Liquid dispensing device

Abstract

To provide a liquid discharge device capable of reducing a possibility of instantaneous increase in power consumption.SOLUTION: A liquid discharge device performs gradation expression with multiple gradation levels by discharging liquid droplets onto a medium. In the liquid discharge device, a period in which a first drive circuit outputs a second drive waveform as a first drive signal at least partially overlaps a period in which a second drive circuit outputs a fourth drive waveform as a second drive signal; a period in which the first drive circuit outputs a third drive waveform as the first drive signal does not overlap the period in which the second drive circuit outputs the fourth drive waveform as the second drive signal; and in a drive cycle, the first drive circuit outputs a first drive waveform as the first drive signal, subsequently outputs the second drive waveform as the first drive signal, and then outputs the third drive waveform as the first drive signal.SELECTED DRAWING: Figure 5

Description

Technical Field

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

Background Art

[0002] Liquid ejection devices that eject droplets to form images or documents on a medium are known that use drive elements such as piezoelectric elements. In such a liquid ejection device, a drive element is provided corresponding to each of a plurality of nozzles that eject droplets, and when the drive element is driven according to a drive signal, droplets are ejected from the corresponding nozzle.

[0003] For example, Patent Document 1 discloses a liquid ejection device that includes a drive signal generation unit that generates a drive signal for driving a piezoelectric element as a drive element, and the drive signal generated by the drive signal generation unit is supplied to the piezoelectric element to eject droplets.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In view of the recent improvement in the ejection accuracy of droplets, the miniaturization of droplets has been progressing. However, when ejecting droplets from a nozzle, a phenomenon occurs in which the rear end portion of the droplet extends like a tail. Therefore, when ejecting minute droplets, the signal waveform of the drive signal becomes complicated. As a result, when the liquid ejection device ejects minute liquid, the power consumption instantaneously increases. With respect to such an instantaneously increasing power consumption, Patent Document 1 had room for improvement without any description.

Means for Solving the Problems

[0006] One aspect of the liquid ejection device according to the present invention is A liquid dispensing device that performs multi-level tonal expression by dispensing droplets onto a medium, A first drive circuit that outputs a first drive signal, A second drive circuit that outputs a second drive signal, A dispensing unit that dispenses liquid when at least one of the first drive signal and the second drive signal is supplied, A power supply circuit that supplies power to the first drive circuit and the second drive circuit, Equipped with, The first drive signal includes a first drive waveform, a second drive waveform, and a third drive waveform in the drive cycle. The second drive signal includes a fourth drive waveform and a fifth drive waveform in the drive cycle. When the first drive waveform is supplied to the discharge unit, the discharge unit discharges a first droplet amount of liquid. When the second drive waveform is supplied to the discharge unit, the discharge unit discharges a second droplet volume. When the third drive waveform is supplied to the discharge unit, the discharge unit discharges a third droplet amount of liquid. When the fourth drive waveform is supplied to the discharge unit, the discharge unit discharges a fourth droplet volume. When the fifth drive waveform is supplied to the discharge unit, the discharge unit does not discharge droplets. The fourth droplet volume is determined by any of the first droplet volume, the second droplet volume, and the third droplet volume. There are few, The third droplet volume is less than both the first droplet volume and the second droplet volume. The first of the aforementioned multi-level tones is represented using only the fourth drive waveform. The second tone among the aforementioned multi-tones is represented using at least the second drive waveform, without using the first and fourth drive waveforms. The third tone among the aforementioned multi-tones is represented using at least the first drive waveform and without using the fourth drive waveform. The luminance value of the second tone is lower than the luminance value of the first tone. The luminance value of the third grayscale is lower than the luminance value of the second grayscale. The period during which the first drive circuit outputs the second drive waveform as the first drive signal and the period during which the second drive circuit outputs the fourth drive waveform as the second drive signal overlap by at least a portion of each other. The period during which the first drive circuit outputs the third drive waveform as the first drive signal and the period during which the second drive circuit outputs the fourth drive waveform as the second drive signal do not overlap. During the aforementioned drive cycle, the first drive circuit outputs the first drive waveform as the first drive signal, then outputs the second drive waveform, and then outputs the third drive waveform. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows an example of the structure of a liquid dispensing device. [Figure 2] This figure shows an example of the functional configuration of a liquid dispensing device. [Figure 3] This figure shows an example of the arrangement of multiple discharge nozzles in a head unit. [Figure 4] This is a diagram showing an example of the configuration of the dispensing section. [Figure 5] This figure shows an example of the signal waveforms for the drive signals COMA and COMB. [Figure 6] This figure shows an example of the configuration of a drive signal selection circuit. [Figure 7] This figure shows an example of the content decoded by the decoder. [Figure 8] This figure shows an example of the configuration of a selection circuit corresponding to one unit of the dispensing section. [Figure 9] This is a diagram illustrating the operation of the drive signal selection circuit. [Figure 10] This diagram shows the relationship between print data [SIH, SIM, SIL] and the drive signal VOUT. [Figure 11] This figure shows the relationship between the size and number of dots formed within a predetermined grayscale range and the degree of grayscale. [Modes for carrying out the invention]

[0008] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The drawings used are for convenience of explanation. Note that the embodiments described below do not unduly limit the content of the present invention described in the claims. Also, not all of the configurations described below are essential components of the present invention.

[0009] In the following description, as an example of the liquid ejection device according to the present invention, a consumer inkjet printer is used. However, the liquid ejection device is not limited to a consumer inkjet printer, and may be a dyeing printer that performs dyeing printing or a printer multifunction device for offices. Further, the liquid ejection device is not limited to a printer, and may be a color material ejection device used for manufacturing color filters such as liquid crystal displays, an electrode material ejection device used for forming electrodes such as organic EL displays and surface emission displays, a biological organic matter ejection device used for manufacturing biochips, and the like.

[0010] 1. Configuration of Liquid Ejection Device FIG. 1 is a diagram showing an example of the structure of the liquid ejection device 1. As shown in FIG. 1, the liquid ejection device 1 includes a moving body 2, a moving unit 3 that reciprocates the moving body 2 along the main scanning direction, and is provided with.

[0011] The moving unit 3 includes a carriage motor 31 that serves as a driving source for reciprocating movement along the main scanning direction of the moving body 2, a carriage guide shaft 32 whose both ends are fixed, and a timing belt 33 that extends substantially parallel to the carriage guide shaft 32 and is driven by the carriage motor 31.

[0012] The mobile body 2 has a carriage 24. The carriage 24 is supported on a carriage guide shaft 32 so as to be able to move back and forth and is also fixed to a part of the timing belt 33. The timing belt 33 is moved in forward and reverse directions by the carriage motor 31, and the mobile body 2 having the carriage 24 is guided by the carriage guide shaft 32 to move back and forth. A head unit 20 is located on the part of the mobile body 2 that faces the medium P. That is, the head unit 20 is mounted on the carriage 24. Numerous nozzles that eject ink as droplets are located on the surface of the head unit 20 that faces the medium P. Various control signals that control the operation of the head unit 20 are supplied to the head unit 20 via a cable 190. As such a cable 190, a flexible flat cable that can slide in accordance with the reciprocating movement of the mobile body 2 can be used.

[0013] Furthermore, the liquid dispensing device 1 includes a conveying unit 4 that conveys the medium P on the platen 40 along the conveying direction. The conveying unit 4 has a conveying motor 41 which is the driving source for conveying the medium P, and a conveying roller 42 which is rotated by the conveying motor 41 to convey the medium P along the conveying direction.

[0014] In the liquid dispensing device 1 configured as described above, the head unit 20 dispenses ink onto the medium P in synchronization with the timing of the medium P being transported by the transport unit 4. As a result, the ink dispensed by the head unit 20 lands at a desired position on the medium P, and a desired image or character is formed on the surface of the medium P.

