Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-12-15
2003-02-11
Gordon, Raquel Yvette (Department: 2855)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06517195
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an ink jet head for ejecting ink drops and performing printing with the ink drops on paper or the like, and an ink jet recording apparatus with such an ink jet head mounted thereon.
BACKGROUND OF THE INVENTION
Recently, an ink jet recording apparatus has become required to have a very small actuator because it has become higher in printing speed and smaller in size due to its multi-nozzle structure. Therefore, there is an ink jet recording apparatus in which electrostatic power is used for an actuator (for example, JP-A-6-71882). In this ink jet recording apparatus, the actuator is constituted by parallel plate electrodes, so that the apparatus has a feature that the actuator can be miniaturized, and a multi-nozzle structure can be realized.
The summary of this ink jet head driven by an electrostatic actuator will be described on the basis of the sectional view of FIG.
12
and the plan view of FIG.
13
. The ink jet head of
FIGS. 12 and 13
has a stack structure in which an electrode glass substrate
100
, a diaphragm substrate
200
and a nozzle plate
300
are alternately stacked one after another and bonded with each other. Ink
400
supplied to a reservoir
204
from an ink supply port
104
opened in the electrode glass substrate
100
is distributed equally to a plurality of cavities
203
through orifices
302
. The lower surface of each cavity
203
is constituted by a transformable diaphragm
201
so as to face an individual electrode
101
through an insulating film
202
for preventing shortcircuit to thereby constitute an electrostatic actuator
50
. A voltage is applied between the diaphragm
201
and the individual electrode
101
so that an electrostatic attractive force is generated to thereby transform the diaphragm
201
downward. Then, an ink drop
401
is ejected from a nozzle
301
by the pressure of a spring force of the diaphragm
201
generated when the applied voltage is removed.
However, in a direct driving system in which a voltage is applied to individual electrodes
101
directly, n wirings to individual electrode pads
102
and one wiring to a GND pad, that is, (n+1) wirings in total from a control circuit
2
are required when n electrostatic actuators (C
1
to C
n
)
50
are provided, as shown in the circuit diagram of FIG.
14
. Therefore, not only the space for a wiring connection portion increases, but also it is difficult to ensure the reliability. Particularly, the electrostatic capacity of the electrostatic actuators
50
is very small so that it may couple with the electrostatic capacity of each of the individual wirings from the control circuit
2
. Accordingly, there has been a possibility of generation of scattering in the electrical characteristics of the electrostatic actuators
50
.
In addition, JP-A-5-31898 discloses an ink jet head in which, in order to avoid complex wiring, on a substrate having a plurality of exoergic resistance elements arranged thereon, functional elements, integrated circuits and contacts for connecting the substrate to the outside are formed on the substrate. However, this ink jet head adopts a driving method called a bubble jet system, and its configuration is different from that of the above-mentioned ink jet head having the electrostatic actuators. Therefore, it was impossible to apply the head disclosed in the above Publication, as it is, to an ink jet head adopting electrostatic actuators.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide an ink jet head adopting electrostatic actuators in which the total number of wirings is reduced so that not only the reduction of the space of a wiring connection portion can be intended, but also the reliability can be ensured.
It is another object of the present invention to provide an ink jet head in which printing accuracy is improved in addition to the above-mentioned object.
It is a further object of the present invention to provide an ink jet recording apparatus mounted with the above-mentioned ink jet head mounted thereon.
(A) According to the present invention, provided is an ink jet head which comprises an ink jet head chip having a plurality of nozzle holes, a plurality of independent ejection chambers communicating with the nozzle holes respectively, diaphragms constituting at least one-side walls of the ejection chambers, and individual electrodes disposed so as to be opposite to the diaphragms through air gaps respectively, and a control circuit for applying voltages between the diaphragms and the electrodes to perform charging/discharging so as to transform the diaphragms so that ink drops are ejected from the nozzle holes, respectively, wherein at least a part of the control circuit is constituted by an integrated circuit, and provided in the ink jet head chip.
In this invention, the control circuit is provided in the ink jet head chip. Therefore, not only it is possible to reduce the space of the wiring connection portion, but also it is possible to prevent the electrical characteristics of the electrostatic actuators from scattering. Accordingly, also from these points, it is possible to ensure the reliability.
(B) Further, in the above ink jet head according to the present invention, a part of or a whole of the control circuit is provided on a substrate (nozzle substrate) in the ink jet head chip, the plurality of nozzle holes being formed on the substrate.
The reason why control circuit is provided on the nozzle substrate according to the present invention is as follows.
{circle around (1)} The nozzle substrate is preferable for manufacturing an integrated circuit, because the heating step is gentle although the substrate is subjected to the heating step.
{circle around (2)} The nozzle substrate and the diaphragm substrate can be bonded with a bonding agent, and there is no fear that the control circuit is broken.
{circle around (3)} Since any substrate is sufficient for the nozzle substrate so long as a nozzle hole is opened therein, there is less limitation about the thickness in the nozzle substrate, and an Si substrate of a standard thickness (400 to 500 &mgr;m) may be used as the nozzle substrate.
In addition, when the control circuit is provided on the front surface (outside surface) of the nozzle substrate, there is an advantage that the availability of the substrate is high since a one-side mirror wafer can be used as the nozzle substrate.
In addition, when the control circuit is provided on the back surface (bonded surface) of the nozzle substrate, epoxy resin used for bonding the nozzle substrate with the diaphragm substrate may be used for a mold, so that no step is produced in the front surface of the nozzle substrate.
(C) Further, in the above ink jet head according to the present invention, a part of or a whole of the control circuit is provided on a substrate in the ink jet head chip, the diaphragms being formed on the substrate.
The reason why the control circuit is provided on the diaphragm substrate in the present invention is as follows.
{circle around (1)} Since the diaphragm substrate is formed of an Si single-crystal wafer, the control circuit can be built in on one and the same substrate.
{circle around (2)} All the steps other than the wet etching step, that is, the boron diffusion step, the thermal oxidation step, the patterning step of a thermally oxidized film, the electrode sputtering step, and so on, are common to each other between the cavity formation and the integrated circuit formation. Accordingly, it is possible to reduce the number of step.
Particularly, when the control circuit is provided on the back surface (on the electrode glass substrate side) of the diaphragm substrate, the mechanism becomes simple since a current can be applied to the individual electrode only by providing bumps or the like.
(D) Further, in the above ink jet head according to the present invention, a part of or a whole of the control circuit is provided on a substrate in the ink jet head chip, the individual electrodes being formed on the substra
Dickens Charlene
Gordon Raquel Yvette
Seiko Epson Corporation
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