U.S. patent application number 09/747808 was filed with the patent office on 2001-05-03 for zone textured magnetic recording media and methods for their production.
This patent application is currently assigned to AKASHIC MEMORIES CORPORATION. Invention is credited to Hara, Hiroki, Inoue, Naoki, Konishi, Hiroshi, Kurataka, Nobuo, Leigh, Joseph, Shima, Koji, Weiss, Joel R..
Application Number | 20010000771 09/747808 |
Document ID | / |
Family ID | 26667620 |
Filed Date | 2001-05-03 |
United States Patent
Application |
20010000771 |
Kind Code |
A1 |
Weiss, Joel R. ; et
al. |
May 3, 2001 |
Zone textured magnetic recording media and methods for their
production
Abstract
Magnetic recording media are provided having separately textured
data and read/write head landing zones. Separating these zones on
the recording surface allows independent optimization of the
topology to maximize both recording characteristics and mechanical
durability. The landing or contact start stop zone has an average
surface roughness greater than that of the data zone. Preferably, a
transition zone extends between the contact start stop zone and the
data zone, the transition zone varying between the two in average
surface roughness. Preferably, the contact start stop zone is
textured first, followed by the data zone, thereby ensuring uniform
stiction performance. Texture machines for producing such zone
texturing and texturing methods are also provided.
Inventors: |
Weiss, Joel R.; (Fremont,
CA) ; Shima, Koji; (Saratoga, CA) ; Leigh,
Joseph; (Cupertino, CA) ; Konishi, Hiroshi;
(Cupertino, CA) ; Kurataka, Nobuo; (Itami City,
JP) ; Hara, Hiroki; (Itami City, JP) ; Inoue,
Naoki; (Itami City, JP) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW
TWO EMBARCADERO CENTER
EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
AKASHIC MEMORIES
CORPORATION
|
Family ID: |
26667620 |
Appl. No.: |
09/747808 |
Filed: |
December 22, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09747808 |
Dec 22, 2000 |
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09048869 |
Mar 26, 1998 |
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6193590 |
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09048869 |
Mar 26, 1998 |
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08503785 |
Jul 18, 1995 |
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5798164 |
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60000434 |
Jun 23, 1995 |
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Current U.S.
Class: |
451/41 ; 451/303;
G9B/5.236; G9B/5.293; G9B/5.299 |
Current CPC
Class: |
G11B 5/8404 20130101;
G11B 5/82 20130101; G11B 5/64 20130101; Y10T 428/24355 20150115;
B24B 21/06 20130101; Y10S 428/90 20130101 |
Class at
Publication: |
451/41 ;
451/303 |
International
Class: |
B24B 001/00; B24B
021/12 |
Claims
What is claimed is:
1. Magnetic recording media comprising a read/write head
interaction surface including a contact start stop zone having a
relatively high surface roughness to improve durability, and a data
zone having a relatively low surface roughness as compared to the
contact start stop zone to improve magnetic recording
characteristics.
2. Magnetic recording media as claimed in claim 1, wherein the
contact start stop zone has an average surface roughness of at
least 40 .ANG..
3. Magnetic recording media as claimed in claim 2, wherein the data
zone has an average surface roughness of less than 35 .ANG..
4. Magnetic recording media as claimed in claim 1, wherein the
contact start stop zone has an average surface roughness in the
range between 45 .ANG. and 55 .ANG., and wherein the data zone has
an average surface roughness in the range between 15 .ANG. and 35
.ANG..
5. Magnetic recording media as claimed in claim 1, wherein at least
one of the contact start stop zone and the data zone has a
cross-hatched surface texture imposed by oscillating one of the
magnetic recording media and a texturing abrasive mechanism
relative to the other during texturing so that a transition zone of
the head interaction surface varies gradually in surface texture
between the contact start stop zone and the data zone.
6. Magnetic recording media as claimed in claim 1, wherein the
slope of the head interaction surface between the contact start
stop zone and the data zone is less than 0.004.degree..
7. Improved magnetic recording media of the type having a textured
surface, the improvement comprising: a contact start stop zone on
the textured surface having a first surface texture; a data zone on
the textured surface having a second surface texture with a low
average surface roughness compared to the first texture; a
transition zone extending between the contact start stop zone and
the data zone, the transition zone having a transition surface
texture which varies from the first texture adjacent to the contact
start stop zone, to the second texture adjacent to the data
zone.
