, ZnSe, ZnTe, MgO, CdO, CdS, CdSe, CdTe, AlN, GaN, InN and InP as a main component. It is preferable to contain at least one of zinc oxide (ZnO) and aluminum nitride (AlN), and it is more preferable to contain zinc oxide (ZnO). Piezoelectric ceramics having such a wurtzite crystal structure are relatively inexpensive and are safe to the environment and the human body in that they do not contain lead.
  • the "main component" of a certain material means that the ratio of the component to the material (the total ratio of two or more of the compounds listed above) exceeds 50% by mass.
  • it means a component which is 60% by mass or more, preferably 70% by mass or more.
  • Piezoelectric ceramics having a wurtzite crystal structure may contain other kinds of elements (dopants) other than the elements constituting the wurtzite crystal structure. As a result, the control characteristics of the polarity distribution ratio in the inorganic piezoelectric layer 3 are improved, and a piezoelectric element having high piezoelectric response is realized.
  • the other kind element is not particularly limited, but may be at least one selected from the group consisting of an alkali metal element, an alkaline earth metal element, and a Group 13 element. Examples of alkali metal elements as other elements include lithium (Li), sodium (Na) and potassium (K).
  • alkaline earth metal elements examples include magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).
  • Group 13 elements as other elements include aluminum (Al), gallium (Ga) and indium (In).
  • the concentration of the other element can be appropriately set according to the desired electrical characteristics. For example, when the substance (compound) having a wurtzite crystal structure is ZnO and the other element is Li, the atomic concentration of Li is 2 to 7.5 atoms with respect to the sum of the atomic concentrations of Zn and Li. It is preferably in the range of%.
  • the inorganic piezoelectric layer 3 is not limited to the one made of piezoelectric ceramics having a wurtzite crystal structure, and may be made of other piezoelectric ceramics.
  • other piezoelectric ceramics may contain at least one selected from the group consisting of lead titanate, lead zirconate titanate, lead lanthanum zircate titanate, titanium oxide and barium titanate, among which titanate. It preferably contains lead zirconate (PZT).
  • the thickness of the inorganic piezoelectric layer 3 can be appropriately set according to the desired flexibility and electrical characteristics, and is, for example, 0.01 ⁇ m or more, preferably 0.05 ⁇ m or more, for example 3.00 ⁇ m or less, preferably 1. It can be less than .00 ⁇ m.
  • the organic protective layer 5 that covers the inorganic piezoelectric layer 3 is preferably made of an organic material having electrical insulation.
  • a material having a high heat resistant temperature can be selected from various organic materials having an electrically insulating property.
  • the organic protective layer 5 can be made of, for example, a material having a heat resistant temperature of 200 ° C. or higher.
  • the "heat-resistant temperature” means a temperature at which the physical properties of the material are not substantially impaired even when the material is exposed to the temperature, and is a continuous use temperature (long-term heat-resistant temperature) or a short-term heat-resistant temperature. obtain.
  • the short-term heat resistant temperature can be the melting point in the case of a crystalline organic material and the glass transition temperature in the case of a non-crystalline organic material.
  • the material constituting the organic protective layer 5 contains at least one selected from the group consisting of fluororesin, imide resin, aromatic polymer, liquid crystal polymer (LCP), polycarbonate (PC), silicone resin and epoxy resin. obtain. These may be used alone or as a mixture of any two or more.
  • fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and ethylene-tetrafluoroethylene.
  • PTFE polytetrafluoroethylene
  • FEP tetrafluoroethylene-hexafluoropropylene copolymer
  • PFA tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer
  • ethylene-tetrafluoroethylene examples include copolymers (ETFE) and polychlorotrifluoroethylene
  • imide-based resins examples include polyimide (PI), polyamideimide (PAI), and polyetherimide (PEI).
  • aromatic polymers include polyphenylene sulfide resin (PPS) and polyetheretherketone resin (PEEK).
  • the organic protective layer 5 preferably covers the entire outer surface of the inorganic piezoelectric layer 3 so as to protect the inorganic piezoelectric layer 3 (the inorganic piezoelectric layer 3 is not in direct contact with the conductor layer 7).
  • the thickness of the organic protective layer 5 is set within the range of 0.1 to 100 ⁇ m. As a result, it is possible to sufficiently show the piezoelectric response (the sensor can measure the piezoelectric output according to the change with time of the external force, and the actuator can bring about the deformation according to the change with time of the voltage). In particular, when the thickness of the organic protective layer 5 is 0.1 ⁇ m or more, even when the inorganic piezoelectric layer 3 is formed by the coating method described later, the core wire (inner electrode) 1 and the conductor layer (outer side) are formed. It is possible to effectively prevent the occurrence of a short circuit with the electrode) 7.
  • the thickness of the organic protective layer 5 is 100 ⁇ m or less, the function as a piezoelectric element is ensured (more specifically, the piezoelectric output is measured as a sensor and the desired deformation is brought about as an actuator. ) Can be done.
  • the thickness of the organic protective layer 5 is preferably set within the range of 1 to 30 ⁇ m.
  • the conductor layer 7 that covers the organic protective layer 5 may be made of a conductive material so that it can function as an electrode (outer electrode).
  • the conductor layer 7 may be made of, for example, a metal, a composite of metal and ceramics, a conductive heat-resistant resin, a conductive heat-resistant rubber, or the like.
  • the conductor layer 7 preferably covers the entire outer surface of the organic protective layer 5, but is more preferably a part of the outer surface of the organic protective layer 5 (for example, 60% or less, preferably 70% or less of the total surface area). 90% or less) may not be coated with the conductor layer 7.
  • the thickness of the conductor layer 7 can be appropriately set according to the desired flexibility and electrical characteristics, and is, for example, 0.01 ⁇ m or more, preferably 0.05 ⁇ m or more, for example, 3000 ⁇ m or less, preferably 1000 ⁇ m or less. obtain.
  • the external cross-sectional dimension of the conductor layer 7 can be, for example, 10.0 mm or less, preferably 0.1 mm or more and 5.0 mm or less.
  • this provides a so-called "linear" piezoelectric element 10 having a small external cross-sectional dimension (typically a wire diameter) and flexibility. be able to.
  • the piezoelectric element 10 has a high degree of freedom of attachment to a piezoelectric device and can be used in a wide range of applications.
  • the insulator layer (sheath) 9 is made of any suitable insulating material.
  • a flexible sheath known as a flexible sheath for wires and cables, such as a flexible heat-resistant resin and heat-resistant rubber, may be applied to the insulator layer 9.
  • the specific material, form, thickness, and the like of the insulator layer 9 can be appropriately selected depending on the use of the piezoelectric element 10.
  • the piezoelectric element 10 of the present embodiment can be manufactured by any suitable method.
  • the following is an example of the method for manufacturing the piezoelectric element 10 of the present embodiment, but the present invention is not limited to this.
  • the method for manufacturing the piezoelectric element 10 of the present embodiment is as follows. Preparing the core wire 1 having a conductive surface, Forming the inorganic piezoelectric layer 3 that covers the core wire 1. Forming the organic protective layer 5 that covers the inorganic piezoelectric layer 3. The organic protective layer 5 is coated with the conductor layer 7, and if necessary, It may include coating the conductor layer 7 with an insulator layer 9. More details are as follows.
  • the core wire 1 as described above is prepared in the present embodiment.
  • Such a core wire 1 is commercially available or can be easily manufactured.
  • the inorganic piezoelectric layer 3 that covers the core wire 1 is formed.
  • the inorganic piezoelectric layer 3 can be formed by any suitable method such as a coating method (which may also be referred to as a chemical solution deposition method or a sol-gel method), a sputtering method, or a hydrothermal method so as to cover the core wire 1.
  • a coating method which may also be referred to as a chemical solution deposition method or a sol-gel method
  • a sputtering method or a hydrothermal method so as to cover the core wire 1.
  • the inorganic piezoelectric layer 3 is formed by the coating method, it can be continuously produced without using a vacuum device or the like, and the piezoelectric element 10 can be manufactured more easily and at low cost.
  • a first solution (raw material) containing an elemental species constituting a piezoelectric ceramic preferably a piezoelectric ceramic having a wurtzite crystal structure
  • the inorganic piezoelectric layer 3 is formed by drying the formed coating film and firing the dried coating film.
  • the first solution contains a solvent in addition to the element species (including other species elements (dopants), if present) constituting the piezoelectric ceramics (preferably piezoelectric ceramics having a wurtzite crystal structure). May include any suitable additive such as a stabilizer.
  • the solvent include 2-methoxyethanol, 2-propanol, ethanol, 1-butanol, trioctylphosphine, water and the like.
  • the first solution can be applied by using, for example, a dip coating method or a spray coating method.
  • the first solution can be applied to the surface of the core wire 1 in a substantially uniform thickness by immersing the core wire 1 in the first solution and pulling it up at a predetermined speed by a dip coating method.
  • Drying is carried out by drying the coating film at a heat resistant temperature or lower of the core wire 1.
  • the drying temperature is, for example, less than 400 ° C., preferably 300 ° C. or lower, and the drying time is appropriately set.
  • the dry atmosphere is not particularly limited, but may be, for example, an air, an inert gas atmosphere, or a mixed atmosphere of oxygen and an inert gas. Drying can remove solvents and optionally present additives, and the elemental species that make up the piezoelectric ceramics precipitate and aggregate as crystals into particles.
  • the coating film can be an aggregate packed and deposited with such particles (preferably particles of a substance (compound) having a wurtzite crystal structure).
  • a dried coating film can be obtained. If the desired coating film thickness cannot be obtained by one coating and one drying, the coating and drying are set as one set, and a plurality of sets are repeated until the desired coating film thickness is obtained. It's okay.
  • Baking is carried out by firing the coating film at a heat resistant temperature of the core wire 1 or lower.
  • the firing temperature is, for example, less than 600 ° C., preferably 450 ° C. or lower, and the firing time is appropriately set.
  • the firing atmosphere is not particularly limited, but may be, for example, an air, an inert gas atmosphere, or a mixed atmosphere of oxygen and an inert gas.
  • a bonding layer which is a porous body in which the particles are bonded to each other, can be formed.
  • the bond layer can be an aggregate of (randomly) filled and deposited particles of crystals that make up the piezoelectric ceramics, and can be sintered while leaving the shape of the particles.
  • the inorganic piezoelectric layer 3 made of piezoelectric ceramics (preferably piezoelectric ceramics having a wurtzite crystal structure) is formed. If the desired inorganic piezoelectric layer thickness cannot be obtained by coating and drying one set or multiple sets and firing once, "coating and drying one set or multiple sets and firing once". As one set, a plurality of sets may be repeated until a desired inorganic piezoelectric layer thickness is obtained.
