U.S. patent application number 11/797254 was filed with the patent office on 2007-11-15 for contact printing of magnetic media with mechanically reinforced and/or gas venting stamper.
This patent application is currently assigned to Seagate Technology LLC. Invention is credited to Neil Deeman, Joseph Leigh, Koichi Wago, Li-Ping Wang.
Application Number | 20070263308 11/797254 |
Document ID | / |
Family ID | 38015772 |
Filed Date | 2007-11-15 |
United States Patent
Application |
20070263308 |
Kind Code |
A1 |
Deeman; Neil ; et
al. |
November 15, 2007 |
Contact printing of magnetic media with mechanically reinforced
and/or gas venting stamper
Abstract
An apparatus for performing contact printing of a magnetic
transition pattern in a magnetic recording medium, comprising: (a)
a stamper/imprinter including a body formed of at least one
magnetic material having a high saturation magnetization B.sub.sat
and a high permeability, including an imprinting surface adapted to
be placed in intimate contact with a surface of a magnetic layer,
the imprinting surface comprised of a plurality of patterned areas
which separate a plurality of areas which are not patterned, each
of the areas which is not patterned being provided with at least
one of: (i) mechanical reinforcing means for preventing deformation
of the body when the imprinting surface is urged into contact with
the surface of the magnetic layer; and (ii) gas venting means for
facilitating removal of air or other gas from between the
imprinting surface and the surface of the magnetic layer when the
former is urged into contact with the latter.
Inventors: |
Deeman; Neil; (Fremont,
CA) ; Leigh; Joseph; (Campbell, CA) ; Wago;
Koichi; (Sunnyvale, CA) ; Wang; Li-Ping;
(Fremont, CA) |
Correspondence
Address: |
SEAGATE TECHNOLOGY LLC;c/o MCDERMOTT WILL & EMERY LLP
600 13TH STREET, NW
WASHINGTON
DC
20005-3096
US
|
Assignee: |
Seagate Technology LLC
Scotts Valley
CA
|
Family ID: |
38015772 |
Appl. No.: |
11/797254 |
Filed: |
May 2, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10453565 |
Jun 4, 2003 |
7218466 |
|
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11797254 |
May 2, 2007 |
|
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60392829 |
Jun 28, 2002 |
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Current U.S.
Class: |
360/17 ;
G9B/5.306; G9B/5.309 |
Current CPC
Class: |
G11B 5/865 20130101;
G11B 5/82 20130101; G11B 5/855 20130101; G11B 5/743 20130101; B82Y
10/00 20130101 |
Class at
Publication: |
360/017 |
International
Class: |
G11B 5/86 20060101
G11B005/86 |
Claims
1-13. (canceled)
14. A method of forming a magnetic transition pattern in a surface
of a magnetic material, comprising the sequential steps of:
providing a workpiece having a surface comprised of the magnetic
material, the magnetic material including a plurality of magnetic
domains extending from the surface; unidirectionally aligning the
magnetic domains of the magnetic material in a first unidirectional
DC magnetic field having a first direction; contacting the surface
of the magnetic material with an imprinting surface of a stamper,
the stamper including a body formed of at least one magnetic
material having a high saturation magnetization
B.sub.sat.gtoreq.about 0.5 Tesla and a high permeability
.mu..gtoreq.about 5, the imprinting surface adapted to be placed in
contact with the surface of the magnetic material, the imprinting
surface comprised of a plurality of projections and a plurality of
depressions arranged in a pattern corresponding to the magnetic
transition pattern to be formed in the surface of the magnetic
material and including a plurality of patterned areas separating a
plurality of unpatterned areas, and each of the plurality of
unpatterned areas being provided with at least one of: a plurality
of spaced-apart projections, and spaced-apart parallel channels
selectively re-aligning the plurality of magnetic domains in a
second unidirectional DC magnetic field having a second direction
opposite of the first direction where the plurality of magnetic
domains which are in contact with the plurality of projections or
which face the plurality of depressions of the imprinting surface
of the stamper, forming a pattern replicating the pattern of the
plurality of projections and plurality of depressions with aligned
magnetic domains and re-aligned magnetic domains; and removing the
stamper from contact with the surface of the magnetic material.
15. The method according to claim 14, wherein contacting the
surface of the magnetic material includes each of the patterned
areas of the imprinting surface having a plurality of projections
forming plurality of images of a plurality of servo sectors to be
formed in the magnetic layers and each of the unpatterned areas
corresponds to a data zone to be formed in the magnetic layer.
16. The method according to claim 15, wherein each of the plurality
of unpatterned areas corresponding to the data zones are recessed
relative to the plurality of projections forming the images of the
servo sectors, each of the recessed areas corresponding to the data
zones comprises a plurality of spaced-apart projections, and areas
adjacent to the plurality of spaced-apart projections comprise
channels in the data zones.
17. The method according to claim 16, wherein the imprinting
surface is annular disk-shaped with an inner diameter and an outer
diameter, each of the plurality of patterned areas forming the
servo sectors comprises a plurality of spaced-apart parallel
projections extending radially in partial spirals originating at
the inner diameter and extending to the outer diameter, and the
plurality of spaced-apart projections in the data zones form as a
plurality of spaced-apart parallel extending radially in partial
spirals originating at the inner diameter and extending to the
outer diameter.
18. The method according to claim 15, wherein each of the plurality
of unpatterned areas corresponding to the data extends to a height
approximately equal to a height of the projections forming the
images of the servo sectors; and the imprinting surface is annular
disk-shaped with an inner diameter and an outer diameter, each of
the plurality of patterned areas forming the servo sectors
comprises a plurality of spaced-apart parallel projections
extending radially in partial spirals originating at the inner
diameter and extending to the outer diameter, and each of the
plurality of data zones comprises a plurality of spaced-apart
parallel channels extending radially in partial spirals originating
at the inner diameter and extending to the outer diameter.
19. The method according to claim 14, further comprising: erasing
any magnetic transition patterns formed in portions of the magnetic
layer corresponding to the plurality of unpatterned areas of the
imprinting surface of the stamper.
20. The method according to claim 14, wherein providing the
workpiece comprises providing a disk-shaped workpiece for a
magnetic recording medium, the workpiece including a non-magnetic
substrate with a layer of a magnetic recording material overlying a
surface thereof, and the substrate comprised of a non-magnetic
material selected from the group consisting of Al, NiP-plated Al,
Al--Mg alloys, other Al-based alloys, other non-magnetic metals,
other non-magnetic metal-based alloys, glass, ceramics, polymers,
glass-ceramics, and composites and/or laminates thereof; aligning
the plurality of magnetic domains comprises placing the workpiece
in a first unidirectional DC magnetic field having a first
direction and a second unidirectional DC magnetic field having a
second direction opposite the first direction and a strength
sufficient to align each of the plurality of magnetic domains in
the first direction; providing the stamper formed of at least one
magnetic material having high saturation magnetization and high
permeability, selected from the group consisting of Ni, NiFe,
CoNiFe, CoSiFe, CoFe, and CoFeV, and the imprinting surface of the
stamper including a plurality of projections and depressions
arranged in a pattern corresponding to a servo pattern to be formed
in the surface of the magnetic material; and placing the workpiece
with the imprinting surface of the stamper in contact with the
second unidirectional DC magnetic field having a to a strength
lower than the first unidirectional DC magnetic field to
selectively reverse the alignment of said the plurality of magnetic
domains of the portions of the magnetic material which are in
contact with the projections or face the depressions of the
imprinting surface of the stamper, while retaining the first
direction alignment of the plurality of magnetic domains of the
portions of the magnetic material facing the depressions or the
projections, respectively, of the imprinting surface of the
stamper.
21. The method according to claim 14, wherein providing the
workpiece includes a layer of a perpendicular magnetic recording
material; placing the workpiece in the first unidirectional DC
magnetic field having the first direction perpendicular to the
surface of the layer of perpendicular magnetic recording material
and a strength sufficient to align each of the plurality of
magnetic domains along the first direction; and placing the
workpiece with the imprinting surface of the stamper in contact
with the second unidirectional DC magnetic field and a strength
lower than the first unidirectional DC magnetic field to
selectively reverse the alignment of the plurality of magnetic
domains of the portions of the magnetic material in contact with
the projections of the imprinting surface of the stamper, while
retaining the first direction alignment of the plurality of
magnetic domains of the portions of the magnetic material facing
the depressions of the imprinting surface of the stamper, the
stamper having an imprinting surface including a plurality of
projections and depressions arranged in a pattern corresponding to
a servo pattern to be formed in the surface of the layer of
perpendicular magnetic recording material.
