Granted Patent
Utility
US 5,183,647 · App. 07/689,941
Method for purifying nitrogen trifluoride gas
Inventors:
Isao Harada, Hisashi Hokonohara, Toshiaki Yamaguchi
Patented Case
View Patent ↗
Granted: Feb 2, 1993
Filed: May 28, 1991
Inventors
Isao Harada
Hisashi Hokonohara
Toshiaki Yamaguchi
Assignee (at issue)
Mitsui Toatsu Chemicals, Incorporated
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.