The object of the present invention is to provide a multilayer
phase-change information recording medium comprises a substrate, and N
layers of information layer (N represents an integral number of 2 or
more), and each of the information layers comprises at least a recording
layer in which information is recorded by irradiating laser beam to
induce a phase change between crystalline phase and amorphous phase. The
present invention is characterized in that when the information layer is
disposed so that a first information layer, a second information layer, a
third information layer . . . , and N information layer are disposed in
this sequence from the laser beam irradiation side, at least one
information layer other than the N information layer comprises a lower
protective layer, a recording layer, an upper protective layer, a
reflective layer, and a thermal diffusion layer disposed in this sequence
from the laser beam irradiation side; the thermal diffusion layer
comprises at least indium (In) and oxygen (O) and further comprises any
one of titanium (Ti) and zirconia (Zr); and the atomic ratio of indium
(In) to all the metal elements in the thermal diffusion layer, In/all the
metal elements, is 0.75 to 0.9.