JPH06124439A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a dense and hard oxide film having higher durability by repeating alternate processings of sputter etching and grow oxidation on the surface a partial oxide film obtained by vacuum deposition of ferromagnetic metal under the oxygen atmosphere. CONSTITUTION:A processing untreated material 1 is formed on a polymer film by forming Co, Co-Ni or the like with the electron beam vacuum deposition method using a ferromagnetic metal thin film under the oxygen atmosphere and has a surface oxide layer in the thickness of about 100 to 200Angstrom formed at the time of vacuum deposition on the surface of thickness direction. The untreated material 1 is fed to a takeup shaft 5 from a supply shaft 4. While the untreated material 1 is running, it passes a discharge electrodes 6a, 6b and 7a, 7b provided between these shafts. The electrodes 6a, 6b are provided to remove an oxide layer, while the electrodes 7a, 7b to form an another oxide layer. The laternate processings of the sputter etching and glow oxidation on the surface oxide layer can provide dense oxide layer and thereby improve both reliability and electrical characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a magnetic recording medium having a magnetic layer of a ferromagnetic metal thin film suitable for high density magnetic recording and having excellent durability and recording characteristics.

[0002]

2. Description of the Related Art With the progress of information society, the amount of information to be recorded is remarkably increasing, and it is required to increase the recording density of magnetic recording as much as possible. Development of magnetic recording media has been brisk. Although many proposals have been made, the one currently put to practical use is a structure in which the surface of columnar fine particles is coated with an oxide of a ferromagnetic metal itself as disclosed in JP-A-53-58206. It has a well-balanced improvement in recording characteristics and durability, and its constituent elements consist of Co, Ni, and O (JP-A-56-15014), and these magnetic recording layers are formed by oxygen gas. C while intervening
A typical method is electron beam evaporation of o, Co-Ni, and there are some proposals for introducing oxygen, but in the vicinity of the substrate,
A position close to the part for controlling the incident angle is often used (Japanese Patent Laid-Open No. 54-19199, Japanese Patent Laid-Open No. 58-322).
34 publication). Further, while a protective film is being studied in order to improve the practical performance, further improvement has been made by increasing the hardness of the carbon film (Japanese Patent Laid-Open No. 53-143026) or by interposing other thin layers. (For example, JP-A-61-2
42323, JP-A-62-167616). These films are applied after the ferromagnetic metal thin film is formed by vapor deposition by a plasma application, a sputtering method, an ion beam deposition method, a plasma CVD method, or the like.
After further necessary processing, it is processed into a tape shape or a disk shape and used.

[0003]

However, although the coercive force increases with an increase in the amount of oxygen introduced in the above-mentioned conventional structure, the saturation magnetic flux density decreases and S obtained with an optimum amount of introduction.
There is a problem that the maximum value of the / N ratio is lower than the value required for higher density recording, and only a medium having an insufficient balance between durability and S / N ratio can be manufactured.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a method of manufacturing a thin magnetic recording medium having both durability and high output characteristics, which enables narrow track high density recording. And

[0005]

In order to achieve this object, a method of manufacturing a magnetic recording medium according to the present invention uses a surface of a partial oxide film obtained by vapor deposition of a ferromagnetic metal in an oxygen atmosphere by sputter etching and glow oxidation. The alternate processing by is repeated.

[0006]

With this structure, the surface oxide film in the thickness direction of the partial oxide film obtained by vapor-depositing a ferromagnetic metal in an oxygen atmosphere becomes a denser and harder oxide film than the state obtained at the time of vapor deposition. Since it is possible to achieve balance without increasing the layer thickness, it becomes possible to reproducibly manufacture a thin magnetic recording medium having both durability and high S / N.

[0007]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 is a raw material for processing, and the ferromagnetic metal film on the polymer film is C at least in an oxygen atmosphere.
o, Co-Ni or the like is formed by electron beam vapor deposition, and 100 to 2 formed on the surface in the thickness direction during vapor deposition.
It is assumed that the structure has a surface oxide layer of about 00Å. Numerals 2 and 3 are temperature-controlled rotary supports, which can be appropriately selected to be ground potential or have an insulating structure so that a potential can be applied. Reference numeral 4 is a feeding shaft, and 5 is a winding shaft. 6a and 6b are discharge electrodes A, and 7a and 7b are discharge electrodes B. It is not necessary to limit the shape, size, material, etc. of the electrodes to narrow conditions. For example, aluminum is a curved surface and is arranged substantially concentrically with the rotary support. It is enough to set it up. 6
a and 6b are operated for the purpose of removing the oxide layer, and 7a and 7b
Is capable of independently controlling the operating pressure, gas species, etc. in order to operate to newly form an oxide layer. The partition walls, exhaust system, etc. need to optimize known techniques (not shown). Reference numeral 8 is a rotating roller.

