Polyester film, heat-shrinkable label and packaging comprising same

A polyester film, which comprises a polyester resin in which a diol comprising ethylene glycol and diethylene glycol;

• and a dicarboxylic acid are copolymerized,
• wherein the difference between the crystallization temperature (Tc) and the melting temperature (Tm) measured by a differential scanning calorimeter (DSC) is 100° C. or less, and the film has an endothermic peak at 100° C. to 150° C. when measured with a differential scanning calorimeter (DSC) upon treatment with a 1% aqueous solution of NaOH at 85° C. for 15 minutes,
• wherein the polyester film has a difference in reversible heat capacity (ΔC0p) of 0.25 J/g·K or more before and after the glass transition temperature (Tg) as measured when it is subjected to first scan by a differential scanning calorimeter (DSC) from room temperature to 300° C. at a temperature elevation rate of 3° C./minute, followed by cooling thereof, and to second scan under the same conditions,
• wherein the polyester film has a shrinkage ratio of 74 to 80% in a transverse direction (TD) when heat-treated at a temperature of 80° C. for 10 seconds, and
• wherein the difference between the endothermic peak temperature and the melting temperature is 50° C. to 90° C.