Magnetic disk and method of manufacturing same

1. A method of manufacturing magnetic disks comprising a magnetic layer, a carbon-base protective layer, and a lubricating layer on a substrate, said lubricating layer including —COOH and/or —CF 2 COOH atomic groups,

said method comprising preparing lubricant c by mixing lubricant a and lubricant b;

wherein lubricant a is prepared from a lubricant alpha comprising a compound denoted by chemical formula

HO—CH 2 —CH(OH)—CH 2 —O—CH 2 —CF 2 (—O—C 2 F 4 ) p -(O—CF 2 ) q -O—CF 2 —CH 2 —O—CH 2 —CH(OH)—CH 2 —OH  [Chem. 1]

wherein p and q are natural number,

and a compound denoted by chemical formula

HO—CH 2 —CF 2 (—O—C 2 F 4 ) m -(O—CF 2 ) n -O—CF 2 —CH 2 —OH  [Chem. 2]

wherein m and n are natural number,

are fractionated by molecular weight to prepare the lubricant a having a weight average molecular weight (Mw) of from 3,000 to 7,000 and a molecular weight dispersion of less than or equal to 1.2;

a lubricant beta prepared from a compound denoted by the chemical formula

HO—CH 2 —CF 2 (—O—C 2 F 4 ) m -(O—CF 2 ) n -O—CF 2 —CH 2 —OH  [Chem. 3]

wherein m and n are natural number,

fractionated by molecular weight to prepare the lubricant b having a weight average molecular weight (Mw) of from 2,000 to 5,000 and a molecular weight dispersion of less than or equal to 1.2;

and

a film of lubricant c is formed on the carbon—base protective layer to form the lubricating layer.

2. The method of manufacturing magnetic disks of claim 1 , wherein the fractionation by molecular weight is conducted by supercritical extraction.

3. The method of manufacturing magnetic disks of claim 1 , wherein lubricant c is prepared by obtaining a composition A of lubricant a dispersed in a fluorine-base solvent, obtaining a composition B of lubricant b dispersed in a fluorine-base solvent, mixing compositions A and B, and extracting lubricant c from the mixed composition.

4. The method of manufacturing magnetic disks of claim 1 , wherein after forming the lubricating layer, the resultant magnetic disk is exposed to an atmosphere of from 50 to 150° C. to adhere lubricant c to the carbon-base protective layer.

5. The method of manufacturing magnetic disks of claim 1 , wherein the carbon-base protective layer is formed by plasma CVD.

6. A load-unload system magnetic disk device comprising a magnetic disk manufactured by the process of claim 1 .

7. A magnetic disk comprising a magnetic layer, a carbon-base protective layer, and a lubricating layer on a substrate, said lubricating layer including —COOH and/or —CF 2 COOH atomic groups, in which the lubricating layer has been formed on the carbon-base protective layer, said lubricating layer being comprised of a lubricant c,

said lubricant c comprising:

a lubricant a having a weight average molecular weight (Mw) of from 3,000 to 7,000 and a molecular weight dispersion of less than or equal to 1.2 obtained by refining a lubricant alpha comprising the compound denoted by the chemical formula

HO—CH 2 —CH(OH)—CH 2 —O—CH 2 —CF 2 (—O—C 2 F 4 ) p -(O—CF 2 ) q -O—CF 2 —CH 2 —O—CH 2 —CH(OH)—CH 2 —OH  [Chem. 4]

wherein p and q are natural number,

and a compound denoted by chemical formula

HO—CH 2 —CF 2 (—O—C 2 F 4 ) m -(O—CF 2 ) n -O—CF 2 —CH 2 —OH  [Chem. 5]

wherein m and n are natural number,

and a lubricant b having a weight average molecular weight (Mw) of from 2,000 to 5,000 and a molecular weight dispersion of less than or equal to 1.2, comprising a lubricant beta comprising a compound denoted by chemical formula

HO—CH 2 —CF 2 (—O—C 2 F 4 ) m -(O—CF 2 ) n -O—CF 2 —CH 2 —OH  [Chem. 6]

wherein m and n are natural number.

8. A magnetic disk comprising a magnetic layer, a carbon-base protective layer, and a lubricating layer on a substrate, in which the lubricating layer has been formed on the carbon-base protective layer, said lubricating layer comprising a compound denoted by the chemical formula

HO—CH 2 —CH(OH)—CH 2 —O—CH 2 —CF 2 (—O—C 2 F 4 ) p -(O—CF 2 ) q -O—CF 2 —CH 2 —O—CH 2 —CH(OH)—CH 2 —OH  [Chem. 7]

wherein p and q are natural number,

and a compound denoted by the chemical formula

HO—CH 2 —CF 2 (—O—C 2 F 4 ) m -(O—CF 2 ) n -O—CF 2 —CH 2 —OH  [Chem. 8]

wherein m and n are natural number,

and the lubricating layer contains —COOH atomic groups detectable by time of flight secondary ion mass spectrometry.

9. A magnetic disk comprising a magnetic layer, a carbon-base protective layer, and a lubricating layer on a substrate, in which the lubricating layer comprises:

a compound denoted by the chemical formula

HO—CH 2 —CH(OH)—CH 2 —O—CH 2 —CF 2 (—O—C 2 F 4 ) p -(O—CF 2 ) q -O—CF 2 —CH 2 —O—CH 2 —CH(OH)—CH 2 —OH  [Chem. 9]

wherein p and q are natural number,

a compound denoted by the chemical formula

HO—CH 2 —CF 2 (—O—C 2 F 4 ) m -(O—CF 2 ) n -O—CF 2 —CH 2 —OH  [Chem. 10]

wherein m and n are natural number,

and a compound having in its molecular structure —COOH atomic group detectable by time of flight secondary ion mass spectrometry.

10. The magnetic disk of claim 8 , wherein the lubricating layer includes —CF 2 COOH atomic groups.

11. The magnetic disk of claim 9 , wherein the lubricating layer includes —CF 2 COOH atomic groups.