LIQUID EJECTION HEAD DRIVING METHOD AND LIQUID EJECTION APPARATUS

Abstract

To improve discharge performance even when the viscosity of a liquid increases.SOLUTION: A driving method of a liquid discharge head includes: a first step for acquiring physical property information indicating a physical property of a liquid in the liquid discharge head; a second step for determining a waveform of a driving signal on the basis of the physical information; a third step for forming a first liquid column of which a liquid level in a discharge part protrudes in a discharge direction by supplying a first waveform included in the first driving signal out of driving signals having the waveform determined in the second step to a driving element; and a fourth step for discharging some or all of the liquid for forming a second liquid column as a liquid droplet after a second liquid column of which a liquid level in the discharge part protrudes in the discharge direction is formed by supplying a second waveform included in a second driving signal out of the driving signals having the waveform determined in the second step to the driving element when the first liquid column is formed.SELECTED DRAWING: Figure 31

Description

[Technical field]

[0001] The present invention relates to a method for driving a liquid ejection head and a liquid ejection apparatus. [Background technology]

[0002] Patent Document 1 discloses a liquid ejection head that ejects droplets in response to a drive signal being supplied. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-37257 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned conventional technology, there is a risk that the ejection performance may deteriorate if the viscosity of the liquid increases. [Means for solving the problem]

[0005] In order to solve the above problems, a driving method for a liquid ejection head according to a preferred embodiment of the present invention is a recording method for a liquid ejection head having an ejection section including a driving element that is displaced by being supplied with a driving signal including a first driving signal and a second driving signal, a pressure chamber whose internal pressure is increased or decreased in accordance with the displacement of the driving element, and a nozzle that communicates with the pressure chamber and is capable of ejecting liquid filled inside the pressure chamber as droplets in an ejection direction in accordance with the increase or decrease in the pressure inside the pressure chamber, the method comprising the steps of: a first step of acquiring physical property information indicating the physical properties of the liquid in the liquid ejection head; and a second step of determining a waveform of the driving signal based on the physical property information. a third step of forming a first liquid column in which the liquid level in the ejection portion protrudes in the ejection direction by supplying to the drive element a first waveform included in the first drive signal among drive signals having the waveform determined in the second step; and a fourth step of, when the first liquid column is formed, forming a second liquid column in which the liquid level in the ejection portion protrudes in the ejection direction by supplying to the drive element a second waveform included in the second drive signal among drive signals having the waveform determined in the first step, and then ejecting a part or all of the liquid constituting the second liquid column as droplets.

[0006] In order to solve the above problems, a liquid ejection device according to a preferred embodiment of the present invention comprises a liquid ejection head having an ejection unit including a drive element that is displaced when a drive signal including a first drive signal and a second drive signal is supplied, a pressure chamber whose internal pressure is increased or decreased in accordance with the displacement of the drive element, and a nozzle that is in communication with the pressure chamber and is capable of ejecting liquid filled inside the pressure chamber as droplets in an ejection direction in accordance with the increase or decrease in the pressure inside the pressure chamber; and a control unit that controls the liquid ejection head, wherein the control unit obtains physical property information indicating the physical properties of the liquid in the liquid ejection head and controls the liquid ejection head to eject the liquid. a waveform of the drive signal based on the characteristic information, and a first waveform included in the first drive signal among the drive signals having the waveform determined by the control unit is supplied to the drive element, thereby forming a first liquid column with the liquid level in the ejection unit protruding in the ejection direction, and when the first liquid column is formed, a second waveform included in the second drive signal among the drive signals having the waveform determined by the control unit is supplied to the drive element, thereby forming a second liquid column with the liquid level in the ejection unit protruding in the ejection direction, and then part or all of the liquid constituting the second liquid column is ejected as droplets. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a functional block diagram showing an example of the configuration of an inkjet printer 1 according to an embodiment of the present invention. [Diagram 2] 1 is a schematic diagram illustrating an inkjet printer 1. FIG. [Diagram 3] 2 is a schematic partial cross-sectional view of the recording head HD, in which the recording head HD is cut so as to include a discharge portion D. FIG. [Figure 4] FIG. 2 is a block diagram showing an example of the configuration of a liquid ejection head HU. [Diagram 5] FIG. 4 is a timing chart illustrating the operation of the inkjet printer 1 during a recording period Tu[i]. [Figure 6] 5A to 5C are diagrams for explaining five possible driving modes of the individual designation signal Sd[m]. [Figure 7]13 is a diagram for explaining a drive signal Vin based on an individual designation signal Sd[m] of a drive manner α2. [Figure 8] FIG. 4 is a diagram for explaining the meniscus MS at time t1. [Figure 9] FIG. 13 is a diagram for explaining the meniscus MS at time t2. [Figure 10] FIG. 13 is a diagram for explaining the meniscus MS at time t3. [Figure 11] FIG. 13 is a diagram for explaining the meniscus MS at time t4. [Figure 12] FIG. 13 is a diagram for explaining the meniscus MS at time t5. [Figure 13] FIG. 13 is a diagram for explaining the meniscus MS at time t6. [Figure 14] FIG. 13 is a diagram for explaining the meniscus MS at time t7. [Figure 15] FIG. 13 is a diagram for explaining the meniscus MS at time t8. [Figure 16] FIG. 13 is a diagram for explaining the meniscus MS at time t9. [Figure 17] FIG. 13 is a diagram for explaining the meniscus MS at time t10. [Figure 18] FIG. 4 is a diagram for explaining the pressure fluctuation characteristics due to the drive signal Vin. [Figure 19] 4 is a diagram for explaining the fluctuation characteristics of the volume velocity of ink in a nozzle N. FIG. [Figure 20] FIG. 13 is a diagram for explaining the relationship between the period Pw and the discharge performance value. [Figure 21] FIG. 13 is a flowchart showing an example of generation of individual designation signals Sd[1] to Sd[m]. [Figure 22] FIG. 13 is a flowchart showing an example of generation of individual designation signals Sd[1] to Sd[m]. [Diagram 23] 5A to 5C are diagrams showing a specific example of a recording method using a driving waveform signal Com. [Figure 24] 6A to 6C are diagrams for explaining five driving modes in the first modified example. [Diagram 25] 11A to 11C are diagrams showing a specific example of a recording method using a driving waveform signal Com in a first modified example. [Figure 26]13A to 13C are diagrams for explaining six driving modes in the second modified example. [Figure 27] 13A and 13B are diagrams showing a specific example of a recording method using a driving waveform signal Com in a second modified example. [Figure 28] FIG. 13 is a diagram for explaining a drive signal Vin when a droplet DR is ejected in a third modified example. [Figure 29] FIG. 13 is a diagram for explaining a drive signal Vin when a droplet DR is ejected in a fourth modified example. [Diagram 30] FIG. 13 is a functional block diagram showing an example of the configuration of an inkjet printer 1a according to a fifth modified example. [Diagram 31] 5 is a diagram for explaining an example of determining the number of drive pulses PL included in the drive signal Vin1. [Diagram 32] FIG. 23 is a diagram for explaining a driving waveform signal Comb in the seventh modified example. [Diagram 33] FIG. 23 is a diagram for explaining a driving waveform signal Coma in the eighth modified example. [Diagram 34] FIG. 23 is a diagram for explaining a driving waveform signal Comc in a ninth modified example. [Diagram 35] FIG. 23 is a diagram for explaining a drive waveform signal Comd in a tenth modified example. [Diagram 36] FIG. 23 is a diagram for explaining a drive waveform signal Come in an eleventh modified example. [Figure 37] FIG. 23 is a diagram for explaining a driving waveform signal Comf in a twelfth modified example. [Figure 38] FIG. 23 is a diagram showing an example of a discharge section Dg in an 18th modified example. [Figure 39] FIG. 23 is a diagram showing an example of a discharge section Dh in a nineteenth modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the embodiments for carrying out the present invention will be described with reference to the drawings. However, in each drawing, the dimensions and scale of each part are appropriately different from the actual ones. In addition, since the embodiments described below are preferred specific examples of the present invention, various technically preferable limitations are attached, but the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description to the effect that the present invention is limited.

[0009] 1. First embodiment In this embodiment, a liquid ejection device will be described by taking as an example an inkjet printer 1 that ejects ink to form an image on recording paper P. The inkjet printer 1 is an example of a liquid ejection device. Ink is an example of a "liquid." Recording paper P is an example of a medium.

[0010] The ink in this embodiment is assumed to have a higher viscosity than general ink. Specifically, in this embodiment, the viscosity of the ink is 20 millipascal seconds or more, and preferably 40 millipascal seconds. Hereinafter, in the drawings, millipascal seconds may be referred to as "mPa seconds."

[0011] 1.1. Overview of Inkjet Printers 1 The configuration of an inkjet printer 1 according to this embodiment will be described with reference to Figures 1 and 2. Figure 1 is a functional block diagram showing an example of the configuration of an inkjet printer 1 according to this embodiment. Figure 2 is a schematic diagram illustrating the inkjet printer 1.

[0012] The inkjet printer 1 receives print data Img indicating the image to be formed by the inkjet printer 1, and information indicating the number of copies of the image to be formed by the inkjet printer 1, from a host computer such as a personal computer or digital camera. The inkjet printer 1 executes a printing process to form on recording paper P the image indicated by the print data Img supplied from the host computer.

[0013] As illustrated in FIG. 1, the inkjet printer 1 includes a liquid ejection head HU provided with an ejection section D that ejects ink, a control section 6 that controls the operation of each section of the inkjet printer 1, a drive waveform signal generating circuit 2 that generates a drive waveform signal Com for driving the ejection section D, a memory section 5 that stores the control program and other information for the inkjet printer 1, a transport mechanism 7 that transports recording paper P, and a movement mechanism 8 that moves the liquid ejection head HU.

[0014] In this embodiment, the liquid ejection head HU includes a recording head HD having M ejection sections D, and a switching circuit 10. In this embodiment, M is an integer of 1 or more.

[0015] In the following, in order to distinguish between the M discharge sections D provided in the recording head HD, they may be referred to in order as 1st stage, 2nd stage, ..., Mth stage. Furthermore, the mth stage of a discharge section D may be referred to as a discharge section D[m]. The variable m is an integer that satisfies 1 to M. Furthermore, when a component, signal, etc. of the inkjet printer 1 corresponds to the stage number m of the discharge sections D[m], the subscript [m] indicating that the component, signal, etc. corresponds to the stage number m may be added to the symbol representing the component, signal, etc.

[0016] In this embodiment, it is assumed that the inkjet printer 1 is a serial printer. Specifically, as shown in FIG. 2, the inkjet printer 1 executes a printing process by ejecting ink from the ejection unit D while transporting the recording paper P in the sub-scanning direction and moving the liquid ejection head HU in the main scanning direction. In this embodiment, as shown in FIG. 2, the +X direction and the -X direction opposite to the +X direction are the main scanning direction, and the +Y direction is the sub-scanning direction. Hereinafter, the +X direction and the -X direction are collectively referred to as the "X-axis direction", and the +Y direction and the -Y direction opposite to the +Y direction are collectively referred to as the "Y-axis direction". Furthermore, the direction perpendicular to the X-axis direction and the Y-axis direction and the ink ejection direction is referred to as the -Z direction. The -Z direction and the +Z direction opposite to the -Z direction are collectively referred to as the "Z-axis direction". The +Z direction is an example of a "retraction direction".

[0017] The print head HD and the ejection sections D provided in the print head HD will be described with reference to FIG.

[0018] FIG. 3 is a schematic partial cross-sectional view of the recording head HD, in which the recording head HD is cut so as to include a discharge portion D. As shown in FIG. 3, the ejection section D includes a piezoelectric element PZ that is displaced by being supplied with a drive signal Vin having a waveform selected from a plurality of waveforms included in the drive waveform signal Com, a cavity 320 whose internal pressure increases or decreases according to the displacement of the piezoelectric element PZ, a nozzle N that communicates with the cavity 320 and can eject ink filled inside the cavity 320 as droplets in the -Z direction according to the increase or decrease in the internal pressure of the cavity 320, and a vibration plate 310. The piezoelectric element PZ is an example of a "drive element." The cavity 320 is an example of a "pressure chamber." The cavity 320 is a space defined by a cavity plate 340, a nozzle plate 330 in which the nozzle N is formed, and the vibration plate 310. The cavity 320 communicates with a reservoir 350 via an ink supply port 360. The reservoir 350 communicates with a liquid container 14 corresponding to the ejection section D via an ink intake port 370.

[0019] In this embodiment, the piezoelectric element PZ is of a unimorph type as shown in Fig. 3. Note that the piezoelectric element PZ is not limited to the unimorph type, and a bimorph type, a laminated type, or the like may also be used.

[0020] The piezoelectric element PZ has an upper electrode Zu, a lower electrode Zd, and a piezoelectric body Zm provided between the upper electrode Zu and the lower electrode Zd. The piezoelectric element PZ is a passive element that deforms in response to a change in potential of a drive signal Vin. When the lower electrode Zd is electrically connected to a power supply line LHb set to a constant potential Vbs and the drive signal Vin is supplied to the upper electrode Zu, a voltage is applied between the upper electrode Zu and the lower electrode Zd. The piezoelectric element PZ is displaced in the +Z direction or the -Z direction in response to the applied voltage, and as a result of this displacement, the piezoelectric element PZ vibrates.

[0021] A vibration plate 310 is placed at the opening on the top surface of the cavity plate 340. A lower electrode Zd is bonded to the vibration plate 310. Therefore, when the piezoelectric element PZ is driven to vibrate by the drive signal Vin, the vibration plate 310 also vibrates. The volume of the cavity 320 changes due to the vibration of the vibration plate 310, and the ink filled in the cavity 320 is ejected from the nozzle N. When the ink in the cavity 320 decreases due to the ejection of the ink, ink is supplied from the reservoir 350.

[0022] The transport mechanism 7 transports the recording paper P in the +Y direction. Specifically, the transport mechanism 7 includes a transport roller (not shown) whose rotation axis is parallel to the X-axis direction, and a motor (not shown) that rotates the transport roller under the control of the control unit 6.

[0023] The moving mechanism 8 reciprocates the liquid ejection head HU along the X axis under the control of the control unit 6. As illustrated in Fig. 2, the moving mechanism 8 includes a substantially box-shaped conveying body 82 that houses the liquid ejection head HU, and an endless belt 81 to which the conveying body 82 is fixed.

[0024] The storage unit 5 includes volatile memory such as RAM, and non-volatile memory such as ROM, EEPROM, or PROM, and stores various information such as print data Img supplied from the host computer and the control program for the inkjet printer 1. RAM is an abbreviation for Random Access Memory. ROM is an abbreviation for Read Only Memory. EEPROM is an abbreviation for Electrically Erasable Programmable Read-Only Memory. PROM is an abbreviation for Programmable ROM.

[0025] The control unit 6 includes a CPU. CPU is an abbreviation for Central Processing Unit. However, the control unit 6 may include a programmable logic device such as an FPGA instead of the CPU. FPGA is an abbreviation for Field Programmable Gate Array.

[0026] The control unit 6 has a CPU that operates according to a control program stored in the storage unit 5, causing the inkjet printer 1 to execute the printing process.

[0027] The control unit 6 generates a print signal SI for controlling the liquid ejection head HU, a waveform designation signal dCom for controlling the drive waveform signal generating circuit 2, a signal for controlling the transport mechanism 7, and a signal for controlling the movement mechanism 8. Here, the waveform designation signal dCom is a digital signal that defines the waveform of the drive waveform signal Com. The drive waveform signal Com is an analog signal for driving the discharge section D. The drive waveform signal generating circuit 2 includes a DA conversion circuit, and generates the drive waveform signal Com having a waveform defined by the waveform designation signal dCom. Moreover, the print signal SI is a digital signal for specifying the type of operation of the ejection section D. Specifically, the print signal SI specifies whether or not to supply the drive waveform signal Com to the ejection section D, thereby specifying whether or not ink is ejected from the ejection section D when the ejection section D is driven.

[0028] 1.2.Configuration of Liquid Ejection Head HU The configuration of the liquid ejection head HU will be described below with reference to FIG.

[0029] 4 is a block diagram showing an example of the configuration of the liquid ejection head HU. As described above, the liquid ejection head HU includes the recording head HD and the switching circuit 10. The liquid ejection head HU also includes internal wiring LHa to which the driving waveform signal Com is supplied from the driving waveform signal generating circuit 2.

[0030] 4, the switching circuit 10 includes M switches SWa, ie, switches SWa[1] to SWa[M], and a connection state designation circuit 11 that designates the connection state of each switch. Each switch may be, for example, a transmission gate. The switch SWa[m] switches between electrical continuity and non-conduction between the internal wiring LHa and the upper electrode Zu[m] of the piezoelectric element PZ[m] provided in the discharge section D[m] in response to the connection state designation signal SLa[m]. For example, the switch SWa[m] is turned on when the connection state designation signal SLa[m] is at a high level, and turned off when the connection state designation signal SLa[m] is at a low level.

[0031] 1.3. Head unit operation Hereinafter, the operation of the liquid ejection head HU will be described with reference to FIGS.

[0032] In this embodiment, the operating period of the inkjet printer 1 includes multiple recording periods Tu. It is assumed that the inkjet printer 1 according to this embodiment drives each ejection section D in the printing process during each recording period Tu. In the following description, the operating period of the inkjet printer 1 has I recording periods Tu, where I is an integer greater than or equal to 2. Furthermore, the i-th recording period Tu may be referred to as recording period Tu[i], where i is an integer from 1 to I. Generally, an inkjet printer 1 forms an image represented by the print data Img by repeatedly executing a printing process over multiple continuous or intermittent recording periods Tu and ejecting ink from each ejection section D one or multiple times.

[0033] FIG. 5 is a timing chart for explaining the operation of the inkjet printer 1 during a recording period Tu[i]. 5, the control unit 6 outputs a latch signal LAT having a pulse PlsL and a change signal CH having a pulse PlsC. As a result, the control unit 6 defines a recording period Tu[i] as a period from the rising edge of the pulse PlsL to the rising edge of the next pulse PlsL. In addition, the control unit 6 divides the recording period Tu[i] into control periods Tcu1, Tcu2, Tcu3, Tcu4, and Tcu5 by the pulse PlsC.

[0034] As shown in FIG. 5, the drive waveform signal generating circuit 2 outputs the drive waveform signal Com. The drive waveform signal Com has a drive pulse PL1 provided in a control period Tcu1, a drive pulse PL2 provided in a control period Tcu2, a drive pulse PL3 provided in a control period Tcu3, a drive pulse PL4 provided in a control period Tcu4, and a drive pulse PL5 provided in a control period Tcu5. In this embodiment, the drive pulse PL supplied to the piezoelectric element PZ from the control period Tcu1 to the control period Tcu3 is referred to as a waveform PH1, and the drive pulse PL supplied to the piezoelectric element PZ from the control period Tcu4 to the control period Tcu5 during which the droplet DR is discharged from the nozzle N is referred to as a waveform PH2. In the following description, the waveform PH1 and the waveform PH2 may be collectively referred to as a "waveform PH", and the drive pulses PL1 to PL5 may be collectively referred to as a "drive pulse PL".

[0035] The driving pulse PL1 has driving components DC1 and DC2. The driving pulse PL2 has driving components DC3 and DC4. The driving pulse PL3 has driving components DC5 and DC6. The driving pulse PL4 has driving components DC7 and DC8. The driving pulse PL5 has driving components DC9 and DC10. The driving components DC1, DC3, DC5, DC7, and DC9 decrease the pressure in the cavity 320. The driving components DC2, DC4, DC6, DC8, and DC10 increase the pressure in the cavity 320. In the following description, the driving components DC1 to DC10 may be collectively referred to as "driving components DC."

[0036] As shown in Fig. 5, the start potential and end potential of each of drive pulses PL1, PL2, PL3, PL4, and PL5 are set to a reference potential V0. In this embodiment, the reference potential V0 is also the highest potential of the drive pulses PL1 to PL5. Potential VL1 shown in Fig. 5 is the lowest potential of the drive pulses PL1 to PL5. As illustrated in FIG. 5, the difference between the maximum potential and the minimum potential in the driving pulses PL1 to PL5 is the potential difference Vh. That is, the difference between the maximum potential and the minimum potential in the waveform PH1 is the potential difference Vh. Similarly, the difference between the maximum potential and the minimum potential in the waveform PH2 is the potential difference Vh. In the following description, the difference between the maximum potential and the minimum potential in the waveform PH may be referred to as the "potential difference of the waveform PH". The potential difference of the waveform PH1 is approximately equal to the potential difference of the waveform PH2. "Approximately equal" includes cases where they are completely equal, as well as cases where they can be considered equal in consideration of measurement errors. The potential difference of the waveform PH is 80% or more of the maximum potential difference that can be supplied to the piezoelectric element PZ. The larger the potential difference of the waveform PH, the greater the ejection amount, so it is preferable that the potential difference of the waveform PH is as close to the maximum potential difference that can be supplied to the piezoelectric element PZ as possible. The designer of the inkjet printer 1 adjusts the potential difference of the waveform PH so as to approach the maximum potential difference that can be supplied to the piezoelectric element PZ.

