Liquid dispensing device

Abstract

To perform high-speed printing in a plurality of gradations having adequate density differences.SOLUTION: A liquid ejection device comprises a nozzle, a pressure chamber, a driving element, a driving signal generating part and a control part, where a driving signal includes, in a unit period of time, a first ejection pulse at which the driving element is driven so that the nozzle ejects liquid, a second ejection pulse at which the driving element is driven so that the nozzle ejects liquid and a non-ejection pulse at which the driving element is driven so that the nozzle does not eject liquid, at timings different from one another. The control part, when making the nozzle eject a first quantity of liquid in the unit period of time, selects the first ejection pulse and the second ejection pulse as pulses which are supplied to the driving element, and when making the nozzle eject a second quantity of liquid which is smaller than the first quantity of liquid in the unit period of time, selects the non-ejection pulse and the second ejection pulse as the pulses which are supplied to the driving element, where the second quantity of liquid is larger than a quantity of liquid that is ejected from the nozzle by supplying only the second ejection pulse to the driving element.SELECTED DRAWING: Figure 9

Description

[Technical field]

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

[0002] A liquid ejection device, such as an inkjet printer, generally has a liquid ejection head that ejects liquid such as ink. As disclosed in Patent Document 1, for example, the liquid ejection head includes a nozzle that ejects liquid, a pressure chamber that communicates with the nozzle, and a drive element that applies pressure fluctuations to the liquid in the pressure chamber in response to a drive signal.

[0003] In Patent Document 1, the drive signal includes a plurality of pulses within a printing cycle, and these pulses are selectively used to drive drive elements, thereby performing printing in multiple gradations. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-81013 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, there is a problem that when the printing cycle becomes shorter as the printing speed increases, it is not possible to print in multiple gradations with appropriate shading differences. [Means for solving the problem]

[0006] In order to solve the above problems, a liquid ejection device according to a preferred aspect of the present disclosure includes a nozzle that ejects liquid, a pressure chamber that communicates with the nozzle, a drive element that applies pressure fluctuations to the liquid in the pressure chamber in response to a drive signal, a drive signal generation unit that generates the drive signal, and a control unit that controls supply of the drive signal to the drive element for each unit period of a predetermined cycle, wherein the drive signal includes a first ejection pulse that drives the drive element to eject liquid from the nozzle, a second ejection pulse that drives the drive element to eject liquid from the nozzle, and a control unit that controls supply of the drive signal to the drive element without ejecting liquid from the nozzle. and a non-ejection pulse that drives a driving element at different timings within the unit period, and the control unit selects the first ejection pulse and the second ejection pulse as pulses to be supplied to the driving element when a first amount of liquid is to be ejected from the nozzle within the unit period, and selects the non-ejection pulse and the second ejection pulse as pulses to be supplied to the driving element when a second amount of liquid less than the first amount is to be ejected from the nozzle within the unit period, and the second amount is greater than the amount of liquid ejected from the nozzle by supplying only the second ejection pulse to the driving element. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of the configuration of a liquid ejection device according to a first embodiment. [Diagram 2] FIG. 2 is a diagram showing an electrical configuration of the liquid ejection device according to the first embodiment. [Diagram 3] FIG. 2 is a cross-sectional view showing an example of a head chip. [Figure 4] FIG. 2 is a diagram for explaining a switching circuit. [Diagram 5] FIG. 3 is a diagram for explaining a drive signal used in the first embodiment. [Figure 6] 5 is a diagram for explaining a signal supplied from a switching circuit to a head chip. FIG. [Figure 7] 13 is a graph showing the relationship between the interval between the non-ejection pulse and the second ejection pulse, and the ejection amount when a medium dot is formed. [Figure 8]13 is a diagram illustrating a supply signal when a large dot is formed with a first amount of ink in each of a first period and a second period that are two successive unit periods. FIG. [Figure 9] 11 is a graph showing the relationship between the interval between a first ejection pulse and a second ejection pulse and the ejection amount when a large dot is formed. [Figure 10] 11A and 11B are diagrams illustrating the relationship between the order of pulses within a unit period of a drive signal and the effect. [Figure 11] FIG. 11 is a diagram for explaining a drive signal used in the second embodiment. [Figure 12] FIG. 11 is a diagram for explaining a driving signal used in the third embodiment. [Figure 13] FIG. 13 is a diagram for explaining a driving signal used in the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, preferred embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that the dimensions and scale of each part in the drawings may differ from the actual dimensions, and some parts are shown diagrammatically to facilitate understanding. In addition, the scope of the present disclosure is not limited to these forms unless otherwise specified in the following description to the effect that the present disclosure is limited.

[0009] In the following description, the mutually intersecting X-axis, Y-axis, and Z-axis are appropriately used. In the following description, one direction along the X-axis is the X1 direction, and the direction opposite to the X1 direction is the X2 direction. Similarly, the opposite directions along the Y-axis are the Y1 direction and the Y2 direction. The opposite directions along the Z-axis are the Z1 direction and the Z2 direction.

[0010] Typically, the Z axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. However, the Z axis does not have to be a vertical axis. Also, the X axis, the Y axis, and the Z axis are typically perpendicular to each other, but are not limited to this, and may intersect at an angle within a range of 80° to 100°, for example.

[0011] A: First embodiment A1: Overall configuration of the liquid ejection device 1 is a schematic diagram showing an example of the configuration of a liquid ejection device 100 according to a first embodiment. The liquid ejection device 100 is an inkjet printing device that ejects liquid such as ink as droplets onto a medium M. The medium M is, for example, printing paper. Note that the medium M is not limited to printing paper, and may be a printing target made of any material, such as a resin film or fabric.

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

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

[0014] The control unit 20 controls the operation of each element of the liquid ejection device 100. The control unit 20 includes, for example, one or more processing circuits such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), and one or more storage circuits such as a semiconductor memory. A detailed configuration of the control unit 20 will be described later with reference to FIG. 2.

[0015] The transport mechanism 30 transports the medium M in the Y1 direction under the control of the control unit 20. The movement mechanism 40 reciprocates the 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 transport belt 42 to which the carriage 41 is fixed. The number of liquid ejection heads 50 mounted on the carriage 41 is not limited to one, and may be multiple. In addition to the liquid ejection head 50, the above-mentioned liquid container 10 may be mounted on the carriage 41.

[0016] Under the control of the control unit 20, the liquid ejection head 50 ejects ink supplied from the liquid container 10 from each of a plurality of nozzles onto the medium M. This ejection is performed in parallel with the transportation of the medium M by the transport mechanism 30 and the reciprocating movement of the liquid ejection head 50 by the movement mechanism 40, thereby forming an image in ink on the surface of the medium M.

[0017] A2: Electrical configuration of the liquid ejection device Fig. 2 is a diagram showing the electrical configuration of the liquid ejection device 100 according to the first embodiment. Below, the control unit 20 will be explained based on Fig. 2, but prior to this, the liquid ejection head 50 will be briefly explained.

[0018] As shown in FIG. 2, the liquid ejection head 50 includes a head chip 51 and a switching circuit 52.

[0019] The head chip 51 has a plurality of drive elements 51f, and ink is ejected from the nozzles by appropriately driving the plurality of drive elements 51f. Here, each drive element 51f applies pressure to the ink upon receiving a supply signal Vin. Details of the head chip 51 will be described later with reference to Figures 3 to 5.

[0020] Under the control of the control unit 20, the switching circuit 52 switches whether or not to supply the drive signal Com output from the control unit 20 as the supply signal Vin to each of the multiple drive elements 51f of the head chip 51. Details of the switching circuit 52 will be described later with reference to FIG.

[0021] In the example shown in FIG. 2, the liquid ejection head 50 has one head chip 51, but the number of head chips 51 is not limited to this, and the liquid ejection head 50 may have two or more head chips 51. In the following, when the number of nozzles N of the head chip 51 is M, in order to distinguish each of the M driving elements 51f corresponding to the M nozzles, the driving elements 51f may be written as driving elements 51f[m] using the subscript [m]. However, M is a natural number of 1 or more, and m is a natural number of 1 to M. In addition, for M other components or signals corresponding to the nozzle N or the driving element 51f in the liquid ejection device 100, the subscript [m] may be used to indicate the correspondence with the nozzle N or the driving element 51f[m].