8. Improved magnetic recording media as claimed in claim 7, wherein
the second texture is imposed after the first texture.
9. Improved magnetic recording media as claimed in claim 8, wherein
at least a portion of the transition zone has the second surface
texture imposed over the first surface texture.
10. Improved magnetic recording medial as claimed in claim 9,
wherein at least one of the first and second textures is imposed by
oscillating one of the magnetic recording media and an associated
texturing mechanism relative to the other during texturing so that
the surface roughness of the transition zone varies smoothly from
the first texture to the second texture, and wherein oscillations
are controlled to within 0.006 inch during texturing.
11. Improved magnetic recording media as claimed in claim 7,
wherein a slope of the transition zone from the contact start stop
zone to the data zone is less than 0.004.degree..
12. Improved magnetic recording media as claimed in claim 7,
wherein the first texture has an average surface roughness in the
range between 45 .ANG. and 55 .ANG., and wherein the second texture
has an average surface roughness in the range between 15 .ANG. and
35 .ANG..
13. An improved machine for texturing magnetic recording media of
the type having an abrasive tape and a texture roller for biasing
the abrasive tape against the magnetic recording media, the
improvement comprising: a step on the texture roller, the step
having a large diameter relative to a body portion of the texture
roller, wherein the abrasive tape rolls against the step and
extends beyond the step toward the body portion of the texture
roller.
14. A machine for texturing magnetic recording media, the machine
comprising: a magnetic recording media restraint; an abrasive tape;
a texture roller for biasing the abrasive tape against the magnetic
recording media; and an oscillation mechanism disposed between the
recording media restraint and the texture roller, the oscillation
mechanism allowing adjustment to oscillations with a tolerance of
less than 0.006 inch.
15. A texturing machine as claimed in claim 14, further comprising
a tape guide having a slot which engages an edge of the abrasive
tape to control the axial position of the tape, and a pressure pad
which biases the abrasive tape against the tape guide.
16. A method for texturing a read/write head interaction zone of
magnetic recording media, the method comprising: texturing a
contact start stop zone with a first surface texture, the contact
start stop zone being on the head interaction surface; texturing a
data zone with a second surface texture having a relatively smooth
average surface roughness as compared to the first texture, the
data zone being on the head interaction surface.
17. A method as claimed in claim 16, wherein the contact start stop
zone texturing step comprises texturing at least a portion of a
transition zone, and wherein the data zone texturing step comprises
texturing over at least a portion of the textured portion of the
transition zone, the transition zone extending between the contact
start stop zone and the data zone.
18. A method as claimed in claim 17, wherein the contact start stop
texturing step comprises biasing an abrasive tape against the head
interaction surface with a stepped texturing roller.
19. A method as claimed in claim 18, wherein the contact start stop
zone texturing step comprises oscillating one of the stepped roller
and the surface relative to the other.
20. A method as claimed in claim 16, wherein the data zone
texturing step comprises biasing an abrasive tape against the head
interaction surface with a texturing roller, oscillating one of the
texturing roller and the head interaction surface relative to the
other, and guiding an edge of the abrasive tape to control
positional tolerance of the data zone to within 0.006 inch.
21. A method as claimed in claim 16, wherein at least one of the
contact start stop zone texturing step and the data zone texturing
step comprises oscillating the surface relative to a texturing
mechanism to produce a transition zone extending between the
contact start stop zone and the data zone, the transition zone
having a surface roughness which varies from the first texture
adjacent to the contact start stop zone to the second texture
adjacent to the data zone.
22. A method as claimed in claim 21, further comprising controlling
the contact start stop zone and data zone texturing steps to limit
a slope of the transition zone from the contact start stop zone to
the data zone to less than 0.004.degree..
Description
1. This application is a continuation-in-part of Provisional
Application Ser. No. ______ (Attorney Docket No. 14089-001800),
filed on Jun. 23, 1995, the full disclosure of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
2. 1. Field of the Invention
3. The present invention relates to generally to magnetic recording
media, and more particularly to recording media having a landing
zone with an independently optimized surface texture.
