Liquid discharge apparatus and method of driving liquid discharge apparatus

Abstract

To easily unite droplets up to a desired position while securing a liquid amount of a united liquid.SOLUTION: A liquid ejection apparatus including an ejection unit and a drive signal generation unit that generates a drive signal, the drive signal corresponding to at least three droplets that coalesce before landing on a medium, the drive signal including at least three ejection pulses each having a filling element and an ejection element, a connection element that connects adjacent ejection pulses, and a damping element that attenuates residual vibration of liquid in the pressure chamber after the last ejection pulse, wherein, in each ejection pulse, a period from the start of the filling element to the start of the ejection element is set to 0.3 times or more and 0.7 times or less the natural vibration period of the ejection unit, the absolute value of the potential change width of the ejection element of a certain ejection pulse is larger than the absolute value of the potential change width of the ejection element of the previous ejection pulse, and the potential maintained by one connection element other than the last connection element is between the terminal potential of the filling element of the first ejection pulse and the potential maintained by the connection element after the one connection element.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection apparatus and a method for driving the liquid ejection apparatus. [Background technology]

[0002] A liquid ejection device, such as an inkjet printer, includes a nozzle for ejecting liquid, a pressure chamber connected to the nozzle, and a driving element, such as a piezoelectric element, that applies pressure fluctuations to the liquid in the pressure chamber in response to a driving signal. In such a liquid ejection device, as disclosed in Patent Document 1, for example, multiple droplets may be sequentially ejected from the nozzle so that they coalesce before landing on the medium, in order to increase the size of the dots formed on the medium. Patent Document 1 also discloses that the driving voltage for subsequent droplets is set higher than the driving voltage for preceding droplets. By slowing the flight speed of the preceding droplets compared to the flight speed of the following droplets, these droplets can be allowed to coalesce before landing on the medium. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-140761 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with conventional technology, the more droplets that are merged to increase the volume of the combined liquid, the longer the interval between the ejection of the first droplet and the ejection of the last droplet, making it difficult to combine the aforementioned several droplets to the desired position. On the other hand, if the absolute value of the potential change width of the driving voltage for the leading droplets is reduced to suppress the flight speed of the leading droplets in order to combine them to the desired position, the volume of the leading droplets decreases, resulting in a smaller volume of the combined droplets. In other words, with conventional technology, it was difficult to combine droplets to the desired position while ensuring the volume of the combined liquid. [Means for solving the problem]

[0005] A liquid ejection device according to a preferred aspect of the present disclosure includes: an ejection unit having a nozzle that ejects droplets to be landed on a medium, a pressure chamber that communicates with the nozzle, and a drive element that generates pressure fluctuations in the liquid in the pressure chamber when a drive signal is supplied; and a drive signal generation unit that generates the drive signal, wherein the drive signal corresponds to at least three droplets that combine before landing on the medium, and includes at least three ejection pulses each having a filling element that generates negative pressure in the pressure chamber by changing a potential, and an ejection element that generates positive pressure in the pressure chamber by changing a potential, thereby ejecting droplets from the nozzle; at least two connection elements that connect adjacent ejection pulses among the at least three ejection pulses while maintaining a potential; and a vibration damping element that generates negative pressure in the pressure chamber after the droplets are ejected from the nozzle after the last ejection pulse of the at least three ejection pulses, thereby damping residual vibrations of the liquid in the pressure chamber. and, when a natural vibration period of the ejection unit is Tc, in each of the at least three ejection pulses, a period from the start of a filling element to the start of an ejection element is set to be 0.3Tc or more and 0.7Tc or less, an absolute value of a potential change width of an ejection element of an ejection pulse other than a first ejection pulse among the at least three ejection pulses is greater than an absolute value of a potential change width of an ejection element of an ejection pulse positioned before an ejection pulse other than the first ejection pulse, one of the at least two connection elements maintains a terminal potential of an ejection element of an earlier ejection pulse of two ejection pulses connected before and after the one connection element and connects to a starting end of a filling element of a later ejection pulse of the two ejection pulses, and a potential maintained by a connection element other than a last connection element among the at least two connection elements is between a terminal potential of the filling element of the first ejection pulse and a potential maintained by a connection element positioned after a connection element other than the last connection element.

[0006] A driving method for a liquid ejection device according to a preferred aspect of the present disclosure is a driving method for a liquid ejection device including: an ejection section having a nozzle that ejects droplets to be landed on a medium, a pressure chamber that communicates with the nozzle, and a drive element that generates pressure fluctuations in the liquid in the pressure chamber when a drive signal is supplied; and a drive signal generation section that generates the drive signal, wherein the drive signal corresponds to at least three droplets that combine before landing on the medium, and includes at least three ejection pulses each having a filling element that generates negative pressure in the pressure chamber by changing a potential, and an ejection element that generates positive pressure in the pressure chamber by changing a potential, thereby ejecting droplets from the nozzle; at least two connection elements that connect adjacent ejection pulses among the at least three ejection pulses while maintaining a potential; and a drive signal generation section that generates negative pressure in the pressure chamber after the droplets are ejected from the nozzle after the last ejection pulse of the at least three ejection pulses, thereby generating residual vibrations of the liquid in the pressure chamber. and a damping element that attenuates vibrations of the discharge unit, wherein, when a natural vibration period of the discharge unit is Tc, in each of the at least three discharge pulses, a period from the start of a filling element to the start of a discharge element is set to be 0.3Tc or more and 0.7Tc or less, an absolute value of a potential change width of a discharge element of a discharge pulse other than a first discharge pulse among the at least three discharge pulses is greater than an absolute value of a potential change width of a discharge element of a discharge pulse positioned before the discharge pulse other than the first discharge pulse, one of the at least two connection elements maintains a terminal potential of a discharge element of a first discharge pulse among two discharge pulses connected before and after the one connection element and is connected to a starting end of a filling element of a second discharge pulse among the two discharge pulses, and a potential maintained by a connection element other than a last connection element among the at least two connection elements is between a terminal potential of a filling element of the first discharge pulse and a potential maintained by a connection element positioned after the connection element other than the last connection element. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram showing an example of the configuration of a liquid ejection device 100 according to a first embodiment. [Figure 2]FIG. 2 is a diagram showing the electrical configuration of the liquid ejection device 100 according to the first embodiment. [Figure 3] FIG. 3 is a cross-sectional view showing an example of a head chip 51. [Figure 4] FIG. 3 is a diagram for explaining a switching circuit 52. [Figure 5] FIG. 3 is a diagram for explaining a drive signal Com used in the first embodiment. [Figure 6] 10 is a diagram for explaining a combined droplet DRA obtained by combining three droplets DR sequentially ejected from a nozzle N. FIG. [Figure 7] FIG. 10 is a diagram for explaining a drive signal Coma in a first modified example. [Figure 8] FIG. 10 is a diagram for explaining a drive signal Comb in a second modified example. [Figure 9] FIG. 10 is a diagram for explaining a drive signal Comc in a third modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments for carrying out the present disclosure will be described with reference to the drawings. However, in each drawing, the dimensions and scale of each part are appropriately different from those of the actual parts. Furthermore, since the embodiments described below are preferred specific examples of the present disclosure, various technically preferable limitations are applied, but 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.

[0009] A: First embodiment A1: Overall configuration of the liquid ejection device 1 is a schematic diagram showing an example of the configuration of a liquid ejection device 100 according to a first embodiment. The liquid ejection device 100 is an inkjet printing device that ejects liquid such as ink as droplets onto a medium M. The medium M is, for example, printing paper. Note that 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.

[0010] 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 head 50.

[0011] The liquid container 10 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.

[0012] The control unit 20 controls the operation of each element of the liquid ejection device 100. The control unit 20 includes, for example, one or more processing circuits such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), and one or more storage circuits such as a semiconductor memory. The detailed configuration of the control unit 20 will be described later with reference to FIG. 2.

[0013] The transport mechanism 30 transports the medium M in the Y1 direction under the control of the control unit 20. The movement mechanism 40 reciprocates the head 50 along the X axis under the control of the control unit 20. The movement mechanism 40 has a substantially box-shaped carriage 41 that houses the head 50, and an endless transport belt 42 to which the carriage 41 is fixed. Note that the number of heads 50 mounted on the carriage 41 is not limited to one, and may be multiple. In addition to the head 50, the carriage 41 may also be equipped with the aforementioned liquid container 10.

[0014] Under the control of the control unit 20, the head 50 ejects ink supplied from the liquid container 10 from each of the multiple nozzles N onto 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 head 50 by the movement mechanism 40, so that an image is formed on the surface of the medium M using ink.

[0015] A2: Electrical configuration of the liquid ejection device Fig. 2 is a diagram showing the electrical configuration of the liquid ejection device 100 according to the first embodiment. Below, the control unit 20 will be explained based on Fig. 2, but before that, the head 50 will be briefly explained.

[0016] As shown in FIG. 2, the head 50 includes a head chip 51 and a switching circuit 52.

[0017] The head chip 51 has a plurality of ejection units D, and by appropriately driving the plurality of ejection units D, ink is ejected from the nozzles N. Here, each ejection unit D applies pressure to the ink upon receiving a supply signal Vin. Details of the head chip 51 will be described later with reference to FIGS. 3 to 5.

[0018] Under the control of the control unit 20, the switching circuit 52 switches whether or not to supply the drive signal Com output from the control unit 20 as the supply signal Vin to each of the multiple discharge units D of the head chip 51. Details of the switching circuit 52 will be described later with reference to FIG.

[0019] 2, the head 50 has one head chip 51, but the number is not limited to this, and the head 50 may have two or more head chips 51. Hereinafter, when the number of nozzles N of the head chip 51 is M, in order to distinguish between the M discharge units D corresponding to the M nozzles, the discharge units D may be written as discharge unit D[m] using the subscript [m]. Here, M is an integer equal to or greater than 1, and m is an integer equal to or greater than 1 and equal to or less than M. In addition, in the liquid discharge device 100, the subscript [m] may also be used for elements included in the discharge unit D.

[0020] 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."

[0021] 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.

[0022] The memory circuitry 22 stores various programs executed by the control circuitry 21 and various data such as print data Img processed by the control circuitry 21. The memory circuitry 22 includes 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 a digital camera. The memory circuitry 22 may be configured as part of the control circuitry 21.

[0023] 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 each section 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 head 50. The power supply potential VHV is also supplied to the drive signal generation circuit 24.

[0024] The drive signal generation circuit 24 is a circuit that generates a drive signal Com that drives each discharge section D. Specifically, the drive signal generation circuit 24 has, for example, a DA conversion circuit and an amplifier circuit. In the drive signal generation circuit 24, the DA conversion circuit converts the waveform designation 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 drive signal Com. Here, of the waveforms included in the drive signal Com, the signal with the waveform that is actually supplied to the discharge section D is the aforementioned supply signal Vin. The waveform designation signal dCom is a digital signal that defines the waveform of the drive signal Com.

[0025] 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.

[0026] 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 ejection unit D. 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.

[0027] A3: Specific structure of the head chip Fig. 3 is a cross-sectional view showing an example of a head chip 51. As shown in Fig. 3, the head chip 51 has a plurality of nozzles N arranged in a direction along the Y axis. The plurality of nozzles N are divided into a first row L1 and a second row L2 arranged at intervals in a direction along the X axis. Each of the first row L1 and the second row L2 is a collection of a plurality of nozzles N arranged linearly in a direction along the Y axis.

[0028] The head chips 51 are configured to be approximately symmetrical with respect to each other in the direction along the X-axis. However, the positions of the multiple nozzles N in the first row L1 and the multiple nozzles N in the second row L2 in the direction along the Y-axis may or may not match. Figure 3 illustrates a configuration in which the positions of the multiple nozzles N in the first row L1 and the multiple nozzles N in the second row L2 in the direction along the Y-axis match each other.

[0029] As shown in FIG. 3, the head chip 51 has a flow path substrate 51a, a pressure chamber substrate 51b, a nozzle plate 51c, a vibration absorber 51d, a vibration plate 51e, a plurality of drive elements 51f, a protective plate 51g, a case 51h, and a wiring substrate 51i.

