WO2024111322A1

WO2024111322A1 - Liquid droplet ejection device, method for driving liquid droplet ejection device, and program

Info

Publication number: WO2024111322A1
Application number: PCT/JP2023/038336
Authority: WO
Inventors: 奨唐鎌; 昇平倉持
Original assignee: コニカミノルタ株式会社
Priority date: 2022-11-25
Filing date: 2023-10-24
Publication date: 2024-05-30

Abstract

A liquid droplet ejection device 1 comprises: a liquid droplet ejection head 23 equipped with a head drive unit 24 that deforms a pressure chamber 25 connected to a nozzle 21; and a control unit 40 that generates a drive signal W composed of a plurality of drive pulses, that changes the capacity of the pressure chamber 25 by applying the drive signal W to the head drive unit 24, and that causes liquid droplets to be ejected from the nozzle 21 to perform recording operation on a recording medium. The control unit 40 sequentially generates, as the drive pulses, a first expansion pulse W1 that causes the capacity of the pressure chamber 25 to increase, a contraction pulse W2 that has a pulse width t2 of 0.1-0.5 AL and that causes the capacity of the pressure chamber 25 to decrease, and a second expansion pulse W3 that has a pulse width t3 of 1.2-2.8 AL and that causes the capacity of the pressure chamber 25 to increase again.

Description

Droplet ejection device, method and program for driving the droplet ejection device

The present invention relates to a droplet ejection device, a method for driving a droplet ejection device, and a program.

　Conventionally, there is known a droplet ejection device that ejects droplets onto the recording surface of a recording medium to record an image. In such a droplet ejection device, droplets are ejected from the nozzles of a droplet ejection head at appropriate timing based on image data.

Specifically, a droplet ejection device is known that ejects droplets by sequentially applying a first expansion pulse that expands the volume of a pressure chamber, a contraction pulse that contracts the volume of the pressure chamber, and a second expansion pulse that expands the volume of the pressure chamber again (see, for example, Patent Document 1). Such a droplet ejection device can eject small droplets at a high drive frequency.

JP 2011-037260 A

However, when the droplet ejection device of Patent Document 1 ejects small droplets at high speed, minute droplets called satellites may be generated after the droplets are ejected. Satellites are droplets that are not necessary for image recording operations, and the landing position and timing are shifted from the original intention. Therefore, if satellites adhere to the formed image, the image quality is reduced. In addition, if the satellites do not reach the recording medium and adhere to the nozzle or the periphery of the nozzle opening and solidify, the droplet ejection performance is deteriorated.
For this reason, in a droplet ejection device, it is preferable to suppress the occurrence of satellites.

The present invention has been made in consideration of these circumstances. Its purpose is to provide a droplet ejection device, a method for driving a droplet ejection device, and a program that can reduce the occurrence of satellites even when ejecting small droplets.

In order to solve the above problems, the present invention provides a droplet ejection device, comprising:
a droplet ejection head including a head drive unit that deforms a pressure chamber that communicates with a nozzle;
A drive signal generating unit that generates a drive signal consisting of a plurality of drive pulses;
a discharge control unit that applies the drive signal to the head drive unit to change the volume of the pressure chamber and discharges droplets from the nozzle to perform a recording operation on a recording medium,
the drive signal generating section generates, as the drive pulse, a first expansion pulse for expanding the volume of the pressure chamber, a contraction pulse for contracting the volume of the pressure chamber, and a second expansion pulse for expanding the volume of the pressure chamber again, in that order;
When AL is half the acoustic resonance period of the pressure chamber, the pulse width of the contraction pulse is not less than 0.1 AL and not more than 0.5 AL, and the pulse width of the second expansion pulse is not less than 1.2 AL and not more than 2.8 AL.

The present invention relates to a droplet ejection device, comprising:
The pulse width of the first expansion pulse is not less than 0.8 AL and not more than 1.5 AL.

The present invention relates to a droplet ejection device according to claim 1 or 2,
The potential of the contraction pulse is the opposite potential of the first expansion pulse.

The invention according to claim 4 is the droplet ejection device according to claim 1 or 2,
The pulse width of the first expansion pulse is equal to or less than the sum of the pulse width of the contraction pulse and the pulse width of the second expansion pulse.

