On the de rham complex of mixed twistor D-modules

Given a complex manifold S, we introduce for each complex manifold X a t-structure on the bounded derived category of C-constructible complexes of OS-modules on X × S. We prove that the de Rham complex of a holonomic DX×S/S-module which is OS-flat as well as its dual object is perverse relatively to this t-structure. This result applies to mixed twistor D-modules.