JP2015126605A - Piezoelectric actuator, piezoelectric vibration device having the same, portable terminal, acoustic generator, and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator which inhibits a flexible substrate from being peeled off due to influence of vibration of a piezoelectric element and has excellent durability, and also to provide a piezoelectric vibration device having the piezoelectric actuator, a portable terminal, an acoustic generator, and an electronic apparatus.SOLUTION: A piezoelectric actuator 1 includes: a piezoelectric element 11 equipped with a laminate 14 formed by laminating an internal electrode 12 and a piezoelectric layer 13 and a surface electrode 15 electrically connected to the internal electrode 12 on one main surface of the laminate 14; and a flexible substrate 2 which is equipped with a base film 21 and a wiring conductor 22 provided on the lower surface of the base film 21 and whose part is joined to one main surface of the laminate 14 via a conductive joining member 3 so that the wiring conductor 22 is electrically connected to the surface electrode 15. The conductive joining member 3 has a portion extending from an overlapping region of the piezoelectric element 11 and the flexible substrate 2 to the outside of the overlapping region.

Description

  The present invention relates to a piezoelectric actuator suitable for a piezoelectric vibration device, a portable terminal, and the like, and a piezoelectric vibration device including the piezoelectric actuator, a portable terminal, an acoustic generator, and an electronic device.

  As the piezoelectric actuator, a bimorph type piezoelectric element in which a surface electrode is formed on the surface of a laminated body in which a plurality of internal electrodes and piezoelectric layers are laminated (see Patent Document 1), a piezoelectric element and a flexible element are used. There is known one in which a substrate is bonded and a surface electrode of a piezoelectric element and a wiring conductor of a flexible substrate are electrically connected (see Patent Document 2).

JP 2002-10393 A JP-A-6-14396

  Here, the vibration of the piezoelectric element is transmitted to the flexible substrate, and the flexible substrate also vibrates with the vibration of the piezoelectric element. Accordingly, there is a problem that the flexible substrate may be peeled off from the piezoelectric element due to the influence of the vibration when driven for a long time.

  Further, in the piezoelectric vibration device, the portable terminal, the sound generator, and the electronic device provided with the above-described piezoelectric actuator, there is a problem that durability is poor because the flexible substrate constituting the piezoelectric actuator is peeled off from the piezoelectric element.

  The present invention has been made in view of the above circumstances, and a piezoelectric actuator excellent in durability, in which peeling of a flexible substrate due to the influence of vibration of a piezoelectric element is suppressed, a piezoelectric vibration device including the piezoelectric actuator, a portable terminal, and sound generation An object is to provide a container and an electronic device.

  The piezoelectric actuator of the present invention includes a laminated body in which an internal electrode and a piezoelectric layer are laminated, a piezoelectric element including a surface electrode electrically connected to the internal electrode on one main surface of the laminated body, and a base A wiring conductor provided on the lower surface of the film and the base film, and a part of the laminated body via a conductive bonding material so that the wiring conductor is electrically connected to the surface electrode And the conductive bonding material has a portion extending from the overlapping region of the piezoelectric element and the flexible substrate to the outside of the overlapping region. It is characterized by.

  Moreover, the piezoelectric actuator of the present invention is characterized in that, in the above configuration, the conductive bonding material is an anisotropic conductive material.

  Moreover, the piezoelectric actuator of the present invention is characterized in that, in the above configuration, the conductive bonding material is provided so as to go around the side surface of the piezoelectric element.

  Moreover, the piezoelectric actuator of the present invention is characterized in that, in the above configuration, the conductive bonding material is provided so as to wrap around the side surface of the flexible substrate.

  Moreover, the piezoelectric actuator of the present invention is characterized in that, in the above structure, the conductive bonding material has a portion extending in a direction in which the flexible substrate is extended.

  In the piezoelectric actuator of the present invention, in the above configuration, a cover film is provided so that the flexible substrate covers the wiring conductor except in the vicinity of a region where the piezoelectric element and the flexible substrate overlap each other. The wiring conductor is exposed from the cover film in the vicinity of a region where the element and the flexible substrate overlap, and the conductive bonding material covers the wiring conductor exposed from the cover film. .

  Further, one end of the piezoelectric element and one end of the flexible substrate are overlapped so as to be orthogonal to each other, and the conductive bonding material is the piezoelectric in the outer periphery of the region where the piezoelectric element and the flexible substrate overlap. It has the part extended from the edge by the side of the one end part of an element, It is characterized by the above-mentioned.

  In the piezoelectric actuator of the present invention, in the above configuration, the conductive bonding material includes conductive particles and a resin adhesive, and the number of the conductive particles included in the conductive bonding material is equal to that of the piezoelectric element and the piezoelectric element. It is characterized in that it is smaller per unit volume in a portion extending from a region overlapping with the flexible substrate.

  According to another aspect of the present invention, there is provided a piezoelectric vibration device including the piezoelectric actuator and a vibration plate bonded to the other main surface of the laminate.

  A portable terminal of the present invention includes the piezoelectric actuator, an electronic circuit, a display, and a housing, and the other main surface of the laminate is bonded to the display or the housing. It is characterized by.

  The portable terminal according to the present invention is characterized in that, in the above-described configuration, the display or the casing generates a vibration for transmitting sound information through an ear cartilage or air conduction.

  The acoustic generator of the present invention includes a piezoelectric actuator, the piezoelectric actuator attached thereto, a vibration plate that vibrates with the piezoelectric actuator due to vibration of the piezoelectric actuator, and at least a part of a peripheral portion of the vibration plate. And a support body that supports the diaphragm.

  According to another aspect of the invention, there is provided an electronic apparatus including the above-described acoustic generator, an electronic circuit connected to the acoustic generator, and a housing that houses the electronic circuit and the acoustic generator. It has a function of generating sound.

  According to the present invention, since the conductive bonding material has a portion extending from the piezoelectric element, a piezoelectric actuator in which peeling of the flexible substrate due to the influence of vibration of the piezoelectric element is suppressed even when driven for a long time is obtained. be able to.

