TW201401591A - Piezoelectric actuator, piezoelectric vibration device, and mobile terminal - Google Patents

Abstract

To provide a mobile terminal, a piezoelectric vibration device, and a piezoelectric actuator capable of stably driving for extended periods of time without a flexible wiring board bonded to a piezoelectric element separating from the piezoelectric element, even when driving for extended periods of time. A piezoelectric actuator (1) according to an embodiment of the present invention is characterized by having: a piezoelectric element (10) which is provided with a stacked body (4) having internal electrodes (2) and piezoelectric layers (3) stacked therein, and which is provided with surface electrodes (5) on one main surface of the stacked body (4), said surface electrodes (5) being electrically connected with the internal electrodes (2); and a flexible wiring board (6) which has a portion thereof bonded above the one main surface via a conductive adhesive agent (7) including conductive particles and resin, and which is provided with a wiring conductor (61) electrically connected with the surface electrodes (5). The piezoelectric actuator (1) is further characterized in that, in a bonding area between the flexible wiring board (6) and the piezoelectric element (10), more of the conductive particles are disposed in at least a peripheral edge section (601) than in other sections.

Description

Piezoelectric actuator, piezoelectric vibration device and mobile terminal

The present invention relates to a piezoelectric actuator, a piezoelectric vibration device, and a mobile terminal.

As a piezoelectric actuator, as shown in FIG. 8, a bimorph type pressure is formed by forming a surface electrode 104 on the surface of a laminated body 103 in which a plurality of internal electrodes 101 and piezoelectric layers 102 are laminated. In the electric component 10 (see Patent Document 1), the flexible wiring board 105 is bonded to the main surface of the piezoelectric element 10 by the conductive bonding member 106, and the surface electrode 104 of the piezoelectric element 10 and the wiring conductor of the flexible wiring substrate 105 are connected. 107 Electrical connection (refer to Patent Document 2).

Further, a piezoelectric vibration device in which a central portion or one end of a piezoelectric element of a bimorph type piezoelectric element is fixed to a diaphragm is known (see Patent Documents 3 and 4).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2002-10393

[Patent Document 2] Japanese Patent Laid-Open No. Hei 6-14396

[Patent Document 3] International Publication No. 2005/004535

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2006-238072

Here, as the conductive bonding member 106 that bonds the flexible wiring substrate 105 and the piezoelectric element 10, solder or a conductive adhesive is used.

However, when solder is used as the conductive bonding member 106 for bonding, since the rigidity of the solder is high, the vibration from the outside generated by the flexible wiring substrate 105 or the resonance of the flexible wiring substrate 105 itself does not follow. In the vibration of the flexible wiring board 105 which is abnormal in the vibration of the piezoelectric actuator, a stress distribution such as shearing or bending is caused in the vicinity of the end surface of the joint portion between the piezoelectric element 10 and the flexible wiring substrate 105, and the flexible wiring substrate is provided. 105 is peeled off from the piezoelectric element 10.

In the case where the bonding is performed only by the conductive adhesive, when the piezoelectric element 10 is driven at a high speed by flowing a large current, since the electrical conductivity and the thermal resistance of the conductive adhesive are high, the piezoelectric element is used. The heat generated by the vibration of the element 10 or the Joule heat of the conductive adhesive itself causes the resin constituting the conductive adhesive to thermally deteriorate, and the bonding strength is lowered. As a result, the flexible wiring substrate 105 is peeled off from the piezoelectric element 10.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a piezoelectric device that can be stably driven for a long period of time without being peeled off from the piezoelectric element even if it is driven for a long time and bonded to the flexible wiring substrate of the piezoelectric element. Actuator, piezoelectric vibration device and mobile terminal.

A piezoelectric actuator according to the present invention includes: a piezoelectric element including a laminated body in which an internal electrode and a piezoelectric layer are laminated, and a surface electrode electrically connected to the internal electrode on one main surface of the laminated body And a flexible wiring board, wherein a part of the flexible wiring board is bonded to the one main surface via a conductive adhesive containing conductive particles and a resin, and includes a wiring conductor electrically connected to the surface electrode; and the flexible wiring substrate and the piezoelectric layer In at least a part of the peripheral portion of the joint region of the element, the ratio of the conductive particles per unit area when the surface of the conductive adhesive is observed is larger than a portion other than the peripheral portion.

Moreover, the piezoelectric vibration device of the present invention includes the piezoelectric actuator and a diaphragm that is joined to the other main surface of the piezoelectric element.

Further, the mobile terminal of the present invention includes the piezoelectric actuator, the electronic circuit, the display, and the casing, and the other main surface of the piezoelectric actuator is coupled to the display or the casing.

According to the present invention, it is possible to obtain a piezoelectric actuator in which a piezoelectric element does not abnormally vibrate and which is not peeled off from the piezoelectric element even if driven for a long period of time, and a piezoelectric vibration device including the piezoelectric actuator And mobile terminals.

