Dynamic magnetic information storage or retrieval – Record copying
Reexamination Certificate
2001-06-13
2004-04-13
Farber, Alan T. (Department: 2651)
Dynamic magnetic information storage or retrieval
Record copying
C360S077030, C360S078110
Reexamination Certificate
active
06721113
ABSTRACT:
This application is based on Patent Application No. 2000-177506 filed Jun. 13, 2000 in Japan, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of writing a data write/read head positioning servo signal written to the magnetic recording disk by the magnetic transfer technology in the hard disk drive (HDD) using as a recording material a magnetic film which is normally used as a mainstream of an external storage device of a computer, and more specifically to a method of recognizing a master disk positioning mark.
2. Description of the Prior Art
It is well known that a hard disk drive device records and reads data while a magnetic head is floating while keeping interval of several tens nano-meter on the revolving magnetic recording disk using a floating mechanism referred to as a slider. The bit information on the magnetic disk is stored on the data track concentrically provided on the disk, and the data record/read head records and reproduces data on the target data track on the disk surface by quickly moving and positioning the head.
On the magnetic recording disk surface, a positioning signal (servo signal) for detection of the relative position between the head and the data track is concentrically written, and the head for recording and reproducing data detects the position of itself at predetermined time intervals. After incorporating the recording disk into the HDD device, the servo signal is written using a dedicated device referred to as a servo track writer so that the center of the servo write signal cannot be deviated from the center of the disk (or the center of the orbit of the head).
Currently, the recording disk has the recording density of about 20 Gbits/in
2
at the development stage, and the recording capacity increases at the rate of 60% annually. With the above mentioned progress, the density of a servo signal for detection of the position of the head itself also increases, and the writing time of a servo signal has been increased year by year. An increasing writing time of the servo signal is a main factor of reducing the productivity of the HDD, thereby increasing the entire cost.
Recently, to replace the system of writing the servo signal using the signal write head of the above mentioned servo track writer, the technology has been developed to collectively write servo signals by a magnetic transfer, and thereby remarkably shorten the servo information writing time.
FIGS. 7A
,
7
B,
7
C,
8
A and
8
B illustrate the magnetic transfer technology.
FIG. 7A
shows the process of moving a permanent magnet on the surface of a magnetic recording disk
3
while keeping a predetermined interval (1 mm or shorter). The arrow recorded on the magnetic layer shown in
FIG. 7A
shows a moving path of the permanent magnet, and the magnetic layer is evenly magnetized radiantly. This process is referred to as an initial demagnetizing process.
FIG. 7B
shows the process of aligning a magnetic transfer master disk
7
(hereinafter referred to as a master disk) by setting it on the magnetic recording disk
3
.
FIG. 7C
shows the magnetic transfer process performed by setting the master disk
7
as choereing the surface of the magnetic recording disk
3
and moving the magnetic transfer permanent magnet along the moving path (indicated by the arrow shown in FIG.
7
C).
FIG. 8A
shows the initial demagnetizing process. The process of a permanent magnet
42
of a head
41
moving on the surface of a magnetic recording disk
3
while keeping a predetermined interval (1 mm or shorter) is shown from the sectional portion of a substrate
31
. A magnetic layer
32
filmed on the substrate
31
is not initially magnetized in a predetermined direction, but can be magnetized in a predetermined direction by a magnetic field leaking from the gap of the permanent magnet
42
.
FIG. 8B
shows a transfer pattern writing process for performing a magnetic transfer. As shown in
FIG. 8B
, the master disk
7
has the structure of a soft magnetic film
8
(Co type soft magnetic film in
FIG. 8B
) embedded into the surface of a silicon substrate
71
touching the surface of a medium. As shown in
FIG. 8B
, if there is the substrate
71
embedded a pattern of the soft magnetic film
8
between the permanent magnet
42
of the head
41
and the magnetic recording disk
3
, the magnetic field (the direction of the transfer signal write magnetic field is opposite the direction of the demagnetized field) leaking from the permanent magnet
42
and passing through the silicon substrate
71
can pass through the silicon substrate
71
again and magnetize the magnetic layer
32
of the magnetic recording disk
3
at the point where there is no soft magnetic film
8
, but it passes through the soft magnetic film
8
at the point where there is a soft magnetic pattern
8
such that a magnetic path can be formed with smaller magnetic resistance. Therefore, at the point where there is the soft magnetic film
8
, the magnetic field leaking from the silicon substrate
71
is small, and no magnetic write is newly made. With the above mentioned mechanism, a magnetic transfer of a servo signal is performed.
To perform such above mentioned magnetic transfer, it is necessary for the center of the servo pattern (soft magnetic pattern embedded into the surface of the master disk) embedded into the master disk
7
to match the center of the magnetic medium
3
(magnetic recording disk). To make these centers match each other, it is necessary to determine the positions of the center of the magnetic medium
3
and the center of the servo pattern on the master disk
7
respectively. The method of confirming the central position of the magnetic medium
3
can be realized by revolving the medium held by a chuck with a laser light illuminated on the outer edge of the medium, and determining the amount of deviation of the center of the chuck from the center of the medium based on the variation of the reflected light from the outer edge.
FIG. 9
illustrates the method of recognizing the position of the center of the soft magnetic pattern
8
on the master disk
7
by the conventional technology. The master disk
7
is moved closer to the magnetic recording disk
3
held by a chuck
4
, the position of the master disk
7
is recognized using a positioning mark
9
(a circular pattern (200-300 &mgr;m&phgr;) having a simple plane form, a cross pattern, etc. (200-300 &mgr;m square)) provided at the center of the master disk
7
immediately before the magnetic medium
3
touches the master disk
7
, and the position of the master disk
7
is adjusted such that the center of the magnetic medium
3
can match the center of the master disk
7
, thereby setting the magnetic medium
3
closely touching the master disk
7
.
Practically, as shown in
FIG. 9
, a small incandescent lamp
1
(for example, a halogen lamp) irradiates the vicinity of the positioning mark
9
from behind the chuck
4
, a CCD camera
2
receives the reflected light from the positioning mark
9
, and an obtained electric signal is processed into an image, thereby recognizing the position of the master disk
7
.
The chuck
4
has a hollow structure, and the magnetic medium
3
is donut-shaped with an open hole at the center. Therefore, the light from behind the magnetic medium
3
can easily and directly reach the surface of the master disk
7
. Inside the portion indicated by numeral
10
of the chuck
4
is hollow. Since the material (Co type alloy) of the positioning mark
9
and the material (single crystal silicon) of the substrate have different reflectance, the position of the positioning mark
9
can be easily recognized.
FIGS. 10A
to
10
D are sectional views of the process for forming the soft magnetic embedding patterns
8
and
9
into the surface of the silicon substrate
71
of the master disk
7
. Described below is each of the processes.
FIG. 10A
shows the process of applying up to 1 &mgr;m of photo resist
19
onto the silicon substrate
71
,
Matsuda Nobuhide
Saito Akira
Farber Alan T.
Matsushita Electric - Industrial Co., Ltd.
Sartori Michael A.
Venable LLP
Vivarelli Daniel G.
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