Method of manufacturing a perpendicular magnetic recording medium, a method of manufacturing a substrate for a perpendicular magnetic recording medium, and a medium and a substrate manufactured by the methods
View Patent ↗A method of manufacturing a perpendicular magnetic recording medium and a substrate for the medium are disclosed, in which abnormal protrusions on an underlayer made of a Ni—P alloy are automatically eliminated while maintaining a flat surface with high accuracy on the underlayer, and appropriate texture traces remain to promote magnetization alignment in the vertical direction in a perpendicular magnetic recording medium without adversely affecting the magnetization alignment. In the method, texture processing is carried out on an underlayer made of a Ni—P alloy on a nonmagnetic base plate using a polishing tape while supplying mixed slurry of a surfactant and abrasive grains of polycrystalline diamond, and then, texture polishing is carried out on the underlayer processed by the texture processing, using a polishing tape while supplying slurry containing an abrasive material and an organic acid until the surface of the underlayer is polished to an arithmetic mean roughness Ra of at most 0.5 nm, preferably in the range of 0.05 nm to 0.2 nm.
1. A method of manufacturing a perpendicular magnetic recording medium comprising, in succession:
a preliminary polishing process to smooth an underlayer made of Ni—P alloy on a substrate,
a 2-step texturing process:
a first texturing process using a nonwoven fabric tape and a slurry of polycrystalline diamond slurry and surfactant to form a plurality of grooves on an underlayer made of a Ni—P alloy that is on a substrate using a first polishing tape made of nonwoven fabric while supplying a first slurry that contains a surfactant and a first abrasive material; and
a second texture polishing in which a surface of the underlayer processed by the texturing process is polished to have a surface roughness comprising texture traces that promote magnetization alignment in a vertical direction, using a second polishing tape made of a porous material while supplying a second slurry containing an acid citric, malic, maleic, phosphoric, succinic, or formic acid or a mixture thereof and colloidal silica a second abrasive material having a grain diameter smaller than a mean diameter of perforations of the second polishing tape wherein the second abrasive material is colloidal silica; and
a sputtering process to deposit first a non-magnetic layer and then a magnetic layer on the textured surface.
2. The method of manufacturing a perpendicular magnetic recording medium according to claim 1 , wherein texture polishing is carried out until the surface of the underlayer is polished to an arithmetic mean roughness Ra in the range of 0.05 nm to 0.2 nm.
3. The method of manufacturing a perpendicular magnetic recording medium according to claim 1 , wherein the acid is selected from the group consisting of citric acid, maleic acid, malic acid, phosphoric acid, succinic acid, formic acid, and a mixture of these acids.
4. The method of manufacturing a perpendicular magnetic recording medium according to claim 1 , wherein the second polishing tape made of a porous material is a urethane pad.
5. A method of manufacturing a substrate for a perpendicular magnetic recording medium comprising, in succession:
a preliminary polishing process to smooth an underlayer made of Ni—P alloy on a substrate,
a 2-step texturing process:
a first texturing process using a nonwoven fabric tape and a slurry of polycrystalline diamond slurry and surfactant to form a plurality of grooves on an underlayer made of a Ni—P alloy that is on a substrate using a first polishing tape made of nonwoven fabric while supplying a first slurry that contains a surfactant and a first abrasive material; and
a second texture polishing in which a surface of the underlayer processed by the texturing process is polished to have a surface roughness comprising texture traces that promote magnetization alignment in a vertical direction, using a second polishing tape made of a porous material while supplying a second slurry containing an acid citric, malic, maleic, phosphoric, succinic, or formic acid or a mixture thereof and colloidal silica a second abrasive material having a grain diameter smaller than a mean diameter of perforations of the second polishing tape wherein the second abrasive material is colloidal silica; and
a sputtering process to deposit a non-magnetic layer on the textured surface.
6. The method of manufacturing a substrate for a perpendicular magnetic recording medium according to claim 5 , wherein the step of texture polishing is carried out until the surface of the underlayer is polished to an arithmetic mean roughness Ra in the range of 0.05 nm to 0.2 nm.
7. The method of manufacturing a substrate for a perpendicular magnetic recording medium according to claim 5 , wherein the acid is selected from the group consisting of citric acid, maleic acid, malic acid, phosphoric acid, succinic acid, formic acid, and a mixture of these acids.
8. The method of manufacturing a substrate for a perpendicular magnetic recording medium according to claim 5 , wherein the second polishing tape made of a porous material is a urethane pad.
9. The method of manufacturing a perpendicular magnetic recording medium according to claim 1 , wherein the first abrasive material is diamond.
10. The method of manufacturing a perpendicular magnetic recording medium according to claim 5 , wherein the first abrasive material is diamond.
11. The method of manufacturing a perpendicular magnetic recording medium according to claim 1 additionally comprising, in order:
forming a soft magnetic backing layer on the NiP layer on the substrate;
forming a nonmagnetic seed layer on the soft magnetic backing layer,
forming a perpendicular magnetic recording layer on the nonmagnetic seed layer, and
forming a protective layer on the perpendicular magnetic recording layer.