JPS6134727A - Composite magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance the quality of a reproduction signal by forming the first magnetic layer consisting of a lengthwise recording medium on a substrate, and forming the second magnetic layer having an isotropic magnetic characteristic on the first layer to obtain a composite structure. CONSTITUTION:A coating soln. wherein acicular fine particles of porous Fe2O3 having 0.5mu length and 10/1 acicular ratio are dispersed in a binder is coated on a substrate while impressing a magnetic field oriented in the lengthwise direction in the surface, and successively a coating soln. wherein Co-coated porous Fe2O3 fine particles having 0.1mu length and 2/1 acicular ratio are dispersed is coated without impressing an oriented magnetic field. Then after drying and calendering, a surfae lubricating treatment is carried out. Then the coated substrate is cut in specified width to obtain a magnetic tape having a composite magnetic recording medium. The thicknesses of the first and the second layer are regulated respectively to 5.0mu and 0.5mu.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording medium used in magnetic recording bodies such as magnetic tapes and magnetic disks.

Improving the recording density in conventional magnetic recording devices is a constant challenge in the field. In the conventional longitudinal recording method, this has been achieved by improving the media properties (thinner layers, higher coercive force, higher residual magnetization, etc.) and improving the magnetic head (higher saturation magnetization, higher magnetic permeability, narrower gap length). Improvements have been made to date. However, on the other hand, attempts have also been made to achieve further improvements using recording methods different from those of conventional longitudinal recording media. One of these methods is to use an isotropic recording medium.

This is because conventional longitudinal recording media have a large acicular shape (for example, 1
: 10) Magnetic iron oxide acicular particles or magnetic metal particles connected in a cascade are oriented and applied in the longitudinal direction of the recording trunk, whereas isotropic media have small acicularization (usually 2 to 3 ) Magnetic iron oxide or metal particles are applied without an orienting magnetic field to create a magnetically isotropic magnetic media layer. By combining such an isotropic medium with a narrow gap length ring head, it is possible to achieve higher density recording than by combining a longitudinal recording medium with the same narrow gap head. (Figure 2) The reason for this is that the recording magnetic field generated within the medium by the ring head is vector-like.
In particular, near the medium surface in contact with the head, there is a considerable amount of magnetic field component perpendicular to the medium surface, but in isotropic media, magnetization orientation with respect to this vector magnetic field is possible. This is because a stable magnetization distribution can be achieved.

Problems to be Solved by the Invention Incidentally, recently, in consumer J@VTRs, recording has been performed using a deep recording method, and attempts have been made to improve image and audio quality. In this method, an image signal is recorded on the surface layer of the magnetic recording layer, and an audio signal is recorded on the deeper layer using respective heads (FIG. 3). However, since the medium conventionally used in this method was a single-layer longitudinal recording medium, the surface layer magnetization
Separation of deep magnetization is not sufficient, and further long-term recording will be required in the future.
In order to improve the quality of reproduced signals, there is a need for media with even better recording density characteristics.

In view of the need for a means to solve the problem, the inventor of the present invention made extensive studies and came up with the idea of using the above-mentioned isotropic medium. That is,
The method proposed by the present inventor is to form a composite structure in which a first magnetic layer made of a longitudinal recording medium is formed on a substrate, and a second magnetic layer made of an isotropic medium is formed thereon.

Of course, by adopting a structure with such a function, it is possible to obtain recording density characteristics that surpass those of conventional longitudinal recording media, and when this composite medium is applied to the deep recording method described above, the image signal is transferred to the second layer. Since the audio signal is mainly recorded on the first longitudinal medium layer of the isotropic medium layer, the separation of both signals is good, and characteristics that leave room for higher density can be obtained.

The present invention will be explained in detail below with reference to Examples.

Example On the substrate, holes Fe with a length of 0.5 μm and a needle ratio of 10:1 were formed.
A coating liquid containing 2O3 acicular fine particles dispersed in a binder is applied with a longitudinal in-plane orientation magnetic field and applied with X, followed by a CO deposition hole F with a length of 0.1 μm and an acicular ratio of 2:1. . 2
Another coating liquid in which 03 fine particles were dispersed was applied this time without applying an orienting magnetic field. Thereafter, it was subjected to a drying and calendering process, a surface lubrication treatment, and cut into a predetermined width to obtain a magnetic tape A having a composite magnetic recording medium according to the present invention. The thickness of the first layer and the second layer is 5.
They were 0 μm and 0.5 μm. For comparison, a longitudinal recording medium tape B (magnetic layer thickness: 5.0 μm) was also produced in which the second layer step was omitted and only the first layer was included. Two types of tape A,
B is the same narrow gear spring head (gap length 0.3μ)
When the combination recording density characteristics and output level were compared with m), as shown in FIG. 1, Tape A exhibited characteristics that exceeded the conventional longitudinal recording medium Tape B in both recording density and output level.

Also, when this tape was installed in a current HiFi VTH and the quality of the reproduced image and audio signal was compared, Tape A exceeded that of Tape B.
It was good.

In the above example, iron oxide fine particles with a small acicular ratio were used as the isotropic medium, but in addition to this, Fe.

It may be a ferromagnetic metal or alloy containing CO etc.
Further, dice-shaped or spherical iron oxide/metal alloy particles may be used. Furthermore, the longitudinal recording medium is not limited to rFf1203 acicular particles, but may also be bead-shaped metal alloy particles, co02 acicular particles, or the like.

The optimum thickness of the second isotropic medium layer is determined by the gap length of the magnetic head used, and a range of 1 to 2 is appropriate for the gap length.

Effects of the Invention As described above, a composite magnetic recording medium in which an isotropic medium layer is added as a second magnetic layer to the surface of a conventionally used longitudinal recording medium has a higher recording performance than a longitudinal recording medium. It has the advantage of improved density characteristics and output characteristics, and can be used as a higher-performance recording medium to support higher performance shared equipment in the future.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the recording density characteristics of the composite magnetic recording medium according to the present invention in comparison with conventional media, and FIG. 2 is a diagram showing the recording density characteristics of a conventionally known longitudinal recording medium and an isotropic recording medium. , FIG. 3 is a conceptual diagram for explaining the deep recording method in a VTR.

Claims (1)

[Claims] A composite magnetic recording medium characterized in that a first magnetic layer made of a longitudinal recording medium is formed on a substrate, and a second magnetic layer having isotropic magnetic properties is formed thereon.