Methods for driving liquid ejection heads and liquid ejection devices

Abstract

This invention provides a method for driving a liquid ejector head and a liquid ejection device. The method for driving the liquid ejector head includes: a first step of acquiring physical property information representing the physical properties of a liquid in the liquid ejector head; a second step of determining a waveform of a driving signal based on the physical property information; a third step of forming a first liquid column protruding in the ejection direction from a liquid surface within an ejection section by supplying a first waveform included in a first driving signal of a driving signal having the waveform determined in the second step to a driving element; and a fourth step of ejecting a portion or all of the liquid constituting the second liquid column as droplets after the formation of the first liquid column by supplying a second waveform included in a second driving signal of a driving signal having the waveform determined in the second step to a driving element.

Description

Technical Field

[0001] This invention relates to a method for driving a liquid ejector head and a liquid ejection device. Background Technology

[0002] Patent document 1 discloses a liquid ejector head that ejects droplets by being supplied with a driving signal.

[0003] However, in the aforementioned prior art, when the viscosity of the liquid increases, the ejection performance may deteriorate.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2011-37257 Summary of the Invention

[0005] To address the above problems, a preferred embodiment of the present invention relates to a method for driving a liquid ejector head, comprising a method for driving a liquid ejector head having an ejection section, wherein the ejection section includes a drive element that is displaced by being supplied with drive signals including a first drive signal and a second drive signal, a pressure chamber whose internal pressure is increased or decreased according to the displacement of the drive element, and a nozzle communicating with the pressure chamber and capable of ejecting liquid filled inside the pressure chamber as droplets in an ejection direction according to the increase or decrease of the internal pressure of the pressure chamber. The driving method includes: a first step of acquiring physical property information representing the physical properties of the liquid in the liquid ejector head; and a second step of acquiring physical property information based on the physical properties of the liquid in the liquid ejector head. The third step involves determining the waveform of the drive signal using material properties information; then, by supplying the drive element with a first waveform included in the first drive signal of the drive signal having the waveform determined in the second step, a first liquid column protruding in the ejection direction is formed from the liquid surface within the ejection section; and finally, after the formation of the first liquid column, by supplying the drive element with a second waveform included in the second drive signal of the drive signal having the waveform determined in the second step, a portion or all of the liquid constituting the second liquid column is ejected as droplets.

[0006] Furthermore, to address the above-mentioned problems, a preferred embodiment of the liquid ejection device of the present invention comprises: a liquid ejection head having an ejection section, the ejection section comprising a drive element that is displaced by being supplied with drive signals including a first drive signal and a second drive signal, a pressure chamber whose internal pressure is increased or decreased according to the displacement of the drive element, and a nozzle communicating with the pressure chamber and capable of ejecting liquid filled inside the pressure chamber as droplets in an ejection direction according to the increase or decrease of the internal pressure of the pressure chamber; and a control unit that controls the liquid ejection head, the control unit performing control such that it acquires an indication of the liquid in the liquid ejection head. The physical property information is used to determine the waveform of the drive signal. By supplying the drive element with a first waveform included in the first drive signal of the drive signal having the waveform determined by the control unit, a first liquid column protruding from the liquid surface in the ejection section in the ejection direction is formed. When the first liquid column is formed, by supplying the drive element with a second waveform included in the second drive signal of the drive signal having the waveform determined by the control unit, after the second liquid column protruding from the liquid surface in the ejection section in the ejection direction is formed, part or all of the liquid constituting the second liquid column is ejected as droplets. Attached Figure Description

[0007] Figure 1 This is a functional block diagram illustrating an example of the structure of the inkjet printer 1 in this embodiment.

[0008] Figure 2 This is a schematic diagram illustrating inkjet printer 1.

[0009] Figure 3 This is a schematic partial cross-sectional view of the recording head HD, showing a section including the ejection section D.

[0010] Figure 4 A block diagram illustrating an example of the structure of a liquid ejector head HU.

[0011] Figure 5 A timing diagram illustrating the actions during the recording period Tu[i] of inkjet printer 1.

[0012] Figure 6 This diagram illustrates the five driving modes available for a single specified signal Sd[m].

[0013] Figure 7 This is a diagram illustrating the drive signal Vin used to describe the individually specified signal Sd[m] based on drive mode α2.

[0014] Figure 8 This figure illustrates the meniscus MS at time point t1.

[0015] Figure 9 This figure illustrates the meniscus MS at time point t2.

[0016] Figure 10 This figure illustrates the meniscus MS at time point t3.

[0017] Figure 11 This figure illustrates the meniscus MS at time point t4.

[0018] Figure 12 This figure illustrates the meniscus MS at time point t5.

[0019] Figure 13 This figure illustrates the meniscus MS at time point t6.

[0020] Figure 14 This figure illustrates the meniscus MS at time point t7.

[0021] Figure 15 This figure illustrates the meniscus MS at time point t8.

[0022] Figure 16 This figure illustrates the meniscus MS at time point t9.

[0023] Figure 17 This figure illustrates the meniscus MS at time point t10.

[0024] Figure 18 This is a diagram used to illustrate the variation characteristics of the pressure generated by the drive signal Vin.

[0025] Figure 19 This diagram illustrates the variation characteristics of the volumetric velocity of ink within nozzle N.

[0026] Figure 20 This is a graph used to illustrate the relationship between Pw and ejection performance values ​​during the period.

[0027] Figure 21 This is a flowchart illustrating the generation of a single specified signal Sd[1] to Sd[m].

[0028] Figure 22 This is a flowchart illustrating the generation of a single specified signal Sd[1] to Sd[m].

[0029] Figure 23 The diagram illustrates a specific example of a recording method using the drive waveform signal Com.

[0030] Figure 24 This is a diagram used to illustrate the five driving methods in the first modified example.

[0031] Figure 25 The figure shows a specific example of the recording method for the drive waveform signal Com used in the first modified example.

[0032] Figure 26 This is a diagram used to illustrate the six driving methods in the second modified example.

[0033] Figure 27 The figure shows a specific example of the recording method for the drive waveform signal Com used in the second modified example.

[0034] Figure 28 This is a diagram used to illustrate the drive signal Vin in the case of ejected droplets DR in the third modified example.

[0035] Figure 29 This is a diagram used to illustrate the drive signal Vin in the case of ejected droplets DR in the fourth modified example.

[0036] Figure 30 A functional block diagram illustrating an example of the structure of the inkjet printer 1a in the fifth modified example.

[0037] Figure 31 This diagram illustrates an example of determining the number of drive pulses PL contained in the drive signal Vin1.

[0038] Figure 32 This is a diagram used to illustrate the drive waveform signal Comb in the seventh modified example.

[0039] Figure 33 This is a diagram used to illustrate the drive waveform signal Coma in the eighth modified example.

[0040] Figure 34 This is a diagram used to illustrate the drive waveform signal Comc in the ninth modified example.

[0041] Figure 35 This is a diagram used to illustrate the drive waveform signal Comd in the tenth modified example.

[0042] Figure 36 This is a diagram used to illustrate the drive waveform signal Come in the eleventh modified example.

[0043] Figure 37 This is a diagram used to illustrate the drive waveform signal Comf in the twelfth modified example.

[0044] Figure 38A diagram illustrating an example of the ejector section Dg in the eighteenth modified example.

[0045] Figure 39 A diagram illustrating an example of the ejector section Dh in the nineteenth modified example. Detailed Implementation

[0046] Hereinafter, the methods for implementing the present invention will be described with reference to the accompanying drawings. However, the dimensions and scales of the various parts in the drawings differ appropriately from the actual situation. Furthermore, although various technically preferred limitations have been imposed on the embodiments described below as preferred examples of the present invention, the scope of the present invention is not limited to these methods unless otherwise specifically limited in the following description.

[0047] 1. First Implementation Method

[0048] In this embodiment, an inkjet printer 1 that forms an image on recording paper P by ejecting ink is illustrated, thereby describing a liquid ejection device. The inkjet printer 1 is an example of a liquid ejection device. The ink is an example of a "liquid". The recording paper P is an example of a medium.

[0049] The following scenario is envisioned: the ink in this embodiment has a higher viscosity than general inks. Specifically, in this embodiment, the viscosity of the ink is 20 mPa·s or higher, preferably 40 mPa·s. Hereinafter, in the accompanying drawings, mPa·s will sometimes be referred to as "mPa second".

[0050] 1.1. Overview of Inkjet Printer 1

[0051] In reference Figure 1 as well as Figure 2 At the same time, the structure of the inkjet printer 1 in this embodiment will be described. Here, Figure 1 This is a functional block diagram illustrating an example of the structure of the inkjet printer 1 in this embodiment. Furthermore, Figure 2 This is a schematic diagram illustrating inkjet printer 1.

[0052] In inkjet printer 1, printing data Img representing the image to be formed by inkjet printer 1 and information representing the number of copies of the image to be formed by inkjet printer 1 are supplied from a host computer such as a personal computer or digital camera. Inkjet printer 1 performs printing processing to form the image represented by the printing data Img supplied from the host computer onto recording paper P.

[0053] As in Figure 1As illustrated, the inkjet printer 1 includes: a liquid ejector head HU, which is provided with an ink ejection section D; a control unit 6, which controls the operation of each part of the inkjet printer 1; a drive waveform signal generation circuit 2, which generates a drive waveform signal Com for driving the ejection section D; a storage unit 5, which stores the control program and other information of the inkjet printer 1; a transport mechanism 7, which transports recording paper P; and a moving mechanism 8, which moves the liquid ejector head HU.

[0054] 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.

[0055] In the following text, to distinguish each of the M ejector sections D set on the recording head HD, they are sometimes referred to sequentially as level 1, level 2, ..., level M. Furthermore, the ejector section D of level m is sometimes referred to as ejector section D[m]. The variable m is an integer satisfying the condition of 1 or more and M or less. Additionally, when the constituent elements or signals of the inkjet printer 1 correspond to the level m of the ejector section D[m], a suffix [m] indicating the correspondence to the level m is sometimes added to the symbol representing that constituent element or signal.

[0056] In this embodiment, it is envisioned that the inkjet printer 1 is a serial printer. Specifically, as follows: Figure 2 As shown, the inkjet printer 1 performs printing by feeding recording paper P in the sub-scanning direction and ejecting ink from the ejection section D while moving the liquid ejection head HU in the main scanning direction. In this embodiment, as... Figure 2 As shown, the +X direction and the -X direction (opposite to +X) are designated as the main scanning directions, and the +Y direction as the secondary scanning direction. Hereinafter, the +X and -X directions will be collectively referred to as the "X-axis direction," and the +Y direction and the -Y direction (opposite to +Y) will be collectively referred to as the "Y-axis direction." Further, the direction perpendicular to both the X-axis and Y-axis directions, and which is the ink ejection direction, will be referred to as the -Z direction. The -Z direction and the +Z direction (opposite to -Z) will be collectively referred to as the "Z-axis direction." The +Z direction is an example of a "pull-in direction."

[0057] In reference Figure 3 At the same time, the recording head HD and the ejection section D set on the recording head HD will be explained.

[0058] Figure 3 This is a schematic partial cross-sectional view of the recording head HD, showing a section including the ejection section D.

[0059] like Figure 3 As shown, the ejector section D includes: a piezoelectric element PZ, which is displaced by a drive signal Vin having a waveform selected from a plurality of waveforms in a drive waveform signal Com; a chamber 320, which increases or decreases the internal pressure according to the displacement of the piezoelectric element PZ; a nozzle N, which communicates with the chamber 320 and is capable of ejecting ink filled inside the chamber 320 in the form of droplets in the -Z direction according to the increase or decrease of the internal pressure of the chamber 320; and a vibrating plate 310. The piezoelectric element PZ is an example of a "drive element". The chamber 320 is an example of a "pressure chamber". The chamber 320 is a space divided by a chamber plate 340, a nozzle plate 330 on which the nozzle N is formed, and a vibrating plate 310. The chamber 320 communicates with a reservoir 350 via an ink supply port 360. The reservoir 350 communicates with a liquid container 14 corresponding to the ejector section D via an ink inlet 370.

[0060] In this embodiment, PZ is used as the piezoelectric element, and the following is employed: Figure 3 The piezoelectric element PZ is shown as a single-chip type. However, the piezoelectric element PZ is not limited to the single-chip type; it can also be a dual-chip type or a stacked type, etc.

[0061] The piezoelectric element PZ has an upper electrode Zu, a lower electrode Zd, and a piezoelectric body Zm disposed between the upper electrode Zu and the lower electrode Zd. The piezoelectric element PZ is a passive element that deforms according to the potential change of a drive signal Vin. When the lower electrode Zd is electrically connected to a power supply line LHb set to a fixed potential Vbs and a 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 or -Z direction according to the applied voltage, resulting in vibration of the piezoelectric element PZ.

[0062] A vibrating plate 310 is provided on the upper opening of the chamber plate 340. A lower electrode Zd is attached to the vibrating plate 310. Therefore, when the piezoelectric element PZ is driven to vibrate according to the drive signal Vin, the vibrating plate 310 also vibrates. Then, the vibration of the vibrating plate 310 causes a change in the volume of the chamber 320, thereby ejecting the ink filled in the chamber 320 from the nozzle N. When the ink in the chamber 320 decreases due to ink ejection, ink is supplied from the reservoir 350.

[0063] The conveying mechanism 7 conveys the recording paper P in the +Y direction. Specifically, the conveying mechanism 7 includes a conveying roller (not shown) with its rotation axis parallel to the X-axis direction, and a motor (not shown) that rotates the conveying roller under the control of the control unit 6.

[0064] The moving mechanism 8, under the control of the control unit 6, causes the liquid nozzle HU to reciprocate along the X-axis. For example, in Figure 2 As illustrated, the moving mechanism 8 has a generally box-shaped conveyor body 82 that houses the liquid nozzle HU, and a seamless belt 81 to which the conveyor body 82 is fixed.

[0065] The storage unit 5 is configured with volatile memory such as RAM and non-volatile memory such as ROM, EEPROM, or PROM, and stores various information such as printing data Img supplied from the host computer and the control program of the inkjet printer 1. RAM is short for Random Access Memory. ROM is short for Read Only Memory. EEPROM is short for Electrically Erasable Programmable Read-Only Memory. PROM is short for Programmable ROM.

[0066] The control unit 6 is configured to include a CPU. CPU stands for Central Processing Unit. However, the control unit 6 can also replace the CPU with a programmable logic device such as an FPGA. FPGA stands for Field Programmable Gate Array.

[0067] The control unit 6 causes the CPU installed in the control unit 6 to operate according to the control program stored in the storage unit 5, thereby causing the inkjet printer 1 to perform printing processing.

[0068] The control unit 6 generates a printing signal SI for controlling the liquid ejector head HU, a waveform specification signal dCom for controlling the drive waveform signal generation circuit 2, a signal for controlling the conveying mechanism 7, and a signal for controlling the moving mechanism 8.

[0069] Here, the waveform specification signal dCom refers to a digital signal that specifies the waveform of the drive waveform signal Com. Furthermore, the drive waveform signal Com refers to an analog signal used to drive the ejector section D. The drive waveform signal generation circuit 2 includes a DA conversion circuit and generates a drive waveform signal Com having the waveform specified by the waveform specification signal dCom.

[0070] Furthermore, the printing signal SI refers to a digital signal used to specify the type of operation of the ejector unit D. Specifically, the printing signal SI is a signal that specifies whether ink is ejected from the ejector unit D when it is driven, by specifying whether a drive waveform signal Com is supplied to the ejector unit D.

[0071] 1.2. Structure of the liquid ejector head HU

[0072] The following is in reference Figure 4 At the same time, the structure of the liquid ejector head HU will be explained.

[0073] Figure 4 This is a block diagram illustrating an example of the structure of a liquid ejector head HU. As described above, the liquid ejector head HU includes a recording head HD and a switching circuit 10. Furthermore, the liquid ejector head HU includes an internal wiring LHa that receives a drive waveform signal Com from the drive waveform signal generation circuit 2.

[0074] like Figure 4 As shown, the switching circuit 10 includes switches SWA[1] to SWA[M] as M switches SWA, and a connection state specifying circuit 11 for specifying the connection state of each switch. In addition, each switch can be, for example, a transmission gate.

[0075] The switch SWA[m] switches the conduction and deconduction of the internal wiring LHa and the upper electrode Zu[m] of the piezoelectric element PZ[m] located on the ejector section D[m] according to the connection state specification signal SLa[m]. For example, the switch SWA[m] is set to conduction when the connection state specification signal SLa[m] is high, and set to deconduction when it is low.

[0076] 1.3. Head Unit Actions

[0077] The following is in reference Figures 5-7 At the same time, the action of the liquid ejection head HU is explained.

[0078] In this embodiment, the operation period of the inkjet printer 1 includes multiple recording periods Tu. In the inkjet printer 1 according to this embodiment, it is envisioned that the driving of each ejector section D in the printing process is performed within each recording period Tu. In the following description, the operation period of the inkjet printer 1 has I recording periods Tu. I is an integer greater than or equal to 2. Further, the i-th recording period Tu is sometimes referred to as recording period Tu[i]. I is an integer from 1 to 1.

[0079] In addition, under normal circumstances, inkjet printer 1 repeatedly performs printing processing across multiple recording periods Tu, ejecting ink once or multiple times from each ejection section D, thereby forming an image representing printing data Img.

[0080] Figure 5 Here, is a timing diagram used to illustrate the actions in Tu[i] during the recording period of inkjet printer 1.

[0081] like Figure 5 As shown, the control unit 6 outputs a latch signal LAT with a pulse PLsL and a conversion signal CH with a pulse PLsC. Therefore, the control unit 6 defines the recording period Tu[i] as the period from the rising edge of the pulse PLsL to the rising edge of the next pulse PLsL. Furthermore, based on the pulse PLsC, the control unit 6 divides the recording period Tu[i] into control period Tcu1, control period Tcu2, control period Tcu3, control period Tcu4, and control period Tcu5.

[0082] like Figure 5 As shown, the drive waveform signal generation circuit 2 outputs a drive waveform signal Com. The drive waveform signal Com includes: a drive pulse PL1 set during control period Tcu1, a drive pulse PL2 set during control period Tcu2, a drive pulse PL3 set during control period Tcu3, a drive pulse PL4 set during control period Tcu4, and a drive pulse PL5 set during control period Tcu5. In this embodiment, the drive pulse PL supplied to the piezoelectric element PZ from control period Tcu1 to control period Tcu3 is referred to as waveform PH1, and the drive pulse PL supplied to the piezoelectric element PZ from control period Tcu4 to control period Tcu5 from the droplet DR ejected from the nozzle N is referred to as waveform PH2. In the following description, waveform PH1 and waveform PH2 are sometimes collectively referred to as "waveform PH," and drive pulses PL1 to PL5 are sometimes collectively referred to as "drive pulse PL."

[0083] Drive pulse PL1 has drive components DC1 and DC2. Drive pulse PL2 has drive components DC3 and DC4. Drive pulse PL3 has drive components DC5 and DC6. Drive pulse PL4 has drive components DC7 and DC8. Drive pulse PL5 has drive components DC9 and DC10. Drive components DC1, DC3, DC5, DC7, and DC9 reduce the pressure in chamber 320. Drive components DC2, DC4, DC6, DC8, and DC10 increase the pressure in chamber 320. In the following description, drive components DC1 to DC10 are sometimes collectively referred to as "drive component DC".

[0084] like Figure 5 As shown, the starting and ending potentials of drive pulses PL1, PL2, PL3, PL4, and PL5 are all set to a reference potential V0. In this embodiment, the reference potential V0 is also the highest potential of drive pulses PL1 to PL5. Figure 5 The potential VL1 shown is the lowest potential of the driving pulses PL1 to PL5.

[0085] As in Figure 5 As illustrated, the difference between the highest and lowest potentials in the drive pulses PL1 to PL5 is the potential difference Vh. That is, the difference between the highest and lowest potentials in waveform PH1 is the potential difference Vh. Similarly, the difference between the highest and lowest potentials in waveform PH2 is the potential difference Vh. In the following description, the difference between the highest and lowest potentials in waveform PH is sometimes referred to as the "potential difference of waveform PH". The potential difference of waveform PH1 is approximately equal to the potential difference of waveform PH2. "Approximately equal" means that, in addition to being completely equal, it also includes cases where measurement errors can be considered as equal. The potential difference of waveform PH is more than 80% of the maximum potential difference that can be supplied to the piezoelectric element PZ. Since a larger potential difference in waveform PH results in a greater ejection volume, it is preferable for the potential difference of waveform PH to be closer to the maximum potential difference that can be supplied to the piezoelectric element PZ. The designer of the inkjet printer 1 adjusts the potential difference of waveform PH to be close to the maximum potential difference that can be supplied to the piezoelectric element PZ.

