WO2023053750A1 - Élément piézoélectrique et convertisseur électro-acoustique - Google Patents

Élément piézoélectrique et convertisseur électro-acoustique Download PDF

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Publication number
WO2023053750A1
WO2023053750A1 PCT/JP2022/030855 JP2022030855W WO2023053750A1 WO 2023053750 A1 WO2023053750 A1 WO 2023053750A1 JP 2022030855 W JP2022030855 W JP 2022030855W WO 2023053750 A1 WO2023053750 A1 WO 2023053750A1
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Prior art keywords
piezoelectric
layer
piezoelectric element
electrode layer
projecting portion
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PCT/JP2022/030855
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English (en)
Japanese (ja)
Inventor
栄貴 小沢
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富士フイルム株式会社
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Priority to CN202280060037.6A priority Critical patent/CN117957858A/zh
Priority to JP2023550437A priority patent/JPWO2023053750A1/ja
Publication of WO2023053750A1 publication Critical patent/WO2023053750A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers
    • H04R17/02—Microphones

Definitions

  • the present invention relates to piezoelectric elements and electroacoustic transducers.
  • Piezoelectric elements are used for various purposes as so-called exciters, which vibrate and produce sound by attaching them to various items. For example, by attaching an exciter to an image display panel, a screen, or the like and vibrating them, sound can be produced instead of a speaker.
  • piezoelectric element As a piezoelectric element, it has been proposed to use a piezoelectric film in which a piezoelectric layer is sandwiched between electrode layers and protective layers. It is also proposed to laminate a plurality of piezoelectric films and use them as a piezoelectric element.
  • Patent Document 1 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 kHz by dynamic viscoelasticity measurement has a maximum value of 0.1 or more in the temperature range of more than 50 ° C. and 150 ° C. or less, and the value at 50 ° C. is 0.08 or more.
  • a piezoelectric film is described.
  • Patent Document 1 describes a piezoelectric element in which a piezoelectric film is folded one or more times to laminate a plurality of piezoelectric films.
  • a piezoelectric element made by folding a piezoelectric film is attached to a diaphragm, and by vibrating the diaphragm, the diaphragm generates sound.
  • a projection projecting in the plane direction is provided from the laminated part in which the piezoelectric films are laminated, and the external power supply is connected to the electrode layer at this projection. is considered.
  • a piezoelectric element formed by laminating piezoelectric films is capable of suppressing variations in sound pressure while suppressing heat generation. and to provide an electroacoustic transducer.
  • a piezoelectric film having a piezoelectric layer, electrode layers provided on both sides of the piezoelectric layer, and protective layers provided on the electrode layers is folded once or more to form a piezoelectric film having a plurality of layers,
  • a piezoelectric element formed by lamination In a plan view, the piezoelectric film has a projecting portion projecting from a laminated portion in which two or more layers are stacked, The protruding part has a connection part for connecting the electrode layer and an external power supply,
  • a piezoelectric element and an electroacoustic transducer that can suppress variations in sound pressure while suppressing heat generation in a piezoelectric element formed by laminating piezoelectric films.
  • FIG. 2 is a perspective view of the piezoelectric element shown in FIG. 1;
  • FIG. 2 is a plan view of the piezoelectric element shown in FIG. 1;
  • FIG. 4 is a diagram for explaining the area of a laminated portion, the area of a protruding portion, and the length of a side where the protruding portion and the laminated portion are in contact;
  • FIG. 4 is a plan view schematically showing another example of the piezoelectric element of the present invention;
  • FIG. 4 is a plan view schematically showing another example of the piezoelectric element of the present invention;
  • FIG. 4 is a plan view schematically showing another example of the piezoelectric element of the present invention;
  • FIG. 4 is a plan view schematically showing another example of the piezoelectric element of the present invention;
  • FIG. 4 is a plan view schematically showing another example of the piezoelectric element of the present invention;
  • FIG. 1 is a perspective view of the piezoelectric element shown in FIG.
  • FIG. 4 is a plan view schematically showing another example of the piezoelectric element 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. It is a conceptual diagram for explaining an example of a method of manufacturing a piezoelectric film.
  • 1 is a diagram schematically showing an example of an electroacoustic transducer of the present invention having a piezoelectric element of the present invention; FIG.
  • a numerical range represented by "-" means a range including the numerical values before and after "-" as lower and upper limits.
  • the piezoelectric element of the present invention is A piezoelectric film having a piezoelectric layer, electrode layers provided on both sides of the piezoelectric layer, and protective layers provided on the electrode layers is folded one or more times to laminate a plurality of piezoelectric films.
  • a piezoelectric element that In a plan view, the piezoelectric film has a projecting portion projecting from a laminated portion in which two or more layers are stacked,
  • the protruding part has a connection part for connecting the electrode layer and an external power supply,
  • the ratio of the area of the projecting portion to the area of the laminated portion is in the range of 0.02 to 0.3, and the length of the side where the projecting portion is in contact with the laminated portion is 4 mm or more.
  • FIG. 1 shows a side view schematically showing an example of the piezoelectric element of the present invention.
  • FIG. 2 shows a perspective view of the piezoelectric element of FIG.
