OPTICAL FILM, ITS MANUFACTURING METHOD, PROTECTIVE FILM FOR POLARIZATION PLATE USING IT AND LIQUID CRYSTAL DISPLAY DEVICE

PROBLEM TO BE SOLVED: To provide an optical film suitable as a protective film for a polarization plate, its manufacturing method, the protective film for the polarization plate capable of enhancing the optical characteristics, especially brightness of a display by imparting polarized scattering anisotropy to the protective film itself for the polarization plate and excellent in productivity and durability, the polarization plate using the protective film for the polarization plate, and a liquid crystal display device using the polarization plate. SOLUTION: A molten material, which is obtained by melting and kneading a thermoplastic resin and indeterminate shape particles to extrude them, is passed through the manifold part 3 and slit part 4 of a casting die 1 to be cast on a support to manufacture the optical film. When the flow velocity of the dope in the inlet pipe of the casting die is set at V=Q/A, and the flow velocity of the dope in the manifold part and slit part of the casting die is set at Vm=Q/Am, the ratio of these flow velocities, Rvm=Vm/V is 0.8≤Rvm≤20. The die slit part passing time (t) of the dope is preferably 0.002-10 (sec). COPYRIGHT: (C)2008,JPO&INPIT