  • the organic protective layer 5 that covers the inorganic piezoelectric layer 3 is formed.
  • the organic protective layer 5 can be formed by any suitable method depending on the raw material of the organic insulator used so as to cover the inorganic piezoelectric layer 3, but is preferably formed by a coating method.
  • the organic protective layer 5 is formed by a coating method, more specifically, Applying the second solution (raw material) constituting the organic protective layer 5 to the surface of the inorganic piezoelectric layer 3 to form a coating film. Drying the formed coating film and, optionally, The organic protective layer 5 is formed by subjecting the dried coating film to heat treatment.
  • the second solution may contain a solvent and optionally any suitable additive such as a stabilizer, in addition to the material constituting the organic protective layer (which may be a precursor before the reaction is completed).
  • the application of the second solution can be carried out by using, for example, a dip coating method or a spray coating method, and preferably the dip coating method is used.
  • the second solution can be applied to the surface of the inorganic piezoelectric layer 3 with a substantially uniform thickness. it can.
  • the drying conditions can be appropriately selected according to the materials constituting the organic protective layer.
  • a dried coating film can be obtained. If the desired coating film thickness cannot be obtained by one coating and one drying, the coating and drying are set as one set, and a plurality of sets are repeated until the desired coating film thickness is obtained. It's okay.
  • the dried coating film may be subjected to heat treatment.
  • heat treatment can be carried out, for example, to allow the reaction to proceed in the material constituting the organic protective layer.
  • the heat treatment conditions can be appropriately selected depending on the material constituting the organic protective layer.
  • the organic protective layer 5 is formed. If the desired organic protective layer thickness cannot be obtained by applying and drying one or more sets and one heat treatment, "one or more sets of application and drying and one heat treatment" is performed. As one set, a plurality of sets may be repeated until a desired organic protective layer thickness is obtained.
  • the conductor layer 7 can be formed by any suitable method so as to cover the organic protective layer 5. For example, it can be formed by vapor deposition, winding, or the like. If necessary, the conductor layer 7 may be coated with the insulator layer (sheath) 9. The insulator layer 9 can be formed by any suitable method so as to cover the conductor layer 7.
  • the piezoelectric element 10 of the present embodiment can be obtained.
  • the organic protective layer 5 is not exposed to the firing temperature which is necessary for forming the inorganic piezoelectric layer 3 and is relatively high, so that the organic protective layer 5 is heated. It is possible to avoid deterioration and / or decomposition due to the above. Further, when the inorganic piezoelectric layer 3 and the organic protective layer 5 are sequentially formed by the coating method, the process can be carried out in a continuous process, so that the long piezoelectric element 10 can be efficiently manufactured.
  • the electrode can be pulled out by appropriately exposing the core wire 1 (more specifically, the conductive portion) and the conductor layer 7 (in the figure, the electrode terminals are schematically shown by black circles). ).
  • the conductor layer 9 may be ground, in which case it may also function as a shield.
  • the piezoelectric element 10 of this embodiment can be used as various sensors and / or actuators in piezoelectric devices for various purposes.
  • the piezoelectric element 10 of this embodiment can be used as a sensor by utilizing the positive piezoelectric effect of the piezoelectric body.
  • the piezoelectric element 10 can be attached to and / or embedded in an object to be detected, and can detect when an external force is applied to the piezoelectric element 10 as a pressure-sensitive sensor or to be detected. It can be used as a sensor to detect the internal fatigue of an object.
  • a knitted fabric or a woven fabric can be formed by using a plurality of piezoelectric elements 10 and used as a fibrous piezoelectric sensor or a vibration type power generation element.
  • security sensors nursing / watching sensors, impact sensors, wearable sensors, biometric signal sensors (breathing / pulse), pinch prevention sensors for vehicles, bumper collision sensors for vehicles, air flow sensors for vehicles, weather detection sensors ( It can be used for piezoelectric devices for various purposes such as rain / snow), fire detection sensors, underwater acoustic sensors, tactile sensors for robots, tactile sensors for medical devices, fiber sheet pressure distribution sensors, and power generation wires for environmental vibrations. ..
  • the piezoelectric element 10 of the present embodiment can be used as an actuator by utilizing the inverse piezoelectric effect of the piezoelectric body in place of / in addition to the above.
  • the piezoelectric element 10 can be used, for example, as an actuator that excites vibration when a drive voltage is applied to the piezoelectric element 10, and can also be used as an actuator drive sensor that utilizes the vibration as a sensor.
  • it can be used for piezoelectric devices for various purposes such as robot joint drive actuators, artificial muscle actuators, drive actuators for medical device operation wires, fiberscope drive actuators, ultrasonic motors, and piezoelectric motors.
  • the piezoelectric element 10 of the present embodiment can be preferably used in applications requiring high response characteristics.
  • the piezoelectric element and the piezoelectric device including the piezoelectric element in one embodiment of the present invention have been described in detail above, but the present embodiment can be modified in various ways.
  • Example 1 The piezoelectric element of the above embodiment described in detail with reference to FIG. 1 was manufactured as follows.
  • Second Solution Pure water (30 g) was added to polyamide-imide varnish (HPC-1000 manufactured by Hitachi Kasei Co., Ltd.) (22.5 g), and the mixture was stirred for 30 minutes and mixed uniformly. As a result, a second solution was prepared.
  • the core wire 1 prepared above was dipped in the first solution prepared above and coated to form a coating film of the first solution on the surface of the core wire 1. Then, it was dried at 250 ° C. for 1 minute, and such one application and one drying were set as one set, and a total of three sets were repeated under the same conditions. Next, the dry coating film thus obtained was calcined at 400 ° C. for 1 minute. Such "three sets of one coating and one drying and one firing" was set as one set, and a total of three sets were repeated under the same conditions. As a result, a layer made of zinc oxide (ZnO) having a wurtzite crystal structure was formed as the inorganic piezoelectric layer 3 covering the core wire 1. The thickness of the inorganic piezoelectric layer 3 was 0.1 ⁇ m.
  • Conductor Layer Aluminum was vapor-deposited on the surface of the organic protective layer 5 formed above to form a layer made of aluminum as the conductor layer 7.
  • the thickness of the conductor layer 7 was 0.2 ⁇ m.
  • the piezoelectric element 10 of Example 1 was manufactured as described above.
  • Example 2 In forming the organic protective layer, a piezoelectric element was produced in the same manner as in Example 1 except that only one set of "one coating, one drying and one firing" was carried out (not repeated). did.
  • the thickness of the organic protective layer in the piezoelectric element of Example 2 was 1 ⁇ m.
  • Example 3 In the formation of the organic protective layer, the piezoelectric element is the same as in Example 1 except that "one coating, one drying and one firing" are set as one set and a total of 30 sets are repeated under the same conditions. Was produced.
  • the thickness of the organic protective layer in the piezoelectric element of Example 3 was 30 ⁇ m.
  • Example 1 A piezoelectric element was produced in the same manner as in Example 1 except that the organic protective layer was not formed and the conductor layer was formed on the surface of the inorganic piezoelectric layer.
  • lead wires are connected to the region near one end of the exposed core wire 1 and the region near the other end of the conductor layer 7, respectively. Then, the core wire 1 (inner electrode) and the conductor layer 7 (outer electrode) are pulled out and connected to an oscilloscope (UDS-1G02S-10K, manufactured by Hagiwara Solutions Co., Ltd.) via an analog amplifier circuit (2000 times amplification). The voltage signal generated between these electrodes can be output over time.
  • an oscilloscope ULS-1G02S-10K, manufactured by Hagiwara Solutions Co., Ltd.
  • the evaluation piezoelectric element with the lead wire connected as described above is set in the electromagnetic force type micro tester (Micro Servo MMT-101NV-10 manufactured by Shimadzu Corporation), and the wire direction of the evaluation piezoelectric element. (Frequency 1 Hz, stress 1N to 3N) was vibrated, and the stress was repeatedly applied. While carrying out such a test, the voltage signal generated between the core wire 1 (inner electrode) and the conductor layer 7 (outer electrode) was measured over time as a piezoelectric output. Representatively, the measurement results of the piezoelectric elements of Example 1 and Comparative Example 1 are shown in FIGS. 2 and 3, respectively.
  • the peak peak value (difference between the maximum value and the minimum value) of the piezoelectric output was 95.00 mVpp. Further, as can be seen from FIG. 2, a periodic waveform was observed in the piezoelectric output, and one period was about 1 second, that is, a frequency of 1 Hz. Since the frequency of this piezoelectric output matched the frequency of excitation, it was confirmed that the frequency was followed. Therefore, the piezoelectric element of Example 1 showed an excellent piezoelectric response.
  • the piezoelectric elements of Examples 2 and 3 showed excellent piezoelectric responses.
  • 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 has excellent flexibility and can be realized with a small external cross-sectional dimension (typically, wire diameter). For example, when an external force is applied to the piezoelectric element. It can be used as a pressure-sensitive sensor or the like capable of detecting this.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)
  • General Electrical Machinery Utilizing Piezoelectricity, Electrostriction Or Magnetostriction (AREA)

Abstract

Provided is a novel flexible piezoelectric element that has high heat resistance and an elongated linear shape as a whole, the piezoelectric element exhibiting sufficient piezoelectric responsiveness. The piezoelectric element includes a core wire having a conductive surface, an inorganic piezoelectric layer covering the core wire, an organic protective layer covering the inorganic piezoelectric layer, and a conductor layer covering the organic protective layer, wherein the organic protective layer has a thickness of 0.1-100 μm, and the core wire and the conductor layer function as respective electrodes with the inorganic piezoelectric layer and the organic protective layer interposed therebetween.

Description

圧電素子および圧電装置Piezoelectric elements and piezoelectric devices
　本発明は、圧電素子に関し、より詳細には、ケーブル状またはワイヤー状などと称され得る、全体として細長い線状の形態を有する圧電素子に関する。また、本発明はかかる圧電素子を含む圧電装置に関する。 The present invention relates to a piezoelectric element, and more particularly to a piezoelectric element having an elongated linear shape as a whole, which may be referred to as a cable shape or a wire shape. The present invention also relates to a piezoelectric device including such a piezoelectric element.
