Liquid discharge device

Abstract

To provide a liquid discharge device capable of suppressing discharge instability and a decrease in printing speed.SOLUTION: In a liquid discharge device, one drive cycle of a common drive signal includes n+1 discharge pulses during a first period corresponding to two consecutive pixels on a medium, where n is an even number. (n / 2)+1 consecutive discharge pulses constitute a first discharge pulse group and (n / 2) discharge pulses constitute a second discharge pulse group. When printing no dot on a first pixel and printing a third dot on a second pixel, a drive control part supplies, to a drive element, a second gradation drive signal generated by selecting all discharge pulses in the second discharge pulse group but not selecting at least n / 2 discharge pulses in the first discharge pulse group to print a fourth dot on the first pixel. When printing no dot on the second pixel, the drive control part supplies, to the drive element, a third gradation drive signal generated by selecting at least n / 2 discharge pulses in the first discharge pulse group but not selecting all discharge pulses in the second discharge pulse group.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] 2. Description of the Related Art Liquid ejection devices that eject liquid such as ink onto a medium such as printing paper have been proposed.

[0003] Patent Document 1 discloses a driving device for an inkjet recording head that ejects ink droplets from nozzle openings by activating pressure-generating elements provided corresponding to the nozzle openings. The device has a driving signal generating circuit that generates a driving signal to the pressure-generating elements. The driving signal is composed of a first pulse and a second pulse in a recording cycle corresponding to one recording pixel. Then, the ink droplet corresponding to the first pulse and the ink droplet corresponding to the second pulse land at approximately the same position on the paper, forming a large dot on the paper. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-20165 Summary of the Invention [Problem to be solved by the invention]

[0005] When increasing the number of ejection pulses to form larger dots per pixel, narrowing the interval between ejection pulses can easily cause unstable ejection, while widening the interval between ejection pulses can lengthen the drive cycle for one pixel, reducing printing speed. [Means for solving the problem]

[0006] a drive control unit that selects ejection pulses corresponding to image data from among the plurality of ejection pulses of the common drive signal to generate the individual drive signal and supplies the individual drive signal to the drive element; wherein one drive cycle of the common drive signal includes n+1 ejection pulses during a first period corresponding to two consecutive pixels on the medium, n being an even number; the n+1 ejection pulses of the common drive signal constitute a first ejection pulse group consisting of consecutive (n / 2)+1 ejection pulses; and a second ejection pulse group consisting of (n / 2) ejection pulses that are consecutively aligned with the ejection pulses of the first ejection pulse group, and prints a first dot on a first pixel on the medium and a second dot on a second pixel that is consecutively aligned with the first pixel. and supplies, as the individual drive signal, to the drive element a first gradation drive signal generated by selecting all of the ejection pulses included in the first period from the common drive signal; when printing no dot at the first pixel and printing a third dot at the second pixel, the drive control unit supplies, as the individual drive signal, to the drive element a second gradation drive signal generated by not selecting at least n / 2 of the ejection pulses of the first ejection pulse group from the common drive signal and selecting all of the ejection pulses of the second ejection pulse group; when printing a fourth dot at the first pixel and not printing a dot at the second pixel, the drive control unit supplies, as the individual drive signal, to the drive element a third gradation drive signal generated by selecting at least n / 2 of the ejection pulses of the first ejection pulse group from the common drive signal and not selecting all of the ejection pulses of the second ejection pulse group; and [Brief explanation of the drawings]

[0007] [Figure 1]1 is a schematic diagram illustrating an example of the configuration of a liquid ejection device according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing the electrical configuration of the liquid ejection device according to the first embodiment. [Figure 3] FIG. 3 is a diagram showing a plurality of head chips shown in FIG. [Figure 4] 4 is a cross section showing a part of the head chip shown in FIG. 3. [Figure 5] 3 is a diagram for explaining a first common drive signal generated by the drive signal generating section shown in FIG. 2. FIG. [Figure 6] 6 is a diagram showing a first individual drive signal generated from the first common drive signal of FIG. 5. FIG. [Figure 7] 7 is a diagram showing dots formed on a medium when the first individual drive signal of FIG. 6 is supplied to a first drive element. FIG. [Figure 8] 6 is a diagram showing a second individual drive signal generated from the first common drive signal of FIG. 5. FIG. [Figure 9] 9 is a diagram showing dots formed on a medium when the second individual drive signal in FIG. 8 is supplied to a second drive element. [Figure 10] 9 is a diagram for explaining the supply timing of the first individual drive signal of FIG. 6 and the second individual drive signal of FIG. 8. FIG. [Figure 11] FIG. 10 is a diagram for explaining the supply timing of a first individual drive signal and a second individual drive signal in the second embodiment. [Figure 12] FIG. 10 is a diagram showing dots formed on a medium in the second embodiment. [Figure 13] FIG. 11 is a diagram for explaining a second common drive signal in the third embodiment. [Figure 14] 14 is a diagram showing a second individual drive signal generated from the second common drive signal of FIG. 13. FIG. [Figure 15] 10A and 10B are diagrams illustrating dots formed on a medium in the third embodiment. [Figure 16] FIG. 10 is a diagram for explaining a first individual drive signal in the fourth embodiment. [Figure 17] FIG. 10 is a diagram for explaining another first individual drive signal in the fourth embodiment. [Figure 18] 17 is a diagram showing dots formed on a medium when the first individual drive signal of FIG. 16 is supplied to a first drive element. FIG. [Figure 19] 18 is a diagram showing dots formed on a medium when the first individual drive signal of FIG. 17 is supplied to a first drive element. FIG. [Figure 20] FIG. 13 is a diagram for explaining a common drive signal in the fifth embodiment. [Figure 21] FIG. 21 is a diagram showing a first gradation drive signal generated from the common drive signal of FIG. 20. [Figure 22] 22 is a diagram showing dots formed on a medium when the first gradation drive signal of FIG. 21 is supplied to a drive element. FIG. [Figure 23] FIG. 23 is a diagram for explaining a second gradation drive signal in the sixth embodiment. [Figure 24] FIG. 20 is a diagram for explaining a third gradation drive signal in the sixth embodiment. [Figure 25] 24 is a diagram showing dots formed on a medium when the second gradation drive signal of FIG. 23 is supplied to a drive element. FIG. [Figure 26] 25 is a diagram showing dots formed on a medium when the third gradation drive signal of FIG. 24 is supplied to a drive element. FIG. [Figure 27] FIG. 20 is a diagram for explaining a second gradation drive signal in the seventh embodiment. [Figure 28] FIG. 20 is a diagram for explaining a third gradation drive signal in the seventh embodiment. [Figure 29] 28 is a diagram showing dots formed on a medium when the second gradation drive signal of FIG. 27 is supplied to a drive element. FIG. [Figure 30] 29 is a diagram showing dots formed on a medium when the third gradation drive signal of FIG. 28 is supplied to a drive element. FIG. [Figure 31] FIG. 20 is a diagram for explaining a fourth gradation drive signal in the eighth embodiment. [Figure 32] 32 is a diagram showing dots formed on a medium when the fourth gradation drive signal of FIG. 31 is supplied to a drive element. FIG. [Figure 33]FIG. 10 is a diagram for explaining a fifth gradation drive signal of the first modified example. [Figure 34] 34 is a diagram showing dots formed on a medium when the fourth gradation drive signal of FIG. 33 is supplied to a drive element. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] Preferred embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that the dimensions and scale of each part in the drawings may differ from the actual dimensions and are shown schematically to facilitate understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description to the effect that the present disclosure is limited.

[0009] The following description will use the mutually intersecting X-axis, Y-axis, and Z-axis as appropriate. In the following, one direction along the X-axis is the X1 direction, and the direction opposite the X1 direction is the X2 direction. Similarly, the Y1 and Y2 directions are opposite directions along the Y-axis. The Z1 and Z2 directions are opposite directions along the Z-axis. Typically, the Z-axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. However, the Z-axis does not have to be a vertical axis. Furthermore, the X-axis, Y-axis, and Z-axis are typically perpendicular to each other, but this is not a limitation. For example, they may intersect at an angle between 80° and 100°. In this specification, "equal" refers not only to strict equality but also to manufacturing and assembly errors.

[0010] A: First embodiment A1: Overall configuration of the liquid ejection device 100 Fig. 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 shown in Fig. 1 is an inkjet printing device that ejects liquid such as ink as droplets onto a medium M. The medium M is a printing target made of any material, such as printing paper, a resin film, or fabric.

[0011] As shown in FIG. 1, the liquid ejection device 100 includes a liquid container 9, a control unit 20, a transport mechanism 22, a moving mechanism 23, a support member 27, and a liquid ejection head 50.

[0012] The liquid container 9 stores liquid. Specific embodiments of the liquid container 9 include, for example, a cartridge that is detachable from the liquid ejection device 100, a bag-shaped liquid pack made of flexible film, and a liquid tank that can be refilled with liquid.

[0013] 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.