22. The method according to claim 14, wherein. providing the
workpiece includes a layer of a longitudinal magnetic recording
material; placing the workpiece in the first direction parallel to
the surface of the layer of longitudinal magnetic recording
material and a high strength to align each of the plurality of
magnetic domains along the first direction; and step (c) comprises
placing the workpiece with the imprinting surface of the stamper in
the second unidirectional DC magnetic field parallel to the surface
of the longitudinal magnetic recording layer and a lower strength
than the strength of the first direction to selectively reverse the
alignment of the plurality of magnetic domains of the portions of
the magnetic recording layer facing the depressions of the
imprinting surface of the stamper, while aligning the plurality of
magnetic domains of the portions of the magnetic recording layer in
contact with the projections of the imprinting surface of the
stamper in the first direction, and the stamper having an
imprinting surface including a plurality of projections and
depressions arranged in a pattern corresponding to a servo pattern
to be formed in the surface of the longitudinal magnetic recording
material.
23. (canceled)
24. A method of forming a magnetic transition pattern on a surface
of a magnetic material provided on a workpiece, the magnetic
material including a plurality of magnetic domains extending from
the surface, comprising the sequential steps of: aligning the
plurality of magnetic domains of the magnetic material in a first
unidirectional DC magnetic field having a first direction;
contacting the surface of the magnetic material with an imprinting
surface of a stamper, the imprinting surface comprised of a
plurality of projections and plurality of depressions arranged in a
pattern corresponding to the magnetic transition pattern to be
formed in the surface of the magnetic material and including a
plurality of patterned areas separating a plurality of unpatterned
areas, and each of the unpatterned areas being provided with at
least one spaced-apart projections and at least one spaced-apart
parallel channel; selectively re-aligning the plurality of magnetic
domains which are in contact with the plurality of projections in a
second unidirectional DC magnetic field having a second direction
opposite the first direction; and forming a pattern replicating the
magnetic transition of the plurality of projections and plurality
of depressions with aligned magnetic domains and re-aligned
magnetic domains.
25. The method according to claim 24, wherein the stamper further
comprises: a body formed of at least one magnetic material having a
high saturation magnetization B.sub.sat.gtoreq.about 0.5 Tesla.
26. The method according to claim 24, wherein the stamper further
comprises: a body formed of at least one magnetic material having a
high permeability .mu..gtoreq.about 5.
27. The method according to claim 24, wherein the imprinting
surface is adapted to be placed in contact with the surface of the
magnetic material.
28. The method according to claim 24, wherein the stamper further
comprises: a body formed of at least one magnetic material having a
high saturation magnetization B.sub.sat.gtoreq.about 0.5 Tesla and
a high permeability .mu..gtoreq.about 5, and the body including the
imprinting surface adapted to be placed in contact with the surface
of the magnetic material.
29. The method according to claim 24, wherein contacting the
surface of the magnetic material includes each of the patterned
areas of the imprinting surface having a plurality of projections
forming a plurality of images of a plurality of servo sectors to be
formed in the magnetic layer, and each of the unpatterned areas
correspond to a data zone to be formed in the magnetic layer.
30. The method according to claim 29, wherein each of the
unpatterned areas corresponding to the data zones are recessed
relative to the projections forming the plurality of images of the
plurality of servo sectors, each of the recessed areas
corresponding to the data zones comprises a plurality of
spaced-apart projections, and areas adjacent to the plurality of
spaced-apart projections comprise channels in the data zones.
31. A method of forming a magnetic transition pattern on a surface
of a magnetic recording layer having a plurality of magnetic
domains extending from the surface, comprising: aligning the
plurality of magnetic domains in a first unidirectional DC magnetic
field having a first direction; contacting the surface of the
magnetic recording layer with an imprinting surface of a stamper,
the imprinting surface having a plurality of projections and
plurality of depressions arranged in a pattern corresponding to the
magnetic transition pattern to be formed in the surface of the
magnetic recording layer; re-aligning the plurality of magnetic
domains in a second unidirectional DC magnetic field having a
second direction opposite the first direction; and forming a
pattern replicating the magnetic transition pattern of the
plurality of projections and plurality of depressions with the
aligned magnetic domains and the re-aligned magnetic domains.
32. The method according to claim 31, wherein the stamper further
comprises: a body formed of at least one magnetic material having a
high saturation magnetization B.sub.sat.gtoreq.about 0.5 Tesla and
a high permeability .mu..gtoreq.about 5, and the body including the
imprinting surface adapted to be placed in contact with the surface
of the magnetic recording layer.
33. The method according to claim 31, wherein the imprinting
surface further comprises: a plurality of patterned areas
separating a plurality of unpatterned areas, and each of the
unpatterned areas being provided with at least one spaced-apart
projection and at least one spaced-apart parallel channel.
34. The method according to claim 33, comprising: forming a
plurality of images having a plurality of servo sectors in the
magnetic recording layer and each of the unpatterned areas, wherein
the plurality of servo sectors has a plurality of spaced-apart
parallel projections extending radially in partial spirals
originating at an inner diameter of each of the servo sectors and
extending to an outer diameter of each of the servo sectors.
35. The method according to claim 34, comprising: each of the
plurality of unpatterned areas corresponds to a data zone to be
formed in the magnetic recording layer, and are recessed relative
to the spaced-apart parallel projections forming the plurality of
images of the plurality of servo sectors.
Description
CROSS-REFERENCE TO PROVISIONAL APPLICATION
[0001] This application claims priority from U.S. provisional
patent application Ser. No. 60/392,829 filed Jun. 28, 2002, the
entire disclosure of which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to methods and devices for
forming magnetic transition patterns in a layer or body of magnetic
material. The invention has particular utility in the formation of
servo patterns in the surfaces of magnetic recording layers of
magnetic data/information storage and retrieval media, e.g., hard
disks.
BACKGROUND OF THE INVENTION
[0003] Magnetic recording media are widely used in various
applications, e.g., in hard disk form, particularly in the computer
industry for storage and retrieval of large amounts of
data/information in magnetizable form. Such media are
conventionally fabricated in thin film form and are generally
classified as "longitudinal" or "perpendicular", depending upon the
orientation (i.e., parallel or perpendicular) of the magnetic
domains of the grains of the magnetic material constituting the
active magnetic recording layer, relative to the surface of the
layer.
[0004] A portion of a conventional thin-film, longitudinal-type
recording medium 1 utilized in disk form in computer-related
applications is schematically depicted in FIG. 1 and comprises a
non-magnetic substrate 10, typically of metal, e.g., 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 (C), e.g., diamond-like carbon ("DLC"), and a
lubricant topcoat layer 15, typically of a perfluoropolyether
compound applied by dipping, spraying, etc.
[0005] In operation of medium 1, the magnetic layer 13 is locally
magnetized by a write transducer or write head (not shown in FIG. 1
for simplicity) 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 applied 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 applied 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.
[0006] A typical recording system 20 utilizing a thin-film,
vertically oriented, perpendicular-type magnetic medium 1' is
illustrated in FIG. 2, wherein reference numerals 10, 11, 12A, 12B
and 13', respectively, indicate the substrate, plating layer, soft
magnetic underlayer, at least one non-magnetic interlayer, and
vertically oriented, hard magnetic recording layer of
perpendicular-type magnetic medium 1, and reference numerals 7 and
8, respectively, indicate the single and auxiliary poles of
single-pole magnetic transducer head 6. Relatively thin interlayer
12B (also referred to as an "intermediate" layer), comprised of one
or more layers of non-magnetic materials, serves to (1) prevent
magnetic interaction between the soft underlayer 12A and the hard
recording layer 13' and (2) promote desired microstructural and
magnetic properties of the hard recording layer. As shown by the
arrows in the figure indicating the path of the magnetic flux
.phi., flux .phi. is seen as emanating from single pole 7 of
single-pole magnetic transducer head 6, entering and passing
through vertically oriented, hard magnetic recording layer 13'
(which, as is known, may comprise a Co-based alloy, an iron oxide,
or a multilayer magnetic superlattice structure) in the region
above single pole 7, entering and travelling along soft magnetic
underlayer 12A for a distance, and then exiting therefrom and
passing through vertically oriented, hard magnetic recording layer
13' in the region above auxiliary pole 8 of single-pole magnetic
transducer head 6. The direction of movement of perpendicular
magnetic medium 1 past transducer head 6 is indicated in the figure
by the arrow above medium 1.