[0037] The print signal SI includes individual designation signals Sd[1]-Sd[M] that designate the driving mode of the discharge sections D[1]-D[M] during each recording period Tu. When a print process is performed during a recording period Tu[i], the control section 6 supplies the print signal SI including the individual designation signals Sd[1]-Sd[M] to the connection state designation circuit 11 in synchronization with the clock signal CL prior to the start of the recording period Tu[i], as shown in FIG. 5. In this case, the connection state designation circuit 11 generates a connection state designation signal SLa[m] based on the individual designation signal Sd[m] during the recording period Tu[i].

[0038] The individual designation signal Sd[m] according to the present embodiment is a signal that designates one of the five driving modes from driving mode α1 to driving mode α5 shown below during each recording period Tu. In the present embodiment, as an example, it is assumed that the individual designation signal Sd[m] is a 5-bit digital signal.

[0039] 6 is a diagram for explaining five possible driving modes of the individual designation signal Sd[m]. The individual designation signal Sd[m] indicates one of the following values: a value (1,1,1,1,1) indicating the driving mode α1; a value (0,0,0,1,1) indicating the driving mode α2; a value (0,0,1,1,1) indicating the driving mode α3; a value (0,1,1,1,1) indicating the driving mode α4; and a value (0,0,0,0,0) indicating the driving mode α5. When the x-th bit of the individual designation signal Sd[m] is "1", the connection state designation circuit 11 sets the connection state designation signal SLa[m] to a high level in the control period Tcux, and when the x-th bit is "0", the connection state designation signal SLa[m] to a low level in the control period Tcux. x is an integer from 1 to 5.

[0040] Specifically, when the individual designation signal Sd[m] indicates the driving mode α1, the connection state designation circuit 11 sets the connection state designation signal SLa[m] to a high level in the control periods Tcu1, Tcu2, Tcu3, Tcu4, and Tcu5. When the individual designation signal Sd[m] indicates the driving mode α2, the connection state designation circuit 11 sets the connection state designation signal SLa[m] to a low level in the control periods Tcu1, Tcu2, and Tcu3, and sets the connection state designation signal SLa[m] to a high level in the control periods Tcu4 and Tcu5. When the individual designation signal Sd[m] indicates the driving mode α3, the connection state designation circuit 11 sets the connection state designation signal SLa[m] to a low level in the control period Tcu1 and the control period Tcu2, and sets the connection state designation signal SLa[m] to a high level in the control period Tcu3, the control period Tcu4, and the control period Tcu5. When the individual designation signal Sd[m] indicates the driving mode α4, the connection state designation circuit 11 sets the connection state designation signal SLa[m] to a low level in the control period Tcu1, and sets the connection state designation signal SLa[m] to a high level in the control period Tcu2, the control period Tcu3, the control period Tcu4, and the control period Tcu5. When the individual designation signal Sd[m] indicates the driving mode α5, the connection state designation circuit 11 sets the connection state designation signal SLa[m] to a low level in the control period Tcu1, the control period Tcu2, the control period Tcu3, the control period Tcu4, and the control period Tcu5. As an example of the drive signal Vin, a drive signal Vin based on the individual designation signal Sd[m] of the drive manner α2 is shown in FIG.

[0041] In this embodiment, which will be described in detail later, when the ejection section D is in a stationary state with a reference potential V0 supplied to the piezoelectric element PZ and the position of the meniscus MS is stationary at the initial position Z0, when a drive signal Vin based on the individual designation signal Sd[m] of the drive mode α1 is supplied to the piezoelectric element PZ, a droplet DR is ejected from the nozzle N from the control period Tcu4 to the control period Tcu5. FIG. 7 is a diagram for explaining the drive signal Vin based on the individual designation signal Sd[m] of the drive mode α2. The drive signal Vin includes a drive signal Vin1 and a drive signal Vin2. The drive signal Vin1 is the drive signal Vin from the start of the control period Tcu1 to the end of the control period Tcu3. The drive signal Vin2 is the drive signal Vin from the start of the control period Tcu4 to the end of the control period Tcu5. As shown in FIG. 7, the drive signal Vin1 included in the drive signal Vin based on the individual designation signal Sd[m] of the drive mode α2 does not drive the discharge section D from the start of the control period Tcu1 to the end of the control period Tcu3. The drive signal Vin2 included in the drive signal Vin based on the individual designation signal Sd[m] of the drive mode α2 drives the discharge section D from the start of the control period Tcu4 to the end of the control period Tcu5. In other words, the drive signal Vin based on the individual designation signal Sd[m] of the drive mode α2 does not have a waveform PH1 but has a waveform PH2. The drive signal Vin1 is an example of a “first drive signal.” The drive signal Vin2 is an example of a “second drive signal.”

[0042] 1.4. Relationship between drive signal Vin and liquid level at discharge section D Next, referring to Figs. 8 to 17, in a stationary state of the ejection section D where the reference potential V0 is supplied to the piezoelectric element PZ and the position of the meniscus MS is stationary at the initial position Z0, when a drive signal Vin based on the individual designation signal Sd[m] of the drive mode α2 to drive mode α5 is supplied to the piezoelectric element PZ, a droplet DR is not ejected from the nozzle N, and when a drive signal Vin based on the individual designation signal Sd[m] of the drive mode α1 is supplied to the piezoelectric element PZ, an example will be described. The state of the liquid surface of the ejection section D at each of time t1, time t2, time t3, time t4, time t5, time t6, time t7, time t8, time t9, and time t10 shown in Fig. 5 will be described. Figs. 8 to 17 show cross-sectional views of the vicinity of the nozzle N cut along the XZ plane at time t1 to t10. The liquid surface in the ejection section D indicates the liquid surface in the nozzle N. The liquid level in the nozzle N is the liquid level located inside the wall of the nozzle N when the discharge portion D is viewed along the -Z direction. Therefore, when the discharge portion D is viewed in a direction perpendicular to the -Z direction, for example along the Y-axis direction, the liquid level located outside the wall of the nozzle N, that is, the liquid level protruding from the nozzle N in the -Z direction, is also included in the liquid level in the nozzle N, so long as it is the liquid level located inside the wall of the nozzle N when the discharge portion D is viewed along the -Z direction. Hereinafter, the liquid level in the nozzle N will be referred to as the "meniscus MS."

[0043] In the first embodiment, even if a drive signal Vin having only one drive pulse PL is supplied to the piezoelectric element PZ from a stationary state of the discharge section D where a reference potential V0 is supplied to the piezoelectric element PZ and the position of the meniscus MS is stationary at the initial position Z0 shown in FIG. 8 etc., the viscosity of the liquid is high and the pressure fluctuation on the ink in the cavity 320 cannot be large, so the discharge section D does not discharge a droplet DR. The initial position Z0 is a state in which the position of the meniscus MS is approximately aligned with the surface of the nozzle plate 330 in the -Z direction in the Z axis direction. In reality, the ink in the discharge section D is in a moderate negative pressure state so that the ink does not drip from the nozzle N, so the center of the meniscus MS has a concave curved shape recessed toward the cavity 320 side. In the first embodiment, the discharge section D discharges droplets by supplying a drive signal Vin having drive pulses PL1, PL2, PL3, PL4, and PL5 to the piezoelectric element PZ. Note that even if the drive signal Vin having drive pulses PL1, PL2, PL3, and PL4 but no drive pulse PL5 is supplied to the piezoelectric element PZ, the discharge section D discharges droplets. By supplying the drive signal Vin having drive pulses PL1, PL2, PL3, PL4, and PL5 to the piezoelectric element PZ, more stable discharge can be achieved compared to the case where the drive signal Vin having drive pulses PL1, PL2, PL3, and PL4 but no drive pulse PL5 is supplied to the piezoelectric element PZ.

[0044] FIG. 8 is a diagram for explaining the meniscus MS at time t1. Time t1 is within the control period Tcu1 and is the time when the supply of the driving component DC1 ends. The switching circuit 10 supplies the driving signal Vin having the driving component DC1 to the piezoelectric element PZ, so that the meniscus MS, which has a concave curved shape with the central portion of the meniscus MS recessed toward the cavity 320 side, i.e., toward the +Z direction, is retracted in the +Z direction while stretching the concave curved shape in the Z-axis direction. At this time, the portion of the meniscus MS that is retracted the most in the +Z direction is retracted to the retraction position Zp1. The portion of the meniscus MS that is retracted the most in the +Z direction is the central portion of the meniscus MS in a plan view in the Z-axis direction, and corresponds to the bottom portion of the concave curved shape. In a plan view in the Z-axis direction, the central portion of the meniscus MS approximately coincides with the central portion of the nozzle N. Hereinafter, for simplicity of explanation, the central portion of the meniscus MS in a plan view in the Z-axis direction will be simply referred to as the "central portion of the meniscus MS". Moreover, the periphery of the central portion of the meniscus MS will be simply referred to as “the peripheral portion of the meniscus MS.” The retracted position Zp1 is located in the +Z direction from the initial position Z0.

[0045] FIG. 9 is a diagram for explaining the meniscus MS at time t2. Time t2 is the end time of the control period Tcu1 and the end time of the supply of the driving component DC2. When the switching circuit 10 supplies the driving signal Vin having the driving component DC2 to the piezoelectric element PZ, the meniscus MS is pushed in the -Z direction, and a liquid column LC2 protruding in the -Z direction is formed in the center of the meniscus MS. In the following description, the liquid column is defined as a protruding columnar or spindle-shaped liquid surface of the meniscus MS from the position furthest on the +Z direction side to the position furthest on the -Z direction side. The tip of the liquid column LC2 in the -Z direction is located at the pushing position Zm1. The pushing position Zm1 is located in the -Z direction from the initial position Z0.

[0046] FIG. 10 is a diagram for explaining the meniscus MS at time t3. Time t3 is within the control period Tcu2 and is the time when the supply of the driving component DC3 ends. The switching circuit 10 supplies the driving signal Vin having the driving component DC3 to the piezoelectric element PZ, thereby drawing in the meniscus MS in the +Z direction, which has a concave shape recessed in the +Z direction at the periphery of the meniscus MS and a liquid column LC3 protruding in the -Z direction at the center of the meniscus MS. At that time, the part of the meniscus MS that is drawn in the most in the +Z direction is drawn in to the drawing position Zp2. The drawing position Zp2 at time t3 is located in the +Z direction from the initial position Z0 and in the -Z direction from the drawing position Zp1 at time t1. In other words, by supplying drive component DC3 to piezoelectric element PZ, the pressure of the ink in cavity 320 decreases and ink in nozzle N is drawn in the +Z direction, but as shown in Figure 10, at time t3, a liquid column LC3 protruding in the -Z direction is formed in the central portion of meniscus MS. The liquid column LC3 is formed in the central portion of meniscus MS. When viewed in the -Z direction from retraction position Zp2, the central portion of meniscus MS can also be said to form a convex shape. The liquid surface around liquid column LC3 is concave in the +Z direction.

[0047] FIG. 11 is a diagram illustrating the meniscus MS at time t4. Time t4 is the end of the control period Tcu2 and also the end of the supply of the drive component DC4. When the switching circuit 10 supplies a drive signal Vin having the drive component DC4 to the piezoelectric element PZ, the meniscus MS is pushed in the -Z direction, and a liquid column LC4 protruding in the -Z direction is formed at the center of the meniscus MS. The tip of the liquid column LC4 in the -Z direction is located at the push-out position Zm2. The push-out position Zm2 at time t4 is located further in the -Z direction than the push-out position Zm1 at time t2.

[0048] FIG. 12 is a diagram for explaining the meniscus MS at time t5. Time t5 is within the control period Tcu3 and is the time when the supply of the driving component DC5 ends. The switching circuit 10 supplies the driving signal Vin having the driving component DC5 to the piezoelectric element PZ, thereby drawing in the meniscus MS in the +Z direction, which has a concave shape recessed in the +Z direction at the periphery of the meniscus MS and a liquid column LC5 protruding in the -Z direction at the center of the meniscus MS. At that time, the portion of the meniscus MS furthest in the +Z direction is drawn in to the drawing position Zp3. The drawing position Zp3 at time t5 is located in the +Z direction from the initial position Z0 and in the -Z direction from the drawing position Zp2 at time t3. In other words, even though the pressure of the ink in the cavity 320 is reduced by supplying the driving component DC5 to the piezoelectric element PZ and the ink in the nozzle N is drawn in the +Z direction, as shown in FIG. 12, at time t5, the liquid column LC5 protruding in the -Z direction is formed at the center of the meniscus MS. The liquid column LC5 at time t5 is larger than the liquid column LC3 at time t3. The liquid column LC5 is formed in the center of the meniscus MS. When viewed in the -Z direction from the retracted position Zp3, the center of the meniscus MS can be said to form a convex shape. The liquid surface around the liquid column LC5 is concave in the +Z direction.

[0049] 13 is a diagram illustrating the meniscus MS at time t6. Time t6 is the end of the control period Tcu3 and also the end of the supply of the drive component DC6. When the switching circuit 10 supplies a drive signal Vin having the drive component DC6 to the piezoelectric element PZ, the meniscus MS is pushed out in the -Z direction, forming a liquid column LC6 protruding in the -Z direction. The tip of the liquid column LC6 in the -Z direction is located at the push-out position Zm3. The push-out position Zm3 at time t6 is located further in the -Z direction than the push-out position Zm2 at time t4.

[0050] FIG. 14 is a diagram for explaining the meniscus MS at time t7. Time t7 is within the control period Tcu4 and is the time when the supply of the driving component DC7 ends. The switching circuit 10 supplies the driving signal Vin having the driving component DC7 to the piezoelectric element PZ, thereby drawing in the meniscus MS in the +Z direction, which has a concave shape recessed in the +Z direction at the periphery of the meniscus MS and a liquid column LC7 protruding in the -Z direction at the center of the meniscus MS. At that time, the portion of the meniscus MS that is drawn in the most in the +Z direction is drawn in to the drawing position Zp4. The drawing position Zp4 at time t7 is located in the +Z direction further than the drawing position Zp3 at time t5 and in the -Z direction further than the drawing position Zp1 at time t1. In other words, by supplying drive component DC7 to piezoelectric element PZ, the pressure of the ink in cavity 320 decreases and ink in nozzle N is drawn in the +Z direction, but at time t7, a liquid column LC7 protruding in the -Z direction is formed in the center of meniscus MS as shown in Figure 14. The liquid column LC7 at time t7 is larger than the liquid column LC5 at time t5. 14 shows the meniscus MS at time t7 when the driving signal Vin having the driving pulses PL1, PL2, PL3, PL4, and PL5 is supplied to the piezoelectric element PZ. That is, the state of the meniscus MS shown in FIG. 14 is the state when the driving pulses PL1 to PL3 are supplied to the piezoelectric element PZ before the driving pulse PL4 is supplied to the piezoelectric element PZ. If the driving signal Vin having only the driving pulse PL4 is supplied to the piezoelectric element PZ, the driving pulse PL4 is supplied to the piezoelectric element PZ in a stationary state of the ejection section D where the reference potential V0 is supplied to the piezoelectric element PZ and the position of the meniscus MS is stationary at the initial position Z0, so that the meniscus MS at time t7 becomes equivalent to the meniscus MS at time t1 shown in FIG. In other words, when a drive signal Vin having only a drive pulse PL4 is supplied to the piezoelectric element PZ, the meniscus MS has a concave curved shape in the central part that is recessed in the +Z direction, and the position of the part of the meniscus MS that is most retracted in the +Z direction is the retracted position Zp1.

[0051] FIG. 15 is a diagram illustrating the meniscus MS at time t8. Time t8 is the end time of the control period Tcu4 and also the time when the supply of the drive component DC8 ends. When the switching circuit 10 supplies the drive signal Vin having the drive component DC8 to the piezoelectric element PZ, the meniscus MS is pushed out in the -Z direction, and a liquid column LC8 protruding in the -Z direction is formed in the central part of the meniscus MS. The length of the liquid column LC8 in the Z-axis direction at time t8 is shorter than the liquid column LC7 at time t7. The tip of the liquid column LC8 in the -Z direction is spherical, and a constriction occurs midway along the liquid column LC8.

[0052] FIG. 16 is a diagram for explaining the meniscus MS at time t9. Time t9 is within the control period Tcu5 and is the time when the supply of the driving component DC9 ends. The switching circuit 10 supplies the driving signal Vin having the driving component DC9 to the piezoelectric element PZ, thereby drawing in the meniscus MS in the +Z direction, which has a concave shape recessed in the +Z direction at the peripheral portion of the meniscus MS and a liquid column LC9 protruding in the -Z direction at the center portion of the meniscus MS. At that time, the portion of the meniscus MS that is drawn in the +Z direction the most is drawn in the +Z direction from the initial position Z0. Meanwhile, by supplying the driving component DC9 to the piezoelectric element PZ, the pressure of the ink in the cavity 320 is reduced and the ink in the nozzle N is drawn in the +Z direction, but the tip of the liquid column LC8 formed at time t8 in the meniscus MS continues to move in the -Z direction, forming the liquid column LC9 at the center portion of the meniscus MS. As the constricted portion of the liquid column LC9 becomes thinner and longer, the -Z direction tip of the liquid column LC9 separates from the meniscus MS and flies in the -Z direction as a droplet DR. As the tip of the liquid column LC8 formed at time point t8 continues to move in the -Z direction, supplying a drive signal Vin having a drive component DC9 to the piezoelectric element PZ reduces the pressure of the ink in the cavity 320, drawing the ink in the nozzle N in the +Z direction and moving the peripheral portion of the meniscus MS in the +Z direction, causing the droplet DR to tear off from the liquid column LC9. Figure 16 shows the state immediately before the droplet DR separates from the meniscus MS.

[0053] FIG. 17 is a diagram illustrating the meniscus MS at time t10. Time t10 is within the control period Tcu5 and is the time when the supply of the drive component DC10 ends. The switching circuit 10 supplies the drive signal Vin having the drive component DC10 to the piezoelectric element PZ, so that the meniscus MS approaches the initial position Z0. As shown in FIG. 17, the central portion of the meniscus MS forms a liquid column LC10 protruding in the -Z direction. However, the meniscus MS is vibrating, and after time t10, the central portion of the meniscus MS is retracted in the +Z direction. FIG. 17 shows a droplet DR that is separated immediately after time t9.

[0054] By supplying the driving component DC10 to the piezoelectric element PZ, the position of the meniscus MS is returned to the initial position Z0 without further droplets DR being continuously discharged from the discharge portion D, so the amount of change in potential per unit period in the driving component DC10 is smaller than those of the driving components DC2, DC4, DC6, and DC8. In the first embodiment, the amount of change in potential per unit period in the driving component DC10 is constant while the driving component DC10 is being supplied, but it may change while the driving component DC10 is being supplied. The amount of change in potential per unit period in the driving components DC1, DC3, DC5, DC7, and DC9 is approximately equal. The amount of change in potential per unit period in the driving components DC2, DC4, DC6, and DC8 is approximately equal.

[0055] As shown in Figures 8 to 17, when a drive signal Vin based on an individual designation signal Sd[m] that designates a drive mode α1 is supplied to the piezoelectric element PZ, when the drive component DC1 of the first drive pulse PL1 is supplied to the piezoelectric element PZ, the meniscus MS is pulled in the +Z direction the most, and thereafter, each time a drive pulse PL2 and a drive pulse PL3 are supplied to the piezoelectric element PZ, the meniscus MS is pushed out in the -Z direction, and the liquid column formed in the center of the meniscus MS also grows along the Z-axis direction. When a drive pulse PL4 is further supplied to the piezoelectric element PZ, this liquid column grows even longer and thinner in the Z-axis direction, and a part of the liquid column LC9 flies in the -Z direction as a droplet DR. Note that when a drive signal Vin based on an individual designation signal Sd[m] that designates a drive mode α5 is supplied to the piezoelectric element PZ, the droplet DR does not fly. An example in which a drive signal Vin based on an individual designation signal Sd[m] that designates any one of the drive manner α2, the drive manner α3, and the drive manner α4 is supplied to the piezoelectric element PZ will be described later with reference to FIGS.

[0056] 1.5.Pressure Fluctuation Due to Drive Signal Vin 8 to 17, the movement of the meniscus MS when the driving pulses PL1 to PL5 are sequentially supplied to the piezoelectric element PZ is described. Next, the fluctuation of the pressure in the cavity 320 due to the driving signal Vin will be described with reference to FIG. 18. Graphs G1 and G2 shown in FIG. 18 show the fluctuation of the pressure in the cavity 320 obtained by a fluid analysis simulation. The horizontal axis of the graph G1 and the horizontal axis of the graph G2 show time, and the vertical axis of the graph G1 and the vertical axis of the graph G2 show pressure. The pressure in the cavity 320 in a stationary state of the discharge section D where the reference potential V0 is supplied to the piezoelectric element PZ is set to zero on the vertical axis of the graph G1 and the vertical axis of the graph G2. The unit of pressure is Pascal, and is shown as "Pa" in the graphs G1 and G2. When the pressure is a positive value, it indicates that the volume of the cavity 320 is shrinking and the pressure inside the cavity 320 is increasing, and when the pressure is a negative value, it indicates that the volume of the cavity 320 is expanding and the pressure inside the cavity 320 is decreasing. +i where i is 5 or 6.

