JP2002059541A - Driving method and driving apparatus for inkjet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for driving an electrostatic ink jet head capable of preventing deformation of an isolation wall between ink pressure chambers even when the isolation wall between ink pressure chambers is thinned by high density. . SOLUTION: Discharge nozzle 1 of ink jet head 1
In addition to the vibration plate 51 (3) of 1 (3), the vibration plate 51 (2) of the adjacent non-discharge nozzle 11 (2) also adsorbs to the individual electrode, and the discharge nozzle 11 ( 3)
To eject ink droplets. After that, the diaphragm 51
(2) Gently detach from the individual electrode side. Since the compliance of the ink pressure chamber 5 (2) on the non-ejection nozzle side is maintained so as to be small, it is possible to prevent the separation wall 8 (2) between the ejection nozzle and the non-ejection nozzle from being deformed due to ink pressure fluctuation. Can be blocked. Therefore, it is possible to prevent the ink ejection characteristics from deteriorating due to the deformation of the isolation wall, and it is possible to easily realize a printing operation with high definition and fine print quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic ink jet that ejects ink droplets by elastically displacing a diaphragm defining a part of an ink pressure chamber communicating with an ink nozzle by electrostatic force. The present invention relates to a head driving method. More specifically, the present invention relates to a method of driving an electrostatic ink jet head capable of preventing crosstalk of ink pressure between adjacent ink pressure chambers even when ink pressure chambers are arranged at high density.

[0002] The present invention also relates to an electrostatic ink jet head driving apparatus capable of preventing cross-talk of ink pressure between adjacent ink pressure chambers even when ink pressure chambers are arranged at high density. is there.

Further, the present invention is provided with a driving device for an electrostatic ink jet head capable of preventing crosstalk of ink pressure between adjacent ink pressure chambers even when ink pressure chambers are arranged at high density. Related to an inkjet printer.

[0004]

2. Description of the Related Art As disclosed in Japanese Patent Application Laid-Open No. 2-219351, for example, an electrostatic type ink jet head is provided with a common electrode formed on the bottom surface of an ink pressure chamber constituting an ink flow path. It has a diaphragm and an electrode plate as an individual electrode facing the diaphragm with a small gap therebetween. A drive voltage is applied between these opposing electrodes to apply an electrostatic force to bend the vibrating plate to change the volume in the ink pressure chamber. The recording is performed by discharging ink droplets from the ink nozzles.

[0005] In such an electrostatic ink jet head, it is necessary to arrange a large number of ink nozzles at high density in order to improve the quality of an output image. To do this,
Ink flow path with which each ink nozzle communicates, that is,
Each of the ink pressure chambers also needs to be arranged at a high density, and as a result, it is necessary to reduce the thickness of the partition wall separating the ink pressure chambers.

[0006]

Here, if the partition wall separating the ink pressure chambers becomes thinner, the partition walls may bend due to fluctuations in the internal pressure of the ink pressure chambers. That is, as shown in FIG. 13A, the vibration plate 23 (3) of the ink pressure chamber 22 (3) to which the driving ink nozzle 21 (3) for discharging the ink droplet communicates is connected to the individual electrode 25.
When the ink is adsorbed to (3), there is a possibility that the separation walls 24 (2) and 24 (3) may be bent due to the change in the internal pressure of the ink pressure chamber 22 (3).

Similarly, as shown in FIG. 13 (b), the vibrating body 23 (3) is connected to the individual electrodes 25 during ink ejection.
When the ink pressure chamber 22 is released from (3),
The isolation wall 24 (2), 24 due to the internal pressure fluctuation of (3)
(3) may be bent.

[0008] If the separation wall is bent during ink ejection,
Pressure loss may occur in the ink pressure chamber 22 (3), and ink droplets of an appropriate amount or particle diameter may not be ejected from the driving ink nozzle 21 (3).

On the side of the non-drive ink nozzles 21 (2) and 21 (4) adjacent to the drive ink nozzle 21 (3), the separating walls 24 (2) and 24 (3) may be bent. As a result, the ink pressure chamber 2 on the non-driven ink nozzle side
Internal pressure fluctuations occur in 2 (2) and 22 (4), and in some cases, a small amount of ink droplets may be unnecessarily ejected.

Further, as described above, the partition wall 24 (2),
Since the pressure fluctuation leaks to the adjacent ink pressure chamber via 24 (3), in other words, crosstalk of pressure occurs, one ink nozzle drives adjacent ink nozzles at the same time. If not, the pressure fluctuation state generated in the ink pressure chamber will be different. As a result, the ink ejection characteristics (ink ejection speed and ink ejection amount) of one ink nozzle may fluctuate in accordance with the driving state of the adjacent ink nozzle, which may cause a decrease in print quality.

A method for avoiding such an adverse effect is as follows.
For example, JP-A-5-69544 and JP-A-7-1703
No. 9 discloses this. In the method disclosed in these publications, among the ink nozzles arranged in a line, even-numbered ink nozzles and odd-numbered ink nozzles arranged adjacent thereto eject ink droplets from the nozzles. These ejection times are shifted back and forth by using a delay circuit.

However, when such a method is adopted, a new disadvantage arises in that the driving circuit of the ink jet head is complicated and the cost is increased. Further, there is a new problem that the time required for printing becomes long.

In addition, the ink ejection characteristics may be deteriorated due to the crosstalk of the pressure in the ink pressure chamber even if the nozzles are not adjacent nozzles. That is, since the ink pressure chambers of the respective ink nozzles are generally communicated via the common ink chamber, the crosstalk of the pressure via the common ink chamber deteriorates the ink ejection characteristics of the non-adjacent ink nozzles. Normal and stable ejection of ink droplets may not be expected.

SUMMARY OF THE INVENTION 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, thereby preventing pressure crosstalk between ink pressure chambers even when the density is increased. It is another object of the present invention to provide a method and a device for driving an electrostatic inkjet head, which can easily ensure high-definition and precise printing quality.

Another object of the present invention is to make it possible to perform an ink discharge operation without bending a partition wall between ink pressure chambers without complicating a drive circuit of an ink jet head and lowering a printing speed. Accordingly, the present invention proposes a driving method and a driving apparatus for an electrostatic ink jet head which can prevent pressure crosstalk between ink pressure chambers even if the density is increased, and can easily secure high-definition and precise printing quality. is there.

Further, an object of the present invention is to prevent pressure crosstalk between ink pressure chambers communicating with each ink nozzle when a large number of ink nozzles are arranged in a line, thereby achieving high definition. An object of the present invention is to propose a driving method and a driving apparatus for an electrostatic ink jet head which can easily secure a fine print quality.

In addition, another object of the present invention is to propose an ink jet printer equipped with a driving device for an electrostatic ink jet head having such a novel configuration.

[0018]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention communicates with at least a first ink pressure chamber and a second ink pressure chamber partitioned by a partition wall, and each ink pressure chamber. First and second ink nozzles, first and second diaphragms that are elastically displaceable and form part of the walls of the first and second ink pressure chambers, and a first diaphragm facing each diaphragm. And a second individual electrode, wherein a drive voltage is applied between the first diaphragm and the first individual electrode to elastically displace the first diaphragm, thereby causing ink droplets to be discharged from the first ink nozzle. A method of driving an electrostatic ink jet head for discharging, wherein a step of attracting the second diaphragm to a side of the second individual electrode and bringing the second diaphragm into a state of being attracted to the individual electrode; The first diaphragm is elastically displaced and A discharge step of discharging the ink droplets from the first ink nozzle, characterized in that it comprises a.

In the method of 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 with the first ink nozzle. The second diaphragm in the two-ink pressure chamber is attracted to the second individual electrode. Therefore, the elastic displacement of the second diaphragm is restrained, the rigidity thereof is kept high, and the compliance of the second ink pressure chamber is set to be small. As a result, the bending of the partition wall separating the second ink pressure chamber and the first ink pressure chamber on the driving side is prevented, and crosstalk of the pressure via the partition wall is prevented or suppressed.

This will be described. The thickness of the diaphragm is the separating wall that separates the pressure chambers (for example, the thickness is 15 μm).
Alternatively, it is thinner than the thickness of the nozzle plate (for example, 77 μm), for example, 0.8 μm. When pressure is applied to the ink in the pressure chamber of the ejection nozzle, the pressure propagates to the isolation wall → the ink in the pressure chamber of the non-ejection nozzle → the diaphragm and the nozzle plate.

