OPTICAL FILM, ITS MANUFACTURING METHOD, PROTECTIVE FILM FOR POLARIZING PLATE, POLARIZING PLATE USING IT, AND LIQUID CRYSTAL DISPLAY UNIT

PROBLEM TO BE SOLVED: To provide an optical film suitable for a protective film for a polarizing plate, a manufacturing method for the optical film, the protective film for the polarizing plate, which can improve the optical characteristics, particularly, luminance of a display because the protective film itself possesses polarized scattering anisotropy and which is excellent in productivity and durability, the polarizing plate using the protective film for the polarizing plate, and to provide a liquid crystal display unit using the polarizing plate. SOLUTION: The optical film is manufactured by casting a dope, containing a polymer, an organic solvent and indefinite particles, onto a substrate through the manifold portion and slit portion of a casting die. The flow velocity V of the dope in a casting-die inlet pipe is expressed by the expression: V=Q/A. The flow velocity Vm of the dope in the manifold portion and slit portion of the casting die is expressed by the expression: Vm=Q/Am. The ratio Rvm between the flow velocities V and Vm is expressed by the expression: Rvm=Vm/V. In this case, the ratio Rvm satisfies the inequality: 0.8≤Rvm≤20. Preferably, a time t for the passage of the dope through the die slit portion is in the range of 0.005 to 5 (sec). COPYRIGHT: (C)2008,JPO&INPIT