[0086] The printing signal SI includes individual designation signals Sd[1] to Sd[M] that specify the driving mode of the ejector sections D[1] to D[M] in each recording period Tu. Furthermore, when printing processing is performed during the recording period Tu[i], the control unit 6 will... Figure 5As shown, before the start of the recording period Tu[i], the printed signal SI, including the individual designation signals Sd[1] to Sd[M], is supplied to the connection state designation circuit 11 in a manner synchronized with the clock signal CL. In this case, the connection state designation circuit 11 generates the connection state designation signal SLa[m] based on the individual designation signal Sd[m] during the recording period Tu[i].

[0087] Furthermore, the individually specified signal Sd[m] involved in this embodiment is a signal that specifies any one of the five driving modes α1 to α5 shown below during each recording period Tu. In this embodiment, as an example, the case where the individually specified signal Sd[m] is a five-bit digital signal is envisioned.

[0088] Figure 6 This diagram illustrates the five driving modes obtainable by the individually specified signal Sd[m]. The individually specified signal Sd[m] represents any one of the following values: driving mode α1 (1, 1, 1, 1, 1), driving mode α2 (0, 0, 0, 1, 1), driving mode α3 (0, 0, 1, 1, 1), driving mode α4 (0, 1, 1, 1, 1), and driving mode α5 (0, 0, 0, 0, 0). When the x-th bit of the individually specified signal Sd[m] is "1", the connection state specifying circuit 11 sets the connection state specifying signal SLa[m] to a high level during the control period Tcux; when the x-th bit is "0", the connection state specifying signal SLa[m] is set to a low level during the control period Tcux. x is an integer from 1 to 5.

[0089] Specifically, when the connection state specifying circuit 11 indicates driving mode α1 using the separate specifying signal Sd[m], it sets the connection state specifying signal SLa[m] to a high level during control periods Tcu1, Tcu2, Tcu3, Tcu4, and Tcu5. When the connection state specifying circuit 11 indicates driving mode α2 using the separate specifying signal Sd[m], it sets the connection state specifying signal SLa[m] to a low level during control periods Tcu1, Tcu2, and Tcu3, and sets it to a high level during control periods Tcu4 and Tcu5. When the connection state specifying circuit 11 indicates driving mode α3 using the separate specifying signal Sd[m], it sets the connection state specifying signal SLa[m] to a low level during control periods Tcu1 and Tcu2, and sets it to a high level during control periods Tcu3, Tcu4, and Tcu5. When the connection state specifying circuit 11 indicates drive mode α4 with the sole specifying signal Sd[m], it sets the connection state specifying signal SLa[m] to a low level during control period Tcu1, and sets it to a high level during control periods Tcu2, Tcu3, Tcu4, and Tcu5. When the connection state specifying circuit 11 indicates drive mode α5 with the sole specifying signal Sd[m], it sets the connection state specifying signal SLa[m] to a low level during control periods Tcu1, Tcu2, Tcu3, Tcu4, and Tcu5. As an example of the drive signal Vin, using... Figure 7 Let Vin be the driving signal Sd[m] based on the driving mode α2.

[0090] In this embodiment, although the details will be described later, when the ejector part D, which is supplied with a reference potential V0 to the piezoelectric element PZ, is in a static state and the position of the meniscus MS is static at the initial position Z0, and when a drive signal Vin based on a separate specified signal Sd[m] based on the drive mode α1 is supplied to the piezoelectric element PZ, droplets DR will be ejected from the nozzle N during the control period Tcu4 to the control period Tcu5. Figure 7This diagram illustrates the drive signal Vin for a single specified signal Sd[m] based on drive mode α2. The drive signal Vin includes drive signal Vin1 and drive signal Vin2. Drive signal Vin1 is the drive signal Vin that runs from the start of control period Tcu1 to the end of control period Tcu3. Drive signal Vin2 is the drive signal Vin that runs from the start of control period Tcu4 to the end of control period Tcu5. (The diagram is repeated in the original text.) Figure 7 As shown, the drive signal Vin1 included in the drive signal Vin based on the individually specified signal Sd[m] of drive mode α2 sets the ejector D to non-driven from the start of control period Tcu1 to the end of control period Tcu3. The drive signal Vin2 included in the drive signal Vin based on the individually specified signal Sd[m] of drive mode α2 drives the ejector D from the start of control period Tcu4 to the end of control period Tcu5. In other words, the drive signal Vin based on the individually specified signal Sd[m] of drive mode α2 does not have waveform PH1, but has waveform PH2.

[0091] Additionally, drive signal Vin1 is an example of a "first drive signal". Drive signal Vin2 is an example of a "second drive signal".

[0092] 1.4. Relationship between the drive signal Vin and the liquid level at the ejection section D

[0093] Next, refer to Figures 8 to 17 Therefore, the following example will be used to illustrate this: In an example where, due to the high viscosity of the ink, when the ejector section D, supplied with a reference potential V0 by the piezoelectric element PZ, is stationary and the meniscus MS is stationary at its initial position Z0, and a drive signal Vin based on a individually specified signal Sd[m] of drive mode α2 to drive mode α5 is supplied to the piezoelectric element PZ, the droplet DR is not ejected from the nozzle N; however, when a drive signal Vin based on a individually specified signal Sd[m] of drive mode α1 is supplied to the piezoelectric element PZ, the droplet DR is ejected from the nozzle N. For example... Figure 5 The state of the liquid surface at the ejector section D at each of the following time points—t1, t2, t3, t4, t5, t6, t7, t8, t9, and t10—is described. Figures 8 to 17The diagram shows a cross-sectional view taken along the XZ plane at time points t1 to t10, showing the area near nozzle N. The liquid surface within the ejection section D represents the liquid surface within nozzle N. The liquid surface within nozzle N is defined as the liquid surface located inside the wall of nozzle N when viewing ejection section D along the -Z direction. Therefore, if the liquid surface located on the outer side of the wall of nozzle N when viewing ejection section D in a direction perpendicular to the -Z direction, such as along the Y-axis—that is, the liquid surface protruding from nozzle N in the -Z direction—is also located inside the wall of nozzle N when viewing ejection section D along the -Z direction, it is also included within the liquid surface within nozzle N. Hereinafter, the liquid surface within nozzle N will be referred to as the "curved surface MS".

[0094] In the first embodiment, even when the ejector portion D, which is supplied with a reference potential V0 from the positive piezoelectric element PZ, is in a static state and the position of the meniscus MS is... Figure 8 Starting from the initial position Z0, which is in a static state, a drive signal Vin with only one drive pulse PL is supplied to the piezoelectric element PZ. Due to the high viscosity of the liquid, the pressure variation of the ink within the chamber 320 cannot increase, and therefore the ejector section D does not eject droplets DR. The initial position Z0 is such that, in the Z-axis direction, the position of the meniscus MS is approximately aligned with the -Z direction surface of the nozzle plate 330. In practice, to maintain a proper negative pressure state for the ink within the ejector section D and prevent it from drooping from the nozzle N, the center of the meniscus MS is formed as a concave surface recessed towards the chamber 320. In the first embodiment, by supplying the piezoelectric element PZ with a drive signal Vin having drive pulses PL1, PL2, PL3, PL4, and PL5, the ejector section D ejects droplets. Furthermore, even if a drive signal Vin with drive pulses PL1, PL2, PL3, and PL4 but without drive pulse PL5 is supplied to the piezoelectric element PZ, the ejector section D will still eject droplets. By supplying the piezoelectric element PZ with drive signals Vin having drive pulses PL1, PL2, PL3, PL4 and PL5, a more stable ejection can be achieved compared to supplying the piezoelectric element PZ with drive signals Vin having drive pulses PL1, PL2, PL3 and PL4 but without drive pulse PL5.

[0095] Figure 8This diagram illustrates the meniscus MS at time point t1. Time point t1 is the point within the control period Tcu1 where the supply of the driving component DC1 ends. The switching circuit 10 supplies a driving signal Vin with the driving component DC1 to the piezoelectric element PZ, thereby elongating the concave surface shape of the meniscus MS (which has its central portion recessed towards the chamber 320, i.e., the +Z direction) in the Z-axis direction while simultaneously pulling it inward in the +Z direction. At this time, the portion of the meniscus MS that is pulled in the most in the +Z direction is pulled to the pull-in position Zp1. The portion of the meniscus MS that is pulled in the most in the +Z direction, when viewed from above in the Z-axis direction, is the central portion of the meniscus MS and corresponds to the bottom portion of the concave surface shape. When viewed from above in the Z-axis direction, the central portion of the meniscus MS is approximately aligned with the central portion of the nozzle N. For the sake of simplicity, the central portion of the meniscus MS when viewed from above along the Z-axis will be referred to as the "central portion of the meniscus MS". Furthermore, the area surrounding the central portion of the meniscus MS will be referred to as the "peripheral portion of the meniscus MS". The pull-in position Zp1 is located in the +Z direction compared to the initial position Z0.

[0096] Figure 9 This diagram illustrates the meniscus MS at time point t2. Time point t2 is the end of the control period Tcu1 and the end of the supply of the driving component DC2. A driving signal Vin with driving component DC2 is supplied to the piezoelectric element PZ via the switching circuit 10, causing the meniscus MS to be extruded in the -Z direction, thereby forming a liquid column LC2 protruding in the -Z direction at the central portion of the meniscus MS. In the following description, a liquid column is defined as a protruding columnar or hammer-shaped liquid surface in the meniscus MS, extending from the position closest to the +Z direction side to the position closest to the -Z direction side. The top of the liquid column LC2 in the -Z direction is located at the extrusion position Zm1. The extrusion position Zm1 is located in the -Z direction relative to the initial position Z0.

[0097] Figure 10The diagram illustrates the meniscus MS at time point t3. Time point t3 is the point within the control period Tcu2 where the supply of the driving component DC3 ends. A driving signal Vin containing the driving component DC3 is supplied to the piezoelectric element PZ via the switching circuit 10, thereby pulling the meniscus MS in the +Z direction. The meniscus MS has a concave shape at its periphery that indents towards the +Z direction and a liquid column LC3 protruding towards the -Z direction at its central portion. At this time, the portion of the meniscus MS that is pulled in the +Z direction the most is pulled in until the pull-in position Zp2 is reached. The pull-in position Zp2 at time point t3 is located in the +Z direction relative to the initial position Z0 and in the -Z direction relative to the pull-in position Zp1 at time point t1. In other words, by supplying the driving component DC3 to the piezoelectric element PZ, even though the ink pressure in the chamber 320 decreases and the ink in the nozzle N is pulled in the +Z direction, it still... Figure 10 As shown, at time point t3, a liquid column LC3 protruding in the -Z direction is formed in the central portion of the meniscus MS. Liquid column LC3 is formed in the central portion of the meniscus MS. When observed from the pull-in position Zp2 in the -Z direction, it can also be said that the central portion of the meniscus MS forms a convex shape. The liquid surface surrounding liquid column LC3 is concave in the +Z direction.

[0098] Figure 11 This diagram illustrates the meniscus MS at time point t4. Time point t4 is the end time of control period Tcu2 and the end time of supplying the driving component DC4. A driving signal Vin containing the driving component DC4 is supplied to the piezoelectric element PZ via switching circuit 10, causing the meniscus MS to be extruded in the -Z direction, forming a liquid column LC4 protruding in the -Z direction at the central portion of the meniscus MS. The tip of the liquid column LC4 in the -Z direction is located at the extrusion position Zm2. The extrusion position Zm2 at time point t4 is located further in the -Z direction than the extrusion position Zm1 at time point t2.

[0099] Figure 12The diagram illustrates the meniscus MS at time point t5. Time point t5 is the point within the control period Tcu3 where the supply of the driving component DC5 ends. A driving signal Vin with the driving component DC5 is supplied to the piezoelectric element PZ via the switching circuit 10, thereby pulling the meniscus MS in the +Z direction. The meniscus MS has a concave shape at its periphery that indents towards the +Z direction and a liquid column LC5 protruding towards the -Z direction at its central portion. At this time, the portion of the meniscus MS that is pulled in the +Z direction the most is pulled in until the pull-in position Zp3 is reached. The pull-in position Zp3 at time point t5 is located in the +Z direction relative to the initial position Z0 and in the -Z direction relative to the pull-in position Zp2 at time point t3. In other words, by supplying the driving component DC5 to the piezoelectric element PZ, even though the ink pressure in the chamber 320 decreases and the ink in the nozzle N is pulled in the +Z direction, it still... Figure 12 As shown, at time point t5, a liquid column LC5 protruding in the -Z direction is formed in the central portion of the meniscus MS. Furthermore, the liquid column LC5 at time point t5 is larger than the liquid column LC3 at time point t3. The liquid column LC5 is formed in the central portion of the meniscus MS. When observed from the pull-in position Zp3 in the -Z direction, it can also be said that the central portion of the meniscus MS forms a convex shape. The liquid surface around the liquid column LC5 is concave in the +Z direction.

[0100] Figure 13 This diagram illustrates the meniscus MS at time point t6. Time point t6 is the end time of control period Tcu3 and the end time of supplying the driving component DC6. A driving signal Vin containing the driving component DC6 is supplied to the piezoelectric element PZ via switching circuit 10, causing the meniscus MS to be extruded 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 extrusion position Zm3. The extrusion position Zm3 at time point t6 is located further in the -Z direction than the extrusion position Zm2 at time point t4.

[0101] Figure 14The diagram illustrates the meniscus MS at time point t7. Time point t7 is the point within the control period Tcu4 where the supply of the driving component DC7 ends. A driving signal Vin containing the driving component DC7 is supplied to the piezoelectric element PZ via the switching circuit 10, thereby pulling the meniscus MS in the +Z direction. The meniscus MS has a concave shape at its periphery that is recessed towards the +Z direction and a liquid column LC5 protruding towards the -Z direction at its central portion. At this time, the portion of the meniscus MS that is pulled in the +Z direction the most is pulled in until the pull-in position Zp4 is reached. The pull-in position Zp4 at time point t7 is located closer to the +Z direction than the pull-in position Zp3 at time point t5, and closer to the -Z direction than the pull-in position Zp1 at time point t1. In other words, by supplying the driving component DC7 to the piezoelectric element PZ, even though the ink pressure in the chamber 320 decreases and the ink in the nozzle N is pulled in the +Z direction, it still... Figure 14 As shown, at time point t7, a liquid column LC7 protruding in the -Z direction forms in the central portion of the meniscus MS. The liquid column LC7 at time point t7 is larger than the liquid column LC5 at time point t5. Furthermore, at... Figure 14 The figure shows the meniscus MS at time point t7 when drive signals Vin with drive pulses PL1, PL2, PL3, PL4, and PL5 are supplied to the piezoelectric element PZ. That is, Figure 14 The state of the meniscus MS shown is the case where drive pulses PL1 to PL3 are supplied to the piezoelectric element PZ before drive pulse PL4 is supplied to it. Assuming that a drive signal Vin consisting only of drive pulse PL4 is supplied to the piezoelectric element PZ, and the ejector portion D, which is currently supplied with a reference potential V0, is in a stationary state while the meniscus MS is stationary at its initial position Z0, drive pulse PL4 is supplied to the piezoelectric element PZ. Therefore, at time point t7, the meniscus MS will be in the same state as... Figure 8 The meniscus MS at time point t1 is equivalent. That is, when the drive signal Vin with only the drive pulse PL4 is supplied to the piezoelectric element PZ, the meniscus MS has a concave curved surface shape that is recessed in the +Z direction at its central part, and the position of the part of the meniscus MS that is pulled in the +Z direction the most is the pull-in position Zp1.

[0102] Figure 15The diagram illustrates the meniscus MS at time point t8. Time point t8 is the end time of control period Tcu4 and the end time of supplying the driving component DC8. A driving signal Vin containing the driving component DC8 is supplied to the piezoelectric element PZ via switching circuit 10, causing the meniscus MS to be extruded in the -Z direction, thus forming a liquid column LC8 protruding in the -Z direction at the central portion of the meniscus MS. The length of the liquid column LC8 in the Z-axis direction at time point t8 is shorter than that of the liquid column LC7 at time point t7. The tip of the liquid column LC8 in the -Z direction is spherical, and a necking occurs midway through the liquid column LC8.

[0103] Figure 16 The diagram illustrates the meniscus MS at time point t9. Time point t9 is the point within the control period Tcu5 where the supply of the driving component DC9 ends. A driving signal Vin containing the driving component DC9 is supplied to the piezoelectric element PZ via the switching circuit 10, thereby pulling the meniscus MS in the +Z direction. The meniscus MS has a concave shape at its periphery that is recessed towards the +Z direction and a liquid column LC9 protruding towards the -Z direction at its central portion. At this time, the portion of the meniscus MS that is pulled in the most in the +Z direction is pulled to a position closer to the +Z direction than the initial position Z0. On the other hand, by supplying the driving component DC9 to the piezoelectric element PZ, although the ink pressure in the chamber 320 decreases and the ink in the nozzle N is pulled in the +Z direction, the tip of the liquid column LC8 formed in the meniscus MS at time t8 continues to move in the -Z direction, forming a liquid column LC9 at the central part of the meniscus MS. As the necked portion of the liquid column LC9 becomes thinner and longer, the tip portion of the liquid column LC9 in the -Z direction 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 t8 continues to move in the -Z direction, by supplying the piezoelectric element PZ with a driving signal Vin containing the driving component DC9, the ink pressure in the chamber 320 decreases, causing the ink in the nozzle N to be pulled in the +Z direction and the peripheral portion of the meniscus MS to move in the +Z direction, thus the droplet DR is torn off from the liquid column LC9. Figure 16 The image shows the state of the droplet DR just before it is about to separate from the meniscus MS.

[0104] Figure 17 This diagram illustrates the meniscus MS at time point t10. Time point t10 is the point within the control period Tcu5, and the time when the supply of the driving component DC10 ends. A driving signal Vin containing the driving component DC10 is supplied to the piezoelectric element PZ via the switching circuit 10, thereby causing the meniscus MS to approach its initial position Z0. Figure 17 As shown, a liquid column LC10 protruding in the -Z direction is formed in the central portion of the meniscus MS. However, the meniscus MS vibrates, and after time point t10, the central portion of the meniscus MS is pulled in the +Z direction. Figure 17 The image shows the droplet DR that was separated after time point t9.

[0105] Because the position of the meniscus MS returns to the initial position Z0 without causing the droplet DR to continue being ejected from the ejector section D by supplying the driving component DC10 to the piezoelectric element PZ, the amount of potential change per unit period in the driving component DC10 is smaller compared to that of the driving components DC2, DC4, DC6, and DC8. Furthermore, although in the first embodiment the amount of potential change per unit period in the driving component DC10 is fixed during the period in which the driving component DC10 is supplied, it can also vary during the period in which the driving component DC10 is supplied. The amount of potential change per unit period in the driving components DC1, DC3, DC5, DC7, and DC9 is approximately equal. The amount of potential change per unit period in the driving components DC2, DC4, DC6, and DC8 is approximately equal.

[0106] like Figures 8 to 17 As shown, when a drive signal Vin based on a single specified signal Sd[m] specifying the drive mode α1 is supplied to the piezoelectric element PZ, the meniscus MS is pulled in the +Z direction to the maximum extent when the drive component DC1 of the initial drive pulse PL1 is supplied to the piezoelectric element PZ. Subsequently, with each drive pulse PL2 and drive pulse PL3 supplied to the piezoelectric element PZ, the meniscus MS is squeezed out in the -Z direction, and the liquid column formed in the central portion of the meniscus MS also grows along the Z-axis direction. Furthermore, when a drive pulse PL4 is supplied to the piezoelectric element PZ, the liquid column grows further thinner and longer in the Z-axis direction, causing a portion of the liquid column LC9 to fly in the -Z direction as a droplet DR. However, when a drive signal Vin based on a single specified signal Sd[m] specifying the drive mode α5 is supplied to the piezoelectric element PZ, the droplet DR does not fly. An example of supplying a drive signal Vin to the piezoelectric element PZ based on a separately specified signal Sd[m] determined by any one of the drive modes α2, α3, and α4 will be used. Figures 21-25 This will be explained later.