[0015] Next, the functional configuration of the liquid dispensing device 1 will be described. Figure 2 shows an example of the functional configuration of the liquid dispensing device 1. As shown in Figure 2, the liquid dispensing device 1 comprises a control unit 10, a head unit 20, a moving unit 3, a transport unit 4, and a cable 190. The cable 190 electrically connects the control unit 10 and the head unit 20.

[0016] The control unit 10 includes a power supply circuit 11, a control circuit 100, and drive circuits 50a and 50b.

[0017] The power supply circuit 11 generates voltage signals VHV and VDD of predetermined voltage values ​​from a commercial AC power supply provided from outside the liquid dispensing device 1 and outputs them to various components of the liquid dispensing device 1. Here, the voltage signal VHV output by the power supply circuit 11 is, for example, a DC voltage of 42V, and the voltage signal VDD is, for example, a DC voltage of 3.3V. Such a power supply circuit 11 may be configured to include, for example, an AC / DC converter that generates the voltage signal VHV from a commercial AC power supply, and a DC / DC converter that generates the voltage signal VDD from the voltage signal VHV. In addition to the voltage signals VHV and VDD, the power supply circuit 11 may also output DC voltages of different voltage values.

[0018] The control circuit 100 receives image data from an external device (not shown) located outside the liquid dispensing device 1, such as a host computer. The control circuit 100 performs various image processing operations on the supplied image data to generate various control signals for controlling each part of the liquid dispensing device 1, and outputs them to the corresponding configuration.

[0019] Specifically, the control circuit 100 generates a control signal Ctrl1 to control the reciprocating movement of the mobile body 2 and outputs it to the carriage motor 31 included in the mobile unit 3. The control circuit 100 also generates a control signal Ctrl2 to control the transport of the medium P and outputs it to the transport motor 41 included in the transport unit 4. As a result, the reciprocating movement of the mobile body 2 along the main scanning direction and the transport of the medium P along the transport direction are controlled by the control circuit 100. Consequently, the head unit 20 can eject ink onto the medium P at a predetermined timing synchronized with the transport of the medium P. This allows the ink to land at the desired position on the medium P, forming the desired image or characters on the medium P.

[0020] The control circuit 100 may also supply a control signal Ctrl1 for controlling the reciprocating movement of the mobile body 2 to the mobile unit 3 via a carriage motor driver (not shown), and similarly, it may supply a control signal Ctrl2 for controlling the transport of the medium P to the transport unit 4 via a transport motor driver (not shown).

[0021] Furthermore, the control circuit 100 outputs a base drive signal dA to the drive circuit 50a. The base drive signal dA is a signal that includes data defining the signal waveform of the drive signal COMA, and is, for example, a digital signal. The drive circuit 50a operates using the voltage signals VHV,VDD output by the power supply circuit 11 as the power supply voltage. The drive circuit 50a then converts the input digital base drive signal dA into an analog signal, and then amplifies the converted signal to a voltage value based on the voltage signal VHV to generate the drive signal COMA. The drive circuit 50a then supplies the generated drive signal COMA to the head unit 20.

[0022] Furthermore, the control circuit 100 outputs a base drive signal dB to the drive circuit 50b. The base drive signal dB is a signal that includes data defining the signal waveform of the drive signal COMB, and is, for example, a digital signal. The drive circuit 50b operates using the voltage signals VHV,VDD output by the power supply circuit 11 as the power supply voltage. The drive circuit 50b then converts the input digital base drive signal dB into an analog signal, and then amplifies the converted signal to a voltage value based on the voltage signal VHV to generate the drive signal COMB. The drive circuit 50b then supplies the generated drive signal COMB to the head unit 20.

[0023] Such drive circuits 50a and 50b can have a similar configuration and operate based on the base drive signals dA and dB, and can amplify the voltage value of the signal waveform defined by the base drive signals dA and dB to a voltage based on the voltage signal VHV. For example, various amplification signals including Class A amplifiers, Class B amplifiers, Class AB amplifiers, and Class D amplifiers can be used.

[0024] Furthermore, the control circuit 100 generates a clock signal SCK, a latch signal LAT, change signals CHA, CHB, and a print data signal SI for controlling the operation of the head unit 20, and outputs them to the head unit 20.

[0025] The head unit 20 includes a drive signal selection circuit 200 and a liquid discharge head 21. The liquid discharge head 21 also has a plurality of discharge sections 600, each of which contains a piezoelectric element 60. In the following description, the number of discharge sections 600 in the liquid discharge head 21 may be assumed to be n.

[0026] The drive signal selection circuit 200 receives the clock signal SCK, latch signal LAT, change signals CHA and CHB, and print data signal SI as inputs.

[0027] The drive signal selection circuit 200 is configured using the latch signal LAT and the change signals CHA and CHB. At a predetermined timing, the drive signal VOUT is generated by selecting or deselecting the signal waveforms included in the drive signal COMA and the signal waveforms included in the drive signal COMB, based on the print data signal SI propagated by the clock signal SCK. The drive signal selection circuit 200 then supplies the generated drive signal VOUT to one end of the piezoelectric element 60 included in each of the corresponding ejection units 600. A reference voltage signal VBS is supplied to the other end of the piezoelectric element 60 included in each of the multiple ejection units 600. The reference voltage signal VBS is a signal that functions as a reference potential for driving the piezoelectric element 60, and is a signal with a constant potential, such as 5.5V or 6V. The piezoelectric element 60 is then driven according to the potential difference between the drive signal VOUT supplied to one end and the reference voltage signal VBS supplied to the other end. This driving of the piezoelectric element 60 causes ink to be ejected from the ejection unit 600 which includes the piezoelectric element 60.

[0028] Although Figure 2 illustrates a case where the head unit 20 has one liquid ejection head 21, the number of liquid ejection heads 21 in the head unit 20 is not limited to one. The head unit 20 may have multiple liquid ejection heads 21 depending on the type and number of inks to be ejected.

[0029] As described above, the liquid dispensing device 1 in this embodiment controls the signal waveform of the drive signal VOUT supplied to the piezoelectric element 60, controls the amount of liquid droplets dispensed onto the medium P, and thereby performs multi-gradation expression on the medium. The device comprises a drive circuit 50a that outputs a drive signal COMA, a drive circuit 50b that outputs a drive signal COMB, a dispensing unit 600 that dispenses liquid when at least one of the drive signal COMA and the drive signal COMB is supplied, and a power supply circuit 11 that supplies power to the drive circuit 50a and the drive circuit 50b.

[0030] 2. Configuration and operation of the discharge unit Next, an example of the arrangement of multiple discharge units 600 in the head unit 20, and the configuration of the multiple discharge units 600 in the head unit 20 will be described. Figure 3 is a diagram showing an example of the arrangement of multiple discharge units 600 in the head unit 20. Note that Figure 3 illustrates the case where the head unit 20 has four liquid discharge heads 21.

[0031] As shown in Figure 3, each of the four liquid discharge heads 21 has a plurality of discharge sections 600 arranged in a row in one direction. That is, each liquid discharge head 21 includes a nozzle row nL in which the nozzles 651, which will be described later, included in the discharge section 600 are arranged in one direction. Furthermore, in the head unit 20, the liquid discharge heads 21 are positioned in a direction intersecting the nozzle row nL. That is, the head unit 20 has the same number of nozzle rows nL as the number of liquid discharge heads 21. Note that the arrangement of the nozzles 651 in the nozzle row nL of the liquid discharge head 21 is not limited to a single row. For example, they may be arranged in a staggered pattern such that the positions of the even-numbered nozzles 651 counted from one end of the plurality of nozzles 651 differ from the positions of the odd-numbered nozzles 651 counted from one end of the plurality of nozzles 651. In the liquid discharge head 21, a single nozzle row nL may be formed by arranging the plurality of nozzles 651 in two or more rows.

