JPS5966106A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent electromagnetic transducing characteristics by a method wherein a magnetic layer containing Co, Ni, Cr and oxygen each in a thermally determined quantity is formed on a nonmagnetic macromolecule film by a rhombic evaporation method. CONSTITUTION:A magnetic layer composed at least of Co, Ni, Cr and oxygen and formed by a trimetric evaporation method is provided on a nonmagnetic macromolecule film 13. In this magnetic layer, the average content of Cr is made to be 2-8 atom%, the average content of oxygen 5-25 atom% and the ratio in the average number of atoms of oxygen to Cr 2-10, and the distribution of the ratio in the number of atoms of oxygen to Cr in the direction of the thickness of the film is made to be larger as nearer to the nonmagnetic macromolecule film side. The minimum trimetric incidence angle theta min formed when the magnetic layer is evaporated by the rhombic evaporation method is preferably 30 to 70 degrees for practical use.

Description

Detailed Description of the Invention The present invention involves forming ferromagnetic crystal columns obliquely with respect to the support by making a vapor flow obtained by heating and vaporizing a ferromagnetic material in a vacuum atmosphere enter the support from an oblique direction. The present invention relates to improvements in magnetic recording media having so-called obliquely deposited magnetic layers.

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 the development of metal thin-film magnetic recording media as an ideal high-density magnetic recording medium is actively underway. Film thinning techniques include various methods such as vacuum evaporation, ion blating, sputtering, and wet plating, but in order to stably obtain a high coercive force medium suitable for high-density recording, The so-called oblique evaporation method disclosed in No. 19,389 is an excellent method. The oblique evaporation method is a process in which a vapor flow obtained by heating and evaporating a ferromagnetic material such as Co or Co-Ni in a vacuum atmosphere is applied to a non-magnetic support made of a polymer, etc., in the direction of the vapor flow and the support. This is a vacuum evaporation method in which ferromagnetic crystal columns are formed obliquely to the support by making the ferromagnetic crystal pillars incident on the support at an angle of usually 45 degrees or more with the normal line erected above. A magnetic layer formed by this oblique evaporation method is called an oblique evaporation type magnetic layer. In order to obtain a high coercive force of about 1.0000e using Co or Co-Ni material, the minimum oblique incidence angle θmin usually needs to be about 60 degrees or more.

However, when θmln is deposited under conditions of 60 degrees or higher, the rate at which the vapor flow is obstructed by the mask increases rapidly, the amount of vapor flow adhering to the support material decreases significantly, and the vapor deposition efficiency becomes extremely low. In addition, there are disadvantages such as a decrease in the deposition speed. As a method for improving these drawbacks, an oblique evaporation method in oxygen has been disclosed. The oblique evaporation method in oxygen is a method of performing oblique evaporation in an oxygen atmosphere, and by this method, it is possible to increase the coercive force, and therefore, it is possible to reduce θmin. That is, the oblique evaporation method in oxygen is an excellent method in terms of increasing the coercive force or decreasing the angle of incidence. However, Co or C produced by oblique evaporation method or oblique evaporation method in oxygen
The o-Ni obliquely deposited magnetic layer still has insufficient rust resistance, which has been a major obstacle to its practical use. In an attempt to improve the rust resistance of the magnetic layer, a method of adding Cr has been proposed. However, in order to obtain the desired rust resistance, this method requires the addition of a large amount of Cr, for example, 10 atomic percent (hereinafter referred to as at%), which causes a rapid decrease in magnetic flux density and a significant deterioration of electromagnetic conversion characteristics. It has the following disadvantages.

The inventors of the present invention aimed to develop a magnetic recording medium with excellent rust resistance and magnetic properties (we investigated the effect of adding Cr in detail and repeated experiments. As a result, Co.

He discovered that a magnetic recording medium with excellent rust resistance and magnetic properties could be obtained by containing Ni, Cr, and oxygen, and by combining Cr and oxygen within a certain range, and filed a patent application (September 1982). Patent application dated 30th Applicant: Fuji Photo Film Co., Ltd., Agent: Masashi Yanagida and others 1
given name).

After further intensive research, it was discovered that the distribution of oxygen relative to Cr along the thickness direction of the magnetic layer is extremely important for electromagnetic conversion characteristics, leading to the present invention.

The present invention provides a magnetic recording medium having a magnetic layer containing at least Co, Ni, Cr and oxygen on a non-magnetic polymer film by an oblique evaporation method, in which the average content of Cr is 2 to 8 at% and the content of oxygen is Average content is 5 to 25 at
%, average atomic ratio of oxygen to Cr is 2 to 10, Cr
The distribution in the film thickness direction of the average atomic ratio of oxygen to the non-magnetic polymer film is characterized in that the closer it is to the non-magnetic polymer film, the more uniform the distribution becomes.