　圧電素子は、圧電体を使用した素子であり、例えば、圧電体の正圧電効果を利用する（圧電体に加えられた外力を電圧に変換する）ことによってセンサとして、また、圧電体の逆圧電効果を利用する（圧電体に印加された電圧を力に変換する）ことによってアクチュエータとして、さまざまな用途の圧電装置において使用されている。 The piezoelectric element is an element using a piezoelectric body. For example, it can be 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 inverse piezoelectric of the piezoelectric body. It is used in piezoelectric devices for various purposes as an actuator by utilizing the effect (converting the voltage applied to the piezoelectric body into force).
　圧電体は、圧電セラミックスに代表される無機圧電体と、圧電ポリマーに代表される有機圧電体とに大別され得る。一般的に、無機圧電体は有機圧電体に比べて硬く、有機圧電体は可撓性であり得る。圧電セラミックスから成る無機圧電体を使用した圧電素子は、通常、面状の形態で（例えば面状センサとして）構成される（特許文献１参照）。他方、ケーブル状またはワイヤー状などと称され得る、全体として細長い線状の形態を有する圧電素子では、柔軟性を有する（曲げ可能である）ように、可撓性の有機圧電体が使用され得る（特許文献２参照）。 Piezoelectric materials can be roughly classified into inorganic piezoelectric materials represented by piezoelectric ceramics and organic piezoelectric materials represented by piezoelectric polymers. In general, the inorganic piezoelectric material is harder than the organic piezoelectric material, and the organic piezoelectric material can be flexible. A piezoelectric element using an inorganic piezoelectric material made of piezoelectric ceramics is usually configured in a planar form (for example, as a planar sensor) (see Patent Document 1). On the other hand, in a piezoelectric element having an elongated linear shape as a whole, which may be referred to as a cable shape or a wire shape, a flexible organic piezoelectric material may be used so as to have flexibility (bendability). (See Patent Document 2).
特開２００４－２６５８９９号公報Japanese Unexamined Patent Publication No. 2004-265899 特開２０１７－１８３５７０号公報Japanese Unexamined Patent Publication No. 2017-183570
　一般的に、無機圧電体は、高温に曝されても安定であり得、有機圧電体に比べて高い耐熱温度を有する。本発明者らは、全体として細長い線状の形態を有し、柔軟性を有し、かつ、高い耐熱性を有する新規な圧電素子を実現すべく、圧電素子に無機圧電体を適用することについて検討した。しかしながら、柔軟性を有する圧電素子を、導電性の表面を有する芯線（内側電極）と、芯線を被覆する無機圧電体層と、無機圧電体層を被覆する導電体層（外側電極）とから形成すると、圧電応答性を示さないことがあり、センサとしては外力の経時変化に応じた圧電出力を計測できず、アクチュエータとしては電圧の経時変化に応じた変形をもたらせないという問題があることが判明した。 In general, inorganic piezoelectrics can be stable even when exposed to high temperatures and have a higher heat resistant temperature than organic piezoelectrics. The present inventors have applied an inorganic piezoelectric material to a piezoelectric element in order to realize a novel piezoelectric element having an elongated linear shape as a whole, flexibility, and high heat resistance. investigated. However, the flexible piezoelectric element is formed of a core wire (inner electrode) having a conductive surface, an inorganic piezoelectric layer covering the core wire, and a conductor layer (outer electrode) covering the inorganic piezoelectric layer. Then, there is a problem that the piezoelectric response may not be exhibited, the sensor cannot measure the piezoelectric output according to the time change of the external force, and the actuator cannot bring about the deformation according to the time change of the voltage. There was found.
　本発明は、全体として細長い線状の形態を有し、柔軟性を有し、かつ、高い耐熱性を有する新規な圧電素子であって、圧電応答性を十分に示す圧電素子を提供することを目的とする。また、本発明は、かかる圧電素子を含む圧電装置を提供することを目的とする。 The present invention provides a novel piezoelectric element having an elongated linear shape as a whole, flexibility, and high heat resistance, and which exhibits sufficient piezoelectric responsiveness. The purpose. Another object of the present invention is to provide a piezoelectric device including such a piezoelectric element.
　本発明の１つの要旨によれば、導電性の表面を有する芯線と、前記芯線を被覆する無機圧電体層と、前記無機圧電体層を被覆する有機保護層と、前記有機保護層を被覆する導電体層とを含み、前記有機保護層が、０．１～１００μｍの厚さを有し、前記芯線および前記導電体層が、それらの間に前記無機圧電体層および前記有機保護層が介挿された電極としてそれぞれ機能する、圧電素子が提供される。 According to one gist of the present invention, the core wire having a conductive surface, the inorganic piezoelectric layer covering the core wire, the organic protective layer covering the inorganic piezoelectric layer, and the organic protective layer are coated. The organic protective layer includes a conductor layer and has a thickness of 0.1 to 100 μm, and the core wire and the conductor layer are interposed between the inorganic piezoelectric layer and the organic protective layer. Piezoelectric elements are provided that each function as an inserted electrode.
　本発明のもう１つの要旨によれば、上記本発明の圧電素子を含む圧電装置が提供される。 According to another gist of the present invention, a piezoelectric device including the above-mentioned piezoelectric element of the present invention is provided.
　本発明の圧電素子は、導電性の表面を有する芯線（内側電極）と、芯線を被覆する無機圧電体層と、無機圧電体層を被覆する有機保護層と、有機保護層を被覆する導電体層（外側電極）とを含んで構成され、これにより、全体として細長い線状の形態を有し、柔軟性を有する新規な圧電素子が提供される。本発明の圧電素子によれば、無機圧電体層を０．１～１００μｍの厚さを有する有機保護層で被覆して保護しており、これにより、圧電応答性を十分に示すことができる。更に、本発明の圧電素子によれば、無機圧電体層を使用しており、有機保護層は、電気絶縁性を有する有機材料から自由に選択可能であるので、高い耐熱性を有する圧電素子を実現することができる。更に、本発明の圧電素子を含む圧電装置も提供される。 The piezoelectric element of the present invention has a core wire (inner electrode) having a conductive surface, an inorganic piezoelectric layer covering the core wire, an organic protective layer covering the inorganic piezoelectric layer, and a conductor covering the organic protective layer. It is configured to include a layer (outer electrode), which provides a novel piezoelectric element having an elongated linear shape as a whole and having flexibility. According to the piezoelectric element of the present invention, the inorganic piezoelectric layer is covered with an organic protective layer having a thickness of 0.1 to 100 μm to protect the inorganic piezoelectric layer, whereby the piezoelectric responsiveness can be sufficiently exhibited. Further, according to the piezoelectric element of the present invention, an inorganic piezoelectric layer is used, and the organic protective layer can be freely selected from organic materials having electrical insulation, so that a piezoelectric element having high heat resistance can be used. It can be realized. Further, a piezoelectric device including the piezoelectric element of the present invention is also provided.
本発明の１つの実施形態における圧電素子を示す概略図であって、（ａ）は圧電素子の部分切除側面図を示し、（ｂ）は（ａ）のＡ－Ａ線に沿った断面図を示す。It is the schematic which shows the piezoelectric element in one Embodiment of this invention, (a) shows the partial cut side view of the piezoelectric element, (b) is the sectional view along the line AA of (a). Shown. 本発明の実施例１における圧電素子からの出力を示す、電圧信号の経時変化グラフである（縦軸の１目盛りは５０ｍＶに相当し、横軸の１目盛りは１秒に相当する）。It is a time-dependent graph of the voltage signal which shows the output from the piezoelectric element in Example 1 of this invention (1 scale of a vertical axis corresponds to 50 mV, and 1 scale of a horizontal axis corresponds to 1 second). 比較例１における圧電素子からの出力を示す、電圧信号の経時変化グラフである（縦軸の１目盛りは５０ｍＶに相当し、横軸の１目盛りは１秒に相当する）。It is a time-dependent graph of a voltage signal showing an output from a piezoelectric element in Comparative Example 1 (1 scale on the vertical axis corresponds to 50 mV, and 1 scale on the horizontal axis corresponds to 1 second).
　以下、本発明の実施形態について図面を参照しながら詳述する。なお、添付の図面中、電極端子を黒丸にて模式的に示す。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the attached drawings, the electrode terminals are schematically shown by black circles.
　図１を参照して、本実施形態の圧電素子１０は、導電性の表面を有する芯線１と、芯線１を被覆する無機圧電体層３と、無機圧電体層３を被覆する有機保護層５と、有機保護層５を被覆する導電体層７とを含む。有機保護層５は、０．１～１００μｍの厚さを有する。芯線１および導電体層７は、それらの間に無機圧電体層３および有機保護層５が介挿された電極（内側電極および外側電極）としてそれぞれ機能する（図１（ｂ）参照）。本実施形態に必須ではないが、圧電素子１０は、導電体層７を被覆する絶縁体層（シース）９を更に含んでいてよい。かかる圧電素子１０は、ケーブル状またはワイヤー状などと称され得る、全体として細長い線状の形態を有し、圧電素子全体として柔軟性を有する（曲げ可能である）ように構成される。本明細書において、「柔軟性を有する」とは、別の表現では可撓性であることを意味する。 With reference to FIG. 1, the piezoelectric element 10 of the present embodiment includes a core wire 1 having a conductive surface, an inorganic piezoelectric layer 3 covering the core wire 1, and an organic protective layer 5 covering the inorganic piezoelectric layer 3. And a conductor layer 7 that covers the organic protective layer 5. The organic protective layer 5 has a thickness of 0.1 to 100 μm. The core wire 1 and the conductor layer 7 function as electrodes (inner electrode and outer electrode) in which the inorganic piezoelectric layer 3 and the organic protective layer 5 are interposed between them (see FIG. 1 (b)). Although not essential to this embodiment, the piezoelectric element 10 may further include an insulator layer (sheath) 9 that covers the conductor layer 7. 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 is configured to have flexibility (bendability) as a whole piezoelectric element. As used herein, "flexible" means, in other words, flexible.
　芯線１は、電極（内側電極）として機能し得るように、少なくとも表面が導電性であればよい。芯線１は、例えば金属ワイヤーや任意の導電性材料（金属、金属とセラミックスとの複合体等）から成る線材や、任意の線状母材（耐熱性樹脂線等）の表面を導電性材料層（金属、導電性耐熱樹脂、導電性耐熱ゴム等）で被覆してなる線材などであってよい。また、芯線１は、実質的に円形、楕円、矩形、多角形などの任意の断面形状を有し得、中空および中実のいずれであってもよく、単線、撚り線および編み線などであってもよい。また、これら線材が２種以上組み合わせて用いられてもよい。 The core wire 1 may have at least a conductive surface so that it can function as an electrode (inner electrode). The core wire 1 has a conductive material layer on the surface of, for example, a metal wire, a wire made of an arbitrary conductive material (metal, a composite of metal and ceramics, etc.), or an arbitrary linear base material (heat-resistant resin wire, etc.). It may be a wire rod coated with (metal, conductive heat-resistant resin, conductive heat-resistant rubber, etc.). Further, the core wire 1 may have substantially any cross-sectional shape such as a circle, an ellipse, a rectangle, a polygon, and may be hollow or solid, and may be a single wire, a stranded wire, a braided wire, or the like. You may. Further, two or more kinds of these wire rods may be used in combination.
