Granted Patent
Utility
US 4,426,231 · App. 06/407,644
Light stable quinacridonequinone pigments
Inventor:
Wilfried G. Holtje
Patented Case
View Patent ↗
Granted: Jan 17, 1984
Filed: Aug 12, 1982
Inventor
Wilfried G. Holtje
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.