[0030] The flow path substrate 51a and the pressure chamber substrate 51b are stacked in this order in the Z1 direction to form a flow path for supplying ink to the multiple nozzles N. A diaphragm 51e, multiple drive elements 51f, a protective plate 51g, a case 51h, and a wiring substrate 51i are installed in an area located further in the Z1 direction than the stack of flow path substrate 51a and pressure chamber substrate 51b. On the other hand, a nozzle plate 51c and a vibration absorber 51d are installed in an area located further in the Z2 direction than the stack. Each element of the head chip 51 is roughly a plate-like member that is elongated in the Y direction, and is joined to each other by, for example, an adhesive. Each element of the head chip 51 will be described in order below.

[0031] The nozzle plate 51c is a plate-like member provided with a plurality of nozzles N in a first row L1 and a second row L2. Each of the plurality of nozzles N is a through-hole that allows ink to pass through. The surface of the nozzle plate 51c facing the Z2 direction is the nozzle surface FN. 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. Furthermore, the cross-sectional shape of the nozzle is typically circular, but is not limited thereto and may be a non-circular shape such as a polygonal or elliptical shape.

[0032] The flow path substrate 51a is provided with a space R1, a plurality of supply flow paths Ra, and a plurality of communication flow paths Na for each of the first row L1 and the second row L2. The space R1 is an elongated opening extending in the direction along the Y axis in a plan view seen in the direction along the Z axis. Each of the supply flow paths Ra and the communication flow paths Na is a through hole formed for each nozzle N. Each supply flow path Ra is in communication with the space R1.

[0033] The pressure chamber substrate 51b is a plate-like member in which a plurality of pressure chambers C, called cavities, are provided in each of a first row L1 and a second row L2. The plurality of pressure chambers C are arranged in a direction along the Y axis. Each pressure chamber C is formed for each nozzle N and is an elongated space extending in a direction along the X axis in a plan view. Like the nozzle plate 51c described above, the flow path substrate 51a and the pressure chamber substrate 51b are each manufactured by processing a silicon single crystal substrate using semiconductor manufacturing technology, for example. However, other known methods and materials may also be used as appropriate to manufacture the flow path substrate 51a and the pressure chamber substrate 51b.

[0034] The pressure chambers C are spaces located between the flow path substrate 51a and the vibration plate 51e. A plurality of pressure chambers C are arranged in the direction along the Y axis in each of the first row L1 and the second row L2. The pressure chambers C are also connected to the communication flow path Na and the supply flow path Ra. Therefore, the pressure chambers C are connected to the nozzle N via the communication flow path Na and to the space R1 via the supply flow path Ra.

[0035] 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 can vibrate elastically. The diaphragm 51e has, for example, a first layer and a second layer, which are stacked in this order in the Z1 direction. The first layer is, for example, an elastic film made of silicon oxide (SiO2). The elastic film is formed, for example, by thermally oxidizing one surface of a silicon single crystal substrate. The second layer is, for example, an insulating film made of zirconium oxide (ZrO2). The insulating film is formed, for example, by forming a zirconium layer by sputtering and then thermally oxidizing the layer. Note that the diaphragm 51e is not limited to the configuration of the stack of the first and second layers described above, and may be, for example, a single layer or three or more layers.

[0036] On the surface of the vibration plate 51e facing the Z1 direction, a plurality of drive elements 51f corresponding to the nozzles N are arranged in each of the first row L1 and the second row L2. Each drive element 51f is a passive element that deforms when a drive signal is supplied. Each drive element 51f has an elongated shape extending in the direction along the X axis in a plan view. The plurality of drive elements 51f are arranged in the direction along the Y axis so as to correspond to the plurality of pressure chambers C. The drive elements 51f overlap the pressure chambers C in a plan view.

[0037] Each drive element 51f is a piezoelectric element and includes a first electrode, a piezoelectric layer, and a second electrode (not shown), which are stacked in this order in the Z1 direction. One of the first and second electrodes is an individual electrode spaced apart from each other for each drive element 51f, and a supply signal Vin is applied to the one electrode. The other of the first and second electrodes is a strip-shaped common electrode extending continuously along the Y-axis across the plurality of drive elements 51f, and an offset potential VBS is supplied to the other electrode. Examples of metal materials for these electrodes include platinum (Pt), aluminum (Al), nickel (Ni), gold (Au), and copper (Cu). These metal materials can be used singly or in combination of two or more in the form of an alloy or a laminate. The piezoelectric layer is made of a piezoelectric material such as lead zirconate titanate (Pb(Zr,Ti)O3) and has, for example, a strip shape extending continuously along the Y-axis across the plurality of drive elements 51f. However, the piezoelectric layer may be integral across the plurality of drive elements 51f. In this case, through-holes that penetrate the piezoelectric layer and extend along the X-axis are provided in areas that correspond in plan view to the gaps between adjacent pressure chambers C. When the diaphragm 51e vibrates in conjunction with the deformation of the drive elements 51f, the pressure in the pressure chambers C fluctuates, causing ink to be ejected from the nozzles N.

[0038] The protective plate 51g is a plate-like member installed on the surface of the diaphragm 51e facing the Z1 direction, and protects the multiple drive elements 51f and reinforces the mechanical strength of the diaphragm 51e. The multiple drive elements 51f are housed between the protective plate 51g and the diaphragm 51e. The protective plate 51g is made of, for example, a resin material.

[0039] The case 51h is a member for storing ink to be supplied to the multiple pressure chambers C. The case 51h is made of, for example, a resin material. A space R2 is provided in the case 51h for each of the first row L1 and the second row L2. The space R2 is a space that communicates with the aforementioned space R1, and together with the space R1, functions as a reservoir R that stores ink to be supplied to the multiple pressure chambers C. The case 51h is provided with an inlet IH for supplying ink to each reservoir R. The ink in each reservoir R is supplied to the pressure chamber C via each supply flow path Ra.

[0040] The vibration absorber 51d is also called a compliance substrate and is a flexible resin film that forms the wall surface of the reservoir R, and absorbs pressure fluctuations of the ink inside the reservoir R. The vibration absorber 51d may also be a flexible thin metal plate. The surface of the vibration absorber 51d facing the Z1 direction is bonded to the flow path substrate 51a with an adhesive or the like.

[0041] The wiring board 51i is mounted on the surface of the diaphragm 51e facing the Z1 direction, and is a mounting component for electrically connecting the control unit 20 and the head chip 51. The wiring board 51i is a flexible wiring board such as a COF (Chip On Film), an FPC (Flexible Printed Circuit), or an FFC (Flexible Flat Cable). A switching circuit 52 for supplying a drive voltage to each drive element 51f is mounted on the wiring board 51i of this embodiment.

[0042] As illustrated in FIG. 3, one ejection section D includes one drive element 51f, one pressure chamber C, and one nozzle N. That is, the M drive elements 51f correspond one-to-one to the M pressure chambers C. As can be understood from FIG. 3 and other figures, the drive element 51f corresponding to a pressure chamber C refers to the drive element 51f that overlaps part or all of the pressure chamber C in a plan view in the Z2 direction. When a drive signal Com is supplied to the drive element 51f based on a print data signal SI, the ejection section D ejects ink from the pressure chamber C from the nozzle N by driving the drive element 51f with the drive signal Com.

[0043] A4: Driving the driving element 51f 4 is a diagram for explaining the switching circuit 52. The driving element 51f is driven by a supply signal Vin from the switching circuit 52. The switching circuit 52 will be explained below with reference to FIG.

[0044] As shown in FIG. 4, a line LHa is connected to the switching circuit 52. The line LHa is a signal line that transmits a drive signal Com. In FIG. 4, one of the first electrode and second electrode of the drive element 51f described above is shown as electrode Zd[m], and the other is shown as electrode Zu[m]. A line LHd is connected to the electrode Zd[m]. The line LHd is a power supply line to which an offset potential VBS is supplied.

[0045] The switching circuit 52 has M switches SWa, ie, switches SWa[1] to SWa[M], and a connection state designation circuit 52a that designates the connection states of these switches.

[0046] The switch SWa[m] is a switch that switches between conduction and non-conduction between the wiring LHa for transmitting the drive signal Com and the electrode Zu[m] of the drive element 51f[m]. Each of these switches is, for example, a transmission gate.

[0047] The connection state designation circuit 52a generates connection state designation signals SLa[1] to SLa[M] that designate the on / off states of the switches SWa[1] to SWa[M] based on the clock signal CLK, print data signal SI, latch signal LAT, and change signal CNG supplied from the control circuit 21.

[0048] For example, although not shown, the connection state designation circuit 52a includes multiple transfer circuits, multiple latch circuits, and multiple decoders in one-to-one correspondence with the drive elements 51f[1] to 51f[M]. Of these, the transfer circuit receives a print data signal SI. The print data signal SI includes an individual designation signal for each drive 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[m] based on the individual designation signal, the latch signal LAT, and the change signal CNG.

[0049] The switch SWa[m] is switched on and off according to the connection state designation signal SLa[m] generated as described above. For example, the switch SWa[m] is in an on state when the connection state designation signal SLa[m] is at a high level, and in an off state when the connection state designation signal SLa[m] is at a low level. As described above, the switching circuit 52 supplies part or all of the waveform included in the drive signal Com as the supply signal Vin to the drive elements 51f of one or more discharge units D selected from the M discharge units D.

[0050] A5: Drive signal FIG. 5 is a diagram illustrating the drive signal Com used in the first embodiment. As shown in FIG. 5, the latch signal LAT includes a pulse PL for defining a unit period Tu. The unit period Tu corresponds to a printing cycle for forming ink dots from the nozzle N on the medium M. The unit period Tu is defined, for example, as the period from the rising edge of a pulse PL to the rising edge of the next pulse PL. The specific length or period of the unit period Tu is not particularly limited. In this embodiment, the length of the unit period Tu is approximately 60 μs. μs stands for microseconds. FIG. 5 also illustrates the range of potential from 0% to 100%, where the minimum potential VL of the drive signal Com is 0% and the maximum potential VH is 100%. For example, the potential difference between 0% and 100% is 42 V. V stands for volts, a unit of potential.

[0051] The drive signal Com of this embodiment includes, in a unit period Tu, a first ejection pulse PA1, a first connection element EJ1, a second ejection pulse PA2, a second connection element EJ2, a third ejection pulse PA3, a potential maintaining element EM4, and a vibration damping element ED, in this order.

[0052] In the following description, each of the first ejection pulse PA1, the second ejection pulse PA2, and the third ejection pulse PA3 may be referred to as an ejection pulse PA. Also, each of the first connecting element EJ1 and the second connecting element EJ2 may be referred to as a connecting element EJ.

[0053] The first ejection pulse PA1, the second ejection pulse PA2, and the third ejection pulse PA3 are three ejection pulses PA that sequentially eject three droplets from the nozzle N after being ejected from the nozzle N and combining before landing on the medium M, and are arranged in a time sequence corresponding to the three droplets. Here, each of the first connection element EJ1 and the second connection element EJ2 is interposed between two ejection pulses PA that are adjacent to each other in time sequence among the three ejection pulses PA.

[0054] Note that three ejection pulses PA are an example of "at least three ejection pulses." Three droplets are an example of "at least three droplets." Two connection elements EJ are an example of "at least two connection elements." The number of connection elements EJ is one less than the number of ejection pulses PA.

[0055] The ejection pulse PA is a potential pulse that drives the driving element 51f to generate a pressure fluctuation in the pressure chamber C that is strong enough to eject ink from the nozzle N. When the ejection pulse PA is supplied to the driving element 51f, ink is ejected from the nozzle N as droplets.

