WO2021199800A1 - 積層圧電素子 - Google Patents
積層圧電素子 Download PDFInfo
- Publication number
- WO2021199800A1 WO2021199800A1 PCT/JP2021/007032 JP2021007032W WO2021199800A1 WO 2021199800 A1 WO2021199800 A1 WO 2021199800A1 JP 2021007032 W JP2021007032 W JP 2021007032W WO 2021199800 A1 WO2021199800 A1 WO 2021199800A1
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- Prior art keywords
- piezoelectric
- layer
- laminated
- piezoelectric film
- film
- Prior art date
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Images
Classifications
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- H04R7/00—Diaphragms for electromechanical transducers; Cones
- H04R7/02—Diaphragms for electromechanical transducers; Cones characterised by the construction
- H04R7/04—Plane diaphragms
- H04R7/06—Plane diaphragms comprising a plurality of sections or layers
- H04R7/10—Plane diaphragms comprising a plurality of sections or layers comprising superposed layers in contact
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/88—Mounts; Supports; Enclosures; Casings
- H10N30/883—Additional insulation means preventing electrical, physical or chemical damage, e.g. protective coatings
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- H—ELECTRICITY
- 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
- H10N30/50—Piezoelectric or electrostrictive devices having a stacked or multilayer structure
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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
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R17/00—Piezoelectric transducers; Electrostrictive transducers
- H04R17/005—Piezoelectric transducers; Electrostrictive transducers using a piezoelectric polymer
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R31/00—Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor
- H04R31/003—Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor for diaphragms or their outer suspension
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/01—Manufacture or treatment
- H10N30/09—Forming piezoelectric or electrostrictive materials
- H10N30/092—Forming composite materials
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/20—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
- H10N30/50—Piezoelectric or electrostrictive devices having a stacked or multilayer structure
- H10N30/501—Piezoelectric or electrostrictive devices having a stacked or multilayer structure having a non-rectangular cross-section in a plane parallel to the stacking direction, e.g. polygonal or trapezoidal in side view
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- 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
- H10N30/50—Piezoelectric or electrostrictive devices having a stacked or multilayer structure
- H10N30/508—Piezoelectric or electrostrictive devices having a stacked or multilayer structure adapted for alleviating internal stress, e.g. cracking control layers
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/88—Mounts; Supports; Enclosures; Casings
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- H—ELECTRICITY
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- H04R2499/00—Aspects covered by H04R or H04S not otherwise provided for in their subgroups
- H04R2499/10—General applications
- H04R2499/15—Transducers incorporated in visual displaying devices, e.g. televisions, computer displays, laptops
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
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- H10N30/80—Constructional details
- H10N30/85—Piezoelectric or electrostrictive active materials
- H10N30/852—Composite materials, e.g. having 1-3 or 2-2 type connectivity
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/87—Electrodes or interconnections, e.g. leads or terminals
- H10N30/872—Interconnections, e.g. connection electrodes of multilayer piezoelectric or electrostrictive devices
Definitions
- the present invention relates to a laminated piezoelectric element.
- Piezoelectric elements are used for various purposes as so-called exciters that vibrate articles and make sounds when they are attached in contact with various articles. 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.
- the exciter when attaching an exciter to a flexible image display device, a retractable screen, etc., the exciter itself must be flexible (rollable) at least when not in use.
- Patent Document 1 describes a polymer composite piezoelectric body in which piezoelectric particles are dispersed in a viscoelastic matrix made of a polymer material having viscoelasticity at room temperature, and is formed on one surface of the polymer composite piezoelectric body.
- the upper thin film electrode having an area of less than or equal to the polymer composite piezoelectric material, the upper protective layer formed on the surface of the upper thin film electrode and having an area of more than or equal to the upper thin film electrode, and the opposite surface of the upper thin film electrode of the polymer composite piezoelectric body.
- a piezoelectric laminate having a lower thin film electrode having an area of less than or equal to the polymer composite piezoelectric body, and a piezoelectric laminate having an area of more than or equal to the lower thin film electrode formed on the surface of the lower thin film electrode, and an upper portion.
- a metal foil for drawing out the upper electrode, which is laminated on a part of the thin film electrode and at least a part is located outside the plane direction of the polymer composite piezoelectric material, and a part of the lower thin film electrode, which is laminated on a part, and at least a part is high.
- an electroacoustic conversion film having a metal foil for drawing out a lower electrode located outside the plane direction of the molecular composite piezoelectric body.
- the piezoelectric film in which the piezoelectric layer is sandwiched between the electrode layer and the protective layer is formed into a long shape by, for example, roll-to-roll, and then cut into a desired size. When cut, burrs of the metal constituting the electrode layer may occur. Therefore, it has been found that when such piezoelectric films are laminated, there is a problem that the electrode layers of adjacent piezoelectric films are short-circuited due to burrs because the distance between the layers is short.
- An object of the present invention is to solve such a problem of the prior art, and in a laminated piezoelectric element in which a plurality of layers of a piezoelectric film formed by sandwiching a piezoelectric layer between an electrode layer and a protective layer are laminated.
- An object of the present invention is to provide a laminated piezoelectric element capable of suppressing a short circuit between films.
- the present invention has the following configuration.
- a plurality of layers of a piezoelectric film having a piezoelectric layer, two electrode layers sandwiching the piezoelectric layer, and two protective layers covering the electrode layers are laminated.
- each piezoelectric film has an end face coating layer that covers the end face of the piezoelectric film.
- the piezoelectric layer is polarized in the thickness direction and is polarized.
- the laminated piezoelectric element according to any one of [1] to [3], wherein the plurality of piezoelectric films are laminated so that the polarization directions alternate.
- a plurality of layers of the piezoelectric film are formed by folding back the piezoelectric film having the piezoelectric layer, the two electrode layers sandwiching the piezoelectric layer, and the two protective layers covering the electrode layers one or more times.
- Laminated A laminated piezoelectric element in which the ends of adjacent layers are located at different positions in the plane direction.
- a laminated piezoelectric element in which a plurality of layers of a piezoelectric film formed by sandwiching a piezoelectric layer between an electrode layer and a protective layer are laminated, short-circuiting between the piezoelectric films can be suppressed. Can be provided.
- FIG. 8 is a cross-sectional view taken along the line BB of FIG. It is a figure which conceptually shows the state in which the laminated piezoelectric element of FIG. 18 is opened.
- the description of the constituent elements described below may be based on a typical embodiment of the present invention, but the present invention is not limited to such an embodiment.
- the numerical range represented by using "-" means a range including the numerical values before and after "-" as the lower limit value and the upper limit value.
- the laminated piezoelectric element according to the first embodiment of the present invention A plurality of layers of a piezoelectric film having a piezoelectric layer, two electrode layers sandwiching the piezoelectric layer, and two protective layers covering each of the electrode layers are laminated. Laminated piezoelectric elements in which the respective ends of adjacent piezoelectric films are located at different positions in the plane direction.
- FIG. 1 conceptually shows an example of the laminated piezoelectric element of the present invention.
- the laminated piezoelectric element 10 shown in FIG. 1 has a configuration in which five piezoelectric films are laminated and adjacent piezoelectric films are attached by an adhesive layer (adhesion layer) 14. Each piezoelectric film is connected to a power source that applies a driving voltage that expands and contracts the piezoelectric film (not shown).
- the laminated piezoelectric element 10 shown in FIG. 1 is formed by laminating five layers of piezoelectric films, but the present invention is not limited to this.
- the number of laminated piezoelectric films may be 2 to 4 layers, or 6 or more layers. The same applies to the laminated piezoelectric element described later in this respect.
- FIG. 2 conceptually shows the piezoelectric film 12 by a cross-sectional view.
- the piezoelectric films 12a to 12e have the same configuration except that the stacking order and width are different. Therefore, in the following description, when it is not necessary to distinguish the piezoelectric films, the piezoelectric films 12 are collectively described. Also called.
- the piezoelectric film 12 includes a piezoelectric layer 20 which is a sheet-like material having piezoelectricity, a first electrode layer 24 laminated on one surface of the piezoelectric layer 20, and a first electrode layer. It has a first protective layer 28 laminated on 24, a second electrode layer 26 laminated on the other surface of the piezoelectric layer 20, and a second protective layer 30 laminated on the second electrode layer 26. .. That is, the piezoelectric film 12 has a protective layer that sandwiches the piezoelectric layer 20 between two electrode layers and covers each electrode layer. The piezoelectric film 12 will be described in detail later.
- the end sides of adjacent piezoelectric films are at different positions in the plane direction.
- the plane direction is the plane direction of the main surface of the piezoelectric film.
- the main surface is the maximum surface of a sheet-like material (layer, film, plate-like material).
- the piezoelectric film 12a laminated on the uppermost side in FIG. 1 and the piezoelectric film 12b laminated adjacent to the lower layer of the piezoelectric film 12a have different widths in the left-right direction in the drawing, and are piezoelectric.
- the positions of the end edges of the film 12 in the surface direction, that is, in the left-right direction in the drawing are different.
- the width of the piezoelectric film 12b is longer than that of the piezoelectric film 12a, and the left end edge of the piezoelectric film 12b in the drawing is located on the left side of the left edge of the piezoelectric film 12a, and the piezoelectric film 12b is also located.
- the right end of the figure is located on the right side of the right end of the piezoelectric film 12a.
- the piezoelectric film 12b and the piezoelectric film 12c laminated adjacent to the lower layer of the piezoelectric film 12b have different widths in the left-right direction in the drawing, and the plane direction of the piezoelectric film 12, that is, the left-right direction in the drawing. The positions of the edges are different. More specifically, the width of the piezoelectric film 12c is longer than that of the piezoelectric film 12b, and the left end edge of the piezoelectric film 12c in the drawing is located on the left side of the left edge of the piezoelectric film 12b, and the piezoelectric film 12c The right end of the figure is located on the right side of the right end of the piezoelectric film 12b.
- the width in the left-right direction in the figure is different, and the position of the end side in the surface direction of the piezoelectric film 12, that is, the left-right direction in the figure is different. More specifically, the piezoelectric film 12 in the lower layer is wider than the piezoelectric film 12 adjacent to the piezoelectric film 12, and the left and right ends of the piezoelectric film 12 in the lower layer are adjacent to each other. It is located outside the edge.
- the piezoelectric film in which the piezoelectric layer is sandwiched between the electrode layer and the protective layer is formed into a long shape by, for example, roll-to-roll, and then cut into a desired size.
- burrs of the metal constituting the electrode layer may occur. Therefore, when the piezoelectric films cut to the same size are laminated, the distance between the layers becomes short, so that there is a problem that the electrode layers of the adjacent piezoelectric films are short-circuited due to burrs. rice field.
- the plurality of piezoelectric films 12 have a configuration in which the end sides of the adjacent piezoelectric films 12 are laminated so as to be at different positions in the plane direction.
- the distance between the electrode layers of the adjacent piezoelectric films can be increased, and short-circuiting of the electrode layers can be suppressed.
- the size of the piezoelectric film increases from the upper layer to the lower layer, but if the edges of the adjacent piezoelectric films are at different positions in the plane direction, this is used. There is no limitation.
- FIG. 3 is a diagram conceptually showing another example of the laminated piezoelectric element of the present invention.
