Metal-free disazo and polyazo compounds having at least one 6-hydroxypyrid-2-one coupling component radical linked to a 1-amino- or hydroxy-3-amino- or hydroxybenzene coupling component radical and metal complexes thereof

Granted: Mar 19, 1991 Filed: Dec 19, 1989

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.