JP2001310464A - Method and device for driving electrostatic ink jet head and ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic ink jet head capable of preventing deformation of an isolation wall between ink pressurizing chambers in an ink ejection operation even when the thickness of the isolation wall is reduced in order to achieve the high density. SOLUTION: A diaphragm 51 (3) of a nozzle 11 (3) to be driven and a diaphragm 51 (2) of a non-driven nozzle 11 (2) adjacent thereto in the ink jet head 1 are allowed to be attracted to individual electrodes and are maintained to be attracted in standby conditions, respectively. An ink drop is ejected from the driven nozzle 11 (3). After that, the diaphragm 51 (1) is attracted to the individual electrode to be in the standby condition again. As the diaphragm 51 (1) is maintained such that a compliance of an ink pressurizing chamber 5 (2) in a side of the non-driven nozzle becomes small, it is possible to prevent the isolation wall between the driven nozzle and the non-driven nozzle from being deformed by fluctuation of a pressure of ink. As a result, it is possible to prevent deterioration in a characteristic of ejection of ink due to the deformation of the isolation wall and to readily achieve the printing operation with the quality of printing in high resolution and high density.

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 for driving an electrostatic ink jet head capable of preventing cross talk of ink pressure between adjacent ink pressure chambers even when ink pressure chambers are arranged at high density.

[0003]

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.

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.

[0005]

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. 11A, the vibration plate 23 (3) of the ink pressure chamber 22 (3) to which the driving ink nozzle 21 (3) for discharging ink droplets communicates is connected to the individual electrode 25.
When suction is performed in (3), there is a possibility that the isolation 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. 11 (b), the diaphragm 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.

[0007] If the isolation 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) are 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.

On the other hand, in JP-A-5-69544 and JP-A-7-17039, the ejection time of the ink droplets from the nozzles adjacent to each other even and odd nozzles is delayed by a delay circuit. Was made to respond. However, these conventional techniques have a problem that the driving device is further complicated and a problem that the time required for printing is long.

SUMMARY OF THE INVENTION In view of the foregoing problems, an object of the present invention is to enable an ink ejection operation to be performed without bending an isolation wall between ink pressure chambers. Driving of an electrostatic ink jet head that can prevent high pressure crosstalk between the ink jet heads and ensure high-definition and precise print quality without lowering the printing speed without complicating the driving device of the ink jet head It is to propose a method and a device thereof.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides at least first and second ink pressure chambers separated by a partition wall, and communicates with each of the ink pressure chambers. First and second ink nozzles, first and second diaphragms elastically displaceable in an out-of-plane direction that define a part of each ink pressure chamber, and a first diaphragm facing each diaphragm. A first and a second individual electrode, between the first diaphragm and the first individual electrode, and between the first diaphragm and the second individual electrode.
Electrostatic ink jet head for ejecting ink droplets from the first and second ink nozzles by applying a drive voltage between the vibration plate and the second individual electrode to elastically displace each vibration plate In the driving method, the first
And a suction step of sucking the second diaphragm and the second diaphragm toward the first and second individual electrodes, respectively, and adsorbing the first and second diaphragms to the first and second individual electrodes. A first holding step of holding the liquid crystal in a state of being attracted to the individual electrode, a discharging step of elastically displacing the first vibration plate to discharge ink droplets from the first ink nozzle, and After the step, a second holding step of again holding the first diaphragm by attracting the first diaphragm to the first individual electrode is included.

Here, according to the driving method of the present invention, the second
After the holding step, a detaching step of detaching the first and second diaphragms from the first and second individual electrodes,
In the detaching step, the second diaphragm is detached at a speed at which ink droplets are not ejected from the first and second ink nozzles.

[0014] Further, the present invention provides a driving apparatus for an electrostatic ink jet head to which the above-mentioned method for driving an electrostatic ink jet head is applied, wherein the electric potential of the first and second diaphragms and the electric potential of the first and second individual sheets are adjusted. The electrostatic inkjet head is driven by switching means for switching the potential of the electrode and driving pulse generating means for generating a driving pulse. The driving pulse generated by the driving pulse generating means is switched by the switching means. It is characterized by the following.

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 toward 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 that separates the second ink pressure chamber and the first ink pressure chamber on the driving side is prevented, and crosstalk of pressure through the partition wall is prevented or suppressed.