1‧‧‧ Piezoelectric actuator

2‧‧‧Internal electrodes

3‧‧‧ piezoelectric layer

4‧‧‧Layered body

5‧‧‧ surface electrode

6‧‧‧Soft wiring board

7‧‧‧ Conductive adhesive

10‧‧‧Piezoelectric components

21‧‧‧1st pole

22‧‧‧2nd pole

41‧‧‧Active Department

42‧‧‧Inertial Department

51‧‧‧1st surface electrode

52‧‧‧2nd surface electrode

53‧‧‧3rd surface electrode

61‧‧‧Wiring conductor

81‧‧‧vibration board

82‧‧‧Joining members

91‧‧‧ display

92‧‧‧Shell

93‧‧‧Material materials

101‧‧‧Internal electrodes

102‧‧‧piezoelectric layer

103‧‧‧Layered body

104‧‧‧ surface electrode

105‧‧‧Soft wiring board

106‧‧‧Electrically conductive joint members

107‧‧‧Wiring conductor

601‧‧‧The Peripheral Department

602‧‧‧A region between the outer perimeter of the main surface and the surface electrode

921‧‧‧Shell body

922‧‧‧vibration board

Fig. 1 is a schematic perspective view showing an example of an embodiment of a piezoelectric actuator of the present invention.

Fig. 2(a) is a schematic cross-sectional view taken along the line A-A shown in Fig. 1(b), and Fig. 2(b) is a partially enlarged plan perspective view showing the piezoelectric actuator shown in Fig. 1.

Fig. 3 is a partially enlarged plan perspective view showing another example of Fig. 2(b).

Fig. 4 is a schematic perspective view showing a piezoelectric vibration device according to an embodiment of the present invention.

Fig. 5 is a schematic perspective view showing a mobile terminal according to an embodiment of the present invention.

Fig. 6 is a schematic cross-sectional view taken along the line A-A shown in Fig. 5.

Fig. 7 is a schematic cross-sectional view taken along the line B-B shown in Fig. 5.

Fig. 8(a) is a schematic perspective view showing an example of a conventional piezoelectric actuator, and Fig. 8(b) is a schematic cross-sectional view taken along line A-A shown in Fig. 8(a).

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

1 is a schematic perspective view showing an example of an embodiment of a piezoelectric actuator according to the present invention, and FIG. 2(a) is a schematic cross-sectional view taken along line AA shown in FIG. 1(b), and FIG. 2(b) A partially enlarged plan perspective view of the piezoelectric actuator shown in FIG.

The piezoelectric actuator 1 shown in FIG. 1 is characterized by comprising a piezoelectric element 10 including a laminated body 4 in which an internal electrode 2 and a piezoelectric layer 3 are laminated, and a main surface and an internal electrode of the laminated body 4. 2 electrically connected surface electrode 5; and a flexible wiring board 6, a part of which is bonded to a main surface via a conductive adhesive 7 containing conductive particles and resin, and includes a wiring conductor 61 electrically connected to the surface electrode 5; In at least a part of the peripheral portion 601 in the joint region of the flexible wiring substrate 6 and the piezoelectric element 10, the ratio of the conductive particles per unit area when the surface of the conductive adhesive 7 is observed is larger than the peripheral portion except the above-mentioned peripheral portion. Outside part.

The laminated body 4 constituting the piezoelectric element 10 is formed by laminating the internal electrode 2 and the piezoelectric layer 3, and includes an active portion 41 in which a plurality of internal electrodes 2 are superposed in the stacking direction, and an inert portion 42 other than the laminated portion 4, for example, formed as Long strips. In the case of a piezoelectric actuator mounted on a display or a housing of a mobile terminal, the length of the laminated body 4 is preferably, for example, 18 mm to 28 mm, and more preferably 22 mm to 25 mm. The width of the laminated body 4 is, for example, preferably from 1 mm to 6 mm, and more preferably from 3 mm to 4 mm. The thickness of the laminated body 4 is, for example, preferably 0.2 mm to 1.0 mm, and more preferably 0.4 mm to 0.8 mm.

The internal electrode 2 constituting the laminated body 4 is formed by firing simultaneously with the ceramic forming the piezoelectric layer 3, and includes the first pole 21 and the second pole 22. For example, the first pole 21 serves as a ground electrode, and the second pole 22 serves as a positive electrode or a negative electrode. The piezoelectric layer 3 is alternately laminated with the piezoelectric layer 3, and the first electrode 21 and the second electrode 22 are disposed in this order, whereby a driving voltage is applied to the piezoelectric layer 3 interposed therebetween. . As the material for forming, for example, a conductor containing silver or a silver-palladium alloy having low reactivity with a piezoelectric ceramic, or a conductor containing copper or platinum, or the like, or a ceramic component or glass may be used. ingredient.

