U.S. patent application number 10/615293 was filed with the patent office on 2004-06-03 for master information carrier for magnetic transfer.
This patent application is currently assigned to FUJI PHOTO FILM CO., LTD.. Invention is credited to Komatsu, Kazunori, Usa, Toshihiro.
Application Number | 20040106013 10/615293 |
Document ID | / |
Family ID | 32375676 |
Filed Date | 2004-06-03 |
United States Patent
Application |
20040106013 |
Kind Code |
A1 |
Komatsu, Kazunori ; et
al. |
June 3, 2004 |
Master information carrier for magnetic transfer
Abstract
A master information carrier has a pattern of a magnetic layer
representing information to be transferred to a high-density
recording slave medium where the track width is not larger than 0.3
.mu.m. The pattern is drawn by scanning a given track a plurality
of times with an electron beam whose drawing diameter is smaller
than the track width.
Inventors: |
Komatsu, Kazunori;
(Odawara-shi, JP) ; Usa, Toshihiro; (Odawara-shi,
JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
FUJI PHOTO FILM CO., LTD.
|
Family ID: |
32375676 |
Appl. No.: |
10/615293 |
Filed: |
July 9, 2003 |
Current U.S.
Class: |
428/826 ;
G9B/5.293; G9B/5.309 |
Current CPC
Class: |
G11B 5/65 20130101; Y10S
425/81 20130101; G11B 5/865 20130101; B82Y 10/00 20130101; G11B
5/82 20130101; G11B 5/743 20130101 |
Class at
Publication: |
428/694.0TR ;
428/694.00R |
International
Class: |
G11B 005/66 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 11, 2002 |
JP |
202629/2002 |
Claims
What is claimed is;
1. A master information carrier having thereon a pattern of a
magnetic layer representing information to be transferred to a
high-density recording slave medium where the track width is not
larger than 0.3 .mu.m, wherein the improvement comprises that the
pattern is drawn by scanning a given track a plurality of times
with an electron beam whose drawing diameter is smaller than the
track width.
2. A master information carrier as defined in claim 1 in which,
when it is assumed that W represents the track width, n represents
the number of times by which one track is scanned by the electron
beam, d represents the drawing diameter of the electron beam and k
represents a coefficient representing the degree of overlap,
W=[n-(n-1)k].times.d, and the value of k is in the range of not
smaller than 0 and not larger than 0.8.
3. A master information carrier as defined in claim 2 in which the
value of k is in the range of not smaller than 0.2 and not larger
than 0.8.
4. A master information carrier as defined in claim 1 in which the
master information carrier is produced by drawing a pattern by
scanning each track a plurality of times with an electron beam
whose drawing diameter is smaller than the track width and which is
modulated according to the information to be transferred while
rotating a disc coated with photoresist, making a substrate having
an irregularity pattern by mastering on the basis of the pattern
drawn by the electron beam, and forming a magnetic layer on the
substrate.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a master information carrier for
magnetic transfer carrying thereon information to be transferred to
a slave medium.
[0003] 2. Description of the Related Art
[0004] As a method of recording information on a magnetic recording
medium, magnetic transfer has been used. In the magnetic transfer,
the surface of a master information carrier having thereon an
irregularity pattern (a pattern of protruding portions and recessed
portions) of magnetic material representing information to be
transferred is brought into close contact with a surface of a slave
medium (a magnetic recording medium) having a magnetic layer and a
transfer magnetic field is applied to the slave medium and the
master information carrier in this state, thereby recording on the
slave medium a magnetization pattern representing the information
(e.g., a servo signal) on the master information carrier. See, for
instance, Japanese Unexamined Patent Publication No.
63(1988)-183623 and U.S. Pat. Nos. 6,347,016 and 6,567,227.
[0005] The master information carrier generally comprises a
substrate of, for instance, silicon or glass and an irregularity
pattern of magnetic material formed on the substrate by
photolithography, sputtering, etching or the like.
[0006] Further, the master information carrier may be produced by
the use of lithography technology which has been used in producing
semiconductors, stamper producing technology which has been used in
producing optical disc stampers, or the like.
[0007] In order to improve the quality of the signal transferred by
the magnetic transfer, it is necessary to accurately form a pattern
of a magnetic layer on the master information carrier. It has been
found that the shape of the protruding portions of the pattern
varies according to the system for drawing the pattern and the
magnetic transfer characteristics of the master information carrier
are affected by the shape of the protruding portions of the
pattern.