[0014] The support member 27 supports the medium M. The transport mechanism 22 transports the medium M in the Y2 direction under the control of the control unit 20. The transport mechanism 22 includes a transport roller 221 that transports the medium M. The movement mechanism 23 reciprocates the liquid ejection head 50 along the Y axis under the control of the control unit 20. For example, the movement mechanism 23 moves the liquid ejection head 50 in the Y2 direction when ejecting liquid, and moves the liquid ejection head 50 in the Y1 direction each time the movement in the Y2 direction is completed. The movement mechanism 23 includes a substantially box-shaped carriage 231 that houses the liquid ejection head 50 and an endless transport belt 232 to which the carriage 231 is fixed. The transport mechanism 22 and the movement mechanism 23 move the relative positions of the liquid ejection head 50 and the medium M along the Y axis. Note that, for example, the movement mechanism 23 may be omitted. As a result, while the transport mechanism 22 stops transporting the medium M, the movement mechanism 23 prints an image while moving the liquid ejection head 50 in the Y2 direction, and after printing of the image is completed, the transport mechanism 22 transports the medium M in the Y2 direction, and the movement mechanism 23 moves the liquid ejection head 50 in the Y1 direction.

[0015] Furthermore, the number of liquid ejection heads 50 mounted on the carriage 231 is not limited to one, and may be more than one. In addition to the liquid ejection heads 50, the carriage 231 may also be equipped with the liquid containers 9 described above.

[0016] The liquid ejection head 50 ejects the liquid supplied from the liquid container 9 from a plurality of nozzles N onto the medium M under the control of the control unit 20. This ejection is performed in parallel with the transport of the medium M by the movement mechanism 23 and the movement of the liquid ejection head 50 by the movement mechanism 23, thereby forming an image on the surface of the medium M.

[0017] A2: Electrical configuration of the liquid ejection device 100 2 is a diagram showing the electrical configuration of the liquid ejection device 100 according to the first embodiment. As shown in FIG.

[0018] Each head chip 51 has a plurality of ejection units 510. As will be described later, each ejection unit 510 has a nozzle N that ejects liquid and a drive element E. Under the control of the control unit 20, the drive control unit 52 switches whether or not to supply a common drive signal Com output from the control unit 20 to each of the plurality of ejection units 510 as an individual drive signal Vin.

[0019] The control unit 20 includes a control circuit 21, a memory circuit 26, a power supply circuit 25, and a drive signal generating section 24.

[0020] The control circuit 21 has a function to control the operation of each part of the liquid ejection device 100 and a function to process various data. The control circuit 21 includes, for example, one or more processors such as a CPU (Central Processing Unit). Note that the control circuit 21 may include a programmable logic device such as an FPGA (Field-Programmable Gate Array) instead of or in addition to a CPU. Furthermore, when the control circuit 21 is made up of multiple processors, the multiple processors may be mounted on different boards or the like.

[0021] Furthermore, the control circuit 21 generates a control signal Sk1, a control signal Sk2, a print data signal SI, and a waveform designation signal dCom as signals for controlling the operation of each part of the liquid ejection device 100 by executing the program.

[0022] The control signal Sk1 is a signal for controlling the driving of the transport mechanism 22. The control signal Sk2 is a signal for controlling the driving of the movement mechanism 23. The print data signal SI is a digital signal for specifying the operating state of the drive elements E. The print data signal SI includes a latch signal LAT and a change signal CH, which are timing signals for determining the drive timing of the drive elements E (described below) of the ejection unit 510. The timing signals are generated, for example, based on the output of an encoder that detects the position of the carriage 231 described above. The waveform designation signal dCom is a digital signal for determining the waveform of the common drive signal Com.

[0023] The memory circuit 26 stores various programs executed by the control circuit 21 and various data such as image data Img processed by the control circuit 21. The memory circuit 26 includes, for example, one or both of semiconductor memories: 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 read-only memory (PROM). The image data Img is supplied from an external device 200 such as a personal computer or a digital camera. The memory circuit 26 may be configured as a part of the control circuit 21.

[0024] The power supply circuit 25 receives power from a commercial power supply (not shown) and generates various predetermined potentials. The generated potentials are supplied to each section of the liquid ejection device 100 as appropriate. For example, the power supply circuit 25 generates a power supply potential VHV and an offset potential VBS. The offset potential VBS is supplied to the liquid ejection head 50. The power supply potential VHV is also supplied to the drive signal generation section 24.

[0025] The drive signal generation unit 24 is a circuit that repeatedly generates a common drive signal Com for driving each drive element E included in each ejection unit 510. Specifically, the drive signal generation unit 24 has, for example, a DA conversion circuit and an amplifier circuit. In the drive signal generation unit 24, the DA conversion circuit converts the waveform designation signal dCom from the control circuit 21 from a digital signal to an analog signal. The amplifier circuit amplifies the analog signal using the power supply potential VHV from the power supply circuit 25, thereby generating the common drive signal Com. Of the waveforms included in the common drive signal Com, the signal with the waveform that is actually supplied to the drive element E is the individual drive signal Vin described above.

[0026] A3: Arrangement of multiple head chips 51 Fig. 3 is a diagram showing the plurality of head chips 51 shown in Fig. 2. In the example shown in Fig. 3, the liquid ejection head 50 has six head chips 51. Each head chip 51 is elongated and extends in the direction along the X axis when viewed in the Z1 direction. The plurality of head chips 51 are arranged at intervals from each other in the direction along the Y axis, which is the transport direction of the medium M.

[0027] Each head chip 51 has a plurality of nozzles N. The plurality of nozzles N are divided into two nozzle rows L and aligned along the longitudinal direction of the head chip 51. Each nozzle row L is a collection of a plurality of nozzles N aligned in a straight line along the X axis. The row direction of each nozzle row L is perpendicular to the Y2 direction, which is the transport direction of the liquid ejection head 50. The nozzles N belonging to each nozzle row L are aligned at equal intervals. The planar shape of the plurality of nozzles N is, for example, circular, and they are formed to have the same opening area.

[0028] The longitudinal direction of head chip 51 and the row direction of nozzle row L do not have to coincide with the direction along the X axis. For example, the longitudinal direction of head chip 51 and the row direction of nozzle row L may intersect with the X axis and Y axis when viewed in the direction along the Z axis. Furthermore, the two nozzle rows of each head chip 51 are arranged so that the nozzles N are offset by half a pitch, but they do not have to be offset by half a pitch.

[0029] A4: Partial configuration of each head chip 51 Fig. 4 is a cross-section showing a portion of the head chip 51 shown in Fig. 3. As shown in Fig. 4, the head chip 51 has a nozzle plate 11, a vibration absorber 12, a flow path substrate 13, a pressure chamber substrate 14, a diaphragm 15, a wiring substrate 16, a housing unit 17, and a drive circuit 18. The nozzle plate 11, the vibration absorber 12, the flow path substrate 13, the pressure chamber substrate 14, the diaphragm 15, the wiring substrate 16, and the housing unit 17 are each a plate-like member that is elongated in the direction along the Y axis. The nozzle plate 11, the flow path substrate 13, the pressure chamber substrate 14, the diaphragm 15, and the wiring substrate 16 are arranged in this order in the Z1 direction.

[0030] The nozzle plate 11 is a plate-like member in which a plurality of nozzles N are formed. Each of the plurality of nozzles N is a circular through-hole that allows a liquid to pass through. The nozzles N eject the liquid by vibration of the vibration plate 15. The nozzle plate 11 is bonded to the flow path substrate 13 with, for example, an adhesive.

[0031] The flow path substrate 13 is formed with flow paths for supplying liquid to the multiple nozzles N. Specifically, the flow path substrate 13 is formed with a space Ra, multiple supply flow paths 131, multiple communication flow paths 132, and a supply liquid chamber 133. The space Ra is an elongated opening extending in a direction along the X axis in a plan view seen in a direction along the Z axis. Each of the supply flow path 131 and the communication flow path 132 is a through-hole formed for each nozzle N. The supply liquid chamber 133 is an elongated space extending in a direction along the X axis across the multiple nozzles N, and connects the space Ra and the multiple supply flow paths 131 to each other. Each of the multiple communication flow paths 132 overlaps with one nozzle N corresponding to that communication flow path 132 in a plan view. A pressure chamber substrate 14 is bonded to the flow path substrate 13 with, for example, an adhesive.

[0032] The pressure chamber substrate 14 is provided with a plurality of pressure chambers C. Each pressure chamber C is formed for each nozzle N and is an elongated space extending in a direction along the Y axis in a plan view. The plurality of pressure chambers C are arranged in a direction along the X axis. The pressure chamber C is a space located between the flow path substrate 13 and the vibration plate 15. The pressure chamber C communicates with the nozzle N via a communication flow path 132, and also communicates with the space Ra via a supply flow path 131 and a supply liquid chamber 133.

[0033] The nozzle plate 11, the flow path substrate 13, and the pressure chamber substrate 14 are each manufactured by processing a silicon single crystal substrate using, for example, dry etching, wet etching, etc. However, other known methods may also be used as appropriate to manufacture the nozzle plate 11, the flow path substrate 13, and the pressure chamber substrate 14.

[0034] A diaphragm 15 is disposed on the surface facing the Z1 direction of the pressure chamber substrate 14. The diaphragm 15 is a plate-like member that can vibrate elastically.