Further, the electrostatic ink jet head of the present invention has at least a first and a second ink pressure chamber partitioned by a partition wall and a first and a second ink pressure chamber communicating with each of the ink pressure chambers. Ink nozzles, first and second diaphragms elastically displaced 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 cause each diaphragm to In the electrostatic ink jet head which ejects ink droplets from the first and second ink nozzles by elastically displacing, the first and second diaphragms are respectively placed on the side of the first and second individual electrodes. To the individual electrode. Then, the first and second diaphragms are held in a state of being attracted to the first and second individual electrodes, and the first diaphragm is elastically displaced so that the ink liquid flows from the first ink nozzle. It is characterized by including control means for causing the droplet to be ejected and controlling the first diaphragm to be attracted and held by the first individual electrode again after the ejection.

Further, the ink jet printer of the present invention is provided with a plurality of nozzles for ejecting ink to the outside, and provided in communication with the plurality of nozzles, respectively. When an electrostatic force is applied, the ink is discharged from the plurality of nozzles. A plurality of diaphragms that are displaced in a non-discharging direction, wherein the plurality of diaphragms discharge ink from the plurality of nozzles that communicate with each other by rapidly releasing the applied electrostatic force. In an electrostatic ink jet printer that discharges ink from the nozzles to perform printing on a recording medium, the plurality of nozzles include a driving nozzle that discharges ink and a non-driving nozzle that does not discharge ink. The electrostatic force is applied to the first diaphragm communicating with the driving nozzle and the second diaphragm communicating with the non-driving nozzle for a predetermined period. Then, the application of the electrostatic force to the first diaphragm is released while the electrostatic force is being applied to the second diaphragm, and then the electrostatic force is re-applied to the first diaphragm. It is characterized by comprising control means for controlling.

Here, the non-drive nozzles are not limited to the non-discharge nozzles adjacent to the drive nozzles, but are preferably all non-discharge nozzles. This allows all non-driven nozzles to act as low compliance.

According to these configurations, high-definition and high-speed operation can be performed with simple control.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for driving an electrostatic ink jet head according to the present invention will be described below with reference to the drawings.

(Overall Configuration) First, referring to FIGS.
The configuration of an electrostatic inkjet head to which the driving method of the present invention can be applied will be described. Here, FIG. 1 is a transverse sectional view of the electrostatic ink jet head of the present embodiment, FIG. 2 is a plan view thereof, and FIG. 3 is a longitudinal sectional view.

As shown in these figures, the electrostatic ink jet head 1 of this embodiment sandwiches a silicon substrate 2, has 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 wet etching using KOH (aqueous solution) from its surface having the (110) plane orientation, thereby forming five independent elongated ink pressure chambers 5 (1) to 5 ( 5), one common ink chamber 6 and each ink pressure chamber 5
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, 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 electrode 10 a of the corresponding individual electrode 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 22 is formed on the surface of the silicon substrate 2 on the nozzle plate 3 side by depositing a noble metal thin film such as platinum on the surface thereof.
A drive voltage pulse is applied by the voltage applying means 21 between (1) and (5). 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 sucked toward the individual electrode, the 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 diaphragm 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).

In this embodiment, a face eject type in which ink droplets are ejected from nozzle holes provided on the upper surface of the substrate 3, but an edge eject type in which ink droplets are ejected from nozzle holes provided at an end of the substrate may be used. .

(Driving Method) With reference to FIG. 4, an outline of a driving method of the ink jet head 1 of this embodiment will be described. Now, it is assumed that the ink nozzle from which the ink droplets are ejected (referred to as “drive nozzle”) is the ink nozzle 11 (3).
The ink nozzles 11 (2) and 11 (4) adjacent to both sides of the driving nozzle 11 (3) are ink nozzles that do not discharge ink droplets (referred to as “non-driving nozzles”). And

In the driving method of this embodiment, first, the vibration plates 51 (2) to 51 (2) to the ink nozzles 11 (2) to 11 (4) are used.
A voltage is applied between the individual electrodes 51 (4) and the individual electrodes 10 (2) to 10 (4) to generate a potential difference.
51 (4) is simultaneously sucked into the individual electrodes 10 (2) to 10 (4). As a result, the suction state of each of the vibration plates 51 (2) to 51 (4) as shown in FIG. 4A is formed. While maintaining the potential difference in the suction state, each diaphragm 51
(2) to 51 (4) are held in a suction state, and the apparatus stands by. (Standby state) At this time, the diaphragms 51 (2) to 51 (4) and the individual electrodes 10 (2) to 1 (1)
The voltage applied during 0 (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 low.

