JP2011249990A - Piezoelectric loudspeaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric loudspeaker which can obtain high acoustic pressure.SOLUTION: In a piezoelectric loudspeaker, a pair of piezoelectric elements 1 and 2, constituted by interposing piezoelectric layers 7 between electrode layers 9 and 15, is respectively joined to each surface of a two-sided resin support film 3, facing each other. Each of resin cover films 4 and 5 to respectively cover the pair of piezoelectric elements 1 and 2 is laminated on the support film 3. And the support film 3 and the cover films 4 and 5 around the piezoelectric elements 1 and 2 are fixed to a fixing frame member 6, thereby high acoustic pressure can be obtained.

Description

  The present invention relates to a piezoelectric speaker, and more particularly to a piezoelectric speaker used in a computer, a mobile phone, a small terminal device, an acoustic device, or the like.

  Conventionally, a piezoelectric speaker is known as a small low current drive acoustic device using a piezoelectric body as an electroacoustic transducer, and is used as an acoustic output device of a small device. Generally, a piezoelectric speaker has a structure in which a piezoelectric element having an electrode such as a silver thin film is provided on a metal diaphragm. The sound generation mechanism of a piezoelectric speaker is generated by applying an alternating current to both sides of the piezoelectric element to cause shape distortion in the piezoelectric element and vibrating a metal diaphragm.

  A conventional piezoelectric speaker is known in which a bimorph type vibrating body is formed by providing piezoelectric elements on the upper and lower surfaces of a metal diaphragm, and the outer periphery of the metal diaphragm is fixed by a fixed frame member (see Patent Document 1). ).

  In the piezoelectric speaker described in Patent Document 1, in order to suppress unnecessary vibration, it is described that a bimorph type vibrating body is sandwiched between a polymer film as a damper material from the upper and lower surfaces and laminated.

  This bimorph-type vibrator repeats vibrations in which the metal diaphragm protrudes or dents on the piezoelectric element formation side by applying an electric current to the piezoelectric elements on both sides of the metal vibrator so that when one is extended, the other contracts. become.

JP 2001-285994 A

  However, in the conventional piezoelectric speaker described in Patent Document 1, since the piezoelectric element using the thin piezoelectric layer is bonded to the upper and lower surfaces of the metal diaphragm, the piezoelectric element sufficiently vibrates the highly rigid metal vibrator. There was a problem that it was difficult to obtain high sound pressure.

  An object of this invention is to provide the piezoelectric speaker which can obtain a high sound pressure.

  In the piezoelectric speaker according to the present invention, a pair of piezoelectric elements each having a piezoelectric layer sandwiched between electrode layers are joined so as to face both surfaces of a resin support film, and the pair of piezoelectric elements are respectively covered. A resin-coated film is laminated on the support film, and the support film and the cover film around the piezoelectric element are fixed to a fixed frame member.

  In the piezoelectric speaker of the present invention, the supporting film to which the piezoelectric element is bonded and the covering film that covers the piezoelectric element are fixed to the fixed frame member, and the supporting film and the covering film serve as a vibration plate, and the metal vibration Compared to a conventional piezoelectric speaker in which a piezoelectric element is bonded to a plate and a metal diaphragm is fixed by a fixed frame member, the amplitude is large and a high sound pressure can be obtained.

  In the piezoelectric speaker of the present invention, the covering film may have a recess, and the piezoelectric element may be accommodated in the recess.

  In such a piezoelectric speaker, the covering film can be integrated with the piezoelectric element, whereby the amplitude of the support film can be increased and the sound pressure of the piezoelectric speaker can be improved.

  Furthermore, in the piezoelectric speaker of the present invention, a resin may be filled between the support film and the covering film. In this case, the covering film, the piezoelectric element and the support film can be integrated, whereby the amplitude of the support film can be increased and the sound pressure of the piezoelectric speaker can be improved.

  In the piezoelectric speaker of the present invention, the amplitude of the support film is larger and the sound pressure is higher than that of a conventional piezoelectric speaker in which a piezoelectric element is bonded to a metal diaphragm and the metal diaphragm is fixed by a fixed frame. Obtainable.

