JP4038958B2 - Electrostatic inkjet head driving method and electrostatic inkjet printer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a driving method of an electrostatic ink jet head that ejects ink droplets by elastically displacing a diaphragm defining a part of an ink pressure chamber communicating with an ink nozzle by an electrostatic force. is there.
[0002]
More specifically, the present invention relates to a driving method of an electrostatic ink jet head capable of preventing crosstalk of ink pressure between adjacent ink pressure chambers even when the ink pressure chambers are arranged at high density.
[0003]
[Prior art]
An electrostatic ink jet head includes, for example, a diaphragm as a common electrode formed on the bottom surface of an ink pressure chamber constituting an ink flow path, as disclosed in JP-A-2-219351. And an electrode plate as an individual electrode facing the diaphragm with a slight gap. The volume of the ink pressure chamber is changed by applying a driving voltage between these counter electrodes and applying an electrostatic force to bend the diaphragm, and the ink pressure fluctuation caused thereby is communicated with the ink pressure chamber. Recording is performed by ejecting ink droplets from the ink nozzles.
[0004]
In such an electrostatic ink jet head, in order to improve the quality of an output image, it is necessary to arrange a large number of ink nozzles at high density. For this purpose, it is necessary to arrange the ink flow paths to which each ink nozzle communicates, that is, each ink pressure chamber, at a high density, and as a result, it is necessary to make the isolation walls partitioning the ink pressure chambers thin. is there.
[0005]
[Problems to be solved by the invention]
Here, when the separating walls partitioning the ink pressure chambers are thinned, the separating walls may be bent due to fluctuations in the internal pressure of the ink pressure chambers. That is, as shown in FIG. 11A, the vibration plate 23 (3) of the ink pressure chamber 22 (3) with which the drive ink nozzle 21 (3) for discharging ink droplets communicates is connected to the individual electrode 25 ( 3), the separation walls 24 (2) and 24 (3) may be bent due to fluctuations in the internal pressure of the ink pressure chamber 22 (3).
[0006]
Similarly, as shown in FIG. 11B, when the diaphragm 23 (3) is detached from the individual electrode 25 (3) even during ink ejection, the internal pressure fluctuation of the ink pressure chamber 22 (3) is changed. May cause the isolation walls 24 (2) and 24 (3) to bend.
[0007]
If the separating wall bends during ink ejection, pressure loss occurs in the ink pressure chamber 22 (3), and there is a risk that ink droplets of an appropriate amount or particle diameter will not be ejected from the drive ink nozzle 21 (3).
[0008]
Further, on the side of the non-driving ink nozzles 21 (2) and 21 (4) adjacent to the driving ink nozzle 21 (3), the separating walls 24 (2) and 24 (3) are bent, Internal pressure fluctuations occur in the ink pressure chambers 22 (2) and 22 (4) on the non-driven ink nozzle side, and in some cases, a small amount of ink droplets may be unnecessarily ejected.
[0009]
Furthermore, since the pressure fluctuation leaks to the adjacent ink pressure chambers through the isolation walls 24 (2) and 24 (3) in this way, in other words, pressure crosstalk occurs. The pressure fluctuation state generated in the ink pressure chamber differs depending on whether the adjacent ink nozzles are driven simultaneously or not. As a result, the ink ejection characteristics (ink ejection speed, ink ejection amount) of one ink nozzle may fluctuate depending on the driving state of the adjacent ink nozzle, which may cause a decrease in print quality.
[0010]
On the other hand, in Japanese Patent Application Laid-Open Nos. 5-69544 and 7-17039, the discharge time of the ink droplets from the nozzles adjacent to the even-numbered nozzle and the odd-numbered nozzle is delayed by a delay circuit and discharged. It corresponded. However, these conventional techniques have the problem that the driving device becomes more complicated and the problem that the time required for printing becomes longer.
[0011]
In view of such a problem, an object of the present invention is to make it possible to perform an ink discharge operation without bending an isolation wall between ink pressure chambers. Electrostatic ink jet head driving method capable of preventing crosstalk of pressure and easily ensuring high-definition and precise print quality without lowering printing speed without complicating the ink-jet head drive device and its To propose a device.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides at least first and second ink pressure chambers partitioned by a separating wall, and first and second ink nozzles communicating with the respective ink pressure chambers. And first and second diaphragms elastically displaceable in an out-of-plane direction defining a part of each ink pressure chamber, and first and second individual electrodes facing each diaphragm. Each of the diaphragms is elastically displaced by applying a driving voltage between the first diaphragm and the first individual electrode and between the second diaphragm and the second individual electrode. Thus, in the method of driving an electrostatic ink jet head that discharges ink droplets from the first and second ink nozzles, the first and second diaphragms are arranged on the first and second individual electrode sides, respectively. Suction to the individual electrode. A step of holding the first and second diaphragms in the state of being adsorbed to the first and second individual electrodes after the adsorption step, and the second step following the holding step. In a state where the diaphragm is adsorbed to the second individual electrode, the first diaphragm is detached from the first individual electrode, and is elastically displaced to remove ink droplets from the first ink nozzle. A discharge step for discharging, and after the discharge step, the second diaphragm is held in a state of being attracted to the second individual electrode, and the first diaphragm is again attached to the first diaphragm. And a second holding step of holding the magnet by adsorbing it to the individual electrode.
[0013]
Preferably, the driving method of the electrostatic ink jet head further includes a detaching step of detaching the first and second diaphragms from the first and second individual electrodes after the second holding step. In the separation step, the second diaphragm is separated at a speed at which ink droplets are not ejected from the first and second ink nozzles.
[0014]
Furthermore, the electrostatic ink jet head driving device of the present invention is an electrostatic ink jet head driving device that executes the driving method, wherein the potentials of the first and second diaphragms and the first and first vibration plates are the same. The electrostatic ink jet head includes a switching unit that switches the potential of the two individual electrodes and a driving pulse generation unit that generates a driving pulse, and the driving pulse generated by the driving pulse generation unit is switched by the switching unit. It is characterized by driving.
