Magnetic recording medium and magnetic recording device
View Patent ↗A magnetic recording medium having excellent durability and corrosion resistance as well as a magnetic recording device equipped with the magnetic recording medium is provided. The protective layer of the magnetic recording medium is composed of two layers, that is, a lower layer contacting with the magnetic layer and an upper layer on the lower layer. The internal stress of the lower layer is made smaller than that of the upper layer, and the surface free energy of the lower layer is made smaller than that of the upper layer.
1. A magnetic recording medium formed by layering on a substrate, a magnetic layer, a protective layer and a lubricant layer in this order, wherein:
said protective layer consists only of two layers, that is, a lower layer contacting with the magnetic layer and an upper layer on the lower layer;
the internal stress of the lower layer is smaller than that of the upper layer; and
the surface free energy of the lower layer is smaller than that of the upper layer,
wherein both of said lower layer and said upper layer are formed by deposition by the Filtered Cathodic Arc method,
wherein said lower layer comprises an amorphous carbon and fluorine as main components, and said upper layer comprises an amorphous carbon as a main component.
2. A magnetic recording medium according to claim 1 , wherein not less than 90 atom % of said upper layer is composed of carbon.
3. A magnetic recording medium according to claim 1 , wherein from 50 to 80 atom % of said lower layer is composed of carbon.
4. A magnetic recording medium according to claim 1 , wherein the total content of hydrogen and fluorine in said lower layer is larger than that of said upper layer.
5. A magnetic recording medium according to claim 1 , wherein the composition of said lower layer is formed by adding hydrogen, or fluorine, or hydrogen and fluorine to a composition that is the same as that of the upper layer.
6. A magnetic recording medium according to claim 1 , wherein said lower layer has an internal stress of not more than 5 GPa.
7. A magnetic recording medium according to claim 1 , wherein said lower layer has a surface free energy of not more than 40 mN/m.
8. A magnetic recording medium according to claim 1 , wherein said upper layer has a hardness of not less than 20 GPa.
9. A magnetic recording medium according to claim 1 , wherein said upper layer has a density of not less than 2.5 g/cm3.
10. A magnetic recording medium according to claim 1 , wherein the ratio of the film thickness of said lower layer to that of said upper layer is in the range of from 3:7 to 7:3.
11. A magnetic recording medium according to claim 1 , wherein the film thickness of said protective layer is not more than 5 nm.
12. A magnetic recording device equipped with a magnetic recording medium according to one of claims 1 , 2 and 3 to 11 .