Method of manufacturing a recording medium

Details Method of manufacturing a recording medium Method of manufacturing a recording medium

2000-03-06

2001-10-09

Pianalto, Bernard (Department: 1762)

Coating processes

Direct application of electrical, magnetic, wave, or...

Polymerization of coating utilizing direct application of...

C427S130000, C427S131000, C427S132000, C427S385500, C427S407100, C427S535000, C427S558000, C427S559000

Reexamination Certificate

active

06299946

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method of manufacturing a recording medium. The present invention particularly relates to the method of manufacturing a magnetic recording medium for use in a magnetic recording and reproduction device serving as external storage device of computers.
2. Description of the Related Art
Recently, there is an increasing need for high-density recording in magnetic storage devices known as hard-disk device. In such a hard-disk device for high-density recording, it is necessary to reduce the magnetic spacing, which is a space formed between a magnetic head provided in the magnetic disk device and the surface of a magnetic disk serving as a recording medium in the main body of the hard-disk device, as much as possible. In other words, the gap between the magnetic head and the magnetic disk surface, scanned by the magnetic head, should be as small as possible. Recently, a spacing of about 50 nm or less is used.
FIG. 1
is a schematic diagram showing a magnetic disk device
100
including a magnetic head
20
and a rotating magnetic disk
10
of the related art.
FIG. 1
is illustrated in an enlarged view, so as to clearly show the layered structure of the magnetic disk
10
and a magnetic spacing S.
Referring to
FIG. 1
, the magnetic disk has a structure including a substrate
11
, an underlayer
13
formed on the substrate
11
, and a magnetic layer
15
formed on the underlayer
13
. A protection layer
17
of amorphous carbon is provided further on the magnetic layer
15
. Further, a lubrication layer
19
of a fluorocarbon compound is formed on the protection layer
17
.
As described above, in such a hard-disk device designed for high-density recording, there is a need to reduce the size of the magnetic spacing S as much as possible. On the other hand, such a reduction of the spacing S invites an increased chance that the magnetic head
20
hits the surface of the magnetic disk
10
during the operation of the hard-disk device
100
. In view of the situation noted above, it is preferable to smooth the surface of the magnetic disk
10
as much as possible. Further, technical improvement is required, such as a reduction in thickness of the magnetic disk
10
.
The magnetic disk device
100
described above generally operates in accordance with the so-called contact-start-stop (CSS) mode. With the CSS mode, a lift surface
20
a
of the magnetic head
20
contacts and slides over the surface of the magnetic disk
10
at the start or stop phase of rotation of the magnetic disk
10
. On the magnetic disk
10
, for the CSS-mode operation, it should be noted that friction and abrasion of the disk surface primarily depends on the nature of the protection layer
17
and the lubrication layer
19
. Thus, the protection layer
17
and the lubrication layer
19
are important for maintaining the reliability of the magnetic disk device
100
. Particularly, due to the recent trend of technology to reduce the spacing between the floating magnetic head and the magnetic layer
15
carrying a high-density record of information, there is a need for maintaining stable friction and abrasion properties for the lubrication layer
19
over a longer period of time.
FIGS. 2A
to
2
F are diagrams showing various steps of manufacturing the magnetic disk
10
according to the related art. Referring to
FIG. 2A
, a non-magnetic substrate
11
of a material such as Al plated with NiP is prepared. Next, in the step of
FIG. 2B
, very small irregularities, or textures, are formed on the non-magnetic substrate
11
. Next, in the step of
FIG. 2C
, a deposition process, such as a sputtering process is implemented, and an underlayer
13
of a Cr alloy, a magnetic layer
15
of a Co alloy, and a protection layer
17
of amorphous carbon are deposited consecutively on the substrate
11
. Then, in the step of
FIG. 2D
, a pre-heat treatment is applied to the structure obtained in the step of
FIG. 2C. A
lubrication layer
19
of fluorocarbon compound is uniformly applied to the surface of the protection layer
17
in
FIG. 2E
by dipping the structure of
FIG. 3D
into a solution of the fluorocarbon compound. After the lubrication layer
19
has been thus formed, a heating process or UV (ultraviolet beam) curing process is implemented in the step of
FIG. 2F
for curing the fluorocarbon lubrication layer
19
. As a result of the curing process of
FIG. 2F
, it should be noted that the proportion of the lubrication layer
19
bonded firmly to the surface of the protection layer
17
is increased. The part of the lubrication layer
19
bonded to the surface of the layer
17
is hereinafter referred to as a bonding layer part.
Meanwhile, when the surface of the magnetic disk
10
is entirely smooth and flat, there will be an increase in the contact area between the magnetic head
20
and the magnetic disk
10
. Thus, in order to prevent a part of lubrication layer from being taken away and transferred to the magnetic head
20
under the situation noted above, it is preferable to provide the lubrication layer
19
with a small thickness of about 1 to 2 nm.
As has been described above, there have been various efforts made on the lubrication layer
19
substantially serving as the surface of the magnetic disk
10
. Such efforts include reducing the thickness of the lubrication layer
19
and improving the bonding strength between the lubrication layer
19
and the protection layer
17
. In relation to increases in data transfer rates between a hard disk drive and the computer, and further in relation increases in the recording densities the rotational speed of the magnetic disk
10
is also increasing. Presently, a considerably high speed of about 7,200 to 10,000 rpm is used in the advanced high-density hard disk devices. It should be noted that such high rotational speed of the magnetic disk
10
results in an increased centrifugal force. Thus, there is a tendency, in the lubrication layer
19
of the related art, for the part of the layer
19
not bonded to the surface of the protection layer
17
to undergo spin off as a result of the large centrifugal force. The proportion of the unbonded part, or a so-called mobile layer part, of the lubrication layer
19
reaches as much as 50% to 70%. As a result of the spin-off of the mobile layer part
19
, the thickness of the lubrication layer
19
can be reduced to as small as only a few Ångstroms, while such an extreme thinning of the lubrication layer
19
is problematic in that a stable lubrication functions of the layer
19
cannot be guaranteed over a long period of time.
In view of the need for reducing the friction force of the magnetic head
20
against the above-described magnetic disk
10
in the CSS mode operation of the hard disk device, recent hard disk technology tends to use very small protrusions on the lift surface
20
a
of the magnetic head and/or on the CSS region (not shown) of the magnetic disk
10
. While such a structure may be useful for reducing the friction, there arises a in that the pressure between the magnetic disk surface and the magnetic head will increase in correspondence to the contacting part as compared with the structure where the lift surface
2
a
and/or the CSS region are/is flat. Therefore, with the lubrication layer
19
of the magnetic disk
10
of the related art, the lubrication layer
19
may break due to the contact and sliding of the magnetic head
20
. Accordingly, this poses a problem in that the protrusions may be worn down within a short period of time, thus causing an increased aberration.
In order to solve the problem described above, it is certainly possible to provide the lubrication layer
19
with an increased thickness. However, with the related art, the amount of the bonding layer part bonded to the protection layer
17
, by the heating or UV curing process (see FIG.
2
F), is not sufficient. In other words, there is still a considerable amount of mobile layer part included in the lubrication layer
17
. This mobil

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