Magnetic recording disk having pre-patterned surface features and planarized surface
View Patent ↗A method for planarizing a magnetic recording disk that has surface features of elevated lands and recessed grooves includes forming two coatings of cured perfluorinated polyether (PFPE) polymers over the surface features. The disk may have a protective carbon overcoat with a surface that replicates the topography of lands and grooves. A liquid functionalized-PFPE is applied over the disk surface and then cured to form a first coating with the functionalized end groups bonding to the carbon overcoat. A liquid non-functionalized-PFPE polymer is then applied over the functionalized-PFPE coating and cured to form a second coating. The combined coatings substantially planarize the disk surface so that there is minimal recession between the top of the coating over the lands and the top of the coating over the grooves.
1. A magnetic recording disk comprising:
a substrate having a plurality of elevated lands and recessed grooves;
a magnetic recording layer on the elevated lands;
a carbon-containing protective overcoat on the magnetic recording layer and recessed grooves, the recessed grooves having a gap width W, the gap depth D from the top of the overcoat on the lands to the top of the overcoat on the recessed grooves being equal to or greater than 30 nm; and
a coating on the overcoat on the lands and in the recessed grooves and comprising:
a cross-linked functionalized-perfluorinated polyether (PFPE) layer having functional end groups bonded to the carbon-containing overcoat and a recession R1 between the top of said functionalized-PFPE layer on the lands and the top of said functionalized-PFPE layer in the recessed grooves, where a negative value of R1 is measured in the direction from the top of said functionalized-PFPE layer on the lands toward the substrate; and
a cross-linked non-functionalized-PFPE layer on the functionalized-PFPE layer, wherein the recession between the top of said non-functionalized-PFPE layer on the lands and the top of said non-functionalized-PFPE layer in the recessed grooves is R2, where a negative value of R2 is measured in the direction from the top of said non-functionalized-PFPE layer on the lands toward the substrate;
wherein for a D of 30 nm or greater than 30 nm, the recession improvement (R1-R2)is equal to minus 5 nm or more negative than minus 5 nm for a W between about 70 nm and 100 nm.
2. The disk of claim 1 wherein the functionalized-PFPE contains end groups selected from hydroxyl end groups and acrylate end groups.
3. The disk of claim 1 wherein the disk is a discrete track disk and wherein the lands comprise radially-spaced concentric tracks and the grooves comprise radially-spaced guard bands.
4. The disk of claim 1 wherein the disk is a patterened-media disk and wherein the lands comprise discrete data islands and the grooves comprise regions between the data islands.
5. The disk of claim 1 wherein the lands comprise generally radially-directed servo blocks and the grooves comprise regions between the servo blocks.