　芯線１の表面の全部が導電性であることが好ましいが、芯線１の表面の一部（全表面積の例えば２０％以下、好ましくは１０％以下、より好ましくは５％以下）は導電性でなくてもよい。例えば、芯線１が、非導電性の線状母材の表面に導電性材料から成るテープを巻き付けて構成される場合、巻き付けたテープの端縁間にギャップが存在し、該ギャップにおいて非導電性の線状母材が露出していてよい。 It is preferable that the entire surface of the core wire 1 is conductive, but a part of the surface of the core wire 1 (for example, 20% or less, preferably 10% or less, more preferably 5% or less of the total surface area) is not conductive. You may. For example, when the core wire 1 is formed by wrapping a tape made of a conductive material on the surface of a non-conductive linear base material, a gap exists between the edges of the wound tape, and the gap is non-conductive. The linear base material may be exposed.
　芯線１の外形断面寸法（線方向に対して垂直な断面の最大寸法、円形断面を有する場合は線径、以下同様）は、特に限定されないが、芯線１それ自体が可撓性であるように選択される。 The external cross-sectional dimension of the core wire 1 (the maximum dimension of the cross section perpendicular to the line direction, the wire diameter when having a circular cross section, the same applies hereinafter) is not particularly limited, but the core wire 1 itself is flexible. Be selected.
　芯線１を被覆する無機圧電体層３は、圧電セラミックスから成り、樹脂を含まない。圧電セラミックスは、１種の圧電セラミックスであってもよいが、２種以上の圧電セラミックスの混合物であってもよい。本明細書において、「・・・（材料）から成る」とは、当該材料から実質的に成っていればよく、不可避的に混入および／または残留し得る物質が存在していてもよいことを意味する。例えば、無機圧電体層３に、無機圧電体層を形成するための原料（例えば後述する第１溶液）に使用した溶媒や安定剤等が残存していてもよい。圧電セラミックスは、無機材料故に高い耐熱性を有する。 The inorganic piezoelectric layer 3 that covers the core wire 1 is made of piezoelectric ceramics and does not contain resin. The piezoelectric ceramic may be one kind of piezoelectric ceramic, but may be a mixture of two or more kinds of piezoelectric ceramics. As used herein, the term "consisting of (material)" means that it may be substantially composed of the material, and that there may be a substance that can inevitably be mixed and / or remain. means. For example, the solvent, stabilizer, or the like used as a raw material for forming the inorganic piezoelectric layer (for example, the first solution described later) may remain in the inorganic piezoelectric layer 3. Piezoelectric ceramics have high heat resistance because they are inorganic materials.
　無機圧電体層３は、特に、ウルツ鉱型結晶構造を有する圧電セラミックスから成ることが好ましい。ウルツ鉱型結晶構造を有する物質（化合物）は、その結晶配向性をｃ軸方向に揃え、さらに双極子配向度を制御することにより圧電性を示すことが知られている（特許文献１参照）。そのため、圧電ポリマー（例えばポリフッ化ビニリデン）の製造では必要とされる分極処理工程を要することなく圧電素子１０を製造することができる。 The inorganic piezoelectric layer 3 is particularly preferably made of piezoelectric ceramics having a wurtzite crystal structure. It is known that a substance (compound) having a wurtzite crystal structure exhibits piezoelectricity by aligning its crystal orientation in the c-axis direction and further controlling the degree of dipole orientation (see Patent Document 1). .. Therefore, the piezoelectric element 10 can be manufactured without requiring the polarization treatment step required in the manufacture of the piezoelectric polymer (for example, polyvinylidene fluoride).
　ウルツ鉱型結晶構造を有する圧電セラミックスは、主成分として、ＺｎＯ、ＺｎＳ、ＺｎＳｅ、ＺｎＴｅ、ＭｇＯ、ＣｄＯ、ＣｄＳ、ＣｄＳｅ、ＣｄＴｅ、ＡｌＮ、ＧａＮ、ＩｎＮおよびＩｎＰからなる群より選択される少なくとも１つを含み得、なかでも、酸化亜鉛（ＺｎＯ）および窒化アルミニウム（ＡｌＮ）の少なくとも一方を含むことが好ましく、酸化亜鉛（ＺｎＯ）を含むことが更に好ましい。かかるウルツ鉱型結晶構造を有する圧電セラミックスは、比較的安価であり、鉛を含まない点で環境や人体に対して安全である。本明細書において、ある材料の「主成分」とは、その材料に占める当該成分の割合（上記に列記した化合物が２つ以上存在する場合にはそれらの合計の割合）が、５０質量％超、例えば６０質量％以上、好ましくは７０質量％以上である成分を意味する。 The piezoelectric ceramic having a wurtzite type crystal structure is at least one selected from the group consisting of ZnO, ZnS, ZnSe, ZnTe, MgO, CdO, CdS, CdSe, CdTe, AlN, GaN, InN and InP as a main component. It is preferable to contain at least one of zinc oxide (ZnO) and aluminum nitride (AlN), and it is more preferable to contain zinc oxide (ZnO). Piezoelectric ceramics having such a wurtzite crystal structure are relatively inexpensive and are safe to the environment and the human body in that they do not contain lead. In the present specification, the "main component" of a certain material means that the ratio of the component to the material (the total ratio of two or more of the compounds listed above) exceeds 50% by mass. For example, it means a component which is 60% by mass or more, preferably 70% by mass or more.
　ウルツ鉱型結晶構造を有する圧電セラミックスは、ウルツ鉱型結晶構造を構成する元素以外の他種元素（ドーパント）を含んでいてもよい。これにより、無機圧電体層３における極性分布割合の制御特性が向上し、圧電応答性が高い圧電素子が実現される。他種元素は、特に限定されないが、アルカリ金属元素、アルカリ土類金属元素および第１３族元素からなる群より選択される少なくとも１つであってよい。他種元素としてのアルカリ金属元素は、リチウム（Ｌｉ）、ナトリウム（Ｎａ）およびカリウム（Ｋ）、が例示される。他種元素としてのアルカリ土類金属元素は、マグネシウム（Ｍｇ）、カルシウム（Ｃａ）、ストロンチウム（Ｓｒ）、バリウム（Ｂａ）が例示される。他種元素としての第１３族元素は、アルミニウム（Ａｌ）、ガリウム（Ｇａ）およびインジウム（Ｉｎ）が例示される。他種元素の濃度は、所望の電気特性に応じて適宜設定され得る。例えば、ウルツ鉱型結晶構造を有する物質（化合物）がＺｎＯで、他種元素がＬｉの場合には、ＺｎとＬｉの原子濃度の和に対して、Ｌｉの原子濃度が２～７．５原子％の範囲内であることが好ましい。 Piezoelectric ceramics having a wurtzite crystal structure may contain other kinds of elements (dopants) other than the elements constituting the wurtzite crystal structure. As a result, the control characteristics of the polarity distribution ratio in the inorganic piezoelectric layer 3 are improved, and a piezoelectric element having high piezoelectric response is realized. The other kind element is not particularly limited, but may be at least one selected from the group consisting of an alkali metal element, an alkaline earth metal element, and a Group 13 element. Examples of alkali metal elements as other elements include lithium (Li), sodium (Na) and potassium (K). Examples of alkaline earth metal elements as other elements include magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). Examples of Group 13 elements as other elements include aluminum (Al), gallium (Ga) and indium (In). The concentration of the other element can be appropriately set according to the desired electrical characteristics. For example, when the substance (compound) having a wurtzite crystal structure is ZnO and the other element is Li, the atomic concentration of Li is 2 to 7.5 atoms with respect to the sum of the atomic concentrations of Zn and Li. It is preferably in the range of%.
　しかしながら、無機圧電体層３は、ウルツ鉱型結晶構造を有する圧電セラミックスから成るものに限定されず、他の圧電セラミックスから成っていてもよい。例えば、他の圧電セラミックスは、チタン酸鉛、チタン酸ジルコン酸鉛、チタン酸ジルコン酸ランタン鉛、酸化チタンおよびチタン酸バリウムからなる群より選択される少なくとも１つを含み得、なかでも、チタン酸ジルコン酸鉛（PZT）を含むことが好ましい。 However, the inorganic piezoelectric layer 3 is not limited to the one made of piezoelectric ceramics having a wurtzite crystal structure, and may be made of other piezoelectric ceramics. For example, other piezoelectric ceramics may contain at least one selected from the group consisting of lead titanate, lead zirconate titanate, lead lanthanum zircate titanate, titanium oxide and barium titanate, among which titanate. It preferably contains lead zirconate (PZT).
　無機圧電体層３の厚さは、所望の柔軟性および電気特性に応じて適宜設定され得るが、例えば０．０１μｍ以上、好ましくは０．０５μｍ以上であり、例えば３．００μｍ以下、好ましくは１．００μｍ以下であり得る。 The thickness of the inorganic piezoelectric layer 3 can be appropriately set according to the desired flexibility and electrical characteristics, and is, for example, 0.01 μm or more, preferably 0.05 μm or more, for example 3.00 μm or less, preferably 1. It can be less than .00 μm.
　無機圧電体層３を被覆する有機保護層５は、電気絶縁性を有する有機材料から成ることが好ましい。有機保護層５には、電気絶縁性を有する様々な有機材料から、高い耐熱温度を有する材料を選択することができる。有機保護層５は、例えば２００℃以上の耐熱温度を有する材料から成り得る。本明細書において、「耐熱温度」は、その材料が当該温度に曝されても物理的性状が実質的に損なわれない温度を意味し、連続使用温度（長期耐熱温度）または短期耐熱温度であり得る。短期耐熱温度は、結晶性の有機材料である場合には融点であり得、非結晶性の有機材料である場合にはガラス転移温度であり得る。 The organic protective layer 5 that covers the inorganic piezoelectric layer 3 is preferably made of an organic material having electrical insulation. For the organic protective layer 5, a material having a high heat resistant temperature can be selected from various organic materials having an electrically insulating property. The organic protective layer 5 can be made of, for example, a material having a heat resistant temperature of 200 ° C. or higher. In the present specification, the "heat-resistant temperature" means a temperature at which the physical properties of the material are not substantially impaired even when the material is exposed to the temperature, and is a continuous use temperature (long-term heat-resistant temperature) or a short-term heat-resistant temperature. obtain. The short-term heat resistant temperature can be the melting point in the case of a crystalline organic material and the glass transition temperature in the case of a non-crystalline organic material.
