Liquid dispensing device and driving method

Abstract

To suppress the generation of mist. [Solution] The discharge unit comprises a nozzle for discharging liquid, a pressure chamber communicating with the nozzle, and a drive element that drives the liquid in the pressure chamber to produce pressure fluctuations in response to a supplied drive signal, and a drive signal generation circuit that generates a drive signal, wherein the drive signal includes a first discharge pulse that discharges liquid from the nozzle, and the first discharge pulse comprises a first depressurization potential change element that drives the drive element to decrease the pressure of the liquid in the pressure chamber, and a first pressurization potential change element that drives the drive element after the first depressurization potential change element to increase the pressure of the liquid in the pressure chamber so that the liquid surface protrudes from the nozzle, wherein the potential change width of the first depressurization potential change element is 40% or more of the potential change width of the first pressurization potential change element, and the potential change rate of the first depressurization potential change element is 1 V / microsecond or more and 2 V / microsecond or less.

Description

Technical Field

[0001] The present invention relates to a liquid ejection device and a driving method.

Background Art

[0002] Conventionally, there has been a liquid ejection apparatus having a nozzle for ejecting a liquid such as ink, a pressure chamber communicating with the nozzle, and a driving element that drives the liquid in the pressure chamber to generate pressure fluctuations in response to a supplied driving signal, and the liquid ejection apparatus forms an image on a medium such as recording paper and has become widespread.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in a liquid ejection apparatus, mist-like fine droplets, so-called mist, may be generated due to trailing of the ejected liquid. When mist is generated, the mist adheres around the nozzle, which may cause deterioration of ejection performance and ejection failure. Deterioration of ejection performance and ejection failure reduce the quality of the image formed on the medium.

Means for Solving the Problems

[0005] A liquid dispensing device according to a preferred embodiment of the present disclosure comprises a dispensing unit having a nozzle for dispensing liquid, a pressure chamber communicating with the nozzle, and a drive element that drives the liquid in the pressure chamber to produce pressure fluctuations in response to a supplied drive signal, and a drive signal generation circuit that generates the drive signal, wherein the drive signal includes a first dispensing pulse for dispensing liquid from the nozzle, the first dispensing pulse having a first depressurizing potential change element that drives the drive element to decrease the pressure of the liquid in the pressure chamber, and a first pressurizing potential change element that drives the drive element after the first depressurizing potential change element to increase the pressure of the liquid in the pressure chamber so that the liquid surface protrudes from the nozzle, the potential change width of the first depressurizing potential change element being 40% or more of the potential change width of the first pressurizing potential change element, and the rate of change of the potential of the first depressurizing potential change element being 1 V / microsecond or more and 2 V / microsecond or less.

[0006] A driving method according to a preferred embodiment of the present disclosure is a driving method for a liquid dispensing device comprising: a dispensing unit having a nozzle for dispensing liquid; a pressure chamber communicating with the nozzle; and a driving element that drives the liquid in the pressure chamber to produce a pressure fluctuation in response to a supplied driving signal; and a driving signal generation circuit that generates the driving signal, wherein the driving signal includes a first dispensing pulse for dispensing liquid from the nozzle, and the first dispensing pulse includes a first pressure reduction potential change element that drives the driving element to decrease the pressure of the liquid in the pressure chamber, and the first pressure reduction potential change element The device includes a first pressurizing potential changing element that drives the drive element to increase the pressure of the liquid in the pressure chamber so that the liquid surface protrudes from the nozzle, wherein the potential change width of the first depressurizing potential changing element is 40% or more of the potential change width of the first pressurizing potential changing element, and the rate of change of the potential of the first depressurizing potential changing element is 1 V / microsecond or more and 2 V / microsecond or less, and the device performs a first step of supplying the first depressurizing potential changing element to the drive element of the discharge unit, and a second step of supplying the first pressurizing potential changing element to the drive element of the discharge unit. [Brief explanation of the drawing]

[0007] [Figure 1]A schematic diagram showing an example configuration of the liquid dispensing device 100 according to the first embodiment. [Figure 2] A diagram showing the electrical configuration of the liquid dispensing device 100 according to the first embodiment. [Figure 3] A cross-sectional view showing an example of a head tip 51. [Figure 4] A diagram illustrating the switching circuit 52. [Figure 5] A diagram illustrating the reason why mist is generated in the small dot discharge pulse in the comparative configuration. [Figure 6] A diagram illustrating the drive signal Com used to generate the supply signal Vin supplied to the head chip 51. [Figure 7] A diagram illustrating each element of the small dot discharge pulse WS. [Figure 8] A diagram showing a flowchart illustrating the operation of the liquid dispensing device 100 in the first embodiment. [Figure 9] A diagram illustrating the small dot discharge pulse WSb in the first modified example. [Figure 10] A diagram illustrating the small dot discharge pulse WSc in the second modified example. [Figure 11] A diagram illustrating the large dot discharge pulse WLd in the third modified example. [Figure 12] A diagram illustrating the large dot discharge pulse WLe in the fourth modified example. [Figure 13] A diagram illustrating the large-dot discharge pulse WLf in the fifth modified example. [Modes for carrying out the invention]

[0008] The embodiments for implementing this disclosure will be described below with reference to the drawings. However, the dimensions and scale of each part in each drawing have been appropriately altered from those of the actual parts. Furthermore, the embodiments described below are preferred examples of this disclosure and are subject to various technically preferred limitations. However, the scope of this disclosure is not limited to these embodiments unless otherwise stated in the following description.

[0009] The following explanation will use the X, Y, and Z axes, which intersect with each other, as appropriate. In the following, one direction along the X axis is the X1 direction, and the direction opposite to the X1 direction is the X2 direction. Similarly, opposite directions along the Y axis are the Y1 and Y2 directions. Opposite directions along the Z axis are the Z1 and Z2 directions.

[0010] Here, typically, the Z-axis is the vertical axis, and the Z2 direction corresponds to the downward direction in the vertical. However, the Z-axis does not necessarily have to be the vertical axis. Also, the X, Y, and Z axes are typically orthogonal to each other, but are not limited to this; for example, they can intersect at an angle within the range of 80° to 100°.

[0011] A: First Embodiment A1: Overall configuration of the liquid dispensing device Figure 1 is a schematic diagram showing an example configuration of a liquid dispensing device 100 according to the first embodiment. The liquid dispensing device 100 is an inkjet printing device that dispenses ink, which is an example of a liquid, as droplets onto a medium PP. The medium PP is, for example, printing paper. However, the medium PP is not limited to printing paper, and may be any material to be printed on, such as resin film or fabric.

[0012] As shown in Figure 1, the liquid dispensing device 100 includes a liquid container 10, a control unit 20, a transport mechanism 30, a moving mechanism 40, and a liquid dispensing head 50.

[0013] The liquid container 10 stores ink. Specific examples of the liquid container 10 include a cartridge detachable from the liquid dispensing device 100, a bag-shaped ink pack made of flexible film, and an ink tank from which ink can be refilled. The type of ink stored in the liquid container 10 is arbitrary.

[0014] The control unit 20 controls the operations 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 based on FIG. 2.

[0015] The conveyance mechanism 30 conveys the medium PP in the Y1 direction under the control of the control unit 20. The movement mechanism 40 reciprocates the liquid ejection 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 liquid ejection head 50, and an endless conveyor belt 42 to which the carriage 41 is fixed. Note that the number of liquid ejection heads 50 mounted on the carriage 41 is not limited to one, and may be a plurality. Also, in addition to the liquid ejection head 50, the aforementioned liquid container 10 may be mounted on the carriage 41.

[0016] The liquid ejection head 50 ejects the ink supplied from the liquid container 10 from each of the plurality of nozzles N onto the medium PP under the control of the control unit 20. By performing this ejection in parallel with the conveyance of the medium PP by the conveyance mechanism 30 and the reciprocating movement of the liquid ejection head 50 by the movement mechanism 40, an image by ink is formed on the surface of the medium PP.

[0017] A2: Electrical Configuration of the Liquid Ejection Device 100 FIG. 2 is a diagram showing the electrical configuration of the liquid ejection device 100 according to the first embodiment. As shown in FIG. 2, the liquid ejection head 50 has one head chip 51. However, the liquid ejection head 50 may have a plurality of head chips 51.

[0018] The head tip 51 has a switching circuit 52 and M dispensing sections D. Hereinafter, when the number of dispensing sections D in the head tip 51 is M, the subscript [m] may be used to distinguish each of the M dispensing sections D, and each dispensing section D may be written as dispensing section D[m]. However, M is an integer of 2 or more, and m is an integer between 1 and M. In addition, the subscript [m] may also be used for elements included in the dispensing section D in the liquid dispensing device 100.

[0019] The switching circuit 52, under the control of the control unit 20, switches whether or not to supply the drive signal Com output from the control unit 20 as a supply signal Vin to each of the M ejection units D. In this embodiment, the switching circuit 52 is included in the head chip 51, but the switching circuit 52 may not be included in the head chip 51.

[0020] 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.

[0021] The control circuit 21 has the function of controlling the operation of each part of the liquid dispensing device 100 and the function of processing various data. The control circuit 21 includes, for example, one or more processors such as CPUs. The control circuit 21 may also include a programmable logic device such as an FPGA instead of a CPU, or in addition to a CPU. Furthermore, if the control circuit 21 is composed of multiple processors, these multiple processors may be mounted on different boards or the like.

