JPH01179218A - Production of perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To easily produce a perpendicularly oriented film which is well oriented by using a continuous film which has the axis of easy magnetization in the direction perpendicular to the surface of a substrate and exhibits residual magnetization in the easy axis direction as an underlying film. CONSTITUTION:The continuous Co-Cr film which has the axis of easy magnetization in the direction perpendicular to the substrate surface and exhibits the residual magnetization in the easy axis direction is previously formed as the underlying film on the nonmagnetic substrate. After this underlying is magnetized in the direction of the axis of easy magnetization, a magnetic coating compd. is coated thereon under the high shearing force exerted thereto. As a result, the direction of the axis of easy magnetization of the fine particles of the planar magnetic powder magnetized in the coating compd. is unified in the direction perpendicular to the substrate surface by the perpendicular magnetic field generated by the continuous underlying film; in addition, the orientability thereof is maintained by the residual magnetization of the underlying film. The recording film having the extremely good orientability is, therefore, produced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a perpendicular magnetic recording medium, and particularly to a method for manufacturing a recording medium by applying a paint containing magnetic fine particles onto a non-magnetic substrate. It is about improvement.

Conventional magnetic recording generally uses magnetization in the plane of a recording medium. However, with this recording method that uses magnetization in the in-plane direction, when attempting to achieve a high recording density, the demagnetizing field within the recording medium increases, making it difficult to achieve a high recording density above a certain level.

In order to overcome such limitations in recording density, a perpendicular magnetic recording method has been proposed in recent years that uses magnetization in a direction perpendicular to the surface of a recording medium. This perpendicular magnetic recording system has a characteristic that the higher the recording density, the closer the demagnetizing field in the recording medium becomes to zero, and it can be said that this is a recording system that naturally allows high recording densities.

The recording medium used in the perpendicular magnetic recording method is C.

-A continuous film such as a Cr vapor-deposited alloy film or hexagonal plate-shaped barium ferrite magnetic powder fine particles is mixed in a resin binder with a concentration of nI1.
There is a coating film. In particular, recently, coating film type perpendicular magnetic recording media have been attracting attention from the viewpoint of cost advantages and practicality such as durability.

In the case of a coated film type perpendicular magnetic recording medium, the plate-like particles have an axis of easy magnetization perpendicular to the plate surface, and the easy axis of magnetization is easily oriented perpendicular to the surface of the non-magnetic substrate during coating. . However, even though magnetism is easy to orient15), it is not possible to obtain sufficient orientation simply by coating.As a method for increasing this orientation,
Some methods have been proposed or implemented, such as a method of orienting the material in a magnetic field of a constant strength after coating, or a method of adjusting the viscosity of the coating material and orienting it by shearing force during coating.

Problems to be Solved by the Invention However, when using the above-mentioned method, even if the viscosity of the paint is increased, sufficient orientation cannot be obtained by shearing force alone during coating; It is difficult to obtain recording density, and in the method of orientation in a magnetic field, it is necessary to apply the coating at high speed and then maintain it in a uniform magnetic field until it dries and solidifies.The structure of the equipment is also difficult, and it is large and expensive. Not only is it difficult to apply a magnetic field, but if the magnetic field becomes non-uniform, the orientation will be disturbed, and there are many instability factors that can cause a decrease in the degree of orientation and noise generation.

As described above, with conventional methods, it is currently difficult to achieve both vertical alignment and stable productivity at a high level.

In view of the above problems, the present invention provides a method for stably manufacturing a well-oriented vertical alignment film.

Means for Solving the Problems In order to solve the above-mentioned problems, the method for manufacturing a perpendicular (ff) recording medium of the present invention is based on a continuous film having an axis of easy magnetization perpendicular to the surface of a non-magnetic substrate. After forming a base magnetic film and magnetizing it in the direction of the axis of easy magnetization, a magnetic material for forming a recording layer is coated on the base magnetic film.

Operation According to the present invention, a magnetic coating material for forming a magnetic recording layer is first applied with high shear force onto the base film 61i formed on the surface of a non-magnetic substrate by the method described above. At this time, plate-shaped tB magnetic powder particles in the paint! The direction of the easy nization axis (thickness direction of the plate-like fine particles) is oriented to some extent with respect to the nonmagnetic substrate surface by shearing force. At this time, the magnetic flux density becomes quite high in the immediate vicinity of the underlying magnetic film. For this reason, the direction of the axis of easy magnetization (thickness direction of the plate-like fine particles) of the magnetized plate-like magnetic powder particles in the paint is caused by the magnetic field perpendicular to the non-magnetic substrate surface generated by the continuous underlying film. Due to the large residual magnetization of the continuous underlayer film aligned in the perpendicular direction, the orientation of the -degree oriented magnetic powder particles is maintained, forming a magnetic recording layer with very good perpendicular orientation.

Examples Examples of the method for manufacturing a perpendicular magnetic recording medium of the present invention will be described below.

Example 1 The following composition was used as a magnetic paint! PJ was manufactured, put into a sand mill, and subjected to crosstalk fractionation to produce a magnetic paint.

