Piezoelectric device and liquid ejection apparatus

Abstract

To provide a piezoelectric device which dissolves residual strain of a piezoelectric layer, and can suppress reduction in a displacement amount of a piezoelectric actuator, a liquid jet head, and a liquid jet device.SOLUTION: A piezoelectric device includes: a substrate 10 where a plurality of recesses 12 are formed so as to be aligned in a first direction; a diaphragm 50; and a piezoelectric actuator 300 having a first electrode 61, a second electrode 62, a third electrode 63, a fourth electrode 80, and a piezoelectric layer 70, and has a plurality of active parts 311, 312 and 313, wherein the second electrode 62 and the third electrode 63 are provided from the edge part of a region opposite to the recesses 12 to outside of the recesses, the first electrode 61 is formed between the second electrode 61 and the third electrode 63, the second electrode 62, the third electrode 63 and the fourth electrode 80 constitute a common electrode of the plurality of active parts 311, 312 and 313, and the first electrode 61 constitutes individual electrodes each independently provided on the active parts 311.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a piezoelectric device having a piezoelectric actuator, a liquid ejection head that ejects liquid from a nozzle, and a liquid ejection apparatus, and more particularly to an ink jet recording head and an ink jet recording apparatus that eject ink as the liquid. [Background technology]

[0002] Inkjet recording heads are known as liquid ejection heads, which are one type of electronic device. Inkjet recording heads include a substrate provided with pressure chambers communicating with nozzles, a vibration plate provided on one side of the substrate, and a piezoelectric actuator having a piezoelectric layer provided on the vibration plate. Driving the piezoelectric actuator causes a pressure change in the ink in the pressure chambers, causing ink droplets to be ejected from the nozzles (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-208204 Summary of the Invention [Problem to be solved by the invention]

[0004] However, piezoelectric actuators have a problem in that repeated driving causes residual strain to accumulate in the layer of piezoelectric material, reducing the amount of displacement of the piezoelectric actuator.

[0005] It should be noted that this problem is not limited to liquid ejection heads such as ink jet recording heads, but also exists in other piezoelectric devices. [Means for solving the problem]

[0006] An aspect of the present invention that solves the above problem includes a substrate on which a plurality of recesses are formed aligned in a first direction, a vibration plate, a first electrode, a second electrode, a third electrode, and a fourth electrode stacked in this order, and a piezoelectric actuator having a piezoelectric layer between the first electrode and the fourth electrode, between the second electrode and the fourth electrode, and between the third electrode and the fourth electrode, and the piezoelectric actuator has a plurality of active sections in which the piezoelectric layer is sandwiched between the first electrode, the second electrode, the third electrode, and the fourth electrode, and the second electrode and the third electrode are provided at both ends of the recess in the first direction from an edge of a region facing the recess as viewed in the stacking direction to an outer side of the recess, and the first electrode is formed between the second electrode and the third electrode in the first direction, the second electrode, the third electrode, and the fourth electrode form a common electrode for the plurality of active sections, and the first electrode forms an individual electrode independently provided for each of the active sections. the second electrode, the third electrode, the first electrode, and the fourth electrode are arranged in this order in the stacking direction, and a distance between the first electrode and the fourth electrode in the stacking direction is narrower than a distance between the second electrode and the third electrode and the fourth electrode; The piezoelectric device is characterized by the above.

[0009] Another aspect of the present invention is a piezoelectric actuator including a substrate on which a plurality of pressure chambers communicating with nozzles that eject liquid are formed, arranged in a first direction; a vibration plate; a first electrode, a second electrode, a third electrode, and a fourth electrode stacked in this order, the piezoelectric actuator having piezoelectric layers between the first electrode and the fourth electrode, between the second electrode and the fourth electrode, and between the third electrode and the fourth electrode; and a control unit that drives the piezoelectric actuator, the piezoelectric actuator having a plurality of active portions in which the piezoelectric layer is sandwiched between the first electrode, the second electrode, the third electrode, and the fourth electrode, and the second electrode and the third electrode are arranged in a first direction at both ends of the pressure chambers in the first direction as viewed in the stacking direction. a liquid injection device characterized in that the first electrode extends from the edge of an area facing the pressure chamber to outside the pressure chamber, the first electrode is formed between the second electrode and the third electrode in the first direction, the second electrode, the third electrode and the fourth electrode form a common electrode for a plurality of the active sections, and the first electrode forms an individual electrode provided independently for each of the active sections, the control unit supplies an ejection pulse to the first electrode to eject liquid from the nozzle, and the control unit supplies a vibration damping pulse to the second electrode and the third electrode to drive the piezoelectric actuator so as not to eject liquid from the nozzle at least after the ejection pulse. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of an ink jet recording apparatus. [Figure 2] FIG. 2 is an exploded perspective view of the recording head according to the first embodiment. [Figure 3] FIG. 2 is a plan view of a flow path forming substrate according to the first embodiment. [Figure 4] 2 is an enlarged plan view of a main part of the flow path forming substrate according to the first embodiment. FIG. [Figure 5] 1 is a cross-sectional view of a recording head according to a first embodiment. [Figure 6] 1 is a cross-sectional view of a main part of a recording head according to a first embodiment. [Figure 7] FIG. 2 is a block diagram showing the electrical configuration of the ink jet recording apparatus. [Figure 8] 10 shows the drive waveforms of the bias potential, the first drive signal, and the second drive signal. [Figure 9] 5A and 5B are cross-sectional views illustrating deformation states of a piezoelectric actuator and a vibration plate. [Figure 10] 5A and 5B are cross-sectional views illustrating deformation states of a piezoelectric actuator and a vibration plate. [Figure 11] 5A and 5B are cross-sectional views illustrating deformation states of a piezoelectric actuator and a vibration plate. [Figure 12] 5A and 5B are cross-sectional views illustrating deformation states of a piezoelectric actuator and a vibration plate. [Figure 13] 5A and 5B are cross-sectional views illustrating deformation states of a piezoelectric actuator and a vibration plate. [Figure 14] 10 shows the drive waveforms of the bias potential, the first drive signal, and the third drive signal. [Figure 15] 10 shows modified drive waveforms of a bias potential, a first drive signal, and a second drive signal. [Figure 16] 10 is an enlarged plan view of a main part of a flow path forming substrate according to a second embodiment. FIG. [Figure 17] FIG. 10 is a cross-sectional view of a main part of a recording head according to a second embodiment. [Figure 18] 10 shows the bias potential and the drive waveforms of the fourth drive signal and the fifth drive signal. [Figure 19] 5A and 5B are cross-sectional views illustrating deformation states of a piezoelectric actuator and a vibration plate. [Figure 20] 5A and 5B are cross-sectional views illustrating deformation states of a piezoelectric actuator and a vibration plate. [Figure 21] 5A and 5B are cross-sectional views illustrating deformation states of a piezoelectric actuator and a vibration plate. [Figure 22] 10 is an enlarged plan view of a main part of a flow path forming substrate of a modified example of the second embodiment. FIG. [Figure 23] 10 shows modified drive waveforms of a bias potential, a fourth drive signal, and a fifth drive signal. [Figure 24] 10 shows modified drive waveforms of a bias potential, a fourth drive signal, and a fifth drive signal. [Figure 25]FIG. 10 is a cross-sectional view of a main part of a recording head according to another embodiment. [Figure 26] FIG. 10 is a cross-sectional view of a main part of a recording head according to another embodiment. [Figure 27] FIG. 10 is a cross-sectional view of a main part of a recording head according to another embodiment. [Figure 28] FIG. 10 is a cross-sectional view of a main part of a recording head according to another embodiment. [Figure 29] FIG. 10 is a cross-sectional view of a main part of a recording head according to another embodiment. [Figure 30] FIG. 10 is an enlarged plan view of a main part of a flow path forming substrate according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below based on embodiments. However, the following description illustrates one aspect of the present invention and can be modified as desired within the scope of the present invention. In each drawing, the same reference numerals indicate the same components, and their description will be omitted as appropriate. In each drawing, X, Y, and Z represent three spatial axes that are mutually orthogonal. In this specification, the directions along these axes are referred to as the X, Y, and Z directions. The direction indicated by the arrow in each drawing is the positive (+) direction, and the direction opposite the arrow is the negative (-) direction. The three spatial axes X, Y, and Z, which are not limited to the positive and negative directions, will be referred to as the X, Y, and Z axes. In each of the following embodiments, the "first direction" is the +X direction, and the "second direction" is the +Y direction, as an example. The "stacking direction" is the -Z direction. However, the configuration in the stacking direction will be described with reference to the drawings viewed in the +Z direction.

[0013] (Embodiment 1) FIG. 1 is a diagram schematically illustrating an ink jet recording apparatus 1, which is an example of a liquid ejecting apparatus according to a first embodiment of the present invention.

[0014] 1, an inkjet recording device 1, which is an example of a liquid ejection device, is a printing device that ejects and impacts ink, which is a type of liquid, as ink droplets onto a medium S, such as printing paper, and prints an image or the like by forming an array of dots on the medium S. Note that the medium S can be made of any material, such as recording paper, resin film, or cloth.

[0015] In the following, of the three spatial axes X, Y, and Z, the movement direction of the recording head 2 described below (in other words, the main scanning direction) is defined as the X axis, the transport direction of the medium S perpendicular to the main scanning direction is defined as the Y axis, the plane parallel to the nozzle surface on which the nozzles 21 of the recording head 2 are formed is defined as the XY plane, the direction intersecting the nozzle surface, i.e., the direction perpendicular to the XY plane in this embodiment, is defined as the Z axis, and ink droplets are ejected in the +Z direction along the Z axis.

[0016] The inkjet recording apparatus 1 includes a liquid container 3, a transport mechanism 4 for transporting the medium S, a control device 5, a moving mechanism 6, and an inkjet recording head 2 (hereinafter also simply referred to as the recording head 2).

[0017] The liquid containers 3 individually store multiple types of ink (for example, multiple colors) to be ejected from the recording head 2. Examples of the liquid containers 3 include cartridges that can be attached to and detached from the inkjet recording device 1, bag-shaped ink packs made of flexible film, and ink tanks that can be refilled with ink. Although not specifically shown, the liquid containers 3 store multiple types of ink with different colors and types.

[0018] The control device 5, which will be described in detail later, is configured to include, for example, a control processing unit such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array) and a storage device such as a semiconductor memory. The control device 5 comprehensively controls each element of the inkjet recording device 1, i.e., the transport mechanism 4, the movement mechanism 6, the recording head 2, etc., by executing a program stored in the storage device.

[0019] The transport mechanism 4 is controlled by the control device 5 to transport the medium S along the Y axis, and includes, for example, a transport roller 4a. Note that the transport mechanism 4 that transports the medium S is not limited to the transport roller 4a, and may transport the medium S using a belt or a drum.

[0020] The moving mechanism 6 is controlled by the control device 5 to reciprocate the recording head 2 in the +X and −X directions along the X axis. Specifically, the moving mechanism 6 of this embodiment includes a conveyor 7 and a conveyor belt 8. The conveyor 7 is a generally box-shaped structure, a so-called carriage, that houses the recording head 2 and is fixed to the conveyor belt 8. The conveyor belt 8 is an endless belt that is stretched along the X axis. As the conveyor belt 8 rotates under the control of the control device 5, the recording head 2 moves back and forth together with the conveyor 7 in the +X and −X directions along a guide rail (not shown). It is also possible to mount a liquid container 3 on the conveyor 7 together with the recording head 2.

[0021] The recording head 2 ejects ink supplied from the liquid container 3 as ink droplets from each of the multiple nozzles 21 toward the +Z direction onto the medium S under the control of the control device 5. The ejection of ink droplets from the recording head 2 is performed in parallel with the transport of the medium S by the transport mechanism 4 and the reciprocating movement of the recording head 2 by the movement mechanism 6, thereby forming an ink image on the surface of the medium S, that is, printing is performed.

[0022] Fig. 2 is an exploded perspective view of an ink jet recording head 2, which is an example of a liquid jet head according to this embodiment. Fig. 3 is a plan view of a flow path forming substrate 10 of the recording head 2, viewed in the +Z direction. Fig. 4 is an enlarged plan view of a main portion of the flow path forming substrate 10 of the recording head 2. Fig. 5 is a cross-sectional view of the recording head 2 taken along line AA' in Fig. 3. Fig. 6 is a cross-sectional view of the recording head 2 taken along line BB' in Fig. 4.

[0023] As shown in the figure, the recording head 2 of this embodiment includes a flow path forming substrate 10 as an example of a "substrate." The flow path forming substrate 10 is made of a silicon substrate, a glass substrate, an SOI substrate, or any of various ceramic substrates.

[0024] In the flow channel forming substrate 10, a plurality of pressure chambers 12 are arranged along the +X direction, which is a first direction. When viewed in the -Z direction, the pressure chambers 12 are formed so that the +X direction is the short side direction and the +Y direction is the long side direction. In this embodiment, the pressure chambers 12 have a rectangular shape when viewed in the -Z direction, but this is not particularly limited thereto. The pressure chambers 12 may be a parallelogram, a rounded rectangular shape (also known as a track shape) in which both longitudinal ends are semicircular based on a rectangular shape, or a polygonal shape. The plurality of pressure chambers 12 are arranged on a straight line along the +X direction so that their positions in the +Y direction are the same. Pressure chambers 12 adjacent to each other in the +X direction are partitioned by partition walls 11. Of course, the arrangement of the pressure chambers 12 is not particularly limited thereto. For example, the pressure chambers 12 arranged side by side in the +X direction may be arranged in a staggered arrangement, in which every other pressure chamber 12 is shifted in the +Y direction.

[0025] Furthermore, the shape of the pressure chambers 12 in this embodiment when viewed in the +Z direction may be a rectangle, a parallelogram, or a rectangular shape with semicircular ends at both longitudinal ends, i.e., a rounded rectangle, an oval shape such as an ellipse or an egg shape, a circle, a polygon, or the like. In this embodiment, the pressure chambers 12 have their short sides in the +X direction and their long sides in the +Y direction. By arranging the pressure chambers 12 side by side in the +X direction, which is the short side direction, the pressure chambers 12 can be arranged at high density. These pressure chambers 12 correspond to "recesses" provided in the "substrate."

[0026] On the +Z direction side of the flow path forming substrate 10, a communication plate 15 and a nozzle plate 20 are stacked in this order.

[0027] The communication plate 15 is provided with a nozzle communication passage 16 that connects the pressure chamber 12 and the nozzle 21 to each other.

[0028] The communication plate 15 is also provided with a first manifold portion 17 and a second manifold portion 18 which constitute a part of a manifold 100 which serves as a common liquid chamber to which the plurality of pressure chambers 12 are commonly connected. The first manifold portion 17 is provided so as to penetrate the communication plate 15 in the +Z direction. The second manifold portion 18 is provided so as to open on the surface on the +Z direction side without penetrating the communication plate 15 in the +Z direction.

[0029] Furthermore, the communication plate 15 is provided with supply communication passages 19 that communicate with one end of the pressure chamber 12 in the direction along the Y axis, independently for each pressure chamber 12. The supply communication passages 19 communicate between the second manifold portion 18 and the pressure chamber 12, and supply ink in the manifold 100 to the pressure chamber 12.

[0030] A silicon substrate, an SOI substrate, various ceramic substrates, a metal substrate such as a stainless steel substrate, or the like can be used as the communicating plate 15. It is preferable that the communicating plate 15 be made of a material having approximately the same thermal expansion coefficient as the flow path forming substrate 10. By using materials having approximately the same thermal expansion coefficient for the flow path forming substrate 10 and the communicating plate 15, it is possible to reduce the occurrence of warping due to heat caused by differences in the thermal expansion coefficients.

[0031] The nozzle plate 20 is provided on the side of the communication plate 15 opposite to the flow path forming substrate 10, that is, on the surface on the +Z direction side.

[0032] The nozzle plate 20 is formed with nozzles 21 that communicate with each pressure chamber 12 via nozzle communication passages 16. In this embodiment, the nozzles 21 are arranged in two rows spaced apart in the +Y direction, with the nozzles 21 aligned in a line along the +X direction. That is, the nozzles 21 in each row are aligned at the same position in the +Y direction. Of course, the arrangement of the nozzles 21 is not particularly limited to this. For example, the nozzles 21 may be aligned in a line along the +X direction, but alternately aligned in a staggered arrangement, in which the nozzles 21 are aligned in a line along the +X direction but shifted in the +Y direction. Such a nozzle plate 20 may be made of a silicon substrate, a glass substrate, an SOI substrate, various ceramic substrates, a metal substrate such as a stainless steel substrate, or an organic substrate such as a polyimide resin. It is preferable that the nozzle plate 20 be made of a material with approximately the same thermal expansion coefficient as the communicating plate 15. By using materials with approximately the same thermal expansion coefficient for the nozzle plate 20 and the communicating plate 15, warping due to heat caused by differences in thermal expansion coefficients can be reduced. The surface of the nozzle plate 20 in the −Z direction where the nozzles 21 open serves as a liquid ejection surface 20a.

[0033] A vibration plate 50 and a piezoelectric actuator 300 are sequentially stacked on the surface of the flow path forming substrate 10 on the -Z direction side. That is, the flow path forming substrate 10, the vibration plate 50, and the piezoelectric actuator 300 are stacked in this order toward the -Z direction. Details of the vibration plate 50 and the piezoelectric actuator 300 will be described later.

[0034] As shown in FIGS. 2 and 5 , a protective substrate 30 having approximately the same size as the flow path forming substrate 10 is bonded to the surface of the flow path forming substrate 10 in the −Z direction. The protective substrate 30 has holding portions 31, which are spaces that protect the piezoelectric actuators 300. The holding portions 31 are provided independently for each row of the piezoelectric actuators 300 arranged side by side in the +X direction, and two holding portions 31 are formed side by side in the +Y direction. The protective substrate 30 also has a through hole 32 that penetrates in the +Z direction between the two holding portions 31 arranged side by side in the +Y direction. Ends of a first individual lead electrode 91, a first common lead electrode 92, and a second common lead electrode 93 drawn from the electrodes of the piezoelectric actuators 300 extend so as to be exposed within the through hole 32. The first individual lead electrode 91, the first common lead electrode 92, and the second common lead electrode 93 are electrically connected to a wiring substrate 120 connected to the control device 5 within the through hole 32.

