JPH0320814B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetic disk used for high-density magnetic recording, and particularly to a structure with high sliding strength and a method for manufacturing the same.

[Background of the invention]

FIG. 1 is a conceptual diagram of a magnetic disk device used as a storage device for electronic computers and the like.

In FIG. 1, a plurality of magnetic disks 3 are attached to a shaft 2 rotatably supported by a base 1, and the magnetic disks 3 are rotated at high speed via the shaft 2 by a driving means 4.

On the other hand, a magnetic head 7 is supported via a gimbal 6 on a carriage 5 which is slidably supported on the base 1.

The magnetic head 7 is moved in the radial direction of the magnetic disk 3 in response to a command from the computer main body (not shown), and records are written and read at a desired position on the magnetic disk 3.

Next, FIG. 2 is a sectional view of the magnetic disk 3. As shown in FIG.

In FIG. 2, the substrate 11 is a disk made of a non-magnetic material such as aluminum.

A magnetic film 12 made of a mixture of a binder and fine powder of a magnetic material is coated on both sides of the substrate 11.

In the floating head system that is commonly used in the above-mentioned magnetic disk devices, air currents generated on the surface of the magnetic disk 3 due to high-speed rotation create a small gap between the surface of the magnetic disk 3 and the magnetic head 7. is formed so that the magnetic head 7 does not come into contact with the surface of the magnetic disk.

However, for some reason, the magnetic head 7 may occasionally come into contact with the surface of the magnetic disk, and if this happens frequently, the magnetic film 1 on the surface of the magnetic disk
A sliding accident may occur where the material peels off.

If the magnetic film 12 peels off as described above, the information recorded on the magnetic disk will be lost.
This will be an extremely serious accident.

Conventionally, as a countermeasure against the above-mentioned sliding accidents, a method has been used in which fine alumina powder called a filler is mixed in the composition of the magnetic film 12 in addition to a magnetic material and a binder.

If hard fine alumina powder is mixed into the magnetic film as described above, when the magnetic head comes into contact with the magnetic film, it will hit the protrusions of the fine alumina powder. There is no direct contact with the parts, so peeling can be prevented.

However, when performing high-density recording, it is difficult to obtain good electromagnetic properties with a magnetic film coated with a mixture of a magnetic material, a binder, and a filler as described above.
Research and development is being conducted on the idea that a method of directly depositing a thin magnetic layer on top of the magnetic material can achieve good characteristics.

However, in the above-mentioned sputtering method, it is not possible to mix an alumina filler, so even if the electromagnetic properties are good, the sliding strength is low and it is not practical.

Furthermore, the minute gap between the magnetic disk 3 and the magnetic head 7, that is, the flying height of the magnetic head, needs to be made smaller in order to increase the recording density. Since the probability of an accident increases, it has been difficult to put into practical use magnetic disks manufactured by the sputtering method, which have low sliding strength.

Furthermore, in the conventional method of applying a mixture containing filler, it is difficult to set the height of the protrusions formed by the filler uniformly and precisely, so that the flying height of the magnetic head cannot be set very small.

[Purpose of the invention]

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for manufacturing a magnetic disk that enables high-density recording and has high sliding strength.

[Summary of the invention]

In order to achieve the above object, the method for manufacturing a magnetic disk of the present invention involves applying fine powder of a highly hard material onto a substrate, and pressing the fine powder between mirror-finished flat plates. By etching the substrate surface to a thickness less than the required spacing, a substrate with a large number of minute protrusions whose height from the substrate surface is less than the required spacing is created. A magnetic layer is attached to the surface. Note that the required spacing is the design value of the flying height of the magnetic head mentioned above.
This value is selected based on the required recording density, safety against sliding accidents, etc.

According to the above manufacturing method, the height of the protrusions on the substrate surface can be set uniformly and precisely, and the protrusions can be firmly formed on the substrate surface.

[Embodiments of the invention]

The present invention will be described in detail below based on Examples.

FIG. 3 is a process diagram showing the method for manufacturing a magnetic disk of the present invention.

First, in step 21, an aluminum disk to be used as a substrate is manufactured by cutting.

Next, in step 22, the surface of the aluminum disk is polished. The process up to this point is the same as the conventional one.

Next, in step 23, fine alumina powder is applied to the surface of the aluminum disk.

Specifically, fine alumina powder with a particle size of approximately 0.3 μm to 2 μm was selected in consideration of the required spacing, and as a result of coating, the number of particles per 1 cm ² was 100 to 2 μm.
A suspension of fine alumina powder in a liquid (for example, amyl acetate) containing a suitable binder (for example, nitrocellulose) is applied by spin coating so that about 1000 particles are distributed, and then dried.

Note that spin coating is a method in which the suspension is dripped onto an aluminum disk while it is being rotated, and the suspension is applied uniformly and thinly by centrifugal force.

Further, in the above example, fine alumina powder was used, but other materials may be used as long as they are highly hard and stable.

Next, in step 24, the aluminum disk coated with fine alumina powder is sandwiched between separately prepared stainless steel plates (other materials with high hardness can be used) with mirror-polished surfaces, and pressed with a high-pressure press. , alumina fine powder is embedded into the aluminum disk surface.

