WO2021095511A1 - 圧電素子 - Google Patents
圧電素子 Download PDFInfo
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- WO2021095511A1 WO2021095511A1 PCT/JP2020/040245 JP2020040245W WO2021095511A1 WO 2021095511 A1 WO2021095511 A1 WO 2021095511A1 JP 2020040245 W JP2020040245 W JP 2020040245W WO 2021095511 A1 WO2021095511 A1 WO 2021095511A1
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- layer
- piezoelectric
- protective layer
- conductive foil
- piezoelectric element
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Images
Classifications
-
- 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
- H10N30/852—Composite materials, e.g. having 1-3 or 2-2 type connectivity
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R17/00—Piezoelectric transducers; Electrostrictive transducers
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R17/00—Piezoelectric transducers; Electrostrictive transducers
- H04R17/005—Piezoelectric transducers; Electrostrictive transducers using a piezoelectric polymer
-
- 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
- H10N30/80—Constructional details
- H10N30/85—Piezoelectric or electrostrictive active materials
-
- 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
- H10N30/87—Electrodes or interconnections, e.g. leads or terminals
-
- 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
- H10N30/87—Electrodes or interconnections, e.g. leads or terminals
- H10N30/875—Further connection or lead arrangements, e.g. flexible wiring boards, terminal pins
-
- 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
- H10N30/883—Additional insulation means preventing electrical, physical or chemical damage, e.g. protective coatings
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R17/00—Piezoelectric transducers; Electrostrictive transducers
- H04R17/02—Microphones
- H04R17/025—Microphones using a piezoelectric polymer
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2217/00—Details of magnetostrictive, piezoelectric, or electrostrictive transducers covered by H04R15/00 or H04R17/00 but not provided for in any of their subgroups
- H04R2217/01—Non-planar magnetostrictive, piezoelectric or electrostrictive benders
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2499/00—Aspects covered by H04R or H04S not otherwise provided for in their subgroups
- H04R2499/10—General applications
- H04R2499/11—Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's
Definitions
- the present invention relates to a piezoelectric element.
- the speakers used in these thin displays are also required to be lighter and thinner. Further, in a flexible display having flexibility, flexibility is also required in order to integrate into the flexible display without impairing lightness and flexibility. As such a lightweight, thin and flexible speaker, it is considered to adopt a sheet-shaped piezoelectric element (electroacoustic conversion film) having a property of expanding and contracting in response to an applied voltage.
- a sheet-shaped piezoelectric element electroacoustic conversion film
- Patent Document 1 has a thin film electrode formed on both sides of a dielectric layer, a dielectric layer (piezoelectric layer), and a protective layer formed on the surfaces of both thin film electrodes. Further, an electroacoustic conversion film having at least one of the protective layers having a thin layer portion having a film thickness thinner than that of the peripheral portion is described.
- a vapor-deposited film having a thickness of 1 ⁇ m or less is suitable for the electrode layer.
- Patent Document 1 describes a configuration in which a recess is provided in the protective layer, a conductive material is inserted into the recess, and a lead wire for electrically connecting the electrode layer and an external device is connected to the conductive material. Has been done. It is described that this makes it possible to ensure the electrical connection between the electrode layer and the lead-out wiring, and that the electrode layer is completely covered with a protective layer, so that deterioration of the electrode layer due to oxidation or the like can be prevented. ing.
- the electrode layer in the portion where the protective layer is removed is easily torn by a slight external force. Therefore, when a conductive material is inserted into the hole of the protective layer to provide an electrical contact, when an external force is directly applied to the conductive material, an external force is applied to the electrode layer due to a force that separates the conductive material from the electrode layer. As a result, there is a problem that the electrode layer is torn and poor connection to the electrode layer occurs.
- An object of the present invention is to solve such a problem of the prior art, and to provide a piezoelectric element capable of preventing the occurrence of poor connection to the electrode layer.
- a piezoelectric element having a piezoelectric layer, electrode layers formed on both sides of the piezoelectric layer, and a protective layer laminated on the surface of the electrode layer opposite to the surface on the piezoelectric layer side. It has a conductive foil laminated on the surface opposite to the electrode layer of the protective layer.
- the protective layer has holes that penetrate from the surface to the electrode layer.
- the conductive foil has an opening at a position overlapping the hole of the protective layer in the surface direction.
- a piezoelectric element having a conductive member that is inserted into a through hole of a covering member and electrically connected to a conductive foil. [2] The piezoelectric element according to [1], wherein the covering member covers the entire surface of the filling member and the conductive foil.
- the protective layer has a plurality of holes and has a plurality of holes. Filling members are provided in each of the plurality of holes.
- a piezoelectric element capable of preventing the occurrence of poor connection to the electrode layer.
- FIG. 1 is a cross-sectional view taken along the line AA of FIG.
- FIG. 1 is a cross-sectional view taken along the line BB of FIG.
- the description of the constituent elements described below may be based on typical embodiments of the present invention, but the present invention is not limited to such embodiments.
- the numerical range represented by using "-" means a range including the numerical values before and after "-" as the lower limit value and the upper limit value.
- the piezoelectric element of the present invention is A piezoelectric element having a piezoelectric layer, electrode layers formed on both sides of the piezoelectric layer, and a protective layer laminated on the surface of the electrode layer opposite to the surface on the piezoelectric layer side. It has a conductive foil laminated on the surface opposite to the electrode layer of the protective layer.
- the protective layer has holes that penetrate from the surface to the electrode layer.
- the conductive foil has an opening at a position overlapping the hole of the protective layer in the surface direction.
- a filling member made of a conductive material which is formed on at least a part of the surface of the conductive foil from the hole of the protective layer and the opening of the conductive foil and is electrically connected to the electrode layer and the conductive foil. It has a filling member and a covering member that covers the conductive foil, The covering member has a through hole at a position that does not overlap with the filling member in the surface direction.
- a piezoelectric element having a conductive member that is inserted into a through hole of a covering member and electrically connected to a conductive foil.
- FIG. 1 shows a plan view schematically showing an example of the piezoelectric element of the present invention.
- FIG. 2 shows a cross-sectional view taken along the line AA of the piezoelectric element of FIG.
- FIG. 3 shows an enlarged cross-sectional view of a part of the BB line cross section and the CC line cross section of the piezoelectric element of FIG.
- the cross section taken along the line BB is shown on the upper side of the figure
- the cross section taken along the line CC is shown on the lower side of the figure.
- the piezoelectric element 10 shown in FIGS. 1 to 3 has a piezoelectric layer 20 which is a sheet-like material having piezoelectricity, a lower electrode 24 laminated on one surface of the piezoelectric layer 20, and a lower electrode laminated on the lower electrode 24.
- the conductive member 76 is a sheet-like material having piezoelectricity
- the piezoelectric layer 20 shown in FIG. 1 contains piezoelectric particles 36 in a matrix 34 containing a polymer material.
- the lower electrode 24 and the upper electrode 26 are the electrode layers in the present invention.
- the lower protective layer 28 and the upper protective layer 30 are protective layers in the present invention.
- the conductive foil 72 with an adhesive layer is the conductive foil in the present invention.
- the adhesive layer of the conductive foil 72 with an adhesive layer is a layer for adhering the protective layer and the conductive foil, but the conductive foil is not limited to the conductive foil with an adhesive layer, and an adhesive or an adhesive may be used. It may be used and adhered to the protective layer.
- the pressure-sensitive adhesive or adhesive is not particularly limited as long as the protective layer and the conductive foil can be adhered to each other, but acrylic-based, urethane-based, and silicon-based pressure-sensitive adhesives (adhesives) are preferably used.
- the piezoelectric element 10 piezoelectric layer 20
- the piezoelectric element 10 is polarized in the thickness direction as a preferred embodiment.
- the upper protective layer 30 has a hole 31 penetrating from the surface to the upper electrode 26. That is, the hole portion 31 is formed so as to penetrate the upper protective layer 30 from the surface opposite to the upper electrode 26 to the interface on the upper electrode 26 side. As shown in FIG. 1, the hole portion 31 is formed in the vicinity of the end portion of the upper protective layer 30 in the plane direction.
- the lower protective layer 28 has a hole 29 penetrating from the surface to the lower electrode 24. That is, the hole 29 is formed so as to penetrate the lower protective layer 28 from the surface opposite to the lower electrode 24 to the interface on the lower electrode 24 side. As shown in FIG. 1, the hole 29 is formed in the vicinity of the end of the lower protective layer 28 in the plane direction.
