JP6193748B2 - Piezoelectric actuator, piezoelectric vibration device including the same, portable terminal, acoustic generator, electronic device - Google Patents

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. A substrate in which a substrate is bonded with a conductive bonding material and a surface electrode of a piezoelectric element and a wiring conductor of a flexible substrate are electrically connected is known (see Patent Document 2).

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

  Here, when a stress is repeatedly applied to the conductive bonding material due to external vibration or bending vibration of the piezoelectric element, there is a possibility that a gap may be formed at the boundary between the conductive bonding material and the piezoelectric element and spark may be generated. As a result, the connection resistance increases and the amount of displacement may decrease. A strong bond that is durable against vibration is required between the surface electrode of the piezoelectric element and the wiring conductor of the flexible substrate.

  The present invention has been made in view of the above circumstances, and a piezoelectric actuator in which a gap is formed at the boundary between the conductive bonding material and the piezoelectric element to suppress a spark, a piezoelectric vibration device including the piezoelectric actuator, and a mobile phone An object is to provide a terminal, a sound generator, and an electronic device.

The present invention relates to a laminate in which an internal electrode and a piezoelectric layer are laminated, a plurality of surface electrodes provided on at least one main surface of the laminate and electrically connected to the internal electrode, and conductive bonding A flexible substrate having a wiring conductor partially connected to the one main surface through a material and electrically connected to the plurality of surface electrodes, the first main surface of the multilayer body The piezoelectric actuator is characterized in that a region where a plurality of surface electrodes are provided has a protruding portion protruding from each other portion, and a concave portion is provided between adjacent surface electrodes .

Moreover, the piezoelectric actuator of the present invention is characterized in that, in the above configuration, the flexible substrate is deformed along the raised portion .

Further, the present invention provides a laminate in which an internal electrode and a piezoelectric layer are laminated, a plurality of surface electrodes provided on at least one main surface of the laminate and electrically connected to the internal electrode, A flexible substrate having a wiring conductor partially connected to the one main surface through a conductive bonding material and electrically connected to the plurality of surface electrodes, and the one main surface of the laminate The piezoelectric actuator is characterized in that in each of the regions where the plurality of surface electrodes are provided, there are raised portions that are raised from other portions, and the flexible substrate is deformed along the raised portions. .

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

Moreover, the piezoelectric actuator of the present invention is characterized in that, in the above configuration, the conductive bonding material protrudes from a region where the laminate and the flexible substrate overlap .

  Moreover, this invention is a piezoelectric vibration apparatus characterized by having a diaphragm joined to the said other main surface of the said laminated body.

  In addition, the present invention includes the above-described 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. Mobile terminal.

  In addition, the present invention is provided on at least a part of the piezoelectric actuator, the diaphragm to which the piezoelectric actuator is attached, the diaphragm that vibrates together with the piezoelectric actuator by the vibration of the piezoelectric actuator, and the outer periphery of the diaphragm. And a support for supporting the diaphragm.

  The present invention also includes the above sound generator, an electronic circuit connected to the sound generator, and a housing that houses the electronic circuit and the sound generator, and generates sound from the sound generator. It is an electronic device characterized by having a function of

  According to the present invention, a stress that peels off the flexible substrate due to vibration is applied to the region where the plurality of surface electrodes are provided on one main surface of the laminate, each having a raised portion that is higher than the other portion. However, the stress is relieved by the deformation of the raised portion. Therefore, it is possible to obtain a piezoelectric actuator in which no spark is generated over a long period of time and the displacement of the laminate is stable.

FIG. 1A is a schematic perspective view showing an example of an embodiment of the piezoelectric actuator of the present invention, and FIG. 1B is a schematic cross-sectional view taken along line AA shown in FIG. 1 (c) is a schematic cross-sectional view cut along the line BB shown in FIG. 1 (a). 2A and 2B are schematic plan views of internal electrodes constituting the piezoelectric actuator of the present invention, in which FIG. 2A is a first electrode, FIG. 2B is a second electrode disposed on one main surface side of the laminate, c) has shown the 3rd electrode arrange | positioned at the other main surface side of the laminated body. It is a schematic sectional drawing which shows the other example of FIG.1 (b). It is a schematic sectional drawing which shows the other example of FIG.1 (b). It is a schematic sectional drawing which shows the other example of FIG.1 (b). 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. 10A is a schematic plan view showing a schematic configuration of the embodiment of the sound generator of the present invention, and FIG. 10B is an example cut along the line AA in FIG. FIG. 10C is a schematic cross-sectional view of another example cut along the line AA in FIG. 10A. 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, and FIG. 1B is a schematic cross-sectional view taken along line AA shown in FIG. 1 (c) is the same as FIG.
It is the schematic sectional drawing cut | disconnected by the BB line shown to).