  • FIG. 3 shows a plan view of the piezoelectric element of FIG. Note that the plan view is a view of the piezoelectric film 10 laminated in a plurality of layers and viewed from the lamination direction.
  • the piezoelectric element 50a shown in FIGS. 1 to 3 is obtained by laminating five layers of the piezoelectric film 10 by folding one rectangular piezoelectric film 10 four times in one direction. That is, this piezoelectric element 50a is a laminated piezoelectric element in which five layers of piezoelectric films 10 are laminated. 2, the piezoelectric film 10 has electrode layers on both sides of the piezoelectric layer 20, covering both electrode layers and It has a protective layer. Further, in the following description, the direction in which the piezoelectric film 10 is folded back (horizontal direction in FIG. 1) is referred to as the folding direction.
  • the piezoelectric element 50a has a protruding portion 10a that protrudes outward in the plane direction from a laminated portion 10b in which five layers of piezoelectric films 10 are superimposed. That is, when one piezoelectric film 10 is folded back four times, the piezoelectric element 50a is arranged so that the four layers from the bottom side in FIG. By making the length of the piezoelectric film 10, which is the side layer, longer than the piezoelectric films 10 of the other layers so that one end in the folding direction does not overlap the piezoelectric films 10 of the other layers, the projecting portion 10a is formed. It was established.
  • the layers of the piezoelectric film 10 adjacent to each other in the laminated portion 10b are adhered by the adhesive layer 14.
  • the laminated portion 10b is a region in which two or more layers of piezoelectric films overlap in plan view, ie, when the piezoelectric element is viewed from above (or below) in FIG. That is, as shown in FIG. 3, the area where five layers of the piezoelectric film 10 overlap is the laminated portion 10b.
  • the protruding portion 10a is a region that protrudes in the plane direction from the laminated portion 10b, and is a region that does not overlap with other layers in plan view.
  • the right end of the uppermost layer is the projecting portion 10a.
  • the projecting portion 10a is formed with a connection portion 40 for connecting the first electrode layer 24 and the second electrode layer 26 (hereinafter collectively referred to as electrode layers) to an external electrode. It is In the illustrated example, through holes are formed in the protective layers (the first protective layer 28 and the second protective layer 30) of the protrusion 10a to expose the electrode layer and provide the connecting section 40. As shown in FIG.
  • the method for forming the through-holes is not limited, and known methods such as laser processing, removal by dissolution using a solvent, and mechanical processing such as mechanical polishing may be used depending on the material for forming the protective layer. .
  • the connecting portion 40 is connected to a wiring that is filled with a known conductive material such as a conductive metal paste such as silver paste, a conductive carbon paste, and a conductive nanoink and is connected to an external power supply.
  • a known conductive material such as a conductive metal paste such as silver paste, a conductive carbon paste, and a conductive nanoink.
  • the piezoelectric element 50a of the present invention drives the piezoelectric element 50a by applying a voltage to the electrode layer using an external power source via the connecting portion 40 provided on the projecting portion 10a.
  • the piezoelectric element 50a expands and contracts in the plane direction, bending the diaphragm to which the piezoelectric element 50a is attached, and as a result vibrating the diaphragm to generate sound.
  • the diaphragm vibrates according to the magnitude of the driving voltage applied to the piezoelectric element 50a, and generates sound according to the driving voltage applied to the piezoelectric element 50a. That is, the piezoelectric element 50a can be used as an exciter.
  • the protruding portion 10a when a voltage is applied from the connecting portion 40 between the electrode layer provided on the protruding portion 10a and the external power supply to drive the piezoelectric element 50a, the protruding portion 10a generates heat remarkably. , thermal runaway may occur and continuous drive may not be possible. In order to suppress such heat generation, it is preferable that the area of the projecting portion 10a is large.
  • the length Ya of the side where the projecting portion 10a and the laminated portion 10b are in contact is 4 mm or more.
  • the ratio Ps of the area Sa of the protruding portion 10a to the area Sb of the laminated portion 10b is too small, that is, if the area Sa of the protruding portion 10a is too small, when a voltage is applied to the piezoelectric element 50a, a current is generated in the protruding portion 10a. Density increases. Therefore, the protruding portion 10a generates heat remarkably. Also, if the length Ya of the side where the projecting portion 10a and the laminated portion 10b contact each other is too short, the current density at the projecting portion 10a also becomes high, resulting in significant heat generation at the projecting portion 10a.
  • the ratio Ps of the area Sa of the projecting portion 10a to the area Sb of the laminated portion 10b is set to 0.02 or more, that is, the area Sa of the projecting portion 10a is increased. Accordingly, it is possible to suppress an increase in current density in the protruding portion 10a, thereby suppressing heat generation of the protruding portion 10a. Further, by setting the length Ya of the side where the protruding portion 10a and the laminated portion 10b are in contact with each other to 4 mm or more, it is possible to suppress an increase in the current density in the protruding portion 10a and suppress the heat generation of the protruding portion 10a. .
  • the ratio Ps of the area Sa of the protruding portion 10a to the area Sb of the laminated portion 10b is too large, that is, if the area Sa of the protruding portion 10a is too large, when a plurality of piezoelectric elements 50a having the same specifications are manufactured, , there is a problem that the variation of the sound pressure, especially in the high frequency band, becomes large.