- the laminated piezoelectric element 10 shown in FIG. 3 has a configuration in which five piezoelectric films are laminated and adjacent piezoelectric films are attached by an adhesive layer (adhesion layer) 14.
- the piezoelectric film 12a laminated on the uppermost side in FIG. 3 and the piezoelectric film 12b laminated adjacent to the lower layer of the piezoelectric film 12a have different widths in the left-right direction in the drawing, and are in the plane direction of the piezoelectric film 12. That is, the positions of the end edges in the left-right direction in the figure are different. More specifically, the width of the piezoelectric film 12a is longer than that of the piezoelectric film 12b, and the left edge of the piezoelectric film 12a in the drawing is located on the left side (outside) of the left edge of the piezoelectric film 12b. The right end of the piezoelectric film 12a in the drawing is located on the right side (outside) of the right end of the piezoelectric film 12b.
- the piezoelectric film 12b and the piezoelectric film 12c laminated adjacent to the lower layer of the piezoelectric film 12b have different widths in the left-right direction in the drawing, and the plane direction of the piezoelectric film 12, that is, the left-right direction in the drawing. The positions of the edges are different. More specifically, the width of the piezoelectric film 12c is longer than that of the piezoelectric film 12b, and the left end edge of the piezoelectric film 12c in the drawing is located on the left side (outside) of the left edge of the piezoelectric film 12b. The right end of the piezoelectric film 12c in the drawing is located on the right side (outside) of the right end of the piezoelectric film 12b.
- the piezoelectric film 12d laminated on the lower layer of the piezoelectric film 12c has a shorter width than the piezoelectric film 12c, and the left end of the piezoelectric film 12c in the drawing is on the left side (outside) of the left end of the piezoelectric film 12d. ), And the right end of the piezoelectric film 12c in the figure is located on the right side (outside) of the right end of the piezoelectric film 12d.
- the piezoelectric film 12e laminated on the lower layer of the piezoelectric film 12d is longer than the piezoelectric film 12d, and the left end of the piezoelectric film 12e in the drawing is on the left side (outside) of the left end of the piezoelectric film 12d. ), And the right end of the piezoelectric film 12e in the drawing is located on the right side (outside) of the right end of the piezoelectric film 12d.
- the long-width piezoelectric film 12 and the short-width piezoelectric film 12 are alternately laminated, and the long-width piezoelectric film 12 and the short-width piezoelectric film 12 are on the left and right ends. The position of is different.
- FIG. 4 is a diagram conceptually showing another example of the laminated piezoelectric element of the present invention.
- the laminated piezoelectric element 10 shown in FIG. 4 has a configuration in which five piezoelectric films are laminated and adjacent piezoelectric films are attached by an adhesive layer (adhesion layer) 14.
- the piezoelectric film 12a laminated on the uppermost side in FIG. 3 and the piezoelectric film 12b laminated adjacent to the lower layer of the piezoelectric film 12a have different widths in the left-right direction in the drawing, and are in the plane direction of the piezoelectric film 12. That is, the positions of the end edges in the left-right direction in the figure are different. More specifically, the width of the piezoelectric film 12a is longer than that of the piezoelectric film 12b, and the left edge of the piezoelectric film 12a in the drawing is located on the left side (outside) of the left edge of the piezoelectric film 12b. The right end of the piezoelectric film 12a in the drawing is located on the right side (outside) of the right end of the piezoelectric film 12b.
- the piezoelectric film 12b and the piezoelectric film 12c laminated adjacent to the lower layer of the piezoelectric film 12b have different widths in the left-right direction in the drawing, and the plane direction of the piezoelectric film 12, that is, the left-right direction in the drawing. The positions of the edges are different. More specifically, the width of the piezoelectric film 12b is longer than that of the piezoelectric film 12c, and the left end edge of the piezoelectric film 12b in the drawing is located on the left side (outside) of the left edge of the piezoelectric film 12c. The right end of the piezoelectric film 12b in the drawing is located on the right side (outside) of the right end of the piezoelectric film 12c.
- the piezoelectric film 12d laminated on the lower layer of the piezoelectric film 12c is longer than the piezoelectric film 12c, and the left end of the piezoelectric film 12d in the drawing is on the left side (outside) of the left end of the piezoelectric film 12c. ), And the right end of the piezoelectric film 12d in the drawing is located on the right side (outside) of the right end of the piezoelectric film 12c.
- the piezoelectric film 12e laminated on the lower layer of the piezoelectric film 12d is longer than the piezoelectric film 12d, and the left end of the piezoelectric film 12e in the drawing is on the left side (outside) of the left end of the piezoelectric film 12d. ), And the right end of the piezoelectric film 12e in the drawing is located on the right side (outside) of the right end of the piezoelectric film 12d.
- the size of the piezoelectric film increases from the center to the outside (surface side) in the stacking direction.
- each piezoelectric film 12 may have an end face covering layer that covers the end face of the piezoelectric film 12.
- FIG. 5 conceptually shows the piezoelectric film 12 by a cross-sectional view.
- the piezoelectric film 12 includes a piezoelectric layer 20 which is a sheet-like material having piezoelectricity, a first electrode layer 24 laminated on one surface of the piezoelectric layer 20, and a first electrode layer.
- the first protective layer 28 laminated on the 24, the second electrode layer 26 laminated on the other surface of the piezoelectric layer 20, the second protective layer 30 laminated on the second electrode layer 26, and the second It has one protective layer 28, a first electrode layer 24, a piezoelectric layer 20, a second electrode layer 26, and an end face covering layer 32 covering the end faces of the laminated body in which the second protective layer 30 is laminated in this order.
- the end face coating layer 32 has an insulating property. In the example shown in FIG. 5, the end face covering layer 32 covers a region from a part of the surface of the first protective layer 28 to the end face of the laminated body and a part of the surface of the second protective layer 30. There is. The end face covering layer 32 will be described in detail later.
- FIGS. 6 to 8 show an example in which the piezoelectric films 12 having the end face covering layer 32 are laminated so that the end sides of the adjacent piezoelectric films 12 are at different positions in the plane direction.
- the example shown in FIG. 6 is an example in which the piezoelectric film 12 is laminated in the same manner as the example shown in FIG. 1 except that the piezoelectric film 12 has an end face coating layer.
- the example shown in FIG. 7 is an example in which the piezoelectric film 12 is laminated in the same manner as the example shown in FIG. 3, except that the piezoelectric film 12 has an end face coating layer.
- the example shown in FIG. 8 is an example in which the piezoelectric film 12 is laminated in the same manner as the example shown in FIG. 4, except that the piezoelectric film 12 has an end face coating layer.
- the end face covering layer 32 is also formed on the surface of the protective layer at the end as shown in FIG. Therefore, the end face covering layer 32 makes the thickness of the piezoelectric film 12 thicker at both ends than in the central portion, resulting in a distribution in thickness.
- piezoelectric films having such an end face coating layer are laminated with the same size, thick portions at both ends (parts on which the end face coating layer is formed) are laminated and viewed as a laminated piezoelectric element. At that time, the difference between the thickness of both ends and the thickness of the central portion becomes larger.
- the edges of adjacent piezoelectric films are located at different positions in the plane direction. Therefore, as shown in FIGS. 6 to 8, the portions of the adjacent piezoelectric films 12 on which the end face covering layer 32 is formed do not overlap in the plane direction. Therefore, when viewed as a laminated piezoelectric element, the difference between the thickness of both end portions and the thickness of the central portion can be reduced, and the occurrence of a rigidity difference can be suppressed. As a result, when the laminated piezoelectric body is attached to a windable screen or the like as an exciter, it is possible to suppress the formation of dents on the screen during winding.
- the distance between the ends of the adjacent piezoelectric films 12 in the plane direction is 0. It is preferably 05 mm to 5 mm, more preferably 0.2 mm to 3 mm, and even more preferably 0.3 mm to 2 mm.
- the distance between the end sides of the adjacent piezoelectric films 12 in the plane direction is the distance in the direction orthogonal to the extending direction of the short side. That is, it is the distance in the perpendicular direction of the end face.
- the edge of the adjacent piezoelectric film may be at different positions in the plane direction, but from the viewpoint of preventing a short circuit, the adjacent piezoelectric film covers the entire edge of the piezoelectric film. It is preferable that the edge of the film is different from the edge in the plane direction.
- the end edges may be at different positions in the surface direction, and it is preferable that the end edges are in different positions in the surface direction in all the sets of adjacent piezoelectric films. That is, there may be a set in which the end edges of adjacent piezoelectric films are at the same position in the plane direction.
- each piezoelectric film 12 has an end face covering layer 32 as in the example shown in FIGS. 6 to 8, as shown in FIG. 9, the end face covering layers 32 of the adjacent piezoelectric films 12 are connected to each other. It is preferable to set the distance in the plane direction between the ends of the adjacent piezoelectric films 12 so that the films do not overlap when viewed from the plane direction.
- the end face coating layer 32 may be a coating layer formed by coating or the like, or may be a layer formed by attaching an insulating tape, etc. In either case, the end face coating layer 32 is formed.
- the maximum length of the portion of the portion 32 that rides on the main surface in the surface direction is about 5 mm. Therefore, from the viewpoint of preventing the end face covering layers 32 of the adjacent piezoelectric films 12 from overlapping each other, the distance between the end sides of the adjacent piezoelectric films 12 in the plane direction is preferably about 5 mm at the maximum.
- the end face covering layers 32 of the adjacent piezoelectric films 12 may overlap each other.
- the end face coating layer 32 is a coating layer, as shown in FIG. 10, the thickness of the portion of the end face covering layer 32 that rides on the main surface gradually decreases as the distance from the end face of the piezoelectric film 12 increases. ing. In this way, the portion where the thickness of the end face covering layer 32 is gradually reduced may overlap with the end face covering layer 32 of the adjacent piezoelectric film 12.
- a plurality of piezoelectric films 12 having the end face covering layer 32 are laminated, that is, a structure in which the end face covering layer 32 is formed on each piezoelectric film 12 and laminated.
- the configuration may include an end face covering layer 32 that covers the end faces of the laminated body in which a plurality of piezoelectric films 12 are laminated. That is, after laminating a plurality of piezoelectric films 12 on which the end face covering layer 32 is not formed, the end face covering layer covering the end face of the laminated body may be formed.
- each piezoelectric film is not particularly limited, and can be various shapes such as a circular shape, an elliptical shape, a rectangular shape, a polygonal shape, and an indefinite shape.
- the plurality of piezoelectric films to be laminated may have similar shapes in which adjacent piezoelectric films have different sizes in the plane direction.
- the laminated piezoelectric element 10 of the present invention is used as an exciter for being adhered to a diaphragm by an adhesive layer and generating sound from the diaphragm.
- the piezoelectric layer 20 constituting the piezoelectric film 12 in which a plurality of layers are laminated is formed by dispersing the piezoelectric particles 36 in the viscoelastic matrix 34. Is preferable. Further, the first electrode layer 24 and the second electrode layer 26 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 shrinks in the thickness direction.
- the piezoelectric film expands and contracts in the plane direction due to the pore ratio. This expansion and contraction is about 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 the maximum.
- the piezoelectric film that is, the piezoelectric layer 20
- the piezoelectric film has a size much larger than the thickness in the plane direction. Therefore, for example, if the length of the piezoelectric film is 20 cm, the piezoelectric film expands and contracts by a maximum of about 0.2 mm when a voltage is applied.
