BIAXIALLY ORIENTED POLYESTER FILM

摘要

PROBLEM TO BE SOLVED: To provide a biaxially oriented polyester film which can form a transfer image excellent in shape reproducibility and gradation, is resistant to breakage and high in productivity, and is useful as a base film of good flatness for a thermal transfer ribbon. SOLUTION: The polyester film which is manufactured by a simultaneous biaxial orientation method contains 0.1-2 wt.% of porous fine silica particles 0.5-5μm in average particle size. The surface of the film has at least 100/mm2 projections at least 0.8μm high. The longitudinal heat shrinkage ratio (HS: %) at 200 deg.C for 10 min and longitudinal F-5 value (F5: N/mm2) at 23 deg.C of the film meat formula of (HS/F5)<=0.028.