- a conductive foil 72 with an adhesive layer is attached to the surface of the upper protective layer 30 near the hole 31.
- the conductive foil 72 with an adhesive layer is provided with an adhesive layer on one surface of the conductive foil, and is attached to the upper protective layer 30 by laminating the adhesive layer side toward the upper protective layer 30. ..
- the conductive foil 72 with the adhesive layer has an opening 73 at a position overlapping the hole 31 of the upper protective layer 30 in the surface direction.
- the filling member 70 is made of a conductive material, is filled in the holes 31 and the openings 73, and is formed so as to cover a part of the surface of the conductive foil 72 with an adhesive layer.
- the filling member 70 is in contact with the upper electrode 26 in the hole 31 and is electrically connected to the upper electrode 26. Further, the filling member 70 is connected to the conductive foil 72 with an adhesive layer on the surface of the conductive foil 72 with an adhesive layer.
- the covering member 74 is an insulating sheet-like member, and is laminated so as to cover at least a part of the filling member 70 and the conductive foil 72 with an adhesive layer in the plane direction. In the example shown in FIG. 1, the covering member 74 is laminated so as to cover the entire surface of the filling member 70 and the conductive foil 72 with the adhesive layer.
- the covering member 74 has a through hole 75 penetrating in the thickness direction at a position where it does not overlap with the filling member 70 in the surface direction and overlaps with the conductive foil 72 with an adhesive layer.
- the conductive member 76 is a sheet-shaped or wire-shaped member having conductivity.
- the conductive member 76 is inserted into the through hole 75 of the covering member 74 and electrically connected to the conductive foil 72 with an adhesive layer.
- a conductive foil 72 with an adhesive layer having an opening 73 is attached to the surface of the lower protective layer 28 near the hole 29, and the filling member 70 has the hole 31 and the opening.
- the portion 73 is filled, the covering member 74 is laminated so as to cover at least a part of the filling member 70 and the conductive foil 72 with the adhesive layer, and the conductive member 76 is inserted into the through hole 75 of the covering member 74. It is electrically connected to the conductive foil 72 with an adhesive layer.
- the conductive member 76 is electrically connected to the conductive foil 72 with the adhesive layer, and the conductive foil 72 with the adhesive layer is electrically connected to the filling member 70. Is electrically connected to the electrode layer. Therefore, the conductive member 76 can be used as a drawer wiring, and the wiring can be connected to the conductive member 76. Alternatively, the conductive member 76 can be used as wiring.
- the electrode layer in the portion where the protective layer is removed is easily torn by a slight external force. Therefore, when a conductive material is inserted into the hole of the protective layer to provide an electrical contact, when an external force is directly applied to the conductive material, an external force is applied to the electrode layer due to a force that separates the conductive material from the electrode layer. As a result, there is a problem that the electrode layer is torn and poor connection to the electrode layer occurs.
- the filling member filled in the hole of the protective layer is covered with the covering member, it is possible to prevent the filling member from being pulled by an external force. Therefore, it is possible to prevent the electrode layer from being broken due to an external force applied to the electrode layer due to the force of peeling the conductive material and the electrode layer. Further, since the filling member and the hole portion are covered with the covering member, it is possible to suppress the oxidation of the filling member and / or the electrode layer. Further, since the covering member has a through hole and the conductive member is electrically connected to the electrode layer via the conductive foil with the adhesive layer and the filling member in the through hole, the electrical connection to the electrode layer is made. Can be done reliably.
- the shape of the opening surface of the holes 29 and 31 of the protective layer is not limited, and may be various shapes such as a circular shape, an elliptical shape, a rectangular shape, a polygonal shape, and an indefinite shape.
- a circular shape is preferable from the viewpoint of ease of formation and the like.
- the size of the opening surface of the hole is not particularly limited as long as the electrical connection with the filling member 70 can be secured and the piezoelectric element can operate properly.
- the equivalent circle diameter of the opening surface of the hole is preferably 0.5 mm to 20 mm, more preferably 1.5 mm to 5 mm, still more preferably 2 mm to 3 mm.
- the shape of the opening surface of the opening 73 of the conductive foil 72 with an adhesive layer is not limited, and may be various shapes such as a circular shape, an elliptical shape, a rectangular shape, a polygonal shape, and an indefinite shape. A circular shape is preferable from the viewpoint of ease of formation and the like.
- the size of the opening surface of the opening 73 is not particularly limited as long as the electrical connection with the filling member 70 can be secured and the piezoelectric element can operate properly. From the viewpoint of ensuring electrical connection, the opening 73 preferably has a shape and size including the hole 31. For example, when the diameter of the hole 31 is 3 mm, the equivalent circle diameter of the opening surface of the opening 73 is preferably 4 mm to 20 mm, more preferably 5 mm to 15 mm, still more preferably 5 mm to 12 mm.
- the size (size in the plane direction) of the filling member 70 on the conductive foil 72 with the adhesive layer is not particularly limited as long as the electrical connection with the conductive foil 72 with the adhesive layer can be secured.
- the equivalent circle diameter of the filling member 70 on the conductive foil 72 with the adhesive layer is preferably 1 mm to 40 mm, more preferably 2 mm to 30 mm, still more preferably 2 mm to 20 mm.
- the shape of the opening surface of the through hole 75 of the covering member 74 is not limited, and may be various shapes such as a circular shape, an elliptical shape, a rectangular shape, a polygonal shape, and an indefinite shape.
- the size of the opening surface of the through hole 75 is not particularly limited as long as the electrical connection with the conductive member 76 can be secured and the piezoelectric element can operate properly.
- the area of the opening surface of the through hole 75 should be sufficiently larger than the total area of the holes 31. For example, when the diameter of the hole 31 is 3 mm and the number of holes is 5, the total area of the holes is about 141 mm 2 , but the size of the opening surface of the through hole 75 is 150 mm 2 or more. Is preferable, 150 mm 2 to 1000 mm 2 is more preferable, and 200 mm 2 to 700 mm 2 is further preferable.
- the configuration has one hole portion 31 and one filling member 70, but the present invention is not limited to this, and a plurality of hole portions 31 and filling member 70 may be provided.
- the opening 73 of the conductive foil 72 with an adhesive layer is preferably sized to include the two or more holes 31, and the opening 73 is formed. It is preferable that each hole 31 is filled with the filling member 70 through the holes 31.
- the conductive foil 72 with an adhesive layer has a plurality of openings 73 corresponding to each holes 31, and each hole 31 passes through each opening 73. May be configured to be filled with the filling member 70.
- the conductive member 76 electrically connected to the upper electrode 26 via the filling member 70 and the conductive foil 72 with the adhesive layer on the upper protective layer 30 side, and the lower protective layer 28.
- the conductive member 76 which is electrically connected to the lower electrode 24 via the filling member 70 and the conductive foil 72 with an adhesive layer on the side, is preferably arranged so that the positions in the plane direction do not overlap. As a result, it is possible to prevent the conductive member 76 on the upper electrode side 26 and the conductive member 76 on the lower electrode side 24 from coming into contact with each other to cause a short circuit.
- such a piezoelectric element 10 generates (reproduces) sound due to vibration in response to an electric signal in various acoustic devices (audio equipment) such as speakers, microphones, and pickups used in musical instruments such as guitars. It is also used to convert sound vibrations into electrical signals.
- the piezoelectric element can also be used for a pressure sensitive sensor, a power generation element, and the like.
- the piezoelectric element 10 when used for a speaker, it may be used as a sound generated by the vibration of the film-shaped piezoelectric element 10 itself.
- the piezoelectric element 10 may be attached to a diaphragm and used as an exciter that vibrates the diaphragm by the vibration of the piezoelectric element 10 to generate sound.
- each component of the piezoelectric element of the present invention will be described.
- the piezoelectric layer 20 may be a layer made of a known piezoelectric material.
- the piezoelectric layer 20 is preferably a polymer composite piezoelectric body containing the piezoelectric particles 36 in the matrix 34 containing the polymer material.
- the material of the matrix 34 (matrix and binder) of the polymer composite piezoelectric body constituting the piezoelectric layer 20 it is preferable to use a polymer material having viscoelasticity at room temperature.
- the piezoelectric element 10 of the present invention is suitably used for a speaker having flexibility such as a speaker for a flexible display.