[0022] As shown in FIG. 2, the control unit 20 includes a control circuit 21, a memory circuit 22, a power supply circuit 23, and a drive signal generating circuit 24.

[0023] The control circuit 21 has a function of controlling the operation of each part of the liquid ejection device 100 and a function of processing various data. The control circuit 21 includes, for example, one or more processors such as a CPU (Central Processing Unit). Note that the control circuit 21 may include a programmable logic device such as an FPGA (field-programmable gate array) instead of or in addition to a CPU. Furthermore, when the control circuit 21 is composed of multiple processors, the multiple processors may be mounted on different boards or the like.

[0024] The memory circuit 22 stores various programs executed by the control circuit 21 and various data such as print data Img processed by the control circuit 21. The memory circuit 22 includes one or both of semiconductor memories, for example, a volatile memory such as a random access memory (RAM) and a non-volatile memory such as a read only memory (ROM), an electrically erasable programmable read-only memory (EEPROM) or a programmable ROM (PROM). The print data Img is supplied from an external device 200 such as a personal computer or a digital camera. The memory circuit 22 may be configured as a part of the control circuit 21.

[0025] The power supply circuit 23 receives power from a commercial power supply (not shown) and generates various predetermined potentials. The generated various potentials are appropriately supplied to each section of the liquid ejection device 100. For example, the power supply circuit 23 generates a power supply potential VHV and an offset potential VBS. The offset potential VBS is supplied to the liquid ejection head 50. In addition, the power supply potential VHV is supplied to the drive signal generation circuit 24.

[0026] The drive signal generating circuit 24 is a circuit that generates a drive signal Com for driving each drive element 51f. Specifically, the drive signal generating circuit 24 has, for example, a DA conversion circuit and an amplifier circuit. In the drive signal generating circuit 24, the DA conversion circuit converts the waveform designation signal dCom from the control circuit 21 from a digital signal to an analog signal, and the amplifier circuit amplifies the analog signal using the power supply potential VHV from the power supply circuit 23 to generate the drive signal Com. Here, among the waveforms included in the drive signal Com, the signal of the waveform that is actually supplied to the drive element 51f is the aforementioned supply signal Vin. The waveform designation signal dCom is a digital signal for defining the waveform of the drive signal Com.

[0027] The control circuit 21 executes a program stored in the memory circuit 22 to control the operation of each part of the liquid ejection device 100. Here, the control circuit 21 generates control signals Sk1 and Sk2, a print data signal SI, a waveform designation signal dCom, a latch signal LAT, a change signal CNG, and a clock signal CLK as signals for controlling the operation of each part of the liquid ejection device 100 by executing the program.

[0028] The control signal Sk1 is a signal for controlling the driving of the transport mechanism 30. The control signal Sk2 is a signal for controlling the driving of the movement mechanism 40. The print data signal SI is a digital signal for specifying the operating state of the drive element 51f. The latch signal LAT and the change signal CNG are used in conjunction with the print data signal SI and are timing signals that define the timing of ink ejection from each nozzle of the head chip 51. These timing signals are generated, for example, based on the output of an encoder that detects the position of the carriage 41 described above.

[0029] A4: Specific structure of the head chip Fig. 3 is a cross-sectional view showing an example of the head chip 51. As shown in Fig. 3, the head chip 51 has a plurality of nozzles N arranged in a direction along the Y axis. The plurality of nozzles N are divided into a first row L1 and a second row L2 arranged at intervals in a direction along the X axis. Each of the first row L1 and the second row L2 is a collection of a plurality of nozzles N arranged linearly in the direction along the Y axis.

[0030] The head chips 51 are configured to be substantially symmetrical to each other in the direction along the X-axis. However, the positions of the multiple nozzles N in the first row L1 and the multiple nozzles N in the second row L2 in the direction along the Y-axis may be the same or different. Fig. 3 illustrates a configuration in which the positions of the multiple nozzles N in the first row L1 and the multiple nozzles N in the second row L2 in the direction along the Y-axis are the same.

[0031] As shown in FIG. 3, the head chip 51 has a flow path substrate 51a, a pressure chamber substrate 51b, a nozzle plate 51c, a vibration absorber 51d, a vibration plate 51e, a plurality of driving elements 51f, a protective plate 51g, a case 51h, and a wiring substrate 51i.

[0032] The flow path substrate 51a and the pressure chamber substrate 51b are laminated in this order in the Z1 direction to form a flow path for supplying ink to the multiple nozzles N. A vibration plate 51e, multiple driving elements 51f, a protective plate 51g, a case 51h, and a wiring substrate 51i are provided in an area located in the Z1 direction from the laminate consisting of the flow path substrate 51a and the pressure chamber substrate 51b. On the other hand, a nozzle plate 51c and a vibration absorber 51d are provided in an area located in the Z2 direction from the laminate. Each element of the head chip 51 is generally a plate-like member elongated in the Y direction, and is joined to each other by, for example, an adhesive. Each element of the head chip 51 will be described in order below.

[0033] The nozzle plate 51c is a plate-like member in which a plurality of nozzles N are provided in each of a first row L1 and a second row L2. Each of the plurality of nozzles N is a through hole that allows ink to pass through. Here, the surface of the nozzle plate 51c facing the Z2 direction is the nozzle surface FN. The nozzle plate 51c is manufactured by processing a silicon single crystal substrate by a semiconductor manufacturing technique using a processing technique such as dry etching or wet etching. However, other known methods and materials may be appropriately used to manufacture the nozzle plate 51c. In addition, the cross-sectional shape of the nozzle is typically circular, but is not limited thereto, and may be a non-circular shape such as a polygonal or elliptical shape.

[0034] The flow path substrate 51a is provided with a space R1, a plurality of supply flow paths Ra, and a plurality of communication flow paths Na for each of the first row L1 and the second row L2. The space R1 is an elongated opening extending in the direction along the Y axis in a plan view seen in the direction along the Z axis. Each of the supply flow paths Ra and the communication flow paths Na is a through hole formed for each nozzle N. Each supply flow path Ra communicates with the space R1.

[0035] The pressure chamber substrate 51b is a plate-like member in which a plurality of pressure chambers C called cavities are provided for each of the first row L1 and the second row L2. The plurality of pressure chambers C are arranged in a direction along the Y axis. Each pressure chamber C is formed for each nozzle N and is an elongated space extending in a direction along the X axis in a plan view. Similarly to the nozzle plate 51c described above, each of the flow path substrate 51a and the pressure chamber substrate 51b is manufactured by processing a silicon single crystal substrate by, for example, a semiconductor manufacturing technique. However, other known methods and materials may be appropriately used for manufacturing each of the flow path substrate 51a and the pressure chamber substrate 51b.

[0036] The pressure chambers C are spaces located between the flow path substrate 51a and the vibration plate 51e. A plurality of pressure chambers C are arranged in the direction along the Y axis in each of the first row L1 and the second row L2. The pressure chambers C are also connected to the communication flow path Na and the supply flow path Ra. Therefore, the pressure chambers C are connected to the nozzle N via the communication flow path Na, and are connected to the space R1 via the supply flow path Ra.

[0037] A vibration plate 51e is disposed on the surface of the pressure chamber substrate 51b facing the Z1 direction. The vibration plate 51e is a plate-shaped member that can vibrate elastically. The vibration plate 51e has, for example, a first layer and a second layer, which are laminated in this order in the Z1 direction. The first layer is, for example, an elastic film made of silicon oxide (SiO2). The elastic film is formed, for example, by thermally oxidizing one surface of a silicon single crystal substrate. The second layer is, for example, an insulating film made of zirconium oxide (ZrO2). The insulating film is formed, for example, by forming a layer of zirconium by a sputtering method and thermally oxidizing the layer. Note that the vibration plate 51e is not limited to the configuration of the laminate of the first layer and the second layer described above, and may be, for example, a single layer or three or more layers.

