Piezoelectric device, piezoelectric actuator, and ultrasonic apparatus

Abstract

The invention relates to a piezoelectric device, a piezoelectric actuator, and an ultrasonic apparatus. Provided is a highly durable piezoelectric device having a low possibility of breakage even if the amount of displacement of a vibrating plate increases. A piezoelectric device is provided with: a substrate having an opening; a diaphragm having a first surface and a second surface on the opposite side to the first surface, the first surface being bonded to the substrate and closing the opening; and a piezoelectric element provided on the second surface of the vibrating plate, the vibrating plate including a first region overlapping the piezoelectric element when viewed from a thickness direction of the vibrating plate and a second region not overlapping the piezoelectric element, the thickness of the second region in the thickness direction of the diaphragm is thinner than the thickness of the first region, the second region is provided with a reinforcing portion of a material having a higher fracture toughness than the first region of the diaphragm, the thickness of the second region in the thickness direction is fixed, and the thickness of the reinforcing portion is fixed.

Description

Technical Field

[0001] The present invention relates to a piezoelectric device, a piezoelectric actuator including the piezoelectric device, and an ultrasonic device including the piezoelectric device. Background Art

[0002] Conventionally, a piezoelectric device in which a first electrode, a piezoelectric element, and a second electrode are laminated on a substrate has been known. In the piezoelectric device described in Patent Document 1, on a diaphragm (support), a piezoelectric body covers the first electrode, and a recess that is recessed toward the diaphragm side is provided outside a region of the diaphragm that overlaps the first electrode. The piezoelectric body is provided so as to cover the first electrode. Further, the second electrode is provided across the diaphragm including the recess from the piezoelectric body. In such a configuration, the displacement characteristics of the diaphragm can be improved by the recess.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2017-126628

[0004] However, if the thickness of the diaphragm is made thin as in Patent Document 1 to increase the displacement amount, there is a case where the diaphragm is damaged because it cannot withstand the deformation of the diaphragm. Therefore, the displacement amount of the diaphragm that can be driven by the piezoelectric element is limited, and a highly durable piezoelectric device is required in which the displacement amount of the diaphragm is large but the possibility of breakage is low. Summary of the Invention

[0005] The piezoelectric device according to the first aspect of the present disclosure includes: a substrate having an opening; a diaphragm having a first surface and a second surface on the side opposite to the first surface, the first surface being joined to the substrate to close the opening; and a piezoelectric element provided on the second surface of the diaphragm. The diaphragm includes a first region that overlaps the piezoelectric element when viewed in the thickness direction of the diaphragm and a second region that does not overlap the piezoelectric element. The thickness of the second region in the thickness direction of the diaphragm is thinner than the thickness of the first region. A reinforcing portion made of a material having a higher fracture toughness than the first region of the diaphragm is provided in the second region. The thickness of the second region in the thickness direction is constant, and the thickness of the reinforcing portion is constant. Brief Description of the Drawings

[0006] Figure 1 It is a diagram showing a schematic configuration of an ultrasonic device according to the first embodiment.

[0007] Figure 2 It is a top view showing a schematic configuration of the piezoelectric device according to the first embodiment.

[0008] Figure 3 It is a schematic cross-sectional view when the piezoelectric device is cut along line A-A of Figure 2

[0009] Figure 4 This is Figure 2 a schematic cross-sectional view when the piezoelectric device is cut along the B-B line.

[0010] Figure 5 a graph showing the approximate Young's modulus and fracture toughness of each material.

[0011] Figure 6 a graph showing the distribution of the deformation in the X direction applied to the vibrating body 35 when the piezoelectric device of the first embodiment is driven with a driving voltage of 10 (V).

[0012] Figure 7 a graph showing the distribution of the deformation in the X direction applied to the vibrating body 35 when the piezoelectric device of the first embodiment is driven with a driving voltage of 100 (V).

[0013] Figure 8 a graph showing the deformation in the X direction at each position in the X direction on the -Z side surface of the vibrating body when the piezoelectric device of the first embodiment is driven with driving voltages of 10 (V) and 100 (V).

[0014] Figure 9 a graph showing the deformation in the X direction at each position in the X direction on the +Z side surface of the vibrating body when the piezoelectric device of the first embodiment is driven with driving voltages of 10 (V) and 100 (V).

[0015] Figure 10 a graph showing the deformation in the X direction at each position in the thickness direction of the vibrating body in the piezoelectric device of the first embodiment.

[0016] Figure 11 a graph showing the displacement amount of the vibrating part when the driving voltage is changed in the existing example and the present embodiment.

[0017] Figure 12 a graph showing the displacement amount of the vibrating part when the frequency of the ultrasonic wave output from the piezoelectric device is changed.

[0018] Figure 13 a top view showing the schematic configuration of the piezoelectric device of the second embodiment.

[0019] Figure 14 This is Figure 13 a schematic cross-sectional view when the piezoelectric device is cut along the C-C line.

[0020] Figure 15 This is Figure 13 a schematic cross-sectional view when the piezoelectric device is cut along the D-D line.

[0021] Figure 16 a diagram showing the schematic configuration of a liquid ejection device that is a piezoelectric actuator as the third embodiment.