In the example shown in FIG. 1, the end portions of the first pole 21 and the second pole 22 are alternately led out to the opposite side faces of the laminated body 4. In the case of a piezoelectric actuator mounted on a display or a housing of a mobile terminal, the length of the internal electrode 2 is preferably, for example, 17 mm to 25 mm, and more preferably 21 mm to 24 mm. The width of the internal electrode 2 is preferably, for example, 1 mm. ~5mm, and further preferably 2mm~4mm. The thickness of the internal electrode 2 is preferably, for example, 0.1 to 5 μm.

The piezoelectric layer 3 constituting the laminated body 4 is formed of a ceramic having piezoelectric characteristics, and as such a ceramic, for example, a perovskite-type oxide containing lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ) or lithium niobate can be used. (LiNbO ₃ ), lithium niobate (LiTaO ₃ ), and the like. In order to drive at a low voltage, the thickness of one layer of the piezoelectric layer 3 is preferably set to, for example, 0.01 to 0.1 mm. Further, in order to obtain a large bending vibration, it is preferable to have a piezoelectric d31 constant of 200 pm/V or more.

On one main surface of the laminated body 4, a surface electrode 5 electrically connected to the internal electrode 2 is provided. The surface electrode 5 of the form shown in FIG. 1 includes a first surface electrode 51 having a large area, a second surface electrode 52 having a small area, and a third surface electrode 53. For example, the first surface electrode 51 is electrically connected to the internal electrode 2 that is the first pole 21, and the second surface electrode 52 is electrically connected to the internal electrode 2 that is disposed on the main surface side and that is the second electrode 22. The third surface is electrically connected to the third surface. The electrode 53 is electrically connected to the internal electrode 2 which is disposed on the other main surface side and serves as the second electrode 22. In the case of a piezoelectric actuator mounted on a display or a housing of a mobile terminal, the length of the first surface electrode 51 is, for example, preferably 17 mm to 23 mm, and more preferably 19 mm to 21 mm. The width of the first surface electrode 51 is, for example, preferably 1 mm to 5 mm, and more preferably 2 mm to 4 mm. The length of the second surface electrode 52 and the third surface electrode 53 is preferably, for example, 1 mm to 3 mm. The width of the second surface electrode 52 and the third surface electrode 53 is preferably, for example, 0.5 mm to 1.5 mm.

Further, the piezoelectric actuator 1 includes a part of the flexible wiring board 6 joined to one main surface of the laminated body 4 constituting the piezoelectric element 10 via a conductive adhesive 7 containing conductive particles and a resin.

The flexible wiring board 6 includes a wiring conductor 61, and one of the flexible wiring boards 6 is partially bonded to one main surface of the laminated body 4 so that the surface electrode 5 and the wiring conductor 61 are electrically connected via the conductive adhesive 7.

The flexible wiring board 6 is, for example, a flexible ‧ printed wiring board in which two wiring conductors 61 are embedded in a resin film, and a connector for connecting to an external circuit is connected at one end (not Graphic).

The conductive adhesive 7 is, for example, dispersed in a conductive powder containing a metal powder such as a silver powder or a gold powder or a conductive coating such as gold plating on a resin ball, in a polyimide, a polyimide, or a polyimide. It is a resin with a low modulus of elasticity (Young's modulus) such as ketone rubber or synthetic rubber. Thereby, the stress generated by the vibration can be reduced as compared with the solder. More preferably, the conductive adhesive 7 is preferably an anisotropic conductive material. The anisotropic conductive material includes conductive particles that are electrically bonded and a resin adhesive that is carried over. The anisotropic conductive material is electrically connected in the thickness direction and is insulated in the in-plane direction. Therefore, even in a narrow pitch wiring, there is no electrical short circuit between the surface electrodes of the different poles, so that the flexible wiring can be used. The connection portion of the substrate 6 is miniaturized.

Further, at least a part of the peripheral portion 601 in the joint region of the flexible wiring board 6 and the piezoelectric element 10 is disposed with more conductive particles than at other portions (in at least a part of the peripheral portion 601, when the conductive adhesive 7 is viewed in plan) The ratio of the conductive particles per unit area is larger than the portion other than the peripheral portion 601). Here, the bonding region is a region occupied by the electrical adhesive 7, and the peripheral portion 601 of the bonding region indicates a region within 0.4 mm from the end surface of the bonding region (conductive adhesive 7). In addition, a part of the peripheral portion 601 is disposed in a portion other than the peripheral portion 601, and the conductive particles are formed on the periphery of the conductive adhesive 7 when the flexible wiring substrate 6 is peeled off and observed on the surface of the conductive adhesive 7 by an electron microscope. The ratio of the conductive particles per unit area in one portion of the portion 601 is larger than a portion other than the peripheral portion 601 (for example, the central portion of the joint region).

