Liquid discharge device, and driving method of liquid discharge device

Abstract

To stably obtain appropriate discharge characteristics.SOLUTION: The liquid discharge device comprises: a vibration plate which has a first surface and a second surface pointing in the opposite direction of a direction of the first surface; a pressure chamber substrate, which is laminated on the first surface, and has a bulkhead partitioning a pressure chamber communicating with a nozzle for discharging liquid; a piezoelectric element, which is laminated on the second surface, 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; and a driving signal generating part that generates a discharging signal that is supplied to either of the first active part and the second active part to make the nozzle discharge the liquid and a correction signal that is supplied to the other of the first active part and the second active part, where an electric potential of the discharging signal varies with time and an electric potential of the correction signal remains constant, in a discharging period of time during which the nozzle discharges the liquid.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejection apparatus and a method for driving a liquid ejection head. [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, as disclosed in Patent Documents 1 to 3, for example. The pressure chamber contains a liquid, such as ink. The piezoelectric element deforms the diaphragm, thereby 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 3, for example. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-12261 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-260295 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-25225 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the device described in Patent Document 3 has the problem that the ejection characteristics change over time due to deterioration of the piezoelectric element, and variations or errors occur in the ejection characteristics due to manufacturing errors, etc., and as a result, it is not possible to stably obtain good ejection characteristics. [Means for solving the problem]

[0006] In order to solve the above problems, one 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 to 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 an ejection signal that is supplied to one of the first active part and the second active part to eject liquid from the nozzle, and a correction signal that is supplied to the other of the first active part and the second active part, wherein during an ejection period in which liquid is ejected from the nozzle, the potential of the ejection signal changes over time and the potential of the correction signal is constant.

[0007] One aspect of a method for driving a liquid ejection head according to the present disclosure is a method for driving a liquid ejection head comprising: a vibration plate having a first surface and a second surface facing in the opposite direction to 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; and 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, wherein an ejection signal that ejects liquid from the nozzle is supplied to one of the first active part and the second active part, and a correction signal is supplied to the other of the first active part and the second active part, and during an ejection period in which liquid is ejected from the nozzle, the potential of the ejection signal is changed over time and the potential of the correction signal is maintained constant. [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 in the first embodiment. [Figure 8] 5A and 5B are diagrams for explaining ejection signals and correction signals in the first embodiment. [Figure 9] 5A and 5B are schematic diagrams for explaining deformation of a diaphragm. [Figure 10] 5A and 5B are schematic diagrams for explaining deformation of a diaphragm. [Figure 11] 10 is a diagram showing the relationship between the position of the diaphragm and the amount of deflection for each voltage applied to the piezoelectric element. FIG. [Figure 12] FIG. 10 is a diagram showing the electrical configuration of a liquid ejection device according to a second embodiment. [Figure 13] FIG. 10 is a diagram for explaining a switching circuit according to a second embodiment. [Figure 14] FIG. 10 is a diagram showing the electrical configuration of a liquid ejection device according to a third embodiment. [Figure 15] FIG. 10 is a diagram showing the electrical configuration of a liquid ejection device according to a fourth embodiment. [Figure 16] FIG. 10 is a diagram showing the electrical configuration of a liquid ejection device according to a fifth embodiment. [Figure 17] FIG. 13 is a diagram showing the electrical configuration of a liquid ejection device according to a sixth embodiment. [Figure 18] FIG. 13 is a diagram for explaining a switching circuit in the sixth embodiment. 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 ejection units D that eject ink. Each of the plurality of ejection units D has a piezoelectric element 51f. Here, each piezoelectric element 51f has an active unit P1, which is an example of a "first active unit," and active units P2 and P3, which are examples of a "second active unit." The active unit P1 is driven by a supply signal Vin-A. Meanwhile, the active units P2 and P3 are driven by a supply signal Vin-B. Although not shown in FIG. 2, each ejection unit D includes a nozzle N and a pressure chamber C, which will be described later, in addition to the piezoelectric element 51f. The head chip 51 will be described in detail 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 ejection signal Com output from the control unit 20 as a supply signal Vin-A to the active part P1 for each of the plurality of piezoelectric elements 51f of the head chip 51. In this embodiment, the switching circuit 52 supplies the correction signal DC as a supply signal Vin-B to the active parts P2 and P3 of each piezoelectric element 51f. 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, which is an example of a "controller", a memory circuit 22, a power supply circuit 23, and a drive signal generating circuit 24, which is an example of a "drive signal generating 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 ejection signal Com and the correction signal DC. 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 ejection signal Com. In the drive signal generation circuit 24, the DA conversion circuit converts the voltage specification signal dDC 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 correction signal DC. Here, among the waveforms included in the ejection signal Com, the signal with the waveform actually supplied to the active part P1 of the piezoelectric element 51f is the aforementioned supply signal Vin-A. The correction signal DC is supplied to the active part P2 or P3 of the piezoelectric element 51f as the aforementioned supply signal Vin-B. The waveform designation signal dCom is a digital signal for defining the waveform of the ejection signal Com. The voltage designation signal dDC is a digital signal for defining the voltage value of the correction signal DC.

