Granted Patent
Utility
US 4,496,731 · App. 06/469,222
Process for the preparation of perylene-3,4,9,10-tetracarboxylic acid N,N'- d
Inventors:
Ernst Spietschka, Manfred Urban
Patented Case
View Patent ↗
Granted: Jan 29, 1985
Filed: Feb 24, 1983
Inventors
Ernst Spietschka
Manfred Urban
Assignee (at issue)
Hoechst GmbH
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.