[0008] For example, in the case where the slave medium is in the
form of a rotary magnetic recording disc, an irregularity pattern
representing a servo signal comprises protruding portions which are
of a square or a rectangle longer in the direction of width of the
recording tracks (in a radial direction of the recording disc). The
pattern is generally drawn by projecting a laser beam modulated
according to the information to be transferred onto a disc-like
substrate coated with photoresist while rotating the substrate.
[0009] However, as the track width is narrowed to not larger than
0.3 .mu.m, for instance, to meet a demand for a higher recording
density, the drawing diameter of a laser beam (the diameter at
which a laser beam draws an image on the substrate) comes not to be
able to be thinned to draw a pattern of protruding portions in such
a narrow tracks. As a result, the protruding portions come to have
arcuate end portions and cannot be rectangular in shape. Arcuate
end portions of the protruding portions cause a recording loss
(azimuth loss) in the transfer magnetic field applied to the master
information carrier and the slave medium which are held in close
contact with each other, which results in imperfect formation of a
magnetization pattern on the slave medium, whereby the signal
transferred to the slave medium becomes unsharp.
SUMMARY OF THE INVENTION
[0010] In view of the foregoing observations and description, the
primary object of the present invention is to provide a master
information carrier which can suppress recording loss and provide a
high-quality transferred signal even if the track width is
narrowed.
[0011] In accordance with the present invention, there is provided
a master information carrier having thereon a pattern of a magnetic
layer representing information to be transferred to a high-density
recording slave medium where the track width is not larger than 0.3
.mu.m, wherein the improvement comprises that the pattern is drawn
by scanning a given track a plurality of times with an electron
beam whose drawing diameter is smaller than the track width.
[0012] When W represents the track width, n represents the number
of times by which one track is scanned by the electron beam, d
represents the drawing diameter of the electron beam and k
represents a coefficient representing the degree of overlap,
W=[n-(n-1)k].times.d. At this time, the value of k should be in the
range of not smaller than 0 and not larger than 0.8 and is
preferably in the range of not smaller than 0.2 and not larger than
0.8. The value of n should be not smaller than 2, and as the value
of n increases and as the value of d decreases, the shape of the
protruding portions approximates a rectangle though the drawing
time is elongated.
[0013] It is preferred that the master information carrier be
produced by drawing a pattern by scanning each track a plurality of
times with an electron beam whose drawing diameter is smaller than
the track width and which is modulated according to the information
to be transferred while rotating a disc coated with photoresist,
making a substrate having an irregularity pattern by mastering on
the basis of the pattern drawn by the electron beam, and forming a
magnetic layer on the substrate.
[0014] In accordance with the master information carrier of the
present invention, each protruding portion of the irregularity
pattern has end portions which is substantially straight and not
arcuate and the fine pattern can be accurately formed, whereby the
recording loss in the transfer magnetic field is reduced, and the
magnetization pattern transferred to the slave medium becomes
sharp, which results in a high quality transferred signal.
BREIF DESCRIPTION OF THE DRAWINGS
[0015] FIGS. 1A to 1C are views for illustrating the basic steps of
magnetic transfer,
[0016] FIGS. 2A and 2B are views respectively illustrating ways of
drawing the protruding portions in a master information carrier in
accordance with embodiments of the present invention,
[0017] FIGS. 3A to 3D are cross-sectional views illustrating an
example of steps of producing the master information carrier,
and
[0018] FIGS. 4A and 4B are views respectively illustrating ways of
drawing the protruding portions in a master information carrier in
accordance with other embodiments of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0019] Basic steps of magnetic transfer to an in-plane magnetic
recording medium will be described with reference to FIGS. 1A to
1C, hereinbelow.
[0020] An initial magnetostatic field Hin is first applied to the
slave medium 2 in one direction parallel to the recording tracks
thereof, thereby magnetizing the slave medium 2 in an initial
magnetization (DC erasure) as shown in FIG. 1A. Thereafter, the
magnetic layer 32 on the upper surface of the protruding portions
of the irregularity pattern on the surface of the substrate 31 of
the master information carrier 3 is brought into a close contact
with the recording surface of the slave medium 2. In this state, a
transfer magnetic field Hdu is applied in the direction opposite to
the initial magnetic field Hin as shown in FIG. 1B, thereby
magnetically transferring the information on the master information
carrier 3 to the slave medium 2. Since the transfer magnetic field
Hdu is absorbed in the magnetic layer 32 on the upper surface of
the protruding portions of the irregularity pattern on the surface
of the substrate 31 and accordingly, the magnetic field is not
reversed at portions opposed to the protruding portions and is
reversed at portions not opposed to the protruding portions. As a
result, magnetization pattern corresponding to the irregularity
pattern on the master information carrier 3 is transferred to the
tracks of the slave medium 2 as shown in FIG. 1C.