[0035] A plurality of drive elements E corresponding to the nozzles N are arranged on the surface of the vibration plate 15 facing the Z1 direction. Each drive element E has an elongated shape extending in the direction along the Y axis in a plan view. The plurality of drive elements E correspond to a plurality of pressure chambers C and are arranged in the direction along the X axis. The drive elements E are driven to change the volume of the pressure chambers C in accordance with the individual drive signal Vin generated from the common drive signal Com. In other words, the drive elements E are deformed by the application of a voltage. When the vibration plate 15 vibrates in conjunction with this deformation, the pressure in the pressure chambers C changes, causing liquid to be ejected from the nozzles N.

[0036] The housing 17 is a case for storing the liquid to be supplied to the multiple pressure chambers C. As shown in FIG. 4, a space Rb is formed in the housing 17. The space Rb in the housing 17 and the space Ra in the flow path substrate 13 are connected to each other. The space formed by the spaces Ra and Rb functions as a liquid storage chamber R, which is a reservoir that stores the liquid to be supplied to the multiple pressure chambers C. The liquid is supplied to the liquid storage chamber R via an inlet 171 formed in the housing 17. The liquid in the liquid storage chamber R is supplied to the pressure chambers C via the supply liquid chamber 133 and each supply flow path 131.

[0037] The vibration absorber 12 is a flexible film that forms the wall surface of the liquid storage chamber R. The vibration absorber 12 is a compliant substrate that absorbs pressure fluctuations of the liquid in the liquid storage chamber R.

[0038] The wiring board 16 is a plate-like member on which wiring is formed for electrically connecting the drive circuit 18 and the multiple drive elements E. The wiring board 16 is, for example, a rigid board. The wiring board 16 has wiring formed on its surface facing the Z1 direction to electrically connect the drive circuit 18 mounted on the surface facing the Z2 direction to the multiple bumps 16B required for driving each drive element E. The drive circuit 18 constitutes part or all of the aforementioned drive control unit 52 and has an IC (Integrated Circuit) chip that outputs an individual drive signal Vin and an offset potential VBS based on a common drive signal Com for driving each drive element E. A flexible wiring board (not shown) that is connected to the control unit 20 is also connected to the wiring board 16.

[0039] The wiring board 16 may be a flexible board such as an FFC (Flexible Flat Cable), or may be an FPC (Flexible Printed Circuits) or a COF (Chip On Film) on which the drive circuit 18 is mounted.

[0040] In the head chip 51, each of the aforementioned ejection sections 510 includes a nozzle N, a pressure chamber C, and a driving element E. In this embodiment, one ejection section 510 is configured by the nozzle N, the pressure chamber C, the supply flow path 131, the communication flow path 132, and the portion of the diaphragm 15 that corresponds to the driving element E.

[0041] Furthermore, any one nozzle N among the multiple nozzles N will be referred to as the "first nozzle Na." In this case, the discharge section 510 to which the first nozzle Na belongs, the pressure chamber C communicating with the first nozzle Na, and the drive element E that drives the pressure chamber C to generate pressure fluctuations in the liquid in the pressure chamber C will be referred to as the "first discharge section 510a," the "first pressure chamber Ca," and the "first drive element Ea." Furthermore, within the same nozzle N, the nozzle N that is adjacent to the first nozzle Na along the X-axis without any other nozzle N in between will be referred to as the "second nozzle Nb." In this case, the discharge section 510 to which the second nozzle Nb belongs, the pressure chamber C communicating with the second nozzle Nb, and the drive element E that drives the pressure chamber C to generate pressure fluctuations in the liquid in the pressure chamber C will be referred to as the "second discharge section 510b," the "second pressure chamber Cb," and the "second drive element Eb."

[0042] The configuration of each head chip 51 is not limited to the example shown in Fig. 4. Each head chip 51 may have, for example, a circulation flow path for circulating a liquid.

[0043] A5: First common drive signal ComA Fig. 5 is a diagram for explaining the first common drive signal ComA generated by the drive signal generation section 24 shown in Fig. 2. The drive signal generation section 24 shown in Fig. 2 generates the first common drive signal ComA shown in Fig. 5.

[0044] The latch signal LAT shown in Fig. 5 includes a pulse PlsL for defining a drive period Tu. The drive period Tu corresponds to a printing period for forming dots D on a medium M using droplets from a nozzle N. The drive period Tu is defined as, for example, 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 drive period Tu is not particularly limited.

[0045] The change signal CH1 includes a pulse PL1 for dividing the drive period Tu into a preceding control period Ta1 and a succeeding control period Ta2. The control period Ta1 is, for example, the period from the rising edge of the pulse PlsL to the rising edge of the pulse PL1. The control period Ta2 is, for example, the period from the rising edge of the pulse PL1 to the rising edge of the pulse PlsL.

[0046] One drive cycle Tu of the first common drive signal ComA includes a first period Ta corresponding to two consecutive pixels Pi on the medium M. In this embodiment, one drive cycle Tu corresponds to the first period Ta and corresponds to two pixels Pi to be recorded on the medium M. The first common drive signal ComA includes multiple ejection pulses P0 during the first period Ta. Specifically, the first common drive signal ComA includes ejection pulses P0 for a total of two pixels Pi within one first period Ta.

[0047] The number of ejection pulses P0 included in the first period Ta of the first common drive signal ComA is n+1, where n is an even number. In the illustrated example, the number of ejection pulses P0 included in the first period Ta is 5, where n is 4. The number of ejection pulses P0 may be n+1, i.e., an odd number, and may be 3, 7, or more.

[0048] Of these n+1 ejection pulses P0, i.e., five ejection pulses P0, (n / 2)+1 consecutive ejection pulses P0, i.e., three ejection pulses P0, constitute a first ejection pulse group G1. Also, (n / 2) consecutive ejection pulses P0, i.e., two ejection pulses P0, which are consecutive to the three ejection pulses P0 of the first ejection pulse group G1, constitute a second ejection pulse group G2.

[0049] Each ejection pulse P0 includes a waveform that drops from a reference potential E0 to a potential lower than the reference potential E0, maintains that potential, then rises to a potential higher than the reference potential E0, maintains that potential, and then returns to the reference potential E0.

[0050] In this embodiment, the ejection pulses P0 are substantially equal to each other, but the durations of the connecting elements CA that connect them are different. Note that the ejection pulses P0 may have different pulse widths, rise times, and fall times.

[0051] The first common drive signal ComA is supplied as an individual drive signal Vin from the drive control unit 52 to one electrode of each drive element E. An offset potential VBS is supplied to the other electrode of each drive element E. Although not shown in detail, the drive control unit 52 in FIG. 2 includes a switching circuit 701. Although not shown in detail, the switching circuit 701 is connected to a signal line transmitting the individual drive signal Vin, a signal line transmitting a print data signal SI, a signal line transmitting a clock signal, a change signal CH, and a signal line transmitting a latch signal LAT. The switching circuit 701 switches between conduction (ON) and non-conduction (OFF) between the signal line transmitting the first common drive signal ComA and one electrode of each drive element E based on the clock signal, the print data signal SI, the change signal CH, and the latch signal LAT.

[0052] A6: First individual drive signal Vin1 Fig. 6 is a diagram showing the first individual drive signal Vin1 generated from the first common drive signal ComA of Fig. 5. The drive control unit 52 of Fig. 2 selects an ejection pulse P0 corresponding to the image data Img from the multiple ejection pulses P0 of the first common drive signal ComA of Fig. 5, and supplies the generated individual drive signal Vin to the first drive element Ea as the first individual drive signal Vin1.

[0053] The drive control unit 52 selects n+1, i.e., five, ejection pulses P0 from the first common drive signal ComA and generates an individual drive signal Vin, which is defined as a first individual drive signal Vin1. The first individual drive signal Vin1 includes a first ejection pulse group G1 consisting of (n / 2)+1, i.e., three, consecutive ejection pulses P0, and a second ejection pulse group G2 consisting of (n / 2), i.e., two, ejection pulses P0.

[0054] A7: Dot D formed on medium M FIG. 7 is a diagram showing dots D formed on the medium M when the first individual drive signal Vin1 of FIG. 6 is supplied to the first drive element Ea. As shown in FIG. 7, when the drive control unit 52 supplies the first individual drive signal Vin1 to the first drive element Ea, a first dot D1 is formed by droplets ejected from the first nozzle Na corresponding to the first drive element Ea onto a first pixel Pi1 on the medium M using a first ejection pulse group G1. Furthermore, a second dot D2 is formed by droplets ejected from the first nozzle Na onto a second pixel Pi2 on the medium M adjacent to the first pixel Pi1 using a second ejection pulse group G2. The first dot D1 and the second dot D2 are formed by droplets ejected from the same first nozzle Na. The first pixel Pi1 and the second pixel Pi2 are aligned in the Y2 direction, which is the movement direction of the liquid ejection head 50 relative to the medium M. Note that the first pixel Pi1 is any one of the multiple pixels Pi.

[0055] The droplets are ejected as the liquid ejection head 50 is moved by the movement mechanism 23. As a result, a first dot D1 is formed in the first pixel Pi1, and a second dot D2 is formed in the second pixel Pi2 adjacent to the first pixel Pi1. The three ejection pulses P0 included in the first ejection pulse group G1 may combine with each other before landing on the medium M, or may combine on the medium M. Similarly, the two ejection pulses P0 included in the second ejection pulse group G2 may combine with each other before landing on the medium M, or may combine on the medium M.

