Burnishing tape and method of manufacturing the same, and method of burnishing magnetic disk

Abstract

Disclosed is a burnishing tape, a method of producing the same and a method of burnishing a magnetic disk with which a surface of the magnetic disk may be smoothed while contamination of a magnetic disk caused by crushed abrasive grains is prevented. A burnishing tape (1) manufactured by the method of manufacturing of the burnishing tape according to an embodiment of the invention is used to burnish the magnetic disk. The method includes: kneading and dispersing abrasive grains (5) and a binder (6) to prepare slurry; applying the slurry on the support (2) to form a coating layer; curing the coating layer to form an abrasive grain layer (3); and forming a liquid lubricant layer (4) on a surface of the abrasive grain layer (3).

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority of Japanese Patent Application No. 2008-172598 filed Jul. 1, 2008, the content of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a burnishing tape used for polishing a surface of a magnetic disk used in, for example, a hard disk device, a method of manufacturing the same, and a method of burnishing the magnetic disk.

2. Background Art

Recently, data is recorded on a magnetic disk in a hard disk device with increasingly higher density. A recording head is spaced from a magnetic recording surface when moved with respect thereto. The surface of the magnetic disk should be fairly smooth in order to reduce the distance between the recording head and the magnetic recording surface. Accordingly, in the manufacturing process of the magnetic disk, after a magnetic layer and a protective layer are formed on a nonmagnetic substrate, a surface of the outermost layer is burnished with a burnishing tape so as to remove bumps formed or deposited on the surface.

Burnishing is conducted using, for example, a burnishing tape having an alumina coating material applied thereto. The burnishing tape is pressed against a medium surface by a rubber contact roll so that the medium surface is polished lightly. Since any abnormal bumps on the medium surface may be removed during the burnishing process, the distance between the recording head and the magnetic recording surface may be reduced in a hard disk device (see, for example JP-A-11-277339).

An exemplary burnishing tape (i.e., a burnishing tape) used in the burnishing process may typically be a tape which includes a polyester base film having an abrasive layer formed thereon. The abrasive layer is made to contact and slide against the surface of the magnetic disk at the side of the magnetic layer. With this process, fine dust adhering to the surface of the magnetic disk is removed and the surface is polished to remove the abnormal bumps on the surface. In this manner, the surface is smoothed. Examples of the abrasive may include particles having an average particle diameter of about 0.05 to 50 micrometers. Namely, the abrasive may be particles of chromic oxide, α-alumina, silicon carbide, nonmagnetic iron oxide, diamond, γ-alumina, α,γ-alumina, fused alumina, corundum and synthetic diamond (see, for example, JP-A-09-054943).

JP-A-2001-079774 discloses, regarding a polishing film for burnishing a hard disk protective layer, covering the surfaces of abrasive particles with a coating agent in order to prevent transfer of ionic impurities from a polishing film to a surface of the hard disk protective layer. JP-A-9-85628 discloses increasing the polishing force of a burnishing tape and preventing scratching generated on a polishing surface by providing a ceramic coating layer on a surface of the burnishing tape.

SUMMARY OF THE INVENTION

Burnishing of a magnetic disk is typically a process of polishing a surface of a magnetic disk using a burnishing tape. In particular, an abrasive grain surface of the burnishing tape is pressed against a surface of the magnetic disk at the side of a magnetic layer while the magnetic disk is being rotated. In this manner, the magnetic disk surface is polished to remove bumps and thus the magnetic disk surface may be smoothed.

The burnishing tape is extended between a feed reel and a take-up reel. The burnishing tape is sequentially supplied from the feed reel and is taken up by the take-up reel. In the course of the burnishing tape being moved from the feed reel to the take-up reel, a surface of the burnishing tape opposite to the abrasive grain surface (i.e., a back surface) may be pressed by, for example, a rubber backing roll or a felt piece such that the polishing surface of the burnishing tape may be pressed against the surface of the magnetic disk. The burnishing tape is supplied from the reel. The used burnishing tape is taken up and collected by another reel.

Recently, data is recorded on a magnetic disk with increasingly high density. To increase the recording density, the distance between the magnetic head and the magnetic disk is reduced. Now, contamination of the magnetic disk surface during the burnishing process has become a problem.

According to the study of the present inventors, it has been found that contaminant of the magnetic disk surface contains alumina particles, which are produced during the burnishing process. In particular, abrasive grains are separated from the burnishing tape or crushed to produce the alumina particles contained in the contaminant. More particularly, it has been found that, when the magnetic disk surface is polished to remove the bumps formed thereon during the burnishing process, the abrasive grains adhering to the burnishing tape are separated or the surfaces of the abrasive grains are crushed (i.e., split) slightly and the separated grains or the abrasive grain powder produced by the crushing may adhere to the magnetic disk surface, thereby contaminating the magnetic disk surface.

Recently, the abrasive grains used for the burnishing tape are often deposited particles (i.e., crystal growth particles) instead of crushed grains. This is because higher processing accuracy has been demanded in the burnishing process. In particular, variation in the particle diameter and the shape of the abrasive grains is small in the deposited particles, which may prevent production of slight scratches on the surface to be burnished. However, since the deposited particles have smooth and spherical surfaces as compared to the crushed grains, it is difficult to stably keep the deposited particles on a support of the burnishing tape. It is therefore considered that the abrasive grains are easily separated from the burnishing tape during burnishing of the magnetic disk surface.

The invention has been made in view of the aforementioned and an object thereof is to provide a burnishing tape, a method of producing the same and a method of burnishing a magnetic disk with which contamination of a surface of the magnetic disk may be prevented during a burnishing process of the magnetic disk.