  The piezoelectric actuator 1 of this embodiment shown in FIG. 1 is provided on a laminate 11 in which an internal electrode and a piezoelectric layer are laminated, and at least one main surface of the laminate 11 and is electrically connected to the internal electrode. Including a plurality of surface electrodes 12 and a flexible substrate 13 including a wiring conductor 131 partially bonded to one main surface via a conductive bonding material and electrically connected to the plurality of surface electrodes 12; In the region where the plurality of surface electrodes 12 are provided on one main surface of the multilayer body 11, there are raised portions 15 that are raised from the other portions.

  The laminated body 11 constituting the piezoelectric actuator 1 of this example is formed by laminating an internal electrode and a piezoelectric layer and forming a plate shape. The plurality of internal electrodes have an active portion that overlaps in the stacking direction, and the other plurality of internal electrodes have an inactive portion that does not overlap in the stacking direction. In the case of a piezoelectric actuator attached to a display or casing of a portable terminal, the laminate 11 is formed in a long shape, for example, and the length of the laminate 11 is preferably, for example, 18 mm to 28 mm, and more preferably 22 mm to 25 mm. preferable. The width of the laminated body 11 is preferably 1 mm to 6 mm, for example, and more preferably 3 mm to 4 mm. The thickness of the laminated body 11 is preferably 0.2 mm to 1.0 mm, for example, and more preferably 0.4 mm to 0.8 mm. In the example shown in the figure, the laminate 11 is formed in a rectangular plate shape in plan view, but is not limited to this shape. For example, the laminate 11 has a shape such as square, rectangle, or circle in plan view. It may be a plate-like body.

  The internal electrode constituting the multilayer body 11 is formed by simultaneous firing with the ceramic forming the piezoelectric layer, 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 are alternately stacked to sandwich the piezoelectric layers from above and below, and the first electrode and the second electrode are arranged in the stacking order, so that the driving voltage is applied to the piezoelectric layers sandwiched between them. Is applied. When the laminate 11 is, for example, a plate-like body having a rectangular shape in plan view, the internal electrode 171 serving as the first electrode is formed in a rectangular shape in plan view as shown in FIG. 2A, for example. Further, in this case, the internal electrode 172 serving as the second electrode disposed on the one main surface side has, for example, a rectangular opposing portion and a width wider than the opposing portion in plan view as shown in FIG. The internal electrode 173 that is formed in a shape including a narrow lead portion and is the second electrode disposed on the other main surface side is opposed to the rectangular facing portion in plan view, for example, as shown in FIG. The inner electrode 172 that is the second electrode disposed on the one main surface side is reversed left and right. 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.

  Although not shown, the end portions of the first electrode and the second electrode are led out alternately to a pair of opposite side surfaces of the stacked body 11. In the case of a piezoelectric actuator attached to a display or casing of a portable terminal, the length of the internal electrode 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 is preferably 1 mm to 5 mm, and more preferably 2 mm to 4 mm. The thickness of the internal electrode is preferably 0.1 to 5 μm, for example.

The piezoelectric layer constituting the multilayer body 11 is formed of ceramics having piezoelectric characteristics. As such ceramics, for example, perovskite oxides made of lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ), niobium Lithium oxide (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 plurality of surface electrodes 12 electrically connected to the internal electrodes are provided on at least one main surface of the multilayer body 11. The surface electrode 12 shown in the drawing is composed of, for example, a first surface electrode 121 having a large area, a second surface electrode 122 having a small area, and a third surface electrode 123. For example, the first surface electrode 121 is electrically connected to the internal electrode 171 serving as the first electrode, and the second surface electrode 122 is the internal electrode serving as the second electrode disposed on one main surface side. The third surface electrode 123 is electrically connected to an internal electrode 173 serving as a second electrode disposed on the other main surface side.