  • the protrusion 10a when the protrusion 10a is provided, when the piezoelectric element 50a is driven, the protrusion 10a also vibrates and generates a sound. It is presumed that the sound pressure generated from the protruding portion 10a varies due to variations, variations in the state of warping, and the like. Since the size of the projecting portion 10a is smaller than the diaphragm to which the piezoelectric element 50a is adhered, the variation in sound pressure generated from the projecting portion 10a has a greater effect especially in a high frequency band.
  • the ratio Ps of the area Sa of the projecting portion 10a to the area Sb of the laminated portion 10b is 0.3 or less, that is, the area Sa of the projecting portion 10a is reduced. Therefore, variations in the shape of the projecting portion 10a, variations in the state of warping, etc. can be reduced, and variations in sound pressure can be reduced.
  • the length Ya of the side where the protruding portion 10a and the laminated portion 10b are in contact is preferably 4 mm or longer, more preferably 10 mm or longer, and even more preferably 20 mm or longer.
  • the ratio Ps of the area Sa of the projecting portion 10a to the area Sb of the laminated portion 10b is preferably 0.02 or more, more preferably 0.04 or more, and 0.06 or more. is more preferred.
  • the ratio Ps of the area Sa of the projecting portion 10a to the area Sb of the laminated portion 10b is preferably 0.3 or less, more preferably 0.2 or less, and 0.1 or less. More preferred.
  • FIG. 4 is a plan view of the piezoelectric element 50a.
  • the area Sb of the laminated portion 10b and the area Sa of the projecting portion 10a are the areas in plan view.
  • the area Sb of the laminated portion 10b is Lb ⁇ Wb, where Lb is the length in the folded direction of the laminated portion 10b in plan view, and Wb is the width in the direction orthogonal to the folded direction.
  • the area Sa of the projection 10a is La ⁇ Wa.
  • the width Wa of the projecting portion 10a and the width Wb of the laminated portion 10b are the same.
  • the length Ya of the side where the protruding portion 10a and the laminated portion 10b are in contact is the same as the width Wa of the protruding portion 10a (the width Wb of the laminated portion 10b).
  • the width Wa of the protruding portion 10a is substantially the same as the width Wb of the laminated portion 10b, but it is not limited to this.
  • FIG. 5 shows a plan view of another example of the piezoelectric element of the present invention.
  • a piezoelectric element 50b shown in FIG. 5 has a rectangular laminated portion 10b and a rectangular protruding portion 10a, and the width Wa of the protruding portion 10a is shorter than the width Wb of the laminated portion 10b. Therefore, the length Ya of the side where the protruding portion 10a and the laminated portion 10b contact is the same as the width Wa of the protruding portion 10a.
  • the protruding portion 10a is arranged substantially in the center in the width direction of the laminated portion 10b, but is not limited to this, and is arranged at any position in the width direction of the laminated portion 10b. may be
  • the projecting portion 10a has a substantially square shape, but is not limited to this and may have a rectangular shape.
  • the width direction of the projecting portion 10a may be the long side of the rectangle, or the length direction (folding direction) of the projecting portion 10a may be the long side of the rectangle.
  • the shape of the projecting portion 10a is not limited to a rectangular shape.
  • the shape of the projecting portion 10a may have a polygonal shape such as a hexagonal shape. It may be in shape.
  • the protruding portion 10a is configured to protrude from the laminated portion 10b in the folding direction, but the present invention is not limited to this.
  • the protruding portion 10a may be configured to protrude from the laminated portion 10b in the width direction orthogonal to the folding direction.
  • the length La of the projecting portion 10a in the folding direction is equal to the length Ya of the side where the projecting portion and the laminated portion are in contact with each other.
  • the piezoelectric element is configured to have one projecting portion, but the configuration is not limited to this.
  • FIG. 8 shows a plan view of another example of the piezoelectric element of the present invention.
  • a piezoelectric element 50e shown in FIG. 8 has a rectangular laminated portion 10b and a plurality of rectangular protruding portions 10a arranged on one side of the laminated portion 10b.
  • a connecting portion 40 for connecting the first electrode layer 24 and/or the second electrode layer 26 to an external electrode is formed on each projecting portion 10a.
  • Either one of the first electrode layer 24 and the second electrode layer 26 may be connected to an external electrode in one projecting portion 10a. It is preferable that both the first electrode layer 24 and the second electrode layer 26 are connected to the external electrode in one projecting portion 10a. That is, it is preferable that both the first electrode layer 24 and the second electrode layer 26 are connected to the external electrode in each of the plurality of protrusions 10a.
  • the area Sa of the protrusions 10a is the total area of the plurality of protrusions 10a. That is, the ratio of the total area of the plurality of projecting portions 10a to the area of the laminated portion 10b should be in the range of 0.02 to 0.3.
  • the length Ya of the side where the protruding portion 10a and the laminated portion 10b contact is the length Ya of the side of each protruding portion 10a that contacts the laminated portion 10b. Therefore, in each projecting portion 10a, the length Ya of the side in contact with the laminated portion 10b should be 4 mm or more.
  • the number of protrusions 10a is preferably 12 or less, more preferably 10 or less.