[0032] Next, an example of the configuration of the dispensing unit 600 will be described. Figure 4 is a diagram showing an example of the configuration of the dispensing unit 600. As shown in Figure 4, the dispensing unit 600 includes a piezoelectric element 60, a diaphragm 621, a cavity 631, and a nozzle 651. The diaphragm 621 is displaced in conjunction with the driving of the piezoelectric element 60, which is provided on the upper surface in Figure 4. The diaphragm 621 functions as a diaphragm that expands / contracts the internal volume of the cavity 631. The inside of the cavity 631 is filled with ink. The cavity 631 functions as a pressure chamber whose internal volume changes due to the displacement of the diaphragm 621 caused by the driving of the piezoelectric element 60. The nozzle 651 is formed in the nozzle plate 632 and is an opening that communicates with the cavity 631. Then, as the internal volume of the cavity 631 changes, the ink stored inside the cavity 631 is ejected from the nozzle 651.

[0033] The piezoelectric element 60 has a structure in which a piezoelectric body 601 is sandwiched between a pair of electrodes 611 and 612. In this structure, the piezoelectric body 601, electrodes 611 and 612, and the central portion of the diaphragm 621, flex in the vertical direction shown in Figure 4 relative to both ends, depending on the potential difference between electrodes 611 and 612.

[0034] Specifically, a drive signal VOUT is supplied to electrode 611, which is one end of the piezoelectric element 60, and a reference voltage signal VBS is supplied to electrode 612, which is the other end. When the piezoelectric element 60 is driven upward in response to a change in the voltage value of the drive signal VOUT, the diaphragm 621 is displaced upward, and as a result, the internal volume of the cavity 631 expands. Therefore, the ink stored in the reservoir 641 is drawn into the cavity 631. On the other hand, when the piezoelectric element 60 is driven downward in response to a change in the voltage value of the drive signal VOUT, the diaphragm 621 is displaced downward, and as a result, the internal volume of the cavity 631 shrinks. Therefore, an amount of ink corresponding to the degree of reduction in the internal volume of the cavity 631 is ejected from the nozzle 651.

[0035] As described above, the liquid ejection head 21 includes a piezoelectric element 60, and ejects ink onto the medium P by driving the piezoelectric element 60. Note that the piezoelectric element 60 and the ejection unit 600 are not limited to the illustrated structure, and any structure that allows ink to be ejected from the nozzle 651 by the displacement of the piezoelectric element 60 is acceptable.

[0036] 3. Signal waveforms of drive signals COMA and COMB Next, we will describe an example of the signal waveforms of the drive signal COMA output by the drive circuit 50a and the drive signal COMB output by the drive circuit 50b. Figure 5 shows an example of the signal waveforms of the drive signals COMA and COMB.

[0037] As shown in Figure 5, the drive circuit 50a outputs a drive signal COMA which includes a trapezoidal waveform Adp1 arranged during the period ta1 from when the latch signal LAT rises until when the change signal CHA rises; a trapezoidal waveform Adp2 arranged during the period ta2 after period ta1 until the next rise of the change signal CHA; and a trapezoidal waveform Adp3 arranged during the period ta3 after period ta2 until the next rise of the latch signal LAT. In other words, the drive signal COMA includes trapezoidal waveforms Adp1, Adp2, and Adp3 in a period T consisting of periods ta1, ta2, and ta3.

[0038] The trapezoidal waveform Adp1 is a signal waveform that, when supplied to the electrode 612 of the piezoelectric element 60 of the ejection unit 600, causes the corresponding ejection unit 600 to eject a larger amount of ink than a predetermined amount. That is, when the trapezoidal waveform Adp1 is supplied to the ejection unit 600, the ejection unit 600 ejects a larger amount of ink than a predetermined amount. The voltage value of such a trapezoidal waveform Adp1 starts at voltage Vc, becomes lower than voltage Vc, becomes higher than voltage Vc, and then ends at voltage Vc.

[0039] The trapezoidal waveform Adp2 is a signal waveform that, when supplied to the electrode 612 of the piezoelectric element 60 of the ejection unit 600, causes the corresponding ejection unit 600 to eject a larger amount of ink than a predetermined amount. That is, when the trapezoidal waveform Adp2 is supplied to the ejection unit 600, the ejection unit 600 ejects a larger amount of ink than a predetermined amount. The voltage value of such a trapezoidal waveform Adp2 starts at voltage Vc, becomes lower than voltage Vc, becomes higher than voltage Vc, and then ends at voltage Vc.

[0040] When the trapezoidal waveform Adp3 is supplied to the electrode 612 of the piezoelectric element 60 of the discharge unit 600, This is a signal waveform that causes a predetermined amount of ink to be ejected from the corresponding ejection unit 600. That is, when a trapezoidal waveform Adp3 is supplied to the ejection unit 600, the ejection unit 600 ejects a predetermined amount of ink. The voltage value of such a trapezoidal waveform Adp3 starts at voltage Vc, rises above voltage Vc, then falls below voltage Vc, rises above voltage Vc again, and then ends at voltage Vc. With such a trapezoidal waveform Adp3, by raising the voltage value above voltage Vc, then lowering it below voltage Vc, and then raising it above voltage Vc again, the phenomenon of the trailing end of the ink ejected from the nozzle 651 extending like a tail can be reduced. As a result, the amount of ink ejected from the nozzle 651 when a trapezoidal waveform Adp3 is supplied to the electrode 612 of the piezoelectric element 60 can be made less than the amount of ink ejected from the nozzle 651 when trapezoidal waveforms Adp1 and Adp2 are supplied to the electrode 612 of the piezoelectric element 60.

[0041] Here, the power consumption of the drive circuit 50a increases instantaneously when the voltage value of the output drive signal COMA changes. Therefore, the power consumption when the trapezoidal waveform Adp3, which has a large voltage change, is supplied to the discharge unit 600 is greater than the power consumption when the trapezoidal waveform Adp1 is supplied to the discharge unit 600, and when the trapezoidal waveform Adp2 is supplied to the discharge unit 600.

[0042] As described above, the drive circuit 50a outputs a trapezoidal waveform Adp1 as the drive signal COMA, then outputs a trapezoidal waveform Adp2, and then outputs a trapezoidal waveform Adp3. Furthermore, in the drive signal COMA output by the drive circuit 50a, trapezoidal waveforms Adp1, Adp2, and Adp3 all start and end at voltage Vc. In other words, the drive signal COMA output by the drive circuit 50a includes a signal waveform in which trapezoidal waveforms Adp1, Adp2, and Adp3 and voltage Vc are consecutive.

[0043] As shown in Figure 5, the drive circuit 50b outputs a drive signal COMB which includes a trapezoidal waveform Bdp1 arranged during the period tb1 from when the latch signal LAT rises until when the change signal CHB rises, and a trapezoidal waveform Bdp2 arranged during the period tb2 after period ta1 until the next time the latch signal LAT rises. In other words, the drive signal COMB includes trapezoidal waveforms Bdp1 and Bdp2 in a period T consisting of periods tb1 and tb2.

[0044] The trapezoidal waveform Bdp1 is a signal waveform that, when supplied to the electrode 612 of the piezoelectric element 60 of the ejection unit 600, causes the corresponding ejection unit 600 to eject a smaller amount of ink than a predetermined amount. That is, when the trapezoidal waveform Bdp1 is supplied to the ejection unit 600, the ejection unit 600 ejects a smaller amount of ink than a predetermined amount. Therefore, when the trapezoidal waveform Bdp1 is supplied to the electrode 612 of the piezoelectric element 60 of the ejection unit 600, the amount of ink ejected from the corresponding ejection unit 600 is less than any of the amount of ink ejected when the trapezoidal waveforms Adp1, Adp2, and Adp3 are supplied to the electrode 612 of the piezoelectric element 60 of the ejection unit 600.

