U.S. patent application number 10/008749 was filed with the patent office on 2003-02-06 for method of surface treatment for recording medium.
This patent application is currently assigned to FUJITSU LIMITED. Invention is credited to Itai, Yuichiro, Kasamatsu, Yoshiharu, Katayama, Masaki.
Application Number | 20030026918 10/008749 |
Document ID | / |
Family ID | 19032520 |
Filed Date | 2003-02-06 |
United States Patent
Application |
20030026918 |
Kind Code |
A1 |
Itai, Yuichiro ; et
al. |
February 6, 2003 |
METHOD OF SURFACE TREATMENT FOR RECORDING MEDIUM
Abstract
Ultraviolet rays are radiated over a lubricant film formed on
the surface of a recording medium such as a hard disk. The
recording medium is then subjected to exposure to bases. The
radiation of the ultraviolet rays allows the lubricant film to
uniformly spread over the surface of the recording medium. The
repellency can be enhanced over the surface of the recording
medium. The friction can be reduced on the recording medium.
Moreover, when the recording medium is exposed to the base, organic
acid existing on the surface of the recording medium and/or in the
lubricant film can be transformed into salt. The organic acid can
be washed off or removed from the surface of the recording medium
and/or out of the lubricant film in this manner. Less organic acid
greatly contributes to prevention of generation of corrosion mounds
on the recording medium over a longer period.
Inventors: |
Itai, Yuichiro; (Kawasaki,
JP) ; Katayama, Masaki; (Kawasaki, JP) ;
Kasamatsu, Yoshiharu; (Kawasaki, JP) |
Correspondence
Address: |
Patrick G. Burns, Esq.
GREER, BURNS & CRAIN, LTD.
Suite 2500
300 South Wacker Dr.
Chicago
IL
60606
US
|
Assignee: |
FUJITSU LIMITED
|
Family ID: |
19032520 |
Appl. No.: |
10/008749 |
Filed: |
December 6, 2001 |
Current U.S.
Class: |
427/558 ;
427/337; G9B/5.3 |
Current CPC
Class: |
G11B 5/8408
20130101 |
Class at
Publication: |
427/558 ;
427/337 |
International
Class: |
B05D 003/06; B05D
003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 27, 2001 |
JP |
2001-194373 |
Claims
What is claimed is:
1. A method of surface treatment for a recording medium,
comprising: radiating an ultraviolet ray over a lubricant film
formed on the surface of the recording medium; and subjecting the
recording medium to exposure to a base after radiation of the
ultraviolet ray.
2. The method of surface treatment according to claim 1, wherein
said base is a weak base.
3. The method of surface treatment according to claim 1, wherein
said base is an amine compound.
4. The method of surface treatment according to claim 1, wherein
said base is an aliphatic amine compound.
5. The method of surface treatment according to claim 1, wherein
said recording medium is dipped into a solution including the
base.
6. The method of surface treatment according to claim 5, wherein a
solvent of the solution is a hydrofluoroether compound.
7. The method of surface treatment according to claim 1, wherein
said lubricant film comprises a perfluoroether compound.
8. The method of surface treatment according to claim 1, wherein
said ultraviolet ray has a wavelength equal to or smaller than 200
nm.
9. A method of surface treatment for a recording medium,
comprising: forming a lubricant film over the surface of the
recording medium; and subjecting the recording medium to exposure
to a base.
10. The method of surface treatment according to claim 9, wherein
said base is a weak base.
11. The method of surface treatment according to claim 9, wherein
said base is an amine compound.
12. The method of surface treatment according to claim 9, wherein
said base is an aliphatic amine compound.
13. The method of surface treatment according to claim 9, wherein
said recording medium is dipped into a solution including the
base.
14. The method of surface treatment according to claim 13, wherein
a solvent of the solution is a hydrofluoroether compound.
15. The method of surface treatment according to claim 9, wherein
said lubricant film comprises a perfluoroether compound.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a recording medium such as
a magnetic recording disk incorporated into a hard disk drive
(HDD), for example. In particular, the invention relates to a
method of surface treatment for forming a lubricant film over the
surface of the recording medium.
