JPS63184927A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve productivity and the efficiency of utilizing nitrogen ions by projecting the vapor flow of a magnetic material essentially consisting of iron in such a manner as to attain the max. density of the ion beam near the position where the angle between said vapor flow and the normal of a substrate is max. at the time of forming a thin magnetic iron nitride film on the substrate. CONSTITUTION:The substrate 3 is continuously conveyed along a cylindrical drum 2 provided in a vacuum vessel 1 and the magnetic material 4 essentially consisting of iron such as iron or iron alloy is heated and evaporated by and electron gun 5, by which the vapor thereof is diagonally projected to the substrate and the ionized gaseous ions are supplied from an ion gun 6 to form the thin magnetic film layer of iron oxide on the substrate. The ion gun 6 for supplying the ionized gaseous nitrogen is so disposed as to maximize the density of the ion beam in the position where the angle between the vapor flow of the iron, etc., and the normal of the substrate is max. The efficiency of utilizing the ions is thereby improved and the productivity, i.e., thin film forming speed, is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing an iron nitride magnetic thin film magnetic recording medium. In particular, the present invention relates to a method for manufacturing an iron nitride magnetic thin film magnetic recording medium with excellent productivity and improved film formation speed.

[Conventional technology]

So-called coating-type magnetic recording media, which have a magnetic layer in which ferromagnetic powder is dispersed in a binder, are widely used as magnetic recording media, but in recent years, with the increasing demand for high-density recording, vacuum evaporation, sputtering, etc. Co, Ni, F
Magnetic recording media having thin film magnetic layers made of alloys such as E are beginning to attract attention. These thin film magnetic recording media have the advantage of being able to be made into ultra-thin layers for higher density, but have the disadvantage of poor corrosion resistance and rusting when stored and used for long periods of time.

As an attempt to eliminate this drawback, iron nitride (Fe
χN: χ is 2 to 8) A magnetic recording medium in which a magnetic thin film is formed has been proposed.

(For example, Japanese Unexamined Patent Publication No. 60-236113) [Problems to be solved by the invention] The magnetic recording medium having the above-mentioned iron nitride magnetic film has good magnetic properties, excellent corrosion resistance, and high-density magnetic properties. Although it is suitable as a recording medium, it has problems with productivity. That is, in the method for manufacturing a magnetic recording medium disclosed in the above publication, iron or iron alloy is subjected to ion blasting or the like in a nitrogen gas atmosphere (low pressure) to form iron nitride on the substrate, which reduces productivity. This is bad and the utilization efficiency of nitride ions is poor. Recently, a method has also been used in which nitrogen gas is ionized using an ion gun, applied to the substrate, and reacted with Fe evaporated from the Fe source to form an iron nitride film, but special consideration must be given to the placement of the ion gun, etc. However, there were still problems with productivity and nitrogen ion utilization efficiency.

An object of the present invention is to overcome these drawbacks and provide a method for manufacturing an iron nitride magnetic thin film magnetic recording medium with improved productivity and nitrogen ion utilization efficiency.

[Means for solving problems]

The present inventors have conducted various studies regarding the position of the ion gun, etc. for forming an iron nitride magnetic thin film, and have found that there is a position that is most efficient, and have achieved the present invention.

That is, in the present invention, while a non-magnetic substrate is conveyed along the outer circumference of a cylindrical drum, a magnetic material mainly composed of iron is deposited on the substrate by an oblique evaporation method, and at the same time, an ion beam mainly composed of nitrogen ions is emitted. In a method for manufacturing a magnetic recording medium in which an iron nitride magnetic thin film is formed on a substrate by irradiation,
The ion beam mainly composed of nitrogen ions is irradiated so that the ion beam density is maximized near the position where the angle between the vapor flow of the magnetic material mainly composed of iron and the normal to the substrate is maximum. This is a method for manufacturing a magnetic recording medium.

The present invention will be explained in detail below.

Examples of the base material used in the present invention include polyesters such as polyethylene terephthalate and polyethylene 2,6-naphthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate; plastics such as polycarbonate, polyimide, and polyamideimide; etc. There is.

In the present invention, in order to provide a thin film magnetic layer of iron nitride, for example, the first
A vacuum evaporation apparatus as schematically shown in the figure is used.

As shown in the figure, the substrate 3 is continuously conveyed along a cylindrical drum (cooling can) 2 provided in a vacuum chamber 1, and a magnetic material 4 mainly composed of iron such as iron or iron alloy is deposited on the substrate 3. The electron gun 5 heats and evaporates the material and obliquely injects it into the substrate, and the ion gun 6 supplies ionized nitrogen gas to form a thin magnetic layer of iron nitride on the substrate. In this case, the vacuum chamber is maintained at a pressure of about 10"3 to 10-7 Torr. Note that 7 is a mask that prevents iron vapor from adhering to unnecessary parts of the substrate.