[0045] The voltage value of this trapezoidal waveform Bdp1 starts at voltage Vc, rises above voltage Vc, falls below voltage Vc, and then rises above voltage Vc again. After that, the voltage value of the trapezoidal waveform Bdp1 falls below voltage Vc again, rises above voltage Vc again, and then ends at voltage Vc. In other words, the trapezoidal waveform Bdp1 repeats the operation of rising above voltage Vc, falling below voltage Vc, and rising above voltage Vc again multiple times at a predetermined frequency. This further reduces the phenomenon of the trailing end of the ink ejected from the nozzle 651 extending like a tail. As a result, the amount of ink ejected from the nozzle 651 when the trapezoidal waveform Bdp1 is supplied to the electrode 612 of the piezoelectric element 60 can be made less than the amount of ink ejected from the nozzle 651 when the trapezoidal waveforms Adp1, Adp2, and Adp3 are supplied to the electrode 612 of the piezoelectric element 60. When such a trapezoidal waveform Bdp1 is supplied to the electrode 612 of the piezoelectric element 60, the amount of ink ejected from the nozzle 651 is, for example, For example, it may be 5 picoliters or less.

[0046] As mentioned above, drive circuits 50a and 50b have similar circuit configurations. Therefore, similar to drive circuit 50a, the power consumption of drive circuit 50b increases instantaneously when the voltage value of the output drive signal COMB changes. Consequently, when trapezoidal waveform Bdp1, which has a greater voltage change than trapezoidal waveform Adp3, is supplied to the discharge unit 600, the power consumption is greater than that when trapezoidal waveform Adp1 is supplied to the discharge unit 600, when trapezoidal waveform Adp2 is supplied to the discharge unit 600, and when trapezoidal waveform Adp3 is supplied to the discharge unit 600.

[0047] The trapezoidal waveform Bdp2, when supplied to the electrode 612 of the piezoelectric element 60 of the ejection unit 600, is a signal waveform that causes the ink near the nozzle 651 to vibrate instead of ejecting ink from the corresponding ejection unit 600. In other words, when the trapezoidal waveform Bdp2 is supplied to the ejection unit 600, the ejection unit 600 does not eject ink. The voltage value of such a trapezoidal waveform Bdp2 starts at voltage Vc, becomes lower than voltage Vc, and then ends at voltage Vc.

[0048] As described above, the drive circuit 50b outputs a trapezoidal waveform Bdp1 as the drive signal COMB, and then outputs a trapezoidal waveform Bdp2. In addition, in the drive signal COMB output by the drive circuit 50a, both the trapezoidal waveform Bdp1 and the trapezoidal waveform Bdp2 start and end at voltage Vc. That is, the drive signal COMB output by the drive circuit 50b includes a signal waveform in which the trapezoidal waveform Bdp1, the trapezoidal waveform Bdp2, and the voltage Vc are in sequence.

[0049] The drive signals COMA and COMB described above are repeatedly output in a period T defined by the latch signal LAT. Specifically, drive signal COMA repeatedly outputs trapezoidal waveforms Adp1, Adp2, and Adp3 in each period T, and drive signal COMB repeatedly outputs trapezoidal waveforms Bdp1 and Bdp2 in each period T. At this time, the control circuit 100 outputs a change signal CHA that defines the end of period ta2 and the start of period ta3, and a change signal CHB that defines the end of period tb1 and the start of period ta2, during the period when drive circuit 50a outputs a constant voltage Vc as drive signal COMA, and drive circuit 50b outputs a constant voltage Vc as drive signal COMB. This reduces the risk of distortion in the signal waveform of the drive signal VOUT generated by the drive signal selection circuit 200, described later, selecting or deselecting drive signal COMA and drive signal COMB.

[0050] In other words, trapezoidal waveforms Adp2 and Bdp1 are arranged such that the period during which drive circuit 50a outputs trapezoidal waveform Adp2 as drive signal COMA and the period during which drive circuit 50b outputs trapezoidal waveform Bdp1 as drive signal COMB overlap at least partially, while trapezoidal waveforms Adp3 and Bdp1 are arranged such that the period during which drive circuit 50a outputs trapezoidal waveform Adp3 as drive signal COMA and the period during which drive circuit 50b outputs trapezoidal waveform Bdp1 as drive signal COMB do not overlap. Furthermore, as shown in Figure 5, trapezoidal waveforms Adp1 and Bdp1 may be arranged such that the period during which drive circuit 50a outputs trapezoidal waveform Adp1 as drive signal COMA and the period during which drive circuit 50b outputs trapezoidal waveform Bdp1 as drive signal COMB overlap at least partially.

[0051] Here, the signal waveforms of the drive signals COMA and COMB shown in Figure 5 are just examples and are not limited to these. Various signal waveforms with different shapes may be included, depending on the physical properties of the ink ejected by the liquid ejection head 21, the length of the period T of the drive signals COMA and COMB, the transport speed of the medium P, etc.

[0052] 4. Configuration and operation of the selection control circuit Next, the configuration and operation of the drive signal selection circuit 200 will be described. Drive signal selection circuit Based on the clock signal SCK, latch signal LAT, change signals CHA, CHB, and print data signal SI, the 200 generates a drive signal VOUT supplied to the piezoelectric element 60 of each of the multiple ejection units 600 by selecting or deselecting the signal waveforms contained in the respective drive signals COMA and COMB. Figure 6 shows an example of the configuration of the drive signal selection circuit 200. As shown in Figure 6, the drive signal selection circuit 200 has a selection control circuit 210 and n selection circuits 230 corresponding to each of the n ejection units 600.

[0053] The selection control circuit 210 receives the clock signal SCK, latch signal LAT, change signals CHA, CHB, and print data signal SI. The selection control circuit 210 also has a set of shift register (S / R) 212, latch circuit 214, and decoder 216 corresponding to each of the n output units 600. That is, the drive signal selection circuit 200 has n shift registers 212, n latch circuits 214, and n decoders 216.

[0054] The print data signal SI is input to the selection control circuit 210 in synchronization with the clock signal SCK. This print data signal SI serially contains 3 bits of print data [SIH, SIM, SIL] corresponding to each of the n ejection units 600, for selecting the dot sizes formed on the medium P by the ejection of ink from the ejection units 600: "extra-large dot LL", "large dot L", "medium dot M", "small dot S", and "micro-vibration BSD". In other words, the print data signal SI is a serial signal of 3n bits or more.

[0055] The print data [SIH, SIM, SIL] contained in the print data signal SI is held in n shift registers 212 corresponding to n ejection units 600. Specifically, the n shift registers 212 corresponding to the ejection units 600 are connected in cascaded order, and the serially input print data signal SI is sequentially transferred to the subsequent shift registers 212 according to the clock signal SCK. When the print data [SIH, SIM, SIL] is held in the corresponding shift registers 212, the supply of the clock signal SCK is stopped. In other words, when the supply of the clock signal SCK is stopped, the print data [SIH, SIM, SIL] contained in the print data signal SI is held in the corresponding shift registers 212. Note that in Figure 6, to distinguish the n shift registers 212, they are labeled as 1st stage, 2nd stage, ..., nth stage in order from the upstream side where the print data signal SI is input to the downstream side.

[0056] Each of the n latch circuits 214 simultaneously latches the print data [SIH, SIM, SIL] held in the corresponding shift register 212 on the rising edge of the latch signal LAT. The print data [SIH, SIM, SIL] latched by the latch circuits 214 is input to the corresponding decoder 216.