  In the case of a piezoelectric actuator attached to a display or casing of a mobile terminal, the length of the first surface electrode 121 is preferably, for example, 17 mm to 23 mm, and more preferably 19 mm to 21 mm. For example, the width of the first surface electrode 121 is preferably 1 mm to 5 mm, and more preferably 2 mm to 4 mm. The lengths of the second surface electrode 122 and the third surface electrode 123 are preferably 1 mm to 3 mm, for example. The widths of the second surface electrode 122 and the third surface electrode 123 are preferably 0.5 mm to 1.5 mm, for example. Further, the length of the internal electrode 171 is preferably, for example, 17 mm to 23 mm, and more preferably 19 mm to 21 mm. The width of the internal electrode 171 is preferably 1 mm to 5 mm, for example, and more preferably 2 mm to 4 mm. The lengths of the lead portions in the internal electrode 172 and the internal electrode 173 are preferably 1 mm to 3 mm, for example. The width of the lead portion in the internal electrode 172 and the internal electrode 173 is preferably, for example, 0.5 mm to 1.5 mm.

  In addition, the piezoelectric actuator 1 of this example includes a flexible substrate 13 including a wiring conductor 131 that is partially bonded to one main surface via a conductive bonding material and electrically connected to the plurality of surface electrodes 12. Contains.

  Specifically, the flexible substrate 13 is, for example, a flexible printed wiring board in which a plurality of (for example, two) wiring conductors 131 are provided on the main surface of the resin base film 132 facing the laminate 11. The wiring conductor 131 is electrically connected to the surface electrode 12 through a conductive bonding material. A cover film 133 may be provided so as to cover a part of the wiring conductor 131. Here, the cover film 133 may be provided in a region excluding the connection portion between the wiring conductor 131 and the surface electrode 12, but the cover film 133 is not provided in a region overlapping the laminated body 11 and its vicinity region. Thus, reliable electrical connection can be obtained without being affected by the thickness of the cover film 133. For example, the flexible substrate 13 is joined to the laminated body 11 at one end and is joined to an external circuit (connector) at the other end.

  As the conductive bonding material, a conductive adhesive, solder, or the like is used, and a conductive adhesive is preferable. For example, by using a conductive adhesive in which conductive particles made of resin balls such as gold, copper, nickel, or gold plating are dispersed in a resin such as an acrylic resin, an epoxy resin, a silicone resin, a polyurethane resin, or a synthetic rubber. This is because stress generated by vibration can be reduced as compared with solder.

  More preferably, among the conductive adhesives, an anisotropic conductive adhesive 14 as shown in the figure is preferable. The anisotropic conductive adhesive 14 includes conductive particles 141 responsible for electrical joining and a resin adhesive 142 responsible for adhesion. Specifically, one conductive particle 141 is in contact with the surface electrode 12 and the wiring conductor 131. This anisotropic conductive adhesive 14 can conduct in the thickness direction and insulate in the in-plane direction, so that even in a narrow pitch wiring, there is no electrical short between the surface electrodes of different polarity, A connection part with the flexible substrate 13 can be made compact.

  Here, in the region where the plurality of surface electrodes 12 are provided on one main surface of the multilayer body 11, there are raised portions 15 that are raised from the other portions. Here, the raised portion 15 is a region that is, for example, 0.1 to 100 μm higher than other portions (a surrounding region that is not raised). The raised portion 15 is provided, for example, in a region having an area of 2% or more with respect to the area of each of the plurality of surface electrodes 12 (first surface electrode 121, second surface electrode 122, and third surface electrode 123). Further, the raised portion 15 may have a shape (convex shape having an apex) that gradually rises away from another part (a surrounding area that is not raised), and is the highest. There may be one or more parts (vertices).

  With this configuration, even if a stress that peels off the flexible substrate 13 is applied by vibration, the stress can be relieved by the deformation of the raised portion. In addition, an effect of suppressing vibration transmission can be obtained. As a result, it is possible to stabilize the amount of displacement of the laminate without causing sparks over a long period of time.

