Liquid ejection device

Abstract

The present application provides a liquid ejecting apparatus capable of reducing the possibility of instantaneous increase in power consumption. The liquid ejecting apparatus performs multi-gray scale gradation representation by ejecting liquid droplets onto a medium, a first drive circuit outputs a second drive waveform as a first drive signal during a period in which a second drive circuit outputs a fourth drive waveform as a second drive signal, and the period during which the first drive circuit outputs the second drive waveform as the first drive signal at least partially overlaps with the period during which the second drive circuit outputs the fourth drive waveform as the second drive signal, the period during which the first drive circuit outputs a third drive waveform as the first drive signal does not overlap with the period during which the second drive circuit outputs the fourth drive waveform as the second drive signal, and within a drive cycle, as the first drive signal, the first drive circuit outputs the second drive waveform after outputting the first drive waveform, and thereafter, outputs the third drive waveform.

Description

TECHNICAL FIELD

[0001] The present application relates to a liquid ejection apparatus. BACKGROUND

[0002] A technology is known in which a piezoelectric element or the like is used as a drive element in a liquid ejection apparatus that ejects liquid droplets and forms an image or a document on a medium. Such a liquid ejection apparatus is provided with a drive element corresponding to each of a plurality of nozzles that eject liquid droplets, the drive element being driven in accordance with a drive signal, thereby ejecting liquid droplets from the corresponding nozzles.

[0003] For example, in Patent Literature 1, a liquid ejection apparatus is disclosed that is provided with a drive signal generation section that generates a drive signal that drives a piezoelectric element that is a drive element, and liquid droplets are ejected by supplying the drive signal generated by the drive signal generation section to the piezoelectric element.

[0004] From the viewpoint of improving the ejection precision of liquid droplets in recent years, the miniaturization of liquid droplets is being promoted. However, when a liquid droplet is ejected from a nozzle, a phenomenon occurs in which the trailing end portion of the liquid droplet extends like a tail. Therefore, in the case of ejecting a small liquid droplet, the signal waveform of the drive signal becomes complex. As a result, when a liquid ejection apparatus ejects a small liquid, the instantaneous power consumption increases. With regard to such instantaneous increases in power consumption, there is no mention of this in Patent Literature 1, and there is room for improvement.

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2009-090467 SUMMARY

[0006] One embodiment of a liquid ejecting apparatus according to the present application is a liquid ejecting apparatus that performs multi-level gray scale expression by ejecting liquid droplets onto a medium, the liquid ejecting apparatus including: a first drive circuit that outputs a first drive signal; a second drive circuit that outputs a second drive signal; an ejecting portion that ejects liquid by being supplied with at least one of the first drive signal and the second drive signal; and a power supply circuit that supplies power to the first drive circuit and the second drive circuit, the first drive signal including a first drive waveform, a second drive waveform, and a third drive waveform in a drive period, the second drive signal including a fourth drive waveform and a fifth drive waveform in the drive period, the ejecting portion ejecting a first liquid droplet amount of liquid droplets when the first drive waveform is supplied to the ejecting portion, the ejecting portion ejecting a second liquid droplet amount of liquid droplets when the second drive waveform is supplied to the ejecting portion, the ejecting portion ejecting a third liquid droplet amount of liquid droplets when the third drive waveform is supplied to the ejecting portion, the ejecting portion ejecting a fourth liquid droplet amount of liquid droplets when the fourth drive waveform is supplied to the ejecting portion, the ejecting portion not ejecting liquid droplets when the fifth drive waveform is supplied to the ejecting portion, the fourth liquid droplet amount being less than any one of the first liquid droplet amount, the second liquid droplet amount, and the third liquid droplet amount, the third liquid droplet amount being less than any one of the first liquid droplet amount and the second liquid droplet amount, a first gray scale of the multi-level gray scales being expressed using only the fourth drive waveform, a second gray scale of the multi-level gray scales being expressed using at least the second drive waveform and not using the first drive waveform and the fourth drive waveform, a third gray scale of the multi-level gray scales being expressed using at least the first drive waveform and not using the fourth drive waveform, a luminance value of the second gray scale being lower than a luminance value of the first gray scale, a luminance value of the third gray scale being lower than a luminance value of the second gray scale, a period during which the first drive circuit outputs the second drive waveform as the first drive signal at least partially overlaps with a period during which the second drive circuit outputs the fourth drive waveform as the second drive signal, a period during which the first drive circuit outputs the third drive waveform as the first drive signal does not overlap with the period during which the second drive circuit outputs the fourth drive waveform as the second drive signal, and the first drive circuit outputs, as the first drive signal, the second drive waveform after outputting the first drive waveform and then outputs the third drive waveform in the drive period. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 FIG. 1 is a diagram illustrating an example of a configuration of a liquid ejecting apparatus.

[0008] Figure 2FIG. 1 is a diagram for showing an example of a functional configuration of a liquid ejecting apparatus.

[0009] Figure 3 FIG. 2 is a diagram for showing an example of a configuration of a plurality of ejecting portions in a head unit.

[0010] Figure 4 FIG. 3 is a diagram for showing an example of a structure of an ejecting portion.

[0011] Figure 5 FIG. 4 is a diagram for showing an example of signal waveforms of drive signals COMA, COMB.

[0012] Figure 6 FIG. 5 is a diagram for showing an example of a structure of a drive signal selection circuit.

[0013] Figure 7 FIG. 6 is a diagram for showing an example of a decoding content in a decoder.

[0014] Figure 8 FIG. 7 is a diagram for showing an example of a structure of a selection circuit corresponding to one ejecting portion.

[0015] Figure 9 FIG. 8 is a diagram for explaining an operation of a drive signal selection circuit.

[0016] Figure 10 FIG. 9 is a diagram for showing a relationship between print data [SIH, SIM, SIL] and a drive signal VOUT.

[0017] Figure 11 FIG. 10 is a diagram for showing a relationship between a size and a number of dots formed in a predetermined gray scale range and a gray scale. DETAILED DESCRIPTION

[0018] Hereinafter, a preferred embodiment of the present application will be described with reference to the drawings. The drawings used herein are diagrams for facilitating the explanation. In addition, the embodiment described below does not improperly limit the content of the present application described in the technical solution. Furthermore, the structure described below is not necessarily all of the essential structural elements of the present application.

[0019] In the following description, as an example of the liquid discharge apparatus to which the present application is applied, an inkjet printer for consumers is used. However, the liquid discharge apparatus is not limited to the inkjet printer for consumers, and can be a textile printer that performs textile printing or an office-oriented printing multifunction peripheral. Furthermore, the liquid discharge apparatus is not limited to the printer, and can be a color material discharge apparatus used in the manufacture of color filters of liquid crystal displays and the like, an electrode material discharge apparatus used in the formation of electrodes of organic EL (Electro Luminescence) displays, surface-emitting displays, and the like, a biological organic matter discharge apparatus used in the manufacture of biochips, and the like.

[0020] 1. Configuration of liquid discharge apparatus

[0021] Figure 1 A diagram showing an example of the configuration of the liquid discharge apparatus 1. As shown in Figure 1 the liquid discharge apparatus 1 is provided with a moving body 2 and a moving unit 3 that reciprocally moves the moving body 2 in a main scanning direction.

[0022] The moving unit 3 has a carriage motor 31 that becomes a drive source of the reciprocating movement of the moving body 2 in the main scanning direction, a carriage guide shaft 32 whose both ends are fixed, and a synchronous belt 33 that extends substantially in parallel with the carriage guide shaft 32 and is driven by the carriage motor 31.

[0023] The moving body 2 has a carriage 24. The carriage 24 is supported on the carriage guide shaft 32 in a manner that is movable in a reciprocating manner, and is fixed to a portion of the synchronous belt 33. Furthermore, the synchronous belt 33 is caused to run in the forward and reverse directions by the carriage motor 31, so that the moving body 2 having the carriage 24 is guided by the carriage guide shaft 32 to be reciprocally moved. In addition, a head unit 20 is provided at a portion of the moving body 2 that opposes the medium P. That is, the head unit 20 is mounted on the carriage 24. Furthermore, a plurality of nozzles that discharge ink as droplets are located on a face of the head unit 20 that opposes the medium P. In addition, 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 or the like that can slide in accordance with the reciprocating movement of the moving body 2 can be used.

