JPS5812135A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance both the vertical orientation properties and the surface properties of a coated film, by orienting particles by means of an AC magnetic field. CONSTITUTION:A coating material containing the hexagonal ferrite magnetic particles having the magnetization facilitating axes in the direction of the axis C is coated on a supporter 1, e.g., a polyethylene terephthalate film. Thus a film 2 is formed. This film is then traveled in an AC magnetic field 3, and the magnetic particles are oriented vetically so that the direction a magnetic field is perpendicular to the film surface.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic recording medium, and more particularly to a method for manufacturing a medium suitable for high-density magnetic recording by improving the orientation of particles in magnetic coating 1 [K]. .

Magnetic recording has so far been widely used for recording audio, digital, etc., but these recording methods use magnetization in the in-plane direction of the recording medium. However, in recent years, as the density of magnetic recording has been promoted, in recording using magnetization within the plane of the medium as described above, as the size of the minimum recording unit becomes smaller, the demagnetization effect within the medium increases. Therefore, it has become clear that there is a limit to increasing local density.

On the other hand, if a recording method is adopted that uses magnetization in the perpendicular direction of the recording medium, as the minimum recording unit becomes smaller, the demagnetizing effect described above will conversely become smaller. Recording becomes possible.

However, in the case where the above-mentioned perpendicular magnetization recording medium is prepared by applying a magnetic coating material to a support.

We need to reconsider point F.

First, the size of the magnetic particles in the magnetic paint must be equal to or smaller than the shortest wavelength or bit length of the wire, and the benefits become clear.

Since the minimum recording unit is a submicron domain, it is desirable that the magnetic particles have a size of submicron or less.

By the way, in general, such minimum-sized magnetic particles have a single domain structure, that is, they are easily magnetically coupled to each other in a round shape that becomes a minute magnet, and in order to obtain a uniform dispersion state in the binder, it is necessary to Need to pay attention.

Furthermore, even if uniform dispersion is achieved and the desired magnetic obstetric paint is obtained, inconveniences such as T1 occur when such a magnetic paint is coated on a support and oriented vertically.

That is, between the opposing magnetic poles of the N8 pole, a support coated with magnetic paint is run perpendicular to the direction of the magnetic field to orient the magnetic particles perpendicularly, and then the external magnetic field is turned off or the medium is removed from the magnetic field. If this occurs, magnetic poles remain on both sides of the coating, thereby creating a demagnetizing field in the opposite direction to the orienting magnetic field. Magnetic particles forming an angle with the direction of the demagnetizing field are subjected to a torque in the in-plane direction, so when the particles are allowed to rotate in the binder, their orientation after the orientation magnetic field is removed is significant.
Decrease.

As a countermeasure against these problems, there is a method of forced drying in an orienting magnetic field, but short-term forced drying is inconvenient because it roughens the surface of the coating film and leads to a decrease in the surface quality of the recording medium. arise.

The present invention has been made to eliminate the above-mentioned drawbacks, and uses an alternating current magnetic field to orient the particles, thereby improving the vertical alignment and surface properties of the coating film.

That is, the present invention relates to a method for manufacturing a magnetic recording medium obtained by vertically aligning a coating material having an axis of easy magnetization in the 0-axis direction and containing hexagonal ferrite magnetic particles in an alternating magnetic field.
, relates to a method of manufacturing a magnetic recording medium characterized in that an AC magnetic field is perpendicular to the coating film on the bottle lIc411.

By using this method, we.

It was possible to improve the vertical alignment of the magnetic particles, and also to achieve rounding without the need for forced drying in a short period of time, and to significantly improve the surface properties of the coating film. The present invention will be explained below with reference to actual examples.

Example First, a coprecipitate was obtained from an aqueous solution containing barium salt, iron salt, cobalt salt, and titanium salt, and then heated to obtain Oe-TI-substituted hexagonal paricum ferrite mold particles. These have crystal grains of less than 0.1s and plate-like properties.

The magnetic properties of this object are saturation magnetization @ Qemu/g @ coercive force 10000.5 Next, a magnetic paint was made using this magnetic powder and applied to a 15 μm thick polyethylene terephthalate film with Ik cloth. .

The film coated with the magnetic paint was vertically oriented by running in an alternating current magnetic field so that the direction of the magnetic field and the main surface of the film were perpendicular to each other, as shown in FIG. Thereafter, the coating film was dried to obtain a magnetic recording medium. The magnitude of the orientation magnetic field is 1000.2000
．． It was set to 30,000a.

Comparative Example 1 A film coated with magnetic paint prepared in exactly the same manner as in Example was run in a magnetic field with N8 poles facing each other perpendicular to the film to achieve vertical alignment. Afterwards, the film was dried outside the magnetic field and a magnetic tape was applied. I got a body. The orientation magnetic field at this time is 2000,
30000e, Comparative Example 2 A magnetic paint prepared in exactly the same manner as in Example was applied, and the film was run in a magnetic field with N8 poles orthogonal to the film facing each other to perform vertical alignment.

A magnetic recording medium is obtained by forcibly drying the magnetic recording medium in a short period of time while maintaining the magnetic field in that direction in a good condition.
The strength was set to be the same as that of

For each sample obtained above, the vertical O-square ratio was determined by measuring v vs. Shown in the table.

It can be seen from the table that the vertical squareness ratio and surface properties of the media obtained by the method of the present invention are improved in terms of deviation.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention. 1...Support, 2...Coating film, 3...AC magnetic field, 4
...Magnetic particles before orientation, 5...Magnetic particles after orientation. Agent: Patent attorney Noriyuki Chika (1 person) Figure 1

Claims (1)

[Claims] (1) A method for manufacturing a magnetic recording medium obtained by vertically aligning a paint containing hexagonal ferrite magnetic particles having an easy axis of magnetization in the C-axis direction in an alternating current magnetic field. (2. The method for manufacturing a magnetic recording medium according to item 1 of the patent claim, characterized in that the alternating current magnetic field is perpendicular to the coating film.