- the laminated piezoelectric element 10 is attached to the diaphragm by an adhesive layer. Therefore, the expansion and contraction of the piezoelectric film causes the diaphragm to bend, and as a result, the diaphragm vibrates in the thickness direction. Due to this vibration in the thickness direction, the diaphragm emits a sound. That is, the diaphragm vibrates according to the magnitude of the voltage (driving voltage) applied to the piezoelectric film, and generates a sound corresponding to the driving voltage applied to the piezoelectric film.
- a general piezoelectric film made of a polymer material such as PVDF the molecular chains are oriented with respect to the stretching direction by stretching in the uniaxial direction after the polarization treatment, and as a result, a large piezoelectric property is exhibited in the stretching direction. It is known to be obtained. Therefore, a general piezoelectric film has in-plane anisotropy in the piezoelectric characteristics, and has anisotropy in the amount of expansion and contraction in the plane direction when a voltage is applied.
- a piezoelectric film having a polymer composite piezoelectric body in which piezoelectric particles are dispersed in a viscoelastic matrix can obtain large piezoelectric characteristics without stretching treatment after polarization treatment, so that the piezoelectric characteristics are in-plane. It has no anisotropy and expands and contracts isotropically in all directions in the plane direction. That is, the piezoelectric film expands and contracts isotropically and two-dimensionally.
- the laminated piezoelectric element 10 in which such an isotropically two-dimensionally expanding and contracting piezoelectric film is laminated vibrates with a larger force than when a general piezoelectric film such as PVDF that expands and contracts greatly in only one direction is laminated.
- the board can be vibrated and a louder and more beautiful sound can be generated.
- the laminated piezoelectric element of the present invention is obtained by laminating a plurality of such piezoelectric films. Therefore, even if the rigidity of each piezoelectric film is low and the stretching force is small, the rigidity is increased by laminating the piezoelectric films, and the stretching force of the laminated piezoelectric element 10 is increased. As a result, in the laminated piezoelectric element 10 of the present invention, even if the diaphragm has a certain degree of rigidity, the diaphragm is sufficiently flexed with a large force to sufficiently vibrate the diaphragm in the thickness direction. , Can generate sound in the diaphragm.
- the preferable thickness of the piezoelectric layer 20 is about 300 ⁇ m at the maximum, so that even if the voltage applied to each piezoelectric film is small, it is sufficient. , The piezoelectric film can be expanded and contracted.
- the absolute amount of expansion and contraction of the piezoelectric layer 20 in the thickness direction is very small, and the expansion and contraction of the piezoelectric film is substantially only in the plane direction. Therefore, even if the polarization directions of the laminated piezoelectric films are opposite, all the piezoelectric films expand and contract in the same direction as long as the polarities of the voltages applied to the first electrode layer 24 and the second electrode layer 26 are correct.
- the diaphragm to which the laminated piezoelectric element is attached is not limited, and various articles can be used.
- vibrating plates include plate materials such as resin plates and glass plates, advertising / announcement media such as signs, office equipment and furniture such as tables, whiteboards and projection screens, and organic electroluminescence (OLED (Organic)).
- OLED Organic electroluminescence
- Display devices such as displays and liquid crystal displays, vehicle members such as consoles, A-pillars, ceilings and bumpers, and building materials such as walls of houses are exemplified.
- the piezoelectric film 12 includes a piezoelectric layer 20 which is a sheet-like material having piezoelectricity, a first electrode layer 24 laminated on one surface of the piezoelectric layer 20, and a first electrode layer 24.
- the piezoelectric film 12 has a structure in which the first protective layer 28, the first electrode layer 24, the piezoelectric layer 20, the second electrode layer 26, and the second protective layer 30 are laminated in this order.
- the piezoelectric film 12 (piezoelectric layer 20) is polarized in the thickness direction.
- the electrode layer and the protective layer on the upstream side in the polarization direction of the piezoelectric film 12 are the first electrode layer 24 and the first protective layer 28, and the electrode layer and the protective layer on the downstream side are the second electrode layer 26 and the second protective layer 30. do.
- the piezoelectric layer 20 preferably disperses the piezoelectric particles 36 in a viscoelastic matrix 34 made of a polymer material having viscoelasticity at room temperature, as conceptually shown in FIG. It is made of a polymer composite piezoelectric body.
- room temperature refers to a temperature range of about 0 to 50 ° C.
- the polymer composite piezoelectric body (piezoelectric layer 20) preferably has the following requirements.
- (I) Flexibility For example, when gripping in a state of being loosely bent like a document like a newspaper or a magazine for carrying, 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 body is hard, a correspondingly large bending stress is generated, cracks are generated at the interface between the polymer matrix and the piezoelectric particle, and there is a possibility that it will eventually lead to fracture. Therefore, the polymer composite piezoelectric body is required to have appropriate softness. Further, if the strain energy can be diffused to the outside as heat, the stress can be relaxed. Therefore, it is required that the loss tangent of the polymer composite piezoelectric body 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 soft against vibrations of several Hz or less. Further, the loss tangent of the polymer composite piezoelectric body is required to be appropriately large for vibrations of all frequencies of 20 kHz or less. Further, it is preferable that the spring constant can be easily adjusted by laminating according to the rigidity (hardness, stiffness, spring constant) of the mating material (diaphragm) to be attached, and at that time, the adhesive layer 14 is thinned. The thinner it is, the more energy efficient it can be.
- polymer solids have a viscoelastic relaxation mechanism, and large-scale molecular motion causes a decrease in storage elastic modulus (Young's modulus) (relaxation) or a maximum loss elastic modulus (absorption) as the temperature rises or the frequency decreases. Observed as. Among them, the relaxation caused by the micro-Brownian motion of the molecular chain in the amorphous region is called main dispersion, and a very large relaxation phenomenon is observed. The temperature at which this main dispersion occurs is the glass transition point (Tg), and the viscoelastic relaxation mechanism appears most prominently.
- Tg glass transition point
- the polymer composite piezoelectric body (piezoelectric layer 20), by using a polymer material having a glass transition point at room temperature, in other words, a polymer material having viscoelasticity at room temperature, for vibration of 20 Hz to 20 kHz.
- a polymer composite piezoelectric material that is hard and behaves softly against slow vibrations of several Hz or less is realized.
- the polymer material having viscoelasticity at room temperature various known materials can be used.
- a polymer material having a maximum value of tangent Tan ⁇ at a frequency of 1 Hz by a dynamic viscoelasticity test of 0.5 or more is used at room temperature, that is, at 0 to 50 ° C.
- the polymer material having viscoelasticity at room temperature preferably has a storage elastic modulus (E') at a frequency of 1 Hz by dynamic viscoelasticity measurement of 100 MPa or more at 0 ° C. and 10 MPa or less at 50 ° C.
- E' storage elastic modulus
- the polymer material having viscoelasticity at room temperature is more preferably having a relative permittivity of 10 or more at 25 ° C.
- a voltage is applied to the polymer composite piezoelectric body, a higher electric field is applied to the piezoelectric particles in the polymer matrix, so that a large amount of deformation can be expected.
- the polymer material has a relative permittivity of 10 or less at 25 ° C.
- polymer material having viscoelasticity at room temperature satisfying such conditions examples include cyanoethylated polyvinyl alcohol (cyanoethylated PVA), polyvinyl acetate, polyvinylidene chloride core acrylonitrile, polystyrene-vinyl polyisoprene block copolymer, and polyvinylmethyl. Examples thereof include ketones and polybutyl methacrylate. Further, as these polymer materials, commercially available products such as Hybler 5127 (manufactured by Kuraray Co., Ltd.) can also be preferably used.
- Hybler 5127 manufactured by Kuraray Co., Ltd.
- the polymer material it is preferable to use a material having a cyanoethyl group, and it is particularly preferable to use cyanoethylated PVA.
- these polymer materials may use only 1 type, and may use a plurality of types in combination (mixing).
- a plurality of polymer materials may be used in combination, if necessary. That is, in addition to the viscoelastic material such as cyanoethylated PVA, other dielectric polymer materials may be added to the viscoelastic matrix 34 for the purpose of adjusting the dielectric properties and mechanical properties. ..
- dielectric polymer material examples include polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, and vinylidene fluoride-trifluoroethylene copolymer.
- fluoropolymers such as polyvinylidene fluoride-tetrafluoroethylene copolymer, vinylidene cyanide-vinyl acetate copolymer, cyanoethyl cellulose, cyanoethyl hydroxysaccharose, cyanoethyl hydroxycellulose, cyanoethyl hydroxypurrane, cyanoethyl methacrylate, cyanoethyl acrylate, cyanoethyl.
- Cyano groups such as hydroxyethyl cellulose, cyanoethyl amylose, cyanoethyl hydroxypropyl cellulose, cyanoethyl dihydroxypropyl cellulose, cyanoethyl hydroxypropyl amylose, cyanoethyl polyacrylamide, cyanoethyl polyacrylate, cyanoethyl pullulan, cyanoethyl polyhydroxymethylene, cyanoethyl glycidol pullulan, cyanoethyl saccharose and cyanoethyl sorbitol.
- polymers having a cyanoethyl group synthetic rubbers such as nitrile rubber and chloroprene rubber, and the like are exemplified. Among them, a polymer material having a cyanoethyl group is preferably used. Further, in the viscoelastic matrix 34 of the piezoelectric layer 20, the dielectric polymer added in addition to the material having viscoelasticity at room temperature such as cyanoethylated PVA is not limited to one type, and a plurality of types are added. May be good.
- the viscoelastic matrix 34 includes a vinyl chloride resin, a polyethylene, a polystyrene, a methacrylic resin, a polybutene, a thermoplastic resin such as isobutylene, and a thermoplastic resin for the purpose of adjusting the glass transition point Tg.
- a phenol resin, a urea resin, a melamine resin, an alkyd resin, and a thermosetting resin such as mica may be added.
- a tackifier such as rosin ester, rosin, terpene, terpene phenol, and petroleum resin may be added.
- the amount added when a material other than the polymer material having viscoelasticity such as cyanoethylated PVA is added is not particularly limited, but is a ratio to the viscoelastic matrix 34. It is preferably 30% by mass or less.
- the characteristics of the polymer material to be added can be exhibited without impairing the viscoelastic relaxation mechanism in the viscoelastic matrix 34, so that the dielectric constant is increased, the heat resistance is improved, and the adhesion to the piezoelectric particles 36 and the electrode layer is increased. Preferred results can be obtained in terms of improvement and the like.
- the piezoelectric particles 36 are made of ceramic particles having a perovskite-type or wurtzite-type crystal structure.
- the ceramic particles constituting the piezoelectric particles 36 include lead zirconate titanate (PZT), lead lanthanate lanthanate titanate (PLZT), barium titanate (BaTIO 3 ), zinc oxide (ZnO), and the like.
- PZT lead zirconate titanate
- PLA 3 lead lanthanate lanthanate titanate
- BaTIO 3 barium titanate
- ZnO zinc oxide
- Examples thereof include a solid solution (BFBT) of barium titanate and bismuth ferrite (BiFe 3).
- the particle size of the piezoelectric particles 36 is not limited, and may be appropriately selected depending on the size of the piezoelectric film 12 and the application of the laminated piezoelectric element 10.