[0024] In addition, the liquid discharge apparatus 1 is provided with a conveyance unit 4 that conveys the medium P on the platen 40 in a conveyance direction. The conveyance unit 4 has a conveyance motor 41 that is a drive source of the conveyance of the medium P, and a conveyance roller 42 that is rotated by the conveyance motor 41 to convey the medium P in the conveyance direction.

[0025] In the liquid discharge device 1 configured in the manner as above, the head unit 20 discharges ink to the medium P in synchronization with the timing at which the medium P is transported by the transport unit 4. As a result, the ink discharged by the head unit 20 is landed on the desired position of the medium P, and as a result, a desired image or text is formed on the surface of the medium P.

[0026] Next, the functional configuration of the liquid discharge device 1 will be described. Figure 2 Fig. 1 is a diagram showing one example of the functional configuration of the liquid discharge device 1. As shown in Fig. 1, the liquid discharge device 1 is provided with 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. Figure 2

[0027] The control unit 10 has a power supply circuit 11, a control circuit 100, and drive circuits 50a, 50b.

[0028] The power supply circuit 11 generates voltage signals VHV, VDD of predetermined voltage values from a commercial alternating current power supply supplied from the outside of the liquid discharge device 1, and outputs to various structures of the liquid discharge device 1. Here, the voltage signal VHV output by the power supply circuit 11 is, for example, a direct current voltage of 42 V, and the voltage signal VDD is, for example, a direct current voltage of 3.3 V. Such a power supply circuit 11 can also be configured to include an AC / DC converter that generates the voltage signal VHV from the commercial alternating current power supply, and a DC / DC converter that generates the voltage signal VDD from the voltage signal VHV, for example. In addition, the power supply circuit 11 can output direct current voltages of different voltage values in addition to the voltage signals VHV, VDD.

[0029] To the control circuit 100, image data is supplied from an unillustrated external device such as a host computer or the like provided outside the liquid discharge device 1. The control circuit 100 generates various control signals for controlling each part of the liquid discharge device 1 by performing various image processing and the like on the supplied image data, and outputs to the corresponding structures.

[0030] ​Specifically, the control circuit 100 generates a control signal Ctrl 1 for controlling the reciprocating movement of the moving body 2, and outputs it to the carriage motor 31 included in the moving unit 3. Further, the control circuit 100 generates a control signal Ctrl 2 for controlling the conveyance of the medium P, and outputs it to the conveyance motor 41 included in the conveyance unit 4. Thereby, the reciprocating movement of the moving body 2 along the main scanning direction and the conveyance of the medium P along the conveyance direction are controlled by the control circuit 100. As a result, the head unit 20 is able to eject ink onto the medium P at a predetermined timing in synchronization with the conveyance of the medium P. Thereby, the ink is landed on a desired position of the medium P, and a desired image or text is able to be formed on the medium P.

[0031] In addition, the control circuit 100 can supply the control signal Ctrl 1 for controlling the reciprocating movement of the moving body 2 to the moving unit 3 via a carriage motor driver not shown, and also can supply the control signal Ctrl 2 for controlling the conveyance of the medium P to the conveyance unit 4 via a conveyance motor driver not shown.

[0032] Further, the control circuit 100 outputs a basic drive signal dA to the drive circuit 50a. The basic drive signal dA is a signal containing data that specifies the signal waveform of the drive signal COMA, and is, for example, a digital signal. The drive circuit 50a operates as a power supply circuit using the voltage signals VHV, VDD output from the power supply circuit 11 as power supply voltages. Further, the drive circuit 50a generates the drive signal COMA by amplifying the signal converted from the input digital basic drive signal dA to an analog signal to a voltage value based on the voltage signal VHV. Further, the drive circuit 50a supplies the generated drive signal COMA to the head unit 20.

[0033] Further, the control circuit 100 outputs a basic drive signal dB to the drive circuit 50b. The basic drive signal dB is a signal containing data that specifies the signal waveform of the drive signal COMB, and is, for example, a digital signal. The drive circuit 50b operates as a power supply circuit using the voltage signals VHV, VDD output from the power supply circuit 11 as power supply voltages. Then, the drive circuit 50b generates the drive signal COMB by amplifying the signal converted from the input digital basic drive signal dB to an analog signal to a voltage value based on the voltage signal VHV. Then, the drive circuit 50b supplies the generated drive signal COMB to the head unit 20.

[0034] Such drive circuits 50a, 50b are only required to be the same structure and be able to operate based on the base drive signals dA, dB to amplify the voltage values of the signal waveforms defined by the base drive signals dA, dB to the voltage based on the voltage signal VHV, and various amplification signals including class A amplification circuits, class B amplification circuits, class AB amplification circuits, and class D amplification circuits can be used, for example.

[0035] Further, the control circuit 100 generates a clock signal SCK, a latch signal LAT, switching 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.

[0036] The head unit 20 has a drive signal selection circuit 200 and a liquid ejection head 21. Further, the liquid ejection head 21 has a plurality of ejection portions 600 each including a piezoelectric element 60. In the following description, there are cases where the number of ejection portions 600 included in the liquid ejection head 21 is set to n.

[0037] The clock signal SCK, the latch signal LAT, the switching signals CHA, CHB, and the print data signal SI are input to the drive signal selection circuit 200.

[0038] The drive signal selection circuit 200 sets the signal waveforms included in the drive signal COMA and the signal waveforms included in the drive signal COMB to be selected or not selected based on the print data signal SI transmitted by the clock signal SCK at the timings defined by the latch signal LAT and the switching signals CHA, CHB, and generates a drive signal VOUT. Then, the drive signal selection circuit 200 supplies the generated drive signal VOUT to one end of the piezoelectric element 60 included in each of the corresponding ejection portions 600. Further, a reference voltage signal VBS is supplied to the other end of the piezoelectric element 60 included in each of the plurality of ejection portions 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 of a constant potential such as 5.5 V or 6 V, for example. Furthermore, the piezoelectric element 60 is driven in accordance with the potential difference between the drive signal VOUT supplied to the one end and the reference voltage signal VBS supplied to the other end. Ink is ejected from the ejection portion 600 including the piezoelectric element 60 by the driving of the piezoelectric element 60.

[0039] Further, although in Figure 2 the head unit 20 is illustrated as having one liquid ejection head 21, the number of liquid ejection heads 21 included in the head unit 20 is not limited to one, and the head unit 20 can have a plurality of liquid ejection heads 21 depending on the kind, number, and the like of the ink to be ejected.

[0040] As the above, the liquid ejecting apparatus 1 in the present embodiment is a liquid ejecting apparatus that performs gradation expression of multiple gray scales on a medium by controlling the amount of liquid droplets ejected toward the medium P by controlling the signal waveform of the drive signal VOUT supplied to the piezoelectric element 60, and has the drive circuit 50a that outputs the drive signal COMA, the drive circuit 50b that outputs the drive signal COMB, the ejecting section 600 that ejects liquid by supplying at least one of the drive signal COMA and the drive signal COMB, and the power supply circuit 11 that supplies power to the drive circuit 50a and the drive circuit 50b.

[0041] 2. Structure and operation of ejecting section

[0042] Next, one example of the arrangement of the plurality of ejecting sections 600 in the head unit 20 and the structure of the plurality of ejecting sections 600 possessed by the head unit 20 will be described. Figure 3 is a view that shows one example of the arrangement of the plurality of ejecting sections 600 in the head unit 20. In addition, in Figure 3 , a case in which the head unit 20 has four liquid ejecting heads 21 is exemplified.

[0043] As Figure 3 indicated, the four liquid ejecting heads 21 each have a plurality of ejecting sections 600 arranged in a column in one direction. That is, the liquid ejecting head 21 includes a nozzle column nL in which the nozzles 651 described later included in the ejecting section 600 are arranged in one direction. Further, the liquid ejecting heads 21 are arranged side by side in the head unit 20 in a direction that intersects the nozzle column nL. That is, in the head unit 20, the same number of nozzle columns nL as the number of the liquid ejecting heads 21 are formed. In addition, the arrangement of the nozzles 651 in the nozzle column nL possessed by the liquid ejecting head 21 is not limited to one column, and for example, the nozzles 651 can be arranged in a staggered manner in which the positions of the even-numbered nozzles 651 counted from one end of the plurality of nozzles 651 and the odd-numbered nozzles 651 counted from the one end of the plurality of nozzles 651 are different, or two or more columns of nozzles 651 can be arranged side by side in the liquid ejecting head 21 to form one nozzle column nL.

