Granted Patent
Utility
US 4,806,451 · App. 07/066,125
Process for the production of multicolor proofs using precolored toning films
Inventor:
Helmut Fröhlich
Patented Case
View Patent ↗
Granted: Feb 21, 1989
Filed: Jun 24, 1987
Inventor
Helmut Fröhlich
Assignee (at issue)
E.I. DU PONT DE NEMOURS AND COMPANY
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.