This invention describes a heat sensitive composition comprising: (A-I) a compound
which is represented by the following general formula (I) and generates a radical
when heated, and (B-I) a compound having physical and chemical properties that
are changed irreversibly by a radical,
wherein R represents an alkyl group or aryl group, and M+ represents
a counter cation selected from sulfonium, iodonium, diazonium, ammonium and azinium;
and a negative planographic printing plate precursor which can be recorded by heat
mode using this composition. This invention also describes a planographic printing
plate precursor comprising a substrate having disposed thereon a photosensitive
layer containing (C-II) a light-heat converting agent, (B-II) a compound having
a polymerizable unsaturated group, and (A-II) an onium salt having at least two
cation parts in one molecule.
