JPH05144624A - Magnetic recording medium and manufacture thereof - Google Patents

Abstract

PURPOSE:To enhance the durability of the title magnetic recording medium by a method wherein the magnetic recording medium is formed in a thin sheet of a specific thickness, which is composed of an alloy containing specific amounts of cobalt and chrome, the rest part being iron and further containing specific additional elements, are magnetically isotropic and has a surface roughness of a specific value. CONSTITUTION:A mixture or alloy composed of 5-25wt.% of cobalt, 15-35wt.% of chrome and remaining wt.% of iron as essential components, furthermore, 0.05-10wt.% of one or exceeding two kinds of elements out of Ti, V, Nb, Mo, W, Ta, Zr, Si, Al is melted down to be cast in an ingot. This ingot is melted down and forged and then cold and/or hot-rolled into a thin sheet. This thin sheet is aging-processed and then finished in thinner sheet surface roughness not exceeding 1/10 of recording wavelength and thickness of 0.001-3mm. Through these procedures, a durable magnetic recording medium of a high recording density can be manufactured by a simple method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium for magnetic and digital and / or analog recording which is composed of a magnetically isotropic thin plate magnetic material.

[0002]

2. Description of the Related Art In recent years, electronic information devices centering on computers have been developed, and a magnetic recording device as an external recording device for information is required to have a large capacity, a small size, and stability of information storage. There are a hard disk device in which a disk-shaped recording medium is placed in a hermetically sealed drive and a flexible disk device in which the medium can be easily replaced.

The magnetic recording medium used in these magnetic recording devices is obtained by coating magnetic powder on the surface of a non-magnetic substrate such as a resin film, aluminum or glass, or
It is manufactured by plating or sputtering a magnetic material. The thickness of the magnetic layer responsible for magnetic recording is several μm in the case of coating and several tens of nm in the case of sputtering.

In any of the magnetic recording medium manufacturing methods, the surface of the substrate is required to have a highly adjusted surface roughness, and the magnetic layer is formed under strictly controlled conditions.

Further, magnetic cards such as cash cards, credit cards and prepaid cards are magnetic recording media for magnetically recording a personal identification number, a balance and the like on a magnetic layer coated on the card. Since the recording density of the magnetic recording layer of each card is low, only a minimum amount of information is recorded.
Most of the information is stored in a central storage device, and operations such as withdrawal and payment are performed while the terminal handling the card inquires the central information.

[0006]

The magnetic recording medium manufactured by the above method is expensive when a magnetic layer for magnetic recording is formed, such as a magnetic material coating device or an in-line type sputtering device. Equipment is required, which is a major cause of increased manufacturing cost.

On the other hand, these conventional magnetic recording media have a drawback that the magnetic layer is easily damaged because the thickness of the magnetic layer is extremely thin, such as several tens nm to several μm.

The magnetic recording medium used in the flexible disk device is manufactured on the assumption that the recording / reproducing head and the recording medium are used in contact with each other.
Although it can be said that the magnetic recording layer has high durability against external mechanical action such as scratching, the magnetic recording density is low because a non-continuous magnetic layer made of magnetic powder or the like is used as a recording medium.

As a magnetic recording medium for a hard disk device, a non-contact type flying head is used because the medium is fixedly used in the device, and although the magnetic recording density is high, it is caused by an external impact or the like. The contact between the head and the medium causes damage immediately and causes an irreparable state. Further, since the gap between the head and the medium is several thousand angstroms, it is necessary to maintain an atmosphere free from dust or the like in the apparatus within this size.

On the other hand, since the magnetic card is carried by the user himself to the terminal and is handled relatively roughly, the magnetic recording medium for recording information has a structure focusing on durability. The magnetic layer is formed by coating a resin card with an oxide magnetic material kneaded with a binder in a thickness of several μm, and a thick film protective layer of about 100 μm is formed thereon.

Therefore, in the magnetic card, there is a gap for the protective layer between the magnetic head for recording and reproducing and the magnetic layer,
Since high-density magnetic recording is not possible, only limited information such as personal identification number and balance is recorded.

The present invention provides a magnetic recording medium for improving the above-mentioned drawbacks of the prior art. The magnetic thin plate itself can be manufactured as a magnetic recording medium by a simple method.
In addition, it has high recording density and robustness.