[0038] On the surface of the vibration plate 51e facing the Z1 direction, a plurality of drive elements 51f corresponding to the nozzles N are arranged in each of the first row L1 and the second row L2. Each drive element 51f is a passive element that deforms when a drive signal is supplied. Each drive element 51f has an elongated shape extending in a direction along the X-axis in a plan view. The multiple drive elements 51f are arranged in a direction along the Y-axis so as to correspond to the multiple pressure chambers C. The drive elements 51f overlap the pressure chambers C in a plan view.

[0039] Each driving element 51f is a piezoelectric element, and although not shown, has a first electrode, a piezoelectric layer, and a second electrode, which are laminated in this order in the Z1 direction. One of the first electrode and the second electrode is an individual electrode that is arranged separately from each other for each driving element 51f, and a supply signal Vin is applied to the one electrode. The other of the first electrode and the second electrode is a band-shaped common electrode that extends in the direction along the Y axis so as to be continuous across the multiple driving elements 51f, and an offset potential VBS is supplied to the other electrode. Examples of metal materials for these electrodes include metal materials such as platinum (Pt), aluminum (Al), nickel (Ni), gold (Au), and copper (Cu), and among these, one type can be used alone, or two or more types can be used in combination in the form of an alloy or laminate. The piezoelectric layer is made of a piezoelectric material such as lead zirconate titanate (Pb(Zr,Ti)O3) and has, for example, a band shape extending in the direction along the Y axis so as to be continuous across the multiple driving elements 51f. However, the piezoelectric layer may be integral across the multiple driving elements 51f. In this case, the piezoelectric layer is provided with through holes extending in the direction along the X axis in areas corresponding to the gaps between adjacent pressure chambers C in a plan view. When the vibration plate 51e vibrates in conjunction with the deformation of the driving elements 51f, the pressure in the pressure chambers C fluctuates, causing ink to be ejected from the nozzles N.

[0040] The protective plate 51g is a plate-like member provided on the surface of the diaphragm 51e facing the Z1 direction, and protects the multiple driving elements 51f and reinforces the mechanical strength of the diaphragm 51e. The multiple driving 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.

[0041] The case 51h is a member for storing ink to be supplied to the multiple pressure chambers C. The case 51h is made of, for example, a resin material. The case 51h is provided with a space R2 for each of the first row L1 and the second row L2. The space R2 is a space that communicates with the above-mentioned space R1, and functions as a reservoir R that stores ink to be supplied to the multiple pressure chambers C together with the space R1. The case 51h is provided with an inlet IH for supplying ink to each reservoir R. The ink in each reservoir R is supplied to the pressure chamber C via each supply flow path Ra.

[0042] The vibration absorber 51d is also called a compliance substrate, and is a flexible resin film that constitutes the wall surface of the reservoir R, and absorbs pressure fluctuations of the ink in the reservoir R. The vibration absorber 51d may be a flexible thin metal plate. The surface of the vibration absorber 51d facing the Z1 direction is bonded to the flow path substrate 51a with an adhesive or the like.

[0043] The wiring board 51i is mounted on the surface of the diaphragm 51e facing the Z1 direction, and is a mounting component for electrically connecting the control unit 20 and the head chip 51. The wiring board 51i is a flexible wiring board such as a COF (Chip On Film), an FPC (Flexible Printed Circuit), or an FFC (Flexible Flat Cable). A switching circuit 52 for supplying a drive voltage to each drive element 51f is mounted on the wiring board 51i of this embodiment.

[0044] A6: Driving the driving element 51f 4 is a diagram for explaining the switching circuit 52. The driving element 51f is driven by a supply signal Vin from the switching circuit 52. Hereinafter, the switching circuit 52 will be explained with reference to FIG.

[0045] As shown in Fig. 4, a wiring LHa is connected to the switching circuit 52. The wiring LHa is a signal line that transmits a drive signal Com. In Fig. 4, one of the first electrode and the second electrode of the drive element 51f described above is shown as an electrode Zd[m], and the other is shown as an electrode Zu[m]. A wiring LHd is connected to the electrode Zd[m]. The wiring LHd is a power supply line to which an offset potential VBS is supplied.

[0046] The switching circuit 52 has M switches SWa (SWa[1]] to SWa[M]) and a connection state designation circuit 52a that designates the connection states of these switches.

[0047] The switch SWa[m] is a switch that switches between conduction (ON) and non-conduction (OFF) between the wiring LHa for transmitting the drive signal Com and the electrode Zu[m] of the drive element 51f[m]. Each of these switches is, for example, a transmission gate.

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

[0049] For example, although not shown, the connection state designation circuit 52a has a plurality of transfer circuits, a plurality of latch circuits, and a plurality of decoders so as to correspond one-to-one to the driving elements 51f[1] to 51f[M]. Of these, the print data signal SI is supplied to the transfer circuit. Here, the print data signal SI includes an individual designation signal for each driving element 51f, and the individual designation signal is supplied serially, and for example, the individual designation signal is transferred in sequence to the plurality of transfer circuits in synchronization with the clock signal CLK. Also, the latch circuit latches the individual designation signal supplied to the transfer circuit based on the latch signal LAT. Also, the decoder generates a connection state designation signal SLa[m] based on the individual designation signal, the latch signal LAT, and the change signal CNG.

[0050] The switch SWa[m] is switched on and off according to the connection state designation signal SLa[m] generated as described above. For example, the switch SWa[m] is in an on state when the connection state designation signal SLa[m] is at a high level, and is in an off state when the connection state designation signal SLa[m] is at a low level. As described above, the switching circuit 52 supplies a part or all of the waveform included in the drive signal Com as the supply signal Vin to one or more drive elements 51f selected from the multiple drive elements 51f.

[0051] A7: Drive signal 5 is a diagram for explaining the drive signal Com used in the first embodiment. As shown in FIG. 5, the latch signal LAT includes a pulse PlsL for defining a unit period Tu. The unit period Tu corresponds to a printing cycle for forming dots of ink from the nozzle N on the medium M. The unit period Tu is defined, for example, as the period from the rising edge of a pulse PlsL to the rising edge of the next pulse PlsL. The specific length or period of the unit period Tu is not particularly limited, but is, for example, about 80 μsec from the viewpoint of achieving both high printing speed and high image quality.

[0052] The change signal CNG includes a pulse PlsC for dividing the unit period Tu into a control period Tu1, a control period Tu2, a control period Tu3, and a control period Tu4. The control period Tu1, the control period Tu2, the control period Tu3, and the control period Tu4 are arranged in this order. The control period Tu1 is, for example, the period from the rising edge of the pulse PlsL to the rising edge of the first pulse PlsC. The control period Tu2 is, for example, the period from the rising edge of the first pulse PlsC to the rising edge of the subsequent second pulse PlsC. The control period Tu3 is, for example, the period from the rising edge of the second pulse PlsC to the rising edge of the subsequent third pulse PlsC. The control period Tu4 is, for example, the period from the rising edge of the third pulse PlsC to the rising edge of the pulse PlsL. In the example shown in FIG. 5, control period Tu1, control period Tu2, control period Tu3, and control period Tu4 are of equal length, but this is not limited to this, and at least two of control period Tu1, control period Tu2, control period Tu3, and control period Tu4 may be of different lengths.

[0053] The driving signal Com has an ejection pulse PA1 provided in a control period Tu1, an ejection pulse PA2 provided in a control period Tu2, a non-ejection pulse PA3 provided in a control period Tu3, and an ejection pulse PA4 provided in a control period Tu4. Here, the ejection pulse PA2 is an example of a "first ejection pulse". The ejection pulse PA4 is an example of a "second ejection pulse". The ejection pulse PA1 is an example of a "third ejection pulse".

[0054] The ejection pulse PA1 is a potential pulse that drives the driving element 51f to generate a pressure fluctuation in the pressure chamber C that is strong enough to eject ink from the nozzle N. When the ejection pulse PA1 is supplied to the driving element 51f, a small amount of ink is ejected from the nozzle N as an ink droplet.

