Abstract: The present invention provides an optical film exhibiting wavelength dispersion such that a retardation value is smaller on the shorter wavelength side, and capable of being also formed comparatively thinly. The optical film of the present invention is an optical film including a polyimide-based polymer represented by the following general formula (I). In the formula (I), m is 40% by mol or more and 100% by mol or less. R1 and R2 each independently denote a substituent having a carbon-carbon double bond or a triple bond. A, A?, B, B?, E, G, and H each denote a substituent, and small letters corresponding to these alphabets denote substitution number thereof. X and Y each independently denote bond part such as a covalent bond. The substituents having a carbon-carbon double bond or a triple bond represented by R1 and R2 are a substituted or unsubstituted aryl group, a substituted or unsubstituted vinyl group, and a substituted or unsubstituted ethynyl group.

Abstract: An optical film of the present invention comprises a polyimide-based polymer represented by the following general formula (V). The optical film of the present invention exhibits an optical property such that wavelength dispersion of retardation scarcely changes ranging from the short wavelength side to the long wavelength side. Typically, the optical film of the present invention may be used as a retardation film of a liquid crystal display device.

Abstract: The retardation film of the present invention contains a thermoplastic polymer having at least a side chain component (A) oriented in a direction substantially orthogonal to a slow axis, and the absorption edge wavelength (?cut-off) of the side chain component (A) is 330 nm or more, and an in-plane retardation value (Re[450]) at a wavelength of 450 nm is smaller than that (Re[650]) at a wavelength of 650 nm. In the above-mentioned retardation film, the difference (?Re650?450=Re[650]?Re[450]) between the in-plane retardation value (Re[650]) at a wavelength of 650 nm and the in-plane retardation value (Re[450]) at a wavelength of 450 nm is preferably 10 nm or more. The retardation film of the present invention exhibits optical characteristics in which the in-plane birefringence is large and the difference between a retardation value on the short wavelength side and a retardation value on the long wavelength side is large.

Abstract: The object of the present invention is to provide an optical film excellent in transparency, heat resistance and processability.