[0035] 5, a case member 40 is fixed on the protective substrate 30. The case member 40, which defines, together with the flow path forming substrate 10, a manifold 100 that communicates with the multiple pressure chambers 12. The case member 40 has substantially the same shape as the above-mentioned communicating plate 15 in a plan view seen in the +Z direction, and is bonded to the protective substrate 30 and also to the above-mentioned communicating plate 15. In this embodiment, the case member 40 is bonded to the communicating plate 15. Although not specifically shown, the case member 40 is also bonded to the protective substrate 30.

[0036] The case member 40 has a recess 41 on the protective substrate 30 side that is deep enough to accommodate the flow path forming substrate 10 and the protective substrate 30. The case member 40 also has a third manifold 42 that communicates with the first manifold 17. The third manifold 42 has a recessed shape that opens to a surface in the +Z direction. The first manifold 17 and the second manifold 18 provided in the communication plate 15 and the third manifold 42 provided in the case member 40 form a manifold 100 of this embodiment. The manifold 100 is provided continuously along the +X direction in which the pressure chambers 12 are arranged side by side. The case member 40 also has an inlet 44 that communicates with the manifolds 100 and supplies ink to each manifold 100. The case member 40 also has a connection port 43 that communicates with a through hole 32 in the protective substrate 30, which will be described in detail later, and through which a wiring substrate 120 is inserted.

[0037] Furthermore, a compliance substrate 45 is provided on the surface of the communicating plate 15 on the +Z direction side where the first manifold portion 17 and the second manifold portion 18 open. This compliance substrate 45 seals the openings of the first manifold portion 17 and the second manifold portion 18 on the liquid ejection surface 20a side. In this embodiment, such a compliance substrate 45 includes a sealing film 46 made of a flexible thin film, and a fixed substrate 47 made of a hard material such as metal. The region of the fixed substrate 47 facing the manifold 100 is an opening 48 that is completely removed in the thickness direction, and therefore one surface of the manifold 100 forms a compliance portion 49 that is a flexible portion sealed only by the flexible sealing film 46.

[0038] The diaphragm 50 and the piezoelectric actuator 300 of this embodiment will be described.

[0039] As shown in FIGS. 5 and 6 , the diaphragm 50 is provided in the −Z direction of the flow path forming substrate 10 and includes an elastic film 51 made of silicon oxide provided on the flow path forming substrate 10 side and an insulating film 52 made of zirconium oxide provided on the −Z direction side of the elastic film 51. The flow paths, such as the pressure chambers 12, are formed by anisotropically etching the flow path forming substrate 10, and the −Z direction surface of the pressure chambers 12 is defined by the elastic film 51. Note that in this embodiment, the elastic film 51 and the insulating film 52 are laminated to form the diaphragm 50, but this is not particularly limited, and the diaphragm 50 may include only one of the elastic film 51 and the insulating film 52. The diaphragm 50 may also have a configuration in which other layers are laminated in addition to the elastic film 51 and the insulating film 52.

[0040] 4 to 6, the piezoelectric actuator 300, also referred to as a piezoelectric element, is a pressure generating means that generates a pressure change in the ink inside the pressure chamber 12. The piezoelectric actuator 300 includes a first electrode 61, a second electrode 62, a third electrode 63, a fourth electrode 80, and a piezoelectric layer 70.

[0041] The first electrode 61, the second electrode 62, and the third electrode 63 are located in the +Z direction relative to the fourth electrode 80. In other words, the fourth electrode 80 is located in the -Z direction relative to the first electrode 61, the second electrode 62, and the third electrode 63. In other words, the first electrode 61, the second electrode 62, the third electrode 63, and the fourth electrode 80 are stacked in this order toward the -Z direction. Here, the stacking of the first electrode 61, the second electrode 62, the third electrode 63, and the fourth electrode 80 means that another layer is interposed between the first electrode 61, the second electrode 62, the third electrode 63, and the fourth electrode 80 in the direction along the Z axis. In this embodiment, the piezoelectric actuator 300 has a piezoelectric layer 70 between the first electrode 61 and the fourth electrode 80 in the direction along the Z axis. The piezoelectric actuator 300 also has a piezoelectric layer 70 between the second electrode 62 and the fourth electrode 80. Furthermore, the piezoelectric actuator 300 has a piezoelectric layer 70 between the third electrode 63 and the fourth electrode 80. Note that the piezoelectric layer 70 is not provided on the +Z direction side of the first electrode 61, which is the pressure chamber 12 side.

[0042] The first electrode 61, the second electrode 62, and the third electrode 63 are provided on the −Z direction surface of the diaphragm 50. In other words, the first electrode 61, the second electrode 62, and the third electrode 63 are provided at the same position in the direction along the Z axis.

[0043] The second electrode 62 and the third electrode 63 are provided at both ends of the pressure chamber 12 in the +X direction, i.e., at the end in the +X direction and the end in the −X direction, from the end of the region facing the pressure chamber 12 to the outside of the pressure chamber 12, as viewed in the −Z direction, which is the stacking direction. In this embodiment, the second electrode 62 is provided at the end in the −X direction of the pressure chamber 12, from the edge of the region facing the pressure chamber 12 to above the partition wall 11 on the outside of the pressure chamber 12 in the −X direction, as viewed in the −Z direction. The third electrode 63 is provided at the end in the +X direction of the pressure chamber, from the edge of the region facing the pressure chamber 12 as viewed in the −Z direction to above the partition wall 11 on the outside of the pressure chamber 12 in the +X direction.

[0044] The second electrode 62 and the third electrode 63 provided for one pressure chamber 12 are provided in electrical conduction on the flow-channel-forming substrate 10. Specifically, the second electrode 62 and the third electrode 63 are connected to a common communication portion 64 provided continuously in the +X direction on one of the outer sides of the pressure chamber 12 in the direction along the Y axis, thereby electrically conducting through the common communication portion 64. In this embodiment, the second electrode 62, the third electrode 63, and the common communication portion 64 are provided in a continuous manner by patterning the same metal layer. Of course, the second electrode 62, the third electrode 63, and the common communication portion 64 may each be formed in a different layer. In other words, the electrical conduction between the second electrode 62 and the third electrode 63 on the flow-channel-forming substrate 10 also includes conduction via another member. Furthermore, the phrase "the second electrode 62 and the third electrode 63 are continuous on the flow-path forming substrate 10" includes both cases where the second electrode 62 and the third electrode 63 are directly continuous on the flow-path forming substrate 10 and cases where the second electrode 62 and the third electrode 63 are continuous on the vibration plate 50 provided on the flow-path forming substrate 10. In other words, "on the substrate" includes both directly above the substrate and above where another member is interposed between them.

[0045] Furthermore, the second electrode 62 and the third electrode 63 are provided continuously, without being separated, on the partition wall 11 between the pressure chambers 12 adjacent to each other in the +X direction. In other words, for two pressure chambers 12 aligned in the +X direction, the third electrode 63 provided for one pressure chamber 12 and the second electrode 62 provided for the other pressure chamber 12 are provided continuously, without interruption, on the partition wall 11 between the two pressure chambers 12. In this embodiment, the second electrode 62 and the third electrode 63 of two pressure chambers 12 aligned in the +X direction are referred to by separating them at the center of the partition wall 11 in the +X direction.

[0046] The first electrode 61 is disposed between the second electrode 62 and the third electrode 63 in the +X direction. Here, the fact that the first electrode 61 is formed between the second electrode 62 and the third electrode 63 in the +X direction means that the center of the first electrode 61 in the +X direction is disposed between the centers of the second electrode 62 and the third electrode 63 in the +X direction. In this embodiment, the first electrode 61, the second electrode 62, and the third electrode 63 are disposed on the flat surface of the diaphragm 50 in the -Z direction, and are thereby disposed at the same position in the -Z direction. Therefore, the first electrode 61, the second electrode 62, and the third electrode 63 are disposed at positions that do not overlap with each other when viewed in the -Z direction. In other words, the first electrode 61 is disposed with a gap between it and the second electrode 62 in the +X direction of the second electrode 62, and is disposed with a gap between it and the third electrode 63 in the -X direction of the third electrode 63. Of course, if the first electrode 61, the second electrode 62, and the third electrode 63 are arranged at different positions in the -Z direction, the first electrode 61, the second electrode 62, and the third electrode 63 may be arranged at positions where they partially overlap when viewed in the -Z direction.

[0047] The piezoelectric layer 70 is provided continuously in the +X direction so as to have a predetermined width in the +Y direction. That is, the piezoelectric layer 70 is provided continuously in the +X direction over the first electrode 61, the second electrode 62, and the third electrode 63. The piezoelectric layer 70 is provided continuously and without interruption in the +X direction for the multiple pressure chambers 12. The piezoelectric layer 70 is provided so as to have approximately the same thickness in the +X direction. Note that recesses corresponding to the partition walls 11 may be formed in the piezoelectric layer 70. The width of the recesses in the +X direction may be narrower than the width of the partition walls 11. The recesses may be provided so as to penetrate the piezoelectric layer 70 in the +Z direction, which is the thickness direction, or may be provided partway through the thickness of the piezoelectric layer 70. That is, the piezoelectric layer 70 may be completely removed from the bottom surface of the recess in the +Z direction, or a portion of the piezoelectric layer 70 may remain.

[0048] The piezoelectric layer 70 is formed on the nozzle 21 side along the Y axis outside the pressure chamber 12 and with a length shorter than the end of the first electrode 61, and the end of the first electrode 61 on the nozzle 21 side is not covered by the piezoelectric layer 70.

[0049] Furthermore, the piezoelectric layer 70 is formed on the opposite side of the nozzle 21 along the Y axis outside the pressure chamber 12 and with a length shorter than the ends of the second electrode 62 and the third electrode 63, and the ends of the second electrode 62 and the third electrode 63 on the opposite side of the nozzle 21, i.e., the parts that communicate with the common communication part 64, are not covered by the piezoelectric layer 70.

[0050] Such a piezoelectric layer 70 is formed using a piezoelectric material made of a complex oxide with a perovskite structure represented by the general formula ABO3. Examples of the complex oxide with a perovskite structure used for the piezoelectric layer 70 include lead-based piezoelectric materials containing lead and lead-free piezoelectric materials containing no lead. In this embodiment, lead zirconate titanate (PZT) is used for the piezoelectric layer 70. Because the diaphragm 50 contains zirconium oxide, the Young's modulus of the diaphragm 50 is greater than the Young's modulus of the piezoelectric layer 70 made of lead zirconate titanate. Furthermore, by using zirconium oxide on the piezoelectric layer 70 side of the diaphragm 50, it is possible to prevent lead contained in the piezoelectric layer 70 from diffusing into the diaphragm 50.

[0051] The fourth electrode 80 is provided on the surface of the piezoelectric layer 70 on the -Z direction side. When viewed in the +Z direction, the fourth electrode 80 covers the pressure chamber 12 in the +X direction. That is, when viewed in the +Z direction, the fourth electrode 80 is disposed at a position overlapping the pressure chamber 12 in the +X direction. In this embodiment, the fourth electrode 80 is provided continuously across the surface of the piezoelectric layer 70 on the -Z direction side. That is, the fourth electrode 80 is provided continuously so as to include positions overlapping the first electrode 61, the second electrode 62, and the third electrode 63 when viewed in the +Z direction. In other words, the piezoelectric layer 70 is formed between the first electrode 61 and the fourth electrode 80, between the second electrode 62 and the fourth electrode 80, and between the third electrode 63 and the fourth electrode 80. Furthermore, in this embodiment, the first electrode 61, the second electrode 62, and the third electrode 63 are arranged at the same position in the +Z direction, so that the distance between the first electrode 61 and the fourth electrode 80 is the same as the distance between the second electrode 62 and the third electrode and the fourth electrode 80 in the +Z direction.

[0052] In such a piezoelectric actuator 300, when a voltage is applied between two opposing electrodes, a portion sandwiched between the two electrodes and where piezoelectric strain occurs in the piezoelectric layer 70 is referred to as an active portion. In this embodiment, the portion sandwiched between the first electrode 61 and the fourth electrode 80 is referred to as a first active portion 311, the portion sandwiched between the second electrode 62 and the fourth electrode 80 is referred to as a second active portion 312, and the portion sandwiched between the third electrode 63 and the fourth electrode 80 is referred to as a third active portion 313. In other words, a total of three first active portions 311, one second active portion 312, and one third active portion 313 are provided for one pressure chamber 12. In two pressure chambers 12 adjacent to each other in the +X direction, the second electrode 62 provided for one pressure chamber 12 is continuous with the third electrode 63 provided for the other pressure chamber 12, and therefore the second active portion 312 provided for one pressure chamber 12 is continuous with the third active portion 313 provided for the other pressure chamber 12. In this embodiment, the second active portion 312 and the third active portion 313 of two pressure chambers 12 aligned in the +X direction are referred to as being separated at the position separating the second electrode 62 and the third electrode 63 described above, that is, at the center of the partition wall 11 in the +X direction.

[0053] The first electrodes 61 are individually separated for each pressure chamber 12, thereby constituting individual electrodes independently provided for each active section. Here, the fact that the first electrodes 61 are individual electrodes for each active section means that the multiple first electrodes 61 provided in the multiple first active sections 311 on the flow path forming substrate 10 are not electrically connected to each other and are provided independently. Furthermore, "on the flow path forming substrate 10" includes not only directly above the flow path forming substrate 10 as described above, but also above a state in which another member, for example, the vibration plate 50, is interposed therebetween.

[0054] The second electrode 62 and the third electrode 63 constitute a common electrode for the plurality of active sections. Here, the second electrode 62 being a common electrode for the plurality of active sections means that the plurality of second electrodes 62 provided in the plurality of second active sections 312 are electrically connected to each other on the flow path forming substrate 10. Furthermore, the third electrode 63 being a common electrode for the plurality of active sections means that the plurality of third electrodes 63 provided in the plurality of third active sections 313 are electrically connected to each other on the flow path forming substrate 10. In this embodiment, the second electrode 62 and the third electrode 63 are electrodes common to the second active section 312 and the third active section 313 corresponding to one pressure chamber 12. Therefore, the second electrode 62 and the third electrode 63 are both common electrodes common to the plurality of second active sections 312 and the plurality of third active sections 313 corresponding to the plurality of pressure chambers 12.

[0055] By using the second electrode 62 and the third electrode 63 as common electrodes for the plurality of second active portions 312 and the plurality of third active portions 313 in this way, it is not necessary to provide space to separate the second electrode 62 and the third electrode 63 on the partition wall 11, and it is possible to arrange the pressure chambers 12 at high density in the +X direction. Furthermore, since it is not necessary to draw out individual wiring from the second electrode 62 and the third electrode 63 on the flow path forming substrate 10, there is no need for space for drawing out and routing the wiring, and the recording head 2 can be made smaller.

[0056] The fourth electrode 80 constitutes a common electrode shared by the multiple active portions. Here, the fact that the fourth electrode 80 is a common electrode for the multiple active portions means that the fourth electrode 80 is provided in common to all of the active portions, that is, the multiple first active portions 311, the multiple second active portions 312, and the multiple third active portions 313.

[0057] In this piezoelectric actuator 300, the portion facing the pressure chamber 12 in the direction along the Z axis is a flexible portion, and the portion outside the pressure chamber 12 is a non-flexible portion.

[0058] 4, a first individual lead electrode 91, which is a lead-out wiring, is connected to each first electrode 61. One end of the first individual lead electrode 91 is connected to one end of the first electrode 61, and the other end is drawn out onto the flow path forming substrate 10 so as to be positioned between two rows of pressure chambers 12 in the Y axis. The first individual lead electrode 91 is provided independently for each of the first electrodes 61, so that the first electrodes 61 are not electrically connected to each other.

[0059] 3 and 4, a first common lead electrode 92, which is an extraction wiring, is connected to the second electrode 62 and the third electrode 63. One end of the first common lead electrode 92 is connected to one of the second electrodes 62 and the third electrode 63, which are arranged side by side along the X-axis, and the other end is extracted so as to be positioned between two rows of pressure chambers 12 along the Y-axis. Because the second electrode 62 and the third electrode 63 are arranged continuously, it is sufficient that the first common lead electrode 92 is connected to either the second electrode 62 or the third electrode 63.

[0060] 3, a second common lead electrode 93, which is a lead wiring, is connected to the fourth electrode 80. One end of the second common lead electrode 93 is connected to one end of the fourth electrode 80 in the direction along the X-axis, and the other end is drawn out so as to be positioned between the two rows of pressure chambers 12 in the Y-axis.

[0061] A flexible wiring board 120 is connected to the ends of the first individual lead electrode 91, the first common lead electrode 92, and the second common lead electrode 93 opposite to the ends connected to the piezoelectric actuator 300. A drive circuit 121 having a switching element for driving the piezoelectric actuator 300 is mounted on the wiring board 120. The end of the wiring board 120 opposite to the ends connected to the first individual lead electrode 91, the first common lead electrode 92, and the second common lead electrode 93 is connected to the control device 5, and a control signal from the control device 5 is supplied to the recording head 2 via the wiring board 120.

[0062] The control device 5 of this embodiment will now be described with reference to Fig. 7. Fig. 7 is a block diagram showing the control configuration of the ink jet recording apparatus 1.

[0063] 7, the inkjet recording apparatus 1 includes a printer controller 210, which is a control unit of this embodiment, and a print engine 220. The printer controller 210 is an element that controls the entire inkjet recording apparatus 1, and in this embodiment, is provided within a control device 5 provided in the inkjet recording apparatus 1.