In order to further clarify the effect of this embodiment, a magnetic recording medium will be made by using the apparatus having the above-mentioned constitution, and the result of the characteristic comparison with that obtained by the conventional method will be described in detail. .

The thickness is 7.1 μm, the Young's modulus is 540 and 590 [Kg / mm ² ] in the longitudinal direction and the width direction, respectively, and the average roughness is 3
0Å polyethylene terephthalate film (diameter 15
Using 0 Å ultrafine particles of SiO ₂ with an average density of 20 particles / μm ² resin-fixed coating layer was placed in advance), the oxygen was wound up along a rotary can cooled to 20 ° C. with a diameter of 1 m. Then, Co was electron beam evaporated to form a magnetic layer of 0.18 μm. The oxygen gas introduction nozzle has a minimum incident angle of 40 degrees, and a 0.8 mm diameter stainless steel pipe with 0.2 mm diameter holes at a 15 mm pitch is arranged at the tip of the mask that determines the incident angle.
It was introduced by controlling to 1 / min. Surface oxide layer is 110
It was ~ 115Å. This state is referred to as an original fabric A, and the original fabric A is the device shown in FIG. 1 and is equipped with a rotary support (diameter 50 cm, ground potential, 2 pieces), discharge electrode A (Al, curvature 28 cm, circumference 30).
cm), discharge electrode B (Al, curvature 29 cm, circumference 40 cm),
Sputter etching conditions: DC; 800V, 1KW, A
r0.02 Torr, glow oxidation condition; RF100KH
Under the same conditions of z, 800 W and oxygen of 0.08 Torr, tapes were prepared by changing the feed rate of the raw fabric A and the number of times of treatment (counted as one by etching and glow oxidation).
The number of treatments of 3 or more is that of rewinding in a vacuum using a reversing mechanism and repeating treatment.

Feeding speed 10 m / min, processing 2 times (tape 1a), 10 m / min, 3 times (tape 1b), feeding speed 20 m / min, 2 times (tape 1c), 20 m / m
In, 4 times (tape 1d), 20 m / min, 6 times (tape 1e), the conventional example was not processed.

For each of 1a to 1e, a diamond-like hard carbon film was formed on the magnetic layer by 60 liters. Only the conventional example has two thicknesses of 60Å and 150Å. The formation was performed by a plasma CVD method in which methane gas was ionized by high frequency discharge to form a carbon film. Perfluoropolyether as a lubricant was further placed on the carbon film by a 40 Å solution coating method, a back coat layer was formed to 0.45 μm, and a magnetic tape having a width of 8 mm was experimentally manufactured and the characteristics were compared. The characteristics of the magnetic tapes are compared with each other by modifying the high-band 8 mm video deck and recording at a recording wavelength of 0.47 μm and a track pitch of 9 μm.
The relative comparison of the / N ratio was performed. The length of the magnetic tape is 100
m, randomly selected 5 rolls and displayed as the average value of 5 rolls. Still characteristics are 4 by increasing the tension to 25g.
Comparison was performed at 0 ° C. and 5% RH. The characteristics of the magnetic recording medium according to this example and the characteristics of the magnetic recording medium of the comparative example are shown in comparison with each other (Table 1).

[0013]

[Table 1]

As is clear from (Table 1), the magnetic recording medium manufactured according to the present example has an excellent effect of achieving durability and high S / N ratio in high density recording in narrow track recording. It is understood that is an excellent manufacturing method.

As described above, according to the manufacturing method of this embodiment,
By repeatedly performing alternate processing by sputter etching and glow oxidation on the surface of the partial oxide film obtained by depositing a ferromagnetic metal in an oxygen atmosphere, an excellent S / N ratio is repeatedly used in high density recording with a narrow track. In the above, it is possible to obtain a large number of magnetic recording media that can be stably held with good reproducibility.

(Second Embodiment) A second embodiment of the present invention will be described below. The structure of the main part of the magnetic recording medium manufacturing apparatus for carrying out the method of manufacturing the magnetic recording medium of the second embodiment of the present invention is the same as that of the first embodiment. Two types of discharge gas were used: oxygen gas 100% and gas in which the ratio of oxygen and hydrogen was 10: 1.