Here, when the diaphragm on the non-ejection nozzle side is not in contact with the electrode and is in a free state, the diaphragm thinner than the nozzle plate bends. For this reason, since the pressure propagation from the discharge nozzle is not interrupted, the isolation wall also bends. Therefore, the ink in the pressure chamber on the side of the discharge nozzle does not discharge the ink from the nozzle, but acts to deflect the isolation wall.

On the other hand, when the diaphragm is in contact with the electrode,
The pressure propagation from the discharge nozzle side propagates to the diaphragm via the isolation wall, but since the diaphragm does not bend, the isolation wall does not eventually bend. Therefore, no pressure propagation occurs. Therefore, crosstalk from the ejection nozzle to the non-ejection nozzle does not occur.

Here, typically, the driving method of the present invention comprises a step of attracting the first diaphragm to the first individual electrode and bringing the first diaphragm into a state of being attracted to the individual electrode. And the step of attracting the first diaphragm and the step of attracting the second diaphragm are performed simultaneously.

After the discharging step, the second diaphragm is released from a state in which the second diaphragm is attracted to the second individual electrode.
A step of detaching the diaphragm, wherein the step of detaching the second diaphragm elastically displaces the second diaphragm at a speed at which ink droplets are not ejected from the second ink nozzle. I have.

Next, the method for driving an electrostatic ink jet head according to the present invention includes the step of adsorbing the second diaphragm, the step of discharging, the step of adsorbing and holding the second diaphragm, And a suction state return step of returning the first diaphragm to a state in which the first diaphragm is attracted to the first individual electrode after the discharging step. The suction holding step is performed after the discharge step.
The method is characterized by including a step of maintaining a suction state of the diaphragm.

In the method for driving an electrostatic ink jet head according to the present invention, a state is formed in which both the vibrating plates of the ink nozzles on the driving side and the non-driving side are attracted to the individual electrodes. Ink droplets are ejected from one ink nozzle. Therefore, at the time of ejecting ink droplets, the elastic displacement of the second diaphragm in the non-drive side ink nozzle is restrained and its rigidity is kept high, and the compliance of the second ink pressure chamber is reduced. As a result, the bending of the partition wall separating the second ink pressure chamber and the first ink pressure chamber on the driving side is prevented, and crosstalk of the pressure via the partition wall is prevented or suppressed.

Here, in the driving method of the electrostatic ink jet head according to the present invention, the first and second diaphragms are respectively moved to the first and second diaphragms after the suction state returning step.
A detaching step of releasing from an adsorption state with respect to the individual electrode, wherein in the detaching step, the first and second ink nozzles are discharged at a speed such that ink droplets are not ejected from the first and second ink nozzles
And the second diaphragm is elastically displaced. That is, when a series of printing operations is completed, each diaphragm is returned to the initial state.

Typically, the potential difference between the second diaphragm and the second individual electrode is kept constant during the period from the step of adsorbing the first and second diaphragms to just before the step of releasing the diaphragm. The second diaphragm can be held in a suction state with respect to the second individual electrode. In addition, the first and second diaphragms are maintained at a constant potential during a period from the step of adsorbing the first and second diaphragms to immediately before the step of separating, and the first and second diaphragms are driven with respect to the first individual electrodes in the discharging step. A voltage may be applied. In this case, after the detaching step, a residual charge between the first diaphragm and the first individual electrode and a residual charge between the second diaphragm and the second individual electrode are removed. It is desirable to add a residual charge removing step.

Here, in order to prevent the ejection of the ink droplets from the ink nozzles that are not arranged adjacently from becoming unstable, the non-ejection nozzles other than the adjacent second ink nozzle are also required to be discharged. It is desirable to control the drive in the same manner as the second ink nozzle.

Next, the present invention relates to a driving device for an electrostatic ink jet head. The driving device for an electrostatic ink jet head according to the present invention controls the ejection operation of ink droplets by the driving method of the present invention described above. A driving device for an electrostatic ink jet head, comprising: switching means for switching the potentials of the first and second diaphragms and the potentials of the first and second individual electrodes; and driving pulse generating means for generating a driving pulse. And control means for controlling the driving of the first and second ink nozzles by switching the driving pulse generated by the driving pulse generating means by the switching means.

Next, the present invention provides an electrostatic ink jet head having a plurality of ink nozzles, a moving means for moving the electrostatic ink jet head relative to a recording medium, and a moving means for moving the electrostatic ink jet head relative to a recording medium. A driving unit for driving the electrostatic ink jet head in synchronization with the vibration plate by ejecting ink droplets from each of the ink nozzles by applying a driving voltage between the individual electrode and the vibration plate disposed to face each other. The present invention relates to an ink-jet printer which is performed by elastically deforming an image by an electrostatic force. The driving means of the inkjet printer of the present invention, the vibration plate of the non-ejection nozzles in which the ink droplets contained in the ink nozzles are not ejected are attracted to the corresponding individual electrodes, and in this state, the It is characterized in that the vibration plate of the discharge nozzle from which the ink droplets contained in the ink nozzles are discharged is elastically displaced to discharge the ink droplets from the discharge nozzles.

Here, a state is formed in which each of the diaphragms of the discharge nozzle and the non-discharge nozzle is attracted to the corresponding individual electrode, and the respective diaphragms of the discharge nozzle are elastically displaced from the state of being attracted to the individual electrode. Then, each nozzle can be driven so that the ink droplet is ejected from the ejection nozzle.

Further, the ink jet head of the present invention comprises:
A nozzle hole, an ink pressure chamber communicating with the nozzle hole,
A diaphragm that bends so that ink in the ink pressure chamber is ejected from the nozzle holes to the outside, and a fixing member to which the diaphragm is fixed by externally applying a force to the diaphragm. In the ink jet head, when the diaphragm discharges ink from the nozzle holes,
When the ink in the ink pressure chamber is bent so as to be discharged from the nozzle to the outside, and is not discharged from the nozzle hole, the ink is fixed to the fixing member.

Further, in the method of driving an ink jet head according to the present invention, there is provided a nozzle hole, an ink pressure chamber communicating with the nozzle hole, and a vibrating plate which bends to discharge ink in the ink pressure chamber from the nozzle hole to the outside. And a fixing member to which the vibration plate is fixed by applying a force to the vibration plate from the outside, and a method for driving an ink jet head, wherein when discharging ink from the nozzle holes,
The vibration plate is bent so that the ink in the ink pressure chamber is discharged from the nozzle to the outside, and the vibration plate is fixed to the fixing member when the ink is not discharged from the nozzle hole.

According to these configurations, the present invention can be applied to the vibration of the diaphragm by the piezoelectric vibrator represented by piezo.

[0036]

According to the present invention, the influence of the pressure chamber on the non-ejection nozzle side can be prevented by attaching and fixing the diaphragm of the non-ejection nozzle to the individual electrode side. When printing between adjacent nozzles, there is no need to shift the time.

Here, the ink system on the non-ejection nozzle side is as follows.
If there is a weak part somewhere, the pressure will concentrate there and the ink will move, so the separating wall will also move, but by attaching the diaphragm which is the weakest part to the individual electrode side, It becomes harder and the ink system becomes harder as a whole. Therefore, the isolation wall does not move.

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, a method for driving an electrostatic ink jet head to which the present invention is applied, a driving device for realizing the driving method, and an electrostatic ink jet head according to the present invention will be described below. An embodiment of an ink jet printer equipped with the above driving device will be described.

(Electrostatic Ink Jet Head) First, a configuration of an electrostatic ink jet head to which the driving method of the present invention can be applied will be described with reference to FIGS. FIG. 1 is a cross-sectional view of the electrostatic ink jet head of the present embodiment, and FIG.
Is a plan view thereof, and FIG. 3 is a longitudinal sectional view thereof.

As shown in these figures, the electrostatic ink-jet head 1 of this embodiment sandwiches a silicon substrate 2, sandwiches a nozzle plate 3 also made of silicon on the upper side, and borosilicate whose thermal expansion coefficient is close to that of silicon on the lower side. It has a three-layer structure in which the glass substrates 4 are laminated.

The central silicon substrate 2 is subjected to anisotropic etching with KOH (aqueous solution) from the surface having a crystal orientation of (110) plane, thereby forming five independent elongated ink pressure chambers 5 (1) to 5 (1). 5 (5), one common ink chamber 6, and this common ink chamber 6
Grooves functioning as ink supply ports 7 communicating with (1) to (5) are formed. These grooves are closed by the nozzle plate 3, and the portions 5, 6, and 7 are defined. Each ink pressure chamber 5 (1) to 5 (5)
Are separated by separating walls 8 (1) to 8 (4), respectively.

