Thermographic material with good stability useful with optical mark reader

摘要

In thermographic material having a base with a thermographic layer contg. a colourless or slightly coloured basic dye and an acceptor, (a) the basic dye comprises fluoran deriv(s). (I) forming a black dye and phenothiazine deriv(s). of formula (II) in an amt. of 5-100 wt.% w.r.t. (I); and (b) the acceptor comprises diphenyl sulphone deriv(s). of formula (III): R1-4 = 1-4C alkyl; R5 = H,halogen, 1-4C alkyl or 1-4C alkoxy; R6, R7 = 1-4C alkyl, 2-4C alkenyl, 1-4C alkoxy,benzyloxy or halogen; m,p, q = 0-2; n = 1-3.