A thermal transfer sheet is provided which, during storage up to use
thereof, is less likely to cause a dye contained in a thermally
transferable ink layer to migrate to a heat-resistant protective layer in
contact with the thermally transferable ink layer and, in actually
performing thermal printing, does not cause heat fusing between a thermal
head and the sheet. The thermal transfer sheet comprises: a substrate
sheet; a thermally transferable ink layer provided on one surface of the
substrate sheet; and provided on the other surface of the substrate sheet,
a heat-resistant protective layer comprising a primer layer and a
heat-resistant slip layer provided in that order, the primer layer being
formed of a composition comprising a synthetic resin which has a storage
modulus G' of not less than 10.sup.6 Pa at 40.degree. C. and a loss
modulus G" of not less than 10.sup.4 Pa at 120.degree. C.
