Thermographic system using naphthoylated leuco phenazine dyes
AssigneeMinnesota Mining and Manufacturing Company
InventorsHarvey A. Brown, Louis M. Leichter, Alan G. Miller
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Abstract
Thermographic composition comprising a leuco dye, a nitrate salt, and, optionally, an acid and stabilizing compound. The leuco dye contains a phenazine nucleus with naphthoyl substitutents on the 10-position and, optionally on one or both of the 3- and 7-positions through an amino group. In their oxidized form, the leuco dyes of this invention provide access to a range of red and magenta colors which exhibit greater stability when subjected to light and temperatures characteristic of the stage of overhead projectors than that exhibited by previously available leuco dyes of this color range.
Claims9
A thermally imageable layer consisting essentially of a polymeric binder, and at least one leuco dye in reactive association with a nitrate salt, wherein the action of heat can oxidize said at least one leuco dye to give a change in color, said at least one leuco dye having the structural formula ##STR3## wherein R.sup.1 is selected from the group consisting of alkyl radicals, aryl radicals, alkoxy radicals, and aroyl radicals,
- R.sup.2 is selected from the group consisting of 1-naphthyl radical and 2-naphthyl radical,
- R.sup.3 and R.sup.4 are independently selected from the group consisting of hydrogen, halogens, substituted or unsubstituted alkyl radicals, and aromatic rings condensed on the 1, 2 and 8, 9 positions,
- Z is selected from the group consisting of hydrogen, -OH, -SH, substituted or unsubstituted alkyl radicals, alkoxy radicals, --NR.sup.5 R.sup.6, and --NR.sup.7 R.sup.8,
- R.sup.5 and R.sup.6 are independently selected from the group consisting of hydrogen, alkyl radicals, aryl radicals, aralkyl radicals, 1-naphthoyl radical, and 2-naphthoyl radical, provided that if either R.sup.5 or R.sup.6 is hydrogen, the other is not hydrogen,
- R.sup.7 and R.sup.8 are independently selected form the group consisting of hydrogen, alkyl radicals, aryl radicals, and aralkyl radicals, 1-naphthoyl radical, and 2-naphthoyl radical, provided that if either R.sup.7 or R.sup.8 is hydrogen, the other is not hydrogen.
Dependencies are inferred from the claim text.