JP7501148B2 - Liquid ejection device, drive waveform generating device, and head driving method - Google Patents

Description

The present invention relates to a liquid ejection device, a drive waveform generation device, and a head drive method.

When ejecting liquid from a liquid ejection head, it is necessary to suppress satellite droplets caused by tailing that occurs when ejecting main droplets.

Conventionally, a drive waveform is known in which a satellite shortening waveform that increases the speed of satellite droplets and shortens their tail is placed after the contraction waveform element of the drive pulse that ejects the main droplet (Patent Document 1).

There is also known a configuration in which a main pulse is applied after an auxiliary pulse is applied, in which the time interval Td between the auxiliary pulse and the main pulse is an integer multiple of 1/2T, for example T to (3/2)T, relative to the period T of the residual pressure wave (Patent Document 2).

Patent No. 5712710 JP 2002-326357 A

However, further satellite suppression is required.

The present invention was made in consideration of the above problems, and aims to suppress satellites.

In order to solve the above problems, a liquid ejection device according to the present invention comprises:
a drive waveform generating unit that generates a drive waveform including a plurality of drive pulses to be applied to the liquid ejection head;
the drive waveform includes a non-ejection pulse that does not eject liquid and an ejection pulse that ejects liquid, the non-ejection pulse being arranged in time series successively;
When the crest value of the non-ejection pulse is Vp1, the time interval between the non-ejection pulse and the ejection pulse is Td, the natural vibration period of the pressure chamber of the liquid ejection head is Tc , the crest value of the ejection pulse is Vp2, and the crest value Vp2 of the ejection pulse is fixed and the crest value Vp1 of the non-ejection pulse is changed, the crest value Vp1 at which the droplet velocity becomes a minimum value with respect to the change in the crest value Vp1 of the non-ejection pulse is set to be Vpp1 ,
the time interval Td is within a range of Tc-0.2Tc to Tc+0.45Tc,
The non-ejection pulse has a peak value Vp1 within a range of −10% to +10% of the peak value Vpp1 at which the droplet speed of the liquid ejected by the ejection pulse reaches a minimum value.

The present invention makes it possible to suppress satellites.

1 is a schematic explanatory diagram of a printing apparatus as a liquid ejecting apparatus according to a first embodiment of the present invention. FIG. 2 is a plan view illustrating a discharge unit of the printing apparatus. FIG. 2 is an explanatory cross-sectional view of an example of a head taken in a direction perpendicular to the nozzle arrangement direction. FIG. 4 is a cross-sectional explanatory view taken along the nozzle arrangement direction. FIG. 2 is a block diagram illustrating a portion relating to a head drive control device of the printing apparatus. FIG. 4 is an explanatory diagram illustrating a driving waveform in the first embodiment of the present invention. FIG. 11 is an explanatory diagram showing an example of the relationship between the crest value of a non-ejection pulse, the droplet velocity, and the droplet volume. FIG. 11 is an explanatory diagram showing an example of the relationship between the peak value of a non-ejection pulse and the peak value of an ejection pulse. FIG. 11 is an explanatory diagram showing an example of changes in the peak value of a non-ejection pulse, the peak value of an ejection pulse, and the droplet velocity of a satellite droplet. FIG. 11 is an explanatory diagram showing an example of changes in the peak value of a non-ejection pulse, the peak value of an ejection pulse, and the droplet velocity of a satellite droplet. FIG. 11 is an explanatory diagram showing an example of changes in the peak value of a non-ejection pulse, the peak value of an ejection pulse, and the droplet velocity of a satellite droplet. FIG. 11 is an explanatory diagram showing an example of changes in the peak value of a non-ejection pulse, the peak value of an ejection pulse, and the droplet velocity of a satellite droplet. FIG. 11 is an explanatory diagram showing an example of changes in the peak value of a non-ejection pulse, the peak value of an ejection pulse, and the droplet velocity of a satellite droplet. FIG. 13 is an explanatory diagram showing an example of the relationship between the maximum and minimum crest values of a non-ejection pulse that results in a satellite-less state and the voltage ratio thereof. FIG. 11 is an explanatory diagram for explaining the time interval Td at which a satellite becomes zero and the peak value of a non-ejection pulse. FIG. 11 is an explanatory diagram for explaining the time interval Td at which a satellite becomes zero and the peak value of a non-ejection pulse. FIG. 11 is an explanatory diagram for explaining the time interval Td at which a satellite becomes zero and the peak value of a non-ejection pulse. FIG. 11 is an explanatory diagram for explaining the time interval Td at which a satellite becomes zero and the peak value of a non-ejection pulse. FIG. 13 is an explanatory diagram showing voltage characteristics when a simple pull waveform is used. 11 is an explanatory diagram showing voltage characteristics when the time interval between a non-ejection pulse and an ejection pulse is set as a natural vibration period. FIG. 13 is an explanatory diagram illustrating a time interval Td at which a satellite becomes zero and a peak value of a non-ejection pulse in a second embodiment of the present invention. FIG. FIG. 11 is an explanatory diagram for explaining the time interval Td at which a satellite becomes zero and the peak value of a non-ejection pulse. FIG. 11 is an explanatory diagram for explaining the time interval Td at which a satellite becomes zero and the peak value of a non-ejection pulse. 13 is an explanatory diagram illustrating a time interval Td at which a satellite becomes zero and a peak value of a non-ejection pulse in a third embodiment of the present invention. FIG. FIG. 11 is an explanatory diagram for explaining the time interval Td at which a satellite becomes zero and the peak value of a non-ejection pulse. FIG. 11 is an explanatory diagram for explaining the time interval Td at which a satellite becomes zero and the peak value of a non-ejection pulse.