[0107] 1.5. Pressure variation generated by the drive signal Vin

[0108] Although Figures 8 to 17The description focuses on the action of the meniscus MS when drive pulses PL1 to PL5 are sequentially supplied to the piezoelectric element PZ, but the following section will use... Figure 18 This section explains the pressure variation in chamber 320 generated by the drive signal Vin. Figure 18 The curves G1 and G2 shown represent the pressure variations within chamber 320 obtained through fluid reanalysis simulation. The horizontal axis of curves G1 and G2 represents time, while the vertical axis represents pressure. Furthermore, the pressure of chamber 320 in its stationary state, with the ejector D supplying a reference potential V0 to the piezoelectric element PZ, is set as the zero point of the vertical axis of curves G1 and G2. The unit of pressure is Pascal, expressed as "Pa" in curves G1 and G2. A positive pressure value indicates a decrease in the volume of chamber 320 and an increase in the internal pressure; a negative pressure value indicates an increase in the volume of chamber 320 and a decrease in the internal pressure. "E+0i" in curves G1 and G2 represents 10... +i i is 5 or 6.

[0109] Figure 18This is a graph used to illustrate the pressure variation characteristics generated by the drive signal Vin. Graph G1 shows the pressure variation characteristics Pa1 and Pn1 of the piezoelectric element PZ on the ink in chamber 320, respectively, when a drive signal Vin with drive pulse PL4 but without drive pulses PL1, PL2, PL3, and PL5 is supplied to the piezoelectric element PZ. In other words, graph G1 corresponds to the pressure variation characteristics Pa1 of the ink in chamber 320 and Pn1 of the ink in nozzle N when a drive signal Vin with only waveform PH2 and without waveform PH1 is supplied to the piezoelectric element PZ. Point Pn1p within the pressure variation characteristic Pn1 represents the highest pressure that can be applied to the ink in nozzle N when only drive pulse PL4 is supplied to the piezoelectric element PZ, and the time point at which this pressure is generated. The pressure represented by point Pn1p is approximately 1.2 × 1006 Pascals. Furthermore, the pressure represented by point Pn1p corresponds to the increase in pressure of the ink within nozzle N when only the drive pulse PL4 is supplied to the piezoelectric element PZ, representing the change in pressure towards the positive pressure side from the pressure of the ink within nozzle N in the static state of the ejection section D. Point Pn1m within the pressure variation characteristic Pn1 represents the minimum pressure that can be applied to the ink within nozzle N, and the time point at which that pressure is generated. The pressure represented by point Pn1m is approximately -1.2 × 10⁻⁶. 06 Pascal. Furthermore, the pressure represented by point Pn1m is equivalent to the amount of change, i.e., the reduction, in the pressure of the ink in nozzle N from the stationary state of the ejection section D when only the drive pulse PL4 is supplied to the piezoelectric element PZ, towards the negative pressure side.

[0110] Curve G2 represents the pressure variation characteristics Pa2 and Pn2 of the ink in chamber 320, respectively, when a drive signal Vin with drive pulses PL1, PL2, PL3, and PL4 is supplied to the piezoelectric element PZ. In other words, curve G2 corresponds to the pressure variation characteristics Pa2 and Pn2 of the ink in nozzle N when a drive signal Vin including waveforms PH1 and PH2 is supplied to the piezoelectric element PZ. Point Pn2p within the pressure variation characteristic Pn2 represents the highest pressure that can be applied to the ink in nozzle N during the period when the piezoelectric element PZ supplies the drive signal Vin with drive pulses PL1, PL2, PL3, and PL4, and during the period when the piezoelectric element PZ supplies the drive pulse PL4, and the time point at which this pressure is generated. The pressure represented by point Pn2p is approximately 1.2 × 10⁻⁶. 06 Pascal. Furthermore, the pressure represented by point Pn2p is equivalent to the pressure of the ink in nozzle N when drive pulse PL4 is supplied to piezoelectric element PZ during the period when drive signal Vin with drive pulses PL1, PL2, PL3 and PL4 is supplied to piezoelectric element PZ, and is the amount of change, i.e., the increase, from the pressure of the ink in nozzle N in the stationary state of ejection section D towards the positive pressure side.

[0111] The point Pn2m within the pressure variation characteristic Pn2 represents the lowest pressure that can be applied to the ink in nozzle N during the period when the positive piezoelectric element PZ supplies drive signals Vin with drive pulses PL1, PL2, PL3, and PL4, and specifically during the period when the positive piezoelectric element PZ supplies drive pulse PL4, and the time point at which this pressure is generated. The pressure represented by point Pn2m is approximately -1.2 × 10⁻⁶. 06 Pascal. Furthermore, the pressure represented by point Pn2m is equivalent to the pressure of the ink in nozzle N when drive pulse PL4 is supplied to piezoelectric element PZ during the period when drive signal Vin with drive pulses PL1, PL2, PL3 and PL4 is supplied to piezoelectric element PZ, and is the amount of change, i.e., the decrease, from the pressure of the ink in nozzle N in the stationary state of ejection section D towards the negative pressure side.

[0112] Furthermore, the time points represented by Pn1m and Pn2m coincide with the end time of the supply of driving component DC7. Additionally, the time points represented by Pn1p and Pn2p coincide with the end time of the supply of driving component DC8.

[0113] like Figure 18 As shown in graph G1, the pressure variations on both the positive and negative sides within nozzle N when only a drive signal Vin with drive pulse PL4 is supplied to piezoelectric element PZ are present is approximately equal to the pressure variations on both the positive and negative sides within nozzle N when drive signals Vin with drive pulses PL1, PL2, PL3, and PL4 are supplied to piezoelectric element PZ. The pressure variation is defined as the sum of the increase and decrease in pressure. Specifically, the pressure represented by point Pn1p is approximately 1.2 × 10⁻⁶. 06 As shown by Pascal's line segment LPnp, the pressure represented by point Pn2p is approximately equal to that represented by point Pn1m. Furthermore, the pressure represented by point Pn1m is approximately -1.2 × 10⁻⁶. 06 As shown by Pascal's line segment LPnm, it is approximately equal to the pressure represented by point Pn2m.

[0114] Typically, when using inks with a viscosity less than 20 mPascals per second, by setting the interval of multiple drive pulses to a resonant timing, the pressure variation generated by subsequent drive pulses and the pressure variation generated by preceding drive pulses resonate and become larger. Consequently, the pressure variation of the liquid in the nozzle when a subsequent drive pulse is supplied to the piezoelectric element is larger than the pressure variation of the liquid in the nozzle when a preceding drive pulse is supplied to the piezoelectric element. However, in this embodiment, the pressure variation of the liquid in the nozzle when only drive pulse PL4 shown in curve G1 is supplied, and the pressure variation of the liquid in the nozzle when drive pulses PL1, PL2, PL3, and PL4 shown in curve G2 are continuously supplied to the piezoelectric element PZ, are approximately equal as described above. This can be considered as indicating that, since the ink in this embodiment has a high viscosity, it means that the pressure variation generated by the preceding drive pulse PL and the pressure variation generated by the subsequent drive pulse PL do not resonate.

[0115] 1.6. Volumetric velocity generated by the driving signal Vin

[0116] Next, use Figure 19 The volumetric velocity of the ink within nozzle N, generated by the drive signal Vin, will be explained. The volumetric velocity of the ink within nozzle N is the movement speed of the ink within nozzle N in the Z-axis direction. Figure 19 The curves G3 and G4 shown represent the volumetric velocity obtained through fluid reanalysis simulation. The horizontal axis of curves G3 and G4 represents time, while the vertical axis of curves G3 and G4 represents the volumetric velocity of the ink within nozzle N. The unit of volumetric velocity is cubic meters per second, expressed in "m" in curves G3 and G4.3 The value is shown in the form " / s". The volumetric velocity of the ink in nozzle N is the volume of ink that moves in nozzle N per unit period. A positive volumetric velocity in nozzle N indicates that the ink has moved in the +Z direction, and a negative volumetric velocity in nozzle N indicates that the ink has moved in the -Z direction. "E-06" in graphs G3 and G4 indicates 10... -06 .

[0117] Figure 19 This is a graph illustrating the variation characteristics of the volumetric velocity of ink within nozzle N. Curve G3 shows the variation characteristic Vn3 of the volumetric velocity of ink within nozzle N when a drive signal Vin with drive pulse PL4 is supplied to piezoelectric element PZ, but without drive pulses PL1, PL2, PL3, and PL5. Point Vn3p within the variation characteristic Vn3 represents the maximum volumetric velocity of ink within nozzle N in the +Z direction, and the time point at which this volumetric velocity occurs. The volumetric velocity represented by point Vn3p is approximately 2.7 × 10⁻⁶. -6 cubic meters per second. The point Vn3m within the variation characteristic Vn3 represents the maximum volumetric velocity in the -Z direction and the time point at which this volumetric velocity occurs. The volumetric velocity represented by point Vn3m is approximately -3.3 × 10⁻⁶. -6 cubic meters per second.

[0118] Curve G4 represents the variation characteristic Vn4 of the volumetric velocity of ink within nozzle N when a drive signal Vin with drive pulses PL1, PL2, PL3, and PL4 is supplied to the piezoelectric element PZ. Point Vn4p within the variation characteristic Vn4 represents the maximum volumetric velocity of ink within nozzle N in the +Z direction, and the time point at which this volumetric velocity is generated, when drive pulse PL4 is supplied to the piezoelectric element PZ. The volumetric velocity represented by point Vn4p is approximately 2.7 × 10⁻⁶. -06 cubic meters per second. The point Vn4m within the variation characteristic Vn4 represents the maximum volumetric velocity in the -Z direction and the time point at which this volumetric velocity is generated when the driving pulse PL4 is supplied to the piezoelectric element PZ. The volumetric velocity represented by point Vn4m is approximately -3.3 × 10⁻⁶. -6 cubic meters per second.

[0119] Furthermore, the time points represented by Vn3p and Vn4p coincide with the end time of the supply of driving component DC7. Additionally, the time points represented by Vn3m and Vn4m coincide with the end time of the supply of driving component DC8.

[0120] like Figure 19As shown, the volumetric velocity of the ink in nozzle N when a drive signal Vin with only drive pulse PL4 is supplied to the piezoelectric element PZ is approximately equal to the volumetric velocity of the ink in nozzle N when a drive signal Vin with drive pulses PL1, PL2, PL3, and PL4 is supplied to the piezoelectric element PZ. Specifically, the volumetric velocity represented by point Vn3p is approximately 2.7 × 10⁻⁶. -06 The volume velocity represented by the line segment LVnp, in cubic meters per second, is approximately equal to the volume velocity represented by the point Vn4p. Furthermore, the volume velocity represented by the point Vn3m is approximately -3.3 × 10⁻⁶. 6 The velocity represented by the line segment LVnm in cubic meters per second is approximately equal to the volume velocity represented by the point Vn4m.

[0121] This can be considered as demonstrating the following situation, namely, compared with the reference. Figure 18 As previously described, the pressure variation characteristics generated by the drive signal Vin are the same. Since the ink in this embodiment is of high viscosity, the pressure variation generated by the preceding drive pulse PL and the pressure variation generated by the subsequent drive pulse PL do not resonate.

[0122] 1.7. Appropriate conditions for the driving waveform signal Com

[0123] Return to the instructions Figure 5 .like Figure 5 As shown, the periods Pw24 from time point tDC2 to time point tDC4, Pw46 from time point tDC4 to time point tDC6, and Pw68 from time point tDC6 to time point tDC8 are approximately the same. "Approximately the same" means that, in addition to being completely identical, they also include cases where measurement errors are taken into account. In the following description, periods Pw24, Pw46, and Pw68 will sometimes be collectively referred to as "period Pw". Time point tDC2 is the starting time of the supply of drive component DC2. Time point tDC4 is the starting time of the supply of drive component DC4. Time point tDC6 is the starting time of the supply of drive component DC6. Time point tDC8 is the starting time of the supply of drive component DC8. Alternatively, period Pw can be described as the timing interval of the start of the drive component DC in the continuous drive pulses PL that increase the pressure in chamber 320. Figure 20 This section explains the relationship between Pw and ejection performance values ​​during the period.

[0124] Figure 20 This is a graph used to illustrate the relationship between Pw and ejection performance values ​​during the period. The ejection performance values ​​are obtained by multiplying the volume of the droplet DR by the velocity of the droplet DR ejected from nozzle N. The unit of the ejection performance values ​​is Newton-second. Figure 20 In the curve G5 shown, it is represented in the form of "Ns". "E-10" in curve G5 represents 10. -10 .like Figure 20 The horizontal axis of the curve G5 shown is the value obtained by dividing Pw by the natural vibration period TC of the ejector part D during the period.

[0125] The natural vibration period TC is the reciprocal of the natural vibration number of the ejector part D, which can generally be expressed by the following equation (1).

[0126] Mathematical Formula 1

[0127]

[0128] In equation (1) above, M represents the inertia of the flow channel, and C represents the flexibility of the vibrating plate 310. V And the compressibility of ink C L The sum. ζ is a value less than 1 and can be expressed by equation (2) shown below.

[0129] Mathematical formula 2

[0130]

[0131] In equation (2) above, R represents the viscous resistance of the flow channel and is proportional to the viscosity of the ink.

[0132] Hereinafter, the value of Pw divided by the natural vibration period TC of the ejector section D is called the "pulse interval ratio". The vertical axis of graph G5 represents the ejection performance value mentioned above. The multiple black dots in graph G5 represent the pulse interval ratio and ejection performance value obtained through experiments, respectively. Furthermore, graph G5 shows the characteristic CPw of the pulse interval ratio, calculated based on the pulse interval ratio and ejection performance value obtained through experiments. The characteristic CPw is calculated, for example, using the least squares method.

[0133] As shown in graph G5, a pulse interval ratio of 1 or higher but less than 2 corresponds to an ejection performance value of approximately 1.8 × 10⁻⁶. -10Compared to pulse interval ratios of 1 to 1, and pulse interval ratios greater than 2, the ejection performance value can be increased. For example, when the pulse interval ratio during period Pw68 is less than 1, the drive component DC8 is started while the volume of chamber 320 is still expanding. That is, since the drive component DC8 is started at a smaller volume at time tDC8 compared to the volume of chamber 320 at the time point tDC8 when the pulse interval ratio during period Pw68 is less than 1, the ejection performance value decreases. A pulse interval ratio of 1.2 to 1.6 results in an ejection performance value of approximately 2.3 × 10⁻⁶. -10 Compared to methods with pulse interval ratios of more than Newton-seconds and less than 1.2, and methods with pulse interval ratios greater than 1.6, this increases ejection performance. Additionally, approximately 1.8 × 10⁻⁶ -10 A Newton-second is equivalent to 20 ng × 9 m / s, or 2.3 × 10⁻⁶ m / s. -10 A Newton-second is equivalent to 23 ng × 10⁻⁶ m / s. 1 ng represents 10⁻⁶ m / s. -9 gram.

[0134] 1.8. A recording method using the drive waveform signal Com was employed.

[0135] like Figure 17As shown, after the droplet DR is ejected, a liquid column also exists on the meniscus MS. Even if the droplet DR is ejected during a recording period Tu[i], there is a possibility that the liquid column will continue to exist on the meniscus MS, even if the recording period Tu[j] begins at the end of the recording period Tu[i]. j is an integer from 2 to 1, and is 1 greater than i. If a liquid column exists on the meniscus MS during the recording period Tu[j], when the drive signal Vin, based on the separate specified signal Sd[m] specifying the drive mode α1, is supplied to the piezoelectric element PZ, there is a possibility that the droplet DR will be ejected before the drive component DC8 is supplied. Since the liquid ejector head HU and the recording paper P are moving relative to each other at a predetermined speed, if the droplet DR is ejected at a time that is not the intended time, the position where the droplet DR lands on the recording paper P will deviate from the intended position, thus degrading the print quality. In order to ensure that the droplet DR is ejected at the intended location, in the first embodiment, when the droplet DR is ejected during the recording period Tu[j], the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j] is determined based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ during a predetermined recording period Tux prior to the recording period Tu[j]. More specifically, the control unit 6 generates a separate designated signal Sd[m] for the recording period Tu[j] based on a separate designated signal Sd[m] during the predetermined recording period Tux prior to the recording period Tu[j].

[0136] More specifically, the processing of the control unit 6 will be explained. When the droplet DR is ejected from the nozzle N during the recording period Tu[j], the control unit 6 generates the separate designation signal Sd[m] for the recording period Tu[j] based on the separate designation signal Sdx for the predetermined recording period Tu[j] that precedes the recording period Tu[j], namely the separate designation signal Sd[m] for the recording period Tu[j-1], the separate designation signal Sd[m] for the recording period Tu[j-2], and the separate designation signal Sd[m] for the recording period Tu[j-3]. More specifically, when the droplet DR is ejected from the nozzle N during the recording period Tu[j], the control unit 6 determines whether to select drive pulse PL1, drive pulse PL2 and drive pulse PL3 from the drive signal Vin1 of the drive signal Vin provided to the recording period Tu[j], based on the separate designation signal Sdx of the predetermined recording period Tux that precedes the recording period Tu[j], that is, the separate designation signal Sd[m] of the recording period Tu[j-1], the separate designation signal Sd[m] of the recording period Tu[j-2] and the separate designation signal Sd[m] of the recording period Tu[j-3]. On the other hand, when droplets DR are ejected during the recording period Tu[j], the control unit 6 does not rely on the separately designated signal Sdx for the predetermined recording period Tux preceding the recording period Tu[j], that is, the separately designated signal Sd[m] for the recording period Tu[j-1], the separately designated signal Sd[m] for the recording period Tu[j-2], and the separately designated signal Sd[m] for the recording period Tu[j-3]. Instead, it determines the drive signal Vin2 of the drive signal Vin supplied to the recording period Tu[j] as waveform PH2, which includes drive pulses PL4 and PL5. For a more specific recording method, the following will be used Figure 21 as well as Figure 22 Let me explain.

[0137] Figure 21 as well as Figure 22 Here is a flowchart illustrating the generation of individual specified signals Sd[1] to Sd[m] during the recording period Tu[j]. Additionally, in Figure 21 as well as Figure 22 In the flowchart shown, for simplicity, the illustration is limited to cases where j is 4 or higher. For cases where j is 2 and j is 3, the diagram is presented in a way that... Figure 21 as well as Figure 22 The explanation will follow after the flowchart shown is finished.

[0138] In step S2, control unit 6 substitutes 1 into variable m. Next, in step S4, control unit 6 determines whether the ejector section D[m] ejects droplets during the recording period Tu[j] based on the printing data Img. When the determination result of step S4 is positive, in step S6, control unit 6 obtains the individual designation signal Sd[m] of the recording period Tu[i], i.e., the recording period Tu[j-1], from storage unit 5. Next, in step S8, control unit 6 determines whether the ejector section D[m] ejects droplets DR during the recording period Tu[j-1] based on the individual designation signal Sd[m] of the recording period Tu[j-1]. For example, if the individual designation signal Sd[m] of the recording period Tu[j-1] specifies any one of the driving modes α1, α2, α3, and α4, control unit 6 determines that the ejector section D[m] ejected droplets DR during the recording period Tu[j-1]. On the other hand, when the separate designation signal Sd[m] of Tu[j-1] specifies the driving mode α5 during the recording period, the control unit 6 determines that no droplets DR are ejected from the ejection part D[m] in Tu[j-1] during the recording period.

[0139] When the judgment result of step S8 is negative, in step S10, the control unit 6 obtains the individual designated signal Sd[m] of the recording period Tu[j-2] from the storage unit 5. Next, in step S12, the control unit 6 determines whether the ejection part D[m] ejected droplets DR during the recording period Tu[j-2] based on the individual designated signal Sd[m] of the recording period Tu[j-2].

[0140] When the judgment result of step S12 is negative, in step S14, the control unit 6 obtains the individual designated signal Sd[m] of the recording period Tu[j-3] from the storage unit 5. Next, in step S16, the control unit 6 determines whether the ejection part D[m] ejected droplets DR during the recording period Tu[j-3] based on the individual designated signal Sd[m] of the recording period Tu[j-3].

[0141] When the judgment result of step S16 is negative, that is, when no droplets DR are ejected from the ejector section D[m] during the three preceding recording periods Tu[j-1], Tu[j-2], and Tu[j-3], in step S18, the control unit 6 generates a separate designated signal Sd[m] for the driving mode α1. Alternatively, in the processing of step S18, the control unit 6 determines the driving signal Vin1 as waveform PH1, which includes the three driving pulses PL1, PL2, and PL3. After the processing of step S18 is completed, in step S32, the control unit 6 causes the storage unit 5 to store the generated separate designated signal Sd[m].

[0142] When the judgment result of step S4 is negative, that is, when no droplets DR are ejected from the ejector section D[m] during the recording period Tu[j], in step S20, the control unit 6 generates a separate designation signal Sd[m] for the drive mode α5. Then, in step S32, the control unit 6 causes the storage unit 5 to store the generated separate designation signal Sd[m].