[0057] FIG. 18 is a diagram for explaining the pressure fluctuation characteristics due to the drive signal Vin. Graph G1 shows pressure fluctuation characteristics Pa1, which indicate the behavior of the pressure fluctuation applied to the ink in the cavity 320 by the piezoelectric element PZ, and pressure fluctuation characteristics Pn1, which indicate the behavior of the pressure fluctuation applied to the ink in the nozzle N by the piezoelectric element PZ, when the drive signal Vin having the drive pulse PL4 and not having the drive pulses PL1, PL2, PL3, and PL5 is supplied to the piezoelectric element PZ. In other words, graph G1 corresponds to the pressure fluctuation characteristics Pa1 of the ink in the cavity 320 and the pressure fluctuation characteristics Pn1 of the ink in the nozzle N, when the drive signal Vin having only the waveform PH2, not the waveform PH1, is supplied to the piezoelectric element PZ. Point Pn1p in the pressure fluctuation characteristics Pn1 indicates the highest pressure that can be applied to the ink in the nozzle N and the time point at which this pressure occurs, when only the drive pulse PL4 is supplied to the piezoelectric element PZ. The pressure indicated by point Pn1p is approximately 1.2×10 06 It is in Pascals. The pressure indicated by point Pn1p corresponds to the increase in the pressure of the ink in the nozzle N when only the drive pulse PL4 is supplied to the piezoelectric element PZ, which is the amount of fluctuation towards the positive pressure side from the pressure of the ink in the nozzle N when the ejection section D is in a stationary state. Point Pn1m in the pressure fluctuation characteristic Pn1 indicates the lowest pressure that can be applied to the ink in the nozzle N and the point in time when this pressure occurs. The pressure indicated by point Pn1m is approximately -1.2×10 06 The pressure indicated by point Pn1m corresponds to the amount of decrease in the pressure of the ink in the nozzle N when only the drive pulse PL4 is supplied to the piezoelectric element PZ, which is the amount of change toward the negative pressure side from the pressure of the ink in the nozzle N when the discharge portion D is in a stationary state.

[0058] Graph G2 shows pressure fluctuation characteristics Pa2, which indicate the behavior of the pressure fluctuation applied to the ink in the cavity 320 by the piezoelectric element PZ when a drive signal Vin having drive pulses PL1, PL2, PL3, and PL4 is supplied to the piezoelectric element PZ, and pressure fluctuation characteristics Pn2, which indicate the behavior of the pressure fluctuation applied to the ink in the nozzle N by the piezoelectric element PZ. In other words, graph G2 corresponds to the pressure fluctuation characteristics Pa2 of the ink in the cavity 320 and the pressure fluctuation characteristics Pn2 of the ink in the nozzle N when a drive signal Vin including both waveforms PH1 and PH2 is supplied to the piezoelectric element PZ. Point Pn2p in the pressure fluctuation characteristics Pn2 indicates the highest pressure that can be applied to the ink in the nozzle N and the time point at which this pressure occurred while the drive signal Vin having drive pulses PL1, PL2, PL3, and PL4 is being supplied to the piezoelectric element PZ, among the pressures at which the drive pulse PL4 is being supplied to the piezoelectric element PZ. The pressure indicated by point Pn2p is approximately 1.2×10 06 The pressure indicated by point Pn2p corresponds to an increase in the pressure of the ink in the nozzle N when the ejection section D is stationary, which is a fluctuation amount toward the positive pressure side, when the drive pulse PL4 is supplied to the piezoelectric element PZ during the period when the drive signal Vin having the drive pulses PL1, PL2, PL3, and PL4 is supplied to the piezoelectric element PZ. Point Pn2m in the pressure fluctuation characteristic Pn2 indicates the lowest pressure that can be applied to the ink in the nozzle N while the drive signal Vin having drive pulses PL1, PL2, PL3, and PL4 is being supplied to the piezoelectric element PZ, and the point in time at which this pressure occurs. The pressure indicated by point Pn2m is approximately -1.2×10 06 The pressure indicated by point Pn2m corresponds to the amount of decrease, which is the amount of change from the ink pressure in the nozzle N when the ejection section D is stationary to the negative pressure side, in the case where drive pulse PL4 is supplied to the piezoelectric element PZ during the period in which drive signal Vin having drive pulses PL1, PL2, PL3, and PL4 is supplied to the piezoelectric element PZ. The time indicated by point Pn1m and the time indicated by point Pn2m coincide with the time when the supply of the drive component DC7 ends, and the time indicated by point Pn1p and the time indicated by point Pn2p coincide with the time when the supply of the drive component DC8 ends.

[0059] As shown in graph G1 of Fig. 18, the amount of fluctuation in the pressure on the positive and negative sides in the nozzle N when a drive signal Vin having only a drive pulse PL4 is supplied to the piezoelectric element PZ is approximately equal to the amount of fluctuation in the pressure of the ink on the positive and negative sides in the nozzle N when a drive signal Vin having drive pulses PL1, PL2, PL3, and PL4 is supplied to the piezoelectric element PZ. The amount of pressure fluctuation is a general term for the amount of pressure increase and the amount of pressure decrease. Specifically, the pressure indicated by point Pn1p is approximately 1.2 x 10 06 As the line segment LPnp, which indicates Pascal, shows, the pressure is approximately equal to the pressure shown by point Pn2p. Also, the pressure shown by point Pn1m is approximately -1.2×10 06 As indicated by the line segment LPnm, which shows pascals, it is approximately equal to the pressure indicated by point Pn2m. Normally, when ink with a viscosity of less than 20 mPascal seconds is used, the pressure fluctuation caused by the rear drive pulse resonates with the pressure fluctuation caused by the leading drive pulse and becomes larger by setting the interval between multiple drive pulses as the resonance timing, and accordingly, the pressure fluctuation of the liquid in the nozzle when the rear drive pulse is supplied to the piezoelectric element is larger than the pressure fluctuation of the liquid in the nozzle when the leading drive pulse is supplied to the piezoelectric element. However, in this embodiment, the pressure fluctuation of the liquid in the nozzle when only the drive pulse PL4 shown in graph G1 is supplied and the pressure fluctuation of the liquid in the nozzle when the drive pulses PL1, PL2, PL3, and PL4 shown in graph G2 are successively supplied to the piezoelectric element PZ are approximately equal as described above. This is considered to indicate that the pressure fluctuation caused by the leading drive pulse PL and the pressure fluctuation caused by the trailing drive pulse PL do not resonate because the ink in this embodiment has a high viscosity.

[0060] 1.6. Volume velocity by driving signal Vin Next, the volume velocity of ink in nozzle N due to drive signal Vin will be described with reference to FIG. 19. The volume velocity of ink in nozzle N is the moving speed of ink in nozzle N in the Z-axis direction. Graphs G3 and G4 shown in FIG. 19 show the volume velocity determined by fluid analysis simulation. The horizontal axis of graph G3 and the horizontal axis of graph G4 indicate time, and the vertical axis of graph G3 and the vertical axis of graph G4 indicate the volume velocity of ink in nozzle N. The unit of volume velocity is cubic meters per second, and in graphs G3 and G4, "m 3 / s". The ink volume velocity in nozzle N is the volume of ink moving in nozzle N per unit time. When the ink volume velocity in nozzle N is a positive value, it indicates that ink is moving in the +Z direction, and when the ink volume velocity in nozzle N is a negative value, it indicates that ink is moving in the -Z direction. "E-06" in graphs G3 and G4 is a 10 -06 Shows.

[0061] 19 is a diagram illustrating the fluctuation characteristics of the volumetric velocity of ink in nozzle N. Graph G3 shows fluctuation characteristics Vn3 that indicate the behavior of the volumetric velocity of ink in nozzle N when a drive signal Vin having a drive pulse PL4 but not drive pulses PL1, PL2, PL3, and PL5 is supplied to piezoelectric element PZ. Point Vn3p in the fluctuation characteristics Vn3 indicates the volumetric velocity of ink in nozzle N that is greatest in the +Z direction and the point in time at which this volumetric velocity occurred. The volumetric velocity indicated by point Vn3p is approximately 2.7×10 -6 cubic meters per second. Point Vn3m in the fluctuation characteristic Vn3 indicates the maximum volume velocity in the -Z direction and the time when this volume velocity occurred. The volume velocity indicated by point Vn3m is approximately -3.3×10 -6 cubic metres per second.

[0062] Graph G4 shows a fluctuation characteristic Vn4 that indicates the behavior of the volumetric velocity of ink in nozzle N when a drive signal Vin having drive pulses PL1, PL2, PL3, and PL4 is supplied to the piezoelectric element PZ. Point Vn4p in the fluctuation characteristic Vn4 indicates the volumetric velocity of ink in nozzle N that is greatest in the +Z direction and the point in time at which this volumetric velocity occurred when drive pulse PL4 is supplied to the piezoelectric element PZ. The volumetric velocity indicated by point Vn4p is approximately 2.7×10 -06 cubic meters per second. Point Vn4m in the fluctuation characteristic Vn4 indicates the maximum volume velocity in the -Z direction and the time point at which this volume velocity occurs when the drive pulse PL4 is supplied to the piezoelectric element PZ. The volume velocity indicated by point Vn4m is approximately -3.3×10 -6 cubic metres per second. The time indicated by points Vn3p and Vn4p coincides with the time when the supply of the drive component DC7 ends, and the time indicated by points Vn3m and Vn4m coincides with the time when the supply of the drive component DC8 ends.

[0063] 19, the volumetric velocity of ink in the nozzle N when the drive signal Vin having only the drive pulse PL4 is supplied to the piezoelectric element PZ is approximately equal to the volumetric velocity of ink in the nozzle N when the drive signal Vin having the drive pulses PL1, PL2, PL3, and PL4 is supplied to the piezoelectric element PZ. Specifically, the volumetric velocity indicated by point Vn3p is approximately 2.7×10 -06 As shown by the line segment LVnp, which indicates cubic meters per second, the volume velocity indicated by point Vn4p is approximately equal to the volume velocity indicated by point Vn3m. Also, the volume velocity indicated by point Vn3m is approximately -3.3×10 6 As shown by the line segment LVnm, which indicates cubic meters per second, it is approximately equal to the volume velocity indicated by point Vn4m. This is thought to indicate that, similar to the pressure fluctuation characteristics due to the drive signal Vin described earlier with reference to Figure 18, the ink in this embodiment has a high viscosity, so that the pressure fluctuation due to the preceding drive pulse PL and the pressure fluctuation due to the following drive pulse PL do not resonate.

[0064] 1.7. Appropriate conditions for drive waveform signal Com Returning to FIG. 5 for explanation. As shown in FIG. 5, the period Pw24 from time tDC2 to time tDC4, the period Pw46 from time tDC4 to time tDC6, and the period Pw68 from time tDC6 to time tDC8 are substantially the same. "Substantially the same" includes the case where they are completely the same, as well as the case where they are considered to be the same when measurement errors are taken into consideration. In the following description, the period Pw24, the period Pw46, and the period Pw68 may be collectively referred to as "period Pw". The time tDC2 is the time when the supply of the driving component DC2 starts. The time tDC4 is the time when the supply of the driving component DC4 starts. The time tDC6 is the time when the supply of the driving component DC6 starts. The time tDC8 is the time when the supply of the driving component DC8 starts. The period Pw can also be said to be the interval between the start timings of the driving components DC that increase the pressure of the cavity 320 in the successive driving pulses PL. The relationship between the period Pw and the discharge performance value will be described with reference to FIG.

[0065] FIG. 20 is a diagram for explaining the relationship between the period Pw and the discharge performance value. The discharge performance value is a value obtained by multiplying the volume of the droplet DR by the flying speed of the droplet DR discharged from the nozzle N. The unit of the discharge performance value is Newton seconds, which is shown as "Ns" in the graph G5 shown in FIG. 20. "E-10" in the graph G5 is 10 -10 20, the horizontal axis of the graph G5 indicates the value obtained by dividing the period Pw by the natural vibration period TC of the discharge section D. The natural vibration period TC is the reciprocal of the natural vibration frequency of the discharge portion D, and can generally be expressed by the following formula (1).

number

number

[0066] As shown in graph G5, in the embodiment in which the pulse interval ratio is 1 or more and 2 or less, the ejection performance value is about 1.8×10 -10 The ejection performance value can be increased compared to the aspect where the pulse interval ratio is Newton seconds or more and the aspect where the pulse interval ratio is less than 1 and the aspect where the pulse interval ratio is more than 2. For example, when the period Pw68 is less than 1, the driving component DC8 is started in a state where the volume of the cavity 320 is still in the middle of expanding. In other words, when the period Pw68 is less than 1, the driving component DC8 is started in a state where the volume of the cavity 320 is smaller than the volume of the cavity 320 at the time tDC8 when the driving component DC8 is started in a case where the pulse interval ratio for the period Pw68 is 1 or more and less than 2, and therefore the ejection performance value decreases. In the embodiment where the pulse interval ratio is 1.2 or more and 1.6 or less, the ejection performance value is about 2.3×10 -10 The discharge performance value can be increased by about 1.8×10 Newton seconds or more, compared to the embodiment in which the pulse interval ratio is less than 1.2 and the embodiment in which the pulse interval ratio is more than 1.6. -10 A Newton second is equivalent to 20ng x 9m / s, or 2.3 x 10 -10 A Newton second is equivalent to 23ng × 10m / s. 1ng is 10 -9 The grams are shown.

[0067] 1.8. Recording method using driving waveform signal Com As shown in FIG. 17, a liquid column exists in the meniscus MS even after the droplet DR is discharged. After the droplet DR is discharged during the recording period Tu[i], the liquid column may continue to exist in the meniscus MS during the recording period Tu[j] that starts at the end of the recording period Tu[i]. j is an integer between 2 and I, and is greater than i by 1. When a liquid column exists in the meniscus MS during the recording period Tu[j], if a drive signal Vin based on an individual designation signal Sd[m] that designates the drive mode α1 is supplied to the piezoelectric element PZ, the droplet DR may be discharged before the drive component DC8 is supplied. Since the liquid discharge head HU and the recording paper P move relative to each other at a predetermined speed, if the droplet DR is discharged at a timing other than the timing when it should be discharged, the position where the droplet DR lands on the recording paper P is shifted from the position where it should be discharged, and the print quality is deteriorated. In the first embodiment, when ejecting droplets DR in a recording period Tu[j] in order to cause the droplets DR to land at the positions where they should originally land, the waveform of the drive signal Vin supplied to the piezoelectric element PZ in the recording period Tu[j] is determined based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ in a predetermined recording period Tux preceding the recording period Tu[j]. More specifically, the control unit 6 generates an individual designation signal Sd[m] for the recording period Tu[j] based on the individual designation signal Sd[m] for the predetermined recording period Tux preceding the recording period Tu[j].

[0068] A more specific description will be given of the processing of the control unit 6. When the control unit 6 ejects droplets DR from the nozzles N during the recording period Tu[j], the control unit 6 generates an individual designation signal Sd[m] for the recording period Tu[j] based on the individual designation signal Sd[m] for the recording period Tu[j-1], the individual designation signal Sd[m] for the recording period Tu[j-2], and the individual designation signal Sd[m] for the recording period Tu[j-3], which are the individual designation signals Sdx for a predetermined recording period Tux preceding the recording period Tu[j]. More specifically, when ejecting droplets DR from nozzle N during recording period Tu[j], the control unit 6 determines whether to select drive pulse PL1, drive pulse PL2, and drive pulse PL3 for drive signal Vin1 of drive signal Vin to be supplied during recording period Tu[j], based on the individual designation signal Sd[m] for recording period Tu[j-1], the individual designation signal Sd[m] for recording period Tu[j-2], and the individual designation signal Sd[m] for recording period Tu[j-3], which are the individual designation signals Sdx for a predetermined recording period Tux preceding the recording period Tu[j]. On the other hand, when ejecting droplets DR in the recording period Tu[j], the control unit 6 determines the drive signal Vin2 of the drive signal Vin to be supplied in the recording period Tu[j] to be a waveform PH2 including drive pulses PL4 and PL5, regardless of the individual designation signal Sd[m] of the recording period Tu[j-1], the individual designation signal Sd[m] of the recording period Tu[j-2], and the individual designation signal Sd[m] of the recording period Tu[j-3], which are the individual designation signals Sdx of the predetermined recording period Tu[j] preceding the recording period Tu[j]. A more specific recording method will be described with reference to Figs. 21 and 22.

[0069] Figures 21 and 22 are flowcharts showing an example of generation of individual designation signals Sd[1] to Sd[m] in a recording period Tu[j]. For the sake of simplicity, the flowcharts shown in Figures 21 and 22 are shown only when the value of j is 4 or more. The cases when the value of j is 2 and 3 will be explained after the explanation of the flowcharts shown in Figures 21 and 22 is finished.

[0070] In step S2, the control unit 6 assigns 1 to the variable m. Next, in step S4, the control unit 6 determines whether or not to cause the discharge unit D[m] to discharge droplets during the recording period Tu[j] based on the print data Img. If the determination result in step S4 is positive, in step S6, the control unit 6 acquires the individual designation signal Sd[m] for the recording period [i], i.e., the recording period [j-1], from the storage unit 5. Next, in step S8, the control unit 6 determines whether or not the discharge unit D[m] discharged droplets DR during the recording period Tu[j-1] based on the individual designation signal Sd[m] for the recording period [j-1]. For example, when the individual designation signal Sd[m] for the recording period Tu[j-1] designates any one of the driving modes α1, α2, α3, and α4, the control unit 6 determines that the discharge unit D[m] discharged droplets DR during the recording period Tu[j-1]. On the other hand, when the individual designation signal Sd[m] for the recording period Tu[j-1] designates the driving mode α5, the control unit 6 determines that the discharge unit D[m] did not discharge droplets DR during the recording period Tu[j-1].

[0071] If the determination result in step S8 is negative, in step S10, the control unit 6 acquires the individual designation signal Sd[m] for the recording period Tu[j-2] from the memory unit 5. Next, in step S12, the control unit 6 determines whether or not the ejection unit D[m] ejected droplets DR during the recording period Tu[j-2] based on the individual designation signal Sd[m] for the recording period Tu[j-2].

[0072] If the determination result in step S12 is negative, in step S14, the control unit 6 acquires the individual designation signal Sd[m] for the recording period Tu[j-3] from the memory unit 5. Next, in step S16, the control unit 6 determines whether or not the discharge unit D[m] discharged droplets DR during the recording period Tu[j-3] based on the individual designation signal Sd[m] for the recording period Tu[j-3].

[0073] If the determination result of step S16 is negative, that is, if the ejection section D[m] has not ejected droplets DR in the three preceding recording periods Tu[j-1], Tu[j-2], and Tu[j-3], in step S18, the control section 6 generates an individual designation signal Sd[m] of the driving mode α1. The process of step S18 can also be said to be the control section 6 determining the driving signal Vin1 to be a waveform PH1 including three driving pulses PL, namely, driving pulse PL1, driving pulse PL2, and driving pulse PL3. After the process of step S18 is completed, in step S32, the control section 6 stores the generated individual designation signal Sd[m] in the storage section 5.

[0074] If the determination result in step S4 is negative, that is, if the discharge unit D[m] does not discharge droplets DR during the recording period Tu[j], in step S20, the control unit 6 generates an individual designation signal Sd[m] for the driving mode α5. Then, in step S32, the control unit 6 stores the generated individual designation signal Sd[m] in the storage unit 5.

[0075] If the determination result of step S8 is positive, that is, if the discharge section D[m] discharged the droplet DR in the recording period Tu[j-1], in step S22, the control section 6 generates an individual designation signal Sd[m] of the driving mode α2. The process of step S22 can also be said to be the control section 6 determining the driving signal Vin1 to have zero driving pulses PL, that is, to have no waveform PH1. Also, in the process of step S8, the control section 6 determines whether or not the driving signal Vin supplied to the piezoelectric element PZ in the recording period Tu[j] includes the waveform PH1, based on the waveform of the driving signal Vin supplied to the piezoelectric element PZ in a predetermined recording period Tux. After completing the process of step S22, the control unit 6 causes the storage unit 5 to store the generated individual designation signal Sd[m] in step S32.

[0076] If the determination result of step S12 is positive, that is, if the discharge section D[m] did not discharge droplets DR during the recording period Tu[j-1] but discharged droplets DR during the recording period Tu[j-2], then in step S24, the control section 6 generates an individual designation signal Sd[m] of the driving mode α3. The process of step S24 can also be said to be the control section 6 determining the driving signal Vin1 to be a waveform PH1 including one driving pulse PL of the driving pulses PL3. After the process of step S22 is completed, in step S32, the control section 6 stores the generated individual designation signal Sd[m] in the storage section 5.