Embodiments of the present invention will be described below with reference to the accompanying drawings. A printing device as a device for ejecting liquid according to a first embodiment of the present invention will be described with reference to Figs. 1 and 2. Fig. 1 is a schematic diagram of the printing device, and Fig. 2 is a plan view of an ejection unit of the printing device.

The printing device 1 is a device that ejects liquid, and includes an input section 10 that inputs sheet material P, a pretreatment section 20, a printing section 30, a drying section 40, and an output section 50. In the printing device 1, the pretreatment section 20, which is a pretreatment means, applies (coats) pretreatment liquid to the sheet material P input (supplied) from the input section 10 as necessary, the printing section 30 applies liquid to perform the required printing, the drying section 40 dries the liquid adhering to the sheet material P, and then the sheet material P is discharged to the output section 50.

The loading section 10 includes an input tray 11 (lower input tray 11A, upper input tray 11B) that stores multiple sheet materials P, and a feeding device 12 (12A, 12B) that separates and sends out the sheet materials P one by one from the input tray 11, and supplies the sheet materials P to the pre-processing section 20.

The pre-treatment unit 20 includes an application unit 21, which is a treatment liquid application means that applies a treatment liquid to the printing surface of the sheet material P, for example, to cause the ink to aggregate and prevent show-through.

The printing unit 30 includes a drum 31, which is a support member (rotating member) that supports the sheet material P on its circumferential surface and rotates, and a liquid ejection unit 32 that ejects liquid toward the sheet material P supported by the drum 31.

The printing section 30 also includes a transfer cylinder 34 that receives the sheet material P sent from the pre-processing section 20 and transfers the sheet material P between the drum 31, and a transfer cylinder 35 that receives the sheet material P transported by the drum 31 and transfers it to the drying section 40.

The sheet material P transported from the pre-processing section 20 to the printing section 30 has its leading edge gripped by a gripping means (sheet gripper) provided on the transfer cylinder 34, and is transported as the transfer cylinder 34 rotates. The sheet material P transported by the transfer cylinder 34 is transferred to the drum 31 at a position opposite the drum 31.

A gripping means (sheet gripper) is also provided on the surface of the drum 31, and the leading edge of the sheet material P is gripped by the gripping means (sheet gripper). A number of suction holes are formed in a distributed manner on the surface of the drum 31, and the suction means generates a suction airflow that flows inward from the required suction holes of the drum 31.

Then, the sheet material P transferred from the transfer cylinder 34 to the drum 31 has its leading edge gripped by the sheet gripper, is adsorbed and supported on the drum 31 by the suction airflow from the suction means, and is transported as the drum 31 rotates.

The liquid ejection section 32 is equipped with ejection units 33 (33A to 33D) which are liquid ejection means. For example, ejection unit 33A ejects cyan (C) liquid, ejection unit 33B ejects magenta (M) liquid, ejection unit 33C ejects yellow (Y) liquid, and ejection unit 33D ejects black (K) liquid. In addition, ejection units that eject special liquids such as white and gold (silver) can also be used.

The ejection unit 33 is, for example, a full-line type head in which multiple liquid ejection heads (hereinafter simply referred to as "heads") 100, each having multiple nozzle rows in which multiple nozzles 104 are arranged, are arranged in a staggered pattern on a base member 331, as shown in FIG. 2.

The ejection operation of each ejection unit 33 of the liquid ejection section 32 is controlled by a drive signal corresponding to the printing information. When the sheet material P supported on the drum 31 passes through the area facing the liquid ejection section 32, liquid of each color is ejected from the ejection unit 33, and an image corresponding to the printing information is printed.

The drying section 40 dries the liquid that has been applied to the sheet material P by the printing section 30. This causes the water content in the liquid and other liquid components to evaporate, the colorant contained in the liquid to be fixed on the sheet material P, and curling of the sheet material P is suppressed.

The reversing mechanism 60 is a mechanism that reverses the sheet material P using a switchback method when performing double-sided printing on the sheet material P that has passed through the drying section 40, and the reversed sheet material P is sent back upstream of the transfer cylinder 34 through the conveying path 61 of the printing section 30.

The discharge section 50 is equipped with a discharge tray 51 on which multiple sheet materials P are stacked. The sheet materials P transported from the drying section 40 via the reversing mechanism section 60 are stacked and held in order on the discharge tray 51.

Next, an example of the head 100 will be described with reference to Figures 3 and 4. Figure 3 is a cross-sectional explanatory diagram in a direction perpendicular to the nozzle arrangement direction of the head, and Figure 4 is a cross-sectional explanatory diagram along the nozzle arrangement direction of the head.

The liquid ejection head 100 of this embodiment is formed by laminating and bonding a nozzle plate 101, a flow path plate 102 which is an individual flow path member, and a vibration plate member 103 which serves as a wall member. It also includes a piezoelectric actuator 111 which displaces the vibration region (vibration plate) 130 of the vibration plate member 103, and a common flow path member 120 which also serves as a frame member for the head.

The nozzle plate 101 has multiple nozzle rows in which multiple nozzles 104 that eject liquid are arranged.

The flow path plate 102 forms a number of pressure chambers 106 that communicate with a number of nozzles 104, individual supply flow paths 107 that also serve as fluid resistance sections that communicate with each pressure chamber 106, and an intermediate supply flow path 108 that serves as a liquid introduction section that communicates with two or more individual supply flow paths 107.

