JPS5812130A - High-density magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To increase the recording density, by distributing the magnetization facilitating axis of magnetic particles having the uniaxial anisotropy at the area between a direction vertical to the face of a magnetic recording medium and the traveling direction of a magnetic head. CONSTITUTION:A magnetic recording medium 1 is obtained by coating a magnetic coating material containing uniaxial anisotropic magnetic particles of hexagonal ferrite, metallic cobalt, etc. on a supporter of a polyethylene terephthalate film, etc. The magnetic fields of different directions of application are successively applied within a plane including the lengthwise direction of the medium 1 and the direction vertical to the medium 1 with use of an orienting magnet 2 wile traveling the medium 1 toward an arrow 3. In this case, the magnetic field is lessened with each change of the direction of the applied magnetic field or the coated film is heated. Thus the viscosity is successively increased for the coated liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording medium suitable for non-explosion flJa high-density magnetic recording.

As is well known, in magnetic recording media used for video recording, combination data recording, audio recording, etc., in order to achieve larger recording capacity, smaller size, and lighter weight, the recording density is strongly increased. Conventionally, desired magnetic recording media include r-ν·, 0. .

Magnetic powders such as Orb@, which are made of magnetic powder tIk that grows needle-like shapes and are oriented in the indicated direction, have been widely used. In order to increase the recording density of this type of magnetic recording medium, the size of the magnetic particles is made finer. There are methods such as increasing the coercive force of the magnetic material and reducing the thickness of the coating film, and each method has been taken. However, if the magnetic particle size limit value is reduced by 1, the stability of the magnetic properties will decrease, if the coercive force is too large, it will be difficult to record one line on the magnetic head, and if the film thickness is made thinner, the reproduced signal will be output There are problems such as a decrease in the density, and it is thought that a limit has already been reached in increasing the density using this L method. On the other hand, perpendicular magnetization recording is being researched as another means of achieving high-density direct fIk, but the housing and recording medium used for this are limited to 0o-Orl, and film uniformity, durability, etc. In addition to the problem of blindness, the perpendicular magnetization writing method is contradictory to the conventional recording method, so there is no compatibility.11
This is a problem in putting the pipe into practical use.

The present inventors focused on the problems of the above-mentioned high-density recording media, and
As a result of various research studies, we found that using magnetic particles with -axis anisotropy tV, we distributed the magnetic particles between the direction perpendicular to the axis of easy magnetization tts body #1 and the running direction of the magnetic head. They discovered that it was possible to improve the recording density and developed the present invention.That is, in the present invention, a direction perpendicular to the medium 1liK and a direction in which the magnetic head runs (hereinafter referred to as the longitudinal direction of the medium) are used. This is a magnetic recording medium in which the easy axis of magnetization of magnetic particles is distributed in a plane parallel to a plane containing the magnetic particles. Further, it is characterized in that a magnetic material having a hexagonal crystal structure, such as hexagonal ferrite or metallic cobalt, is used as the magnetic particles. Furthermore, if the magnetic recording medium of the present invention is characterized by magnetic properties, the coercive force of the magnetization curve measured in any direction between the direction perpendicular to the medium II and the running direction of the magnetic head is ,
1.2 of coercive force measured in the direction perpendicular to the head running direction
This is indicated by more than double the amount. Here, more than 1 or 2 times [9
The reason for this is that if the value is less than this value, the easy axis distribution of the magnetic particles will not be sufficient, and the effect of improving the recording density, which is a feature of the present invention, will not be sufficiently achieved.

The above magnetic recording medium according to the present invention can be easily manufactured as follows. That is, minus-axis anisotropic magnetic material fine particles, for example, 0 to T1 substitution product fine particles of barium ferrite, 100
Resin as a binder, such as vinyl chloride, vinyl acetate copolymer, polyurethane resin, etc. 10 parts by weight
~40 parts by weight, as a dispersant, lecithin, etc., 0.5~
Mix and disperse about 200 parts by weight of a solvent such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, toluene, etc. using a dispersing machine such as a sand grinder, ball mill, or three-roll mill to form a paint. A magnetic composition is prepared. A curing agent such as an isocyanate is appropriately added to this composition, and the mixture is coated onto a holding substrate such as a polyethylene terephthalate film using a coating machine such as a reverse coater, gravure coater, or spin coater, and is coated in the longitudinal direction of the medium using an electromagnet or permanent magnet. Magnetic fields with different application directions are sequentially applied within a plane including a direction perpendicular to the . At this time, the magnetic field is weakened every time the applied magnetic field direction tf increases, or the viscosity of the applied coating liquid is increased by 1-*vc by heating the coating film.
In this way, 19, a magnetic recording medium is obtained in which the easy axis of magnetization of the magnetic particles is distributed within a required plane.