[0015]
In the method and apparatus for driving an electrostatic ink jet head according to the present invention, when ink droplets are ejected from the first ink nozzle on the driving side, the second ink nozzle on the non-driving side communicates. The second diaphragm of the second ink pressure chamber is sucked to the second individual electrode side. Accordingly, the elastic displacement of the second diaphragm is constrained and the rigidity thereof is kept high, and the compliance of the second ink pressure chamber is set to be small. As a result, bending of the isolation wall that partitions the second ink pressure chamber from the driving-side first ink pressure chamber is prevented, and crosstalk of pressure through the isolation wall is prevented or suppressed.
[0016]
The electrostatic ink jet head of the present invention is
At least first and second ink pressure chambers partitioned by an isolation wall;
First and second ink nozzles respectively communicating with each ink pressure chamber;
First and second diaphragms elastically displaceable in an out-of-plane direction defining a part of each ink pressure chamber, and first and second individual electrodes facing each diaphragm And applying a drive voltage between the first diaphragm and the first individual electrode and between the second diaphragm and the second individual electrode to elastically displace each diaphragm. In the electrostatic inkjet head that discharges ink droplets from the first and second ink nozzles,
The first and second diaphragms are attracted to the first and second individual electrodes, respectively, and adsorbed to the individual electrodes, and the first and second diaphragms are attracted to the first and second diaphragms, respectively. The first diaphragm is held by being attracted to the individual electrode, and the first diaphragm is elastically displaced to eject ink droplets from the first ink nozzle. After the ejection, the first diaphragm is again mounted. Control means for controlling the first individual electrode to adsorb and hold the first individual electrode is included.
[0017]
Furthermore, the ink jet printer of the present invention is provided with a plurality of nozzles that eject ink to the outside, and a direction in which ink is not ejected from the plurality of nozzles when an electrostatic force is applied. And the plurality of diaphragms are displaced in a direction of ejecting ink from the plurality of nozzles communicating with each other by abruptly releasing the applied electrostatic force. In the electrostatic inkjet printer that discharges ink from the nozzle and prints on a recording medium, when the plurality of nozzles include a drive nozzle that discharges ink and a non-drive nozzle that does not discharge ink, The electrostatic force is applied for a predetermined period to the first diaphragm communicating with the driving nozzle and the second diaphragm communicating with the non-driving nozzle. Thereafter, the application of the electrostatic force to the first diaphragm is canceled while the electrostatic force is applied to the second diaphragm, and then the first electrostatic force is applied to the second diaphragm. Control means for controlling to reapply electrostatic force to one diaphragm is provided.
[0018]
Here, the non-driving nozzles are not limited to the non-ejection nozzles adjacent to the driving nozzles, but are preferably all non-ejection nozzles. In this way, all non-driven nozzles can act as low compliance.
[0019]
According to these configurations, high-definition and high-speed can be performed with simple control.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
A method for driving an electrostatic ink jet head to which the present invention is applied will be described below with reference to the drawings.
[0021]
(overall structure)
First, with reference to FIGS. 1-3, the structure of the electrostatic inkjet head which can apply the drive method of this invention is demonstrated. Here, FIG. 1 is a cross-sectional view of the electrostatic ink jet head of this example, FIG. 2 is a plan view thereof, and FIG. 3 is a vertical cross-sectional view thereof.
[0022]
As shown in these figures, the electrostatic ink jet head 1 of this example has a silicon substrate 2 sandwiched between the same, a silicon nozzle plate 3 on the upper side, and a borosilicate glass substrate 4 having a thermal expansion coefficient close to that of silicon on the lower side. Has a three-layer structure in which each is stacked.
[0023]
The central silicon substrate 2 is subjected to KOH (anisotropic wet etching with an aqueous solution) from its surface in the (110) plane orientation, so that five elongated ink pressure chambers 5 (1) to 5 (5) are provided. One common ink chamber 6 and grooves that function as the ink supply ports 7 that communicate the common ink chamber 6 with the ink pressure chambers 5 (1) to 5 (5) are processed. The groove is closed by the nozzle plate 3, and the respective sections 5, 6, and 7 are defined, and the ink pressure chambers 5 (1) to 5 (5) are separated from the separating walls 8 (1) to 8 (4), respectively. ).
[0024]
In addition, an ink intake port 12 is formed at a portion defining the lower surface of the common ink chamber 6 so as to communicate with the ink supply port 7. Accordingly, ink is supplied from an external ink tank (not shown) through the ink intake port 12 to the common ink chamber 6, and from here through each ink supply port 7, each independent ink pressure chamber 5 ( 1) to 5 (5).
[0025]
In the nozzle plate 3, the ink nozzles 11 (1) are located at positions corresponding to the tip side portions of the ink pressure chambers 5 (1) to 5 (5), that is, positions opposite to the ink supply ports 7. To 11 (5) are formed and communicate with the corresponding pressure chambers 5 (1) to 5 (5).
[0026]
As the diaphragms 51 (1) to 51 (5), the bottom surfaces of the independent ink pressure chambers 5 (1) to 5 (5) are thin and elastically displaceable in the out-of-plane direction, that is, in the vertical direction in FIG. It is set to function (only the diaphragm 51 (1) is shown in the figure).
[0027]
Next, in the glass substrate 4 located on the lower side of the silicon substrate 2, the bottom surfaces of the pressure chambers 5 (1) to 5 (5) of the silicon substrate 2 are attached to the upper surface of the glass substrate 4 that is bonded to the silicon substrate 2. Recesses 9 (1) to 9 (5) that are etched shallowly are formed at positions facing the prescribed diaphragms 51 (1) to 51 (5), respectively. Individual electrodes 10 (1) to 10 (5) corresponding to the diaphragms 51 (1) to 51 (5) are formed on the bottom surfaces of the recesses 9 (1) to 9 (5), respectively. Each of the individual electrodes 10 (1) to 10 (5) has a segment electrode 10a made of ITO and a terminal portion 10b.
[0028]
By bonding the glass substrate 4 to the silicon substrate 2, the diaphragms 51 (1) to 51 (5) defining the bottom surface of each ink pressure chamber 5 and the segment electrodes 10a in the corresponding individual electrodes are Are opposed to each other with a narrow gap G therebetween. The gap G is sealed by a sealant 60 disposed between the silicon substrate 2 and the glass substrate 4 and is in a sealed state.