[0143] When the determination result of step S8 is affirmative, that is, when the ejector D[m] is ejecting droplets DR during the recording period Tu[j-1], in step S22, the control unit 6 generates a separate designated signal Sd[m] for the driving mode α2. Alternatively, in the processing of step S22, the control unit 6 determines the driving signal Vin1 to be a signal with zero driving pulses PL, i.e., without the waveform PH1. Furthermore, in the processing of step S8, the control unit 6 determines whether the driving signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j] includes the waveform PH1 based on the waveform of the driving signal Vin supplied to the piezoelectric element PZ during the predetermined recording period Tu[j].

[0144] After the processing in step S22 is completed, in step S32, the control unit 6 causes the storage unit 5 to store the generated individual specified signal Sd[m].

[0145] When the judgment result of step S12 is positive, that is, when the ejector D[m] does not eject droplets DR during the recording period Tu[j-1], but ejects droplets DR during the recording period Tu[j-2], in step S24, the control unit 6 generates a separate designated signal Sd[m] for the driving mode α3. Alternatively, in the processing of step S24, the control unit 6 determines the driving signal Vin1 as waveform PH1, which includes the driving pulse PL3. After the processing of step S22 is completed, in step S32, the control unit 6 causes the storage unit 5 to store the generated separate designated signal Sd[m].

[0146] When the judgment result of step S16 is positive, that is, when the ejector D[m] does not eject droplets DR during recording periods Tu[j-1] and Tu[j-2], but ejects droplets DR during recording period Tu[j-3], in step S26, the control unit 6 generates a separate designated signal Sd[m] for the driving mode α4. Alternatively, in the processing of step S26, the control unit 6 determines the driving signal Vin1 as waveform PH1, including the two driving pulses PL2 and PL3. After the processing of step S26 is completed, in step S32, the control unit 6 causes the storage unit 5 to store the generated separate designated signal Sd[m].

[0147] In the processing of steps S12 and S16, when the control unit 6 determines that the drive signal Vin1 supplied to the piezoelectric element PZ during the recording period Tu[j] includes the waveform PH1 based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the predetermined recording period Tux, it will further determine the number of drive pulses PL contained in the waveform PH1.

[0148] Furthermore, in the processing of steps S8, S12, and S16, the control unit 6 determines the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j] in such a way that the number of drive pulses PL contained in the drive signal Vin1 supplied to the piezoelectric element PZ during the recording period Tu[j-1] when no droplet DR is ejected from the ejection section D 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 Tu[j-1] when droplet DR is ejected from the ejection section D 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 Tu[j-1].

[0149] After the processing in step S32 is completed, in step S34, the control unit 6 determines whether the variable m has reached M, which is the number of ejector parts D. If the determination result of step S34 is negative, the control unit 6 increments the value of variable m by 1 in step S38 and returns the processing to step S4. If the determination result of step S34 is positive, the control unit 6 outputs the individually specified signals Sd[1] to Sd[M] to the switching circuit 10 in step S36. After the processing in step S36 is completed, the control unit 6 ends. Figure 21 as well as Figure 22 The series of processes shown.

[0150] The case where variable j has a value of 2 will be explained. If the judgment result of step S8 is negative, control unit 6 will execute step S18 instead of step S10. Next, the case where variable j has a value of 3 will be explained. If the judgment result of step S12 is negative, control unit 6 will execute step S18 instead of step S14. After the processing of step S18 is completed, since... Figure 21 as well as Figure 22 The series of processes shown are the same, so the explanation after the processing of step S18 is omitted. Furthermore, during the recording period Tu[1], the control unit 6 determines whether the ejector D[m] ejects droplets during the recording period Tu[1] based on the printing data Img. When the ejector D[m] ejects droplets, the control unit 6 generates a separate designation signal Sd[m] for drive mode α1. When the ejector D[m] does not eject droplets, the control unit 6 generates a separate designation signal Sd[m] for drive mode α5.

[0151] Figure 23 The diagram illustrates a specific example of a recording method using the drive waveform signal Com. Figure 23 In the diagram, four ejection methods are shown in the ejection section D[m]. Figure 23 In the diagram, below each recording period Tu, black dots or white dots drawn with dashed lines are shown. Black dots indicate that droplets DR were ejected during that recording period Tu, while white dots drawn with dashed lines indicate that droplets DR were not ejected during that recording period Tu. Additionally, in... Figure 23 The future Figure 25 , Figure 27 , Figure 28 The black dots shown and the white dots depicted with dashed lines also have the same characteristics as... Figure 23 The black dots shown and the white dots depicted with dashed lines have the same meaning. Hereinafter, the recording period Tu during which droplets DR are ejected is sometimes referred to as "ejection recording period Tu-D", and the recording period Tu during which droplets DR are not ejected is referred to as "non-ejection recording period Tu-N".

[0152] Figure 23 The first stage of the ejection method is to eject droplets DR during the recording period Tu[1] and the recording period Tu[2]. For the recording period Tu[1], the control unit 6 generates a separate designated signal Sd[m] for the driving mode α1 and outputs the generated separate designated signal Sd[m] to the switching circuit 10. Thus, in the ejection section D[m], during the recording period Tu[1], a driving signal Vin with driving pulses PL1, PL2, PL3, PL4 and PL5 is supplied.

[0153] For the recording period Tu[2], the control unit 6 executes the following when the value of variable j is 2: Figure 21 as well as Figure 22 The flowchart is shown. Since the judgment result of step S8 is positive, the control unit 6 generates a separate designated signal Sd[m] for drive mode α2 by executing the processing of step S22, and outputs the generated separate designated signal Sd[m] to the switching circuit 10. As a result, in the ejection unit D[m], during the recording period Tu[1], a drive signal Vin with drive pulses PL4 and PL5 is supplied.

[0154] Figure 23 The second stage of the ejection method is characterized by ejecting droplets DR during the recording period Tu[1] and the recording period Tu[3], but not ejecting droplets DR during the recording period Tu[2]. Regarding the recording period Tu[1], since and Figure 23 The first-level recording period Tu[1] is the same, so the explanation is omitted. For the recording period Tu[2], the control unit 6 executes when the value of variable j is 2. Figure 21 as well as Figure 22 The flowchart is shown. Since the recording period Tu[2] is the non-ejection recording period Tu-N, the judgment result of step S4 is negative, and the control unit 6 generates a separate designated signal Sd[m] for the drive mode α5 through the processing of step S20, and outputs the generated separate designated signal Sd[m] to the switching circuit 10. Thus, in the ejection section D[m], during the recording period Tu[2], a drive signal Vin that sets the ejection section D to non-drive is supplied.

[0155] For the recording period Tu[3], control unit 6 executes when the value of variable j is 3. Figure 21 as well as Figure 22 The flowchart is shown. Since the judgment result of step S12 is positive, the control unit 6 generates a separate designated signal Sd[m] for drive mode α3 through the processing of step S24, and outputs the generated separate designated signal Sd[m] to the switching circuit 10. As a result, in the ejection unit D[m], during the recording period Tu[3], a drive signal Vin with drive pulses PL3, PL4 and PL5 is supplied.

[0156] Figure 23 The third stage of the ejection method is characterized by ejecting droplets DR during recording periods Tu[1] and Tu[4], and not ejecting droplets DR during recording periods Tu[2] and Tu[3]. Regarding recording periods Tu[1] and Tu[2], due to... Figure 23The recording period Tu[1] and recording period Tu[2] shown in the second level are the same, so the explanation is omitted. For the recording period Tu[3], the control unit 6 executes the following when the value of variable j is 3: Figure 21 as well as Figure 22 The flowchart is shown. Since the recording period Tu[3] is the non-ejection recording period Tu-N, the judgment result of step S4 is negative. The control unit 6 generates a separate designated signal Sd[m] for drive mode α5 through the processing of step S20, and outputs the generated separate designated signal Sd[m] to the switching circuit 10. Thus, in the ejection section D[m], during the recording period Tu[3], a drive signal Vin that sets the ejection section D to non-drive is supplied. For the recording period Tu[4], since the judgment result of step S16 is positive, the control unit 6 generates a separate designated signal Sd[m] for drive mode α4 through the processing of step S26, and outputs the generated separate designated signal Sd[m] to the switching circuit 10. Thus, in the ejection section D[m], during the recording period Tu[4], a drive signal Vin with drive pulses PL2, PL3, PL4 and PL5 is supplied.

[0157] Figure 23 The fourth stage of the ejection method is characterized by ejecting droplets DR during recording periods Tu[1] and Tu[5], and not ejecting droplets DR during recording periods Tu[2], Tu[3], and Tu[4]. Regarding recording periods Tu[1], Tu[2], and Tu[3], due to... Figure 23 The recording periods Tu[1], Tu[2], and Tu[3] shown in the third level are the same, so the explanation is omitted. Since the recording period Tu[4] is the non-ejection recording period Tu-N, the judgment result of step S4 is negative. The control unit 6 generates a separate designation signal Sd[m] for the drive mode α5 through the processing of step S20, and outputs the generated separate designation signal Sd[m] to the switching circuit 10. Thus, in the ejection section D[m], during the recording period Tu[4], a drive signal Vin that sets the ejection section D to non-drive is supplied.

[0158] During the recording period Tu[5], since the judgment result of step S16 is negative, the control unit 6 generates a separate designated signal Sd[m] for the drive mode α1 through the processing of step S18, and outputs the generated separate designated signal Sd[m] to the switching circuit 10. Thus, in the ejection unit D[m], during the recording period Tu[5], a drive signal Vin with drive pulses PL1, PL2, PL3, PL4 and PL5 is supplied.

[0159] 1.9. Summary of the First Implementation Method

[0160] The first embodiment will be summarized below.

[0161] 1.9.1. Summary of waveforms PH1 and PH2

[0162] As explained above, the liquid ejector head HU in the first embodiment has M ejection sections D. Each ejection section D includes: a piezoelectric element PZ that is displaced by a drive signal Vin; a chamber 320 whose internal pressure increases or decreases according to the displacement of the piezoelectric element PZ; and a nozzle N communicating with the chamber 320 and capable of ejecting ink filled inside the chamber 320 as droplets in the -Z direction according to the increase or decrease of the internal pressure of the chamber 320. The liquid ejector head HU performs a driving method having a first step and a second step as shown below. In the first step, a drive signal Vin1 having a waveform PH1 is supplied to the piezoelectric element PZ, thereby forming a liquid column LC6 protruding in the -Z direction from a meniscus MS, wherein the waveform PH1 includes drive pulses PL1, PL2, PL3 having drive components DC1, DC3, DC5 that decrease the internal pressure of the chamber 320 and drive components DC2, DC4, DC6 that increase the internal pressure of the chamber 320. In the second step, after the liquid column LC6 is formed, a drive signal Vin2 with the waveform PH2 is supplied to the piezoelectric element PZ. This causes the liquid column LC8, which protrudes in the -Z direction from the meniscus MS, to be formed. Then, part or all of the ink constituting the liquid column LC8 is ejected as droplets DR. The waveform PH2 includes drive pulses PL4 and PL5 with drive components DC7 and DC9 that reduce the pressure inside the chamber 320, and drive components DC8 and DC10 that increase the pressure inside the chamber 320. When a drive signal Vin with waveform PH1 but not waveform PH2 is supplied to the piezoelectric element PZ, droplets DR are not ejected from the ejection section D.

[0163] Specifically, the driving signal Vin with waveform PH1 is a driving signal Vin based on a separate specified signal Sd[m] that specifies the driving mode α1, driving mode α3, and driving mode α4.

[0164] Additionally, in the section "Summary of Waveforms PH1 and PH2", waveform PH1 is an example of a "first waveform". Waveform PH2 is an example of a "second waveform". Liquid column LC6 is an example of a "first liquid column". Liquid column LC8 is an example of a "second liquid column". Furthermore, drive pulses PL1, PL2, and PL3 are examples of "first drive pulses", and drive pulses PL4 and PL5 are examples of "second drive pulses". Furthermore, drive components DC1, DC3, and DC5 are examples of "first drive components that reduce the internal pressure of the pressure chamber", drive components DC2, DC4, and DC6 are examples of "second drive components that increase the internal pressure of the pressure chamber", drive components DC7 and DC9L are examples of "third drive components that reduce the internal pressure of the pressure chamber", and drive components DC8 and DC10 are examples of "fourth drive components that increase the internal pressure of the pressure chamber".

[0165] Here, when the ink viscosity reaches 20 mPascals per second or higher, the ink in the ejection section D is held in a standby state under a fixed negative pressure, and there is a possibility that droplets DR cannot be ejected under a single drive pulse PL1. Although it is possible to increase the difference between the highest and lowest potentials of the drive signal Vin in order to eject high-viscosity ink, there are physical limitations. Furthermore, although it is possible to increase the excluded volume of the chamber 320, when the volume of the chamber 320 is increased, the structure of the ejection section D becomes more easily deformed due to the force applied to it, that is, the flexibility of the flow channel in the ejection section D increases. The excluded volume refers to the amount of volume change of the pressure chamber caused by the vibration of the vibrating plate 310. When the flexibility of the flow channel in the ejection section D increases, the pressure fluctuation caused by the displacement of the piezoelectric element PZ is easily mitigated by the deformation of the structure of the ejection section D, thus making it difficult to eject droplets DR. Furthermore, when the capacity of chamber 320 is increased, the pressure generated by the displacement of piezoelectric element PZ is easily absorbed by the compression of ink, thus making it difficult to eject droplets DR.

[0166] Therefore, according to the first embodiment, when a liquid column LC6 is formed by a drive signal Vin1 having waveform PH1, a drive signal Vin2 having waveform PH2 is supplied to the piezoelectric element PZ, thereby causing the liquid column formed on the curved surface MS to grow, and thus enabling part or all of the ink constituting the liquid column LC8 to be ejected as droplets DR.

[0167] Furthermore, when a drive signal Vin having waveform PH2 but not waveform PH1 is supplied to the piezoelectric element PZ, the amount of pressure change of the ink in the nozzle N towards the negative pressure side when the drive component DC7 of waveform PH2 contained in the drive signal Vin is supplied to the piezoelectric element PZ, i.e., the first reduction amount, is approximately equal to the amount of pressure change of the ink in the nozzle N towards the negative pressure side when a drive signal Vin having waveforms PH1 and PH2 is supplied to the piezoelectric element PZ, i.e., the second reduction amount, when the drive component DC7 of waveform PH2 contained in the drive signal Vin is supplied to the piezoelectric element PZ. Furthermore, when a drive signal Vin having waveform PH2 but not waveform PH1 is supplied to the piezoelectric element PZ, the first increase in pressure of the ink in the nozzle when the drive component DC8 of waveform PH2 included in the drive signal Vin is supplied to the piezoelectric element PZ is approximately equal to the second increase in pressure of the ink in the nozzle N when the drive signal Vin having waveforms PH1 and PH2 is supplied to the piezoelectric element PZ, the second increase in pressure of the ink in the nozzle N when the drive component DC8 of waveform PH2 included in the drive signal Vin is supplied to the piezoelectric element PZ is supplied to the piezoelectric element PZ is approximately equal to the first increase in pressure of the ink in the nozzle N when the drive signal Vin having waveforms PH1 and PH2 is supplied to the piezoelectric element PZ is supplied to the piezoelectric element PZ is supplied to the piezoelectric element PZ.

[0168] When the viscosity of the ink increases, the decay of residual vibration occurs earlier. Therefore, after waveform PH1 is supplied to piezoelectric element PZ, at the time when waveform PH2 is supplied to piezoelectric element PZ, the residual vibration generated by waveform PH1 decays, making it impossible for waveform PH2 and the residual vibration generated by waveform PH1 to resonate synchronously. In the first embodiment, since the first reduction and the second reduction are approximately equal, and further, the first increase and the second increase are approximately equal, the residual vibration generated by waveform PH1 and the pressure vibration generated by waveform PH2 do not resonate. However, in the first embodiment, since the liquid column formed on the meniscus MS is formed by multiple drive pulses PL, thereby ejecting droplets DR, waveforms PH1 and PH2 are not adjusted in a way that generates waveform PH2 by resonating the residual vibration generated by waveform PH1, but rather by forming the meniscus MS by multiple drive pulses PL. Therefore, according to the first embodiment, even high-viscosity inks can be ejected by forming a liquid column on the meniscus MS using waveforms PH1 and PH2.

[0169] When a drive signal with waveform PH2 is supplied to the piezoelectric element PZ following a drive signal Vin1 with waveform PH1, and the drive component DC7 of waveform PH2 is supplied to the piezoelectric element PZ, the position Zp4 of the meniscus MS in the ejection section D, which is the part that is pulled in the most in the +Z direction, is located in the +Z direction compared to the position Zp1 of the meniscus MS, which is the part that is pulled in the most in the +Z direction, when a drive signal with waveform PH2 is supplied to the piezoelectric element PZ without supplying a drive signal Vin1 with waveform PH1 to the piezoelectric element PZ, and the drive component DC7 of waveform PH2 is supplied to the piezoelectric element PZ.

[0170] In this manner, in the first embodiment, by supplying multiple drive pulses PL to the piezoelectric element PZ, the portion of the meniscus MS that is pulled in the +Z direction most deeply moves in the -Z direction, and thus the liquid column formed on the meniscus MS also moves in the -Z direction. Because the liquid column moves in the -Z direction, the tip of the liquid column in the -Z direction moves away from the initial position Z0 in the -Z direction, making it easier to separate part or all of the liquid column, thereby enabling the ejection of the separated droplet DR.

[0171] Furthermore, in the second step, as the top of the liquid column LC8 moves in the -Z direction, the driving component DC9 of the driving pulse PL5 of the driving signal Vin is supplied to the piezoelectric element PZ.

[0172] When the tip of the liquid column LC8 moves in the -Z direction, the droplet DR can be torn off the liquid column LC9 by supplying a drive signal Vin containing the drive component DC9 to the piezoelectric element PZ. According to this embodiment, more stable ejection can be achieved compared to supplying a drive signal Vin without the drive component DC9 to the piezoelectric element PZ.

[0173] Waveform PH1 includes drive pulses PL1, PL2, and PL3. Drive pulse PL1 includes drive components DC1 and DC2. Drive pulse PL2 includes drive components DC3 and DC4. Drive pulse PL3 includes drive components DC5 and DC6.

[0174] Like a reference Figures 8 to 17As explained, as exemplified by the action of the meniscus MS when a drive signal Vin, based on a single specified signal Sd[m] specifying the drive mode α1, is supplied to the piezoelectric element PZ, in high-viscosity inks, a single drive pulse PL is insufficient to induce a pressure variation in the ejection section D sufficient to eject droplets 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 chamber 320, a liquid column is formed on the meniscus MS, and this column is further grown, thereby enabling part or all of the liquid column to fly as droplets DR from the nozzle N in the -Z direction.

[0175] In this embodiment, since waveform PH1 has three driving pulses PL, even if droplets DR cannot be ejected with one driving pulse PL, the driving signal Vin of waveform PH1 with two or three driving pulses PL can be supplied to the piezoelectric element PZ to grow the liquid column formed on the meniscus MS, thereby enabling part or all of the ink that forms the liquid column LC8 through waveform PH2 to be ejected as droplets DR.

[0176] For reference Figure 21 as well as Figure 22 As explained, when the predetermined recording period Tux prior to the recording period Tu[j] is a non-ejection recording period Tu-N, a drive signal Vin, including drive pulses PL2 and PL3, or drive pulses PL1, PL2 and PL3, is supplied to the piezoelectric element PZ during the recording period Tu[j], so that after the drive component DC8 of the waveform PH2 during the recording period Tu[j] is supplied to the piezoelectric element PZ, a droplet DR is ejected from the ejection part D.

[0177] Furthermore, the viscosity of the ink in the liquid ejector head HU is 20 mPa·s or higher, preferably 40 mPa·s. Although when the viscosity of the ink is 20 mPa·s or higher, there is a possibility that the droplet DR cannot be ejected with only one drive pulse PL4 of waveform PH2, the drive method implemented in this embodiment, which has waveform PH1 preceding waveform PH2, enables the ejection of droplet DR even for inks with a viscosity of 20 mPa·s or higher.

[0178] The difference between the highest and lowest potentials in waveform PH1 is approximately equal to the difference between the highest and lowest potentials in waveform PH2. More specifically, the lowest potentials in waveform PH1 and PH2 are approximately equal to potential VL1, and the highest potentials in waveform PH1 and PH2 are approximately equal to reference potential V0. By setting the highest potential achievable in inkjet printer 1 as the highest potentials of waveforms PH1 and PH2, and setting the lowest potential achievable in inkjet printer 1 as the lowest potentials of waveforms PH1 and PH2, even high-viscosity inks can grow a liquid column on the meniscus MS through waveform PH1, thereby enabling droplets DR to be ejected in waveform PH2.