[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 voltage designation signal dDC, 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] The control circuit 21 also adjusts the voltage value indicated by the voltage specification signal dDC in accordance with the print data signal SI. This adjusts the correction signal DC. As a result, the size of the ink droplets ejected from the nozzles N is adjusted for each unit period Tu, which will be described later. Here, the print data signal SI is an example of "droplet volume information," and is information relating to the amount of ink ejected from the nozzles N per ejection.

[0031] Furthermore, during the printing period, which is the period during which the liquid ejection head 50 continuously ejects ink, the control circuit 21 controls the driving of the drive signal generation circuit 24 to generate the correction signal DC, but during periods other than the printing period, such as a standby period, the control circuit 21 either lowers the potential of the correction signal DC or stops the generation of the correction signal DC by the drive signal generation circuit 24. As a result, during periods other than the ejection period T, which will be described later, the potential of the correction signal DC is lowered, or the correction signal DC is not supplied to any of the active units P1, P2, and P3.

[0032] 1-3. Overall configuration of liquid ejection head

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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 apply pressure to the ink filled in 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 has an elongated shape extending in a direction along the X axis. The X2-direction end of each pressure chamber C communicates with a corresponding supply flow path Ra. Meanwhile, the X1-direction end of each pressure chamber C communicates with a corresponding communication flow path Na. 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. 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.

[0038] 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.

[0039] 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 an ejection signal Com and a correction signal DC, 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] The diaphragm 51e has a first layer 51e1 and a second layer 51e2, 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 51e2 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.

[0048] 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 51e2 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 51e2. In other words, the first layer 51e1 or the second layer 51e2 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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. An ejection signal Com 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 correction signal DC is supplied to the individual electrodes 51f1b and 51f1c via wiring.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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, it is smaller than the width of the pressure chamber C along the Y axis and is 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.

[0067] 1-5. Switching circuit configuration Fig. 7 is a diagram for explaining the switching circuit 52 in the first embodiment. The switching circuit 52 will be explained below with reference to Fig. 7. In Fig. 7, a discharge unit D_1 and a discharge unit D_2 are representatively illustrated as two discharge units D out of the plurality of discharge units D.

[0068] 7, the switching circuit 52 is connected to a wiring LHa and a wiring LHb. The wiring LHa is a signal line that transmits the ejection signal Com. The wiring LHb is a signal line that transmits the correction signal DC. Furthermore, a wiring LHd is connected to the second electrode layer 51f3 of the piezoelectric element 51f. The wiring LHd is a power supply line that supplies an offset potential VBS.

[0069] In this embodiment, the wiring LHb is electrically connected to the individual electrodes 51f1b, 51f1c of the first electrode layer 51f1 of the piezoelectric element 51f. Note that, although the wiring LHb passes through the switching circuit 52 in the example shown in Fig. 7, the wiring LHb may be electrically connected to the individual electrodes 51f1b, 51f1c of the first electrode layer 51f1 without passing through the switching circuit 52.

[0070] The switching circuit 52 has a plurality of switches SWa 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.

[0071] The switch SWa is a switch that switches between conduction (ON) and non-conduction (OFF) between the wiring LHa for transmitting the ejection signal Com and the individual electrode 51f1a of the piezoelectric element 51f. Each of these switches is, for example, a transmission gate.

[0072] The connection state designation circuit 52a generates a connection state designation signal SLa that designates the on / off states of the switches SWa based on the clock signal CLK, print data signal SI, latch signal LAT, and change signal CNG supplied from the control circuit 21.

[0073] 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.

[0074] The switch SWa is switched on and off according to the connection state designation signal SLa generated as described above. For example, the switch SWa is in an on state when the connection state designation signal SLa is at a high level, and in an off state 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 ejection signal Com as the supply signal Vin-A to one or more piezoelectric elements 51f selected from the plurality of piezoelectric elements 51f, and supplies the correction signal DC as the supply signal Vin-B.

[0075] 1-6. Discharge signal and correction signal 8 is a diagram for explaining the ejection signal Com and the correction signal DC in the first embodiment. The vertical axis "voltage" in FIG. 8 represents the potential difference between the ejection signal Com or the correction signal DC and the offset potential VBS. Note that the vertical axis "voltage" in FIG. 8 may also represent the potential of the ejection signal Com or the correction signal DC.

[0076] The ejection signal Com is a signal that, when supplied to the active part P1, causes liquid to be ejected from the nozzle N. As shown in FIG. 8, the ejection signal Com has a waveform that changes for each unit period Tu of a predetermined cycle. The unit period Tu is determined by the aforementioned latch signal LAT and the like, and corresponds to the printing cycle for forming dots of ink from the nozzle N on the medium M. The unit period Tu for ejecting ink from the nozzle N is the ejection period T.

[0077] 8, the ejection signal Com has a waveform that, with the intermediate potential Vc as a reference potential, changes from the intermediate potential Vc to a potential VL and a potential VH in this order and then returns to the intermediate potential Vc within a unit period Tu. Here, the intermediate potential Vc is, for example, a potential higher than the offset potential VBS. The potential VL is a potential lower than the intermediate potential Vc. The potential VH is a potential higher than the intermediate potential Vc.

