Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2002-09-12
2004-01-13
Meier, Stephen D. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S009000, C347S010000
Reexamination Certificate
active
06676238
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a driving method and apparatus for a liquid discharge head for use in printing as well as in manufacturing color filters, thin film transistors, light-emitting devices, DNA devices, and the like.
2. Related Background Art
A liquid discharge apparatus has begun to be used for producing printed materials as well as for a patterning process in manufacturing color filters, thin film transistors, light-emitting devices, DNA devices, and the like.
Photolithography is widely adopted for such an industrial patterning method. However, the photolithography requires many steps and the cost for devices is huge, while providing extremely low material-use efficiency. Meanwhile, offset printing has a limitation on use as an industrial patterning technique due to the precision thereof.
Under the circumstances, a patterning method using a liquid discharge head, which is also called ink jet method, has become popular. The ink jet method allows for direct plotting on a patterning portion, thereby providing extremely high material-use efficiency while requiring a small number of steps, which is a useful patterning technique with low running cost.
Well-known ink jet methods are of the Kyser type described in Japanese Patent Publication No. 53-12138 and of the thermal jet type disclosed in Japanese Patent Publication No. 61-59914 (U.S. Pat. No. 5,754,194).
A shear-mode ink jet method using a piezoelectric ceramic is disclosed in Japanese Patent Application Laid-Open No. 63-247051 (U.S. Pat. No. 4,879,568).
As shown in
FIGS. 9A and 9B
, an ink jet head (liquid discharge head)
500
incorporating a shear-mode pressure generating device includes a bottom wall
501
, a top wall
502
, and shear-mode actuator walls
503
. Each of the actuator walls
503
is formed of a lower wall
507
which is bonded to the bottom wall
501
and which is polarized in the direction indicated by an arrow
511
, and an upper wall
505
which is bonded to the top wall
502
and which is polarized in the direction indicated by an arrow
509
. A pair of adjacent actuator walls
503
forms an ink flow path (pressure-applying portion)
506
. An air chamber
508
formed of a gap containing no ink is provided between adjacent ink flow paths
506
.
An orifice plate
512
having a nozzle
510
is bonded to one end of each ink flow path
506
, and electrodes
513
and
514
are provided as metallized layers on both sides of each actuator wall
503
. More specifically, each actuator wall
503
is provided with the electrode
514
on the side of the ink flow path
506
, and is provided with the electrode
513
on the side of the air chamber
508
. The electrodes
513
facing the air chamber
508
are connected to a control circuit
520
for supplying an actuator driving signal, while the electrodes
514
defining the ink flow path
506
are connected to a ground.
A voltage is applied by the control circuit
520
to the electrodes
513
beside the air chambers
508
, thus causing the actuator walls
503
to produce shear strain deformation in the direction where the volume of the ink flow paths
506
increases.
For example, as shown in
FIG. 10
, when a driving voltage is applied to the electrodes
513
beside the air chambers
508
, an electric field is generated in the actuator walls
505
and
507
in the directions orthogonal to the respective polarizations as indicated by arrows, thus causing shear strain deformation of the actuator walls
505
and
507
in the direction where the volume of the ink flow path
506
increases. Then, a pressure decreases in the ink flow path
506
including the vicinity of the nozzle
510
, so that ink is dispensed from an ink common flow path (not shown) on an ink supply side.
If the hydrodynamic resonant frequency of the inside of the ink flow path
506
is indicated by Fr, an inverse thereof is indicated by Tr (=1/Fr), and the time during which the voltage is applied is set to Tr/2, resonance across the system can be used, thereby making the amount of deformation greater than the original amount obtained as shear strain (non-resonance).
The hydrodynamic resonant frequency Fr can be determined by electric measurement using a well-known impedance measurement device.
FIG. 11
shows the relationship between the measurement data obtained by the impedance measurement device (the frequency dependency of impedance) and the hydrodynamic resonant frequency Fr.
After the lapse of the voltage-applying time Tr/2, the voltage applied to the electrodes
513
beside the air chambers
508
is reset to zero. Then, the actuator walls
505
and
507
are deformed so that the ink flow path
506
may contract more than the normal state where the actuator walls
505
and
507
are not deformed and form a straight flow path, thus causing ink to be pressurized. This allows the ink to flow into the nozzles
510
, and ink droplets are expelled from the nozzles
510
.
In conventional ink ejecting apparatuses of this type, the volume of an ink droplet to be ejected depends upon the shape of an ink flow path, a driving voltage, and the like. Therefore, the shape of an ink flow path and the driving voltage are determined so that desired volume of an ink droplet can be obtained. If an ink jet apparatus is used as an industrial plotter, however, there are demands for high-definition ink jet performance, and for shorter plotting time. In order to shorten the plotting time, it is necessary to reduce the number of pulses required for plotting as much as possible. For higher definition, the pitch of an ink flow path is made narrower, thereby increasing the definition. In order to narrow the pitch of an ink flow path, in view of the limitation of machining, the thickness of a PZT (lead zirconate titanate) wall, which is a piezoelectric ceramic wall and which can change the volume of the ink flow path, must be reduced, and the depth of the ink flow path must also be reduced. This further leads to a limitation of driving voltage. Eventually, a high-definition head reduces the amount of deformation cause by the PZT wall, resulting in a reduced amount of discharge per dot.
On the other hand, Japanese Patent Publication No. 3-30506 (U.S. Pat. No. 4,563,689) describes that an additional pulse is applied before an application of the main pulse in order to determine the top position of ink meniscus in a nozzle, thereby controlling the volume of an ink droplet. By applying an additional pulse, the volume of an ink droplet can be slightly, but not significantly, increased.
Japanese Patent Application Laid-Open No. 2000-280463 describes a proposed method in which the volume of an ink droplet is increased by providing a pulse having a width of 0.30 T to 1.10 T as an additional emission (first emission) pulse before an application of a main emission (second emission) pulse, where T denotes the pulse width of the main emission pulse. In this method, two ink droplets are discharged to form one dot, thus making it possible to increase the volume of an ink droplet by a factor of up to about 1.5. However, it is difficult to further increase the amount of discharge.
As proposed in Japanese Patent Publication No. 6-55513 (U.S. Pat. No. 5,202,659), in order to increase the amount of discharge, a plurality of ink droplets which are sequentially ejected using a resonant frequency are combined in the air to control the volume of the ink droplets. With this approach, it can be expected that the volume of ink droplets sufficiently increases.
In an industrial ink jet apparatus, however, if the distance between a nozzle and a plotted base is extremely shortened in order to increase the deposition precision, a plurality of liquid drops are not combined in the air, but reach the base individually. In other words, there occurs a time lag in ink droplets to be applied for one-dot plotting, causing the reached drops do not form perfect circles, resulting in a failure of deposition precision.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention t
Fujimura Hidehiko
Horie Ryoko
Canon Kabushiki Kaisha
Dudding Alfred E
Fitzpatrick ,Cella, Harper & Scinto
Meier Stephen D.
LandOfFree
Driving method and apparatus for liquid discharge head does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Driving method and apparatus for liquid discharge head, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Driving method and apparatus for liquid discharge head will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3224416