Magnetic recording medium and manufacturing method of the same

1 . A magnetic recording medium comprising:

a support;

an under layer comprising at least one of a metal and an alloy; and

a granular magnetic layer comprising ferromagnetic metal particles and a nonmagnetic oxide,

wherein the magnetic recording medium has a surface resistivity of from 1 to 100 Ω/□.

2 . The magnetic recording medium as claimed in claim 1 , wherein the under layer and the granular magnetic layer are provided by a vacuum deposition method.

3 . The magnetic recording medium as claimed in claim 1 , wherein the surface resistivity is from 1 to 50 Ω/□.

4 . The magnetic recording medium as claimed in claim 1 , wherein the under layer comprises at least one element selected from Cr, Ti, Ru, Re and Pt.

5 . The magnetic recording medium as claimed in claim 1 , wherein the under layer comprises Ru or an Ru alloy.

6 . The magnetic recording medium as claimed in claim 1 , wherein the under layer has a thickness of 50 nm or less.

7 . The magnetic recording medium as claimed in claim 1 , wherein the support is a flexible polymer support.

8 . The magnetic recording medium as claimed in claim 2 , wherein the vacuum deposition method comprises:

introducing rare gas into a vacuum deposition apparatus after satisfying that a vacuum degree in the vacuum deposition apparatus is no more than 1×10 −4 Pa and a partial pressure of water in the vacuum deposition apparatus is no more than 7×10 −5 Pa; and

forming the under layer and the granular magnetic layer over a support introduced into the vacuum film-forming apparatus, after the introducing.

9 . The magnetic recording medium as claimed in claim 8 , wherein a temperature of the support at the time of forming the under layer and the granular magnetic layer is less than 80° C.

10 . A method for manufacturing the magnetic recording medium claimed in claim 2 , the method comprising:

introducing rare gas into a vacuum deposition apparatus after satisfying that a vacuum degree in the vacuum deposition apparatus is no more than 1×10 −4 Pa and a partial pressure of water in the vacuum deposition apparatus is no more than 7×10 −5 Pa; and

forming the under layer and the granular magnetic layer over a support introduced into the vacuum film-forming apparatus, after the introducing.

11 . The method as claimed in claim 10 , wherein a temperature of the support at the time of forming the under layer and the granular magnetic layer is less than 80° C.

12 . The method as claimed in claim 10 , wherein the support is a flexible polymer support fed in a rolled form, and the method comprises: unwinding the support from an unwinding roller in a vacuum film-forming apparatus; forming at least the under layer and the granular magnetic layer while the flexible support is transported; and winding the resulting magnetic recording medium with a winding roller.