WO2023149073A1 - Piezoelectric device - Google Patents

Piezoelectric device Download PDF

Info

Publication number
WO2023149073A1
WO2023149073A1 PCT/JP2022/045101 JP2022045101W WO2023149073A1 WO 2023149073 A1 WO2023149073 A1 WO 2023149073A1 JP 2022045101 W JP2022045101 W JP 2022045101W WO 2023149073 A1 WO2023149073 A1 WO 2023149073A1
Authority
WO
WIPO (PCT)
Prior art keywords
piezoelectric
piezoelectric film
layer
film
laminated
Prior art date
Application number
PCT/JP2022/045101
Other languages
French (fr)
Japanese (ja)
Inventor
哲 三好
Original Assignee
富士フイルム株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 富士フイルム株式会社 filed Critical 富士フイルム株式会社
Publication of WO2023149073A1 publication Critical patent/WO2023149073A1/en

Links

Images

Classifications

    • 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
    • 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
    • H10N30/01—Manufacture or treatment
    • H10N30/04—Treatments to modify a piezoelectric or electrostrictive property, e.g. polarisation characteristics, vibration characteristics or mode tuning
    • H10N30/045—Treatments to modify a piezoelectric or electrostrictive property, e.g. polarisation characteristics, vibration characteristics or mode tuning by polarising
    • 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
    • H10N30/01—Manufacture or treatment
    • H10N30/07—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base
    • 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
    • H10N30/80—Constructional details
    • H10N30/85—Piezoelectric or electrostrictive active materials

