Reversible multi-color thermal recording medium

A reversible multi-color thermal recording medium comprising

• an irreversible thermal composition recording layer containing a colorless or pale basic achromatic dye and an organic irreversible heat-resistant color developer as main components and
• a reversible multi-color thermal composition recording layer containing a colorless or pale basic achromatic dye and an organic reversible heat-resistant color developer as main components laminated on a support,
• wherein the reversible heat-resistant color developer is represented by the following formula (I):
• ##STR15## wherein X is selected from the group consisting of a hydrogen atom, alkyl group having 1 to 12 carbon atoms, halogenated alkyl group having 1 to 3 carbon atoms, alkoxy group having 1 to 12 carbon atoms, alkoxycarbonyl group having 1 to 12 carbon atoms, acyl group having 1 to 12 carbon atoms, dialkylamino group having 1 to 12 carbon atoms, nitro group, cyano group and halogen atom, m is an integer of 1 to 12, and n is an integer of 1 to 3, and
• the irreversible heat-resistant color developer is represented by the following formula (II):
• ##STR16## wherein X is selected from the group consisting of a lower alkyl group having 1 to 4 carbon atoms, alkoxy group having 1 to 3 carbon atoms, hydrogen atom, nitro group, cyano group and halogen atom, and m is an integer of 1 to 3.

A reversible multi-color thermal recording medium comprising

• an irreversible thermal composition recording layer containing a colorless or pale basic achromatic dye and an organic irreversible heat-resistant color developer as main components and
• a reversible multi-color thermal composition recording layer containing a colorless or pale basic achromatic dye and an organic reversible heat-resistant color developer as main components laminated on a support,
• wherein the reversible heat-resistant color developer is represented by the following formula (I'):
• ##STR17## wherein R is an alkyl group having 12 to 22 carbon atoms, A is selected from the group consisting of a lower alkyl group, lower alkoxy group, lower alkoxycarbonyl group, nitro group, halogen atom and hydrogen atom, and n is an integer of 1 to 3, and
• the irreversible heat-resistant color developer is represented by the following formula (II):
• ##STR18## wherein X is selected from the group consisting of a lower alkyl group having 1 to 4 carbon atoms, alkoxy group having 1 to 3 carbon atoms, hydrogen atom, nitro group, cyano group and halogen atom, and m is an integer of 1 to 3.