JP5680202B2 - Piezoelectric vibration device and portable terminal - Google Patents

Description

  The present invention relates to a piezoelectric vibration device, a piezoelectric actuator suitable for a portable terminal, a piezoelectric vibration device using the piezoelectric actuator, and a portable terminal.

  As a piezoelectric actuator, as shown in FIG. 11, a bimorph type piezoelectric element 10 in which a surface electrode 104 is formed on the surface of a laminate 103 in which a plurality of internal electrodes 101 and a plurality of piezoelectric layers 102 are laminated, (Refer to Patent Document 1), a flexible substrate 105 is joined to the main surface of the piezoelectric element 10 with a conductive joining member 106, and the surface electrode 104 of the piezoelectric element 10 and the wiring conductor 107 of the flexible substrate 105 are electrically connected. It is known (see Patent Document 2).

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

Japanese Patent Laid-Open No. 2002-10393 JP-A-6-14396 International Publication No. 2005/004535 JP 2006-238072 A

  The piezoelectric actuator as shown in FIG. 11 can generate a bending vibration in which the main surface is bent. Moreover, by applying to a piezoelectric vibration device, a portable terminal, etc., it can be set as the vibration source of these devices.

  By the way, in recent years, the demand for energy saving is further increased, and it is desired that a large bending vibration can be obtained with smaller electric power.

  The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a piezoelectric actuator, a piezoelectric vibration device, and a portable terminal that can obtain larger bending vibration.

The piezoelectric vibration device of the present invention is
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 provided in the laminating direction of the laminated body,
The internal electrode includes a first pole and a second pole;
The stacked body includes an active part in which the first pole and the second pole of the internal electrode overlap in the stacking direction, and an inactive part other than the active part,
The entire other main surface between the side surfaces of the laminate is flat,
The thickness of the active part is thicker than the thickness of the inactive part,
The laminate is a piezoelectric actuator that bends and vibrates in the lamination direction ;
It has a diaphragm joined to the other principal surface of the layered product .

  The portable terminal of the present invention includes the piezoelectric actuator, an electronic circuit, a display, and a housing, and the other main surface of the piezoelectric actuator is bonded to the display or the housing. This is a featured mobile terminal.

According to the present invention, the thickness of the inactive portion is thinner than that of the active portion, while the shape of the main surface makes it easier to draw a force in the bending direction. A vibration device can be realized.

(A) is a schematic perspective view which shows an example of embodiment of the piezoelectric actuator of this invention, (b) is a schematic sectional drawing cut | disconnected by the AA line shown to (a), (c) is ( It is the schematic sectional drawing cut | disconnected by the BB line shown to a). It is a schematic sectional drawing which shows the other example of FIG.1 (c). It is a schematic sectional drawing which shows the other example of FIG.1 (c). It is a schematic sectional drawing which shows the other example of FIG.1 (c). It is a schematic sectional drawing which shows the other example of FIG.1 (c). (A) is a schematic perspective view which shows the other example of embodiment of the piezoelectric actuator of this invention, and is the schematic sectional drawing cut | disconnected by the BB line shown to (a). 1 is a schematic perspective view schematically showing a piezoelectric vibration device according to an embodiment of the present invention. It is a schematic perspective view which shows typically the portable terminal of embodiment 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. It is a schematic perspective view which shows an example of embodiment of the conventional piezoelectric actuator, (b) is a schematic sectional drawing cut | disconnected by the AA line shown to (a), (c) is B shown to (a). It is the schematic sectional drawing cut | disconnected by the -B line.

  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. FIG.1 (c) is the schematic sectional drawing cut | disconnected by the BB line | wire shown to Fig.1 (a).

  A piezoelectric actuator 1 of the present invention shown in FIG. 1 includes a laminate 4 in which an internal electrode 2 and a piezoelectric layer 3 are laminated, and a surface electrode 5 electrically connected to the internal electrode 2 on one main surface of the laminate 4. The internal electrode 2 includes a first electrode 21 and a second electrode 22, and an active part 41 in which the first electrode 21 and the second electrode 22 of the internal electrode 2 overlap in the stacking direction, and an active part Inactive portions 42 other than 41 are included, the thickness of the active portion 41 is greater than the thickness of the inactive portion 42, and the other main surface of the laminate 4 is flat.