4. Magnetic recording disks generally comprise a disk substrate
having a magnetic layer and a number of underlayers and overlayers
deposited thereon. The nature and composition of each layer is
selected to provide desired magnetic recording characteristics. An
exemplary present day disk is illustrated in FIG. 1 and comprises a
non-magnetic disk substrate 10 typically composed of an aluminum
alloy. Alternative substrates comprise non-metallic materials such
as glass, ceramics, glass ceramic composites, carbon, carbon
ceramic composites, and the like. Generally, an amorphous nickel
phosphorus (Ni--P) layer 12 is formed over each surface of disk
substrate 10, typically by plating. The Ni--P layer is hard, and
imparts rigidity to aluminum alloy substrates. A chromium ground
layer 14 is formed over the Ni--P layer 12, typically by
sputtering, and the magnetic layer 16 is formed over the ground
layer 14. The magnetic layer 16 comprises a thin film of a
ferromagnetic material, typically including an alloy of cobalt.
Usually, a protective layer 18, such as a carbon film, is formed
over the magnetic layer 16, and a lubricating layer 20 is formed
over the protective layer.
5. The presence of the Ni--P layer 12 and the chromium ground layer
14 has been found to improve the recording characteristics of the
magnetic layer 16. In particular, the chromium ground layer formed
over an Ni--P layer has been found to provide enhanced coercivity
and reduced noise characteristics. Such improvements are further
enhanced when the Ni--P layer is treated by mechanical texturing to
create a roughened surface prior to formation of the chromium
ground layer. The texturing may be circumferential or crosswise,
with the preferred geometry depending on the particular composition
of the cobalt-containing magnetic layer.
6. Such magnetic recording disk structures have been very
successful and allow for high recording densities. As with all
successes, however, it is presently desired to provide magnetic
recording disks having even higher recording densities. Recording
densities can be improved by reducing the spacing between the
recording transducer (read/write head) and the magnetic disk
surface while the disk is rotating. In modern magnetic recording
systems, the read/write head often glides over the recording
surface on an "air bearing," a layer of air which moves with the
rotating disk. Thus, the spacing between the read/write head and
recording surface, referred to as the "glide height," depends in
part on the surface topology of the disk.
7. Surface topology affects both the magnetic recording
characteristics and durability of magnetic recording media. Surface
topology is often measured by surface roughness (Ra), the
arithmetic average of the absolute height and depth of peaks and
valleys in a profiler scan. Recording densities generally benefit
from low glide heights which are associated with smooth recording
surfaces having a low surface roughness. As might be expected,
magnetic recording media noise, as measured in terms of bit shift,
increases as roughness increases. Furthermore, certification errors
per data track, the number of individual bits which exhibit less
than a threshold percentage of the nominal signal strength, also
increase with increasing roughness. Thus, magnetic recording
characteristics generally benefit from recording surfaces having a
relatively low average surface roughness.
8. Unfortunately, the reliability of magnetic recording systems
generally improves with increased recording surface roughness.
Smooth surfaces do not build up the moving layer of air over the
disk's surface required to "fly" the read/write head as quickly as
rough surfaces. Frictional contact between the rotating disk and
read/write head, called "stiction," is particularly problematic
during start up and stopping of the magnetic recording system, and
has a profound impact on the durability of magnetic recording
media.
9. For these reasons, it would be desirable to provide improved
magnetic recording media having optimized surface topologies and
methods for their fabrication. It would be particularly desirable
if such recording media provided improved magnetic recording
characteristics of low surface roughness without compromising the
mechanical durability of magnetic recording systems. The methods
should provide for texturing the substrate or layer structure of
magnetic recording media without greatly increasing production
costs and capital equipment requirements.
10. 2. Description of the Background Art
11. U.S. Pat. No. 4,786,564 describes the texturing of a nickel
phosphorus layer over an aluminum substrate to enable a read/write
head to fly over the surface of the disk. U.S. Pat. No. 5,314,745
describes a magnetic recording media having a glass substrate with
an optionally textured Ni--P layer.
SUMMARY OF THE INVENTION
12. Magnetic recording media according to the principles of the
present invention comprise a read/write head interaction surface
including a contact start stop zone having a relatively high
surface roughness to improve durability, and data zone having a
relatively low surface roughness as compared to the contact start
stop zone to improve magnetic recording characteristics. As used
herein, a "read/write head interaction surface" means the surface
over which the head glides, lands, rests or slides during standard
operation of a magnetic recording media system of the type
utilizing an air bearing. The data storage of the present magnetic
recording media is physically separated from the read/write head
landing site, allowing the surface topology of the specialized
zones to be individually optimized for either mechanical durability
or data storage. Specifically, the relatively high surface
roughness of the contact start stop zone exhibits excellent head
glide height, stiction, and durability performance, while the
relatively low surface roughness of the data zone promotes a low
glide height to improve data density, minimize media noise as
measured in bit shift errors, and reduce the incidence of
certification errors, particularly at higher threshold
percentages.