  • the piezoelectric element 50a shown in FIG. 1 is formed by laminating five layers of piezoelectric films 10, but the present invention is not limited to this. That is, the piezoelectric element may have two to four layers of the piezoelectric film 10, or may have six or more layers.
  • the piezoelectric elements 50a to 50e are collectively referred to as the piezoelectric element 50 when there is no need to distinguish them.
  • 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 preferably a polymeric composite piezoelectric body containing piezoelectric particles 36 in a matrix 34 containing a polymeric material, as conceptually shown in FIG.
  • 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 body preferably satisfies the following requirements.
  • 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.
  • the flexible polymer composite piezoelectric material used as an exciter is required to behave hard against vibrations of 20 Hz to 20 kHz and softly against vibrations of several Hz or less.
  • 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.
  • the spring constant can be easily adjusted by laminating according to the rigidity (hardness, stiffness, spring constant) of the mating material (diaphragm) to which the adhesive layer 104 is attached. The thinner it is, the more energy efficient it can be.
  • 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 polymer material having viscoelasticity at room temperature may use a plurality of polymer materials together, if necessary. That is, in addition to a viscoelastic material such as cyanoethylated PVA, other dielectric polymer materials may be added to the matrix 34 as necessary for the purpose of adjusting dielectric properties and mechanical properties.
  • a viscoelastic material such as cyanoethylated PVA
  • other dielectric polymer 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 may also include 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, ros
  • 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.
  • PZT lead zirconate titanate
  • PLAT lead zirconate lanthanate titanate
  • BaTiO 3 barium titanate
  • ZnO zinc oxide
  • BFBT solid solution
  • 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 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 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
  • 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 element 50, and It may be appropriately set according to the characteristics required for the piezoelectric element 50 .
  • 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 element 50 , the number of layers of the piezoelectric film in the piezoelectric element 50 , the properties required of the piezoelectric film 10 , and the like. , should be set.
  • the thickness of the piezoelectric layer 20 is preferably 10 to 300 ⁇ m, more preferably 20 to 200 ⁇ m, even more preferably 30 to 150 ⁇ m.
  • the piezoelectric layer 20 is preferably polarized (poled) in the thickness direction.
  • the piezoelectric layer 20 is a polymeric composite piezoelectric body containing piezoelectric particles 36 in a matrix 34 made of a polymer material having viscoelasticity at room temperature, such as cyanoethylated PVA, as described above. No restrictions. That is, in the piezoelectric film 10 of the present invention, various known piezoelectric layers can be used as the piezoelectric layer.
  • a high-performance dielectric material containing similar piezoelectric particles 36 in a matrix containing a dielectric polymer material such as the polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene copolymer, and vinylidene fluoride-trifluoroethylene copolymer described above may be used.
  • Molecular composite piezoelectric material, piezoelectric layer made of polyvinylidene fluoride, piezoelectric layer made of fluorine resin other than polyvinylidene fluoride, piezoelectric layer made by laminating a film made of poly-L-lactic acid and a film made of poly-D-lactic acid, etc. is also available.
  • 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 second electrode layer 26 and the second protective layer 30 as well as the first electrode layer 24 and the first protective layer 28 are attached for the sake of convenience in describing the piezoelectric film 10 . Therefore, the first and second aspects of the present invention have no technical significance and are irrelevant to the actual usage conditions.
  • the piezoelectric film 10 includes, in addition to these layers, an adhesive layer for attaching the electrode layer and the piezoelectric layer 20 and an adhesive layer for attaching the electrode layer and the protective layer. It may have a layer.
  • the adhesive may be an adhesive or an adhesive.
  • the same material as the matrix 34 that is, the polymer material obtained by removing the piezoelectric particles 36 from the piezoelectric layer 20, can be preferably used as the adhesive.
  • 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 on only one of the first electrode layer 24 side and the second electrode layer 26 side. good.
  • the second protective layer 30 and the first protective layer 28 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 second protective layer 30 and the first protective layer 28 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 second protective layer 30 and the first protective layer 28 are also not limited. Also, the thicknesses of the second protective layer 30 and the first protective layer 28 are basically the same, but may be different. Here, if the rigidity of the second protective layer 30 and the first protective layer 28 is too high, not only will the expansion and contraction of the piezoelectric layer 20 be constrained, but also the flexibility will be impaired. Therefore, the thinner the second protective layer 30 and the first protective layer 28, the better, except when mechanical strength and good handling properties as a sheet-like article are required.
  • the thicknesses of the second protective layer 30 and the first protective layer 28 are 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 second protective layer 30 and the first protective layer 28 are made of PET, the thicknesses of the second protective layer 30 and the first protective layer 28 are preferably 100 ⁇ m or less. 50 ⁇ m or less is more preferable, and 25 ⁇ m or less is even more preferable.
  • the second electrode layer 26 is provided between the piezoelectric layer 20 and the second protective layer 30, and the first electrode layer 24 is provided between the piezoelectric layer 20 and the first protective layer 28. It is formed.
  • the second electrode layer 26 and the first electrode layer 24 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 second electrode layer 26 and the first electrode layer 24 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 second electrode layer 26 and the first electrode layer 24 .
