Browse Prior Art Database

Spiral Texture for Thin Film Magnetic Disks

IP.com Disclosure Number: IPCOM000116812D
Original Publication Date: 1995-Nov-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 6 page(s) / 197K

Publishing Venue

IBM

Related People

Gregory, TA: AUTHOR [+3]

Abstract

A process which produces a spiral texture pattern on thin film disks is disclosed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 35% of the total text.

Spiral Texture for Thin Film Magnetic Disks

      A process which produces a spiral texture pattern on thin film
disks is disclosed.

      On all current disk products that use a mobile
Perfluoropolyether (PFPE) lubricant, it is observed that centrifugal
force from normal use will cause the mobile lubricant to be slowly
spun off from the disk's surface --- a phenomenon referred to as lube
spin-off.  For example, one type of disk will loose about 80% of its
9 angstrom film of mobile Z-Dol lubricant after 1 year of operation
in a hard disk file (near upper-limit temperature conditions).  The
consequences of lube spin-off is a higher rate of wear to the
Head/Disk Interface (HDI).  The spiral texture pattern described here
can reduce or essentially eliminate lube spin-off thereby prolonging
good tribological performance.

      The spiral texture pattern should provide an additional
tribological benefit because more mobile lubricant will be actively
distributed within the HDI.

      The predominant disk process used by most of the thin-film
disk industry is a repetitive sweeping motion in texturing disks.
This
process produces a texture pattern that has intersecting grooves,
blamed for a reduction in magnetic signal-to-noise performance.  The
spiral texture pattern proposed here is an effective way to avoid
this source of signal degradation.

      In this proposal, thin film disks are given a deliberate
counter-clockwise spiral texture (as defined by the direction of
texture lines from Inner Diameter (ID) to Outer Diameter (OD).  With
a disk so textured, the effect of normal HDI friction will result in
mobile lubricant being driven toward the disk's ID hub --- in
opposition to the effect of lube spin-off.

      The physics of this invention is explained in Fig. 1, where a
typical 180 degree spiral texture is shown.  This texture is the
result of an abrasive surface being swept at constant velocity from
the OD edge of the disk to the ID edge, while the disk is rotated 180
degrees counter-clockwise at constant angular velocity.  The
perspective of this description is identical to the top-view of an
operational file, which also rotates counter-clockwise.  Now imagine
the small abrasive pad used to make this texture being gently loaded
onto the S/S track of a disk with a spiral texture.  As the abrasive
particles cog with the texture, the counter-clockwise rotation of the
disk will result in the pad being translated toward the ID, if
confined to a radial line.  Next envision the mobile lubricant
interacting with a stationary head running on the S/S track.
Frictional interaction would normally result in the lubricant film
slowly migrating clockwise around the disk in a circumferential
track*.  But the deliberate spiral pattern will direct this lubricant
flow toward the ID as diagrammed in Fig. 1.  Of course, centrifugal
force will oppose this ID-directed flow of lubricant, which suggests
the need for balancing...