Selection Methods for Biaxially Extended Plastic Films, Polarizing Plates, Image Display Devices, and Biaxially Extended Plastic Films for Optical Applications

Abstract

This invention provides an optical biaxially extended plastic film, a polarizing plate, and an image display device that can suppress blackouts when using polarized sunglasses or polarized goggles for visual perception without increasing the in-plane phase difference. Furthermore, this invention provides a method for selecting the optical biaxially extended plastic film. This invention is an optical biaxially extended plastic film having a region that satisfies the following conditions 1 and 2: <Condition 1> The difference (L1.n - L2.n) between the brightness obtained in a specific measurement 1 and the brightness obtained in a specific measurement 2 is calculated using 100 measurement points. The "brightness difference deviation 3σ" calculated from the brightness difference of the 100 measurement points is 100 or more. <Condition 2> The in-plane phase difference (Re) is 2500 nm or less. none

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