Thermal transfer printing: hetero-aromatic azo dye

Claim 2

A thermal transfer printing sheet comprising a substrate having a coating comprising at least one azo dye of the formula: A--N═N--E I wherein: A is the residue of a diazotisable heteroaromatic amine, A--NH 2 , in which A is selected from imidazolyl, pyrazolyl, isothiazolyl, pyridoisothiazolyl and thienyl, substituted by groups selected only from cyano, thiocyano, nitro, halogen, C 1-4 -alkoxy, formyl, cyano-C 1-4 -alkyl, C 1-4 -alkylsulphonyl, trifluoromethyl, fluorosulphonyl, C 1-4 -alkylcarbonyl and C 1-4 -alkoxycarbonyl; and E is a group of the formula: ##STR4## wherein R 1 is selected from H, chloro, C 1-4 -alkyl and C 1-4 -alkylcarbonylamino; and R 2 and R 3 are selected from H, C 1-4 -alkyl and C 1-4 -alkyl, substituted by a group selected from phenyl chloro, cyano, C 1-4 -alkoxy, C 1-4 -alkoxycarbonyl and C 1-4 -alkycarbonyloxy.

Claim 3

A thermal transfer printing sheet according to claim 1 wherein A, is selected form 1-cyanomethyl-4-5-dicyanoimidazol-2-yl; 4-cyanoisothiazol-5-yl; 3-methyl-4-cyanoisothiazol-5-yl; 1-cyanomethyl-3,4-dicyanopyrazol-5-yl; pyrido-(2-,3-c)-isothiazol-3-yl substituted in the 5, 6 or 5 and 6 positions by a group selected from cyano, nitro, methyl and methoxy; and thien-2-yl, substituted in the 3, 5 or 3 and 5 positions by a group selected from cyano, nitro, methylaminocarbonyl and in the 4 position by a group selected from H, methyl and methoxy.

Claim 4

A transfer printing sheet according to claim 1 wherein the azo dye conforms to the formula: ##STR5## wherein A is selected from 1-cyanomethyl-4,5-dicyanomidazol-2 yl; 4-cyanoisothiazol-5-yl; 3-methyl-4-cyanoisothiazol-5-yl; 1-cyanomethyl-3,4-dicyanopyrazol-5-yl; pryido(2,3-c)isothiazol-3-yl substituted in the 5, 6 or 5 and 6 positions by a group selected from cyano, nitro, methyl and methoxy; and thien-2-yl, substituted in the 3, 5 or 3 and 5 positions by one or more groups selected from methylaminocarbonyl, cyano and nitro and in the 4 position by a group selected from H, methyl and methoxy; R 1 is selected from H, chloro, C 1-4 -alkyl, C 1-4 -alkylcarbonyl-amino; and R 2 and R 3 are each independently selected from H; C 1-4 -alkyl, C 1-4 -alky substituted by a group selected from C 1-4 -alkoxy, C 1-4 -alkoxycarbonyl, C 1-4 -alkylcarbonyloxy, cyano and chloro.

Claim 5

A transfer printing process which comprises contacting a transfer sheet coated with a dye according to claim 1 with a receiver sheet, so that the dye is adjacent to the receiver sheet, and selectively heating areas of the transfer sheet to a temperature from >300° C. to 400° C. for a period from 2 to 10 milliseconds whereby dye in the heated areas of the transfer sheet may be selectively transferred to the receiver sheet.

Claim 6

A thermal transfer printing sheet according to claim 1 wherein the azo dye is selected from 3-methyl-4-(3-cyanomethyl-4,5-dicyanoimidazol-2-ylazo)-N-n-butyl-N-(3-(methoxycarbonyl)-propyl)-aniline, 3-methyl-4-(1-cyanomethyl-3,4-dicyanopyrazol-5-ylazo)-N-n-butyl-N-(2-(ethoxycarbonyl)ethyl)aniline, 3-methyl-4-(1-cyanomethyl-3,4-dicyanopyrazol-5-ylazo)-N-n-butyl-N-ethyl-aniline, 3-acetylamino-4-(1-cyanomethyl-3,4-dicyanopyrazol-5-ylazo)-N-n-butyl-N-ethylaniline, 3-methyl-4-(1-cyanomethyl-3,4-dicyanopyrazol-5-ylazo)-N,N-diethylaniline, 3-methyl-4-(3-methyl-4-cyanoisothiazol-5-ylazo)-N,N-diethylaniline, 4-(3-methyl-4-cyanoisothiazol-5-ylazo)-N,N-diethylaniline, 4-(3-methyl-4-cyanoisothiazol-5-ylazo)-N-ethyl-N-(2-ethoxyethyl)aniline, 3-methyl-4-(3-methyl-4-cyanoisothiazol-5-ylazo)-N,N-di(2-acetoxyethyl)-aniline, 3-methyl-4-(3-methyl-4-cyanoisothiazol-5-ylazo)-N-n-butyl-N-(2-(ethoxycarbonyl)ethyl)aniline, 3-methyl-4-(3-methyl-4-cyanoisothiazol-5-ylazo)-N-n-ethyl-N-(2-(ethoxy-carbonyl)ethyl)aniline, 3-methyl-4-(3-methyl-4-cyanoisothiazol-5-ylazo)-N-n-ethyl-N-(2-ethoxyethyl)aniline, 3-methyl-4-(3,5-dinitrothien-2-ylazo)-N,N-diethylaniline and 3-methyl-4-(3,5-dicyano-4-methylthien-2-ylazo)-N,N-di(2-acetoxyethyl)aniline.