[0007] With continued reference to FIG. 2, vertical lines 9
indicate grain boundaries of each polycrystalline (i.e., granular)
layer of the layer stack constituting medium 1. As apparent from
the figure, the width of the grains (as measured in a horizontal
direction) of each of the polycrystalline layers constituting the
layer stack of the medium is substantially the same, i.e., each
overlying layer replicates the grain width of the underlying layer.
Not shown in the figure, for illustrative simplicity, are a
protective overcoat layer 14, such as of a diamond-like carbon
(DLC) formed over hard magnetic layer 13', and a lubricant topcoat
layer 15, such as of a perfluoropolyethylene material, formed over
the protective overcoat layer. As with the longitudinal-type
recording medium 1 shown in FIG. 1, substrate 10 is typically
disk-shaped and comprised of a non-magnetic metal or alloy, e.g.,
Al or an Al-based alloy, such as Al--Mg having an Ni--P plating
layer 11 on the deposition surface thereof, or substrate 10 is
comprised of a suitable glass, ceramic, glass-ceramic, polymeric
material, or a composite or laminate of these materials; soft
underlayer 12A is typically comprised of an about 500 to about
4,000 .ANG. thick layer of a soft magnetic material selected from
the group consisting of Ni, NiFe (Permalloy), Co, CoZr, CoZrCr,
CoZrNb, CoFe, Fe, FeN, FeSiAl, FeSiAlN, etc.; thin interlayer 12B
typically comprises an up to about 100 .ANG. thick layer of a
non-magnetic material, such as TiCr; and hard magnetic layer 13' is
typically comprised of an about 100 to about 250 .ANG. thick layer
of a Co-based alloy including one or more elements selected from
the group consisting of Cr, Fe, Ta, Ni, Mo, Pt, V, Nb, Ge, and B,
iron oxides, such as Fe.sub.3O.sub.4 and .delta.-Fe.sub.2O.sub.3,
or a (CoX/Pd or Pt).sub.n multilayer magnetic superlattice
structure, where n is an integer from about 10 to about 25, each of
the alternating, thin layers of Co-based magnetic alloy is from
about 2 to about 3.5 .ANG. thick, X is an element selected from the
group consisting of Cr, Ta, B, Mo, and Pt, and each of the
alternating thin, non-magnetic layers of Pd or Pt is about 1 .ANG.
thick. Each type of hard magnetic recording layer material has
perpendicular anisotropy arising from magneto-crystalline
anisotropy (1.sup.st type) and/or interfacial anisotropy (2.sup.nd
type).
[0008] A typical contact start/stop (CSS) method employed during
use of disk-shaped media involves a floating transducer head
gliding at a predetermined distance from the surface of the disk
due to dynamic pressure effects caused by air flow generated
between mutually sliding surfaces of the transducer head and the
disk. During reading and recording (writing) 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 transducer head is freely movable in both
the circumferential and radial directions, thereby allowing data to
be recorded and retrieved from the disk at a desired position in a
data zone.
[0009] Adverting to FIG. 3, shown therein, in simplified, schematic
plan view, is a magnetic recording disk 30 (of either longitudinal
or perpendicular type) having a data zone 34 including a plurality
of servo tracks, and a contact start/stop (CSS) zone 32. A servo
pattern 40 is formed 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 data tracks.
[0010] Although only a relatively few of the servo tracking zones
are shown in FIG. 3 for illustrative simplicity, it should be
recognized that the 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] In conventional hard disk drives, data is stored in terms of
bits along the data tracks. In operation, the disk is rotated at a
relatively high speed, and the magnetic head assembly is mounted on
the end of a support or actuator arm, which radially positions the
head on the disk surface. If the actuator arm is held stationary,
the magnetic head assembly will pass over a circular path on the
disk, i.e., over a data 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 that track. By
moving the actuator arm, the magnetic head assembly is moved
radially on the disk surface between tracks. Many actuator arms are
rotatable, wherein the magnetic head assembly is moved between
tracks by activating a servomotor which pivots the actuator arm
about an axis of rotation. Alternatively, a linear actuator may be
used to move a magnetic head assembly radially inwardly or
outwardly along a straight line.
[0012] As has been stated above, to record information on the disk,
the transducer creates and applies a highly concentrated magnetic
field in close proximity to the magnetic recording medium. During
writing, the strength of the concentrated magnetic field directly
under the write transducer is greater than the coercivity of the
recording medium, and grains of the recording medium at that
location are magnetized in a direction which matches the direction
of the applied magnetic field. The grains of the recording medium
retain their magnetization after the magnetic field is removed. As
the disk rotates, the direction of the writing magnetic field is
alternated, based on bits of the information being stored, thereby
recording a magnetic pattern on the track directly under the write
transducer.
[0013] On each track, eight "bits" typically form one "byte" and
bytes of data are grouped as sectors. Reading or writing a sector
requires knowledge of the physical location of the data in the data
zone so that the servo-controller of the disk drive can accurately
position the read/write head in the correct location at the correct
time. Most disk drives use disks with embedded "servo patterns" of
magnetically readable information. The servo patterns are read by
the magnetic head assembly to inform the disk drive of track
location. In conventional disk drives, tracks typically include
both data sectors and servo patterns and each servo pattern
typically includes radial indexing information, as well as a "servo
burst". A servo burst is a centering pattern to precisely position
the head over the center of the track. Because of the locational
precision needed, writing of servo patterns requires expensive
servo-pattern writing equipment and is a time consuming
process.
[0014] Commonly assigned U.S. Pat. No. 5,991,104 to Bonyhard, the
entire disclosure of which is incorporated herein by reference,
discloses a method for forming a servo pattern in a magnetic disk,
comprising the steps of:
[0015] 1) aligning a magnetic disk immediately adjacent a master
servo-writer medium, the latter having a greater magnetic
coercivity than the former, wherein the servo-writer medium has a
master servo pattern magnetically stored thereon which defines a
plurality of concentric tracks;
[0016] 2) applying a magnetic assist field to the aligned master
servo-writer medium and magnetic disk, the magnetic assist field
having a substantially equal magnitude at all tracks on the aligned
master servo-writer medium and magnetic disk; and
[0017] 3) rotating the aligned master servo-writer medium and
magnetic disk relative to the magnetic assist field.
[0018] However, the above-described method incurs several drawbacks
associated with its implementation in an industrially viable
manner. Specifically, a "one-of-a-kind" master writer with a very
high write field gradient is necessary for writing the requisite
high intensity, master magnetic servo pattern onto the master disk,
and a complicated means for rotating the aligned master
servo-writer disk and "slave" workpiece magnetic disk is required,
as is a complex system for controlling/regulating/rotating the
intensity (i.e., magnitude) and directions of the magnetic assist
field.
[0019] Commonly assigned, co-pending U.S. patent application Ser.
No. 10/082,178, filed Feb. 26, 2002 (Attorney Docket No.
50103-401), the entire disclosure of which is incorporated herein
by reference, discloses an improvement over the invention disclosed
in the aforementioned commonly assigned U.S. Pat. No. 5,991,104,
and is based upon the discovery that very sharply defined magnetic
transition patterns can be reliably, rapidly, and cost-effectively
formed in a magnetic medium containing a longitudinal or
perpendicular type magnetic recording layer: (1) without requiring
expensive, complicated fabrication of a master disk (alternatively
referred to as a "stamper/imprinter") having a contacting (i.e.,
imprinting) surface comprised of a plurality of magnets or
magnetized areas corresponding to the desired magnetic transition
pattern to be formed in the magnetic disk (i.e., "slave"), and (2)
without requiring rotation of the master/slave pair in a magnetic
assist field of variable strength and polarity.
