Granted Patent
Utility
US 4,921,653 · App. 07/266,134
Method of forming a porous polyolefin film
Inventors:
Mari Aoyama, Michiyasu Ito, Syoichi Tsuji, Toshiyuki Ishii, Tomohide Tanaka
Patented Case
View Patent ↗
Granted: May 1, 1990
Filed: Nov 2, 1988
Inventors
Mari Aoyama
Michiyasu Ito
Syoichi Tsuji
Toshiyuki Ishii
Tomohide Tanaka
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.