Magnetic disc medium
View Patent ↗A magnetic disc medium comprising: a magnetic sheet in the form of a disk; a case encasing the magnetic sheet so as to be capable of rotating; and a nonwoven liner fastened on an inner face of the case so as to face the magnetic sheet, wherein the magnetic sheet comprises a support, a substantially nonmagnetic lower layer, and a magnetic layer containing hexagonal ferrite powder dispersed in a binder and having central plane average surface roughness of from 1 nm to 4 nm, and the liner comprises polyethylene terephthalate in an amount of 20% by weight or more.
1. A magnetic disc medium comprising:
a magnetic sheet in the form of a disk;
a case encasing the magnetic sheet so as to be capable of rotating; and
a nonwoven liner fastened on an inner face of the case so as to face the magnetic sheet,
wherein the magnetic sheet comprises a support, a substantially nonmagnetic lower layer, and a magnetic layer containing hexagonal ferrite powder dispersed in a binder and having central plane average surface roughness of from 1 nm to 4 nm, and the liner comprises polyethylene terephthalate in an amount of 20% by weight or more.
2. The magnetic disc medium according to claim 1 , wherein the liner comprises polyethylene terephthalate in an amount of 50% by weight.
3. The magnetic disc medium according to claim 1 , wherein the magnetic layer has central plane average surface roughness of from 1 nm to 3 nm.
4. The magnetic disc medium according to claim 1 , wherein the magnetic layer has central plane average surface roughness of from 1 nm to 2 nm.
5. The magnetic disc medium according to claim 1 , wherein a surface of the magnetic layer has 100 or less of projections having a height of 20 nm or more measured by AFM at an area of 30 μm square.
6. The magnetic disc medium according to claim 1 , wherein the lower layer comprises a carbon black.
7. The magnetic disc medium according to claim 6 , wherein the carbon black has a particle size of from 5 to 80 nm.
8. The magnetic disc medium according to claim 6 , wherein the carbon black has a particle size of from 10 to 50 nm.
9. The magnetic disc medium according to claim 6 , wherein the carbon black has a particle size of from 10 to 40 nm.
10. The magnetic disc medium according to claim 1 , wherein the magnetic layer comprises a carbon black.
11. The magnetic disc medium according to claim 10 , wherein the carbon black has a particle size of from 5 to 300 mμ.
12. The magnetic disc medium according to claim 1 , wherein the lower layer comprises a metallic oxide, a metallic carbonate, a metallic sulfate, a metallic nitride, a metallic carbide or a metallic sulfide.
13. The magnetic disc medium according to claim 1 , wherein the lower layer comprises a titanium dioxide, a zinc oxide, an iron oxide or a barium sulfate.
14. The magnetic disc medium according to claim 1 , wherein the lower layer comprises a titanium dioxide or an alpha-iron oxide.