JP2021024090A - Liquid ejection device and driving method of liquid ejection device - Google Patents

Abstract

To provide a liquid ejection device and a driving method of liquid ejection device which increases an ejection amount of ink within a unit period while reducing the generation of mist.SOLUTION: A liquid ejection device includes a liquid ejection part having a nozzle which ejects liquid, a pressure chamber which is communicated with the nozzle and a driving element which ejects liquid within the pressure chamber from the nozzle and a driving part capable of supplying a first ejection waveform which ejects liquid of a first quantity from the nozzle and a second ejection waveform which ejects liquid from a second quantity more than the first quantity from the nozzle to the driving element. Therein, waveform of two or more besides the last of a plurality of ejection waveform supplied to the driving element within unit period are the second ejection waveform, and the last ejection waveform, of the plurality of ejection waveforms is the first ejection waveform.SELECTED DRAWING: Figure 5

Description

The present invention relates to a liquid discharge device and a method for driving the liquid discharge device.

A liquid discharge device that discharges a liquid from a nozzle has been conventionally proposed. Patent Document 1 discloses a configuration in which a liquid is discharged from a nozzle by supplying a discharge pulse to the piezoelectric element. Specifically, a plurality of ejection pulses are supplied to the piezoelectric element within the recording cycle, so that a predetermined ejection amount of ink is ejected from the nozzle.

Japanese Unexamined Patent Publication No. 2004-249686

In the technique of Patent Document 1, in order to increase the ejection amount within a predetermined period, a preliminary pulse that displaces the liquid surface of the ink in the nozzle (hereinafter referred to as “meniscus”) without ejecting droplets is set before the ejection pulse. Supply to the piezoelectric element. However, when the ink is ejected by the ejection pulse after the preliminary pulse is supplied, the phenomenon that the ink extends in a columnar shape from the nozzle (hereinafter referred to as "tail pulling") becomes remarkable. Therefore, there is a problem that fine droplets (hereinafter referred to as "mist") separated from the columnar ink float in the space between the nozzle and the medium without landing on the medium. On the other hand, in the configuration that does not use the preliminary pulse, the tailing is suppressed, but it is difficult to secure a sufficient discharge amount. Therefore, it is necessary to increase the number of discharge pulses within a predetermined period. As a result, it is necessary to lengthen the predetermined period, and there is a problem that the printing speed is lowered.

In order to solve the above problems, the liquid discharge device of the present invention has a liquid having a nozzle for discharging the liquid, a pressure chamber communicating with the nozzle, and a driving element for discharging the liquid in the pressure chamber from the nozzle. A discharge unit 90, a first discharge waveform for discharging a first amount of liquid from the nozzle, and a second discharge waveform for discharging a second amount of liquid larger than the first amount from the nozzle are provided to the driving element. A drive unit capable of supplying the liquid, and two or more discharge waveforms other than the last of the plurality of discharge waveforms supplied to the drive element within a unit period are the second discharge waveforms, and the plurality of discharge waveforms. The last discharge waveform is the first discharge waveform.

A method for driving a liquid discharge device according to a preferred embodiment of the present invention is a liquid discharge having a nozzle for discharging a liquid, a pressure chamber communicating with the nozzle, and a driving element for discharging the liquid in the pressure chamber from the nozzle. A unit 90, a first discharge waveform for discharging a first amount of liquid from the nozzle, and a second discharge waveform for discharging a second amount of liquid larger than the first amount from the nozzle are supplied to the drive element. A method of driving a liquid discharge device including a possible drive unit, wherein a plurality of discharge waveforms are supplied to the drive element within a unit period, and two or more discharge waveforms other than the last of the plurality of discharge waveforms are supplied. Is the second discharge waveform, and the last discharge waveform among the plurality of discharge waveforms is the first discharge waveform.

It is a block diagram of the liquid discharge device which concerns on 1st Embodiment. It is an exploded perspective view of the liquid discharge head. It is sectional drawing of the liquid discharge head. It is a block diagram which illustrates the structure of the drive part. It is a waveform diagram of a drive signal. It is a waveform diagram of the first discharge waveform. It is a waveform diagram of the second discharge waveform. It is a chart which shows the result of having investigated the effect which mist is reduced by the 1st discharge waveform. It is a waveform diagram of the drive signal which concerns on 2nd Embodiment. It is a waveform diagram of the drive signal which concerns on 3rd Embodiment. It is a block diagram which illustrates the structure of the drive part. It is a truth table showing the operation of the decoder.

A. 1st Embodiment FIG. 1 is a block diagram which illustrates the liquid discharge device 100 which concerns on 1st Embodiment of this invention. The liquid ejection device 100 of the first embodiment is an inkjet printing apparatus that ejects ink, which is an example of a liquid, onto a medium 12. The medium 12 is typically printing paper, but a printing target of any material such as a resin film or a cloth is used as the medium 12. As illustrated in FIG. 1, a liquid container 14 for storing ink is installed in the liquid ejection device 100. For example, a cartridge that can be attached to and detached from the liquid ejection device 100, a bag-shaped ink pack made of a flexible film, or an ink tank that can be refilled with ink is used as the liquid container 14.

As illustrated in FIG. 1, the liquid discharge device 100 includes a control unit 20, a transfer mechanism 22, a moving mechanism 24, and a liquid discharge head 26. The control unit 20 includes, for example, a processing circuit such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array) and a storage circuit such as a semiconductor memory, and comprehensively controls each element of the liquid discharge device 100. The control unit 20 of the first embodiment includes a signal generation unit 201 that generates various signals for ejecting ink.

The transport mechanism 22 transports the medium 12 in the Y-axis direction under the control of the control unit 20. The moving mechanism 24 reciprocates the liquid discharge head 26 along the X axis under the control of the control unit 20. The X-axis intersects the Y-axis on which the medium 12 is conveyed. Specifically, the X-axis and the Y-axis are orthogonal to each other. The moving mechanism 24 of the first embodiment includes a substantially box-shaped transport body 242 that accommodates the liquid discharge head 26, and a transport belt 244 to which the transport body 242 is fixed. It should be noted that a configuration in which a plurality of liquid discharge heads 26 are mounted on the transport body 242 or a configuration in which the liquid container 14 is mounted on the transport body 242 together with the liquid discharge head 26 may be adopted.