[0057] Figure 7 shows an example of the decoding content in decoder 216. Decoder 216 outputs logical level selection signals S1 and S2 according to the input print data [SIH,SIM,SIL]. Specifically, when print data [SIH,SIM,SIL]=[0,1,0] is input to decoder 216, decoder 216 outputs selection signal S1 which is L level in period ta1, H level in period ta2, and L level in period ta3, and selection signal S2 which is L level in period tb1 and L level in period tb2.

[0058] The selection signals S1 and S2 output by the decoder 216 are input to the selection circuit 230. The selection circuit 230 is provided for each of the n ejection units 600. That is, the drive signal selection circuit 200 has n selection circuits 230, the same number as the n ejection units 600. Figure 8 shows an example of the configuration of the selection circuit 230 corresponding to one ejection unit 600. As shown in Figure 8, the selection circuit 230 includes inverters 232a, 232b and transfer gates 234a, 234b, which are NOT gates.

[0059] The selection signal S1 is input to the positive control terminal of the transfer gate 234a that is not marked with a circle, and after its logic level is inverted by the inverter 232a, it is also input to the negative control terminal of the transfer gate 234a that is marked with a circle. In addition, the drive signal COMA is supplied to the input terminal of the transfer gate 234a. When a high-level selection signal S1 is input to the transfer gate 234a, the input terminal and output terminal become conductive, and when a low-level selection signal S1 is input to the transfer gate 234a, the input terminal and output terminal become non-conductive. That is, when the logic level of the input selection signal S1 is high, the transfer gate 234a outputs the signal waveform included in the drive signal COMA from its output terminal, and when the logic level of the input selection signal S1 is low, it does not output the signal waveform included in the drive signal COMA from its output terminal.

[0060] Furthermore, the selection signal S2 is input to the positive control terminal of the transfer gate 234b that is not marked with a circle, and after its logic level is inverted by the inverter 232b, it is also input to the negative control terminal of the transfer gate 234b that is marked with a circle. In addition, the drive signal COMB is supplied to the input terminal of the transfer gate 234b. When a high-level selection signal S2 is input to the transfer gate 234b, the input terminal and output terminal become conductive, and when a low-level selection signal S2 is input to the transfer gate 234b, the input terminal and output terminal become non-conductive. That is, when the logic level of the input selection signal S2 is high, the transfer gate 234b outputs the signal waveform included in the drive signal COMB from its output terminal, and when the logic level of the input selection signal S2 is low, it does not output the signal waveform included in the drive signal COMB from its output terminal.

[0061] Then, the output terminals of transfer gate 234a and transfer gate 234b are connected in common, and the drive signal selection circuit 200 outputs the signal at this connection point as the drive signal VOUT.

[0062] Here, the operation of the drive signal selection circuit 200 will be explained using Figure 9. Figure 9 is a diagram illustrating the operation of the drive signal selection circuit 200. The print data signal SI is input to the selection control circuit 210 as a serial signal synchronized with the clock signal SCK. The print data signal SI is then sequentially transferred in n shift registers 212 corresponding to n ejection units 600, in synchronization with the clock signal SCK. After that, when the input of the clock signal SCK stops, the shift registers 212 hold the print data [SIH, SIM, SIL] corresponding to each of the n ejection units 600. The print data signal SI contains the print data [SIH, SIM, SIL] in the order corresponding to the nth, ..., 2nd, and 1st stages of the ejection unit 600 in the shift registers 212.

[0063] Then, when the latch signal LAT rises, each of the latch circuits 214 simultaneously latches the print data [SIH, SIM, SIL] held in the shift register 212. The print data [SIH, SIM, SIL] latched by the latch circuits 214 is input to the corresponding decoder 216. Note that LT1, LT2, ..., LTn shown in Figure 9 correspond to the print data [SIH, SIM, SIL] latched by the latch circuits 214 corresponding to the 1st, 2nd, ..., nth stage shift registers 212.

[0064] The decoder 216 decodes the input print data [SIH, SIM, SIL] to generate the logic level selection signals S1 and S2 shown in Figure 7, and outputs them to the corresponding selection circuit 230. The selection circuit 230 then selects the signal waveforms included in the drive signals COMA and COMB according to the logic level of the selection signals S1 and S2 output by the decoder 216. By deselecting, a drive signal VOUT corresponding to each of the n discharge units 600 is generated and output to the corresponding discharge unit 600.

[0065] Figure 10 shows the relationship between the print data [SIH,SIM,SIL] and the drive signal VOUT. As shown in Figure 10, when the print data [SIH,SIM,SIL]=[1,1,1] is input to the decoder 216, the decoder 216 outputs a selection signal S1 of the H,H,H level for periods ta1, ta2, and ta3, and a selection signal S2 of the L,L level for periods tb1 and tb2. As a result, the selection circuit 230 outputs a drive signal VOUT consisting of a series of trapezoidal waveforms Adp1, Adp2, and Adp3. Then, the drive signal VOUT consisting of a series of trapezoidal waveforms Adp1, Adp2, and Adp3 is supplied to the electrode 612 of the piezoelectric element 60 of the corresponding ejection unit 600, causing the corresponding ejection unit 600 to eject a larger-than-determined amount of ink, a larger-than-determined amount of ink, and a predetermined amount of ink. The ink ejected from this ejection unit 600 lands on the medium P and combines with it, forming an extra-large dot LL on the medium P.

[0066] Furthermore, when the decoder 216 receives print data [SIH,SIM,SIL]=[0,1,1], the decoder 216 outputs a selection signal S1 of L,H,H levels for periods ta1, ta2, and ta3, and a selection signal S2 of L,L levels for periods tb1 and tb2. As a result, the selection circuit 230 outputs a drive signal VOUT consisting of a continuous trapezoidal waveform Adp2 and trapezoidal waveform Adp3. This drive signal VOUT, consisting of a continuous trapezoidal waveform Adp2 and trapezoidal waveform Adp3, is supplied to the electrode 612 of the piezoelectric element 60 of the corresponding ejection unit 600, causing the corresponding ejection unit 600 to eject a larger amount of ink than a predetermined amount and a predetermined amount of ink. The ink ejected from this ejection unit 600 lands on the medium P and combines, forming a large dot L on the medium P.

[0067] Furthermore, when the decoder 216 receives print data [SIH,SIM,SIL]=[0,1,0], the decoder 216 outputs a selection signal S1 of L,H,L levels for periods ta1, ta2, and ta3, and a selection signal S2 of L,L levels for periods tb1 and tb2. As a result, the selection circuit 230 outputs a trapezoidal waveform Adp2 as a drive signal VOUT. The trapezoidal waveform Adp2 is then supplied as a drive signal VOUT to the electrode 612 of the piezoelectric element 60 of the corresponding ejection unit 600, causing a predetermined amount of ink to be ejected from the corresponding ejection unit 600. When this ink ejected from the ejection unit 600 lands on the medium P, a dot M is formed on the medium P.

[0068] Furthermore, when the decoder 216 receives print data [SIH,SIM,SIL]=[0,0,1], the decoder 216 outputs a selection signal S1 of L,L,L level for periods ta1, ta2, and ta3, and a selection signal S2 of H,L level for periods tb1 and tb2. As a result, the selection circuit 230 outputs a trapezoidal waveform Bdp1 as a drive signal VOUT. The trapezoidal waveform Bdp1 is then supplied as a drive signal VOUT to the electrode 612 of the piezoelectric element 60 of the corresponding ejection unit 600, causing a smaller amount of ink than a predetermined amount to be ejected from the corresponding ejection unit 600. When this ink ejected from the ejection unit 600 lands on the medium P, small dots S are formed on the medium P.

