JPH04360016A - Magnetic recording medium and production thereof - Google Patents

Abstract

PURPOSE:To provide the magnetic recording medium which has a residual magnetic flux density and coercive force, high output and good S/N, capable of high-density recording, substantially obviates the wear by a magnetic head and to provide the process for producing the above-mentioned medium having substantially no fluctuations in quality easily at a low cost and good production yield. CONSTITUTION:This magnetic recording medium consists essentially of 5 to 25wt.% Co, 15 to 35wt.% Cr and Fe as a balance component, further, consists of 0.1 to 5wt.% V, 0.1 to 5wt.% Mo, 0.1 to 5wt.% W, and 0.1 to 3wt.% Fe, has the nature to be magnetized in a vertical direction, has 0.001 to 3mm thickness, and has the surface roughness of <=1/10 the recording wavelength. The ingot having the above-mentioned alloy compsn. is subjected to a soln. heat treatment and cold rolling to form a sheet. While this sheet is subjected to a heat treatment, the sheet is subjected to an aging treatment by impressing a magnetic field perpendicularly to the rolling surface and is then subjected to finish working.

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 made of a thin plate of an alloy having a specific composition, and a method for manufacturing the same.

0002

[Prior Art] Conventionally, as a magnetic recording medium, a magnetic card is produced by dispersing magnetic powder such as iron oxide in a solvent together with a binder and coating it on a film-like or plate-like support to form a magnetic layer. Coated magnetic recording media such as magnetic tapes, magnetic recording media for VTRs, and floppy disks are widely used.

0003

[Problems to be Solved by the Invention] However, since such magnetic recording media contain a binder in the magnetic layer,
Its residual magnetic flux density and coercive force are low, making it unsuitable for high-output, high-density recording. Therefore, magnetic recording media have been developed in which a magnetic layer is formed as a thin film on a support by vacuum evaporation, sputtering, ion plating, etc. However, such magnetic recording media do not contain a binder in the magnetic layer. Therefore, it has a high residual magnetic flux density and coercive force, and is suitable for high-output, high-density recording, but the magnetic layer is formed on a film-like or plate-like support by vacuum evaporation, sputtering, ion plating, etc. Therefore, the abrasion resistance is low, and the magnetic layer is abraded and peeled off due to sliding contact with the magnetic head, resulting in a decrease in magnetic properties.

For this reason, a protective layer must be formed on the magnetic layer, which increases the distance between the magnetic head and the tape, making it unsuitable for high-output, high-density recording. Therefore, we have developed a system that solves the problem of wear resistance of multilayer magnetic recording media in which a magnetic layer is formed on a film-like or plate-like support. This has been achieved by molding an alloy having a composition of Cu-Ni-Fe into a thin wire or thin plate to form a magnetic recording medium.

[0005] However, in order to impart magnetic properties to the alloy having the above composition, drawing processing is essential. Therefore, there is a problem in that the magnetic recording medium having the above composition can only be obtained in the form of a linear or rod-like body, and that a magnetic recording medium in the form of a thin plate cannot be obtained.

The present invention solves the above-mentioned problems, and is made of a thin alloy plate with a specific composition, has high residual magnetic flux density and coercive force, has high output, has a good S/N ratio, and achieves high-density recording. In addition, it provides a magnetic recording medium with almost no wear due to sliding contact with a magnetic head, and is relatively simple and inexpensive.
Compared to C cards, it can be manufactured at an incomparably cheaper price, and there is no cracking, improving manufacturing yields.
It is an object of the present invention to provide a method for manufacturing a magnetic recording medium with almost no variation in quality.

[0007]

[Means for Solving the Problems] The magnetic recording medium of the present invention contains 5 to 25% by weight of cobalt, 15 to 35% by weight of chromium,
The thickness is 0, formed of an alloy with the balance substantially composed of iron.
．． The thin plate is characterized by having a property of being magnetized in a direction perpendicular to the surface of the thin plate, and having a surface roughness of 1/10 or less of the recording wavelength.