13. Optimization of the read/write head interface surface of
magnetic recording media for both mechanical durability and
high-density recording characteristics has been problematic,
requiring compromises between competing criteria. In connection
with the present invention, it has been discovered that friction
between the read/write head and separately optimized contact start
stop zone increases greatly when the contact start stop zone has a
roughness (Ra) of less than 40 .ANG.. Conversely, surface
topologies having a roughness of over 55 .ANG. suffer head crash at
a higher rate than lower roughness surfaces. Mechanical durability
is optimized where the contact start stop zone has an average
surface roughness in the range between 45 .ANG. and 55.ANG.. It has
further been discovered that recording density can be increased by
limiting the average surface roughness of the data zone to 35 .ANG.
or less. Glide height, certification errors, and media noise are
optimized with a data zone surface topology having an average
surface roughness in the range between 15 .ANG. and 35.ANG..
14. In another aspect, the present invention provides improved
magnetic recording media of the type having a textured surface.
Such textured surfaces are generally imposed on an underlayer or
the substrate of the magnetic recording media, typically by
abrading an Ni--P underlayer with an abrasive tape, a diamond
slurry, or the like. The improvement comprises a contact start stop
zone on the textured surface having a first surface texture, and a
data zone on the textured surface having a second surface texture,
in which the second texture has a lower average surface roughness
than the first texture. A transition zone extends between the
contact start stop zone and the data zone, and has a surface
texture which varies from the first texture adjacent to the contact
start stop zone to the second texture adjacent to the data
zone.
15. Generally, the transition zone will be textured at least in
part during texturing of both the data zone and the contact start
stop zone. As with most surface preparation procedures, the surface
topology depends on which of the two textures is imposed last on
the transition zone. Preferably, at least a portion of the
transition zone has the second surface texture imposed over the
first surface texture. Thus, the contact start stop zone should
then be textured first, followed by the texturing of the data zone.
This helps to ensure that most of the relatively rough texture
patterns generated by the contact start stop zone texturing process
within the transition zone are polished out during the data zone
texturing process. Additionally, imposing the data zone texturing
over the contact start stop zone texture ensures that stiction
performance is not compromised, but cannot guarantee the error
performance of the data zone. Conversely, imposing the contact
start stop zone texturing over the data zone texture guarantees the
error performance throughout the data zone, but compromises the
stiction performance. Although optimized magnetic recording media
require both maximum stiction and error performance, error
performance can be easily and quickly tested on individual disks
using a production level certifier. In contrast, verification of
stiction performance requires a lengthy testing process. Therefore,
it is preferable to texture the data zone last, and ensure error
performance by testing.
16. Generally, the first and second textures are imposed by
oscillating the magnetic recording media relative to an associated
texturing mechanism so that the surface roughness of the transition
zone varies smoothly from the first texture to the second texture.
The oscillations of the latter applied texture process must be
controlled to within tight tolerances, ideally being controlled to
within 0.006 inch to ensure the integrity and alignment of the data
zone on the recording surface.
17. Separately imposing the first texture on the contact start stop
zone and the second texture on the data zone typically results in a
disparity In height between the contact start stop zone and the
data zone. The transition zone will thus often have a slope, the
angle of which depends on the relative difference in heights and on
the distance between the contact start stop zone and data zone. In
connection with the present invention, it has been discovered that
this slope of the texture zone has a significant impact on the
likelihood of head crashing. Generally, the slope angle should be
as low as possible, ideally being less than 0.004.degree..
18. An improved machine for texturing a zone on magnetic recording
media is also provided. The texturing machine is of the type having
an abrasive tape and a texture roller for biasing the abrasive tape
against the magnetic recording media. The improvement comprises a
step on the texture roller having a large diameter relative to a
body portion. The abrasive tape rolls against the step and extends
beyond the step toward the body portion of the texture roller, and
is thereby locally biased against the magnetic recording media in
the area of the step. Advantageously, the tape is biased against
the recording media only locally at the step, allowing texturing of
a limited contact start stop zone without major modifications to
the texturing machine. The tape provides a gradual reduction in
texturing beyond the step, particularly when the roller is
oscillated relative to the recording media.