Definitions

  • the present invention relates to piezoelectric devices.
  • a flexible display has superiority in lightness, thinness, flexibility, etc., compared with a display using a conventional glass substrate, and can be provided on a curved surface such as a cylinder.
  • PDAs personal digital assistants
  • a speaker which is an acoustic device for generating sound
  • a conventional speaker shape a so-called funnel-like cone shape, a spherical dome shape, or the like is generally used.
  • the speaker is externally attached, it is troublesome to carry, and it is difficult to install it on a curved wall, which may spoil the aesthetic appearance.
  • the piezoelectric film (electroacoustic conversion film) described in Patent Document 1 is known as a speaker that can be integrated into a flexible display without impairing its light weight and flexibility.
  • the piezoelectric film of Patent Document 1 is formed on both surfaces of a polymer composite piezoelectric body in which piezoelectric particles are dispersed in a viscoelastic matrix made of a polymer material having viscoelasticity at room temperature, and a polymer composite piezoelectric body. It has a thin film electrode and a protective layer formed on the surface of the thin film electrode, and the temperature range of 0 to 50 ° C. where the loss tangent at a frequency of 1 Hz by dynamic viscoelasticity measurement is 0.1 or more. exists in
  • the piezoelectric film described in Patent Document 1 exhibits excellent flexibility and sound quality at room temperature (0 to 50°C).
  • the environment in which the speaker is used is not limited to normal temperature, and depending on the country, region, and place of use, it may be used in an environment below freezing.
  • Patent Document 2 discloses a polymer composite piezoelectric body in which piezoelectric particles are dispersed in a matrix containing a polymer material, and electrode layers formed on both sides of the polymer composite piezoelectric body.
  • the loss tangent at a frequency of 1 Hz by dynamic viscoelasticity measurement has a maximum value of 0.1 or more in the temperature range of -80 ° C. or more and less than 0 ° C., and the value at 0 ° C. is 0.05.
  • a piezoelectric film is thus described.
  • the piezoelectric film described in Patent Document 2 uses, as a matrix, a polymer composite piezoelectric material mixed with a polymer material having viscoelasticity at a low temperature (below freezing point), thereby moving the central position of the glass transition point of the matrix below freezing point. , which provides good flexibility below freezing.
  • the piezoelectric film described in Patent Document 2 has good flexibility below freezing, but the flexibility at room temperature is inferior to that at below freezing. Therefore, it was found that there is a problem that sufficient reliability cannot be obtained when the piezoelectric film is repeatedly bent with a small radius of curvature.
  • the object of the present invention is to solve the problems of the prior art, and to provide a piezoelectric device that has excellent flexibility in both normal temperature and sub-zero environments.
  • the present invention has the following configurations. [1] It has a piezoelectric layer containing piezoelectric particles in a matrix containing a polymer material and electrode layers formed on both sides of the piezoelectric layer, and the loss tangent at a frequency of 1 Hz is measured by dynamic viscoelasticity measurement. A piezoelectric film having a maximum value of 0.1 or more in a temperature range of 0 ° C. to 50 ° C., and A piezoelectric device comprising a heating mechanism for heating a piezoelectric film.
  • the heating mechanism includes a temperature sensor and a controller, The piezoelectric device according to [1], wherein the controller drives the heating mechanism to heat the piezoelectric film according to the temperature measured by the temperature sensor.
  • the piezoelectric device according to [4], wherein the sinusoidal AC signal has an effective voltage of 1 Vrms to 10 Vrms.
  • the piezoelectric device according to any one of [1] to [8], wherein the piezoelectric film has a protective layer provided on the surface of the electrode layer.
  • the piezoelectric device according to any one of [1] to [9], wherein the piezoelectric layer is polarized in the thickness direction.
  • the piezoelectric device according to any one of [1] to [10], which has a lead wire for connecting the electrode layer and the signal source.
  • the piezoelectric device according to any one of [1] to [11], wherein a plurality of piezoelectric films are laminated.
  • FIG. 4 is a perspective view schematically showing another example of the piezoelectric device of the present invention
  • 3 is a cross-sectional view of the piezoelectric device shown in FIG. 2
  • FIG. 4 is a diagram schematically showing another example of the piezoelectric device of the present invention
  • FIG. 4 is a diagram schematically showing another example of the piezoelectric device of the present invention
  • FIG. 6 is a partially enlarged view of FIG. 5
  • 6 is a diagram for explaining another example of the configuration of a piezoelectric film included in the piezoelectric device shown in FIG. 5;
  • FIG. 4 is a perspective view schematically showing another example of the piezoelectric device of the present invention
  • 3 is a cross-sectional view of the piezoelectric device shown in FIG. 2
  • FIG. 4 is a diagram schematically showing another example of the piezoelectric device of the present invention
  • FIG. 4 is a diagram schematically showing another example of the piezoelectric device of the present invention
  • FIG. 6 is
  • FIG. 6 is a diagram for explaining another example of the configuration of a piezoelectric film included in the piezoelectric device shown in FIG. 5;
  • FIG. FIG. 4 is a diagram schematically showing an example of a piezoelectric film included in the piezoelectric device of the present invention; It is a conceptual diagram for explaining an example of a method of manufacturing a piezoelectric film. It is a conceptual diagram for explaining an example of a method of manufacturing a piezoelectric film. It is a conceptual diagram for explaining an example of a method of manufacturing a piezoelectric film. It is a conceptual diagram for explaining an example of a method of manufacturing a piezoelectric film.
  • a numerical range represented by "-" means a range including the numerical values before and after "-" as lower and upper limits.
  • the piezoelectric device of the present invention is It has a piezoelectric layer containing piezoelectric particles in a matrix containing a polymer material and electrode layers formed on both sides of the piezoelectric layer, and the loss tangent at a frequency of 1 Hz by dynamic viscoelasticity measurement is 0.0.
  • a piezoelectric device comprising a heating mechanism for heating a piezoelectric film.
  • FIG. 1 shows a side view schematically showing an example of the piezoelectric device of the present invention.
  • the piezoelectric device 100 shown in FIG. 1 has a piezoelectric film 10, a signal source 102, a temperature sensor 104, and a control section 106.
  • the piezoelectric film 10 includes a piezoelectric layer 20 containing piezoelectric particles in a matrix containing a polymer material, and a first electrode layer 24 and a second electrode layer 26 formed on both main surfaces of the piezoelectric layer 20. , a first protective layer 28 provided on the first electrode layer 24 and a second protective layer 30 provided on the second electrode layer 26 .
  • the first electrode layer 24 and the second electrode layer 26 are electrode layers in the present invention.
  • the first protective layer 28 and the second protective layer 30 are protective layers in the present invention.
  • the piezoelectric film 10 is preferably polarized in the thickness direction.
  • the piezoelectric film 10 vibrates according to the magnitude of the driving voltage applied to the piezoelectric film 10 and generates sound according to the driving voltage applied to the piezoelectric film 10 . Therefore, when a signal in the audible range is applied to the piezoelectric film 10, the piezoelectric film 10 itself vibrates to generate sound in the audible range.
  • the piezoelectric film 10 has a maximum value of 0.1 or more in loss tangent at a frequency of 1 Hz by dynamic viscoelasticity measurement in a temperature range of 0°C to 50°C. The piezoelectric film 10 will be detailed later.
  • a signal source 102 for applying a driving voltage (driving signal) is connected to the first electrode layer 24 and the second electrode layer 26 of the piezoelectric film 10 .
  • a temperature sensor 104 is arranged on the surface of the piezoelectric film 10 .
  • the temperature sensor 104 is arranged near the edge of the surface of the first protective layer 28 .
  • a temperature sensor 104 measures the temperature of the piezoelectric film 10 .
  • the temperature sensor 104 may be of a contact type or a non-contact type, and various known temperature sensors such as thermocouples and infrared sensors can be used.
  • the temperature sensor 104 is arranged on the surface of the first protective layer 28, but the configuration is not limited to this, and the temperature sensor 104 is arranged on the surface of the second protective layer 30. may be In addition, in the example shown in FIG. 1, the temperature sensor 104 is configured to be disposed near the edge in the plane direction of the piezoelectric film 10, but the present invention is not limited to this. It may be arranged at any position.
  • the configuration is such that the temperature of the piezoelectric film 10 itself is measured.
  • the ambient temperature in the vicinity of the piezoelectric film 10 may be measured. It is preferable to measure the temperature of the piezoelectric film 10 itself.
  • the control unit 106 is connected to the signal source 102 and the temperature sensor 104 and controls the signal source 102 to apply a predetermined signal to the piezoelectric film 10 according to the temperature measured by the temperature sensor 104 .
  • the control unit 106 is composed of a CPU (Central Processing Unit) and an operation program for causing the CPU to perform various processes.
  • the control unit 106 may be configured by a processor such as a PC (personal computer).
  • the control unit 106 may be configured with a digital circuit.
  • the piezoelectric film 10 to which a predetermined signal is applied from the signal source 102 vibrates and self-heats to be heated. That is, in the configuration shown in FIG. 1, the piezoelectric film 10, the signal source 102, the temperature sensor 104 and the controller 106 constitute a heating mechanism.
  • the control unit 106 sends a predetermined signal (hereinafter also referred to as a heating signal) to the signal source 102.
  • a predetermined signal hereinafter also referred to as a heating signal
  • the piezoelectric film 10 is heated by vibrating and self-heating according to a predetermined signal applied from the signal source 102 . Since the piezoelectric film 10 has a maximum value of 0.1 or more in the loss tangent at a frequency of 1 Hz as measured by dynamic viscoelasticity measurement in a temperature range of 0° C. to 50° C., the piezoelectric film 10 is heated. When the temperature is 0°C or higher, excellent flexibility is exhibited.
  • a flexible piezoelectric film is known as a speaker that can be integrated into a flexible display without impairing its flexibility. Since a flexible speaker can be rolled up and stored or folded, even a large-sized device can be improved in portability.
  • a flexible piezoelectric film cannot exhibit sufficient flexibility depending on the temperature. For example, a piezoelectric film having a maximum loss tangent value of 0.1 or more at a frequency of 1 Hz by dynamic viscoelasticity measurement exists in the temperature range of 0 to 50°C. Although it exhibits flexibility, it was difficult to exhibit sufficient flexibility below freezing.
  • the loss tangent at a frequency of 1 Hz by dynamic viscoelasticity measurement has a maximum value of 0.1 or more in the temperature range of -80 ° C. or more and less than 0 ° C., and the value at 0 ° C. is 0.05.
  • the above piezoelectric film exhibits good flexibility below freezing, the flexibility at room temperature is inferior to that at below freezing. In other words, the conventional piezoelectric film could not exhibit excellent flexibility in both normal temperature environment and sub-zero environment.
  • the maximum value of the loss tangent at a frequency of 1 Hz measured by dynamic viscoelasticity measurement is 0.1 or more, and the maximum value exists in the temperature range of 0° C. to 50° C. , and a heating mechanism for heating the piezoelectric film 10 . Therefore, the piezoelectric film 10 exhibits excellent flexibility in a normal temperature environment, and excellent flexibility is achieved by heating the piezoelectric film 10 to a temperature of 0° C. or higher in a subzero environment. You can express your sexuality. Therefore, the piezoelectric device 100 of the present invention can exhibit excellent flexibility regardless of whether it is used in a normal temperature environment or a subzero environment.
  • the signal (heating signal) applied from the signal source 102 to the piezoelectric film 10 is preferably a sinusoidal AC signal with a frequency higher than 15 kHz.
  • a signal with an easily audible frequency of 15 kHz or less is applied to the piezoelectric film 10
  • the piezoelectric film 10 generates unnecessary sounds.
  • a sinusoidal AC signal with a frequency higher than 15 kHz to the piezoelectric film 10
  • the piezoelectric film 10 can be heated without producing an audible unnecessary sound.
  • the sine wave AC signal supplied by the signal source 102 may be any of sine wave, triangular wave and rectangular wave.
  • the frequency of the sinusoidal AC signal applied to the piezoelectric film 10 is more preferably 20 kHz to 100 kHz, and even more preferably 20 kHz to 40 kHz. That is, it is preferable that the signal has a frequency higher than the audible range (frequency of 20 Hz to 20 kHz). Alternatively, a signal containing different frequency components with a frequency exceeding 20 kHz may be applied to the piezoelectric film 10 . From the viewpoint of preventing unnecessary sound from being generated from the piezoelectric film 10, the signal applied to the piezoelectric film 10 preferably does not contain frequency components of 15 kHz or less, and more preferably does not contain frequency components of 20 kHz or less.
  • the effective voltage of the sinusoidal AC signal (heating signal) applied to the piezoelectric film 10 is preferably 1 Vrms to 40 Vrms, more preferably 1 Vrms to 20 Vrms. 1 Vrms to 10 Vrms is more preferred.
  • the piezoelectric film 10 may be heated during operation (during sound generation).
  • the signal applied to the piezoelectric film 10 includes a frequency component in the audible range generated by the piezoelectric film 10 and a frequency component (heating signal) of 15 kHz to 100 kHz.
  • the signal applied to the piezoelectric film 10 is a non-sinusoidal AC signal, and at least one frequency of the sinusoidal AC signal obtained by Fourier analysis of the non-sinusoidal AC signal is in the range of 15 kHz to 100 kHz.
  • the piezoelectric film 10 can be appropriately heated regardless of sound pressure in the audible range.
  • self-heating in the piezoelectric film increases as the flowing current increases.
  • the higher the frequency the lower the impedance. Therefore, even if a signal of the same voltage is applied to the piezoelectric film, the higher the frequency, the larger the current that flows and the more likely it is to generate heat. Therefore, the signal applied to the piezoelectric film contains a signal component for heating with a frequency of 15 kHz to 100 kHz, so that the piezoelectric film can easily generate heat.
  • the effective voltage of the sinusoidal AC signal (heating signal) of 20 kHz to 100 kHz applied to the piezoelectric film 10 is preferably 1 Vrms to 40 Vrms. ⁇ 20 Vrms is more preferred, and 1 Vrms to 10 Vrms is even more preferred.
  • the temperature at which the control unit 106 starts applying a signal with a frequency of more than 15 kHz from the signal source 102 to the piezoelectric film 10, that is, the temperature threshold at which heating of the piezoelectric film 10 is started is -40°C to 10°C. -20°C to 5°C is more preferred, and -10°C to 0°C is more preferred.
  • control unit 106 should be controlled so as to terminate the application of a signal with a frequency exceeding 15 kHz to the piezoelectric film 10, that is, the heating of the piezoelectric film 10 at the timing when the temperature measured by the temperature sensor 104 reaches or exceeds a predetermined temperature.
  • the threshold temperature for ending heating of the piezoelectric film 10 is preferably 0.degree. C. to 35.degree. C., more preferably 10.degree.
  • the control unit 106 terminates the heating of the piezoelectric film 10 when the temperature exceeds the maximum value at which the loss tangent at a frequency of 1 Hz measured by dynamic viscoelasticity is 0.1 or more. good too.
  • control unit 106 may control the piezoelectric film 10 to be heated until a predetermined time has elapsed from the start of heating. That is, the application of the signal for heating may be terminated when a predetermined time has elapsed from the start of heating.
  • the heating time application time of the signal for heating
  • the heating time may be appropriately set according to the size of the piezoelectric film, the thickness of each layer, the material (thermal conductivity, specific heat), and the like.
  • the piezoelectric device 100 has the temperature sensor 104, and the control unit 106 is configured to control the application of the heating signal to the piezoelectric film according to the temperature. is not done.
  • the piezoelectric device does not have a temperature sensor, but has a sensor that detects an operation such as bending and stretching the piezoelectric film or winding and stretching.
  • a signal source 102 may be controlled to heat (apply a signal for heating) 10 .
  • the controller 106 may control the signal source 102 to heat the piezoelectric film 10 (to apply a signal for heating). Further, in this case, when the rotation of the winding shaft stops, the control unit 106 controls the signal source 102 so as to stop heating the piezoelectric film 10 (stop applying the signal for heating).
  • the control unit 106 heats the piezoelectric film 10 before winding or drawing ( Alternatively, the signal source 102 may be controlled to apply a heating signal to heat the piezoelectric film 10 and after a predetermined period of time has passed, winding or unwinding may be performed.
  • the user of the piezoelectric device may arbitrarily heat the piezoelectric film with a switch or the like at the timing of winding, bending, or the like of the piezoelectric film.
  • a heating signal is applied to the piezoelectric film to heat the piezoelectric film by self-heating of the piezoelectric film, but the present invention is not limited to this, and the heating mechanism has an external heater. may be configured.
  • FIG. 2 shows a perspective view schematically showing another example of the piezoelectric device of the present invention.
  • FIG. 3 shows a cross-sectional view of FIG.
  • the piezoelectric device 100b shown in FIGS. 2 and 3 includes the piezoelectric film 10, a housing 120 having an opening 120a, an external heater 122, a winding shaft 124, and a guide member 126.
  • the piezoelectric film 10 is the same as the piezoelectric film 10 included in the piezoelectric device 100 shown in FIG. 1, so description thereof will be omitted.
  • the housing 120 has a substantially cylindrical shape, has a portion that protrudes outward from the peripheral surface of the cylinder, and has an opening 120a in the protruding portion.
  • the housing 120 accommodates the piezoelectric film 10 wound around the winding shaft 124 .
  • a winding shaft 124 is rotatably supported on the cylindrical portion of the housing 120 .
  • the opening 120 a of the housing 120 has a height substantially equal to the width of the piezoelectric film 10 to be pulled out in a direction orthogonal to the pulling direction, and has a width larger than the thickness of the piezoelectric film 10 .
  • the piezoelectric film 10 is passed through the opening 120 a and is wound around the winding shaft 124 in the housing 120 and pulled out from the winding shaft 124 . That is, for example, when the piezoelectric film 10 is used as a speaker, the piezoelectric device 100b can be used by pulling out the piezoelectric film 10 from the housing 120, and when the piezoelectric device 100b is carried, the piezoelectric film 10 can be removed. It can be wound up on a winding shaft 124 in the housing 120 to reduce the size.
  • a guide member 126 is provided in the opening 120a so as to sandwich the piezoelectric film 10 for smoothly inserting and removing the piezoelectric film 10 and preventing damage to the piezoelectric film 10 due to inserting and removing.
  • the guide member 126 is made of, for example, felt.
  • An external heater 122 is provided in the opening 120a.
  • the external heater 122 heats the piezoelectric film 10 that is inserted into and removed from the opening 120a.
  • the external heater 122 may or may not be in contact with the piezoelectric film 10 as long as it can heat the piezoelectric film 10 .
  • the external heater 122 is not particularly limited, and various known heaters can be used.
  • Examples of the external heater 122 that also serves as the guide member 126 include a rubber heater.
  • the external heater 122 may use standby power when the power is turned on to always heat the piezoelectric film 10 to maintain a predetermined temperature or higher (for example, 0° C. or higher).
  • the rotation of the shaft 124 may be detected by a displacement sensor, and the external heater 122 may be driven to heat the piezoelectric film 10 when the winding shaft 124 starts rotating.
  • it may have a temperature sensor for measuring the temperature of the piezoelectric film 10, housing 120, winding shaft 124, or the like, and drive the external heater 122 according to the temperature.
  • the external heater 122 heats the piezoelectric film 10 before winding or pulling out the piezoelectric film 10 .
  • a predetermined time for example, about 3 seconds
  • the piezoelectric film 10 can be accommodated in the housing 120 by rotating the take-up shaft 124.
  • the piezoelectric film 10 can be pulled out from the housing 120 by pulling the piezoelectric film 10 or rotating the take-up shaft 124 . Therefore, the piezoelectric film 10 is bent and stretched with a high curvature by the winding shaft 124 during winding and unwinding.
  • the piezoelectric film 10 is heated by the external heater 122, so that the temperature of the piezoelectric film 10 can be raised to 0° C. or higher even in a sub-zero environment, and excellent flexibility can be exhibited. Therefore, the piezoelectric device 100b of the present invention can exhibit excellent flexibility regardless of whether it is used in a normal temperature environment or a subzero environment.
  • FIG. 4 shows a perspective view schematically showing another example of the piezoelectric device of the present invention.
  • a piezoelectric device 100d shown in FIG. 4 includes a piezoelectric film 10, a flexible display 130, and a housing 120 having an opening 120a. Although not shown, the piezoelectric device 100d has an external heater 122, a winding shaft 124, and a guide member 126 inside the housing 120, like the piezoelectric device 100b.
  • a piezoelectric device 100d shown in FIG. 4 has a flexible display 130 in which the piezoelectric film 10 is attached to the back surface (the surface opposite to the display surface) instead of the piezoelectric film 10 in the piezoelectric device 100b shown in FIG. Other than that, they have the same configuration. That is, the flexible display 130 with the piezoelectric film 10 adhered to the back surface can be rolled up and housed on the winding shaft 124 in the housing 120 to be miniaturized, for example, when being carried. When used as a display, the flexible display 130 and the piezoelectric film 10 are pulled out from the opening 120a of the housing 120 and used as a speaker for reproducing images and generating sound.
  • the flexible display 130 is not particularly limited as long as it is a flexible display, and includes organic electroluminescence (OLED (Organic Light Emitting Diode)) displays, liquid crystal displays, micro LED (Light Emitting Diode) displays, and inorganic Known display devices such as electroluminescence displays are suitable for use.
  • OLED Organic Light Emitting Diode
  • LCD Organic Light Emitting Diode
  • micro LED Light Emitting Diode
  • electroluminescence displays are suitable for use.
  • FIG. 5 shows a diagram schematically showing another example of the piezoelectric device of the present invention.
  • FIG. 6 shows a partially enlarged view of FIG.
  • a piezoelectric device 100c shown in FIGS. 5 and 6 has a piezoelectric film 10, a diaphragm 12, a signal source 102, a temperature sensor 104, and a controller .
  • the piezoelectric film 10 is formed by laminating three layers of the piezoelectric film 10 by folding one long rectangular piezoelectric film 10 twice in one direction. It is.
  • the piezoelectric film 10 laminated in this manner is also called a laminated piezoelectric element.
  • FIG. 6 the illustration of the first protective layer and the second protective layer is omitted in order to clearly show the configuration of the piezoelectric device 100c. Further, in the following description, the direction in which the piezoelectric film 10 is folded back (horizontal direction in FIG. 6) is referred to as the folding direction.
  • the layers of the piezoelectric film 10 are adhered by an adhesive layer 19 . Also, the piezoelectric film 10 and the diaphragm 12 are adhered by an adhesive layer 16 .
  • the laminated piezoelectric element is obtained by laminating and adhering the piezoelectric films 10 . Therefore, when the piezoelectric film 10 expands and contracts, the laminated piezoelectric element 14 also expands and contracts. Also, the diaphragm 12 is attached to the laminated piezoelectric element with an adhesive layer 16 . Therefore, by applying a voltage to the electrode layers of the piezoelectric film 10 using the signal source 102, the laminated piezoelectric element (laminated piezoelectric film 10) is driven.
  • the laminated piezoelectric element When the laminated piezoelectric element is driven, the laminated piezoelectric element expands and contracts in the plane direction, bending the diaphragm 12 to which the laminated piezoelectric element is adhered, and as a result vibrating the diaphragm in the thickness direction to generate sound.
  • the diaphragm vibrates according to the magnitude of the driving voltage applied to the laminated piezoelectric element and generates sound according to the driving voltage applied to the piezoelectric device 100 . That is, the piezoelectric device 100c has a configuration in which a laminated piezoelectric element (laminated piezoelectric film 10) is used as an exciter.
  • the diaphragm 12 is flexible, and the piezoelectric film 10 as an exciter is also bent when it is wound and stored or bent.
  • the diaphragm 12 can be wound up and stored in the housing 120. It can be a piezoelectric device.
  • the diaphragm 12 is wound, the laminated piezoelectric element adhered to the diaphragm 12 is also wound and bent.
  • the piezoelectric device 100c has a temperature sensor 104 and a control unit 106.
  • the control unit 106 controls the signal source 102
  • a heating signal is applied to the piezoelectric film 10 to cause the piezoelectric film 10 to vibrate.
  • the piezoelectric film 10 is heated by vibrating and self-heating according to a predetermined signal applied from the signal source 102 . Since the piezoelectric film 10 has a maximum value of 0.1 or more in the loss tangent at a frequency of 1 Hz as measured by dynamic viscoelasticity measurement in a temperature range of 0° C. to 50° C., the piezoelectric film 10 is heated. When the temperature is 0°C or higher, excellent flexibility is exhibited. Therefore, the piezoelectric device 100c can exhibit excellent flexibility regardless of whether it is used in a normal temperature environment or a sub-zero environment.
  • the longitudinal direction of the piezoelectric film before folding may be the folding direction, or the lateral direction may be the folding direction.
  • the laminated piezoelectric element has a configuration in which three layers of the piezoelectric film 10 are laminated, but the present invention is not limited to this. A laminated structure may also be used. Regarding this point, the laminated piezoelectric element shown in FIG. 7 and the laminated piezoelectric element shown in FIG. 8, which will be described later, are the same.
  • the structure is such that the laminated piezoelectric element in which the piezoelectric films are laminated is used as the exciter. good too.
  • a piezoelectric film is used as an exciter, a larger output is required, so it is preferable to use a laminated piezoelectric element in which piezoelectric films are multilayered.
  • the laminated piezoelectric element is obtained by laminating a plurality of piezoelectric films 10 .
  • the adjacent piezoelectric films 10 are further adhered to each other with an adhesive layer 19 . Therefore, even if the rigidity of each piezoelectric film 10 is low and the expansion/contraction force is small, by laminating the piezoelectric films 10, the rigidity is increased and the expansion/contraction force as a laminated piezoelectric element is increased.
  • the laminated piezoelectric element can sufficiently flex the diaphragm 12 with a large force and sufficiently vibrate the diaphragm 12 in the thickness direction. A sound can be generated in the diaphragm 12 .
  • the thicker the piezoelectric layer 20 the greater the expansion/contraction force of the piezoelectric film 10, but the drive voltage required to expand/contract the film by the same amount is increased accordingly.
  • the preferred thickness of the piezoelectric layer 20 is at most about 300 ⁇ m. Therefore, in the structure in which the piezoelectric films 10 are laminated, even if the voltage applied to each piezoelectric film 10 is small, the piezoelectric films 10 can be expanded and contracted sufficiently.
  • the laminated piezoelectric element shown in FIGS. 5 and 6 can be constructed with only one long piezoelectric film 10, and only one signal source 102 for applying the drive voltage is required. Furthermore, the electrodes may be led out from the piezoelectric film 10 at one point. Therefore, as shown in FIGS. 7 and 8, which will be described later, a laminated piezoelectric element in which a plurality of sheets of piezoelectric film 10 are laminated can be obtained by reducing the number of parts and simplifying the configuration. As a result, reliability can be improved, and cost reduction can be achieved.
  • the piezoelectric film 10 is polarized in the thickness direction (the direction indicated by the arrow in FIG. 6).
  • the polarization directions of the piezoelectric films 10 adjacent (facing) in the stacking direction are opposite directions as indicated by arrows in FIG. become. Therefore, in the laminated piezoelectric element formed by folding one piezoelectric film 10, the first electrode layers 24 face each other on one side of the adjacent layers of the piezoelectric film 10, and the second electrode layers 26 on the other side. face each other. Therefore, even if the electrode layers of the adjacent piezoelectric films 10 come into contact with each other, there is no danger of short-circuiting.
  • the first electrode layer 24 and the second electrode layer 26 of the piezoelectric film 10 are formed of a metal deposition film or the like. If the vapor-deposited metal film is bent at an acute angle, cracks or the like are likely to occur, and the electrode layer may be disconnected. That is, in the laminated piezoelectric element shown in FIG. 6, cracks or the like easily occur in the electrodes inside the bent portion.
  • the laminated piezoelectric element in which the piezoelectric film 10 is folded back by inserting the core rod 58 into the folded portion of the piezoelectric film 10, the first electrode layer 24 and the second electrode layer 26 are prevented from being folded. Therefore, it is possible to suitably prevent disconnection from occurring.
  • the laminated piezoelectric element has a structure in which the piezoelectric film 10 is folded and laminated, but the present invention is not limited to this.
  • 7 and 8 are diagrams each showing an example of another configuration of the laminated piezoelectric element of the piezoelectric device of the present invention.
  • Each of the laminated piezoelectric elements shown in FIGS. 7 and 8 is obtained by laminating three layers of sheet-shaped piezoelectric films 10 .
  • the piezoelectric films 10 are adhered together by an adhesive layer 19 .
  • a signal source 102 for applying a drive voltage is connected to each piezoelectric film 10 .
  • the first protective layer and the second protective layer are omitted in order to simplify the drawings.
  • all piezoelectric films 10 have both the first protective layer and the second protective layer.
  • the laminated piezoelectric element is not limited to this, and a piezoelectric film having a protective layer and a piezoelectric film not having a protective layer may be mixed. Furthermore, when the piezoelectric film has a protective layer, the piezoelectric film may have only the first protective layer or only the second protective layer. As an example, in the case of a laminated piezoelectric element having a three-layer structure as shown in FIG. 7, the uppermost piezoelectric film in the figure has only the second protective layer on the second electrode layer 26, and the central piezoelectric film protects the second protective layer. A configuration in which no layers are provided and the lowest piezoelectric film has only the first protective layer on the first electrode layer 24 may be used. Regarding this point, the laminated piezoelectric element shown in FIG. 8 is the same.
  • the polarization directions of adjacent piezoelectric films 10 are opposite to each other, and a plurality of layers (three layers in the illustrated example) of piezoelectric films 10 are arranged. It has a configuration in which the piezoelectric films 10 are laminated and the adjacent piezoelectric films 10 are adhered with an adhesive layer 19 .
  • a plurality of layers (three layers in the illustrated example) of piezoelectric films 10 are laminated such that the polarization directions of adjacent piezoelectric films 10 (directions indicated by arrows in FIG. 8) are the same. It has a configuration in which adjacent piezoelectric films 10 are adhered with an adhesive layer 19 . That is, in the laminated piezoelectric element shown in FIG. 8, the polarization directions of the piezoelectric films 10 are all the same.
  • the polarity of the voltage applied to the piezoelectric layer 20 depends on the polarization direction. Therefore, the polarities of the applied voltages are as follows: All piezoelectric films 10 are matched. In the illustrated example, the electrode on the side of the arrow indicating the polarization direction is the first electrode layer 24, and the electrode on the opposite side is the second electrode layer 26. In all of the piezoelectric films 10, the first electrode layer 24 and the second The polarity is the same as that of the electrode layer 26 . Therefore, in a laminated piezoelectric element in which the polarization directions of the piezoelectric layers 20 of the adjacent piezoelectric films 10 are opposite to each other as shown in FIG.
  • the adhesive layer 19 In order to expand and contract the laminated piezoelectric element with good energy efficiency, it is preferable to make the adhesive layer 19 thin so that the adhesive layer 19 does not interfere with the expansion and contraction of the piezoelectric layer 20 .
  • the adhesive layer 19 may be omitted. Even if it does, the adhesive layer 19 can be made extremely thin if the required adhesive strength is obtained. Therefore, the laminated piezoelectric element can be expanded and contracted with high energy efficiency.
  • the absolute amount of expansion and contraction of the piezoelectric layer 20 in the thickness direction is very small, and the expansion and contraction of the piezoelectric film 10 is substantially only in the plane direction. Therefore, even if the polarization directions of the laminated piezoelectric films 10 are opposite, all the piezoelectric films 10 expand and contract in the same direction as long as the polarity of the voltage applied to the first electrode layer 24 and the second electrode layer 26 is correct. .
  • the polarization direction of the piezoelectric film 10 can be detected with a d33 meter or the like.
  • the polarization direction of the piezoelectric film 10 may be known from the treatment conditions of corona poling treatment, which will be described later.
  • the laminated piezoelectric element shown in FIGS. 7 and 8 is preferably obtained by manufacturing a long (large area) piezoelectric film, cutting out individual piezoelectric films 10 from the long piezoelectric film, and laminating the piezoelectric films 10 .
  • the plurality of piezoelectric films 10 forming the laminated piezoelectric element are all the same.
  • the laminated piezoelectric element includes a structure in which piezoelectric films having different layer structures are laminated, such as a piezoelectric film having a first protective layer and a second protective layer and a piezoelectric film not having the first protective layer and a second protective layer, and a piezoelectric layer.
  • Various configurations are available, such as a stack of 20 different thickness piezoelectric films.
  • one layer of the piezoelectric film 10 is configured to have a protruding portion that protrudes outward in the plane direction from the laminated portion in which the piezoelectric film 10 is laminated,
  • a connecting portion for connecting the first electrode layer 24 and the second electrode layer 26 to the signal source 102 is preferably formed on the protruding portion.
  • the method of connecting the electrode layer and the wiring in the protruding portion is not limited, and various known methods can be used.
  • FIG. 9 shows an enlarged view of a portion of the piezoelectric film 10.
  • the piezoelectric film 10 shown in FIG. 9 includes a piezoelectric layer 20 that is a sheet-like material having piezoelectricity, a second electrode layer 26 that is laminated on one surface of the piezoelectric layer 20 , and a piezoelectric layer of the second electrode layer 26 .
  • the piezoelectric layer 20 is composed of a polymeric composite piezoelectric body containing piezoelectric particles 36 in a matrix 34 containing a polymeric material.
  • the material of the polymer composite piezoelectric matrix 34 (matrix and binder) that constitutes the piezoelectric layer 20 it is preferable to use a polymer material that has viscoelasticity at room temperature.
  • "ordinary temperature” refers to a temperature range of about 0 to 50.degree.
  • the polymer composite piezoelectric (piezoelectric layer 20) preferably satisfies the following requirements.
  • the lowest resonance frequency f 0 of the speaker diaphragm is given by the following equation. where s is the stiffness of the vibration system and m is the mass. At this time, as the degree of curvature of the piezoelectric film, that is, the radius of curvature of the curved portion increases, the mechanical stiffness s decreases, so the lowest resonance frequency f0 decreases. That is, the sound quality (volume and frequency characteristics) of the speaker changes depending on the radius of curvature of the piezoelectric film.
  • a flexible polymer composite piezoelectric material used as a speaker is required to behave hard against vibrations of 20 Hz to 20 kHz and softly against vibrations of several Hz or less. Also, the loss tangent of the polymer composite piezoelectric body is required to be moderately large with respect to vibrations of all frequencies of 20 kHz or less.
  • polymer solids have a viscoelastic relaxation mechanism, and as the temperature rises or the frequency decreases, large-scale molecular motion causes a decrease (relaxation) in the storage elastic modulus (Young's modulus) or a maximum loss elastic modulus (absorption). is observed as Among them, the relaxation caused by the micro-Brownian motion of the molecular chains in the amorphous region is called principal dispersion, and a very large relaxation phenomenon is observed.
  • the temperature at which this primary 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 as a matrix, it is possible to suppress vibrations of 20 Hz to 20 kHz. This realizes a polymer composite piezoelectric material that is hard at first and behaves softly with respect to slow vibrations of several Hz or less.
  • a polymer material having a glass transition point at room temperature ie, 0 to 50° C. at a frequency of 1 Hz, for the matrix of the polymer composite piezoelectric material, because this behavior is favorably expressed.
  • the polymer material having viscoelasticity at room temperature Preferably, a polymer material having a maximum value of 0.5 or more in loss tangent Tan ⁇ at a frequency of 1 Hz in a dynamic viscoelasticity test at normal temperature, ie, 0 to 50° C., is used.
  • a polymer material having a maximum value of 0.5 or more in loss tangent Tan ⁇ at a frequency of 1 Hz in a dynamic viscoelasticity test at normal temperature, ie, 0 to 50° C. is used.
  • the polymer material having viscoelasticity at room temperature preferably has a storage elastic modulus (E') at a frequency of 1 Hz measured by dynamic viscoelasticity of 100 MPa or more at 0°C and 10 MPa or less at 50°C.
  • E' storage elastic modulus
  • the polymer material having viscoelasticity at room temperature has a dielectric constant of 10 or more at 25°C.
  • a voltage is applied to the polymer composite piezoelectric material, a higher electric field is applied to the piezoelectric particles in the matrix, so a large amount of deformation can be expected.
  • the polymer material in consideration of ensuring good moisture resistance and the like, it is also suitable for the polymer material to have a dielectric constant of 10 or less at 25°C.
  • polymeric materials having viscoelasticity at room temperature examples include cyanoethylated polyvinyl alcohol (cyanoethylated PVA), polyvinyl acetate, polyvinylidene chloride core acrylonitrile, polystyrene-vinylpolyisoprene block copolymer, and polyvinylmethyl. Examples include ketones and polybutyl methacrylate. Commercially available products such as Hybler 5127 (manufactured by Kuraray Co., Ltd.) can also be suitably used as these polymer materials. Among them, as the polymer material, it is preferable to use a material having a cyanoethyl group, and it is particularly preferable to use cyanoethylated PVA.
  • the piezoelectric layer 20 preferably uses a polymer material having a cyanoethyl group as the matrix 34, and particularly preferably uses cyanoethylated PVA.
  • the above-mentioned polymeric materials represented by cyanoethylated PVA are collectively referred to as "polymeric materials having viscoelasticity at room temperature”.
  • These polymer materials having viscoelasticity at room temperature may be used alone or in combination (mixed).
  • the matrix 34 using such a polymeric material having viscoelasticity at room temperature may use a plurality of polymeric materials together, if necessary. That is, in addition to viscoelastic materials such as cyanoethylated PVA, other dielectric polymeric materials may be added to the matrix 34 as necessary for the purpose of adjusting dielectric properties and mechanical properties.
  • dielectric polymer materials examples include polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, and polyvinylidene fluoride-trifluoroethylene copolymer.
  • fluorine-based polymers such as polyvinylidene fluoride-tetrafluoroethylene copolymer, vinylidene cyanide-vinyl acetate copolymer, cyanoethylcellulose, cyanoethylhydroxysaccharose, cyanoethylhydroxycellulose, cyanoethylhydroxypullulan, cyanoethylmethacrylate, cyanoethylacrylate, cyanoethyl Cyano groups such as hydroxyethylcellulose, cyanoethylamylose, cyanoethylhydroxypropylcellulose, cyanoethyldihydroxypropylcellulose, cyanoethylhydroxypropylamylose, cyanoethylpolyacrylamide, cyanoethylpolyacrylate, cyanoethylpullulan, cyanoethylpolyhydroxymethylene, cyanoethylglycidolpullul
  • polymers having cyanoethyl groups and synthetic rubbers such as nitrile rubber and chloroprene rubber are exemplified. Among them, polymer materials having cyanoethyl groups are preferably used. Moreover, in the matrix 34 of the piezoelectric layer 20, these dielectric polymer materials are not limited to one type, and a plurality of types may be added.
  • the matrix 34 also contains thermoplastic resins such as vinyl chloride resin, polyethylene, polystyrene, methacrylic resin, polybutene, and isobutylene for the purpose of adjusting the glass transition point Tg, and Thermosetting resins such as phenolic resins, urea resins, melamine resins, alkyd resins, and mica may be added. Furthermore, a tackifier such as rosin ester, rosin, terpene, terpene phenol, and petroleum resin may be added for the purpose of improving adhesiveness.
  • thermoplastic resins such as vinyl chloride resin, polyethylene, polystyrene, methacrylic resin, polybutene, and isobutylene for the purpose of adjusting the glass transition point Tg
  • Thermosetting resins such as phenolic resins, urea resins, melamine resins, alkyd resins, and mica may be added.
  • a tackifier such as rosin ester, rosin
  • the addition amount is not particularly limited, but the ratio of the material to the matrix 34 is 30% by mass or less. is preferable.
  • the characteristics of the polymer material to be added can be expressed 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 between the piezoelectric particles 36 and the electrode layer can be improved. favorable results can be obtained in terms of
  • the piezoelectric layer 20 is a layer made of a polymeric composite piezoelectric material containing piezoelectric particles 36 in such a matrix 34 .
  • Piezoelectric particles 36 are dispersed in the matrix 34 .
  • the piezoelectric particles 36 are uniformly (substantially uniformly) dispersed in the matrix 34 .
  • the piezoelectric particles 36 are made of ceramic particles having a perovskite or wurtzite crystal structure.
  • ceramic particles constituting the piezoelectric particles 36 include lead zirconate titanate (PZT), lead zirconate lanthanate titanate (PLZT), barium titanate (BaTiO 3 ), zinc oxide (ZnO), and A solid solution (BFBT) of barium titanate and bismuth ferrite (BiFe 3 ) is exemplified. Only one kind of these piezoelectric particles 36 may be used, or a plurality of kinds thereof may be used together (mixed).
  • the particle size of the piezoelectric particles 36 is not limited, and may be appropriately selected according to the size of the piezoelectric film 10, the application of the piezoelectric device 100, and the like.
