WO2023188929A1 - Film piézoélectrique, élément piézoélectrique et transducteur électroacoustique - Google Patents

Film piézoélectrique, élément piézoélectrique et transducteur électroacoustique Download PDF

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WO2023188929A1
WO2023188929A1 PCT/JP2023/005174 JP2023005174W WO2023188929A1 WO 2023188929 A1 WO2023188929 A1 WO 2023188929A1 JP 2023005174 W JP2023005174 W JP 2023005174W WO 2023188929 A1 WO2023188929 A1 WO 2023188929A1
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piezoelectric
layer
piezoelectric film
electrode layer
protective layer
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PCT/JP2023/005174
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English (en)
Japanese (ja)
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順平 石田
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富士フイルム株式会社
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R7/00—Diaphragms for electromechanical transducers; Cones
    • H04R7/02—Diaphragms for electromechanical transducers; Cones characterised by the construction
    • H04R7/04—Plane diaphragms
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/20—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/85—Piezoelectric or electrostrictive active materials

Definitions

  • the present invention relates to a piezoelectric film, a piezoelectric element, and an electroacoustic transducer.
  • Patent Document 1 discloses a polymer composite piezoelectric body formed by dispersing piezoelectric particles in a matrix containing a polymer material, and an electrode layer formed on both sides of the polymer composite piezoelectric body,
  • the loss tangent at a frequency of 1 kHz determined 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 or more.
  • a piezoelectric film is described.
  • a piezoelectric film can be used as a piezoelectric element to attach to various articles in contact with it, and use the article as a diaphragm to vibrate and produce sound, a so-called exciter. For example, by attaching an exciter to an image display panel, screen, etc., and causing these to vibrate, it is possible to produce sound instead of a speaker.
  • Patent Document 2 discloses an electroacoustic transducer including an exciter on one main surface of a diaphragm, in which the loss tangent at a frequency of 1 Hz measured by dynamic viscoelasticity of the exciter is determined at a temperature of 0 to 50°C.
  • the maximum value is within the range, the maximum value is 0.08 or more, and the product of the exciter thickness and the storage modulus at a frequency of 1 Hz and 25°C measured by dynamic viscoelasticity is the same as that of the diaphragm.
  • Electroacoustic transducers are described that have a thickness that is less than or equal to three times the product of Young's modulus.
  • Flexible displays are designed to be pulled out when in use, and rolled up when stored to make them more compact.
  • a piezoelectric film used with a flexible display having such a configuration and a piezoelectric element used by being attached to a diaphragm are sometimes wound up and stored.
  • An object of the present invention is to solve the problems of the prior art, and to provide a piezoelectric film, a piezoelectric element, and an electrical
  • An object of the present invention is to provide an acoustic transducer.
  • the present invention has the following configuration.
  • a piezoelectric layer made of a polymer composite piezoelectric material containing piezoelectric particles in a matrix containing a polymer material, two electrode layers provided on both sides of the piezoelectric layer, and a protective layer provided on the electrode layer.
  • a piezoelectric element formed by laminating a plurality of piezoelectric films according to [1].
  • An electroacoustic transducer comprising the piezoelectric film according to [1] or the piezoelectric element according to [2] attached to a windable diaphragm.
  • a piezoelectric film, a piezoelectric element, and an electroacoustic transducer that can suppress appearance defects when stored in a rolled state for a long time.
  • FIG. 1 is a diagram schematically showing an example of a piezoelectric film of the present invention.
  • FIG. 2 is a conceptual diagram for explaining the action of the piezoelectric film of the present invention.
  • 3 is a partially enlarged view of the piezoelectric film of FIG. 2.
  • FIG. FIG. 2 is a conceptual diagram for explaining a conventional piezoelectric film.
  • FIG. 2 is a conceptual diagram for explaining a conventional piezoelectric film.
  • FIG. 2 is a conceptual diagram for explaining another example of a conventional piezoelectric film.
  • FIG. 2 is a conceptual diagram for explaining a conventional piezoelectric film.
  • FIG. 2 is a conceptual diagram for explaining the action of the piezoelectric film of the present invention.
  • FIG. 7 is a conceptual diagram for explaining the operation of another example of the piezoelectric film of the present invention.
  • 1 is a diagram conceptually showing an example of an electroacoustic transducer having a piezoelectric film of the present invention.
  • 1 is a diagram conceptually showing an example of an electroacoustic transducer having a piezoelectric element having a piezoelectric film of the present invention.
  • 12 is a partially enlarged view of the electroacoustic transducer shown in FIG. 11.
  • FIG. It is a figure which shows typically another example of the piezoelectric element of this invention.
  • FIG. 2 is a conceptual diagram for explaining an example of a method for manufacturing a piezoelectric film.
  • FIG. 2 is a conceptual diagram for explaining an example of a method for manufacturing a piezoelectric film.
  • FIG. 2 is a conceptual diagram for explaining an example of a method for manufacturing a piezoelectric film.
  • FIG. 2 is a conceptual diagram for explaining an example of
  • the piezoelectric film of the present invention is A piezoelectric layer made of a polymer composite piezoelectric material containing piezoelectric particles in a matrix containing a polymer material, two electrode layers provided on both sides of the piezoelectric layer, and a protective layer provided on the electrode layer.
  • a piezoelectric film having The piezoelectric film is a piezoelectric film in which the difference between the creep deformation rate of the piezoelectric film and the creep deformation rate of the first laminate of the electrode layer and the protective layer is 1.5% or less.
  • FIG. 1 shows a diagram schematically showing an example of the piezoelectric film of the present invention.
  • the piezoelectric film 10 shown in FIG. A first protective layer 28 that is laminated on the surface opposite to the body layer 20, a second electrode layer 26 that is laminated on the other surface of the piezoelectric layer 20, and a layer that is opposite to the piezoelectric layer 20 of the second electrode layer 26.
  • a second protective layer 30 is laminated on the side surface. That is, the piezoelectric film 10 has a structure 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.
  • first and second in the first electrode layer 24 and the first protective layer 28, as well as the second electrode layer 26 and the second protective layer 30 are added for convenience in order to explain the piezoelectric film 10. It is something that exists. Therefore, the first and second aspects of the present invention have no technical meaning and are unrelated to actual usage conditions.
  • first protective layer 28 and the second protective layer 30 are basically the same in structure, except for their arrangement positions. 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.
  • 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 piezoelectric film 10 is driven as a piezoelectric body by expanding and contracting the piezoelectric layer 20 by applying a voltage to the first electrode layer 24 and the second electrode layer 26.
  • the piezoelectric film 10 expands and contracts in the plane direction, and as a result, the piezoelectric film 10 vibrates in the thickness direction to generate sound.
  • the piezoelectric film 10 vibrates according to the magnitude of the applied driving voltage, and generates sound according to the applied driving voltage.
  • the piezoelectric layer 20, electrode layer, and protective layer will be described in detail later.
  • the difference between the creep deformation rate of the piezoelectric film 10 and the creep deformation rate of the first laminate, which is a laminate of the electrode layer and the protective layer, is 1.5% or less.
  • a laminate of the first electrode layer 24 and the first protective layer 28 and a laminate of the second electrode layer 26 and the second protective layer 30 correspond to the first laminate.
