JPH0334619B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing a thin film magnetic recording medium mainly made of iron. [Prior Art and Background of the Invention] Thin-film magnetic recording media are being put into practical use as high-density magnetic recording media. Conventional magnetic recording media of this type with the best magnetic properties are manufactured by vacuum-depositing cobalt or a cobalt alloy, which is a ferromagnetic material, onto a substrate such as a polymer film. However, there are two major problems in putting this cobalt-based magnetic recording medium into practical use. First, the cobalt-based magnetic film itself does not have sufficient corrosion resistance for practical use. Secondly, cobalt is a scarce resource and expensive, so there are concerns about the stability of supply of magnetic recording media, and the price is also high. As a result of studies to solve these conventional problems, the inventors of the present invention have obtained magnetic properties comparable to cobalt-based magnetic recording media, such as a coercive force of 10,000e or more and a squareness ratio of 0.9 or more. We proposed a method for producing iron-based thin-film magnetic recording media that has corrosion resistance comparable to that of films (Patent Application No. 86727-1983).
issue). The method involves vacuum-depositing iron onto a non-magnetic base material, simultaneously ionizing a mixed gas of nitrogen gas and oxygen gas, and irradiating this onto the base material to create a magnetic film. be. In this method, in order to manufacture a magnetic recording medium with excellent magnetic properties, it is important that the amount of iron atoms and ions of the mixed gas incident on the substrate be maintained at a constant ratio. For example, when the mixed gas is air, the number of ions in the mixed gas relative to iron atoms must be 0.5 or more, otherwise it will not be possible to obtain practically sufficient magnetic properties. [Problems to be solved by the invention] In order to obtain high industrial productivity in manufacturing thin-film magnetic recording media, it is necessary to increase the deposition rate of the magnetic film, which requires It is essential to maximize the amount of iron vapor incident on the steel. However, when increasing the amount of iron incident on the substrate for the above-mentioned reasons, it is necessary to correspondingly increase the amount of oxygen gas and nitrogen gas ions that are incident on the base material. Generally, in order to increase the amount of ions supplied, it is necessary to either increase the size of the ionization means or install many of them, but none of these measures can be taken in a narrow vacuum chamber. There are also limits. As a result of considering these problems, the inventors of the present invention found that when certain types of ionization means are combined, when the magnetic film deposition rate exceeds a certain value with each ionization means, the amount of ionization increases. The inventors focused on the fact that, in contrast to the fact that the magnetic properties sharply deteriorate due to an increase in the ionization rate, the combination of the above-mentioned ionization means allows sufficient magnetic properties to be obtained even at a somewhat high film-forming rate. The present invention has been made based on this, and aims to obtain higher productivity in the method for manufacturing the above-mentioned thin film magnetic recording medium. [Means for Solving the Problems] First, the manufacturing method according to the present invention will be explained with reference to FIG. It is heated and evaporated by irradiating an electron beam from the gun 7, and the generated vapor is transferred to non-magnetic glass,
The light is irradiated onto a base material 2 made of a polymer film or the like. A filament 6 for emitting thermionic electrons and an ionizing electrode 5 opposite thereto are arranged near the iron vapor irradiation path, so that a discharge region b is formed on the irradiation path a. Further, a nozzle 8 is arranged in this irradiation path a, and oxygen gas, nitrogen gas, or a mixed gas thereof is supplied to the discharge region b via a bulb 4b. These gases are ionized together with iron atoms in the same discharge region b, and are irradiated onto the base material 2. On the other hand, a so-called Kauffman type ion gas 3 is arranged in the vacuum chamber in addition to the ionization means. In this ion gun 3, the gas introduced into the cell 9 via the valve 4a is transferred to the filament 1.
It is ionized by electrons emitted from zero.
The gas ions are held in the cell 9 by the magnetic field formed by the magnet 11, and are further accelerated by a voltage applied between the ion gun 3 and the base material 2, and are deposited on the base material 2. irradiated. In this case, a common method is to introduce a mixed gas of oxygen gas and nitrogen gas into both discharge region b and cell 9, but it is not recommended to introduce only oxygen gas into one and only nitrogen gas into the other. It is also possible to ionize it. FIG. 2 shows an apparatus for manufacturing a magnetic tape by the method of the present invention, in which a base material 2 made of a long polymer film or the like is unwound from one reel 13, and then a cooling drum 14 Served with
Then, it is wound onto the other reel 15. In the manufacturing method using this device, gas ionization in the discharge area b and the Kauffman type ion gun 3 are performed.
The ionization of the gas is the same as in the above case, but a high frequency discharge type ion gun 16 is also used as the ion gun. In this ion gun 16, gas is introduced between the cooling drum 14 and the electrode 17 via the valve 4c, and
During this time, a high frequency voltage is applied to generate a high frequency discharge, and while this discharge is confined by the magnetic field generated by the coil 18, the generated gas ions are made to enter the surface of the base material 2. [Examples and Comparative Examples] Next, Examples of the present invention and Comparative Examples thereof will be described. Example Using iron with a purity of 99.9% as the evaporation source 1,
Using the apparatus shown in the figure, a magnetic film was formed on a 35 mm square glass substrate 2 under the following conditions, and a magnetic recording medium was manufactured. The initial pressure in the vacuum chamber is
The iron vapor emitted from the evaporation source ¹ was made to enter the base material 2 at an angle of 80°. At the same time, air was introduced as a mixed gas into the cell 9 and the discharge region b via the valves 4a and 4b, and the air was ionized and made to be incident on the base material 2 for reactive vapor deposition.
At this time, a positive potential of 40 V was applied to the ionization electrode 5, and a direct current of 40 A was applied to the filament 6 to generate arc discharge. Further, the amount of ions irradiated onto the base material 2 from the ion gun 3 was maintained at a constant value of 0.2 mA/cm ² . Also,
The evaporation rate from the evaporation source 1 was controlled while being measured using a crystal vibrating film thickness meter installed at the same height as the substrate 2, and was carried out in four stages from 20 Å/s to 50 Å/s. The degree of vacuum in the vacuum chamber during vapor deposition was 2×10 ⁻⁴ Torr. Regarding the magnetic recording media made in this way, each sample was measured using a vibrating magnetometer to determine the magnetic film thickness.

