Retardation film, method of producing the same and image display device

A retardation film comprising:

• only one type of a resin component,
• wherein the only one type of resin component is either an epoxy resin cured product or an epoxy (meth)acrylate resin cured product,
• wherein an in-plane birefringence index of the retardation film at a wavelength of 590 nm is 0.001 or more and a birefringence index in a thickness direction thereof at a wavelength of 590 nm is 0.001 or more,
• the retardation film is a stretched film, and
• an index ellipsoid of the retardation film satisfies one of the relationships of nx>ny>nz, nx>nz>ny, or nx>ny=nz, wherein nx represents refractive index in the direction in which in-plane refractive index of the retardation film is maximum (X axial direction), ny represents refractive index in the direction orthogonal to the X axial direction in the same plane (Y axial direction), and nz represents refractive index in the direction orthogonal to the X axial direction and Y axial direction (thickness direction), and
• the in-plane birefringence index is determined from the expression:
• Δnxy [590]=nx−ny, and the birefringence index in the thickness direction is determined from the expression:
• Δnxz [590]=nx−nz.