[0029]
A common electrode terminal 22 is formed on the silicon substrate 2 by attaching a noble metal thin film such as platinum to the surface on the nozzle plate 3 side, and between this and each individual electrode 10 (1) -10 (5). In addition, a driving voltage pulse is applied by the voltage applying means 21. Since the silicon substrate 2 is conductive, the diaphragms 51 (1) to 51 (5) function as a common electrode.
[0030]
The diaphragms 51 (1) to 51 (5) and the diaphragms 51 (1) to 51 (5) are generated by an electrostatic force generated by applying a drive voltage between the individual electrodes 10 (1) to 10 (5). ) Is attracted to the individual electrode side, the diaphragms 51 (1) to 51 (5) are elastically displaced to bend toward the segment electrode 10 a and are adsorbed on the surface of the segment electrode 10 a. As a result, the volume of the ink pressure chambers 5 (1) to 5 (5) is increased, and ink is supplied from the ink supply port 7 to the ink pressure chambers 5 (1) to 5 (5).
[0031]
When the electrostatic attraction force is released, the diaphragms 51 (1) to 51 (5) are separated from the surface of the segment electrode 10a by the elastic force to return to the initial state, and the ink pressure chambers 5 (1) to 5 ( 5) The volume decreases rapidly. At this time, due to ink pressure vibration generated in the ink pressure chamber, a part of the ink in the ink pressure chamber is ejected as ink droplets from the ink nozzles 11 communicating with the ink pressure chambers 5 (1) to 5 (5). Is done.
[0032]
In this example, it is a face eject type that ejects ink droplets from nozzle holes provided on the upper surface of the substrate 3, but an edge eject type that ejects ink droplets from nozzle holes provided at the end of the substrate may also be used.
[0033]
(Driving method)
With reference to FIG. 4, the outline of the driving method of the ink jet head 1 of this example will be described. Assume that the ink nozzle (referred to as “driving nozzle”) from which ink droplets are ejected is the ink nozzle 11 (3). Further, the ink nozzles 11 (2) and 11 (4) adjacent to both sides of the drive nozzle 11 (3) are ink nozzles that do not discharge ink droplets (referred to as “non-drive nozzles”). And
[0034]
In the driving method of this example, first, a voltage is applied between the diaphragms 51 (2) to 51 (4) and the individual electrodes 10 (2) to 10 (4) in the ink nozzles 11 (2) to 11 (4). Application is made to generate a potential difference, and the diaphragms 51 (2) to 51 (4) are simultaneously sucked into the individual electrodes 10 (2) to 10 (4). Thereby, the adsorption | suction state of each diaphragm 51 (2) -51 (4) as shown to Fig.4 (a) is formed. While maintaining the potential difference in the suction state, the diaphragms 51 (2) to 51 (4) are held in the suction state and stand by. (Standby state) At this time, the voltage applied between the diaphragms 51 (2) to 51 (4) and the individual electrodes 10 (2) to 10 (4) in order to maintain the adsorption state forms an adsorption state. The voltage may be lower than the applied voltage. This is because once the suction state is secured, the electrostatic pressure is high even if the voltage required to hold the suction is low.
[0035]
Next, the drive nozzle 11 is kept in a state where the diaphragms 51 (2) and 51 (4) of the non-drive nozzles 11 (2) and 11 (4) are attracted to the individual electrodes 10 (2) and 10 (4). The diaphragm 51 (3) of (3) is quickly detached from the individual electrode 11 (3). In order to quickly detach the diaphragm 51 (3) from the individual electrode 11 (3), a driving voltage is applied to the individual electrode 10 (3) so as to have the same potential as that of the diaphragm 51 (3), and the charge between these counter electrodes. To quickly discharge. As a result, as shown in FIG. 4B, the diaphragm 51 (3) is elastically restored, the volume of the ink pressure chamber 5 (3) is rapidly reduced, and the ink is discharged from the drive nozzle 11 (3). A droplet is ejected.
[0036]
After the ink droplets are ejected from the drive nozzle 11 (3), the diaphragm 51 (3) is again sucked by the individual electrode 10 (3) to be in the suction state, and the diaphragm 51 (3) is attached to the individual electrode 10 (3). Adsorption and holding are performed again to a standby state shown in FIG.
[0037]
Through the above steps, one ink droplet ejection operation is completed. The above steps are repeated when ink droplets are repeatedly ejected.
[0038]
When the series of ejection operations is completed and the standby state is released, the diaphragms 51 (2) to 51 (4) of the nozzles 11 (2) to 11 (4) in the standby state are moved to the individual electrodes 10 (2). -10 (4). This separation speed is performed at a slow speed at which ink droplets are not ejected from the nozzles 11 (2) to 11 (4).
[0039]
(flowchart)
FIG. 5 shows a flowchart for explaining a driving method of the ink jet head 1 of this example described with reference to FIG. When print data is transmitted at SS0, printing is started. In the diaphragm suction step SS1, a voltage is applied between all the diaphragms 51 corresponding to all the ink nozzles 11 and the individual electrodes 10 to generate a potential difference, and the diaphragm 51 is sucked into the individual electrodes 10 and sucked. State. In the diaphragm holding step SS2, a potential difference is continuously maintained between the diaphragm 51 and the individual electrode 10, the suction state is held, and the process is on standby. In SS5, in the case of the drive nozzle 11 (3), the vibration plate 51 (3) of the drive nozzle 11 (3) is quickly detached from the individual electrode 11 (3) in the discharge process SS6, and the ink liquid Let the droplets be ejected. In SS5, in the case of the non-driven nozzles 11 (2) and 11 (4), the diaphragms 51 (2) and 51 (4) are still attracted to the individual electrodes 10 (2) and 10 (4). Hold. That is, the standby state of the diaphragm holding step SS2 is maintained.
[0040]
After the ink droplets are ejected in the ejection process SS6, the diaphragm 51 (3) of the drive nozzle 11 (3) is again sucked and adsorbed to the individual electrode 11 (3) in the diaphragm suction process SS7. . Thereafter, the process returns to the diaphragm holding step SS2, and again enters a standby state in which the diaphragm 51 (3) is attracted and held by the individual electrode 11 (3).
