Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2001-03-02
2002-11-12
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C347S101000
Reexamination Certificate
active
06478418
ABSTRACT:
TECHNICAL FIELD
The present invention is directed to inkjet inks, and, more particularly, to inkjet inks that evidence improved directionality during jetting through nozzles of an inkjet cartridge.
BACKGROUND ART
Thermal inkjet print cartridges operate by rapidly heating a small volume of ink to cause the ink to vaporize and be ejected through one of a plurality of orifices so as to print a dot of ink on a recording medium, such as a sheet of paper. Typically, the orifices are arranged in one or more linear arrays in a nozzle member. The properly sequenced ejection of ink from each orifice causes characters or other images to be printed upon the paper as the printhead is moved relative to the paper. The paper is typically shifted each time the printhead has moved across the paper. The thermal inkjet printer is fast and quiet, as only the ink strikes the paper. These printers produce high quality printing and can be made both compact and affordable.
In one prior art design, the inkjet printhead generally includes: (1) ink channels to supply ink from an ink reservoir to each vaporization chamber proximate to an orifice; (2) a metal orifice plate or nozzle member in which the orifices are formed in the required pattern; and (3) a silicon substrate containing a series of thin film resistors, one resistor per vaporization chamber.
To print a single dot of ink, an electrical current from an external power supply is passed through a selected thin film resistor. The resistor is then heated, in turn superheating a thin layer of the adjacent ink within a vaporization chamber, causing explosive vaporization, and, consequently, causing a droplet of ink to be ejected through an associated orifice onto the paper.
A recurring problem over the years involves drop trajectory as the drop is ejected through the orifice onto a print medium, e.g., paper. For example, whenever an ink drop is ejected from an orifice of an orifice plate, a trailing portion or “tail” of ink moves with the drop. A small amount of the ink tail may separate and land on the outer surface of the plate as an ink droplet. Residual ink that collects on the orifice plate outer surface near the edges of the orifices may contact subsequently ejected ink drops, thereby altering the trajectory of those drops, which reduces the quality of the printed image.
Also, in the event that a substantial amount of residual ink accumulates on the orifice plate outer surface, a continuous liquid path between the ink within the orifice and the ink on the outer surface may be formed, thereby facilitating leakage of the ink out of the orifice. Further, when a substantial amount of ink accumulates on an orifice plate, this large pool of ink can interfere with drop ejection to the extent that no drops are ejected, i.e., a single drop is unable to pass through the large pool of ink. Moreover, the residual ink on the outer surface of the plate tends to trap minute particles, such as paper fibers, thereby interfering with the trajectory of subsequently-ejected drops.
For many years, ink jet technologies which have been developed to produce printheads for ink jet printers and the like have included sub-categories or sub-technologies directed specifically to forming the output ink ejection orifice plate or nozzle plate for controlling the ink drop patterns and ink trajectories onto an adjacent print medium. As is well-known to those skilled in the art, these orifice plate technologies include those for making silicon orifice plates, glass orifice plates, plastic orifice plates, and metal orifice plates of many different kinds of materials in each of the latter four types of orifice plate categories. In addition, these metal (e.g., nickel) orifice plate technologies include electroforming and electroplating processes including the fabrication of mandrels for making small geometry precision architecture orifice plates for attachment to thin film printhead substrates.