The invention according to claim 5 is the droplet ejection device according to claim 1 or 2,
The droplets have a viscosity of 8 cp or more.

A sixth aspect of the present invention is a method for driving a droplet ejection device, comprising the steps of:
A method for driving a droplet ejection device including a droplet ejection head having a head drive unit that deforms a pressure chamber that communicates with a nozzle, comprising:
A drive signal generating step of generating a drive signal including a plurality of drive pulses;
an ejection control step of applying the drive signal to the head drive unit to change the volume of the pressure chamber and eject droplets from the nozzle to perform a recording operation on a recording medium,
the drive signal generating step sequentially generates, as the drive pulse, a first expansion pulse for expanding a volume of the pressure chamber, a contraction pulse for contracting the volume of the pressure chamber, and a second expansion pulse for expanding the volume of the pressure chamber again;
When AL is half the acoustic resonance period of the pressure chamber, the pulse width of the contraction pulse is set to 0.1 AL or more and 0.5 AL or less, and the pulse width of the second expansion pulse is set to 1.2 AL or more and 2.8 AL or less.

The invention described in claim 7 is a program,
A computer of a droplet ejection device including a droplet ejection head having a head drive unit that deforms a pressure chamber that communicates with a nozzle,
a drive signal generating unit that generates a drive signal consisting of a plurality of drive pulses;
a discharge control unit that applies the drive signal to the head drive unit to change the volume of the pressure chamber and discharges droplets from the nozzle to perform a recording operation on a recording medium;
causing the drive signal generating unit to generate, as the drive pulse, a first expansion pulse for expanding the volume of the pressure chamber, a contraction pulse for contracting the volume of the pressure chamber, and a second expansion pulse for expanding the volume of the pressure chamber again, in that order;
When AL is half the acoustic resonance period of the pressure chamber, the pulse width of the contraction pulse is set to 0.1 AL or more and 0.5 AL or less, and the pulse width of the second expansion pulse is set to 1.2 AL or more and 2.8 AL or less.

According to the present invention, the occurrence of satellites can be reduced even when small droplets are ejected.

1 is a block diagram of a droplet ejection device according to the present invention. 4 is a schematic diagram of a pressure chamber and a nozzle as viewed in the axial direction of the nozzle, showing a change in the pressure chamber in response to an expansion pulse. 1 is a schematic diagram of a pressure chamber and a nozzle as viewed in the axial direction of the nozzle, showing the pressure chamber when the potential is returned to zero. 4 is a schematic diagram of a pressure chamber and a nozzle as viewed in the axial direction of the nozzle, showing a change in the pressure chamber in response to a contraction pulse. 13 is a diagram showing a drive signal for applying a plurality of pulses within one pixel period for ejecting droplets. FIG. FIG. 13 is a diagram showing the state of ink in a nozzle when a first expansion pulse is applied. 13A and 13B are diagrams showing the state of ink in a nozzle when a contraction pulse is applied. FIG. 13 is a diagram showing the state of ink in a nozzle when a second expansion pulse is applied. FIG. 13 is a diagram showing the state of ink in a nozzle when a cancellation waveform is applied.

Below, one embodiment of the present invention will be described with reference to the drawings. The following description is intended to illustrate one embodiment of the present invention and is not intended to limit the present invention.

[Overall configuration of inkjet recording apparatus]
First, as a droplet ejection device according to the present embodiment, a configuration example of an inkjet recording device 1 including an inkjet head 23 that is a droplet ejection head will be disclosed.
FIG. 1 is a block diagram showing the functional configuration of an inkjet recording apparatus 1. As shown in FIG.

The inkjet recording device 1 includes, for example, a conveying unit 10, an image forming unit 20, a cleaning unit 30, a control unit 40, a memory unit 50, a communication unit 60, an operation reception unit 70, a display unit 80, and a power supply unit 90.

(Transportation section)
The conveying unit 10 moves a recording medium on which an image is to be recorded. The conveying unit 10 then brings the recording medium into opposition to a recording area of the image forming unit 20.

The conveying unit 10 includes a conveying motor 11 that pulls out a long recording medium wound up in a roll at a predetermined speed. The recording medium is, for example, paper, but may also be fabric or other materials.

