Thermal transfer printing cationic dye with soft anionic base

Claim 2

A thermal transfer printing process which comprises contacting a transfer sheet, coated with a dye of the formula: D--A wherein D is a cationic chromophore and A is a soft anionic base, and a receiver sheet so that the dye is adjacent to the receiver sheet and selectively heating areas of the transfer sheet at a temperature of from 300° C. to 400° C. for a period of from 1 to 10 msec. whereby dye in the heated areas of the transfer sheet may be selectively transferred to the receiver sheet.

Claim 3

A thermal transfer printing process according to claim 1 wherein the cationic chromophore D incorporates a positively charged ammonium or phosphonium group.

Claim 4

A thermal transfer printing process according to claim 2 wherein the charge on the ammonium or phosphonium ion is delocalised.

Claim 5

A thermal transfer printing process according to claim 2 wherein the chromophore is selected from, (i) hemicyanines and diazahemicyanines of the formulae ##STR10## (ii) azacarbocyanines of the formulae: ##STR11## (iii) diazacarbocyanines of the formula: ##STR12## (iv) phenoxazines, phenothiazines and phenazines of the formula: ##STR13## wherein X is O, S or N--R respectively, (v) di- and tri-arylmethanes of the general formula: ##STR14## (vi) naphtholactams of the general formula: ##STR15## (vii) pyridine derivatives of azobenzenes of the formula: ##STR16## (viii) pyridine derivatives of azopyridones of the formula: ##STR17## and (ix) anthraquinones of the formula: ##STR18## wherein R is selected from H, C 1-4 -alkyl, mono- and bi-cyclic aryl and heteroaryl; Ar is selected from mono- and bi-cyclic aryl and heteroaryl; B is mono- or bi-cyclic heteroaryl comprising a five-membered heterocycle, optionally fused to a benzene ring, either or both of which may be substituted, and Y is C 1-4 -alkylene or 1,4-phenylene.

Claim 6

A thermal transfer printing process according to claim 1 wherein A has a nucleophilic reactivity constant greater than four.

Claim 7

A thermal transfer printing process according to claim 1 wherein A is selected from I - , SCN - , BF 4 - , RS - , S 2 O 3 2- , CN - , ZCS 2 - , ZCOS - and ZCO 2 - wherein Z is C 1-4 -alkyl or phenyl.

Claim 8

A thermal transfer printing process according to claim 1 wherein the coating comprises a resinous or polymeric binder to provide adhesion between the dye and the substrate.

Claim 9

A thermal transfer printing process according to claim 7 wherein the binder is ethylhydroxyethylcellulose.

Claim 10

A thermal transfer printing process according to claim 1 wherein the substrate is a flexible sheet material with a thickness of less than 50 micrometers and capable of withstanding a temperature up to 400° C. for a period of 20 milliseconds.

Claim 11

A transfer printing process according to claim 1 wherein the receiver sheet is a white polyester sheet material.