As described above, at least a part of the peripheral portion 601 of the joint region of the flexible wiring board 6 and the piezoelectric element 10 is disposed with more conductive particles (in at least a part of the peripheral portion 601) than the peripheral portion 601. When the conductive adhesive 7 is viewed in plan, the ratio of the conductive particles per unit area is larger than the portion other than the peripheral portion 601, whereby the thermal conductivity of the portion is improved, so that even a large current flows at a high speed. In the case of driving, since the heat generated by the vibration of the piezoelectric element 10 or the focus of the conductive adhesive 7 is promoted Since the heat of the ear heat is transmitted and diffused, the problem that the resin constituting the conductive adhesive 7 is thermally deteriorated and the flexible wiring board 6 is peeled off from the piezoelectric element 10 can be greatly reduced.

Further, since a large number of conductive particles are disposed in at least a part of the peripheral portion 601, shearing or stretching is performed by the lower Young's modulus of the resin and the fretting of the conductive particles in the resin. The stress concentration is reduced. Therefore, cracks are prevented from being generated from the portion to the conductive adhesive 7. In particular, in the case where the flexible wiring board 6 is biased in the direction in which the flexible wiring board 6 is connected to the outside, the soft wiring board 6 in the joint portion of the flexible wiring board 6 and the bonding portion of the conductive adhesive 7 The end portion of the extending direction side concentrates a large shear or tensile stress, but since a large number of conductive particles are disposed in the peripheral portion 601 as described above, the conductive particles of the conductive adhesive 7 are similar. In particular, it is possible to suppress the concentration of the shear stress, and it is possible to greatly suppress the occurrence of cracks in the root portion of the joint portion and to peel off the flexible wiring board 6. The portion where the conductive particles are large is preferably the entire circumference of the peripheral portion 601.

Further, in at least a part of the peripheral portion 601 in which a large number of conductive particles are disposed, for example, the number or ratio of conductive particles per unit area is preferably compared with a portion other than the peripheral portion 601. It is 5~20% more. In other words, it is preferable that when a portion of the peripheral portion 601 in which a large amount of conductive particles are disposed is compared with a portion other than the peripheral portion 601, a portion of the conductive particles is disposed in a portion per unit area. The ratio of conductive particles is 5-20% larger.

This ratio can be obtained by peeling off the flexible wiring board 6 and observing it with an electron microscope.

Further, as shown in FIG. 3, the above portion is located in a region between the outer periphery of one main surface of the piezoelectric element 10 and the surface electrode 5, whereby the lower Young's modulus of the resin or the rotation of the conductive particles is more The stress generated by the external vibration or the resonance of the flexible wiring substrate 6 itself, which does not follow the vibration of the actuator, can be reduced, and the viscoelasticity of the resin can reduce the amplitude of such non-following vibration.

Further, the thickness of the conductive adhesive 7 bonded to the region between the outer periphery of one of the principal surfaces of the piezoelectric element 10 and the surface electrode 5 is thicker than the conductive adhesive which is electrically connected to the surface electrode 5 and the wiring conductor 61. Since the thickness of 7 is increased, the thermal resistance is increased. However, by providing a large amount of conductive particles having a high thermal conductivity in this region, it is possible to realize a connection having a function of suppressing heat conduction with an increase in thermal resistance. As a result, the heat generated by the vibration of the piezoelectric element 10 or the Joule heat of the conductive adhesive 7 itself is thermally conducted and diffused, and the occurrence of cracks due to deterioration of the resin constituting the conductive adhesive 7 can be reduced.

In the above-described configuration, when the conductive adhesive 7 is an anisotropic conductive material containing, for example, a gold-plated resin ball as a conductive particle, the surface electrode 5 and the wiring conductor 61 overlap each other in a plan view. The conductive particles constituting the conductive adhesive 7 electrically connect the surface electrode 5 and the wiring conductor 61, and the conductive particles are not bonded to each other. In other regions, the piezoelectric element 10 and the flexible wiring substrate 6 are mainly formed. The connection form of the conductive particles that are not connected or connected to only one of them. In such a connection form, high thermal conductivity can be maintained as described above to suppress stress concentration in shearing or stretching, but a bonding material or a bonding process in which an anisotropic conductive material or the like is not necessarily used may be used.

As described above, in order to effectively improve the heat transfer or the stress concentration, it is preferable that the conductive particles that are not connected to any of the piezoelectric element 10 and the flexible wiring substrate 6 are 70% or more of the whole. This ratio is obtained by measuring any of the piezoelectric element 10 and the flexible wiring substrate 6 in an arbitrary cross section perpendicular to the principal surface of the piezoelectric element 10 including the piezoelectric element 10 and the flexible wiring board 6. The number of per unit areas of conductive particles that are not in contact with each other.