　有機保護層５を構成する材料は、フッ素樹脂、イミド系樹脂、芳香族系ポリマー、液晶ポリマー（LCP）、ポリカーボネート（PC）、シリコーン樹脂およびエポキシ樹脂からなる群より選択される少なくとも１つを含み得る。これらは単独で使用されても、任意の２種以上の混合物として使用されてもよい。フッ素樹脂の例としては、ポリテトラフルオロエチレン（PTFE）、テトラフルオロエチレン―ヘキサフルオロプロピレン共重合体（FEP）、テトラフルオロエチレン―パーフルオロアルキルビニルエーテル共重合体（PFA)、エチレン―テトラフルオロエチレン共重合体（ETFE）、ポリクロロトリフルオロエチレン（PCTFE）が挙げられる。イミド系樹脂の例としては、ポリイミド（PI）、ポリアミドイミド（PAI）、ポリエーテルイミド（PEI）が挙げられる。芳香族系ポリマーの例としては、ポリフェニレンサルファイド樹脂（PPS）、ポリエーテルエーテルケトン樹脂（PEEK）が挙げられる。 The material constituting the organic protective layer 5 contains at least one selected from the group consisting of fluororesin, imide resin, aromatic polymer, liquid crystal polymer (LCP), polycarbonate (PC), silicone resin and epoxy resin. obtain. These may be used alone or as a mixture of any two or more. Examples of fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and ethylene-tetrafluoroethylene. Examples include copolymers (ETFE) and polychlorotrifluoroethylene (PCTFE). Examples of imide-based resins include polyimide (PI), polyamideimide (PAI), and polyetherimide (PEI). Examples of aromatic polymers include polyphenylene sulfide resin (PPS) and polyetheretherketone resin (PEEK).
　有機保護層５は、無機圧電体層３を保護する（無機圧電体層３を導電体層７と直接接触させない）ように、無機圧電体層３の外側表面の全部を被覆することが好ましい。 The organic protective layer 5 preferably covers the entire outer surface of the inorganic piezoelectric layer 3 so as to protect the inorganic piezoelectric layer 3 (the inorganic piezoelectric layer 3 is not in direct contact with the conductor layer 7).
　有機保護層５の厚さは、０．１～１００μｍの範囲以内で設定される。これにより、圧電応答性を十分に示すこと（センサとしては外力の経時変化に応じた圧電出力を計測でき、アクチュエータとしては電圧の経時変化に応じた変形をもたらすこと）ができる。特に、有機保護層５の厚さが０．１μｍ以上であることで、無機圧電体層３を後述する塗布法により形成する場合であっても、芯線（内側電極）１と導電体層（外側電極）７との間での短絡の発生を効果的に防止することができる。また、有機保護層５の厚さが１００μｍ以下であることで、圧電素子としての機能を確保すること（より詳細には、センサとしては圧電出力を計測し、アクチュエータとしては所望の変形をもたらすこと）ができる。有機保護層５の厚さは、好ましくは１～３０μｍの範囲以内で設定される。 The thickness of the organic protective layer 5 is set within the range of 0.1 to 100 μm. As a result, it is possible to sufficiently show the piezoelectric response (the sensor can measure the piezoelectric output according to the change with time of the external force, and the actuator can bring about the deformation according to the change with time of the voltage). In particular, when the thickness of the organic protective layer 5 is 0.1 μm or more, even when the inorganic piezoelectric layer 3 is formed by the coating method described later, the core wire (inner electrode) 1 and the conductor layer (outer side) are formed. It is possible to effectively prevent the occurrence of a short circuit with the electrode) 7. Further, when the thickness of the organic protective layer 5 is 100 μm or less, the function as a piezoelectric element is ensured (more specifically, the piezoelectric output is measured as a sensor and the desired deformation is brought about as an actuator. ) Can be done. The thickness of the organic protective layer 5 is preferably set within the range of 1 to 30 μm.
　有機保護層５を被覆する導電体層７は、電極（外側電極）として機能し得るように、導電性材料から構成されていればよい。導電体層７は、例えば金属、金属とセラミックスとの複合体、導電性耐熱樹脂、導電性耐熱ゴム等からなり得る。 The conductor layer 7 that covers the organic protective layer 5 may be made of a conductive material so that it can function as an electrode (outer electrode). The conductor layer 7 may be made of, for example, a metal, a composite of metal and ceramics, a conductive heat-resistant resin, a conductive heat-resistant rubber, or the like.
　導電体層７は、有機保護層５の外側表面の全部を被覆することが好ましいが、有機保護層５の外側表面の一部（全表面積の例えば６０％以下、好ましくは７０％以下、より好ましくは９０％以下）は導電体層７で被覆されていなくてもよい。 The conductor layer 7 preferably covers the entire outer surface of the organic protective layer 5, but is more preferably a part of the outer surface of the organic protective layer 5 (for example, 60% or less, preferably 70% or less of the total surface area). 90% or less) may not be coated with the conductor layer 7.
　導電体層７の厚さは、所望の柔軟性および電気特性に応じて適宜設定され得るが、例えば０．０１μｍ以上、好ましくは０．０５μｍ以上であり、例えば３０００μｍ以下、好ましくは１０００μｍ以下であり得る。 The thickness of the conductor layer 7 can be appropriately set according to the desired flexibility and electrical characteristics, and is, for example, 0.01 μm or more, preferably 0.05 μm or more, for example, 3000 μm or less, preferably 1000 μm or less. obtain.
　導電体層７の外形断面寸法は、例えば１０．０ｍｍ以下であり得、好ましくは０．１ｍｍ以上５．０ｍｍ以下であり得る。導電体層７が圧電素子１０の最外層である場合、これにより、外形断面寸法（代表的には線径）が小さく、かつ柔軟性を有する、いわゆる「線状」の圧電素子１０を提供することができる。かかる圧電素子１０は、圧電装置への取り付けの自由度が高く、幅広い用途に利用され得る。 The external cross-sectional dimension of the conductor layer 7 can be, for example, 10.0 mm or less, preferably 0.1 mm or more and 5.0 mm or less. When the conductor layer 7 is the outermost layer of the piezoelectric element 10, this provides a so-called "linear" piezoelectric element 10 having a small external cross-sectional dimension (typically a wire diameter) and flexibility. be able to. The piezoelectric element 10 has a high degree of freedom of attachment to a piezoelectric device and can be used in a wide range of applications.
　存在する場合、絶縁体層（シース）９は、任意の適切な絶縁材料から成る。かかる絶縁体層９には、ワイヤーやケーブルのための可撓性シースとして既知のもの、例えば可撓性の耐熱樹脂、耐熱ゴム等を適用してよい。絶縁体層９の具体的な材料、形態および厚さ等は、圧電素子１０の用途に応じて適宜選択され得る。 If present, the insulator layer (sheath) 9 is made of any suitable insulating material. A flexible sheath known as a flexible sheath for wires and cables, such as a flexible heat-resistant resin and heat-resistant rubber, may be applied to the insulator layer 9. The specific material, form, thickness, and the like of the insulator layer 9 can be appropriately selected depending on the use of the piezoelectric element 10.
　かかる本実施形態の圧電素子１０は、任意の適切な方法で製造可能である。以下に、本実施形態の圧電素子１０の製造方法の一例を示すが、これに限定されない。 The piezoelectric element 10 of the present embodiment can be manufactured by any suitable method. The following is an example of the method for manufacturing the piezoelectric element 10 of the present embodiment, but the present invention is not limited to this.
　本実施形態の圧電素子１０の製造方法は、
　導電性の表面を有する芯線１を準備すること、
　芯線１を被覆する無機圧電体層３を形成すること、
　無機圧電体層３を被覆する有機保護層５を形成すること、
　有機保護層５を導電体層７で被覆すること、および要すれば、
　導電体層７を絶縁体層９で被覆すること
を含み得る。より詳細には以下の通りである。 The method for manufacturing the piezoelectric element 10 of the present embodiment is as follows.
Preparing the core wire 1 having a conductive surface,
Forming the inorganic piezoelectric layer 3 that covers the core wire 1.
Forming the organic protective layer 5 that covers the inorganic piezoelectric layer 3.
The organic protective layer 5 is coated with the conductor layer 7, and if necessary,
It may include coating the conductor layer 7 with an insulator layer 9. More details are as follows.
　まず、本実施形態において上述したような芯線１を準備する。かかる芯線１は、市販で入手可能であり、あるいは、容易に作製可能である。 First, the core wire 1 as described above is prepared in the present embodiment. Such a core wire 1 is commercially available or can be easily manufactured.
　次に、芯線１を被覆する無機圧電体層３を形成する。無機圧電体層３は、芯線１を被覆するように、塗布法（化学溶液堆積法またはゾルゲル法とも称され得る）、スパッタリング法、水熱法等の任意の適切な方法により形成可能であるが、好ましくは塗布法により形成され得る。無機圧電体層３を塗布法で形成すると、真空装置等を用いることなく、連続的に生産することが可能となり、より簡便かつ低コストで圧電素子１０を製造することができる。 Next, the inorganic piezoelectric layer 3 that covers the core wire 1 is formed. The inorganic piezoelectric layer 3 can be formed by any suitable method such as a coating method (which may also be referred to as a chemical solution deposition method or a sol-gel method), a sputtering method, or a hydrothermal method so as to cover the core wire 1. , Preferably can be formed by a coating method. When the inorganic piezoelectric layer 3 is formed by the coating method, it can be continuously produced without using a vacuum device or the like, and the piezoelectric element 10 can be manufactured more easily and at low cost.
　無機圧電体層３を塗布法で形成する場合、より詳細には、
　圧電セラミックス（好ましくはウルツ鉱型結晶構造を有する圧電セラミックス）を構成する元素種を含有する第１溶液（原料）を、芯線１の表面に塗布して塗布膜を形成すること、
　形成された塗布膜を乾燥させること、および
　乾燥させた塗布膜を焼成すること
によって、無機圧電体層３が形成される。 When the inorganic piezoelectric layer 3 is formed by the coating method, more specifically,
A first solution (raw material) containing an elemental species constituting a piezoelectric ceramic (preferably a piezoelectric ceramic having a wurtzite crystal structure) is applied to the surface of the core wire 1 to form a coating film.
