Fullerene compound, lubricant for magnetic recording medium, and magnetic recording medium

1. A fullerene compound, which is an ionic liquid represented by general formula (1),

wherein the ionic liquid is formed from a Bronsted acid (H n1 X) and a Bronsted base ([(R 2 R 3 )N—] m1 —R 1 );

one of the Bronsted acid and the Bronsted base comprises a group having a fullerene; and

the other one of the Bronsted acid and the Bronsted base comprises a perfluoroalkyl chain,

[Formula 1]

wherein at least one of R 1 , R 2 , and R 3 is a hydrocarbon group having 1 to 20 carbon atoms;

at least one of X, R 1 , R 2 , and R 3 has a fullerene skeleton, and at least one of X, R 1 , R 2 , and R 3 has a perfluoroalkyl chain;

R 2 and R 3 may be bonded to each other to form a nitrogen-containing heterocycle; and

n 1 , n 2 , m 1 , and m 2 are integers of 1 to 6, and n 1 ×n 2 =m 1 ×m 2 .

2. The fullerene compound according to claim 1 ,

wherein the Bronsted acid, in a molecule, comprises

a fullerene skeleton, and

a sulfonic acid group or a carboxylic acid group; and

the Bronsted base comprises a perfluoropolyether chain.

3. The fullerene compound according to claim 1 ,

wherein the Bronsted acid, in a molecule, comprises

a perfluoropolyether chain, and

a sulfonic acid group or a carboxylic acid group; and

the Bronsted base comprises a fullerene skeleton.

4. The fullerene compound according to claim 1 ,

wherein the Bronsted acid is a compound represented by formula (6), (7), or (8);

the Bronsted base is a compound represented by formula (10) or (11),

C n (OH) x-y (OSO 3 H) y   (6)

wherein C n represents a fullerene which is a base structure of polyhydroxylated fullerene hydrogen sulfate ester;

x is a number in the range of 10 to 30;

y is a number in the range of 5 to 10; and

C n is at least one kind selected from C 60 , C 70 , C 76 , C 78 , C 80 , C 82 , and C 84 .

NH 2 (CH 2 CH 2 O) p CH 2 CF 2 —(OCF 2 CF 2 ) m (OCF 2 ) n —OCF 2 CH 2 (OCH 2 CH 2 ) q NH 2   (10)

wherein p and q are 1 to 3; m is 1 to 30; and n is 0 to 30,

CF 3 CF 2 CF 2 CF 2 —(OCF 2 CF 2 ) 2 —OCF 2 CH 2 OCH 2 CH 2 NH 2   (11)

5. The fullerene compound according to claim 1 ,

wherein the Bronsted acid is a compound represented by any one of the following formulae (12) to (15); and

the Bronsted base is a compound represented by formula (16),

HO 3 S(CH 2 ) 3 OCH 2 CF 2 —(OCF 2 CF 2 ) m (OCF 2 ) n —OCF 2 CH 2 O(CH 2 ) 3 SO 3 H   (12)

wherein m is 1 to 30 and n is 0 to 30,

CF 3 CF 2 CF 2 CF 2 —(OCF 2 CF 2 ) 2 —OCF 2 CH 2 O(CH 2 ) 3 SO 3 H   (13)

HOOCCF 2 —(OCF 2 CF 2 ) m (OCF 2 ) n —OCF 2 COOH   (14)

wherein m is 1 to 30 and n is 0 to 30,

CF 3 CF 2 CF 2 CF 2 —(OCF 2 CF 2 ) 2 —OCF 2 COOH   (15)

6. The fullerene compound according to claim 1 ,

wherein a thermal decomposition temperature of the ionic liquid is 300° C. or higher.

7. The fullerene compound according to claim 1 ,

wherein a number average molecular weight is in the range of 500 to 20,000.

8. A lubricant for a magnetic recording medium, comprising the fullerene compound according to claim 1 .

9. A magnetic recording medium in which at least a magnetic layer, a protective layer, and a lubricant layer are sequentially provided on a substrate,

wherein the lubricant layer contains the fullerene compound according to claim 1 .

10. The magnetic recording medium according to claim 9 ,

wherein the lubricant layer has an average thickness of 0.5 nm to 2.5 nm.