Patent ID: 7829655

Claim:
A heat-shrinkable polyester film comprising ethylene terephthalate as a main constituent and containing 10% by mole or more of one or more kind(s) of monomer component(s) that become amorphous component(s) in all polyester resin components, being formed in a long shape with a constant width, and a main shrinkage direction thereof being a longitudinal direction, the heat-shrinkable film satisfying the following requirements (1) to (4): (1) the hot-water heat shrinkage ratio in the longitudinal direction is 15% or more and 80% or less when the film is treated in hot water at 90° C. for 10 seconds; (2) the hot-water heat shrinkage ratio in a width direction orthogonal to the longitudinal direction is 0% or more and 17% or less when the film is treated in hot water at 90° C. for 10 seconds; (3) the refractive indexes in the longitudinal direction and the width direction are both 1.570 or more and 1.620 or less; and (4) the natural shrinkage ratio in the main shrinkage direction after aging at 40° C. and 65% RH for 700 hours is 0.05% or more and 1.5% or less.