[Table] Measure M-H characteristics, find coercive force and squareness ratio,
The thickness of the magnetic film was also measured using an optical interference film thickness meter. The results are shown in Table 1. Note that the thickness of the magnetic film was 1000 to 1500 Å in all cases. Comparative Example 1 Using the same apparatus shown in FIG. 1 as in the above example, no positive potential was applied to the ionization electrode 5, no current was applied to the filament 6, and no air was supplied from the nozzle 8. A magnetic recording medium was manufactured under the same conditions as in the above example. However, in this case, the degree of vacuum in the vacuum chamber is 1×
It was 10 ^-4 Torr. The magnetic properties of the thus obtained magnetic recording medium were measured in the same manner as in the above examples, and the results are shown in Table 2. Comparative Example 2 The same apparatus shown in FIG. 1 as in the above example was used, but no positive potential was applied to the ion gun 3, no current was applied to the filament 10, and no air was supplied to the cell 9. A magnetic recording medium was manufactured under the same conditions as in the above example. In addition,
In this case, the evaporation rate from evaporation source 1 is 5 Å/s
It was carried out in five steps from 50 Å/s to 50 Å/s. The magnetic properties of the thus obtained magnetic recording medium were measured in the same manner as in the above examples, and the results are shown in Table 2.

〔Effect of the invention〕

As described above, according to the present invention, a magnetic recording medium could be produced with excellent magnetic properties and a deposition rate that far exceeds the value expected when both of the above-mentioned ionization means are used together. This makes it possible to improve the productivity of the medium.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are explanatory diagrams showing respective embodiments of the present invention. 1... Evaporation source, 2... Base material, 3, 16... Ion gun, a... Iron vapor irradiation path, b... Discharge area.

Claims (1)

[Claims] 1. By injecting iron vapor onto a non-magnetic base material and ionizing nitrogen gas and oxygen gas or a mixed gas thereof and irradiating the same onto the base material, In a method for manufacturing a thin film magnetic recording medium in which a magnetic film is formed on the substrate, a discharge region is formed on the irradiation path of iron vapor, and in the same discharge region, one of the above gases or a mixed gas is ionized together with iron to form a base material. A method for manufacturing a thin-film magnetic recording medium, characterized in that the above substrate is irradiated with ionized gas or a mixed gas, and the ionized gas or mixed gas is separately irradiated onto the substrate. 2. The method for manufacturing a magnetic recording medium according to claim 1, wherein the mixed gas is air.