An optical film includes: a structured-surface layer and a supporting layer bonded with the structured-surface layer, wherein the structured-surface layer includes a plurality of upper prismatic or structured protrusions formed on an upper portion of the structured-surface layer and having a plurality of lower prismatic protrusions or lower protrusions formed on a bottom portion of the structured-surface layer. The supporting layer is recessed with a plurality of notches to be engaged with the lower protrusions of the structured-surface layer to thereby firmly interlock the structured-surface layer with the supporting layer to increase the film strength and also to increase the brightness of the optical film.