  The laminated body 4 constituting the piezoelectric actuator 1 is formed by laminating an internal electrode 2 and a piezoelectric layer 3, and includes an active portion 41 in which a plurality of internal electrodes 2 overlap in the laminating direction and other inactive portions 42. For example, it is formed in a long shape. In the case of a piezoelectric actuator attached to a display or casing of a mobile terminal, the length of the laminate 4 is preferably, for example, 18 mm to 28 mm, and more preferably 22 mm to 25 mm. The width of the laminate 4 is preferably 1 mm to 6 mm, for example, and more preferably 3 mm to 4 mm. The thickness of the laminate 4 is preferably, for example, 0.2 mm to 1.0 mm, and more preferably 0.4 mm to 0.8 mm.

  The internal electrode 2 constituting the multilayer body 4 is formed by simultaneous firing with the ceramic forming the piezoelectric layer 3, and includes a first electrode 21 and a second electrode 22. For example, the first electrode 21 is a ground electrode, and the second electrode 22 is a positive electrode or a negative electrode. In addition, a region where the first electrode 21 and the second electrode 22 of the internal electrode 2 overlap in the stacking direction is the active portion 41, and other regions (for example, a region without the internal electrode 2 when viewed from the stacking direction, the first The region where only the first electrode 21 or only the second electrode 22 overlaps) is the inactive portion 42. Piezoelectric layers 3 are alternately stacked to sandwich the piezoelectric layers 3 from above and below, and the first pole 21 and the second pole 22 are arranged in the stacking order, so that the piezoelectric body sandwiched between them. A driving voltage is applied to the layer 3. As this forming material, for example, a conductor mainly composed of silver or silver-palladium alloy having low reactivity with piezoelectric ceramics, or a conductor containing copper, platinum or the like can be used. You may make it contain.

  In the example shown in FIG. 1, the end portions of the first pole 21 and the second pole 22 are led out alternately to a pair of side surfaces facing the stacked body 4. In the case of a piezoelectric actuator attached to a display or casing of a mobile terminal, the length of the internal electrode 2 is preferably 17 mm to 25 mm, for example, and more preferably 21 mm to 24 mm. For example, the width of the internal electrode 2 is preferably 1 mm to 5 mm, and more preferably 2 mm to 4 mm. The thickness of the internal electrode 2 is preferably 0.1 to 5 μm, for example.

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

  A surface electrode 5 electrically connected to the internal electrode 2 is provided on at least one main surface of the laminate 4. The surface electrode 5 in 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. As shown in FIG. 1, for example, the first surface electrode 51 is electrically connected to the internal electrode 2 to be the first electrode 21, and the second surface electrode 52 is a second electrode disposed on one main surface side. The internal electrode 2 serving as the second electrode 22 and the third surface electrode 53 are electrically connected to the internal electrode 2 serving as the second electrode 22 disposed on the other main surface side. In the case of a piezoelectric actuator attached to a display or casing of a portable terminal, the length of the first surface electrode 51 is preferably, for example, 17 mm to 23 mm, and more preferably 19 mm to 21 mm. The width of the first surface electrode 51 is preferably 1 mm to 5 mm, for example, and more preferably 2 mm to 4 mm. The lengths of the second surface electrode 52 and the third surface electrode 53 are preferably, for example, 1 mm to 3 mm. The widths of the second surface electrode 52 and the third surface electrode 53 are preferably 0.5 mm to 1.5 mm, for example.

  Then, as shown in FIGS. 1B and 1C, the multilayer body 4 includes an active portion 41 in which the first electrode 21 and the second electrode 22 of the internal electrode 2 overlap each other in the stacking direction, Inactive portions 42 other than 41 are included, the thickness of the active portion 41 is thicker than the thickness of the inactive portion 42, and the other main surface of the laminate 4 is flat.