[0064] The printer controller 210 comprises an external interface 211 (hereinafter referred to as external I / F 211), a RAM 212 that temporarily stores various data, a ROM 213 that stores control programs and the like, and a control processing unit 214 that includes a CPU, etc. The printer controller 210 also comprises an oscillator circuit 215 that generates a clock signal, a drive signal generation unit 216 that generates a drive signal to be supplied to the recording head 2, and an internal interface 217 (hereinafter referred to as internal I / F 217) that transmits to the print engine 220 dot pattern data (bitmap data) developed based on the drive signal and print data, etc.

[0065] The external I / F 211 receives print data, which is composed of, for example, character codes, graphic functions, image data, etc., from an external device 230 such as a host computer. In addition, a busy signal (BUSY) and an acknowledge signal (ACK) are output to the external device 230 via this external I / F 211.

[0066] The RAM 212 functions as a receive buffer 212A, an intermediate buffer 212B, an output buffer 212C, and a work memory (not shown). The receive buffer 212A temporarily stores print data received by the external I / F 211, the intermediate buffer 212B stores intermediate code data converted by the control processing unit 214, and the output buffer 212C stores dot pattern data. This dot pattern data is composed of print data obtained by decoding (translating) the gradation data.

[0067] The ROM 213 also stores control programs (control routines) for performing various data processes, as well as font data, graphic functions, and the like.

[0068] The control processing unit 214 reads the print data from the receive buffer 212A and converts the print data to obtain intermediate code data, which is then stored in the intermediate buffer 212B. The control processing unit 214 also analyzes the intermediate code data read from the intermediate buffer 212B and expands the intermediate code data into dot pattern data by referencing the font data, graphic functions, and the like stored in the ROM 213. The control processing unit 214 then performs any necessary decoration processing and then stores the expanded dot pattern data in the output buffer 212C.

[0069] Then, when one line of dot pattern data is obtained by the recording head 2, this one line of dot pattern data is output to the recording head 2 via the internal I / F 217. Furthermore, when one line of dot pattern data is output from the output buffer 212C, the expanded intermediate code data is erased from the intermediate buffer 212B, and the expansion process is performed on the next intermediate code data.

[0070] The print engine 220 includes a recording head 2, a transport mechanism 4, and a movement mechanism 6. The transport mechanism 4 and the movement mechanism 6 have been described above, so a duplicated description will be omitted.

[0071] The recording head 2 includes a drive circuit 121 having a shift register 122, a latch circuit 123, a level shifter 124, and a switch 125, and a piezoelectric actuator 300. The shift register 122, the latch circuit 123, the level shifter 124, and the switch 125 generate an application pulse from a drive signal generated by a drive signal generation unit 216. Here, the application pulse is actually applied to the piezoelectric actuator 300.

[0072] Here, we will explain the drive waveforms that represent the drive signals generated by drive signal generation unit 216. Fig. 8 shows drive waveforms that represent bias potential vbs, first drive signal 201, and second drive signal 202. Figs. 9 to 13 are cross-sectional views taken along line BB' that show the piezoelectric actuator 300 and diaphragm 50 deformed by the drive signals.

[0073] 8, the drive signal generation unit 216 generates, as drive signals, a first drive signal 201 and a second drive signal 202. The first drive signal 201 is supplied to the first electrode 61, and the second drive signal 202 is supplied to the second electrode 62 and the third electrode 63.

[0074] The first drive signal 201 and the second drive signal 202 are repeatedly generated by a drive signal generation unit 216 for each unit period T defined by a clock signal oscillated by an oscillation circuit 215. The unit period T is also called an ejection period T or a recording period T, and corresponds to one pixel of an image or the like to be printed on a medium S. In this embodiment, the unit period T is divided into two periods: a first period T1 and a second period T2.

[0075] The first drive signal 201 is a signal having an ejection pulse DP for a first period T1 within one recording cycle T, which drives the first active portion 311 of the piezoelectric actuator 300 to eject ink droplets from the nozzles 21, and is repeatedly generated for each recording cycle T. When a dot pattern for one line (one raster) is formed in the recording area of ​​the medium S during printing, the ejection pulse DP of the first drive signal 201 is selectively supplied to the first active portion 311 of the piezoelectric actuator 300 corresponding to each nozzle 21. In other words, the control unit generates an application pulse from the head control signal and the first drive signal 201 for each first active portion 311 corresponding to each nozzle 21, and supplies the application pulse to the piezoelectric actuator 300.

[0076] The applied pulse generated from the first drive signal 201 is supplied to the first electrode 61, which is an individual electrode of each first active unit 311. A bias potential vbs is supplied to the fourth electrode 80, which is a common electrode for the multiple first active units 311. Therefore, the potential applied to the first electrode 61 by the applied pulse is referenced to the bias potential vbs applied to the fourth electrode 80. The bias potential vbs supplied to the fourth electrode 80 corresponds to the "second potential" in the claims. In this embodiment, the applied pulse supplied to the first electrode 61 is described using the first drive signal 201. Each potential of the first drive signal 201 is described as a potential supplied to the first electrode 61. However, as described above, the voltage actually applied between the first electrode 61 and the fourth electrode 80 is the potential difference between the potential supplied to the first electrode 61 by the first drive signal 201 and the bias potential vbs supplied to the fourth electrode 80.

[0077] The ejection pulse DP includes a first expansion element P1, a first expansion sustain element P2, a first contraction element P3, a first contraction sustain element P4, and a first return element P5. Furthermore, the applied pulse generated from the first drive signal 201 always supplies a first potential V1, which is an intermediate potential, to the first electrode 61 when the ejection pulse DP is not supplied. Therefore, within a unit period T of the first drive signal 201, a first reference element B1 and a second reference element B2, which supply the first potential V1, are provided before and after the ejection pulse DP. In other words, the first drive signal 201 generates the first reference element B1, the ejection pulse DP, and the second reference element B2, in this order, within the unit period T. Furthermore, the second reference element B2 is generated during a period that includes the second period T2.

[0078] The first reference element B1 and the second reference element B2 maintain a state in which the piezoelectric actuator 300 and the diaphragm 50 are deflected and deformed toward the +Z direction toward the pressure chamber 12 by continuously applying a first potential V1, which is greater than the bias potential vbs, to the first electrode 61. This maintains the volume of the pressure chamber 12 at a first volume that is contracted from the reference volume. In this embodiment, the deformation of the piezoelectric actuator 300 and the diaphragm 50 in the +Z direction toward the pressure chamber 12 refers to the deformation of the surface of the piezoelectric actuator 300 facing the +Z direction toward the pressure chamber 12, as shown in FIG. 9 . However, if the initial deflection of the piezoelectric actuator 300 deforms the surface to protrude convexly toward the -Z side, which is the opposite side to the pressure chamber 12, this also includes the deformation of the piezoelectric actuator 300 by the first reference element B1 and the second reference element B2 so that the amount of protrusion in the -Z direction decreases while the surface remains deflected convexly toward the -Z side. In other words, when the piezoelectric actuator 300 and the diaphragm deform in the +Z direction toward the pressure chamber 12, this also includes the case where the surface on the -Z side opposite the pressure chamber 12 remains convex. The orientation of the piezoelectric actuator 300 determined by the first reference element B1 and the second reference element B2 is determined by the characteristics of the laminated film including the diaphragm 50 that determine the initial deflection of the piezoelectric actuator 300, i.e., the internal stress and neutral line position of each film, and the magnitude of the first potential V1 due to the first reference element B1 and the second reference element B2 relative to the displacement characteristics of the piezoelectric layer 70, i.e., the amount of displacement. The reference volume refers to the volume of the pressure chamber 12 when no voltage is applied to the piezoelectric actuator 300, i.e., when the first active portion 311, the second active portion 312, and the third active portion 313 are not driven.

[0079] The first expansion element P1 applies a first potential V1 to a second potential V2 to the first electrode 61, causing the piezoelectric actuator 300 and the vibration plate 50 to deform in the -Z direction, as shown in Fig. 10. This causes the volume of the pressure chamber 12 to expand from the first volume to the second volume, drawing the ink meniscus in the nozzle 21 toward the pressure chamber 12, and simultaneously supplying ink to the pressure chamber 12 from the manifold 100 side.

[0080] The first expansion maintaining element P2 continues to apply the second potential V2 to the first electrode 61, and maintains the volume of the pressure chamber 12 expanded by the first expansion element P1 at the second volume for a certain period of time.

[0081] The first contraction element P3 applies a second potential V2 to a third potential V3 to the first electrode 61, causing the piezoelectric actuator 300 and the diaphragm 50 to deform in the +Z direction, as shown in Fig. 11. This causes the volume of the pressure chamber 12 to suddenly decrease from the second volume to the third volume, pressurizing the ink in the pressure chamber 12 and causing an ink droplet to be ejected from the nozzle 21.

[0082] The first contraction maintaining element P4 continues to apply the third potential V3 to the first electrode 61, maintaining the volume of the pressure chamber 12 at the third volume for a certain period of time. While this first contraction maintaining element P4 is being supplied, the ink pressure in the pressure chamber 12, which has decreased due to the ejection of the ink droplet, decays by repeatedly rising and falling due to its natural vibration.

[0083] The first return element P5 applies a potential from the fourth potential V4 to the first potential V1 to the first electrode 61, causing the piezoelectric actuator 300 and the diaphragm 50 to deform in the -Z direction, as shown in Fig. 12. This causes the volume of the pressure chamber 12 to expand and return from the third volume to the first volume.

[0084] Thereafter, the first potential V1 continues to be applied to the first active portion 311 by the second reference element B2, thereby maintaining the volume of the pressure chamber 12 at the first volume which is smaller than the reference volume.

[0085] In such a first drive signal 201, the ejection pulse DP is not supplied to the first electrode 61 of the first active section 311 of the piezoelectric actuator 300 that does not eject ink droplets, and the first potential V1 of the first reference element B1 and the second reference element B2 is applied as an intermediate potential.

[0086] As shown in FIG. 8 , the second drive signal 202 is repeatedly generated by the drive signal generation unit 216 for each unit period T defined by a clock signal oscillated by the oscillation circuit 215. In this embodiment, the second drive signal is a signal having a damping pulse SVP for a second period T2 within one recording period T, which drives the second active portion 312 and the third active portion 313 of the piezoelectric actuator 300 to prevent ink droplets from being ejected from the nozzles 21, and is repeatedly generated for each recording period T. Then, when forming a dot pattern for one line (one raster) in the recording area of ​​the medium S during printing, the damping pulse SVP of the second drive signal 202 is selectively applied to the second active portion 312 and the third active portion 313 of the piezoelectric actuator 300 corresponding to each nozzle 21. That is, the control unit generates application pulses for the second active portion 312 and the third active portion 313 corresponding to each nozzle 21 from the head control signal and the second drive signal 202 and supplies the application pulses to the piezoelectric actuator 300.

[0087] The applied pulse generated from such a second drive signal 202 is supplied to the second electrode 62 and the third electrode 63, which are common electrodes for the plurality of second active units 312 and the plurality of third active units 313. Furthermore, as described above, the bias potential vbs is supplied to the fourth electrode 80, which is a common electrode for the plurality of second active units 312 and the plurality of third active units 313. Therefore, the potentials applied to the second electrode 62 and the third electrode 63 by the applied pulse have the bias potential vbs applied to the fourth electrode 80 as a reference potential. In this embodiment, the applied pulses supplied to the second electrode 62 and the third electrode 63 are described using the second drive signal 202. Furthermore, each potential of the second drive signal 202 is described as a potential supplied to the second electrode 62 and the third electrode 63. However, as described above, the voltage actually applied between the second electrode 62 and the third electrode 63 and the fourth electrode 80 is the potential difference between the potential supplied to the second electrode 62 and the third electrode 63 of the second drive signal 202 and the bias potential vbs supplied to the fourth electrode 80.

[0088] Here, the vibration damping pulse SVP supplied to the second electrode 62 and the third electrode 63 includes a second expansion element P10, a second expansion maintaining element P11, and a second return element P12. Furthermore, the applied pulse generated from the second drive signal 202 always supplies the second electrode 62 and the third electrode 63 with a fourth potential V4, which is an intermediate potential, when the vibration damping pulse SVP is not supplied. Therefore, within the unit period T of the second drive signal 202, a third reference element B3 and a fourth reference element B4, which supply the fourth potential V4, are included before and after the vibration damping pulse SVP. In other words, the second drive signal 202 generates the third reference element B3, the vibration damping pulse SVP, and the fourth reference element B4, in this order, within the unit period T. Furthermore, the third reference element B3 is generated during a period that includes the first period T1.

[0089] The third reference element B3 and the fourth reference element B4 supply a fourth potential V4, which is the same as the bias potential vbs, to the second electrode 62 and the third electrode 63, thereby maintaining a state in which the second active portion 312 and the third active portion 313 are not driven. The third reference element B3 is supplied during the first period T1 in which the piezoelectric actuator 300 is driven by the ejection pulse DP. Therefore, when the ejection pulse DP drives the first active portion 311 to eject ink droplets from the nozzle 21, the damping pulse SVP does not affect the ejection of ink droplets by the ejection pulse DP because the second active portion 312 and the third active portion 313 are not driven. Furthermore, because the third reference element B3 does not drive the second active portion 312 and the third active portion 313, the volume of the pressure chamber 12 after the first period T1 of the third reference element B3 is the same as after the ejection pulse DP, i.e., the first volume determined by the second reference element B2.

[0090] The second expansion element P10, the second expansion maintenance element P11, and the second return element P12 are supplied to the second electrode 62 and the third electrode 63 during the second period T2, as described above, i.e., while the second reference element B2 of the first drive signal 201 is supplied.

[0091] The second expansion element P10 applies a fifth potential V5 to the second electrode 62 and the third electrode 63, and as shown in Fig. 13, deforms the piezoelectric actuator 300 and the diaphragm 50 in the -Z direction, which is the opposite side to the pressure chamber 12. As a result, the volume of the pressure chamber 12 expands from the first volume to the fourth volume.

[0092] The second active portion 312 and the third active portion 313 are provided from the region overlapping with the pressure chamber 12 to the region overlapping with the partition wall 11 when viewed in the +Z direction, that is, so as to straddle the wall of the pressure chamber 12. Therefore, when the second active portion 312 and the third active portion 313 are driven, the piezoelectric actuator 300 and the diaphragm 50 deform in the -Z direction, which is the opposite side to the pressure chamber 12. In this embodiment, the deformation of the piezoelectric actuator 300 and the diaphragm 50 in the -Z direction, which is the opposite side to the pressure chamber 12, refers to the deformation of the surface of the piezoelectric actuator 300 facing in the -Z direction, which is the opposite side to the pressure chamber 12, so that it deforms in a convex shape, as shown in FIG. However, in this embodiment, when the initial deflection of the piezoelectric actuator 300 and the diaphragm 50 is deformed by the second reference element B2 such that the surfaces in the +Z direction protrude convexly, the deformation by the second expansion element P10 also includes the piezoelectric actuator 300 and the diaphragm 50 remaining deformed so as to protrude convexly in the +Z direction, but with the amount of protrusion in the +Z direction reduced. In other words, the deformation of the piezoelectric actuator 300 and the diaphragm 50 in the -Z direction opposite the pressure chamber 12 also includes the piezoelectric actuator 300 and the diaphragm 50 remaining deformed so that the surfaces in the +Z direction facing the pressure chamber 12 protrude convexly. The orientation of the piezoelectric actuator 300 and the diaphragm 50 due to the second expansion element P10 is determined by the orientation of the piezoelectric actuator 300 relative to the second reference element B2 and the magnitude of the fifth potential V5, i.e., the amount of displacement.

[0093] Furthermore, it is preferable that the fifth potential V5 of the second expansion element P10 be the same as the first potential V1 of the first reference element B1 of the first drive signal 201 or the third potential V3 of the first contraction element P3. By setting the fifth potential V5 of the second expansion element P10 to the same as the first potential V1 of the first reference element B1 of the first drive signal 201 or the third potential V3 of the first contraction element P3, the circuitry of the drive signal generation unit 216 can be simplified compared to when different potentials are generated.

[0094] The second expansion maintaining element P11 continues to apply the fifth potential V5 to the second electrode 62 and the third electrode 63, and maintains the volume of the pressure chamber 12 expanded by the second expansion element P10 at the fourth volume for a certain period of time.

[0095] The second return element P12 applies a potential from the fifth potential V5 to the fourth potential V4 to the second electrode 62 and the third electrode 63, thereby deforming the piezoelectric actuator 300 and the diaphragm 50 in the +Z direction. As a result, the volume of the pressure chamber 12 contracts and returns from the fourth volume to the first volume.

[0096] By adding the second expansion element P10, the second expansion maintenance element P11, and the second return element P12 of the vibration damping pulse SVP after the ejection pulse DP, the residual vibration of the ink in the pressure chamber 12 after the ink is ejected from the nozzle 21 can be quickly converged. That is, when the second active portion 312 and the third active portion 313 of the piezoelectric actuator 300 are driven by the vibration damping pulse SVP, as shown in FIG. 13 , the second active portion 312 and the third active portion 313 contract along the Z axis, deforming the piezoelectric actuator 300 and the diaphragm 50 so that they protrude convexly in the −Z direction, which is the opposite side of the pressure chamber 12. At this time, tensile stress is applied to the portion including the first active portion 311 sandwiched between the second active portion 312 and the third active portion 313, increasing the apparent Young's modulus. The increase in the apparent Young's modulus of the piezoelectric actuator 300 allows the residual vibration of the ink in the pressure chamber 12 after the ink is ejected to be quickly converged.