The piezoelectric speaker of this embodiment is shown, in which (a) is a longitudinal sectional view, (b) is a sectional view taken along line AA in (a), and (c) is taken along line CC in (a). FIG. It is a longitudinal cross-sectional view for demonstrating a part of process of producing the piezoelectric speaker of FIG. The form of the piezoelectric speaker which accommodated the piezoelectric element in the recessed part of the coating sheet is shown, (a) is a longitudinal cross-sectional view, (b) is a longitudinal cross-sectional view of a coating film. It is a longitudinal cross-sectional view which shows the state with which resin p was filled between the coating film and support film of the piezoelectric speaker of FIG. It is a longitudinal cross-sectional view which shows the state with which resin p was filled between the coating film and support film of the piezoelectric speaker of FIG. The form of the piezoelectric speaker which clamped between coating films with the fastening member is shown, (a) is a longitudinal cross-sectional view, (b) is a top view. (A)-(d) is sectional drawing for demonstrating fixation to the fixed frame of a support film and a covering film.

  Hereinafter, an embodiment of a piezoelectric speaker will be described with reference to FIG. FIG. 1 shows a piezoelectric speaker. For easy understanding, the thickness direction y of the multilayer piezoelectric element is shown enlarged. The same applies to FIGS.

  As shown in FIG. 1, the piezoelectric speaker is made of a resin-coated film that joins the piezoelectric elements 1 and 2 so as to face both surfaces of the resin-made support film 3 and covers the piezoelectric elements 1 and 2 respectively. 4 and 5 are respectively laminated on both sides of the support film 3, and the support film 3 and the covering films 4 and 5 around the piezoelectric elements 1 and 2 are fixed to the fixed frame member 6.

  The piezoelectric element 1 includes a laminate 13 in which piezoelectric layers 7 a and 7 b made of two ceramic layers and one internal electrode layer 9 a are alternately laminated, and a surface formed on both upper and lower surfaces of the laminate 13. Electrode layers 15 a and 15 b and a pair of external electrodes 17 and 19 provided at both ends in the longitudinal direction x of the laminate 13 are provided.

The external electrode layer 17 is connected to the surface electrode layers 15a and 15b, and the external electrode layer 19 is connected to one internal electrode layer 9a.

  The piezoelectric element 2 includes a laminate 14 in which piezoelectric layers 7c and 7d made of two ceramic layers and one internal electrode layer 9b are alternately laminated, and surfaces formed on both upper and lower surfaces of the laminate 14. Electrode layers 15 c and 15 d and a pair of external electrodes 18 and 20 provided at both ends in the longitudinal direction x of the laminate 14 are provided.

The external electrode layer 18 is connected to the surface electrode layers 15c and 15d, and the external electrode layer 20 is connected to one internal electrode layer 9b.

  Piezoelectric layers 7a, 7b, 7c, and 7d (hereinafter sometimes referred to as piezoelectric layers 7) of the piezoelectric elements 1 and 2 are alternately polarized as shown by arrows in FIG. , 7b is configured such that a voltage is applied to the external electrode layers 17, 18, 19, 20 so that the piezoelectric layers 7c, 7d extend.

  As the piezoelectric layer 7, conventionally used piezoelectric ceramics such as PZ, PZT, Bi layered compounds, lead-free piezoelectric materials such as tungsten bronze structure compounds, and the like can be used. The thickness of the piezoelectric layer 7 is set to 10 to 100 μm from the viewpoint of low voltage driving.

  The internal electrode layers 9a and 9b (hereinafter sometimes referred to as the internal electrode layer 9) preferably contain a metal component composed of silver and palladium and a material component that constitutes the piezoelectric layer 7. By containing the ceramic component constituting the piezoelectric layer 7 in the internal electrode layer 9, the stress due to the difference in thermal expansion between the piezoelectric layer 7 and the internal electrode layer 9 can be reduced, and the piezoelectric element has almost no stacking failure. 1 and 2 can be obtained. The internal electrode layer 9 is not particularly limited to a metal component composed of silver and palladium, and is not limited to a material component constituting the piezoelectric layer 7 as a ceramic component. It may be.

  The surface electrode layers 15a, 15b, 15c, and 15d (hereinafter sometimes referred to as the surface electrode layer 15) and the external electrodes 17, 18, 19, and 20 preferably contain a glass component in a metal component made of silver. By containing the glass component, it is possible to obtain a strong adhesion between the piezoelectric layer 7 and the internal electrode layer 9 and the surface electrode layer 15 or the external electrodes 17, 18, 19, 20.

