JP3097001B2 - Polishing composition for texturing of magnetic disk substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk substrate (memory
The present invention relates to a polishing composition for texturing a P-plated surface.

[0002]

2. Description of the Related Art In recent years, memory hard disks used in magnetic disk devices have been increasing in capacity and density, and magnetic media have been changed from conventional coating type media to thin film media by sputtering or plating. Migrating. As the density increases, the distance between the memory hard disk and the magnetic bed, that is, the flying height of the head, has become smaller and smaller than 0.1 μm recently. As described above, since the flying height of the head is extremely small, if there is a projection on the disk surface, a head crash may be caused, which may damage the magnetic medium or the magnetic head on the disk surface, or a minute amount that does not lead to a head crash. Even protrusions tend to cause various errors in reading and writing information due to disturbance of magnetic properties of the protrusions. Therefore, it is important to prevent the occurrence of projections in the step of polishing the memory hard disk substrate before forming the magnetic medium.

On the other hand, the magnetic disk drive has been downsized in parallel with the increase in capacity and density, and the motor for rotating the spindle has also become smaller. The phenomenon of not floating while sticking to the disk surface is likely to occur. As a means for preventing the sticking of the head by reducing the contact area between the head and the substrate surface, a so-called "texturing method" is employed. In this method, fine grooves are formed on the substrate surface of a magnetic disk. Generally, as a texturing method, a method of pressing a lapping tape having abrasive grains having an average grain size of 1 to 15 μm fixed on the surface of a rotating magnetic disk substrate with a pressure roller or the like, so-called “tape wrapping” is used. Is mainly used.

Japanese Patent Application Laid-Open No. Sho 62-236664 discloses that
"Wrapping tape while rotating the magnetic disk base
A magnetic disk characterized by comprising a first step of pressing a lap against a base surface with a pressure roller, and a second step of polishing using abrasive grains smaller than the average abrasive grains of the wrapping tape used in the first step. Texturing method for the base. Is disclosed. Also, JP-A-2-31326
Japanese Patent Application Laid-Open Publication No. H11-163873 states that “a concentric circular light streak having no projections and good uniformity was previously held on a surface of an aluminum alloy plate provided with a Ni-P plating head with a water-soluble binder. A method for manufacturing a magnetic disk substrate, which is formed by releasing abrasive grains in a polishing liquid during polishing using a polishing cloth tape. "

[0005]

However, when texturing with a conventional wrapping tape is performed, bulging-like projections called burrs are generated on the substrate surface, which lowers the head flying performance and reduces the projection. Disturbances in magnetic characteristics caused by various factors tend to cause various errors in reading and writing information. For example, FIG. 5 is a differential interference micrograph (720-fold magnification) of a processed surface on a substrate in the case of lapping tape texturing using aluminum oxide (average particle diameter 3 μm) as abrasive grains.
As shown in FIG. 5, projections occur on the substrate surface, and a uniform processed surface cannot be obtained. An object of the present invention is to convert from a tape wrapping method to a slurry texturing method in order to meet these demands, and to obtain a polishing composition for texturing a magnetic disk substrate conforming to this method.

[0006]

According to the present invention, ethylene glycol, propylene glycol or
It is a polishing composition for texturing a magnetic disk substrate obtained by mixing and using them to disperse abrasive grains of diamond, silicon carbide, and aluminum oxide.

[0007]

When the surface to be polished of a memory hard disk is polished using the polishing composition of the present invention, Table 3 in Examples described later is used.
Dispersion media can be used as shown in, Ru quality machining surface without generation of projections as compared to the conventional methods are obtained. FIG. 6 is a differential interference micrograph (720-fold magnification) of a processed surface on a substrate when diamond (average particle diameter: 3 μm) is used as abrasive grains and water is used as a dispersion medium. When general water is used as a dispersion medium, it is non-uniform as shown in FIG.
Protrusions occur and the quality of the machined surface decreases. In the polishing composition of the present invention, if the abrasive grain concentration is less than 0.002% by weight, workability is insufficient, and if it exceeds 50.0% by weight, it becomes difficult to maintain a slurry state. ~ 5
0.0% by weight is preferred.

[0008]

EXAMPLES (Example 1) Under the following polishing machine and polishing conditions shown below, propylene glycol was used as a dispersion medium, and diamond abrasive grains having an average particle diameter of 3 μm were prepared in various amounts of 0.002 to 50.0% by weight. A polishing test was carried out using a polishing composition having a different abrasive grain concentration, and the processing amount was measured. Table 1 shows the results.
FIG. 1 shows a photograph (720-fold magnification) of a processed surface on a substrate observed by a differential interference microscope when a diamond (average particle diameter: 3 μm) abrasive particle concentration of 0.5 % by weight is used in this example.