[0044] Next, one example of the structure of the ejecting section 600 will be described. Figure 4 is a view that shows one example of the structure of the ejecting section 600. As Figure 4 indicated, the ejecting section 600 includes the piezoelectric element 60, the vibration plate 621, the cavity 631, and the nozzle 651. The vibration plate 621 is vibrated in conjunction with the Figure 4The piezoelectric element 60 disposed on the upper surface is displaced by the drive. The vibrating plate 621 functions as a diaphragm that expands or contracts the internal volume of the cavity 631. The cavity 631 is filled with ink. Moreover, the cavity 631 functions as a pressure chamber whose internal volume changes due to the displacement of the vibrating plate 621 caused by the drive of the piezoelectric element 60. The nozzle 651 is an opening formed on the nozzle plate 632 and communicating with the cavity 631. Moreover, as the internal volume of the cavity 631 changes, the ink stored inside the cavity 631 is ejected from the nozzle 651.

[0045] The piezoelectric element 60 is constructed by sandwiching a piezoelectric body 601 between a pair of electrodes 611 and 612. Based on the potential difference between the electrodes 611 and 612, the piezoelectric body 601 causes the electrodes 611 and 612, as well as the central portion of the vibrating plate 621, to move relative to the two end portions. Figure 4 It flexes in the vertical direction.

[0046] Specifically, a drive signal VOUT is supplied to one end of the piezoelectric element 60, namely electrode 611, and a reference voltage signal VBS is supplied to the other end, namely electrode 612. Furthermore, when the piezoelectric element 60 is driven upward according to the change in the voltage value of the drive signal VOUT, the vibrating plate 621 displaces upward, resulting in an increase in the internal volume of the cavity 631. 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 according to the change in the voltage value of the drive signal VOUT, the vibrating plate 621 displaces downward, resulting in a decrease in the internal volume of the cavity 631. Therefore, an amount of ink corresponding to the degree of decrease in the internal volume of the cavity 631 is ejected from the nozzle 651.

[0047] As described above, the liquid ejector head 21 includes a piezoelectric element 60, and ink is ejected from the medium P by driving the piezoelectric element 60. Furthermore, the piezoelectric element 60 and the ejection section 600 are not limited to the configuration shown in the figure; any configuration that allows ink to be ejected from the nozzle 651 by displacement via the piezoelectric element 60 is acceptable.

[0048] 3. Signal waveforms of drive signals COMA and COMB

[0049] Next, an example of the signal waveforms of the drive signal COMA output by drive circuit 50a and the drive signal COMB output by drive circuit 50b will be described. Figure 5 This is a diagram showing an example of the signal waveforms for the drive signals COMA and COMB.

[0050] like Figure 5As shown, the drive circuit 50a outputs a drive signal COMA including a trapezoidal waveform Adpl configured in a period tal from the rising of the latch signal LAT to the rising of the conversion signal CHA, a trapezoidal waveform Adp2 configured in a period ta2 from after the period tal to the next rising of the conversion signal CHA, and a trapezoidal waveform Adp3 configured in a period ta3 from after the period ta2 to the rising of the latch signal LAT. That is, the drive signal COMA includes the trapezoidal waveform Adpl, the trapezoidal waveform Adp2, and the trapezoidal waveform Adp3 in a cycle T constituted by the periods tal, ta2, and ta3.

[0051] The trapezoidal waveform Adpl is a signal waveform that causes an amount of ink more than a predetermined amount to be ejected from the corresponding ejecting section 600 in the case where the electrode 612 of the piezoelectric element 60 of the ejecting section 600 is supplied with the trapezoidal waveform Adpl. That is, in the case where the trapezoidal waveform Adpl is supplied to the ejecting section 600, an amount of ink more than a predetermined amount is ejected from the ejecting section 600. The voltage value of such a trapezoidal waveform Adpl starts with the voltage Vc, becomes lower than the voltage Vc after that, becomes higher than the voltage Vc, and ends with the voltage Vc.

[0052] The trapezoidal waveform Adp2 is a signal waveform that causes an amount of ink more than a predetermined amount to be ejected from the corresponding ejecting section 600 in the case where the electrode 612 of the piezoelectric element 60 of the ejecting section 600 is supplied with the trapezoidal waveform Adp2. That is, in the case where the trapezoidal waveform Adp2 is supplied to the ejecting section 600, the ejecting section 600 ejects an amount of ink more than a predetermined amount. The voltage value of such a trapezoidal waveform Adp2 starts with the voltage Vc, becomes lower than the voltage Vc after that, becomes higher than the voltage Vc, and ends with the voltage Vc.

[0053] The trapezoidal waveform Adp3 is a signal waveform that causes a predetermined amount of ink to be ejected from the corresponding ejecting section 600 in the case where the electrode 612 of the piezoelectric element 60 of the ejecting section 600 is supplied with the trapezoidal waveform Adp3. That is, in the case where the trapezoidal waveform Adp3 is supplied to the ejecting section 600, the ejecting section 600 ejects a predetermined amount of ink. The voltage value of such a trapezoidal waveform Adp3 starts with the voltage Vc, becomes lower than the voltage Vc after that, becomes higher than the voltage Vc again, and ends with the voltage Vc. In such a trapezoidal waveform Adp3, by making the voltage value lower than the voltage Vc after making it higher than the voltage Vc, and making it higher than the voltage Vc again, it is possible to reduce the phenomenon in which the rear end portion of the ink ejected from the nozzle 651 extends like a tail. Thus, it is possible to make the amount of ink ejected from the nozzle 651 in the case where the trapezoidal waveform Adp3 is supplied to the electrode 612 of the piezoelectric element 60 smaller than the amount of ink ejected from the nozzle 651 in the case where the trapezoidal waveforms Adpl and Adp2 are supplied to the electrode 612 of the piezoelectric element 60.

[0054] Here, the consumed power of the drive circuit 50a momentarily increases in a case where the voltage value of the output drive signal COMA has changed. Therefore, the consumed power in a case where the trapezoidal waveform Adp3 having a large change in voltage value is supplied to the ejection section 600 is larger than the consumed power in a case where the trapezoidal waveform Adpl is supplied to the ejection section 600 and the consumed power in a case where the trapezoidal waveform Adp2 is supplied to the ejection section 600.

[0055] As above, the drive circuit 50a outputs the trapezoidal waveform Adp2 after outputting the trapezoidal waveform Adpl as the drive signal COMA, and then outputs the trapezoidal waveform Adp3. Further, the trapezoidal waveform Adpl, the trapezoidal waveform Adp2, and the trapezoidal waveform Adp3 in the drive signal COMA output by the drive circuit 50a each starts with the voltage Vc and ends with the voltage Vc. That is, the drive signal COMA output by the drive circuit 50a includes the trapezoidal waveform Adpl, the trapezoidal waveform Adp2, and the trapezoidal waveform Adp3, and a signal waveform continuous with the voltage Vc.

[0056] Further, as shown in FIG. 6, the drive circuit 50b outputs the drive signal COMB including the trapezoidal waveform Bdl disposed within the period tb1 from the rise of the latch signal LAT to the rise of the conversion signal CHB, and the trapezoidal waveform Bdp2 disposed within the period tb2 from after the period tb1 to the rise of the next latch signal LAT. That is, the drive signal COMB includes the trapezoidal waveform Bdl and the trapezoidal waveform Bdp2 within the period T composed of the periods tb1 and tb2. Figure 5 The trapezoidal waveform Bdl is a signal waveform that causes an amount of ink less than a predetermined amount to be ejected from the corresponding ejection section 600 in a case where the electrode 612 of the piezoelectric element 60 of the ejection section 600 is supplied with the trapezoidal waveform Bdl. That is, in a case where the trapezoidal waveform Bdl is supplied to the ejection section 600, the ejection section 600 ejects an amount of ink less than a predetermined amount. Therefore, the amount of ink ejected from the corresponding ejection section 600 in a case where the electrode 612 of the piezoelectric element 60 of the ejection section 600 is supplied with the trapezoidal waveform Bdl is less than any one of the amounts of ink ejected from the corresponding ejection section 600 in a case where the electrode 612 of the piezoelectric element 60 of the ejection section 600 is supplied with the trapezoidal waveforms Adpl, Adp2, and Adp3.

