Patents by Inventor Palitha Wickramanayake

Palitha Wickramanayake has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Ink formulations by mixing anionic waterfast dyes containing two or more carboxyl groups
    Patent number: 5062893
    Abstract: Inks are provided comprising (a) at least two dyes corresponding to the formula ##STR1## wherein W is COOH,X is H, or COOH,Y is H, COOH, or SO.sub.3 H,Z is H, COOH, or SO.sub.3 H, andR is H, CH.sub.2 COOH, or CH.sub.2 CH.sub.2 COOH;with the proviso that there are at least two COOH groups and that the number of COOH groups is equal to or greater than the number of SO.sub.3 H groups, and (b) a solvent which may be water or a mixture of water and a water-soluble organic solvent provide excellent waterfast prints on paper. The inks preferably have a pH from about 7 to about 9.5. Also preferably, a phosphate is added to reduce kogation and a metal chelating agent is added to further reduce nozzle clogging.
    Type: Grant
    Filed: June 22, 1990
    Date of Patent: November 5, 1991
    Assignee: Hewlett-Packard Company
    Inventors: Raymond J. Adamic, Palitha Wickramanayake, Suraj L. Hindagolla, Garold E. Radke, David J. Halko