The average content of Cr and oxygen in the present invention is the average value for the magnetic layer excluding the surface oxidized layer, and the atomic ratio of oxygen to Cr is the average value for the magnetic layer excluding the surface oxidized layer. It is.

The magnetic layer of the magnetic recording medium of the present invention is made of Co and Ni.

Elements other than Cr and oxygen may be contained within a range that does not impair desired characteristics. In addition, the magnetic layer is a single layer,
It may be a multilayer structure of two or more layers or a combination of an intermediate layer and a base layer. Furthermore, in order to further improve practical performance, various treatments may be applied to the magnetic layer side and the non-magnetic polymer film side.

The magnetic layer of the magnetic recording medium of the present invention is formed by an oblique evaporation method, and the minimum oblique incidence angle θmin during evaporation is practically 3.
Preferably it is between 0 degrees and 70 degrees.

Hereinafter, the present invention will be explained in detail with reference to drawings and examples.

FIG. 1 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 figure includes a vapor deposition chamber 11 whose interior is evacuated by a vacuum pump 12 and maintained at a desired degree of vacuum, and a tape-shaped non-woven fabric fed out from a tape delivery roll 6 provided inside the vapor deposition chamber 11. a cooling can 8 that guides and supports the magnetic polymer film 13 to the tape winding roll 7;
Three evaporation sources 1 and 2 are charged with the evaporator 1, which forms a magnetic layer on the non-magnetic polymer film 13 by heating and evaporating, and the minimum body of the vapor flow during vapor deposition. It consists of a mask 9 that defines an incident angle θ+1IIn. Further, oxygen outlets 4 and 5 for supplying oxygen into the vapor deposition chamber 11 are open to the inside of the vapor deposition chamber 11,
By adjusting the amount of oxygen introduced into these two oxygen outlets 1 and 5, the distribution of oxygen in the film thickness direction can be changed. Further, near the center of the deposition chamber 11, an adhesion prevention plate 10 is provided which also serves to separate the transport system for the non-magnetic polymer film 13 from the evaporation section.

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

The interior of the deposition chamber 11 is maintained at an appropriate degree of vacuum by a vacuum pump 12. The evaporation source 3 is charged with evaporation material Co-Ni. In addition, either one of the evaporation sources 1 and 2,
Alternatively, both are charged with evaporation material Cr. By using either 1 or 2 or both at the same time as a Cr evaporation source, the distribution of Cr in the thickness direction of the formed magnetic layer can be changed. The evaporation material charged in the evaporation source is heated by a conventionally known heating means. Examples of this heating means include electron beam heating,
Induction heating, resistance heating, etc. can be used.

The heated evaporation material melts and vaporizes, rises upward inside the deposition chamber 11 as a vapor flow, and is deposited on the nonmagnetic polymer film 13. At this time, oxygen is introduced into the deposition chamber 11 from the oxygen outlets 4 and 5, and the deposition is performed in an appropriate oxygen atmosphere. Therefore, the amount of oxygen introduced into the deposition chamber 11 is adjusted. By doing so, oxygen is taken in with a desired distribution in the film thickness direction. When the non-magnetic polymer film 13 sent out from the tape delivery roll 6 is guided to the cooling can 8, the oblique incidence angle θ becomes a high angle (
So-called oblique deposition is performed while changing the angle from approximately 90 degrees to a lower angle, and when the minimum oblique incidence angle θmin is exceeded, the deposition ends and the tape is wound onto a tape take-up roll 7.

Next, the present invention will be explained with reference to practical examples.

Examples: 10 μm thick polyethylene terephthalate (PET) as a non-magnetic polymer film, Co9oNi as an evaporation material.
Oblique evaporation was carried out using the vapor deposition apparatus shown in FIG. 1 using 1° and Cr and setting the minimum oblique incidence angle θmin to 42°, and using 161° electron beam heating as the heating means for the evaporation source. The conveyance speed of the non-magnetic polymer film is 10 m/
min and the degree of vacuum was on the order of 10 Torr.