[0057] The trapezoidal waveform Bdp2 is a signal waveform that causes an amount of ink less than a predetermined amount to be ejected from the corresponding ejection section 600 in a case where the electrode 612 of the piezoelectric element 60 of the ejection section 600 is supplied with the trapezoidal waveform Bdp2. That is, in a case where the trapezoidal waveform Bdp2 is supplied to the ejection section 600, the ejection section 600 ejects an amount of ink less than a predetermined amount. Therefore, the amount of ink ejected from the corresponding ejection section 600 in a case where the electrode 612 of the piezoelectric element 60 of the ejection section 600 is supplied with the trapezoidal waveform Bdp2 is less than any one of the amounts of ink ejected from the corresponding ejection section 600 in a case where the electrode 612 of the piezoelectric element 60 of the ejection section 600 is supplied with the trapezoidal waveforms Adpl, Adp2, and Adp3.

[0058] The voltage value of such a trapezoidal waveform Bdp1 starts with the voltage Vc, becomes higher than the voltage Vc, becomes lower than the voltage Vc, and again becomes higher than the voltage Vc. Thereafter, the voltage value of the trapezoidal waveform Bdp1 becomes lower than the voltage Vc again, becomes higher than the voltage Vc again, and thereafter ends with the voltage Vc. That is, in the trapezoidal waveform Bdp1, the operation of becoming higher than the voltage Vc, becoming lower than the voltage Vc, and again becoming higher than the voltage Vc is repeated a plurality of times at a predetermined frequency. Thus, the phenomenon of the trailing end of the ink ejected from the nozzle 651 extending like a tail can be further reduced. Thus, the amount of the ink ejected from the nozzle 651 when the trapezoidal waveform Bdp1 is supplied to the electrode 612 of the piezoelectric element 60 can be less than the amount of the 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. The amount of the ink ejected from the nozzle 651 when such a trapezoidal waveform Bdp1 is supplied to the electrode 612 of the piezoelectric element 60 can be, for example, 5 picoliter or less.

[0059] Here, as described above, the drive circuit 50a and the drive circuit 50b are the same circuit structure. Thus, as in the case of the drive circuit 50a, the power consumption of the drive circuit 50b momentarily increases when the voltage value of the output drive signal COMB changes. Thus, the power consumption when the trapezoidal waveform Bdp1, in which the voltage value changes more than the trapezoidal waveform Adp3, is supplied to the ejection section 600 is greater than any one of the power consumption when the trapezoidal waveform Adp1 is supplied to the ejection section 600, the power consumption when the trapezoidal waveform Adp2 is supplied to the ejection section 600, and the power consumption when the trapezoidal waveform Adp3 is supplied to the ejection section 600.

[0060] The trapezoidal waveform Bdp2 is a signal waveform that does not cause the ink to be ejected from the corresponding ejection section 600 but causes the ink in the vicinity of the nozzle 651 to vibrate when supplied to the electrode 612 of the piezoelectric element 60 of the ejection section 600. That is, when the trapezoidal waveform Bdp2 is supplied to the ejection section 600, the ejection section 600 does not eject the ink. The voltage value of such a trapezoidal waveform Bdp2 starts with the voltage Vc and ends with the voltage Vc without becoming lower than the voltage V.

[0061] As described above, the drive circuit 50b outputs the trapezoidal waveform Bdp2 after outputting the trapezoidal waveform Bdp1 as the drive signal COMB. Further, in the drive signal COMB output by the drive circuit 50a, the trapezoidal waveform Bdp1 and the trapezoidal waveform Bdp2 each start with the voltage Vc and end with the voltage Vc. That is, the drive signal COMB output by the drive circuit 50b includes the trapezoidal waveform Bdp1 and the trapezoidal waveform Bdp2 and the signal waveform in which the voltage Vc is continuous.

[0062] The drive signal COMA and the drive signal COMB as above are repeatedly output within the period T prescribed by the latch signal LAT. That is, the drive signal COMA repeatedly outputs the trapezoidal waveforms Adp1, Adp2, Adp3 in accordance with the period T, and the drive signal COMB repeatedly outputs the trapezoidal waveforms Bdp1, Bdp2 in accordance with the period T. At this time, the control circuit 100 outputs the switching signal CHA that prescribes the end of the period ta2 and the start of the period ta3, and the switching signal CHB that prescribes the end of the period tb1 and the start of the period tb2, within the period in which the drive circuit 50a outputs the voltage Vc that is constant in voltage value as the drive signal COMA and the drive circuit 50b outputs the voltage Vc that is constant in voltage value as the drive signal COMB. Thereby, the likelihood of distortion occurring in the signal waveform of the drive signal VOUT generated by the drive signal selection circuit 200 described later by setting the drive signal COMA to be selected or not selected and the drive signal COMB to be selected or not selected is reduced.

[0063] That is, the trapezoidal waveform Adp2 and the trapezoidal waveform Bdp1 are configured in such a manner that the period in which the drive circuit 50a outputs the trapezoidal waveform Adp2 as the drive signal COMA and the period in which the drive circuit 50b outputs the trapezoidal waveform Bdp1 as the drive signal COMB at least partially overlap, and the trapezoidal waveform Adp3 and the trapezoidal waveform Bdp1 are configured in such a manner that the period in which the drive circuit 50a outputs the trapezoidal waveform Adp3 as the drive signal COMA and the period in which the drive circuit 50b outputs the trapezoidal waveform Bdp1 as the drive signal COMB do not overlap. Also, as shown in FIG. 6, the trapezoidal waveform Adp1 and the trapezoidal waveform Bdp1 can be configured in such a manner that the period in which the drive circuit 50a outputs the trapezoidal waveform Adp1 as the drive signal COMA and the period in which the drive circuit 50b outputs the trapezoidal waveform Bdp1 as the drive signal COMB at least partially overlap. Figure 5

[0064] In this case, Figure 5 The signal waveforms of the drive signals COMA and COMB shown in FIG. 5 are one example and are not limited thereto, and can include various shapes of signal waveforms corresponding to 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 conveyance speed of the medium P, and the like.

[0065] 4. Structure and operation of selection control circuit

[0066] ​Next, the structure and operation of the drive signal selection circuit 200 will be described. The drive signal selection circuit 200 sets the signal waveforms included in the drive signals COMA, COMB to be selected or not selected, respectively, based on the clock signal SCK, the latch signal LAT, the conversion signals CHA, CHB, and the print data signal SI, and generates the drive signals VOUT supplied to the piezoelectric elements 60 provided to the plurality of ejection sections 600, respectively. Figure 6 FIG. 6 is a diagram showing an example of the structure of the drive signal selection circuit 200. As shown in FIG. 6, the drive signal selection circuit 200 has a selection control circuit 210, and n selection circuits 230 corresponding to the n ejection sections 600, respectively. Figure 6

[0067] The clock signal SCK, the latch signal LAT, the conversion signals CHA, CHB, and the print data signal SI are input to the selection control circuit 210. The selection control circuit 210 has a group of a shift register (S / R) 212, a latch circuit 214, and a decoder 216 corresponding to each of the n ejection sections 600. That is, the drive signal selection circuit 200 has n shift registers 212, n latch circuits 214, and n decoders 216.

[0068] The print data signal SI is input to the selection control circuit 210 in synchronization with the clock signal SCK. The print data signal SI includes 3-bit print data [SIH, SIM, SIL] for selecting the dot sizes, i.e., "large dot L", "medium dot M", "small dot S", "micro shake BSD", and "extra large dot LL" formed on the medium P by ejecting ink from the ejection section 600, in series corresponding to each of the n ejection sections 600. That is, the print data signal SI is a serial signal of 3n bits or more.

