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Device for Lubrication of Thin Film Disks

IP.com Disclosure Number: IPCOM000115738D
Original Publication Date: 1995-Jun-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 105K

Publishing Venue

IBM

Related People

Coffey, KR: AUTHOR [+4]

Abstract

Thin film disks may be lubricated by physical and/or chemical absorption of vapor phase lubricants onto the disk surface without the use of solvents. A uniform equilibrium lubricant thickness can be achieved by maintaining the lubricant partial pressure at the disk surface at some fixed value below that required for bulk condensation of the liquid phase of the lubricant. The resultant coating thickness will be thin (fractional to a few monolayers) and adherent.

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Device for Lubrication of Thin Film Disks

      Thin film disks may be lubricated by physical and/or chemical
absorption of vapor phase lubricants onto the disk surface without
the use of solvents.  A uniform equilibrium lubricant thickness can
be achieved by maintaining the lubricant partial pressure at the disk
surface at some fixed value below that required for bulk condensation
of the liquid phase of the lubricant.  The resultant coating
thickness will be thin (fractional to a few monolayers) and adherent.

      The variation of the mount of absorbed material on a surface
with the vapor pressure of the material (below the condensation
pressure) is commonly known as the equilibrium surface absorption
isotherm.  Of importance to the application of this phenomenon as a
coating technique is that many materials display significant
hysteresis in their absorption characteristics, which allows a
thickness established by vapor exposure to be maintained when the
source of vapor is removed.  In principle, this coating technique can
be used to coat any vapor phase material onto any surface, given that
sufficient hysteresis is present in the absorption characteristics of
the material on the surface of interest.

      This technique is readily applied to the coating of
conventional perfluoropolyether lubricants with reactive end groups
(such as Fomblin AM2001, Fomblin Zdol, Demnum SA and Demnum SP) to
thicknesses near 10 angstroms on disks with sputtered carbon
overcoats.  Perflouropolyethers do not degrade when heated in the
range of 150 degrees C to 200 degrees C, yet they have adequate vapor
pressures to establish an equilibrium absorbed thickness in a
reasonable time.

      The most convenient coating process is to place the disks and
the lubricant in a closed atmosphere oven and heat them together.
Examples of suitable ovens are the common laboratory vacuum oven
(operated at one atmosphere) or an oven using closed loop air
recirculation.  A liquid lubricant source (a few drops to a few
milliliters) is placed in an open container in the oven with the
disks.  The oven is then operated between 150 degrees C and
200 degrees C for one-half hour to twenty-four hours.  The disks may
then be removed.  The lubricant film thickness may be measured by XPS
and is found to be uniform on each disk surface and uniform from disk
to disk within the oven.  The lubricant is typically adherent or
"bonded" in the sense that it is not readily removed by rinsing with
Freon solvent.  The stop/start wear performance of disks lubricated
in this fashion is equivalent to that of disks lubricated by dip
coating.  The coating thickness is not observed to be greatly
dependent upon the amount of lubricant placed in the oven or the disk
exposure time (given that a minimu...