[0056] Furthermore, when the drive control unit 52 repeatedly supplies the first individual drive signal Vin1 to the first drive element Ea, a first dot D1 formed by droplets ejected by the first ejection pulse group G1 and a second dot D2 formed by droplets ejected by the second ejection pulse group G2 are printed alternately and continuously in the Y2 direction on the medium M.

[0057] As described above, the first ejection pulse group G1 is composed of (n / 2)+1 consecutive ejection pulses P0, i.e., three ejection pulses P0, and the second ejection pulse group G2 is composed of (n / 2) consecutive ejection pulses P0, i.e., two ejection pulses P0. Therefore, the plane area of ​​the first dot D1 is larger than the plane area of ​​the second dot D2. Therefore, the first dot D1 and the smaller second dot D2 are printed alternately and continuously.

[0058] According to this first individual drive signal Vin1, by including an odd number of ejection pulses P0 in the first period Ta for two pixels Pi, it is possible to increase the number of ejection pulses P0 corresponding to one pixel Pi compared to the number of ejection pulses P0 corresponding to the other pixel Pi. Therefore, while increasing the area covered by the liquid that has landed on the region for two pixels Pi, it is possible to shorten the first period Ta including the ejection pulses P0 for two pixels Pi compared to when the number of ejection pulses P0 is increased for each of the two pixels Pi.

[0059] If the first dot D1 formed by the first ejection pulse group G1, each consisting of three ejection pulses P0, is continuous, i.e., if both the first ejection pulse group G1 and the second ejection pulse group G2 are each composed of three ejection pulses P0, the pulse interval between the ejection pulses P0 included in the first period Ta becomes narrow, which may result in unstable ejection. On the other hand, if the pulse interval is made sufficiently wide, the first period Ta becomes long, resulting in a decrease in printing speed. In contrast, in this embodiment, the first dot D1 formed by the first ejection pulse group G1, each consisting of three ejection pulses P0, and the second dot D2 formed by the second ejection pulse group G2, each consisting of two ejection pulses P0, are alternately printed consecutively, thereby preventing the above-mentioned unstable ejection and a decrease in printing speed. Therefore, if it is desired to increase the number of ejection pulses to form a larger dot D in each pixel Pi, including an odd number of ejection pulses P0 in the first period Ta for two pixels Pi can prevent the above-mentioned unstable ejection and a decrease in printing speed.

[0060] A8: Second individual drive signal Vin2 Fig. 8 is a diagram showing the second individual drive signal Vin2 generated from the first common drive signal ComA of Fig. 5. The drive control unit 52 of Fig. 2 selects an ejection pulse P0 corresponding to the image data Img from the multiple ejection pulses P0 of the first common drive signal ComA and generates the individual drive signal Vin, which is supplied as the second individual drive signal Vin2 to the second drive element Eb. The second drive element Eb is included in the second ejection unit 510b adjacent to the first ejection unit 510a including the first drive element Ea.

[0061] The drive control unit 52 selects n+1, i.e., five, ejection pulses P0 from the first common drive signal ComA to generate an individual drive signal Vin, which is defined as the second individual drive signal Vin2. The second individual drive signal Vin2 includes a first ejection pulse group G1 consisting of (n / 2)+1, i.e., three, consecutive ejection pulses P0, and a second ejection pulse group G2 consisting of (n / 2), i.e., two, ejection pulses P0. In this embodiment, the first individual drive signal Vin1 and the second individual drive signal Vin2 have the same waveform although they are applied to different drive elements E.

[0062] A9: Dot D formed on medium M 9 is a diagram showing a dot D formed on the medium M when the first individual drive signal Vin1 of FIG. 6 is supplied to the first drive element Ea and the second individual drive signal Vin2 of FIG. 8 is supplied to the second drive element Eb at the same time. As shown in FIG. 9, when the drive control unit 52 supplies the second individual drive signal Vin2 to the second drive element Eb, a third dot D3 is formed by droplets ejected from the second nozzle Nb corresponding to the second drive element Eb onto a third pixel Pi3 on the medium M using the first ejection pulse group G1. Furthermore, a fourth dot D4 is formed by droplets ejected from the second nozzle Nb using the second ejection pulse group G2 onto a fourth pixel Pi4 on the medium M that is adjacent to the third pixel Pi3. The third pixel Pi3 and the fourth pixel Pi4 are aligned in the Y2 direction, which is the direction of movement of the liquid ejection head 50 relative to the medium M.

[0063] The third dot D3 and the fourth dot D4 are formed by droplets ejected from the same second nozzle Nb. The droplets are ejected as the movement mechanism 23 moves the liquid ejection head 50. Therefore, the third dot D3 is formed in the third pixel Pi3, and the fourth dot D4 is formed in the fourth pixel Pi4 adjacent to the third pixel Pi3. When the drive control unit 52 repeatedly supplies the second individual drive signal Vin2 to the second drive element Eb, the third dot D3 formed by droplets ejected by the first ejection pulse group G1 and the fourth dot D4 formed by droplets ejected by the second ejection pulse group G2 are printed alternately and continuously in the Y2 direction on the medium M.

[0064] The first ejection pulse group G1 is made up of (n / 2)+1 consecutive ejection pulses P0, i.e., three ejection pulses, and the second ejection pulse group G2 is made up of (n / 2) consecutive ejection pulses P0, i.e., two ejection pulses, so the plane area of ​​the third dot D3 is larger than the plane area of ​​the fourth dot D4. As a result, the third dot D3 and the smaller fourth dot D4 are printed alternately and continuously.

[0065] By alternately and continuously printing the third dots D3 and the smaller fourth dots D4, it is possible to suppress the risk of ejection becoming unstable and the decrease in printing speed compared to when the third dots D3 are lined up continuously.

[0066] FIG. 10 is a diagram illustrating the supply timing of the first individual drive signal Vin1 of FIG. 6 and the second individual drive signal Vin2 of FIG. 8. As shown in FIG. 10, in this embodiment, the supply timing of the first individual drive signal Vin1 and the second individual drive signal Vin2 is the same. Therefore, the supply timing of each first ejection pulse group G1 of the first individual drive signal Vin1 and the second individual drive signal Vin2 is the same, and the supply timing of each second ejection pulse group G2 is the same. Therefore, as shown in FIG. 9, the first dot D1 and the third dot D3 are aligned in the direction along the X-axis. Furthermore, the second dot D2 and the fourth dot D4 are aligned in the direction along the X-axis.

[0067] B. Second embodiment In the second embodiment exemplified below, for elements whose actions or functions are similar to those of the first embodiment, the symbols used in the description of the first embodiment will be used and detailed descriptions of each will be omitted as appropriate.

[0068] 11 is a diagram illustrating the supply timing of the first individual drive signal Vin1 and the second individual drive signal Vin2 in the second embodiment. In this embodiment, when the first individual drive signal Vin1 is repeatedly supplied to the first drive element Ea and the second individual drive signal Vin2 is repeatedly supplied to the second drive element Eb, the supply timing of the first ejection pulse group G1 of the first individual drive signal Vin1 to the first drive element Ea differs from the supply timing of the first ejection pulse group G1 of the second individual drive signal Vin2 to the second drive element Eb.

[0069] In the example of FIG. 11, the supply of the second individual drive signal Vin2 begins after the supply of the first individual drive signal Vin1 begins. First, during the period in which the two leading ejection pulses P0 of the first ejection pulse group G1 of the first individual drive signal Vin1 are supplied, the second individual drive signal Vin2 is not supplied. This period overlaps with the delay period T0. The supply of the second individual drive signal Vin2 begins after the delay period T0. Therefore, the supply timing of the first individual drive signal Vin1 and the second individual drive signal Vin2 is shifted by the delay period T0.

[0070] 11, the supply timing of the second ejection pulse group G2 of the first individual drive signal Vin1 coincides with the supply timing of the first ejection pulse group G1 of the second individual drive signal Vin2, and therefore the supply timing of the first ejection pulse group G1 of the first individual drive signal Vin1 coincides with the supply timing of the second ejection pulse group G2 of the second individual drive signal Vin2.

[0071] FIG. 12 is a diagram showing dots D formed on a medium M in the second embodiment. As shown in FIG. 12, when a first individual drive signal Vin1 is supplied to a first drive element Ea, a first dot D1 is formed in a first pixel Pi1 on the medium M from a first nozzle Na corresponding to the first drive element Ea, and a second dot D2 is formed in a second pixel Pi2 adjacent to the first pixel Pi1. The first dot D1 and the second dot D2 are formed by droplets ejected from the same first nozzle Na. The first dot D1 and the second dot D2 are adjacent to each other along a first axis Ya. The plane area of ​​the first dot D1 is larger than the plane area of ​​the second dot D2. The first axis Ya may also be referred to as the "first axis."

[0072] When the second individual drive signal Vin2 is supplied to the second drive element Eb, a third dot D3 is formed at a third pixel Pi3 on the medium M from the second nozzle Nb corresponding to that second drive element Eb, and a fourth dot D4 is formed at a fourth pixel Pi4 adjacent to the third pixel Pi3. The third dot D3 and the fourth dot D4 are formed by droplets ejected from the same second nozzle Nb. The third dot D3 and the fourth dot D4 are adjacent to each other along the second axis Yb, which is parallel to the "first axis." The plane area of ​​the third dot D3 is larger than the plane area of ​​the fourth dot D4. Therefore, the third dot D3 and the smaller fourth dot D4 are printed alternately and consecutively along the second axis Yb.