[0041]
When the print data is completed in SS4 or the standby state is terminated for other reasons such as canceling the print standby state and performing another operation, all the nozzles in the standby state are stopped in the diaphragm removing step SS8. The diaphragm is detached from the individual electrode and released from the held state. The separation of the diaphragm at this time is performed at a slow speed so that ink droplets are not ejected from the nozzles.
[0042]
(Timing chart)
FIG. 6 shows an example of a pulse waveform of the drive voltage applied between the diaphragm, which is a common electrode, and the individual electrodes in order to realize the above operation. Such a drive voltage pulse is generated by the drive control device 100.
[0043]
FIG. 6 shows an example of a pulse waveform of the drive voltage applied between the diaphragm and the individual electrodes, accompanied by the discharge of the series of ink droplets described with reference to FIG. 4, in the period from time t1 to time t7. ing. In this period, for example, the ink droplet is ejected twice. In addition, a driving pattern for performing potential reversal control without ink droplet ejection is shown from time t8 to time t10. The potential inversion control will be described later.
[0044]
First, FIG. 6B shows a basic voltage pulse waveform Vp of the drive voltage. The ink droplet is ejected once for each pulse of the basic voltage pulse waveform Vp. For example, between time t2 and t4 and between time t4 and t6 are each one discharge cycle. Ink droplets are ejected from the ink nozzles by abrupt changes in the voltage waveform at time t3 and time t5 of the basic voltage pulse waveform Vp. These first and second discharge cycles are repeatedly executed. In this basic voltage waveform pulse Vp, its rise (change in voltage from time t3 and t5 to voltage Vh) is steep, and its fall (change to ground potential GND starting from time t4 and t6) rises. Compared to a gentle slope.
[0045]
In addition, Vh shown in FIG. 6A is a high breakdown voltage power supply potential. Vh has the same amount of change in the rise from time t1 and the slope of the fall from time t7, and this change is caused even if the change in potential difference due to Vh and the GND potential acts between the diaphragm and the individual electrodes. The gradient is gentle so as not to eject ink droplets.
[0046]
The three ink nozzles 11 (2) to 11 (4) shown in FIG. 4 will be described as an example. The applied voltages of the diaphragms 51 (2) to 51 (4) functioning as common electrodes are as shown in FIG. As shown in (c), the voltage has the same shape as the power supply potential Vh of the high withstand voltage system from time t1 to time t7. After time t2, the diaphragms 51 (2) to 51 (4) are attracted and held by the individual electrodes 10 (2) to 10 (4), and are in a standby state. Further, it is held at the ground potential GND from time t8 to time t10 when the potential inversion control is performed.
[0047]
As shown in FIG. 6D, the individual electrode potential of the drive nozzle 11 (3), that is, the potential of the diaphragm 51 (3) is a basic voltage pulse waveform from time t1 to time t7 in the discharge cycle. The voltage has the same shape as Vp. In the first ejection cycle, the voltage suddenly rises to Vh, which is the common electrode potential, at time t3, and thereafter is held at the same potential as the common electrode potential until time t4. After time t4, it is held at the ground potential GND again. In the second ejection cycle, the potential rises sharply at time t5, and is held at a high potential until time t6. After time t6, the potential is held again at the ground potential GND.
[0048]
As a result, the potential difference between the diaphragm 51 (3) and the individual electrode 10 (3) in the drive nozzle 11 (3) is a positive potential difference state between time points t2 and t3 in the standby state, as shown in FIG. Between the time points t3 and t4 which are the first discharge cycle and between the time points t5 and t6 in the second discharge cycle. In other words, no electrostatic force that attracts the diaphragm to the individual electrode is generated. At other time points, the positive potential difference state is maintained, an electrostatic force that attracts the diaphragm and the individual electrodes acts, and the diaphragm is attracted and held by the individual electrodes.
[0049]
Therefore, in the first discharge cycle, the diaphragm 51 (3) suddenly separates from the individual electrode 10 (3) and elastically returns from the time point t3, and the operation of the diaphragm causes the drive nozzle 11 (3) to return from the driving nozzle 11 (3). Ink droplets are ejected at a time after a predetermined time from time t3. Thereafter, at time t4, the diaphragm 51 (3) is attracted to the individual electrode 10 (3) and returns to the standby state. Similarly, in the second discharge cycle, the diaphragm 51 (3) suddenly detaches from the individual electrode 10 (3) and elastically returns from the time t5, and the operation of the diaphragm causes the drive nozzle 11 (3) to return. Ink droplets are ejected at a time after a predetermined time from time t5. Thereafter, at time t6, the diaphragm 51 (3) is attracted to the individual electrode 10 (3) and returns to the standby state.
[0050]
On the other hand, in the non-driving nozzle 11 (2) adjacent to the driving nozzle 11 (3), the individual electrode potential is as shown in FIG. 6 (f) through the first and second ejection cycles. Held at ground potential.
[0051]
As a result, as shown in FIG. 6G, the potential difference state between the diaphragm 51 (2) and the individual electrode 10 (2) in the non-driven nozzle 11 (2) is the first discharge cycle and the second discharge cycle. In FIG. 4, the power supply potential Vh is similar to that of the high withstand voltage system.
[0052]
Accordingly, the diaphragm 51 (2) is attracted to the individual electrode 10 (2) from the time point t1 in the first discharge cycle, and is held in the suction state until the time point t7.
[0053]
At the end of the standby state, the potential difference gradually decreases after time t7. That is, the discharge between both electrodes is gradually performed. For this reason, separation of the diaphragms 51 (2) to 51 (4) starts at a position until the potential difference after the time point t7 disappears, and elastically returns at a slower speed than at the time of suction.
[0054]
FIG. 6H shows the diaphragm 51 (FIG. 6E) that is driven by the potential difference between the diaphragm 51 (3) and the individual electrode 10 (3) in the drive nozzle 11 (3). The state of displacement at each time point of 3) is shown. 6 (i) shows the diaphragms 51 (2) and 51 (4) and the individual electrodes 10 (2) in the non-driving nozzles 11 (2) and 11 (4) shown in FIG. The state of displacement at each time point of the diaphragms 51 (2) and 51 (4) operated by the potential difference between the electrodes of 10 (4) is shown.