  • the piezoelectric film 10 used with the flexible display may be rolled up and stored as shown in FIG. According to the inventor's study, when the piezoelectric film 10 is stored in a rolled state for a long time and then stretched, a striped deformation Q occurs in the piezoelectric film 210 as shown in FIG. 4, resulting in poor appearance. I found out that it does.
  • the piezoelectric film 10 in a wound state is curved in the circumferential direction and held in a state where stress is applied as shown by the arrow. Therefore, creep deformation occurs in which the amount of displacement increases with time, and at this time, in the case of the piezoelectric film 210 where the difference between the creep deformation rate of the piezoelectric layer and the creep deformation rate of the protective layer is large, as shown in FIG. It was assumed that a streak-like deformation Q as shown in Fig. 2 would occur. For example, when the creep deformation rate of the piezoelectric layer 220 is large and the creep deformation rates of the first protective layer 228 and the second protective layer 230 are small, as conceptually shown in FIG.
  • the protective layer deforms in an elongated state depending on the direction, the deformation in the plane direction of the protective layer becomes smaller.
  • the piezoelectric layer 220 and the protective layer are in close contact with each other, and the piezoelectric layer 220 is restrained, so internal stress is generated at the interface due to the force of deformation, and in order to release this stress, As shown in FIG. 7, a concave or convex streak-like deformation Q occurs on the surface of the piezoelectric film 210.
  • the protective layer is While the piezoelectric layer 220 is deformed into an elongated state, the deformation in the plane direction of the piezoelectric layer 220 is small.
  • the protective layer is restrained, internal stress is generated at the interface due to the force of deformation, and in order to release this stress, concave or convex stripes are formed on the surface of the piezoelectric film 210 as shown in FIG. A deformation Q occurs.
  • the difference between the creep deformation rate of the piezoelectric film 10 and the creep deformation rate of the first laminate, which is a laminate of a protective layer and an electrode layer, is 1.5% or less. It is. Therefore, for example, when the creep deformation rate of the piezoelectric layer 20 is small and the creep deformation rates of the first protective layer 28 and the second protective layer 30 are small, as conceptually shown in FIG. The deformation in the plane direction of both the protective layer and the protective layer becomes small.
  • the generation of internal stress at the interface between the piezoelectric layer 20 and the protective layer can be suppressed (reduced), and the occurrence of concave or convex streak-like deformation on the surface of the piezoelectric film 10 can be suppressed.
  • the creep deformation rate of the piezoelectric layer 20 is large and the creep deformation rates of the first protective layer 28 and the second protective layer 30 are large, as conceptually shown in FIG. The deformation in the plane direction of each layer becomes large. Therefore, the generation of internal stress at the interface between the piezoelectric layer 20 and the protective layer can be suppressed (reduced), and the occurrence of concave or convex streak-like deformation on the surface of the piezoelectric film 10 can be suppressed.
  • the creep deformation rate of the piezoelectric layer 20 can be replaced by the creep deformation rate of the piezoelectric film 10
  • the creep deformation rate of the protective layer can be replaced by the creep deformation rate of the first laminate of the protective layer and the electrode layer. . Therefore, by setting the difference between the creep deformation rate of the piezoelectric film 10 and the creep deformation rate of the first laminate to 1.5% or less, streaky deformation Q occurs in the piezoelectric film 10, resulting in poor appearance. This can be prevented.
  • the method for measuring the creep deformation rate of the piezoelectric film 10 is as follows. A sample with a width of 4 mm and a length of 20 mm is cut out from the piezoelectric film 10, set in a thermomechanical analyzer (TMA, e.g. TMA402 manufactured by NETZSCH) so that the distance between the chucks in the length direction is approximately 10 mm, and then the temperature is is set to 25°C, a tensile stress of 0.2 N/mm 2 is applied in the length direction, and the length in this state is defined as the reference position dimension A before creep. Next, while continuing to apply a tensile stress of 0.2 N/mm 2 , the temperature was raised at a rate of 10° C./min until it reached 90° C.
  • TMA thermomechanical analyzer
  • a tensile stress of 10 N/mm 2 is applied and heat treatment is performed for 3 hours.
  • the temperature was lowered to 25°C at a rate of 10°C/min while applying a tensile stress of 10 N/mm 2 , and after the temperature reached 25°C, the tensile stress was set to 0.2 N/mm 2 , and then The dimension after 10 minutes has passed is defined as dimension B after creep.
  • the creep deformation rate can be determined from the formula (B-A)/A [%].
  • the method for measuring the creep deformation rate of the first laminate is as follows.
  • the end of the piezoelectric film 10 is cut into a strip with a width of 8 mm and a length of 24 mm so that four sides are exposed to the atmosphere, and is immersed in a solvent (for example, MEK (methyl ethyl ketone)) for a predetermined time (for example, about 48 hours).
  • a solvent for example, MEK (methyl ethyl ketone)
  • a predetermined time for example, about 48 hours.
  • the first laminate of the protective layer and the electrode layer was cut into strips with a width of 4 mm and a length of 20 mm, and the distance between the chucks in the longitudinal direction was measured using a thermomechanical analyzer (TMA, e.g., TMA402 manufactured by NETZSCH).
  • TMA thermomechanical analyzer
  • the length is set to about 10 mm, then the temperature is set to 25°C, a tensile stress of 0.2 N/mm 2 is applied in the longitudinal direction, and the length in this state is defined as the reference position dimension A before creep.
  • the temperature was raised at a rate of 10° C./min to reach 90° C.
  • a tensile stress of 10 N/mm 2 is applied and heat treatment is performed for 3 hours.
  • the temperature was lowered to 25°C at a rate of 10°C/min while applying a tensile stress of 10 N/mm 2 , and after the temperature reached 25°C, the tensile stress was set to 0.2 N/mm 2 , and then The dimension after 10 minutes has passed is defined as dimension B after creep.
  • the creep deformation rate can be determined from the formula (BA)/A [%].
  • the creep deformation rate of the piezoelectric film 10 can be adjusted by heat treatment. Further, the creep deformation rate of the first laminate can be adjusted by heat treatment and stretching conditions when producing the protective layer by biaxial stretching. This point will be discussed later.
  • the difference between the creep deformation rate of the piezoelectric film 10 and the creep deformation rate of the first laminate is preferably 1.5% or less, and 1.0% or less. More preferred.
  • the creep deformation rate of the piezoelectric film 10 is preferably 5.0% or less, more preferably 3.0% or less, and even more preferably 2.0% or less.
  • Such a piezoelectric film 10 can be used integrally with a flexible display.
  • the example shown in FIG. 10 has a configuration in which a piezoelectric film 10 is attached to the back surface (the surface opposite to the display surface) of a flexible display 110.
  • the flexible display 110 can be made windable. In this case, even if the piezoelectric film 10 is stored in a rolled state for a long time, it is possible to suppress appearance defects from occurring in the piezoelectric film 10.
  • the flexible display 110 includes display devices such as organic electroluminescent (OLED) displays, liquid crystal displays, micro LED (light emitting diode) displays, and inorganic electroluminescent displays, and projector screens. etc.
  • display devices such as organic electroluminescent (OLED) displays, liquid crystal displays, micro LED (light emitting diode) displays, and inorganic electroluminescent displays, and projector screens. etc.