[0078] Here, the waveform portion of the ejection signal Com that drops the potential from the intermediate potential Vc to the potential VL is an expansion element EEa1 that expands the volume of the pressure chamber C. The waveform portion of the ejection signal Com that maintains the potential at the potential VL is a hold element ERa1. The waveform portion of the ejection signal Com that raises the potential from the potential VL to the potential VH is a contraction element ESa that contracts the volume of the pressure chamber C. The waveform portion of the ejection signal Com that maintains the potential at the potential VH is a hold element ERa2. The waveform portion of the ejection signal Com that drops the potential from the potential VH to the intermediate potential Vc is an expansion element EEa2 that expands the volume of the pressure chamber C.

[0079] The waveform of the ejection signal Com is not limited to the example shown in FIG. 8 and may be any waveform as long as it can cause the liquid to be ejected from the nozzle N when supplied to the active part P1.

[0080] On the other hand, the correction signal DC is a signal of a constant potential of potential VH1. The potential VH1 is preferably a potential higher than the intermediate potential Vc, but may be a potential lower than the intermediate potential Vc. In the example shown in FIG. 8, the potential VH1 is lower than the potential VH. Note that the potential VH1 may be higher than the potential VH.

[0081] 9 and 10 are schematic diagrams illustrating deformation of diaphragm 51e. For ease of explanation, these figures omit illustration of piezoelectric element 51F and illustrate diaphragm 51e in a schematic manner. Also, in FIGS. 9 and 10, diaphragm 51e in its natural state, which is an ideal reference state, is indicated by a two-dot chain line. The "natural state of diaphragm 51e" refers to the state of diaphragm 51e when no voltage is applied to piezoelectric element 51f.

[0082] When the holding element ERa1 of the ejection signal Com is supplied to the active portion P1, the vibration plate 51e is deformed so that the first surface F1 becomes concave, as shown in FIG. 9. This causes the volume of the pressure chamber C to expand. Thereafter, when the holding element ERa2 of the ejection signal Com is supplied to the active portion P1, the vibration plate 51e is deformed so that the first surface F1 becomes convex, as shown in FIG. 10. This causes the volume of the pressure chamber C to contract. As a result, ink is ejected from the nozzle N.

[0083] 9 and 10, the natural state of the diaphragm 51e may not be the state shown by the two-dot chain lines, but may be slightly bent so that the first surface F1 is convex due to manufacturing errors, etc. In this case, if the piezoelectric element 51f is driven using only the ejection signal Com, variations in the ejection characteristics may occur.

[0084] Fig. 11 is a diagram showing the relationship between the position and the amount of deflection of diaphragm 51e for each voltage applied to piezoelectric element 51f. Fig. 11 shows the relationship between the position and the amount of deflection of diaphragm 51e for each applied voltage when diaphragm 51e is in an ideal natural state.

[0085] 11, the higher the voltage applied to the piezoelectric element 51f, the greater the amount of deflection of the diaphragm 51e. However, the higher the voltage applied to the piezoelectric element 51f, the smaller the amount of deflection of the diaphragm 51e per unit voltage of the applied voltage. This indicates that when the diaphragm 51e is naturally deflected so that the first surface F1 is convex, the driving efficiency of the piezoelectric element 51f decreases.

[0086] Therefore, the correction signal DC is used. When the active units P2 and P3 receive the correction signal DC, they deform the diaphragm 51e in the opposite direction to when the active unit P1 receives the ejection signal Com. This is because, of the ends of the active units P2 and P3 along the Y axis, the displacement of the end closer to the partition wall 511 is restricted by the partition wall 511, while the displacement of the end farther from the partition wall 511 is less restricted. Here, the correction signal DC drives the piezoelectric element 51f so that the diaphragm 51e is in its ideal natural state when the ejection signal Com is not supplied to the piezoelectric element 51f. As a result, the driving efficiency of the piezoelectric element 51f can be improved. Furthermore, variations in ejection characteristics can be reduced when comparing the ejection units D.

[0087] 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." The vibration plate 51e has a first surface F1 and a second surface F2 facing the opposite direction from the first surface F1. The pressure chamber substrate 51b is layered on the first surface F1 and has partition walls 51b1 that define pressure chambers C, which communicate with nozzles N that eject ink, an example of a "liquid." The piezoelectric element 51f is layered on the second surface F2 and has an active portion P1 that overlaps the center of the pressure chamber C in the thickness direction of the vibration plate 51e, and active portions P2 and P3 that overlap the pressure chamber C at positions closer to the outer edge BD of the pressure chamber C than the active portion P1. The drive signal generation circuit 24 generates an ejection signal Com and a correction signal DC.

[0088] The ejection signal Com is supplied to one of the active unit P1 and the active units P2 and P3 to eject ink from the nozzle N. The correction signal DC is supplied to the other of the active unit P1 and the active units P2 and P3. During the ejection period T during which ink is ejected from the nozzle N, the potential of the ejection signal Com changes over time, and the potential of the correction signal DC is constant.

