JPS5974605A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve S/N ratio by forming a rhombic deposition type magnetic layer which contains Co, Cr and O or Co, Ni, Cr and O as main components and Mg of a specific % of number of atoms on a supporting body. CONSTITUTION:A deposition equipment is evacuated by an exhausting system 9 and a vacuum chamber 8 is kept at a required degree of vacuum. A supporting body 5 of tape-shape made of polyethylene terephthalate is supplied by a pay-off roll 6 and supported by a cylindrical cooling can 1 and guided to a take-up roll 7. Co-Ni-Cr-Mg alloy or Co-Cr-Mg alloy is charged to an evaporating source 2. A mask 3 determines a minimum slant incident angle thetamin. Oxygen is taken into the magnetic layer by exposing the layer to an oxygen atmosphere after deposition is completed. A rhombic deposition type magnetic layer which contains Co, Cr and O or Co, Ni, Cr and O as main components and Mg of 0.05-3% of number of atoms is formed on the supporting body and improved S/N ratio is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method of forming ferromagnetic crystal columns obliquely with respect to the support by making a vapor flow obtained by heating and vaporizing a ferromagnetic material obliquely incident on the support in a vacuum atmosphere. The present invention relates to an improvement in a magnetic recording medium having a so-called obliquely deposited magnetic layer.

In recent years, with the increase in the amount of information, there has been a desire for the emergence of high-density magnetic recording media, and in particular, development of metal thin film type magnetic recording media is actively underway as an ideal high-density magnetic recording medium.

Film thinning techniques include various methods such as vacuum evaporation, ion blating, spackling, and wet plating, but in order to stably obtain a coercive force medium suitable for high-density recording, -Disclosed in No. 19,389,
The so-called oblique evaporation method is an excellent method.

The oblique evaporation method is used to deposit Co, Co-Ni in a vacuum atmosphere.
A vapor flow obtained by heating and evaporating a ferromagnetic material such as ferromagnetic material such as This is a vacuum evaporation method in which ferromagnetic crystal columns are formed obliquely to the support by making the light incident on the support at an angle of . As part of this oblique evaporation method, in addition to mere thermal evaporation, a so-called ion blating type oblique evaporation method is known, in which a part of the vapor flow is forcibly ionized and made to be incident obliquely on the support. There is. An itli layer formed by such an oblique evaporation method is called an oblique evaporation type magnetic layer.

The ferromagnetic material is usually Co or C.

An alloy material containing CO as a main component, such as a -Ni alloy, or an alloy composition in which an acid system is added thereto is used. However, these obliquely deposited magnetic layers still lack sufficient stability over time, which has been a major obstacle to their practical application. The present inventors have prepared Co, Co-Ni, Co-0, or Co-
By adding a small amount of Cr, etc. to Ni-0, etc., or by increasing the average density of the obliquely evaporated magnetic layer to a certain value or more, it is possible to create an obliquely evaporated magnetic layer with excellent stability over time and electromagnetic conversion characteristics. A magnetic recording medium with layers was proposed.

However, the composition and film structure of these obliquely deposited magnetic layers are not yet completely satisfactory in terms of S/N, and improvements such as reduction in noise have been desired.

The present invention was made in view of these circumstances,
The main object of the present invention is to provide a magnetic recording medium having an obliquely deposited magnetic layer that has excellent stability over time, low noise, and an improved SIN ratio.

The present inventors have conducted extensive research in order to improve the above-mentioned drawbacks, and as a result, by adding a small amount of Mg to Co-Cr-0 or Co-Ni-Cr-0 as the magnetic layer composition, The inventors have discovered that a magnetic recording medium with low noise and an excellent SIN ratio can be obtained, leading to the present invention. , The magnetic recording medium of the present invention has Co, Cr, O or C01Ni,%Cr,0 as the main component on the support, and 0.05 to 3
It is characterized by having an obliquely deposited magnetic layer containing an atomic coefficient of I\1g.

