PROTECTING FILM FOR POLARIZATION PLATE WITH OPTIMUM RETARDATION VALUES, POLARIZATION PLATE AND LCD

摘要

PURPOSE: A protecting film for a polarization plate, a polarization plate and an LCD are provided to optimizing retardation values in a thickness direction and in a surface of the protecting film simultaneously for obtaining wide viewing angles with superior gray level characteristics. CONSTITUTION: A protecting film for a polarization plate is to be a cellulose ester film having a retardation value(Rth) in a thickness direction of 70-350§^, and a retardation value(Re) in a surface of 20-100§^, wherein an exchange degree of acetyl group is 1.5-2.3 and an exchange degree of propionyl group is 0.5-0.9. Rth is ((nx+ny)/2-nz)xd, and Re is (nx-ny)xd. nx represents a refraction index in an earth axis direction in a surface. ny represents a refraction index in a direction perpendicular to the earth axis. nz represents a refraction index in the thickness direction. d represents the thickness(nm) of the film.