The present inventors have intensively studied to solve the problem and found that separation or crushing of the abrasive grains may be prevented by a novel burnishing tape for burnishing the magnetic disk and thus contamination of the magnetic disk surface caused by the burnishing tape may be reduced. In particular, a surface of an abrasive grain layer on the support may be coated with a liquid lubricant layer having the thickness of 0.0001 to 10 micrometers to stabilize the shearing force (i.e., the coefficient of dynamic friction) applied to the burnishing tape. The invention has the following aspects.

(1) A first aspect of the invention is a burnishing tape used to burnish a magnetic disk, the tape including: a support; an abrasive grain layer provided on the support, the abrasive grain layer containing abrasive grains; and a liquid lubricant layer with which a surface of the abrasive grain layer is coated.

(2) In a second aspect of the invention, the thickness of the liquid lubricant layer may be in a range of 0.0001 to 10 micrometers.

(3) In a third aspect of the invention, the liquid lubricant layer may include a compound which has a perfluoropolyether structure.

(4) A fourth aspect of the invention is a method of manufacturing a burnishing tape used to burnish a magnetic disk, the method including: kneading and dispersing abrasive grains and a binder to prepare slurry; applying the slurry on a support to form a coating layer; curing the coating layer to form an abrasive grain layer; and forming a liquid lubricant layer on a surface of the abrasive grain layer.

(5) In a fifth aspect of the invention, the thickness of the liquid lubricant layer may be in a range of 0.0001 to 10 micrometers.

(6) In a sixth aspect of the invention, the liquid lubricant layer may include a compound which has a perfluoropolyether structure.

(7) A seventh aspect of the invention is a method of burnishing a magnetic disk in which an abrasive grain surface of a burnishing tape supplied to a magnetic disk surface is pressed against and polishes the magnetic disk surface while a magnetic disk is being rotated, the disk including, on a nonmagnetic substrate, at least an underlayer, a magnetic layer and a protective layer, wherein the burnishing tape supplied to the magnetic disk surface is the burnishing tape according to any one of above (1) to (3).

(8) A eighth aspect of the invention is a method of burnishing a magnetic disk in which an abrasive grain surface of a burnishing tape supplied to a magnetic disk surface is pressed against and polishes the magnetic disk surface while a magnetic disk is being rotated, the disk including, on a nonmagnetic substrate, at least an underlayer, a magnetic layer and a protective layer, wherein: the burnishing tape supplied to the magnetic disk surface includes a support and an abrasive grain layer which contains abrasive grains and is provided on the support; and a liquid lubricant is supplied between the support and the abrasive grain layer when the magnetic disk surface is polished by the burnishing tape.

According to the burnishing tape of an aspect of the invention, the liquid lubricant layer may prevent crushing of the abrasive grains included in the abrasive grain layer or removal of the crushed grains during burnishing of the magnetic disk. Thus, contamination of the magnetic disk surface caused by the crushed abrasive grains may be prevented. With this configuration, a surface-smoothed magnetic disk, which is sufficiently clean, may be provided.

According to the method of manufacturing a burnishing tape of an aspect of the invention, an excellent burnishing tape may be provided easily and reliably.

According to the method of burnishing according to an aspect of the invention, the liquid lubricant layer may prevent crushing of the abrasive grains included in the abrasive grain layer of the burnishing tape or removal of the crushed grains. Thus, contamination of the magnetic disk surface caused by the crushed abrasive grains may be prevented. With this configuration, a surface-smoothed magnetic disk, which is sufficiently clean, may be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of an exemplary burnishing tape according to an embodiment of the invention.

FIG. 2A is a schematic diagram showing an exemplary burnisher in which the burnishing tape shown in FIG. 1 is incorporated.

FIG. 2B is a schematic diagram showing an exemplary burnisher in which the burnishing tape shown in FIG. 1 is incorporated.

FIG. 3 is a longitudinal cross-sectional view of an exemplary magnetic disk to be burnished in the burnisher shown in FIGS. 2A and 2B.

FIG. 4A is a cross-sectional view of a burnishing tape in which a very thin binder layer is formed on an abrasive grain layer.

FIG. 4B is a cross-sectional view of a related art burnishing tape in which abrasive grains are separated or abrasive grains are chipped.

FIG. 4C is a cross-sectional view of an exemplary burnishing tape according to an embodiment of the invention.

FIG. 5 is a schematic configuration diagram showing an exemplary magnetic recording and reproducing device in which the magnetic disk shown in FIG. 3 is incorporated.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a burnishing tape, a method of manufacturing the same and a method of burnishing according to embodiments of the invention will be described.

Burnishing Tape

First, a burnishing tape according to an embodiment of the invention will be described.

FIG. 1 is a longitudinal cross-sectional view of a burnishing tape according to an embodiment of the invention.

A burnishing tape 1 according to the present embodiment smoothes a surface of a magnetic disk 10 in the following manner: a surface of the burnishing tape 1 is made to slide against a surface of the magnetic disk 10 shown in FIGS. 2A and 2B to polish the surface of the magnetic disk 10 and remove abnormal bumps formed thereon.

The burnishing tape 1 includes a support 2, an abrasive grain layer 3 provided on the support 2 and a liquid lubricant layer 4 with which a surface of the abrasive grain layer 3 is coated.

The material of the support 2 is not particularly limited and may be various resin materials, such as polyethylene terephthalate.

The abrasive grain layer 3 includes abrasive grains 5 and a binder 6. The surface of the abrasive grain layer 3 has bumps that reflect the shape of the abrasive grains 5.

Examples of the abrasive grains 5 may include particles of chromic oxide, α-alumina, silicon carbide, nonmagnetic iron oxide, diamond, γ-alumina, α,γ-alumina, fused alumina, corundum and synthetic diamond. These substances may be used alone or in combination thereof.