  The piezoelectric actuator 1 of the present invention is used by sticking the other main surface of the laminate 4 to an object (such as a vibration plate to be described later) that mainly applies vibration, but the other main surface of the laminate 4 is flat. Therefore, it becomes easy to cause bending vibration integrally with the object to which vibration is applied, and the efficiency of bending vibration can be improved as a whole. Furthermore, the thickness of the active portion 41 where the first electrode 21 and the second electrode 22 of the internal electrode 2 overlap in the stacking direction is greater than the thickness of the inactive portion 42, that is, one main surface of the stacked body 4. Since the inactive portion 42 is thinner than the active portion 41 and the bending rigidity of the vibration device integrated with the object to be vibrated is lowered, the force in the bending direction during bending vibration can be easily extracted. ing. Thereby, the piezoelectric actuator 1 and the piezoelectric vibration device can perform larger bending vibration with a small electric power. Further, as a result of the effective use of energy by bending, it occurs at the boundary between the active part 41 and the inactive part 42 of the internal electrode close to one main surface (the boundary between the internal electrode 2 and the piezoelectric layer 3). The generation of microcracks can be reduced by reducing unnecessary stress, and deterioration of the piezoelectric actuator 1 due to deterioration can be suppressed. Note that the thickness of the active portion 41 is preferably 2 to 10% thicker than the thickness of the inactive portion 42.

  In the piezoelectric actuator 1 of the present invention, as shown in FIG. 2, it is preferable that one main surface is inclined from the active portion 41 to the inactive portion 42, so that the active portion 41 continuously passes through the inactive portion 42. Therefore, the stress in the bending direction can be easily extracted without bending stress on the surface of the laminate 4.

  In addition, as shown in FIG. 2, all the internal electrodes 2 may have a planar shape (straight section), but are arranged on one main surface side of the laminate 4 as shown in FIG. 1 (c). The formed internal electrode 2 may have an end located near the boundary between the active portion 41 and the inactive portion 42 curved toward the other main surface. According to this configuration, the curved shape of the end portion of the internal electrode 2 facilitates drawing out the force in the bending direction when bending. Thereby, the piezoelectric actuator 1 can perform larger bending vibration with small electric power. Further, as a result of the effective use of energy by bending, it occurs at the boundary between the active part 41 and the inactive part 42 of the internal electrode close to one main surface (the boundary between the internal electrode 2 and the piezoelectric layer 3). The generation of microcracks can be reduced by reducing unnecessary stress, and deterioration of the piezoelectric actuator 1 due to deterioration can be suppressed. As for the degree of bending, the bending is such that the tangent at the end of the internal electrode 2 is inclined by 5 ° or more, particularly 10 ° or more with respect to the tangent drawn along the plane portion of the internal electrode 2. It is effective in that it is easy to draw out the force in the direction of.

  Although not shown, the end portions of the internal electrode 2 located near the boundary between the active portion 41 and the inactive portion 42 may all be curved toward the other main surface side. When the diaphragm is joined, the force in the bending direction when bending can be more easily pulled out. As a result, unnecessary stress generated at the boundary between the active part 41 and the inactive part 42 of the internal electrode is reduced to reduce the occurrence of microcracks, and the piezoelectric actuator 1 is deteriorated and the amount of displacement is reduced. Can be suppressed.

  Further, as shown in FIG. 3, the end portions of the internal electrode 2 arranged on both main surfaces of the laminate 4 that are located in the vicinity of the boundary between the active portion 41 and the inactive portion 42 are curved toward the inside. This makes it easy to draw out the force in the direction of bending when the object to be vibrated is thin and has low rigidity, when bending to both main surfaces. In addition, as a result of the effective use of energy by bending, it occurs at the boundary between the active part 41 and the inactive part 42 of the internal electrode (boundary between the internal electrode 2 and the piezoelectric layer 3) near both main surfaces. The generation of microcracks can be reduced by reducing unnecessary stress, and deterioration of the piezoelectric actuator 1 due to deterioration can be suppressed.