Next, the non-drive nozzles 11 (2), 11
The diaphragms 51 (2) and 51 (4) of (4) are
(2) The diaphragm 51 (3) of the driving nozzle 11 (3) is separated from the individual electrodes 11 (3) while being adsorbed on the 10 (4).
Quickly get out of The diaphragm 51 (3) is connected to the individual electrode 1
1 (3), the individual electrodes 10
(3) A drive voltage is applied to make the potential the same as that of the diaphragm 51 (3), and the electric charge between these counter electrodes is quickly discharged. As a result, as shown in FIG.
(3) is elastically restored, the volume of the ink pressure chamber 5 (3) is rapidly reduced, and ink droplets are ejected from the driving nozzle 11 (3).

After the ink droplets are ejected from the driving nozzle 11 (3), the vibration plate 51 (3) is again sucked into the individual electrode 10 (3) to be in the suction state, and the vibration plate 51 (3) is moved to the individual electrode 1 (3).
Attach and hold at 0 (3), and return to the standby state shown in FIG.

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.

When a series of ejection operations is completed and the standby state is released, the nozzles 11 (2) to 11 (11) in the standby state
The diaphragms 51 (2) to 51 (4) of (4) are
(2) to release from (4) to (4). This departure speed is
The operation is performed at a low speed at which ink droplets are not ejected from the nozzles 11 (2) to 11 (4).

(Flowchart) FIG. 5 is a flowchart illustrating a method for driving the ink jet head 1 of the present embodiment described with reference to FIG. When the print data is transmitted in SS0, printing is started. Diaphragm adsorption process SS1
Now, all the vibration plates 51 corresponding to all the ink nozzles 11 will be described.
By applying a voltage between the and the individual electrode 10 to generate a potential difference, the diaphragm 51 is attracted to the individual electrode 10 and brought into a suction state. In the diaphragm holding step SS2, a potential difference is maintained between the diaphragm 51 and the individual electrode 10, the suction state is maintained, and the apparatus stands by. In SS5, the driving nozzle 11 (3)
In the case of, the diaphragm 51 (3) of the driving nozzle 11 (3) is quickly separated from the individual electrode 11 (3) in the step of the discharging step SS6 to discharge ink droplets. SS5
In the case of the non-drive nozzles 11 (2) and 11 (4), the vibration plates 51 (2) and 51 (4) are
(2) Maintain the state of being adsorbed to 10 (4).
That is, the standby state of the diaphragm holding step SS2 is maintained.

After the ink droplets are ejected in the ejection step SS6, the driving nozzles 11 are ejected in the diaphragm suction step SS7.
The diaphragm 51 (3) of (3) is again sucked and adsorbed to the individual electrode 11 (3). 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).

If the print data is terminated in SS4, or if the standby state is terminated for the reason of canceling the standby state for printing and performing another operation, all of the standby states are determined in the diaphragm detaching step SS8. Is released from the individual electrode and released from the held state. The detachment of the diaphragm at this time is performed at a low speed so that the ink droplets are not ejected from the nozzles.

(Timing Chart) FIG. 6 shows an example of a pulse waveform of a drive voltage applied between the diaphragm serving as a common electrode and the individual electrodes in order to realize the above operation. Such a drive voltage pulse is applied to the drive control device 1
00.

In FIG. 6, an example of the pulse waveform of the drive voltage applied between the diaphragm and the individual electrode, which involves the ejection of a series of ink droplets described with reference to FIG. 4, is a period from time t1 to time t7. Is shown in In this period, in the example,
The ink droplets are ejected twice. Further, a drive pattern for performing potential inversion control without discharging ink droplets is shown from time t8 to time t10. The potential inversion control will be described later.

First, FIG. 6B 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, a period between time points t2 and t4 and a period between time points t4 and t6 are each one ejection cycle. An ink droplet is ejected from an ink nozzle due to a sudden change in the voltage waveform of the basic voltage pulse waveform Vp at times t3 and t5. These first and second ejection cycles are repeatedly executed. In the basic voltage waveform pulse Vp, the rising (change in voltage from time t3 and t5 to voltage Vh) starting from time t5 is steep, and its falling (change from time t4 to ground potential GND starting from time t6) changes to rising. The slope is gentler than that.