[0056] More specifically, the first ejection pulse PA1 is the first ejection pulse PA among the three ejection pulses PA within the unit period Tu. In the example shown in FIG. 5, the first ejection pulse PA1 includes a fill element EF1 and an ejection element ET1, in this order. The fill element EF1 and the ejection element ET1 are connected by a potential maintaining element EM1 that maintains a minimum potential VL. The fill element EF1 changes from a reference potential V0 to a minimum potential VL. The reference potential V0 is the potential at the start of the unit period Tu. In the example shown in FIG. 5, the reference potential V0 is a potential of approximately 60%. The minimum potential VL is a potential lower than the reference potential V0. The ejection element ET1 connects to the first connection element EJ1 by changing from the minimum potential VL to the reference potential V0.

[0057] In this way, the first ejection pulse PA1 is a potential pulse with a waveform that starts at the reference potential V0, passes through the lowest potential VL, and then returns to the reference potential V0. When the drive element 51f receives the first ejection pulse PA1, it generates a negative pressure in the pressure chamber C based on the fill element EF1, and then generates a positive pressure in the pressure chamber C based on the ejection element ET1, thereby ejecting a droplet from the nozzle N. When negative pressure is generated in the pressure chamber C, the surface of the ink in the nozzle N is pulled in the direction opposite to the ejection direction in which the droplet is ejected. Hereinafter, the surface of the ink in the nozzle N may be referred to as a "meniscus." Pulling the meniscus in the direction opposite to the ejection direction may also be referred to as "pull." When positive pressure is generated in the pressure chamber C, the meniscus is pushed in the ejection direction. Hereinafter, pushing the meniscus in the ejection direction may also be referred to as a "push." Furthermore, as can be understood from the above description, in this embodiment, a drop in the potential supplied to the driving element 51f generates a negative pressure in the pressure chamber C, and an increase in the potential supplied to the driving element 51f generates a positive pressure in the pressure chamber C. A drop in potential and an increase in potential are examples of "a change in potential."

[0058] The first ejection pulse PA1 is connected to the second ejection pulse PA2 via a first connection element EJ1. In the example shown in Fig. 5, the starting point of the first connection element EJ1 is connected to the ending point of the ejection element ET1 of the first ejection pulse PA1. The first connection element EJ1 maintains the reference potential V0.

[0059] The second ejection pulse PA2 is the second ejection pulse PA of the three ejection pulses PA within the unit period Tu. In the example shown in FIG. 5, the second ejection pulse PA2 has a fill element EF2 and an ejection element ET2, in this order. The fill element EF2 and the ejection element ET2 are connected by a potential maintaining element EM2 that maintains the minimum potential VL. The fill element EF2 changes from the reference potential V0 to the minimum potential VL. The ejection element ET2 changes from the minimum potential VL to a potential V1, thereby connecting to the second connecting element EJ2. The potential V1 is a potential between the reference potential V0 and the maximum potential VH. In the example shown in FIG. 5, the potential V1 is approximately 80%.

[0060] In this way, the second ejection pulse PA2 is a potential pulse having a waveform that goes from the reference potential V0 through the minimum potential VL to the potential V1. When the drive element 51f receives the second ejection pulse PA2, it generates a negative pressure in the pressure chamber C based on the filling element EF2, and then generates a positive pressure in the pressure chamber C based on the ejection element ET2, thereby ejecting a droplet from the nozzle N.

[0061] The second ejection pulse PA2 is connected to the third ejection pulse PA3 via the second connection element EJ2. In the example shown in Fig. 5, the starting point of the second connection element EJ2 is connected to the ending point of the ejection element ET2 of the second ejection pulse PA2. The second connection element EJ2 maintains the potential V1.

[0062] The third ejection pulse PA3 is the last ejection pulse PA among the three ejection pulses PA within the unit period Tu. In the example shown in FIG. 5, the third ejection pulse PA3 has a fill element EF3 and an ejection element ET3 in this order. The fill element EF3 and the ejection element ET3 are connected by a potential maintaining element EM3 that maintains the minimum potential VL. The fill element EF3 changes from potential V1 to the minimum potential VL. The ejection element ET3 changes from the minimum potential VL to the maximum potential VH, thereby connecting to the potential maintaining element EM4.

[0063] In this way, the third ejection pulse PA3 is a potential pulse having a waveform that goes from the potential V1 through the minimum potential VL to the maximum potential VH. When the drive element 51f receives the third ejection pulse PA3, it generates a negative pressure in the pressure chamber C based on the filling element EF3, and then generates a positive pressure in the pressure chamber C based on the ejection element ET3, thereby ejecting a droplet from the nozzle N.

[0064] The third ejection pulse PA3 is connected to the damping element ED via the potential maintaining element EM4. In the example shown in Fig. 5, the starting end of the potential maintaining element EM4 is connected to the ending end of the ejection element ET3 of the third ejection pulse PA3. The potential maintaining element EM4 maintains the highest potential VH.

[0065] The vibration suppression element ED generates a negative pressure in the pressure chamber C after a droplet is ejected from the nozzle N, thereby damping the residual vibration of the ink in the pressure chamber C. The vibration suppression element ED changes from the highest potential VH to the reference potential V0.

[0066] Hereinafter, each of the filling elements EF1, EF2, and EF3 may be referred to as a filling element EF, and each of the discharge elements ET1, ET2, and ET3 may be referred to as a discharge element ET.

[0067] The three ejection pulses PA of the drive signal Com in this embodiment have a so-called pull-push waveform. However, after the third ejection pulse PA3, which is the last ejection pulse PA, there is a damping element ED that generates negative pressure in the pressure chamber C. Therefore, if the third ejection pulse PA3 and the damping element ED are treated as a single pulse, this pulse can be considered to have a so-called pull-push-pull waveform.

[0068] As shown in FIG. 5, the start time TS EF1 to the start time TS of the discharge element ET1 ET1 The period T1_1 from the start of the filling element EF2 of the second ejection pulse PA2 to the start of the filling element EF2 of the second ejection pulse PA2 is set to be equal to or greater than 0.3Tc and equal to or less than 0.7Tc, and the closer to 0.5Tc the better. Tc is the natural vibration period of the ejection part D. Similarly, the start time TS EF2 to the start time TS of the discharge element ET2 ET2 The period T1_2 from the start time TS to the start time TS is set to 0.3Tc or more and 0.7Tc or less, and the closer to 0.5Tc the better. EF3 to the start time TS of the discharge element ET3 ET3 The period T1_3 from 0.3Tc to 0.7Tc is set to be equal to or greater than 0.3Tc and equal to or less than 0.7Tc, and the closer to 0.5Tc is the better. Hereinafter, the periods T1_1, T1_2, and T1_3 may each be referred to as period T1. To summarize the above, the period T1 is set to be equal to or greater than 0.3Tc and equal to or less than 0.7Tc, and the closer to 0.5Tc is the better.

[0069] Furthermore, the absolute value of the potential change width of the ejection element ET of a certain ejection pulse PA is larger as the absolute value of the potential change width of the ejection element ET of the later ejection pulse PA. Specifically, the absolute value of the potential change width of the ejection element ET1 is V0-VL, and the absolute value of the potential change width of the ejection element ET2 is V1-VL, where V1 is higher than V0. Therefore, the absolute value of the potential change width of the ejection element ET2 is larger than the absolute value of the potential change width of the ejection element ET1. Furthermore, the absolute value of the potential change width of the ejection element ET3 is VH-VL, where VH is higher than V1. Therefore, the absolute value of the potential change width of the ejection element ET3 is larger than the absolute value of the potential change width of the ejection element ET2. Note that in the first embodiment, when the second ejection pulse PA2 corresponds to an "ejection pulse other than the first ejection pulse," the first ejection pulse PA1 corresponds to an "ejection pulse located before an ejection pulse other than the first ejection pulse." Furthermore, when the third ejection pulse PA3 corresponds to "an ejection pulse other than the first ejection pulse," the first ejection pulse PA1 and the second ejection pulse PA2 correspond to "an ejection pulse positioned before an ejection pulse other than the first ejection pulse."

[0070] As can be understood from the above description, each of the two connection elements EJ maintains the terminal potential of the ejection element ET of the earlier of the two ejection pulses PA connected before and after, and connects to the starting end of the filling element EF of the later of the two ejection pulses PA. Note that the first connection element EJ1 and the second connection element EJ2 correspond to "one of at least two connection elements."

[0071] Furthermore, the reference potential V0, which is the potential maintained by the first connection element EJ1, is between the minimum potential VL, which is the terminal potential of the filling element EF1 of the first ejection pulse PA1, which is the first ejection pulse PA of the three ejection pulses PA, and the potential V1 maintained by the second connection element EJ2 located after the first connection element EJ1. Note that in the first embodiment, the first connection element EJ1 corresponds to "a connection element other than the last connection element of at least two connection elements," and the second connection element EJ2 corresponds to "a connection element located after a connection element other than the last connection element."

[0072] As can be seen from FIG. 5 , the reference potential V0, which is the terminal potential of the ejection element ET1 of the first ejection pulse PA1, which is the first of the three ejection pulses PA, is equal to the reference potential V0, which is the starting potential of the filling element EF1. In this disclosure, "two potentials being equal" refers not only to the two potentials completely matching, but also to the case where the two potentials can be considered equal considering an error. Furthermore, in the second and subsequent ejection pulses PA of the three ejection pulses PA, the absolute value of the potential change width of the ejection element ET is greater than the absolute value of the potential change width of the filling element EF. Specifically, the absolute value of the potential change width of the ejection element ET2 of the second ejection pulse PA2, which is the second ejection pulse PA, is V1-VL, and the absolute value of the potential change width of the filling element EF2 is V0-VL. Therefore, the absolute value of the potential change width of the ejection element ET2 is greater than the absolute value of the potential change width of the filling element EF2. Similarly, the absolute value of the potential change width of the ejection element ET3 of the third ejection pulse PA3, which is the third ejection pulse PA, is VH-VL, and the absolute value of the potential change width of the filling element EF2 is V1-VL, where VH is higher than V1. Therefore, the absolute value of the potential change width of the ejection element ET3 is larger than the absolute value of the potential change width of the filling element EF3.

[0073] That is, in the first ejection pulse PA1, the potential immediately after the push and the potential immediately before the pull are the same, at the reference potential V0. In the second ejection pulse PA2, which is the middle of the three ejection pulses PA, the potential immediately after the push is set higher than the potential immediately before the pull. In the third ejection pulse PA3, which is the last ejection pulse PA, the potential change width is also set to the maximum range that the drive signal Com can take, that is, from the minimum potential VL to the maximum potential VH, thereby ensuring the speed of the droplets ejected by the third ejection pulse PA3. Furthermore, the third ejection pulse PA3 and the vibration damping element ED can be considered to be a pull-push-pull waveform, and by increasing the potential change width of this vibration damping element ED, the impact of residual vibration on the next unit period Tu can be suppressed.

[0074] 5, the absolute value of the potential change width of the filling element EF3 of the third ejection pulse PA3, which is the last ejection pulse PA among the three ejection pulses PA, is greater than the absolute value of the potential change width of the filling element EF1 of the first ejection pulse PA1, which is the first ejection pulse PA. Specifically, the absolute value of the potential change width of the filling element EF3 is V1-VL, and the absolute value of the potential change width of the filling element EF1 is V0-VL, so the absolute value of the potential change width of the filling element EF3 is greater than the absolute value of the potential change width of the filling element EF1.

[0075] 5, the potential difference between the reference potential V0 and the minimum potential VL is 50% to 70% of the potential difference between the minimum potential VL and the maximum potential VH. In the example of FIG. 5, the potential difference between the reference potential V0 and the minimum potential VL is 60% of the potential difference between the minimum potential VL and the maximum potential VH. The minimum potential VL is the potential farthest from the reference potential V0 within the range of potentials that the three ejection pulses PA can take, from the minimum potential VL to the maximum potential VH.