[0069] The print data [SIH, SIM, SIL] included in the print data signal SI is held in the n shift registers 212 corresponding to the n ejection sections 600. Specifically, the n shift registers 212 corresponding to the n ejection sections 600 are connected in cascade with each other, and the print data signal SI input in series is sequentially transferred to the shift register 212 at the next stage in accordance with the clock signal SCK. Further, the print data [SIH, SIM, SIL] is held in the corresponding shift register 212 by stopping the supply of the clock signal SCK. In other words, the print data [SIH, SIM, SIL] included in the print data signal SI is held in the corresponding shift register 212 by stopping the supply of the clock signal SCK. In addition, the print data [SIH, SIM, SIL] held in the corresponding shift register 212 is output to the selection circuit 230 corresponding to the ejection section 600. Figure 6 ​In the present embodiment, in order to distinguish the n shift registers 212, from the upstream side toward the downstream side of the input print data signal SI, they are sequentially labeled as stage 1, stage 2,..., and stage n.

[0070] The n latch circuits 214 latch the print data [SIH, SIM, SIL] held in the corresponding shift registers 212 all at once by the rise of the latch signal LAT. The print data [SIH, SIM, SIL] latched by the latch circuits 214 are input to the corresponding decoders 216.

[0071] Figure 7 A diagram showing one example of the decoding contents in the decoders 216. The decoders 216 output selection signals S1, S2 of the logic levels corresponding to the input print data [SIH, SIM, SIL]. Specifically, in the case where the print data [SIH, SIM, SIL] = [0, 1, 0] is input to the decoders 216, the decoders 216 output the selection signal S1 and the selection signal S2, the selection signal S1 becomes the L level during the period ta1, and the H level during the period ta2, and the L level during the period ta3, and the selection signal S2 becomes the L level during the period tb1, and the L level during the period tb2.

[0072] The selection signals S1, S2 output by the decoders 216 are input to the selection circuit 230. The selection circuit 230 is provided in a manner corresponding to the n ejection sections 600 respectively. That is, the drive signal selection circuit 200 has n selection circuits 230 in the same number as the n ejection sections 600. Figure 8 A diagram showing one example of the structure of the selection circuit 230 corresponding to one ejection section 600. As shown in FIG. 8, the selection circuit 230 includes inverters 232a, 232b and transmission gates 234a, 234b as non-circuits. Figure 8

[0073] ​The selection signal S1 is input to the positive control terminal of the transmission gate 234a which is not marked with a circular mark, and, after the logic level is inverted by the inverter 232a, is also input to the negative control terminal of the transmission gate 234a which is marked with a circular mark. Further, the input terminal of the transmission gate 234a is supplied with the drive signal COMA. Also, the transmission gate 234a makes the input terminal and the output terminal conductive in the case where the selection signal S1 of H level is input, and makes the input terminal and the output terminal non-conductive in the case where the selection signal S1 of L level is input. That is, the transmission gate 234a outputs the signal waveform included in the drive signal COMA from the output terminal in the case where the logic level of the input selection signal S1 is H level, and does not output the signal waveform included in the drive signal COMA from the output terminal in the case where the logic level of the input selection signal S1 is L level.

[0074] Further, the selection signal S2 is input to the positive control terminal of the transmission gate 234b which is not marked with a circular mark, and, after the logic level is inverted by the inverter 232b, is also input to the negative control terminal of the transmission gate 234b which is marked with a circular mark. Further, the input terminal of the transmission gate 234b is supplied with the drive signal COMB. Also, the transmission gate 234b makes the input terminal and the output terminal conductive in the case where the selection signal S2 of H level is input, and makes the input terminal and the output terminal non-conductive in the case where the selection signal S2 of L level is input. That is, the transmission gate 234b outputs the signal waveform included in the drive signal COMB from the output terminal in the case where the logic level of the input selection signal S2 is H level, and does not output the signal waveform included in the drive signal COMB from the output terminal in the case where the logic level of the input selection signal S2 is L level.

[0075] Also, the output terminal of the transmission gate 234a and the output terminal of the transmission gate 234b are commonly connected, and the drive signal selection circuit 200 outputs the signal at this connection point as the drive signal VOUT.

[0076] Here, the drive signal selection circuit 200 is configured by using Figure 9 The operation of the drive signal selection circuit 200 will be described. Figure 9Fig. 6 is a diagram for explaining 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. Then, the print data signal SI is sequentially transferred in the n shift registers 212 corresponding to the n ejection sections 600 in synchronization with the clock signal SCK. Thereafter, when the input of the clock signal SCK is stopped, the print data [SIH, SIM, SIL] corresponding to the n ejection sections 600, respectively, are held in the shift registers 212. In addition, in the print data signal SI, the print data [SIH, SIM, SIL] are contained in the order corresponding to the n stage,..., 2 stage, 1 stage of the shift registers 212 and the ejection sections 600.

[0077] Then, when the latch signal LAT rises, the latch circuits 214 latch the print data [SIH, SIM, SIL] held in the shift registers 212 all at once, respectively. The print data [SIH, SIM, SIL] latched by the latch circuits 214 are input to the corresponding decoders 216. In addition, Figure 9 The LT1, LT2,..., LTn shown correspond to the print data [SIH, SIM, SIL] latched by the latch circuits 214 corresponding to the 1 stage, 2 stage,..., n stage of the shift registers 212.

[0078] The decoders 216 generate the selection signals S1, S2,..., Sn by decoding the print data [SIH, SIM, SIL] input thereto. Figure 7 The selection signals S1, S2,..., Sn of the logic levels shown are output to the corresponding selection circuits 230. Then, the selection circuits 230 generate the drive signals VOUT corresponding to the n ejection sections 600, respectively, by setting the signal waveforms contained in the drive signals COMA, COMB to be selected or not selected in accordance with the logic levels of the selection signals S1, S2,..., Sn output from the decoders 216, and output to the corresponding ejection sections 600.

[0079] Figure 10 Fig. 7 is a diagram for showing the relationship between the print data [SIH, SIM, SIL] and the drive signals VOUT. As shown in Fig. 7, the print data [SIH, SIM, SIL] are sequentially transferred in the n shift registers 212 corresponding to the n ejection sections 600 in synchronization with the clock signal SCK. Then, when the input of the clock signal SCK is stopped, the print data [SIH, SIM, SIL] corresponding to the n ejection sections 600, respectively, are held in the shift registers 212. Figure 10As shown, in the case where the print data [SIH, SIM, SIL] = [1, 1, 1] is input to the decoder 216, the decoder 216 outputs the selection signal SI which is the H, H, H level during the periods tai, ta2, ta3, and the selection signal S2 which is the L, L level during the periods tbi, tb2. Thereby, the selection circuit 230 outputs the drive signal VOUT in which the trapezoidal waveform Adpl, the trapezoidal waveform Adp2, and the trapezoidal waveform Adp3 are continuous. Then, the drive signal VOUT in which the trapezoidal waveform Adpl, the trapezoidal waveform Adp2, and the trapezoidal waveform Adp3 are continuous is supplied to the electrode 612 of the piezoelectric element 60 possessed by the corresponding ejecting section 600, and thereby the ink of more than the predetermined amount, the ink of more than the predetermined amount, and the ink of the predetermined amount are ejected from the corresponding ejecting section 600. The ink ejected from the ejecting section 600 is sprayed and combined on the medium P, and thereby the extra-large dot LL is formed on the medium P.

[0080] Further, in the case where the print data [SIH, SIM, SIL] = [0, 1, 1] is input to the decoder 216, the decoder 216 outputs the selection signal SI which is the L, H, H level during the periods tai, ta2, ta3, and the selection signal S2 which is the L, L level during the periods tbi, tb2. Thereby, the selection circuit 230 outputs the drive signal VOUT in which the trapezoidal waveform Adp2 and the trapezoidal waveform Adp3 are continuous. Then, the drive signal VOUT in which the trapezoidal waveform Adp2 and the trapezoidal waveform Adp3 are continuous is supplied to the electrode 612 of the piezoelectric element 60 possessed by the corresponding ejecting section 600, and thereby the ink of more than the predetermined amount and the ink of the predetermined amount are ejected from the corresponding ejecting section 600. The ink ejected from the ejecting section 600 is sprayed and combined on the medium P, and thereby the large dot L is formed on the medium P.

