U.S. patent application number 10/871047 was filed with the patent office on 2004-12-30 for disk biasing for manufacture of servo patterned media.
This patent application is currently assigned to SEAGATE TECHNOLOGY LLC. Invention is credited to Curtiss, Donald Everett, Wago, Koichi.
Application Number | 20040264019 10/871047 |
Document ID | / |
Family ID | 32510799 |
Filed Date | 2004-12-30 |
United States Patent
Application |
20040264019 |
Kind Code |
A1 |
Curtiss, Donald Everett ; et
al. |
December 30, 2004 |
Disk biasing for manufacture of servo patterned media
Abstract
A method of manufacturing a patterned data/information storage
and retrieval medium in the form of an annular disk having an outer
diameter, a central opening defining an inner diameter, and opposed
first and second major surfaces, the method comprising inserting a
smaller diameter cylindrical shaft of a stamping/imprinting tool in
the central opening and biasing the inner diameter of the disk into
contact with the cylindrical shaft at a pre-selected location along
the inner diameter of said disk during stamping/imprinting of a
pre-selected pattern such as a servo pattern in at least one of the
first and second major surfaces of the disk, the biasing creating a
space between the inner diameter of the disk and the surface of the
cylindrical shaft which has a maximum width at a location
diametrically opposite said pre-selected location. A disk drive
system is then formed by mounting the patterned medium on a drive
spindle shaft with the medium biased into contact with the shaft at
the pre-selected location along the inner diameter of the medium,
whereby proper centering of the servo pattern is provided.
Inventors: |
Curtiss, Donald Everett;
(Los Gatos, CA) ; Wago, Koichi; (Sunnyvale,
CA) |
Correspondence
Address: |
McDermott, Will & Emery
600 13th Street, N.W.
Washington
DC
20005-3096
US
|
Assignee: |
SEAGATE TECHNOLOGY LLC
Scotts Valley
CA
|
Family ID: |
32510799 |
Appl. No.: |
10/871047 |
Filed: |
June 21, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10871047 |
Jun 21, 2004 |
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10056070 |
Jan 28, 2002 |
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6757116 |
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60312927 |
Aug 16, 2001 |
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Current U.S.
Class: |
360/15 ;
G9B/5.293 |
Current CPC
Class: |
B82Y 10/00 20130101;
Y10S 425/81 20130101; G11B 5/82 20130101; G11B 5/743 20130101 |
Class at
Publication: |
360/015 |
International
Class: |
G11B 005/86 |
Claims
What is claimed is:
1. A method of manufacturing a patterned data/information storage
and retrieval medium in the form of an annular disk having an outer
diameter, a central opening defining an inner diameter, and opposed
first and second major surfaces, said method comprising inserting a
smaller diameter cylindrical shaft of a stamping/imprinting tool in
said central opening of said disk and biasing said inner diameter
of said disk into contact with said cylindrical shaft at a
pre-selected location along said inner diameter of said disk during
stamping/imprinting of a pre-selected pattern in at least one of
said first and second major surfaces of said disk, said biasing
creating a space between said inner diameter of said disk and said
surface of said cylindrical shaft which has a maximum width at a
location diametrically opposite said pre-selected location.
2. The method according to claim 1, wherein said disk is a thin
film magnetic recording medium or a substrate therefor and said
pattern comprises a plurality of concentric tracks including data
zones and servo tracking zones.
3. The method according to claim 1, comprising stamping/imprinting
said pre-selected pattern in both of said first and second major
surfaces of said disk.
4. The method according to claim 1, wherein said
stamping/imprinting of said pattern comprises performing thermal
imprint lithography of a layer of a thermoplastic material on at
least one of said first and second major surfaces of said disk.
5. The method according to claim 4, further comprising utilizing
the thermally imprinted layer(s) as a patterned mask during
processing for selectively removing material of said disk exposed
through openings formed in said thermally imprinted layer(s).
6. The method according to claim 1, wherein said
stamping/imprinting of said pattern comprises embossing of a layer
of a partially dried, soft silica sol-gel material on at least one
of said first and second major surfaces of said disk.
7. The method according to claim 6, further comprising sintering
said partially dried, soft silica sol-gel layer subsequent to
embossing for forming a fully densified glass layer having a
density and hardness approaching that of silica glass.
8. The method according to claim 1, comprising the steps of: (a)
providing a said disk including an indicator mark at a location
along said inner diameter or said outer diameter of said disk and
radially aligned with said pre-selected location along said inner
diameter of said disk; (b) providing a stamping/imprinting tool
comprising: (i) an elongated cylindrical shaft having a slightly
smaller diameter than said inner diameter of said disk, said
cylindrical shaft including a location along the length thereof for
positioning said disk thereat via said inner diameter thereof; and
(ii) at least one annular disk-shaped stamper/imprinter means
axially movably mounted on said elongated shaft, said at least one
stamper/imprinter means having an imprinting surface including a
negative image of said pattern, said at least one stamper/imprinter
means being adapted to urge said imprinting surface against a
respective facing first or second major surface of said disk; (c)
inserting said shaft in said central opening of said disk and
positioning said disk at said location along said length of said
shaft such that at least one of said first and second surfaces
thereof faces said imprinting surface of said at least one
stamper/imprinter means; (d) utilizing said indicator mark as an
alignment means in biasing said inner diameter of said disk into
contact with the surface of said cylindrical shaft at said
pre-selected location along said inner diameter of said disk,
whereby a space is created between said inner diameter of said disk
and said surface of said cylindrical shaft which has a maximum
width at a location diametrically opposite said pre-selected
location; and (e) urging said imprinting surface of said at least
one stamper/imprinter against said at least one facing surface of
said disk to imprint said pattern therein.
9. The method according to claim 8, wherein: step (b)(ii) comprises
providing a pair of axially movable, annular disk-shaped
stamper/imprinter means for imprinting both major surfaces of said
disk with said pattern; and step (b)(i) comprises providing said
elongated cylindrical shaft with a pair of resilient means for
mounting and centering said pair of stamper/imprinter means on said
cylindrical shaft.
10. A method of manufacturing a disk drive system, comprising steps
of: (a) forming a patterned, annular disk-shaped data/information
storage and retrieval medium having an outer diameter, a central
opening defining an inner diameter, and opposed first and second
major surfaces, comprising inserting a smaller diameter cylindrical
shaft of a stamping/imprinting tool in said central opening of said
disk and biasing said inner diameter of said disk into contact with
said cylindrical shaft at a pre-selected location along said inner
diameter of said disk during stamping/imprinting of a pre-selected
pattern in at least one of said first and second major surfaces of
said disk; and (b) mounting said patterned disk on a smaller
diameter cylindrical drive spindle shaft of a disk drive by
inserting said drive spindle shaft in the central opening of said
disk, such that said inner diameter of said disk is biased into
contact with said cylindrical drive spindle shaft of said disk
drive at said pre-selected location, and a space is created between
said inner diameter of said disk and said surface of said
cylindrical drive spindle shaft which has a maximum width at a
location diametrically opposite said pre-selected location.
