Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2000-08-24
2002-10-08
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031290, C106S031610, C106S031860, C106S031870
Reexamination Certificate
active
06461417
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to phase change conductive inks that possess the quality of transmitting electrical signals generated by electric field assisted acoustic inkjet printing processes and apparatuses with controlled jeftability leading to low edge raggedness such as for example, less than about three microns. The phase change ink is preferably an ink that changes from a liquid state to solid state in a suitable period of time, for example from about 1 to about 100 milliseconds and preferably in less than about 10, such as from about 2 to about 7 milliseconds. The conductivity of a material such as an ink is measured in terms of reciprocal of resistivity, which refers to the capacity for electrical resistance. The conductivity values of inks expressed as log (pico.mho/cm) and recited herein were measured under melt conditions at 150° C. by placing an aluminum electrode in the molten ink and reading the resistivity output on a Gen Rad 1689 precision RLC Digibridge at a frequency of 1 K.Hz.
More specifically, the present invention relates to inks with a melting point of about 60° C. and about 150° C., and preferably about 70 to about 90° C., especially useful for electric field assisted acoustic inkjet printing with enhanced jettability, acoustic ink processes and apparatuses, reference, for example, U.S. Pat. No. 5,121,141, U.S. Pat. No. 5,111,220, U.S. Pat. No. 5,128,726, U.S. Pat. No. 5,371,531, the disclosures of which are totally incorporated herein by reference, including especially acoustic ink processes as illustrated in some of the aforementioned copending applications and patents, such as an acoustic ink printer for printing images on a record medium. The inks of the present invention in embodiments thereof are comprised of (1) an ink vehicle with for example, a melting point of about 75° C. and about 150° C., and more specifically about 90 to about 130° C. and which vehicle is selected from the group consisting of an alkyl alkyl, alkyl aryl, or aryl aryl ketones, (2) a viscosity modifying compound that can reduce the viscosity of ink from about 20 to 6 centipoise and which compound is selected from mono and diketones, (3) a phase-change conductive sulfonate compound and that for example, can fill the pores of the paper, and which compound has a melting point of lower than about 135° C. and preferably about 70 to about 100° C., and with a low acoustic loss value of below about 100 dB/mm, (4) an antioxidant compound (5) a UV absorbing compound and (6) a colorant such as a dye, a pigment or mixtures thereof and wherein there can be generated with such inks in embodiments excellent developed images on plain and coated papers with acceptable image permanence, excellent projection efficiency on transparencies without a post fusing step, and excellent crease resistance, and wherein the inks possess acceptable, and in embodiments superior lighffastness values of about 90 to 100 percent and superior waterfastness values of about 95 to 100 percent. Moreover, in embodiments of the present invention there is enabled the elimination, or minimization of undesirable paper curl since water need not be present, and it is preferred in embodiments that there be an absence of water. When water is not present in the inks a dryer can be avoided thereby minimizing the cost of the acoustic ink jet apparatus and process.
PRIOR ART
In acoustic ink printing, the printhead produces approximately 2.2 picoliter droplets by an acoustic energy process. The ink under these conditions should display a melt viscosity of about 5 to 10 centipoise or less at the jetting temperature. Furthermore, once the ink is jetted onto the paper, the ink image should possess excellent crease properties, should be non-smearing, waterfast, of excellent transparency and excellent fix qualities. In selecting an ink for such applications, it is desirable that the vehicle display a low melt viscosity, such as from about 1 centipoise to about 25 centipoise in the acoustic head, while also displaying solid like properties after being jetted onto paper. Since the acoustic head can tolerate a temperature up to about 180° C., and preferably up to a temperature of from about 140° C. to about 160° C., the vehicle for the ink should preferably display liquid like properties such as a viscosity of 1 to about 10 centipoise at a temperature of from about 75° C. to about 165° C., and solidify or harden after jetting onto paper such that the ink displays a hardness value of from about 0.1 to about 0.5 millimeter utilizing a penetrometer according to the ASTM penetration method D1321.
Ink jet-printing processes that employ inks that are solid at room temperature and liquid at elevated temperatures are known. For example, U.S. Pat. No. 4,490,731, the disclosure of which is totally incorporated herein by reference, discloses an apparatus for dispensing certain solid inks for printing on a substrate such as paper. The ink dye vehicle is selected to have a melting point above room temperature so that the ink, which is melted in the apparatus, will not be subject to evaporation or spillage during periods of nonprinting. In thermal ink jet printing processes employing phase-change inks, the solid ink is melted by a heater in the printing apparatus and utilized as a liquid in a manner similar to that of conventional thermal ink jet printing. Upon contact with the printing substrate, the molten ink solidifies rapidly, enabling the dye to remain on the surface instead of being carried into the paper by capillary action, thereby attempting to enable higher print density than is generally obtained with liquid inks. Phase-change ink jets are somewhat similar to thermal ink jets; however, a phase-change ink contains no solvent. Thus, rather than being liquid at room temperature, a phase-change ink is typically a solid or phase-change with for example, a wax-like consistency. These inks usually need to be heated, for example, to approximately 100° C. before the ink melts and turns into a liquid. With phase-change inks, a plurality of ink jet nozzles is provided in a printhead. A piezoelectric vibrating element is located in each ink channel upstream from a nozzle so that the piezoelectric oscillations propel ink through the nozzle. After the phase-change ink is applied to the substrate, freezing on the substrate resolidifies the ink.
Each of these types of known ink jets, however, has a number of advantages and disadvantages. One advantage of thermal ink jets is their compact design for the integrated electronics section of the printhead. Thermal ink jets are disadvantageous in that the thermal ink has a tendency to soak into a plain paper medium. This blurs the print or thins out the print locally thereby adversely affecting print quality. Problems have been encountered with thermal ink jets in attempting to rid the ink of moisture fast enough so that the ink does not soak into a plain paper medium. This is particularly true when printing with color. Therefore, usually when printing with thermal ink, one needed to use coated papers, which are more expensive than plain paper.
One advantage of phase-change ink is its ability to print on plain paper since the phase-change ink quickly solidifies as it cools and, since it is waxy in nature, does not normally soak into a paper medium. However, phase-change inkjet system can be cumbersome in structure and in design, that is, the associated integrated electronics of a thermal ink jet head are considerably more compact than those of a phase-change ink jet head.
In addition, U.S. Pat. No. 4,751,528, the disclosure of which is totally incorporated herein by reference, discloses a phase-change ink jet system which includes a temperature-controlled platen provided with a heater and a thermoelectric cooler electrically connected to a heat pump and a temperature control unit for controlling the operation of the heater and the heat pump to maintain the platen temperature at a desired level. The apparatus also includes a second thermoelectric cooler to solidify phase-change i
Breton Marcel P.
Malhotra Shadi L.
Wong Raymond W.
Faison Veronica F.
Klemanski Helene
Palazzo E. O.
Xerox Corporation
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