Diazo-type thermosensitive recording material

A diazo-type thermosensitive recording material comprising a diazo-type thermosensitive coloring layer formed on a support material, the diazo-type thermosensitive coloring layer comprising a diazo compound, a coupler capable of forming an azo dye in the reaction between the diazo compound and the coupler, and a petroleum resin with a melting or softening point ranging from 50 DEG C. to 150 DEG C., and with the addition of auxiliary components for improving the properties of the thermosensitive recording material. By the use of such a petroleum resin in the thermosensitive coloring layer, the diazo compound and the coupler are separated from each other, and the coloring reaction between the two is prevented during storage, so that excellent preservation over a long period is attained, while when image formation is done by heat application, the coupling reaction between the diazo compound and the coupler is accelerated due to the low melting point of the petroleum resin present in the thermosensitive coloring layer, whereby efficient thermal response to thermal heads is attained.