Co Tll barium ferrite magnetic powder (average particle diameter 0.08 μm, plate ratio (particle diameter/particle thickness) 8. Coercive force 6400e) --100 parts vinyl chloride resin
・・・・・・ 10 parts polyurethane resin ・・
・・・・・・ 10 parts α-alumina ・・・・・・
・ 5th part carbon blank ・・・・・・
5 parts Methyl isobutyl ketone 99 parts Toluene 66 parts Cyclohexanone 33 parts On the other hand, on the polyimide heat-resistant film (13 μml!7), C
An o-Cr film was formed by vacuum evaporation to produce a Co-Cr perpendicular magnetization film with a thickness of about 2,500 mm. Furthermore, this co-
The CR film is passed through magnets with opposite polarities and magnetized in the direction perpendicular to the surface of the heat-resistant film. Then, the magnetic paint is applied onto the surface of the perpendicularly magnetized film on the heat-resistant film on which the perpendicularly magnetized film was prepared using an applicator. - After coating with a blade coater method with a gear of 30 μm at a coating speed of about 10 Il/min, the coating film of Example 1 was obtained by drying and curing.

Example 2 The magnetic powder of the magnetic paint used in Example 1 was made of Co-TiHA.
Barium ferrite magnetic powder (average particle size 0.07μm
, plate ratio (particle diameter/particle thickness) 5. Coercive force 6100e・
... 100 parts, and a coating film of Example 2 was obtained in the same manner as in Example 1 in all other respects.

Comparative Example 1 The magnetic paint used for the top coat layer in Example 1 was applied alone on a 13 μm'fl polyester film on which no perpendicular magnetization film was formed, and the film surface was immediately maintained in a direction perpendicular to the magnetic field. The coating film of Comparative Example 1 was obtained by passing through an applied magnetic field of about 10,000 e and magnetizing it.

Comparative Example 2 A Go-Cr film was formed under the same conditions as Example 1.
After magnetizing the film in the direction perpendicular to the film surface in the same manner as above, it was completely demagnetized using an AC demagnetizer, and the magnetic paint used for the top coat layer in Example 1 was applied to obtain a coating film of Comparative Example 2.

Comparative Example 3 A nickel-cobalt alloy was formed on a 13 μm thick polyester film by oblique evaporation, and magnetized in the direction perpendicular to the film surface in the same manner as in Example 1. A paint was applied to obtain a coating film of Comparative Example 3.

Comparative Example 4 The magnetic paint used for the top coat layer in Example 2 was applied, and immediately after being magnetized by passing it through an applied magnetic field of about 10,000 e while keeping the film surface perpendicular to the magnetic field, the magnetic paint used in Example 2 was applied. Comparative Example 4
A coating film was obtained.

In order to investigate the vertical alignment state of the coating films obtained above, the magnetic properties of each coating film were measured and evaluated using a vibrating sample magnetometer.

1) From the obtained magnetic hysteresis curve, the squareness ratio in the vertical direction (M r / M s ) and the ratio of the residual magnetic flux density in the vertical direction and the in-plane direction (B % / nr
) was determined and evaluated based on this.

Table 1 shows the squareness ratio and residual magnetic flux density ratio of each sample.

As is clear from the above results, the samples of the present invention have larger squareness ratios and residual magnetic flux density ratios (vertical orientation ratios) in the direction perpendicular to the nonmagnetic substrate surface than the comparative samples. It can be seen that the method of manufacturing a perpendicular magnetic recording medium of the present invention is extremely effective.

In the examples, Co-Tl-substituted barium ferrite was used for the overcoat layer, but it is not limited to this as long as it has a plate-like shape and an axis of easy magnetization in the direction perpendicular to the plate surface. ,Also, although a Co-0r perpendicularly magnetized film was used as the underlayer, it is possible to use a Co-0r perpendicularly magnetized film that has an easy axis of magnetization in the direction perpendicular to the nonmagnetic substrate surface and exhibits residual magnetization in the direction of the easy axis of magnetization.
As long as it is a t-film, it is not limited to this.

(Left below) Table 1 Effects of the Invention As described above, according to the present invention, it is possible to easily produce a perpendicular magnetic recording medium by simply depositing magnetic paint while utilizing the large perpendicular magnetization of the underlying magnetic continuous film. can.

Therefore, a highly oriented recording medium suitable for high-density recording can be easily provided.

Claims (1)

[Claims] A base magnetic film having an axis of easy magnetization in a direction perpendicular to the surface of the non-magnetic base is formed on a non-magnetic substrate in advance, and after magnetization in the direction of the easy axis, a plate-shaped magnetic film is formed on the base magnetic film. In a method for manufacturing a perpendicular magnetic recording medium, the base magnetic film is perpendicular to the surface of the non-magnetic substrate. 1. A method for manufacturing a perpendicular magnetic recording medium, comprising a continuous film having an axis of easy magnetization in the direction of the magnetization direction and exhibiting residual magnetization in the direction of the easy axis of magnetization.