  • copper is more preferable from the viewpoint of conductivity, cost, flexibility, and the like.
  • the method of forming the second electrode layer 26 and the first electrode layer 24 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.
  • thin films of copper, aluminum, or the like formed by vacuum deposition are preferably used as the second electrode layer 26 and the first electrode layer 24 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 second electrode layer 26 and the first electrode layer 24 are not limited. Also, the thicknesses of the second electrode layer 26 and the first electrode layer 24 are basically the same, but may be different.
  • the second protective layer 30 and the first protective layer 28 if the rigidity of the second electrode layer 26 and the first electrode layer 24 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 second electrode layer 26 and the first electrode layer 24, the better, as long as the electrical resistance does not become too high.
  • the product of the thickness of the second electrode layer 26 and the first electrode layer 24 and the Young's modulus is less than the product of the thickness of the second protective layer 30 and the first protective layer 28 and the Young's modulus , is preferred because it does not significantly impair flexibility.
  • the second protective layer 30 and the first protective layer 28 are made of PET (Young's modulus: about 6.2 GPa), and the second electrode layer 26 and the first electrode layer 24 are made of copper (Young's modulus: about 130 GPa).
  • the thickness of the second protective layer 30 and the first protective layer 28 is 25 ⁇ m
  • the thickness of the second electrode layer 26 and the first electrode layer 24 is preferably 1.2 ⁇ m or less, more preferably 0.3 ⁇ m or less. , it is preferably 0.1 ⁇ m or less.
  • the piezoelectric film 10 includes the piezoelectric layer 20 formed by dispersing the piezoelectric particles 36 in the matrix 34 containing a polymer material, sandwiched between the second electrode layer 26 and the first electrode layer 24, and This laminate has a structure in which the second protective layer 30 and the first protective layer 28 are sandwiched.
  • the maximum value of the loss tangent (Tan ⁇ ) at a frequency of 1 Hz by dynamic viscoelasticity measurement preferably exists at room temperature, and the maximum value of 0.1 or more exists at room temperature. more preferred.
  • 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.
  • a power source (external power source) is connected to the second electrode layer 26 and the first electrode layer 24 of the piezoelectric film 10 to apply a drive voltage for expanding and contracting the piezoelectric film 10 , that is, to supply drive power.
  • the power source may be a DC power source or an AC power source.
  • 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.
  • electrodes are led out from the second electrode layer 26 and the first electrode layer 24 at the projecting portion 10a.
  • the method of extracting electrodes from the second electrode layer 26 and the first electrode layer 24 there are no restrictions on the method of extracting electrodes from the second electrode layer 26 and the first electrode layer 24, and various known methods can be used.
  • a method of connecting a conductor such as a copper foil to the second electrode layer 26 and the first electrode layer 24 to lead the electrodes to the outside and a method of penetrating the second protective layer 30 and the first protective layer 28 by a laser or the like.
  • Examples include a method of forming a hole, filling the through hole with a conductive material, and leading an electrode to the outside.
  • 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.
  • 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 12a having a second protective layer 30 and a second electrode layer 26 formed thereon as shown in FIG. 10 is prepared. Further, a sheet-like material 12c having the first electrode layer 24 formed on the surface of the first protective layer 28 conceptually shown in FIG. 12 is prepared.
  • the sheet 12a 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.
  • the sheet 12c 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.
  • a commercially available sheet having a copper thin film or the like formed on a protective layer may be used as the sheet 12a and/or the sheet 12c.
  • the sheet-like material 12a and the sheet-like material 12c 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 the electrode layer and protective layer are thermocompression bonded.
  • a paint (coating composition) that will form the piezoelectric layer 20 is applied onto the second electrode layer 26 of the sheet 12a, and then cured to form the piezoelectric layer 20.
  • a piezoelectric laminate 12b in which the sheet-like material 12a and the piezoelectric layer 20 are laminated is produced.
  • a piezoelectric layer 20 depending on the material forming the piezoelectric layer 20 .
  • 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.
  • the paint is cast (applied) on the sheet-like material 12a and dried by evaporating the organic solvent.
  • a piezoelectric laminate 12b having the second electrode layer 26 on the second protective layer 30 and the piezoelectric layer 20 laminated on the second electrode layer 26 is produced. do.
  • a piezoelectric layered body 12b as shown in FIG. 11 may be produced by extruding a sheet onto the shaped object 12a and cooling it.
  • the matrix 34 may be added with a polymeric piezoelectric material such as PVDF, in addition to the polymeric material having viscoelasticity at room temperature.
  • a polymeric piezoelectric material such as PVDF
  • 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 desired. 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 hot press, hot rollers, or the like to flatten the surface.
  • the piezoelectric layer 20 of the piezoelectric laminate 12b having the second electrode layer 26 on the second protective layer 30 and the piezoelectric layer 20 formed on the second electrode layer 26 is subjected to a polarization treatment ( polling).
  • the polarization treatment of the piezoelectric layer 20 may be performed before calendering, but is preferably performed after calendering.
  • 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.
  • the first electrode layer 24 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-like material 12c is laminated on the piezoelectric layer 20 side of the piezoelectric layered body 12b subjected to the polarization treatment, with the first electrode layer 24 facing the piezoelectric layer 20. do.
