Patents by Inventor D. L. Chang

D. L. Chang 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).

  • P-phenylenediamine substituted by a quaternary ammonium group and an electron withdrawing group
    Patent number: 5198584
    Abstract: p-phenylenediamines having a quaternary ammonium group and substituted with an electron withdrawing group, derivatives thereof, compositions containing same, and their use as developers for dyeing keratinous fibers, are disclosed.
    Type: Grant
    Filed: June 4, 1992
    Date of Patent: March 30, 1993
    Assignee: Clairol Inc.
    Inventors: A. C. Chan, Y. G. Pan, D. L. Chang