The binder 6 is able to bond the abrasive grains 5 and the support 2 or bond the abrasive grains 5 together. The material of the binder is not particularly limited and may be a thermosetting resin, thermoplastic resin and photosensitive resin.

Examples of the thermosetting resin may include urea resin, melamine resin, phenol resin, epoxy resin, unsaturated polyester resin, alkyd resin and urethane resin.

Examples of the thermoplastic resin may include acrylonitrile styrene butadiene rubber (ABS) resin, styrene butadiene rubber resin, polybutadiene resin and acrylic rubber-based MBS resin.

Examples of the photosensitive resin may include methacrylic resin, phenol resin, urea resin, melamine resin, polystyrene resin, polyacetal resin, polycarbonate resin and epoxy resin.

These resin materials may be used alone or in combination thereof.

The burnishing tape 1 according to the present embodiment of the invention is characterized in that the surface of the abrasive grain layer 3 is coated with the liquid lubricant layer 4.

The thickness of the liquid lubricant layer 4 may preferably be in a range of 0.0001 to 10 micrometers, and more preferably in a range of 0.1 to 3 micrometers. With the liquid lubricant layer 4 having the thickness in this range, separation or crushing of the abrasive grains may be prevented. Even if separation or crushing of the abrasive grains occurs, scattering of the abrasive grain powder may be prevented. With this configuration, adhesion of contaminant that may inhibit the magnetic head from moving in a manner spaced from the magnetic disk in a hard disk device incorporating the magnetic disk may be prevented.

If the thickness of the liquid lubricant layer 4 is smaller than 0.0001 micrometers, an effect of preventing the occurrence of the crushed powder may be impaired. If the thickness of the liquid lubricant layer 4 is larger than 10 micrometers, the occurrence of the crushed powder may be decreased but the liquid lubricant may easily be transferred to the material to be polished. As a result, the likelihood of occurrence of contamination of the surface of the material to be polished may be increased.

In the present embodiment, the liquid lubricant layer may preferably include a compound having a perfluoropolyether structure. If the liquid lubricant layer is provided on the surface of the abrasive grain layer, the liquid lubricant may be transferred to the magnetic disk during the burnishing process as described above. Since the compound having a perfluoropolyether structure is generally used as a lubricant to be applied onto a magnetic disk surface, the likelihood of causing problems is reduced even if the liquid lubricant of the magnetic tape is transferred to the magnetic disk.

The liquid lubricant layer 4 provided on the surface of the abrasive grain layer 3 may protect the abrasive grains 5 included in the abrasive grain layer 3. The liquid lubricant layer 4 may prevent crushing, or removal of the crushed grains during burnishing of the magnetic disk 10 using the burnishing tape 1 may be prevented. The surface of the magnetic disk 10 may be smoothed while preventing contamination of the magnetic disk 10 caused by the crushed grains of the abrasive grains 5.

With the liquid lubricant layer 4 having the thickness in the above-described range provided on the abrasive grain layer 3, slight scattering of the crushed grains produced by the crushing of the abrasive grains 5 during burnishing of the magnetic disk 10 may be reliably prevented. As a result, it is possible to reliably prevent contaminant (i.e., crushed abrasive grains), which may inhibit the magnetic head from moving in a manner spaced from the magnetic disk, from adhering onto the surface of the magnetic disk 10.

If the thickness of the liquid lubricant layer 4 is smaller than 0.0001 micrometers, an effect of preventing the occurrence of the crushing of abrasive grains 5 or removal of the crushed grains may become insufficient. If the thickness of the coating layer 4 is larger than 10 micrometers, the occurrence of crushing of the abrasive grains 5 or removal of the crushed grains may be reliably prevented. However, the thickness of the lubricant layer 4 covering the surface of abrasive grains 5 may be excessively large, and thus the function as the burnishing tape may become poor.

Method of Manufacturing Burnishing Tape

Next, a method of manufacturing the burnishing tape according to an embodiment of the invention will be described. The method of manufacturing the burnishing tape according to an embodiment of the invention may include: (1) kneading and dispersing the abrasive grains and the binder to prepare a slurry; (2) applying the slurry onto the support to form a coating layer; (3) making the coating layer cured to form the abrasive grain layer 3; and (4) forming the liquid lubricant layer 4 on the surface of the abrasive grain layer 3. Hereinafter, each process will be described.

(1) Preparation of Slurry

First, the abrasive grains 5 and the binder 6 are kneaded and dispersed to prepare a slurry.

If the above-described resin is used as the binder 6, the resin material may be kneaded and dispersed with the abrasive grains in the form of a precursor thereof. The precursor of the resin may be a monomer or an oligomer which reacts in various processes in the manufacturing process to yield a target resin.

The slurry may contain a solvent, which helps adjust the viscosity of the slurry suitable for application which will be described later.

The solvent is not particularly limited, but may be a ketone-based solvent, ester-based solvent, aromatic hydrocarbon solvent, alcohol-based solvent and ether-based solvent.

The content of the abrasive grains 5 in the slurry is preferably in a range of 100 to 400 parts by mass and more preferably 200 to 400 parts by weight with respect to the content of the binder 6 or its precursor. If the content of the abrasive grains 5 is larger than 400 parts by mass, the likelihood of the removal of the abrasive grains 5 in the obtained abrasive grain layer 3 may be increased. If the content of the abrasive grains 5 is smaller than 100 parts by mass, the abrasive grains 5 may be buried into the binder 6, and it will become difficult to form bumps that reflect the shape of the abrasive grains 5 on the surface of the abrasive grain layer 3.

Any kneader may be used so long as it is usually employed in the method of manufacturing this kind of burnishing tape.

(2) Formation of Coating Layer

Next, the slurry is applied onto the support 2 to form a coating layer.