[0003] 2. Description of the Prior Art
[0004] More or less organic acid such as oxalic acid and acetic
acid exists over a diamond-like-carbon (DLC) surface layer of the
magnetic disk as well as within a lubricant film formed to spread
over the surface of the magnetic recording disk. The organic acid
tends to get dissolved into water or moisture on the surface of the
magnetic recording disk. The dissolved organic acid often induces
corrosion or rust of the magnetic recording disk. The corrosion
results in mounds on the surface of the magnetic recording
disk.
[0005] For example, the lubricant film is subjected to exposure to
ultraviolet rays in the process of production of the recording
medium. Radiation of the ultraviolet rays serves to uniformly
spread the lubricant film over the surface of the magnetic
recording disk. In addition, the magnetic recording disk is allowed
to obtain a higher repellency over the surface thereof. The
magnetic recording disk may suffer from less friction. On the other
hand, the radiation of the ultraviolet rays serves to generate
organic acid of a quite amount over the surface of the magnetic
recording disk as well as in the lubricant film. Corrosion of the
magnetic recording disk may be promoted.
[0006] A hard disk drive is supposed to require a smaller flying
height of a flying head slider so as to realize the magnetic
recordation of a still higher density. As the flying height gets
smaller, the head slider suffers from a higher probability of
colliding against corrosion mounds on the magnetic recording disk
during rotation of the magnetic recording disk. The collision of
the head slider against the corrosion mound may induce damages of
the head slider and/or a read/write element on the head slider.
SUMMARY OF THE INVENTION
[0007] It is accordingly an object of the present invention to
provide a method of surface treatment for a recording medium, which
is capable of preventing generation of corrosion mounds on the
recording medium.
[0008] According to a first aspect of the present invention, there
is provided a method of surface treatment for a recording medium,
comprising: radiating an ultraviolet ray over a lubricant film
formed on the surface of the recording medium; and subjecting the
recording medium to exposure to a base after radiation of the
ultraviolet ray.
[0009] In general, when the ultraviolet ray is radiated over the
lubricant film on the recording medium, the lubricant film is
allowed to uniformly spread over the surface of the recording
medium. At the same time, the repellency can be enhanced over the
surface of the recording medium. The friction can be reduced on the
recording medium.
[0010] Moreover, when the recording medium is exposed to the base,
organic acid existing on the surface of the recording medium and/or
in the lubricant film can be transformed into salt. The organic
acid can thus be consumed. The organic acid can be washed off or
removed from the surface of the recording medium and/or out of the
lubricant film in this manner. Less organic acid greatly
contributes to prevention of generation of corrosion mounds over a
longer period. In particular, the radiation of an ultraviolet leads
to generation of organic acid in a quite quantity on the surface of
the recording medium and/or in the lubricant film. However, it has
been proved that the base is remarkably effective to reduce the
quantity of the corrosion mounds on the recording medium.
[0011] The base may be a weak base. In particular, the base may be
an amine compound. Such an amine compound may include an aliphatic
amine compound, for example.
[0012] When the recording medium is exposed to the base, the
recording medium may be dipped into a solution including the base.
The solution may comprise a solvent such as hydrofluoroether
compound, for example. The base may be resolved into the
solvent.
[0013] The lubricant film may comprise a perfluoroether compound,
for example. In particular, the perfluoroether compound may be a
perfluoropolyether compound having piperonyl radicals at both
terminals.
[0014] The ultraviolet ray preferably has a wavelength equal to or
smaller than 200 nm. The ultraviolet ray of this wavelength is
supposed to realize an efficient generation of ozone molecules out
of oxygen molecules. Accordingly, reaction of oxidation can be
promoted over the surface of the recording medium. The oxidation
serves to uniformly spread the lubricant film over the surface of
the recording medium.
[0015] According to a second aspect of the present invention, there
is provided a method of surface treatment for a recording medium,
comprising: forming a lubricant film over the surface of the
recording medium; and subjecting the recording medium to exposure
to a base.
