PURPOSE: To form a color image having color reproducibility suitable for color recording, especially, high transparency, high brightness and high due, by incorporating metal salt of specific dialkylphosphoric ester in an ink layer.

CONSTITUTION: In a thermal transfer recording medium wherein an ink layer having a colorant contained in the vehicle thereof and melted by heating is formed to the single surface of a heat resistant base material, a metal salt of dialkylphosphoric ester represented by general formula (wherein R1, R2, R3 and R4 are a 12W31C straight chain alcohol residue, an iso-acid residue, an an iso-acid residue and/or an oxyacid residue and M is calcium, zinc or barium) is contained in the ink layer. The ink layer pref. has m.p. of 40W150°C, viscosity of 10W20,000cps at 100°C and penetration of 0.1W30. This composition is constituted of 1W30% of a colorant, 95W70% of vehicle and 0W2% of an additive and prepared by dispersing said component in a proper solvent or hot melt and applied to a base material to form the ink layer.