- the polymer composite piezoelectric body (piezoelectric layer 20) used for the flexible speaker preferably has the following requirements. Therefore, it is preferable to use a polymer material having viscoelasticity at room temperature as a material satisfying the following requirements.
- room temperature refers to a temperature range of about 0 to 50 ° C.
- (Ii) Sound quality A speaker vibrates piezoelectric particles at a frequency in the audio band of 20 Hz to 20 kHz, and the vibration energy causes the entire polymer composite piezoelectric body (piezoelectric element) to vibrate as a unit, thereby reproducing sound. To. Therefore, in order to increase the transmission efficiency of vibration energy, the polymer composite piezoelectric material is required to have an appropriate hardness. Further, if the frequency characteristic of the speaker is smooth, the amount of change in sound quality when the minimum resonance frequency changes with the change in curvature also becomes small. Therefore, the loss tangent of the polymer composite piezoelectric material is required to be moderately large.
- the polymer composite piezoelectric material is required to behave hard against vibrations of 20 Hz to 20 kHz and soft against vibrations of several Hz or less. Further, the loss tangent of the polymer composite piezoelectric body is required to be appropriately large for vibrations of all frequencies of 20 kHz or less.
- polymer solids have a viscoelastic relaxation mechanism, and large-scale molecular motion decreases (Relaxation) or maximizes loss elastic modulus (absorption) as the temperature rises or the frequency decreases.
- Relaxation large-scale molecular motion decreases
- absorption loss elastic modulus
- main dispersion the relaxation caused by the micro-Brownian motion of the molecular chain in the amorphous region is called main dispersion, and a very large relaxation phenomenon is observed.
- the temperature at which this main dispersion occurs is the glass transition point (Tg), and the viscoelastic relaxation mechanism appears most prominently.
- the polymer composite piezoelectric body (piezoelectric layer 20), by using a polymer material having a glass transition point at room temperature, in other words, a polymer material having viscoelasticity at room temperature, for vibration of 20 Hz to 20 kHz.
- a polymer composite piezoelectric material that is hard and behaves softly against slow vibrations of several Hz or less is realized.
- the polymer material having viscoelasticity at room temperature various known materials can be used as long as they have dielectric properties.
- a polymer material having a maximum loss tangent value of 0.5 or more at a frequency of 1 Hz by a dynamic viscoelasticity test at room temperature, that is, 0 ° C. to 50 ° C. is used.
- the polymer material preferably has a storage elastic modulus (E') at a frequency of 1 Hz measured by dynamic viscoelasticity measurement of 100 MPa or more at 0 ° C. and 10 MPa or less at 50 ° C.
- E' storage elastic modulus
- the polymer material has a relative permittivity of 10 or more at 25 ° C.
- a voltage is applied to the polymer composite piezoelectric body, a higher electric field is applied to the piezoelectric particles in the matrix, so that a large amount of deformation can be expected.
- the polymer material has a relative permittivity of 10 or less at 25 ° C.
- polymer material satisfying such conditions examples include cyanoethylated polyvinyl alcohol (cyanoethylated PVA), polyvinyl acetate, polyvinylidene chloride core acrylonitrile, polystyrene-vinyl polyisoprene block copolymer, polyvinyl methyl ketone, and polybutyl. Methacrylate and the like are exemplified. Further, as these polymer materials, commercially available products such as Hybler 5127 (manufactured by Kuraray Co., Ltd.) can also be preferably used.
- Hybler 5127 manufactured by Kuraray Co., Ltd.
- the polymer material it is preferable to use a material having a cyanoethyl group, and it is particularly preferable to use cyanoethylated PVA.
- these polymer materials may use only 1 type, and may use a plurality of types in combination (mixing).
- a plurality of polymer materials may be used in combination, if necessary. That is, in addition to the polymer material having viscoelasticity at room temperature, other dielectric polymer materials may be added to the matrix 34 for the purpose of adjusting the dielectric properties and mechanical properties. ..
- dielectric polymer material examples include polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, and vinylidene fluoride-trifluoroethylene copolymer.
- fluoropolymers such as polyvinylidene fluoride-tetrafluoroethylene copolymer, vinylidene cyanide-vinyl acetate copolymer, cyanoethyl cellulose, cyanoethyl hydroxysaccharose, cyanoethyl hydroxycellulose, cyanoethyl hydroxypurrane, cyanoethyl methacrylate, cyanoethyl acrylate, cyanoethyl.
- Cyano groups such as hydroxyethyl cellulose, cyanoethyl amylose, cyanoethyl hydroxypropyl cellulose, cyanoethyl dihydroxypropyl cellulose, cyanoethyl hydroxypropyl amylose, cyanoethyl polyacrylamide, cyanoethyl polyacrylate, cyanoethyl pullulan, cyanoethyl polyhydroxymethylene, cyanoethyl glycidol pullulan, cyanoethyl saccharose and cyanoethyl sorbitol.
- a polymer having a cyanoethyl group a synthetic rubber such as a nitrile rubber or a chloroprene rubber, and the like are exemplified.
- a polymer material having a cyanoethyl group is preferably used.
- the dielectric polymer material added in addition to the polymer material having viscoelasticity at room temperature such as cyanoethylated PVA is not limited to one type, and a plurality of types are added. You may.
- the matrix 34 contains a thermoplastic resin such as vinyl chloride resin, polyethylene, polystyrene, methacrylic resin, polybutene, and isobutylene, and phenol for the purpose of adjusting the glass transition point.
- a resin, a urea resin, a melamine resin, an alkyd resin, and a thermosetting resin such as mica may be added.
- a tackifier such as rosin ester, rosin, terpene, terpene phenol, and petroleum resin may be added.
- the amount of the material other than the viscoelastic polymer material such as cyanoethylated PVA added to the matrix 34 of the piezoelectric layer 20 is not particularly limited, but is 30% by mass or less in proportion to the matrix 34. It is preferable to do so. As a result, the characteristics of the polymer material to be added can be exhibited without impairing the viscoelastic relaxation mechanism in the matrix 34, so that the dielectric constant can be increased, the heat resistance can be improved, and the adhesion to the piezoelectric particles 36 and the electrode layer can be improved. In this respect, favorable results can be obtained.
- the piezoelectric layer 20 is a polymer composite piezoelectric body containing piezoelectric particles 36 in such a matrix 34.
- the piezoelectric particles 36 are made of ceramic particles having a perovskite-type or wurtzite-type crystal structure. Examples of the ceramic particles constituting the piezoelectric particles 36 include lead zirconate titanate (PZT), lead lanthanate lanthanate titanate (PLZT), barium titanate (BaTIO 3 ), zinc oxide (ZnO), and zinc oxide (ZnO). Examples thereof include a solid solution (BFBT) of barium titanate and bismuth ferrite (BiFe 3). Only one type of these piezoelectric particles 36 may be used, or a plurality of types may be used in combination (mixed).
- the particle size of the piezoelectric particles 36 is not limited, and may be appropriately selected depending on the size and application of the polymer composite piezoelectric body (piezoelectric element 10).
- the particle size of the piezoelectric particles 36 is preferably 1 to 10 ⁇ m. By setting the particle size of the piezoelectric particles 36 in this range, it is possible to obtain preferable results in that the polymer composite piezoelectric body (piezoelectric element 10) can achieve both high piezoelectric characteristics and flexibility.
- the piezoelectric particles 36 in the piezoelectric layer 20 are uniformly and regularly dispersed in the matrix 34, but the present invention is not limited to this. That is, the piezoelectric particles 36 in the piezoelectric layer 20 may be irregularly dispersed in the matrix 34 as long as they are preferably uniformly dispersed.
- the amount ratio of the matrix 34 and the piezoelectric particles 36 in the piezoelectric layer 20 is not limited, and the size and thickness of the piezoelectric layer 20 in the plane direction and the polymer It may be appropriately set according to the use of the composite piezoelectric body, the characteristics required for the polymer composite piezoelectric body, and the like.
- the volume fraction of the piezoelectric particles 36 in the piezoelectric layer 20 is preferably 30 to 80%, more preferably 50% or more, and therefore more preferably 50 to 80%.
- the thickness of the piezoelectric layer 20 is not limited, and may be appropriately set according to the application of the polymer composite piezoelectric body, the characteristics required for the polymer composite piezoelectric body, and the like.
- the thickness of the piezoelectric layer 20 is preferably 10 to 300 ⁇ m, more preferably 20 to 200 ⁇ m, and even more preferably 30 to 150 ⁇ m.