  In addition, according to the piezoelectric vibration device, the portable terminal, the sound generator, and the electronic device of the present invention including the piezoelectric actuator, it is excellent in durability and can be driven stably for a long time.

FIG. 1A is a schematic perspective view showing an example of an embodiment of the piezoelectric actuator of the present invention, FIG. 1B is a schematic cross-sectional view taken along the line AA shown in FIG. ) Is a schematic cross-sectional view taken along line B-B shown in FIG. 2A is a schematic sectional view similar to FIG. 1B of another example of the embodiment of the piezoelectric actuator of the present invention, and FIG. 2B is still another embodiment of the piezoelectric actuator of the present invention. It is a schematic sectional drawing similar to FIG.1 (b) of the example of. 1 is a schematic perspective view schematically showing an embodiment of a piezoelectric vibration device of the present invention. It is a schematic perspective view which shows typically embodiment of the portable terminal of this invention. It is the schematic sectional drawing cut | disconnected by the AA line shown in FIG. It is the schematic sectional drawing cut | disconnected by the BB line shown in FIG. Fig.7 (a) is a typical top view which shows schematic structure of embodiment of the acoustic generator of this invention, FIG.7 (b) is an example cut | disconnected by the AA line of Fig.7 (a) FIG. 7C is a schematic cross-sectional view of another example cut along line AA in FIG. 7A. It is a figure which shows the structure which concerns on embodiment of the electronic device of this invention.

  An example of an embodiment of a piezoelectric actuator of the present invention will be described in detail with reference to the drawings.

  FIG. 1A is a schematic perspective view showing an example of an embodiment of the piezoelectric actuator of the present invention, FIG. 1B is a schematic cross-sectional view taken along the line AA shown in FIG. ) Is a schematic cross-sectional view taken along line B-B shown in FIG. FIG. 2 (a) is a schematic sectional view similar to FIG. 1 (b) of another example of the embodiment of the piezoelectric actuator of the present invention, and FIG. 2 (b) is an embodiment of the piezoelectric actuator of the present invention. It is a schematic sectional drawing similar to FIG.1 (b) of another example.

  The piezoelectric actuator 1 of the example shown in FIG. 1 and FIG. 2 is electrically connected to the internal electrode 12 on one main surface of the laminated body 14 in which the internal electrode 12 and the piezoelectric layer 13 are laminated, and the laminated body 14. The laminated body 14 includes the piezoelectric element 11 including the surface electrode 15, the base film 21 and the wiring conductor 22 provided on the lower surface of the base film 21, and the wiring conductor 22 is electrically connected to the surface electrode 15. And a flexible substrate 2 partially bonded to the one main surface via the conductive bonding material 3, and the conductive bonding material 3 overlaps from the overlapping region of the piezoelectric element 11 and the flexible substrate 2. It has a portion that extends to the outside of the region.

  The piezoelectric actuator 1 of this example has a piezoelectric element 11, and a laminated body 14 constituting the piezoelectric element 11 is formed by laminating an internal electrode 12 and a piezoelectric layer 13 and forming a plate shape. . The piezoelectric actuator 1 has an active portion in which a plurality of internal electrodes 12 overlap in the stacking direction and an inactive portion other than the active portion, and is formed in a long shape, for example. In the case of a piezoelectric actuator attached to a display or casing of a mobile terminal, the length of the laminate 14 is preferably, for example, 18 mm to 28 mm, and more preferably 22 mm to 25 mm. The width of the laminated body 14 is preferably 1 mm to 6 mm, for example, and more preferably 3 mm to 4 mm. The thickness of the laminate 14 is preferably, for example, 0.2 mm to 1.0 mm, and more preferably 0.4 mm to 0.8 mm.

  The internal electrode 12 constituting the laminated body 14 is formed by simultaneous firing with the ceramics forming the piezoelectric layer 13 and includes a first electrode and a second electrode. For example, the first electrode is a ground electrode, and the second electrode is a positive electrode or a negative electrode. The piezoelectric layers 13 are alternately stacked to sandwich the piezoelectric layers 13 from above and below, and the first electrode and the second electrode are arranged in the stacking order, so that the piezoelectric layers 13 sandwiched between them are arranged. A drive voltage is applied to the. As this forming material, for example, a conductor mainly composed of silver or silver-palladium alloy having low reactivity with piezoelectric ceramics, or a conductor containing copper, platinum or the like can be used. You may make it contain.

  In the example illustrated in FIGS. 1 and 2, the end portions of the first electrode and the second electrode are alternately led to a pair of side surfaces facing each other of the stacked body 14. In the case of a piezoelectric actuator attached to a display or casing of a mobile terminal, the length of the internal electrode 12 is preferably, for example, 17 mm to 25 mm, and more preferably 21 mm to 24 mm. For example, the width of the internal electrode 12 is preferably 1 mm to 5 mm, and more preferably 2 mm to 4 mm. The thickness of the internal electrode 12 is preferably 0.1 μm to 5 μm, for example.

The piezoelectric layer 13 constituting the laminated body 14 is formed of ceramics having piezoelectric characteristics. As such ceramics, for example, a perovskite oxide made of lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ), Lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), or the like can be used. The thickness of one layer of the piezoelectric layer is preferably set to 0.01 to 0.1 mm, for example, so as to be driven at a low voltage. In order to obtain a large bending vibration, it is preferable to have a piezoelectric constant d31 of 200 pm / V or more.