  • the particle size of the piezoelectric particles 36 is preferably 1 to 10 ⁇ m. By setting the particle size of the piezoelectric particles 36 within this range, favorable results can be obtained in that the piezoelectric film 10 can achieve both high piezoelectric characteristics and flexibility.
  • the piezoelectric particles 36 in the piezoelectric layer 20 may be uniformly and regularly dispersed in the matrix 34, or if they are uniformly dispersed, they may be dispersed irregularly in the matrix 34. may have been Furthermore, the piezoelectric particles 36 may or may not have uniform particle diameters.
  • the quantitative 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 film 10 in the plane direction, the application of the piezoelectric device 100, and It may be appropriately set according to the characteristics required for the piezoelectric device 100 .
  • 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 particularly limited, and may be appropriately determined according to the application of the piezoelectric device 100 , the number of layers of piezoelectric films in the piezoelectric device 100 , the properties required of the piezoelectric film 10 , and the like. , should be set.
  • the thickness of the piezoelectric layer 20 is preferably 8-300 ⁇ m, more preferably 8-200 ⁇ m, still more preferably 10-150 ⁇ m, particularly preferably 15-100 ⁇ m.
  • the piezoelectric layer 20 is preferably polarized (poled) in the thickness direction.
  • the piezoelectric film 10 has a second electrode layer 26 on one surface of the piezoelectric layer 20, and a second protective layer 30 thereon. has a first electrode layer 24 on the surface thereof, and a first protective layer 28 thereon.
  • the first electrode layer 24 and the second electrode layer 26 form an electrode pair.
  • both surfaces of the piezoelectric layer 20 are sandwiched between electrode pairs, that is, the second electrode layer 26 and the first electrode layer 24 , and this laminate is formed into the second protective layer 30 and the first protective layer 28 . It has a configuration sandwiched between.
  • the region sandwiched between the second electrode layer 26 and the first electrode layer 24 expands and contracts according to the applied voltage.
  • the first and second numbers in the first electrode layer 24 and the second electrode layer 26 and the first protective layer 28 and the second protective layer 30 are attached for convenience in order to explain the piezoelectric film 10. It is. Therefore, the first and second aspects of the present invention have no technical significance and are irrelevant to the actual usage conditions.
  • the first protective layer 28 and the second protective layer 30 cover the first electrode layer 24 and the second electrode layer 26, and provide the piezoelectric layer 20 with appropriate rigidity and mechanical strength. is responsible for That is, in the piezoelectric film 10, the piezoelectric layer 20 made up of the matrix 34 and the piezoelectric particles 36 exhibits excellent flexibility against slow bending deformation, but depending on the application, the rigidity may increase. and mechanical strength may be insufficient.
  • the piezoelectric film 10 is provided with a second protective layer 30 and a first protective layer 28 to compensate.
  • the first protective layer 28 and the second protective layer 30 have the same configuration, except for the arrangement position. Therefore, in the following description, when there is no need to distinguish between the first protective layer 28 and the second protective layer 30, both members are collectively referred to as protective layers.
  • Various sheet materials can be used for the first protective layer 28 and the second protective layer 30 without limitation, and various resin films are preferably exemplified as examples.
  • various resin films are preferably exemplified as examples.
  • PET polyethylene terephthalate
  • PP polypropylene
  • PS polystyrene
  • PC polycarbonate
  • PPS polyphenylene sulfite
  • PMMA polymethyl methacrylate
  • PET polyethylene terephthalate
  • PET polypropylene
  • PS polystyrene
  • PC polycarbonate
  • PPS polyphenylene sulfite
  • PMMA polymethyl methacrylate
  • PET polyethylene terephthalate
  • PEI polyetherimide
  • PI polyimide
  • PEN polyethylene naphthalate
  • TAC triacetyl cellulose
  • cyclic olefin resins and the like are preferably used.
  • the thicknesses of the first protective layer 28 and the second protective layer 30 are also not limited. Also, the thicknesses of the first protective layer 28 and the second protective layer 30 are basically the same, but may be different. Here, if the rigidity of the first protective layer 28 and the second protective layer 30 is too high, not only will the expansion and contraction of the piezoelectric layer 20 be restricted, but also the flexibility will be impaired. Therefore, the thinner the first protective layer 28 and the second protective layer 30, the better, except for cases where mechanical strength and good handling properties as a sheet-like article are required.
  • the thickness of the first protective layer 28 and the second protective layer 30 is not more than twice the thickness of the piezoelectric layer 20, it is possible to ensure both rigidity and appropriate flexibility. favorable results can be obtained.
  • the thickness of the piezoelectric layer 20 is 50 ⁇ m and the first protective layer 28 and the second protective layer 30 are made of PET, the thicknesses of the first protective layer 28 and the second protective layer 30 are preferably 100 ⁇ m or less. 50 ⁇ m or less is more preferable, and 25 ⁇ m or less is even more preferable.
  • a first electrode layer 24 is provided between the piezoelectric layer 20 and the first protective layer 28, and a second electrode layer 26 is provided between the piezoelectric layer 20 and the second protective layer 30. It is formed.
  • the first electrode layer 24 and the second electrode layer 26 are provided for applying voltage to the piezoelectric layer 20 (piezoelectric film 10).
  • the first electrode layer 24 and the second electrode layer 26 are basically the same except for their positions. Therefore, in the following description, when there is no need to distinguish between the first electrode layer 24 and the second electrode layer 26, both members are collectively referred to as electrode layers.
  • the materials for forming the first electrode layer 24 and the second electrode layer 26 are not limited, and various conductors can be used. Specifically, metals such as carbon, palladium, iron, tin, aluminum, nickel, platinum, gold, silver, copper, titanium, chromium and molybdenum, alloys thereof, laminates and composites of these metals and alloys, Also, indium tin oxide and the like are exemplified. Alternatively, conductive polymers such as PEDOT/PPS (polyethylenedioxythiophene-polystyrenesulfonic acid) are also exemplified.
  • PEDOT/PPS polyethylenedioxythiophene-polystyrenesulfonic acid
  • copper, aluminum, gold, silver, platinum, and indium tin oxide are preferably exemplified as the first electrode layer 24 and the second electrode layer 26 .
  • copper is more preferable from the viewpoint of conductivity, cost, flexibility, and the like.
  • the method of forming the first electrode layer 24 and the second electrode layer 26 is not limited, and may be a vapor phase deposition method (vacuum film formation method) such as vacuum deposition or sputtering, a film formation by plating, or the formation of the above materials.
  • a vapor phase deposition method vacuum film formation method
  • sputtering a film formation by plating
  • a variety of known methods are available, such as affixing the foils.
  • a thin film of copper, aluminum, or the like formed by vacuum deposition is particularly preferably used as the first electrode layer 24 and the second electrode layer 26 because the flexibility of the piezoelectric film 10 can be ensured.
  • a copper thin film formed by vacuum deposition is particularly preferably used.
  • the thicknesses of the first electrode layer 24 and the second electrode layer 26 are not limited. Also, the thicknesses of the first electrode layer 24 and the second electrode layer 26 are basically the same, but may be different.
  • the first protective layer 28 and the second protective layer 30 described above if the rigidity of the first electrode layer 24 and the second electrode layer 26 is too high, not only will the expansion and contraction of the piezoelectric layer 20 be restricted, Flexibility is also impaired. Therefore, the thinner the first electrode layer 24 and the second electrode layer 26, the better, as long as the electrical resistance does not become too high.
  • the product of the thickness of the first electrode layer 24 and the second electrode layer 26 and the Young's modulus is less than the product of the thickness of the first protective layer 28 and the second protective layer 30 and the Young's modulus , is preferred because it does not significantly impair flexibility.
  • the first protective layer 28 and the second protective layer 30 are made of PET (Young's modulus: about 6.2 GPa), and the first electrode layer 24 and the second electrode layer 26 are made of copper (Young's modulus: about 130 GPa).
  • the thickness of the first protective layer 28 and the second protective layer 30 is 25 ⁇ m
  • the thickness of the first electrode layer 24 and the second electrode layer 26 is preferably 1.2 ⁇ m or less, more preferably 0.3 ⁇ m or less. , it is preferably 0.1 ⁇ m or less.
  • the piezoelectric layer 20 formed by dispersing the piezoelectric particles 36 in the matrix 34 containing a polymer material is sandwiched between the first electrode layer 24 and the second electrode layer 26, and further, It has a configuration in which this laminate is sandwiched between a first protective layer 28 and a second protective layer 30 .
  • such a piezoelectric film 10 has a maximum value of loss tangent (Tan ⁇ ) at a frequency of 1 Hz by dynamic viscoelasticity measurement, which is 0.1 or more at room temperature (0° C. to 50° C.). A maximum exists at normal temperature. As a result, even if the piezoelectric film 10 receives a relatively slow and large bending deformation of several Hz or less from the outside at room temperature, the strain energy can be effectively diffused to the outside as heat. , the occurrence of cracks at the interface between the polymer matrix and the piezoelectric particles can be prevented.
  • Tan ⁇ loss tangent
  • the piezoelectric film 10 preferably has a storage elastic modulus (E') at a frequency of 1 Hz measured by dynamic viscoelasticity measurement of 10 to 30 GPa at 0°C and 1 to 10 GPa at 50°C. Note that this condition applies to the piezoelectric layer 20 as well. Accordingly, the piezoelectric film 10 can have a large frequency dispersion in the storage elastic modulus (E') at room temperature. That is, it can act hard against vibrations of 20 Hz to 20 kHz and soft against vibrations of several Hz or less.
  • E' storage elastic modulus
  • the piezoelectric film 10 has a product of thickness and storage elastic modulus (E′) at a frequency of 1 Hz determined by dynamic viscoelasticity measurement of 1.0 ⁇ 10 5 to 2.0 ⁇ 10 6 N/m at 0° C. , 1.0 ⁇ 10 5 to 1.0 ⁇ 10 6 N/m at 50°C. Note that this condition applies to the piezoelectric layer 20 as well. As a result, the piezoelectric film 10 can have appropriate rigidity and mechanical strength within a range that does not impair flexibility and acoustic properties.
  • E′ thickness and storage elastic modulus
  • the piezoelectric film 10 preferably has a loss tangent (Tan ⁇ ) of 0.05 or more at 25° C. and a frequency of 1 kHz in a master curve obtained from dynamic viscoelasticity measurement. This condition applies to the piezoelectric layer 20 as well. As a result, the frequency characteristics of the speaker using the piezoelectric film 10 are smoothed, and the amount of change in sound quality when the lowest resonance frequency f0 changes as the curvature of the speaker changes can be reduced.
  • Tan ⁇ loss tangent
  • the storage elastic modulus (Young's modulus) and loss tangent of the piezoelectric film 10, piezoelectric layer 20, etc. may be measured by known methods.
  • the dynamic viscoelasticity measuring device DMS6100 manufactured by SII Nanotechnology Co., Ltd. manufactured by SII Nanotechnology Co., Ltd. (manufactured by SII Nanotechnology Co., Ltd.) may be used for measurement.
  • 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.
  • a heating rate of 2° C./min in a nitrogen atmosphere
  • a sample size of 40 mm ⁇ 10 mm including the clamping area
  • a distance between chucks of 20 mm may be measured by known methods.
  • the piezoelectric film 10 of the present invention covers the electrode lead-out portions for leading the electrodes from the first electrode layer 24 and the second electrode layer 26 and the area where the piezoelectric layer 20 is exposed.
  • it may have an insulating layer or the like for preventing short circuits or the like.
  • a method in which the electrode layer and the protective layer are provided with portions protruding outward in the plane direction of the piezoelectric layer 20 and a lead wire is connected to the portion to lead out the electrodes to the outside, the first electrode layer 24 and the second electrode.
  • suitable methods for extracting electrodes include the method described in Japanese Patent Application Laid-Open No.
  • each electrode layer is not limited to one electrode lead-out portion, and may have two or more electrode lead-out portions.
  • three or more electrode lead-out portions are provided in order to ensure more reliable conduction of electricity. is preferred.
  • a signal source 102 is connected to the first electrode layer 24 and the second electrode layer 26 of the piezoelectric film 10 to apply a drive voltage for expanding and contracting the piezoelectric film 10 , that is, to supply drive power.
  • a commercially available power amplifier or the like can be used as the signal source 102 as long as it can output a desired signal.
  • the signal provided by the signal source 102 is not limited and may be a DC signal or an AC signal.
  • the driving voltage may be appropriately set according to the thickness of the piezoelectric layer 20 of the piezoelectric film 10, the forming material, and the like, so that the piezoelectric film 10 can be properly driven.
  • the piezoelectric device 100 shown in FIG. 1 in the case of a configuration in which a heating signal is applied to the piezoelectric film 10 to cause the piezoelectric film 10 to generate heat by itself, it is preferable to use an AC power supply as the power supply.
  • FIG. 10 An example of a method for manufacturing the piezoelectric film 10 will be described below with reference to FIGS. 10 to 12.
  • FIG. 10 An example of a method for manufacturing the piezoelectric film 10 will be described below with reference to FIGS. 10 to 12.
  • FIG. 10 An example of a method for manufacturing the piezoelectric film 10 will be described below with reference to FIGS. 10 to 12.
  • FIG. 10 An example of a method for manufacturing the piezoelectric film 10 will be described below with reference to FIGS. 10 to 12.
  • a sheet-like object 11a having a first protective layer 28 on which a first electrode layer 24 is formed is prepared as shown in FIG. Furthermore, a sheet-like object 11c conceptually shown in FIG. 12 is prepared in which the second electrode layer 26 is formed on the surface of the second protective layer 30 .
  • the sheet 11a may be produced by forming a copper thin film or the like as the first electrode layer 24 on the surface of the first protective layer 28 by vacuum deposition, sputtering, plating, or the like.
  • the sheet 11c may be produced by forming a copper thin film or the like as the second electrode layer 26 on the surface of the second protective layer 30 by vacuum deposition, sputtering, plating, or the like.
  • a commercially available sheet having a copper thin film or the like formed on a protective layer may be used as the sheet 11a and/or the sheet 11c.
  • the sheet-like material 11a and the sheet-like material 11c may have the same configuration or different configurations.
  • a protective layer with a separator temporary support
  • PET or the like having a thickness of 25 to 100 ⁇ m can be used as the separator.
  • the separator may be removed after the electrode layer and protective layer are thermocompression bonded.
  • a coating (coating composition) that will form the piezoelectric layer 20 is applied on the first electrode layer 24 of the sheet 11a, and then cured to form the piezoelectric layer 20.
  • a laminated body 11b in which the sheet-like material 11a and the piezoelectric layer 20 are laminated is produced.
  • a polymer material such as cyanoethylated PVA is dissolved in an organic solvent, and piezoelectric particles 36 such as PZT particles are added and stirred to prepare a coating material.
  • Organic solvents are not limited, and various organic solvents such as dimethylformamide (DMF), methyl ethyl ketone (MEK), and cyclohexanone can be used.
  • DMF dimethylformamide
  • MEK methyl ethyl ketone
  • cyclohexanone can be used.
  • the paint is cast (applied) on the sheet-like material 11a and dried by evaporating the organic solvent.
  • a laminate 11b having the first electrode layer 24 on the first protective layer 28 and the piezoelectric layer 20 on the first electrode layer 24 is produced. .
  • the coating material there are no restrictions on the method of casting the coating material, and known methods (coating equipment) such as bar coaters, slide coaters and doctor knives can all be used.
  • coating equipment such as bar coaters, slide coaters and doctor knives can all be used.
  • the polymer material is heat-meltable, the polymer material is heat-melted and the piezoelectric particles 36 are added to prepare a melt, which is then extruded into the sheet shown in FIG.
  • a laminate 11b as shown in FIG. 11 may be produced by extruding a sheet onto the object 11a and cooling it.
  • the matrix 34 may be added with a polymeric piezoelectric material such as PVDF (polyvinylidene fluoride), in addition to the polymeric material having viscoelasticity at room temperature.
  • a polymeric piezoelectric material such as PVDF (polyvinylidene fluoride)
  • the polymeric piezoelectric materials to be added to the paint may be dissolved.
  • the polymer piezoelectric material to be added may be added to a polymer material that has been melted by heating and has viscoelasticity at room temperature, and then melted by heating.
  • the piezoelectric layer 20 After the piezoelectric layer 20 is formed, it may be calendered, if necessary. Calendering may be performed once or multiple times. As is well known, calendering is a process in which a surface to be treated is heated and pressed by a heating press, a heating roller, or the like to flatten the surface. Note that the calendering treatment may be performed after the polarization treatment described later. However, if the calendering process is performed after the polarization process, the piezoelectric particles 36 pushed in by the pressure will rotate, which may reduce the effect of the polarization process. Considering this point, the calendering treatment is preferably performed before the polarization treatment.
  • the piezoelectric layer 20 of the laminate 11b having the first electrode layer 24 on the first protective layer 28 and the piezoelectric layer 20 formed on the first electrode layer 24 is subjected to polarization treatment (poling). )I do.
  • the polarization treatment of the piezoelectric layer 20 may be performed before the calendering treatment, but is preferably performed after the calendering treatment.
  • the method of polarization treatment of the piezoelectric layer 20 is not limited, and known methods can be used.
  • electric field poling in which a DC electric field is directly applied to an object to be polarized, is exemplified.
  • the second electrode layer 26 may be formed before the polarization treatment, and the electric field poling treatment may be performed using the first electrode layer 24 and the second electrode layer 26.
  • the polarization treatment is preferably performed in the thickness direction of the piezoelectric layer 20, not in the plane direction.
  • the previously prepared sheet 11c is laminated on the piezoelectric layer 20 side of the laminated body 11b subjected to the polarization treatment, with the second electrode layer 26 facing the piezoelectric layer 20.
  • this laminate is thermocompression bonded using a hot press device, a heating roller, or the like while sandwiching the first protective layer 28 and the second protective layer 30, thereby joining the laminate 11b and the sheet-like material 11c.
  • a piezoelectric film 10 as shown in FIG. 9 is produced.
  • the piezoelectric film 10 may be produced by bonding the laminated body 11b and the sheet-like material 11c together using an adhesive and preferably further pressing them together.
  • Such a piezoelectric film 10 may be manufactured using cut-sheet-shaped sheet-like materials 11a and 11c, or the like, or may be manufactured using roll-to-roll. good too.
  • the produced piezoelectric film may be cut into a desired shape according to various uses.
  • the piezoelectric film 10 produced in this manner is polarized in the thickness direction rather than in the plane direction, and excellent piezoelectric properties can be obtained without stretching after the polarization treatment. Therefore, the piezoelectric film 10 has no in-plane anisotropy in piezoelectric properties, and expands and contracts isotropically in all directions in the plane direction when a drive voltage is applied.
  • Such a piezoelectric film can be used in a piezoelectric speaker, in which the piezoelectric film itself is used as a vibrating diaphragm.
  • Piezoelectric speakers can also be used as microphones, sensors, and the like. Furthermore, this piezoelectric speaker can also be used as a vibration sensor.
  • the piezoelectric film can also be used as a so-called exciter that is attached to the diaphragm and vibrates the diaphragm.
  • a piezoelectric film is used as an exciter, a laminated piezoelectric element formed by laminating piezoelectric films is preferable in order to obtain a higher output.
  • the vibration plate 12 is not particularly limited as long as it preferably has flexibility, and various sheet-like materials (plate-like material, film) can be used.
  • sheet-like materials plate-like material, film
  • Examples include polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyphenylene sulfite (PPS), polymethyl methacrylate (PMMA), polyetherimide (PEI), polyimide (PI), Resin films made of polyethylene naphthalate (PEN), triacetyl cellulose (TAC), cyclic olefin resins, etc., expanded polystyrene, expanded plastics made of expanded styrene, expanded polyethylene, etc., plywood, cork board, leather such as cowhide, Examples include various types of paperboard such as carbon sheets and Japanese paper, and various types of corrugated board made by pasting another paperboard onto one or both sides of corrugated paperboard.
  • the diaphragm 12 may be an organic electroluminescence (OLED (Organic Light Emitting Diode)) display, a liquid crystal display, a micro LED (Light Emitting Diode) display, or an inorganic electroluminescence display.
  • OLED Organic Light Emitting Diode
  • a display device such as a display, a projector screen, and the like are also suitable for use.
  • Adhesive layer 19 for adhering piezoelectric films 10 to each other, and adhesive layer 16 for adhering piezoelectric film 10 (laminated piezoelectric element) and diaphragm 12 are formed of piezoelectric films 10 and piezoelectric film 10 and diaphragm 12, respectively.
  • the adhesive layer has fluidity at the time of bonding and then becomes a solid.
  • Even a layer made of an adhesive is a gel-like (rubber-like) soft solid at the time of bonding and remains gel-like thereafter. It may be a layer made of an adhesive whose state does not change, or a layer made of a material having the characteristics of both an adhesive and an adhesive.
  • the adhesive layer may be formed by applying an adhesive agent having fluidity such as a liquid, or may be formed by using a sheet-like adhesive agent.
  • the piezoelectric device 100c by expanding and contracting the piezoelectric film 10 (laminated piezoelectric element), the diaphragm 12 is flexed and vibrated to generate sound. Therefore, in the piezoelectric device 100 c , it is preferable that the expansion and contraction of the piezoelectric film 10 is directly transmitted to the diaphragm 12 . If a substance having a viscosity that reduces vibration is present between the diaphragm 12 and the piezoelectric film 10, the efficiency of transmission of the energy of expansion and contraction of the piezoelectric film 10 to the diaphragm 12 is lowered, resulting in a piezoelectric device 100c. drive efficiency is reduced.
  • the adhesive layer 16 that bonds the piezoelectric film 10 and the diaphragm 12 is an adhesive layer made of an adhesive that provides a solid and harder adhesive layer 16 than an adhesive layer made of an adhesive.
  • an adhesive layer made of a thermoplastic type adhesive such as a polyester adhesive and a styrene-butadiene rubber (SBR) adhesive is exemplified. Adhesion, unlike sticking, is useful in seeking high adhesion temperatures. Further, a thermoplastic type adhesive is suitable because it has "relatively low temperature, short time, and strong adhesion".
  • the thickness of the adhesive layer 16 is not limited, and the thickness may be appropriately set according to the material of the adhesive layer 16 so as to obtain a sufficient sticking force (adhesive force, cohesive force).
  • the thinner the adhesive layer 16 the higher the effect of transmitting the expansion/contraction energy (vibration energy) of the piezoelectric film 10 to the vibration plate 12, and the higher the energy efficiency.
  • the adhesive layer 16 is thick and rigid, it may restrict the expansion and contraction of the piezoelectric film 10 .
  • the adhesive layer 16 is preferably thinner.
  • the thickness of the adhesive layer 16 after sticking is preferably 0.1 to 50 ⁇ m, more preferably 0.1 to 30 ⁇ m, even more preferably 0.1 to 10 ⁇ m.
  • the adhesive layer 16 is provided as a preferred embodiment and is not an essential component. Therefore, the piezoelectric device 100c does not have the adhesive layer 16, and the vibration plate 12 and the piezoelectric film 10 may be fixed using known crimping means, fastening means, fixing means, or the like.
  • the shape of the piezoelectric film 10 is rectangular in plan view, the four corners may be fastened with members such as bolts and nuts to form an electroacoustic transducer, or the four corners and the central portion may be bolted together.
  • the electroacoustic transducer may be configured by fastening with a member such as a nut.
  • the piezoelectric film 10 expands and contracts independently of the diaphragm 12 when a drive voltage is applied from the power source. is not transmitted to the diaphragm 12.
  • the piezoelectric film 10 expands and contracts independently of the diaphragm 12
  • the vibration efficiency of the diaphragm 12 due to the piezoelectric film 10 decreases.
  • the diaphragm 12 cannot be sufficiently vibrated.
  • it is preferable that the diaphragm 12 and the piezoelectric film 10 are adhered with the adhesive layer 16 .
  • the laminated piezoelectric element expands and contracts a plurality of laminated piezoelectric films 10 to vibrate the diaphragm 12 and generate sound. Therefore, it is preferable that the expansion and contraction of each piezoelectric film 10 is directly transmitted to the laminated piezoelectric element. If a substance having a viscosity that reduces vibration is present between the piezoelectric films 10, the efficiency of transmission of the energy of expansion and contraction of the piezoelectric films 10 is lowered, and the driving efficiency of the laminated piezoelectric element is lowered.
  • the adhesive layer 19 that bonds the piezoelectric films 10 to each other is an adhesive layer made of an adhesive that provides a solid and harder adhesive layer 19 than an adhesive layer made of an adhesive.
  • a more preferable adhesive layer 19 is an adhesive layer made of a thermoplastic type adhesive such as a polyester-based adhesive and a styrene-butadiene rubber (SBR)-based adhesive.
  • the thickness of the adhesive layer 19 is not limited, and the thickness that can exhibit sufficient adhesive strength may be appropriately set according to the material forming the adhesive layer 19 .
  • the thinner the adhesive layer 19 is the higher the effect of transmitting the expansion/contraction energy of the piezoelectric film 10 can be and the higher the energy efficiency can be.
  • the adhesive layer 19 is thick and rigid, it may restrict the expansion and contraction of the piezoelectric film 10 .
  • the adhesive layer 19 is preferably thinner than the piezoelectric layer 20 . That is, in the laminated piezoelectric element, the adhesive layer 19 is preferably hard and thin.
  • the thickness of the adhesive layer 19 after sticking is preferably 0.1 to 50 ⁇ m, more preferably 0.1 to 30 ⁇ m, even more preferably 0.1 to 10 ⁇ m. 6 and 7, the polarization directions of the adjacent piezoelectric films are opposite to each other, and there is no risk of short-circuiting between the adjacent piezoelectric films 10, so the adhesive layer 19 can be made thinner.
  • the spring constant of the adhesive layer 19 is equal to or less than the spring constant of the piezoelectric film 10 .
  • the product of the thickness of the adhesive layer 19 and the storage elastic modulus (E′) at a frequency of 1 Hz as measured by dynamic viscoelasticity is 2.0 ⁇ 10 6 N/m or less at 0° C. and 50° C. is preferably 1.0 ⁇ 10 6 N/m or less.
  • the internal loss at a frequency of 1 Hz by dynamic viscoelasticity measurement of the adhesive layer 19 is 1.0 or less at 25 ° C. in the case of the adhesive layer 19 made of adhesive, and It is preferably 0.1 or less at 25°C.
  • the adhesive layer 19 is provided as a preferred embodiment, and is not an essential component. Therefore, the laminated piezoelectric element does not have the adhesive layer 19, and the piezoelectric film 10 is laminated and adhered using known crimping means, fastening means, fixing means, or the like to form the laminated piezoelectric element.
  • the piezoelectric film 10 is rectangular, the four corners may be fastened with bolts and nuts to form a laminated piezoelectric element, or the four corners and the central portion may be fastened with bolts and nuts or the like to form a laminated piezoelectric element. may be configured.
  • an adhesive tape may be adhered to the peripheral portion (end face) to fix the laminated piezoelectric films 10 to form a laminated piezoelectric element.
  • the individual piezoelectric films 10 expand and contract independently, and in some cases, each layer of the piezoelectric films 10 bends in the opposite direction, creating a gap. put away.
  • the driving efficiency of the laminated piezoelectric element decreases, and the expansion and contraction of the laminated piezoelectric element as a whole becomes small, and the diaphragm 12 in contact etc. may not be sufficiently vibrated.
  • the laminated piezoelectric element preferably has an adhesive layer 19 for adhering the adjacent piezoelectric films 10 together like the laminated piezoelectric element in the illustrated example.
  • the piezoelectric device 100c has a configuration in which a laminated piezoelectric element is attached to the diaphragm 12, the thickness of the laminated piezoelectric element and the dynamic viscoelasticity measurement at a frequency of 1 Hz and 25° C.
  • the product with the storage elastic modulus is preferably 0.1 to 3 times the product of the thickness of diaphragm 12 and Young's modulus.
  • the piezoelectric film 10 of the present invention has excellent flexibility in a room temperature environment, and a laminated piezoelectric element obtained by laminating the piezoelectric film 10 also exhibits excellent flexibility in a room temperature environment. have sex.
  • the diaphragm 12 has a certain degree of rigidity. When such a diaphragm 12 is combined with a highly rigid laminated piezoelectric element, it is hard and difficult to bend, which is disadvantageous in terms of the flexibility of the piezoelectric device 100c.
  • the product of the thickness of the laminated piezoelectric element and the storage elastic modulus at a frequency of 1 Hz and 25° C. by dynamic viscoelasticity measurement is the ratio between the thickness of diaphragm 12 and Young's modulus. It is preferably 3 times or less of the product. That is, the laminated piezoelectric element preferably has a spring constant of three times or less that of the diaphragm 12 for slow motion.
  • the piezoelectric device 100c can behave softly against slow movements caused by external forces such as bending and rolling. Flexibility is expressed.
  • the product of the thickness of the laminated piezoelectric element and the storage elastic modulus at a frequency of 1 Hz and 25° C. measured by dynamic viscoelasticity measurement is two times or less the product of the thickness of the diaphragm 12 and Young's modulus. , more preferably 1-fold or less, and particularly preferably 0.3-fold or less.
  • the product of the thickness of the laminated piezoelectric element and the storage elastic modulus at 25° C. at a frequency of 1 Hz by dynamic viscoelasticity measurement is , the product of the thickness of the diaphragm 12 and the Young's modulus, preferably 0.1 times or more.
  • the product of the thickness of the laminated piezoelectric element and the storage modulus at 25° C. at a frequency of 1 kHz in the master curve obtained from the dynamic viscoelasticity measurement is the product of the thickness of the diaphragm 12 and the Young's modulus. , preferably 0.3 to 10 times. That is, the laminated piezoelectric element preferably has a spring constant of 0.3 to 10 times that of the diaphragm 12 in fast motion in a driven state.
  • the piezoelectric device 100c generates sound by vibrating the diaphragm 12 due to expansion and contraction of the laminated piezoelectric element in the plane direction. Therefore, the laminated piezoelectric element preferably has a certain degree of rigidity (hardness, stiffness) with respect to the diaphragm 12 at frequencies in the audio band (20 Hz to 20 kHz).
  • the product of the thickness of the laminated piezoelectric element and the storage elastic modulus at a frequency of 1 kHz and 25° C. in the master curve obtained from the dynamic viscoelasticity measurement is the product of the thickness of the diaphragm 12 and Young's modulus, preferably 0.5. 3 times or more, more preferably 0.5 times or more, further preferably 1 time or more. That is, the spring constant of the laminated piezoelectric element is preferably 0.3 times or more, more preferably 0.5 times or more, and more preferably 1 time or more that of the diaphragm 12 for fast movement. is more preferred. This ensures sufficient rigidity of the laminated piezoelectric element with respect to the diaphragm 12 at frequencies in the audio band, so that the piezoelectric device 100c can output sound with high sound pressure with high energy efficiency.
  • the product of the thickness of the laminated piezoelectric element and the storage elastic modulus at a frequency of 1 kHz and 25 ° C. by dynamic viscoelasticity measurement is the vibration It is preferably 10 times or less the product of the thickness of the plate 12 and Young's modulus.
  • the product of the thickness of the laminated piezoelectric element (exciter) and the storage elastic modulus at a frequency of 1 Hz and 25° C. measured by dynamic viscoelasticity measurement is, of course, the thickness of the adhesive layer 19.
  • physical properties such as the storage elastic modulus of the adhesive layer 19 also have a great effect.
  • the product of the thickness of the diaphragm 12 and the Young's modulus, that is, the spring constant of the diaphragm is greatly affected not only by the thickness of the diaphragm but also by the physical properties of the diaphragm.
  • the product of the thickness of the laminated piezoelectric element and the storage elastic modulus of the laminated piezoelectric element at a frequency of 1 Hz and 25° C. by dynamic viscoelasticity measurement is the product of the thickness of the diaphragm 12 and Young's modulus.
  • the thickness and material of the adhesive layer 19 and the thickness and material of the diaphragm are important.
  • the product of the thickness of the laminated piezoelectric element and the storage elastic modulus of the laminated piezoelectric element at a frequency of 1 kHz and 25° C. is 0.3 to 10 times the product of the thickness of the diaphragm 12 and Young's modulus.
  • the thickness and material of the adhesive layer 19 and the thickness and material of the diaphragm 12 are also important in order to satisfy the condition.
  • the thickness and material of the adhesive layer 19 and the thickness and material of the diaphragm 12 are appropriately adjusted so as to satisfy the above conditions. preferably selected.
  • the thickness and material of the adhesive layer 19 and the thickness and material of the vibration plate 12 are appropriately selected in accordance with the characteristics of the piezoelectric film 10, so that the laminated piezoelectric film can be obtained.
  • the product of the thickness of the element and the storage elastic modulus of the laminated piezoelectric element at a frequency of 1 Hz and 25° C. measured by dynamic viscoelasticity measurement is 0.1 to 3 times the product of the thickness of the diaphragm 12 and the Young's modulus.
  • the product of the thickness of the laminated piezoelectric element and the storage elastic modulus of the laminated piezoelectric element at a frequency of 1 kHz and 25° C. is 0.3 to 10 of the product of the thickness of the diaphragm 12 and Young's modulus. It becomes possible to satisfy the condition of being double.
  • the above-mentioned product of thickness and storage elastic modulus is the same when a single-layer piezoelectric film 10 is used as an exciter instead of a laminated piezoelectric element.
  • Example 1 [Preparation of piezoelectric film] A piezoelectric film was produced by the method shown in FIGS. 10 to 12 described above. First, cyanoethylated PVA (CR-V, manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved in dimethylformamide (DMF) at the following compositional ratio. After that, PZT particles as piezoelectric particles were added to this solution at the following composition ratio, and the mixture was stirred with a propeller mixer (rotation speed: 2000 rpm) to prepare a paint for forming a piezoelectric layer.
  • DMF dimethylformamide
  • ⁇ PZT particles ⁇ 300 parts by mass ⁇ Cyanoethylated PVA ⁇ 30 parts by mass ⁇ DMF ⁇ 70 parts by mass
  • the PZT particles used were obtained by sintering a commercially available PZT raw material powder at 1000 to 1200° C. and then pulverizing and classifying the sintered particles to an average particle size of 5 ⁇ m.
  • a sheet-like material was prepared by vacuum-depositing a copper thin film with a thickness of 0.3 ⁇ m on a PET film with a thickness of 4 ⁇ m. That is, in this example, the first electrode layer and the second electrode layer are 0.3 ⁇ m thick copper-deposited thin films, and the first protective layer and the second protective layer are 4 ⁇ m thick PET films.
  • the previously prepared coating material for forming the piezoelectric layer was applied onto the first electrode layer (copper-deposited thin film) of the sheet.
  • the paint was applied so that the thickness of the coating film after drying was 50 ⁇ m.
  • the sheet-like material coated with the paint was dried by heating on a hot plate at 120° C. to evaporate the DMF.
  • a laminate having a first electrode layer made of copper on a first protective layer made of PET and a piezoelectric layer (polymer composite piezoelectric layer) having a thickness of 50 ⁇ m thereon was produced. .
  • the produced piezoelectric layer was subjected to polarization treatment in the thickness direction.
  • a sheet-like material obtained by vapor-depositing a copper thin film on a PET film was laminated on the piezoelectric laminate that had been subjected to the polarization treatment, with the second electrode layer (copper thin film side) facing the piezoelectric layer.
  • the laminate of the piezoelectric laminate and the sheet-like material is thermocompression bonded at a temperature of 120° C. using a laminator device, thereby adhering and bonding the piezoelectric layer and the second electrode layer.
  • a film was produced.
  • the piezoelectric film had a local maximum value (maximum value) of 0.40 at 25°C in loss tangent at a frequency of 1 Hz.
  • the produced piezoelectric film was connected to a power amplifier (STR-DH190 manufactured by SONY) as a signal source.
  • a sheathed thermocouple (DS-1010 manufactured by AS ONE) was attached as a temperature sensor along the edge of the piezoelectric film.
  • a piezoelectric device was fabricated by connecting a signal source and a temperature sensor to a controller. When the temperature measured by the temperature sensor falls within the range of ⁇ 40° C. to 0° C., the controller applies a sinusoidal alternating current with a frequency of 20 kHz and an effective voltage of 2 Vrms to the piezoelectric film from the signal source so that the target temperature is 20° C. It is configured to apply a signal.
  • Example 2 Example except that the controller applies a sinusoidal AC signal with a frequency of 40 kHz and an effective voltage of 1 Vrms from the signal source to the piezoelectric film when the temperature measured by the temperature sensor enters the range of -40 ° C. to 0 ° C.
  • a piezoelectric device was produced in the same manner as in 1.
  • Example 3 Except that the control unit applies a sine wave AC signal with a frequency of 25 kHz and an effective voltage of 0.5 Vrms from the signal source to the piezoelectric film when the temperature measured by the temperature sensor enters the range of -40 ° C. to 0 ° C.
  • a piezoelectric device was produced in the same manner as in Example 1.
  • Example 1 A piezoelectric device was fabricated in the same manner as in Example 1, except that the temperature sensor and the controller were not provided and the heating signal was not applied.
  • Example 2 The piezoelectric film described in Example 1 of International Publication No. 2020/196807 was produced, and a piezoelectric device was produced in a configuration without a temperature sensor and a controller and without application of a heating signal.
  • the produced piezoelectric film had a loss tangent at a frequency of 1 Hz with a local maximum value (maximum value) of 0.25 at -30°C.
  • Comparative Example 1 which does not have a heating mechanism, is inferior in flexibility below freezing.
  • Comparative Example 2 in which a polymer composite piezoelectric material mixed with a polymer material having viscoelasticity at low temperatures (below freezing) is used as a matrix, has excellent flexibility below freezing and good flexibility at room temperature.
  • the flexibility (flexibility 2) under more severe conditions with a radius of curvature of 5 mm is inferior at room temperature.
  • the effective voltage of the sinusoidal AC signal which is the signal for heating, is preferably 1 Vrms or more.
  • Example 4 Example 1 except that a polyimide heater (FL heater manufactured by Shinwa Kiseki Co., Ltd.) was provided instead of applying a signal for heating to the piezoelectric film to generate heat by itself, and the piezoelectric film was heated by the polyimide heater.
  • a piezoelectric device was produced in the same manner as in the above.
  • the polyimide heater was arranged so as to be in contact with the vicinity of the edge of one surface of the piezoelectric film. Also, when the temperature measured by the temperature sensor fell within the range of -40°C to 0°C, the ON/OFF of the polyimide heater was controlled so that the target temperature was 20°C.
  • Flexibility 1 and Flexibility 2 were evaluated in the same manner as above for the produced piezoelectric device. Flexibility 1 at a radius of curvature of 5 cm was rated A in both the low temperature test and normal temperature test. Flexibility 2 at a radius of curvature of 5 mm was rated A in both the low temperature test and normal temperature test. Therefore, it can be seen that the piezoelectric device of Example 4 has excellent flexibility in both the low temperature test (below freezing point) and the normal temperature test (under normal temperature).
  • Example 5 A piezoelectric film produced in the same manner as in Example 1 was cut into a size of 200 mm ⁇ 150 mm and folded twice in the lateral direction to produce a three-layer piezoelectric element (200 mm ⁇ 50 mm). The folded piezoelectric films were adhered to each other with a thermal adhesive sheet (G5 manufactured by Kurabo Industries, Ltd.).
  • the manufactured piezoelectric element was connected to a power amplifier (SONY STR-DH190) as a signal source.
  • a sheathed thermocouple (DS-1010 manufactured by AS ONE) was attached as a temperature sensor along the edge of the piezoelectric element.
  • a signal source and a temperature sensor were connected to the controller.
  • the control unit was configured to apply a sinusoidal AC signal with a frequency of 20 kHz and an effective voltage of 2 Vrms from the signal source to the piezoelectric element while the temperature measured by the temperature sensor was between -40°C and 0°C.
  • Flexibility 1 and flexibility 2 were evaluated in the same manner as described above for the produced piezoelectric element. Flexibility 1 at a radius of curvature of 5 cm was rated A in both the low temperature test and normal temperature test. Flexibility 2 at a radius of curvature of 5 mm was rated A in both the low temperature test and normal temperature test. Therefore, it can be seen that the piezoelectric device of Example 5 has excellent flexibility in both the low temperature test (below freezing point) and the normal temperature test (under normal temperature). From the above, the effect of the present invention is clear.
  • the piezoelectric device of the present invention can be used, for example, in various sensors such as sound wave sensors, ultrasonic sensors, pressure sensors, tactile sensors, strain sensors, and vibration sensors (especially for infrastructure inspection such as crack detection and manufacturing site inspection such as foreign matter contamination detection).
  • sensors such as sound wave sensors, ultrasonic sensors, pressure sensors, tactile sensors, strain sensors, and vibration sensors (especially for infrastructure inspection such as crack detection and manufacturing site inspection such as foreign matter contamination detection).
  • acoustic devices such as microphones, pickups, speakers and exciters (specific applications include noise cancellers (used in cars, trains, airplanes, robots, etc.), artificial vocal cords, buzzers for preventing insects and vermin from entering , furniture, wallpaper, photographs, helmets, goggles, headrests, signage, robots, etc.), automobiles, smartphones, smart watches, haptics used for games, etc.