[0055] In the example shown in FIG. 5, the ejection pulse PA1 has a waveform that goes from the reference potential V0 through potentials E11, E12, E13, E14, E15, and E16 in this order, and then returns to the reference potential V0. Here, the reference potential V0 is, for example, a potential higher than the offset potential VBS. Each of the potentials E11, E12, E14, and E16 is a potential higher than the reference potential V0. Also, among the potentials E11, E12, E14, and E16, the potential E14 is the highest potential, and the potential E12 is the lowest potential. The potentials E11 and E16 may be equal to or different from each other. In contrast, each of the potentials E13 and E15 is a potential lower than the reference potential V0. The potential E13 is a potential lower than the potential E15. The waveform of the ejection pulse PA1 is not limited to the example shown in FIG. 5, and is arbitrary.

[0056] The ejection pulse PA2 is a potential pulse that drives the driving element 51f to generate a pressure fluctuation in the pressure chamber C that is strong enough to eject ink from the nozzle N. When the ejection pulse PA2 is supplied to the driving element 51f, a medium amount of ink is ejected from the nozzle N as an ink droplet.

[0057] In the example shown in Fig. 5, the ejection pulse PA2 has a waveform that goes from a reference potential V0 to a potential E21 and a potential E22 in this order, and then returns to the reference potential V0. Here, the potential E21 is a potential lower than the reference potential V0. In contrast, the potential E22 is a potential higher than the reference potential V0. The voltage amplitude V2 of the ejection pulse PA2 is the potential difference between the potential E21 and the potential E22. The waveform of the ejection pulse PA2 is not limited to the example shown in Fig. 5, and may be the same waveform as that of the ejection pulse PA4, for example.

[0058] The non-ejection pulse PA3 is a potential pulse that drives the driving element 51f to generate a pressure fluctuation in the pressure chamber C that is strong enough not to eject ink from the nozzle N. By supplying the non-ejection pulse PA3 to the driving element 51f, the ink meniscus in the nozzle N is slightly vibrated without ejecting ink from the nozzle N.

[0059] In the example shown in Fig. 5, the non-ejection pulse PA3 has a waveform that goes from the reference potential V0 through a potential E31 and then returns to the reference potential V0. Here, the potential E31 is a potential lower than the reference potential V0. In addition, the timing of the potential E31 is after the midpoint of the control period Tu3. Note that the waveform of the non-ejection pulse PA3 is not limited to the example shown in Fig. 5, and may be, for example, a waveform that goes through a potential higher than the reference potential V0.

[0060] The ejection pulse PA4 is a potential pulse that drives the driving element 51f to generate a pressure fluctuation in the pressure chamber C that is strong enough to eject ink from the nozzle N. When the ejection pulse PA4 is supplied to the driving element 51f, a medium amount of ink is ejected from the nozzle N as an ink droplet.

[0061] In the example shown in FIG. 5, the ejection pulse PA4 has a waveform that goes from the reference potential V0 to the potential E41, the potential E42, and the potential E43 in this order, and then returns to the reference potential V0. Here, the potential E41 and the potential E43 are each higher than the reference potential V0. In contrast, the potential E42 is lower than the reference potential V0. The voltage amplitude V4 of the ejection pulse PA4 is the potential difference between the potential E41 and the potential E42, and is equal to the voltage amplitude V2 of the ejection pulse PA2. The waveform of the ejection pulse PA4 is not limited to the example shown in FIG. 5, and may be the same waveform as the ejection pulse PA2, for example. The voltage amplitude V4 of the ejection pulse PA4 may be different from the voltage amplitude V2 of the ejection pulse PA2.

[0062] The above-mentioned ejection pulses PA1, PA2, PA4 and non-ejection pulse PA3 are appropriately selected and used for the supply signal Vin, which makes it possible to adjust the amount of ink ejected from the nozzle N, or to slightly vibrate the ink in the nozzle N without ejecting ink from the nozzle N.

[0063] A8: 1st amount, 2nd amount and 3rd amount Fig. 6 is a diagram for explaining the supply signal Vin from the switching circuit 52 to the head chip 51. Fig. 6 shows waveforms of the supply signal Vin for forming a large dot with a first amount of ink, a medium dot with a second amount of ink, and a small dot with a third amount of ink on the medium M, for forming the ink in the nozzle N by micro-vibrating without ejecting ink from the nozzle N, and for forming the ink in the nozzle N by micro-vibrating without ejecting ink from the nozzle N.

[0064] When forming a large dot on the medium M, the supply signal Vin within the unit period Tu has a waveform that includes an ejection pulse PA2 in the control period Tu2 and an ejection pulse PA4 in the control period Tu4. Here, the supply signal Vin is maintained at the reference potential V0 throughout each of the control periods Tu1 and Tu3.

[0065] By supplying such a supply signal Vin to the driving element 51f, a medium amount of ink droplets are ejected twice in succession from the nozzle N. As a result, these ink droplets land within a target range on the medium M, forming a large dot of the first amount of ink on the medium M. The first amount is greater than the sum of the amount of ink ejected from the nozzle N by supplying only the ejection pulse PA2 to the driving element 51f and the amount of ink ejected from the nozzle N by supplying only the ejection pulse PA4 to the driving element 51f. This will be described in detail later with reference to FIG. 9.

[0066] When forming a medium dot on the medium M, the supply signal Vin within the unit period Tu has a waveform that includes a non-ejection pulse PA3 in the control period Tu3 and an ejection pulse PA4 in the control period Tu4. Here, the supply signal Vin is maintained at the reference potential V0 throughout each of the control periods Tu1 and Tu2.

[0067] By supplying such a supply signal Vin to the driving element 51f, a medium amount of ink droplet is ejected from the nozzle N. As a result, this ink droplet lands on the medium M, and a medium dot is formed on the medium M with a second amount of ink that is less than the first amount. The second amount is greater than the amount of ink ejected from the nozzle N by supplying only the ejection pulse PA4 to the driving element 51f. This will be described in detail later with reference to FIG. 7.

[0068] When forming small dots on the medium M, the supply signal Vin within the unit period Tu has a waveform that includes an ejection pulse PA1 in the control period Tu1. Here, the supply signal Vin is maintained at the reference potential V0 throughout each of the control periods Tu2, Tu3, and Tu4.

[0069] By supplying such a supply signal Vin to the drive element 51f, a small amount of ink droplet is ejected from the nozzle N. As a result, when this ink droplet lands on the medium M, a small dot is formed on the medium M with a third amount of ink that is smaller than the second amount.

[0070] When the meniscus of the ink in the nozzle N is slightly vibrated without ejecting ink from the nozzle N, the supply signal Vin within the unit period Tu has a waveform that includes a non-ejection pulse PA3 in the control period Tu3.

[0071] By supplying such a supply signal Vin to the drive element 51f, the ink in the nozzle is vibrated slightly without ejecting ink droplets from the nozzle N. In this case, no dots are formed on the medium M. The slight vibration can reduce thickening of the ink in the nozzle N.

[0072] When ink is not ejected from the nozzle N without micro-vibrating the meniscus of the ink in the nozzle N, the supply signal Vin within the unit period Tu has a waveform that is maintained at the reference potential V0 throughout each of the control periods Tu1, Tu2, Tu3, and Tu4. By supplying such a supply signal Vin to the drive element 51f, ink in the nozzle N is not micro-vibrated and ink is not ejected from the nozzle N. In this case as well, no dots are formed on the medium M.

[0073] As described above, the ejection pulses PA1, PA2, PA4 and the non-ejection pulse PA3 are used appropriately during the ejection period in which ink is ejected from the nozzle N. Also, during the non-ejection period in which ink is not ejected from the nozzle N, the non-ejection pulse PA3 is used without using the ejection pulses PA1, PA2, PA4, or none of the ejection pulses PA1, PA2, PA4 and the non-ejection pulse PA3 is used.

[0074] Moreover, multiple gradations are printed using large dots of the first amount of ink, medium dots of the second amount of ink, and small dots of the third amount of ink. From the viewpoint of optimizing the contrast between the multiple gradations, it is preferable that the difference between the ratio of the second amount to the third amount and the ratio of the first amount to the second amount is 10% or less. From the same viewpoint, it is preferable that the first amount is within a range of 1.8 to 2.2 times the second amount, and it is also preferable that the second amount is within a range of 1.8 to 2.2 times the third amount.