Further, when the other main surface of the piezoelectric element 10 is flatter and more flat than the main surface, for example, when the other main surface is bonded to an object to be vibrated (for example, a vibrating plate or the like described below), It is easy to cause bending vibration by being integrated with an object to be vibrated, and the efficiency of bending vibration as a whole can be improved.

Furthermore, the piezoelectric actuator 1 shown in FIG. 1 is a piezoelectric actuator of a so-called bimorph type. And inputting an electric signal from the surface electrode 5 to perform bending vibration so that one main surface and the other main surface become curved surfaces, but the piezoelectric actuator of the present invention is not limited to the bimorph type, and The single layer type may be a single layer type, for example, by bonding (bonding) the other main surface of the piezoelectric actuator, and even if it is a single layer type, it may be bent and vibrated.

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

First, a ceramic green sheet to be the piezoelectric layer 3 is produced. Specifically, a calcined powder of a piezoelectric ceramic, a binder containing an organic polymer such as an acrylic or butyral resin, and a plasticizer are mixed to prepare a ceramic slurry. Then, the ceramic green sheet is produced using the ceramic slurry by a belt molding method such as a doctor blade method or a calender roll method. The piezoelectric ceramic may be a piezoelectric property, and for example, a perovskite oxide containing lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ) may be used. Further, as the plasticizer, dibutyl phthalate (DBP), dioctyl phthalate (DOP) or the like can be used.

Next, a conductive paste to be the internal electrode 2 was produced. Specifically, a conductive paste is prepared by adding a mixed binder and a plasticizer to the metal powder of the silver-palladium alloy. This conductive paste was applied onto the above ceramic green sheet by a screen printing method in the pattern of the internal electrode 2. Further, the ceramic green sheets on which the conductive paste is printed are laminated, and the debonding treatment is performed at a specific temperature, and then calcined at a temperature of 900 to 1200 ° C, and a specific shape is performed using a flat grinding disc or the like. By the rubbing treatment, the laminated body 4 including the internal electrodes 2 and the piezoelectric layers 3 which are alternately laminated is produced.

The laminate 4 is not limited to those produced by the above-described production method, and any laminate can be produced by any manufacturing method as long as the laminate 4 in which a plurality of internal electrodes 2 and piezoelectric layers 3 are laminated.

After that, a silver-containing glass conductive paste prepared by adding a binder, a plasticizer, and a solvent to a conductive particle and a glass containing silver as a main component by a screen printing method is used as the surface electrode 5 The pattern is printed on the main surface and the side surface of the laminated body 4, and dried, and then subjected to a baking treatment at a temperature of 650 to 750 ° C to form the surface electrode 5.

Further, when the surface electrode 5 and the internal electrode 2 are electrically connected to each other, a through hole penetrating through the piezoelectric layer 3 may be formed and connected, and a side surface electrode may be formed on the side surface of the laminated body 4, which may be manufactured by any means. Made by method.

Then, the flexible wiring board 6 is connected and fixed (bonded) to the piezoelectric element 10 by using the conductive adhesive 7.

First, a slurry for a conductive adhesive is applied to a specific position of the piezoelectric element 10 by a method such as screen printing. Thereafter, the conductive adhesive slurry is cured in a state in which the flexible wiring board 6 is brought into contact with each other, whereby the flexible wiring board 6 is connected and fixed to the piezoelectric element 10. Further, the slurry for a conductive adhesive may be applied to the side of the flexible wiring substrate 6 by coating.

When the resin constituting the conductive adhesive 7 contains a thermoplastic resin, the piezoelectric element 10 and the flexible wiring are formed after the conductive adhesive is applied to a specific position of the piezoelectric element 10 or the flexible wiring substrate 6. The substrate 6 is heated and pressurized while being in contact with the conductive adhesive, whereby the thermoplastic resin softens and flows, and thereafter returns to normal temperature, whereby the thermoplastic resin is hardened again, and the flexible wiring board 6 is connected and fixed to the pressure. Electrical component 10.

Here, in order to arrange a large number of conductive particles constituting the conductive adhesive 7 in the peripheral portion of the region overlapping the piezoelectric element 10 in the flexible wiring substrate 6 in plan view, it is necessary to prepare a conductive material having a higher content of conductive particles. The adhesive slurry may be applied to the peripheral portion to form a conductive adhesive slurry having a high content of conductive particles.

In particular, when an anisotropic conductive member is used as the conductive bonding member 7, it is necessary to control the amount of pressing in such a manner that the conductive particles are not in contact with each other.

In the above, the method of applying the conductive adhesive 7 to the piezoelectric element 10 or the flexible wiring substrate 6 is shown. However, the sheet formed of the conductive adhesive 7 in the form of a sheet may be sandwiched in advance. The piezoelectric element 10 and the flexible wiring board 6 are joined by heating and pressing.

As shown in FIG. 4, the piezoelectric vibration device of the present embodiment includes a piezoelectric actuator 1 and a diaphragm 81 joined to the other main surface of the piezoelectric actuator 1.

