Polyester sealant film, laminate and package

A polyester sealant film consisting of a two-kind two-layer structure of a heat sealing layer and a heat resistant layer, wherein both the heat sealing layer and the heat resistant layer consist of a polyester component which comprises ethylene terephthalate as a main component, and wherein the polyester sealant film satisfies following requirements (1) to (6):

• (1) a heat sealing strength of the heat sealing layer being heat-sealed to another heat sealing layer of an identical polyester film at 140° C. and 0.2 MPa for 2 seconds is 8 N/15 mm or more and 20 N/15 mm or less;
• (2) the heat sealing layer has a difference in reversible heat capacity (ΔCp) between a glass transition temperature and 140° C. of 0.61 J/g/K or more and 1.1 J/g/K or less when measured with a temperature modulated DSC;
• (3) the heat resistant layer has a ΔCp of 0.1 J/g/K or more and less than 0.6 J/g/K when measured with the temperature modulated DSC;
• (4) the film has a fold holding angle of 20 degrees or more and 60 degrees or less;
• (5) the film has a curvature radius of 50 mm or more and 300 mm or less in either a longitudinal direction or a widthwise direction, whichever has a smaller curvature radius;
• and
• (6) the film has a heat shrinkage ratio of −5% or more and 5% or less in both a longitudinal direction and a widthwise direction after immersed in hot water of 80° C. for 10 seconds,
• wherein
• the polyester component constituting the heat sealing layer comprises a diol monomer component other than ethylene glycol as a monomer component,
• the polyester component constituting the heat resistant layer comprises a diol monomer component other than ethylene glycol as a monomer component;
• the content of the diol monomer component in the heat sealing layer is 32% or more by mol and 50% or less by mol;
• the content of the diol monomer component in the heat resistant layer is 9% or more by mol and 20% or less by mol;
• and
• a difference of the content of the diol monomer component between the heat sealing layer and the heat resistant layer is 20% or more by mol and 35% or less by mol.