[0097] Furthermore, by driving the second active portion 312 and the third active portion 313 of the piezoelectric actuator 300 with a damping pulse SVP, the piezoelectric actuator 300 is deformed so as to protrude convexly in the -Z direction opposite the pressure chamber 12, thereby eliminating the residual strain in the piezoelectric layer 70. In other words, by repeatedly driving the piezoelectric actuator 300 with the ejection pulse DP, the piezoelectric actuator 300 repeatedly deforms in only one direction—in this embodiment, the direction toward the pressure chamber 12, that is, the +Z direction—and this generates residual strain in the piezoelectric layer 70, preventing it from returning to its original state even when the piezoelectric actuator 300 is not driven. Furthermore, if the residual strain in the piezoelectric actuator 300 is large, the amount of displacement of the piezoelectric actuator 300 decreases when the piezoelectric actuator 300 is driven, and the ejection characteristics, such as the weight and flight speed of the ink droplets, deteriorate. In this embodiment, by driving the piezoelectric actuator 300 with the vibration damping pulse SVP, the piezoelectric actuator 300 can be deformed so as to protrude convexly in a direction different from the ejection pulse DP, i.e., in the -Z direction, thereby eliminating residual strain in the piezoelectric layer 70 and preventing a decrease in the displacement of the piezoelectric actuator 300 even when repeatedly driven. Therefore, a decrease in the ejection characteristics of ink droplets ejected from the nozzles 21 can be prevented.

[0098] Incidentally, because the second electrode 62 and the third electrode 63 are common electrodes for the multiple second active portions 312 and multiple third active portions 313, the second active portions 312 and third active portions 313 corresponding to the pressure chambers 12 communicating with the nozzles 21 that do not eject ink droplets are also simultaneously driven by the vibration damping pulse SVP. However, because the vibration damping pulse SVP drives the piezoelectric actuator 300 so as not to eject ink droplets, there is no particular problem if the second active portions 312 and third active portions 313 corresponding to the nozzles 21 that do not eject ink droplets are driven by the vibration damping pulse SVP. In addition, because the vibration damping pulse SVP also functions as a so-called micro-vibration pulse, driving the second active portions 312 and third active portions 313 corresponding to the nozzles 21 that do not eject ink droplets with the vibration damping pulse SVP causes micro-vibrations in the ink near the nozzles 21. Therefore, it is possible to suppress sedimentation of components contained in the ink near the pressure chambers 12 and the nozzles 21, and to suppress retention of thickened ink, thereby suppressing ejection failure of ink droplets caused by thickened ink. In other words, it is preferable to supply the vibration damping pulse SVP to the second electrode 62 and third electrode 63 corresponding to the pressure chambers 12 that communicate with the nozzles 21 to which no ejection pulse is supplied.

[0099] In the above-described configuration, the bias potential vbs is supplied to the fourth electrode 80, and the fifth potential V5, which is the same as the bias potential vbs, is supplied to the second electrode 62 and the third electrode 63 by the third reference element B3 and the fourth reference element B4, but this is not particularly limited. For example, the bias potential vbs may not be supplied to the fourth electrode 80, but may be ground (GND), and the fifth potential V5 of the third reference element B3 and the fourth reference element B4 may be ground (GND).

[0100] A modified example of the control unit of this embodiment will now be described with reference to Fig. 14. Fig. 14 shows drive waveforms indicating the bias potential vbs, the first drive signal 201, and the third drive signal 203.

[0101] 14, a third drive signal 203 is supplied to the second electrode 62 and the third electrode 63. The third drive signal 203 does not include a vibration suppression pulse SVP. The third drive signal 203 supplies a sixth potential V6, which is an intermediate potential, to the second electrode 62 and the third electrode 63. In other words, the third drive signal 203 can be said to be composed of a fifth reference element B5 that supplies the sixth potential V6.

[0102] Here, the sixth potential V6 supplied to the second electrode 62 and the third electrode 63 is a potential different from the potential supplied to the fourth electrode 80, which in this embodiment is the bias potential vbs. In this embodiment, the sixth potential V6 is preferably greater than the bias potential vbs. In other words, it is preferable to satisfy the relationship sixth potential V6 > bias potential vbs. By setting the sixth potential V6 to a potential greater than the bias potential vbs in this manner, it is possible to prevent an electric field in the opposite direction to the ejection pulse DP from being applied to the piezoelectric actuator 300. Therefore, it is possible to prevent cracks or damage to the piezoelectric actuator 300. Note that this sixth potential V6 corresponds to the "first potential" in embodiment 1. That is, in the configuration shown in FIG. 8, the fourth potential V4 is the same potential as the bias potential vbs supplied to the fourth electrode 80, and in the configuration shown in FIG. 14, the sixth potential V6 is greater than the bias potential vbs, which is the second potential. A condition that satisfies both the configurations of FIG. 8 and FIG. 14 is that the relationship of the potential supplied to the second electrode 62 and the third electrode 63≧bias potential vbs is satisfied.

[0103] Furthermore, by constantly supplying the sixth potential V6 to the second electrode 62 and the third electrode 63 while the ejection pulse DP is supplied to the first electrode 61, it is possible to eliminate the increase in residual strain that occurs when the piezoelectric actuator 300 is repeatedly driven with the ejection pulse DP, even without supplying the vibration-damping pulse SVP, and suppress the decrease in displacement due to repeated driving. Furthermore, by maintaining the supply of the sixth potential V6 to the second electrode 62 and the third electrode 63, it is possible to adjust the natural vibration period Tc of the pressure chamber 12. Here, the magnitude of the sixth potential V6 supplied to the second electrode 62 and the third electrode 63 and the magnitude of the natural vibration period Tc of the pressure chamber 12 are inversely proportional to each other. Therefore, by supplying the sixth potential V6 to the second electrode 62 and the third electrode 63, the natural vibration period Tc of the pressure chamber 12 is reduced, enabling continuous ejection of ink droplets at high speed. Furthermore, in an ink jet recording device 1 having a head unit in which a plurality of recording heads 2 are unitized or a plurality of recording heads 2, even if there is variation in the natural vibration period Tc among the plurality of recording heads 2, it is possible to reduce the variation in the natural vibration period Tc among the plurality of recording heads 2 by changing the sixth potential V6 of each recording head 2. Therefore, it is possible to suppress variation in the ejection characteristics, such as the ink weight and ejection speed, of the ink droplets ejected from the plurality of recording heads 2.

[0104] This configuration in which the sixth potential V6 is constantly supplied to the second electrode 62 and the third electrode 63 while the ejection pulse DP is supplied to the first electrode 61 may also be applied to the second drive signal 202 having the vibration damping pulse SVP. A configuration in which the sixth potential V6 is applied to the second drive signal 202 is shown in FIG. 15. FIG. 15 shows drive waveforms illustrating modified examples of the bias potential vbs, the first drive signal 201, and the second drive signal 202.

[0105] 15, when the second drive signal 202 does not supply the vibration damping pulse SVP, it always supplies the sixth potential V6, which is an intermediate potential, to the second electrode 62 and the third electrode 63. In other words, the second drive signal 202 includes the third reference element B3, the vibration damping pulse SVP, and the fourth reference element B4, and supplies the sixth potential V6 to the second electrode 62 and the third electrode 63 via the third reference element B3 and the fourth reference element B4.

[0106] The third reference element B3 and the fourth reference element B4 supply a sixth potential V6, which is greater than the bias potential vbs, to the second electrode 62 and the third electrode 63. That is, the third reference element B3 supplies the sixth potential V6 to the second electrode 62 and the third electrode 63 during the first period T1 in which the ejection pulse DP is supplied to the first electrode 61. This makes it possible to reduce the natural vibration period Tc of the pressure chamber 12 while the ejection pulse DP is being supplied, and also to adjust the natural vibration period Tc. Furthermore, the second drive signal 202 includes a vibration damping pulse SVP, and therefore exhibits the same effects as those described above due to the vibration damping pulse SVP.

[0107] 15, the waveform of the vibration control pulse SVP is the same as that of Fig. 8, so that the fourth potential V4 is a potential greater than the third potential V3, but this is not particularly limited, and the fourth potential V4 may be the same potential as the third potential V3. This allows the circuitry of the drive signal generation unit 216 to be simplified compared to when different potentials are generated for the fourth potential V4 and the third potential V3.

[0108] As described above, the recording head 2, which is an example of a piezoelectric device of the present invention, includes a flow path forming substrate 10, which is a substrate on which pressure chambers 12, which are recesses communicating with nozzles 21 that eject liquid, are formed and arranged in a first direction (+X direction), a vibration plate 50, and a piezoelectric actuator 300. The piezoelectric actuator 300 has a first electrode 61, a second electrode 62, a third electrode 63, and a fourth electrode 80, in this order. The piezoelectric actuator 300 also has a piezoelectric layer 70 between the first electrode 61 and the fourth electrode 80, between the second electrode 62 and the fourth electrode 80, and between the third electrode 63 and the fourth electrode 80. The piezoelectric actuator 300 also has a plurality of first active portions 311, second active portions 312, and third active portions 313, which are active portions where the piezoelectric layer 70 is sandwiched between the first electrode 61, the second electrode 62, the third electrode 63, and the fourth electrode 80. The second electrode 62 and the third electrode 63 are provided at both ends of the pressure chamber 12 in the +X direction, from the edge of the region facing the pressure chamber 12 when viewed in the −Z direction, which is the stacking direction, to the outside of the pressure chamber 12. The first electrode 61 is formed between the second electrode 62 and the third electrode 63 in the +X direction, and the fourth electrode 80 constitutes a common electrode for the multiple first active portions 311, second active portions 312, and third active portions 313.

[0109] In this way, by providing the first electrode 61 that drives the piezoelectric actuator 300 to deform toward the pressure chamber 12 and the second electrode 62 and third electrode 63 that drive the piezoelectric actuator 300 to deform toward the opposite side of the pressure chamber 12, residual strain is less likely to occur in the piezoelectric layer 70 even when the piezoelectric actuator 300 is repeatedly driven, compared to when the piezoelectric actuator 300 is deformed in only one direction along the Z axis. Therefore, a decrease in the amount of displacement can be suppressed even when the piezoelectric actuator 300 is repeatedly driven. Therefore, even when the piezoelectric actuator 300 is repeatedly driven, a decrease in the ink weight and other ejection characteristics of the ink droplets ejected from the nozzles 21 can be suppressed, allowing for continuous high-quality printing. Furthermore, the amount of displacement can be improved compared to when the piezoelectric actuator 300 is driven in only one direction along the Z axis. Therefore, the weight of the ink droplets ejected from the nozzles 21 can be increased.

[0110] A recording head 2, which is an example of a piezoelectric device of the present invention, includes a flow path forming substrate 10, which is a substrate on which pressure chambers 12, which are recesses communicating with nozzles 21 that eject liquid, are formed and arranged in a first direction (+X direction), a vibration plate 50, and a piezoelectric actuator 300. The piezoelectric actuator 300 has a first electrode 61, a second electrode 62, a third electrode 63, and a fourth electrode 80, in this order. The piezoelectric actuator 300 also has a piezoelectric layer 70 between the first electrode 61 and the fourth electrode 80, between the second electrode 62 and the fourth electrode 80, and between the third electrode 63 and the fourth electrode 80. The piezoelectric actuator 300 also has a plurality of active portions 1311, second active portions 312, and third active portions 313, in which the piezoelectric layer 70 is sandwiched between the first electrode 61, the second electrode 62, the third electrode 63, and the fourth electrode 80. The second electrode 62 and the third electrode 63 are provided at both ends of the pressure chamber 12 in the +X direction, from the edge of the region facing the pressure chamber 12 when viewed in the −Z direction, which is the stacking direction, to the outside of the pressure chamber 12. The first electrode 61 is formed between the second electrode 62 and the third electrode 63 in the +X direction, and the second electrode 62, the third electrode 63, and the fourth electrode 80 form a common electrode for the multiple first active sections 311, the second active sections 312, and the third active sections 313, and the first electrode 61 forms an individual electrode provided independently for each of the first active sections 311.

[0111] In this way, by providing the first electrode 61 that drives the piezoelectric actuator 300 to deform toward the pressure chamber 12, and the second electrode 62 and third electrode 63 that drive the piezoelectric actuator 300 to deform toward the opposite side from the pressure chamber 12, it is possible to reduce the residual strain in the piezoelectric layer 70 when the piezoelectric actuator 300 is repeatedly driven, and to suppress a decrease in displacement due to repeated driving. Therefore, it is possible to suppress a decrease in ejection characteristics such as the weight and flight speed of ink droplets ejected from the nozzle 21 when the piezoelectric actuator 300 is repeatedly driven.

[0112] Furthermore, since the second electrode 62 constitutes a common electrode for the plurality of second active portions 312 and the third electrode 63 constitutes a common electrode for the plurality of third active portions 313, it is possible to reduce the number of second common lead electrodes 93, which are lead wirings drawn out from the second electrode 62 and the third electrode 63. This reduces the space required for routing the wiring, reduces the area of ​​the flow path forming substrate 10 in the XY plane, and makes it possible to miniaturize the recording head 2.

[0113] Furthermore, the piezoelectric layer 70 and the fourth electrode 80 do not need to be patterned to match the first electrode 61. That is, the piezoelectric layer 70 and the fourth electrode 80 can be formed with a substantially uniform thickness across the first electrode 61, the second electrode 62, and the third electrode 63. This makes it possible to prevent the piezoelectric layer 70 from being altered by patterning, and to prevent partial deterioration of the piezoelectric properties.

[0114] Furthermore, in the recording head 2 of this embodiment, it is preferable that the distance between the first electrode 61 and the fourth electrode 80 in the −Z direction, which is the stacking direction, is the same as the distance between the second electrode 62 and the third electrode 63 and the fourth electrode 80. This simplifies the structure, reduces the number of manufacturing steps, and reduces costs. In addition, since the distances are the same, it is preferable because residual strain in the piezoelectric layer 70 is less likely to vary.

[0115] Furthermore, in the recording head 2 of this embodiment, it is preferable that the piezoelectric layer 70 is not provided on the pressure chamber 12 side, which is the recess of the first electrode 61. In this way, the piezoelectric layer 70 that increases the dielectric tangent tanδ is not present on the pressure chamber 12 side of the first electrode 61, and heat generation due to dielectric loss when the piezoelectric actuator 300 is driven is unlikely to occur, so the temperature of the ink in the pressure chamber 12 is unlikely to rise.

[0116] Furthermore, in the recording head 2 of this embodiment, it is preferable that the first electrode 61, the second electrode 62, and the third electrode 63 do not overlap one another in the +X direction, which is the first direction, when viewed in the stacking direction. This makes it possible to prevent electrical conduction between the first electrode 61 and the second electrode 62 and the third electrode 63. Furthermore, because the first electrode 61, the second electrode 62, and the third electrode 63 do not overlap in the +X direction, they can be formed at the same position in the -Z direction. Therefore, the first electrode 61, the second electrode 62, and the third electrode 63 can be formed simultaneously in the same layer, reducing the number of manufacturing steps and lowering costs.

[0117] Furthermore, in the recording head 2 of this embodiment, it is preferable that the fourth electrode 80 covers the pressure chamber 12, which is a recess, in the +X direction, which is the first direction, when viewed in the −Z direction, which is the stacking direction. Since the first electrode 61 and the piezoelectric layer 70 provided in the −Z direction of the pressure chamber 12 are covered with the fourth electrode 80, it is possible to prevent the piezoelectric layer 70 from being corroded by moisture and to prevent the life of the piezoelectric layer 70 from being shortened.

[0118] Furthermore, in the recording head 2 of this embodiment, it is preferable that the pressure chambers 12, which are recesses, have a longitudinal direction that is the +Y direction, which is a second direction orthogonal to the +X direction, which is the first direction, when viewed in the -Z direction, which is the stacking direction. This allows the pressure chambers 12 to be arranged densely in the +X direction while ensuring the volume of the pressure chambers 12.

[0119] In the recording head 2 of this embodiment, the vibration plate 50 preferably contains zirconium oxide. When a material containing lead is used for the piezoelectric layer 70, the diffusion of lead into the vibration plate 50 can be suppressed.

[0120] Furthermore, an ink jet recording apparatus 1, which is an example of a liquid ejecting apparatus of the present invention, is equipped with the above-described recording head 2. A highly reliable ink jet recording apparatus 1 can be realized in which print quality is unlikely to deteriorate even after repeated printing.

[0121] An inkjet recording apparatus 1, which is an example of a liquid ejecting apparatus according to this embodiment, includes a flow path forming substrate 10 on which pressure chambers 12, which are recesses communicating with nozzles 21 that eject liquid, are formed and aligned in a first direction (+X direction), a vibration plate 50, a piezoelectric actuator 300, and a control unit that drives the piezoelectric actuator 300. The piezoelectric actuator 300 includes a first electrode 61, a second electrode 62, a third electrode 63, and a fourth electrode 80, in this order. The piezoelectric actuator 300 also includes piezoelectric layers 70 between the first electrode 61 and the fourth electrode 80, between the second electrode 62 and the fourth electrode 80, and between the third electrode 63 and the fourth electrode 80. The piezoelectric element also has a plurality of first active portions 311, second active portions 312, and third active portions 313, which are active portions in which the piezoelectric layer 70 is sandwiched between the first electrode 61, the second electrode 62, the third electrode 63, and the fourth electrode 80. The second electrode 62 and the third electrode 63 are provided at both ends of the pressure chamber 12 in the +X direction, from the edge of the area facing the pressure chamber 12 to the outside of the pressure chamber 12 when viewed in the −Z direction, which is the stacking direction. The first electrode 61 is formed between the second electrode 62 and the third electrode 63 in the +X direction, and the second electrode 62, the third electrode 63, and the fourth electrode 80 form a common electrode for the plurality of first active portions 311, second active portions 312, and third active portions 313, and the first electrode 61 forms an individual electrode independently provided for each of the first active portions 311. The control unit also supplies an ejection pulse DP to the first electrode 61 to eject liquid from the nozzle 21, and the control unit supplies a vibration damping pulse SVP to the second electrode 62 and the third electrode 63 to drive the piezoelectric actuator 300 so as not to eject liquid from the nozzle 21 at least after the ejection pulse DP.