19. A machine for texturing magnetic recording media according to
the principles of the present invention comprises a magnetic
recording media restraint, an abrasive tape, and a texture roller
for biasing the abrasive tape against the magnetic recording media.
Additionally, an oscillation mechanism is disposed between the
recording media restraint and the texture roller. The oscillation
mechanism allows adjustments to oscillations with a tolerance of
less than 0.006 inch. Typically, the magnetic recording media
restraint allows rotation of a magnetic recording disk, while the
precise control of the oscillation mechanism ensures the integrity
and positioning of the contact start stop zones, transition zones,
and data zones of magnetic recording media according to the
principles of the present invention. Ideally, the oscillation
mechanism has a tolerance of less than 0.0005 inch. Such precise
control is available using an eccentric cam with threadably
adjustable upper and lower cam followers.
20. A method for texturing a surface of magnetic recording media
according to the principles of the present invention comprises
texturing a contact start stop zone with a first texture, and
texturing a data zone with a second surface texture. The second
texture has a relatively smooth average surface roughness as
compared to the first texture.
BRIEF DESCRIPTION OF THE DRAWINGS
21. FIG. 1 is a cross-sectional view of an exemplary prior art
magnetic recording disk, as described in the background section
hereinabove.
22. FIG. 2 is an illustration of a zone textured magnetic recording
disk according to the principles of the present invention.
23. FIG. 3 schematically illustrates the texture of the contact
start stop zone and data zone of the magnetic recording disk of
FIG. 2.
24. FIGS. 4A and 4B schematically illustrate alternative
transitional zone surface topologies for the magnetic recording
disk of FIG. 2.
25. FIGS. 5A and 5B schematically illustrate a contact start stop
zone texturing machine having a stepped texture roller according to
the principles of the present invention.
26. FIGS. 6A-6D illustrate a data zone texturing machine according
to the principles of the present invention.
27. FIGS. 7-12 show experimental data, as described in detail in
the Experimental Section.
DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENTS
28. Referring now to FIG. 2, magnetic recording media according to
the present invention will usually be in the form of a magnetic
recording disk 30 having a contact start stop zone 32 and a data
zone 34. These zones are distinguished by the surface texture, the
properties of which will be described with reference to the
outermost surface of the disk as it is used in a magnetic recording
system. The actual texturing processes may be performed on the
substrate, on an underlayer below the magnetic recording layers, on
the magnetic recording layer itself, or on an overlayer.
29. Typically, an underlayer is textured, most commonly an Ni--P
layer. The average surface roughness, and other surface topology
described herein, refers specifically to the surface
characteristics of the outermost layer, rather than the
characteristics of the textured surface prior to application of any
overlayers. Although the data zone is shown in an outward location,
the relative radial position of the zones may be reversed. Clearly,
the zone positioning must be carefully coordinated with the disk
drive design.
30. Referring now to FIG. 3, a landing texture 42 has been imposed
on contact start stop zone 32 having a relatively large average
variation in absolute height and depth of the peaks and valleys. In
contrast, a data texture 44 has much smaller variations in height,
and therefore a lower surface roughness.
31. Although there is a considerable difference in the average
surface roughness between the contact start stop zone and the data
zone, both zones benefit from minimizing peak asperities (Rp). High
peak asperities increase the air layer thickness which moves with
the rotating disk, and increases the bit shift errors, thereby
negatively impacting data zone performance. High peak asperities
also increase the friction and wear between the contact start stop
zone and the read/write head, which is deleterious to durability of
the contact start stop zone.
32. Between landing texture 42 and data texture 44, a transition
zone 46 will exhibit some of the properties of each of the adjacent
textures. As described hereinbelow, texturing of either or both the
landing zone 42 and data zone 44 generally involves the use of an
oscillating abrasive tape or texturing slurry deposited on an
absorbent pad. These oscillations create a "cross-hatched" texture
pattern which is beneficial for contact start stop performance, and
also allows increases in data density. Additionally, a trailing-off
phenomenon occurs at the extreme of the oscillating tape due to the
decrease in texturing time. Thus, the transition zone need not be
independently textured, but is preferably the result of the
trailing off of the-contact start stop and data texturing
processes. The surface finish in the transition zone depends in
part on which texturing process is performed last.
