Abstract: A thermal transfer ink sheet adopted to be repeatedly reused several times in a printing operation by means of a thermal printer. The thermal transfer ink sheet comprises a sheet-like base such as paper or a plastic film, a hot-melt ink layer stacked on the base with an adhesive layer disposed therebetween, and an ink-holding porous membrane layer filled with hot-melt ink and stacked on the ink layer. Another hot-melt ink layer may be further stacked on the ink-holding porous membrane layer.

Abstract: A diazotype heat development recording medium of the present invention has excellent shelf life and heat sensitivity. The medium comprises a support and a recording layer which is formed on said support and which comprises a diazo compound, a coupler, an acid stabilizer, a thermal developer, and a polymeric binder. The thermal developer is a salt of an organic or inorganic acid having a primary dissociation constant of 2.times.10.sup.-1 to 1.times.10.sup.-4 and an alkyl-substituted guanidine represented by the general formula: ##STR1## (wherein at least one of R1 and R2 is an alkyl group of C.sub.8 to C.sub.24, and the other of R1 and R2 is a hydrogen atom or an alkyl group of C.sub.1 or more).