Next, in step 25, the surface of the aluminum disk is etched using chemicals or sputtering.

During this etching, only the soft aluminum is removed and the fine alumina powder remains intact.
A large number of minute protrusions are formed on the surface of the aluminum disk in the form of half-embedded alumina fine powder.

Also, the etching depth should be less than or equal to the required spacing.

Through the above steps, it is possible to form a large number of minute protrusions that are all uniform in height on the surface of the aluminum disk.

As the chemical solution for etching, for example, a solution of 300 g of red blood salt and 20 g of caustic potash dissolved in 1 part of water can be used.

Also, after etching, the process of thoroughly washing with water or alcohol and drying is the same as in normal etching.

Next, in step 26, a magnetic layer is attached to the surface of the aluminum disk on which the projections are formed.

In this case, if the magnetic layer is formed using a sputtering method, a magnetic layer with excellent electromagnetic properties can be obtained, but a conventional coating method can also be used.

Next, in step 27, a lubricant (for example, oil) is applied to reduce the impact force when the magnetic head comes into contact with the magnetic head.

In addition, when using the sputtering method in step 26,
The adhesion of the magnetic layer may be better if the substrate surface is an aluminum oxide film.

In such a case, a step 25' may be provided between steps 25 and 26 in which the surface of the aluminum disk after the projections are formed is oxidized or alumite-treated.

Next, FIG. 4 is a sectional view of a magnetic disk manufactured by the method of the present invention.

FIG. 4A shows a large number of minute protrusions 4 formed on the surface of the substrate (aluminum disk) 13 in step 25.

FIG. 4B is an enlarged sectional view of the vicinity of the substrate surface, and 15 indicates a magnetic layer.

Note that the actual thickness of the magnetic layer 15 is 0.1 μm or less, which is a very small value compared to the required spacing (slightly larger than the height of the protrusion).

In the magnetic disk described above, a large number of minute protrusions 14 are formed on the substrate surface, so even if the magnetic head comes into contact with it, it will only hit the tips of the protrusions and will not contact the magnetic layer. The magnetic layer will not peel off.

Even if the magnetic layer on the protrusions peels off when the magnetic head comes into contact with the protrusions, the area of the protrusions is extremely small compared to the total area of the substrate surface, so this is not a problem for magnetic disks used for recording and reproducing digital signals. It is not.

〔Effect of the invention〕

As explained above, since the magnetic disk manufactured by the method of the present invention uses a substrate on which minute projections are formed in advance, the magnetic layer can be directly attached thereon using the sputtering method. This improves electromagnetic properties and enables high-density recording.

Furthermore, since there is no fear that the magnetic head will come into direct contact with the magnetic layer due to the minute protrusions made of a highly hard material formed on the substrate surface, it has excellent durability against sliding accidents.

In addition, in the method for manufacturing a magnetic disk of the present invention, fine protrusions are formed by coating the substrate surface with fine powder of a highly hard material, pressing it with a flat plate to embed the fine powder, and then etching the substrate surface. Since the height of the protrusion is configured to be formed, the height of the protrusion can be made uniform and can be set precisely. Therefore, the required spacing value can be set small, and the recording density can be improved.

Furthermore, since minute protrusions can be firmly formed on the substrate surface, there are many effects such as improved durability against sliding accidents.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram of a magnetic disk device, Fig. 2 is a sectional view of an example of a conventional magnetic disk, Fig. 3 is a process diagram of an embodiment of the manufacturing method of the present invention, and Fig. 4 is a method of the present invention. FIG. 2 is a cross-sectional view of an example of a magnetic disk manufactured by. Explanation of symbols, 1...Base, 2...Axis, 3...
Magnetic disk, 4... Drive means, 5... Carriage, 6... Gimbal, 7... Magnetic head, 11...
...Substrate, 12...Magnetic film, 13...Substrate, 14...
...protrusion, 15...magnetic layer.

Claims (1)

[Claims] 1. Apply fine powder of a high-hardness substance onto a substrate, press it between mirror-finished flat plates to embed the fine powder into the substrate surface, and then shape the substrate surface as required. The feature is that by etching a thickness that is less than the spacing, a substrate with a large number of minute protrusions whose height from the substrate surface is less than the required spacing is created, and then a magnetic layer is attached to the substrate surface. A method for manufacturing a magnetic disk. 2 Apply fine alumina powder onto an aluminum disk, sandwich it between mirror-finished stainless steel plates, and press with a high-pressure press to embed the fine alumina powder into the surface of the aluminum disk. An aluminum disk having a large number of alumina fine powder protrusions with a height less than or equal to the required spacing is created by etching the aluminum disk to a thickness less than or equal to the required spacing using a chemical or a sputter. A method for manufacturing a magnetic disk according to claim 1, characterized in that a magnetic layer is attached to the surface. 3 The particle size of the above fine alumina powder is 0.3 μm to 2 μm.
A method for manufacturing a magnetic disk according to claim 2, characterized in that: