Patents by Inventor Andrew W. Yates

Andrew W. Yates 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).

  • Tetra-aza indene compounds
    Patent number: 4728601
    Abstract: Tetra-aza indene compounds of the formula ##STR1## wherein R.sub.1 is alkyl or a ring system and R.sub.2 and R.sub.3 are hydrogen or alkyl.These compounds are of use as image toners in photographic materials.
    Type: Grant
    Filed: April 1, 1986
    Date of Patent: March 1, 1988
    Assignee: Ciba-Geigy AG
    Inventors: David Rowland, Michael E. Dale, Geoffrey E. Ficken, William E. Long, Andrew W. Yates
  • Process for the preparation of a silver halide emulsion
    Patent number: 4533627
    Abstract: Process for the preparation of silver halide emulsions containing populations of monodispersed silver halide crystals, which comprises transferring an amount of monodispersed silver halide crystals from a reaction vessel to a holding vessel, effecting growth of the silver halide crystals remaining in the reaction vessel, transferring the monodispersed silver halide crystals thus obtained to a further holding vessel followed by another growth step of the silver halide crystals left in the reaction vessel, combining all the populations of monodispersed silver halide crystals of different crystal size, and carrying out the steps required to produce a fully sensitized and concentrated silver halide emulsion.These emulsions when used in photographic materials exhibit a reduced contrast and a relatively high sensitivity.
    Type: Grant
    Filed: July 18, 1983
    Date of Patent: August 6, 1985
    Assignee: Ciba-Geigy AG
    Inventors: Andrew W. Yates, Brian D. Harradine, Michael A. Wraith