11. A patterned data/information storage and retrieval medium
comprising: an annular disk having an outer diameter, a central
opening defining an inner diameter, and opposed first and second
major surfaces, at least one of said first and second major
surfaces including a pattern formed therein by a method comprising
an imprinting or embossing step, said disk further including an
indicator mark at a pre-selected location along said inner diameter
or said outer diameter of said disk for use in precisely biasing
said inner diameter into contact with a cylindrical shaft of
smaller diameter at said pre-selected location when said shaft is
inserted in said central opening of said disk.
12. The medium as in claim 11, wherein: said medium is a thin film
magnetic recording medium and said pattern comprises a plurality of
concentric tracks including data zones and servo tracking
zones.
13. The medium as in claim 11, wherein: said pattern is formed in
both of said first and second major surfaces of said disk by a
method comprising an imprinting or embossing step.
14. The medium as in claim 11, wherein: said at least one of said
first and second major surfaces including said pattern formed
therein comprises a glass layer.
15. A disk drive system, comprising: (a) an annular disk having an
outer diameter, a central opening defining an inner diameter, and
opposed first and second major surfaces, at least one of said first
and second major surfaces including a pattern formed therein by a
method comprising an imprinting or embossing step, said disk
further including an indicator mark at a pre-selected location
along said inner diameter or said outer diameter of said disk for
use in precisely biasing said inner diameter into contact with a
cylindrical drive spindle shaft of smaller diameter at said
pre-selected location when said cylindrical shaft is inserted in
said central opening of said disk; and (b) a said smaller diameter
cylindrical drive spindle shaft extending through said central
opening of said annular disk, said inner diameter of said disk
being biased into contact with said cylindrical shaft at said
pre-selected location, whereby a space is created between said
inner diameter of said disk and said cylindrical shaft which has a
maximum width at a location diametrically opposite said
pre-selected location.
16. A tool for performing stamping/imprinting/embossing of a
pre-selected pattern in at least one major surface of an annular
disk-shaped substrate including an outer diameter and a central
opening defining an inner diameter, comprising: (a) an elongated
cylindrical shaft, said cylindrical shaft including a location
along the length thereof for positioning thereat a said annular
disk-shaped substrate having a central opening defining a said
inner diameter which is slightly larger than that of said
cylindrical shaft; (b) at least one annular disk-shaped
stamper/imprinter means axially movably mounted on said elongated
shaft, said at least one stamper/imprinter means having an
imprinting surface including a negative image of said pre-selected
pattern, said at least one stamper/imprinter means being adapted to
urge said imprinting surface against a respective facing major
surface of said disk; and (c) mounting means for mounting a said
annular disk-shaped substrate in said tool such that said elongated
shaft extends through said central opening of said substrate, said
imprinting surface of said at least one stamper/imprinter faces a
major surface of said disk, and a pre-selected location along said
inner diameter of said disk is biased into contact with said
cylindrical shaft, whereby a space is created between said inner
diameter of said disk and said cylindrical shaft which has a
maximum width at a location diametrically opposite said
pre-selected location.
17. The stamping/imprinting/embossing tool according to claim 16,
further comprising a pair of axially movable, annular disk-shaped
stamper/imprinter means (b) for imprinting both major surfaces of
said disk-shaped substrate with said pre-selected pattern.
18. The stamping/imprinting/embossing tool according to claim 17,
further comprising a resilient mounting/centering means on said
elongated cylindrical shaft (a) for mounting and centering each of
said pair of stamper/imprinter means (b) on said elongated
cylindrical shaft (a).
19. The stamping/imprinting/embossing tool according to claim 18,
wherein each of said resilient mounting/centering means comprises a
resiliently compressible collet or polymeric ring mounted on said
elongated cylindrical shaft.
20. A patterned data/information storage and retrieval medium,
comprising: (a) an annular disk-shaped substrate having inner and
outer diameters and including a pattern formed in at least one of
the major surfaces thereof; and (b) means for centering said
pattern when said disk-shaped substrate is mounted on a cylindrical
shaft extending through said inner diameter.
Description
CROSS-REFERENCE TO PROVISIONAL APPLICATION
[0001] This application claims priority from U.S. provisional
patent application Ser. No. 60/312,927 filed Aug. 16, 2001, the
entire disclosure of which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to methods and apparatus for
forming servo patterns in annular disk-shaped substrates for
recording media utilized in high areal, high track density
applications. The invention has particular utility in the
manufacture of magnetic data/information storage and retrieval
media, e.g., hard disks utilized in computer and computer-related
applications.
BACKGROUND OF THE INVENTION
[0003] Magnetic recording media are widely used in various
applications, particularly in the computer industry. Referring now
to FIG. 1, shown therein, in simplified, schematic cross-sectional
view, is a portion of a dual-sided, thin-film magnetic disk medium
1 of the type contemplated by the present invention, comprising a
rigid, non-magnetic substrate 10, typically comprised of an
aluminum (Al) alloy, e.g., Al--Mg. Alternative materials for use as
substrate 10 include glass, ceramics, glass-ceramics composites and
laminates, polymers, and other non-magnetic metals and alloys.
Al-based substrate 10 is provided, in sequence, at both major
surfaces, with a polished and/or textured amorphous Ni--P
underlayer 12, a polycrystalline seed layer 14, typically a
Cr-based layer deposited by sputtering, a magnetic layer 16
comprised of a ferromagnetic material, e.g., an oxide or a Co-based
alloy, a protective overcoat layer 18, typically of a diamond-like
carbon (DLC) material, and a lubricant topcoat layer 20, e.g., of a
fluorine-containing polymer.
[0004] In operation of medium 1, the magnetic layer 13 can be
locally magnetized by a write transducer or write head, to record
and store data/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 pattern of
magnetization of the recording medium can subsequently produce an
electrical response in a read transducer, allowing the stored
medium to be read.
[0005] 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.
[0006] It is considered desirable during reading and recording
operations, and for obtainment of high areal recording densities,
to maintain the transducer head(s) as close to the associated
recording surface(s) as is possible, i.e., to minimize the "flying
height" of the head(s). 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 surface
to be positioned in close proximity, with an attendant increase in
predictability and consistent behavior of the air bearing
supporting the head during motion.
