Abstract: A method for producing optical films is provided which comprises the steps of: melt-extruding a thermoplastic resin into a film through a die of an extruder, pressing the melt-extruded thermoplastic resin layer together with a supporting layer between a cooling roll which is made of metal or ceramic and a rubber roll which is pressed against the cooling roll and rolled in the same circumferential direction, carrying the thermoplastic resin layer together with the supporting layer under taking off tension until the thermoplastic resin layer is cooled down, and peeling and separating the supporting layer from the thermoplastic resin layer to obtain a thermoplastic resin film. Optical films are provided by a melt-extrusion method which have less optical surface defects such as die lines and gear marks and less fluctuations in film thickness and have uniform optical characteristics, which are useful as a material for various optical films used in liquid crystal displays, especially, a retardation film.

Abstract: A prism sheet having a plurality of substantially triangular prism-shaped lens units with their longitudinal axes almost parallel to each other arranged on one side and having the other side roughened, and with a characteristic value of 100 when said roughned side is smooth, the characterstic values are not less than 50 in glossiness, not more than 70 in internal reflective ability, and not more than 70 in friction coefficient when the plane including the prism peaks is rubbed by the roughened surface. The prism sheet of the present invention is therefrom free from interference fringes, substantially safe from scratching and uniform and high in brightness, being thus useful for liquid crystal devices etc.