[0022] Explanation of Reference Numerals

[0023] 1…Ultrasonic device, 2…Housing, 3…Measurement terminal, 7…Liquid ejection device (piezoelectric actuator), 10, 10A…Piezoelectric device, 20…Substrate, 21, 21A…Opening, 22…Partition portion, 30…Vibrating plate, 30A…Vibrating portion, 30B…Arm portion, 30C…Base portion, 31…First surface, 32…Second surface, 33…Recess, 35…Vibrating body, 40…Piezoelectric element, 41…First electrode, 42…Piezoelectric body film, 43…Second electrode, 50…Reinforcing portion, 51…Extended portion, 52…Third surface, 53…Insulating groove, 60…Sealing plate, 61…Wall portion, 70…Pressure chamber, 71…Nozzle, 72…Introduction portion, 301…First layer, 302…Second layer, A1…First region, A2…Second region. Detailed Description of the Embodiment

[0024] First Embodiment

[0025] Hereinafter, an ultrasonic device including the piezoelectric device according to the first embodiment of the present disclosure will be described.

[0026] Figure 1 FIG. is a schematic configuration diagram of the ultrasonic device 1 according to the present embodiment.

[0027] The ultrasonic device 1 of the present embodiment includes a piezoelectric device 10 that functions as an ultrasonic sensor, a housing 2 that houses the piezoelectric device 10, and a measurement terminal 3. In addition, although not shown, various control circuits for controlling the piezoelectric device 10, a battery, a communication unit for outputting the measurement result to the outside, etc. may be housed in the housing 2.

[0028] The ultrasonic device 1 performs ultrasonic measurement of transmitting ultrasonic waves from the piezoelectric device 10 to the measurement object and receiving the ultrasonic waves reflected by the measurement object. The measurement result of the ultrasonic measurement output from the ultrasonic device 1 is transmitted to the measurement terminal 3. The measurement terminal 3 is a computer constituted by, for example, a dedicated computer, a smart phone, a tablet terminal, etc. The measurement terminal 3 performs various arithmetic processes based on the measurement result of the ultrasonic measurement, for example, generates an internal tomographic image of a living body, observes the state or measures the thickness of a predetermined tissue in the living body, etc.

[0029] Hereinafter, the piezoelectric device 10 used in such an ultrasonic device 1 will be described.

[0030] Figure 2 FIG. is a top view showing a schematic configuration of the piezoelectric device 10. Figure 3 and Figure 4 FIG. is a cross-sectional view showing a schematic configuration of the piezoelectric device 10 of the present embodiment. In addition, Figure 3 Indicates thatFigure 2 The cross-section of the piezoelectric device 10 taken along the A-A line, Figure 4 which shows the cross-section of the piezoelectric device 10 taken along the B-B line indicated by Figure 2 .

[0031] As shown in Figure 3 and Figure 4 , the piezoelectric device 10 of the present embodiment includes a substrate 20, a diaphragm 30 laminated on the substrate 20, a piezoelectric element 40 laminated on the diaphragm 30, a reinforcing portion 50 provided at a predetermined portion of the diaphragm 30, and a sealing plate 60. In the present embodiment, the substrate thickness direction of the substrate 20 is defined as the Z direction, the direction orthogonal to the Z direction is defined as the X direction, and the direction orthogonal to the Z direction and the X direction is defined as the Y direction.

[0032] The substrate 20 is a plate-like member having a predetermined thickness and has an opening 21 penetrating in the thickness direction. By laminating the diaphragm 30 on the substrate 20, the opening 21 is closed by the diaphragm 30.

[0033] As shown in Figures 2 to 4 , the opening 21 is formed to be long in the Y direction, and a plurality of openings 21 are provided along the X direction. The partition portion 22 surrounding the opening 21 in the substrate 20 defines a vibrating portion 30A that vibrates under the drive of the piezoelectric element 40 in the laminate of the diaphragm 30 and the reinforcing portion 50.

[0034] In addition, in the present disclosure, a vibrating body 35 is constituted by the diaphragm 30 and the reinforcing portion 50. The vibrating portion 30A refers to the portion of the vibrating body 35 surrounded by the partition portion 22. That is, in the diaphragm 30 and the reinforcing portion 50, the portion overlapping the partition portion 22 in the Z direction becomes a base portion 30C where vibration is suppressed, and the portion surrounded by the partition portion 22 becomes the vibrating portion 30A that vibrates under the drive of the piezoelectric element 40. In addition, the base portion 30C refers to the portion of the vibrating body 35 overlapping the partition portion 22 in the Z direction.

[0035] The diaphragm 30 has a first surface 31 (the surface on the +Z side) facing the substrate 20 and a second surface 32 (the surface on the -Z side) opposite to the first surface 31, and the opening 21 is closed by joining the first surface 31 so as to cover the -Z side surface of the substrate 20.

[0036] The diaphragm 30 is, for example, a laminate including a first layer 301 made of SiO2 and a second layer 302 made of ZrO2, and is formed by processing an element substrate having the first layer 301 disposed on the +Z side and the second layer 302 disposed on the -Z side. Specifically, when a portion of the diaphragm 30 where the piezoelectric element 40 is laminated is defined as a first region A1 and a portion other than the first region A1 is defined as a second region A2, a recess 33 is formed in at least a part of the second region A2 by processing from the second surface 32 side by etching or the like. That is, in the first region A1 of the diaphragm 30, it is composed of the first layer 301 and the second layer 302, and in the second region A2 of the diaphragm 30, the thickness in the Z direction is thinner than that of the first region A1, the second layer 302 made of ZrO2 does not exist, and it is composed only of the first layer 301 made of SiO2. The groove depth of the recess 33 in the Z direction is more than half of the thickness of the first region A1. That is, the thickness of the second region A2 is less than half of the thickness of the first region A1 and becomes a uniform thickness.