[0055]
In the charts shown in FIGS. 6H and 6I, the vertical direction indicates the displacement of the diaphragm, and the horizontal direction indicates the passage of time. G indicates a gap when no electric field is applied between the diaphragm 51 and the individual electrodes 10. The direction in which the distance between the diaphragm 51 and the individual electrode 10 decreases is (−), and the direction in which the distance increases is (+).
[0056]
Here, FIG. 6 (h) is compared with FIG.
[0057]
t1 to t2: The diaphragm 51 (3) of the drive nozzle 11 (3) is adsorbed to the individual electrode 10 (3) between time t1 and time t2. (First diaphragm adsorption step SS1)
t2 to t3: The diaphragm 51 (3) is held in a state of being adsorbed to the individual electrode 10 (3) until time t3 after the adsorption. (First diaphragm holding step SS2)
t3 to t4: At time t3, the diaphragm 51 (3) is suddenly detached and returned, pressurizing the ink in the pressure chamber 5 (3), and ink from the drive nozzle 11 (3) at the time indicated by the arrow h1. A droplet is discharged. (Discharge process SS6)
Thereafter, the vibration plate 51 (3) vibrates so that the potential difference between the electrodes is generated again at the time when the displacement amount of the vibration plate substantially coincides with the vibration cycle of the vibration plate 51 (3) at the time of going to (−). Is applied to the individual electrode 10 (3), and is attracted to the individual electrode 10 (3) again at time t4. (Second diaphragm adsorption step SS7)
t4 to t5: Thereafter, until time t5, the diaphragm 51 (3) is held in the state of being attracted to the individual electrode 10 (3) until time t5 in preparation for the next discharge. (Second diaphragm holding step SS2).
[0058]
t5 to t7: In the driving nozzle 11 (3), the diaphragm is further subjected to a similar cycle (cycle from the discharge process SS6 to the diaphragm holding process SS7 to the diaphragm holding process SS2) from the time point t5 to t7. 51 (3) is driven, and ink droplets are ejected at the time indicated by arrow h2 (when ejecting twice or more, t5 to t7 are repeated).
[0059]
t7 to t8: At the driving nozzle 11 (3), the diaphragm 51 (3) is gradually detached from the individual electrode 10 (3) at time t7, and the series of printing control steps (standby state) is completed. At this time, ink droplets are not ejected from the nozzle 11 (3). (Diaphragm removal step SS8)
In FIG. 6 (i), the diaphragms 51 (2) and 51 (4) of the non-driving nozzles 11 (2) and 11 (4) are individually electroded 10 (2) and 10 (4) between time t1 and time t2. ). (Vibration plate adsorption step SS1) The vibration plates 51 (2) and 51 (4) are held in a state of being adsorbed to the individual electrodes 10 (2) and 10 (4) after the adsorption until time t7. The (Vibration plate holding step SS2) Since these non-driving nozzles 11 (2) and 11 (4) do not eject ink droplets, the vibration plate 51 (2) is also used when the driving nozzle 11 (3) is in the ejection step. ), 51 (4) are attracted and held by the individual electrodes 10 (2), 10 (4), and the compliance of the flow paths of these ink chambers 5 (2), 5 (4) is small. ing. In the holding process, since the compliance of these flow paths is small, the partition walls 8 (1) to 8 (4) are deformed even in the discharge process of the drive nozzle 11 (3), and the pressure chamber 5 of the drive nozzle 11 (3). Since the pressure loss of (3) does not occur, there is no variation from the drive nozzle 11 (3), and stable ink droplet ejection is possible.
[0060]
At the drive nozzles 11 (2) and 11 (4), the diaphragms 51 (2) and 51 (4) are gradually detached from the individual electrodes 10 (2) and 10 (4) at time t7, and a series of printing is performed. The standby state in the control process is terminated. At this time, ink droplets are not ejected from the nozzles 11 (2) and 11 (4). (Diaphragm removal step SS8)
Thus, on the non-driving nozzle 11 (2) side, the diaphragm 51 (2) is sucked and held during the period of separation and suction operation of the diaphragm 51 (3) on the driving nozzle 11 (3) side. In the standby state shown in FIG. 4A, all nozzles are attracted to the individual electrodes. Next, in this suction holding state, ink droplets are ejected from the drive nozzle 11 (3). At the end of the standby state, the diaphragm 51 (2) on the non-driving nozzle 11 (2) side separates from the individual electrode 10 (2) and gently recovers elastically. By adjusting the elastic return speed of the diaphragm, it is possible to completely prevent ink droplets from being ejected from the non-driving nozzle 11 (2) when the diaphragm 51 (2) is elastically restored.
[0061]
The non-driving nozzle 11 (4) operates in the same manner as the non-driving nozzle 11 (2).
[0062]
As described above, in the driving method of the electrostatic ink jet head of this example, the diaphragm 51 (2) also in the non-driving nozzles 11 (2) and 11 (4) adjacent to the driving nozzle 11 (3). , 51 (4) are held by suction on the individual electrodes 10 (2) and 10 (4), so that their rigidity is kept high. As a result, the compliance of the ink pressure chambers 5 (2) and 5 (4) of the non-driven nozzle can be reduced.
[0063]
Therefore, the separation wall 8 (2) partitioning the ink pressure chamber 5 (3) on the driving nozzle side with small compliance from the ink pressure chambers 5 (2) and 5 (4) on the non-driving nozzle side with the same compliance. ), 8 (4) can be prevented or suppressed from bending due to pressure fluctuations in the ink pressure chamber on the drive nozzle side.
[0064]
Therefore, the crosstalk of the pressure in the ink pressure chamber can be prevented or suppressed regardless of whether or not the adjacent ink nozzle is driven. Even if the density of the ink jet head is increased and the isolation wall is thinned, it is caused by the deflection. It is possible to prevent or suppress the deterioration of the ink ejection characteristics of each ink nozzle. For this reason, if the driving method of this example is adopted, high-definition and precise print quality can be easily ensured.
