Patent ID: 7867581

Claim:
A retardation film, formed by stretching a film comprising a norbornene-based ring-opening polymer containing a structural unit (A) represented by the following general formula (1): wherein n represents an integer of any one of 0 and 1, X 1 represents any one of a group represented by a formula: —CH═CH— and a group represented by a formula: —CH 2 CH 2 —, R 1 , R 2 , R 3 , and R 4 , which may be the same or different, each represent any one of atoms and groups selected from the group consisting of: a hydrogen atom; halogen atoms; substituted or unsubstituted hydrocarbon groups, each of which may include at least one linking group selected from the group consisting of an oxygen atom, a nitrogen atom, a sulfur atom, and a silicon atom, and which has 1 to 30 carbon atoms; and polar groups, wavy lines a and b each represent a configuration of any one of an endo and an exo, and a wavy line c represents a configuration of any one of an endo and an exo, wherein a content percentage of a structural unit (A-1), in which the wavy line c represents an exo configuration, among the structural units (A) is in a range from 20 mol % to 100 mol %.