To provide a highly heat-resisting polymer precursor film capable of forming an optical film excellent in film forming property and suitable for applications of optical elements excellent in transparency and heat resistance, to provide an optical film using the precursor film, to provide a method for producing the optical film, and to provide an image display device using the optical film and excellent in displaying quality.

The optical film having ≥200°C glass-transition temperature (Tg) is produced by effecting heat or an active energy ray on a highly heat-resisting polymer precursor film to release a releasable group, wherein the highly heat-resisting polymer precursor film comprises a polymer having a releasable group releasable by effecting heat or an active energy ray at ≤350°C and having ≥200°C glass transition temperature (Tg) after releasing the releasable group.