[0020] Specifically, the invention disclosed in co-pending,
commonly assigned U.S. patent application Ser. No. 10/082,178 is
based upon recognition that a stamper/imprinter ("master")
comprised of a magnetic material having a high saturation
magnetization, B.sub.sat, i.e., B.sub.sat.gtoreq.about 0.5 Tesla,
and a high permeability, .mu., i.e., .mu..gtoreq.about 5, e.g.,
selected from Ni, NiFe, CoNiFe, CoSiFe, CoFe, and CoFeV, can be
effectively utilized as a "master" contact mask (or
"stamper/imprinter") for "imprinting" of a magnetic transition
pattern, e.g., a servo pattern, in the surface of a magnetic
recording layer of a magnetic medium ("slave"), whether of
longitudinal or perpendicular type. A key feature of the invention
is the use of a stamper/imprinter having an imprinting surface
including a topographical pattern, i.e., comprised of projections
and depressions, corresponding to a desired magnetic transition
pattern, e.g., a servo pattern, to be formed in the magnetic
recording layer. An advantage afforded by the invention is the
ability to fabricate the topographically patterned imprinting
surface of the stamper/imprinter, as well as the substrate or body
therefor, of a single material, as by use of well-known and
economical electro-forming techniques.
[0021] According to the disclosed invention, the magnetic domains
of the magnetic recording layer of the slave medium are first
unidirectionally aligned (i.e., "erased" or "initialized"), as by
application of a first external, unidirectional magnetic field
H.sub.initial of first direction and high strength greater than the
saturation field of the magnetic recording layer, typically
.gtoreq.2,000 and up to about 20,000 Oe. The imprinting surface of
the stamper/imprinter (master) is then brought into intimate (i.e.,
touching) contact with the surface of the magnetic recording layer
(slave). With the assistance of a second externally applied
magnetic field of second, opposite direction and lower but
appropriate strength H.sub.re-align, determined by B.sub.sat/.mu.
of the stamper material (typically .gtoreq.100 Oe, e.g., from about
2,000 to about 4,500 Oe), the alignment of the magnetic domains at
the areas of contact between the projections of the imprinting
surface of the stamper/imprinter or at the areas facing the
depressions of the imprinting surface of the stamper/imprinter and
the magnetic recording layer of the medium to be patterned (slave)
is selectively reversed, while the alignment of the magnetic
domains at the non-contacting areas (defined by the depressions in
the imprinting surface of the stamper/imprinter) or at the
contacting areas, respectively, is unaffected, whereby a sharply
defined magnetic transition pattern is created within the magnetic
recording layer of the medium to be patterned (slave) which
essentially mimics the topographical pattern of projections and
depressions of the imprinting surface (master). According to the
invention, high B.sub.sat and high .mu. materials are preferred for
use as the stamper/imprinter in order to: (1) avoid early magnetic
saturation of the stamper/imprinter at the contact points between
the projections of the imprinting surface and the magnetic
recording layer, and (2) provide an easy path for the magnetic flux
lines which enter and/or exit at the side edges of the
projections.
[0022] Stampers/imprinters for use in a typical application
according to the disclosed invention, e.g., servo pattern formation
in the recording layer of a disk-shaped, thin film, longitudinal or
perpendicular magnetic recording medium, are formed according to
conventional techniques, and typically comprise an imprinting
surface having topographical features consisting of larger area
data zones separated by smaller areas with well-defined patterns of
projections and depressions corresponding to conventionally
configured servo sectors, as for example, disclosed in the
aforementioned commonly assigned U.S. Pat. No. 5,991,104. For
example, a suitable topography for forming the servo sectors may
comprise a plurality of projections having a height in the range
from about 20 to about 500 nm, a width in the range from about 0.01
to about 1 .mu.m, and a spacing of at least about 0.01 .mu.m.
Stampers/imprinters comprising imprinting surfaces with suitable
surface topographies may be readily formed by a variety of
techniques, such as electroforming onto a planar-surfaced substrate
through an apertured, non-conductive mask, or by pattern formation
in a planar-surfaced substrate by means photolithographic wet
(i.e., chemical) or dry (e.g., plasma, sputter, or ion beam)
etching techniques.
[0023] FIG. 4 illustrates a sequence of steps for performing
magnetic transition patterning by contact printing of a
perpendicular recording medium, e.g., medium 1' depicted in FIG. 2
and comprised of a non-magnetic substrate 10 and an overlying thin
layer 13' of a perpendicular-type magnetic recording material
(where plating layer 11, soft magnetic underlayer 12A, and
non-magnetic interlayer 12B are omitted from FIG. 4 in order to not
unnecessarily obscure the essential features/aspects of the present
invention) is subjected to a DC erase or magnetic initialization
process for unidirectionally aligning the perpendicularly oriented
magnetic domains 13.sub..perp. of magnetic recording layer 13'.
Magnetic initialization of perpendicular medium 1' is accomplished
by applying a first, high strength, unidirectional DC magnetic
initialization field H.sub.initial normal to the opposed major
surfaces thereof, i.e., normal to the lower surface of substrate 10
and upper surface of magnetic recording layer 13', wherein
H.sub.initial.gtoreq.coercivity of layer 13' and is typically in
the range from above about 2,000 to about 20,000 Oe.
[0024] According to the next step of the process sequence, a
stamper/imprinter 16 composed of composed of a body of magnetic
material having a high saturation magnetization, B.sub.sat, i.e.,
B.sub.sat.gtoreq.about 0.5 Tesla, and a high permeability, .mu.,
i.e., .mu..gtoreq.about 5, e.g., selected from Ni, NiFe, CoNiFe,
CoSiFe, CoFe, and CoFeV, and having an imprinting surface 17 having
a topography comprised of a plurality of projections 18 and
depressions 19 arranged in a pattern corresponding to a magnetic
transition pattern to be formed in the surface of magnetic
recording layer 13', e.g., a plurality of data zones separated by
servo sectors, is placed in intimate (i.e., touching) contact with
the surface of layer 13'. By way of illustration only, a suitable
topography for the imprinting surface 17 of a contact mask-type
stamper/imprinter 16 for use in forming a recording medium with
data zones separated by servo sectors according to the invention
may comprise a plurality of projections 18 having a height in the
range from about 20 to about 500 nm, a width in the range from
about 0.01 to about 1 .mu.m, and a spacing (defining the
depressions 19) of at least about 0.01 .mu.m). A second,
unidirectional DC magnetic re-alignment field H.sub.re-align of
direction reverse that of the DC magnetic initialization field
H.sub.initial is then applied normal to the upper surface of
stamper/imprinter 16 and the lower surface of substrate 10 of
medium 1', the strength of H.sub.re-align being lower than that of
H.sub.initial and optimized at a value determined by B.sub.sat/.mu.
of the stamper material (typically .gtoreq.100 Oe, e.g., from about
2,000 to about 4,500 Oe for the above-listed high B.sub.sat high
.mu. materials). According to the invention, due to the high
permeability .mu. of the stamper material, the magnetic flux .phi.
provided by the re-alignment field H.sub.re-align tends to
concentrate at the projections 18 of the stamper/imprinter 16,
which projections are in touching contact with the surface of
magnetic recording layer 13'. As a consequence, the surface areas
of magnetic recording layer 13' immediately beneath the projections
18 experience a significantly higher magnetic field than the
surface areas at the non-contacting areas facing the depressions
19. If the re-alignment field strength H.sub.re-align is optimized
(e.g., as described supra), the direction of magnetization (i.e.,
alignment) of the perpendicularly oriented magnetic domains
13.sub..perp. is selectively reversed (as indicated by the arrows
in the figure) at the areas of the magnetic recording layer 13'
where the projections 18 of the imprinting surface 17 of the
stamper/imprinter 16 contact the surface of the magnetic recording
layer 13', and the magnetic alignment of the perpendicularly
oriented magnetic domains 13.sub..perp. facing the depressions 19
in the imprinting surface 17 is retained. Consequently, upon
removal of the stamper/imprinter 16 and the re-alignment field
H.sub.re-align in the next (i.e., final) step according to the
inventive methodology, a perpendicular recording medium 1' is
formed with a magnetic transition pattern comprising a plurality of
data zones separated by servo sectors each comprising a plurality
of reversely oriented perpendicular magnetic domains 13.sub..perp.R
corresponding to the desired servo pattern.
[0025] FIG. 5 illustrates a similar sequence of steps for
performing magnetic transition patterning by contact printing of a
longitudinal recording medium, e.g., medium 1 depicted in FIG. 1
and comprised of a non-magnetic substrate 10 and an overlying thin
layer 13 of a longitudinal-type magnetic layer (where plating layer
11, polycrystalline underlayer 12, protective overcoat layer 14,
and lubricant topcoat layer 15 are omitted from FIG. 5 in order not
to unnecessarily obscure the essential features/aspects of the
present invention) is initially subjected to a magnetic erase (or
"initialization") process for unidirectionally aligning the
longitudinally oriented magnetic domains 13.sub.= of magnetic
recording layer 13. Magnetic initialization of longitudinal medium
1 is accomplished by applying a first, high strength,
unidirectional magnetic field H.sub.initial parallel to the surface
of the magnetic recording layer, such that
H.sub.initial.gtoreq.coercivity of layer 13' and is typically in
the range from about 2,000 to about 20,000 Oe. In this instance,
H.sub.initial is applied perpendicularly (i.e., normal) to the side
edges of medium 1, whereas, by contrast, H.sub.initial for a
perpendicular medium would be applied normal to the upper and lower
major surfaces of the medium.
