Optical stack is disclosed. The optical stack includes a light redirecting film that includes a first structured major surface that includes a plurality of unitary discrete structures. The optical stack also includes an optical adhesive layer that is disposed on the light directing film. At least portions of at least some unitary discrete structures in the plurality of unitary discrete structures penetrate into the optical adhesive layer. At least portions of at least some unitary discrete structures in the plurality of unitary discrete structures do not penetrate into the optical adhesive layer. The peel strength of the light redirecting film and the optical adhesive layer is greater than about 30 grams/inch. The average effective transmission of the optical stack is not less or is less than by no more than about 10% as compared to an optical stack that has the same construction except that no unitary discrete structure penetrates into the optical adhesive layer.