The inorganic piezoelectric layer 3 is formed by drying the formed coating film and firing the dried coating film.
　第１溶液は、圧電セラミックス（好ましくはウルツ鉱型結晶構造を有する圧電セラミックス）を構成する元素種（存在する場合には、他種元素（ドーパント）を含む）に加えて、溶媒を含み、場合により安定剤等の任意の適切な添加剤を含み得る。溶媒の例としては、２－メトキシエタノール、２－プロパノール、エタノール、１－ブタノール、トリオクチルフォスフィン、水等が挙げられる。 The first solution contains a solvent in addition to the element species (including other species elements (dopants), if present) constituting the piezoelectric ceramics (preferably piezoelectric ceramics having a wurtzite crystal structure). May include any suitable additive such as a stabilizer. Examples of the solvent include 2-methoxyethanol, 2-propanol, ethanol, 1-butanol, trioctylphosphine, water and the like.
　第１溶液の塗布は、例えばディップコート法やスプレーコート法を用いて実施可能である。好ましくは、ディップコート法により、芯線１を第１溶液に浸漬して所定の速度で引き上げることにより芯線１の表面に第１溶液を概ね均一な厚さで塗布することができる。 The first solution can be applied by using, for example, a dip coating method or a spray coating method. Preferably, the first solution can be applied to the surface of the core wire 1 in a substantially uniform thickness by immersing the core wire 1 in the first solution and pulling it up at a predetermined speed by a dip coating method.
　乾燥は、芯線１の耐熱温度以下で、塗布膜を乾燥させることにより実施される。乾燥温度は、例えば４００℃未満、好ましくは３００℃以下であり、乾燥時間は適宜設定される。乾燥雰囲気は特に限定されないが、例えば空気、不活性ガス雰囲気、酸素と不活性ガスとの混合雰囲気であってよい。乾燥により、溶媒および場合により存在し得る添加剤が除去され得ると共に、圧電セラミックスを構成する元素種が結晶として析出および凝集して、粒子になる。塗布膜は、かかる粒子（好ましくはウルツ鉱型結晶構造を有する物質（化合物）の粒子）が充填および堆積した集合体であり得る。 Drying is carried out by drying the coating film at a heat resistant temperature or lower of the core wire 1. The drying temperature is, for example, less than 400 ° C., preferably 300 ° C. or lower, and the drying time is appropriately set. The dry atmosphere is not particularly limited, but may be, for example, an air, an inert gas atmosphere, or a mixed atmosphere of oxygen and an inert gas. Drying can remove solvents and optionally present additives, and the elemental species that make up the piezoelectric ceramics precipitate and aggregate as crystals into particles. The coating film can be an aggregate packed and deposited with such particles (preferably particles of a substance (compound) having a wurtzite crystal structure).
　これにより、乾燥させた塗布膜が得られる。１回の塗布および１回の乾燥により、所望の塗布膜厚さが得られない場合には、塗布および乾燥を１セットとして、所望の塗布膜厚さが得られるまで、複数セット繰り返して実施してよい。 As a result, a dried coating film can be obtained. If the desired coating film thickness cannot be obtained by one coating and one drying, the coating and drying are set as one set, and a plurality of sets are repeated until the desired coating film thickness is obtained. It's okay.
　焼成は、芯線１の耐熱温度以下で、塗布膜を焼成することにより実施される。焼成温度は、例えば６００℃未満、好ましくは４５０℃以下であり、焼成時間は適宜設定される。焼成雰囲気は特に限定されないが、例えば空気、不活性ガス雰囲気、酸素と不活性ガスとの混合雰囲気であってよい。焼成により、上記粒子が互いに結合してなる多孔体である結合層が形成され得る。この結合層は、圧電セラミックスを成す結晶の粒子が（無秩序に）充填および堆積した集合体であり得、粒子の形状を残した状態で焼結したものであり得る。 Baking is carried out by firing the coating film at a heat resistant temperature of the core wire 1 or lower. The firing temperature is, for example, less than 600 ° C., preferably 450 ° C. or lower, and the firing time is appropriately set. The firing atmosphere is not particularly limited, but may be, for example, an air, an inert gas atmosphere, or a mixed atmosphere of oxygen and an inert gas. By firing, a bonding layer, which is a porous body in which the particles are bonded to each other, can be formed. The bond layer can be an aggregate of (randomly) filled and deposited particles of crystals that make up the piezoelectric ceramics, and can be sintered while leaving the shape of the particles.
　これにより、圧電セラミックス（好ましくはウルツ鉱型結晶構造を有する圧電セラミックス）から成る無機圧電体層３が形成される。１セットまたは複数セットの塗布および乾燥と１回の焼成とにより、所望の無機圧電体層厚さが得られない場合には、「１セットまたは複数セットの塗布および乾燥と１回の焼成と」を１セットとして、所望の無機圧電体層厚さが得られるまで、複数セット繰り返して実施してよい。 As a result, the inorganic piezoelectric layer 3 made of piezoelectric ceramics (preferably piezoelectric ceramics having a wurtzite crystal structure) is formed. If the desired inorganic piezoelectric layer thickness cannot be obtained by coating and drying one set or multiple sets and firing once, "coating and drying one set or multiple sets and firing once". As one set, a plurality of sets may be repeated until a desired inorganic piezoelectric layer thickness is obtained.
　次に、無機圧電体層３を被覆する有機保護層５を形成する。有機保護層５は、無機圧電体層３を被覆するように、使用する有機絶縁体の原料に応じて任意の適切な方法により形成可能であるが、好ましくは塗布法により形成され得る。 Next, the organic protective layer 5 that covers the inorganic piezoelectric layer 3 is formed. The organic protective layer 5 can be formed by any suitable method depending on the raw material of the organic insulator used so as to cover the inorganic piezoelectric layer 3, but is preferably formed by a coating method.
　有機保護層５を塗布法で形成する場合、より詳細には、
　有機保護層５を構成する第２溶液（原料）を、無機圧電体層３の表面に塗布して塗布膜を形成すること、
　形成された塗布膜を乾燥させること、および場合により、
　乾燥させた塗布膜を熱処理に付すこと
によって、有機保護層５が形成される。 When the organic protective layer 5 is formed by a coating method, more specifically,
Applying the second solution (raw material) constituting the organic protective layer 5 to the surface of the inorganic piezoelectric layer 3 to form a coating film.
Drying the formed coating film and, optionally,
The organic protective layer 5 is formed by subjecting the dried coating film to heat treatment.
　第２溶液は、有機保護層を構成する材料（反応完了前の前駆体であってもよい）に加えて、溶媒を含み、場合により安定剤等の任意の適切な添加剤を含み得る。 The second solution may contain a solvent and optionally any suitable additive such as a stabilizer, in addition to the material constituting the organic protective layer (which may be a precursor before the reaction is completed).
　第２溶液の塗布は、例えばディップコート法やスプレーコート法を用いて実施可能であり、好ましくは、ディップコート法を用いる。無機圧電体層３で被覆された芯線１を第２溶液に浸漬して塗布するディップコート法によれば、無機圧電体層３の表面に第２溶液を概ね均一な厚さで塗布することができる。 The application of the second solution can be carried out by using, for example, a dip coating method or a spray coating method, and preferably the dip coating method is used. According to the dip coating method in which the core wire 1 coated with the inorganic piezoelectric layer 3 is dipped in the second solution and applied, the second solution can be applied to the surface of the inorganic piezoelectric layer 3 with a substantially uniform thickness. it can.
　乾燥条件は、有機保護層を構成する材料に応じて適宜選択され得る。 The drying conditions can be appropriately selected according to the materials constituting the organic protective layer.
　これにより、乾燥させた塗布膜が得られる。１回の塗布および１回の乾燥により、所望の塗布膜厚さが得られない場合には、塗布および乾燥を１セットとして、所望の塗布膜厚さが得られるまで、複数セット繰り返して実施してよい。 As a result, a dried coating film can be obtained. If the desired coating film thickness cannot be obtained by one coating and one drying, the coating and drying are set as one set, and a plurality of sets are repeated until the desired coating film thickness is obtained. It's okay.
　場合により、乾燥させた塗布膜を熱処理に付してよい。かかる熱処理は、例えば、有機保護層を構成する材料中で反応を進行させるために実施され得る。熱処理条件は、有機保護層を構成する材料に応じて適宜選択され得る。 In some cases, the dried coating film may be subjected to heat treatment. Such heat treatment can be carried out, for example, to allow the reaction to proceed in the material constituting the organic protective layer. The heat treatment conditions can be appropriately selected depending on the material constituting the organic protective layer.
　これにより、有機保護層５が形成される。１セットまたは複数セットの塗布および乾燥と１回の熱処理とにより、所望の有機保護層厚さが得られない場合には、「１セットまたは複数セットの塗布および乾燥と１回の熱処理と」を１セットとして、所望の有機保護層厚さが得られるまで、複数セット繰り返して実施してよい。 As a result, the organic protective layer 5 is formed. If the desired organic protective layer thickness cannot be obtained by applying and drying one or more sets and one heat treatment, "one or more sets of application and drying and one heat treatment" is performed. As one set, a plurality of sets may be repeated until a desired organic protective layer thickness is obtained.
　次に、有機保護層５を導電体層７で被覆する。導電体層７は、有機保護層５を被覆するように、任意の適切な方法により形成可能である。例えば、蒸着、巻き付けなどにより形成され得る。要すれば、導電体層７を絶縁体層（シース）９で被覆してよい。絶縁体層９は、導電体層７を被覆するように、任意の適切な方法により形成可能である。 Next, the organic protective layer 5 is coated with the conductor layer 7. The conductor layer 7 can be formed by any suitable method so as to cover the organic protective layer 5. For example, it can be formed by vapor deposition, winding, or the like. If necessary, the conductor layer 7 may be coated with the insulator layer (sheath) 9. The insulator layer 9 can be formed by any suitable method so as to cover the conductor layer 7.
　以上のようにして本実施形態の圧電素子１０を得ることができる。無機圧電体層３および有機保護層５を順次形成すると、有機保護層５は、無機圧電体層３の形成に必要でかつ比較的高温である焼成温度に曝されないので、有機保護層５が熱により劣化および／または分解されることを回避できる。更に、無機圧電体層３および有機保護層５を塗布法により順次形成する場合、連続するプロセスで実施できるので、長尺の圧電素子１０を効率的に製造することができる。 As described above, the piezoelectric element 10 of the present embodiment can be obtained. When the inorganic piezoelectric layer 3 and the organic protective layer 5 are sequentially formed, the organic protective layer 5 is not exposed to the firing temperature which is necessary for forming the inorganic piezoelectric layer 3 and is relatively high, so that the organic protective layer 5 is heated. It is possible to avoid deterioration and / or decomposition due to the above. Further, when the inorganic piezoelectric layer 3 and the organic protective layer 5 are sequentially formed by the coating method, the process can be carried out in a continuous process, so that the long piezoelectric element 10 can be efficiently manufactured.