[0013]

In order to achieve the above object, the magnetic recording medium according to the present invention comprises cobalt 5-25.
%, Chromium 15 to 35% by weight, the balance iron as an essential component, titanium, vanadium, niobium, molybdenum,
One or more of tungsten, tantalum, zirconium, silicon and aluminum 0.005-10
A thin plate having a thickness of 0.001 to 3 mm formed of an alloy containing wt%, the thin plate is magnetically isotropic, and the surface roughness of the thin plate is 1/10 or less of the recording wavelength. It is characterized by

According to the present invention, the mixture or alloy having the above composition is melted, cast into an ingot, the obtained ingot is subjected to solution treatment, and then cast.
Then, after cold rolling and / or hot rolling to make a thin plate, after subjecting the obtained thin plate to an aging treatment, the surface roughness of the thin plate is 1/10 or less of the recording wavelength, and the thickness of the thin plate is 0.001 to This is a method for manufacturing a magnetic recording medium, characterized in that 3 mm is subjected to finishing processing.

The magnetic recording medium of the present invention having the above-mentioned structure is usually used by being formed on a so-called magnetic disk of a thin disk having a diameter of 0.5 to 8 inches or a rectangular magnetic card having a side of several tens mm. ..

In the case of a magnetic disk, the magnetic recording medium is rotated and the magnetic head is moved in the diameter direction to record information on concentric circles. In the case of a magnetic card, information is recorded by linearly moving the magnetic head on the card.

The medium responsible for magnetic recording is the thin plate itself of the magnetic recording medium and is a continuous magnetic body. Therefore, the magnetic recording density is equivalent to that of a conventional hard disk, and since a limited thin magnetic layer is not used as a recording medium, it has high durability against contact and collision between the head and the magnetic body and mechanical action from the outside. To have.

Here, in manufacturing the magnetic recording medium of the present invention, it is necessary that the above magnetic body can be easily manufactured in a thin plate shape.

The magnetic material used as the magnetic recording medium of the present invention comprises iron, cobalt, and chromium as main constituent elements. The components shown in the claims have been subjected to cold rolling and the like before the final aging heat treatment. It is a material that can be plastically deformed and machined. This is a great advantage in manufacturing a magnetic recording medium, and a magnetic material showing hard or semi-hard magnetism, which is capable of general magnetic recording, is a large manufacturing process compared to being manufactured by a casting method or a powder metallurgy method. It becomes a cost advantage.
The magnetic characteristics are isotropic materials and the residual magnetic flux density is 7 to 10k.
G, coercive force of 300 to 450 Oe, and excellent characteristics as a magnetic recording medium. It is generally clear that there is no magnetic material that can be plastically deformed or machined while exhibiting this excellent magnetic property, other than the magnetic material constituting the present invention.

The magnetic material constituting the magnetic recording medium of the present invention is magnetically isotropic, and magnetic recording can be magnetized in the direction parallel and / or perpendicular to the plane of the thin plate. Therefore,
The magnetic recording medium of the present invention is compatible with the conventional longitudinal recording system and can be applied as a perpendicular magnetic recording medium. Naturally, it can be applied as a magnetic recording medium of a hybrid type of in-plane / perpendicular magnetization. For example, the perpendicular magnetic recording portion can be used as a high-density recording memory for recording large-scale information such as an image, and the other can be configured as an in-plane recording method compatible with the conventional method.

[0021]

EXAMPLES Next, the present invention will be specifically described based on examples.

Example 1 Cobalt 10% by weight, chromium 22% by weight, vanadium 1.5% by weight, titanium 0.5% by weight, zirconium 1.5% by weight, niobium 0.1% by weight, silicon 0.2% by weight, aluminum 0.1% by weight, and the balance iron. The following ingot was manufactured by the vacuum high frequency melting method, then cast into a predetermined shape, and then cold rolled to obtain a steel plate with a thickness of 1.2 mm. The steel plate was kept in an argon gas atmosphere at a temperature of 1,100 ° C for 1 hour. Solution treatment was performed under the conditions. Then, after straightening the steel plate into a flat steel plate, it was punched into a disk having a diameter of 76.2 mm (3 inches), and a hole having a diameter of 7.8 mm was formed in the center by the same method.
Then, the disk is kept in a heat treatment furnace at 640 ° C. for 1 hour,
620 ℃ 1 hour, 600 ℃ 1 hour, 580 ℃ 1 hour, 560 ℃
A multi-step aging treatment was carried out for 2 hours, 540 ° C. for 4 hours, and 500 ° C. for 6 hours.