[0122] In this way, when ejecting ink droplets, the control unit supplies an ejection pulse DP to the first electrode 61 to deform the piezoelectric actuator 300 toward the pressure chamber 12. Furthermore, by supplying a damping pulse SVP after the ejection pulse DP, the piezoelectric actuator 300 is deformed toward the side opposite the pressure chamber 12. Therefore, even when ink droplets are repeatedly ejected using the ejection pulse DP, supplying the damping pulse SVP can prevent an increase in residual strain in the piezoelectric layer 70 and prevent a decrease in the amount of displacement due to repeated driving of the piezoelectric actuator 300. Furthermore, by inputting the damping pulse SVP after the ejection pulse DP, the apparent Young's modulus of the piezoelectric layer 70 can be increased, and residual vibrations after the ejection pulse DP can be quickly converged. Therefore, ink droplets can be repeatedly ejected in a short time, achieving high-speed continuous ejection. Furthermore, by supplying a vibration damping pulse SVP to the second electrode 62 and the third electrode 63 corresponding to the pressure chamber 12 that does not eject ink droplets, the ink in the vicinity of the pressure chamber 12 and the nozzle 21 is slightly vibrated, thereby suppressing the settling of components contained in the ink and preventing the stagnation of thickened ink, thereby suppressing poor ejection of ink droplets caused by thickened ink.

[0123] Furthermore, in the ink jet recording apparatus 1 of this embodiment, it is preferable that the control unit uses the vibration damping pulse SVP to deform the diaphragm 50 so that it becomes convex on the side opposite the pressure chambers 12. By using the vibration damping pulse SVP to deform the diaphragm 50 so that it becomes convex in the -Z direction opposite the pressure chambers 12 in this way, it is possible to reduce residual strain in the piezoelectric layer 70 caused by repeated driving with the ejection pulse DP.

[0124] Furthermore, in the ink jet recording apparatus 1 of this embodiment, it is preferable that the control unit uses the ejection pulse DP to deform the vibration plate 50 so that it becomes convex toward the pressure chamber 12. This improves the driving efficiency of the piezoelectric actuator 300 and can improve the ejection characteristics of ink droplets.

[0125] Furthermore, in the ink jet recording apparatus 1 of this embodiment, it is preferable that the control unit supplies the first electrode 61 with a first drive signal 201 including an ejection pulse DP, and while the first drive signal 201 is being supplied to the first electrode 61, supplies the second electrode 62 and the third electrode 63 with a sixth potential V6, which is a first potential different from the potential supplied to the fourth electrode 80. In this way, by maintaining the supply of the sixth potential V6 to the second electrode 62 and the third electrode 63 while the first drive signal 201 is being supplied to the first electrode 61, it is possible to adjust the natural vibration period Tc of the pressure chamber 12. Therefore, by reducing the natural vibration period Tc of the pressure chamber 12, it is possible to eject ink droplets continuously at high speed. Furthermore, in a head unit in which multiple recording heads 2 are unitized, or in an inkjet recording apparatus 1 equipped with multiple recording heads 2, even if there is variation in the natural vibration period Tc among the multiple recording heads 2, by changing the sixth potential V6 of each recording head 2, it is possible to reduce the variation in the natural vibration period Tc among the multiple recording heads 2. Therefore, it is possible to suppress variation in the ejection characteristics, such as the ink weight and ejection speed, of the ink droplets ejected from the multiple recording heads 2. Note that, in the above example, the bias potential vbs is supplied to the fourth electrode 80, but this is not particularly limited, and the fourth electrode 80 may be ground (GND).

[0126] An inkjet recording apparatus 1, which is an example of a liquid ejecting apparatus according to this embodiment, includes a flow path forming substrate 10, which is a substrate on which pressure chambers 12, which are recesses communicating with nozzles 21 that eject liquid, are formed and arranged in a first direction (+X direction), a vibration plate 50, a piezoelectric actuator 300, and a control unit that drives the piezoelectric actuator 300. The piezoelectric actuator 300 has a first electrode 61, a second electrode 62, a third electrode 63, and a fourth electrode 80, in this order. The piezoelectric actuator 300 also has piezoelectric layers 70 between the first electrode 61 and the fourth electrode 80, between the second electrode 62 and the fourth electrode 80, and between the third electrode 63 and the fourth electrode 80. The piezoelectric element also has a plurality of first active portions 311, second active portions 312, and third active portions 313, which are active portions in which the piezoelectric layer 70 is sandwiched between the first electrode 61, the second electrode 62, the third electrode 63, and the fourth electrode 80. The second electrode 62 and the third electrode 63 are provided at both ends of the pressure chamber 12 in the +X direction, from the edge of the area facing the pressure chamber 12 to the outside of the pressure chamber 12 when viewed in the −Z direction, which is the stacking direction. The first electrode 61 is formed between the second electrode 62 and the third electrode 63 in the +X direction, and the second electrode 62, the third electrode 63, and the fourth electrode 80 form a common electrode for the plurality of first active portions 311, second active portions 312, and third active portions 313, and the first electrode 61 forms an individual electrode independently provided for each of the first active portions 311. The control unit also supplies a first drive signal 201 to the first electrode 61, which includes an ejection pulse DP that ejects liquid from the nozzle 21, and while the control unit is supplying the first drive signal 201 to the first electrode 61, the control unit supplies a sixth potential V6, which is a first potential different from the potential supplied to the fourth electrode 80, to the second electrode 62 and the third electrode 63.

[0127] According to this, by maintaining the supply of the sixth potential V6 to the second electrode 62 and the third electrode 63 while supplying the first drive signal 201 to the first electrode 61, the natural vibration period Tc of the pressure chamber 12 can be adjusted. Therefore, the natural vibration period Tc of the pressure chamber 12 can be reduced, enabling continuous high-speed ejection of ink droplets. Furthermore, in a head unit in which multiple recording heads 2 are unitized or in an inkjet recording apparatus 1 equipped with multiple recording heads 2, even if there is variation in the natural vibration period Tc among the multiple recording heads 2, the variation in the natural vibration period Tc among the multiple recording heads 2 can be reduced by changing the sixth potential V6 of each recording head 2. Therefore, variation in ejection characteristics, such as the ink weight and ejection speed of ink droplets ejected from the multiple recording heads 2, can be suppressed. In the above example, the bias potential vbs is supplied to the fourth electrode 80. However, this is not limited to this, and the fourth electrode 80 may be ground (GND).

[0128] Furthermore, in the ink jet recording apparatus 1 of this embodiment, it is preferable that the control unit supplies the bias potential vbs, which is the second potential, to the fourth electrode 80 while supplying the first drive signal 201, and that the sixth potential V6, which is the first potential, is equal to or greater than the bias potential vbs. By setting the sixth potential V6 to a potential greater than the bias potential vbs in this manner, it is possible to prevent an electric field in the opposite direction to the ejection pulse DP from being applied to the piezoelectric actuator 300. This makes it possible to prevent cracks and damage to the piezoelectric actuator 300.

[0129] (Embodiment 2) Fig. 16 is an enlarged plan view of a main part of a flow path forming substrate 10 of an ink jet recording head 2, which is an example of a liquid jet head according to a second embodiment of the present invention, viewed in the +Z direction. Fig. 17 is a cross-sectional view taken along line CC' in Fig. 16. Note that the same members as those in the above-described embodiments are given the same reference numerals, and redundant explanations will be omitted.

[0130] As shown in the figure, the piezoelectric actuator 300 includes a first electrode 61, a second electrode 62, a third electrode 63, a piezoelectric layer 70, and a fourth electrode 80 for one pressure chamber 12.

[0131] The first electrode 61, the second electrode 62, and the third electrode 63 are located in the +Z direction relative to the fourth electrode 80. In other words, the fourth electrode 80 is located in the -Z direction relative to the first electrode 61, the second electrode 62, and the third electrode 63. In other words, the first electrode 61, the second electrode 62, the third electrode 63, and the fourth electrode 80 are stacked in this order toward the -Z direction. Here, the stacking of the first electrode 61, the second electrode 62, the third electrode 63, and the fourth electrode 80 means that another layer is interposed between the first electrode 61, the second electrode 62, the third electrode 63, and the fourth electrode 80 in the direction along the Z axis. In this embodiment, the piezoelectric actuator 300 has a piezoelectric layer 70 between the first electrode 61 and the fourth electrode 80 in the direction along the Z axis. The piezoelectric actuator 300 also has a piezoelectric layer 70 between the second electrode 62 and the fourth electrode 80. Furthermore, the piezoelectric actuator 300 has a piezoelectric layer 70 between the third electrode 63 and the fourth electrode 80 .

[0132] The first electrode 61, the second electrode 62, and the third electrode 63 are provided on the −Z direction surface of the diaphragm 50. In other words, the first electrode 61, the second electrode 62, and the third electrode 63 are provided at the same position in the direction along the Z axis.

[0133] The second electrode 62 and the third electrode 63 are provided at both ends of the pressure chamber 12 in the +X direction, i.e., at the end in the +X direction and the end in the −X direction, from the end of the region facing the pressure chamber 12 to the outside of the pressure chamber 12, as viewed in the −Z direction, which is the stacking direction. In this embodiment, the second electrode 62 is provided at the end in the −X direction of the pressure chamber 12, from the edge of the region facing the pressure chamber 12 to above the partition wall 11 on the outside of the pressure chamber 12 in the −X direction, as viewed in the −Z direction. The third electrode 63 is provided at the end in the +X direction of the pressure chamber, from the edge of the region facing the pressure chamber 12 as viewed in the −Z direction to above the partition wall 11 on the outside of the pressure chamber 12 in the +X direction.

[0134] The second electrode 62 and the third electrode 63 are separated for each pressure chamber 12, thereby constituting individual electrodes independently provided for each active section. Here, the second electrode 62 and the third electrode 63 being individual electrodes for each active section means that, in this embodiment, the second electrodes 62 provided in the second active sections 312 on the flow path forming substrate 10 are not electrically connected to each other and are independently provided. Furthermore, "on the flow path forming substrate 10" includes not only directly above the flow path forming substrate 10 as described above, but also a state where another member, for example, the vibration plate 50, is interposed therebetween, i.e., so-called "above." Furthermore, in two pressure chambers 12 aligned in the +X direction, the second electrode 62 of one pressure chamber 12 and the third electrode 63 of the other pressure chamber 12 are spaced apart from each other on the partition wall 11 that separates the two pressure chambers 12 in the +X direction so as not to communicate with each other.

[0135] In this embodiment, the second electrode 62 and the third electrode 63 provided for one pressure chamber 12 are provided in electrical conduction on the flow-channel-forming substrate 10. Specifically, the second electrode 62 and the third electrode 63 are connected to individual communication portions 64A that are provided independently for each pressure chamber 12 on one outer side of the pressure chamber 12 in the direction along the Y axis, and are electrically connected via the individual communication portions 64A. In this embodiment, the second electrode 62, the third electrode 63, and the individual communication portions 64A are continuously provided by patterning the same metal layer. Of course, the second electrode 62, the third electrode 63, and the individual communication portions 64A may each be formed in a different layer. In other words, the electrical conduction between the second electrode 62 and the third electrode 63 on the flow-channel-forming substrate 10 also includes conduction via another member. Furthermore, the phrase "the second electrode 62 and the third electrode 63 provided corresponding to one pressure chamber 12 are continuous on the flow path forming substrate 10" includes the second electrode 62 and the third electrode 63 being directly above the flow path forming substrate 10 and above the flow path forming substrate 10. By electrically connecting the second electrode 62 and the third electrode 63 provided corresponding to one pressure chamber 12 in this manner, it is not necessary to provide lead wiring for each of the second electrode 62 and the third electrode 63 or to connect terminals of the wiring substrate 120. Therefore, space for routing wiring on the flow path forming substrate 10 and space for connecting the wiring substrate 120 are not required, and the area of ​​the flow path forming substrate 10 along the XY plane can be reduced. However, by electrically connecting the second electrode 62 and the third electrode 63 provided corresponding to one pressure chamber 12, the second active portion 312 and the third active portion 313 cannot be driven individually but are driven simultaneously. Furthermore, a second individual lead electrode 94, which is a lead wiring, is connected to the individual communication portion 64A. The second individual lead electrode 94 is provided along the Y-axis so that one end is connected to the individual communicating portion 64A and the other end is located outside the two rows of pressure chambers along the Y-axis. For this reason, although not particularly shown, a wiring board separate from the wiring board 120 is connected to the second individual lead electrode 94. Of course, the second individual lead electrode 94 may be drawn out in the same direction as the first individual lead electrode 91 from either the second electrode 62 or the third electrode 63 provided for one pressure chamber 12.By drawing out the first individual lead electrode 91 and the second individual lead electrode 94 in the same direction in this way, they can be connected to one wiring board 120. However, by drawing out the first individual lead electrode 91 and the second individual lead electrode 94 in the same direction, there is a risk that the pressure chambers 12 cannot be arranged densely along the +X direction in order to secure space for routing the wiring, and that the flow path forming substrate 10 may become larger in size in the +X direction.

[0136] Furthermore, the piezoelectric layer 70 and the fourth electrode 80 are the same as those in the first embodiment, and therefore redundant explanations will be omitted. In other words, the fourth electrode 80 serves as a common electrode for a plurality of active portions, in this case, a plurality of first active portions 311, a plurality of second active portions 312, and a plurality of third active portions 313.

[0137] The drive signals for driving the recording head 2 having such a piezoelectric actuator 300 will be described with reference to Fig. 18. Fig. 18 shows drive waveforms indicating the bias potential, the fourth drive signal 204, and the fifth drive signal 205. Figs. 19 to 21 are cross-sectional views taken along line CC' showing the piezoelectric actuator 300 and the diaphragm 50 deformed by the drive signals.

[0138] 18, the drive signal generation unit 216 generates a fourth drive signal 204 and a fifth drive signal 205 as drive signals. The fourth drive signal 204 corresponds to the "first drive signal" in the second embodiment, and is supplied to the first electrode 61. The fifth drive signal 205 is supplied to the second electrode 62 and the third electrode 63.

[0139] The fourth drive signal 204 and the fifth drive signal 205 are repeatedly generated by the drive signal generation unit 216 for each unit period T defined by a clock signal oscillated by an oscillation circuit 215. The unit period T is also called an ejection period T or a recording period T, and corresponds to one pixel of an image to be printed on the medium S. In this embodiment, the unit period T is divided into two periods: a first period T1 and a second period T2.

[0140] The fourth drive signal 204 is a signal having a first ejection pulse DP1 for driving the first active portion 311 during a second period T2 within one recording cycle T, and is repeatedly generated for each recording cycle T. The first ejection pulse DP1 is selectively supplied to the first active portion 311 corresponding to the pressure chamber 12 communicating with the nozzle 21 that ejects liquid. That is, the control unit generates an application pulse from the head control signal and the fourth drive signal 204 for each first active portion 311 corresponding to each nozzle 21, and supplies the application pulse to the piezoelectric actuator 300. The application pulse generated from the fourth drive signal 204 is supplied to the first electrode 61 of the first active portion 311. A bias potential vbs is supplied to the fourth electrode 80, which is a common electrode for multiple first active portions 311. Therefore, the potential applied to the first electrode 61 by the application pulse is referenced to the bias potential vbs applied to the fourth electrode 80. The bias potential vbs applied to the fourth electrode 80 corresponds to the "second potential" described in the claims.

[0141] The first ejection pulse DP1 includes a third contraction element P20, a third contraction maintaining element P21, and a third return element P22. When the ejection pulse DP is not supplied, the applied pulse generated from the fourth drive signal 204 always applies a tenth potential V 1 , which is an intermediate potential, to the first electrode 61. 10 Therefore, within the unit period T of the fourth drive signal 204, the tenth potential V 10 The fourth drive signal 204 includes a sixth reference element B6 and a seventh reference element B7 that supply the first ejection pulse DP1 and the seventh reference element B7. That is, the fourth drive signal 204 generates the sixth reference element B6, the first ejection pulse DP1, and the seventh reference element B7 in this order within the unit period T. The sixth reference element B6 is generated during a period that includes the first period T1.

[0142] In the sixth reference element B6 and the seventh reference element B7, a tenth potential V 10 , which is smaller than the bias potential vbs, is applied to the first electrode 61. 10 19, the piezoelectric actuator 300 and the vibration plate 50 are maintained in a state of being deflected and deformed in the +Z direction toward the pressure chamber 12. As a result, the volume of the pressure chamber 12 is maintained at a tenth volume that is contracted from the reference volume.

[0143] The third contraction element P20 of the first ejection pulse DP1 applies a tenth potential V 10 to the 11th potential V 11 21, the piezoelectric actuator 300 and the diaphragm 50 are deformed in the +Z direction, causing the volume of the pressure chamber 12 to contract from the tenth volume to the eleventh volume.

[0144] The third contraction maintenance element P21 applies an eleventh potential V 11 is continuously applied, and the volume of the pressure chamber 12 expanded by the third contraction element P20 is maintained at the eleventh volume for a certain period of time.

[0145] The third return element P22 applies an eleventh potential V 11 to the 10th potential V 10 to deform the piezoelectric actuator 300 and the diaphragm 50 in the +Z direction. As a result, the volume of the pressure chamber 12 contracts and returns from the eleventh volume to the tenth volume.

