Piezoelectric device and ultrasonic device

Abstract

The invention provides a piezoelectric device and an ultrasonic device. The deformation amount of a vibration plate is large. A piezoelectric device is provided with: a substrate having a vibration region and a non-vibration region surrounding the vibration region; a first electrode provided across the vibration region and the non-vibration region; a second electrode disposed inside the vibration region and disposed apart from the first electrode; a piezoelectric body provided across the substrate, the first electrode, and the second electrode; and a third electrode that is provided on the piezoelectric body and overlaps at least the first electrode and the second electrode in the vibration region when viewed from the thickness direction of the substrate.

Description

Technical Field

[0001] This invention relates to piezoelectric devices and ultrasonic devices. Background Technology

[0002] Previously, piezoelectric devices were known in which a piezoelectric element was arranged on a vibrating plate, and the vibrating plate was vibrated by applying a voltage to the piezoelectric element (for example, see Patent Document 1).

[0003] Patent Document 1 discloses a piezoelectric device that is an ultrasonic device, comprising: a silicon substrate having a void portion; a vibrating plate disposed on the silicon substrate covering the void portion; a first electrode disposed on the vibrating plate; a piezoelectric body disposed at a position overlapping the void portion when viewed from the thickness direction; and a second electrode disposed on the piezoelectric body. In this ultrasonic device, when the width of the void portion is Cw and the width of the piezoelectric body is Pw, ... The piezoelectric element is configured in this way.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2021-153293

[0005] However, in conventional piezoelectric devices such as Patent Document 1, there is a problem that when a voltage is applied to the piezoelectric body, the vibrating plate flexes towards the gap, but since it does not flex towards the side opposite to the gap, the deformation of the vibrating plate is small. Therefore, when the piezoelectric device is used as an ultrasonic device, the sound pressure of the output ultrasonic wave is also small due to the small deformation of the vibrating plate. Summary of the Invention

[0006] The piezoelectric device of the first aspect of this disclosure comprises: a substrate having a vibrating region and a non-vibrating region surrounding the vibrating region; a first electrode disposed across the vibrating region and the non-vibrating region; a second electrode disposed inside the vibrating region and separately disposed from the first electrode; a piezoelectric body disposed across the substrate, the first electrode and the second electrode; and a third electrode disposed on the piezoelectric body, wherein, viewed from the thickness direction of the substrate, the third electrode overlaps at least with the first electrode and the second electrode in the vibrating region.

[0007] The ultrasonic device of the second aspect of this disclosure includes the piezoelectric device of the first aspect described above, and drives the piezoelectric device to transmit ultrasonic waves. Attached Figure Description

[0008] Figure 1 This is a cross-sectional view showing the schematic structure of the ultrasonic device according to the first embodiment.

[0009] Figure 2 This is a top view showing the outline structure of the ultrasonic device according to the first embodiment.

[0010] Figure 3 This is a diagram showing the displacement of the vibration region when the ultrasonic device of the first embodiment is driven.

[0011] Figure 4 This is a graph showing the driving efficiency when (W1+W2) / Wc is varied in the first embodiment.

[0012] Figure 5 This is a graph showing the drive efficiency when W1 / W2 is varied in the first embodiment.

[0013] Figure 6 This is a graph showing the driving efficiency when the phase difference between the first driving voltage and the second driving voltage is changed in the first embodiment.

[0014] Figure 7 This is a cross-sectional view showing the schematic structure of the ultrasonic device according to the second embodiment.

[0015] Figure 8 This is a schematic diagram showing the outline structure of the head according to the third embodiment.

[0016] Figure 9 This is a top view showing the outline structure of the piezoelectric device of Modified Example 2.

[0017] Label Explanation

[0018] 10, 10A: Ultrasonic device; 10B, 10C: Piezoelectric device; 11: Substrate; 11A: Vibration area; 11B: Non-vibration area; 12: First electrode; 13: Second electrode; 14: Piezoelectric element; 15: Third electrode; 16: Vibration suppression part; 17: Support substrate; 20: Voltage control part; 21: First power supply; 22: Second power supply; 23: Common potential part; 171: Support leg; 172: Through hole. Detailed Implementation

[0019] [First Implementation Method]

[0020] The first embodiment of this disclosure will be described.

[0021] Figure 1 This is a cross-sectional view showing the outline structure of the ultrasonic device, which is a piezoelectric device according to this embodiment. Figure 2 This is a top view showing the general structure of the ultrasonic device.

[0022] like Figure 1 As shown, the ultrasonic device 10 includes a substrate 11, a first electrode 12, a second electrode 13, a piezoelectric element 14, a third electrode 15, a vibration suppression unit 16, and a voltage control unit 20. Furthermore, in Figure 2The piezoelectric element 14 and the third electrode 15 are omitted from the diagram.

