Preparation of a coupling product of bisiazotized 2,2',5,5'-tetrachloro-4,4'-diaminobiphenyl with two equivalents of n-acetoacetyl-2,4-dimethylanilide

Granted: Mar 16, 1993 Filed: Apr 30, 1991

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.