Abstract:
In a piezoelectric oscillation device in which a support substrate is oscillated using a bimorph-type piezoelectric oscillation element, the click sensation when the support substrate is operated is improved, and shock resistance of a control panel is improved. Provided is a piezoelectric oscillation device in which wiring is not easily broken. On the rear side of a touch panel ( 16 ), one main surface of a bimorph-type piezoelectric oscillation element ( 20 ) is entirely bonded via an elastic body ( 18 ) having a tensile elasticity of 20-100 MPa as measured according to JIS K7161. The piezoelectric oscillation element ( 20 ) has surface electrode layers ( 30 A,  30 B) connected to terminal electrodes ( 36 A,  36 B) via wiring lines ( 38 A,  38 B). The wiring lines ( 38 A,  38 B) are formed on top of a wiring protection layer ( 32 ) made of an elastic body provided on the rear side of the touch panel ( 16 ), and because the wiring lines can move following the displacement and are therefore resistant to breakage. When the piezoelectric oscillation element ( 20 ) is displaced toward the touch panel ( 16 ), it can transmit a greater amount of displacement to the touch panel ( 16 ) than when it is displaced to the opposite side.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a piezoelectric oscillation device such as a force feedback touch panel (a panel that vibrates when touched by a finger), for example. 
       BACKGROUND ART 
       [0002]    A piezoelectric element has a feature of generating bulk strain by the reverse piezoelectric effect, and actuators that utilize this feature are commercialized in various fields. Piezoelectric elements are also used for electronic devices such as a touch panel and a display device equipped with an input sensor. Japanese Patent Application Laid-Open Publication No. 2005-222326 (Patent Document 1), for example, discloses a tablet device in which a single layer piezoelectric body is bonded to a support substrate that supports an operation panel from the rear side thereof, and the support substrate vibrates when the operator conducts an input operation on the operation panel, thereby applying vibrations to the operator in response to the input. 
       Related Art Document 
     Patent Document 
       [0003]    Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2005-222326 
       SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
       [0004]    However, in the technology disclosed in Patent Document 1 above, the piezoelectric body utilizes a piezoelectric element having a single layer unimorph structure, and because the piezoelectric element vibrates in parallel with the support substrate, in order to allow the operator to feel the vibration, it is necessary to use an adhesive agent that has a high elasticity. Bimorph piezoelectric elements that can obtain a large displacement with a low input voltage are also known as a type of piezoelectric oscillation elements, and there is a demand for a touch panel device that is equipped with such a bimorph piezoelectric element and that can reliably apply vibrations to the user in response to the operation. In such a touch panel device, it is necessary to make the operation panel move largely by the vibration of the bimorph piezoelectric element, to improve the shock resistance of the operation panel, and to ensure the stable connection between wiring lines. 
         [0005]    An embodiment of the present invention aims at improving response to a click in operating the support substrate, along with improving the shock resistance of the operation panel, in a piezoelectric oscillation device in which the support substrate is caused to vibrate by a bimorph piezoelectric oscillation element. An embodiment of the present invention further provides a piezoelectric oscillation device in which wire disconnections are not likely to occur. 
       Means for Solving the Problems 
       [0006]    A piezoelectric oscillation device according to an embodiment of the present invention includes a support substrate and a piezoelectric oscillation element that causes the support substrate to vibrate. In one embodiment, the piezoelectric oscillation element is a bimorph piezoelectric element, and one main surface of the piezoelectric oscillation element is entirely bonded to the support substrate through an elastic body having a tensile elasticity of 20 to 100 MPa as measured according to JIS K7161 (measured at a temperature of 25° C. and humidity of 60%; below, unless otherwise specified, the tensile elasticity was measured under the same conditions). In one embodiment, the thickness of the elastic body is 50 to 160 μm. 
         [0007]    In a piezoelectric oscillation device according to another embodiment, the support substrate includes: a terminal substrate that is disposed on the same surface as the surface on which the piezoelectric oscillation element is bonded, the terminal substrate having a terminal electrode; a wiring line that connects the terminal electrode of the terminal substrate to an electrode of the piezoelectric oscillation element, and a wiring protective layer that is disposed between the wiring line and the support substrate, the wiring protective layer being made of an elastic material. In a piezoelectric oscillation device according to yet another embodiment, the elastic body interposed between the support substrate and the piezoelectric oscillation element and the wiring protective layer are made of the same material. 
