An object of the present invention is to provide a heat sensitive recording
material which can develop color at high density by the inclusion of a
novel guanidine compound which is strongly basic and superior in diffusion
resistance. The present invention for attaining the above-described object
is a heat sensitive recording material comprising a substrate supporting
thereon a heat sensitive recording layer containing a diazonium salt
compound, a coupler which reacts with the diazonium salt compound when
heated to develop color, and a base, wherein the heat sensitive recording
layer includes as the base at least one of the guanidine compounds
represented by the general formula (1):
##STR1##
wherein, in the general formula (1), R.sup.1 and R.sup.2 represent an alkyl
group or aryl group and may be the same or different, R.sup.3 and R.sup.4
represent a hydrogen atom, alkyl group or halogen atom and may be the same
or different, and X represents a divalent connecting group.
