Granted Patent
Utility
US 5,175,261 · App. 07/739,099
Azopyridone dyes
Inventor:
Denis Robert Annesley Ridyard
Patented Case
View Patent ↗
Granted: Dec 29, 1992
Filed: Aug 1, 1991
Inventor
Denis Robert Annesley Ridyard
Assignee (at issue)
IMPERIAL CHEMICAL INDUSTRIES LIMITED
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.