Production method of optical film

A method for producing an optical film, comprising:

• treating a polymer film with steam, of which a temperature is from 50° C. to 150° C., for from 10 seconds to 1 hour before a heat-treatment,
• forming an optical layer on a surface of the polymer film after the steam treatment,
• subjecting the polymer film, on the surface of which the optical layer is formed, to a heat-treatment to adjust an asymmetry property of the polymer film,
• wherein the heat-treatment is performed for from 10 seconds to 1,000 seconds,
• wherein a shrinkage force of the polymer film before the heat-treatment along a first direction is from 5.5N to 15N,
• wherein a ratio (S1/S2) of the shrinkage force (S1) of the polymer film before the heat-treatment along the first direction relative to a shrinkage force (S2) of the polymer film before the heat-treatment along a second direction perpendicular to the first direction is 10 or more,
• wherein the heat-treatment is performed at a temperature satisfying Equation 2 below
• (Tg−60° ° C.)≤T≤(Tg+50° ° C.) [Equation 2]
• wherein, Tg is a glass transition temperature of the polymer film, T is a temperature of the heat-treatment, and each of units of the glass transition temperature and the temperature of the heat-treatment is ° C.