Lubricant composition for magnetic recording media

1. A lubricant composition for use as a lubricant for magnetic recording media, comprising a first liquid lubricant and a second liquid lubricant, wherein the first liquid lubricant contains a cyclotriphosphazene ring attached to at least one perfluoropolyether having a single terminal hydroxyl group and has the structure of formula (I)

wherein, x is an integer from 1 to 5, p is an integer from 5 to 36 and q is an integer from 4 to 30 and, wherein the second liquid lubricant contains a perfluoropolyether selected from compounds having the structure of formula (IIa), formula (IIb), and combinations thereof, wherein formulae (IIa) and (IIb) have the structures

R—[CH 2 ] r —[CF 2 O] s —[CF 2 CF 2 O] t —[CF 2 O] u —CF 2 —[CH 2 ] v —R 1   (IIa)

R 1 RN—[CH 2 ] r —[CF 2 O] s —[CF 2 CF 2 O] t —[CF 2 O] u —CF 2 —[CH 2 ] v —NRR 1   (IIb)

in which r, s, t, u and v are independently zero or an integer, with the proviso that s, t and u are not all zero,

wherein when the second lubricant contains a perfluoropolyether having a structure of formula (IIa)

R and R 1 are independently selected from

—CH 2 CH 2 OH,

and

—CH 2 CH 2 CH 3 ;

and

wherein when the second lubricant contains a perfluoropolyether having a structure of formula (IIb)

R and R 1 are independently selected from

—CH 2 CH 2 OH,

and

—CH 2 CH 2 CH 3 ;

wherein y is an integer from 1 to 6.

2. The lubricant composition of claim 1 , wherein x is 5 such that the first liquid lubricant has the structure of formula (Ia)

3. The lubricant composition of claim 1 , wherein the perfluoropolyether of the first liquid lubricant has a number average molecular weight of about 2000 to about 6000.

4. The lubricant composition of claim 1 , wherein the perfluoropolyether of the second liquid lubricant has a number average molecular weight of about 1000 to about 6000.

5. The lubricant composition of claim 1 , wherein r is zero or an integer from 1 to 6, s is zero or an integer from 1 to 40, t is zero or an integer from 1 to 40, u is zero or an integer from 1 to 6, and v is zero or an integer from 1 to 6.

6. The lubricant composition of claim 5 , wherein r, u and v are each independently 0, 1 or 2, and s and t are each independently zero or an integer from 2 to 20.

7. The lubricant composition of claim 1 , wherein the second liquid lubricant is selected from

and combinations thereof.

8. The lubricant composition of claim 1 , wherein the amount of the first liquid lubricant is from about 2% to about 98% by weight and the amount of the second liquid lubricant is from about 98% to about 2% by weight based on the weight of the first and second lubricants.

9. The lubricant composition of claim 8 , wherein the amount of the first liquid lubricant is from about 25% to about 75% by weight and the amount of the second liquid lubricant is from about 75% to about 25% by weight based on the weight of the first and second lubricants.

10. The lubricant composition of claim 1 , wherein the lubricant composition provides substantially reduced lubricant thickness variations when used as a disk lubricant for a magnetic media hard disk compared with a lubricant composition containing the first liquid lubricant but not the second liquid lubricant.

11. A magnetic recording media comprising a substrate, a magnetic layer, an overcoat layer and a lubricant layer thereon, wherein the lubricant layer is formed from the lubricant composition of claim 1 .

12. The magnetic recording media of claim 1 , wherein the first liquid lubricant has the structure of formula (Ia)

and the second liquid lubricant is selected from

and combinations thereof.

13. The magnetic recording media of claim 12 , wherein the magnetic recording media contains a hard disk and the lubricant composition provides substantially reduced lubricant thickness variations when applied to a surface of the hard disk compared with a lubricant composition containing the first liquid lubricant but not the second liquid lubricant.

14. In a magnetic recording media that includes a substrate, a magnetic layer, an overcoat layer and a lubricant layer thereon, wherein the lubricant contains a cyclotriphosphazene ring attached to at least one perfluoropolyether, the improvement which comprises utilizing a lubricant layer formed from a lubricant composition that includes a lubricant composition of claim 1 as a first liquid lubricant and a second liquid lubricant that contains a perfluoropolyether having two end groups selected from hydroxyl, tertiary amine, and combinations thereof.

15. The magnetic recording media of claim 14 , wherein the liquid composition provides substantially reduced lubricant thickness variations on a surface of the magnetic recording media compared with a lubricant composition containing the first liquid lubricant but not the second liquid lubricant.

16. A method of making a magnetic recording media comprising:

forming a magnetic layer on a substrate;

forming a protective overcoat layer on the magnetic layer; and

forming a lubricant layer on the surface of the overcoat layer by applying the lubricant composition of claim 1 to the surface on the overcoat layer.