- the particle size of the piezoelectric particles 36 is preferably 1 to 10 ⁇ m. By setting the particle size of the piezoelectric particles 36 in this range, favorable results can be obtained in that the piezoelectric film 12 can achieve both high piezoelectric characteristics and flexibility.
- the piezoelectric particles 36 in the piezoelectric layer 20 are uniformly and regularly dispersed in the viscoelastic matrix 34, but the present invention is not limited to this. That is, the piezoelectric particles 36 in the piezoelectric layer 20 may be irregularly dispersed in the viscoelastic matrix 34 as long as they are preferably uniformly dispersed.
- the amount ratio of the viscoelastic matrix 34 to the piezoelectric particles 36 in the piezoelectric layer 20 is not limited, and the size and thickness of the piezoelectric film 12 in the plane direction and the use of the laminated piezoelectric element 10 , And the characteristics required for the piezoelectric film 12, etc., may be appropriately set.
- 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 above-mentioned piezoelectric film 12 is preferably a polymer composite piezoelectric layer in which the piezoelectric layer 20 is formed by dispersing piezoelectric particles in a viscoelastic matrix containing a polymer material having viscoelasticity at room temperature.
- the present invention is not limited to this, and various known piezoelectric layers used in known piezoelectric elements can be used as the piezoelectric layer of the piezoelectric film.
- a piezoelectric layer made of the above-mentioned dielectric polymer material of polyvinylidene fluoride (PVDF) and vinylidene fluoride-tetrafluoroethylene copolymer, and PZT, PLZT, barium titanate, zinc oxide, BFBT and the like. Examples thereof include a piezoelectric layer made of the above-mentioned piezoelectric material.
- the thickness of the piezoelectric layer 20 is not particularly limited, and depends on the application of the laminated piezoelectric element 10, the number of laminated piezoelectric films in the laminated piezoelectric element 10, the characteristics required for the piezoelectric film 12, and the like. , It may be set as appropriate.
- 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 film 12 of the illustrated example has a first electrode layer 24 on one surface of such a piezoelectric layer 20, a first protective layer 28 on the first electrode layer 24, and is a piezoelectric layer.
- the other surface of the 20 has a second electrode layer 26 and a second protective layer 30 on the second electrode layer 26.
- the second electrode layer 26 and the first electrode layer 24 form an electrode pair.
- the piezoelectric film 12 may have, for example, an end face covering layer that covers a region where the piezoelectric layer 20 is exposed, such as a side surface, to prevent short circuits and the like. The end face coating layer will be described in detail later.
- the piezoelectric film 12 sandwiches both sides of the piezoelectric layer 20 between electrode pairs, that is, the first electrode layer 24 and the second electrode layer 26, and this laminated body is sandwiched between the first protective layer 28 and the second protective layer 30. It has a structure that is sandwiched between.
- the region held by the first electrode layer 24 and the second electrode layer 26 is expanded and contracted according to the applied voltage.
- the first electrode layer 24 and the first protective layer 28, and the second electrode layer 26 and the second protective layer 30 are named according to the polarization direction of the piezoelectric layer 20. Is. Therefore, the first electrode layer 24 and the second electrode layer 26, and the first protective layer 28 and the second protective layer 30 have basically the same configuration.
- the first protective layer 28 and the second protective layer 30 have a role of covering the second electrode layer 26 and the first electrode layer 24 and imparting appropriate rigidity and mechanical strength to the piezoelectric layer 20. Is responsible for. That is, in the piezoelectric film 12, the piezoelectric layer 20 composed of the viscoelastic matrix 34 and the piezoelectric particles 36 exhibits extremely excellent flexibility against slow bending deformation, but depending on the application. , Rigidity and mechanical strength may be insufficient.
- the piezoelectric film 12 is provided with a first protective layer 28 and a second protective layer 30 to supplement the piezoelectric film 12.
- the first protective layer 28 and the second protective layer 30 are not limited, and various sheet-like materials can be used.
- various resin films are preferably exemplified.
- PET polyethylene terephthalate
- PP polypropylene
- PS polystyrene
- PC polycarbonate
- PPS polyphenylene sulfide
- PMMA polymethylmethacrylate
- PEI Polyetherimide
- PEI polyimide
- PEN polyethylene naphthalate
- TAC triacetyl cellulose
- a resin film made of a cyclic olefin resin or the like are preferably used.
- the thickness of the first protective layer 28 and the second protective layer 30 there is no limitation on the thickness of the first protective layer 28 and the second protective layer 30. Further, the thicknesses of the first protective layer 28 and the second protective layer 30 are basically the same, but may be different. Here, if the rigidity of the first protective layer 28 and the second protective layer 30 is too high, not only the expansion and contraction of the piezoelectric layer 20 is restrained, but also the flexibility is impaired. Therefore, the thinner the first protective layer 28 and the second protective layer 30, the more advantageous it is, except when mechanical strength and good handleability as a sheet-like material are required.
- the thickness of the 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 ensure both rigidity and appropriate flexibility. A favorable result can be obtained in terms of points.
- the thickness of the first protective layer 28 and the second protective layer 30 is preferably 100 ⁇ m or less. 50 ⁇ m or less is more preferable, and 25 ⁇ m or less is further preferable.
- a first electrode layer 24 is provided between the piezoelectric layer 20 and the first protective layer 28, and a second electrode layer 26 is provided between the piezoelectric layer 20 and the second protective layer 30. It is formed.
- the first electrode layer 24 and the second electrode layer 26 are provided to apply a voltage to the piezoelectric layer 20 (piezoelectric film 12).
- the materials for forming the first electrode layer 24 and the second electrode layer 26 are not limited, and various conductors can be used. Specifically, metals such as carbon, palladium, iron, tin, aluminum, nickel, platinum, gold, silver, copper, titanium, chromium and molybdenum, alloys thereof, laminates and composites of these metals and alloys, In addition, indium tin oxide and the like are exemplified. Among them, copper, aluminum, gold, silver, platinum, and indium tin oxide are preferably exemplified as the first electrode layer 24 and the second electrode layer 26.
- first electrode layer 24 and the second electrode layer 26 are formed by a vapor deposition method (vacuum film deposition method) such as vacuum deposition and sputtering, a film formation by plating, or the above materials.
- a vapor deposition method vacuum film deposition method
- Various known methods such as a method of attaching a foil are available.
- thin films such as copper and aluminum formed by vacuum deposition are preferably used as the first electrode layer 24 and the second electrode layer 26 because the flexibility of the piezoelectric film 12 can be ensured.
- NS a copper thin film produced by vacuum deposition is preferably used.
- the thickness of the first electrode layer 24 and the second electrode layer 26 There is no limitation on 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, not only the expansion and contraction of the piezoelectric layer 20 is restricted, but also the expansion and contraction of the piezoelectric layer 20 is restricted. Flexibility is also impaired. Therefore, the thinner the first electrode layer 24 and the second electrode layer 26 are, the more advantageous they are, as long as the electrical resistance does not become too high.
- the product of the thickness of the first electrode layer 24 and the second electrode layer 26 and the Young's modulus is less than the product of the thickness of the first protective layer 28 and the second protective layer 30 and the Young's modulus.
- 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. Above all, it is preferably 0.1 ⁇ m or less.
- the piezoelectric film 12 includes a piezoelectric layer 20 in which piezoelectric particles 36 are dispersed in a viscoelastic matrix 34 containing a polymer material having viscoelasticity at room temperature, and a first electrode layer 24 and a second electrode. It has a structure in which the first protective layer 28 and the second protective layer 30 are sandwiched between the layers 26 and the laminated body.
- the maximum value of the loss tangent (Tan ⁇ ) at a frequency of 1 Hz by dynamic viscoelasticity measurement exists at room temperature, and the maximum value of 0.1 or more exists at room temperature. More preferred.
- the piezoelectric film 12 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. It is possible to prevent cracks from occurring at the interface of.
- the piezoelectric film 12 preferably has a storage elastic modulus (E') at a frequency of 1 Hz as measured by dynamic viscoelasticity measurement of 10 to 30 GPa at 0 ° C. and 1 to 10 GPa at 50 ° C.
- E' storage elastic modulus
- the piezoelectric film 12 can have a large frequency dispersion in the storage elastic modulus (E') at room temperature. That is, it can behave hard for vibrations of 20 Hz to 20 kHz and soft for vibrations of several Hz or less.
- the product of the thickness and the storage elastic modulus (E') at a frequency of 1 Hz measured by dynamic viscoelasticity is 1.0 ⁇ 10 6 to 2.0 ⁇ 10 6 N / m at 0 ° C. , It is preferably 1.0 ⁇ 10 5 to 1.0 ⁇ 10 6 N / m at 50 ° C.
- the piezoelectric film 12 can be provided with appropriate rigidity and mechanical strength as long as the flexibility and acoustic characteristics are not impaired.
- the piezoelectric film 12 preferably has a loss tangent (Tan ⁇ ) of 0.05 or more at 25 ° C. and a frequency of 1 kHz in the master curve obtained from the dynamic viscoelasticity measurement.
- Ton ⁇ loss tangent
- the frequency characteristics of the speaker using the piezoelectric film 12 become smooth, and the amount of change in sound quality when the minimum resonance frequency f 0 changes with the change in the curvature of the speaker can be reduced.
- the end face covering layer 32 covers the end face of the laminated body in which the first protective layer 28, the first electrode layer 24, the piezoelectric layer 20, the second electrode layer 26, and the second protective layer 30 are laminated in this order. Is formed in.
- the material for forming the end face coating layer 32 is not limited, and various known materials can be used as long as they have insulating properties.
- various known materials can be used as long as they have insulating properties.
- polyimide, heat-resistant polyethylene terephthalate and the like are exemplified.
- the thickness of the end face coating layer 32 is preferably 3 ⁇ m to 100 ⁇ m.
- the water vapor transmission rate of the end face covering layer 32 may be set to 100 g / (m 2 ⁇ day) or less, and the end face covering layer 32 may have a gas barrier property.
- various known adhesive layers 14 can be used as long as the adjacent piezoelectric film 12 can be attached. Therefore, the adhesive layer 14 has fluidity when bonded, and then becomes a solid. Even a layer made of an adhesive is a soft solid gel-like (rubber-like) when bonded, and is subsequently gel-like. It may be a layer made of an adhesive that does not change the state of the above, or a layer made of a material having the characteristics of both an adhesive and an adhesive.
- the laminated piezoelectric element 10 of the present invention is attached to a diaphragm, for example, and by expanding and contracting a plurality of laminated piezoelectric films, the diaphragm is vibrated to generate sound. Therefore, in the laminated piezoelectric element 10 of the present invention, it is preferable that the expansion and contraction of each piezoelectric film is directly transmitted. If a substance having a viscosity that alleviates vibration is present between the piezoelectric films, the efficiency of transmitting the expansion and contraction energy of the piezoelectric film is lowered, and the driving efficiency of the laminated piezoelectric element 10 is lowered.
- the adhesive layer 14 is preferably an adhesive layer made of an adhesive, which can obtain a solid and hard adhesive layer 14 rather than an adhesive layer made of an adhesive.
- an adhesive layer made of a thermoplastic type adhesive such as a polyester adhesive and a styrene-butadiene rubber (SBR) adhesive is preferably exemplified. Adhesion, unlike adhesion, is useful when seeking high adhesion temperatures. Further, the thermoplastic type adhesive has "relatively low temperature, short time, and strong adhesion" and is suitable.
