Polaroid Corporation

Richard L Cournoyer

James W Foley

David P Waller

Ernest W Ellis

Roger A Boggs

Stephen J Telfer

Alan L Borror

Patrick R Conlon

Michael J Zuraw

Sandra E Russo-Rodriguez

Colorless precursors of preformed image dyes are provided which are useful as the color image-forming materials in thermal imaging systems. These colorless precursors possess at least one thermal protecting group that undergoes fragmentation upon heating and at least one leaving group that undergoes irreversible elimination upon heating, said protecting and leaving groups maintaining the precursor in its colorless form until heat is applied to effect removal of these groups whereby the precursor is converted to an image dye.

Thermal imaging dye precursors

Leuco dyes are provided which comprise the coupling product of a N-acyl substituted aromatic amino color developer and a dye-forming coupler moiety substituted at the coupling carbon with a thermally removable leaving group. Thermal imaging systems employing these leuco dyes have the advantage of reduced bubble formation relative to thermal imaging systems employing prior art leuco dyes containing a group which thermally fragments into one or more gases.

Thermal imaging methods and materials

A thermal imaging method for forming color images is provided which employs as the color image-forming material, a colorless precursor of a preformed image dye possessing at least one thermal protecting group that undergoes fragmentation upon heating and at least one leaving group that undergoes irreversible elimination upon heating, said protecting and leaving groups maintaining the precursor in its colorless form until heat is applied to effect removal of these groups whereby the precursor is converted to an image dye.

Thermal imaging method

In one embodiment, the present invention is concerned with novel xanthene compounds selected from those of the formulae ##STR1## wherein each R.sup.1 the same or different is alkyl, each R.sup.2 the same or different is an electron-withdrawing group having a positive sigma value greater than 0.6, X is ##STR2## wherein R.sup.3 is alkyl, Y is an electron-withdrawing group, n is 0 or 1 and A is an anion. In another embodiment, the present invention is concerned with photographic products and processes employing these xanthene compounds, e.g., as photographic light-screening dyes.

Xanthene compounds

The present invention is concerned with photographic products and processes employing certain pH-sensitive xanthene compounds as light-screening dyes, which compounds may be represented by the formulae ##STR1## wherein A and A', the same or different, are selected from ##STR2## each R is hydrogen or an electron-withdrawing group; each R.sup.1 is hydrogen or alkyl; each R.sup.2 is hydrogen, alkyl or an electron-withdrawing group; R.sup.3 is hydrogen or alkyl; R.sup.4 is alkyl; and n is 0 or 1 and which compounds in their colored, i.e., ring-opened form may be represented by the formulae ##STR3## wherein A, A', R.sup.3, R.sup.4 and n have the same meaning given above and Z is an anion.

Photographic products and processes with a pH sensitive xanthene light

The present invention is concerned with novel xanthene compounds of the formula ##STR1## wherein R' is alkyl and n is 0 or 1, which compounds are useful in photographic products and processes.

The present invention is concerned with novel xanthene compounds of the formulae ##STR1## and ##STR2## wherein each R.sup.1 the same or different is alkyl or benzyl; each R.sup.2 the same or different is an electron-withdrawing group having a positive sigma value greater than 0.6; R.sup.3 is hydrogen or alkyl; R.sup.4 is alkyl; and n is 0 or 1, said R.sup.2 group being ortho, meta or para to said N atom. The subject compounds are useful as light-screening dyes in photographic products and processes.

Novel xanthene compounds and photographic products and processes

In one embodiment, the present invention is concerned with novel xanthene compounds of the formula ##STR1## wherein X is ##STR2## wherein R' is alkyl, Y is an electron-withdrawing group and n is 0 or 1. In another embodiment, the present invention is concerned with photographic products and processes employing these xanthene compounds.

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Waltham, MA, United States of America

Richard L Cournoyer