The liquid ejection head 26 ejects the ink supplied from the liquid container 14 from a plurality of nozzles to the medium 12 under the control of the control unit 20. For example, various signals for ejecting the ink generated by the control unit 20 are supplied to the liquid ejection head 26. A desired image is formed on the surface of the medium 12 by each liquid ejection head 26 ejecting ink to the medium 12 in parallel with the transfer of the medium 12 by the transfer mechanism 22 and the repetitive reciprocation of the transfer body 242. ..

FIG. 2 is an exploded perspective view of the liquid discharge head 26, and FIG. 3 is a cross-sectional view taken along the line aa in FIG. As illustrated in FIGS. 2 and 3, the axis perpendicular to the XY plane is hereinafter referred to as the Z axis. The ink from each liquid ejection head 26 is ejected along the Z axis. The XY plane is, for example, a plane parallel to the surface of the medium 12.

As illustrated in FIGS. 2 and 3, the liquid discharge head 26 includes a long, substantially rectangular flow path substrate 32 along the Y axis. A pressure chamber substrate 34, a diaphragm 36, a plurality of piezoelectric elements 38, and a housing portion 42 are installed on a surface of the flow path substrate 32 in the negative direction on the Z axis. On the other hand, the nozzle plate 46 and the vibration absorbing body 48 are installed on the surface of the flow path substrate 32 in the positive direction on the Z axis. Each element of the liquid discharge head 26 is generally a long plate-shaped member along the Y-axis like the flow path substrate 32, and is joined to each other by using, for example, an adhesive.

As illustrated in FIG. 2, the nozzle plate 46 is a plate-shaped member in which a plurality of nozzles N arranged in the Y-axis direction are formed. Each nozzle N is a through hole through which ink passes. The flow path substrate 32, the pressure chamber substrate 34, and the nozzle plate 46 are formed by processing, for example, a silicon (Si) single crystal substrate by a semiconductor manufacturing technique such as etching. However, the material and manufacturing method of each element of the liquid discharge head 26 are arbitrary.

The flow path substrate 32 is a plate-shaped member for forming a flow path of ink. As illustrated in FIGS. 2 and 3, the flow path substrate 32 is formed with an opening 322, a supply flow path 324, and a communication flow path 326. The opening 322 is a long through hole along the Y axis in a plan view from the direction of the Z axis so as to be continuous over the plurality of nozzles N. On the other hand, the supply flow path 324 and the communication flow path 326 are through holes individually formed for each nozzle N. Further, as illustrated in FIG. 3, a relay flow path 328 spanning a plurality of supply flow paths 324 is formed on the surface of the flow path substrate 32 in the positive direction on the Z axis. The relay flow path 328 is a flow path for communicating the opening 322 and the plurality of supply flow paths 324. The surface of the nozzle plate 46 in the positive direction on the Z axis is the nozzle surface FN of the nozzle N provided with an opening for ejecting ink.

The housing portion 42 is, for example, a structure manufactured by injection molding of a resin material, and is fixed to the surface of the flow path substrate 32 in the negative direction on the Z axis. As illustrated in FIG. 3, the housing portion 42 is formed with a housing portion 422 and an introduction port 424. The accommodating portion 422 is a concave portion having an outer shape corresponding to the opening 322 of the flow path substrate 32, and the introduction port 424 is a through hole communicating with the accommodating portion 422. As can be understood from FIG. 3, the space in which the opening 322 of the flow path substrate 32 and the accommodating portion 422 of the housing portion 42 communicate with each other functions as the liquid storage chamber R. The ink supplied from the liquid container 14 and passing through the introduction port 424 is stored in the liquid storage chamber R. The vibration absorber 48 is a flexible film that constitutes the wall surface of the liquid storage chamber R, and absorbs pressure fluctuations of ink in the liquid storage chamber R.

As illustrated in FIGS. 2 and 3, the pressure chamber substrate 34 is a plate-shaped member in which a plurality of pressure chambers C corresponding to different nozzles N are formed. The plurality of pressure chambers C are arranged along the Y axis. Each pressure chamber C is a long opening along the X axis in a plan view. The end of the pressure chamber C in the positive direction of the X axis overlaps one supply flow path 324 of the flow path substrate 32 in a plan view, and the end of the pressure chamber C in the negative direction of the X axis is a flow path substrate in a plan view. It overlaps with one communication flow path 326 of 32. The pressure chamber C and the nozzle N communicate with each other via the communication flow path 326.

A diaphragm 36 is installed on the surface of the pressure chamber substrate 34 opposite to the flow path substrate 32. The diaphragm 36 is a plate-shaped member that can be elastically deformed. By selectively removing a part of the plate-shaped member having a predetermined plate thickness in the plate thickness direction in the region corresponding to the pressure chamber C, the pressure chamber substrate 34 and a part or all of the diaphragm 36 can be removed. It may be formed integrally.

As can be understood from FIG. 3, the flow path substrate 32 and the diaphragm 36 face each other at a distance inside each pressure chamber C. The pressure chamber C is located between the flow path substrate 32 and the diaphragm 36, and is a space for applying pressure to the ink filled in the pressure chamber C. The ink stored in the liquid storage chamber R branches from the relay flow path 328 to each supply flow path 324, and is supplied and filled in parallel to the plurality of pressure chambers C. As understood from the above description, the diaphragm 36 constitutes a part of the wall surface of the pressure chamber C.

As illustrated in FIGS. 2 and 3, a plurality of piezoelectric elements 38 corresponding to different nozzles N are formed on the surface of the diaphragm 36 opposite to the pressure chamber C. Each piezoelectric element 38 is a driving element that ejects ink from the nozzle N by varying the pressure of the ink in the pressure chamber C. Each piezoelectric element 38 is formed in a long shape along the X axis in a plan view, for example. The piezoelectric element 38 is an example of a “driving element”.

As illustrated in FIG. 3, for example, a wiring board 50 is joined to the surface of the diaphragm 36. The wiring board 50 is a mounting component on which a plurality of wirings for electrically connecting the control unit 20 and the liquid discharge head 26 are formed. For example, a flexible substrate such as FPC (Flexible Printed Circuit) or FFC (Flexible Flat Cable) is preferably adopted as the wiring board 50. The drive unit 62 of FIG. 2 is mounted on the wiring board 50 in the form of an IC chip, for example. The output terminal of the drive unit 62 is electrically connected to the terminal of the piezoelectric element 38 formed on the surface of the diaphragm 36. The nozzle N, the pressure chamber C, and the piezoelectric element 38 function as a liquid discharge unit 90.