The method for manufacturing a magnetic recording medium of the present invention includes melting a mixture or alloy having a composition consisting of 5 to 25% by weight of cobalt, 15 to 35% by weight of chromium, and the balance essentially consisting of iron, and then casting. The obtained ingot was subjected to solution treatment, and then cold rolled to form a thin plate. A magnetic field was applied perpendicular to the rolling surface while heat treating the obtained thin plate, and then After the thin plate is subjected to an aging treatment, the thin plate is subjected to finishing processing such that 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 3 mm.

The magnetic recording medium of the present invention contains the above-mentioned cobalt (Co), chromium (Cr), and iron (Fe) as essential components. First, Co increases residual magnetic flux density and coercive force. If the Co content is low, the residual magnetic flux density and coercive force will be low;
If the content is too high, it becomes brittle and difficult to form into a thin plate, so the content is set at 5 to 25% by weight. Preferably 8-1
It is 7% by weight. More preferably, it is 10 to 12% by weight.

[0010] Cr is an effective component for increasing the holding force, and if the Cr content is low, the holding force will be small, and on the other hand, if the Cr content is high, the holding force will also be small. The content shall be 35% by weight. Preferably it is 20 to 28% by weight.

[0011] Fe is a base component and functions as a balance component of the alloy according to the invention.

The magnetic recording medium of the present invention may be an alloy further containing vanadium (V), molybdenum (Mo), tungsten (W), and titanium (Ti).

V is an effective component for imparting malleability and ductility, and if the V content is low, it becomes brittle and difficult to process into a thin plate. On the other hand, if the V content is high, magnetic Since the properties deteriorate, the content is set at 0.1 to 5% by weight. Preferably it is 0.3 to 2% by weight.

[0014] Mo is an effective component for increasing the holding force, and if the content of Mo is small, the holding force will be small. On the other hand, if the content of Mo is large, the holding force will also be small. The amount is 1 to 5% by weight. Preferably it is 0.3 to 3% by weight.

[0015] W is an effective component for increasing the holding force, and when the content of W is small, the holding force becomes small;
If the content of 0.
The amount is 1 to 5% by weight. Preferably it is 0.3 to 3% by weight.

[0016] Ti is an effective component for improving magnetic anisotropy, and if the Ti content is low, the magnetic anisotropy will deteriorate, while if the Ti content is high, the magnetic anisotropy will deteriorate. Since the properties deteriorate, the content is set at 0.1 to 3% by weight. Preferably it is 0.2 to 1.5% by weight.

[0017] A thin plate made of an alloy having the above composition is
The thickness is 0.001 to 3 mm. This is because if the thickness is less than 0.001 mm, it will be easy to break, the manufacturing yield will be poor, and the residual magnetic flux density will be low, and if the thickness exceeds 3 mm, it will be heavy and economically disadvantageous. Preferably 0
．． It is 03 to 2 mm.

The thickness of the magnetic recording medium of the present invention is 0.001
If it is as thin as ~0.1 mm, its mechanical strength is low as it is, so it can be used as a magnetic recording medium by backing it with a backing material or coating material, or by wrapping it in a coating material to increase its strength. can.

The surface roughness of the magnetic recording medium of the present invention is 1/10 or less of the recording wavelength. This is because if the wavelength is larger than 1/10 of the recording wavelength, the S/N ratio will be low due to a slight residual magnetism that has not been demagnetized. For example, when recording on the magnetic recording medium of the present invention at a recording wavelength of 100 μm, the surface roughness will be 10 μm or less. Preferably, it is 1/50 or less of the recording wavelength.

The method for manufacturing the magnetic recording medium of the present invention will be explained below. First, an alloy containing a predetermined amount or a predetermined composition of each of the essential components described above is melted, for example, by high-frequency heating in a vacuum, and then cast to form an ingot.