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)

Abstract

Provided is a piezoelectric device having excellent flexibility in both normal temperature and sub-zero environments. The piezoelectric device is provided with: a piezoelectric film including a piezoelectric layer containing piezoelectric particles in a matrix containing a polymeric material and electrode layers formed on both surfaces of the piezoelectric layer and having a maximum value, at which the loss tangent at a frequency of 1 Hz is 0.1 or more according to dynamic viscoelasticity measurement, in a temperature range of 0°C to 50°C; and a heating mechanism for heating the piezoelectric film.

Description

圧電デバイスpiezoelectric device
　本発明は、圧電デバイスに関する。 The present invention relates to piezoelectric devices.
　近年、プラスチック等の可撓性基板を用いたフレキシブルディスプレイに関する研究が進められている。
　フレキシブルディスプレイは、従来のガラス基板を用いたディスプレイと比較して、軽量性、薄さ、可撓性等において優位性を持っており、円柱等の曲面に備えることも可能である。また、丸めて収納することが可能であるため、大画面であっても携帯性を損なうことがなく、広告等の掲示用や、ＰＤＡ（携帯情報端末）等の表示装置として注目されている。 In recent years, researches on flexible displays using flexible substrates such as plastic have been advanced.
A flexible display has superiority in lightness, thinness, flexibility, etc., compared with a display using a conventional glass substrate, and can be provided on a curved surface such as a cylinder. In addition, since it can be rolled up and stored, even if it has a large screen, it does not impair portability, and is attracting attention as a display device for posting advertisements and the like, and for PDAs (personal digital assistants).
　このようなフレキシブルディスプレイを、テレビジョン受像機等のように画像と共に音声を再生する画像表示装置兼音声発生装置として使用する場合、音声を発生するための音響装置であるスピーカーが必要である。
　ここで、従来のスピーカー形状としては、漏斗状のいわゆるコーン型や、球面状のドーム型等が一般的である。しかしながら、これらのスピーカーを上述のフレキシブルディスプレイに内蔵しようとすると、フレキシブルディスプレイの長所である軽量性や可撓性を損なう虞れがある。また、スピーカーを外付けにした場合、持ち運び等が面倒であり、曲面状の壁に設置することが難しくなり美観を損ねる虞れもある。 When such a flexible display is used as an image display device and sound generator that reproduces sound together with an image, such as a television receiver, a speaker, which is an acoustic device for generating sound, is required.
Here, as a conventional speaker shape, a so-called funnel-like cone shape, a spherical dome shape, or the like is generally used. However, when it is attempted to incorporate these speakers into the flexible display described above, there is a risk of impairing the lightness and flexibility, which are advantages of the flexible display. In addition, when the speaker is externally attached, it is troublesome to carry, and it is difficult to install it on a curved wall, which may spoil the aesthetic appearance.
　このような中、軽量性や可撓性を損なうことなくフレキシブルディスプレイに一体化可能なスピーカーとして、特許文献１に記載の圧電フィルム（電気音響変換フィルム）が知られている。 Under these circumstances, the piezoelectric film (electroacoustic conversion film) described in Patent Document 1 is known as a speaker that can be integrated into a flexible display without impairing its light weight and flexibility.
　特許文献１の圧電フィルムは、常温で粘弾性を有する高分子材料からなる粘弾性マトリックス中に圧電体粒子を分散してなる高分子複合圧電体と、高分子複合圧電体の両面に形成された薄膜電極と、薄膜電極の表面に形成された保護層とを有し、かつ、動的粘弾性測定による周波数１Ｈｚでの損失正接が０．１以上となる極大値が０～５０℃の温度範囲に存在する、というものである。 The piezoelectric film of Patent Document 1 is formed on both surfaces of a polymer composite piezoelectric body in which piezoelectric particles are dispersed in a viscoelastic matrix made of a polymer material having viscoelasticity at room temperature, and a polymer composite piezoelectric body. It has a thin film electrode and a protective layer formed on the surface of the thin film electrode, and the temperature range of 0 to 50 ° C. where the loss tangent at a frequency of 1 Hz by dynamic viscoelasticity measurement is 0.1 or more. exists in
　特許文献１に記載される圧電フィルムは、常温（０～５０℃）であれば、優れた可撓性および音質を発現する。しかしながら、スピーカーが使用される環境は、常温のみとは限らず、国、地域および使用場所によっては、氷点下の環境下で使用される場合も有る。ところが、特許文献１に記載される圧電フィルムは、氷点下のような低温の環境下では、十分な可撓性および音質を発現することが困難であった。 The piezoelectric film described in Patent Document 1 exhibits excellent flexibility and sound quality at room temperature (0 to 50°C). However, the environment in which the speaker is used is not limited to normal temperature, and depending on the country, region, and place of use, it may be used in an environment below freezing. However, it is difficult for the piezoelectric film described in Patent Document 1 to exhibit sufficient flexibility and sound quality in a low-temperature environment such as below freezing.
　これに対して、特許文献２には、高分子材料を含むマトリックス中に圧電体粒子を分散してなる高分子複合圧電体と、高分子複合圧電体の両面に形成された電極層とを有し、動的粘弾性測定による周波数１Ｈｚでの損失正接が、－８０℃以上０℃未満の温度範囲に０．１以上となる極大値が存在し、かつ、０℃での値が０．０５以上である圧電フィルムが記載されている。特許文献２に記載の圧電フィルムは、低温（氷点下）で粘弾性を有する高分子材料を混合した高分子複合圧電体をマトリックスとして用いることで、マトリックスのガラス転移点の中心位置を氷点下に移動させ、氷点下での良好な可撓性を実現している。 On the other hand, Patent Document 2 discloses a polymer composite piezoelectric body in which piezoelectric particles are dispersed in a matrix containing a polymer material, and electrode layers formed on both sides of the polymer composite piezoelectric body. However, the loss tangent at a frequency of 1 Hz by dynamic viscoelasticity measurement has a maximum value of 0.1 or more in the temperature range of -80 ° C. or more and less than 0 ° C., and the value at 0 ° C. is 0.05. A piezoelectric film is thus described. The piezoelectric film described in Patent Document 2 uses, as a matrix, a polymer composite piezoelectric material mixed with a polymer material having viscoelasticity at a low temperature (below freezing point), thereby moving the central position of the glass transition point of the matrix below freezing point. , which provides good flexibility below freezing.
特開２０１５－２９２７０号公報JP 2015-29270 A 国際公開第２０２０／１９６８０７号WO2020/196807
　しかしながら、本発明者の検討によれば、特許文献２に記載の圧電フィルムは、氷点下では良好な可撓性を有する一方で、常温下での可撓性は氷点下での場合に比べて劣っており、小さな曲率半径で圧電フィルムが繰り返し曲げられる場合に、十分な信頼性を得られないという課題があることがわかった。 However, according to studies by the present inventors, the piezoelectric film described in Patent Document 2 has good flexibility below freezing, but the flexibility at room temperature is inferior to that at below freezing. Therefore, it was found that there is a problem that sufficient reliability cannot be obtained when the piezoelectric film is repeatedly bent with a small radius of curvature.
　本発明の課題は、このような従来技術の問題点を解決することにあり、常温および氷点下のいずれの環境下においても、優れた可撓性を有する圧電デバイスを提供することにある。 The object of the present invention is to solve the problems of the prior art, and to provide a piezoelectric device that has excellent flexibility in both normal temperature and sub-zero environments.
　上述した課題を解決するために、本発明は、以下の構成を有する。
　［１］　高分子材料を含むマトリックス中に圧電体粒子を含有する圧電体層と、圧電体層の両面に形成された電極層とを有し、動的粘弾性測定による周波数１Ｈｚでの損失正接が０．１以上となる極大値が０℃から５０℃の温度範囲に存在する圧電フィルム、および、
　圧電フィルムを加熱するための加熱機構を備える、圧電デバイス。
　［２］　加熱機構が、温度センサーと、制御部と、を備え、
　制御部は、温度センサーが測定した温度に応じて、加熱機構を駆動して圧電フィルムを加熱する、［１］に記載の圧電デバイス。
　［３］　加熱機構が、外部ヒーターを有する、［１］または［２］に記載の圧電デバイス。
　［４］　加熱機構が、圧電フィルムに周波数１５ｋＨｚ以上の正弦波交流信号を印加して、圧電フィルムを自己発熱させるものである、［１］または［２］に記載の圧電デバイス。
　［５］　正弦波交流信号の実効電圧が１Ｖｒｍｓ～１０Ｖｒｍｓである、［４］に記載の圧電デバイス。
　［６］　自己発熱が圧電フィルムに非正弦波交流信号を印加することでもたらされるものであり、非正弦波交流信号をフーリエ解析して得られた正弦波交流信号の周波数の少なくとも一つ以上が１５ｋＨｚ～１００ｋＨｚの範囲に存在する、［４］に記載の圧電デバイス。
　［７］　１５ｋＨｚ～１００ｋＨｚの範囲に存在する正弦波交流信号の実効電圧が１Ｖｒｍｓ～１０Ｖｒｍｓである、［６］に記載の圧電デバイス。
　［８］　圧電フィルムの少なくとも一部の曲率半径が変動するタイミングで、加熱機構が圧電フィルムを加熱する、［１］～［７］のいずれかに記載の圧電デバイス。
　［９］　圧電フィルムは、電極層の表面に設けられた保護層を有する、［１］～［８］のいずれかに記載の圧電デバイス。
　［１０］　圧電体層が厚さ方向に分極されたものである、［１］～［９］のいずれかに記載の圧電デバイス。
　［１１］　電極層と信号源とを接続するための引き出し線を有する、［１］～［１０］のいずれかに記載の圧電デバイス。
　［１２］　圧電フィルムが複数層、積層されている、［１］～［１１］のいずれかに記載の圧電デバイス。
　［１３］　圧電フィルムが、厚さ方向に分極されたものであり、かつ、隣接する圧電フィルムの分極方向が逆である、［１２］に記載の圧電デバイス。
　［１４］　圧電フィルムを、１回以上、折り返すことにより、圧電フィルムを、複数層、積層したものである、［１２］または［１３］に記載の圧電デバイス。
　［１５］　隣接する圧電フィルムを貼着する貼着層を有する、［１２］～［１４］のいずれかに記載の圧電デバイス。
　［１６］　圧電フィルムが振動板に貼付されてなる、［１］～［１５］のいずれかに記載の圧電デバイス。 In order to solve the problems described above, the present invention has the following configurations.
[1] It has a piezoelectric layer containing piezoelectric particles in a matrix containing a polymer material and electrode layers formed on both sides of the piezoelectric layer, and the loss tangent at a frequency of 1 Hz is measured by dynamic viscoelasticity measurement. A piezoelectric film having a maximum value of 0.1 or more in a temperature range of 0 ° C. to 50 ° C., and
A piezoelectric device comprising a heating mechanism for heating a piezoelectric film.
[2] The heating mechanism includes a temperature sensor and a controller,
The piezoelectric device according to [1], wherein the controller drives the heating mechanism to heat the piezoelectric film according to the temperature measured by the temperature sensor.
[3] The piezoelectric device according to [1] or [2], wherein the heating mechanism has an external heater.
[4] The piezoelectric device according to [1] or [2], wherein the heating mechanism applies a sinusoidal AC signal with a frequency of 15 kHz or more to the piezoelectric film to cause the piezoelectric film to self-heat.
[5] The piezoelectric device according to [4], wherein the sinusoidal AC signal has an effective voltage of 1 Vrms to 10 Vrms.
[6] Self-heating is caused by applying a non-sinusoidal AC signal to the piezoelectric film, and at least one frequency of the sinusoidal AC signal obtained by Fourier analysis of the non-sinusoidal AC signal is The piezoelectric device according to [4], present in the range of 15 kHz to 100 kHz.
[7] The piezoelectric device according to [6], wherein the sinusoidal AC signal present in the range of 15 kHz to 100 kHz has an effective voltage of 1 Vrms to 10 Vrms.
[8] The piezoelectric device according to any one of [1] to [7], wherein the heating mechanism heats the piezoelectric film at the timing when the radius of curvature of at least part of the piezoelectric film varies.
[9] The piezoelectric device according to any one of [1] to [8], wherein the piezoelectric film has a protective layer provided on the surface of the electrode layer.
[10] The piezoelectric device according to any one of [1] to [9], wherein the piezoelectric layer is polarized in the thickness direction.
[11] The piezoelectric device according to any one of [1] to [10], which has a lead wire for connecting the electrode layer and the signal source.
[12] The piezoelectric device according to any one of [1] to [11], wherein a plurality of piezoelectric films are laminated.
[13] The piezoelectric device according to [12], wherein the piezoelectric film is polarized in the thickness direction, and adjacent piezoelectric films have opposite polarization directions.
[14] The piezoelectric device according to [12] or [13], wherein a plurality of piezoelectric films are laminated by folding the piezoelectric film once or more.
[15] The piezoelectric device according to any one of [12] to [14], which has an adhesive layer for attaching adjacent piezoelectric films.
[16] The piezoelectric device according to any one of [1] to [15], wherein the piezoelectric film is attached to a diaphragm.
　本発明によれば、常温および氷点下のいずれの環境下においても、優れた可撓性を有する圧電デバイスを提供することができる。 According to the present invention, it is possible to provide a piezoelectric device having excellent flexibility in both normal temperature and sub-zero environments.
本発明の圧電デバイスの一例を模式的に示す図である。It is a figure which shows typically an example of the piezoelectric device of this invention. 本発明の圧電デバイスの他の一例を模式的に示す斜視図である。FIG. 4 is a perspective view schematically showing another example of the piezoelectric device of the present invention; 図２に示す圧電デバイスの断面図である。3 is a cross-sectional view of the piezoelectric device shown in FIG. 2; FIG. 本発明の圧電デバイスの他の一例を模式的に示す図である。FIG. 4 is a diagram schematically showing another example of the piezoelectric device of the present invention; 本発明の圧電デバイスの他の一例を模式的に示す図である。FIG. 4 is a diagram schematically showing another example of the piezoelectric device of the present invention; 図５の部分拡大図である。FIG. 6 is a partially enlarged view of FIG. 5; 図５に示す圧電デバイスが有する圧電フィルムの構成の他の一例を説明するための図である。6 is a diagram for explaining another example of the configuration of a piezoelectric film included in the piezoelectric device shown in FIG. 5; FIG. 図５に示す圧電デバイスが有する圧電フィルムの構成の他の一例を説明するための図である。6 is a diagram for explaining another example of the configuration of a piezoelectric film included in the piezoelectric device shown in FIG. 5; FIG. 本発明の圧電デバイスが有する圧電フィルムの一例を模式的に示す図である。FIG. 4 is a diagram schematically showing an example of a piezoelectric film included in the piezoelectric device of the present invention; 圧電フィルムの作製方法の一例を説明するための概念図である。It is a conceptual diagram for explaining an example of a method of manufacturing a piezoelectric film. 圧電フィルムの作製方法の一例を説明するための概念図である。It is a conceptual diagram for explaining an example of a method of manufacturing a piezoelectric film. 圧電フィルムの作製方法の一例を説明するための概念図である。It is a conceptual diagram for explaining an example of a method of manufacturing a piezoelectric film.
　以下、本発明の圧電デバイスについて、添付の図面に示される好適実施例を基に、詳細に説明する。 The piezoelectric device of the present invention will now be described in detail based on preferred embodiments shown in the accompanying drawings.
　以下に記載する構成要件の説明は、本発明の代表的な実施態様に基づいてなされることがあるが、本発明はそのような実施態様に限定されるものではない。
　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。 The description of the constituent elements described below may be made based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.
In this specification, a numerical range represented by "-" means a range including the numerical values before and after "-" as lower and upper limits.
［圧電デバイス］
　本発明の圧電デバイスは、
　高分子材料を含むマトリックス中に圧電体粒子を含有する圧電体層と、圧電体層の両面に形成された電極層とを有し、動的粘弾性測定による周波数１Ｈｚでの損失正接が０．１以上となる極大値が０℃から５０℃の温度範囲に存在する圧電フィルム、および、
　圧電フィルムを加熱するための加熱機構を備える、圧電デバイスである。 [Piezoelectric device]
The piezoelectric device of the present invention is
It has a piezoelectric layer containing piezoelectric particles in a matrix containing a polymer material and electrode layers formed on both sides of the piezoelectric layer, and the loss tangent at a frequency of 1 Hz by dynamic viscoelasticity measurement is 0.0. A piezoelectric film having a maximum value of 1 or more in a temperature range of 0° C. to 50° C.;
A piezoelectric device comprising a heating mechanism for heating a piezoelectric film.
　図１に、本発明の圧電デバイスの一例を模式的に表す側面図を示す。 FIG. 1 shows a side view schematically showing an example of the piezoelectric device of the present invention.
　図１に示す圧電デバイス１００は、圧電フィルム１０と、信号源１０２と、温度センサー１０４と、制御部１０６と、を有する。 The piezoelectric device 100 shown in FIG. 1 has a piezoelectric film 10, a signal source 102, a temperature sensor 104, and a control section 106.
　圧電フィルム１０は、高分子材料を含むマトリックス中に圧電体粒子を含有する圧電体層２０と、圧電体層２０の両主面それぞれに形成された第１電極層２４および第２電極層２６と、第１電極層２４の上に設けられる第１保護層２８と、第２電極層２６の上に設けられる第２保護層３０と、を有する。第１電極層２４および第２電極層２６は本発明における電極層である。また、第１保護層２８および第２保護層３０は本発明における保護層である。
　後述するが圧電フィルム１０は厚さ方向に分極されていることが好ましい。 The piezoelectric film 10 includes a piezoelectric layer 20 containing piezoelectric particles in a matrix containing a polymer material, and a first electrode layer 24 and a second electrode layer 26 formed on both main surfaces of the piezoelectric layer 20. , a first protective layer 28 provided on the first electrode layer 24 and a second protective layer 30 provided on the second electrode layer 26 . The first electrode layer 24 and the second electrode layer 26 are electrode layers in the present invention. Also, the first protective layer 28 and the second protective layer 30 are protective layers in the present invention.
As will be described later, the piezoelectric film 10 is preferably polarized in the thickness direction.
　圧電フィルム１０は、圧電フィルム１０に印加した駆動電圧の大きさに応じて振動して、圧電フィルム１０に印加した駆動電圧に応じた音を発生する。従って、圧電フィルム１０は、可聴域の信号を印加されることで、圧電フィルム１０自体が振動して可聴域の音を発生する。
　本発明において、圧電フィルム１０は、動的粘弾性測定による周波数１Ｈｚでの損失正接が０．１以上となる極大値が０℃から５０℃の温度範囲に存在するものである。
　圧電フィルム１０については後に詳述する。 The piezoelectric film 10 vibrates according to the magnitude of the driving voltage applied to the piezoelectric film 10 and generates sound according to the driving voltage applied to the piezoelectric film 10 . Therefore, when a signal in the audible range is applied to the piezoelectric film 10, the piezoelectric film 10 itself vibrates to generate sound in the audible range.
In the present invention, the piezoelectric film 10 has a maximum value of 0.1 or more in loss tangent at a frequency of 1 Hz by dynamic viscoelasticity measurement in a temperature range of 0°C to 50°C.
The piezoelectric film 10 will be detailed later.
　圧電フィルム１０の第１電極層２４および第２電極層２６には、駆動電圧（駆動信号）を印加するための信号源１０２が接続されている。 A signal source 102 for applying a driving voltage (driving signal) is connected to the first electrode layer 24 and the second electrode layer 26 of the piezoelectric film 10 .
　また、圧電フィルム１０の表面には、温度センサー１０４が配置されている。図１に示す例においては、温度センサー１０４は、第１保護層２８の表面の端部近傍に配置されている。
　温度センサー１０４は、圧電フィルム１０の温度を測定する。 A temperature sensor 104 is arranged on the surface of the piezoelectric film 10 . In the example shown in FIG. 1, the temperature sensor 104 is arranged near the edge of the surface of the first protective layer 28 .
A temperature sensor 104 measures the temperature of the piezoelectric film 10 .
　温度センサー１０４としては特に制限はない。温度センサー１０４は、接触式でも非接触式のものであってもよく、例えば、熱電対、赤外線センサー等の種々の公知の温度センサーを用いることができる。 There is no particular limitation for the temperature sensor 104. The temperature sensor 104 may be of a contact type or a non-contact type, and various known temperature sensors such as thermocouples and infrared sensors can be used.
　なお、図１に示す例では、温度センサー１０４は、第１保護層２８の表面に配置される構成としたがこれに限定はされず、温度センサー１０４は、第２保護層３０の表面に配置されてもよい。また、図１に示す例では、温度センサー１０４は、圧電フィルム１０の面方向の端部近傍に配置される構成としたがこれに限定はされず、圧電フィルム１０の面方向の中央位置等、いずれの位置に配置されてもよい。 In the example shown in FIG. 1, the temperature sensor 104 is arranged on the surface of the first protective layer 28, but the configuration is not limited to this, and the temperature sensor 104 is arranged on the surface of the second protective layer 30. may be In addition, in the example shown in FIG. 1, the temperature sensor 104 is configured to be disposed near the edge in the plane direction of the piezoelectric film 10, but the present invention is not limited to this. It may be arranged at any position.
　また、図１に示す例では、圧電フィルム１０自体の温度を測定する構成としたが、これに限定はされず、圧電フィルム１０を支持する支持体または筐体等の温度を測定してもよいし、圧電フィルム１０（圧電デバイス１００）近傍の外気温を測定してもよい。圧電フィルム１０自体の温度を測定するのが好ましい。 Further, in the example shown in FIG. 1, the configuration is such that the temperature of the piezoelectric film 10 itself is measured. Alternatively, the ambient temperature in the vicinity of the piezoelectric film 10 (piezoelectric device 100) may be measured. It is preferable to measure the temperature of the piezoelectric film 10 itself.
　制御部１０６は、信号源１０２および温度センサー１０４に接続されており、温度センサー１０４が測定した温度に応じて、信号源１０２から所定の信号を圧電フィルム１０に印加するように制御する。 The control unit 106 is connected to the signal source 102 and the temperature sensor 104 and controls the signal source 102 to apply a predetermined signal to the piezoelectric film 10 according to the temperature measured by the temperature sensor 104 .
　制御部１０６は、ＣＰＵ（Central Processing Unit）と、ＣＰＵに各種の処理を行わせるための動作プログラムから構成される。あるいは、制御部１０６は、ＰＣ（パーソナルコンピュータ）等のプロセッサによって構成されるものであっても良い。あるいは、制御部１０６をデジタル回路で構成してもよい。 The control unit 106 is composed of a CPU (Central Processing Unit) and an operation program for causing the CPU to perform various processes. Alternatively, the control unit 106 may be configured by a processor such as a PC (personal computer). Alternatively, the control unit 106 may be configured with a digital circuit.
　制御部１０６による制御によって、信号源１０２から所定の信号を印加された圧電フィルム１０は、振動して自己発熱して加熱される。すなわち、図１に示す構成においては、圧電フィルム１０、信号源１０２、温度センサー１０４および制御部１０６とにより加熱機構が構成される。 Under the control of the control unit 106, the piezoelectric film 10 to which a predetermined signal is applied from the signal source 102 vibrates and self-heats to be heated. That is, in the configuration shown in FIG. 1, the piezoelectric film 10, the signal source 102, the temperature sensor 104 and the controller 106 constitute a heating mechanism.
　具体的には、例えば、温度センサー１０４が測定した圧電フィルム１０の温度が０℃未満になった場合に、制御部１０６は、信号源１０２に所定の信号（以下、加熱用の信号ともいう）を圧電フィルム１０に印加するように制御して、圧電フィルム１０を振動させる。圧電フィルム１０は、信号源１０２から印加される所定の信号に応じて振動し自己発熱することで加熱される。圧電フィルム１０は、動的粘弾性測定による周波数１Ｈｚでの損失正接が０．１以上となる極大値が０℃から５０℃の温度範囲に存在するものであるため、圧電フィルム１０が加熱されて温度が０℃以上になることで、優れた可撓性を発現するものとなる。 Specifically, for example, when the temperature of the piezoelectric film 10 measured by the temperature sensor 104 is less than 0° C., the control unit 106 sends a predetermined signal (hereinafter also referred to as a heating signal) to the signal source 102. is applied to the piezoelectric film 10 to vibrate the piezoelectric film 10 . The piezoelectric film 10 is heated by vibrating and self-heating according to a predetermined signal applied from the signal source 102 . Since the piezoelectric film 10 has a maximum value of 0.1 or more in the loss tangent at a frequency of 1 Hz as measured by dynamic viscoelasticity measurement in a temperature range of 0° C. to 50° C., the piezoelectric film 10 is heated. When the temperature is 0°C or higher, excellent flexibility is exhibited.
　前述のとおり、可撓性を損なうことなくフレキシブルディスプレイに一体化可能なスピーカーとして可撓性を有する圧電フィルムが知られている。可撓性を有するスピーカーは、巻取って収納したり、折り曲げることが可能であるため、大型の装置であっても携帯性を向上することができる。
　しかしながら、可撓性を有する圧電フィルムは、その温度によって十分な可撓性を発現できなくなる。例えば、動的粘弾性測定による周波数１Ｈｚでの損失正接が０．１以上となる極大値が０～５０℃の温度範囲に存在する圧電フィルムは常温（０℃～５０℃）では、優れた可撓性を発現するものの、氷点下では十分な可撓性を発現するのは困難であった。一方、動的粘弾性測定による周波数１Ｈｚでの損失正接が、－８０℃以上０℃未満の温度範囲に０．１以上となる極大値が存在し、かつ、０℃での値が０．０５以上である圧電フィルムでは、氷点下での良好な可撓性を発現するものの、常温下での可撓性が氷点下での場合に比べて劣っていた。すなわち、従来の圧電フィルムは、常温の環境下および氷点下の環境下のいずれの環境で用いられても優れた可撓性を発現するものにはできなかった。 As described above, a flexible piezoelectric film is known as a speaker that can be integrated into a flexible display without impairing its flexibility. Since a flexible speaker can be rolled up and stored or folded, even a large-sized device can be improved in portability.
However, a flexible piezoelectric film cannot exhibit sufficient flexibility depending on the temperature. For example, a piezoelectric film having a maximum loss tangent value of 0.1 or more at a frequency of 1 Hz by dynamic viscoelasticity measurement exists in the temperature range of 0 to 50°C. Although it exhibits flexibility, it was difficult to exhibit sufficient flexibility below freezing. On the other hand, the loss tangent at a frequency of 1 Hz by dynamic viscoelasticity measurement has a maximum value of 0.1 or more in the temperature range of -80 ° C. or more and less than 0 ° C., and the value at 0 ° C. is 0.05. Although the above piezoelectric film exhibits good flexibility below freezing, the flexibility at room temperature is inferior to that at below freezing. In other words, the conventional piezoelectric film could not exhibit excellent flexibility in both normal temperature environment and sub-zero environment.
　これに対して、本発明の圧電デバイス１００は、動的粘弾性測定による周波数１Ｈｚでの損失正接が０．１以上となる極大値が０℃から５０℃の温度範囲に存在する圧電フィルム１０と、圧電フィルム１０を加熱する加熱機構と、を有する。そのため、常温の環境下では圧電フィルム１０が優れた可撓性を発現し、かつ、氷点下の環境下では、圧電フィルム１０を加熱して圧電フィルム１０の温度を０℃以上にして優れた可撓性を発現させることができる。従って、本発明の圧電デバイス１００は、常温の環境下および氷点下の環境下のいずれの環境で用いられても優れた可撓性を発現することができる。 On the other hand, in the piezoelectric device 100 of the present invention, the maximum value of the loss tangent at a frequency of 1 Hz measured by dynamic viscoelasticity measurement is 0.1 or more, and the maximum value exists in the temperature range of 0° C. to 50° C. , and a heating mechanism for heating the piezoelectric film 10 . Therefore, the piezoelectric film 10 exhibits excellent flexibility in a normal temperature environment, and excellent flexibility is achieved by heating the piezoelectric film 10 to a temperature of 0° C. or higher in a subzero environment. You can express your sexuality. Therefore, the piezoelectric device 100 of the present invention can exhibit excellent flexibility regardless of whether it is used in a normal temperature environment or a subzero environment.
　ここで、図１に示す圧電デバイス１００において、信号源１０２から圧電フィルム１０に印加される信号（加熱用の信号）は、周波数１５ｋＨｚ超の正弦波交流信号であることが好ましい。圧電フィルム１０に１５ｋＨｚ以下の聞こえやすい周波数の信号を印加すると、圧電フィルム１０が不要な音を発生していまう。これに対して、圧電フィルム１０に周波数１５ｋＨｚ超の正弦波交流信号を印加することにより、聞こえやすい不要な音を発生することなく、圧電フィルム１０を加熱することができる。
　なお、信号源１０２が供給する正弦波交流信号は、サイン波、三角波および矩形波のいずれであってもよい。 Here, in the piezoelectric device 100 shown in FIG. 1, the signal (heating signal) applied from the signal source 102 to the piezoelectric film 10 is preferably a sinusoidal AC signal with a frequency higher than 15 kHz. When a signal with an easily audible frequency of 15 kHz or less is applied to the piezoelectric film 10, the piezoelectric film 10 generates unnecessary sounds. On the other hand, by applying a sinusoidal AC signal with a frequency higher than 15 kHz to the piezoelectric film 10, the piezoelectric film 10 can be heated without producing an audible unnecessary sound.
The sine wave AC signal supplied by the signal source 102 may be any of sine wave, triangular wave and rectangular wave.
　圧電フィルム１０に印加する正弦波交流信号の周波数は、２０ｋＨｚ～１００ｋＨｚがより好ましく、２０ｋＨｚ～４０ｋＨｚがさらに好ましい。すなわち、可聴域（周波数２０Ｈｚ～２０ｋＨｚ）よりも高い周波数の信号であることが好ましい。
　また、周波数２０ｋＨｚ超の、互いに異なる周波数成分を含む信号を圧電フィルム１０に印加してもよい。
　また、圧電フィルム１０から不要な音を発生させない観点から、圧電フィルム１０に印加する信号は、１５ｋＨｚ以下の周波数成分を含まないことが好ましく、２０ｋＨｚ以下の周波数成分を含まないことがより好ましい。 The frequency of the sinusoidal AC signal applied to the piezoelectric film 10 is more preferably 20 kHz to 100 kHz, and even more preferably 20 kHz to 40 kHz. That is, it is preferable that the signal has a frequency higher than the audible range (frequency of 20 Hz to 20 kHz).
Alternatively, a signal containing different frequency components with a frequency exceeding 20 kHz may be applied to the piezoelectric film 10 .
From the viewpoint of preventing unnecessary sound from being generated from the piezoelectric film 10, the signal applied to the piezoelectric film 10 preferably does not contain frequency components of 15 kHz or less, and more preferably does not contain frequency components of 20 kHz or less.
　また、圧電フィルム１０を適正に加熱する観点から、圧電フィルム１０に印加する正弦波交流信号（加熱用の信号）の実行電圧は、１Ｖｒｍｓ～４０Ｖｒｍｓであることが好ましく、１Ｖｒｍｓ～２０Ｖｒｍｓがより好ましく、１Ｖｒｍｓ～１０Ｖｒｍｓがさらに好ましい。 From the viewpoint of properly heating the piezoelectric film 10, the effective voltage of the sinusoidal AC signal (heating signal) applied to the piezoelectric film 10 is preferably 1 Vrms to 40 Vrms, more preferably 1 Vrms to 20 Vrms. 1 Vrms to 10 Vrms is more preferred.
　また、圧電フィルム１０の動作中（発音中）に加熱するものであってもよい。その際、圧電フィルム１０に印加される信号が、圧電フィルム１０が発音する可聴域の周波数成分と、１５ｋＨｚ～１００ｋＨｚの周波数成分（加熱用の信号）とを含むことが好ましい。言い換えると、圧電フィルム１０に印加される信号が非正弦波交流信号であり、非正弦波交流信号をフーリエ解析して得られた正弦波交流信号の周波数の少なくとも一つ以上が１５ｋＨｚ～１００ｋＨｚの範囲に存在することが好ましい。圧電フィルム１０に印加される信号が、１５ｋＨｚ～１００ｋＨｚの周波数成分を含むことにより、可聴域の音圧等によらず、適切に圧電フィルム１０を加熱することができる。
　ここで、圧電フィルムにおける自己発熱は、流れる電流が大きいほど発熱量が多くなる。一般にインピーダンスは周波数が高くなるほど小さくなるため、圧電フィルムに同じ電圧の信号を印加した場合でも、周波数が高いほど流れる電流が大きくなり、発熱しやすくなる。従って、圧電フィルムに印加される信号が、周波数１５ｋＨｚ～１００ｋＨｚの加熱用の信号成分を含むことで、圧電フィルムを容易に発熱させることができる。 Alternatively, the piezoelectric film 10 may be heated during operation (during sound generation). At this time, it is preferable that the signal applied to the piezoelectric film 10 includes a frequency component in the audible range generated by the piezoelectric film 10 and a frequency component (heating signal) of 15 kHz to 100 kHz. In other words, the signal applied to the piezoelectric film 10 is a non-sinusoidal AC signal, and at least one frequency of the sinusoidal AC signal obtained by Fourier analysis of the non-sinusoidal AC signal is in the range of 15 kHz to 100 kHz. is preferably present in Since the signal applied to the piezoelectric film 10 includes a frequency component of 15 kHz to 100 kHz, the piezoelectric film 10 can be appropriately heated regardless of sound pressure in the audible range.
Here, self-heating in the piezoelectric film increases as the flowing current increases. In general, the higher the frequency, the lower the impedance. Therefore, even if a signal of the same voltage is applied to the piezoelectric film, the higher the frequency, the larger the current that flows and the more likely it is to generate heat. Therefore, the signal applied to the piezoelectric film contains a signal component for heating with a frequency of 15 kHz to 100 kHz, so that the piezoelectric film can easily generate heat.
　この場合も、圧電フィルム１０を適正に加熱する観点から、圧電フィルム１０に印加する２０ｋＨｚ～１００ｋＨｚの正弦波交流信号（加熱用の信号）の実行電圧は、１Ｖｒｍｓ～４０Ｖｒｍｓであることが好ましく、１Ｖｒｍｓ～２０Ｖｒｍｓがより好ましく、　１Ｖｒｍｓ～１０Ｖｒｍｓがさらに好ましい。 Also in this case, from the viewpoint of properly heating the piezoelectric film 10, the effective voltage of the sinusoidal AC signal (heating signal) of 20 kHz to 100 kHz applied to the piezoelectric film 10 is preferably 1 Vrms to 40 Vrms. ~20 Vrms is more preferred, and 1 Vrms to 10 Vrms is even more preferred.
　また、制御部１０６が、信号源１０２から圧電フィルム１０への周波数１５ｋＨｚ超の信号の印加を開始する温度、すなわち、圧電フィルム１０の加熱を開始する温度の閾値は、－４０℃～１０℃が好ましく、－２０℃～５℃がより好ましく、－１０℃～０℃がより好ましい。 The temperature at which the control unit 106 starts applying a signal with a frequency of more than 15 kHz from the signal source 102 to the piezoelectric film 10, that is, the temperature threshold at which heating of the piezoelectric film 10 is started is -40°C to 10°C. -20°C to 5°C is more preferred, and -10°C to 0°C is more preferred.
　また、制御部１０６は、温度センサー１０４の測定温度が所定の温度以上になったタイミングで圧電フィルム１０への周波数１５ｋＨｚ超の信号の印加、すなわち、圧電フィルム１０の加熱を終了するように制御すればよい。この場合、圧電フィルム１０の加熱を終了する温度の閾値は、０℃～３５℃が好ましく、１０℃～３０℃がより好ましく、２０℃～２５℃がより好ましい。また、制御部１０６は、動的粘弾性測定による周波数１Ｈｚでの損失正接が０．１以上となる極大値が存在する温度以上になった場合に、圧電フィルム１０の加熱を終了するようにしてもよい。 In addition, the control unit 106 should be controlled so as to terminate the application of a signal with a frequency exceeding 15 kHz to the piezoelectric film 10, that is, the heating of the piezoelectric film 10 at the timing when the temperature measured by the temperature sensor 104 reaches or exceeds a predetermined temperature. Just do it. In this case, the threshold temperature for ending heating of the piezoelectric film 10 is preferably 0.degree. C. to 35.degree. C., more preferably 10.degree. In addition, the control unit 106 terminates the heating of the piezoelectric film 10 when the temperature exceeds the maximum value at which the loss tangent at a frequency of 1 Hz measured by dynamic viscoelasticity is 0.1 or more. good too.
　あるいは、制御部１０６は、加熱開始から所定の時間が経過するまでの間、圧電フィルム１０を加熱するように制御してもよい。すなわち、加熱開始から所定の時間が経過したら加熱用の信号の印加を終了するようにしてもよい。加熱時間（加熱用の信号の印加時間）は、圧電フィルムの大きさ、各層の厚さ、および、材料（熱伝導率、比熱）等に応じて適宜設定すればよい。 Alternatively, the control unit 106 may control the piezoelectric film 10 to be heated until a predetermined time has elapsed from the start of heating. That is, the application of the signal for heating may be terminated when a predetermined time has elapsed from the start of heating. The heating time (application time of the signal for heating) may be appropriately set according to the size of the piezoelectric film, the thickness of each layer, the material (thermal conductivity, specific heat), and the like.
　また、図１に示す例では、圧電デバイス１００は、温度センサー１０４を有し、制御部１０６が、温度に応じて圧電フィルムへの加熱用の信号の印加を制御する構成としたがこれに限定はされない。例えば、圧電デバイスは、温度センサーを有さず、圧電フィルムの曲げ伸ばし、または、巻取り引き延ばし等の動作を検知するセンサーを有し、この動作を検知した際に、制御部１０６は、圧電フィルム１０を加熱するように（加熱用の信号を印加するように）信号源１０２を制御してもよい。 In addition, in the example shown in FIG. 1, the piezoelectric device 100 has the temperature sensor 104, and the control unit 106 is configured to control the application of the heating signal to the piezoelectric film according to the temperature. is not done. For example, the piezoelectric device does not have a temperature sensor, but has a sensor that detects an operation such as bending and stretching the piezoelectric film or winding and stretching. A signal source 102 may be controlled to heat (apply a signal for heating) 10 .
　例えば、後述する図２および図３に示すように圧電デバイスが圧電フィルムを巻き取る巻取り軸を有する構成の場合には、巻取り軸の回転を変位センサーで検知して、巻取り軸の回転が開始された場合に、制御部１０６が、圧電フィルム１０を加熱するように（加熱用の信号を印加するように）信号源１０２を制御してもよい。また、この場合は、巻取り軸の回転が停止した場合に、制御部１０６が、圧電フィルム１０の加熱を停止するように（加熱用の信号の印加を停止するように）信号源１０２を制御してもよい。
　あるいは、圧電フィルムの巻取りおよび引出しがスイッチ等の動作に合わせて自動（電動）で行われる場合には、巻取りまたは引出しの前に、制御部１０６が、圧電フィルム１０を加熱するように（加熱用の信号を印加するように）信号源１０２を制御して圧電フィルム１０を加熱して所定の時間経過後に巻取りまたは引出しを行うようにしてもよい。 For example, as shown in FIGS. 2 and 3 to be described later, when the piezoelectric device has a winding shaft for winding the piezoelectric film, rotation of the winding shaft is detected by a displacement sensor, and rotation of the winding shaft is detected. is started, the controller 106 may control the signal source 102 to heat the piezoelectric film 10 (to apply a signal for heating). Further, in this case, when the rotation of the winding shaft stops, the control unit 106 controls the signal source 102 so as to stop heating the piezoelectric film 10 (stop applying the signal for heating). You may
Alternatively, when the piezoelectric film is automatically (electrically) wound and drawn in accordance with the operation of a switch or the like, the control unit 106 heats the piezoelectric film 10 before winding or drawing ( Alternatively, the signal source 102 may be controlled to apply a heating signal to heat the piezoelectric film 10 and after a predetermined period of time has passed, winding or unwinding may be performed.
　あるいは、圧電デバイスの使用者が、圧電フィルムの巻取り、および、折り曲げ等を行うタイミングで、スイッチ等によって任意に圧電フィルムの加熱を行う構成であってもよい。 Alternatively, the user of the piezoelectric device may arbitrarily heat the piezoelectric film with a switch or the like at the timing of winding, bending, or the like of the piezoelectric film.
　また、図１に示す例では、圧電フィルムに加熱用の信号を印加して圧電フィルムの自己発熱により、圧電フィルムを加熱する構成としたがこれに限定はされず、加熱機構が外部ヒーターを有する構成としてもよい。 In the example shown in FIG. 1, a heating signal is applied to the piezoelectric film to heat the piezoelectric film by self-heating of the piezoelectric film, but the present invention is not limited to this, and the heating mechanism has an external heater. may be configured.
　図２に本発明の圧電デバイスの他の一例を模式的に表す斜視図を示す。図３に、図２の断面図を示す。
　図２および図３に示す圧電デバイス１００ｂは、圧電フィルム１０と、開口部１２０ａを有する筐体１２０と、外部ヒーター１２２と、巻取り軸１２４と、ガイド部材１２６と、を有する。 FIG. 2 shows a perspective view schematically showing another example of the piezoelectric device of the present invention. FIG. 3 shows a cross-sectional view of FIG.
The piezoelectric device 100b shown in FIGS. 2 and 3 includes the piezoelectric film 10, a housing 120 having an opening 120a, an external heater 122, a winding shaft 124, and a guide member 126.