[0146] The fourth drive signal 204 is a signal having a second ejection pulse DP2 that drives the second active section 312 and the third active section 313 during a first period T1 within one recording cycle T, and is repeatedly generated for each recording cycle T. The second ejection pulse DP2 is selectively supplied to the second active section 312 and the third active section 313 corresponding to the pressure chamber 12 that communicates with the nozzle 21 that ejects liquid. That is, the control unit generates an application pulse from the head control signal and the fifth drive signal 205 for each pair of the second active section 312 and the third active section 313 corresponding to each nozzle 21, and supplies the application pulse to the piezoelectric actuator 300. The application pulse generated from the fifth drive signal 205 is supplied to the second electrode 62 and the third electrode 63 of the second active section 312 and the third active section 313. In this embodiment, the application pulse is simultaneously supplied to one pair of the second electrode 62 and the third electrode 63 via the individual communication section 64A. A bias potential vbs is supplied to the fourth electrode 80, which is a common electrode for the plurality of second active portions 312 and the plurality of third active portions 313. Therefore, the bias potential vbs applied to the fourth electrode 80 serves as a reference potential for the potentials applied to the second electrode 62 and the third electrode 63 by the applied pulse. The second ejection pulse DP2 is generated during the first period T1 in which the first ejection pulse DP1 of the fourth drive signal 204 is not generated. In other words, the first ejection pulse DP1 and the second ejection pulse DP2 are not input simultaneously.

[0147] The second ejection pulse DP2 includes a fourth expansion component P30, a fourth expansion maintenance component P31, and a fourth return component P32. When the second ejection pulse DP2 is not supplied, the applied pulse generated from the fourth drive signal 204 always applies a twelfth potential V 1 , which is an intermediate potential, to the second electrode 62 and the third electrode 63. 12 Therefore, within the unit period T of the fourth drive signal 204, the twelfth potential V 12The fifth drive signal 205 includes an eighth reference element B8 and a ninth reference element B9 that supply the eighth reference element B8, the second ejection pulse DP2, and the ninth reference element B9, which are generated in this order within the unit period T. The ninth reference element B9 is generated during a period that includes the second period T2 during which the first ejection pulse DP1 of the fourth drive signal 204 is generated.

[0148] The eighth and ninth reference elements B8 and B9 apply a twelfth potential V, which is the same as the bias potential vbs, to the second and third electrodes 62 and 63. 12 , maintaining a state in which the second active portion 312 and the third active portion 313 are not driven. The ninth reference element B9 is supplied during the second period T2 in which the piezoelectric actuator 300 is driven by the first ejection pulse DP1. Therefore, while the first active portion 311 is being driven by the first ejection pulse DP1, the second active portion 312 and the third active portion 313 are not driven, thereby not affecting the driving of the first active portion 311. Furthermore, since the eighth reference element B8 and the ninth reference element B9 do not drive the second active portion 312 and the third active portion 313, the volumes of the pressure chambers 12 in the eighth reference element B8 and the ninth reference element B9 are determined by the state of the fourth drive signal 204, i.e., the driving state of the first active portion 311.

[0149] The fourth expansion component P30 of the second injection pulse DP2 applies a twelfth potential V 12 to the 13th potential V 13 20, the piezoelectric actuator 300 and the vibration plate 50 are deformed in the -Z direction. As a result, the volume of the pressure chamber 12 expands from the original volume to a twelfth volume. As described above, in the eighth reference element B8, the volume of the pressure chamber 12 is increased by applying a tenth potential V 10 is supplied, the volume of the pressure chamber 12 becomes a tenth volume, which is a volume that is reduced from the reference volume when nothing is driven. Therefore, the fourth expansion element P30 can expand from the tenth volume, which is reduced from the reference volume, to the twelfth volume, which is a larger expansion than when expanding from the reference volume to the twelfth volume. This thirteenth potential V13 is the 11th potential V of the first ejection pulse DP1 11 It is preferable that the potential is the same as the thirteenth potential V 13 is the maximum potential of the second ejection pulse DP2, and the eleventh potential V 11 is the maximum potential of the first ejection pulse DP1. Therefore, it is preferable to set the maximum potentials of the first ejection pulse DP1 and the second ejection pulse DP2 to the same potential. By setting the maximum potentials of the first ejection pulse DP1 and the second ejection pulse DP2 to the same potential, the circuitry of the drive signal generation unit 216 can be simplified compared to when different potentials are generated.

[0150] The fourth expansion maintaining element P31 applies a thirteenth potential V to the second electrode 62 and the third electrode 63. 13 is continuously applied, and the volume of the pressure chamber 12 expanded by the fourth expansion element P30 is maintained at the twelfth volume for a certain period of time.

[0151] The fourth return element P32 applies a thirteenth potential V to the second electrode 62 and the third electrode 63. 13 to the 12th potential V 12 to deform the piezoelectric actuator 300 and the vibration plate 50 in the +Z direction. This causes the volume of the pressure chamber 12 to contract from the twelfth volume to the tenth volume.

[0152] The timing at which the second ejection pulse DP2 ends is the same as the timing at which the first ejection pulse DP1 begins. In other words, the timing at which the fourth return element P32 of the second ejection pulse DP2 ends is the same as the timing at which the third contraction element P20 of the first ejection pulse DP1 begins. However, as long as the first ejection pulse DP1 and the second ejection pulse DP2 are not supplied simultaneously, the timing at which the fourth return element P32 of the second ejection pulse DP2 ends may be different from the timing at which the third contraction element P20 of the first ejection pulse DP1 begins. For example, it is preferable that the interval between the timing at which the fourth return element P32 of the second ejection pulse DP2 ends and the timing at which the third contraction element P20 of the first ejection pulse DP1 begins is ½ the natural vibration period Tc of the pressure chamber 12. This allows the second ejection pulse DP2 to be supplied when the meniscus in the nozzle 21 moves in the +Z direction due to residual vibration caused by the first ejection pulse DP1, and prevents the movement of the ink meniscus caused by the driving of the first ejection pulse DP1 from being hindered by the driving of the second ejection pulse DP2, allowing ink droplets to be ejected.

[0153] Then, when the first ejection pulse DP1 and the second ejection pulse DP2 are supplied to the first electrode 61, the second electrode 62, and the third electrode 63, respectively, ink droplets are ejected from the corresponding nozzles 21.

[0154] Specifically, first, from the state in which the volume of the pressure chamber 12 shown in Fig. 19 is the tenth volume, the fourth expansion element P30 of the second ejection pulse DP2 moves the piezoelectric actuator 300 and the vibration plate 50 in the -Z direction, as shown in Fig. 20, expanding the volume of the pressure chamber 12 from the tenth volume to the twelfth volume. As a result, the meniscus of the ink in the nozzle 21 is drawn toward the pressure chamber 12, and ink is supplied to the pressure chamber 12 from the manifold 100 side.

[0155] Next, after the 12th volume expanded by the fourth expansion maintaining element P31 is maintained for a certain period of time, the piezoelectric actuator 300 and the vibration plate 50 are moved in the +Z direction by the fourth return element P32, causing the volume of the pressure chamber 12 to contract from the 12th volume to the 10th volume.

[0156] 21, the piezoelectric actuator 300 and the vibration plate 50 are further moved in the +Z direction by the third contraction element P20 of the first ejection pulse DP1 supplied following the fourth return element P32, thereby contracting the volume of the pressure chamber 12 from the tenth volume to the eleventh volume. In other words, by supplying the fourth return element P32 of the second ejection pulse DP2 and the third contraction element P20 of the first ejection pulse DP1 in succession, the piezoelectric actuator 300 and the vibration plate 50 rapidly contract the volume of the pressure chamber 12 from the twelfth volume to the eleventh volume. This pressurizes the ink in the pressure chamber 12, causing an ink droplet to be ejected from the nozzle 21.

[0157] After the ink droplet is ejected, the 11th volume is maintained for a certain period of time by the third contraction maintenance element P21 of the first ejection pulse DP1. While this third contraction maintenance element P21 is being supplied, the ink pressure in the pressure chamber 12, which was reduced by the ejection of the ink droplet, is attenuated by repeatedly rising and falling due to its natural vibration, and then expanded and returned to the original 10th volume by the third return element P22.

[0158] In this way, by driving the first active portion 311 with the first ejection pulse DP1 and driving the second active portion 312 and the third active portion 313 with the second ejection pulse DP2 to eject ink droplets, it is possible to increase the excluded volume when contracting from the 12th volume to the 11th volume, thereby making it possible to eject ink droplets with a large ink weight.

[0159] Furthermore, ink droplets are ejected by a first ejection pulse DP1 that deforms the piezoelectric actuator 300 and the diaphragm 50 so that they protrude convexly in the +Z direction toward the pressure chamber 12, and a second ejection pulse DP2 that deforms the piezoelectric actuator 300 and the diaphragm 50 so that they protrude convexly in the -Z direction opposite the pressure chamber 12. Therefore, compared to when ink droplets are ejected by deforming the piezoelectric actuator 300 in only one direction, residual strain is less likely to occur in the piezoelectric layer 70 even when the piezoelectric actuator 300 is repeatedly driven. Therefore, it is possible to prevent a decrease in the amount of displacement even when the piezoelectric actuator 300 is repeatedly driven.

[0160] Furthermore, since trapezoidal waves with relatively simple shapes can be used as the first ejection pulse DP1 and the second ejection pulse DP2, there is no need to generate waveforms with complex shapes as ejection pulses, and the circuit configuration of the drive signal generation unit 216 can be simplified, making control easier.

[0161] As described above, the recording head 2, which is an example of a piezoelectric device of the present invention, includes a flow path forming substrate 10, which is a substrate on which pressure chambers 12, which are recesses communicating with nozzles 21 that eject liquid, are formed and arranged in a first direction (+X direction), a vibration plate 50, and a piezoelectric actuator 300. The piezoelectric actuator 300 has a first electrode 61, a second electrode 62, a third electrode 63, and a fourth electrode 80, in this order. The piezoelectric actuator 300 also has a piezoelectric layer 70 between the first electrode 61 and the fourth electrode 80, between the second electrode 62 and the fourth electrode 80, and between the third electrode 63 and the fourth electrode 80. The piezoelectric actuator 300 also has a plurality of active portions 1311, second active portions 312, and third active portions 313, in which the piezoelectric layer 70 is sandwiched between the first electrode 61, the second electrode 62, the third electrode 63, and the fourth electrode 80. The second electrode 62 and the third electrode 63 are provided at both ends of the pressure chamber 12 in the +X direction, from the edge of the region facing the pressure chamber 12 when viewed in the −Z direction, which is the stacking direction, to the outside of the pressure chamber 12. The first electrode 61 is formed between the second electrode 62 and the third electrode 63 in the +X direction, and the fourth electrode 80 constitutes a common electrode for the multiple first active portions 311, second active portions 312, and third active portions 313.

[0162] In this way, by providing the first electrode 61 that drives the piezoelectric actuator 300 to deform toward the pressure chamber 12 and the second electrode 62 and third electrode 63 that drive the piezoelectric actuator 300 to deform toward the opposite side of the pressure chamber 12, residual strain is less likely to occur in the piezoelectric layer 70 even when the piezoelectric actuator 300 is repeatedly driven, compared to when the piezoelectric actuator 300 is deformed in only one direction along the Z axis. Therefore, a decrease in the amount of displacement can be suppressed even when the piezoelectric actuator 300 is repeatedly driven. Therefore, even when the piezoelectric actuator 300 is repeatedly driven, a decrease in the ink weight and other ejection characteristics of the ink droplets ejected from the nozzles 21 can be suppressed, allowing for continuous high-quality printing. Furthermore, the amount of displacement can be improved compared to when the piezoelectric actuator 300 is driven in only one direction along the Z axis. Therefore, the weight of the ink droplets ejected from the nozzles 21 can be increased.

[0163] Furthermore, in the recording head 2 of this embodiment, the second electrode 62 and the third electrode 63 preferably constitute individual electrodes independently provided for the second active portions 312 and the third active portions 313, which are active portions. That is, the second electrode 62 serves as an individual electrode for each of the second active portions 312 for the multiple second active portions 312, and the third electrode 63 serves as an individual electrode for each of the third active portions 313 for the multiple third active portions 313. In this way, by making the second electrode 62 and the third electrode 63 individual electrodes for the second active portions 312 and the third active portions 313, respectively, it is possible to selectively drive the second active portions 312 and the third active portions 313 for the multiple pressure chambers 12.

[0164] Furthermore, in the recording head 2 of this embodiment, it is preferable that the second electrode 62 and the third electrode 63 provided for one pressure chamber 12, which is a recess, are electrically connected on the flow path forming substrate 10, which is a substrate. By electrically connecting the second electrode 62 and the third electrode 63 provided for one pressure chamber 12 on the flow path forming substrate 10, it is not necessary to provide a second individual lead electrode 94 independently for each of the second electrode 62 and the third electrode 63, and space for routing the second individual lead electrode 94 on the flow path forming substrate 10 and space for connecting to the wiring substrate 120 are not required. Therefore, the number of second individual lead electrodes 94 can be reduced, and the flow path forming substrate 10 can be made smaller.

[0165] An inkjet recording apparatus 1, which is an example of a liquid ejecting apparatus according to this embodiment, includes a flow path forming substrate 10 on which pressure chambers 12, which are recesses communicating with nozzles 21 that eject liquid, are formed and aligned in a first direction (+X direction), a vibration plate 50, a piezoelectric actuator 300, and a control unit that drives the piezoelectric actuator 300. The piezoelectric actuator 300 includes a first electrode 61, a second electrode 62, a third electrode 63, and a fourth electrode 80, in this order. The piezoelectric actuator 300 also includes piezoelectric layers 70 between the first electrode 61 and the fourth electrode 80, between the second electrode 62 and the fourth electrode 80, and between the third electrode 63 and the fourth electrode 80. The piezoelectric actuator 300 also has a plurality of first active portions 311, second active portions 312, and third active portions 313, which are active portions in which the piezoelectric layer 70 is sandwiched between the first electrode 61, the second electrode 62, the third electrode 63, and the fourth electrode 80. The second electrode 62 and the third electrode 63 are provided at both ends of the pressure chamber 12 in the +X direction, from the edge of the area facing the pressure chamber 12 to the outside of the pressure chamber 12 when viewed in the −Z direction, which is the stacking direction. The first electrode 61 is formed between the second electrode 62 and the third electrode 63 in the +X direction, and the fourth electrode 80 constitutes a common electrode for the plurality of first active portions 311, second active portions 312, and third active portions 313. The control unit also drives the first electrode 61 by supplying a first ejection pulse DP1 to the first electrode 61 when deforming the piezoelectric actuator 300 toward the pressure chamber 12. Furthermore, when deforming the piezoelectric actuator 300 toward the side opposite to the pressure chamber 12, the control unit drives the second electrode 62 and the third electrode 63 by supplying a second ejection pulse DP2 to them. Then, the control unit ejects liquid from the nozzle 21 using the first ejection pulse DP1 and the second ejection pulse DP2.

[0166] In this way, by driving the piezoelectric actuator 300 with the first ejection pulse DP1 and the second ejection pulse DP2, the control unit is less likely to generate residual strain in the piezoelectric layer 70 even when repeatedly driving the piezoelectric actuator 300, compared to when the piezoelectric actuator 300 is deformed in only one direction along the Z axis. Therefore, a decrease in the amount of displacement can be suppressed even when the piezoelectric actuator 300 is repeatedly driven. Therefore, even when the piezoelectric actuator 300 is repeatedly driven, a decrease in the ejection characteristics, such as the ink weight of the ink droplets ejected from the nozzle 21, can be suppressed, allowing for continuous high-quality printing. Furthermore, the amount of displacement can be improved compared to when the piezoelectric actuator 300 is driven in only one direction along the Z axis. Therefore, the weight of the ink droplets ejected from the nozzle 21 can be increased.

[0167] In addition, in the ink jet recording apparatus 1 of this embodiment, it is preferable that the control unit does not simultaneously supply the first ejection pulse DP1 and the second ejection pulse DP2, thereby preventing the piezoelectric actuator 300 from being subjected to excessive deformation and preventing damage such as cracks from occurring in the piezoelectric actuator 300.

[0168] In the ink jet recording apparatus 1 of this embodiment, it is preferable that the first ejection pulse DP1 and the second ejection pulse DP2 have the same maximum potential. 13 and the eleventh potential V, which is the maximum potential of the first ejection pulse DP1. 11 By setting the potentials to be the same, the circuitry of the drive signal generating section 216 can be simplified compared to when different potentials are generated.

[0169] In the above example, the second electrode 62 and the third electrode 63 provided corresponding to one pressure chamber 12 are electrically connected on the flow path forming substrate 10, but this is not particularly limited. A modified example of the recording head 2 of this embodiment is shown in Fig. 22. Fig. 22 is a plan view of the flow path forming substrate 10 showing a modified example of the recording head 2 according to embodiment 2, viewed in the +Z direction.

[0170] 22, the second electrode 62 and the third electrode 63 provided corresponding to one pressure chamber 12 are separated and provided so as not to be electrically connected to each other on the flow path forming substrate 10. In addition, second individual lead electrodes 94 are provided independently for each of the second electrode 62 and the third electrode 63.

[0171] In this way, by not electrically conducting the second electrode 62 and the third electrode 63 for one pressure chamber 12 on the flow path forming substrate 10, it is possible to supply different waveforms, i.e., different potentials, to the second electrode 62 and the third electrode 63. For example, the 13th potential V 13 By varying the potentials of the second electrode 62 and the third electrode 63, the flight direction of the ink droplets ejected from the nozzle 21 can be bent in the direction along the X axis. Therefore, when the ink droplets do not fly in the +Z direction perpendicular to the liquid ejection surface 20a, the 13th potential V 13 That is, the thirteenth potential V supplied to each of the second electrode 62 and the third electrode 63 is adjusted. 13 By adjusting the above, the flight direction of the ink droplets can be adjusted, and deviation in the landing position of the ink droplets on the medium S can be suppressed, thereby improving the print quality.

[0172] 22, it is preferable that the second electrode 62 and the third electrode 63 are not electrically connected on the flow path forming substrate 10, which is the substrate. This allows the second electrode 62 and the third electrode 63 to be driven by supplying different potentials to them. Therefore, by driving the second electrode 62 and the third electrode 63 by supplying different potentials to them, it is possible to adjust the angle of the ejection direction of the ink droplets, that is, the tilt angle in the +X direction with respect to the +Z direction.