  • the piezoelectric element of the present invention is a piezoelectric element formed by laminating a plurality of layers of the piezoelectric films described above.
  • the electroacoustic transducer of the present invention is an electroacoustic transducer in which the piezoelectric film or the piezoelectric element described above is attached to a diaphragm that can be rolled up.
  • FIG. 11 is a diagram conceptually showing an example of an electroacoustic transducer having a piezoelectric element of the present invention.
  • FIG. 12 is a partially enlarged view of the electroacoustic transducer of FIG. 11.
  • the electroacoustic transducer 100 shown in FIG. 11 includes a piezoelectric element 50, a diaphragm 102, and an adhesive layer 104 disposed between the piezoelectric element 50 and the diaphragm 102.
  • the piezoelectric element 50 and the diaphragm 102 are adhered to each other with an adhesive layer 104.
  • the diaphragm 102 is flexible enough to be rolled up.
  • having flexibility is synonymous with having flexibility in a general interpretation, and indicates that it is possible to bend and bend. , indicating that it can be bent and stretched without breaking or damage.
  • the diaphragm 102 is not limited as long as it has flexibility, and various sheet-like materials (plate-like materials, films) can be used.
  • sheet-like materials plate-like materials, films
  • 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) and cyclic olefin resins, foamed polystyrene, foamed plastics made of foamed styrene and foamed polyethylene, etc., veneer boards, cork boards, leather such as cowhide, Carbon sheets, various paperboards such as Japanese paper, various corrugated cardboard materials made by pasting other paperboards on one or both sides of corrugated paperboard, various metals such as stainless
  • an organic electroluminescent (OLED (Organic Light Emitting Diode)) display may be used as long as the diaphragm 102 has flexibility.
  • OLED Organic Light Emitting Diode
  • liquid crystal display a liquid crystal display
  • micro LED Light Emitting Diode
  • inorganic electroluminescent display may be used.
  • Display devices such as displays, projector screens, and the like can also be suitably used.
  • the piezoelectric element 50 is used as a so-called exciter that exhibits piezoelectricity in response to an applied voltage and causes the diaphragm 102 to vibrate.
  • the piezoelectric element 50 is made by laminating three layers of piezoelectric films 10 by folding one long rectangular piezoelectric film 10 twice in one direction. Note that in FIG. 12, illustration of the protective layer is omitted in order to clearly show the configuration of the piezoelectric element 50.
  • a power source is connected to the first electrode layer 24 and the second electrode layer 26 of the piezoelectric film 10 that constitute the piezoelectric element 50.
  • the piezoelectric element 50 (piezoelectric film 10) is driven as a piezoelectric body by applying a voltage to the first electrode layer 24 and the second electrode layer 26, so that the piezoelectric layer 20 expands and contracts.
  • the piezoelectric element 50 expands and contracts in the plane direction, bends the diaphragm 102 to which the piezoelectric element 50 is attached, and as a result vibrates the diaphragm 102 in the thickness direction to produce sound. generate.
  • the diaphragm 102 vibrates according to the magnitude of the driving voltage applied to the piezoelectric element 50, and the electroacoustic transducer 100 generates sound according to the applied driving voltage. That is, the electroacoustic transducer 100 has a configuration in which the piezoelectric element 50 (laminated piezoelectric film 10) is used as an exciter.
  • the adhesion layer 104 is for adhering the diaphragm 102 and the piezoelectric element 50.
  • the thickness of the adhesive layer 104 there is no limit to the thickness of the adhesive layer 104, and a thickness that provides sufficient adhesive strength (adhesive strength, adhesive strength) may be appropriately set depending on the material of the adhesive layer 104. Specifically, the thickness of the adhesive layer 104 after attachment is preferably 0.1 ⁇ m to 50 ⁇ m, more preferably 0.1 ⁇ m to 30 ⁇ m, and even more preferably 0.1 ⁇ m to 10 ⁇ m.
  • the adhesive layer 104 is a layer made of an adhesive that has fluidity when pasted together and then becomes solid, it remains a gel-like (rubber-like) soft solid when pasted together, and it remains a gel-like (rubber-like) solid when pasted together. It may be a layer made of an adhesive whose shape does not change, or a layer made of a material that has characteristics of both an adhesive and a pressure-sensitive adhesive. Further, the adhesive (pressure-sensitive adhesive) may be any of a moisture-curable adhesive, a thermoplastic adhesive, and a thermosetting adhesive. Further, as the adhesive layer 104, double-sided tape, adhesive sheet, etc. may be used.
  • the diaphragm 102 can be wound up, and by winding it up, the size can be reduced during storage, transportation, etc.
  • the piezoelectric element 50 piezoelectric film 10
  • the piezoelectric element 50 can be prevented from being deformed in a striped manner, and the appearance defects can be prevented from occurring. can.
  • the piezoelectric element 50 shown in FIGS. 11 and 12 is made by folding and laminating three layers of the piezoelectric film 10, but the present invention is not limited to this. That is, the piezoelectric element may have one layer (one sheet) of the piezoelectric film 10, or may have a plurality of layers laminated. When a plurality of piezoelectric films 10 are laminated, the number of piezoelectric films 10 laminated may be two or four or more. Regarding this point, the piezoelectric element shown in FIG. 13, which will be described later, is also similar.
  • the piezoelectric element 50 has a piezoelectric film laminated in multiple layers by folding the elongated piezoelectric film 10 one or more times, but the piezoelectric element 50 is not limited to this.
  • the piezoelectric element may have a structure in which a plurality of sheet-like (cut sheet-like) piezoelectric films 10 are laminated.
  • the piezoelectric film 10 is polarized in the thickness direction, and the polarization directions of adjacent piezoelectric films 10 are opposite to each other. Therefore, in the adjacent piezoelectric films 10, the first electrode layers 24 and the second electrode layers 26 face each other. Therefore, whether the power source is an AC power source or a DC power source, power of the same polarity is always supplied to the facing electrodes. Therefore, in the piezoelectric element shown in FIG. 13, even if the electrodes of adjacent piezoelectric films 10 come into contact with each other, there is no risk of short-circuiting.
  • the polarization direction of the piezoelectric film 10 may be detected using a d33 meter or the like. Alternatively, the polarization direction of the piezoelectric film 10 may be determined from the polarization processing conditions described below.
  • the polarization directions of adjacent piezoelectric films 10 are opposite to each other, but the invention is not limited to this, and the polarization directions of adjacent piezoelectric films 10 may be the same.
  • a piezoelectric element made by folding and laminating long piezoelectric films has the following advantages. That is, when a plurality of cut sheet-shaped piezoelectric films 10 are laminated, it is necessary to connect the first electrode layer 24 and the second electrode layer 26 for each piezoelectric film to a driving power source. On the other hand, in a structure in which long piezoelectric films 10 are folded and laminated, the laminate can be constructed from only one long piezoelectric film 10. Further, in the structure in which long piezoelectric films 10 are folded and laminated, only one power source is required for applying the driving voltage, and furthermore, the electrodes need only be drawn out from the piezoelectric film 10 at one location. Furthermore, in the structure in which long piezoelectric films 10 are folded and laminated, the polarization directions of adjacent piezoelectric films are necessarily opposite to each other.
