Heat shrinkable film and preparation method thereof

A heat shrinkable film, which comprises a polyester resin,

• wherein heat shrinkage characteristics of the heat shrinkable film in a direction perpendicular to a main shrinkage direction satisfy the following Relationships 1 and 2:
• −15≤ΔT70-65≤0 [Relationship 1]
• 0≤ΔT100-95≤5 [Relationship 2]
• wherein ΔTX-Y is a value obtained by subtracting a heat shrinkage rate of the heat shrinkable film in the direction perpendicular to the main shrinkage direction after the heat shrinkable film is immersed in a water bath for 10 seconds at Y° C. from a heat shrinkage rate of the heat shrinkable film in the direction perpendicular to the main shrinkage direction after the heat shrinkable film is immersed in a water bath for 10 seconds at X° C.;
• wherein the polyester resin comprises a dicarboxylic acid component and a diol component;
• wherein the diol component comprises neopentyl glycol in an amount of 10 to 30 mol % based on a total number of moles of the diol component;
• and
• wherein a heat of crystallization (ΔHc) measured by differential scanning calorimetry (DSC) of the heat shrinkable film is 0 to 30 J/g.