[0022] Furthermore, the control circuit 21 generates control signals Sk1 and Sk2, print data signal SI, waveform specification signal dCom, latch signal LAT, change signal CH, and clock signal CLK as signals for controlling the operation of each part of the liquid dispensing device 100 by executing the program.

[0023] Control signal Sk1 is a signal for controlling the drive of the transport mechanism 30. Control signal Sk2 is a signal for controlling the drive of the moving mechanism 40. The print data signal SI is a digital signal for specifying the operating state of the drive element 51f. The latch signal LAT and the change signal CH are used in conjunction with the print data signal SI and are timing signals that define the ink ejection timing from each nozzle N of the head chip 51.

[0024] Furthermore, the control circuit 21 reads the program stored in the memory circuit 22 and executes the read program, thereby executing the driving method in this embodiment.

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

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

[0027] The drive signal generation circuit 24 is a circuit that repeatedly generates a drive signal Com for driving each drive element 51f included in each discharge unit D. Specifically, the drive signal generation circuit 24 includes, for example, a DA conversion circuit and an amplification circuit. In the drive signal generation circuit 24, the DA conversion circuit converts the waveform specification signal dCom from the control circuit 21 from a digital signal to an analog signal. The amplification circuit amplifies the analog signal using the power supply potential VHV from the power supply circuit 23 to generate the drive signal Com. Of the waveforms included in the drive signal Com, the signal of the waveform actually supplied to the drive element 51f is the aforementioned supply signal Vin. The waveform specification signal dCom is a digital signal for defining the waveform of the drive signal Com. The control circuit 21 generates the waveform specification signal dCom based on the waveform information CI. Details of the waveform information CI will be described later in Figure 5.

[0028] A3: Specific structure of head tip 51 Figure 3 is a cross-sectional view showing an example of a head tip 51. As shown in Figure 3, the head tip 51 has M nozzles N arranged in the direction along the Y axis. These M nozzles N are divided into a first row L1 and a second row L2, which are spaced apart from each other in the direction along the X axis. Each of the first row L1 and the second row L2 is a set of 0.5 × M nozzles N arranged linearly in the direction along the Y axis.

[0029] The head tip 51 has a configuration that is approximately symmetrical with respect to 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 along the Y-axis may coincide or differ. 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 along the Y-axis coincide.

[0030] As shown in Figure 3, the head chip 51 includes a flow channel substrate 51a, a pressure chamber substrate 51b, a nozzle plate 51c, a vibration absorber 51d, a diaphragm 51e, a plurality of drive elements 51f, a protective plate 51g, a case 51h, and a wiring board 51i.

[0031] The flow channel substrate 51a and the pressure chamber substrate 51b are stacked in this order in the Z1 direction, forming a flow channel for supplying ink to M nozzles N. In the region located in the Z1 direction from the stack consisting of the flow channel substrate 51a and the pressure chamber substrate 51b, the diaphragm 51e, M drive elements 51f, protective plate 51g, case 51h, and wiring board 51i are installed. On the other hand, in the region located in the Z2 direction from the stack, the nozzle plate 51c and vibration absorber 51d are installed. Each element of the head chip 51 is generally a plate-shaped member that is elongated in the Y direction, and is joined to each other, for example, by adhesive. The elements of the head chip 51 will be described in order below.

[0032] The nozzle plate 51c is a plate-shaped member provided with M nozzles N in each of the first row L1 and the second row L2. Each of the M nozzles N is a through-hole through which ink passes. These nozzles N are provided on the nozzle surface FN, which is the surface of the nozzle plate 51c facing the Z2 direction. The nozzle plate 51c is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing technology, such as dry etching or wet etching. However, other known methods and materials may be used in the manufacture of the nozzle plate 51c as appropriate. In addition, the cross-sectional shape of the nozzles N is typically circular, but is not limited to this, and may be non-circular, such as polygonal or elliptical.

[0033] The flow channel substrate 51a is provided with a space R1, M supply channels Ra, and M communication channels Na for each of the first row L1 and second row L2. Space R1 is a long opening extending in the direction along the Y axis when viewed in a plan view along the Z axis. Each of the supply channels Ra and communication channels Na is a through hole formed for each nozzle N. Each supply channel Ra communicates with space R1.

[0034] The pressure chamber substrate 51b is a plate-shaped member provided with M pressure chambers C, referred to as cavities, in each of the first row L1 and the second row L2. The M pressure chambers C are arranged in the direction along the Y axis. Each pressure chamber C is formed for each nozzle N and is a long space extending in the direction along the X axis in a plan view. The flow channel substrate 51a and the pressure chamber substrate 51b are manufactured, for example, by processing a silicon single crystal substrate using semiconductor manufacturing technology, similar to the nozzle plate 51c described above. However, other known methods and materials may be used as appropriate for the manufacture of the flow channel substrate 51a and the pressure chamber substrate 51b.

[0035] The pressure chamber C is the space located between the flow channel substrate 51a and the diaphragm 51e. For each of the first row L1 and the second row L2, M pressure chambers C are arranged in a direction along the Y axis. The pressure chamber C also communicates with the communication channel Na and the supply channel Ra, respectively. Therefore, the pressure chamber C communicates with the nozzle N via the communication channel Na and with the space R1 via the supply channel Ra.

[0036] A diaphragm 51e is positioned on the surface of the pressure chamber substrate 51b facing the Z1 direction. The diaphragm 51e is an elastically vibrating plate-shaped member. 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 composed of silicon oxide (SiO2). This elastic film is formed, for example, by thermal oxidation of one surface of a silicon single crystal substrate. The second layer is, for example, an insulating film composed of zirconium oxide (ZrO2). This 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 stacked configuration of the first and second layers described above, and may be composed of, for example, a single layer or three or more layers.

[0037] On the surface of the diaphragm 51e facing the Z1 direction, M drive elements 51f are arranged in each of the first row L1 and the second row L2, each corresponding to a nozzle N. Each drive element 51f is a passive element that deforms in response to the supply of a drive signal Com. Each drive element 51f is elongated in a direction along the X axis in a plan view. The M drive elements 51f are arranged along the Y axis to correspond to M pressure chambers C. The drive elements 51f overlap the pressure chambers C in a plan view.

[0038] Each driving element 51f is a piezoelectric element, and although not shown in the figure, it has a first electrode, a piezoelectric layer, and a second electrode, which are stacked in this order in the Z1 direction. One of the first and second electrodes is an individual electrode that is spaced apart from each other for each driving element 51f, and a supply signal Vin is applied to this electrode. The other electrode is a common strip-shaped electrode that extends along the Y axis so as to be continuous across 0.5 × M driving elements 51f, and an offset potential VBS is supplied to this electrode. Examples of metallic materials for these electrodes include platinum (Pt), aluminum (Al), nickel (Ni), gold (Au), and copper (Cu), and one of these can be used alone or two or more can be used in combination in the form of an alloy or stacking. The piezoelectric layer is made of a piezoelectric material such as lead zirconate titanate (Pb(Zr,Ti)O3) and, for example, is a strip-shaped layer extending along the Y-axis so as to be continuous across 0.5 × M drive elements 51f. However, the piezoelectric layer may be a single unit across the 0.5 × M drive elements 51f. In this case, the piezoelectric layer is provided with through holes extending along the X-axis in regions corresponding to the gaps between adjacent pressure chambers C in a plan view. When the diaphragm 51e vibrates in conjunction with the deformation of the drive elements 51f, the pressure in the pressure chamber C fluctuates, causing ink to be ejected from the nozzle N.

[0039] The protective plate 51g is a plate-shaped member installed on the surface of the diaphragm 51e facing the Z1 direction, protecting the M drive elements 51f and reinforcing the mechanical strength of the diaphragm 51e. Here, the M 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.

[0040] Case 51h is a component for storing ink supplied to M pressure chambers C. Case 51h is made of, for example, a resin material. Each of the first row L1 and second row L2 of Case 51h is provided with a space R2. Space R2 is in communication with the aforementioned space R1 and, together with space R1, functions as a reservoir R for storing ink supplied to the M pressure chambers C. 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 channel Ra.

[0041] The vibration absorber 51d, also called the compliance substrate, is a flexible resin film that forms the wall surface of the reservoir R and absorbs pressure fluctuations of the ink in the reservoir R. The vibration absorber 51d may also be a flexible thin plate made of metal. The surface of the vibration absorber 51d facing the Z1 direction is joined to the flow channel substrate 51a with an adhesive or the like.

[0042] 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 COF (Chip On Film), FPC (Flexible Printed Circuit), or FFC (Flexible Flat Cable). In this embodiment, a switching circuit 52 for supplying a drive voltage to each drive element 51f is mounted on the wiring board 51i.

[0043] As illustrated in Figure 3, one ejection unit D includes one drive element 51f, one pressure chamber C, and one nozzle N. That is, M drive elements 51f correspond one-to-one with M pressure chambers C. A drive element 51f corresponding to a pressure chamber C means a drive element 51f that overlaps with part or all of the pressure chamber C in a plan view in the Z2 direction, as can be understood from Figure 3, etc. When a drive signal Com is supplied to a drive element 51f based on a print data signal SI, the drive element 51f is driven by the drive signal Com, causing the ink in the pressure chamber C to be ejected from the nozzle N.

[0044] A4: Driving element 51f Figure 4 is a diagram illustrating the switching circuit 52. The drive element 51f is driven by the supply signal Vin from the switching circuit 52. The switching circuit 52 will be described below based on Figure 4.

