JPS5836411B2 - magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of magnetic recording media, and aims to provide an effective method for improving recording density in the audio and video fields, regardless of whether they are magnetic tapes or magnetic disks. be.

In recent years, there has been a remarkable increase in recording density in magnetic recording, and improvements are being made in both recording media and recording/reproducing systems.

One way to do this is to improve high-frequency characteristics by applying a two-layer coating.

This is a C
The basic idea was to similarly coat and dry a magnetic material with a higher coercive force than r-Fe203, such as rO2, to create a two-layer structure, but in order to stably obtain a long length using the coating and drying technique, the coating thickness was reduced to about 1 μm. The limit is to lower it to 4.5, and the improvement that can be obtained by adjusting the coercivity of the lower and upper layers, mutual adjustment of squareness ratio, packing factor, coating thickness, etc. 7 5 c
At a tape speed of rn/sec, the recording head gap is 5μ.
This is about 7 to 8 dB at a frequency of 10 KHz, and further improvement is expected in the field of shortening the recording wavelength, such as the video field.

The present invention has been made to satisfy such demands, and an example of the cross-sectional structure of a recording medium is shown in FIG.

FIG. 1 shows fine particles of, for example, an iron group element or an alloy thereof, and nonmagnetic fine particles, such as Si, coated and fixed together with a binder on the surface of a nonmagnetic base material 1 made of a polymer molded product or a nonmagnetic metal. 1 to 10μ, preferably 1 to 3
A coating-type magnetic layer 2 of μ is disposed, and a non-magnetic layer 3 made of the same material as the non-magnetic fine particles, that is, a layer made of Si, is formed on the magnetic layer 2 by vacuum evaporation, ion plating, sputtering, etc. This shows a magnetic recording medium in which a magnetic layer 4 made of the obtained ferromagnetic metal thin film with a thickness of at most 0.5 μm is disposed, and a protective layer 5 of an inorganic substance, an organic substance, etc. is further disposed on top of the magnetic layer 4 as required. .

The appropriate mixing ratio of the ferromagnetic particles and non-magnetic particles is 10 to 60% by weight (most preferably 10 to 20% by weight) of nonmagnetic particles, ferromagnetic particles + nonmagnetic particles.

As an example, a case of manufacturing by applying a vacuum evaporation method will be described using FIG. 2.

Cylindrical cooling cans 1 and 8 and evaporation sources 9 and 1 are placed inside the vacuum chamber 6.
0.11 are arranged facing each other.

12 is a winding shaft, 13 is a winding shaft, and the non-magnetic substrate 1 is passed through the roller 14 to the cylindrical cooling can 8,
7 from the winding shaft 13 to the winding shaft 12.

Although 15 indicates a slit, it is unnecessary if there is no need to maintain a pressure difference.

A space 1γ almost partitioned by the partition plate 16 and the cans 7 and 8
, 18, 19, and 21'l have a structure that can maintain a differential pressure state, but it is needless to say that the structure is not limited to this.

21, 22 are vacuum exhaust systems, 23, 24, 25 are heating sources,
26 is a variable leak valve, which has a structure that allows gas to be introduced as needed.

Note that 21 is an insulation introduction terminal. Evaporation source 9, io, i
Although the resistive heating method is shown in FIG. 1 as a simulation, any known method may be used in addition to the heating method using an electron beam.

The operation will be explained below.

A polyethylene terephthalate film (12μ thick) was used as the non-magnetic base material 1, and a film on which Fe fine particles and Si fine particles were coated and fixed to a thickness of 3 μm together with a binder was used as a new base material. The base material is moved and conveyed through a heating medium of 70° C. without operating the evaporation source, and uncured substances and hygroscopic gases from the coating layer are released to stabilize the base material.

This step is of course not essential, and can be omitted depending on the use of the binder.

Thereafter, for example, Si is evaporated by the evaporation source 10 and Co is evaporated by the evaporation source 9, thereby forming the Si layer 3 and the Co layer 4 on the base material 1.

Thereafter, the substrate is turned over, the evaporation source 11 is activated, and S t
02 protective layer 5 is formed.

Of course, the formation of the protective layer is not limited to vacuum deposition, and any method may be used as long as it forms a layer that is thinner than the coating method, has an effect on runnability, and has an anticorrosion effect.