In order to communicate with the ink supply port 7,
An ink inlet 12 is formed in a portion that defines the lower surface of the common ink chamber 6. Accordingly, ink is supplied from an external ink tank (not shown) to the common ink chamber 6 through the ink intake port 12, and further from this, passes through each ink supply port 7, and becomes independent of each ink pressure chamber 5.
(1) to (5).

Each of the ink pressure chambers 5 is provided in the nozzle plate 3.
The ink nozzles 11 (1) to 11 (5) are formed at positions corresponding to the tip side portions of (1) to 5 (5), that is, at positions opposite to the ink supply port 7. These communicate with the corresponding pressure chambers 5 (1) to 5 (5).

Independent ink pressure chambers 5 (1) to 5 (5)
The bottom surface of (5) is thin, and the diaphragms 51 (1) to 51 (1) to 5 (5) are elastically displaceable in an out-of-plane direction, that is, vertically in FIG.
It is set to function as 1 (5) (only the diaphragm 51 (1) is shown in the figure).

Next, in the glass substrate 4 located below the silicon substrate 2, each of the pressure chambers 5 (1) to 5 (5) to 5
Each of the diaphragms 51 (1) to 51 defining the bottom surface of (5)
In the position facing (5), a shallowly etched recess 9
(1) to 9 (5) are formed respectively. Each recess 9
Diaphragms 51 (1) to 51 (51) are provided on the bottom surfaces of (1) to 9 (5).
Individual electrodes 10 (1) to 10 respectively corresponding to (5)
(5) is formed. Each individual electrode 10 (1) to 10
(5) is a segment electrode 1 made of ITO, respectively.
0a and a terminal portion 10b.

By bonding the glass substrate 4 to the silicon substrate 2, the vibration plates 51 (1) to 51 (5) defining the bottom surface of each ink pressure chamber 5 and the segment electrodes 10 a of the corresponding individual electrodes are formed. Are opposed to each other with a very narrow gap G therebetween. This 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.

A common electrode terminal 220 is formed on the surface of the silicon substrate 2 by depositing a noble metal thin film such as platinum on the surface. A common electrode terminal 220 is provided between the common electrode terminal 220 and each of the individual electrodes 10 (1) to 10 (5). The driving voltage pulse is applied by the driving voltage applying unit 210. Since the silicon substrate 2 is conductive,
Each of the vibration plates 51 (1) to 51 (5) functions as a common electrode.

Each of the vibration plates 51 (1) to 51 (5) is driven by an electrostatic force generated by applying a drive voltage between the individual electrodes 10 (1) to 10 (5). 5
When 1 (5) is attracted to the individual electrode side, diaphragm 51 (1)
51 to (5) are elastically displaced and bent toward the segment electrode 10a, and are attracted to the surface of the segment electrode 10a.
As a result, the volumes of the ink pressure chambers 5 (1) to 5 (5) are increased, and the ink pressure chambers 5 (1) to 5 (5)
The ink is supplied to (5).

When the electrostatic attraction force is released, the vibration plate 51
(1) to 51 (5) are separated from the surface of the segment electrode 10a by the elastic force and return to the initial state, and the volumes of the ink pressure chambers 5 (1) to 5 (5) are rapidly reduced. At this time, due to the ink pressure vibration generated in the ink pressure chamber,
A part of the ink in the ink pressure chamber is
The ink droplets are ejected from the ink nozzles 11 communicating with (1) to (5).

Here, when an ink jet head having an ink nozzle density of 180 to 360 dpi is formed, the distance G between the individual electrode and the diaphragm is generally about 1400 to 1900 angstroms. The electrical air gap of the interval G in the above is about 1700 to 2200 angstroms.

Note that the ink jet head 1 of this embodiment is
The face-ejection type in which ink droplets are ejected from nozzle holes provided on the upper surface of the substrate 3, but the edge-ejection type in which ink droplets are ejected from nozzle holes provided at the end of the substrate 3 are driven by the present invention. Of course, the method is equally applicable.

(Driving Method) FIGS. 4A and 4B are explanatory diagrams showing a driving method of the ink jet head 1 of this embodiment, and FIG. 5 is a schematic flowchart showing a driving procedure.
The outline of the driving method of the inkjet head 1 will be described with reference to these drawings.

First, in FIG. 4, it is assumed that the ink nozzle from which ink droplets are ejected (referred to as "ejection nozzle") is the ink nozzle 11 (3). In addition, this discharge nozzle 1
Ink nozzles 11 adjacent to both sides of 1 (3)
It is assumed that (2) and 11 (4) are ink nozzles that do not discharge ink droplets (referred to as “non-discharge nozzles”).

When print data is transmitted and printing is started (step ST51 in FIG. 5), each ink nozzle 11
Vibration plates 51 (2) to 51 in (2) to 11 (4)
A driving voltage pulse is applied between (4) and the individual electrodes 10 (2) to 10 (4), and the respective vibration plates 51 (2) to 51 (4)
Is simultaneously adsorbed to the individual electrodes 10 (2) to 10 (4).
Thereby, each diaphragm 51 as shown in FIG.
The suction states of (2) to 51 (4) are formed (step ST53 in FIG. 5: suction step of the first and second diaphragms).

Next, the non-ejection nozzles 11 (2), 11
The diaphragms 51 (2) and 51 (4) of (4) are
(2) In a state where the suction is performed at 10 (4) (steps ST54 and ST55 in FIG. 5: a step of holding and holding the second diaphragm).
The vibration plate 51 (3) of the discharge nozzle 11 (3) is
Quickly leave 1 (3). As a result, FIG.
As shown in the figure, the diaphragm 51 (3) elastically returns,
The volume of the ink pressure chamber 5 (3) decreases rapidly, and ink droplets are ejected from the ejection nozzle 11 (3) (steps ST54 and ST56 in FIG. 5: ejection process).

Thereafter, the non-ejection nozzles 11 (2) and 11 (2)
The diaphragms 51 (2) and 51 (4) of (4) are
(2) Detach from 10 (4) (Step S in FIG. 5)
T57: Separation step of diaphragm). The detachment speed is set at a low speed at which no ink droplets are ejected from the non-ejection nozzles 11 (2) and 11 (4). Through the above steps,
One ejection operation of the ink droplet ends. Such an ink droplet ejection operation is repeated by the amount corresponding to the print data, and the printing operation is completed (steps ST52 and ST58 in FIG. 5).

FIG. 6 shows that in order to realize the above operation,
An example of a pulse waveform of a drive voltage applied between a diaphragm serving as a common electrode and an individual electrode is shown. Such a drive voltage pulse is generated by the drive voltage application unit 210 of FIG. 2, specifically, the head driver IC 109 (see FIG. 9) described later.

First, FIG. 6 (f) shows a basic voltage pulse waveform of the drive voltage Vp. An ink droplet ejection operation is performed once for each pulse of the basic voltage waveform. For example, one discharge cycle is performed between time t1 and t6 and between time t6 and t11. These first and second ejection cycles are repeatedly executed. In this basic voltage waveform pulse, its rise (from time t1 to t2)
) Is sharp, and its fall (from time t4 to time t4)
5) is a gentle slope.

The three ink nozzles 11 (2) shown in FIG.
To explain by taking as an example, the voltage applied to each of the vibration plates 51 (2) to 51 (4) functioning as a common electrode is, as shown in FIG. At time points t1 to t6, a voltage pulse having the same shape as the basic voltage waveform is formed, and at time points t6 to t6, which is the next second ejection cycle.
At t11, it is held at the ground potential GND.

As shown in FIG. 6B, the individual electrode potential of the discharge nozzle 11 (3), that is, the potential of the vibration plate 51 (3) is changed from the time point t1 to the time point t3 in the first discharge cycle. During this period, the potential is maintained at the ground potential, sharply rises to the common electrode potential at time t3, and thereafter, is maintained at the same potential as the common electrode potential until time t6. In the second discharge cycle, the potential rises sharply at time t6 and is kept at a high potential until time t8. At this time, the potential is sharply dropped to the ground potential. Thereafter, the potential is kept at the ground potential until time t11. Is done.

As a result, the potential difference between the diaphragm 51 (3) and the individual electrode 10 (3) in the discharge nozzle 11 (3) is, as shown in FIG. 6C, between the times t1 and t3 in the first discharge cycle. During the period from time t6 to time t8 in the second ejection cycle, the negative potential difference state is maintained. In other words, an electrostatic force is generated to attract the diaphragm to the individual electrodes. At other times, no potential difference is maintained and no electrostatic force is generated.

