Liquid dispensing device

Abstract

To provide a liquid discharge device improved in discharge characteristics.SOLUTION: The liquid discharge device comprises: a pressure chamber substrate, which is laminated on a first surface of a vibration plate, and has a bulkhead partitioning a pressure chamber communicating with a nozzle for discharging liquid; a piezoelectric element, which is laminated on a second surface of the vibration plate, and has a first active part overlapping with a center of the pressure chamber when viewed in a thickness direction of the vibration plate and a second active part overlapping with the pressure chamber, at a position closer to an outer edge of the pressure chamber than the first active part; a driving signal generating part that generates a first driving signal for driving the first active part and a second driving signal for driving the second active part. The first driving signal includes a first contractile element for contracting a volume of the pressure chamber for each periodic unit period, and the second driving signal includes a second contractile element for contracting the volume of the pressure chamber for unit period. The liquid discharge device executes a contraction process in which a first period during which the first contractile element is supplied to the first acting part and a second period during which the second contractile element is supplied to the second acting part overlap with each other.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejection device. [Background technology]

[0002] Liquid ejection devices, such as piezoelectric inkjet printers, generally employ a configuration in which a piezoelectric element is disposed on a diaphragm that forms part of the wall of a pressure chamber that communicates with a nozzle. The pressure chamber contains a liquid, such as ink. The piezoelectric element deforms the diaphragm, expanding or contracting the volume of the pressure chamber, thereby ejecting the liquid from the nozzle.

[0003] The piezoelectric element of such a liquid ejection device may be divided into an active part that overlaps the center of the pressure chamber when viewed in the thickness direction of the vibration plate, and an active part that overlaps the end of the pressure chamber, as disclosed in Patent Document 1, for example. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-25225 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is no disclosure regarding specific drive signals for driving the two active parts mentioned above in Patent Document 1. Under these circumstances, it is desirable to realize a liquid ejection device with excellent ejection characteristics. [Means for solving the problem]

[0006] In order to solve the above problems, one aspect of the liquid ejection device according to the present disclosure includes a vibration plate having a first surface and a second surface facing in a direction opposite to the first surface, a pressure chamber substrate laminated on the first surface and having partition walls that define pressure chambers that communicate with nozzles that eject liquid, a piezoelectric element laminated on the second surface and having a first active part that overlaps with the center of the pressure chamber in the thickness direction of the vibration plate and a second active part that overlaps with the pressure chamber at a position closer to the outer edge of the pressure chamber than the first active part, and a drive mechanism for driving the first active part. a drive signal generating unit that generates a first drive signal that drives the second active unit and a second drive signal that drives the second active unit, wherein the first drive signal includes a first contraction element that contracts the volume of the pressure chamber for each periodic unit period, and the second drive signal includes a second contraction element that contracts the volume of the pressure chamber for each unit period, and a contraction step is executed in which a first period in which the first contraction element is supplied to the first active unit and a second period in which the second contraction element is supplied to the second active unit overlap each other.

[0007] Another aspect of a liquid ejection device according to the present disclosure comprises a vibration plate having a first surface and a second surface facing in the opposite direction from the first surface; a pressure chamber substrate stacked on the first surface and having partitions that define pressure chambers that communicate with nozzles that eject liquid; a piezoelectric element stacked on the second surface and having a first active part that overlaps the center of the pressure chamber when viewed in the thickness direction of the vibration plate and a second active part that overlaps the pressure chamber at a position closer to the outer edge of the pressure chamber than the first active part; and a drive signal generation unit that generates a first drive signal that drives the first active part and a second drive signal that drives the second active part, wherein the first drive signal includes a first period during which it changes from a first potential to a second potential for each periodic unit period, and the second drive signal includes a second period during which it changes from a third potential to a fourth potential for each unit period, and the first period and the second period overlap with each other. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a configuration diagram that schematically illustrates a liquid ejection device according to a first embodiment. [Figure 2]FIG. 2 is a diagram showing the electrical configuration of the liquid ejection device according to the first embodiment. [Figure 3] FIG. 2 is an exploded perspective view of a head chip. [Figure 4] FIG. 4 is a cross-sectional view taken along line AA in FIG. [Figure 5] FIG. 2 is a plan view of a head chip. [Figure 6] FIG. 6 is a cross-sectional view taken along line BB in FIG. 5. [Figure 7] FIG. 2 is a diagram for explaining a switching circuit. [Figure 8] 5A and 5B are diagrams for explaining a first drive signal and a second drive signal in the first embodiment. [Figure 9] FIG. 4 is a diagram for explaining a shrinking step in the first embodiment. [Figure 10] 5A and 5B are schematic diagrams for explaining deformation of a diaphragm due to a first drive signal. [Figure 11] 10A and 10B are schematic diagrams for explaining deformation of the diaphragm due to a second drive signal. [Figure 12] FIG. 10 is a diagram for explaining a shrinking step in the second embodiment. [Figure 13] FIG. 10 is a diagram for explaining a first drive signal and a second drive signal in the third embodiment. [Figure 14] 10A and 10B are diagrams for explaining a contraction process and an expansion process in the third embodiment. [Figure 15] 10A and 10B are diagrams for explaining a contraction process and an expansion process in the fourth embodiment. [Figure 16] 13A to 13C are diagrams for explaining a contraction process, an expansion process, and a vibration damping process in the fifth embodiment. [Figure 17] FIG. 13 is a diagram for explaining a first drive signal and a second drive signal in the sixth embodiment. [Figure 18] 13A to 13C are diagrams for explaining a contraction process and an expansion process in the sixth embodiment. [Figure 19] 13A and 13B are diagrams for explaining a contraction process and an expansion process in the seventh embodiment. [Figure 20] FIG. 13 is a diagram for explaining a first drive signal and a second drive signal in the eighth embodiment. [Figure 21] 13A to 13C are diagrams for explaining a contraction process, a first expansion process, and a second expansion process in the eighth embodiment. [Figure 22] 13A to 13C are diagrams for explaining a contraction process, a first expansion process, and a second expansion process in the ninth embodiment. [Figure 23] 13A to 13C are diagrams for explaining a contraction process and an expansion process in the tenth embodiment. [Figure 24] 10A and 10B are diagrams for explaining a contraction process and an expansion process in Modification 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Preferred embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that the dimensions and scale of each part in the drawings may differ from the actual dimensions and are shown schematically to facilitate understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description to the effect that the present disclosure is limited.

[0010] For convenience, the following description will use the mutually intersecting X-axis, Y-axis, and Z-axis as appropriate. In the following description, one direction along the X-axis is the X1 direction, and the direction opposite the X1 direction is the X2 direction. Similarly, the opposite directions along the Y-axis are the Y1 direction and the Y2 direction. Furthermore, the opposite directions along the Z-axis are the Z1 direction and the Z2 direction. Viewing in the direction along the Z-axis is sometimes referred to as "planar view."

[0011] Typically, the Z axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. However, the Z axis does not have to be a vertical axis. Furthermore, the X axis, Y axis, and Z axis are typically perpendicular to each other, but are not limited to this. For example, they may intersect at an angle between 80° and 100°.

[0012] 1. First embodiment 1-1. Overall configuration of the liquid ejection device FIG. 1 is a schematic diagram illustrating a configuration of a liquid ejection device 100 according to a first embodiment. The liquid ejection device 100 is an inkjet printing device that ejects ink, an example of a liquid, as droplets onto a medium M. The medium M is typically printing paper. However, the medium M is not limited to printing paper, and may be a printing target made of any material, such as a resin film or fabric.

[0013] As shown in FIG. 1, the liquid ejection device 100 includes a liquid container 10, a control unit 20, a transport mechanism 30, a moving mechanism 40, and a liquid ejection head 50.

[0014] The liquid container 10 is a container that stores ink. Specific examples of the liquid container 10 include a cartridge that is detachable from the liquid ejection device 100, a bag-shaped ink pack made of flexible film, and an ink tank that can be refilled with ink. The type of ink stored in the liquid container 10 is arbitrary.

[0015] The control unit 20 includes a processing circuit such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array) and a storage circuit such as a semiconductor memory, and controls the operation of each element of the liquid ejection device 100.

[0016] The transport mechanism 30 transports the medium M in the Y2 direction under the control of the control unit 20. The movement mechanism 40 reciprocates the liquid ejection head 50 in the X1 direction and the X2 direction under the control of the control unit 20. In the example shown in FIG. 1, the movement mechanism 40 has a substantially box-shaped carriage 41 that houses the liquid ejection head 50, and an endless transport belt 42 to which the carriage 41 is fixed. Note that the number of liquid ejection heads 50 mounted on the carriage 41 is not limited to one, and may be multiple. In addition to the liquid ejection head 50, the carriage 41 may also be equipped with the aforementioned liquid container 10.

[0017] Under the control of the control unit 20, the liquid ejection head 50 ejects ink supplied from the liquid container 10 from each of the multiple nozzles in the Z2 direction toward the medium M. This ejection is performed in parallel with the transport of the medium M by the transport mechanism 30 and the reciprocating movement of the liquid ejection head 50 by the movement mechanism 40, so that an image is formed on the surface of the medium M using ink.

[0018] 1-2. Electrical configuration of the liquid ejection device 2 is a diagram showing the electrical configuration of the liquid ejection device 100 according to the first embodiment. The control unit 20 will be described below with reference to FIG. 2, but prior to this, the liquid ejection head 50 will be briefly described.

[0019] As shown in FIG. 2, the liquid ejection head 50 includes a head chip 51 and a switching circuit 52.

[0020] The head chip 51 has a plurality of piezoelectric elements 51f, which are appropriately driven to eject ink from the nozzles. Each piezoelectric element 51f has an active portion P1, which is an example of a "first active portion," an active portion P2, which is an example of a "second active portion," and an active portion P3, which is an example of a "third active portion." The active portion P1 is driven by a supply signal Vin-A. Meanwhile, the active portions P2 and P3 are each driven by a supply signal Vin-B. Details of the head chip 51 will be described later with reference to FIGS. 3 to 6.

[0021] Under the control of the control unit 20, the switching circuit 52 switches whether or not to supply the first drive signal Com-A and the second drive signal Com-B output from the control unit 20 to each of the multiple piezoelectric elements 51f of the head chip 51. The first drive signal Com-A is supplied to the active unit P1 as a supply signal Vin-A. The second drive signal Com-B is supplied to the active units P2 and P3 as a supply signal Vin-B. Details of the switching circuit 52 will be described later with reference to FIG. 7.

[0022] In the example shown in FIG. 2, the liquid ejection head 50 has one head chip 51, but the number is not limited to this, and the liquid ejection head 50 may have two or more head chips 51.

[0023] As shown in FIG. 2, the control unit 20 includes a control circuit 21, a memory circuit 22, a power supply circuit 23, and a drive signal generation circuit 24, which is an example of a "drive signal generation section."