  As shown in FIG. 1B, the fixed frame member 6 has a rectangular shape and is formed by bonding two rectangular frame-shaped fixed frame members 6a and 6b, and the fixed frame member 6a, The outer peripheral portions of the resin films 3, 4, and 5 are sandwiched between 6 b and are bonded and fixed by an adhesive. In FIG. 1, the description of the adhesive is omitted. The fixed frame members 6a and 6b are made of stainless steel having a thickness of 100 to 1000 μm, for example. In the present invention, the thickness and material of the fixed frame members 6a and 6b are not particularly limited.

  As shown in FIG. 1A, the support film 3 is formed to be thicker than the covering films 4 and 5, and the support film 3 is sandwiched between the outer peripheral portions of the support film 3 between the fixed frame members 6a and 6b. Is fixed to the fixed frame members 6a and 6b in a state where tension is applied in the surface direction, and the support film 3 and the covering films 4 and 5 serve as a diaphragm. The thickness of the support film 3 is, for example, 10 to 100 μm, the thickness of the coating films 4 and 5 is, for example, 5 to 50 μm, and the thickness of the support film 3 is thicker than that of the coating films 4 and 5. .

  The support film 3 and the covering films 4 and 5 are made of a resin such as polyethylene or polyimide, for example. In this embodiment, the thickness, material, and the like of the support film 3 and the covering films 4 and 5 are not particularly limited.

  As shown in FIG. 1A, the covering films 4 and 5 are thinner than the support film 3 and are configured to be easily deformed to some extent. The covering films 4 and 5 are arranged above and below the support film 3. The piezoelectric elements 1 and 2 are covered, and the piezoelectric elements 1 and 2 are laminated with the films 3, 4 and 5. In the piezoelectric speaker of this embodiment, the frame is fixed to the fixed frame members 6a and 6b with at least a tension applied to the support film 3.

  As shown in FIGS. 1B and 1C, lead wires 21a, 21b, 21c, and 21d are connected to the external electrodes 17, 18, 19, and 20, respectively, and are drawn to the outside. These lead wires 21a and 21b are sandwiched between the support film 3 and the covering film 4, and are further sandwiched between the fixed frame members 6a and 6b. The lead wires 21c and 21d are supported by the support film. 3 and the covering film 5, and further sandwiched between the fixed frame members 6a and 6b.

  A method for manufacturing a piezoelectric speaker will be described. First, laminated piezoelectric elements 1 and 2 are prepared. In the piezoelectric element 1, first, a binder, a dispersant, a plasticizer, and a solvent are kneaded with a powder of a piezoelectric material to prepare a slurry. As the piezoelectric material, any of lead-based and non-lead-based materials can be used.

  Next, the obtained slurry can be formed into a sheet to obtain a green sheet, and an internal electrode pattern is formed by printing an internal electrode paste on the green sheet, and the green sheet on which the internal electrode pattern is formed Only a green sheet is laminated on the upper surface of the laminate to produce a laminated molded body.

  Next, the laminate 13 can be obtained by degreasing, firing, and cutting the laminate compact to a predetermined size. The laminated body 13 processes the outer peripheral portion as necessary, and prints the paste of the surface electrode layers 15a and 15b on the main surface in the lamination direction of the piezoelectric layers 7a and 7b of the laminated body 13, The piezoelectric element 1 shown in FIG. 1 can be obtained by printing pastes of the external electrodes 17 and 19 on both side surfaces in the longitudinal direction x and baking the electrodes at a predetermined temperature. Similarly, the piezoelectric element 2 can be obtained.

Next, in order to impart piezoelectricity to the piezoelectric element 1, a DC voltage is applied through the surface electrode layers 15 a and 15 b or the external electrodes 17 and 19 to polarize the piezoelectric layers 7 a and 7 b of the piezoelectric element 1. Similarly, the piezoelectric element 2 is polarized. The polarization is in the direction indicated by the arrow in FIG.

  Next, the support film 3 is prepared, and the outer peripheral portion of the support film 3 is sandwiched between temporary fixing frame members 26a and 26b as shown in FIG. 2, and fixed in a state where tension is applied to the support film 3. Thereafter, an adhesive is applied to the support film 3, the surface electrode 15b side of the piezoelectric element 1 is pressed onto the support film 3, and then the adhesive is cured by irradiation with heat or ultraviolet rays. Then, the covering film 4 is covered up to the upper surfaces of the piezoelectric element 1 and the temporary fixing frame member 26a, and the air between the supporting film 3 and the covering film 4 is heat-sealed between the supporting film 3 and the covering film 4. And the support film 3 is brought into close contact with the piezoelectric element 1 and the covering film 4.