- the thickness of the adhesive layer 14 is not limited, and a thickness capable of exhibiting sufficient adhesive force (adhesive force, adhesive force) can be appropriately adjusted according to the material for forming the adhesive layer 14. , Just set it.
- adhesive force adhesive force
- the adhesive layer 14 is thick and has high rigidity, it may restrain the expansion and contraction of the piezoelectric film.
- the adhesive layer 14 can be made thin. Considering this point, the adhesive layer 14 is preferably thinner than the piezoelectric layer 20. That is, in the laminated piezoelectric element 10 of the present invention, the adhesive layer 14 is preferably hard and thin. Specifically, the thickness of the adhesive layer 14 is preferably 0.1 to 50 ⁇ m, more preferably 0.1 to 30 ⁇ m, and even more preferably 0.1 to 10 ⁇ m after sticking.
- the spring constant of the adhesive layer 14 is high, the expansion and contraction of the piezoelectric film 12 may be restricted. Therefore, the spring constant of the adhesive layer 14 is preferably equal to or less than the spring constant of the piezoelectric film 12.
- the spring constant is "thickness x Young's modulus".
- the product of the thickness of the adhesive layer 14 and the storage elastic modulus (E') at a frequency of 1 Hz by dynamic viscoelasticity measurement is 2.0 ⁇ 10 6 N / m or less at 0 ° C., 50 ° C. It is preferably 1.0 ⁇ 10 6 N / m or less.
- the internal loss at a frequency of 1 Hz by the dynamic viscoelasticity measurement of the adhesive layer is 1.0 or less at 25 ° C. in the case of the adhesive layer 14 made of an adhesive, and in the case of the adhesive layer 14 made of an adhesive. It is preferably 0.1 or less at 25 ° C.
- a sheet-like object 11a in which the first electrode layer 24 is formed on the first protective layer 28 is prepared.
- 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 deposition, sputtering, plating or the like.
- the first protective layer 28 with a separator temporary support
- PET or the like having a thickness of 25 to 100 ⁇ m can be used.
- the separator may be removed after the second electrode layer 26 and the second protective layer 30 are thermocompression bonded, and before any member is laminated on the first protective layer 28.
- a polymer material having viscoelasticity at room temperature such as cyanoethylated PVA is dissolved in an organic solvent, and piezoelectric particles 36 such as PZT particles are further added and stirred to prepare a dispersed coating material. ..
- a polymer material having viscoelasticity at room temperature such as cyanoethylated PVA
- the organic solvent is not limited, and various organic solvents such as dimethylformamide (DMF), methylethylketone, and cyclohexanone can be used.
- the casting method of this paint is not particularly limited, and all known coating methods (coating devices) such as a slide coater and a doctor knife can be used.
- the viscoelastic material is a material that can be melted by heating, such as cyanoethylated PVA
- the viscoelastic material is heated and melted to prepare a melt obtained by adding / dispersing the piezoelectric particles 36 to the viscoelastic material, and extruding the material.
- the first electrode layer 24 is provided on the first protective layer 28 as shown in FIG. 13 by extruding the sheet-like material 11a shown in FIG. 12 into a sheet shape and cooling the sheet-like material 11a.
- a laminated body 11b formed by forming a piezoelectric layer 20 on one electrode layer 24 may be produced.
- a polymer piezoelectric material such as PVDF may be added to the viscoelastic matrix 34 in addition to the viscoelastic material such as cyanoethylated PVA.
- the polymer piezoelectric materials to be added to the paint described above may be dissolved.
- the polymer piezoelectric material to be added may be added to the heat-melted viscoelastic material described above and heat-melted.
- a calendar treatment may be performed if necessary.
- the calendar treatment may be performed once or multiple times.
- the calendar treatment is a treatment in which the surface to be treated is pressed while being heated by a heating press, a heating roller, or the like to perform flattening or the like.
- the polarization treatment (polling) of the piezoelectric layer 20 is performed. )I do.
- the method for polarization treatment of the piezoelectric layer 20 is not limited, and known methods can be used.
- electric field polling in which a DC electric field is directly applied to an object to be polarized is exemplified.
- the first electrode layer 14 may be formed before the polarization treatment, and the electric field polling treatment may be performed using the first electrode layer 14 and the second electrode layer 16. .
- the piezoelectric film 10 of the present invention when the piezoelectric film 10 of the present invention is produced, the polarization treatment performs polarization in the thickness direction of the piezoelectric layer 12 instead of in the plane direction.
- a sheet-like material 11c in which the second electrode layer 26 is formed on the second protective layer 30 is prepared.
- 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 vapor deposition, sputtering, plating or the like.
- the second electrode layer 26 is directed toward the piezoelectric layer 20, and the sheet-like material 11c is laminated on the laminated body 11b that has completed the polarization treatment of the piezoelectric layer 20.
- the laminated body of the laminated body 11b and the sheet-like material 11c is sandwiched between the second protective layer 30 and the first protective layer 28, and thermocompression bonding is performed by a heating press device or a heating roller or the like. As described above, the piezoelectric film 12 is produced.
- the piezoelectric film it is preferable to prepare a long (large area) piezoelectric film and cut the long piezoelectric film into individual piezoelectric films. Therefore, in this case, the layer configurations (thickness, material, etc. of each layer) of the plurality of piezoelectric films constituting the laminated piezoelectric element 10 are all the same.
- the present invention is not limited to this. That is, various configurations can be used for the laminated piezoelectric element of the present invention, for example, a configuration in which piezoelectric films having different layer configurations are laminated, and a configuration in which piezoelectric films having different thicknesses of the piezoelectric layer 20 are laminated. ..
- a method of forming the end face covering layer 32 on the end face of the piezoelectric film 12 will be described.
- a known forming method (film forming method) according to the forming material of the end face covering layer 32 can be used.
- Examples thereof include a method of dissolving the resin to be the end face coating layer 32 in a solvent, spraying the resin, and drying the resin.
- Examples of the insulating adhesive tape include an adhesive tape made of polyimide, polyethylene terephthalate, or the like.
- the method for applying the liquid at this time is not limited, and various known methods can be used. As an example, spray coating, immersion coating and the like are exemplified. Further, depending on the forming method, the end face covering layer 32 is likely to be formed up to the main surface of the first protective layer 28 and / or the second protective layer 30.
- a part of the main surfaces of the first protective layer 28 and the second protective layer 30 is also immersed in the solution, so that the end face coating layer 32 is immersed in the solution.
- the main surfaces of the first protective layer 28 and the second protective layer 30 are formed.
- a plurality of layers of the piezoelectric film 12 may be laminated, and then the end face covering layer 32 may be formed on the end face of the laminated film.
- the piezoelectric layer 20 of the piezoelectric film 12 is preferably polarized.
- the piezoelectric layer 20 is polarized, the plurality of piezoelectric films 12 are laminated so that the polarization directions are the same if the phases of the voltages applied to the electrode layers are matched according to the polarization direction.
- some may be laminated so that the polarization directions are opposite to each other. That is, a voltage having the same phase may be applied to the first electrode layer 24 of each piezoelectric film 12, and a voltage having the same phase may be applied to the second electrode layer 26.
- the plurality of piezoelectric films 12 are laminated so that the polarization directions alternate. That is, it is preferable that the polarization directions of the adjacent piezoelectric films 12 are opposite to each other.
- the adjacent piezoelectric films 12 face each other with the second electrode layers 26 or the first electrode layers 24 facing each other. .. Therefore, even if the electrode layers of adjacent piezoelectric films come into contact with each other, there is no risk of short-circuiting, which is preferable.
- the polarization direction of the piezoelectric film may be detected by a d33 meter or the like.
- the polarization direction of the piezoelectric layer 20 may be known from the processing conditions of the corona polling process described above.
- Each piezoelectric film 12 may be provided with an electrode lead-out portion for connecting the first electrode layer 24 and the second electrode layer 26 to a power source.
- the electrode lead-out portion is not limited, and a known electrode lead-out portion configuration can be appropriately used.
- FIG. 15 is a diagram conceptually showing an example of the laminated piezoelectric element of the present invention.
- FIG. 16 is an exploded view of FIG.
- FIG. 17 is a diagram showing a plurality of piezoelectric films included in the laminated piezoelectric element of FIG.
- the examples shown in FIGS. 15 and 16 have a configuration in which five piezoelectric films are laminated.
- the piezoelectric films are laminated so that the polarization directions alternate.
- FIGS. 16 and 17 the surface of the piezoelectric film on the second protective layer side is shown with hatching. That is, in FIG. 16, the first-layer piezoelectric film 12a in FIG.
- the sixth-layer piezoelectric film 12e is laminated with the first protective layer 28 side facing upward.
- each piezoelectric film has a rectangular main portion and two projecting portions 15 projecting from the long side side of the main portion toward the outside in the plane direction.
- the two projecting portions 15 are provided so as to project from the opposite long sides of the main portion.
- the size of the main part of each piezoelectric film is different, and the positions of the end sides in the plane direction are different, but this point is omitted in FIGS. 15 to 16.
- the first-layer piezoelectric film 12a has a protruding portion 15 formed on one end side on the long side.
- the protruding portion 15 is formed at a position deviated from the position of the protruding portion 15 of the first layer piezoelectric film 12a toward the other end side.
- the protruding portion 15 is formed at a position deviated from the position of the protruding portion 15 of the second layer piezoelectric film 12b toward the other end side.
- the protruding portion 15 is formed at a position deviated from the position of the protruding portion 15 of the third layer piezoelectric film 12c toward the other end side.
- the protruding portion 15 is formed at a position deviated from the position of the protruding portion 15 of the fourth layer piezoelectric film 12d toward the other end side.
- the protruding portion of each piezoelectric film is formed at a position deviated by one protruding portion from the position of the protruding portion of the adjacent piezoelectric film.
- a hole 28a penetrating the first protective layer 28 is provided in the protrusion 15 on one long side of each piezoelectric film, and the first electrode layer 24 is exposed in the hole 28a. ..
- the protruding portion 15 on the other long side of each piezoelectric film is provided with a hole portion 30a penetrating the second protective layer 30, and the second electrode layer 26 is exposed in the hole portion 30a. ..
- the protrusion 15 is not adhered to the adjacent piezoelectric film. Therefore, wiring or the like can be connected to the first electrode layer 24 in the hole 28a.
- the hole portion 28a (the first electrode layer 24 in the hole portion 28a) is also referred to as a first contact point.
- the hole portion 30a (the second electrode layer 26 in the hole portion 30a) is also referred to as a second contact point. That is, the first contact 28a is formed on the protruding portion 15 on one long side of each piezoelectric film, and the second contact 30a is formed on the protruding portion 15 on the other long side.
- the protruding portions 15 of the piezoelectric films are arranged so as not to overlap each other in the plane direction. Further, a first contact 28a is formed on each of the protruding portions 15 on the long side side (long side side on the right side in FIG. 16) of each piezoelectric film. As described above, since the piezoelectric films of the first, third, and fifth layers and the piezoelectric films of the second and fourth layers are laminated in opposite directions, the first contact 28a is formed on the surfaces opposite to each other.
- a conductive film 60a is attached to the five protrusions 15 on which the first contact points 28a are formed from the front surface to the back surface. As a result, the first contact 28a of each piezoelectric film is easily electrically connected.