In the present invention, the support includes polyethylene terephthalate (hereinafter referred to as 1h),
Molecular materials such as polyimide, non-magnetic metal materials such as KL and Cu, or inorganic supports such as glass and ceramics can also be used. The shape, thickness, etc. of these supports are arbitrarily selected depending on the intended use.

The magnetic layer composition in the present invention is Co, Cr, Ol or
CO1 CO thread alloy composition mainly composed of Ni, Cr, 0.05 to 3 atomic percent (hereinafter referred to as at% for simplicity)
In addition, an appropriate amount of Cr and Δ4g of 0 and 0.05 to 3 at % are added to the alloy composition containing 0 to 25 at % of Ni with respect to Co. Compositions containing the following are preferred.

The amount of Cr added depends on the stability over time of the magnetic layer and the magnetic properties (
It is determined by taking into consideration the coercive force and magnetic flux density. If the amount of Cr added is large, the stability over time will improve, but the magnetic flux density will decrease, and therefore the reproduction output will decrease. In the present invention, C
The amount of r added is preferably 1 to 20 at% on average, particularly preferably 2 to 8 at%.

The amount of acid added is determined by considering the magnetic properties and stability over time of the magnetic layer, but it is usually 3 to 30 a on average.
t% is preferred, particularly 10 to 20 at%. The distribution of oxygen in the magnetic layer does not necessarily have to be uniform. Further, even when viewed microscopically, it is not necessary to be uniformly contained in the columnar structure of the magnetic layer, and for example, it may be present in large quantities at the interface or surface of the columnar structure. In order to add an acid system into the magnetic layer, it is not necessarily necessary to use a vapor deposition material containing an acid system. All you have to do is mix in an acid type.

The amount of Mg added is preferably 0.05 to 3 at%.

The cause of the I'v1g addition effect has not yet been fully elucidated, but for example, it may be due to the effect of reducing the size of the columnar structure formed in the obliquely evaporated magnetic layer by /J. It is presumed that this has the effect of suppressing fluctuations in the size of the columnar structure.

Further, trace amounts of additives may be included within the range that does not impair the essential properties of the alloy composition of the present invention.

In the present invention, the film thickness of the obliquely evaporated magnetic layer is usually 5.
Approximately 00 to 5000A is desirable.

Further, the magnetic layer in the present invention may be a single layer, a multilayer structure of two or more layers, or a multilayer structure in combination with an intermediate layer and an underlayer.

Various desired surface treatments may be applied to the magnetic layer side or the support side in order to improve various practical properties.

The present invention will be explained in detail below with reference to drawings and examples.

The drawing is a schematic cross-sectional view of a preferred vapor deposition apparatus for manufacturing the magnetic recording medium of the present invention.

The vapor deposition apparatus shown in the drawing includes a vacuum chamber 8 whose interior is evacuated by an evacuation system 9 and maintained at a desired degree of vacuum, and a tape-shaped film fed from a tape feed roll 6 provided inside the vacuum chamber 8. A cylindrical cooling can 1 guides and supports the support 5 to the tape take-up roll 7, an evaporation source 2 is charged with an evaporation material that forms a magnetic layer on the support 5 by heating and evaporating it, and oblique evaporation is performed. The mask 3 defines a minimum oblique incidence angle θmin of a vapor flow of 51M.

In the vapor deposition apparatus configured as described above, the magnetic recording medium of the present invention is manufactured, for example, as follows.

The vacuum chamber 8 has an evaporation source 2 whose interior is maintained at an appropriate degree of vacuum by an evacuation system 9, and an evaporation material Co-Ni-C.
An r-Mg alloy or a Co-Cr-Mg alloy is charged. The evaporation material charged in the evaporation source 2 is heated by conventionally known heating means. As this heating means, for example, electron beam heating, induction heating, resistance heating, etc. can be used. The heated evaporation material melts and vaporizes, becomes a vapor flow, and rises toward the inside of the vacuum chamber 8 -F. When the tape delivery roll 6 is also delivered to the support 5 and guided to the cylindrical cooling can 1, the oblique incidence angle θ is at a high angle (about 9
The vapor flow of the evaporation material is evaporated while changing from 0 g2 ) to a low angle, and oblique evaporation is performed. When the minimum oblique incidence angle θ1 is passed, the evaporation ends and the tape is wound on the tape take-up roll 7. taken.