Therefore, in the first discharge cycle, the time t
From 1, the diaphragm 51 (3) is rapidly attracted toward the individual electrode 10 (3) and is attracted there (attraction step of the first diaphragm), and at time t <b> 3, the diaphragm 51 (3)
Suddenly detaches from the individual electrode 10 (3) and returns elastically (ejection step). By the operation of the vibration plate, the ink droplets are ejected from the ejection nozzle 11 (3) at a time point after a predetermined time from the time point t3. Similarly, in the second discharge cycle, the diaphragm 51 (3) suddenly changes the individual electrode 1 from time t6.
The diaphragm 51 (3) suddenly detaches from the individual electrode 10 (3) at time t8 when it is adsorbed toward 0 (3) and becomes adsorbed there (first diaphragm adsorbing step). It returns elastically (ejection process). By the operation of this diaphragm,
The ink droplets are ejected from the ejection nozzle 11 (3) at a point in time after a predetermined time from the point in time t8.

The reason why the polarity of the potential difference between the individual electrode and the common electrode is reversed in the first discharge cycle and the second discharge cycle is that the polarity of the potential difference is always the same if these electrodes are always the same. Charge accumulates on the diaphragm, the diaphragm adheres to the individual electrodes, and even if the voltage applied to the diaphragm is released, the flexure of the diaphragm does not return, and a desired discharge may not be obtained. is there.

On the other hand, in the non-discharge nozzle 11 (2) adjacent to the discharge nozzle 11 (3), in the first discharge cycle, as shown in FIG. Held at ground potential, and in the second ejection cycle,
The potential state is the same as the basic drive voltage pulse waveform. That is, the first electrode 51 in the diaphragm 51 (2) serving as the common electrode.
And the potential state in the second ejection cycle is maintained in the opposite state.

As a result, the potential difference between the diaphragm 51 (2) and the individual electrode 10 (2) in the non-ejection nozzle 11 (2) is, as shown in FIG. In the discharge cycle, the state becomes similar to the basic voltage waveform.

Accordingly, the diaphragm 51 (2) is attracted to the individual electrode 10 (2) from the time point t1 in the first discharge cycle (the step of attracting the second diaphragm), and is held in the attracted state until the time point t4. (Step of holding and holding the second diaphragm). Thereafter, the potential difference gradually decreases. That is, discharge between both electrodes is gradually performed. For this reason, detachment of the diaphragm 51 (2) starts at a position between the time point t4 and the time point t5,
It returns elastically at a slower speed than during adsorption (release step).
Similarly, the diaphragm 51 (2) is attracted to the individual electrode 10 (2) from the time point t6 in the second discharge cycle (second time).
The diaphragm is held in the sucked state until time t9 (suction holding step of the second diaphragm). Thereafter, the potential difference gradually decreases. That is, discharge between both electrodes is gradually performed. For this reason, the detachment of the diaphragm 51 (2) starts at a position between the time point t9 and the time point t10, and the diaphragm 51 (2) elastically returns at a lower speed than at the time of suction (separation step).

As described above, on the non-discharge nozzle 11 (2) side, the suction operation of the vibration plate 51 (2) is synchronized with the suction operation of the vibration plate 51 (3) on the discharge nozzle 11 (3) side. As a result, as shown in FIG. 4A, all the nozzles are attracted to the individual electrodes. Next, in this suction state, ink droplets are ejected from the ejection nozzle 11 (3). Thereafter, the diaphragm 5 on the non-ejection nozzle 11 (2) side
1 (2) is detached from the individual electrode 10 (2) and gently elastically returns. By adjusting the elastic return speed of the diaphragm, it is possible to completely prevent the ink droplets from being ejected from the non-ejection nozzle 11 (2) when the diaphragm 51 (2) elastically restores. The non-ejection nozzle 11 (4) operates similarly to the non-ejection nozzle 11 (2).

Here, specific values for the elastic return speed and the like will be described for reference. Nozzle density is typical 18
In the case of 0 to 360 dpi, as described above, the gap G between the diaphragm and the individual electrode is in the range of about 1400 to 1900 angstroms in the current design. This gap G
Is a typical value of 1750 Å, the time required for elastic return is about 1 μsec, and the average elastic return speed of the diaphragm is about 0.175 m / s. On the other hand, the electric field intensity generated between the diaphragm and the individual electrode when the first and second diaphragms are attracted and detached is about 1.1 to 1.3 MV / cm, and each diaphragm is attracted to the individual electrode. In this state, the electric field strength is about 2.2 to 3.3 MV / cm.

As described above, in the method of driving the electrostatic ink jet head of this embodiment, the discharge nozzle 11 (3)
The non-discharge nozzles 11 (2) and 11 (4) adjacent to the individual electrodes 10 (2) and 51 (4)
(2) By holding by suction at 10 (4), its rigidity is maintained in a high state. As a result, the compliance of the ink pressure chambers 5 (2) and 5 (4) of the non-ejection nozzle can be reduced.

Therefore, the ink pressure chambers 5 (3) on the ejection nozzle side with small compliance and the ink pressure chambers 5 (2), 5 on the non-ejection nozzle side with small compliance are also used.
Separation walls 8 (2) and 8 (3) separating (4)
It is possible to prevent or suppress the deflection due to the pressure fluctuation of the ink pressure chamber on the ejection nozzle side.

Therefore, regardless of whether the adjacent ink nozzles are driven or not, cross talk of the pressure in the ink pressure chamber can be prevented or suppressed. Therefore, it is possible to prevent or suppress the deterioration of the ink ejection characteristics of each ink nozzle due to the above. For this reason, if the driving method of this example is adopted, high-definition and precise printing quality can be easily secured.

(Modification of Driving Method) The driving voltage waveform shown in FIG. 6 is an example for realizing the driving method of the present invention, and it is possible to adopt a different driving form.

For example, in the above-described driving method, the vibrating plates 51 (2) to 51 (4) of the ejection nozzles and the non-ejection nozzles are connected to the individual electrodes 10 (2) to 51 (4) every ejection cycle of the ink droplet. 10 (4), the diaphragms 51 (2) to 51 (2) to 51 (2) to 51 (2) are not used until a series of print data is printed.
(4) is held in an adsorbed state with respect to the individual electrodes 10 (2) to 10 (4), and only the vibration plate on the ejection nozzle side is elastically displaced when ejecting ink droplets to temporarily separate from the individual electrode. Alternatively, a driving method for returning the ink droplets to the suction state after the ejection of the ink droplets may be employed.

FIG. 7 is a schematic flowchart showing such a driving method. With reference to FIGS. 4 and 7, a driving method of the inkjet head 1 of the present embodiment will be described. Also in the following description, it is assumed that the ink nozzle (ejection nozzle) from which the ink droplet is ejected is the ink nozzle 11 (3). It is also assumed that the ink nozzles 11 (2) and 11 (4) adjacent to both sides of the discharge nozzle 11 (3) are ink nozzles (non-discharge nozzles) from which ink droplets are not discharged.

When the print data is transmitted, printing starts (step ST70 in FIG. 7). When printing is started, first, the vibration plates 51 (2) to 51 (4) and the individual electrodes 10 (2) to 1 (1) in each of the ink nozzles 11 (2) to 11 (4).
Voltage is applied during 0 (4) to generate a potential difference, and each of the vibration plates 51 (2) to 51 (4) is attracted to the individual electrodes 10 (2) to 10 (4) to be in an attracted state ( Step ST71 in FIG. 7: first and second diaphragm adsorbing steps). Thereafter, by maintaining the potential difference between each of the diaphragms 51 (2) to 51 (4) and the individual electrode 10 (2) to 10 (4) as it is, the suction holding state of each diaphragm is formed ( Step ST72 of FIG. 7: suction holding step).

In order to maintain the suction state, the diaphragm 5
1 (2) to 51 (4) and individual electrodes 10 (2) to 10
The voltage applied during (4) may be lower than the voltage applied when forming the adsorption state. Once the adsorption state is secured, the voltage required to hold the adsorption is
This is because the electrostatic pressure is large even if it is lowered.

Next, the non-ejection nozzles 11 (2), 11
In the case of (4), these diaphragms 51 (2), 51
The state where (4) is adsorbed on the individual electrodes 10 (2) and 10 (4) is maintained (steps ST74 and ST7 in FIG. 7).
2: adsorption holding step). In contrast, the discharge nozzle 10
In the case of (3), the diaphragm 51 (3) is connected to the individual electrode 1
Quickly leave 1 (3). In order to quickly separate the diaphragm 51 (3) from the individual electrode 11 (3), a driving voltage is applied to the individual electrode 10 (3) to make the same potential as that of the diaphragm 51 (3). Discharge charge quickly. As a result, as shown in FIG.
1 (3) returns elastically, the volume of the ink pressure chamber 5 (3) decreases rapidly, and ink droplets are ejected from the ejection nozzle 11 (3) (step ST75 in FIG. 7: ejection step).