[0024] The control circuit 21 has a function to control the operation of each part of the liquid ejection device 100 and a function to process various data. The control circuit 21 includes, for example, one or more processors such as a CPU (Central Processing Unit). Note that the control circuit 21 may include a programmable logic device such as an FPGA (Field-Programmable Gate Array) instead of or in addition to a CPU. Furthermore, when the control circuit 21 is made up of multiple processors, the multiple processors may be mounted on different boards or the like.

[0025] The memory circuit 22 stores various programs executed by the control circuit 21 and various data such as print data Img processed by the control circuit 21. The memory circuit 22 includes, for example, one or both of semiconductor memories: a volatile memory such as RAM (Random Access Memory) and a non-volatile memory such as ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or PROM (Programmable ROM). The print data Img is supplied from an external device 200 such as a personal computer or digital camera. The memory circuit 22 may be configured as part of the control circuit 21.

[0026] The power supply circuit 23 receives power from a commercial power supply (not shown) and generates various predetermined potentials. The generated potentials are supplied to various parts of the liquid ejection device 100 as appropriate. For example, the power supply circuit 23 generates a power supply potential VHV and an offset potential VBS. The offset potential VBS is supplied to the liquid ejection head 50. The power supply potential VHV is also supplied to the drive signal generation circuit 24.

[0027] The drive signal generation circuit 24 generates the first drive signal Com-A and the second drive signal Com-B. Specifically, the drive signal generation circuit 24 includes, for example, a DA conversion circuit and an amplifier circuit. In the drive signal generation circuit 24, the DA conversion circuit converts the waveform specification signal dCom from the control circuit 21 from a digital signal to an analog signal, and the amplifier circuit amplifies the analog signal using the power supply potential VHV from the power supply circuit 23 to generate the first drive signal Com-A and the second drive signal Com-B, respectively. Among the waveforms included in the first drive signal Com-A, the signal having the waveform actually supplied to the active portion P1 of the piezoelectric element 51f is the aforementioned supply signal Vin-A. Among the waveforms included in the second drive signal Com-B, the signal having the waveform actually supplied to the active portion P2 or P3 of the piezoelectric element 51f is the aforementioned supply signal Vin-B. The waveform specification signal dCom is a digital signal that defines the waveforms of the first drive signal Com-1 and the second drive signal Com-B.

[0028] The control circuit 21 executes a program stored in the memory circuit 22 to control the operation of each part of the liquid ejection device 100. Here, by executing the program, the control circuit 21 generates control signals Sk1 and Sk2, a print data signal SI, a waveform designation signal dCom, a latch signal LAT, a change signal CNG, and a clock signal CLK as signals for controlling the operation of each part of the liquid ejection device 100.

[0029] The control signal Sk1 is a signal for controlling the driving of the transport mechanism 30. The control signal Sk2 is a signal for controlling the driving of the movement mechanism 40. The print data signal SI is a digital signal for specifying the operating state of the piezoelectric element 51f. The latch signal LAT and the change signal CNG are used in conjunction with the print data signal SI and are timing signals that determine the timing of ink ejection from each nozzle of the head chip 51. These timing signals are generated, for example, based on the output of an encoder that detects the position of the carriage 41 mentioned above.

[0030] 1-3. Overall configuration of liquid ejection head

[0031] Fig. 3 is an exploded perspective view of head chip 51. Fig. 4 is a cross-sectional view taken along line AA in Fig. 3. As shown in Fig. 3 and Fig. 4, head chip 51 has a flow path substrate 51a, a pressure chamber substrate 51b, a nozzle plate 51c, a vibration absorber 51d, a diaphragm 51e, a plurality of piezoelectric elements 51f, a cover 51g, a case 51h, and a wiring substrate 51i.

[0032] Here, a pressure chamber substrate 51b, a vibration plate 51e, a plurality of piezoelectric elements 51f, a case 51h, and a cover 51g are disposed in an area positioned further in the Z1 direction than the flow path substrate 51a. On the other hand, a nozzle plate 51c and a vibration absorber 51d are disposed in an area positioned further in the Z2 direction than the flow path substrate 51a. Each element of the liquid ejection head 50 is generally a plate-like member that is elongated in the direction along the Y axis, and is joined to one another by, for example, an adhesive.

[0033] As shown in FIG. 3, the nozzle plate 51c is a plate-shaped member provided with a plurality of nozzles N arranged in a direction along the Y axis. Each nozzle N is a through-hole that allows ink to pass through. The nozzle plate 51c is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing techniques such as dry etching or wet etching. However, other known methods and materials may also be used as appropriate to manufacture the nozzle plate 51c.

[0034] The flow path substrate 51a is a plate-like member for forming ink flow paths. As shown in FIGS. 2 and 3, the flow path substrate 51a is provided with an opening R1, multiple supply flow paths Ra, and multiple communication flow paths Na. The opening R1 is an elongated through-hole extending in the Y-axis direction in a plan view along the Z-axis so as to connect to the multiple nozzles N. On the other hand, the supply flow paths Ra and the communication flow paths Na are through-holes individually provided for each nozzle N. Each of the multiple supply flow paths Ra communicates with the opening R1. Like the nozzle plate 51c described above, the flow path substrate 51a is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing technology, for example. However, other known methods and materials may also be used to manufacture the flow path substrate 51a. Note that a portion of the supply flow path Ra may be formed in the pressure chamber substrate 51b.

[0035] The pressure chamber substrate 51b is a plate-like member in which multiple pressure chambers C corresponding to the multiple nozzles N are formed. The pressure chambers C are spaces called cavities located between the flow path substrate 51a and the vibration plate 51e, and are used to apply pressure to the ink filling the pressure chambers C. The multiple pressure chambers C are arranged in a direction along the Y axis. Each pressure chamber C is formed by a hole that opens on both sides of the pressure chamber substrate 51b and is elongated in a direction along the X axis. The X2-direction end of each pressure chamber C communicates with a corresponding supply flow path Ra. The cross-sectional area of ​​the supply flow path Ra is narrower than that of the pressure chambers C, and this portion functions as a flow path resistance, thereby suppressing backflow when pressure is applied to the ink. Meanwhile, the X1-direction end of each pressure chamber C communicates with a corresponding communication flow path Na. Like the nozzle plate 51c described above, the pressure chamber substrate 51b is manufactured by processing a silicon single crystal substrate using, for example, semiconductor manufacturing technology. However, other known methods and materials may be used appropriately to manufacture each of the pressure chamber substrates 51b.

[0036] A diaphragm 51e is disposed on the surface of the pressure chamber substrate 51b facing the Z1 direction. The diaphragm 51e is a plate-like member that is elastically deformable. In the example shown in FIG. 4, the diaphragm 51e has a first layer 51e1 that is an elastic film and a second layer 51e2 that is an insulating film, which are laminated in this order in the Z1 direction. Details of the diaphragm 51e will be described later with reference to FIG. 6.

[0037] A plurality of piezoelectric elements 51f corresponding to different nozzles N or pressure chambers C are arranged on the surface of the vibration plate 51e facing the Z1 direction. Each piezoelectric element 51f is a passive element that deforms in response to the supply of a first drive signal Com-A and a second drive signal Com-B, and has an elongated shape extending in the direction along the X axis. The plurality of piezoelectric elements 51f are arranged in the direction along the Y axis so as to correspond to the plurality of pressure chambers C. When the vibration plate 51e vibrates in conjunction with the deformation of the piezoelectric elements 51f, the pressure in the pressure chambers C fluctuates, causing ink to be ejected from the nozzles N. Details of the piezoelectric elements 51f will be described later with reference to FIG. 6.

[0038] The case 51h is a case for storing ink to be supplied to the multiple pressure chambers C, and is bonded to the surface of the flow path substrate 51a facing the Z1 direction with an adhesive or the like. The case 51h is made of, for example, a resin material and manufactured by injection molding. The case 51h is provided with a storage section R2 and an inlet IH. The storage section R2 is a recessed portion whose outer shape corresponds to the opening R1 of the flow path substrate 51a. The inlet IH is a through-hole that communicates with the storage section R2. The space formed by the opening R1 and the storage section R2 functions as a liquid storage chamber R, which is a reservoir that stores ink. Ink is supplied to the liquid storage chamber R from the liquid container 10 via the inlet IH.

[0039] The vibration absorber 51d is an element for absorbing pressure fluctuations within the liquid storage chamber R. The vibration absorber 51d is, for example, a compliance substrate that is a flexible sheet member that can be elastically deformed. Here, the vibration absorber 51d is arranged on the surface of the flow path substrate 51a facing the Z2 direction so as to close the opening R1 and the multiple supply flow paths Ra of the flow path substrate 51a and form the bottom surface of the liquid storage chamber R.

[0040] The cover 51g is a structure that protects the multiple piezoelectric elements 51f and reinforces the mechanical strength of the pressure chamber substrate 51b and the vibration plate 51e. The cover 51g is bonded to the surface of the vibration plate 51e with, for example, an adhesive. The cover 51g is provided with recesses that accommodate the multiple piezoelectric elements 51f.

[0041] A wiring board 51i is bonded to the surface of the pressure chamber substrate 51b or the vibration plate 51e facing the Z1 direction. The wiring board 51i is a mounting component on which a plurality of wires are formed for electrically connecting the control unit 20 and the liquid ejection head 50. The wiring board 51i is a flexible wiring board such as an FPC (Flexible Printed Circuit) or an FFC (Flexible Flat Cable). A switching circuit 52 is mounted on the wiring board 51i.

[0042] 1-4. Details of the diaphragm and piezoelectric element Fig. 5 is a plan view of the head chip 51. Fig. 6 is a cross-sectional view taken along line BB in Fig. 5. In Fig. 5, the planar shape of the pressure chamber C is indicated by a two-dot chain line. A wall-like partition 51b1 extending along the X direction is provided between two adjacent pressure chambers C of the pressure chamber substrate 51b. The partition 51b1 divides the pressure chambers C.

[0043] In the example shown in FIG. 5, the pressure chamber C has a parallelogram shape in a plan view. The pressure chamber C having such a shape in a plan view is formed, for example, by anisotropically etching a silicon single crystal substrate having a (110) surface orientation. An etchant used in the anisotropic etching is, for example, an aqueous potassium hydroxide solution (KOH). In the anisotropic etching, the first layer 51e1 of the diaphragm 51e is used as an etching stop layer. The shape of the pressure chamber C in a plan view is not limited to the example shown in FIG. 5 and may be any shape.

[0044] As shown in Fig. 6, the vibration plate 51e has a first surface F1 and a second surface F2 facing in the opposite direction to the first surface F1. In the example shown in Fig. 6, the thickness direction of the vibration plate 51e is along the Z axis. Therefore, the first surface F1 is the surface of the vibration plate 51e facing in the Z2 direction, and the second surface F2 is the surface of the vibration plate 51e facing in the Z1 direction. A piezoelectric element 51f is disposed on the second surface F2. A pressure chamber substrate 51b is disposed on the first surface F1.