The vibration plate member 103 has a plurality of displaceable vibration plates (vibration regions) 130 that form the walls of the pressure chamber 106 of the flow path plate 102. Here, the vibration plate member 103 has a two-layer structure (not limited to this) and is composed of a first layer 103A that forms a thin portion from the flow path plate 102 side, and a second layer 103B that forms a thick portion.

The thin first layer 103A forms a deformable vibration region 130 in the area corresponding to the pressure chamber 106. Within the vibration region 130, the thick convex portion 130a is formed in the second layer 103B, which is bonded to the piezoelectric actuator 111.

A piezoelectric actuator 111 including an electromechanical conversion element is disposed on the opposite side of the vibration plate member 103 from the pressure chamber 106, as a driving means (actuator means, pressure generating element) for deforming the vibration region 130 of the vibration plate member 103.

This piezoelectric actuator 111 is formed by forming grooves in a piezoelectric member bonded to a base member 113 by half-cut dicing, and forming a required number of columnar piezoelectric elements 112 in a comb shape at specified intervals in the nozzle arrangement direction. Every other piezoelectric element 112 is bonded to a protrusion 130a, which is a thick portion formed in the vibration region 130 of the vibration plate member 103.

This piezoelectric element 112 is made by alternately stacking piezoelectric layers and internal electrodes, with the internal electrodes each extending to the end faces and connected to an external electrode (end face electrode), and a flexible wiring member 115 is connected to the external electrode.

The common flow path member 120 forms a common supply flow path 110. The common supply flow path 110 communicates with the intermediate supply flow path 108, which serves as a liquid introduction section, via an opening 109 that also serves as a filter section provided in the vibration plate member 103, and communicates with the individual supply flow paths 107 via the intermediate supply flow path 108.

In this liquid ejection head 100, for example, by lowering the voltage applied to the piezoelectric element 112 from the reference potential (intermediate potential), the piezoelectric element 112 contracts, and the vibration area 130 of the vibration plate member 103 is pulled, expanding the volume of the pressure chamber 106, and liquid flows into the pressure chamber 106.

Then, the voltage applied to the piezoelectric element 112 is increased to expand the piezoelectric element 112 in the stacking direction, and the vibration area 130 of the vibration plate member 103 is deformed in a direction toward the nozzle 104, contracting the volume of the pressure chamber 106, thereby pressurizing the liquid in the pressure chamber 106 and ejecting the liquid from the nozzle 104.

Next, the section related to the head drive control device that drives the head will be explained with reference to the block diagram in Figure 5.

The head drive control device 400, which applies a drive waveform to the head 100, includes a head control unit 401, a drive waveform generating unit 402 and a waveform data storage unit 403 that constitute a drive waveform generating means, a head driver 410, and an ejection timing generating unit 404 for generating ejection timing.

When the head control unit 401 receives the ejection timing pulse stb, it outputs an ejection synchronization signal LINE, which triggers the generation of a drive waveform, to the drive waveform generation unit 402. The head control unit 401 also outputs an ejection timing signal CHANGE, which corresponds to the amount of delay from the ejection synchronization signal LINE, to the drive waveform generation unit 402.

The drive waveform generation unit 402 generates a common drive waveform Vcom at a timing based on the ejection synchronization signal LINE and the ejection timing signal CHANGE.

The head control unit 401 receives image data and generates a mask control signal MN based on this image data to select a specific waveform of the common drive waveform signal Vcom depending on the size of the liquid to be ejected from each nozzle 104 of the head 100. The mask control signal MN is a signal whose timing is synchronized with the ejection timing signal CHANGE.

Then, the head control unit 401 transfers the image data SD, the synchronization clock signal SCK, the latch signal LT that commands the latching of the image data, and the generated mask control signal MN to the head driver 410.

The head driver 410 includes a shift register 411, a latch circuit 412, a gradation decoder 413, a level shifter 414, and an analog switch array 415.

The shift register 411 inputs the image data SD and the synchronous clock signal SCK transferred from the head control unit 401. The latch circuit 412 latches each register value of the shift register 411 by the latch signal LT transferred from the head control unit 401.

The gradation decoder 413 decodes the value (image data SD) latched by the latch circuit 412 and the mask control signal MN and outputs the result. The level shifter 414 converts the logic level voltage signal of the gradation decoder 413 to a level at which the analog switch AS of the analog switch array 415 can operate.

The analog switch AS of the analog switch array 415 is a switch that is turned on/off by the output of the gradation decoder 413 provided via the level shifter 414. This analog switch AS is provided for each nozzle 104 of the head 100, and is connected to the individual electrodes of the piezoelectric elements 112 corresponding to each nozzle 104. In addition, a common drive waveform signal Vcom from the drive waveform generating unit 402 is input to the analog switch AS. Also, as described above, the timing of the mask control signal MN is synchronized with the timing of the common drive waveform Vcom.

Therefore, the analog switch AS is switched on/off at an appropriate timing according to the output of the gradation decoder 413 provided via the level shifter 414, and the drive pulse to be applied to the piezoelectric element 112 corresponding to each nozzle 104 is selected from the drive pulses constituting the common drive waveform signal Vcom. As a result, the size of the droplet ejected from the nozzle 104 is controlled.

The ejection timing generation unit 404 generates and outputs an ejection timing pulse stb each time the sheet material P is moved a predetermined amount based on the detection result of the rotary encoder 405, which detects the amount of rotation of the drum 31. The rotary encoder 405 is composed of an encoder wheel that rotates together with the drum 31, and an encoder sensor that reads the slits of the encoder wheel.