[0089] In the liquid ejection device 100 described above, the tension of the diaphragm 51e can be appropriately adjusted by supplying a correction signal DC of a constant potential to the other of the active portion P1 and the active portions P2 and P3 during the ejection period T. This reduces the effects of deterioration of the piezoelectric element 51f, manufacturing variations between ejection portions D, and the like on the ejection characteristics of ink from the nozzles N. As a result, good ejection characteristics can be stably obtained. Furthermore, by adopting a driving method using the ejection signal Com and the correction signal as described above as a method for driving the liquid ejection head 50, good ejection characteristics can be stably obtained.

[0090] In this embodiment, as described above, the ejection signal Com is supplied to the active unit P1. Meanwhile, the correction signal DC is supplied to the active units P2 and P3. As a result, stress acts on the active units P2 and P3 so that the diaphragm 51e is displaced in a direction that makes the second surface F2 concave, i.e., in a direction that makes the second surface F2 convex overall. This alleviates the deflection of the diaphragm 51e in a direction that makes the first surface F1 convex, which may be caused by manufacturing errors or the like. This suppresses a decrease in the drive efficiency of the piezoelectric element 51f and reduces the effects of manufacturing variations between the ejection units D. Furthermore, because the active units P2 and P3 are located at both ends of the pressure chamber C in the direction along the Y axis, it is easier to finely adjust the overall tension of the diaphragm 51e than in a configuration in which the correction signal DC is supplied to the active unit P1. As a result, the reliability of the diaphragm 51e can be improved.

[0091] As described above, the liquid ejection device 100 includes an ejection section D_1, which is an example of a "first ejection section," and an ejection section D_2, which is an example of a "second ejection section." Each of the ejection sections D_1 and D_2 has a nozzle N, a pressure chamber C, an active section P1, and active sections P2 and P3. The potential of the correction signal DC used for the ejection section D_1 is equal to the potential of the correction signal DC used for the ejection section D_2. Therefore, the circuit configuration of the drive signal generation circuit 24 can be simplified compared to a configuration in which the correction signal DC is generated individually for each ejection section D.

[0092] Furthermore, as described above, the amount of deflection of the diaphragm 51e when the correction signal DC is supplied to either the active portion P1 or the active portions P2 and P3 is smaller than the amount of deflection of the diaphragm 51e when the correction signal DC is not supplied to either the active portion P1 or the active portions P2 and P3. This reduces the initial deflection of the diaphragm 51e. As a result, the amount of deflection of the diaphragm 51e when ink is ejected from the nozzle N can be increased.

[0093] As described above, the liquid ejection device 100 further includes a control circuit 21, which is an example of a "control unit." The control circuit 21 controls the driving of the drive signal generation circuit 24. Here, the control circuit 21 adjusts the correction signal DC, thereby optimizing or improving the ejection characteristics.

[0094] As described above, the control circuit 21 adjusts the correction signal DC based on the print data signal SI, which is an example of "droplet volume information." The print data signal SI is information related to the volume of ink ejected from the nozzle N per ejection. This makes it possible to eject ink droplets of different sizes from the nozzle N using a single waveform of the ejection signal Com.

[0095] Furthermore, as mentioned above, during periods other than the ejection period T, the potential of the correction signal DC can be lowered or the correction signal DC can be not supplied to either the active part P1 or the active parts P2 and P3, thereby reducing the power consumption of the liquid ejection device 100.

[0096] 2. Second embodiment A second embodiment of the present disclosure will be described below, focusing on the differences from the first embodiment.

[0097] 12 is a diagram showing the electrical configuration of a liquid ejection device 100A according to the second embodiment. The liquid ejection device 100A has the same configuration as the liquid ejection device 100 of the first embodiment described above, except that the control unit 20 and the liquid ejection head 50 are replaced with a control unit 20A and a liquid ejection head 50A.

[0098] The control unit 20A has the same configuration as the control unit 20 described above, except that it adds a deterioration information generation circuit 25 and adjusts the correction signal DC accordingly. The deterioration information generation circuit 25 generates deterioration information DD. The deterioration information DD is information regarding deterioration of at least one of the nozzle plate 51c having the nozzles N, the pressure chamber substrate 51b, the diaphragm 51e, and the piezoelectric element 51f. Examples of deterioration include the adhesion of foreign matter near the nozzles, an increase in ink viscosity, the intrusion of air bubbles into the pressure chambers, and fatigue of the piezoelectric element or diaphragm.

[0099] The deterioration information generating circuit 25 measures the number of times the piezoelectric element 51f is driven or the period of use based on the print data signal SI etc. from the control circuit 21, and generates the deterioration information DD based on the measurement results. In this embodiment, the deterioration information generating circuit 25 also generates the deterioration information DD based on the residual vibration signal NVT from the liquid ejection head 50A.

[0100] In this embodiment, the control circuit 21 controls the driving of the drive signal generation circuit 24 so as to adjust the correction signal DC based on the deterioration information DD. Specifically, the control circuit 21 adjusts the correction signal DC so as to increase the potential as the degree of deterioration indicated by the deterioration information DD increases.