[0076] Furthermore, the period T2_1 of the first connection element EJ1, which is the first of the two connection elements EJ, is set to be equal to or greater than (n1-0.25)×Tc and equal to or less than (n1+0.25)×Tc, with the closer to n1×Tc being preferable. Similarly, the period T2_2 of the second connection element EJ2, which is the last of the two connection elements EJ, is set to be equal to or greater than (n1-0.25)×Tc and equal to or less than (n1+0.25)×Tc, with the closer to n1×Tc being preferable. n1 is an integer equal to or greater than 1. Hereinafter, the periods T2_1 and T2_2 may each be referred to as period T2. To summarize the above, the period T2 is set to be equal to or greater than (n1-0.25)×Tc and equal to or less than (n1+0.25)×Tc, with the closer to n1×Tc being preferable. n1 may be the same value for the periods T2 of the two connection elements EJ, or may be different values. In the example of FIG. 5, n1 is 1 in the period T2_1, and n1 is 2 in the period T2_2.

[0077] Furthermore, the period T2_2 of the second connection element EJ2, which is the last connection element EJ of the two connection elements EJ, is longer than Tc and equal to or shorter than 2Tc. In the following description, the period T2 of the last connection element EJ of the two connection elements EJ may be referred to as period T2Last. In the first embodiment, as shown in FIG. 5, the period T2_2 is period T2Last.

[0078] Furthermore, the period T2 of the connection element EJ other than the last connection element EJ of the two connection elements EJ is shorter than the period T2Last of the last connection element EJ. Specifically, the period T2_1 of the first connection element EJ1, which is the first connection element EJ, is shorter than the period T2_2 of the second connection element EJ2, which is the last connection element EJ.

[0079] Also, the start time TS of the ejection element ET1 of the first ejection pulse PA1 ET1 From the start time TS of the ejection element ET2 of the second ejection pulse PA2, ET2 The interval T3_1 until the start time TS is set to be equal to or greater than (n2-0.4)×Tc and equal to or less than n2×Tc, where n2 is an integer equal to or greater than 2. Similarly, ET2 to the start time TS of the ejection element ET3 of the third ejection pulse PA3 ET3 The interval T3_2 to the period T3_1 is set to be equal to or greater than (n2-0.4)×Tc and equal to or less than n2×Tc. Hereinafter, each of the periods T3_1 and T3_2 may be referred to as period T3. To summarize the above description, the interval T3 is set to be equal to or greater than (n2-0.4)×Tc and equal to or less than n2×Tc. n2 may be the same value or different values ​​in the periods T3 of the two connection elements EJ. In the example of FIG. 5, n2 is 2 in the period T3_1 and 3 in the period T3_2.

[0080] Fig. 6 is a diagram illustrating a combined droplet DRA obtained by combining three droplets DR sequentially ejected from a nozzle N. In Fig. 6, the three droplets DR are indicated by solid lines as droplet DR1 corresponding to the first ejection pulse PA1, droplet DR2 corresponding to the second ejection pulse PA2, and droplet DR3 corresponding to the third ejection pulse PA3. Also, in Fig. 6, the combined droplet DRA obtained by combining the droplets DR1, DR2, and DR3 is indicated by a two-dot chain line. The respective positions, sizes, shapes, and other aspects of the droplets DR1, DR2, DR3, and combined droplet DRA are not limited to the example shown in Fig. 6.

[0081] 5 is supplied to the drive element 51f, droplets DR1, DR2, and DR3 are ejected from the nozzle N in this order, as shown in Fig. 6. Here, ejection conditions such as the flight speed and ejection timing of the droplets DR1, DR2, and DR3 are set so that the subsequent droplet DR catches up with the preceding droplet DR among the droplets DR1, DR2, and DR3 before it lands on the medium M. As a result, a combined droplet DRA is obtained by combining the droplets DR1, DR2, and DR3.

[0082] A6: Summary of the first embodiment As described above, the liquid ejection device 100 in the first embodiment includes a nozzle N that ejects droplets to land on a medium M, a pressure chamber C that communicates with the nozzle N, an ejection unit D that includes a drive element 51f that generates pressure fluctuations in the ink in the pressure chamber C when a drive signal Com is supplied, and a drive signal generation circuit 24 that generates the drive signal Com. The drive signal Com includes three ejection pulses PA, two connection elements EJ, and a damping element ED. The three ejection pulses PA correspond to the three droplets that combine before landing on the medium M, and each include a fill element EF that generates negative pressure in the pressure chamber C by changing the potential, and an ejection element ET that generates positive pressure in the pressure chamber C by changing the potential, causing droplets to be ejected from the nozzle N. The two connection elements EJ connect adjacent ones of the three ejection pulses PA while maintaining the potential. The vibration damping element ED generates a negative pressure in the pressure chamber C after the last of the three ejection pulses PA, ejecting a droplet from the nozzle N, thereby damping residual vibration of the ink in the pressure chamber C. When the natural vibration period of the ejection section D is Tc, the period T1 from the start of the fill element EF to the start of the ejection element ET in each of the three ejection pulses is set to be 0.3Tc or more and 0.7Tc or less. The absolute value of the potential change width of the ejection element ET of one of the three ejection pulses PA is greater than the absolute value of the potential change width of the ejection element ET of the ejection pulse PA positioned before the one ejection pulse PA. One of the two connection elements EJ maintains the terminal potential of the ejection element ET of the earlier of the two ejection pulses PA connected before and after the one connection element EJ, and connects to the starting end of the fill element EF of the later of the two ejection pulses PA. The potential maintained by the connection elements EJ other than the last connection element EJ of the two connection elements EJ is between the terminal potential of the filling element EF of the first ejection pulse PA of the three ejection pulses PA and the potential maintained by the connection elements EJ located after the connection elements EJ other than the last connection element EJ. In the first embodiment, the terminal potential of the filling element EF is the lowest potential VL, so in other words, the potential maintained by the connection elements EJ other than the last connection element EJ is lower than the potential maintained by the connection elements EJ located after the connection elements EJ other than the last connection element EJ. The greater the deviation of the potential before and after the change to the minimum potential VL from the minimum potential VL, the greater the absolute value of the potential change width before and after this change. Therefore, according to the first embodiment, the potential maintained by the later of the two connection elements EJ is higher than the potential maintained by the earlier connection element EJ. This makes it easier to increase the potential change width of the fill element EF and the ejection element ET of the ejection pulse PA connected to the later connection element EJ, compared to an embodiment in which the two connection elements EJ maintain the same potential. Furthermore, since the potential maintained by the later connection element EJ is higher than the potential maintained by the earlier connection element EJ, the absolute value of the potential change width of the damping element ED can also be increased, allowing the damping element ED to sufficiently damp the residual vibration. Therefore, in this embodiment, the period required to sufficiently damp the residual vibration can be shortened, and there is no need to lengthen the unit period Tu, compared to an embodiment in which so-called two-stage damping is performed, in which the terminal potential of the damping element ED is changed below the reference potential V0 and then raised to the reference potential V0. As described above, according to this embodiment, the amount of droplets can be secured by easily increasing the potential change width of the fill element EF and the ejection element ET of the ejection pulse PA, while there is no need to lengthen the unit period Tu, making it easy to merge the droplets to the desired position. Furthermore, by setting the period T1 to be greater than or equal to 0.3Tc and less than or equal to 0.7Tc, the pressure fluctuation that begins to pull the meniscus in the opposite direction to the ejection direction can be efficiently utilized to push the meniscus in the ejection direction, compared to embodiments in which the period T1 is less than 0.3Tc or greater than 0.7Tc. Furthermore, since the first ejection pulse PA1 and the second ejection pulse PA2 do not have the damping element ED, the connecting element EJ can be made longer compared to an embodiment in which the first ejection pulse PA1 and the second ejection pulse PA2 have the damping element ED. By making the connecting element EJ longer, it is possible to suppress unstable ejection caused by variations in the dimensions of the flow path of the ejection section D. Unstable ejection can occur, for example, when the ejection direction of droplets deviates from a predetermined direction, when droplets are not ejected from the nozzle N, or when the amount of droplets varies.

[0083] In the first ejection pulse PA1, the terminal potential of the ejection element ET1 is equal to the starting potential of the filling element EF1, and in the second and subsequent ejection pulses PA among the three ejection pulses PA, the absolute value of the potential change width of the ejection element ET is greater than the absolute value of the potential change width of the filling element EF. In other words, in the second and subsequent ejection pulses PA, in this embodiment, the terminal potential of the ejection element ET is higher than the starting potential of the filling element EF. In the first ejection pulse PA1, the terminal potential of the ejection element ET1 is equal to the starting potential of the fill element EF1, so the velocity of the droplets ejected by the first ejection pulse PA1 can be reduced compared to when the terminal potential of the ejection element ET1 is higher than the starting potential of the fill element EF1. Furthermore, in the second and subsequent ejection pulses PA, the terminal potential of the ejection element ET is higher than the starting potential of the fill element EF, so the absolute value of the potential change width of the ejection element ET is increased, and the velocity of the droplets can be increased. As described above, according to the first embodiment, by reducing the velocity of the preceding droplet and increasing the velocity of the succeeding droplet, it is easy to combine three droplets.

[0084] Moreover, the absolute value of the potential change width of the filling element EF3 of the third ejection pulse PA3 is greater than the absolute value of the potential change width of the filling element EF1 of the first ejection pulse PA1. Because the absolute value of the potential change width of the fill element EF3 is larger than the absolute value of the potential change width of the fill element EF1, the residual vibration of the ink in the pressure chamber C when the ejection element ET3 is supplied to the drive element 51f is larger than the residual vibration of the ink in the pressure chamber C when the ejection element ET1 is supplied to the drive element 51f. This makes it possible to increase the velocity of droplets ejected by the third ejection pulse PA3 and decrease the velocity of droplets ejected by the first ejection pulse PA1. Furthermore, compared to an embodiment in which the absolute value of the potential change width of the fill element EF3 is smaller than the absolute value of the potential change width of the fill element EF1, the velocity of droplets ejected by the first ejection pulse PA1 can be decreased relative to the velocity of droplets ejected by the third ejection pulse PA3. Therefore, according to the first embodiment, by making the velocity of the preceding droplet slower than the velocity of the succeeding droplet, it becomes easier to merge three droplets.

[0085] In addition, the potential difference between the reference potential V0 of the drive signal Com and the minimum potential VL, which is the potential farthest from the reference potential among the range of potentials that the three ejection pulses PA can take, is 50% or more and 70% or less of the potential difference in the range from the minimum potential VL to the maximum potential VH. When the potential difference between the reference potential V0 and the minimum potential VL is less than 50% of the potential difference in the range from the minimum potential VL to the maximum potential VH, the absolute value of the potential change width of the fill element EF1 and the ejection element ET1 of the first ejection pulse PA1 becomes small, making it difficult to ensure the amount of droplets. On the other hand, when the potential difference between the reference potential V0 and the minimum potential VL is more than 70% of the potential difference in the range from the minimum potential VL to the maximum potential VH, the absolute value of the potential change width of the damping element ED becomes small, requiring the aforementioned two-stage damping and a longer unit period Tu. As described above, according to the first embodiment, the absolute value of the potential change width of the fill element EF1 and the ejection element ET1 can be increased, ensuring the amount of droplets while eliminating the need to lengthen the unit period Tu, making it easier to coalesce droplets to the desired position.

[0086] Furthermore, the period T2 of each of the two connection elements EJ is set to be equal to or greater than (n1-0.25) x Tc and equal to or less than (n1+0.25) x Tc, where n1 is an integer equal to or greater than 1. After the ink is ejected, the ink in the ejection section D vibrates according to the natural vibration period Tc of the ejection section D. When the period T2 approaches an integer multiple of Tc, the residual vibration can be effectively utilized to increase the droplet velocity even if the ejection pulse PA does not have a vibration damping element ED. As described above, according to the first embodiment, by increasing the droplet velocity, the droplets can be ejected stably.

[0087] Furthermore, the period T2Last of the last of the two connection elements EJ is longer than Tc and equal to or shorter than 2Tc. By making the period T2 longer than Tc, the final ejection pulse PA is ejected after the vibration of the meniscus has attenuated to a certain extent, which stabilizes the ejection of the final ejection pulse PA, which has high ejection capability, and also suppresses the generation of satellite droplets. Satellite droplets are tiny droplets that separate from the original droplet when it is ejected. If satellite droplets land on the medium M, the quality of the image formed on the medium M will deteriorate. Furthermore, by making the period T2Last 2Tc or less, it becomes easier to coalesce the droplets to the desired position compared to an embodiment in which the period T2Last is longer than 2Tc.

