JPH0444621A - Magnetic recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording medium suitable for short wavelength recording, etc., and in particular to magnetic recording media obtained by applying a paint containing magnetic fine particles onto a substrate. It's about the medium.

BACKGROUND OF THE INVENTION Magnetic recording has generally been based on a method that 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 increase the recording density, the demagnetizing field within the recording medium increases, making it difficult to achieve a higher recording density than a certain level.

In order to overcome the limitations of recording density, a perpendicular magnetic recording system has recently been proposed that uses magnetization in a direction perpendicular to the surface of the recording medium. This perpendicular magnetic recording system has a characteristic that the demagnetizing field in the recording medium is reduced at high recording densities, and can be said to be essentially a recording system suitable for high-density recording.

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

There are continuous films such as -Cr vapor deposited films, and coated films in which hexagonal plate-shaped barium ferrite fine particles are dispersed in resin. In particular, recently, coating film type perpendicular magnetic recording media have been attracting attention because of the practicality of the coating type, such as its cost advantages and 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 preferably oriented in the direction perpendicular to the substrate surface during coating. However, even though magnetic powder is easily oriented,
It is not possible to obtain sufficient orientation just by applying it normally. As methods to increase this degree of orientation, methods have been implemented or proposed, such as a method of orienting in a magnetic field of a constant strength after coating, or a method of adjusting the viscosity of the paint and causing orientation by shear core force during coating. It's coming.

Furthermore, in the current longitudinal recording system, recording and reproduction are performed using a combination of a ring head and a longitudinally oriented magnetic medium. Considering the magnetization pattern actually recorded on the medium, it can be said that ideally, a horseshoe-shaped recording mode is preferable in the short wavelength region. From this point of view, recent metal-coated tapes in which the magnetic powder in the surface layer is oriented at an angle to the substrate and alloy metal obliquely deposited magnetic recording media are expected to be used as high-density recording media. ing.

Problem to be Solved by the Invention However, when using the conventional method as described above, even if the viscosity of the paint is increased (even if the viscosity of the paint is increased, sufficient orientation cannot be obtained only by the shear core force during coating). Moreover, in order to orient perpendicular to the substrate in a magnetic field, the length of the magnetic field must be made as long as possible to achieve high orientation. However, if the magnetic recording medium is oriented in a similar manner, the surface quality will deteriorate.Furthermore, metal-deposited magnetic recording media still have many issues in terms of manufacturing costs, running stability, and long-term reliability. There is.

As described above, the conventional method has a problem in that it is difficult to achieve both anisotropy of the axis of easy magnetization and stable productivity at a high level.

The present invention solves the above-mentioned conventional problems, and aims to provide a magnetic recording medium that can stably produce a well-oriented anisotropic oriented coating film.

Means for Solving the Problems In order to solve the above problems, the magnetic recording medium of the present invention is a coated magnetic recording medium in which the magnetic layer is coated so that the axis of easy magnetization is within the range of 45 degrees to 90 degrees with respect to the substrate surface. It is composed of a recording medium.

Function: As described above, the magnetic paint for forming the magnetic recording layer is applied with high shear core force. 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 core force. After this, before the coating film dries and solidifies and the magnetic powder becomes unable to rotate, a magnetic field is applied to the substrate coated with this magnetic paint at an angle of 45 degrees or more and 90 degrees or less with respect to the substrate surface. When this is applied, the magnetic powder in the magnetic paint is magnetized in a direction of 45 degrees or more and 90 degrees or less with respect to the plate-like surface, forming a magnetic recording layer with very good orientation.

Examples Examples of the magnetic recording medium of the present invention will be described below.

Example 1 The following components were prepared as a paint composition, put into a grind mill, and mixed and dispersed to produce a magnetic paint.

○ Barium ferrite/Co-Nb-Zn substitute powder (average particle size 0.05 μm, plate ratio (plate diameter/plate thickness) 4, coercive force 8000e) -----1.200
Part O Polyvinyl chloride polymer ---20 parts Polyurethane ---20 parts Dispersant (lecithin) ---8 parts After applying the coating at a coating speed of approximately 10 m/min using a blade coater with a distance of 15 μm and a blade thickness of 15 μm and the substrate surface at a coating speed of approximately 10 m/min, immediately hold the coating so that the substrate surface faces at a 70 degree angle with the magnetic field. The applied magnetic paint was magnetized by passing through a magnetic field such that a magnetic field of about 4000 Gauss was applied, and then dried and cured to obtain the coating film of Example 1.