[0023] In this embodiment, a first electrode 12 and a second electrode 13 are stacked on a substrate 11, and a piezoelectric material 14 is then stacked to cover the substrate 11, the first electrode 12, and the second electrode 13. A third electrode 15 is then stacked on the piezoelectric material 14. In the following description, the thickness direction of the substrate 11, i.e., the stacking direction of the substrate 11, the first electrode 12 (or the second electrode 13), the piezoelectric material 14, and the third electrode 15, is defined as the Z-direction. Furthermore, a plane orthogonal to the Z-direction is defined as the XY-plane, and the two orthogonal axes contained within the XY-plane are defined as the X-direction and the Y-direction, respectively.

[0024] The substrate 11 includes a base portion 111 and a surface layer portion 112. The base portion 111 is a flat, plate-shaped substrate made of a semiconductor substrate; in this embodiment, the semiconductor substrate is made of Si. The surface layer portion 112 is the portion on which the surface of the base portion 111 has been surface-processed. For example, in this embodiment, one side of the Si-made base portion 111 is oxidized to form SiO2, and then a ZrO2 layer is deposited by sputtering or the like. That is, in this embodiment, the surface layer portion 112 is composed of a SiO2 layer and a ZrO2 layer.

[0025] Furthermore, if the -Z side (the side without the surface layer 112) of the substrate 11 is designated as the first surface 113, the first surface 113 is formed with an arithmetic surface roughness in the range of 0.4 ± 0.5 μm. That is, in this embodiment, the first surface 113 of the substrate 11 is formed by grinding. As a result, compared with the case where the first surface 113 of the substrate 11 is formed by etching or the like, the arithmetic surface roughness can be reduced.

[0026] like Figure 1 and Figure 2 As shown, the substrate 11 includes a vibration region 11A and a non-vibration region 11B surrounding the vibration region 11A.

[0027] In addition, Figure 2 In the diagram, the dashed line represents the boundary between the vibrating region 11A and the non-vibrating region 11B. The area outside the dashed line is the non-vibrating region 11B, and the area inside the dashed line is the vibrating region 11A.

[0028] The vibration region 11A is the region in which the piezoelectric body 14 vibrates due to the deformation caused by applying voltage between the first electrode 12 and the third electrode 15, and between the second electrode 13 and the third electrode 15. Ultrasonic waves are output from the ultrasonic device 10 through the vibration of the vibration region 11A.

[0029] On the other hand, the non-vibration region 11B is the region where vibration is restricted. In this embodiment, by providing a vibration suppression portion 16 on the first surface 113 of the non-vibration region 11B of the substrate 11, vibration of the non-vibration region 11B can be suppressed.

[0030] The vibration damping section 16 uses a resin with vibration damping effect. The resin used is not particularly limited; for example, epoxy resin, acrylic resin, phenolic varnish resin, or other resist resins can be used. The vibration damping section 16 is provided to cover the entire non-vibration area 11B, but is not provided in the vibration area 11A.

[0031] Viewed from the Z direction, the first electrode 12 is disposed on the surface portion 112 of the substrate 11, spanning from the vibration region 11A to the non-vibration region 11B.

[0032] In this embodiment, such as Figure 2 As shown, viewed from the Z direction, the vibration region 11A is circular, and the first electrode 12 is formed circumferentially across the vibration region 11A. Furthermore, a cutout 121 is provided in a portion of the first electrode 12. The cutout 121 is a portion for a second connecting electrode 131, which is connected to the second electrode 13, to extend from the vibration region 11A to the non-vibration region 11B. Additionally, in... Figure 2 The example shown is an example of providing only one cutout 121. However, considering the stress balance during vibration of the vibration region 11A, multiple cutouts 121 can also be provided at positions symmetrical to the center of the vibration region 11A. For example, a pair of cutouts 121 that are point-symmetrical to the center of the vibration region 11A can be provided, or multiple cutouts 121 can be provided at positions (equal angular intervals) that are rotationally symmetrical to the center of the vibration region 11A.

[0033] Furthermore, in this embodiment, as described above, the first electrode 12 is formed along the circumferential direction of the vibration region 11A. This means that: in Figure 1 When viewed in the cross-section shown (across section other than the location where the cut 121 is set), the first electrode 12 is positioned to sandwich the second electrode 13.

[0034] Additionally, a first connecting electrode 122 (see reference) is connected to the first electrode 12. Figure 1 The first connecting electrode 122 is electrically connected to the voltage control unit 20 via a first terminal (not shown) provided on the surface portion 112 of the substrate 11.