  Here, since the conductive bonding material is the anisotropic conductive adhesive 14, the conductive particles 141 are sandwiched near the apex of the raised portion 15 in the region where the respective surface electrodes 12 are provided, and the surface electrodes 12 and The conductive particles 141 easily bite into each of the wiring conductors 131, and a reliable connection is obtained. Further, since the conductive particles 141 are crushed and the cross-sectional area is increased, the contact resistance can be reduced. As a result, the amount of displacement of the stacked body 11 can be stabilized without causing sparks.

  Further, as shown in FIG. 3, it is preferable that there is a recess 16 between the adjacent surface electrode 12 and the surface electrode 12. Here, the concave portion 16 is a region that is recessed by, for example, 0.1 to 100 μm from another portion (a surrounding region that is not recessed). By providing the concave portion 111, when a conductive adhesive is used as the conductive bonding material, the thickness of the conductive adhesive increases, so that the stress can be relieved and spark can be generated for a longer period of time. Therefore, the displacement amount of the laminated body can be stabilized. In particular, when the anisotropic conductive adhesive 14 is used, the ratio of the resin of the conductive adhesive above the recess 16 can be increased, which is more effective.

  Further, as shown in FIG. 4, it is preferable that the conductive bonding material (conductive adhesive, particularly anisotropic conductive adhesive 14) protrudes from the region where the laminate 11 and the flexible substrate 13 overlap. When the portion is bonded to the flexible substrate 13 or bonded to the side surface of the laminated body 11, the bonding force can be increased and the stress can be further reduced. In addition, it is effective that it protrudes by 0.02 to 2 mm. In particular, it is preferable to reach the cover film 133 in that the effect of protecting the wiring conductor 131 is also added.

  Further, as shown in FIG. 5, the flexible substrate 13 is preferably deformed along the raised portion 15. Since the flexible substrate 13 is deformed along the raised portions 15, the stress can be dispersed in different directions. Further, the raised portion 15 can be further easily deformed. Therefore, the stress can be further relaxed and the peeling of the flexible substrate 13 can be made difficult to progress.

  In addition, by making the other main surface of the laminate 11 flat, for example, when the other main surface is bonded to an object to be subjected to vibration (for example, a vibration plate described later), It becomes easy to cause bending vibration integrally, and the efficiency of bending vibration can be improved as a whole.

The piezoelectric actuator 1 of this example is a so-called bimorph type piezoelectric actuator that receives an electric signal from the surface electrode 12 and bends 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, by bonding (bonding) the other main surface of the laminate 11 to a diaphragm described later, Even a unimorph type can be bent and vibrated.

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

First, a ceramic green sheet to be a piezoelectric layer 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 an internal electrode 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 above ceramic green sheet in a pattern of internal electrodes using a screen printing method. Further, a plurality of ceramic green sheets printed with this conductive paste are laminated.

  Here, in order to make the raised portion 15 raised from each other portion in the region where the plurality of surface electrodes 12 are provided on one main surface of the multilayer body 11, for example, a region overlapping the surface electrode 12 The ceramic green sheet of this part is laminated by partially laminating the ceramic green sheet, partially applying the ceramic paste, or partially forming a pattern that overlaps the lead part of the internal electrode. After laminating to increase the thickness of the laminated body, a sheet-like body rich in elasticity is arranged on one main surface side and a plate-like body is arranged on the other main surface side, and these are ceramic green sheet laminated bodies And a method of pressing and adhering. In addition, in order to make the laminated body 11 have a concave portion 16 that is recessed from other portions, for example, a green sheet hollowed out in the shape of the concave portion 16 only in this portion is laminated, or the internal electrodes partially overlap with each other. After forming a pattern, a sheet-like body rich in elasticity is arranged on one main surface side, and a plate-like body is arranged on the other main surface side opposite to the ceramic green sheet laminated body to press and close The method of making it wear is mentioned. By this method, the raised portion 15 and the recessed portion 16 can be formed on the one main surface side.

  Then, after the binder removal treatment is performed at a predetermined temperature, firing is performed at a temperature of 900 to 1200 ° C., and grinding is performed so as to have a predetermined shape using a surface grinder or the like, thereby alternately stacking the inside. A laminate including an electrode and a piezoelectric layer is produced.