  Next, an adhesive is applied to the support film 3, the surface electrode 15c side of the piezoelectric element 2 is pressed onto the support film 3, and then the adhesive is cured by irradiation with heat or ultraviolet rays. Then, the covering film 5 is covered up to the upper surfaces of the piezoelectric element 2 and the temporary fixing frame member 26b, and the air between the supporting film 3 and the covering film 5 is thermally fused between the supporting film 3 and the covering film 5. The cover film 5 is brought into close contact with the piezoelectric element 2 and the support film 3.

  Thereafter, the inner portions of the temporary fixing frame members 26a and 26b, in other words, the outer peripheral portion of the support film 3 and the portion where the covering films 4 and 5 are laminated are sandwiched between the fixing frame members 6a and 6b, and the adhesive. The piezoelectric speaker of the present embodiment can be obtained by bonding and fixing with and removing the temporarily fixing frame members 26a and 26b.

  In the piezoelectric speaker configured as described above, the piezoelectric elements 1 and 2 in which the piezoelectric layers 7 and the internal electrode layers 9 are alternately laminated are bonded to the support film 3, and the surface of the piezoelectric elements 1 and 2 is covered with the coating film 4. 5, and the outer peripheral portions of the support film 3 and the cover films 4 and 5 are fixed by the fixed frame member 6. Therefore, the piezoelectric elements 1 and 2 are accommodated and integrated between the support film 3 and the cover films 4 and 5. In addition, since the resin support film 3 and the covering films 4 and 5 become diaphragms and the amplitude of the resin films 3, 4 and 5 can be increased, a high sound pressure can be obtained.

  Further, even if the piezoelectric layer 7 is thin, it is laminated with the covering films 4 and 5 as a whole, so that cracks and the like are hardly generated, and the reliability is improved. Moreover, peeling from the support film 3 of the piezoelectric elements 1 and 2 can be prevented by the covering films 4 and 5.

  In the piezoelectric speaker of FIG. 1, the number of stacked piezoelectric layers 7 in the piezoelectric elements 1 and 2 is two. However, in the piezoelectric speaker of this embodiment, the number of stacked piezoelectric layers 7 in the piezoelectric elements 1 and 2 is It is not specifically limited, For example, 1 layer may be sufficient and 3 layers or more may be sufficient. When the piezoelectric layer is a single layer, a surface electrode layer is formed on the surface.

  FIG. 3 shows still another form of the piezoelectric speaker. In this form, as shown in FIG. 3 (b), the cover films 4 and 5 are respectively formed with recesses 33 in advance, and the recesses 33. The piezoelectric elements 1 and 2 are accommodated therein. The depth of the recess 33 of the covering films 4 and 5 is equal to the thickness of the piezoelectric elements 1 and 2.

  In such a piezoelectric speaker, the covering films 4 and 5 can be integrated with the piezoelectric elements 1 and 2, whereby the amplitude can be increased and the sound pressure of the piezoelectric speaker can be improved.

  FIG. 4 shows another embodiment of the piezoelectric speaker. Between the support film 3 and the covering films 4 and 5 of FIG. 1, the periphery of the piezoelectric elements 1 and 2 is filled with a resin p. 1 and 2 are bonded and fixed between the support film 3 and the covering films 4 and 5.

  The piezoelectric speaker between the support film 3 and the covering films 4 and 5 and filled with the resin p around the piezoelectric elements 1 and 2 is formed on the upper surface of the piezoelectric elements 1 and 2 and the upper surface of the support film 3 in the vicinity thereof. It can be produced by applying the resin p, covering it with the coating films 4 and 5, and removing the air between the support film 3 and the coating films 4 and 5.

  In such a piezoelectric speaker, not only the support film 3 but also the cover films 4 and 5 can be diaphragms, and the piezoelectric elements 1 and 2 are securely bonded between the support film 3 and the cover films 4 and 5. The amplitude of the films 3, 4, and 5 that can be fixed and function as diaphragms can be further improved.

  In addition, between the support film 3 and the covering films 4 and 5 which have the recessed part 33 which accommodates the piezoelectric elements 1 and 2, around the piezoelectric elements 1 and 2, as shown in FIG. Of course, it may be filled. In this case, the same effect as described above can be obtained. Such a piezoelectric speaker can also be manufactured in the same manner as the piezoelectric speaker shown in FIG.