[0069] Furthermore, when the decoder 216 receives print data [SIH,SIM,SIL]=[0,0,0], the decoder 216 outputs a selection signal S1 of L,L,L level for periods ta1, ta2, and ta3, and a selection signal S2 of L,H level for periods tb1 and tb2. As a result, the selection circuit 230 outputs a trapezoidal waveform Bdp2 as a drive signal VOUT. The trapezoidal waveform Bdp2 is then supplied as a drive signal VOUT to the electrode 612 of the piezoelectric element 60 of the corresponding ejection unit 600, causing ink not to be ejected from the corresponding ejection unit 600 and resulting in the execution of micro-vibration BSD.

[0070] As described above, the drive signal selection circuit 200 selects or deselects the signal waveforms included in the drive signals COMA and COMB based on the print data signal SI, thereby generating drive signals VOUT corresponding to "extra-large dot LL", "large dot L", "medium dot M", "small dot S", and "micro-vibration BSD", and supplies them to the multiple piezoelectric elements 60.

[0071] 5. An example of multi-tone gradation representation The liquid dispensing device 1, configured as described above, performs multi-level tonal expression by changing the dot size and number of dots formed on the medium P. Figure 11 is a diagram showing the relationship between the size and number of dots formed and the degree of gradation within a predetermined gradation range. The horizontal axis of Figure 11 shows the gradation values ​​of the multi-level tonal expression formed within the predetermined gradation range in 256 steps from "0" to "255". The vertical axis of Figure 11 shows the number of dots formed within the predetermined gradation range in 256 steps from "0" to "255". Here, the predetermined gradation range corresponds to the range in which pixels on which dots are formed are formed on the matrix. A dot quantity of "0" means that there are no pixels with dots formed within the predetermined gradation range, a dot quantity of "128" means that approximately half of the pixels in the predetermined gradation range have dots formed, and a dot quantity of "255" means that dots are formed on all pixels included in the predetermined gradation range.

[0072] As shown in Figure 11, when the grayscale value of medium P is "0", no dots are formed within a predetermined grayscale range of medium P. As the grayscale value of medium P increases, the number of small dots S formed within the predetermined grayscale range of medium P also increases. Furthermore, when the number of small dots S formed within the predetermined grayscale range of medium P reaches a predetermined threshold th, the number of small dots S formed within the predetermined grayscale range of medium P begins to decrease as the grayscale value of medium P increases, and medium dots M begin to form within the predetermined grayscale range of medium P. Here, in the following explanation, the grayscale value at which the number of small dots S formed within the predetermined grayscale range of medium P begins to decrease and the formation of medium dots M begins may be referred to as "g1".

[0073] Subsequently, as the tonal value of the medium P increases, when the number of medium dots M formed within a predetermined tonal range of the medium P reaches a predetermined threshold th, the number of medium dots M formed within the predetermined tonal range of the medium P begins to decrease as the tonal value of the medium P increases, and large dots L begin to form within the predetermined tonal range of the medium P. Here, in the following explanation, the tonal value at which the number of medium dots M formed within the predetermined tonal range of the medium P begins to decrease and the formation of large dots L begins may be referred to as "g2".

[0074] Subsequently, as the grayscale value of medium P increases, when the number of large dots L formed within a predetermined grayscale range of medium P reaches a predetermined threshold th, the number of large dots L formed within the predetermined grayscale range of medium P begins to decrease as the grayscale value of medium P increases, and extra-large dots LL begin to form within the predetermined grayscale range of medium P. Here, in the following explanation, the grayscale value at which the number of large dots L formed within the predetermined grayscale range of medium P begins to decrease and the formation of extra-large dots LL begins may be referred to as "g3".

[0075] Subsequently, as the gradation value of medium P increases, the number of extra-large dots LL formed within a predetermined gradation range of medium P increases, and when the gradation value becomes "g4", all dots formed within the predetermined gradation range of medium P become extra-large dots LL. Subsequently, when the gradation value becomes "255", all dots within the predetermined gradation range of medium P become extra-large dots LL.

[0076] As described above, the liquid dispensing device 1 expresses grayscale using only the drive signal VOUT corresponding to the small dot S within the range of grayscale values ​​from "0" to "g1". In other words, the liquid dispensing device 1 expresses grayscale using only the trapezoidal waveform Bdp1 within the range of grayscale values ​​from "0" to "g1". express.

[0077] Furthermore, the liquid dispensing device 1 expresses gradation using a drive signal VOUT corresponding to a small dot S and a drive signal VOUT corresponding to a medium dot M in the range of gradation values ​​from "g1" to "g2" where the luminance is lower than the gradation value range of "0" to "g1". In other words, the liquid dispensing device 1 expresses gradation using a trapezoidal waveform Bdp1 and a trapezoidal waveform Adp3 in the range of gradation values ​​from "g1" to "g2".

[0078] Furthermore, the liquid dispensing device 1 expresses gradation using the drive signal VOUT corresponding to the medium dot M and the drive signal VOUT corresponding to the large dot L in the range of gradation values ​​from "g2" to "g3" where the luminance is lower than the gradation value range of "0" to "g2". In other words, the liquid dispensing device 1 expresses gradation using the trapezoidal waveform Adp2 and the trapezoidal waveform Adp3 in the range of gradation values ​​from "g2" to "g3".

[0079] Furthermore, the liquid dispensing device 1 expresses gradation using a drive signal VOUT corresponding to a large dot L and a drive signal VOUT corresponding to an extra-large dot LL in the range of gradation values ​​from "g3" to "g4" where the luminance is lower than the gradation value range of "0" to "g3". In other words, the liquid dispensing device 1 expresses gradation using trapezoidal waveforms Adp1, Adp2, and Adp3 in the range of gradation values ​​from "g3" to "g4".

[0080] Furthermore, the liquid dispensing device 1 expresses gradation using only the drive signal VOUT corresponding to the extra-large dot LL in the range of gradation values ​​from "g4" to "255" where the luminance is lower than the gradation value range of "0" to "g4". In other words, the liquid dispensing device 1 expresses gradation using trapezoidal waveform Adp1, trapezoidal waveform Adp2, and trapezoidal waveform Adp3 in the range of gradation values ​​from "g4" to "255".

[0081] As described above, in the liquid dispensing device 1 of this embodiment, when the gradation value of the image formed on the medium P is low, i.e., when the brightness value is high, the piezoelectric element 60 is driven using the drive signal VOUT corresponding to the small dot S with a small dot size formed on the medium P, and the piezoelectric element 60 is not driven using the drive signal VOUT corresponding to the extra-large dot LL with a large dot size formed on the medium P. When the gradation value of the image formed on the medium P is high, i.e., when the brightness value is low, the piezoelectric element 60 is driven using the drive signal VOUT corresponding to the extra-large dot LL with a large dot size formed on the medium P, and the piezoelectric element 60 is not driven using the drive signal VOUT corresponding to the small dot S with a small dot size formed on the medium P. As a result, when the liquid dispensing device 1 performs multi-gradation expression within a predetermined gradation range of the medium P, the risk of dots of significantly different sizes being formed within that predetermined gradation range is reduced. As a result, the quality of the multi-gradation expression formed on the medium P is improved.

