Method for producing magnetic recording medium, and magnetic recording/reproducing apparatus
View Patent ↗A method for producing a magnetic recording medium having a magnetically partitioned magnetic recording pattern on at least one surface of a nonmagnetic substrate, characterized by comprising a step of reacting portions of a magnetic layer, formed on the non-magnetic substrate, with ozone to modify magnetic properties of said portions of the magnetic layer for forming the magnetically partitioned magnetic recording pattern. The magnetic layer can be a two-layer structure comprising a magnetic layer having a granular structure and formed thereon a magnetic layer having a non-granular structure. The produced magnetic recording medium exhibits a greatly enhanced recording density while recording/reproducing characteristics equal to or better than those of the heretofore proposed magnetic recording mediums are maintained, and it can be produced with an enhanced efficiency.
1. A method for producing a magnetic recording medium having a magnetically partitioned magnetic recording pattern on at least one surface of a nonmagnetic substrate, characterized by comprising the following nine steps (A1) through (G1) carried out in this order:
(A1) a step of forming, on at least one surface of a non-magnetic substrate, a magnetic layer having a granular structure comprised of magnetic particles surrounded by an oxide,
(A2) a step of forming a magnetic layer having a non-granular structure on the magnetic layer having a granular structure,
(B1) a step of forming a mask layer on the magnetic layer having a non-granular structure,
(C1) a step of forming a resist layer on the mask layer,
(D1) a step of forming a negative pattern of the magnetic recording pattern on the resist layer,
(E1) a step of removing regions of the mask layer corresponding to the negative pattern of the magnetic recording pattern,
(E2) a step of removing regions of the magnetic layer having a non-granular structure corresponding to the negative pattern of the magnetic recording pattern,
(E3) a step of removing surface layer portions having a thickness in the range of 0.1 nm to 15 nm in the exposed regions of the magnetic layer having the granular structure which have been exposed by the step (E2),
(F1) a step of contacting the exposed regions of the magnetic layer having the granular structure, which have been exposed by the removal of the surface layer portions of the magnetic layer in step (E3), with ozone whereby the magnetic layer having the granular structure is reacted with ozone to modify the magnetic properties in the exposed regions of the magnetic layer having the granular structure, and
(G1) a step of removing the residual mask layer, or the residual mask layer and resist layer.
2. A method for producing a magnetic recording medium according to claim 1 , wherein, after step (E3) of removing surface layer portions in the exposed regions of the magnetic layer having the granular structure, but, prior to contacting said exposed regions of the magnetic layer having the granular structure with ozone in step (F1),
said exposed regions of the magnetic layer having the granular structure are exposed to a fluorine-containing gas.
3. A method for producing a magnetic recording medium according to claim 1 , wherein the reaction of the exposed regions of the magnetic layer with ozone is effected by contacting said exposed regions of the magnetic layer with ozone gas or a liquid containing ozone gas.
4. A method for producing a magnetic recording medium according to claim 1 , wherein the mask layer is formed from carbon.
5. A method for producing a magnetic recording medium according to claim 4 , wherein the carbon mask layer formed has a thickness in the range of 5 nm to 40 nm.
6. A method for producing a magnetic recording medium according to claim 1 , wherein the formation of the negative pattern of the magnetic recording pattern on the resist layer in step (D1) is carried out by transfer printing using a stamp.
7. A method for producing a magnetic recording medium according to claim 1 , which further comprises:
(H) a step of, after step (G1) for removing the residual resist layer, or the residual resist layer and mask layer, etching a surface layer portion of the magnetic layer by using an inert gas.
8. A method for producing a magnetic recording medium according to claim 1 , wherein the reaction of the exposed regions of the magnetic layer with ozone in the step (F1) is effected by contacting the exposed regions of the magnetic layer with an ozone-containing aqueous solution.