The magnetic layer thus provided on the support 5 is exposed to an oxygen atmosphere, and oxygen is taken into the magnetic layer.

Note that the apparatus and method for manufacturing the magnetic recording medium of the present invention are not necessarily limited to the above-described apparatus and method. Needless to say, it can also be used.

Next, the present invention will be explained by examples.

[Example 1] Using the oblique evaporation apparatus shown in the figure, the inside of the vacuum chamber was heated to 5.
It was evacuated to a pressure of 10'-5 Torr or less, and the Co-Ni-Cr-Mg alloy charged in the evaporation source was melted and evaporated by electron beam heating, and the temperature was selected to be around 45°. The transport speed of the support and the heating power to the evaporation source were controlled so that the film thickness was about 15mm.

Regarding the compositions of Co and N1, since their vapor pressures were approximately equal, they could be deposited on the support at a nearly constant composition ratio. As for Cr and Mg, since the difference in vapor pressure between Co and Ni is large, the heating power to the evaporation source was controlled so as to obtain a magnetic layer with a desired composition.

After the vapor deposition was completed, oxygen was incorporated into the magnetic layer by exposing it to an oxygen atmosphere. The composition of the obtained magnetic layer was analyzed using Auger electron analysis and a group X microanalyzer. The composition of Co, Ni, Cr, and O in this example was 71:8:6:15 in atomic ratio.

Further, the obtained magnetic recording medium was slit into a 172-inch wide tape shape, and the tape was assembled into a VH8 type small video cartridge, and the electromagnetic conversion characteristics were measured.

Table 1 shows the relationship between the amount of Mg added and the S/N of tape-shaped samples with good magnetostatic properties and aging properties selected from among the obtained tape-shaped samples with various compositions.

Table 1 (CO71-Nig-Cr6-Ots) M against K
g addition effect As is clear from Table 1 <0.05 to 3.2at
The addition of Mg improves the S/N by up to +2. The result was that the ldb was improved.

It has been found that the contributing factor to the improvement in S/l'J is that the reproduction output is almost the same and the noise is reduced.

Even with compositions other than the Co-Ni-Cr-0 compositions listed in Table 1, almost the same S/N improvement was obtained by adding 4g of l'.

[Example 2] Co-Cr-0-M was produced in the same manner as in Example 1 except that Co, Cr-Mg alloy was used as the vapor deposition material.
A magnetic layer consisting of G was prepared and evaluated. The composition of Co, Cr, and 0 in non-examples is 83:4 in atomic %.
It was 13. Among tape-shaped samples of various compositions obtained in the same manner as in Example 1, those with good magnetostatic properties and stability over time were selected, and the relationship between the amount of Mg added and S/N is shown in Table 2. .

Table 2 Effect of adding 4g to (CO83-Cr4-013) As is clear from Table 2, Mg
The addition improved the S/N ratio by a maximum of 1.5 db. In this example as well, the improvement in the S/N ratio was due to the reduction in noise.

In addition, M
Almost the same S/N improvement was obtained by adding g.

As is clear from the examples below, Co-Cr-0,
Or a magnetic layer made of Co-Ni-Cr-0 is coated with 0.
By adding 05 to 3 at% Mg, S/
It is clear that N is greatly improved, and the present invention
This will greatly contribute to the practical application of vapor-deposited tape.

[Brief explanation of drawings]

The drawing is a schematic cross-sectional view of a preferred vapor deposition apparatus used to manufacture the magnetic recording medium of the present invention. ■...Cylindrical cooling can 2...Steam
Source 3...Mass 4...
Steam flow 5...Support 6...
...Feeding roll 7...Take-up roll 8
...Vacuum tank 9...Vacuum exhaust system

Claims (1)

[Claims] Co, Cr, 0, Co, 1'Ji,
Cr, 'O as main components, Mg with a range of 0.05 to 3 atoms
A magnetic recording medium characterized by having an obliquely evaporated magnetic layer.