[0173] Here, a modified example of the fifth drive signal 205 of this embodiment will be described with reference to Fig. 23. Fig. 23 shows drive waveforms illustrating modified examples of the bias potential vbs, the fourth drive signal 204, and the fifth drive signal 205.

[0174] As shown in FIG. 23, the fifth drive signal 205 has an eighth reference element B8, a second ejection pulse DP2, and a ninth reference element B9.

[0175] The eighth and ninth reference elements B8 and B9 are connected to the second and third electrodes 62 and 63, respectively, at a potential supplied to the fourth electrode 80, which in this embodiment is a fourteenth potential V 14 Here, the 14th potential V 14 corresponds to the "first potential" in the second embodiment. 14 In this embodiment, the fourteenth potential V is a potential smaller than the bias potential vbs. 14 <The relationship of bias potential vbs is satisfied. 14 is the tenth potential V of the sixth reference element B6 and the seventh reference element B7 of the first ejection pulse DP1. 10 The fourteenth potential V 14 and the 10th potential V 10 By setting the potentials to be the same, the circuitry of the drive signal generating section 216 can be simplified compared to when different potentials are generated.

[0176] The fourth expansion component P30 of the second ejection pulse DP2 applies a fourteenth potential V 14 to the 13th potential V 13 The fourth return element P32 applies a thirteenth potential V 13 to the 14th potential V 14 The 13th potential V 13 is the tenth potential V of the first ejection pulse DP1 10It is preferable to set the first ejection pulse DP1 and the second ejection pulse DP2 to the same potential. This allows the first ejection pulse DP1 and the second ejection pulse DP2 to have the same waveform shape. Here, the first ejection pulse DP1 and the second ejection pulse DP2 having the same waveform shape means that they have the same minimum potential, maximum potential, and slope. By setting the first ejection pulse DP1 and the second ejection pulse DP2 to have the same waveform shape in this way, it is possible to easily control the drive signal generation unit 216.

[0177] Then, the eighth reference element B8 and the ninth reference element B9 apply a fourteenth potential V 14 By maintaining the state in which the fourteenth potential V is supplied, it is possible to adjust the natural vibration period Tc of the pressure chamber 12. 14 The magnitude of the potential V 14 By supplying the pressure chamber 12 with the ink, the natural vibration period Tc of the pressure chamber 12 can be reduced, and ink droplets can be ejected continuously at high speed.

[0178] In addition, in a head unit in which a plurality of recording heads 2 are unitized, even if there is a variation in the natural vibration period Tc among the plurality of recording heads 2, the 14th potential V 14 By changing the natural vibration period Tc, it is possible to reduce the variation in the natural vibration period Tc among the multiple recording heads 2. Therefore, it is possible to suppress the variation in the ejection characteristics, such as the ink weight and ejection speed, of the ink droplets ejected from the multiple recording heads 2.

[0179] 23, in the ink jet recording apparatus 1, the control unit supplies the first electrode 61 with a fourth drive signal 204, which is a first drive signal including a first ejection pulse DP1, and while the control unit is supplying the fourth drive signal 204 to the first electrode 61, the control unit supplies the second electrode 62 and the third electrode 63 with a fourteenth potential V 14According to this, while the fourth drive signal 204 is being supplied to the first electrode 61, the second electrode 62 and the third electrode 63 are supplied with the fourteenth potential V 14 By maintaining the state in which the voltage V is supplied, it is possible to adjust the natural vibration period Tc of the pressure chamber 12. Therefore, the natural vibration period Tc of the pressure chamber 12 can be reduced, and ink droplets can be continuously ejected at high speed. Furthermore, in an ink jet recording apparatus 1 having a head unit in which a plurality of recording heads 2 are unitized or a plurality of recording heads 2, even if there is a variation in the natural vibration period Tc among the plurality of recording heads 2, the 14th potential V of each recording head 2 can be adjusted. 14 By changing the natural vibration period Tc, it is possible to reduce the variation in the natural vibration period Tc among the plurality of recording heads 2. Therefore, it is possible to suppress the variation in the ejection characteristics, such as the ink weight and ejection speed, of the ink droplets ejected from the plurality of recording heads 2. Note that, in the above example, the bias potential vbs is supplied to the fourth electrode 80, but this is not particularly limited, and the fourth electrode 80 may be ground (GND).

[0180] In the ink jet recording apparatus 1 of this embodiment, the control unit supplies the bias potential vbs, which is the second potential, to the fourth electrode 80 while supplying the fourth drive signal 204, which is the first drive signal, and supplies the bias potential vbs, which is the first potential, to the fourth electrode 80. 14 It is preferable that the fourteenth potential V is equal to or greater than the bias potential vbs. 14 is set to a potential greater than the bias potential vbs, it is possible to prevent an electric field in the opposite direction to the ejection pulse DP from being applied to the piezoelectric actuator 300. Therefore, it is possible to prevent the piezoelectric actuator 300 from cracking or being destroyed.

[0181] 23, it is preferable that the first ejection pulse DP1 and the second ejection pulse DP2 have the same waveform shape in the ink jet recording apparatus 1. This can simplify the control of the drive signal generation unit 216.

[0182] Furthermore, the fifth drive signal 205 may include the damping pulse SVP of the first embodiment described above in addition to the second ejection pulse DP2. Such a modified example of the fifth drive signal 205 is shown in Fig. 24. Fig. 24 shows the drive waveforms of the bias potential vbs, the fourth drive signal 204, and the fifth drive signal 205.

[0183] As shown in FIG. 24, the unit period T of the fourth drive signal 204 and the fifth drive signal 205 is divided into three periods: a first period T1, a second period T2, and a third period T3.

[0184] The first ejection pulse DP1 of the fourth drive signal 204 is generated in the second period T2, and the second ejection pulse DP2 of the fifth drive signal 205 is generated in the first period T1.

[0185] Furthermore, a vibration damping pulse SVP is generated during the third period T3 of the fifth drive signal 205. The fifth drive signal 205 includes an eighth reference element B8, a second ejection pulse DP2, a ninth reference element B9, a vibration damping pulse SVP, and a tenth reference element B10, in this order. The tenth reference element B10 has the same twelfth potential V as the eighth reference element B8 and the ninth reference element B9. 12 is supplied to the second electrode 62 and the third electrode 63. A twelfth potential V 12 is the same potential as the bias potential vbs as described above.

[0186] The vibration suppression pulse SVP includes a fifth expansion element P40, a fifth expansion maintaining element P41, and a fifth return element P42.

[0187] The fifth expansion element P40 applies a twelfth potential V to the second electrode 62 and the third electrode 63. 12 to the 15th potential V 15 to deform the piezoelectric actuator 300 and the vibration plate 50 in the −Z direction opposite to the pressure chamber 12. As a result, the volume of the pressure chamber 12 expands from the tenth volume to the thirteenth volume.

[0188] Also, the 15th potential V of the fifth expansion element P40 15is the 13th potential V of the second injection pulse DP2 13 The 15th potential V 15 and the 13th potential V 13 By setting the potentials to be the same, the circuitry of the drive signal generating section 216 can be simplified compared to when different potentials are generated.

[0189] The fifth expansion maintaining element P41 applies a fifteenth potential V 15 is continuously applied, and the volume of the pressure chamber 12 expanded by the fifth expansion element P40 is maintained at the thirteenth volume for a certain period of time.

[0190] The fifth return element P42 applies a fifteenth potential V to the second electrode 62 and the third electrode 63. 15 to the 12th potential V 12 to deform the piezoelectric actuator 300 and the vibration plate 50 in the +Z direction. As a result, the volume of the pressure chamber 12 contracts and returns to the tenth volume from the thirteenth volume.

[0191] By inserting the damping pulse SVP after the second ejection pulse DP2 and the first ejection pulse DP1 in this way, residual vibrations of ink in the pressure chamber 12 after ink is ejected from the nozzle 21 can be quickly converged. That is, when the damping pulse SVP drives the second active portion 312 and the third active portion 313 of the piezoelectric actuator 300, the second active portion 312 and the third active portion 313 contract along the Z axis, as shown in FIG. 20 , causing the piezoelectric actuator 300 and the diaphragm 50 to deform so as to protrude convexly in the −Z direction, which is the opposite side of the pressure chamber 12. At this time, tensile stress is applied to the portion including the first active portion 311 sandwiched between the second active portion 312 and the third active portion 313, increasing the apparent Young's modulus. The increase in the apparent Young's modulus of the piezoelectric actuator 300 allows residual vibrations of ink in the pressure chamber 12 after ink droplets are ejected to be quickly converged.

[0192] Of course, as with the fifth drive signal 205 having the vibration control pulse SVP, the natural vibration period Tc of the pressure chamber 12 can be adjusted by setting the potential supplied to the second electrode 62 and the third electrode 63 at the eighth reference element B8, the ninth reference element B9 and the tenth reference element B10 to a potential different from the bias potential vbs, as in Figure 23.

[0193] 24, in the inkjet recording apparatus 1, after supplying the first ejection pulse DP1 and the second ejection pulse DP2, the control unit preferably supplies a vibration damping pulse SVP to the second electrode 62 and the third electrode 63 to drive the piezoelectric actuator so that liquid is not ejected from the nozzle 21. By inputting the vibration damping pulse SVP after the ejection pulse DP, the apparent Young's modulus of the piezoelectric layer 70 can be increased, and residual vibrations after the first ejection pulse DP1 and the second ejection pulse DP2 can be converged in a short time. Therefore, ink droplets can be ejected repeatedly in a short time, achieving high-speed continuous ejection.

[0194] It is also possible to supply a vibration damping pulse SVP to the second electrode 62 and the third electrode 63 corresponding to the pressure chamber 12 that does not eject ink droplets. This causes the ink in the vicinity of the pressure chamber 12 and the nozzle 21 to vibrate slightly, thereby suppressing the settling of components contained in the ink and suppressing the retention of thickened ink, thereby preventing ejection failure of ink droplets due to thickened ink.

[0195] 18, 23, and 24 of this embodiment, the driving of the print head 2 by the drive signals shown in FIGS. 18, 23, and 24 can also be used in the configuration of the first embodiment described above, i.e., the configuration in which the second electrode 62 constitutes a common electrode for a plurality of second active units 312 and the third electrode 63 constitutes a common electrode for a plurality of third active units 313. That is, the control unit supplies the fourth drive signal 204 to the first electrode 61 constituting an individual electrode, and supplies the fifth drive signal 205 to the second electrode 62 and the third electrode 63 constituting a common electrode. The second ejection pulse DP2 is also supplied to the second active units 312 and the third active units 313 that do not eject ink droplets. However, if the second ejection pulse DP2 alone does not eject ink droplets, in other words, if ink droplets are ejected only when the second ejection pulse DP2 is combined with the first ejection pulse DP1, ink droplets can be selectively ejected from the nozzles 21. Furthermore, by supplying only the second ejection pulse DP2, the second ejection pulse DP2 also functions as a micro-vibration pulse, so that by driving the second active units 312 and third active units 313 corresponding to the nozzles 21 that do not eject ink droplets with the second ejection pulse DP2, it is possible to micro-vibrate the ink near the nozzles 21. This makes it possible to suppress sedimentation of components contained in the ink near the pressure chambers 12 and the nozzles 21, and to suppress retention of thickened ink, thereby suppressing ejection failure of ink droplets due to thickened ink. Of course, the second ejection pulse DP2 may also be supplied as a micro-vibration pulse to the second active units 312 and third active units 313 that constitute the individual electrodes of this embodiment.

[0196] (Other embodiments) Although the embodiments of the present invention have been described above, the basic configuration of the present invention is not limited to those described above.

[0197] Here, the piezoelectric actuator 300 and the vibration plate 50 are not limited to those described above. Modified examples of the piezoelectric actuator 300 and the vibration plate 50 are shown in Figs. 25 to 30. Figs. 25 to 29 are cross-sectional views of the main part of a recording head 2 according to another embodiment of the present invention. Fig. 30 is a plan view of a flow path forming substrate 10 according to another embodiment of the present invention, viewed in the +Z direction. Note that the same reference numerals are used to designate the same members as those in the above-described embodiments, and redundant explanations will be omitted.

[0198] 25, recessed grooves 81 are formed in the +X direction on the -Z direction surface of the fourth electrode 80 opposite the piezoelectric layer 70, between the first electrode 61 and the second electrode 62 and between the first electrode 61 and the third electrode 63. For example, the piezoelectric layer 70 may be formed on the first electrode 61, the second electrode 62, and the third electrode 63 by a liquid-phase deposition method such as a sol-gel method or an MOD method, thereby forming the recesses 71 on the -Z direction surface of the piezoelectric layer 70, and then the fourth electrode 80 may be formed on the -Z direction surface of the piezoelectric layer 70 on which the recesses 71 are formed, thereby forming the grooves 81. Of course, the grooves 81 may also be formed in the first and second embodiments described above. Alternatively, the -Z direction surface of the piezoelectric layer 70 may be polished and flattened by chemical mechanical polishing (CMP) to prevent the grooves 81 from being formed in the fourth electrode 80. Furthermore, if the surface of the piezoelectric layer 70 in the -Z direction is flat, the recesses 71 can be formed and the grooves 81 can be formed by partially etching the surface of the piezoelectric layer 70 in the -Z direction through a mask.

[0199] In the recording head 2 shown in Figure 25, it is preferable to form concave groove portions 81 on the surface of the fourth electrode 80 opposite the piezoelectric layer 70 between the first electrode 61 and the second electrode 62, and between the first electrode 61 and the third electrode 63 in the first direction, the +X direction, as this makes the recording head 2 more susceptible to deformation.

[0200] Furthermore, it is preferable that the diaphragm 50 has a lower Young's modulus than the piezoelectric layer 70. For example, in each of the above-described embodiments, zirconium oxide (ZrO XIt includes the insulator film 52 of ). Since the piezoelectric layer 70 uses lead zirconate titanate (PZT), the diaphragm 50 has a lower Young's modulus than the piezoelectric layer 70. Therefore, as shown in FIG. 26, when viewed in the +Z direction, the diaphragm 50 has the thickness in the +Z direction at both ends in the +X direction thinner than that at the central portion in the region corresponding to the pressure chamber 12. That is, when viewed in the -Z direction, the diaphragm 50 has a first vibrating portion 50a with a thickness d1 provided in the region overlapping the first electrode 61, and a second vibrating portion 50b with a thickness d2 provided in the region overlapping the second electrode 62 and the third electrode 63, satisfying the relationship d1 > d2.

[0201] The first vibrating portion 50a and the second vibrating portion 50b are formed such that the surface in the +Z direction is a flat surface. The first vibrating portion 50a protrudes in the -Z direction, which is opposite to the pressure chamber 12 compared to the second vibrating portion 50b, resulting in a thicker film thickness. Therefore, in the +Z direction, the distance t1 between the first electrode 61 and between the first electrode 61 and the fourth electrode 80 is narrower than the distance t2 between the second electrode 62 and the third electrode 63 and the fourth electrode 80. That is, it satisfies the relationship t1 < t2. The distance t1 between the first electrode 61 and the fourth electrode 80, and the distance t2 between the second electrode 62 and the third electrode 63 and the fourth electrode 80 can be replaced by the thicknesses in the -Z direction of the piezoelectric layer 70, respectively.

[0202] Also, the first vibrating portion 50a and the second vibrating portion 50b of the diaphragm 50 in FIG. 26 can adjust the overall thicknesses d1 and d2 of the diaphragm 50, for example, by changing the thickness of the elastic film 51.

[0203] 26, the second electrode 62, the third electrode 63, the first electrode 61, and the fourth electrode 80 are arranged in the −Z direction, which is the stacking direction. Furthermore, the distance t1 between the first electrode 61 and the fourth electrode 80 in the −Z direction is preferably narrower than the distance t2 between the second electrode 62, the third electrode 63, and the fourth electrode 80. By making the distance t1 between the first electrode 61 and the fourth electrode 80 narrower than the distance t2, the electric field strength of the first active section 311 can be increased. Furthermore, an electric field in a direction tilted with respect to the +Z direction can be applied to the piezoelectric layer 70 between the first electrode 61 and the fourth electrode 80 in the XZ plane defined by the X-axis and the Z-axis, thereby improving the driving efficiency.

[0204] 27, the first vibrating portion 50a and the second vibrating portion 50b are formed so that their surfaces in the -Z direction are flat, and the film thickness may be increased by having the first vibrating portion 50a protrude further than the second vibrating portion 50b in the +Z direction, which is the side opposite the pressure chamber 12. Note that the first vibrating portion 50a and the second vibrating portion 50b of the diaphragm 50 in FIG. 27 can have their overall thicknesses d1 and d2 adjusted by, for example, changing the thickness of the elastic film 51.

[0205] 26 and 27, it is preferable that the vibration plate 50 has a larger Young's modulus than the piezoelectric layer 70, and that in the region of the vibration plate 50 facing the pressure chamber 12, which is a recess when viewed in the +Z direction, which is the stacking direction, the second vibration portions 50b, which are both ends in the +X direction, which is the first direction, are thinner in the +Z direction than the first vibration portion 50a, which is the central portion. By providing the second vibration portions 50b, which are thinner than the first vibration portion 50a, at both ends in the +X direction of the vibration plate 50 in this way, the vibration plate 50 is more likely to deform along the Z axis, and a large amount of displacement can be obtained with a relatively low voltage, which means that the displacement efficiency can be improved.

[0206] Furthermore, by making the thickness d1 of the first vibrating portion 50a of the diaphragm 50 thicker than the thickness d2 of the second vibrating portion 50b, the first active portion 311 can be spaced apart from the position of the neutral axis of the diaphragm 50. Therefore, the displacement efficiency of the first active portion 311 can be improved.

[0207] Also, as shown in FIG. 28, the thickness d2 of the second vibrating portion 50b of the diaphragm 50 may be greater than the thickness d1 of the first vibrating portion 50a, that is, the relationship d1 < d2 may be satisfied. Even with such a configuration, the same effect as that of FIG. 27 can be achieved.