[0088] Furthermore, the period T2 of the connection element EJ other than the last connection element EJ of the two connection elements EJ is shorter than the period T2Last of the last connection element EJ. In an aspect in which multiple droplets are combined, satellite droplets generated by preceding droplets can be collected by combining with subsequent droplets before the satellite droplets land on the medium M. Satellite droplets generated by droplets other than the last droplet can be collected before they land on the medium M, but satellite droplets generated by the last droplet cannot be collected before they land on the medium M. Therefore, in this embodiment, by making the period T2Last longer than the period T2 of connection elements EJ other than the last connection element EJ, the last connection element EJ can be adjusted to be longer so that the last ejection pulse PA is supplied at a timing that prevents satellite droplets from being generated from the last droplet ejected by the last ejection pulse PA.

[0089] Furthermore, the interval T3 between the start of the ejection elements ET of two adjacent ejection pulses PA among the three ejection pulses PA is set to be equal to or greater than (n2-0.4)×Tc and equal to or less than n2×Tc, where n2 is an integer of 2 or greater. The interval T3 is synonymous with the interval between the starts of two ejection pulses PA. When the interval T3 approaches an integer multiple of Tc, even if the ejection pulses PA other than the last ejection pulse PA do not have the vibration damping element ED, the residual vibration from the previous ejection pulse PA can be efficiently used to increase the velocity of the droplets ejected by the next ejection pulse PA. By increasing the velocity of the droplets, the liquid ejection device 100 can stably eject droplets.

[0090] B: Modified example The above-described embodiments can be modified in various ways. Specific modifications that can be applied to the above-described embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples can be combined as appropriate within the scope of not mutually contradictory.

[0091] B1: First modified example 7 is a diagram illustrating the drive signal Coma in the first modified example. The drive signal Coma differs from the drive signal Com in that it has three ejection pulses PAa instead of the three ejection pulses PA, two connection elements EJa instead of the two connection elements EJ, and a vibration damping element EDa instead of the vibration damping element ED. The three ejection pulses PAa differ from the three ejection pulses PA in that it has a first ejection pulse PAa1 instead of the first ejection pulse PA1, a second ejection pulse PAa2 instead of the second ejection pulse PA2, and a third ejection pulse PAa3 instead of the third ejection pulse PA3. The two connection elements EJa differ from the two connection elements EJ in that it has a first connection element EJa1 instead of the first connection element EJ1 and a second connection element EJa2 instead of the second connection element EJ2.

[0092] The first ejection pulse PAa1, the second ejection pulse PAa2, and the third ejection pulse PAa3 are three ejection pulses PAa that sequentially eject three droplets from the nozzle N after being ejected from the nozzle N and combining before landing on the medium M, and are arranged in a time sequence corresponding to the three droplets. The connection between the three ejection pulses PAa and the two connection elements EJa is the same as the connection between the three ejection pulses PA and the two connection elements EJ, and therefore a description thereof will be omitted.

[0093] The first ejection pulse PAa1 differs from the first ejection pulse PA1 in that it has a fill element EFa1 instead of the fill element EF1, a potential maintaining element EMa1 instead of the potential maintaining element EM1, and an ejection element ETa1 instead of the ejection element ET1, but the shape of the first ejection pulse PAa1 is substantially the same as the shape of the first ejection pulse PA1.

[0094] The second ejection pulse PAa2 differs from the second ejection pulse PA2 in that it has a fill element EFa2 instead of the fill element EF2, a potential maintaining element EMa2 instead of the potential maintaining element EM2, and an ejection element ETa2 instead of the ejection element ET2. The ejection element ETa2 differs from the ejection element ET2 in that it changes from the minimum potential VL to a potential V1a. The potential V1a is a potential between the reference potential V0 and the potential V1. Specifically, the potential V1a is approximately 74% of the reference potential V0. The second connection element EJa2 maintains the potential V1a.

[0095] The third ejection pulse PAa3 differs from the third ejection pulse PA3 in that it has a fill element EFa3 instead of the fill element EF3, a potential maintaining element EMa3 instead of the potential maintaining element EM3, and an ejection element ETa3 instead of the ejection element ET3. Furthermore, the third ejection pulse PAa3 differs from the third ejection pulse PA3 in that it is connected to the damping element EDi via a potential maintaining element EMa4, a damping expansion element EGa, a potential maintaining element EMa5, a damping contraction element EHa, and a potential maintaining element EMa6. Furthermore, the amount of droplets ejected by the third ejection pulse PAa3 is smaller than the amount of droplets ejected by the third ejection pulse PA3.

[0096] Hereinafter, each of the filling elements EFa1, EFa2, and EFa3 may be referred to as a filling element EFa, and each of the discharge elements ETa1, ETa2, and ETa3 may be referred to as a discharge element ETa.

[0097] The ejection element ETa3 changes from the minimum potential VL to a potential V2a, thereby connecting to the potential maintaining element EMa4. The potential V2a is a potential between the potential V1a and the maximum potential VH. Specifically, the potential V2a is approximately 90% potential. The potential maintaining element EMa4 maintains the potential V2a and connects to the vibration-damping expansion element EGa at its end. The vibration-damping expansion element EGa changes from the potential V2a to a potential V3a to expand the pressure chamber C, and connects to the potential maintaining element EMa5 at its end. The potential V3a is a potential between the reference potential V0 and the minimum potential VL. Specifically, the potential V3a is approximately 20% potential. The potential maintaining element EMa5 maintains the potential V3a and connects to the vibration-damping contraction element EHa at its end. The vibration-damping contraction element EHa changes from the potential V3a to the maximum potential VH to contract the pressure chamber C, and connects to the potential maintaining element EMa6 at its end. The potential maintaining element EMa6 maintains the highest potential VH and is connected at its end to the vibration suppression element EDa.

[0098] As in the first embodiment, the start time TS EFa1 to the start time TS of the discharge element ETa1 ETa1 The period T1a_1 from the start time TS to the start time TS is set to 0.3Tc or more and 0.7Tc or less, and the closer to 0.5Tc the better. EFa2 to the start time TS of the discharge element ETa2 ETa2 The period T1a_2 from the start time TS to the start time TS is set to 0.3Tc or more and 0.7Tc or less, and the closer to 0.5Tc the better. EFa3 to the start time TS of the discharge element ETa3 ETa3 The period T1a_3 from the time of the start of the pulse to the time of the pulse is set to 0.3Tc or more and 0.7Tc or less, and the closer to 0.5Tc the better.

[0099] Furthermore, the absolute value of the potential change width of the ejection element ETa of a certain ejection pulse PAa is larger as the absolute value of the potential change width of the ejection element ETa of the later ejection pulse PAa. Specifically, the absolute value of the potential change width of the ejection element ETa1 is V0-VL, and the absolute value of the potential change width of the ejection element ETa2 is V1a-VL, where V1a is higher than V0. Therefore, the absolute value of the potential change width of the ejection element ETa2 is larger than the absolute value of the potential change width of the ejection element ETa1. Furthermore, the absolute value of the potential change width of the ejection element ETa3 is V2a-VL, where V2a is higher than V1a. Therefore, the absolute value of the potential change width of the ejection element ETa3 is larger than the absolute value of the potential change width of the ejection element ETa2.

[0100] In addition, the reference potential V0, which is the potential maintained by the first connection element EJa1, is between the minimum potential VL, which is the terminal potential of the filling element EFa1 of the first ejection pulse PAa1, which is the first ejection pulse PAa of the three ejection pulses PAa, and the potential V1a maintained by the second connection element EJa2, which is located after the first connection element EJa1.

[0101] Furthermore, as in the first embodiment, the reference potential V0, which is the terminal potential of the ejection element ETa1 of the first ejection pulse PAa1, which is the first of the three ejection pulses PAa, is equal to the reference potential V0, which is the starting potential of the filling element EFa1. Furthermore, in the second and subsequent ejection pulses PAa of the three ejection pulses PAa, the absolute value of the potential change width of the ejection element ETa is greater than the absolute value of the potential change width of the filling element EFa. Specifically, the absolute value of the potential change width of the ejection element ETa2 of the second ejection pulse PAa2 is V1a-VL, and the absolute value of the potential change width of the filling element EFa2 is V0-VL. Therefore, the absolute value of the potential change width of the ejection element ETa2 is greater than the absolute value of the potential change width of the filling element EFa2. Similarly, the absolute value of the potential change width of the ejection element ETa3 of the third ejection pulse PAa3 is V2a-VL, and the absolute value of the potential change width of the filling element EFa3 is V1a-VL, where V2a is higher than V1a. Therefore, the absolute value of the potential change width of the ejection element ETa3 is larger than the absolute value of the potential change width of the filling element EFa3.

[0102] Furthermore, as in the first embodiment, the absolute value of the potential change width of the filling element EFa3 of the third ejection pulse PAa3, which is the last ejection pulse PAa of the three ejection pulses PAa, is greater than the absolute value of the potential change width of the filling element EFa1 of the first ejection pulse PAa1, which is the first ejection pulse PAa. Specifically, the absolute value of the potential change width of the filling element EFa3 is V1a-VL, and the absolute value of the potential change width of the filling element EFa1 is V0-VL. Therefore, the absolute value of the potential change width of the filling element EFa3 is greater than the absolute value of the potential change width of the filling element EFa1.

[0103] Furthermore, the period T2a_1 of the first connection element EJa1, which is the first connection element EJa of the two connection elements EJa, is set to be equal to or greater than (n1-0.25)×Tc and equal to or less than (n1+0.25)×Tc, with the closer to n1×Tc being preferable. Similarly, the period T2a_2 of the second connection element EJa2, which is the last connection element EJa of the two connection elements EJa, is set to be equal to or greater than (n1-0.25)×Tc and equal to or less than (n1+0.25)×Tc, with the closer to n1×Tc being preferable. Hereinafter, each of the periods T2a_1 and T2a_2 may be referred to as period T2a.

[0104] Furthermore, the period T2a_2 of the second connection element EJa2, which is the last connection element EJa of the two connection elements EJa, is longer than Tc and is equal to or shorter than 2Tc. In the following description, the period T2a of the last connection element EJa of the two connection elements EJa may be referred to as period T2aLast. In the first modified example, as shown in FIG. 7, the period T2a_2 is period T2aLast.

[0105] Furthermore, the period T2a of the connection element EJa other than the last connection element EJa of the two connection elements EJa is shorter than the period T2aLast of the last connection element EJa. Specifically, the period T2a_1 of the first connection element EJa1, which is the first connection element EJa, is shorter than the period T2a_2 of the second connection element EJa2, which is the last connection element EJa.

[0106] Also, the start time TS of the ejection element ETa1 of the first ejection pulse PAa1 ETa1From the start time TS of the ejection element ETa2 of the second ejection pulse PAa2, ETa2 The interval T3a_1 until the start time TS is set to be equal to or greater than (n2-0.4)×Tc and equal to or less than n2×Tc. ETa2 to the start time TS of the ejection element ETa3 of the third ejection pulse PAa3 ETa3 The interval T3a_2 to the point is set to be equal to or greater than (n2-0.4)×Tc and equal to or less than n2×Tc.

[0107] B2: Second variant 8 is a diagram illustrating a drive signal Comb in a second modified example. The drive signal Comb differs from the drive signal Com in that it has four ejection pulses PAb instead of three ejection pulses PA, three connection elements EJb instead of two connection elements EJ, and a damping element EDb instead of the damping element ED. The four ejection pulses PAb differ from the three ejection pulses PA in that it has a first ejection pulse PAb1 instead of the first ejection pulse PA1, a second ejection pulse PAb2 instead of the second ejection pulse PA2, a third ejection pulse PAb3 instead of the third ejection pulse PA3, and further includes a fourth ejection pulse PAb4. The three connection elements EJb differ from the two connection elements EJ in that it has a first connection element EJb1 instead of the first connection element EJ1, a second connection element EJb2 instead of the second connection element EJ2, and further includes a third connection element EJb3. The four ejection pulses PAb are an example of "at least three ejection pulses." The three connection elements EJb are an example of "at least two connection elements."

