Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-03-12
2001-12-18
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S063000
Reexamination Certificate
active
06331049
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the structure of printheads that are used in ink jet printers and the like and, more specifically, to varying the thickness of the passivation layer thereof to improve performance and protect circuit components.
BACKGROUND OF THE INVENTION
Ink jet printers are known in the art and include those made by Hewlett-Packard, Canon and Epson, among other producers. Ink jet printers function by several actuation mechanisms, including thermal (heating resistor) or mechanical (piezo-electric) actuators. While the discussion herein is primarily directed toward thermally actuated printheads, it should be recognized that the varied passivation layer thickness of the present invention are also applicable to mechanically actuated printheads. As discussed in more detail below, the present invention is concerned with providing a thick passivation layer to protect circuitry on a printhead die, while providing a thin passivation layer over the ink expulsion element to reduce ink expulsion energy. A thin passivation layer reduces the energy required to expel ink, regardless of the type of actuator and thus the present invention is applicable to all ink jet and related printers.
FIG. 1
illustrates a representative printhead structure of a prior art ink jet printhead that is thermally actuated. The structure of
FIG. 1
includes a substrate
10
usually of semiconductive material in which is formed a resistive layer and element
12
. A layer of conductive material
14
(usually aluminum or the like) is formed on the substrate, generally as shown. A passivation layer
20
(normally Si
3
N
4
/SiC or the like) is formed on the substrate, and a metallic layer
26
and contact pad
28
(coupled through via
25
) are formed on the passivation layer. The metallic or conductive layer may include a protection/cavitation layer
24
and a surface conductor
26
. An inkwell
31
, barrier layer
32
and orifice plate
33
are provided as is known. A printhead “fire” signal is propagated from circuit
50
or from an off-chip source to the resistive element and there produces sufficient heat to cause a drop of ink to be expelled through the orifice plate
33
.
The amount of energy required to expel a drop of ink is often referred to as the turn-on energy (TOE). TOE is related to passivation layer thickness in that the thicker the passivation layer, the more energy required to expel a drop of ink. Thus, to reduce TOE a thin passivation layer is desired.
A thin passivation layer, however, has disadvantageous aspects. One disadvantageous aspect is that as the passivation layer thickness is reduced, the likelihood of a passivation layer crack or other defect increases. To minimize the possibility of passivation layer cracking, steps such as beveling the transitions of the underlying topology, particularly those near the resistive element (which is a place of higher physical stress) have been undertaken. For example, edges
13
,
15
of the conductive layer
14
proximate resistive element
12
may be beveled. While beveling reduces physical stresses on the passivation layer, it is significantly more difficult to precisely position a beveled edge than to position a straight (vertical) edge. The significant margins of error in beveled edge placement result in significant variability in the defined resistor size and amount of heat generated thereby. This in turn results in inconsistent firing of the printhead and inconsistent print intensity, among other problems.
Another disadvantageous aspect of a thin passivation layer relates to the expanded use of the printhead die or substrate
10
for processing logic
50
. As the number of individual firing chambers in a printhead die increases, the number of power conductors and signal conductors for these firing chambers increases. These conductors are usually formed on top of the passivation layer. As passivation layer thicknesses decrease and the provision of surface conductors increases, the likelihood of capacitive coupling or the like effecting circuitry within the substrate increases. Thus, in order to protect circuitry within the substrate, it is necessary to have a sufficiently thick passivation layer. As stated above, however, increasing passivation layer thickness disadvantageously increases the TOE.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a printhead structure that provides a passivation layer that is appropriately thick where necessary to protect underlying circuit components and appropriately thin where necessary to foster a low turn on energy.
It is another object of the present invention to provide methods for forming such a printhead.
It is also an object of the present invention to provide such a printhead that has a more precisely defined ink expulsion element.
These and related objects of the present invention are achieved by use of a printhead having varied thickness passivation layer and method of making same as described herein.
The attainment of the foregoing and related advantages and features of the invention should be more readily apparent to those skilled in the art, after review of the following more detailed description of the invention taken together with the drawings.
REFERENCES:
patent: 4339762 (1982-07-01), Shirato et al.
patent: 4354309 (1982-10-01), Gardiner et al.
patent: 4513298 (1985-04-01), Scheu
patent: 4535343 (1985-08-01), Wright et al.
patent: 4616408 (1986-10-01), Lloyd
patent: 4686544 (1987-08-01), Ikeda et al.
patent: 4792818 (1988-12-01), Eldridge et al.
patent: 4872028 (1989-10-01), Lloyd
patent: 4931813 (1990-06-01), Pan et al.
patent: 4951063 (1990-08-01), Hawkins et al.
patent: 4982199 (1991-01-01), Dunn
patent: 4990939 (1991-02-01), Sekiya et al.
patent: 5066963 (1991-11-01), Kimura et al.
patent: 5083137 (1992-01-01), Badyal et al.
patent: 5168284 (1992-12-01), Yeung
patent: 5187500 (1993-02-01), Bhorquez et al.
patent: 5194877 (1993-03-01), Lam et al.
patent: 5227812 (1993-07-01), Watanabe et al.
patent: 5257042 (1993-10-01), Buhler
patent: 5357081 (1994-10-01), Bohorquez
patent: 5530465 (1996-06-01), Hasegawa et al.
patent: 5636441 (1997-06-01), Meyer et al.
patent: 5660739 (1997-08-01), Ozaki et al.
patent: 5682188 (1997-10-01), Meyer et al.
patent: 5883650 (1999-03-01), Figueredo et al.
patent: 6007188 (1999-12-01), MacLeod et al.
patent: 6042221 (2000-03-01), Komuro
patent: 6070969 (2000-06-01), Buonanno
patent: 6224195 (2001-05-01), Maru et al.
patent: 0729834A2 (1996-09-01), None
patent: 0750991A2 (1997-01-01), None
patent: 0750990A2 (1997-09-01), None
patent: 0794057A1 (1997-09-01), None
patent: 0816089A2 (1998-01-01), None
patent: 0825026A2 (1998-02-01), None
patent: 0887186A1 (1998-12-01), None
patent: 07276639 (1995-10-01), None
European Search Report; Dated Nov. 9, 2000.
E. V. Bhaskar, J. S. Aden “Development of the Thin-Film Structure for the ThinkJet Printhead” Hewlett-Packard Journal, May 1985, pp. 27-33.
R. A. Askeland, W. D. Childers, W. R. Sperry, “The Second-Generation Thermal InkJet Structure”, Hewlett-Packard Journal, Aug. 1988, pp. 28-31.
J. S. Aden, et al. “The Third-Generation HP Thermnal InkJet Printhead” Hewlett-Packard Journal, Feb. 1994, pp. 41-45.
Barlow John
Hewlett--Packard Company
Mouttet Blaise L.
LandOfFree
Printhead having varied thickness passivation layer and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Printhead having varied thickness passivation layer and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Printhead having varied thickness passivation layer and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2582058