JPH04206033A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To make it possible to obtain a magnetic recording medium having a high C/N ratio from a low recording density over to a high recording density by treating the surface of a macro-molecular base by an ion beam and by forming a magnetic layer at a specific surface temperature. CONSTITUTION:A macromolecular base 1 is treated first on the surface of a cylindrical can 4 by an ion beam 8 emitted from an ion gun 7. Next, metal evaporation atoms 12 flying from an evaporation source 11 held in a crucible 10 react with a gas coming out of a reaction gas introducing pipe 13, and in the process of the reaction, a thin-film magnetic layer is formed on the macromolecular base 1. At this time, the surface of the cylindrical can 4 is heated to a temperature from 80 deg.C to 170 deg.C. Accordingly, macromolecules of the surface of the macromolecular base 1 are put in an active state and come into contact with Co and O atoms, thereby the occasion of occurrence of nuclei is increased and a crystal grain is fractionized. Besides, the temperature of the base becomes high and thereby separation of Co from Co-O is facilitated. According to this constitution, a magnetic recording medium having a high C/N ratio from a low recording density over to a high recording density can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention controls conditions during the growth process of a thin film magnetic layer and optimizes the microcrystals constituting the magnetic layer. The present invention relates to a method of manufacturing a magnetic recording medium having a high C/N ratio.

BACKGROUND OF THE INVENTION The amount of information required of magnetic recording media continues to increase. Magnetic recording media are no exception; conventional coating-type magnetic recording media are approaching their limits in increasing the density, and thin-film magnetic recording media are beginning to be put into practical use. Among the 11-layer magnetic recording media, perpendicular magnetic recording media are inherently suitable for high-density recording, and are expected to be the next generation of high-density magnetic recording media. As a single-film type perpendicular magnetic recording medium, Go-0, C
Materials such as o-Ni-0, Co-Cr, and Co-Cr-Ni have growth potential. Among these, Go-0, Co-Ni-0
The material of the membrane is almost the same as that of the currently commercialized metal vapor deposition tape, and there is hope that mass production technology can be easily completed. A commercially available metal evaporation tape runs along the periphery of a cylindrical can cooled below room temperature in an oxygen atmosphere, and then is obliquely evaporated onto a polymer film at an incident angle of 40° or more. As a result, a magnetic layer is formed by elongating crystal grains having a magnetization axis in a direction tilted from the in-plane direction. Therefore, the magnetic recording direction is between in-plane and perpendicular.

Problems to be Solved by the Invention Although the metal-deposited tape and the magnetic material are the same, the Co-0 perpendicular magnetic recording medium obtained by changing the manufacturing process conditions has a higher C/N than the current metal-deposited tape at high recording density.
However, a sufficient C/N ratio could not be obtained at low recording density, and it was insufficient for use as a next-generation magnetic recording tape.

The present invention is intended to solve these conventional problems, and aims to provide a magnetic recording medium having a high C/N ratio over a range from low recording density to high recording density.

Means for Solving the Problems In order to achieve the above object, the present invention provides a method for manufacturing a magnetic recording medium in which a thin film magnetic layer mainly consisting of Co and oxygen or CO and Ni and oxygen is formed on a polymer substrate. A first step of treating the surface of the polymer substrate with an ion beam emitted from an ion gun, and a second step of forming a magnetic layer while maintaining the surface temperature of the polymer substrate at 80°C or more and 170°C or less. It is characterized by having the following.

In the working Co-01 film, a large coercive force is generated because the 0 ferromagnetic Co layer in which Coo and CO crystal grains are mixed is magnetically separated by the nonmagnetic 000 layer, resulting in magnetic recording. This is one of the reasons why it exhibits excellent recording and reproducing characteristics as a medium. First, in the first step of the present invention, when the surface of a polymer substrate is irradiated with an ion beam in advance, some of the bonds of the polymer on the surface of the polymer substrate are separated and become active.

When it comes into contact with CO and O atoms in this state, it combines with the active bonds of the polymer, increasing the chance of nucleation, thereby fragmenting the crystal grains. Furthermore, when the substrate temperature is increased in the second step of the present invention, separation of Co and Co-0 within the crystal grains is promoted. In order to make a Co-0 thin film into an excellent magnetic recording medium, it is necessary to make the crystal grains small and to clearly separate the 00 grains and the Co-0 grains. The recording/reproducing characteristics of the -0 film are significantly improved.

EXAMPLE Hereinafter, a method of manufacturing a magnetic recording medium according to an example of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view schematically showing a vacuum evaporation apparatus for carrying out a manufacturing method according to an embodiment of the present invention.

In the figure, reference numeral 1 denotes a polymer substrate, which is unwound from an unwinding roll 2, runs on the surface of a cylindrical can 4 in the direction of the arrow, and is wound onto a winding roll 3. Here, 5.6 is a guide roll. During this time, the polymer substrate 1 is first exposed to the ion beam 8 emitted from the ion gun 7 on the surface of the cylindrical can 4.
Processed by

Next, metal evaporated atoms 12 entering the crucible 10 and coming from the evaporation source 11 react with the gas coming out from the reaction gas introduction tube 13, forming a thin magnetic layer on the polymer substrate 1. At this time, the surface of the cylindrical can 4 is heated between 80°C and 170°C. The above is an outline of an example of the method for manufacturing a magnetic recording medium of the present invention. Note that 9 is a shielding plate.