　本実施形態の圧電素子１０は、芯線１（より詳細には導電性部分）および導電体層７を適宜露出させて電極を引き出すことができる（図中、電極端子を黒丸にて模式的に示す）。導電体層９は、グランドであってよく、その場合、シールドとしても機能し得る。 In the piezoelectric element 10 of the present embodiment, the electrode can be pulled out by appropriately exposing the core wire 1 (more specifically, the conductive portion) and the conductor layer 7 (in the figure, the electrode terminals are schematically shown by black circles). ). The conductor layer 9 may be ground, in which case it may also function as a shield.
　本実施形態の圧電素子１０は、様々な用途の圧電装置において、各種のセンサおよび／またはアクチュエータとして利用可能である。 The piezoelectric element 10 of this embodiment can be used as various sensors and / or actuators in piezoelectric devices for various purposes.
　本実施形態の圧電素子１０は、圧電体の正圧電効果を利用してセンサとして利用可能である。圧電素子１０は、例えば、被検知対象物に取付および／または埋込等して、圧電素子１０に外力が加えられたときにこれを検知することが可能な感圧センサとして、あるいは、被検知対象物の内部疲労を検知するセンサとして利用され得る。また、複数の圧電素子１０を用いて編物または織物を構成して、繊維状圧電センサや振動型発電素子として利用することもできる。その他にも、例えば防犯センサ、介護／見守りセンサ、衝撃センサ、ウェアラブルセンサ、生体信号センサ（呼吸／脈拍）、車両用挟み込み防止センサ、車両用バンパー衝突センサ、車両用エア流量センサ、気象検知センサ（雨／雪）、火災検知センサ、水中音響センサ、ロボット用触覚センサ、医療機器用触覚センサ、繊維シート状圧力分布センサ、環境振動用発電ワイヤーなどの種々の用途の圧電装置に利用することができる。 The piezoelectric element 10 of this embodiment can be used as a sensor by utilizing the positive piezoelectric effect of the piezoelectric body. The piezoelectric element 10 can be attached to and / or embedded in an object to be detected, and can detect when an external force is applied to the piezoelectric element 10 as a pressure-sensitive sensor or to be detected. It can be used as a sensor to detect the internal fatigue of an object. Further, a knitted fabric or a woven fabric can be formed by using a plurality of piezoelectric elements 10 and used as a fibrous piezoelectric sensor or a vibration type power generation element. In addition, for example, security sensors, nursing / watching sensors, impact sensors, wearable sensors, biometric signal sensors (breathing / pulse), pinch prevention sensors for vehicles, bumper collision sensors for vehicles, air flow sensors for vehicles, weather detection sensors ( It can be used for piezoelectric devices for various purposes such as rain / snow), fire detection sensors, underwater acoustic sensors, tactile sensors for robots, tactile sensors for medical devices, fiber sheet pressure distribution sensors, and power generation wires for environmental vibrations. ..
　本実施形態の圧電素子１０は、上記に代えて／加えて、圧電体の逆圧電効果を利用してアクチュエータとして利用可能である。圧電素子１０は、例えば、圧電素子１０に対して駆動電圧を加えた際に、振動を励振するアクチュエータとして利用され得、また更に、その振動をセンサとして利用したアクチュエータ駆動センサとしても利用され得る。その他にも、例えばロボット関節駆動アクチュエータ、人工筋肉アクチュエータ、医療機器操作ワイヤー用駆動アクチュエータ、ファイバースコープ用駆動アクチュエータ、超音波モーター、圧電モーターなどの種々の用途の圧電装置に利用することができる。 The piezoelectric element 10 of the present embodiment can be used as an actuator by utilizing the inverse piezoelectric effect of the piezoelectric body in place of / in addition to the above. The piezoelectric element 10 can be used, for example, as an actuator that excites vibration when a drive voltage is applied to the piezoelectric element 10, and can also be used as an actuator drive sensor that utilizes the vibration as a sensor. In addition, it can be used for piezoelectric devices for various purposes such as robot joint drive actuators, artificial muscle actuators, drive actuators for medical device operation wires, fiberscope drive actuators, ultrasonic motors, and piezoelectric motors.
　なかでも、本実施形態の圧電素子１０は、高い応答特性が求められる用途に好ましく利用され得る。 Among them, the piezoelectric element 10 of the present embodiment can be preferably used in applications requiring high response characteristics.
　以上、本発明の１つの実施形態における圧電素子およびこれを含む圧電装置について詳述したが、本実施形態は種々の改変が可能である。 The piezoelectric element and the piezoelectric device including the piezoelectric element in one embodiment of the present invention have been described in detail above, but the present embodiment can be modified in various ways.
（実施例１）
　図１を参照して詳述した上記実施形態の圧電素子を下記の通り作製した。 (Example 1)
The piezoelectric element of the above embodiment described in detail with reference to FIG. 1 was manufactured as follows.
　第１溶液の調製
　ガラス製容器に、溶媒として２－メトキシエタノール（４８．２０ｇ）および安定剤として２－アミノエタノール（１．８３ｇ）を入れ、大気雰囲気下、常温にて５分間撹拌した。次に、これにより得られた混合液に酢酸亜鉛二水和物（６．３９ｇ）を加えて、溶解するまで大気雰囲気下、常温にて撹拌した。次に、これにより得られた混合液に酢酸リチウム二水和物（０．０９５ｇ）を加えて、大気雰囲気下、常温にて１時間撹拌した。これにより、第１溶液を調製した。 Preparation of First Solution 2-methoxyethanol (48.20 g) as a solvent and 2-aminoethanol (1.83 g) as a stabilizer were placed in a glass container, and the mixture was stirred at room temperature for 5 minutes in an air atmosphere. Next, zinc acetate dihydrate (6.39 g) was added to the resulting mixed solution, and the mixture was stirred at room temperature in an air atmosphere until it was dissolved. Next, lithium acetate dihydrate (0.095 g) was added to the resulting mixed solution, and the mixture was stirred at room temperature for 1 hour in an air atmosphere. As a result, the first solution was prepared.
　第２溶液の調製
　ポリアミドイミドワニス（日立化成株式会社製、HPC-1000）（２２．５ｇ）に純水（３０ｇ）を加えて、３０分間撹拌して均一に混合した。これにより、第２溶液を調製した。 Preparation of Second Solution Pure water (30 g) was added to polyamide-imide varnish (HPC-1000 manufactured by Hitachi Kasei Co., Ltd.) (22.5 g), and the mixture was stirred for 30 minutes and mixed uniformly. As a result, a second solution was prepared.
　芯線１の準備
　芯線１としてＳＵＳ製ワイヤ（ＳＵＳ３０４、直径０．２８ｍｍ）を準備した。 Preparation of core wire 1 A SUS wire (SUS304, diameter 0.28 mm) was prepared as the core wire 1.
　無機圧電体層の形成
　上記で準備した芯線１を、上記で調製した第１溶液に浸漬して塗布することにより、芯線１の表面に第１溶液の塗布膜を形成した。その後、２５０℃で１分間乾燥させ、このような１回の塗布および１回の乾燥を１セットとして、同条件で合計３セット繰り返した。次に、これにより得られた乾燥塗布膜を、４００℃で１分間焼成した。このような「１回の塗布および１回の乾燥の３セットと１回の焼成と」を１セットとして、同条件で合計３セット繰り返した。これにより、芯線１を被覆する無機圧電体層３として、ウルツ鉱型結晶構造を有する酸化亜鉛（ＺｎＯ）からなる層を形成した。無機圧電体層３の厚さは、０．１μｍであった。 Formation of Inorganic Piezoelectric Layer The core wire 1 prepared above was dipped in the first solution prepared above and coated to form a coating film of the first solution on the surface of the core wire 1. Then, it was dried at 250 ° C. for 1 minute, and such one application and one drying were set as one set, and a total of three sets were repeated under the same conditions. Next, the dry coating film thus obtained was calcined at 400 ° C. for 1 minute. Such "three sets of one coating and one drying and one firing" was set as one set, and a total of three sets were repeated under the same conditions. As a result, a layer made of zinc oxide (ZnO) having a wurtzite crystal structure was formed as the inorganic piezoelectric layer 3 covering the core wire 1. The thickness of the inorganic piezoelectric layer 3 was 0.1 μm.
　有機保護層の形成
　上記で無機圧電体層３を形成した芯線１を、上記で調製した第２溶液に浸漬して塗布することにより、無機圧電体層３の表面に第２溶液の塗布膜を形成した。その後、２００℃で１分間乾燥させ、得られた乾燥塗布膜を、３５０℃で３分間の熱処理に付した。このような「１回の塗布、１回の乾燥および１回の焼成」を１セットとして、同条件で合計５セット繰り返した。これにより、無機圧電体層３を被覆する有機保護層５としてポリアミドイミドから成る層を形成した。有機保護層５の厚さは、５μｍであった。 Formation of Organic Protective Layer By immersing the core wire 1 on which the inorganic piezoelectric layer 3 is formed above in the second solution prepared above and applying the coating, a coating film of the second solution is applied to the surface of the inorganic piezoelectric layer 3. Formed. Then, it was dried at 200 ° C. for 1 minute, and the obtained dry coating film was subjected to heat treatment at 350 ° C. for 3 minutes. Such "one application, one drying and one firing" was set as one set, and a total of five sets were repeated under the same conditions. As a result, a layer made of polyamide-imide was formed as the organic protective layer 5 for covering the inorganic piezoelectric layer 3. The thickness of the organic protective layer 5 was 5 μm.
　導電体層の形成
　上記で形成した有機保護層５の表面にアルミニウムを蒸着させて、導電体層７としてアルミニウムから成る層を形成した。導電体層７の厚さは、０．２μｍであった。 Formation of Conductor Layer Aluminum was vapor-deposited on the surface of the organic protective layer 5 formed above to form a layer made of aluminum as the conductor layer 7. The thickness of the conductor layer 7 was 0.2 μm.
　以上のようにして実施例１の圧電素子１０を作製した。 The piezoelectric element 10 of Example 1 was manufactured as described above.