Vh shown in FIG. 6A is the power supply potential of the high breakdown voltage system. Vh has the same amount of change in the slope of the rise from time t1 and the slope of the fall from time t7. This change is effective even if the change in the potential difference between Vh and the GND potential acts between the diaphragm and the individual electrodes. The gradient is gentle so that ink droplets are not ejected.

The three ink nozzles 11 (2) shown in FIG.
To describe this by taking as an example 11 to (4), the voltage applied to each of the diaphragms 51 (2) to 51 (4) functioning as a common electrode is, as shown in FIG. In this case, the voltage has the same shape as the power supply potential Vh of the high breakdown voltage system. After time t2, diaphragms 51 (2) to 51 (4)
The individual electrodes 10 (2) to 10 (4) are attracted and held by the individual electrodes, and enter 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. 6D, the individual electrode potential of the driving nozzle 11 (3), that is, the potential of the diaphragm 51 (3), is changed from the time point t1 to the time point t7 in the discharge cycle.
Until then, the voltage has the same shape as the basic voltage pulse waveform Vp. In the first discharge cycle, the potential is sharply raised to Vh which is the common electrode potential at time t3, and thereafter, is kept at the same potential as the common electrode potential until time t4. After the time point t4, it is again held at the ground potential GND. Further, in the second ejection cycle, the potential rises sharply at time t5, is kept at a high potential until time t6, and is again kept at the ground potential GND after time t6.

As a result, the potential difference between the vibration plate 51 (3) and the individual electrode 10 (3) in the driving nozzle 11 (3) is, as shown in FIG.
During the period 3, the positive potential difference state is maintained, and between the time points t3 and t4 in the first ejection cycle and the time points t5 and t6 in the second ejection cycle, no potential difference is maintained. In other words, no electrostatic force for attracting the diaphragm to the individual electrodes is generated. At times other than these, the positive potential difference state is maintained, and an electrostatic force for attracting the diaphragm and the individual electrode acts to attract and hold the diaphragm to the individual electrode.

Therefore, in the first discharge cycle, the time t
The diaphragm 51 (3) suddenly detaches from the individual electrode 10 (3) from 3 and elastically returns, and the operation of the diaphragm causes the drive nozzle 11 (3) to return from the drive 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 attracted to the individual electrode 10 (3), and returns to the standby state. Similarly, in the second ejection cycle, the diaphragm 51 (3) suddenly separates from the individual electrode 10 (3) and elastically returns from the time point t5, and the operation of the diaphragm causes the driving nozzle 11 (3) to move from the driving nozzle 11 (3). At time t
The ink droplets are ejected at a point in time after 5 from a predetermined time. Thereafter, at time t6, diaphragm 51 (3)
The state is attracted to (3) and returns to the standby state.

On the other hand, in the non-driving nozzle 11 (2) adjacent to the driving nozzle 11 (3), the individual electrode potentials in FIG.
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-drive nozzle 11 (2) is, as shown in FIG. 6 (g), the first discharge cycle and the second discharge cycle. In the discharge cycle, the state becomes similar to the power supply potential Vh of the high breakdown voltage system.

Therefore, the diaphragm 51 (2) is sucked by 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.

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) to 51
The separation of (4) starts, and the elastic recovery is performed at a slower speed than at the time of suction.

FIG. 6 (h) shows the vibration driven by the potential difference between the diaphragm 51 (3) and the individual electrode 10 (3) in the driving nozzle 11 (3) shown in FIG. 6 (e). The state of displacement of the plate 51 (3) at each time is shown.
FIG. 6 (i) shows the diaphragm 51 in the non-drive nozzles 11 (2) and 11 (4) shown in FIG. 6 (g).
(2), 51 (4) and individual electrodes 10 (2), 10 (4)
Diaphragms 51 (2), 5 operated by the potential difference between the electrodes
The state of displacement at each point in time 1 (4) is shown.

The vertical direction of the charts shown in FIGS. 6H and 6I indicates the displacement of the diaphragm, and the horizontal direction indicates the passage of time. 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 (+).

Here, FIG. 6H and FIG. 5 will be described in comparison.