[0045] The diaphragm 51e has a first layer 51e1 and a second layer 51e1, which are stacked in this order in the Z1 direction. The first layer 51e1 is an elastic film made of, for example, silicon oxide (SiO2). The elastic film is formed, for example, by thermally oxidizing one surface of a silicon single crystal substrate. The second layer 51e1 is an insulating film made of, for example, zirconium oxide (ZrO2). The insulating film is formed, for example, by forming a zirconium layer by sputtering and then thermally oxidizing the layer.

[0046] The first layer 51e1 is not limited to silicon oxide and may be made of other elastic materials such as silicon alone. The material of the second layer 51e1 is not limited to zirconium oxide and may be other insulating materials such as silicon nitride. Another layer such as a metal oxide may be interposed between the first layer 51e1 and the second layer 51e1. In other words, the first layer 51e1 or the second layer 51e1 may be made of multiple layers, which may be the same or different from each other. A part or all of the diaphragm 51e may be made integral with the pressure chamber substrate 51b using the same material. The diaphragm 51e may also be made of a layer of a single material.

[0047] 5, the piezoelectric element 51f overlaps the pressure chamber C in a plan view. As shown in Fig. 6, the piezoelectric element 51f has a first electrode layer 51f1, a piezoelectric layer 51f2, and a second electrode layer 51f3, which are stacked in this order in the Z1 direction.

[0048] Other layers, such as layers for improving adhesion, may be interposed between the layers of the piezoelectric elements 51f or between the piezoelectric elements 51f and the diaphragm 51e. A seed layer may be provided between the first electrode layer 51f1 and the piezoelectric layer 51f2. The seed layer functions to improve the orientation of the piezoelectric layer 51f2 when the piezoelectric layer 51f2 is formed. The seed layer may be made of, for example, titanium (Ti) or a complex oxide having a perovskite structure, such as Pb(Fe,Ti)O3. When the seed layer is made of titanium, islands of Ti serve as crystal nuclei during the formation of the piezoelectric layer 51f2, improving the orientation of the piezoelectric layer 51f2. In this case, the seed layer is formed to a thickness of approximately 3 nm to 20 nm using a known film formation technique, such as sputtering, and a known processing technique using photolithography and etching. Furthermore, when the seed layer is made of the complex oxide, the crystal structure of the seed layer affects the piezoelectric layer 51f2 during formation, improving the orientation of the piezoelectric layer 51f2. In this case, the seed layer is formed by, for example, forming a precursor layer of the complex oxide by a sol-gel method or a metal organic decomposition (MOD) method, and then firing the precursor layer to crystallize it.

[0049] The first electrode layer 51f1 has individual electrodes 51f1a, 51f1b, and 51f1c for each piezoelectric element 51f. Each of the individual electrodes 51f1a, 51f1b, and 51f1c extends in the direction along the X-axis. The individual electrodes 51f1a, 51f1b, and 51f1c are arranged at intervals from one another in the direction along the Y-axis.

[0050] Here, the individual electrode 51f1a is disposed in the center of the pressure chamber C in the width direction in a plan view, and overlaps with the center of the pressure chamber C. A first drive signal Com-A is supplied to the individual electrode 51f1a via wiring. On the other hand, the individual electrodes 51f1b and 51f1c are each disposed at an end of the pressure chamber C in the width direction in a plan view, and overlap with the pressure chamber C at a position closer to the outer edge BD of the pressure chamber C than the individual electrode 51f1a. A second drive signal Com-B is supplied to the individual electrodes 51f1b and 51f1c via wiring.

[0051] The first electrode layer 51f1 has, for example, a first layer made of titanium (Ti), a second layer made of platinum (Pt), and a third layer made of iridium (Ir), which are stacked in this order in the Z1 direction. The first electrode layer 51f1 is formed by, for example, a known film formation technique such as sputtering, and a known processing technique using photolithography, etching, etc.

[0052] Here, the first layer of the first electrode layer 51f1 functions as an adhesion layer that improves adhesion of the first electrode layer 51f1 to the diaphragm 51e. The thickness of the first layer is not particularly limited, but is, for example, about 3 nm to 50 nm. The material of the first layer is not limited to titanium; for example, chromium may be used instead of titanium.

[0053] Furthermore, the platinum constituting the second layer and the iridium constituting the third layer of the first electrode layer 51f1 are both electrode materials with excellent conductivity and similar chemical properties. This allows the first electrode layer 51f1 to have excellent electrode characteristics. The thickness of the second layer is not particularly limited, but is, for example, approximately 50 nm to 200 nm. The thickness of the third layer is not particularly limited, but is, for example, approximately 4 nm to 20 nm.

[0054] The configuration of the first electrode layer 51f1 is not limited to the above example. For example, either the second or third layer may be omitted, or a layer made of iridium may be provided between the first and second layers. Furthermore, instead of or in addition to the second and third layers, a layer made of an electrode material other than iridium and platinum may be used. Examples of such electrode materials include metal materials such as aluminum (Al), nickel (Ni), gold (Au), and copper (Cu). One of these materials may be used alone, or two or more may be combined in the form of a laminate or alloy.

[0055] The piezoelectric layer 51f2 is disposed between the first electrode layer 51f1 and the second electrode layer 51f3. The piezoelectric layer 51f2 has a strip shape extending in the direction along the Y axis so as to be continuous across the plurality of piezoelectric elements 51f. Note that the piezoelectric layer 51f2 may be provided individually for each piezoelectric element 51f or for each active portion P1, P2, and P3.

[0056] The piezoelectric layer 51f2 is made of a piezoelectric material having a perovskite crystal structure represented by the general composition formula ABO3. Examples of such piezoelectric materials include lead titanate (PbTiO3), lead zirconate titanate (Pb(Zr,Ti)O3), lead zirconate (PbZrO3), lead lanthanum titanate ((Pb,La),TiO3), lead lanthanum zirconate titanate ((Pb,La)(Zr,Ti)O3), lead zirconium niobate titanate (Pb(Zr,Ti,Nb)O3), and lead magnesium zirconium niobate titanate (Pb(Zr,Ti)(Mg,Nb)O3). Among these, lead zirconate titanate is preferably used as the material for the piezoelectric layer 51f2. The piezoelectric layer 51f2 may contain small amounts of other elements, such as impurities. The piezoelectric material forming the piezoelectric layer 51f2 may be a lead-free material such as barium titanate.

[0057] The piezoelectric layer 51f2 is formed by forming a piezoelectric precursor layer by a liquid phase method such as a sol-gel method or a metal organic decomposition (MOD) method, and then baking and crystallizing the precursor layer. Here, the piezoelectric layer 51f2 may be composed of a single layer, but if it is composed of multiple layers, there is an advantage that the characteristics of the piezoelectric layer 51f2 can be easily improved even if the thickness of the piezoelectric layer 51f2 is increased.

[0058] The second electrode layer 51f3 is a strip-shaped common electrode that extends continuously in the direction along the Y-axis across the plurality of piezoelectric elements 51f. An offset potential VBS is supplied to the second electrode layer 51f3 as a predetermined reference voltage.

[0059] The second electrode layer 51f3 has, for example, a layer made of iridium (Ir) and a layer made of titanium (Ti), which are stacked in this order in the Z1 direction. The second electrode layer 51f3 is formed by, for example, a known film formation technique such as sputtering, and a known processing technique using photolithography, etching, etc.

[0060] The constituent materials of the second electrode layer 51f3 are not limited to iridium and titanium, and may be, for example, metal materials such as platinum (Pt), aluminum (Al), nickel (Ni), gold (Au), or copper (Cu). The second electrode layer 51f3 may be composed of one of these metal materials alone, or may be composed of two or more of them combined in the form of a laminate or alloy. The second electrode layer 51f3 may also be composed of a single layer.

[0061] The above-described piezoelectric element 51f has active portions P1, P2, and P3. The active portion P1 is a portion of the piezoelectric element 51f where the individual electrode 51f1a, the piezoelectric layer 51f2, and the second electrode layer 51f3 all overlap when viewed in the thickness direction of the diaphragm 51e. The active portion P2 is a portion of the piezoelectric element 51f where the individual electrode 51f1b, the piezoelectric layer 51f2, and the second electrode layer 51f3 all overlap when viewed in the thickness direction of the diaphragm 51e. The active portion P3 is a portion of the piezoelectric element 51f where the individual electrode 51f1c, the piezoelectric layer 51f2, and the second electrode layer 51f3 all overlap when viewed in the thickness direction of the diaphragm 51e.

[0062] Active portion P1 is disposed between active portion P2 and active portion P3. In the example shown in Fig. 6, active portion P2, active portion P1, and active portion P3 are arranged in this order in the Y1 direction. Each of active portions P1, P2, and P3 extends in the direction along the X axis.

[0063] Here, the active portion P1 overlaps the center of the pressure chamber C when viewed in the thickness direction of the diaphragm 51e, but does not overlap the outer edge BD of the pressure chamber C. On the other hand, the active portion P2 and the active portion P3 each overlap the pressure chamber C at a position closer to the outer edge BD of the pressure chamber C than the active portion P1 when viewed in the thickness direction of the diaphragm 51e. In the example shown in Fig. 6, the active portion P2 and the active portion P3 are each disposed across the pressure chamber C and the partition wall 51b1 when viewed in the thickness direction of the diaphragm 51e, and overlap the outer edge BD.

[0064] The width W1 of the active portion P1 along the Y axis is smaller than the width of the pressure chamber C along the Y axis, preferably smaller than the width of the pressure chamber C along the Y axis and at least half the width of the pressure chamber C along the Y axis. Furthermore, the width W2 of the active portion P2 along the Y axis is smaller than the width of the pressure chamber C along the Y axis, preferably not more than half the width of the pressure chamber C along the Y axis. Similarly, the width W3 of the active portion P3 along the Y axis is smaller than the width of the pressure chamber C along the Y axis, preferably not more than half the width of the pressure chamber C along the Y axis. Here, the widths W2 and W3 may be equal to or different from each other.

[0065] 1-5. Switching circuit configuration 7 is a diagram for explaining the switching circuit 52. The switching circuit 52 will be explained below with reference to FIG.

[0066] 7, the switching circuit 52 is connected to a line LHa and a line LHb. The line LHa is a signal line that transmits a first drive signal Com-A. The line LHb is a signal line that transmits a second drive signal Com-B. The second electrode layer 51f3 of the piezoelectric element 51f is connected to a line LHd. The line LHd is a power supply line that supplies an offset potential VBS.

[0067] The switching circuit 52 has a plurality of switches SWa and a plurality of switches SWb that correspond one-to-one to the plurality of piezoelectric elements 51f, and a connection state designation circuit 52a that designates the connection state of these switches.

[0068] The switch SWa switches between conduction (ON) and non-conduction (OFF) between the wiring LHa for transmitting the first drive signal Com-A and the individual electrode 51f1a of the piezoelectric element 51f. The switch SWb switches between conduction (ON) and non-conduction (OFF) between the wiring LHa for transmitting the second drive signal Com-B and the individual electrodes 51f1b and 51f1c of the piezoelectric element 51f. Each of these switches is, for example, a transmission gate.