  A surface electrode 15 electrically connected to the internal electrode 12 is provided on one main surface of the multilayer body 14. The surface electrode 15 in the form shown in FIGS. 1 and 2 includes a first surface electrode 151 having a large area, a second surface electrode 152 having a small area, and a third surface electrode 153. For example, the first surface electrode 151 is electrically connected to the internal electrode 12 serving as the first pole, and the second surface electrode 152 is, for example, the internal electrode 12 serving as the second pole disposed on one main surface side. The third surface electrode 153 is electrically connected to, for example, the internal electrode 12 serving as a second pole disposed on the other main surface side. In the case of a piezoelectric actuator attached to a display or casing of a portable terminal, the length of the first surface electrode 151 is preferably, for example, 17 mm to 23 mm, and more preferably 19 mm to 21 mm. The width of the first surface electrode 151 is, for example, preferably 1 mm to 5 mm, and more preferably 2 mm to 4 mm. The lengths of the second surface electrode 152 and the third surface electrode 153 are preferably 1 mm to 3 mm, for example. The widths of the second surface electrode 152 and the third surface electrode 153 are preferably 0.5 mm to 1.5 mm, for example.

  The piezoelectric actuator 1 has a flexible substrate 2 that is electrically joined to the surface electrode 15. Specifically, the flexible substrate 2 has a wiring conductor 22 provided on the surface (lower surface) of a resin base film 21, for example. In this example, a cover film 23 is further provided in a region excluding the joint portion with the piezoelectric element 11 and the vicinity thereof. A part of the flexible substrate 2 is bonded to one main surface of the multilayer body 14 constituting the piezoelectric element 11 via the conductive bonding material 3, and the wiring conductor 22 is connected to the surface electrode 15 via the conductive bonding material 3. Electrically connected.

  The cover film 23 only needs to be provided in a region excluding the connection portion between the wiring conductor 22 and the surface electrode 15. However, the cover film 23 is not provided in the region overlapping with the piezoelectric element 11 and the vicinity thereof. A reliable electrical connection can be obtained without being affected by the thickness of the cover film 23. For example, the flexible substrate 2 is joined to the piezoelectric element 11 at one end, and joined to an external circuit (connector) at the other end.

As the conductive bonding material 3, a conductive adhesive, solder, or the like is used, but a conductive adhesive is preferable. For example, conductive particles 31 made of, for example, gold, copper, nickel, or gold-plated resin balls are dispersed in a resin adhesive 32 such as acrylic resin, epoxy resin, silicone resin, polyurethane resin, or synthetic rubber. This is because the use of an adhesive can reduce stress caused by vibration compared to solder. More preferably, the conductive adhesive is preferably an anisotropic conductive material. The anisotropic conductive material is composed of conductive particles 31 responsible for electrical bonding and a resin adhesive 32 responsible for adhesion, and one conductive particle 31 is in contact with the surface electrode 15 and the wiring conductor 22. That is, the respective conductive particles 31 between the surface electrode 15 and the wiring conductor 22 are in contact with the surface electrode 15 and the wiring conductor 22. Since this anisotropic conductive material can conduct in the thickness direction and insulate in the in-plane direction, even in a narrow pitch wiring, there is no electrical short between the surface electrodes of different polarities, and a flexible substrate The connection part with 2 can be made compact.

  Although not shown, the piezoelectric actuator 1 may include a reinforcing plate fixed to a region overlapping the piezoelectric element 11 when viewed from above the flexible substrate 2. The reinforcing plate is used to reinforce the bonding region of the flexible substrate 2 with the piezoelectric element 11, for example, resin such as glass epoxy (FR-4), composite (CEM-3), polyetherimide, polyimide, polyester, etc. , Stainless steel, aluminum, and alloys thereof, for example, having a thickness of 50 to 200 μm.

  The piezoelectric actuator 1 has a portion where the conductive bonding material 3 extends from the overlapping region of the piezoelectric element 11 and the flexible substrate 2 to the outside of the overlapping region. The extended conductive bonding material 3 is bonded to the piezoelectric element 11 or the flexible substrate 2 in the extended region. The extended distance d1 is set to 0.05 mm to 1.5 mm, for example.

  According to this configuration, the bonding area between the piezoelectric element 11 and the flexible substrate 2 is increased by the extended conductive bonding material 3, so that the bonding strength is enhanced and the effect of absorbing vibration is increased. Moreover, it will become difficult to destroy by moving to the edge part of the electroconductive joining material 3 in which the fracture start point extended. As a result, the flexible substrate 2 can be prevented from peeling from the piezoelectric element 11 even when driven for a long time.

  Here, as shown in FIGS. 1B and 1C, it is preferable that the conductive bonding material 3 is provided so as to go around the side surface of the piezoelectric element 11. According to this configuration, separation from the starting point between the conductive bonding material 3 and the piezoelectric element 11 is suppressed. Further, the heat generated by the vibration of the piezoelectric element 11 is transmitted to the extending portion, and the metal is contained in the conductive bonding material 3 so that the heat can be easily radiated. 2 can be further prevented from peeling from the piezoelectric element 11.

  On the other hand, as shown in FIG. 2A and FIG. 2B, it may be provided so as to go around the side surface of the flexible substrate 2. According to this configuration, peeling starting from between the conductive bonding material 3 and the flexible substrate 2 is suppressed. Further, the vibration of the flexible substrate 2 is absorbed, so that the flexible substrate 2 can be further prevented from being peeled off from the piezoelectric element 11 even when driven for a long time.

  Further, as shown in FIGS. 1B and 2, the conductive bonding material 3 preferably has a portion extending in the direction in which the flexible substrate 2 extends. In the direction in which the flexible substrate 2 is extended, the flexible substrate 2 vibrates, and the end of the conductive bonding material 3 located in this direction is likely to be subjected to a vibration load. Therefore, the flexible substrate 2 is extended. Since the conductive bonding material 3 extends in the direction in which the flexible substrate 2 is disposed, the flexible substrate 2 can be further prevented from peeling off from the piezoelectric element 11 even when driven for a long time.

Furthermore, the flexible substrate 2 is provided with a cover film 23 so as to cover the wiring conductor 22 except in the vicinity of the region where the piezoelectric element 11 and the flexible substrate 2 overlap, and in the vicinity of the region where the piezoelectric element 11 and the flexible substrate 2 overlap. Then, the wiring conductor 22 may be exposed from the cover film 23, and the conductive bonding material 3 may cover the wiring conductor 22 exposed from the cover film 23, thereby increasing the bonding strength and absorbing vibration. In addition to the increase, the effect of protecting the wiring conductor 22 and preventing the wiring conductor 22 from being damaged is also added.