- the piezoelectric element 10 of the illustrated example has a lower electrode 24 on one surface of the piezoelectric layer 20, a lower protective layer 28 on the surface thereof, and an upper portion on the other surface of the piezoelectric layer 20. It has an electrode 26 and has an upper protective layer 30 on its surface.
- the upper electrode 26 and the lower electrode 24 form an electrode pair.
- the piezoelectric element 10 has a configuration in which both sides of the piezoelectric layer 20 are sandwiched between electrode pairs, that is, the upper electrode 26 and the lower electrode 24, and the laminate is sandwiched between the lower protective layer 28 and the upper protective layer 30. Have. In this way, in the piezoelectric element 10, the region held by the upper electrode 26 and the lower electrode 24 is expanded and contracted according to the applied voltage.
- the lower protective layer 28 and the upper protective layer 30 cover the upper electrode 26 and the lower electrode 24, and also play a role of imparting appropriate rigidity and mechanical strength to the piezoelectric layer 20. That is, in the piezoelectric element 10, the piezoelectric layer 20 composed of the matrix 34 and the piezoelectric particles 36 exhibits extremely excellent flexibility with respect to slow bending deformation, but on the other hand, depending on the application, rigidity or Mechanical strength may be insufficient.
- the piezoelectric element 10 is provided with a lower protective layer 28 and an upper protective layer 30 to supplement the piezoelectric element 10.
- the lower protective layer 28 and the upper protective layer 30 are not limited, and various sheet-like materials can be used, and as an example, various resin films are preferably exemplified.
- various resin films are preferably exemplified.
- PET polyethylene terephthalate
- PP polypropylene
- PS polystyrene
- PC polycarbonate
- PPS polyphenylene sulfide
- PMMA polymethylmethacrylate
- PET polyethylene terephthalate
- PET polypropylene
- PS polystyrene
- PC polycarbonate
- PPS polyphenylene sulfide
- PMMA polymethylmethacrylate
- PEI Polyetherimide
- PI Polystyrene
- PEN Polyethylene Naphthalate
- TAC Triacetyl Cellulose
- a resin film made of a cyclic olefin resin or the like are preferably used.
- the thickness of the lower protective layer 28 and the upper protective layer 30 there is also no limitation on the thickness of the lower protective layer 28 and the upper protective layer 30. Further, the thicknesses of the lower protective layer 28 and the upper protective layer 30 are basically the same, but may be different. Here, if the rigidity of the lower protective layer 28 and the upper protective layer 30 is too high, not only the expansion and contraction of the piezoelectric layer 20 is restricted, but also the flexibility is impaired. Therefore, the thinner the lower protective layer 28 and the upper protective layer 30, the more advantageous it is, except when mechanical strength and good handleability as a sheet-like material are required.
- the thickness of the lower protective layer 28 and the upper protective layer 30 is preferably 3 ⁇ m to 100 ⁇ m, more preferably 3 ⁇ m to 50 ⁇ m, further preferably 3 ⁇ m to 30 ⁇ m, and particularly preferably 4 ⁇ m to 10 ⁇ m.
- the thickness of the lower protective layer 28 and the upper protective layer 30 is twice or less the thickness of the piezoelectric layer 20, it is possible to ensure both rigidity and appropriate flexibility. In terms of points, favorable results can be obtained.
- the thickness of the piezoelectric layer 20 is 50 ⁇ m and the lower protective layer 28 and the upper protective layer 30 are made of PET
- the thickness of the lower protective layer 28 and the upper protective layer 30 is preferably 100 ⁇ m or less, more preferably 50 ⁇ m or less. , 25 ⁇ m or less is more preferable.
- a lower electrode 24 is formed between the piezoelectric layer 20 and the lower protective layer 28, and an upper electrode 26 is formed between the piezoelectric layer 20 and the upper protective layer 30.
- the lower electrode 24 and the upper electrode 26 are provided to apply a driving voltage to the piezoelectric layer 20.
- the materials for forming the lower electrode 24 and the upper electrode 26 are not limited, and various conductors can be used. Specifically, alloys such as carbon, palladium, iron, tin, aluminum, nickel, platinum, gold, silver, copper, titanium, chromium and molybdenum, laminates and composites of these metals and alloys, and Examples thereof include indium tin oxide. Among them, copper, aluminum, gold, silver, platinum, and indium tin oxide are preferably exemplified as the lower electrode 24 and the upper electrode 26.
- a vapor phase deposition method such as vacuum deposition and sputtering, a film formation by plating, and a foil formed of the above materials
- Various known methods such as a method of sticking can be used.
- thin films such as copper and aluminum formed by vacuum deposition are preferably used as the lower electrode 24 and the upper electrode 26 because the flexibility of the piezoelectric element 10 can be ensured.
- a copper thin film produced by vacuum deposition is preferably used.
- the thickness of the lower electrode 24 and the upper electrode 26 There is no limitation on the thickness of the lower electrode 24 and the upper electrode 26. Further, the thicknesses of the lower electrode 24 and the upper electrode 26 are basically the same, but may be different.
- the lower electrode 24 and the upper electrode 26 are preferably thin film electrodes.
- the thickness of the lower electrode 24 and the upper electrode 26 is thinner than that of the protective layer, preferably 0.05 ⁇ m to 10 ⁇ m, more preferably 0.05 ⁇ m to 5 ⁇ m, further preferably 0.08 ⁇ m to 3 ⁇ m, and 0.1 ⁇ m to 2 ⁇ m. Especially preferable.
- the piezoelectric element 10 if the product of the thickness of the lower electrode 24 and the upper electrode 26 and the Young's modulus is less than the product of the thickness of the lower protective layer 28 and the upper protective layer 30 and the Young's modulus, the piezoelectric element 10 is flexible. It is suitable because it does not significantly impair the properties.
- the lower protective layer 28 and the upper protective layer 30 are made of PET (Young's modulus: about 6.2 GPa) and the lower electrode 24 and the upper electrode 26 are made of copper (Young's modulus: about 130 GPa)
- the lower protective layer 28 is used.
- the thickness of the lower electrode 24 and the upper electrode 26 is preferably 1.2 ⁇ m or less, more preferably 0.3 ⁇ m or less, and particularly preferably 0.1 ⁇ m or less.
- the piezoelectric element 10 preferably has a maximum value of loss tangent (Tan ⁇ ) at a frequency of 1 Hz as measured by dynamic viscoelasticity measurement at room temperature, and more preferably has a maximum value of 0.1 or more at room temperature.
- Tan ⁇ loss tangent
- the piezoelectric element 10 preferably has a storage elastic modulus (E') at a frequency of 1 Hz measured by dynamic viscoelasticity measurement of 10 GPa to 30 GPa at 0 ° C. and 1 GPa to 10 GPa at 50 ° C.
- E' storage elastic modulus
- the piezoelectric element 10 can have a large frequency dispersion in the storage elastic modulus (E'). That is, it can behave hard for vibrations of 20 Hz to 20 kHz and soft for vibrations of several Hz or less.
- the product of the thickness and the storage elastic modulus at a frequency of 1 Hz by dynamic viscoelasticity measurement is 1.0 ⁇ 10 5 to 2.0 ⁇ 10 6 (1.0E + 05 to 2. It is preferably 0E + 06) N / m, and preferably 1.0 ⁇ 10 5 to 1.0 ⁇ 10 6 (1.0E + 05 to 1.0E + 06) N / m at 50 ° C.
- the piezoelectric layer 20 can be provided with appropriate rigidity and mechanical strength as long as the flexibility and acoustic characteristics are not impaired.
- the piezoelectric element 10 preferably has a loss tangent of 0.05 or more at 25 ° C. and a frequency of 1 kHz in the master curve obtained from the dynamic viscoelasticity measurement. The same applies to the piezoelectric layer 20 with respect to this condition. As a result, the frequency characteristics of the speaker using the piezoelectric element 10 become smooth, and the change in sound quality when the minimum resonance frequency f 0 changes with the change in the curvature of the speaker can be reduced.
- the storage elastic modulus (Young's modulus) and the loss tangent of the piezoelectric element 10 and the piezoelectric layer 20 may be measured by a known method.
- the measurement may be performed using a dynamic viscoelasticity measuring device DMS6100 manufactured by SII Nanotechnology Inc. (manufactured by SII Nanotechnology Inc.).