T1 to t2: The vibration plate 51 (3) of the driving nozzle 11 (3) is set to the individual electrode 1 between the time t1 and the time t2.
It is adsorbed to 0 (3). (1st diaphragm adsorption process SS
1) t2 to t3: After the suction, the diaphragm 51 (3) is held in a state of being sucked by the individual electrode 10 (3) until time t3. (First diaphragm holding step SS2) t3 to t4: At time t3, the diaphragm 51 (3) suddenly separates and returns, pressurizes ink in the pressure chamber 5 (3), and presses the arrow h1. At this point, ink droplets are ejected from the driving nozzle 11 (3). (Discharge Step SS6) Thereafter, the vibration plate 51 (3) vibrates, and at the time when the amount of displacement of the vibration plate substantially coincides with the vibration cycle of the vibration plate 51 (3) at the time of going to (-), the distance between the electrodes is again increased. A potential is applied to the individual electrode 10 (3) so that a potential difference is generated, and the time t
At 4, it is adsorbed again to the individual electrode 10 (3). (Second diaphragm adsorbing step SS7) t4 to t5: Until time t5, diaphragm 51 (3) keeps individual electrode 1 until time t5 in preparation for the next ejection.
It is held in a state of being adsorbed to 0 (3). (Second diaphragm holding step SS2).

T5 to t7: In the driving nozzle 11 (3),
Further, the diaphragm 51 is subjected to a similar cycle from the time point t5 to the time point t7 (a cycle from the discharge step SS6 to the diaphragm holding step SS2 via the diaphragm suction step SS7).
(3) is driven, and ink droplets are ejected at the time point indicated by the arrow h2 (when ejecting two or more times, t5 to t7 are repeated).

T7 to t8: In the driving nozzle 11 (3),
At time t7, the vibration plate 51 (3) gradually
(3), a series of print control steps (standby state)
To end. At this time, no ink droplet is ejected from the nozzle 11 (3). (Diaphragm detachment step SS8) In FIG. 6 (i), the non-drive nozzles 11 (2), 11
The diaphragms 51 (2) and 51 (4) of (4) are attracted to the individual electrodes 10 (2) and 10 (4), respectively, from time t1 to time t2. (Vibration plate adsorption step SS1) Vibration plate 5
After the suction, 1 (2) and 51 (4) are held by the individual electrodes 10 (2) and 10 (4), respectively, until time t7. (Vibration plate holding step SS2) Since the non-driving nozzles 11 (2) and 11 (4) do not discharge ink droplets, the vibration plate 51 (2) can be used even when the driving nozzle 11 (3) is in the discharging step. ), 51 (4) are adsorbed and held by the individual electrodes 10 (2), 10 (4),
The compliance of the flow paths of these ink chambers 5 (2) and 5 (4) is small. In the holding step, since the compliance of these flow paths is small, the partition walls 8 (1) to 8 (1) are also used in the discharge step of the driving nozzle 11 (3).
8 (4) is deformed, and the pressure chamber 5 of the drive nozzle 11 (3) is deformed.
Since the pressure loss of (3) does not occur, the driving nozzle 11
There is no variation from (3), and stable ejection of ink droplets is possible.

In the driving 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 printing control steps ends. At this time, no ink droplets are ejected from the nozzles 11 (2) and 11 (4). (Vibrating plate detachment step SS8) As described above, on the non-driving nozzle 11 (2) side, the diaphragm 51 (3) on the driving nozzle 11 (3) side detaches and vibrates during the suction operation. 2) is held by suction,
In the standby state shown in FIG. 4A, all the nozzles are in a state of being attracted to the individual electrodes. Next, in this suction holding state, ink droplets are ejected from the driving nozzle 11 (3). At the end of the standby state, the diaphragm 51 (2) on the side of the non-drive nozzle 11 (2) is
It detaches from (2) and gently elastically returns. By adjusting the elastic return speed of the diaphragm, the diaphragm 51 is adjusted.
At the time of the elastic recovery in (2), the ejection of the ink droplets from the non-drive nozzle 11 (2) can be completely prevented.

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

As described above, in the method of driving the electrostatic ink jet head of the present embodiment, the driving nozzle 11 (3)
The diaphragms 51 (2) and 51 (4) are also connected to the individual electrodes 10 in the non-drive nozzles 11 (2) and 11 (4) adjacent to the
(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-driven nozzles can be reduced.

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

Accordingly, 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 inverted after the time point 8 because if the polarity of the potential difference is always the same, charges accumulate between these electrodes and This is because there is a possibility that the electrostatic attraction force of the above 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.

The potential inversion control is a method of driving an ink jet head in which ink droplets are ejected by deforming a vibration plate by using an electrostatic force, and eliminates the influence of residual charges remaining on the vibration plate. This is a method for controlling the driving of an ink jet head which is performed for the purpose of always performing a good ink droplet discharging operation, and is another invention by the present applicant.