[0069] The connection state designation circuit 52a generates a connection state designation signal SLa that designates the on / off states of the multiple switches SWa and multiple switches SWb based on the clock signal CLK, print data signal SI, latch signal LAT, and change signal CNG supplied from the control circuit 21.

[0070] For example, although not shown, the connection state designation circuit 52a includes multiple transfer circuits, multiple latch circuits, and multiple decoders, each corresponding to one of the piezoelectric elements 51f. Of these, the transfer circuit receives a print data signal SI. The print data signal SI includes an individual designation signal for each piezoelectric element 51f. The individual designation signals are serially supplied and transferred sequentially to the multiple transfer circuits in synchronization with a clock signal CLK. The latch circuit latches the individual designation signal supplied to the transfer circuit based on a latch signal LAT. The decoder generates a connection state designation signal SLa based on the individual designation signal, the latch signal LAT, and the change signal CNG.

[0071] The switches SWa and SWb are switched on and off according to the connection state designation signal SLa generated as described above. For example, the switches SWa and SWb are turned on when the connection state designation signal SLa is at a high level, and turned off when the connection state designation signal SLa is at a low level. As described above, the switching circuit 52 supplies part or all of the waveform included in the first drive signal Com-A as the supply signal Vin-A, and supplies part or all of the waveform included in the second drive signal Com-B as the supply signal Vin-B, to one or more piezoelectric elements 51f selected from the plurality of piezoelectric elements 51f.

[0072] 1-6. First drive signal and second drive signal Fig. 8 is a diagram for explaining the first drive signal Com-A and the second drive signal Com-B in the first embodiment. The vertical axis "voltage" in the upper part of Fig. 8 is the potential difference between the first drive signal Com-A and the offset potential VBS, and the vertical axis "voltage" in the lower part of Fig. 8 is the potential difference between the second drive signal Com-B and the offset potential VBS. Note that the vertical axis "voltage" in the upper part of Fig. 8 may be the potential of the first drive signal Com-A, and the vertical axis "voltage" in the lower part of Fig. 8 may be the potential of the second drive signal Com-B.

[0073] 8, the first drive signal Com-A and the second drive signal Com-B each have a waveform that changes every unit period Tu of a predetermined cycle. The unit period Tu is determined by the latch signal LAT and the like, and corresponds to the printing cycle in which dots are formed on the medium M using ink from the nozzles N.

[0074] 8, the first drive signal Com-A has a waveform that, with the intermediate potential Vca as a reference potential, changes from the intermediate potential Vca via a potential VHa and back to the intermediate potential Vca within a unit period Tu. Here, the intermediate potential Vca is an example of a "first potential" and a "fifth potential," and is, for example, a potential equal to or lower than the offset potential VBS. The potential VHa is an example of a "second potential," and is a potential higher than the offset potential VBS and higher than the intermediate potential Vca.

[0075] Here, the potential of the first drive signal Com-A is maintained at the intermediate potential Vca for a period P1a, then rises from the intermediate potential Vca to a potential VHa for a period P2a, is maintained at the potential VHa for a period P3a, then falls from the potential VHa to the intermediate potential Vca for a period P4a, and is maintained at the intermediate potential Vca for a period P5a. The period P2a is an example of a "first period." The period P3a is an example of a "first hold period." The period P4a is an example of a "third period." The periods P1a, P2a, P3a, P4a, and P5a are included, in this order, between the start and end points of the unit period Tu.

[0076] The waveform portion of the first drive signal Com-A during period P2a is a contraction element ESa that contracts the volume of the pressure chamber C. The contraction element ESa is an example of a "first contraction element." The waveform portion of the first drive signal Com-A during period P3a is a hold element ERa, which is an example of a "first hold element." The waveform portion of the first drive signal Com-A during period P4a is an expansion element EEa that expands the volume of the pressure chamber C.

[0077] On the other hand, the second drive signal Com-B has a waveform that, with the intermediate potential Vcb as a reference potential, changes from the intermediate potential Vcb via the potential VHb and back to the intermediate potential Vcb within the unit period Tu. Here, the intermediate potential Vcb is an example of the "third potential" and "sixth potential," and is, for example, a potential equal to or lower than the offset potential VBS. The potential VHb is an example of the "fourth potential," and is a potential higher than the offset potential VBS and also higher than the intermediate potential Vcb.

[0078] Here, the potential of the second drive signal Com-B is maintained at the intermediate potential Vcb for a period P1b, then rises from the intermediate potential Vcb to a potential VHb for a period P2b, is maintained at the potential VHb for a period P3b, then falls from the potential VHb to the intermediate potential Vcb for a period P4b, and is maintained at the intermediate potential Vcb for a period P5b. The period P4b is an example of a "second period." The period P3b is an example of a "second hold period." The period P2b is an example of a "fourth period." The periods P1b, P2b, P3b, P4b, and P5b are included, in this order, between the start and end points of the unit period Tu.

[0079] The waveform portion of the second drive signal Com-B during period P2b is an expansion element EEb that expands the volume of the pressure chamber C. The waveform portion of the second drive signal Com-B during period P3b is a hold element ERb, which is an example of a "second hold element." The waveform portion of the second drive signal Com-B during period P4b is a contraction element ESb that contracts the volume of the pressure chamber C. The contraction element ESb is an example of a "second contraction element."

[0080] In this embodiment, the first drive signal Com-A and the second drive signal Com-B have substantially identical waveforms. However, the first drive signal Com-A and the second drive signal Com-B are supplied with waveforms that are out of phase with each other. Note that "substantially identical waveforms" means that the patterns match when waveforms due to electrical noise and errors are removed.

[0081] That is, the length of period P1a of the first drive signal Com-A is longer than the length of period P1b of the second drive signal Com-B. The length of period P2a of the first drive signal Com-A and the length of period P2b of the second drive signal Com-B are equal. The length of period P3a of the first drive signal Com-A and the length of period P3b of the second drive signal Com-B are equal. The length of period P4a of the first drive signal Com-A and the length of period P4b of the second drive signal Com-B are equal. The length of period P5a of the first drive signal Com-A is shorter than the length of period P5b of the second drive signal Com-B.

[0082] The waveforms of the first drive signal Com-A and the second drive signal Com-B may be different from each other. However, if the waveforms of the first drive signal Com-A and the second drive signal Com-B are substantially the same, the drive signal generation circuit 24 may be able to generate a single waveform and supply it with a phase shift. This has the advantage of simplifying the configuration of the drive signal generation circuit 24 compared to when the waveforms of the first drive signal Com-A and the second drive signal Com-B are different from each other.

[0083] The start timing of the period P3a of the first drive signal Com-A is after the end timing of the period P3b of the second drive signal Com-B.

[0084] Here, at least a portion of the period P2a of the first drive signal Com-A and at least a portion of the period P4b of the second drive signal Com-B overlap each other in time during the period PS.

[0085] 8, within the unit period Tu, the start timing of the period P2a is later than the start timing of the period P4b, and accordingly, within the unit period Tu, the end timing of the period P2a is later than the end timing of the period P4b.

[0086] 1-7. Shrinkage process Fig. 9 is a diagram for explaining the contraction process SS in the first embodiment. In Fig. 9, the first drive signal Com-A is indicated by a solid line, and the second drive signal Com-B is indicated by a dashed line. In the example shown in Fig. 9, the potentials VHa and VHb are equal to each other, and the intermediate potentials Vca and Vcb are equal to each other.

[0087] The potentials VHa and VHb may be different from each other, and the intermediate potentials Vca and Vcb may be different from each other. However, when the potentials VHa and VHb are equal to each other and the intermediate potentials Vca and Vcb are equal to each other, there is an advantage in that the configuration of the drive signal generation circuit 24 can be simplified compared to when they are not.

[0088] As described above, after the supply of the hold element ERb of the second drive signal Com-B to the active units P2 and P3 is completed, the supply of the hold element ERa of the first drive signal Com-A to the active unit P1 begins after the period PS. Here, during the period PS, the contraction process SS is executed.

[0089] FIG. 10 is a schematic diagram illustrating the deformation of the diaphragm 51e due to the first drive signal Com-A. FIG. 11 is a schematic diagram illustrating the deformation of the diaphragm due to the second drive signal Com-B. In these figures, for the sake of convenience, the piezoelectric element 51F is omitted from the illustration, and the diaphragm 51e is shown schematically. In addition, in FIGS. 10 and 11, the diaphragm 51e in its natural state, which is its reference state, is indicated by a two-dot chain line. Note that the "natural state of the diaphragm 51e" refers to the state of the diaphragm 51e when no voltage is applied to the piezoelectric element 51f.

[0090] When a voltage is applied in the direction along the Z axis, each of the active parts P1, P2, and P3 expands along the Z axis and attempts to contract in a direction perpendicular to the Z axis. At this time, because the surfaces of the active parts P1, P2, and P3 facing the Z2 direction are fixed to the diaphragm 51e, the amount of contraction of the surfaces of the active parts P1, P2, and P3 facing the Z2 direction is smaller than the amount of contraction of the surfaces of the active parts P1, P2, and P3 facing the Z1 direction. As a result, the active parts P1, P2, and P3 deform so as to warp in the direction along the Z axis, and the diaphragm 51e also deforms accordingly.

[0091] Here, of the two ends of each of the active portions P2 and P3 in the direction along the Y axis, the end closest to the partition wall 511 of the pressure chamber C is restricted in displacement by the partition wall 511, while the end farther from the partition wall 511 of the pressure chamber C is less restricted in displacement. Therefore, when the active portions P2 and P3 attempt to contract in the direction along the Y axis, the farther end is displaced in the Z1 direction. As a result, the diaphragm 51e deforms so that the first surface F1 becomes concave. Therefore, when the holding element ERb of the second drive signal Com-B is supplied to the active portions P2 and P3, the diaphragm 51e deforms so that the first surface F1 becomes concave, as shown in FIG. 10. This causes the volume of the pressure chamber C to expand.

[0092] On the other hand, both ends of the active part P1 in the direction along the Y axis are located relatively far from the partition wall 511 of the pressure chamber C, and displacement is less likely to be restricted by the partition wall 511. Therefore, when the active part P1 attempts to contract in the direction along the Y axis, the diaphragm 51e deforms so that the first surface F1 becomes convex. Therefore, when the holding element ERa of the first drive signal Com-A is supplied to the active part P1, the diaphragm 51e deforms so that the first surface F1 becomes convex, as shown in FIG. 11. This causes the volume of the pressure chamber C to contract.

[0093] Here, during the period in which the contraction element ESb of the second drive signal Com-B is supplied, the active units P2 and P3 attempt to return the diaphragm 51e from the state shown by the solid line to the state shown by the two-dot chain line in Fig. 10. Also, during the period in which the active unit P1 receives the contraction element ESa of the first drive signal Com-A, the active unit P1 attempts to deform the diaphragm 51e from the state shown by the two-dot chain line to the state shown by the solid line in Fig. 11.

