Patent ID: 11971567

Abstract:
Provided is an optical film that can eliminate rainbow unevenness when viewed with the naked eyes and provide favorable color tone uniformity when viewed at an oblique angle. This optical film has a low-refractive index layer on a plastic film, the plastic film has a slow axis that is an axis with the largest refractive index in a plane, and a fast axis that is an axis orthogonal to the slow axis in the plane of the plastic film, and the low-refractive index layer is located on the surface of the optical film. Linearly polarized light is incident, under predetermined conditions, from a surface on a side opposite to the low-refractive index layer of the optical film, and transmitted light of the linearly polarized light is used to measure the a* value and b* value of the L*a*b* color system at 11 measurement points with different angles. The measurements at the 11 measurement points are used to calculate a sum of square of a difference in a* between adjacent measurement points and square of a difference in b* between the adjacent measurement points. The sum was calculated for each of 10 adjacent points. The optical film has a ΣT, which indicates a total of the above sums, within a predetermined range.