Polyester film for sealant use, laminate, and packaging bag

A polyester film for sealant use, comprising

• a polyester resin having ethylene terephthalate as a main structural component and including one or more monomer components that may serve as amorphous components so that the total amount of the monomer components being not less than 12 mol % and not more than 30 mol % among total monomer components,
• wherein, the polyester film is uniaxially or biaxially stretched, and satisfies the following requirements (1) to (4):
• (1) the heat-sealing strength is not less than 2 N/15 mm and not more than 20 N/15 mm when the polyester films are heat-sealed to each other at 130° C.;
• (2) the heat-sealing strength is not less than 2 N/15 mm and not more than 8 N/15 mm when the polyester film is heat-sealed to other biaxially stretched polyester film formed of a crystalline polyester at 130° C.;
• (3) the heat-sealing strength is not less than 2 N/15 mm and not more than 20 N/15 mm when the polyester film is heat-sealed to other unstretched polyester film formed of a crystalline polyester at 130° C.;
• and
• (4) the crystal melting heat capacity ΔHm measured by differential scanning calorimetry (DSC) is not less than 10 (J/g) and not more than 40 (J/g).