  The scope of this work concerns the adaptation of the parallelizability
pp-wave (Ppp-wave) process to D=10 type IIB string backgrounds in the presence
of the non-trivial anti-self dual R-R 5-form $\QTR{cal}{F}$. This is important
in the sense that it gives rise to some unsuspected properties. In fact, exact
solutions of type IIB string backgrounds on Ppp-waves are discussed. For the
$u$-dependence of the dilaton field $\Phi $, we establish explicitly a
correspondence between type IIB supergravity equations of motion and
2d-conformal Liouville field theory. We show also that the corresponding
conserved conformal current $T(\Phi)$ coincides exactly with the trace of the
symmetric matrix $\mu_{ij}$ appearing in the quadratic front factor $F=\mu
_{ij}x^{i}x^{j}$ of the Ppp-wave. Furthermore, we consider the transverse space
dependence of the dilaton $\Phi $ and show that the supergravity equations are
easily solved for the linear realization of the dilaton field. Other remarkable
properties related to this case are also discussed.
