PURPOSE: To provide an ink ribbon, cassette which allows optimal. conditions to be set, regardless of a change in the ambient temperature of circumstances for the timing of peeling an ink ribbon off a recording sheet after printing, without providing a special mechanism at a thermal transfer printer itself, when a ribbon cassette storing an ink ribbon with applied thermal melting ink is used in such a way that it is mounted on the thermal transfer printer.

CONSTITUTION: A peel-off time adjustment member 16 is installed on an ink ribbon cassette which stores an ink ribbon 15 and is used on a thermal transfer printer with a thermal head 11. The peel-off time adjustment member 16 becomes activated automatically in accordance with ambient temperatures of the surroundings, and works to prolong the peel-off time of ink ribbon 15 by continuing pressing the ink ribbon 15 to a recording sheet for a specified time, even after the printing of the recording sheet due to heating by the thermal head 11, if the ambient temperature exceeds a specified level.