[0045] As shown in Figure 4, the switching circuit 52 is connected to wiring LHa. Wiring LHa is a signal line that transmits the drive signal Com. In Figure 4, for each integer m from 1 to M, one of the first and second electrodes of the aforementioned drive element 51f is shown as electrode Zd[m] and the other as electrode Zu[m]. Wiring LHd is connected to electrode Zd[m]. Wiring LHd is a power supply line to which the offset potential VBS is supplied.

[0046] The switching circuit 52 includes M switches SWa[1] to SWa[M], and a connection state specifying circuit 52a that specifies the connection state of these switches.

[0047] For each integer m from 1 to M, the switch SWa[m] is a switch that toggles between conduction and non-conductivity between the wiring LHa for the transmission of 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.

[0048] The connection state specification circuit 52a generates connection state specification signals SLa[1] to SLa[M] that specify the on / off state of switches SWa[1] to SWa[M] based on the clock signal CLK, print data signal SI, latch signal LAT, and change signal CH supplied from the control circuit 21.

[0049] For example, although not shown in the diagram, the connection state designation circuit 52a has multiple transfer circuits, multiple latch circuits, and multiple decoders so as to correspond one-to-one with the drive elements 51f[1] to 51f[M]. Of these, the transfer circuits are supplied with a print data signal SI. Here, the print data signal SI includes an individual designation signal Sd, as shown in Figure 6, for each drive element 51f. The individual designation signals Sd are supplied serially, and for example, the individual designation signals Sd are transferred sequentially to the multiple transfer circuits in synchronization with the clock signal CLK. The latch circuits latch the individual designation signals Sd supplied to the transfer circuits based on the latch signal LAT. The decoders generate connection state designation signals SLa[m], SLb[m], and SLc[m] for each integer m from 1 to M, based on the individual designation signals Sd and the latch signal LAT.

[0050] For each integer m from 1 to M, the on / off state of the switch SWa[m] is switched according to the connection state specification signal SLa[m] generated as described above. For example, the switch SWa[m] is on when the connection state specification signal SLa[m] is high level and off when it is low level. As described above, the switching circuit 52 supplies a part or all of the waveform included in the drive signal Com as a supply signal Vin to the drive elements 51f of one or more discharge units D selected from the M discharge units D.

[0051] A5: About mist To improve the ejection performance, which is one or both of the amount and speed of ink ejected from nozzle N, it is conceivable to generate a drive signal Com having an ejection pulse based on the natural vibration period Tc of the ejection unit D. The ejection pulse causes ink to be ejected from nozzle N.

[0052] Furthermore, during ink ejection, fine, misty ink droplets, or what is commonly known as mist, may be generated due to the trailing of the ejected ink. When mist is generated, it can adhere to the area around nozzle N, potentially causing deterioration in ejection performance and resulting in ejection failure.

[0053] Furthermore, the drive signal Com may have a large-dot ejection pulse that ejects an amount of ink corresponding to a large dot, and a small-dot ejection pulse that ejects an amount of ink corresponding to a small dot. Hereinafter, the large-dot ejection pulse and the small-dot ejection pulse may be referred to simply as the ejection pulse. The inventors' experiments have shown that if the ejection speed of the ejection pulse is set to the extent desired by the manufacturer of the liquid ejection head 50, mist may be generated in the ejection pulse. Hereinafter, this ejection pulse may be referred to as the ejection pulse in the comparative embodiment. Furthermore, each of the two types of ejection pulses in the comparative embodiment may be referred to as the large-dot ejection pulse in the comparative embodiment and the small-dot ejection pulse in the comparative embodiment. The manufacturer of the liquid ejection head 50 may also be referred to as the head manufacturer. The reason why mist is generated in the small-dot ejection pulse in the comparative embodiment will be explained using Figure 6.

[0054] Figure 5 is a diagram illustrating the reason for mist generation in the small dot ejection pulse in the comparative configuration. Graph g1 in Figure 5 shows the potential of the small dot ejection pulse WSa and the ink pressure in the ejection unit D in the comparative configuration. The pressure characteristic CHPa shown in graph g1 shows the characteristics of the ink pressure in the ejection unit D when the small dot ejection pulse WSa in the comparative configuration is supplied to the ejection unit D. The horizontal axis of graph g1 represents time, the vertical axis of graph g1 represents potential relative to the small dot ejection pulse WSa, and the vertical axis of graph g1 represents pressure relative to the pressure in the ink. In graph g1, [μs] means microseconds, which is the unit of time, [V] means volts, which is the unit of potential, and [kPa] means kilopascals, which is the unit of pressure.

[0055] In the comparative embodiment, the small dot discharge pulse WSa includes a first depressurization potential change element Pwd1a, a first potential maintenance element Pwh1a, a first pressurization potential change element Pwc1a, a third potential maintenance element Pwh3a, a second depressurization potential change element Pwd2a, a fourth potential maintenance element Pwh4a, a second pressurization potential change element Pwc2a, a second potential maintenance element Pwh2a, and a third depressurization potential change element Pwd3a. Hereinafter, the first depressurization potential change element Pwd1a, the second depressurization potential change element Pwd2a, and the third depressurization potential change element Pwd3a may be referred to as the depressurization potential change element Pwda without distinction. The first pressurization potential change element Pwc1a and the second pressurization potential change element Pwc2a may be referred to as the pressurization potential change element Pwca without distinction. The first potential-maintaining element Pwh1a, the third potential-maintaining element Pwh3a, the fourth potential-maintaining element Pwh4a, and the second potential-maintaining element Pwh2a are sometimes referred to collectively as potential-maintaining element Pwha.

[0056] The depressurizing potential changing element Pwda drives the drive element 51f so that the pressure of the ink in pressure chamber C decreases. The pressurizing potential changing element Pwca drives the drive element 51f so that the pressure of the ink in pressure chamber C increases. The potential maintaining element Pwha maintains the potential from the beginning to the end of the potential maintaining element Pwha.

[0057] The starting point of the first pressure-reducing potential-changing element Pwd1a coincides with the starting point of the small-dot discharge pulse WSa. The first pressure-reducing potential-changing element Pwd1a changes from a reference potential E0, which is the starting potential of the small-dot discharge pulse WSa, to a potential E1a, thereby creating negative pressure in the pressure chamber C. The reference potential E0 is approximately 9.6 [V]. The potential E1a is approximately 0 [V]. The rate of potential change of the first pressure-reducing potential-changing element Pwd1a is greater than 2 V / microsecond. The rate of potential change is the value obtained by dividing the potential change amplitude by the length of the period during which the potential changed. The potential change amplitude is the potential difference between the potential at the start time and the potential at the end time of the period during which the potential changed. In this specification, the potential difference between two potentials is the absolute value of the difference between the value of one potential and the value of the other potential.

[0058] The first potential-maintaining element Pwh1a is connected to the end of the first depressurizing potential-changing element Pwd1a, maintaining the potential E1a. The first pressurizing potential-changing element Pwc1a is connected to the end of the first potential-maintaining element Pwh1a, changing the potential from E1a to E2a and creating positive pressure in the pressure chamber C. The potential E2a is approximately 16[V]. The third potential-maintaining element Pwh3a is connected to the end of the first pressurizing potential-changing element Pwc1a, maintaining the potential E2a. The second depressurizing potential-changing element Pwd2a changes the potential from E2a to E3a and creates negative pressure in the pressure chamber C. The potential E3a is approximately 10.3[V]. The fourth potential-maintaining element Pwh4a is connected to the end of the second depressurizing potential-changing element Pwd2a, maintaining the potential E3a. The second pressurizing potential-changing element Pwc2a is connected to the end of the fourth potential-maintaining element Pwh4a, changing the potential from E3a to E4a and generating positive pressure in the pressure chamber C. The potential E4a is approximately 20[V]. The second potential-maintaining element Pwh2a is connected to the end of the second pressurizing potential-changing element Pwc2a and maintains the potential E4a. The third depressurizing potential-changing element Pwd3a is connected to the end of the second potential-maintaining element Pwh2a, changing the potential from E4a to the reference potential E0 and generating negative pressure in the pressure chamber C.

[0059] Furthermore, Figure 5 shows the state in which an ink droplet DR is being ejected from the nozzle N. More specifically, a liquid column is formed along the Z-axis (not shown) at the meniscus MN, which is the liquid surface of the nozzle N, and the ink droplet DR is ejected when the liquid column splits. A trailing TL is formed on the ink droplet DR when the liquid column is cut. Also, as can be understood from Figure 5, the meniscus MN is pulled in the Z1 direction when the third depressurization potential changing element Pwd3a is supplied to the driving element 51f. Therefore, a force acts in the Z1 direction at the Z1 position of the liquid column, i.e., at the base of the liquid column, while a force acts in the Z2 direction at the tip of the liquid column. Consequently, since two opposing forces act on the liquid column, the inventors' experiments have shown that a large amount of mist is generated when trying to achieve the ejection speed desired by the head manufacturer.

[0060] Therefore, in this embodiment, the amount of mist generated is suppressed by adjusting the timing of the splitting of the liquid column. The drive signal Com, which includes the small dot discharge pulse WS in this embodiment, will be explained with reference to Figures 6 and 7.

[0061] A6: Drive signal COM Figure 6 is a diagram illustrating the drive signal Com for generating the supply signal Vin supplied to the head chip 51. In this embodiment, the operating period of the liquid dispensing device 100 includes one or more unit periods Tu. Generally, the liquid dispensing device 100 forms the image shown in the image data Img by dispensing liquid one or more times from each dispensing unit D over multiple continuous or intermittent unit periods Tu.

