THERMAL RECORDING MEDIUM

PURPOSE:To enhance sensitivity of a thermal recording medium, to improve oil resistance, plasticizer resistance of a color developed image and to hence enhance long-term stability of the image by forming developer contained together with dye precursor in a thermal color developed layer of the medium of compound having a specific structure. CONSTITUTION:The thermal recording medium comprises a sheetlike base, and a thermal color developed layer formed at least on one surface of the base and containing colorless or light-color dye precursor and developer for color developing the precursor in reaction by heating. The developer contains at least one type of compound represented by a formula (wherein X is O, S, R is at least aromatic group substituted with at least one member selected from non-substituted aromatic group, lower alkyl group, lower alkoxy group and halogen atom, A is bivalent or higher group, and n is integer of 2 or more). As a result, the medium in which the image having excellent oil resistance, plasticizer resistance, moisture resistance, heat resistance, etc., i.e., excellent long-term preservability can be formed can be obtained.