[0065]
Note that the polarity of the potential difference between the individual electrode and the common electrode is reversed after the time point 8 because if the polarity of the potential difference is always the same, charge accumulates between these electrodes and the desired electrostatic potential is reversed. This is because the suction force may not be obtained. By performing these controls, the charge accumulated between the electrodes is wiped out, so that a stable diaphragm operation can always be obtained. These controls are referred to as potential inversion control.
[0066]
Potential reversal control is a method of driving an ink jet head that discharges ink droplets by deforming the diaphragm using electrostatic force, and always eliminates the influence of residual charges remaining on the diaphragm. This is an ink jet head drive control method for the purpose of performing a good ink droplet ejection operation, and is another invention of the present applicant.
[0067]
The diaphragm is deformed in a first driving form in which a voltage having a first polarity is applied between the diaphragm and the electrode, and ink droplets are ejected from the nozzles. The second polarity opposite to the first polarity is provided between the vibrating plate and the electrode so that the ink droplet is not ejected from the nozzle at every fixed period during which the ink droplet ejection operation is performed. A method of driving an electrostatic ink jet head that deforms the diaphragm in a second driving mode that applies a voltage of polarity, wherein the residual charge accumulated in the first driving mode is removed in the second driving mode. An ink-jet head driving method characterized in that:
[0068]
Since there is a concern about charge accumulation due to the difference in frequency between the first drive mode and the second drive mode, for example, a mode in which an inkjet head performs sub-scanning on a print medium and printing is performed by scanning the print medium. In the recording apparatus, the potential inversion control of the second form is performed for each drive pass. Furthermore, in a line-type inkjet head that performs printing only by main scanning of the printing medium, the potential reversal control of the second form is performed for each transaction printing. As a result, the accumulation of residual charges remaining on the diaphragm is suppressed due to the difference in frequency between the first drive mode and the second drive mode, and the effect thereof is at a level that can be ignored in practice.
[0069]
In the potential inversion control after time t8, the common electrode potential shown in FIG. 6C is set to the ground potential GND level. Further, each individual electrode potential shown in FIGS. 6D and 6F is set to the same potential as Vh of the high-voltage power supply potential. Accordingly, the potential difference between the electrodes shown in FIGS. 6E and 6G has a similar potential difference waveform opposite to the high-voltage power supply potential Vh.
[0070]
The above-described potential inversion control is performed with the driving form from time t1 to t7 as the first driving form and the driving form from time t8 to t10 as the second driving form, and the method for controlling the electrostatic ink jet head of the present invention It is possible to apply the potential inversion control to stabilize the operation of the diaphragm and ensure the ink droplet ejection performance.
[0071]
In the driving method described with reference to FIG. 6, the potential inversion control is applied in order to remove the residual charges and stabilize the operation of the diaphragm. However, in the driving method of the electrostatic inkjet head of the present invention, In order to remove charges, before or after the drive mode in which the ink droplet discharge operation described above is performed, as a preliminary operation of the electrostatic ink jet head, thickened ink that is driven with a polarity opposite to the drive electric field polarity is used as an ink nozzle. Alternatively, driving for removal or diffusion into the ink chamber may be performed. In this case as well, as in the above-described potential inversion control, all the nozzles are operated simultaneously and driven.
[0072]
Further, the drive voltage waveform shown in FIG. 6 is an example for realizing the drive method of the present invention, and a drive mode different from this can be adopted.
[0073]
(Driver)
The electrostatic ink jet head driving apparatus of the present invention to which the above driving method is applied will be described below with reference to the drawings.
[0074]
FIG. 7 is a schematic block diagram of a drive control apparatus for an inkjet head to which the present invention is applied. The ink jet head that is driven and controlled by the drive control device 100 shown in this figure is the same as that shown in FIG. 1, and therefore, the same reference numerals are given and description thereof is omitted.
[0075]
The ink jet head drive control apparatus 100 includes an ink jet head control unit 102, and the ink jet head control unit 102 is configured around a CPU. That is, print information is supplied to the CPU from the external device 103 via the bus. The CPU is connected to a ROM, a RAM, and a character generator 104 via an internal bus. The control program stored in the ROM is executed using a storage area in the RAM as a work area, and the character generator 104 is executed. A control signal for driving the ink jet head is generated based on the character information generated from. The gate array 105 supplies a drive control signal corresponding to the print information from the CPU to the head driver IC 109 by a control signal, and supplies a control signal for generating a drive voltage pulse to the drive voltage pulse generation circuit 106.
[0076]
The drive voltage pulse generation circuit 106 is supplied with a control signal from the gate array, generates a drive voltage pulse, and supplies the drive pulse Vp to the head driver IC 109. The drive voltage pulse generation circuit 106 converts a control signal as digital information into an analog drive voltage pulse waveform by a D / A (digital-analog) converter. That is, the drive voltage pulse generation circuit 106 generates a drive pulse waveform from a control signal related to pulse signal waveform generation conditions such as the pulse length, voltage, pulse rise time, and fall time of the drive voltage pulse. In order to generate the drive voltage pulse waveform with high accuracy by configuring the drive pulse generation circuit 106 with a D / A converter, it is only necessary to increase the number of bits of the D / A converter used to increase the resolution of the waveform. Therefore, the accuracy of the drive voltage pulse waveform can be easily improved. The drive pulse generation circuit 106 may be constituted by a CR circuit. If the drive pulse generation circuit 106 is constituted by a CR circuit, it is possible to make the circuit configuration cheaper than the case where it is constituted by a D / A converter.
[0077]
The drive control signal and the drive voltage pulse are supplied to the head driver IC 109 formed on the head substrate 108 via the connector 107. The head driver IC 109 operates by being supplied with a high-voltage drive voltage Vh and a logic circuit drive voltage Vcc from the power supply circuit 110, and switches the drive voltage pulse and the GND potential according to the supplied drive control signal to The voltage is applied between the counter electrodes corresponding to each ink nozzle. As a result, the diaphragm 51 in which the potential difference is generated by the drive pulse between the counter electrodes is attracted to the counter electrode, and the diaphragm 51 is retained in the state of being attracted to the counter electrode 10 between the counter electrodes in which the potential difference is maintained. Then, in the ink nozzle in which the potential difference is suddenly canceled and changed, the vibration plate 51 vibrates and ink droplets are ejected.