  • the piezoelectric film 10 includes a piezoelectric layer 20 that is a sheet-like material having piezoelectricity, a first electrode layer 24 laminated on one surface of the piezoelectric layer 20, and a piezoelectric layer 24 of the first electrode layer 24.
  • a first protective layer 28 that is laminated on the surface opposite to the body layer 20, a second electrode layer 26 that is laminated on the other surface of the piezoelectric layer 20, and a layer that is opposite to the piezoelectric layer 20 of the second electrode layer 26.
  • a second protective layer 30 is laminated on the side surface.
  • the piezoelectric layer 20 is a polymer composite piezoelectric material containing piezoelectric particles 36 in a matrix 34 containing a polymer material, as conceptually shown in FIG.
  • the material for the matrix 34 (matrix and binder) of the polymer composite piezoelectric material constituting the piezoelectric layer 20 it is preferable to use a polymer material that has viscoelasticity at room temperature.
  • "normal temperature” refers to a temperature range of about 0 to 50°C.
  • the polymer composite piezoelectric material (piezoelectric layer 20) preferably satisfies the following requirements.
  • Flexibility For example, when holding a newspaper or magazine in a loosely bent state like a document for portable use, it is constantly subjected to 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 will be generated, and cracks will occur at the interface between the polymer matrix and the piezoelectric particles, which may eventually lead to destruction. Therefore, a polymer composite piezoelectric material is required to have appropriate softness. Moreover, if strain energy can be diffused to the outside as heat, stress can be alleviated.
  • the loss tangent of the polymer composite piezoelectric material is required to be appropriately large.
  • Sound quality A speaker vibrates piezoelectric particles at a frequency in the audio band of 20Hz to 20kHz, and the vibration energy causes the entire polymer composite piezoelectric material (piezoelectric film) to vibrate as one, thereby reproducing sound. Ru. Therefore, the polymer composite piezoelectric material is required to have appropriate hardness in order to increase the efficiency of vibrational energy transmission. Furthermore, if the frequency characteristics of the speaker are smooth, the amount of change in sound quality when the lowest resonant frequency changes due to a change in curvature will also be small. Therefore, the loss tangent of the polymer composite piezoelectric material is required to be appropriately large.
  • a polymer composite piezoelectric material is required to behave hard against vibrations of 20 Hz to 20 kHz, and to behave softly against vibrations of several Hz or less. Further, the loss tangent of the polymer composite piezoelectric material is required to be appropriately large for vibrations of all frequencies below 20 kHz.
  • the spring constant can be easily adjusted by laminating layers according to the rigidity (hardness, stiffness, spring constant) of the mating material (diaphragm) to which it is attached.
  • polymer solids have a viscoelastic relaxation mechanism, and as the temperature increases or the frequency decreases, large-scale molecular motion causes a decrease (relaxation) in the storage modulus (Young's modulus) or a maximum in the loss modulus (absorption). It is observed as Among these, the relaxation caused by micro-Brownian motion of molecular chains in the amorphous region is called principal dispersion, and a very large relaxation phenomenon is observed. The temperature at which this main dispersion occurs is the glass transition point (Tg), and the viscoelastic relaxation mechanism appears most prominently.
  • Tg glass transition point
  • the polymer composite piezoelectric material (piezoelectric layer 20), by using a polymer material whose glass transition point is at room temperature, in other words, a polymer material that has viscoelasticity at room temperature, for the matrix, it can withstand vibrations of 20Hz to 20kHz. This results in a polymer composite piezoelectric material that is hard and behaves softly when subjected to slow vibrations of several Hz or less. In particular, in order to suitably exhibit this behavior, it is preferable to use a polymer material whose glass transition point at a frequency of 1 Hz is at room temperature, that is, 0 to 50° C., for the matrix of the polymer composite piezoelectric material.
  • Various known polymer materials can be used as the polymer material having viscoelasticity at room temperature.
  • a polymer material having a maximum value of loss tangent Tan ⁇ of 0.5 or more at a frequency of 1 Hz in a dynamic viscoelasticity test at room temperature, ie, 0 to 50° C. is used.
  • the polymer composite piezoelectric material is slowly bent by an external force, stress concentration at the interface between the polymer matrix and the piezoelectric particles at the maximum bending moment portion is alleviated, and high flexibility can be expected.
  • the polymer material having viscoelasticity at room temperature preferably has a storage modulus (E') at a frequency of 1 Hz measured by dynamic viscoelasticity measurement of 100 MPa or more at 0°C and 10 MPa or less at 50°C.
  • E' storage 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 securing good moisture resistance, etc., it is also suitable for the polymer material to have a dielectric constant of 10 or less at 25°C.
  • polymeric materials that have viscoelasticity at room temperature that meet these conditions include cyanoethylated polyvinyl alcohol (cyanoethylated PVA), polyvinyl acetate, polyvinylidene chloride core acrylonitrile, polystyrene-vinyl polyisoprene block copolymer, and polyvinyl methyl.
  • cyanoethylated polyvinyl alcohol cyanoethylated PVA
  • polyvinyl acetate polyvinylidene chloride core acrylonitrile
  • polystyrene-vinyl polyisoprene block copolymer 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 polymeric materials.
  • the polymer material it is preferable to use a material having a cyanoethyl group, and it is particularly preferable to use
  • the polymeric material having viscoelasticity at room temperature it is preferable to use a polymeric material having a cyanoethyl group, and it is particularly preferable to use cyanoethylated PVA. That is, in the present invention, it is preferable for the piezoelectric layer 20 to use a polymeric material having a cyanoethyl group as the matrix 34, and it is particularly preferable to use cyanoethylated PVA.
  • the above-mentioned polymeric materials represented by cyanoethylated PVA are also collectively referred to as "polymeric materials having viscoelasticity at room temperature.”
  • polymeric materials having viscoelasticity at room temperature may be used alone or in combination (mixture) of multiple types.
  • the matrix 34 using such a polymeric material having viscoelasticity at room temperature may be made of a plurality of polymeric materials in combination, if necessary. That is, in addition to the viscoelastic material 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, cyanoethylhydroxysucrose, cyanoethylhydroxycellulose, cyanoethylhydroxypullulan, cyanoethyl methacrylate, cyanoethyl acrylate, cyanoethyl Cyano groups such as hydroxyethyl cellulose, cyanoethyl amylose, cyanoethyl hydroxypropyl cellulose, cyanoethyl dihydroxypropyl cellulose, cyanoethyl hydroxypropyl amylose, cyanoethyl polyacrylamide, cyanoethyl polyacrylate, cyanoethyl pullulan, cyanoethyl polyhydroxymethylene, cyanoethyl glycido
  • the matrix 34 also includes 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 phenol resins, urea resins, melamine resins, alkyd resins, and mica may also be added. Furthermore, for the purpose of improving tackiness, tackifiers such as rosin ester, rosin, terpene, terpene phenol, and petroleum resin may be added.
  • thermoplastic resins such as vinyl chloride resin, polyethylene, polystyrene, methacrylic resin, polybutene, and isobutylene
  • Thermosetting resins such as phenol resins, urea resins, melamine resins, alkyd resins, and mica may also be added.