　圧電フィルム１０は、図１に示す圧電デバイス１００が有する圧電フィルム１０と同様であるので説明は省略する。 The piezoelectric film 10 is the same as the piezoelectric film 10 included in the piezoelectric device 100 shown in FIG. 1, so description thereof will be omitted.
　筐体１２０は、略円筒形状で、円筒の周面から外方向に突出する部位を有し、この突出する部位に開口部１２０ａを有する、いわゆる、写真フィルムのパトローネのような形状を有する。
　筐体１２０は、圧電フィルム１０を巻取り軸１２４に巻き取って収容する。筐体１２０の円筒形状の部位には、巻取り軸１２４が回転自在に軸支される。 The housing 120 has a substantially cylindrical shape, has a portion that protrudes outward from the peripheral surface of the cylinder, and has an opening 120a in the protruding portion.
The housing 120 accommodates the piezoelectric film 10 wound around the winding shaft 124 . A winding shaft 124 is rotatably supported on the cylindrical portion of the housing 120 .
　筐体１２０の開口部１２０ａは、引き出される圧電フィルム１０の引出し方向と直交する方向の幅と略同じ高さで、圧電フィルム１０の厚さよりも大きい幅を有する。圧電フィルム１０は、開口部１２０ａを挿通して、筐体１２０内の巻取り軸１２４に巻き取られ、また、巻取り軸１２４から引き出される。すなわち、例えば、圧電デバイス１００ｂは、圧電フィルム１０をスピーカーとして用いる場合には、圧電フィルム１０を筐体１２０から引き出して使用することができ、また、持ち運び等を行う際には、圧電フィルム１０を筐体１２０内の巻取り軸１２４に巻き取って小型化することができる。 The opening 120 a of the housing 120 has a height substantially equal to the width of the piezoelectric film 10 to be pulled out in a direction orthogonal to the pulling direction, and has a width larger than the thickness of the piezoelectric film 10 . The piezoelectric film 10 is passed through the opening 120 a and is wound around the winding shaft 124 in the housing 120 and pulled out from the winding shaft 124 . That is, for example, when the piezoelectric film 10 is used as a speaker, the piezoelectric device 100b can be used by pulling out the piezoelectric film 10 from the housing 120, and when the piezoelectric device 100b is carried, the piezoelectric film 10 can be removed. It can be wound up on a winding shaft 124 in the housing 120 to reduce the size.
　また、開口部１２０ａには、圧電フィルム１０の出し入れを円滑に行い、かつ、出し入れによる圧電フィルム１０の損傷を防止するためのガイド部材１２６が、圧電フィルム１０を挟持するように設けられる。このガイド部材１２６は、例えば、フェルト等で形成される。 In addition, a guide member 126 is provided in the opening 120a so as to sandwich the piezoelectric film 10 for smoothly inserting and removing the piezoelectric film 10 and preventing damage to the piezoelectric film 10 due to inserting and removing. The guide member 126 is made of, for example, felt.
　また、開口部１２０ａには、外部ヒーター１２２が設けられている。外部ヒーター１２２は、開口部１２０ａを出し入れされる圧電フィルム１０を加熱するものである。外部ヒーター１２２は、圧電フィルム１０を加熱することができれば、圧電フィルム１０と接していてもよいし、接していなくてもよい。 An external heater 122 is provided in the opening 120a. The external heater 122 heats the piezoelectric film 10 that is inserted into and removed from the opening 120a. The external heater 122 may or may not be in contact with the piezoelectric film 10 as long as it can heat the piezoelectric film 10 .
　外部ヒーター１２２としては特に制限はなく、種々の公知のヒーターを用いることができる。 The external heater 122 is not particularly limited, and various known heaters can be used.
　また、図３に示す例では、ガイド部材１２６と外部ヒーター１２２とを有する構成としたが、外部ヒーター１２２がガイド部材１２６を兼ねる構成であってもよい。ガイド部材１２６を兼ねる外部ヒーター１２２としては、例えば、ラバーヒーター等が挙げられる。 Further, although the example shown in FIG. Examples of the external heater 122 that also serves as the guide member 126 include a rubber heater.
　外部ヒーター１２２は、電源ＯＮ時には待機電力を使って、常に圧電フィルム１０を加熱して所定の温度以上（例えば、０℃以上）を維持させるものであってもよいし、前述のとおり、巻取り軸１２４の回転を変位センサ―で検出して、巻取り軸１２４の回転が開始された場合に、圧電フィルム１０を加熱するように外部ヒーター１２２を駆動する構成としてもよい。あるいは、圧電フィルム１０、筐体１２０または巻取り軸１２４等の温度を測定する温度センサーを有し、温度に応じて外部ヒーター１２２を駆動する構成であってもよい。あるいは、圧電フィルムの巻取りおよび引出しがスイッチ等の動作に合わせて自動（電動）で行われる場合には、巻取りまたは引出しの前に、外部ヒーター１２２が圧電フィルム１０を加熱して圧電フィルム１０を加熱して所定の時間（例えば、３秒程度）経過後に巻取りまたは引き出しを行うようにしてもよい。 The external heater 122 may use standby power when the power is turned on to always heat the piezoelectric film 10 to maintain a predetermined temperature or higher (for example, 0° C. or higher). The rotation of the shaft 124 may be detected by a displacement sensor, and the external heater 122 may be driven to heat the piezoelectric film 10 when the winding shaft 124 starts rotating. Alternatively, it may have a temperature sensor for measuring the temperature of the piezoelectric film 10, housing 120, winding shaft 124, or the like, and drive the external heater 122 according to the temperature. Alternatively, when the piezoelectric film is automatically (electrically) wound and pulled out in accordance with the operation of a switch or the like, the external heater 122 heats the piezoelectric film 10 before winding or pulling out the piezoelectric film 10 . may be heated, and after a predetermined time (for example, about 3 seconds) has elapsed, winding or drawing may be performed.
　このような圧電デバイス１００ｂは、巻取り軸１２４を回転させることで、圧電フィルム１０を筐体１２０に収容できる。また、圧電フィルム１０を引っ張る、または、巻取り軸１２４を回転させることで、圧電フィルム１０を筐体１２０から引き出すことができる。従って、圧電フィルム１０は、巻取り時、および、引き出し時に、巻取り軸１２４によって高い曲率での曲げ延ばしを行われる。その際、圧電フィルム１０は、外部ヒーター１２２によって加熱されることで、氷点下の環境下であっても、圧電フィルム１０の温度を０℃以上にして優れた可撓性を発現させることができる。従って、本発明の圧電デバイス１００ｂは、常温の環境下および氷点下の環境下のいずれの環境で用いられても優れた可撓性を発現することができる。 In such a piezoelectric device 100b, the piezoelectric film 10 can be accommodated in the housing 120 by rotating the take-up shaft 124. In addition, the piezoelectric film 10 can be pulled out from the housing 120 by pulling the piezoelectric film 10 or rotating the take-up shaft 124 . Therefore, the piezoelectric film 10 is bent and stretched with a high curvature by the winding shaft 124 during winding and unwinding. At this time, the piezoelectric film 10 is heated by the external heater 122, so that the temperature of the piezoelectric film 10 can be raised to 0° C. or higher even in a sub-zero environment, and excellent flexibility can be exhibited. Therefore, the piezoelectric device 100b of the present invention can exhibit excellent flexibility regardless of whether it is used in a normal temperature environment or a subzero environment.
　ここで、図２および図３に示す例では、圧電フィルム１０単体を筐体１２０内に巻取り可能か構成としたが、これに限定はされない。
　図４に本発明の圧電デバイスの他の一例を模式的に表す斜視図を示す。 Here, in the examples shown in FIGS. 2 and 3, the piezoelectric film 10 alone is configured so that it can be wound into the housing 120, but the configuration is not limited to this.
FIG. 4 shows a perspective view schematically showing another example of the piezoelectric device of the present invention.
　図４に示す圧電デバイス１００ｄは、圧電フィルム１０と、フレキシブルディスプレイ１３０と、開口部１２０ａを有する筐体１２０と、を有する。また、図示は省略するが、圧電デバイス１００ｄは、圧電デバイス１００ｂと同様に、筐体１２０内に外部ヒーター１２２と、巻取り軸１２４と、ガイド部材１２６と、を有する。 A piezoelectric device 100d shown in FIG. 4 includes a piezoelectric film 10, a flexible display 130, and a housing 120 having an opening 120a. Although not shown, the piezoelectric device 100d has an external heater 122, a winding shaft 124, and a guide member 126 inside the housing 120, like the piezoelectric device 100b.
　図４に示す圧電デバイス１００ｄは、図２に示す圧電デバイス１００ｂにおいて、圧電フィルム１０に代えて、圧電フィルム１０を裏面（表示面とは反対側の面）に貼着されたフレキシブルディスプレイ１３０を有する以外は同様の構成を有する。すなわち、圧電フィルム１０を裏面に貼着されたフレキシブルディスプレイ１３０は、例えば、持ち運び等の際には、筐体１２０内の巻取り軸１２４に巻き取られて収容され小型化することができる。また、ディスプレイとして使用する際には、フレキシブルディスプレイ１３０および圧電フィルム１０は、筐体１２０の開口部１２０ａから引き出されて、画像を再生するとともに、音声を発生するスピーカーとして使用される。 A piezoelectric device 100d shown in FIG. 4 has a flexible display 130 in which the piezoelectric film 10 is attached to the back surface (the surface opposite to the display surface) instead of the piezoelectric film 10 in the piezoelectric device 100b shown in FIG. Other than that, they have the same configuration. That is, the flexible display 130 with the piezoelectric film 10 adhered to the back surface can be rolled up and housed on the winding shaft 124 in the housing 120 to be miniaturized, for example, when being carried. When used as a display, the flexible display 130 and the piezoelectric film 10 are pulled out from the opening 120a of the housing 120 and used as a speaker for reproducing images and generating sound.
　フレキシブルディスプレイ１３０としては、可撓性を有するディスプレイであれば特に制限はなく、有機エレクトロルミネセンス（ＯＬＥＤ（Organic Light Emitting Diode））ディスプレイ、液晶ディスプレイ、マイクロＬＥＤ（Light Emitting Diode）ディスプレイ、および、無機エレクトロルミネセンスディスプレイなどの公知の表示デバイスが好適に利用可能である。 The flexible display 130 is not particularly limited as long as it is a flexible display, and includes organic electroluminescence (OLED (Organic Light Emitting Diode)) displays, liquid crystal displays, micro LED (Light Emitting Diode) displays, and inorganic Known display devices such as electroluminescence displays are suitable for use.
　図１等に示す例では、圧電フィルム１０自体が振動して音を発生する構成としたがこれに限定はされない。
　図５に本発明の圧電デバイスの他の一例を模式的に表す図を示す。図６に図５の部分拡大図を示す。 In the example shown in FIG. 1 and the like, the piezoelectric film 10 itself is configured to vibrate and generate sound, but the configuration is not limited to this.
FIG. 5 shows a diagram schematically showing another example of the piezoelectric device of the present invention. FIG. 6 shows a partially enlarged view of FIG.
　図５および図６に示す圧電デバイス１００ｃは、圧電フィルム１０と、振動板１２と、信号源１０２と、温度センサー１０４と、制御部１０６と、を有する。 A piezoelectric device 100c shown in FIGS. 5 and 6 has a piezoelectric film 10, a diaphragm 12, a signal source 102, a temperature sensor 104, and a controller .
　図５および図６に示す圧電デバイス１００ｃにおいて、圧電フィルム１０は、矩形状の長尺な１枚の圧電フィルム１０を、一方向に２回、折り返すことにより、３層の圧電フィルム１０を積層したものである。このように積層した圧電フィルム１０を、積層圧電素子ともいう。 In the piezoelectric device 100c shown in FIGS. 5 and 6, the piezoelectric film 10 is formed by laminating three layers of the piezoelectric film 10 by folding one long rectangular piezoelectric film 10 twice in one direction. It is. The piezoelectric film 10 laminated in this manner is also called a laminated piezoelectric element.
　なお、図６では、圧電デバイス１００ｃの構成を明瞭に示すために、第１保護層および第２保護層の図示を省略している。
　また、以下の説明では、圧電フィルム１０を折り返す方向（図６中左右方向）を折り返し方向という。 In FIG. 6, the illustration of the first protective layer and the second protective layer is omitted in order to clearly show the configuration of the piezoelectric device 100c.
Further, in the following description, the direction in which the piezoelectric film 10 is folded back (horizontal direction in FIG. 6) is referred to as the folding direction.
　圧電フィルム１０の層同士は、接着層１９によって貼着されている。また、圧電フィルム１０と振動板１２とは、接着層１６によって貼着されている。 The layers of the piezoelectric film 10 are adhered by an adhesive layer 19 . Also, the piezoelectric film 10 and the diaphragm 12 are adhered by an adhesive layer 16 .
　本発明の圧電デバイス１００ｃにおいて、積層圧電素子は、圧電フィルム１０を積層して貼着したものである。従って、圧電フィルム１０が伸縮すれば、積層圧電素子１４も伸縮する。また、振動板１２は、接着層１６によって積層圧電素子に貼着されている。従って、信号源１０２を用いて圧電フィルム１０の電極層に電圧を印加することで、積層圧電素子（積層された圧電フィルム１０）が駆動される。積層圧電素子が駆動されると、積層圧電素子が面方向に伸縮し、積層圧電素子が貼着された振動板１２を撓ませて、結果として振動板を厚さ方向に振動させて音を発生させる。振動板は、積層圧電素子に印加した駆動電圧の大きさに応じて振動して、圧電デバイス１００に印加した駆動電圧に応じた音を発生する。
　すなわち、圧電デバイス１００ｃは、積層圧電素子（積層された圧電フィルム１０）を、エキサイターとして用いる構成である。 In the piezoelectric device 100c of the present invention, the laminated piezoelectric element is obtained by laminating and adhering the piezoelectric films 10 . Therefore, when the piezoelectric film 10 expands and contracts, the laminated piezoelectric element 14 also expands and contracts. Also, the diaphragm 12 is attached to the laminated piezoelectric element with an adhesive layer 16 . Therefore, by applying a voltage to the electrode layers of the piezoelectric film 10 using the signal source 102, the laminated piezoelectric element (laminated piezoelectric film 10) is driven. When the laminated piezoelectric element is driven, the laminated piezoelectric element expands and contracts in the plane direction, bending the diaphragm 12 to which the laminated piezoelectric element is adhered, and as a result vibrating the diaphragm in the thickness direction to generate sound. Let The diaphragm vibrates according to the magnitude of the driving voltage applied to the laminated piezoelectric element and generates sound according to the driving voltage applied to the piezoelectric device 100 .
That is, the piezoelectric device 100c has a configuration in which a laminated piezoelectric element (laminated piezoelectric film 10) is used as an exciter.
　このように圧電フィルム１０をエキサイターとして用いる構成の場合にも、振動板１２が可撓性を有し、巻取って収納したり、折り曲げる際に、エキサイターとしての圧電フィルム１０も折り曲げられる。例えば、図２に示す圧電デバイス１００ｂにおいて、圧電フィルム１０を、積層圧電素子が貼着された振動板１２に代えた構成とすることで、振動板１２を筐体１２０内に巻き取って収納できる圧電デバイスとすることができる。振動板１２が巻き取られる際に、振動板１２に貼着された積層圧電素子も巻き取られて折り曲げられる。 Even in the configuration using the piezoelectric film 10 as an exciter in this way, the diaphragm 12 is flexible, and the piezoelectric film 10 as an exciter is also bent when it is wound and stored or bent. For example, in the piezoelectric device 100b shown in FIG. 2, by replacing the piezoelectric film 10 with the diaphragm 12 to which the laminated piezoelectric element is adhered, the diaphragm 12 can be wound up and stored in the housing 120. It can be a piezoelectric device. When the diaphragm 12 is wound, the laminated piezoelectric element adhered to the diaphragm 12 is also wound and bent.
　ここで、圧電デバイス１００ｃは、温度センサー１０４および制御部１０６を有し、例えば、温度センサー１０４が測定した圧電フィルム１０の温度が０℃未満になった場合に、制御部１０６は、信号源１０２に加熱用の信号を圧電フィルム１０に印加するように制御して、圧電フィルム１０を振動させる。圧電フィルム１０は、信号源１０２から印加される所定の信号に応じて振動し自己発熱することで加熱される。圧電フィルム１０は、動的粘弾性測定による周波数１Ｈｚでの損失正接が０．１以上となる極大値が０℃から５０℃の温度範囲に存在するものであるため、圧電フィルム１０が加熱されて温度が０℃以上になることで、優れた可撓性を発現するものとなる。
　従って、圧電デバイス１００ｃは、常温の環境下および氷点下の環境下のいずれの環境で用いられても優れた可撓性を発現することができる。 Here, the piezoelectric device 100c has a temperature sensor 104 and a control unit 106. For example, when the temperature of the piezoelectric film 10 measured by the temperature sensor 104 is less than 0° C., the control unit 106 controls the signal source 102 A heating signal is applied to the piezoelectric film 10 to cause the piezoelectric film 10 to vibrate. The piezoelectric film 10 is heated by vibrating and self-heating according to a predetermined signal applied from the signal source 102 . Since the piezoelectric film 10 has a maximum value of 0.1 or more in the loss tangent at a frequency of 1 Hz as measured by dynamic viscoelasticity measurement in a temperature range of 0° C. to 50° C., the piezoelectric film 10 is heated. When the temperature is 0°C or higher, excellent flexibility is exhibited.
Therefore, the piezoelectric device 100c can exhibit excellent flexibility regardless of whether it is used in a normal temperature environment or a sub-zero environment.
　なお、圧電フィルムを折り返して積層圧電素子とする場合には、折り返す前の圧電フィルムの長手方向を折り返し方向としてもよく、短手方向を折り返し方向としてもよい。 When the piezoelectric film is folded back to form a laminated piezoelectric element, the longitudinal direction of the piezoelectric film before folding may be the folding direction, or the lateral direction may be the folding direction.
　また、図５および図６に示す例では、積層圧電素子は、３層の圧電フィルム１０を積層する構成としたがこれに限定はされず、２層または４層以上の圧電フィルム１０の層を積層する構成としてもよい。この点に関しては、後述する図７に示す積層圧電素子および図８に示す積層圧電素子も同様である。 In the examples shown in FIGS. 5 and 6, the laminated piezoelectric element has a configuration in which three layers of the piezoelectric film 10 are laminated, but the present invention is not limited to this. A laminated structure may also be used. Regarding this point, the laminated piezoelectric element shown in FIG. 7 and the laminated piezoelectric element shown in FIG. 8, which will be described later, are the same.
　また、図５および図６に示す例では、圧電フィルムを積層した積層圧電素子をエキサイターとして用いる構成としたが、これに限定はされず、１層の圧電フィルムをエキサイターとしても用いる構成であってもよい。しかしながら、圧電フィルムをエキサイターとして用いる場合には、より大きな出力が必要になるため、圧電フィルムを多層化した積層圧電素子とすることが好ましい。 In addition, in the examples shown in FIGS. 5 and 6, the structure is such that the laminated piezoelectric element in which the piezoelectric films are laminated is used as the exciter. good too. However, when a piezoelectric film is used as an exciter, a larger output is required, so it is preferable to use a laminated piezoelectric element in which piezoelectric films are multilayered.
　図５および図６に示す例では、積層圧電素子は、圧電フィルム１０を、複数枚、積層したものである。また、積層圧電素子は、好ましい態様として、さらに、隣接する圧電フィルム１０同士を、接着層１９で貼着している。
　そのため、１枚毎の圧電フィルム１０の剛性が低く、伸縮力は小さくても、圧電フィルム１０を積層することにより、剛性が高くなり、積層圧電素子としての伸縮力は大きくなる。その結果、積層圧電素子は、振動板１２がある程度の剛性を有するものであっても、大きな力で振動板１２を十分に撓ませて、厚さ方向に振動板１２を十分に振動させて、振動板１２に音を発生させることができる。
　また、圧電フィルム１０は、圧電体層２０が厚い方が、圧電フィルム１０の伸縮力は大きくなるが、その分、同じ量、伸縮させるのに必要な駆動電圧は大きくなる。後述するように、好ましい圧電体層２０の厚さは、最大でも３００μｍ程度である。従って、圧電フィルム１０を積層した構成は、個々の圧電フィルム１０に印加する電圧が小さくても、十分に、圧電フィルム１０を伸縮させることが可能である。 In the examples shown in FIGS. 5 and 6, the laminated piezoelectric element is obtained by laminating a plurality of piezoelectric films 10 . In addition, as a preferred embodiment of the laminated piezoelectric element, the adjacent piezoelectric films 10 are further adhered to each other with an adhesive layer 19 .
Therefore, even if the rigidity of each piezoelectric film 10 is low and the expansion/contraction force is small, by laminating the piezoelectric films 10, the rigidity is increased and the expansion/contraction force as a laminated piezoelectric element is increased. As a result, even if the diaphragm 12 has a certain degree of rigidity, the laminated piezoelectric element can sufficiently flex the diaphragm 12 with a large force and sufficiently vibrate the diaphragm 12 in the thickness direction. A sound can be generated in the diaphragm 12 .
In the piezoelectric film 10, the thicker the piezoelectric layer 20, the greater the expansion/contraction force of the piezoelectric film 10, but the drive voltage required to expand/contract the film by the same amount is increased accordingly. As will be described later, the preferred thickness of the piezoelectric layer 20 is at most about 300 μm. Therefore, in the structure in which the piezoelectric films 10 are laminated, even if the voltage applied to each piezoelectric film 10 is small, the piezoelectric films 10 can be expanded and contracted sufficiently.
　また、図５および図６に示す積層圧電素子は、一枚の長尺な圧電フィルム１０のみで積層圧電素子を構成でき、また、駆動電圧を印加するための信号源１０２が１個で済み、さらに、圧電フィルム１０からの電極の引き出しも１か所でよい。
　そのため、後述する図７および図８に示すような、枚葉状の圧電フィルム１０を複数層、積層した積層圧電素子に対して、部品点数を低減し、かつ、構成を簡略化して、積層圧電素子としての信頼性を向上し、さらに、コストダウンを図ることができる。 The laminated piezoelectric element shown in FIGS. 5 and 6 can be constructed with only one long piezoelectric film 10, and only one signal source 102 for applying the drive voltage is required. Furthermore, the electrodes may be led out from the piezoelectric film 10 at one point.
Therefore, as shown in FIGS. 7 and 8, which will be described later, a laminated piezoelectric element in which a plurality of sheets of piezoelectric film 10 are laminated can be obtained by reducing the number of parts and simplifying the configuration. As a result, reliability can be improved, and cost reduction can be achieved.
　また、圧電フィルム１０は、厚さ方向（図６中矢印で示す方向）に分極されている。厚さ方向に分極された１枚の圧電フィルム１０を、折り返して積層することで、積層方向に隣接（対面）する圧電フィルム１０の分極方向は、図６中に矢印で示すように、逆方向になる。従って、１枚の圧電フィルム１０を折り返してなる積層圧電素子は、隣接する圧電フィルム１０の層同士では、一方の面で第１電極層２４同士が対面し、他方の面で第２電極層２６同士が対面する。そのため、隣接する圧電フィルム１０の電極層同士が接触しても、ショート（短絡）する恐れがない。 Also, the piezoelectric film 10 is polarized in the thickness direction (the direction indicated by the arrow in FIG. 6). By folding and stacking one piezoelectric film 10 polarized in the thickness direction, the polarization directions of the piezoelectric films 10 adjacent (facing) in the stacking direction are opposite directions as indicated by arrows in FIG. become. Therefore, in the laminated piezoelectric element formed by folding one piezoelectric film 10, the first electrode layers 24 face each other on one side of the adjacent layers of the piezoelectric film 10, and the second electrode layers 26 on the other side. face each other. Therefore, even if the electrode layers of the adjacent piezoelectric films 10 come into contact with each other, there is no danger of short-circuiting.
　図６に示す積層圧電素子のように、圧電フィルム１０を折り返した積層圧電素子では、圧電フィルム１０の折り返し部に、圧電フィルム１０に当接して芯棒５８を挿入するのが好ましい。
　圧電フィルム１０の第１電極層２４および第２電極層２６は、金属の蒸着膜等で形成される。金属の蒸着膜は、鋭角で折り曲げられると、ヒビ（クラック）等が入りやすく、電極層が断線してしまう可能性がある。すなわち、図６に示す積層圧電素子では、屈曲部の内側において、電極にヒビ等が入り易い。
　これに対して、圧電フィルム１０を折り返した積層圧電素子において、圧電フィルム１０の折り返し部に芯棒５８を挿入することにより、第１電極層２４および第２電極層２６が折り曲げられることを防止して、断線が生じることを好適に防止できる。 In a laminated piezoelectric element in which the piezoelectric film 10 is folded back like the laminated piezoelectric element shown in FIG.
The first electrode layer 24 and the second electrode layer 26 of the piezoelectric film 10 are formed of a metal deposition film or the like. If the vapor-deposited metal film is bent at an acute angle, cracks or the like are likely to occur, and the electrode layer may be disconnected. That is, in the laminated piezoelectric element shown in FIG. 6, cracks or the like easily occur in the electrodes inside the bent portion.
On the other hand, in the laminated piezoelectric element in which the piezoelectric film 10 is folded back, by inserting the core rod 58 into the folded portion of the piezoelectric film 10, the first electrode layer 24 and the second electrode layer 26 are prevented from being folded. Therefore, it is possible to suitably prevent disconnection from occurring.
　ここで、図６に示す例では、積層圧電素子は、圧電フィルム１０を折り返して積層した構成としたがこれに限定はされない。
　図７および図８はそれぞれ、本発明の圧電デバイスが有する積層圧電素子の他の構成の一例を示す図である。 Here, in the example shown in FIG. 6, the laminated piezoelectric element has a structure in which the piezoelectric film 10 is folded and laminated, but the present invention is not limited to this.
7 and 8 are diagrams each showing an example of another configuration of the laminated piezoelectric element of the piezoelectric device of the present invention.
　図７および図８に示す積層圧電素子はそれぞれ、枚葉状の圧電フィルム１０を３層積層したものである。圧電フィルム１０同士は、接着層１９によって貼着されている。各圧電フィルム１０には、駆動電圧を印加するための信号源１０２が接続されている。なお、図７および図８においては、図面を簡略化するために、第１保護層および第２保護層を省略している。しかしながら、図７および図８に示す積層圧電素子は、好ましい態様として、全ての圧電フィルム１０が、第１保護層および第２保護層の両方を有している。 Each of the laminated piezoelectric elements shown in FIGS. 7 and 8 is obtained by laminating three layers of sheet-shaped piezoelectric films 10 . The piezoelectric films 10 are adhered together by an adhesive layer 19 . A signal source 102 for applying a drive voltage is connected to each piezoelectric film 10 . 7 and 8, the first protective layer and the second protective layer are omitted in order to simplify the drawings. However, in the laminated piezoelectric element shown in FIGS. 7 and 8, as a preferred embodiment, all piezoelectric films 10 have both the first protective layer and the second protective layer.
　なお、積層圧電素子は、これに制限はされず、保護層を有する圧電フィルムと、有さない圧電フィルムとが混在してもよい。さらに、圧電フィルムが保護層を有する場合には、圧電フィルムは、第１保護層のみを有してもよく、第２保護層のみを有してもよい。一例として、図７に示すような３層構成の積層圧電素子であれば、図中最上層の圧電フィルムが第２電極層２６上の第２保護層のみを有し、真ん中の圧電フィルムが保護層を有さず、最下層の圧電フィルムが第１電極層２４上の第１保護層のみを有するような構成でもよい。この点に関しては、図８に示す積層圧電素子も同様である。 The laminated piezoelectric element is not limited to this, and a piezoelectric film having a protective layer and a piezoelectric film not having a protective layer may be mixed. Furthermore, when the piezoelectric film has a protective layer, the piezoelectric film may have only the first protective layer or only the second protective layer. As an example, in the case of a laminated piezoelectric element having a three-layer structure as shown in FIG. 7, the uppermost piezoelectric film in the figure has only the second protective layer on the second electrode layer 26, and the central piezoelectric film protects the second protective layer. A configuration in which no layers are provided and the lowest piezoelectric film has only the first protective layer on the first electrode layer 24 may be used. Regarding this point, the laminated piezoelectric element shown in FIG. 8 is the same.
　図７に示す積層圧電素子は、好ましい態様として、隣接する圧電フィルム１０の分極方向（図７中矢印で示す方向）を互いに逆にして、複数層（図示例は３層）の圧電フィルム１０を積層し、隣接する圧電フィルム１０を接着層１９で貼着した構成を有する。
　一方、図８に示す積層圧電素子は、隣接する圧電フィルム１０の分極方向（図８中矢印で示す方向）を同じにして、複数層（図示例は３層）の圧電フィルム１０を積層し、隣接する圧電フィルム１０を接着層１９で貼着した構成を有する。すなわち、図８に示す積層圧電素子は、圧電フィルム１０の分極方向が、全て同方向である。 In the laminated piezoelectric element shown in FIG. 7, as a preferred embodiment, the polarization directions of adjacent piezoelectric films 10 (directions indicated by arrows in FIG. 7) are opposite to each other, and a plurality of layers (three layers in the illustrated example) of piezoelectric films 10 are arranged. It has a configuration in which the piezoelectric films 10 are laminated and the adjacent piezoelectric films 10 are adhered with an adhesive layer 19 .
On the other hand, in the laminated piezoelectric element shown in FIG. 8, a plurality of layers (three layers in the illustrated example) of piezoelectric films 10 are laminated such that the polarization directions of adjacent piezoelectric films 10 (directions indicated by arrows in FIG. 8) are the same. It has a configuration in which adjacent piezoelectric films 10 are adhered with an adhesive layer 19 . That is, in the laminated piezoelectric element shown in FIG. 8, the polarization directions of the piezoelectric films 10 are all the same.
　圧電フィルム１０において、圧電体層２０に印加する電圧の極性は、分極方向に応じたものとなる。従って、印加する電圧の極性は、矢印で示す分極方向において、矢印が向かう方向側（矢印の下流側）の電極層の極性と、逆側（矢印の上流側）の電極層の極性とは、全ての圧電フィルム１０で一致させる。
　図示例においては、分極方向を示す矢印が向かう方向側の電極を第１電極層２４、逆側の電極を第２電極層２６として、全ての圧電フィルム１０において、第１電極層２４と第２電極層２６との極性を同極性にする。
　従って、図７に示すように隣接する圧電フィルム１０の圧電体層２０の分極方向が、互いに逆である積層圧電素子においては、隣接する圧電フィルム１０では、一方の面で第１電極層２４同士が対面し、他方の面で第２電極層２６同士が対面する。そのため、図７に示す積層圧電素子では、隣接する圧電フィルム１０の電極層同士が接触しても、ショート（短絡）する恐れがない。 In the piezoelectric film 10, the polarity of the voltage applied to the piezoelectric layer 20 depends on the polarization direction. Therefore, the polarities of the applied voltages are as follows: All piezoelectric films 10 are matched.
In the illustrated example, the electrode on the side of the arrow indicating the polarization direction is the first electrode layer 24, and the electrode on the opposite side is the second electrode layer 26. In all of the piezoelectric films 10, the first electrode layer 24 and the second The polarity is the same as that of the electrode layer 26 .
Therefore, in a laminated piezoelectric element in which the polarization directions of the piezoelectric layers 20 of the adjacent piezoelectric films 10 are opposite to each other as shown in FIG. face each other, and the second electrode layers 26 face each other on the other side. Therefore, in the laminated piezoelectric element shown in FIG. 7, even if the electrode layers of the adjacent piezoelectric films 10 come into contact with each other, there is no fear of short circuiting.
　積層圧電素子を良好なエネルギー効率で伸縮するためには、接着層１９が圧電体層２０の伸縮を妨害しないように、接着層１９を薄くするのが好ましい。これに対して、隣接する圧電フィルム１０の電極層同士が接触しても、ショートする恐れが無い図７に示す積層圧電素子では、接着層１９が無くてもよく、好ましい態様として接着層１９を有する場合でも、必要な貼着力が得られれば、接着層１９を極めて薄くできる。そのため、高いエネルギー効率で積層圧電素子を伸縮させることができる。 In order to expand and contract the laminated piezoelectric element with good energy efficiency, it is preferable to make the adhesive layer 19 thin so that the adhesive layer 19 does not interfere with the expansion and contraction of the piezoelectric layer 20 . On the other hand, in the laminated piezoelectric element shown in FIG. 7 in which there is no risk of short-circuiting even if the electrode layers of the adjacent piezoelectric films 10 come into contact with each other, the adhesive layer 19 may be omitted. Even if it does, the adhesive layer 19 can be made extremely thin if the required adhesive strength is obtained. Therefore, the laminated piezoelectric element can be expanded and contracted with high energy efficiency.
　なお、圧電フィルム１０においては、厚さ方向の圧電体層２０の伸縮の絶対量は非常に小さく、圧電フィルム１０の伸縮は、実質的に、面方向のみとなる。従って、積層される圧電フィルム１０の分極方向が逆であっても、第１電極層２４および第２電極層２６に印加する電圧の極性さえ正しければ、全ての圧電フィルム１０は同じ方向に伸縮する。 In the piezoelectric film 10, the absolute amount of expansion and contraction of the piezoelectric layer 20 in the thickness direction is very small, and the expansion and contraction of the piezoelectric film 10 is substantially only in the plane direction. Therefore, even if the polarization directions of the laminated piezoelectric films 10 are opposite, all the piezoelectric films 10 expand and contract in the same direction as long as the polarity of the voltage applied to the first electrode layer 24 and the second electrode layer 26 is correct. .
　なお、圧電フィルム１０の分極方向は、ｄ３３メーター等で検出すれば良い。または、後述するコロナポーリング処理の処理条件から、圧電フィルム１０の分極方向を知見してもよい。 The polarization direction of the piezoelectric film 10 can be detected with a d33 meter or the like. Alternatively, the polarization direction of the piezoelectric film 10 may be known from the treatment conditions of corona poling treatment, which will be described later.
　また、図７および図８に示す積層圧電素子は、好ましくは、長尺（大面積）の圧電フィルムを作製し、長尺な圧電フィルムから個々の圧電フィルム１０を切り出して積層する。この場合は、積層圧電素子を構成する複数枚の圧電フィルム１０は、全て同じものである。 In addition, the laminated piezoelectric element shown in FIGS. 7 and 8 is preferably obtained by manufacturing a long (large area) piezoelectric film, cutting out individual piezoelectric films 10 from the long piezoelectric film, and laminating the piezoelectric films 10 . In this case, the plurality of piezoelectric films 10 forming the laminated piezoelectric element are all the same.
　しかしながら、本発明はこれに制限はされない。すなわち、本発明において、積層圧電素子は、例えば、第１保護層および第２保護層を有する圧電フィルムと有さない圧電フィルムなど、異なる層構成の圧電フィルムを積層した構成、および、圧電体層２０の厚さが異なる圧電フィルムを積層した構成等、各種の構成が利用可能である。 However, the present invention is not limited to this. That is, in the present invention, the laminated piezoelectric element includes a structure in which piezoelectric films having different layer structures are laminated, such as a piezoelectric film having a first protective layer and a second protective layer and a piezoelectric film not having the first protective layer and a second protective layer, and a piezoelectric layer. Various configurations are available, such as a stack of 20 different thickness piezoelectric films.
　また、図６～８に示すような圧電フィルム１０を積層した構成において、１層の圧電フィルム１０の、圧電フィルム１０を積層した積層部から面方向の外側に突出する突出部を有する構成とし、突出部に、第１電極層２４および第２電極層２６と、信号源１０２とを接続するための接続部が形成されることが好ましい。なお、突出部における電極層と配線との接続方法には、制限はなく、公知の各種の方法が利用可能である。 In the structure in which the piezoelectric films 10 are laminated as shown in FIGS. 6 to 8, one layer of the piezoelectric film 10 is configured to have a protruding portion that protrudes outward in the plane direction from the laminated portion in which the piezoelectric film 10 is laminated, A connecting portion for connecting the first electrode layer 24 and the second electrode layer 26 to the signal source 102 is preferably formed on the protruding portion. The method of connecting the electrode layer and the wiring in the protruding portion is not limited, and various known methods can be used.
　以下、本発明の圧電素子の構成要素について説明する。 The constituent elements of the piezoelectric element of the present invention will be described below.
　図９に、圧電フィルム１０の一部を拡大して示す。
　図９に示す圧電フィルム１０は、圧電性を有するシート状物である圧電体層２０と、圧電体層２０の一方の面に積層される第２電極層２６と、第２電極層２６の圧電体層２０と反対側の面に積層される第２保護層３０と、圧電体層２０の他方の面に積層される第１電極層２４と、第１電極層２４の圧電体層２０と反対側の面に積層される第１保護層２８と、を有する。すなわち、圧電フィルム１０は、圧電体層２０を電極層で挟持し、電極層の圧電体層が接触していない面に保護層が積層された構成を有する。 FIG. 9 shows an enlarged view of a portion of the piezoelectric film 10. As shown in FIG.
The piezoelectric film 10 shown in FIG. 9 includes a piezoelectric layer 20 that is a sheet-like material having piezoelectricity, a second electrode layer 26 that is laminated on one surface of the piezoelectric layer 20 , and a piezoelectric layer of the second electrode layer 26 . A second protective layer 30 laminated on the surface opposite to the body layer 20, a first electrode layer 24 laminated on the other surface of the piezoelectric layer 20, and the first electrode layer 24 opposite to the piezoelectric layer 20. and a first protective layer 28 laminated on the side surface. That is, the piezoelectric film 10 has a configuration in which the piezoelectric layer 20 is sandwiched between electrode layers, and a protective layer is laminated on the surface of the electrode layer that is not in contact with the piezoelectric layer.
　本発明において、圧電体層２０は、図９に概念的に示すように、高分子材料を含むマトリックス３４中に、圧電体粒子３６を含む、高分子複合圧電体からなるものである。 In the present invention, as conceptually shown in FIG. 9, the piezoelectric layer 20 is composed of a polymeric composite piezoelectric body containing piezoelectric particles 36 in a matrix 34 containing a polymeric material.
　圧電体層２０を構成する高分子複合圧電体のマトリックス３４（マトリックス兼バインダ）の材料として、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。 As the material of the polymer composite piezoelectric matrix 34 (matrix and binder) that constitutes the piezoelectric layer 20, it is preferable to use a polymer material that has viscoelasticity at room temperature. In this specification, "ordinary temperature" refers to a temperature range of about 0 to 50.degree.
　ここで、高分子複合圧電体（圧電体層２０）は、次の用件を具備したものであるのが好ましい。 Here, the polymer composite piezoelectric (piezoelectric layer 20) preferably satisfies the following requirements.
　（ｉ）　可撓性
　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、高分子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。 (i) Flexibility For example, when gripping a loosely bent state like a document like a newspaper or magazine for portable use, it is constantly subjected to a relatively slow and large bending deformation of several Hz or less from the outside. become. At this time, if the polymer composite piezoelectric material is hard, a correspondingly large bending stress is generated, and cracks occur at the interface between the polymer matrix and the piezoelectric particles, which may eventually lead to destruction. Therefore, the polymer composite piezoelectric body is required to have appropriate softness. Moreover, stress can be relieved if strain energy can be diffused to the outside as heat. Therefore, it is required that the loss tangent of the polymer composite piezoelectric material is appropriately large.
　（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振動板（高分子複合圧電体）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ｆ0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。 (ii) Sound quality A speaker vibrates piezoelectric particles at frequencies in the audio band of 20 Hz to 20 kHz, and the vibration energy causes the entire diaphragm (polymer composite piezoelectric body) to vibrate as one to reproduce sound. be. Therefore, the polymer composite piezoelectric body is required to have appropriate hardness in order to increase the transmission efficiency of vibration energy. Also, if the frequency characteristics of the speaker are smooth, the amount of change in sound quality when the lowest resonance frequency f 0 changes as the curvature changes becomes small. Therefore, the loss tangent of the polymer composite piezoelectric body is required to be moderately large.
　スピーカー用振動板の最低共振周波数ｆ0は、下記式で与えられるのは周知である。ここで、ｓは振動系のスチフネス、ｍは質量である。

