White polyester film, laminate, and packaging bag

A white polyester film which is formed with a polyester resin whose main constituent is ethylene terephthalate, and satisfies the following requirements (1) to (6):

• (1) the film consists of either (a) two layers:
• a white layer and a heat sealing layer or (b) three layers:
• a heat sealing layer/a white layer/a heat sealing layer, wherein at least one of the film surfaces is the heat sealing layer, and the white layer comprises a thermoplastic resin immiscible with the polyester;
• (2) the film has a peeling strength of 4 N/15 mm or more and 25 N/15 mm or less when the heat sealing layers of two identical polyester films are heat-sealed to each other at 160° C. and 0.2 MPa for 2 seconds;
• (3) the heat sealing layer of the polyester film has a difference in reversing heat capacity of 0.18 J/g·K or more and 0.35 J/g·K or less, and wherein the difference in reversing heat capacity is measured between at a lower and a higher temperature than a glass transition temperature with a temperature modulated DSC;
• (4) the film has a heat shrinkage of −10% or more and 10% or less both in a longitudinal direction and in a width direction when treated in hot water at 80° C. for 10 seconds;
• (5) the film has a total light transmittance of 20% or more and 40% or less;
• and
• (6) the film has an apparent specific gravity of 0.90 or more and 1.30 or less.