[0101] In this embodiment, the control circuit 21 can also perform a detection operation using a detection circuit 53, which will be described later. This detection operation is performed by driving the active part P1 of the piezoelectric element 51f with the ejection signal Com, and detecting the residual vibrations resulting from this drive using the detection circuit 53, which detects the output signal Vout resulting from the electromotive forces of the active parts P2 and P3 of the piezoelectric element 51f. Here, the waveform of the ejection signal Com is an example of a "detection waveform." The execution timing of this detection operation, etc., is determined appropriately according to a preset program or user operation, etc. The ejection signal Com may also include a detection waveform separate from the waveform described above.

[0102] The liquid ejection head 50A has the same configuration as the liquid ejection head 50 described above, except that it has a switching circuit 52A instead of the switching circuit 52 and a detection circuit 53 is added.

[0103] The detection circuit 53 generates a residual vibration signal NVT based on the output signal Vout generated by the piezoelectric element 51f. For example, the detection circuit 53 generates the residual vibration signal NVT by amplifying the output signal Vout after removing noise. The residual vibration signal NVT indicates residual vibration, which is vibration remaining in the ink flow path in the head chip 51 after the piezoelectric element 51f is driven.

[0104] 13 is a diagram illustrating a switching circuit 52A according to the second embodiment. The switching circuit 52A has the same configuration as the switching circuit 52 described above, except that it has a connection state designation circuit 52b instead of the connection state designation circuit 52a, and that it also has a wiring LHs and a plurality of switches SWs.

[0105] 13, the switching circuit 52A is connected to lines LHd, LHa, and LHs. The line LHs is a signal line that transmits the output signal Vout.

[0106] The switching circuit 52A has a plurality of switches SWa and SWs that correspond one-to-one to the plurality of piezoelectric elements 51f, and a connection state designation circuit 52b that designates the connection state of these switches.

[0107] The switches SWs are switches that switch between conduction (ON) and non-conduction (OFF) between the wiring LHs for transmitting the output signal Vout and the individual electrodes 51f1b, 51f1c of the piezoelectric element 51f. Each of these switches is, for example, a transmission gate.

[0108] The connection state designation circuit 52b generates a connection state designation signal SLa that designates the on / off of multiple switches SWa and a connection state designation signal SLs that designates the on / off of multiple switches SWs based on the clock signal CLK, print data signal SI, latch signal LAT, and change signal CNG supplied from the control circuit 21.

[0109] The switch SWa is switched on and off in response to the connection state designation signal SLa generated as described above. The switch SWs is switched on and off in response to the connection state designation signal SLs. As described above, the switching circuit 52A supplies the detection circuit 46 with the output signal Vout from one or more piezoelectric elements 51f selected from the plurality of piezoelectric elements 51f.

[0110] The second embodiment described above also makes it possible to stably obtain good ejection characteristics. In this embodiment, as described above, the control circuit 21 adjusts the correction signal DC based on the deterioration information DD. The deterioration information DD is information regarding deterioration of at least one of the nozzle plate 51c having the nozzle N, the pressure chamber substrate 51b, the diaphragm 51e, and the piezoelectric element 51f. This makes it possible to reduce fluctuations in ejection characteristics due to deterioration of at least one of the nozzle plate 51c having the nozzle N, the pressure chamber substrate 51b, the diaphragm 51e, and the piezoelectric element 51f.

[0111] As described above, the liquid ejection device 100A further includes a detection circuit 53. The drive signal generation circuit 24 generates an ejection signal Com as an inspection signal to be supplied to one of the active unit P1 and the active units P2 and P3. The detection circuit 53 supplies the ejection signal Com to one of the active unit P1 and the active units P2 and P3, and detects the electromotive force generated in the other of the active unit P1 and the active units P2 and P3 as an output signal Vout. This allows for higher inspection accuracy and shorter inspection time than a configuration in which a single active unit is used to both drive the liquid ejection device 100A with an inspection signal and output the electromotive force resulting from that drive.

[0112] 3. Third embodiment The third embodiment of the present disclosure will be described below, focusing on the differences from the first embodiment.

[0113] 14 is a diagram showing the electrical configuration of a liquid ejection apparatus 100B according to the third embodiment. The liquid ejection apparatus 100B is configured similarly to the liquid ejection apparatus 100 of the first embodiment described above, except that it includes a control unit 20B and a liquid ejection head 50A instead of the control unit 20 and the liquid ejection head 50. That is, the liquid ejection apparatus 100B is configured similarly to the liquid ejection apparatus 100A of the second embodiment described above, except that it includes a control unit 20B instead of the control unit 20A.

[0114] The control unit 20B has a viscosity information generation circuit 26 instead of the deterioration information generation circuit 25, and is configured similarly to the control unit 20A described above, except for the corresponding method of adjusting the correction signal DC. The viscosity information generation circuit 26 generates viscosity information DV. The viscosity information DV is information related to the viscosity of the ink ejected from the nozzle N.

[0115] The viscosity information generating circuit 26 generates viscosity information DV based on the residual vibration signal NVT from the liquid ejection head 50A.