[0062] As shown in Figure 6, the control circuit 21 outputs a latch signal LAT having a pulse PlsL and a change signal CH having a pulse PlsC. Thus, the control circuit 21 defines a unit period Tu as the period from the rising edge of pulse PlsL to the rising edge of the next pulse PlsL. The specific length or period of the unit period Tu is not particularly limited. Furthermore, the control circuit 21 divides the unit period Tu into two control periods Tu1 and Tu2 using pulse PlsC.

[0063] The print data signal SI includes individual designation signals Sd[1] to Sd[M] that specify the mode of driving the ejection units D[1] to D[M] in each unit period Tu. As described above, the connection state designation circuit 52a generates a connection state designation signal SLa[m] for each integer m from 1 to M in the unit period Tu, based on the individual designation signal Sd[m].

[0064] The individual designation signal Sd[m] is a signal that, for each unit period Tu, specifies to the ejection unit D[m] one of three drive modes: ejection of an amount of ink corresponding to a large dot, ejection of an amount of ink corresponding to a small dot, or no ejection.

[0065] As shown in Figure 6, the drive signal generation circuit 24 outputs a drive signal Com in one unit period Tu, having in this order an initial potential maintenance element as, a small dot discharge pulse WS, a connecting element ai, a large dot discharge pulse WL, and an ending potential maintenance element ae. The portion including the start time of the initial potential maintenance element as, the small dot discharge pulse WS, and the connecting element ai is provided within the control period Tu1. The portion including the end time of the connecting element ai, the large dot discharge pulse WL, and the ending potential maintenance element ae are provided within the control period Tu2.

[0066] The start potential maintenance element as maintains the reference potential E0 from the start of one unit period Tu to the start of the small dot discharge pulse WS. The connection element ai maintains the reference potential E0 from the end of the small dot discharge pulse WS to the start of the large dot discharge pulse WL. The end potential maintenance element ae maintains the reference potential E0 from the end of the large dot discharge pulse WL to the end of one unit period Tu.

[0067] Each element of the small dot ejection pulse WS will be explained using Figure 7. The large dot ejection pulse WL has, in this order, a filling element Pld1, a potential maintenance element Plh1, an ejection element Plc1, a vibration damping maintenance element Plh2, and a vibration damping expansion element Pld2. The filling element Pld1 changes from a reference potential E0 to a minimum potential ELA, creating negative pressure in the pressure chamber C. The minimum potential ELA is the lowest potential in the large dot ejection pulse WL. The end of the filling element Pld1 is connected to the beginning of the potential maintenance element Plh1. The potential maintenance element Plh1 maintains the minimum potential ELA. The end of the potential maintenance element Plh1 is connected to the ejection element Plc1. The ejection element Plc1 changes from a minimum potential ELA to a maximum potential EHA, creating positive pressure in the pressure chamber C. The maximum potential EHA is the highest potential in the large dot ejection pulse WL. When the drive element 51f receives a supply from the ejection element Plc1, it ejects ink droplets from the nozzle N. The vibration damping maintenance element Plh2 maintains the highest potential EHA from the end of the discharge element Plc1. The vibration damping expansion element Pld2 starts the potential change from the end of the vibration damping maintenance element Plh2 and expands the pressure chamber C. The vibration damping expansion element Pld2 changes the potential from the highest potential EHA to the reference potential E0.

[0068] For each integer m from 1 to M, if the individual designation signal Sd[m] specifies to the ejection unit D[m] to eject an amount of ink equivalent to a small dot, the connection state designation circuit 52a is set to a high level during control period Tu1 and to a low level during control period Tu2. In this case, the ejection unit D[m] is driven by the small dot ejection pulse WS during control period Tu1 and ejects an amount of ink equivalent to a small dot.

[0069] For each integer m from 1 to M, if the individual designation signal Sd[m] specifies to the ejection unit D[m] to eject an amount of ink equivalent to a large dot, the connection state designation circuit 52a is set to a low level during control period Tu1 and to a high level during control period Tu2. In this case, the ejection unit D[m] is driven by the large dot ejection pulse WL during control period Tu2 to eject ink.

[0070] In Figure 6, the unit period Tu is divided into two control periods Tu1 and Tu2, and the drive signal Com has one discharge pulse for each of the control periods Tu1 and Tu2, but this is not limited to this. For example, the drive signal Com may have two separate signals, drive signal Com-A and drive signal Com-B, with one signal having a small dot discharge pulse WS and the other having a large dot discharge pulse WL.

[0071] Figure 7 is a diagram illustrating each element of the small dot ejection pulse WS. Furthermore, graph g2 shown in Figure 7 shows the potential of the small dot ejection pulse WS and the pressure of the ink in the ejection unit D. The pressure characteristic CHP shown in graph g2 shows the characteristics of the ink pressure in the ejection unit D when the small dot ejection pulse WS is supplied to the ejection unit D.

[0072] The small dot discharge pulse WS has, in this order, a first depressurization potential change element Pwd1, a first potential maintenance element Pwh1, a first pressurization potential change element Pwc1, a third potential maintenance element Pwh3, a second depressurization potential change element Pwd2, a fourth potential maintenance element Pwh4, a second pressurization potential change element Pwc2, a second potential maintenance element Pwh2, and a third depressurization potential change element Pwd3. Hereinafter, the first depressurization potential change element Pwd1, the second depressurization potential change element Pwd2, and the third depressurization potential change element Pwd3 may be referred to as the depressurization potential change element Pwd without distinction. The first pressurization potential change element Pwc1 and the second pressurization potential change element Pwc2 may be referred to as the pressurization potential change element Pwc without distinction. The first potential-maintaining element Pwh1, the third potential-maintaining element Pwh3, the fourth potential-maintaining element Pwh4, and the second potential-maintaining element Pwh2 are sometimes referred to simply as potential-maintaining elements Pwh. Note that the small dot discharge pulse WS is an example of the "first discharge pulse".

[0073] The depressurizing potential changing element Pwd drives the drive element 51f so that the pressure of the ink in the pressure chamber C decreases. The pressurizing potential changing element Pwc drives the drive element 51f so that the pressure of the ink in the pressure chamber C increases. The potential maintaining element Pwh maintains the potential from the beginning to the end of the potential maintaining element Pwh. The potential E1 maintained by the first potential maintaining element Pwh1 is approximately the same as potential E1a. The potential E2 maintained by the third potential maintaining element Pwh3 is approximately the same as potential E2a. The potential E3 maintained by the fourth potential maintaining element Pwh4 is approximately the same as potential E3a. The potential E4 maintained by the second potential maintaining element Pwh2 is approximately the same as potential E4a.

[0074] The waveform information CI shown in Figure 2 defines the small dot discharge pulse WS and the large dot discharge pulse WL of the drive signal Com. Specifically, the waveform information CI includes termination information that indicates the termination time and termination potential of each element of the drive signal Com. For example, the waveform information CI includes termination information for the start potential maintenance element as, termination information for the small dot discharge pulse WS, termination information for the connection element ai, termination information for the large dot discharge pulse WL, and termination information for the end potential maintenance element ae. The termination information for the small dot discharge pulse WS includes the termination information for the first depressurizing potential change element Pwd1, the termination information for the first potential maintenance element Pwh1, the termination information for the first pressurizing potential change element Pwc1, the termination information for the third potential maintenance element Pwh3, the termination information for the second depressurizing potential change element Pwd2, the termination information for the fourth potential maintenance element Pwh4, the termination information for the second pressurizing potential change element Pwc2, the termination information for the second potential maintenance element Pwh2, and the termination information for the third depressurizing potential change element Pwd3. The termination information for the large dot discharge pulse WL includes the termination information for the filling element Pld1, the termination information for the potential maintenance element Plh1, the termination information for the discharge element Plc1, the termination information for the vibration damping maintenance element Plh2, and the termination information for the vibration damping expansion element Pld2. The information indicating the termination time included in the termination information of the termination potential maintenance element ae represents one unit period Tu.

[0075] The durations of each element in the small dot discharge pulse WS are described below. For example, the duration Twd1 of the first depressurization potential change element Pwd1 is 0.63 times the length of Tc. The duration Twh1 of the first potential maintenance element Pwh1 is 0.15 times the length of Tc. The duration Twc1 of the first pressurization potential change element Pwc1 is 0.26 times the length of Tc. The duration Twh3 of the third potential maintenance element Pwh3 is 0.16 times the length of Tc. The duration Twd2 of the second depressurization potential change element Pwd2 is 0.14 times the length of Tc. The duration Twh4 of the fourth potential maintenance element Pwh4 is 0.10 times the length of Tc. The duration Twc2 of the second pressurization potential change element Pwc2 is 0.20 times the length of Tc. The duration Twh2 of the second potential maintenance element Pwh2 is 0.76 times the length of Tc. The duration Twd3 of the third pressure-reducing potential change element Pwd3 is 0.63 times the length of Tc. The differences from the elements of the small dot discharge pulse WSa in the comparative embodiment are described below.

[0076] The potential change range V1 of the first depressurization potential change element Pwd1 is 40% or more of the potential change range V2 of the first pressurization potential change element Pwc1. The potential change range V1 is the potential difference from the reference potential E0 to potential E1. The potential change range V2 is the potential difference from potential E1 to potential E2. For example, the potential change range V1 is 60% of the potential change range V2.