[0077] If the determination result of step S16 is positive, that is, if the discharge section D[m] did not discharge droplets DR during the recording period Tu[j-1] and the recording period Tu[j-2], but discharged droplets DR during the recording period Tu[j-3], in step S26, the control section 6 generates an individual designation signal Sd[m] of the driving mode α4. The process of step S26 can also be said to be the control section 6 determining the driving signal Vin1 to be a waveform PH1 including two driving pulses PL, the driving pulse PL2 and the driving pulse PL3. After the process of step S26 is completed, in step S32, the control section 6 stores the generated individual designation signal Sd[m] in the memory section 5. In the processing of steps S12 and S16, when the control unit 6 determines, based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ in a predetermined recording period Tux, that the drive signal Vin1 supplied to the piezoelectric element PZ in the recording period [j] includes a waveform PH1, it further determines the number of drive pulses PL included in the waveform PH1. In addition, the processing of steps S8, S12, and S16 determines the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the recording period [j] so that the number of drive pulses PL contained in the drive signal Vin1 supplied to the piezoelectric element PZ during the recording period [j] when the control unit 6 does not eject droplets DR from the ejection section D during the recording period [j-1] is greater than the number of drive pulses PL contained in the drive signal Vin1 supplied to the piezoelectric element PZ during the recording period [j] when droplets DR are ejected from the ejection section D during the recording period [j-1].

[0078] After completing the process of step S32, in step S34, the control unit 6 determines whether or not the variable m has reached M, which is the number of discharge units D. If the determination result of step S34 is negative, the control unit 6 increments the value of the variable m by 1 in step S38, and returns the process to step S4. If the determination result of step S34 is positive, the control unit 6 outputs the individual designation signals Sd[1] to Sd[M] to the switching circuit 10 in step S36. After completing the process of step S36, the control unit 6 ends the series of processes shown in FIGS. 21 and 22.

[0079] A case where the value of the variable j is 2 will be described. If the determination result of step S8 is negative, the control unit 6 executes the process of step S18 instead of the process of step S10. Next, a case where the value of the variable j is 3 will be described. If the determination result of step S12 is negative, the control unit 6 executes the process of step S18 instead of the process of step S14. Since the process after step S18 is the same as the series of processes shown in FIG. 21 and FIG. 22, the description after the process after step S18 is omitted. Also, in the recording period Tu[1], the control unit 6 determines whether or not to cause the discharge unit D[m] to discharge droplets during the recording period Tu[1] based on the print data Img. If the discharge unit D[m] is to discharge droplets, the control unit 6 generates an individual designation signal Sd[m] of the driving mode α1. If the discharge unit D[m] is not to discharge droplets, the control unit 6 generates an individual designation signal Sd[m] of the driving mode α5.

[0080] FIG. 23 is a diagram showing a specific example of a recording method using a driving waveform signal Com. In FIG. 23, four discharge modes are shown in the discharge section D[m]. In FIG. 23, a black circle or a white circle drawn with a dashed line is displayed below each recording period Tu. A black circle means that a droplet DR is discharged during this recording period Tu, and a white circle drawn with a dashed line means that a droplet DR is not discharged during this recording period Tu. Note that the black circle and the white circle drawn with a dashed line displayed in FIG. 23 and subsequent FIG. 25, FIG. 27, and FIG. 28 have the same meaning as the black circle and the white circle drawn with a dashed line shown in FIG. 23. Hereinafter, the recording period Tu in which the droplet DR is discharged may be referred to as an "ejection recording period Tu-D", and the recording period Tu in which the droplet DR is not discharged may be referred to as a "non-ejection recording period Tu-N".

[0081] 23 is a mode in which droplets DR are discharged during the recording period Tu[1] and the recording period Tu[2]. For the recording period Tu[1], the control unit 6 generates an individual designation signal Sd[m] of the driving mode α1 and outputs the generated individual designation signal Sd[m] to the switching circuit 10. As a result, the discharge unit D[m] is supplied with a driving signal Vin having driving pulses PL1, PL2, PL3, PL4, and PL5 during the recording period Tu[1]. 21 and 22 in a state where the value of the variable j is 2. Since the determination result of step S8 is positive, the control unit 6 executes the process of step S22 to generate an individual designation signal Sd[m] of the driving mode α2, and outputs the generated individual designation signal Sd[m] to the switching circuit 10. As a result, a drive signal Vin having drive pulses PL4 and PL5 is supplied to the discharge unit D[m] in the recording period Tu[1].

[0082] The discharge mode shown in the second row of FIG. 23 is a mode in which droplets DR are discharged during the recording period Tu[1] and the recording period Tu[3], and droplets DR are not discharged during the recording period Tu[2]. The recording period Tu[1] is the same as the recording period Tu[1] in the first row of FIG. 23, so a description thereof will be omitted. Regarding the recording period Tu[2], the control unit 6 executes the flowcharts shown in FIG. 21 and FIG. 22 in a state in which the value of the variable j is 2. Since the recording period Tu[2] is the non-ejection recording period Tu-N, the determination result of step S4 is negative, and the control unit 6 generates an individual designation signal Sd[m] of the driving mode α5 by the process of step S20, and outputs the generated individual designation signal Sd[m] to the switching circuit 10. As a result, the discharge unit D[m] is supplied with a drive signal Vin that causes the discharge unit D to be non-driven during the recording period Tu[2]. 21 and 22 in a state where the value of the variable j is 3. Since the determination result in step S12 is positive, the control unit 6 generates an individual designation signal Sd[m] of the driving mode α3 by the process in step S24, and outputs the generated individual designation signal Sd[m] to the switching circuit 10. As a result, the discharge unit D[m] is supplied with the drive signal Vin having drive pulses PL3, PL4, and PL5 in the recording period Tu[3].

[0083] The discharge mode shown in the third row of FIG. 23 is a mode in which droplets DR are discharged during the recording period Tu[1] and the recording period Tu[4], and droplets DR are not discharged during the recording period Tu[2] and the recording period Tu[3]. The recording period Tu[1] and the recording period Tu[2] are the same as the recording period Tu[1] and the recording period Tu[2] shown in the second row of FIG. 23, and therefore a description thereof will be omitted. For the recording period Tu[3], the control unit 6 executes the flowcharts shown in FIG. 21 and FIG. 22 in a state in which the value of the variable j is 3. Since the recording period Tu[3] is the non-ejection recording period Tu-N, the determination result of step S4 is negative, and the control unit 6 generates an individual designation signal Sd[m] of the driving mode α5 by the process of step S20, and outputs the generated individual designation signal Sd[m] to the switching circuit 10. As a result, the discharge section D[m] is supplied with the drive signal Vin that causes the discharge section D to be non-driven during the recording period Tu[3]. Regarding the recording period Tu[4], since the determination result in step S16 is positive, the control unit 6 generates an individual designation signal Sd[m] of the driving mode α4 by the process of step S26, and outputs the generated individual designation signal Sd[m] to the switching circuit 10. As a result, the discharge unit D[m] is supplied with the drive signal Vin having drive pulses PL2, PL3, PL4, and PL5 during the recording period Tu[4].

[0084] The ejection mode shown in the fourth row of FIG. 23 is an ejection mode in which droplets DR are ejected during the recording period Tu[1] and the recording period Tu[5], and droplets DR are not ejected during the recording period Tu[2], the recording period Tu[3], and the recording period Tu[4]. The recording period Tu[1], the recording period Tu[2], and the recording period Tu[3] are the same as the recording period Tu[1], the recording period Tu[2], and the recording period Tu[3] shown in the third row of FIG. 23, so that the description will be omitted. Since the recording period Tu[4] is the non-ejection recording period Tu-N, the determination result of step S4 is negative, and the control unit 6 generates an individual designation signal Sd[m] of the driving mode α5 by the process of step S20, and outputs the generated individual designation signal Sd[m] to the switching circuit 10. As a result, the discharge section D[m] is supplied with the drive signal Vin that causes the discharge section D to be non-driven during the recording period Tu[4]. Regarding the recording period Tu[5], since the determination result in step S16 is negative, the control unit 6 generates an individual designation signal Sd[m] of the driving mode α1 by the process of step S18, and outputs the generated individual designation signal Sd[m] to the switching circuit 10. As a result, the discharge unit D[m] is supplied with the drive signal Vin having drive pulses PL1, PL2, PL3, PL4, and PL5 during the recording period Tu[5].

[0085] 1.9. Summary of the First Embodiment The first embodiment will be summarized below.

[0086] 1.9.1. Summary of Waveform PH1 and Waveform PH2 As described above, the liquid ejection head HU in the first embodiment has M ejection units D. The ejection units D are provided with a piezoelectric element PZ that is displaced when a drive signal Vin is supplied, a cavity 320 in which the internal pressure increases or decreases according to the displacement of the piezoelectric element PZ, and a nozzle N that communicates with the cavity 320 and is capable of ejecting ink filled inside the cavity 320 as droplets in the -Z direction according to the increase or decrease in the internal pressure of the cavity 320. The liquid ejection head HU executes a driving method having a first step and a second step described below. In the first step, a drive signal Vin1 having a waveform PH1 including drive pulses PL1, PL2, and PL3 having drive components DC1, DC3, and DC5 that reduce the internal pressure of the cavity 320 and drive components DC2, DC4, and DC6 that increase the internal pressure of the cavity 320 is supplied to the piezoelectric element PZ, thereby forming a liquid column LC6 in which the meniscus MS protrudes in the -Z direction. In the second step, when the liquid column LC6 is formed, a drive signal Vin2 having a waveform PH2 including drive pulses PL4, PL5 having drive components DC7, DC9 which reduce the pressure inside the cavity 320 and drive components DC8, DC10 which increase the pressure inside the cavity 320 is supplied to the piezoelectric element PZ, thereby forming a liquid column LC8 with a meniscus MS protruding in the -Z direction, and then ejecting part or all of the ink constituting the liquid column LC8 as a droplet DR. When the drive signal Vin having the waveform PH1 and not the waveform PH2 is supplied to the piezoelectric element PZ, a droplet DR is not ejected from the ejection portion D, and when the drive signal Vin having the waveform PH2 and not the waveform PH1 is supplied to the piezoelectric element PZ, a droplet DR is not ejected from the ejection portion D. Specifically, the drive signal Vin having the waveform PH1 is a drive signal Vin based on an individual designation signal Sd[m] that designates the drive manner α1, the drive manner α3, and the drive manner α4. In the section "Summary of the waveforms PH1 and PH2", the waveform PH1 is an example of the "first waveform". The waveform PH2 is an example of the "second waveform". The liquid column LC6 is an example of the "first liquid column". The liquid column LC8 is an example of the "second liquid column". The drive pulses PL1, PL2, and PL3 are examples of the "first drive pulse", and the drive pulses PL4 and PL5 are examples of the "second drive pulse". The drive components DC1, DC3, and DC5 are examples of the "first drive component that reduces the pressure inside the pressure chamber", the drive components DC2, DC4, and DC6 are examples of the "second drive component that increases the pressure inside the pressure chamber", the drive components DC7 and DC9L are examples of the "third drive component that reduces the pressure inside the pressure chamber", and the drive components DC8 and DC10 are examples of the "fourth drive component that increases the pressure inside the pressure chamber". Here, if the viscosity of the ink is 20 mPascal seconds or more, in the standby state where the ink in the ejection section D is held at a constant negative pressure, there is a possibility that a single drive pulse PL1 cannot eject the droplet DR. In order to eject ink with high viscosity, it is possible to increase the difference between the maximum potential and the minimum potential of the drive signal Vin, but there is a physical limit to this. In addition, it is possible to increase the excluded volume of the cavity 320, but if the capacity of the cavity 320 is increased, the structure of the ejection section D becomes more likely to deform due to the force applied to this structure, that is, the compliance of the flow path in the ejection section D becomes larger. The excluded volume means the amount of change in the volume of the pressure chamber due to the vibration of the vibration plate 310. If the compliance of the flow path in the ejection section D becomes larger, the pressure fluctuation generated by the deformation of the piezoelectric element PZ is more likely to be alleviated by the deformation of the structure of the ejection section D, making it difficult to eject the droplet DR. Furthermore, if the capacity of the cavity 320 is increased, the pressure generated by the deformation of the piezoelectric element PZ is more likely to be absorbed by the compression of the ink, making it difficult to eject the droplet DR. Therefore, according to the first embodiment, when a liquid column LC6 is formed by a drive signal Vin1 having a waveform PH1, by supplying a drive signal Vin having a waveform PH2 to the piezoelectric element PZ, the liquid column formed in the meniscus MS can be grown, and some or all of the ink constituting the liquid column LC8 can be ejected as a droplet DR.

[0087] In addition, when a drive signal Vin having waveform PH2 and not waveform PH1 is supplied to the piezoelectric element PZ, the first decrease amount, which is the amount of fluctuation in the pressure of the ink in the nozzle N toward the negative pressure side when the drive component DC7 of the waveform PH2 contained in the drive signal Vin is supplied to the piezoelectric element PZ, is approximately equal to the second decrease amount, which is the amount of fluctuation in the pressure of the ink in the nozzle N toward the negative pressure side when the drive component DC7 of the waveform PH2 contained in the drive signal Vin is supplied to the piezoelectric element PZ when a drive signal Vin having waveforms PH1 and PH2 is supplied to the piezoelectric element PZ. In addition, when a drive signal Vin having waveform PH2 and not waveform PH1 is supplied to the piezoelectric element PZ, the first increase amount, which is the amount of change in the pressure of the ink in the nozzle N toward the positive pressure side when the drive component DC8 of the waveform PH2 contained in the drive signal Vin is supplied to the piezoelectric element PZ, is approximately equal to the second increase amount, which is the amount of change in the pressure of the ink in the nozzle N toward the positive pressure side when the drive component DC8 of the waveform PH2 contained in the drive signal Vin is supplied to the piezoelectric element PZ when a drive signal Vin having waveforms PH1 and PH2 is supplied to the piezoelectric element PZ. When the viscosity of the ink is high, the residual vibration attenuates quickly. Therefore, after the waveform PH1 is supplied to the piezoelectric element PZ, the residual vibration due to the waveform PH1 attenuates at the time when the waveform PH2 is supplied to the piezoelectric element PZ, and the waveform PH2 cannot be synchronized with the residual vibration due to the waveform PH1 to generate resonance. In the first embodiment, the above-mentioned first decrease amount and the second decrease amount are approximately equal, and further, the first increase amount and the second increase amount are approximately equal, so that the residual vibration due to the waveform PH1 and the pressure vibration generated by the waveform PH2 do not resonate. However, in the first embodiment, in order to eject the droplet DR by forming a liquid column to be formed in the meniscus MS by multiple driving pulses PL, the waveforms PH1 and PH2 are not adjusted so that the waveform PH2 is generated so as to resonate with the residual vibration due to the waveform PH1, but are adjusted so that the meniscus MS is formed by multiple driving pulses PL. Therefore, according to the first embodiment, even if the ink is highly viscous, it is possible to eject a droplet DR by forming a liquid column at the meniscus MS using the waveforms PH1 and PH2.

[0088] When a drive signal Vin1 having a waveform PH1 is followed by a drive signal Vin2 having a waveform PH2 to be supplied to the piezoelectric element PZ, the retraction position Zp4, which is the position of the part of the meniscus MS in the discharge section D that is retracted most in the +Z direction when the drive component DC7 of the waveform PH2 is supplied to the piezoelectric element PZ, is located in the +Z direction further than the retraction position Zp1, which corresponds to the part of the meniscus MS that is retracted most in the +Z direction when the drive component DC7 of the waveform PH2 is supplied to the piezoelectric element PZ when a drive signal Vin having a waveform PH2 is supplied to the piezoelectric element PZ without supplying the drive signal Vin1 having the waveform PH1 to the piezoelectric element PZ. Thus, in the first embodiment, by supplying multiple drive pulses PL to the piezoelectric element PZ, the portion of the meniscus MS that is most drawn in in the +Z direction moves in the -Z direction, and the liquid column formed in the meniscus MS also moves in the -Z direction. As the liquid column moves in the -Z direction, the -Z direction tip of the liquid column moves away from the initial position Z0 in the -Z direction, making it easier for part or all of the liquid column to separate, and the droplet DR that separates from the liquid column can be ejected.

[0089] In the second step, when the tip of the liquid column LC8 is moving in the -Z direction, the drive component DC9 of the drive pulse PL5 of the drive signal Vin is supplied to the piezoelectric element PZ. When the tip of the liquid column LC8 is moving in the -Z direction, a droplet DR is torn off from the liquid column LC9 by supplying a drive signal Vin having a drive component DC9 to the piezoelectric element PZ. According to this embodiment, more stable ejection can be achieved compared to the embodiment in which a drive signal Vin without a drive component DC9 is supplied to the piezoelectric element PZ.

[0090] The waveform PH1 includes drive pulses PL1, PL2, and PL3. The drive pulse PL1 includes drive components DC1 and DC2. The drive pulse PL2 includes drive components DC3 and DC4. The drive pulse PL3 includes drive components DC5 and DC6. 8 to 17, as shown by the behavior of the meniscus MS when the drive signal Vin based on the individual designation signal Sd[m] designating the drive mode α1 is supplied to the piezoelectric element PZ, with high viscosity ink, only one drive pulse PL cannot generate pressure fluctuations in the discharge section D sufficient to discharge a droplet DR from the nozzle N. In other words, by continuously supplying multiple drive pulses PL to the piezoelectric element PZ and repeatedly decreasing and increasing the pressure inside the cavity 320, a liquid column is formed in the meniscus MS, which then grows, and part or all of the liquid column can be ejected in the -Z direction from the nozzle N as a droplet DR. In this embodiment, the waveform PH1 has three drive pulses PL, so even if a droplet DR cannot be ejected with one drive pulse PL, by supplying a drive signal Vin having a waveform PH1 having two or three drive pulses PL to the piezoelectric element PZ, the liquid column formed in the meniscus MS can be grown, and part or all of the ink that constitutes the liquid column LC8 can be ejected as a droplet DR by the waveform PH2. As explained with reference to Figures 21 and 22, if a specified recording period Tux preceding a recording period Tu[j] is a non-ejection recording period Tu-N, a drive pulse PL2 and a drive pulse PL3, or a drive signal Vin including drive pulses PL1, PL2, and PL3, are supplied to the piezoelectric element PZ in the recording period Tu[j] so that a droplet DR is ejected from the ejection section D after the drive component DC8 of the waveform PH2 is supplied to the piezoelectric element PZ in the recording period Tu[j].

[0091] Furthermore, the viscosity of the ink in the liquid ejection head HU is 20 mPascal-second or more, and preferably 40 mPascal-second. If the viscosity of the ink is 20 mPascal-second or more, there is a possibility that the droplets DR cannot be ejected by only one driving pulse PL4 of the waveform PH2, but by using the driving method according to the present embodiment, which has the waveform PH1 before the waveform PH2, the droplets DR can be ejected even from ink having a viscosity of 20 mPascal-second or more.

[0092] The difference between the maximum and minimum potentials in the waveform PH1 is approximately equal to the difference between the maximum and minimum potentials in the waveform PH2. More specifically, the minimum potential in the waveform PH1 and the minimum potential in the waveform PH2 are approximately equal at potential VL1, and the maximum potential in the waveform PH1 and the maximum potential in the waveform PH2 are approximately equal at reference potential V0. By setting the maximum potential achievable in the inkjet printer 1 to the maximum potential of the waveforms PH1 and PH2, and setting the minimum potential achievable in the inkjet printer 1 to the minimum potential of the waveforms PH1 and PH2, it is possible to grow a liquid column at the meniscus MS by the waveform PH1, and to eject a droplet DR by the waveform PH2, even with high-viscosity ink.

[0093] 1.9.2. Summary of appropriate conditions for drive waveform signal Com As described above, the liquid ejection head HU in the first embodiment executes a driving method having the first and second steps described above. The waveform PH1 has three driving pulses PL having driving components DC1, DC3, DC5 that reduce the pressure inside the cavity 320 and driving components DC2, DC4, DC6 that increase the pressure inside the cavity 320. The waveform PH2 has two driving pulses PL having driving components DC7, DC9 that reduce the pressure inside the cavity 320 and driving components DC8, DC10 that increase the pressure inside the cavity 320. The waveform PH2 starts at the end of the waveform PH1. The period Pw68, which is the interval between the rearmost driving pulse PL3 of the driving pulses PL of the waveform PH1 and the frontmost driving pulse PL4 of the driving pulses PL of the waveform PH2, is equal to or greater than one time and equal to or less than two times the natural vibration period TC of the ejection section D. The period Pw68 is the period from the time tDC6 when the supply of the drive component DC6 of the last drive pulse PL3 of the three drive pulses PL of the waveform PH1 begins to the time tDC8 when the supply of the drive component DC8 of the first drive pulse PL4 of the two drive pulses PL of the waveform PH2 begins. By having the period Pw68 be greater than or equal to 1 and less than or equal to 2 times the natural vibration period TC, the discharge performance value can be increased compared to the case where the period Pw68 is less than 1 time the natural vibration period TC and the case where the period Pw68 is more than twice the natural vibration period TC. The drive pulses PL1, PL2, and PL3 of the waveform PH1 are examples of a "first drive pulse." The drive components DC1, DC3, and DC5 are examples of a "first drive component." The drive components DC2, DC4, and DC6 are examples of a "second drive component." The drive pulses PL4 and PL5 of the waveform PH2 are examples of a "second drive pulse." The drive components DC7 and DC9 are examples of a "third drive component." The drive components DC8 and DC10 are examples of a "fourth drive component." Period Pw68 corresponds to the "first period."