[0035] The second electrode 13 is disposed separately from the first electrode 12 within the vibration region 11A of the substrate 11. Viewed from the Z direction, the second electrode 13 is preferably formed with the same shape as the vibration region 11A. In this embodiment, as... Figure 2As shown, the vibration region 11A is circular, so the second electrode 13 is also formed in a circular shape, and the vibration region 11A and the second electrode 13 are concentric circles.

[0036] Furthermore, as described above, the second electrode 13 is connected to the second connecting electrode 131, which extends from the vibration region 11A to the non-vibration region 11B through the cutouts 121 of the first electrode 12. The second connecting electrode 131 is electrically connected to the voltage control unit 20 via a second terminal (not shown) provided in the non-vibration region 11B. Moreover, as described above, when multiple cutouts 121 of the first electrode 12 are provided symmetrically with respect to the center point of the vibration region 11A, it is preferable to provide the second connecting electrode 131 at each of these cutouts 121. This allows stress balance to be maintained within the vibration region 11A.

[0037] Here, in the XZ section passing through the center of the circle of vibration region 11A ( Figure 1 In the diagram, the width of the first electrode 12 in the vibration region 11A is W11 and W12, the width of the second electrode 13 is W2, and the width of the vibration region 11A is Wc.

[0038] In this embodiment, the vibration region 11A is circular, and the width Wc of the vibration region 11A is the diameter of the circular vibration region 11A.

[0039] The first electrode 12 is formed with a uniform width in the circumferential direction along the outer periphery of the vibration region 11A, and protrudes with the same width in the circumferential direction within the vibration region 11A. Therefore, the widths W11 and W12 of the first electrode 12 in the vibration region 11A are W11 = W12. Furthermore, in Figure 1 In such a cross-sectional view, the sum of the widths of the pair of first electrodes 12 sandwiched between the second electrode 13 in the vibration region 11A is defined as W1. That is, W1 = W11 + W12, and in this embodiment, W1 = 2W11.

[0040] The second electrode 13 is a circle concentric with the vibration region 11A, and the width W2 of the second electrode 13 is the diameter of the second electrode 13.

[0041] Furthermore, in the ultrasonic device 10 of this embodiment, the sum of the widths W1 of the first electrode 12 in the vibration region 11A, the width W2 of the second electrode 13, and the width Wc of the vibration region 11A satisfy the following relationship:

[0042] ,

[0043] ,

[0044] .

[0045] The piezoelectric element 14 is disposed on the surface portion 112 of the substrate 11 from the vibration region 11A to the non-vibration region 11B, covering the first electrode 12 and the second electrode 13. That is, the piezoelectric element 14 covers the entire vibration region 11A, the first electrode 12, and the second electrode 13. The piezoelectric element 14 may also be disposed across the entire surface of the substrate 11. The piezoelectric element 14 is, for example, made of a perovskite-type transition metal oxide containing Pb, and in this embodiment, it is PZT containing Pb, Zr, and Ti.

[0046] The third electrode 15 is disposed on the piezoelectric body 14 from the vibration region 11A to the non-vibration region 11B. That is, when viewed from the Z direction, the third electrode 15 covers the first electrode 12 and the second electrode 13 within the vibration region 11A.

[0047] A third connecting electrode 151 is connected to the third electrode 15. The third connecting electrode 151 is electrically connected to the voltage control unit 20 via a third terminal (not shown) provided in the non-vibration region 11B.

[0048] Next, the voltage control unit 20 will be described.

[0049] As described above, the voltage control unit 20 is electrically connected to the first electrode 12, the second electrode 13, and the third electrode 15.

[0050] The voltage control unit 20 includes a first power supply 21 that applies voltage to the first electrode 12, a second power supply 22 that applies voltage to the second electrode 13, and a common potential unit 23 connected to the third electrode 15. The first power supply 21 and the second power supply 22 apply a driving voltage of a predetermined frequency.

[0051] The common potential section 23, for example, sets the third electrode 15 to a predetermined common potential.

[0052] Furthermore, in this embodiment, when driving the ultrasonic device 10, the voltage control unit 20 sets a phase difference by staggering the phase of the first driving voltage applied to the first electrode 12 from the first power supply 21 and the phase of the second driving voltage applied to the second electrode 13 from the second power supply 22.

[0053] Specifically, the phase difference Δφ between the first driving voltage and the second driving voltage is: .

[0054] [Driving efficiency of ultrasonic device 10]

[0055] Next, the driving efficiency of the ultrasonic device 10 described above will be explained.

[0056] Figure 3 This is a diagram showing the displacement of the vibration region 11A when the ultrasonic device 10 is driven.

[0057] In this embodiment, by applying a second driving voltage to the second electrode 13, such as Figure 3 As shown in the figure above, the piezoelectric element 14 between the second electrode 13 and the third electrode 15 deforms in a manner that protrudes towards the -Z side, and the vibration region 11A shifts in a manner that protrudes towards the -Z side.