FIG. 4 is a block diagram illustrating a functional configuration of the liquid discharge device 100. As illustrated in FIG. 4, the liquid discharge head 26 of the first embodiment includes a plurality of piezoelectric elements 38 corresponding to different nozzles N, and a drive unit 62 for driving each of the plurality of piezoelectric elements 38. .. Each of the plurality of piezoelectric elements 38 ejects ink in response to a signal supplied from the drive unit 62. It is also possible to install the drive unit 62 outside the liquid discharge head 26.

A drive signal COM is used to drive the piezoelectric element 38. That is, the drive signal COM is a voltage signal used for ejecting ink by the liquid ejection head 26. FIG. 5 is a waveform diagram of the drive signal COM. As illustrated in FIG. 5, the drive signal COM fluctuates with time in a unit period T with reference to a predetermined voltage. The drive signal COM is generated by the signal generation unit 201. The details of the drive signal COM will be described later.

When the diaphragm 36 vibrates in conjunction with the deformation of the piezoelectric element 38, the pressure in the pressure chamber C fluctuates. As a result, the ink filled in the pressure chamber C passes through the communication flow path 326 and the nozzle N and is ejected. The volume of the pressure chamber C changes according to the voltage value of the drive signal COM supplied from the drive unit 62. Specifically, the lower the voltage of the drive signal COM supplied from the drive unit 62, the larger the volume of the pressure chamber C, and the higher the voltage of the drive signal COM supplied from the drive unit 62, the larger the volume of the pressure chamber C. The piezoelectric element 38 is displaced so as to decrease. That is, the lower the voltage of the drive signal COM, the lower the pressure in the pressure chamber C, and the higher the voltage, the higher the pressure in the pressure chamber C.

As illustrated in FIG. 4, the drive unit 62 includes a shift register 621, a latch circuit 623, a decoder 625, and a switch 627 for each piezoelectric element 38. The control data D, the latch signal LAT, and the drive signal COM are supplied from the control unit 20 to the drive unit 62.

Each of the plurality of control data D corresponding to the different nozzles N is sequentially supplied to the shift register 621 corresponding to the nozzle N. The control data D of each nozzle N is data instructing the ejection / non-ejection of ink by the nozzle N.

The latch circuit 623 captures and outputs the control data D held in the shift register 621 at the timing specified by the latch signal LAT. FIG. 5 shows a waveform diagram of the latch signal LAT. The latch signal LAT is a signal that defines a unit period T. Specifically, the latch signal LAT is a signal in which pulses are set at a period corresponding to a unit period T. In the first embodiment, the unit period T corresponds to one cycle of the drive signal COM. As illustrated in FIG. 5, the pulse of the latch signal LAT is set to rise at the start point of the unit period T. In the latch signal LAT, the period between two pulses before and after each other corresponds to the unit period T. That is, the unit period T is one cycle of the latch signal LAT. In other words, the period for ejecting the amount of ink corresponding to the region corresponding to one pixel is the unit period T. As understood from the above description, the latch signal LAT of the first embodiment is a signal that defines a unit period T in the drive signal COM.

The decoder 625 generates an instruction signal S from the control data D output by the latch circuit 623. The level of the indicator signal S is determined at a time specified according to the latch signal LAT. Specifically, the level of the instruction signal S is determined at the start point of each unit period T. Specifically, the decoder 625 sets the instruction signal S to a high level when the control data D instructs ink ejection, and sets the instruction signal S when the control data D instructs non-ink ejection. Set to low level.

The switch 627 is interposed between the output terminal of the decoder 625 and the piezoelectric element 38. The instruction signal S output from the decoder 625 is supplied to the control terminal of the switch 627. Each switch 627 is composed of, for example, a transfer gate, and switches whether or not to supply the drive signal COM to the piezoelectric element 38 according to the instruction signal S. When the instruction signal S is set to a high level, the switch 627 is controlled to be on, and the drive signal COM is supplied to the piezoelectric element 38. On the other hand, when the instruction signal S is set to the low level, the switch 627 is controlled to the off state, and the drive signal COM is not supplied to the piezoelectric element 38. The instruction signal S is a signal for controlling the on / off of the switch 627.

As illustrated in FIG. 5, the drive signal COM includes a plurality of discharge waveforms W (W1, W2) for each unit period T. Each ejection waveform W is a waveform for ejecting a predetermined amount of ink from the nozzle N. The plurality of discharge waveforms W in the unit period T include a first discharge waveform W1 and two or more second discharge waveforms W2. Specifically, two or more discharge waveforms W other than the last among the plurality of discharge waveforms W in the unit period T are the second discharge waveforms W2, and at least the last discharge waveform W among the plurality of discharge waveforms W is the first. 1 Discharge waveform W1. In the first embodiment, four discharge waveforms W are supplied to the piezoelectric element 38 within the unit period T. Of the four discharge waveforms W, the third discharge waveform W from the beginning is the second discharge waveform W2, and the last discharge waveform W is the first discharge waveform W1. As understood from the above description, when the switch 627 is controlled to be in the ON state, the portion of the drive signal COM corresponding to the unit period T is supplied to the piezoelectric element 38. That is, the first discharge waveform W1 and the second or more second discharge waveforms W2 are supplied to the piezoelectric element 38 from the drive signal COM. As understood from the above description, the drive unit 62 can supply the first discharge waveform W1 and the second discharge waveform W2 to the piezoelectric element 38.

The first ejection waveform W1 is a waveform for ejecting a first amount of ink from the nozzle N. That is, when the first ejection waveform W1 is supplied to the piezoelectric element 38, the piezoelectric element 38 causes pressure fluctuation in the ink in the pressure chamber C, and the first amount of ink is ejected from the nozzle N. On the other hand, the second ejection waveform W2 is a waveform that ejects a second amount of ink, which is larger than the first amount, from the nozzle N. That is, when the second ejection waveform W2 is supplied to the piezoelectric element 38, the piezoelectric element 38 causes a pressure fluctuation in the ink in the pressure chamber C, and the second amount of ink is ejected from the nozzle N. An amount of ink corresponding to a plurality of ejection waveforms W within the unit period T is ejected from the nozzle N to a region corresponding to one pixel. Further, the ejection speed of the ink ejected from the nozzle N by the first ejection waveform W1 is slower than, for example, the ejection speed of the ink ejected from the nozzle N by the second ejection waveform W2. However, the ejection speed of the ink ejected from the nozzle N by the first ejection waveform W1 may be faster than the ejection speed of the ink ejected from the nozzle N by the second ejection waveform W2. The droplets ejected from the nozzle N by the first ejection waveform W1 may or may not be coalesced with the preceding droplets ejected from the nozzle N by the second ejection waveform W2. However, when the droplets formed by the first ejection waveform W1 and the droplets formed by the second ejection waveform W2 are not united, the graininess of the printed matter is improved and the image quality is improved.