[0094] Furthermore, the period Pw68 is 1.2 times or more and 1.6 times or less than the natural vibration period TC. By having the period Pw68 be 1.2 times or more and 1.6 times or less than the natural vibration period TC, the discharge performance value can be increased compared to the case where the period Pw68 is less than 1.2 times the natural vibration period TC and the case where the period Pw68 is more than 1.6 times the natural vibration period TC.

[0095] Furthermore, periods Pw24 and Pw46, which are the intervals between the pulses of drive pulses PL1 to PL3 of waveform PH1, are greater than or equal to one and less than or equal to two times the natural vibration period TC. Period Pw24 is the period from time tDC2 when supply of drive component DC2 of drive pulse PL1 of the three drive pulses PL of waveform PH1 begins to time tDC4 when supply of drive component DC4 of drive pulse PL2 next to drive pulse PL1 begins to time tDC4 when supply of drive component DC4 of drive pulse PL2 of the three drive pulses PL of waveform PH1 begins to time tDC6 when supply of drive component DC6 of drive pulse PL3 next to drive pulse PL2 begins. By the periods Pw24 and Pw46 being greater than or equal to 1 and less than or equal to 2 times the natural vibration period TC, the discharge performance value can be increased compared to the case where the periods Pw24 and Pw46 are less than 1 time the natural vibration period TC, and the case where the periods Pw24 and Pw46 are greater than 2 times the natural vibration period TC. It should be noted that periods Pw24 and Pw46 are examples of a "second period." When period Pw24 is an example of a "second period," drive pulse PL1 corresponds to a "first drive pulse," and drive pulse PL2 corresponds to a "first drive pulse following the first drive pulse." When period Pw46 is an example of a "second period," drive pulse PL2 corresponds to a "first drive pulse," and drive pulse PL3 corresponds to a "first drive pulse following the first drive pulse."

[0096] Furthermore, the periods Pw24 and Pw46 are 1.2 times or more and 1.6 times or less than the natural vibration period TC. By having the periods Pw24 and Pw46 be 1.2 times or more and 1.6 times or less than the natural vibration period TC, the discharge performance value can be increased compared to the case where the periods Pw24 and Pw46 are less than 1.2 times the natural vibration period TC and the case where the periods Pw24 and Pw46 are more than 1.6 times the natural vibration period TC.

[0097] 1.9.3. Summary of recording method using driving waveform signal Com As described above, the liquid ejection head HU in the first embodiment has M ejection units D. The ejection units D include a piezoelectric element PZ, a cavity 320, and a nozzle N. The piezoelectric element PZ is displaced in response to a drive signal Vin including a drive signal Vin1 and a drive signal Vin2 supplied in each of a plurality of recording periods Tu including a recording period Tu[j]. The control unit 6 executes a recording method having a first step. In the first step, when ejecting droplets from the nozzle N in the recording period Tu[j], the waveform of the drive signal Vin supplied to the piezoelectric element PZ in the recording period Tu[j] is determined based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ in the recording periods Tu[j-1] to Tu[j-3], which are the recording periods Tu preceding the recording period Tu[j]. When the drive signal Vin having a waveform determined in the first step has a waveform PH1 in the drive signal Vin1 and a waveform PH2 in the drive signal Vin2, in the recording period Tu[j], the drive signal Vin1 is supplied to the piezoelectric element PZ to form a liquid column LC6 with the meniscus MS protruding in the -Z direction, and when the liquid column LC6 is formed, the drive signal Vin2 is supplied to the piezoelectric element PZ to form a liquid column LC8 with the meniscus MS protruding in the -Z direction, and then some or all of the ink constituting the liquid column LC8 is ejected as droplets. For example, when the ejection section D is in a stationary state and a drive signal Vin based on an individual designation signal Sd[m] specifying the drive mode α1 is supplied to the piezoelectric element PZ, if the ink has a viscosity such that a droplet DR is ejected at the timing when the waveform PH2 is supplied, and after the droplet DR is ejected during the recording period Tu[j-1] preceding the recording period Tu[j], if a drive signal Vin based on the individual designation signal Sd[m] specifying the drive mode α1 is supplied to the piezoelectric element PZ during the recording period Tu[j], the droplet DR will be ejected at a time other than the timing when it should be ejected, for example when the waveform PH1 is being supplied, which may result in a deterioration in print quality. The state of the meniscus MS at the start of the recording period Tu[j] can be estimated from the waveform of the drive signal Vin supplied to the piezoelectric element PZ in a predetermined recording period Tux preceding the recording period Tu[j]. Therefore, by determining the waveform of the drive signal Vin supplied to the piezoelectric element PZ in the recording period Tu[j] based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ in the recording period Tu[j], the droplets DR can be ejected closer to the timing at which they should originally be ejected, thereby suppressing deterioration of print quality. The recording period Tu[j] is an example of a "first recording period", and a predetermined recording period Tux preceding the recording period Tu[j] used to determine the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j], in this embodiment, the recording periods Tu[j-1] to Tu[j-3] are examples of a "predetermined recording period preceding the first recording period".

[0098] The predetermined recording period Tux preceding the recording period Tu[j] used to determine the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j] includes a recording period Tu[j-1] that ends at the start of the recording period Tu[j]. Of the two or more recording periods Tu that end before the start of the recording period Tu[j], the waveform that has the greatest effect on the meniscus MS at the start of the recording period Tu[j] is the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j-1]. Therefore, by determining the individual designation signal Sd[m] for the recording period Tu[j] based on the individual designation signal Sd[m] for a predetermined recording period Tux that precedes the recording period Tu[j] including the recording period Tu[j-1], deterioration of print quality can be further suppressed compared to a configuration in which the individual designation signal Sd[m] for the recording period Tu[j] is determined based on the individual designation signal Sd[m] for a predetermined recording period Tu that precedes the recording period Tu[j] that does not include the recording period Tu[j-1]. The recording period Tu[j-1] is an example of a "second recording period."

[0099] In the first step of the section "Summary of the recording method using the drive waveform signal Com", the predetermined recording period Tux preceding the recording period Tu[j] and used to determine the drive signal Vin supplied to the piezoelectric element PZ in the recording period Tu[j] includes the recording period [j-1] and includes consecutive recording periods Tu[j-1] to Tu[j-3] that end before the start of the recording period Tu[j]. The waveform of the drive signal Vin supplied to the piezoelectric element PZ in the recording period Tu[j-1] has the greatest effect on the meniscus MS at the start of the recording period Tu[j], but the waveform of the drive signal Vin supplied to the piezoelectric element PZ in the recording period Tu prior to the recording period Tu[j-1] also affects the meniscus MS at the start of the recording period Tu[j]. Therefore, according to this embodiment, the state of the meniscus MS at the start of the recording period Tu[j] can be estimated more accurately than in a mode in which the waveform of the drive signal Vin supplied to the piezoelectric element PZ in the recording period Tu[j] is determined based only on the waveform of the drive signal Vin supplied to the piezoelectric element PZ in the recording period Tu[j-1], and therefore deterioration of print quality can be more effectively suppressed. Note that the recording periods Tu[j-1] to Tu[j-3] are an example of "two or more consecutive recording periods that include the second recording period and end before the start of the first recording period".

[0100] The first step in the section “Summary of the recording method using the drive waveform signal Com” is to determine the waveform of the drive signal Vin1 supplied to the piezoelectric element PZ in the recording period Tu[j] based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ in a predetermined recording period Tux preceding the recording period Tu[j]. By adjusting the waveform of the drive signal Vin1, the droplets DR can be ejected closer to the timing at which they should originally be ejected, so that deterioration of print quality can be further suppressed.

[0101] In addition, the first step in the section "Summary of the recording method using the drive waveform signal Com" determines whether or not the waveform PH1 is included in the drive signal Vin1 supplied to the piezoelectric element PZ in the recording period Tu[j], based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ in a predetermined recording period Tux preceding the recording period Tu[j], which is used to determine the drive signal Vin supplied to the piezoelectric element PZ in the recording period Tu[j]. In addition, the first step in the section "Summary of the recording method using the drive waveform signal Com" is to determine the drive signal Vin to be supplied to the piezoelectric element PZ in the recording period Tu[j]. If it is determined that the drive signal Vin1 to be supplied to the piezoelectric element PZ in the recording period Tu[j] includes a waveform PH1 based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ in a predetermined recording period Tux preceding the recording period Tu[j], the number of drive pulses PL to be included in the waveform PH1 is further determined. The embodiment in which the number of drive pulses PL included in the drive signal Vin1 is adjusted can be realized with an easier configuration than the embodiment in which the minimum and maximum potentials of the drive pulses PL included in the drive signal Vin1 are adjusted. The embodiment in which the minimum and maximum potentials of the drive pulses PL are adjusted can be realized, for example, with the following configuration. The drive waveform signal generating circuit 2 generates a first drive waveform signal Com-A and a second drive waveform signal Com-B. The difference between the minimum and maximum potentials of the drive pulses PL corresponding to the drive signal Vin1 of the first drive waveform signal Com-A is larger than the difference between the minimum and maximum potentials of the drive pulses PL corresponding to the drive signal Vin1 of the second drive waveform signal Com-B. The switching circuit 10 supplies one of the first drive waveform signal Com-A and the second drive waveform signal Com-B to the piezoelectric element PZ. However, in the above configuration, if the number of types of the drive waveform signal Com is increased, the drive waveform generating circuit becomes larger, and the configuration becomes more complicated compared to the embodiment. Furthermore, although there is a limit to the minimum and maximum potentials that can be supplied to the piezoelectric element PZ in the inkjet printer 1, as described above, by supplying multiple drive pulses PL to the piezoelectric element PZ, the pressure inside the cavity 320 can be repeatedly decreased and increased, thereby causing even highly viscous ink to grow a liquid column and be ejected as a droplet DR. Therefore, according to this embodiment, compared to the aspect of adjusting the minimum and maximum potentials of the drive pulse PL contained in the drive signal Vin1, a waveform of the drive signal Vin1 that matches the state of the meniscus MS at the start of the recording period Tu[j] can be generated with a simpler configuration.

[0102] The predetermined recording period Tux preceding the recording period Tu[j] used to determine the drive signal Vin supplied to the piezoelectric element PZ in the recording period Tu[j] includes the recording period Tu[j-1]. The first step of the "Summary of the recording method using the drive waveform signal Com" section determines the waveform of the drive signal Vin1 supplied to the piezoelectric element PZ in the recording period Tu[j] such that the first number of drive pulses PL contained in the drive signal Vin1 supplied to the piezoelectric element PZ in the recording period Tu[j] when the discharge section D does not discharge the droplets DR in the recording period Tu[j-1] is greater than the second number of drive pulses contained in the drive signal Vin1 supplied to the piezoelectric element PZ in the recording period Tu[j] when the discharge section D discharges the droplets DR in the recording period Tu[j-1]. In the first situation where the recording period Tu[j-1] is the non-ejection recording period Tu-N, the liquid column formed in the meniscus MS at the start of the recording period Tu[j] is smaller than the liquid column formed in the meniscus MS at the start of the recording period Tu[j] in the second situation where the recording period Tu[j-1] is the ejection recording period Tu-D. Therefore, in order to eject the droplets DR at the timing when they should be ejected in the first situation, it is necessary to supply the piezoelectric element PZ with a driving signal Vin1 having more driving pulses PL than in the second situation. Therefore, by determining the waveform of the driving signal Vin1 supplied to the piezoelectric element PZ in the recording period Tu[j] so that the first number is greater than the second number, the droplets DR can be ejected at the timing when they should be ejected.

[0103] When droplets are ejected from the nozzle N during the recording period Tu[j], the drive signal Vin2 in the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j] has a predetermined waveform PH2, regardless of the waveform of the drive signal Vin supplied to the piezoelectric element PZ during a predetermined recording period Tux preceding the recording period Tu[j], which is used to determine the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j]. Therefore, when generating a drive signal Vin that matches the state of the meniscus MS at the start of the recording period Tu[j], it is only necessary to adjust the waveform of the drive signal Vin1, and there is no need to adjust the waveform of the drive signal Vin2.

[0104] 1.9.4. Summary of the relationship between the drive signal Vin and the meniscus MS As described above, the liquid ejection head HU can be said to execute a driving method having a first step and a second step described below. In the first step, a driving signal having a waveform PH1 is supplied to the piezoelectric element PZ to form a liquid column LC6 with a meniscus MS protruding in the ejection direction. In the second step, when the liquid column LC6 is formed, a driving signal having a waveform PH2 is supplied to the piezoelectric element PZ to form a liquid column LC8 with a meniscus MS protruding in the -Z direction, and then a part or all of the ink constituting the liquid column LC8 is ejected as a droplet DR. The waveform PH2 includes a driving component DC7 that reduces the pressure inside the cavity 320 and a driving component DC8 that increases the pressure inside the cavity 320. In the second step, before the liquid column LC8 is formed, the driving component DC7 is supplied to the piezoelectric element PZ to form a liquid column LC7 with a meniscus MS protruding in the -Z direction. In the second step, when the liquid column LC7 is formed, the driving component DC8 is supplied to the piezoelectric element PZ to form the liquid column LC8. According to the first embodiment, when a liquid column LC6 is formed, the liquid column to be formed into a meniscus MS can be grown by supplying a drive signal Vin having a drive component DC7 to the piezoelectric element PZ, and further, when a liquid column LC7 is formed, a part or all of the ink constituting the liquid column LC8 can be ejected as a droplet DR by supplying a drive signal Vin having a drive component DC8 to the piezoelectric element PZ. In addition, in the section "Summary of the relationship between the drive signal Vin and the meniscus MS", waveform PH1 is an example of a "first waveform". Waveform PH2 is an example of a "second waveform". Drive component DC7 is an example of a "first pull-in drive component". Drive component DC8 is an example of a "first push-in drive component". Liquid column LC6 is an example of a "first liquid column". Liquid column LC7 is an example of a "third liquid column". Liquid column LC8 is an example of a "second liquid column".

[0105] The waveform PH1 has three drive pulses PL having a first drive component that reduces the pressure inside the cavity 320 and a second drive component that increases the pressure inside the cavity 320. In the first step of the section "Summary of the relationship between the drive signal Vin and the meniscus MS", when a drive signal having a drive component DC1 of the front drive pulse PL1 of the three drive pulses PL of the waveform PH1 is supplied to the piezoelectric element PZ, the liquid surface having a concave curved shape in the discharge portion D is pulled in toward the +Z direction, and when a drive signal having a drive component DC5 of the rearmost drive pulse PL3 of the three drive pulses PL of the waveform PH1 is supplied to the piezoelectric element PZ, the meniscus MS that forms the liquid column LC5 protruding in the -Z direction is pulled in toward the +Z direction. According to the first embodiment, when a drive signal having drive component DC1 of the first drive pulse PL1 of waveform PH1 is supplied to piezoelectric element PZ, no liquid column is generated in the meniscus MS, and the central portion of the meniscus MS has a concave curved shape recessed in the +Z direction. However, by supplying drive component DC2 of drive pulse PL1 and drive components DC3 and DC4 of drive pulse PL2 to piezoelectric element PZ, and by supplying drive component DC5 of drive pulse PL3 to piezoelectric element PZ, a liquid column LC5 can be formed in the central portion of the meniscus MS. In the section "Summary of the relationship between the drive signal Vin and the meniscus MS", the drive components DC1, DC3, and DC5 are an example of the "first drive component". The drive components DC2, DC4, and DC6 are an example of the "second drive component". The meniscus MS that forms the liquid column LC5 is an example of "a liquid surface that protrudes in the ejection direction by supplying the first drive component of the latest drive pulse among the multiple drive pulses of the first waveform to the drive element".

[0106] The first step in the section "Summary of the relationship between drive signal Vin and meniscus MS" is to draw in the meniscus MS, which has formed liquid column LC3, in the +Z direction by supplying to piezoelectric element PZ a drive signal having drive component DC3 of drive pulse PL2 between the earliest drive pulse PL1 and the latest drive pulse PL3 of the three drive pulses PL of waveform PH1. The liquid column LC3 due to drive component DC3 of drive pulse PL2 is smaller than the liquid column LC6 due to drive component DC5 of drive pulse PL3. In this way, by repeatedly supplying the drive pulse PL to the piezoelectric element PZ, the liquid column can be gradually grown larger. By growing the liquid column larger, even if the ink is highly viscous, a droplet DR can be ejected when the waveform PH2 is supplied to the piezoelectric element PZ. The liquid column LC3 is an example of the "fourth liquid column."

[0107] 2. Variations Each of the above embodiments may be modified in various ways. Specific modified embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples may be appropriately combined within a range that does not contradict each other. In the modified examples exemplified below, the elements whose actions and functions are equivalent to those of the embodiment will be appropriately omitted by using the symbols referenced in the above explanation.

[0108] 2.1. First modified example In the first embodiment, when the recording period Tu[j] is the non-ejection recording period Tu-N, the control unit 6 generates an individual designation signal Sd[m] for the drive mode α5, but may also generate an individual designation signal Sd[m] for a drive mode other than the drive mode α5.

[0109] FIG. 24 is a diagram for explaining five drive modes that the individual designation signal Sd[m] can take in the first modified example. In the first modified example, the individual designation signal Sd[m] is a signal that designates one of the five drive modes, namely, the drive mode α1 to the drive mode α4 and the drive mode α6. The individual designation signal Sd[m] of the drive mode α6 is generated when the ejection section D[m] is not caused to eject droplets. That is, in the first modified example, when the ejection section D[m] is not caused to eject droplets, the control section 6 generates the individual designation signal Sd[m] of the drive mode α6 instead of the individual designation signal Sd[m] of the drive mode α5, which is different from the first embodiment. The value indicating the individual designation signal Sd[m] of the drive mode α6 is (0,0,0,1,0). When the individual designation signal Sd[m] indicates the driving mode α6, the connection state designation circuit 11 sets the connection state designation signal SLa[m] to a low level in the control period Tcu1, the control period Tcu2, the control period Tcu3, and the control period Tcu5, and sets the connection state designation signal SLa[m] to a high level in the control period Tcu4.

[0110] Fig. 25 is a diagram showing a specific example of a recording method using the driving waveform signal Com in the first modified example. Compared with Fig. 23 shown in the first embodiment, in the first modified example, the individual designation signal Sd[m] in the recording period Tu in which the droplets DR are not ejected is replaced from the driving mode α5 to the driving mode α6. More specifically, the individual designation signal Sd[m] in the recording period Tu[2] shown in the second row of Fig. 25, the recording period Tu[2] and the recording period Tu[3] shown in the third row of Fig. 25, and the recording period Tu[2], the recording period Tu[3], and the recording period Tu[4] shown in the fourth row of Fig. 25 are replaced from the driving mode α5 to the driving mode α6.

[0111] According to the first modified example, even during a recording period Tu[j] that is a non-ejection recording period Tu-N, a driving pulse PL that does not eject droplets DR is supplied to the piezoelectric element PZ, so that a liquid column can be maintained in the meniscus MS at the start of the next recording period Tu[j+1] after the non-ejection recording period Tu-N, or a liquid column can be easily formed in the recording period Tu[j]. When this next recording period Tu[j+1] is an ejection recording period Tu-D, the fluctuation of the meniscus MS during the recording period Tu[j-1] can be utilized.

[0112] In the first modified example, the drive signal Vin2 having the drive pulse PL4 is selected as the drive pulse PL to be supplied to the piezoelectric element PZ as the drive pulse PL that does not eject the droplet DR in the non-ejection recording period Tu-N, but the selected drive pulse PL is not limited to this. For example, any one of the drive pulses PL1, PL2, PL3, PL4, and PL5 may be selected, or multiple drive pulses PL may be selected. However, it is preferable that the drive pulse PL selected in the recording period Tu[j], which is the non-ejection recording period Tu-N, is close to the drive pulse PL4 of the next recording period [j+1]. When the next recording period Tu[j+1] is the ejection recording period Tu-D, by selecting a drive pulse PL close to the drive pulse PL4 included in the waveform PH2, which is the ejection timing of the droplet DR in the recording period Tu[j+1], for the drive signal Vin of the recording period Tu[j], which is the non-ejection recording period Tu-N, the interval between the drive pulse PL selected in the recording period Tu[j] and the drive pulse PL selected in the recording period Tu[j+1] becomes shorter, and it becomes more likely that the liquid column formed in the meniscus MS in the recording period Tu[j], or the fluctuation of the meniscus MS, can be utilized in the recording period Tu[j+1]. Furthermore, when the recording period Tu[j-1] immediately preceding the recording period Tu[j] which is the non-ejection recording period Tu-N is the ejection recording period Tu-D, by selecting a drive pulse PL away from the drive pulse PL4 contained in the waveform PH2, which is the ejection timing of the droplet DR in the recording period Tu[j-1], as the drive signal Vin for the recording period Tu[j], it is possible to prevent the droplet DR from being ejected in the recording period Tu[j-1] due to fluctuations in the liquid column or meniscus MS formed after the droplet DR is ejected.