[0179] 1.9.2. Summary of appropriate conditions for the driving waveform signal Com

[0180] As explained above, the liquid ejector head HU in the first embodiment performs a driving method having the first and second steps described above. Waveform PH1 has three driving pulses PL, namely, driving components DC1, DC3, and DC5 that reduce the pressure inside chamber 320, and driving components DC2, DC4, and DC6 that increase the pressure inside chamber 320. Waveform PH2 has two driving pulses PL, namely, driving components DC7 and DC9 that reduce the pressure inside chamber 320, and driving components DC8 and DC10 that increase the pressure inside chamber 320. Waveform PH2 begins at the end time of waveform PH1. The interval Pw68 between the last driving pulse PL3 of waveform PH1 and the first driving pulse PL4 of waveform PH2 is more than one and less than two times the natural vibration period TC of the ejector part D. The period Pw68 is the period from the time point tDC6 when the supply of the driving component DC6 of the last driving pulse PL3 of the three driving pulses PL of waveform PH1 begins, until the time point tDC8 when the supply of the driving component DC8 of the first driving pulse PL4 of the two driving pulses PL of waveform PH2 begins.

[0181] Since the period Pw68 is more than one time and less than two times the natural vibration period TC, the ejection performance value can be increased compared with the method where the period Pw68 is less than one time the natural vibration period TC and the method where the period Pw68 is more than twice the natural vibration period TC.

[0182] Additionally, the drive pulses PL1, PL2, and PL3 of waveform PH1 are an example of a "first drive pulse." Drive components DC1, DC3, and DC5 are an example of a "first drive component." Drive components DC2, DC4, and DC6 are an example of a "second drive component." The drive pulses PL4 and PL5 of waveform PH2 are an example of a "second drive pulse." Drive components DC7 and DC9 are an example of a "third drive component." Drive components DC8 and DC10 are an example of a "fourth drive component." Period Pw68 corresponds to the "first period."

[0183] Furthermore, the period Pw68 is more than 1.2 times and less than 1.6 times the natural vibration period TC. Since the period Pw68 is more than 1.2 times and less than 1.6 times the natural vibration period TC, the ejection performance value can be increased compared with the method where the period Pw68 is less than 1.2 times the natural vibration period TC and the method where the period Pw68 is greater than 1.6 times the natural vibration period TC.

[0184] Furthermore, the pulse intervals, i.e., periods Pw24 and Pw46, of the driving pulses PL1 to PL3 in waveform PH1 are more than one and less than two times the natural vibration period TC. Period Pw24 is the period from the time point tDC2 when the supply of the driving component DC2 of the driving pulse PL1 in waveform PH1 begins until the time point tDC4 when the supply of the driving component DC4 of the next driving pulse PL2 in waveform PH1 begins. Period Pw46 is the period from the time point tDC4 when the supply of the driving component DC4 of the driving pulse PL2 in waveform PH1 begins until the time point tDC6 when the supply of the driving component DC6 of the next driving pulse PL3 in waveform PH1 begins.

[0185] Since the periods Pw24 and Pw46 are more than one and less than two times the natural vibration period TC, the ejection performance value can be increased compared with the periods Pw24 and Pw46 being less than one time the natural vibration period TC and the periods Pw24 and Pw46 being more than twice the natural vibration period TC.

[0186] Additionally, periods Pw24 and Pw46 are examples of a "second period". In the case where period Pw24 is an example of a "second period", drive pulse PL1 corresponds to "a first drive pulse", and drive pulse PL2 corresponds to "the next first drive pulse after a first drive pulse". In the case where period Pw46 is an example of a "second period", drive pulse PL2 corresponds to "a first drive pulse", and drive pulse PL3 corresponds to "the next first drive pulse after a first drive pulse".

[0187] Furthermore, during this period, Pw24 and Pw46 are more than 1.2 times and less than 1.6 times the natural vibration period TC. Since Pw24 and Pw46 are more than 1.2 times and less than 1.6 times the natural vibration period TC, the ejection performance value can be increased compared to methods where Pw24 and Pw46 are less than 1.2 times the natural vibration period TC, and methods where Pw24 and Pw46 are greater than 1.6 times the natural vibration period TC.

[0188] 1.9.3. Summary of the recording method using the driving waveform signal Com

[0189] As explained above, the liquid ejector head HU in the first embodiment has M ejection sections D. Each ejection section D includes a piezoelectric element PZ, a chamber 320, and a nozzle N. The piezoelectric element PZ is displaced according to a drive signal Vin, including drive signals Vin1 and Vin2, supplied during 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 a droplet is ejected from the nozzle N during a recording period Tu[j], the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j] is determined based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the recording periods Tu[j] preceding the recording period Tu[j], i.e., recording periods Tu[j-1] to Tu[j-3]. When the drive signal Vin, which has the waveform determined in the first step, has waveform PH1 in drive signal Vin1 and waveform PH2 in drive signal Vin2, drive signal Vin1 is supplied to piezoelectric element PZ during the recording period Tu[j], thereby causing the meniscus MS to form a liquid column LC6 protruding in the -Z direction. When the liquid column LC6 is formed, drive signal Vin2 is supplied to piezoelectric element PZ, thereby causing part or all of the ink constituting the liquid column LC8 to be ejected as droplets after the meniscus MS has formed a liquid column LC8 protruding in the -Z direction.

[0190] For example, when the ejector section D is stationary, and a drive signal Vin based on a single specified signal Sd[m] specifying the drive mode α1 is supplied to the piezoelectric element PZ, if, in ink of a viscosity such that droplets DR are ejected at a timing when waveform PH2 is supplied, after droplets DR are ejected during a recording period Tu[j-1] prior to the recording period Tu[j], and then during the recording period Tu[j], a drive signal Vin based on a single specified signal Sd[m] specifying the drive mode α1 is supplied to the piezoelectric element PZ, there is a possibility that droplets DR may be ejected at a timing when they should not be ejected, for example, when waveform PH1 is being supplied, thereby degrading the print quality.

[0191] Based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ during a predetermined recording period Tu[j] prior to the recording period Tu[j], the state of the meniscus MS at the start time of the recording period Tu[j] can be inferred. Therefore, since the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j] is determined based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the predetermined recording period Tu[j] prior to the recording period Tu[j], the ejection can be performed at a timing close to that of the droplet DR that should be ejected, thereby suppressing the deterioration of print quality.

[0192] In addition, the recording period Tu[j] is an example of a "first recording period". The predetermined recording period Tux that precedes the recording period Tu[j] is used in determining the drive signal Vin supplied to the piezoelectric element PZ within the recording period Tu[j]. The recording periods Tu[j-1] to Tu[j-3] in this embodiment are examples of "predetermined recording periods that precede the first recording period".

[0193] The predetermined recording period Tux preceding the recording period Tu[j] used in determining the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j] includes the recording period Tu[j-1] that ends at the beginning of the recording period Tu[j]. Among the two or more recording periods Tu that end before the beginning of the recording period Tu[j], the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j-1] has the greatest impact on the meniscus MS at the start time of the recording period Tu[j]. Therefore, by determining the individual designated signal Sd[m] of the recording period Tu[j] based on a separately designated signal Sd[m] of a predetermined recording period Tu[j] that precedes the recording period Tu[j], including the recording period Tu[j-1], the degradation of print quality can be suppressed more effectively compared with the method of determining the individual designated signal Sd[m] of the recording period Tu[j] that precedes the recording period Tu[j] but does not include the recording period Tu[j-1].

[0194] Additionally, the recording period Tu[j-1] is an example of a "second recording period".

[0195] In the first step of the section “Summary of Recording Method Using Drive Waveform Signal Com”, the predetermined recording period Tux that precedes the recording period Tu[j] and is used in determining the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j] includes the recording period Tu[j-1] and includes the continuous recording periods Tu[j-1] to Tu[j-3] that end before the start of the recording period Tu[j].

[0196] Although the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j-1] has the greatest impact on the meniscus MS at the start time of the recording period Tu[j], the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu earlier than the recording period Tu[j-1] also affects the meniscus MS at the start time of the recording period Tu[j]. Therefore, according to this embodiment, compared with the method of determining the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j] solely based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j-1], the state of the meniscus MS at the start time of the recording period Tu[j] can be inferred with higher accuracy, thus further suppressing the degradation of print quality.

[0197] Additionally, 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".

[0198] In the first step of the section “Summary of Recording Method Using Drive Waveform Signal Com”, the waveform of the drive signal Vin1 supplied to the piezoelectric element PZ during the recording period Tu[j] is determined based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the predetermined recording period Tu[j] prior to the recording period Tu[j].

[0199] By adjusting the waveform of the drive signal Vin1, the liquid droplets can be ejected at a timing close to that of the DR droplets, thus further suppressing the deterioration of print quality.

[0200] Furthermore, in the first step of the section “Summary of Recording Method Using Drive Waveform Signal Com”, based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ during a predetermined recording period Tux prior to the recording period Tu[j], it is determined whether the drive signal Vin1 supplied to the piezoelectric element PZ during the recording period Tu[j] contains the waveform PH1.

[0201] Furthermore, in the first step of the section “Summary of Recording Method Using Drive Waveform Signal Com”, based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j], which is used in determining the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j], if the drive signal Vin1 supplied to the piezoelectric element PZ during the recording period Tu[j] contains waveform PH1, the number of drive pulses PL included in waveform PH1 will be further determined.

[0202] In this embodiment, adjusting the number of drive pulses PL included in the drive signal Vin1 is easier to implement than adjusting the lowest and highest potentials of the drive pulses PL included in the drive signal Vin1. Adjusting the lowest and highest potentials of the drive pulses PL can be implemented, for example, with the following structure: The drive waveform signal generation circuit 2 generates a first drive waveform signal Com-A and a second drive waveform signal Com-B. The difference between the lowest and highest potentials of the drive pulses PL corresponding to the first drive waveform signal Com-A and the drive signal Vin1 is greater than the difference between the lowest and highest potentials of the drive pulses PL corresponding to the second drive waveform signal Com-B and the drive signal Vin1. 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, increasing the number of drive waveform signals Com in the above structure would result in a larger drive waveform generation circuit and a more complex structure compared to this embodiment. Furthermore, although there are limits on the lowest and highest potentials that can be supplied to the piezoelectric element PZ in the inkjet printer 1, as described above, by repeatedly reducing and increasing the internal pressure of the chamber 320 by supplying multiple drive pulses PL to the piezoelectric element PZ, even high-viscosity inks can be made to grow into a liquid column and be ejected as droplets DR.

[0203] Therefore, according to this embodiment, compared with the method of adjusting the lowest and highest potentials of the drive pulse PL contained in the drive signal Vin1, it is possible to generate the waveform of the drive signal Vin1 that conforms to the state of the meniscus MS at the start time of the recording period Tu[j] through a simpler structure.

[0204] The predetermined recording period Tux preceding the recording period Tu[j] used in determining the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j] includes the recording period Tu[j-1]. In the first step of the section "Summary of the recording method using the drive waveform signal Com", the waveform of the drive signal Vin1 supplied to the piezoelectric element PZ during the recording period Tu[j] is determined in such a way that the first number of the drive pulses PL contained in the drive signal Vin1 supplied to the piezoelectric element PZ during the recording period Tu[j-1] when no droplet DR is ejected from the ejector D during the recording period Tu[j-1] is greater than the second number of the drive pulses PL contained in the drive signal Vin1 supplied to the piezoelectric element PZ during the recording period Tu[j-1] when a droplet DR is ejected from the ejector D during the recording period Tu[j-1].

[0205] During the recording period Tu[j-1], which is the non-ejection recording period Tu-N (i.e., the first condition), the liquid column formed on the meniscus MS at the beginning of the recording period Tu[j] is smaller than that during the recording period Tu[j-1], which is the ejection recording period Tu-D (i.e., the second condition). Therefore, in order to eject the droplet DR at the timing it should have been ejected in the first condition, compared to the second condition, a drive signal Vin1 with more drive pulses PL needs to be supplied to the piezoelectric element PZ. Therefore, by determining the waveform of the drive signal Vin1 supplied to the piezoelectric element PZ during the recording period Tu[j] in such a way that the first number is greater than the second number, the droplet DR can be ejected at the timing it should have been ejected.

[0206] When droplets are ejected from nozzle N during the recording period Tu[j], the drive signal Vin2 in the drive signal Vin supplied to piezoelectric element PZ during the recording period Tu[j] has a preset waveform PH2, regardless of the waveform of the drive signal Vin supplied to piezoelectric element PZ during the recording period Tu[j], which is used in determining the drive signal Vin supplied to 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 time of the recording period Tu[j], only the waveform of drive signal Vin1 needs to be adjusted, and the waveform of drive signal Vin2 does not need to be adjusted.

[0207] 1.9.4. Summary of the relationship between the driving signal Vin and the meniscus MS

[0208] As explained above, the liquid ejector head HU can also be described as performing a driving method having the first and second steps described below. In the first step, a liquid column LC6 with the meniscus MS protruding in the ejection direction is formed by supplying a driving signal having waveform PH1 to the piezoelectric element PZ. In the second step, after the liquid column LC6 has been formed, a portion or all of the ink constituting the liquid column LC8 is ejected as droplets DR after a liquid column LC8 with the meniscus MS protruding in the -Z direction is formed by supplying a driving signal having waveform PH2 to the piezoelectric element PZ. Waveform PH2 includes a driving component DC7 that reduces the pressure inside the chamber 320 and a driving component DC8 that increases the pressure inside the chamber 320. In the second step, the liquid column LC7 with the meniscus MS protruding in the -Z direction is formed by supplying driving component DC7 to the piezoelectric element PZ before the liquid column LC8 is formed. In the second step, after the liquid column LC7 has been formed, the liquid column LC8 is formed by supplying driving component DC8 to the piezoelectric element PZ.

[0209] According to the first embodiment, when a liquid column LC6 is formed, by supplying a drive signal Vin having a drive component DC7 to the piezoelectric element PZ, the liquid column formed on the curved surface MS can be grown. Furthermore, when a liquid column LC7 is formed, by supplying a drive signal Vin having a drive component DC8 to the piezoelectric element PZ, a portion or all of the ink constituting the liquid column LC8 can be ejected as droplets DR.

[0210] Additionally, in the section "Summary of the Relationship between Drive Signal Vin and Meniscus MS", waveform PH1 is an example of the "First Waveform". Waveform PH2 is an example of the "Second Waveform". Drive component DC7 is an example of the "First Pull-in Drive Component". Drive component DC8 is an example of the "First Extrusion Drive Component Displacement". Liquid column LC6 is an example of the "First Liquid Column". Liquid column LC7 is an example of the "Third Liquid Column". Liquid column LC8 is an example of the "Second Liquid Column".

[0211] Waveform PH1 has three driving pulses PL, each having a first driving component that reduces the pressure inside chamber 320 and a second driving component that increases the pressure inside chamber 320. In the first step of the section “Summary of the Relationship between Driving Signal Vin and Meniscus MS”, when the driving signal of the driving component DC1 of the first of the three driving pulses PL of waveform PH1 is supplied to the piezoelectric element PZ, the liquid surface with the concave curved shape in the ejection section D is pulled in towards the +Z direction. Furthermore, by supplying the driving signal of the driving component DC5 of the last of the three driving pulses PL of waveform PH1 to the piezoelectric element PZ, the meniscus MS, which forms a liquid column LC5 protruding towards the -Z direction, is pulled in towards the +Z direction.

[0212] According to the first embodiment, when the drive signal of the drive component DC1 of the initial drive pulse PL1 with waveform PH1 is supplied to the piezoelectric element PZ, although no liquid column is generated on the meniscus MS, but instead the central part of the meniscus MS is concave in the +Z direction, by supplying the drive components DC2, DC3 and DC4 of the drive pulse PL1 to the piezoelectric element PZ, and by supplying the drive component DC5 of the drive pulse PL3 to the piezoelectric element PZ, a liquid column LC5 can be formed at the central part of the meniscus MS.

[0213] Furthermore, in the section "Summary of the Relationship between Drive Signal Vin and Meniscus MS", drive components DC1, DC3, and DC5 are examples of "first drive components". Drive components DC2, DC4, and DC6 are examples of "second drive components". The meniscus MS that forms the liquid column LC5 is an example of "a liquid surface protruding in the ejection direction by supplying the first drive component of the last drive pulse among the multiple drive pulses of the first waveform to the drive element".

[0214] In the first step of the section "Summary of the Relationship between Driving Signal Vin and Meniscus MS", the driving signal of the driving component DC3 of the driving pulse PL2 between the first driving pulse PL1 and the last driving pulse PL3 of the three driving pulses PL with waveform PH1 is supplied to the piezoelectric element PZ, thereby pulling the meniscus MS, which forms the liquid column LC3, toward the +Z direction. The liquid column LC3 formed by the driving component DC3 of driving pulse PL2 is smaller than the liquid column LC6 formed by the driving component DC5 of driving pulse PL3.

[0215] In this way, by repeatedly driving the pulse PL and supplying it to the piezoelectric element PZ, the liquid column can be gradually grown larger. By making the liquid column grow larger, even high-viscosity inks can be ejected as droplets DR when the waveform PH2 is supplied to the piezoelectric element PZ.

[0216] Additionally, liquid column LC3 is an example of a "fourth liquid column".

[0217] 2. Change the example

[0218] The above methods can be implemented in various variations. Specific variations are illustrated below. Two or more methods selected from the following examples can be appropriately combined within the scope of non-contradiction. Furthermore, elements that function or have the same effect as the implementation method in the following modified examples will use the same symbols referenced in the above description, and detailed descriptions will be omitted where appropriate.

[0219] 2.1. First Modified Example

[0220] Although in the first embodiment, when the recording period Tu[j] is the non-ejection recording period Tu-N, the control unit 6 generates a separate designation signal Sd[m] for the drive mode α5, it is also possible to generate a separate designation signal Sd[m] for a drive mode other than drive mode α5.

[0221] Figure 24 This diagram illustrates the five driving modes obtainable by the individually specified signal Sd[m] in the first modified example. In the first modified example, the individually specified signal Sd[m] is a signal that specifies any one of the five driving modes α1 to α4 and α6. The individually specified signal Sd[m] for driving mode α6 is generated without causing the ejector D[m] to eject droplets. That is, in the first modified example, it differs from the first embodiment in that the control unit 6 generates the individually specified signal Sd[m] for driving mode α6 instead of the individually specified signal Sd[m] for driving mode α5, without causing the ejector D[m] to eject droplets. The value of the individually specified signal Sd[m] for driving mode α6 is (0, 0, 0, 1, 0). When the connection state specifying circuit 11 specifies the driving mode α6 by the separate specifying signal Sd[m], it sets the connection state specifying signal SLa[m] to a low level during the control periods Tcu1, Tcu2, Tcu3 and Tcu5, and sets the connection state specifying signal SLa[m] to a high level during the control period Tcu4.

[0222] Figure 25The diagram illustrates a specific example of the recording method for the drive waveform signal Com used in the first modified example. If compared with the diagram shown in the first embodiment... Figure 23 In comparison, in the first modified example, the individually specified signal Sd[m] within Tu during the recording period of DR without ejecting droplets is replaced from driving mode α5 to driving mode α6. More specifically, Figure 25 The second level shows the recording period Tu[2], Figure 25 The third level shows the recording period Tu[2] and the recording period Tu[3]. Figure 25 The individual specified signal Sd[m] within the recording period Tu[2], recording period Tu[3], and recording period Tu[4] shown in the fourth level is replaced by the driving mode α6 from the driving mode α5.

[0223] According to the first modified example, even during the recording period Tu[j] which is a non-ejection recording period Tu-N, by supplying a drive pulse PL of the degree of non-ejection droplet DR to the piezoelectric element PZ, it is possible to maintain the meniscus MS at the start time of the next recording period Tu[j+1] of the non-ejection recording period Tu-N, or to facilitate the formation of a liquid column within the recording period Tu[j]. When the next recording period Tu[j+1] is an ejection recording period Tu-D, the variation of the meniscus MS within the recording period Tu[j-1] can be utilized.