[0073] The first nozzle Na and the second nozzle Nb are arranged side by side along the X-axis. When the first individual drive signal Vin1 is repeatedly supplied to the first drive element Ea and the second individual drive signal Vin2 is repeatedly supplied to the second drive element Eb, the timing at which the second ejection pulse group G2 of the first individual drive signal Vin1 is supplied to the first drive element Ea coincides with the timing at which the first ejection pulse group G1 of the second individual drive signal Vin2 is supplied to the second drive element Eb. Therefore, the second dot D2 and the third dot D3 are arranged consecutively along the third axis Xa, which is perpendicular to the "first axis."

[0074] In this manner, in this embodiment, a delay period T0 is provided to shift the positions of the first dot D1 and the third dot D3 in the Y2 direction, which is the direction of movement of the liquid ejection head 50 relative to the medium M. Specifically, the delay period T0 is set so that the first dot D1 and the third dot D3 are shifted by one pixel Pi in the Y2 direction, which is the direction of movement of the liquid ejection head 50 relative to the medium M. The delay period T0 can be set appropriately through experiments or the like to a length that reduces differences in density in the print image quality. For example, the delay period T0 can be set to a length equivalent to half of one drive cycle Tu.

[0075] According to the second embodiment, when printing a solid image, the difference in shade between the first dot D1 and the second dot D2, and the difference in shade between the third dot D3 and the fourth dot D4 can be visually reduced compared to the first embodiment.

[0076] C. Third embodiment In the third embodiment exemplified below, for elements whose actions or functions are similar to those of the first embodiment, the symbols used in the description of the first embodiment will be used and detailed descriptions of each will be omitted as appropriate.

[0077] Fig. 13 is a diagram for explaining the second common drive signal ComB in the third embodiment. In this embodiment, the drive signal generation unit 24 generates the second common drive signal ComB shown in Fig. 13 in addition to the first common drive signal ComA shown in Fig. 5 described above.

[0078] The change signal CH2 includes a pulse PL2 for dividing the drive cycle Tu into a preceding control period Ta3 and a following control period Ta4. The control period Ta3 is, for example, the period from the rising edge of the pulse PlsL to the rising edge of the pulse PL2. The control period Ta4 is, for example, the period from the rising edge of the pulse PL2 to the rising edge of the pulse PlsL.

[0079] One drive cycle Tu of the second common drive signal ComB includes a first period Ta corresponding to two consecutive pixels Pi on the medium M. In this embodiment, one drive cycle Tu corresponds to the first period Ta and corresponds to two pixels Pi to be recorded on the medium M. The second common drive signal ComB includes multiple ejection pulses P0 during the first period Ta. Specifically, the second common drive signal ComB includes ejection pulses P0 for a total of two pixels Pi within one first period Ta.

[0080] The number of ejection pulses P0 included in the first period Ta of the second common drive signal ComB is n+1. In the illustrated example, the number of ejection pulses P0 included in the first period Ta is 5. n is an even number, and is 4 in this embodiment. Note that the number of ejection pulses P0 may be n+1, i.e., an odd number, and may be 3 or 7 or more.

[0081] The third ejection pulse group G3 is composed of (n / 2) consecutive ejection pulses P0 out of the n+1 ejection pulses P0, i.e., five ejection pulses P0, i.e., two ejection pulses P0. The fourth ejection pulse group G4 is composed of (n / 2)+1 consecutive ejection pulses P0, i.e., three ejection pulses P0, which are consecutive to the two ejection pulses P0 of the third ejection pulse group G3.

[0082] Furthermore, the time lengths of the multiple connection elements CA included in the first common drive signal ComA of FIG. 5 and the time lengths of the multiple connection elements CA included in the second common drive signal ComB of FIG. 13 are different from each other.

[0083] Fig. 14 is a diagram showing the second individual drive signal Vin3 generated from the second common drive signal ComB of Fig. 13. The drive control unit 52 of Fig. 2 selects an ejection pulse P0 corresponding to the image data Img from the multiple ejection pulses P0 of the second common drive signal ComB of Fig. 13, and supplies the generated individual drive signal Vin to the second drive element Eb as the second individual drive signal Vin3.

[0084] The drive control unit 52 selects n+1, i.e., five, ejection pulses P0 from the second common drive signal ComB and generates an individual drive signal Vin, which is defined as the second individual drive signal Vin3. The second individual drive signal Vin3 includes a third ejection pulse group G3 consisting of (n / 2), i.e., two, consecutive ejection pulses P0, and a fourth ejection pulse group G4 consisting of (n / 2)+1, i.e., three, ejection pulses P0.

[0085] FIG. 15 is a diagram showing dots D formed on a medium M in the third embodiment. FIG. 15 is a diagram showing dots D formed on a medium M when the first individual drive signal Vin1 of FIG. 6 is supplied to the first drive element Ea and the second individual drive signal Vin3 of FIG. 14 is simultaneously supplied to the second drive element Eb. As shown in FIG. 15, when the drive control unit 52 supplies the second individual drive signal Vin3 to the second drive element Eb, a third dot D3 is formed by droplets ejected from the second nozzle Nb corresponding to the second drive element Eb to a third pixel Pi3 on the medium M using the third ejection pulse group G3. Furthermore, a fourth dot D4 is formed by droplets ejected from the second nozzle Nb using the fourth ejection pulse group G4 to a fourth pixel Pi4 on the medium M adjacent to the third pixel Pi3. Note that the first individual drive signal Vin1 is supplied to the first nozzle Na.

[0086] The third dot D3 and the fourth dot D4 are formed by droplets ejected from the same second nozzle Nb. The third dot D3 is formed in the third pixel Pi3, and the fourth dot D4 is formed in the fourth pixel Pi4 adjacent to the third pixel Pi3. The plane area of ​​the third dot D3 is smaller than the plane area of ​​the fourth dot D4. Therefore, the third dot D3 and the larger fourth dot D4 are printed alternately and consecutively in the Y2 direction.

[0087] The first nozzle Na and the second nozzle Nb are arranged side by side along the X-axis. Therefore, when the first individual drive signal Vin1 is repeatedly supplied to the first drive element Ea and the second individual drive signal Vin3 is repeatedly supplied to the second drive element Eb, the timing at which the first ejection pulse group G1 of the first individual drive signal Vin1 is supplied to the first drive element Ea coincides with the timing at which the third ejection pulse group G3 of the second individual drive signal Vin3 is supplied to the second drive element Eb. Therefore, the first dot D1 and the second dot D2 are arranged consecutively along the first axis Ya. The third dot D3 and the fourth dot D4 are arranged consecutively along the second axis Yb parallel to the "first axis." The first dot D1 and the third dot D3 are arranged consecutively along the third axis Xa perpendicular to the "first axis." The second dot D2 and the fourth dot D4 are arranged consecutively along the fourth axis Xb parallel to the third axis Xa.

[0088] According to the third embodiment, when printing solid images, the difference in shade between the first dot D1 and the second dot D2, and the difference in shade between the third dot D3 and the fourth dot D4 can be visually reduced compared to the first embodiment.

[0089] D. Fourth embodiment In the fourth embodiment exemplified below, for elements whose actions or functions are similar to those of the first embodiment, the symbols used in the description of the first embodiment will be used and detailed descriptions of each will be omitted as appropriate.

[0090] Fig. 16 is a diagram for explaining the first individual drive signal Vin4 in the fourth embodiment. In this embodiment, the drive signal generation unit 24 selects and generates the first individual drive signal Vin4 in Fig. 27 by selecting the ejection pulse P0 corresponding to the image data Img from the multiple ejection pulses P0 of the first common drive signal ComA in Fig. 5, and supplies the first individual drive signal Vin4 to the first drive element Ea as the individual drive signal Vin.

[0091] Specifically, the first individual drive signal Vin4 is generated by selecting all the ejection pulses P0 of the first ejection pulse group G1 and not selecting all the ejection pulses P0 of the second ejection pulse group G2. Therefore, the first individual drive signal Vin4 includes (n / 2)+1 consecutive ejection pulses P0, i.e., three ejection pulses P0.

[0092] Fig. 17 is a diagram for explaining another first individual drive signal Vin5 in the fourth embodiment. In this embodiment, the drive signal generation unit 24 selects and generates an ejection pulse P0 corresponding to the image data Img from the multiple ejection pulses P0 of the first common drive signal ComA in Fig. 5, and supplies the generated first individual drive signal Vin5 in Fig. 17 to the first drive element Ea as the individual drive signal Vin.

[0093] Specifically, the first individual drive signal Vin5 is generated by selecting all of the ejection pulses P0 in the second ejection pulse group G2 without selecting all of the ejection pulses P0 in the first ejection pulse group G1. Therefore, the first individual drive signal Vin5 includes (n / 2) consecutive ejection pulses P0, i.e., two ejection pulses P0.