(Image forming section)
The image forming unit 20 ejects ink droplets onto a recording medium to record an image.

The image forming unit 20 has a plurality of inkjet heads 23 arranged along the transport direction of the recording medium. The inkjet heads 23 have a number of nozzles 21 arranged in a predetermined pattern and piezoelectric elements 22 that eject ink droplets from openings.

The image forming unit 20 also includes a head drive unit 24. Based on the control of the control unit 40, the head drive unit 24 applies a drive signal W (see FIG. 3) including multiple drive pulses to the piezoelectric element 22. As the piezoelectric element 22 deforms due to the drive pulse, it deforms the side wall 26 of the ink flow path (pressure chamber) 25 that communicates with the nozzle 21 to supply ink, as shown in FIGS. 2A to 2C. This deformation causes the pressure chamber 25 to expand or contract, causing pressure fluctuations in the ink inside, resulting in the ejection of ink droplets from the opening of the nozzle 21.

(Cleaning Department)
Returning to FIG. 1, the cleaning unit 30 cleans the nozzle surface of the inkjet head 23 on which the openings of the nozzles 21 are arranged.

The cleaning unit 30 includes a wiping member 32 that wipes off ink and solidified ink adhering to the nozzle surface. The cleaning unit 30 also includes a drive unit 31 that drives the wiping member 32.
The wiping member 32 is not particularly limited, but may be, for example, a nonwoven fabric that absorbs ink, or a blade-shaped resin member that scrapes off solid matter.

(Control Unit)
The control unit 40 is a processor that controls the overall operation of the inkjet recording apparatus 1 .

The control unit 40 includes, for example, a central processing unit (CPU) 41 and a random access memory (RAM) 42. The CPU 41 performs calculations and executes various control processes.
The RAM 42 provides a working memory space for the CPU 41 and stores temporary data.
The control unit 40 executes a predetermined program to function as a drive signal generating unit and an ejection control unit.

The control unit 40 serves as a drive signal generating unit and generates a drive signal W made up of a plurality of drive pulses.
Furthermore, the control unit 40 , functioning as an ejection control unit, controls the head driving unit 24 to output a driving signal W to the piezoelectric element 22 , thereby ejecting ink droplets from the nozzle 21 .
The drive signal W, the deformation of the pressure chamber 25 due to the drive signal W, and the ejection of ink droplets accompanying the deformation will be described in detail later.

(Memory unit)
The storage unit 50 stores image data to be recorded, processing data thereof, other setting data, and programs. Image data may be stored in, for example, a dynamic random access memory (DRAM) capable of temporarily storing large amounts of data and outputting data at high speed. Setting data and programs are stored in a non-volatile memory such as a flash memory and/or a hard disk drive (HDD).
In this way, even if the power supply to the inkjet recording apparatus 1 is stopped, the setting data can be stored.

(Communications Department)
The communication unit 60 controls data transmission and reception with external devices in accordance with a predetermined communication standard, for example, TCP/IP (Transmission Control Protocol/Internet Protocol).

The communication unit 60 may be connected to a LAN (Local Area Network) and may be connectable to the external Internet via a router. The communication unit 60 may also be connectable directly to peripheral devices via a Universal Serial Bus (USB) cable connected to a USB terminal.

(Operation reception unit)
The operation reception unit 70 receives an input operation by the user, and outputs the received content to the control unit 40 as an input signal.

The operation reception unit 70 includes, for example, a touch panel and a push button switch. The touch panel is positioned so as to overlap with the display screen of the display unit 80, and the operation content may be specified in synchronization with the display content on the display screen.

(Display)
The display unit 80 displays status and selection menus to the user.

The display unit 80 has, for example, a display screen and an indicator (lamp). The indicator may be, for example, an LED (Light Emitting Diode) lamp that is used to indicate the presence or absence of power supply or the presence or absence of an operational abnormality.
The display unit 80 has, for example, a liquid crystal display, and can display various characters and figures on the display screen in a dot matrix format.

(Power supply section)
The power supply unit 90 supplies power from a power source to the inkjet recording apparatus 1 .

