We investigate the structure of thin films of polymer blend solutions at equilibrium, taking into account the influence of the solvent concentration. Concentration profiles are obtained by numerical integration of the Hamiltonian flow associated with the mean-field Flory-Huggins-de Gennes theory supplemented by appropriate boundary terms. We focus, in particular, on the case of symmetric polymer blend solutions confined between walls that are antisymmetric with respect to both polymers and symmetric with respect to the solvent. It is shown that, as the system evolves from the one-phase region to the two-phase region, the equilibrium structure of the film undergoes a transition from a monolayer to a bilayer type of structure. Then, depending on whether T is, respectively, greater or smaller than the wetting transition temperature of the solvent free polymer blend, the equilibrium configuration either remains a bilayer or becomes a laterally phase separated structure as solvent is removed from the film. We finally uncover a complete family of new unstable solutions having no analogues in the solvent free case and exhibiting a possibly chaotic behavior of the system.