- a second contact 30a is formed on each of the protruding portions 15 on the other long side side (the long side side on the left side in FIG. 16) of each piezoelectric film.
- the second contact 30a is formed on the surfaces opposite to each other.
- a conductive film 60b is attached to the five protrusions 15 on which the second contact points 30a are formed from the front surface to the back surface. As a result, the second contact 30a of each piezoelectric film is easily electrically connected.
- the shapes of the hole 28a formed in the first protective layer 28 of the protrusion 15 and the hole 30a formed in the second protective layer 30 are not particularly limited as long as they can be reliably connected to the electrode layer. It can have various shapes such as a circular shape, an elliptical shape, a rectangular shape, a polygonal shape, and an indefinite shape.
- the sizes of the hole 28a and the hole 30a are not particularly limited as long as they can be reliably connected to the electrode layer.
- the diameter equivalent to a circle is preferably 1 mm to 10 mm, more preferably 2 mm to 4 mm. Further, it is preferable that a plurality of holes are formed in one protruding portion.
- the formation positions of the hole portion (first contact) 28a and the hole portion (second contact) 30a are not particularly limited, but each piezoelectric film can be easily connected to each other. It is preferable that the hole portion (first contact point) 28a and the hole portion (second contact point) 30a of the film are formed on the same side of the main portion, respectively.
- Examples of the method for forming the pores include a method of removing the protective layer by laser processing, solvent etching, mechanical polishing, and the like.
- conductive films 60a and 60b sheet-like materials formed of a conductive metal material such as a copper foil film may be used. Further, the conductive film and the first contact 28a and the second contact 30a may be connected via a conductive paint such as silver paste.
- each piezoelectric film has two protrusions, the first contact 28a is formed on one of the two protrusions 15, and the second contact 30a is formed on the other.
- the configuration is not limited to this.
- Each piezoelectric film may have one protruding portion, and the first contact 28a and the second contact 30a may be formed on the one protruding portion 15. Further, in this case, the first contact 28a and the second contact 30a may be formed at overlapping positions in the plane direction, but it is preferable that the first contact 28a and the second contact 30a are formed at different positions.
- the first contact 28a formed on the protruding portion 15 of the piezoelectric film faces one of the same surface sides.
- the second contact 30a is formed so as to face the same surface side of the other. Therefore, a conductive film is attached to the surface of the protrusion 15 on the side where the first contact 28a is formed, and the first contact 28a of each piezoelectric film is easily electrically connected. Similarly, another conductive film is attached to the surface of the protruding portion 15 on which the second contact 30a is formed. As a result, the second contact 30a of each piezoelectric film is easily electrically connected.
- all the protrusions 15 of the piezoelectric films are arranged at positions that do not overlap each other in the plane direction, but the present invention is not limited to this, and there are overlapping protrusions. You may.
- the protrusions of the piezoelectric films are arranged at positions where they do not overlap each other in the plane direction, but the present invention is not limited to this.
- the projecting portions of the piezoelectric films may project from the same position of the adhesive portion in the surface direction so that the lengths in the projecting directions are different from each other, and contacts may be formed in the exposed regions of the projecting portions. ..
- each piezoelectric film is not limited to that formed in a part of the width direction of the end edge of the main portion where the protrusion is formed, and the protrusion is the width in the direction orthogonal to the protrusion direction. However, it may be the same as the width of the edge of the main part where this protrusion is formed.
- the laminated piezoelectric element of the second embodiment of the present invention A plurality of layers of the piezoelectric film were laminated by folding back the piezoelectric film having the piezoelectric layer, the two electrode layers sandwiching the piezoelectric layer, and the two protective layers covering the electrode layers one or more times. Is a thing It is a laminated piezoelectric element in which the end edges of the adjacent layers are located at different positions in the plane direction.
- FIG. 18 is a diagram conceptually showing another example of the laminated piezoelectric element of the present invention.
- FIG. 19 is a cross-sectional view taken along the line BB of FIG.
- FIG. 20 is a diagram conceptually showing a state in which the laminated piezoelectric element of FIG. 18 is opened.
- the laminated piezoelectric element 10b shown in FIG. 18 is formed by laminating a plurality of layers of a piezoelectric film by folding back the piezoelectric film 12L a plurality of times.
- the piezoelectric film 12L is folded back four times to have a structure in which five layers of the piezoelectric film are laminated. Each layer is attached with an adhesive layer 14.
- the width direction orthogonal to the folding direction (longitudinal direction of the piezoelectric film 12L) differs depending on the position in the longitudinal direction.
- wide regions (13a, 13c, 13e) and narrow regions (13b, 13d) are alternately formed in the longitudinal direction.
- the first layer 13a laminated on the uppermost side in FIG. 19 and the second layer 13b laminated adjacent to the lower layer of the first layer 13a are shown in FIG.
- the widths in the middle and left and right directions are different, and the positions of the end edges in the plane direction, that is, in the left and right directions in FIG. 19 are different. More specifically, the width of the first layer 13a is longer than that of the second layer 13b, and the left edge of the first layer 13a in the figure is located on the left side (outside) of the left edge of the second layer 13b. Further, the right edge of the first layer 13a in the drawing is located on the right side (outside) of the right edge of the second layer 13b.
- the second layer 13b and the third layer 13c laminated adjacent to the lower layer of the second layer 13b have different widths in the left-right direction in the drawing, and are in the plane direction, that is, the left-right direction in FIG.
- the positions of the edges in are different. More specifically, the width of the third layer 13c is longer than that of the second layer 13b, and the left edge of the third layer 13c in the figure is located on the left side (outside) of the left edge of the second layer 13b. Further, the right edge of the third layer 13c in the figure is located on the right side (outside) of the right edge of the second layer 13b.
- the width of the fourth layer 13d laminated on the lower layer of the third layer 13c is shorter than that of the third layer 13c, and the left edge of the third layer 13c in the figure is the left edge of the fourth layer 13d. It is located on the left side (outside) of the third layer 13c, and the right edge of the third layer 13c in the figure is located on the right side (outside) of the right edge of the fourth layer 13d.
- the fifth layer 13e laminated on the lower layer of the fourth layer 13d is wider than the fourth layer 13d, and the left edge of the fifth layer 13e in the figure is the left edge of the fourth layer 13d.
- the right end of the fifth layer 13e in the figure is located on the left side (outside) of the fourth layer 13d, and is located on the right side (outside) of the right end of the fourth layer 13d.
- layers having a long width and layers having a short width are alternately laminated, and the positions of the left and right ends are different between the layer having a long width and the layer having a short width.
- the ends of the adjacent layers are laminated so as to be at different positions in the plane direction.
- the layers having a long width and the layers having a short width are alternately laminated, but this is limited to the case where the edges of the adjacent layers are at different positions in the plane direction. Will not be done.
- the width of the layer may increase from the upper layer to the lower layer.
- the width of the layer may increase from the center to the outside (surface side) in the stacking direction.
- the end face coating layer covering the end face of the piezoelectric film may be provided.
- the end face covering layer preferably covers both end faces of the piezoelectric film in the width direction orthogonal to the folding direction.
- the end face coating layer By having the end face coating layer, it is possible to more preferably suppress short-circuiting between the electrode layers of the adjacent layers. Further, since the end edges of the adjacent layers are located at different positions in the surface direction, the difference in thickness between the end portion and the central portion can be reduced when the end face covering layer is formed.
- the distance between the ends of the adjacent piezoelectric films 12 in the plane direction is 0. It is preferably 05 mm to 5 mm, more preferably 0.2 mm to 3 mm, and even more preferably 0.3 mm to 2 mm.
- the laminated piezoelectric element 10b is formed by folding the piezoelectric film 12L in the longitudinal direction, but the present invention is not limited to this, and the piezoelectric film 12L may be folded back in the lateral direction. ..
- the laminated piezoelectric element of the present invention has been described in detail above, the present invention is not limited to the above-mentioned example, and various improvements and changes may be made without departing from the gist of the present invention. Of course.