  The laminate is not limited to those produced by the above manufacturing method, and any production method can be used as long as a laminate comprising a plurality of internal electrodes and piezoelectric layers can be produced. Good.

  After that, 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 to form a main electrode and side surfaces of the laminate in a surface electrode pattern. After being 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 surface electrodes.

In addition, when electrically connecting the surface electrode and the internal electrode, a via that penetrates the piezoelectric layer may be formed or connected, or a side electrode may be formed on the side surface of the laminated body. It may be produced by a method.

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

  First, a conductive adhesive paste is applied and formed at a predetermined position of the laminate using a method such as screen printing. Then, the flexible substrate is connected and fixed to the piezoelectric element by curing the conductive adhesive paste in a state where the flexible substrate 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 to a predetermined position of the laminate or flexible substrate, and then the laminate and the flexible substrate are interposed via the conductive adhesive. The thermoplastic resin is softened and fluidized by heating and pressing in the contacted state, and then returned to room temperature, whereby the thermoplastic resin is cured again and the flexible substrate is connected and fixed to the laminate.

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

  In the above description, the method of applying and forming the conductive adhesive on the laminate or the flexible substrate has been shown. However, in a state where the sheet of the laminate formed in advance in a sheet shape is sandwiched between the laminate and the flexible substrate. You may heat-press and join.

  As shown in FIG. 6, 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 11 constituting the piezoelectric actuator 1. In addition, the flexible substrate joined to one main surface of the laminated body 11 is abbreviate | 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 joined to the other main surface of the multilayer body 11 via a joining 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 (laminated body 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 multilayer body 11 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 11 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 (laminate 11). Deform.

At this time, since the anti-phase vibration reflected from the vibration plate 81 can be reduced by the deformable joining member 82, the piezoelectric actuator 1 (laminated body 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 formed of a viscoelastic body, strong vibration from the piezoelectric actuator 1 (laminated body 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 joining member 82 is preferably larger than the amplitude of the bending vibration of the piezoelectric actuator 1 (laminated body 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 flexures and vibrates the piezoelectric actuator 1 (laminated body 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).

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

  The piezoelectric vibration device of this example is configured by using the piezoelectric actuator 1 that does not generate a spark for a long period of time and has a stable displacement of the laminated body. It can be set as a vibration device.

  As shown in FIGS. 7 to 9, the mobile 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. 7 is a schematic perspective view schematically showing the portable terminal of the present invention, FIG. 8 is a schematic cross-sectional view taken along line AA shown in FIG. 7, and FIG. 9 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 11 is omitted in FIGS.

  Here, it is preferable that the laminated body 11 and the housing 92 are joined using a deformable joining member. That is, in FIG. 8 and FIG. 9, the joining member 82 is a deformable joining member.

  By joining the laminate 11 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 (laminated body 11). Deform.

At this time, the anti-phase vibration reflected from the casing 92 can be mitigated by the deformable joining member 82, so that the piezoelectric actuator 1 (laminated body 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 bonding member 82 is formed of a viscoelastic body, strong vibration from the piezoelectric actuator 1 (laminated body 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 11 is attached to a part of the casing 92 that serves as a cover for the display 91, and a part of the casing 92 functions as the diaphragm 922.

  In this example, the laminated body 11 is bonded to the housing 92, but the laminated body 11 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.

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 mobile terminal of this example brings the diaphragm (display 91 or housing 92) into contact with the ear directly or through another object,
Sound information can be transmitted by transmitting vibration to the cartilage of the ear. 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 by using the piezoelectric actuator 1 in which no spark is generated for a long period of time and the amount of displacement of the laminated body is stable, it is excellent in durability and stable and of high quality for a long period of time. Sound information can be transmitted.

  Further, as shown in FIG. 10, the acoustic generator 10 of the present embodiment is provided with the piezoelectric actuator 1 described above and the piezoelectric actuator 1, and the diaphragm 2 that vibrates with the piezoelectric actuator 1 due to the vibration of the piezoelectric actuator 1. And a frame 3 provided on the outer peripheral portion of the diaphragm 2.