The vibrating plate 81 has a rectangular thin plate shape. The vibrating plate 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, for example, to 0.4 mm to 1.5 mm.

The diaphragm 81 is joined to the other main surface of the piezoelectric actuator 1 via the joint member 82. The entire surface of the other main surface may be joined to the vibrating plate 81 via the joint member 82, or substantially the entire surface may be joined.

The joint member 82 has a film shape. Further, the joint member 82 is formed of a softer and more deformable member than the vibrating plate 81, and the elastic modulus or rigidity such as Young's modulus, rigid modulus, and bulk modulus is smaller than that of the vibrating plate 81. That is, the joint member 82 is deformable, and is deformed to a greater extent than the vibration plate 81 when the same force is applied. Further, the other main surface of the piezoelectric actuator 1 (the main surface on the -z direction side) is integrally fixed to one main surface of one of the joint members 82 (the main surface on the +z direction side in the drawing). One of the main surfaces of the joint member 82 (the main surface on the -z direction side of the drawing) is fixed to one of the main surfaces of the diaphragm 81 (the main surface on the +z direction side in the drawing).

The joint member 82 may be a single body or a composite body including a plurality of members. Such a joining member 82 can be preferably used, for example, in a double-sided tape in which an adhesive is adhered to both surfaces of a base material such as a nonwoven fabric, or an elastic adhesive which is an elastic adhesive. Further, it is preferable that the thickness of the joint member 82 is larger than the amplitude of the bending vibration of the piezoelectric actuator 1, but if it is too thick, the vibration is attenuated, and therefore it is set to, for example, 0.1 mm to 0.6 mm. However, in the piezoelectric vibration device of the present invention, the material of the joint member 82 is not limited, and the joint member 82 may be formed of a stronger and less deformable member than the diaphragm 81. Further, it may be a configuration that does not include the joint member 82 as the case may be.

In the piezoelectric vibration device of the present example having such a configuration, the piezoelectric actuator 1 is bent and vibrated by applying an electric signal, thereby functioning as a piezoelectric vibration device that vibrates the diaphragm 81. Furthermore, the length of the vibrating plate 81 can also be supported by a support member not shown. The other end of the direction (the end in the -y direction of the figure) or the peripheral portion of the vibrating plate 81.

The piezoelectric vibration device of this example is configured by using the piezoelectric actuator 1 which reduces the occurrence of unnecessary vibration, and therefore can be used as a piezoelectric vibration device which reduces the occurrence of unnecessary vibration.

Further, in the piezoelectric vibration device of this example, the diaphragm 81 is joined to the other main surface of the piezoelectric actuator 1. Thereby, it can be used as a piezoelectric vibration device in which the piezoelectric actuator 1 and the vibration plate 81 are firmly joined.

As shown in FIGS. 5 to 7, the mobile terminal device of the present embodiment includes a piezoelectric actuator 1, an electronic circuit (not shown), a display 91, and a casing 92, and the other of the piezoelectric actuators 1 The main surface is joined to the housing 92. 5 is a schematic perspective view showing the mobile terminal of the present invention, FIG. 6 is a schematic cross-sectional view taken along line AA shown in FIG. 5, and FIG. 7 is a BB line shown in FIG. A schematic cross-sectional view of the cut.

Here, it is preferable that the piezoelectric actuator 1 and the housing 92 are joined using a deformable joining member. That is, in FIGS. 6 and 7, the joint member 82 is a deformable joint member.

The piezoelectric actuator 1 is engaged with the housing 92 by the deformable engaging member 82, and when the vibration is transmitted from the piezoelectric actuator 1, the deformable engaging member 82 is deformed to a greater extent than the housing 92.

At this time, the deformable joint member 82 can be used to mitigate the vibration of the opposite phase reflected from the casing 92, so that the piezoelectric actuator 1 can be transmitted to the casing 92 without being affected by the surrounding vibration. vibration.

Wherein at least a portion of the joint member 82 includes a viscoelastic body, whereby a strong vibration from the piezoelectric actuator 1 can be transmitted to the housing 92, and on the other hand, the joint member 82 can absorb the reflection from the housing 92. The weaker vibration is preferred in this respect. For example, a bonding member including a double-sided tape to which an adhesive is applied on both surfaces of a substrate including a nonwoven fabric or the like, or a bonding agent having an elastic adhesive can be used, and a thickness of, for example, 10 μm to 2000 μm can be used.

Further, in this example, the piezoelectric actuator 1 is attached to a part of the casing 92 which is the outer casing of the display 91, and one of the casings 92 functions as the vibration plate 922.

Further, in this example, the piezoelectric actuator 1 is joined to the casing 92, but the piezoelectric actuator 1 may be joined to the display 91.