After the ejection of the ink droplets from the ejection nozzle 11 (3), the vibration plate 51 (3) is again
(3), the state is attracted to the individual electrode 10 (3) (step ST76 in FIG. 7: step of returning the first diaphragm to the attracted state), and this attracted state is continued (step ST72 in FIG. 7). ). As a result, the state shown in FIG. 4A is formed again.

Through the above steps, one ejection operation of the ink droplet is completed. When the ink droplets are repeatedly ejected, the above steps are repeated. After the end of the series of ejection operations, the vibration plates 51 (2) to 51 (4) in the suction holding state are individually connected to the individual electrodes 10 (2) to 10 (4) in the nozzles 11 (2) to 11 (4). ) (Fig. 7)
Steps ST73 and ST77: diaphragm detachment step). The separation speed of the vibration plate is set at a low speed at which ink droplets are not ejected from the nozzles 11 (2) to 11 (4).
Thus, the printing operation of the transmitted print data is completed (step ST78 in FIG. 7).

FIG. 8 shows that in order to realize the above operation,
An example of a pulse waveform of a drive voltage applied between a diaphragm serving as a common electrode and an individual electrode is shown. Such a drive voltage pulse is generated by the drive voltage pulse applying means 21 of FIG. 2, specifically, the head driver IC of the drive control circuit 100 shown in FIG.

In FIG. 8, a period from time t1 to time t7 is a period during which a series of printing operations is performed. In this period, two ejections of ink droplets are performed in the illustrated example. The subsequent period from time t8 to t10 is a period during which the potential inversion control without discharging the ink droplets is performed. This potential inversion control will be described later.

First, FIG. 8B shows a basic voltage pulse waveform Vp of the drive voltage. An ink droplet ejection operation is performed once for each pulse of the basic voltage pulse waveform Vp. For example, one discharge cycle is performed between the time points t2 and t4 and between the time points t4 and t6. An ink droplet is ejected from an ink nozzle due to a sharp change in the voltage waveform at each of the time points t3 and t5 of the basic voltage pulse waveform Vp. These first and second ejection 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 (time
The change up to the ground potential GND starting at t4 and t6) has a gentler gradient than the rise.

Vh shown in FIG. 8A is a power supply potential of a high withstand voltage system (for example, 25 to 36 V). Vh is the time
The slope of the rise from t1 and the slope of the fall from time t7 have the same change amount, and this change amount is equal to the power supply potential Vh.
The change in the potential difference between the voltage and the ground potential GND has a gentle gradient so that ink droplets are not ejected even when they act between the diaphragm and the individual electrodes.

Here, the three ink nozzles 1 shown in FIG.
1 (2) to 11 (4) will be described as an example. The voltage applied to each of the diaphragms 51 (2) to 51 (4) functioning as a common electrode is, as shown in FIG. From time t1 to time t7, the voltage has the same shape as the power supply potential Vh of the high breakdown voltage system. After time t2, diaphragms 51 (2) -51
(4) is adsorbed and held by the individual electrodes 10 (2) to 10 (4) and enters a standby state. Further, from time t8 to time t10 when the potential inversion control is performed, the potential is maintained at the ground potential GND.

As shown in FIG. 8 (d), the individual electrode potential of the discharge nozzle 11 (3), that is, the potential of the diaphragm 51 (3), is basic during the discharge cycle from time t1 to time t7. The voltage has the same shape as the voltage pulse waveform Vp. In the first ejection cycle, at time t3, the potential is sharply raised to the power supply potential Vh, which is the common electrode potential, and thereafter, the same potential as the common electrode potential is maintained until time t4. After the time point t4, it is kept at the ground potential GND again. In the second ejection cycle,
At time t5, the potential rises steeply and is kept at a high potential until time t6. After time t6, the ground potential GND is again applied.
Is held.

As a result, the potential difference between the diaphragm 51 (3) and the individual electrode 10 (3) in the discharge nozzle 11 (3) is, as shown in FIG.
The positive potential difference state between 2 and t3 is maintained, and between the time points t3 and t4 as the first ejection cycle and the time points t5 and t6 in the second ejection cycle, there is no potential difference state. . In other words, no static electricity is generated to attract the diaphragm to the individual electrodes. At times other than these, the positive potential difference state is maintained, and static electricity attracting the diaphragm and the individual electrodes acts thereon, thereby attracting and holding the diaphragm to the individual electrodes.

Therefore, in the first discharge cycle, the time t
The diaphragm 51 (3) suddenly separates from the individual electrode 10 (3) from 3 and elastically returns, and the operation of the diaphragm causes the discharge nozzle 11 (3) to return from the discharge nozzle 11 (3) at a time after a predetermined time from the time t3. Ink droplets are ejected. Thereafter, at time t4, the diaphragm 51 (3) is in a state of being sucked by the individual electrode 10 (3), and returns to the suction holding state (standby state). Similarly, in the second discharge cycle, the diaphragm 51 starts from time t5.
(3) suddenly separates from the individual electrode 10 (3) and resiliently returns, and the operation of the diaphragm causes the discharge nozzle 11
From (3), ink droplets are ejected at a point in time after a predetermined time from point in time t5. Thereafter, at time t6, the diaphragm 51
(3) is in a state of being adsorbed to the individual electrode 10 (3),
Return to the standby state.

On the other hand, in the non-discharge nozzle 11 (2) adjacent to the discharge nozzle 11 (3), the individual electrode potential is maintained at the level shown in FIG. 8 throughout the first and second discharge cycles.
As shown in (f), it is kept at the ground potential.

As a result, the potential difference between the diaphragm 51 (2) and the individual electrode 10 (2) in the non-ejection nozzle 11 (2) is, as shown in FIG. 8 (g), the first ejection cycle and the second ejection cycle. In the discharge cycle of FIG.
The state is similar to h.

Therefore, the point in the first discharge cycle
The diaphragm 51 (2) is attracted to the individual electrode 10 (2) from t1, and is kept in the attracted state until time t7.

At the end of the standby state, after the time point t7,
The potential difference gradually decreases. That is, discharge between both electrodes is gradually performed. For this reason, the diaphragms 51 (2) to 51 (2) are located at positions before the potential difference disappears after time t7.
The separation of (4) starts, and elastic recovery is performed at a lower speed than at the time of adsorption.

FIG. 8H shows the displacement of the diaphragm 51 (3) at each point in the discharge nozzle 11 (3). FIG. 8 (i) shows the non-discharge nozzle 11
(2), diaphragm 51 (2), 51 in 11 (4)
The state of displacement at each point in (4) is shown. The vertical direction in these charts indicates the displacement of the diaphragm,
G indicates a gap between the diaphragm 51 and the individual electrodes 10 when no electric field is applied. The direction in which the distance between the diaphragm 51 and the individual electrode 10 is reduced is (-), and the direction in which the distance is increased is (+).
There is.

Here, the state of the discharge nozzle diaphragm 51 (3) shown in FIG. 8 (h) at each point will be described in comparison with each step of the flowchart shown in FIG. For reference, the required time in the case of a typical electrostatic inkjet head is shown in parentheses.

The period from t1 to t2 (about 2 μm to 1 m
s): The diaphragm 51 (3) of the discharge nozzle 11 (3) is at the time
The individual electrode 10 (3) is attracted to the individual electrode 10 (3) from time t1 to time t2 (the first diaphragm attracting step ST71).

Period from t2 to t3 (approximately 40 μs or more): After the diaphragm 51 (3) has been adsorbed,
It is held in a state of being attracted to the individual electrode 10 (3) (the first diaphragm attracting / holding step ST72).

The period from t3 to t4 (time from t3 to actual ejection of ink droplets: about 30 to 125 μs,
Time from actual ink droplet ejection to t4: about 10μ
s): At time t3, the diaphragm 51 (3) suddenly separates and returns, pressurizing the ink in the pressure chamber 5 (3),
At the time point of arrow h1, ink droplets are ejected from the ejection nozzle 11 (3) (ejection step ST74). Then, the diaphragm 51
(3) vibrates, and at the time when the amount of displacement of the diaphragm substantially coincides with the vibration cycle of the diaphragm (3) at the time of going to (-), the individual electrode 10 is set so that the potential difference between the electrodes is generated again.
The potential is applied to (3), and at time t4, the individual electrode 1
0 (3) (adsorption state return step S of first diaphragm)
T76).

The period from t4 to t5 (about 2 to 25 μm)
s): After that, the diaphragm 51 (3) keeps the individual electrode 10 (3) until the time t5 in preparation for the next ejection until the time t5.
The first diaphragm is held in a suction state (step ST72).