[0037] In addition, in Figure 3 the example shown, a part of the second layer 302 in the first region A1 is removed. This is a concave portion generated by over-etching when the piezoelectric element 40 is formed in the diaphragm 30 in the first region A1, and the depth in the Z direction is much smaller than that of the recess 33.

[0038] When viewed from the top in the Z direction, the piezoelectric element 40 is laminated on the first region A1. The second region A2 is provided at a position sandwiching the first region A1 at least in the X direction.

[0039] In the vibrating body 35, the second region A2 includes a base portion 30C overlapping with the partition portion 22 of the substrate 20 and an arm portion 30B between the base portion 30C and the first region A1. The recess 33 is provided at least from the arm portion 30B to the base portion 30C, and a reinforcing portion 50 that constitutes the vibrating body 35 together with the diaphragm 30 is provided in the recess 33.

[0040] The piezoelectric element 40 is provided on the second surface 32 of the diaphragm 30 at a position overlapping with the first region A1 of the diaphragm 30. The piezoelectric element 40 is, for example, composed of a laminate in which a first electrode 41, a piezoelectric film 42, and a second electrode 43 are laminated from the diaphragm 30 toward the -Z side.

[0041] The piezoelectric element 40 is formed as follows. First, after forming an electrode film on the diaphragm 30, the first electrode 41 is patterned by etching. Next, after forming the piezoelectric film 42 covering the first electrode 41, the piezoelectric film 42 is patterned by etching. Further, after forming an electrode film covering the piezoelectric film 42 and the first electrode 41, the second electrode 43 is patterned by etching. Thus, as Figure 3 、Figure 4 As shown, the side surface of the piezoelectric element 40 is a conical surface inclined with respect to the Z direction.

[0042] In the present embodiment, the vibration unit 30A and the piezoelectric element 40 constitute an ultrasonic transducer.

[0043] In such an ultrasonic transducer, by applying a rectangular wave voltage (driving signal) of a specified frequency between the first electrode 41 and the second electrode 43, the piezoelectric film 42 expands and contracts. Due to the expansion and contraction of the piezoelectric film 42, the vibration unit 30A vibrates, and ultrasonic waves are sent out to the +Z side. In addition, when the vibration unit 30A vibrates due to ultrasonic waves, the piezoelectric film 42 flexes, thereby generating a potential difference between the first electrode 41 side and the second electrode 43 side of the piezoelectric film 42. Thus, by detecting the potential difference generated between the first electrode 41 and the second electrode 43, the reception of ultrasonic waves can be detected.

[0044] The reinforcing portion 50 is disposed in the recess 33 provided in the second region A2 of the diaphragm 30 with a uniform thickness. The thickness of the reinforcing portion 50 at the position of the recess 33 is at least more than half of the thickness of the first region A1. The third surface 52, which is the -Z side surface of the reinforcing portion 50, is preferably on the same plane as the second surface 32 of the first region A1 of the diaphragm 30, or is located on the -Z side of the second surface 32.

[0045] In addition, a part of the reinforcing portion 50 is formed so as to extend from the second region A2 to the first region A1. That is, the reinforcing portion 50 is formed on the diaphragm 30 on which the piezoelectric element 40 is formed by a method such as sputtering. Therefore, as Figure 3 shown, a part of the reinforcing portion 50 extends along the conical surface of the second electrode 43 from the second region A2, constituting an extended portion 51. In addition, as Figures 2 to 4 shown, the reinforcing portion 50 may also be provided to cover the piezoelectric element 40. In this case, as Figure 1 、 Figure 3 shown, on the ±Y sides of the piezoelectric element 40 sandwiching the vibration unit 30A, the reinforcing portion 50 is removed (for example, by etching etc.) until the surfaces of the piezoelectric film 42 and the diaphragm 30 are exposed, thereby forming an insulating groove 53. Thus, it is possible to prevent the first electrode 41 and the second electrode 43 from being electrically connected by the conductive reinforcing portion 50.

[0046] Furthermore, when driving each piezoelectric element 40 arranged in the X direction independently, the reinforcing portion 50 at the ±Y side ends of the diaphragm 30 is removed to prevent the first electrodes 41 of the respective piezoelectric elements 40 from being electrically connected. Thus, the end portions of the first electrodes 41 of the respective piezoelectric elements 40 are exposed on the diaphragm 30.

[0047] The reinforcing portion 50 is made of a material having a fracture toughness higher than that of the diaphragm 30. More preferably, the reinforcing portion 50 is made of a material having a Young's modulus smaller than that of the material having the highest Young's modulus constituting the diaphragm 30. In the present embodiment, the diaphragm 30 is a laminate of a first layer 301 of SiO2 and a second layer 302 of ZrO2. When the Young's modulus of SiO2 is 70 (GPa) and the Young's modulus of the ZrO2 layer is 200 (GPa), it is preferable to use a material having at least a Young's modulus smaller than that of the ZrO2 layer for the reinforcing portion 50.

[0048] Figure 5 is a diagram showing the approximate Young's modulus and fracture toughness of each material. As the reinforcing portion 50, from Figure 5 it can be seen that when the first region A1 is a laminate of an SiO2 layer and a ZrO2 layer, any one of Au, Cu, Al, Ir, and NiCr having a greater fracture toughness is used. In addition, it is preferable to use Au, Cu, or Al having a Young's modulus smaller than that of the ZrO2 layer. In addition, since the Young's modulus of Cu is greater than those of Au and Al, it is difficult to flex, and the fracture toughness of Al is smaller than those of Au and Cu. Therefore, it is most preferable to use Au as the reinforcing portion 50.