[0082] Here, period T is an example of a drive period, drive signal COMA is an example of a first drive signal, drive signal COMB is an example of a second drive signal, drive circuit 50a that outputs drive signal COMA is an example of a first drive circuit, and drive circuit 50b that outputs drive signal COMB is an example of a second drive circuit. Furthermore, the trapezoidal waveform Adp1 included in drive signal COMA is an example of a first drive waveform, the trapezoidal waveform Adp2 included in drive signal COMA is an example of a second drive waveform, the trapezoidal waveform Adp3 included in drive signal COMA is an example of a third drive waveform, the trapezoidal waveform Bdp1 included in drive signal COMB is an example of a fourth drive waveform, and the trapezoidal waveform Bdp2 included in drive signal COMB is an example of a fifth drive waveform. Furthermore, when trapezoidal waveform Adp1 is supplied to the discharge unit 600, an amount greater than a predetermined amount discharged by the discharge unit 600 is an example of the first droplet volume; when trapezoidal waveform Adp2 is supplied to the discharge unit 600, an amount greater than a predetermined amount discharged by the discharge unit 600 is an example of the second droplet volume; and when trapezoidal waveform Adp3 is supplied to the discharge unit 600, a predetermined amount discharged by the discharge unit 600 is an example of the third droplet volume. When a trapezoidal waveform Bdp1 is supplied to the discharge unit 600, an example of the fourth droplet volume is an amount less than a predetermined amount discharged by the discharge unit 600. Also, an example of the first grayscale value is any of the grayscale values ​​in the range [0] to [g1] expressed using only the trapezoidal waveform Bdp1, and an example of the second grayscale value is any of the grayscale values ​​in the range [g2] to [g3] expressed using the trapezoidal waveform Adp2 without using the trapezoidal waveform Adp1 and the trapezoidal waveform Bdp1, and an example of the second grayscale value is an amount less than the grayscale value corresponding to the second grayscale value, and a trapezoidal waveform Adp1 is used. An example of a third grayscale value is any of the grayscale values ​​in the range of [g3] to

[0255] that are expressed without using shape Bdp1, and an example of a fourth grayscale value is any of the grayscale values ​​in the range of [g2] to [g4] that are expressed using trapezoidal waveform Adp2 and either trapezoidal waveform Adp1 or trapezoidal waveform Adp3, without using trapezoidal waveform Bdp1.

[0083] 6. Effects In the liquid dispensing device 1 configured as described above, when trapezoidal waveform Bdp1 is supplied to the dispensing unit 600, the amount of ink dispensed by the dispensing unit 600 is less than the amount of ink dispensed by the dispensing unit 600 when trapezoidal waveform Adp1 is supplied to the dispensing unit 600, the amount of ink dispensed by the dispensing unit 600 when trapezoidal waveform Adp2 is supplied to the dispensing unit 600, and the amount of ink dispensed by the dispensing unit 600 when trapezoidal waveform Adp3 is supplied to the dispensing unit 600. Furthermore, when trapezoidal waveform Adp3 is supplied to the dispensing unit 600, the amount of ink dispensed by the dispensing unit 600 is less than the amount of ink dispensed by the dispensing unit 600 when trapezoidal waveform Adp1 is supplied to the dispensing unit 600, and the amount of ink dispensed by the dispensing unit 600 when trapezoidal waveform Adp2 is supplied to the dispensing unit 600. Therefore, the voltage value displacement in the signal waveform of trapezoidal waveform Bdp1 is greater than the voltage value displacement in the respective signal waveforms of trapezoidal waveform Adp1, Adp2, and Adp3, and the voltage value displacement in the signal waveform of trapezoidal waveform Adp3 is greater than the voltage value displacement in the respective signal waveforms of trapezoidal waveform Adp1 and Adp2. Consequently, the power consumption when trapezoidal waveform Bdp1 is supplied to the discharge unit 600 is greater than the power consumption when trapezoidal waveform Adp1 is supplied to the discharge unit 600, when trapezoidal waveform Adp2 is supplied to the discharge unit 600, and when trapezoidal waveform Adp3 is supplied to the discharge unit 600, and the power consumption when trapezoidal waveform Adp3 is supplied to the discharge unit 600 is greater than the power consumption when trapezoidal waveform Adp1 is supplied to the discharge unit 600, and when trapezoidal waveform Adp2 is supplied to the discharge unit 600.

[0084] In such a liquid dispensing device 1, the period during which the drive circuit 50a outputs a trapezoidal waveform Adp3 as a drive signal COMA and the period during which the drive circuit 50b outputs a trapezoidal waveform as a drive signal COMB do not overlap. This reduces the risk of an instantaneous increase in power consumption when the drive signals COMA and COMB are supplied to the dispensing unit 600 as a drive signal VOUT.

[0085] Furthermore, at least a portion of the period during which the drive circuit 50a outputs the trapezoidal waveform Adp2 as the drive signal COMA and the period during which the drive circuit 50b outputs the trapezoidal waveform Bdp2 as the drive signal COMB overlap, thereby shortening the time required for the propagation of the drive signals COMA and COMB. This also reduces the risk of a decrease in the ink ejection speed in the liquid ejection device 1.

[0086] Although embodiments and modified examples have been described above, the present invention is not limited to these embodiments and can be implemented in various forms without departing from its spirit. For example, the above embodiments can be combined as appropriate.

[0087] The present invention includes configurations substantially identical to those described in the embodiments (for example, configurations with the same function, method and result, or configurations with the same purpose and effect). Furthermore, the present invention includes configurations that are substantially identical to those described in the embodiments. This includes configurations in which non-essential parts of the configuration described in the embodiments are replaced. Furthermore, this invention includes configurations that produce the same effects or achieve the same objectives as the configuration described in the embodiments. Furthermore, this invention includes configurations in which known technology is added to the configuration described in the embodiments.

[0088] The following conclusions can be drawn from the embodiments described above.

[0089] One embodiment of a liquid dispensing device is: A liquid dispensing device that performs multi-level tonal expression by dispensing droplets onto a medium, A first drive circuit that outputs a first drive signal, A second drive circuit that outputs a second drive signal, A dispensing unit that dispenses liquid when at least one of the first drive signal and the second drive signal is supplied, A power supply circuit that supplies power to the first drive circuit and the second drive circuit, Equipped with, The first drive signal includes a first drive waveform, a second drive waveform, and a third drive waveform in the drive cycle. The second drive signal includes a fourth drive waveform and a fifth drive waveform in the drive cycle. When the first drive waveform is supplied to the discharge unit, the discharge unit discharges a first droplet amount of liquid. When the second drive waveform is supplied to the discharge unit, the discharge unit discharges a second droplet volume. When the third drive waveform is supplied to the discharge unit, the discharge unit discharges a third droplet amount of liquid. When the fourth drive waveform is supplied to the discharge unit, the discharge unit discharges a fourth droplet volume. When the fifth drive waveform is supplied to the discharge unit, the discharge unit does not discharge droplets. The fourth droplet volume is less than any of the first droplet volume, the second droplet volume, and the third droplet volume. The third droplet volume is less than both the first droplet volume and the second droplet volume. The first of the aforementioned multi-level tones is represented using only the fourth drive waveform. The second tone among the aforementioned multi-tones is represented using at least the second drive waveform, without using the first and fourth drive waveforms. The third tone among the aforementioned multi-tones is represented using at least the first drive waveform and without using the fourth drive waveform. The luminance value of the second tone is lower than the luminance value of the first tone. The luminance value of the third grayscale is lower than the luminance value of the second grayscale. The period during which the first drive circuit outputs the second drive waveform as the first drive signal and the period during which the second drive circuit outputs the fourth drive waveform as the second drive signal overlap by at least a portion of each other. The period during which the first drive circuit outputs the third drive waveform as the first drive signal and the period during which the second drive circuit outputs the fourth drive waveform as the second drive signal do not overlap. During the aforementioned drive cycle, the first drive circuit outputs the first drive waveform as the first drive signal, then outputs the second drive waveform, and then outputs the third drive waveform.

[0090] With this liquid dispensing device, the period during which the first drive circuit outputs a third drive waveform, which has a small droplet discharge volume and therefore high power consumption, as the first drive signal, and the period during which the second drive circuit outputs a fourth drive waveform, which also has a small droplet discharge volume and therefore high power consumption, as the second drive signal, do not overlap, thereby reducing the risk of instantaneous increases in power consumption.