  Further, as shown in FIG. 4, it is preferable that the degree of curvature of the end portion of the internal electrode 2 increases as it approaches the one main surface. With this configuration, it is possible to further draw out the force in the bending direction when further bending, and in the vicinity of the end portion of the internal electrode 2 to which stress is most applied (on the vicinity of the end portion of the internal electrode 2 closest to the main surface) Since the stress can be relaxed as a result, a microcrack is generated at the boundary between the active portion 41 and the inactive portion 42 of the internal electrode 2 that is closest to the main surface (the boundary between the internal electrode 2 and the piezoelectric layer 3). Can be further reduced.

  Furthermore, as shown in FIGS. 2 to 4, the internal electrode 2 closest to the other main surface of the multilayer body 4 may be flat, and the other main surface is attached to an object (such as a diaphragm described later) to which vibration is applied. When bonded together, it becomes easy to cause bending vibration integrally with the object to which vibration is applied, and the efficiency of bending vibration can be further improved as a whole.

  Further, the surface electrode 5 is preferably provided from the active part 41 to the inactive part 42. Since the surface electrode 5 (first surface electrode 51) is provided so as to extend in the width direction from the active portion 41 to the inactive portion 42, it is possible to further draw out the force in the bending direction when bending. it can. By connecting the surface electrode 5 and the internal electrode 2 so as to apply a voltage to the piezoelectric layer 3 positioned between the surface electrode 5 and the internal electrode 2 closest to the surface electrode 5, a region to which a voltage is applied can be obtained. Since the piezoelectric layer 3 sandwiched between the other internal electrodes 2 can be made wider in the width direction as well as in the longitudinal direction, a voltage is applied to the region of the inactive portion 42 to effectively bend it. This is because the displacement of can be induced. As a result, the stress generated at the boundary between the active part 41 and the inactive part 42 of the internal electrode 2 (the boundary between the internal electrode 2 and the piezoelectric layer 3) is reduced and the occurrence of microcracks is suppressed. Can do. It is more effective to curve the surface electrode 5 along the curve of the internal electrode 2.

  Furthermore, as shown in FIG. 5, there is a region where the thickness of the inactive portion 42 in the stacking direction is equal to or less than the thickness from the upper surface of the uppermost internal electrode 2 to the lower surface of the lowermost internal electrode 2 in the active portion 41. The surface electrode 5 (first surface electrode 51) is preferably provided up to this region.

  Thereby, it is possible to further easily draw out the force in the bending direction when further bending. By connecting the surface electrode 5 and the internal electrode 2 so as to apply a voltage to the piezoelectric layer 3 positioned between the surface electrode 5 and the internal electrode 2 closest to the surface electrode 5, a region to which a voltage is applied can be obtained. This is because the width can be further increased in the width direction, so that a voltage can be further applied to the region of the inactive portion 42 to effectively induce bending displacement. As a result, the stress generated at the boundary between the active part 41 and the inactive part 42 of the internal electrode 2 (the boundary between the internal electrode 2 and the piezoelectric layer 3) is further reduced, and the generation of microcracks is further reduced. Can be suppressed.

  Further, as shown in FIG. 6, the piezoelectric actuator 1 of the present invention includes a flexible substrate 6 having a wiring conductor 61, and the surface electrode 5 and the wiring conductor 61 are electrically connected via a conductive bonding member 7. As described above, a part of the flexible substrate 6 may be bonded to one main surface of the laminate 4.

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

  The conductive bonding member 7 is made of a conductive adhesive, solder, or the like, and is preferably a conductive adhesive. For example, a conductive adhesive is used in which conductive particles 72 made of resin balls such as gold, copper, nickel, or gold plating are dispersed in a resin 71 such as an acrylic resin, an epoxy resin, a silicone resin, a polyurethane resin, or a synthetic rubber. This is because the stress caused by vibration can be reduced compared to solder. More preferably, the conductive adhesive is preferably an anisotropic conductive material. The anisotropic conductive material is composed of conductive particles responsible for electrical bonding and a resin adhesive responsible for adhesion. Since this anisotropic conductive material can conduct in the thickness direction and insulate in the in-plane direction, even in a narrow pitch wiring, there is no electrical short between the surface electrodes of different polarities, and a flexible substrate The connection part with 6 can be made compact.