The slurry may be coated by any method usually employed in the method of manufacturing this kind of burnishing tape. For example, the slurry may be coated through roll coating or applying.

(3) Curing of Coating Layer

Next, the coating layer formed on the support 2 is made to cure and form the abrasive grain layer 3.

The method of curing may be selected according to the types of the binder included in the coating layer and may include heat-treatment or ultraviolet irradiation.

In this process, the abrasive grain layer 3 having bumps that reflect the shape of the abrasive grains 5 may be formed on the surface.

(4) Formation of Lubricant Layer

Next, the liquid lubricant layer 4 is formed on the abrasive grain layer 3.

The liquid lubricant layer 4 may be formed on the abrasive grain layer 3 by applying a liquid lubricant or a lubricant solution in which a lubricant is dissolved in a solvent.

The liquid lubricant layer 4 may be applied by the same methods described in the process (2).

Conventional burnishing tapes are usually manufactured in the processes (1) to (3) among the described processes (1) to (4). In this method of manufacturing, the abrasive grains are kneaded with the binder in the process of (1) so that the surface of the abrasive grain is covered with the binder. If the abrasive grain is made to cure as an abrasive grain layer on the support, the surface of the abrasive grain layer is slightly coated with a solid binder. The thickness of the coating layer of the binder, however, is very small and may be as thin as less than 0.01 micrometers according to analysis of the present inventors. This is because the binder covering an upper surface of the abrasive grains 5 as shown in FIG. 4A will gather on the support 2 due to self-weight at the time of curing, and the thickness of the binder 6 on the surface 5c of the abrasive grains 5 becomes very thin.

If the conventional burnishing tape including the abrasive grain layer 3 is used to burnish the magnetic disk, as shown in FIG. 4B, the abrasive grains 5 contained in the burnishing tape may be separated to produce traces 8 of separation or produce crushed abrasive grains 7. Abrasive grains separated or crushed are removed from the burnishing tape and contaminate the magnetic disk surface during burnishing.

In order to prevent the occurrence of such a phenomenon, as shown in FIG. 4C, the invention includes the liquid lubricant layer 4 provided on the surface of the abrasive grain layer 3 of the conventional burnishing tape prepared in the processes of (1) to (3). With this configuration, the shearing force applied to the burnishing tape 1 of an embodiment of the invention during burnishing may be stabilized. Thus, the separation or crushing of the abrasive grains 5 which constitute the abrasive grain layer 3 of the burnishing tape may be prevented. As a result, contamination of the magnetic disk surface during burnishing may be prevented.

Burnishing

Next, a method of burnishing according to an embodiment of the invention will be described.

FIGS. 2A and 2B are schematic diagrams of an exemplary burnisher used in a burnishing process of the invention. FIG. 3 is a longitudinal cross-sectional view of an exemplary magnetic disk to be burnished according to an embodiment of the invention.

In the burnishing of the invention, the polishing surface S (i.e., the surface of the liquid lubricant layer) is pressed against a surface of the magnetic disk 10 to make them slide against each other to polish the surface of magnetic disk 10 and remove the abnormal bumps on the surface.

First, an exemplary magnetic disk to which the burnishing of the invention is applied will be described with reference to FIG. 3.

The magnetic disk 10 shown in FIG. 3 schematically includes an underlayer 12, an intermediate layer 13, a magnetic layer 14 and a protective layer 15 laminated successively on both main surfaces of a nonmagnetic substrate 11. A lubricant layer 16 is provided on top of these layers.

The material of the nonmagnetic substrate 11 is not particularly limited and may include a nonmagnetic aluminum alloy material and glass material usually employed as a material for the magnetic disk 10. Examples of the glass material may include usual soda glass, alumino silicate-based glass and amorphous glass. Examples of the aluminum alloy material may include an Al—Mg alloy consisting mainly of Al. Alternatively, the nonmagnetic substrate 11 may be formed of any nonmagnetic substances, such as silicon, titanium and ceramic, and various resin materials.

The nonmagnetic substrate 11 may contain an substrate of aluminum or glass and a surface layer in which one or more layers consisting of NiP, NiP alloy or another alloy are formed on the substrate of aluminum or glass by plating, sputtering or other processes.

The underlayer 12 may be formed of Cr or a Cr alloy consisting of Cr and one or more of Ti, Mo, Al, Ta, W, Ni, B, Si, Mn and V.

When the underlayer 12 is formed as a multilayered nonmagnetic underlayer, at least one of layers constituting the nonmagnetic underlayer may be formed of Cr or the above-described Cr alloy.

The nonmagnetic underlayer may consist of a NiAl-based alloy, a RuAl-based alloy or a Cr alloy (an alloy which consists of Cr and one or more of Ti, Mo, Al, Ta, W, Ni, B, Si and V).

If a multilayered nonmagnetic underlayer is used, at least one of the layers constituting the nonmagnetic underlayer may consist of a NiAl-based alloy, RuAl-based alloy or the above-described Cr alloy.

The intermediate layer 13 preferably uses a nonmagnetic material formed of a Co alloy consisting mainly of Co and having an hcp structure from a viewpoint of promoting epitaxial growth of the Co alloy. Examples of the Co alloy may include a Co—Cr-based alloy, Co—Cr—Ru-based alloy, Co—Cr—Ta-based alloy and Co—Cr—Zr-based alloy. The intermediate layer 13 may preferably include one or more of these Co-based alloys.

The magnetic layer 14 preferably uses a material formed of a Co alloy consisting mainly of Co and having an hcp structure. Examples of the Co alloy may include a Co—Cr—Ta-based alloy, Co—Cr—Pt-based alloy, Co—Cr—Pt—Ta-based alloy, Co—Cr—Pt—B-based and Co—Cr—Pt—B—Cu-based alloy. The magnetic layer 14 may preferably include one or more of these Co-based alloys. The magnetic disk according to the present embodiment may also have a layered structure consisting or two or more magnetic layers.