[0049] The sealing plate 60 is provided on the side of the diaphragm 30 opposite to the substrate 20 and is joined to the diaphragm 30 or the reinforcing portion 50 via a resist resin or the like. A gap having a predetermined size is provided between the sealing plate 60 and the diaphragm 30 and the reinforcing portion 50. Thus, the sealing plate 60 does not contact the piezoelectric element 40 or the like due to the vibration of the vibrating portion 30A. The sealing plate 60 is, for example, a plate-like member having a thickness dimension larger than that of the diaphragm 30 or the substrate 20, and strengthens the substrate 20 and the diaphragm 30 by being joined to the diaphragm 30.

[0050] The displacement characteristics of the piezoelectric device 10

[0051] Next, the displacement characteristics of the piezoelectric device 10 of the present embodiment described above will be described.

[0052] Figure 6 is a diagram showing the distribution of the deformation in the X direction applied to the vibrating body 35 when the piezoelectric device 10 of the present embodiment is driven with a driving voltage of 10 (V). Figure 7 is a diagram showing the distribution of the deformation in the X direction applied to the vibrating body 35 when the piezoelectric device 10 of the present embodiment is driven with a driving voltage of 100 (V). In addition, Figure 8 is a diagram showing the deformation in the X direction at each position in the X direction of the -Z side surface of the vibrating body 35 when the piezoelectric device 10 of the present embodiment is driven with driving voltages of 10 (V) and 100 (V). Figure 9This is a diagram showing the deformation in the X - direction at each position in the X - direction on the +Z side surface of the vibrating body 35 when the piezoelectric device 10 of this embodiment is driven with driving voltages of 10 (V) and 100 (V). Figure 10 This is a diagram showing the deformation in the X - direction at each position in the thickness direction of the vibrating body 35. In Figure 10 as an example, the measurement results of the deformation at the central position of the arm portion 30B (the intermediate position between the first region A1 and the base portion 30C) when the driving voltage is 10 (V), at a position near the first region A1 of the arm portion 30B when the driving voltage is 10 (V), and at a position near the first region A1 of the arm portion 30B when the driving voltage is 100 (V) are shown.

[0053] As Figure 6 and Figure 7 shown, when the driving voltage input to the piezoelectric device 10 is 100 (V), compared with the case where the driving voltage is 10 (V), the deformation in the X - direction becomes larger, especially in the first region A1 of the vibrating plate 30, the deformation also becomes larger.

[0054] However, when the deformation is balanced between the +Z side (the first surface 31 side) and the -Z side (the second surface 32 of the vibrating plate 30 and the third surface 52 side of the reinforcing portion 50) of the vibrating body 35, such deformation in the X - direction absorbs each other's deformation and is eliminated, so that the influence of the deformation on the breakage of the vibrating plate 30 and the like is small.

[0055] When the driving voltage is 10 (V), as Figure 6 、 Figure 8 、 Figure 9 shown, the deformation at the position of the arm portion 30B of the vibrating plate 30 is larger than the deformation in the first region A1, but the difference in this deformation is small. In this case, as Figure 10 shown, near the mid - point in the thickness direction (Z - direction) of the vibrating plate 30, the deformation becomes "0". The position where the deformation becomes "0" becomes the neutral point where the deformation on the +Z side and the -Z side of the vibrating body 35 cancel each other out. When the driving voltage is 10 (V), this neutral point is near the mid - point position in the thickness direction (Z - direction) of the vibrating plate 30.

[0056] On the other hand, if the driving voltage of the vibrating plate 30 is further increased, as Figures 7 to 9As shown, not only does the deformation in the X direction in the first region A1 increase for the arm portion 30B, but particularly on the +Z side surface of the vibrating body 35, the deformation within the first region A1 increases, and near the boundary between the first region A1 and the second region A2 (arm portion 30B), the direction of deformation (compression or elongation) also reverses. Additionally, on the -Z side surface of the vibrating body 35, although the deformation within the first region A1 is small, the deformation at the arm portion 30B significantly increases. By generating such deformation, as Figure 10 shown, the balance of deformation between the +Z side and the -Z side of the vibrating body 35 is disrupted, and the neutral point shifts toward the first surface 31 side (+Z side).

[0057] As described above, the deformation during the displacement of the vibration plate 30 is not only a problem on the surface of the vibration plate 30, but also changes occur at various positions in the thickness direction (Z direction) of the vibration plate 30. In particular, if the drive voltage is increased, the neutral point moves toward the first surface 31 side, and thus the deformation becomes larger in the portion closer to the second surface 32 side than this neutral point.

[0058] In contrast, in the present embodiment, in the vibration plate 30, recesses 33 with a depth of more than half of the thickness dimension of the vibration plate 30 are provided from the arm portion 30B outside the outer edge of the first region A1 to the base portion 30C, and a reinforcing portion 50 is laminated in the recesses 33. The third surface 52 of the reinforcing portion 50 and the second surface 32 of the first region A1 of the vibration plate 30 become the same surface. As described above, the reinforcing portion 50 is made of a material having a fracture toughness greater than that of the first region A1 of the vibration plate 30. The depth of the recesses 33 and the thickness of the reinforcing portion 50 are preferably appropriately set according to the maximum drive power input to the piezoelectric device 10 so that the neutral point is located within the reinforcing portion 50.