[0058] Assuming that the ultrasonic device 10 only has a second electrode 13 and no first electrode 12, the vibration region 11A only experiences displacement due to the application of a driving voltage to the second electrode 13, that is, only a displacement towards the -Z side. In this case, after the vibration region 11A shifts towards the -Z side, it only shifts towards the +Z side through the elastic restoring force of the vibration region 11A. A large displacement cannot be obtained solely through this restoring force.

[0059] In contrast, in this embodiment, a first driving voltage is applied between the first electrode 12 and the third electrode 15, out of phase with the second driving voltage applied to the second electrode 13. In this case, by applying the second driving voltage to the second electrode 13, after the vibration region 11A shifts towards the -Z side, the piezoelectric element 14 between the first electrode 12 and the third electrode 15 deforms in a warping manner towards the +Z side. Therefore, as... Figure 3 As shown in the figure below, the vibration region 11A is significantly displaced towards the +Z side due to the deformation of the piezoelectric body 14 between the first electrode 12 and the third electrode 15 and the elastic restoring force of the vibration region 11A.

[0060] In this embodiment, the vibration region 11A is in Figure 3 The state in the upper diagram alternates between the state in the lower diagram. Compared with the case where only the second electrode 13 and the third electrode 15 are provided, the vibration amplitude of the vibration region 11A can be increased. As a result, the sound pressure of the ultrasonic wave output from the ultrasonic device 10 also increases.

[0061] Figure 4 This is a graph showing the driving efficiency when (W1+W2) / Wc is varied. That is, it shows the driving efficiency corresponding to the value of the sum of the widths W1 of the first electrode 12 and the sum of the widths W2 of the second electrode 13 relative to the width Wc of the vibration region 11A.

[0062] Figure 5 This is a graph showing the driving efficiency when W1 / W2 is varied. That is, it represents the driving efficiency corresponding to the value of the sum of the widths W1 of the first electrode 12 relative to the width W2 of the second electrode 13.

[0063] Figure 6 This is a graph showing the driving efficiency when the phase difference Δφ between the first driving voltage and the second driving voltage is varied.

[0064] Additionally, here, the driving efficiency represents the amplitude when the maximum amplitude of vibration in the vibration region 11A is set to 1.

[0065] like Figure 4 As shown, a drive efficiency of 0.5 or higher is obtained in the range of 0.5 < (W1 + W2) / Wc < 1. More preferably, the range is 0.6 < (W1 + W2) / Wc < 0.8, in which case a drive efficiency of 0.9 or higher can be obtained.

[0066] like Figure 5 As shown, a drive efficiency of over 0.8 is obtained within the range of 0.25≤W1 / W2≤1.

[0067] like Figure 6 As shown, a driving efficiency of over 0.9 is obtained within the range of 150°≤Δφ≤210°.

[0068] In this embodiment, as described above, the following conditions are met. ,and The conditions are met, and the voltage applied by the voltage control unit 20 to the first electrode 12 and the second electrode 13 satisfies... .

[0069] Therefore, the amplitude of the vibration region 11A can be further increased, and the driving efficiency of the ultrasonic device 10 can be significantly improved.

[0070] [Effects of this implementation method]

[0071] The ultrasonic device 10 of this embodiment includes a substrate 11, a first electrode 12, a second electrode 13, a piezoelectric element 14, and a third electrode 15. The substrate 11 has a vibrating region 11A and a non-vibrating region 11B surrounding the vibrating region 11A. The first electrode 12 is disposed across the vibrating region 11A and the non-vibrating region 11B on the +Z side of the substrate 11. The second electrode 13 is disposed inside the vibrating region 11A and is disposed separately from the first electrode 12. The piezoelectric element 14 is disposed across the substrate 11, the first electrode 12, and the second electrode 13. The third electrode 15 is disposed on the piezoelectric element 14 and overlaps with the first electrode 12 and the second electrode 13 within the vibrating region 11A when viewed from the Z direction.

[0072] In such an ultrasonic device 10, by shifting the phase of the first driving voltage applied between the first electrode 12 and the third electrode 15 to that of the second driving voltage applied between the second electrode 13 and the third electrode 15, stresses that cause the vibration region 11A to flex in both positive and negative directions (±Z sides) in the Z direction can be generated, thereby increasing the deformation (vibration amplitude) of the vibration region 11A. This also increases the sound pressure level of the ultrasonic waves output from the ultrasonic device 10.

[0073] In the ultrasonic device 10 of this embodiment, the first electrode 12 is disposed with the second electrode 13 sandwiched between them.

[0074] Therefore, the stress balance in the vibration region 11A is symmetrical, which can increase the displacement during vibration.