[0007] Disk drives typically comprise a magnetic head assembly
mounted on the end of a support or actuator arm which positions the
head radially over the disk surface. If the actuator arm is held
stationary, the magnetic head assembly will pass over a circular
path on the disk surface known as a track, and information can be
read from or written to that track. Each concentric track has a
unique radius, and reading and writing information from or to a
specific track requires the magnetic head to be located above the
track. By moving the actuator arm, the magnetic head assembly is
moved radially over the disk surface between tracks.
[0008] The disk drive must be able to differentiate between tracks
on the disk and to center the magnetic head over any particular
track. Most disk drives use embedded "servo patterns" of
magnetically recorded information on the disk. The servo patterns
are read by the magnetic head assembly to inform the disk drive of
the track location. Tracks typically include both data sectors and
servo patterns. Each data sector contains a header followed by a
data section. The header may include synchronization information to
synchronize various timers in the disk drive to the speed of disk
rotation, while the data section is used for recording data.
Typical servo patterns are described in, for example, U.S. Pat.
Nos. 6,086,961 and 6,139,936, the entire disclosures of which are
incorporated herein by reference.
[0009] Adverting to FIG. 2, shown therein, in simplified, schematic
plan view, is a magnetic recording disk 30 having a data zone 34
including a plurality of discrete servo tracks, and a contact
start/stop (CSS) zone 32. A discrete servo pattern 40 is formed on
or within the data zone 34, and includes a number of data track
zones 38 separated by servo tracking zones 36. The data storage
function of disk 30 is confined to the data track zones 38, while
servo tracking zones 36 provide information to the disk drive which
allows a read/write head to maintain alignment on the individual,
tightly-spaced discrete data tracks.
[0010] Although only a relatively few of the servo tracking zones
are shown in FIG. 2 for illustrative simplicity, it should be
recognized that the discrete track patterns of the media
contemplated herein may include several hundreds of servo zones to
improve head tracking during each rotation of the disk. In
addition, the servo tracking zones need not be straight radial
zones as shown in the figure, but may instead comprise arcs,
intermittent zones, or irregularly-shaped zones separating
individual data tracks.
[0011] Referring now to FIG. 3, shown therein in simplified,
schematic perspective view, is an enlarged portion of a discrete
servo track pattern 40 formed on or within the recording media thin
film layer structure 41 (corresponding to layers 12-20 of FIG. 1),
which in turn is disposed on the surface of substrate 42 for a
discrete track medium (corresponding to substrate 10 of FIG. 1).
The various elements or features of pattern 40 are generally
defined by a difference in height between recessed zones or regions
44 and raised zones or regions 46. As illustrated, pattern 40
includes a pair of discrete track zones 38 separated by a servo
tracking zone 36.
[0012] Servo tracking zone 36 generally includes track
identification (ID) bars 50 and tracking position bars 52. ID bars
50 provide the identification for each of the discrete tracks 48 of
the discrete track pattern 40. Tracking bars 52 provide the disk
drive with feedback of the accuracy with which the read/write head
is tracking a particular discrete track 48. Typically, tracking
bars 52 extend to approximately the middle of the path defined by
each track 48 and are staggered, so that each discrete track 48
includes at least one tracking bar 52 extending from the middle of
the track path toward the axis of the disk, and one tracking bar 52
which extends radially outward from the middle of the track
path.
[0013] Servo patterns are usually written on the disk during
manufacture of the disk drive, after the drive is assembled and
operational. The servo pattern information, and particularly the
track spacing and centering information, needs to be located very
precisely on the disk surface. However, at the time the servo
patterns are written, there are no reference locations on the disk
surface which can be perceived by the disk drive. Accordingly, a
highly specialized device known as a "servo-writer" is used during
writing of the servo-patterns. Largely because of the locational
precision needed, servo-writers are expensive, and servo-writing is
a time-consuming process.
[0014] One approach (i.e., "PERM" disks, manufactured by Sony
Corp.) to avoid traditional servo-writing has been to injection
mold or stamp servo patterns on a polymer-based substrate disk. A
constant thickness layer of magnetic recording material is then
applied over the entire disk surface, including the depressions and
protrusions of the servo patterns. After all of the constituent
layers of the medium have been applied to the disk, a magnetic bias
is recorded on the servo patterns. For example, a first magnetic
field may magnetically initialize the entire disk at a one setting.
Then a second magnetic field, located at the surface of the disk
and e.g., provided by the magnetic head of the disk drive, is used
to magnetize the protruding portions of the servo patterns relative
to the depressions. Because the protrusions are closer than the
depressions to the magnetic initialization, the magnetization
carried by the protrusions may be different than the magnetization
carried by the depressions. When read, the resulting disk servo
patterns show magnetic transitions between the depressions and the
protrusions.
[0015] A recently developed, low cost technique which can be
utilized for forming "patterned media" e.g., media comprising a
discrete track pattern (e.g., pattern 40 of FIG. 3) in the surface
of a magnetic recording medium, without requiring the use of a
servo-writer or equivalent device, is disclosed in U.S. Pat. No.
5,772,905, the entire disclosure of which is incorporated herein by
reference. As utilized herein, the term or expression "patterned
magnetic media" is taken as including thin film, high areal
density, longitudinal or perpendicular magnetic media which are
patterned to include at least one of a servo pattern, a data track
pattern, and an identification number or symbol, as well as
magnetic media comprising a large plurality of discrete magnetic
nano-structures, e.g., columns or pillars of magnetic material.
[0016] In essence, the thermal imprint lithographic technique
disclosed in the above patent, when applied to the manufacture of
patterned magnetic media, involves etching or ion milling a
magnetic recording layer or laminate of layers on a suitable
substrate, utilizing a resist mask formed by thermal imprint
lithography rather than optical (photo) lithography. A typical
thermal imprint lithographic process for forming nano-dimensioned
patterns/features in a surface of a thin film magnetic recording
medium or a substrate therefor is illustrated with reference to the
simplified, schematic cross-sectional views of FIGS. 4(A)-4(D).
[0017] Referring to FIG. 4(A), shown therein is a mold 60 (also
known as a stamper or imprinter) including a main body 62 having
upper and lower opposed surfaces, with a molding layer 64 (also
referred to as an imprinting surface) formed on the lower opposed
surface. As illustrated, molding layer 64 includes a plurality of
features 66 having a desired shape or surface contour. A thin film
magnetic recording medium 68 comprised of a stack of thin film
layers on a substrate, or only the substrate therefor (also
identified by reference numeral 68), either one carrying a thin
film layer 70 on an upper surface thereof, is positioned below, and
in facing relation to the molding layer 64. Thin film layer 70,
comprised of a resist or thermoplastic polymer material, e.g., a
polymethyl methacrylate (PMMA), may be formed on the
substrate/workpiece surface by any appropriate technique, e.g.,
spin coating.