[0026] According to the next step of the process sequence, a
stamper/imprinter 16 comprised of a body of magnetic material
having a high saturation magnetization, B.sub.sat, i.e.,
B.sub.sat.gtoreq.about 0.5 Tesla, and a high permeability, .mu.,
i.e., .mu..gtoreq.about 5, e.g., selected from Ni, NiFe, CoNiFe,
CoSiFe, CoFe, and CoFeV, and having an imprinting surface 17 having
a topography comprised of a plurality of projections 18 and
depressions 19 arranged in a pattern corresponding to a magnetic
transition pattern to be formed in the surface of magnetic
recording layer 13, e.g., a plurality of data zones separated by
servo sectors, is placed in intimate (i.e., touching) contact with
the surface of layer 13. By way of illustration only, a suitable
topography for the imprinting surface 17 of a contact mask-type
stamper/imprinter 16 for use in forming a recording medium with
data zones separated by servo sectors in longitudinal recording
layer 13 according to the invention may comprise a plurality of
projections 18 having a height in the range from about 20 to about
500 nm, a width of at least about 0.01 .mu.m, and a spacing
(defining the depressions 19) in the range from about 0.01 to about
1 .mu.m. A second, unidirectional magnetic re-alignment field
H.sub.re-align parallel to the major surface of magnetic recording
layer 13 but of lower strength and direction reverse that of the
magnetic initialization field H.sub.initial is then applied normal
to the side edge surfaces of stamper/imprinter 16, the strength of
H.sub.re-align being optimized at a value determined by
B.sub.sat/.mu. of the stamper material (typically .gtoreq.100 Oe,
e.g., from about 2,000 to about 4,500 Oe for the above-listed high
B.sub.sat, high .mu. materials).
[0027] According to the invention, due to the high permeability
.mu. of the stamper material, the magnetic flux .phi. provided by
the re-alignment field H.sub.re-align enters and exits the side
edges of the projections and tends to concentrate at the
depressions 19 of the stamper/imprinter 16 (rather than at the
projections 18). As a consequence, the non-contacted surface areas
of magnetic recording layer 13 immediately beneath the depressions
19 experience a significantly higher magnetic field than the
surface areas of the magnetic recording layer 13 in contact with
the projections 18. If the re-alignment field strength
H.sub.re-align is optimized, the direction of magnetization (i.e.,
alignment) of the longitudinally oriented magnetic domains 13.sub.=
of the magnetic recording layer 13 will be selectively reversed (as
indicated by the arrows in the figure) at the areas facing the
depressions 19 of the imprinting surface 17 of the
stamper/imprinter 16, whereas the alignment of the longitudinally
oriented magnetic domains 13.sub.= of the magnetic recording layer
13 in contact with the projections 18 of the imprinting surface 17
of the stamper/imprinter 16 will be retained. Consequently, upon
removal of the stamper/imprinter 16 and the re-alignment field
H.sub.re-align in the next (i.e., final) step according to the
inventive methodology, a longitudinal recording medium 1 is formed
with a magnetic transition pattern comprising a plurality of data
zones separated by servo sectors each comprising of a plurality of
reversely longitudinally oriented magnetic domains 13.sub.=R
corresponding to the desired servo pattern.
[0028] Referring to FIGS. 6 (A) and 8 (A), portions of first and
second types of conventionally configured stampers/imprinters 16
for performing contact printing are illustrated (not to scale) in
simplified, schematic cross-section, which stampers/imprinters 16
each comprise an imprinting surface 17 including a plurality of
larger area data zones DZ (only one such zone being shown in the
figure for illustrative simplicity), which data zones typically
occupy about 80-90% of the surface area of the imprinting surface,
and are separated by pairs of smaller area servo sectors SS
occupying the remaining 10-20% of the surface area of the
imprinting surface. Servo sectors SS are defined by a plurality of
protrusions or fingers 18 extending from the main body MB of the
stamper 16, which protrusions are spaced apart by depressions
19.
[0029] According to the first type of stamper, shown in FIG. 6 (A),
the unpatterned, larger area data zones DZ are not designed to
contact the media surface during contact printing and thus are
recessed relative to the protrusions or fingers 18 of the servo
sectors SS; whereas, according to a second type of stamper, shown
in FIG. 8 (A), the unpatterned, larger area data zones DZ are
designed to contact the media surface during contact printing, and
therefore project to the same level or height as the projections of
the servo sectors SS.
[0030] FIG. 7 is a plan view of the imprinting surface of an
annular disk-shaped embodiment of the first type of conventionally
configured stamper/imprinter 16 illustrated in FIGS. 6 (A) and 6
(B), showing a plurality of data zones DZ separated by servo
sectors SS in the form of radially extending partial spirals
originating at the inner diameter ID and extending to the outer
diameter OD, wherein the servo sectors SS occupy about 10 to about
20% of the imprinting surface (with the data zones DZ occupying
about 80 to about 90% of the imprinting surface) and are comprised
of a plurality of projections (best seen in FIG. 6) having a height
in the range from about 20 to about 500 nm, a width in the range
from about 0.01 to about 1 .mu.m, and a spacing between adjacent
projections of at least about 0.01 .mu.m.
[0031] In use, however, stampers/imprinters 16 of the first type
shown in FIGS. 6-7, wherein the unpatterned data zones DZ are
recessed relative to the protruding servo sectors SS, incur a
problem in that flexural deformation/distortion of the
stamper/imprinter occurs, as schematically illustrated (in an
extreme or exaggerated case) in FIG. 6 (B), when a downwardly
directed pressure (as shown by the arrows in the figure) is applied
during the contact printing process for placing the imprinting
surface 17 in intimate contact with the surface of the magnetic
recording layer 13 of the medium to be patterned. As a consequence
of the poor/uneven contact between the pattern features 18 of
imprinting surface 17 and the surface of the magnetic recording
layer 13, the resultant servo pattern is distorted, in turn leading
to poor servo performance.
[0032] FIG. 9 is a plan view of the imprinting surface of an
annular disk-shaped embodiment of the second type of conventionally
configured stamper/imprinter 16 illustrated in FIGS. 8 (A) and 8
(B), showing a plurality of projecting data zones DZ (with only 2
such projecting data zones DZ shown in black for illustrative
convenience) separated by servo sectors SS in the form of radially
extending partial spirals originating at the inner diameter ID and
extending to the outer diameter OD, wherein the servo sectors SS
occupy about 10 to about 20% of the imprinting surface (with the
data zones DZ occupying about 80 to about 90% of the imprinting
surface) and are comprised of a plurality of projections (best seen
in FIG. 8) having a height in the range from about 20 to about 500
nm, a width in the range from about 0.01 to about 1 .mu.m, and a
spacing between adjacent projections of at least about 0.01 .mu.m,
wherein each of the projecting data zones DZ (also best seen in
FIG. 8) has a height substantially equal to the height of the
projections forming the servo sectors SS.
[0033] Stampers/imprinters 16 of the second type shown in FIGS.
8-9, while substantially free of the problem of pressure-induced,
flexural deformation/distortion associated with use of the first
type of stamper/imprinter 16, incur a different problem, as
schematically shown (also in an extreme or exaggerated case) in
FIG. 8 (B), in that air pockets tend to become entrapped in the
space between the imprinting surface 17 and the surface of the
magnetic recording layer 13 as the imprinting surface 17 approaches
the surface of the magnetic recording layer 13, which pockets of
entrapped air form particularly in the regions where the
unpatterned data zones DZ face the media surface, leading to poor
contact/separation between the imprinting surface 17 and surface of
the magnetic recording layer 13. The poor contact in turn leads to
loss of resolution of the resultant magnetic transition pattern of
the servo sectors SS, hence poor servo performance.
[0034] Accordingly, there exists a need for means and methodology
for performing servo patterning by contact printing which are free
of the above-described drawbacks and disadvantages associated with
the use of conventionally-configured/structured
stampers/imprinters, and facilitate high quality replication of
servo patterns in magnetic recording media via contact printing.
