Coating processes – Direct application of electrical – magnetic – wave – or... – Pretreatment of substrate or post-treatment of coated substrate
Reexamination Certificate
2002-02-04
2002-10-22
Pianalto, Bernard (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Pretreatment of substrate or post-treatment of coated substrate
C427S128000, C427S129000, C427S131000, C427S132000
Reexamination Certificate
active
06468600
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a recording medium such as a magnetic recording disk incorporated within a storage device such as a hard disk drive (HDD), for example. In particular, the invention relates to a method of forming a texture on the surface of a substrate for the recording medium.
2. Description of the Prior Art
A method of texturing is often employed to form a magnetic recording disk incorporated in a hard disk drive (HDD), as disclosed in Japanese Patent Application Laid-open No. 7-244845. The method of texturing employs an abrasive tape urged against the surface of a disk-shaped substrate which rotates around a rotation shaft. An abrasive slurry containing abrasive grains is supplied to the abrasive tape. The abrasive grains sticking onto the abrasive tape scratch the surface of the substrate so as to form a texture on the surface of the substrate. A magnetic layer is thereafter formed over the textured surface of the substrate. The magnetic recording disk is thus obtained. The texture serves to prevent a head slider from adhering to the magnetic recording disk in a hard disk drive. At the same time, the texture contributes to establishment of the magnetic anisotropy in the magnetic layer. A higher recording density can be expected.
A further improvement in the recording density requires a fine texture on a magnetic recording disk. The abrasive grains of a smaller size should be contained in the abrasive slurry so as to establish the fine texture. However, if the grain size of the abrasive grains gets smaller, the efficiency of abrasion remarkably drops. It takes a longer time to establish a uniform texture of a specific roughness over the surface of the substrate. It leads to deterioration of the productivity of the magnetic recording disks.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide a method of texturing the surface of a substrate for a recording medium, which contributes to establishment of a fine texture within a shortened operating time.
According to a first aspect of the present invention, there is provided a method of texturing a substrate for a recording medium, comprising: enhancing hydrophilicity on a surface of the substrate; and forming a texture on the surface of the substrate with an aqueous slurry in which abrasive grains are dispersed.
Since the hydrophilicity is enhanced over the surface of the substrate, the surface of the substrate is expected to exhibit an enhanced property of wetness to the aqueous slurry. The aqueous slurry easily spreads over and contacts the surface of the substrate even from the initial stage of the process. The abrasive grains in the aqueous slurry are reliably allowed to uniformly spread over the surface of the substrate. When the aqueous slurry is supplied onto the surface of the substrate, establishment of the texture can be started on the surface of the substrate at an earlier stage. Even with the abrasive grains of a smaller grain size, a fine and uniform texture of a predetermined surface roughness can be established on the surface of the substrate within a shortened period. Increase in the operating period of abrasion can remarkably be suppressed irrespective of the reduced size of the abrasive grains.
On the other hand, if a higher repellency is maintained over the surface of the substrate, the abrasive grains hardly touch the repellent surfaces of the substrate. It takes a longer time to start establishing the texture on the substrate. This becomes prominent as the grain size of the abrasive grains gets smaller. A conventional texturing process thus suffers from a remarkable drop in the efficiency of abrasion as the grain size of the abrasive grains gets smaller. It takes a still longer time to establish a fine and uniform texture of a predetermined surface roughness on the substrate. The operating period of abrasion remarkably increases. The productivity of the recording media gets deteriorated.
Exposure of the substrate to ozone gas is effective to enhance the hydrophilicity. The ozone gas is expected to promote the reaction of oxidation over the surface of the substrate. The oxidation serves to enhance the hydrophilicity of the substrate.
In order to generate ozone gas, an ultraviolet ray may be radiated to the substrate in an oxygenic atmosphere. The ultraviolet ray serves to generate ozone molecules out of oxygen molecules. In this case, the ultraviolet ray may have the wavelength equal to or smaller than 200 nm, for example. The ultraviolet ray of this type is supposed to promote generation of ozone gas.
The substrate may be covered with an NiP layer spreading over the surface of the substrate. Otherwise, the abrasive grain in the aqueous slurry may have a grain size equal to or smaller than 1.0 &mgr;m, for example.
According to a second aspect of the present invention, there is provided a method of texturing a substrate for a recording medium, comprising: enhancing property of wetness to a predetermined liquid on a surface of the substrate; and forming a texture on the surface of the substrate with a slurry in which abrasive grains are dispersed in the predetermined liquid.
Since the surface of the substrate is expected to exhibit an enhanced property of wetness to the predetermined liquid, the slurry including the liquid easily spreads over and contacts the surface of the substrate even from the initial stage of the process. The abrasive grains in the slurry are reliably allowed to uniformly spread over the surface of the substrate. When the slurry is supplied onto the surface of the substrate, establishment of the texture can be started on the surface of the substrate at an earlier stage. Even with the abrasive grains of a smaller grain size, a fine and uniform texture of a predetermined surface roughness can be established on the surface of the substrate within a shortened period. Increase in the operating period of abrasion can remarkably be suppressed irrespective of the reduced size of the abrasive grains. The slurry may be an aqueous slurry, an oleaginous slurry, or the like.
REFERENCES:
patent: 7-244845 (1995-09-01), None
Itai Yuichiro
Kasamatsu Yoshiharu
Takahashi Toshiro
Yoshida Susumu
Fujitsu Limited
Greer Burns & Crain Ltd.
Pianalto Bernard
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