[About the drive signal]
3 shows a driving signal W for implementing the driving method according to the present embodiment. As shown in FIG. 3, the driving signal W includes, in chronological order, a first expansion pulse W1, a contraction pulse W2, and a second expansion pulse W3.
FIG. 4 is a cross-sectional view of one nozzle 21, showing the state of ink when each drive pulse is applied.

In FIG. 3, the horizontal axis indicates time (AL (Acoustic Length; 1/2 the acoustic resonance period of the pressure chamber 25)) and the vertical axis indicates voltage. Also in FIG. 3, t1 indicates the pulse width of the first expansion pulse W1, t2 indicates the pulse width of the contraction pulse W2, and t3 indicates the pulse width of the second expansion pulse W3.

The AL is obtained by applying a rectangular wave driving pulse to the side wall 26, which is an electromechanical conversion means, and measuring the speed of the ink droplets ejected from the nozzle 21.
Specifically, AL is determined as the pulse width at which the flying speed of the ink droplets becomes maximum when the voltage value of the square wave is kept constant and the pulse width is changed. Therefore, AL is determined depending on the structure of the inkjet head 23, the density of the ink, etc.

A pulse is a rectangular wave with a constant voltage peak value. The pulse width is the time between 10% of the beginning of the rise or fall from 0V and 10% of the beginning of the fall or rise, where 0V is 0% and the peak value voltage is 100%. A rectangular wave is a waveform in which the rise time and fall time between 10% and 90% of the voltage are both within 1/10 of the AL, and preferably within 1/20 of the AL.

As shown in FIG. 3, the head driver 24 applies a first expansion pulse W1 (P1), which is a rectangular wave that rises to a predetermined positive voltage, the Von voltage value, and then is maintained for a certain period of time. Then, as shown in FIG. 2A, the

side walls

26, 26 on both sides deform toward the outside, and the volume of the pressure chamber 25 expands. This generates a negative pressure in the ink in the pressure chamber 25, causing the ink to flow in. Also, as shown in FIG. 4A, the ink in the nozzle is maintained with the meniscus pulled into the nozzle 21.

After t1 has elapsed since the application of the first expansion pulse W1, the potential is returned to 0 (P2). Then, the

side walls

26, 26 return from the expansion position to the neutral position shown in FIG. 2B, and high pressure is applied to the ink in the pressure chamber 25.

The head driver 24 then applies a contraction pulse W2 (P3), which is a rectangular wave that falls to Voff, which is the voltage of the opposite potential to the first expansion pulse W1. As the contraction pulse W2 falls, the

side walls

26, 26 deform in opposite directions, as shown in FIG. 2C, and the volume of the pressure chamber 25 contracts. This contraction applies even higher pressure to the ink in the pressure chamber 25. As a result, an ink column protrudes from the opening of the nozzle 21, as shown in FIG. 4B.

After t2 has elapsed since the application of the contraction pulse W2, the potential is returned to 0 (P4). Then, a second expansion pulse W3 consisting of a square wave that rises to a predetermined positive voltage is applied (P5). Then, as shown in FIG. 2A, the volume of the pressure chamber 25 expands again, and a high negative pressure is again applied to the ink in the pressure chamber 25. This causes the ink meniscus to retract, and the rear end of the protruding ink pillar is pulled back, as shown in FIG. 4C. Then, after a predetermined time has elapsed, the diameter of the ink pillar narrows and the ink droplet is detached.

After t3 has elapsed since the application of the second expansion pulse W3, the potential is returned to 0 (P6). Then, by returning the pressure chamber 25 from the state shown in FIG. 2A to the state shown in FIG. 2B, the pressure wave can be rapidly attenuated. As a result, as shown in FIG. 4D, the ink in the nozzle is held in a state where the meniscus is pulled into the nozzle 21.

The inkjet head 23 is driven by repeatedly applying the above series of drive signals W. Therefore, the more the pressure wave is damped, the faster the ink for the next pixel can be ejected, allowing for faster printing, which is preferable.