Moreover, there exists a need for methodology and means, e.g.,
improved stampers/imprinters for performing rapid, cost-effective
servo patterning of thin film, high areal recording density
magnetic recording media which do not engender the above-stated
concerns and disadvantages associated with existing
methodologies/instrumentalities for patterning magnetic recording
media by contact printing.
[0035] The present invention addresses and solves the
above-described problems, disadvantages, and drawbacks associated
with prior methodologies for servo pattern formation in thin film
magnetic recording media, while maintaining full compatibility with
the requirements of automated hard disk manufacturing
technology.
DISCLOSURE OF THE INVENTION
[0036] An advantage of the present invention is an improved
apparatus for performing contact printing of a magnetic transition
pattern in a magnetic recording medium.
[0037] Another advantage of the present invention is an improved
apparatus for performing contact printing of servo patterns in
longitudinal or perpendicular magnetic recording media.
[0038] Yet another advantage of the present invention is an
improved method for performing contact printing of a magnetic
transition pattern in a magnetic recording medium.
[0039] Another advantage of the present invention is an improved
method for performing contact printing of servo patterns in
longitudinal or perpendicular magnetic recording media.
[0040] Additional advantages and other 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 as particularly pointed out in the
appended claims.
[0041] According to one aspect of the present invention, the
foregoing and other advantages are obtained in part by an apparatus
for performing contact printing of a magnetic transition pattern in
a magnetic recording medium, comprising:
[0042] (a) a stamper/imprinter including a body formed of at least
one magnetic material having a high saturation magnetization
B.sub.sat.gtoreq.about 0.5 Tesla and a high permeability
.mu..gtoreq.about 5, the body including an imprinting surface
adapted to be placed in intimate contact with a surface of a
magnetic layer, the imprinting surface comprised of a plurality of
patterned areas which separate a plurality of areas which are not
patterned, each of the plurality of areas which is not patterned
being provided with at least one of: [0043] (i) mechanical
reinforcing means for preventing deformation of the body when the
imprinting surface is urged into contact with the surface of the
magnetic layer; and [0044] (ii) gas venting means for facilitating
removal of air or other gas from between the imprinting surface and
the surface of the magnetic layer when the imprinting surface is
urged into contact with the surface of the magnetic layer.
[0045] According to embodiments of the present invention, each of
the plurality of patterned areas of the imprinting surface forms an
image of a servo sector to be formed in the magnetic layer and each
of the areas which is not patterned corresponds to a data zone to
be formed in the magnetic layer; the plurality of patterned areas
forming the servo sectors occupy from about 2 to about 20% of the
imprinting surface and the plurality of areas corresponding to the
data zones which are not patterned occupy from about 80 to about
98% of the imprinting surface; each of the plurality of patterned
areas of the imprinting surface includes a plurality of projections
forming the image of the servo sectors; each of the plurality of
projections has a height in the range from about 20 to about 500
nm, a width in the range from about 0.01 to about 1 .mu.m, and a
spacing between adjacent projections of at least about 0.01
.mu.m.
[0046] In accordance with certain embodiments of the present
invention, each of the plurality of areas corresponding to the data
zones which are not patterned is recessed relative to the
projections forming the image of the servo sectors; each of the
recessed areas corresponding to the data zones comprises mechanical
reinforcing means (i) in the form of a plurality of spaced-apart
projections; adjacent ones of the plurality of spaced-apart
projections comprising the mechanical reinforcing means (i) form
channels in the data zones comprising the gas venting means (ii);
and the imprinting surface is annular disk-shaped with inner and
outer diameters, each of the plurality of patterned areas forming
the servo sectors comprises a plurality of parallel spaced-apart
projections extending radially in partial spirals originating at
the inner diameter and extending to the outer diameter, and the
plurality of spaced-apart projections comprising the mechanical
reinforcing means (i) in the data zones form the gas venting means
(ii) as parallel spaced-apart channels extending radially in
partial spirals originating at the inner diameter and extending to
the outer diameter.
[0047] According to certain other embodiments of the present
invention, each of the plurality of areas corresponding to the data
zones which are not patterned is in the form of a projection
extending to the same height as the projections forming the
negative image of the servo sectors; and the imprinting surface is
annular disk-shaped with inner and outer diameters, each of the
plurality of patterned areas forming the servo sectors comprises a
plurality of parallel spaced-apart projections extending radially
in partial spirals originating at the inner diameter and extending
to the outer diameter, and each of the data zones comprises a
plurality of gas venting means (ii) in the form of parallel
spaced-apart channels extending radially in partial spirals
originating at the inner diameter and extending to the outer
diameter.
[0048] Embodiments of the present invention include those wherein
the body of the stamper/imprinter formed of at least one magnetic
material having a high saturation magnetization
B.sub.sat.gtoreq.about 0.5 Tesla and a high permeability
.mu..gtoreq.about 5 comprises at least one material selected from
the group consisting of Ni, NiFe, CoNiFe, CoSiFe, CoFe, and
CoFeV.
[0049] Further embodiments of apparatus according to the present
invention additionally comprise:
[0050] (b) magnet means for applying a unidirectional magnetic
field to the stamper/imprinter for effecting selective re-alignment
of magnetic domains of a magnetic material in contact with the
imprinting surface of the stamper/imprinter.
[0051] Another aspect of the present invention is a method of
forming a magnetic transition pattern in a surface of a magnetic
material, comprising the sequential steps of:
[0052] (a) providing a workpiece including a surface comprised of
the magnetic material, the magnetic material including a plurality
of magnetic domains extending to the surface;
[0053] (b) unidirectionally aligning the magnetic domains of the
magnetic material in a first direction;
[0054] (c) contacting the surface of the magnetic material with an
imprinting surface of a stamper/imprinter, the stamper/imprinter
including a body formed of at least one magnetic material having a
high saturation magnetization B.sub.sat.gtoreq.about 0.5 Tesla and
a high permeability .mu..gtoreq.about 5, the body including an
imprinting surface adapted to be placed in intimate contact with
the surface of the magnetic material, the imprinting surface
comprised of a plurality of projections and depressions arranged in
a pattern corresponding to the magnetic transition pattern to be
formed in the surface of the magnetic material and including a
plurality of patterned areas which separate a plurality of areas
which are not patterned, each of the plurality of areas which is
not patterned being provided with at least one of: [0055] (i)
mechanical reinforcing means for preventing deformation of the body
when the imprinting surface is urged into contact with the surface
of the magnetic layer; and [0056] (ii) gas venting means for
facilitating removal of air or other gas from between the
imprinting surface and the surface of the magnetic layer when the
imprinting surface is urged into contact with the surface of the
magnetic layer;
[0057] (d) selectively re-aligning the magnetic domains of those
portions of the surface of the magnetic material which are in
contact with the projections or which face the depressions of the
imprinting surface of the stamper, such that the magnetic domains
of the contacted portions or the facing portions are
unidirectionally aligned in a second direction reverse that of the
first direction and the combination of aligned .phi. re-aligned
magnetic domains forms a pattern replicating the pattern of the
projections and depressions; and
[0058] (e) removing the stamper from contact with the surface of
the magnetic material.
[0059] According to embodiments of the present invention, step (c)
comprises contacting the surface of the magnetic material with an
imprinting surface of a stamper/imprinter wherein each of the
plurality of patterned areas of the imprinting surface includes a
plurality of projections forming an image of a servo sector to be
formed in the magnetic layer and each of the areas which is not
patterned corresponds to a data zone to be formed in the magnetic
layer.
[0060] In accordance with certain embodiments of the present
invention, each of the plurality of areas corresponding to the data
zones which are not patterned is recessed relative to the
projections forming the images of the servo sectors; each of the
recessed areas corresponding to the data zones comprises mechanical
reinforcing means (i) in the form of a plurality of spaced-apart
projections, adjacent ones of the plurality of spaced-apart
projections comprising the mechanical reinforcing means (i) form
channels in the data zones comprising the gas venting means (ii);
and the imprinting surface is annular disk-shaped with inner and
outer diameters, each of the plurality of patterned areas forming
the servo sectors comprises a plurality of parallel spaced-apart
projections extending radially in partial spirals originating at
the inner diameter and extending to the outer diameter, and the
plurality of spaced-apart projections comprising the mechanical
reinforcing means (i) in the data zones form the gas venting means
(ii) as parallel spaced-apart channels extending radially in
partial spirals originating at the inner diameter and extending to
the outer diameter.