  • tackifiers such as rosin ester, rosin, terpene, terpene
  • the proportion in the matrix 34 is 30% by mass or less. It is preferable that This allows the properties of the added polymer material to be expressed without impairing the viscoelastic relaxation mechanism in the matrix 34, resulting in higher dielectric constant, improved heat resistance, improved adhesion between the piezoelectric particles 36 and the electrode layer, etc. Favorable results can be obtained in this respect.
  • the piezoelectric layer 20 is a layer made of a polymer composite piezoelectric material that includes such a matrix 34 and piezoelectric particles 36. Piezoelectric particles 36 are dispersed in matrix 34 . Preferably, 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.
  • the ceramic particles constituting the piezoelectric particles 36 include lead zirconate titanate (PZT), lead lanthanate zirconate titanate (PLZT), barium titanate (BaTiO 3 ), zinc oxide (ZnO), and
  • PZT lead zirconate titanate
  • PLAT lead lanthanate zirconate titanate
  • BaTiO 3 barium titanate
  • ZnO zinc oxide
  • An example is a solid solution of barium titanate and bismuth ferrite (BiFe 3 ) (BFBT).
  • the particle size of the piezoelectric particles 36 there is no limit to the particle size of the piezoelectric particles 36, and it may be selected as appropriate depending on the size of the piezoelectric film 10, the use of the piezoelectric element 50, 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 have both high piezoelectric properties 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 irregularly dispersed in the matrix 34. may have been done.
  • the ratio of the matrix 34 to the piezoelectric particles 36 in the piezoelectric layer 20 there is no limit to the ratio of the matrix 34 to the piezoelectric particles 36 in the piezoelectric layer 20, and it is subject to the size and thickness of the piezoelectric film 10 in the plane direction, the use of the piezoelectric film 10, and It may be set as appropriate depending on the characteristics required of the piezoelectric film 10.
  • 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 even more preferably 50 to 80%.
  • the thickness of the piezoelectric layer 20 is not particularly limited, and may be determined as appropriate depending on the use of the piezoelectric film 10, the number of laminated piezoelectric films in the piezoelectric element 50, the characteristics required of the piezoelectric film 10, etc. , just set it.
  • the thickness of the piezoelectric layer 20 is preferably 10 to 300 ⁇ m, more preferably 20 to 200 ⁇ m, and even more preferably 30 to 150 ⁇ m.
  • the piezoelectric layer 20 is preferably polarized (poled) in the thickness direction.
  • the piezoelectric film 10 has a first electrode layer 24 on one side of the piezoelectric layer 20, a first protective layer 28 thereon, and a first electrode layer 24 on one side of the piezoelectric layer 20. It has a structure in which it has a second electrode layer 26 on its surface and a second protective layer 30 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 an electrode pair, that is, a first electrode layer 24 and a second electrode layer 26, and this laminate is sandwiched between a first protective layer 28 and a second protective layer 30. It has a structure in which it is sandwiched between. In this way, in the piezoelectric film 10, the region sandwiched between the first electrode layer 24 and the second electrode layer 26 expands and contracts depending on the applied voltage.
  • the piezoelectric film 10 includes, in addition to these layers, an adhesive layer for pasting the electrode layer and the piezoelectric layer 20, and a pasting layer for pasting the electrode layer and the protective layer. It may have an attached layer.
  • the adhesive may be an adhesive or a pressure-sensitive adhesive.
  • a polymeric material obtained by removing the piezoelectric particles 36 from the piezoelectric layer 20, that is, the same material as the matrix 34 can also be suitably used.
  • the adhesive layer may be provided on both the first electrode layer 24 side and the second electrode layer 26 side, or may be provided only on one of the first electrode layer 24 side and the second electrode layer 26 side. good.
  • the first protective layer 28 and the second protective layer 30 cover the first electrode layer 24 and the second electrode layer 26, and also serve to impart appropriate rigidity and mechanical strength to the piezoelectric layer 20.
  • the piezoelectric layer 20 consisting of the matrix 34 and the piezoelectric particles 36 exhibits excellent flexibility against slow bending deformation, but depending on the application, it may have low rigidity. or mechanical strength may be insufficient.
  • the piezoelectric film 10 is provided with a first protective layer 28 and a second protective layer 30 to compensate for this.
  • first protective layer 28 and the second protective layer 30 there are no restrictions on the first protective layer 28 and the second protective layer 30, and various sheet-like materials can be used, and various resin films are suitably exemplified as an example.
  • various resin films are suitably exemplified as an example.
  • PET polyethylene terephthalate
  • PP polypropylene
  • PS polystyrene
  • PC polycarbonate
  • PPS polyphenylene sulfite
  • PMMA polymethyl methacrylate
  • PEI polyetherimide
  • PI polyimide
  • PEN polyethylene naphthalate
  • TAC triacetyl cellulose
  • cyclic olefin resin and the like are suitably used.
  • the thickness of the first protective layer 28 and the second protective layer 30 there is also no limit to the thickness of the first protective layer 28 and the second protective layer 30.
  • the thicknesses of the first protective layer 28 and the second protective layer 30 are basically the same, but may be different.
  • 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, it is advantageous for the first protective layer 28 and the second protective layer 30 to be thinner, unless mechanical strength or good handling properties as a sheet-like material are required.
  • the thickness of the first protective layer 28 and the second protective layer 30 is twice or less the thickness of the piezoelectric layer 20, it is possible to achieve both rigidity and appropriate flexibility.
  • the thickness of the first protective layer 28 and the second protective layer 30 is preferably 100 ⁇ m or less, The thickness is more preferably 50 ⁇ m or less, and even more preferably 25 ⁇ m or less.
  • 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 to apply voltage to the piezoelectric layer 20 (piezoelectric film 10).
  • the materials for forming the first electrode layer 24 and the second electrode layer 26 there are no restrictions on the materials for forming the first electrode layer 24 and the second electrode layer 26, and various conductors can be used.
  • 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, Further, indium tin oxide and the like are exemplified.
  • conductive polymers such as PEDOT/PPS (polyethylenedioxythiophene-polystyrene sulfonic acid) are also exemplified.
  • 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 viewpoints of conductivity, cost, flexibility, and the like.
  • the method of forming the first electrode layer 24 and the second electrode layer 26 may be formed using a vapor deposition method (vacuum film forming method) such as vacuum evaporation and sputtering, plating, or using the above-mentioned materials.
  • a vapor deposition method vacuum film forming method
  • Various known methods can be used, such as a method of pasting a foil that has been prepared.
  • thin films of copper, aluminum, etc. formed by vacuum deposition are particularly preferably used as the first electrode layer 24 and the second electrode layer 26 because they can ensure the flexibility of the piezoelectric film 10.
  • Ru a copper thin film formed by vacuum evaporation is particularly preferably used.
  • the thickness of the first electrode layer 24 and the second electrode layer 26 there is no limit to the thickness of the first electrode layer 24 and the second electrode layer 26. Further, the thicknesses of the first electrode layer 24 and the second electrode layer 26 are basically the same, but may be different.
  • the rigidity of the first electrode layer 24 and the second electrode layer 26 is too high, it not only restricts the expansion and contraction of the piezoelectric layer 20, but also Flexibility is also impaired. Therefore, it is advantageous for the first electrode layer 24 and the second electrode layer 26 to be thinner, 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 Young's modulus is less than the product of the thickness of the first protective layer 28 and the second protective layer 30 and Young's modulus, then , is suitable 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) is used.