[0059] Thereby, when a drive voltage greater than, for example, 100 (V) is input to the piezoelectric device 10, the position closer to the second surface 32 (third surface 52) side than the neutral point with a larger deformation in the X direction becomes within the reinforcing portion 50, and breakage caused by deformation can be suppressed.

[0060] In addition to this, the reinforcing portion 50 has a Young's modulus smaller than that of the second layer 302 constituting the first region A1 of the vibration plate 30. Thereby, it is easy to displace when a drive voltage is input, and the vibration displacement amount of the vibration plate 30 can be increased.

[0061] Figure 11 is a graph showing the displacement amount of the vibration portion 30A when the drive voltage in the conventional example and the present embodiment changes, Figure 12 is a graph showing the displacement amount of the vibration portion 30A when the frequency of the ultrasonic wave output from the piezoelectric device 10 changes.

[0062] In addition, the following piezoelectric device is used in the existing example: no recess 33 or reinforcing portion 50 is provided on the diaphragm 30 of the present embodiment, and the entire diaphragm 30 has the same configuration as the first region A1 (a laminate of SiO2 and ZrO2).

[0063] In the piezoelectric device of the existing example, the entire diaphragm is composed of a laminate of SiO2 and ZrO2. In this case, ZrO2 having a large Young's modulus is provided in a portion corresponding to the arm portion 30B that contributes to displacement, and the displacement amount cannot be sufficiently increased. In contrast, in the present embodiment, in the arm portion 30B, there is no ZrO2 due to the recess 33, and instead, a reinforcing portion 50 having a small Young's modulus is used. Therefore, as Figure 11 shown, in the piezoelectric device 10 of the present embodiment, the vibrating portion 30A can be displaced by a larger displacement amount than the piezoelectric device of the existing example with respect to the input driving voltage. In addition, as described above, even when the driving voltage is increased, breakage of the diaphragm 30 can be suppressed.

[0064] In addition, in the piezoelectric device 10, by changing the frequency of the input driving voltage, the frequency of the ultrasonic wave output from the piezoelectric device 10 can be changed. As Figure 12 shown, even when the frequency of the ultrasonic wave is changed, the piezoelectric device 10 of the present embodiment can increase the displacement amount of the diaphragm 30 compared to the piezoelectric device of the comparative example.

[0065] In addition, by making the natural frequency of the piezoelectric device 10 coincide with the frequency of the driving voltage, the displacement amount can be made larger by the resonance effect of the diaphragm 30.

[0066] Function and effect of the present embodiment

[0067] The piezoelectric device 10 of the present embodiment includes: a substrate 20 having an opening 21; a diaphragm 30 having a first surface 31 and a second surface 32, the first surface 31 being joined to the substrate 20 to close the opening 21; and a piezoelectric element 40 provided on the second surface 32 of the diaphragm 30. In addition, the diaphragm 30 includes a first region A1 that overlaps the piezoelectric element 40 when viewed from the Z direction and a second region A2 that does not overlap the piezoelectric element 40, and the thickness of the second region A2 in the Z direction is thinner than the thickness of the first region A1. Moreover, a reinforcing portion 50 is provided in the second region A2, and the reinforcing portion 50 is made of a material having a higher fracture toughness than the first region A1 of the diaphragm 30. The thickness of the second region A2 of the diaphragm 30 in the Z direction is constant, and the thickness of the reinforcing portion 50 is also constant.

[0068] Thus, the piezoelectric device 10 according to the present embodiment can suppress breakage of the vibrating body 35 in the second region A2 by disposing a reinforcing portion 50 having high fracture toughness in the second region A2 where displacement is greater than that in the first region A1.

[0069] In the present embodiment, the vibrating plate 30 has a recess 33 recessed from the second surface 32 side in the second region A2. The groove depth of the recess 33 is more than half of the thickness of the first region A1, and the reinforcing portion 50 is disposed in the recess 33.

[0070] In the piezoelectric device 10 as in the present embodiment, when the drive voltage input to the piezoelectric element 40 is increased, the deformation of the vibrating body 35 in the X direction becomes different in size in the Z direction, and the neutral point does not become the center of the vibrating body 35 in the Z direction but shifts toward the first surface 31 side. Therefore, the deformation of the vibrating body 35 in the X direction on the second surface 32 side becomes larger than that at the neutral point. In contrast, in the present embodiment, the thickness of the reinforcing portion 50 is more than half of the thickness of the first region A1. That is, in the Z direction, in the second region A2 of the vibrating body 35, the reinforcing portion 50 having high fracture toughness occupies more than half of the thickness. Thereby, breakage in the second region A2 can be more effectively suppressed.

[0071] In the present embodiment, when viewed from the Z direction, the reinforcing portion 50 extends to a position straddling the boundary between the first region A1 and the second region A2. That is, the reinforcing portion 50 has an extended portion 51 extending along the tapered surface of the second electrode 43.

[0072] When the vibrating portion 30A is displaced, since the arm portion 30B is displaced significantly, the load is concentrated at the boundary between the first region A1 and the arm portion 30B (second region A2). In contrast, by disposing the extended portion 51 of the reinforcing portion 50 having high fracture toughness across this boundary, breakage of the vibrating body 35 at the boundary between the first region A1 and the arm portion 30B (second region A2) can be suppressed.

[0073] In the present embodiment, the portion of the second region A2 that overlaps with the partition portion 22 surrounding the opening 21 of the substrate 20 is defined as the base portion 30C, and the portion between the base portion 30C and the first region A1 is defined as the arm portion 30B, and the reinforcing portion 50 is provided from the base portion 30C to the arm portion 30B.