[0108] The first ejection pulse PAb1, the second ejection pulse PAb2, the third ejection pulse PAb3, and the fourth ejection pulse PAb4 are four ejection pulses PAb that sequentially eject four droplets from the nozzle N after being ejected from the nozzle N and coalescing before landing on the medium M, and are arranged in a time sequence corresponding to the four droplets. The connection between the three ejection pulses PAb other than the last ejection pulse PAb of the four ejection pulses PAb and the two connection elements EJb other than the last connection element EJb of the three connection elements EJb is the same as the connection between the three ejection pulses PA and the two connection elements EJ, and therefore a description thereof will be omitted.

[0109] The first ejection pulse PAb1 differs from the first ejection pulse PA1 in that it has a fill element EFb1 instead of the fill element EF1, a potential maintaining element EMb1 instead of the potential maintaining element EM1, and an ejection element ETb1 instead of the ejection element ET1, but the shape of the first ejection pulse PA1b is substantially the same as the shape of the first ejection pulse PA1.

[0110] The second ejection pulse PAb2 differs from the second ejection pulse PA2 in that it has a fill element EFb2 instead of the fill element EF2, a potential maintaining element EMb2 instead of the potential maintaining element EM2, and an ejection element ETb2 instead of the ejection element ET2. The ejection element ETb2 differs from the ejection element ET2 in that it changes from the minimum potential VL to a potential V1b. The potential V1b is a potential between the reference potential V0 and the potential V1. Specifically, the potential V1b is a potential of approximately 65%. The second connection element EJb2 maintains the potential V1b.

[0111] The third ejection pulse PAb3 differs from the third ejection pulse PA3 in that it has a fill element EFb3 instead of the fill element EF3, a potential maintaining element EMb3 instead of the potential maintaining element EM3, and an ejection element ETb3 instead of the ejection element ET3. The fill element EFb3 differs from the fill element EF3 in that it changes from a potential V1b to a minimum potential VL. The ejection element ETb3 differs from the ejection element ET3 in that it changes from a minimum potential VL to a potential V2b. The potential V2b is a potential between the potential V1b and the maximum potential VH. Specifically, the potential V2b is a potential of approximately 70%.

[0112] The third ejection pulse PAb3 is connected to the fourth ejection pulse PAb4 via a third connection element EJb3. ​​In the example shown in Fig. 8, the starting point of the third connection element EJb3 is connected to the ending point of the ejection element ETb3 of the third ejection pulse PAb3. The third connection element EJb3 maintains the potential V2b.

[0113] The fourth ejection pulse PAb4 is the last ejection pulse PA of the four ejection pulses PA within the unit period Tu. In the example shown in FIG. 8, the fourth ejection pulse PAb4 has a fill element EFb4 and an ejection element ETb4, in this order. The fill element EFb4 and the ejection element ETb4 are connected by a potential maintaining element EMb4 that maintains the minimum potential VL. The fill element EFb4 changes from the potential V2b to the minimum potential VL. The ejection element ETb4 changes from the minimum potential VL to the maximum potential VH, thereby connecting to the potential maintaining element EMb5.

[0114] In this way, the fourth ejection pulse PAb4 is a potential pulse having a waveform that goes from the potential V2b through the minimum potential VL to the maximum potential VH. When the drive element 51f receives the fourth ejection pulse PAb4, it generates a negative pressure in the pressure chamber C based on the fill element EFb4, and then generates a positive pressure in the pressure chamber C based on the ejection element ETb4, thereby ejecting a droplet from the nozzle N.

[0115] The fourth ejection pulse PAb4 is connected to the damping element EDb via the potential maintaining element EMb5. In the example shown in Fig. 8, the starting point of the potential maintaining element EMb5 is connected to the ending point of the ejection element ETb4 of the fourth ejection pulse PAb4. The potential maintaining element EMb5 maintains the highest potential VH.

[0116] Hereinafter, each of the filling elements EFb1, EFb2, EFb3, and EFb4 may be referred to as a filling element EFb, and each of the discharge elements ETb1, ETb2, ETb3, and ETb4 may be referred to as a discharge element ETb.

[0117] As in the first embodiment, the start time TS EFb1 to the start time TS of the discharge element ETb1 ETb1 The period T1b_1 from the start time TS to the start time TS is set to 0.3Tc or more and 0.7Tc or less, and the closer to 0.5Tc the better. EFb2 From the start time TS of the discharge element ETb2 ETb2The period T1b_2 from the start time TS to the start time TS is set to 0.3Tc or more and 0.7Tc or less, and the closer to 0.5Tc the better. EFb3 to the start time TS of the discharge element ETb3 ETb3 The period T1b_3 from the start time TS to the start time TS is set to 0.3Tc or more and 0.7Tc or less, and the closer to 0.5Tc the better. EFb4 to the start time TS of the discharge element ETb4 ETb4 The period T1b_4 until the end of the pulse period is set to 0.3Tc or more and 0.7Tc or less, and the closer to 0.5Tc the better.

[0118] Furthermore, the absolute value of the potential change width of the ejection element ETb of a certain ejection pulse PAb is larger as the absolute value of the potential change width of the ejection element ETb of the later ejection pulse PAb. Specifically, the absolute value of the potential change width of the ejection element ETb1 is V0-VL, and the absolute value of the potential change width of the ejection element ETb2 is V1b-VL, where V1b is higher than V0. Therefore, the absolute value of the potential change width of the ejection element ETb2 is larger than the absolute value of the potential change width of the ejection element ETb1. Furthermore, the absolute value of the potential change width of the ejection element ETb3 is V2b-VL, where V2b is higher than V1b. Therefore, the absolute value of the potential change width of the ejection element ETb3 is larger than the absolute value of the potential change width of the ejection element ETb2. Furthermore, the absolute value of the potential change width of the ejection element ETb4 is VH-VL, where VH is higher than V2b. Therefore, the absolute value of the potential change width of the ejection element ETb4 is larger than the absolute value of the potential change width of the ejection element ETb3. In the second modified example, when the fourth ejection pulse PAb4 corresponds to the "ejection pulse other than the first ejection pulse", the first ejection pulse PAb1, the second ejection pulse PAb2, and the third ejection pulse PAb3 correspond to the "ejection pulses positioned before the ejection pulses other than the first ejection pulse".

[0119] Furthermore, the reference potential V0, which is the potential maintained by the first connection element EJb1, is between the minimum potential VL, which is the terminal potential of the fill element EFb1 of the first ejection pulse PAb1, which is the first ejection pulse PAb of the four ejection pulses PAb, and the potential V1b maintained by the second connection element EJb2 located after the first connection element EJb1. It can also be said that the reference potential V0 is between the minimum potential VL, which is the terminal potential of the fill element EFb1, and the potential V2b maintained by the third connection element EJb3 located after the first connection element EJb1. In the second modified example, if the first connection element EJb1 corresponds to "a connection element other than the last connection element of at least two connection elements," the second connection element EJb2 and the third connection element EJb3 correspond to "connection elements located after a connection element other than the last connection element." Furthermore, if the second connection element EJb2 corresponds to "a connection element other than the last connection element among at least two connection elements," the third connection element EJb3 corresponds to "a connection element located after a connection element other than the last connection element."

[0120] Also, as in the first embodiment, the reference potential V0, which is the terminal potential of the ejection element ETb1 of the first ejection pulse PAb1, which is the first ejection pulse PAb of the four ejection pulses PAb, is equal to the reference potential V0, which is the starting potential of the filling element EFb1. Furthermore, in the second and subsequent ejection pulses PAb of the four ejection pulses PAb, the absolute value of the potential change width of the ejection element ETb is greater than the absolute value of the potential change width of the filling element EFb. Specifically, the absolute value of the potential change width of the ejection element ETb2 of the second ejection pulse PAb2 is V1b-VL, and the absolute value of the potential change width of the filling element EFb2 is V0-VL. Therefore, the absolute value of the potential change width of the ejection element ETb2 is greater than the absolute value of the potential change width of the filling element EFb2. Moreover, the absolute value of the potential change width of the ejection element ETb3 of the third ejection pulse PAb3 is V2b-VL, and the absolute value of the potential change width of the filling element EFb3 is V1b-VL, where V2b is higher than V1b. Therefore, the absolute value of the potential change width of the ejection element ETb3 is larger than the absolute value of the potential change width of the filling element EFb3. Moreover, the absolute value of the potential change width of the ejection element ETb4 of the fourth ejection pulse PAb4 is VH-VL, and the absolute value of the potential change width of the filling element EFb4 is V2b-VL, where VH is higher than V2b. Therefore, the absolute value of the potential change width of the ejection element ETb4 is larger than the absolute value of the potential change width of the filling element EFb4.

[0121] Furthermore, similarly to the first embodiment, the absolute value of the potential change width of the filling element EFb4 of the fourth ejection pulse PAb4, which is the last ejection pulse PAb among the four ejection pulses PAb, is greater than the absolute value of the potential change width of the filling element EFb1 of the first ejection pulse PAb1, which is the first ejection pulse PAb. Specifically, the absolute value of the potential change width of the filling element EFb4 is V2b-VL, and the absolute value of the potential change width of the filling element EFb1 is V0-VL. Therefore, the absolute value of the potential change width of the filling element EFb4 is greater than the absolute value of the potential change width of the filling element EFb1.

[0122] Furthermore, the period T2b_1 of the first connection element EJb1, which is the first connection element EJb of the three connection elements EJb, is set to be equal to or greater than (n1-0.25) x Tc and equal to or less than (n1+0.25) x Tc, with the closer to n1 x Tc being preferable. Similarly, the period T2b_2 of the second connection element EJb2, which is the second connection element EJb of the three connection elements EJb, is set to be equal to or greater than (n1-0.25) x Tc and equal to or less than (n1+0.25) x Tc, with the closer to n1 x Tc being preferable. Furthermore, the period T2b_3 of the third connection element EJb3, which is the last connection element EJb of the three connection elements EJb, is set to be equal to or greater than (n1-0.25) x Tc and equal to or less than (n1+0.25) x Tc, with the closer to n1 x Tc being preferable. Hereinafter, each of the periods T2b_1, T2b_2, and T2b_3 may be referred to as period T2b.

[0123] Furthermore, the period T2b_3 of the third connection element EJb3, which is the last connection element EJb of the three connection elements EJb, is longer than Tc and is equal to or shorter than 2Tc. In the following description, the period T2b of the last connection element EJb of the three connection elements EJb may be referred to as period T2bLast. In the second modified example, as shown in FIG. 8, period T2b_3 is period T2bLast.

[0124] Furthermore, the periods T2b of the connection elements EJb other than the last connection element EJb among the three connection elements EJb are shorter than the period T2bLast of the last connection element EJb. Specifically, the period T2b_1 of the first connection element EJb1, which is the first connection element EJb, and the period T2b_2 of the second connection element EJb2, which is the second connection element EJb, are shorter than the period T2b_3 of the third connection element EJb3, which is the last connection element EJb.

[0125] Also, the start time TS of the ejection element ETb1 of the first ejection pulse PAb1 ETb1 From the start time TS of the ejection element ETb2 of the second ejection pulse PAb2, ETb2 The interval T3b_1 until the start time TS is set to be equal to or greater than (n2-0.4)×Tc and equal to or less than n2×Tc. ETb2 to the start time TS of the ejection element ETb3 of the third ejection pulse PAb3 ETb3The interval T3b_2 from the start time TS to the start time TS is set to be equal to or greater than (n2-0.4)×Tc and equal to or less than n2×Tc. ETb3 to the start time TS of the ejection element ETb4 of the fourth ejection pulse PAb4 ETb4 The interval T3b_3 to the point is set to be equal to or greater than (n2-0.4)×Tc and equal to or less than n2×Tc.

