Optical film, multilayer optical film including same, and method for producing optical film

A method for producing an optical film having an absolute value of an in-plane retardation Re represented by Formula (1) below at a wavelength of 550 nm is 10 nm or lower, and whose thickness-direction retardation Rth represented by Formula (2) below at a wavelength of 550 nm is 40 nm or more:

• Re=(Nx−Ny)×d (1)
• Rth=((Nx+Ny)/2−Nz)×d (2),
• the method comprising holding and molding a molten resin as a material of the optical film between an elastic metal roller as a first cooling roller and a non-elastic metal roller as a second cooling roller,
• wherein:
• in Formulae (1) and (2), Nx represents a refractive index in a direction with the largest refractive index on the plane of the film, Ny represents a refractive index in a direction vertical to the Nx direction, Nz represents a refractive index in the thickness direction of the film, and d represents the thickness of the optical film;
• and
• during the holding and molding the molten resin as the material of the optical film between the first and second cooling rollers, a linear pressure upon holding is 12-25 kgf/cm, a take-up speed is 8-20 m/min, and a surface temperature (Tr) of the first and second rollers is:
• (Th−10° C.)≤Tr≤(Th+20° C.)
• with respect to a thermal deformation temperature (Th) of the resin.