[0075] In the ultrasonic device 10 of this embodiment, when the sum of the widths of the portions of the first electrode 12 disposed in the vibration region 11A is W1, the width of the second electrode 13 is W2, and the width of the vibration region 11A is Wc, the following conditions are met:

[0076] ,

[0077] .

[0078] This increases the deformation of the vibration region 11A, and maintains a high driving efficiency for the ultrasonic device 10.

[0079] The ultrasonic device 10 of this embodiment includes a voltage control unit 20. The voltage control unit 20 includes a first power supply 21 that applies a first driving voltage between the first electrode 12 and the third electrode 15, and a second power supply 22 that applies a second driving voltage between the second electrode 13 and the third electrode 15. Furthermore, the voltage control unit 20 inputs a voltage to the ultrasonic device 10 such that the phase of the first driving voltage is different from the phase of the second driving voltage.

[0080] By applying a second driving voltage between the second electrode 13 and the third electrode 15, the vibration region 11A flexes towards the -Z side due to the deformation of the piezoelectric body 14. By applying a first driving voltage between the first electrode 12 and the third electrode 15, the vibration region 11A flexes towards the +Z side due to the deformation of the piezoelectric body 14. By shifting the phases of the first driving voltage and the second driving voltage, the timing of applying stress to the vibration region 11A to flex towards the +Z side is shifted from the timing of applying stress to the vibration region 11A to flex towards the -Z side, thereby increasing the displacement of the vibration region 11A.

[0081] At this point, assuming the phase difference between the phase of the first driving voltage and the phase of the second driving voltage is Δφ, the following condition is met: .

[0082] Therefore, after applying stress to the vibration region 11A to flex towards the -Z side using the second driving voltage, when the vibration region 11A returns to the +Z side by means of the elastic force of the substrate 11, the first driving voltage can apply stress to the vibration region 11A to flex towards the +Z side. Similarly, after applying stress to the vibration region 11A to flex towards the +Z side using the first driving voltage, when the vibration region 11A returns to the -Z side by means of the elastic force of the substrate 11, the second driving voltage can apply stress to the vibration region 11A to flex towards the -Z side. That is, in this embodiment, the deformation amount of the vibration region 11A can be further increased by the combined force of the elastic force of the substrate 11 and the stress generated by the deformation of the piezoelectric body 14.

[0083] [Second Implementation]

[0084] In the first embodiment described above, a vibration suppression portion 16 is provided on the first surface 113, which is the -Z side of the substrate 11. However, it may also be configured such that a vibration suppression portion is provided on the +Z side of the substrate 11.

[0085] Figure 7 This is a diagram showing the outline structure of the ultrasonic device 10A according to the second embodiment. Furthermore, in the following description, the same reference numerals will be used to denote the structures already described, and their descriptions will be omitted.

[0086] like Figure 7 As shown, the ultrasonic device 10A of the second embodiment includes a substrate 11, a first electrode 12, a second electrode 13, a piezoelectric element 14, a third electrode 15, a support substrate 17, and a voltage control unit 20.

[0087] In the ultrasonic device 10A of this embodiment, a support substrate 17 is provided, which is disposed on the +Z side of the substrate 11 and faces the third electrode 15. This support substrate 17 is provided, for example, to reinforce the thin substrate 11, and is bonded to at least one of the substrate 11, the piezoelectric element 14, and the third electrode 15 via support legs 171. Similar to the vibration suppression part 16 of the first embodiment, the support legs 171 can, for example, use photoresist resins such as epoxy resin, acrylic resin, or phenolic varnish resin to suppress vibration in the non-vibration region 11B. Figure 7 In the example shown, the support leg 171 engages with the entire non-vibration region 11B. Thus, the support leg 171 functions similarly to the vibration suppression part 16 of the first embodiment.

[0088] Furthermore, when viewed from the Z direction, a through hole 172 that penetrates the support substrate 17 in the Z direction can also be provided at the position where the support substrate 17 overlaps with the vibration region 11A.

[0089] By providing such a through hole 172, the ultrasonic waves generated by the vibration region 11A can be output to both the ±Z sides.

[0090] In addition, Figure 7 In the example, the piezoelectric element 14 and the third electrode 15 cover the entire non-vibration region 11B, but it can also be configured such that the third electrode 15 only covers a portion of the non-vibration region 11B, with the edge of the third electrode 15 located on the piezoelectric element 14. In this case, by covering the edge of the third electrode 15 and the piezoelectric element 14 with the support leg 171, cracks and burn-off at the boundary between the edge of the third electrode 15 and the piezoelectric element 14 can be suppressed.

[0091] Alternatively, the piezoelectric body 14 and the third electrode 15 may be configured to cover only a portion of the non-vibration region 11B. In this case, the support leg 171 is joined to the end edge of the third electrode 15, the end edge of the piezoelectric body 14, and the surface portion 112 of the substrate 11 where the piezoelectric body 14 and the third electrode 15 are not disposed.