         [0008]    A touch panel device according to an embodiment of the present invention includes: a support substrate; a bimorph piezoelectric oscillation element that causes the support substrate to vibrate; a frame that supports the support substrate; a display part that displays information, the display part being disposed on a rear side of the support substrate; and a driver that drives the piezoelectric oscillation element in response to a contact operation conducted by a user on the support substrate, wherein one main surface of the piezoelectric oscillation element is entirely bonded to the support substrate through an elastic body having a tensile elasticity of 20 to 100 Mpa as measured according to JIS K7161. Additional objects, features, and advantages of the present invention will become apparent from the detailed description below and appended drawings. 
       Effects of the Invention 
       [0009]    According to an embodiment of the present invention, it is possible to improve response to a click for operating the support substrate, along with improving the shock resistance of the operation panel, in a piezoelectric oscillation device in which the support substrate is caused to vibrate by a bimorph piezoelectric oscillation element. Also, with an embodiment of the present invention, a piezoelectric oscillation device in which wire disconnections are not likely to occur is provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  shows diagrams illustrating a touch panel device of an embodiment of the present invention.  FIG. 1(A)  is an exterior perspective view of the entire touch panel device when viewed from the rear side.  FIG. 1(B)  is a cross-sectional view along the line #A-#A of  FIG. 1(A)  when viewed from the direction of the arrow.  FIG. 1(C)  is a cross-sectional view of an example of a multi-layer structure of a piezoelectric element. 
           [0011]      FIG. 2  is a cross-sectional view illustrating an operation of the touch panel device of  FIG. 1 . 
           [0012]      FIG. 3  is a diagram showing a temporal change in relative displacement of the touch panel device of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0013]    Below, an embodiment of the present invention will be explained in detail based on examples. 
         [0014]    First, a piezoelectric oscillation generating device of an embodiment of the present invention will be explained with reference to  FIGS. 1 to 3 . The piezoelectric oscillation generating device of an embodiment of the present invention is applied to a force feedback touch panel device, for example. 
         [0015]    As shown in  FIG. 1 , a touch panel device  10  of an embodiment of the present invention includes a touch panel (support substrate)  16 , and the periphery of the touch panel  16  is supported by a receiving section  15  provided in an opening  14  of a frame  12 . On the rear surface of the touch panel  16 , a piezoelectric oscillation element  20  is bonded along the short side direction. One main surface of the piezoelectric oscillation element  20  is bonded to the rear surface of the touch panel  16  through an elastic body  18 . The entire main surface of the piezoelectric oscillation element  20  may be directly bonded to the touch panel  16  so as to improve a shock resistance of the touch panel  16 . The location of the piezoelectric oscillation element  20  is not limited to that shown in  FIG. 1 , and may be appropriately changed. The frame  12  is formed of an aluminum alloy, for example. The touch panel  16  is formed by layering a not-shown transparent electrode such as a transparent conductive film (ITO) on a polycarbonate resin, a quartz glass, or the like, for example. The elastic body  18  is made of an elastic material such as polyurethane or EPDM (ethylene propylene diene monomer rubber), for example, but is not limited thereto. When the tensile elasticity of the elastic body  18 , which was measured according to JIS K7161 (below, when simply referred to as the “elasticity,” it means the tensile elasticity that was measured according to JIS K7161 unless indicated otherwise), is smaller than 20 MPa, it becomes harder for the touch panel  16  to receive the vibration of the piezoelectric vibration element  20 . On the other hand, when the elasticity exceeds 100 MPa, a difference in rigidity between when a compressive force is applied to the elastic body  18  and when a pulling force is applied to the elastic body  18  is made smaller, which makes it difficult to transmit the vibration of the piezoelectric oscillation element  20  to the touch panel  16  in an asymmetric manner, as described below. Thus, in one embodiment of the present invention, the elasticity of the elastic body  18  is to be within a range of 20 to 100 MPa. In one embodiment, the thickness of the elastic body  18  is set to 50 to 160 μm. When the thickness of the elastic body  18  is smaller than 50 μm, it becomes harder for the operator to sense the elastic displacement of the elastic body  18 , and as a result, a sufficient response to a click, which will be described later, cannot be achieved. On the other hand, if the thickness exceeds 160 μm, it becomes harder for the vibration of the piezoelectric oscillation element  20  to be transmitted to the touch panel  16 . Between the touch panel  16  and the elastic body  18 , and between the elastic body  18  and the piezoelectric oscillation element  20 , an epoxy adhesive, an acrylic adhesive, or a silicon adhesive, for example, is provided in a thickness of approximately 20 to 50 μm, for example. 
