| 摘要 |
PROBLEM TO BE SOLVED: To provide a polyester film for a magnetic recording medium that is given cushion properties by controlling voids while having suitable runnability of a magnetic recording tape and frictional properties, and also has superior slipperiness, durability and electric characteristics by preventing transfer marks of film surface projections.SOLUTION: There is provided a polyester film for magnetic recording medium that is a laminated film having a void layer on one surface of a base material layer, and characterized in that the void layer has a center line surface roughness SRa of 10-30 nm and a porosity of 2-10%, and a layer thickness (L1) of the void layer and a length (L2) of a gap of the void layer in a film thickness direction satisfy an expression (1) of 0.1≤L2/L1≤0.3. |