[0224] In the first modified example, although during the non-ejection recording period Tu-N, the drive pulse PL with drive pulse PL4 is selected as the drive pulse PL supplied to the piezoelectric element PZ as the drive pulse PL of the degree of non-ejection droplet DR, the selected drive pulse PL is not limited to this. For example, any one of the drive pulses PL1, PL2, PL3, PL4 and PL5 can be selected, or multiple drive pulses PL can be selected. However, for the drive pulse PL selected during the recording period Tu[j] which is the non-ejection recording period Tu-N, it is preferable to be the drive pulse PL PL that is close to the drive pulse PL4 of the next recording period Tu[j+1]. This is because, when the next recording period Tu[j+1] is the ejection recording period Tu-D, by selecting the drive pulse PL of the drive pulse PL4 included in the waveform PH2 of the ejection timing of the droplet DR which is the recording period Tu[j+1] as the drive signal Vin of the non-ejection recording period Tu-N, i.e. the recording period Tu[j], 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] is shortened, and the possibility of utilizing the liquid column or the change of the meniscus MS formed on the meniscus MS in the recording period Tu[j+1] is increased. Furthermore, when the recording period Tu[j-1] preceding the recording period Tu[j] which is the non-ejection recording period Tu-N is the ejection recording period Tu-D, by selecting the drive pulse PL that is far from 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] as the drive signal Vin of the recording period Tu[j], it is possible to suppress the situation where the droplet DR is ejected in the non-ejection recording period Tu-N, i.e. the recording period Tu[j], due to the change of the liquid column or the meniscus MS formed after the droplet DR is ejected in the recording period Tu[j-1].

[0225] Furthermore, when no droplets are ejected from nozzle N during the recording period Tu[j], a drive signal Vin having at least one of waveform PH1, which includes at least one of drive pulses PL1, PL2, and PL3, and waveform PH2, which includes at least one of drive pulses PL4 and PL5, is supplied to piezoelectric element PZ. This causes the pressure of the ink inside chamber 320 to increase or decrease to a level that prevents droplets from being ejected from nozzle N during the recording period Tu[j]. Through the above processing, even during the recording period Tu[j] when no droplets are ejected from nozzle N, by supplying a drive signal Vin having at least one of waveforms PH1 and PH2 to piezoelectric element PZ, the vibration of the ink in ejection section D can be maintained during the recording period Tu[j], and this vibration can be utilized during the recording period Tu[j+1]. Furthermore, when droplets DR are ejected from nozzle N during recording period Tu[j+1], if vibration is applied during recording period Tu[j] using waveform PH2, which is closer to recording period Tu[j+1], it can be utilized before the vibration applied during recording period Tu[j] decreases compared to the case where vibration is applied only using waveform PH1 during recording period Tu[j]. Additionally, when droplets DR are ejected from nozzle N during recording period Tu[j-1], if a drive signal Vin excluding waveform PH1, which is closer to recording period Tu[j+1], is supplied during recording period Tu[j], it can prevent ejection even during recording period Tu[j].

[0226] 2.2. Second Change Example

[0227] Although 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 a separate designated signal Sd[m] of the same driving mode, it is also possible to generate separate designated signals Sd[m] of different driving modes between multiple non-ejection recording periods Tu-N.

[0228] Figure 26This diagram illustrates the six driving modes obtainable by the individually specified signal Sd[m] in the second modification example. In the second modification example, the individually specified signal Sd[m] is a signal that specifies any one of the six driving modes α1 to α4, α7, and α8. The individually specified signal Sd[m] for driving mode α7 and driving mode α8 are generated without causing the ejector D[m] to eject droplets. That is, the second modification example differs from the first embodiment in that, without causing the ejector D[m] to eject droplets, the control unit 6 generates either the individually specified signal Sd[m] for driving mode α7 or the individually specified signal Sd[m] for driving mode α8, instead of the individually specified signal Sd[m] for driving mode α5.

[0229] The value of the individually specified signal Sd[m] representing drive mode α7 is (0, 1, 0, 0, 0). When the individually specified signal Sd[m] represents drive mode α7, the connection state specifying circuit 11 sets the connection state specifying signal SLa[m] to a low level during control periods Tcu1, Tcu3, Tcu4, and Tcu5, and sets it to a high level during control period Tcu2. The value of the individually specified signal Sd[m] representing drive mode α8 is (1, 0, 1, 0, 0). When the individually specified signal Sd[m] represents drive mode α8, the connection state specifying circuit 11 sets the connection state specifying signal SLa[m] to a low level during control periods Tcu2, Tcu4, and Tcu5, and sets it to a high level during control periods Tcu1 and Tcu3.

[0230] Regarding which of the two driving modes, α7 and α8, is being generated, in the second modified example, a situation is envisioned where there is a continuous non-ejection recording period Tu-N. The control unit 6 generates the individual designated signal Sd[m] for driving mode α7 during the k-th non-ejection recording period Tu-N within the continuous non-ejection recording period Tu-N, and generates the individual designated signal Sd[m] for driving mode α8 during the (k+1)-th non-ejection recording period Tu-N. The variable k is an integer from 1 up to the continuous non-ejection recording period Tu-N.

[0231] Figure 27 The diagram illustrates a specific example of the recording method for the drive waveform signal Com used in the second modified example. If compared with the diagram shown in the first embodiment... Figure 23In comparison, in the second modified example, the individually specified signal Sd[m] during the recording period Tu of the non-discharged droplet DR is replaced from drive mode α5 to drive mode α7 or drive mode α8. More specifically, Figure 27 The second level shows the recording period Tu[2], Figure 27 The third level shows the recording period Tu[2], and Figure 27 The recording period Tu[2] and the separately specified signal Sd[m] within the recording period Tu[4] shown in the fourth level are replaced by driving mode α7 from driving mode α5. Figure 27 The third level shows the recording period Tu[3] and Figure 27 The individually designated signal Sd[m] during the recording period Tu[3] shown in the fourth level is replaced by driving mode α8 instead of driving mode α5. Alternatively, it can be configured such that the control unit 6 selects any one of driving modes α5 to α8 from the individually designated signal Sd[m] during the non-ejection recording period Tu-N. Furthermore, it can be configured such that the driving signal Vin supplied during the non-ejection recording period Tu-N includes one or more driving pulses PL from driving pulses PL1 to PL4.

[0232] As shown in the second modified example, the control unit 6 can also adjust the number of drive pulses PL supplied during the non-ejection recording period Tu-N to the degree to which droplets DR are not ejected during the non-ejection recording period Tu-N. Regarding the specific number of drive pulses PL, the designer of the inkjet printer 1 specifically specifies the relationship between viscosity and the number of drive pulses PL through experiments, and stores a table showing the relationship between ink viscosity and the number of drive pulses PL, or a formula for calculating the number of drive pulses PL based on ink viscosity, in the storage unit 5.

[0233] Furthermore, as a modification of the second modification, the control unit 6 can also vary the drive pulse PL supplied during the non-ejection recording period Tu-N to the extent that droplets DR are not ejected during the non-ejection recording period Tu-N. For example, the control unit 6 can also generate a separate designated signal Sd[m]を during the k-th non-ejection recording period Tu-N of the continuous non-ejection recording period Tu-N, which generates a drive signal Vin that only has drive pulse PL3, and generate a separate designated signal Sd[m] during the (k+1)-th non-ejection recording period Tu-N, which generates a drive signal Vin that only has drive pulse PL4. The variable k is an integer from 1 up to the continuous non-ejection recording period Tu-N.

[0234] 2.3. Third Change Example

[0235] Although in the first embodiment, the first modified example, and the second modified example, the viscosity of the ink is such that, when the ejector portion D, which supplies the reference potential V0 to the piezoelectric element PZ, is in a static state and the position of the meniscus MS is static at the initial position Z0, and when the driving signal Vin based on the driving mode α1 of the individual specified signal Sd[m] is supplied to the piezoelectric element PZ within a recording period Tu[i], there is also a case where the viscosity of the ink is so high that even when the driving signal Vin based on the driving mode α1 of the individual specified signal Sd[m] is supplied to the piezoelectric element PZ within a recording period Tu[i], it is impossible to eject the ink within a recording period Tu[i]. In the third modified example, when the printing process starts from the recording period Tu[1], by supplying a drive signal that generates micro-vibration outside the printed characters to the piezoelectric element PZ before the recording period Tu[1], droplets DR can be ejected during the recording period Tu[1]. Afterwards, by utilizing the liquid column formed on the meniscus MS during the recording period Tu[j-1] or the change of the meniscus MS, droplets DR can be ejected during the recording period Tu[j].

[0236] Figure 28 This is a diagram used to illustrate the driving signal Vin in the case of ejecting droplets DR in the third modified example. Figure 28 The first stage shows an ejection method in which droplets DR are ejected during the initial recording period Tu[1] of the printing process and the subsequent recording period Tu[2]. During the period Tbu before the recording period Tu[1], the control unit 6 supplies a drive signal Vin that generates micro-vibration outside the printed characters to the piezoelectric element PZ. Thus, during the period Tbu, a drive signal Vin that generates micro-vibration outside the printed characters is supplied to the ejection unit D[m]. The drive signal Vin that generates micro-vibration outside the printed characters includes a waveform containing multiple pulses, which include a drive component that reduces the pressure inside the chamber 320 and a drive component that increases the pressure inside the chamber 320.

[0237] For the recording period Tu[1], the control unit 6 generates a separate designated signal Sd[m] for the drive mode α1 and outputs the generated separate designated signal Sd[m] to the switching circuit 10. Thus, during the recording period Tu[1], the ejector D[m] is supplied with a drive signal Vin having drive pulses PL1, PL2, PL3, PL4 and PL5. Since at the beginning of the recording period Tu[1], a liquid column is formed on the meniscus MS by micro-vibration outside the print, or the meniscus MS is changed, the ejector D can eject droplets DR during the recording period Tu[1].

[0238] For the recording period Tu[2], the control unit 6 generates a separate designated signal Sd[m] for the driving mode α2 and outputs the generated separate designated signal Sd[m] to the switching circuit 10. Thus, during the recording period Tu[2], the ejector D[m] is supplied with a driving signal Vin having driving pulses PL4 and PL5. Since the driving signal Vin having driving pulses PL1, PL2, PL3, PL4 and PL5 is supplied during the recording period Tu[1], a liquid column is formed on the meniscus MS at the beginning of the recording period Tu[2], or the meniscus MS is changed, so the ejector D can eject droplets DR during the recording period Tu[1].

[0239] Figure 28 The second stage shows an ejection method in which droplets DR are ejected during the recording period Tu[1] and the recording period Tu[3], but no droplets DR are ejected during the recording period Tu[2]. Regarding the period Tbu and the recording period Tu[1], since... Figure 28 The first stage shows the same period Tbu and recording period Tu[1], so the explanation is omitted. Since the recording period Tu[2] is the non-ejection recording period Tu-N, a drive signal Vin with a drive pulse PL that includes the degree of non-ejection droplet DR is supplied, such as a drive signal Vin with drive pulses PL2 and PL3.

[0240] For the recording period Tu[3], since the prior predetermined recording period Tux is the non-ejection recording period Tu-N, it is supplied with the same... Figure 28 The first stage shown has a driving signal Vin with more driving pulses PL compared to the previous recording period Tu[1] of the ejection recording period Tu-D, such as driving signals Vin with driving pulses PL3, PL4 and PL5. Since driving signals Vin with driving pulses PL2 and PL3 are supplied during the recording period Tu[2], a liquid column is formed on the meniscus MS or the meniscus MS is changed at the beginning of the recording period Tu[3], so that the ejection part D can eject droplets DR during the recording period Tu[3].

[0241] Furthermore, in the third modified example, during the initial recording period Tu[1] of the printing process, the waveform PH1 contained in the micro-vibration outside the printed characters and the drive signal Vin of the recording period Tu[1] is another example of the "first waveform" described in the aforementioned embodiment and modified example, and the waveform PH2 contained in the drive signal Vin of the recording period Tu[1] is another example of the "second waveform" described in the aforementioned embodiment and modified example. In addition, during the recording period Tu after the initial recording period Tu[1] of the printing process, the waveform PH1 contained in the drive signal Vin of the recording period Tu[j-1] and the drive signal Vin of the recording period Tu[j] is another example of the "first waveform" described in the aforementioned embodiment and modified example, and the waveform PH2 contained in the drive signal Vin of the recording period Tu[j] is another example of the "second waveform" described in the aforementioned embodiment and modified example. Furthermore, during the initial recording period Tu[1] of the printing process, the multiple pulses contained in the drive signal Vin generated by the micro-vibration outside the printed characters, and the drive pulse PL contained in the waveform PH1 of the drive signal Vin included in the recording period Tu[1], are another example of the "first drive pulse" described in the aforementioned embodiment and modified examples. The drive pulse PL contained in the waveform PH2 of the drive signal Vin included in the recording period Tu[1] is another example of the "second drive pulse" described in the aforementioned embodiment and modified examples. Furthermore, during the recording period Tu after the initial recording period Tu[1] of the printing process, the drive pulse PL contained in the drive signal Vin of the recording period Tu[j-1] and the drive pulse PL contained in the waveform PH1 of the drive signal Vin included in the recording period Tu[j] are another example of the "first drive pulse" described in the aforementioned embodiment and modified examples. The drive pulse PL contained in the waveform PH2 of the drive signal Vin included in the recording period Tu[j] is another example of the "second waveform" described in the aforementioned embodiment and modified examples.

[0242] 2.4. Fourth Change Example

[0243] Although the third modification example describes an example where the ink viscosity is so high that even if a drive signal Vin based on a single specified signal Sd[m] of drive mode α1 is supplied to the piezoelectric element PZ during the recording period Tu[i], the ink cannot be ejected within one recording period Tu[i]. In this example, a droplet DR is ejected during the recording period Tu[1] by supplying a drive signal generated by micro-vibration outside the printed characters to the piezoelectric element PZ before the initial recording period Tu[1] of the printing process. In the fourth modification example, a droplet DR is ejected from the ejection section D during the multiple recording periods Tu[i] by supplying a drive signal Vin to the piezoelectric element PZ during the multiple recording periods Tu[i] while the ejection section D is in a static state with the reference potential V0 supplied from the positive piezoelectric element PZ and the position of the meniscus MS is static at the initial position Z0.

[0244] Figure 29 This diagram illustrates the drive signal Vin during the ejection of droplets DR in the fourth modified example. To ensure consistent ejection intervals, or in other words, point intervals, among the multiple ejection sections D, the control unit 6 assigns a predetermined number of recording periods Tu to each point. The predetermined number is an integer greater than or equal to 2. Figure 29 The example shown is a predetermined quantity of 2. Furthermore, the control unit 6 controls the moving mechanism 8 in such a way that the moving speed of the liquid nozzle HU is the value obtained by dividing the moving speed of the liquid nozzle HU in the first embodiment by the predetermined quantity.

[0245] exist Figure 29 In this design, the following state is envisioned: at the beginning of the recording period Tu[i], the ejector D, which supplies the reference potential V0 to the piezoelectric element PZ, is in a static state, and the meniscus MS is stationary at its initial position Z0. Printing of one point is performed within two recording periods Tu[i] and one recording period Tu[i+1]. Within the recording periods Tu[i] and Tu[i+1], the control unit 6 generates a separate specified signal Sd[m] for the drive mode α1.

[0246] Next, even within the two recording periods Tu[i+2] and Tu[i+3] following the recording period Tu[i+1], a point is printed. During the recording period Tu[i+2], the control unit 6 generates a separate designation signal Sd[m] for the value (1, 1, 1, 0, 0), and during the recording period Tu[i+3], the control unit 6 generates a separate designation signal Sd[m] for the driving mode α1.

[0247] Furthermore, in the fourth modified example, the waveform PH1 contained 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 aforementioned implementation and modified example; the waveform PH2 contained in the drive signal Vin during the recording period Tu[i+1] is another example of the "second waveform" described in the aforementioned implementation and modified example. Additionally, the waveform PH1 contained 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 aforementioned implementation and modified example; the waveform PH2 contained in the drive signal Vin during the recording period Tu[i+3] is another example of the "second waveform" described in the aforementioned implementation and modified example. Furthermore, the drive pulse PL included in the drive signal Vin during the recording period Tu[i] and the drive pulse PL included in the waveform PH1 of the drive signal Vin during the recording period Tu[i+1] are another example of the "first drive pulse" described in the aforementioned embodiment and modified examples. The drive pulse PL included in the waveform PH2 of the drive signal Vin during the recording period Tu[i+1] is another example of the "second drive pulse" described in the aforementioned embodiment and modified examples. Furthermore, 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 of the drive signal Vin during the recording period Tu[i+3] are another example of the "first drive pulse" described in the aforementioned embodiment and modified examples. The drive pulse PL included in the waveform PH2 of the drive signal Vin during the recording period Tu[i+3] is another example of the "second drive pulse" described in the aforementioned embodiment and modified examples.

[0248] As described in the first embodiment, when the droplet DR is ejected during the two recording periods Tu[j] and Tu[j+1], the waveform of the drive signal Vin supplied to the piezoelectric element PZ during 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 during a predetermined recording period Tux preceding the two recording periods Tu[j] and Tu[j+1]. In order to eject the droplet DR during the recording period Tu[i+1] preceding the two recording periods Tu[i+2] and Tu[i+3], the number of drive pulses PL contained in the drive signal Vin during the recording period Tu[i+2] is less than the number of drive pulses PL contained in the drive signal Vin during the recording period Tu[i] during which the droplet DR is not ejected in the preceding period.

[0249] Furthermore, in the fourth modification, as in the third modification, a drive signal to generate micro-vibrations outside the printed characters can be supplied to the piezoelectric element PZ before the start of the printing process. By generating micro-vibrations outside the printed characters before the initial recording period Tu[1] of the printing process, the number of recording periods Tu corresponding to a point can be reduced compared to the case where the micro-vibrations outside the printed characters are not generated, thereby suppressing the case where the moving speed of the liquid ejection head HU slows down.

[0250] 2.5. Fifth Change Example

[0251] Although in the first embodiment and the first to fourth modifications, when droplets DR are ejected during the recording period Tu[j], the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j] is determined based on 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]. Specifically, the selection of one of the drive modes α1 to α4 during the recording period Tu[j] is determined based on the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the predetermined recording period Tux, it is not limited to this. In the fifth modification, the waveform of the drive signal Vin can also be determined based on the viscosity of the ink, specifically by varying the number of drive pulses PL included in the drive signal Vin.

[0252] Figure 30 Here is a functional block diagram illustrating an example of the structure of the inkjet printer 1a in the fifth modified example. 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 a control unit 6.

[0253] The viscosity information acquisition unit 9 acquires viscosity information VI, which represents the viscosity of the liquid in the liquid ejector head HU. Viscosity information VI is an example of "physical property information".

[0254] The viscosity information acquisition unit 9 acquires viscosity information VI, for example, by any one of the three methods shown below. In the first method, the viscosity information acquisition unit 9 acquires viscosity information VI based on the waveform of the residual vibration of the vibrating plate 310. In the second method, the viscosity information acquisition unit 9 acquires the viscosity information VI of the ink held in the liquid container 14. In the 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.

[0255] 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. Figure 31 The following example illustrates the determination of the number of drive pulses PL of waveform PH1 contained in drive signal Vin1.

[0256] Figure 31 This is a diagram illustrating an example of determining the number of drive pulses PL for the waveform PH1 contained in the drive signal Vin1. (See diagram for example.) Figure 31 As shown, when the viscosity represented by viscosity information VI is less than 20 mPa·s, the control unit 6a sets the number of drive pulses PL of waveform PH1 included in the drive signal Vin1 to 0. When the viscosity represented by viscosity information VI is 20 mPa·s or more but less than 30 mPa·s, the control unit 6a sets the number of drive pulses PL of waveform PH1 included in the drive signal Vin1 to 1. When the viscosity represented by viscosity information VI is 30 mPa·s or more but less than 50 mPa·s, the control unit 6a sets the number of drive pulses PL of waveform PH1 included in the drive signal Vin1 to 2. When the viscosity represented by viscosity information VI is 50 mPa·s or more but less than 70 mPa·s, the control unit 6a sets the number of drive pulses PL of waveform PH1 included in the drive signal Vin1 to 3.

[0257] When the number of drive pulses PL for the waveform PH1 contained in the drive signal Vin1 is determined to be 1, the control unit 6a determines the waveform of the drive signal Vin1 to be a waveform PH1 having any one of the drive pulses PL1, PL2, and PL3 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 a drive pulse PL3.

[0258] 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 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.

[0259] Furthermore, regardless of the viscosity information VI, the control unit 6a determines the waveform of the drive signal Vin2 as waveform PH2.

[0260] In addition, when a drive pulse PL containing waveform PH1 is selected from drive pulses PL1, PL2 and PL3, by selecting a drive pulse PL close to waveform PH2, it is possible to easily eject droplet DR from nozzle N when waveform PH2 is supplied to piezoelectric element PZ.

[0261] Return to the instructions Figure 30 The control unit 6a generates a separately specified signal Sd[m] in a manner that can generate a drive signal Vin, including a drive signal Vin1 that determines the waveform, and a drive signal Vin2 that determines the waveform. For example, when it is determined that the drive signal Vin1 includes a waveform PH1 that only has a drive pulse PL3, the control unit 6a generates... Figure 6 The control unit 6a outputs the generated individual specified signal Sd[m] to the switching circuit 10 for the driving mode α3 shown.