  • 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. Among them, it is preferably 0.1 ⁇ m or less.
  • the piezoelectric film 10 has a piezoelectric layer 20 formed by dispersing piezoelectric particles 36 in a matrix 34 containing a polymeric material, sandwiched between the first electrode layer 24 and the second electrode layer 26, and further includes:
  • This laminate has a structure in which a first protective layer 28 and a second protective layer 30 are sandwiched between them.
  • the maximum value of the loss tangent (Tan ⁇ ) at a frequency of 1 Hz as measured by dynamic viscoelasticity exists at room temperature, and it is preferable that the maximum value of 0.1 or more exists at room temperature. More preferred.
  • the piezoelectric film 10 is subjected to a relatively slow and large bending deformation of several Hz or less from the outside, the strain energy can be effectively diffused to the outside as heat, so that the polymer matrix and piezoelectric particles are This can prevent cracks from forming at the interface.
  • the piezoelectric film 10 preferably has a storage 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 also applies to the piezoelectric layer 20. This allows the piezoelectric film 10 to have a large frequency dispersion in storage modulus (E') at room temperature. That is, it is hard against vibrations of 20 Hz to 20 kHz, and can behave soft against vibrations of several Hz or less.
  • E' storage modulus
  • the piezoelectric film 10 has a product of thickness and storage modulus (E') at a frequency of 1 Hz measured 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 also applies to the piezoelectric layer 20. Thereby, the piezoelectric film 10 can have appropriate rigidity and mechanical strength without impairing its flexibility and acoustic properties.
  • E' thickness and storage 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. Regarding this condition, the piezoelectric layer 20 is also the same. 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 f 0 changes due to a change in the curvature of the speaker can also be reduced.
  • Tan ⁇ loss tangent
  • the storage modulus (Young's modulus) and loss tangent of the piezoelectric film 10, piezoelectric layer 20, etc. may be measured by a known method.
  • the measurement may be performed using a dynamic viscoelasticity measuring device DMS6100 manufactured by SII Nanotechnology.
  • the measurement frequency is 0.1Hz to 20Hz (0.1Hz, 0.2Hz, 0.5Hz, 1Hz, 2Hz, 5Hz, 10Hz and 20Hz)
  • the measurement temperature is -50 to 150°C. Examples include a temperature increase rate of 2° C./min (in a nitrogen atmosphere), a sample size of 40 mm ⁇ 10 mm (including the clamp area), and a distance between chucks of 20 mm.
  • a power source is connected to the first electrode layer 24 and the second electrode layer 26 of each piezoelectric film 10, which applies a driving voltage to expand and contract the piezoelectric film 10, that is, supplies driving power.
  • the power source is not limited and may be either a direct current power source or an alternating current power source.
  • the drive voltage may be appropriately set to a drive voltage that can appropriately drive the piezoelectric film 10, depending on the thickness and forming material of the piezoelectric layer 20 of the piezoelectric film 10.
  • the method of drawing out the electrodes from the first electrode layer 24 and the second electrode layer 26 there is no limit to the method of drawing out the electrodes from the first electrode layer 24 and the second electrode layer 26, and various known methods can be used.
  • a method of connecting a conductive material such as copper foil to the first electrode layer 24 and the second electrode layer 26 and drawing out the electrodes to the outside and a method of penetrating the first protective layer 28 and the second protective layer 30 with a laser or the like are available.
  • Examples include a method of forming a hole, filling the through hole with a conductive material, and drawing out an electrode to the outside.
  • suitable electrode extraction methods include the method described in JP-A No. 2014-209724 and the method described in JP-A No. 2016-015354.
  • a connecting portion for connecting the first electrode layer 24 and the second electrode layer 26 to a power source be formed in the protruding portion. Note that there is no restriction on the method of connecting the electrode layer and the wiring in the protrusion, and various known methods can be used.
  • the piezoelectric layer 20 includes piezoelectric particles 36 in the matrix 34. Further, a first electrode layer 24 and a second electrode layer 26 are provided so as to sandwich the piezoelectric layer 20 in the thickness direction.
  • a voltage is applied to the first electrode layer 24 and the second electrode layer 26 of the piezoelectric film 10 having such a piezoelectric layer 20
  • the piezoelectric particles 36 expand and contract in the polarization direction according to the applied voltage.
  • the piezoelectric film 10 contracts in the thickness direction.
  • the piezoelectric film 10 also expands and contracts in the in-plane direction due to Poisson's ratio. This expansion/contraction is approximately 0.01 to 0.1%.
  • the thickness of the piezoelectric layer 20 is preferably about 10 to 300 ⁇ m. Therefore, the expansion and contraction in the thickness direction is very small, about 0.3 ⁇ m at most.
  • the piezoelectric film 10, that is, the piezoelectric layer 20 has a size much larger than its thickness in the plane direction. Therefore, for example, if the length of the piezoelectric film 10 is 20 cm, the piezoelectric film 10 expands and contracts by a maximum of about 0.2 mm in the plane direction by applying a voltage.
  • the diaphragm 102 is attached to the piezoelectric film 10 (piezoelectric element 50) with an adhesive layer. Therefore, the diaphragm 102 is bent by the expansion and contraction of the piezoelectric film 10, and as a result, the diaphragm 102 vibrates in the thickness direction. Due to this vibration in the thickness direction, the diaphragm 102 generates sound. That is, the diaphragm 102 vibrates according to the magnitude of the voltage (driving voltage) applied to the piezoelectric film 10 and generates sound according to the driving voltage applied to the piezoelectric film 10.
  • the sound pressure level can be improved by adjusting the mass of the piezoelectric film 10 (piezoelectric element 50) according to the spring constant of the diaphragm 102. If the mass of the piezoelectric element 50 is large, the diaphragm 102 will bend, which may suppress the vibration of the diaphragm 102 during driving. On the other hand, when the mass of the piezoelectric element 50 is small, the resonance frequency becomes high, and vibration of the diaphragm 102 at low frequencies may be suppressed. Considering these points, it is preferable that the mass of the piezoelectric element 50 is appropriately adjusted according to the spring constant of the diaphragm 102.
  • the piezoelectric films 10 are adhered to each other by an adhesive layer 19.
  • an adhesive layer 19 for adhering the piezoelectric films 10 to each other various known ones can be used as long as they are capable of adhering adjacent piezoelectric films 10 to each other.
  • the same material as the adhesive layer 104 to be adhered can be used.
  • a sheet-like material 11a shown in FIG. 14 in which the first electrode layer 24 is formed on the surface of the first protective layer 28 is prepared. Furthermore, a sheet-like material 11c, conceptually shown in FIG. 16, in which a second electrode layer 26 is formed on the surface of a second protective layer 30 is prepared.
  • the sheet-like material 11a and the sheet-like material 11c are the first laminate in the present invention.
  • the sheet-like material 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 evaporation, sputtering, plating, or the like.
  • the sheet-like material 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 evaporation, sputtering, plating, or the like.
  • a commercially available sheet material in which a copper thin film or the like is formed on a protective layer may be used as the sheet material 11a and/or the sheet material 11c.