[0081] Further, in the case where the print data [SIH, SIM, SIL] = [0, 1, 0] is input to the decoder 216, the decoder 216 outputs the selection signal SI which is the L, H, L level during the periods tai, ta2, ta3, and the selection signal S2 which is the L, L level during the periods tbi, tb2. Thereby, the selection circuit 230 outputs the drive signal VOUT in which the trapezoidal waveform Adp2 is continuous. Then, the drive signal VOUT in which the trapezoidal waveform Adp2 is continuous is supplied to the electrode 612 of the piezoelectric element 60 possessed by the corresponding ejecting section 600, and thereby the ink of the predetermined amount is ejected from the corresponding ejecting section 600. The ink ejected from the ejecting section 600 is sprayed on the medium P, and thereby the medium dot M is formed on the medium P.

[0082] Further, in a case where the print data [SIH, SIM, SIL] = [0, 0, 1] is input to the decoder 216, the decoder 216 outputs the selection signal SI that is the L, L, L level during the periods t al, t a2, t a3, and the selection signal S2 that is the H, L level during the periods t bl, t b2. Thereby, the selection circuit 230 outputs the trapezoidal waveform Bdp 1 as the drive signal VOUT. Then, the electrode 612 of the piezoelectric element 60 possessed by the corresponding ejection section 600 is supplied with the trapezoidal waveform Bdp 1 as the drive signal VOUT, whereby a small amount of ink compared to the predetermined amount is ejected from the corresponding ejection section 600. The ink ejected from this ejection section 600 is dropped on the medium P, whereby a small dot S is formed on the medium P.

[0083] Further, in a case where the print data [SIH, SIM, SIL] = [0, 0, 0] is input to the decoder 216, the decoder 216 outputs the selection signal SI that is the L, L, L level during the periods t al, t a2, t a3, and the selection signal S2 that is the L, H level during the periods t bl, t b2. Thereby, the selection circuit 230 outputs the trapezoidal waveform Bdp 2 as the drive signal VOUT. Then, the electrode 612 of the piezoelectric element 60 possessed by the corresponding ejection section 600 is supplied with the trapezoidal waveform Bdp 2 as the drive signal VOUT, whereby no ink is ejected from the corresponding ejection section 600, and micro-vibration BSD is performed.

[0084] As described above, the drive signal selection circuit 200 generates the drive signal VOUT corresponding to the "super-large dot LL", "large dot L", "medium dot M", "small dot S", and "micro-vibration BSD" respectively, by setting the signal waveforms included in the drive signals COMA, COMB to be selected or not selected based on the print data signal SI, and supplies the same to the plurality of piezoelectric elements 60.

[0085] 5. One example of multi-gray scale gradation expression

[0086] The liquid ejection apparatus 1 configured in the above manner performs multi-gray scale gradation expression by changing the dot size and the number of dots formed on the medium P. Figure 11 is a graph showing the relationship between the size and the number of dots formed in a predetermined gray scale range and the gray scale. In addition, in the horizontal axis of Figure 11 , 256 levels of "0" to "255" show the gray scale values of the multi-gray scale gradation expression formed in the predetermined gray scale range. Further, in the vertical axis of Figure 11On the vertical axis, 256 levels from "0" to "255" represent the number of dots formed within a predetermined grayscale range. Here, the predetermined grayscale range corresponds to the range of pixels on the matrix where dots are formed. Furthermore, a dot value of "0" indicates that no pixels form dots within the predetermined grayscale range, a dot value of "128" indicates that approximately half of the pixels form dots within the predetermined grayscale range, and a dot value of "255" indicates that dots are formed among all pixels included in the predetermined grayscale range.

[0087] like Figure 11 As shown, when the grayscale value of medium P is "0", no dots are formed within a predetermined grayscale range of medium P. Furthermore, as the grayscale value of medium P increases, the number of small dots S formed within the predetermined grayscale range of medium P increases. Moreover, 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 decreases with increasing grayscale value, and a midpoint M begins to form within the predetermined grayscale range of medium P. In the following explanation, the grayscale value at which the number of small dots S formed within the predetermined grayscale range of medium P decreases and the midpoint M begins to form is referred to as "g1".

[0088] Subsequently, as the grayscale value of medium P increases, when the number of midpoints M formed within a predetermined grayscale range of medium P reaches a predetermined threshold th, the number of midpoints M formed within the predetermined grayscale range of medium P decreases with the increase of the grayscale value of medium P, and large points L begin to form within the predetermined grayscale range of medium P. In the following description, the grayscale value at which the number of midpoints M formed within the predetermined grayscale range of medium P decreases and large points L begin to form is referred to as "g2".

[0089] 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 decreases with the increase of the grayscale value of medium P, and extra-large dots LL begin to form within the predetermined grayscale range of medium P. In the following description, there exists a case where the grayscale value at which the number of large dots L formed within the predetermined grayscale range of medium P decreases and extra-large dots LL begin to form is referred to as "g3".

[0090] Thereafter, as the gray scale value of the medium P increases, the number of large dots LL formed in the predetermined gray scale range of the medium P increases, and by the gray scale value becoming "g4", all the dots formed in the predetermined gray scale range of the medium P become large dots LL. Thereafter, by the gray scale value becoming "255", all the dots in the predetermined gray scale range of the medium P become large dots LL.

[0091] As described above, the liquid discharge apparatus 1 expresses the gray scale using only the drive signal VOUT corresponding to the small dot S in the range of the gray scale value of "0" to "gl". That is, the liquid discharge apparatus 1 expresses the gray scale using only the trapezoidal waveform Bdp1 in the range of the gray scale value of "0" to "gl".

[0092] Further, the liquid discharge apparatus 1 expresses the gray scale using the drive signal VOUT corresponding to the small dot S and the drive signal VOUT corresponding to the medium dot M in the range of the gray scale value of "gl" to "g2" which is lower in luminance than the range of the gray scale value of "0" to "gl". That is, the liquid discharge apparatus 1 expresses the gray scale using the trapezoidal waveform Bdp1 and the trapezoidal waveform Adp3 in the range of the gray scale value of "gl" to "g2".

[0093] Further, the liquid discharge apparatus 1 expresses the gray scale 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 the gray scale value of "g2" to "g3" which is lower in luminance than the range of the gray scale value of "0" to "g2". That is, the liquid discharge apparatus 1 expresses the gray scale using the trapezoidal waveform Adp2 and the trapezoidal waveform Adp3 in the range of the gray scale value of "g2" to "g3".

[0094] Further, the liquid discharge apparatus 1 expresses the gray scale using the drive signal VOUT corresponding to the large dot L and the drive signal VOUT corresponding to the large dot LL in the range of the gray scale value of "g3" to "g4" which is lower in luminance than the range of the gray scale value of "0" to "g3". That is, the liquid discharge apparatus 1 expresses the gray scale using the trapezoidal waveform Adp1, the trapezoidal waveform Adp2 and the trapezoidal waveform Adp3 in the range of the gray scale value of "g3" to "g4".

[0095] Further, the liquid discharge apparatus 1 expresses the gray scale using only the drive signal VOUT corresponding to the large dot LL in the range of the gray scale value of "g4" to "255" which is lower in luminance than the range of the gray scale value of "0" to "g4". That is, the liquid discharge apparatus 1 expresses the gray scale using the trapezoidal waveform Adp1, the trapezoidal waveform Adp2 and the trapezoidal waveform Adp3 in the range of the gray scale value of "g4" to "255".

[0096] As described above, in the liquid ejecting apparatus 1 of the present embodiment, in a case where the gray scale value of the image formed on the medium P is low, that is, in a case where the luminance value is high, the piezoelectric element 60 is driven using the drive signal VOUT corresponding to the small dot S having a small dot size formed on the medium P, and not using the drive signal VOUT corresponding to the large dot LL having a large dot size formed on the medium P, and in a case where the gray scale value of the image formed on the medium P is high, that is, in a case where the luminance value is low, the piezoelectric element 60 is driven using the drive signal VOUT corresponding to the large dot LL having a large dot size formed on the medium P, and not using the drive signal VOUT corresponding to the small dot S having a small dot size formed on the medium P. Thereby, in a case where the liquid ejecting apparatus 1 performs the gray scale expression of the multi-gray scale within a predetermined gray scale range of the medium P, the possibility of forming dots having largely different sizes within the predetermined gray scale range is reduced. Thereby, the quality of the gray scale expression of the multi-gray scale formed on the medium P is improved.