[0074] When drive power is input to the piezoelectric element 40 to vibrate the vibrating portion 30A, the arm portion 30B is displaced significantly, and the deformation in the X direction also becomes larger. In addition, the deformation in the X direction not only extends to the arm portion 30B, but also as Figure 6 、 Figure 7The shown secondary arm 30B extends over the base 30C. In the present embodiment, since the reinforcing portion 50 is provided from the secondary arm 30B over the base 30C, deformation in the X direction as described above can be resisted, and breakage of the vibrating body 35 can be further suppressed.

[0075] The diaphragm 30 of the present embodiment is composed of a plurality of different materials. The Young's modulus of the reinforcing portion 50 is smaller than the Young's modulus of the material having the highest Young's modulus among the materials constituting the diaphragm 30. For example, when the diaphragm 30 is a laminate of SiO2 and ZrO2, the Young's modulus of SiO2 is about 70 (GPa), and the Young's modulus of ZrO2 is about 200 (GPa). In the second region A2, there is no ZrO2 having a high Young's modulus, and the reinforcing portion 50 is provided on SiO2. The Young's modulus of the reinforcing portion 50 is smaller than that of ZrO2.

[0076] Accordingly, the displacement amount of the vibrating portion 30A can be increased as compared with the case where the second region A2 is composed of SiO2 and ZrO2.

[0077] In the present embodiment, the reinforcing portion 50 is made of any one of Au, Cu, and Al.

[0078] The reinforcing portion 50 made of these materials has a fracture toughness higher than that of SiO2 and ZrO2 constituting the first region A1, and has a Young's modulus smaller than that of ZrO2. Therefore, by the reinforcing portion 50 made of such a material, the displacement amount at the time of displacement of the vibrating portion 30A can be increased, and even in the case of a large displacement, breakage of the vibrating body 35 can be suppressed by the high fracture toughness.

[0079] Second Embodiment

[0080] Next, the second embodiment will be described.

[0081] In the above-described first embodiment, the diaphragm 30 is laminated on the substrate 20 having the opening 21, and the region of the vibrating portion 30A in the vibrating body 35 is defined by the partition portion 22 forming the opening 21. However, the difference between the present embodiment and the above-described first embodiment is that the vibrating portion 30A is defined by a suppressing portion provided on the opposite side of the substrate 20.

[0082] Figure 13 is a plan view showing a schematic configuration of the piezoelectric device 10A according to the second embodiment, Figure 14 is Figure 13 a schematic cross-sectional view of the piezoelectric device 10A taken along line C-C in Figure 15 is Figure 13 a schematic cross-sectional view of the piezoelectric device 10A taken along line D-D in

[0083] In addition, in the following description, components that have been described are denoted with the same reference numerals, and their descriptions are omitted or simplified.

[0084] In the present embodiment, as Figures 13 to 15 shown, the opening 21A of the substrate 20 is formed in a substantially rectangular shape, and in a region overlapping with one opening 21A, a plurality of piezoelectric elements 40 that are long in the Y direction are arranged in the X direction.

[0085] Moreover, in the present embodiment, a wall portion 61 as a suppression portion is provided on the -Z side surface of the vibrating body 35 so as to surround each piezoelectric element 40.

[0086] This wall portion 61 has the same function as the partition portion 22 of the substrate 20 in the first embodiment. That is, in the vibrating body 35 composed of the vibrating plate 30 and the reinforcing portion 50, a portion overlapping with the wall portion 61 in the Z direction becomes the base portion 30C where vibration is suppressed. In addition, between the first region A1 and the base portion 30C becomes the arm portion 30B.

[0087] In addition, the configurations of the vibrating plate 30, the piezoelectric element 40, and the reinforcing portion 50 are the same as those in the first embodiment.

[0088] In such a present embodiment, the displacement characteristics described in the first embodiment can also be obtained. That is, compared with the case where the drive voltage is 10 (V), when a drive voltage of 100 (V) is input to the piezoelectric device 10A, the vibration displacement amount of the vibrating portion 30A becomes larger. However, correspondingly, the deformation in the X direction also increases. As Figures 6 to 10 shown, the larger the drive voltage, the more the deformation in the X direction shifts toward the first surface 31 side, and thus, the deformation in the X direction on the second surface 32 side of the vibrating body 35 becomes larger. Figures 8 to 10 shown, the larger the drive voltage, the more the deformation in the X direction shifts toward the first surface 31 side, whereby the deformation in the X direction on the second surface 32 side of the vibrating body 35 becomes larger.

[0089] In contrast, in the present embodiment, the same reinforcing portion 50 as in the first embodiment is also provided. Thereby, the influence of the increase in the deformation in the X direction can be suppressed. That is, even when a high drive voltage is input to the piezoelectric device 10A, breakage of the vibrating body 35 can be suppressed, and as Figure 11 and Figure 12 shown, the vibration displacement amount of the vibrating portion 30A can also be increased.

[0090] Operational effects of the present embodiment

[0091] The piezoelectric device 10A of the present embodiment includes a wall portion 61 (suppression portion) that is provided on the second surface 32 side of the vibrating plate 30 at a position sandwiching the piezoelectric element 40 and suppresses the vibration of the vibrating plate 30 (vibrating body 35).

[0092] In such a piezoelectric device 10A, the regions of the respective vibrating portions 30A in the vibrating body 35 can be defined in the same manner as in the first embodiment. Further, as in the first embodiment, the reinforcing portion 50 can suppress breakage of the vibrating body 35 and can increase the displacement amount of the vibrating portion 30A.

