Granted Patent
Utility
US 4,637,698 · App. 06/635,696
Photochromic compound and articles containing the same
Inventors:
Won S. Kwak, Rodney J. Hurditch
Patented Case
View Patent ↗
Granted: Jan 20, 1987
Filed: Jul 30, 1984
Inventors
Won S. Kwak
Rodney J. Hurditch
Assignee (at issue)
PPG Industries, Inc.
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.