JPH01179221A - Production of perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To stably produce a recording medium having high orientability by coating a magnetic coating compd. on an underlying film, then impressing a magnetic field in the direction perpendicular to a substrate thereto before the coating is solidified by drying. CONSTITUTION:The underlying magnetic film which has the axis of easy magnetization in the direction perpendicular to the substrate surface and exhibits residual magnetization in the easy axis direction is previously formed on the nonmagnetic substrate. After the magnetic coating compd. is coated on this film, the magnetic field of about 1,500 gauss in the direction perpendicular to the substrate surface is impressed for about 2sec on the coating before the coating is solidified by drying. As a result, the magnetic powder in the magnetic coating compd. is magnetized in the direction perpendicular to the plate plane and the underlying magnetic film is magnetized in the direction perpendicular to the substrate surface; thereafter, the orientability is maintained by the residual magnetization of the underlying film. The recording medium having excellent values of 2.9-3.4 orientation ratio in the direction perpendicular to the substrate surface and 0.85-0.90 squareness ratio is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to perpendicular magnetic recording media! ! The present invention relates to an improvement in a manufacturing method, particularly a method for manufacturing a recording medium by applying a paint containing magnetic fine particles onto a substrate.

Conventional magnetic recording is generally based on a method using magnetization in the in-plane direction of a medium. However, 611 in this in-plane direction
In the recording method using the 3Q recording medium, if an attempt is made to increase the recording density, the demagnetizing field within the 3Q recording medium increases, making it difficult to achieve a higher recording density than a certain level.

In order to overcome such limitations in recording density, a perpendicular magnetic recording system using 6n in the irf direction perpendicular to the surface of the recording medium has been proposed in recent years. This perpendicular and parallel recording system has the characteristic that the demagnetizing field in the recording medium is reduced at high recording densities, and is essentially a recording system suitable for high-density recording.

How to record Kawamukai r11 1. (The recording medium used for is G.

-i! of Cr vapor deposited film, etc. l! There is a continuous film and a coating film in which hexagonal plate-shaped barium ferra, C1, fine particles, etc. are deposited in resin. 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 perpendicular magnetic recording medium with a flat film, the plate-like particles have an axis of easy magnetization in the direction perpendicular to the plate surface, and when coating
Use a material whose easy-to-cure axis is easily oriented perpendicular to the substrate surface. However, even though the stone powder is easily oriented, it is not possible to obtain sufficient orientation just by applying it normally.

As a method to increase the degree of orientation, there is a method of orienting in a magnetic field of a constant strength after coating (Japanese Patent Application Laid-Open No. 57-58243, Japanese Patent Application Laid-open No. 57-58246), or adjusting the viscosity of the paint during coating. A method of orienting by shear stress (Japanese Unexamined Patent Publication No. 57-58240) has been implemented or proposed.

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 only by the shear stress during coating, and the problem is extremely high. It is difficult to obtain high recording density, and the method of aligning in a magnetic field
After coating at high speed, it is necessary to hold it in a uniform magnetic field until it is dried and assimilated, which makes the device difficult to construct, large-scale and expensive, and it is even more difficult to apply a magnetic field.
Non-uniformity results in disordered orientation, resulting in a decrease in the degree of orientation,
There are many unstable factors such as causing noise generation.

As described above, the reality is that with conventional methods, it has been difficult to achieve both vertical alignment and stable productivity at a high level.

In view of the above-mentioned problems, the present invention stably produces a well-oriented vertically oriented coating with 1! ! It provides a method for creating.

Means for Solving the Problems In order to solve the above-mentioned problems, the method for producing a perpendicular magnetic recording medium of the present invention has an axis of easy magnetization in the direction perpendicular to the substrate surface, and Residual t in the direction of the axis
■Il shown below! ! After forming a magnetic film and applying a magnetic coating for forming a recording layer on the base magnetic film, a magnetic field is applied in a direction perpendicular to the substrate surface until drying and solidification.

According to the method described above, the present invention first applies a magnetic paint for forming a magnetic recording medium onto a base magnetic film formed on a substrate surface under high shear stress. At this time, the direction of the axis of easy magnetization (thickness direction of the plate-like fine particles) of the plate-shaped magnetic fine particles in the paint is oriented to some extent with respect to the substrate surface due to the shear stress. After this, before the coating film dries and solidifies and the magnetic powder becomes unable to rotate, a magnetic field perpendicular to the substrate surface is applied to the substrate coated with magnetic paint. The powder is turned into ζn in the direction perpendicular to the plate surface, and the underlying magnetic film on the substrate surface is turned into ζn in the direction perpendicular to the substrate surface. At this time, the magnetic flux density becomes quite high in the immediate vicinity of the underlying magnetic film. Therefore, the direction of the axis of easy magnetization of the magnetized plate-shaped magnetic fine particles in the paint (thickness direction of the plate-shaped fine particles) is
Because it is aligned in the direction perpendicular to the substrate surface by the magnetic field perpendicular to the substrate surface generated by the underlying magnetic film, it is less susceptible to disturbances in the magnetic field when it exits the applied magnetic field.
Since the magnetic field generated by the underlying magnetic film remains even after exiting the magnetic field, the orientation of the -degree oriented magnetic particles is maintained, and a magnetic recording layer with very good perpendicular alignment is formed. Become.