[0075] 7 is a graph showing the relationship between the interval T34 between the non-ejection pulse PA3 and the ejection pulse PA4 and the amount of ink ejected from the nozzle N by the non-ejection pulse PA3 and the ejection pulse PA4. The interval T34 is the time length from the end point of the contraction element indicating the change from the potential E31 of the non-ejection pulse PA3 to the reference potential V0 to the start point of the expansion element indicating the change from the potential E41 to the potential E42 of the ejection pulse PA4.

[0076] As shown in FIG. 7, the smaller the interval T34, the larger the ejection amount when a medium dot is formed. Here, as the interval T34 becomes larger, the ejection amount when a medium dot is formed is repeatedly decreased and increased, and the multiple maximum values ​​gradually become smaller. This corresponds to the influence of the vibration of the meniscus in the nozzle N. Therefore, the effect of increasing the ejection amount when a medium dot is formed is obtained by the contribution of the vibration of the meniscus of the ink in the nozzle N by the non-ejection pulse PA3 to the ejection of ink from the nozzle N by the ejection pulse PA4. Therefore, it is preferable that the interval T34 is 1 / 4 or less of the natural vibration period of the meniscus of the ink in the nozzle N. The natural vibration period of the meniscus of the ink in the nozzle N is, for example, about 80 μsec or more and 120 μsec or less. Furthermore, the interval between the multiple maximum values ​​corresponds to the natural vibration period of the ink in the flow path from the supply flow path Ra to the nozzle N. In the example shown in FIG. 7, the interval between the multiple maximum values ​​or the natural vibration period is about 6 μsec to 9 μsec.

[0077] As can be understood from the above, from the viewpoint of increasing the ejection volume when forming a medium dot, the interval T34 is preferably less than 1 / 4 of the natural vibration period of the ink meniscus in the nozzle N, and an integer multiple of the natural vibration period of the ink in the flow path from the supply flow path Ra to the nozzle N, and more preferably 1 time the natural vibration period of the ink in the flow path from the supply flow path Ra to the nozzle N.

[0078] FIG. 8 is a diagram for explaining the supply signal Vin when a large dot is formed with a first amount of ink in each of a first period Tu_1 and a second period Tu_2 that are two consecutive unit periods Tu.

[0079] As shown in Fig. 8, during the period from the start point of the first period Tu_1 to the end point of the second period Tu_2, the ejection pulse PA2 and the ejection pulse PA4 appear alternately. Here, a control period Tu3 exists between the ejection pulse PA2 and the ejection pulse PA4 in each of the first period Tu_1 and the second period Tu_2. Therefore, compared with the case where the control period Tu3 does not exist, the interval T24 between the ejection pulse PA2 and the ejection pulse PA4 in each of the first period Tu_1 and the second period Tu_2 can be made larger. The interval T24 is the time length from the end point of the contraction element indicating the change from the potential E21 to the potential E22 of the ejection pulse PA2 to the end point of the contraction element indicating the change from the potential E42 to the potential E43 of the ejection pulse PA4.

[0080] Between the ejection pulse PA4 of the first period Tu_1 and the ejection pulse PA2 of the second period Tu_2, there is a control period Tu1 of the second period Tu_2. Therefore, compared with the case where the control period Tu1 does not exist, the interval T42 between the ejection pulse PA4 of the first period Tu_1 and the ejection pulse PA2 of the second period Tu_2 can be made larger. The interval T42 is the time length from the end point of the contraction element indicating the change from the potential E42 to the potential E43 of the ejection pulse PA4 to the end point of the contraction element indicating the change from the potential E21 to the potential E22 of the ejection pulse PA2. In the example shown in FIG. 8, the interval T24 and the interval T42 are equal to each other.

[0081] As described above, even if the unit period Tu is shortened, it is possible to increase both the interval T24 and the interval T42. As a result, it is possible to increase the ejection volume when forming a large dot. This point will be explained below with reference to FIG.

[0082] Fig. 9 is a graph showing the relationship between the interval T24 between the ejection pulse PA2 and the ejection pulse PA4 and the ejection amount when forming a large dot. The ejection amount in Fig. 9 is the average value of the ejection amount in the first period Tu_1 and the ejection amount in the second period Tu_2 when forming a large dot with a first amount of ink in each of the first period Tu_1 and the second period Tu_2. Also, an increase in the interval T24 in Fig. 9 indicates a decrease in the interval T42.

[0083] As shown in FIG. 9, the closer the interval T24 is to the interval T42, that is, the smaller the difference between the interval T24 and the interval T42, the larger the ejection amount when the large dot is formed. Here, when the interval T24 and the interval T42 are equal to each other, the ejection amount when the large dot is formed is maximum and extremely large. The effect of increasing the ejection amount when the large dot is formed is obtained by the contribution of the vibration of the meniscus of the ink in the nozzle N by the ejection pulse PA2 to the ejection of the ink from the nozzle N by the ejection pulse PA4. Therefore, from the viewpoint of increasing the ejection amount when the large dot is formed, each of the interval T24 and the interval T42 is preferably 0.4 times or more and 0.6 times or less, and more preferably 0.40 times or more and 0.54 times or less, of the natural vibration period of the meniscus of the ink in the nozzle N. When each of the interval T24 and the interval T42 is within this range, the ejection amount can be made larger than the amount VL1.

[0084] A9: Pulse order and its effect Hereinafter, the order of the ejection pulses PA1, PA2, PA4 and the non-ejection pulse PA3 and their effects will be described with reference to FIG.

[0085] FIG. 10 is a diagram showing the relationship between the order of pulses in a unit period Tu of the drive signal Com and the effect. In FIG. 10, the presence or absence of effect is described for samples No. 1 to No. 12, which have different orders of ejection pulses PA1, PA2, PA4 and non-ejection pulse PA3. In FIG. 10, the "large dot" column shows "P" if an increase in the ejection amount is observed when a large dot is formed. In FIG. 10, the "medium dot" column shows "P" if an increase in the ejection amount is observed when a medium dot is formed. In FIG. 10, the "small dot" column shows "P" if the ejection speed of ink from nozzle N can be slowed down when a small dot is formed.

[0086] As shown in Figure 10, an increase in the ejection volume when forming large dots is observed in samples Nos. 3, 5, 8, and 11. An increase in the ejection volume when forming medium dots is observed in samples Nos. 4, 5, and 8 to 11. Samples Nos. 7 to 9 and 12 are able to slow down the ink ejection speed from nozzle N when forming small dots.

[0087] Here, sample No. 8 corresponds to this embodiment, and an increase in the ejection amount when forming large dots and medium dots is observed, and the ink ejection speed from nozzle N can be slowed down when forming small dots. Also, in each of samples No. 5 and No. 11, although the ink ejection speed from nozzle N cannot be slowed down when forming small dots, an increase in the ejection amount when forming large dots and medium dots is observed. Sample No. 5 corresponds to the second embodiment described later. Sample No. 11 corresponds to the third embodiment described later.

[0088] A10: Summary of the first embodiment As described above, the liquid ejection device 100 includes a nozzle N, a pressure chamber C, a driving element 51f, a driving signal generation circuit 24 which is an example of a "driving signal generation section", and a control circuit 21 which is an example of a "control section". The nozzle N ejects ink which is an example of a "liquid". The pressure chamber C is in communication with the nozzle N. The driving element 51f applies pressure fluctuations to the ink in the pressure chamber C in response to the driving signal Com. The driving signal generation circuit 24 generates the driving signal Com. The control circuit 21 controls the supply of the driving signal Com to the driving element 51f for each unit period Tu of a predetermined cycle.

[0089] As described above, the drive signal Com includes an ejection pulse PA2, which is an example of a "first ejection pulse," an ejection pulse PA4, which is an example of a "second ejection pulse," and a non-ejection pulse PA3, at different timings within a unit period Tu. Each of the ejection pulse PA2 and the ejection pulse PA4 drives the drive element 51f to eject ink from the nozzle N. In contrast, the non-ejection pulse PA3 drives the drive element 51f without ejecting ink from the nozzle N.