In a first driving mode in which a voltage of a first polarity is applied between the diaphragm and the electrode, the diaphragm is deformed to discharge ink droplets from the nozzles, and Every predetermined period during which the ink droplets are ejected by the above-described driving mode, the first polarity is opposite to the first polarity between the vibration plate and the electrode so that the ink droplets are not ejected from the nozzles. A method of driving an electrostatic ink jet head that deforms the diaphragm in a second driving mode in which a voltage of a second polarity is applied. In the second driving mode, the residual ink accumulated in the first driving mode is used. This is a method for driving an ink-jet head, which comprises removing charges.

Since the frequency of the first driving mode and the second driving mode are different in frequency, there is a concern that electric charges may be accumulated. For example, the ink jet head performs sub-scan on the print medium and prints by scanning the print medium. In the recording device of the form to perform,
The second form of potential inversion control is performed for each drive path. Furthermore, in a line type ink jet 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, the common electrode potential shown in FIG. 6C is set to the ground level GND level. 6D and 6F.
Are set to the same potential as the power supply potential Vh of the high withstand voltage system. As a result, the potential difference between the electrodes shown in FIGS. 6E and 6G has a similar potential difference waveform opposite to the power supply potential Vh of the high breakdown voltage system.

The above-described potential inversion control is performed by setting the driving mode from time t1 to t7 to the first driving mode and the driving mode from time t8 to t10 to the second driving mode. 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. 6, 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, all the nozzles are operated and driven at the same time as in the above-described potential inversion control.

The driving voltage waveform shown in FIG. 6 is an example for realizing the driving method of the present invention, and a driving mode different from this can be adopted.

(Driving Apparatus) A driving apparatus for an electrostatic ink jet head according to the present invention to which the above-described driving method is applied will be described below with reference to the drawings.

FIG. 7 is a schematic block diagram of a drive control device for an ink jet head to which the present invention is applied. The ink jet heads whose driving is controlled by the driving control device 100 shown in this figure are the same as those shown in FIG. 1, and therefore, the same reference numerals are given and their explanation is omitted.

Drive control device 10 for ink jet head
0 has an inkjet head control unit 102, and the inkjet head control unit 102 is mainly configured by 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 CPU executes a control program stored in the ROM using a storage area in the RAM as a work area.
A control signal for driving the inkjet head is generated based on the character information generated from. Gate array 1
05 is a head driver IC 1 according to a control signal from the CPU.
09, a drive control signal corresponding to the print information is supplied, and a control signal for generating a drive voltage pulse is supplied to the drive voltage pulse generation circuit 106.

The drive voltage pulse generation circuit 106 is supplied with a control signal from the gate array, generates a drive voltage pulse, and supplies a drive pulse Vp to the head driver IC 109. In the drive voltage pulse generation circuit 106, a control signal as digital information is converted 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 relating to pulse signal waveform generation conditions such as the pulse length, voltage, pulse rise time, and fall time of the drive voltage pulse. By forming the drive pulse generating circuit 106 with a D / A converter, a drive voltage pulse waveform can be generated with high accuracy only by increasing 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. Drive pulse generation circuit 10
6 may be constituted by a CR circuit. If the drive pulse generation circuit 106 is configured by a CR circuit, a circuit configuration that is less expensive than when the drive pulse generation circuit 106 is configured by a D / A converter can be achieved.

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 driving voltage Vh of a high voltage system and a driving voltage Vcc of a logic circuit system from a power supply circuit 110, and switches between a driving voltage pulse and a GND potential according to the supplied driving control signal, and The voltage is applied between the opposing electrodes corresponding to each ink nozzle. As a result, the diaphragm 51 having a potential difference caused by the driving pulse between the opposed electrodes is attracted to the opposed electrode, and the diaphragm 51 is retained in a state attracted by the opposed electrode 10 between the opposed electrodes where the potential difference is maintained. Then, the vibration plate 51 vibrates at the ink nozzle where the potential difference is suddenly released and a change occurs, and an ink droplet is ejected.

FIG. 8 is a schematic block diagram showing the inside of the head driver IC 109 to which the present invention is applied, which is shown in the block diagram of FIG. The head driver IC 109 operates by being supplied with a driving voltage Vh of a high voltage system and a driving voltage Vcc of a logic circuit system from the power supply circuit 110. Further, the head driver IC 109 switches between the driving voltage pulse Vp and the GND potential according to the supplied driving control signal, and applies the switching between the opposing electrodes corresponding to the respective ink nozzles of the inkjet head 1.