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Abstract
Description
例えば、特許文献1には、常温で粘弾性を有する高分子材料からなる粘弾性マトリックス中に圧電体粒子を分散してなる高分子複合圧電体、高分子複合圧電体の一方の面に形成された、面積が高分子複合圧電体以下である上部薄膜電極、上部薄膜電極の表面に形成される、面積が上部薄膜電極以上である上部保護層、高分子複合圧電体の上部薄膜電極の逆面に形成される、面積が高分子複合圧電体以下である下部薄膜電極、および、下部薄膜電極の表面に形成される、面積が下部薄膜電極以上である下部保護層を有する圧電積層体と、上部薄膜電極の一部に積層されて、少なくとも一部が高分子複合圧電体の面方向外部に位置する上部電極引出し用金属箔と、下部薄膜電極の一部に積層されて、少なくとも一部が高分子複合圧電体の面方向外部に位置する下部電極引出し用金属箔と、を有する電気音響変換フィルムが記載されている。
[1] 圧電体層と、圧電体層を挟持する2つの電極層と、電極層をそれぞれ覆う2つの保護層とを有する圧電フィルムを、複数層、積層してなり、
隣接する圧電フィルムのそれぞれの端辺の少なくとも一部が、面方向において異なる位置にある積層圧電素子。
[2] 各圧電フィルムは、圧電フィルムの端面を覆う端面被覆層を有する[1]に記載の積層圧電素子。
[3] 隣接する圧電フィルムの端辺間の距離が0.05mm~2mmである[1]または[2]に記載の積層圧電素子。
[4] 圧電体層は、厚さ方向に分極されており、
複数の圧電フィルムは、分極方向が交互になるように積層されている[1]~[3]のいずれかに記載の積層圧電素子。
[5] 圧電体層と、圧電体層を挟持する2つの電極層と、電極層をそれぞれ覆う2つの保護層とを有する圧電フィルムを、1回以上、折り返すことにより、圧電フィルムを、複数層、積層したものであり、
隣接する層それぞれの端辺が、面方向において異なる位置にある積層圧電素子。
[6] 圧電フィルムは、圧電フィルムの、折り返し方向と直交する幅方向の両端面を覆う端面被覆層を有する[5]に記載の積層圧電素子。
[7] 隣接する層の端辺間の最短距離が0.05mm~5mmである[5]または[6]に記載の積層圧電素子。
なお、本明細書において、「~」を用いて表される数値範囲は、「~」の前後に記載される数値を下限値および上限値として含む範囲を意味する。
圧電体層と、圧電体層を挟持する2つの電極層と、電極層をそれぞれ覆う2つの保護層とを有する圧電フィルムを、複数層、積層してなり、
隣接する圧電フィルムのそれぞれの端辺が、面方向において異なる位置にある積層圧電素子である。
図1に示す積層圧電素子10は、圧電フィルムを、5枚、積層して、隣接する圧電フィルムを、接着層(貼着層)14で貼着した構成を有する。各圧電フィルムは、圧電フィルムを伸縮させる駆動電圧を印加する電源に接続される(図示省略)。
なお、図1に示す積層圧電素子10は、圧電フィルムを、5層、積層したものであるが、本発明は、これに制限はされない。すなわち、本発明の積層圧電素子は、圧電フィルムを、複数層、積層したものであれば、圧電フィルムの積層数は、2層~4層でもよく、あるいは、6層以上であってもよい。この点に関しては、後述する積層圧電素子も、同様である。
図3に示す積層圧電素子10は、圧電フィルムを、5枚、積層して、隣接する圧電フィルムを、接着層(貼着層)14で貼着した構成を有する。
図4に示す積層圧電素子10は、圧電フィルムを、5枚、積層して、隣接する圧電フィルムを、接着層(貼着層)14で貼着した構成を有する。
図5に圧電フィルム12を断面図によって概念的に示す。
図5に示す例では、端面被覆層32は、第1保護層28の表面の一部から、積層体の端面、および、第2保護層30の表面の一部に至るまでの領域を覆っている。
端面被覆層32については後に詳述する。
図7に示す例は、圧電フィルム12が端面被覆層を有する以外は、図3に示す例と同様に圧電フィルム12を積層した例である。
図8に示す例は、圧電フィルム12が端面被覆層を有する以外は、図4に示す例と同様に圧電フィルム12を積層した例である。
なお、隣接する圧電フィルム12の端辺間の、面方向における距離は、短辺の延在方向と直交する方向における距離である。すなわち、端面の垂線方向における距離である。
また、隣接する圧電フィルムの少なくとも1組において、端辺が面方向において異なる位置にあればよく、全ての隣接する圧電フィルムの組において、端辺が面方向において異なる位置にあることが好ましい。すなわち、隣接する圧電フィルムの端辺が、面方向において同じ位置にある組が存在していてもよい。
図11に示す例のように、複数の圧電フィルム12を積層した積層体の端面を覆う端面被覆層32を有する構成としてもよい。すなわち、端面被覆層32が形成されていない圧電フィルム12を複数積層した後に、この積層体の端面を覆う端面被覆層を形成してもよい。
この伸縮は、0.01~0.1%程度である。
圧電体層20の厚さは、好ましくは10~300μm程度である。従って、厚さ方向の伸縮は、最大でも0.3μm程度と非常に小さい。
これに対して、圧電フィルムすなわち圧電体層20は、面方向には、厚さよりもはるかに大きなサイズを有する。従って、例えば、圧電フィルムの長さが20cmであれば、電圧の印加によって、最大で0.2mm程度、圧電フィルムは伸縮する。
この厚さ方向の振動によって、振動板は、音を発する。すなわち、振動板は、圧電フィルムに印加した電圧(駆動電圧)の大きさに応じて振動して、圧電フィルムに印加した駆動電圧に応じた音を発生する。
そのため、1枚毎の圧電フィルムの剛性が低く、伸縮力は小さくても、圧電フィルムを積層することにより、剛性が高くなり、積層圧電素子10としての伸縮力は大きくなる。その結果、本発明の積層圧電素子10は、振動板がある程度の剛性を有するものであっても、大きな力で振動板を十分に撓ませて、厚さ方向に振動板を十分に振動させて、振動板に音を発生させることができる。
従って、積層される圧電フィルムの分極方向が逆であっても、第1電極層24および第2電極層26に印加する電圧の極性さえ正しければ、全ての圧電フィルムは同じ方向に伸縮する。
振動板としては、一例として、樹脂製の板およびガラス板等の板材、看板などの広告・告知媒体、テーブル、ホワイトボードおよび投映用スクリーン等のオフィス機器および家具、有機エレクトロルミネセンス(OLED(Organic Light Emitting Diode)ディスプレイおよび液晶ディスプレイ等の表示デバイス、コンソール、Aピラー、天井およびバンパー等自動車などの車両の部材、ならびに、住宅の壁などの建材等が例示される。
図2および図5に示すように、圧電フィルム12は、圧電性を有するシート状物である圧電体層20と、圧電体層20の一方の面に積層される第1電極層24と、第1電極層24上に積層される第1保護層28と、圧電体層20の他方の面に積層される第2電極層26と、第2電極層26上に積層される第2保護層30とを有する。すなわち、圧電フィルム12は、第1保護層28、第1電極層24、圧電体層20、第2電極層26および第2保護層30の順に積層した構成を有する。後述するが、好ましい態様として、圧電フィルム12(圧電体層20)は、厚さ方向に分極されている。圧電フィルム12の分極方向の上流側の電極層および保護層を第1電極層24および第1保護層28とし、下流側の電極層および保護層を第2電極層26および第2保護層30とする。
(i) 可撓性
例えば、携帯用として新聞や雑誌のように書類感覚で緩く撓めた状態で把持する場合、絶えず外部から、数Hz以下の比較的ゆっくりとした、大きな曲げ変形を受けることになる。この時、高分子複合圧電体が硬いと、その分大きな曲げ応力が発生し、高分子マトリックスと圧電体粒子との界面で亀裂が発生し、やがて破壊に繋がる恐れがある。従って、高分子複合圧電体には適度な柔らかさが求められる。また、歪みエネルギーを熱として外部へ拡散できれば応力を緩和することができる。従って、高分子複合圧電体の損失正接が適度に大きいことが求められる。
さらに、貼り付ける相手材(振動板)の剛性(硬さ、コシ、バネ定数)に合わせて、積層することで、簡便にバネ定数を調節できるのが好ましく、その際、接着層14は薄ければ薄いほど、エネルギー効率を高めることができる。
高分子複合圧電体(圧電体層20)において、ガラス転移点が常温にある高分子材料、言い換えると、常温で粘弾性を有する高分子材料をマトリックスに用いることで、20Hz~20kHzの振動に対しては硬く、数Hz以下の遅い振動に対しては柔らかく振舞う高分子複合圧電体が実現する。特に、この振舞いが好適に発現する等の点で、周波数1Hzでのガラス転移点が常温、すなわち、0~50℃にある高分子材料を、高分子複合圧電体のマトリックスに用いるのが好ましい。
これにより、高分子複合圧電体が外力によってゆっくりと曲げられた際に、最大曲げモーメント部における高分子マトリックスと圧電体粒子との界面の応力集中が緩和され、高い可撓性が期待できる。
これにより、高分子複合圧電体が外力によってゆっくりと曲げられた際に発生する曲げモーメントが低減できると同時に、20Hz~20kHzの音響振動に対しては硬く振る舞うことができる。
しかしながら、その反面、良好な耐湿性の確保等を考慮すると、高分子材料は、比誘電率が25℃において10以下であるのも、好適である。
なお、これらの高分子材料は、1種のみを用いてもよく、複数種を併用(混合)して用いてもよい。
すなわち、粘弾性マトリックス34には、誘電特性や機械特性の調節等を目的として、シアノエチル化PVA等の粘弾性材料に加え、必要に応じて、その他の誘電性高分子材料を添加しても良い。
中でも、シアノエチル基を有する高分子材料は、好適に利用される。
また、圧電体層20の粘弾性マトリックス34において、シアノエチル化PVA等の常温で粘弾性を有する材料に加えて添加される誘電性ポリマーは、1種に限定はされず、複数種を添加してもよい。
さらに、粘着性を向上する目的で、ロジンエステル、ロジン、テルペン、テルペンフェノール、および、石油樹脂等の粘着付与剤を添加しても良い。
これにより、粘弾性マトリックス34における粘弾性緩和機構を損なうことなく、添加する高分子材料の特性を発現できるため、高誘電率化、耐熱性の向上、圧電体粒子36および電極層との密着性向上等の点で好ましい結果を得ることができる。
圧電体粒子36を構成するセラミックス粒子としては、例えば、チタン酸ジルコン酸鉛(PZT)、チタン酸ジルコン酸ランタン酸鉛(PLZT)、チタン酸バリウム(BaTiO3)、酸化亜鉛(ZnO)、および、チタン酸バリウムとビスマスフェライト(BiFe3)との固溶体(BFBT)等が例示される。
圧電体粒子36の粒径をこの範囲とすることにより、圧電フィルム12が高い圧電特性とフレキシビリティとを両立できる等の点で好ましい結果を得ることができる。
すなわち、圧電体層20中の圧電体粒子36は、好ましくは均一に分散されていれば、粘弾性マトリックス34中に不規則に分散されていてもよい。
圧電体層20中における圧電体粒子36の体積分率は、30~80%が好ましく、50%以上がより好ましく、従って、50~80%とするのが、さらに好ましい。
粘弾性マトリックス34と圧電体粒子36との量比を上記範囲とすることにより、高い圧電特性とフレキシビリティとを両立できる等の点で好ましい結果を得ることができる。
一例として、ポリフッ化ビニリデン(PVDF)およびフッ化ビニリデン-テトラフルオロエチレン共重合体の上述した誘電性高分子材料からなる圧電体層、ならびに、PZT、PLZT、チタン酸バリウム、酸化亜鉛およびBFBT等の上述した圧電体からなる圧電体層等が例示される。
圧電体層20が厚いほど、いわゆるシート状物のコシの強さなどの剛性等の点では有利であるが、同じ量だけ圧電フィルム12を伸縮させるために必要な電圧(電位差)は大きくなる。
圧電体層20の厚さは、10~300μmが好ましく、20~200μmがより好ましく、30~150μmがさらに好ましい。
圧電体層20の厚さを、上記範囲とすることにより、剛性の確保と適度な柔軟性との両立等の点で好ましい結果を得ることができる。
なお、圧電フィルム12は、これらの層に加えて、例えば、側面などの圧電体層20が露出する領域を覆って、ショート等を防止する端面被覆層等を有していてもよい。端面被覆層については後に詳述する。
このように、圧電フィルム12において、第1電極層24および第2電極層26で挾持された領域は、印加された電圧に応じて伸縮される。
なお、前述のとおり、第1電極層24および第1保護層28、ならびに、第2電極層26および第2保護層30は、圧電体層20の分極方向に応じて名称を付しているものである。従って、第1電極層24と第2電極層26、ならびに、第1保護層28と第2保護層30とは基本的に同様の構成を有する。