[0018] Adverting to FIG. 4(B), shown therein is a compressive
molding step, wherein mold 60 is pressed into the thin film layer
70 in the direction shown by arrow 72, so as to form depressed,
i.e., compressed, regions 74. In the illustrated embodiment,
features 66 of the molding layer 64 are not pressed all of the way
into the thin film layer 70 and thus do not contact the surface of
the underlying magnetic medium or substrate 68. However, the top
surface portions 74a of thin film 70 may contact depressed surface
portions 66a of molding layer 64. As a consequence, the top surface
portions 74a substantially conform to the shape of the depressed
surface portions 66a, for example, flat. When contact between the
depressed surface portions 66a of molding layer 64 and thin film
layer 70 occurs, further movement of the molding layer 64 into the
thin film layer 70 stops, due to the sudden increase in contact
area, leading to a decrease in compressive pressure when the
compressive force is constant.
[0019] FIG. 4(C) shows the cross-sectional surface contour of the
thin film layer 70 following removal of stamper or mold 60. The
molded, stamped, or imprinted thin film layer 70 includes a
plurality of recesses formed at compressed regions 74 which
generally conform to the shape or surface contour of features 76 of
the molding layer 64. Referring to FIG. 4(D), in a next step, the
surface-molded workpiece comprising the magnetic medium or
substrate 68 therefor is subjected to further processing to remove
the compressed portions 74 of thin film 70 for selectively exposing
portions 78 of the underlying magnetic medium or substrate 68
therefor, separated by raised features 76. Selective removal of the
compressed portions 74 may be accomplished by any appropriate
process, e.g., reactive ion etching (RIE) or wet chemical etching.
The thus-patterned thin film layer 70 may subsequently be utilized
as a mask for selective removal of the exposed substrate portions
78, after which the patterned thin film layer 70 is itself
selectively removed, leaving a patterned magnetic medium or
substrate 68 therefor.
[0020] The above-described imprint lithographic processing is
capable of providing sub-micron-dimensioned features, such as the
servo and data tracking features illustrated in FIG. 3, by
utilizing a stamper or mold 60 provided with patterned features 66
comprising pillars, bars, holes, trenches, etc., by means of e-beam
lithography, RIE, or other appropriate patterning method. Typical
depths of features 66 range from about 5 to about 200 nm, depending
upon the desired lateral dimension. The material of the molding
layer 64 is typically selected to be hard relative to the thin-film
layer 70, the latter typically comprising a thermoplastic resist
material which is softened when heated. Thus, suitable materials
for use as the molding layer 64 include metals such as Ni,
dielectrics, semiconductors, ceramics, and composite materials.
Suitable resist materials for use as thin film layer 70 include
thermoplastic polymers which can be heated to above their glass
temperature, T.sub.g, such that the material exhibits low viscosity
and enhanced flow.
[0021] Yet another recently developed approach for forming servo
patterns in hard-surfaced, high modulus alternative substrate
materials, such as the glass, ceramic, and glass-ceramic materials
described above, without requiring the use of traditional
servo-writing means, is based upon the discovery that the surfaces
of such materials may be modified, i.e., reduced in hardness, so as
to facilitate formation of servo patterns therein, as by a simple
and conveniently performed embossing process. According to this
methodology, modification (i.e., reduction) of surface hardness of
high modulus substrates for use in the manufacture of thin film
magnetic recording media is obtained by first forming a relatively
soft coating layer on the substrate surface, embossing the desired
servo pattern in the exposed upper surface of the relatively soft
coating layer, and then converting the relatively soft layer to a
relatively hard layer while retaining the embossed servo pattern
therein. The thus-formed substrate with embossed servo pattern in
the exposed surface thereof is then subjected to thin film
deposition thereon for forming the layer stack constituting the
magnetic recording medium. Thus, the method advantageously provides
servo-patterned magnetic recording media without requiring
servo-writing subsequent to media fabrication.
[0022] More specifically, according to the above methodology, a
relatively soft layer of a sol-gel is initially formed on the
surface of the high modulus glass, ceramic, or glass-ceramic
composite substrate, e.g., in disk form. By way of illustration,
but not limitation, a sol-gel layer having a thickness of from
about 0.2 to about 1 .mu.m may be formed on the substrate surface
by any convenient technique, e.g., spin coating of a solution of
the sol-gel. A suitable sol-gel solution for use according to the
invention may be prepared by mixing an alkoxide, e.g., a silicon
alkoxide such as tetraethoxysilane ("TEOS") or tetramethoxysilane
("TMOS"), water, and nitric acid at molar ratios of TEOS or
TMOS/H.sub.2O/HNO.sub.3 of 1/4-30/>0.05. The nitric acid acts as
a catalyst for conversion of the TEOS or TMOS to a SiO.sub.2 sol
according to the following reaction (1), illustratively shown for
TEOS:
nSi(OC.sub.2H.sub.5).sub.4+2nH.sub.2O>nSiO.sub.2+4nC.sub.2H.sub.5OH
(1)
[0023] with ethanol (C.sub.2H.sub.5OH) being produced as a reaction
product in solution. After completion of reaction, butanol
(C.sub.4H.sub.9OH) is added to the solution as a drying retardation
agent at molar ratios of TEOS/H.sub.2O/HNO.sub.3/C.sub.4H.sub.9OH
of e.g., 1/5/0.05/>4. Such solution, when applied to the
substrate surface, e.g., by spin coating, forms a very smooth film
with a minimum amount of surface microwaves. The spin coating
process effects removal, e.g., by centrifugation and evaporation,
of a portion of the solvents from the initially applied solution.
The resultant partially dried film or layer is glass-like,
principally comprised of silica (SiO.sub.2) molecular clusters
together with the various solvents (H.sub.2O, C.sub.2H.sub.5OH,
C.sub.4H.sub.9OH), and adheres well to the substrate surface. The
sol-gel film or layer is of a porous structure with the solvents
saturated in the micropores thereof.
[0024] The as-deposited, relatively soft sol-gel film or layer
applied to the hard-surfaced substrate is then subjected to an
embossing process (similar in essential respects to the
stamping/imprinting process shown in FIG. 4) for forming a servo
pattern in the surface thereof, comprising a patterned plurality of
depressions and protrusions, e.g., by utilizing a stamper/imprinter
(or mold) having an imprinting surface including a negative image
of the desired servo pattern.