[0077] Furthermore, the rate of change of the potential of the first depressurization potential change element Pwd1 is between 1 V / microsecond and 2 V / microsecond. The rate of change of the potential of the first depressurization potential change element Pwd1 is the value obtained by dividing the potential change width V1 by the length of the period Twd1 of the first depressurization potential change element Pwd1. The rate of change of the potential of the first depressurization potential change element Pwd1 is 1.92 V / microsecond.

[0078] Furthermore, the period Twh1 of the first potential-maintaining element Pwh1 and the period Twh3 of the third potential-maintaining element Pwh3 are between 0.1 and 0.25 times Tc. For example, as mentioned above, period Twh1 is 0.15 times Tc, and as mentioned above, period Twh3 is 0.16 times Tc.

[0079] Furthermore, the rate of change of the potential of the first pressurized potential change element Pwc1 is 4 V / microsecond or more. For example, the rate of change of the potential of the first pressurized potential change element Pwc1 is 7.62 V / microsecond. It is also preferable that the rate of change of the potential of the second depressurized potential change element Pwd2 and the rate of change of the potential of the second pressurized potential change element Pwc2 are also 4 V / microsecond or more. For example, the rate of change of the potential of the second depressurized potential change element Pwd2 is 5.45 V / microsecond. The rate of change of the potential of the second pressurized potential change element Pwc2 is 6.25 V / microsecond. On the other hand, the rate of change of the potential of the third depressurized potential change element Pwd3 is 2.08 V / microsecond, which is less than 4 V / microsecond.

[0080] Furthermore, the period Twd1 of the first depressurization potential change element Pwd1 is less than or equal to Tc. For example, as mentioned above, the period Twd1 is 0.63 times Tc.

[0081] Furthermore, the period Tc2d3, from the start of the second pressurized potential change element Pwc2 to the start of the third depressurized potential change element Pwd3, is 0.75 times or more Tc. For example, the period Tc2d3 is 0.96 times Tc.

[0082] Furthermore, the period Tc1c2, from the start of the first pressurized potential change element Pwc1 to the start of the second pressurized potential change element Pwc2, is between 0.5 and 0.75 times the length of Tc. For example, the period Tc1c2 is 0.66 times the length of Tc.

[0083] Furthermore, the potential change range V4 of the second pressurized potential change element Pwc2 is between 50% and 70% of the potential change range V2 of the first pressurized potential change element Pwc1. The potential change range V4 is the potential difference from potential E3 to potential E4. For example, the potential change range V4 is 63% of the potential change range V2.

[0084] Furthermore, the duration Twh2 of the second potential maintenance element Pwh2 is 0.5 times or more Tc. For example, the duration Twh2 is 0.76 times Tc.

[0085] The potential change range V3 of the second pressure-reducing potential change element Pwd2 is between 20% and 50% of the potential change range V2. The potential change range V3 is the potential difference from potential E2 to potential E3. For example, the potential change range V3 is 38% of the potential change range V2.

[0086] The pressure characteristic CHP will be explained by comparing it with the pressure characteristic CHPa. In the comparative embodiment, the rate of change of the potential of the first depressurization potential change element Pwd1a is greater than 2V / microsecond, so as shown in the pressure characteristic CHPa, the pressure oscillations generated in the ink within the ejection section D become larger. Specifically, as shown in the pressure characteristic CHPa, from the start of the first depressurization potential change element Pwd1a to the end of the first pressurization potential change element Pwc1a, the ink pressure decreases to approximately -200kPa and then rises to approximately 650kPa. On the other hand, in this embodiment, the rate of change of the potential of the first depressurization potential change element Pwd1 is between 1V / microsecond and 2V / microsecond, so as shown in the pressure characteristic CHP, the magnitude of the pressure oscillations generated in the ink within the ejection section D is suppressed compared to the comparative embodiment. Specifically, as shown in the pressure characteristic CHP, from the start of the first depressurization potential change element Pwd1 to the end of the first pressurization potential change element Pwc1, the ink pressure decreases to approximately 0 kPa and then increases to approximately 450 kPa. However, the amplitude of the ink pressure oscillation in the pressure characteristic CHP is smaller than the amplitude of the ink pressure oscillation in the pressure characteristic CHPa.

[0087] Furthermore, Figure 7 shows the state of the meniscus MN inside the nozzle N when each element of the small dot discharge pulse WS is supplied to the drive element 51f. At the start of the first depressurization potential change element Pwd1, the meniscus MN is positioned approximately parallel to the XY plane. At the start of the first potential maintenance element Pwh1, the meniscus MN is pulled in the Z1 direction by the first depressurization potential change element Pwd1, and the tip of the central part of the meniscus MN is positioned in the Z1 direction relative to the nozzle surface FN. During the period of the first potential maintenance element Pwh1, the tip of the central part of the meniscus MN gradually moves in the Z2 direction, but even at the start of the first pressurization potential change element Pwc1, the tip of the meniscus MN is positioned in the Z1 direction relative to the nozzle surface FN.

[0088] The first pressurized potential-changing element Pwc1 pushes the meniscus MN in the Z2 direction, and at the start of the third potential-maintaining element Pwh3, the meniscus MN is located near the opening of the nozzle N. At the start of the second depressurized potential-changing element Pwd2, the meniscus MN pushed in the Z2 direction by the first pressurized potential-changing element Pwc1 forms a liquid column LC protruding in the Z2 direction.

[0089] At the start of the fourth potential maintenance element Pwh4, the second depressurization potential change element Pwd2 exerts a force in the Z1 direction at the base of the liquid column LC, while a force in the Z2 direction acts at the tip of the liquid column LC in the Z2 direction. Therefore, two opposing forces act on the liquid column LC, causing it to grow along the Z axis.

[0090] Subsequently, the second pressurized potential-changing element Pwc2 pushes the ink in nozzle N out again in the Z2 direction. At the start of the second potential-maintaining element Pwh2, the tip of the liquid column LC continues to move in the Z2 direction and grows along the Z-axis direction. During the period of the second potential-maintaining element Pwh2, ink is pushed out from nozzle N to the base of the liquid column LC by the second pressurized potential-changing element Pwc2. Furthermore, at the start of the third depressurized potential-changing element Pwd3, the ink pushed out by the second pressurized potential-changing element Pwc2 at the base of the liquid column LC moves toward the tip of the liquid column LC, and the tip of the liquid column LC also moves in the Z2 direction, causing the liquid column LC to grow thinner and longer along the Z-axis direction.

[0091] As the third pressure-reducing potential-changing element Pwd3 is supplied and the ink in the nozzle N is drawn in the Z1 direction, the liquid column LC splits between the ink pushed out by the second pressure-reducing potential-changing element Pwc2 and the tip portion, and an ink droplet DR is ejected. At the time the liquid column LC splits, the base portion of the liquid column LC is moving in the Z1 direction, but the splitting of the liquid column LC occurs mainly due to the action of surface tension in the portion where two opposing forces are not acting between the ink pushed out by the second pressure-reducing potential-changing element Pwc2 and the tip portion. By setting the duration Twh2 of the second potential maintenance element Pwh2 after the second pressurizing potential change element Pwc2 to at least 0.5 times the length of Tc, the tip portion of the liquid column LC moves in the Z2 direction. Without applying a force to pull the liquid column LC in the Z1 direction due to the displacement of the driving element 51f, a constriction that becomes a splitting point is created in the liquid column LC due to the velocity distribution between the tip, the middle, and the base of the liquid column LC. The tip portion of the liquid column LC splits into ink droplets DR mainly due to the action of surface tension. Therefore, compared to the comparative embodiment, mist generation can be suppressed.

[0092] At the end of the third depressurization potential change element Pwd3, the ink droplet DR has moved in the Z2 direction, and the tip of the liquid column LC, which has split from the ink droplet DR, has moved in the Z1 direction.

[0093] A7: Operation of the first embodiment Figure 8 is a flowchart showing the operation of the liquid dispensing device 100 in the first embodiment. The series of processes shown in Figure 8 are executed when image data Img is received from an external device 200. In step S2, the control circuit 21 acquires waveform information CI from the storage circuit 22. Next, in step S4, the control circuit 21 generates a waveform specification signal dCom based on the waveform information CI. Then, in step S6, the control circuit 21 outputs the waveform specification signal dCom to the drive signal generation circuit 24. By executing step S6, the drive signal generation circuit 24 outputs a drive signal Com to the liquid dispensing head 50. By outputting the waveform specification signal dCom to the drive signal generation circuit 24, the control circuit 21 causes the drive signal generation circuit 24 to supply the drive signal Com to the dispensing unit D. After the completion of the process in step S6, in step S8, the control circuit 21 outputs the print data signal SI generated based on the image data Img to the liquid dispensing head 50 for each unit period Tu. Let's assume that for any m from 1 to M, the individual designation signal Sd[m] included in the print data signal SI is a signal that specifies the amount of ink to be ejected corresponding to a small dot. In this assumption, an example of the "first step" is when the drive signal generation circuit 24 supplies the first depressurization potential change element Pwd1 included in the small dot ejection pulse WS to the drive element 51f of the ejection unit D[m], and an example of the "second step" is when the first pressure potential change element Pwc1 included in the small dot ejection pulse WS to the drive element 51f of the ejection unit D[m]. When an image is formed on the medium PP after executing step S8 multiple times, the control circuit 21 terminates the series of processes shown in Figure 8.