  The piezoelectric actuator 1 shown in FIG. 1 is a so-called bimorph type piezoelectric actuator that receives an electric signal from the surface electrode 5 and vibrates and vibrates so that one main surface and the other main surface are bent surfaces. However, the piezoelectric actuator of the present invention is not limited to the bimorph type, and may be a unimorph type. For example, by joining (bonding) the other principal surface of the piezoelectric actuator to a diaphragm described later, It 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 the piezoelectric layer 3 is produced. Specifically, a ceramic slurry is prepared by mixing a calcined powder of piezoelectric ceramic, a binder made of an organic polymer such as acrylic or butyral, and a plasticizer. And a ceramic green sheet is produced using this ceramic slurry by using tape molding methods, such as a doctor blade method and a calender roll method. As the piezoelectric ceramic, any material having piezoelectric characteristics may be used. For example, a perovskite oxide made of lead zirconate titanate (PbZrO ₃ —PbTiO ₃ ) can be used. As the plasticizer, dibutyl phthalate (DBP), dioctyl phthalate (DOP), or the like can be used.

  Next, a conductive paste to be the internal electrode 2 is produced. Specifically, a conductive paste is prepared by adding and mixing a binder and a plasticizer to a silver-palladium alloy metal powder. This conductive paste is applied on the ceramic green sheet in the pattern of the internal electrode 2 using a screen printing method. Furthermore, after laminating a plurality of ceramic green sheets on which this conductive paste is printed, after performing a binder removal treatment at a predetermined temperature, firing at a temperature of 900 to 1200 ° C., using a surface grinder or the like By performing a grinding process so as to obtain a shape, a laminated body 4 including the internal electrodes 2 and the piezoelectric body layers 3 that are alternately laminated is manufactured.

  In such a manufacturing process, after laminating a plurality of ceramic green sheets printed with conductive paste, for example, a mold or a resin mold having a dent is used as an upper mold (one main surface side) of the press device. , By using a flat mold or resin mold as the lower mold (the other main surface side) of the press device, the thickness of the active part 41 is thicker than the thickness of the other inactive part 42, The piezoelectric actuator 1 in which the other main surface of the laminate 4 is flat can be produced.

  In addition, the laminated body 4 is not limited to what is produced by said manufacturing method, You may give a grinding process so that it may become a predetermined shape.

  Thereafter, a silver glass-containing conductive paste prepared by adding a binder, a plasticizer, and a solvent to a mixture of conductive particles mainly composed of silver and glass is used as a main electrode of the laminate 4 in the pattern of the surface electrode 5. After printing on the side and the side by a screen printing method or the like and drying, a baking process is performed at a temperature of 650 to 750 ° C. to form the surface electrode 5.

  When the surface electrode 5 and the internal electrode 2 are electrically connected, a via that penetrates the piezoelectric layer 3 may be formed or connected, or a side electrode may be formed on the side surface of the multilayer body 4. It may be produced by any manufacturing method.

  Next, the flexible substrate 6 is connected and fixed (bonded) to the piezoelectric element 10 using the conductive bonding member 7.

  First, a conductive bonding member paste is applied and formed on a predetermined position of the piezoelectric element 10 using a technique such as screen printing. Then, the flexible substrate 6 is connected and fixed to the piezoelectric element 10 by curing the conductive bonding member paste in a state where the flexible substrate 6 is brought into contact therewith. The conductive bonding member paste may be applied and formed on the flexible substrate 6 side.

  When the conductive bonding member 7 is a conductive adhesive, and the resin constituting the conductive adhesive is made of a thermoplastic resin, the conductive adhesive is placed at a predetermined position on the piezoelectric element 10 or the flexible substrate 6. After coating and forming, the thermoplastic resin softens and flows by heating and pressurizing the piezoelectric element 10 and the flexible substrate 6 in contact with a conductive adhesive. The plastic resin is cured, and the flexible substrate 6 is connected and fixed to the piezoelectric element 10.

  In particular, when an anisotropic conductive member is used as the conductive bonding member 7, it is necessary to control the amount of pressurization 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 piezoelectric element 10 or the flexible substrate 6 has been described. However, a sheet of the conductive adhesive formed in advance in a sheet shape is formed between the piezoelectric element 10 and the flexible substrate 6. You may heat-press and join in the state pinched | interposed.