　このとき、圧電フィルムの湾曲程度すなわち湾曲部の曲率半径が大きくなるほど機械的なスチフネスｓが下がるため、最低共振周波数ｆ0は小さくなる。すなわち、圧電フィルムの曲率半径によってスピーカーの音質（音量、周波数特性）が変わることになる。 It is well known that the lowest resonance frequency f 0 of the speaker diaphragm is given by the following equation. where s is the stiffness of the vibration system and m is the mass.

At this time, as the degree of curvature of the piezoelectric film, that is, the radius of curvature of the curved portion increases, the mechanical stiffness s decreases, so the lowest resonance frequency f0 decreases. That is, the sound quality (volume and frequency characteristics) of the speaker changes depending on the radius of curvature of the piezoelectric film.
　以上をまとめると、スピーカーとして用いるフレキシブルな高分子複合圧電体は、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求められる。また、高分子複合圧電体の損失正接は、２０ｋＨｚ以下の全ての周波数の振動に対して、適度に大きいことが求められる。 In summary, a flexible polymer composite piezoelectric material used as a speaker is required to behave hard against vibrations of 20 Hz to 20 kHz and softly against vibrations of several Hz or less. Also, the loss tangent of the polymer composite piezoelectric body is required to be moderately large with respect to vibrations of all frequencies of 20 kHz or less.
　一般に、高分子固体は粘弾性緩和機構を有しており、温度上昇あるいは周波数の低下とともに大きなスケールの分子運動が貯蔵弾性率（ヤング率）の低下（緩和）あるいは損失弾性率の極大（吸収）として観測される。その中でも、非晶質領域の分子鎖のミクロブラウン運動によって引き起こされる緩和は、主分散と呼ばれ、非常に大きな緩和現象が見られる。この主分散が起きる温度がガラス転移点（Ｔｇ）であり、最も粘弾性緩和機構が顕著に現れる。
　高分子複合圧電体（圧電体層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でのガラス転移点が常温、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。 In general, polymer solids have a viscoelastic relaxation mechanism, and as the temperature rises or the frequency decreases, large-scale molecular motion causes a decrease (relaxation) in the storage elastic modulus (Young's modulus) or a maximum loss elastic modulus (absorption). is observed as Among them, the relaxation caused by the micro-Brownian motion of the molecular chains in the amorphous region is called principal dispersion, and a very large relaxation phenomenon is observed. The temperature at which this primary dispersion occurs is the glass transition point (Tg), and the viscoelastic relaxation mechanism appears most prominently.
In 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 as a matrix, it is possible to suppress vibrations of 20 Hz to 20 kHz. This realizes a polymer composite piezoelectric material that is hard at first and behaves softly with respect to slow vibrations of several Hz or less. In particular, it is preferable to use a polymer material having a glass transition point at room temperature, ie, 0 to 50° C. at a frequency of 1 Hz, for the matrix of the polymer composite piezoelectric material, because this behavior is favorably expressed.
　常温で粘弾性を有する高分子材料としては、公知の各種のものが利用可能である。好ましくは、常温、すなわち０～５０℃において、動的粘弾性試験による周波数１Ｈｚにおける損失正接Ｔａｎδの極大値が、０．５以上有る高分子材料を用いる。
　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、最大曲げモーメント部における高分子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、高い可撓性が期待できる。 Various known materials can be used as the polymer material having viscoelasticity at room temperature. Preferably, a polymer material having a maximum value of 0.5 or more in loss tangent Tan δ at a frequency of 1 Hz in a dynamic viscoelasticity test at normal temperature, ie, 0 to 50° C., is used.
As a result, when the polymer composite piezoelectric body is slowly bent by an external force, the stress concentration at the interface between the polymer matrix and the piezoelectric particles at the maximum bending moment is relaxed, and high flexibility can be expected.
　また、常温で粘弾性を有する高分子材料は、動的粘弾性測定による周波数１Ｈｚでの貯蔵弾性率（Ｅ’）が、０℃において１００ＭＰａ以上、５０℃において１０ＭＰａ以下、であるのが好ましい。
　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。 The polymer material having viscoelasticity at room temperature preferably has a storage elastic modulus (E') at a frequency of 1 Hz measured by dynamic viscoelasticity of 100 MPa or more at 0°C and 10 MPa or less at 50°C.
As a result, the bending moment generated when the polymeric composite piezoelectric body is slowly bent by an external force can be reduced, and at the same time, it can behave rigidly against acoustic vibrations of 20 Hz to 20 kHz.
　また、常温で粘弾性を有する高分子材料は、比誘電率が２５℃において１０以上有ると、より好適である。これにより、高分子複合圧電体に電圧を印加した際に、マトリックス中の圧電体粒子にはより高い電界が掛かるため、大きな変形量が期待できる。
　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。 Further, it is more preferable that the polymer material having viscoelasticity at room temperature has a dielectric constant of 10 or more at 25°C. As a result, when a voltage is applied to the polymer composite piezoelectric material, a higher electric field is applied to the piezoelectric particles in the matrix, so a large amount of deformation can be expected.
On the other hand, however, in consideration of ensuring good moisture resistance and the like, it is also suitable for the polymer material to have a dielectric constant of 10 or less at 25°C.
　このような条件を満たす常温で粘弾性を有する高分子材料としては、シアノエチル化ポリビニルアルコール（シアノエチル化ＰＶＡ）、ポリ酢酸ビニル、ポリビニリデンクロライドコアクリロニトリル、ポリスチレン－ビニルポリイソプレンブロック共重合体、ポリビニルメチルケトン、および、ポリブチルメタクリレート等が例示される。また、これらの高分子材料としては、ハイブラー５１２７（クラレ社製）などの市販品も、好適に利用可能である。なかでも、高分子材料としては，シアノエチル基を有する材料を用いることが好ましく、シアノエチル化ＰＶＡを用いるのが特に好ましい。 Examples of polymeric materials having viscoelasticity at room temperature that meet these conditions include cyanoethylated polyvinyl alcohol (cyanoethylated PVA), polyvinyl acetate, polyvinylidene chloride core acrylonitrile, polystyrene-vinylpolyisoprene block copolymer, and polyvinylmethyl. Examples include ketones and polybutyl methacrylate. Commercially available products such as Hybler 5127 (manufactured by Kuraray Co., Ltd.) can also be suitably used as these polymer materials. Among them, as the polymer material, it is preferable to use a material having a cyanoethyl group, and it is particularly preferable to use cyanoethylated PVA.
　常温で粘弾性を有する高分子材料としては、シアノエチル基を有する高分子材料を用いるのが好ましく、シアノエチル化ＰＶＡを用いるのが特に好ましい。すなわち、本発明において、圧電体層２０は、マトリックス３４として、シアノエチル基を有する高分子材料を用いるのが好ましく、シアノエチル化ＰＶＡを用いるのが特に好ましい。
　以下の説明では、シアノエチル化ＰＶＡを代表とする上述の高分子材料を、まとめて『常温で粘弾性を有する高分子材料』とも言う。 As the polymer material having viscoelasticity at room temperature, it is preferable to use a polymer material having a cyanoethyl group, and it is particularly preferable to use cyanoethylated PVA. That is, in the present invention, the piezoelectric layer 20 preferably uses a polymer material having a cyanoethyl group as the matrix 34, and particularly preferably uses cyanoethylated PVA.
In the following description, the above-mentioned polymeric materials represented by cyanoethylated PVA are collectively referred to as "polymeric materials having viscoelasticity at room temperature".
　なお、これらの常温で粘弾性を有する高分子材料は、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。 These polymer materials having viscoelasticity at room temperature may be used alone or in combination (mixed).
　このような常温で粘弾性を有する高分子材料を用いるマトリックス３４は、必要に応じて、複数の高分子材料を併用してもよい。
　すなわち、マトリックス３４には、誘電特性や機械特性の調節等を目的として、シアノエチル化ＰＶＡ等の粘弾性材料に加え、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。 The matrix 34 using such a polymeric material having viscoelasticity at room temperature may use a plurality of polymeric materials together, if necessary.
That is, in addition to viscoelastic materials such as cyanoethylated PVA, other dielectric polymeric materials may be added to the matrix 34 as necessary for the purpose of adjusting dielectric properties and mechanical properties.
　添加可能な誘電性高分子材料としては、一例として、ポリフッ化ビニリデン、フッ化ビニリデン－テトラフルオロエチレン共重合体、フッ化ビニリデン－トリフルオロエチレン共重合体、ポリフッ化ビニリデン－トリフルオロエチレン共重合体およびポリフッ化ビニリデン－テトラフルオロエチレン共重合体等のフッ素系高分子、シアン化ビニリデン－酢酸ビニル共重合体、シアノエチルセルロース、シアノエチルヒドロキシサッカロース、シアノエチルヒドロキシセルロース、シアノエチルヒドロキシプルラン、シアノエチルメタクリレート、シアノエチルアクリレート、シアノエチルヒドロキシエチルセルロース、シアノエチルアミロース、シアノエチルヒドロキシプロピルセルロース、シアノエチルジヒドロキシプロピルセルロース、シアノエチルヒドロキシプロピルアミロース、シアノエチルポリアクリルアミド、シアノエチルポリアクリレート、シアノエチルプルラン、シアノエチルポリヒドロキシメチレン、シアノエチルグリシドールプルラン、シアノエチルサッカロースおよびシアノエチルソルビトール等のシアノ基またはシアノエチル基を有するポリマー、ならびに、ニトリルゴムやクロロプレンゴム等の合成ゴム等が例示される。
　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、圧電体層２０のマトリックス３４において、これらの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。 Examples of dielectric polymer materials that can be added include polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, and polyvinylidene fluoride-trifluoroethylene copolymer. and fluorine-based polymers such as polyvinylidene fluoride-tetrafluoroethylene copolymer, vinylidene cyanide-vinyl acetate copolymer, cyanoethylcellulose, cyanoethylhydroxysaccharose, cyanoethylhydroxycellulose, cyanoethylhydroxypullulan, cyanoethylmethacrylate, cyanoethylacrylate, cyanoethyl Cyano groups such as hydroxyethylcellulose, cyanoethylamylose, cyanoethylhydroxypropylcellulose, cyanoethyldihydroxypropylcellulose, cyanoethylhydroxypropylamylose, cyanoethylpolyacrylamide, cyanoethylpolyacrylate, cyanoethylpullulan, cyanoethylpolyhydroxymethylene, cyanoethylglycidolpullulan, cyanoethylsaccharose and cyanoethylsorbitol. Alternatively, polymers having cyanoethyl groups, and synthetic rubbers such as nitrile rubber and chloroprene rubber are exemplified.
Among them, polymer materials having cyanoethyl groups are preferably used.
Moreover, in the matrix 34 of the piezoelectric layer 20, these dielectric polymer materials are not limited to one type, and a plurality of types may be added.
　また、マトリックス３４には、誘電性高分子材料以外にも、ガラス転移点Ｔｇを調節する目的で、塩化ビニル樹脂、ポリエチレン、ポリスチレン、メタクリル樹脂、ポリブテン、および、イソブチレン等の熱可塑性樹脂、ならびに、フェノール樹脂、尿素樹脂、メラミン樹脂、アルキド樹脂、および、マイカ等の熱硬化性樹脂を添加しても良い。
　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。 In addition to the dielectric polymer material, the matrix 34 also contains thermoplastic resins such as vinyl chloride resin, polyethylene, polystyrene, methacrylic resin, polybutene, and isobutylene for the purpose of adjusting the glass transition point Tg, and Thermosetting resins such as phenolic resins, urea resins, melamine resins, alkyd resins, and mica may be added.
Furthermore, a tackifier such as rosin ester, rosin, terpene, terpene phenol, and petroleum resin may be added for the purpose of improving adhesiveness.
　圧電体層２０のマトリックス３４において、シアノエチル化ＰＶＡ等の粘弾性を有する高分子材料以外の材料を添加する際の添加量には、特に限定は無いが、マトリックス３４に占める割合で３０質量％以下とするのが好ましい。
　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。 When adding a material other than a polymer material having viscoelasticity, such as cyanoethylated PVA, to the matrix 34 of the piezoelectric layer 20, the addition amount is not particularly limited, but the ratio of the material to the matrix 34 is 30% by mass or less. is preferable.
As a result, the characteristics of the polymer material to be added can be expressed without impairing the viscoelastic relaxation mechanism in the matrix 34, so that the dielectric constant can be increased, the heat resistance can be improved, and the adhesion between the piezoelectric particles 36 and the electrode layer can be improved. favorable results can be obtained in terms of
　圧電体層２０は、このようなマトリックス３４に、圧電体粒子３６を含む、高分子複合圧電体からなる層である。圧電体粒子３６は、マトリックス３４に分散されている。好ましくは、圧電体粒子３６は、マトリックス３４に均一（略均一）に分散される。 The piezoelectric layer 20 is a layer made of a polymeric composite piezoelectric material containing piezoelectric particles 36 in such a matrix 34 . Piezoelectric particles 36 are dispersed in the matrix 34 . Preferably, the piezoelectric particles 36 are uniformly (substantially uniformly) dispersed in the matrix 34 .
　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。 The piezoelectric particles 36 are made of ceramic particles having a perovskite or wurtzite crystal structure.
Examples of ceramic particles constituting the piezoelectric particles 36 include lead zirconate titanate (PZT), lead zirconate lanthanate titanate (PLZT), barium titanate (BaTiO 3 ), zinc oxide (ZnO), and A solid solution (BFBT) of barium titanate and bismuth ferrite (BiFe 3 ) is exemplified.
Only one kind of these piezoelectric particles 36 may be used, or a plurality of kinds thereof may be used together (mixed).
　圧電体粒子３６の粒径には制限はなく、圧電フィルム１０のサイズ、および、圧電デバイス１００の用途等に応じて、適宜、選択すれば良い。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、圧電フィルム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。 The particle size of the piezoelectric particles 36 is not limited, and may be appropriately selected according to the size of the piezoelectric film 10, the application of the piezoelectric device 100, and the like. The particle size of the piezoelectric particles 36 is preferably 1 to 10 μm. By setting the particle size of the piezoelectric particles 36 within this range, favorable results can be obtained in that the piezoelectric film 10 can achieve both high piezoelectric characteristics and flexibility.
　なお、圧電体層２０中の圧電体粒子３６は、マトリックス３４中に、均一かつ規則性を持って分散されていてもよいし、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。
　さらに、圧電体粒子３６は、粒径が揃っていても、揃っていなくてもよい。 The piezoelectric particles 36 in the piezoelectric layer 20 may be uniformly and regularly dispersed in the matrix 34, or if they are uniformly dispersed, they may be dispersed irregularly in the matrix 34. may have been
Furthermore, the piezoelectric particles 36 may or may not have uniform particle diameters.
　圧電フィルム１０において、圧電体層２０中におけるマトリックス３４と圧電体粒子３６との量比には、制限はなく、圧電フィルム１０の面方向の大きさおよび厚さ、圧電デバイス１００の用途、ならびに、圧電デバイス１００に要求される特性等に応じて、適宜、設定すればよい。
　圧電体層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。 In the piezoelectric film 10, the quantitative 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 film 10 in the plane direction, the application of the piezoelectric device 100, and It may be appropriately set according to the characteristics required for the piezoelectric device 100 .
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%.
By setting the amount ratio between the matrix 34 and the piezoelectric particles 36 within the above range, favorable results can be obtained in terms of achieving both high piezoelectric characteristics and flexibility.
　圧電フィルム１０において、圧電体層２０の厚さには、特に限定はなく、圧電デバイス１００の用途、圧電デバイス１００における圧電フィルムの積層数、圧電フィルム１０に要求される特性等に応じて、適宜、設定すればよい。
　圧電体層２０が厚いほど、いわゆるシート状物のコシの強さなどの剛性等の点では有利であるが、同じ量だけ圧電フィルム１０を伸縮させるために必要な電圧（電位差）は大きくなる。
　圧電体層２０の厚さは、８～３００μｍが好ましく、８～２００μｍがより好ましく、１０～１５０μｍがさらに好ましく、１５～１００μｍが特に好ましい。
　圧電体層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。 In the piezoelectric film 10 , the thickness of the piezoelectric layer 20 is not particularly limited, and may be appropriately determined according to the application of the piezoelectric device 100 , the number of layers of piezoelectric films in the piezoelectric device 100 , the properties required of the piezoelectric film 10 , and the like. , should be set.
The thicker the piezoelectric layer 20 is, the more advantageous it is in terms of rigidity such as stiffness of the so-called sheet-like material, but the voltage (potential difference) required to expand and contract the piezoelectric film 10 by the same amount is increased.
The thickness of the piezoelectric layer 20 is preferably 8-300 μm, more preferably 8-200 μm, still more preferably 10-150 μm, particularly preferably 15-100 μm.
By setting the thickness of the piezoelectric layer 20 within the above range, favorable results can be obtained in terms of ensuring both rigidity and appropriate flexibility.
　また、圧電体層２０は、厚さ方向に分極処理（ポーリング）されているのが好ましい。 Also, the piezoelectric layer 20 is preferably polarized (poled) in the thickness direction.
　図９に示すように、圧電フィルム１０は、このような圧電体層２０の一面に、第２電極層２６を有し、その上に第２保護層３０を有し、圧電体層２０の他方の面に、第１電極層２４を有し、その上に第１保護層２８を有してなる構成を有する。ここで、第１電極層２４と第２電極層２６とが電極対を形成する。 As shown in FIG. 9, the piezoelectric film 10 has a second electrode layer 26 on one surface of the piezoelectric layer 20, and a second protective layer 30 thereon. has a first electrode layer 24 on the surface thereof, and a first protective layer 28 thereon. Here, the first electrode layer 24 and the second electrode layer 26 form an electrode pair.
　すなわち、圧電フィルム１０は、圧電体層２０の両面を電極対、すなわち、第２電極層２６および第１電極層２４で挟持し、この積層体を、第２保護層３０および第１保護層２８で挟持してなる構成を有する。
　このように、圧電フィルム１０において、第２電極層２６および第１電極層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。
　なお、第１電極層２４および第２電極層２６、ならびに、第１保護層２８および第２保護層３０における第１および第２は圧電フィルム１０を説明するために、便宜的に付しているものである。従って、本発明における第１および第２には、技術的な意味は無く、また、実際の使用状態とは無関係である。 That is, in the piezoelectric film 10 , both surfaces of the piezoelectric layer 20 are sandwiched between electrode pairs, that is, the second electrode layer 26 and the first electrode layer 24 , and this laminate is formed into the second protective layer 30 and the first protective layer 28 . It has a configuration sandwiched between.
Thus, in the piezoelectric film 10, the region sandwiched between the second electrode layer 26 and the first electrode layer 24 expands and contracts according to the applied voltage.
Note that the first and second numbers in the first electrode layer 24 and the second electrode layer 26 and the first protective layer 28 and the second protective layer 30 are attached for convenience in order to explain the piezoelectric film 10. It is. Therefore, the first and second aspects of the present invention have no technical significance and are irrelevant to the actual usage conditions.
　圧電フィルム１０において、第１保護層２８および第２保護層３０は、第１電極層２４および第２電極層２６を被覆すると共に、圧電体層２０に適度な剛性と機械的強度を付与する役目を担っている。すなわち、圧電フィルム１０において、マトリックス３４と圧電体粒子３６とからなる圧電体層２０は、ゆっくりとした曲げ変形に対しては、非常に優れた可撓性を示す一方で、用途によっては、剛性や機械的強度が不足する場合がある。圧電フィルム１０は、それを補うために第２保護層３０および第１保護層２８が設けられる。
　第１保護層２８と第２保護層３０とは、配置位置が異なるのみで、構成は同じである。従って、以下の説明においては、第１保護層２８および第２保護層３０を区別する必要がない場合には、両部材をまとめて、保護層ともいう。 In the piezoelectric film 10, the first protective layer 28 and the second protective layer 30 cover the first electrode layer 24 and the second electrode layer 26, and provide the piezoelectric layer 20 with appropriate rigidity and mechanical strength. is responsible for That is, in the piezoelectric film 10, the piezoelectric layer 20 made up of the matrix 34 and the piezoelectric particles 36 exhibits excellent flexibility against slow bending deformation, but depending on the application, the rigidity may increase. and mechanical strength may be insufficient. The piezoelectric film 10 is provided with a second protective layer 30 and a first protective layer 28 to compensate.
The first protective layer 28 and the second protective layer 30 have the same configuration, except for the arrangement position. Therefore, in the following description, when there is no need to distinguish between the first protective layer 28 and the second protective layer 30, both members are collectively referred to as protective layers.
　第１保護層２８および第２保護層３０には、制限はなく、各種のシート状物が利用可能であり、一例として、各種の樹脂フィルムが好適に例示される。
　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。 Various sheet materials can be used for the first protective layer 28 and the second protective layer 30 without limitation, and various resin films are preferably exemplified as examples.
Among them, polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyphenylene sulfite (PPS), polymethyl methacrylate (PMMA), due to their excellent mechanical properties and heat resistance. ), polyetherimide (PEI), polyimide (PI), polyethylene naphthalate (PEN), triacetyl cellulose (TAC), cyclic olefin resins, and the like are preferably used.
　第１保護層２８および第２保護層３０の厚さにも制限はない。また、第１保護層２８および第２保護層３０の厚さは、基本的に同じであるが、異なってもよい。
　ここで、第１保護層２８および第２保護層３０の剛性が高過ぎると、圧電体層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、第１保護層２８および第２保護層３０は、薄いほど有利である。 The thicknesses of the first protective layer 28 and the second protective layer 30 are also not limited. Also, the thicknesses of the first protective layer 28 and the second protective layer 30 are basically the same, but may be different.
Here, if the rigidity of the first protective layer 28 and the second protective layer 30 is too high, not only will the expansion and contraction of the piezoelectric layer 20 be restricted, but also the flexibility will be impaired. Therefore, the thinner the first protective layer 28 and the second protective layer 30, the better, except for cases where mechanical strength and good handling properties as a sheet-like article are required.
　圧電フィルム１０においては、第１保護層２８および第２保護層３０の厚さが、圧電体層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、圧電体層２０の厚さが５０μｍで第１保護層２８および第２保護層３０がＰＥＴからなる場合、第１保護層２８および第２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。 In the piezoelectric film 10, if the thickness of the first protective layer 28 and the second protective layer 30 is not more than twice the thickness of the piezoelectric layer 20, it is possible to ensure both rigidity and appropriate flexibility. favorable results can be obtained.
For example, when the thickness of the piezoelectric layer 20 is 50 μm and the first protective layer 28 and the second protective layer 30 are made of PET, the thicknesses of the first protective layer 28 and the second protective layer 30 are preferably 100 μm or less. 50 μm or less is more preferable, and 25 μm or less is even more preferable.
　圧電フィルム１０において、圧電体層２０と第１保護層２８との間には第１電極層２４が、圧電体層２０と第２保護層３０との間には第２電極層２６が、それぞれ形成される。　第１電極層２４および第２電極層２６は、圧電体層２０（圧電フィルム１０）に電圧を印加するために設けられる。 In the piezoelectric film 10, a first electrode layer 24 is provided between the piezoelectric layer 20 and the first protective layer 28, and a second electrode layer 26 is provided between the piezoelectric layer 20 and the second protective layer 30. It is formed. The first electrode layer 24 and the second electrode layer 26 are provided for applying voltage to the piezoelectric layer 20 (piezoelectric film 10).
　第１電極層２４および第２電極層２６は、位置が異なる以外は、基本的に同じものである。従って、以下の説明においては、第１電極層２４および第２電極層２６を区別する必要がない場合には、両部材をまとめて、電極層ともいう。 The first electrode layer 24 and the second electrode layer 26 are basically the same except for their positions. Therefore, in the following description, when there is no need to distinguish between the first electrode layer 24 and the second electrode layer 26, both members are collectively referred to as electrode layers.
　本発明において、第１電極層２４および第２電極層２６の形成材料には制限はなく、各種の導電体が利用可能である。具体的には、炭素、パラジウム、鉄、錫、アルミニウム、ニッケル、白金、金、銀、銅、チタン、クロムおよびモリブデン等の金属、これらの合金、これらの金属および合金の積層体および複合体、ならびに、酸化インジウムスズ等が例示される。あるいは、ＰＥＤＯＴ／ＰＰＳ（ポリエチレンジオキシチオフェン－ポリスチレンスルホン酸）などの導電性高分子も例示される。中でも、銅、アルミニウム、金、銀、白金、および、酸化インジウムスズは、第１電極層２４および第２電極層２６として好適に例示される。その中でも、導電性、コストおよび可撓性等の観点から銅がより好ましい。 In the present invention, the materials for forming the first electrode layer 24 and the second electrode layer 26 are not limited, and various conductors can be used. Specifically, metals such as carbon, palladium, iron, tin, aluminum, nickel, platinum, gold, silver, copper, titanium, chromium and molybdenum, alloys thereof, laminates and composites of these metals and alloys, Also, indium tin oxide and the like are exemplified. Alternatively, conductive polymers such as PEDOT/PPS (polyethylenedioxythiophene-polystyrenesulfonic acid) are also exemplified. Among them, copper, aluminum, gold, silver, platinum, and indium tin oxide are preferably exemplified as the first electrode layer 24 and the second electrode layer 26 . Among them, copper is more preferable from the viewpoint of conductivity, cost, flexibility, and the like.
　また、第１電極層２４および第２電極層２６の形成方法にも制限はなく、真空蒸着およびスパッタリング等の気相堆積法（真空成膜法）、めっきによる成膜、ならびに、上記材料で形成された箔を貼着する方法等、公知の方法が、各種、利用可能である。 In addition, the method of forming the first electrode layer 24 and the second electrode layer 26 is not limited, and may be a vapor phase deposition method (vacuum film formation method) such as vacuum deposition or sputtering, a film formation by plating, or the formation of the above materials. A variety of known methods are available, such as affixing the foils.
　中でも特に、圧電フィルム１０の可撓性が確保できる等の理由で、真空蒸着によって成膜された銅およびアルミニウム等の薄膜は、第１電極層２４および第２電極層２６として、好適に利用される。その中でも特に、真空蒸着による銅の薄膜は、好適に利用される。 Among them, a thin film of copper, aluminum, or the like formed by vacuum deposition is particularly preferably used as the first electrode layer 24 and the second electrode layer 26 because the flexibility of the piezoelectric film 10 can be ensured. be. Among them, a copper thin film formed by vacuum deposition is particularly preferably used.
　第１電極層２４および第２電極層２６の厚さには、制限はない。また、第１電極層２４および第２電極層２６の厚さは、基本的に同じであるが、異なってもよい。
　ここで、前述の第１保護層２８および第２保護層３０と同様に、第１電極層２４および第２電極層２６の剛性が高過ぎると、圧電体層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、第１電極層２４および第２電極層２６は、電気抵抗が高くなり過ぎない範囲であれば、薄いほど有利である。 The thicknesses of the first electrode layer 24 and the second electrode layer 26 are not limited. Also, the thicknesses of the first electrode layer 24 and the second electrode layer 26 are basically the same, but may be different.
Here, as with the first protective layer 28 and the second protective layer 30 described above, if the rigidity of the first electrode layer 24 and the second electrode layer 26 is too high, not only will the expansion and contraction of the piezoelectric layer 20 be restricted, Flexibility is also impaired. Therefore, the thinner the first electrode layer 24 and the second electrode layer 26, the better, as long as the electrical resistance does not become too high.
　圧電フィルム１０においては、第１電極層２４および第２電極層２６の厚さと、ヤング率との積が、第１保護層２８および第２保護層３０の厚さとヤング率との積を下回れば、可撓性を大きく損なうことがないため、好適である。
　例えば、第１保護層２８および第２保護層３０がＰＥＴ（ヤング率：約６．２ＧＰａ）で、第１電極層２４および第２電極層２６が銅（ヤング率：約１３０ＧＰａ）からなる組み合わせの場合、第１保護層２８および第２保護層３０の厚さが２５μｍだとすると、第１電極層２４および第２電極層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。 In the piezoelectric film 10, if the product of the thickness of the first electrode layer 24 and the second electrode layer 26 and the Young's modulus is less than the product of the thickness of the first protective layer 28 and the second protective layer 30 and the Young's modulus , is preferred because it does not significantly impair flexibility.
For example, the first protective layer 28 and the second protective layer 30 are made of PET (Young's modulus: about 6.2 GPa), and the first electrode layer 24 and the second electrode layer 26 are made of copper (Young's modulus: about 130 GPa). In this case, if the thickness of the first protective layer 28 and the second protective layer 30 is 25 μm, the thickness of the first electrode layer 24 and the second electrode layer 26 is preferably 1.2 μm or less, more preferably 0.3 μm or less. , it is preferably 0.1 μm or less.
　上述したように、圧電フィルム１０は、高分子材料を含むマトリックス３４に圧電体粒子３６を分散してなる圧電体層２０を、第１電極層２４および第２電極層２６で挟持し、さらに、この積層体を、第１保護層２８および第２保護層３０で挟持してなる構成を有する。 As described above, in the piezoelectric film 10, the piezoelectric layer 20 formed by dispersing the piezoelectric particles 36 in the matrix 34 containing a polymer material is sandwiched between the first electrode layer 24 and the second electrode layer 26, and further, It has a configuration in which this laminate is sandwiched between a first protective layer 28 and a second protective layer 30 .
　本発明においては、このような圧電フィルム１０は、動的粘弾性測定による周波数１Ｈｚでの損失正接（Ｔａｎδ）の極大値が常温（０℃～５０℃）に存在し、０．１以上となる極大値が常温に存在する。
　これにより、圧電フィルム１０は、常温下において、圧電フィルム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、高分子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。 In the present invention, such a piezoelectric film 10 has a maximum value of loss tangent (Tan δ) at a frequency of 1 Hz by dynamic viscoelasticity measurement, which is 0.1 or more at room temperature (0° C. to 50° C.). A maximum exists at normal temperature.
As a result, even if the piezoelectric film 10 receives a relatively slow and large bending deformation of several Hz or less from the outside at room temperature, the strain energy can be effectively diffused to the outside as heat. , the occurrence of cracks at the interface between the polymer matrix and the piezoelectric particles can be prevented.
　圧電フィルム１０は、動的粘弾性測定による周波数１Ｈｚでの貯蔵弾性率（Ｅ’）が、０℃において１０～３０ＧＰａ、５０℃において１～１０ＧＰａであるのが好ましい。なお、この条件に関しては、圧電体層２０も同様である。
　これにより、常温で圧電フィルム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。 The piezoelectric film 10 preferably has a storage elastic modulus (E') at a frequency of 1 Hz measured by dynamic viscoelasticity measurement of 10 to 30 GPa at 0°C and 1 to 10 GPa at 50°C. Note that this condition applies to the piezoelectric layer 20 as well.
Accordingly, the piezoelectric film 10 can have a large frequency dispersion in the storage elastic modulus (E') at room temperature. That is, it can act hard against vibrations of 20 Hz to 20 kHz and soft against vibrations of several Hz or less.
　また、圧電フィルム１０は、厚さと動的粘弾性測定による周波数１Ｈｚでの貯蔵弾性率（Ｅ’）との積が、０℃において１．０×１０5～２．０×１０6Ｎ／ｍ、５０℃において１．０×１０5～１．０×１０6Ｎ／ｍであるのが好ましい。なお、この条件に関しては、圧電体層２０も同様である。
　これにより、圧電フィルム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。 In addition, the piezoelectric film 10 has a product of thickness and storage elastic modulus (E′) at a frequency of 1 Hz determined by dynamic viscoelasticity measurement of 1.0×10 5 to 2.0×10 6 N/m at 0° C. , 1.0×10 5 to 1.0×10 6 N/m at 50°C. Note that this condition applies to the piezoelectric layer 20 as well.
As a result, the piezoelectric film 10 can have appropriate rigidity and mechanical strength within a range that does not impair flexibility and acoustic properties.
　さらに、圧電フィルム１０は、動的粘弾性測定から得られたマスターカーブにおいて、２５℃、周波数１ｋＨｚにおける損失正接（Ｔａｎδ）が、０．０５以上であるのが好ましい。この条件に関しては、圧電体層２０も同様である。
　これにより、圧電フィルム１０を用いたスピーカの周波数特性が平滑になり、スピーカ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量も小さくできる。 Furthermore, the piezoelectric film 10 preferably has a loss tangent (Tan δ) of 0.05 or more at 25° C. and a frequency of 1 kHz in a master curve obtained from dynamic viscoelasticity measurement. This condition applies to the piezoelectric layer 20 as well.
As a result, the frequency characteristics of the speaker using the piezoelectric film 10 are smoothed, and the amount of change in sound quality when the lowest resonance frequency f0 changes as the curvature of the speaker changes can be reduced.
　なお、本発明において、圧電フィルム１０および圧電体層２０等の貯蔵弾性率（ヤング率）および損失正接は、公知の方法で測定すればよい。一例として、エスアイアイ・ナノテクノロジー社製（ＳＩＩナノテクノロジー社製）の動的粘弾性測定装置ＤＭＳ６１００を用いて測定すればよい。
　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。 In the present invention, the storage elastic modulus (Young's modulus) and loss tangent of the piezoelectric film 10, piezoelectric layer 20, etc. may be measured by known methods. As an example, the dynamic viscoelasticity measuring device DMS6100 manufactured by SII Nanotechnology Co., Ltd. (manufactured by SII Nanotechnology Co., Ltd.) may be used for measurement.
As an example of the measurement conditions, 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), and the measurement temperature is -50 to 150 ° C. , a heating rate of 2° C./min (in a nitrogen atmosphere), a sample size of 40 mm×10 mm (including the clamping area), and a distance between chucks of 20 mm.
　さらに、本発明の圧電フィルム１０は、これらの層に加え、第１電極層２４および第２電極層２６からの電極の引出しを行う電極引出し部、ならびに、圧電体層２０が露出する領域を覆って、ショート等を防止する絶縁層等を有していてもよい。
　第１電極層２４および第２電極層２６から電極の引き出し方法には、制限はなく、公知の各種の方法が利用可能である。 Furthermore, in addition to these layers, the piezoelectric film 10 of the present invention covers the electrode lead-out portions for leading the electrodes from the first electrode layer 24 and the second electrode layer 26 and the area where the piezoelectric layer 20 is exposed. In addition, it may have an insulating layer or the like for preventing short circuits or the like.
There are no restrictions on the method of extracting electrodes from the first electrode layer 24 and the second electrode layer 26, and various known methods can be used.
　一例として、電極層および保護層に、圧電体層２０の面方向外部に突出する部位を設けて、此処に引き出し線を接続して外部に電極を引き出す方法、第１電極層２４および第２電極層２６に銅箔等の導電体（引き出し線）を接続して外部に電極を引き出す方法、ならびに、レーザ等によって第１保護層２８および第２保護層３０に貫通孔を形成して、この貫通孔に導電性材料を充填して導電性材料と引き出し線とを接続して外部に電極を引き出す方法、等が例示される。
　好適な電極の引き出し方法として、特開２０１４－２０９７２４号公報に記載される方法、および、特開２０１６－０１５３５４号公報に記載される方法等が例示される。
　なお、各電極層において、電極引出し部は１つには制限されず、２以上の電極引出し部を有していてもよい。特に、保護層の一部を除去して孔部に導電性材料を挿入して電極引出し部とする構成の場合には、より確実に通電を確保するために、電極引出し部を３以上有するのが好ましい。 As an example, a method in which the electrode layer and the protective layer are provided with portions protruding outward in the plane direction of the piezoelectric layer 20 and a lead wire is connected to the portion to lead out the electrodes to the outside, the first electrode layer 24 and the second electrode. A method of connecting a conductor (lead wire) such as a copper foil to the layer 26 to draw out an electrode to the outside, and a method of forming through holes in the first protective layer 28 and the second protective layer 30 by a laser or the like, and Examples include a method of filling a hole with a conductive material, connecting the conductive material and a lead wire, and leading an electrode to the outside.
Examples of suitable methods for extracting electrodes include the method described in Japanese Patent Application Laid-Open No. 2014-209724 and the method described in Japanese Patent Application Laid-Open No. 2016-015354.
Note that each electrode layer is not limited to one electrode lead-out portion, and may have two or more electrode lead-out portions. In particular, in the case of a configuration in which a part of the protective layer is removed and a conductive material is inserted into the hole to form the electrode lead-out portion, three or more electrode lead-out portions are provided in order to ensure more reliable conduction of electricity. is preferred.
　圧電デバイス１００において、圧電フィルム１０の第１電極層２４および第２電極層２６には、圧電フィルム１０を伸縮させる駆動電圧を印加すなわち駆動電力を供給する、信号源１０２が接続される。
　信号源１０２としては、所望の信号を出力できるものであればよく、市販のパワーアンプ等を用いることができる。信号源１０２が供給する信号には、制限はなく、直流信号でも交流信号でもよい。また、駆動電圧も、圧電フィルム１０の圧電体層２０の厚さおよび形成材料等に応じて、圧電フィルム１０を適正に駆動できる駆動電圧を、適宜、設定すればよい。 In the piezoelectric device 100 , a signal source 102 is connected to the first electrode layer 24 and the second electrode layer 26 of the piezoelectric film 10 to apply a drive voltage for expanding and contracting the piezoelectric film 10 , that is, to supply drive power.
A commercially available power amplifier or the like can be used as the signal source 102 as long as it can output a desired signal. The signal provided by the signal source 102 is not limited and may be a DC signal or an AC signal. Also, the driving voltage may be appropriately set according to the thickness of the piezoelectric layer 20 of the piezoelectric film 10, the forming material, and the like, so that the piezoelectric film 10 can be properly driven.
　ここで、図１に示す圧電デバイス１００のように、圧電フィルム１０に加熱用の信号を印加して、圧電フィルム１０に自己発熱させる構成の場合には、電源として交流電源を用いることが好ましい。 Here, as in the piezoelectric device 100 shown in FIG. 1, in the case of a configuration in which a heating signal is applied to the piezoelectric film 10 to cause the piezoelectric film 10 to generate heat by itself, it is preferable to use an AC power supply as the power supply.
　以下、図１０～図１２を参照して、圧電フィルム１０の製造方法の一例を説明する。 An example of a method for manufacturing the piezoelectric film 10 will be described below with reference to FIGS. 10 to 12. FIG.
　まず、図１０に示す、第１保護層２８の表面に第１電極層２４が形成されたシート状物１１ａを準備する。さらに、図１２に概念的に示す、第２保護層３０の表面に第２電極層２６が形成されたシート状物１１ｃを準備する。 First, a sheet-like object 11a having a first protective layer 28 on which a first electrode layer 24 is formed is prepared as shown in FIG. Furthermore, a sheet-like object 11c conceptually shown in FIG. 12 is prepared in which the second electrode layer 26 is formed on the surface of the second protective layer 30 .
　シート状物１１ａは、第１保護層２８の表面に、真空蒸着、スパッタリング、および、めっき等によって第１電極層２４として銅薄膜等を形成して作製すればよい。同様に、シート状物１１ｃは、第２保護層３０の表面に、真空蒸着、スパッタリング、および、めっき等によって第２電極層２６として銅薄膜等を形成して作製すればよい。
　あるいは、保護層の上に銅薄膜等が形成された市販品のシート状物を、シート状物１１ａおよび／またはシート状物１１ｃとして利用してもよい。
　シート状物１１ａおよびシート状物１１ｃは、同じ構成でもよく、異なる構成でもよい。 The sheet 11a may be produced by forming a copper thin film or the like as the first electrode layer 24 on the surface of the first protective layer 28 by vacuum deposition, sputtering, plating, or the like. Similarly, the sheet 11c may be produced by forming a copper thin film or the like as the second electrode layer 26 on the surface of the second protective layer 30 by vacuum deposition, sputtering, plating, or the like.
Alternatively, a commercially available sheet having a copper thin film or the like formed on a protective layer may be used as the sheet 11a and/or the sheet 11c.
The sheet-like material 11a and the sheet-like material 11c may have the same configuration or different configurations.
　なお、保護層が非常に薄く、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）付きの保護層を用いても良い。なお、セパレータとしては、厚さ２５～１００μｍのＰＥＴ等を用いることができる。セパレータは、電極層および保護層の熱圧着後、取り除けばよい。 In addition, when the protective layer is very thin and the handling property is poor, a protective layer with a separator (temporary support) may be used as necessary. As the separator, PET or the like having a thickness of 25 to 100 μm can be used. The separator may be removed after the electrode layer and protective layer are thermocompression bonded.
　次いで、図１１に示すように、シート状物１１ａの第１電極層２４上に、圧電体層２０となる塗料（塗布組成物）を塗布した後、硬化して圧電体層２０を形成する。これにより、シート状物１１ａと圧電体層２０とを積層した積層体１１ｂを作製する。 Next, as shown in FIG. 11, a coating (coating composition) that will form the piezoelectric layer 20 is applied on the first electrode layer 24 of the sheet 11a, and then cured to form the piezoelectric layer 20. As a result, a laminated body 11b in which the sheet-like material 11a and the piezoelectric layer 20 are laminated is produced.
　圧電体層２０の形成は、圧電体層２０を形成する材料に応じて、各種の方法が利用可能である。
　一例として、まず、有機溶媒に、上述したシアノエチル化ＰＶＡ等の高分子材料を溶解し、さらに、ＰＺＴ粒子等の圧電体粒子３６を添加し、攪拌して塗料を調製する。
　有機溶媒には制限はなく、ジメチルホルムアミド（ＤＭＦ）、メチルエチルケトン（ＭＥＫ）、および、シクロヘキサノン等の各種の有機溶媒が利用可能である。
　シート状物１１ａを準備し、かつ、塗料を調製したら、この塗料をシート状物１１ａにキャスティング（塗布）して、有機溶媒を蒸発して乾燥する。これにより、図１１に示すように、第１保護層２８の上に第１電極層２４を有し、第１電極層２４の上に圧電体層２０を積層してなる積層体１１ｂを作製する。 Various methods can be used for forming the piezoelectric layer 20 depending on the material forming the piezoelectric layer 20 .
As an example, first, a polymer material such as cyanoethylated PVA is dissolved in an organic solvent, and piezoelectric particles 36 such as PZT particles are added and stirred to prepare a coating material.
Organic solvents are not limited, and various organic solvents such as dimethylformamide (DMF), methyl ethyl ketone (MEK), and cyclohexanone can be used.
After the sheet-like material 11a is prepared and the paint is prepared, the paint is cast (applied) on the sheet-like material 11a and dried by evaporating the organic solvent. As a result, as shown in FIG. 11, a laminate 11b having the first electrode layer 24 on the first protective layer 28 and the piezoelectric layer 20 on the first electrode layer 24 is produced. .
　塗料のキャスティング方法には制限はなく、バーコーター、スライドコーターおよびドクターナイフ等の公知の方法（塗布装置）が、全て、利用可能である。
　あるいは高分子材料が加熱溶融可能な物であれば、高分子材料を加熱溶融して、これに圧電体粒子３６を添加してなる溶融物を作製し、押し出し成形等によって、図１０に示すシート状物１１ａの上にシート状に押し出し、冷却することにより、図１１に示すような、積層体１１ｂを作製してもよい。 There are no restrictions on the method of casting the coating material, and known methods (coating equipment) such as bar coaters, slide coaters and doctor knives can all be used.
Alternatively, if the polymer material is heat-meltable, the polymer material is heat-melted and the piezoelectric particles 36 are added to prepare a melt, which is then extruded into the sheet shown in FIG. A laminate 11b as shown in FIG. 11 may be produced by extruding a sheet onto the object 11a and cooling it.
　なお、上述のように、圧電体層２０において、マトリックス３４には、常温で粘弾性を有する高分子材料以外にも、ＰＶＤＦ（ポリフッ化ビニリデン）等の高分子圧電材料を添加しても良い。
　マトリックス３４に、これらの高分子圧電材料を添加する際には、上記塗料に添加する高分子圧電材料を溶解すればよい。あるいは、加熱溶融した常温で粘弾性を有する高分子材料に、添加する高分子圧電材料を添加して加熱溶融すればよい。 As described above, in the piezoelectric layer 20, the matrix 34 may be added with a polymeric piezoelectric material such as PVDF (polyvinylidene fluoride), in addition to the polymeric material having viscoelasticity at room temperature.
When these polymeric piezoelectric materials are added to the matrix 34, the polymeric piezoelectric materials to be added to the paint may be dissolved. Alternatively, the polymer piezoelectric material to be added may be added to a polymer material that has been melted by heating and has viscoelasticity at room temperature, and then melted by heating.
　圧電体層２０を形成したら、必要に応じて、カレンダー処理を行ってもよい。カレンダー処理は、１回でもよく、複数回、行ってもよい。周知のように、カレンダー処理とは、加熱プレスや加熱ローラ等によって、被処理面を加熱しつつ押圧して、平坦化等を施す処理である。
　なお、カレンダー処理は、後述する分極処理の後に行ってもよい。しかしながら、分極処理を行った後にカレンダー処理を行うと、押圧によって押し込まれた圧電体粒子３６が回転してしまい、分極処理の効果が低下する可能性がある。この点を考慮すると、カレンダー処理は、分極処理の前に行うのが好ましい。 After the piezoelectric layer 20 is formed, it may be calendered, if necessary. Calendering may be performed once or multiple times. As is well known, calendering is a process in which a surface to be treated is heated and pressed by a heating press, a heating roller, or the like to flatten the surface.
Note that the calendering treatment may be performed after the polarization treatment described later. However, if the calendering process is performed after the polarization process, the piezoelectric particles 36 pushed in by the pressure will rotate, which may reduce the effect of the polarization process. Considering this point, the calendering treatment is preferably performed before the polarization treatment.
　次いで、第１保護層２８の上に第１電極層２４を有し、第１電極層２４の上に圧電体層２０を形成してなる積層体１１ｂの圧電体層２０に、分極処理（ポーリング）を行う。圧電体層２０の分極処理は、カレンダー処理の前に行ってもよいが、カレンダー処理を行った後に行うのが好ましい。 Next, the piezoelectric layer 20 of the laminate 11b having the first electrode layer 24 on the first protective layer 28 and the piezoelectric layer 20 formed on the first electrode layer 24 is subjected to polarization treatment (poling). )I do. The polarization treatment of the piezoelectric layer 20 may be performed before the calendering treatment, but is preferably performed after the calendering treatment.
　圧電体層２０の分極処理の方法には制限はなく、公知の方法が利用可能である。例えば、分極処理を行う対象に、直接、直流電界を印加する、電界ポーリングが例示される。なお、電界ポーリングを行う場合には、分極処理の前に、第２電極層２６を形成して、第１電極層２４および第２電極層２６を利用して、電界ポーリング処理を行ってもよい。
　また、本発明の圧電フィルム１０においては、分極処理は、圧電体層２０の面方向ではなく、厚さ方向に分極を行うのが好ましい。 The method of polarization treatment of the piezoelectric layer 20 is not limited, and known methods can be used. For example, electric field poling, in which a DC electric field is directly applied to an object to be polarized, is exemplified. When electric field poling is performed, the second electrode layer 26 may be formed before the polarization treatment, and the electric field poling treatment may be performed using the first electrode layer 24 and the second electrode layer 26. .
Moreover, in the piezoelectric film 10 of the present invention, the polarization treatment is preferably performed in the thickness direction of the piezoelectric layer 20, not in the plane direction.
　次いで、図１２示すように、分極処理を行った積層体１１ｂの圧電体層２０側に、先に準備したシート状物１１ｃを、第２電極層２６を圧電体層２０に向けて積層する。
　さらに、この積層体を、第１保護層２８および第２保護層３０を挟持するようにして、加熱プレス装置および加熱ローラ等を用いて熱圧着して、積層体１１ｂとシート状物１１ｃとを貼り合わせ、図９に示すような圧電フィルム１０を作製する。
　あるいは、積層体１１ｂとシート状物１１ｃとを、接着剤を用いて貼り合わせて、好ましくは、さらに圧着して、圧電フィルム１０を作製してもよい。 Next, as shown in FIG. 12, the previously prepared sheet 11c is laminated on the piezoelectric layer 20 side of the laminated body 11b subjected to the polarization treatment, with the second electrode layer 26 facing the piezoelectric layer 20. Next, as shown in FIG.
Furthermore, this laminate is thermocompression bonded using a hot press device, a heating roller, or the like while sandwiching the first protective layer 28 and the second protective layer 30, thereby joining the laminate 11b and the sheet-like material 11c. By bonding, a piezoelectric film 10 as shown in FIG. 9 is produced.
Alternatively, the piezoelectric film 10 may be produced by bonding the laminated body 11b and the sheet-like material 11c together using an adhesive and preferably further pressing them together.
　このような圧電フィルム１０は、カットシート状のシート状物１１ａおよびシート状物１１ｃ等を用いて製造してもよく、あるいは、ロール・トゥ・ロール（Ｒｏｌｌ　ｔｏ　Ｒｏｌｌ）を利用して製造してもよい。 Such a piezoelectric film 10 may be manufactured using cut-sheet-shaped sheet- like materials 11a and 11c, or the like, or may be manufactured using roll-to-roll. good too.
　作製された圧電フィルムは、各種用途に合わせて、所望の形状に裁断されてもよい。