[0025] Subsequent to servo pattern formation (and mechanical
texturing, if desired) of the as-deposited, partially dried,
relatively soft sol-gel film or layer, a sintering process is
performed at an elevated temperature of from about 300 to above
about 1000.degree. C. (depending upon the withstand temperature of
the substrate material, which temperature is higher for
ceramic-based substrates than for glass-based substrates), to
evaporate the solvents so as to effect at least partial collapse of
the micro-pores, with resultant densification of the sol-gel film
or layer into a substantially fully densified glass layer having a
density and hardness approaching that of typical silica glass
(<1.5 g/cm.sup.3), or into a partially densified "glass-like"
layer. The embossed servo pattern (and mechanical texturing) formed
in the exposed upper surface of the relatively soft sol-gel layer
is preserved in the corresponding exposed upper surface of the
sintered glass or glass-like layer.
[0026] Formation of thin film magnetic media on the thus-formed
glass-coated, servo patterned/mechanically textured substrates is
accomplished utilizing conventional thin film deposition
techniques, e.g., sputtering, for forming the layer stack
comprising a seed layer, polycrystalline underlayer, magnetic
layer, and protective overcoat layer. The sol-gel-based process
thus combines the advantages of low-cost processing techniques for
servo patterning with the superior optical, mechanical, and
chemical properties of silica glass (SiO.sub.2) for fabricating
high performance, servo-patterned magnetic recording media.
[0027] As indicated above, the servo pattern information,
particularly the track spacing and centering information, must be
very precisely located on the disk surface. According to
traditional methodology utilizing a servo-writer or equivalently
performing device subsequent to installation of the disk(s) in the
disk drive utilizes a disk biasing procedure for this purpose.
FIGS. 5(A)-5(B), which are illustrative of such disk biasing
technique, are schematic plan and cross-sectional views,
respectively, of an annular disk D of inner diameter ID and outer
diameter OD assembled onto the slightly smaller diameter, rotatable
drive spindle shaft DSS of a disk drive for performing precise
servo patterning of the disk. According to traditional methodology
for obtaining precisely formed and centered servo patterns when
utilizing a servo-writer or equivalently performing device
subsequent to installation of the disk(s) D in the disk drive, the
disk(s) D is (are) assembled onto the rotatable drive spindle shaft
DSS of the disk drive with the inner diameter ID of the disk(s) D
being pressed (i.e., biased) against the outer surface of the drive
spindle shaft DSS at a (randomly located) point of contact x
thereof, with a small spacing of maximum width y being formed
between the disk inner diameter ID and the surface of the drive
spindle shaft DSS at a location diametrically opposite the point of
contact x. With the disk(s) D thus installed, the servo pattern SP
is written on the surface(s) of the disk(s) by using the head
gimbal assembly ("HGA") of the disk drive (not shown in the figure
for illustrative simplicity) together with an interferometer or
equivalently performing device for feedback of the HGA position to
the disk drive electronics/control system. As a consequence of the
above physical arrangement of disk(s) D and drive spindle shaft
DSS, the servo pattern is written onto the surface(s) of the
disk(s) D in as concentric a fashion as permitted by the HGA, HGA
positioning system, and inherent system wobble due to spacing y
arising from the biased mounting of the disk(s) D.
[0028] However, despite installation of the disk in a biased,
off-centered fashion, the servo pattern(s) SP formed on the
surface(s) of the disk(s) D by the above conventional process is
(are) sufficiently concentric with the axis of rotation of the
drive spindle shaft DSS for the disk drive electronics/control
system to compensate for any deviations from concentricity of the
servo pattern(s). On the other hand, when servo-patterned media are
produced by any of the above-described alternative processes
wherein a stamper/imprinter is utilized for servo patterning of the
media (or substrate therefor) prior, rather than subsequent to
installation in the disk drive, a problem arises when the thus
servo-patterned disk(s) D is (are) installed on the drive spindle
shaft DSS. Specifically, the servo-patterned disk(s) D must be
installed on the drive spindle shaft DSS such that the servo
pattern(s) SP is (are) sufficiently concentric with the axis of
rotation of the drive spindle shaft DSS to permit an adequate
amount of compensation for deviations from concentricity of the
servo pattern(s) by the electronics/control system of the disk
drive. However, the apparent or straightforward solution to the
problem, involving first precisely centering the servo pattern on
the disk surface and then precisely centering the disk on the drive
spindle shaft, would be time consuming and very costly to implement
when applied to large scale, automated manufacture of patterned
media and disk drives including same.
[0029] In view of the above, there exists a need for a means and
methodology for forming patterned media, i.e., servo patterned
disk-shaped media and/or substrates therefor, prior to installation
of the media in the disk drive, which means and methodology
eliminate any possibility of poor disk/shaft registration leading
to excessive deviations from concentricity of the servo patterns
which cannot be adequately compensated for by conventional disk
drive electronics/control systems. Moreover, there exists a need
for a method and means for performing servo patterning of
disk-shaped media which permits simple installation of the
patterned media in the disk drive, as by conventional biasing
against the disk drive spindle shaft.
[0030] The present invention addresses and solves the
above-described problems attendant upon the formation and
installation of pre-servo-patterned media in conventional
disk-drive systems, while maintaining full compatibility with all
aspects of automated manufacturing technology for servo-patterned
media formation by means of a stamping/imprinting process for
embossing the servo patterns in the surface(s) of a disk-shaped
recording medium (or substrate therefor).
DISCLOSURE OF THE INVENTION
[0031] An advantage of the present invention is an improved method
of manufacturing a patterned data/information storage and retrieval
medium in the form of an annular disk.
[0032] Another advantage of the present invention is an improved
method of manufacturing a disk drive system.
[0033] Yet another advantage of the present invention is an
improved patterned data/information storage and retrieval
medium.
[0034] Still another advantage of the present invention is an
improved disk drive system comprising a patterned data/information
storage and retrieval medium.
[0035] A further advantage of the present invention is an improved
tool for performing stamping/imprinting/embossing of a pre-selected
pattern in at least one major surface of an annular disk-shaped
substrate.
[0036] Additional advantages and other aspects and features of the
present invention will be set forth in the description which
follows and in part will become apparent to those having ordinary
skill in the art upon examination of the following or may be
learned from the practice of the present invention. The advantages
of the present invention may be realized and obtained as
particularly pointed out in the appended claims.
