Granted Patent
Utility
US 4,197,404 · App. 05/903,948
Preparation of .gamma.-quinacridone pigment
Inventor:
Roger A. Johnson
Patented Case
View Patent ↗
Granted: Apr 8, 1980
Filed: May 8, 1978
Inventor
Roger A. Johnson
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.