[0094] A8: Summary of the first embodiment The liquid dispensing device 100 includes a dispensing unit D having a nozzle N for dispensing ink, a pressure chamber C communicating with the nozzle N, and a drive element 51f that drives to cause pressure fluctuations in the ink in the pressure chamber C in response to a supplied drive signal Com, and a drive signal generation circuit 24 that generates the drive signal Com. The drive signal Com includes a small dot dispensing pulse WS that causes ink to be dispensed from the nozzle N. The small dot dispensing pulse WS includes a first depressurization potential change element Pwd1 that drives the drive element 51f to decrease the pressure of the ink in the pressure chamber C, and a first pressurization potential change element Pwc1 that drives the drive element 51f after the first depressurization potential change element Pwd1 to increase the pressure of the ink in the pressure chamber C so that the liquid surface protrudes from the nozzle N. The potential change range V1 of the first depressurization potential change element Pwd1 is 40% or more of the potential change range V2 of the first pressurization potential change element Pwc1, and the rate of potential change of the first depressurization potential change element Pwd1 is 1 V / microsecond or more and 2 V / microsecond or less. Furthermore, in the first embodiment, it can also be defined as a method for driving a liquid dispensing device 100 having a dispensing unit D and a drive signal generation circuit 24. The drive signal generation circuit 24 performs the steps of supplying a first pressure-reducing potential-changing element Pwd1 to the drive element 51f of the dispensing unit D, and supplying a first pressure-reducing potential-changing element Pwc1 to the drive element 51f of the dispensing unit D. In the embodiment where the rate of change of the first pressure-reducing potential-changing element Pwd1 is greater than 2V / microsecond, the amplitude of pressure oscillations generated in the ink within the ejection section D becomes large, as shown in the comparative embodiment, making trailing more likely. On the other hand, in the embodiment where the rate of change of the first pressure-reducing potential-changing element Pwd1 is less than 1V / microsecond, it takes time to sufficiently fill the pressure chamber C with ink, and the amplitude of pressure oscillations generated in the ink within the ejection section D becomes too small. If the amplitude of pressure oscillations generated in the ink within the ejection section D becomes too small, it becomes difficult to ensure the speed of ink droplets DR separated from the meniscus MN at the first pressure-reducing potential-changing element Pwc1, which follows the first pressure-reducing potential-changing element Pwd1. As described above, according to the first embodiment, the pressure chamber C is sufficiently filled with ink before the meniscus MN is ejected, and the amplitude of pressure oscillations generated in the ink within the ejection section D is not made excessively large, so that trailing TL can be reduced while ensuring the ejection speed of ink droplets DR separated from the meniscus MN.

[0095] Furthermore, the small dot discharge pulse WS also includes a first potential maintenance element Pwh1 that connects the end of the first depressurization potential change element Pwd1 to the start of the first pressurization potential change element Pwc1, maintaining the potential E1 as a predetermined potential. The duration of the first potential maintenance element Pwh1 is between 0.1 and 0.25 times Tc. In the embodiment where the duration of the first potential maintenance element Pwh1 is longer than 0.25 times Tc, the timing at which the ink in the ejection unit D is pressurized by the supply of the first pressurized potential change element Pwc1 coincides with the timing at which the pressure of the ink in the ejection unit D decreases, causing the pressure oscillation of the ink in the ejection unit D to be attenuated. On the other hand, in the first embodiment, compared to the embodiment where the duration of the first potential maintenance element Pwh1 is longer than 0.25 times Tc, the timing at which the ink in the ejection unit D is pressurized by the supply of the first pressurized potential change element Pwc1 coincides with the timing at which the pressure of the ink in the ejection unit D increases due to pressure oscillation. Therefore, according to the first embodiment, the increase in the pressure of the ink in the ejection unit D can be synergistically increased, so that the ejection speed of the ink droplet DR by the small dot ejection pulse WS can be ensured.

[0096] Furthermore, the rate of change of the potential of the first pressurized potential change element Pwc1 is 4V / microsecond or more. According to the first embodiment, compared to an embodiment in which the rate of change of the first pressurized potential changing element Pwc1 is less than 4V / microsecond, the ejection speed of ink droplets DR by the small dot ejection pulse WS can be ensured.

[0097] Furthermore, the first depressurization potential change element Pwd1 is the period below Tc. In the embodiment where the duration of the first depressurization potential change element Pwd1 is longer than Tc, the amplitude of pressure oscillations generated in the ink within the ejection section D becomes too small, making it difficult to ensure the velocity of the ink droplets DR separated from the meniscus MN by the first pressurization potential change element Pwc1 that follows the first depressurization potential change element Pwd1. Therefore, according to the first embodiment, compared to the embodiment where the duration of the first depressurization potential change element Pwd1 is longer than Tc, the velocity of the ink droplets DR separated from the meniscus MN can be ensured by the first pressurization potential change element Pwc1.

[0098] Furthermore, the small dot ejection pulse WS further includes a second depressurizing potential changing element Pwd2 that drives a drive element 51f to decrease the ink pressure in the pressure chamber C after the first pressurizing potential changing element Pwc1, a second pressurizing potential changing element Pwc2 that drives a drive element 51f to increase the ink pressure in the pressure chamber C after the second depressurizing potential changing element Pwd2, a second potential maintaining element Pwh2 that maintains the potential from the end of the second pressurizing potential changing element Pwc2, and a third depressurizing potential changing element Pwd3 connected to the end of the second potential maintaining element Pwh2 that drives a drive element 51f to decrease the ink pressure in the pressure chamber C. The period Tc2d3 from the start of the second pressurizing potential changing element Pwc2 to the start of the third depressurizing potential changing element Pwd3 is 0.75 times or more Tc. The small dot ejection pulse WS repeatedly switches between a pressurized potential change element Pwc and a depressurized potential change element Pwd to adjust the weight of the ink droplet DR. According to the first embodiment, trailing TL can be reduced compared to an embodiment in which the period Tc2d3 is less than 0.75 times Tc.

[0099] Furthermore, the period Tc1c2 from the start of the first pressurized potential change element Pwc1 to the start of the second pressurized potential change element Pwc2 is between 0.5 and 0.75 times Tc, and the potential change range V4 of the second pressurized potential change element Pwc2 is between 50% and 70% of the potential change range V2 of the first pressurized potential change element Pwc1. According to the first embodiment, when a portion of the liquid column LC separates from the ink in the nozzle N, the rear end of the liquid column LC can be made to follow the front end of the liquid column LC without reducing its velocity. By making the rear end of the liquid column LC follow the front end of the liquid column LC without reducing its velocity, trailing TL can be reduced.

[0100] Furthermore, the duration Twh2 of the second potential maintenance element Pwh2 is 0.5 times or more than Tc. In the first embodiment, compared to the embodiment in which the period Twh2 is less than 0.5 times Tc, pressure fluctuations occurring in the ink in the pressure chamber C due to the driving of the driving element 51f after the second pressurized potential change element Pwc2 can be suppressed. As a result, according to the first embodiment, the pressure oscillation of the ink is suppressed, and thus trailing TL can be reduced.

[0101] The small dot discharge pulse WS further includes a third potential maintenance element Pwh3 that maintains the potential from the end of the first pressurized potential change element Pwc1. The duration Twh3 of the third potential maintenance element Pwh3 is between 0.1 and 0.25 times Tc. Furthermore, the potential change width V3 of the second depressurized potential change element Pwd2 is between 20% and 50% of the potential change width V2 of the first pressurized potential change element Pwc1. According to the first embodiment, the weight of the ink droplet DR can be adjusted to a desired amount without destabilizing the meniscus MN.

[0102] 2. Variations Each of the forms exemplified above can be modified in various ways. Specific examples of modifications that can be applied to each of the aforementioned forms are given below. Two or more forms arbitrarily selected from the following examples can be combined as appropriate, provided they do not contradict each other.

[0103] 2-1. First variation In the first embodiment, the period Tc2d3 was 0.75 times or more of Tc, but it may be less than 0.75 times Tc.

[0104] Figure 9 is a diagram illustrating the small dot ejection pulse WSb in the first modified example. Furthermore, graph g3 in Figure 9 shows the potential of the small dot ejection pulse WSb and the pressure of the ink in the ejection unit D. The pressure characteristic CHPb shown in graph g3 shows the characteristics of the ink pressure in the ejection unit D when the small dot ejection pulse WSb is supplied to the ejection unit D.

[0105] The small dot discharge pulse WSb differs from the small dot discharge pulse WS in that it has a second potential maintenance element Pwh2b instead of the second potential maintenance element Pwh2, and a third pressure reduction potential change element Pwd3b instead of the third pressure reduction potential change element Pwd3.

[0106] The second potential maintenance element Pwh2b differs from the second potential maintenance element Pwh2b in that its duration Twh2b is less than 0.5 times Tc. Furthermore, the third pressure-reducing potential-changing element Pwd3b differs from the third pressure-reducing potential-changing element Pwd3b in that its rate of potential change is 4V / microsecond or greater.

[0107] Even in the first modified example, the potential change range V1 of the first depressurized potential change element Pwd1 is 40% or more of the potential change range V2 of the first pressurized potential change element Pwc1, and the potential change rate of the first depressurized potential change element Pwd1 is 1 V / microsecond or more and 2 V / microsecond or less. Therefore, similar to the first embodiment, ink is sufficiently filled into the pressure chamber C before the meniscus MN is ejected, and the amplitude of pressure vibrations generated in the ink in the ejection section D is not made excessively large, so that the ejection speed of the ink droplets DR after separation from the meniscus MN can be ensured while reducing trailing TL.