[Polishing machine] YAC texture machine [Polishing pad (tape)] Tape-shaped flocking cloth (CYD-
2501 EG) [Disk] Ni-P plated disk,
3.5 ″ φ, (mirror finished product) [Rotation speed] 250 rpm (disk rotation speed) [Processing pressure] 0.8 kg / cm ² [Slurry supply amount] 6 ml / min [Tape feed speed] 6 cm / min [Processing amount ] Indicates the polishing amount for 20 seconds.

[0010]

[Table 1]

As shown in Table 1, if the abrasive grain concentration is less than 0.002% by weight, the workability is insufficient, and if it exceeds 50.0% by weight, it becomes difficult to maintain the slurry state. 0.002 to 50.0% by weight. Also, compared with the conventional tape wrapping or the slurry texturing method using water as a dispersion medium, the processed surface quality has no protrusions, and a high processed surface quality can be obtained.

(Example 2) Using propylene glycol as a dispersion medium, the type of abrasive grains was changed to three types of diamond, silicon carbide and aluminum oxide at an average particle diameter of 1 μm and an abrasive grain concentration of 0.4% by weight. A polishing test was performed under the same polishing conditions as in Example 1. The results are shown in Table 2 and FIGS. 2, 3, and 4. FIGS. 2, 3 and 4 are photographs of a processed surface on a substrate observed by a differential interference microscope in the case of using three types of abrasive grains, diamond, silicon carbide and aluminum oxide, each having an average particle diameter of 1 μm in this embodiment. (Magnification 7
20 times).

[0013]

[Table 2]

In the table, Rms represents the root mean square roughness,
Ra indicates average roughness, and PV indicates maximum roughness. As shown in Table 2, FIG. 2, FIG. 3, and FIG. 4, even when the type of the abrasive grains was changed using propylene glycol as the dispersion medium, there was a difference in the processing amount due to the difference in the hardness of the abrasive grains, but all of them were on the processed surface. Has no projections and is uniform and has high processed surface quality. In particular, polishing slurries using diamond abrasive grains have a large amount of processing,
Excellent quality such as machined surface roughness. The dispersion medium used in the present invention is shown in Table 3 below.

[0015]

[Table 3]

[0016]

According to the present invention, ethylene glycol is used as a dispersion medium.
When water is used as a conventional dispersion medium in a polishing composition for texturing a magnetic disk substrate obtained by dispersing abrasive grains of diamond, silicon carbide, and aluminum oxide using coal, propylene glycol or a mixture thereof. In addition, a remarkably processed surface quality which is uniform and has no protrusion as compared with the tape texture can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a differential interference photograph of a processed surface on a substrate obtained in Example 1 (abrasive grains: diamond) of the present invention.

FIG. 2 is an explanatory view of a differential interference photograph of a processed surface on a substrate obtained in Example 2 (abrasive grains: diamond) of the present invention.

FIG. 3 is an explanatory view of a differential interference photograph of a processed surface on a substrate obtained in Example 2 of the present invention (abrasive grains: silicon carbide).

FIG. 4 Example 2 of the present invention (abrasive grains: aluminum oxide)
FIG. 4 is an explanatory diagram of a differential interference photograph of a processed surface on a substrate obtained in FIG.

FIG. 5 is a differential interference micrograph of a processed surface on a substrate in the case of conventional wrapping tape texturing.

FIG. 6 is an explanatory diagram of a differential interference photograph of a processed surface on a substrate when water is used as a dispersion medium.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-267931 (JP, A) JP-A-64-87673 (JP, A) JP-A-61-207479 (JP, A) (58) Field (Int. Cl. ⁷ , DB name) C09K 3/14 550 B24B 37/00 G11B 5/84

Claims (2)

(57) [Claims] 1. A dispersion medium comprising ethylene glycol,
A polishing composition for texturing a magnetic disk substrate, which is obtained by dispersing abrasive grains of diamond, silicon carbide, and aluminum oxide using propylene glycol or a mixture thereof. 2. The composition according to claim 1, wherein said abrasive grains occupy a ratio of 0.
2. The polishing composition for texturing a substrate for a magnetic disk according to claim 1, wherein the amount is from 002 to 50% by weight.