The second discharge waveform W2 includes a first portion W21 and a second portion W22 located behind the first portion W21. The first portion W21 causes pressure vibration in the ink in the pressure chamber C to the extent that the ink is not ejected from the nozzle N. That is, the first portion W21 pre-vibrates the ink in the pressure chamber C and the ink in the nozzle N. The second portion W22 discharges ink from the nozzle N by further causing a pressure fluctuation in the ink in the pressure chamber C so as to resonate with the preliminary vibration generated by the first portion W21. The second portion W22 vibrates the ink in the pressure chamber C and the ink in the nozzle N with a stronger intensity than that of the first portion W21. The first portion W21 and the second portion W22 are continuously supplied to the piezoelectric element 38, so that a second amount of ink is ejected from the nozzle N. On the other hand, the first ejection waveform W1 ejects a first amount of ink from the nozzle N without giving a preliminary vibration to the ink in the nozzle N.

In the first embodiment, the second portion W22 of the second discharge waveform W2 and the first discharge waveform W1 have the same shape. Since the second ejection waveform W2 includes the first portion W21 that pre-vibrates the ink in the nozzle immediately before the second portion W22, the second amount ejected by the second ejection waveform W2 is ejected by the first ejection waveform W1. More than the first amount. The amount of ink ejected from the nozzle N in the unit period T (hereinafter referred to as “unit ejection amount”) is the total value of the amount of ink ejected from the nozzle N by each ejection waveform W in the unit period T.

Actually, the drive unit 62 can supply the piezoelectric element 38 with a discharge waveform W different from the first discharge waveform W1 and the second discharge waveform W2. For example, the piezoelectric element 38 may be supplied with a third ejection waveform that ejects a third amount of ink smaller than the first amount from the nozzle N. The third discharge waveform is, for example, a waveform having a smaller amplitude than the first discharge waveform W1.

FIG. 6 is a waveform diagram of the first discharge waveform W1, and FIG. 7 is a waveform diagram of the second discharge waveform W2. As illustrated in FIGS. 6 and 7, the first discharge waveform W1 and the second discharge waveform W2 have a range from the voltage value VL on the low potential side to the voltage value VH on the high potential side with reference to a predetermined voltage V0. It fluctuates with. As illustrated in FIG. 6, the first discharge waveform W1 includes the first section P1, the holding section Pa, the second section P2, the holding section Pb, and the third section P3 in this order. The first section P1 is a section for expanding the pressure chamber C, and is a section in which the voltage drops with time from the voltage V0 to the voltage value VL. The holding section Pa is a section held at the voltage value VL. The second section P2 is a section for contracting the pressure chamber C, and is a section in which the voltage rises with time from the voltage value VL to the voltage value VH. The holding section Pb is a section held at the voltage value VH. The third section P3 is a section for expanding the pressure chamber C, and is a section in which the voltage drops with time from the voltage value VH to the voltage V0.

As illustrated in FIG. 7, the second discharge waveform W2 includes the fourth section P4, the holding section Pc, the fifth section P5, the holding section Pd, the sixth section P6, the holding section Pe, and the seventh section P7 in this order. Including with. The fourth section P4 is a section for contracting the pressure chamber C, and is a section in which the voltage rises with time from the voltage V0 to the voltage value VM. The voltage value VM is lower than the voltage value VH. The holding section Pc is a section maintained at the voltage value VM. The fifth section P5 is a section in which the pressure chamber C is expanded, and the voltage drops with time from the voltage value VM to the voltage value VL. Specifically, the fifth section P5 includes a section P51 and a section P52. In the section P51, the voltage drops from the voltage value VM to the voltage V0. In the section P52, the voltage drops from the voltage V0 to the voltage value VL. The holding section Pd is a section held at the voltage value VL. The sixth section P6 is a section for contracting the pressure chamber C, and is a section in which the voltage rises with time from the voltage value VL to the voltage value VH. The holding section Pe is a section held at the voltage value VH. The seventh section P7 is a section for expanding the pressure chamber C, and is a section in which the voltage drops with time from the voltage value VH to the voltage V0.

The first portion W21 of the second discharge waveform W2 includes a fourth section P4, a holding section Pc, and a section P51 of the fifth section P5. Specifically, the first portion W21 is a portion of the second discharge waveform W2 that fluctuates in the range from the voltage V0 to the voltage value VM. The second portion W22 of the second discharge waveform W2 includes a section P52 of the fifth section P5, a holding section Pd, a sixth section P6, a holding section Pe, and a seventh section P7. Specifically, the second portion W22 is a portion of the second discharge waveform W2 that fluctuates in the range from the voltage value VL to the voltage value VH. The fifth section P5 covers both the first portion W21 and the second portion W22. The amplitude ΔV21 of the first portion W21 is smaller than the amplitude ΔV22 of the second portion W22. The amplitude ΔV21 is the difference between the voltage V0 and the voltage value VM, and the amplitude ΔV22 is the difference between the voltage value VL and the voltage value VH. Further, the time length Δt21 of the first portion W21 is shorter than the time length Δt22 of the second portion W22.

As described above, the first discharge waveform W1 and the second portion W22 of the second discharge waveform W2 have the same shape. Specifically, in the first section P1 and the section P52, the voltage amplitude ΔVa and the rate of change are equal. The amplitude ΔVa is the difference between the voltage V0 and the voltage value VL. The rate of change is the amount of change in voltage per unit time. In the second section P2 and the sixth section P6, the voltage amplitude ΔVb and the rate of change are equal. The amplitude ΔVb is the difference between the voltage value VL and the voltage value VH. In the third section P3 and the seventh section P7, the voltage amplitude ΔVc and the rate of change are equal. The amplitude ΔVc is the difference between the voltage value VH and the voltage V0. Further, the time length Δta is equal in the holding section Pa and the holding section Pd, and the time length Δtb is equal in the holding section Pb and the holding section Pe.