Here, the head driver IC 109 is a CM
A description will be given as a 64-bit output high withstand voltage driver of the OS. The head driver IC 109 corresponds to the voltage application unit 21 in FIG. 2, and the configuration of the voltage application unit 21 is achieved by setting each bit configuration of the head driver IC 109 to 5 bits.

In FIG. 8, reference numeral 91 denotes a 64-bit shift register, which converts a 64-bit DI signal input transmitted from the logic gate array 5 as serial data into a D signal.
X which is a basic clock pulse synchronized with the I signal
Data is shifted up by SCL pulse signal input,
This is a static shift register stored in a register in the shift register 91. As the DI signal, a control signal for ON / OFF of the selection information of each of the 64 nozzles is transmitted as serial data.

Reference numeral 92 denotes a 64-bit latch circuit which latches 64-bit data stored in the shift register 61 by a latch pulse LP and stores the data, and transmits the stored data to a 64-bit inversion circuit 93 as a signal. This is the output clutch. In the latch circuit 92, the DI signal of the serial data is converted into a 64-bit parallel signal for outputting 64 segments for driving each nozzle.

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 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 transmission gate output of 64 channels. Depending on the input of the level shifter 94, the segment output of SEG1 to SEG64 is applied to the drive voltage pulse Vp (= Vp1) input or the GND input. Is output.

The COM driver 96 has a Vsel input of H
(Logic), the drive voltage pulse V
p (= Vp1) input or GND input to CO
Output to M output. 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, a driving voltage pulse Vp is connected to the Vp1 input. Vp2 has GND
Connect. With this configuration, the potential inversion control described above 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 as the preliminary operation described above, 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 SEG 1 to SEG 64 are output from the corresponding ink nozzles 1 of the ink jet head 1.
Each of them is electrically connected to a terminal 10b of one counter electrode 10. 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.

By configuring the head driver IC 109 in this manner, 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. 9 shows a schematic circuit configuration inside the main part of the above-described head driver IC 109. FIG.
(A) shows a CMOS circuit configuration of a 1-bit driver of the SEG driver 95, and (b) shows a CMOS circuit configuration of the COM driver 96.

The SEG driver 95 has SEGn (n = 1,
2,..., 64), Vp1 or GND is switched 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. Here, the COM driver 96 is configured as a bidirectional transmission gate.

By configuring the SEG driver 95 and the COM driver 96 in this way, 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. Various types of electrostatic actuator drive control, such as potential inversion control for erasing electric charges accumulated in the actuator, are easily realized.

(Inkjet Printer) Next, FIG.
FIG. 1 shows an external perspective view of an embodiment of a printing apparatus according to the present invention.
The printing apparatus 200 includes an electrostatic inkjet head 201.
Is installed. The inkjet head 201 is mounted on the printing apparatus 200 as a line inkjet head. The inkjet head 201 has a 1440 pitch at a pitch of 70 μm (360 dpi = dot per inch).
Are arranged in a line in the longitudinal direction on the surface facing the recording paper 210.

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 ink jet head 201 in synchronization with the transport speed of the recording paper 210. Then, printing is performed. 203 is a storage unit 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 sends the ink to the line inkjet head 201 and simultaneously collects the ink, an ink tank, an ink circulation pump mechanism, and a line inkjet head. An ink pipe is provided between the ink supply mechanisms 201 and 201, and these are stored in a storage section 203 of the ink supply mechanism.

The printing apparatus 200 has a configuration including the drive control apparatus 100 shown in FIG. 7 in addition to the above.
The drive control device 100 includes the line inkjet head 2
01, drive control of the transport mechanism 202 and the ink supply mechanism 203, data transmission / reception to / from a higher-level device such as a barcode scanner or a network, and data printing processing.

In the above example, the ink jet head 20
1 describes a line type ink jet printer which performs printing by transporting the recording paper 210 while being fixed to the printing apparatus. However, as a printing apparatus of the present invention, an ink jet head is sub-scanned on the recording paper to discharge ink droplets. A serial type ink jet printer that performs printing while discharging and transporting the recording paper in the main scanning direction may be used.