[0093] In the present embodiment, the reinforcing portion 50 has a base portion 30C that overlaps a partition wall portion surrounding the opening of the substrate 20, and the reinforcing portion 50 is provided from the base portion 30C over the arm portion 30B.

[0094] In the present embodiment, since the reinforcing portion 50 is provided from the arm portion 30B over the base portion 30C, it is possible to resist deformation in the X direction and suppress breakage of the vibrating body 35 in the same manner as in the first embodiment.

[0095] Third Embodiment

[0096] The piezoelectric devices 10 and 10A of the present disclosure can be used as various piezoelectric actuators in addition to the ultrasonic device shown in the first embodiment.

[0097] In the third embodiment, a liquid ejection device that is a piezoelectric actuator using the piezoelectric device 10 is illustrated as an example.

[0098] Figure 16 It is a diagram showing an example of the liquid ejection device.

[0099] In Figure 16 the liquid ejection device 7 of the present embodiment includes: a pressure chamber 70 in which the piezoelectric device 10 is disposed, a nozzle 71 disposed in a part of the pressure chamber 70, and an introduction portion 72 that introduces a liquid into the pressure chamber 70.

[0100] In the present embodiment, a liquid such as ink is introduced into the pressure chamber 70 from the introduction portion 72, so that the pressure chamber 70 is filled with the liquid.

[0101] Moreover, when a drive voltage is input to the piezoelectric device 10, the vibrating portion 30A performs displacement driving, so that the pressure in the pressure chamber 70 becomes high and the liquid is ejected from the nozzle 71. In addition, the piezoelectric device 10A described in the second embodiment can be used instead of the piezoelectric device 10.

[0102] In such a liquid ejection device 7, for example, the pressure applied to the pressure chamber 70 may be increased depending on the volume of the pressure chamber 70 and the distance from the liquid ejection device 7 to the ejection target. In this case, by increasing the drive voltage input to the piezoelectric device 10, the pressure in the pressure chamber 70 can be further increased. However, as described above, the deformation in the X direction of the vibrating body 35 becomes large by increasing the drive power.

[0103] In contrast, by using the piezoelectric device 10, breakage of the vibrating body 35 due to the reinforcing portion 50 can be suppressed. In addition, with respect to the input drive voltage, since the displacement amount can be increased compared to existing piezoelectric devices, the pressure in the pressure chamber 70 can also be increased with less voltage.

[0104] Modification

[0105] Furthermore, the present invention is not limited to the above-described embodiments, and modifications, improvements, and configurations obtained by appropriately combining the respective embodiments within the scope that can achieve the object of the present invention are included in the present invention.

[0106] Modification 1

[0107] In the second embodiment, a configuration in which the diaphragm 30 is disposed on the substrate 20 is illustrated, but a configuration in which the substrate 20 is not provided may also be formed. That is, in the second embodiment, even if the substrate 20 is not provided, the vibrating portion 30A can be divided by the wall portion 61 serving as a suppressing portion.

[0108] Modification 2

[0109] In the above-described embodiment, the reinforcing portion 50 is provided such that the upper surface (third surface 52) of the reinforcing portion 50 and the second surface 32 of the diaphragm 30 are flush, but it is not limited thereto. The thickness of the reinforcing portion 50 may be thin, and the third surface 52 may be located closer to the first surface 31 side than the second surface 32. Alternatively, the thickness of the reinforcing portion 50 may be thick, and the third surface 52 may be located closer to the sealing plate 60 side than the second surface 32.

[0110] Summary of the present disclosure

[0111] The piezoelectric device according to the first aspect of the present disclosure includes: a substrate having an opening; a diaphragm having a first surface and a second surface on the side opposite to the first surface, the first surface being joined to the substrate to close the opening; and a piezoelectric element disposed on the second surface of the diaphragm. The diaphragm includes a first region that overlaps the piezoelectric element when viewed in the thickness direction of the diaphragm and a second region that does not overlap the piezoelectric element. The thickness of the second region in the thickness direction of the diaphragm is thinner than the thickness of the first region. A reinforcing portion made of a material having a higher fracture toughness than the first region of the diaphragm is provided in the second region. The thickness of the second region in the thickness direction is constant, and the thickness of the reinforcing portion is constant.

[0112] Accordingly, even when a high drive power is input to the piezoelectric device, breakage of the diaphragm and the reinforcing portion can be suppressed, and the diaphragm and the reinforcing portion can be displaced with a large displacement amount.

[0113] In the piezoelectric device of this embodiment, it is preferable that the diaphragm has a recess recessed from the second surface side in the second region, the groove depth in the thickness direction of the recess is more than half of the thickness of the first region, the reinforcing portion is disposed in the recess, and the thickness in the thickness direction of the reinforcing portion is not less than the groove depth.

[0114] Accordingly, when high driving power is input to the piezoelectric device, the reinforcing portion having high fracture toughness is provided on the side of the second surface with large deformation, and breakage of the diaphragm and the reinforcing portion can be suppressed.

[0115] In the piezoelectric device of this embodiment, it is preferable that when viewed from the thickness direction, the reinforcing portion extends to a position straddling the boundary between the first region and the second region.

[0116] Accordingly, the boundary between the first region and the second region where load is likely to concentrate can be covered with the reinforcing portion having high fracture toughness, and breakage of the diaphragm and the reinforcing portion at the boundary can be suppressed.

[0117] In the piezoelectric device of this embodiment, it is preferable that a portion of the second region overlapping with the partition portion surrounding the opening of the substrate is defined as a base portion, a portion between the base portion and the first region is defined as an arm portion, and the reinforcing portion is provided from the base portion to the arm portion.