  • this laminate is thermocompression bonded using a hot press device, a heating roller, etc., with the first protective layer 28 and the second protective layer 30 sandwiched between them, thereby forming the piezoelectric laminate 12b and the sheet-like material 12c. are bonded together to produce a piezoelectric film 10 as shown in FIG.
  • the piezoelectric film 10 may be produced by bonding the piezoelectric laminate 12b and the sheet-like material 12c together using an adhesive and preferably further pressing them together.
  • the piezoelectric film 10 may be manufactured using the cut-sheet-like sheet-like material 12a and the sheet-like material 12c, etc., or may be manufactured using a roll-to-roll process. 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.
  • the adhesive layer 14 for attaching the piezoelectric films to each other various known adhesive layers can be used as long as the adjacent piezoelectric films 10 can be attached. Materials similar to the deposition layer 104 can be used.
  • the electroacoustic transducer of the present invention is This is an electroacoustic transducer in which the piezoelectric element described above is attached to a diaphragm.
  • FIG. 13 shows a diagram schematically showing an example of the electroacoustic transducer of the present invention having the piezoelectric element of the present invention.
  • the electroacoustic transducer 100 shown in FIG. 13 has the above-described piezoelectric element 50a, a diaphragm 102, and a bonding layer 104 for bonding the piezoelectric element 50a to the diaphragm 102.
  • the piezoelectric element 50a is attached to the diaphragm 102 on the laminated portion 9 on the side of the piezoelectric element 50a having the projecting portion 10a.
  • the diaphragm 102 has flexibility as a preferred embodiment.
  • having flexibility is synonymous with having flexibility in general interpretation, and indicates that it is possible to bend and bend, specifically , indicating that it can be bent and stretched without fracture and damage.
  • Diaphragm 102 is not 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 composed of polyethylene naphthalate (PEN), triacetyl cellulose (TAC), cyclic olefin resins, etc.; expanded polystyrene, expanded plastics composed of expanded styrene, expanded polyethylene, etc.; Examples include various corrugated cardboard materials made by pasting paperboards of the above.
  • the diaphragm 102 may be an organic electroluminescence (OLED (Organic Light Emitting Diode)) display, a liquid crystal display, a micro LED (Light Emitting Diode) display, as long as it has flexibility. , and display devices such as inorganic electroluminescence displays can also be suitably used.
  • OLED Organic Light Emitting Diode
  • liquid crystal display a liquid crystal display
  • micro LED Light Emitting Diode
  • display devices such as inorganic electroluminescence displays can also be suitably used.
  • the diaphragm 102 and the piezoelectric element 50 are adhered by the adhesion layer 104 .
  • the adhesive layer 104 has fluidity at the time of bonding and then becomes a solid. Even a layer made of an adhesive, which is a gel-like (rubber-like) soft solid at the time of bonding, remains gel-like after that. It may be a layer made of an adhesive that does not change its shape, or a layer made of a material that has the characteristics of both an adhesive and an adhesive.
  • the diaphragm 102 is bent and vibrated to generate sound. Therefore, in the electroacoustic transducer 100 , it is preferable that the expansion and contraction of the piezoelectric element 50 is directly transmitted to the diaphragm 102 . If a substance having a viscosity that reduces vibration is present between the diaphragm 102 and the piezoelectric element 50, the efficiency of transmission of the expansion and contraction energy of the piezoelectric element 50 to the diaphragm 102 is lowered, resulting in electroacoustic conversion. The driving efficiency of the device 100 is lowered.
  • the sticking layer 104 is preferably an adhesive layer made of an adhesive that provides a solid and hard sticking layer 104 rather than a sticky 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 104 is not limited, and the thickness that provides sufficient adhesive strength (adhesive strength, cohesive strength) may be appropriately set according to the material of the adhesive layer 104 .
  • the thinner the adhesive layer 104 the higher the effect of transmitting the stretching energy (vibrational energy) of the piezoelectric element 50 to the diaphragm 102, and the higher the energy efficiency.
  • the adhesive layer 104 is thick and rigid, it may restrict expansion and contraction of the piezoelectric element 50 .
  • the adhesive layer 104 is preferably thinner.
  • the thickness of the adhesive layer 104 is preferably 0.1 to 50 ⁇ m, more preferably 0.1 to 30 ⁇ m, and even more preferably 0.1 to 10 ⁇ m after being attached.
  • the adhesive layer 104 is provided as a preferred embodiment and is not an essential component. Therefore, the electroacoustic transducer 100 does not have the adhesive layer 104, and the diaphragm 102 and the piezoelectric element 50 may be fixed using known crimping means, fastening means, fixing means, or the like.
  • the shape of the piezoelectric element 50 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 element 50 expands and contracts independently of the diaphragm 102 when a drive voltage is applied from the power supply. is not transmitted to the diaphragm 102. In this way, when the piezoelectric element 50 expands and contracts independently of the diaphragm 102, the efficiency of vibration of the diaphragm 102 by the piezoelectric element 50 decreases. There is a possibility that the diaphragm 102 cannot be sufficiently vibrated. Considering this point, it is preferable that the vibration plate 102 and the piezoelectric element 50 are adhered with an adhesion layer 104 as shown in FIG.