[0116] In this embodiment, the control circuit 21 controls the driving of the drive signal generation circuit 24 so as to adjust the correction signal DC based on the viscosity information DV. Specifically, the control circuit 21 adjusts the correction signal DC so that the potential increases as the viscosity indicated by the viscosity information DV increases.

[0117] According to the third embodiment described above, it is also possible to stably obtain good ejection characteristics. In this embodiment, as described above, the control circuit 21 adjusts the correction signal DC based on the viscosity information DV relating to the viscosity of the ink ejected from the nozzle N. This makes it possible to reduce fluctuations in the ejection characteristics due to changes in the viscosity of the ink ejected from the nozzle N.

[0118] 4. Fourth embodiment The fourth embodiment of the present disclosure will be described below, focusing on the differences from the first embodiment.

[0119] 15 is a diagram showing the electrical configuration of a liquid ejection device 100C according to the fourth embodiment. The liquid ejection device 100C has the same configuration as the liquid ejection device 100 of the first embodiment described above, except that the control unit 20 and the liquid ejection head 50 are replaced with a control unit 20C and a liquid ejection head 50C.

[0120] The control unit 20C is configured in the same manner as the control unit 20 described above, except that it adds a temperature information generation circuit 27 and adjusts the correction signal DC accordingly. The temperature information generation circuit 27 generates temperature information DT. The temperature information DT is information relating to the temperature of the ink ejected from the nozzle N.

[0121] The temperature information generating circuit 27 generates temperature information DT based on the output from a temperature sensor 54, which will be described later.

[0122] In this embodiment, the control circuit 21 controls the driving of the drive signal generation circuit 24 so as to adjust the correction signal DC based on the temperature information DT. Specifically, the control circuit 21 adjusts the correction signal DC so that the potential increases as the temperature indicated by the temperature information DT decreases.

[0123] The liquid ejection head 50C has the same configuration as the above-described liquid ejection head 50, except for the addition of a temperature sensor 54. The temperature sensor 54 is an element such as a thermistor that detects the temperature of ink ejected from the nozzles N. For example, the temperature sensor 54 is installed inside the head chip 51.

[0124] According to the fourth embodiment described above, it is also possible to stably obtain good ejection characteristics. In this embodiment, as described above, the control circuit 21 adjusts the correction signal DC based on the temperature information DT relating to the temperature of the ink ejected from the nozzle N. This makes it possible to reduce fluctuations in the ejection characteristics due to changes in the temperature of the ink ejected from the nozzle N.

[0125] 5. Fifth embodiment The fifth embodiment of the present disclosure will be described below, focusing on the differences from the first embodiment.

[0126] FIG. 16 is a diagram showing the electrical configuration of a liquid ejection device 100D according to the fifth embodiment. The liquid ejection device 100D is configured in the same manner as the liquid ejection device 100 of the first embodiment described above, except that an ejection signal Com is supplied to active parts P2 and P3, and a correction signal DC is supplied to the active part P1.

[0127] The fifth embodiment described above also makes it possible to stably obtain good ejection characteristics. In this embodiment, as described above, the ejection signal Com is supplied to the active units P2 and P3, and the correction signal DC is supplied to the active unit P1. Therefore, compared to a configuration in which the ejection signal Com is supplied to the active unit P1, it is easier to increase the amount of displacement of the diaphragm 51e, and as a result, the efficiency of ink ejection from the nozzles N can be improved.

[0128] 6. Sixth embodiment The sixth embodiment of the present disclosure will be described below, focusing on the differences from the first embodiment.

[0129] 17 is a diagram showing the electrical configuration of a liquid ejection device 100E according to the sixth embodiment. The liquid ejection device 100E has the same configuration as the liquid ejection device 100 of the first embodiment described above, except that the control unit 20 and the liquid ejection head 50 are replaced with a control unit 20E and a liquid ejection head 50E.

[0130] The control unit 20E is configured similarly to the control unit 20 described above, except that it includes a drive signal generation circuit 24E instead of the drive signal generation circuit 24. The drive signal generation circuit 24E is an example of a "drive signal generation section" and generates correction signals DC1 and DC2 based on the voltage specification signal dDC. The correction signals DC1 and DC2 are each constant potential signals. However, the potentials of the correction signals DC1 and DC2 are different from each other. In this embodiment, the control circuit 21 generates a signal for selecting either the correction signal DC1 or the correction signal DC2. This signal may be generated independently or may be included in the print data signal SI, etc.

[0131] The liquid ejection head 50E is configured similarly to the liquid ejection head 50 described above, except that it has a switching circuit 52E instead of the switching circuit 52. Under the control of the control unit 20E, the switching circuit 52E switches, for each of the plurality of piezoelectric elements 51f, whether to supply the ejection signal Com output from the control unit 20E as the supply signal Vin-A to the active portion P1. The switching circuit 52E also selects one of the correction signals DC1 and DC2 based on the print data signal SI, etc., and supplies it as the supply signal Vin-B to the active portions P2 and P3 of each piezoelectric element 51f.

