JPS6251030A - Manufacture of magnetic disk - Google Patents

Abstract

PURPOSE:To improve the degree of orientation of a formed film with no deterioration of productivity by setting the relative speed at <=200rpm between the revolutions per minutes of an orientation magnet and the high revolutions per minutes for spin coating and performing the orientation of a magnetic field concurrently with the spin coating. CONSTITUTION:The relative speed is set at <=200rpm between the revolutions per minutes of an orientation magnet and the high revolutions per minutes for spin coating. Then the orientation of a magnetic field is carried out concurrently with the spin coating. For formation of a film, a disk substrate 11 held by a spindle 10 is revolved at a low speed, e.g., 80-350rpm and the magnetic coating material is supplied onto the substrate 11 through a coating nozzle 12 while seeking the surface of the substrate 11. The coating material spreads entirely on the surface of the substrate 11 with >=2mum thickness during the medium-speed revolutions. Then the substrate 11 is revolved at a high speed to get rid of the extra coating material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for manufacturing a magnetic disk, particularly in the formation of a coating film in the manufacturing process of a magnetic disk.

The present invention relates to a method of manufacturing a magnetic disk suitable for improving the degree of orientation of a coating film.

[Background of the invention]

To form a coating film on a magnetic disk, a magnetic coating film is formed on a disk substrate using a centrifugal coating method, etc., and in order to align the axis of easy magnetization of the magnetic material in one direction, magnetic field orientation ( (hereinafter simply referred to as orientation). To explain the above-mentioned centrifugal coating method, a magnetic paint mainly composed of magnetic particles, organic resin, and non-magnetic load-bearing particles is dropped onto a disk substrate rotating at a low speed, and then the coating is applied continuously or stepwise. Excessive magnetic paint on the disk substrate is shaken off by centrifugal force controlled by coating conditions determined by a combination of the rotation speed and rotation time of the disk substrate.

During such a conventional coating film forming process, important factors in obtaining a high degree of orientation in the orientation performed after the above-mentioned centrifugal coating process are: (i) drying rate and drying state of the coating film;
(11) Surrounding atmosphere, (iii) dynamic viscosity, (iv)
Many other parameters such as orientation magnetic field strength, (V) orientation time, etc. can be increased. Among these, the dry state and dynamic viscosity of the coating film are said to be the most important factors.

The above-mentioned magnetic field orientation can be divided into two methods: a method in which a magnetic material is coated on a disk substrate and then transported to another station for orientation, and a method in which the application and orientation are performed continuously in the same station. Considering the dry state and dynamic viscosity of the coating film mentioned above, the latter method is effective. As a method of this kind, Japanese Patent Application Laid-Open No. 58-222445
Publication No. This method allows coating and orientation to be performed continuously, and can also be performed without slowing down the high-speed rotation after spin coating, making it an effective method for improving the degree of orientation when aiming for thinner films. I can say that. However, since the orientation is started after performing spin coating to form the thickness of the coating film, there is a problem that the processing time becomes correspondingly longer. In addition, because the orientation is performed at high speed rotation after spin coating, the coating dries more rapidly than when orientation is performed at low speed rotation. There was no consideration given to productivity and the condition of the coating film on the side receiving orientation, such as the possibility of unbalance.

[Purpose of the invention]

An object of the present invention is to solve such conventional problems and to improve the degree of orientation of the formed coating film in forming a coating film on a magnetic disk without reducing productivity in manufacturing the magnetic disk. An object of the present invention is to provide a method for manufacturing a magnetic disk.

[Summary of the invention]

In order to achieve the above object, the method for manufacturing a magnetic disk of the present invention includes supporting a disk substrate with a spindle, rotating the disk substrate, dropping a magnetic material onto the substrate, and applying spin coating to increase the magnetic film thickness. A method for manufacturing a magnetic disk, which comprises determining the above-mentioned disk substrate, and rotating an alignment magnet provided on one or both sides of the disk substrate in the same direction as the substrate to perform magnetic field alignment and forming a coating film. The present invention is characterized in that the relative speed between the rotational speed of the orientation magnet and the high-speed coating rotational speed during spin coating is set within a range of 200 rPm, and the magnetic field orientation is performed simultaneously with the spin coating.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

First, the present invention will be explained in detail.

In general, almost all magnetic paints used for magnetic disks have a structure that allows thixotropic flow, and at high shear rates such as when spin coating the paint, the viscosity decreases and the flow improves. When the shear rate is low immediately after coating, the viscosity is high and exhibits stable behavior. Therefore, in order to improve the degree of orientation when forming a coating film on a magnetic disk, the dry state of the coating film and the dynamic viscosity must be adjusted. During spin coating, which is the most suitable method for spin coating, the orientation magnet and magnet base, which are coaxially attached to the disk substrate, are installed parallel to the disk substrate and rotated in the same direction as the rotation direction of the disk substrate. The orientation is performed at the same time as spin coating by setting the angle within the range of ±20 Orpm with respect to that of the disk substrate.

FIG. 1 is a schematic diagram of a coating film forming apparatus showing an embodiment of the present invention.

In FIG. 1, 10 is a spindle for rotating a disk substrate 11, 11 is a disk substrate to which a magnetic paint is applied, 30 is an orientation magnet base to which an orientation magnet 31 is attached, and 31 is for aligning the axis of easy magnetization of the magnetic material in one direction. Orientation magnet for.

32 is a timing belt that transmits the driving force from the magnet drive motor 33; 33 is a magnet drive motor that rotates the disk substrate attached to the spindle 10 and the orientation magnet 30 in synchronization; I have it.

In the state shown in FIG. 1, the application arm 13 is moved onto the disk substrate 11 by the application mechanism shown in FIG.