[0094] In the contraction process SS, when the diaphragm 51e is deformed from the state indicated by the two-dot chain line in FIG. 11 to the state indicated by the solid line, the force that attempts to return the diaphragm 51e from the state indicated by the solid line in FIG. 10 to the state indicated by the two-dot chain line can be utilized. That is, in the contraction process SS, when the active part P1 deforms the diaphragm 51e from the reference state to the state that contracts the volume of the pressure chamber C, the forces that the active parts P2 and P3 attempt to return the diaphragm 51e from the state in which the volume of the pressure chamber C is expanded to the reference state can be utilized. Therefore, the amount of deformation of the diaphragm 51e can be made larger compared to a configuration in which only the active part P1 is driven by the first drive signal Com-A. As a result, ink can be ejected efficiently from the nozzle N.

[0095] In contrast, if the start timing of the supply of the contraction element ESa of the first drive signal Com-A to the active part P1 coincides with or is later than the end timing of the supply to the active parts P2 and P3, when deforming the vibration plate 51e from the state shown by the dotted line in Figure 11 to the state shown by the solid line, it is not possible to utilize the force that tries to return the vibration plate 51e from the state shown by the solid line in Figure 10 to the state shown by the dotted line, and the above-mentioned effect cannot be obtained.

[0096] As described above, the liquid ejection device 100 includes a vibration plate 51e, a pressure chamber substrate 51b, a piezoelectric element 51f, and a drive signal generation circuit 24, which is an example of a "drive signal generation unit." As described above, the vibration plate 51e has a first surface F1 and a second surface F2 facing in the opposite direction from the first surface F1. The pressure chamber substrate 51b is stacked on the first surface F1 and has partition walls 51b1 that define pressure chambers C that communicate with nozzles N that eject ink, which is an example of a "liquid." The piezoelectric element 51f is stacked on the second surface F2 and has an active portion P1, which is an example of a "first active portion," and an active portion P2, which is an example of a "second active portion." The active portion P1 overlaps the center of the pressure chamber C in the thickness direction of the vibration plate 51e. The active portion P2 overlaps the pressure chamber C at a position closer to the outer edge of the pressure chamber C than the active portion P1 in the thickness direction of the vibration plate 51e. The drive signal generation circuit 24 generates a first drive signal Com-A that drives the active portion P1 and a second drive signal Com-B that drives the active portion P2.

[0097] The first drive signal Com-A includes a contraction element ESa, which is an example of a "first contraction element," for each periodic unit period Tu. On the other hand, the second drive signal Com-B includes a contraction element ESb, which is an example of a "second contraction element," for each unit period Tu. The contraction element ESa and the contraction element ESb each contract the volume of the pressure chamber C. The liquid ejection device 100 then executes a contraction process SS. The contraction process SS is a period in which a period P2a, which is an example of a "first period," and a period P4b, which is an example of a "second period," overlap with each other. During the period P2a, the contraction element ESa is supplied to the active portion P1. During the period P4b, the contraction element ESb is supplied to the active portion P2.

[0098] Here, the period P2a is a period during which the potential changes from an intermediate potential Vca, which is an example of a "first potential," to a potential VHa, which is an example of a "second potential," every unit period Tu. The period P4b is a period during which the potential changes from an intermediate potential Vcb, which is an example of a "third potential," to a potential VHb, which is an example of a "fourth potential," every unit period Tu.

[0099] In the liquid ejection device 100 described above, the periods P2a and P4b overlap with each other during the contraction step SS, so the amount of displacement of the diaphragm 51e can be increased and the displacement speed of the diaphragm 51e can be increased compared to a configuration in which these periods do not overlap with each other. This makes it possible to increase the ink ejection speed from the nozzle N and the amount of ink ejected from the nozzle N per ejection. Furthermore, by increasing the displacement speed of the diaphragm 51e, it is possible to shorten the ink ejection cycle from the nozzle N. As described above, the ejection characteristics of the liquid ejection device 100 can be improved.

[0100] As described above, during the contraction step SS, the magnitude relationship between the potentials of the first drive signal Com-A and the second drive signal Com-B is reversed. That is, during the period when period P2a and period P4b overlap, the magnitude relationship between the potentials of the first drive signal Com-A and the second drive signal Com-B is reversed.

[0101] Furthermore, as described above, in the unit period Tu, the start timing of the contraction element ESa is later than the start timing of the contraction element ESb. That is, in the unit period Tu, the start timing of the period P2a is later than the start timing of the period P4b. This prevents excessive stress from occurring between the portion of the diaphragm 51e deformed by the active portion P1 and the portion of the diaphragm 51e deformed by the active portion P2. As a result, damage such as cracks in the diaphragm 51e can be reduced.

[0102] As described above, the end timing of the contraction element ESa is later than the end timing of the contraction element ESb in the unit period Tu. Therefore, the start timing of the contraction element ESa can be later than the start timing of the contraction element ESb in the unit period Tu.

[0103] Furthermore, as described above, the piezoelectric element 51f further includes an active portion P3, which is an example of a "third active portion." The active portion P3 overlaps the pressure chamber C at a position closer to the outer edge of the pressure chamber C than the active portion P1 in the thickness direction of the vibration plate 51e. The active portion P1 is located between the active portions P2 and P3 in the thickness direction of the vibration plate 51e. This allows the active portion P3 to function in the same way as the active portion P2.

[0104] As described above, the piezoelectric element 51f includes a first electrode layer 51f1, a piezoelectric layer 51f2, and a second electrode layer 51f3, in this order, away from the diaphragm 51e. The piezoelectric layer 51f2 and the second electrode layer 51f3 are commonly provided across the active portions P1, P2, and P3. In contrast, the first electrode layer 51f1 includes multiple individual electrodes 51f1a, 51f1b, and 51f1c, which are individually provided for the active portions P1, P2, and P3. This simplifies wiring compared to a configuration in which the second electrode layer 51f3 includes individual electrodes for each active portion. Furthermore, this configuration simplifies manufacturing of the piezoelectric layer 51f2 compared to a configuration in which the piezoelectric layer 51f2 is divided into sections for each active portion.

[0105] 2. Second embodiment A second embodiment of the present disclosure will be described below, focusing on the differences from the first embodiment.

[0106] 12 is a diagram illustrating the contraction process SS in the second embodiment. This embodiment is similar to the first embodiment described above, except that the intermediate potential Vcb of the second drive signal Com-B is higher than the intermediate potential Vca of the first drive signal Com-A, as shown in FIG.

[0107] The second embodiment described above also improves the ejection characteristics of the liquid ejection device 100. In this embodiment, as described above, the intermediate potential Vcb is higher than the intermediate potential Vca. Therefore, by appropriately setting the difference between these potentials, the hardness of the diaphragm 51e can be adjusted. As a result, even if there are manufacturing variations, the ejection characteristics can be made uniform among multiple head chips 51.

[0108] 3. Third embodiment The third embodiment of the present disclosure will be described below, focusing on the differences from the first embodiment.

[0109] 13 is a diagram illustrating the first drive signal Com-A and the second drive signal Com-B in the third embodiment. In the example shown in Fig. 13, the first drive signal Com-A has a waveform that, with the intermediate potential Vca as the reference potential, changes from the intermediate potential Vca to a potential VLa and a potential VHa in that order, and then returns to the intermediate potential Vca within a unit period Tu. The potential VLa is a potential lower than the intermediate potential Vca.

[0110] Here, the potential of the first drive signal Com-A is maintained at the intermediate potential Vca for a period P1c, then drops from the intermediate potential Vca to a potential VLa for a period P2c, is maintained at the potential VLa for a period P3c, then rises from the potential VLa to a potential VHa for a period P4c, is maintained at the potential VHa for a period P5c, then drops from the potential VHa to the intermediate potential Vca for a period P6c, and is maintained at the intermediate potential Vca for a period P7c. The period P2c is an example of a "third period." The period P4c is an example of a "first period." Note that the periods P1c, P2c, P3c, P4c, P5c, P6c, and P7c are included, in this order, between the start and end points of the unit period Tu.

[0111] The waveform portion of the first drive signal Com-A during period P2c is an expansion element EEa1 that expands the volume of the pressure chamber C. The expansion element EEa1 is an example of a "first expansion element." The waveform portion of the first drive signal Com-A during period P3c is a hold element ERa1. The waveform portion of the first drive signal Com-A during period P4c is a contraction element ESa that contracts the volume of the pressure chamber C. The contraction element ESa is an example of a "first contraction element." The waveform portion of the first drive signal Com-A during period P5c is a hold element ERa2. The waveform portion of the first drive signal Com-A during period P6c is an expansion element EEa2 that expands the volume of the pressure chamber C.

[0112] 13 has a waveform that, with the intermediate potential Vcb as the reference potential, changes from the intermediate potential Vcb to a potential VLb and a potential VHb in that order, and then returns to the intermediate potential Vcb within the unit period Tu. The potential VLb is a potential lower than the intermediate potential Vcb.

[0113] Here, the potential of the second drive signal Com-B is maintained at the intermediate potential Vcb for a period P1d, then drops from the intermediate potential Vcb to a potential VLb for a period P2d, is maintained at the potential VLb for a period P3d, then rises from the potential VLb to a potential VHb for a period P4d, is maintained at the potential VHb for a period P5d, then drops from the potential VHb to the intermediate potential Vcb for a period P6d, and is maintained at the intermediate potential Vcb for a period P7d. The period P4d is an example of a "fourth period." The period P6d is an example of a "second period." Note that the periods P1d, P2d, P3d, P4d, P5d, P6d, and P7d are included, in this order, between the start and end points of the unit period Tu.

[0114] The waveform portion of the second drive signal Com-B during period P2d is a contraction element ESb1 that contracts the volume of the pressure chamber C. The waveform portion of the second drive signal Com-B during period P3d is a hold element ERb1. The waveform portion of the second drive signal Com-B during period P4d is an expansion element EEb that expands the volume of the pressure chamber C. The expansion element EEb is an example of a "second expansion element." The waveform portion of the second drive signal Com-B during period P5d is a hold element ERb2. The waveform portion of the second drive signal Com-B during period P6d is a contraction element ESb2 that contracts the volume of the pressure chamber C. The contraction element ESb2 is an example of a "second contraction element."

[0115] In this embodiment, the first drive signal Com-A and the second drive signal Com-B have substantially the same waveform, except that the waveforms of the first drive signal Com-A and the second drive signal Com-B are supplied out of phase with each other.

[0116] Here, the length of period P1c of the first drive signal Com-A is longer than the length of period P1d of the second drive signal Com-B. The length of period P2c of the first drive signal Com-A and the length of period P2d of the second drive signal Com-B are equal to each other. The length of period P3c of the first drive signal Com-A and the length of period P3d of the second drive signal Com-B are equal to each other. The length of period P4c of the first drive signal Com-A and the length of period P4d of the second drive signal Com-B are equal to each other. The length of period P5c of the first drive signal Com-A and the length of period P5d of the second drive signal Com-B are equal to each other. The length of period P6c of the first drive signal Com-A and the length of period P6d of the second drive signal Com-B are equal to each other. The length of period P7c of the first drive signal Com-A is shorter than the length of period P7d of the second drive signal Com-B.