[0262] Furthermore, in the fifth modification, as further explained in the first embodiment, when the droplet DR is ejected during the recording period Tu[j], the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the predetermined recording period Tu[j] prior to the recording period Tu[j] is also taken into consideration, thereby enabling the determination of the waveform of the drive signal Vin supplied to the piezoelectric element PZ during the recording period Tu[j].

[0263] 2.5.1. Summary of the Fifth Modified Example

[0264] As explained above, in the inkjet printer 1a of 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, representing the viscosity of the ink in the liquid ejector head HU, is acquired. In the second step, the waveform of the drive signal Vin is determined based on the viscosity information VI. In the third step, by supplying the waveform PH1 contained in the drive signal Vin1, which has the waveform determined in the second step, to the piezoelectric element PZ, a liquid column LC6 protruding in the -Z direction from the meniscus MS is formed. In the fourth step, when the liquid column LC6 is formed, by supplying the waveform PH2 contained in the drive signal Vin2, which has the waveform determined in the second step, to the piezoelectric element PZ, after the liquid column LC8 protruding in the -Z direction from the meniscus MS is formed, part or all of the liquid constituting the liquid column LC8 is ejected as droplets DR.

[0265] If the number of drive pulses PL for waveform PH1 is increased despite the ink viscosity being low, the droplet DR will be ejected earlier than the expected ejection timing. On the other hand, if the number of drive pulses PL for waveform PH1 is decreased despite the ink viscosity being high, the droplet DR will be ejected later than the expected ejection timing, or the droplet DR will not be ejected at all.

[0266] Since the waveform of the drive signal Vin is determined by the viscosity represented by the viscosity information VI, the liquid droplets can be ejected at a timing close to that of the original droplet DR, thus suppressing the deterioration of print quality.

[0267] In the second step of the “Summary of the Fifth Change Example”, the waveform of the drive signal Vin1 is determined based on the viscosity information VI.

[0268] By adjusting the waveform of the drive signal Vin1, it is possible to eject the droplets DR at a timing close to the original timing.

[0269] In the second step of the “Summary of the Fifth Modification Example” section, the number of drive pulses PL of waveform PH1 contained in the drive signal Vin1 is determined based on the viscosity information VI.

[0270] As described in the section "Summary of Recording Method Using Drive Waveform Signal Com" of the first embodiment, the method of adjusting the number of drive pulses PL is a simpler structure compared to the method of adjusting the lowest and highest potentials of drive pulses PL.

[0271] 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 through a simpler structure.

[0272] In the fifth modified example, the drive signal Vin2 has a predefined waveform PH2 regardless of the viscosity information VI. Therefore, when generating a drive signal Vin that matches the viscosity of the ink, it is only necessary to adjust the waveform of the drive signal Vin1, and it is also possible not to adjust the waveform of the drive signal Vin2.

[0273] In the second step of the "Summary of the Fifth Modification Example" section, the waveform of the drive signal Vin1 is determined in such a way that the third number of the drive pulse PL of the waveform PH1 contained in the drive signal Vin1 when the viscosity information VI represents the first viscosity is greater than the fourth number of the drive pulse PL of the waveform PH1 contained in the drive signal Vin1 when the viscosity information VI represents the second viscosity, which is lower than the first viscosity.

[0274] Since the first viscosity is higher than the second viscosity, when viscosity information VI represents the first viscosity, a drive signal Vin1 with more drive pulses PL needs to be supplied to the piezoelectric element PZ compared to when viscosity information VI represents the second viscosity. Therefore, by determining the waveform of the drive signal Vin1 in a way that the third number is greater than the fourth number, it is possible to eject the droplets at the timing that would otherwise be ejected as DR.

[0275] 2.6. Sixth Change Example

[0276] Although the fifth modification example described an example of physical property information as viscosity information VI, physical property information is not limited to viscosity information VI. For example, physical property information can also be any one of the following: information representing the surface tension of the ink, information representing the bulk modulus of elasticity of the ink, and information representing the specific gravity of the ink.

[0277] When the physical property information is information representing the surface tension of the ink, the control unit 6 determines the waveform of the drive signal Vin1 in such a way that the number of drive pulses PL contained in the drive signal Vin1 is greater than the number of drive pulses PL contained in the drive signal Vin1 when the surface tension of the ink represents a first value.

[0278] When the physical property information is information representing the bulk modulus of the ink, the control unit 6 determines the waveform of the drive signal Vin1 in such a way that the number of drive pulses PL contained in the drive signal Vin1 is greater than the number of drive pulses PL contained in the drive signal Vin1 when the bulk modulus of the ink represents a third value.

[0279] When the physical property information is information representing the specific gravity of the ink, the control unit 6 determines the waveform of the drive signal Vin1 in such a way that the number of drive pulses PL contained in the drive signal Vin1 is greater than the number of drive pulses PL contained in the drive signal Vin1 when the bulk elastic modulus of the ink represents a fifth value, compared to the fifth value.

[0280] 2.7. Seventh Change Example

[0281] Although in the first embodiment and the first to sixth modifications, the drive waveform signal Com has a waveform PH2 that has drive pulses PL4 and PL5, it is not limited thereto. In the seventh modification, the drive waveform signal Com has a waveform PH2b that has only drive pulse PL4.

[0282] Figure 32 This diagram illustrates the drive waveform signal Comb in the seventh modified example. The drive waveform signal Comb has waveforms PH1 and PH2b. Waveform PH2b has a drive pulse PL4b. Drive pulse PL4b has drive components DC7 and DC8b. ​​Since the potential change per unit period in drive component DC8b is greater than the potential change per unit period in drive components DC2, DC4, and DC6, the energy for the liquid column LC8 formed by supplying drive component DC8b to the piezoelectric element PZ to move in the -Z direction is increased. Therefore, even if there is no drive pulse PL after drive pulse PL4b, part or all of the liquid column can be ejected as droplets DR.

[0283] 2.8. Eighth Change Example

[0284] Although in the first embodiment and the first to seventh modifications, the potential difference between the highest and lowest potentials in the driving pulses PL included in waveforms PH1 and PH2 is a potential difference Vh, it is not limited to this. The potential difference of waveform PH1 only needs to be at least 0.5 times the potential difference of waveform PH2. In the eighth modification, the potential difference Vh2a of the driving pulse PL4a included in waveform PH2a is greater than the potential difference Vh1 of the driving pulses PL1, PL2, and PL3 of waveform PH1, and the potential difference Vh3a of the driving pulse PL5a included in waveform PH2 is less than the potential difference Vh1 of the driving pulses PL1, PL2, and PL3 of waveform PH1.

[0285] Figure 33 This diagram illustrates the drive waveform signal Coma in the eighth modified example. The drive waveform signal Coma has waveforms PH1 and PH2a. Waveform PH2a has drive pulses PL4a and PL5a. Drive pulse PL5a has drive components DC9a and DC10a. The lowest potential of drive pulse PL4a is potential VL2a. Potential VL2a is lower than potential VL1. The potential difference of drive pulse PL4a is potential difference Vh2a. Potential difference Vh2a is greater than the potential difference Vh1 of drive pulses PL1, PL2, and PL3. More specifically, for the drive component DC7a of drive pulse PL4a, the initial potential is set to the reference potential V0, and the final potential is set to potential VL2a. For the drive component DC8a of drive pulse PL4a, the initial potential is set to potential VL2a, and the final potential is set to the reference potential V0. Furthermore, the lowest potential of drive pulse PL5a is potential VL3a. Potential VL3a is higher than potential VL1. The potential difference of driving pulse PL5a is potential difference Vh3a. Potential difference Vh3a is less than the potential difference Vh1 of driving pulses PL1, PL2, and PL3. More specifically, for the driving component DC9a of driving pulse PL5a, the initial potential is set to the reference potential V0, and the final potential is set to potential VL3a. For the driving component DC10a of driving pulse PL5a, the initial potential is set to potential VL3a, and the final potential is set to the reference potential V0.

[0286] The potential difference Vh1 of the driving pulses PL1, PL2, and PL3 of waveform PH1 can be set to a potential suitable for proper liquid column growth without generating unnecessary ink leakage from nozzle N. Furthermore, since liquid column growth will be impossible when the potential difference Vh1 is small, it is preferable that the potential difference Vh1 of the driving pulses PL1, PL2, and PL3 is at least 0.5 times the potential difference Vh2a of the driving pulse PL4a of waveform PH2a.

[0287] Furthermore, in this modified example, the potential difference Vh3a of the driving pulse PL5a of waveform PH2a is made smaller than the potential differences Vh1 and Vh2a. In this way, the possibility of ink seeping into the -Z direction surface of the nozzle plate 330 due to the driving component DC10a of the driving pulse PL5a can be suppressed. Additionally, when it is difficult for ink to seep into the -Z direction surface of the nozzle plate 330 due to the driving component DC10a of the driving pulse PL5a, the potential difference Vh3a of the driving pulse PL5a can be set to be greater than or equal to the potential difference Vh2a.

[0288] In addition, the potential differences of the driving pulses PL1, PL2 and PL3 of waveform PH1 can be set to different values.

[0289] 2.9. Ninth Modification Example

[0290] Although the potential difference and potential difference Vh between the highest and lowest potentials in the drive pulses PL included in waveforms PH1 and PH2 are approximately equal in the first embodiment and from the first to the eighth modification, this is not a limitation. The potential difference of waveform PH1 only needs to be at least 0.5 times the potential difference of waveform PH2. In the ninth modification, the potential difference of the drive pulse PL5 included in waveform PH2 is greater than the potential difference of waveform PH1.

[0291] Figure 34 This diagram illustrates the driving waveform signal Comc in the ninth modified example. The driving waveform signal Comc has waveforms PH1 and PH2c. Waveform PH2c has driving pulses PL4 and PL5c. Driving pulse PL5c has driving components DC9c and DC10c. The lowest potential of driving pulse PL5c is potential VL2. Potential VL2 is lower than potential VL1. The potential difference of driving pulse PL5c is potential difference Vh2. More specifically, regarding driving component DC9c, the initial potential is set to a reference potential V0, and the final potential is set to potential VL2. Regarding driving component DC10c, the initial potential is set to potential VL2, and the final potential is set to a reference potential V0. Potential difference Vh2 is greater than the potential difference Vh of driving pulses PL1, PL2, PL3, and PL4. By making the potential difference Vh2 of driving pulse PL5c greater than the potential difference Vh, the force required to tear the droplet DR from the liquid column LC9 can be increased.

[0292] According to the ninth modification, since the potential difference of waveform PH1 is set to be more than 0.5 times the potential difference of waveform PH2c, the design freedom of the driving waveform signal Com can be increased compared to a method where the potential differences of waveform PH1 and waveform PH2 are approximately equal. For example, by setting the potential difference of waveform PH2 to be greater than the potential difference of waveform PH1, the force for tearing the droplet DR off the liquid column LC9 can be increased. More preferably, the driving pulse PL5c of waveform PH2c has a driving component DC9c supplied to the piezoelectric element PZ when the tip of the liquid column LC8 moves in the -Z direction, and by making the difference between the highest and lowest potentials of the driving pulse PL5c greater than the difference between the highest and lowest potentials in waveform PH1, the force for tearing the droplet DR off the liquid column LC9 can be increased.

[0293] Additionally, the driving pulse PL5c is an example of "a driving pulse contained in the second driving pulse of the second waveform", and the driving component DC9c is an example of "a third driving component supplied to the driving element when the tip of the second liquid column moves in the ejection direction".

[0294] On the other hand, by making the potential difference of waveform PH1 smaller than the potential difference of waveform PH2c, droplets DR can be prevented from being ejected from the ejection section D when waveform PH1 is supplied to the piezoelectric element PZ, while droplets DR can be reliably ejected when waveform PH2c is supplied to the piezoelectric element PZ. Furthermore, although excessive ejection of droplets is prevented under waveform PH2 when the potential difference of waveform PH2c is greater than that of waveform PH1, there is a possibility of ink seeping into the -Z direction surface of the nozzle plate 330. By making the potential difference of waveform PH1 greater than that of waveform PH2, the possibility of ink seeping into the -Z direction surface of the nozzle plate 330 can be suppressed. The designer of the inkjet printer 1 can design the drive waveform signal Com considering the viscosity of the ink.

[0295] 2.10. Tenth Change Example

[0296] Although in the first embodiment and the first to ninth modifications, the period from the start of supplying the driving components DC9, DC9a, and DC9c included in the driving pulses PL5, PL5a, and PL5c to the end of supplying the driving components DC10, DC10a, and DC10c is longer than the period from the start of supplying the first driving component DC1, DC3, DC5, and DC7 included in any of the other driving pulses PL included in the driving waveform signals Com, Coma, and Comc to the end of supplying the second driving component DC2, DC4, DC6, and DC8, it is not limited to this.

[0297] Figure 35 This diagram illustrates the drive waveform signal Comd in the tenth modified example. The drive waveform signal Comd has waveforms PH1 and PH2d. Waveform PH2d has drive pulses PL4 and PL5d. Drive pulse PL5d has drive components DC9d and DC10d. The period Pw5, from the start of supplying drive component DC9d to the end of supplying drive component DC10d, is shorter than, for example, the period Pw1, from the start of supplying drive component DC1 (driven pulse PL1) to the end of supplying drive component DC2. Period Pw5 is shorter than the inherent vibration period TC of the ejector D, for example, 0.25 times the inherent vibration period TC. By making period Pw5 shorter than period Pw1, an opportunity can be generated to tear the droplet DR off the liquid column LC9.

[0298] Furthermore, although the tearing drive pulse PL is a single drive pulse PL5, it can also be multiple drive pulses PL.

[0299] 2.11. Eleventh Change Example

[0300] Although the highest potential and the initial potential of the driving pulse PL are the same in the first embodiment and the first to tenth modified examples, the highest potential and the initial potential may also be different.

[0301] Figure 36 This is a diagram used to illustrate the drive waveform signal Come in the eleventh modified example. The drive waveform signal Come has waveforms PH1e and PH2e. Waveform PH1e has drive pulses PL1e, PL2, and PL3. Waveform PH2e has drive pulses PL4 and PL5e.

[0302] For drive pulse PL1e, the initial potential is set to the reference potential V0, and the final potential is set to the highest potential Vh1. The highest potential Vh1 is higher than the reference potential V0. Drive pulse PL1e has drive components DC1e and DC2. For drive component DC1e, the initial potential is set to the reference potential V0, and the final potential is set to the lowest potential VL1. For drive pulses PL2, PL3, and PL4, the initial and final potentials are both set to the highest potential Vh1. For drive pulse PL5e, the initial potential is set to the highest potential Vh1, and the final potential is set to the reference potential V0. Drive pulse PL5e has drive components DC9 and DC10e. For drive component DC10e, the initial potential is set to the lowest potential VL1, and the final potential is set to the reference potential V0.

[0303] According to the eleventh modification, since the potential difference between the highest and lowest potentials of the driving component DC10e is smaller than the potential difference between the highest and lowest potentials of the driving component DC10, unnecessary ejection can be suppressed compared to the aforementioned embodiments and modifications. Alternatively, in the embodiment, even if droplets DR are not ejected by the driving component DC10, there is a possibility that ink may seep into the -Z direction surface of the nozzle plate 330. In the tenth modification, compared to the embodiment, the seepage of ink into the -Z direction surface of the nozzle plate 330 can be suppressed.

[0304] 2.12. Twelfth Change Example

[0305] Although in the eleventh modified example, the reference potential V0 is between the highest potential Vh1 and the lowest potential VL1, it is also possible to make the reference potential V0 and the lowest potential VL1 coincide.

[0306] Figure 37 This is a diagram used to illustrate the drive waveform signal Comf in the twelfth modified example. The drive waveform signal Comf has waveforms PH1f and PH2f. Waveform PH1f has drive pulses PL1f, PL2, and PL3. Waveform PH2f has drive pulses PL4 and PL5f.

[0307] For drive pulse PL1f, the initial potential is set to the reference potential V0, and the final potential is set to the maximum potential Vh1. The maximum potential Vh1 is higher than the reference potential V0. Drive pulse PL1f has a drive component DC2 but no drive component DC1. For drive pulses PL2, PL3, and PL4, the initial and final potentials are set to the maximum potential Vh1. For drive pulse PL5f, the initial potential is set to the maximum potential Vh1, and the final potential is set to the reference potential V0. Drive pulse PL5e has a drive component DC9 but no drive component DC10.

[0308] According to the twelfth modification, since it does not contain the driving component DC10, unnecessary ejection can be suppressed compared to the tenth modification. Alternatively, even in the eleventh modification, even if droplets DR are not ejected due to the driving component DC10, there is still a possibility of ink seeping into the -Z direction surface of the nozzle plate 330. According to the eleventh modification, since it does not contain the driving component DC10, the seepage of ink into the -Z direction surface of the nozzle plate 330 can be suppressed compared to the tenth modification.

[0309] 2.13. Thirteenth Change Example

[0310] Although in the first embodiment, the control unit 6 determines the waveform of the individual designated signal Sd[m] for the recording period Tu[j] based on the individual designated signals Sd[m] of the recording periods Tu[j-1] to Tu[j-3], which are predetermined recording periods Tux preceding the recording period Tu[j], it is not limited to this. For example, the control unit 6 may also determine the individual designated signal Sd[m] for the recording period Tu[j] based on the individual designated signals Sd[m] of two or more consecutive recording periods Tu that include the recording period Tu[j-1] and end before the start of the recording period Tu[j]. Furthermore, for example, the control unit 6 may determine the individual designated signal Sd[m] for the recording period Tu[j] based solely on the individual designated signal Sd[m] of the recording period Tu[j-1].

[0311] 2.14. Fourteenth Change Example

[0312] Although the fourteenth modification describes a situation where the control unit 6 determines the individual designation signal Sd[m] of the recording period Tu[j] based on the individual designation signal Sd[m] of two or more recording periods Tu[j-1] that are predetermined recording periods Tu[j] preceding the recording period Tu[j], it is also possible to determine the individual designation signal Sd[m] of the recording period Tu[j] based on the individual designation signal Sd[m] of one or more recording periods Tu[j-1] that are predetermined recording periods Tu[j] preceding the recording period Tu[j].

[0313] 2.15. Fifteenth Change Example

[0314] The control unit 6 may also 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 from which droplets DR are ejected from the ejector D to the number of recording periods Tu from which droplets DR are not ejected from the ejector D within a predetermined recording period Tu[j-1] that includes two or more consecutive recording periods Tu that end before the start of the recording period Tu[j]. For example, the control unit 6 calculates the following equation (3).

[0315] Ejection ratio = Number of droplets DR ejected from ejection section D during the recording period Tu / Number of droplets Tux during the predetermined recording period (3)

[0316] Furthermore, the control unit 6 ensures that the number of drive pulses PL during the recording period of Tu when the calculated ejection ratio is the first ratio is less than the number of drive pulses PL during the recording period of Tu when the ejection ratio is the second ratio. The first ratio is greater than the second ratio.

[0317] When the ejection ratio is large, the liquid column formed on the meniscus MS at the start time of Tu[j] during the recording period will be larger. Therefore, since the waveform of the drive signal Vin during the recording period is determined based on the ejection ratio, the droplet DR can be ejected in a manner close to the original ejection timing, thus suppressing the deterioration of print quality.

[0318] 2.16. Sixteenth Change Example

[0319] Although the waveform PH1 has three drive pulses PL in the first embodiment and the first to fifteenth modifications, it is not limited to this. The waveform PH1 may have only one drive pulse PL or four or more drive pulses PL. In the case where the waveform PH1 has four or more drive pulses PL, in the fifth modification, when the viscosity represented by the viscosity information VI is 70 mPa·s or more, the control unit 6a determines that the number of drive pulses PL included in the drive signal Vin1 is four or more. For example, when the viscosity represented by the viscosity information VI is 70 mPa·s or more and less than 100 mPa·s, the control unit 6a determines that the number of drive pulses PL included in the drive signal Vin1 is four.

[0320] 2.17. Seventeenth Change Example

[0321] Although in the first embodiment, the liquid column is defined as a columnar or hammer-shaped liquid surface protruding from the position closest to the +Z direction towards the -Z direction within the meniscus MS, in the case of a droplet temporarily separated from the meniscus MS, the columnar or hammer-shaped liquid surface of that droplet can also serve as a liquid column. A droplet temporarily separated from the meniscus MS refers to a droplet that, although separated during the supply of one driving component DC, re-aggregates during the supply of the next driving component DC. Specifically, Figure 14 The liquid column LC7 shown exhibits a temporary separation from the meniscus MS. The separated liquid column LC7 is re-bonded to the meniscus MS by the supply of driving component DC8.

[0322] 2.18. Eighteenth Change Example

[0323] The methods described above can also be applied to a method in which multiple chambers 320 supply ink to a single nozzle N.