Here, when the ejection waveform W is supplied to the piezoelectric element 38 and the ink is ejected from the nozzle N, a tail trail following the main droplet occurs. The tailing portion is divided by surface tension to form a plurality of fine droplets (so-called mist). The length of the tailing generated by the ejection of the ink by the first ejection waveform W1 is shorter than the length of the tailing generated by the ejection of the ink by the second ejection waveform W2. The longer the tail, the greater the amount of mist generated when the ink is ejected. That is, the amount of mist generated when ink is ejected from the nozzle N by supplying the first ejection waveform W1 to the piezoelectric element 38 is when ink is ejected from the nozzle N by supplying the second ejection waveform W2 to the piezoelectric element 38. Less than the amount of mist generated in.

In order to print with high image quality in a short time, it is necessary to increase the unit ejection amount. In order to increase the unit discharge amount, for example, a configuration in which a plurality of discharge waveforms W in the unit period T are all set to the second discharge waveform W2 (hereinafter referred to as “Comparative Example 1”) is assumed. In Comparative Example 1, although the unit discharge amount increases, tailing occurs remarkably. That is, there is a problem that the amount of mist generated in the unit period T increases. On the other hand, in the configuration in which the plurality of discharge waveforms W in the unit period T are all set to the first discharge waveform W1 (hereinafter referred to as "Comparative Example 2"), there is a problem that the tailing is suppressed but the unit discharge amount cannot be sufficiently secured. is there. In Comparative Example 2, in order to increase the unit discharge amount, it is necessary to increase the number of the first discharge waveforms W1 in the unit period T. Alternatively, a configuration is also assumed in which the unit discharge amount is increased by applying the rear first discharge waveform W1 at the timing of resonating with the residual vibration due to the front first discharge waveform W1. However, in the above configuration, it is necessary to increase the interval of the first discharge waveform W1. As described above, in order to increase the unit ejection amount in Comparative Example 2, it is necessary to lengthen the time length of the unit period T, and there is a problem that the printing speed is lowered.

On the other hand, in the first embodiment, of the plurality of discharge waveforms W in the unit period T, two or more discharges other than the last are the second discharge waveform W2, and the last discharge waveform W is the first discharge waveform W1. is there. In the above configuration, the mist generated by the ink ejection by the second ejection waveform W2 is coalesced with the ink droplets ejected by the first ejection waveform W1, and the coalesced droplets land on the medium 12. That is, the unit discharge amount can be increased while reducing the amount of mist generated in the unit period T. In addition, in order to increase the unit discharge amount, it is assumed that the amplitude of each discharge waveform W within the unit period T is increased. However, in reality, it may be difficult to increase the amplitude due to factors such as the characteristics of the piezoelectric element 38. On the other hand, in the first embodiment, the unit ejection amount can be increased by a simple configuration in which the first portion W21 for pre-vibrating the ink in the nozzle N is added to the second portion W22. Further, although a configuration is assumed in which the unit ejection amount is increased by increasing the nozzle diameter, there is a problem that a minute amount of ink cannot be ejected when the nozzle diameter is increased. On the other hand, in the first embodiment, the unit discharge amount can be increased by using the second discharge waveform W2 without increasing the nozzle diameter. That is, it is possible to both eject a fine amount of ink and increase the unit ejection amount. As described above, in the first embodiment, for example, a third amount of ink smaller than the first amount can be ejected by the third ejection waveform.

According to the configuration of the first embodiment in which the unit period T is one cycle of the latch signal LAT, the unit ejection amount of the ink with respect to the region corresponding to one pixel can be increased. That is, high-quality printing becomes possible in a short time. In the first embodiment, since the first discharge waveform W1 and the second discharge waveform W2 are supplied to the piezoelectric element 38 from the drive signal COM including the plurality of discharge waveforms W, for example, the drive signal COM including the first discharge waveform W1. The first discharge waveform W1 and the first discharge waveform W1 are compared with the configuration in which the first discharge waveform W1 is supplied to the piezoelectric element 38 and the second discharge waveform W2 is supplied to the piezoelectric element 38 from the drive signal COM including the second discharge waveform W2. There is an advantage that the control of supplying the two discharge waveforms W2 to the piezoelectric element 38 is simple.

In the first embodiment, since the amount of mist generated when the ink is ejected by the first ejection waveform W1 is smaller than the amount of mist generated when the ink is ejected by the second ejection waveform W2, the unit period T The effect of reducing the amount of mist throughout is remarkable. Further, in the first embodiment, the first discharge waveform W1 includes the first section P1, the second section P2, and the third section P3, while the second discharge waveform W2 includes the fifth section P5 and the sixth section P6. In addition to the 7th section P7 and the 7th section P7, a 4th section P4 that pre-vibrates the ink in the nozzle N is included in front of the 5th section P5. Therefore, when the entire second ejection waveform W2 is supplied to the piezoelectric element 38, a second amount of ink larger than the first amount can be ejected from the nozzle N. According to the configuration of the first embodiment in which the voltage amplitude and the rate of change are the same in the second section P2 and the sixth section P6, the first discharge waveform W1 can be diverted to the second portion W22 of the second discharge waveform W2. 2 Discharge waveform W2 can be easily generated.

The conditions for combining the mist generated by the ink ejection by the second ejection waveform W2 with the ink droplets (hereinafter referred to as “first droplets”) ejected by the first ejection waveform W1 will be described in detail. FIG. 8 shows the mist generated by the second discharge waveform W2 in each of a plurality of cases in which the interval (hereinafter referred to as “waveform interval”) U between the second discharge waveform W2 and the first discharge waveform W1 immediately after that is changed. Is a chart showing the result of investigating whether or not is combined with ink droplets according to the first ejection waveform W1. In FIG. 8, the results of the investigation are shown for each of a plurality of cases in which the distance (hereinafter referred to as “platen gap”) PG between the surface of the medium 12 and the nozzle surface FN is different. As illustrated in FIG. 5, the waveform interval U means the time difference between the start point of the second discharge waveform W2 located immediately before the first discharge waveform W1 and the start point of the first discharge waveform W1. “Effective” in FIG. 8 means that the first droplet has an effect of suppressing mist, and “no effect” means that the effect of suppressing mist by the first droplet cannot be sufficiently obtained. means.

