Granted Patent
Utility
US 4,996,302 · App. 07/280,802
Process for the preparation of polyazo dyes
Inventor:
Horst Langfeld
Patented Case
View Patent ↗
Granted: Feb 26, 1991
Filed: Dec 7, 1988
Inventor
Horst Langfeld
Assignee (at issue)
Ciba-Geigy
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.