According to the printing apparatus of the present invention, since 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, high-definition printing is performed. Can be performed at high speed. Further, since complicated control of the ink jet head is not required, the number of times the ink jet head scans on the recording paper is small, and the above-described high-definition and high-speed printing apparatus can be realized by simple control.

[0096]

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

Therefore, when the driving nozzle is driven, the compliance of the ink pressure chamber on the non-driving nozzle side can be reduced, so that the deformation of the partition wall separating the ink pressure chamber of the driving nozzle and the ink pressure chamber of the non-driving nozzle can be reduced. It 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 apparatus of the present invention, it is possible to realize a high-density ink-jet head without deteriorating the ink ejection characteristics, thereby achieving high-definition and high-density printing. it can.

In addition, the density of the ink-jet head can be increased without complicating the driving device and lowering the printing speed. Therefore, it is possible to easily realize the printing speed while securing 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 view of the electrostatic inkjet head shown in FIG.

FIG. 3 is a schematic cross-sectional view when the electrostatic inkjet head shown in FIG. 1 is cut in a direction perpendicular to the direction.

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

FIG. 5 is a flowchart illustrating a method for driving an inkjet head according to the present invention.

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

FIG. 7 is a block diagram illustrating an example of a driving device for realizing the operation of FIG. 6;

FIG. 8 is a block diagram showing the inside of the head driver IC in FIG. 7;

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.

FIG. 10 is a view showing an ink jet printer of the present invention.

FIG. 11 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 21 Voltage applying means 22 Common electrode terminal 51 (1) to 51 (5) Vibration plate 60 Sealant 100 Inkjet head control device 102 Inkjet control unit 109 Head driver IC

Continuation of front page (72) Inventor Yasushi Matsuno 3-3-5 Yamato, Suwa-shi, Nagano Seiko Epson Corporation F-term (reference) 2C057 AF09 AF21 AG12 AG54 AR08 BA04 BA15

Claims (4)

[Claims] At least first and second ink pressure chambers separated by a partition wall, first and second ink nozzles respectively communicating with the respective ink pressure chambers,
It has first and second diaphragms elastically displaceable in an out-of-plane direction that define a part of each ink pressure chamber, and first and second individual electrodes facing each diaphragm. By 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 method of driving an electrostatic ink jet head for discharging ink droplets from the first and second ink nozzles, the first and second diaphragms are attracted to the first and second individual electrodes, respectively. A first holding step of holding the first and second diaphragms in a state of being sucked by the first and second individual electrodes; and a first holding step of holding the first and second diaphragms in a state of being sucked by the first and second individual electrodes. Elastically displaces the vibrating plate from the first ink nozzle to And a second holding step of again adsorbing and holding the first diaphragm on the first individual electrode after the discharging step. A method for driving an electrostatic inkjet head. 2. The method according to claim 1, further comprising, after the second holding step, a separating step of separating the first and second diaphragms from the first and second individual electrodes. A method for driving the electrostatic inkjet head, wherein the second diaphragm is detached at a speed at which ink droplets are not ejected from the first and second ink nozzles. 3. A driving apparatus for an electrostatic ink jet head to which the method for driving an electrostatic ink jet head according to claim 1 or 2 is applied, wherein a potential of the first and second diaphragms and a potential of the first and second diaphragms are adjusted. A switching unit for switching the potential of the second individual electrode; and a driving pulse generating unit for generating a driving pulse. The driving pulse generated by the driving pulse generating unit is switched by the switching unit, and the electrostatic inkjet A driving device for an electrostatic inkjet head, which drives the head. 4. A plurality of nozzles for discharging ink to the outside, provided in communication with the plurality of nozzles, and displaced in a direction in which ink is not discharged from the plurality of nozzles when an electrostatic force is applied. A plurality of diaphragms, wherein the plurality of diaphragms are displaced in a direction in which ink is ejected from the plurality of nozzles communicating with each other by suddenly releasing the applied electrostatic force. In an electrostatic inkjet printer that prints on a recording medium by discharging ink from the plurality of nozzles, when including a driving nozzle that discharges ink and a non-drive nozzle that does not discharge ink,
The electrostatic force was applied for a predetermined period to a first diaphragm communicating with the driving nozzle and a second diaphragm communicating with the non-driving nozzle, and then the electrostatic force was applied to the second diaphragm. The application of the electrostatic force to the first diaphragm is released as it is,
An electrostatic ink jet printer, further comprising control means for controlling so as to reapply electrostatic force to the first diaphragm.