Actuator for inkjet print head

Details Actuator for inkjet print head Actuator for inkjet print head

1999-12-01

2002-08-20

Barlow, Jr., John E. (Department: 2853)

Incremental printing of symbolic information

Ink jet

Ejector mechanism

Reexamination Certificate

active

06435671

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an actuator for an inkjet print head, and more particularly, to an actuator for an inkjet print head, in which a chamber plate has hard etch stopper films formed at its upper and lower surfaces, respectively, and solution chamber walls arranged between solution chambers formed in the chamber plate have a thickness such that they have a smaller width at a middle portion than at a upper portion or a lower portion, thereby increasing a rigidity of the chamber plate and a bonding force of the chamber plate to a member being bonded thereto.
2. Description of the Prior Art
Generally, an inkjet printer is a kind of printer by which ink in the form of droplets is jetted out and printed onto a paper.
In such an inkjet printer, a printer head is a part on which a print quality and performance of the inkjet printer is dependent. The printer head, in the past, has employed the electrification or deflection mechanism of ink such that it is configured to require a high voltage. At present day, however, the printer head mainly uses a drop-on-demand (DOD) mechanism. Such DOD manner enables easier printing by jetting out droplets of a recording solution onto a paper under atmospheric pressure on demand.
The printer head in the inkjet printer has very various configurations depending on a driving means, but the recent printer head has configurations using a piezoelectric material, particularly oxide piezoelectric material. Among such configurations, a configuration illustrated in
FIG. 1
is typically used.
As shown in
FIG. 1
, the inkjet printer head includes a nozzle plate
100
, a reservoir plate
200
, a channel plate
300
, a restrictor plate
400
, a chamber plate
500
, and a vibrating plate
600
, which are laminated in sequence. On the vibrating plate
600
, there is laminated a microactuator
700
which consists of a plurality of patterned electrodes spaced apart from each other by a certain distance and a plurality of patterned oxide piezoelectric elements spaced apart from each other.
The nozzle plate
100
, the reservoir plate
200
, the channel plate
300
, and the restrictor plate
400
, which are placed below the chamber plate
500
, each has a channel serving to introduce ink into a solution chamber formed on the chamber
500
or jet out ink from the solution chamber. These plates may be also partially omitted, if necessary, such that the channels of various configurations are obtained. That is to say, some of the plates may omitted, and the channels formed in the plates, thus, have various configurations, depending on an ink channel desired by a manufacturer.
Meanwhile, in the printer head including an oxide piezoelectric element as a driving means, the fabrication of the vibrating plate and the chamber plate is very critical. In other words, for an excellent performance of the printer head, the vibrating plate must have a mechanical rigidity sufficient to interlock with a driving means. Consequently, it is preferred that the vibrating plate is thinner and more uniform in thickness.
Furthermore, as the chamber plate is a part in which ink is temporarily stored, it must be sufficient in storage capacity of ink, and maintained at a stable state when introducing or jetting out ink.
For this reason, in fabricating the actuator of the inkjet printer head, there are some cases where the chamber plate is mechanically processed to form solution chambers therein. Recently, however, while the vibrating plate and the chamber plate are formed in such a manner that they are integrally coupled by a electroforming process, etc. with each other, the solution chambers in the chamber plate are formed using an etching process. This enables an increase in the rigidity of the vibrating plate, and also allows the solution chambers to be uniformly formed at the desired shape and size.
FIG. 2
is a cross-sectional view illustrating the formation of laminated plates used for an actuator in the printer head of FIG.
1
. As illustrated in
FIG. 2
, a vibrating plate
810
and a chamber plate
820
are bonded to opposite surfaces of an etch stopper film
830
made of silver (Ag) or platinum (Pt), respectively. After that, the resulting structure is subjected to a photolithographic process on the surface of the chamber plate
820
opposite to the bonded etch stopper film to form solution chambers.
That is to say, as shown in
FIG. 3
, a photoresist film
840
is applied on one surface of the chamber plate
820
to a desired thickness, and the applied photoresist film
840
is exposed to light using a mask, developed, and then partially removed by a washing process to be patterned in a shape as shown in FIG.
4
.
Portions of the chamber plate
820
exposed through the patterned photoresist film
840
generally have a width smaller than that of the respective solution chambers to be formed in the chamber plate
820
. Where the exposed portions of the chamber plate
820
are impregnated with an etching solution as shown in
FIG. 5
, the chamber plate
820
is etched slowly to form the solution chambers
821
. The etching solution used in the etching process etches the chamber plate
820
at a very high etching speed until the etching reaches the etch stopper film
830
by its self controlling-reaction property.
When etching vertically the chamber plate
820
until the etching solution reaches the etch stopper
830
, the chamber plate
830
is also laterally etched to an etched degree similar with the vertically etched degree.
However, when the etching is vertically gradually diffused in a sequence indicated as hidden lines in FIG.
5
and reaches the etch stopper
830
, the chamber plate
830
is more laterally etched in a portion adjacent to the photoresist film
840
than in a portion adjacent to the etch stopper
830
. Consequently, a width of the solution chambers formed in the chamber plate is gradually larger toward the photoresist film
840
.
By etching the chamber plate
820
according to the above mentioned process, the solution chambers
821
having a shape as in
FIG. 6
are formed in the chamber plate
820
. Then, the photoresist film
840
remaining on the upper portion of the chamber plate
840
is removed by washing again. Subsequently, on the vibrating plate
810
, the electrodes
710
(see,
FIG. 1
) and the piezoelectric material
720
(see,
FIG. 1
) are formed on the vibrating plate
810
which is aligned vertically concentrically with the solution chambers
821
. In this way, a print head is fabricated.
As the solution chambers so formed are shaped to have a width gradually larger from a portion on which the etch stopper
830
is laminated, solution chamber walls
822
partitioning the solution chambers are shaped to have a width gradually smaller from an end bonded to the etch stopper
830
, toward the opposite end.
Meanwhile, to the end of the respective solution chamber walls
822
, to which the etch stopper
830
is bonded, and to the opposite end, there is conventionally bonded a channel plate or restrictor plate, in which an ink channel for introducing ink into the solution chambers or ejecting ink from the ink chambers.
Accordingly, when the solution chamber walls
822
are formed such that their ends, to which the channel or restrictor plate is bonded, are smaller in width, as compared to that of their opposite ends, to which the etch stopper
830
is bonded, a bonding force of the solution chamber walls to the channel plate or the restrictor plate is poor, as compared with a bonding force to the etch stopper
830
. This results in a reduction in the rigidity of the chamber plate
820
, and makes the tightness between the solution chambers unstable.
Moreover, where the adjustment in an etching time for forming the solution chambers
821
is not accurately controlled, the chamber plate
820
is excessively etched at a portion adjacent to the photoresist film
840
, while severely deforming open ends of the photoresist film
840
, as shown FIG.
7
. This makes a shape of the solution chambers n

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