Example 2 The magnetic powder to be oriented in the magnetic paint in Example 1 was
0.05 μm, plate ratio (plate diameter/plate thickness) 3, coercive force 1.0
000e) ---------200 parts, hold it so that the substrate surface is at an angle of 75 degrees with the magnetic field, and add about 4
The applied magnetic paint was magnetized by passing it through a magnetic field such that a magnetic field of 0.000 Gauss was applied, and then dried and cured. All other conditions were the same as in Example 1. I got it.

Example 3 In the same manner as in Example 1, the orientation magnetic field was set at 60° with respect to the substrate surface.
Example 3 was prepared by passing the sample through a gap provided with an orientation magnet so as to have an angle of 100 degrees.

Example 4 In the same manner as in Example 3, the Sn-Mg substituted barium ferrite magnetic powder used in Example 2 was made into a paint, and an orienting magnet was set so that the orienting magnetic field was at an angle of 55 degrees with respect to the substrate surface. A magnetic coating film was prepared by passing through the provided gap, and was designated as Example 4.

Example 5 In the same manner as in Example 1, the orientation magnetic field was set at 90° with respect to the substrate surface.
Example 5 was prepared by passing the sample through a gap provided with an orientation magnet so as to have an angle of 100 degrees.

Comparative Example 1 The same paint as in Example 1 was applied under the same conditions as in Example 1.
Comparative Example 1
A coating film was obtained.

Comparative Example 2 A coating film of Comparative Example 2 was obtained by applying the same paint as in Example 1 under the same conditions as in Example 1 and preparing a sample without applying a magnetic field.

Comparative Example 3 The same paint as in Example 1 was applied under the same conditions as in Example 1, and the paint was passed through a gap between opposing magnets with different polarities arranged at an angle of 25 degrees with respect to the substrate surface. A coating of Example 3 was obtained.

In order to investigate the particle orientation state of the obtained coating film, the coating film was peeled off from the substrate and measured using a two-axis sample vibration type magnetization measuring device, and the angle showing the maximum residual magnetic flux density with respect to the applied magnetic field was determined. Ta.

The results are shown in Table 1 together with the three-dimensional surface properties of each sample. In addition, the magnetic properties of the examples and comparative examples were cut into 81 widths using a rotating cylinder drum tester at a relative speed of 3.8 m/s using a HiR Hendust head (gap length 0.20 μm, track width 20 μm). The output characteristics of the coating film were measured and evaluated. Further, as Comparative Example 4, a commercially available coated metal tape was measured and evaluated, and the output of this tape was set as OdB, and the values of each sample are also shown in Table 1.

From Table 1, it was found that in both Examples and Comparative Examples, an axis of easy magnetization existed in the angular direction of the magnetic field applied during coating. Further, from the results of the output characteristics, it is clear that the medium having an axis of easy magnetization in a specific direction as in each of the present examples exhibits a high output.

As can be seen from the above results, the example using the present invention has anisotropy in a certain direction with respect to the substrate surface, compared to the comparative sample that does not use this, and that direction is the direction of the ring head. Since this direction coincides with the direction in which demagnetization is difficult in recording and reproducing, it can be a magnetic recording medium that can achieve high output in a shorter wavelength region. Moreover, since the magnetic behavior similar to that of the metal vapor deposition type can be achieved with the conventional coated type, it can be seen that a magnetic recording medium that is mass-producible and highly stable and reliable can be obtained.

Table 1 (Part 1) Table (Part 2) Effects of the Invention As described above, according to the present invention, after applying the magnetic paint, it is only necessary to provide an orienting magnetic field having a predetermined angle with respect to the substrate. Since a magnetic coating film having magnetic properties similar to that of a vapor-deposited medium can be obtained, a recording medium having high anisotropy suitable for high-density recording can be provided. Therefore, as a coating-type magnetic recording medium, it is highly mass-producible and can satisfy high output characteristics comparable to metal vapor-deposited media while maintaining long-term stable reliability.

Claims (1)

[Claims] 1. Applying a magnetic paint having a plate-like shape and dispersing magnetic fine particles having an axis of easy magnetization in a direction perpendicular to the plate-like surface to a substrate, and orienting the magnetic fine particles. an anisotropic magnetic recording medium having the easy magnetization axis in a certain direction with respect to the coating surface, the easy magnetization axis having the easy magnetization axis in a direction of 45 degrees or more and 90 degrees or less with respect to the substrate surface on the substrate surface; A magnetic recording medium configured to have.