Time period from t5 to t7 (time from t5 to actual ejection of ink droplets: about 30 to 125 μs, time from actual ink droplet ejection to t6: about 10 μs, t6
To time t7: about 2 to 25 μs): In the discharge nozzle 11 (3), a similar cycle (time from the time t5 to the time t7) (from the discharge step ST75 to the diaphragm suction holding step through the diaphragm suction step ST76). In the cycle leading to ST72), the diaphragm 51 (3) is driven, and the arrow h2
The ink droplets are ejected at the time shown in (2) (when ejected twice or more, t5 to t7 are repeated).

The period from t7 to t8 (time from t7 until the diaphragm detaches and elastically returns to the original position: about 0.
2 ms to 1 ms): In the discharge nozzle 11 (3), the diaphragm 51 (3) gradually turns the individual electrode 10 (3) at time t7.
, And a series of printing control steps is ended. At this time, no ink droplet is ejected from the nozzle 11 (3) (the diaphragm detaching step ST77).

Next, in FIG. 8 (i), the diaphragms 51 (2), 51 (2) of the non-ejection nozzles 11 (2), 11 (4).
(4) shows the individual electrode 10 between the time point t1 and the time point t2.
(2) and 10 (4) are adsorbed respectively (diaphragm adsorption step ST71). The diaphragms 51 (2) and 51 (4) hold the individual electrodes 10 (2), 10 (
The state (4) is held in the state of being sucked, respectively (diaphragm suction holding step ST72).

These non-ejection nozzles 11 (2), 11
In (4), since the ink droplets are not ejected, even when the ejection nozzle 11 (3) is in the ejection process, the vibration plate 51
(2), 51 (4) are individual electrodes 10 (2), 10 (4)
The ink chambers 5
(2) The compliance of the flow path of 5 (4) is small. In the holding step, the compliance of these flow paths is small, so even in the discharge step of the discharge nozzle 11 (3), the separation walls 8 (1) to 8 (4) are deformed and the pressure of the discharge nozzle 11 (3) is changed. Since no pressure loss occurs in the chamber 5 (3), the discharge nozzle 11 (3)
There is no variation, and stable ejection of ink droplets becomes possible.

In the discharge nozzles 11 (2) and 11 (4),
At time t7, the diaphragms 51 (2) and 51 (4) gradually separate from the individual electrodes 10 (2) and 10 (4), respectively, and the standby state in the series of print control steps ends. At this time, no ink droplets are ejected from the nozzles 11 (2) and 11 (4) (vibrating plate detachment step ST77).

As described above, on the side of the non-ejection nozzle 11 (2), the diaphragm 51 (2) is adsorbed during the period of separation and adsorption of the diaphragm 51 (3) on the side of the ejection nozzle 11 (3). In the standby state shown in FIG. 4A, all the nozzles are held by the individual electrodes. Next, in this suction holding state, the discharge nozzle 11 (3)
Ejects ink droplets. At the end of the standby state, the diaphragm 51 (2) on the side of the non-ejection nozzle 11 (2) separates from the individual electrode 10 (2) and slowly returns to elasticity. By adjusting the elastic return speed of this diaphragm,
When the diaphragm 51 (2) returns elastically, the non-ejection nozzle 11
The ejection of ink droplets from (2) can be completely prevented.

The non-ejection nozzle 11 (4) operates similarly to the non-ejection nozzle 11 (2).

As described above, in the driving method of the electrostatic ink jet head of this embodiment, the discharge nozzle 11 (3)
The non-discharge nozzles 11 (2) and 11 (4) adjacent to the individual electrodes 1 (2) and 51 (4)
By holding by suction at 0 (2) and 10 (4), its rigidity is kept high. As a result, the compliance of the ink pressure chambers 5 (2) and 5 (4) of the non-ejection nozzle can be reduced.

Therefore, the ink pressure chamber 5 (3) on the ejection nozzle side with low compliance and the ink pressure chamber 5 (2) on the non-ejection nozzle side with low compliance,
Separation walls 8 (2), 8 (4) separating 5 (4)
However, it is possible to prevent or suppress warping due to pressure fluctuation in the ink pressure chamber on the ejection nozzle side.

Therefore, regardless of whether the adjacent ink nozzles are driven or not, the crosstalk of the pressure in the ink pressure chamber can be prevented or suppressed. Therefore, it is possible to prevent or suppress the deterioration of the ink ejection characteristics of each ink nozzle due to the above. For this reason, if the driving method of this example is adopted, high-definition and precise printing quality can be easily secured.

Note that the polarity of the potential difference between the individual electrode and the common electrode is reversed after time t8 because, if the polarity of the potential difference is always the same, charges accumulate between these electrodes and the diaphragm This is because there is a possibility that the ink sticks to the electrode, the deflection does not return, and a desired ink ejection force cannot be obtained. By performing these controls, the electric charge accumulated between the electrodes is wiped out, and a stable operation of the diaphragm is always obtained. These controls are called potential inversion control.

That is, the potential inversion control is performed by a method of driving an electrostatic ink jet head that discharges ink droplets by deforming a diaphragm using electrostatic force.
This is a drive control method for an inkjet head that is performed for the purpose of always performing a good ink droplet ejection operation while eliminating the influence of residual charges remaining on a diaphragm.

In this potential inversion control, the diaphragm is deformed in the first driving mode in which a voltage of the first polarity is applied between the diaphragm and the electrode, so that ink droplets are ejected from the nozzles. The first polarity between the diaphragm and the electrode so that the nozzles do not discharge ink droplets at regular intervals during which the ink droplet discharge operation according to the first driving mode is performed. The second driving mode in which a voltage having a second polarity opposite to that of the first driving mode is applied is characterized in that residual charges accumulated in the first driving mode are removed.

As described above, since the frequency of the first driving mode and the frequency of the second driving mode are different from each other, there is a concern that electric charges may be accumulated. In a printing apparatus that performs printing by scanning, the potential inversion control of the second mode is performed for each drive path. Further, in a line-type inkjet head that performs printing only by main scanning of a print medium, the second form of potential inversion control is performed for each transaction printing. Thus, the accumulation of the residual charge remaining on the diaphragm due to the difference in frequency between the first driving mode and the second driving mode is suppressed, and the effect becomes a level that can be practically ignored.

In the potential inversion control after time t8 in FIG. 8, the common electrode potential shown in FIG.
It is set to the ground potential GND level. Each of the individual electrode potentials shown in FIGS. 8D and 8F is set to the same potential as the high withstand voltage power supply potential Vh. As a result, FIG.
Each of the potential differences between the electrodes shown in (e) and (g) has a similar potential difference waveform opposite to the power supply potential Vh of the high breakdown voltage system.

The driving mode from time t1 to time t7 is the first driving mode, and the driving mode from time t8 to t10 is the second driving mode, and the above-described potential inversion control is performed. By applying the potential inversion control to the control method described above, it is possible to stabilize the operation of the diaphragm and secure the ejection performance of the ink droplets.

In the driving method described with reference to FIG. 8, the potential inversion control is applied to remove the residual charges and stabilize the operation of the diaphragm. In order to remove the residual charge, before or after the driving mode in which the above-described ink droplet discharging operation is performed, as a preliminary operation of the electrostatic ink jet head, the thickened ink which is driven with the polarity opposite to the driving electric field polarity is used. May be removed to the outside of the ink nozzle or driven to diffuse into the ink chamber. Also in this case, as in the case of the above-described potential inversion control, all the nozzles may be operated and driven simultaneously.

(Driving Apparatus for Electrostatic Ink Jet Head) Next, an embodiment of a driving apparatus for an electrostatic ink jet head to which each of the above driving methods can be applied will be described.

FIG. 9 is a schematic block diagram of a driving device for an electrostatic ink jet head according to this embodiment. The electrostatic ink-jet head driven and controlled by the driving device 100 shown in this figure is the same as that shown in FIGS. 1 to 3, and the corresponding parts are denoted by the same reference numerals and description thereof will be omitted. .

Driving device 1 for electrostatic ink jet head
00 is an inkjet head control unit 102 (control means)
The inkjet head control unit 102 has C
The PU is mainly configured, and print information is supplied to the CPU from the external device 103 via a bus. Also, 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 the storage area in the ROM as a work area, and a control signal for driving the inkjet head is generated based on character information generated from the character generator 104. The gate array 105 supplies a drive control signal corresponding to print information to the head driver IC 109 by a control signal from the CPU, and a drive voltage pulse generation circuit 106
To supply a control signal for generating a drive voltage pulse.