[0021] The master information carrier 3 is generally disc-shaped
and has an irregularity pattern of a magnetic layer 32 representing
information such as a servo signal on one side thereof. The master
information carrier 3 is brought into a close contact with the
slave medium 2 with the other side thereof held by a holder (not
shown). Sometimes a pair of master information carriers are
simultaneously brought into a close contact with the opposite sides
of the slave medium 2 to transfer information to the opposite sides
of the slave medium 2 at one time, and sometimes, a master
information carrier is brought into a close contact with one side
of the slave medium and then another master information carrier is
subsequently brought into a close contact with the other side of
the slave medium to transfer information to the opposite sides of
the slave medium in sequence.
[0022] As shown in FIGS. 2A and 2B, protruding portions 32a of the
master information carrier 3 are formed on the basis drawings by an
electron beam EB. The track width W is not larger than
0.3.quadrature.m and the drawings are made by scanning a given
track a plurality of times with an electron beam EB whose drawing
diameter is not larger than the track width W. For example, the
drawings may be made by scanning a given track five times with an
electron beam EB whose drawing diameter is relatively small as
shown in FIG. 2A, and the drawings may be made by scanning a given
track twice with an electron beam EB whose drawing diameter is
relatively large as shown in FIG. 2B.
[0023] When W represents the track width, n represents the number
of times by which one track is scanned by the electron beam, d
represents the drawing diameter of the electron beam and k
represents a coefficient representing the degree of overlap,
W=[n-(n-1)k].times.d. At this time, the value of k should be in the
range of not smaller than 0 and not larger than 0.8 and is
preferably in the range of not smaller than 0.2 and not larger than
0.8. As the degree of overlap increases, the value of the
coefficient k increases. The value of n should be not smaller than
2, and as the value of n increases, as the value of d decreases,
and as the value of k increases, the shape of the protruding
portions approximates a rectangle though the drawing time is
elongated.
[0024] The roundness of the corners of each protruding portion 32a
is governed by the drawing diameter d of the electron beam.
Further, the areas of the end faces (the leading end face and the
trailing end face as seen in the direction of the tracks) of each
protruding portion 32a are governed by the drawing diameter d of
the electron beam, the value of n and the value of the coefficient
k, and in order to reduce the recording loss, to reduce the drawing
diameter d, to increase the value of n and to increase the value of
the coefficient k are effective. Taking into account these points,
it is preferred to set the value of n as small as possible in order
to improve the drawing efficiency.
[0025] Though not shown, the actual servo signal includes also
protruding portions which are positioned shifted from the tracks by
a half track pitch. Such shifted protruding portions are also drawn
in the same manner.
[0026] In the case where the irregularity pattern representing
information to be transferred is a negative pattern reverse to the
positive pattern shown in FIGS. 1A to 1C, the information can be
magnetically transferred to the slave medium 2 by reversing the
directions of the initial DC magnetic field Hin and the transfer
magnetic field Hdu. It is preferred that a protective film such as
of DLC (diamond-like carbon) be provided on the magnetic layer 32.
A lubricant layer may be further provided. It is further preferred
that a DLC film 5 to 30 nm thick and a lubricant layer exist. A
reinforcement layer such as a Si layer may be provided between the
magnetic layer 32 and the protective film to enhance the contact
therebetween. The lubricant layer suppresses deterioration in
durability of the magnetic layer 32 such as scratches due to
friction, which occurs in correcting for a shift generated when the
magnetic layer 32 is brought into contact with the slave medium
2.
[0027] The substrate 31 of the master information carrier 3 may be
formed, for instance, of, nickel, silicon, glass, quartz, aluminum,
alloy ceramics, synthetic resin or the like. The irregularity
pattern or the pattern of the protruding portions can be formed,
for instance, by the use of stamper method.
[0028] An example of production of the substrate 31 of the master
information carrier will be described with reference to FIGS. 3A to
3D, hereinbelow.
[0029] As shown in FIG. 3A, a photoresist solution is applied to a
disc 10 of glass or quartz having a smooth surface by spin coating,
thereby forming a photoresist layer 11. Thereafter, an electron
beam EB modulated according to the information to be transferred
such as a servo signal is caused to scan the disc 10 with the
photoresist layer 11, while rotating the disc 10, to expose the
photoresist 11 along the tracks in a predetermined pattern. The
electron beam EB is converged to a drawing diameter d not larger
than the track width W by a known electron gun 15. When the
scanning times n is 5 (n=5), the position where the electron beam
EB impinges upon the photoresist layer 11 is slightly shifted each
time the disc 10 makes one rotation so that the protruding portions
on one track are drawn in five rotations of the disc 10.
