NOVEL COLOUR DEVELOPER FOR A THERMO-SENSITIVE RECORDING MEDIUM, AND A HEAT-SENSITIVE RECORDING MATERIAL BASED ON PLA

The present invention provides an agent capable of reacting with a leuco dye upon heating, wherein said agent meets Formula (A-I):wherein: R1 and R2 are independently a hydrogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group or a halogen atom; R3, R4, R5 and R6 are independently a hydrogen atom, a C1-C6 alkyl group, a C3-C6 cycloalkyl group or a C2-C6 alkenyl group; X is O, S or NH; and, a and b are integer values meeting the conditions a ≥ 0, b ≥ 0 and (a+b) ≥ 1. The present invention also provides a thermosensitive recording medium having a colour developing layer comprising: a leuco dye; and, a colour developer which reacts with said leuco dye upon heating to form a colour layer, wherein said colour developer comprises an agent meeting said Formula (A-I). The present invention also relates to a coating composition for forming a heat-sensitive recording material or heat-sensitive recording layer, comprising one or more dye precursors and one or more colour developers based on lactic acid units, and also to a coating colour for forming a coating composition or a heat-sensitive recording layer, comprising one or more dye precursors and one or more colour developers based on lactic acid units, and further to a heat-sensitive recording material comprising a supporting substrate and a heat-sensitive recording layer of the invention, and also to a method of forming this heat-sensitive recording material and to the use of this heat-sensitive recording material. The present invention here also relates to such a coating composition or heat-sensitive recording layer as further contains at least one further colour developer not based on lactic acid units. The invention lastly also relates to a compound based on lactic acid units, preferably for use as a colour developer in the above context, to such a use itself, and to a method of forming this compound based on lactic acid units.