Next, examples of the present invention will be described.

Example O' of barium ferrite with an average diameter of 0.1 sya
Per 80 parts by weight of o e Ti-substituted fine particle powder, 10 parts by weight of vinyl chloride and vinyl acetate copolymer as a binder, 4 parts by weight of lecithin as a dispersant, 80 parts by weight of methyl isobutyl ketone and 80 parts by weight of toluene as a solvent. ,
80 parts by weight of Nakasanon was added to the cyclo, and a dispersion paint was prepared using a sand mill. To this coating material, a hardening agent of 10 weight m+t was added to a polyethylene terephthalate film ff1K, and after that, an in-plane orientation magnetic field of 2 KO, was applied to the film, and then, while heating the film, a magnetic field of 2 KO was applied in the perpendicular direction to the film fiJK. * was applied and drying was performed to produce a magnetic recording medium. When the magnetostatic measurement of this magnetic recording medium was carried out, it was found that the direction of application of the orientation magnetic field in the film 1 was TE, residual magnetization Br = 1100G - coercive force H
a = 10000・, as a result of demagnetizing field correction in the direction perpendicular to the film surface of the casing, Br-1000G, Hc = 9
It was 60'Oe.

On the other hand, in the 111 plane, B in the direction perpendicular to the direction of applying the alignment magnetic field.
According to the magnetic foot measurement results of 0 or more at r = 600G and Haz 7000s, the direction of application of the in-plane orientation magnetic field and the film surface are -
Br and Ha in the normal direction are large and Br and He in the direction perpendicular to these two directions are small.From this result, it can be seen that the axis of easy magnetization of the magnetic particles is distributed in a plane that includes the above two directions. .

Next, high-density recording was performed on this magnetic recording medium using a ferrite core and a magnetic head, by running the head in the direction of the Yamauchi alignment magnetic field, and the reproduction output tg was determined. The results are shown in Fig. 3. As a comparative example, the magnetic coating prepared above was coated with the magnetic paint (Br = 8000/Ha-8000-), which was dried without any release. Figure 1 VCL shows the results of the meeting at the same time.
It can be seen that the reproduction output of the recording medium according to the embodiment of the present invention is significantly different from the above in the high-density region. That is, record c
It can be seen that the recording density of tT11@ has significantly increased as above.The question of why cloth-covered magnetic recording media are suitable for high-density recording is an issue that must be fully researched and clarified in the future. However, the reasons that can be considered at the moment are: ■ Particles oriented perpendicular to the film surface are effective for high-density recording *t-processing Vc, and ■ Particles oriented in other directions are effective. With combination K, a current magnetization pattern is possible, and (1) particles with orientations that are not effective for magnetic recording media are reduced. I would like to point out three points.

[Brief explanation of drawings]

Figures 1 and 2 are magnet arrangement diagrams for the magnetization axis distribution of magnetic particles for manufacturing the magnetic recording medium of the present invention, and Figure 3 is an example of the construction of the magnetic recording medium of the present invention. FIG. 4 is a recording density-reproduction output characteristic curve diagram of a comparative example. 1... Magnetic recording medium, 2... Orienting magnet, 3... Medium running direction, 4...
Magnetic field direction.

Claims (1)

[Claims] (1) The magnetization axis of the magnetic particles is distributed within a plane [1i and parallel to the plane including the direction perpendicular to the medium fl:jl and the running direction of the magnetic head. A high-density magnetic recording medium characterized by t. (2. High-density magnetic recording medium characterized in that the magnetic particles in claim 1 are magnetic materials having a hexagonal crystal structure. (3) Claims In the description of claim 1, the high-density magnetic recording medium is characterized in that the magnetic particles are hexagonal ferrite. (4) In the description of claim 11!1!!!111, the magnetic particles are metal wire. A high-density magnetic recording medium made of cobalt-1 or an alloy thereof. (5) In the description of claim i! The coercive force of the magnetization am measured in any direction is 1 of the coercive force of the magnetization curve measured in the direction perpendicular to the head running direction within the medium plane.
, a high-density magnetic recording medium with t% moldiness of at least twice as much (6) After coating the magnetic paint on the support substrate, the application direction is different in the longitudinal direction of the medium and in the plane including the direction perpendicular to the medium. High-density magnetic recording #ll with magnetic field t* applied as t4I mold
I&body manufacturing method.