[0030] Then, as shown in FIG. 3B, the photoresist 11 is developed
and is removed from the areas exposed to the electron beam EB,
whereby an original 12 is obtained.
[0031] Then a thin conductive layer is formed on the surface of the
original 12 and electroforming is applied to the thin conductive
layer (mastering), whereby a metal substrate 31 having a positive
irregularity pattern following the original 12 is obtained as shown
in FIG. 3C. Thereafter, the metal substrate 31 in a predetermined
thickness is peeled off the original as shown in FIG. 3D.
[0032] The irregularity pattern on the metal substrate 31 is
reverse to the irregularity pattern on the original 12. After the
back side of the metal substrate 31 is polished, and the metal
substrate 31 is provided with a magnetic layer 32 on the surface of
irregularity pattern, the metal substrate 31 may be used as a
master information carrier 3.
[0033] Otherwise, the original may be plated to form a second
original and the second original may be plated to form a metal disc
having a negative irregularity pattern. Further, a third original
may be formed by plating the second original or pressing a resin
syrup against the surface of the second original and curing the
resin syrup, and a metal disc having a positive irregularity
pattern may be formed by plating the third original.
[0034] Whereas, an original may be obtained by etching the disc 10
after the disc 10 is provided with a photoresist pattern to form
holes through the disc 10 and removing the photoresist 11 after
etching. Thereafter, a metal substrate 31 can be obtained from the
original in the same manner as described above.
[0035] The metal substrate 31 may be formed of Ni or Ni alloys. The
metal substrate 31 may be formed by various metal film forming
techniques including electroless plating, electroforming,
sputtering, and ion plating. The depth of the irregularity pattern
(the height of the protrusions) of the metal substrate 31 is
preferably 80 nm to 800 nm, and more preferably 100 nm to 600
nm.
[0036] The magnetic layer 32 is formed by forming film of a
magnetic material by, for instance, vacuum film forming techniques
such as sputtering or ion plating or plating. As the magnetic
material, Co, Co alloys (e.g., CoNi, CoNiZr, or CoNbTaZr), Fe, Fe
alloys (e.g., FeCo, FeCoNi, FeNiMo, FeAlSi, FeAl, or FeTaN), Ni or
Ni alloys (e.g., NiFe) can be employed. FeCo and FeCoNi are
especially preferred. The thickness of the magnetic layer 32 is
preferably 50 nm to 500 nm, and more preferably 100 nm to 400
nm.
[0037] A master information carrier may be formed by forming a
resin substrate by the use of the original produced in the manner
described above and providing a magnetic layer on the surface of
the resin substrate. As the material of the resin substrate,
acrylic resins such as polycarbonate or polymethyl methacrylate,
vinyl chloride resins such as polyvinyl chloride, or vinyl chloride
copolymer, epoxy resins, amorphous polyolefins, polyesters or the
like may be used. Among those, polycarbonate is preferred in view
of the humidity resistance, dimensional stability, cost and/or the
like. Flash on the product should be removed by varnishing or
polishing. Otherwise, ultraviolet curing resin or electron beam
curing resin may be coated on the original, for instance, by spin
coating or bar coating. The height of the protrusion on the resin
substrate is preferably 50 to 1000 nm and more preferably 100 to
500 nm. A magnetic layer is provided over the fine pattern on the
surface of the resin substrate, thereby obtaining a master
information carrier. The magnetic layer is formed by forming film
of a magnetic material by, for instance, vacuum film forming
techniques such as sputtering or ion plating or plating.
[0038] In the case of perpendicular recording, a master information
carrier 3 substantially the same as that employed in in-plane
recording is employed. In the case of perpendicular recording, the
magnetic layer of the slave medium 2 is magnetized in advance in a
perpendicular direction and a transfer magnetic field is applied to
the slave medium 2 and the master information carrier 3 in close
contact with each other in the direction substantially opposite to
the initial magnetic field, whereby the transfer magnetic field is
absorbed in the magnetic layer 32 on the upper surface of the
protruding portions 32a of the irregularity pattern on the surface
of the substrate 31 and accordingly, the magnetic field is not
reversed at portions opposed to the protruding portions 32a and is
reversed at portions not opposed to the protruding portions 32a. As
a result, magnetization pattern corresponding to the irregularity
pattern on the master information carrier 3 is transferred to the
tracks of the slave medium 2.