The protective layer 15 may be formed of a carbon-based material, such as CVD carbon, amorphous carbon, hydrogen-containing carbon, nitrogen-containing carbon and fluorine-containing carbon, which are formed by plasma CVD, and ceramic-based materials, such as silica and zirconia. Among these, hard and fine CVD carbon is suitably used from the viewpoint of economical efficiency and productivity. The thickness of the protective layer 15 may preferably be 0 to 150 angstroms (1 to 15 nm), and more preferably be 20 to 60 angstroms (2 to 6 nm). If the protective layer 15 is too thin, durability may become insufficient. If the protective layer 15 is too thick, loss during recording and reproduction may become large.

The lubricant layer 16 which is the top layer may be formed of a material containing a polymer of polymerized unsaturated group-containing perfluoropolyether compound. The polymerized unsaturated group-containing perfluoropolyether compound may be a compound which includes an organic group having a polymerizable unsaturated bonding at least one end of perfluoropolyether, which is a main chain.

The magnetic disk to be burnished by the method according to the invention may be an in-plane magnetic disk or a perpendicular magnetic disk.

Next, an exemplary burnisher used to burnish in the invention will be described with reference to FIGS. 2A and 2B.

A burnisher 20 shown in FIGS. 2A and 2B includes a magnetic disk rotary drive mechanism 21, burnishing tapes 1a and 1b, a burnishing tape running system 22 and a burnishing tape pressing device 23.

The magnetic disk rotary drive mechanism 21 includes a spindle 24 which is driven to rotate by an unillustrated spindle motor, and a magnetic disk holding mechanism 25 attached to the center of the spindle 24. The central portion of the magnetic disk 10 is secured to the magnetic disk holding mechanism 25, which holds the magnetic disk 10. When the spindle 24 is driven to rotate with the magnetic disk 10 held by the magnetic disk holding mechanism 25, the magnetic disk 10 is rotated according to the rotational direction and the rotational rate of the spindle 24.

The magnetic disk rotary drive mechanism 21 is configured to rotate the magnetic disk 10 in a rotational direction (the direction of arrow r in FIGS. 2A and 2B) such that the scanning direction of a track of the magnetic disk 10 which is rotated is opposite to the running direction of a first burnishing tape 1a which is moved between a first guide roll 26 and a second guide roll 27 (i.e., the direction of arrow Ra in FIGS. 2A and 2B), which will be described later, and is opposite to the running direction of a second burnishing tape 1b which is moved between a fifth guide roll 30 and a sixth guide roll 31 (i.e., the arrow Rb direction in FIGS. 2A and 2B).

The burnishing tapes 1a and 1b are elongated tapes fabricated in the method of manufacturing of the burnishing tape described above.

A burnisher 20 includes a first burnishing tape 1a and a second burnishing tape 1b. The first burnishing tape 1a is moved such that a polishing surface S thereof is moved opposing a first main surface 10a of the magnetic disk 10. The second burnishing tape 1b is moved such that a polishing surface S thereof is moved opposing a second main surface 10b of the magnetic disk 10.

The burnishing tape running system 22 has a first burnishing tape running system 22a and a second burnishing tape running system 22b, and the magnetic disk 10 is disposed between the burnishing tape running system 22a and the second burnishing tape running system 22b. The first burnishing tape running system 22a includes an unillustrated supply roll, a take-up roll and first to fourth guide rolls 26 to 29 disposed below the supply roll and the take-up roll.

The first to fourth guide rolls 26 to 29 are disposed such that each rotation axis thereof is substantially parallel to a first main surface 10a of the magnetic disk 10 and rotation axes thereof are mutually substantially parallel to each other. The first and second guide rolls 26 and 27 are disposed such that their distances from the first main surface 10a of the magnetic disk 10 are substantially equal to each other. The third and fourth guide rolls 28 and 29 are disposed such that their distances from the first main surface 10a of the magnetic disk 10 are substantially equal to each other at a position further apart from the magnetic disk 10 than the first and second guide rolls 26 and 27

In the thus-configured first burnishing tape running system 22a, the elongated first burnishing tape 1a is sequentially fed out from the supply roll. The first burnishing tape 1a fed from the supply roll is moved along a substantially U-shaped running route while being guided by the first to fourth guide rolls 26 to 29, and then taken up by the take-up roll. Here, the polishing surface S of the first burnishing tape 1a opposes the first main surface 10a of the magnetic disk 10 when moving between the first and second guide rolls 26 and 27.

The second burnishing tape running system 22b includes an unillustrated supply roll, a take-up roll and fifth to eighth guide rolls 30 to 33. The fifth to eighth guide rolls 30 to 33 are disposed symmetrically with the first to fourth guide rolls 26 to 29 at both sides of the magnetic disk 10.

In the thus-configured second burnishing tape running system 22b, an elongated second burnishing tape 1b is sequentially fed from the supply roll. The second burnishing tape 1b fed from the supply roll is moved along a substantially U-shaped running route while being guided by the fifth to eighth guide rolls 30 to 33 and then taken up by the take-up roll. Here, the polishing surface S of the second burnishing tape 1b opposes the second main surface 10b of the magnetic disk 10 when moving between the fifth and sixth guide rolls 30 and 31.

