JPS6083224A - Manufacture of magnetic disk - Google Patents

Abstract

PURPOSE:To obtain a vertical magnetic film having the degree of orientation by coating a nonmagnetic substrate with magnetic paint obtained by kneading magnetic powder with a binder and a solvent, then applying a magnetic field at right angles to the substrate and rotating and oscillating the substrate with an ultrasonic wave, and drying the paint. CONSTITUTION:A pulley 2 and a disk support base 3 linked with it are installed between pole pieces 1 of electromagnets, and rotated by a belt 6 which connects the rotating shaft 5 of a motor 4 and pulley 2. The substrate 11 coated with a magnetic film is set on the disk support base 3 of a device, and rotated and oscillated with an ultrasonic wave while applied with a magnetic field to accelerate the orientation of ferrite. The rotation of the substrate accelerates the drying of the film and also make an effect upon the uniforming of the orientation of the ferrite effectively, which is effectively, specially, when a permanent magnet is used for magnetic field application.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method of manufacturing a magnetic disk using a perpendicular magnetic recording method.

(b) Background of the technology A magnetic disk is made of a non-magnetic material such as an aluminum alloy or synthetic resin, and a thin film (hereinafter referred to as a magnetic film) made of a magnetic recording medium is deposited on a disc-shaped substrate approximately 2 mm thick. It consists of formed things.

By holding the magnetic head with a small gap between the magnetic film and the magnetic disk while the magnetic disk is rotating at high speed, information can be recorded on a large number of concentric tracks, and the recorded information can also be reproduced. be exposed.

Conventionally, magnetic iron oxide powder, such as 3
, iron dioxide (r-Fe20g) and nickel/cobalt (
Magnetic alloy films such as Ni-co) and cobalt-chromium (co-Cr) were used, and magnetic recording was performed by a horizontal magnetic recording method. However, in response to the increase in recording density, perpendicular magnetic recording systems have been developed and are being put into practical use.

(c) Conventional technology and problems When recording information on tracks provided on a magnetic substrate, the perpendicular recording method can significantly increase the recording density when compared with the horizontal recording method, and has excellent recording power and formula. I can say that.

The reason for this can be thought of as being equivalent to arranging permanent magnets with an exposed length along a track when recording digital information; in this case, the magnitude of the demagnetizing field of a unit magnet is In the case of the perpendicular recording method, the magnetization of the magnets is arranged parallel to the substrate surface, so the demagnetizing field is strengthened by the external magnetic field from the magnets on both sides, whereas in the case of the perpendicular recording method, it is weakened. There is an advantage to that. In addition, when shortening the unit length of the permanent magnet, in order to keep the ζ demagnetizing field value constant, in the case of horizontal recording, the film thickness must be thinned and the coercive force (H
e), but in the case of perpendicular recording, the demagnetizing field decreases as the unit length becomes shorter.

From these points of view, as the recording density increases, the perpendicular recording method is advantageous, but until now no suitable magnetic recording medium or method in which magnetization is maintained perpendicular to the medium surface ζ has been developed. However, recently, a technology has been developed to magnetize co-Cr, barium (Ba) ferrite, etc. perpendicularly to the substrate, and this technology is being put into practical use. In other words, in the case of alloy films such as co-Cr and cobalt-vanadium (co-■), thin films are formed by sputtering or vacuum evaporation, and in the case of metal films such as Co, the temperature and current density of the plating solution are By appropriately selecting , it has become possible to obtain a magnetic film in which the long axes of the acicular particles are aligned perpendicularly to the film surface.

On the other hand, in the case of Ba ferrite, powder with a particle size of 0.1 [μm] or less is mixed with a binder or solvent to make a magnetic paint, which is applied to a substrate to form a magnetic thin film, which is then oriented in a magnetic field. A method of drying was developed.

Although various methods have been developed and used in this way,
The magnetic film coating method is also used in the conventional horizontal recording system, and is considered to be the most suitable method for mass production.

However, a technique for obtaining a sufficiently vertically oriented magnetic film using this method has not yet been established.

(d) Object of the Invention An object of the present invention is to provide a method for obtaining a perpendicular magnetic film with a good degree of orientation using a method of applying a Ba ferrite magnetic paint.

(e) Structure of the Invention The purpose of the present invention is to apply a magnetic paint obtained by kneading magnetic powder with a binder and a solvent onto a non-magnetic substrate, apply a magnetic field perpendicularly to the substrate, and apply rotation and ultrasonic vibration to the substrate. This can be achieved by a method of manufacturing a magnetic disk characterized by applying and drying the magnetic disk.