- the measurement frequency is 0.1 Hz to 20 Hz (0.1 Hz, 0.2 Hz, 0.5 Hz, 1 Hz, 2 Hz, 5 Hz, 10 Hz and 20 Hz)
- the measurement temperature is -50 to 150 ° C.
- the temperature rise rate is 2 ° C./min (in a nitrogen atmosphere)
- the sample size is 40 mm ⁇ 10 mm (including the clamp region)
- the inter-chuck distance is 20 mm, respectively.
- the filling member 70 is a cured liquid conductive material.
- As the conductive material used as the filling member 70 silver paste, metal nanoparticle ink (Ag, Au) and the like can be used.
- the viscosity of the conductive material is preferably 10 mPa ⁇ s (millipascal seconds) to 20 Pa ⁇ s (pascal seconds), more preferably 0.1 Pa ⁇ s to 15 Pa ⁇ s, and further preferably 0.5 Pa ⁇ s to 10 Pa ⁇ s. preferable.
- the specific resistance of the filling member 70 after curing is preferably 1 ⁇ 10 ⁇ -6 ( ⁇ ⁇ cm) to 1 ⁇ 10 ⁇ -3 ( ⁇ ⁇ cm), and 1 ⁇ 10 ⁇ -6 ( ⁇ ⁇ cm) to 8 ⁇ .
- 10 ⁇ -4 ( ⁇ ⁇ cm) is more preferable, and 1 ⁇ 10 ⁇ -6 ( ⁇ ⁇ cm) to 1 ⁇ 10 ⁇ -4 ( ⁇ ⁇ cm) is even more preferable.
- the conductive foil 72 with an adhesive layer has an adhesive layer on one surface of a conductive sheet which is a sheet-like material formed of a conductive metal material. Copper, aluminum, gold, silver and the like are preferably exemplified as the material of the conductive sheet.
- the adhesive layer of the conductive foil 72 with an adhesive layer may be such that the conductive sheet and the protective layer can be adhered to each other.
- a conductive acrylic adhesive material is preferably exemplified.
- the shape and size of the conductive foil 72 with an adhesive layer are not particularly limited.
- the shape and size of the conductive foil 72 with an adhesive layer are such that the opening 73 can be formed, the filling member 70 can be formed, the conductive member 76 can be connected, and the drive of the piezoelectric element 10 is not constrained. Goodbye.
- the thickness of the conductive foil 72 with an adhesive layer is not particularly limited as long as it can secure electrical connection with the filling member 70 and the conductive member 76 and does not restrain the drive of the piezoelectric element 10. Good.
- the covering member 74 is an insulating sheet-like member.
- Examples of the material of the covering member 74 include polyimide and heat-resistant PET.
- the shape and size of the covering member 74 are not particularly limited.
- the shape and size of the covering member 74 can prevent the filling member 70 from being pulled by covering at least a part of the filling member 70 and the conductive foil 72 with an adhesive layer, and a through hole is provided at a position not overlapping with the filling member 70.
- the shape and size may be such that the drive of the piezoelectric element 10 is not restricted.
- the covering member 74 preferably covers the entire surface of the filling member 70, and preferably covers the entire surface of the conductive foil 72 with an adhesive layer.
- the thickness of the covering member 74 is not particularly limited as long as it can suppress the filling member 70 from being pulled and does not restrain the drive of the piezoelectric element 10.
- the conductive member 76 is a sheet-like or wire-like material formed of a conductive metal material.
- a conductive metal material As the material of the conductive member 76, copper, aluminum, gold, silver and the like are preferably exemplified.
- the shape and size of the conductive member 76 are not particularly limited.
- the shape and size of the conductive member 76 may be any shape and size that can be electrically connected to the conductive foil 72 with an adhesive layer in the through hole 75 of the covering member 74 and can be used as a drawer electrode.
- the method of connecting the conductive member 76 to the conductive foil 72 with an adhesive layer is not particularly limited, and known methods such as a method using solder, a method using a conductive adhesive, and welding can be used.
- a sheet-like object 10a in which the lower electrode 24 is formed on the lower protective layer 28 is prepared.
- the sheet-like material 10a may be produced by forming a copper thin film or the like as the lower electrode 24 on the surface of the lower protective layer 28 by vacuum deposition, sputtering, plating or the like.
- the lower protective layer 28 with a separator temporary support
- PET or the like having a thickness of 25 ⁇ m to 100 ⁇ m can be used.
- the separator may be removed after the upper electrode 26 and the upper protective layer 30 are thermocompression-bonded and before any member is laminated on the lower protective layer 28.
- a polymer material to be a matrix material is dissolved in an organic solvent, and piezoelectric particles 36 such as PZT particles are added and stirred to prepare a dispersed coating material.
- organic solvent there are no restrictions on the organic solvent other than the above substances, and various organic solvents can be used.
- the paint is cast (applied) to the sheet-like material 10a to evaporate the organic solvent and dry it.
- a laminated body 10b having a lower electrode 24 on the lower protective layer 28 and forming a piezoelectric layer 20 on the lower electrode 24 is produced.
- the lower electrode 24 is an electrode on the base material side when the piezoelectric layer 20 is applied, and does not indicate the vertical positional relationship in the laminated body.
- a dielectric polymer material may be added to the matrix 34 in addition to the viscoelastic material such as cyanoethylated PVA.
- the polymer materials to be added to the paint described above may be dissolved.
- the laminated body 10b having the lower electrode 24 on the lower protective layer 28 and forming the piezoelectric layer 20 on the lower electrode 24 is produced, it is preferable to perform the polarization treatment (polling) of the piezoelectric layer 20.
- the method for polarization treatment of the piezoelectric layer 20 is not limited, and known methods can be used.
- a calendar treatment may be performed in which the surface of the piezoelectric layer 20 is smoothed by using a heating roller or the like. By performing this calendar processing, the thermocompression bonding process described later can be smoothly performed.
- a sheet-like material 10c in which the upper electrode 26 is formed on the upper protective layer 30 is prepared.
- the sheet-like material 10c may be produced by forming a copper thin film or the like as the upper electrode 26 on the surface of the upper protective layer 30 by vacuum deposition, sputtering, plating or the like.
- the upper electrode 26 is directed toward the piezoelectric layer 20, and the sheet-like material 10c is laminated on the laminated body 10b that has completed the polarization treatment of the piezoelectric layer 20. Further, the laminate of the laminate 10b and the sheet-like material 10c is thermocompression-bonded with a heating press device or a heating roller or the like so as to sandwich the upper protective layer 30 and the lower protective layer 28.
- a laminated body in which an electrode layer and a protective layer are laminated on both sides of the piezoelectric layer 20 is produced.
- the produced laminate may be cut into a desired shape according to various uses.
- Such a laminate may be produced using a cut sheet-like sheet, or may be produced by roll-to-roll (hereinafter, also referred to as RtoR).
- a hole is provided in the protective layer of the laminated body, the conductive foil with the adhesive layer is laminated, the filling member is filled and covered with the covering member, and the conductive member is connected to the conductive foil with the adhesive layer.
- a hole 31 is formed in the upper protective layer 30, and a hole 29 is formed in the lower protective layer 28.
- the hole 31 is formed by laser processing (carbon dioxide laser, etc.) or by pressing to make a cut in the protective layer in the depth direction (for example, the thickness of the protective layer is 10 ⁇ m and the thickness of the electrode layer is 2 ⁇ m.
- the protective layer is formed by making a circular cut from 8 to 9.5 ⁇ m in the thickness direction of the protective layer and then peeling off the circular portion), the protective layer may be peeled off.
- the conductive foil 72 with the adhesive layer is laminated on the protective layer as shown in FIG.
- the conductive foil 72 with the adhesive layer may be laminated at a position where the opening 73 overlaps the hole of the protective layer.
- the conductive foil 72 with an adhesive layer on which the opening 73 is not formed may be laminated so as to cover the holes, and then the conductive foil 72 with an adhesive layer may be provided with the opening 73.
- a liquid conductive material 84 is applied from the opening 73 to the hole of the conductive foil 72 with the adhesive layer.
- the conductive material 84 is applied so as to protrude from the opening 73 to the surface of the conductive foil 72 with the adhesive layer.
- silk screen printing, dropping with a dispenser, coating with a brush, and the like can be used as a coating method of the conductive material 84.
- the conductive material 84 is cured to form the filling member 70.
- the method for curing the conductive material 84 may be a method according to the conductive material 84.
- heat drying and the like can be mentioned.
- the covering member 74 is laminated on the filling member 70 and the conductive foil 72 with an adhesive layer.
- the covering member 74 may be laminated at a position where the through hole 75 does not overlap with the filling member 70 and overlaps with the conductive foil 72 with an adhesive layer. Good.
- the through hole 75 may be provided at a position overlapping the conductive foil 72 with the adhesive layer. Good.
- the covering member 74 may be adhered to the conductive foil 72 with an adhesive layer or a protective layer with an adhesive, an adhesive, or the like.
- the conductive member 76 is electrically connected to the conductive foil 72 with an adhesive layer in the through hole 75 of the covering member 74.
- the conductive member 76 and the conductive foil 72 with an adhesive layer may be connected by solder, a conductive adhesive, or the like.
- the piezoelectric element of the present invention is produced by the above steps.
- the piezoelectric element 10 when a voltage is applied to the lower electrode 24 and the upper electrode 26, the piezoelectric particles 36 expand and contract in the polarization direction according to the applied voltage. As a result, the piezoelectric element 10 (piezoelectric layer 20) shrinks in the thickness direction. At the same time, the piezoelectric element 10 expands and contracts in the in-plane direction due to the pore ratio. This expansion and contraction is about 0.01 to 0.1%. As described above, it expands and contracts isotropically in all directions in the in-plane direction. As described above, the thickness of the piezoelectric layer 20 is preferably about 10 to 300 ⁇ m. Therefore, the expansion and contraction in the thickness direction is very small, about 0.3 ⁇ m at the maximum.
- the piezoelectric element 10 that is, the piezoelectric layer 20, has a size much larger than the thickness in the plane direction. Therefore, for example, if the length of the piezoelectric element 10 is 20 cm, the piezoelectric element 10 expands and contracts by a maximum of about 0.2 mm when a voltage is applied. Further, when pressure is applied to the piezoelectric element 10, electric power is generated by the action of the piezoelectric particles 36. By utilizing this, the piezoelectric element 10 can be used for various purposes such as a speaker, a microphone, and a pressure-sensitive sensor, as described above.
- a general piezoelectric element made of a polymer material such as PVDF has in-plane anisotropy in the piezoelectric characteristics, and has anisotropy in the amount of expansion and contraction in the plane direction when a voltage is applied.
- the piezoelectric layer made of a polymer composite piezoelectric material containing piezoelectric particles in a matrix containing a polymer material has no in-plane anisotropy in the piezoelectric characteristics and is isotropic in all directions in the in-plane direction. Expands and contracts.
- the piezoelectric element 10 that expands and contracts isotropically and two-dimensionally, it is possible to vibrate with a larger force than when a general piezoelectric element such as PVDF that expands and contracts greatly in only one direction is laminated. , Can generate louder and more beautiful sound.
- the configuration is such that one piezoelectric element 10 is provided, but the present invention is not limited to this, and a plurality of piezoelectric elements 10 of the present invention may be laminated. Further, the piezoelectric element 10 of the present invention may have a long shape and may be folded back once or more, preferably a plurality of times in the longitudinal direction to form a stack of a plurality of layers of the piezoelectric element 10.
- Piezoelectric element 10a 10c Sheet-like material 10b Laminated body 20 Piezoelectric layer 24 Lower electrode 26 Upper electrode 28 Lower protective layer 29, 31 Holes 30 Upper protective layer 34 Matrix 36 Piezoelectric particles 70 Filling member 72 Conductive foil with adhesive layer 73 Opening 74 Covering member 75 Through hole 76 Conductive member 84 Conductive material
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Abstract
Description
しかしながら、蒸着膜のような薄い電極層は、電気音響変換フィルムの面外に引き出すことは困難である。また、蒸着膜のような薄い電極を、配線との接続のために外部に剥き出しにして、この状態で保管すると、保管環境によっては電極が酸化して、導電性が低下してしまう。
[1] 圧電層、圧電層の両面に形成される電極層、および、電極層の、圧電層側の面とは反対側の面に積層される保護層を有する圧電素子であって、
保護層の電極層とは反対側の面に積層される導電箔を有し、
保護層は、表面から電極層まで貫通する孔部を有し、
