Granted Patent
Utility
US 4,948,571 · App. 07/334,529
Process for purifying nitrogen trifluoride gas
Inventors:
Isao Harada, Hisashi Hokonohara, Toshiaki Yamaguchi
Patented Case
View Patent ↗
Granted: Aug 14, 1990
Filed: Apr 7, 1989
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.