[0097] Here, the period T is one example of a drive period, the drive signal COMA is one example of a first drive signal, the drive signal COMB is one example of a second drive signal, the drive circuit 50a that outputs the drive signal COMA is one example of a first drive circuit, and the drive circuit 50b that outputs the drive signal COMB is one example of a second drive circuit. Further, the trapezoidal waveform Adp1 included in the drive signal COMA is one example of a first drive waveform, the trapezoidal waveform Adp2 included in the drive signal COMA is one example of a second drive waveform, the trapezoidal waveform Adp3 included in the drive signal COMA is one example of a third drive waveform, the trapezoidal waveform Bdp1 included in the drive signal COMB is one example of a fourth drive waveform, and the trapezoidal waveform Bdp2 included in the drive signal COMB is one example of a fifth drive waveform. Further, the amount more than the predetermined amount that is ejected by the ejection section 600 in the case where the trapezoidal waveform Adp1 is supplied to the ejection section 600 is one example of a first droplet amount, the amount more than the predetermined amount that is ejected by the ejection section 600 in the case where the trapezoidal waveform Adp2 is supplied to the ejection section 600 is one example of a second droplet amount, the predetermined amount that is ejected by the ejection section 600 in the case where the trapezoidal waveform Adp3 is supplied to the ejection section 600 is one example of a third droplet amount, and the amount less than the predetermined amount that is ejected by the ejection section 600 in the case where the trapezoidal waveform Bdp1 is supplied to the ejection section 600 is one example of a fourth droplet amount. Further, any one of the gradation values in the range of [0] to [g1] expressed using only the trapezoidal waveform Bdp1 is one example of a first gradation value, any one of the gradation values in the range of [g2] to [g3] expressed using the trapezoidal waveform Adp2 and not using the trapezoidal waveforms Adp1 and Bdp1 is one example of a second gradation value, any one of the gradation values in the range of [g3] to

[255] expressed using the trapezoidal waveform Adp1 and not using the trapezoidal waveform Bdp1 is one example of a third gradation value, and any one of the gradation values in the range of [g2] to [g4] expressed using either one of the trapezoidal waveforms Adp2 and Adp1 and the trapezoidal waveform Adp3 and not using the trapezoidal waveform Bdp1 is one example of a fourth gradation value.

[0098] 6. Effects

[0099] In the liquid ejection device 1 configured as described above, when the trapezoidal waveform Bdp1 is supplied to the ejection section 600, the amount of ink ejected by the ejection section 600 is less than the amount of ink ejected by the ejection section 600 when the trapezoidal waveform Adp1 is supplied to the ejection section 600, the amount of ink ejected by the ejection section 600 when the trapezoidal waveform Adp2 is supplied to the ejection section 600, and the amount of ink ejected by the ejection section 600 when the trapezoidal waveform Adp3 is supplied to the ejection section 600, the amount of ink ejected by the ejection section 600 when the trapezoidal waveform Adp3 is supplied to the ejection section 600 is less than the amount of ink ejected by the ejection section 600 when the trapezoidal waveform Adp1 is supplied to the ejection section 600, and the amount of ink ejected by the ejection section 600 when the trapezoidal waveform Adp2 is supplied to the ejection section 600. Therefore, the voltage displacement in the signal waveform of trapezoidal waveform Bdp1 is greater than the voltage displacement in the individual signal waveforms of trapezoidal waveforms Adp1, Adp2, and Adp3, and the voltage displacement in the signal waveform of trapezoidal waveform Adp3 is greater than the voltage displacement in the individual signal waveforms of trapezoidal waveforms Adp1 and Adp2. Therefore, the power consumption when trapezoidal waveform Bdp1 is supplied to the ejection section 600 is greater than the power consumption when trapezoidal waveform Adp1, Adp2, and Adp3 are supplied to the ejection section 600, and the power consumption when trapezoidal waveform Adp3 is supplied to the ejection section 600 is greater than the power consumption when trapezoidal waveform Adp1, Adp2, and Adp2 are supplied to the ejection section 600.

[0100] In such a liquid ejection device 1, when the period during which the trapezoidal waveform Adp3 is output as the drive signal COMA by the drive circuit 50a does not overlap with the period during which the trapezoidal waveform Bdp1 is output as the drive signal COMB by the drive circuit 50b, and thus the drive signals COMA and COMB are supplied to the ejection section 600 as the drive signal VOUT, the possibility of an increase in instantaneous power consumption is reduced.

[0101] Furthermore, the period during which the trapezoidal waveform Adp2 is output by the drive circuit 50a as the drive signal COMA at least partially overlaps with the period during which the trapezoidal waveform Bdp1 is output by the drive circuit 50b as the drive signal COMB, thereby shortening the transmission time required for the drive signals COMA and COMB and reducing the possibility of a decrease in the ink ejection speed in the liquid ejection device 1.

[0102] While the embodiments and modifications have been described above, the present application is not limited to these embodiments, and can be implemented in various ways without departing from the gist thereof. For example, the above-described embodiments can be appropriately combined.

[0103] The present application includes structures (for example, structures having the same function, method, and result, or structures having the same purpose and effect) substantially the same as the structures described in the embodiments. In addition, the present application includes structures in which non-essential parts of the structures described in the embodiments are replaced. Furthermore, the present application includes structures that can achieve the same functional effects as the structures described in the embodiments or structures that can achieve the same purpose. In addition, the present application includes structures in which known technologies are added to the structures described in the embodiments.

[0104] According to the above-described embodiments, the following is derived.

[0105] One mode of a liquid ejection device performs multi-gray-scale gray-scale representation by ejecting liquid droplets to a medium, the liquid ejection device including: a first drive circuit that outputs a first drive signal; a second drive circuit that outputs a second drive signal; an ejection section that ejects liquid by being supplied with at least one of the first drive signal and the second drive signal; a power supply circuit that supplies power to the first drive circuit and the second drive circuit, the first drive signal including a first drive waveform, a second drive waveform, and a third drive waveform in a drive period, the second drive signal including a fourth drive waveform and a fifth drive waveform in the drive period, the ejection section ejecting a first liquid droplet amount of liquid droplets in a case where the first drive waveform is supplied to the ejection section, the ejection section ejecting a second liquid droplet amount of liquid droplets in a case where the second drive waveform is supplied to the ejection section, the ejection section ejecting a third liquid droplet amount of liquid droplets in a case where the third drive waveform is supplied to the ejection section, the ejection section ejecting a fourth liquid droplet amount of liquid droplets in a case where the fourth drive waveform is supplied to the ejection section, the ejection section not ejecting liquid droplets in a case where the fifth drive waveform is supplied to the ejection section, the fourth liquid droplet amount being less than any one of the first liquid droplet amount, the second liquid droplet amount, and the third liquid droplet amount, the third liquid droplet amount being less than any one of the first liquid droplet amount and the second liquid droplet amount, a first gray scale among the multi-gray scales being represented using only the fourth drive waveform, a second gray scale among the multi-gray scales being represented using at least the second drive waveform and not using the first drive waveform and the fourth drive waveform, a third gray scale among the multi-gray scales being represented using at least the first drive waveform and not using the fourth drive waveform, a luminance value of the second gray scale being lower than a luminance value of the first gray scale, a luminance value of the third gray scale being lower than a luminance value of the second gray scale, a period during which the first drive circuit outputs the second drive waveform as the first drive signal at least partially overlaps with a period during which the second drive circuit outputs the fourth drive waveform as the second drive signal, a period during which the first drive circuit outputs the third drive waveform as the first drive signal does not overlap with the period during which the second drive circuit outputs the fourth drive waveform as the second drive signal, and in the drive period, the first drive circuit outputs the second drive waveform after outputting the first drive waveform and then outputs the third drive waveform as the first drive signal.

[0106] According to the liquid ejecting apparatus, the period during which the third drive waveform, which is a drive waveform in which the amount of liquid droplets ejected is small and the power consumed is large, is output as the first drive signal by the first drive circuit, and the period during which the fourth drive waveform, which is a drive waveform in which the amount of liquid droplets ejected is small and the power consumed is large, is output as the second drive signal by the second drive circuit, do not overlap, and thus the possibility of an instantaneous increase in power consumption is reduced.