[0117] The waveforms of the first drive signal Com-A and the second drive signal Com-B may be different from each other. However, if the waveforms of the first drive signal Com-A and the second drive signal Com-B are the same, the drive signal generation circuit 24 may be able to generate a single waveform and supply it with a phase shift. This has the advantage of simplifying the configuration of the drive signal generation circuit 24 compared to when the waveforms of the first drive signal Com-A and the second drive signal Com-B are different from each other.

[0118] The start timing of period P3c of the first drive signal Com-A is later than the end timing of period P3d of the second drive signal Com-B. Similarly, the start timing of period P5c of the first drive signal Com-A is later than the end timing of period P5d of the second drive signal Com-B.

[0119] Here, at least a portion of the period P2c of the first drive signal Com-A and at least a portion of the period P4d of the second drive signal Com-B overlap each other in time during the period PE.

[0120] 13, within the unit period Tu, the start timing of period P2c is before the start timing of period P4d. Furthermore, within the unit period Tu, the end timing of period P2c is before the end timing of period P4d. Note that within the unit period Tu, the start timing of period P2c may be after the start timing of period P4d, and the end timing of period P2c may be after the end timing of period P4d.

[0121] Furthermore, at least a portion of the period P4c of the first drive signal Com-A and at least a portion of the period P6d of the second drive signal Com-B overlap each other in time during the period PS.

[0122] 13, within the unit period Tu, the start timing of period P4c is before the start timing of period P6d. Also, within the unit period Tu, the end timing of period P2c is before the end timing of period P4d. Note that within the unit period Tu, the start timing of period P4c may be after the start timing of period P6d, and the end timing of period P2c may be after the end timing of period P4d.

[0123] Fig. 14 is a diagram illustrating the contraction process SS and the expansion process SE in the third embodiment. In Fig. 14, the first drive signal Com-A is indicated by a solid line, and the second drive signal Com-B is indicated by a dashed line. In the example shown in Fig. 14, the potentials VLa and VLb are equal to each other, the potentials VHa and VHb are equal to each other, and the intermediate potentials Vca and Vcb are equal to each other.

[0124] Note that the potentials VLa and VLb may be different from each other, the potentials VHa and VHb may be different from each other, or the intermediate potentials Vca and Vcb may be different from each other. However, when the potentials VLa and VLb are equal to each other, the potentials VHa and VHb are equal to each other, and the intermediate potentials Vca and Vcb are equal to each other, there is an advantage in that the configuration of the drive signal generation circuit 24 can be simplified compared to when they are not.

[0125] As described above, after the supply of the hold element ERb1 of the second drive signal Com-B to the active units P2 and P3 is completed, the supply of the hold element ERa1 of the first drive signal Com-A to the active unit P1 begins after the period PE. Here, during the period PE, the expansion step SE is executed. The contraction step SS is the same as in the first embodiment.

[0126] During the period in which the holding element ERb1 of the second drive signal Com-B is supplied to the active units P2 and P3, the diaphragm 51e deforms so that the first surface F1 becomes convex. As a result, the volume of the pressure chamber C becomes contracted. On the other hand, during the period in which the holding element ERa1 of the first drive signal Com-A is supplied to the active unit P1, the diaphragm 51e deforms so that the first surface F1 becomes concave. As a result, the volume of the pressure chamber C becomes expanded.

[0127] As described above, in the expansion process SE in which the volume of the pressure chamber C changes from a contracted state to an expanded state, when the active part P1 deforms the diaphragm 51e from its reference state to a state in which the volume of the pressure chamber C expands, the force of the active parts P2 and P3 attempting to return the diaphragm 51e from the state in which the volume of the pressure chamber C has been contracted to its reference state can be utilized. This allows for a greater amount of deformation of the diaphragm 51e than in a configuration in which only the active part P1 is driven by the first drive signal Com-A. As a result, ink can be ejected from the nozzle N efficiently.

[0128] The third embodiment described above also improves the ejection characteristics of the liquid ejection device 100. In this embodiment, as described above, the first drive signal Com-A includes an expansion element EEa1, which is an example of a "first expansion element." Furthermore, the second drive signal Com-B includes an expansion element EEb, which is an example of a "second expansion element." The expansion elements EEa1 and EEb each expand the volume of the pressure chamber C for each unit period Tu. The liquid ejection device 100 then executes an expansion process SE. The expansion process SE is a period in which a period P2c, which is an example of a "third period," and a period P4d, which is an example of a "fourth period," overlap with each other. During the period P2c, the expansion element EEa1 is supplied to the active portion P1. During the period P4d, the expansion element EEb is supplied to the active portions P2 and P3.

[0129] In the expansion step SE, the period P2c and the period P4d overlap each other, so the momentum of the ink introduced into the pressure chamber C can be increased compared to a configuration in which these periods do not overlap. Also, the ink ejection cycle from the nozzle N can be shortened compared to a configuration in which these periods do not overlap.

[0130] As described above, the expansion process SE is executed before the contraction process SS in the unit period Tu, which allows the amount of ink ejected from the nozzle N per ejection to be increased.

[0131] Furthermore, as described above, periods P4c and P4d do not overlap, and periods P2c and P6d do not overlap. This prevents excessive stress from occurring between the portion of diaphragm 51e deformed by active portion P1 and the portion of diaphragm 51e deformed by active portion P2. As a result, damage such as cracks to diaphragm 51e can be reduced.

[0132] 4. Fourth embodiment The fourth embodiment of the present disclosure will be described below, focusing on the differences from the first embodiment.

[0133] 15 is a diagram illustrating the contraction process SS and the expansion process SE in the fourth embodiment. This embodiment is similar to the third embodiment described above, except that the contraction element ESb1 and the hold element ERb1 of the second drive signal Com-B are omitted. Therefore, the second drive signal Com-B of this embodiment is similar to the second drive signal Com-B of the first embodiment.

[0134] According to the fourth embodiment described above, the ejection characteristics of the liquid ejection device 100 can also be improved.

[0135] 5. Fifth embodiment The fifth embodiment of the present disclosure will be described below, focusing on the differences from the first embodiment.

[0136] 16 is a diagram illustrating the contraction process SS, the expansion process SE, and the vibration damping process SC in the fifth embodiment. This embodiment is similar to the third embodiment except that the first drive signal Com-A and the second drive signal Com-B have different phases.

[0137] In this embodiment, the contraction process SS is executed when the period of the contraction element ESa of the first drive signal Com-A and the period of the contraction element ESb1 of the second drive signal Com-B overlap over a period PS. The expansion process SE is executed when the period of the expansion element EEa2 of the first drive signal Com-A and the period of the expansion element EEb of the second drive signal Com-B overlap over a period PE. After the expansion process SE, a damping process SC is executed, in which a damping force is applied to the diaphragm 51e by the hold element ERb2 of the second drive signal Com-B. The timing of the damping process SC and the potential VHb of the damping process SC are preferably determined appropriately depending on the vibration period and amplitude of the diaphragm 51e caused by the processes prior to the expansion process SE.

[0138] The fifth embodiment described above also improves the ejection characteristics of the liquid ejection device 100. In this embodiment, as described above, the expansion process SE is executed after the contraction process SS in the unit period Tu. Therefore, the expansion process SE can supply ink to the pressure chamber C, from which ink has been reduced by the contraction process SS. Furthermore, after the active part P1 is driven by the first drive signal Com-A, the vibration of the diaphragm 51e can be damped by the damping process SC. As a result, the ejection cycle can be shortened while improving print quality.

[0139] 6. Sixth embodiment The sixth embodiment of the present disclosure will be described below, focusing on the differences from the first embodiment.

[0140] Fig. 17 is a diagram for explaining the first drive signal Com-A and the second drive signal Com-B in the sixth embodiment. In the example shown in Fig. 17, the first drive signal Com-A is the same as the first drive signal COM-A in the first embodiment.

[0141] On the other hand, the second drive signal Com-B shown in Fig. 17 is a signal of opposite phase to the first drive signal Com-A. That is, the second drive signal Com-B shown in Fig. 17 has a waveform that, with the intermediate potential Vcb as the reference potential, changes from the intermediate potential Vcb via potential VLb and back to the intermediate potential Vcb within the unit period Tu. The intermediate potential Vcb is an example of the "third potential" and "sixth potential." Potential VLb is an example of the "fourth potential."

[0142] Here, the potential of the second drive signal Com-B is maintained at the intermediate potential Vcb for a period P1b, then drops from the intermediate potential Vcb to a potential VLb for a period P2b, is maintained at the potential VLb for a period P3b, then rises from the potential VLb to the intermediate potential Vcb for a period P4b, and is maintained at the intermediate potential Vcb for a period P5b. The period P2b is an example of a "second period." The period P4b is an example of a "fourth period."

[0143] The waveform portion of the second drive signal Com-B in period P2b described above is an example of a "second contraction element" and is a contraction element ESb that contracts the volume of the pressure chamber C. The waveform portion of the second drive signal Com-B in period P3b is a hold element ERb that is an example of a "second hold element." The waveform portion of the second drive signal Com-B in period P4b is an example of a "second expansion element" and is an expansion element EEb that expands the volume of the pressure chamber C.

[0144] Here, at least a portion of period P2a of the first drive signal Com-A and at least a portion of period P2b of the second drive signal Com-B overlap in time during period PS. Furthermore, at least a portion of period P4a of the first drive signal Com-A and at least a portion of period P4b of the second drive signal Com-B overlap in time during period PE. By providing such periods PS and PE, it is possible to improve the ejection characteristics, as in the other embodiments.

[0145] In the example shown in Figure 17, the length of period P1a and the length of period P1b are equal to each other. The length of period P2a and the length of period P2b are equal to each other. The length of period P3a and the length of period P3b are equal to each other. The length of period P4a and the length of period P4b are equal to each other. The length of period P5a and the length of period P5b are equal to each other. When the waveforms of the first drive signal Com-A and the second drive signal Com-B are in opposite phase to each other, there is an advantage in that the configuration of drive signal generation circuit 24 can be simplified compared to when they are not.

[0146] 17, the lengths of the periods P3a and P3b are the same, but they may be different. That is, the length of the period P3a may be longer or shorter than the length of the period P3b. In this case, there is an advantage that fluctuations in the ejection characteristics can be easily reduced even if an error occurs in the phase of the first drive signal Com-A and the second drive signal Com-B for some reason.

[0147] Fig. 18 is a diagram for explaining the contraction process SS and the expansion process SE in the sixth embodiment. In Fig. 18, the first drive signal Com-A is indicated by a solid line, and the second drive signal Com-B is indicated by a dashed line. In the example shown in Fig. 18, the potential VHa and the intermediate potential Vcb are equal to each other, and the intermediate potential Vca and the potential VLb are equal to each other.

