Heat-shrinkable polyester film having longitudinal (lengthwise) direction as main shrinkage direction

A uniaxial drawn heat-shrinkable polyester film having a main shrinkage direction in a longitudinal direction of the film, wherein

• the film is a single layer which comprises 40 mol % or more of ethylene glycol in 100 mol % of polyhydric alcohol constituents and 8 mol % or more and 40 mol % or less of 1,4-butanediol in 100 mol % of polyhydric alcohol constituents,
• the film has a shrinkage of 35% or more and 70% or less in the longitudinal direction after 10 seconds immersion in hot water of 80° C.,
• the film has a shrinkage of −8% or more and 7% or less in a width direction orthogonal to the longitudinal direction after 10 seconds immersion in hot water of 80° C.,
• the film has a change rate of 5% or more and 22% or less in the width direction of the film, and the change rate is measured by fixing the film in the longitudinal direction with fixed-length in the longitudinal direction and gripping the film in hot air of 90° C. for 10 seconds,
• the film has a change rate of 5% or more and 20% or less in the width direction of the film, and the change rate is measured by fixing the film in the longitudinal direction with 10% of slack in the longitudinal direction and gripping the film in hot air of 90° C. for 10 seconds,
• the film has a maximum shrinkage stress of 2 MPa or more and 10 MPa or less in the longitudinal direction measured under hot air of 90° C., and
• the film has a stress at 10% elongation of 1 MPa or more and 5 MPa or less in the longitudinal direction and 0.5 MPa or more and 3 MPa or less in the width direction when measured under hot air of 90° C.