Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Reexamination Certificate
1999-12-29
2002-01-01
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
C428S336000, C428S690000, C428S690000, C428S690000, C428S900000, C360S128000
Reexamination Certificate
active
06335080
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a polymeric or polymer-based substrate for a magnetic hard disk recording medium, a magnetic hard disk recording medium comprising the polymeric or polymer-based substrate, and a hard disk drive system including a magnetic hard disk recording medium comprising the polymeric or polymer-based substrate. The invention has particular utility in the manufacture of lower cost magnetic hard disk systems for use in computer applications.
BACKGROUND OF THE INVENTION
Magnetic media are widely used in various applications, particularly in the computer industry. A conventional longitudinal recording disk medium
1
used in computer-related applications is schematically depicted in FIG.
1
and comprises a non-magnetic metal substrate
10
, typically of an aluminum (Al) alloy, such as an aluminum-magnesium (Al—Mg) alloy, having sequentially deposited thereon a plating layer
11
, such as of amorphous nickel-phosphorus (NiP), a polycrystalline underlayer
12
, typically of chromium (Cr) or a Cr-based alloy, a magnetic layer
13
, e.g., of a cobalt (Co)-based alloy, a protective overcoat layer
14
, typically containing carbon, e.g., diamond-like carbon (DLC) formed, as is known, by sputtering of a carbon target in an appropriate atmosphere or by ion beam deposition (IBD) utilizing appropriate precursor gases, and a lubricant topcoat layer
15
, typically of a perfluoropolyether compound applied, as is known, by dipping, etc. The Co-based alloy magnetic layer
13
deposited by conventional techniques, e.g., sputtering, comprises polycrystallites epitaxially grown on the polycrystalline Cr or Cr-based alloy underlayer
12
.
In operation of medium
1
, the magnetic layer
13
can be locally magnetized by a write transducer or write head, to record and store information. The write transducer creates a highly concentrated magnetic field which alternates direction based on the bits of information being stored. When the local magnetic field produced by the write transducer is greater than the coercivity of the recording medium layer
13
, then the grains of the polycrystalline medium at that location are magnetized. The grains retain their magnetization after the magnetic field produced by the write transducer is removed. The direction of the magnetization matches the direction of the applied magnetic field. The magnetization of the recording medium can subsequently produce an electrical response in a read transducer, allowing the stored information to be read.
Thin film magnetic recording media are conventionally employed in disk form for use with disk drives for storing large amounts of data in magnetizable form. Typically, one or more disks are rotated on a central axis in combination with data transducer heads. In operation, a typical contact start/stop (CSS) method commences when the head begins to slide against the surface of the disk as the disk begins to rotate. Upon reaching a predetermined high rotational speed, the head floats in air at a predetermined distance from the surface of the disk due to dynamic pressure effects caused by the air flow generated between the sliding surface of the head and the disk. During reading and recording operations, the transducer head is maintained at a controlled distance from the recording surface, supported on a bearing of air as the disk rotates, such that the head can be freely moved in both the circumferential and radial directions, allowing data to be recorded on and retrieved from the disk at a desired position. Upon terminating operation of the disk drive, the rotational speed of the disk decreases and the head again begins to slide against the surface of the disk and eventually stops in contact with and pressing against the disk. Thus, the transducer head contacts the recording surface whenever the disk is stationary, accelerated from the static position, and during deceleration just prior to completely stopping. Each time the head and disk assembly is driven, the sliding surface of the head repeats the cyclic sequence consisting of stopping, sliding against the surface of the disk, floating in air, sliding against the surface of the disk, and stopping.
Referring now to
FIG. 2
, shown therein, in perspective view, is a conventionally configured magnetic recording disk
30
having a CSS (i.e., landing) zone
36
and a data (i.e., recording) zone
40
. More specifically,
FIG. 2
illustrates an annularly-shaped magnetic recording disk
30
including an inner diameter
32
and an outer diameter
34
. Adjacent to the inner diameter is an annularly-shaped, inner diameter CSS zone
36
. When the disk
30
is operated in conjunction with a magnetic transducer head (not shown), the CSS zone
36
is the region where the head makes contact with the disk during start-stop cycles or other intermittent occurrences. In
FIG. 2
, the edge of the CSS zone is indicated by line
38
, which is the boundary between the head landing zone
36
and the data zone
40
where information in magnetic form is stored within the magnetic recording layer of the disk.
It is considered desirable during reading and recording operations to maintain each transducer head as close to its associated recording surface as possible, i.e., to minimize the “flying height” of the head. Thus, a smooth recording surface is preferred, as well as a smooth opposing surface of the associated transducer head, thereby permitting the head and the disk to be positioned in close proximity, with an attendant increase in predictability and consistent behavior of the air bearing supporting the head during motion. However, if the head surface and the recording surface are too flat, the precision match of these surfaces gives rise to excessive stiction and friction during the start-up and stopping phases of the cyclic sequence, thereby causing wear to the head and recording surfaces, eventually leading to what is referred to as “head crash”. Thus, there are competing goals of reducing head/disk friction and minimizing transducer flying height.
Conventional practices for addressing these apparent competing objectives involve providing a magnetic disk recording medium with a toughened recording surface to reduce head/disk friction by techniques generally known as “texturing”. Conventional texturing techniques involve circumferential polishing or localized laser heating to create a “bump” pattern with precisely defined features on the surface of a disk substrate, e.g., of Al—Mg alloy, to provide a texture thereon prior to subsequent deposition thereon of layers, such as an underlayer, a magnetic layer, a protective overcoat, and a lubricant topcoat, wherein the textured surface of the underlying substrate is intended to be substantially replicated in the subsequently deposited layers.
The continuing trend toward the manufacture of very low cost (e.g., <$500) personal computers (PCs) necessitates a reduction in the cost of hard disk drives utilized in such computers. Accordingly, the use of lower cost materials, e.g., polymers, glass, ceramics, and glass-ceramics as replacements for the conventional Al-alloy based substrates for magnetic disk media has been proposed. However, only glass and glass-ceramic composite materials have been successfully utilized for the manufacture of practical disk drives. The extreme difficulty associated with grinding and lapping of glass and glass-ceramic composite materials have limited their use to only higher cost applications such as mobile disk drives for “notebook”-type computers. Poor mechanical and tribological performance, track mis-registration (TMR) and poor flyability have been particularly problematic in the case of polymer-based substrates fabricated as to essentially copy or mimic conventional hard disk design features and criteria.
Accordingly, there exists a need for improved polymeric or polymer-based substrates suitable for use in the manufacture of hard disk magnetic recording media. In addition, there exists a need for improved hard disk drive systems including polymer substrate-based magnetic reco
Boutaghou Zine-Eddine
Shima Koji
Weiss Joel
Kiliman Leszek
Seagate Technology LLC
LandOfFree
Magnetic disk media and disk drives utilizing polymeric disk... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic disk media and disk drives utilizing polymeric disk..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic disk media and disk drives utilizing polymeric disk... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2871109