Further, in order to clarify the effect of this embodiment, a magnetic recording medium is prototyped using the apparatus having the above-mentioned constitution, and the result of the characteristic comparison with that obtained by the conventional method will be described in detail. .

A polyimide film having a thickness of 6.1 μm, a Young's modulus of 940 and 1050 [Kg / mm ² ] in the longitudinal and width directions and an average roughness of 30 Å (SiO _{2 having a} diameter of 150 Å)
Of the ultrafine particles of which the average density was 20 / μm ² was fixed on the resin, and the coating layer was previously arranged).
While winding along a rotary can cooled to 0 ° C., oxygen was introduced and Co was electron beam evaporated to form a magnetic layer of 0.1%.
8μ was formed. The oxygen gas inlet nozzle has a minimum incident angle of 20 degrees, and the diameter of the tip of the mask that determines the incident angle is 8 mm.
Oxygen gas introduction nozzles having a diameter of 0.2 mm arranged at a pitch of 15 mm were introduced into the stainless steel pipe of No. 1 at 0.81 / min. The maximum incident angle is 42 degrees, and the Co-O film with the easy axis of oxidation in the vertical direction is 120-
It was 125Å. This state is referred to as an original fabric B, and the original fabric B is the device shown in FIG. 1 and is equipped with a rotary support (diameter 50 cm, ground potential, 2 pieces), discharge electrode A (Al, curvature 28 cm, circumference 30).
cm), discharge electrode B (Al, curvature 29 cm, circumference 40 cm),
Sputter etching conditions: DC; 900V, 1KW,
0.02 Torr, glow oxidation condition; RF100KHz,
Unify the conditions of 700W and 0.09 Torr, and fabric B
The tape was prepared by changing the feed rate and the number of times of treatment (counted once for etching and glow oxidation). The number of treatments of 3 or more is that of rewinding in a vacuum using a reversing mechanism and repeating treatment.

Feed speed 10 m / min, treatment 2 times (tape 2a), 10 m / min, 3 times (tape 2b), feed speed 20 m / min, 2 times (tape 2c), 20 m / m
In, 4 times (tape 2d), 20 m / min, 6 times (tape 2e) were prepared, which were not processed in the conventional example.

For each of 2a to 2e, a diamond-like hard carbon film having a thickness of 60Å was formed on the magnetic layer. Only the conventional example has two thicknesses of 60Å and 150Å. The formation was performed by a plasma CVD method in which methane gas was ionized by high frequency discharge to form a carbon film. Perfluoropolyether as a lubricant was further placed on the carbon film by a 40Å solution coating method to form a back coat layer of 0.45 μm and processed into a magnetic tape of 8 mm width. Modified these tapes 8
Milli-video was used to perform digital recording with a 5μ track and a bit length of 0.2μ, and the relative error rates were compared. The durability was also evaluated by the error rate after adding 100 pass histories at 5 ° C. and 85% RH.

The characteristics of the magnetic recording medium according to this embodiment and the characteristics of the conventional magnetic recording medium are shown in comparison with each other (Table 2).

[0022]

[Table 2]

As is clear from (Table 2), the magnetic recording medium manufactured according to this example has an excellent effect that high-density digital recording can be performed under a narrow track condition with a good error rate. is there.

As described above, according to this embodiment, the surface of the partial oxide film obtained by vapor-depositing the ferromagnetic metal in the oxygen atmosphere is repeatedly subjected to the alternating treatment by the sputter etching using the discharge gas containing oxygen and the glow oxidation. By doing so, the surface oxide film in the thickness direction of the partial oxide film obtained by vapor deposition of a ferromagnetic metal in an atmosphere containing oxygen becomes a denser and harder oxide film than the state obtained at the time of vapor deposition. Since it is possible to achieve balance without increasing the layer thickness, it becomes possible to reproducibly manufacture a thin magnetic recording medium having both durability and a high S / N ratio.

(Embodiment 3) A third embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a configuration diagram of essential parts of a magnetic recording medium manufacturing apparatus for carrying out the method of manufacturing a magnetic recording medium according to the third embodiment of the present invention. In FIG. 2, the same components as in FIG. 1 are given the same numbers as in FIG. Reference numeral 9 is a rotary support, which has a circulating medium and an induction heating type heating element built-in so that heating can be controlled. Reference numeral 10 is a hydrogen beam irradiation nozzle, 11 is an oxygen atom beam irradiation nozzle, and 12 is a partition plate. Atomic beams can be generated, for example, by extracting ions from plasma of hydrogen or oxygen, neutralizing them with an electron shower, and then passing them through a magnetic field to separate them.