[0092] In the ultrasonic device 10A of the second embodiment described above, it can also achieve the same effect as the ultrasonic device 10 of the first embodiment.

[0093] In addition, in the ultrasonic device 10A of this embodiment, a support substrate 17 is provided on the +Z side of the substrate 11, which is disposed opposite to the third electrode 15. The support substrate 17 is connected to at least one of the substrate 11, the piezoelectric body 14, and the third electrode 15 in the non-vibration region 11B via support legs 171. That is, in this embodiment, by connecting the support legs 171 to the non-vibration region 11B, the vibration of the non-vibration region 11B is suppressed, resulting in a structure in which the vibration region 11A can vibrate.

[0094] In this structure, the support substrate 17 can be used to strengthen the substrate 11, and damage to the substrate 11 can be suppressed. In addition, by joining the support leg 171 to the non-vibration region 11B, it is not necessary to provide a vibration suppression part 16 on the -Z side of the substrate 11.

[0095] Alternatively, in the ultrasonic device 10A of this embodiment, a through hole 172 may be provided in the portion of the support substrate 17 that overlaps with the vibration region 11A when viewed from the Z direction.

[0096] Therefore, the ultrasonic waves generated by the vibration of the vibration region 11A can be output to both the ±Z sides of the substrate 11.

[0097] [Third Implementation Method]

[0098] In the first embodiment described above, an ultrasonic device 10 that outputs ultrasonic waves is exemplified as a piezoelectric device, but it is not limited thereto.

[0099] For example, the piezoelectric device disclosed herein can be applied to piezoelectric devices that apply pressure to an object, such as piezoelectric devices disposed in the head of an inkjet printer.

[0100] Figure 8 This is a diagram showing the outline structure of a head equipped with a piezoelectric device 10B.

[0101] exist Figure 8 In the middle, the first 30 is a device installed in an inkjet printer (illustration omitted) that ejects ink onto the printing medium.

[0102] The head 30 is configured to move along a specified scanning direction via a moving mechanism 31 provided on the inkjet printer.

[0103] In addition, the head 30 has an ink chamber 32 for storing ink, and a supply pipe 33 for supplying ink and a circulation pipe 34 for circulating ink are connected to the ink chamber 32. Furthermore, a nozzle 35 opposite to the printing medium and a piezoelectric device 10B for applying pressure to the ink in the ink chamber 32 are provided in the ink chamber 32.

[0104] In such a head 30, after the head 30 is moved to a predetermined position on the printing medium by the control of the controller (omitted in the figure), the piezoelectric device 10B is driven by the controller to spray ink from the ink chamber 32 to the printing medium via the nozzle 35.

[0105] At this time, as described above, the piezoelectric device 10B can increase the vibration amplitude in the vibration region 11A, enabling the ink to be properly ejected from the nozzle.

[0106] [Variation Example]

[0107] It should be noted that the present invention is not limited to the above-described embodiments. Structures obtained by modifications, improvements, and appropriate combinations of the embodiments within the scope of achieving the purpose of the present invention are included in the present invention.

[0108] [Variation Example 1]

[0109] For example, in the second embodiment, a structure is adopted in which a support substrate 17 and a support leg 171 are provided. However, in the first embodiment, a structure in which a support substrate 17 and a support leg 171 are provided on the +Z side of the substrate 11 can also be adopted.

[0110] In this case, in the non-vibration region 11B, a vibration suppression part 16 and a support leg part 171 are provided on the ±Z side of the substrate 11.

[0111] In addition, in the second embodiment, a structure with a support base plate 17 is shown, but it is also possible to have a structure with only a support leg 171 provided and no support base plate 17 provided.

[0112] [Variation Example 2]

[0113] In the first embodiment described above, an example of a circular vibration region 11A is shown, but the vibration region 11A can also be formed into other shapes having a minor axis direction and a major axis direction.

[0114] Figure 9 This is a top view of the piezoelectric device 10C with the vibration region 11A in a rectangular shape. Figure 9 The piezoelectric element 14 and the third electrode 15 are omitted from the diagram.

[0115] For example, in Figure 9 In the piezoelectric device 10C shown, the vibration region 11A is configured as a rectangle with the X direction as the minor axis and the Y direction as the major axis.

[0116] In this case, the first electrode 12 is arranged to extend from the vibration region 11A to the non-vibration region 11B along a pair of long sides parallel to the long axis direction.

[0117] The second electrode 13 is disposed in the vibration region 11A in the same manner as in the embodiment described above. Since the first electrodes 12 are disposed along a pair of long sides of the vibration region 11A, the second electrode 13, which is a long rectangular shape in the long axis direction, is disposed in such a way that it is sandwiched between these first electrodes 12.