[0148] The potential VHa and the intermediate potential Vcb may be different from each other, and the intermediate potential Vca and the potential VLb may be different from each other. However, when the potential VHa and the intermediate potential Vcb are equal to each other and the intermediate potential Vca and the potential VLb are equal to each other, there is an advantage in that the configuration of the drive signal generation circuit 24 can be simplified compared to when they are not.

[0149] In the period PS, a contraction process SS is performed, followed by an expansion process SE in the period PE.

[0150] The sixth embodiment described above can also improve the ejection characteristics of the liquid ejection device 100, similarly to the first embodiment. In this embodiment, as described above, the first drive signal Com-A includes a period P3a in which a voltage is maintained after the contraction element ESa, which is an example of a "first hold period." Meanwhile, the second drive signal Com-B includes a period P3b in which a voltage is maintained after the contraction element ESb, which is an example of a "second hold period." Here, if the lengths of the periods P3a and P3b are different from each other, even if a slight phase error occurs between the first drive signal Com-A and the second drive signal Com-B, the length of the overlapping period between the periods P3a and P3b is unlikely to vary. This reduces variations in the amount of ink ejected from the nozzle N due to such errors. In contrast, if the lengths of the periods P3a and P3b are equal to each other, the length of the overlapping period between the periods P3a and P3b is likely to vary due to such errors. This makes it easy for variations in the amount of ink ejected from the nozzle N to occur. However, in this case, there is an advantage that the drive signal generating circuit 24 can be simplified.

[0151] As described above, the first drive signal Com-A and the second drive signal Com-B are opposite in phase to each other. This reduces the influence of electrical noise (electrical crosstalk) between two adjacent ejection elements. Furthermore, in this case, the elements included in the first drive signal Com-A and the second drive signal Com-B are executed simultaneously, so the overall time required for the unit period Tu can be shortened compared to the first to fifth embodiments.

[0152] Furthermore, as described above, the intermediate potential Vcb is higher than the intermediate potential Vca. Therefore, in a standby state in which ink is not ejected from the nozzle N, the second drive signal Com-B maintains the expanded volume of the pressure chamber C. This applies tension to the diaphragm 51e, increasing the spring constant of the diaphragm 51e. As a result, the natural vibration period of the diaphragm 51e can be shortened, thereby shortening the ink ejection period from the nozzle N.

[0153] As described above, the first drive signal Com-A includes, for each unit period Tu, a period P3a that is an example of a "first hold period" and a period P4a that is an example of a "third period." The period P3a follows the period P2a that is an example of a "first period" and holds a potential VHa that is an example of a "second potential." The period P4a follows the period P3a and changes from the potential VHa to an intermediate potential Vca that is an example of a "fifth potential." Meanwhile, the second drive signal Com-B includes, for each unit period Tu, a period P3b that is an example of a "second hold period" and a period P4b that is an example of a "fourth period." The period P3b follows the period P2b that is an example of a "second period" and holds a potential VLb that is an example of a "fourth potential." The period P4b follows the period P3b and changes from the potential VLb to an intermediate potential Vcb that is an example of a "sixth potential." The periods P4a and P4b overlap each other. That is, the expansion step SE is executed. This makes it possible to increase the momentum of the ink introduced into the pressure chamber C. Also, the ink ejection cycle from the nozzle N can be shortened.

[0154] As described above, during the period PE in which the periods P4a and P4b overlap each other, the magnitude relationship between the potentials of the first drive signal Com-A and the second drive signal Com-B is reversed.

[0155] 7. Seventh embodiment The seventh embodiment of the present disclosure will be described below, focusing on the differences from the first embodiment.

[0156] 19 is a diagram for explaining the contraction process and the expansion process in the seventh embodiment. As shown in FIG. 19, this embodiment is similar to the sixth embodiment except that the intermediate potential Vcb of the second drive signal Com-B is different from the potential VHa of the first drive signal Com-A.

[0157] The seventh embodiment described above also improves the ejection characteristics of the liquid ejection device 100. In this embodiment, as described above, the intermediate potential Vcb is different from the potential VHa. Therefore, by appropriately setting the intermediate potential Vcb, it is possible to adjust the hardness of the diaphragm 51e, etc. As a result, even if there are manufacturing variations, it is possible to make the ejection characteristics uniform among the multiple head chips 51 or the multiple pressure chambers C.

[0158] 8. Eighth embodiment The eighth embodiment of the present disclosure will be described below, focusing on the differences from the first embodiment.

[0159] Fig. 20 is a diagram for explaining the first drive signal and the second drive signal in the eighth embodiment. In the example shown in Fig. 20, the first drive signal Com-A is the same as the first drive signal COM-A in the sixth embodiment.

[0160] On the other hand, the second drive signal Com-B shown in Fig. 20 is a signal with an opposite phase to the first drive signal Com-A. That is, the second drive signal Com-B shown in Fig. 20 has a waveform that, with the intermediate potential Vcb as the reference potential, changes from the intermediate potential Vcb to the potential VHb and the potential VLb in that order before returning to the intermediate potential Vcb within the unit period Tu.

[0161] Here, the potential of the second drive signal Com-B is maintained at the intermediate potential Vcb for a period P1d, then rises from the intermediate potential Vcb to a potential VHb for a period P2d, is maintained at the potential VHb for a period P3d, then falls from the potential VHb to a potential VLb for a period P4d, is maintained at the potential VLb for a period P5d, then rises from the potential VLb to the intermediate potential Vcb for a period P6d, and is maintained at the intermediate potential Vcb for a period P7d. The period P4d is an example of a "second period." The period P6d is an example of a "fourth period."

[0162] The waveform portion of the second drive signal Com-B in period P2d described above is an example of a "second expansion element" and is an expansion element EEb1 that expands the volume of the pressure chamber C. The waveform portion of the second drive signal Com-B in period P3d is a hold element ERb1 that is an example of a "second hold element." The waveform portion of the second drive signal Com-B in period P4d is an example of a "second contraction element" and is a contraction element ESb that contracts the volume of the pressure chamber C. The waveform portion of the second drive signal Com-B in period P5d is a hold element ERb2 that is an example of a "second hold element." The waveform portion of the second drive signal Com-B in period P6d is an example of a "second expansion element" and is an expansion element EEb2 that expands the volume of the pressure chamber C.

[0163] In this embodiment, the waveform portion of period P2c of the first drive signal Com-A is an example of a "first expansion element" and is an expansion element EEa1 that expands the volume of the pressure chamber C. The waveform portion of period P3c of the first drive signal Com-A is a hold element ERa1 that is an example of a "first hold element". The waveform portion of period P4c of the first drive signal Com-A is an example of a "first contraction element" and is a contraction element ESa that contracts the volume of the pressure chamber C. The waveform portion of period P5c of the first drive signal Com-A is a hold element ERa2 that is an example of a "first hold element". The waveform portion of period P6c of the first drive signal Com-A is an example of a "first expansion element" and is an expansion element EEa2 that expands the volume of the pressure chamber C.

[0164] Here, at least a portion of period P2c of the first drive signal Com-A and at least a portion of period P2d of the second drive signal Com-B overlap in time during period PE1. At least a portion of period P4c of the first drive signal Com-A and at least a portion of period P4d of the second drive signal Com-B overlap in time during period PS. Furthermore, at least a portion of period P6c of the first drive signal Com-A and at least a portion of period P6d of the second drive signal Com-B overlap in time during period PE2.

[0165] Fig. 21 is a diagram illustrating the contraction process SS, the first expansion process SE1, and the second expansion process SE2 in the eighth embodiment. In Fig. 21, the first drive signal Com-A is indicated by a solid line, and the second drive signal Com-B is indicated by a dashed line. In the example shown in Fig. 21, the potentials VHa and VHb are equal to each other, and the potentials VLa and VLb are equal to each other. Furthermore, the intermediate potential Vcb is higher than the intermediate potential Vca.

[0166] The potentials VHa and VHb may be different from each other, and the potentials VLa and VLb may be different from each other.

[0167] In the period PE1, the first expansion step SE1 is performed. Then, in the period PS, the contraction step SS is performed. Next, in the period PE2, the second expansion step SE2 is performed. Each of the first expansion step SE1 and the second expansion step SE2 has the same effect as the expansion step SE described above. In other words, the first expansion step SE1 and the second expansion step SE2 can be said to be included in the expansion step SE.

[0168] The eighth embodiment described above also improves the ejection characteristics of the liquid ejection device 100. In this embodiment, as described above, the expansion process SE includes a first expansion process SE1 and a second expansion process SE2. Furthermore, in the unit period Tu, the contraction process SS is executed between the first expansion process SE1 and the second expansion process SE2. Therefore, as in the other embodiments, the amount of ink ejected from the nozzle N per ejection can be increased. Additionally, because the elements included in the first drive signal Com-A and the second drive signal Com-B are executed simultaneously, the overall time required for the unit period Tu can be shortened compared to the first to fifth embodiments. In other words, it is possible to achieve both an increased ejection volume and a shorter ejection cycle of the liquid from the nozzle N.

[0169] 9. Ninth embodiment The ninth embodiment of the present disclosure will be described below, focusing on the differences from the first embodiment.

[0170] 22 is a diagram illustrating the contraction process SS, the first expansion process SE1, and the second expansion process SE2 in the ninth embodiment. This embodiment is similar to the eighth embodiment except that the potential difference between the intermediate potential Vca and the intermediate potential Vcb is different.

[0171] In this embodiment, the potential difference between the intermediate potential Vca and the intermediate potential Vcb is smaller than in the eighth embodiment. In the example shown in Fig. 22, although the intermediate potential Vcb is slightly higher than the intermediate potential Vca, the potential difference between the intermediate potential Vca and the intermediate potential Vcb is extremely small. Note that the intermediate potential Vca and the intermediate potential Vcb may be equal to each other, or the intermediate potential Vcb may be lower than the intermediate potential Vca.

[0172] According to the above ninth embodiment, the ejection characteristics of the liquid ejection device 100 can be improved, similarly to the eighth embodiment.

[0173] 10. Tenth embodiment The tenth embodiment of the present disclosure will be described below, focusing on the differences from the first embodiment.

[0174] 23 is a diagram illustrating the contraction process SS and the expansion process SE in the tenth embodiment. This embodiment is the same as the sixth embodiment, except that a waveform for the vibration suppression process SC is added to the second drive signal Com-B.

[0175] In this embodiment, the vibration damping process SC is performed by causing the potential of the second drive signal Com-B to drop from the intermediate potential Vcb to the potential VLb1 after the expansion process SE. The potential VLb1 is a potential between the intermediate potential Vcb and the potential VLb.

[0176] The above-described tenth embodiment also improves the ejection characteristics of the liquid ejection device 100. In this embodiment, in addition to the same effects as the sixth embodiment, the effect of the vibration damping step SC can be obtained.

[0177] 11. Variations Each of the above-mentioned exemplary embodiments can be modified in various ways. Specific modified embodiments that can be applied to each of the above-mentioned embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples can be appropriately combined within the scope of not contradicting each other.

