| 摘要 |
PROBLEM TO BE SOLVED: To prepare a biaxially oriented polyester film useful as a base film for a magnetic recording medium having excellent electromagnetic conversion characteristics, drop out, abrasion resistance, running durability, or the like, further for a magnetic recording medium without a back coating layer formed on the opposite surface of a magnetic layer, especially for a digital signal recording type magnetic tape (e.g. a D-VHS tape). SOLUTION: This biaxially oriented polyester film for the magnetic recording medium is characterized as follows. The central surface average roughness WRa on the film surface is 10-25 nm and the height of protrusions formed on the film surface due to lubricant particles contained in the film is >=0.2μm. The number of coarse protrusions having >=5μm diameter of the bottom parts of the protrusions is 200-500 based on 10 cm<2> of the film surface.
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