Lubricant, magnetic recording medium and head slider

Abstract

A lubricant is provided that achieves a sufficiently small one-molecule-layer film thickness even when it has a high molecular weight, and has an increased reliability in a wide temperature range environment without losing the flying stability, by making the film thickness of a lubricant layer very small when it is used for the magnetic recording medium lubricant layer and/or head slider lubricant layer of a magnetic recording device. This lubricant comprises a fluorine-containing polymer, the lubricant having a relationship: Y<−1.4475X+2.815, wherein Y is a natural logarithm of diffusion coefficient at 23° C. (unit:μm2/s); and X is a viscosity at 20° C. (unit: Pas), or it comprises a fluorine-containing polymer having a particular structure, and with molecular chains between adjacent polar groups that have a number-average molecular weight of not less than 500.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the state of a fluorine-containing polymer attached to a surface to be coated with the polar groups, Pols;

FIG. 2 is another schematic view showing the state of a fluorine-containing polymer attached to a surface to be coated with the polar groups, Pols;

FIG. 3 is another schematic view showing the state of a fluorine-containing polymer attached to a surface to be coated with the polar groups, Pols;

FIG. 4 is a view illustrating how to calculate the number-average molecular weight of molecular chains between adjacent polar groups;

FIG. 5 is an FT-IR chart of a compound provided in EXAMPLE 1;

FIG. 6 is a ¹HNMR chart of a compound provided in EXAMPLE 1;

FIG. 7 is a ¹³CNMR chart of a compound provided in EXAMPLE 1;

FIG. 8 is a ¹⁹FNMR chart of a compound provided in EXAMPLE 1;

FIG. 9 is a chart obtained by an ellipsometer showing the cross-sectional profile of a lubricant film thickness;

FIG. 10 is a graph showing the relationship between the number-average molecular weight (Mc) of the structural parts between adjacent hydroxy groups and the one-molecule-layer film thickness;

FIG. 11 is a chart showing the result of a glide test;

FIG. 12 is another chart showing the result of a glide test;

FIG. 13 is a chart showing the test results of TDV and TOV;

FIG. 14 is another chart showing the test results of TDV and TOV;

FIG. 15 is a graph showing the temperature-dependent viscosity properties of lubricants;

FIG. 16 shows charts of film thickness profiles just immediately after the application;

FIG. 17 shows charts of the film thickness profiles 140 hours after the application;

FIG. 18 shows a chart of a film thickness profile just immediately after the application;

FIG. 19 shows a chart of the film thickness profile 140 hours after the application;

FIG. 20 is a graph showing the relationship between the viscosity at 20° C. and a natural logarithm of the diffusion coefficient at 23° C.;

FIG. 21 is a schematic plan view of a hard disk device showing the inner structures; and

FIG. 22 is a schematic cross-sectional view of a hard disk device showing the relationship between the head and the magnetic recording medium.

Claims

1. A lubricant comprising a fluorine-containing polymer, said lubricant having a relationship: Y<−1.4475X+2.815, wherein Y is a natural logarithm of diffusion coefficient at 23° C. (unit:μm2/s); and X is a viscosity at 20° C. (unit: Pas).

2. A lubricant comprising a fluorine-containing polymer having a structure represented by formula 1, and with molecular chains between adjacent polar groups that have a number-average molecular weight of not less than 500: H—{(XZ)m, (YZ)n}—(Xδ, Y(1-δ)—H   (1)

3. A lubricant according to claim 2, wherein the average molecular weight of said fluorine-containing polymer is not less than 2,000 and not more than 12,000.

4. A lubricant according to claim 2, wherein said Pol is a hydroxy group.

5. A lubricant according to claim 2, wherein the number-average molecular weight of molecular chains between adjacent polar groups of said fluorine-containing polymer is not more than 3,000.

6. A lubricant according to claim 2 wherein said fluorine-containing polymer has a terminal group with a structure represented by formula 3, —R   (3)

7. A lubricant according to claim 2 wherein part or the whole of the structure units of CF2O and C2F4O of formula 1 is replaced with either one of structures represented by formulae 4 and 5.

8. A lubricant according to claim 2 wherein said fluorine-containing polymer has no polar group except for a hydroxy group.

9. A lubricant according to claim 2 wherein said fluorine-containing polymer has from 1.0to 10.0 hydroxy groups on an average in a molecule at intermediate sections of the molecular chains.

10. A lubricant comprising a fluorine-containing polymer formed by reacting a compound having a structure represented by formula 2 and epichlorohydrin, having a number-average molecular weight of not less than 2,000 and not more than 12,000, and having from 1.0 to 10.0 hydroxy groups on an average in a molecule at intermediate sections of the molecular chains, HO(CH2CH2O)xCH2CF2O(CF2CF2O)p″(CF2O)q″CF2CH2(OCH2CH2)yOH   (2)

11. A lubricant according to claim 10, said lubricant comprising a fluorine-containing polymer formed by reacting a compound having a structure represented by formula 2 and epichlorohydrin followed by reaction with glycidol, having a number-average molecular weight of not less than 2,000 and not more than 12,000, and having from 1.0 to 10.0 hydroxy groups on an average in a molecule at intermediate sections of the molecular chains.

12. A lubricant according to claim 10, wherein said fluorine-containing polymer has a terminal group with a structure represented by formula 3, —R   (3)

13. A lubricant according to claim 10, wherein part or the whole of the structure units of CF2O and C2F4O of formula 2 is replaced with either one of structures represented by formulae 4 and 5. —CF2CF2CF2—  (4)

14. A lubricant according to claim 2, said lubricant comprising a fluorine-containing compound other than said fluorine-containing polymer.

15. A lubricant according to claim 14, wherein said fluorine-containing compound other than said fluorine-containing polymer is at least one compound selected from the group consisting of compounds having structures represented by formulae 9, 10 and 11,

16. A lubricant according to claim 2, wherein said lubricant comprising a fluorine-containing polymer has a relationship: Y<−1.4475X+2.815, wherein Y is a natural logarithm of diffusion coefficient at 23° C. (unit:μm2/s); and X is a viscosity at 20° C. (unit: Pas).

17. A magnetic recording medium comprising a magnetic layer, a protective layer over said magnetic layer, and a magnetic recording medium lubricant layer on the protective layer, wherein said magnetic recording medium lubricant layer is formed by application of a lubricant according to claim 1.

18. A magnetic recording medium comprising a magnetic layer, a protective layer over said magnetic layer, and a magnetic recording medium lubricant layer on the protective layer, wherein said magnetic recording medium lubricant layer is formed by application of a lubricant according to claim 2.

19. A head slider equipped with a record transducer for recording/record-reproducing to/from a magnetic recording medium, said head slider having, on the surface facing said magnetic recording medium, a protective layer and a head slider lubricant layer formed by application of a lubricant according to claim 1.

20. A head slider equipped with a record transducer for recording/record-reproducing to/from a magnetic recording medium, said head slider having, on the surface facing said magnetic recording medium, a protective layer and a head slider lubricant layer formed by application of a lubricant according to claim 2.