導電箔は、面方向において、保護層の孔部と重複する位置に開口部を有し、
保護層の孔部および導電箔の開口部内から導電箔の表面の少なくとも一部に形成され、電極層と導電箔とに電気的に接続される、導電性材料からなる充填部材と、
充填部材および導電箔の少なくとも一部を覆う被覆部材を有し、
被覆部材は、面方向において、充填部材と重複しない位置に貫通孔を有し、
被覆部材の貫通孔に挿入されて導電箔と電気的に接続される導電性部材、を有する圧電素子。
[2] 被覆部材は、充填部材および導電箔の全面を覆っている[1]に記載の圧電素子。
[3] 保護層は、孔部を複数有し、
複数の孔部それぞれに充填部材が設けられており、
複数の充填部材が、導電箔の表面において連結している[1]または[2]に記載の圧電素子。
[4] 保護層の厚みは3μm~100μmである[1]~[3]のいずれかに記載の圧電素子。
[5] 電極層の厚みは0.05μm~10μmである[1]~[4]のいずれかに記載の圧電素子。
[6] 圧電層は、高分子材料を含むマトリックス中に圧電体粒子を含む高分子複合圧電体からなる[1]~[5]のいずれかに記載の圧電素子。
なお、本明細書において、「~」を用いて表される数値範囲は、「~」の前後に記載される数値を下限値および上限値として含む範囲を意味する。
本発明の圧電素子は、
圧電層、圧電層の両面に形成される電極層、および、電極層の、圧電層側の面とは反対側の面に積層される保護層を有する圧電素子であって、
保護層の電極層とは反対側の面に積層される導電箔を有し、
保護層は、表面から電極層まで貫通する孔部を有し、
導電箔は、面方向において、保護層の孔部と重複する位置に開口部を有し、
保護層の孔部および導電箔の開口部内から導電箔の表面の少なくとも一部に形成され、電極層と導電箔とに電気的に接続される、導電性材料からなる充填部材と、
充填部材および導電箔を覆う被覆部材を有し、
被覆部材は、面方向において、充填部材と重複しない位置に貫通孔を有し、
被覆部材の貫通孔に挿入されて導電箔と電気的に接続される導電性部材、を有する圧電素子である。
なお、粘着層付き導電箔72の粘着層は、保護層と導電箔とを接着するための層であるが、導電箔は、粘着層付き導電箔に限定はされず、粘着剤あるいは接着剤を用いて保護層に接着されてもよい。その際、粘着剤あるいは接着剤は、保護層と導電箔とを接着できれば特に限定はされないが、アクリル系、ウレタン系、および、シリコン系等の粘着剤(接着剤)が好適に用いられる。
後述するが、圧電素子10(圧電層20)は、好ましい態様として、厚さ方向に分極されている。
同様に、下部保護層28は表面から下部電極24まで貫通する孔部29を有する。すなわち、孔部29は、下部電極24とは反対側の表面から下部電極24側の界面まで下部保護層28を貫通して形成されている。図1に示すように、孔部29は、面方向において、下部保護層28の端部近傍に形成されている。
図3に示すように、粘着層付き導電箔72には、面方向において、上部保護層30の孔部31と重複する位置に開口部73を有する。
また、孔部の開口面の大きさとしては、充填部材70との電気的接続が確保でき、圧電素子が適正に動作できる大きさであれば特に限定はない。孔部の開口面の円相当直径は、0.5mm~20mmが好ましく、1.5mm~5mmがより好ましく、2mm~3mmがさらに好ましい。
また、開口部73の開口面の大きさとしては、充填部材70との電気的接続が確保でき、圧電素子が適正に動作できる大きさであれば特に限定はない。電気的接続を確保する観点から、開口部73は、孔部31を包含する形状および大きさであるのが好ましい。
例えば、孔部31の直径が3mmの場合には、開口部73の開口面の円相当直径は、4mm~20mmが好ましく、5mm~15mmがより好ましく、5mm~12mmがさらに好ましい。
また、貫通孔75の開口面の大きさとしては、導電性部材76との電気的接続が確保でき、圧電素子が適正に動作できる大きさであれば特に限定はない。好ましい形態としては、貫通孔75の開口面の面積は孔部31の合計面積よりも十分大きいほうがよい。例えば、孔部31の直径を3mmとし、孔部の数を5個とした場合には穴部の総面積は約141mm2であるが、貫通孔75の開口面の大きさは、150mm2以上が好ましく、150mm2~1000mm2がより好ましく、200mm2~700mm2がさらに好ましい。
例えば、2つ以上の孔部31を有する場合には、粘着層付き導電箔72の開口部73は、2つ以上の孔部31を包含する大きさであるのが好ましく、この開口部73を介して各孔部31に充填部材70が充填されるのが好ましい。また、2つ以上の孔部31を有する場合には、粘着層付き導電箔72は各孔部31に対応して複数の開口部73を有し、各開口部73を介して各孔部31に充填部材70が充填される構成であってもよい。
また、圧電素子は、これ以外にも、感圧センサおよび発電素子等にも利用可能である。
以下、本発明の圧電素子の各構成要素について説明する。
圧電層20は、公知の圧電体からなる層であればよい。本発明において、圧電層20は、高分子材料を含むマトリックス34に、圧電体粒子36を含む高分子複合圧電体であるのが好ましい。
本発明の圧電素子10は、フレキシブルディスプレイ用のスピーカーなど、フレキシブル性を有するスピーカー等に好適に用いられる。ここで、フレキシブル性を有するスピーカーに用いられる高分子複合圧電体(圧電層20)は、次の用件を具備したものであるのが好ましい。従って、以下の要件を具備する材料として、常温で粘弾性を有する高分子材料を用いるのが好ましい。
なお、本明細書において、「常温」とは、0~50℃程度の温度域を指す。
例えば、携帯用として新聞や雑誌のように書類感覚で緩く撓めた状態で把持する場合、絶えず外部から、数Hz以下の比較的ゆっくりとした、大きな曲げ変形を受けることになる。この時、高分子複合圧電体が硬いと、その分大きな曲げ応力が発生し、マトリックスと圧電体粒子との界面で亀裂が発生し、やがて破壊に繋がる恐れがある。従って、高分子複合圧電体には適度な柔らかさが求められる。また、歪みエネルギーを熱として外部へ拡散できれば応力を緩和することができる。従って、高分子複合圧電体の損失正接が適度に大きいことが求められる。
(ii) 音質
スピーカーは、20Hz~20kHzのオーディオ帯域の周波数で圧電体粒子を振動させ、その振動エネルギーによって高分子複合圧電体(圧電素子)全体が一体となって振動することで音が再生される。従って、振動エネルギーの伝達効率を高めるために高分子複合圧電体には適度な硬さが求められる。また、スピーカーの周波数特性が平滑であれば、曲率の変化に伴い最低共振周波数が変化した際の音質の変化量も小さくなる。従って、高分子複合圧電体の損失正接は適度に大きいことが求められる。
高分子複合圧電体(圧電層20)において、ガラス転移点が常温にある高分子材料、言い換えると、常温で粘弾性を有する高分子材料をマトリックスに用いることで、20Hz~20kHzの振動に対しては硬く、数Hz以下の遅い振動に対しては柔らかく振舞う高分子複合圧電体が実現する。特に、この振舞いが好適に発現する等の点で、周波数1Hzでのガラス転移温度が常温、すなわち、0~50℃にある高分子材料を、高分子複合圧電体のマトリックスに用いるのが好ましい。
これにより、高分子複合圧電体が外力によってゆっくりと曲げられた際に、最大曲げモーメント部におけるマトリックスと圧電体粒子との界面の応力集中が緩和され、良好な可撓性が得られる。
これにより、高分子複合圧電体が外力によってゆっくりと曲げられた際に発生する曲げモーメントが低減できると同時に、20Hz~20kHzの音響振動に対しては硬く振る舞うことができる。
しかしながら、その反面、良好な耐湿性の確保等を考慮すると、高分子材料は、比誘電率が25℃において10以下であるのも、好適である。
なお、これらの高分子材料は、1種のみを用いてもよく、複数種を併用(混合)して用いてもよい。
すなわち、マトリックス34には、誘電特性や機械的特性の調節等を目的として、常温で粘弾性を有する高分子材料に加え、必要に応じて、その他の誘電性高分子材料を添加しても良い。
中でも、シアノエチル基を有する高分子材料は、好適に利用される。
また、圧電層20のマトリックス34において、シアノエチル化PVA等の常温で粘弾性を有する高分子材料に加えて添加される誘電性高分子材料は、1種に限定はされず、複数種を添加してもよい。
さらに、粘着性を向上する目的で、ロジンエステル、ロジン、テルペン、テルペンフェノール、および、石油樹脂等の粘着付与剤を添加しても良い。
これにより、マトリックス34における粘弾性緩和機構を損なうことなく、添加する高分子材料の特性を発現できるため、高誘電率化、耐熱性の向上、圧電体粒子36および電極層との密着性向上等の点で好ましい結果を得ることができる。
圧電体粒子36は、ペロブスカイト型またはウルツ鉱型の結晶構造を有するセラミックス粒子からなるものである。
圧電体粒子36を構成するセラミックス粒子としては、例えば、チタン酸ジルコン酸鉛(PZT)、チタン酸ジルコン酸ランタン酸鉛(PLZT)、チタン酸バリウム(BaTiO3)、酸化亜鉛(ZnO)、および、チタン酸バリウムとビスマスフェライト(BiFe3)との固溶体(BFBT)等が例示される。
これらの圧電体粒子36は、1種のみを用いてもよく、複数種を併用(混合)して用いてもよい。
圧電体粒子36の粒径は、1~10μmが好ましい。圧電体粒子36の粒径をこの範囲とすることにより、高分子複合圧電体(圧電素子10)が高い圧電特性とフレキシビリティとを両立できる等の点で好ましい結果を得ることができる。
すなわち、圧電層20中の圧電体粒子36は、好ましくは均一に分散されていれば、マトリックス34中に不規則に分散されていてもよい。
圧電層20中における圧電体粒子36の体積分率は、30~80%が好ましく、50%以上がより好ましく、従って、50~80%とするのが、さらに好ましい。
マトリックス34と圧電体粒子36との量比を上記範囲とすることにより、高い圧電特性と可撓性とを両立できる等の点で好ましい結果を得ることができる。
圧電層20の厚さは、10~300μmが好ましく、20~200μmがより好ましく、30~150μmがさらに好ましい。
圧電層20の厚さを、上記範囲とすることにより、剛性の確保と適度な柔軟性との両立等の点で好ましい結果を得ることができる。
