Granted Patent
Utility
US 5,023,366 · App. 07/111,763
Salicylic acid copolymers and their metal salts, production process thereof, color-developing agents comprising metal salts of the copolymers, and color-developing sheets employing the agents
Inventors:
Keizaburo Yamaguchi, Yoshimitsu Tanabe, Makoto Asano, Akihiro Yamaguchi
Patented Case
View Patent ↗
Granted: Jun 11, 1991
Filed: Oct 23, 1987
Inventors
Keizaburo Yamaguchi
Yoshimitsu Tanabe
Makoto Asano
Akihiro 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.