  • the piezoelectric layer 20 contains the piezoelectric particles 36 in the matrix 34 .
  • a second electrode layer 26 and a first electrode layer 24 are provided so as to sandwich the piezoelectric layer 20 in the thickness direction.
  • the piezoelectric particles 36 expand and contract in the polarization direction according to the applied voltage.
  • the piezoelectric film 10 shrinks in the thickness direction.
  • the piezoelectric film 10 also expands and contracts in the in-plane direction. This expansion and contraction is about 0.01 to 0.1%.
  • the thickness of the piezoelectric layer 20 is preferably about 10-300 ⁇ m. Therefore, the expansion and contraction in the thickness direction is as small as about 0.3 ⁇ m at maximum.
  • the piezoelectric film 10, that is, the piezoelectric layer 20 has a size much larger than its thickness in the planar direction. Therefore, for example, if the length of the piezoelectric film 10 is 20 cm, the piezoelectric film 10 expands and contracts by about 0.2 mm at maximum due to voltage application.
  • the diaphragm 102 is attached to the piezoelectric film 10 with an adhesive layer 104 . Therefore, the expansion and contraction of the piezoelectric film 10 bends the diaphragm 102, 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. If the mass of the piezoelectric film 10 is large, the diaphragm 102 will be bent, which may suppress vibration of the diaphragm 102 during driving. On the other hand, if the mass of the piezoelectric film 10 is small, the resonance frequency will be high, possibly suppressing the vibration of the diaphragm 102 at low frequencies. Considering these points, it is preferable to appropriately adjust the mass of the piezoelectric film 10 according to the spring constant of the diaphragm 102 .
  • 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. Using a slide coater, the previously prepared paint for forming the piezoelectric layer was applied onto the second electrode layer (copper-deposited thin film) of the sheet-like material. In addition, the paint was applied so that the thickness of the coating film after drying was 50 ⁇ m. Next, the sheet-like material coated with the paint was dried by heating on a hot plate at 120° C.
  • a piezoelectric laminate having a second electrode layer made of copper on a second protective layer made of PET and a piezoelectric layer (polymer composite piezoelectric layer) having a thickness of 50 ⁇ m thereon is produced. bottom.
  • the produced piezoelectric layer was subjected to polarization treatment in the thickness direction.
  • a sheet-like material obtained by vapor-depositing the same thin film on a PET film was laminated on the piezoelectric laminate that had been subjected to the polarization treatment, with the first 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 first electrode layer.
  • a film was produced.
  • Example 1 The produced piezoelectric film was cut into a size of 170 mm x 150 mm, folded four times in the direction of the 170 mm side, and the piezoelectric films were laminated with an adhesive layer (acrylic adhesive) to form a laminated portion of length Lb 30 mm x width Wb 150 mm, A piezoelectric element having a protruding portion with a length La of 9 mm and a width of Wa of 150 mm was produced. A ratio Ps of the area Sa of the projecting portion to the area Sb of the laminated portion is 0.3. The length Ya of the side where the projecting portion and the laminated portion are in contact is 150 mm. Ten such piezoelectric elements were produced.
  • Example 2 Ten piezoelectric elements were produced in the same manner as in Example 1, except that there were 12 protrusions each having a length La of 11 mm and a width of Wa 10 mm (see FIG. 8). The ratio Ps of the (total) area Sa of the protrusions to the area Sb of the laminated part is 0.29. The length Ya of the side where the projecting portion and the laminated portion are in contact is 10 mm. In addition, the first electrode layer and the second electrode layer were connected to the external power source at each of the plurality of projecting portions.
  • Example 3 Ten piezoelectric elements were produced in the same manner as in Example 1, except that 14 projecting portions each having a length La of 9.5 mm and a width of Wa of 10 mm were provided.
  • the ratio Ps of the (total) area Sa of the protrusions to the area Sb of the laminated part is 0.30.
  • the length Ya of the side where the projecting portion and the laminated portion are in contact is 10 mm.
  • the first electrode layer and the second electrode layer were connected to the external power source at each of the plurality of projecting portions.
  • Example 4 Ten piezoelectric elements were produced in the same manner as in Example 1, except that one projecting portion having a length La of 37 mm and a width of Wa of 37 mm was provided. A ratio Ps of the area Sa of the projecting portion to the area Sb of the laminated portion is 0.30. The length Ya of the side where the projecting portion and the laminated portion are in contact is 37 mm.
  • Example 5 Ten piezoelectric elements were produced in the same manner as in Example 1, except that one hexagonal protrusion with a side length of 22.5 mm was provided (see FIG. 6). A ratio Ps of the area Sa of the projecting portion to the area Sb of the laminated portion is 0.29. The length Ya of the side where the projecting portion and the laminated portion are in contact is 22.5 cm.
  • Example 6 Ten piezoelectric elements were produced in the same manner as in Example 1, except that one projecting portion having a length La of 60 mm and a width of Wa 4 mm was provided. A ratio Ps of the area Sa of the projecting portion to the area Sb of the laminated portion is 0.05. The length Ya of the side where the projecting portion and the laminated portion are in contact is 4 mm.
