| 摘要 |
PURPOSE: A biaxially stretched/co-extruded laminated polyester film is provided to upgrade frictional characteristics by constituting two outer layers having a specific number of protrusions whose protrusion height is specific. CONSTITUTION: The surface of the laminated polyester film is formed of an outer layer A and an outer layer C with a base layer inserted in between. The outer layer A meets conditions for the number Na of protrusions per 0.36 mm2 and the height ha of protrusions represented by formula I. The outer layer C shows a higher surface roughness Ra value than the surface roughness Ra value of the outer layer A and also meets conditions for the number Nc of protrusions per 0.36 mm2 and the height hc of protrusions represented by formula II. In addition, the surface gas flow rate time representing the surface shape of the outer layer C is longer than 550 sec, provided, however, that in formula I, A1=300, A2=7,000, B1=7.0, B2=8.0 and 0.01=<ha =<1.0 micrometer and in formula II, F1=8,000, F2=12,000, G1=8.0, G2=12.0 and 0.01=<hc =<1.0 micrometer.
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