Next, the drive waveform in the first embodiment of the present invention will be described with reference to FIG. 6. FIG. 6 is an explanatory diagram for the same description.

The driving waveform Va in this embodiment is composed of a non-ejection pulse P1 that pressurizes the liquid in the pressure chamber 106 to an extent that it is not ejected, and an ejection pulse P2 that pressurizes the liquid in the pressure chamber 106 to an extent that it is ejected. The non-ejection pulse P1 and the ejection pulse P2 are generated continuously in time series.

The non-ejection pulse P1 is composed of an expansion waveform element a1 that expands the pressure chamber 106, a retention waveform element b1 that maintains the state expanded by the expansion waveform element a1, and a contraction waveform element c1 that contracts the pressure chamber 106 from the state maintained by the retention waveform element b1.

The expansion waveform element a1 of the non-ejection pulse P1 is a waveform that falls from an intermediate potential (or reference potential) Vm to a potential V1, the hold waveform element b1 is a waveform that holds the potential V1, and the contraction waveform element c1 is a waveform that rises from the potential V1 to the intermediate potential Vm. The peak value of this non-ejection pulse P1 is Vp1.

The ejection pulse P2 is composed of an expansion waveform element a2 that expands the pressure chamber 106, a retention waveform element b2 that maintains the expanded state caused by the expansion waveform element a2, and a contraction waveform element c2 that contracts the pressure chamber 106 from the state maintained by the retention waveform element b2.

The expansion waveform element a2 of the ejection pulse P2 is a waveform that falls from an intermediate potential (or reference potential) Vm to a potential V2, the hold waveform element b2 is a waveform that holds the potential V2, and the contraction waveform element c2 is a waveform that rises from the potential V2 to the intermediate potential Vm. The peak value of this ejection pulse P2 is Vp2 (Vp2>Vp1).

The waveform from the end of the contraction waveform element c1 of the non-ejection pulse P1 to the start of the expansion waveform element a2 of the ejection pulse P2 is defined as the inter-pulse hold waveform element d, and the time of the inter-pulse hold waveform element d (the time interval between the non-ejection pulse P1 and the ejection pulse P2) is defined as Td.

Here, the time interval Td between the non-ejection pulse P1 and the ejection pulse P2 is set within the range of -(1/3)Tc to +(1/3)Tc, where Tc is the natural vibration period (resonance period) of the pressure chamber 106 of the liquid ejection head 100.

The peak value Vp1 of the non-ejection pulse P1 is set within the range of -10% to +10% of the minimum value of the droplet velocity Vj when liquid is ejected by the ejection pulse P2.

This makes it possible to suppress satellites in the droplets ejected by the ejection pulse P2.

The effects of this embodiment are described in detail below with reference to Figure 7 onwards.

First, FIG. 7 shows an example of the change in droplet velocity Vj and droplet volume Mj when the crest value Vp2 of the ejection pulse P2 is fixed and the crest value Vp1 of the non-ejection pulse P1 is changed. Note that the time interval Td between the non-ejection pulse P1 and the ejection pulse P2 is the natural vibration period Tc.

From the results in Figure 7, the peak value Vp1 can be broadly divided into three ranges S1, S2, and S3.

In other words, when the crest value Vp1 of the non-ejection pulse P1 is within the range S1, the droplet velocity Vj increases as the crest value Vp1 increases. This indicates that the meniscus vibration increases as the crest value Vp1 of the non-ejection pulse P1 increases, and as a result, the droplet velocity Vj of the droplet caused by the ejection pulse P2 increases.

When the peak value Vp1 of the non-ejection pulse P1 is within range S2, the boundary between ranges S1 and S2 is the maximum value, and the droplet velocity Vj drops. This indicates that the meniscus vibration has become too large and exceeds the simple vibration of the meniscus, in other words, that the meniscus is on the verge of overflowing. Because the meniscus is on the verge of overflowing, the energy from the ejection pulse P2 is not transmitted efficiently, and the droplet velocity Vj drops.

When the crest value Vp1 of the non-ejection pulse P1 is within range S3, the boundary between ranges S2 and S3 is a minimum value (the crest value Vp1 at this time is the peak crest value Vpp1), and the droplet velocity Vj increases.

It can also be seen that while the droplet volume Mj increases at a constant rate in ranges S1 and S2, the rate of increase becomes steeper in range S3. This indicates that the voltage of the peak value Vp1 of the non-ejection pulse P1 has become so high that the non-ejection pulse P1 itself is beginning to eject droplets (in this case, the non-ejection pulse P1 essentially becomes an ejection pulse).

In other words, because the droplets are ejected by the non-ejection pulse P1, the ejection pulse P2 ejects droplets due to normal resonance, and the droplet velocity Vj increases as the pulse height Vp1 increases. At the same time, because both the droplets ejected by the non-ejection pulse P1 and the droplets ejected by the ejection pulse P2 are being ejected, the gradient of the droplet volume Mj is larger than in ranges S1 and S2.

Next, FIG. 8 shows an example of the relationship between the peak value Vp1 of the non-ejection pulse P1 and the peak value Vp2 of the ejection pulse P2 when the droplet velocity Vj is constant. Note that here too, the time interval Td between the non-ejection pulse P1 and the ejection pulse P2 is the natural vibration period Tc.

Here too, as in the case of Figure 7, the non-ejection pulse P1 can be divided into three ranges S1, S2, and S3 depending on the value of the peak value Vp1.

