Base film

A base film for elongation comprising a thermoplastic polyurethane which is a reaction product of a mixture comprising a polyol, a multivalent isocyanate and a chain extender,

• wherein said multivalent isocyanate comprises a multivalent isocyanate having an aromatic core having 12 or more carbon atoms and a multivalent isocyanate having an aromatic core having less than 12 carbon atoms, and
• wherein the base film satisfies the following Equation 1:
• E/R≥5 [Equation 1]
• wherein, E is an elongation rate (unit:
• %) of said base film measured at room temperature, and R is a recovery rate (unit:
• %), and said recovery rate is a value measured by substituting a longitudinal length (T) of the base film, which is measured after elongating a laminate prepared by attaching to one side of said base film tailored to have a width of 50 mm and a length of 100 mm a PVA film having the same width and length and a thickness of 30 μm in water (temperature:
• 60° C.) five times in the longitudinal direction, and then taking it out from water, peeling said PVA film off, and maintaining the base film at room temperature for 1 hour, into an equation “100×(T−A)/A,” where A is a longitudinal length of said base film before elongation,
• wherein the ratio (C/D) of the weight (C) of the multivalent isocyanate having an aromatic core having 12 or more carbon atoms and the weight (D) of the multivalent isocyanate having an aromatic core having less than 12 carbon atoms is 5 to 30.