The burnishing tape pressing device 23 includes a first burnishing tape pressing device 23a and a second burnishing tape pressing device 23b. The first burnishing tape pressing device 23a presses the first burnishing tape 1a which is moved between the first and second guide rolls 26 and 27 to bring into contact with (i.e., dab against) the first main surface 10a of the magnetic disk 10. The second burnishing tape pressing device 23b presses the second burnishing tape 1b which is moved between the fifth and sixth guide rolls 30 and 31 to bring into contact with (i.e., dab against) the second main surface 10b of the magnetic disk 10.

In a state in which the magnetic disk 10 is driven to rotate in the direction of arrow r shown in FIGS. 2A and 2B by the magnetic disk rotary drive mechanism 21, if the first burnishing tape 1a moving between the first and second guide rolls 26 and 27 is pressed against the first main surface 10a of the magnetic disk 10 by the first burnishing tape pressing device 23a, and the second burnishing tape 1b moving between the fifth and sixth guide rolls 30 and 31 is pressed against the second main surface 10b of the magnetic disk 10 by the second burnishing tape pressing device 23b, the polishing surface S of the first burnishing tape 1a is made to slide against the first main surface 10a and the polishing surface S of the second burnishing tape 1a is made to slide against the second main surface 10b. In this manner, both main the surfaces 10a and 10b of the magnetic disk 10 are polished by the burnishing tapes 1a and 1b so that bumps on both the main surfaces 10a and 10b are removed to provide smooth main surfaces. Here, in the burnisher 20 of the present embodiment, since unused burnishing tapes 1a and 1b are sequentially fed from the supply roll, used for polishing and then taken up to the take-up roll, unused burnishing tapes 1a and 1b are always supplied to each main surface of the magnetic disk 10. Thus, each main surface 10a and 10b of the magnetic disk 10 may be polished efficiently.

The first and second burnishing tape pressing devices 23a and 23b are preferably formed of a material having flexibility at an area to be in contact with the burnishing tapes 1a and 1b. With this configuration, the polishing surfaces S of the burnishing tapes 1a and 1b may be pressed against the surfaces of the magnetic disk 10 sufficiently close to each other so as to efficiently polish the surface of the magnetic disk 10. Exemplary first and second burnishing tape pressing devices 23a and 23b may be, for example, a pad consisting of resin or textile or a device having a pressing member, such as a rubber roller, which will be made to abut a back surface of the burnishing tape so as to press the burnishing tapes 1a and 1b against the magnetic disk 10.

In the burnisher 20 of the present embodiment, the first and second burnishing tape pressing devices 23a and 23b each include metal blocks 34 and 35, pads 36 and 37 attached to one side surface of the metal blocks 34 and 35 and a driving means (not shown) which makes the metal blocks 34 and 35 reciprocate in a horizontal direction (i.e., a direction perpendicular to each main surface of the magnetic disk, indicated by arrows F1 and F2 in FIGS. 2A and 2B).

In such burnishing tape pressing devices 23a and 23b, as shown in FIG. 2A, when the driving means makes the metal blocks 34 and 35 move in the direction of arrow F1 with the pads 36 and 37 being spaced apart from the burnishing tapes 1a and 1b (i.e., a stand-by state), the pads 36 and 37 abut the back surface of the burnishing tapes 1a and 1b and press the burnishing tapes 1a and 1b against the magnetic disk 10. As a result, as shown in FIG. 2B, the polishing surfaces S of the burnishing tapes 1a and 1b are brought into contact with the main surfaces of the magnetic disk 10. In this state, when the driving means makes the metal blocks 34 and 35 move in the direction indicated by the arrow F2, the burnishing tapes 1a and 1b move apart from the magnetic disk 10, and further, the pads 36 and 37 move apart from the burnishing tapes 1a and 1b, and the driving means returns to its stand-by state.

Next, an operation of the burnisher 20 will be described.

The first burnishing tape 1a is placed on the first burnishing tape running system 22a and the second burnishing tape 1b is placed on the second burnishing tape running system 22b.

The magnetic disk holding mechanism 25 is mounted on and held by the magnetic disk 10.

As shown in FIG. 2A, in the initial state of the burnisher 20, each of the pads 36 and 37 of the first and second burnishing tape pressing devices 23a and 23b is spaced apart from the burnishing tapes 1a and 1b (i.e., stand-by state).

Next, when operation of each part is turned on, the magnetic disk rotating drive mechanism 21 drives the magnetic disk 10 to rotate in the direction of arrow r shown in FIG. 4A. Each supply roll sequentially feeds the first and second burnishing tapes 1a and 1b. The fed first burnishing tape 1a is moved along the substantially U-shaped running route while being guided by the first to fourth guide rolls 26 to 29, and then taken up by the take-up roll. The fed second burnishing tape 1b is moved along the substantially U-shaped running route while being guided by the fifth to eighth guide rolls 30 to 33, and then taken up by the take-up roll.

The polishing surface S of the first burnishing tape 1a which is moved between first and second guide rolls 26 and 27 opposes the first main surface 10a of the magnetic disk 10 and is moved in a direction opposite the scanning direction of the track of the magnetic disk 10.

The polishing surface S of the second burnishing tape 1b which is moved between the fifth guide roll 30 and the sixth guide roll 31 opposes the second main surface 10b of the magnetic disk 10 and is moved in a direction opposite the scanning direction of the track of the magnetic disk 10.

Next, the first burnishing tape pressing device 23a presses the first burnishing tape 1a moving between the first and second guide rolls 26 and 27 against the first main surface 10a of the magnetic disk 10 and brings the polishing surface S of the burnishing tape 1a in contact with (i.e., dab against) the first main surface 10a. The second burnishing tape pressing device 23b presses the second burnishing tape 1a which is moved between the fifth and sixth guide rolls 26 and 27 against the second main surface 10b of the magnetic disk 10 and brings the polishing surface S of the burnishing tape 1b in contact with (i.e., dab against) the second main surface 10b.