The drive voltage pulse generation circuit 106 (drive pulse generation means) is supplied with a control signal from the gate array, generates a drive voltage pulse, and
9 is supplied with a drive voltage pulse Vp. In the drive voltage pulse generation circuit 106, a control signal as digital information is
It is converted into an analog drive voltage pulse waveform by an / A (digital-analog) converter. That is, in the drive voltage pulse generation circuit 106, the pulse length of the drive voltage pulse,
A drive pulse waveform is generated from a control signal relating to pulse signal generation conditions such as voltage, pulse rise time, and fall time.

By forming the drive voltage pulse generating circuit 106 with a D / A converter, the number of bits of the D / A converter used to increase the resolution of the waveform can be used to generate the drive voltage pulse waveform with high accuracy. , It is possible to easily improve the accuracy of the drive voltage pulse waveform. The drive voltage pulse generating circuit 106 may be constituted by a CR circuit. Drive voltage pulse generation circuit 106
Is configured by a CR circuit, it is possible to make the circuit configuration cheaper than the case of configuring by a D / A converter.

The driving control signal and the driving voltage pulse are supplied to a head driver IC 109 formed on a head substrate 108 via a connector 107. The head driver IC 109 (switching means) receives from the power supply circuit 110 a high withstand voltage driving power supply Vh and a logic circuit driving voltage Vh.
cc is supplied and operated, and the driving voltage pulse and the ground potential GND are switched by the supplied driving control signal,
The voltage is applied between opposing electrodes corresponding to each ink nozzle of the electrostatic inkjet head 1. As a result, the diaphragm 51 having a potential difference caused by the drive voltage pulse between the opposing electrodes is attracted to the opposing electrodes. Between the opposing electrodes holding the potential difference, the vibration plate 51 is adsorbed to the opposing electrode 10 and held there. In the ink nozzle where the potential difference is suddenly canceled and a change occurs, the vibration plate 511 vibrates, and ink droplets are ejected.

FIG. 10 is a schematic block diagram showing the inside of the head driver IC 109 shown in the schematic block diagram of FIG. The head driver IC 109 of this example operates by being supplied with a high-voltage drive voltage Vh and a logic circuit drive voltage Vcc from the power supply circuit 110. The head driver IC 109 switches between the driving voltage pulse Vp and the ground potential GND according to the supplied driving control signal, and applies the switching between the opposing electrodes of the ink droplets corresponding to the respective ink nozzles.

Here, the head driver IC 109 is
A description will be given as a 64-bit output high voltage driver of MOS. The head driver IC 109 corresponds to the drive voltage applying means 210 in FIG.
By setting each bit configuration of 9 to 5 bits, the configuration of the drive voltage application unit 210 is obtained.

In FIG. 10, reference numeral 91 denotes a 64-bit shift register, which receives a 64-bit DI signal input transmitted from the logic gate array 5 as serial data.
XSCL which is a basic clock pulse synchronized with the DI signal
This is a static shift register that shifts up data by a pulse signal input and stores the data in a register in the shift register 91. The DI signal is a signal for transmitting selection information of each of the 64 nozzles as serial data including a control signal by ON / OFF.

Reference numeral 92 denotes a 64-bit latch circuit which latches 64-bit data stored in the shift register 91 by a latch pulse LP and stores the data, and outputs the stored data to a 64-bit inversion circuit 93 as a signal. This is a static latch. The shift register circuit 91 converts the serial data DI signal into a 64-bit parallel signal for outputting a 64-bit segment for driving each nozzle.

The inverting circuit 93 outputs the 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 a logic system voltage level (5 V level or 3.3 V level) to a head drive system voltage level (0 V to 45 V level).

The SEG driver 95 has a 64-channel transmission gate output. Depending on the input of the level shifter 94, the segment output of SEG1 to SEG64 can be either a drive voltage pulse Vp (= Vp1) input or a GND input. Is output.

In the COM driver 96, the Vsel input is H
(Logic), the drive voltage pulse V
p (= Vp1) input or GND input to CO
Output to M output.

Here, in order to realize each of the driving methods described above, a driving voltage pulse Vp is connected to the Vp1 input. Further, GND may be connected to Vp2. Also, Vse
By setting the input to L, the above-mentioned FIGS.
The potential inversion control in the driving method shown in FIG. Further, by setting the Vsel input to H, it is possible to easily realize the driving as the preliminary operation described above, that is, the driving with the reverse polarity in the driving pattern and the driving in which the driving electric field polarity is alternately changed.

The segment outputs of SEG1 to SEG64 are electrically connected to the terminal 10b of the counter electrode 10 of the ink nozzle 11 corresponding to the ink droplet. The COM output is electrically connected to the diaphragm 51 via the common electrode 22.

The XSCL, DI, LP, and REV signals are logic-system voltage level signals, and are signals transmitted from the logic gate array 105 to the head driver IC 109.

As described above, by configuring the head driver IC 109, even when the number of segments to be driven (the number of nozzles) increases, the driving voltage pulse Vp for driving each nozzle of the head and GND are easily switched.
In addition, the above-described potential inversion control can be easily realized.

FIG. 11 shows a schematic circuit configuration inside the main part of the head driver IC 109. FIG. 11A shows a CMOS circuit configuration of a 1-bit driver of the SEG driver 95, and FIG.
The M driver 96 shows a COMS circuit configuration.

The SEG driver 95 outputs SEGn (n = 1,
2,... 64) For output, switch Vp1 or GND and output. The COM driver 96 is configured to switch and output one of Vh, Vp1, Vp2, and GND with respect to the COM output. Where C
The OM driver 96 is configured as a bidirectional transmission gate.

By configuring the SEG driver 95 and the COM driver 96 in this manner, the potentials of the diaphragm 51 and the individual electrode 10 on the common electrode side are inverted as described in the timing chart of FIG. Driving control of various electrostatic actuators such as potential inversion control for erasing electric charges accumulated in the actuator can be easily realized.

(Inkjet Printer) Next, FIG.
FIG. 1 is an external perspective view showing an embodiment of an inkjet printer to which the above driving method can be applied. The inkjet printer 200 includes an electrostatic inkjet head 201.
Is installed. The inkjet head 201 is a line inkjet head, and its basic configuration is the same as the electrostatic inkjet head shown in FIGS. In the inkjet head 201, 1440 ink nozzles are arranged in a line in the longitudinal direction on a surface facing the recording paper 10 at a pitch of 70 μm (360 dpi = dot per inch).

The ink jet printer 200 has a recording paper transport mechanism 202 (moving means).
2, the recording paper 212 is transported in the direction of arrow A, and the inkjet head 2 is synchronized with the transport speed of the recording paper 212.
01, ink droplets are ejected, thereby performing printing.

Reference numeral 203 denotes a storage section of the ink supply mechanism.
The ink supply mechanism further includes an ink tank (not shown) for storing the ink, an ink circulation pump mechanism (not shown) for sending and collecting the ink to the line inkjet head 201, and an ink tank and an ink circulation pump. An ink pipe (not shown) provided between the mechanism and the line inkjet head 201 is provided, and these are housed in the housing 203 of the ink supply mechanism.

The ink jet printer 200 of this configuration
Is mounted with a driving device 100 (driving means) driven by the above-described driving method to perform a printing operation. The driving device 100 includes a line inkjet head 20.
1. In addition to controlling the drive of the transport mechanism 202 and the ink supply mechanism of the ink supply unit, the data transmission / reception is performed with a higher-level device such as a barcode scanner or a network, and the data is printed.

In the above example, the ink jet head 20
Reference numeral 1 denotes a line type printer which is fixed to an ink jet printer and conveys the recording paper 212 to perform printing. In the ink jet printer of the present invention, the ink jet head scans the recording paper to discharge ink droplets, A serial type ink jet printer that performs printing while conveying the recording paper in synchronization with this may be used.

According to the ink jet printer of the present invention, the high density ink jet head 201 is mounted,
The electrostatic inkjet head 20 is driven by the driving device 100.
Since printing is performed by performing the driving of No. 1, high-definition printing can be performed. In addition, the number of scans of the inkjet head is small, and the above-described high-definition and high-speed printing apparatus can be realized with simple control.

Although the driving method of the present invention has been described in the embodiment with respect to the electrostatic method, it can be applied to any method having a pressure chamber and changing the volume in the pressure chamber by a vibration plate. A method as shown in FIG. 16 of JP-A-9-314837 can be applied to driving of a piezoelectric element.