Si layer 3: 0.05μ, Co layer 420. 05μ, Sin2 layer 5: Magnetic properties when formed on 0.05μ polyethylene terephthalate film (12μ thickness) are saturation magnetic flux density 14000CG), squareness ratio 100
%, and the coercive force was 720 [Oe].

These are Fe fine particles and non-magnetic fine particles with an average particle size of 300.
Add 15% by weight (based on Fe) of Si fine particles of X and apply and fix with 3μ of binder (packing factor 46%)
The layer was deposited on the magnetic layer (coercive force 5000e) under conditions to obtain the above layer.

4. 7 5 At a tape speed of CIrL/sec, recording with a recording head gap of 5μ is performed using a recording head with a frequency of 10KH.
z was recorded and compared.

It is 7 d better to form a Co layer than to form a coating layer only.
B It was expensive.

Depending on the combination, a co layer of 0.02 to 0.1μ was formed on the same ferromagnetic coating layer and compared, but the coercive force was 6.
5dB to 12dT3I in the range of 000e to 12000e
The effect of increasing v output was confirmed.

Note that for the nonmagnetic layer 3, Ti, AA, Sn, In
, Cu, Cr, and oxides of these non-magnetic metals, but no significant difference was found.

Furthermore, if the Co layer is not formed as a single layer but is formed to have a thickness of 0.09μ, for example, the thickness of the Co layer may be 0.03μ, and the non-magnetic layer described above may be formed with a thickness of 0.09μ.
The basic effect was the same even in the case where three layers were stacked with a thickness of 0.02 to 0.04 μm.

In all of the above-mentioned examples, commercially available γ-Fe2
Comparing with 03 coated tape and CrO2 tape, 14-2
An improvement of 0 dB was observed, and the improvement was 6 to 1 dB compared to the type with a two-layer coating layer5 or a type with improved high frequency characteristics.
An even higher output improvement of 2 dB was observed.

This is true in the video field as well as in the field of magnetic recording technology where recording wavelengths are being shortened.

As described above, the magnetic recording medium according to the present invention has a non-magnetic layer made of the same material as the non-magnetic fine particles mixed in the coat-type magnetic layer between the coat-type magnetic layer and the metal thin film-type magnetic layer. With this structure, the wear characteristics of the magnetic recording medium were further improved.

FIG. 3 shows the relationship between the amount of wear and the amount of Si fine particles added.

The figure uses a ferrite magnetic head and the tape speed is 4.
This is the variation characteristic of 10 samples at 75 cm/sec.

The above effect is due to an increase in the adhesion strength between both magnetic layers, and is of great value in the current system in which a magnetic head and a magnetic recording medium slide in contact with each other.

Conventionally, media have been seen that have a laminated structure of a coated magnetic layer and a metal thin film magnetic layer, but in this type of media, the adhesion between the magnetic layers is not sufficient, and the top magnetic layer peels off. However, in the present invention, the non-magnetic layer made of the same material as the non-magnetic fine particles in the coated magnetic layer turns into powder and further abrades the medium. The adhesive strength of the adhesive is increased, so there is no peeling, and wear caused by peeling can be prevented.

As described above, the magnetic recording medium according to the present invention has a feature of excellent wear resistance, and its industrial applicability is excellent.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an embodiment of a magnetic recording medium according to the present invention, FIG. 2 is a cross-sectional front view of an embodiment of an apparatus for manufacturing the magnetic recording medium, and FIG. 3 is a magnetic recording medium according to the present invention. FIG. 3 is a diagram showing wear characteristics of a medium. DESCRIPTION OF SYMBOLS 1...Nonmagnetic base material, 2...First magnetic layer, 3...Nonmagnetic layer, 4...Second magnetic layer, 5 ...protective layer.

Claims (1)

[Claims] 1. A first magnetic layer is formed by mixing ferromagnetic metal fine particles and nonmagnetic fine particles in a binder on the surface of a nonmagnetic base material such as a polymer molded product or a nonmagnetic metal, and the fourth forming a non-magnetic layer of the same material as the non-magnetic fine particles on the magnetic layer;
A magnetic recording medium characterized in that a ferromagnetic metal thin film is formed as a second magnetic layer on the nonmagnetic layer.