There is provided an optical film for backlight units or illuminators. The optical film comprises a light- incident portion and a light exit portion. Here, the optical film is characterized in that it comprises a plurality of protrusions formed on at least one of the light- incident portion and the light exit portion, wherein a plurality of the protrusions satisfies the requirements of the following Equation: 80xH1/3<=P<=200xH1/3 and 0.1xD<=H<=D, provided that a mean diameter of protrusions is represented by 'D', a mean height of protrusions is represented by 1H', and a mean distance between adjacent protrusions is represented by 'P'. Therefore, the optical film may be useful to suppress blocking between films and the formation of surface defects, which are caused by the Moire, Newton ring and wet-out phenomena, without degrading the brightness.