中でも、優れた機械的特性および耐熱性を有するなどの理由により、ポリエチレンテレフタレート(PET)、ポリプロピレン(PP)、ポリスチレン(PS)、ポリカーボネート(PC)、ポリフェニレンサルファイト(PPS)、ポリメチルメタクリレート(PMMA)、ポリエーテルイミド(PEI)、ポリイミド(PI)、ポリエチレンナフタレート(PEN)、トリアセチルセルロース(TAC)、および、環状オレフィン系樹脂等からなる樹脂フィルムが、好適に利用される。
ここで、第1保護層28および第2保護層30の剛性が高過ぎると、圧電体層20の伸縮を拘束するばかりか、可撓性も損なわれる。そのため、機械的強度やシート状物としての良好なハンドリング性が要求される場合を除けば、第1保護層28および第2保護層30は、薄いほど有利である。
例えば、圧電体層20の厚さが50μmで第1保護層28および第2保護層30がPETからなる場合、第1保護層28および第2保護層30の厚さは、100μm以下が好ましく、50μm以下がより好ましく、25μm以下がさらに好ましい。
第1電極層24および第2電極層26の厚さには、制限はない。また、第1電極層24および第2電極層26の厚さは、基本的に同じであるが、異なってもよい。
例えば、第1保護層28および第2保護層30がPET(ヤング率:約6.2GPa)で、第1電極層24および第2電極層26が銅(ヤング率:約130GPa)からなる組み合わせの場合、第1保護層28および第2保護層30の厚さが25μmだとすると、第1電極層24および第2電極層26の厚さは、1.2μm以下が好ましく、0.3μm以下がより好ましく、中でも0.1μm以下とするのが好ましい。
このような圧電フィルム12は、動的粘弾性測定による周波数1Hzでの損失正接(Tanδ)の極大値が常温に存在するのが好ましく、0.1以上となる極大値が常温に存在するのがより好ましい。
これにより、圧電フィルム12が外部から数Hz以下の比較的ゆっくりとした、大きな曲げ変形を受けたとしても、歪みエネルギーを効果的に熱として外部へ拡散できるため、高分子マトリックスと圧電体粒子との界面で亀裂が発生するのを防ぐことができる。
これにより、常温で圧電フィルム12が貯蔵弾性率(E’)に大きな周波数分散を有することができる。すなわち、20Hz~20kHzの振動に対しては硬く、数Hz以下の振動に対しては柔らかく振る舞うことができる。
これにより、圧電フィルム12が可撓性および音響特性を損なわない範囲で、適度な剛性と機械的強度を備えることができる。
これにより、圧電フィルム12を用いたスピーカの周波数特性が平滑になり、スピーカの曲率の変化に伴い最低共振周波数f0が変化した際の音質の変化量も小さくできる。
一例として、ポリイミド、および、耐熱性のポリエチレンテレフタレート等が例示される。
従って、接着層14は、貼り合わせる際には流動性を有し、その後、固体になる、接着剤からなる層でも、貼り合わせる際にゲル状(ゴム状)の柔らかい固体で、その後もゲル状の状態が変化しない、粘着剤からなる層でも、接着剤と粘着剤との両方の特徴を持った材料からなる層でもよい。
接着は、粘着とは異なり、高い接着温度を求める際に有用である。また、熱可塑タイプの接着剤は『比較的低温、短時間、および、強接着』を兼ね備えており、好適である。
ここで、本発明の積層圧電素子10は、接着層14が薄い方が、圧電体層20の伸縮エネルギ(振動エネルギ)の伝達効果を高くして、エネルギ効率を高くできる。また、接着層14が厚く剛性が高いと、圧電フィルムの伸縮を拘束する可能性もある。さらに、本発明の積層圧電素子10は、隣接する圧電フィルム12同士がショートしにくいので、接着層14を薄くできる。
この点を考慮すると、接着層14は、圧電体層20よりも薄いのが好ましい。すなわち、本発明の積層圧電素子10において、接着層14は、硬く、薄いのが好ましい。
具体的には、接着層14の厚さは、貼着後の厚さで0.1~50μmが好ましく、0.1~30μmがより好ましく、0.1~10μmがさらに好ましい。
また、貼着層の動的粘弾性測定による周波数1Hzでの内部損失が、粘着剤からなる接着層14の場合には25℃において1.0以下、接着剤からなる接着層14の場合には25℃において0.1以下であるのが好ましい。
第1保護層28が非常に薄く、ハンドリング性が悪い時などは、必要に応じて、セパレータ(仮支持体)付きの第1保護層28を用いても良い。なお、セパレータとしては、厚さ25~100μmのPET等を用いることができる。セパレータは、第2電極層26および第2保護層30を熱圧着した後、第1保護層28に何らかの部材を積層する前に、取り除けばよい。
有機溶媒には制限はなく、ジメチルホルムアミド(DMF)、メチルエチルケトン、シクロヘキサノン等の各種の有機溶媒が利用可能である。
シート状物11aを準備し、かつ、塗料を調製したら、この塗料をシート状物11aにキャスティング(塗布)して、有機溶媒を蒸発して乾燥する。これにより、図13に示すように、第1保護層28の上に第1電極層24を有し、第1電極層24の上に圧電体層20を形成してなる積層体11bを作製する。
なお、粘弾性材料がシアノエチル化PVAのように加熱溶融可能な物であれば、粘弾性材料を加熱溶融して、これに圧電体粒子36を添加/分散してなる溶融物を作製し、押し出し成形等によって、図12に示すシート状物11aの上にシート状に押し出し、冷却することにより、図13に示すような、第1保護層28の上に第1電極層24を有し、第1電極層24の上に圧電体層20を形成してなる積層体11bを作製してもよい。
粘弾性マトリックス34に、これらの高分子圧電材料を添加する際には、上述した塗料に添加する高分子圧電材料を溶解すればよい。または、上述した加熱溶融した粘弾性材料に、添加する高分子圧電材料を添加して加熱溶融すればよい。
周知のように、カレンダ処理とは、加熱プレスや加熱ローラ等によって、被処理面を加熱しつつ押圧して、平坦化等を施す処理である。
例えば、分極処理を行う対象に、直接、直流電界を印加する、電界ポーリングが例示される。なお、電界ポーリングを行う場合には、分極処理の前に、第1電極層14を形成して、第1電極層14および第2電極層16を利用して、電界ポーリング処理を行ってもよい。
また、本発明の圧電フィルム10を製造する際には、分極処理は、圧電体層12の面方向ではなく、厚さ方向に分極を行う。
次いで、図14に示すように、第2電極層26を圧電体層20に向けて、シート状物11cを、圧電体層20の分極処理を終了した積層体11bに積層する。
さらに、この積層体11bとシート状物11cとの積層体を、第2保護層30と第1保護層28とで挟持するようにして、加熱プレス装置や加熱ローラ対等で熱圧着する。以上によって、圧電フィルム12が作製される。
しかしながら、本発明は、これに制限はされない。すなわち、本発明の積層圧電素子は、例えば、異なる層構成の圧電フィルムを積層した構成、および、圧電体層20の厚さが異なる圧電フィルムを積層した構成等、各種の構成が利用可能である。
積層体の端面への端面被覆層32の形成方法には、制限はなく、端面被覆層32の形成材料に応じた、公知の形成方法(成膜方法)が利用可能である。
一例として、絶縁性の粘着テープを貼着する方法、端面被覆層32となる材料を溶解した液体を塗布して乾燥する方法、端面被覆層32となる材料を加熱溶融した液体を塗布して硬化する方法、端面被覆層32となる樹脂を溶剤に溶して、スプレーして乾燥させる方法等が例示される。絶縁性の粘着テープとしては、ポリイミドおよびポリエチレンテレフタレート等からなる粘着テープが例示される。
この際における液体の塗布方法には、制限はなく、公知の方法が、各種、利用可能である。一例として、スプレー塗布、および、浸漬塗布等が例示される。
また、形成方法によって、端面被覆層32は、第1保護層28および/または第2保護層30の主面まで形成されやすい。例えば、端面被覆層32となる樹脂を溶かした溶液に浸漬する場合には、第1保護層28および第2保護層30の主面の一部も溶液に浸漬されるため、端面被覆層32は、第1保護層28および第2保護層30の主面まで形成される。
圧電体層20が分極されている場合には、分極方向に応じて、電極層に印加する電圧の位相を合わせれば、複数の圧電フィルム12は、分極方向が同じになるように積層されていてもよいし、分極方向が逆になるように積層されるものがあってもよい。すなわち、各圧電フィルム12の第1電極層24に同じ位相の電圧を印加し、第2電極層26に同じ位相の電圧を印加すればよい。
圧電体層20の分極方向が、交互になるように圧電フィルム12を積層した積層圧電素子10においては、隣接する圧電フィルム12は、第2電極層26同士または第1電極層24同士が対面する。そのため、隣接する圧電フィルムの電極層同士が接触しても、ショート(短絡)する恐れがない点で好ましい。
または、上述した際のコロナポーリング処理の処理条件から、圧電体層20の分極方向を知見してもよい。
図15は、本発明の積層圧電素子の一例を概念的に示す図である。図16は、図15の分解図である。図17は、図15の積層圧電素子が有する複数の圧電フィルムを示す図である。
図15および図16に示す例は、圧電フィルムを5枚積層された構成を有する。各圧電フィルムは、分極方向が交互になるように積層されている。図16および図17においては、圧電フィルムの第2保護層側の面にハッチングを付して示す。すなわち、図16においては、図16中上側の1層目の圧電フィルム12aは、第1保護層28側を上に向けて積層され、2層目の圧電フィルム12bは、第2保護層30側を上に向けて積層され、3層目の圧電フィルム12cは、第1保護層28側を上に向けて積層され、4層目の圧電フィルム12dは、第2保護層30側を上に向けて積層され、5層目の圧電フィルム12eは、第1保護層28側を上に向けて積層されている。
図17に示す例では、各圧電フィルムの突出部は、隣接する圧電フィルムの突出部の位置から、突出部1つ分ズレた位置に形成されている。
すなわち、各圧電フィルムの一方の長辺側の突出部15に第1接点28aが形成され、他方の長辺側の突出部15に第2接点30aが形成されている。
また、各圧電フィルムの一方の長辺側(図16中右側の長辺側)の突出部15にはいずれも、第1接点28aが形成されている。前述のとおり、1、3、5層目の圧電フィルムと、2,4層目の圧電フィルムとは逆向きで積層されるため、第1接点28aは互いに逆側の面に形成されている。
圧電体層と、圧電体層を挟持する2つの電極層と、電極層をそれぞれ覆う2つの保護層とを有する圧電フィルムを、1回以上、折り返すことにより、圧電フィルムを、複数層、積層したものであり、
隣接する層それぞれの端辺が、面方向において異なる位置にある積層圧電素子である。
その場合、端面被覆層は、圧電フィルムの、折り返し方向と直交する幅方向の両端面を覆うことが好ましい。
また、隣接する層の端辺が、面方向において異なる位置にあるため、端面被覆層を形成した場合に端部と中央部分の厚さの差を小さくできる。
11a、11c シート状物
11b 積層体
12,12a~12j,12L 圧電フィルム
13a~13e 層
14 接着層
15 突出部
20 圧電体層
24 第1電極層
26 第2電極層
28 第1保護層
28a 孔部(第1接点)
30 第2保護層
30a 孔部(第2接点)
34 粘弾性マトリックス
36 圧電体粒子
40 コロナ電極
42 直流電源
60a~60b 導電性フィルム
Claims (7)
- 圧電体層と、前記圧電体層を挟持する2つの電極層と、前記電極層をそれぞれ覆う2つの保護層とを有する圧電フィルムを、複数層、積層してなり、
隣接する前記圧電フィルムのそれぞれの端辺の少なくとも一部が、面方向において異なる位置にある積層圧電素子。 - 各前記圧電フィルムは、前記圧電フィルムの端面を覆う端面被覆層を有する請求項1に記載の積層圧電素子。
- 隣接する前記圧電フィルムの端辺間の距離が0.05mm~2mmである請求項1または2に記載の積層圧電素子。
- 前記圧電体層は、厚さ方向に分極されており、
複数の前記圧電フィルムは、分極方向が交互になるように積層されている請求項1~3のいずれか一項に記載の積層圧電素子。 - 圧電体層と、前記圧電体層を挟持する2つの電極層と、前記電極層をそれぞれ覆う2つの保護層とを有する圧電フィルムを、1回以上、折り返すことにより、前記圧電フィルムを、複数層、積層したものであり、
隣接する層それぞれの端辺が、面方向において異なる位置にある積層圧電素子。 - 前記圧電フィルムは、前記圧電フィルムの、折り返し方向と直交する幅方向の両端面を覆う端面被覆層を有する請求項5に記載の積層圧電素子。
- 隣接する前記層の端辺間の最短距離が0.05mm~5mmである請求項5または6に記載の積層圧電素子。
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