  Further, as shown in FIG. 1C, one end of the piezoelectric element 11 and one end of the flexible substrate 2 are overlapped so as to be orthogonal to each other, and the conductive bonding material 3 includes the piezoelectric element 11 and the flexible substrate 2. May extend from one end of the piezoelectric element 11 in the outer periphery of the overlapping region, and stress is applied to one end of the piezoelectric element 11 when stress is applied to the flexible substrate 2 such that the flexible substrate 2 is twisted. Since the load is easily applied, the flexible substrate 2 can be further prevented from peeling from the piezoelectric element 11 even when driven for a long time.

  In addition, the conductive bonding material 3 includes conductive particles 31 and a resin adhesive 32, and the number of conductive particles included in the conductive bonding material 3 extends from a region where the piezoelectric element 11 and the flexible substrate 2 overlap. It is preferable that there is a small amount per unit volume at the site. In the extended part where the stress load is most likely to be applied, since the vibration absorbing effect by the conductive bonding material 3 is enhanced by the large amount of the resin adhesive 32, the flexible substrate 2 is peeled off from the piezoelectric element 11 even if driven for a long time. Can be further suppressed.

  Then, by flattening the other main surface of the piezoelectric element 11, for example, when the other main surface is bonded to an object to be vibrated (for example, a vibration plate described later), it is integrated with the object to be vibrated. As a result, bending vibration is easily generated, and the efficiency of bending vibration can be increased as a whole, and the sound pressure can be improved.

  The piezoelectric actuator 1 according to the present invention is a so-called bimorph type piezoelectric actuator that receives an electrical signal from the surface electrode 15 and vibrates and vibrates so that one main surface and the other main surface are bent surfaces. However, the piezoelectric actuator of the present invention is not limited to the bimorph type, and may be a unimorph type. For example, the other main surface of the piezoelectric actuator is bonded (bonded) to a diaphragm described later, so that the unimorph type can be bent. Can be vibrated.

  Next, a method for manufacturing the piezoelectric actuator 1 of the present embodiment will be described.

First, a ceramic green sheet to be the piezoelectric layer 13 is produced. Specifically, a ceramic slurry is prepared by mixing a calcined powder of piezoelectric ceramic, a binder made of an organic polymer such as acrylic or butyral, and a plasticizer. And a ceramic green sheet is produced using this ceramic slurry by using tape molding methods, such as a doctor blade method and a calender roll method. As the piezoelectric ceramic, any material having piezoelectric characteristics may be used. For example, a perovskite oxide made of lead zirconate titanate (PbZrO ₃ —PbTiO ₃ ) can be used. As the plasticizer, dibutyl phthalate (DBP), dioctyl phthalate (DOP), or the like can be used.

  Next, a conductive paste to be the internal electrode 12 is produced. Specifically, a conductive paste is prepared by adding and mixing a binder and a plasticizer to a silver-palladium alloy metal powder. This conductive paste is applied on the ceramic green sheet in the pattern of the internal electrodes 12 using a screen printing method. Furthermore, after laminating a plurality of ceramic green sheets printed with this conductive paste and performing a binder removal treatment at a predetermined temperature, firing at a temperature of 900 to 1200 ° C., using a surface grinder or the like By performing a grinding process so as to have a shape, a laminated body 14 including the internal electrodes 12 and the piezoelectric body layers 13 that are alternately laminated is manufactured.

The laminated body 14 is not limited to the one produced by the above manufacturing method, and any production method can be used as long as the laminated body 14 formed by laminating a plurality of internal electrodes 12 and piezoelectric layers 13 can be produced. It may be produced.

  Thereafter, a silver glass-containing conductive paste prepared by adding a binder, a plasticizer, and a solvent to a mixture of conductive particles mainly composed of silver and glass is used as a main electrode of the laminate 14 in a pattern of the surface electrode 15. After the surface and side surfaces are printed and dried by a screen printing method or the like, a baking process is performed at a temperature of 650 to 750 ° C. to form the surface electrode 15.

  When the surface electrode 15 and the internal electrode 12 are electrically connected, a via that penetrates the piezoelectric layer 13 may be formed or connected, or a side electrode may be formed on the side surface of the multilayer body 14, It may be produced by any manufacturing method.

  Next, the flexible substrate 2 is connected and fixed (bonded) to the laminate 14 using, for example, a conductive adhesive as the conductive bonding material 3.

  First, a conductive adhesive paste is applied and formed at a predetermined position of the laminate 14 using a technique such as screen printing. Then, the flexible substrate 2 is connected and fixed to the piezoelectric element 11 by curing the conductive adhesive paste in a state where the flexible substrate 2 is brought into contact therewith. The conductive adhesive paste may be applied and formed on the flexible substrate 6 side.

  When the resin constituting the conductive adhesive is made of a thermoplastic resin, the conductive adhesive is applied and formed on a predetermined position of the laminate 14 or the flexible substrate 2 and then the laminate 14 and the flexible substrate 2 are made conductive. The thermoplastic resin softens and flows by being heated and pressed in a state of being brought into contact with the adhesive, and then returned to room temperature, so that the thermoplastic resin is cured again, and the flexible substrate 2 is connected and fixed to the laminate 14. Is done.

  In particular, when an anisotropic conductive material is used as the conductive bonding material 3, it is necessary to control the amount of pressurization so that adjacent conductive particles do not come into contact with each other.

  In order to have a configuration in which the conductive bonding material 3 has a portion extending from the overlapping region of the piezoelectric element 11 and the flexible substrate 2 to the outside of the overlapping region, an anisotropic conductive material or the like After the conductive bonding material 3 is applied and formed in a predetermined position on the laminate 14 or the flexible substrate 2, the laminate 14 and the flexible substrate 2 may be pressure-bonded so as to extend the conductive bonding material 3. . At this time, the thickness of the coating is preferably 30 μm or more.

