To require a retardation film exhibiting viewing angle properties and wavelength dispersion properties excellent in a thin film from the viewpoint of suitability for the thinning of an optical member.SOLUTION: An optical film includes an ester based resin showing a negative birefringence and a wavelength dispersion control agent showing a positive wavelength dispersion. When setting a film in-plane refractive index in the fast axis direction to nx, a refractive index in a film in-plane direction orthogonal to the fast axis direction to ny and a film out-of-plane refractive index in the vertical direction to nz, a relationship thereamong is nx<ny less than or equal to nz, and the ratio (R450/R550) of an in-plane retardation (R450) measured at a wavelength of 450 nm to an in-plane retardation (R550) measured at a wavelength of 550 nm, shown by the following formula (a) is 1.00 or less. Re=(ny-nx)xd (a) (where, nx shows the...

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