33. Referring now to FIG. 4A, a magnetic recording media which is
first textured with a landing texture 42 leaves a tapered trailing
landing texture 47 imposed on at least a portion of the transition
zone. Subsequent imposition of a data texture 44 substantially
erases the landing texture from the transition zone, and results in
a varying transition texture 48 exhibiting remnants of the landing
texture. Hence, the error performance of the transition zone is
left somewhat in question. Nonetheless, the stiction and mechanical
performance of landing texture 42 is uncompromised.
34. Referring now to FIG. 4B, alternative textured disk 50 has been
processed by first imposing data texture 44, which extends in a
tapering fashion over at least a portion of the transition zone.
The landing texture 42 has then been applied over the contact start
stop zone, and again extends onto at least a portion of the
transition zone. The resulting transition texture 54 exhibits
significant remnants of both the landing texture 42 and the data
texture 44. Although error performance of the data zone remains
uncompromised, the error performance throughout the transition zone
cannot be guaranteed because of the remnant high roughness from the
landing texture. Additionally, stiction performance remains suspect
throughout the transition zone. Nonetheless, this overlapping
condition can be optimized to perform acceptably.
35. Referring now to FIGS. 5A and 5B, a preferred landing texture
machine 60 axially restrains zone texture disk 30 in contact with
abrasive tapes 64. A pair of stepped rollers 62 bias abrasive tape
64 against zone texture disk 30 in the area of contact start stop
zone 32. Adhesive tape 64 (shown clear for purposes of
illustration) is in rolling contact with both a step 66 and body
portion 68 of stepped roller 62, ensuring stability over the width
of the tape. The rollers area of pressure against the disk surface
is substantially limited to the step width w. Extending the
abrasive tape beyond the step ensures a smooth and gradual edge on
the textured zone. Alternatively, abrasive tape 64 extends beyond
step 66 but does not contact body portion 68.
36. The roller has a specific hardness, which together with the
flexibility of the abrasive tape, the depth d of step 66, and the
pinch distance 72 between the roller and the disk will define an
abrasion pressure profile. The hardness of the roller limits the
minimum width of the step, but by reducing step depth d, the width
w can be further reduced. The step is reproduced on alternative end
70 so that step roller 62 may be flipped over and reused. The
abrasive tape must be thin enough to fit in between the steps so
that the tape does not contact the data zone. Care must be taken so
that no slippage of the tape occurs. Optionally, stepped rollers 62
and adhesive tape 64 are oscillated with respect to rotating zone
textured disk 30.
37. Referring now to FIG. 6A through 6D, the machine for texturing
a data zone comprises rollers 82 biasing fine abrasive tape 84
against zone textured disk 30. As used herein, the term "abrasive
tape" specifically encompasses texturing slurry deposited on a
buffing tape. The zone textured disk is again axially restrained by
a disk restraint mechanism, here schematically illustrated as edge
rollers 106. An alternative disk restraint mechanism restrains the
axial location of the disk from the inner diameter. Rollers 82
oscillate relative to zone textured disk 30 as the disk rotates.
The contact start stop zone 32 has been previously textured, hence,
control over the location and oscillation characteristics of
rollers 82 will define the size and surface topology
characteristics of the transition zone. Such positioning will also
determine the location of data zone 34, which is critical for
optimal stiction and error performance. If it is placed too close
to the contact start stop zone stiction may occur. Alternatively,
if the data zone is placed too far from the contact start stop
zone, excessive disk errors may arise.
38. The roller location controls the position of fine abrasive tape
84. The slurry laden tape, however, tends to slip out of position
if it is not properly guided at the point of use. Tape guide
assembly 85, comprising a pressure pad 88 which gently pushes the
lower edge of the tape against a slotted guide set 86, and thus
improves tape tracking, reducing tape tracking errors by as much as
50 percent. Clearly, slotted guide set 86 must be properly
positioned.
39. The effects of data zone texturing tape positioning is
schematically illustrated in FIG. 6C. Landing texture 42 has
previously been imposed on the disk, leaving tapering landing
texture residue 47 on transition zone 90. As data texture 44 is
imposed over the data zone, tapering landing texture residue 47 is
erased, but transition zone 90 is left with a slope 92. Depending
on the relative amounts of material removed during the landing
texturing and data zone processes, as well as on the distance
between the contact start stop zone and data zone, a large slope
angle can be generated. Excessive slope 92 angles increase the
incidence of head crash, particularly when slope 92 is greater than
0.004.degree.. Thus, texturing time and pressure should be
controlled to avoid removing too much material from either
zone.