[0094] Fig. 18 is a diagram showing a first dot D1 formed on the medium M when the first individual drive signal Vin4 of Fig. 16 is supplied to the first drive element Ea. As shown in Fig. 18, when the drive control unit 52 supplies the first individual drive signal Vin4 to the first drive element Ea, the first dot D1 is formed in the first pixel Pi1, and no dot D is formed in the second pixel Pi2. The first dot D1 formed in the first pixel Pi1 is formed by droplets ejected by (n / 2)+1 ejection pulses P0 of the first ejection pulse group G1, three ejection pulses P0 in this embodiment.

[0095] Fig. 19 is a diagram showing a dot D formed on the medium M when the first individual drive signal Vin5 of Fig. 17 is supplied to the first drive element Ea. As shown in Fig. 19, when the drive control unit 52 supplies the first individual drive signal Vin5 to the first drive element Ea, no dot D is formed in the first pixel Pi1, and a second dot D2 is formed in the second pixel Pi2. The second dot D2 formed in the second pixel Pi2 is formed by droplets ejected by (n / 2) ejection pulses P0 of the second ejection pulse group G2, two ejection pulses P0 in this embodiment.

[0096] By using the first individual drive signals Vin1, Vin4, and Vin5 of the above-described embodiment, it becomes possible to express four types of gradation in the area combining the first pixel Pi1 and the second pixel Pi2: forming dots in the first pixel Pi1 and the second pixel Pi2, forming dots only in the first pixel Pi1, forming dots only in the second pixel Pi2, and not forming dots in the first pixel Pi1 and the second pixel Pi2.

[0097] E. Fifth embodiment In the fifth embodiment exemplified below, for elements whose actions or functions are similar to those of the first embodiment, the symbols used in the description of the first embodiment will be used and detailed descriptions of each will be omitted as appropriate.

[0098] 20 is a diagram for explaining the common drive signal ComC in the fifth embodiment. The drive signal generating section 24 generates the common drive signal ComC shown in FIG.

[0099] The change signals CH3 and CH4 include pulses PL3 to PL6 for dividing the drive cycle Tu into a plurality of control periods Tb. For example, the control period Tb1 is the period from the rising edge of the pulse PlsL to the rising edge of the pulse PL3. The control period Tb2 is the period from the rising edge of the pulse PL3 to the rising edge of the pulse PlsL. The control period Tb3 is the period from the rising edge of the pulse PlsL to the rising edge of the pulse PL4. The control period Tb4 is the period from the rising edge of the pulse PL4 to the rising edge of the pulse PlsL. Furthermore, for example, the control period Tb5 is the period from the rising edge of the pulse PL5 to the rising edge of the pulse PL6.

[0100] One drive cycle Tu of the common drive signal ComC includes a first period Ta corresponding to two consecutive pixels Pi on the medium M. In this embodiment, one drive cycle Tu corresponds to the first period Ta and corresponds to two pixels Pi to be recorded on the medium M. The common drive signal ComC includes multiple ejection pulses P0 during the first period Ta. Specifically, the common drive signal ComC includes ejection pulses P0 for a total of two pixels Pi within one first period Ta.

[0101] The number of ejection pulses P0 included in the first period Ta of the common drive signal ComC is n+1, which is five in this embodiment. n is an even number, which is four in this embodiment. The number of ejection pulses P0 may be n+1, i.e., an odd number, and may be three, seven, or more. In the following, the ejection pulse P0 of the first ejection pulse group G1 that is adjacent to the ejection pulse P0 of the second ejection pulse group G2 will be referred to as the "first ejection pulse P01."

[0102] Of these n+1 ejection pulses P0, i.e., five ejection pulses P0, (n / 2)+1 consecutive ejection pulses P0, i.e., three ejection pulses P0, constitute a first ejection pulse group G1. Also, (n / 2) consecutive ejection pulses P0, i.e., two ejection pulses P0, which are consecutive to the three ejection pulses P0 of the first ejection pulse group G1, constitute a second ejection pulse group G2.

[0103] Fig. 21 is a diagram showing the first gradation drive signal Vina generated from the common drive signal ComC of Fig. 20. The drive control unit 52 selects an ejection pulse P0 corresponding to the image data Img from the multiple ejection pulses P0 of the common drive signal ComC of Fig. 20, and supplies the generated first gradation drive signal Vina to the drive element E as an individual drive signal Vin.

[0104] 21, the drive control unit 52 selects all of the ejection pulses P0 included in the first period Ta from the common drive signal ComC and generates a first gradation drive signal Vina, which is defined as the first individual drive signal Vin1. The first gradation drive signal Vina includes a first ejection pulse group G1 consisting of (n / 2)+1 consecutive ejection pulses P0, i.e., three ejection pulses P0, and a second ejection pulse group G2 consisting of (n / 2) consecutive ejection pulses P0, i.e., two ejection pulses P0.

[0105] 22 is a diagram showing dots D formed on a medium M when the first gradation drive signal Vina of FIG. 21 is supplied to a drive element E as an individual drive signal Vin. As shown in FIG. 22, when the drive control unit 52 supplies the first gradation drive signal Vina to a drive element E, a first dot D1 is printed by droplets ejected from a nozzle N corresponding to the drive element E to a first pixel Pi1 on the medium M by all ejection pulses P0 of a first ejection pulse group G1. Furthermore, a second dot D2 is printed by droplets ejected from the nozzle N to a second pixel Pi2 on the medium M that is adjacent to the first pixel Pi1 by all ejection pulses P0 of a second ejection pulse group G2. The first dot D1 and the second dot D2 are formed by droplets ejected from the same nozzle N.

[0106] Furthermore, when the drive control unit 52 repeatedly supplies the first gradation drive signal Vina to the drive element E, first dots D1 formed by droplets ejected by the first ejection pulse group G1 and second dots D2 formed by droplets ejected by the second ejection pulse group G2 are printed alternately and continuously in the Y2 direction on the medium M.

[0107] As described above, the first ejection pulse group G1 is composed of (n / 2)+1 consecutive ejection pulses P0, i.e., three ejection pulses P0, and the second ejection pulse group G2 is composed of (n / 2) consecutive ejection pulses P0, i.e., two ejection pulses P0. Therefore, the plane area of ​​the first dot D1 is larger than the plane area of ​​the second dot D2.

[0108] In this embodiment, as in the first embodiment, by including an odd number of ejection pulses P0 in a first period Ta corresponding to two pixels Pi, the number of ejection pulses P0 corresponding to one pixel Pi can be increased compared to the number of ejection pulses P0 corresponding to the other pixel Pi. As a result, the area covered by the liquid that has landed on the region corresponding to two pixels Pi can be increased, and the first period Ta including the ejection pulses P0 for two pixels Pi can be shortened compared to when the ejection pulses P0 are increased for each of the two pixels Pi. Also, in this embodiment, as in the first embodiment, the risk of unstable ejection and a decrease in printing speed as described above can be suppressed.

[0109] F. Sixth embodiment In the sixth embodiment exemplified below, for elements whose actions or functions are similar to those of the fifth embodiment, the symbols used in the description of the fifth embodiment will be used and detailed descriptions of each will be omitted as appropriate.

[0110] Fig. 23 is a diagram for explaining the second gradation drive signal Vinb1 in the sixth embodiment. In this embodiment, the drive signal generation unit 24 selects and generates the ejection pulse P0 corresponding to the image data Img from the plurality of ejection pulses P0 of the common drive signal ComC in Fig. 20, and supplies the second gradation drive signal Vinb1 in Fig. 23 to the drive element E as the individual drive signal Vin.

[0111] Specifically, the second gradation driving signal Vinb1 is generated by selecting at least n / 2 ejection pulses P0 of the first ejection pulse group G1 (in this embodiment, the two preceding ejection pulses P0 are not selected), but by selecting the first ejection pulse P01 and all the ejection pulses P0 of the second ejection pulse group G2. Therefore, the second gradation driving signal Vinb1 includes (n / 2)+1 consecutive ejection pulses P0, i.e., three ejection pulses P0.

[0112] Fig. 24 is a diagram for explaining the third gradation drive signal Vinb2 in the sixth embodiment. In this embodiment, the drive signal generation unit 24 selects and generates an ejection pulse P0 corresponding to the image data Img from the plurality of ejection pulses P0 of the common drive signal ComC in Fig. 20, and supplies the third gradation drive signal Vinb2 in Fig. 24 to the drive element E as the individual drive signal Vin.

[0113] Specifically, the third gradation driving signal Vinb2 is generated by selecting at least n / 2 ejection pulses P0 (all ejection pulses P0 in this embodiment) from the ejection pulses P0 of the first ejection pulse group G1, and not selecting all ejection pulses P0 of the second ejection pulse group G2. Therefore, the third gradation driving signal Vinb2 includes (n / 2)+1 consecutive ejection pulses P0, i.e., three ejection pulses P0.

[0114] Fig. 25 is a diagram showing a dot D formed on a medium M when the second gradation drive signal Vinb1 of Fig. 23 is supplied to a drive element E. As shown in Fig. 25, when the drive control unit 52 supplies the second gradation drive signal Vinb1 to a drive element E, no dot is printed in the first pixel Pi1, and a third dot D5 is printed in the second pixel Pi2. The third dot D5 is formed by a droplet ejected by three ejection pulses P0, which are a combination of the first ejection pulse P01 and all the ejection pulses P0 of the second ejection pulse group G2.