[0118] Accordingly, even when high driving power is input to the piezoelectric device and the deformation from the arm portion to the base portion becomes large, breakage caused by the deformation can be suppressed by the reinforcing portion.

[0119] The piezoelectric device of this embodiment includes a suppressing portion that is disposed on the second surface side of the diaphragm at a position sandwiching the piezoelectric element and suppresses vibration of the diaphragm.

[0120] Even in the configuration in which the suppressing portion is provided on the second surface side of the diaphragm as in this embodiment, the vibration region of the diaphragm where the piezoelectric element is disposed can be defined.

[0121] In the piezoelectric device of this embodiment, it is preferable that a portion of the second region overlapping with the suppressing portion of the substrate is defined as a base portion, a portion between the base portion and the first region is defined as an arm portion, and the reinforcing portion is provided from the base portion to the arm portion.

[0122] Accordingly, as in the above embodiment, even when high driving power is input to the piezoelectric device and the deformation from the arm portion to the base portion becomes large, breakage caused by the deformation can be suppressed by the reinforcing portion.

[0123] In the piezoelectric device of this mode, the diaphragm is composed of a plurality of different materials, and the Young's modulus of the reinforcing portion is smaller than the Young's modulus of the material having the highest Young's modulus among the materials constituting the diaphragm.

[0124] Thus, as described in the above mode, it is possible to suppress breakage of the diaphragm and further increase the displacement amount of the diaphragm.

[0125] In the piezoelectric device of this mode, it is preferable that the reinforcing portion is any one of Au, Cu, and Al.

[0126] Thus, as described in the above mode, it is possible to suppress breakage of the diaphragm and further increase the displacement amount of the diaphragm. In addition, by forming the reinforcing portion of these conductive materials, the reinforcing portion can function as a wiring electrode or as an electromagnetic shield.

[0127] In the piezoelectric device of this mode, the piezoelectric element is a laminate in which a first electrode, a piezoelectric film, and a second electrode are laminated in this order from the diaphragm.

[0128] By disposing such a piezoelectric element, the diaphragm can be vibrationally driven.

[0129] The piezoelectric actuator according to the second mode of the present disclosure includes the piezoelectric device according to the first mode.

[0130] As described above, even if the displacement amount of the diaphragm is increased, the piezoelectric device can suppress breakage of the diaphragm. As a result, a piezoelectric actuator capable of outputting a large driving force can be provided.

[0131] The ultrasonic device according to the third mode of the present disclosure includes the piezoelectric device according to the first mode.

[0132] As described above, even if the displacement amount of the diaphragm is increased, the piezoelectric device can suppress breakage of the diaphragm. As a result, an ultrasonic device capable of outputting a large sound pressure can be provided.

Claims

1. A piezoelectric device, characterized in that: have: A substrate having an opening; a vibration plate having a first surface and a second surface opposite to the first surface, wherein the first surface is bonded to the substrate to close the opening; and a piezoelectric element disposed on the second surface of the vibration plate, The vibration plate includes a first region overlapping with the piezoelectric element and a second region not overlapping with the piezoelectric element when viewed in the thickness direction of the vibration plate. The thickness of the second region in the thickness direction of the vibration plate is thinner than the thickness of the first region. A reinforcement portion having a material having a higher fracture toughness than that of the first region of the vibration plate is provided in the second region, The thickness of the second region in the thickness direction is constant, and the thickness of the reinforcing portion is constant.

2. The piezoelectric device according to claim 1, characterized in that: The vibration plate includes a recessed portion recessed from the second surface in the second region. The groove depth of the recessed portion in the thickness direction is at least half of the thickness of the first region. The reinforcing portion is disposed in the recessed portion, and a thickness of the reinforcing portion in the thickness direction is equal to or greater than a depth of the groove.

3. The piezoelectric device according to claim 1, characterized in that: The reinforcing portion extends to a position straddling a boundary between the first region and the second region when viewed in the thickness direction.

4. The piezoelectric device according to claim 1, characterized in that: A portion of the second region that overlaps with a partition wall surrounding the opening of the substrate is defined as a base portion, a portion from the base portion to the first region is defined as an arm portion, and the reinforcing portion is provided from the base portion to the arm portion.

5. The piezoelectric device according to claim 1, characterized in that: The piezoelectric device includes a suppression portion provided on the second surface side of the vibration plate at a position sandwiching the piezoelectric element and suppressing vibration of the vibration plate.

6. The piezoelectric device according to claim 5, characterized in that: A portion of the second region overlapping with the suppression portion of the substrate is defined as a base portion, a portion from the base portion to the first region is defined as an arm portion, and the reinforcement portion is provided from the base portion to the arm portion.

7. The piezoelectric device according to claim 1, characterized in that: The vibration plate is made of a plurality of different materials, and the Young's modulus of the reinforcement portion is smaller than the Young's modulus of the material constituting the vibration plate having the highest Young's modulus.

8. The piezoelectric device according to claim 1, characterized in that: The reinforcing portion is any one of Au, Cu, and Al.

9. The piezoelectric device according to claim 1, characterized in that: The piezoelectric element is a stacked body in which a first electrode, a piezoelectric film, and a second electrode are stacked in this order from the vibration plate.

10. A piezoelectric actuator, characterized in that: A piezoelectric device according to claim 1 is provided.

11. An ultrasonic device, characterized in that: A piezoelectric device according to claim 1 is provided.

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