| 摘要 |
This invention provides an optical film for use in various display devices such as liquid crystal display devices, and a method for manufacturing the optical film. The degree of orientation of irregular particles in the optical film has been enhanced to enhance optical properties and strength of the optical film, for example, brightness improvement. Further, the optical film is suitable as a polarizing plate protective film and, at the same time, is excellent in production stability. In the method for manufacturing an optical film by a melt casting film formation method, a casting die comprises an inlet part into which a melt flows, a manifold part, and a slit part, comprising a stretching part and a land part for discharging a filmy melt, in that order from the upstream side in a melt extrusion direction. The sectional form of the stretching part and the sectional form of the land part satisfy formulae (1) and (2), respectively: A1 < A2 formula (1), and A3 = A4 formula (2). In the formulae, A1 and A2 represent the sectional area in position P1 of the die stretching part and the sectional area in position P2 which is located on the upstream side of position P1 in the extrusion direction; and A3 and A4 respectively represent the sectional area of different positions P3 and P4 in the land part. |
