Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-08-20
2002-07-30
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06425656
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an ink-jet head for ejecting ink drops to paper or the like to perform printing, a method of manufacturing the same, and an ink-jet recording apparatus on which the ink-jet head is mounted.
BACKGROUND ART
Recently, a very small actuator has been demanded for use in an ink-jet recording apparatus for the purpose of high-speed and high-precision printing with the development of a multi-nozzle structure and for the purpose of miniaturization of the apparatus. To this end, there is an ink-jet recording apparatus using static electricity for an actuator (for example, JP-A-6-71882). The ink-jet head is characterized in that an electrostatic actuator is formed of parallel plate electrodes, so that the actuator can be miniaturized and a multi-nozzle structure can be realized.
FIGS. 10 and 11
are a sectional view and a plan view, respectively, of a conventional ink-jet head driven by an electrostatic actuator. The ink-jet head shown in FIG.
10
and
FIG. 11
has a lamination structure in which an electrode glass substrate
100
, a diaphragm substrate
200
, and a nozzle plate
300
are laid on the top of one another and bonded with each other. An ink supply port
104
is formed in the electrode glass substrate
100
, and ink
400
is supplied from the ink supply port
104
to a reservoir
204
formed in the diaphragm substrate
200
. The ink
400
is equally distributed to a plurality of cavities
203
through orifices
302
defined by the nozzle plate
300
and recess portions of the diaphragm substrate
200
. The lower surface of each of the cavities
203
is constituted by a transformable diaphragm
201
. This diaphragm
201
faces an individual electrode
101
through an air gap and an insulating film
200
for preventing short-circuit so as to constitute an electrostatic actuator. A common electrode
205
is disposed on the diaphragm substrate
200
. An voltage is applied between the diaphragm
201
and the individual electrode
101
through this common electrode
205
, so that an electrostatic attractive force is generated to transform the diaphragm
201
downward. After that, an ink drop
401
is ejected from a nozzle
301
by the pressure due to the spring force of the diaphragm
201
which is generated when the applied voltage is removed.
In the above-mentioned electrostatically driven ink-jet head, it is regarded as being preferable, from the point of practical view, to drive the electrostatic actuator by a driving voltage of 100 V or less. In order to drive the electrostatic actuator by a driving voltage of 100 V or less, the distance between the insulating film
202
of the electrostatic actuator and the individual electrode
101
is formed accurately to be in a range of from 2,000 to 3,000 angstroms. To this end, a diaphragm substrate constituted by a silicon single-crystal substrate having a bonded surface mirror-finished with high precision was required to be bonded, by anode-bonding, directly with an electrode glass substrate constituted by a borosilicate glass substrate and provided with a step by etching. In this case, however, there is a problem that such a silicon substrate mirror-finished with high precision is expensive and hard to obtain. In addition, in order to obtain required strength, it is necessary to use a thin silicon single-crystal substrate and reduce the height of partitions between respective cavities because the thickness of the partitions are reduced in accordance with the high density of nozzles. However, it is extremely difficult to handle such a thin silicon single-crystal substrate, and particularly there is another problem that it is difficult to increase the size of the substrate.
By the way, there is a method in which etching of a sacrificial layer is used to produce such a narrow gap as described above. For example, a method in which a sacrificial layer is formed and then the sacrificial layer is removed by etching so as to form air gaps is proposed in JP-A-10-510374, page 8 and U.S. Pat. No. 5,459,610 in FIG.
2
. However, all the air gaps are provided for electrostatically modulating positions of the reflecting surface of a light valve. In addition, all the air gaps are made open, unlike closed air gaps formed between insulating film and individual electrodes of an electrostatic actuator of an ink-jet head. It is therefore impossible to apply the technique disclosed in the above-mentioned publications or the like as it is to the manufacturing of an ink-jet head.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide an ink-jet head and a manufacturing method thereof, in which a substrate low in cost, easy to handle and large in size can be used to improve the productivity.
It is another object of the present invention to provide an ink-jet recording apparatus mounted with an ink-jet head manufactured by the above-mentioned manufacturing method.
(1) One aspect of the present invention is an ink jet head comprising a plurality of nozzle holes, ejection chambers independent of each other and communicating with the nozzle holes respectively, electrically conductive diaphragms constituting parts of the respective ejection chambers, and individual electrodes facing the diaphragms through air gaps respectively, and ejecting ink in the ejection chambers toward recording paper through the respective nozzle holes by applying voltages between the diaphragms and the individual electrodes to thereby transform the diaphragms, wherein the air gaps are formed by sacrificial layer etching. In the present invention, since the air gaps are formed by sacrificial layer etching, the air gaps can be formed with high precision, for example, in a range of from 2,000 to 3,000 angstroms, so that it is possible to drive the ink-jet head by a driving voltage of 100 V or less. In addition, it is not necessary to use a silicon single-crystal substrate, so that the substrate can be made layer in size. Therefore, the inkjet head can be suitably adapted for a line printer or the like having a multi-nozzle.
(2) Another aspect of the present invention is a method of manufacturing an ink-jet head comprising a plurality of nozzle holes, ejection chambers independent of each other and communicating with the nozzle holes respectively, electrically conductive diaphragms constituting parts of the respective ejection chambers, and individual electrodes facing the diaphragms through air gaps respectively, and ejecting ink in the ejection chambers toward recording paper through the respective nozzle holes by applying voltages between the diaphragms and the individual electrodes to thereby transform the diaphragms, wherein the air gaps are formed by sacrificial layer etching. In the present invention, since a sacrificial layer can be formed in a thin film process such as vapor deposition, CVD, or the like, a silicon single-crystal substrate mirror-finished with high precision is not required and electrostatic actuators can be formed only in such a thin film process. It is therefore possible to use a large-sized glass substrate, and thereby improve the productivity.
(3) A further aspect of the present invention is a method of manufacturing an ink-jet head based on the above-mentioned manufacturing method (2), wherein the individual electrodes are formed on a substrate; an insulating film, a sacrificial layer and a diaphragm layer are subsequently formed so as to cover the individual electrodes; and window portions are formed in the diaphragm layer in part of predetermined positions where support portions of the diaphragms are to be located to perform the sacrificial layer etching through the window portions. Since the window portions are formed at places corresponding to the support portions of the diaphragms in such a manner and no aperture portion is formed in the diaphragms themselves, there is no deterioration in the properties of the diaphragms. In addition, it will go well if etching liquid permeates the sacrificial layer in its short-side direction through the window portions. Therefore, there is an adv
Barlow John
Ladas & Parry
Seiko Epson Corporation
Tran Ly
LandOfFree
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