Magnetic disk and manufacturing method thereof
View Patent ↗A magnetic disk having at least a magnetic layer, a carbon protective layer, and a lubrication layer sequentially provided on a substrate. The lubrication layer is a film formed by a lubricant that contains two types of compounds having a perfluoropolyether main chain in the structure, a molecular weight distribution of the two types in total being within a range of 1 to 1.2. The two types of compounds include a compound a having a hydroxyl group at the end and a compound b having a number average molecular weight smaller than the number average molecular weight of the compound a and not more than 1500. A content of the compound b in the two types of compounds is not more than 10%.
1. A magnetic disk comprising:
a substrate;
at least a magnetic layer, a protective layer, and a lubrication layer sequentially provided on the substrate,
wherein the lubrication layer is a film formed by a lubricant that contains two types of compounds each having a perfluoropolyether main chain in its structure,
wherein the two types of compounds includes a compound a having two or four hydroxyl groups in total at ends of a molecule of the compound a and a compound b, and wherein the compound b has a number average molecular weight that is smaller than the number average molecular weight of the compound a and not more than 1500;
wherein a molecular weight distribution of the two types of compounds in total is within a range of 1 to 1.2;
wherein a content of the compound b in the two types of compounds is not more than 10%; and
wherein the compound b is selected from the group consisting of the following compounds represented by formula (1), formula (2), formula (3) and formula (4):
wherein Rf represents —(OC 2 F 4 )m(OCF 2 )n- and m and n each represents an integer of not less than 1.
2. The magnetic disk according to claim 1 , wherein
the number average molecular weight of said lubricant contained in said lubrication layer is within a range of 1000 to 10000.
3. The magnetic disk according to claim 2 , wherein
said protective layer is a carbon protective layer formed by a plasma CVD method.
4. The magnetic disk according to claim 2 , wherein
the magnetic disk is a magnetic disk mounted on a Load-Unload method magnetic disk device.
5. The magnetic disk according to claim 1 , wherein
said protective layer is a carbon protective layer formed by a plasma CVD method.
6. The magnetic disk according to claim 5 , wherein
the magnetic disk is a magnetic disk mounted on a Load-Unload method magnetic disk device.
7. The magnetic disk according to claim 1 , wherein
the magnetic disk is a magnetic disk mounted on a Load-Unload method magnetic disk device.
8. A manufacturing method of a magnetic disk having at least a magnetic layer, a protective layer, and a lubrication layer sequentially provided on a substrate, characterized in that
said lubrication layer is formed by:
performing molecular distillation of a lubricant containing
two types of compounds each having a perfluoropolyether main chain in its structure,
wherein the two types of compounds includes a compound a having two or four hydroxyl groups in total at ends of a molecule of the compound a and a compound b, and wherein the compound b has a number average molecular weight that is smaller than the number average molecular weight of the compound a and not more than 1500;
wherein a molecular weight distribution of the two types of compounds in total is within a range of 1 to 1.2;
wherein a content of the compound b in the two types of compounds is not more than 10%; and
wherein the compound b is selected from the group consisting of the following compounds represented by formula (1), formula (2), formula (3) and formula (4):
wherein Rf represents —(OC 2 F 4 )m(OCF 2 )n- and m and n each represents an integer of not less than 1; and
forming a film of the lubricant on said protective layer.
9. The manufacturing method of a magnetic disk according to claim 8 , wherein
after said film of the lubrication layer is formed, said magnetic disk is exposed to an atmosphere of 50 to 150° C.