[0132] This selection is not particularly limited and may be made arbitrarily, but may be determined, for example, according to variations in the ejection characteristics of the multiple ejection sections D. This selection may also be made based on the deterioration information DD, viscosity information DV, or temperature information DT described above.

[0133] 18 is a diagram illustrating a switching circuit 52E according to the sixth embodiment. The switching circuit 52E has the same configuration as the switching circuit 52 described above, except that it has a connection state designation circuit 52c and lines LHb1 and LHb2 instead of the connection state designation circuit 52a and line LHb, and that it also has multiple switches SWb and multiple switches SWc.

[0134] 18, the switching circuit 52E is connected to lines LHd, LHa, LHb1, and LHb2. The line LHb1 is a signal line that transmits the correction signal DC1. The line LHb2 is a signal line that transmits the correction signal DC2.

[0135] The switching circuit 52E has a plurality of switches SWa, SWb and SWc corresponding one-to-one to the plurality of piezoelectric elements 51f, and a connection state designation circuit 52c that designates the connection state of these switches.

[0136] The switch SWb is a switch that switches between conduction (ON) and non-conduction (OFF) between the wiring LHb1 and the individual electrodes 51f1b, 51f1c of the piezoelectric element 51f. The switch SWc is a switch that switches between conduction (ON) and non-conduction (OFF) between the wiring LHb2 and the individual electrodes 51f1b, 51f1c of the piezoelectric element 51f. Each of these switches is, for example, a transmission gate.

[0137] The connection state designation circuit 52c generates a connection state designation signal SLa that designates the on / off states of the multiple switches SWa, a connection state designation signal SLb that designates the on / off states of the multiple switches SWb, and a connection state designation signal SLc that designates the on / off states of the multiple switches SWc, based on a signal from the control circuit 21. Here, in the same discharge section D, when one of the switches SWb and SWc is on, the other is off.

[0138] The switch SWa is switched on and off in response to the connection state designation signal SLa generated as described above. The switch SWb is switched on and off in response to the connection state designation signal SLb. The switch SWc is switched on and off in response to the connection state designation signal SLc. As described above, the switching circuit 52E can change the potentials of the individual electrodes 51f1b and 51f1c. It is also possible to use the correction signal DC1 for one of the discharge section D_1 and the discharge section D_2, and the correction signal DC2 for the other.

[0139] The sixth embodiment described above also makes it possible to stably obtain good ejection characteristics. In this embodiment, as described above, the liquid ejection device 100E includes a plurality of ejection units D that eject ink. Each of the plurality of ejection units D has a nozzle N, a pressure chamber C, an active unit P1, and active units P2 and P3. A correction signal DC1 is used for one of the ejection units D_1 and D_2, and a correction signal DC2 is used for the other. Here, the potential of the correction signal DC1 is different from the potential of the correction signal DC2. This allows the tension of the diaphragm 51e to be adjusted individually for each ejection unit D.

[0140] 6. 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. Note that two or more embodiments arbitrarily selected from the following examples can be appropriately combined within the scope of not contradicting each other.

[0141] 6-1. Variation 1 In the above-described embodiment, a piezoelectric layer is interposed between an individual electrode and a common electrode, but the present invention is not limited to this and may be configured such that a piezoelectric layer is interposed between individual electrodes. Also, a configuration may be adopted in which the first electrode layer 51f1 serves as a common electrode and the second electrode layer 52f3 serves as an individual electrode.

[0142] 6-2. Variation 2 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.

[0143] 6-3. Variation 3 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]

[0144] 10...liquid container, 20...control unit, 20A...control unit, 20B...control unit, 20C...control unit, 20E...control unit, 21...control circuit, 22...memory circuit, 23...power supply circuit, 24...drive signal generation circuit, 24E...drive signal generation circuit, 25...deterioration information generation circuit, 26...viscosity information generation circuit, 27...temperature information generation circuit, 30...conveyance mechanism, 40...movement mechanism, 41...carriage, 42...conveyor belt, 46...detection circuit, 50...liquid ejection head, 50A...liquid ejection head, 50C...liquid ejection head, 50E...liquid ejection head, 51...head chip, 5 1F...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...cover, 51h...case, 51i...wiring substrate, 52...switching circuit, 52A...switching circuit, 52E...switching circuit, 52a...connection state designation circuit, 52b...connection state designation circuit, 52c...connection state designation circuit, 52f3...second electrode layer, 53...detection circuit, 54...temperature Degree sensor, 100...liquid ejection device, 100A...liquid ejection device, 100B...liquid ejection device, 100C...liquid ejection device, 100D...liquid ejection device, 100E...liquid ejection device, 200...external device, 51e1...first layer, 51e2...second layer, ABO3...general composition formula, BD...outer edge, C...pressure chamber, CLK...clock signal, CNG...change signal, Com...ejection signal, D...ejection unit, DC...correction signal, DC1...correction signal, DC2...correction signal, DD...deterioration information, DT...temperature information, DV...viscosity information, D_1...ejection unit, D_2...ejection unit, EEa1...expansion element, EEa2...expansion Element, ERa1...holding element, ERa2...holding element, ESa...contraction element, F1...first surface, F2...second surface, IH...inlet, Img...print data, LAT...latch signal, LHa...wiring, LHb...wiring, LHb1...wiring, LHb2...wiring, LHd...wiring, LHs...wiring, M...medium, N...nozzle, NVT...residual vibration signal, Na...communicating flow path, P1...active part, P2...active part, P3...active part, R...liquid storage chamber, R1...opening, R2...storage part, Ra...supply flow path, SI...print data signal, SLa...connection state designation signal, SLb...connection state designation signal, SLc...connection state designation signal,SLs...connection state designation signal, SWa...switch, SWb...switch, SWc...switch, SWs...switch, Sk1...control signal, Sk2...control signal, T...discharge period, Tu...unit period, VBS...offset potential, VH...potential, VH1...potential, VHV...power supply potential, VL...potential, Vc...intermediate potential, Vca...intermediate potential, Vin-A...supply signal, Vin-B...supply signal, Vout...output signal, W1...width, W2...width, W3...width, dCom...waveform designation signal, dDC...voltage designation signal.