  In particular, the conductive bonding material 3 extends around the side surface of the piezoelectric element 11, extends around the side surface of the flexible substrate 2, or covers the wiring conductor 22 exposed from the cover film 23. For this purpose, a particularly large amount of coating may be applied at these sites.

  Similarly, the conductive bonding material 3 extends in the extending direction of the flexible substrate 2 or extends from one end of the piezoelectric element 11. In particular, a large amount of coating may be applied.

  In addition, in order to have a configuration in which the number of conductive particles 31 included in the conductive bonding material 3 is smaller per unit volume in a portion extending from a region where the piezoelectric element 11 and the flexible substrate 2 overlap, The pattern of the surface electrode 15 or the wiring conductor 22 is formed so that the conductive particles remain in the region where the piezoelectric element 11 and the flexible substrate 2 overlap, and the pressure is controlled, and then the resin adhesive is allowed to flow. .

As shown in FIG. 3, the piezoelectric vibration device according to the present embodiment includes a piezoelectric actuator 1 and a vibration plate 81 bonded to the other main surface of the multilayer body 14 constituting the piezoelectric element 11 included in the piezoelectric actuator 1. It is what you have. Note that the flexible substrate 2 bonded to one main surface of the laminate 14 constituting the piezoelectric element 11 is omitted in FIG.

  The diaphragm 81 is, for example, a rectangular thin plate. The diaphragm 81 can be preferably formed using a material having high rigidity and elasticity, such as acrylic resin or glass. Moreover, the thickness of the diaphragm 81 is set to 0.4 mm to 1.5 mm, for example.

  The diaphragm 81 is bonded to the other main surface of the multilayer body 14 constituting the piezoelectric element 11 via a bonding member 82. The entire surface of the other main surface may be bonded to the vibration plate 81 via the bonding member 82, or the substantially entire surface may be bonded.

  The joining member 82 has a film shape. Further, the joining member 82 is formed of a material that is softer and more easily deformed than the vibration plate 81, and has a smaller elastic modulus and rigidity such as Young's modulus, rigidity, and bulk elastic modulus than the vibration plate 81. That is, the joining member 82 can be deformed when the diaphragm 81 is vibrated by driving the piezoelectric actuator 1 (piezoelectric element 11), and deforms more greatly than the diaphragm 81 when the same force is applied. is there. Then, the other main surface (main surface on the −z direction side in the drawing) of the laminate 14 is fixed to one main surface (main surface on the + z direction side in the drawing) of the bonding member 82, so A part of one main surface (main surface on the + z direction side in the drawing) of the diaphragm 81 is fixed to the other main surface (main surface on the −z direction side in the drawing).

  By joining the laminate 14 and the diaphragm 81 with the deformable joining member 82, the deformable joining member 82 is larger than the diaphragm 81 when vibration is transmitted from the piezoelectric actuator 1 (piezoelectric element 11). Deform.

  At this time, the anti-phase vibration reflected from the vibration plate 81 can be mitigated by the deformable joining member 82, so that the piezoelectric actuator 1 (piezoelectric element 11) is not affected by the surrounding vibration and the vibration plate 81. Strong vibrations can be transmitted.

  In particular, since at least a part of the joining member 82 is made of a viscoelastic body, strong vibration from the piezoelectric actuator 1 (piezoelectric element 11) is transmitted to the vibration plate 81, while weak vibration reflected from the vibration plate 81. Is preferable in that the bonding member 82 can absorb. For example, it is possible to use a double-sided tape in which an adhesive is attached to both surfaces of a base material made of nonwoven fabric or the like, or a joining member including an adhesive having elasticity, and the thickness thereof is, for example, 10 μm to 2000 μm. Can be used.

  The joining member 82 may be a single member or a composite made up of several members. As such a joining member 82, for example, a double-sided tape in which a pressure-sensitive adhesive is attached to both surfaces of a base material made of a nonwoven fabric or the like, various elastic adhesives that are adhesives having elasticity, and the like can be suitably used. Further, the thickness of the bonding member 82 is preferably larger than the amplitude of the bending vibration of the piezoelectric actuator 1 (piezoelectric element 11). However, if the thickness is too thick, the vibration is attenuated. Is set. However, in the piezoelectric vibration device of the present invention, the material of the bonding member 82 is not limited, and the bonding member 82 may be formed of a material that is harder and more difficult to deform than the vibration plate 81. Moreover, depending on the case, the structure which does not have the joining member 82 may be sufficient.

  The piezoelectric vibration device of this example having such a configuration functions as a piezoelectric vibration device that flexibly vibrates the piezoelectric actuator 1 (piezoelectric element 11) by applying an electric signal, thereby vibrating the vibration plate 81. The other end in the length direction of the diaphragm 81 (the end in the −y direction in the figure, the peripheral edge of the diaphragm 81, etc. may be supported by a support member not shown).

  In the piezoelectric vibration device of this example, the vibration plate 81 is joined to the other flat main surface of the piezoelectric element 11. Thereby, it can be set as the piezoelectric vibration apparatus with which the laminated body 14 and the diaphragm 81 were joined firmly.

  Since the piezoelectric vibration device of this example is configured using the piezoelectric actuator 1 in which peeling of the flexible substrate 2 is suppressed, the piezoelectric vibration device is excellent in durability and can be driven stably for a long period of time. .

  As shown in FIGS. 4 to 6, the portable terminal of the present embodiment includes the piezoelectric actuator 1, an electronic circuit (not shown), a display 91, and a housing 92, and The other main surface is joined to the housing 92. 4 is a schematic perspective view schematically showing the portable terminal of the present invention, FIG. 5 is a schematic cross-sectional view taken along line AA shown in FIG. 4, and FIG. 6 is a line BB shown in FIG. It is the schematic sectional drawing cut | disconnected by. The flexible substrate joined to one main surface of the laminated body 14 is omitted in FIGS.