[0113] Furthermore, when droplets are not ejected from the nozzle N during the recording period Tu[j], a drive signal Vin having at least one of a waveform PH1 including at least one of drive pulses PL1, PL2, and PL3, and a waveform PH2 including at least one of drive pulses PL4 and PL5 is supplied to the piezoelectric element PZ so as to increase or decrease the pressure of the ink inside the cavity 320 to an extent that droplets are not ejected from the nozzle N during the recording period Tu[j]. By the above process, even during the recording period Tu[j] when droplets are not ejected from the nozzle N, the drive signal Vin having at least one of the waveforms PH1 and PH2 is supplied to the piezoelectric element PZ to the ink in the ejection portion D, thereby maintaining the vibration of the ink in the ejection portion D during the recording period Tu[j] and utilizing the vibration during the recording period Tu[j+1]. In addition, when droplets DR are discharged from nozzle N in recording period Tu[j+1], if vibration is applied in recording period Tu[j] by waveform PH2 closer to recording period Tu[j+1], it can be used in recording period Tu[j+1] before the vibration applied in recording period Tu[j] becomes smaller than when vibration is applied only by waveform PH1 in recording period Tu[j]. Also, when droplets DR are discharged from nozzle N in recording period Tu[j-1], it is more effective to prevent discharge in recording period Tu[j] by supplying drive signal Vin that does not include waveform PH1 closer to recording period Tu[j+1] in recording period Tu[j].

[0114] 2.2. Second variant In the first embodiment and the first modified example, when the recording period Tu[j] is a non-ejection recording period Tu-N, the control unit 6 always generates an individual designation signal Sd[m] of the same driving mode, but may generate individual designation signals Sd[m] of different driving modes between multiple non-ejection recording periods Tu-N.

[0115] FIG. 26 is a diagram for explaining six possible drive modes of the individual designation signal Sd[m] in the second modified example. In the second modified example, the individual designation signal Sd[m] is a signal that designates one of the six drive modes, namely, the drive mode α1 to the drive mode α4, the drive mode α7, and the drive mode α8. The individual designation signal Sd[m] of the drive mode α7 and the individual designation signal Sd[m] of the drive mode α8 are generated when the ejection section D[m] is not caused to eject droplets. That is, in the second modified example, when the ejection section D[m] is not caused to eject droplets, the control section 6 generates the individual designation signal Sd[m] of the drive mode α7 or the individual designation signal Sd[m] of the drive mode α8 instead of the individual designation signal Sd[m] of the drive mode α5, which is different from the first embodiment.

[0116] The value indicating the individual designation signal Sd[m] of the driving mode α7 is (0,1,0,0,0). When the individual designation signal Sd[m] indicates the driving mode α7, the connection state designation circuit 11 sets the connection state designation signal SLa[m] to a low level in the control period Tcu1, the control period Tcu3, the control period Tcu4, and the control period Tcu5, and sets the connection state designation signal SLa[m] to a high level in the control period Tcu2. The value indicating the individual designation signal Sd[m] of the driving mode α8 is (1,0,1,0,0). When the individual designation signal Sd[m] indicates the driving mode α8, the connection state designation circuit 11 sets the connection state designation signal SLa[m] to a low level in the control period Tcu2, the control period Tcu4, and the control period Tcu5, and sets the connection state designation signal SLa[m] to a high level in the control period Tcu1 and the control period Tcu3.

[0117] In the second modified example, regarding whether to generate the individual designation signal Sd[m] of the driving mode α7 or the individual designation signal Sd[m] of the driving mode α8, a situation is assumed in which there are consecutive non-ejection recording periods Tu-N. The control unit 6 generates the individual designation signal Sd[m] of the driving mode α7 in the k-th non-ejection recording period Tu-N among the consecutive non-ejection recording periods Tu-N, and generates the individual designation signal Sd[m] of the driving mode α8 in the k+1-th non-ejection recording period Tu-N. The variable k is an integer from 1 to the consecutive non-ejection recording periods Tu-N.

[0118] 27 is a diagram showing a specific example of a recording method using the driving waveform signal Com in the second modified example. Compared with FIG. 23 shown in the first embodiment, in the second modified example, the individual designation signal Sd[m] in the recording period Tu in which the droplets DR are not discharged is replaced from the driving mode α5 to the driving mode α7 or the driving mode α8. More specifically, the individual designation signal Sd[m] in the recording period Tu[2] shown in the second row of FIG. 27, the recording period Tu[2] shown in the third row of FIG. 27, and the recording period Tu[2] and the recording period Tu[4] shown in the fourth row of FIG. 27 are replaced from the driving mode α5 to the driving mode α7, and the individual designation signal Sd[m] in the recording period Tu[3] shown in the third row of FIG. 27 and the recording period Tu[3] shown in the fourth row of FIG. 27 are replaced from the driving mode α5 to the driving mode α8. Alternatively, the control unit 6 may select one of the driving modes α5 to α8 for the individual designation signal Sd[m] in the non-ejection recording period Tu-N. Furthermore, the driving signal Vin supplied to the non-ejection recording period Tu-N may include one or more driving pulses PL from the driving pulses PL1 to PL4.

[0119] As shown in a second modified example, the control unit 6 may adjust the number of drive pulses PL supplied during the non-ejection recording period Tu-N to the extent that no droplets DR are ejected during the non-ejection recording period Tu-N. Regarding the specific number of drive pulses PL, the designer of the inkjet printer 1 identifies the relationship between the viscosity and the number of drive pulses PL through experiments, and stores in the storage unit 5 a table showing the relationship between the viscosity of the ink and the number of drive pulses PL, or a formula for calculating the number of drive pulses PL from the viscosity of the ink.

[0120] As a modification of the second modification, the control unit 6 may change the driving pulse PL supplied to the non-ejection recording period Tu-N to such an extent that the droplets DR are not ejected during the non-ejection recording period Tu-N. For example, the control unit 6 may generate an individual designation signal Sd[m] for generating a driving signal Vin having only a driving pulse PL3 during the k-th non-ejection recording period Tu-N among the consecutive non-ejection recording periods Tu-N, and may generate an individual designation signal Sd[m] for generating a driving signal Vin having only a driving pulse PL4 during the k+1-th non-ejection recording period Tu-N. The variable k is an integer ranging from 1 to the consecutive non-ejection recording periods Tu-N.

[0121] 2.3.Third Modification In the first embodiment, the first modified example, and the second modified example, the viscosity of the ink was such that when the ejection section D was in a stationary state with a reference potential V0 supplied to the piezoelectric element PZ and the position of the meniscus MS was stationary at the initial position Z0, if a drive signal Vin based on an individual designation signal Sd[m] of the drive mode α1 was supplied to the piezoelectric element PZ within one recording period Tu[i], a droplet DR could be ejected within one recording period Tu[i]. However, there are also cases where the viscosity of the ink is so high that ink cannot be ejected within one recording period Tu[i], even if a drive signal Vin based on an individual designation signal Sd[m] of the drive mode α1 is supplied to the piezoelectric element PZ within the recording period Tu[i]. In the third variant, when the printing process starts from the recording period Tu[1], a drive signal that generates non-printing micro-vibrations is supplied to the piezoelectric element PZ immediately before the recording period Tu[1], thereby making it possible to eject a droplet DR during the recording period Tu[1], and thereafter, it is possible to eject a droplet DR during the recording period Tu[j] by utilizing the liquid column formed in the meniscus MS during the recording period Tu[j-1] or the fluctuation of the meniscus MS.

[0122] FIG. 28 is a diagram for explaining the drive signal Vin when droplets DR are discharged in the third modified example. The discharge mode shown in the first row of FIG. 28 is a mode in which droplets DR are discharged in the first recording period Tu[1] of the printing process and the subsequent recording period Tu[2]. In the period Tbu immediately before the recording period Tu[1], the control unit 6 supplies the drive signal Vin that generates non-printing micro-vibrations to the piezoelectric element PZ. As a result, the discharge unit D[m] is supplied with the drive signal Vin that generates non-printing micro-vibrations in the period Tbu. The drive signal Vin that generates non-printing micro-vibrations includes a waveform including a plurality of pulses including a drive component that reduces the pressure inside the cavity 320 and a drive component that increases the pressure inside the cavity 320. During the recording period Tu[1], the control unit 6 generates an individual designation signal Sd[m] of the driving mode α1 and outputs the generated individual designation signal Sd[m] to the switching circuit 10. As a result, the discharge unit D[m] is supplied with the drive signal Vin having drive pulses PL1, PL2, PL3, PL4, and PL5 during the recording period Tu[1]. At the start of the recording period Tu[1], a liquid column is formed in the meniscus MS due to the non-printing micro-vibration, or the meniscus MS is fluctuating, so the discharge unit D can discharge droplets DR during the recording period Tu[1]. For the recording period Tu[2], the control unit 6 generates an individual designation signal Sd[m] of the driving mode α2 and outputs the generated individual designation signal Sd[m] to the switching circuit 10. As a result, the discharge unit D[m] is supplied with the drive signal Vin having drive pulses PL4 and PL5 during the recording period Tu[2]. By supplying the drive signal Vin having drive pulses PL1, PL2, PL3, PL4 and PL5 during the recording period Tu[1], a liquid column is formed in the meniscus MS at the start of the recording period Tu[2], or the meniscus MS is fluctuating, so that the discharge unit D can discharge droplets DR during the recording period Tu[1].

[0123] The ejection mode shown in the second row of Fig. 28 is an ejection mode in which droplets DR are ejected during the recording period Tu[1] and the recording period Tu[3], and droplets DR are not ejected during the recording period Tu[2]. The period Tbu and the recording period Tu[1] are the same as the period Tbu and the recording period Tu[1] shown in the first row of Fig. 28, and therefore a description thereof will be omitted. Since the recording period Tu[2] is a non-ejection recording period Tu-N, a drive signal Vin including a drive pulse PL that does not eject droplets DR, for example, a drive signal Vin having drive pulses PL2 and PL3, is supplied. With respect to the recording period Tu[3], since the preceding predetermined recording period Tux is a non-ejection recording period Tu-N, a drive signal Vin having more drive pulses PL, for example, a drive signal Vin having drive pulses PL3, PL4 and PL5, is supplied compared to the case of the recording period Tu[2] in which the immediately preceding recording period Tu[1] was an ejection recording period Tu-D shown in the first row of Fig. 28. By supplying the drive signal Vin having drive pulses PL2 and PL3 to the recording period Tu[2], a liquid column is formed in the meniscus MS at the start of the recording period Tu[3], or the meniscus MS is fluctuating, so that the ejection section D can eject droplets DR in the recording period Tu[3]. In the third modified example, in the first recording period Tu[1] of the printing process, the non-printing micro-vibration and the waveform PH1 included in the driving signal Vin in the recording period Tu[1] are another example of the "first waveform" described in the above-mentioned embodiment and modified example, and the waveform PH2 included in the driving signal Vin in the recording period Tu[1] is another example of the "second waveform" described in the above-mentioned embodiment and modified example. In addition, in the recording period Tu after the first recording period Tu[1] of the printing process, the driving signal Vin in the recording period Tu[j-1] and the waveform PH1 included in the driving signal Vin in the recording period Tu[j] are another example of the "first waveform" described in the above-mentioned embodiment and modified example, and the waveform PH2 included in the driving signal Vin in the recording period Tu[j] is another example of the "second waveform" described in the above-mentioned embodiment and modified example. In addition, in the first recording period Tu[1] of the printing process, the multiple pulses included in the driving signal Vin that generates the non-printing micro-vibration and the driving pulse PL included in the waveform PH1 included in the driving signal Vin in the recording period Tu[1] are another example of the "first driving pulse" described in the above-mentioned embodiment and modified example, and the driving pulse PL included in the waveform PH2 included in the driving signal Vin in the recording period Tu[1] is another example of the "second driving pulse" described in the above-mentioned embodiment and modified example. In addition, in the recording period Tu after the first recording period Tu[1] of the printing process, the driving pulse PL included in the driving signal Vin in the recording period Tu[j-1] and the driving pulse PL included in the waveform PH1 included in the driving signal Vin in the recording period Tu[j] are another example of the "first driving pulse" described in the above-mentioned embodiment and modified example, and the driving pulse PL of the waveform PH2 included in the driving signal Vin in the recording period Tu[j] is another example of the "second waveform" described in the above-mentioned embodiment and modified example.

[0124] 2.4. Fourth Variation In the third modified example, when the ink viscosity is high enough that ink cannot be ejected within one recording period Tu[i] even if the driving signal Vin based on the individual designation signal Sd[m] of the driving mode α1 is supplied to the piezoelectric element PZ during the recording period Tu[i], a driving signal that generates a non-printing micro vibration is supplied to the piezoelectric element PZ immediately before the first recording period Tu[1] of the print process to eject a droplet DR during the recording period Tu[1], but this is not limited to the above. In the fourth modified example, from a state in which the ejection section D is in a stationary state in which the reference potential V0 is supplied to the piezoelectric element PZ and the position of the meniscus MS is stationary at the initial position Z0, a driving signal Vin is supplied to the piezoelectric element PZ over multiple recording periods Tu[i], thereby making it possible to eject one droplet DR from the ejection section D during the multiple recording periods Tu[i].

[0125] Fig. 29 is a diagram for explaining the drive signal Vin when discharging droplets DR in the fourth modified example. In order to align the discharge intervals, in other words the dot intervals, among a plurality of discharge sections D, the control section 6 makes a predetermined number of recording periods Tu correspond to one dot. The predetermined number is an integer of 2 or more. Fig. 29 shows an example in which the predetermined number is 2. Then, the control section 6 controls the movement mechanism 8 so that the movement speed of the liquid discharge head HU becomes a value obtained by dividing the movement speed of the liquid discharge head HU in the first embodiment by the predetermined number.

[0126] 29, at the start of the recording period Tu[i], it is assumed that the discharge section D is in a stationary state with the reference potential V0 supplied to the piezoelectric element PZ and the meniscus MS is stationary at the initial position Z0. One dot is printed in two recording periods Tu[i] and Tu[i+1]. In the recording period Tu[i] and the recording period Tu[i+1], the control section 6 generates an individual designation signal Sd[m] of the driving mode α1. Then, one dot is printed in the two recording periods Tu[i+2] and Tu[i+3] following the recording period Tu[i+1]. In the recording period Tu[i+2], the control unit 6 generates an individual designation signal Sd[m] with values ​​(1, 1, 1, 0, 0), and in the recording period Tu[i+3], the control unit 6 generates an individual designation signal Sd[m] with driving mode α1. In the fourth modified example, the waveform PH1 included in the drive signal Vin during the recording period Tu[i] and the drive signal Vin during the recording period Tu[i+1] is another example of the "first waveform" described in the above-mentioned embodiment and modified example, and the waveform PH2 included in the drive signal Vin during the recording period Tu[i+1] is another example of the "second waveform" described in the above-mentioned embodiment and modified example. Also, the waveform PH1 included in the drive signal Vin during the recording period Tu[i+2] and the drive signal Vin during the recording period Tu[i+3] is another example of the "first waveform" described in the above-mentioned embodiment and modified example, and the waveform PH2 included in the drive signal Vin during the recording period Tu[i+3] is another example of the "second waveform" described in the above-mentioned embodiment and modified example. Moreover, the drive pulse PL included in the drive signal Vin during the recording period Tu[i] and the drive pulse PL of the waveform PH1 included in the drive signal Vin during the recording period Tu[i+1] are another example of the "first drive pulse" described in the above-mentioned embodiment and modified example, and the drive pulse PL included in the waveform PH2 included in the drive signal Vin during the recording period Tu[i+1] is another example of the "second drive pulse" described in the above-mentioned embodiment and modified example. Moreover, the drive pulse PL included in the drive signal Vin during the recording period Tu[i+2] and the drive pulse PL included in the waveform PH1 included in the drive signal Vin during the recording period Tu[i+3] are another example of the "first drive pulse" described in the above-mentioned embodiment and modified example, and the drive pulse PL included in the waveform PH2 included in the drive signal Vin during the recording period Tu[i+3] is another example of the "second drive pulse" described in the above-mentioned embodiment and modified example. As described in the first embodiment, when droplets DR are discharged in two recording periods Tu[j] and Tu[j+1], the waveform of the drive signal Vin supplied to the piezoelectric element PZ in the two recording periods Tu[j] and Tu[j+1] is determined based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ in a predetermined recording period Tux preceding the two recording periods Tu[j] and Tu[j+1]. In order to discharge droplets DR in the recording period Tu[i+2] and Tu[i+1] preceding the recording period Tu[i+3], the number of drive pulses PL included in the drive signal Vin in the recording period Tu[i+2] is less than the number of drive pulses PL included in the drive signal Vin in the recording period Tu[i] in which no droplets DR are discharged in the preceding period.

[0127] Also, in the fourth modification, a drive signal for generating non-printing micro-vibrations can be supplied to the piezoelectric element PZ immediately before the start of the printing process, as in the third modification. By generating non-printing micro-vibrations before the first recording period Tu[1] of the printing process, the number of recording periods Tu corresponding to one dot can be reduced compared to the case where the non-printing micro-vibrations are not generated, and the movement speed of the liquid ejection head HU can be prevented from slowing down.

[0128] 2.5. Fifth Variant In the first embodiment and the first to fourth modified examples, when a droplet DR is ejected in a recording period Tu[j], the waveform of the drive signal Vin supplied to the piezoelectric element PZ in the recording period Tu[j] is determined based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ in a predetermined recording period Tux preceding the recording period Tu[j], specifically, which of the drive modes α1 to α4 is selected in the recording period Tu[j] is determined based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ in the predetermined recording period Tux, but this is not limited to this. In the fifth modified example, the waveform of the drive signal Vin is determined based on the viscosity of the ink, specifically, the number of drive pulses PL included in the drive signal Vin may be changed.

[0129] 30 is a functional block diagram showing an example of the configuration of an inkjet printer 1a in Modification 5. The inkjet printer 1a differs from the inkjet printer 1 in that it has a viscosity information acquisition unit 9 and a control unit 6a instead of the control unit 6.

[0130] The viscosity information acquisition unit 9 acquires viscosity information VI that indicates the viscosity of the liquid in the liquid ejection head HU. The viscosity information VI is an example of "physical property information".

[0131] The viscosity information acquisition unit 9 acquires the viscosity information VI, for example, by any one of the following three methods. In a first method, the viscosity information acquisition unit 9 acquires the viscosity information VI based on the waveform of the residual vibration of the diaphragm 310. In a second method, the viscosity information acquisition unit 9 acquires the viscosity information VI of the ink held in the liquid container 14. In a third method, the user inputs the viscosity information VI of the ink, and the viscosity information acquisition unit 9 acquires the viscosity information VI input by the user.

[0132] The control unit 6a determines the waveform of the drive signal Vin based on the viscosity information VI. Specifically, the control unit 6a determines the number of drive pulses PL of the waveform PH1 included in the drive signal Vin1 based on the viscosity information VI. An example of determining the number of drive pulses PL of the waveform PH1 included in the drive signal Vin1 will be described with reference to FIG. 31.

[0133] FIG. 31 is a diagram for explaining an example of determining the number of drive pulses PL of the waveform PH1 included in the drive signal Vin1. As shown in FIG. 31, when the viscosity indicated by the viscosity information VI is less than 20 mPascal seconds, the control unit 6a determines the number of drive pulses PL of the waveform PH1 included in the drive signal Vin1 to be 0. When the viscosity indicated by the viscosity information VI is 20 mPascal seconds or more and less than 30 mPascal seconds, the control unit 6a determines the number of drive pulses PL of the waveform PH1 included in the drive signal Vin1 to be 1. When the viscosity indicated by the viscosity information VI is 30 mPascal seconds or more and less than 50 mPascal seconds, the control unit 6a determines the number of drive pulses PL of the waveform PH1 included in the drive signal Vin1 to be 2. When the viscosity indicated by the viscosity information VI is 50 mPascal seconds or more and less than 70 mPascal seconds, the control unit 6a determines the number of drive pulses PL of the waveform PH1 included in the drive signal Vin1 to be 3.