[0118] Similar to the embodiment described above, the piezoelectric element 14 and the third electrode 15 are arranged from the vibration region 11A to the non-vibration region 11B, covering the first electrode 12 and the second electrode 13. Additionally, as in the first embodiment, a vibration suppression portion 16 is disposed in the non-vibration region 11B of the first surface 113 of the substrate 11. Alternatively, as in the second embodiment, a support substrate 17 opposite the third electrode 15 may be disposed, with a support leg 171 joined at the portion corresponding to the non-vibration region 11B.

[0119] Therefore, the cross-section of the piezoelectric device 10C when cut along the XZ plane is similar to... Figure 1 The first embodiment shown or Figure 7 The second embodiment shown is the same.

[0120] In this case, the sum of the widths W11 and W12 of the portion within the vibration region 11A of the first electrode 12 along the minor axis is set as W1, and the width of the second electrode 13 along the minor axis is set as W2, so that the vibration region 11A, the first electrode 12, and the second electrode 13 are configured in such a way that the following conditions are met:

[0121] W1 < W2,

[0122] 0.25≤W1 / W2≤1

[0123] 0.5 < (W1 + W2) / Wc < 1.

[0124] Therefore, similar to the above-described embodiments, the vibration amplitude of the vibration region 11A can be increased, thereby improving the driving efficiency.

[0125] In addition, Figure 9 In the example shown, a pair of first electrodes 12 are arranged along the long side of the vibration region 11A, but the first electrodes 12 can also be arranged around the outer periphery of the vibration region 11A in the same manner as the above embodiment.

[0126] [Variation Example 3]

[0127] In the above embodiments and Figure 9 In the modified example 2 shown, an example is illustrated where the first electrode 12 is positioned to sandwich the second electrode 13, but this is not a limitation. For example, in the above embodiment, the first electrode 12 may also be configured to be disposed only on the +X side (or only on the -X side) of the second electrode 13. Figure 9 If the vibration region 11A is rectangular, the first electrode 12 can be configured to be positioned along only one long side of the vibration region 11A. In this case, the width of the first electrode 12 in the vibration region 11A is set to W1, and the vibration region 11A, the first electrode 12, and the second electrode 13 are configured in a manner that satisfies the following conditions:

[0128] W1 < W2,

[0129] 0.25≤W1 / W2≤1

[0130] 0.5 < (W1 + W2) / Wc < 1.

[0131] [Summary of this disclosure]

[0132] The piezoelectric device of the first aspect of this disclosure comprises: a substrate having a vibrating region and a non-vibrating region surrounding the vibrating region; a first electrode disposed across the vibrating region and the non-vibrating region; a second electrode disposed inside the vibrating region and separately disposed from the first electrode; a piezoelectric body disposed across the substrate, the first electrode and the second electrode; and a third electrode disposed on the piezoelectric body and, when viewed from the thickness direction of the substrate, on the piezoelectric body, the third electrode overlapping at least with the first electrode and the second electrode in the vibrating region.

[0133] In such a piezoelectric device, by making the driving voltage applied between the first and third electrodes phase-shifted from the driving voltage applied between the second and third electrodes, stresses that cause the vibration region to flex toward the piezoelectric body and stresses that flex toward the opposite side of the piezoelectric body can be generated alternately, thereby increasing the deformation (vibration amplitude) of the vibration region.

[0134] In the piezoelectric device of this method, it is preferable that, viewed from the thickness direction, the width of the portion of the first electrode disposed in the vibration region is less than the width of the second electrode, and the sum of the width of the first electrode disposed in the vibration region and the width of the second electrode is less than the width of the vibration region.

[0135] Therefore, compared to the case where the width of the portion of the first electrode disposed in the vibration region is greater than the width of the second electrode, the deformation of the piezoelectric device can be further increased.

[0136] In the piezoelectric device of this type, it is preferable that the first electrode is sandwiched between the second electrode.

[0137] Therefore, the stress balance in the vibration region becomes symmetrical, which increases the displacement during vibration. In this piezoelectric device, it is preferable that, when the sum of the widths of the portions of the first electrode disposed in the vibration region is W1, the width of the second electrode is W2, and the width of the vibration region is Wc, the following condition is met:

[0138] 0.25 < W1 / W2 ≤ 1,

[0139] 0.5 < (W1 + W2) / Wc < 1.

[0140] Therefore, compared with the cases of 0.25 > W1 / W2 and 0.5 > (W1+W2) / Wc, the deformation of the piezoelectric device can be further increased.

[0141] In the piezoelectric device of this type, it is preferable to include a voltage application section that applies a voltage between the first electrode and the third electrode, and between the second electrode and the third electrode, wherein the voltage application section causes the phase of the voltage applied between the first electrode and the third electrode to be different from the phase of the voltage applied between the second electrode and the third electrode.