　このようにして作製される圧電フィルム１０は、面方向ではなく厚さ方向に分極されており、かつ、分極処理後に延伸処理をしなくても大きな圧電特性が得られる。そのため、圧電フィルム１０は、圧電特性に面内異方性がなく、駆動電圧を印加すると、面方向では全方向に等方的に伸縮する。 The produced piezoelectric film may be cut into a desired shape according to various uses.
The piezoelectric film 10 produced in this manner is polarized in the thickness direction rather than in the plane direction, and excellent piezoelectric properties can be obtained without stretching after the polarization treatment. Therefore, the piezoelectric film 10 has no in-plane anisotropy in piezoelectric properties, and expands and contracts isotropically in all directions in the plane direction when a drive voltage is applied.
　このような圧電フィルムは、圧電フィルム自体が振動する振動板として用いる、圧電スピーカーに用いることができる。なお、圧電スピーカーは、マイクロフォンおよびセンサー等として使用することも可能である。さらに、この圧電スピーカーは、振動センサーとしても利用可能である。 Such a piezoelectric film can be used in a piezoelectric speaker, in which the piezoelectric film itself is used as a vibrating diaphragm. Piezoelectric speakers can also be used as microphones, sensors, and the like. Furthermore, this piezoelectric speaker can also be used as a vibration sensor.
　また、圧電フィルムは、振動板に貼着され、振動板を振動させるいわゆるエキサイターとして用いることもできる。前述のとおり、圧電フィルムをエキサイターとして用いる場合には、より高い出力を得るために、圧電フィルムを積層してなる積層圧電素子とすることが好ましい。 The piezoelectric film can also be used as a so-called exciter that is attached to the diaphragm and vibrates the diaphragm. As described above, when a piezoelectric film is used as an exciter, a laminated piezoelectric element formed by laminating piezoelectric films is preferable in order to obtain a higher output.
　振動板１２は、好ましくは可撓性を有するものであれば、制限はなく、各種のシート状物（板状物、フィルム）が利用可能である。
　一例として、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、発泡ポリスチレン、発泡スチレンおよび発泡ポリエチレン等からなる発泡プラスチック、べニア板、コルクボード、牛革などの皮革類、カーボンシート、和紙などの各種板紙、ならびに、波状にした板紙の片面または両面に他の板紙をはりつけてなる各種の段ボール材等が例示される。 The vibration plate 12 is not particularly limited as long as it preferably has flexibility, and various sheet-like materials (plate-like material, film) can be used.
Examples include polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyphenylene sulfite (PPS), polymethyl methacrylate (PMMA), polyetherimide (PEI), polyimide (PI), Resin films made of polyethylene naphthalate (PEN), triacetyl cellulose (TAC), cyclic olefin resins, etc., expanded polystyrene, expanded plastics made of expanded styrene, expanded polyethylene, etc., plywood, cork board, leather such as cowhide, Examples include various types of paperboard such as carbon sheets and Japanese paper, and various types of corrugated board made by pasting another paperboard onto one or both sides of corrugated paperboard.
　また、可撓性を有するものであれば、振動板１２として、有機エレクトロルミネセンス（ＯＬＥＤ（Organic Light Emitting Diode））ディスプレイ、液晶ディスプレイ、マイクロＬＥＤ（Light Emitting Diode）ディスプレイ、および、無機エレクトロルミネセンスディスプレイなどの表示デバイス、および、プロジェクター用スクリーン等も好適に利用可能である。 In addition, as long as it has flexibility, the diaphragm 12 may be an organic electroluminescence (OLED (Organic Light Emitting Diode)) display, a liquid crystal display, a micro LED (Light Emitting Diode) display, or an inorganic electroluminescence display. A display device such as a display, a projector screen, and the like are also suitable for use.
　圧電フィルム１０同士を貼着する接着層１９、および、圧電フィルム１０（積層圧電素子）と振動板１２とを貼着する接着層１６として、それぞれ圧電フィルム１０同士、および圧電フィルム１０と振動板１２とを貼着可能であれば、公知のものが、各種、利用可能である。
　従って、接着層は、貼り合わせる際には流動性を有し、その後、固体になる、接着剤からなる層でも、貼り合わせる際にゲル状（ゴム状）の柔らかい固体で、その後もゲル状の状態が変化しない、粘着剤からなる層でも、接着剤と粘着剤との両方の特徴を持った材料からなる層でもよい。また、接着層は、液体等の流動性を有する貼着剤を塗布して形成するものでも、シート状の貼着剤を用いて形成するものでもよい。 Adhesive layer 19 for adhering piezoelectric films 10 to each other, and adhesive layer 16 for adhering piezoelectric film 10 (laminated piezoelectric element) and diaphragm 12 are formed of piezoelectric films 10 and piezoelectric film 10 and diaphragm 12, respectively. Various known ones can be used as long as they can be attached.
Therefore, the adhesive layer has fluidity at the time of bonding and then becomes a solid. Even a layer made of an adhesive is a gel-like (rubber-like) soft solid at the time of bonding and remains gel-like thereafter. It may be a layer made of an adhesive whose state does not change, or a layer made of a material having the characteristics of both an adhesive and an adhesive. Further, the adhesive layer may be formed by applying an adhesive agent having fluidity such as a liquid, or may be formed by using a sheet-like adhesive agent.
　ここで、圧電デバイス１００ｃでは、圧電フィルム１０（積層圧電素子）を伸縮させることで、振動板１２を撓ませ振動させて、音を発生させる。従って、圧電デバイス１００ｃでは、圧電フィルム１０の伸縮が、直接的に振動板１２に伝達されるのが好ましい。振動板１２と圧電フィルム１０との間に、振動を緩和するような粘性を有する物質が存在すると、振動板１２への圧電フィルム１０の伸縮のエネルギーの伝達効率が低くなってしまい、圧電デバイス１００ｃの駆動効率が低下してしまう。
　この点を考慮すると、圧電フィルム１０と振動板１２とを貼着する接着層１６は、粘着剤からなる粘着剤層よりも、固体で硬い接着層１６が得られる、接着剤からなる接着剤層であるのが好ましい。より好ましい接着層１６としては、具体的には、ポリエステル系接着剤およびスチレン・ブタジエンゴム（ＳＢＲ）系接着剤等の熱可塑タイプの接着剤からなる貼着層が例示される。
　接着は、粘着とは異なり、高い接着温度を求める際に有用である。また、熱可塑タイプの接着剤は『比較的低温、短時間、および、強接着』を兼ね備えており、好適である。 Here, in the piezoelectric device 100c, by expanding and contracting the piezoelectric film 10 (laminated piezoelectric element), the diaphragm 12 is flexed and vibrated to generate sound. Therefore, in the piezoelectric device 100 c , it is preferable that the expansion and contraction of the piezoelectric film 10 is directly transmitted to the diaphragm 12 . If a substance having a viscosity that reduces vibration is present between the diaphragm 12 and the piezoelectric film 10, the efficiency of transmission of the energy of expansion and contraction of the piezoelectric film 10 to the diaphragm 12 is lowered, resulting in a piezoelectric device 100c. drive efficiency is reduced.
Considering this point, the adhesive layer 16 that bonds the piezoelectric film 10 and the diaphragm 12 is an adhesive layer made of an adhesive that provides a solid and harder adhesive layer 16 than an adhesive layer made of an adhesive. is preferred. As a more preferable adhesive layer 16, specifically, an adhesive layer made of a thermoplastic type adhesive such as a polyester adhesive and a styrene-butadiene rubber (SBR) adhesive is exemplified.
Adhesion, unlike sticking, is useful in seeking high adhesion temperatures. Further, a thermoplastic type adhesive is suitable because it has "relatively low temperature, short time, and strong adhesion".
　接着層１６の厚さには、制限はなく、接着層１６の材料に応じて、十分な貼着力（接着力、粘着力）が得られる厚さを、適宜、設定すればよい。
　ここで、圧電デバイス１００ｃにおいては、接着層１６が薄い方が、振動板１２に伝達する圧電フィルム１０の伸縮エネルギー（振動エネルギー）の伝達効果を高くして、エネルギー効率を高くできる。また、接着層１６が厚く剛性が高いと、圧電フィルム１０の伸縮を拘束する可能性もある。
　この点を考慮すると、接着層１６は、薄い方が好ましい。具体的には、接着層１６の厚さは、貼着後の厚さで０．１～５０μｍが好ましく、０．１～３０μｍがより好ましく、０．１～１０μｍがさらに好ましい。 The thickness of the adhesive layer 16 is not limited, and the thickness may be appropriately set according to the material of the adhesive layer 16 so as to obtain a sufficient sticking force (adhesive force, cohesive force).
Here, in the piezoelectric device 100c, the thinner the adhesive layer 16, the higher the effect of transmitting the expansion/contraction energy (vibration energy) of the piezoelectric film 10 to the vibration plate 12, and the higher the energy efficiency. Also, if the adhesive layer 16 is thick and rigid, it may restrict the expansion and contraction of the piezoelectric film 10 .
Considering this point, the adhesive layer 16 is preferably thinner. Specifically, the thickness of the adhesive layer 16 after sticking is preferably 0.1 to 50 μm, more preferably 0.1 to 30 μm, even more preferably 0.1 to 10 μm.
　なお、圧電デバイス１００ｃにおいて、接着層１６は、好ましい態様として設けられるものであり、必須の構成要素ではない。
　従って、圧電デバイス１００ｃは、接着層１６を有さず、公知の圧着手段、締結手段、および、固定手段等を用いて、振動板１２と圧電フィルム１０とを固定してもよい。例えば、圧電フィルム１０の平面視の形状が矩形である場合には、四隅をボルトナットのような部材で締結して電気音響変換器を構成してもよく、または、四隅と中心部とをボルトナットのような部材で締結して電気音響変換器を構成してもよい。 In addition, in the piezoelectric device 100c, the adhesive layer 16 is provided as a preferred embodiment and is not an essential component.
Therefore, the piezoelectric device 100c does not have the adhesive layer 16, and the vibration plate 12 and the piezoelectric film 10 may be fixed using known crimping means, fastening means, fixing means, or the like. For example, when the shape of the piezoelectric film 10 is rectangular in plan view, the four corners may be fastened with members such as bolts and nuts to form an electroacoustic transducer, or the four corners and the central portion may be bolted together. The electroacoustic transducer may be configured by fastening with a member such as a nut.
　しかしながら、この場合には、電源から駆動電圧を印加した際に、振動板１２に対して圧電フィルム１０が独立して伸縮してしまい、場合によっては、圧電フィルム１０のみが撓んで、圧電フィルム１０の伸縮が振動板１２に伝わらない。このように、振動板１２に対して圧電フィルム１０が独立して伸縮した場合には、圧電フィルム１０による振動板１２の振動効率が低下してしまい。振動板１２を十分に振動させられなくなってしまう可能性がある。
　この点を考慮すると、振動板１２と圧電フィルム１０とは、接着層１６で貼着するのが好ましい。 However, in this case, the piezoelectric film 10 expands and contracts independently of the diaphragm 12 when a drive voltage is applied from the power source. is not transmitted to the diaphragm 12. In this way, when the piezoelectric film 10 expands and contracts independently of the diaphragm 12, the vibration efficiency of the diaphragm 12 due to the piezoelectric film 10 decreases. There is a possibility that the diaphragm 12 cannot be sufficiently vibrated.
Considering this point, it is preferable that the diaphragm 12 and the piezoelectric film 10 are adhered with the adhesive layer 16 .
　また、積層圧電素子は、積層した複数枚の圧電フィルム１０を伸縮させることで、振動板１２を振動させて、音を発生させる。従って、積層圧電素子は、各圧電フィルム１０の伸縮が、直接的に伝達されるのが好ましい。圧電フィルム１０の間に、振動を緩和するような粘性を有する物質が存在すると、圧電フィルム１０の伸縮のエネルギーの伝達効率が低くなってしまい、積層圧電素子の駆動効率が低下してしまう。
　この点を考慮すると、圧電フィルム１０同士を貼着する接着層１９は、粘着剤からなる粘着剤層よりも、固体で硬い接着層１９が得られる、接着剤からなる接着剤層であるのが好ましい。より好ましい接着層１９としては、具体的には、ポリエステル系接着剤およびスチレン・ブタジエンゴム（ＳＢＲ）系接着剤等の熱可塑タイプの接着剤からなる貼着層が好適に例示される。 The laminated piezoelectric element expands and contracts a plurality of laminated piezoelectric films 10 to vibrate the diaphragm 12 and generate sound. Therefore, it is preferable that the expansion and contraction of each piezoelectric film 10 is directly transmitted to the laminated piezoelectric element. If a substance having a viscosity that reduces vibration is present between the piezoelectric films 10, the efficiency of transmission of the energy of expansion and contraction of the piezoelectric films 10 is lowered, and the driving efficiency of the laminated piezoelectric element is lowered.
Considering this point, the adhesive layer 19 that bonds the piezoelectric films 10 to each other is an adhesive layer made of an adhesive that provides a solid and harder adhesive layer 19 than an adhesive layer made of an adhesive. preferable. Specifically, a more preferable adhesive layer 19 is an adhesive layer made of a thermoplastic type adhesive such as a polyester-based adhesive and a styrene-butadiene rubber (SBR)-based adhesive.
　積層圧電素子において、接着層１９の厚さには制限はなく、接着層１９の形成材料に応じて、十分な貼着力を発現できる厚さを、適宜、設定すればよい。
　ここで、積層圧電素子は、接着層１９が薄い方が、圧電フィルム１０の伸縮エネルギーの伝達効果を高くして、エネルギー効率を高くできる。また、接着層１９が厚く剛性が高いと、圧電フィルム１０の伸縮を拘束する可能性もある。
　この点を考慮すると、接着層１９は、圧電体層２０よりも薄いのが好ましい。すなわち、積層圧電素子において、接着層１９は、硬く、薄いのが好ましい。具体的には、接着層１９の厚さは、貼着後の厚さで０．１～５０μｍが好ましく、０．１～３０μｍがより好ましく、０．１～１０μｍがさらに好ましい。
　なお、図６および図７に示す例の積層圧電素子は、隣接する圧電フィルムの分極方向が互いに逆であり、隣接する圧電フィルム１０同士がショートする恐れが無いので、接着層１９を薄くできる。 In the laminated piezoelectric element, the thickness of the adhesive layer 19 is not limited, and the thickness that can exhibit sufficient adhesive strength may be appropriately set according to the material forming the adhesive layer 19 .
Here, in the laminated piezoelectric element, the thinner the adhesive layer 19 is, the higher the effect of transmitting the expansion/contraction energy of the piezoelectric film 10 can be and the higher the energy efficiency can be. Also, if the adhesive layer 19 is thick and rigid, it may restrict the expansion and contraction of the piezoelectric film 10 .
Considering this point, the adhesive layer 19 is preferably thinner than the piezoelectric layer 20 . That is, in the laminated piezoelectric element, the adhesive layer 19 is preferably hard and thin. Specifically, the thickness of the adhesive layer 19 after sticking is preferably 0.1 to 50 μm, more preferably 0.1 to 30 μm, even more preferably 0.1 to 10 μm.
6 and 7, the polarization directions of the adjacent piezoelectric films are opposite to each other, and there is no risk of short-circuiting between the adjacent piezoelectric films 10, so the adhesive layer 19 can be made thinner.
　積層圧電素子においては、接着層１９のバネ定数（厚さ×ヤング率）が高いと、圧電フィルム１０の伸縮を拘束する可能性がある。従って、接着層１９のバネ定数は圧電フィルム１０のバネ定数と同等か、それ以下であるのが好ましい。 In the laminated piezoelectric element, if the spring constant (thickness×Young's modulus) of the adhesive layer 19 is high, the expansion and contraction of the piezoelectric film 10 may be restricted. Therefore, it is preferable that the spring constant of the adhesive layer 19 is equal to or less than the spring constant of the piezoelectric film 10 .
　具体的には、接着層１９の厚さと、動的粘弾性測定による周波数１Ｈｚでの貯蔵弾性率（Ｅ’）との積が、０℃において２．０×１０6Ｎ／ｍ以下、５０℃において１．０×１０6Ｎ／ｍ以下であるのが好ましい。
　また、接着層１９の動的粘弾性測定による周波数１Ｈｚでの内部損失が、粘着剤からなる接着層１９の場合には２５℃において１．０以下、接着剤からなる接着層１９の場合には２５℃において０．１以下であるのが好ましい。 Specifically, the product of the thickness of the adhesive layer 19 and the storage elastic modulus (E′) at a frequency of 1 Hz as measured by dynamic viscoelasticity is 2.0×10 6 N/m or less at 0° C. and 50° C. is preferably 1.0×10 6 N/m or less.
In addition, the internal loss at a frequency of 1 Hz by dynamic viscoelasticity measurement of the adhesive layer 19 is 1.0 or less at 25 ° C. in the case of the adhesive layer 19 made of adhesive, and It is preferably 0.1 or less at 25°C.
　なお、積層圧電素子において、接着層１９は、好ましい態様として設けられるものであり、必須の構成要素ではない。
　従って、積層圧電素子は、接着層１９を有さず、公知の圧着手段、締結手段、および、固定手段等を用いて、圧電フィルム１０を積層して、密着させて、積層圧電素子を構成してもよい。例えば、圧電フィルム１０が矩形である場合には、四隅をボルトナット等で締結して積層圧電素子を構成してもよく、または、四隅と中心部とをボルトナット等で締結して積層圧電素子を構成してもよい。あるいは、圧電フィルム１０を積層した後、周辺部（端面）に粘着テープを貼着することで、積層した圧電フィルム１０を固定して、積層圧電素子を構成してもよい。 In addition, in the laminated piezoelectric element, the adhesive layer 19 is provided as a preferred embodiment, and is not an essential component.
Therefore, the laminated piezoelectric element does not have the adhesive layer 19, and the piezoelectric film 10 is laminated and adhered using known crimping means, fastening means, fixing means, or the like to form the laminated piezoelectric element. may For example, when the piezoelectric film 10 is rectangular, the four corners may be fastened with bolts and nuts to form a laminated piezoelectric element, or the four corners and the central portion may be fastened with bolts and nuts or the like to form a laminated piezoelectric element. may be configured. Alternatively, after laminating the piezoelectric films 10, an adhesive tape may be adhered to the peripheral portion (end face) to fix the laminated piezoelectric films 10 to form a laminated piezoelectric element.
　しかしながら、この場合には、電源から駆動電圧を印加した際に、個々の圧電フィルム１０が独立して伸縮してしまい、場合によっては、各圧電フィルム１０各層が逆方向に撓んで空隙ができてしまう。このように、個々の圧電フィルム１０が独立して伸縮した場合には、積層圧電素子としての駆動効率が低下してしまい、積層圧電素子全体としての伸縮が小さくなって、当接した振動板１２等を十分に振動させられなくなってしまう可能性がある。特に、各圧電フィルム１０各層が逆方向に撓んで空隙ができてしまった場合には、積層圧電素子としての駆動効率の低下は大きい。
　この点を考慮すると、積層圧電素子は、図示例の積層圧電素子のように、隣接する圧電フィルム１０同士を貼着する接着層１９を有するのが好ましい。 However, in this case, when a driving voltage is applied from a power supply, the individual piezoelectric films 10 expand and contract independently, and in some cases, each layer of the piezoelectric films 10 bends in the opposite direction, creating a gap. put away. In this way, when the individual piezoelectric films 10 expand and contract independently, the driving efficiency of the laminated piezoelectric element decreases, and the expansion and contraction of the laminated piezoelectric element as a whole becomes small, and the diaphragm 12 in contact etc. may not be sufficiently vibrated. In particular, when each layer of the piezoelectric film 10 bends in the opposite direction and a gap is formed, the driving efficiency of the laminated piezoelectric element is greatly reduced.
Considering this point, the laminated piezoelectric element preferably has an adhesive layer 19 for adhering the adjacent piezoelectric films 10 together like the laminated piezoelectric element in the illustrated example.
　ここで、図５に示すように圧電デバイス１００ｃが積層圧電素子を振動板１２に貼着した構成を有する場合には、積層圧電素子の厚さと動的粘弾性測定による周波数１Ｈｚ、２５℃での貯蔵弾性率との積が、振動板１２の厚さとヤング率との積の、０．１～３倍であるのが好ましい。 Here, as shown in FIG. 5, when the piezoelectric device 100c has a configuration in which a laminated piezoelectric element is attached to the diaphragm 12, the thickness of the laminated piezoelectric element and the dynamic viscoelasticity measurement at a frequency of 1 Hz and 25° C. The product with the storage elastic modulus is preferably 0.1 to 3 times the product of the thickness of diaphragm 12 and Young's modulus.
　上述したように、本発明の圧電フィルム１０は、常温下の環境で優れた可撓性を有するものであり、この圧電フィルム１０を積層した積層圧電素子も、常温下の環境で優れた可撓性を有する。
　一方、振動板１２は、ある程度の剛性を有するものである。このような振動板１２に剛性の高い積層圧電素子が組み合わされると、硬く、曲げにくくなり、圧電デバイス１００ｃの可撓性の点で不利である。 As described above, the piezoelectric film 10 of the present invention has excellent flexibility in a room temperature environment, and a laminated piezoelectric element obtained by laminating the piezoelectric film 10 also exhibits excellent flexibility in a room temperature environment. have sex.
On the other hand, the diaphragm 12 has a certain degree of rigidity. When such a diaphragm 12 is combined with a highly rigid laminated piezoelectric element, it is hard and difficult to bend, which is disadvantageous in terms of the flexibility of the piezoelectric device 100c.
　これに対して、本発明においては、好ましくは、積層圧電素子の厚さと動的粘弾性測定による周波数１Ｈｚ、２５℃での貯蔵弾性率との積が、振動板１２の厚さとヤング率との積の、３倍以下であることが好ましい。すなわち、積層圧電素子は、ゆっくりとした動きに対しては、バネ定数が、振動板１２の３倍以下であるのが好ましい。 On the other hand, in the present invention, preferably, the product of the thickness of the laminated piezoelectric element and the storage elastic modulus at a frequency of 1 Hz and 25° C. by dynamic viscoelasticity measurement is the ratio between the thickness of diaphragm 12 and Young's modulus. It is preferably 3 times or less of the product. That is, the laminated piezoelectric element preferably has a spring constant of three times or less that of the diaphragm 12 for slow motion.
　このような構成を有することにより、圧電デバイス１００ｃは、折り曲げる、および、丸める等の外力によるゆっくりした動きに対しては、柔らかく振舞うことができ、すなわち、ゆっくりとした動きに対して、良好な可撓性を発現する。 With such a configuration, the piezoelectric device 100c can behave softly against slow movements caused by external forces such as bending and rolling. Flexibility is expressed.
　圧電デバイス１００ｃにおいて、積層圧電素子の厚さと動的粘弾性測定による周波数１Ｈｚ、２５℃での貯蔵弾性率との積は、振動板１２の厚さとヤング率との積の、２倍以下であるのがより好ましく、１倍以下であるのがさらに好ましく、０．３倍以下であるのが特に好ましい。 In the piezoelectric device 100c, the product of the thickness of the laminated piezoelectric element and the storage elastic modulus at a frequency of 1 Hz and 25° C. measured by dynamic viscoelasticity measurement is two times or less the product of the thickness of the diaphragm 12 and Young's modulus. , more preferably 1-fold or less, and particularly preferably 0.3-fold or less.
　他方、積層圧電素子に利用される材料、および、好ましい積層圧電素子の構成等を考慮すると、積層圧電素子の厚さと動的粘弾性測定による周波数１Ｈｚ、２５℃での貯蔵弾性率との積は、振動板１２の厚さとヤング率との積の、０．１倍以上であるのが好ましい。 On the other hand, considering the materials used for the laminated piezoelectric element and the preferable structure of the laminated piezoelectric element, the product of the thickness of the laminated piezoelectric element and the storage elastic modulus at 25° C. at a frequency of 1 Hz by dynamic viscoelasticity measurement is , the product of the thickness of the diaphragm 12 and the Young's modulus, preferably 0.1 times or more.
　圧電デバイス１００ｃにおいて、積層圧電素子の厚さと動的粘弾性測定から得られたマスターカーブにおける周波数１ｋＨｚ、２５℃での貯蔵弾性率との積が、振動板１２の厚さとヤング率との積の、０．３～１０倍であるのが好ましい。すなわち、積層圧電素子は、駆動された状態の早い動きでは、バネ定数が、振動板１２の０．３～１０倍であるのが好ましい。 In the piezoelectric device 100c, the product of the thickness of the laminated piezoelectric element and the storage modulus at 25° C. at a frequency of 1 kHz in the master curve obtained from the dynamic viscoelasticity measurement is the product of the thickness of the diaphragm 12 and the Young's modulus. , preferably 0.3 to 10 times. That is, the laminated piezoelectric element preferably has a spring constant of 0.3 to 10 times that of the diaphragm 12 in fast motion in a driven state.
　上述したように、圧電デバイス１００ｃは、積層圧電素子の面方向の伸縮によって振動板１２を振動させることにより、音を発生する。従って、積層圧電素子は、オーディオ帯域の周波数（２０Ｈｚ～２０ｋＨｚ）では、振動板１２に対して、ある程度の剛性（硬さ、コシ）を有するのが好ましい。 As described above, the piezoelectric device 100c generates sound by vibrating the diaphragm 12 due to expansion and contraction of the laminated piezoelectric element in the plane direction. Therefore, the laminated piezoelectric element preferably has a certain degree of rigidity (hardness, stiffness) with respect to the diaphragm 12 at frequencies in the audio band (20 Hz to 20 kHz).
　積層圧電素子の厚さと動的粘弾性測定から得られたマスターカーブにおける周波数１ｋＨｚ、２５℃での貯蔵弾性率との積を、振動板１２の厚さとヤング率との積の、好ましくは０．３倍以上、より好ましくは０．５倍以上、さらに好ましくは１倍以上とする。すなわち、積層圧電素子は、早い動きに対しては、バネ定数が、振動板１２の０．３倍以上であるのが好ましく、０．５倍以上であるのがより好ましく、１倍以上であるのがさらに好ましい。
　これにより、オーディオ帯域の周波数において、振動板１２に対する積層圧電素子の剛性を十分に確保して、圧電デバイス１００ｃが、高いエネルギー効率で、高い音圧の音を出力できる。 The product of the thickness of the laminated piezoelectric element and the storage elastic modulus at a frequency of 1 kHz and 25° C. in the master curve obtained from the dynamic viscoelasticity measurement is the product of the thickness of the diaphragm 12 and Young's modulus, preferably 0.5. 3 times or more, more preferably 0.5 times or more, further preferably 1 time or more. That is, the spring constant of the laminated piezoelectric element is preferably 0.3 times or more, more preferably 0.5 times or more, and more preferably 1 time or more that of the diaphragm 12 for fast movement. is more preferred.
This ensures sufficient rigidity of the laminated piezoelectric element with respect to the diaphragm 12 at frequencies in the audio band, so that the piezoelectric device 100c can output sound with high sound pressure with high energy efficiency.
　他方、積層圧電素子に利用可能な材料、好ましい積層圧電素子の構成等を考慮すると、積層圧電素子の厚さと動的粘弾性測定による周波数１ｋＨｚ、２５℃での貯蔵弾性率との積は、振動板１２の厚さとヤング率との積の、１０倍以下であるのが好ましい。 On the other hand, considering the materials that can be used for the laminated piezoelectric element, the preferable configuration of the laminated piezoelectric element, etc., the product of the thickness of the laminated piezoelectric element and the storage elastic modulus at a frequency of 1 kHz and 25 ° C. by dynamic viscoelasticity measurement is the vibration It is preferably 10 times or less the product of the thickness of the plate 12 and Young's modulus.
　上述の説明からも明らかなように、積層圧電素子（エキサイター）の厚さと、動的粘弾性測定による周波数１Ｈｚ、２５℃での貯蔵弾性率との積には、接着層１９の厚さはもちろん、接着層１９の貯蔵弾性率等の物性も、大きく影響する。
　他方、振動板１２の厚さとヤング率との積、すなわち、振動板のバネ定数には、振動板の厚さはもちろん、振動板の物性も、大きく影響する。
　従って、本発明において、積層圧電素子の厚さと、動的粘弾性測定による周波数１Ｈｚ、２５℃での積層圧電素子の貯蔵弾性率との積が、振動板１２の厚さとヤング率との積の０．１～３倍である条件を満たすためには、接着層１９の厚さおよび材料、ならびに、振動板の厚さおよび材料が重要である。また、本発明において、積層圧電素子の厚さと、周波数１ｋＨｚ、２５℃での積層圧電素子の貯蔵弾性率との積が、振動板１２の厚さとヤング率との積の０．３～１０倍である条件を満たすためにも、同様に、接着層１９の厚さおよび材料、ならびに、振動板１２の厚さおよび材料が重要である。 As is clear from the above description, the product of the thickness of the laminated piezoelectric element (exciter) and the storage elastic modulus at a frequency of 1 Hz and 25° C. measured by dynamic viscoelasticity measurement is, of course, the thickness of the adhesive layer 19. , physical properties such as the storage elastic modulus of the adhesive layer 19 also have a great effect.
On the other hand, the product of the thickness of the diaphragm 12 and the Young's modulus, that is, the spring constant of the diaphragm, is greatly affected not only by the thickness of the diaphragm but also by the physical properties of the diaphragm.
Therefore, in the present invention, the product of the thickness of the laminated piezoelectric element and the storage elastic modulus of the laminated piezoelectric element at a frequency of 1 Hz and 25° C. by dynamic viscoelasticity measurement is the product of the thickness of the diaphragm 12 and Young's modulus. To satisfy the condition of 0.1 to 3 times, the thickness and material of the adhesive layer 19 and the thickness and material of the diaphragm are important. In the present invention, the product of the thickness of the laminated piezoelectric element and the storage elastic modulus of the laminated piezoelectric element at a frequency of 1 kHz and 25° C. is 0.3 to 10 times the product of the thickness of the diaphragm 12 and Young's modulus. Similarly, the thickness and material of the adhesive layer 19 and the thickness and material of the diaphragm 12 are also important in order to satisfy the condition.
　すなわち、本発明において、圧電デバイスが振動板１２を有する構成の場合には、上述の条件を満たすように、接着層１９の厚さおよび材料、ならびに、振動板１２厚さおよび材料を、適宜、選択するのが好ましい。
　言い換えれば、本発明においては、圧電フィルム１０の特性等に応じて、接着層１９の厚さおよび材料、ならびに、振動板１２の厚さおよび材料を、適宜、選択することで、好適に積層圧電素子の厚さと、動的粘弾性測定による周波数１Ｈｚ、２５℃での積層圧電素子の貯蔵弾性率との積が、振動板１２の厚さとヤング率との積の０．１～３倍であるという条件、および／または、積層圧電素子の厚さと、周波数１ｋＨｚ、２５℃での積層圧電素子の貯蔵弾性率との積が、振動板１２の厚さとヤング率との積の０．３～１０倍であるという条件を満たすことが可能になる。 That is, in the present invention, when the piezoelectric device has a diaphragm 12, the thickness and material of the adhesive layer 19 and the thickness and material of the diaphragm 12 are appropriately adjusted so as to satisfy the above conditions. preferably selected.
In other words, in the present invention, the thickness and material of the adhesive layer 19 and the thickness and material of the vibration plate 12 are appropriately selected in accordance with the characteristics of the piezoelectric film 10, so that the laminated piezoelectric film can be obtained. The product of the thickness of the element and the storage elastic modulus of the laminated piezoelectric element at a frequency of 1 Hz and 25° C. measured by dynamic viscoelasticity measurement is 0.1 to 3 times the product of the thickness of the diaphragm 12 and the Young's modulus. and/or the product of the thickness of the laminated piezoelectric element and the storage elastic modulus of the laminated piezoelectric element at a frequency of 1 kHz and 25° C. is 0.3 to 10 of the product of the thickness of the diaphragm 12 and Young's modulus. It becomes possible to satisfy the condition of being double.
　上述した厚さと貯蔵弾性率との積に関しては、積層圧電素子に変えて、単層の圧電フィルム１０をエキサイターとして用いる場合にも同様である。 The above-mentioned product of thickness and storage elastic modulus is the same when a single-layer piezoelectric film 10 is used as an exciter instead of a laminated piezoelectric element.
　以上、本発明の圧電デバイスについて詳細に説明したが、本発明は上述の例に限定はされず、本発明の要旨を逸脱しない範囲において、各種の改良や変更を行ってもよいのは、もちろんである。 Although the piezoelectric device of the present invention has been described in detail above, the present invention is not limited to the above examples, and various improvements and modifications may be made without departing from the gist of the present invention. is.
　以下、本発明の具体的実施例を挙げ、本発明についてより詳細に説明する。なお、本発明はこの実施例に限定されるものでなく、以下の実施例に示す材料、使用量、割合、処理内容、処理手順などは、本発明の趣旨を逸脱しない限り適宜変更することができる。 Hereinafter, the present invention will be described in more detail by giving specific examples of the present invention. The present invention is not limited to this example, and the materials, amounts used, proportions, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. can.
［実施例１］
　［圧電フィルムの作製］
　上述した図１０～図１２に示す方法によって、圧電フィルムを作製した。
　まず、下記の組成比で、シアノエチル化ＰＶＡ（ＣＲ－Ｖ　信越化学工業社製）をジメチルホルムアミド（ＤＭＦ）に溶解した。その後、この溶液に、圧電体粒子としてＰＺＴ粒子を下記の組成比で添加して、プロペラミキサー（回転数２０００ｒｐｍ）で攪拌して、圧電体層を形成するための塗料を調製した。
・ＰＺＴ粒子・・・・・・・・・・・３００質量部
・シアノエチル化ＰＶＡ・・・・・・・３０質量部
・ＤＭＦ・・・・・・・・・・・・・・７０質量部
　なお、ＰＺＴ粒子は、市販のＰＺＴ原料粉を１０００～１２００℃で焼結した後、これを平均粒径５μｍになるように解砕および分級処理したものを用いた。 [Example 1]
[Preparation of piezoelectric film]
A piezoelectric film was produced by the method shown in FIGS. 10 to 12 described above.
First, cyanoethylated PVA (CR-V, manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved in dimethylformamide (DMF) at the following compositional ratio. After that, PZT particles as piezoelectric particles were added to this solution at the following composition ratio, and the mixture was stirred with a propeller mixer (rotation speed: 2000 rpm) to prepare a paint for forming a piezoelectric layer.
・PZT particles・・・・・・・・・・300 parts by mass ・Cyanoethylated PVA・・・・・・・・30 parts by mass ・DMF・・・・・・・・・・・・70 parts by mass The PZT particles used were obtained by sintering a commercially available PZT raw material powder at 1000 to 1200° C. and then pulverizing and classifying the sintered particles to an average particle size of 5 μm.
　一方、厚さ４μｍのＰＥＴフィルムに、厚さ０．３μｍの銅薄膜を真空蒸着してなるシート状物を用意した。すなわち、本例においては、第１電極層および第２電極層は、厚さ０．３μｍの銅蒸着薄膜であり、第１保護層および第２保護層は、厚さ４μｍのＰＥＴフィルムとなる。 On the other hand, a sheet-like material was prepared by vacuum-depositing a copper thin film with a thickness of 0.3 μm on a PET film with a thickness of 4 μm. That is, in this example, the first electrode layer and the second electrode layer are 0.3 μm thick copper-deposited thin films, and the first protective layer and the second protective layer are 4 μm thick PET films.
　シート状物の第１電極層（銅蒸着薄膜）の上に、スライドコーターを用いて、先に調製した圧電体層を形成するための塗料を塗布した。なお、塗料は、乾燥後の塗膜の膜厚が５０μｍになるように、塗布した。
　次いで、シート状物に塗料を塗布した物を、１２０℃のホットプレート上で加熱乾燥することでＤＭＦを蒸発させた。これにより、ＰＥＴ製の第１保護層の上に銅製の第１電極層を有し、その上に、厚さが５０μｍの圧電体層（高分子複合圧電体層）を有する積層体を作製した。 Using a slide coater, the previously prepared coating material for forming the piezoelectric layer was applied onto the first electrode layer (copper-deposited thin film) of the sheet. In addition, the paint was applied so that the thickness of the coating film after drying was 50 μm.
Next, the sheet-like material coated with the paint was dried by heating on a hot plate at 120° C. to evaporate the DMF. Thus, a laminate having a first electrode layer made of copper on a first protective layer made of PET and a piezoelectric layer (polymer composite piezoelectric layer) having a thickness of 50 μm thereon was produced. .
　作製した圧電体層を、厚さ方向に分極処理した。 The produced piezoelectric layer was subjected to polarization treatment in the thickness direction.
　分極処理を行った圧電積層体の上に、第２電極層（銅薄膜側）を圧電体層に向けて、ＰＥＴフィルムに銅薄膜を蒸着したシート状物を積層した。
　次いで、圧電積層体とシート状物との積層体を、ラミネータ装置を用いて、温度１２０℃で熱圧着することで、圧電体層と第２電極層とを貼着して接着して、圧電フィルムを作製した。 A sheet-like material obtained by vapor-depositing a copper thin film on a PET film was laminated on the piezoelectric laminate that had been subjected to the polarization treatment, with the second electrode layer (copper thin film side) facing the piezoelectric layer.
Next, the laminate of the piezoelectric laminate and the sheet-like material is thermocompression bonded at a temperature of 120° C. using a laminator device, thereby adhering and bonding the piezoelectric layer and the second electrode layer. A film was produced.
　［動的粘弾性試験］
　作製した圧電フィルムから、１ｃｍ×４ｃｍの短冊状試験片を作製した。
　この試験片の動的粘弾性（貯蔵弾性率Ｅ’（ＧＰａ）および損失正接Ｔａｎδ）を、動的粘弾性試験機（ＳＩＩナノテクノロジー　ＤＭＳ６１００粘弾性スペクトロメーター）を使用して測定した。測定条件を以下に示す。
　　測定温度範囲：－１００℃～１００℃
　　昇温速度：２℃／分
　　測定周波数：０．１Ｈｚ、０．２Ｈｚ、０．５Ｈｚ、１．０Ｈｚ、２．０Ｈｚ、５．０Ｈｚ、１０Ｈｚ、２０Ｈｚ
　　測定モード：引っ張り測定
　　チャック間距離：２０ｍｍ [Dynamic viscoelasticity test]
A strip-shaped test piece of 1 cm×4 cm was produced from the produced piezoelectric film.
The dynamic viscoelasticity (storage modulus E′ (GPa) and loss tangent Tan δ) of this specimen was measured using a dynamic viscoelasticity tester (SII Nanotechnology DMS6100 viscoelasticity spectrometer). Measurement conditions are shown below.
Measurement temperature range: -100°C to 100°C
Heating rate: 2°C/min Measurement frequency: 0.1 Hz, 0.2 Hz, 0.5 Hz, 1.0 Hz, 2.0 Hz, 5.0 Hz, 10 Hz, 20 Hz
Measurement mode: Tensile measurement Distance between chucks: 20mm
　測定の結果、圧電フィルムは、周波数１Ｈｚでの損失正接が、２５℃に０．４０の極大値（最大値）を有していた。 As a result of the measurement, the piezoelectric film had a local maximum value (maximum value) of 0.40 at 25°C in loss tangent at a frequency of 1 Hz.
　［圧電デバイスの作製］
　作製した圧電フィルムを信号源であるパワーアンプ（ＳＯＮＹ社製　ＳＴＲ－ＤＨ１９０）に接続した。また、圧電フィルムの端部縁に沿って温度センサーとしてシース熱電対（アズワン社製　ＤＳ－１０１０）を貼着した。信号源および温度センサーを制御部と接続し圧電デバイスを作製した。制御部は、温度センサーが測定した温度が－４０℃～０℃の範囲になった場合に目標温度２０℃として加熱するように、信号源から圧電フィルムに周波数２０ｋＨｚ、実行電圧２Ｖｒｍｓの正弦波交流信号を印加する構成とした。 [Fabrication of piezoelectric device]
The produced piezoelectric film was connected to a power amplifier (STR-DH190 manufactured by SONY) as a signal source. A sheathed thermocouple (DS-1010 manufactured by AS ONE) was attached as a temperature sensor along the edge of the piezoelectric film. A piezoelectric device was fabricated by connecting a signal source and a temperature sensor to a controller. When the temperature measured by the temperature sensor falls within the range of −40° C. to 0° C., the controller applies a sinusoidal alternating current with a frequency of 20 kHz and an effective voltage of 2 Vrms to the piezoelectric film from the signal source so that the target temperature is 20° C. It is configured to apply a signal.
　［実施例２］
　制御部が、温度センサーが測定した温度が－４０℃～０℃の範囲に入ったら、信号源から圧電フィルムに周波数４０ｋＨｚ、実行電圧１Ｖｒｍｓの正弦波交流信号を印加する構成とした以外は実施例１と同様にして圧電デバイスを作製した。 [Example 2]
Example except that the controller applies a sinusoidal AC signal with a frequency of 40 kHz and an effective voltage of 1 Vrms from the signal source to the piezoelectric film when the temperature measured by the temperature sensor enters the range of -40 ° C. to 0 ° C. A piezoelectric device was produced in the same manner as in 1.
　［実施例３］
　制御部が、温度センサーが測定した温度が－４０℃～０℃の範囲に入ったら、信号源から圧電フィルムに周波数２５ｋＨｚ、実行電圧０．５Ｖｒｍｓの正弦波交流信号を印加する構成とした以外は実施例１と同様にして圧電デバイスを作製した。 [Example 3]
Except that the control unit applies a sine wave AC signal with a frequency of 25 kHz and an effective voltage of 0.5 Vrms from the signal source to the piezoelectric film when the temperature measured by the temperature sensor enters the range of -40 ° C. to 0 ° C. A piezoelectric device was produced in the same manner as in Example 1.
　［比較例１］
　温度センサー、および、制御部を有さない構成とし、加熱用の信号を印加しない構成とした以外は実施例１と同様にして圧電デバイスを作製した。
　［比較例２］
　国際公開第２０２０／１９６８０７号の実施例１に記載の圧電フィルムを作製し、温度センサー、および、制御部を有さない構成とし、加熱用の信号を印加しない構成として圧電デバイスを作製した。 [Comparative Example 1]
A piezoelectric device was fabricated in the same manner as in Example 1, except that the temperature sensor and the controller were not provided and the heating signal was not applied.
[Comparative Example 2]
The piezoelectric film described in Example 1 of International Publication No. 2020/196807 was produced, and a piezoelectric device was produced in a configuration without a temperature sensor and a controller and without application of a heating signal.
　作製した圧電フィルムは、周波数１Ｈｚでの損失正接が、－３０℃に０．２５の極大値（最大値）を有していた。 The produced piezoelectric film had a loss tangent at a frequency of 1 Hz with a local maximum value (maximum value) of 0.25 at -30°C.
［評価］
　作製した各実施例および比較例の圧電デバイスについて、可撓性の評価を行った。 [evaluation]
Flexibility was evaluated for the fabricated piezoelectric devices of Examples and Comparative Examples.
＜可撓性１＞
　鉄製の丸棒を用い、圧電フィルムの中央部が曲率半径５ｃｍになるように１８０°折り返す屈曲試験を、１００００回、行った。なお、可撓性の評価は、低温（－３０℃）、および、常温（２５℃）の、２つの温度環境に１０分間、放置後に行った。 <Flexibility 1>
Using an iron round bar, a bending test was performed 10,000 times in which the piezoelectric film was bent 180° so that the central portion of the piezoelectric film had a radius of curvature of 5 cm. The evaluation of flexibility was carried out after standing for 10 minutes in two temperature environments, low temperature (−30° C.) and normal temperature (25° C.).
　１００００回の屈曲試験を行っても、いずれの界面からも剥離を生じない場合をＡ；
　１０００～９９９９回の屈曲試験の間に、何れかの界面から剥離を生じた場合をＢ；
　９９９回までの屈曲試験の間に、何れかの界面から剥離を生じた場合をＣ；
と評価した。 A when no peeling occurs from any interface even after 10000 bending tests;
B when peeling occurs from any interface during the bending test of 1000 to 9999 times;
C when peeling occurs from either interface during the bending test up to 999 times;
and evaluated.
＜可撓性２＞
　鉄製の丸棒を用い、圧電フィルムの長手方向（２００ｍｍ）の中央部が曲率半径５ｍｍになるように１８０°折り返す屈曲試験を、１００００回、行った。なお、可撓性の評価は、低温（－３０℃）、および、常温（２５℃）の、２つの温度環境に１０分間放置後に行った。 <Flexibility 2>
A bending test was performed 10,000 times using an iron round bar, in which the piezoelectric film was bent 180° so that the central portion in the longitudinal direction (200 mm) had a radius of curvature of 5 mm. The evaluation of flexibility was carried out after standing for 10 minutes in two temperature environments, low temperature (−30° C.) and normal temperature (25° C.).
　１００００回の屈曲試験を行っても、いずれの界面からも剥離を生じない場合をＡ；
　１０００～９９９９回の屈曲試験の間に、何れかの界面から剥離を生じた場合をＢ；
　９９９回までの屈曲試験の間に、何れかの界面から剥離を生じた場合をＣ；
と評価した。
　結果を表１に示す。 A when no peeling occurs at any interface even after 10000 bending tests;
B when peeling occurs from any interface during the bending test of 1000 to 9999 times;
C when peeling occurs from either interface during the bending test up to 999 times;
and evaluated.
Table 1 shows the results.
　表１から、本発明の実施例は低温試験（氷点下）、および、常温試験（常温下）のいずれの場合でも優れた可撓性を有することがわかる。
　加熱機構を有さない比較例１は、氷点下での可撓性に劣ることがわかる。
　低温（氷点下）で粘弾性を有する高分子材料を混合した高分子複合圧電体をマトリックスとして用いる比較例２は、氷点下での可撓性は優れ、また、常温下での可撓性も良好であるものの、曲率半径５ｍｍのより厳しい条件での可撓性（可撓性２）が常温下で劣ることがわかる。 From Table 1, it can be seen that the examples of the present invention have excellent flexibility in both the low temperature test (below freezing point) and the normal temperature test (under normal temperature).
It can be seen that Comparative Example 1, which does not have a heating mechanism, is inferior in flexibility below freezing.
Comparative Example 2, in which a polymer composite piezoelectric material mixed with a polymer material having viscoelasticity at low temperatures (below freezing) is used as a matrix, has excellent flexibility below freezing and good flexibility at room temperature. However, it can be seen that the flexibility (flexibility 2) under more severe conditions with a radius of curvature of 5 mm is inferior at room temperature.
　また、実施例１および２と実施例３との対比から、加熱用の信号である正弦波交流信号の実効電圧は１Ｖｒｍｓ以上が好ましいことがわかる。 Also, from a comparison between Examples 1 and 2 and Example 3, it can be seen that the effective voltage of the sinusoidal AC signal, which is the signal for heating, is preferably 1 Vrms or more.
　［実施例４］
　圧電フィルムに加熱用の信号を印加して自己発熱させる構成に代えて、ポリイミドヒーター（シンワ測定社製　ＦＬヒーター）を有し、ポリイミドヒーターにより圧電フィルムを加熱する構成とした以外は、実施例１と同様にして圧電デバイスを作製した。 [Example 4]
Example 1 except that a polyimide heater (FL heater manufactured by Shinwa Kiseki Co., Ltd.) was provided instead of applying a signal for heating to the piezoelectric film to generate heat by itself, and the piezoelectric film was heated by the polyimide heater. A piezoelectric device was produced in the same manner as in the above.
　ポリイミドヒーターは、圧電フィルムの一方の面の端部近傍に接するように配置した。
　また、温度センサーが測定した温度が－４０℃～０℃の範囲になった場合に目標温度２０℃として加熱するようにポリイミドヒーターのＯＮ・ＯＦＦを制御した。 The polyimide heater was arranged so as to be in contact with the vicinity of the edge of one surface of the piezoelectric film.
Also, when the temperature measured by the temperature sensor fell within the range of -40°C to 0°C, the ON/OFF of the polyimide heater was controlled so that the target temperature was 20°C.
　作製した圧電デバイスについて、上記と同様にして可撓性１および可撓性２の評価を行った。曲率半径５ｃｍでの可撓性１は、低温試験、常温試験ともに評価Ａであった。また、曲率半径５ｍｍでの可撓性２は、低温試験、常温試験ともに評価Ａであった。
　従って、実施例４の圧電デバイスは、低温試験（氷点下）、および、常温試験（常温下）のいずれの場合でも優れた可撓性を有することがわかる。 Flexibility 1 and Flexibility 2 were evaluated in the same manner as above for the produced piezoelectric device. Flexibility 1 at a radius of curvature of 5 cm was rated A in both the low temperature test and normal temperature test. Flexibility 2 at a radius of curvature of 5 mm was rated A in both the low temperature test and normal temperature test.
Therefore, it can be seen that the piezoelectric device of Example 4 has excellent flexibility in both the low temperature test (below freezing point) and the normal temperature test (under normal temperature).
　［実施例５］
　実施例１と同様にして作製した圧電フィルムを２００ｍｍ×１５０ｍｍに切り出し、短手方向に２回折り返して、３層の圧電素子（２００ｍｍ×５０ｍｍ）を作製した。折り返した圧電フィルム同士は、熱接着シート（クラボウ社製　Ｇ５）で貼着した。 [Example 5]
A piezoelectric film produced in the same manner as in Example 1 was cut into a size of 200 mm×150 mm and folded twice in the lateral direction to produce a three-layer piezoelectric element (200 mm×50 mm). The folded piezoelectric films were adhered to each other with a thermal adhesive sheet (G5 manufactured by Kurabo Industries, Ltd.).
　作製した圧電素子を信号源であるパワーアンプ（ＳＯＮＹ社製　ＳＴＲ－ＤＨ１９０）に接続した。また、圧電素子の端部縁に沿って温度センサーとしてシース熱電対（アズワン社製　ＤＳ－１０１０）を貼着した。信号源および温度センサーを制御部と接続した。制御部は、温度センサーが測定した温度が－４０℃～０℃の間の期間、信号源から圧電素子に周波数２０ｋＨｚ、実行電圧２Ｖｒｍｓの正弦波交流信号を印加する構成とした。 The manufactured piezoelectric element was connected to a power amplifier (SONY STR-DH190) as a signal source. A sheathed thermocouple (DS-1010 manufactured by AS ONE) was attached as a temperature sensor along the edge of the piezoelectric element. A signal source and a temperature sensor were connected to the controller. The control unit was configured to apply a sinusoidal AC signal with a frequency of 20 kHz and an effective voltage of 2 Vrms from the signal source to the piezoelectric element while the temperature measured by the temperature sensor was between -40°C and 0°C.
　作製した圧電素子に対して上記と同様にして可撓性１および可撓性２の評価を行った。曲率半径５ｃｍでの可撓性１は、低温試験、常温試験ともに評価Ａであった。また、曲率半径５ｍｍでの可撓性２は、低温試験、常温試験ともに評価Ａであった。
　従って、実施例５の圧電デバイスは、低温試験（氷点下）、および、常温試験（常温下）のいずれの場合でも優れた可撓性を有することがわかる。
　以上から本発明の効果は明らかである。 Flexibility 1 and flexibility 2 were evaluated in the same manner as described above for the produced piezoelectric element. Flexibility 1 at a radius of curvature of 5 cm was rated A in both the low temperature test and normal temperature test. Flexibility 2 at a radius of curvature of 5 mm was rated A in both the low temperature test and normal temperature test.
Therefore, it can be seen that the piezoelectric device of Example 5 has excellent flexibility in both the low temperature test (below freezing point) and the normal temperature test (under normal temperature).
From the above, the effect of the present invention is clear.
　本発明の圧電デバイスは、例えば、音波センサー、超音波センサー、圧力センサー、触覚センサー、歪みセンサーおよび振動センサー等の各種センサー(特に、ひび検知等のインフラ点検や異物混入検知等の製造現場検査に有用である)、マイクロフォン、ピックアップ、スピーカーおよびエキサイター等の音響デバイス（具体的な用途としては、ノイズキャンセラー(車、電車、飛行機、ロボット等に使用)、人工声帯、害虫・害獣侵入防止用ブザー、家具、壁紙、写真、ヘルメット、ゴーグル、ヘッドレスト、サイネージ、ロボットなどが例示される）、自動車、スマートフォン、スマートウォッチ、ゲーム等に適用して用いるハプティクス、超音波探触子およびハイドロホン等の超音波トランスデューサ、水滴付着防止、輸送、攪拌、分散、研磨等に用いるアクチュエータ、容器、乗り物、建物、スキーおよびラケット等のスポーツ用具に用いる制振材（ダンパー）、ならびに、道路、床、マットレス、椅子、靴、タイヤ、車輪およびパソコンキーボード等に適用して用いる振動発電装置として好適に使用することができる。 The piezoelectric device of the present invention can be used, for example, in various sensors such as sound wave sensors, ultrasonic sensors, pressure sensors, tactile sensors, strain sensors, and vibration sensors (especially for infrastructure inspection such as crack detection and manufacturing site inspection such as foreign matter contamination detection). useful), acoustic devices such as microphones, pickups, speakers and exciters (specific applications include noise cancellers (used in cars, trains, airplanes, robots, etc.), artificial vocal cords, buzzers for preventing insects and vermin from entering , furniture, wallpaper, photographs, helmets, goggles, headrests, signage, robots, etc.), automobiles, smartphones, smart watches, haptics used for games, etc. Ultrasonic probes and hydrophones Acoustic transducers, actuators used for water drop adhesion prevention, transport, agitation, dispersion, polishing, etc., dampers used in containers, vehicles, buildings, sports equipment such as skis and rackets, and roads, floors, mattresses, and chairs , shoes, tires, wheels, and personal computer keyboards.
　１０　圧電フィルム
　１１ａ、１１ｃ　シート状物
　１１ｂ　圧電積層体
　１２　振動板
　１６、１９　接着層
　２０　圧電体層
　２４　第１電極層
　２６　第２電極層
　２８　第１保護層
　３０　第２保護層
　３４　マトリックス
　３６　圧電体粒子
　５８　芯棒
　１００、１００ｂ、１００ｃ　圧電デバイス
　１０２　交流電源
　１０４　温度センサー
　１０６　制御部
　１２０　筐体
　１２０ａ　開口部
　１２２　外部ヒーター
　１２４　巻取り軸
　１２６　ガイド部材
　１３０　フレキシブルディスプレイ REFERENCE SIGNS LIST 10 piezoelectric film 11a, 11c sheet 11b piezoelectric laminate 12 diaphragm 16, 19 adhesive layer 20 piezoelectric layer 24 first electrode layer 26 second electrode layer 28 first protective layer 30 second protective layer 34 matrix 36 piezoelectric body Particle 58 Core rod 100, 100b, 100c Piezoelectric device 102 AC power supply 104 Temperature sensor 106 Control unit 120 Case 120a Opening 122 External heater 124 Winding shaft 126 Guide member 130 Flexible display

