| 摘要 |
PROBLEM TO BE SOLVED: To provide a laminated film good in magnetic tape characteristics when being used as a base for vapor-deposited magnetic recording medium, by suppressing the precipitation of oligomers after storing at the normal temperature and in vapor deposition process. SOLUTION: The laminated polyester film includes a laminated structure containing at least a polyester layer A constituting one outermost surface and a polyester layer B constituting the other outermost surface and containing at least two kinds of particles; and the polyester layer B has a constitution satisfying conditions (1)-(5), that is, (1) the content of particlesαis 0.4-1 mass% when being assumed that particlesαare those having smallest average particle size among the particles contained, (2) the content of particlesβis 0.01-0.3 mass% when being assumed that particlesβare those having largest average particle size among the particles contained, (3) the content of the oligomers is one mass% or less, (4) the ratio of cyclic trimers in the oligomers is 20-70 mass%, and (5) the content of Mg is 100-400 ppm (in terms of mass). COPYRIGHT: (C)2009,JPO&INPIT
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