Patent ID: 7749584

Claim:
A heat-shrinkable polyester film in which the content of 1,4-cyclohexane dimethanol is 10 to 50% by mole based on a polyhydric alcohol component, and heat shrinkage factors (A), (B), and (C) of a 10 cm square sample of the film are 30 to 40%, 50 to 60%, and 65 to 77%, respectively: wherein (A) is a heat shrinkage factor of the square sample in a maximal shrinkage direction under the condition that the square sample is immersed in hot water of 75° C. for 10 seconds, and then in water of 25° C. for 10 seconds; (B) is a heat shrinkage factor of the square sample in the maximal shrinkage direction under the condition that the square sample is immersed in hot water of 85° C. for 10 seconds, and then in water of 25° C. or 10 seconds; and (C) is a heat shrinkage factor of the square sample in the maximal shrinkage direction under the condition that the square sample is immersed in hot water of 95° C. for 10 seconds, and then in water of 25° C. for 10 seconds, said film is made by a process comprising: drawing the film in at least one direction in three or more stages, wherein the drawing temperature in the second drawing stage or thereafter is substantially identical to or about 1 to 10° C lower than the drawing temperature in the immediate prior stage, wherein in the first drawing stage, the film is drawn to 1.1 to 1.5 times longer than the undrawn film, wherein in the second drawing stage, the film is drawn to 1.3 to 1.7 times longer than the film after the first drawing stage, wherein in the final stage, the film is drawn to 1.5 to 2.5 times longer than the film after the second drawing stage, and wherein during the final drawing stages the film is drawn to 3 to 6 times longer than the undrawn film.