[0037] According to an aspect of the present invention, the
foregoing and other advantages are obtained in part by a method of
manufacturing a patterned data/information storage and retrieval
medium in the form of an annular disk having an outer diameter, a
central opening defining an inner diameter, and opposed first and
second major surfaces, the method comprising inserting a smaller
diameter cylindrical shaft of a stamping/imprinting tool in the
central opening of the disk and biasing the inner diameter of the
disk into contact with the cylindrical shaft at a pre-selected
location along the inner diameter of the disk during
stamping/imprinting of a pre-selected pattern in at least one of
the first and second major surfaces of the disk, the biasing
creating a space between the inner diameter of the disk and the
surface of the cylindrical shaft which has a maximum width at a
location diametrically opposite the pre-selected location.
[0038] According to various embodiments of the present invention,
the disk is a thin film magnetic recording medium or a substrate
therefor and the pattern comprises a plurality of concentric tracks
including data zones and servo tracking zones; and the method
comprises stamping/imprinting the pre-selected pattern in both the
first and second major surfaces of the disk.
[0039] In accordance with certain embodiments of the present
invention, the stamping/imprinting of the pattern comprises
performing thermal imprint lithography of a layer of a
thermoplastic material on at least one of the first and second
major surfaces of the disk, and the method further comprises
utilizing the thermally imprinted layer(s) as a patterned mask
during processing for selectively removing material of the disk
exposed through openings formed in the thermally imprinted
layer(s); whereas, according to certain other embodiments of the
present invention, the stamping/imprinting of the pattern comprises
embossing of a layer of a partially dried, soft silica sol-gel
material on at least one of the first and second major surfaces of
the disk, and further comprises sintering the partially dried, soft
silica sol-gel layer subsequent to embossing for forming a fully
densified glass layer having a density and hardness approaching
that of silica glass.
[0040] According to a specific embodiment of the present invention,
the method comprises the steps of:
[0041] (a) providing a disk including an indicator mark at a
location along the inner diameter or the outer diameter of the disk
and radially aligned with the pre-selected location along the inner
diameter of the disk;
[0042] (b) providing a stamping/imprinting tool comprising:
[0043] (i) an elongated cylindrical shaft having a slightly smaller
diameter than the inner diameter of the disk, the cylindrical shaft
including a location along the length thereof for positioning the
disk thereat via the inner diameter thereof; and
[0044] (ii) at least one annular disk-shaped stamper/imprinter
means axially movably mounted on the elongated shaft, the at least
one stamper/imprinter means having an imprinting surface including
a negative image of the pattern, the at least one stamper/imprinter
means being adapted to urge the imprinting surface against a
respective facing first or second major surface of the disk;
[0045] (c) inserting the shaft in the central opening of the disk
and positioning the disk at the stated location along the length of
the shaft such that at least one of the first and second surfaces
thereof faces the imprinting surface of the at least one
stamper/imprinter means;
[0046] (d) utilizing the indicator mark as an alignment means in
biasing the inner diameter of the disk into contact with the
surface of the cylindrical shaft at the pre-selected location along
the inner diameter of the disk, whereby a space is created between
the inner diameter of the disk and the surface of the cylindrical
shaft which has a maximum width at a location diametrically
opposite the pre-selected location; and
[0047] (e) urging the imprinting surface of the at least one
stamper/imprinter against the at least one facing surface of the
disk to imprint the pattern therein.
[0048] In accordance with embodiments of the present invention,
step (b)(ii) comprises providing a pair of axially movable, annular
disk-shaped stamper/imprinter means for imprinting both major
surfaces of the disk with the pattern; and step (b)(i) comprises
providing the elongated cylindrical shaft with a pair of resilient
means--for mounting and centering the pair of stamper/imprinter
means on the cylindrical shaft.
[0049] Another aspect of the present-invention is a method of
manufacturing a disk drive system, comprising steps of:
[0050] (a) forming a patterned, annular disk-shaped
data/information storage and retrieval medium having an outer
diameter, a central opening defining an inner diameter, and opposed
first and second major surfaces, comprising inserting a smaller
diameter cylindrical shaft of a stamping/imprinting tool in the
central opening of the disk and biasing the inner diameter of the
disk into contact with the cylindrical shaft at a pre-selected
location along the inner diameter of the disk during
stamping/imprinting of a pre-selected pattern in at least one of
the first and second major surfaces of the disk; and
[0051] (b) mounting the patterned disk on a smaller diameter
cylindrical drive spindle shaft of a disk drive by inserting the
drive spindle shaft in the central opening of the disk, such that
the inner diameter of the disk is biased into contact with the
cylindrical drive spindle shaft of the disk drive at the
pre-selected location, and a space is created between the inner
diameter of the disk and the surface of the cylindrical drive
spindle shaft which has a maximum width at a location diametrically
opposite the pre-selected location.
[0052] Yet another aspect of the present invention is a patterned
data/information storage and retrieval medium comprising:
[0053] an annular disk having an outer diameter, a central opening
defining an inner diameter, and opposed first and second major
surfaces, at least one of the first and second major surfaces
including a pattern formed therein by a method comprising an
imprinting or embossing step, the disk further including an
indicator mark at a pre-selected location along the inner diameter
or the outer diameter of the disk for use in precisely biasing the
inner diameter into contact with a cylindrical shaft of smaller
diameter at the pre-selected location when the shaft is inserted in
the central opening of the disk.
[0054] According to embodiments of the present invention, the
medium is a thin film magnetic recording medium and the pattern
comprises a plurality of concentric tracks including data zones and
servo tracking zones; and the pattern is formed in both the first
and second major surfaces of the disk by a method comprising an
imprinting or embossing step.
[0055] In accordance with particular embodiments of the present
invention, at least one of the first and second major surfaces of
the disk including the pattern formed therein comprises a glass
layer.
[0056] Still another aspect of the present invention is a disk
drive system, comprising:
[0057] (a) an annular disk having an outer diameter, a central
opening defining an inner diameter, and opposed first and second
major surfaces, at least one of the first and second major surfaces
including a pattern formed therein by a method comprising an
imprinting or embossing step, the disk further including an
indicator mark at a pre-selected location along the inner diameter
or the outer diameter of the disk for use in precisely biasing the
inner diameter into contact with a cylindrical drive spindle shaft
of smaller diameter at the pre-selected location when the
cylindrical shaft is inserted in the central opening of the disk;
and
[0058] (b) a smaller diameter cylindrical drive spindle shaft
extending through the central opening of the annular disk, the
inner diameter of the disk being biased into contact with the
cylindrical shaft at the pre-selected location, whereby a space is
created between the inner diameter of the disk and the cylindrical
shaft which has a maximum width at a location diametrically
opposite the pre-selected location.