In the present invention, the pulse width t2 of the contraction pulse W2 is not less than 0.1 AL and not more than 0.5 AL.
If the pulse width t2 of the contraction pulse W2 is less than 0.1 AL, the

side walls

26, 26 are insufficiently contracted, and small ink droplets cannot be formed. If the pulse width t2 of the contraction pulse W2 is more than 0.5 AL, the volume of the ink droplets increases rapidly, and small ink droplets cannot be formed.
On the other hand, when the pulse width t2 of the contraction pulse W2 is set to be equal to or greater than 0.1 AL and equal to or less than 0.5 AL, small ink droplets can be formed.

The pulse width t3 of the second expansion pulse W3 is not less than 1.2 AL and not more than 2.8 AL.
The likelihood of satellites forming depends on the length of the tail of the ink droplet before it separates from the meniscus, i.e., shortening the length of the tail of the ink droplet can suppress the formation of satellites.
If the pulse width t3 is less than 1.2 AL, the cancel waveform is applied before the ink droplet is separated from the meniscus, which tends to result in a long tail and makes it difficult to suppress the generation of satellites.
Furthermore, if the pulse width t3 of the second expansion pulse W3 is greater than 2.8 AL, a phenomenon known as droplet separation, in which minute droplets separate from a main droplet, becomes more likely to occur.
On the other hand, when the pulse width t3 is set to 1.2 AL or more, the cancel waveform is added after the ink droplet is separated from the meniscus, so that the tail is less likely to become long and the occurrence of satellites can be suppressed. Also, when the pulse width t3 is set to 2.8 AL or less, droplet separation is less likely to occur.

Furthermore, it is preferable that the pulse width t1 of the first expansion pulse W1 is 0.8 AL or more and 1.5 AL or less. The pulse width t1 of the first expansion pulse W1 has a large effect on the ejection force of the ink droplets, and if the pulse width t1 is in the above range, the ejection force of the ink droplets, i.e., the ejection speed, can be further increased.

The pressure wave in the pressure chamber 25 also repeatedly inverts every 1 AL. For this reason, it is particularly preferable to set the pulse width t1 of the first expansion pulse W1 to 1 AL. When the pulse width t1 of the first expansion pulse W1 is set to 1 AL, the pressure wave in the pressure chamber 25 that has inverted to a positive pressure overlaps with the positive pressure wave generated by the contraction of the pressure chamber 25 due to the falling edge of the first expansion pulse W1 and the falling edge of the contraction pulse W2. As a result, the most efficient ejection force is obtained, and the ejection speed of the ink droplets can be increased.

Moreover, it is preferable to control the volume of the ink droplet by appropriately changing the pulse width t2 of the contraction pulse W2 within a range from 0.1 AL to 0.5 AL.
This is because even when printing is performed using the same drive signal W based on the same image data, the size of the dots formed on the printing medium P becomes unstable depending on the temperature of the inkjet head 23 .

Specifically, when the temperature of the inkjet head 23 is low, the volume of the ink droplets ejected from the nozzles 21 and the dots recorded by the ink droplets become smaller. Conversely, when the temperature of the inkjet head 23 is high, the volume of the ink droplets ejected from the nozzles 21 and the dots recorded by the ink droplets become larger.
If the size of the printed dots is unstable in this way, the image density will not be stable, which may cause density unevenness.

Therefore, it is preferable that the control unit 40 appropriately changes the pulse width t2 of the contraction pulse W2 to control the volume of the ink droplets ejected from the nozzles 21. This makes it possible to keep the volume of the ink droplets within a predetermined control range even if the temperature of the inkjet head 23 changes, and thus makes it possible to suppress the occurrence of density unevenness.
The volume of the ink droplet may be controlled according to conditions other than the temperature of the inkjet head 23, such as the resolution and gradation of the image. Specifically, to reduce the volume of the ink droplet, the pulse width t2 of the contraction pulse W2 is narrowed. To increase the volume of the ink droplet, the pulse width t2 of the contraction pulse W2 is widened.

Moreover, it is preferable that the pulse width t1 of the first expansion pulse W1 is smaller than the sum of the pulse width t2 of the contraction pulse W2 and the pulse width t3 of the second expansion pulse W3.
This is because when the pulse width t1 of the first expansion pulse W1 is small, a small ink droplet is ejected from the nozzle 21.

Next, the results of evaluation of preferred configurations of the present invention will be described.
In the following, the present invention will be specifically described based on examples, but the present invention is not limited to the following specific examples.