This figure shows a droplet (applying) of organic resin and non-magnetic load-bearing particles.

FIG. 2 is a diagram for explaining the coating mechanism shown in FIG. 1. Here, when applying the magnetic paint to the disk substrate 11, the spindle 10 is rotated at a low speed.

In FIG. 2, reference numeral 12 is a coating nozzle for ejecting magnetic material or the like to coat the disk substrate 11, and 13 is a coating arm that is attached to the coating nozzle 12 and moves over the disk substrate 11. These coating mechanisms are normally stored in the housing part (not shown) of the coating film forming apparatus shown in FIG. 1, and are moved onto the disk substrate 11 when dropping (coating) magnetic material (magnetic paint). It is now possible to do so.

FIG. 3 is a diagram showing a state in which magnetic paint is applied to the disk substrate 11 by the coating mechanism shown in FIG.

In this state, the disk substrate 11 is rotated at a medium speed.

Hereinafter, the process of forming a coating film will be explained in detail using FIGS. 1 to 3.

First, the disk substrate 11 held by the spindle IO is rotated at a low speed of approximately 80 to 350 rpm11, and the first
The coating arm 13 of the coating mechanism stored in the housing part (not shown) of the coating film forming apparatus shown in the figure is moved onto the disk substrate 11, and the coating nozzle 12 held by this coating arm 13 is moved onto the disk substrate 11. Drop the magnetic paint while seeking the top.

At this time, since the orientation magnet base 30 is isolated from the disk substrate 11, it is assumed that there is no influence of the orientation magnet 31 bonded to the orientation magnet base 30. Next, when the dripping of the magnetic paint is completed, the applicator arm 13 is retracted to the storage area (not shown).

When this evacuation is completed, the disk substrate 11 on which the magnetic paint has been applied as shown in FIG. 3 enters the stage of medium speed rotation. At this stage, the film has a thickness of 2μ1 or more and has spread over the entire surface of the disk substrate 11. Here, the medium speed rotation speed of the disk substrate 11 is approximately 400~
700 rpm was used. Next, at the same time that the spindle 10 enters the spin coating state (rotating the disk substrate 11 coated with magnetic paint at high speed to shake off excess paint), the magnet drive motor 33 is driven to rotate the orientation magnet 31. Fixed orientation magnet base 30
While rotating in the same direction as the spindle 10, the disk substrate 11 is brought close to a predetermined distance, and orientation is performed for a predetermined time. Here, the rotation speed No of the orientation magnet base 30 was set in advance to 1104 Orp, and the high speed rotation speed NH of the disk substrate 11 was set to 1100 rpi+.

Therefore, the relative rotation speed between the disk substrate 11 and the orientation magnet 31 is 60 rpm.6Also, the orientation method is N
, the distance between the orientation magnet 31 and the surface of the coating film on the disk substrate 11 was set to 2 mm due to the repulsive magnetic field of the S pole. The main components of the magnetic paint used in this prototype were γFe2O3 particles,
Alumina particles, pvB resin.

These include epoxy resins, phenolic resins, and cellosolve solvents.

FIG. 4 is a diagram showing the evaluation results of the degree of orientation according to the present invention. Here, a indicates the evaluation result according to the present invention, and b indicates the evaluation result according to the prior art.

As shown in Figure 4, the degree of orientation is evaluated using the ratio of the residual magnetic flux density Br on magnetic hysteresis to the saturation magnetic flux density Bs (referred to as the squareness ratio) Br/Bs, the coating film surface roughness, and the average center line roughness. ) Ra, the vertical axis shows the squareness ratio (Br/Bs), and the horizontal axis shows the coating film surface roughness Ra. As is clear from FIG. 4, when comparing this example with the conventional case where orientation was started 10 seconds after high-speed rotation (spin coating), both Br/Bs and Ra were improved. I know that there is.

As described above, in this example, in forming a coating film on a magnetic disk, spin coating, which is most suitable in terms of the drying state and dynamic viscosity of the coating film, and the oriented magnet base attached coaxially with the disk substrate are used. is installed parallel to the disk substrate and rotated in the same direction as the rotation direction of the disk substrate, making simultaneous orientation possible, thereby improving the degree of orientation of the coating film.

〔Effect of the invention〕

As explained above, according to the present invention, in forming a coating film on a magnetic disk, the degree of orientation of the coating film formed on the disk substrate can be improved without reducing productivity.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a coating film forming apparatus showing an embodiment of the present invention, FIG. 2 is a diagram for explaining the coating mechanism of FIG. 1,
FIG. 3 is a diagram showing a state in which a disk substrate onto which magnetic paint has been dropped is rotated at a medium speed, and FIG. 4 is a diagram showing evaluation results of the degree of orientation of a coating film formed according to the present invention. 10: Nissin spindle, 11: disk substrate, 12: coating nozzle, 13:! ! ! [Cloth arm, 20: Magnetic paint. 30: Orientation magnet base, 31: Orientation magnet,
32: Timing belt, 33: Magnet drive motor. Figure 1 Figure 2

Claims (1)

[Claims] (1) Support a disk substrate with a spindle, rotate the disk substrate, drop a magnetic material onto the substrate, determine the magnetic film thickness by spin coating, and place the disk substrate parallel to the disk substrate. In a method for manufacturing a magnetic disk in which a coating film is formed by rotating an orientation magnet provided on one or both sides of the substrate in the same direction as the substrate to perform magnetic field orientation, the number of rotations of the orientation magnet and the coating during spin coating are determined. A method for manufacturing a magnetic disk, characterized in that the relative speed of the high speed rotation is set within a range of 200 rpm, and the magnetic field orientation is performed simultaneously with the spin coating.