40. An oscillation mechanism 100 provides precise control over the
limits of oscillations during texturing.
41. Eccentric cam 101 rotates between upper and lower cam followers
108, 110. Upper and lower adjuster screws 102, 104 adjust the upper
and lower cam followers 108, 110, thereby varying the height of
roller 182 relative to zone textured disk 30, and hence providing
control over the radial location of data zone 34. Upper and lower
adjuster screws 102, 104 allow adjustment with a precision of
one-half mil (the dial indicator resolution), while the data zone
radial tolerance is within .+-.0.003 inch.
EXPERIMENTAL
42. Standard production quality disk substrates were plated with an
Ni--P layer to a standard thickness. The Ni--P layer was zone
textured in two operations: first, a contact start stop zone, and
second, a data zone. All texturing was performed on modified
EDC.RTM. 800HDF texturing machines.
43. The contact start stop zone was textured using the stepped
roller described above. The disk was textured to create a contact
start stop zone at an inner radial position. The final recording
surface roughness of the contact start stop zone, after deposition
of all layers, ranged between 45 .ANG. and 65 .ANG..
44. The data zone was textured using a slurry laden abrasive tape
which was offset from the center of the disk to an outer radial
position. The tape was held in position during texturing by the
tape guide described above, and oscillations were adjusted using
the adjustable cam and follower mechanism. The final recording
surface roughness of the data zone, after deposition of all layers,
was in the range between 20 .ANG. and 40 .ANG..
45. The disks were then sputtered with a conventional magnetic
recording media layer structure. The recording surface of the disks
provided a visible demarkation between the contact start stop zone
and the data zone. Surface roughness measurements were performed
using a Tencor Instruments.RTM. P-2 with a standard head and a 0.2
micrometer stylus. Two hundred micrometer scans were performed at
maximum resolution with a 25 micrometer cut-off filter.
46. The glide performance of the disks was tested by measuring the
hit voltage with the head at a glide height of 1.mu.. The hit
voltage was found to vary with the surface roughness, as shown in
FIG. 7. The lower range of surface roughnesses can be seen to have
lower hit voltages, and are therefore better suited to lower glide
heights.
47. The media noise of the disks, specifically the bit-shift, was
also measured as a function of surface roughness. Noise increases
as roughness increases, particularly in the range from 25 .ANG. to
35 .ANG., as seen in FIG. 8. Certification errors encountered at a
given track were also plotted against surface roughness for a range
of certification threshold percentages (see FIG. 9). Both of these
plots indicate that magnetic data recording characteristics benefit
from lower surface roughnesses.
48. FIG. 10 is a plot of the maximum friction between the disk and
the head across the range of surface roughness. Friction can be
seen to increase significantly for surface roughnesses below 40
.ANG.. Surface roughnesses greater than this value are thus
preferred where the disk and head will be in sliding contact.
49. The slope of the transition zone varied with the relative
amounts of Ni--P stock removed during the texturing processes. FIG.
11 is a plot of the incidence of head crash against the transition
slope angle. Head crash rate was also found to vary with the
surface roughness, the crash rate increasing significantly for
roughnesses of over 55 .ANG., as seen in FIG. 12.
50. Although the foregoing invention has been described in some
detail by way of illustration and example, for purposes of clarity
and understanding, certain modifications will be obvious to those
of skill in the art. For example, a physical, mechanical, or
chemical mask may cover one zone (either the contact start stop
zone or data zone) while the other is being textured. It should be
noted that the entire zone need not be masked, rather, only the
regions closest to the transition region. A physical mask might
comprise a special spindle chuck system which hides either a
contact start stop or data zone on the disk surface. Alternatively,
a mechanical mask might comprise an edge surface which limited the
roller or tape motion as it approached the transition zone region.
One must be careful to avoid inhibiting the motion to such a degree
that the overall texturing pattern is affected. A chemical mask
comprises a protective layer at a given zone position which is worn
away during texturing, but which protects the disk's surface
underneath. Additional process steps are required both for adding a
protective coating, and for removal of excess material after
texturing. Such modifications may be practiced within the scope of
the present invention, which is limited solely by the appended
claims.
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