[0134] When the number of drive pulses PL of the waveform PH1 included in the drive signal Vin1 is determined to be one, the control unit 6a determines the waveform of the drive signal Vin1 to be the waveform PH1 having any one drive pulse PL selected from the drive pulses PL1, PL2, and PL3. For example, the control unit 6a determines the waveform of the drive signal Vin1 to be the waveform PH1 having the drive pulse PL3. Similarly, when the number of drive pulses PL included in the drive signal Vin1 is determined to be two, the control unit 6a determines the waveform of the drive signal Vin1 to be a waveform PH1 having any two drive pulses PL selected from the drive pulses PL1, PL2, and PL3. For example, the waveform of the drive signal Vin1 is determined to be a waveform PH1 having drive pulses PL2 and PL3. Moreover, the control unit 6a determines the waveform of the drive signal Vin2 to be the waveform PH2, regardless of the viscosity information VI. Furthermore, when selecting a drive pulse PL to be included in waveform PH1 from among drive pulses PL1, PL2, and PL3, selecting a drive pulse PL close to waveform PH2 makes it easier to eject a droplet DR from nozzle N when waveform PH2 is supplied to piezoelectric element PZ.

[0135] Returning to Fig. 30 for explanation, the control unit 6a generates the individual designation signal Sd[m] so that a drive signal Vin is generated that includes a drive signal Vin1 whose waveform has been determined and a drive signal Vin2 whose waveform has been determined. For example, when it is determined that the drive signal Vin1 includes a waveform PH1 having only a drive pulse PL3, the control unit 6a generates the individual designation signal Sd[m] of the drive mode α3 shown in Fig. 6. The control unit 6a outputs the generated individual designation signal Sd[m] to the switching circuit 10. In addition, in the fifth variant, as further described in the first embodiment, when a droplet DR is ejected in the recording period Tu[j], the waveform of the drive signal Vin supplied to the piezoelectric element PZ in the recording period Tu[j] can also be determined taking into account the waveform of the drive signal Vin supplied to the piezoelectric element PZ in a predetermined recording period Tux preceding the recording period Tu[j].

[0136] 2.5.1. Summary of the fifth modification As described above, in the inkjet printer 1a in the fifth modified example, the control unit 6 executes a recording method having a first step, a second step, a third step, and a fourth step. In the first step, viscosity information VI indicating the viscosity of the ink in the liquid ejection head HU is acquired. In the second step, a waveform of the drive signal Vin is determined based on the viscosity information VI. In the third step, a waveform PH1 included in the drive signal Vin1 of the drive signal Vin having the waveform determined in the second step is supplied to the piezoelectric element PZ, thereby forming a liquid column LC6 with a meniscus MS protruding in the -Z direction. In the fourth step, when the liquid column LC6 is formed, a waveform PH2 included in the drive signal Vin2 of the drive signal Vin having the waveform determined in the second step is supplied to the piezoelectric element PZ, thereby forming a liquid column LC8 with a meniscus MS protruding in the -Z direction, and then a part or all of the liquid constituting the liquid column LC8 is ejected as a droplet DR. If the number of drive pulses PL of the waveform PH1 is increased even when the viscosity of the ink is low, the droplets DR will be ejected earlier than they should be. On the other hand, if the number of drive pulses PL of the waveform PH1 is decreased even when the viscosity of the ink is high, the droplets DR will be ejected later than they should be, or will not be ejected at all. By determining the waveform of the drive signal Vin based on the viscosity indicated by the viscosity information VI, the droplets DR can be ejected closer to the timing at which they should originally be ejected, thereby suppressing deterioration of print quality.

[0137] The second step in the "Summary of the fifth modified example" is to determine the waveform of the drive signal Vin1 based on the viscosity information VI. By adjusting the waveform of the drive signal Vin1, the droplets DR can be ejected closer to the timing at which they should originally be ejected.

[0138] The second step in the section "Summary of the Fifth Modification" determines the number of drive pulses PL of the waveform PH1 included in the drive signal Vin1 based on the viscosity information VI. As described in the section “Summary of the recording method using the drive waveform signal Com” in the first embodiment, adjusting the number of drive pulses PL is an easier configuration than adjusting the minimum and maximum potentials of the drive pulses PL. Therefore, according to the fifth modified example, it is possible to generate a waveform of the drive signal Vin1 that matches the viscosity of the ink with a simpler configuration.

[0139] In the fifth modified example, the drive signal Vin2 has a predetermined waveform PH2 regardless of the viscosity information VI. Therefore, when generating a drive signal Vin that matches the viscosity of the ink, it is necessary to adjust only the waveform of the drive signal Vin1, and there is no need to adjust the waveform of the drive signal Vin2.

[0140] The second step in the section "Summary of the fifth variant" is to determine the waveform of the drive signal Vin1 so that the third number of drive pulses PL of the waveform PH1 contained in the drive signal Vin1 when the viscosity information VI indicates a first viscosity is greater than the fourth number of drive pulses PL of the waveform PH1 contained in the drive signal Vin1 when the viscosity information VI indicates a second viscosity lower than the first viscosity. Since the first viscosity is higher than the second viscosity, when the viscosity information VI indicates the first viscosity, it is necessary to supply the drive signal Vin1 having more drive pulses PL to the piezoelectric element PZ compared to when the viscosity information VI indicates the second viscosity. Therefore, by determining the waveform of the drive signal Vin1 so that the third number is greater than the fourth number, the droplets DR can be ejected at the timing when they should originally be ejected.

[0141] 2.6. Sixth Modification In the fifth modified example, an example of the physical property information is described as the viscosity information VI, but the physical property information is not limited to the viscosity information VI. For example, the physical property information may be any one of information indicating the surface tension of the ink, information indicating the bulk modulus of the ink, and information indicating the specific gravity of the ink.

[0142] When the physical property information is information indicating the surface tension of the ink, the control unit 6 determines the waveform of the drive signal Vin1 so that the number of drive pulses PL contained in the drive signal Vin1 when the surface tension of the ink indicates a first value is greater than the number of drive pulses PL contained in the drive signal Vin1 when the surface tension of the ink indicates a second value smaller than the first value.

[0143] When the physical property information is information indicating the bulk modulus of the ink, the control unit 6 determines the waveform of the drive signal Vin1 so that the number of drive pulses PL contained in the drive signal Vin1 when the bulk modulus of the ink indicates a third value is greater than the number of drive pulses PL contained in the drive signal Vin1 when the bulk modulus of the ink indicates a fourth value lower than the third value.

[0144] When the physical property information is information indicating the specific gravity of the ink, the control unit 6 determines the waveform of the drive signal Vin1 so that the number of drive pulses PL contained in the drive signal Vin1 when the bulk modulus of the ink indicates a fifth value is greater than the number of drive pulses PL contained in the drive signal Vin1 when the bulk modulus of the ink indicates a sixth value that is greater than the fifth value.

[0145] 2.7. Seventh Variation In the first embodiment and the first to sixth modifications, the drive waveform signal Com has a waveform PH2 having drive pulses PL4 and PL5, but is not limited to this. In the seventh modification, the drive waveform signal Comb has a waveform PH2b having only the drive pulse PL4.

[0146] 32 is a diagram for explaining the drive waveform signal Comb in the seventh modified example. The drive waveform signal Comb has a waveform PH1 and a waveform PH2b. The waveform PH2b has a drive pulse PL4b. The drive pulse PL4b has a drive component DC7 and a drive component DC8b. ​​The amount of change in potential per unit period in the drive component DC8b is greater than the amount of change in potential per unit period in the drive components DC2, DC4, and DC6, so that the energy for moving the liquid column LC8 formed by supplying the drive component DC8b to the piezoelectric element PZ in the -Z direction becomes greater, and even if there is no drive pulse PL after the drive pulse PL4b, part or all of the liquid column is ejected as a droplet DR.

[0147] 2.8. Eighth Variation In the first embodiment and the first to seventh modified examples, the potential difference between the maximum and minimum potentials of the drive pulses PL included in the waveforms PH1 and PH2 is the potential difference Vh, but this is not limited to this. The potential difference of the waveform PH1 may be at least 0.5 times the potential difference of the waveform PH2. In the eighth modified example, the potential difference Vh2a of the drive pulse PL4a included in the waveform PH2a is larger than the potential difference Vh1 of the drive pulses PL1, PL2, and PL3 of the waveform PH1, and the potential difference Vh3a of the drive pulse PL5a included in the waveform PH2 is smaller than the potential difference Vh1 of the drive pulses PL1, PL2, and PL3 of the waveform PH1.

[0148] FIG. 33 is a diagram for explaining the driving waveform signal Coma in the eighth modified example. The driving waveform signal Coma has a waveform PH1 and a waveform PH2a. The waveform PH2a has driving pulses PL4a and PL5a. The driving pulse PL5a has driving components DC9a and DC10a. The minimum potential of the driving pulse PL4a is a potential VL2a. The potential VL2a is lower than the potential VL1. The potential difference of the driving pulse PL4a is a potential difference Vh2a. The potential difference Vh2a is larger than the potential difference Vh1 of the driving pulses PL1, PL2, and PL3. More specifically, the driving component DC7a of the driving pulse PL4a has a starting potential set to the reference potential V0 and an ending potential set to the potential VL2a. The driving component DC8a of the driving pulse PL4a has a starting potential set to the potential VL2a and an ending potential set to the reference potential V0. Further, the minimum potential of the drive pulse PL5a is potential VL3a. The potential VL3a is higher than the potential VL1. The potential difference of the drive pulse PL5a is potential difference Vh3a. The potential difference Vh3a is smaller than the potential difference Vh1 of the drive pulses PL1, PL2, and PL3. More specifically, the drive component DC9a of the drive pulse PL5a has a starting potential set to the reference potential V0 and an ending potential set to the potential VL3a. The drive component DC10a of the drive pulse PL5a has a starting potential set to the potential VL3a and an ending potential set to the reference potential V0. The potential difference Vh1 between the drive pulses PL1, PL2, and PL3 of the waveform PH1 can be set to any potential suitable for appropriately growing the liquid column and preventing unnecessary leakage of ink from the nozzle N. Note that if the potential difference Vh1 is small, the liquid column cannot grow, so it is preferable that the potential difference Vh1 between the drive pulses PL1, PL2, and PL3 be 0.5 or more times the potential difference Vh2a of the drive pulse PL4a of the waveform PH2a. In addition, in this modified example, the potential difference Vh3a of the drive pulse PL5a of the waveform PH2a is set smaller than the potential difference Vh1 and the potential difference Vh2a. This makes it possible to suppress the possibility that the drive component DC10a of the drive pulse PL5a will cause the ink to seep onto the -Z direction surface of the nozzle plate 330. Note that if the drive component DC10a of the drive pulse PL5a does not easily cause the ink to seep onto the -Z direction surface of the nozzle plate 330, the potential difference Vh3a of the drive pulse PL5a can be set to be equal to or larger than the potential difference Vh2a. It should be noted that the potential differences of the driving pulses PL1, PL2, and PL3 of the waveform PH1 can also be set to different values.

[0149] 2.9. Ninth Variation In the first embodiment and the first to seventh modified examples, the potential difference between the maximum and minimum potentials in the drive pulses PL included in the waveforms PH1 and PH2 is approximately equal to the potential difference Vh, but this is not limited thereto. The potential difference of the waveform PH1 may be at least 0.5 times the potential difference of the waveform PH2. In the ninth modified example, the potential difference of the drive pulse PL5 included in the waveform PH2 is greater than the potential difference of the waveform PH1.

[0150] FIG. 34 is a diagram for explaining the drive waveform signal Comc in the ninth modified example. The drive waveform signal Comc has a waveform PH1 and a waveform PH2c. The waveform PH2c has drive pulses PL4 and PL5c. The drive pulse PL5c has drive components DC9c and DC10c. The lowest potential of the drive pulse PL5c is potential VL2. The potential VL2 is lower than the potential VL1. The potential difference of the drive pulse PL5c is potential difference Vh2. More specifically, for the drive component DC9c, the potential at the start is set to the reference potential V0, and the potential at the end is set to the potential VL2. For the drive component DC10c, the potential at the start is set to the potential VL2, and the potential at the end is set to the reference potential V0. The potential difference Vh2 is larger than the potential difference Vh of the drive pulses PL1, PL2, PL3, and PL4. The potential difference Vh2 of the drive pulse PL5c is larger than the potential difference Vh, so that the force that tears off the liquid droplet DR from the liquid column LC9 can be made large.

[0151] According to the ninth modified example, the potential difference of the waveform PH1 is set to 0.5 times or more the potential difference of the waveform PH2c, which improves the degree of freedom in designing the drive waveform signal Com compared to an embodiment in which the potential difference of the waveform PH1 and the potential difference of the waveform PH2 are approximately equal. For example, the force for tearing off the liquid droplet DR from the liquid column LC9 can be increased by making the potential difference of the waveform PH2 larger than the potential difference of the waveform PH1. More preferably, the drive pulse PL5c of the waveform PH2c has a drive component DC9c that is supplied to the piezoelectric element PZ when the tip of the liquid column LC8 is moving in the -Z direction, and the difference between the maximum and minimum potentials of the drive pulse PL5c is set to be larger than the difference between the maximum and minimum potentials of the waveform PH1, which increases the force for tearing off the liquid droplet DR from the liquid column LC9. In addition, the drive pulse PL5c is an example of "one drive pulse included in the second drive pulse of the second waveform", and the drive component DC9c is an example of "a third drive component supplied to the drive element when the tip of the second liquid column is moving in the ejection direction". On the other hand, by making the potential difference of the waveform PH1 smaller than the potential difference of the waveform PH2c, droplets DR are not ejected from the ejection section D when the waveform PH1 is supplied to the piezoelectric element PZ, and droplets DR can be reliably ejected when the waveform PH2c is supplied to the piezoelectric element PZ. Also, when the potential difference of the waveform PH2c is larger than the potential difference of the waveform PH1, droplets are not ejected excessively with the waveform PH2, but there is a possibility that ink may seep onto the surface of the nozzle plate 330 in the -Z direction. By making the potential difference of the waveform PH1 larger than the potential difference of the waveform PH2, the possibility of ink seeping onto the surface of the nozzle plate 330 in the -Z direction can be suppressed. The designer of the inkjet printer 1 can design the drive waveform signal Com taking into account the viscosity of the ink.

[0152] 2.10. Tenth Variation In the first embodiment and the first to ninth variants, the period from the point when the supply of drive components DC9, DC9a, DC9c contained in drive pulses PL5, PL5a, PL5c starts to the point when the supply of drive components DC10, DC10a, DC10c ends is longer than the period from the point when the supply of the first drive component DC1, DC3, DC5, DC7 contained in any of the other drive pulses PL contained in the drive waveform signals Com, Coma, Comc starts to the point when the supply of the second drive component DC2, DC4, DC6, DC8 ends.

[0153] FIG. 35 is a diagram for explaining the driving waveform signal Comd in the tenth modified example. The driving waveform signal Comd has a waveform PH1 and a waveform PH2d. The waveform PH2d has driving pulses PL4 and PL5d. The driving pulse PL5d has a driving component DC9d and a driving component DC10d. The period Pw5 from the time when the supply of the driving component DC9d is started to the time when the supply of the driving component DC10d is ended is shorter than, for example, the period Pw1 from the time when the supply of the driving component DC1 of the driving pulse PL1 is started to the time when the supply of the driving component DC2 is ended. The period Pw5 is shorter than the natural vibration period TC of the discharge section D, and is, for example, 0.25 times the natural vibration period TC. Since the period Pw5 is shorter than the period Pw1, a trigger for tearing off the droplet DR from the liquid column LC9 can be generated.

[0154] Furthermore, the driving pulse PL that causes tearing is one driving pulse PL5, but it may be a plurality of driving pulses PL.

[0155] 2.11. 11th Variation In the first embodiment and the first to tenth modified examples, the maximum potential and the initial potential of the driving pulse PL are the same, but the maximum potential and the initial potential may be different.

[0156] 36 is a diagram for explaining the drive waveform signal Come in the 11th modified example. The drive waveform signal Come has a waveform PH1e and a waveform PH2e. The waveform PH1e has drive pulses PL1e, PL2, and PL3. The waveform PH2e has drive pulses PL4 and PL5e.

[0157] For the drive pulse PL1e, the potential at the start is set to the reference potential V0, and the potential at the end is set to the maximum potential VH1. The maximum potential VH1 is higher than the reference potential V0. The drive pulse PL1e has drive components DC1e and DC2. For the drive component DC1e, the potential at the start is set to the reference potential V0, and the potential at the end is set to the minimum potential VL1. For the drive pulses PL2, PL3, and PL4, the potential at the start and the potential at the end are set to the maximum potential VH1. For the drive pulse PL5e, the potential at the start is set to the maximum potential VH1, and the potential at the end is set to the reference potential V0. The drive pulse PL5e has drive components DC9 and DC10e. For the drive component DC10e, the potential at the start is set to the minimum potential VL1, and the potential at the end is set to the reference potential V0.

[0158] According to the eleventh modification, the potential difference between the maximum potential and the minimum potential of the driving component DC10e is smaller than the potential difference between the maximum potential and the minimum potential of the driving component DC10, so that it is possible to suppress unnecessary ejection compared to the above-described embodiment and modification. Alternatively, in the embodiment, even if the driving component DC10 does not eject the droplet DR, there is a possibility that the ink may seep out onto the surface of the nozzle plate 330 in the -Z direction. In the tenth modification, it is possible to suppress the ink from seeping out onto the surface of the nozzle plate 330 in the -Z direction compared to the embodiment.

[0159] 2.12. 12th Variation In the eleventh modification, the reference potential V0 is between the maximum potential VH1 and the minimum potential VL1, but the reference potential V0 may be equal to the minimum potential VL1.

[0160] 37 is a diagram for explaining the drive waveform signal Comf in the twelfth modified example. The drive waveform signal Comf has a waveform PH1f and a waveform PH2f. The waveform PH1f has drive pulses PL1f, PL2, and PL3. The waveform PH2f has drive pulses PL4 and PL5f.

[0161] For the drive pulse PL1f, the potential at the start is set to the reference potential V0, and the potential at the end is set to the highest potential VH1. The highest potential VH1 is higher than the reference potential V0. The drive pulse PL1f has a drive component DC2, and does not have a drive component DC1. For the drive pulses PL2, PL3, and PL4, the potential at the start and the potential at the end are set to the highest potential VH1. For the drive pulse PL5f, the potential at the start is set to the highest potential VH1, and the potential at the end is set to the reference potential V0. The drive pulse PL5e has a drive component DC9, and does not have a drive component DC10.

[0162] According to the 12th modified example, since it does not have the driving component DC10, it is possible to suppress unnecessary ejection compared to the 10th modified example. Or, even in the 11th modified example, even if the droplet DR is not ejected by the driving component DC10, there is a possibility that the ink may seep out onto the surface of the nozzle plate 330 in the -Z direction. According to the 11th modified example, since it does not have the driving component DC10, it is possible to suppress the ink from seeping out onto the surface of the nozzle plate 330 in the -Z direction compared to the 10th modified example.

[0163] 2.13. Thirteenth Variation In the first embodiment, the control unit 6 determines the waveform of the individual designation signal Sd[m] of the recording period [j] based on the individual designation signal Sd[m] of the recording periods Tu[j-1] to Tu[j-3] as a predetermined recording period Tux preceding the recording period Tu[j], but is not limited to this. For example, the control unit 6 may determine the individual designation signal Sd[m] of the recording period [j] based on the individual designation signal Sd[m] of two or more consecutive recording periods Tu including the recording period Tu[j-1] and ending before the start of the recording period Tu[j]. Also, for example, the control unit 6 may determine the individual designation signal Sd[m] of the recording period [j] based on the individual designation signal Sd[m] of only the recording period Tu[j-1].

[0164] 2.14. Fourteenth Variation In the fourteenth variant, it has been described that the control unit 6 determines the individual designation signal Sd[m] of the recording period Tu[j] based on the individual designation signals Sd[m] of two or more recording periods Tu including the recording period Tu[j-1] as the predetermined recording period Tux preceding the recording period Tu[j]. However, the individual designation signal Sd[m] of the recording period Tu[j] may also be determined based on the individual designation signals Sd[m] of one or more recording periods Tu not including the recording period Tu[j-1] as the predetermined recording period Tux preceding the recording period Tu[j].

[0165] 2.15. Fifteenth Variation The control unit 6 may determine the waveform of the drive signal Vin for the recording period Tu[j] based on the ratio of the number of recording periods Tu in which droplets DR are ejected from the ejection unit D to the number of recording periods Tu in which droplets DR are not ejected from the ejection unit D, among a predetermined recording period Tux that includes the recording period Tu[j-1] and includes two or more consecutive recording periods Tu that end before the start of the recording period[j]. For example, the control unit 6 calculates the following formula (3). Discharge ratio = number of droplets DR discharged from discharge section D during recording period Tu / number of droplets during a given recording period Tux (3)

[0166] Then, the control unit 6 makes the number of driving pulses PL in the recording period Tu when the calculated ejection ratio is the first ratio smaller than the number of driving pulses PL in the recording period Tu when the ejection ratio is the second ratio. The first ratio is greater than the second ratio. If the ejection ratio is high, the liquid column formed in the meniscus MS at the start of the recording period Tu[j] will be large. Therefore, by determining the waveform of the drive signal Vin for the recording period Tu[j] based on the ejection ratio, the droplets DR can be ejected closer to the timing at which they should be ejected, thereby suppressing deterioration of print quality.

