JPH11167715A - Production of magnetic disk substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic disk substrate capable of sufficiently dealing with the narrowing of a spacing between a head and a medium by the lower floating of the magnetic head with a recent trend toward higher density recording by making it possible to rapidly obtain the disk substrate having polishing quality of <=5 pieces of scratches of Ra<=5 Å, Rmax<=80 Å and depth >=50 Åwithin the plane and <=5 pieces of pits of a depth <=50 Åwithin the plane by the simple process. SOLUTION: This process for producing the magnetic disk substrate made of aluminum is characterized in that polishing is executed by using a colloidal polishing agent contg. 0.03 to 4.0 mol/l, more preferably 0.1 to 2.0 mol/l aluminum nitrate and silica particles of a grain size below 0.5 μm after processing to Ra=10 Å and Rmax=100 Å in a polishing stage after an Ni-P plating treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Ni-P for a high-capacity hard disk using an MR head or the like.
The present invention relates to a method of manufacturing a plated aluminum magnetic disk substrate.

[0002]

2. Description of the Related Art Usually, a magnetic disk substrate is blanked by punching a rolled aluminum alloy coil, and the blank is ground to remove scratches and undulations on the substrate to obtain a substrate. After finishing polishing, a magnetic film is formed by magnetic sputtering and overcoated to obtain a sputtering medium. In order to keep the surface roughness and flatness within the required ranges from this step, the non-woven organic polymer polishing cloth is used for the magnetic disk substrate in the grinding process performed after the (blank) Ni-P plating step. It has been performed by sandwiching the substrate between the attached polishing disks, supplying an abrasive having oxide particles such as alumina as abrasive grains to the polishing surface, and moving the abrasive while applying a constant pressure. In these conventional polishing methods,
The polished substrate has Ra = 7 to 15 ° and Rmax = 80 to 150 °.
Therefore, it was not possible to avoid the presence of several scratches having a depth of 80 to 150 mm and several pits having a depth of 100 mm or less on the polished surface.

[0003]

Generally, the recording density of a Ni-P plated aluminum magnetic disk substrate for a hard disk of a storage device such as a computer has been improved year by year. Demands have become more stringent, and the density and capacity have tended to increase. Therefore, it has become important for a magnetic disk substrate used in the substrate to have the required surface roughness and flatness. In particular, the realization of high-density recording is remarkably progressing in lowering the flying height by improving the head side, and the spacing between the head and the medium is becoming narrower. There is a demand for as little as possible. Specifically, a polishing quality is demanded in which Ra ≦ 5 °, Rmax ≦ 80 °, no scratches with a depth of 50 ° or more, and no pits with a depth of 50 ° or more. However, in the conventional polishing method, alumina, titania, zirconia and the like have been performed with a polishing solution using abrasive particles as abrasive grains, but these oxides are obtained by grinding and distributing a huge raw material lump. ,
At the stage of dispensing, it was not possible to prevent a small amount of large-sized particles from being mixed, and a scratch with a depth of 50 mm or more was generated due to the effect of the mixed particles.

When polishing is performed using silica particles in a suspended state, which are known fine and uniform particles, polishing takes a long time because the particles are small. When a chemical agent is added, silica gels, the uniformity of the silica particles is lost, and a surface with Ra ≦ 5 ° and Rmax ≦ 80 ° cannot be obtained.

[0005]

According to the present invention, in a polishing step after a Ni-P plating process in a manufacturing process of an aluminum magnetic disk substrate, Ra = 15 ° or less according to a conventional method.
max = 200 ° or less, preferably Ra = 10 ° or less, Rmax = 1
After processing to less than 000.0, 0.03 ~ 4.0mol / l, preferably
0.1-2.0 mol / l aluminum nitrate, or 0.03-2.0 mol / l,
Preferably contains 0.1-1.0 mol / l nitric acid and has a particle size of 0.5μ
The polishing is performed by using a colloidal abrasive containing silica particles of m or less, thereby solving the above-mentioned problem.

[0006]

Hereinafter, the present invention will be described in more detail. As described above, the present invention employs a conventional method,
Ra = 15 ° or less, Rmax = 200 ° or less, preferably Ra = 10 ° or less, using a 0.3 to 2.0 μm alumina abrasive
max = 100mm or less, 0.03-4.0mol / l,
Preferably 0.1 to 2.0 mol / l aluminum nitrate, or 0.03 to
Polishing using a colloidal abrasive containing 2.0 mol / l, preferably 0.1 to 1.0 mol / l nitric acid, and silica particles having a particle size of 0.5 μm or less. In other words, since only a colloidal abrasive containing silica particles requires a long time to obtain a predetermined surface roughness, first, a particle size of 0.3 to 0.3 is required.
The disk substrate is rounded using a 2.0 μm alumina abrasive
Processing is performed to a = 15 ° and Rmax = 200 ° or less, preferably Ra = 10 ° or less and Rmax = 100 ° or less. Thereafter, polishing is performed using a colloidal abrasive containing silica particles.
The silica particles used in the present invention are preferably a silica sol obtained by a known method for producing from a silicic acid aqueous solution, i.e., a particle size having a uniformity that cannot be obtained by pulverization and classification, 0.5 μm or less, Preferably
The final polishing is performed using spherical or oval spherical silica abrasive grains of 0.05 to 0.3 μm. In the abrasive used in this silica polishing step, 0.03 to 4.0 mol / l, preferably 0.1 to 2.0 mol / l aluminum nitrate, or 0.03 to 2.0 mol / l with the intention of preventing gelation and dramatically improving the polishing rate. l, preferably 0.1 to
Add 1.0 mol / l nitric acid. If the addition amount of aluminum nitrate or nitric acid is less than 0.03 mol / l, the effect of the addition is not sufficient, and conversely, aluminum nitrate exceeds 4.0 mol / l or nitric acid
If it exceeds 2.0 mol / l, the effect of addition will be rather deteriorated. In particular, when the addition amount of nitric acid exceeds 2.0 mol / l, a gel which impairs the roughness of the polished surface at the time of polishing is generated, which causes the generation of projections and pits.