[0061] According to certain other embodiments of the present
invention, each of the plurality of areas corresponding to the data
zones which are not patterned is in the form of a projection
extending to the same height as the projections forming the images
of the servo sectors; the imprinting surface is annular disk-shaped
with inner and outer diameters, each of the plurality of patterned
areas forming the servo sectors comprises a plurality of parallel
spaced-apart projections extending radially in partial spirals
originating at the inner diameter and extending to the outer
diameter, and each of the plurality of data zones comprises a
plurality of gas venting means (ii) in the form of parallel
spaced-apart channels extending radially in partial spirals
originating at the inner diameter and extending to the outer
diameter.
[0062] According to embodiments of the present invention, the
method further comprises a step of:
[0063] (f) erasing any magnetic transition patterns formed in step
(d) in portions of the magnetic layer corresponding to the
plurality of areas of the imprinting surface of the
stamper/imprinter which are not patterned.
[0064] Further embodiments of the present invention include those
wherein:
[0065] step (a) comprises providing a disk-shaped workpiece for a
magnetic recording medium, the workpiece including a non-magnetic
substrate with a layer of a magnetic recording material overlying a
surface thereof, the substrate comprised of a non-magnetic material
selected from the group consisting of Al, NiP-plated Al, Al--Mg
alloys, other Al-based alloys, other non-magnetic metals, other
non-magnetic metal-based alloys, glass, ceramics, polymers,
glass-ceramics, and composites and/or laminates thereof, step (b)
comprises placing the workpiece in a first unidirectional DC
magnetic field having a first direction and a high strength
sufficient to align each of the magnetic domains in the first
direction;
[0066] step (c) comprises contacting the surface of the magnetic
material with the imprinting surface of a stamper formed of at
least one magnetic material having high saturation magnetization
and high permeability, selected from the group consisting of Ni,
NiFe, CoNiFe, CoSiFe, CoFe, and CoFeV, the stamper/imprinter having
an imprinting surface including a plurality of projections and
depressions arranged in a pattern corresponding to a servo pattern
to be formed in the surface of the magnetic material; and
[0067] step (d) comprises placing the workpiece with the imprinting
surface of the stamper in contact therewith in a second
unidirectional DC magnetic field having a second direction opposite
the first direction and a lower but sufficient strength to
selectively reverse the alignment of the magnetic domains of the
portions of the magnetic material which are in contact with the
projections or face the depressions of the imprinting surface of
the stamper, while retaining the first direction alignment of the
magnetic domains of the portions of the magnetic material facing
the depressions or the projections, respectively, of the imprinting
surface of the stamper.
[0068] According to certain embodiments of the present
invention,
[0069] step (a) comprises providing a workpiece including a layer
of a perpendicular magnetic recording material;
[0070] step (b) comprises placing the workpiece in a first
unidirectional DC magnetic field having a first direction
perpendicular to the surface of the layer of perpendicular magnetic
recording material and a high strength sufficient to align each of
the magnetic domains along the first direction; and
[0071] step (c) comprises placing the workpiece with the imprinting
surface of the stamper in contact therewith in a second
unidirectional DC magnetic field having a second direction opposite
the first direction and a lower but sufficient strength to
selectively reverse the alignment of the magnetic domains of the
portions of the magnetic material in contact with the projections
of the imprinting surface of the stamper, while retaining the first
direction alignment of the magnetic domains of the portions of the
magnetic material facing the depressions of the imprinting surface
of the stamper, the stamper having an imprinting surface including
a plurality of projections and depressions arranged in a pattern
corresponding to a servo pattern to be formed in the surface of the
layer of perpendicular magnetic recording material.
[0072] In accordance with certain other embodiments of the present
invention,
[0073] step (a) comprises providing a workpiece including a layer
of a longitudinal magnetic recording material;
[0074] step (b) comprises placing the workpiece in a first,
unidirectional DC magnetic field having a first direction parallel
to the surface of the layer of longitudinal magnetic recording
material and a high strength sufficient to align each of the
magnetic domains along the first direction; and
[0075] step (c) comprises placing the workpiece with the imprinting
surface of the stamper in contact therewith in a second
unidirectional DC magnetic field parallel to the surface of the
longitudinal magnetic recording layer but having a second direction
opposite the first direction and a lower but sufficient strength to
selectively reverse the alignment of the magnetic domains of the
portions of the magnetic recording layer facing the depressions of
the imprinting surface of the stamper, while retaining the first
direction alignment of the magnetic domains of the portions of the
magnetic recording layer in contact with the projections of the
imprinting surface of the stamper, the stamper having an imprinting
surface including a plurality of projections and depressions
arranged in a pattern corresponding to a servo pattern to be formed
in the surface of the layer of longitudinal magnetic recording
material.
[0076] Yet another aspect of the present invention is a
stamper/imprinter for performing contact printing of a magnetic
transition pattern in the surface of a magnetic recording medium,
comprising:
[0077] (a) a body formed of at least one magnetic material having a
high saturation magnetization and high permeability and including a
patterned imprinting surface; and
[0078] (b) means for preventing deformation of the body during use
and/or for venting air or other gas from the imprinting surface
during use.
[0079] 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, all without departing
from the spirit of the present invention. Accordingly, the drawings
and description are to be regarded as illustrative in nature, and
not limitative.
BRIEF DESCRIPTION OF THE DRAWINGS
[0080] 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 features, and in which like reference
numerals are employed throughout to designate similar features,
wherein:
[0081] FIG. 1 illustrates, in schematic, simplified cross-sectional
view, a portion of a longitudinal-type thin film magnetic recording
medium;
[0082] FIG. 2 illustrates, in schematic, simplified cross-sectional
view, a portion of a magnetic recording, storage, and retrieval
system comprised of a perpendicular-type magnetic recording medium
and a single-pole transducer head;
[0083] FIG. 3 is a simplified, schematic plan view, of a magnetic
recording disk for illustrating the data, servo pattern, and CSS
zones thereof;
[0084] FIG. 4 illustrates, in schematic, simplified cross-sectional
view, a sequence of process steps performed according to the
invention for creating a magnetic transition pattern in the surface
of a perpendicular magnetic recording layer, utilizing a
stamper/imprinter having an imprinting surface corresponding to the
desired magnetic transition pattern and formed of a high saturation
magnetization, high permeability magnetic material;
[0085] FIG. 5 illustrates, in schematic, simplified cross-sectional
view, a similar sequence of process steps performed according to
the invention for creating a magnetic transition pattern in the
surface of a longitudinal magnetic recording layer;
[0086] FIGS. 6 (A) and 6 (B) illustrate, in schematic, simplified
cross-sectional view, a portion of a conventionally configured
stamper/imprinter comprised of projection-patterned servo sectors
SS and recessed, unpatterned data zones DZ, prior to and during
use, respectively;
[0087] FIG. 7 is a plan view of the imprinting surface of an
annular disk-shaped embodiment of the conventionally configured
stamper/imprinter shown in FIGS. 6 (A) and 6 (B);
[0088] FIGS. 8 (A) and 8 (B) illustrate, in schematic, simplified
cross-sectional view, a portion of a conventionally configured
stamper/imprinter comprised of projection-patterned servo sectors
SS and projecting, unpatterned data zones DZ, prior to and during
use, respectively;
[0089] FIG. 9 is a plan view of the imprinting surface of an
annular disk-shaped embodiment of a conventionally configured
stamper/imprinter corresponding to that shown in cross-sectional
view in FIGS. 8 (A) and 8 (B);
[0090] FIGS. 10 (A) and 10 (B) illustrate, in schematic, simplified
cross-sectional view, a portion of an embodiment of a
stamper/imprinter according to the invention, comprised of
projection-patterned servo sectors SS and recessed, unpatterned
data zones DZ modified to include a plurality of mechanical
reinforcement ribs R, prior to and during use in patterning a
magnetic recording medium, respectively;
[0091] FIG. 11 is a plan view of the imprinting surface of an
annular disk-shaped stamper/imprinter corresponding to the
embodiment of the invention shown in cross-sectional view in FIGS.
10 (A) and 10 (B); and
[0092] FIG. 12 is a plan view of the imprinting surface of an
annular disk-shaped stamper/imprinter of the type shown in
cross-sectional view in FIGS. 8 (A) and 8 (B), and in plan view in
FIG. 9, modified according to the invention.