[0090] Then, when the control circuit 21 ejects a first amount of ink from the nozzle N within the unit period Tu, it selects an ejection pulse PA2 and an ejection pulse PA4 as pulses to be supplied to the drive element 51f. When the control circuit 21 ejects a second amount of ink, which is less than the first amount, from the nozzle N within the unit period Tu, it selects a non-ejection pulse PA3 and an ejection pulse PA4 as pulses to be supplied to the drive element 51f. Here, the second amount is greater than the amount of ink ejected from the nozzle N by supplying only the ejection pulse PA4 to the drive element 51f.

[0091] In the above liquid ejection device 100, since the second amount is greater than the amount of ink ejected from the nozzle N by supplying only the ejection pulse PA4 to the driving element 51f, there is an advantage in that it is easier to optimize the balance between the first amount and the second amount compared to a configuration in which the amount of ink ejected from the nozzle N and the second amount are equal by supplying only the ejection pulse PA4 to the driving element 51f. Here, when ejecting the second amount of ink from the nozzle N, by using not only the ejection pulse PA4 but also the non-ejection pulse PA3 in combination, particularly by using the non-ejection pulse PA3 and the ejection pulse PA4 consecutively in this order, it is possible to make the second amount greater than the amount of ink ejected from the nozzle N by supplying only the ejection pulse PA4 to the driving element 51f.

[0092] Also, within the unit period Tu, the pulses can be arranged in the order of the ejection pulse PA2, the non-ejection pulse PA3, and the ejection pulse PA4. Therefore, even if the pulse interval is shortened, when ejecting the first amount of ink from the nozzle N, the interval between the ejection pulse PA2 and the ejection pulse PA4 can be set to an interval that ensures that the ejection of the ink from the nozzle N by the subsequent ejection pulse PA4 is not unintentionally affected by the residual vibration of the meniscus of the ink in the nozzle N by the preceding ejection pulse PA2, and that ensures the ejection of a sufficient first amount, while providing the non-ejection pulse PA3 for ensuring the second amount between the ejection pulse PA2 and the ejection pulse PA4. As a result, it is possible to reduce the decrease in the first amount due to the unintentional influence, and to ensure the second amount. Therefore, even if the printing speed is increased, the shading difference of the multiple gradations can be optimized.

[0093] Here, as described above, the first amount is greater than the sum of the amount of ink ejected from the nozzle N by supplying only the ejection pulse PA2 to the driving element 51f and the amount of ink ejected from the nozzle N by supplying only the ejection pulse PA4 to the driving element 51f. Therefore, the difference between the first amount and the second amount can be made greater than in a configuration in which the first amount is equal to the sum. In addition, by continuously using the non-ejection pulse PA3 and the ejection pulse PA4 in this order, the second amount can be made greater than the amount of ink ejected from the nozzle N by supplying only the ejection pulse PA4 to the driving element 51f, so that the ratio of the second amount to the first amount can be made appropriate to optimize the difference in gradation density.

[0094] From the viewpoint of increasing the difference between the first amount and the second amount, as mentioned above, it is preferable that the interval T24 between the ejection pulse PA2 and the ejection pulse PA4 within the unit period Tu is within the range of 0.4 to 0.6 times the natural vibration period of the meniscus of the ink in the nozzle N.

[0095] In this case, when ejecting a first amount of ink from the nozzle N, the ejection of ink from the nozzle N by the latter pulse of the ejection pulse PA2 and the ejection pulse PA4 can effectively utilize the residual vibration of the meniscus of the ink in the nozzle N by the preceding pulse so that the first amount is larger. As a result, the first amount can be made larger than the sum of the amount of ink ejected from the nozzle N by supplying only the ejection pulse PA2 to the drive element 51f and the amount of ink ejected from the nozzle N by supplying only the ejection pulse PA4 to the drive element 51f.

[0096] In this embodiment, as described above, within the unit period Tu, the timing of the ejection pulse PA4 is after the timing of the ejection pulse PA2. Here, when each of the first period Tu_1 and the second period Tu_2 that follows the first period Tu_1 is defined as a unit period Tu, when a first amount of ink is ejected from the nozzle N within each of the first period Tu_1 and the second period Tu_2, from the viewpoint of increasing the difference between the first amount and the second amount, it is preferable that the interval between the ejection pulse PA4 within the first period Tu_1 and the ejection pulse PA2 within the second period Tu_2 is within a range of 0.4 to 0.6 times the natural vibration period of the meniscus of the ink in the nozzle N.

[0097] In this case, when ejecting a first amount of ink from the nozzle N, the ejection of ink from the nozzle N by the ejection pulse PA2 can effectively utilize the residual vibration of the meniscus of the ink in the nozzle N by the ejection pulse PA4 so that the first amount is greater in both the consecutive first period Tu_1 and second period Tu_2. As a result, in both the consecutive first period Tu_1 and second period Tu_2, the first amount can be made greater than the sum of the amount of ink ejected from the nozzle N by supplying only the ejection pulse PA2 to the drive element 51f and the amount of ink ejected from the nozzle N by supplying only the ejection pulse PA4 to the drive element 51f.

[0098] As described above, the voltage amplitude V2 of the ejection pulse PA2 and the voltage amplitude V4 of the ejection pulse PA4 are equal to each other. Therefore, it is easier to generate the drive signal Com compared to a configuration in which the voltage amplitude V2 of the ejection pulse PA2 and the voltage amplitude V4 of the ejection pulse PA4 are different from each other. Alternatively, the voltage amplitude V2 of the ejection pulse PA2 and the voltage amplitude V4 of the ejection pulse PA4 can be set to the maximum voltage amplitude possible in the structure of the liquid ejection device 100, and the first amount can be increased.

[0099] Furthermore, as described above, within the unit period Tu, the timing of the non-ejection pulse PA3 is immediately before the timing of the ejection pulse PA4. Therefore, the amount of ink ejected from the nozzle N by the ejection pulse PA4 can be increased by using the vibration of the meniscus caused by the non-ejection pulse PA3. As a result, the second amount can be made larger than the amount of ink ejected from the nozzle N by supplying only the ejection pulse PA4 to the drive element 51f.

[0100] As described above, the timing of the ejection pulse PA2 is immediately before the timing of the non-ejection pulse PA3 within the unit period Tu. Therefore, the non-ejection pulse PA3 and the ejection pulse PA4 can be used consecutively in this order.

[0101] Furthermore, as described above, the drive signal Com includes an ejection pulse PA1, which is an example of a "third ejection pulse," in the unit period Tu at a different timing from the ejection pulse PA2, the ejection pulse PA4, and the non-ejection pulse PA3. The ejection pulse PA1 drives the drive element 51f to eject ink from the nozzle N. When ejecting a third amount of ink, which is less than the second amount, from the nozzle N within the unit period Tu, the control circuit 21 selects the ejection pulse PA1 as the pulse to be supplied to the drive element 51f. Therefore, the number of gradations can be increased compared to a configuration that does not use the third amount.

[0102] In this embodiment, as described above, the ejection pulse PA1, the ejection pulse PA2, the non-ejection pulse PA3, and the ejection pulse PA4 are arranged in this order within the unit period Tu. Therefore, the non-ejection pulse PA3 and the ejection pulse PA4 are used continuously in this order, and the interval between the ejection pulse PA2 and the ejection pulse PA4 can be optimized. Furthermore, compared to a configuration in which the timing of the ejection pulse PA1 is after the timing of any of the other pulses, even if the ejection speed of the ink from the nozzle N by the ejection pulse PA1 is slowed down, the third amount of dots can be landed at a desired position on the medium M corresponding to the landing position of the first amount of dots and the second amount of dots. Therefore, the degree of freedom in designing the waveform of the ejection pulse PA1 can be increased. As a result, the tailing of ink from the nozzle N by the ejection pulse PA1 can be reduced. In addition, in the first period Tu_1 and the second period Tu_2 following the first period Tu_1, the interval between the ejection pulse PA4 in the first period Tu_1 and the ejection pulse PA2 in the second period Tu_2 can be set to an interval that ensures sufficient ejection of the first amount while preventing the ejection of ink from the nozzle N by the latter ejection pulse PA2 from being unintentionally affected by the residual vibration of the meniscus of the ink in the nozzle N by the former ejection pulse PA4, and provides an ejection pulse PA1 for ejecting the third amount between the former ejection pulse PA4 and the latter ejection pulse PA2. This allows the ejection pulse PA1, the ejection pulse PA2, the non-ejection pulse PA3, and the ejection pulse PA4 to be arranged at appropriate timing without lengthening the unit period Tu.