First, in range S1, there is a tendency for the peak value Vp2 of the ejection pulse P2 to decrease as the peak value Vp1 of the non-ejection pulse P1 increases. This shows that the meniscus vibration increases as the peak value Vp1 of the non-ejection pulse P1 increases, so the droplet velocity Vj can be kept constant even if the peak value Vp2 of the ejection pulse P2 is reduced.

In range S2, the boundary between ranges S1 and S2 is a minimum value, and the droplet velocity Vj increases. This indicates that the meniscus vibration has become too large and exceeds the simple vibration of the meniscus, in other words, that the meniscus is on the verge of overflowing. Because the meniscus is on the verge of overflowing, the energy from the ejection pulse P2 is not transmitted efficiently, and unless more energy is added, the droplet velocity Vj cannot be kept constant.

In range S3, the boundary between ranges S2 and S3 is the maximum value, and the droplet velocity Vj decreases. As with the results in Figure 7 above, droplets are ejected by the non-ejection pulse P1, so the ejection pulse P2 is ejected by normal resonance, and the residual vibration increases as the pulse height Vp1 increases, indicating that the droplet velocity Vj can be kept constant even if the pulse height Vp2 is reduced.

Next, Figure 9 shows an example of the change in satellite droplets when the peak value Vp2 of the ejection pulse P2 is adjusted so that the droplet velocity Mj is constant.

The satellite droplet velocity Vjs becomes slightly faster as the peak value Vp1 of the non-ejection pulse P1 increases. However, there is a region S0 in which the satellite droplet velocity Vjs becomes 0 (satelliteless) around the peak value Vp1 of the non-ejection pulse P1, which corresponds to the vicinity where the peak value Vp2 of the ejection pulse P2 is at its maximum value (near the boundary between the ranges S2 and S3 described above).

The above satellite-less region is obtained when the time interval Td between the non-ejection pulse and the ejection pulse is set to the same as the natural vibration period Tc (Td = Tc). Therefore, the time interval Td between the non-ejection pulse and the ejection pulse is made different from the natural vibration period Tc, and the peak value Vp2 of the ejection pulse P2 is adjusted so that the droplet velocity Mj is constant, as described above, and the change in satellite droplets in response to the change in the non-ejection pulse P1 is evaluated.

First, FIG. 10 shows a case where the time interval Td between the non-ejection pulse and the ejection pulse is (2/5)Tc shorter than the natural vibration period Tc (Td=Tc-(2/5)Tc).

Under these conditions, there is no condition for the peak value Vp1 of the non-ejection pulse P1 to be satellite-less.

Next, FIG. 11 shows a case where the time interval Td between the non-ejection pulse and the ejection pulse is shortened by (1/4)Tc relative to the natural vibration period Tc (Td=Tc-(1/4)Tc).

Under these conditions, the range of the peak value Vp1 of the non-ejection pulse P1 is narrower than when Td = Tc, but a satellite-less region S0 was confirmed.

Next, FIG. 12 shows a case where the time interval Td between the non-ejection pulse and the ejection pulse is made longer by (1/3)Tc than the natural vibration period Tc (Td = Tc + (1/3)Tc).

Under these conditions, the range of the peak value Vp1 of the non-ejection pulse P1 is narrower than when Td = Tc, but a satellite-less region S0 was confirmed.

Next, FIG. 13 shows a case where the time interval Td between the non-ejection pulse and the ejection pulse is made longer by (1/2)Tc than the natural vibration period Tc (Td = Tc + 1/2Tc).

Under these conditions, the condition of the peak value Vp1 of the non-ejection pulse P1 that results in satellite-less printing was not observed. Furthermore, even if the time interval Td was made longer than (Tc + (1/2) Tc), the condition of satellite-less printing could not be confirmed.

Next, based on the above results, the relationship between the time interval Td between the non-ejection pulse and the ejection pulse, which allows satellites to be eliminated, and the natural vibration period Tc, as well as the peak value Vp1 of the non-ejection pulse P1, will be explained with reference to Figures 14 to 18.

Figure 14 shows the relationship between the maximum and minimum values of the peak value Vp1 of the non-ejection pulse P1 that generates the satellite-less region S0 and its voltage ratio.

The horizontal axis in Figure 14 represents the Tc ratio difference (Tc ratio conversion) from the natural vibration period Tc (resonance timing) of the time interval Td between the non-ejection pulse P1 and the ejection pulse P2. For example, a Tc ratio difference of "0.1" represents the evaluation result at a time interval Td (Td = Tc + 0.1Tc) that is longer than the time interval Td equal to the natural vibration period Tc by (0.1 x Tc).

Figure 15 shows a summary of the maximum and minimum values of the crest value Vp1 of the non-ejection pulse P1 that results in satelliteless, and the crest value Vp1 when the crest value Vp2 of the ejection pulse P2 reaches its peak (when the droplet speed of the liquid ejected by the ejection pulse reaches its minimum value) (this is called the "peak crest value Vpp1").

The horizontal axis in Figure 15, like Figure 14, represents the Tc ratio difference (Tc ratio conversion) from the natural vibration period Tc (resonance timing) of the time interval Td between the non-ejection pulse P1 and the ejection pulse P2. For example, a Tc ratio difference of "0.1" represents the evaluation result at a time interval Td (Td = Tc + 0.1Tc) that is longer than the time interval Td equal to the natural vibration period Tc by (0.1 x Tc).