  Here, it is preferable that the laminated body 14 and the housing 92 are joined using a deformable joining member. That is, in FIG. 5 and FIG. 6, the joining member 82 is a deformable joining member.

  By joining the laminate 14 and the housing 92 with the deformable joining member 82, the deformable joining member 82 is larger than the housing 92 when vibration is transmitted from the piezoelectric actuator 1 (piezoelectric element 11). Deform.

  At this time, the antiphase vibration reflected from the casing 92 can be mitigated by the deformable joining member 82, so that the piezoelectric actuator 1 (piezoelectric element 11) is not affected by the surrounding vibration and the casing 92 is not affected. Strong vibrations can be transmitted.

  In particular, since at least a part of the joining member 82 is formed of a viscoelastic body, strong vibration from the piezoelectric actuator 1 (piezoelectric element 11) is transmitted to the housing 92, while weak vibration reflected from the housing 92. Is preferable in that the bonding member 82 can absorb. For example, it is possible to use a double-sided tape in which an adhesive is attached to both surfaces of a base material made of nonwoven fabric or the like, or a joining member including an adhesive having elasticity, and the thickness thereof is, for example, 10 μm to 2000 μm. Can be used.

  In this example, the laminated body 14 is attached to a part of the casing 92 that serves as a cover of the display 91, and a part of the casing 92 functions as the diaphragm 922.

  In this example, the laminated body 14 is bonded to the housing 92, but the laminated body 14 may be bonded to the display 91.

  The housing 92 includes a box-shaped housing main body 921 having one surface opened, and a diaphragm 922 that closes the opening of the housing main body 921. The casing 92 (the casing main body 921 and the diaphragm 922) can be formed preferably using a material such as a synthetic resin having high rigidity and elastic modulus.

  A peripheral edge portion of the vibration plate 922 is attached to the housing main body 921 via a bonding material 93 so as to vibrate. The bonding material 93 is formed of a material that is softer and easier to deform than the diaphragm 922, and has a smaller elastic modulus and rigidity such as Young's modulus, rigidity, and bulk modulus than the diaphragm 922. That is, the bonding material 93 can be deformed, and deforms more greatly than the diaphragm 922 when the same force is applied.

  The bonding material 93 may be a single material or a composite material composed of several members. As such a bonding material 93, for example, a double-sided tape in which an adhesive is attached to both surfaces of a base material made of a nonwoven fabric or the like can be suitably used. The thickness of the bonding material 93 is set so that vibration is not attenuated due to being too thick, and is set to, for example, 0.1 mm to 0.6 mm. However, in the mobile terminal of the present invention, the material of the bonding material 93 is not limited, and the bonding material 93 may be formed of a material that is harder than the vibration plate 922 and hardly deforms. Moreover, depending on the case, the structure which does not have the joining material 93 may be sufficient.

  Examples of the electronic circuit (not shown) include a circuit that processes image information displayed on the display 91 and audio information transmitted by the mobile terminal, a communication circuit, and the like. At least one of these circuits may be included, or all the circuits may be included. Further, it may be a circuit having other functions. Furthermore, you may have a some electronic circuit. The electronic circuit and the piezoelectric actuator 1 are connected by a connection wiring (not shown).

  The display 91 is a display device having a function of displaying image information. For example, a known display such as a liquid crystal display, a plasma display, and an organic EL display can be suitably used. The display 91 may have an input device such as a touch panel. Moreover, the cover (diaphragm 922) of the display 91 may have an input device such as a touch panel. Further, the entire display 91 or a part of the display 91 may function as a diaphragm.

  Since the portable terminal of this example is configured using the piezoelectric actuator 1 in which the peeling of the flexible substrate 2 is suppressed, the portable terminal can be a portable terminal that has excellent durability and can be driven stably for a long period of time.

  In addition, the mobile terminal according to the present embodiment is characterized in that the display 91 or the casing 92 generates vibration that transmits sound information through the ear cartilage or air conduction. The portable terminal of this example can transmit sound information by transmitting a vibration to the cartilage of the ear by bringing the diaphragm (display 91 or housing 92) into contact with the ear directly or via another object. That is, sound information can be transmitted by bringing a vibration plate (display 91 or housing 92) into direct or indirect contact with the ear and transmitting vibration to the cartilage of the ear. Thereby, for example, even when the surroundings are noisy, sound information can be transmitted clearly, and a portable terminal capable of recognizing voice even by a hearing impaired person can be obtained. Note that the object interposed between the diaphragm (display 91 or housing 92) and the ear may be, for example, a cover of a mobile terminal, a headphone or an earphone, and any object that can transmit vibration. Anything can be used. Further, it may be a portable terminal that transmits sound information by propagating sound generated from the diaphragm (display 91 or housing 92) in the air. Furthermore, it may be a portable terminal that transmits sound information via a plurality of routes.

  Since the portable terminal of this example is configured using the piezoelectric actuator 1 in which the peeling of the flexible substrate 2 is suppressed, it is excellent in durability and can stably transmit high-quality sound information over a long period of time. it can.

  Further, as shown in FIG. 7, the acoustic generator 10 of the present embodiment is provided with the piezoelectric actuator 1 described above and the piezoelectric actuator 1, and a diaphragm 20 that vibrates with the piezoelectric actuator 1 due to vibration of the piezoelectric actuator 1. And a frame 30 as a support body that is provided on at least a part of the outer peripheral portion of the diaphragm 20 and supports the diaphragm 20.

  The piezoelectric actuator 1 is an exciter that excites the diaphragm 20 by vibrating under application of a voltage. The main surface of the piezoelectric actuator 1 and the main surface of the vibration plate 20 are joined by an adhesive such as an epoxy resin, and the piezoelectric actuator 1 bends and vibrates, so that the piezoelectric actuator 1 gives a certain vibration to the vibration plate 20. Sound can be generated.

