| abstract |
A thermal-dye-bleach construction comprising a thermal nucleophile-generating agent in association with a polymethine dye having a nucleus of general formula (I): ##STR1## in which: n is 0, 1, 2 or 3; n R 1 and R 4 are independently selected from the group consisting of hydrogen atoms, optionally substituted alkyl groups of up to 30 carbon atoms, optionally substituted alkenyl groups of up to 30 carbon atoms and optionally substituted aryl groups of up to 14 carbon atoms; and n R 1 and R 2 together and/or R 3 and R 4 together may represent the necessary atoms to complete a 5 or 6-membered optionally substituted heterocyclic ring; or n one or more of R 1 to R 4 may represent the necessary atoms to complete an optionally substituted 5 or 6-membered heterocyclic ring fused to the phenyl ring on which the NR 1 R 2 or NR 3 R 4 group is attached; n R 5 and R 6 are independently selected from the group consisting of hydrogen atoms, tertiary amino groups, optionally substituted alkyl groups of up to 10 carbon atoms, optionally substituted aryl groups of up to 10 carbon atoms, optionally substituted heterocyclic rings comprising up to 6 ring atoms, optionally substituted carbocyclic rings comprising up to 6 carbon atoms and optionally substituted fused ring systems comprising up to 14 ring atoms, and, n X.sup.⊖ is an anion. |