[0115] Fig. 26 is a diagram showing dots D formed on the medium M when the third gradation drive signal Vinb2 of Fig. 24 is supplied to the drive element E. As shown in Fig. 26, when the drive control unit 52 supplies the third gradation drive signal Vinb2 to the drive element E, a fourth dot D6 is printed in the first pixel Pi1, and no dot D is printed in the second pixel Pi2. The fourth dot D6 is formed by droplets ejected by the three ejection pulses P0 of the first ejection pulse group G1.

[0116] As shown in FIGS. 25 and 26, the third dot D5 and the fourth dot D6 are both formed by three ejection pulses P0, and have the same size, specifically, the same plane area.

[0117] By using the second gradation drive signal Vinb1 and the third gradation drive signal Vinb2, it is possible to achieve gradation expression. Furthermore, by using the second gradation drive signal Vinb1 and the third gradation drive signal Vinb2 of this embodiment in addition to the first gradation drive signal Vina of the fifth embodiment, it is possible to widen the range of gradation expression. In particular, by forming the third dots D5 and the fourth dots D6 with the same number of ejection pulses P0, it is possible to make the sizes of the third dots D5 and the fourth dots D6 the same. Therefore, the granularity of the dots on the medium M can be improved compared to when the dot sizes are different.

[0118] G. Seventh embodiment In the seventh embodiment exemplified below, for elements whose actions or functions are similar to those of the fifth embodiment, the symbols used in the description of the fifth embodiment will be used and detailed descriptions of each will be omitted as appropriate.

[0119] Fig. 27 is a diagram for explaining the second gradation drive signal Vinc1 in the seventh embodiment. In this embodiment, the drive signal generation unit 24 selects and generates an ejection pulse P0 corresponding to the image data Img from the plurality of ejection pulses P0 of the common drive signal ComC in Fig. 20, and supplies the second gradation drive signal Vinc1 in Fig. 27 to the drive element E as the individual drive signal Vin.

[0120] Specifically, the second gradation driving signal Vinc1 is generated by selecting at least n / 2 ejection pulses P0 from the first ejection pulse group G1 (in this embodiment, all preceding ejection pulses P0 are not selected), but all ejection pulses P0 from the second ejection pulse group G2. Therefore, the second gradation driving signal Vinc1 includes consecutive (n / 2) ejection pulses P0, i.e., two ejection pulses P0.

[0121] Fig. 28 is a diagram for explaining the third gradation drive signal Vinc2 in the seventh embodiment. In this embodiment, the drive signal generation unit 24 selects and generates an ejection pulse P0 corresponding to the image data Img from the plurality of ejection pulses P0 of the common drive signal ComC in Fig. 20, and supplies the third gradation drive signal Vinc2 in Fig. 28 to the drive element E as the individual drive signal Vin.

[0122] Specifically, the third gradation driving signal Vinc2 is generated by selecting at least n / 2 ejection pulses P0 (the two leading ejection pulses P0 in this embodiment) from the ejection pulses P0 of the first ejection pulse group G1, but not selecting all of the ejection pulses P0 of the first ejection pulse P01 and the second ejection pulse group G2. Therefore, the third gradation driving signal Vinc2 includes (n / 2) consecutive ejection pulses P0, i.e., two ejection pulses P0. Note that instead of the two leading ejection pulses P0 from the first ejection pulse group G1, the two consecutive ejection pulses P0 from the second ejection pulse group G2 may be selected.

[0123] Fig. 29 is a diagram showing a dot D formed on a medium M when the second gradation drive signal Vinc1 of Fig. 27 is supplied to a drive element E. As shown in Fig. 29, when the drive control unit 52 supplies the second gradation drive signal Vinc1 to the drive element E, no dot is printed at the first pixel Pi1, and a third dot D7 is printed at the second pixel Pi2. The third dot D7 is formed by droplets ejected by (n / 2) ejection pulses P0 of the second ejection pulse group G2, two ejection pulses P0 in this embodiment.

[0124] Fig. 30 is a diagram showing a dot D formed on a medium M when the third gradation drive signal Vinc2 of Fig. 28 is supplied to a drive element E. As shown in Fig. 30, when the drive control unit 52 supplies the third gradation drive signal Vinc2 to the drive element E, a fourth dot D8 is printed in the first pixel Pi1, and no dot D is printed in the second pixel Pi2. The fourth dot D8 is formed by a droplet ejected by (n / 2) ejection pulses P0 of the first ejection pulse group G1, two ejection pulses P0 in this embodiment.

[0125] 29 and 30, the third dot D7 and the fourth dot D8 are both formed by two ejection pulses P0 and have the same size, specifically, the same area. Note that the areas of the third dot D7 and the fourth dot D8 in this embodiment are smaller than the areas of the third dot D5 and the fourth dot D6 in the sixth embodiment.

[0126] By using the second gradation drive signal Vinc1 and the third gradation drive signal Vinc2, it is possible to achieve gradation expression. In particular, by forming the third dot D7 and the fourth dot D8 using the same number of ejection pulses P0, it is possible to make them the same size. This allows for improved granularity of the dots on the medium M compared to when the dot sizes are different.

[0127] Furthermore, by using the second gradation drive signal Vinc1 and the third gradation drive signal Vinc2 of this embodiment in addition to the first gradation drive signal Vina of the fifth embodiment and the second gradation drive signal Vinb1 and the third gradation drive signal Vinb2 of the sixth embodiment, the range of gradation expression can be expanded.

[0128] Note that the second gradation drive signal Vinc1 of this embodiment is generated by selecting the fourth and fifth ejection pulses P0 from among the ejection pulses P0 included in the common drive signal ComC in FIG. 20. The third gradation drive signal Vinc2 is generated by selecting the first and second ejection pulses P0 from among the ejection pulses P0 included in the common drive signal ComC. However, the second gradation drive signal Vinc1 may also be generated by selecting the third and fifth ejection pulses P0 from among the ejection pulses P0 included in the common drive signal ComC, for example. The third gradation drive signal Vinc2 may also be generated by selecting the first and third ejection pulses P0 from among the ejection pulses P0 included in the common drive signal ComC. In other words, the second gradation drive signal Vinc1 and the third gradation drive signal Vinc2 may each be generated by selecting ejection pulses P0 in any order from the (n+1) ejection pulses P0 included in the common drive signal ComC.

[0129] H. Eighth embodiment In the eighth embodiment exemplified below, for elements whose actions or functions are similar to those of the fifth embodiment, the symbols used in the description of the fifth embodiment will be used and detailed descriptions of each will be omitted as appropriate.

[0130] Fig. 31 is a diagram for explaining the fourth gradation drive signal Vind in the eighth embodiment. In this embodiment, the drive signal generation unit 24 selects and generates an ejection pulse P0 corresponding to the image data Img from the plurality of ejection pulses P0 of the common drive signal ComC in Fig. 20, and supplies the fourth gradation drive signal Vind in Fig. 31 to the drive element E as the individual drive signal Vin.

[0131] Specifically, the fourth gradation driving signal Vind is generated by selecting n / 2 ejection pulses P0 from the first ejection pulse group G1 (in this embodiment, the two leading ejection pulses P0) and all ejection pulses P0 from the second ejection pulse group G2. The first ejection pulse P01 is not selected. Therefore, the fourth gradation driving signal Vind includes two sets of consecutive (n / 2) ejection pulses P0, i.e., two sets of two ejection pulses P0.

[0132] 32 is a diagram showing dots D formed on the medium M when the fourth gradation drive signal Vind of FIG. 31 is supplied to the drive element E. As shown in FIG. 32, when the drive control unit 52 supplies the fourth gradation drive signal Vind to the drive element E, a fifth dot D9 is formed in the first pixel Pi1, and a sixth dot D10 is formed in the second pixel Pi2. The fifth dot D9 is formed by droplets ejected by (n / 2) ejection pulses P0 of the first ejection pulse group G1, two ejection pulses in this embodiment. The sixth dot D10 is formed by droplets ejected by all ejection pulses P0 of the second ejection pulse group G2.

[0133] The fifth dot D9 and the sixth dot D10 are both formed by two ejection pulses P0 and have the same size, specifically, the same area. Therefore, by using the fourth gradation drive signal Vind, dots of the same size can be formed consecutively. In other words, even if the first period Ta for two pixels Pi includes an odd number of ejection pulses P0, dots of the same size can be formed consecutively in consecutive pixels Pi.

[0134] By using the fourth gradation drive signal Vind of this embodiment in addition to the first gradation drive signal Vina of the fifth embodiment, the second gradation drive signal Vinb1 and the third gradation drive signal Vinb2 of the sixth embodiment, and the second gradation drive signal Vinc1 and the third gradation drive signal Vinc2 of the seventh embodiment, the range of gradation expression can be expanded.

[0135] In this embodiment, the fourth gradation drive signal Vind is generated by selecting the first, second, fourth, and fifth ejection pulses P0 from among the ejection pulses P0 included in the common drive signal ComC. However, the fourth gradation drive signal Vind may also be generated by selecting, for example, the first, second, third, and fourth ejection pulses P0 from among the ejection pulses P0 included in the common drive signal ComC. In other words, the fourth gradation drive signal Vind may be generated by selecting ejection pulses P0 in any order from the (n+1) ejection pulses P0 included in the common drive signal ComC.