(f) Embodiments of the Invention In the present invention, since simply applying a magnetic field after applying a magnetic paint is insufficient to achieve orientation, rotation and vibration are applied to uniformize and promote orientation.

The composition of Ba ferrite is represented by the molecular formula of B aF e12 oIJ, and the crystal is flat, the plate diameter is sufficiently larger than the plate thickness, and the magnetization direction is perpendicular to the plate surface.

Therefore, if an environment that facilitates orientation is provided after coating, most of the fine particles should be able to be oriented in the direction of the magnetic field. Therefore, after applying the magnetic paint, immediately place it between the balls of a magnet and when applying a magnetic field, apply ultrasonic vibration to the support holding the substrate and rotate the substrate to promote and equalize the orientation. We aim to

Here, the application of ultrasonic vibration is to help orient the Ba ferrite microcrystals in the direction of the magnetic field, and the rotation is to make the magnetic field distribution uniform, and at the same time, drying is promoted.

The figure shows an example of the configuration for carrying out the present invention, and the method for producing magnetic paint and the configuration of the apparatus will be explained as follows. A synthetic resin such as epoxy resin or acrylic resin is added as a binder to Ba ferrite magnetic powder with a particle size of 1 [μm] or less, and a solvent such as toluene, xylene, or cellosolve acetate is added as a solvent, and these are placed in a ball mill and thoroughly kneaded. A magnetic coating material is prepared, and then a magnetic film with a thickness of approximately 2 [μm] is obtained by distributing this onto a substrate made of an aluminum alloy using a spin cord method.

Next, the substrate coated with the magnetic film is subjected to orientation of Ba ferrite and drying of the coating using an orientation apparatus shown in the figure.

That is, in the device of this embodiment, the quasi-magnetic pole bee 21
Between the pulley 2 and the disk support 3 connected to it
It is configured to rotate from a belt 6ζ connecting the rotating shaft 5 of the motor 4 and the pulley 2.

Further, there is a rotation shaft 7 in the center of the pulley 2 and the disk support base 3, which is positioned perpendicularly to the quasi-magnetic pole piece 1 by a pivot bearing 8 and rotated.

Further, an ultrasonic vibrator 9 is provided on the lower side of the pulley 2 and is connected to a lower pivot bearing 8'.
The pivot bearing 8' is connected to the pivot bearing 8', and is configured to apply a vibration of 20 to 40 [t] to the pivot bearing 8', through which vibration is applied to the rotating shaft 7.

The substrate 11 coated with the magnetic film is set on the disk support 3 of such an apparatus, and the orientation of the Ba ferrite is promoted by applying rotation and ultrasonic vibration while applying a magnetic field.

In order to speed up the drying process, it is effective to heat the substrate 11 to 70 to 80° C. by infrared heating or by blowing hot air, which was conventionally done for about 5 minutes. Natural drying time can be shortened to less than 1 minute.

Next, rotation of the substrate helps dry the coating film and is effective in making the orientation of the Ba ferrite uniform, and this is particularly effective when the magnetic field is applied using a permanent magnet. For example, when using a permanent magnet of 30001:Oe as an example, there is a change of about 300 [Oe] depending on the position, which tends to cause non-uniform orientation of Ba ferrite, but rotation makes it possible to apply a uniform magnetic field. It becomes possible.

In this way, by applying vibration in addition to the conventional magnetic field application and rotating the substrate, it is possible to obtain a magnetic film that is uniform and has a good degree of orientation.

(g) Effects of the Invention The present invention was made to solve the problem that when applying a magnetic paint to make a magnetic film for perpendicular magnetic recording, the orientation is insufficient and it takes a long time to dry using the conventional method. Therefore, by carrying out the present invention, the object is achieved and it becomes possible to manufacture a magnetic film having a uniform degree of orientation.

[Brief explanation of the drawing]

The figure is a front view showing the configuration of an alignment device for implementing the present invention. In the figure, 1 is a magnet pole piece, 2 is a pulley,
3 is a disk support base, 4 is a motor, 6 is a belt, 7 is a rotating shaft, and 8.8' is a pivot bearing. 9 is an ultrasonic transducer, and 11 is a substrate.

Claims (1)

[Claims] A magnetic disk characterized in that a magnetic paint obtained by kneading magnetic powder with a binder or a solvent is applied onto a non-magnetic substrate, and then a magnetic field is applied perpendicularly to the substrate, and the substrate is dried by applying rotation and ultrasonic vibration. manufacturing method.