DESCRIPTION OF THE INVENTION
[0093] The present invention addresses and solves problems and
drawbacks attendant upon use of conventionally configured
stampers/imprinters utilized in performing high quality contact
printing of recording layers of magnetic recording media for
forming magnetic transition patterns therein, e.g., servo patterns,
in a cost-efficient manner at high product throughput rates.
Specifically, the present invention is based upon recognition by
the inventors that modification of the design of the imprinting
surfaces of the stampers/imprinters currently employed for
patterning of magnetic recording media via contact printing is
necessary for obtaining further improvement in pattern replication
fidelity and product quality. The present invention, therefore, has
as its aim or objective, improvement of the design features of the
imprinting surfaces of the stampers/imprinters in order to
eliminate, or at least substantially reduce, the tendency for
occurrence of poor or uneven contact with the surface of the
magnetic layer or material to be patterned.
[0094] A feature of the present invention, in the case of
stampers/imprinters wherein the unpatterned data zones are recessed
relative to the patterned servo sectors and thus are not intended
to contact the surface of the magnetic material or layer during
patterning, as for example shown in FIGS. 6 (A)-6 (B) and 7, is the
provision of a plurality of mechanical reinforcement means in the
data zone, e.g., a plurality of spaced-apart, radially extending
reinforcing ribs in the form of projections of the same height as
the projections of the servo sector patterns, which reinforcing
ribs provide additional mechanical support of the imprinting
surface of the stamper/imprinter during use, hence eliminating, or
at least substantially reducing, flexural deformation of the main
body of the stamper/imprinter upon application of pressure thereto
for urging the imprinting surface into intimate contact with the
surface of the magnetic recording layer or material. Further
according to the invention, the partial spiral-shaped channels
formed between adjacent reinforcing ribs advantageously also serve
to vent air or other gas which may be present or otherwise
entrapped in the space between the imprinting surface of the
stamper/imprinter and the surface of the magnetic recording layer
or material, thereby eliminating, or at least substantially
reducing, another factor leading to poor contact between the
imprinting surface and the magnetic layer.
[0095] Similarly, a feature of the present invention in the case of
stampers/imprinters wherein the unpatterned data zones extend for
the same depth as the patterned servo sectors and thus are intended
to contact the surface of the magnetic material or layer during
patterning, as for example shown in FIGS. 8 (A)-8 (B) and 9, is the
provision of a plurality of spaced-apart, radially extending
channels in the data zones, which partial spiral-shaped channels
advantageously serve to vent air or other gas which may be present
or otherwise entrapped in the space between the imprinting surface
of the stamper/imprinter and the surface of the magnetic recording
layer or material, thereby eliminating, or at least substantially
reducing, a major factor leading to poor contact between the
imprinting surface and the magnetic layer when the former contacts
the latter during contact printing.
[0096] In either instance, according to the inventive methodology,
any magnetic transition patterns formed in the data zones during
the contact printing process due to the presence of the reinforcing
ribs or gas venting channels are erased in conventional manner
subsequent to contact printing.
[0097] Referring now to FIGS. 10 (A)-10 (B) shown therein, in
schematic, simplified cross-sectional view, is a portion of an
embodiment of a stamper/imprinter 16' of the first type (shown in
FIGS. 6-7) modified according to the invention, comprised of
projection-patterned servo sectors SS and recessed, unpatterned
data zones DZ which are modified to include a plurality of
mechanical reinforcement ribs RR spaced apart by gas venting
channels GC, prior to and during use, respectively; and FIG. 11 is
a plan view of the imprinting surface of an annular disk-shaped
stamper/imprinter 16' corresponding to the embodiment of the
invention shown in FIGS. 10 (A) and 10 (B).
[0098] With particular reference to FIG. 10 (B) illustrating
stamper/imprinter 16' in use, i.e., in contact with the surface of
a magnetic recording layer 13 on substrate 10, it is evident that
the large plurality of mechanical reinforcement ribs RR in the data
zone DZ which project for the same distance as the pattern features
(projections 18) of the servo sectors SS, and thus also contact the
magnetic recording layer 13 during use, effectively prevent, or at
least minimize flexural distortion of the main body MB of the
stamper during use, as for example shown in FIG. 6 (B), leading to
poor pattern replication fidelity. By way of illustration only, a
stamper/imprinter 16' according to the invention, having 25 and 100
mm inner and outer diameters, respectively, utilized for contact
printing servo patterns in 95 mm diameter workpieces for hard
disks, typically comprises data zones DZ having a width of about
0.4 mm at the inner diameter ID and a width of about 1.5 mm at the
outer diameter, provided with reinforcement ribs RR from about
0.0001 to about 0.01 mm wide at the inner diameter and from about
0.0004 to about 0.04 mm wide at the outer diameter, spaced apart by
gas venting channels GC from about 0.0001 to about 0.01 mm wide at
the inner diameter ID and from about 0.0004 to about 0.04 mm wide
at the outer diameter OD, which mechanical reinforcement ribs RR
project from the main body MB of the stamper/imprinter 16' for a
distance substantially equal to that of the pattern features 18 of
the servo sector SS, e.g., from about 20 to about 500 nm.
[0099] Adverting to FIG. 11, showing a plan view of the embodiment
of the stamper/imprinter 16' shown in cross-sectional view in FIGS.
10 (A)-10 (11), according to the invention, each of the
spaced-apart mechanical reinforcement ribs RR extends radially in a
partial spiral-shaped manner from the inner diameter ID to the
outer diameter OD, thereby forming a plurality of correspondingly
partial-spiral shaped gas venting channels GC extending from the
inner diameter to the outer diameter in the spaces between adjacent
reinforcement ribs. Typical radii of curvature of each of the
partial spiral-shaped reinforcement ribs RR and gas venting
channels GC of the illustrative embodiment, wherein the annular
disk has 25 and 95 mm inner and outer diameters, respectively, are
from about 20 to about 100 nm.
[0100] Referring now to FIG. 12, shown therein is a plan view of
the imprinting surface of an annular disk-shaped stamper/imprinter
16'' of the type shown in cross-sectional view in FIGS. 8 (A) and 8
(B), and in plan view in FIG. 9, modified according to the
invention. Specifically, according to this embodiment, a plurality
of spaced-apart, radially extending, partial spiral-shaped gas
venting channels GC, similar to those of the preceding embodiment,
are provided in the projecting data zones DZ of the imprinting
surface. As in the preceding embodiment, the partial spiral-shaped
channels advantageously serve to vent air or other gas which may be
present or otherwise entrapped in the space between the imprinting
surface of the stamper/imprinter and the surface of the magnetic
recording layer or material, thereby eliminating, or at least
substantially reducing, a major factor leading to poor contact
between the imprinting surface and the magnetic layer when the
former contacts the latter during contact printing.
[0101] By way of illustration only, a stamper/imprinter 16''
according to the invention, having 25 and 100 mm inner and outer
diameters, respectively, utilized for contact printing servo
patterns in 95 mm diameter workpieces for hard disks, typically
comprises projecting data zones DZ having a width of about 0.4 mm
at the inner diameter ID and a width of about 1.5 mm at the outer
diameter, provided with gas venting channels GC from about 0.0001
to about 0.01 mm wide at the inner diameter and from about 0.0004
to about 0.04 mm wide at the outer diameter. According to the
invention, each of the spaced-apart gas venting channels GC extends
radially in a partial spiral-shaped manner from the inner diameter
ID to the outer diameter OD. Typical radii of curvature of the
partial spiral-shaped gas venting channels GC of the illustrative
embodiment, wherein the annular disk has 25 and 95 mm inner and
outer diameters, respectively, are from about 20 to about 100
nm.
[0102] It should be apparent to one of ordinary skill in the art
that the present invention provides a significant improvement over
the art such as has been described above, particularly with respect
to the improved pattern replication fidelity afforded by the
invention. Further, the imprinting surface of the
stampers/imprinters according to the invention can be formed with a
wide variety of magnetic transition patterns, whereby the inventive
methodology and apparatus can be rapidly, easily, and
cost-effectively implemented in the automated manufacture of a
number of articles, devices, etc., requiring magnetic transition
patterning, of which servo patterning of longitudinal and
perpendicular magnetic recording media merely constitute examples
of the versatility and utility of the invention.
[0103] In the previous description, numerous specific details are
set forth, such as specific materials, structures, 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.
[0104] 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 as expressed herein.
* * * * *