Thus, according to the present invention, Ra ≦ 5 °, Rmax
≤80 mm, scratches with a depth of 50 mm or more, 5 or less in the plane,
A disk substrate having a polishing quality of 5 or less pits having a depth of 50 mm or less in a plane can be manufactured.

[0008]

EXAMPLE After turning a doughnut-shaped aluminum alloy blank (equivalent to 5086) having a diameter of 3.5 inches and a thickness of about 20 μm, it was subjected to electroless Ni-P plating with a thickness of about 20 μm, and then polished according to the present invention. processed. The surface roughness Ra of the substrate after Ni-P plating was 80 °, and this was processed to Ra = 22 ° and Rmax = 170 ° using an alumina abrasive having an abrasive grain size of 1.3 μm, and then further ground by another processing machine. Polished using an alumina abrasive having a particle size of 0.5 μm, Ra = 10 °, Rmax = 100 °
The final polishing was performed using the material processed to the above as a test material.
Abrasives used for final polishing have particle sizes of 0.1 μm and 0.6 μm
Table 1 shows the amount of aluminum nitric acid or nitric acid used for the purpose of preventing gelation and improving the polishing rate.
The test was performed by changing as shown in FIG. Table 1 shows the overall evaluation of Ra, Rmax, the presence or absence of scratches, pits, and protrusions, and the polishing rate on the obtained substrate surface. In addition, in the case of the scratch evaluation, × indicates the number of pieces / surface is 5 or more, and the depth is 8 nm or less.
Indicates 2 lines / surface and a depth of 4 nm or less. In the case of pit evaluation, × indicates 5 or more / surface, depth of 10 nm or less, ○ indicates 1 to 5 /
Surface, depth 2 to 10 nm, ◎ indicates that no generation was observed. In addition, the height of the projection is 1 height above the average line of the roughness curve by AFM.
In a convex portion (surface) having a length of not less than 00 ° and a cross-sectional length of 30 μm or less, foreign matter adhering to the surface with a strength enough to sufficiently break the head when the head collides with The evaluation means that the surface is convex, and the evaluation ◎ indicates that the number is one or less on each of the front and back surfaces of the ten substrates, the symbol 個 indicates that the number is one on each of the front and back surfaces of 2 to 9, and the symbol X indicates that the number is one or more per substrate. In the case of the evaluation of the polishing rate, × is 0.01 μm / min or less, and ○ is 0.01 to 0.05 μm / mi.
n and ◎ indicate 0.05 μm / min or more.

[0009]

[Table 1]

[0010]

According to the present invention as described above, Ra ≦ 5
Å, Rmax ≦ 80Å, 5 or less scratches with a depth of 50Å or more in the plane, and 5 or less pits with a depth of 50Å or less in the plane. As a result, a magnetic disk substrate can be obtained which can sufficiently cope with a decrease in the distance between the head and the medium due to the low flying height of the magnetic head accompanying the recent high-density recording.

Claims (7)

[Claims] In a polishing process after a Ni—P plating process in a manufacturing process of an aluminum magnetic disk substrate, Ra =
After processing to 15 ° or less and Rmax = 200 ° or less, 0.03 to 4.
A method for producing a magnetic disk substrate, comprising: polishing using a colloidal abrasive containing 0 mol / l of aluminum nitrate and silica particles having a particle size of 0.5 μm or less. 2. The method according to claim 1, wherein the content of aluminum nitrate is 0.1 to 2.0 mol / l. 3. A polishing process after a Ni—P plating process in a manufacturing process of an aluminum magnetic disk substrate, wherein Ra =
After processing to 15 ° or less and Rmax = 200 ° or less, 0.03 to 2.
A method for producing a magnetic disk substrate, comprising: polishing using a colloidal abrasive containing 0 mol / l nitric acid and silica particles having a particle size of 0.5 μm or less. 4. The method for producing a magnetic disk substrate according to claim 3, wherein the content of nitric acid is 0.1 to 1.0 mol / l. 5. The method of manufacturing a magnetic disk substrate according to claim 1, wherein after processing to Ra = 10 ° or less and Rmax = 100 ° or less, polishing is performed using the colloidal abrasive. 6. The method for manufacturing a magnetic disk substrate according to claim 1, wherein the silica particles are obtained by a method generated from a silicic acid aqueous solution. 7. The method for manufacturing a magnetic disk substrate according to claim 1, wherein said silica particles use spherical or oval spherical silica abrasive grains of 0.05 to 0.3 μm.