         [0016]    In one embodiment, the piezoelectric oscillation element  20  is a bimorph piezoelectric oscillation element. As shown in  FIG. 1(C) , the piezoelectric oscillation element  20  includes a piezoelectric element  22  and a piezoelectric element  24 , and the piezoelectric element  22  and the piezoelectric element  24  are each made by laminating piezoelectric layers  28  and electrode layers  30 . The piezoelectric element  22  and the piezoelectric element  22  are stacked, sandwiching an electrode layer  26 . The piezoelectric layer  28  is made of PZT piezoelectric ceramics, for example, and the electrode layer  30  is made of silver, for example. The number and thickness of the piezoelectric layers  28  and the electrode layers  30  constituting the piezoelectric oscillation element  20  are appropriately selected, and are not limited to the number and the thickness that are provided as examples in the present specification. In one example, each piezoelectric layer  28  is formed to a thickness of approximately 18 to 66 μm, and the piezoelectric element  22  and the piezoelectric element  24  include 6 to 20 layers of the piezoelectric layers  28 . As shown in  FIG. 1(B) , each electrode layer  30  is constituted of an electrode layer part  30 A and an electrode layer part  30 B disposed to be separated from each other. The electrode layer  30  may alternatively be constituted of one solid layer. The bimorph piezoelectric oscillation element  20  has not-shown through-holes formed therein, and via these through-holes, the respective piezoelectric layers  28  are connected to each other. 
         [0017]    On the rear surface of the touch panel  16 , a terminal substrate  34  is formed. The terminal substrate  34  includes terminal electrodes  36 A and  36 B that are respectively connected to the electrode layer parts  30 A and  30 B. The terminal substrate  34  is bonded to the touch panel  16  through a wiring protective layer  32  made of an elastic body. The terminal electrodes  36 A and  36 B are connected to the electrode layer parts  30 A and  30 B through wiring lines  38 A and  38 B. The wiring lines  38 A and  38 B are made of a conductive paste, for example. The wiring lines  38 A and  38 B are formed on the wiring protective layer  32  made of an elastic body, and because the wiring lines  38 A and  38 B can move following the vibration of the piezoelectric oscillation element  20 , wire disconnections are not likely to occur. The wiring protective layer  32  is made of a urethane resin or the like, in a manner similar to the elastic body  18 , for example. By making the wiring protective layer  32  of the same material as the elastic body  18 , the bonding strength between the two can be improved. 
         [0018]    On the rear surface of the touch panel  16 , a rear panel  40  is disposed to display various types of information. The rear panel  40  is disposed on the touch panel  16  so as to seal the opening  14  of the frame  12 . A speaker element may be provided in the sealed opening  14  in the touch panel device  10 . The touch panel device  10  includes a known operating position detection mechanism for detecting a pressed position when a pressure was applied to the touch panel  16 . The touch panel device  10  also includes a driver circuit (not shown) that applies a driving voltage for causing the piezoelectric oscillation element  20  to vibrate when the user presses the touch panel  16 . The driver circuit is connected to the electrode layer parts  30 A and  30 B of the piezoelectric oscillation element  20  through the terminal electrodes  36 A and  36 B of the terminal substrate  34  and the wiring lines  38 A and  38 B. 
