| 摘要 |
PROBLEM TO BE SOLVED: To provide a magnetic tape which has a high S/N in an optical servo signal and hardly causes disordered rolling of a tape. SOLUTION: In the magnetic tape provided with a non-magnetic support, a magnetic layer formed on one side of the non-magnetic support, and a back coat layer containing a non-magnetic powder with carbon black as a component and a binder, formed with a recess for optical servo on the relevant back coat layer and having the full thickness of <=6μm, when the full thickness of the magnetic tape is defined as T and an average height per 100 projections in the recessed terminal of the back coat layer (the peripheral portion of the recess for optical servo) is defined as H, an H/T is set to be 1/50 or below. Besides, a contents of the magnetic powder in the back coat layer [(weight of non-magnetic powder)÷(weight of non-magnetic powder+weight of binder)×100] is at least 50 wt.%, an average surface roughness Ra in the flat part of the back coat layer measured by an atomic force microscope is 30 nm or below, and a half-value width of fluctuation caused by the magnetic tape location of the average surface roughness Ra is 5 nm or below.
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