Vapor deposition was carried out in three ways: when only No. 4 was used as the oxygen outlet, when only No. 5 was used, and when No. 4 and No. 5 were used together. The magnetic recording media thus obtained were designated as type A, type B, and type C, respectively. Furthermore, in each case, in order to change the content of Cr and oxygen in the magnetic layer, the heating path for Cr and the amount of oxygen blown out were adjusted. Furthermore, evaporation was carried out in three ways: when only 1 was used as an evaporation source for Cr, when only 2 was used, and when 1 and 2 were used together, and the Cr ratio was varied along the film thickness direction. A magnetic recording medium with a magnetic layer was also created. The composition of the produced magnetic layer and the composition distribution in the film thickness direction were determined by Auger analysis. The average composition of the obtained magnetic layer is (Co9oNi1o)s
It was ocr401s. The thickness of the magnetic layer was measured using a stylus-type thickness meter. The thickness of all the magnetic layers obtained in this example was about 1500λ.

FIGS. 2A, 2B, and 2C are graphs showing the atomic ratio of oxygen to Cr in the thickness direction of the magnetic layer produced as described above.

Figure 2A shows the case where 4 is used as the oxygen outlet (type A), and the closer to the surface of the non-magnetic polymer film the C
The atomic ratio of oxygen to r is a dog. FIG. 2B shows the case (type B) in which No. 5 is used as the oxygen outlet, and the atomic ratio of oxygen to Cr is almost constant. FIG. 2C shows the case (type C) when oxygen outlets 4 and 5 are used, and the atomic ratio of oxygen to Cr decreases as it approaches the surface of the nonmagnetic polymer film. In both cases, there is a region with a lot of oxygen in the magnetic layer very close to the surface, but this is thought to be due to surface oxidation due to oxygen adsorbed after the completion of vapor deposition, and this region with a lot of oxygen is not measured. According to The value was taken as

The magnetic recording medium prepared in two series was slit into 1/2 inch width and assembled into a small VH8 video cassette. Next, a 5'MHz carrier wave is recorded using a video deck, etc., and the 6MHz playback output (signal S) and the modulation noise component at 5MHz (raise N) are measured, and the S/N value is determined. I asked for The S/N value thus obtained is shown in FIG. 3 as a relative value based on the S/N value of tie 7'B.

From FIG. 3, the S/N of type C is slightly lower than that of type B, but the S/N of type A is about 3 dB higher than that of type B. Here, type A includes one in which the Cr content is almost constant along the film thickness direction, and one in which the Cr content gradually changes and becomes smaller as it approaches the non-magnetic polymer film surface (the fourth type). Figure 5) and Cr content that gradually changes and increases as it approaches the surface of the non-magnetic polymer film (Figure 5). For changes along the direction,
S/N showed almost no significant difference. That is, it has been found that the atomic ratio of oxygen to Cr along the thickness direction is important.

The above results are tied to (Co9oNi1o)soczQxe, but also for Co and N1 ratios of 95:5, 80:20, and 78:22 in terms of number of atoms.
The same applies to a magnetic layer in which the average Cr content is 2 to 3 at%, the average oxygen content is 5 to 25 at%, and the average atomic ratio of oxygen to Cr is 2 to 10. The results were obtained.

In addition, although the case where the magnetic layer is a single layer is described in the above example, even when several magnetic layers as described above are laminated on a non-magnetic polymer film, the same result as in the example of the present invention described above can be obtained. A high S/N ratio was obtained.

As described in detail above, the magnetic recording medium of the present invention has excellent electromagnetic conversion characteristics and has extremely high practical value.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a preferred vapor deposition apparatus used for manufacturing the magnetic recording medium of the present invention. FIG. 2 is a distribution of the atomic ratio of oxygen to Cr in the magnetic layer along the thickness direction. Figure 3 shows the S/N of a magnetic recording medium having a magnetic layer with a different distribution of the atomic ratio of oxygen to Cr (0/Cr) along the thickness direction. The S/N of a magnetic recording medium with a magnetic layer that is approximately constant along
Figures 4 and 5 are graphs showing relative values based on the S/N of B). 1, 2.3... Evaporation source 4, 5... Oxygen outlet 6... Tape delivery roll 7... Group... ...Tape winding roll 8...
Cooling can for...9...Group/mass lO......Anti-wear board 11
...... Vapor deposition chamber 12...
...Vacuum pump 13...Non-magnetic polymer film Figure 2A, Figure 1, Figure 2C, Figure 2B

Claims (1)

[Claims] Created by an oblique evaporation method on a non-magnetic polymer film,
In a magnetic recording medium having a magnetic layer consisting of at least Co, Ni, Cr, and oxygen, the average content of Cr is 2 to 8 atomic percent, the average content of oxygen is 5 to 25 atomic percent, and the oxygen relative to the Cr is an average atomic ratio of from 2 to 10, and a distribution of the atomic ratio of the oxygen to the Cr in the film thickness direction increases as it approaches the non-magnetic polymer film side. .