Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-06-26
2003-03-04
Hilten, John S. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06527370
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to ink jet printers. In particular, this invention relates to novel designs and methods of manufacture of ink-jet printheads capable of providing ink-droplet-tail-break-off control and preventing meniscus overshoot in order to overcome the puddling, pen directionality, and ruffle problems associated with thermal-ink-jet printing.
BACKGROUND OF THE INVENTION
The present invention generally relates to printhead structures for use in delivering ink to a substrate, and more particularly to a novel orifice plate designed for attachment to a printhead. The orifice plate includes a number of important structural features that enable high print quality levels to be maintained over the life of the printhead.
Substantial developments have been made in the field of electronic printing, technology. A wide variety of highly efficient printing systems currently exist that are capable of dispensing ink in a rapid and accurate manner. Thermal inkjet systems are especially important in this regard. Printing units using thermal inkjet technology basically involve an apparatus which includes at least one ink reservoir chamber in fluid communication with a substrate (preferably made of silicon [Si] and/or other comparable materials) having a plurality of thin-film heating resistors thereon. The substrate and resistors are maintained within a structure that is conventionally characterized as a “printhead”. Selective activation of the resistors causes thermal excitation of the ink materials stored inside the reservoir chamber and expulsion thereof from the printhead. Representative thermal inkjet systems are discussed in U.S. Pat. No. 4,500,895 to Buck et al.; U.S. Pat. No. 4,771,295 to Baker et al.; U.S. Pat. No. 5,278,584 to Keefe et al.; and the
Hewlett-Packard Journal
, Vol. 39, No. 4 (August 1988), all of which are incorporated herein by reference.
The ink delivery systems described above (and comparable printing units using thermal inkjet and other ink ejection technologies) typically include an ink containment unit (e.g. a housing, vessel, or tank) having a self-contained supply of ink therein in order to form an ink cartridge. In a standard ink cartridge, the ink containment unit is directly attached to the remaining components of the cartridge to produce an integral and unitary structure wherein the ink supply is considered to be on-board” as shown in, for example, U.S. Pat. No. 4,771,295 to Baker et al. However, in other cases, the ink containment unit is provided at a remote location within the printer, with the ink containment unit being operatively connected to and in fluid communication with the printhead using one or more ink transfer conduits. These particular systems are conventionally known as “off-axis” printing units. Representative, non-limiting off-axis ink delivery systems are discussed in co-owned pending U.S. patent application Ser. No. 08/869,446 (filed on Jun. 5, 1997) entitled “AN INK CONTAINMENT SYSTEM INCLUDING A PLURAL-WALLED BAG FORMED OF INNER AND OUTER FILM LAYERS” (Olsen et al.) and co-owned pending U.S. patent application Ser. No. 08/873,612 (filed Jun. 11, 1997) entitled “REGULATOR FOR A FREE-INK INKJET PEN” (Hauck et al.) which are each incorporated herein by reference. The present invention (as discussed below) is applicable to both on-board and off-axis systems which will become readily apparent from the discussion provided herein.
In order to effectively deliver ink materials to a selected substrate, thermal inkjet printheads typically include an outer plate member known as a “nozzle plate” or “orifice plate” which includes a plurality of ink ejection orifices (e.g. openings or bores) therethrough. Initially, these orifice plates were manufactured from one or more metallic compositions including but not limited to gold-plated or palladium-plated nickel and similar materials. However, recent developments in thermal inkjet printhead design have also resulted in the production of orifice plates which are produced from a variety of different organic polymers (e.g. plastics), including but not limited to film products consisting of polytetrafluoroethylene (e.g. Teflon®), polyimide, polymethylmethacrylate, polycarbonate, polyester, polyamide, polyethylene-terephthalate, and mixtures thereof. A representative polymeric (e.g. polyimide-based) composition which is suitable for this purpose is a commercial product sold under the trademark “KAPTON” by E.I. du Pont de Nemours & Company of Wilmington, Del. (USA). Orifice plate structures produced from the non-metallic compositions described above are typically uniform in thickness and highly flexible. Likewise, they provide numerous benefits ranging from reduced production costs to a substantial simplification of the overall printhead structure that translates into improved reliability, economy, and ease of manufacture.
The fabrication of polymeric/plastic film-type orifice plates and the corresponding production of the entire printhead structure is typically accomplished using conventional tape automated bonding (“TAB”) technology as generally discussed in U.S. Pat. No. 4,944,850 to Dion. Additional information regarding polymeric, non-metallic orifice plates of the type described above is provided in the following U.S. Pat. No. 5,278,584 to Keefe et al. and U.S. Pat. No. 5,305,015 to Schantz et al. (incorporated herein by reference). Also of interest is co-pending, co-owned U.S. patent application Ser. No. 08/921,678 (filed on Aug. 28, 1997) entitled “IMPROVED PRINTHEAD STRUCTURE AND METHOD FOR PRODUCING THE SAME” (Meyer et al.) which is likewise incorporated herein by reference. In this document, a number of approaches are outlined for improving the overall durability of polymeric film-type orifice plates. For example, in one embodiment, a protective coating is applied to the top surface and/or the bottom surface of the orifice plate. Representative coatings include diamond-like carbon (which is also known as “DLC”), at least one layer of metal (e.g. chromium, [Cr], nickel [Ni], palladium [Pd], gold [Au], titanium [Ti] tantalum [Ta] aluminum [Al], and mixtures thereof), and/or a selected dielectric, material (e.g. silicon nitride, silicon dioxide, boron nitride, silicon carbide, and silicon carbon oxide.) This approach is designed to improve the overall abrasion and deformation resistance of the thin-film orifice plate structure and avoids “dimpling” problems associated with these components. Furthermore, the overall durability of the completed structures is particularly enhanced through the use of DLC and the other compositions recited above.
However, other important factors must also be considered in order to produce a printhead using a non-metallic orifice plate which is capable of generating clear, distinct, and vivid printed images over prolonged time periods. For example, a condition known as “ruffling” or “ruffles” can occur in printheads, using thin-film polymeric (e.g. plastic) orifice plates of the type discussed herein. This condition can cause a significant deterioration in print quality if not controlled. Thermal inkjet printers of conventional design typically employ at least one wiper element (normally produced from an elastormeric rubber, plastic, or other comparable material) in order to keep the external surface of the orifice plate clean and free from residual ink and other extraneous matter including paper fibers and the like. A representative wiper system used for this purpose is described in U.S. Pat. No. 5,786,830 to Su et al. which is incorporated herein by reference. Printheads which employ thin-film organic polymer-based orifice plates are often adversely affected by the wiping process. Specifically, passage of the wiper element(s) over this type of orifice plate can cause, an “uplifting” of the plate structure along the edges of the orifices, thereby creating a “ruffled” appearance with “ridge”-like structures being formed at the peripheral edges of each orifice. Th
Agarwal Arun K.
Courian Kenneth J.
Feggins K.
Hewlett--Packard Company
Hilten John S.
Law Offices of Michael Dryja
Price Lucinda
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