[0016] When the recording medium is exposed to the base, organic
acid existing on the surface of the recording medium and/or in the
lubricant film can be transformed into salt. The organic acid can
thus be consumed. The organic acid can be washed off or removed
from the surface of the recording medium and/or out of the
lubricant film in this manner. Less organic acid greatly
contributes to prevention of generation of corrosion mounds over a
longer period.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The above and other objects, features and advantages of the
present invention will become apparent from the following
description of the preferred embodiment in conjunction with the
accompanying drawings, wherein:
[0018] FIG. 1 is a schematic view illustrating the structure of a
surface treatment system;
[0019] FIG. 2 illustrates the process of forming a lubricant film
over the surface of a magnetic recording disk;
[0020] FIG. 3 illustrates the process of oxidation induced over the
surface of the magnetic recording disk;
[0021] FIG. 4 illustrates the process of washing off organic acid
molecules from the surface of the magnetic recording disk;
[0022] FIG. 5 is a bar diagram illustrating the mass of oxalic acid
remaining on the surfaces of the magnetic recording disks; and
[0023] FIG. 6 is a bar diagram illustrating the number of corrosion
mound generated on the surfaces of the magnetic recording
disks.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] FIG. 1 schematically illustrates the structure of a surface
treatment system for a recording medium. The surface treatment
system 11 includes a lubricant application apparatus 12 for
application of a lubricant. A lubricant bath 13 is filled with a
solution 14 containing a lubricant in the lubricant application
apparatus 12. A lubricant such as perfluoroether compounds may be
resolved into a fluoride resolvent, for example, in the solution
14. The fluoride resolvent may contain the lubricant in an amount
ranging between 0.005 wt % and 0.05 wt %, for example. In
particular, the lubricant may be perfluoropolyether having
piperonyl radicals at both terminals.
[0025] The surface treatment system 11 further includes an
ultraviolet radiation apparatus 15 for radiation of ultraviolet
rays. The ultraviolet radiation apparatus 15 comprises ultraviolet
lamps 16 disposed within a chamber 17, for example. The ultraviolet
lamps 16 are designed to radiate at least a first ultraviolet ray
of the wavelength equal to or smaller than 200 nm, such as of 185
nm, and a second ultraviolet ray of the wavelength over 200 nm,
such as of 254 nm, for example. An oxygenic atmosphere may be
established within the chamber 17. Air may be filled within the
chamber 17.
[0026] The surface treatment system 11 still further includes a
washing apparatus 18. The washing apparatus 18 comprises a washing
bath 21 filled with a solution 19 containing a base. A weak base
such as amine compounds may be resolved into a fluoride resolvent
such as hydrofluoroether, for example, in the solution 19. The
fluoride resolvent may contain an aliphatic primary amine compound
in an amount ranging between 0.001 wt % and 1.0 wt %, for
example.
[0027] Next, a detailed description will be made on a method of
surface treatment employing the aforementioned surface treatment
system 11. First of all, a magnetic recording medium or disk 22 is
dipped into the solution 14 containing the lubricant, as shown in
FIG. 2. Perfluoropolyether molecules 23 as the lubricant are
allowed to adhere to the surface of the magnetic recording disk 22
in the solution 14. A lubricant film is formed to spread over the
surface of the magnetic recording disk 22 in this manner. Piperonyl
radicals 24 exhibit a superior affinity to a diamond-like-carbon
(DLC) surface layer of the magnetic recording disk 22. The
perfluoropolyether molecules 23 are thus allowed to adhere to the
surface of the magnetic recording disk 22 at a higher
stability.
[0028] Prior to the aforementioned formation of the lubricant film,
the magnetic recording disk 22 may be dipped into a washing liquid,
not shown. Polar liquid such as water, lower alcohol, acetone, and
the like, may be employed as the washing liquid, for example. The
polar liquid serves to wash off hydrophilic ionic contaminants,
such as nitric acid ions, phosphoric acid ions, sulfuric acid ions,
oxalic acid ions, and the like, from the surface of the magnetic
recording disk 22. Otherwise, organic solvent such as toluene,
hexane, and the like, may be employed as the washing liquid. The
organic solvent serves to wash off hydrophobic humic contaminants,
such as silicon organic compounds, for example, from the surface of
the magnetic recording disk 22.