  • the sheet-like material 11a and the sheet-like material 11c may be the same or different.
  • 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 thermocompression bonding of the electrode layer and the protective layer.
  • the prepared sheet-like materials 11a and 11c are subjected to heat treatment to adjust the creep deformation rate.
  • the conditions for the heat treatment are not particularly limited as long as the difference from the creep deformation rate of the piezoelectric film can be reduced, and may be appropriately set depending on the materials, thicknesses, etc. of the protective layer and the electrode layer. For example, if you want to lower the creep deformation rate, it is estimated that by leaving the protective layer at a temperature and humidity within the range where the polymer can move for a long time, the internal crystallinity will increase and the creep deformation rate will decrease. Therefore, it is preferable to perform the heat treatment at a predetermined temperature for a long time. For example, it is preferable to heat at a temperature of 55° C. to 100° C. for 24 hours to 144 hours.
  • the creep deformation rate of the first laminate can also be controlled by changing the stretching conditions when producing the protective layer by biaxial stretching.
  • a paint (coating composition) that will become the piezoelectric layer 20 is applied onto the first electrode layer 24 of the sheet-like material 11a, and then cured to form the piezoelectric layer 20.
  • a laminate 11b in which the sheet-like material 11a and the piezoelectric layer 20 are laminated is produced.
  • a polymer material such as the above-mentioned cyanoethylated PVA is dissolved in an organic solvent, and then piezoelectric particles 36 such as PZT particles are added and stirred to prepare a paint.
  • organic solvent there are no restrictions on the organic solvent, 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 (coated) on the sheet-like material 11a, and the organic solvent is evaporated and dried.
  • a laminate 11b having the first electrode layer 24 on the first protective layer 28 and the piezoelectric layer 20 stacked on the first electrode layer 24 is manufactured. .
  • coating method there are no restrictions on the coating method, and all known methods (coating devices) such as a bar coater, slide coater, and doctor knife can be used.
  • coating devices such as a bar coater, slide coater, and doctor knife can be used.
  • the polymeric material is heat-meltable, the polymeric material is heated and melted, the piezoelectric particles 36 are added thereto to produce a melted product, and the sheet shown in FIG. 14 is formed by extrusion molding or the like.
  • a laminate 11b as shown in FIG. 15 may be produced by extruding it in a sheet form onto the shaped material 11a and cooling it.
  • the matrix 34 may contain a polymeric piezoelectric material such as PVDF (Polyvinylidene DiFluoride) in addition to the polymeric material that has viscoelasticity at room temperature.
  • PVDF Polyvinylidene DiFluoride
  • the polymer piezoelectric materials to be added to the paint may be dissolved.
  • the polymeric piezoelectric material to be added may be added to a polymeric material that is heated and melted and has viscoelasticity at room temperature, and then heated and melted.
  • calendaring may be performed if necessary. Calendar processing may be performed once or multiple times.
  • calendering is a process in which a surface to be treated is heated and pressed using a heated press, a heated roller, etc. to flatten the surface.
  • 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.
  • polarization treatment of the piezoelectric layer 20 may be performed before the calender treatment, it is preferably performed after the calender treatment.
  • any known method can be used. For example, electric field poling is exemplified, in which a DC electric field is directly applied to an object to be polarized.
  • 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. . Furthermore, in the piezoelectric film 10 of the present invention, it is preferable that the polarization treatment is performed not in the plane direction of the piezoelectric layer 20 but in the thickness direction.
  • the previously prepared sheet material 11c is laminated on the piezoelectric layer 20 side of the polarized stack 11b with the second electrode layer 26 facing the piezoelectric layer 20. . Further, this laminate is thermocompressed using a hot press device, a heated roller, etc., with the first protective layer 28 and the second protective layer 30 sandwiched therebetween, thereby bonding the laminate 11b and the sheet-like material 11c.
  • the piezoelectric film 10 as shown in FIG. 1 is produced by bonding them together.
  • the piezoelectric film 10 may be produced by bonding the laminate 11b and the sheet-like material 11c together using an adhesive, and preferably further press-bonding them. As the adhesive at this time, the same material as the matrix of the piezoelectric layer 20 can be used.
  • this piezoelectric film 10 may be manufactured using a cut sheet-like sheet material 11a, a sheet-like material 11c, etc., or may be manufactured using a roll-to-roll method. Good too.
  • the produced piezoelectric film is subjected to heat treatment in order to adjust the creep deformation rate.
  • the conditions for the heat treatment are not particularly limited as long as the difference from the creep deformation rate of the first laminate can be made small, and may be appropriately set depending on the material, thickness, etc. of the piezoelectric layer. For example, if you want to lower the creep deformation rate, leave the piezoelectric layer at a temperature and humidity within the range that allows the polymer to move for a long time to increase the internal crystallinity and lower the creep deformation rate. Therefore, it is preferable to perform heating and humidification treatment at a predetermined temperature for a long time. As an example, it is preferable to perform heating and humidification at a temperature of 45° C. to 65° C. and a relative humidity of 70% to 90% for 24 hours to 144 hours.
  • the produced piezoelectric film may be cut into desired shapes according to various uses. Further, the heat treatment may be performed after cutting.
  • the piezoelectric film 10 produced in this manner is polarized not in the plane direction but in the thickness direction, and has great piezoelectric properties even without stretching after polarization. Therefore, the piezoelectric film 10 has no in-plane anisotropy in its piezoelectric properties, and when a driving voltage is applied, it expands and contracts isotropically in all directions in the plane.
  • Example 1 [Preparation of piezoelectric film] A piezoelectric film as shown in FIG. 1 was produced by the method shown in FIGS. 14 to 16 described above. First, cyanoethylated PVA (CR-V, manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved in methyl ethyl ketone (MEK) in the following composition ratio. Thereafter, PZT particles as piezoelectric particles were added to this solution in the composition ratio shown below, and the mixture was stirred with a propeller mixer (rotation speed: 2000 rpm) to prepare a paint for forming a piezoelectric layer.
  • cyanoethylated PVA CR-V, manufactured by Shin-Etsu Chemical Co., Ltd.
  • MEK methyl ethyl ketone
  • ⁇ PZT particles 300 parts by mass ⁇ Cyanoethylated PVA: 30 parts by mass ⁇ Methyl ethyl ketone: 70 parts by mass
  • Commercially available PZT raw material powder was sintered at 1000 to 1200°C, then crushed and classified to an average particle size of 5 ⁇ m.
  • a sheet-like product (first laminate) was prepared by vacuum-depositing a 0.3- ⁇ m-thick copper thin film onto a 4- ⁇ m-thick PET film. That is, in this example, the first electrode layer and the second electrode layer are copper vapor deposited thin films with a thickness of 0.3 ⁇ m, and the first protective layer and the second protective layer are PET films with a thickness of 4 ⁇ m.
  • This sheet-like material (first laminate) was subjected to heat treatment at a temperature of 90° C. for 72 hours.
  • the previously prepared paint for forming the piezoelectric layer was applied onto the first electrode layer (copper deposited thin film) of the sheet using a slide coater.
  • the coating material was applied so that the thickness of the coating film after drying was 50 ⁇ m.
  • the sheet material coated with the paint was heated and dried on a hot plate at 50° C. to evaporate the methyl ethyl ketone.