[0078]
FIG. 8 is a schematic block diagram of the inside of the head driver IC 109 to which the present invention is applied, shown in the block diagram of FIG. The head driver IC 109 operates by being supplied with a high voltage drive voltage Vh and a logic circuit drive voltage Vcc from the power supply circuit 110. Further, the head driver IC 109 switches between the drive voltage pulse Vp and the GND potential according to the supplied drive control signal, and applies it between the counter electrodes corresponding to each ink nozzle of the inkjet head 1.
[0079]
Here, the head driver IC 109 is described as a CMOS 64-bit output high voltage driver. The head driver IC 109 corresponds to the voltage applying unit 21 in FIG. 2, and the configuration of the voltage applying unit 21 is obtained by setting each bit configuration of the head driver IC 109 to 5 bits.
[0080]
In FIG. 8, reference numeral 91 denotes a 64-bit shift register. An XSCL pulse signal input, which is a basic clock pulse synchronized with the DI signal, is input to the 64-bit DI signal transmitted from the logic gate array 5 as serial data. Thus, the data is shifted up and stored in a register in the shift register 91. As the DI signal, selection information for each nozzle of 64 nozzles is transmitted as serial data by ON / OFF control signals.
[0081]
A 64-bit latch circuit 92 latches 64-bit data stored in the shift register 61 with a latch pulse LP, stores the data, and outputs the stored data to the 64-bit inversion circuit 93 as a signal. It is a tea clutch. In the latch circuit 92, the DI signal of the serial data is converted into a 64-bit parallel signal for performing 64 segment output for driving each nozzle.
[0082]
The inverting circuit 93 outputs an exclusive OR of the signal input from the latch circuit 92 and the REV signal to the level shifter 94. The level shifter 94 is a level interface circuit that converts the voltage level of the signal from the inverting circuit 93 from the logic system voltage level (5 V level or 3.3 V level) to the head drive system voltage level (0 V to 45 V level).
[0083]
The SEG driver 95 is a 64 channel transmission gate output. Depending on the input of the level shifter 94, either the drive voltage pulse Vp (= Vp1) input or the GND input with respect to the segment outputs SEG1 to SEG64. Is output.
[0084]
When the Vsel input is H (logic), the COM driver 96 outputs either the drive voltage pulse Vp (= Vp1) input or the GND input to the COM output with respect to the REV input. When the Vsel input is L (logic), the COM driver 96 outputs either the Vp2 input or the Vh input to the COM output with respect to the REV input. In order to realize the driving method shown in FIG. 6, the driving voltage pulse Vp is connected to the Vp1 input. Also, GND is connected to Vp2. With this configuration, the above-described potential inversion control can be easily performed by setting the Vsel input to L. In addition, by setting the Vsel input to H, it is possible to easily realize the driving with the reverse polarity in the driving pattern and the driving in which the driving electric field polarity is alternately switched, which is the driving as the preliminary operation described above.
[0085]
The segment outputs of SEG1 to SEG64 are electrically connected to the terminal 10b of the counter electrode 10 of the corresponding ink nozzle 11 of the inkjet head 1, respectively. Further, the COM output is electrically connected to the diaphragm 51 through the common electrode 22.
[0086]
The XSCL, DI, LP, and REV signals are logic system voltage level signals that are transmitted from the logic gate array 105 to the head driver IC 109.
[0087]
In this way, by configuring the head driver IC 109, even when the number of segments to be driven (number of nozzles) increases, the drive voltage pulses Vp and GND for driving each nozzle of the head can be easily switched, and the above-described potential can be obtained. Inversion control can be easily realized.
[0088]
FIG. 9 shows a schematic circuit configuration inside the main part of the head driver IC 109 described above. FIG. 9A shows a CMOS circuit configuration of a 1-bit driver of the SEG driver 95, and FIG. 9B shows a CMOS circuit configuration of the COM driver 96.
[0089]
The SEG driver 95 switches Vp1 or GND and outputs the SEGn (n = 1, 2,..., 64) output. The COM driver 96 is configured to switch and output one of Vh, Vp1, Vp2 and GND with respect to the COM output. Here, the COM driver 96 is configured as a bidirectional transmission gate.
[0090]
By configuring the SEG driver 95 and the COM driver 96 in this way, the potentials of the diaphragm 51 on the common electrode side and the individual electrode 10 described in the timing chart of FIG. A variety of electrostatic actuator drive controls such as potential reversal control for erasing accumulated charge are easily realized.
[0091]
(Inkjet printer)
Next, FIG. 10 shows an external perspective view of an embodiment of the printing apparatus according to the present invention. An electrostatic inkjet head 201 is mounted on the printing apparatus 200. The inkjet head 201 is mounted on the printing apparatus 200 as a line inkjet head. In the inkjet head 201, 1440 ink nozzles are arranged in a line in the longitudinal direction on the surface facing the recording paper 210 at a pitch of 70 μm (360 dpi = dot per inch).
[0092]
In FIG. 10, the printing apparatus 200 transports the recording paper 210 in the direction of arrow A by the recording paper transport mechanism 202, and ejects ink droplets from the inkjet head 201 in synchronization with the transport speed of the recording paper 210. To print. A storage unit 203 of the ink supply mechanism. The ink supply mechanism further includes an ink tank that stores ink (not shown), an ink circulation pump mechanism (not shown) that simultaneously collects ink to the line inkjet head 201, and an ink tank, an ink circulation pump mechanism, and a line inkjet head. The ink pipes are arranged between 201 and are stored in the storage unit 203 of the ink supply mechanism.
[0093]
In addition, the printing apparatus 200 includes the drive control apparatus 100 shown in FIG. The drive control device 100 drives and controls the line inkjet head 201, the transport mechanism 202, and the ink supply mechanism 203, and performs data printing processing by transmitting and receiving data to and from a host device such as a barcode scanner or a network. .