[0126] B3: Third variant 9 is a diagram illustrating a driving signal Comc in a third modified example. The driving signal Comc differs from the driving signal Comb in that it has four ejection pulses PAc instead of the four ejection pulses PAb, three connection elements EJc instead of the three connection elements EJb, and a vibration suppression element EDc instead of the vibration suppression element EDb. The four ejection pulses PAc differ from the four ejection pulses PAb in that it has a first ejection pulse PAc1 instead of the first ejection pulse PAb1, a second ejection pulse PAc2 instead of the second ejection pulse PAb2, a third ejection pulse PAc3 instead of the third ejection pulse PAb3, and a fourth ejection pulse PAc4 instead of the fourth ejection pulse PAb4.

[0127] The first ejection pulse PAc1, the second ejection pulse PAc2, the third ejection pulse PAc3, and the fourth ejection pulse PAc4 are four ejection pulses PAc that sequentially eject four droplets from the nozzle N after being ejected from the nozzle N and coalescing before landing on the medium M, and are arranged in time corresponding to the four droplets. The connection between the four ejection pulses PAc and the three connection elements EJc is the same as the connection between the four ejection pulses PAb and the three connection elements EJb, and therefore a description thereof will be omitted.

[0128] The first ejection pulse PAc1 differs from the first ejection pulse PAb1 in that it has a fill element EFc1 instead of the fill element EFb1, a potential maintaining element EMc1 instead of the potential maintaining element EMb1, and an ejection element ETc1 instead of the ejection element ETb1, but the shape of the first ejection pulse PAc1 is substantially the same as the shape of the first ejection pulse PAb1.

[0129] The second ejection pulse PAc2 differs from the second ejection pulse PAb2 in that it has a fill element EFc2 instead of the fill element EFb2, a potential maintaining element EMc2 instead of the potential maintaining element EMb2, and an ejection element ETc2 instead of the ejection element ETb2. The ejection element ETb2 differs from the ejection element ETb2 in that it changes from the minimum potential VL to a potential V1c. The potential V1c is a potential between the reference potential V0 and the potential V1. Specifically, the potential V1c is approximately 70% of the potential. The second connection element EJc2 maintains the potential V1c.

[0130] The third ejection pulse PAc3 differs from the third ejection pulse PAb3 in that it has a fill element EFc3 instead of the fill element EFb3, a potential maintaining element EMc3 instead of the potential maintaining element EMb3, and an ejection element ETc3 instead of the ejection element ETb3. The fill element EFc3 differs from the fill element EFb3 in that it changes from a potential V1c to a minimum potential VL. The ejection element ETc3 differs from the ejection element ETb3 in that it changes from a minimum potential VL to a potential V2c. The potential V2c is a potential between the potential V1c and the maximum potential VH. Specifically, the potential V2c is approximately 80%.

[0131] The fourth ejection pulse PAc4 differs from the third ejection pulse PAb3 in that it has a fill element EFc4 instead of the fill element EFb4, a potential maintaining element EMc4 instead of the potential maintaining element EMb4, and an ejection element ETc4 instead of the ejection element ETb4. The fill element EFc4 differs from the fill element EFb4 in that it changes from the potential V2c to the minimum potential VL. The ejection element ETc4 differs from the ejection element ETb4 in that it changes from the minimum potential VL to the potential V3c. The potential V3c is a potential between the potential V2c and the maximum potential VH. Specifically, the potential V3c is approximately 91% of the potential.

[0132] Furthermore, the fourth ejection pulse PAc4 differs from the fourth ejection pulse PAb4 in that it is connected to the damping element EDc via a potential maintaining element EMc5, a damping expansion element EGc, a potential maintaining element EMc6, a damping contraction element EHc, and a potential maintaining element EMc7. Furthermore, the amount of droplets ejected by the fourth ejection pulse PAc4 is smaller than the amount of droplets ejected by the fourth ejection pulse PAb4.

[0133] Hereinafter, each of the filling elements EFc1, EFc2, EFc3, and EFc4 may be referred to as a filling element EFc. Each of the discharge elements ETc1, ETc2, ETc3, and ETc4 may be referred to as a discharge element ETc.

[0134] The ejection element ETc4 changes from the lowest potential VL to a potential V3c, thereby connecting to the potential maintaining element EMc5. The potential maintaining element EMc5 maintains the potential V3c and connects to the damping expansion element EGc at its end. The damping expansion element EGc changes from the potential V3c to a potential V4c to expand the pressure chamber C, and connects to the potential maintaining element EMc6 at its end. The potential V4c is a potential between the reference potential V0 and the lowest potential VL. Specifically, the potential V4c is approximately 20% potential. The potential maintaining element EMc6 maintains the potential V4c and connects to the damping contraction element EHc at its end. The damping contraction element EHc changes from the potential V4c to the highest potential VH to contract the pressure chamber C, and connects to the potential maintaining element EMc7 at its end. The potential maintaining element EMc7 maintains the highest potential VH and connects to the damping element EDc at its end.

[0135] As in the first embodiment, the start time TS EFc1 to the start time TS of the discharge element ETc1 ETc1 The period T1c_1 from the start time TS EFc2 to the start time TS of the discharge element ETc2 ETc2 The period T1c_2 from the start time TSEFc3 to the start time TS of the discharge element ETc3 ETc3 The period T1c_3 from the start time TS EFc4 to the start time TS of the discharge element ETc4 ETc4 The period T1c_4 until the end of the pulse is set to 0.3Tc or more and 0.7Tc or less, and the closer to 0.5Tc the better.

[0136] Furthermore, the absolute value of the potential change width of the ejection element ETc of a certain ejection pulse PAc is larger as the absolute value of the potential change width of the ejection element ETc of the later ejection pulse PAc. Specifically, the absolute value of the potential change width of the ejection element ETc1 is V0-VL, and the absolute value of the potential change width of the ejection element ETc2 is V1c-VL, where V1c is higher than V0. Therefore, the absolute value of the potential change width of the ejection element ETc2 is larger than the absolute value of the potential change width of the ejection element ETc1. Furthermore, the absolute value of the potential change width of the ejection element ETc3 is V2c-VL, where V2c is higher than V1c. Therefore, the absolute value of the potential change width of the ejection element ETc3 is larger than the absolute value of the potential change width of the ejection element ETc2. Furthermore, the absolute value of the potential change width of the ejection element ETc4 is V3c-VL, where V3c is higher than V2b. Therefore, the absolute value of the potential change width of the discharge element ETc4 is greater than the absolute value of the potential change width of the discharge element ETc3.

[0137] Furthermore, the reference potential V0, which is the potential maintained by the first connection element EJc1, is between the minimum potential VL, which is the terminal potential of the filling element EFc1 of the first ejection pulse PAc1, which is the first ejection pulse PAc of the four ejection pulses PAc, and the potential V1c maintained by the second connection element EJc2, which is located after the first connection element EJc1.

[0138] Furthermore, as in the first embodiment, the reference potential V0, which is the terminal potential of the ejection element ETc1 of the first ejection pulse PAc1, which is the first ejection pulse PAc of the four ejection pulses PAc, is equal to the reference potential V0, which is the starting potential of the filling element EFc1. Furthermore, in the second and subsequent ejection pulses PAc of the four ejection pulses PAc, the absolute value of the potential change width of the ejection element ETc is greater than the absolute value of the potential change width of the filling element EFc. Specifically, the absolute value of the potential change width of the ejection element ETc2 of the second ejection pulse PAc2 is V1c-VL, and the absolute value of the potential change width of the filling element EFc2 is V0-VL. Therefore, the absolute value of the potential change width of the ejection element ETc2 is greater than the absolute value of the potential change width of the filling element EFc2. The absolute value of the potential change width of the ejection element ETc3 of the third ejection pulse PAc3 is V2c-VL, and the absolute value of the potential change width of the filling element EFc3 is V1c-VL, where V2c is higher than V1c. The absolute value of the potential change width of the ejection element ETc4 of the fourth ejection pulse PAc4 is V3c-VL, and the absolute value of the potential change width of the filling element EFc4 is V2c-VL, where V3c is higher than V2c. Therefore, the absolute value of the potential change width of the ejection element ETc4 is larger than the absolute value of the potential change width of the filling element EFc4.

[0139] Furthermore, as in the first embodiment, the absolute value of the potential change width of the filling element EFc4 of the fourth ejection pulse PAc4, which is the last ejection pulse PAc of the four ejection pulses PAc, is greater than the absolute value of the potential change width of the filling element EFc1 of the first ejection pulse PAc1, which is the first ejection pulse PAc. Specifically, the absolute value of the potential change width of the filling element EFc4 is V2c-VL, and the absolute value of the potential change width of the filling element EFc1 is V0-VL. Therefore, the absolute value of the potential change width of the filling element EFc4 is greater than the absolute value of the potential change width of the filling element EFc1.

[0140] Furthermore, the period T2c_1 of the first connection element EJc1, which is the first connection element EJc of the three connection elements EJc, is set to be equal to or greater than (n1-0.25)×Tc and equal to or less than (n1+0.25)×Tc, with the closer to n1×Tc being preferable. Similarly, the period T2c_2 of the second connection element EJc2, which is the second connection element EJc of the three connection elements EJc, is set to be equal to or greater than (n1-0.25)×Tc and equal to or less than (n1+0.25)×Tc, with the closer to n1×Tc being preferable. Furthermore, the period T2c_3 of the third connection element EJc3, which is the last connection element EJc of the three connection elements EJc, is set to be equal to or greater than (n1-0.25)×Tc and equal to or less than (n1+0.25)×Tc, with the closer to n1×Tc being preferable. Hereinafter, each of the periods T2c_1, T2c_2, and T2c_3 may be referred to as period T2c.

[0141] Furthermore, the period T2c_3 of the third connection element EJc3, which is the last connection element EJc of the three connection elements EJc, is longer than Tc and is equal to or shorter than 2Tc. In the following description, the period T2c of the last connection element EJc of the three connection elements EJc may be referred to as period T2cLast. In the third modified example, as shown in FIG. 9, period T2c_3 is period T2cLast.

[0142] Furthermore, the periods T2c of the connection elements EJc other than the last connection element EJc among the three connection elements EJc are shorter than the period T2cLast of the last connection element EJc. Specifically, the period T2c_1 of the first connection element EJc1, which is the first connection element EJc, and the period T2c_2 of the second connection element EJc2, which is the second connection element EJc, are shorter than the period T2c_3 of the third connection element EJc3, which is the last connection element EJc.

[0143] Also, the start time TS of the ejection element ETc1 of the first ejection pulse PAc1 ETc1 From the start time TS of the ejection element ETc2 of the second ejection pulse PAc2, ETc2 The interval T3c_1 until the start time TS is set to be equal to or greater than (n2-0.4)×Tc and equal to or less than n2×Tc. ETc2 to the start time TS of the ejection element ETc3 of the third ejection pulse PAc3 ETc3The interval T3c_2 from the start time TS to the start time TS is set to be equal to or greater than (n2-0.4)×Tc and equal to or less than n2×Tc. ETc3 to the start time TS of the ejection element ETc4 of the fourth ejection pulse PAc4 ETc4 The interval T3c_3 to the point is set to be equal to or greater than (n2-0.4)×Tc and equal to or less than n2×Tc.

[0144] B4: Fourth variant In the above-described embodiments, a negative pressure is generated in the pressure chamber C by a drop in the potential supplied to the drive element 51f, and a positive pressure is generated in the pressure chamber C by an increase in the potential supplied to the drive element 51f, but this is not limiting. For example, a positive pressure may be generated in the pressure chamber C by a drop in the potential supplied to the drive element 51f, and a negative pressure may be generated in the pressure chamber C by an increase in the potential supplied to the drive element 51f. In the fourth modified example, the high-low relationship of the potential of the drive signal Com in the above-described embodiments may be reversed.

[0145] Even when the high-low relationship of the potential of the drive signal Com is reversed, the absolute value of the potential change width of the fill element EF and the absolute value of the potential change width of the ejection element ET are the same as in the above-mentioned aspects.