[0178] 11-1. Variation 1 FIG. 24 is a diagram for explaining the contraction step SS and the expansion step SE in the first modification. The first modification is similar to the sixth embodiment described above, except that a step SX is added before the shrinking step SS.

[0179] In the example shown in FIG. 24, the step SX is executed by repeatedly dropping the potential of the second drive signal Com-B from the intermediate potential Vcb to the potential VLb multiple times before the contraction step SS. The above-described first modification can also improve the ejection characteristics of the liquid ejection device 100. The waveform used in the step SX is not limited to the example shown in FIG. 24 and can be any waveform. According to the step SX, for example, vibrations can be generated to the extent that ink is not ejected, and the pressure chamber C can be expanded immediately before the period PS, so that the vibrations during ejection can be adjusted to be excited. Furthermore, according to the step SX, the intermediate potential Vcb, which is a high potential, is not always maintained during the standby state in which liquid is not ejected, thereby reducing the power consumption of the drive signal generation circuit 24.

[0180] 11-2. Variation 2 In the above-described embodiment, a configuration in which a piezoelectric layer is interposed between an individual electrode and a common electrode is exemplified, but this is not limitative, and a configuration in which a piezoelectric layer is interposed between individual electrodes may also be used.

[0181] 11-3. Variation 3 In each of the above-mentioned embodiments, a serial-type liquid ejection device 100 is exemplified, in which a carriage 41 carrying a liquid ejection head 50 moves back and forth, but the present disclosure can also be applied to a line-type liquid ejection device in which multiple nozzles N are distributed across the entire width of the medium M.

[0182] 11-4. Variation 4 The liquid ejection device 100 exemplified in each of the above-described embodiments can be employed in various devices, such as facsimile machines and copiers, as well as devices dedicated to printing. However, the use of the liquid ejection device of the present disclosure is not limited to printing. For example, a liquid ejection device that ejects a solution of a color material is used as a manufacturing device for forming color filters for liquid crystal display devices. Furthermore, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wiring and electrodes on a wiring board. [Explanation of symbols]

[0183] 10...liquid container, 20...control unit, 21...control circuit, 22...memory circuit, 23...power supply circuit, 24...drive signal generation circuit, 30...transport mechanism, 40...movement mechanism, 41...carriage, 42...transport belt, 50...liquid ejection head, 51...head chip, 51F...piezoelectric element, 51a...flow path substrate, 51b...pressure chamber substrate, 51b1...partition wall, 51c...nozzle plate, 51d...vibration absorber, 51e...vibration plate, 51f...piezoelectric element, 51f1...first electrode layer, 51f1a...individual electrode, 51f1b...individual electrode, 51f1c...individual electrode, 51f2...piezoelectric layer, 51f3...second electrode layer, 51g... Bar, 51h...case, 51i...wiring board, 52...switching circuit, 52a...connection state designation circuit, 100...liquid ejection device, 200...external device, 51e1...first layer, 51e1...second layer, ABO3...general composition formula, BD...outer edge, C...pressure chamber, CLK...clock signal, CNG...change signal, COM-A...first drive signal, Com-1...first drive signal, Com-A...first drive signal, Com-B...second drive signal, EEa...expansion element, EEa1...expansion element, EEa2...expansion element, EEb...expansion element, EEb1...expansion element, EEb2...expansion element, ERa...holding element, ERa1...holding Element, ERa2...holding element, ERb...holding element, ERb1...holding element, ERb2...holding element, ESa...contraction element, ESb...contraction element, ESb1...contraction element, ESb2...contraction element, F1...first surface, F2...second surface, IH...inlet, Img...print data, LAT...latch signal, LHa...wiring, LHb...wiring, LHd...wiring, M...medium, N...nozzle, Na...communicating flow path, P1...active part, P1a...period, P1b...period, P1c...period, P1d...period, P2...active part, P2a...period, P2b...period, P2c...period, P2d...period, P3...active part, P3a...period, P3b...period period, P3c...period, P3d...period, P4a...period, P4b...period, P4c...period, P4d...period, P5a...period, P5b...period, P5c...period, P5d...period, P6c...period, P6d...period, P7c...period, P7d...period, PE...period, PE1...period, PE2...period, PS...period, R...liquid storage chamber, R1...opening, R2...storage section, Ra...supply flow path, SC...vibration damping process, SE...expansion process, SE1...first expansion process, SE2...second expansion process, SI...print data signal, SLa...connection state designation signal, SS...contraction process, SWa...switch, SWb...switch, SX...process,Sk1...control signal, Sk2...control signal, Tu...unit period, VBS...offset potential, VHV...power supply potential, VHa...potential, VHb...potential, VLa...potential, VLb...potential, VLb1...potential, Vca...intermediate potential, Vcb...intermediate potential, Vin-A...supply signal, Vin-B...supply signal, W1...width, W2...width, W3...width, dCom...waveform designation signal.

Claims

1. a diaphragm having a first surface and a second surface facing in an opposite direction to the first surface; a pressure chamber substrate laminated on the first surface side and having partition walls that define pressure chambers that communicate with nozzles that eject liquid; a piezoelectric element laminated on the second surface side, the piezoelectric element having a first active portion overlapping the center of the pressure chamber in the thickness direction of the vibration plate and a second active portion overlapping the pressure chamber at a position closer to the outer edge of the pressure chamber than the first active portion; a drive signal generation unit that generates, for each periodic unit period, a first drive signal that drives the first active unit and a second drive signal that drives the second active unit; the first drive signal includes a first contraction element that contracts the volume of the pressure chamber; the second drive signal includes a second contraction element that contracts the volume of the pressure chamber, performing a contraction step in which a first period during which the first contraction element is supplied to the first active section and a second period during which the second contraction element is supplied to the second active section overlap each other; A liquid ejection device characterized by:

2. During the contraction process, the magnitude relationship between the potentials of the first drive signal and the second drive signal is reversed. The liquid ejection device according to claim 1 .

3. In the unit period, a start timing of the first contraction element is later than a start timing of the second contraction element.

3. The liquid ejection device according to claim 1, wherein the ejection head is a nozzle.

4. In the unit period, an end timing of the first contraction element is later than an end timing of the second contraction element.

4. The liquid ejection device according to claim 3.

5. the first drive signal includes a first expansion element that expands the volume of the pressure chamber for each unit period, the second drive signal includes a second expansion element that expands the volume of the pressure chamber for each unit period, performing an expansion step in which a third period during which the first expansion element is supplied to the first active portion and a fourth period during which the second expansion element is supplied to the second active portion overlap; 4. The liquid ejection device according to claim 1, wherein the ejection head is a nozzle.

6. In the unit period, the expansion step is performed before the contraction step.

6. The liquid ejection device according to claim 5.

7. In the unit period, the expansion step is performed after the contraction step.

6. The liquid ejection device according to claim 5.

8. the expansion step includes a first expansion step and a second expansion step, In the unit period, the contraction step is performed between the first expansion step and the second expansion step.

6. The liquid ejection device according to claim 5.

9. the first drive signal includes a first hold period for holding a voltage after the first contraction element; the second drive signal includes a second hold period in which a voltage is held after the second contraction element; the first holding period and the second holding period have different lengths; 9. The liquid ejection device according to claim 7, wherein the liquid ejection device is a liquid ejection device.

10. the first drive signal and the second drive signal are signals of opposite phases to each other; 9. The liquid ejection device according to claim 7, wherein the liquid ejection device is a liquid ejection device.

11. In a standby state in which liquid is not ejected from the nozzle, the second drive signal maintains the expanded state of the volume of the pressure chamber.

10. The liquid ejection device according to claim 7, wherein the ejection head is a nozzle.

12. the first period and the fourth period do not overlap with each other; the second time period and the third time period do not overlap with each other; 12. The liquid ejection device according to claim 5, wherein the liquid ejection device is a liquid ejection device.

13. a diaphragm having a first surface and a second surface facing in an opposite direction to the first surface; a pressure chamber substrate laminated on the first surface side and having partition walls that define pressure chambers that communicate with nozzles that eject liquid; a piezoelectric element laminated on the second surface side, the piezoelectric element having a first active portion overlapping the center of the pressure chamber in the thickness direction of the vibration plate and a second active portion overlapping the pressure chamber at a position closer to the outer edge of the pressure chamber than the first active portion; a drive signal generation unit that generates, for each periodic unit period, a first drive signal that drives the first active unit and a second drive signal that drives the second active unit; the first drive signal includes a first period during which the first drive signal changes from a first potential to a second potential; the second drive signal includes a second period during which the second drive signal changes from a third potential to a fourth potential; the first period and the second period overlap each other; In the unit period, a start timing of the first period is later than a start timing of the second period. A liquid ejection device characterized by:

14. During a period in which the first period and the second period overlap each other, the magnitude relationship between the voltages of the first drive signal and the second drive signal is reversed. The liquid ejection device according to claim 13 .

15. A diaphragm having a first surface and a second surface facing in the opposite direction to the first surface; a pressure chamber substrate laminated on the first surface side and having partition walls that define pressure chambers that communicate with nozzles that eject liquid; a piezoelectric element laminated on the second surface side, the piezoelectric element having a first active portion overlapping the center of the pressure chamber in the thickness direction of the vibration plate and a second active portion overlapping the pressure chamber at a position closer to the outer edge of the pressure chamber than the first active portion; a drive signal generation unit that generates, for each periodic unit period, a first drive signal that drives the first active unit and a second drive signal that drives the second active unit; the first drive signal includes a first period during which the first drive signal changes from a first potential to a second potential; the second drive signal includes a second period during which the second drive signal changes from a third potential to a fourth potential; the first period and the second period overlap each other; The first drive signal is generated for each unit period as follows: a first holding period following the first period and during which the second potential is held; a third period following the first holding period, in which the potential changes from the second potential to a fifth potential; The second drive signal is generated for each unit period as follows: a second holding period following the second period and holding the fourth potential; a fourth period following the second holding period, in which the potential changes from the fourth potential to a sixth potential; the third period and the fourth period overlap each other; A liquid ejection device characterized by:

16. During a period in which the third period and the fourth period overlap each other, the magnitude relationship between the potentials of the first drive signal and the second drive signal is reversed.

16. The liquid ejection device according to claim 15.

17. the first holding period and the second holding period have different lengths; 17. The liquid ejection device according to claim 15 or 16.

18. the piezoelectric element has a third active portion that overlaps the pressure chamber at a position closer to an outer edge of the pressure chamber than the first active portion in a thickness direction of the vibration plate, the first active section is located between the second active section and the third active section in the thickness direction of the diaphragm; 18. The liquid ejection device according to claim 1, wherein the liquid ejection device is a liquid ejection device.

19. the piezoelectric element has a first electrode layer, a piezoelectric layer, and a second electrode layer in this order in a direction away from the vibration plate; the piezoelectric layer and the second electrode layer are provided in common across the first active section, the second active section, and the third active section; the first electrode layer includes a plurality of individual electrodes provided respectively in the first active portion, the second active portion, and the third active portion; 19. The liquid ejection device according to claim 18.

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