Thermal imaging methods and materials
AssigneePolaroid Corporation
InventorsRoger A. Boggs, Richard L. Cournoyer, Ernest W. Ellis, Sandra E. Russo-Rodriguez, Stephen J. Telfer, David P. Waller, Michael J. Zuraw
Life of this patent
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Abstract
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.
Claims25
A heat-sensitive recording element which comprises a support carrying at least one layer of a leuco dye represented by ##STR26## wherein:
- E represents a thermally removable leaving group;
- tM represents a thermally migratable acyl group;
- Q, Q' and C taken together represent a dye-forming coupler moiety wherein C is the coupling carbon of said coupler moiety;
- and,
- (Y) taken together with N represents an aromatic amino color developer moiety,
- one of said Q, Q' and (Y) containing an atom selected from the atoms comprising Group 5A/Group 6A of the Periodic Table, said groups E and tM maintaining said leuco dye in a substantially colorless form until the application of heat causes said group E to be eliminated from said leuco dye and said group tM to migrate from said N atom to said Group 5A/Group 6A atom thereby forming a dye represented by ##STR27## wherein said dotted lines indicate that said tM group is bonded to said Group 5A/Group 6A atom in one of said Q, Q' and (Y).
A heat-sensitive recording element as defined in claim I wherein said E is a phenoxy group, unsubstituted or substituted with one or more groups selected from alkyl, alkoxy, halo, carboxy, nitro, cyano, --SO.sub.2 alkyl, --SO.sub.2 phenyl, tosyl and N,N-(dialkyl)amino.
A heat-sensitive recording element which comprises a support carrying at least one layer of a leuco dye having the structural formula ##STR32## wherein R.sup.4 is a t-butyl group or other group having a quaternary carbon atom bonded to the ketone carbonyl function;
- R.sup.5 is phenyl, unsubstituted or substituted with one or more groups selected from alkyl, alkoxy, nitro, halo, and carbonamido;
- E is a thermally removable leaving group;
- tM is a thermally migratable acyl group;
- and R.sup.6 and R.sup.7 are selected from hydrogen and lower alkyl groups containing 1 to 6 carbon atoms, said thermally migratable acyl group and said thermally removable leaving group maintaining said leuco dye in its colorless form until the application of heat causes the elimination of the thermally removable leaving group and the migration of the thermally migratable acyl group to the N containing H and R.sup.5 whereby said leuco dye is converted into an image dye represented by the structural formula ##STR33##
A method of thermal imaging which comprises heating imagewise a heat-sensitive element comprising a support carrying at least one layer of a leuco dye having the structural formula:
- ##STR36## wherein:
- E represents a thermally removable leaving group;
- tM represents a thermally migratable acyl group;
- Q, Q' and C taken together represent a dye-forming coupler moiety wherein C is the coupling carbon of said coupler moiety;
- and
- (Y) taken together with N represents an aromatic amino color developer moiety,
- one of said Q, Q' and (Y) containing an atom selected from the atoms comprising Group 5A/Group 6A of the Periodic Table, said groups E and tM maintaining said leuco dye in a substantially colorless form until the application of heat causes said group E to be eliminated from said leuco dye and said group tM to migrate from said N atom to said Group 5A/Group 6A atom thereby forming a dye represented by ##STR37## wherein said dotted lines indicate that said tM group is bonded to said Group 5A/Group 6A atom in one of said Q, Q' and (Y).
Dependencies are inferred from the claim text.