[0094]
In the above-described example, the line type ink jet printer that performs printing by transporting the recording paper 210 while fixing the ink jet head 201 to the printing apparatus has been described. However, as the printing apparatus of the present invention, the ink jet head is placed on the recording paper. A serial type ink jet printer that performs printing while discharging ink droplets and conveying the recording paper in the main scanning direction may be used.
[0095]
According to the printing apparatus of the present invention, the high-density inkjet head 201 is attached to the printing apparatus, and the electrostatic inkjet head is driven by the above-described driving apparatus to perform printing, so high-definition printing is performed at high speed. It is possible to do. In addition, since complicated control of the ink jet head is not required, the above-described high-definition and high-speed printing apparatus can be realized with simple control, and the number of scans of the ink jet head on the recording paper is small.
[0096]
【The invention's effect】
As described above, in the electrostatic ink jet head driving method and apparatus according to the present invention, not only the diaphragm of the first ink nozzle that is the driving nozzle but also the second non-driving nozzle that is adjacent. The vibration plate of the ink nozzle is also attracted to the individual electrodes to be in an adsorption state, and ink droplets are ejected from the drive nozzle while maintaining the adsorption state.
[0097]
Therefore, when the drive nozzle is driven, the compliance of the ink pressure chamber on the non-drive nozzle side can be reduced, so that the deformation of the isolation wall separating the ink pressure chamber of the drive nozzle and the ink pressure chamber of the non-drive nozzle is prevented or suppressed. it can. Therefore, since the crosstalk of the pressure through the isolation wall can be prevented or suppressed, it is possible to prevent or suppress the deterioration of the ink discharge characteristics due to the crosstalk.
[0098]
As a result, according to the driving method and apparatus of the present invention, the density of the ink jet head can be increased without causing deterioration of the ink ejection characteristics, so that high-definition and precise printing quality can be achieved.
[0099]
In addition, since the density of the ink jet head can be increased without complicating the driving device and reducing the printing speed, it can be easily realized while ensuring the printing speed.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view showing an example of an electrostatic ink jet head to which the present invention is applied.
FIG. 2 is a schematic plan view of the electrostatic ink jet head shown in FIG.
FIG. 3 is a schematic cross-sectional view of the electrostatic inkjet head shown in FIG. 1 when cut in a direction orthogonal to each other.
4 is an explanatory diagram for illustrating the operation of the electrostatic inkjet head of FIG. 1; FIG.
FIG. 5 is a flowchart illustrating a method for driving an inkjet head according to the present invention.
6 is a timing chart showing an example of a drive voltage waveform for realizing the operation of FIG. 4; FIG.
7 is a block diagram showing an example of a drive device for realizing the operation of FIG. 6. FIG.
8 is a block diagram inside the head driver IC in FIG. 7. FIG.
9 is a schematic circuit configuration diagram of an SEG driver section (a) and a COM driver section (b) of the head driver IC in FIG. 8;
FIG. 10 is a diagram illustrating an ink jet printer of the present invention.
FIG. 11 is an explanatory diagram for explaining a problem in a conventional inkjet head driving method.
[Explanation of symbols]
1 Electrostatic inkjet head
2 Silicon substrate
3 Nozzle plate
4 Glass substrate
5 (1) -5 (5) Pressure chamber
6 Common ink chamber
7 Ink supply port
8 (1) -8 (5) Isolation wall
9 (1) -9 (5) Recess
10 (1) -19 (5) Individual electrode
10a Segment electrode
10b Terminal section
11 (1) to 11 (5) Ink nozzle
12 Ink outlet
21 Voltage application means
22 Common electrode terminal
51 (1) to 51 (5) Diaphragm
60 Sealant
100 Inkjet head control device
102 Inkjet control unit
109 Head Driver IC

Claims (3)

Defining at least first and second ink pressure chambers partitioned by a separating wall; first and second ink nozzles communicating with each ink pressure chamber; and a portion of each ink pressure chamber. The first diaphragm and the first diaphragm are elastically displaceable in the out-of-plane direction, and the first and second individual electrodes are opposed to each diaphragm. Ink from the first and second ink nozzles by elastically displacing each diaphragm by applying a drive voltage between the individual electrodes and between the second diaphragm and the second individual electrode. In the driving method of the electrostatic inkjet head for discharging droplets,
An adsorption step of sucking the first and second diaphragms toward the first and second individual electrodes, respectively, and adsorbing the first and second diaphragms to the individual electrodes;
A holding step of holding the first and second diaphragms in a state of being sucked by the first and second individual electrodes after the suction step;
Following the holding step, in a state where the second diaphragm is adsorbed to the second individual electrode, the first diaphragm is detached from the first individual electrode to be elastically displaced, and the A discharge step of discharging ink droplets from the first ink nozzle;
After the ejection step, the state where the second diaphragm is adsorbed to the second individual electrode is held, and the first diaphragm is again adsorbed to the first individual electrode and held. A method for driving an electrostatic ink jet head, comprising: a second holding step. In claim 1,
After the second holding step, including a detaching step of detaching the first and second diaphragms from the first and second individual electrodes;
The method of driving an electrostatic ink jet head, wherein in the separation step, the second diaphragm is detached at a speed at which ink droplets are not ejected from the first and second ink nozzles. A plurality of nozzles that eject ink to the outside, and a plurality of diaphragms that are respectively connected to the plurality of nozzles and are displaced in a direction in which ink is not ejected from the plurality of nozzles when an electrostatic force is applied. With
The plurality of diaphragms are displaced in a direction of ejecting ink from the plurality of nozzles communicating with each other by suddenly releasing the applied electrostatic force, and eject ink from the nozzles to the recording medium. In electrostatic inkjet printers that perform printing,
When the plurality of nozzles include a drive nozzle that ejects ink and a non-drive nozzle that does not eject ink, a first diaphragm that communicates with the drive nozzle and a second diaphragm that communicates with the non-drive nozzle The electrostatic force is applied to the second diaphragm for a predetermined time, and then the application of the electrostatic force to the first diaphragm is canceled while the electrostatic force is applied to the second diaphragm, and then the second diaphragm is applied. An electrostatic ink jet printer comprising: control means for controlling to reapply electrostatic force to the first diaphragm while applying the electrostatic force to the first diaphragm.

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