| 摘要 |
PROBLEM TO BE SOLVED: To provide a protective film for a polarizing plate small in intra-plane and three-dimensional optical anisotropy and excellent in resistance against humidity and heat. SOLUTION: The transparent protective film for the polarizing plate is a sheet of a transparent film composed of a thermoplastic resin and having <=1 wt.% water absorption ratio and is characterized by having optical retardation at 450 nm and 550 nm wavelengths simultaneously satisfying the following inequalities (1)-(3).|R(550)|<=15 nm (1)|K(550)|<=35 nm (2) R(450)/R(550)<1 (3) (In the inequalities, R(450) and R(550) express intra-plane optical retardation of the transparent film at 450 nm and 550 nm wavelengths respectively. K(550) is a value of the transparent film at 550 nm wavelength calculated by K=[nz-(nx+ny)/2]×d (in the equation, nx, ny, nz are three-dimensional refractive indexes of the transparent film and are respectively refractive indexes in x, y, z axis directions and d is the film thickness)).
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