Patents Assigned to S. O. Litho Corporation
  • Substractive developer for negative working lithographic plates
    Patent number: 3954472
    Abstract: A subtractive developer for negative working lithographic plates comprising an aqueous solution of an alcohol, preferably n-propanol, a small quantity of ammonium sulfite, and polyvinylpyrolidone in the range of 0.05 - 0.12% by weight. The developer may also contain a small quantity of ammonium sulfate or ammonium chloride.
    Type: Grant
    Filed: August 26, 1974
    Date of Patent: May 4, 1976
    Assignee: S. O. Litho Corporation
    Inventor: John E. Walls