[0324] Figure 38 Here is a diagram representing an example of the ejector section Dg in the eighteenth variation example. Figure 38 The diagram shown is an observation of multiple ejector sections Dg along the -Z direction. For simplicity, [the diagram is omitted]. Figure 38The piezoelectric element PZ, vibrating plate 310, nozzle plate 330, and chamber plate 340 are omitted from the diagram. The ejection section Dg has four chambers 320, a connecting channel 321, and a nozzle N. The four chambers 320 connect to a common ink chamber (not shown) and are supplied with ink. The connecting channel 321 connects to the nozzle N and, further, to each of the four chambers 320 in the -X direction. Although in Figure 38 In the first embodiment, the ejector section Dg has four chambers 320, but it can also have two, three, or more chambers 320. Since increasing the number of chambers 320 in an ejector section D increases the discharge volume of the chambers 320 corresponding to a nozzle N, it is possible to eject ink with a higher viscosity compared to the first embodiment.

[0325] 2.19. Nineteenth Change Example

[0326] The above-described methods can also be applied to an inkjet printer 1 having a circulation mechanism that, while supplying ink to the liquid printhead HU, also recycles ink discharged from the liquid printhead HU.

[0327] Figure 39 Here is a diagram representing an example of the ejector section Dh in the nineteenth modified example. Figure 39 The diagram shown is an observation of multiple ejector sections Dh along the -Z direction. For simplicity, [the diagram is omitted]. Figure 39 The piezoelectric element PZ, vibrating plate 310, nozzle plate 330, and chamber plate 340 are omitted from the diagram. The ejection section Dh has four chambers 320, a connecting channel 321h, and a nozzle N. The connecting channel 321h is connected to two chambers 320 at its -X end and to two chambers 320 at its +X end. The two chambers 320 connected to the -X end of the connecting channel 321h are connected to an ink supply section of a circulation mechanism (not shown), thereby supplying ink from the ink supply section. Furthermore, the two chambers 320 connected to the +X end of the connecting channel 321h are connected to an ink recovery section of a circulation mechanism (not shown), thereby recovering ink through the ink recovery section. Thus, ink circulates from the two chambers 320 in the -X direction to the two chambers 320 in the +X direction via the connecting channel 321h.

[0328] Since the nineteenth modification also increases the discharge volume of the chamber 320 corresponding to one nozzle N, it is possible to spray ink with a higher viscosity compared to the first embodiment. Furthermore, the nineteenth modification, through the circulation mechanism, can suppress ink thickening within the chamber 320 and the connecting flow channel 321h.

[0329] 2.20. Twentieth Change Example

[0330] Although the various embodiments described above exemplify a serial inkjet printer 1 in which the conveyor 82, which houses the liquid ejector head HU, reciprocates in the X-axis direction, the present invention is not limited to such embodiments. An inkjet printer can also be a row-type inkjet printer in which multiple nozzles N are distributed across the entire width of the recording paper P.

[0331] When the inkjet printer 1 is in line mode, the third modification example can also be applied. The control unit 6 controls the conveying mechanism 7 in such a way that the conveying speed of the recording paper P is the value obtained by dividing the conveying speed of the recording paper P by a predetermined number when the twentieth modification example is applied to the first embodiment.

[0332] 2.21. Example of the Twenty-First Change

[0333] Although one example of the "driving element" in the above methods is a piezoelectric element PZ, a heating element can also be used instead of a piezoelectric element PZ.

[0334] 2.22. Example of the Twenty-Second Change

[0335] The inkjet printers exemplified in the various embodiments described above can be used not only in devices specifically designed for printing, but also in various devices such as fax machines and copiers. Clearly, the application 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 color material can be used as a manufacturing apparatus for color filters in liquid crystal display devices. Furthermore, a liquid ejection device that ejects a solution of conductive material can be used as a manufacturing apparatus for wiring and electrodes in wiring boards.

[0336] 3. Notes

[0337] From the examples above, one can, for instance, grasp the following structure.

[0338] The preferred embodiment, Method 1, relates to a method for driving a liquid ejector head. This method describes a method for driving a liquid ejector head having an ejector portion comprising a drive element that is displaced by a drive signal, a pressure chamber whose internal pressure increases or decreases according to the displacement of the drive element, and a nozzle communicating with the pressure chamber and capable of ejecting liquid filled within the pressure chamber as droplets in a ejection direction according to the increase or decrease of the internal pressure of the pressure chamber. The driving method includes a first step in which a first liquid column protruding in the ejection direction is formed by supplying a drive signal having a first waveform to the drive element. The first waveform includes a first drive component that decreases the internal pressure of the pressure chamber and a second drive component that increases the internal pressure of the pressure chamber. The first driving pulse of the driving component; the second step, which, when the first liquid column is formed, supplies a driving signal having a second waveform to the driving element, thereby forming a second liquid column in which the liquid surface in the ejection section protrudes in the ejection direction, and then ejects part or all of the liquid constituting the second liquid column as droplets, wherein the second waveform includes a second driving pulse having a third driving component that reduces the pressure inside the pressure chamber and a fourth driving component that increases the pressure inside the pressure chamber, and, when a driving signal having the first waveform but not the second waveform is supplied to the driving element, droplets are not ejected from the ejection section, and when a driving signal having the second waveform but not the first waveform is supplied to the driving element, droplets are not ejected from the ejection section.

[0339] According to Method 1, when a first liquid column is formed by a drive signal having a first waveform, by supplying a drive signal having a second waveform to the drive element, the liquid column formed on the liquid surface in the ejection section can be grown, thereby causing part or all of the liquid constituting the second liquid column to be ejected as droplets.

[0340] In Method 2, a specific example of Method 1, when a drive signal having the second waveform but not the first waveform is supplied to the drive element, and the third drive component of the second waveform is supplied to the drive element, the amount of pressure change (i.e., reduction) of the liquid in the nozzle toward the negative pressure side is approximately equal to the amount of pressure change (i.e., reduction) of the liquid in the nozzle toward the negative pressure side when a drive signal having both the first and second waveforms is supplied to the drive element, and the third drive component of the second waveform is supplied to the drive element.

[0341] In Method 2, even for high-viscosity liquids, droplets can be ejected by forming a liquid column on the liquid surface within the ejection section using the first and second waveforms.

[0342] In embodiment 3, which is a specific example of embodiment 1 or 2, when a drive signal having the second waveform but not the first waveform is supplied to the drive element, and the fourth drive component having the second waveform is supplied to the drive element, the amount of change (i.e., increase) of the pressure of the liquid in the nozzle toward the positive pressure side is approximately equal to the amount of change (i.e., increase) of the pressure of the liquid in the nozzle toward the positive pressure side when a drive signal having both the first and second waveforms is supplied to the drive element, and the fourth drive component having the second waveform is supplied to the drive element.

[0343] Method 3 is similar to Method 2. Even with high-viscosity liquids, by utilizing the first and second waveforms, a liquid column is formed on the liquid surface within the ejection section, thereby enabling the droplets to be ejected.

[0344] In embodiment 4, which is a specific example of any one of embodiments 1 to 3, when a drive signal having the second waveform is supplied to the drive element after a drive signal having the first waveform, and the fourth drive component of the second waveform contained in the drive signal is supplied to the drive element, the portion of the liquid surface in the ejection section that is pulled in the most in the pull-in direction opposite to the ejection direction is located in the ejection direction, compared to the portion of the liquid surface in the ejection section that is pulled in the most in the pull-in direction when a drive signal having the second waveform is supplied to the drive element without a drive signal having the first waveform being supplied to the drive element, and the fourth drive component of the second waveform is supplied to the drive element.

[0345] In the first embodiment, since the first and second waveforms are supplied to the piezoelectric element PZ, causing a drive signal with a first drive component to be supplied to the drive element, the portion of the liquid surface in the ejection section that is pulled in the most in the pulling direction moves in the ejection direction, and thus the liquid column formed on the liquid surface in the ejection section also moves in the ejection direction. Since the liquid column moves in the ejection direction, the tip of the liquid column in the ejection direction leaves the initial position of the liquid surface in the ejection section, making it easier to separate part or all of the liquid column, thereby enabling the ejection of droplets separated from the liquid column.

[0346] In Method 5, which is a specific example of any one of Methods 1 to 4, in the second step, when the tip of the second liquid column moves in the ejection direction, the third driving component of the second driving pulse of the driving signal is supplied to the driving element.

[0347] When the tip of the second liquid column moves in the ejection direction, a drive signal having a second drive component is supplied to the drive element, thereby tearing the droplet off the second liquid column. According to this embodiment, compared with supplying a drive signal without a second drive component to the drive element, a more stable ejection can be achieved.

[0348] In mode 6, which is a specific example of any one of modes 1 to 5, the first drive pulse of the first waveform includes a plurality of drive pulses.

[0349] Since the first waveform has multiple driving pulses, even if droplets cannot be ejected by a single driving pulse, by supplying a driving signal with a first waveform having multiple driving pulses to the driving element, a liquid column formed on the liquid surface in the ejection section can be grown, and a portion or all of the liquid constituting the second liquid column can be ejected as droplets by the second waveform.

[0350] In Method 7, which is a specific example of any one of Methods 1 to 6, the viscosity of the liquid in the liquid nozzle is 20 mPascals or more.

[0351] Although there is a possibility that a single driving pulse may not be able to eject droplets when the viscosity of a liquid is above 20 mPascals per second, the driving method implemented by means of a first waveform preceding the second waveform enables the ejection of droplets even for liquids with a viscosity above 20 mPascals per second.

[0352] In Method 8, which is a specific example of any of Methods 1 to 7, the difference between the highest and lowest potentials in the first waveform and the difference between the highest and lowest potentials in the second waveform are approximately equal. More specifically, the highest potential in the first waveform and the highest potential in the second waveform are approximately equal, and the lowest potential in the first waveform and the lowest potential in the second waveform are approximately equal.

[0353] 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 high-viscosity liquids can pass through the first waveform, thereby causing a liquid column to grow on the liquid surface in the ejection section, and causing droplets to be ejected in the second waveform.

[0354] The liquid ejection device according to preferred embodiment 9 comprises: a liquid ejection head having an ejection section, the ejection section having a drive element that is displaced by being supplied with a drive signal, a pressure chamber whose internal pressure increases or decreases according to the displacement of the drive element, and a nozzle communicating with the pressure chamber and capable of ejecting liquid filled inside the pressure chamber as droplets in an ejection direction according to the increase or decrease of the internal pressure of the pressure chamber; and a control unit that controls the liquid ejection head, the control unit controlling the formation of a first liquid column protruding from the liquid surface in the ejection section in the ejection direction by supplying a drive signal having a first waveform to the drive element, wherein the first waveform includes a first drive component that reduces the internal pressure of the pressure chamber and a first drive component that increases the internal pressure of the pressure chamber. The first driving pulse of the second driving component with increased force, when the first liquid column is formed, supplies a driving signal having a second waveform to the driving element, thereby causing part or all of the liquid constituting the second liquid column to be ejected as droplets after the liquid surface in the ejection section protrudes in the ejection direction. The second waveform includes a second driving pulse having a third driving component that reduces the pressure inside the pressure chamber and a fourth driving component that increases the pressure inside the pressure chamber. When a driving signal having the first waveform but not the second waveform is supplied to the driving element, droplets are not ejected from the ejection section. When a driving signal having the second waveform but not the first waveform is supplied to the driving element, droplets are not ejected from the ejection section.

[0355] According to method 9, when a first liquid column is formed by a drive signal having a first waveform, by supplying a drive signal having a second waveform to the drive element, the liquid column formed on the liquid surface in the ejection section can be grown, and part or all of the liquid constituting the second liquid column can be ejected as droplets.

[0356] Symbol Explanation

[0357] 1, 1a…Inkjet printer; 2…Drive waveform signal generation circuit; 5…Storage unit; 6, 6a…Control unit; 7…Conveyor mechanism; 8…Moving mechanism; 9…Viscosity information acquisition unit; 10…Switching circuit; 11…Connection status specification circuit; 14…Liquid container; 81…Seamless belt; 82…Conveyor body; 310…Vibrating plate; 320…Cavity; 321…Connecting flow channel; 321h…Connecting flow channel; 330…Nozzle plate; 340…Cavity plate; 350…Reservoir; 360…Ink supply port; 370…Ink inlet; CH…Conversion signal; CL…Clock signal; CPw…Characteristics; Com, Coma, Comb, Comc, Comd, Come Comf…Drive waveform signal; D, Dg, Dh…Ejection section; DC1~DC10, DC7a, DC8a, DC8b, DC9a, DC9c, DC9d, DC10a, DC10c, DC10d, DC10e…Drive components; DR…Droplet; G1, G2, G3, G4, G5…Graph; HD…Recording head; HU…Liquid ejection head; Img…Printed data; LAT…Latch signal; LC2~LC10…Liquid column; LHa…Internal wiring; LHb…Power supply line; LPnm, LPnp, LVnm, LVnp…Line segment; MS…Mediterranean surface; N…Nozzle; P…Recording paper; PH, PH1, PH1e… PH1f, PH2, PH2a, PH2b, PH2c, PH2d, PH2e, PH2f… waveforms; PL, PL1, PL1e, PL1f, PL2, PL3, PL4, PL4a, PL4b, PL5, PL5a, PL5c, PL5d, PL5e, PL5f… drive pulses; PZ… piezoelectric element; Pa1, Pa2… pressure variation characteristics; PLsC, PLsL… pulses; Pn1, Pn2… pressure variation characteristics; Pw, Pw1, Pw24, Pw46, Pw5, Pw68… periods; SI… printed signal; SLa… connection status specification signal; SWA… switch; Sd… individually specified signal; TC …Inherent vibration period; Tbu…period; Tcu1~Tcu5…control period; Tu…recording period; V0…reference potential; Vbs…fixed potential; Vh1…highest potential; VI…viscosity information; VL1…lowest potential; VL2, VL2a, VL3a…potential; Vh, Vh1, Vh2, Vh2a, Vh3a…potential difference; Vin, Vin1, Vin2…drive signal; Vn3, Vn4…variation characteristics; Z0…initial position; Zd…lower electrode; Zm…piezoelectric element; Zm1~Zm3…extrusion position; Zp1~Zp4…pull-in position; Zu…upper electrode; dCom…waveform specification signal; α1~α8…drive mode.

Claims

1. A driving method, characterized in that, It is a method for driving a liquid ejector head having an ejection section, the ejection section comprising a drive element that is displaced by being supplied with a drive signal, a pressure chamber whose internal pressure is increased or decreased according to the displacement of the drive element, and a nozzle that communicates with the pressure chamber and is capable of ejecting liquid filled inside the pressure chamber as droplets in the ejection direction according to the increase or decrease of the internal pressure of the pressure chamber. In the driving method, Obtain physical property information representing the physical properties of the liquid in the liquid ejector head. The waveform of the driving signal is determined based on the aforementioned physical property information. The drive signal has a first waveform and a second waveform. The first waveform includes multiple 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. The second waveform is later than the first waveform and includes second drive pulses having 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 driving component of the initial first driving pulse in the first driving pulse drives the driving element in such a way that it reduces the pressure inside the pressure chamber, and from a state where a reference potential is supplied to the driving element and the liquid surface in the nozzle is stationary at the initial position, it pulls the liquid surface into the nozzle in a concave curved state where the central portion of the liquid surface is recessed towards the pressure chamber side. After the first driving component of the initial first driving pulse is supplied to the driving element, the second driving component of the first driving pulse drives the driving element in such a way that the pressure inside the pressure chamber is increased, and the liquid surface is squeezed out toward the ejection direction compared to the initial position, thereby forming a first liquid column with the central portion of the liquid surface protruding toward the ejection direction. The first driving component of the first driving pulse, which is later than the initial first driving pulse, drives the driving element in such a way that it reduces the pressure inside the pressure chamber and maintains the first liquid column at the central portion of the liquid surface, thereby pulling the liquid surface into the nozzle by pulling the tip of the first liquid column further into the nozzle than the initial position. The second driving component of the first driving pulse, which is later than the initial first driving pulse, drives the driving element in such a way that it increases the pressure inside the pressure chamber and forces the liquid surface out in the ejection direction, so that the tip of the first liquid column reaches an extrusion position further in the ejection direction than the extrusion position reached by the tip of the first liquid column when the second driving component of the preceding first driving pulse is supplied to the driving element. The third driving component drives the driving element in such a way that it reduces the pressure inside the pressure chamber and, while keeping the tip of the first liquid column at the center of the liquid surface protruding towards the ejection direction compared to the initial position, pulls the peripheral portion of the liquid surface into the nozzle. After the third driving component is supplied to the driving element, the fourth driving component drives the driving element in such a way that the pressure inside the pressure chamber is increased, and a second liquid column with a spherical tip and a neck between the peripheral portion of the liquid surface and the tip is formed at the central portion of the liquid surface. Part or all of the second liquid column is ejected from the nozzle as droplets.

2. The driving method as described in claim 1, characterized in that, The physical property information indicates the viscosity of the liquid in the liquid nozzle.

3. The driving method as described in claim 1 or 2, characterized in that, The first waveform is determined based on the aforementioned physical property information.

4. The driving method as described in claim 3, characterized in that, The number of subsequent driving pulses in the first waveform is determined based on the material property information.

5. The driving method as described in claim 1, characterized in that, The second waveform has a waveform that is not based on the material property information and is preset.

6. The driving method as described in claim 2, characterized in that, The waveform of the first driving signal is determined in the following manner, namely, The number of later driving pulses in the waveform when the physical property information represents a first viscosity is greater than the number of later driving pulses in the first waveform when the physical property information represents a second viscosity that is lower than the first viscosity.

7. The driving method as described in claim 1, characterized in that, The viscosity of the liquid in the liquid nozzle is above 20 millipascals.

8. The driving method as described in claim 1, characterized in that, The difference between the highest and lowest potentials of the first waveform and the difference between the highest and lowest potentials of the second waveform are approximately equal.

9. A liquid ejection device, characterized in that, have: A liquid ejector head has an ejection section comprising a drive element that is displaced by being supplied with a drive signal, a pressure chamber that increases or decreases the internal pressure according to the displacement of the drive element, and a nozzle that communicates with the pressure chamber and is capable of ejecting liquid filled inside the pressure chamber as droplets in the ejection direction according to the increase or decrease of the internal pressure of the pressure chamber. The control unit controls the liquid ejection head. The control unit performs the following control: Obtain physical property information representing the physical properties of the liquid in the liquid ejector head. The waveform of the driving signal is determined based on the aforementioned physical property information. The drive signal is generated and supplied to the drive element. The drive signal has a first waveform and a second waveform. The first waveform includes multiple 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. The second waveform is later than the first waveform and includes second drive pulses having 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 includes an initial first drive pulse and a subsequent first drive pulse compared to the initial first drive pulse. The first driving component of the initial first driving pulse drives the driving element in such a way that it reduces the pressure inside the pressure chamber and, starting from a state where a reference potential is supplied to the driving element and the liquid surface in the nozzle is stationary at the initial position, pulls the liquid surface into the nozzle in a concave curved state where the central portion of the liquid surface is recessed towards the pressure chamber side. The second driving component of the initial first driving pulse, after the first driving component of the initial first driving pulse is supplied to the driving element, drives the driving element in such a way that the pressure inside the pressure chamber is increased, and the liquid surface is squeezed out toward the ejection direction compared to the initial position, thereby forming a first liquid column with the central portion of the liquid surface protruding toward the ejection direction. The first driving component of the subsequent first driving pulse drives the driving element in such a way that it reduces the pressure inside the pressure chamber and maintains the first liquid column at the central portion of the liquid surface, thereby pulling the liquid surface into the nozzle by pulling the tip of the first liquid column towards the nozzle compared to the initial position. The second driving component of the subsequent first driving pulse drives the driving element in such a way that it increases the pressure inside the pressure chamber and forces the liquid surface out in the ejection direction, so that the tip of the first liquid column reaches an extrusion position further in the ejection direction than the extrusion position reached by the tip of the first liquid column when the second driving component of the preceding first driving pulse was supplied to the driving element. The third driving component drives the driving element in such a way that it reduces the pressure inside the pressure chamber and, while keeping the tip of the first liquid column at the center of the liquid surface protruding towards the ejection direction compared to the initial position, pulls the peripheral portion of the liquid surface into the nozzle. After the third driving component is supplied to the driving element, the fourth driving component drives the driving element in such a way that the pressure inside the pressure chamber is increased, and a second liquid column with a spherical tip and a neck between the peripheral portion of the liquid surface and the tip is formed at the central portion of the liquid surface. Part or all of the second liquid column is ejected from the nozzle as droplets.

Images