[0029] Thereafter, the magnetic recording disk 22 is brought into
the ultraviolet radiation apparatus 15. When the ultraviolet lamps
16 are turned on in the chamber 17, the ultraviolet rays 27 serves
to transform oxygen molecules 26, which float within the chamber
17, into ozone molecules 28, as shown in FIG. 3. The generated
ozone molecules 28 promote reaction of oxidation over the surface
of the magnetic recording disk 22. The oxidation in this manner
enhances the affinity between the perfluoropolyether molecules 23
and the surface of the magnetic recording disk 22. The
perfluoropolyether molecules 23 is thus allowed to uniformly spread
over the surface of the magnetic recording disk 22. In particular,
the ultraviolet rays 27 of the wavelength equal to or smaller than
200 nm are supposed to promote generation of the ozone molecules
28.
[0030] When the ultraviolet rays 27 are radiated over the
perfluoropolyether molecules 23 on the surface of the magnetic
recording disk 22, the perfluoropolyether molecules 23 are turned
into macromolecules. The macromolecules serve to enhance the
repellency of the lubricant film. At the same time, macromolecules
serve to reduce the friction of the lubricant film. In particular,
the ultraviolet rays 27 of the wavelength larger than 200 nm are
supposed to promote generation of the macro molecules of the
perfluoropolyether molecules 23.
[0031] Thereafter, the magnetic recording disk 22 is brought into
the washing apparatus 18. The magnetic recording disk 22 is dipped
into the solution 19 containing the base. As shown in FIG. 4, the
bases 31 in the solution 19 are allowed to act on organic acid
molecules 32, such as oxalic acid molecules, acetic acid molecules,
and the like, existing on the surface of the magnetic recording
disk 22 as well as within the lubricant film on the magnetic
recording disk 22. The organic acid molecules 32 are thus
transformed into salts 33. The organic acid molecules 32 are
consumed in this manner. The organic acid molecules 32 are thus
washed off from the surface of the magnetic recording disk 22 and
out of the lubricant film. In particular, if the ultraviolet rays
are radiated over the DLC surface layer of the magnetic recording
disk 22 as well as the lubricant film in the aforementioned manner,
the organic acid molecules 32 in a quite quantity may be generated
on the magnetic recording disk 22 and in the lubricant film.
[0032] The inventors have made an experiment so as to prove the
effect of the washing in the solution 19. In the experiment, the
quantity of oxalic acid was measured on the magnetic recording disk
22 after the magnetic recording disk 22 had been dipped into the
solution 19. Ion chromatography was utilized to measure the
quantity of oxalic acid. A comparative example was also prepared in
the experiment. The quantity of oxalic acid was measured right
after a magnetic recording disk of the comparative example had been
irradiated with the ultraviolet rays 27. The magnetic recording
disk of the comparative example was not dipped into the solution 19
prior to measurement. As is apparent from FIG. 5, it has been
proved that the solution 19 containing the base 31 is effective to
reduce the quantity of oxalic acid on the magnetic recording disk
22.
[0033] The inventors have counted corrosion mounds due to sweat on
the surface of the magnetic recording disk 22 according to the
invention. The inventors also counted corrosion mounds on the
surface of the magnetic recording disk of the comparative example.
Prior to the count, the magnetic recording disks were left in the
atmosphere of a higher temperature and a higher humidity. The
temperature was set at 80 degrees Celsius. The humidity was set at
95%. The magnetic recording disks were left in the atmosphere for
two hours. As is apparent from FIG. 6, it has been proved that the
solution 19 containing the base 31 is remarkably effective to
reduce the quantity of the corrosion mounds on the magnetic
recording disk 22.
* * * * *