[0107] Further, according to the liquid ejecting apparatus, the period during which the second drive waveform is output as the first drive signal by the first drive circuit, and the period during which the fourth drive waveform is output as the second drive signal by the second drive circuit, at least partially overlap, and thus the possibility of the drive period of the drive signals COMA and COMB becoming long is reduced, and as a result, the possibility of the ejection speed of liquid droplets in the liquid ejecting apparatus being reduced is reduced.

[0108] In one embodiment of the liquid ejecting apparatus, the fourth liquid droplet amount can be 5 picoliters or less.

[0109] According to the liquid ejecting apparatus, since the possibility of an instantaneous increase in power consumption is reduced, even if the liquid ejected by supplying the fourth drive waveform is very small at 5 picoliters or less, the possibility of an instantaneous increase in power consumption is reduced.

[0110] In one embodiment of the liquid ejecting apparatus, the power consumed when the fourth drive waveform is supplied to the ejection section can be greater than any one of the power consumed when the first drive waveform is supplied to the ejection section, the power consumed when the second drive waveform is supplied to the ejection section, and the power consumed when the third drive waveform is supplied to the ejection section.

[0111] According to the liquid ejecting apparatus, the period during which the second drive waveform is output as the first drive signal by the first drive circuit, and the period during which the fourth drive waveform is output as the second drive signal by the second drive circuit, at least partially overlap, and thus the possibility of the drive period of the drive signals COMA and COMB becoming long is reduced, and as a result, the possibility of the ejection speed of liquid droplets in the liquid ejecting apparatus being reduced is reduced.

[0112] In one embodiment of the liquid ejecting apparatus, the period during which the first drive waveform is output as the first drive signal by the first drive circuit, and the period during which the fourth drive waveform is output as the second drive signal by the second drive circuit, at least partially overlap, and the power consumed when the first drive waveform is supplied to the ejection section is less than the power consumed when the third drive waveform is supplied to the ejection section.

[0113] According to the liquid ejecting apparatus, 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 at least partially overlap, thereby reducing the possibility that the drive periods of the drive signals COMA and COMB become long, as a result of which the possibility that the ejection speed of liquid droplets in the liquid ejecting apparatus decreases is reduced.

[0114] In one embodiment of the liquid ejecting apparatus, the fourth gray scale among the plurality of gray scales can be expressed using any one of the second drive waveform and the first drive waveform and the third drive waveform and not using the fourth drive waveform, the luminance value of the fourth gray scale being lower than the luminance value of the second gray scale and higher than the luminance value of the third gray scale.

[0115] In one embodiment of the liquid ejecting apparatus, the power consumption in the case where the fourth drive waveform is supplied to the ejecting portion can be greater than the power consumption in the case where the third drive waveform is supplied to the ejecting portion, the power consumption in the case where the third drive waveform is supplied to the ejecting portion can be greater than the power consumption in the case where the first drive waveform is supplied to the ejecting portion and the power consumption in the case where the second drive waveform is supplied to the ejecting portion.

[0116] Symbol explanation

[0117] 1… liquid ejecting apparatus; 2… moving body; 3… moving unit; 4… conveyance unit; 10… control unit; 11… power supply circuit; 20… head unit; 21… liquid ejecting head; 24… carriage; 31… carriage motor; 32… carriage guide shaft; 33… synchronous belt; 40… platen; 41… conveyance motor; 42… conveyance roller; 50a, 50b… drive circuit; 60… piezoelectric element; 100… control circuit; 190… electric cable; 200… drive signal selection circuit; 210… selection control circuit; 212… shift register; 214… latch circuit; 216… decoder; 230… selection circuit; 232a, 232b… inverter, 234a, 234b… transmission gate; 600… ejecting portion; 601… piezoelectric body; 611, 612… electrode; 621… vibration plate; 631… cavity; 632… nozzle plate; 641… liquid reservoir; 651… nozzle; P… medium; nL… nozzle row.

Claims

1. A liquid discharge apparatus characterized by comprising: A multi-gray scale gray scale representation is performed by ejecting liquid droplets to a medium, The liquid ejecting apparatus is provided with: a first drive circuit which outputs a first drive signal; a second drive circuit which outputs a second drive signal; an ejecting section which ejects liquid by being supplied with at least one of the first drive signal and the second drive signal; a power supply circuit which supplies electric power to the first drive circuit and the second drive circuit, the first drive signal includes a first drive waveform, a second drive waveform, and a third drive waveform within a drive period, the second drive signal includes a fourth drive waveform and a fifth drive waveform within the drive period, in a case where the first drive waveform is supplied to the ejecting section, the ejecting section ejects liquid droplets in a first liquid droplet amount, in a case where the second drive waveform is supplied to the ejecting section, the ejecting section ejects liquid droplets in a second liquid droplet amount, in a case where the third drive waveform is supplied to the ejecting section, the ejecting section ejects liquid droplets in a third liquid droplet amount, in a case where the fourth drive waveform is supplied to the ejecting section, the ejecting section ejects liquid droplets in a fourth liquid droplet amount, in a case where the fifth drive waveform is supplied to the ejecting section, the ejecting section does not eject liquid droplets, the fourth liquid droplet amount is less than the first liquid droplet amount, and the fourth liquid droplet amount is less than the second liquid droplet amount, and the fourth liquid droplet amount is less than the third liquid droplet amount, the third liquid droplet amount is less than the first liquid droplet amount, and the third liquid droplet amount is less than the second liquid droplet amount, a first gray scale among the multi-gray scales is represented using only the fourth drive waveform, a second gray scale among the multi-gray scales is represented using at least the second drive waveform and not using the first drive waveform and the fourth drive waveform, a third gray scale among the multi-gray scales is represented using at least the first drive waveform and not using the fourth drive waveform, a fourth gray scale among the multi-gray scales is represented using either one of the first drive waveform and the third drive waveform and the second drive waveform and not using the fourth drive waveform, a luminance value of the second gray scale is lower than a luminance value of the first gray scale, a luminance value of the third gray scale is lower than a luminance value of the second gray scale, a luminance value of the fourth gray scale is lower than a luminance value of the second gray scale and higher than a luminance value of the third gray scale, a period during which the first drive circuit outputs the second drive waveform as the first drive signal and a period during which the second drive circuit outputs the fourth drive waveform as the second drive signal at least partially overlap, a period during which the first drive circuit outputs the third drive waveform as the first drive signal and a period during which the second drive circuit outputs the fourth drive waveform as the second drive signal do not overlap, within the drive period, as the first drive signal, the first drive circuit outputs the second drive waveform after outputting the first drive waveform, and thereafter, outputs the third drive waveform.

2. The liquid ejecting apparatus according to claim 1, wherein the fourth liquid droplet amount is 5 picoliters or less.

3. The liquid ejecting apparatus according to claim 1 or 2, wherein the power consumption when the fourth drive waveform is supplied to the ejecting portion is greater than the power consumption when the first drive waveform is supplied to the ejecting portion, and the power consumption when the fourth drive waveform is supplied to the ejecting portion is greater than the power consumption when the second drive waveform is supplied to the ejecting portion, and the power consumption when the fourth drive waveform is supplied to the ejecting portion is greater than the power consumption when the third drive waveform is supplied to the ejecting portion.

4. The liquid ejecting apparatus according to claim 1, wherein the period during which the first drive circuit outputs the first drive waveform as the first drive signal at least partially overlaps with the period during which the second drive circuit outputs the fourth drive waveform as the second drive signal, the power consumption when the first drive waveform is supplied to the ejecting portion is less than the power consumption when the third drive waveform is supplied to the ejecting portion.

5. The liquid ejecting apparatus according to claim 1, wherein the power consumption when the fourth drive waveform is supplied to the ejecting portion is greater than the power consumption when the third drive waveform is supplied to the ejecting portion, the power consumption when the third drive waveform is supplied to the ejecting portion is greater than the power consumption when the first drive waveform is supplied to the ejecting portion, and the power consumption when the third drive waveform is supplied to the ejecting portion is greater than the power consumption when the second drive waveform is supplied to the ejecting portion.

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