[0136] I. Variations The above-described embodiments can be modified in various ways. Specific modifications that can be applied to the above-described embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples can be combined as appropriate within the scope of not mutually contradictory.

[0137] I-1. First modified example Fig. 33 is a diagram for explaining the fifth gradation drive signal Vine of the first modified example. In the first modified example, the drive signal generation unit 24 selects and generates an ejection pulse P0 corresponding to the image data Img from the plurality of ejection pulses P0 of the common drive signal ComC of Fig. 20, and supplies the fifth gradation drive signal Vine of Fig. 33 to the drive element E as the individual drive signal Vin.

[0138] Specifically, the fifth gradation driving signal Vine is generated by selecting n / 2 ejection pulses P0 from the first ejection pulse group G1 (in this embodiment, the second and third two ejection pulses P0) and n / 2-1 ejection pulses P0 from the second ejection pulse group G2. Therefore, the fourth gradation driving signal Vind includes (n / 2)+1 consecutive ejection pulses P0, i.e., three ejection pulses P0.

[0139] Fig. 34 is a diagram showing a dot D formed on a medium M when the fifth gradation drive signal Vine of Fig. 33 is supplied to a drive element E. As shown in Fig. 34, when the drive control unit 52 supplies the fifth gradation drive signal Vine to the drive element E, a seventh dot D11 is formed that straddles the first pixel Pi1 and the second pixel Pi2.

[0140] The range of gradation expression can be expanded by using the fifth gradation drive signal Vine of the first modified example in addition to the first gradation drive signal Vina of the fifth embodiment, the second gradation drive signal Vinb1 and the third gradation drive signal Vinb2 of the sixth embodiment, the second gradation drive signal Vinc1 and the third gradation drive signal Vinc2 of the seventh embodiment, and the fourth gradation drive signal Vind of the eighth embodiment.

[0141] I-2. Other Modifications In the above-described embodiment, each head chip 51 has two nozzle rows L, but the number of nozzle rows included in each head chip 51 may be one, or three or more.

[0142] In the above-described embodiment, the liquid ejection device 100 was a line type in which multiple nozzles N were distributed across the entire width of the medium M, but the present disclosure can also be applied to a serial type liquid ejection device in which a carriage 231 carrying a liquid ejection head 50 is moved back and forth.

[0143] The liquid ejection device 100 exemplified in the above embodiment may be employed in various devices such as facsimile machines and copiers, in addition to devices dedicated to printing, and the applications of the present disclosure are not particularly limited. However, the applications of the liquid ejection device are not limited to printing. For example, a liquid ejection device that ejects a solution of a color material is used as a manufacturing device for forming color filters for display devices such as liquid crystal display panels. Furthermore, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wiring and electrodes on a wiring board. Furthermore, a liquid ejection device that ejects a solution of an organic substance related to a living body is used as a manufacturing device for manufacturing biochips, for example.

[0144] Although the present invention has been described above based on preferred embodiments, the present invention is not limited to the above-described embodiments. Furthermore, the configuration of each part of the present invention can be replaced with any configuration that exhibits the same function as the above-described embodiments, and any configuration can be added. [Explanation of symbols]

[0145] 24...driving signal generating unit, 50...liquid ejection head, 51...head chip, 52...driving control unit, 100...liquid ejection device, 510...ejection unit, 510a...first ejection unit, 510b...second ejection unit, Com...common drive signal, ComA...first common drive signal, ComB...second common drive signal, ComC...common drive signal, D...dot, D1...first dot, D2...second dot, D3...third dot, D4...fourth dot, D9...fifth dot, D10...sixth dot, E...driving element, Ea...first drive element, Eb...second drive element, G1...first ejection pulse group, G2...second ejection pulse group, G3...third ejection pulse group, G4...fourth ejection pulse group, Img...image data, M...medium, N...nozzle, Na...first nozzle, Nb...second nozzle, P01...first ejection pulse, Pi...pixel, Pi1...first pixel, Pi2...second pixel, Pi3...third pixel, Pi4...fourth pixel, Ta...first period, Tu...driving cycle, Vin1...first individual drive signal, Vin2...second individual drive signal, Vin3...second individual drive signal, Vin4...first individual drive signal, Vin5...first individual drive signal, Vina...first gradation drive signal, Vinb1...second gradation drive signal, Vinb2...third gradation drive signal, Vinc1...second gradation drive signal, Vinc2...third gradation drive signal, Vind...fourth gradation drive signal, Xa...third axis, Xb...fourth axis, Ya...first axis, Yb...second axis.

Claims

1. a discharge unit having a nozzle that discharges liquid onto a medium, a pressure chamber that communicates with the nozzle, and a drive element that drives the nozzle in response to a supplied individual drive signal so as to generate a pressure fluctuation in the liquid in the pressure chamber; a drive signal generating unit that generates a common drive signal including a plurality of ejection pulses during one drive cycle; a drive control unit that selects an ejection pulse corresponding to image data from among the plurality of ejection pulses of the common drive signal, generates the individual drive signal, and supplies the individual drive signal to the drive element; Equipped with one drive cycle of the common drive signal includes n+1 ejection pulses during a first period corresponding to two consecutive pixels on the medium; n is an even number, The n+1 ejection pulses of the common drive signal constitute a first ejection pulse group by consecutive (n / 2)+1 ejection pulses, and constitute a second ejection pulse group by consecutive (n / 2) ejection pulses aligned with the ejection pulses of the first ejection pulse group, When printing a first dot on a first pixel on the medium and printing a second dot on a second pixel adjacent to the first pixel, the drive control unit selects all ejection pulses included in the first period from the common drive signal, generates a first gradation drive signal, and supplies the generated first gradation drive signal as the individual drive signal to the drive element; When printing no dot in the first pixel and printing a third dot in the second pixel, the drive control unit supplies a second gradation drive signal generated by selecting all of the ejection pulses of the second ejection pulse group without selecting at least n / 2 ejection pulses of the first ejection pulse group from the common drive signal, as the individual drive signal, to the drive element; when a fourth dot is printed in the first pixel and no dot is printed in the second pixel, the drive control unit selects at least n / 2 ejection pulses from the common drive signal among the ejection pulses of the first ejection pulse group, and supplies a third gradation drive signal generated without selecting any of the ejection pulses of the second ejection pulse group as the individual drive signal to the drive element; A liquid ejection device, characterized in that the number of ejection pulses corresponding to the droplets that form the third dots is equal to the number of ejection pulses corresponding to the droplets that form the fourth dots.

2. the first dot is larger than the second dot; The liquid ejection device according to claim 1 .

3. When the drive control unit supplies the first gradation drive signal to the drive element as the individual drive signal, the first dot is formed by droplets ejected by all ejection pulses of the first ejection pulse group, and the second dot is formed by droplets ejected by all ejection pulses of the second ejection pulse group. The liquid ejection device according to claim 1 .

4. when the drive control unit selects, from the common drive signal, a first ejection pulse of the first ejection pulse group that is consecutive to an ejection pulse of the second ejection pulse group, and all of the ejection pulses of the second ejection pulse group, and supplies, as the individual drive signal, a second gradation drive signal generated without selecting 2 / n ejection pulses other than the first ejection pulse of the first ejection pulse group, to the drive element, the third dot is formed by droplets ejected by (n / 2)+1 ejection pulses, which are the sum of the first ejection pulse and all of the ejection pulses of the second ejection pulse group, when the drive control unit selects all the ejection pulses of the first ejection pulse group from the common drive signal and supplies the generated third gradation drive signal to the drive element as the individual drive signal, without selecting all the ejection pulses of the second ejection pulse group, the fourth dot is formed by droplets ejected by (n / 2)+1 ejection pulses of the first ejection pulse group. The liquid ejection device according to claim 1 .

5. when the drive control unit supplies a second gradation drive signal, which is generated by selecting all the ejection pulses of the second ejection pulse group without selecting all the ejection pulses of the first ejection pulse group from the common drive signal, to the drive elements as the individual drive signal, the third dot is formed by droplets ejected by n / 2 ejection pulses of the second ejection pulse group, When the drive control unit selects n / 2 ejection pulses from the first ejection pulse group from the common drive signal and supplies a third gradation drive signal generated without selecting all of the ejection pulses from the second ejection pulse group as the individual drive signal to the drive element, the fourth dot is formed by droplets ejected by the n / 2 ejection pulses from the first ejection pulse group. The liquid ejection device according to claim 1 .

6. When printing a fifth dot on the first pixel and a sixth dot on the second pixel, the drive control unit selects n / 2 ejection pulses from the first ejection pulse group from the common drive signal, and selects all of the ejection pulses from the second ejection pulse group to generate a fourth gradation drive signal, and supplies the generated fourth gradation drive signal to the drive element as the individual drive signal. The fifth dot is formed by droplets ejected by n / 2 ejection pulses from the first ejection pulse group, and the sixth dot is formed by droplets ejected by all of the ejection pulses from the second ejection pulse group. The liquid ejection device according to claim 1 .

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