[0167] 2.16. 16th Variation In the first embodiment and the first to fifteenth modified examples, the waveform PH1 has three drive pulses PL, but is not limited thereto, and the waveform PH1 may have only one drive pulse PL or may have four or more drive pulses PL. In a case where the waveform PH1 has four or more drive pulses PL, in the fifth modified example, if the viscosity indicated by the viscosity information VI is 70 mPascal-second or more, the control unit 6a determines the number of drive pulses PL included in the drive signal Vin1 to be four or more. For example, if the viscosity indicated by the viscosity information VI is 70 mPascal-second or more and less than 100 mPascal-second, the control unit 6a determines the number of drive pulses PL included in the drive signal Vin1 to be four.

[0168] 2.17. 17th Variation In the first embodiment, the liquid column is defined as a columnar or cone-shaped liquid surface of the meniscus MS that protrudes in the -Z direction from the furthest position in the +Z direction, but in the case of a droplet that temporarily separates from the meniscus MS, the columnar or cone-shaped liquid surface of this droplet may also be defined as a liquid column. A droplet that temporarily separates from the meniscus MS is a droplet that separates when a certain driving component DC is supplied, but rejoins when the next driving component DC is supplied. Specifically, the liquid column LC7 shown in FIG. 14 may temporarily separate from the meniscus MS. The separated liquid column LC7 rejoins the meniscus MS when the driving component DC8 is supplied.

[0169] 2.18. 18th Variation Each of the above-mentioned aspects can also be applied to an aspect in which a plurality of cavities 320 supplies ink to one nozzle N.

[0170] FIG. 38 is a diagram showing an example of the discharge section Dg in the 18th modified example. The diagram shown in FIG. 38 shows a plurality of discharge sections Dg viewed in the -Z direction. For the sake of simplicity, the piezoelectric element PZ, the vibration plate 310, the nozzle plate 330, and the cavity plate 340 are omitted from FIG. 38. The discharge section Dg has four cavities 320, a connection flow path 321, and a nozzle N. The four cavities 320 communicate with a common ink liquid chamber (not shown), and ink is supplied through the connection flow path 321. The connection flow path 321 communicates with the nozzle N, and further communicates with each of the four cavities 320 in the -X direction. In FIG. 38, the discharge section Dg has four cavities 320, but the discharge section Dg may have two cavities 320, three cavities 320, or five or more cavities 320. By increasing the number of cavities 320 in one ejection section D, the excluded volume of the cavity 320 for one nozzle N can be increased, so that ink with a higher viscosity can be ejected compared to the first embodiment.

[0171] 2.19. 19th Variation Each of the above-described aspects can also be applied to an inkjet printer 1 that supplies ink to the liquid ejection head HU and has a circulation mechanism that recovers ink discharged from the liquid ejection head HU for re-supply to the liquid ejection head HU.

[0172] FIG. 39 is a diagram showing an example of a discharge section Dh in a 19th modified example. The diagram shown in FIG. 39 shows a plurality of discharge sections Dg viewed in the -Z direction. For the sake of simplicity, the piezoelectric element PZ, the vibration plate 310, the nozzle plate 330, and the cavity plate 340 are omitted from FIG. 39. The discharge section Dh has four cavities 320, a connection flow path 321h, and a nozzle N. The connection flow path 321 communicates with two cavities 320 at the end in the -X direction, and is connected to two cavities 320 at the end in the +X direction. The two cavities 320 communicating with the end in the -X direction of the connection flow path 321 communicate with an ink supply unit of a circulation mechanism (not shown), and ink is supplied from the ink supply unit. In addition, the two cavities 320 that communicate with the end of the connecting flow path 321 in the +X direction communicate with an ink recovery unit of a circulation mechanism (not shown), and the ink is recovered by the ink recovery unit. This allows ink to circulate from the two cavities 320 in the -X direction to the two cavities 320 on the -X direction side via the connecting flow path 321.

[0173] In the 19th modified example, the displacement volume of the cavity 320 for one nozzle N can also be increased, so ink with a higher viscosity can be ejected compared to the first embodiment. Moreover, in the 18th modified example, the circulation mechanism prevents the ink in the cavity 320 and the connecting flow path 321 from becoming thicker.

[0174] 2.20. 20th Variation In each of the above-mentioned embodiments, a serial type inkjet printer 1 in which the transport body 82 housing the liquid ejection head HU is moved back and forth in the X-axis direction has been exemplified, but the present invention is not limited to such embodiments. The inkjet printer may be a line type inkjet printer in which multiple nozzles N are distributed across the entire width of the recording paper P.

[0175] The third modified example may be applied when the inkjet printer 1 is a line printer. The control unit 6 controls the transport mechanism 7 so that the transport speed of the recording paper P becomes a value obtained by dividing the transport speed of the recording paper P when the twentieth modified example is applied to the first embodiment by a predetermined number.

[0176] 2.21. 21st Variation In the above-described embodiments, an example of the "drive element" is the piezoelectric element PZ, but a heat generating element may be included instead of the piezoelectric element PZ.

[0177] 2.22. 22nd Variation The inkjet printers exemplified in the above-mentioned embodiments can be used in various devices such as facsimile machines and copy machines, in addition to devices dedicated to printing. However, the use of the liquid ejection device of the present invention is not limited to printing. For example, a liquid ejection device that ejects a solution of a coloring material is used as a manufacturing device for forming a color filter of a liquid crystal display device. Furthermore, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wiring and electrodes of a wiring board.

[0178] 3. Notes From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0179] A driving method for a liquid ejection head according to a first preferred embodiment is a recording method for a liquid ejection head having an ejection section including a driving element that is displaced by being supplied with a driving signal including a first driving signal and a second driving signal, a pressure chamber whose internal pressure is increased or decreased in accordance with the displacement of the driving element, and a nozzle that is in communication with the pressure chamber and is capable of ejecting liquid filled inside the pressure chamber as droplets in an ejection direction in accordance with the increase or decrease in the pressure inside the pressure chamber, the method comprising the steps of: a first step of acquiring physical property information indicating the physical properties of the liquid in the liquid ejection head; a second step of determining a waveform of the driving signal based on the physical property information; a third step of forming a first liquid column in which the liquid level in the ejection portion protrudes in the ejection direction by supplying to the drive element a first waveform included in the first drive signal among the drive signals having the waveform determined in the second step; and a fourth step of, when the first liquid column is formed, forming a second liquid column in which the liquid level in the ejection portion protrudes in the ejection direction by supplying to the drive element a second waveform included in the second drive signal among the drive signals having the waveform determined in the first step, and then ejecting part or all of the liquid constituting the second liquid column as droplets. According to the first aspect, by determining the waveform of the drive signal based on the physical properties indicated by the physical property information, it is possible to eject droplets closer to the timing at which they should originally be ejected, thereby suppressing deterioration of print quality.

[0180] In Aspect 2, which is a specific example of Aspect 1, the physical property information indicates a viscosity of the liquid in the liquid ejection head. If the number of drive pulses is increased even though the viscosity of the liquid is low, the droplets will be ejected earlier than the timing at which they should be ejected. On the other hand, if the number of drive pulses is decreased even though the viscosity of the liquid is high, the droplets will be ejected later than the timing at which they should be ejected, or they will not be ejected at all. By determining the waveform of the drive signal based on the viscosity of the liquid indicated by the physical property information, the droplets can be ejected closer to the timing at which they should be ejected, thereby suppressing deterioration of print quality.

[0181] In aspect 3 which is a specific example of aspect 1 or 2, the second step determines a waveform of the first drive signal based on the physical property information. According to the third aspect, by adjusting the waveform of the first drive signal, it is possible to eject droplets closer to the timing at which they should originally be ejected.

[0182] In aspect 4, which is a specific example of aspect 3, the second step determines the number of drive pulses of the first waveform contained in the first drive signal based on the physical property information, and the drive pulses have a drive component that reduces the pressure inside the pressure chamber and a drive component that increases the pressure inside the pressure chamber. Adjusting the number of drive pulses is an easier configuration than adjusting the minimum and maximum potentials of the drive pulses. Therefore, according to aspect 4, a drive signal waveform that matches the viscosity of the liquid can be generated with a simpler configuration.

[0183] In aspect 5, which is a specific example of any one of aspects 1 to 4, the second drive signal has the second waveform that is determined in advance regardless of the physical property information. Therefore, according to the fifth aspect, when generating a drive signal suited to the physical properties of the liquid, it is only necessary to adjust the waveform of the first drive signal, and there is no need to adjust the waveform of the second drive signal.

[0184] In aspect 6, which is a specific example of aspect 2, the second step determines a waveform of the first drive signal so that the number of drive pulses of the first waveform contained in the first drive signal when the physical property information indicates a first viscosity is greater than the number of drive pulses of the first waveform contained in the first drive signal when the physical property information indicates a second viscosity lower than the first viscosity, and the drive pulse has a drive component that reduces the pressure inside the pressure chamber and a drive component that increases the pressure inside the pressure chamber. Since the first viscosity is higher than the second viscosity, when the physical property information indicates the first viscosity, it is necessary to supply a first drive signal having more drive pulses to the drive element compared to when the physical property information indicates the second viscosity. Therefore, according to the sixth aspect, the droplets can be ejected at the timing when they should be ejected.

[0185] In Aspect 7, which is a specific example of any one of Aspects 1 to 6, the viscosity of the liquid in the liquid ejection head is 20 millipascal seconds or more. When the viscosity of the liquid is 20 millipascal seconds or more, it may not be possible to eject droplets with a single drive pulse. However, according to aspect 7, droplets can be ejected even from liquids having a viscosity of 20 millipascal seconds or more.

[0186] In an eighth aspect which is a specific example of any one of the first to seventh aspects, a difference between a maximum potential and a minimum potential of the first waveform is substantially equal to a difference between a maximum potential and a minimum potential of the second waveform. By setting the highest potential achievable in the liquid ejection device as the highest potential of the first waveform and the second waveform, and setting the lowest potential achievable in the liquid ejection device as the lowest potential of the first waveform and the second waveform, even with a highly viscous liquid, a liquid column can be grown on the liquid surface in the ejection section by the first waveform, and a droplet can be ejected by the second waveform.

[0187] A liquid ejection device according to a ninth preferred embodiment includes a liquid ejection head having an ejection unit including a drive element that is displaced by being supplied with a drive signal including a first drive signal and a second drive signal, a pressure chamber whose internal pressure is increased or decreased in accordance with the displacement of the drive element, and a nozzle that is in communication with the pressure chamber and is capable of ejecting liquid filled inside the pressure chamber as droplets in an ejection direction in accordance with the increase or decrease in the pressure inside the pressure chamber, and a control unit that controls the liquid ejection head, wherein the control unit obtains physical property information indicating the physical properties of the liquid in the liquid ejection head, and performs a liquid ejection process based on the physical property information. The control unit determines a waveform of the drive signal, and by supplying a first waveform contained in the first drive signal among the drive signals having the waveform determined by the control unit to the drive element, a first liquid column is formed in which the liquid level in the ejection unit protrudes in the ejection direction, and when the first liquid column is formed, the control unit supplies a second waveform contained in the second drive signal among the drive signals having the waveform determined by the control unit to the drive element, whereby a second liquid column is formed in which the liquid level in the ejection unit protrudes in the ejection direction, and then some or all of the liquid constituting the second liquid column is ejected as droplets. According to the ninth aspect, by determining the waveform of the drive signal based on the physical properties indicated by the physical property information, it is possible to eject droplets closer to the timing at which they should originally be ejected, thereby suppressing deterioration of print quality. [Explanation of symbols]

[0188] 1,1a...inkjet printer, 2...driving waveform signal generating circuit, 5...storage unit, 6,6a...control unit, 7...transport mechanism, 8...movement mechanism, 9...viscosity information acquiring unit, 10...switching circuit, 11...connection state designation circuit, 14...liquid container, 81...endless belt, 82...transport body, 310...vibration plate, 320...cavity, 321...connecting flow path, 321h...connecting flow path, 330...nozzle plate, 340...cavity plate, 350...reservoir, 360...ink supply port, 370...ink intake port, CH...change signal, CL...clock signal, CPw...characteristics, Com,Coma,C omb, Comc, Comd, Come, Comf... driving waveform signal, D, Dg, Dh... ejection section, DC1~DC10, DC7a, DC8a, DC8b, DC9a, DC9c, DC9d, DC10a, DC10c, DC10d, DC10e... driving component, DR... droplet, G1, G2, G3, G4, G5... graph, HD... recording head, HU... liquid ejection head, Img... print data, LAT... latch signal, LC2~LC10... liquid column, LHa... internal wiring, LHb... power supply line, LPnm, LPnp, LVnm, LVnp... line segment, MS... meniscus, N... nozzle, P... recording Recording paper, PH, PH1, PH1e, PH1f, PH2, PH2a, PH2b, PH2c, PH2d, PH2e, PH2f...waveform, PL, PL1, PL1e, PL1f, PL2, PL3, PL4, PL4a, PL4b, PL5, PL5a, PL5c, PL5d, PL5e, PL5f...driving pulse, PZ...piezoelectric element, Pa1, Pa2...pressure fluctuation characteristics, PlsC, PlsL...pulse, Pn1, Pn2...pressure fluctuation characteristics, Pw, Pw1, Pw24, Pw46, Pw5, Pw68...period, SI...print signal, SLa...connection status designation signal, SWa...switch, Sd... Individual designation signal, TC...natural vibration period, Tbu...period, Tcu1 to Tcu5...control period, Tu...recording period, V0...reference potential, Vbs...constant potential, VH1...maximum potential, VI...viscosity information, VL1...minimum potential, VL2, VL2a, VL3a...potential, Vh, Vh1, Vh2, Vh2a, Vh3a...potential difference, Vin, Vin1, Vin2...drive signal, Vn3, Vn4...fluctuation characteristics, Z0...initial position, Zd...lower electrode, Zm...piezoelectric body, Zm1 to Zm3...push-out position, Zp1 to Zp4...retraction position, Zu...upper electrode, dCom...waveform designation signal, α1 to α8...drive mode.

Claims

1. A method for driving a liquid ejection head having an ejection section including a drive element which is displaced when a drive signal is supplied thereto, a pressure chamber whose internal pressure is increased or decreased in accordance with the displacement of the drive element, and a nozzle which is in communication with the pressure chamber and capable of ejecting liquid filled inside the pressure chamber as droplets in an ejection direction in accordance with the increase or decrease in the pressure inside the pressure chamber, comprising: acquiring physical property information indicating the physical property of the liquid in the liquid ejection head; determining a waveform of the drive signal based on the physical property information; the drive signal comprises a first waveform including a plurality of first drive pulses having a first drive component that reduces the pressure inside the pressure chamber and a second drive component that increases the pressure inside the pressure chamber, and a second waveform including a second drive pulse that comes after the first waveform and has a third drive component that reduces the pressure inside the pressure chamber and a fourth drive component that increases the pressure inside the pressure chamber, a first drive component of an initial first drive pulse among the first drive pulses reduces the pressure inside the pressure chamber, and drives the drive element so as to draw the liquid surface into the nozzle in a concave curved state in which a central portion of the liquid surface is recessed toward the pressure chamber from a state in which a reference potential is supplied to the drive element and the liquid surface in the nozzle is stationary at an initial position, a second drive component of an initial first drive pulse among the first drive pulses increases a pressure inside the pressure chamber after the first drive component of the initial first drive pulse is supplied to the drive element, and drives the drive element so as to push the liquid surface in the ejection direction beyond the initial position and form a first liquid column with a central portion of the liquid surface protruding in the ejection direction; a first drive component of a first drive pulse subsequent to an initial first drive pulse among the first drive pulses reduces the pressure inside the pressure chamber, and drives the drive element to draw the liquid surface into the nozzle so as to draw the tip of the first liquid column from the initial position into the nozzle while maintaining the first liquid column at a central portion of the liquid surface, a second drive component of a first drive pulse subsequent to an initial first drive pulse among the first drive pulses increases the pressure inside the pressure chamber, and drives the drive element to push the liquid surface in the ejection direction so that the tip of the first liquid column reaches a pushing-out position that is located in the ejection direction further than a pushing-out position reached by the tip of the first liquid column when the second drive component of the immediately preceding first drive pulse among the first drive pulses is supplied to the drive element; the third driving component reduces the pressure inside the pressure chamber, and drives the driving element to draw in a peripheral portion of the liquid surface into the nozzle while keeping a tip of the first liquid column at a central portion of the liquid surface protruding toward the ejection direction side from the initial position; the fourth driving component is supplied to the driving element, and then the third driving component is supplied to the driving element, and the fourth driving component increases the pressure inside the pressure chamber, and drives the driving element so as to form a second liquid column at a central portion of the liquid surface, the second liquid column having a spherical tip and a constriction between the tip and a peripheral portion of the liquid surface; A part or the whole of the second liquid column is ejected as a droplet from the nozzle. A driving method comprising:

2. A period from a time when the supply of the first drive component of the initial first drive pulse is started to a time when the supply of the first drive component of the subsequent first drive pulse is started is 1.2 times or more and 1.6 times or less of the natural vibration period of the ejection section.

2. The driving method according to claim 1.

3. The physical property information indicates a viscosity of the liquid in the liquid ejection head.

3. The driving method according to claim 1 or 2.

4. Determining the first waveform based on the physical property information.

4. The driving method according to claim 1, wherein the driving method comprises:

5. determining the number of the subsequent driving pulses of the first waveform based on the physical property information.

5. The driving method according to claim 4.

6. The second waveform has a waveform that is determined in advance regardless of the physical property information.

6. The driving method according to claim 1, wherein the driving method comprises:

7. determining a waveform of the drive signal such that the number of the subsequent drive pulses included in the first waveform when the physical property information indicates a first viscosity is greater than the number of the subsequent drive pulses included in the first waveform when the physical property information indicates a second viscosity lower than the first viscosity; 4. The driving method according to claim 3.

8. The viscosity of the liquid in the liquid ejection head is 20 millipascal seconds or more.

8. The driving method according to claim 1, wherein the driving method comprises:

9. A difference between a maximum potential and a minimum potential of the first waveform is substantially equal to a difference between a maximum potential and a minimum potential of the second waveform.

9. The driving method according to claim 1, wherein the driving method comprises:

10. A liquid ejection head having an ejection section including a drive element which is displaced when a drive signal is supplied thereto, a pressure chamber whose internal pressure increases or decreases in accordance with the displacement of said drive element, and a nozzle which is connected to said pressure chamber and is capable of ejecting liquid filled inside said pressure chamber as droplets in an ejection direction in accordance with the increase or decrease in the pressure inside said pressure chamber; A control unit for controlling the liquid ejection head; Equipped with The control unit is acquiring physical property information indicating the physical property of the liquid in the liquid ejection head; determining a waveform of the drive signal based on the physical property information; generating the drive signal and supplying it to the drive element; the drive signal comprises a first waveform including a plurality of first drive pulses having a first drive component that reduces the pressure inside the pressure chamber and a second drive component that increases the pressure inside the pressure chamber, and a second waveform including a second drive pulse that comes after the first waveform and has a third drive component that reduces the pressure inside the pressure chamber and a fourth drive component that increases the pressure inside the pressure chamber, the first waveform comprises an initial first drive pulse and a subsequent first drive pulse after the initial first drive pulse; the first drive component of the initial first drive pulse reduces the pressure inside the pressure chamber, and drives the drive element so as to draw the liquid surface into the nozzle in a concave curved state in which a central portion of the liquid surface is recessed toward the pressure chamber from a state in which a reference potential is supplied to the drive element and the liquid surface in the nozzle is stationary at an initial position, the second drive component of the initial first drive pulse increases the pressure inside the pressure chamber after the first drive component of the initial first drive pulse is supplied to the drive element, and drives the drive element so as to push the liquid surface in the ejection direction beyond the initial position and form a first liquid column with a central portion of the liquid surface protruding in the ejection direction; the first drive component of the subsequent first drive pulse reduces the pressure inside the pressure chamber, and drives the drive element to draw the liquid surface into the nozzle so as to draw the tip of the first liquid column from the initial position into the nozzle while maintaining the first liquid column at a central portion of the liquid surface, the second drive component of the subsequent first drive pulse increases the pressure inside the pressure chamber, and drives the drive element to push the liquid surface in the ejection direction so that the tip of the first liquid column reaches a pushing-out position that is located in the ejection direction further than a pushing-out position reached by the tip of the first liquid column when the second drive component of the immediately preceding first drive pulse among the first drive pulses is supplied to the drive element; the third driving component reduces the pressure inside the pressure chamber, and drives the driving element to draw in a peripheral portion of the liquid surface into the nozzle while keeping a tip of the first liquid column at a central portion of the liquid surface protruding toward the ejection direction side from the initial position; the fourth driving component is supplied to the driving element, and then the third driving component is supplied to the driving element, and the fourth driving component increases the pressure inside the pressure chamber, and drives the driving element so as to form a second liquid column at a central portion of the liquid surface, the second liquid column having a spherical tip and a constriction between the tip and a peripheral portion of the liquid surface; A part or the whole of the second liquid column is ejected as a droplet from the nozzle. A liquid ejection device comprising:

Images