  The periphery of the diaphragm 20 is fixed to the frame 30 in a state where tension is applied, and the diaphragm 20 vibrates with the piezoelectric actuator 1 by the vibration of the piezoelectric element actuator 1. The diaphragm 20 can be formed using various materials such as resin and metal. For example, the diaphragm 20 can be formed of a resin film such as polyethylene, polyimide, or polypropylene having a thickness of 10 to 200 μm. Since the resin film is a material having a lower elastic modulus and mechanical Q value than a metal plate or the like, the diaphragm 20 is made of a resin film, so that the diaphragm 20 bends and vibrates with a large amplitude, thereby reducing the sound pressure. It is possible to reduce the difference between the resonance peak and the dip by widening the width of the resonance peak and reducing the height in the frequency characteristics.

  The frame body 30 functions as a support body that supports the diaphragm 20 at the periphery of the diaphragm 20, and can be formed using various materials such as metals such as stainless steel and resins. The frame 30 may be composed of one frame member (upper frame member 301) as shown in FIG. 7 (b), and two frame members (upper frame member 301 and upper frame member 301 and The lower frame member 302) may be used. In this case, the tension of the diaphragm 20 can be stabilized by sandwiching the diaphragm 20 between the two frame members. The upper frame member 301 and the lower frame member 302 have a thickness of, for example, 100 to 5000 μm.

  In the acoustic generator 10 of this example, as shown in FIGS. 7B and 7C, the acoustic generator 10 is provided so as to cover from the piezoelectric actuator 1 to at least the periphery of the piezoelectric actuator 1 on the surface of the diaphragm 20. It is preferable to further have a resin layer 40. As the resin layer 40, for example, an acrylic resin can be used. By embedding the piezoelectric actuator 1 (piezoelectric element 11) in the resin layer 40, an appropriate damper effect can be induced, so that the resonance phenomenon is suppressed and the peak or dip in the frequency characteristic of the sound pressure is suppressed to be small. Can do. 7B and 7C, the resin layer 40 may be formed to be the same height as the upper frame member 301.

  Since the acoustic generator 10 of this example is configured using the piezoelectric actuator 1 in which the peeling of the flexible substrate 2 is suppressed, it has excellent durability and can be driven stably for a long period of time.

  Next, an electronic device equipped with an acoustic generator will be described with reference to FIG. FIG. 8 is a diagram illustrating a configuration of the electronic device 50 according to the embodiment. In addition, in both figures, only the component required for description is shown and description about a general component is abbreviate | omitted.

  As shown in FIG. 8, the electronic device 50 of this example includes an acoustic generator 10, an electronic circuit 60 connected to the acoustic generator 10, and a housing 70 that houses the electronic circuit 60 and the acoustic generator 10. And having a function of generating sound from the sound generator 10.

  The electronic device 50 includes an electronic circuit 60. The electronic circuit 60 includes, for example, a controller 50a, a transmission / reception unit 50b, a key input unit 50c, and a microphone input unit 50d. The electronic circuit 60 is connected to the sound generator 10 and has a function of outputting an audio signal to the sound generator 10. The sound generator 10 generates sound based on the sound signal input from the electronic circuit 60.

The electronic device 50 includes a display unit 50e, an antenna 50f, and the sound generator 10. Further, the electronic device 50 includes a housing 70 that accommodates these devices. Although FIG. 8 shows a state in which each device including the controller 50a is accommodated in one casing 70, the accommodation form of each device is not limited. In the present embodiment, it is only necessary that at least the electronic circuit 60 and the sound generator 10 are accommodated in one housing 70.

  The controller 50 a is a control unit of the electronic device 50. The transmission / reception unit 50b transmits / receives data via the antenna 50f based on the control of the controller 50a. The key input unit 50c is an input device of the electronic device 50 and accepts a key input operation by an operator. The microphone input unit 50d is also an input device of the electronic device 50, and accepts a voice input operation by an operator. The display unit 50e is a display output device of the electronic device 50, and outputs display information based on the control of the controller 50a.

  The sound generator 10 operates as a sound output device in the electronic device 50. The sound generator 10 is connected to the controller 50a of the electronic circuit 60, and emits sound upon application of a voltage controlled by the controller 50a.

  In FIG. 8, the electronic device 50 is described as a portable terminal device. However, the electronic device 50 is not limited to the type of the electronic device 50, and may be applied to various consumer devices having a function of emitting sound. . For example, flat-screen TVs and car audio devices can of course be used for products having a function of emitting sound such as "speak", for example, various products such as vacuum cleaners, washing machines, refrigerators, microwave ovens, etc. .

  Since such an electronic device 50 is configured using the piezoelectric actuator 1 in which peeling of the flexible substrate 2 is suppressed, it is excellent in durability and can be driven stably for a long period of time. As described above, the structure includes the acoustic generator 10 using the piezoelectric actuator 1 in which the spark does not occur for a long period of time and the displacement amount of the laminated body is stable. Can be driven. In addition, by providing the housing 70, it is possible to increase the low-frequency sound pressure.

  Next, specific examples of the piezoelectric actuator of the present invention will be described.

  A piezoelectric actuator was produced as shown below.

  The piezoelectric element had a long shape with a length of 23.5 mm, a width of 3.3 mm, and a thickness of 0.5 mm. The piezoelectric element has a structure in which piezoelectric layers having a thickness of 30 μm and internal electrodes are alternately stacked, and the total number of piezoelectric layers is 16. The piezoelectric layer was formed of lead zirconate titanate in which part of Zr was replaced with Sb. As the internal electrode, an alloy of silver palladium was used.

  After laminating ceramic green sheets on which a conductive paste made of silver palladium was printed, they were pressed and adhered, degreased at a predetermined temperature, and fired at 1000 ° C. to obtain a laminated sintered body.

  Next, using a conductive paste made of silver, the surface electrode was printed so as to be longer by 1 mm at both ends in the width direction than the internal electrode to obtain a surface electrode.

  A voltage with an electric field strength of 2 kV / mm was applied between the internal electrodes (between the first electrode and the second electrode) via the surface electrode to polarize the piezoelectric element.