In this case, the present invention sets the position of the ion gun 6 that supplies ionized nitrogen gas at a position where the angle between the permeation flow of iron and the normal to the substrate is maximum, that is, near the maximum incident angle θmax. Nitrogen ions are irradiated at a position such that an ion beam containing nitrogen ions as a main component can be irradiated so that the beam density is maximized.

The incident angle θ of the iron vapor referred to in the present invention is the angle θ formed between the direction of incidence at a point a where the iron vapor is incident on the substrate on the drum and the normal to the substrate at that point, as shown in FIG. The iron vapor evaporated from the iron source 4 by the electron gun 5 enters the substrate with a certain spread as shown in the figure, so the angle of incidence θ is
takes a value within a certain range, but the incident angle formed by the outermost 5 points of iron vapor is the maximum, and this is the maximum incident angle θ
It is called max. In the case of Figure 2, θmax = 90°, but by installing an anti-fouling mask in this area, θ
It is also possible to set max<90°.

The present invention improves ion utilization efficiency by irradiating nitrogen ions from an ion gun so that the nitrogen ion beam becomes maximum near point b, that is, near the maximum incident angle θmax at which the ironwork airflow enters the base. , productivity, i.e.
They discovered that it is possible to increase the rate of thin film formation. To irradiate nitrogen ions as described above, the ion gun may be placed so as to most efficiently irradiate the vicinity of where the nitrogen ions are fired.

The ion beam density as referred to in the present invention can be measured as a current density, and can be determined, for example, by arranging several small Faraday cups facing an ion gun and measuring the current value.

- An example is shown in FIG. This shows the beam density at a point A- on a plane 500 mm away from an ion gun with a diameter of 30 mm, and the shape of the beam changes greatly depending on the accelerating voltage. In addition, the shape of the beam varies greatly depending on the shape of the ion gun extraction electrode, distance, degree of vacuum, etc. Here, the points of maximum ion beam density are E and F when the accelerating voltage is 1.5 KV.

In the case of 0.3 KV, any point of C-I is included. Therefore, when this ion gun is arranged as shown in Fig. 2 and operated at an accelerating voltage of 0.3 KV, the present invention also applies when, for example, the maximum incident angle θmax is at point F and the minimum incident angle θmin is to the left of A. It also includes the case where θmax is the H point and θmin is the A point. However, θmax
Combinations such as 1 point for θmin and 0 point for θmin are outside the scope of the present invention.

There are various iron nitrides generally represented by FexN (χ is 2 to 8), such as ε-Fez-IN.

7 Fes N, Fes N, etc. are formed, but since ε-Fez and N are non-magnetic and undesirable, the degree of vacuum, Fe source, amount of ionized nitrogen, accelerating voltage, etc. must be controlled during vapor deposition. It is preferable that ε-Fez~3N be within 50%.

The thickness of iron nitride thin film is 500-5000.

〔Example〕

Hereinafter, the present invention will be explained by examples.

Using an apparatus as shown in Figure 1, a polyethylene triacetate base with a thickness of 12 μm and a width of 100 mm is conveyed along a cylindrical drum with a diameter of 400 mm, and a Kauffman type ion gun with a diameter of 30 mm is placed in the ion extraction chamber to collect nitrogen ions. Irradiation was performed so that the ion beam density was maximized near point b.

At the same time, Fc vapor was injected from the Fe source using an electron gun to form an iron nitride film.

The inside of the vacuum chamber was maintained at 5×10 −5 Torr. The ion current is 10 mA, the acceleration voltage is 0.6 KV, and the film thickness is 15
00 people. Note that the incident angle of oblique evaporation is 70
It was degree.

In this example, the magnetic thin film was formed at a conveyance speed of 3 m/min. The coercive force Hc of the obtained magnetic recording medium was 8200e.

As a comparative example, an ion gun was placed at the conventional position indicated by dotted line 8 to form an iron nitride thin film.
m/min, a thin film with a large coercive force cannot be formed.
The obtained magnetic recording medium had a HC of 8000e.

(Effects of the Invention) According to the present invention, the nitrogen ion beam density can be increased to a maximum angle of incidence θm.
By forming an iron nitride thin film by oblique evaporation while irradiating nitrogen ions so that the maximum is in the vicinity of ax, the conveyance speed of the substrate can be significantly increased compared to the case where nitrogen ion beams are irradiated in other conditions. Moreover, excellent coercive force can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a vapor deposition apparatus used in the present invention, FIG. 2 is a schematic diagram explaining an incident angle in the present invention, and FIG. 3 is an example showing an ion beam density distribution. 2... Cylindrical drum 3... Base 4... Iron source
5... Electron gun 6... Ion gun Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] (1) While conveying a non-magnetic substrate along the outer periphery of a cylindrical drum, a vapor flow of a magnetic material mainly composed of iron is directed onto the substrate using an oblique evaporation method, and at the same time an ion beam mainly composed of nitrogen ions is ejected. In a method for manufacturing a magnetic recording medium in which a magnetic thin film of iron nitride is formed on a substrate by irradiation, nitrogen ions are A method for manufacturing a magnetic recording medium, which comprises irradiating an ion beam containing as a main component.