[0142] In this piezoelectric device, stress is applied by applying a voltage between the second electrode, the piezoelectric element, and the third electrode to shift the vibration region towards the opposite side of the piezoelectric element, and by applying a voltage between the first electrode, the piezoelectric element, and the third electrode to shift the vibration region towards the piezoelectric element. Therefore, by making the phase of the voltage applied between the first and third electrodes different from the phase of the voltage applied between the second and third electrodes, stress can be applied separately for each direction of the vibration region's shift, thereby increasing the amount of shift in the vibration region.

[0143] In this case, it is preferable that, when the phase difference between the phase of the voltage applied between the first electrode and the third electrode and the phase of the voltage applied between the second electrode and the third electrode is Δφ, the following condition is satisfied: 150°≤Δφ≤210°.

[0144] Therefore, by applying a voltage between the second electrode, the piezoelectric element, and the third electrode, the vibration region is shifted to the side opposite to the piezoelectric element. When the vibration region returns to the piezoelectric element side by means of the elastic force of the substrate, applying a voltage between the first electrode, the piezoelectric element, and the third electrode can impart stress to the vibration region that causes it to shift towards the piezoelectric element side through the deformation of the piezoelectric element. Therefore, the resultant force of the elastic force of the substrate and the stress generated by the deformation of the piezoelectric element can further increase the deformation of the vibration region.

[0145] In this type of piezoelectric device, it may also be configured to include: a support substrate, which is disposed opposite to the side of the third electrode opposite to the substrate; and a support leg, which connects at least one of the substrate, the piezoelectric body and the third electrode to the support substrate in the non-vibration region.

[0146] In this structure, the substrate can be reinforced using a support substrate, thus suppressing substrate breakage. Furthermore, by joining the support legs to the non-vibration area, it can function as a vibration suppression component to suppress vibrations in the non-vibration area.

[0147] In this case, the support substrate may also be configured such that, when viewed from the thickness direction, the portion of the substrate overlapping the vibration region has a through hole.

[0148] Therefore, the ultrasonic waves generated by the vibration of the vibration region can be output to both the piezoelectric side of the substrate and the side opposite to the piezoelectric element.

[0149] The ultrasonic device of the second aspect of this disclosure includes a piezoelectric device as described above, and drives the piezoelectric device to transmit ultrasonic waves.

[0150] Therefore, it is possible to output ultrasound with high sound pressure.

Claims

1. A piezoelectric device comprising: A substrate having a vibrating region and a non-vibrating region surrounding the vibrating region; A first electrode is disposed across the vibrating region and the non-vibrating region; The second electrode is disposed inside the vibration region and is separately disposed from the first electrode; A piezoelectric element is disposed across the substrate, the first electrode, and the second electrode; as well as A third electrode, disposed on the piezoelectric material, overlaps at least with the first electrode and the second electrode in the vibration region when viewed from the thickness direction of the substrate.

2. The piezoelectric device according to claim 1, wherein, Viewed from the thickness direction, the width of the portion of the first electrode disposed in the vibration region is less than the width of the second electrode, and the sum of the width of the first electrode disposed in the vibration region and the width of the second electrode is less than the width of the vibration region.

3. The piezoelectric device according to claim 2, wherein, The first electrode is positioned to sandwich the second electrode.

4. The piezoelectric device according to claim 3, wherein, When the sum of the widths of the portions of the first electrode disposed in the vibration region is W1, the width of the second electrode is W2, and the width of the vibration region is Wc, the following conditions are met: , 。 5. The piezoelectric device according to claim 1, wherein, The piezoelectric device includes a voltage application section that applies a voltage between the first electrode and the third electrode, and between the second electrode and the third electrode. The voltage application section causes the phase of the voltage applied between the first electrode and the third electrode to be different from the phase of the voltage applied between the second electrode and the third electrode.

6. The piezoelectric device according to claim 5, wherein, If the phase difference between the voltage applied between the first electrode and the third electrode and the voltage applied between the second electrode and the third electrode is Δφ, then: 。 7. The piezoelectric device according to claim 1, wherein, The piezoelectric device comprises: A support substrate, which is disposed opposite to the side of the third electrode opposite to the substrate; and A support leg that engages at least one of the substrate, the piezoelectric element, and the third electrode with the support substrate in the non-vibration region.

8. The piezoelectric device according to claim 7, wherein, Viewed from the thickness direction, the support substrate has a through hole in the portion that overlaps with the vibration region.

9. An ultrasonic device comprising the piezoelectric element according to any one of claims 1 to 8. The ultrasonic device drives the piezoelectric device to transmit ultrasonic waves.

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