  Moreover, the flexible substrate and the reinforcing plate were produced as follows. First, a copper foil serving as a wiring conductor is bonded to a polyimide film as a sheet in which a large number of base films are arranged (a multi-sheet for base film) using an adhesive. Next, a conductor pattern of the wiring conductor is formed by a photolithography technique, and a polyimide film serving as a cover film is bonded using an adhesive for insulation and protection of the wiring conductor. Next, a gold plating treatment is performed, and a polyimide sheet having a thickness of 125 μm (a multi-sheet for reinforcing plate) serving as a reinforcing plate is not formed with a wiring conductor of a multi-sheet for base film using a thermosetting adhesive. The flexible substrate and the reinforcing plate were produced by bonding to the surface and punching into a desired shape with a mold.

  In order to electrically connect the wiring conductor of the flexible substrate and the surface electrode, a conductive bonding material using anisotropic conductive particles is used. Anisotropic conductive particles are particles having a particle size of about 5 μm, and a particle body made of acrylic resin coated with gold plating with Ni plating as a base coat. The conductive paste as the conductive bonding material is a paste in which the anisotropic conductive particles are dispersed in a synthetic rubber-based adhesive. After printing on the surface electrode by screen printing, press the flexible substrate while heating, A piezoelectric actuator was produced by extending the conductive bonding material. Here, in order to produce the extended portion, the conductive bonding material is applied from the direction in which the flexible substrate is extended and the end on the one end side of the piezoelectric element, with the coating thickness of the conductive bonding material being about 30 μm. Was extended.

  On the other hand, as a comparative example, the application thickness of the conductive bonding material used for bonding in the same method as the above example was set to 20 μm, and a piezoelectric actuator in which the conductive bonding material did not extend from the flexible substrate was manufactured.

  Then, each piezoelectric actuator was attached to a diaphragm and a reliability test was performed. When a 100,000-cycle sine wave signal was continuously applied and driven, the displacement amount of the diaphragm was zero in the piezoelectric actuator of the comparative example. When the inside was analyzed, in the piezoelectric actuator of the comparative example, the flexible substrate was peeled off from the piezoelectric element, and no voltage was applied. On the other hand, in the piezoelectric actuator of the embodiment of the present invention, a displacement of about 4 μm was confirmed on the diaphragm, and the flexible substrate was not peeled off.

1: Piezoelectric actuator 11: Piezoelectric element 12: Internal electrode 13: Piezoelectric layer 14: Laminate 15: Surface electrode 2: Flexible substrate 21: Base film 22: Wiring conductor 23: Cover film 3: Anisotropic conductive material 31: Conductive particles 32: Resin adhesive 81: Vibration plate 82: Bonding member 91: Display 92: Housing 921: Housing body 922: Vibration plate 93: Bonding material 10: Sound generator 20: Vibration plate 30: Frame 301: Upper frame member 302: lower frame member 40: resin layer 50: electronic device 60: electronic circuit 70: housing

Claims (13)

A laminated body in which an internal electrode and a piezoelectric layer are laminated, and a piezoelectric element including a surface electrode electrically connected to the internal electrode on one main surface of the laminated body;
A base film and a wiring conductor provided on the lower surface of the base film are provided, and a conductive bonding material is provided on one main surface of the laminate so that the wiring conductor is electrically connected to the surface electrode. And a flexible substrate to which the parts are joined,
The piezoelectric actuator, wherein the conductive bonding material has a portion extending from an overlapping region between the piezoelectric element and the flexible substrate to an outside of the overlapping region.   The piezoelectric actuator according to claim 1, wherein the conductive bonding material is an anisotropic conductive material.   The piezoelectric actuator according to claim 1, wherein the conductive bonding material is provided so as to go around a side surface of the piezoelectric element.   The piezoelectric actuator according to claim 1, wherein the conductive bonding material is provided so as to wrap around a side surface of the flexible substrate.   4. The piezoelectric according to claim 1, wherein the conductive bonding material has a portion extending in a direction in which the flexible substrate is extended. 5. Actuator. The flexible substrate is provided with a cover film so as to cover the wiring conductor except in the vicinity of the region where the piezoelectric element and the flexible substrate overlap, and in the vicinity of the region where the piezoelectric element and the flexible substrate overlap, the wiring The conductor is exposed from the cover film,
The piezoelectric actuator according to claim 5, wherein the conductive bonding material covers the wiring conductor exposed from the cover film. One end of the piezoelectric element and one end of the flexible substrate overlap so as to be orthogonal,
The conductive bonding material has a portion extending from one end of the piezoelectric element in an outer periphery of a region where the piezoelectric element and the flexible substrate overlap each other. Item 7. The piezoelectric actuator according to any one of Items 6.   The conductive bonding material includes conductive particles and a resin adhesive, and the number of the conductive particles included in the conductive bonding material extends from a region where the piezoelectric element and the flexible substrate overlap. The piezoelectric actuator according to claim 1, wherein the piezoelectric actuator is reduced per unit volume.   A piezoelectric vibration device comprising: the piezoelectric actuator according to claim 1; and a vibration plate bonded to the other main surface of the multilayer body. The piezoelectric actuator according to any one of claims 1 to 8, an electronic circuit, a display, and a housing,
A portable terminal, wherein the other main surface of the laminate is bonded to the display or the casing. The mobile terminal according to claim 10, wherein the display or the casing generates a vibration that transmits sound information through an ear cartilage or air conduction.   9. The piezoelectric actuator according to claim 1, the diaphragm to which the piezoelectric actuator is attached, and a diaphragm that vibrates with the piezoelectric actuator by vibration of the piezoelectric actuator, and a peripheral portion of the diaphragm A sound generator, comprising: a support body that is provided at least in part and supports the diaphragm. A function of generating sound from the sound generator, comprising: the sound generator according to claim 12; an electronic circuit connected to the sound generator; and a housing that houses the electronic circuit and the sound generator. An electronic device comprising: