JPS61229229A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a surface protective layer which has excellent lubricity and wear resistance and exhibits an effect of improving running stability for a long period of time by forming a thin film of chromium carbide on the surface of a magnetic layer. CONSTITUTION:A thin magnetic metallic film 2 which is the magnetic layer and the thin film 3 consisting of chromium carbide are formed in this order on one surface of a non-magnetic substrate. The magnetic layer 2 is obtd. in the form of the thin film of a metal such as Fe or Ni or metallic compd. formed to about 0.04-2.0mum thickness by a vapor deposition or sputtering method on the substrate 1. The compsn. of the chromium carbide to constitute the thin film 3 consisting of the chromium carbide is not particularly limited.

Description

[Detailed Description of the Invention] 11 Momme The present invention relates to the improvement of a metal thin film type magnetic recording medium, and in particular, a protective layer (so-called top coat layer) on the surface of a metal magnetic thin film.
The present invention relates to a magnetic recording medium having improved wear resistance and long-term running stability.

11. Conventionally, so-called coated recording media having a magnetic layer in which ferromagnetic fine particles are dispersed in a polymeric binder have been widely used in magnetic recording media such as magnetic tapes and floppy disks. , in recent years Fe, Ni, Fe-Co,
Co-Ni, Co-Cr, Go-P, Mn-B
1. Fe-Co-B, Co-N1-P, Co
Deposit a thin film of metal or metal compound such as -V, Co-Re, Co-Pt.

Development of thin metal M-type magnetic recording media with higher recording densities, which are formed on non-magnetic supports by methods such as sputtering, is underway.

These magnetic recording media must satisfy magnetic performance such as high-density recording, exhibit smooth running stability with a small coefficient of friction, have excellent wear resistance, and maintain stable running over a long period of time. It is required to have characteristics such as environmental resistance so that it can exhibit stable performance even under environmental conditions.

In metal thin film magnetic recording media, the surface of the metal thin film that is the magnetic layer is left exposed.

Since the magnetic layer is easily damaged by sliding between the magnetic head and the recording medium, there is a strong demand for running stability, wear resistance, etc. by improving the lubricity between the head and the medium. This is because unless these characteristics are obtained, it is impossible to expect that the information recorded at high density in the magnetic layer can be stably maintained over a long period of time and reliably reproduced.

In order to improve the running stability of magnetic recording media, conventional methods include applying lubricants such as fluorine-based or silicone-based oils, surfactants, and lubricants to the surface of the magnetic layer, and applying linear saturated fatty acids or their esters. A method of vapor-depositing it to form a surface protective layer is being considered.

In these methods, it is not only difficult to uniformly mix and apply the coating agent, but also the formed layer of lubricant or fatty acid does not have sufficient durability as a protective layer for the magnetic layer, and its lubricating effect is reduced. Due to its tendency to gradually decrease, it has been difficult to obtain long-term reliable thin protective layers that maintain their lubricating effect over a long period of time.

1 to 1" An object of the present invention is to provide a magnetic recording medium having a surface protective layer that has excellent lubricity and wear resistance and at the same time exhibits the effect of improving running stability over a long period of time.

According to research conducted by the present inventors, it has been found that forming chromium carbide on the surface of the magnetic layer is effective for achieving the above-mentioned objective.

The magnetic recording medium of the present invention is based on this knowledge, and more specifically, it is characterized by forming a metal magnetic thin film and a chromium carbide thin film on a non-magnetic support in this order. be.

−Lightning The present invention will be explained in more detail below.

In the magnetic recording medium of the present invention, as shown in the drawing showing a partial cross-sectional configuration of an embodiment, a thin metal magnetic layer sI2 and a thin chromium carbide Pa3 are formed in this order on one surface of a non-magnetic support l. Become.

As the non-magnetic support l, polyester, polyimide,
A film made of plastic such as polyamide and having a thickness of about 5 to 1100 JL is preferably used, but glass or non-magnetic metal such as aluminum can also be used as necessary. Basically, the desired magnetic layer forming surface is formed. Any non-magnetic solid material that can be used can be used.

The magnetic layer 2 is made of Fe, Ni, etc. formed on the above-mentioned non-magnetic support l by a method such as vapor deposition or sputtering.
, Fe-Co, Co-Ni, C.

-Cr, Co-P, Mn-B1. Fe-Co-B,C
o-N1-P, Go-V, Go-Re.

It is obtained as a thin film of metal or metal compound such as Co--Pt, preferably having a thickness of about 0.04 to 2.0 m.

The composition of chromium carbide constituting the chromium carbide thin film 3 is not particularly limited; for example, Cr3C2, C
Those having compositions such as r7C, Cr23C@ are used.

The thickness of the chromium carbide thin layer 3 is preferably 40 to 300 mm, more preferably 50 to 300 mm. This is because if the chromium carbide film 3 is too thin, long-term durability cannot be obtained, and the protective layer On the other hand, if the chromium carbide thin 115I3 is too thick, the long-term running stability will be improved, but the spacing loss will increase and the reproduced signal output will decrease.

The chromium carbide layer 3 is formed by, for example, CVD (chemical vapor deposition) plasma CVD, high frequency sputtering, magnetron sputtering, ion blating, or the like. Chromium carbide itself is used as a vapor deposition source or sputtering source, or chromium carbide is used as a vapor deposition source or sputtering source and methane, ethane, or carbon monoxide is introduced into a vacuum atmosphere to form chromium carbide through a gas phase reaction. The method is also preferably used. The formation of the chromium carbide layer 3 can be carried out as a continuous process in the same vacuum chamber as the process of forming the metal magnetic thin film 2 (further intermediate layer if necessary) to improve productivity.

1. In the magnetic recording medium of the present invention, in order to improve the characteristics of the magnetic recording medium between the non-magnetic support l and the metal magnetic thin layer I2, Fe-Ni-based or Co-Z amorphous high permeability material is used.
An intermediate layer or other layer such as a soft magnetic film such as r-based, Fe-P-C-based, Co-5i-B-based, or a non-magnetic metal thin film such as Ti or Ge has a thickness of up to about 0.5 uLm, for example. It may be formed as necessary.

Furthermore, the magnetic recording medium of the present invention may take any form such as a disk, sheet, tape, or card as long as the magnetic protective layer is required to have wear resistance.

11 Ritsumeikan J As described above, according to the present invention, by forming a chromium carbide thin film on a metal magnetic thin film, it is possible to achieve excellent lubricity and wear resistance without impairing magnetic properties or productivity. A magnetic recording medium exhibiting long-term running stability can be obtained.

1-1 Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

East"L times"2 12ILm thick polyethylene terephthalate (PET)
) C on one side of the film by vapor deposition.

Thickness 0.2 with a composition of 80 atomic % Ni 20 atomic %
A final metal thin film was formed.

Furthermore, in a magnetron sputtering device with chromium carbide (composition Cr, C2) as a target, the inside of the vacuum chamber was once evacuated to 2.5X10-4 Pa or more, and then argon gas was introduced to make the sputtering pressure 0.3 Pa, and magnetron sputtering was performed. A chromium carbide thin film with a thickness of 150 mm was formed on the surface of the magnetic layer.

This was slit into a width of 8 mm to obtain a magnetic tape according to the present invention.

On the other hand, in the same manner as above, only a Co-Ni metal thin film with a thickness of 0.21 Lm was formed on a polyethylene terephthalate film with a thickness of 124 m, and the film was slit to a width of 8 mm.
It was made into a tape.

The above two types of tapes were tested for dynamic friction coefficient and running durability.

The coefficient of dynamic friction is measured at a temperature of 30°C and a relative humidity of 80% (
According to Euler's friction coefficient measurement method), the dynamic friction coefficient during the 100th reciprocation was further measured.

Running durability was measured as the still playback life in still mode of a commercially available VTR device. The time when the first reproduction output becomes 1/2 in the above-mentioned still mode was defined as the still reproduction life.

The results are shown in Table 1.

A metal thin film with a thickness of 0.5 pm and having a composition of 80 atomic % Co and 2 atomic % Cr2O was formed on one surface of an aramid film 10 pm thick by a sputtering method.

Furthermore, a chromium carbide layer having a thickness of 100 mm was formed by the same magnetron sputtering method as in Example 1 except that the sputtering pressure was 0.4 Pa, and the layer was slit to a width of 8 mm to obtain a magnetic tape according to the present invention. On the other hand, in the same way as above, a thickness of 0.5
A tape of Comparative Example 2 was obtained by forming only a 4 m thick Co--Cr metal thin film and slitting it into a width of 8 mm.

Regarding the above two types of tapes, the dynamic friction coefficient end and still playback life were measured in the same manner as in Example 1. The results are shown in Table 1.

Back "ul] On one side of a polyimide film with a thickness of 40ILm.

Permalloy Fe-Ni with a thickness of 0.5 Bm was made by vapor deposition method.
Co-
Cr (Co80 atomic%, Cr2O atomic%) I8! was formed.

Furthermore, a thickness of 300 mm was obtained by magnetron sputtering in the same manner as in Example 1 except that the sputtering pressure was 0.5 Pa.
Form a layer of human chromium carbide and further cut it into 150
A magnetic disk according to the present invention having a diameter of mm was obtained. On the other hand, Fe-N was applied to a polyimide film with a thickness of 404 m in the same manner as above.
An i film and a co-Cr film were formed and further cut into 15
The disk of Comparative Example 3 had a diameter of 0 mm.

The dynamic friction coefficients of the above two types of disks were measured in the same manner as in Example 1.

Running durability is measured at 1800 rpm and sampling frequency (luminance signal) in a recording/playback device dedicated to the perpendicular recording method.
The measurement was performed as the number of passes until the playback output of an image recorded at 7.16 MHz became 1/2 of the initial value.

The results are shown in Table 1.

As shown in Table 1, the coefficient of dynamic friction of the tape (Examples 1-2) or disk (Example 3) of the present invention with a chromium carbide layer is reduced to about 2/3 of that of each comparative example. Ta. Furthermore, the value of the dynamic friction coefficient during 100 reciprocating cycles hardly changed in Examples 1 to 3 compared to the initial and final value. On the other hand, in Comparative Examples 1 to 3, the dynamic friction coefficient road significantly increased after 100 reciprocations.

On the other hand, still regeneration life as running durability (Example 1-
2) and the number of running passes until the image output was halved (Example 3), the recording medium of the present invention showed significant improvement over the respective comparative examples.

[Brief explanation of the drawing]

The drawing is a partial cross-sectional view of an embodiment of the magnetic recording medium of the present invention. l...Nonmagnetic support, 2...Metal magnetic thin film, 3...
・Chromium carbide thin film.

Claims (1)

[Claims] A magnetic recording medium comprising a metal magnetic thin film and a chromium carbide thin film formed in this order on a nonmagnetic support.