図1に示すように、図示例の圧電素子10は、圧電層20の一面に、下部電極24を有し、その表面に下部保護層28を有し、圧電層20の他方の面に、上部電極26を有し、その表面に上部保護層30を有してなる構成を有する。ここで、上部電極26と下部電極24とが電極対を形成する。
このように、圧電素子10において、上部電極26および下部電極24で挾持された領域は、印加された電圧に応じて伸縮される。
中でも、優れた機械的特性および耐熱性を有するなどの理由により、ポリエチレンテレフタレート(PET)、ポリプロピレン(PP)、ポリスチレン(PS)、ポリカーボネート(PC)、ポリフェニレンサルファイト(PPS)、ポリメチルメタクリレート(PMMA)、ポリエーテルイミド(PEI)、ポリイミド(PI)、ポリエチレンナフタレート(PEN)、トリアセチルセルロース(TAC)、および、環状オレフィン系樹脂等からなる樹脂フィルムが、好適に利用される。
ここで、下部保護層28および上部保護層30の剛性が高過ぎると、圧電層20の伸縮を拘束するばかりか、可撓性も損なわれる。そのため、機械的強度やシート状物としての良好なハンドリング性が要求される場合を除けば、下部保護層28および上部保護層30は、薄いほど有利である。
ここで、圧電素子10においては、下部保護層28および上部保護層30の厚さが、圧電層20の厚さの2倍以下であれば、剛性の確保と適度な柔軟性との両立等の点で好ましい結果を得ることができる。
例えば、圧電層20の厚さが50μmで下部保護層28および上部保護層30がPETからなる場合、下部保護層28および上部保護層30の厚さは、100μm以下が好ましく、50μm以下がより好ましく、25μm以下がさらに好ましい。
下部電極24および上部電極26は、圧電層20に駆動電圧を印加するために設けられる。
下部電極24および上部電極26の厚さには、制限はない。また、下部電極24および上部電極26の厚さは、基本的に同じであるが、異なってもよい。
例えば、下部保護層28および上部保護層30がPET(ヤング率:約6.2GPa)で、下部電極24および上部電極26が銅(ヤング率:約130GPa)からなる組み合わせの場合、下部保護層28および上部保護層30の厚さが25μmだとすると、下部電極24および上部電極26の厚さは、1.2μm以下が好ましく、0.3μm以下がより好ましく、中でも0.1μm以下とするのが好ましい。
これにより、圧電素子10が外部から数Hz以下の比較的ゆっくりとした、大きな曲げ変形を受けたとしても、歪みエネルギーを効果的に熱として外部へ拡散できるため、マトリックスと圧電体粒子との界面で亀裂が発生するのを防ぐことができる。
これにより、圧電素子10が貯蔵弾性率(E’)に大きな周波数分散を有することができる。すなわち、20Hz~20kHzの振動に対しては硬く、数Hz以下の振動に対しては柔らかく振る舞うことができる。
これにより、圧電素子10が可撓性および音響特性を損なわない範囲で、適度な剛性と機械的強度を備えることができる。
これにより、圧電素子10を用いたスピーカーの周波数特性が平滑になり、スピーカーの曲率の変化に伴い最低共振周波数f0が変化した際の音質の変化を小さくできる。
測定条件としては、一例として、測定周波数は0.1Hz~20Hz(0.1Hz、0.2Hz、0.5Hz、1Hz、2Hz、5Hz、10Hzおよび20Hz)が、測定温度は-50~150℃が、昇温速度は2℃/分(窒素雰囲気中)が、サンプルサイズは40mm×10mm(クランプ領域込み)が、チャック間距離は20mmが、それぞれ、例示される。
充填部材70は、液体状の導電性材料を硬化させたものである。
充填部材70として用いられる導電性材料としては、銀ペースト、金属ナノ粒子インク(Ag、Au)等が利用可能である。
粘着層付き導電箔72は、導電性を有する金属材料で形成されるシート状物である導電性シートの一方の表面に粘着層を有するものである。導電性シートの材料は、銅、アルミニウム、金および銀等が好適に例示される。
粘着層付き導電箔72の粘着層は、導電性シートと保護層とを接着できるものであればよい。粘着層の材料は、導電性アクリル粘着材が好適に例示される。
被覆部材74は、絶縁性のシート状の部材である。
被覆部材74の材料は、ポリイミド、耐熱PET等が例示される。
前述のとおり、被覆部材74は、充填部材70の全面を覆うのが好ましく、また、粘着層付き導電箔72の全面を覆うのが好ましい。
導電性部材76は、導電性を有する金属材料で形成されるシート状あるいはワイヤー状の物である。導電性部材76の材料は、銅、アルミニウム、金および銀等が好適に例示される。
下部保護層28が非常に薄く、ハンドリング性が悪い時などは、必要に応じて、セパレータ(仮支持体)付きの下部保護層28を用いても良い。なお、セパレータとしては、厚さ25μm~100μmのPET等を用いることができる。セパレータは、上部電極26および上部保護層30を熱圧着した後、下部保護層28に何らかの部材を積層する前に、取り除けばよい。
上記物質以外の有機溶媒としては制限はなく各種の有機溶媒が利用可能である。
マトリックス34に、これらの高分子材料を添加する際には、上述した塗料に添加する高分子材料を溶解すればよい。
なお、この分極処理の前に、圧電層20の表面を加熱ローラ等を用いて平滑化する、カレンダー処理を施してもよい。このカレンダー処理を施すことで、後述する熱圧着工程がスムーズに行える。
さらに、この積層体10bとシート状物10cとの積層体を、上部保護層30と下部保護層28とを挟持するようにして、加熱プレス装置や加熱ローラ対等で熱圧着する。
このような積層体は、カットシート状のシート状物を用いて製造を行っても良いし、ロール・トゥ・ロール(Roll to Roll 以下、RtoRともいう)によって作製されてもよい。
具体的には、まず、図7に示すように、上部保護層30に孔部31を形成し、また、下部保護層28に孔部29を形成する。
孔部31の形成は、レーザー加工(炭酸ガスレーザーなど)による方法、プレス加工により保護層に深さ方向に切り込みを入れて(例えば、保護層の厚みが10μm、電極層の厚みが2μmとしたとき、保護層の厚み方向に8~9.5μmまで切り込みを円形にいれて、その後その円形部を引きはがすことにより形成する)から保護層を剥離させる方法等によって行えばよい。
あるいは、開口部73が形成されていない粘着層付き導電箔72を孔部を覆うように積層した後に、粘着層付き導電箔72に開口部73を設けてもよい。
導電性材料84の塗布方法としては、シルクスクリーン印刷、ディスペンサーによる滴下、刷毛による塗布などが利用可能である。
導電性材料84の硬化方法は、導電性材料84に応じた方法で行えばよい。例えば、導電性材料84の硬化方法としては、加熱乾燥等が挙げられる。
あるいは、貫通孔75が形成されていない被覆部材74を充填部材70および粘着層付き導電箔72を覆うように積層した後に、粘着層付き導電箔72と重複する位置に貫通孔75を設けてもよい。
前述のとおり、導電性部材76と粘着層付き導電箔72とは、ハンダ、導電性接着剤等によって接続されればよい。
上述したように、圧電層20の厚さは、好ましくは10~300μm程度である。従って、厚さ方向の伸縮は、最大でも0.3μm程度と非常に小さい。
これに対して、圧電素子10すなわち圧電層20は、面方向には、厚さよりもはるかに大きなサイズを有する。従って、例えば、圧電素子10の長さが20cmであれば、電圧の印加によって、最大で0.2mm程度、圧電素子10は伸縮する。
また、圧電素子10に圧力を加えると、圧電体粒子36の作用によって、電力を発生する。
これを利用することで、圧電素子10は、上述のように、スピーカー、マイクロフォン、および、感圧センサ等の各種の用途に利用可能である。
これに対して、高分子材料を含むマトリックス中に圧電体粒子を含む高分子複合圧電体からなる圧電層は、圧電特性に面内異方性がなく、面内方向では全方向に等方的に伸縮する。
このような等方的に二次元的に伸縮する圧電素子10によれば、一方向にしか大きく伸縮しないPVDF等の一般的な圧電素子を積層した場合に比べ、大きな力で振動することができ、より大きく、かつ、美しい音を発生できる。
以上から本発明の効果は明らかである。
10a、10c シート状物
10b 積層体
20 圧電層
24 下部電極
26 上部電極
28 下部保護層
29、31 孔部
30 上部保護層
34 マトリックス
36 圧電体粒子
70 充填部材
72 粘着層付き導電箔
73 開口部
74 被覆部材
75 貫通孔
76 導電性部材
84 導電性材料
Claims (6)
- 圧電層、前記圧電層の両面に形成される電極層、および、前記電極層の、前記圧電層側の面とは反対側の面に積層される保護層を有する圧電素子であって、
前記保護層の前記電極層とは反対側の面に積層される導電箔を有し、
前記保護層は、表面から前記電極層まで貫通する孔部を有し、
前記導電箔は、面方向において、前記保護層の前記孔部と重複する位置に開口部を有し、
前記保護層の前記孔部および前記導電箔の開口部内から前記導電箔の表面の少なくとも一部に形成され、前記電極層と前記導電箔とに電気的に接続される、導電性材料からなる充填部材と、
前記充填部材および前記導電箔の少なくとも一部を覆う被覆部材を有し、
前記被覆部材は、面方向において、前記充填部材と重複しない位置に貫通孔を有し、
前記被覆部材の前記貫通孔に挿入されて前記導電箔と電気的に接続される導電性部材、を有する圧電素子。 - 前記被覆部材は、前記充填部材および前記導電箔の全面を覆っている請求項1に記載の圧電素子。
- 前記保護層は、前記孔部を複数有し、
複数の前記孔部それぞれに前記充填部材が設けられており、
前記複数の充填部材が、前記導電箔の表面において連結している請求項1または2に記載の圧電素子。 - 前記保護層の厚みは3μm~100μmである請求項1~3のいずれか一項に記載の圧電素子。
- 前記電極層の厚みは0.05μm~10μmである請求項1~4のいずれか一項に記載の圧電素子。
- 前記圧電層は、高分子材料を含むマトリックス中に圧電体粒子を含む高分子複合圧電体からなる請求項1~5のいずれか一項に記載の圧電素子。
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