Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-06-18
2003-03-11
Nguyen, Judy (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S071000
Reexamination Certificate
active
06530652
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a micro actuator and an ink jet printer head fabricated using the same, and more particularly, the present invention relates to a micro actuator which is manufactured by patterning a piezoelectric element employing an etching technique and to an ink jet printer head which is fabricated using the micro actuator.
2. Description of the Related Art
Generally, a micro actuator includes a lower structure which has a vibrating plate and a chamber, a piezoelectric element which is coupled onto a substrate and is mechanically deformed when electric power is applied thereto, and an electrodes) which transfers electric power to the piezoelectric element.
Referring to
FIG. 1
, there is shown a cross-sectional view illustrating an example of a micro actuator according to the related art. In the micro actuator as shown in
FIG. 1
, electric power is supplied to electrode
118
and electrode
114
, which is formed on a diaphragm
111
formed over substrate
110
, and electrode
118
, a piezoelectric element
116
vibrates while repeating deformation and return.
In order to manufacture a micro actuator, methods as described below have been used.
In a first method, a lower electrode is formed on a substrate which is patterned into a thin and precise size and then, is baked at a temperature of no less than 1200° C. Then, piezoelectric element paste is formed on the lower electrode by a screen printing method and baked at a high temperature of no less than 1000° C. Thereafter, an upper electrode is formed on the piezoelectric element and baked at a temperature of about 800° C., whereby the micro actuator is manufactured.
In the case that a thin film or a thick film of a piezoelectric element is directly formed on a substrate, the substrate is likely to be deformed due to a high sintering temperature of the piezoelectric element. Accordingly, ceramic which is capable of enduring the sintering temperature of the piezoelectric element, is used as the substrate, and zirconia is widely used among various ceramic materials.
Also, when the screen printing method is used, a problem is caused in that it is difficult to precisely pattern the piezoelectric element paste to a desired fine pattern.
In a second method for manufacturing a micro actuator, a piezoelectric element which is separately formed or manufactured is bonded to a metal substrate by a third material and then, the prepared piezoelectric element plate is machined to have a predetermined size thereby to construct actuators of a desired number. Alternatively, in the second method, a piezoelectric element which is machined to a size which is suitable for one actuator, is bonded onto a metal substrate to construct an actuator.
In this method, since metal is used as the substrate, an advantage is provided in that a process of high precision such as fine machining of ceramic can be avoided.
However, in the case of machining the piezoelectric element plate in order to obtain a desired number of actuators, integration density cannot but be decreased due to a limit in machining, whereby precision and reliability of end products are reduced and it is difficult to achieve competitiveness in quality and productivity.
In addition, in the case that the piezoelectric element which is machined to a predetermined size is bonded onto the metal substrate, since yield rate is reduced for respective actuators, it is difficult to simultaneously manufacture a plurality of actuators.
In order to solve the problems encountered in the related art, in Korean Patent Application No. 98-29816 which was filed by the applicant of the present application, there is disclosed a method for manufacturing a micro actuator, in which a piezoelectric element having a predetermined thickness is attached onto a substrate and then is etched, thereby to form a plurality of piezoelectric elements having a desired thickness.
In this method, when manufacturing the micro actuator, a remaining portion of the piezoelectric element, except for a portion which is integrated with the substrate and used in driving a cell, is wholly removed by etching.
When manufacturing the micro actuator using the above method, advantages are provided in that the problems encountered in the related art can be resolved.
However, the method for manufacturing the micro actuator suffers from defects in that since an amount of the piezoelectric element which is removed by the etching process is fairly large, etching solution is wasted and rapidly degraded. Moreover, the etching solution can impose harmful influences on the substrate.
While the aforementioned micro actuator can be used to manufacture various articles, an ink jet printer head can be exemplified as a typical example which can be manufactured using the micro actuator.
FIG. 2
is a cross-sectional view illustrating an example of an ink jet printer head according to the related art.
As can be readily seen from
FIG. 2
, an ink jet printer head includes a nozzle plate
222
which is formed with a nozzle
220
, a reservoir plate
226
which is formed with a reservoir
224
, a fluid passage plate
230
which is formed with a fluid passage
228
, a restrictor plate
234
which is formed with a restrictor
232
, a chamber plate
210
which defines a chamber
212
, an actuator comprising an upper electrode
218
, a piezoelectric element
216
and a lower electrode
214
, which is formed on a substrate
211
. The nozzle plate
222
, the reservoir plate
226
, the fluid passage plate
230
, the restrictor plate
234
, the chamber plate
210
and the actuator are sequentially stacked one upon another from bottom to top.
By the construction described above, ink moving paths such as the nozzle
220
, the reservoir
234
, the fluid passage
228
, the restrictor
232
and the chamber
212
, which have different sizes and configurations, are defined in the ink jet printer head.
Ink supplied from an ink container (not shown) is stored in the reservoir
224
and is supplied to the chamber
212
through the fluid passage
228
. At this time, the restrictor
232
formed between the fluid passage
228
and the chamber
212
serves to keep velocity of ink flowing into the chamber
212
constant.
If voltage is applied to the upper electrode
218
and the lower electrode
214
of the micro actuator which is formed above the chamber
212
, the piezoelectric element
216
is actuated, and by this actuation of the piezoelectric element
216
, as volume of the chamber
212
is momentarily reduced, ink stored in the chamber
212
is injected through the nozzle.
Due to the fact that the ink jet printer head uses the micro actuator manufactured as described above in order to inject ink, the ink jet printer head also suffers from the same defects as described above with respect to the micro actuator.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a micro actuator wherein a remaining portion of a piezoelectric element, except for a portion which is integrated with a substrate and used in driving a cell, is not wholly removed, and instead, only a boundary portion between a first piezoelectric element portion which is arranged above a space part and is actuated when voltage is applied thereto and a second piezoelectric element portion which is not arranged above the space part and is not actuated when voltage is applied thereto, is etched, thereby accomplishing economy and improving repeatability of processing.
Another object of the present invention is to provide an ink jet printer head which is manufactured using the micro actuator.
In order to achieve the above objects, according to one aspect of the present invention, there is provided a micro actuator comprising: a substrate having a space part which is integrally defined in the substrate and is opened only at a lower end thereof; a first piezoelectric element formed on the substrate in a first area whi
Cho Young Jin
Kim Il
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