The invention relates to a resin solution containing polyester with a specific structure, an optical film containing said polyester, and methods for production thereof. Further, the invention also relates to an optical laminate, a polarizing plate, and an image display device each using the optical film. The polyester may be obtained by condensation polymerization of dicarboxylic acid compound(s) and bisphenol compound(s), and preferably has no halogen atom in its chemical structure. According to the invention, high productivity of the optical film can be achieved since the polyester has a high solubility in solvents, and an environmental loading for production can be reduced.