Magnetic tape having characterized back coating layer, magnetic tape cartridge, and magnetic recording and reproducing apparatus
The magnetic tape includes: a non-magnetic support; a magnetic layer that includes ferromagnetic powder on one surface side of the non-magnetic support; and a back coating layer that includes non-magnetic powder on the other surface side of the non-magnetic support, in which the ferromagnetic powder is ferromagnetic powder selected from the group consisting of hexagonal strontium ferrite powder and ε-iron oxide powder, and the number of protrusions having a height of 50 nm or more and less than 75 nm on a surface of the back coating layer is 700 pieces/6400 μm 2 or less.
1. A magnetic tape comprising:
a non-magnetic support;
a magnetic layer that includes ferromagnetic powder on one surface side of the non-magnetic support; and
a back coating layer that includes non-magnetic powder on the other surface side of the non-magnetic support,
wherein the ferromagnetic powder is ferromagnetic powder selected from the group consisting of hexagonal strontium ferrite powder and ε-iron oxide powder,
the number of protrusions having a height of 50 nm or more and less than 75 nm on a surface of the back coating layer is 700 pieces/6400 μm 2 or less, and
a difference S after −S before between a spacing S after measured on a surface of the magnetic layer by optical interferometry after methyl ethyl ketone cleaning and a spacing S before measured on the surface of the magnetic layer by optical interferometry before methyl ethyl ketone cleaning is more than 0 nm and 15.0 nm or less.
2. The magnetic tape according to claim 1 ,
wherein the number of protrusions having a height of 75 nm or more on the surface of the back coating layer is 200 pieces/6400 μm 2 or less.
3. The magnetic tape according to claim 1 , further comprising:
a non-magnetic layer including non-magnetic powder between the non-magnetic support and the magnetic layer.
4. A magnetic tape cartridge comprising:
the magnetic tape according to claim 1 .
5. The magnetic tape cartridge according to claim 4 ,
wherein the number of protrusions having a height of 75 nm or more on the surface of the back coating layer is 200 pieces/6400 μm 2 or less.
6. The magnetic tape cartridge according to claim 4 ,
wherein the magnetic tape further comprises a non-magnetic layer including non- magnetic powder between the non-magnetic support and the magnetic layer.
7. A magnetic recording and reproducing apparatus comprising:
the magnetic tape according to claim 1 ; and
a magnetic head.
8. The magnetic recording and reproducing apparatus according to claim 7 ,
wherein the number of protrusions having a height of 75 nm or more on the surface of the back coating layer is 200 pieces/6400 μm 2 or less.
9. The magnetic recording and reproducing apparatus according to claim 7 ,
wherein the magnetic tape further comprises a non-magnetic layer including non-magnetic powder between the non-magnetic support and the magnetic layer.