[0142]

As described above, in the method and apparatus for driving an electrostatic ink jet head according to the present invention, not only the vibration plate of the first ink nozzle, which is the discharge nozzle, but also the adjacent non-discharge nozzle The vibrating plate of the second ink nozzle, which is a nozzle, is also attracted to the individual electrode to be in the attracted state, and ink droplets are ejected from the ejection nozzles while maintaining the attracted state.

Accordingly, since the compliance of the ink pressure chamber on the non-ejection nozzle side can be reduced, deformation of the partition wall separating the ink pressure chamber of the ejection nozzle and the ink pressure chamber of the non-ejection nozzle can be prevented or suppressed. Therefore, pressure crosstalk through the isolation wall can be prevented or suppressed, so that deterioration of the ink ejection characteristics due to the crosstalk can be prevented or suppressed.

As a result, according to the driving method and the driving apparatus of the present invention, it is possible to realize a high-density ink-jet head without deteriorating the ink discharge characteristics. Easy to achieve. Further, the driving method and the driving device according to the present invention can realize high density of the ink jet head without complicating the driving device and lowering the printing speed.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view showing an example of an electrostatic inkjet head to which the present invention is applied.

FIG. 2 is a schematic plan configuration diagram of the electrostatic inkjet head shown in FIG. 1, and is a cross-sectional view taken along line II of FIG.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is an explanatory diagram illustrating an operation of the electrostatic inkjet head of FIG. 1;

FIG. 5 is a schematic flowchart showing the operation of the electrostatic inkjet head of FIG. 1;

FIG. 6 is a timing chart showing an example of a drive voltage waveform for realizing the operation of FIG.

FIG. 7 is a schematic flowchart illustrating another example of a method for driving an electrostatic inkjet head to which the present invention is applied.

8 is a timing chart showing an example of a driving voltage waveform for realizing the driving method shown in FIG.

FIG. 9 is a schematic configuration diagram showing a driving device of an electrostatic inkjet head to which the driving method of the present invention can be applied.

10 is a diagram showing a head driver IC in the driving device shown in FIG. 9;
FIG. 2 is a schematic block diagram showing the configuration of FIG.

11A is a schematic block diagram of a SEG driver section of the head driver IC shown in FIG. 10, and FIG. 11B is a schematic block diagram of a COM driver section.

FIG. 12 is an external perspective view illustrating an example of an inkjet printer to which the driving method of the present invention can be applied.

FIG. 13 is an explanatory diagram for describing a problem in a conventional method of driving an inkjet head.

[Explanation of symbols]

 DESCRIPTION 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) Separation wall 9 (1)- 9 (5) Recess 10 (1) to 19 (5) Individual electrode 10a Segment electrode 10b Terminal 11 (1) to 11 (5) Ink nozzle 12 Ink outlet 210 Driving voltage applying means 22 Common electrode terminal 51 (1) To 51 (5) diaphragm 60 sealant 100 electrostatic inkjet head driving device 102 inkjet control unit 103 external device 106 drive pulse generation circuit 109 head driver IC 200 inkjet printer 201 electrostatic inkjet head 202 transport mechanism 203 ink Storage section

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yasushi Matsuno 3-3-5 Yamato, Suwa City, Nagano Prefecture Seiko Epson Corporation F-term (reference) 2C057 AF22 AF34 AF40 AF81 AG12 AG54 AR08 AR09 AR16 BA04 BA14 BA15

Claims (13)

[Claims] A first ink pressure chamber partitioned by a partition wall; a first ink nozzle communicating with each ink pressure chamber; and a second ink nozzle communicating with each ink pressure chamber. An elastically displaceable first and second diaphragm constituting a part of a wall of the pressure chamber, and first and second individual electrodes facing each diaphragm;
A driving method of an electrostatic inkjet head for ejecting ink droplets from said first ink nozzle by applying a driving voltage between a vibration plate and said first individual electrode and elastically displacing said first vibration plate. A step of attracting the second diaphragm to the side of the second individual electrode to bring the second diaphragm into a state of being attracted to the individual electrode; and a step of elastically displacing the first diaphragm to produce the first diaphragm. A method for driving an electrostatic ink jet head, comprising: an ejection step of ejecting ink droplets from an ink nozzle. 2. The method according to claim 1, wherein the second step includes:
The method according to claim 1, further comprising: holding a suction state of the vibration plate during the discharging step, and holding and holding the second vibration plate. 3. The first diaphragm according to claim 1, further comprising a step of attracting the first diaphragm to the first individual electrode and bringing the first diaphragm into a state in which the first diaphragm is attracted to the individual electrode. And a step of sucking the second diaphragm is performed simultaneously. 4. The method according to claim 1, further comprising, after the discharging step, a step of releasing the second diaphragm from a state in which the second diaphragm is attracted to the second individual electrode. In the detaching step, a method of driving an electrostatic inkjet head, wherein the second diaphragm is elastically displaced at a speed at which ink droplets are not ejected from the second ink nozzle. 5. The method according to claim 3, further comprising, after the discharging step, a suction state returning step of returning the first diaphragm to a state in which the first diaphragm is attracted to the first individual electrode. The method for driving an electrostatic ink jet head according to claim 1, further comprising a step of maintaining the suction state of the second diaphragm even after the discharging step. 6. The detaching method according to claim 5, further comprising a detaching step of releasing the first and second diaphragms from the attracted state with respect to the first and second individual electrodes, respectively, after the attracted state returning step. In the driving method, the first and second diaphragms are elastically displaced at a speed at which ink droplets are not ejected from the first and second ink nozzles. 7. The residual charge between the first diaphragm and the first individual electrode and the residual charge between the second diaphragm and the second individual electrode according to claim 6, after the detaching step. A method for driving an electrostatic ink jet head, comprising: a step of removing a residual charge for removing the ink. 8. The method according to claim 1, wherein at least one third ink pressure chamber not arranged adjacent to the first ink pressure chamber, and A third ink nozzle communicating with the third diaphragm, an elastically displaceable third diaphragm, and a third individual electrode facing the third diaphragm; A method for driving an electrostatic ink jet head, wherein drive control is performed in the same manner as a plate. 9. A driving apparatus for an electrostatic ink jet head for performing an ink droplet discharging operation by the method for driving an electrostatic ink jet head according to claim 1. Switching means for switching the potentials of the first and second diaphragms and the potentials of the first and second individual electrodes;
A driving pulse generating means for generating a driving pulse; and a control means for controlling the driving of the first and second ink nozzles by switching the driving pulse generated by the driving pulse generating means by the switching means. For driving an electrostatic inkjet head. 10. An electrostatic ink jet head having a plurality of ink nozzles, moving means for relatively moving the electrostatic ink jet head and a recording medium, and said moving means being synchronized with relative movement by said moving means. Driving means for driving an electrostatic ink jet head, and ejecting ink droplets from each ink nozzle by applying a driving voltage between a fixed individual electrode and a vibration plate which are arranged opposite to each other to cause the vibration plate to generate an electrostatic force. In the ink jet printer performed by elastically deforming, the driving unit causes the diaphragm of a non-ejection nozzle in which the ink droplet included in the ink nozzle is not ejected to be attracted to the corresponding individual electrode. In this state, the diaphragm of the discharge nozzle from which the ink droplets contained in the ink nozzle are discharged is elastically displaced. Inkjet printer was in, characterized in that so as to eject ink droplets from the ejection nozzle. 11. The driving device according to claim 10, wherein the driving unit forms a state in which each of the diaphragms in the discharge nozzle and the non-discharge nozzle is attracted to the corresponding individual electrode, and the diaphragm of the discharge nozzle is An ink jet printer, wherein an ink droplet is ejected from the ejection nozzle by elastically displacing the ink nozzle from a state of being attracted to an individual electrode. 12. A nozzle hole, an ink pressure chamber communicating with the nozzle hole, a vibrating plate that bends so as to discharge ink in the ink pressure chamber to the outside from the nozzle hole, and an external force applied to the vibrating plate. And a fixing member to which the vibration plate is fixed by applying the pressure. When the vibration plate discharges ink from the nozzle hole, the ink in the ink pressure chamber is An ink jet head which is bent to discharge from a nozzle to the outside and is fixed to the fixing member when ink is not discharged from the nozzle hole. 13. A nozzle hole, an ink pressure chamber communicating with the nozzle hole, a vibrating plate that bends to discharge ink in the ink pressure chamber from the nozzle hole to the outside, and an external force applied to the vibrating plate. A fixing member to which the vibration plate is fixed by applying the pressure, wherein the ink in the ink pressure chamber is discharged from the nozzle to the outside when the ink is discharged from the nozzle hole. The method according to claim 1, wherein the diaphragm is bent so that the diaphragm is fixed to the fixing member when ink is not ejected from the nozzle holes.