Next, a more specific example will be described.

As the polymer substrate 1, a polyethylene naphthalate substrate with a thickness of 10 μm and a width of 500 cm was used, and the substrate conveyance speed was 10 m/min. In addition, an aramid substrate, a polyimide substrate, etc. may be used. The inside of the vacuum evaporation equipment is lx10
After evacuation to 4 Torr or less, 99.9% or more of CO is melted using an electron beam as the evaporation source 11, resulting in a film thickness of 2.
A Co-0 thin film with a thickness of 00 nm and a saturation magnetization of about 550 emu/cc was formed. A Kaufmann type ion gun 7 was used, the acceleration voltage was 400μ, and the ion current was 150m.
I gave it an A. An appropriate accelerating voltage is 200 to 500 ■. If it is weaker than 200 square meters, it will not be effective, and if it exceeds 500 square meters, the substrate will be damaged.The temperature of the cylindrical can 4 is suitably between 80°C and 170°C. temperature is 8
At temperatures below 0°C, the separation between the 00 layer and the Co-0 layer is insufficient, and at temperatures above 170°C, fine crystal grains formed by the effect of the ion gun combine to form large crystal grains, resulting in poor magnetic properties. decreases. In this example, the temperature was set at 110°C. Further, as the gas to be ionized, Ar, N2.02, etc. are suitable, but in this example, Ar was used at a flow rate of 40cc/m.
was introduced into the ion gun. The angle of incidence of the vapor-deposited atoms on the substrate was set at an inclination of 55° to 30'' from the normal line of the substrate, and 300 cc/min 7'02 gas was flowed through the reaction gas introduction tube.

The initial incident angle of the evaporated atoms is from 0 to 60", which is the most C.
The characteristics of the o-0 perpendicular magnetization film are excellent. Incident angle is 60°
If it exceeds , the perpendicular magnetic anisotropy will be greatly reduced and the electromagnetic conversion characteristics at high density will be deteriorated.

The Co-0 film produced as described above was evaluated by modifying a part of a commercially available 8 mm video tape recorder (VTR). As a ring type head, the gap is 7” long and 0.1 μm.
) An amorphous head with a rack width of 1101I was used. C/ at recording wavelengths of 3.8 μm and 0.38 μm
The N ratio is shown in the following table.

In the above table, A is an example of the present invention, and the C/N ratio of the conventional example is shown as a relative value compared to A. B is a medium produced in exactly the same manner as A, except that the surface of the substrate is subjected to ion treatment using an ion gun. Also, media C and D were produced in the same manner as A, except that the cylindrical cans were produced at temperatures of 30° C. and 200° C., respectively. However, in D, a polyimide substrate is used as the substrate.

Further, E is a medium produced without surface treatment of the substrate using an ion gun and with the temperature of the cylindrical can being 30°C.

From the above table, it can be seen that Example A of the present invention has a higher C/N ratio than Comparative Examples B-H. 1 or more explained the case where Co was used as the evaporation source, but the corrosion resistance was improved. Almost similar results are obtained when a Co--Ni alloy is used to achieve this. Furthermore, almost the same results can be obtained when a mixed gas of not only 02 but also N2 and 0□ is flowed from the reaction gas inlet pipe.

Effects of the Invention As is clear from the above embodiments, according to the manufacturing method of the present invention, magnetic recording media having high C/N ratios ranging from low recording densities to high recording densities can be easily obtained in large quantities.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a vacuum evaporation apparatus used to carry out a manufacturing method according to an embodiment of the present invention. 1...Polymer substrate, 4...Curved/cylindrical can,
7... Ion gun, 8... Ion beam, 1
1... Evaporation source, 12... Evaporation atom, 1
3...Reaction gas introduction pipe. Name of agent: Patent attorney Haruaki Ogata Two people Figure 1! -・-Polymer substrate II -Evaporation source

Claims (3)

[Claims] (1) Mainly Co and oxygen or Co and N on a polymer substrate
In the method for manufacturing a magnetic recording medium in which a thin magnetic layer is formed of i and oxygen, the first step is to treat the surface of the polymer substrate with an ion beam emitted from an ion gun, and to increase the surface temperature of the polymer substrate to 80℃. A method for manufacturing a magnetic recording medium, comprising a second step of forming a magnetic layer while maintaining the temperature between 170° C. and above. (2) The method for manufacturing a magnetic recording medium according to claim (1), wherein the first step and the second step are performed along the circumferential surface of the cylindrical can. (3) The method for manufacturing a magnetic recording medium according to claim 1 or 2, characterized in that the acceleration voltage of the ion gun is set to 200 V or more and 500 V or less.