  The piezoelectric actuator 1 is an exciter that excites the diaphragm 2 by vibrating under application of a voltage. The main surface of the piezoelectric actuator 1 and the main surface of the diaphragm 2 are joined by an adhesive such as an epoxy resin, and the piezoelectric actuator 1 is flexibly vibrated, so that the piezoelectric actuator 1 gives a certain vibration to the diaphragm 2. Sound can be generated.

  The diaphragm 2 is fixed to the frame 3 in a tensioned state, and vibrates with the piezoelectric actuator 1 by the vibration of the piezoelectric element actuator 1. The diaphragm 2 can be formed using various materials such as resin and metal. For example, the diaphragm 2 can be made 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 2 is made of a resin film to bend and vibrate the diaphragm 2 with a large amplitude so that the sound pressure is reduced. 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 3 functions as a support that supports the diaphragm 2 at the peripheral edge of the diaphragm 2, and can be formed using various materials such as metals such as stainless steel and resins. The frame 3 may be composed of one frame member (upper frame member 31) as shown in FIG. 10 (b), and two frame members (upper frame member 31 and upper frame member 31) as shown in FIG. 10 (c). The lower frame member 32) may be used. In this case, the tension of the diaphragm 2 can be stabilized by sandwiching the diaphragm 2 between the two frame members. The upper frame member 31 and the lower frame member 32 have a thickness of, for example, 100 to 5000 μm.

  In the acoustic generator 10 of this example, as shown in FIGS. 10B and 10C, 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 2. It is preferable to further have a resin layer 4. As the resin layer 4, for example, an acrylic resin can be used. By embedding the piezoelectric actuator 1 (laminated body 11) in the resin layer 4, an appropriate damper effect can be induced, so that the resonance phenomenon is suppressed and the peak and dip in the frequency characteristic of the sound pressure are suppressed to a small level. Can do. 10B and 10C, the resin layer 4 may be formed to have the same height as the upper frame member 31.

  Since the acoustic generator 10 is configured using the piezoelectric actuator 1 that does not generate sparks for a long period of time and has a stable displacement of the laminate as described above, it has excellent durability and is stable for a long period of time. And can be driven.

  Next, an electronic device equipped with an acoustic generator will be described with reference to FIG. FIG. 11 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. 11, 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 40 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 40 that accommodates these devices. Although FIG. 11 shows a state in which each device including the controller 50a is accommodated in one housing 40, 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 40.

  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. 11, the electronic device 50 has been 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 the electronic device 50 is configured to include 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 of the laminate is stable as described above, the electronic device 50 has durability. It can be driven stably for a long time.

  A specific example of the piezoelectric actuator of the present invention will be described. Specifically, the piezoelectric actuator shown in FIG. 1 was manufactured as follows.

  The piezoelectric element had a rectangular parallelepiped 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. As the internal electrode, an alloy of silver palladium was used.

  A ceramic green sheet on which a conductive paste made of silver palladium was printed was laminated. Here, after increasing the thickness of the ceramic green sheet laminate at the part where the raised portion of the surface electrode is to be provided, one main surface side is a sheet-like body rich in elasticity, and the other main surface side is a plate-like body The raised portion was provided by being sandwiched between and pressed and adhered. Then, after degreasing at a predetermined temperature, firing was performed at 1000 ° C. to obtain a laminated sintered body.

  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 layer.

  Thereafter, a conductive adhesive containing 10 vol% of gold-plated resin balls as conductive particles was applied to the surface of the laminate to be bonded to the flexible substrate.

  Then, the flexible substrate was fixed by heating and pressurizing in a state where the flexible substrate was in contact, and a piezoelectric actuator (sample No. 1) according to an example of the present invention was produced. In addition, as the above-mentioned conductive adhesive, an anisotropic conductive adhesive that conducts in the thickness direction and does not conduct in the in-plane direction was used.

  Further, as a comparative example, the above-described sample No. 1 was obtained except that a ceramic green sheet laminate was sandwiched between flat plates and thermocompression bonded to obtain a surface electrode having a flat surface. A piezoelectric actuator (sample No. 2) outside the scope of the present invention having the same configuration as that of No. 1 was produced.