The obtained ingot is subjected to solution treatment. Here, solution treatment is a treatment for removing defects and segregation caused by casting, and is usually performed in a vacuum, an inert atmosphere, or a non-oxidizing atmosphere at a temperature of 1000 to 1300°C for a treatment time of 0.5 to It will be held in 2 hours. Preferably, the temperature is 1100 to 1250°C and the treatment time is 1 to 1.5 hours.

[0022] The ingot after the solution treatment is then subjected to cold rolling to form a plate material. The cold rolling at this time may be performed so that the plate material has the final thickness, but the thickness may be adjusted to take into account the thickness of the thin plate obtained by subsequent finishing processing. The rolling ratio is 30-90%, preferably 60-80%.

Next, after cold rolling, heat treatment is performed while applying a magnetic field perpendicular to the rolling surface. By performing such treatment, a magnetic recording medium having magnetic anisotropy in the direction perpendicular to the rolling surface can be obtained. The strength of the magnetic field at this time is 1000 to 2000 Oe, and the temperature is 620 to 6
The temperature is 60° C. and the treatment time is 0.33 to 1.5 hours. Preferably, the strength of the magnetic field is 1500 to 2000 Oe, and the temperature is 620 Oe.
-640°C, time 0.6-1 hour.

Next, the thin plate that has been heat treated while applying a magnetic field is slowly cooled and subjected to aging treatment. Aging treatment is a process that finally imparts magnetic properties to the thin plate, and the cooling rate is 0.5~
The temperature is 40°C/hour. Preferably, the cooling rate is 4-20°C
/It is time. The final temperature may be 500 to 540°C, and then rapidly cooled to room temperature by water cooling, air cooling, or the like. After applying aging treatment to the thin plate in this way, lapping finish,
Finishing processing such as buffing is applied to a thickness of 0.001~
3 mm, and the surface roughness is finished to be 1/10 or less of the recording wavelength.

The magnetic recording medium thus obtained has the external appearance and internal structure as shown in FIGS. 1 and 2. In other words, a structure in which countless intermetallic compounds (Fe-Co) are grown and fixed perpendicularly to the surface of a magnetic recording medium (thin plate), and another intermetallic compound (Fe-Cr) fills in between the intermetallic compounds. The diameter of one columnar body of intermetallic compounds grown and fixed in countless numbers is about 30 to 80 nm, preferably 40 to 60 nm, and the length is 100 to 600 nm.
Preferably it is 300 to 500 nm.

That is, when these integral columnar bodies are magnetized (perpendicularly), micro magnets are generated and magnetic recording is performed. Therefore, the recording density of the magnetic recording medium of the present invention is extremely high, and it has a recording capacity comparable to that of an IC card of the same area. However, as mentioned above, the manufacturing method is relatively simple, and in terms of price, IC
It can be manufactured at an incomparably low cost compared to cards.

Further, when the obtained magnetic recording medium is used as a magnetic card (87 mm x 56 mm), magnetic recording is performed using a perpendicular magnetization method. Normally, a magnetic card of the above shape has a total capacity of 1 Mbyte, and in some cases up to 10 Mbyte or 40 Mbyte.

[0028]

【Example】

Examples 1 to 6 and Comparative Examples 1 to 7 Alloys having the compositions shown in Table 1 were melted in a vacuum induction melting furnace,
It was cast into ingots. The obtained ingot was held at 1200° C. for 1 hour in an argon atmosphere to undergo solution treatment. The ingot was then cold rolled into a thin plate. 2000O perpendicular to the rolling surface of this thin plate.
The temperature was maintained at 640° C. for 1 hour while applying a magnetic field of e, and then an aging treatment was performed by cooling at a cooling rate of 15° C./hour.