FIG. 6 shows still another embodiment of the piezoelectric speaker. The covering films 4 and 5 of FIG. 1 are fastened to the support film 3 side by the fastening member 35, and the supporting film 3 and the covering films 4 and 5 are the fastening member 35. It is integrated with the tightening part. Four fastening members 35 are arranged around the rectangular piezoelectric elements 1 and 2 at a predetermined interval with respect to each side so as to correspond to each side of the piezoelectric elements 1 and 2. By tightening the respective members provided on the films 4 and 5 side, for example, with screws or the like, the covering films 4 and 5 are fastened to the support film 3 side by the fastening member 35 so as to be integrated.

  In such a piezoelectric speaker, the integration of the piezoelectric elements 1 and 2 with the support film 3 and the covering films 4 and 5 can be further promoted, and the amplitude of the films 3, 4 and 5 functioning as a diaphragm can be further improved. it can.

  In the case of using a resin film as the support plate, unlike the case of using a conventional metal plate as the support plate, it is necessary to bond and fix to the fixed frame member 6 in a state where tension is applied. It is necessary to consider fixing the covering films 4 and 5 to the fixed frame.

  FIG. 7 (a) shows a conventional case in which the support film 3 made of resin and the cover films 4, 5 are joined together with an adhesive 51, and FIG. 7 (b) shows the support film 3, the cover film 4, 5 are formed at predetermined intervals, and the side surfaces of the fixed frame member 6 of the covering films 4 and 5 and the fixed frame member 6 are joined together by the adhesive 51, and the adhesive is placed in the through hole 53. In this case, 51 is filled and the support film 3 and the covering films 4 and 5 are fixed to the fixed frame member 6. In the case of FIG. 7B, even when tension is applied to the support film 3 and the covering films 4 and 5 with respect to the fixed frame member 6, it can be stably fixed. A through-hole is also formed in the fixed frame member 6, and a bolt is inserted into the through-hole of the fixed frame member 6 and the through-hole 53 of the laminate to fix the support frame 3 and the covering frame 6. The films 4 and 5 can be more reliably fixed.

  In FIG. 7C, a through hole is formed in a portion where the support film 3 and the covering films 4 and 5 are laminated outside the fixed frame member 6, and the wedge 55 passes through the through hole. ing. In the case of this FIG.7 (c), even when strong tension | tensile_strength is applied with respect to the fixed frame member 6 to the support film 3, the coating films 4, 5, it can fix stably.

  Further, FIG. 7D shows a widened portion 57 in which the inner portion of the fixed frame member 6 is widened, and the adhesive 59 filled in the widened portion 57 is an adhesive in the outer portion of the fixed frame member 6. It is possible to be more elastically deformed than 61. In the case of FIG. 7D, the supporting film 3 and the covering films 4 and 5 are fixed by the adhesive 61 in the outer portion of the fixed frame member 6, and the supporting film 3 and the covering films 4 and 5 are fixed by the widened portion 57. Large deformation can be allowed. If the fixing by the adhesive 61 is weak, the structure shown in FIG. 7B or the structure shown in FIG. 7C can be adopted.

DESCRIPTION OF SYMBOLS 1, 2 ... Piezoelectric element 3 ... Support film 4, 5 ... Cover film 6, 6a, 6b ... Fixed frame member 7, 7a, 7b, 7c, 7d ... Piezoelectric layer 9, 9a, 9b ... internal electrode layers 13, 14 ... laminates 15, 15a, 15b, 15c, 15d ... surface electrode layers 17, 18, 19, 20 ... external electrode layers 21a, 21b, 21c , 21d, lead-out wiring 33, recess x, longitudinal direction of piezoelectric element y, thickness direction p of piezoelectric element, resin

Claims (3)

  A pair of piezoelectric elements each having a piezoelectric layer sandwiched between electrode layers are bonded so as to face both surfaces of a resin support film, and a resin coating film covering each of the pair of piezoelectric elements is formed as described above. A piezoelectric speaker comprising: a support film, and the support film and the covering film around the piezoelectric element are fixed to a fixed frame member.   The piezoelectric speaker according to claim 1, wherein the covering film has a recess, and the piezoelectric element is accommodated in the recess.   The piezoelectric speaker according to claim 1 or 2, wherein a resin is filled between the support film and the covering film.

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