The casing 92 includes a box-shaped casing body 921 whose opening is open, and a vibration plate 922 that blocks the opening of the casing body 921. The casing 92 (the casing body 921 and the vibration plate 922) can be preferably formed using a material such as a synthetic resin having a large rigidity and a large modulus of elasticity.

The peripheral portion of the vibrating plate 922 is rotatably attached to the casing body 921 via the bonding material 93. The bonding material 93 is formed of a softer and more deformable member than the vibration plate 922, and the elastic modulus or rigidity such as the Young's modulus, the rigid modulus, and the bulk modulus is smaller than the vibration plate 922. That is, the bonding material 93 is deformable, and is deformed to a greater extent than the vibration plate 922 when the same force is applied.

The bonding material 93 may be a single body or a composite body including a plurality of members. As such a bonding material 93, for example, a double-sided tape or the like to which an adhesive is adhered to both surfaces of a substrate including a nonwoven fabric or the like can be preferably used. The thickness of the bonding material 93 is set so as not to be too thick and the vibration is attenuated, and is set, for example, to 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 by being stronger and less deformable than the vibration plate 922. Further, it may be a configuration that does not include the bonding material 93 as the case may be.

As the electronic circuit (not shown), for example, a circuit for processing image information displayed on the display 91 or sound information transmitted from the mobile terminal device, a communication circuit, or the like can be exemplified. It can be at least one of the circuits or all of the circuits. Also, it may be a circuit having other functions. Furthermore, a plurality of electronic circuits may be included. Further, 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, and for example, a liquid crystal display, a plasma display, and an organic EL (Electroluminescence) can be preferably used. A known display such as a light-emitting display. Furthermore, the display 91 can also be an input device including a touch panel. Moreover, the outer casing (vibration plate 922) of the display 91 may also be an input device including a touch panel. Further, the entire display 91 or a part of the display 91 can also function as a diaphragm.

Further, the mobile terminal of the present invention is characterized in that the display 91 or the casing 92 generates vibration for transmitting sound information through cartilage or gas conduction of the ear. The mobile terminal of this example allows the vibrating plate (display 91 or casing 92) to be in contact with the ear directly or via other objects, and transmits vibration to the cartilage of the ear, thereby transmitting sound information. That is, the vibrating plate (display 91 or casing 92) can be brought into direct or indirect contact with the ear to transmit vibration to the cartilage of the ear, thereby transmitting sound information. Thereby, for example, an action terminal that can transmit voice information even when it is around is obtained. Furthermore, the object interposed between the vibrating plate (display 91 or the housing 92) and the ear may be, for example, a housing of a mobile terminal, or a headset or an earphone, as long as it is an object that can transmit vibration. Can be any object. Further, it may be an action terminal that transmits sound information by propagating sound generated from the vibrating plate (display 91 or casing 92) in the air. Furthermore, it may be an action terminal that transmits voice information via a plurality of paths.

The mobile terminal device of this example transmits the sound information by using the piezoelectric actuator 1 which does not require the generation of vibration, and therefore, can transmit high-quality sound information.

[Examples]

A specific example of the piezoelectric actuator of the present invention will be described. Specifically, the piezoelectric actuator shown in Fig. 1 was produced as shown below.

The piezoelectric element has a rectangular parallelepiped shape having a length of 23.5 mm, a width of 3.3 mm, and a thickness of 0.5 mm. Further, the piezoelectric element has a structure in which a piezoelectric layer having a thickness of 30 μm and an internal electrode are alternately laminated, and the total number of the piezoelectric layers is set to 16 layers. The piezoelectric layer is formed of lead zirconate titanate. The internal electrode uses an alloy of silver and palladium.

After the ceramic green sheet on which the conductive paste containing silver palladium is printed is laminated After pressure-bonding and degreasing at a specific temperature, it was calcined at 1000 ° C to obtain a laminated sintered body.

Then, the surface electrode was printed so as to be extended by 1 mm from both ends of the internal electrode in the width direction.

A voltage of an electric field intensity of 2 kV/mm was applied between the internal electrodes (between the first electrodes and the second electrodes) via the surface electrodes, and the piezoelectric elements were polarized.

Thereafter, a conductive adhesive containing a gold-plated resin ball as a conductive particle is formed on the surface of the piezoelectric element bonded to the flexible wiring board. At this time, a conductive adhesive containing 20 vol% of conductive particles is applied to a region of a peripheral portion of the region where the flexible wiring substrate and the piezoelectric element overlap each other by 0.3 mm, and a coating is formed on the inner side in a region containing 10 vol. Conductive adhesive for % conductive particles.

Thereafter, the flexible wiring board is heated and pressurized while being in contact with each other, whereby the flexible wiring board is electrically connected and fixed to the piezoelectric element, thereby producing a piezoelectric actuator (sample No. 1) according to the embodiment of the present invention. ). Further, as the above-mentioned conductive adhesive, an anisotropic conductive material which is electrically connected in the thickness direction and is not electrically conductive in the in-plane direction is used.