In an inkjet recording device 1 equipped with an inkjet head 23, we measured whether satellites were generated from one nozzle when the pulse width t3 of the second expansion pulse W3 of the drive signal W was changed from 0.5 AL to 3.0 AL and the droplet ejection speed was changed from 4.0 m/s to 10.0 m/s.

In the drive signal W in this embodiment, the pulse width t1 of the first expansion pulse W1 is 1 AL, and the pulse width t2 of the contraction pulse W2 is 0.5 AL. The voltage value Von of the first expansion pulse W1 and the second expansion pulse W3 is 16 V, and the voltage value Voff of the contraction pulse W2 is -8 V. The temperature of the inkjet head 23 is 45°C.

The liquid ejected from the inkjet head 23 is UV ink. More specifically, the ink has a viscosity of 10.7 cP at 45° C., a density of 1.1 g/cm ³ , a surface tension of 22.96 mN/m, and an average particle size of 99.8 nm.

Table I shows the results of measuring whether satellites occurred. The evaluation was done visually, with G (Good) being the case where no satellites occurred, and NG (No Good) being the case where satellites occurred or the ejection of ink droplets became unstable.

In the conventional drive signal W, the pulse width t3 of the second expansion pulse W3 is 0.5 AL, and as shown in Table I, a meniscus occurs when the droplet ejection speed is increased to above 4.0 m/s. On the other hand, when the pulse width t3 of the second expansion pulse W3 is set to 1.2 AL or more and 2.8 AL or less, as in the present invention, it can be seen that a meniscus does not occur even if the droplet ejection speed is increased to above 4.0 m/s.

[Effect of the invention]
As described above, the control unit 40 of the droplet ejection device 1 generates the first expansion pulse W1, the contraction pulse W2, and the second expansion pulse W3 in that order. The pulse width t2 of the contraction pulse W2 is set to 0.1 AL or more and 0.5 AL or less, and the pulse width t3 of the second expansion pulse W3 is set to 1.2 AL or more and 2.8 AL or less.
According to this configuration, small droplets can be formed by the contraction pulse W2. Also, according to this configuration, the falling edge of the second expansion pulse W3 occurs after the tail is cut off, so that the generation of satellites can be suppressed.

The pulse width t1 of the first expansion pulse W1 is not less than 0.8 AL and not more than 1.5 AL.
According to this configuration, the droplet ejection speed can be increased.

The voltage of the contraction pulse W2 is the reverse potential of the voltage of the first expansion pulse W1.
According to this configuration, the droplet ejection speed can be increased by the falling edge of the first expansion pulse W1 and the falling edge of the contraction pulse W2.

Moreover, the sum of the pulse width t2 of the contraction pulse W2 and the pulse width t3 of the second expansion pulse W3 is greater than the pulse width t1 of the first expansion pulse W1.
According to this configuration, the pulse width t1 of the first expansion pulse W1 is narrow, so that small droplets can be formed.

Furthermore, the viscosity of the droplets discharged by the droplet discharge device 1 is 8 cp or more.
As shown in the above examples, when a liquid with a high viscosity of 8 cP or more is ejected as droplets, satellites are likely to occur if the droplet ejection speed is increased. However, in the present invention, the occurrence of satellites can be suppressed even if the droplet ejection speed is increased.

[Other configurations]
Although the present invention has been specifically described above based on the embodiment of the present invention, the present invention is not limited to the above embodiment. Of course, various modifications are possible within the scope of the invention described in the claims and its equivalents.

For example, in FIG. 3, the voltage value of the first expansion pulse W1 and the voltage value of the second expansion pulse W3 are both Von, i.e., the same value, as illustrated in the drive signal W, but this is not limited to this. The voltage value of the first expansion pulse W1 and the voltage value of the second expansion pulse W3 may both be different values.

However, it is preferable to set the contraction pulse W2 to a negative voltage and the second expansion pulse W3 to a positive voltage, so that the amount of displacement from the contraction pulse W2 to the second expansion pulse W3 is large. With this configuration, the tail is more easily cut off, and the occurrence of satellites can be further suppressed.

