Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-06-26
2001-11-13
Vo, Anh T. N. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S064000, C438S021000
Reexamination Certificate
active
06315384
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to ink delivery systems, and more particularly to a thermal inkjet printhead which is characterized by improved reliability, increased longevity, diminished production costs, greater versatility, cooler printhead operating temperatures, decreased energy consumption (e.g. diminished “turn-on-energy” [“TOE”] requirements), and greater overall printing efficiency. The claimed invention likewise allows the production of printhead systems having many different size characteristics including the fabrication of “wide-array” devices. These goals are accomplished through the use of a novel polycrystalline silicon resistor system which uses a minimal number of material layers that are specially treated during production to enable various portions of the layers to perform different functions. In this manner, a simple yet highly “differentiated” structure is produced. Likewise, the completed resistor elements are located in a “buried” configuration within the printhead as discussed in considerable detail below.
Substantial developments have been made in the field of electronic printing technology. A wide variety of highly-efficient printing systems currently exist which 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 technology) 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 will be 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 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 U.S. Pat. No. 5,975,686 to Hauck et al. which are each incorporated herein by reference. The present invention is applicable to both on-board and off-axis systems (as well as any other types which include at least one ink containment vessel that is either directly or remotely in fluid communication with a printhead containing at least one ink-ejecting resistor therein as will become readily apparent from the discussion provided below.)
Regardless of the particular ink delivery system being employed, an important factor to consider involves the overall operating efficiency of the printhead with particular reference to the resistor elements that are used to expel ink on-demand during printhead operation. The term “operating efficiency” shall collectively encompass a number of different items including but not limited to internal temperature levels, thermal uniformity, ink delivery speed, expulsion frequency, energy requirements (e.g. current consumption), and the like. Typical and conventional resistor elements used for ink ejection in a thermal inkjet printhead are produced from a number of compositions including but not limited to a mixture of elemental tantalum [Ta] and elemental aluminum [Al] (also known as “TaAl”), as well as other comparable materials including tantalum nitride (“Ta
2
N”). Polycrystalline silicon may likewise be employed in thermal inkjet printing devices, with the term “polycrystalline silicon” being generally used in a conventional manner to describe a silicon material which basically contains an aggregate of multiple individual crystals. Standard ink delivery resistor systems are discussed in considerable detail in U.S. Pat. No. 4,535,343 to Wright et al. and U.S. Pat. No. 5,122,812 to Hess et al. which are each incorporated herein by reference. Also of importance is a characteristic known as “production efficiency” which is generally defined herein to encompass the number of manufacturing steps, procedures, material layers, and the like which are needed to produce the desired resistor/printhead assembly.
However, the chemical and physical characteristics of the resistor elements and interconnection components associated therewith which are selected for use in a thermal inkjet printhead will directly influence the overall operating efficiency of the printhead (and can likewise affect the general degree of production efficiency). The terms “interconnection components”, “interconnect components”, “interconnection structures” and the like as employed herein generally involve the conductive traces and related elements which electrically connect the resistors to the printing control circuitry of the system (e.g. on-board or printer-based drive transistors and the like). The specific printing control circuitry which is chosen for use will depend on the type of printing apparatus under consideration. As discussed further below, the claimed invention shall not be restricted to any particular control systems and instead involves a novel arrangement of resistors and interconnect components designed to provide substantially improved operating/production efficiency.
In any thermal inkjet printing system, it is especially important that the resistor elements (and interconnect components associated therewith) be as energy efficient as possible and capable of operating at low current levels. Resistive compounds having high current requirements are typically characterized by numerous disadvantages including a need for high cost, high-current power supplies in the printer unit under consideration. Likewise, additional losses of electrical efficiency can occur which result from the passage of greater current levels through the electrical interconnect components/structures discussed above that are attached to the resistor(s), with such interconnect structures exhibiting “parasitic resistances”. These parasitic resistances cause increased energy losses as greater current levels pass through the above-listed components, with such energy losses being reduced when current levels are diminished. Likewise, high current requirements in the resistor elements and the “parasitic resistances” mentioned above can result in (1) greater overall temperatures within the printhead (with particular reference to the substrate or “die” on which the printhead components are positioned [discussed further below]); and (2) lower printhead reliability/longevity levels.
Another important consideration in the development of an efficient thermal inkjet printhead is the avoidance of a condition conventionally known as “current crowding”. This term shall be generally defined to involve a situation where current flow
Cao Min
Joseph Victor
Kamins Theodore I.
Prem Anil
Ramaswami Ravi
Hewlett--Packard Company
Vo Anh T. N.
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