When the polishing surface S of the moving first burnishing tape 1a is pressed against the first main surface 10a of the magnetic disk 10 while the magnetic disk 10 being driven to rotate in the direction of arrow r in FIGS. 2A and 2B and the polishing surface S of the moving second burnishing tape 1b is pressed against the second main surface 10b of the magnetic disk 10, the polishing surface S of the first burnishing tape 1a is made to slide against the first main surface 10a and the polishing surface S of the second burnishing tape 1a is made to slide against the second main surface 10b. In this manner, both the main surfaces 10a and 10b of the magnetic disk 10 are polished by the burnishing tapes 1a and 1b so that bumps on both the main surfaces 10a and 10b are removed to provide smooth main surfaces.

Since the lubricant layer 4 having the above-described structure is provided in the burnishing tape 1, the occurrence of crushing of the abrasive grains 5 included in the abrasive grain layer 3 or removal of the crushed grains may be prevented. In this manner, the surface of the magnetic disk 10 may be smoothed while contamination of the magnetic disk 10 caused by the crushed grains is prevented. Even if the thus-processed magnetic disk 10 is incorporated in a magnetic recording and reproducing device (i.e., a hard disk device) in which the distance between the magnetic head and the magnetic disk 10 is very small, collision between the magnetic head and the magnetic disk 10 may be prevented to provide desired operating characteristics.

The burnishing tape 1 used in the present embodiment includes the abrasive grain layer 3 on the support 2 and the surface of the abrasive grain layer 3 is covered by the liquid lubricant layer 4 having the thickness of 0.01 to 10 micrometers. In another embodiment, however, a burnishing tape having no liquid lubricant layer may alternatively be supplied to the burnisher as a burnishing tape 1 and a liquid lubricant may be dropped onto the burnishing surface from above the burnishing tape during burnishing. The dropping amount of the liquid lubricant should be carefully determined. If the dropping amount of the liquid lubricant is too large, the surface of the magnetic disk may be contaminated with the liquid lubricant.

The burnished magnetic disk according to the invention is then processed at a final inspection process (i.e., a tester) and is incorporated in the magnetic recording and reproducing device (i.e., the hard disk device).

In the other embodiment, as a method of burnishing a magnetic disk, which includes a step of polishing a surface of a magnetic disk comprising at least an underlayer, a magnetic layer and a protective layer on a nonmagnetic substrate, after pressing an abrasive grain surface of a burnishing tapes 1a and 1b supplied to the magnetic disk surface, while the magnetic disk is rotated, the burnishing tapes 1a and 1b supplied to the magnetic disk surface includes a support 2 and an abrasive grain layer 3 which contains abrasive grains and is provided on the support 2; and the method of burnishing a magnetic disk further includes a step of supplying a liquid lubricant between the support 1 and the abrasive grain layer when the magnetic disk surface is polished by the burnishing tape 1.

When implementing this method, since viscosity of a 100% lubricant is excessively high, the lubricant may preferably be diluted with a solvent. The concentration of the lubricant may preferably be 0.01% by volume and thus the dripping amount of the diluted solution may preferably be about 0.01 to 1 cc per second. A fluorine-based solvent may be used as the solvent.

As described above, contamination of the magnetic disk surface may be prevented, which has the same effect as the burnishing process in which a lubricant is supplied before the burnishing process and the resulting burnishing tape 1 having the lubricant layer 4 is used during the burnishing, as described previously.

Magnetic Recording and Reproducing Device

Next, an example of a magnetic recording and reproducing device in which the magnetic disk processed by the burnishing process of the invention is incorporated will be described.

FIG. 5 is a schematic configuration diagram of an exemplary magnetic recording and reproducing device.

The magnetic recording and reproducing device 80 includes a burnished magnetic disk 10 according to the embodiment of the invention, a medium driving section 81 which drives to rotate the magnetic disk 10, a magnetic head 82 which records information in the magnetic disk 10 and reproduces the recorded information, a head driving section 83 which drives a magnetic head 27 to move relatively with the magnetic disk 10 and a recording and reproducing signal processing system 84. The recording and reproducing signal processing system 84 is configured to process input data, transmit obtained recording signals to the magnetic head 82, process reproducing signals from the magnetic head 82 and output obtained data.

The surface of the magnetic disk 10 of the magnetic recording and reproducing device 80 is fairly smooth due to the burnishing process of the invention and is thus very clean. Accordingly, even if the distance between the magnetic head 82 and the magnetic disk 10 is very small, collision between the magnetic head 82 and the magnetic disk 10 may be prevented to provide high recording density and reliability.

Example

An Example for demonstrating the invention will be given below for illustrative purposes only. The invention is not limited to the Example.

Fabrication of Magnetic Disk

A washed glass substrate (manufactured by HOYA Corporation, 2.5 inches in outer diameter) is placed in a film forming chamber of a DC magnetron sputtering apparatus (C-3010 manufactured by Canon ANELVA Corporation). A vacuum is formed in film forming chamber so that the ultimate vacuum becomes 1×10⁻⁵ Pa. On this glass substrate, a target of 89Co-4Zr-7Nb (Co content 89 at %, Zr content 4 at % and Nb content 7 at %) is used to form a 100-nm-thick underlayer by sputtering at the substrate temperature of 100° C. or less.

The glass substrate is then heated to 200° C., and a 5-nm-thick intermediate layer is formed on the underlayer using a 65Co-30Cr-5B target. Then, a 25-nm-thick magnetic layer is formed using a 61Co-20Cr-17Pt-2B target. In this sputtering process, a layer is formed using argon as the process gas with the pressure inside the film forming chamber being 0.5 Pa.

A 5-nm-thick protective film layer is formed on the magnetic layer by the plasma CVD.

