JPS60214420A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To attain recording/reproduction with a track width below a specific mum by arranging a ferromagnetic metallic thin film on a substrate as magnetic recording and arranging cracks of specific numbers per unit length mm. to an end face of the position regulating side. CONSTITUTION:A magnetic recording layer 3 is arranged on a substrate 2 and a magnetic recording medium 1 arranged with a lubricating layer and a back coat layer as required is used as a form of tape. When the medium is used as tape form, it is characterized by cracks 4, 5 arranged at both ends and when the tape position regulation side is toward the arrow A, it is required to provide >=10 cracks per mm., and the crack 5 at the other side is not specified especially and no crack is allowed. As the criterion of the number of cracks, the track width of <=10mum is an object and no tracking error is caused with the cracks of >=10 cracks/mm. in the range of the track pitch from 10mum to 3.5mum.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording medium whose magnetic recording layer is a ferromagnetic metal thin film suitable for high-density recording.

Conventional configurations and their problems In recent years, the density of magnetic recording has been significantly increased due to shorter wavelength recording and narrower tracks. In particular, remarkable progress has been made in increasing density using the helical scanning method using a rotating magnetic head. Recently, a new perpendicular recording method has been proposed that breaks the upper limit of the recording density of the conventional long recording method, and it is expected that even higher densities will be achieved. However, it is not possible to exceed optical recording in terms of areal recording density by simply shortening the wavelength, so we have no choice but to work on narrowing the track.Currently, however, we cannot improve the slit accuracy or use the slitting method to reduce tracking defects. This is occurring more frequently, and recording and reproducing with a track width of 10 μm is the practical limit, and improvements are desired.

OBJECTS OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a magnetic recording medium that enables recording and reproduction with a track width of 10 μm or less.

Structure of the Invention The present invention provides a ferromagnetic metal thin film arranged on a substrate as a magnetic recording device, and at least on the end face on the position regulation side, per unit length. l
) 102! This magnetic recording medium has cracks larger than F/wan and can be used in narrow tracks even after repeated use.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an enlarged sectional view of an example of the magnetic recording medium of the present invention. FIG. 2 is a schematic diagram of the magnetic recording layer of the magnetic recording medium of the present invention viewed from above.

In FIG. 1, a magnetic recording layer 3 is arranged on a substrate 2.
The magnetic recording medium 1 is used in the form of a tape and is provided with a lubricant layer and a back coat layer (none of which are shown) as required.

When used in tape form, it is characterized by having cracks 4 and 5 at both ends, as shown in the top view shown in Figure 2, and if the tape position regulation side is on the arrow A side in Figure 1. It is necessary that there are ten or more cracks 4 per 1 mm, and there is no particular limitation on the number of cracks 5 on the opposite side, and there may be no cracks at all.

Cracks 4 cannot be formed with strict regularity due to the processing method, but the angle with respect to the width direction aa' of the tape (indicated by θ in Figure 2) shows no directional dependence within the range of θ of ±600. I couldn't see it.

The critical value for the number of cracks was set at a track pitch of 10 μm or less because the goal was to reduce the track width to 10 μm or less.
It was confirmed through experiments from .mu.m to 3.5 .mu.m that no tracking error occurred in this range as long as the distance was 10 lines/rrvn or more, but the effect remained the same even when the distance was increased to 150 lines/rrvn. When the rate was less than 9 lines/ran, a 20% to 30% error occurred when repeated tracking experiments were performed 100 times.

The reason for this is not necessarily clear, but it is presumed that due to the presence of cracks, the rigidity of the microscopic region at the end does not become bimetallic, and the flexible followability of the polymer substrate tends to dominate.

Substrates that can be used in the present invention include polyesters such as polyethylene terephthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose diacetate and nitrocellulose, polycarbonate, polyvinyl chloride, polyamide, polyimide, etc.
It can also be used with an undercoat layer, underlayer, soft magnetic layer, etc.

The ferromagnetic metal thin film used in the present invention is Co or Fe.

Ni, Co-Fe, Co-Ni, Co-B,
Co-Cu, Co-Go.

Go-Mn, Co-Mg, Co-Mo, Co-p
t, Co-Ru.

