Patent ID: 7279204

Claim:
A heat shrinkable polyester film, which satisfies the following requirements, (A) to (C): (A) when a square test piece cut off from said heat-shrinkable polyester film in a size of 10 cm×10 cm is immersed in hot water at 70° C. for 5 seconds, subsequently in water at 25° C. for 10 seconds, and withdrawn, the heat shrinkage percentage of the test piece in the maximum shrinkage direction is 10 to 50%; (B) when a square test piece cut off from the heat-shrinkable polyester film in a size of 10 cm×10 cm is immersed in hot water at 85° C. for 5 seconds, subsequently in water at 25° C. for 10 seconds, and withdrawn, the heat shrinkage percentage of the test piece in the maximum shrinkage direction is 70% or more and that in the direction orthogonal thereto, 10% or less; and (C) when a square test pieces cut off from the heat-shrinkable polyester film and the film thereof previously 10% heat shrunk in the maximum shrinkage direction in a size of 10 cm×10 cm are immersed in hot water at 95° C. for 5 seconds, subsequently in water at 25° C. for 10 seconds, and withdrawn, the heat shrinkage percentage of the test pieces in the maximum shrinkage direction are designated respectively as X 0 (%) and X 10 (%), the difference in heat shrinkage percentage Δ (%) calculated according to the following equation is 10 to 20%, Δ= X 0 −X 10 .