[0208] Also, as shown in FIG. 26, in the region where the piezoelectric layer 70 faces the pressure chamber 12 which is a concave portion when viewed in the -Z direction which is the stacking direction, it is preferable that the thicknesses of both end portions in the +X direction which is the first direction are greater than the thickness in the -Z direction at the central portion. That is, it is preferable that the thickness t2 of both end portions of the piezoelectric layer 70 is greater than the thickness t1 of the central portion. Thus, by making the thickness t1 of the piezoelectric layer 70 between the first electrode 61 and the fourth electrode 80 thinner than the thickness t2 of the piezoelectric layer 70 between the second electrode 62 and the third electrode 63 and the fourth electrode 80, the electric field strength of the first active portion 311 can be increased. Also, since an electric field in a direction inclined with respect to the +Z direction can be applied to the piezoelectric layer 70 within the XZ plane defined by the X axis and the Z axis between the first electrode 61 and the fourth electrode 80, the driving efficiency can be improved.

[0209] Also, as shown in FIG. 28, the thickness d1 of the first vibrating portion 50a of the diaphragm 50 may be made thinner than the thickness d2 of the second vibrating portion 50b. That is, the relationship d1 < d2 is satisfied. Thus, by making the thickness d1 of the first vibrating portion 50a thinner than the thickness of the second vibrating portion 50b, the driving efficiency of the first active portion 311 can be improved. Also, by making the thickness d2 of the second vibrating portion 50b which is the most bent region of the diaphragm 50 thicker than the thickness d1 of the first vibrating portion 50a, breakage of the second vibrating portion 50b when the piezoelectric actuator 300 is driven can be suppressed.

[0210] Also, as shown in FIG. 29, the piezoelectric layer 70 of the piezoelectric actuator 300 has a first piezoelectric layer 70a, a second piezoelectric layer 70b, and a third piezoelectric layer 70c extending in the -Z direction from the diaphragm 50. The first electrode 61 is provided between the second piezoelectric layer 70b and the third piezoelectric layer 70c. Also, the second electrode 62 and the third electrode 63 are provided between the first piezoelectric layer 70a and the second piezoelectric layer 70b. That is, the second electrode 62 and the third electrode 63, the first electrode 61, and the fourth electrode 80 are arranged in the -Z direction. That is, the first electrode 61 and the second electrode 62 and the third electrode 63 are arranged at different positions in the -Z direction. And the distance t3 between the first electrode 61 and the fourth electrode 80 is smaller than the distance t4 between the second electrode 62 and the third electrode 63 and the fourth electrode 80. That is, the relationship t3 < t4 is satisfied. Also, on the pressure chamber 12 side of the first electrode 61, the first piezoelectric layer 70a and the second piezoelectric layer 70b of the piezoelectric layer 70 are provided.

[0211] Also, the first electrode 61 and the second electrode 62 and the third electrode 63 are arranged at positions that do not overlap each other when viewed in the -Z direction. In the example shown in FIG. 29, since the first electrode 61 and the second electrode 62 and the third electrode 63 are arranged at different positions in the -Z direction, the first electrode 61 and the second electrode 62 and the third electrode 63 may be arranged at positions where a part overlaps in the -Z direction.

[0212] In the configuration shown in FIG. 29, the second electrode 62 and the third electrode 63, the first electrode 61, and the fourth electrode 80 are arranged in the -Z direction, which is the stacking direction. Also, it is preferable that the distance d3 between the first electrode 61 and the fourth electrode 80 in the -Z direction is smaller than the distance d4 between the second electrode 62 and the third electrode 63 and the fourth electrode 80. Thus, by making the distance d3 between the first electrode 61 and the fourth electrode 80 smaller than the distance d4, the electric field strength of the first active part 311 can be increased. Also, since an electric field in a direction inclined with respect to the +Z direction can be applied to the piezoelectric layer 70 within the XZ plane defined by the X axis and the Z axis between the first electrode 61 and the fourth electrode 80, the driving efficiency can be improved.

[0213] 29, it is preferable that the first electrode 61 has a first piezoelectric layer 70a and a second piezoelectric layer 70b on the pressure chamber 12 side, which is the recess of the first electrode 61. By providing the first piezoelectric layer 70a and the second piezoelectric layer 70b on the pressure chamber 12 side of the first electrode 61 in this manner, the distance t3 between the first electrode 61 and the fourth electrode 80 can be made narrower than the distance t4, thereby increasing the electric field strength of the first active section 311. Furthermore, an electric field in a direction tilted with respect to the +Z direction in the XZ plane defined by the X-axis and the Z-axis can be applied to the piezoelectric layer 70 between the first electrode 61 and the fourth electrode 80, thereby improving drive efficiency. Furthermore, an electric field in a direction tilted with respect to the +Z direction in the XZ plane can be applied to the second piezoelectric layer 70b between the first electrode 61 and the second electrode 62 and the third electrode 63, thereby improving drive efficiency.

[0214] 30, the first electrode 61 has a first central portion 61a at the center and first end portions 61b at both ends in the direction along the Y axis at a position overlapping the pressure chamber 12 when viewed in the -Z direction. The width w1 of the first central portion 61a in the +X direction is wider than the width w2 of the first end portions 61b. In other words, the relationship w1>w2 is satisfied. That is, the width of the first electrode 61 in the +X direction is wider on the central side of the pressure chamber 12 in the +Y direction when viewed in the -Z direction than on both ends.

[0215] The second electrode 62 has a second central portion 62a at its center and second end portions 62b at its opposite ends in the direction along the Y axis at a position overlapping the pressure chamber 12 when viewed in the -Z direction. The width w3 of the second central portion 62a in the +X direction is greater than the width w4 of the second end portions 62b. In other words, the relationship w3>w4 is satisfied.

[0216] The third electrode 63 has a third central portion 63a at its center and third end portions 63b at its both end portions in the direction along the Y axis at a position overlapping the pressure chamber 12 when viewed in the -Z direction. The width w5 of the third central portion 63a in the +X direction is wider than the width w6 of the third end portions 63b. In other words, the relationship w5 > w6 is satisfied. That is, the widths of the second electrode 62 and the third electrode 63 in the +X direction are wider on the central side of the pressure chamber 12 in the +Y direction when viewed in the -Z direction than on the both end portions.

[0217] In the example shown in Figure 30, the width in the +X direction of the first electrode 61 and both the second electrode 62 and the third electrode 63 is wider at the center of the pressure chamber 12 in the +Y direction when viewed in the -Z direction than at both ends, but this is not particularly limited to this, and it is sufficient that the width in the +X direction of either the first electrode 61 or the second electrode 62 and the third electrode 63 satisfies the above configuration.

[0218] 30, the width of the first electrode 61 in the +X direction (first direction) is preferably wider at the center of the pressure chamber 12, which is a recess in the +Y direction (second direction perpendicular to the +X direction) when viewed in the −Z direction (lamination direction). By making the width w1 of the first central portion 61a at the center of the first electrode 61 wider than the width w2 of the first end portions 61b at both ends, the area of ​​the first electrode 61 in the XY plane can be increased, thereby improving drive efficiency. Furthermore, because the first end portions 61b have a narrower width w2 than the first central portion 61a, electric field concentration at the end portions of the first active portion 311 can be suppressed. This suppresses damage such as burning and cracking of the piezoelectric layer 70.

[0219] 30, the width of the second electrode 62 and the third electrode 63 in the +X direction (first direction) is preferably wider at the center of the pressure chamber 12, which is a recess in the +Y direction (second direction orthogonal to the +X direction) when viewed in the −Z direction (stacking direction), than at both end portions. In this way, by making the width w3 of the second central portion 62a at the center of the second electrode 62 and the width w5 of the third central portion 63a wider than the width w4 of the second end portion 62b at both end portions and the width w6 of the third end portion 63b at both end portions, the area of ​​the second electrode 62 and the third electrode 63 in the XY plane can be increased, and drive efficiency can be improved.

[0220] Furthermore, in the inkjet recording device 1 described above, the recording head 2 is mounted on a transport body 7 and moves in a direction along the Y axis, which is the main scanning direction, but this is not particularly limited to this, and the present invention can also be applied to, for example, a so-called line-type recording device in which the recording head 2 is fixed and printing is performed simply by moving a medium S, such as paper, in a direction along the X axis, which is the sub-scanning direction.

[0221] Furthermore, in each of the above-described embodiments, the bias potential vbs is supplied to the fourth electrode 80, but this is not particularly limited, and the fourth electrode 80 may be ground (GND).

[0222] In the above embodiment, an inkjet recording head is used as an example of a liquid jet head, and an inkjet recording device is used as an example of a liquid jet device. However, the present invention is directed to a wide range of liquid jet heads and liquid jet devices, and can of course be applied to liquid jet heads and liquid jet devices that jet liquids other than ink. Examples of other liquid jet heads include various recording heads used in image recording devices such as printers, colorant jet heads used in manufacturing color filters for liquid crystal displays, electrode material jet heads used in forming electrodes for organic EL displays, FEDs (field emission displays), and bioorganic material jet heads used in manufacturing biochips, and the present invention can also be applied to liquid jet devices equipped with such liquid jet heads.

[0223] Furthermore, the present invention is not limited to liquid jet heads typified by ink jet recording heads, but can also be applied to piezoelectric devices such as ultrasonic devices, motors, pressure sensors, pyroelectric elements, ferroelectric elements, etc. Furthermore, completed products using these piezoelectric devices, such as liquid jetting apparatuses using the liquid jetting heads, ultrasonic sensors using the ultrasonic devices, robots using the motors as their driving sources, IR sensors using the pyroelectric elements, and ferroelectric memories using ferroelectric elements, are also included in the piezoelectric device. [Explanation of symbols]

[0224] 1...inkjet recording apparatus (liquid ejection apparatus), 2...inkjet recording head (liquid ejection head), 3...liquid container, 4...transport mechanism, 4a...transport roller, 5...control device, 6...movement mechanism, 7...transport body, 8...transport belt, 10...flow path forming substrate, 11...partition wall, 12...pressure chamber, 15...communicating plate, 16...nozzle connecting passage, 17...first manifold portion, 18...second manifold portion, 19...supply connecting passage, 20...nozzle plate, 20a...liquid ejection surface, 21...nozzle, 30...protective substrate, 31...holding portion, 32...through hole, 40...case member, 41...recess, 42...third manifold Solder portion, 43...connection port, 44...inlet port, 45...compliance substrate, 46...sealing film, 47...fixed substrate, 48...opening, 49...compliance portion, 50...diaphragm, 50a...first vibrating portion, 50b...second vibrating portion, 51...elastic film, 52...insulating film, 61...first electrode, 61a...first central portion, 61b...first end portion, 62...second electrode, 62a...second central portion, 62b...second end portion, 63...third electrode, 63a...third central portion, 63b...third end portion, 64...common connecting portion, 64A...individual connecting portion, 70...piezoelectric layer, 70a...first piezoelectric layer, 70b...second piezoelectric layer, 70c...third piezoelectric layer, 71...recess, 80...fourth electrode, 81...groove portion, 91...first individual lead electrode, 92...first common lead electrode, 93...second common lead electrode, 94...second individual lead electrode, 100...manifold, 120...wiring board, 121...drive circuit, 122...shift register, 123...latch circuit, 124...level shifter, 125...switch, 201...first drive signal, 202...second drive signal, 203...third drive signal, 204...fourth drive signal, 205...fifth drive signal, 210...printer controller, 211...external interface, 212A...receiving buffer, 2 12B...intermediate buffer, 212C...output buffer, 214...control processing unit, 215...oscillating circuit, 216...drive signal generating unit, 217...internal interface, 220...print engine, 230...external device, 300...piezoelectric actuator, 311...first active unit, 312...second active unit, 313...third active unit, B1...first reference element, B2...second reference element, B3...third reference element, B4...fourth reference element, B5...fifth reference element, B6...sixth reference element, B7...seventh reference element, B8...eighth reference element, B9...ninth reference element, B10...tenth reference element, DP...ejection pulse,DP1...first ejection pulse, DP2...second ejection pulse, P1...first expansion element, P2...first expansion maintenance element, P3...first contraction element, P4...first contraction maintenance element, P5...first return element, P10...second expansion element, P11...second expansion maintenance element, P12...second return element, P20...third contraction element, P21...third contraction maintenance element, P22...third return element, P30...fourth expansion element, P31...fourth expansion maintenance element, P32...fourth return element, P40...fifth expansion element, P41...fifth expansion maintenance element, P42...fifth return element, S...medium, SVP...vibration control pulse, T...unit period (ejection period, recording period), T1 to T3...first period to third period, Tc...natural vibration period, V1 to V, 15 ...1st potential to 15th potential, vbs...bias potential

Claims

1. a substrate on which a plurality of recesses are formed aligned in a first direction; A diaphragm and a piezoelectric actuator in which a first electrode, a second electrode, a third electrode, and a fourth electrode are stacked in this order, and a piezoelectric layer is provided between the first electrode and the fourth electrode, between the second electrode and the fourth electrode, and between the third electrode and the fourth electrode; and a plurality of active portions in which the piezoelectric layer is sandwiched between the first electrode, the second electrode, the third electrode, and the fourth electrode; the second electrode and the third electrode are provided at both end portions of the recess in the first direction from edges of a region facing the recess to an outer side of the recess as viewed in the stacking direction, the first electrode is formed between the second electrode and the third electrode in the first direction, the second electrode, the third electrode, and the fourth electrode constitute a common electrode for a plurality of the active portions, the first electrode constitutes an individual electrode independently provided on each of the active portions, the second electrode, the third electrode, the first electrode, and the fourth electrode are arranged in this order in the stacking direction, and a distance between the first electrode and the fourth electrode in the stacking direction is narrower than a distance between the second electrode and the third electrode and the fourth electrode; A piezoelectric device characterized by:

2. The first electrode does not have the piezoelectric layer on the recess side.

2. The piezoelectric device according to claim 1 .

3. The piezoelectric layer is provided on the recess side of the first electrode.

3. The piezoelectric device according to claim 1, wherein the piezoelectric element is a piezoelectric material.

4. the first electrode, the second electrode, and the third electrode do not overlap with each other in the first direction when viewed in the stacking direction; 4. The piezoelectric device according to claim 1, wherein the piezoelectric element is a piezoelectric material.

5. the fourth electrode covers the recess in the first direction when viewed in the stacking direction.

5. The piezoelectric device according to claim 1, wherein the piezoelectric element is a piezoelectric material.

6. When viewed in the stacking direction, the recess has a longitudinal direction in a second direction perpendicular to the first direction.

6. The piezoelectric device according to claim 1, wherein the piezoelectric element is a piezoelectric material.

7. a width of the first electrode in the first direction is wider at a center of the recess in a second direction perpendicular to the first direction as viewed in the stacking direction than at both end portions of the recess; 7. The piezoelectric device according to claim 1, wherein the piezoelectric element is a piezoelectric material.

8. a width of each of the second electrode and the third electrode in the first direction is wider at a center of the recess in a second direction perpendicular to the first direction as viewed in the stacking direction than at both end portions of the recess; 8. The piezoelectric device according to claim 1, wherein the piezoelectric element is a piezoelectric material.

9. the vibration plate has a larger Young's modulus than the piezoelectric layer, In a region of the diaphragm facing the recess as viewed in the stacking direction, both end portions in the first direction have a thickness in the stacking direction that is thinner than that of a central portion.

9. The piezoelectric device according to claim 1, wherein the piezoelectric element is a piezoelectric material.

10. In a region of the piezoelectric layer facing the recess as viewed in the stacking direction, both end portions in the first direction have a thickness in the stacking direction that is greater than that of a central portion.

10. The piezoelectric device according to claim 9.

11. The diaphragm contains zirconium oxide.

11. The piezoelectric device according to claim 1, wherein the piezoelectric element is a piezoelectric material.

12. a substrate on which a plurality of pressure chambers communicating with nozzles that eject liquid are formed, arranged in a first direction; A diaphragm and a piezoelectric actuator in which a first electrode, a second electrode, a third electrode, and a fourth electrode are stacked in this order, and a piezoelectric layer is provided between the first electrode and the fourth electrode, between the second electrode and the fourth electrode, and between the third electrode and the fourth electrode; a control unit that drives the piezoelectric actuator; and a plurality of active portions in which the piezoelectric layer is sandwiched between the first electrode, the second electrode, the third electrode, and the fourth electrode; the second electrode and the third electrode are provided at both ends of the pressure chamber in the first direction, extending from edges of a region facing the pressure chamber as viewed in the stacking direction to outside the pressure chamber; the first electrode is formed between the second electrode and the third electrode in the first direction, the second electrode, the third electrode, and the fourth electrode constitute a common electrode for a plurality of the active portions, the first electrode constitutes an individual electrode independently provided on each of the active portions, the control unit supplies an ejection pulse to the first electrode to eject the liquid from the nozzle; the control unit supplies, to the second electrode and the third electrode, a damping pulse that drives the piezoelectric actuator so as not to eject liquid from the nozzle at least after the ejection pulse; A liquid ejection device characterized by:

13. the control unit deforms the vibration plate by the vibration damping pulse so as to be convex on the side opposite to the pressure chamber. The liquid ejection apparatus according to claim 12 .

14. the control unit deforms the vibration plate to be convex toward the pressure chamber by the ejection pulse.

14. The liquid ejecting apparatus according to claim 12 or 13.

15. the control unit supplies a first drive signal including the ejection pulse to the first electrode; supplying a first potential, which is different from a potential supplied to the fourth electrode, to the second electrode and the third electrode while the first drive signal is supplied to the first electrode; 15. The liquid ejecting apparatus according to claim 12, wherein the liquid ejecting apparatus is a liquid ejecting apparatus.

16. the control unit supplies a second potential to the fourth electrode while supplying the first drive signal; the first potential is equal to or greater than the second potential; The liquid ejection apparatus according to claim 15 .

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