Claims

1. a diaphragm 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 communicating with nozzles that eject liquid; a piezoelectric element that is laminated on the second surface and has a first active portion that overlaps with a center of the pressure chamber when viewed in a thickness direction of the vibration plate, and a second active portion that overlaps with the pressure chamber at a position closer to an outer edge of the pressure chamber than the first active portion; a drive signal generating unit that generates a discharge signal that is supplied to one of the first active unit and the second active unit to cause liquid to be discharged from the nozzle, and a correction signal that is supplied to the other of the first active unit and the second active unit; during a discharge period in which liquid is discharged from the nozzle, a potential of the discharge signal changes over time, and a potential of the correction signal is constant; A liquid ejection device comprising:

2. The ejection signal is provided to the first active portion; The correction signal is supplied to the second active portion. The liquid ejection device according to claim 1 .

3. The ejection signal is provided to the second active portion; The correction signal is supplied to the first active portion. The liquid ejection device according to claim 1 .

4. The device includes a first discharge portion and a second discharge portion, each of the first ejection unit and the second ejection unit includes the nozzle, the pressure chamber, the first active unit, and the second active unit; a potential of the correction signal used for the first ejection unit is different from a potential of the correction signal used for the second ejection unit; 4. The liquid ejection device according to claim 1, wherein the liquid ejection device is a liquid ejection device.

5. The device includes a first discharge portion and a second discharge portion, each of the first ejection unit and the second ejection unit includes the nozzle, the pressure chamber, the first active unit, and the second active unit; a potential of the correction signal used for the first ejection unit is equal to a potential of the correction signal used for the second ejection unit; 4. The liquid ejection device according to claim 1, wherein the liquid ejection device is a liquid ejection device.

6. a deflection amount of the diaphragm in a state where the correction signal is supplied to one of the first active unit and the second active unit is smaller than a deflection amount of the diaphragm in a state where the correction signal is not supplied to either the first active unit or the second active unit. The liquid ejection device according to any one of claims 1 to 5.

7. A control unit that controls the driving of the drive signal generating unit is further provided. The control unit adjusts the correction signal.

7. The liquid ejection device according to claim 1, wherein the liquid ejection device is a liquid ejection device.

8. the control unit adjusts the correction signal based on deterioration information relating to deterioration of at least one of a nozzle plate having the nozzles, the pressure chamber substrate, the vibration plate, and the piezoelectric element.

8. The liquid ejection device according to claim 7.

9. the control unit adjusts the correction signal based on viscosity information relating to a viscosity of the liquid ejected from the nozzle.

9. The liquid ejection device according to claim 7, wherein the liquid ejection device is a liquid ejection device.

10. the control unit adjusts the correction signal based on temperature information relating to a temperature of the liquid discharged from the nozzle.

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

11. the control unit adjusts the correction signal based on droplet volume information relating to the amount of liquid discharged from the nozzle per discharge. The liquid ejection device according to any one of claims 7 to 10.

12. In a period other than the ejection period, a potential of the correction signal is lowered, or the correction signal is not supplied to either the first active unit or the second active unit. The liquid ejection device according to any one of claims 1 to 11.

13. A detection circuit is further provided, the drive signal generation unit generates an inspection signal to be supplied to one of the first active unit and the second active unit; the detection circuit detects an electromotive force generated in one of the first active unit and the second active unit by supplying the inspection signal to the other of the first active unit and the second active unit; The liquid ejection device according to any one of claims 1 to 12.

14. a diaphragm 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 communicating with nozzles that eject liquid; a piezoelectric element that is laminated on the second surface and has a first active portion that overlaps with a center of the pressure chamber when viewed in a thickness direction of the vibration plate, and a second active portion that overlaps with the pressure chamber at a position closer to an outer edge of the pressure chamber than the first active portion, supplying an ejection signal to one of the first active unit and the second active unit to eject liquid from the nozzle, and supplying a correction signal to the other of the first active unit and the second active unit; during a discharge period in which liquid is discharged from the nozzle, a potential of the discharge signal is changed over time, and a potential of the correction signal is maintained constant; A method for driving a liquid ejection head comprising the steps of:

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