         [0019]    Next, with reference to  FIG. 2 , an operation of the touch panel device  10  of an embodiment of the present invention will be explained.  FIG. 2  is a cross-sectional view showing a part of the touch panel device  10 , with the top and bottom of the touch panel device  10  being reversed from  FIG. 1(B) .  FIG. 2(A)  shows a state in which a driving voltage is not supplied to the electrode layer parts  30 A and  30 B of the touch panel device  10 . When an AC driving voltage is applied from a not-shown driver circuit to the electrode layer parts  30 A and  30 B via the terminal electrodes  36 A and  36 B and the wiring lines  38 A and  38 B, the piezoelectric oscillation element  20  moves alternately toward the opposite side from the touch panel  16  (the direction indicated with the arrow FA in  FIG. 2(B) ) and toward the touch panel  16  side (the direction indicated with the arrow FB in  FIG. 2(D) ). In other words, when an AC driving voltage is applied, the piezoelectric oscillation element  20  vibrates along the top and bottom direction that is perpendicular to the main surface of the touch panel  16  between the position shown in  FIG. 2(B)  and the position shown in  FIG. 2(D) .  FIG. 2(C)  shows a state in which the piezoelectric oscillation element  20  is at the middle position between the position shown in  FIG. 2(B)  and the position shown in  FIG. 2(D) . When the piezoelectric oscillation element  20  moves toward the opposite side from the touch panel  16 , an external force in a pull direction acts on the electric body  18 , which decreases the rigidity of the elastic body  18 , and on the other hand, when the piezoelectric oscillation element  20  moves toward the touch panel  16 , the elastic body  18  is compressed, which increases the rigidity of the elastic body  18 . Therefore, when the piezoelectric oscillation element  20  moves toward the touch panel  16 , the movement of the piezoelectric oscillation element  20  is transmitted more easily to the touch panel  16  as compared with when moving toward the opposite side, and as a result, the touch panel  16  can be moved to a greater degree by the displacement of the piezoelectric oscillation element  20 . This makes it possible to reliably provide a click feeling to a finger tip of the user who operates the touch panel  16 . As described above, even though the piezoelectric oscillation element  20  vibrates symmetrically along the vertical direction, it is easier for the user to feel the displacement of the piezoelectric oscillation element  20  toward the touch panel  16  side. 
         [0020]    The rigidity is a measure of the resistance of a structural object to deformation, and is typically defined as a product of the cross-sectional shape (elastic secondary moment) of the object and the elasticity of the material (see “Plastic Dictionary” by Kogyo Chosakai Publishing Co., Ltd., for example). The rigidity of an elastic body typically decreases when receiving a pulling force (when deforming in a pull direction), and increases when receiving a compressive force (when deforming in a compressive direction). Due to such characteristics of the elastic body, when the piezoelectric oscillation element  20  moves toward the opposite side from the touch panel  16 , the rigidity of the elastic body  18  decreases, and on the other hand, when the piezoelectric oscillation element  20  moves toward the touch panel  16 , the rigidity of the elastic body  18  increases. As a result, the movement of the piezoelectric oscillation element  20  toward the touch panel  16  is transmitted more easily than the movement away from the touch panel  16 , and the movement of the piezoelectric oscillation element  20  is transmitted to the touch panel  16  in an asymmetric manner. 
         [0021]      FIG. 3  shows a temporal change in relative displacement of the touch panel  16  when the piezoelectric oscillation element  20  is driven with a square wave of a voltage of 18Vpp and a frequency of 200 Hz in the touch panel device  10  in which the piezoelectric oscillation element  20  is made of PZT piezoelectric ceramics (0.2 mm thick with a silver electrode), the elastic body  18  and the wiring protective layer  32  are made of a urethane resin (0.16 mm thick), and the touch panel  16  is made of polycarbonate (0.8 mm thick). In the graph shown in  FIG. 3 , the positive direction of the vertical axis represents a displacement toward the top side of  FIG. 2  above. As shown in the figure, when the piezoelectric oscillation element  20  is driven, the displacement of the touch panel  16  toward the top side becomes greater. This makes it possible to reliably provide a sufficient click feeling to the operator. 
         [0022]    The present invention is not limited to the embodiment described above, and various modifications can be made without departing from the spirit of the present invention. For example, the shapes, dimensions, and materials shown in the present specification are examples, and may be appropriately changed as needed. 
       INDUSTRIAL APPLICABILITY 
       [0023]    The present invention can be applied to a piezoelectric oscillation device such as a force feedback touch panel, for example. 
       DESCRIPTION OF REFERENCE CHARACTERS 
       [0024]      10  touch panel device 
         [0025]      12  frame 
         [0026]      12 A front surface 
         [0027]      12 B rear surface 
         [0028]      14  opening 
         [0029]      15  receiving section 
         [0030]      16  touch panel (support substrate) 
         [0031]      18  elastic body 
         [0032]      20  piezoelectric oscillation element 
         [0033]      22 ,  24  piezoelectric element 
         [0034]      26 ,  30 ,  30 A,  30 B electrode layer 
         [0035]      28  piezoelectric layer 
         [0036]      32  wiring protective layer 
         [0037]      34  terminal substrate 
         [0038]      36 A,  36 B terminal electrode 
         [0039]      38 A,  38 B wiring lines 
         [0040]      40  rear panel