Claims (16)

  1. 　高分子材料を含むマトリックス中に圧電体粒子を含有する圧電体層と、前記圧電体層の両面に形成された電極層とを有し、動的粘弾性測定による周波数１Ｈｚでの損失正接が０．１以上となる極大値が０℃から５０℃の温度範囲に存在する圧電フィルム、および、
    　前記圧電フィルムを加熱するための加熱機構を備える、圧電デバイス。     It has a piezoelectric layer containing piezoelectric particles in a matrix containing a polymer material, and electrode layers formed on both sides of the piezoelectric layer, and has a loss tangent of 0 at a frequency of 1 Hz by dynamic viscoelasticity measurement. a piezoelectric film having a maximum value of .1 or more in a temperature range of 0° C. to 50° C.;
    A piezoelectric device comprising a heating mechanism for heating the piezoelectric film.
  2. 　加熱機構が、温度センサーと、制御部と、を備え、
    　前記制御部は、前記温度センサーが測定した温度に応じて、前記加熱機構を駆動して前記圧電フィルムを加熱する、請求項１に記載の圧電デバイス。     The heating mechanism comprises a temperature sensor and a controller,
    The piezoelectric device according to claim 1, wherein the controller drives the heating mechanism to heat the piezoelectric film according to the temperature measured by the temperature sensor.
  3. 　前記加熱機構が、外部ヒーターを有する、請求項１に記載の圧電デバイス。 The piezoelectric device according to claim 1, wherein the heating mechanism has an external heater.
  4. 　前記加熱機構が、前記圧電フィルムに周波数１５ｋＨｚ以上の正弦波交流信号を印加して、前記圧電フィルムを自己発熱させるものである、請求項１に記載の圧電デバイス。 The piezoelectric device according to claim 1, wherein the heating mechanism applies a sinusoidal AC signal with a frequency of 15 kHz or more to the piezoelectric film to cause the piezoelectric film to self-heat.
  5. 　前記正弦波交流信号の実効電圧が１Ｖｒｍｓ～１０Ｖｒｍｓである、請求項４に記載の圧電デバイス。 The piezoelectric device according to claim 4, wherein the sinusoidal AC signal has an effective voltage of 1 Vrms to 10 Vrms.
  6. 　前記自己発熱が圧電フィルムに非正弦波交流信号を印加することでもたらされるものであり、前記非正弦波交流信号をフーリエ解析して得られた正弦波交流信号の周波数の少なくとも一つ以上が１５ｋＨｚ～１００ｋＨｚの範囲に存在する、請求項４に記載の圧電デバイス。 The self-heating is caused by applying a non-sinusoidal AC signal to the piezoelectric film, and at least one frequency of the sinusoidal AC signal obtained by Fourier analysis of the non-sinusoidal AC signal is 15 kHz. 5. The piezoelectric device of claim 4, wherein the piezoelectric device is present in the range of ~100 kHz.
  7. 　前記１５ｋＨｚ～１００ｋＨｚの範囲に存在する正弦波交流信号の実効電圧が１Ｖｒｍｓ～１０Ｖｒｍｓである、請求項６に記載の圧電デバイス。 The piezoelectric device according to claim 6, wherein the sinusoidal AC signal present in the range of 15 kHz to 100 kHz has an effective voltage of 1 Vrms to 10 Vrms.
  8. 　前記圧電フィルムの少なくとも一部の曲率半径が変動するタイミングで、前記加熱機構が前記圧電フィルムを加熱する、請求項１に記載の圧電デバイス。 The piezoelectric device according to claim 1, wherein the heating mechanism heats the piezoelectric film at the timing when the radius of curvature of at least a portion of the piezoelectric film varies.
  9. 　前記圧電フィルムは、前記電極層の表面に設けられた保護層を有する、請求項１に記載の圧電デバイス。 The piezoelectric device according to claim 1, wherein the piezoelectric film has a protective layer provided on the surface of the electrode layer.
  10. 　前記圧電体層が厚さ方向に分極されたものである、請求項１に記載の圧電デバイス。 The piezoelectric device according to claim 1, wherein the piezoelectric layer is polarized in the thickness direction.
  11. 　前記電極層と信号源とを接続するための引き出し線を有する、請求項１に記載の圧電デバイス。 The piezoelectric device according to claim 1, having a lead wire for connecting the electrode layer and a signal source.
  12. 　前記圧電フィルムが複数層、積層されている、請求項１に記載の圧電デバイス。 The piezoelectric device according to claim 1, wherein the piezoelectric film is laminated in multiple layers.
  13. 　前記圧電フィルムが、厚さ方向に分極されたものであり、かつ、隣接する前記圧電フィルムの分極方向が逆である、請求項１２に記載の圧電デバイス。 13. The piezoelectric device according to claim 12, wherein the piezoelectric film is polarized in the thickness direction, and the polarization directions of adjacent piezoelectric films are opposite to each other.
  14. 　前記圧電フィルムを、１回以上、折り返すことにより、前記圧電フィルムを、複数層、積層したものである、請求項１２に記載の圧電デバイス。 13. The piezoelectric device according to claim 12, wherein a plurality of layers of the piezoelectric film are laminated by folding the piezoelectric film once or more.
  15. 　隣接する前記圧電フィルムを貼着する貼着層を有する、請求項１２に記載の圧電デバイス。 13. The piezoelectric device according to claim 12, having an adhesive layer for attaching the adjacent piezoelectric films.
  16. 　前記圧電フィルムが振動板に貼付されてなる、請求項１～１５のいずれか一項に記載の圧電デバイス。 The piezoelectric device according to any one of claims 1 to 15, wherein the piezoelectric film is attached to a diaphragm.
PCT/JP2022/045101 2022-02-04 2022-12-07 Piezoelectric device WO2023149073A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2022-016318 2022-02-04
JP2022016318 2022-02-04

Publications (1)

Publication Number Publication Date
WO2023149073A1 true WO2023149073A1 (en) 2023-08-10

Family

ID=87552116

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2022/045101 WO2023149073A1 (en) 2022-02-04 2022-12-07 Piezoelectric device

Country Status (1)

Country Link
WO (1) WO2023149073A1 (en)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0545689U (en) * 1991-11-25 1993-06-18 株式会社ケンウツド Projection screen
WO2013047875A1 (en) * 2011-09-30 2013-04-04 富士フイルム株式会社 Electroacoustic converter film, flexible display, vocal cord microphone, and musical instrument sensor
JP2017075841A (en) * 2015-10-14 2017-04-20 株式会社デンソー Object detection device and object detection method
JP2018157347A (en) * 2017-03-16 2018-10-04 ヤマハ株式会社 Vibration transducer
WO2020196807A1 (en) * 2019-03-28 2020-10-01 富士フイルム株式会社 Piezoelectric film, laminated piezoelectric element, and electroacoustic transducer

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0545689U (en) * 1991-11-25 1993-06-18 株式会社ケンウツド Projection screen
WO2013047875A1 (en) * 2011-09-30 2013-04-04 富士フイルム株式会社 Electroacoustic converter film, flexible display, vocal cord microphone, and musical instrument sensor
JP2017075841A (en) * 2015-10-14 2017-04-20 株式会社デンソー Object detection device and object detection method
JP2018157347A (en) * 2017-03-16 2018-10-04 ヤマハ株式会社 Vibration transducer
WO2020196807A1 (en) * 2019-03-28 2020-10-01 富士フイルム株式会社 Piezoelectric film, laminated piezoelectric element, and electroacoustic transducer

Similar Documents

Publication Publication Date Title
JP7137690B2 (en) Piezoelectric Films, Laminated Piezoelectric Elements and Electroacoustic Transducers
JP7265625B2 (en) Electroacoustic conversion film and electroacoustic transducer
JP7166428B2 (en) Electroacoustic transducer
TWI827851B (en) Polymer composite piezoelectric body, and piezoelectric film
JP7137689B2 (en) Piezoelectric Films, Laminated Piezoelectric Elements and Electroacoustic Transducers
WO2022190715A1 (en) Piezoelectric film
WO2023149073A1 (en) Piezoelectric device
WO2023053750A1 (en) Piezoelectric element, and electro-acoustic converter
WO2023153126A1 (en) Piezoelectric element and electroacoustic transducer
WO2023188966A1 (en) Piezoelectric film, piezoelectric element, and electroacoustic transducer
WO2023188929A1 (en) Piezoelectric film, piezoelectric element, and electroacoustic transducer
WO2023047958A1 (en) Multilayer piezoelectric element and electroacoustic transducer
WO2022190807A1 (en) Piezoelectric film and laminated piezoelectric element
WO2023048022A1 (en) Piezoelectric element and piezoelectric speaker
WO2023157636A1 (en) Piezoelectric film and laminated piezoelectric element
WO2023042542A1 (en) Piezoelectric element and electroacoustic transducer
WO2023053751A1 (en) Piezoelectric element, and electro-acoustic converter
WO2023053931A1 (en) Piezoelectric element and piezoelectric speaker
WO2023053758A1 (en) Piezoelectric film and laminated piezoelectric element
WO2023153173A1 (en) Piezoelectric film and laminated piezoelectric element
WO2023286544A1 (en) Piezoelectric film
WO2023181699A1 (en) Electroacoustic transducer
WO2022196202A1 (en) Piezoelectric element
WO2023166892A1 (en) Electroacoustic transducer
WO2023021905A1 (en) Piezoelectric film and laminated piezoelectric element

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 22924977

Country of ref document: EP

Kind code of ref document: A1