[0108] 2-2. Second variation In the first embodiment, the rate of change of the first pressure-reducing potential-changing element Pwd1 was 1 V / microsecond or more and 2 V / microsecond or less, but it is not limited to this, and may be greater than 2 V / microsecond, for example.

[0109] Figure 10 is a diagram illustrating the small dot ejection pulse WSc in the second modified example. Furthermore, graph g4 shown in Figure 10 shows the potential of the small dot ejection pulse WSc and the pressure of the ink in the ejection unit D. The pressure characteristic CHPc shown in graph g4 shows the pressure characteristics of the ink in the ejection unit D when the small dot ejection pulse WSc is supplied to the ejection unit D.

[0110] The small dot discharge pulse WSc differs from the small dot discharge pulse WS in that it has a first pressure-reducing potential changing element Pwd1c instead of the first pressure-reducing potential changing element Pwd1.

[0111] The first pressure-reducing potential-changing element Pwd1c differs from the first pressure-reducing potential-changing element Pwd1c in that its rate of potential change is greater than 2V / microsecond. The duration Twd1c of the first pressure-reducing potential-changing element Pwd1c is less than or equal to Tc, but may be longer than Tc.

[0112] Even in the second modified example, the period Tc2d3 from the start of the second pressurized potential change element Pwc2 to the start of the third depressurized potential change element Pwd3 is 0.75 times or more Tc. Therefore, similar to the first embodiment, the trailing TL can be reduced compared to the embodiment where it is less than 0.75 times Tc.

[0113] 2-3. Third Variation In the embodiments described above, the small dot discharge pulse WS was an example of the "first discharge pulse," but the large dot discharge pulse WL may also be an example of the "first discharge pulse."

[0114] Figure 11 is a diagram illustrating the large dot discharge pulse WLd in the third modified example. The large dot discharge pulse WLd has a filling element Pld1d, a potential maintenance element Plh1d, a discharge element Plc1d, a vibration damping maintenance element Plh2d, and a vibration damping expansion element Pld2d in this order. The large dot discharge pulse WLd is a so-called pull-push-pull waveform. In the third modified example, the large dot discharge pulse WLd is an example of the "first discharge pulse", the filling element Pld1d is an example of the "first depressurization potential change element", the potential maintenance element Plh1d is an example of the "first potential maintenance element", and the discharge element Plc1d is an example of the "first pressurization potential change element".

[0115] The potential change range V1d of the filling element Pld1d is 40% or more of the potential change range V2d of the ejection element Plc1d. Furthermore, the rate of potential change of the filling element Pld1d is 1V / microsecond or more and 2V / microsecond or less. According to the third modification, even in the large dot ejection pulse WL, similar to the small dot ejection pulse WS in the first embodiment, the ink is sufficiently filled into the pressure chamber C before the meniscus MN is ejected, and the amplitude of the pressure oscillation generated in the ink in the ejection section D is not made excessively large, so that the ejection speed of the ink droplet DR after separation from the meniscus MN can be ensured while reducing trailing TL.

[0116] Furthermore, the period Tlh1d of the potential maintenance element Plh1d is between 0.1 and 0.25 times Tc. According to the third modified example, the increase in ink pressure within the ejection section D can be synergistically increased, thereby ensuring the ejection speed of ink droplets DR by the small dot ejection pulse WS.

[0117] Furthermore, the rate of change of the potential of the ejection element Plc1d is 4V / microsecond or more. According to the third modification, compared to the embodiment in which the rate of change of the potential of the ejection element Plc1d is less than 4V / microsecond, the ejection speed of the ink droplet DR by the large dot ejection pulse WLd can be ensured.

[0118] Furthermore, the period Tld1d of the packing element Pld1d is less than or equal to Tc. In the first embodiment, compared to the embodiment in which the period of the first depressurization potential change element Pwd1 is longer than Tc, the first pressurization potential change element Pwc1 can ensure the velocity of the ink droplet DR after separation from the meniscus MN.

[0119] 2-4. Fourth Variation In the third modification, the large dot discharge pulse WLd, which has a pull-push-pull waveform, is an example of the "first discharge pulse," but it is not limited to this. For example, a so-called pull-push waveform may also be an example of the "first discharge pulse."

[0120] Figure 12 is a diagram illustrating the large dot discharge pulse WLe in the fourth modified example. The large dot discharge pulse WLe has a filling element Pld1e, a potential maintenance element Plh1e, and a discharge element Plc1e in that order. The large dot discharge pulse WLe is a so-called pull-push waveform. In the fourth modified example, the large dot discharge pulse WLe is an example of the "first discharge pulse", the filling element Pld1e is an example of the "first depressurization potential change element", the potential maintenance element Plh1e is an example of the "first potential maintenance element", and the discharge element Plc1e is an example of the "first pressurization potential change element".

[0121] The potential change range V1e of the packing element Pld1e is approximately the same as the potential change range V2e of the discharge element Plc1e. Therefore, in the fourth modified example, the condition that the potential change range V1e is 40% or more of the potential change range V2e is also satisfied. In other words, the potential change range V1e may be greater than or equal to the potential change range V2e.

[0122] The rate of change of the potential of the packing element Pld1e is between 1 V / microsecond and 2 V / microsecond. The period Tlh1e of the potential maintenance element Plh1e is between 0.1 and 0.25 times Tc. The rate of change of the potential of the discharge element Plc1e is 4 V / microsecond or more. The period Tld1e of the packing element Pld1e is less than or equal to Tc.

[0123] 2-5. Fifth Variation In the fourth modification, the large-dot discharge pulse WLe, which is a pull-push waveform, is an example of the "first discharge pulse," but it is not limited to this. For example, a so-called pull-push-push waveform may also be an example of the "first discharge pulse."

[0124] Figure 13 is a diagram illustrating the large dot discharge pulse WLf in the fifth modified example. The large dot discharge pulse WLf has, in this order, a filling element Pld1f, a potential maintenance element Plh1f, a discharge element Plc1f, a potential maintenance element Plh3f, a discharge element Plc2f, a vibration damping maintenance element Plh2f, and a vibration damping expansion element Pld2f. The large dot discharge pulse WLf is a so-called pull-push-push waveform. In the fifth modified example, the large dot discharge pulse WLf is an example of the "first discharge pulse," the filling element Pld1f is an example of the "first depressurization potential change element," the potential maintenance element Plh1f is an example of the "first potential maintenance element," and the discharge element Plc1f is an example of the "first pressurization potential change element."

[0125] The potential change range V1f of the packing element Pld1f is greater than the potential change range V2f of the discharge element Plc1f. Therefore, in the fifth modification as well, the condition that the potential change range V1f is 40% or more of the potential change range V2f is satisfied.

[0126] The rate of change of the potential of the packing element Pld1f is between 1 V / microsecond and 2 V / microsecond. The period Tlh1f of the potential maintenance element Plh1f is between 0.1 and 0.25 times Tc. The rate of change of the potential of the discharge element Plc1f is 4 V / microsecond or more. The period Tld1f of the packing element Pld1f is less than or equal to Tc.

[0127] 2-6. Sixth Variation In the first embodiment, the first modification, and the second modification, the period Twh1 of the first potential-maintaining element Pwh1 is 0.1 times or more and 0.25 times or less of Tc, but is not limited to this. For example, the period Twh1 may be less than 0.1 times Tc or longer than 0.25 times Tc. Similarly, in the third to fifth modifications, the period Tlh1d of the potential-maintaining element Plh1 may be less than 0.1 times Tc or longer than 0.25 times Tc.

[0128] 2-7. Seventh Variation In the first embodiment, the first modification, and the second modification, and in the sixth modification based on one of the first embodiment, the first modification, and the second modification, the rate of change of the potential of the first pressurized potential changing element Pwc1 is 4V / microsecond or more, but is not limited thereto. For example, the rate of change of the potential of the first pressurized potential changing element Pwc1 may be less than 4V / microsecond. Similarly, in the third to fifth modifications, and in the sixth modification based on any one of the third to fifth modifications, the rate of change of the potential of the discharge element Plc1 may be less than 4V / microsecond.

[0129] 2-8. Variation 8 In the first embodiment, the first modification, and the second modification, and in the sixth or seventh modification based on one of the first embodiment, the first modification, and the second modification, the first pressure-reducing potential changing element Pwd1 is less than or equal to Tc, but is not limited to this. The first pressure-reducing potential changing element Pwd1 may be longer than Tc. Similarly, in the third to fifth modifications, and in the sixth or seventh modification based on any one of the third to fifth modifications, the packing element Pld1 may be longer than Tc.

[0130] 2-9. Variation 9 In the first embodiment, the first modification, and the second modification, and in the sixth to eighth modifications based on one of the first embodiment, the first modification, and the second modification, the period Tc1c2 from the start of the first pressurized potential change element Pwc1 to the start of the second pressurized potential change element Pwc2 is a period of 0.5 times or more and 0.75 times or less of Tc, but may be less than 0.5 times Tc or longer than 0.75 times Tc. Alternatively, the potential change width V4 of the second pressurized potential change element Pwc2 may be less than 50% of the potential change width V2 of the first pressurized potential change element Pwc1, or may be greater than 70%.

[0131] 2-10. Tenth variation In the first embodiment, the first modified example, and the second modified example, as well as in the sixth to ninth modified examples based on one of the first embodiment, the first modified example, and the second modified example, the period Twh2 of the second potential maintaining element Pwh2 is 0.5 times or more Tc, but may be less than 0.5 times.