In the investigation of FIG. 8, the viscosity of the ink was 1.8 mm ² / sec or more and 6.7 mm ² / sec or less (more specifically, 1.8 mm ² / sec or more and 4.5 mm ² / sec or less). It is assumed that there will be cases. The flight speed of the droplets ejected by the first ejection waveform W1 is 4.2 m / sec or more and 9.8 m / sec or less. The amount of ink ejected by the first ejection waveform W1 and the second ejection waveform W2 is 7.4 ng or more and 8.7 ng or less.

As can be understood from FIG. 8, the smaller the waveform interval U, the easier it is for the mist due to the second ejection waveform W2 to combine with the first droplet over a wide range of the platen gap PG. Specifically, when the waveform interval U is 20 μsec, it is possible to combine the mist with the first droplet over a wide range of the platen gap PG of 1 mm or more and 3.5 mm or less. When the waveform interval U is 30 μsec, it is possible to combine the mist with the first droplet over a range of the platen gap PG of 1.5 mm or more and 3.5 mm or less. When the waveform interval U is 40 μsec, it is possible to combine the mist with the first droplet over a range of the platen gap PG of 2.0 mm or more and 3.5 mm or less. When the waveform interval U is 50 μsec or 60 μsec, it is possible to combine the mist with the first droplet over a range of the platen gap PG of 2.5 mm or more and 3.5 mm or less.

If the mist is sufficiently close to the surface of the medium 12 at the time when the mist is combined with the first droplet, the mist moves over a wide range due to the air flow on the surface or the air flow due to the ejection of ink from the nozzle N. there's a possibility that. Therefore, the effect of suppressing mist is insufficient. “Insufficient effect” in FIG. 8 means that the effect of suppressing mist is insufficient as described above. As can be understood from FIG. 8, it was confirmed by the investigation that the effect is insufficient when the waveform interval U is 70 μsec or more.

Considering the results of the above investigation, it is desirable that the waveform interval U is 60 μsec or less. By setting the waveform interval U to 60 μsec or less, it is possible to sufficiently obtain the effect of suppressing the mist by the first droplet.

B. Second Embodiment The second embodiment will be described below. For the elements having the same functions as those of the first embodiment in each of the following examples, the reference numerals used in the description of the first embodiment will be diverted and detailed description of each will be omitted as appropriate.

FIG. 9 is a waveform diagram of the drive signal COM according to the second embodiment. As illustrated in FIG. 9, the plurality of discharge waveforms W of the unit period T in the drive signal COM of the second embodiment are the same as those of the first embodiment, and two or more discharge waveforms W other than the last of the plurality of discharge waveforms W are discharged. The waveform W is the second discharge waveform W2, and at least the last discharge waveform W of the plurality of discharge waveforms W is the first discharge waveform W1. However, in the second embodiment, the first discharge waveform W1 is also included between the second or more second discharge waveforms W2 in the unit period T. Specifically, in the unit period T, the second discharge waveform W2, the first discharge waveform W1, the second discharge waveform W2, and the first discharge waveform W1 are located in this order. That is, the first discharge waveform W1 is located immediately after each second discharge waveform W2. The liquid discharge device 100 of the second embodiment has the same configuration as that of the first embodiment except that the drive signal COM is different.

When the switch 627 is controlled to the ON state, the portion of the drive signal COM corresponding to the unit period T is supplied to the piezoelectric element 38. That is, within the unit period T, the first discharge waveform W1 is supplied to the piezoelectric element 38 between the two or more second discharge waveforms W2. The same effect as that of the first embodiment is realized in the second embodiment. In the second embodiment, in particular, since the first discharge waveform W1 is located between the two or more second discharge waveforms W2, the second discharge waveform W2 located immediately before the first discharge waveform W1 for each first discharge waveform W1. The occurrence of tailing due to is reduced. Therefore, the effect of reducing the amount of mist generated when the ink is ejected from the nozzle N in the unit period T is remarkable. On the other hand, in the first embodiment, since all the discharge waveforms W other than the last among the plurality of discharge waveforms W in the unit period T are the second discharge waveform W2, the effect of increasing the unit discharge amount is remarkable. Is.

C. Third Embodiment FIG. 10 is a waveform diagram of a drive signal COM according to the third embodiment. Similar to the second embodiment, the drive signal COM includes the second discharge waveform W2, the first discharge waveform W1, the second discharge waveform W2, and the first discharge waveform W1 in this order in the unit period T. In the third embodiment, the unit period T in the drive signal COM is divided into a plurality of sections (hereinafter referred to as “waveform sections”) tn (n = 1 to 4) including a plurality of discharge waveforms W. The waveform section t1 includes the second discharge waveform W2, the waveform section t2 includes the first discharge waveform W1, the waveform section t3 includes the second discharge waveform W2, and the waveform section t4 includes the first discharge waveform W1. In the third embodiment, ink ejection / non-ejection is controlled for each waveform section tn.

FIG. 11 is a block diagram illustrating the configuration of the drive unit 62 according to the third embodiment. As illustrated in FIG. 11, the drive unit 62 includes a shift register 621, a latch circuit 623, a decoder 625, and a switch 627, as in the first embodiment. Similar to the first embodiment, each of the plurality of control data D corresponding to the different nozzles N is sequentially supplied to the shift register 621 corresponding to the nozzle N. The control data D is data for controlling the ejection / non-ejection of ink for each nozzle N, as in the first embodiment. The control data D of the third embodiment indicates one of a plurality of different unit discharge amounts for discharge. Specifically, the control data D indicates which of the unit discharge amount corresponding to the large dot, the unit discharge amount corresponding to the medium dot, and the unit discharge amount corresponding to the small dot is to be discharged. Similar to the first embodiment, the latch circuit 623 captures and outputs the control data D output from the shift register 621 at the timing specified by the latch signal LAT.

A control signal CH is supplied from the control unit 20 to the decoder 625 of the third embodiment in addition to the latch signal LAT similar to that of the first embodiment. The control signal CH is shown in FIG. As illustrated in FIG. 10, the control signal CH is a signal that defines the boundary point of the waveform section tn within the unit period T. The boundary point designated by the control signal CH is located between two adjacent discharge waveforms. The boundary point is designated by the rise of the pulse of the control signal CH at the start point of each waveform section tn.

Specifically, the decoder 625 generates an instruction signal S from the control data D output by the latch circuit 623. In the third embodiment, the level of the instruction signal S is determined at a time point defined by the latch signal LAT and the control signal CH. Specifically, the level of the instruction signal S is determined at the start point of each waveform section tn within the unit period T.

