Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-09-22
2001-11-06
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06312103
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns the use of inkjet printer orifices which are coated with a continuous or discontinuous layer of titanium dioxide. The titanium dioxide acts as a catalyst at ambient pressure and temperature (optionally in the presence of light) to decompose excess ink components (solvents, etc.) to keep the inkjet nozzle free of excess ink and allowing for improved inkjet printing. Light irradiated TiO
2
has an extremely small wetting angle of between about 0.0 to 1.0°.
2. Description of the Problem and Related Art
It is well known that when an inkjet printer is operated that drop trajectory and head/printer cleanliness problems develop due to uncontrolled orifice plate surface energy and/or wetting characteristics. This results in a buildup of ink or ink droplets on the print head which affects ink drop trajectory.
Various methods have been used to reduce or eliminate ink buildup have been used including coating the print head with a hydrophobic material to prevent ink head wetting and coating the print head with a varying alternating hydrophilic and hydrophilic coatings to essentially “pump” ink drops on the head away from the ink head orifice to clean the ink head area around the orifice. See for example, Takemoto et al. in U.S. Pat. No.5,387,440; and Hindagolla et al. in U.S. Pat. Nos. 5,434,606 and 5,595,785.
Orifice plates are mounted to ink-jet pens and include orifices through which ink drops are expelled by any one of a number of drop ejection systems. One such system is known as the thermal type and includes a thin-film resistor that is intermittently heated for vaporizing a portion of ink near an adjacent orifice. The rapid expansion of the vapor forces a drop of ink through the orifice. A partial vacuum or “back pressure” is maintained within the pen to keep ink from leaking out of the orifices when the drop ejection system is inactive.
There may be several orifices formed in a single orifice plate, each orifice having an associated drop ejection system for supplying a drop of ink on demand as the ink jet pen scans across a printing medium.
Some of the ink that is ejected through the orifice does not reach the printing medium (e.g., paper, polymer, etc.), and instead collects on the outer surface of the orifice plate (that is, the surface facing the printing medium). Some of this residual ink accumulates or puddles adjacent to the edge of the orifice and may alter the trajectory of the subsequently ejected drops, thereby reducing the overall quality of the printed image.
Residual ink on the outer surface of the orifice plate also tends to trap stray particles, such as paper fibers. The fibers may be held by the ink near the orifice to partially block the orifice and interfer with the ink drop ejections. Further, residual ink on the orifice plate outer surface may collect near the orifice into a thin sheet that is in fluid communication with ink stored in a supply chamber that is just inside the orifice. As a result, a continuous ink path between the chamber and the outer surface of the orifice plate may be formed. The path promotes ink leakage through the orifice. Accordingly, the outer surface of an inkjet pen orifice plate should be designed so that ink does not puddle in the vicinity of the orifice nor accumulate on the plate in an amount that may trap fibers and facilitates leakage as described above.
The inner surface of an orifice plate is exposed to the supply of ink. The ink flows over the inner surface to each orifice. Preferably, the inner surface of the orifice plate, including the portion defining the orifice, should facilitate the flow of ink from the supply through the orifice so that the drop ejection system receives a continuous and uniform flow of ink.
Additional references of interest include, for example:
A. Gonzalez-Martin et al. in U.S. Pat. No. 5,779,912 disclose a method and an apparatus for mineralizing organic contaminants in water or in air provides a photochemical oxidation in a unique two-phase or three-phase boundary system found in each pore of a TiO
2
membrane in a photocatalytic reactor.
D. J. Halko et al. U.S. Pat. No. 5,598,193 disclose a surface treatment with organic compounds to produce monolayers on an orifice plate for an inkjet printer.
G. T. Hong, U.S. Pat. No. 5,545,337 describes a method of producing a layer of titanium dioxide on a surface using temperatures up to 700° C.
M. A. Anderson et al. in U.S. Pat. No. 5,137,604 disclose a reactor vessel using metal oxide (e.g. TiO
2
) ceramic membranes.
S. L. Hindagolla et al. in U.S. Pat Nos. 5,434,606 and 5,595,785 disclose an orifice plate for an inkjet pen.
B. J. Keefe et al. in U.S. Pat. No. 5,635,966 disclose an edge feed in a delivery thermal inkjet printhead structure and a method of fabrication.
K. Takemoto et al. in U.S. Pat. No. 5,387,440 disclose a nozzle plate for an inkjet recording apparatus and method of preparing a nozzle plate.
C. A. Schantz et al. in U.S. Pat. No. 5,305,015 disclose a laser ablated nozzle member of an inkjet printhead.
S. T. Lam et al. in U.S. Pat. No. 4,773,971 disclose a reusable mandrel and a method of making the mandrel which has a substrate with a conductive film layer.
Other references of general and specific interest include:
R. Wong et al.
Nature
, Vol. 388, pp. 431-2 (Jul. 31, 1997).
S. Strauss (1996)
Technology Review
, Vol. 99 (#2) pp. 23-25.
I. Sopyan, et al. (1996)
Journal of Electroanaytical Chemistry
, Vol. 415, pp.183-186.
C. D. Wheeler (October 1994)
Soap-Cosmetics-Chemical Specialities
, Vol. 70 (#10), P. 54(2).
All articles, references, patents, applications, standards, etc. cited in this application are incorporated herein by reference in their entirety.
It would be useful to have a modified inkjet nozzle having a thin coating of titanium dioxide and a method with which there is improved printing on a medium. The present invention provides such an improved nozzle and an improved method.
SUMMARY OF THE INVENTION
A novel coated ink jet printer head, method of manufacture of the novel coated ink jet head, a novel TiO
2
ink jet head coating and method of application are disclosed herein.
Ink and ink droplet buildup on an inkjet printer head is eliminated by coating the print head with TiO
2
which can be applied by sputtering, sintering or by coating the head surface with a TiO
2
solution and curing the coating on the print head.
Other surfaces of printers which are exposed to ink contamination can also be coated with TiO
2
to provide self-cleaning surfaces which reduce maintenance and down-time on the printers.
An object of this invention is to provide a new, surface treatment of 0.0 degree contact angle to both water and oils, which can be used alone to control head surface energy or with a hydrophobic surface treatment to yield differential surface energy control.
A further object of this invention is to provide self-cleaning ink jet print head surface treatment with titanium dioxide as a catalyst in the self-cleaning activity which might in theory will last for extended periods (“forever”) since it is not consumed in the self-cleaning reaction.
It is a still further object of this invention to provide a physically robust (abrasion resistant) new orifice coating of TiO
2
.
It is another object of the invention to provide a novel TiO
2
coating showing multiple methods and application technologies lending flexibility to how and where the coating can be applied.
It is still a further object of this invention to provide an TiO
2
ink jet coating which can be masked and etched to provide differential surface energy control.
Yet another object is to produce a printer having self-cleaning surfaces.
Another embodiment of the present invention is an orifice plate for an inkjet pen, which plate comprises:
a plate having an inner surface and an outer surface wherein the inner surface portion defining an orifice that extends through the plate between the inner surface and the outer surface;
the outer surface having a first outer surface portion surroun
Barlow John
Brooke Michael S.
Hewlett--Packard Company
LandOfFree
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