（実施例２）
　有機保護層の形成において、「１回の塗布、１回の乾燥および１回の焼成」を１セットのみ実施した（繰り返さなかった）こと以外は、実施例１と同様にして、圧電素子を作製した。実施例２の圧電素子における有機保護層の厚さは、１μｍであった。 (Example 2)
In forming the organic protective layer, a piezoelectric element was produced in the same manner as in Example 1 except that only one set of "one coating, one drying and one firing" was carried out (not repeated). did. The thickness of the organic protective layer in the piezoelectric element of Example 2 was 1 μm.
（実施例３）
　有機保護層の形成において、「１回の塗布、１回の乾燥および１回の焼成」を１セットとして、同条件で合計３０セット繰り返したこと以外は、実施例１と同様にして、圧電素子を作製した。実施例３の圧電素子における有機保護層の厚さは、３０μｍであった。 (Example 3)
In the formation of the organic protective layer, the piezoelectric element is the same as in Example 1 except that "one coating, one drying and one firing" are set as one set and a total of 30 sets are repeated under the same conditions. Was produced. The thickness of the organic protective layer in the piezoelectric element of Example 3 was 30 μm.
（比較例１）
　有機保護層の形成を実施せず、無機圧電体層の表面に導電体層を形成したこと以外は、実施例１と同様にして、圧電素子を作製した。 (Comparative Example 1)
A piezoelectric element was produced in the same manner as in Example 1 except that the organic protective layer was not formed and the conductor layer was formed on the surface of the inorganic piezoelectric layer.
（評価）
　実施例１～３および比較例１で作製した圧電素子を下記のようにして評価した。 (Evaluation)
The piezoelectric elements produced in Examples 1 to 3 and Comparative Example 1 were evaluated as follows.
　評価用の圧電素子（長さ：８０ｍｍ）のうち、露出させた芯線１の上記一方の端部付近の領域と、導電体層７の他方の端部付近の領域とにそれぞれリード線を接続して、芯線１（内側電極）および導電体層７（外側電極）を引き出し、アナログ増幅回路（２０００倍増幅）を介してオシロスコープ（ハギワラソリューションズ株式会社製、ＵＤＳ－１Ｇ０２Ｓ－１０Ｋ）に接続して、これら電極間にて発生する電圧信号を経時的に出力可能なように構成した。 Of the evaluation piezoelectric elements (length: 80 mm), lead wires are connected to the region near one end of the exposed core wire 1 and the region near the other end of the conductor layer 7, respectively. Then, the core wire 1 (inner electrode) and the conductor layer 7 (outer electrode) are pulled out and connected to an oscilloscope (UDS-1G02S-10K, manufactured by Hagiwara Solutions Co., Ltd.) via an analog amplifier circuit (2000 times amplification). The voltage signal generated between these electrodes can be output over time.
　上記のようにリード線を接続した状態の評価用の圧電素子を電磁力式微小試験機（株式会社島津製作所製、マイクロサーボＭＭＴ－１０１ＮＶ－１０）にセットし、評価用の圧電素子の線方向に対して加振（周波数１Ｈｚ、応力１Ｎ～３Ｎ）して、応力を繰り返し負荷した。かかる試験を実施している間に、芯線１（内側電極）および導電体層７（外側電極）の間で発生する電圧信号を圧電出力として経時的に測定した。代表的に、実施例１および比較例１の圧電素子の測定結果をそれぞれ図２および図３に示す。 The evaluation piezoelectric element with the lead wire connected as described above is set in the electromagnetic force type micro tester (Micro Servo MMT-101NV-10 manufactured by Shimadzu Corporation), and the wire direction of the evaluation piezoelectric element. (Frequency 1 Hz, stress 1N to 3N) was vibrated, and the stress was repeatedly applied. While carrying out such a test, the voltage signal generated between the core wire 1 (inner electrode) and the conductor layer 7 (outer electrode) was measured over time as a piezoelectric output. Representatively, the measurement results of the piezoelectric elements of Example 1 and Comparative Example 1 are shown in FIGS. 2 and 3, respectively.
　実施例１の圧電素子では、図２に示すように、圧電出力のピークピーク値（最大値と最小値との差）は９５．００ｍＶｐ－ｐであった。更に、図２から理解されるように、圧電出力に周期的な波形が観測され、１周期が概ね１秒間、即ち、１Ｈｚの周波数であった。この圧電出力の周波数は、加振の周波数に一致していたことから、周波数の追従が確認された。従って、実施例１の圧電素子は、優れた圧電応答を示した。 In the piezoelectric element of Example 1, as shown in FIG. 2, the peak peak value (difference between the maximum value and the minimum value) of the piezoelectric output was 95.00 mVpp. Further, as can be seen from FIG. 2, a periodic waveform was observed in the piezoelectric output, and one period was about 1 second, that is, a frequency of 1 Hz. Since the frequency of this piezoelectric output matched the frequency of excitation, it was confirmed that the frequency was followed. Therefore, the piezoelectric element of Example 1 showed an excellent piezoelectric response.
　実施例２の圧電素子では、圧電出力のピークピーク値は６５．８０ｍＶｐ－ｐであり、周波数の追従が確認された。実施例３の圧電素子では、圧電出力のピークピーク値は６５．８３ｍＶｐ－ｐであり、周波数の追従が確認された。従って、実施例２および３の圧電素子は、優れた圧電応答を示した。 In the piezoelectric element of Example 2, the peak value of the piezoelectric output was 65.80 mVpp-p, and frequency tracking was confirmed. In the piezoelectric element of Example 3, the peak value of the piezoelectric output was 65.83 mVp-p, and frequency tracking was confirmed. Therefore, the piezoelectric elements of Examples 2 and 3 showed excellent piezoelectric responses.
　これに対して、比較例１の圧電素子では、図３に示すように、圧電出力のピークピーク値は４４．１５ｍＶｐ－ｐであった。しかしながら、図３から理解されるように、圧電出力に周期的な波形は観測されず、周波数の追従がないことが確認された。従って、比較例１の圧電素子は、圧電応答を示さなかった。 On the other hand, in the piezoelectric element of Comparative Example 1, as shown in FIG. 3, the peak value of the piezoelectric output was 44.15 mVp-p. However, as can be understood from FIG. 3, no periodic waveform was observed in the piezoelectric output, and it was confirmed that there was no frequency tracking. Therefore, the piezoelectric element of Comparative Example 1 did not show a piezoelectric response.
　本発明の圧電素子は、各種のセンサおよび／またはアクチュエータとして利用可能である。本発明を限定するものではないが、本発明の圧電素子は、柔軟性に優れ、小さい外形断面寸法（代表的には線径）で実現でき、例えば、圧電素子に外力が加えられたときにこれを検知することが可能な感圧センサ等として利用され得る。 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 has excellent flexibility and can be realized with a small external cross-sectional dimension (typically, wire diameter). For example, when an external force is applied to the piezoelectric element. It can be used as a pressure-sensitive sensor or the like capable of detecting this.
　本願は、２０１９年１１月２７日付けで日本国にて出願された特願２０１９－２１４３６８に基づく優先権を主張し、その記載内容の全てが、参照することにより本明細書に援用される。 The present application claims priority based on Japanese Patent Application No. 2019-214368 filed in Japan on November 27, 2019, all of which are incorporated herein by reference.
　　１　芯線（内側電極）
　　３　無機圧電体層
　　５　有機保護層
　　７　導電体層（外側電極）
　　９　絶縁体層（シース）
　　１０　圧電素子 1 Core wire (inner electrode)
3 Inorganic piezoelectric layer 5 Organic protective layer 7 Conductor layer (outer electrode)
9 Insulator layer (sheath)
10 Piezoelectric element

Claims (8)

  1. 　導電性の表面を有する芯線と、
    　前記芯線を被覆する無機圧電体層と、
    　前記無機圧電体層を被覆する有機保護層と、
    　前記有機保護層を被覆する導電体層と
    を含み、前記有機保護層が、０．１～１００μｍの厚さを有し、前記芯線および前記導電体層が、それらの間に前記無機圧電体層および前記有機保護層が介挿された電極としてそれぞれ機能する、圧電素子。     A core wire with a conductive surface and
    The inorganic piezoelectric layer that covers the core wire and
    An organic protective layer that covers the inorganic piezoelectric layer and
    The organic protective layer includes a conductor layer covering the organic protective layer, the organic protective layer has a thickness of 0.1 to 100 μm, and the core wire and the conductor layer are between them. And a piezoelectric element that functions as an electrode with the organic protective layer inserted.
  2. 　前記有機保護層が、２００℃以上の耐熱温度を有する材料から成る、請求項１に記載の圧電素子。 The piezoelectric element according to claim 1, wherein the organic protective layer is made of a material having a heat resistant temperature of 200 ° C. or higher.
  3. 　前記有機保護層が、フッ素樹脂、イミド系樹脂、芳香族系ポリマー、液晶ポリマー、ポリカーボネート、シリコーン樹脂およびエポキシ樹脂からなる群より選択される少なくとも１つを含む、請求項１または２に記載の圧電素子。 The piezoelectric layer according to claim 1 or 2, wherein the organic protective layer contains at least one selected from the group consisting of fluororesins, imide resins, aromatic polymers, liquid crystal polymers, polycarbonates, silicone resins and epoxy resins. element.
  4. 　前記無機圧電体層が、ウルツ鉱型結晶構造を有する圧電セラミックスから成る、請求項１～３のいずれか１項に記載の圧電素子。 The piezoelectric element according to any one of claims 1 to 3, wherein the inorganic piezoelectric layer is made of piezoelectric ceramics having a wurtzite crystal structure.
  5. 　前記ウルツ鉱型結晶構造を有する圧電セラミックスが、酸化亜鉛および窒化アルミニウムの少なくとも一方を含む、請求項４に記載の圧電素子。 The piezoelectric element according to claim 4, wherein the piezoelectric ceramic having the wurtzite crystal structure contains at least one of zinc oxide and aluminum nitride.
  6. 　前記無機圧電体層が、０．０１～３．００μｍの厚さを有する、請求項１～５のいずれか１項に記載の圧電素子。 The piezoelectric element according to any one of claims 1 to 5, wherein the inorganic piezoelectric layer has a thickness of 0.01 to 3.00 μm.
  7. 　前記導電体層を被覆する絶縁体層を更に含む、請求項１～６のいずれか１項に記載の圧電素子。 The piezoelectric element according to any one of claims 1 to 6, further comprising an insulator layer that covers the conductor layer.
  8. 　請求項１～７のいずれか１項に記載の圧電素子を含む圧電装置。 A piezoelectric device including the piezoelectric element according to any one of claims 1 to 7.
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