A lubricant layer consisting of perfluoropolyether is formed by dipping. In this manner, a magnetic disk having various layers formed on the glass substrate is obtained.

Each of the thus-obtained 1000 magnetic disks is placed in a tape burnisher 20 as shown in FIGS. 2A and 2B to polish the surface thereof.

A burnishing tape is fabricated in the following manner. Alumina particles (i.e., crystal growth particles) having an average particle diameter of 0.5 micrometers are made to adhere to a polyethylene terephthalate film by epoxy resin in a single particle layer. Then, a perfluoropolyether liquid lubricant layer is applied to the alumina particle surface to the thickness of about 1 micrometer.

The thickness of the layer formed by using the epoxy resin is about 0.3 micrometers from the surface of the film. The thickness of the epoxy resin layer is about 0.2 micrometers from the upper surfaces of the alumina particles. The burnishing tape is pressed against the magnetic disk surface at the pressure of 98 mN. The magnetic disk is driven to rotate at 300 rpm. The burnishing tape is fed at the rate of 10 mm per second. In this manner, the burnishing is continued for 5 seconds.

Evaluation of Burnishing Tape

Each of the thus-obtained 1000 magnetic disks is placed in a tester (i.e., a surface test device) and the disk surface of each magnetic disk is examined. As a result, separated alumina grains are observed to adhere into the surfaces of three magnetic disks.

Comparative Example

Each of 1000 magnetic disks are fabricated and subject to a tape burnishing process both under the same condition as that in the Example. In this example, the burnishing tape, which is the same as that used in the Example except that no liquid lubricant layer is provided, is used.

Each of the thus-fabricated 1000 magnetic disks is examined under the same condition as that of the Example, and the separated alumina particles are observed to adhere into the surfaces of 55 disks.

According to the comparison result, it is found that the method of Example of the invention has significant effects. In particular, the number of the alumina particles adhering into the surface of the magnetic disks is only three out of 1000 after burnishing the magnetic disks, while the number of the alumina particles adhering into the surface of the magnetic disks is as many as 55 out of 1000 in the Comparative Example in which no liquid lubricant layer is provided.

The burnishing tape according to an embodiment of the invention may smooth the surface of the magnetic disk while magnetic disk contamination caused by crushed abrasive grains is prevented. Thus, the burnishing tape is suited to burnish the magnetic disk which is to be applied to a hard disk device in which the distance between the magnetic head and the magnetic disk is very small.

It is apparent that the present invention is not limited to the above Example, but may be modified and changed without departing from the scope and spirit of the invention.

Claims

1. A burnishing tape used to burnish a magnetic disk, the tape comprising:

a support;

an abrasive grain layer, which comprises abrasive grains and is provided on the support; and

a liquid lubricant layer with which a surface of the abrasive grain layer is coated.

2. The burnishing tape according to claim 1, wherein the thickness of the liquid lubricant layer is in a range of 0.0001 to 10 micrometers.

3. The burnishing tape according to claim 1, wherein the liquid lubricant layer comprises a compound which has a perfluoropolyether structure.

4. The burnishing tape according to claim 2, wherein the liquid lubricant layer comprises a compound which has a perfluoropolyether structure.

5. A method of manufacturing of a burnishing tape used to burnish a magnetic disk, the method comprising:

kneading and dispersing abrasive grains and a binder to prepare a slurry;

applying the slurry on a support to form a coating layer;

curing the coating layer to form an abrasive grain layer; and

forming a liquid lubricant layer on a surface of the abrasive grain layer.

6. The method of manufacturing of the burnishing tape according to claim 5, wherein the thickness of the liquid lubricant layer is in a range of 0.0001 to 10 micrometers.

7. The method of manufacturing the burnishing tape according to claim 5, wherein the liquid lubricant layer comprises a compound which has a perfluoropolyether structure.

8. The method of manufacturing the burnishing tape according to claim 6, wherein the liquid lubricant layer comprises a compound which has a perfluoropolyether structure.

9. A method of burnishing a magnetic disk, which comprises a step of polishing a surface of a magnetic disk comprising at least an underlayer, a magnetic layer and a protective layer on a nonmagnetic substrate, after pressing an abrasive grain surface of a burnishing tape supplied to the magnetic disk surface, while the magnetic disk is rotated,

wherein the burnishing tape supplied to the magnetic disk surface is the burnishing tape according to claim 1.

10. A method of burnishing a magnetic disk, which comprises a step of polishing a surface of a magnetic disk comprising at least an underlayer, a magnetic layer and a protective layer on a nonmagnetic substrate, after pressing an abrasive grain surface of a burnishing tape supplied to the magnetic disk surface, while the magnetic disk is rotated,

wherein the burnishing tape supplied to the magnetic disk surface is the burnishing tape according to claim 2.

11. A method of burnishing a magnetic disk, which comprises a step of polishing a surface of a magnetic disk comprising at least an underlayer, a magnetic layer and a protective layer on a nonmagnetic substrate, after pressing an abrasive grain surface of a burnishing tape supplied to the magnetic disk surface, while the magnetic disk is rotated,

wherein the burnishing tape supplied to the magnetic disk surface is the burnishing tape according to claim 3.

12. A method of burnishing a magnetic disk, which comprises a step of polishing a surface of a magnetic disk comprising at least an underlayer, a magnetic layer and a protective layer on a nonmagnetic substrate, after pressing an abrasive grain surface of a burnishing tape supplied to the magnetic disk surface, while the magnetic disk is rotated,

wherein:

the burnishing tape supplied to the magnetic disk surface comprises a support and an abrasive grain layer which contains abrasive grains and is provided on the support; and

a liquid lubricant is supplied between the support and the abrasive grain layer when the magnetic disk surface is polished by the burnishing tape.