  As shown in FIG. 7, the piezoelectric vibration device of the present invention has a piezoelectric actuator 1 and a vibration plate 81 attached to the other main surface of the piezoelectric actuator 1.

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

  The diaphragm 81 is attached to the other main surface of the piezoelectric actuator 1 via a joining member 82. The entire surface of the other main surface may be bonded to the diaphragm 81 via the bonding member 82, or substantially the 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 diaphragm 81, and has a smaller elastic modulus and rigidity such as Young's modulus, rigidity, and bulk modulus than the diaphragm 81. That is, the joining member 82 is deformable and deforms more greatly than the diaphragm 81 when the same force is applied. Then, the other main surface (main surface on the −z direction side in the drawing) of the piezoelectric actuator 1 is entirely fixed to one main surface (the main surface on the + z direction side in the drawing) of the bonding member 82. 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).

  The joining member 82 may be a single member or a composite body composed 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 substrate made of a nonwoven fabric or the like, various elastic adhesives which are adhesives having elasticity, and the like can be suitably used. The thickness of the joining member 82 is desirably larger than the amplitude of the bending vibration of the piezoelectric actuator 1, but if it is too thick, the vibration is attenuated, so that the thickness is set to 0.1 mm to 0.6 mm, for example. 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 less deformable than the vibration plate 81. In some cases, a configuration without the joining member 82 may be used.

  The piezoelectric vibration device of this example having such a configuration functions as a piezoelectric vibration device that causes the piezoelectric actuator 1 to bend and vibrate by applying an electrical signal, thereby vibrating the vibration plate 81. For example, the other end portion in the length direction of the diaphragm 81 (the end portion in the −y direction in the drawing, the peripheral portion of the diaphragm 81, and the like may be supported by a support member (not shown).

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

  As shown in FIGS. 8 to 10, the portable terminal of the present invention includes the piezoelectric actuator 1, an electronic circuit (not shown), a display 91, and a housing 92, and the other side of the piezoelectric actuator 1. The main surface is joined to the housing 92. 8 is a schematic perspective view schematically showing the portable terminal of the present invention, FIG. 9 is a schematic cross-sectional view taken along line AA shown in FIG. 8, and FIG. 10 is a cross-sectional view taken along line BB shown in FIG. It is the schematic sectional drawing cut | disconnected by the line.

  Here, it is preferable that the piezoelectric actuator 1 and the housing 92 are joined using a deformable joining member. That is, in FIG. 9 and FIG. 10, the joining member 82 is a deformable joining member.

  By joining the piezoelectric actuator 1 and the housing 92 with the deformable joining member 82, the deformable joining member 82 is deformed more greatly than the housing 92 when vibration is transmitted from the piezoelectric actuator 1.

  At this time, since the anti-phase vibration reflected from the casing 92 can be mitigated by the deformable joining member 82, the piezoelectric actuator 1 transmits strong vibration to the casing 92 without being influenced by the surrounding vibration. Can be made.

  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 is transmitted to the housing 92, while weak vibration reflected from the housing 92 is transmitted to the joining member 82. It is preferable in that it can be absorbed. 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 a nonwoven fabric or the like, or a joining member having a configuration including an adhesive having elasticity. Can be used.

  In this example, the piezoelectric actuator 1 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 piezoelectric actuator 1 is bonded to the housing 92, but the piezoelectric actuator 1 may be bonded to the display 91.

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

  The peripheral edge of the diaphragm 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 made up 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 the 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 and more difficult to deform than the diaphragm 922. In some cases, a configuration without the bonding material 93 may be used.

  Examples of the electronic circuit (not shown) include a circuit that processes image information to be 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. Further, 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 portable terminal of the present invention is characterized in that the display 91 or the casing 92 generates vibration that transmits sound information to the inner ear through the cartilage or air conduction of the ear. The portable terminal of this example can transmit sound information by transmitting a vibration to the cartilage of the ear by bringing the diaphragm (display 91 or housing 92) into contact with the ear directly or via another object. That is, sound information can be transmitted by bringing a diaphragm (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, a portable terminal capable of transmitting sound information even when the surroundings are noisy 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 mobile terminal of this example transmits sound information using the piezoelectric actuator 1 that can effectively generate vibration, it can transmit high-quality sound information.