  For each piezoelectric actuator, a sine wave signal having an effective value of ± 10 Vrms was applied to the piezoelectric element at a frequency of 1 kHz via a flexible substrate, and a drive test was performed. For both 1 and 2, bending vibration having a displacement of 100 μm was obtained.

  Thereafter, a driving test was performed by applying a sine wave signal having an effective value of ± 10 Vrms continuously for 100,000 cycles. Sample No. which is outside the scope of the present invention. No. 2 caused a decrease in displacement, and the flexible substrate was peeled off from the laminate in 90,000 cycles.

  On the other hand, sample No. The piezoelectric actuator No. 1 continued to drive without any reduction in displacement even after 100,000 cycles. Also, no cracks or cracks were found in the conductive adhesive connecting and fixing the flexible substrate, and no peeling of the flexible substrate was seen.

  By using the piezoelectric actuator of the present invention, there is no spark, the amount of displacement is stable, and even when driven for a long period of time, there is no problem that the flexible substrate peels off from the laminate, and excellent durability. Was confirmed.

1: Piezoelectric actuator 11: Laminated body 12: Surface electrode 121: First surface electrode 122: Second surface electrode 123: Third surface electrode 13: Flexible substrate 131: Wiring conductor 132: Base film 133: Cover film 14 : Anisotropic conductive adhesive 141: Conductive particles 142: Resin 15: Raised portion 16: Recesses 171, 172, 173: Internal electrode 81: Diaphragm 82: Joining member 91: Display 92: Housing 921: Housing body 922 : Diaphragm 93: Bonding material 10: Sound generator 2: Diaphragm 3: Frame 31: Upper frame member 32: Lower frame member 4: Resin layer 50: Electronic device 60: Electronic circuit 40: Housing 50a: Controller 50b : Transmission / reception unit 50c: Key input unit 50d: Microphone input unit 50e: Display unit 50f: Antenna

Claims (9)

A laminated body in which an internal electrode and a piezoelectric layer are laminated, a plurality of surface electrodes provided on at least one main surface of the laminated body and electrically connected to the internal electrode, and a conductive bonding material A flexible substrate having a wiring conductor partially bonded to the one main surface and electrically connected to the plurality of surface electrodes;
In the region where the plurality of surface electrodes are provided on the one main surface of the laminate, there are raised portions that are raised from other portions, respectively, and there is a recess between the adjacent surface electrode and the surface electrode. A piezoelectric actuator characterized by that.   A laminated body in which an internal electrode and a piezoelectric layer are laminated, a plurality of surface electrodes provided on at least one main surface of the laminated body and electrically connected to the internal electrode, and a conductive bonding material A flexible substrate having a wiring conductor partially bonded to the one main surface and electrically connected to the plurality of surface electrodes;
In the region where the plurality of surface electrodes are provided on the one main surface of the laminate, there are raised portions that are raised from other portions, respectively, and the flexible substrate is deformed along the raised portions. A piezoelectric actuator characterized by that. The piezoelectric actuator according to claim 1, wherein the flexible substrate is deformed along the raised portion. The piezoelectric actuator according to any one of claims 1 to 3, wherein the conductive bonding material is an anisotropic conductive adhesive. The piezoelectric actuator according to any one of claims 1 to 4 , wherein the conductive bonding material protrudes from a region where the laminate and the flexible substrate overlap.   6. A piezoelectric vibration device comprising: the piezoelectric actuator according to claim 1; and a diaphragm bonded to the other main surface of the laminate.   6. The piezoelectric actuator according to claim 1, an electronic circuit, a display, and a housing, wherein the other main surface of the laminate is the display or the housing. A mobile terminal characterized by being joined to the mobile terminal.   A piezoelectric actuator according to any one of claims 1 to 5, a diaphragm to which the piezoelectric actuator is attached, which vibrates with the piezoelectric actuator by vibration of the piezoelectric actuator, and an outer peripheral portion of the diaphragm A sound generator comprising: a frame body provided on the sound generator. A function of generating sound from the sound generator, comprising: the sound generator according to claim 8; an electronic circuit connected to the sound generator; and a housing that houses the electronic circuit and the sound generator. An electronic device comprising:

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