[0132] 2-11. 11th Variation In the first embodiment, the first modified example, and the second modified example, as well as the sixth to tenth modified examples based on one of the first embodiment, the first modified example, and the second modified example, the period Twh3 of the third potential maintenance element Pwh3 is a period of 0.1 times or more and 0.25 times or less of Tc, and the potential change width V3 of the second depressurization potential change element Pwd2 is 20% or more and 50% or less of the potential change width V2 of the first pressurization potential change element Pwc1, but is not limited to this. For example, the period Twh3 may be less than 0.1 times Tc, or longer than 0.25 times Tc. Also, the potential change width V3 may be less than 20% of the potential change width V2, or longer than 50%.

[0133] 2-12. Twelfth Variation In the embodiments described above, a manufacturing method for a serial-type liquid dispensing device 100 in which the liquid dispensing head 50 is reciprocated in a direction along the X axis has been illustrated, but the disclosure is not limited to such embodiments. The liquid dispensing device 100 may also be a line-type liquid dispensing device in which a plurality of nozzles N are distributed over the entire width of the medium PP.

[0134] 2-13. Other variations The liquid dispensing device 100 described above can be used in various devices such as facsimile machines and photocopiers, in addition to equipment dedicated to printing. However, the use of the recording device of the present invention is not limited to printing. For example, a recording device that dispenses a colorant solution can be used as a manufacturing device for forming color filters for liquid crystal display devices. Also, a recording device that dispenses a conductive material solution can be used as a manufacturing device for forming wiring and electrodes for wiring boards. [Explanation of Symbols]

[0135] 10...Liquid container, 20...Control unit, 21...Control circuit, 22...Memory circuit, 23...Power supply circuit, 24...Drive signal generation circuit, 30...Transport mechanism, 40...Movement mechanism, 41...Carriage, 42...Transport belt, 50...Liquid discharge head, 51...Head tip, 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 status specification circuit, 100...Liquid discharge device, 200...External device, C...Pressure chamber, CH...Change signal CHP, CHPa, CHPb, CHPc… Pressure characteristics, CI… Waveform information, CLK… Clock signal, Com… Drive signal, D… Discharge section, DR… Ink droplet, EHA… Highest potential, ELA… Lowest potential, E0… Reference potential, E1, E1a, E2, E2a, E3, E3a, E4, E4a… Potential, FN… Nozzle surface, IH… Inlet, Img… Image data, L1… First column, L2… Second column, LAT… Latch signal, LC… Liquid column, LHa, LHd… Wiring, MN… Meniscus, N… Nozzle, Na… Communicating channel, PP… Medium, Plc1, Plc1d, Plc1e, Plc1f, Pl c2f... Discharge element, Pld1, Pld1d, Pld1e, Pld1f... Filling element, Pld2, Pld2d, Pld2f... Vibration damping expansion element, Plh1, Plh1d, Plh1e, Plh1f... Potential maintenance element, Plh2, Plh2d, Plh2f... Vibration damping maintenance element, Plh3f... Potential maintenance element, PlsC, PlsL... Pulse, Pwc... Pressurized potential change element, Pwc1, Pwc1a... First pressurized potential change element, Pwc2, Pwc2a... Second pressurized potential change element, Pwca... Pressurized potential change element, Pwd... Depressurization potential change element, Pwd1, Pwd1a, Pwd1c... First 1. Reduced pressure potential change element, Pwd2, Pwd2a... 2nd reduced pressure potential change element, Pwd3, Pwd3a, Pwd3b... 3rd reduced pressure potential change element, Pwda... Reduced pressure potential change element, Pwh... Potential maintenance element, Pwh1, Pwh1a... 1st potential maintenance element, Pwh2, Pwh2a, Pwh2b... 2nd potential maintenance element, Pwh3, Pwh3a... 3rd potential maintenance element, Pwh4, Pwh4a... 4th potential maintenance element, Pwha... Potential maintenance element, R... Reservoir, R1, R2... Space, Ra... Supply channel, S2, S4, S6, S8... Step, SI... Print data signal, SLa, SLb,SLc…Connection status specification signal, SWa…Switch, Sd…Individual specification signal, Sk1, Sk2…Control signal, TL…Tail, Tc…Natural oscillation period, Tc1c2, Tc2d3, Tld1d, Tld1e, Tld1f, Tlh1d, Tlh1e, Tlh1f…Period, Tu…Unit period, Tu1, Tu2…Control period, Twc1, Twc2, Twd1, Twd1c, Twd2, Twd3, Twh1, Twh2, Twh2b, Twh3, Twh4…Period V1, V1d, V1e, V1f, V2, V2d, V2e, V2f, V3, V4…Potential change range, VBS…Offset potential, VHV…Power supply potential, Vin…Supply signal, WL, WLd, WLe, WLf…Large dot discharge pulse, WS, WSa, WSb, WSC…Small dot discharge pulse, Zd, Zu…Electrode, ae…End potential maintenance element, ai…Connection element, as…Start potential maintenance element, dCom…Waveform specification signal, g1, g2, g3, g4…Graph.

Claims

1. A discharge unit having a nozzle for discharging liquid, a pressure chamber communicating with the nozzle, and a drive element that drives the liquid in the pressure chamber to produce pressure fluctuations in response to a supplied drive signal, A drive signal generation circuit that generates the aforementioned drive signal, Equipped with, The drive signal includes a first discharge pulse that causes liquid to be discharged from the nozzle. The first discharge pulse is A first pressure-reducing potential-changing element drives the drive element so that the pressure of the liquid in the pressure chamber decreases, Following the first pressure-reducing potential-changing element, a first pressure-reducing potential-changing element drives the drive element to increase the pressure of the liquid in the pressure chamber so that the liquid surface protrudes from the nozzle, It has, The potential change range of the first pressure-reducing potential-changing element is 40% or more of the potential change range of the first pressure-reducing potential-changing element. The rate of change of the potential of the first pressure-reducing potential-changing element is 1 V / microsecond or more and 2 V / microsecond or less. A liquid dispensing device characterized by the following features.

2. The first discharge pulse is further, The first potential-maintaining element connects the end of the first pressure-reducing potential-changing element to the start of the first pressure-reducing potential-changing element and maintains a predetermined potential, The first potential maintenance element has a period of 0.1 times or more and 0.25 times or less of Tc. Tc is the natural vibration period within the discharge section. The liquid dispensing device according to feature 1.

3. The rate of change of potential of the first pressurized potential change element is 4 V / microsecond or more. The liquid dispensing device according to feature 1.

4. The first pressure-reducing potential change element is a period below Tc, Tc is the natural vibration period within the discharge section. The liquid dispensing device according to feature 1.

5. The first discharge pulse is Following the first pressurizing potential changing element, a second depressurizing potential changing element drives the driving element so that the pressure of the liquid in the pressure chamber decreases, Following the second pressure-reducing potential-changing element, a second pressure-reducing potential-changing element drives the driving element so that the pressure of the liquid in the pressure chamber increases, A second potential-maintaining element that maintains the potential from the end of the second pressurized potential-changing element, A third pressure-reducing potential-changing element is connected to the end of the second potential-maintaining element and drives the driving element so that the pressure of the liquid in the pressure chamber decreases, It further possesses, The period from the start of the second pressurized potential change element to the start of the third depressurized potential change element is 0.75 times or more Tc. Tc is the natural vibration period within the discharge section. The liquid dispensing device according to feature 1.

6. The period from the start of the first pressurized potential change element to the start of the second pressurized potential change element is a period of 0.5 times or more and 0.75 times or less of Tc. The potential change range of the second pressurized potential change element is 50% or more and 70% or less of the potential change range of the first pressurized potential change element. The liquid dispensing device according to feature 5.

7. The duration of the second potential maintenance element is 0.5 times or more of Tc. The liquid dispensing device according to feature 5.

8. The first discharge pulse is The system further comprises a third potential-maintaining element that maintains the potential from the end of the first pressurized potential-changing element, The duration of the third potential maintenance element is a period of 0.1 to 0.25 times Tc. The potential change range of the second pressure-reducing potential-changing element is 20% or more and 50% or less of the potential change range of the first pressure-reducing potential-changing element. The liquid dispensing device according to feature 5.

9. A discharge unit having a nozzle for discharging liquid, a pressure chamber communicating with the nozzle, and a drive element that drives the liquid in the pressure chamber to produce pressure fluctuations in response to a supplied drive signal, A drive signal generation circuit that generates the aforementioned drive signal, A method for driving a liquid discharge device, comprising: The drive signal includes a first discharge pulse that causes liquid to be discharged from the nozzle. The first discharge pulse is A first pressure-reducing potential-changing element drives the drive element so that the pressure of the liquid in the pressure chamber decreases, Following the first pressure-reducing potential-changing element, a first pressure-reducing potential-changing element drives the drive element to increase the pressure of the liquid in the pressure chamber so that the liquid surface protrudes from the nozzle, It has, The potential change range of the first pressure-reducing potential-changing element is 40% or more of the potential change range of the first pressure-reducing potential-changing element. The rate of change of the potential of the first pressure-reducing potential-changing element is 1 V / microsecond or more and 2 V / microsecond or less. The first step is to supply the first pressure-reducing potential-changing element to the drive element of the discharge unit, The second step is to supply the first pressurized potential change element to the drive element of the discharge unit, A driving method characterized by performing the following.

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