FIG. 12 is a truth table showing the operation of the decoder 625. FIG. 12 shows the levels of the large dots LD, the medium dots MD1 to MD4, and the small dots SD1 to SD2, which are set by the instruction signal S in each waveform section tn. As illustrated in FIG. 12, the level of the instruction signal S in each waveform section tn differs depending on the dots instructed by the control data D. However, for all the dots, the instruction signal S is generated so that the discharge waveform finally supplied to the piezoelectric element 38 within the unit period T becomes the first discharge waveform W1. The instruction signal S is set so that the last waveform section tn of the one or more waveform sections tn set to the high level in the unit period T becomes the waveform section t2 or the waveform section t4.

For example, when the control data D indicates the large dot LD, the decoder 625 sets the instruction signal S to a high level in all the waveform sections tn in the unit period T. That is, the first discharge waveform W1 is finally supplied within the unit period T. For example, when the control data D indicates the medium dot MD1, the instruction signal S is set to a high level in the waveform section t1 and the waveform section t2, and the instruction signal S is set to a low level in the waveform section t3 and the waveform section t4. .. That is, after the first discharge waveform W1 is supplied in the waveform section t2, the discharge waveform W is not supplied within the unit period T. As can be understood from the above description, for all the dots, the first amount of ink according to the first ejection waveform W1 is ejected at the end of the unit period T.

The switch 627 switches whether or not to supply the drive signal COM to the piezoelectric element 38 according to the instruction signal S. The switch 627 of the third embodiment controls the on / off of the switch 627 for each waveform section tn. Therefore, a unit ejection amount of ink corresponding to any one of the large dot LD, the medium dots MD1 to MD4, and the small dots SD1 to SD2 is ejected from the nozzle N.

The same effect as that of the second embodiment is realized in the third embodiment. In the third embodiment, for each of the plurality of dots, the discharge waveform finally supplied to the piezoelectric element 38 within the unit period T is set to the first discharge waveform W1. Therefore, it is possible to reduce the generation of mist even when the ink with a unit ejection amount corresponding to various dots is ejected.

In the third embodiment, a drive signal COM in which the second discharge waveform W2, the second discharge waveform W2, the first discharge waveform W1 and the first discharge waveform W1 are located in this order within the unit period T is also adopted. .. For example, when a large dot is specified in the control data D, the instruction signal S is set to a high level in all waveform sections tn. When the middle dot is specified in the control data D, the waveform section t1 and the waveform section t4 are set to the low level, and the waveform section t2 and the waveform section t3 are set to the high level. With the above configuration, it is possible to bring the discharge timing within the unit period T closer to the large dot and the medium dot. That is, the landing position in the X-axis direction can be brought closer to the large dot and the medium dot in the region corresponding to one pixel. Therefore, there is an advantage that the image quality is improved.

D. Modification Examples Each of the above-exemplified forms can be variously transformed. Specific modifications that can be applied to each of the above-mentioned forms are illustrated below. In addition, two or more aspects arbitrarily selected from the following examples can be appropriately merged within a range that does not contradict each other.

(1) In each of the above-described embodiments, the shape of the first discharge waveform W1 and the shape of the second discharge waveform W2 are such that the second amount discharged from the nozzle N by the second discharge waveform W2 is the nozzle N by the first discharge waveform W1. It is optional as long as it is larger than the first amount discharged from. Further, although the configuration in which the second portion W22 of the second discharge waveform W2 and the first discharge waveform W1 have the same shape is illustrated, the second amount discharged from the nozzle N by the second discharge waveform W2 is the first discharge waveform. The shape of the second portion W22 of the second discharge waveform W2 and the shape of the first discharge waveform W1 may be different as long as the amount is larger than the first amount discharged from the nozzle N by W1. For example, the amplitude and the time length may differ between the second portion W22 and the first discharge waveform W1.

(2) In each of the above-described embodiments, the first portion W21 of the second ejection waveform W2 is composed of the fourth section P4, the holding section Pc, and the section P51, but the shape of the first portion W21 is that ink is drawn from the nozzle N. It is optional as long as the ink in the nozzle N can be pre-vibrated without being ejected. The first portion W21 may include a section different from the fourth section P4, the holding section Pc, and the section P51. For example, in addition to the fourth section P4, the holding section Pc, and the section P51, a section held at the voltage V0 immediately after the section P51 may be included.

(3) In each of the above-described embodiments, a configuration in which one cycle of the drive signal COM matches the unit period T defined by the latch signal LAT is illustrated, but there is also a configuration in which one cycle of the drive signal COM and the unit period T do not match. Will be adopted. Further, the unit period T is not limited to one cycle of the latch signal LAT.

(4) In each of the above-described embodiments, the configuration in which four discharge waveforms W are supplied to the piezoelectric element 38 within the unit period T is illustrated, but the number of discharge waveforms W supplied to the piezoelectric element 38 within the unit period T is illustrated. Is not limited to four. Of the plurality of discharge waveforms W supplied to the piezoelectric element 38 within the unit period T, two or more discharge waveforms W other than the last are the second discharge waveform W2, and at least the last discharge waveform W is the first discharge waveform W1. If so, the number of discharge waveforms W supplied to the piezoelectric element 38 within the unit period T is arbitrary.

(5) The types of the plurality of discharge waveforms W in the unit period T are not limited to the above-mentioned examples of each form. For example, a configuration in which the first discharge waveform W1, the second discharge waveform W2, the second discharge waveform W2, and the first discharge waveform W1 are located in this order within the unit period T, or the second discharge waveform W2 within the unit period T. A configuration is also adopted in which the second discharge waveform W2, the first discharge waveform W1 and the first discharge waveform W1 are located in this order. Further, the first discharge waveform W1 and the second discharge waveform W2 may include different discharge waveforms within the unit period T. Of the plurality of discharge waveforms W supplied to the piezoelectric element 38 within the unit period T, two or more discharge waveforms W other than the last are the second discharge waveform W2, and at least the last discharge waveform W is the first discharge waveform W1. If so, the type of each discharge waveform W within the unit period T is arbitrary.