[0059] A still further aspect of the present invention is a tool
for performing stamping/imprinting/embossing of a pre-selected
pattern in at least one major surface of an annular disk-shaped
substrate including an outer diameter and a central opening
defining an inner diameter, comprising:
[0060] (a) an elongated cylindrical shaft, the cylindrical shaft
including a location along the length thereof for positioning
thereat an annular disk-shaped substrate having a central opening
defining an inner diameter which is slightly larger than that of
the cylindrical shaft;
[0061] (b) at least one annular disk-shaped stamper/imprinter means
axially movably mounted on the elongated shaft, the at least one
stamper/imprinter means having an imprinting surface including a
negative image of said pre-selected pattern, the at least one
stamper/imprinter means being adapted to urge the imprinting
surface against a respective facing major surface of the disk;
and
[0062] (c) mounting means for mounting an annular disk-shaped
substrate in the tool such that the elongated shaft extends through
the central opening of the substrate, the imprinting surface of the
at least one stamper/imprinter faces a major surface of the disk,
and a pre-selected location along the inner diameter of the disk is
biased into contact with the cylindrical shaft, whereby a space is
created between the inner diameter of the disk and the cylindrical
shaft which has a maximum width at a location diametrically
opposite the pre-selected location.
[0063] According to embodiments of the present invention, the
stamping/imprinting/embossing tool further comprises a pair of
axially movable, annular disk-shaped stamper/imprinter means (b)
for imprinting both major surfaces of the disk-shaped substrate
with the pre-selected pattern, and further comprises a resilient
mounting/centering means on the elongated cylindrical shaft (a) for
mounting and centering each of the pair of stamper/imprinter means
(b) on the elongated cylindrical shaft (a), wherein each of the
resilient mounting/centering means comprises a resiliently
compressible collet or polymeric ring mounted on the elongated
cylindrical shaft.
[0064] A yet further aspect of the present invention is a patterned
data/information storage and retrieval medium, comprising:
[0065] (a) an annular disk-shaped substrate having inner and outer
diameters and including a pattern formed in at least one of the
major surfaces thereof; and
[0066] (b) means for centering the pattern when the disk-shaped
substrate is mounted on a cylindrical shaft extending through the
inner diameter.
[0067] Additional advantages and aspects of the present invention
will become readily apparent to those skilled in the art from the
following detailed description, wherein embodiments of the present
invention are shown and described, simply by way of illustration of
the best mode contemplated for practicing the present invention. As
will be described, the present invention is capable of other and
different embodiments, and its several details are susceptible of
modification in various obvious respects. Accordingly, the drawings
and description are to be regarded as illustrative in nature, and
not as limitative.
BRIEF DESCRIPTION OF THE DRAWINGS
[0068] The following detailed description of the embodiments of the
present invention can best be understood when read in conjunction
with the following drawings, in which the various features are not
necessarily drawn to scale but rather are drawn as to best
illustrate the pertinent aspects and features, wherein:
[0069] FIG. 1 is a simplified, schematic cross-sectional view, of a
portion of a dual-sided, thin-film magnetic disk medium of the type
contemplated for use in the present invention;
[0070] FIG. 2 is a simplified, schematic plan view of a magnetic
recording disk according to the present invention, including a data
zone having a plurality of discrete servo tracks, and a contact
start/stop (CSS) zone;
[0071] FIG. 3 is a simplified, schematic perspective view of an
enlarged portion of a discrete servo track pattern formed on or
within a recording medium of thin film layer structure;
[0072] FIGS. 4(A)-4(D) are simplified, schematic cross-sectional
views illustrating a process sequence for performing thermal
imprint lithography of a thin resist film on a substrate
(workpiece) according to the conventional art;
[0073] FIGS. 5(A)-5(B) are simplified, schematic plan and
cross-sectional views, respectively, of an annular disk with its
inner diameter biased against a slightly smaller diameter,
rotatable drive spindle shaft of a disk drive for performing
precise servo patterning of the disk according to traditional
methodology utilizing a servo-writer or equivalently performing
device subsequent to installation of the disk in the disk
drive;
[0074] FIG. 6 is a simplified, schematic cross-sectional view of a
portion of a stamping/imprinting tool for performing servo
patterning of a biased annular disk medium (or substrate therefor)
according to the method of the present invention; and
[0075] FIG. 7 is a plan view taken along line 6-6' of FIG. 6 for
illustrating the biasing of a pre-selected location along the inner
diameter of the annular disk against a slightly smaller diameter
shaft of the stamping/imprinting tool.
DESCRIPTION OF THE INVENTION
[0076] The present invention addresses and solves problems
attendant upon the use of imprinting or embossing techniques, e.g.,
nano-imprint lithography or embossing of a sol-gel layer, for
forming sub-micron-dimensioned patterns in a substrate/workpiece
surface, as in servo patterning of disk-shaped substrates utilized
in the manufacture of hard disk recording media according to
alternative techniques which obviate the need for performing
expensive, time-consuming, post-fabrication servo patterning
utilizing servo-writers or like devices. Specifically, the present
invention affords a substantial improvement in centering of the
servo pattern of patterned disks produced by either of the
aforementioned alternative servo patterning techniques in disk
drive assemblies, whereby proper alignment/registration of the
servo tracks is consistently and conveniently obtained.
[0077] A key feature of the present invention is based upon the
discovery that proper centering of the servo pattern in the
assembled disk drive, whereby the disk drive electronics/control
system is able to compensate for any deviations from concentricity
of the servo patterns, can be readily and reliably achieved by
biasing the same point or location along the inner diameter of the
annular disk substrate against a central spindle or shaft of the
apparatus utilized for the imprinting or embossing process for
forming the servo pattern and against the rotatable drive spindle
of the disk drive assembly in which the servo patterned disk is
installed. An advantage afforded by the inventive methodology is
full compatibility with all other aspects of automated
manufacturing technology for pattern formation by imprint
lithography and/or sol-gel embossing for servo patterned disk media
formation.