Figures 16 to 18 show the voltage range of the maximum value (max Vp1) and minimum value (min Vp1) of the crest value Vp1 of the non-ejection pulse P1, expressed as the ratio of the voltage difference from the peak crest value Vpp1.

The horizontal axis in Figures 16 to 18, like Figure 15, represents the Tc ratio difference (Tc ratio conversion) from the natural vibration period Tc (resonance timing) of the time interval Td between the non-ejection pulse P1 and the ejection pulse P2. For example, a Tc ratio difference of "0.1" represents the evaluation result at a time interval Td (Td = Tc + 0.1Tc) that is longer than the time interval Td equal to the natural vibration period Tc by (0.1 x Tc).

From this, it can be seen that when the time interval Td between the non-ejection pulse P1 and the ejection pulse P2 shifts with respect to the natural vibration period Tc, the voltage range of the peak value Vp1 of the non-ejection pulse P1 that can be made satellite-less becomes narrower.

The time interval Td between the non-ejection pulse P1 and the ejection pulse P2 that can achieve satelliteless operation is ±1/3Tc (within the range of Tc-(1/3)Tc to Tc+(1/3)Tc) with the natural vibration period Tc at the center.

It can also be seen that the non-ejection pulse P1 is within the range of -10% to +10% of the peak crest value Vpp1, which is the crest value Vp1 when the droplet velocity Vj of the liquid ejected by the ejection pulse P2 reaches a minimum value, in other words, when the crest value Vp2 of the ejection pulse P2 reaches its peak.

Here, in order to ensure a voltage margin of Δ10% (±5%: -5% to +5%) or more, it is preferable that the time interval Td between the non-ejection pulse P1 and the ejection pulse P2 is within the range of (Tc-(1/4)Tc to Tc+(1/4)Tc).

In addition, to ensure a voltage margin of Δ15% (±7.5%: -7.5% to +7.5%) or more, it is preferable that the time interval Td between the non-ejection pulse P1 and the ejection pulse P2 is within the range of (Tc-(1/6)Tc to Tc+(1/6)Tc).

In addition, by setting the time interval Td between the non-ejection pulse P1 and the ejection pulse P2 to the natural vibration period Tc (Td = Tc), a voltage margin of Δ20% (±10.0%: -10.0% to +10.0%) or more can be ensured.

Next, the crest value Vp1 of the non-ejection pulse P1 that becomes satellite-less for each time interval Td between the non-ejection pulse P1 and the ejection pulse P2 was set to a fixed value, and the voltage characteristics due to the crest value Vp2 of the ejection pulse P2 were obtained.

The value of the peak value Vp1 of the non-ejection pulse P1 is approximately the median value between the maximum values of the peak value Vp1 and the peak value Vp2. More specifically, it is set to the value of the peak value Vp1 of the non-ejection pulse P1 when the peak value Vp2 is at its maximum value when the peak value Vp2 of the ejection pulse P2 is adjusted so that the droplet velocity Vj of the ejection pulse P2 is constant.

First, Figure 19 shows the voltage characteristics when a simple pull waveform (corresponding to Vp1 = 0V) is used.

Here, UV ink is used as the liquid to be ejected. In this example, the droplet speed Vj is about 7 m/s, and the satellite droplet speed Vjs is about 5.7 m/s.

Next, Figure 20 shows the voltage characteristics when the time interval Td between the non-ejection pulse P1 and the ejection pulse P2 is set to the natural vibration period Tc.

Here, satellites do not occur until the droplet velocity Vj exceeds 8 m/s.

While the conventional satellite shortening waveform has a satellite shortening effect of about 0.5 to 1.0 m/s, this embodiment has a satellite shortening effect of about 2.5 to 3 m/s, which is a dramatic improvement in the shortening effect.

The droplet velocity Vj is often set to around 7 to 9 m/s due to the accuracy of the landing position and the stability of the ejection, and by being able to prevent satellites from occurring up to around 8 m/s, it is possible to achieve a satellite-free state within a practical range of droplet velocities.

The non-ejection pulse P1 may have a retention time of the timing (retention waveform element b1) of the expansion waveform element a1 and contraction waveform element c1 equal to the natural vibration period Tc, or may have a time shorter than the natural vibration period Tc. If it is set to a time shorter than the natural vibration period Tc, the waveform length can be shortened.

In addition, by positioning the waveform that combines the non-ejection pulse P1 and the ejection pulse P2 at the end of a waveform configuration that forms large droplets with multiple ejection pulses, it is possible to achieve satellite-less or satellite-shortened droplets even with large droplets.

Next, a second embodiment of the present invention will be described with reference to Figs. 21 to 23. Figs. 21 to 23 are explanatory diagrams illustrating the relationship between the time interval Td between the non-ejection pulse and the ejection pulse, which can achieve satelliteless operation, and the natural vibration period Tc, and the crest value Vp1 of the non-ejection pulse P1 in this embodiment.

Figures 21 to 23 show the voltage range of the maximum value (max Vp1) and minimum value (min Vp1) of the crest value Vp1 of the non-ejection pulse P1, expressed as the ratio of the voltage difference from the peak crest value Vpp1.

The horizontal axis in Figures 21 to 23, as in the above embodiment, represents the Tc ratio difference (Tc ratio conversion) from the natural vibration period Tc (resonance timing) of the time interval Td between the non-ejection pulse P1 and the ejection pulse P2. For example, a Tc ratio difference of "0.1" represents the evaluation result at a time interval Td (Td = Tc + 0.1Tc) that is longer than the time interval Td equal to the natural vibration period Tc by (0.1 x Tc).