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

Example! The following components were prepared as a paint composition, put into a grind mill, and mixed 11 times to prepare a &1-based paint.

O barium ferrite/co-Tim conversion powder powder average particle size, plate diameter 0.108 m, plate ratio (plate diameter/4S, J
'7) + 2, coercive force 600.0e)...
200 parts ○ Vinyl chloride polymer ・・・・・・ 20 parts ○
Polyurethane: 20 parts x minutes 11: Agent (lecithin): 8 parts Meanwhile, on a polyimide heat-resistant film (15 μm thick), spatter was applied using a Co-Cr target. , a Go-Cr perpendicular magnetization magnetic film with a thickness of approximately 4000 was formed. The magnetic paint is coated on the perpendicularly magnetized magnetic film forming surface of the film-like substrate on which the perpendicularly magnetized magnetic film is formed using a blade coater with a blade and substrate surface distance of 35 μm and a blade thickness of 3 layers. After coating at a speed of about 10 m/min, immediately pass through the magnetic field so that a 6n field of about 1500 Gauss is applied for about 2 seconds while holding the substrate surface in a direction perpendicular to the magnetic field. After magnetizing the perpendicularly magnetized magnetic film and the applied Gfi coating, the coating film of Example 1 was obtained by drying and curing.

Example 2 The magnetic t5) blended into the C1l paint in Example 1 was mixed with barium ferrite/Co-T i 'IL exchange powder powder average particle size, plate diameter: 0.10 μm, plate ratio (plate diameter/
Plate W): 20, coercive cuff 00. Oe)・・・・・・20
Coating No. 11 of Example 2 was applied at 1:t, except that all other conditions were the same as in Example 1.

Comparative Example 1 The same material as in Example 1 was applied under the same conditions as in Example 1 on a polyester film with a thickness of 5 pm on which no vertical C11 magnetic film was formed, and a sample was prepared by applying a magnetic field and compared. A coating of Example 1 was obtained.

Comparative Example 2 I5B mp that does not form an chlorinated C1l film even after 1 shotu
The same %f as in Example 1 was added to the polyester film J- of l.
=i゛l as an example! 31 (1) was prepared without applying a magnetic field and /:!, lp of Comparative Example 2.
; got j.

Comparative Example 3 The same paint as in Example 2 was applied to the 15 μIn thick polyester fillo, 1-, which does not form a perpendicularly magnetized magnetic film.
A coating film of Comparative Example 3 was obtained by preparing a sample under the same conditions as above and applying a RIT field.

Comparative Example 4 15 μm f7. Example 2 The same paint as in Example 2 was applied on the polyester film of Example 2.
The coating film of Comparative Example 4 was obtained by coating under the same conditions as above and preparing a sample without applying a magnetic field.

In order to examine the particle orientation state of the obtained coating film, the coating film was isolated from the substrate. , II Ut, and the squareness ratio in the vertical direction (total/Ms) and the orientation ratio in the vertical direction and the in-plane direction when the Cnization hysteresis curve is corrected by a demagnetizing field and measured by a sample vibrating magnetization measuring device. The orientation state was evaluated from (Mr/Mr).

The squareness ratio and orientation ratio of these samples were as shown in Table 1.

Table 1 In Table 1, Example 1. Comparative example 1. Comparative Example 2 is a coating film made with the same paint with a plate ratio of 12 and 41, and a comparison of these three samples clearly shows that the example of the present invention has a higher degree of vertical orientation. .

Also, Example 2. Comparative example 3. Comparative Example 4 is a coating film prepared with the same paint using magnetic powder with a platelet ratio of 20, and the comparison of these three samples clearly shows that the example of the present invention has a higher degree of vertical orientation.

As can be seen from the above results, the example using the present invention has a larger orientation ratio in the direction perpendicular to the substrate surface and a larger squareness ratio than the comparative sample that does not use the present invention. It can be seen that the method for producing a perpendicular magnetic recording medium of the present invention is effective in obtaining a coating film with good orientation.

Effects of the Invention As described above, according to the present invention, the magnetic film 11Q with oriented grains can be obtained by simply applying an orienting magnetic field for a short time after applying the hypotonic paint, thereby simplifying the process. Become.

Therefore, it is very useful as a method for obtaining a recording medium with high orientation suitable for high-density recording! ! 1 construction method can be provided.

Claims (1)

[Claims] A magnetic paint in which magnetic fine particles having a plate-like shape and an axis of easy magnetization are dispersed in a direction perpendicular to the plate surface is applied to the substrate, and the magnetic fine particles are oriented in a direction perpendicular to the coating surface. A method for manufacturing a perpendicular magnetic recording medium having an easy axis of magnetization on a substrate surface, wherein the substrate surface has an easy axis of magnetization in advance in a direction perpendicular to the substrate surface, and exhibits residual magnetization in the direction of the easy axis of magnetization. Manufacturing a perpendicular magnetic recording medium characterized in that a magnetic field is applied in a direction perpendicular to a substrate surface after forming a base magnetic film and applying the magnetic paint on the base magnetic film until it is dried and solidified. Method.