The thin plates thus obtained were subjected to lapping to obtain magnetic recording media having the thickness and surface roughness shown in the table. The manufacturing yield at this time is shown in Table 1. The residual magnetic flux density Br, coercive force Hc, squareness ratio B of this magnetic recording medium
r/Bs (Bs is saturation magnetic flux density) was measured, and the results are shown in Table 1. Next, recording was performed at 5 kHz (recording wavelength 5 μm) while a magnetic head was brought into sliding contact with this magnetic recording medium, and the recorded signal at 5 kHz was reproduced. The results are shown in Table 1.

[0030]

[Table 1]

[0031]

[Effects of the Invention] As is clear from the above explanation, the magnetic recording medium of the present invention has a high residual magnetic flux density and a high coercive force, so it can achieve high output, a good S/N ratio, and high density recording. Ru. Therefore, it can be used as a magnetic recording medium in place of an IC card that boasts high density recording. Furthermore, since it is made of a thin plate, there is almost no wear due to sliding contact with the magnetic head. Furthermore, since the surface roughness was made less than 1/10 of the recording wavelength, the output signal became larger.

[0032] Furthermore, the manufacturing method of the present invention is relatively simple;
In terms of price, it can be manufactured at an incomparably low price compared to IC cards. Furthermore, there is no cracking, the manufacturing yield is improved, and there is almost no variation in quality.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the structure of a magnetic recording medium of the present invention in a plane perpendicular to the processing direction.

FIG. 2 is a diagram showing the structure of the magnetic recording medium of the present invention in the processing direction.

Claims (4)

[Claims] Claim 1: Cobalt 5-25% by weight, chromium 15
A thin plate with a thickness of 0.001 to 3 mm, made of an alloy consisting of ~35% by weight and the balance substantially iron, which has the property of being magnetized in a direction perpendicular to the plane of the thin plate, and A magnetic recording medium characterized in that the surface roughness of the thin plate is 1/10 or less of the recording wavelength. Claim 2: Cobalt 5-25% by weight, chromium 15
~35% by weight, with iron as an essential balance component,
Furthermore, vanadium 0.1 to 5% by weight, molybdenum 0.1
~5% by weight, 0.1-5% by weight of tungsten, 0% by weight of titanium
．． A thin plate with a thickness of 0.001 to 3 mm formed of an alloy containing 1 to 3% by weight, which has the property of being magnetized in a direction perpendicular to the plane of the thin plate, and the surface of the thin plate 2. The magnetic recording medium according to claim 1, wherein the roughness is 1/10 or less of the recording wavelength. Claim 3: Cobalt 5-25% by weight, chromium 15
A mixture or alloy having a composition of ~35% by weight, the balance being substantially iron, is melted and then cast into an ingot, and the resulting ingot is solution treated and then cold rolled. After forming a thin plate, a magnetic field is applied perpendicular to the rolling surface while heat treating the obtained thin plate.
Next, after subjecting the thin plate to aging treatment, the surface roughness of the thin plate is set to 1/10 or less of the recording wavelength, and the thickness of the thin plate is set to 0.001 to 3 m.
1. A method for manufacturing a magnetic recording medium, characterized by subjecting m to finishing processing. Claim 4: Cobalt 5-25% by weight, chromium 15
~35% by weight, with iron as an essential balance component,
Furthermore, vanadium 0.1 to 5% by weight, molybdenum 0.1
~5% by weight, 0.1-5% by weight of tungsten, 0% by weight of titanium
．． After melting the mixture or alloy having a composition consisting of 1 to 3% by weight, it is cast into an ingot, the obtained ingot is subjected to solution treatment, and then cold rolled to form a thin plate. A magnetic field is applied perpendicular to the rolled surface while heat-treating the thin plate, and then, after aging treatment, the surface roughness of the thin plate is reduced to 1/10 of the recording wavelength.
4. The method of manufacturing a magnetic recording medium according to claim 3, wherein the thin plate is then subjected to finishing processing to a thickness of 0.001 to 3 mm.