In this embodiment, the time interval Td between the non-ejection pulse P1 and the ejection pulse P2 that can achieve satellite-less printing is within the range of Tc-(1/5)Tc to Tc+(1/3)Tc.

It can also be seen that the non-ejection pulse P1 is within the range of -5% to +10% of the peak crest value Vpp1, which is the crest value Vp1 when the droplet velocity Vj of the liquid ejected by the ejection pulse P2 reaches a minimum value, that is, when the crest value Vp2 of the ejection pulse P2 reaches its peak.

Here, in order to ensure a voltage margin of ±5% (-5% to +5%) or more, it is preferable to set the time interval Td between the non-ejection pulse P1 and the ejection pulse P2 within the range of Tc-(1/10)Tc to Tc+(1/6)Tc, as shown in FIG. 22.

In addition, to ensure a voltage margin of ±7.5% (-7.5% to +7.5%) or more, it is preferable to set the time interval Td between the non-ejection pulse P1 and the ejection pulse P2 within the range of Tc-(1/14)Tc to Tc+(1/10)Tc, as shown in FIG. 23.

Next, a third embodiment of the present invention will be described with reference to Figs. 24 to 26. Figs. 24 to 26 are explanatory diagrams illustrating the relationship between the time interval Td between the non-ejection pulse and the ejection pulse, which can achieve satelliteless operation, and the natural vibration period Tc, and the crest value Vp1 of the non-ejection pulse P1 in this embodiment.

Figures 24 to 26 show the voltage range of the maximum value (Max Vp1) and minimum value (Min Vp1) of the crest value Vp1 of the non-ejection pulse P1, expressed as the ratio of the voltage difference from the peak crest value Vpp1.

The horizontal axis in Figures 24 to 26 represents the Tc ratio difference (Tc ratio conversion) from the natural vibration period Tc (resonance timing) of the time interval Td between the non-ejection pulse P1 and the ejection pulse P2. For example, a Tc ratio difference of "0.1" represents the evaluation result at a time interval Td (Td = Tc + 0.1Tc) that is longer than the time interval Td equal to the natural vibration period Tc by (0.1 x Tc).

In this embodiment, the time interval Td between the non-ejection pulse P1 and the ejection pulse P2 that can achieve satellite-less printing is within the range of Tc-0.2Tc to Tc+0.45Tc.

It can also be seen that the non-ejection pulse P1 is within the range of -5% to +10% of the peak crest value Vpp1, which is the crest value Vp1 when the droplet velocity Vj of the liquid ejected by the ejection pulse P2 reaches a minimum value, that is, when the crest value Vp2 of the ejection pulse P2 reaches its peak.

Here, in order to ensure a voltage margin of ±5% (-5% to +5%) or more, it is preferable to set the time interval Td between the non-ejection pulse P1 and the ejection pulse P2 in the range of Tc-0.1Tc to Tc+0.25Tc, in other words, Tc-(1/10)Tc to Tc+(1/4)Tc, as shown in FIG. 25.

In addition, to ensure a voltage margin of ±7.5% (-7.5% to +7.5%) or more, it is preferable to set the time interval Td between the non-ejection pulse P1 and the ejection pulse P2 in the range of Tc-0.07Tc to Tc+0.2Tc from FIG. 26, in other words, in the range of Tc-(1/14)Tc to Tc+(1/5)Tc.

In the present application, the liquid to be ejected may have a viscosity and surface tension that allows it to be ejected from the head, and is not particularly limited, but it is preferable that the viscosity is 30 mPa·s or less at room temperature and pressure, or by heating or cooling. More specifically, the liquid may be a solution, suspension, emulsion, etc. that contains a solvent such as water or an organic solvent, a colorant such as a dye or pigment, a functionalizing material such as a polymerizable compound, a resin, or a surfactant, a biocompatible material such as DNA, amino acids, proteins, or calcium, an edible material such as a natural dye, etc., and these can be used for applications such as inkjet ink, surface treatment liquid, a liquid for forming a component of an electronic element or a light-emitting element, an electronic circuit resist pattern, a material liquid for three-dimensional modeling, etc.

The energy sources that generate the liquid include piezoelectric actuators (laminated piezoelectric elements and thin-film piezoelectric elements), thermal actuators that use electrothermal conversion elements such as heating resistors, and electrostatic actuators that consist of a vibration plate and an opposing electrode.

In addition, "devices that eject liquid" include not only devices that can eject liquid onto objects to which the liquid can adhere, but also devices that eject liquid into air or liquid.

This "liquid ejecting device" can also include means for feeding, transporting, and discharging items onto which liquid can be attached, as well as pre-processing devices and post-processing devices.

For example, examples of "devices that eject liquid" include image forming devices that eject ink to form an image on paper, and three-dimensional modeling devices that eject modeling liquid onto a powder layer formed from powder in order to create a three-dimensional object.

In addition, a "liquid ejecting device" is not limited to devices that use ejected liquid to visualize meaningful images such as letters and figures. For example, it also includes devices that form patterns that have no meaning in themselves, and devices that create three-dimensional images.

The above phrase "something to which liquid can adhere" refers to something to which liquid can adhere at least temporarily, and to which the liquid adheres and sticks, or adheres and penetrates. Specific examples include media such as paper, recording paper, film, and cloth, electronic circuit boards, electronic components such as piezoelectric elements, powder layers, organ models, and testing cells, and unless otherwise specified, includes all things to which liquid can adhere.

The above-mentioned "materials to which liquid can adhere" include paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics, and other materials to which liquid can adhere even temporarily.