[0146] In addition, the potential difference between the reference potential and the maximum potential VH of the drive signal Com in the fourth modified example is 50% to 70% of the potential difference between the minimum potential VL and the maximum potential VH. In the fourth modified example, the maximum potential VH is the potential farthest from the reference potential within the range of potentials that at least three ejection pulses PA can take, from the minimum potential VL to the maximum potential VH.

[0147] B5: Fifth variant In each of the above-described embodiments, in the first ejection pulse PA, the terminal potential of the ejection element ET is equal to the starting potential of the filling element EF, but this is not limited to this. For example, in the first ejection pulse PA, the terminal potential of the ejection element ET may be different from the starting potential of the filling element EF. Also, in the second and subsequent ejection pulses PA among at least three ejection pulses PA, the absolute value of the potential change width of the ejection element ET is greater than the absolute value of the potential change width of the filling element EF, but this is not limited to this. For example, in the second and subsequent ejection pulses PA, the absolute value of the potential change width of the ejection element ET may be equal to or smaller than the absolute value of the potential change width of the filling element EF.

[0148] B6: 6th variant In each of the above-described embodiments, the absolute value of the potential change width of the filling element EF of the last ejection pulse PA among the at least three ejection pulses PA is larger than the absolute value of the potential change width of the filling element EF of the first ejection pulse PA among the at least three ejection pulses PA, but is not limited to this. For example, the absolute value of the potential change width of the filling element EF of the last ejection pulse PA may be equal to or smaller than the absolute value of the potential change width of the filling element EF of the first ejection pulse PA.

[0149] B7: 7th variant In each of the above-described embodiments, the potential difference between the reference potential V0 and the potential farthest from the reference potential V0 in the range of the potentials that the at least three ejection pulses PA can take is 50% or more and 70% or less of the potential difference in the aforementioned range, but is not limited to this. For example, the potential difference between the reference potential V0 and the potential farthest from the reference potential V0 in the range of the potentials that the at least three ejection pulses PA can take may be less than 50% or more than 70% of the potential difference in the aforementioned range.

[0150] B8: Eighth Variation In each of the above-described embodiments, the period T2 is set to be equal to or greater than (n1-0.25) x Tc and equal to or less than (n1+0.25) x Tc, but is not limited to this. For example, the period T2 may be less than (n1-0.25) x Tc or may be longer than (n1+0.25) x Tc.

[0151] B9: 9th variant In each of the above-described embodiments, the period T2Last of the last connection element EJ among the at least two connection elements EJ is longer than Tc and not longer than 2Tc, but is not limited to this. For example, the period T2Last may be shorter than Tc or longer than 2Tc.

[0152] B10: 10th variant In each of the above-described embodiments, the duration of the connection elements EJ other than the last connection element EJ among the at least two connection elements EJ is shorter than the duration T2Last of the last connection element EJ, but this is not limited to this. For example, the duration of the connection elements EJ other than the last connection element EJ may be longer than the duration T2Last.

[0153] B11: 11th variant In each of the above-described embodiments, the interval T3 between the start of the ejection elements ET of two adjacent ejection pulses PA among the at least three ejection pulses PA is set to be equal to or greater than (n2-0.4)×Tc and equal to or less than n2×Tc, but is not limited thereto. For example, the interval T3 may be less than (n2-0.4)×Tc or longer than n2×Tc.

[0154] B12: 12th variant In the first embodiment and the first modified example, the drive signal Com includes three ejection pulses PA corresponding to three droplets, and in the second and third modified examples, it includes four ejection pulses PA corresponding to four droplets, but this is not limiting. For example, the drive signal Com may include five or more ejection pulses corresponding to five or more droplets.

[0155] B13: 13th variant In each of the above-mentioned embodiments, a serial-type liquid ejection device 100 in which a carriage 41 carrying a head 50 moves back and forth has been exemplified, 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.

[0156] B14: 14th variant The liquid ejection device 100 exemplified in each of the above-described embodiments may be employed in various devices such as facsimile machines and copiers, in addition to devices dedicated to printing, and the applications of the present disclosure are not particularly limited. However, the applications of the liquid ejection device are 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 display devices such as liquid crystal display panels. 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. Furthermore, a liquid ejection device that ejects a solution of an organic substance related to a living body is used as a manufacturing device for manufacturing biochips, for example. [Explanation of symbols]

[0157] 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...head, 51...head chip, 51a...flow path substrate, 51b...pressure chamber substrate, 51c...nozzle plate, 51d...vibration absorber, 51e...diaphragm, 51f...drive element, 51g...protective plate, 51h...case, 51i...wiring board, 52...switching circuit, 52a...connection state designation circuit, 100...liquid ejection device, 200...external device, C...pressure chamber, CLK...clock signal, CNG...change signal signal, Com, Coma, Comb, Comc... drive signal, D... discharge part, DR, DR1, DR2, DR3... droplet, DRA... coalesced droplet, ED, Eda, EDb, EDc... vibration control element, EF1, EF2, EF3, EFa1, EFa2, EFa3, EFb, EFb1, EFb2, EFb3, EFb4, EFc1, EFc2, EFc3, EFc4... filling element, EGa, EGc... vibration control expansion element, EHa, EHc... vibration control contraction element, EJ1, EJ2, EJa1, EJa2, EJb1, EJb2, EJb3, EJc1, EJc2, EJc3... connection element, EM1, EM2, EM3, E M4, EMa1, EMa2, EMa3, ​​EMa4, EMa5, EMa6, EMb1, EMb2, EMb3, EMb4, EMb5, EMc1, EMc2, EMc3, EMc4, EMc5, EMc6, EMc7... potential maintenance elements, ET1, ET2, ET3, ETa1, ETa2, ETa3, ETb1, ETb2, ETb3, ETb4, ETc1, ETc2, ETc3, ETc4... ejection elements, FN... nozzle surface, IH... inlet, Img... print data, L1... first row, L2... second row, LAT... latch signal, LHa, LHd... wiring, M... medium, N... nozzle, Na... connecting flow path , PA1, PA1b, PA2, PA3, PAa1, PAa2, PAa3, PAb1, PAb2, PAb3, PAb4, Pac1, Pac2, Pac3, Pac4...ejection pulse, PL...pulse, R...reservoir, R1, R2...space, Ra...supply channel, SI...print data signal, SLa...connection status designation signal, SWa...switch, Sk1, Sk2...control signal, T1_1, T1_2, T1_3, T1a_1, T1a_2, T1a_3, T1b_1, T1b_2, T1b_3, T1b_4, T1c_1, T1c_2, T1c_3, T1c_4, T2Last, T2_1,T2_2, T2aLast, T2a_1, T2a_2, T2bLast, T2b_1, T2b_2, T2b_3, T2cLast, T2c_1, T2c_2, T2c_3, T3_1, T3_2...period, Tc...natural vibration period, Tu...unit period, V0...reference potential, V1, V1a, V1b, V1c, V2a, V2b, V2c, V3a, V3c, V4c...potential, VBS...offset potential, VH...highest potential, VHV...power supply potential, VL...lowest potential, Vin...supply signal, Zd, Zu...electrode, dCom...waveform specification signal.

Claims

1. a discharge unit having a nozzle that discharges droplets to be landed on a medium, a pressure chamber that communicates with the nozzle, and a drive element that generates a pressure fluctuation in the liquid in the pressure chamber when a drive signal is supplied; a drive signal generation unit that generates the drive signal; Equipped with The drive signal is at least three ejection pulses, each of which corresponds to at least three droplets that coalesce before landing on the medium, and each of which has a filling element that generates a negative pressure in the pressure chamber by changing a potential, and an ejection element that generates a positive pressure in the pressure chamber by changing a potential, thereby ejecting droplets from the nozzle; At least two connection elements that connect adjacent ejection pulses among the at least three ejection pulses while maintaining a potential; a vibration damping element that generates a negative pressure in the pressure chamber after a droplet is ejected from the nozzle after a final ejection pulse of the at least three ejection pulses, thereby damping residual vibration of the liquid in the pressure chamber; When the natural vibration period of the ejection portion is Tc, In each of the at least three ejection pulses, a period from the start of a fill element to the start of an ejection element is set to be equal to or greater than 0.3Tc and equal to or less than 0.7Tc; an absolute value of a potential change width of an ejection element of an ejection pulse other than a first ejection pulse among the at least three ejection pulses is greater than an absolute value of a potential change width of an ejection element of an ejection pulse positioned before the ejection pulse other than the first ejection pulse, One of the at least two connection elements maintains the terminal potential of the ejection element of the previous ejection pulse of two ejection pulses connected before and after the one connection element, and is connected to the starting end of the filling element of the next ejection pulse of the two ejection pulses; a potential maintained by a connection element other than the last connection element among the at least two connection elements is between a terminal potential of a filling element of the first ejection pulse and a potential maintained by a connection element located after the connection element other than the last connection element; Liquid discharge device.

2. In the first ejection pulse, the end potential of the ejection element is equal to the beginning potential of the fill element; In the second or subsequent ejection pulses among the at least three ejection pulses, the absolute value of the potential change width of the ejection element is larger than the absolute value of the potential change width of the filling element. The liquid ejection device according to claim 1 .

3. an absolute value of a potential change width of a filling element of a last ejection pulse among the at least three ejection pulses is greater than an absolute value of a potential change width of a filling element of the first ejection pulse; The liquid ejection device according to claim 1 .

4. a potential difference between a reference potential, which is a potential at the start of the drive signal, and a potential that is the furthest from the reference potential within a range of potentials that the at least three ejection pulses can take is 50% or more and 70% or less of the potential difference of the range; The liquid ejection device according to claim 1 .

5. The period of each of the at least two connection elements is set to be equal to or greater than (n1-0.25) x Tc and equal to or less than (n1+0.25) x Tc; n1 is an integer of 1 or more; The liquid ejection device according to claim 1 .

6. the duration of the last connection element is greater than Tc and less than or equal to 2Tc; The liquid ejection device according to claim 1 .

7. a period of each of the at least two connection elements other than the last connection element is shorter than a period of the last connection element; The liquid ejection device according to claim 1 .

8. an interval between the start of ejection elements of two adjacent ejection pulses among the at least three ejection pulses is set to be equal to or greater than (n2-0.4)×Tc and equal to or less than n2×Tc; n2 is an integer of 2 or greater; The liquid ejection device according to claim 1 .

9. a discharge unit having a nozzle that discharges droplets to be landed on a medium, a pressure chamber that communicates with the nozzle, and a drive element that generates a pressure fluctuation in the liquid in the pressure chamber when a drive signal is supplied; a drive signal generation unit that generates the drive signal; A method for driving a liquid ejection device comprising: The drive signal is at least three ejection pulses, each of which corresponds to at least three droplets that coalesce before landing on the medium, and each of which has a filling element that generates a negative pressure in the pressure chamber by changing a potential, and an ejection element that generates a positive pressure in the pressure chamber by changing a potential, thereby ejecting droplets from the nozzle; At least two connection elements that connect adjacent ejection pulses among the at least three ejection pulses while maintaining a potential; a vibration damping element that generates a negative pressure in the pressure chamber after a droplet is ejected from the nozzle after a final ejection pulse of the at least three ejection pulses, thereby damping residual vibration of the liquid in the pressure chamber; When the natural vibration period of the ejection portion is Tc, In each of the at least three ejection pulses, a period from the start of a fill element to the start of an ejection element is set to be equal to or greater than 0.3Tc and equal to or less than 0.7Tc; an absolute value of a potential change width of an ejection element of an ejection pulse other than a first ejection pulse among the at least three ejection pulses is greater than an absolute value of a potential change width of an ejection element of an ejection pulse positioned before the ejection pulse other than the first ejection pulse, One of the at least two connection elements maintains the terminal potential of the ejection element of the previous ejection pulse of two ejection pulses connected before and after the one connection element, and is connected to the starting end of the filling element of the next ejection pulse of the two ejection pulses; a potential maintained by a connection element other than the last connection element among the at least two connection elements is between a terminal potential of a filling element of the first ejection pulse and a potential maintained by a connection element located after the connection element other than the last connection element; A method for driving a liquid ejection device.

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