Patent ID: 7413810
Filing Date: 2008-08-19
Classification: C09K,G02B,G02F,Y10T

Abstract:
1. A protective film for polarizing plates which comprises a thermoplastic film having a photoelastic coefficient of 9.0×10 −12 Pa −1 or smaller and a saturated water absorption smaller than 0.05% by weight and an antireflection layer formed by alternately laminating high refractivity layers and low refractivity layers at least on one face of the thermoplastic film; wherein said protective film has a reflectance of 0.5% or smaller at a wavelength of 550 nm and has a standard deviation of S of 0.3 or smaller, wherein the standard deviation of S is obtained by obtaining a reflectance R(λ) at a wavelength λ in a region of wavelength of 380 to 780 nm while the wavelength λ is successively increased by an increment of 1 nm from 380 nm to 780 nm, calculating S in accordance with relation (1): which gives a sum of products of the reflectance R(λ) at a wavelength of λ and the increment of the wavelength between two successive measurements of the reflectance Δλ (=1 nm), and calculating the standard deviation of S obtained at 10 points randomly selected within an area of 100 cm 2 on a surface of the film.