| 摘要 |
PROBLEM TO BE SOLVED: To provide such a biaxially oriented polyester film suitable for thermal transfer ribbons as can give transfer pictures with excellent gradation and as has excellent productivity with few breaks and excellent flatness. SOLUTION: This film has the following characteristics: (a) the containing of two kinds of fine particles as follows; A: calcium carbonate with an average particle dia. of 0.5-4 μm, in a content 0.1-2 wt.%. B: aluminum silicate with an average particle dia. of 0.1-2.0 μm, in a content of 0.05-1 wt.%. (b) an average roughness along center line (Ra), 10-40 nm. (c) a space factor, 1-19%. (d) projections with heights of more than 1.5 μm, 300-700/cm2 (e) a height difference between a crest and a bottom adjacent each other (a thickness difference) in a continuous thickness chart, within 8% of the average thickness. |
