Heat shrinkable film and preparation method thereof

A heat shrinkable film, which comprises a polyester resin,

• wherein a maximum expansion rate in direction perpendicular to main shrinking direction of the heat shrinkable film is 5 to 12%;
• wherein the polyester resin comprises a dicarboxylic acid component and a diol component, and the diol component comprises diethylene glycol and neopentyl glycol;
• wherein content of diethylene glycol is 5 to 15% by mole based on the total number of moles of the diol component, and content of neopentyl glycol is 22 to 30% by mole based on the total number of moles of the diol component;
• and
• wherein heat shrinkage characteristics of the heat shrinkable film in the direction perpendicular to the main shrinkage direction satisfy the following Relationships 1b and 2b:
• Relationship 1b −8%≤ΔTX−Y≤−1%, wherein X is 70 and Y is 65,
• Relationship 2b 0.2%≤ΔTX−Y≤1%, wherein X is 100 and Y is 95,
• 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.