[0078] Referring now to FIG. 6, shown therein is a simplified,
schematic cross-sectional view of a portion of a
stamping/imprinting tool ST for performing servo patterning of a
biased annular disk medium D (or substrate therefor) according to
the method of the present invention, comprising an elongated,
cylindrical shaft S of diameter slightly smaller than the inner
diameter ID of annular disk medium D for allowing passage of the
former through the central opening (i.e., inner diameter ID) of the
latter for positioning disk D at a pre-selected location along the
length of shaft S so as to be sandwiched between upper and lower
annular disk-shaped, axially movable stamper/imprinter means
SM.sub.U and SM.sub.L, respectively. Each of the upper and lower
annular disk-shaped stamper/imprinter means SM.sub.U and SM.sub.L
includes an imprinting surface IS (e.g., of Ni) including a
negative image of a pre-selected pattern to be formed in the
respective confronting upper and lower surfaces D.sub.U and D.sub.L
of disk D, e.g., a concentrically arranged servo pattern SP such as
illustrated in FIG. 5(A). Each of the upper and lower annular
disk-shaped stamper/imprinter means SM.sub.U and SM.sub.L further
includes a respective centering means CM.sub.U, CM.sub.L, e.g., in
the form of an expanding collet or resilient polymer ring, for
accurately and positively centering each of the stamper/imprinter
means to shaft S. Stamping/imprinting tool ST further includes a
disk bias means DB for biasing (i.e., urging) the inner diameter ID
of disk D into contact with shaft S at a location x along the inner
diameter ID, so as to create a spacing y between the shaft S and
the disk inner diameter ID, the maximum width of spacing y being at
a location diametrically opposite to contact point x, similar to
the situation shown in FIGS. 5(A)-5(B) illustrating biased mounting
of conventionally servo-patterned disk media in disk drive systems.
As best seen in the plan view of FIG. 7 taken along line 6-6' of
FIG. 6, according to the invention, one of the upper or lower
surfaces D.sub.U or D.sub.L of disk D is provided at the inner
diameter ID thereof with an indicator mark IM for use as a
reference point for accurately determining the point of contact x
of the disk inner diameter ID with shaft S of the
stamping/imprinting tool ST when the disk D is biased against shaft
S by the disk bias means DB. A typical sequence of steps for
performing thermal imprint lithography of a thermoplastic resist
layers on both the upper and lower surfaces D.sub.U and D.sub.L of
an annular disk-shaped substrate D for a recording medium or for
embossing of sol-gel layers on both surfaces of a similar substrate
for a recording medium utilizing the stamping/imprinting tool ST of
FIG. 6 (or similar device) is as follows: a first one of the upper
and lower annular disk-shaped stamper/imprinter means SM.sub.U and
SM.sub.L is placed on shaft S via the central opening thereof and
centered to the shaft via the respective centering means CM.sub.U,
CM.sub.L in the form of an expanding collet or resilient polymer
ring. An annular disk-shaped substrate D for a recording material
with the upper and lower surfaces D.sub.U and D.sub.L thereof
coated with a layer of a thermoplastic or sol-gel material is
placed on shaft S via the central opening (i.e., inner diameter ID)
thereof, the annular disk-shaped substrate D being provided with an
identification mark IM at a suitable location, e.g., the inner
diameter ID or outer diameter OD, illustratively the inner diameter
ID, for use in biasing the inner diameter ID of disc D (via the
disk bias means DB) against shaft S of the stamping/imprinting tool
ST at a location aligned with the identification mark IM. The
second one of the upper and lower annular disk-shaped
stamper/imprinter means SM.sub.U and SM.sub.L is then placed on
shaft S via the central opening thereof and centered to the shaft
via the respective centering means CM.sub.U, CM.sub.L. Each of the
axially movable upper and lower stamper/imprinter means SM.sub.U
and SM.sub.L is then pressed against the respective confronting
upper and lower surfaces D.sub.U and D.sub.L of disk D to imprint
or emboss patterns in the thermoplastic or sol-gel layers on the
upper and lower surfaces D.sub.U and D.sub.L of disk D, e.g., servo
patterns, corresponding to positive images of the patterns formed
in the imprinting surfaces IS thereof. The thus-imprinted disk D is
then removed from shaft S (as by disassembly of the sandwich
structure of upper stamper/imprinter SM.sub.U//disk D//lower
stamper/imprinter SM.sub.L) and subjected to further processing (in
conventional manner as described supra) for forming servo-patterned
recording media, e.g., longitudinal or perpendicular magnetic hard
disk media.
[0079] The servo-patterned, disk-shaped recording media is then
installed on a rotatable spindle shaft of a disk drive such that
the inner diameter of the disk is biased against the spindle shaft
of the disk drive at a location aligned with the identification
mark IM utilized during the above-described process for imprinting
the servo pattern, analogous to the conventional practice
illustrated in FIG. 5(A)-5(B). As a consequence of utilizing the
same location (i.e., contact point) along the inner diameter of the
disk for biasing against the spindle shaft of the disk drive as is
utilized during the imprinting/embossing process for servo
patterning, the imprinted/embossed servo patterns are well centered
to the disk drive spindle shaft, whereby a spindle shaft/disk
arrangement is obtained which closely simulates that which is
obtained when the servo patterns are written onto a biased disk
according to the conventional practice described above. Therefore,
the imprinted/embossed servo patterns provided by the inventive
methodology and apparatus are sufficiently concentric to the
rotation axis so that conventional disk drive electronics and
control systems can adequately compensate for any deviations from
concentricity of the servo patterns.
[0080] It should be apparent to one of ordinary skill that the
stamping/imprinting tool ST of FIG. 6 (or similar device) can, if
desired, be readily modified to include only one of the upper and
lower annular disk-shaped stamper/imprinter means SM.sub.U and
SM.sub.L, whereby only a selected one of the upper and lower
surfaces D.sub.U and D.sub.L of disk D is imprinted/embossed with a
desired pattern, e.g., a servo pattern.
[0081] Thus, the present invention provides means and methodology
for reliably forming pre-servo-patterned media with well-centered
patterns via thermal imprinting lithography or embossing of sol-gel
layers, and for installation of such patterned media in disk drives
therefor, in which the patterns are sufficiently well centered as
to enable use of conventional disk drive electronics and control
systems for compensation of any irregularities, lack of
concentricity, etc., of the imprinted or embossed patterns.
Moreover, the inventive means and methodology maintain full
compatibility with all aspects of automated manufacturing
technology for servo-patterned media formation by means of a
stamping/imprinting process for embossing the servo patterns in the
surface(s) of a disk-shaped recording medium (or substrate
therefor).
[0082] In the previous description, numerous specific details are
set forth, such as specific materials, structures, reactants,
processes, etc., in order to provide a better understanding of the
present invention. However, the present invention can be practiced
without resorting to the details specifically set forth. In other
instances, well-known processing materials and techniques have not
been described in detail in order not to unnecessarily obscure the
present invention.
[0083] Only the preferred embodiments of the present invention and
but a few examples of its versatility are shown and described in
the present disclosure. It is to be understood that the present
invention is capable of use in other combinations and environments
and is susceptible of changes and/or modifications within the scope
of the inventive concept(s) as expressed herein.
* * * * *