  • Example 7 Ten piezoelectric elements were produced in the same manner as in Example 1, except that one projecting portion having a length La of 4 mm and a width of Wa of 25 mm was provided. A ratio Ps of the area Sa of the projecting portion to the area Sb of the laminated portion is 0.02. The length Ya of the side where the projecting portion and the laminated portion are in contact is 25 mm.
  • Example 1 Ten piezoelectric elements were produced in the same manner as in Example 1, except that one projecting portion having a length La of 10 mm and a width of Wa of 150 mm was provided. The ratio Ps of the area Sa of the projecting portion to the area Sb of the laminated portion is 0.33. The length Ya of the side where the projecting portion and the laminated portion are in contact is 150 mm.
  • Example 2 Ten piezoelectric elements were produced in the same manner as in Example 1, except that one projecting portion having a length La of 70 mm and a width of Wa 3 mm was provided. A ratio Ps of the area Sa of the projecting portion to the area Sb of the laminated portion is 0.05. Moreover, the length Ya of the side where the projecting portion and the laminated portion are in contact is 3 mm.
  • Example 3 Ten piezoelectric elements were produced in the same manner as in Example 1, except that one projecting portion having a length La of 4 mm and a width of Wa 10 mm was provided. A ratio Ps of the area Sa of the projecting portion to the area Sb of the laminated portion is 0.01. The length Ya of the side where the projecting portion and the laminated portion are in contact is 10 mm.
  • An electroacoustic transducer was produced by attaching the surface of the produced piezoelectric element opposite to the projecting portion to a diaphragm.
  • a diaphragm a plate member having a size of 500 mm ⁇ 450 mm, a thickness of 0.8 mm, and material: aluminum (A5052) was used.
  • the horizontal direction of the diaphragm and the longitudinal direction of the piezoelectric element were matched, and the center of the laminated part of the piezoelectric element was aligned with the center of the diaphragm and attached.
  • An acrylic pressure-sensitive adhesive was used as a bonding layer for bonding the piezoelectric element and the diaphragm.
  • a sine sweep signal with a frequency of 1 kHz to 20 kHz and an applied voltage of 50 Vrms was inputted to the piezoelectric element, and the sound pressure was measured with a microphone placed at a distance of 1 m from the center of the diaphragm.
  • the above measurement was performed on 10 specimens, and the difference between the maximum and minimum values of sound pressure at 15 kHz was taken as the sound pressure variation.
  • a sound pressure variation of less than 7 dB satisfies the desired characteristics.
  • the piezoelectric element 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.
  • 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,

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  • Piezo-Electric Transducers For Audible Bands (AREA)

Abstract

L'invention concerne un élément piézoélectrique et un convertisseur électro-acoustique qui sont capables de supprimer la variabilité de la pression acoustique tout en supprimant la génération de chaleur, l'élément piézoélectrique étant formé par l'empilement d'un film piézoélectrique. L'élément piézoélectrique est formé en empilant une pluralité de couches du film piézoélectrique, qui comprend une couche piézoélectrique, des couches d'électrode prévues sur les deux surfaces de la couche piézoélectrique, et des couches de protection prévues sur les couches d'électrode, en repliant le film piézoélectrique une ou plusieurs fois, où : dans une vue en plan, l'élément piézoélectrique comprend une partie en saillie qui fait saillie à partir d'une partie empilée dans laquelle deux ou plusieurs couches du film piézoélectrique se chevauchent ; la partie en saillie a une partie de connexion pour connecter la couche d'électrode et une source d'alimentation externe ; un rapport de la surface de la partie en saillie sur la surface de la partie empilée se trouve dans une plage de 0,02 à 0,3 ; et une longueur d'un bord où la partie en saillie et la partie empilée sont en contact l'une avec l'autre est égale ou supérieure à 4 mm.
PCT/JP2022/030855 2021-09-28 2022-08-15 Élément piézoélectrique et convertisseur électro-acoustique WO2023053750A1 (fr)

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JP (1) JPWO2023053750A1 (fr)
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6054486A (ja) * 1983-09-05 1985-03-28 Toshiba Corp 高分子素子のリ−ド線接続部
WO2014157006A1 (fr) * 2013-03-29 2014-10-02 富士フイルム株式会社 Film de conversion électroacoustique
JP2015070110A (ja) * 2013-09-30 2015-04-13 株式会社村田製作所 圧電デバイスおよび圧電デバイスの製造方法
WO2020095812A1 (fr) * 2018-11-08 2020-05-14 富士フイルム株式会社 Élément piézoélectrique stratifié et transducteur électroacoustique
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 (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6054486A (ja) * 1983-09-05 1985-03-28 Toshiba Corp 高分子素子のリ−ド線接続部
WO2014157006A1 (fr) * 2013-03-29 2014-10-02 富士フイルム株式会社 Film de conversion électroacoustique
JP2015070110A (ja) * 2013-09-30 2015-04-13 株式会社村田製作所 圧電デバイスおよび圧電デバイスの製造方法
WO2020095812A1 (fr) * 2018-11-08 2020-05-14 富士フイルム株式会社 Élément piézoélectrique stratifié et transducteur électroacoustique
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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CN117957858A (zh) 2024-04-30
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