[0039] A magnetic recording disc such as a hard disc or a
high-density flexible disc provided with a magnetic layer on one
side or each side thereof is generally employed as the slave medium
2. The magnetic layer thereof is generally of a coated magnetic
material or a metal film. In the case of a slave medium having a
magnetic layer of metal film, the material of the magnetic layer
may be Co, Co alloy (e.g., CoPtCr, CoCr, CoPtCrTa, CoPtCrNbTa,
CoCrB, CoNi, Co/Pd), Fe or Fe alloy (e.g., FeCo, FePt, FeCoNi).
These materials are preferred in view of obtaining clearer magnetic
transfer since the magnetic layer of these materials is higher in
magnetic flux density and has a magnetic anisotropy in the same
direction in which the magnetic field is applied (the in-plane
direction in the case of the in-plane recording and the
perpendicular direction in the case of the perpendicular
recording). It is further preferred that the magnetic layer of the
slave medium 2 be provided with a non-magnetic primer layer in
order to give the magnetic layer a necessary magnetic anisotropy.
The primer layer should match to the magnetic layer in
crystallographic structure and lattice constant. For this purpose,
Cr, CrTi, CoCr, CrTa, CrMo, NiAl, Ru or the like may be employed as
the non-magnetic primer layer.
[0040] The magnetic field generation means for applying the initial
magnetic field and the transfer magnetic field comprises a pair of
ring type electromagnets each disposed on one side of the slave
medium 2 and the master information carrier 3 in a close contact
with each other. Each of the electromagnets comprises a core having
a gap extending in a radial direction of the slave medium 2 and a
winding wound around the core. In the case of the in-plane
recording, the ring type electromagnets on opposite sides of the
slave medium 2 and the master information carrier 3 in a close
contact with each other applies magnetic fields in the same
direction in parallel to the tracks. The magnetic field generation
means applies a magnetic field to the slave medium 2 and the master
information carrier 3 while rotating the slave medium 2 and the
master information carrier 3 held in a close contact with each
other. Instead of rotating the slave medium 2 and the master
information carrier 3, the magnetic field generation means may be
rotated. A ring type electromagnet may be disposed on one side of
the slave medium 2 and the master information carrier 3 or on each
side of the same. A permanent magnet may be employed in place of
the electromagnets.
[0041] In the case of the perpendicular recording, a pair of
electromagnets or a permanent magnets different in polarity are
disposed on opposite sides of the slave medium 2 and the master
information carrier 3 held in a close contact with each other and a
magnetic field is generated in perpendicular to the tracks. When
the magnetic field generation means is of a type which applies a
magnetic field only a part of the slave medium 2 and the master
information carrier 3, the slave medium 2 and the master
information carrier 3 held in a close contact with each other and
the magnetic field are moved with respect to each other so that a
magnetic field is applied to the slave medium 2 and the master
information carrier 3 over the entire area thereof.
[0042] In accordance with the master information carrier 3 of this
embodiment, each protruding portion 32a of the irregularity pattern
has end portions which is substantially straight and not arcuate
and the fine pattern can be accurately formed even if the track
width W is narrowed to not larger than 0.3 .mu.m since the
protruding portion 32a is drawn in a plurality of times by an
electron beam EB whose drawing diameter d is smaller than the track
width W, whereby the recording loss in the transfer magnetic field
is reduced, and the magnetization pattern transferred to the slave
medium becomes sharp, which results in a high quality transferred
signal.
[0043] FIGS. 4A and 4B are views respectively illustrating ways of
drawing the protruding portions in a master information carrier in
accordance with other embodiments of the present invention. Though,
in the embodiments shown in FIGS. 2A and 2B, the electron beam EB
is moved in a direction parallel to the recording tracks, the
electron beam EB is moved in a direction parallel to the direction
of width of the recording tracks (a radial direction of the slave
medium 2) in the embodiments shown in FIGS. 4A and 4B.
[0044] In the embodiment shown in FIG. 4A, the protruding portion
32a is drawn in a direction parallel to the direction of width W of
the recording tracks in a plurality of times by an electron beam EB
whose drawing diameter d is smaller than the track width W, and the
electron beam EB is moved in the same direction in all the scans.
Whereas, in the embodiment shown in FIG. 4B, the protruding portion
32a is drawn in a direction parallel to the direction of width W of
the recording tracks in a plurality of times by an electron beam EB
whose drawing diameter d is smaller than the track width W, and the
electron beam EB is alternately moved in the opposite
directions.
* * * * *