  • a laminate was produced that had a first electrode layer made of copper on a first protective layer made of PET, and a piezoelectric layer (polymer composite piezoelectric layer) with a thickness of 50 ⁇ m thereon. .
  • the produced piezoelectric layer was polarized in the thickness direction.
  • a sheet-like material in which the same thin film was deposited on a PET film was laminated 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 to adhere and bond the piezoelectric layer and the second electrode layer.
  • a piezoelectric film as shown in 1 was produced.
  • the produced piezoelectric film was subjected to heat treatment for 48 hours at a temperature of 60° C. and a humidity of 90% RH.
  • a sample of 4 mm x 20 mm was cut out from the piezoelectric film after heat treatment, set in a thermomechanical analyzer (TMA402 manufactured by NETZSCH) so that the distance between the chucks in the longitudinal direction was approximately 10 mm, and then the temperature was set to 25 °C.
  • a tensile stress of 0.2 N/mm 2 in the length direction was applied, and the length in this state was defined as the reference position dimension A before creep.
  • the temperature was raised at a rate of 10° C./min to reach 90° C.
  • a tensile stress of 10 N/mm 2 was applied and heat treatment was performed for 3 hours.
  • the temperature was lowered to 25°C at a rate of 10°C/min while applying a tensile stress of 10 N/mm 2 , and after the temperature reached 25°C, the tensile stress was set to 0.2 N/mm 2 , and then The dimension after 10 minutes was defined as the dimension B after creep.
  • the creep deformation rate was determined from the formula (B-A)/A [%]. As a result of the measurement, the creep deformation rate of the piezoelectric film was 0.4%.
  • the end of the piezoelectric film was cut into strips with a width of 8 mm and a length of 24 mm using a cutter so that the four sides were exposed to the atmosphere, and then immersed in MEK for 48 hours. ) was eluted, and the first laminate of the protective layer and electrode layer was taken out.
  • the first laminate of the protective layer and the electrode layer was cut into strips with a width of 4 mm and a length of 20 mm, and placed in a thermomechanical analyzer (TMA402 manufactured by NETZSCH) so that the distance between the chucks in the longitudinal direction was approximately 10 mm.
  • the temperature was set to 25° C., a tensile stress of 0.2 N/mm 2 was applied in the length direction, and the length in this state was taken as the reference position dimension A before creep.
  • the temperature was raised at a rate of 10° C./min to reach 90° C.
  • a tensile stress of 10 N/mm 2 was applied and heat treatment was performed for 3 hours.
  • the temperature was lowered to 25°C at a rate of 10°C/min while applying a tensile stress of 10 N/mm 2 , and after the temperature reached 25°C, the tensile stress was set to 0.2 N/mm 2 , and then The dimension after 10 minutes was defined as the dimension B after creep.
  • the creep deformation rate was determined from the formula (BA)/A [%]. As a result of the measurement, the creep deformation rate of the first laminate was 1.4%. Therefore, the difference between the creep deformation rate of the piezoelectric film and the creep deformation rate of the first laminate was 1.0.
  • Examples 2-4, Comparative Examples 1-2 A piezoelectric film was produced in the same manner as in Example 1, except that the heat treatment conditions for the first laminate and the heat treatment conditions for the piezoelectric film were changed as shown in Table 1. The creep deformation rate of the first laminate and the creep deformation rate of the piezoelectric film in each Example and Comparative Example were measured in the same manner as in Example 1.
  • the produced piezoelectric film was cut out into a size of 150 mm x 200 mm and attached to a PET board with a thickness of 0.2 mm and a size of 400 mm x 500 mm.
  • a PET board to which a piezoelectric film was attached was wound up into a cylindrical member with a diameter of 40 mm, and an accelerated test was conducted at a temperature of 70° C. for 48 hours to simulate long-term storage. After the accelerated test, the PET board to which the piezoelectric film was attached was stretched, and the presence or absence of appearance defects was visually confirmed, and evaluated using the following criteria.
  • B Streak deformation was observed. The results are shown in Table 1.
  • Table 1 shows that the examples of the present invention can suppress appearance defects. From the above, the effects of the present invention are clear.
  • the piezoelectric film and piezoelectric element of the present invention can be used, for example, in the manufacture of various sensors such as sonic sensors, ultrasonic sensors, pressure sensors, tactile sensors, strain sensors, and vibration sensors (particularly for infrastructure inspections such as crack detection and foreign object detection).
  • sensors such as sonic sensors, ultrasonic sensors, pressure sensors, tactile sensors, strain sensors, and vibration sensors (particularly for infrastructure inspections such as crack detection and foreign object 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, and pest/vermin intrusion.
  • Examples include protective buzzers, furniture, wallpaper, photographs, helmets, goggles, headrests, signage, robots, etc.), haptics, ultrasonic probes, and hydrophones used in automobiles, smartphones, smart watches, games, etc.
  • ultrasonic transducers such as, actuators used for water droplet prevention, transportation, stirring, dispersion, polishing, etc., vibration dampers used for containers, vehicles, buildings, sports equipment such as skis and rackets, and roads, floors, etc. It can be suitably used as a vibration power generation device for use in mattresses, chairs, shoes, tires, wheels, computer keyboards, and the like.
  • Piezoelectric film 11a 11c Sheet-like material (first laminate) 11b Laminated body 19, 104 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 particles 50 Piezoelectric element 58 Core rod 100 Electroacoustic transducer 102 Diaphragm 110 Flexible display

Landscapes

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

Abstract

L'invention concerne un film piézoélectrique, un élément piézoélectrique et un transducteur électroacoustique capables de supprimer l'apparition d'une mauvaise apparence lorsqu'ils sont stockés pendant une longue période à l'état enroulé.　Un film piézoélectrique ayant une couche piézoélectrique composée d'un corps piézoélectrique composite polymère contenant des particules piézoélectriques dans une matrice contenant un matériau polymère, deux couches d'électrodes respectivement prévues sur les deux surfaces de la couche piézoélectrique, et des couches de protection respectivement prévues sur les couches d'électrodes, dans lequel la différence entre le rapport de déformation de fluage du film piézoélectrique et le rapport de déformation de fluage d'un premier corps en couches composé d'une couche d'électrodes et d'une couche de protection est de 1,5 % ou moins.
PCT/JP2023/005174 2022-03-30 2023-02-15 Film piézoélectrique, élément piézoélectrique et transducteur électroacoustique WO2023188929A1 (fr)

Applications Claiming Priority (2)

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JP2022055425 2022-03-30
JP2022-055425 2022-03-30

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WO2023188929A1 true WO2023188929A1 (fr) 2023-10-05

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6414981A (en) * 1987-07-09 1989-01-19 Ube Industries Vertical effect type monomorph element and method of driving same
WO2021225071A1 (fr) * 2020-05-07 2021-11-11 富士フイルム株式会社 Élément piézoélectrique et haut-parleur piézoélectrique

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6414981A (en) * 1987-07-09 1989-01-19 Ube Industries Vertical effect type monomorph element and method of driving same
WO2021225071A1 (fr) * 2020-05-07 2021-11-11 富士フイルム株式会社 Élément piézoélectrique et haut-parleur piézoélectrique

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