Co-Rh, Co-5i, Co-8m, C
o-8n, Co-Gd.

Co-Ta, Co-V, Co-W, Co-Y, Co-
Zn, Co-Cr, Co-Ce, Co-Ti
, Co-Ni-Cr, etc. and their partial oxide films,
The direction of the axis of easy magnetization can be selected as appropriate depending on the purpose and application, and the manufacturing method can be selected from electron beam evaporation, sputtering, ion blasting, electroless plating, etc. You can choose.

The crack control of the present invention is preferably carried out when slitting to a predetermined width.

For example, when slitting with a shear cutter, you can adjust the lateral pressure of the two combined blades, the temperature of the blades, the shape of the blades, the relative speed of both blades, or in addition, apply ultrasonic vibration to the blades and adjust the frequency. In terms of reproducibility, it is more preferable to control the slit speed.

A more specific embodiment of the present invention will be described below.

On top of polyethylene terephthalate with a thickness of 11.5 μm, Co Ni
(N'i.19chi) was electron beam evaporated. Obtained G
o -N i-0 film is 0.15μm, coercive force 1000
(Oe).

The squareness ratio was 0.88, and the saturation magnetic flux density was 7400 [G].

On top of this, myristic acid dissolved in methyl ethyl ketone was applied and dried to a dry thickness of 50 mm.

Further, on the same substrate, a CoCr (20% Cr) perpendicular magnetization film was formed to a thickness of 0.19 μm by high frequency magnetron sputtering in an argon atmosphere at I x 10' Torr. The obtained Co--Cr film had a coercive force of 600 (Oe) in the vertical direction, 530 (Oe) in the in-plane direction, and a saturation magnetic flux density of 3760 (G).

Myristic acid was also applied onto this in the same manner as described above.

Cracks were made in the two types of ferromagnetic metal thin films described above when slitting them into a 5WrIn width tape.

Cracks are created by applying ultrasonic waves (55KHz to 300KHz) during slitting, and the number of cracks is determined by tape length 8.
Observations were made at 3 arbitrary locations at 0 m from the beginning, and the average value was representative.

These tapes are coated with a co-based amorphous alloy (
The tracking situation was evaluated using a helical scanning method using a rotating cylinder equipped with a head gap of 0.2 μm and a rack width of 10 μm. The table shows the number of passes that caused track misalignment.

The measurement environment was 33° C. and 86% RH.

The recording wavelength was kept constant at 0.6 μm.

In the table above, when the track pitch is 3.6 μm, track deviation is also observed in the case of the present invention, but this phenomenon occurs after 260 passes and is sufficiently practical.

Regarding Co-Cr, even at a recording wavelength o of 36 μm, 3
．． It was confirmed that recording and playback could be performed with a track pitch of 5 μm. The areal recording density at this time is what makes optical recording difficult.

As described above, according to this embodiment, by arranging ten or more cracks on the position regulating side, the tracking performance when narrowing the track is extremely good.

Note that the present invention must be distinguished from tapes with cracks throughout the entire area. This is because cracks that occur throughout the wavelength and track pitch regions targeted by the present invention will not cause noise and will make it impossible to record and reproduce at 0.36 .mu.m.times.3.5 .mu.m.

Therefore, it can be said that it is preferable to suppress cracks to within a length of 100 μm to the inside of the tape.

In this example, specific effects were shown for two types of samples, but it was confirmed that the combination of the above-mentioned materials constituting the present invention also had similar effects.

Effects of the Invention As described above, the present invention provides cracks of 10 $/am or more on at least the end face of the ferromagnetic metal thin film on the position regulating side, thereby allowing 250 cycles at a track pitch of 3.5 μm. It can be used repeatedly and has great practical effects in high-density magnetic recording.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of the magnetic recording medium of the present invention, and FIG. 2 is a top view of the magnetic recording layer of the present invention. 2...Substrate, 3...Magnetic recording layer, 4.
·····crack. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure luxury λ mouth

Claims (1)

[Claims] A ferromagnetic metal thin film is arranged on the substrate as a magnetic recording layer, and at least on the end face on the position regulation side, 10 pieces/rt per unit length.
A magnetic recording medium characterized by having cracks of vn or larger.