  Next, a specific example of the piezoelectric vibration device of the present invention will be described. A piezoelectric vibration device using the piezoelectric actuator shown in FIG. 5 was produced and its characteristics were measured.

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

In order to make the active part thicker than the inactive part, after laminating ceramic green sheets printed with conductive paste, a resin mold having a dent as the mold on the upper side of the press device (the side in contact with the main surface) Was used, and a flat die was used as a die on the lower side of the press device (side in contact with the other main surface) to produce a piezoelectric actuator having the shape shown in FIG.
The surface electrode was printed so as to be longer by 1 mm in the width direction at both ends than the internal electrode. The amount of protrusion in the + z direction in the figure relative to both ends of the central portion on one main surface of the piezoelectric actuator was 10% (0.05 mm) of the thickness of the piezoelectric actuator. The other main surface of the piezoelectric actuator was almost flat.
And while sticking a glass plate to a metal frame with a double-sided tape, the other main surface of the piezoelectric actuator was stuck to the center of one surface of the glass plate with a double-sided tape, and 1 mm away from the other surface of the glass plate A microphone was installed at the position.

  And the sine wave signal of the effective value 3.0V which changed the frequency in the range of 0.3-3.4 kHz was input into the piezoelectric actuator, and the sound pressure detected with a microphone was measured. Furthermore, 100,000 cycles of sine wave signals were continuously added to compare the sound pressure levels before and after the continuous measurement.

  As a result, high sound pressure characteristics were obtained even with low input. This confirmed the effectiveness of the present invention.

1: Piezoelectric actuator 2: Internal electrode
21: First pole
22: Second pole 3: Piezoelectric layer 4: Laminate
41: Active part
42: Inactive part 5: Surface electrode
51: First surface electrode
52: Second surface electrode
53: Third surface electrode 6: Flexible substrate
61: Wiring conductor 7: Conductive bonding member
71: Resin
72: Conductive particles
81: Diaphragm
82: Joining member
91: Display
92: Housing
921: Housing body
922: Diaphragm
93: Bonding material

Claims (8)

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 provided in the laminating direction of the laminated body,
The internal electrode includes a first pole and a second pole;
The stacked body includes an active part in which the first pole and the second pole of the internal electrode overlap in the stacking direction, and an inactive part other than the active part,
The entire other main surface between the side surfaces of the laminate is flat,
The thickness of the active part is thicker than the thickness of the inactive part,
A pressure electrostatic actuator the laminate you flexural vibration in the stacking direction,
A piezoelectric vibration device comprising: a diaphragm bonded to the other main surface of the laminate. 2. The piezoelectric vibration device according to claim 1, wherein the one main surface is gently inclined from the active portion to the inactive portion. The piezoelectric vibration device according to claim 1, wherein the surface electrode is provided from the active portion to the inactive portion. The inactive portion has a region whose thickness is less than or equal to the thickness from the upper surface of the inner electrode of the uppermost layer in the active portion to the lower surface of the inner electrode of the lowermost layer, and the surface electrode is provided up to the region. The piezoelectric vibration device according to claim 3. A flexible substrate having a wiring conductor is provided, and a part of the flexible substrate is placed on the one main surface of the laminate so that the surface electrode and the wiring conductor are electrically connected via an anisotropic conductive material. The piezoelectric vibration device according to claim 1, wherein the piezoelectric vibration device is bonded. Wherein the piezoelectric actuator and the vibration plate, the piezoelectric vibration according to any one of claims 1 to 5, characterized in that it is joined with the soft deformable joining member than the diaphragm apparatus. The piezoelectric vibration device according to any one of claims 1 to 6 , an electronic circuit, a display, and a housing,
The portable terminal, wherein the other main surface of the laminate is bonded to the display or the casing as the diaphragm . The mobile terminal according to claim 7 , wherein the piezoelectric actuator and the display or the housing are joined using a joining member that is softer and easier to deform than the display or the housing.

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