Further, as a comparative example, a piezoelectric actuator (sample No.) outside the scope of the present invention having the same configuration as the above-described sample No. 1 except that the flexible wiring substrate was bonded to the piezoelectric element by solder was produced. .2).

Further, for each of the piezoelectric actuators, a driving test was performed by applying a sine wave signal having a frequency of 1 kHz and an effective value of ±10 Vrms to the piezoelectric element via the flexible wiring substrate, and as a result, both samples No. 1 and 2 were obtained with 100 μm. The bending vibration of the displacement.

Then, a sinusoidal signal having an effective value of 3 V, which has a frequency varying between 0.2 and 5000 Hz, is input, and it is confirmed whether or not abnormal vibration due to cracks in the joint surface of the flexible wiring board is not generated. As a result, Sample No. in the embodiment of the present invention In the piezoelectric actuator of .1, abnormal vibration was not found except for the vibration originating from the resonance of the piezoelectric element and the anti-resonance frequency. On the other hand, in the piezoelectric actuator of sample No. 2 outside the scope of the present invention, the piezoelectric element is derived from Abnormal vibration is measured at frequencies other than vibration of the device.

Thereafter, a driving test was performed by continuously applying a sinusoidal signal of an effective value of ±10 Vrms of 100,000 cycles. Sample No. 2 outside the range of the present invention generated abnormal vibration, and the flexible wiring substrate was peeled off from the piezoelectric element in 90,000 cycles.

On the other hand, the piezoelectric actuator of the sample No. 1 of the embodiment of the present invention continued to drive without generating abnormal vibration even after 100,000 cycles. Further, no crack or crack was observed in the conductive adhesive to which the flexible wiring board was attached, and no peeling of the flexible wiring board was observed.

By using the piezoelectric actuator of the present invention, abnormal vibration does not occur, and even when it is continuously driven for a long period of time, the problem that the flexible wiring substrate is peeled off from the piezoelectric element does not occur, and excellent durability can be confirmed.

1‧‧‧ Piezoelectric actuator

2‧‧‧Internal electrodes

3‧‧‧ piezoelectric layer

4‧‧‧Layered body

5‧‧‧ surface electrode

6‧‧‧Soft wiring board

7‧‧‧ Conductive adhesive

10‧‧‧Piezoelectric components

21‧‧‧1st pole

22‧‧‧2nd pole

41‧‧‧Active Department

42‧‧‧Inertial Department

51‧‧‧1st surface electrode

52‧‧‧2nd surface electrode

53‧‧‧3rd surface electrode

61‧‧‧Wiring conductor

601‧‧‧The Peripheral Department

Claims (11)

A piezoelectric actuator comprising: a piezoelectric element comprising a laminated body having an internal electrode and a piezoelectric layer laminated thereon, and a surface electrode electrically connected to the internal electrode on one main surface of the laminated body; And a flexible wiring board, wherein a part of the flexible wiring board is bonded to the one main surface via a conductive adhesive containing conductive particles and a resin, and includes a wiring conductor electrically connected to the surface electrode; and the flexible wiring substrate and the piezoelectric element In at least a part of the peripheral portion of the joint region, the ratio of the conductive particles per unit area in a plan view of the conductive adhesive is larger than a portion other than the peripheral portion. A piezoelectric actuator according to claim 1, wherein said portion is located in a region between the outer periphery of said one main surface and said surface electrode. The piezoelectric actuator according to claim 1, wherein a ratio of the conductive particles per unit area in a plan view of the conductive adhesive is larger than a portion other than the peripheral portion in the entire circumference of the peripheral portion. The piezoelectric actuator according to any one of claims 1 to 3, wherein the conductive adhesive is an anisotropic conductive material. The piezoelectric actuator according to any one of claims 1 to 3, wherein the conductive particles not connected to any of the piezoelectric element and the flexible wiring substrate are 70% or more of the whole. A piezoelectric actuator according to any one of claims 1 to 3, wherein the other principal surface of the piezoelectric element is flatter than a main surface. A piezoelectric vibration device comprising the piezoelectric actuator according to any one of claims 1 to 6, and a vibration plate joined to the other main surface of the piezoelectric element. The piezoelectric vibration device of claim 7, wherein the piezoelectric actuator and the vibrating plate are joined using a deformable joining member. A mobile terminal device, comprising: the piezoelectric actuator, the electronic circuit, the display, and the housing according to any one of claims 1 to 6, wherein the other main surface of the piezoelectric actuator is bonded to the above Display or the above housing. The mobile terminal of claim 9, wherein the piezoelectric actuator is coupled to the display or the housing using a deformable engaging member. The mobile terminal of claim 9 or 10, wherein the display or the housing generates vibrations that transmit sound information through at least one of cartilage and gas conduction of the ear.