The production method of the present invention will be specifically described in detail by comparing the characteristics of an actually produced magnetic recording medium with those of a conventional example and a comparative example.

On an aramid film having a thickness of 6 μm (average roughness 20 Å, Young's modulus length 900, width 1050 kg / mm ² ), SiO ₂ having an average particle size of 170 Å has an average density of 40 pieces /
Apply and fix with μ ² and 0.2 μm Co-O under the following conditions.
A perpendicular magnetic film was formed. Co was heated and evaporated by an accelerated electron beam in a magnesia container, and Co was deposited along the surface of a rotary support having a diameter of 1 m and an incident angle in the range of 90 to 30 degrees. At that time, oxygen gas was introduced at a rate of 0.91 / min, and vapor deposition was performed twice in 0.1 μm increments. The oxide layer on the surface was 140Å. Hydrogen atom is 0.4 KV
Then, the oxygen atoms were extracted at 0.6 KV, neutralized, and irradiated at 4 × 10 ¹⁶ and 6 × 10 ¹⁶ [atoms / cm ² sec], the feed rate was 10 m / min, and the treatment was performed twice (tape 3
a) 10 m / min, 3 times (tape 3b), feeding speed 20 m / min, 2 times (tape 3c), 20 m / mi
n, 4 times (tape 3d), 20 m / min, 6 times (tape 3e) were prepared without treatment in the conventional example.

A 60-liter diamond-like hard carbon film was formed on each magnetic layer by the plasma CVD method (a conventional example was also trial-produced of 180 liter), and then 30 liter of perfluorostearic acid was placed on the magnetic layer, and a 0.5 μm back film was formed. Coat layers were arranged and processed into magnetic tapes each having a width of 8 mm. By using an 8 mm video modified from these tapes, digital recording with a 5 μ track and a bit length of 0.2 μ was performed and relative error rates were compared. The durability was also evaluated by the error rate after adding a 150-pass history at 3 ° C. and 10% RH. The characteristics of the magnetic recording medium according to this example and the characteristics of the conventional magnetic recording medium are shown in comparison with each other (Table 3).

[0029]

[Table 3]

As is clear from (Table 3), the magnetic recording medium manufactured according to this example has an excellent effect that high-density digital recording under a narrow track condition can be performed with a good error rate. is there.

As described above, according to the manufacturing method of this embodiment, the surface of the partial oxide film obtained by vapor-depositing a ferromagnetic metal in an oxygen atmosphere is treated with hydrogen atoms and oxygen atoms, so that the atoms are extremely active. Therefore, the surface oxide film in the thickness direction of the partial oxide film obtained by vapor deposition of metal becomes a denser, harder, microscopically and chemically uniform oxide film than the state obtained at the time of vapor deposition. Since the balance can be achieved without increasing the thickness of the surface oxide layer, it becomes possible to reproducibly manufacture a thin magnetic recording medium having both durability and high S / N.

[0032]

As described above, according to the present invention, the surface oxide film in the thickness direction of the partial oxide film obtained by vapor deposition of a ferromagnetic metal in an oxygen atmosphere is more dense than that obtained at the time of vapor deposition. The hard oxide film can be balanced without increasing the thickness of the surface oxide layer, so that it is possible to reproducibly manufacture a thin magnetic recording medium having both durability and a high S / N ratio.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a main part of a processing apparatus used for manufacturing a magnetic recording medium according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of a processing apparatus used for manufacturing a magnetic recording medium according to a third embodiment of the present invention.

[Explanation of symbols]

 1 Processing original fabric 6a, 6b Discharge electrode A 7a, 7b Discharge electrode B 10 Hydrogen atom beam irradiation nozzle 11 Oxygen atom beam irradiation nozzle

Claims (3)

[Claims] 1. A method for manufacturing a magnetic recording medium, characterized in that the surface of a partial oxide film obtained by vapor-depositing a ferromagnetic metal in an oxygen atmosphere is repeatedly subjected to alternate treatments by sputter etching and glow oxidation. 2. The alternate treatment by sputter etching using a discharge gas containing oxygen and glow oxidation is repeated on the surface of a partial oxide film obtained by depositing a ferromagnetic metal in an oxygen atmosphere. 1. The method for manufacturing a magnetic recording medium according to 1. 3. A method for manufacturing a magnetic recording medium, characterized in that the surface of a partial oxide film obtained by vapor deposition of a ferromagnetic metal in an oxygen atmosphere is subjected to hydrogen atom treatment and oxygen atom treatment.