Granted Patent
Utility
US 4,988,804 · App. 07/264,581
Polyazo dyes obtained by successive coupling of H-acid and two further anilinic diazo components on resorcinol or the like
Inventor:
Horst Langfeld
Patented Case
View Patent ↗
Granted: Jan 29, 1991
Filed: Oct 31, 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.