[0103] Here, as described above, when the second amount is within the range of 1.8 to 2.2 times the third amount, there is an advantage in that the gradation balance between the second amount and the third amount can be easily optimized.

[0104] Also, as mentioned above, when the difference between the ratio of the second amount to the third amount and the ratio of the first amount to the second amount is 10% or less, there is an advantage in that the gradation balance achieved by the first amount, second amount, and third amount can be easily optimized.

[0105] Furthermore, as described above, when the first amount is within the range of 1.8 to 2.2 times the second amount, there is an advantage that the gradation balance between the first amount and the second amount can be easily optimized.

[0106] Furthermore, as described above, when the control circuit 21 drives the drive element 51f without ejecting ink from the nozzle N within the unit period Tu, the control circuit 21 selects the non-ejection pulse PA3 as the pulse to be supplied to the drive element 51f. Therefore, by vibrating the meniscus of the ink in the nozzle N without ejecting ink from the nozzle N, it is possible to reduce thickening of the ink in the nozzle N, etc.

[0107] B: Second embodiment A second embodiment of the present disclosure will be described below. In the following exemplary embodiment, the elements having the same actions and functions as those in the first embodiment will be referred to by the same reference numerals used in the description of the first embodiment, and detailed descriptions thereof will be omitted as appropriate.

[0108] 11 is a diagram for explaining the driving signal Com-A used in the second embodiment. The driving signal Com-A is similar to the driving signal Com in the first embodiment, except that the timing of the pulses in the unit period Tu is different.

[0109] The driving signal Com-A has an ejection pulse PA2 provided in the control period Tu1, a non-ejection pulse PA3 provided in the control period Tu2, an ejection pulse PA4 provided in the control period Tu3, and an ejection pulse PA1 provided in the control period Tu4. Here, the periods T24 and T34 are each set in the same manner as the driving signal Com of the first embodiment described above.

[0110] As with the first embodiment described above, the second embodiment can optimize the shading difference between multiple gradations even when the printing speed is increased. In this embodiment, the ejection pulse PA1 is provided in the control period Tu4, so compared to the first embodiment, when forming small dots, it is necessary to increase the ejection speed of ink from the nozzle N in accordance with the landing positions of the first amount of dots and the second amount of dots on the medium M. As a result, it is possible to improve the landing accuracy of the ink forming the small dots on the medium M.

[0111] C: Third embodiment The third embodiment of the present disclosure will be described below. In the following exemplary embodiment, for elements whose actions and functions are similar to those of the first embodiment, the reference symbols used in the description of the first embodiment will be used and detailed descriptions of each will be omitted as appropriate.

[0112] 12 is a diagram for explaining the driving signal Com-B used in the third embodiment. The driving signal Com-B is similar to the driving signal Com in the first embodiment, except that the timing of the pulses in the unit period Tu is different.

[0113] The driving signal Com-A has a non-ejection pulse PA3 provided in the control period Tu1, an ejection pulse PA4 provided in the control period Tu2, an ejection pulse PA1 provided in the control period Tu3, and an ejection pulse PA2 provided in the control period Tu4. Here, the periods T24 and T34 are each set in the same manner as the driving signal Com of the first embodiment described above.

[0114] According to the third embodiment, as in the first embodiment, even if the printing speed is increased, the density difference of multiple gradations can be optimized. In this embodiment, the ejection pulse PA1 is provided in the control period Tu3, so compared to the first embodiment, when forming small dots, it is necessary to increase the ejection speed of ink from the nozzle N in accordance with the landing positions of the first amount of dots and the second amount of dots on the medium M. As a result, the landing accuracy of the ink forming the small dots on the medium M can be improved. Also, in this embodiment, as described above, these pulses are arranged in the order of the non-ejection pulse PA3, the ejection pulse PA4, the ejection pulse PA1, and the ejection pulse PA2 within the unit period Tu. Therefore, the interval T24 between the ejection pulse PA2 and the ejection pulse PA4 can be optimized while continuously using the non-ejection pulse PA3 and the ejection pulse PA4 in this order within the unit period Tu.

[0115] D: Fourth embodiment The fourth embodiment of the present disclosure will be described below. In the following exemplary embodiments, the elements having the same actions and functions as those in the first embodiment will be referred to by the same reference numerals used in the description of the first embodiment, and detailed descriptions thereof will be omitted as appropriate.

[0116] 13 is a diagram for explaining the driving signal Com-C used in the fourth embodiment. The driving signal Com-C is similar to the driving signal Com in the first embodiment, except that a non-ejection pulse PA5 is used instead of the non-ejection pulse PA3.

[0117] The non-ejection pulse PA5 is a potential pulse that drives the driving element 51f to generate a pressure fluctuation in the pressure chamber C that is strong enough not to eject ink from the nozzle N. By supplying the non-ejection pulse PA5 to the driving element 51f, the ink meniscus in the nozzle N is slightly vibrated without ejecting ink from the nozzle N.

[0118] 13, the non-ejection pulse PA5 has a waveform that goes from the reference potential V0 to the potential E51 and then returns to the reference potential V0. Here, the potential E51 is a potential higher than the reference potential V0. In addition, the timing of the potential E51 is after the midpoint of the control period Tu3.

[0119] The smaller the interval T54 between the non-ejection pulse PA5 and the ejection pulse PA4, the greater the ejection amount when forming a medium dot. The interval T54 is the time length from the end point of the expansion element indicating the change from the potential E51 of the non-ejection pulse PA5 to the reference potential V0 to the start point of the expansion element indicating the change from the potential E41 to the potential E42 of the ejection pulse PA4.

[0120] Although not shown, as with the interval T34 in the first embodiment described above, as the interval T54 increases, the ejection amount during medium dot formation decreases while taking multiple maximum values. This corresponds to the effect of vibration of the meniscus in the nozzle N. Therefore, the effect of increasing the ejection amount during medium dot formation is obtained by the contribution of the vibration of the meniscus of the ink in the nozzle N by the non-ejection pulse PA5 to the ejection of ink from the nozzle N by the ejection pulse PA4. Therefore, it is preferable that the interval T54 is 1 / 4 or less of the natural vibration period of the meniscus of the ink in the nozzle N. However, since the non-ejection pulse PA5 has a waveform that is an inversion of the non-ejection pulse PA3 in the first embodiment described above, from the viewpoint of increasing the ejection amount during medium dot formation, it is preferable that the interval T54 is (integer-0.5) times the natural vibration period of the ink in the communicating flow channel Na, and more preferably 0.5 times the natural vibration period of the ink in the communicating flow channel Na.

[0121] According to the fourth embodiment, similarly to the first embodiment described above, even if the printing speed is increased, it is possible to optimize the shading difference among multiple gradations.

[0122] E: Variation Each of the above-mentioned exemplary embodiments may be modified in various ways. Specific modified embodiments that may be applied to each of the above-mentioned embodiments are illustrated below. Any embodiment selected from the following examples may be appropriately combined to the extent that they are not inconsistent with each other.

[0123] E1: Variation 1 In each of the above-described embodiments, the nozzle N has a first portion NP1 and a second portion NP2, but the nozzle N is not limited to this configuration. For example, the nozzle N may have a constant width or may have a shape with three or more steps.

[0124] E2: Variation 2 The configuration of the head chip 51 is not limited to the example shown in FIG. 3, and may be any configuration.

[0125] E3: Variation 3 In each of the above-described embodiments, a serial-type liquid ejection device 100 in which a carriage 41 carrying a liquid ejection head 50 is moved back and forth has been exemplified, but the present disclosure can also be applied to a line-type liquid ejection device in which multiple nozzles N are distributed across the entire width of the medium M.