[0091] Furthermore, with this liquid dispensing device, at least a portion of the period during which the first drive circuit outputs the second drive waveform as the first drive signal and the period during which the second drive circuit outputs the fourth drive waveform as the second drive signal overlap, which reduces the risk of the drive cycle of the drive signals COMA and COMB becoming longer, and as a result, reduces the risk of the droplet dispensing speed in the liquid dispensing device decreasing.

[0092] In one embodiment of the liquid dispensing device, The volume of the fourth droplet may be 5 picoliters or less.

[0093] This liquid dispensing device reduces the risk of instantaneous power consumption increases. Therefore, even if the amount of liquid dispensed by supplying the fourth drive waveform is very small, less than 5 picoliters, the risk of instantaneous power consumption increases is reduced.

[0094] In one embodiment of the liquid dispensing device, The power consumption when the fourth drive waveform is supplied to the discharge unit may be greater than any of the power consumption when the first drive waveform is supplied to the discharge unit, the power consumption when the second drive waveform is supplied to the discharge unit, and the power consumption when the third drive waveform is supplied to the discharge unit.

[0095] With this liquid dispensing device, at least a portion of the period during which the first drive circuit outputs the second drive waveform as the first drive signal and the period during which the second drive circuit outputs the fourth drive waveform as the second drive signal overlap, which reduces the risk of the drive cycle of the drive signals COMA and COMB becoming longer, and as a result, reduces the risk of the droplet dispensing speed in the liquid dispensing device decreasing.

[0096] In one embodiment of the liquid dispensing device, The period during which the first drive circuit outputs the first drive waveform as the first drive signal and the period during which the second drive circuit outputs the fourth drive waveform as the second drive signal overlap by at least a portion of each other. The power consumption when the first drive waveform is supplied to the discharge unit may be less than the power consumption when the third drive waveform is supplied to the discharge unit.

[0097] With this liquid dispensing device, at least a portion of the period during which the first drive circuit outputs the first drive waveform as the first drive signal and the period during which the second drive circuit outputs the fourth drive waveform as the second drive signal overlap, which reduces the risk of the drive cycle of the drive signals COMA and COMB becoming longer, and as a result, reduces the risk of the droplet dispensing speed in the liquid dispensing device decreasing.

[0098] In one embodiment of the liquid dispensing device, The fourth tone among the aforementioned multi-tones is represented using the second drive waveform and either the first drive waveform or the third drive waveform, without using the fourth drive waveform. The luminance value of the fourth grayscale may be lower than the luminance value of the second grayscale and higher than the luminance value of the third grayscale.

[0099] In one embodiment of the liquid dispensing device, The power consumption when the fourth drive waveform is supplied to the discharge unit is greater than the power consumption when the third drive waveform is supplied to the discharge unit. The power consumption when the third drive waveform is supplied to the discharge unit may be greater than the power consumption when the first drive waveform is supplied to the discharge unit, and the power consumption when the second drive waveform is supplied to the discharge unit. [Explanation of Symbols]

[0100] 1...Liquid dispensing device, 2...Mobile body, 3...Mobile unit, 4...Conveying unit, 10...Control unit, 11...Power supply circuit, 20...Head unit, 21...Liquid dispensing head, 24...Carriage, 31...Carriage motor, 32...Carriage guide shaft, 33...Timing belt, 40...Platen, 41...Conveying motor, 42...Conveying roller, 50a, 50b...Drive circuit, 60...Piezoelectric element, 100...Control circuit, 190...Cable, 20 0…Drive signal selection circuit, 210…Selection control circuit, 212…Shift register, 214…Latch circuit, 216…Decoder, 230…Selection circuit, 232a,232b…Inverter, 234a,234b…Transfer gate, 600…Discharge section, 601…Piezoelectric element, 611,612…Electrodes, 621…Diaphragm, 631…Cavity, 632…Nozzle plate, 641…Reservoir, 651…Nozzle, P…Medium, nL…Nozzle row

Claims

1. A liquid dispensing device that performs multi-level tonal expression by dispensing droplets onto a medium, A first drive circuit that outputs a first drive signal, A second drive circuit that outputs a second drive signal, A dispensing unit that dispenses liquid when at least one of the first drive signal and the second drive signal is supplied, A power supply circuit that supplies power to the first drive circuit and the second drive circuit, Equipped with, The first drive signal includes a first drive waveform, a second drive waveform, and a third drive waveform in the drive cycle. The second drive signal includes a fourth drive waveform and a fifth drive waveform in the drive cycle. When the first drive waveform is supplied to the discharge unit, the discharge unit discharges a first droplet amount of liquid. When the second drive waveform is supplied to the discharge unit, the discharge unit discharges a second droplet volume. When the third drive waveform is supplied to the discharge unit, the discharge unit discharges a third droplet amount. When the fourth drive waveform is supplied to the discharge unit, the discharge unit discharges a fourth droplet volume. When the fifth drive waveform is supplied to the discharge unit, the discharge unit does not discharge droplets. The fourth droplet volume is less than any of the first droplet volume, the second droplet volume, and the third droplet volume. The third droplet volume is less than both the first droplet volume and the second droplet volume. The first of the aforementioned multi-level tones is represented using only the fourth drive waveform. The second tone among the aforementioned multi-tones is represented using at least the second drive waveform, without using the first and fourth drive waveforms. The third of the aforementioned multi-level tones is represented using at least the first drive waveform and without using the fourth drive waveform. The luminance value of the second tone is lower than the luminance value of the first tone. The luminance value of the third tone is lower than the luminance value of the second tone. The period during which the first drive circuit outputs the second drive waveform as the first drive signal and the period during which the second drive circuit outputs the fourth drive waveform as the second drive signal overlap by at least a portion of each other. The period during which the first drive circuit outputs the third drive waveform as the first drive signal and the period during which the second drive circuit outputs the fourth drive waveform as the second drive signal do not overlap. During the aforementioned drive cycle, the first drive circuit outputs the first drive waveform as the first drive signal, then outputs the second drive waveform, and then outputs the third drive waveform. A liquid dispensing device characterized by the following features.

2. The volume of the fourth droplet is 5 picoliters or less. The liquid dispensing device according to feature 1.

3. The power consumption when the fourth drive waveform is supplied to the discharge unit is greater than the power consumption when the first drive waveform is supplied to the discharge unit, the power consumption when the second drive waveform is supplied to the discharge unit, and the power consumption when the third drive waveform is supplied to the discharge unit. The liquid dispensing device according to feature 1 or 2.

4. The period during which the first drive circuit outputs the first drive waveform as the first drive signal and the period during which the second drive circuit outputs the fourth drive waveform as the second drive signal overlap by at least a portion of each other. The power consumption when the first drive waveform is supplied to the discharge unit is less than the power consumption when the third drive waveform is supplied to the discharge unit. A liquid dispensing device according to any one of claims 1 to 3.

5. The fourth tone among the aforementioned multi-tones is expressed using the second drive waveform and either the first drive waveform or the third drive waveform, without using the fourth drive waveform. The luminance value of the fourth level is lower than the luminance value of the second level and higher than the luminance value of the third level. A liquid dispensing device according to any one of claims 1 to 4.

6. The power consumption when the fourth drive waveform is supplied to the discharge unit is greater than the power consumption when the third drive waveform is supplied to the discharge unit. The power consumption when the third drive waveform is supplied to the discharge unit is greater than the power consumption when the first drive waveform is supplied to the discharge unit, and the power consumption when the second drive waveform is supplied to the discharge unit. A liquid dispensing device according to any one of claims 1 to 5.

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