In addition, the "liquid ejection device" may be a device in which a liquid ejection head and an object to which liquid can be attached move relatively, but is not limited to this. Specific examples include a serial type device in which the liquid ejection head moves, and a line type device in which the liquid ejection head does not move.

Other examples of "liquid ejecting devices" include treatment liquid application devices that eject treatment liquid onto paper to apply the treatment liquid to the surface of the paper for purposes such as modifying the surface of the paper, and spray granulation devices that spray a composition liquid in which raw materials are dispersed through a nozzle to granulate the raw material into fine particles.

In this application, the terms image formation, recording, printing, copying, printing, modeling, etc. are all synonymous.

REFERENCE SIGNS LIST 1 Printing device 10 Carry-in section 20 Pre-treatment section 30 Printing section 40 Drying section 50 Carry-out section 21 Coating section 33 Discharge unit 100 Liquid discharge head (head)
106 Pressure chamber 112 Piezoelectric element 400 Head drive control section 401 Head control section 402 Drive waveform generating section 403 Waveform data storage section 410 Head driver

Claims (8)

a drive waveform generating unit that generates a drive waveform including a plurality of drive pulses to be applied to the liquid ejection head;
the drive waveform includes a non-ejection pulse that does not eject liquid and an ejection pulse that ejects liquid, the non-ejection pulse being arranged in time series successively;
When the crest value of the non-ejection pulse is Vp1, the time interval between the non-ejection pulse and the ejection pulse is Td, the natural vibration period of the pressure chamber of the liquid ejection head is Tc , the crest value of the ejection pulse is Vp2, and the crest value Vp2 of the ejection pulse is fixed and the crest value Vp1 of the non-ejection pulse is changed, the crest value Vp1 at which the droplet velocity becomes a minimum value with respect to the change in the crest value Vp1 of the non-ejection pulse is set to be Vpp1 ,
the time interval Td is within a range of Tc-0.2Tc to Tc+0.45Tc,
A liquid ejection device, characterized in that a peak value Vp1 of the non-ejection pulse is within a range of -10% to +10% of the peak value Vpp1 when the droplet speed of the liquid ejected by the ejection pulse becomes a minimum value. 2. The liquid ejecting device according to claim 1, wherein the time interval Td is within a range of Tc-0.1Tc to Tc+0.25Tc. 2. The liquid ejection device according to claim 1, wherein the time interval Td is within a range of Tc-0.07Tc to Tc+0.2Tc. A liquid ejection device as described in any one of claims 1 to 3, characterized in that the peak value Vp1 of the non-ejection pulse is within the range of -7.5% to +7.5% of the peak value Vpp1 when the droplet speed of the liquid ejected by the ejection pulse becomes a minimum value. A liquid ejection device as described in any one of claims 1 to 3, characterized in that the peak value Vp1 of the non-ejection pulse is within the range of -5.0% to +5.0% of the peak value Vpp1 when the droplet speed of the liquid ejected by the ejection pulse becomes a minimum value. the non-ejection pulse includes an expansion waveform element that expands the pressure chamber, a holding waveform element that holds the expanded state of the pressure chamber, and a contraction waveform element that contracts the pressure chamber from a state that is held in the expanded state,
6. The liquid ejecting device according to claim 1, wherein the hold time of the hold waveform element is shorter than a natural vibration period Tc. A drive waveform generating device that generates a drive waveform including a plurality of drive pulses to be applied to a liquid ejection head,
the drive waveform includes a non-ejection pulse that does not eject liquid and an ejection pulse that ejects liquid, the non-ejection pulse being arranged in time series successively;
When the crest value of the non-ejection pulse is Vp1, the time interval between the non-ejection pulse and the ejection pulse is Td, the natural vibration period of the pressure chamber of the liquid ejection head is Tc , the crest value of the ejection pulse is Vp2, and the crest value Vp2 of the ejection pulse is fixed and the crest value Vp1 of the non-ejection pulse is changed, the crest value Vp1 at which the droplet velocity becomes a minimum value with respect to the change in the crest value Vp1 of the non-ejection pulse is set to be Vpp1 ,
the time interval Td is within a range of Tc-0.2Tc to Tc+0.45Tc,
The non-ejection pulse peak value Vp1 is within a range of −10% to +10% of the peak value Vpp1 when the droplet speed of the liquid ejected by the ejection pulse becomes a minimum value. A head driving method for generating a driving waveform including a plurality of driving pulses to be applied to a liquid ejection head, and applying the driving waveform to the liquid ejection head to eject liquid, comprising the steps of:
the drive waveform includes a non-ejection pulse that does not eject liquid and an ejection pulse that ejects liquid, the non-ejection pulse being arranged in time series successively;
When the crest value of the non-ejection pulse is Vp1, the time interval between the non-ejection pulse and the ejection pulse is Td, the natural vibration period of the pressure chamber of the liquid ejection head is Tc , the crest value of the ejection pulse is Vp2, and the crest value Vp2 of the ejection pulse is fixed and the crest value Vp1 of the non-ejection pulse is changed, the crest value Vp1 at which the droplet velocity becomes a minimum value with respect to the change in the crest value Vp1 of the non-ejection pulse is set to be Vpp1 ,
the time interval Td is within a range of Tc-0.2Tc to Tc+0.45Tc,
The head driving method, wherein the non-ejection pulse peak value Vp1 is within a range of −10% to +10% of the peak value Vpp1 when the droplet speed of the liquid ejected by the ejection pulse becomes a minimum value.

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