(6) In each of the above-described modes, the first discharge waveform W1 and the second discharge waveform W2 are supplied to the piezoelectric element 38 from the common drive signal COM, but the first discharge waveform W1 and the second discharge waveform W2 are separated. The drive signal COM of the above may be supplied to the piezoelectric element 38. Specifically, the first discharge waveform W1 is supplied to the piezoelectric element 38 from the first drive signal including the first discharge waveform W1, and the second discharge waveform W2 is supplied from the second drive signal including the second discharge waveform W2. It may be supplied to the piezoelectric element 38. Also in the above configuration, as in each of the above-described embodiments, two or more second discharge waveforms W2 are supplied to the piezoelectric element 38 within the unit period T, and the first discharge waveform W1 is piezoelectric at least at the end of the unit period T. It may be supplied to the element 38.

(7) The element (driving element) that applies pressure to the inside of the pressure chamber C is not limited to the piezoelectric element 38 exemplified in each of the above-described embodiments. For example, it is also possible to use a heat generating element that generates air bubbles inside the pressure chamber C by heating to fluctuate the pressure as a driving element. As understood from the above examples, the driving element is comprehensively expressed as an element for discharging a liquid (typically, an element for applying pressure to the inside of the pressure chamber C), and an operating method (piezoelectric method /). It doesn't matter what the thermal method is or the specific configuration.

(8) In each of the above-described embodiments, the configuration in which the pressure chamber C expands as the voltage of the drive signal COM supplied to the piezoelectric element 38 decreases is illustrated, but the high and low voltage of the drive signal COM and the expansion of the pressure chamber C / The relationship with contraction is not limited to the above examples. For example, a configuration is also adopted in which the piezoelectric element 38 is displaced so that the pressure chamber C contracts as the voltage of the drive signal COM supplied to the piezoelectric element 38 decreases.

(9) In each of the above-described embodiments, the serial type liquid discharge device 100 for reciprocating the transport body 242 on which the liquid discharge head 26 is mounted is illustrated, but the line type liquid in which a plurality of nozzles N are distributed over the entire width of the medium 12 is illustrated. The present invention can also be applied to a discharge device.

(10) The liquid discharge device 100 illustrated in each of the above-described embodiments can be adopted in various devices such as a facsimile machine and a copier, in addition to a device dedicated to printing. However, the application of the liquid discharge device of the present invention is not limited to printing. For example, a liquid discharge device that discharges a solution of a coloring material is used as a manufacturing device for forming a color filter of a liquid crystal display device. Further, a liquid discharge device that discharges a solution of a conductive material is used as a manufacturing device for forming wirings and electrodes on a wiring board.

100 ... liquid discharge device, 12 ... medium, 14 ... liquid container, 20 ... control unit, 201 ... signal generator, 22 ... transfer mechanism, 24 ... movement mechanism, 242 ... transfer body, 244 ... transfer belt, 26 ... liquid discharge Head, 32 ... Flow path substrate, 322 ... Opening, 324 ... Supply flow path, 326 ... Communication flow path, 328 ... Relay flow path, 34 ... Pressure chamber board, 36 ... Vibration plate, 38 ... Pietryl element, 42 ... Body part, 422 ... Accommodating part, 424 ... Introduction port, 46 ... Nozzle plate, 48 ... Vibration absorber, 50 ... Wiring board, 62 ... Drive unit, 621 ... Shift register, 623 ... Latch circuit, 625 ... Decoder, 627 ... Switch , 90 ... Liquid discharge unit, C ... Pressure chamber, R ... Liquid storage chamber, D ... Control data, CH ... Control signal, COM ... Drive signal, LAT ... Latch signal, S ... Instruction signal, N ... Nozzle, T ... Unit Period, W1 ... 1st discharge waveform, W2 ... 2nd discharge waveform, P1 ... 1st section, P2 ... 2nd section, P3 ... 3rd section, P4 ... 4th section, P5 ... 5th section, P6 ... 6th Section, P7 ... 7th section.

Claims (9)

A liquid discharge unit having a nozzle for discharging a liquid, a pressure chamber communicating with the nozzle, and a driving element for discharging the liquid in the pressure chamber from the nozzle.
A drive unit capable of supplying a first discharge waveform for discharging a first amount of liquid from the nozzle and a second discharge waveform for discharging a second amount of liquid larger than the first amount from the nozzle to the drive element. And equipped with
Of the plurality of discharge waveforms supplied to the driving element within a unit period, two or more discharge waveforms other than the last are the second discharge waveforms, and the last discharge waveform among the plurality of discharge waveforms is the first discharge waveform. A corrugated liquid discharge device. The liquid discharge device according to claim 1, wherein the unit period is one cycle of a latch signal that defines a timing for capturing control data for controlling the discharge of the liquid by the nozzle. The liquid discharge device according to claim 1 or 2, wherein the drive unit supplies the first discharge waveform and the second discharge waveform to the drive element from a drive signal including the plurality of discharge waveforms. The amount of mist generated when the liquid is discharged from the nozzle by supplying the first discharge waveform to the drive element is generated when the liquid is discharged from the nozzle by supplying the second discharge waveform to the drive element. The liquid discharge device according to any one of claims 1 to 3, wherein the amount of mist is smaller than the amount of mist. The first discharge waveform includes a first section for expanding the pressure chamber, a second section for contracting the pressure chamber, and a third section for expanding the pressure chamber.
The second discharge waveform includes a fourth section for contracting the pressure chamber, a fifth section for expanding the pressure chamber, a sixth section for contracting the pressure chamber, and the pressure chamber. The liquid discharge device according to any one of claims 1 to 4, which includes a seventh section for expansion. The liquid discharge device according to claim 5, wherein the voltage amplitude and the rate of change are the same in the second section and the sixth section. The liquid discharge device according to any one of claims 1 to 6, wherein the drive unit can supply a third discharge waveform for discharging a third amount of liquid smaller than the first amount from the nozzle to the drive element. .. The liquid discharge device according to any one of claims 1 to 7, wherein the drive unit supplies the first discharge waveform to the drive element between the two or more second discharge waveforms within the unit period. A liquid discharge unit having a nozzle for discharging a liquid, a pressure chamber communicating with the nozzle, and a driving element for discharging the liquid in the pressure chamber from the nozzle.
A drive unit capable of supplying a first discharge waveform for discharging a first amount of liquid from the nozzle and a second discharge waveform for discharging a second amount of liquid larger than the first amount from the nozzle to the drive element. It is a driving method of a liquid discharge device provided with
A plurality of discharge waveforms are supplied to the driving element within a unit period,
A method for driving a liquid discharge device, wherein two or more discharge waveforms other than the last of the plurality of discharge waveforms are the second discharge waveform, and the last discharge waveform of the plurality of discharge waveforms is the first discharge waveform.

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