Passivated nitrogenated diamond-like carbon layer and method for passivating it
A nitrogenated diamond-like carbon (DLC) layer, like a nitrogenated DLC overcoat on a magnetic recording disk, includes cyanoacrylates that are attached to nitrogenated sites on the surface of the carbon layer. Cyanoacrylates are reactive with surface amine groups, which are among the nitrogenated surface sites that act as adsorption sites for volatile contaminants in the disk drive. The covalent bonding of the cyanoacrylate with the amine groups and other reactive sites on the disk overcoat blocks the adsorption of contaminants when they impinge on the overcoat surface. The cyanoacrylate may be applied to the overcoat by dipping the disk into a solution containing the cyanoacrylate or by exposing the overcoat to a cyanoacrylate vapor.
1. A method for protecting a diamond-like carbon overcoat with a nitrogenated surface on a magnetic recording disk from chemical contaminants, the method comprising:
providing a disk substrate having a magnetic recording layer and a diamond-like carbon overcoat with a nitrogenated surface on the recording layer, the overcoat having nucleophilic surface sites; and
exposing the nitrogenated surface of the overcoat to a cyanoacrylate to attach cyanoacrylate to the surface sites.
2. The method of claim 1 wherein exposing the surface of the overcoat to a cyanoacrylate comprises one from the group of dipping the overcoat into a solution containing the cyanoacrylate and exposing the surface of the overcoat to a cyanoacrylate vapor.
3. The method of claim 1 wherein the overcoat comprises a first film comprising carbon and a second film consisting essentially of nitrogenated carbon on the first film.
4. The method of claim 1 further comprising, after exposing the surface of the overcoat to a cyanoacrylate, applying a liquid lubricant to the overcoat.
5. The method of claim 1 wherein the cyanoacrylate is selected from the group consisting of ethyl, methyl, propyl, isopropyl, perfluoromethyl, perfluoroethyl, perfluoropropyl and perfluoroisopropyl cyanoacrylates.
6. A substrate comprising:
a nitrogenated diamond-like carbon layer having a nitrogenated surface with nucleophilic surface sites, wherein the substrate is a magnetic recording disk having a magnetic recording layer and the carbon layer is a protective overcoat for the recording layer; and
cyanoacrylate molecules on the nitrogenated surface and attached to the nucleophilic surface sites.
7. The substrate of claim 6 wherein the amount of cyanoacrylate attached to the nucleophilic surface sites on the nitrogenated surface, as measured by the carbonyl [C═O] peak area in reflection Fourier transform infrared spectroscopy (FTIR), is greater than 0.02 absorbance units and less than or equal to 0.07 absorbance units.
8. A magnetic recording disk comprising:
a disk substrate;
a magnetic recording layer on the substrate;
a nitrogenated diamond-like carbon overcoat on the recording layer, the overcoat having surface sites containing nitrogen; and
cyanoacrylate attached to the nitrogenated surface sites.
9. The disk of claim 8 further comprising a discontinuous film of liquid lubricant on the overcoat.
10. The disk of claim 8 wherein the cyanoacrylate is selected from the group consisting of ethyl, methyl, propyl, isopropyl, perfluoromethyl, perfluoroethyl, perfluoropropyl and perfluoroisopropyl cyanoacrylates.
11. The disk of claim 8 wherein the amount of cyanoacrylate attached to the surface sites, as measured by the carbonyl [C═O] peak area in reflection Fourier transform infrared spectroscopy (FTIR), is greater than 0.02 absorbance units and less than or equal to 0.07 absorbance units.
12. The disk of claim 8 wherein the surface sites are amines.
13. A magnetic recording disk drive comprising:
the disk of claim 8 ;
a spindle motor for rotating the disk;
an air-bearing slider supporting a head;
an actuator attached to the slider for moving the head across the disk; and
an enclosure surrounding the disk, spindle motor, slider and actuator.
14. The disk drive of claim 13 wherein the disk drive contains volatile organosilicon contaminants within the enclosure, and wherein the nitrogen surface sites are passivated from the contaminants by the cyanoacrylates.
15. The disk drive of claim 13 further comprising a mass of polymerized cyanoacrylate in the enclosure.
16. A method for protecting a diamond-like carbon overcoat with a nitrogenated surface on a magnetic recording disk from chemical contaminants, the method comprising:
providing a disk substrate having a magnetic recording layer, a diamond-like carbon overcoat with a nitrogenated surface on the recording layer, the overcoat having nucleophilic surface sites, and a permeable layer of liquid lubricant on the surface of the overcoat; and
exposing the nitrogenated surface of the overcoat to a cyanoacrylate vapor through the permeable layer of liquid lubricant to attach cyanoacrylate to the surface sites.
17. A method for protecting a diamond-like carbon overcoat with a nitrogenated surface on a magnetic recording disk from chemical contaminants, the method comprising:
providing a rotatable disk located within an enclosure, the disk comprising a substrate, a magnetic recording layer on the substrate, and a diamond-like carbon overcoat with a nitrogenated surface on the recording layer, the overcoat having nucleophilic surface sites; and
exposing the nitrogenated surface of the overcoat to a cyanoacrylate to attach cyanoacrylate to the surface sites by depositing liquid cyanoacrylate in the enclosure and rotating the disk.
18. A method for protecting a diamond-like carbon layer with a nitrogenated surface from chemical contaminants, the method comprising:
providing a substrate comprising a diamond-like carbon layer with a nitrogenated surface, the carbon layer having nucleophilic surface sites, wherein the substrate is a magnetic recording disk drive air-bearing slider and the carbon layer is the air-bearing surface of the slider; and
exposing the nitrogenated surface of the carbon layer to a cyanoacrylate to attach cyanoacrylate to the surface sites.
19. A method for protecting a diamond-like carbon layer with a nitrogenated surface from chemical contaminants, the method comprising:
providing a substrate comprising a diamond-like carbon layer with a nitrogenated surface, the carbon layer having nucleophilic surface sites, wherein the substrate is a magnetic recording disk comprising a magnetic recording layer and the carbon layer is a protective overcoat for the recording layer; and
exposing the nitrogenated surface of the carbon layer to a cyanoacrylate to attach cyanoacrylate to the surface sites.
20. A substrate comprising:
a nitrogenated diamond-like carbon layer having a nitrogenated surface with nucleophilic surface sites, wherein the substrate is a magnetic recording disk drive air-bearing slider and the carbon layer is the air-bearing surface of the slider; and
cyanoacrylate molecules on the nitrogenated surface and attached to the nucleophilic surface sites.