[0126] E4: Variation 4 The liquid ejection device 100 exemplified in the above embodiment may be adopted in various devices such as facsimile machines and copy machines in addition to devices dedicated to printing, and the use of the present disclosure is not particularly limited. However, the use of the liquid ejection device is not limited to printing. For example, a liquid ejection device that ejects a solution of a color material is used as a manufacturing device that forms a color filter of a display device such as a liquid crystal display panel. In addition, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device that forms wiring and electrodes of a wiring board. In addition, a liquid ejection device that ejects a solution of an organic substance related to a living body is used as a manufacturing device that manufactures, for example, a biochip. [Explanation of symbols]

[0127] 10...liquid container, 20...control unit, 21...control circuit (control unit), 22...memory circuit, 23...power supply circuit, 24...drive signal generating circuit (drive signal generating unit), 30...transport mechanism, 40...movement mechanism, 41...carriage, 42...transport belt, 50...liquid ejection head, 51...head chip, 51a...flow path substrate, 51b...pressure chamber substrate, 51c...nozzle plate, 51d...vibration absorber, 51e...vibration plate, 51f...drive element, 51g...protective plate, 51h...case, 51i...wiring substrate, 52...switching circuit , 52a...connection state designation circuit, 100...liquid ejection device, 200...external device, C...pressure chamber, CLK...clock signal, CNG...change signal, Com...drive signal, Com-A...drive signal, Com-B...drive signal, Com-C...drive signal, E11...potential, E12...potential, E13...potential, E14...potential, E15...potential, E16...potential, E21...potential, E22...potential, E31...potential, E41...potential, E42...potential, E43...potential, E51...potential, FN...nozzle surface, IH...inlet , Img...print data, L1...first row, L2...second row, LAT...latch signal, LHa...wiring, LHd...wiring, M...medium, N...nozzle, NP1...first part, NP2...second part, Na...connecting flow path, PA1...ejection pulse (third ejection pulse), PA2...ejection pulse (first ejection pulse), PA3...non-ejection pulse, PA4...ejection pulse (second ejection pulse), PA5...non-ejection pulse, PlsC...pulse, PlsL...pulse, R...reservoir, R1...space, R2...space, Ra...supply flow path, SI...print data signal, SLa...connection state designation signal, SWa...switch, Sk1...control signal, Sk2...control signal, T24...period, T34...period, Tu...unit period, Tu1...control period, Tu2...control period, Tu3...control period, Tu4...control period, Tu_1...first period, Tu_2...second period, V0...reference potential, V2...voltage amplitude, V4...voltage amplitude, VBS...offset potential, VHV...power supply potential, Vin...supply signal, Zd...electrode, Zu...electrode, dCom...waveform designation signal.

Claims

1. A nozzle for discharging a liquid; a pressure chamber communicating with the nozzle; A drive element that applies a pressure fluctuation to the liquid in the pressure chamber in response to a drive signal; A drive signal generating unit that generates the drive signal; a control unit that controls the supply of the drive signal to the drive element for each unit period of a predetermined cycle; 、 Equipped with The drive signal is a first ejection pulse for driving the drive element to eject liquid from the nozzle; a second ejection pulse that drives the drive element to eject liquid from the nozzle; and a non-ejection pulse for driving the driving element without ejecting liquid from the nozzle, included in the unit period at different timings, The control unit is When a first amount of liquid is to be ejected from the nozzle within the unit period, selecting the first ejection pulse and the second ejection pulse as pulses to be ejected, When a second amount of liquid that is smaller than the first amount is ejected from the nozzle within the unit period, In this case, the non-ejection pulse and the second ejection pulse are supplied to the driving element. Select The second amount is determined by supplying only the second ejection pulse to the driving element. The amount of liquid discharged from the nozzle is greater than the amount of liquid discharged from the nozzle. The drive signal is a signal for driving the drive element to eject liquid from the nozzle. The third ejection pulse is different from the first ejection pulse, the second ejection pulse, and the non-ejection pulse. The unit period is included at a timing when The control unit is When a third amount of liquid that is smaller than the second amount is ejected from the nozzle within the unit period, selects the third ejection pulse as the pulse to be supplied to the driving element. Liquid discharge device.

2. A nozzle for discharging a liquid; a pressure chamber communicating with the nozzle; A drive element that applies a pressure fluctuation to the liquid in the pressure chamber in response to a drive signal; A drive signal generating unit that generates the drive signal; a control unit that controls the supply of the drive signal to the drive element for each unit period of a predetermined cycle; 、 Equipped with The drive signal is a first ejection pulse that drives the drive element to eject liquid from the nozzle; a second ejection pulse that drives the drive element to eject liquid from the nozzle; a non-ejection pulse for driving the driving element without ejecting liquid from the nozzle, included in the unit period at different timings, The control unit is When a first amount of liquid is to be ejected from the nozzle within the unit period, selecting the first ejection pulse and the second ejection pulse as pulses to be ejected, When a second amount of liquid that is smaller than the first amount is ejected from the nozzle within the unit period, In this case, the non-ejection pulse and the second ejection pulse are supplied to the driving element. Select The second amount is determined by supplying only the second ejection pulse to the driving element. The amount of liquid discharged from the nozzle is greater than the amount of liquid discharged from the nozzle. The first amount is determined by supplying only the first ejection pulse to the driving element. The amount of liquid discharged from the nozzle and the second discharge pulse are supplied to the driving element. and the amount of liquid ejected from the nozzle is greater than the sum of Liquid discharge device.

3. The interval between the first ejection pulse and the second ejection pulse within the unit period is The natural vibration period of the meniscus of the liquid is in the range of 0.4 to 0.6 times, The liquid ejection device according to claim 1 .

4. Within the unit period, the timing of the second ejection pulse is equal to the timing of the first ejection pulse. After Gu, When the first period and the second period that follows the first period are each defined as the unit period, tree, The first amount of liquid is discharged from the nozzle during each of the first period and the second period. When ejecting a body, the second ejection pulse in the first period and the first ejection pulse in the second period The interval between the ejection pulses is 0.4 times or more the natural vibration period of the meniscus of the liquid in the nozzle. Within the range of 0.6 times or less, The liquid ejection device according to claim 1 .

5. The voltage amplitude of the first ejection pulse and the voltage amplitude of the second ejection pulse are equal to each other. The liquid ejection device according to claim 1 .

6. Within the unit period, the timing of the non-ejection pulse is the timing of the second ejection pulse. Just before The liquid ejection device according to claim 1 .

7. Within the unit period, the timing of the first ejection pulse is equal to the timing of the non-ejection pulse. Just before The liquid ejection device according to claim 1 .

8. The drive signal is a signal for driving the drive element to eject liquid from the nozzle. The third ejection pulse is different from the first ejection pulse, the second ejection pulse, and the non-ejection pulse. The unit period is included at a timing when The control unit is When a third amount of liquid that is smaller than the second amount is ejected from the nozzle within the unit period, selects the third ejection pulse as the pulse to be supplied to the driving element. The liquid ejection device according to claim 2 .

9. Within the unit period, the third ejection pulse, the first ejection pulse, the non-ejection pulse, These pulses are arranged in the order of the second ejection pulse. The liquid ejection device according to claim 8.

10. Within the unit period, the non-ejection pulse, the second ejection pulse, the third ejection pulse, These pulses are arranged in the order of the first ejection pulse. The liquid ejection device according to claim 8.

11. The second amount is in the range of 1.8 times or more and 2.2 times or less of the third amount. The liquid ejection device according to claim 8 .

12. The difference between the ratio of the second amount to the third amount and the ratio of the first amount to the second amount is , 10% or less; The liquid ejection device according to claim 8 .

13. The first amount is in the range of 1.8 times or more and 2.2 times or less of the second amount. The liquid ejection device according to claim 1 .

14. The control unit is When the driving element is driven without ejecting liquid from the nozzle within the unit period, selecting the non-ejection pulse as the pulse to be supplied to the driving element; The liquid ejection device according to claim 1 .

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