In addition, although the droplet ejection head 23 is described above as an inkjet head, the droplets ejected by the droplet ejection head 23 are not limited to ink droplets.

In addition, although the above discloses examples in which a hard disk or semiconductor non-volatile memory is used as a computer-readable medium for the program according to the present invention, the present invention is not limited to this example. Portable recording media such as CD-ROMs can be used as other computer-readable media. Furthermore, carrier waves can also be used as a medium for providing data for the program according to the present invention via a communication line.

The present invention can be used in a droplet ejection device that can reduce the occurrence of satellites even when ejecting small droplets, and a method and program for driving the droplet ejection device.

1. Inkjet recording device (droplet ejection device)
21 Nozzle 23 Inkjet head (droplet ejection head)
25 Pressure chamber 40 Control unit (driving signal generating unit, ejection control unit)
W Drive signal W1 First expansion pulse W2 Contraction pulse W3 Second expansion pulse t1 Pulse width of first expansion pulse t2 Pulse width of contraction pulse t3 Pulse width of second expansion pulse

Claims

a droplet ejection head including a head drive unit that deforms a pressure chamber that communicates with a nozzle;
A drive signal generating unit that generates a drive signal consisting of a plurality of drive pulses;
a discharge control unit that applies the drive signal to the head drive unit to change the volume of the pressure chamber and discharges droplets from the nozzle to perform a recording operation on a recording medium,
the drive signal generating section generates, as the drive pulse, a first expansion pulse for expanding the volume of the pressure chamber, a contraction pulse for contracting the volume of the pressure chamber, and a second expansion pulse for expanding the volume of the pressure chamber again, in that order;
A droplet ejection device, wherein, when AL is half the acoustic resonance period of the pressure chamber, the pulse width of the contraction pulse is not less than 0.1 AL and not more than 0.5 AL, and the pulse width of the second expansion pulse is not less than 1.2 AL and not more than 2.8 AL.
The droplet ejection device according to claim 1, wherein the pulse width of the first expansion pulse is 0.8 AL or more and 1.5 AL or less.
The droplet ejection device according to claim 1 or 2, wherein the potential of the contraction pulse is the opposite potential of the first expansion pulse.
The droplet ejection device according to claim 1 or 2, wherein the pulse width of the first expansion pulse is equal to or less than the sum of the pulse width of the contraction pulse and the pulse width of the second expansion pulse.
The droplet ejection device according to claim 1 or 2, wherein the droplets have a viscosity of 8 cp or more.
A method for driving a droplet ejection device including a droplet ejection head having a head drive unit that deforms a pressure chamber that communicates with a nozzle, comprising:
A drive signal generating step of generating a drive signal including a plurality of drive pulses;
an ejection control step of applying the drive signal to the head drive unit to change the volume of the pressure chamber and eject droplets from the nozzle to perform a recording operation on a recording medium,
the drive signal generating step sequentially generates, as the drive pulse, a first expansion pulse for expanding a volume of the pressure chamber, a contraction pulse for contracting the volume of the pressure chamber, and a second expansion pulse for expanding the volume of the pressure chamber again;
A method for driving a droplet ejection device, wherein the pulse width of the contraction pulse is 0.1 AL or more and 0.5 AL or less, and the pulse width of the second expansion pulse is 1.2 AL or more and 2.8 AL or less, where AL is half the acoustic resonance period of the pressure chamber.
A computer of a droplet ejection device including a droplet ejection head having a head drive unit that deforms a pressure chamber that communicates with a nozzle,
a drive signal generating unit that generates a drive signal consisting of a plurality of drive pulses;
a discharge control unit that applies the drive signal to the head drive unit to change the volume of the pressure chamber and discharges droplets from the nozzle to perform a recording operation on a recording medium;
causing the drive signal generating unit to generate, as the drive pulse, a first expansion pulse for expanding the volume of the pressure chamber, a contraction pulse for contracting the volume of the pressure chamber, and a second expansion pulse for expanding the volume of the pressure chamber again, in that order;
A program for setting the pulse width of the contraction pulse to 0.1 AL or more and 0.5 AL or less, and the pulse width of the second expansion pulse to 1.2 AL or more and 2.8 AL or less, where AL is 1/2 of the acoustic resonance period of the pressure chamber.