In the obtained disk-shaped magnetic material, the central hole was polished to 8 mm, and the flat surface, which is the magnetic recording surface, was polished to a surface roughness of 0.05 μm.

The produced magnetic recording medium is fixed to the rotating shaft of the hard disk drive, and the number of rotations is determined by the magnetic head.
When recording / reproducing was performed at 3,000 rpm and a recording frequency of 6.28 MHz, a reproduced signal waveform corresponding to the recording frequency was obtained. The recording track was set at every 10 μm. This corresponds to a linear recording density of 40 kfci (kilo flux change per inch) and 2,500 TPI. When 1 fc is 1 bit, the magnetic recording medium is 40 Mbyt on one side of a 3 inch disk.
Equivalent to the recording capacity of e.

Example 2 An ingot containing 8% by weight of cobalt, 28% by weight of chromium, 2.0% by weight of molybdenum, 0.5% by weight of tungsten, 1.0% by weight of titanium, 0.5% by weight of zirconium and the balance of iron was prepared by a vacuum high frequency melting method. Then, after casting into a predetermined shape, cold rolling was performed to obtain a steel sheet having a thickness of 0.5 mm, and the steel sheet was subjected to a solution treatment under a condition of keeping the temperature at 1,100 ° C. for 1 hour in an argon gas atmosphere. Then, after straightening to make a flat steel plate, it was cut into a card having a size of 85 × 54 mm. Next, the curd was held in a heat treatment furnace at 610 ° C. for 6 hours, further held at 600 ° C. for 4 hours, and then subjected to an aging treatment at 500 ° C. at a cooling rate of 0.08 ° C./min.

The flat surface portion to be the magnetic recording surface was polished to have a surface roughness of 0.05 μm.

When a contact type magnetic head was recorded / reproduced at a speed of 0.5 m / s and a frequency of 700 KHz in the longitudinal direction of the surface of the produced magnetic card, a reproduction signal waveform corresponding to the recording frequency was obtained. In addition, the recording / playback track was set every 2 mm. This is a linear recording density of 36 kfci (kilo flux change per inch), the total number of tracks is 27 when one side of the card is used as a magnetic recording area, and when 1 fc is 1 bit, the magnetic recording medium is a card. It has a recording capacity of 400 kbytes on one side.

After the above-mentioned recording is performed on the magnetic card, the operation of inserting / removing into / from the commercially available card case is performed 50,000 times,
Furthermore, when the reproduced signal was examined after being left for 1,000 hours in a temperature of 40 ° C. and a humidity of 90%, excellent durability was exhibited without loss of the recorded signal.

[0029]

INDUSTRIAL APPLICABILITY The present invention makes it possible to obtain a robust magnetic recording medium with a high recording density, and to manufacture it by a simple method.

Claims (2)

[Claims] 1. Cobalt 5 to 25% by weight, chromium 15 to 35% by weight, the balance iron as an essential component, and titanium, vanadium, niobium, molybdenum, tungsten, tantalum,
A thin plate formed of an alloy containing 0.005 to 10% by weight of one or more elements of zirconium, silicon and aluminum, and having a thickness of 0.001 to 3 mm, which is magnetically isotropic. And a surface roughness of the thin plate is 1/10 or less of a recording wavelength. 2. Cobalt 5 to 25% by weight, chromium 15 to 35% by weight, the balance iron as an essential component, and further titanium, vanadium, niobium, molybdenum, tungsten, tantalum,
After melting a mixture or alloy having a composition of 0.005 to 10% by weight of one or more of zirconium, silicon and aluminum, it is cast into an ingot, and the solution treatment is applied to the obtained ingot. After being subjected to forging, and then cold-rolled and / or hot-rolled to form a thin plate, the obtained thin plate is subjected to an aging treatment, and the surface roughness of the thin plate is set to 1/10 of the recording wavelength. Hereinafter, a method of manufacturing a magnetic recording medium, characterized in that the thin plate is finished to a thickness of 0.001 to 3 mm.