| 主权项 |
1. An optical film comprising a thermoplastic resin and at least one compound which satisfies all of the following requirements (1) to (5):
(1) the compound has at least two absorption maxima in a wavelength region of from 200 nm to 350 nm in a solution absorption spectrum; (2) when a wavelength of a first absorption maximum of the two absorption maxima in the wavelength region of from 200 nm to 350 nm is designated as λmax1, and a wavelength of a second absorption maximum of the two absorption maxima at shorter wavelengths than the first absorption maximum is designated as λmax2, wherein λmax1−λmax2 is 20 nm or more; (3) an aspect ratio of a molecule of the compound is 1.70 or more; (4) the compound has a non-aromatic hydrocarbon ring, an aromatic heterocyclic ring, or a non-aromatic heterocyclic ring in the molecule; and (5) for a sample film having a thickness of 60 μm and containing the thermoplastic resin and the compound at a proportion of 1% by mass with respect to the thermoplastic resin, when a retardation in an in-plane direction at a wavelength of 550 nm before stretching of the sample film is designated as R0A0(550), and a retardation in the in-plane direction at a wavelength of 550 nm after stretching at a temperature higher by 25° C. than a glass transition temperature of the sample film is designated as R0A1(550), so that a in-plane retardation sensitivity obtained by dividing R0A1(550)−R0A0(550) by actual stretch ratio of the sample film is designated as A; and for a blank film having a thickness of 60 μm and formed from the thermoplastic resin, when a retardation in the in-plane direction at a wavelength of 550 nm before stretching of the blank film is designated as R0B0(550), and a retardation in the in-plane direction at a wavelength of 550 nm after stretching at a temperature higher by 25° C. than a glass transition temperature of the blank film is designated as R0B1(550), so that an in-plane retardation sensitivity obtained by dividing R0B1(550)−R0B0(550) by actual stretch ratio of the blank film is designated as B, an in-plane retardation increase sensitivity defined by A−B is 0.1 or more, wherein when the retardations in the in-plane direction measured at wavelengths of 450 nm, 550 nm and 650 nm are designated as R0(450), R0(550) and R0(650), respectively, the following Formulas (a) to (c) are all satisfied:
110 nm≦R0(550)≦170 nm; (a)0.72≦R0(450)/R0(550)≦0.96; and (b)0.83≦R0(550)/R0(650)≦0.97. (c) |