A variety of solutions have been patented that deal with drop trajectory. Many of these solutions comprise various alterations of the mechanical aspect of the printer, and examples of such solutions include: (1) off-setting the orifice from the resistor (see, e.g., U.S. Pat. No. 4,794,411, entitled “Thermal Ink-Jet Head Structure with Orifice Offset from Resistor”, issued Dec. 27, 1988, to Howard H. Taub et al); (2) providing a drop detector for measuring flight characteristics of the drop and correcting the drop fire timing and image data to produce a higher quality image (see, e.g., U.S. Pat. No. 5,109,239, entitled “Inter Pen Offset Determination and Compensation in Multi-Pen Ink Jet Printing Systems”, issued Apr. 28, 1992, to Keith E. Cobbs et al); (3) eliminating the orifice plate (see, e.g., U.S. Pat. No. 5,371,527, entitled “Orificeless Printhead for an Ink Jet Printer”, issued Dec. 6, 1994, to Robert J. Miller et al); (4) reconfiguring the fabrication of a printhead to prevent bending of a nozzle member, which skews the nozzles, by forming the nozzles at a slight inward angle (see, e.g., U.S. Pat. No. 5,467,115, entitled “Inkjet Printhead Formed to Eliminate Ink Trajectory Errors”, issued Nov. 14, 1995, to Winthrop D. Childers); and (5) altering the architecture of the pen itself, that is, the structural portions, including passageways and peninsulas, that guide the ink to the firing chambers (U.S. Pat. No. 5,685,074, entitled “Method of Forming an Inkjet Printhead with Trench and Backward Peninsulas”, issued Nov. 11, 1997, to Yichuan Pan et al).
Other solutions include: (1) providing selected portions of the orifice plate with wetting and non-wetting surface characteristics (see, e.g., U.S. Pat. No. 5,434,606, entitled “Orifice Plate for an Ink-Jet Pen”, issued Jul. 18, 1995, to Suraj L. Hindagolla et al); and (2) treatment of the inner and outer surfaces of the orifice plate with self-assembled monolayers (see, e.g., U.S. Pat. No. 5,598,193, entitled “Treatment of an Orifice Plate with Self-Assembled Monolayers”, issued Jan. 28, 1997, to David J. Halko et al).
The ink itself has been reformulated in an attempt to overcome drop trajectory problems; see, e.g., (1) U.S. Pat. No. 5,098,476, entitled “Additive to Aqueous-Based Inks to Improve Print Quality”, issued Mar. 24, 1992, to Jeffrey P. Baker and (2) U.S. Pat. No. 5,112,399, entitled “Plain Paper Inks”, issued May 12, 1992, to Leonard Slevin et al.
In U.S. Pat. No. 5,098,476, a low molecular weight alcohol or a surfactant/defoming agent is added to reduce the surface tension of the ink and increase the surface wettability on paper. In U.S. Pat. No. 5,112,399, a viscosity modifier, such as an alginate, is used to increase the viscosity of the ink and thereby reduce spray and improve drop directionality.
Other modifications of inkjet inks involving surface tension control have also been undertaken, for a variety of reasons. For example, U.S. Pat. No. 5,880,758, entitled “Printer with Pen Containing a Low Dot Spread Black Ink and a High Dot Spread Color Ink”, issued Mar. 9, 1999, to John L. Stoffel et al, discloses use of a surface tension in the range of 25 to 40 dyne/cm and a viscosity in the range of 1.5 to 10 cp for a relatively high dot spread ink (color ink) and a surface tension in the range of 45 to 65 dyne/cm and a viscosity in the same range as the color ink for a relatively low dot spread ink (black ink).
The combination of adjusting the surface tension of the ink and the contact angle of the ink and a solid surface, such as the print medium or a surface within the pen has also been considered; see, e.g., U.S. Pat. No. 5,626,655, entitled “Use of Co-Surfactants to Adjust Properties of Inks”, issued May 6, 1997, to Norman E. Pawlowski et al.
See also U.S. Pat. Nos. 4,555,062 and 4,583,690, both entitled “Anti-Wetting in Fluid Nozzles”, issued Nov. 26, 1985 and Apr. 22, 1986, respectively, to Young S. You, which disclose a novel ionic surface preparation for nozzles used in spraying fluid droplets such as used in inkjet printers
In most cases, it appears that the prior art is primarily directed to adjusting the surface tens
Knight William R
Moffatt John R
Reboa Paul F.
Barlow John
Hewlett--Packard Company
Shah Manish S.
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